Background
Spine oncology encompasses both benign and malignant entities that localize to both the vertebral column and the spinal cord and meninges. Conventionally spinal oncology has focused on local control, maintenance of neurologic function, stabilization, and overall patient survival. However, as cancer prognoses have improved over the past 10 to 15 years [ 1 ], there has been increased recognition of the correlation between patient quality of life and overall spinal alignment (specifically sagittal balance) [ 2 , 3 ]. Surgeons are therefore also increasingly considering spinal alignment in these patients. Tumor surgery represents a chance to opportunistically correct spinal deformity, as resection often requires vertebral column resection—a special 3 column osteotomy that affords the chance for significant sagittal plane correction. The present review by the North American Spine Society Section on Spinal Oncology therefore serves as a primer on modern deformity principles for spinal oncology surgeons and focuses on the application of deformity principles to the treatment of spine tumor patients.
Overview of spinal deformity and patient quality of life
Alignment and patient-reported outcomes
Work by Glassman et al. [ 2 , 4 ], noting sagittal, not coronal balance best predicts clinical symptoms in adult spinal deformity (ASD). In the follow-up study [ 2 ], they found sagittal balance positive correlated with both SF-12 physical health status and Oswestry Disability Index. Multiple other studies have looked at alignment and both disease-specific and general health PROs [ 5 , 6 ]. In general these have also found greater sagittal imbalance to correlate with worse pain and quality of life [ 6 ], though there remains no consensus regarding which sagittal alignment parameter best predicts PRO outcomes. One recent study by Zhang et al. [ 6 ] suggested SVA was most highly correlated with outcomes but others have suggested that pelvic incidence (PI)—lumbar lordosis (LL) mismatch (PI-LL) [ [7] , [8] , [9] , [10] ] or pelvic tilt (PT) [ 9 , 11 ] may be an effective predictors. Evidence remains mixed though [ 12 , 13 ]. Within the spine tumor population such literature is even more limited. However, Massier et al. [ 14 ] noted that the Global Alignment and Proportion (GAP) score correlated with patient-reported physical function scores following en bloc resection of mobile spine tumors even after correcting for local disease recurrence.
Summary of modern deformity parameters
Much of ASD surgery focuses on sagittal balance—a description of the body’s “tendency” to try and maintain horizontal gaze and keep the center of gravity of the head and shoulder girdle above the pelvis. This has also been described as the “cone of economy” by Dubousset [ 15 ], who described the increased musculoskeletal strain that occurs when the patient’s posture is displaced too far from the upright position. Patients demonstrate [often subconscious] compensatory mechanisms to maintain sagittal balance, including thoracic spine hypokyphosis, pelvic retroversion, and knee flexion. As a result, patients can present with back, anterior thigh, and buttock pain that worsens throughout the day due to chronic postural muscle activation. Radiographically, the patient’s pelvic retroversion is manifest as an increased PT or a flattening of the iliac crests on posterior-anterior standing radiographs. Head-to-toe radiographs are imperative to fully assess the patient’s spinal deformity and compensatory mechanisms. For some spine tumor patients this may be infeasible owing to pain, neurological deficits, or extremity disease that prohibits them from standing. Supine films may be a reasonable alternative for these patients; however, it should be noted that in most oncology patients, the deformity is mobile, not fixed, and so the deformity may be underestimated on supine images.
Fig. 1 provides an overview of commonly used sagittal balance parameters; these are also in other reviews on ASD [ 16 ]. Global balance can be described by the C7 sagittal vertical axis (C7-SVA)—the horizontal distance between the C7 centroid and the posterior superior corner of the S1 endplate – attempts to describe whether the shoulder girdle falls over the sacrum; normal is ≤4 cm [ 17 ] C7 SVA does not account for compensatory mechanisms and global tilt (GT), L1-pelvic angle (L1PA), and T4-pelvic angle (T4PA) are other metrics that attempt to encapsulate global balance while eliminating the influence of pelvic retroversion and knee flexion. T4PA is increasingly popular due to its high interobserver reliability [ 18 ] and ability to be assessed intraoperatively on prone radiographs. Cervical spine alignment can similarly be quantified using the C2-7 SVA, which is designed to assess whether the patient’s skull sits over the C7 body—the point of transition between the cervical and thoracolumbar spine. Chin-brow vertical angle (CBVA) is also important in cervical deformity correction and describes the patient’s horizontal gaze [ 19 , 20 ]. A patient’s compensatory mechanisms are often attempts to maintain horizontal gaze.
Global balance is itself a sum of the regional balance of the thoracic and lumbar spines, and the degree to which they show lumbopelvic harmony. The normal curvatures of the thoracic and lumbar spine are kyphosis and lordosis, respectively, though there can be a loss of thoracic kyphosis (TK) in the setting of global sagittal imbalance. In the context of spinal malignancy, there is often anterior column collapse with focal hyperkyphosis. Roussouly [ 21 ] also further analyzed the lumbar spine regional curvature, noting interpersonal variation in the apex of the lumbar curvature. As a rule of thumb though, most patients have two-thirds of their LL (usually 35–40°) in the 2 caudal most segments (L4-S1) [ 22 ].
When correcting sagittal plane deformity, surgeons seek to match the LL and PI—a mathematical description of how the sagittal relationship between the mobile spine and pelvis. It is conventionally held to be fixed, though it is increasingly recognized that it changes slightly with position and can even change after pelvic fixation [ 23 ]. Ideal PI-LL mismatch is generally accepted as <10° and residual PI-LL mismatch is associated with increased risk of implant failure and adjacent segment disease in patient undergoing en bloc vertebral column tumor resection [ 24 ]. L1PA also attempts to encapsulate lumbopelvic harmony. Defined as PI/2 – 21°, it may better predict hardware failure than PI-LL [ 25 ] and strongly correlates with T4PA [ 26 ], though results are mixed and L1PA may not effectively predict PROs [ 27 ].
Considerations for spinal realignment
Bone quality
Bone quality and implant selection are key to successful spinal realignment as the ability to perform corrective maneuvers intraoperatively is limited by screw purchase strength. Conventionally, bone quality is assessed with dual-energy X-ray absorptiometry (DXA), which determines the bone mineral density (BMD) based upon the absorption of X-rays projected at the hip, femur, lumbar spine, or wrist [ 28 ]. The calculated BMD is converted to a T-score, classifying their BMD relative to young, sex-matched controls: a T-score >−1 is normal, one between −1 and −2.5 is osteopenia, and T ≤−2.5 is osteoporotic. Low BMD (T-score <−1) has been correlated with a significant increase in vertebral compression fracture risk [ 29 ], a surrogate marker for anterior column structural incompetence under axial loading. Additionally, low BMD is highly correlated ( r =0.93) with screw pullout strength [ 30 ] and construct fatigue resistance, with osteoporotic bone tolerating 55% fewer cycles to failure relative to normal BMD in vitro [ 31 ]. However, DXA imperfectly captures cancellous bone volume and strength [ 32 , 33 ], and may be inaccurate in patients with compression fractures, obesity, or degenerative spine changes [ 28 , 34 ].
Alternatives to DXA of increasing interest are the measurement of Hounsfield Units (HU) on computed tomography (CT) scans and the Vertebral Bone Quality (VBQ) score on magnetic resonance imaging (MRI) [ 28 , [35] , [36] , [37] , [38] ]. HU-based bone strength measures operate on the same principle as DXA with higher bone densities causing greater X-ray absorption and higher HU values. In vitro testing has shown strong correlation to both vertebral body ultimate load and stress on compression [ 39 ]. Additionally, HU on CT have been correlated with biomechanical CT-based measures of vertebral whole-bone strength and trabecular BMD [ 40 ]. Unlike DXA, it can also be measured using imaging routinely obtained for spine tumor patients for example, the CT chest/abdomen/pelvis obtained as part of systemic disease staging. However, this is with the caveat that these staging images commonly use intravenous contrast, which has a small, but significant impact on HU measures [ 41 ]. Additionally, CT-based HU are measured for the bones of interest—those undergoing instrumentation—as compared to DXA, which is usually performed using the appendicular skeleton. For the lumbar spine, HU values of <110 and <160 are considered to be cutoffs for osteoporosis, and osteopenia, respectively, as they correlate with accepted quantitative CT measures of <80mg/cm³ and <120mg/cm³, respectively [ 42 , 43 ]. Similarly, HU values of <341 and <327 have been suggested as markers of osteopenia and osteoporosis in the cervical spine [ 44 ], and HU values of <153 and <231 have been suggested as markers for osteoporosis [ 45 ] and osteopenia [ 46 ] in the mid-thoracic spine [ 45 ]. Several studies have shown HU to predict mechanical complications following instrumented spine surgery [ 35 , 47 ].
VBQ is another alternative and has been shown to predict mechanical complications following spinal fusion [ [48] , [49] , [50] ]. It measures the T1 signal intensity of the bone marrow at multiple levels. Normalization with the signal intensity of adjacent cerebrospinal fluid is intended to overcome differences in MRI field strength and scanner type, though it does not fully overcome these differences which are based on echo time [ 38 ]. It operates on the assumption that cancellous bone trabecular loss is associated with fatty infiltration which produces increased T1 signal [ 51 ]. However, other materials, such as blood product can cause increased T1 signal and tumor-infiltrated vertebra can show increased or decreased T1 signal depending upon the underlying pathology [ 52 ]. Consequently, it may not accurately capture composition and bone quality of the tumor-infiltrated bone, which will affect the biomechanical properties. Direct comparisons of HU and VBQ have demonstrated HU to be more predictive of the occurrence of complications in both the ASD [ 35 ] and spine oncology populations [ 36 ]. Our preference therefore is to employ HU measurements.
An additional consideration in the spinal metastasis population is the Spinal Instability Neoplastic Score (SINS) [ 53 ]. It considers the degree of vertebral body involvement/collapse, posterior element involvement, presence of associated focal deformity, lesion quality (osteolytic, osteoblastic, mixed), the presence of pain (oncologic, mechanical or none), and lesion location along the spine axis. Though developed for spinal metastases, the principles SINS encapsulates include the significant load-bearing performed by the anterior column, the presence of greater stresses at junctional levels, and the crucial contribution of the posterior tension band to maintaining alignment. Despite its utility for identifying underlying instability, SINS does not incorporate assessments of spinal alignment and is likely inadequate for assessing deformity and alignment targets in patients undergoing tumor surgery with concomitant deformity correction.
Implant selection
Implant selection includes selection of longitudinal elements (eg, rods, tethers), anchors employed (eg, screws, hooks), and anterior column support (eg, corpectomy cage). This includes evaluating implant stiffness for maintaining correction postoperatively, use of a multirod constructs for high-stress regions (eg, 3-column osteotomy or corpectomy levels), screw pitch (eg, corticocancellous vs cortical vs pure cancellous thread pitch), rod diameter, and the use of a “soft stop” to prophylax against adjacent segment pathology. Spinal oncology cases must additionally consider the need for postoperative radiotherapy and serial radiographic follow-up for lesion recurrence/progression. Of the conventional implant materials, titanium alloy rods create less artifact than cobalt chrome rods [ 54 ], allowing for improved surveillance and more accurate radiotherapy planning [ 55 ]. They are also less stiff, which can be advantageous when trying to avoid screw pullout from compromised bone.
Anterior column reconstruction with metal implants can further complicate postoperative radiotherapy [ 56 ], as the resultant beam scatter increases spinal cord radiation dosing by 20% [ 57 ]. Reconstruction with polyetheretherketone (PEEK) cages allowed for more consistent radiation dose delivery relative to titanium cages and polymethylmethacrylate (PMMA) based reconstruction [ 58 ]. Carbon fiber-reinforced PEEK (CFR-PEEK) corpectomy devices similarly decrease off-target radiation dosing (up to 68% versus titanium) while offer similar structural stiffness [ 59 ].
CFR-PEEK instrumentation has consequently garnered increased interest. It has similar fatigue tolerance to titanium [ 60 ], with lower imaging artifact [ 61 ] and less radiotherapy dose perturbation [ 62 ] Reduction in radiotherapy dose perturbation is even greater for proton and charged particle radiotherapy (up to 90%) [ 55 , 56 , 63 , 64 ]. However, CFR-PEEK implants are significantly more expensive than comparable metal implants, raising the issue of whether their cost is worth the improved radiographic follow-up. Using hybrid constructs using CFR-PEEK screws only at the tumor level (±1 segment above/below) or using CFR-PEEK only for the corpectomy defect/anterior column reconstruction may help balance the increased costs of CFR-PEEK against its benefits. CFR-PEEK instrumentation additionally cannot be contoured postmanufacture (curvatures are preset by the manufacturer) [ 65 ], limiting their utility for in situ deformity correction. Constructs seeking concomitant deformity correction may therefore employ titanium alloy rods with CFR-PEEK screws, offering some radiographic artifact suppression while still affording intraoperative deformity correction.
Unique features of deformity in the oncology population
Systemic therapy and radiotherapy
Unlike surgery for ASD, which seeks to “cure” the deformity, surgery for vertebral column neoplasms is seldom curative [ 66 ]. Noted exceptions are surgeries for primary bony malignancies, where en bloc resection with negative margins can improve overall survival [ 67 , 68 ]. Additionally, in select selected patients with isolated metastatic disease (usually from renal cell or thyroid primary lesions), en bloc resection can be considered as a strategy for improving overall survival [ 69 ]. However patients should have good cardiopulmonary reserve and well-controlled primary disease. In both primary and metastatic tumor cases; however, there is often an impetus to expedite initiation of radiotherapy and/or resumption of systemic therapy (metastatic disease) as this correlates with improved survival [ 70 ]. Classical chemotherapies [ 71 , 72 ] and anti-VEGF agents [ 73 ] impair wound healing by blocking cell proliferation and angiogenesis. Accordingly, they must generally be held 2 or more weeks perioperatively [ 74 ]. Surgical planning must therefore weigh the need for a more aggressive surgery that aims to correct any concomitant deformity against the need to expedite the resumption of systemic therapy.
Radiotherapy can similarly cause wound complications by killing the rapidly dividing cells involved wound healing and early scar formation. This side effect is reduced with focused photon beam modalities but remains a concern. Clinicians must therefore balance the improved local control afforded by early radiotherapy against the increased risk of wound complications. Various reviews [ 75 ] and survey-based studies [ 74 , 76 ] have suggested delaying radiotherapy 1 to 6 week after surgery but all are based on low-quality evidence. Evidence guiding radiotherapy initiation after surgery for primary malignancies is similarly week, though a position paper by several spinal oncology found most recommend waiting 3 to 8 weeks [ 77 ].
Of additional concern, high-dose radiation causes trabecular bone loss [ 78 ], which may weaken screw purchase [ 79 ], and radiation therapy appears to inhibit bony fusion [ 79 ] with a recent single-center series [ 80 ] noting only 29% of patients had any evidence of arthrodesis and 8.2% had complete fusion. Hardware failure was uncommon (4%) due to short overall survival, but the high nonunion rates suggest success in spine oncology may be measured in terms of successful immobilization and deformity correction, not fusion [ 81 ].
Focal deformity
Deformity in tumors often results from focal kyphosis in the setting of a pathologic compression or burst fracture [ 82 ]. These deformities are generally mobile and associated with mechanical pain. In the absence of epidural disease, vertebral cement augmentation via vertebroplasty or kyphoplasty may be a reasonable option as both have been shown to offer significant improvement in pain [ 83 , 84 ]. Rates of segmental correction vary [ 82 , 85 ], though Kim and colleagues [ 86 ] reported an average of 11° of correction when kyphoplasty followed 2 days of postural fracture reduction. Long-term follow-up suggests that such corrections may not prove robust, with Lim et al. noting complete loss of correction by one-year [ 87 ]. Yet they may be optimal for patients with limited survival, offering symptom palliation without the morbidity of open surgery. Newer percutaneous strategies, such as the SpineJack (Stryker, Kalamazoo, MI) may offer superior radiographic correction to conventional cement-augmentation techniques; however, they are currently contraindicated in the setting of pathologic fracture. Consequently, for patients healthy enough for surgery, correction with pedicle screw instrumentation is likely the best option to correct underlying deformity.
Deformity can also be focal in primary pathologies (see Example Case 1), but this is generally deformity created by the surgeon during tumor resection [ 24 ]. Residual deformity correlates with both poorer PROs [ 14 ] and more mechanical complications, specifically implant failure and adjacent segment disease [ 24 ]. Reconstruction post-tumor delivery should therefore focus on preservation [and if necessary, restoration] of normal alignment.
Multilevel disease
Nearly 40% of spinal metastasis patients have multilevel disease [ 88 ], which can lead to multifocal deformity. Multifocal disease also causes poor bone quality and screw purchase at multiple levels, which may in part be addressed using PMMA cement augmentation [ 89 , 90 ], especially where there is concomitant osteoporosis [ 91 ]. It may therefore allows surgeons to use shorter constructs [ 92 ] with accordingly smaller incisions and potentially faster recovery and resumption of systemic therapy. Fenestrated screws are a popular option for cement-augmentation as then can be used even during percutaneous fixation. However, traditional cement-augmentation with screw tract prefilling may afford greater pullout strength [ 93 ] as fenestrated screws deposit cement predominately at the screw tip [ 94 ] The former may therefore be preferrable for procedures seeking to correct deformity due to the forces required for intraoperative reduction (see Case Example 2). While augmentation with larger cement volumes may improve pullout strength [ 90 ] it is at the cost of increased cement extravasation risk and our tendency is to use 1 to 1.5 mL per screw for thoracic levels and 3 mL per screw for lumbar levels [ 89 , 95 ]; we do not employ cement augmentation at cervical levels.
The need for radiographic follow-up
Spinal tumor patients generally require serial radiographic surveillance, which is negatively impacted by the artifact produced by metal implants [ 96 ] CFR-PEEK instrumentation lacks this artifact though offers limited intraoperative correction as rods cannot undergo in situ contouring [ 81 ] Biomechanically [ 60 , 97 ] it offers similar fatigue resistance [ 60 ], axial loading [ 97 ], and construct stiffness [ 98 , 99 ] with potentially smaller increases in adjacent segment motion and disc pressures with a resultant decrease in adjacent segment disease risk [ 99 ].
Where deformity correction is desired then, a hybrid construct may be optimal, blending the radiographic benefits of CFR-PEEK screws and interbodies with the cost benefits and in situ deformity correction afforded by titanium rods. Hybrid constructs often employ CFR-PEEK screws 1 to 2 levels immediately cranial and caudal to the tumor target with titanium screws elsewhere [ 81 ] CT phantom work [ 64 ] has shown this to significantly cut radiographic artifact and reduce radiographic planning uncertainty to a level approximating that seen with pure CFR-PEEK constructs.
Anterior column reconstruction
Nearly 80% of vertebral column metastases affect the vertebral body [ 100 ] and primary bony malignancies benefitting from en bloc resection [ 67 , 68 , 101 ], also commonly localize to or involve the vertebral body. Spinal tumor treatment consequently often involves partial or complete corpectomy/spondylectomy and anterior column reconstruction. Reconstruction options include strut allograft, vascularized fibular strut autograft, PMMA cement, titanium mesh or expandable cages, and static or expandable CFR-PEEK cages [ [102] , [103] , [104] ]. Defect size, surgical approach, (posterior versus anterior; minimally invasive versus open), adjacent bone quality, and radiotherapy needs guide reconstruction choice. PMMA cement is one of the oldest techniques [ 104 ] and advantages include simplicity of use (requiring minimal carpentry relative to cage reconstruction), relatively low cost, and high cross-sectional area (offering minimal subsidence risk) [ 105 ] CFR-PEEK cages improve radiotherapy planning and off-target dosing relative to titanium cages [ 59 ], and better approximate the Young’s modulus of cancellous and cortical bone [ 106 ], potentially reducing potential subsidence risk. However, they are significantly more expensive than titanium cages. Strut grafts similarly allow for effective postoperative radiological monitoring but potentially altering biomechanics by shifting the instantaneous axis of rotation anteriorly [ 107 ], though this can be corrected with supplementary posterior instrumentation. Additionally, fibular strut grafts have narrow cross-sections that may increase subsidence risk and less capacity for bone graft material relative to nonexpandable cages [ 106 ] Vascularized fibular struts offer reasonable fusion outcomes, with complete union in up to 76% of cases following en bloc spondylectomy [ 103 ]. They may therefore be preferrable in the primary tumor population, where neoadjuvant or adjuvant radiotherapy often results in an environment that is extremely hostile to bone regeneration. However, the additional morbidity associated with vascularized autograft harvest unlikely justified in metastasis surgeries. In these patients, a more minimally invasive approach is often preferred and surgeons should consider if anterior reconstruction is needed or would be tolerated by the adjacent endplates. Separation surgery is popular in such cases [ 66 ], but it affords minimal opportunity for spinal realignment. Additionally, extended anterior column resection can improve local control [ 108 ] and can be achieved through a minimal access approach [ 109 ] to reduce procedural invasiveness. For these mini-open cases, reconstruction with an expandable cage is preferred as it minimizes device profile during placement while still affording substantial anterior column height restoration. Some also have self-adjusting end caps that maintain effective vertebral endplate-cage apposition throughout deformity correction [ 102 ]. This may reduce endplate stresses and subsidence postcorrection [ 110 ]. Both CFR-PEEK and titanium alloy devices with large endplates to minimize endplate stresses exist, though experiences with titanium-based devices are more extensive.
Corpectomy and en bloc spondylectomy are both highly destabilizing and anterior column reconstruction alone is generally insufficient. Construct design must balance the surgical morbidity and associated artifact of increased instrumentation against the benefits of increased stability. Long-segment instrumentation (±3 segments from the corpectomy level) offers the greatest stability and is superior to 1-2-segment instrumentation [ 111 , 112 ]. It also decreases endplate stresses following multilevel corpectomy [ 112 ], though this may also lead to stress shielding and nonunion.
Multirod constructs are popular in ASD surgery, especially at the lumbosacral junction and pedicle subtraction osteotomy (PSO) sites, as the second rod increases construct stability and decreases primary rod strain. Multiple strategies for secondary rod integration have been described, but the use of an accessory rod—one connected to the primary rod—is common. However, such accessory rods may not decrease primary rod strain [ 113 , 114 ], whereas secondary rods directly anchored to the spine reduce primary rod stresses significantly [ 113 ] Offset connectors are not presently marketed for CFR-PEEK rods, so surgeons opting for multirod constructs may have to utilize titanium alloy rods or dual-rod constructs in which both rods have direct pedicle fixation. For cervical lesions, the placement of a tension-band plate as part of the anterior approach offers greater stability than the addition of extra posterior rods [ 115 ] Last, cross-connectors do not decrease stresses on the corpectomy cage, but increase rod stain [ 116 ], and therefore may increase hardware failure risk. Additionally, the artifact created by the cross-connector further complicates radiographic surveillance and radiotherapy planning.
There is a relative paucity of literature comparing outcomes between spinal metastasis patients who undergo corpectomy and those treated with posterolateral instrumented fusion alone. While corpectomy offers the greatest opportunity for deformity correction, cement-augmented instrumented fusion may offer sufficient correction in many oncologic patients and further work is needed to compare local control, deformity correction, pain palliation, and PROs between these strategies.
Pelvic reconstruction
Lumbopelvic reconstruction following sacrectomy is one of the biomechanically most complex operations faced by spinal oncologists owing to the high stresses across the lumbosacral junction [ 117 ] and the potential for poor realignment to create significant sagittal plane deformity. With removal of the sacrum, the patient ostensibly loses their innate pelvic incidence; the new PI is dictated by the relative curvature of the rods linking the bony pelvis to the lumbar spine [ 118 ] Dual rod instrumentation with dual pelvic anchors bilaterally provides the most stable pelvic reconstruction [ [119] , [120] , [121] ] and 4 rod constructs have the lowest risk of mechanical complications following sacrectomy clinically [ 122 ]. Use of a transiliac bar does not appear to afford additional stability [ 119 ] and in our hands, an upper instrumented vertebra of L3 is preferrable to have multiple points of fixation above the sacrectomy defect, especially in older patients with poor bone quality. Long pelvic screws passing ventral to the lumbosacral pivot point offer the greatest resistance against the large angular moments applied at the lumbosacral junction [ 123 , 124 ]. The sacral defect can be reconstructed with an interiliac femur strut but this appears inferior to other options, including bilateral L5-iliac cage struts or an expandable interbody device secured onto a transiliac bar for S1 body replacement [ 125 ]. For dual pelvic fixation we favor using intraoperative navigation to allow for stacked S2AI screw placement [ 126 ].
Fusion
Rates of fusion in spine tumor patients are overall low [ 80 ] perhaps owing to impaired physical reserve and increased rates of malnutrition [ 127 ], which may lead to poor wound and bone healing. Radiotherapy also inhibits bony fusion. Reconstruction with vascularized autograft can improve fusion outcomes [ 103 ], yet the associated morbidity is likely justified only in primary tumors. Consequently, the optimal target for most spine tumor patients may not be successful fusion but rather long-term restoration or maintenance of spinal alignment.
Synthesis
The present review, while not all encompassing, attempts to touch on important aspects of spinal deformity in spine tumor patients; we highlight a general approach to management in Fig. 2 . For isolated primary lesions realignemtn can be far more aggressive than for patients with diffuse metastatic disease. For example, in a patient presenting with a lumbar chordoma with no metastatic disease, the oncologic goal of surgery is cure, which can potentially be achieved with en bloc spondylectomy. This 3-column osteotomy is highly destabilizing but also affords surgeons the opportunity to correct underlying global and focal deformity. While it is clear the construct should be selected to address any focal deformity, the degree to which global deformity should be corrected may be debated. Our preference is to aim for a normative sagittal alignment (SVA <5 cm; PI-LL mismatch <10°) as this appears to correlate with better patient physical function and lower rates of mechanical complications. However, given that high-dose neoadjuvant/adjuvant radiotherapy will likely be given, the construct must offer significant stability given the high odds of nonunion. We prefer a long-segment (±3 levels), multirod construct, taking care to avoid terminating the construct at a junctional level. CFR-PEEK screws/rods are preferrable owing to the need for long-term radiographic surveillance and radiotherapy delivery. However, if there is significant baseline focal deformity, we opt for titanium rods, which allow for in situ deformity correction. In all cases oncologic cure should be prioritized over deformity correction, but where there is noted underlying focal deformity, we favor correction of the underlying deformity over optimal radiographic surveillance. Use of a vascularized fibular autograft should be considered to help maximize the odds of successful fusion, though as mentioned above, stable nonunion with preserved alignment may be a more realistic long-term goal.
By contrast, in a patient with diffuse metastases, the decision to pursue surgery hinges on the presence of epidural disease. For those with epidural disease, separation surgery should be considered, and use of cement-augmented pedicle screws may allow for some focal deformity correction. These patients commonly are malnourished and frail, so we favor more minimally invasive approaches and minimize the use of long- and multirod constructs. In these frail patients, a surgical strategy that employs less invasive surgical techniques to prevent further deformity may be preferrable to a more aggressive strategy that corrects the deformity but with higher attendant morbidity. An even less invasive approach is favored for those without epidural disease; surgery for deformity correction alone is likely counterproductive given the high morbidity in a patient with poor expected survival. Percutaneous stabilization via vertebroplasty or kyphoplasty may therefore be a better option.
For patients with recurrent primary tumors or oligometastatic disease from nonspine primary lesions, the relative weight of deformity and oncologic considerations falls somewhere in the middle. In general, primacy is given to addressing neural element compression, as patient function is the priority. In those with metastatic disease, cure is impossible, and so greater weight is given to correction of local deformity. In patients with very good functional status and healthy adjacent vertebrae with good bone quality, we consider corpectomy to improve local control and facilitate global deformity correction. Cement augmentation should be considered to improve screw-bone purchase and facilitate correction of the deformity. Both titanium and CFR-PEEK implants are reasonable. Similarly, for patients with recurrent primary tumors, local spread is likely. Radiographic surveillance is generally of greater import though and so we would favor CFR-PEEK implants given the lower radiographic artifact. Given that surgery will likely attempt maximally safe cytoreduction, anterior reconstruction may be required. This offers the opportunity for greater local and global deformity correction, but we favor a multirod construct for long-term stability. Vascularized fibular strut autograft can be considered, but such a strategy may not be merited in a patient likely to have further recurrence and the need for additional cytoreductive surgery [ 128 ].
Case 1
A 67-year-old woman presented with mechanical back pain localizing to the upper lumbar spine. She also endorsed progressive bilateral radicular leg pain worse with ambulation and consistent with neurogenic pseudoclaudication. Imaging ( Fig. 3 ) demonstrated a T2-hyperintense, avidly contrast-enhancing lesion of the L2 body with <50% height loss and osteolysis of the left pedicle (SINS), with an accompanying mild focal kyphoscoliosis at the thoracolumbar junction. Biopsy demonstrated aggressive hemangioma. Given the overall preserved sagittal balance, the decision was made to use an intermediate-length construct with an L2 corpectomy to remove the tumor; the defect was reconstructed with a titanium mesh cage. Posterolaterally a dual-rod construct was employed, along with cement-augmentation of the screws to improve purchase and fibular strut allograft secured to the rods with cables to serve as osteoconductive elements for long-term fusion. Titanium implants were used given the oncologically benign process and absence of a need for serial MR follow-up.
Case 2
A woman in her mid-60 s with known history of multiple myeloma presented to the emergency department with acute onset paraparesis. Imaging demonstrated high-grade epidural spinal cord compression, for which she underwent T3-T5 open laminectomy with debulking of epidural disease followed by adjuvant radiotherapy. The patient recovered lower extremity function and initially did well but subsequently returned to clinic with upper back pain and increased gait imbalance; she had a spastic gait consistent with thoracic myelopathy on exam. Imaging ( Fig. 4 ) showed >50% collapse of the T5 and T6 vertebral bodies with focal kyphosis of 36.9° causing bowstringing of the spinal cord. The patient had well-controlled systemic disease and was otherwise healthy, so the decision was made to correct the underlying deformity. She underwent a single stage procedure with T5-6 corpectomy and anterior column reconstruction with a titanium mesh cage. Posterolateral fusion was performed with a long-segment construct (T2-T9) and morselized allograft. Cement-augmentation was used to improve screw purchase and facilitate intraoperative deformity correction, especially given the patients history of myeloma and concern for poor underlying bone quality. Postoperative upright radiographs showed good correction of the focal deformity and restoration of a relatively normal global balance. While her SVA was above 5 cm (6.3 cm), is was more consistent with the age-normative target recommended by Lafage et al. [ 129 ] based upon ODI scores in adult spinal deformity patients. She also had minimal lumbopelvic mismatch (LL 61° vs PI 60°) and showed no pelvic retroversion (19°) to suggest compensation for persistent deformity. Titanium implants were selected so as to improve long-term surveillance relative to cobalt-chrome implants; CFR-PEEK implants were not widely available at the time of her surgery.
Conclusion
Given improvements in survival following diagnosis with spinal malignancy, there is increasing attention being paid to the impact of poor alignment on postoperative outcomes in the spinal oncology population. This review focuses on the application of deformity principles to the spinal oncology patient, discussing the correlation of deformity with patient-reported outcomes, the evaluation of underlying bone quality, instrumentation selection, and bony defect reconstruction. While the present review cannot be all encompassing, we hope that it will serve as an effective primer for those treating patients with bony spine tumors.
IRB
Approval: IRB approval was not required for the present narrative review as it did not meet the definition of human subjects research. ronal balance.
Funding
None.
Declaration of competing interest
None.
Footnotes
This article is available at: https://www.spine.org/Education/Continuing-Education/Event-Details?MeetingId=%7BAFF624BE-A973-F011-BEC2-6045BDA8E3CB%7D .
Author disclosures: ZP: Nothing to disclose. JS: Nothing to disclose. SL: Nothing to disclose. CG: Nothing to disclose. MG: Nothing to disclose. MC: Nothing to disclose. RC: Nothing to disclose. ND: Nothing to disclose. DL: Nothing to disclose. AO : Nothing to disclose. JB: Nothing to disclose. WG : Nothing to disclose. WH: Nothing to disclose. AK : Nothing to disclose. IL : Nothing to disclose. MM: Nothing to disclose. AM : Nothing to disclose. GS: Nothing to disclose. DT: Nothing to disclose. JS: Nothing to disclose. AP: Nothing to disclose. DS: Nothing to disclose.
FDA device/drug status: Approved for this indication (CFE-PEEK screw/rod systems, Titanium alloy screw/rod systems, PMMA cement).
References
1. Rothrock R.J., Barzilai O., Reiner A.S., et al. Survival trends after surgery for spinal metastatic tumors: 20-year cancer center experience. Neurosurgery. 2020;88:402–412. doi: 10.1093/neuros/nyaa380.
2. Glassman S.D., Bridwell K., Dimar J.R., Horton W., Berven S., Schwab F. The impact of positive sagittal balance in adult spinal deformity. Spine (Phila Pa 1976) 2005;30:2024–2029. doi: 10.1097/01.brs.0000179086.30449.96.
3. Sankey E.W., Park C., Howell E.P., et al. Importance of spinal alignment in primary and metastatic spine tumors. World Neurosurg. 2019;132:118–128. doi: 10.1016/j.wneu.2019.08.161.
4. Glassman S.D., Berven S., Bridwell K., Horton W., Dimar J.R. Correlation of radiographic parameters and clinical symptoms in adult scoliosis. Spine (Phila Pa 1976) 2005;30:682–688. doi: 10.1097/01.brs.0000155425.04536.f7.
5. Lehner K., Ehresman J., Pennington Z., Ahmed A.K., Lubelski D., Sciubba D.M. Narrative review of predictive analytics of patient-reported outcomes in adult spinal deformity surgery. Glob Spine J. 2021;11 doi: 10.1177/2192568220963060. 89S–95S.
6. Zhang J., Liu Y., Zeng Y., Yuan L., Li W. Correlations between spinopelvic parameters and health-related quality of life in degenerative lumbar scoliosis patients before and after long -level fusion surgery. BMC Musculoskelet Disord. 2025;26:84. doi: 10.1186/s12891-025-08336-1.
7. LeFever D., Louie P.K., Bansal A., Drolet C., Nemani V.M., Leveque J.-C. Is spinopelvic mismatch associated with increased disability at 2 years following short-segment lumbar fusions? J Neurosurg Spine. 2024;40:412–419. doi: 10.3171/2023.10.SPINE23689.
8. Rubery P.T., Lander S.T., Mesfin A., Sanders J.O., Thirukumaran C.P. Mismatch between pelvic incidence and lumbar lordosis is the key sagittal plane determinant of patient outcome at minimum 40 years after instrumented fusion for adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 2022;47:E169–E176. doi: 10.1097/BRS.0000000000004277.
9. Shi F., Xia C., Zhang J., Chen C., Chen Q. Correlations of spinopelvic parameters with quality of life of patients with adult degenerative scoliosis after posterior correction. Jt Dis Relat Surg. 2024;35:554–561. doi: 10.52312/jdrs.2024.891.
10. Zhou H., Liang Z., Li P., et al. Correlation analysis of surgical outcomes and spino-pelvic parameters in patients with degenerative lumbar scoliosis. Front Surg. 2024;10 doi: 10.3389/fsurg.2023.1319884.
11. Tan L-X, Du X.-K., Tang R.-M., Rong L-M, Zhang L-M. Effect of spinal-pelvic sagittal balance on the clinical outcomes after lumbar fusion surgery. BMC Surg. 2023;23:334. doi: 10.1186/s12893-023-02240-y.
12. Mohanty S., Mikhail C., Lai C., et al. Do adult spinal deformity patients who achieve and maintain PI–LL < 10 have better patient-reported and clinical outcomes compared to patients with PI–LL ≥ 10? A propensity score-matched analysis. Spine Deform. 2024;12:209–219. doi: 10.1007/s43390-023-00766-y.
13. Uribe J.S., Januszewski J., Wang M., et al. Patients with high pelvic tilt achieve the same clinical success as those with low pelvic tilt after minimally invasive adult deformity surgery. Neurosurgery. 2018;83:270–276. doi: 10.1093/neuros/nyx383.
14. Massier J.R.A., Ogink P.T., Schlösser T.P.C., et al. Sagittal spinal parameters after en bloc resection of mobile spine tumors. Spine J. 2019;19:1606–1612. doi: 10.1016/j.spinee.2019.05.012.
15. Hasegawa K., Dubousset J.F. Cone of economy with the chain of balance-historical perspective and proof of concept. Spine Surg Relat Res. 2022;6:2022. doi: 10.22603/ssrr.2022-0038. 0038.
16. Smith J.S., Shaffrey C.I., Ames C.P., Lenke L.G. Treatment of adult thoracolumbar spinal deformity: past, present, and future. J Neurosurg Spine. 2019;30:551–567. doi: 10.3171/2019.1.SPINE181494.
17. Schwab F., Ungar B., Blondel B., et al. Scoliosis Research Society—Schwab Adult Spinal Deformity Classification: a validation study. Spine (Phila Pa 1976) 2012;37:1077–1082. doi: 10.1097/BRS.0b013e31823e15e2.
18. Nakarai H., Simon C.Z., Adida S., et al. Reliability of vertebral pelvic angles in assessment of spinal alignment. Glob Spine J. 2024 doi: 10.1177/21925682241235607.
19. Passias P.G., Onafowokan O.O., Tretiakov P., Dave P., Mir J.M., Janjua M.B. Current concepts in adult cervical spine deformity surgery. J Neurosurg Spine. 2024;40:439–452. doi: 10.3171/2023.10.SPINE22878.
20. Scheer J.K., Lau D., Smith J.S., et al. Alignment, classification, clinical evaluation, and surgical treatment for adult cervical deformity: a complete guide. Neurosurgery. 2021;88:864–883. doi: 10.1093/neuros/nyaa582.
21. Roussouly P., Gollogly S., Berthonnaud E., Dimnet J. Classification of the normal variation in the sagittal alignment of the Human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976) 2005;30:346–353. doi: 10.1097/01.brs.0000152379.54463.65.
22. Diebo B.G., Balmaceno-Criss M., Lafage R., et al. Sagittal alignment in the degenerative lumbar spine. J Bone Jt Surg. 2024;106:445–457. doi: 10.2106/JBJS.23.00672.
23. Pennington Z., Martini M.L., Mikula A.L., et al. Use of pelvic incidence on preoperative prone and supine radiography to predict postoperative pelvic incidence following thoracolumbar fusion for adult spinal deformity. J Neurosurg Spine. 2025:1–10. doi: 10.3171/2025.2.SPINE24706.
24. Cecchinato R., Compagnone D., Verlaan J.-J., et al. Does sagittal alignment after spinal reconstruction following en bloc tumor resection impact revision rate? A preliminary long-term retrospective study. Eur Spine J. 2025 doi: 10.1007/s00586-025-08789-x.
25. Chanbour H., Waddell W.H., Vickery J., et al. L1-pelvic angle: a convenient measurement to attain optimal deformity correction. Eur Spine J. 2023;32:4003–4011. doi: 10.1007/s00586-023-07920-0.
26. Hills J., Lenke L.G., Sardar Z.M., et al. The T4-L1-hip axis: defining a normal sagittal spinal alignment. Spine (Phila Pa 1976) 2022;47:1399–1406. doi: 10.1097/BRS.0000000000004414.
27. Narayanan R., Carter M., Toci G., et al. The role of L1PA in patient-reported outcomes in patients undergoing single-level lumbar fusion for degenerative spondylolisthesis. Spine (Phila Pa 1976) 2024;49:1352–1360. doi: 10.1097/BRS.0000000000005057.
28. Pennington Z., Ehresman J., Lubelski D., et al. Assessing underlying bone quality in spine surgery patients: a narrative review of dual-energy X-ray absorptiometry (DXA) and alternatives. Spine J. 2021;21:321–331. doi: 10.1016/j.spinee.2020.08.020.
29. Marshall D., Johnell O., Wedel H. Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures. BMJ. 1996;312:1254–1259. doi: 10.1136/bmj.312.7041.1254.
30. Halvorson T.L., Kelley L.A., Thomas K.A., Whitecloud T.S., Cook S.D. Effects of bone mineral density on pedicle screw fixation. Spine (Phila Pa 1976) 1994;19:2415–2420. doi: 10.1097/00007632-199411000-00008.
31. Weiser L., Huber G., Sellenschloh K., et al. Insufficient stability of pedicle screws in osteoporotic vertebrae: biomechanical correlation of bone mineral density and pedicle screw fixation strength. Eur Spine J. 2017;26:2891–2897. doi: 10.1007/s00586-017-5091-x.
32. Cosman F., Schnitzer M.B., McCann P.D., Parisien M.V., Dempster D.W., Lindsay R. Relationships between quantitative histological measurements and noninvasive assessments of bone mass. Bone. 1992;13:237–242. doi: 10.1016/8756-3282(92)90203-9.
33. Snyder B.D., Zaltz I., Hall J.E., Emans J.B. Predicting the integrity of vertebral bone screw fixation in anterior spinal instrumentation. Spine (Phila Pa 1976) 1995;20:1568–1574. doi: 10.1097/00007632-199507150-00004.
34. Bolotin H., Sievänen H., Grashuis J. Patient-specific DXA bone mineral density inaccuracies: quantitative effects of nonuniform extraosseous fat distributions. J Bone Miner Res. 2003;18:1020–1027. doi: 10.1359/jbmr.2003.18.6.1020.
35. Pennington Z., Mikula A.L., Lakomkin N., et al. Bone quality as measured by Hounsfield units more accurately predicts proximal junctional kyphosis than vertebral Bone quality following long-segment thoracolumbar fusion. World Neurosurg. 2024;186:e584–e592. doi: 10.1016/j.wneu.2024.04.003.
36. Pennington Z., Mikula A.L., Lakomkin N., et al. Comparison of Hounsfield units and vertebral bone quality score for the prediction of time to pathologic fracture in mobile spine metastases treated with radiotherapy. J Neurosurg Spine. 2023;40:19–27. doi: 10.3171/2023.8.SPINE23420.
37. Ehresman J., Schilling A., Pennington Z., et al. A novel MRI-based score assessing trabecular bone quality to predict vertebral compression fractures in patients with spinal metastasis. J Neurosurg Spine. 2020;32:499–506. doi: 10.3171/2019.9.SPINE19954.
38. Ehresman J., Pennington Z., Schilling A., et al. Novel MRI-based score for assessment of bone density in operative spine patients. Spine J. 2020;20:556–562. doi: 10.1016/j.spinee.2019.10.018.
39. Mi J., Li K., Zhao X., Zhao C.-Q., Li H., Zhao J. Vertebral body compressive strength evaluated by dual-energy X-ray absorptiometry and hounsfield units In vitro. J Clin Densitom. 2018;21:148–153. doi: 10.1016/j.jocd.2016.08.011.
40. Martini M.L., Mikula A.L., Lakomkin N., et al. Opportunistic CT-based hounsfield units strongly correlate with biomechanical CT measurements in the thoracolumbar spine. Spine (Phila Pa 1976) 2024;49:1021–1028. doi: 10.1097/BRS.0000000000004822.
41. Hamouda A.M., Pennington Z., Astudillo Potes M., et al. Impact of contrast administration and CT reconstruction plane on Hounsfield units for assessing underlying bone quality in the lumbar spine. J Neurosurg Spine. 2024;42:1–9. doi: 10.3171/2024.8.SPINE24732.
42. Zou D., He X., Shang Z., Jin D., Li W. Osteoporosis screening using QCT-based cutoff value of Hounsfield units in patients with degenerative lumbar diseases. Eur Spine J. 2024;33:4499–4503. doi: 10.1007/s00586-024-08491-4.
43. Yu J.S., Krishna N.G., Fox M.G., et al. ACR appropriateness criteria® osteoporosis and bone mineral density: 2022 update. J Am Coll Radiol. 2022;19:S417–S432. doi: 10.1016/j.jacr.2022.09.007.
44. Fluss R., Lo Bu R., De la Garza Ramos R., Murthy S.G., Yassari R., Gelfand Y. Nonquantitative CT scan Hounsfield unit as a determinant of cervical spine bone density. J Neurosurg Spine. 2024;41:803–812. doi: 10.3171/2024.5.SPINE24249.
45. Amin M.F.M., Zakaria W.M.W., Yahya N. Correlation between Hounsfield unit derived from head, thorax, abdomen, spine and pelvis CT and t-scores from DXA. Skeletal Radiol. 2021;50:2525–2535. doi: 10.1007/s00256-021-03801-z.
46. Vanier A.T., Colantonio D., Saxena S.K., Rodkey D., Wagner S. Computed tomography of the chest as a screening tool for low bone mineral density. Mil Med. 2023;188:665–669. doi: 10.1093/milmed/usab519.
47. Nakarai H., Kazarian G.S., Lovecchio F.C., Kim H.J. Hounsfield units and vertebral bone quality score for predicting mechanical complications after adult spinal deformity surgery: a systematic review and meta-analysis. Asian Spine J. 2024;18:719–730. doi: 10.31616/asj.2023.0402.
48. Ehresman J., Schilling A., Yang X., et al. Vertebral bone quality score predicts fragility fractures independently of bone mineral density. Spine J. 2021;21:20–27. doi: 10.1016/j.spinee.2020.05.540.
49. Kuo C.C., Soliman M.A.R., Aguirre A.O., et al. Vertebral bone quality score independently predicts proximal junctional kyphosis and/or failure after adult spinal deformity surgery. Neurosurgery. 2023;92:945–954. doi: 10.1227/neu.0000000000002291.
50. Soliman M.A.R., Aguirre A.O., Kuo C.C., et al. Vertebral bone quality score independently predicts cage subsidence following transforaminal lumbar interbody fusion. Spine J. 2022;22:2017–2023. doi: 10.1016/j.spinee.2022.08.002.
51. Shah L.M., Hanrahan C.J. MRI of spinal bone marrow: part 1, techniques and normal age-related appearances. Am J Roentgenol. 2011;197:1298–1308. doi: 10.2214/AJR.11.7005.
52. Hanrahan C.J., Shah L.M. MRI of spinal bone marrow: part 2, T1-weighted imaging-based differential diagnosis. Am J Roentgenol. 2011;197:1309–1321. doi: 10.2214/AJR.11.7420.
53. Fisher C.G., DiPaola C.P., Ryken T.C., et al. A Novel Classification System for Spinal Instability in Neoplastic Disease: an evidence-based approach and expert consensus from the Spine Oncology Study Group. Spine (Phila Pa 1976) 2010;35:E1221–E1229. doi: 10.1097/BRS.0b013e3181e16ae2.
54. Ahmad F.U., Sidani C., Fourzali R., Wang M.Y. Postoperative magnetic resonance imaging artifact with cobalt-chromium versus titanium spinal instrumentation: presented at the 2013 Joint Spine Section Meeting. Clinical article. J Neurosurg Spine. 2013;19:629–636. doi: 10.3171/2013.7.SPINE1359.
55. Porras J.L., Pennington Z., Hung B., et al. Radiotherapy and surgical advances in the treatment of metastatic spine tumors: a narrative review. World Neurosurg. 2021;151:147–154. doi: 10.1016/j.wneu.2021.05.032.
56. Pennington Z., Ehresman J., Elsamadicy A.A., et al. Systematic review of charged-particle therapy for chordomas and sarcomas of the mobile spine and sacrum. Neurosurg Focus. 2021;50:E17. doi: 10.3171/2021.2.FOCUS201059.
57. Yazici G., Sari S.Y., Yedekci F.Y., et al. The dosimetric impact of implants on the spinal cord dose during stereotactic body radiotherapy. Radiat Oncol. 2016;11:71. doi: 10.1186/s13014-016-0649-z.
58. Jackson J.B., Crimaldi A.J., Peindl R., Norton H.J., Anderson W.E., Patt J.C. Effect of polyether ether ketone on therapeutic radiation to the spine: a pilot study. Spine (Phila Pa 1976) 2017;42:E1–E7. doi: 10.1097/BRS.0000000000001695.
59. Mansi A., Rezaii E.G., Wang S., Zhang C., Katzir M. Comparison of dosimetric variability in the cervical spine between carbon fiber and titanium instrumentation. J Neurosurg Spine. 2025:1–9. doi: 10.3171/2024.10.SPINE24584.
60. Lindtner R.A., Schmid R., Nydegger T., Konschake M., Schmoelz W. Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading. Eur Spine J. 2018;27:1775–1784. doi: 10.1007/s00586-018-5538-8.
61. Rijs Z., Kawsar K.A., Saha P., van de Sande M., Lui D. Evaluation of computed tomography artefacts of carbon-fiber and titanium implants in patients with spinal oligometastatic disease undergoing stereotactic ablative radiotherapy. Sci Rep. 2024;14:6700. doi: 10.1038/s41598-024-52498-2.
62. Long J.R., Kalani M.A., Goulding K.A., Ashman J.B., Flug J.A. Carbon-fiber-reinforced polyetheretherketone orthopedic implants in musculoskeletal and spinal tumors: imaging and clinical features. Skeletal Radiol. 2023;52:393–404. doi: 10.1007/s00256-022-04069-7.
63. Poel R., Belosi F., Albertini F., et al. Assessing the advantages of CFR-PEEK over titanium spinal stabilization implants in proton therapy—A phantom study. Phys Med Biol. 2020;65 doi: 10.1088/1361-6560/ab8ba0.
64. Shi C., Lin H., Huang S., et al. Comprehensive evaluation of carbon-Fiber-reinforced polyetheretherketone (CFR-PEEK) spinal hardware for proton and photon planning. Technol Can Res Treat. 2022;21 doi: 10.1177/15330338221091700.
65. Boriani S., Tedesco G., Ming L., et al. Carbon-fiber-reinforced PEEK fixation system in the treatment of spine tumors: a preliminary report. Eur Spine J. 2018;27:874–881. doi: 10.1007/s00586-017-5258-5.
66. Sciubba D.M., Pennington Z., Colman M.W., et al. Spinal metastases 2021: a review of the current state of the art and future directions. Spine J. 2021;21:1414–1429. doi: 10.1016/j.spinee.2021.04.012.
67. Pennington Z., Ehresman J., McCarthy E.F., et al. Chordoma of the sacrum and mobile spine: a narrative review. Spine J. 2021;21:500–517. doi: 10.1016/j.spinee.2020.10.009.
68. Pennington Z., Ehresman J., Pittman P.D., et al. Chondrosarcoma of the spine: a narrative review. Spine J. 2021;21:2078–2096. doi: 10.1016/j.spinee.2021.04.021.
69. Kato S., Demura S., Shinmura K., et al. Surgical metastasectomy in the spine: a review article. Oncologist. 2021;26:e1833–e1843. doi: 10.1002/onco.13840.
70. Chanbour H., Chen J.W., Bendfeldt G.A., et al. Earlier radiation is associated with improved 1-year survival after metastatic spine tumor surgery. World Neurosurg. 2024;187:e509–e516. doi: 10.1016/j.wneu.2024.04.118.
71. Gulcelik M.A., Dinc S., Gulcelik N.E., et al. Optimal timing for surgery after adriamycin treatment in rats. Surg Today. 2004;34:1031–1034. doi: 10.1007/s00595-004-2865-7.
72. Payne W.G., Naidu D.K., Wheeler C.K., et al. Wound healing in patients with cancer. Eplasty. 2008;8:e9.
73. Ladha H., Pawar T., Gilbert M.R., et al. Wound healing complications in brain tumor patients on Bevacizumab. J Neurooncol. 2015;124:501–506. doi: 10.1007/s11060-015-1868-0.
74. Pennington Z., Porras J.L., Larry Lo S.-F., Sciubba D.M. International variability in spinal metastasis treatment: a survey of the AO spine community. Glob Spine J. 2023;13:1622–1634. doi: 10.1177/21925682211046904.
75. Itshayek Eyal, Yamada J., Bilsky M., et al. Timing of surgery and radiotherapy in the management of metastatic spine disease: a systematic review. Int J Oncol. 2010;36:533–544. doi: 10.3892/ijo_00000527.
76. Lee R.S., Batke J., Weir L., Dea N., Fisher C.G. Timing of surgery and radiotherapy in the management of metastatic spine disease: expert opinion. J Spine Surg. 2018;4:368–373. doi: 10.21037/jss.2018.05.05.
77. Dea N., Fisher C.G., Reynolds J.J., et al. Current treatment strategy for newly diagnosed chordoma of the mobile spine and sacrum: results of an international survey. J Neurosurg Spine. 2019;30:119–125. doi: 10.3171/2018.6.SPINE18362.
78. van Wulfften Palthe O., Jee K.-W., Bramer J.A.M., Hornicek F.J., Chen Y.-L.E., Schwab J.H. What is the effect of high-dose radiation on bone in patients with sacral chordoma? A CT study. Clin Orthop Relat Res. 2018;476:520–528. doi: 10.1007/s11999.0000000000000063.
79. Harel R., Chao S., Krishnaney A., Emch T., Benzel E.C., Angelov L. Spine instrumentation failure after Spine tumor resection and radiation: comparing conventional radiotherapy with stereotactic radiosurgery outcomes. World Neurosurg. 2010;74:517–522. doi: 10.1016/j.wneu.2010.06.037.
80. Yee T.J., Saadeh Y.S., Strong M.J., et al. Survival, fusion, and hardware failure after surgery for spinal metastatic disease. J Neurosurg Spine. 2021;34:665–672. doi: 10.3171/2020.8.SPINE201166.
81. Alvarez-Breckenridge C., Almeida R de, Haider A., et al. Carbon Fiber-reinforced polyetheretherketone spinal implants for treatment of spinal tumors: perceived advantages and limitations. Neurospine. 2023;20:317–326. doi: 10.14245/ns.2244920.460.
82. Fourney D.R., Schomer D.F., Nader R., et al. Percutaneous vertebroplasty and kyphoplasty for painful vertebral body fractures in cancer patients. J Neurosurg Spine. 2003;98:21–30. doi: 10.3171/spi.2003.98.1.0021.
83. Sadeghi-Naini M., Aarabi S., Shokraneh F., Janani L., Vaccaro A.R. Rahimi-Movaghar V. Vertebroplasty and kyphoplasty for metastatic spinal lesions. Clin Spine Surg A Spine Publ. 2018;31:203–210. doi: 10.1097/BSD.0000000000000601.
84. Sørensen S.T., Kirkegaard A.O., Carreon L., Rousing R., Andersen M.Ø. Vertebroplasty or kyphoplasty as palliative treatment for cancer-related vertebral compression fractures: a systematic review. Spine J. 2019;19:1067–1075. doi: 10.1016/j.spinee.2019.02.012.
85. Lee J.-H., Kwon J.-T., Kim Y.-B., Suk J.-S. Segmental deformity correction after balloon kyphoplasty in the osteoporotic vertebral compression fracture. J Korean Neurosurg Soc. 2007;42:371. doi: 10.3340/jkns.2007.42.5.371.
86. Kim H.S., Kim S.H., Ju C., Kim S.W., Lee S.M., Shin H. The role of bone cement augmentation in the treatment of chronic symptomatic osteoporotic compression fracture. J Korean Neurosurg Soc. 2010;48:490. doi: 10.3340/jkns.2010.48.6.490.
87. Lim B.-S., Chang U.-K., Youn S.-M. Clinical outcomes after percutaneous vertebroplasty for pathologic compression fractures in osteolytic metastatic spinal disease. J Korean Neurosurg Soc. 2009;45:369. doi: 10.3340/jkns.2009.45.6.369.
88. Zhang H.-R., Qiao R.-Q., Yang X.-G., Hu Y.-C. A multicenter, descriptive epidemiologic survey of the clinical features of spinal metastatic disease in China. Neurol Res. 2020;42:749–759. doi: 10.1080/01616412.2020.1773630.
89. Ehresman J., Pennington Z., Elsamadicy A.A., et al. Fenestrated pedicle screws for thoracolumbar instrumentation in patients with poor bone quality: case series and systematic review of the literature. Clin Neurol Neurosurg. 2021;206 doi: 10.1016/j.clineuro.2021.106675.
90. Elder B.D., Lo S.-F.L., Holmes C., et al. The biomechanics of pedicle screw augmentation with cement. Spine J. 2015;15:1432–1445. doi: 10.1016/j.spinee.2015.03.016.
91. Weiser L., Huber G., Sellenschloh K., et al. Time to augment?! impact of cement augmentation on pedicle screw fixation strength depending on bone mineral density. Eur Spine J. 2018;27:1964–1971. doi: 10.1007/s00586-018-5660-7.
92. Newman W.C., Amin A.G., Villavieja J., Laufer I., Bilsky M.H., Barzilai O. Short-segment cement-augmented fixation in open separation surgery of metastatic epidural spinal cord compression: initial experience. Neurosurg Focus. 2021;50:E11. doi: 10.3171/2021.2.FOCUS217.
93. Chen L-H, Tai C.-L., Lee D-M, et al. Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: a comparative study between cannulated screws with cement injection and solid screws with cement pre-filling. BMC Musculoskelet Disord. 2011;12:33. doi: 10.1186/1471-2474-12-33.
94. Chao K.-H., Lai Y.-S., Chen W.-C., et al. Biomechanical analysis of different types of pedicle screw augmentation: a cadaveric and synthetic bone sample study of instrumented vertebral specimens. Med Eng Phys. 2013;35:1506–1512. doi: 10.1016/j.medengphy.2013.04.007.
95. Leichtle C.I., Lorenz A., Rothstock S., et al. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res. 2016;5:419–426. doi: 10.1302/2046-3758.59.2000580.
96. Nevelsky A., Borzov E., Daniel S., Bar-Deroma R. Perturbation effects of the carbon fiber-PEEK screws on radiotherapy dose distribution. J Appl Clin Med Phys. 2017;18:62–68. doi: 10.1002/acm2.12046.
97. Oikonomidis S., Greven J., Bredow J., et al. Biomechanical effects of posterior pedicle screw-based instrumentation using titanium versus carbon fiber reinforced PEEK in an osteoporotic spine human cadaver model. Clin Biomech. 2020;80 doi: 10.1016/j.clinbiomech.2020.105153.
98. Bruner H.J., Guan Y., Yoganandan N., Pintar F.A., Maiman D.J., Slivka M.A. Biomechanics of polyaryletherketone rod composites and titanium rods for posterior lumbosacral instrumentation. J Neurosurg Spine. 2010;13:766–772. doi: 10.3171/2010.5.SPINE09948.
99. Kang K.-T., Koh Y.-G., Son J., Yeom J.S., Park J.-H., Kim H.-J. Biomechanical evaluation of pedicle screw fixation system in spinal adjacent levels using polyetheretherketone, carbon-fiber-reinforced polyetheretherketone, and traditional titanium as rod materials. Compos Part B Eng. 2017;130:248–256. doi: 10.1016/j.compositesb.2017.07.052.
100. Ecker R.D., Endo T., Wetjen N.M., Krauss W.E. Diagnosis and treatment of vertebral column metastases. Mayo Clin Proc. 2005;80:1177–1186. doi: 10.4065/80.9.1177.
101. Ilaslan H., Sundaram M., Unni K.K., Shives T.C. Primary vertebral osteosarcoma: imaging findings. Radiology. 2004;230:697–702. doi: 10.1148/radiol.2303030226.
102. Stinchfield T., Vadapalli S., Pennington Z., et al. Improvement in vertebral endplate engagement following anterior column reconstruction using a novel expandable cage with self-adjusting, multiaxial end cap. J Clin Neurosci. 2019;67:249–254. doi: 10.1016/j.jocn.2019.06.017.
103. Bongers M.E.R., Ogink P.T., Chu K.F., et al. The use of autologous free vascularized fibula grafts in reconstruction of the mobile spine following tumor resection: surgical technique and outcomes. J Neurosurg Spine. 2021;34:283–292. doi: 10.3171/2020.6.SPINE20521.
104. Miller D.J., Lang F.F., Walsh G.L., Abi-Said D., Wildrick D.M., Gokaslan Z.L. Coaxial double-lumen methylmethacrylate reconstruction in the anterior cervical and upper thoracic spine after tumor resection. J Neurosurg Spine. 2000;92:181–190. doi: 10.3171/spi.2000.92.2.0181.
105. Pokorni A.J., Turbucz M., Kiss R.M., Eltes P.E., Lazary A. Comparison of anterior column reconstruction techniques after en bloc spondylectomy: a finite element study. Sci Rep. 2023;13 doi: 10.1038/s41598-023-45736-6.
106. Heary R.F., Parvathreddy N.K., Qayumi Z.S., Ali N.S., Agarwal N. Suitability of carbon fiber–reinforced polyetheretherketone cages for use as anterior struts following corpectomy. J Neurosurg Spine. 2016;25:248–255. doi: 10.3171/2016.1.SPINE14291.
107. Thongtrangan I., Balabhadra R.S .V, Kim D.H. Management of strut graft failure in anterior cervical spine surgery. Neurosurg Focus. 2003;15:1–8. doi: 10.3171/foc.2003.15.3.4.
108. Pennington Z., Pairojboriboon S., Chen X., et al. Utility of expanded anterior column resection versus decompression-alone for local control in the management of carcinomatous vertebral column metastases undergoing adjuvant stereotactic radiotherapy. Spine J. 2022;22:835–846. doi: 10.1016/j.spinee.2021.10.016.
109. Lau D., Chou D. Posterior thoracic corpectomy with cage reconstruction for metastatic spinal tumors: comparing the mini-open approach to the open approach. J Neurosurg Spine. 2015;23:217–227. doi: 10.3171/2014.12.SPINE14543.
110. Xu H., Wang X., Han Y., et al. Biomechanical comparison of different prosthetic reconstructions in total en bloc spondylectomy: a finite element study. BMC Musculoskelet Disord. 2022;23:955. doi: 10.1186/s12891-022-05919-0.
111. Liang Y., Cao Y., Gong Z., et al. A finite element analysis on comparing the stability of different posterior fixation methods for thoracic total en bloc spondylectomy. J Orthop Surg Res. 2020;15:314. doi: 10.1186/s13018-020-01833-0.
112. Xu H., Ke W., Zhang D., Miao J., Wang B., Yang C. Biomechanical effects of different prosthesis types and fixation ranges in multisegmental total en bloc spondylectomy: a finite element study. Orthop Surg. 2024 doi: 10.1111/os.14171.
113. Shen F.H., Woods D., Miller M., Murrell B., Vadapalli S. Use of the dual construct lowers rod strains in flexion-extension and lateral bending compared to two-rod and two-rod satellite constructs in a cadaveric spine corpectomy model. Spine J. 2021;21:2104–2111. doi: 10.1016/j.spinee.2021.05.022.
114. Pereira B de A., Godzik J., Lehrman J.N., et al. Pedicle subtraction osteotomy construct optimization. A cadaveric study of various multirod and interbody configurations. Spine (Phila Pa 1976) 2022;47:640–647. doi: 10.1097/BRS.0000000000004328.
115. Hartmann S., Thomé C., Abramovic A., et al. The effect of rod pattern, outrigger, and multiple screw-rod constructs for surgical stabilization of the 3-column destabilized cervical spine - A biomechanical analysis and introduction of a novel technique. Neurospine. 2020;17:610–629. doi: 10.14245/ns.2040436.218.
116. Han Y., Ren X., Liang Y., Ma X., Wang X. Biomechanical effects of transverse connectors on total en bloc spondylectomy of the lumbar spine: a finite element analysis. J Orthop Surg Res. 2023;18:484. doi: 10.1186/s13018-023-03977-1.
117. Nagel D.A., Kramers P.C., Rahn B.A., Cordey J., Perren S.M. A paradigm of delayed union and nonunion in the Lumbosacral joint: a study of motion and bone grafting of the lumbosacral spine in sheep. Spine (Phila Pa 1976) 1991;16:553–559. doi: 10.1097/00007632-199105000-00012.
118. Gottfried O.N., Omeis I., Mehta V.A., Solakoglu C., Gokaslan Z.L., Wolinsky J.-P. Sacral tumor resection and the impact on pelvic incidence. J Neurosurg Spine. 2011;14:78–84. doi: 10.3171/2010.9.SPINE09728.
119. Macki M., De la Garza-Ramos R., Murgatroyd A.A., et al. Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model. J Neurosurg Spine. 2017;27:570–577. doi: 10.3171/2017.2.SPINE161128.
120. Mindea S.A., Chinthakunta S., Moldavsky M., Gudipally M., Khalil S. Biomechanical comparison of spinopelvic reconstruction techniques in the setting of total sacrectomy. Spine (Phila Pa 1976) 2012;37:E1622–E1627. doi: 10.1097/BRS.0b013e31827619d3.
121. Yu B.-S., Zhuang X.-M., Zheng Z.-M., Li Z.-M., Wang T.-P., Lu W.W. Biomechanical advantages of dual over single iliac screws in lumbo-iliac fixation construct. Eur Spine J. 2010;19:1121–1128. doi: 10.1007/s00586-010-1343-8.
122. Tang X., Yang R., Qu H., Cai Z., Guo W. Factors associated with spinopelvic fixation mechanical failure after total sacrectomy. Spine (Phila Pa 1976) 2018;43:1268–1274. doi: 10.1097/BRS.0000000000002635.
123. Esmende S.M., Shah K.N., Daniels A.H. Spinopelvic fixation. J Am Acad Orthop Surg. 2018;26:396–401. doi: 10.5435/JAAOS-d-15-00738.
124. Cunningham B.W., Lewis S.J., Long J., Dmitriev A.E., Linville D.A., Bridwell K.H. Biomechanical evaluation of lumbosacral reconstruction techniques for spondylolisthesis. An In vitro porcine model. Spine (Phila Pa 1976) 2002;27:2321–2327. doi: 10.1097/00007632-200211010-00004.
125. Clark A.J., Tang J.A., Leasure J.M., et al. Gait-simulating fatigue loading analysis and sagittal alignment failure of spinal pelvic reconstruction after total sacrectomy: comparison of 3 techniques. J Neurosurg Spine. 2014;20:364–370. doi: 10.3171/2013.12.SPINE13386.
126. Polly D.W., Holton K.J., Soriano P.O., et al. Multiple points of pelvic fixation: stacked S2-Alar-Iliac screws (S2AI) or concurrent S2AI and open sacroiliac joint fusion with triangular titanium rod. JBJS Essent Surg Tech. 2022;12:e21. doi: 10.2106/JBJS.ST.21.00044. .00044.
127. Ehresman J., Ahmed A.K., Schilling A., et al. Preoperative nutrition consults associated with decreased postoperative complication rate and decreased length of hospital stay after spine metastasis surgery. World Neurosurg. 2020;133:e173–e179. doi: 10.1016/j.wneu.2019.08.197.
128. Ailon T., Torabi R., Fisher C.G., et al. Management of locally recurrent chordoma of the mobile spine and sacrum: a systematic review. Spine (Phila Pa 1976) 2016;41:S193–S198. doi: 10.1097/BRS.0000000000001812.
129. Lafage R., Schwab F., Challier V., et al. Defining spino-pelvic alignment thresholds. Should operative goals in adult spinal deformity surgery account for age? Spine (Phila Pa 1976) 2016;41:62–68. doi: 10.1097/BRS.0000000000001171.