Ultra-short stem intercalary prosthetic reconstruction for joint preservation in metaphyseal tumor management: a retrospective review of twenty-five cases.

Introduction

Various techniques have been described for reconstruction of defects following bone tumor resection, including autografts, massive bone allografts, segmental transport techniques, and prosthetic reconstruction [ 1 – 3 ]. Prosthetic reconstruction likely is the most commonly used approach, in part as a result of the ease of use compared with other options and the difficulty of obtaining allografts in some centers in addition to the reported risks of infection, non-union, pseudarthrosis, and fractures [ 4 , 5 ]. In prosthetic reconstruction of diaphyseal tumors involving the metaphysis where residual bone stock is insufficient, joint-sparing surgery becomes essential, as it offers notable advantages over traditional long bone end excision by preserving joint function and enabling a more dependable approach to bone reconstruction [ 6 – 8 ].

Intercalary prostheses have become a preferred joint-sparing option, preserving adjacent joints and critical ligament attachments, thereby yielding superior functional outcomes, reducing complications such as dislocation and infection [ 9 , 10 ]. Despite these advantages, intercalary prostheses are associated with notable risks of mechanical complications, including aseptic loosening (ASL) and structural failures [ 11 , 12 ]. Feltri et al. [ 4 ] conducted a meta-analysis of 202 cases of prosthetic reconstruction for large diaphyseal defects, reporting a 26% complication rate, including infections, aseptic loosening, and structural failures. Similarly, Albergo et al. [ 13 ] analyzed 36 cases of prosthetic reconstruction, observing a 36% failure rate at five years, primarily due to mechanical failures. These findings have led experts to recommend limiting intercalary prostheses to patients with limited life expectancy, where long-term mechanical stability is less critical [ 14 ].

Mechanical failure in intercalary prostheses is closely linked to the length of the intramedullary stem, which impacts prosthetic stability and is a key factor in ASL [ 15 ]. Fuchs et al. [ 16 ] noted that standard prostheses require a minimum of 50 mm of bone for adequate fixation, as shorter segments may lack sufficient anchorage to withstand weight-bearing forces and joint movement. As a result, many researchers advocate for sacrificing the adjacent joint when the remaining bone stock is too short to accommodate standard stems, as this may lead to increased instability, functional loss, and accelerated wear [ 17 ]. In some cases, combining short stems with extracortical plate fixation has been suggested to improve stability and reduce ASL [ 18 , 19 ]. However, there is limited literature on the use of stems shorter than standard lengths, particularly those under 50 mm.

Due to the high failure rates of intercalary prostheses and the potential risk of ASL associated with ultra-short stems, we have developed a novel approach that combines ultra-short stem prostheses with extracortical plate fixation to enhance stability in cases with insufficient bone stock for standard stems. This study retrospectively analyzes outcomes, survival, and ASL incidence in 25 patients who underwent joint-sparing surgery using ultra-short stem intercalary prostheses following tumor resection at our institution.

Patients and methods

Inclusion and exclusion criteria

We retrospectively studied the medical records of patients treated between February 2016 and March 2024 at two musculoskeletal oncology centers. The inclusion criteria were as follows: i) patients with primary malignant or metastatic tumors involving the metaphysis of bone, involving the femur, tibia, or humerus; ii) those who underwent surgical resection followed by reconstruction with a intercalary prosthesis featuring a ultra-short stem (length ≤ 50 mm) and extracortical plates; iii) the modified Tokuhashi scoring system predicts a survival expectancy of over six months for metastatic tumor patients; iiii) retrospective observational study design. Exclusion criteria included: i) intraoperatively tumor invasion of major vessels and nerves prevented en bloc or marginal resection, ii) recurrent tumors; iii) lack of available demographic and medical records.

Patients

A total of 32 patients who underwent tumor resection followed by implantation of an ultra-short stem intercalary prosthesis were initially considered for this study. Two patients were excluded due to intraoperative tumor invasion of major vessels and nerves preventing en bloc or marginal resection, and three patients were excluded due to surgery for recurrent tumors, which could affect the evaluation of tumor recurrence rates and complications. Additionally, two patients were excluded due to missing demographic or medical records, leaving 25 patients included in this study. The cohort consisted of 13 males (52%) and 12 females (48%), with a mean age of 60.9 years (range: 12–82 years). Of these, 9 patients (36%) had primary bone tumors and 16 patients (64%) had metastatic bone lesions. The most common primary tumor was undifferentiated pleomorphic sarcoma (UPS), present in four patients, followed by osteosarcoma in two patients. Among the metastatic cases, renal cancer was the most frequent source, present in five patients, followed by lung cancer and myeloma, each in three patients.

The tumor locations included 11 cases (44%) in the femur, 10 (40%) in the humerus, and 4 (16%) in the tibia. Imaging revealed lytic neoplasms with significant cortical destruction in 18 patients (72%) and soft tissue masses in 13 cases (52%), with no evidence of osteoplastic tumors. Pathological fractures occurred in 56% of patients (14/25), including angulation in six cases and overlap of fragments in five.

Prosthesis

The intercalary prosthesis was custom-designed using preoperative radiographic and MRI measurements and manufactured by Shandong Weigao Company (China). Constructed from titanium alloy (Ti6 A14 V), it consists of distal and proximal stems, as well as extracortical plates. The distal and proximal stems are joined with a lap taper connection, secured by two screws, and, if necessary, an extension piece is attached using a Morse taper. Cemented prostheses feature grooved stems to prevent rotation, while cementless stems are coated with hydroxyapatite (HA) to promote osseointegration. Cementation was preferred for elderly patients with limited mobility or comorbidities that compromised bone viability, such as a history of smoking, cardiovascular disease, diabetes, or prior radiation therapy. In contrast, younger patients without significant comorbidities, particularly those with primary tumors, were more suited for cementless fixation.

Surgical procedure

The operative approach adhered to Enneking et al.’s principles, prioritizing wide resection margins. In cases of primary malignant tumors, the extent of bone and soft tissue involvement was evaluated using MRI, and resection length was determined accordingly. For metastatic tumors, resection was based on radiographic evidence of bone destruction from X-rays and CT, preserving intramedullary segments with intact cortical bone. Remaining tumor tissue was cleared via intraoperative curettage, followed by microwave ablation to eradicate residual cells. After resection, the proximal and distal diaphysis were reamed to a diameter ≥ 2 mm larger for cemented stems or ≥ 1 mm larger for non-cemented cases. The prosthesis was trial-fitted, and lap were secured with two bolts to restore anatomical alignment. Cement was applied using a standard cement gun, with extracortical plates positioned before the cement set. For non-cemented fixation, a tighter press-fit was achieved. Maintaining limb length and rotational alignment was prioritized, with adjustments based on contralateral limb dimensions or trial installation for patients with pathological fractures.

Postoperative management

Intravenous antibiotics were administered for three days postoperatively. Systemic therapy, including radiotherapy, chemotherapy, targeted therapy, hormone therapy, and immunotherapy, was tailored to the type of primary or metastatic tumor and the patient's overall condition. On the second postoperative day, all patients, regardless of cemented or cementless stem fixation, began range-of-motion exercises for adjacent joints and progressive, protective weight-bearing. Most patients were allowed to bear full weight three to four weeks after surgery.

Outcome assessment

The visual analog scale (VAS) was used to assess changes in pain from preoperative to postoperative levels. Extremity function was evaluated using the Musculoskeletal Tumor Society (MSTS) functional score, with a total score of 30, where a higher score indicates better limb function. Patient survival was based on mortality, while prosthesis survival endpoints were defined as the need for any revision or amputation. Complications were classified according to the Henderson system for limb salvage reconstructions into five categories: type I (soft tissue failure), type II (ASL), type III (structural failure), type IV (infection), and type V (tumor progression).

Statistical analysis

SPSS Statistics 27.0.1 (IBM Corp., Armonk, NY, USA) was used for data analysis. Kaplan–Meier curves estimated survival rates for both patients and prostheses, while descriptive statistics (frequency, percentage, mean, and standard deviation) summarized the data. Student's t-test was employed for continuous variables, and Chi-square or Fisher’s exact tests were used for categorical variables, with significance set at p < 0.05.

Results

Table 1 presents the characteristics of the 25 patients, all of whom completed follow-up with a mean duration of 20.2 months (range: 3–101 months). A total of 27 ultra-short stems were implanted: 18 proximally, 9 distally, with an average length of 41.3 ± 9.6 mm. The mean operative time was 164 ± 61.3 min, and average blood loss was 646.4 ± 375.5 ml. The mean defect size after tumor resection was 122 ± 52.1 mm. The results are summarized in Table 2 .

Compared with the preoperative VAS score (7 ± 1), the postoperative score (0.5 ± 0.9) decreased significantly ( p < 0.001). The mean Musculoskeletal Tumor Society (MSTS) score for the entire cohort was 24.2 ± 3.5 (range, 15–29). No statistically significant differences in MSTS scores were observed between male and female patients ( p = 0.457), between patients younger and older than 60 years ( p = 0.224), or between patients with primary tumors and metastatic tumors ( p = 0.278). The mean MSTS score was 24.3 ± 2.9 (range, 20–29) for patients with upper limb tumors and 24.1 ± 3.9 (range, 15–29) for those with lower limb tumors, with no significant difference ( p = 0.909). Three typical cases are presented (Fig. 1 , 2 and 3 ).

At the most recent follow-up, nine patients (36%) had succumbed to the disease, with a median survival time of 16.7 months. Kaplan–Meier survival curve (Fig. 4 ) shows the 1-, 2-, 3-, and 5-year prosthesis survival rates were 91.7%, 91.7%, 91.7%, and 91.7%, respectively, in contrast to the corresponding patient survival rates of 74.5%, 52.7%, 52.7%, and 52.7%.

ASL was observed in one patient at four months postoperatively (Fig. 5 ), but the patient remained asymptomatic throughout the 21-month follow-up period. Postoperative complications occurred in three patients (12%) among the study cohort, totaling four complications, with two cases requiring reoperation. Patient 3, diagnosed with hemangiosarcoma, developed an incisional hematoma(type I failure) two weeks after surgery, which was managed initially with debridement. However, local recurrence of sarcoma was detected five months later, resulting in an amputation. Patient 25, who underwent humeral prosthetic reconstruction, experienced disengagement of the Morse taper one month postoperatively, necessitating reoperation for repositioning.

Discussion

The application of ultra-short stem intercalary prostheses remains relatively uncommon, with a paucity of comprehensive studies in the literature [ 20 ]. The combination of ultra-short stems with extracortical plate fixation presents a promising alternative for limb-sparing procedures, particularly in patients with compromised bone stock [ 21 ]. Unlike conventional joint replacement, which necessitates the sacrifice of the native joint, this technique preserves the integrity of the native joint [ 22 ]. Furthermore, ultra-short stems enable earlier weight-bearing, providing an advantage over biological reconstruction techniques, which generally involve extended periods of bone healing before load-bearing can be safely resumed [ 23 – 25 ].

While joint prosthesis replacement is a widely used approach for treating joint degeneration and bone loss, it involves the removal of native bone structures, which leads to the loss of important mechanical and sensory functions such as proprioception and joint mobility [ 26 ]. These trade-offs can significantly impact postoperative functionality and quality of life. In contrast, ultra-short stem prostheses, by preserving a portion of the native joint, offer a more biologically integrated solution that facilitates functional recovery and enhances rehabilitation options [ 25 , 27 ]. Previous studies have demonstrated that patients undergoing limb-sparing surgeries with ultra-short stems experience faster recovery and improved functional outcomes compared to those treated with total joint arthroplasty [ 28 ].

The precise definition of ultra-short stems remains contentious in the current body of literature. While some studies classify short stems as those under 100 mm in length [ 29 ], others recommend a minimum of 50 mm of intramedullary bone to ensure adequate fixation [ 30 ]. The optimal stem length for intercalary reconstructions remains undefined and varies depending on the type of long bone involved [ 29 ]; when sufficient intramedullary space is available, longer stems are typically preferred for greater stability. When sufficient intramedullary space is available, our team uses stem lengths of 130–150 mm for the femur and 110–130 mm for the tibia and humerus. In cases where the residual intramedullary cavity can accommodate only stems shorter than 100 mm, we supplement the fixation with extracortical plates to enhance the initial stability and durability of the implant. We specifically included cases with stems not exceeding 50 mm in length, defining them as ultra-short stems, as many studies suggest that such short residual bone ends are no longer suitable for joint-preserving reconstructions [ 16 , 25 ]. Although the use of ultra-short stems remains an emerging technique, it is increasingly recognized for its advantages, particularly in patients with insufficient bone stock for standard prosthetic implants [ 31 ]. As demonstrated in previous biomechanical and clinical studies [ 15 , 19 , 31 – 33 ], the supplemental fixation provided by extracortical plates enhances the stability of the prosthesis by distributing the stresses on the implant. Additionally, the use of screws to increase the contact surface area with bone cement further contributes to minimizing the risk of mechanical failure, thereby improving the overall durability of the implant. Moreover, this combination permits earlier rehabilitation, enabling weight-bearing in a reduced time frame compared to biological reconstructions [ 34 ].

In our cohort of 25 patients, followed for an average of 20.2 months, the mean MSTS score was 24.2, indicating that ultra-short stem prostheses can effectively preserve function and yield satisfactory clinical outcomes in patients undergoing limb-sparing procedures. However, one of the major complications associated with ultra-short stem prostheses is ASL, a consequence of insufficient anchorage at the bone-implant interface, particularly under weight-bearing stresses [ 29 , 35 ]. In a series by Sewell et al. [ 3 ], four cases of ASL and two periprosthetic fractures were reported in 18 patients treated for malignant tibial bone tumors, while Damron et al. [ 9 ] observed five cases of ASL in 32 patients undergoing intercalary prosthetic reconstruction for humeral bone tumors. These complications may explain the relatively limited adoption of ultra-short stem prostheses in clinical practice. Nevertheless, the use of extracortical plate fixation, as demonstrated in our study, appears to mitigate the risk of ASL by providing additional stability. In our cohort, despite the average follow-up period of 20.2 months, only one case of ASL was observed.

Histological analysis revealed a single case of local recurrence within our cohort, a notably low recurrence rate likely attributable to the predominance of en bloc resections, which remain the gold standard for achieving clear margins and minimizing recurrence risk [ 36 ]. In the context of metastatic bone disease, the primary goal of surgery is not solely structural restoration but also the enhancement of the patient's quality of life. In this study, we found that extensive resections were not always necessary in patients with metastasis. Using preoperative imaging, we carefully planned the extent of resection, preserving tumor segments with intact cortical structures and strength, which minimized bone defects. Additionally, intraoperative curettage and microwave ablation were employed to address residual tumor tissue, and the local recurrence rate did not increase with this less aggressive approach, supporting the sufficiency of this technique for managing metastatic bone tumors [ 37 ].

The success of limb-sparing procedures is primarily determined by survival rate of the prostheses [ 38 ]. While intercalary prostheses have traditionally been associated with lower survival rates [ 12 , 39 ], particularly in younger, more active patients, the present study demonstrates a favorable short-term prognosis for ultra-short stem prostheses, with 2- and 3-year survival rates of 91.7%. Notably, five patients were followed for over 2 years, with one surpassing 8 years, all without complications or prosthesis failure. These results suggest that ultra-short stem prostheses may offer more durable outcomes in limb-sparing surgery. Hanna et al. [ 10 ] reported survival rates of 85% at 5 years and 68% at 10 years for femoral intercalary prostheses used post-resection for primary bone tumors, which further supports the promising results of our study.

This study has several limitations. As a retrospective analysis, it is subject to selection and recall biases, particularly given the rarity of the procedure. The absence of a control group and the variability in institutional practices and patient demographics limit the ability to generalize the findings. Despite the promising survival rates and clinical outcomes observed with ultra-short stem prostheses, further prospective studies with larger sample sizes and extended follow-up periods are necessary to confirm the long-term efficacy of this technique.

Conclusion

In conclusion, intercalary prosthesis reconstruction using ultra-short stems and extracortical plates remains a viable option for the management of diaphyseal tumors involving the metaphysis. This approach offers significant advantages, including the promotion of early weight-bearing, improved functional outcomes, and an acceptable rate of ASL and failure at short-term follow-up.

Acknowledgements

We appreciate all the participants, local medical workers in the study sites for their collaboration and assistance.

Abbreviations

Visual Analogue Scale

Musculoskeletal Tumor Society

Aseptic loosening

Hydroxyapatite

Undifferentiated pleomorphic sarcoma

Authors’ contributions

L.M. and D.L. wrote the manuscript, analyzed and interpreted the patient data. W.Z., D.L. and S.Z. was responsible for acquisition of data, and analyzed the patient data. J.Z., Y.L. and Y.H. were responsible for designing the study, and the analysis and interpretation of the data. All authors reviewed the manuscript.

Funding

This work was supported by Weifang Health Commission Research Project (WFWSJK-2022–045) and National Key Clinical Specialty Construction Project (Digital Orthopedic Diagnosis and Treatment Center).

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Institutional Review Board/Ethics Committee of Tianjin Hospital in accordance with the Declaration of Helsinki(2021YLS-160). Informed consent was obtained from all individual participants included in the study.

Consent for publication

Human research participants provided written informed consent for publication of identifying images.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Leming Mou and Dayong Liu contributed equally to this work.

Contributor Information

Jingyu Zhang, Email: zhangjingyu2010@163.com.

Yancheng Liu, Email: liutj2001@163.com.

Yongcheng Hu, Email: huycdoctor@163.com.

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Associated Data

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.