The Crane Technique in Cortical Bone Trajectory Screw Lumbar Fusion: Efficacy and Predictors of Spondylolisthesis Reduction.

OBJECTIVE

To evaluate the efficacy of the Crane reduction technique in midline lumbar fusion (MIDLF) with cortical bone trajectory screws for treating degenerative spondylolisthesis, and to identify factors affecting the reduction rate.

METHODS

A retrospective analysis was conducted on 87 patients (64 females and 23 males) with L4-5 degenerative spondylolisthesis who underwent MIDLF and the Crane technique. Patients were categorizing using the spondylolisthesis Meyerding classification system into Grade I (59 patients) and Grade II (28 patients) groups and compared for demographics, radiographic parameters, and the spondylolisthesis reduction rate. Data were analyzed to identify factors influencing the reduction rate.

RESULTS

Grade II patients showed higher preoperative spondylolisthesis slip ratio (29.8 ± 3.7% vs. 19.9 ± 3.2%, P < 0.01) and a lower segmental lordosis than Grade I patients. Postoperatively, Grade II patients achieved higher reduction rates (92.6% [90.8-93.8] vs. 89.9% [86.8-91.4] in Grade I, P < 0.01) and a greater segmental lordosis increase (+2.4° [0.2-5.5] vs. -1.2° [-3.5 to 1.6], P < 0.01). Multivariable analysis revealed vacuum disc phenomenon had a negative impact (β = -0.070, P < 0.01) and spondylolisthesis slip ratio had a positive impact (β = 0.612, P < 0.01) on the slip reduction rate. Complications occurred in 4.6% of cases, including 3 intraoperative durotomy and 1 nut loosening requiring revision surgery.

CONCLUSIONS

The Crane technique combined with MIDLF is an effective and safe surgical approach for treating L4-5 degenerative spondylolisthesis, demonstrating high reduction rates with consistent minimal residual slip, particularly in Grade II cases.