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

Objectives: 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 female and 23 male) 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 (SR) (29.8 ± 3.7% vs. 19.9 ± 3.2%, p < 0.01) and a lower segmental lordosis (SL) 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 SL increase (+2.4° [-0.2-5.5] vs. -1.2° [-3.5-1.6], p < 0.01). Multivariable analysis revealed vacuum disc phenomenon had a negative impact (β = -0.070, p < 0.01) and SR had a positive impact (β = 0.612, p < 0.01) on the slip reduction rate. Complications occurred in 4.6% of cases, including three intraoperative durotomy and one 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.