Posterior Column Osteotomies and Not Lumbar Decompressions Alone Improve Lower Extremity Motor Strength in Adult Spinal Deformity Patients with Preoperative Motor Impairment

Introduction: Lumbar decompressions are traditionally done to alleviate compressed nerves among adult spinal deformity(ASD) patients with lower extremity(LE) weakness. However, patients may still manifest LE weakness early postop despite extensive lumbar decompressions.

Methods: This study is an analysis of a prospective, multicenter cohort of ASD patients with ≥1 procedural and/or radiographic criteria: PI-LL≥25°, TPA≥30°, SVA≥15cm, thoracic scoliosis≥70°, thoracolumbar scoliosis ≥50°, global coronal malalignment≥7cm, ≥12 instrumented levels, and/or undergoing 3CO. Patients with baseline abnormal LEMS, defined as a combined score < 50 (25 per lower extremity) at baseline, were dichotomized based on whether their LEMS improved from baseline(IBL) or deteriorated further(DBL) by the first/6-week postop visit(6W). Patients who maintained their LEMS by 6W compared to baseline were excluded.

Results: 121 patients were included where 90.1% (N=109) improved by 6W while 9.9% (N=12) experienced further deterioration. Both groups had similar BL LEMS when stratified by laterality and nerve root. The groups were identical in age, gender, comorbidities, BMI, number of revision cases, TIL, estimated blood loss (EBL), OR time, and LOS (p>0.05). No differences in radiographic parameters at baseline and 6W were observed aside from DBL experiencing greater ∆L1PA(-8.0±8.3 vs -1.6±7.6,p=0.0413). Despite having similar frequencies of lumbar decompressions performed, DBL had less lumbar posterior column osteotomies(PCOs) performed(50% vs 82.6%,p=0.0169). No differences in 3COs performed were observed. DBL experienced greater intraoperative neuromonitoring(IONM changes) (41.7% vs 8.3%, p=0.0050), all of which were motor deficits. Controlling for ∆L1PA discerned lumbar PCOs as an independent driver of improved LEMS [OR=6.75(1.63 – 27.84)] with great model statistics (p < 0.0001, AUC=0.80, Goodness-of-Fit Test p=0.4178).

Conclusion : Lumbar decompressions alone may not be enough to improve LE weakness among ASD patients with preoperative motor impairment while the use of PCO’s was beneficial for improvement. Thus, more aggressive and thorough decompressions afforded by PCO’s should be considered in this patient population to optimize postop motor strength.