110. Clinical significance of lateral pedicle screw malposition in the lumbar spine

Abstract

BACKGROUND CONTEXT The risks of pedicle screw malposition have largely focused on medial malposition and neurological injury. Although lateral malposition is considered relatively benign, no previously reported study has focused specifically on clinical outcomes associated with lateral screw malposition. We hypothesize that lateral pedicle screw breach has a negative effect on fusion rates and clinical outcomes following elective single-level posterior lumbar fusion (PLF). PURPOSE Not applicable. STUDY DESIGN/SETTING Not applicable. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable. METHODS Retrospective review of a prospective multicenter cohort of patients undergoing single-level instrumented PLF with local autograft bone for degenerative disease. Twelve-month postoperative computed tomography (CT) was reviewed for breach direction, severity of screw-associated pedicle breach and fusion status. Patients with lateral breach were compared to patients with no breach. Patients with nonlateral screw malposition were excluded. Outcomes measures included Oswestry Disability Index (ODI), Numerical Pain Rating Scale (NPRS) for back pain, and SF-36 physical function. Improvement in back pain was defined as a ≥35% change (minimal clinically important difference) at follow-up. Outcomes were analyzed using multivariable linear and logistic regression and were adjusted for age, procedure, level, and/or baseline pain score. RESULTS A total of 154 patients underwent 12-month postoperative CT. Forty-five patients (30.6%) demonstrated one or more lateral breaches and were compared to 102 patients with no breach. After adjusting for baseline scores and fusion level, patients with one or more breaches had, on average, ODI score decreases that were 2.44 points less (p=0.454) and SF-36 score increases that were 2.04 points less (p=0.040) than patients with no lateral breach. Breach was also associated with a large decrease in the odds of achieving back pain relief (OR=0.37, 95%CI: 0.15, 0.91) after adjusting for baseline NPRS. There was no observed effect of breach on the odds of non-union (multiple breaches OR=1.97, 95% CI: 0.66, 5.97). CONCLUSIONS The current study did not observe an association between laterally malpositioned pedicle screws and nonunion or disability scores. However, these results are consistent with a modest negative effect on physical functioning scores and self-reported back pain. This suggests that surgeons may anticipate poorer clinical outcomes among patients with laterally malpositioned screws. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.