P114. Intraoperative transverse process fractures and posterolateral lumbar fusion rates

BACKGROUND CONTEXT Avoidance of intraoperative transverse process fracture (TPF) is a technical dictum of posterior lumbar fusion surgery. Nevertheless, TPF commonly occurs at multiple stages including exposure, hemostatic packing, decortication, graft placement and instrumentation. Although the adverse effect of TPF on posterolateral fusion (PLF) appears self-evident, actual rates of TPF and association with fusion rates have not previously been reported. PURPOSE To determine the effect of TPF on fusion rates after PLF with or without transforaminal lumbar interbody fusion (TLIF). STUDY DESIGN/SETTING Retrospective computed tomography (CT)-based review. PATIENT SAMPLE A total of 147 patients underwent single-level PLF or PLF with TLIF surgery using local autograft bone. OUTCOME MEASURES Fusion was assessed at 6-months and 12-months postoperatively using strict CT criteria. Patient reported outcome measures included visual analogue scale (VAS) scores for back pain and leg pain, Oswestry Disability Index (ODI) and SF-36. METHODS Six-month CTs were reviewed for evidence of TPF. Side (right vs left), vertebral level, and severity of TPF (≥50% or RESULTS A total of 147 patients underwent postoperative CT at both 6 and 12 months. Ninety patients underwent PLF only (PLF group) and 57 underwent PLF with TLIF (TLIF group). Overall TPF rate was 19.0% of patients (28/147) and 4.8% of transverse processes (28/588). No patient demonstrated more than one TPF. TPF rate was higher in the PLF group vs TLIF group (25.6 vs 8.8% of patients, p=0.012). No difference in TPF rate was observed based on gender for PLF (p=0.901) or TLIF (p=0.731) nor age for PLF (p=0.103) or TLIF (p=0.813). In the PLF group, TPF was associated with an 8.7% (2/23 sides) rate of ipsilateral fusion at one year compared to 29.3% (46/157 sides) without TPF (p=0.037). In the TLIF group, TPF was associated with a 0% (0/5 sides) rate of ipsilateral fusion compared to 7.3% (8/109 sides) without TPF (p=1.00). CONCLUSIONS TPF occurs frequently during posterior lumbar fusion surgery and is associated with a decreased rate of successful one-year ipsilateral fusion in the setting of PLF. The association in patients undergoing TLIF remains unknown. Lower fusion rates in this study population may be due to use of only local autograft and different results may be associated with use of extenders or bone graft substitutes. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.