46. Lower limb compensation in the setting of adult spinal deformity

Abstract

<h3>BACKGROUND CONTEXT</h3> Numerous studies have reported the interplay between spinal deformity and pelvis compensatory mechanisms, but little data exist evaluating the contribution of lower extremity compensation (LE) to maintain upright posture. We hypothesis that hip, knee and ankle compensation is proportional to the severity of the spinal deformity and varies by demographics. <h3>PURPOSE</h3> Evaluate the association between spinal alignment and lower limbs compensation. <h3>STUDY DESIGN/SETTING</h3> Multicenter, prospective cohort. <h3>PATIENT SAMPLE</h3> This study included 288 patients treated for complex adult spinal deformity (ASD) with full body images available. <h3>OUTCOME MEASURES</h3> Pelvic retroversion (PT), hip extension (SFA), knee flexion (KA), ankle dorsiflexion (AA), pelvic translation (P.Shift) and patient reported outcomes (ODI, PROMIS and SRS-22). <h3>METHODS</h3> Surgical ASD patients were enrolled into a prospective study based on three criteria: deformity severity (PI-LL>25°, TPA>30°, SVA>15cm, TCobb>70° or TLCobb>50°), procedure complexity (>12 levels fused, 3CO or ACR) and/or age (>65 and >7 levels fused). Associations between lower extremity compensation (hip extension, knee flexion, and ankle dorsiflexion) and the magnitude of spinal deformity, patient demographics, patient frailty, and patient-reported outcomes (ODI, SRS, PROMIS-CAT) were assessed via regressions and partial correlations. <h3>RESULTS</h3> A total of 288/329 patients met inclusion criteria (60±15yo, 70.5% female), had moderate to severe spinal deformity (PI-LL:15±24, TPA:24±14, SVA:65±69mm, lumbar Cobb:34±24), and reported high pain (PROMIS pain interference; PI=62.7±7.8) and reduced physical function (PROMIS physical function; PF=35.6±7.6). Lower extremity compensation included pelvic retroversion (PT:24.1± 11.8), hip extension (SFA: 203±10.5), knee flexion (KA:5.5± 9.6), ankle dorsiflexion (AA: 5.3±4.5), and posterior pelvic translation (P.Shift: 30±51mm). Overall, lower extremity compensation increased with age (all p <0.001), BMI and frailty (all p <0.001, except SFA). For a similar PT, women had greater hip extension than men (SFA: 206 vs 200, p <0.001), with less KA (3.6 vs. 10.1, p <0.001), AA, and P.Shift. Lower extremity compensation increased with PI (r=0.2-0.45, p <0.001), TPA (r=0.5-0.9, p <0.001) and correlated with PROMS (ODI:0.26 - 0.37, PROMIS PF: -0.28 - -0.39, SRS Acti.: -0.20 - -0.33). When controlling for deformity severity and PI, most associations between lower limbs compensation and PROMS were lost. However, P.Shift and SFA remained weakly correlated with physical scores (ODI and PROMIS PF). <h3>CONCLUSIONS</h3> The recruitment of LE compensation is overall proportional to the severity of adult spinal deformity, with different patterns observed between men and women. Patients achieved similar PT by recruiting different patterns of LE compensation. Hip extension and posterior pelvic translation are independently associated with impairment in patient-reported outcomes. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.