Concurrent surgeries are a factor in predicting success of rectus transfer outcomes

Cerebral palsy (CP) patients exhibit a wide range of functional responses to specific surgical interventions. The variability associated with surgical outcomes within this patient population precipitates the need to determine the functional effects in advance of the surgery. Pilot studies have indicated that the application of statistical models towards predicting functional outcomes of surgery produces clinically meaningful results. The purpose of this study was to evaluate the influence of pre-operative kinematic parameters in conjunction with concurrent surgeries on rectus transfer (RT) outcomes. Gait analysis data were collected from 68 patients (94 legs) pre- and post-operatively within a year of surgery. Patients were divided into four groups. Group 1 (N=14) contained only legs experiencing a rectus transfer. Group 2 (N=30) contained legs experiencing RT and hamstring lengthening (HL). Group 3 (N=7) contained legs experiencing RT and lower leg surgeries: either Achilles lengthening (AL), or gastrocnemius lengthening (GL). Finally, Group 4 (N=43) contained legs which experienced all four surgeries (RT+HL+AL+GL) concurrently. Multivariate jackknifed linear regression was used to predict the change in knee range of motion, DeltaROM, due to surgery on a group-by-group basis. In each case, the sole significant pre-surgical variable was the range of motion. Group 1 legs had the best correlation (R=0.846) between pre-surgical ROM and DeltaROM whereas Group 4 legs had the worst correlation (R=0.661). Group 3 results were not significant. Group 1 DeltaROM were also significantly lower as a whole, than all other groups, due to a larger percentage of patients needing the surgery to change timing of flexion in swing phase. When compared to modeling without consideration of surgery, modeling by surgical group produced results with fewer outliers and better correlation coefficients. Regardless of surgical group, patients with a lower pre-surgical ROM (<40 degrees ) were more likely to experience an increase in ROM as a result of surgical intervention compared to their peers with an elevated pre-surgical ROM who were likely to see a decrease in ROM. Pre-surgical ROM therefore serves as a useful predictor of outcome in rectus transfer surgery.