[Common peroneal nerve "pre-release" to avoid nerve palsy in total knee arthroplasty for severe valgus deformities]

Objective: To investigate the clinical efficacy of common peroneal nerve "pre-release" to avoid nerve palsy in total knee arthroplasty for severe valgus deformities. Methods: Twenty patients (22 knees) with severe valgus deformities were prospectively and continuously included in Fujian Province Hospital from January 2010 to January 2016. Medial parapatellar arthrotomy, femoral distal resection using the intramedullary cutting guide with 3° to 5° of valgus and the common peroneal nerve "pre-release" was performed, the patella was routinely resurfaced. A common peroneal nerve checking was performed (LSUHSC system), then, these outcomes were collected independently using visual analogue scale (VAS) of pain, Knee Society Score (KSS), Hospital for Special Surgery Knee Score (HSS), range of motion of knees (ROM), femorotibial angle (FTA), hip-knee-ankle angle (HKA), condylar-hip angle (CHA), plateau- ankle angle (PAA). The paired t test was used to compare the data before and after the operation. Results: Patients were followed up for 18 to 55 (mean, (38±8) months). According to Krackow's classification, all cases were typed Ⅱ. All the patients had a completely normal motor (grade 5) and sensory (LSUHSC score was 5) nerve function of common peroneal nerve postoperatively. No decrease or loss in muscle strength and cutaneous sensation associated with common peroneal nerve was found. The VAS of pain, KSS, HSS, ROM, HKA, CHA, and PAA were all improved after the operation when compared with those before the operation (t=21.602, -70.238, -82.455, -20.560, 16.058, 9.682, 3.439, all P<0.05). The alignment of lower limbs was corrected basically, and the FTA decreased from 31.7°±8.0° before operation to 5.0°±2.0° at the last follow-up, the differences was statistically significant (t=16.725, P<0.05). No common peroneal nerve palsy and transient or late-onset palsy occurred, and no revision was needed for instability during the follow-up in all the patients. Conclusion: Common peroneal nerve "pre-release" for severe valgus knees may be an effective method in protecting the nerve.