Decompression Of The Common Peroneal Nerve To Prevent Nerve Palsy In Severe Valgus Knee Arthroplasty

BackgroundSevere valgus knee deformity refers to valgus Angle greater than 20 degrees or associated with the medial collateral ligament laxity, total knee arthroplasty(TKA) in valgus knee, have certain incidence of Common Peroneal nerve palsy. it has something to do with valgus knee correction when Common Peroneal nerve was oppressed by pulling and pie-crusting in posterolateral gap balanced.How to achieve a better gap balance and avoid the peroneal nerve palsy meanwhile is always the operation difficulty, few good solutions in domestic and foreign literature are put forward. ObjectiveTo evaluate the clinical significance and application of posterolateral assisted small incision to decompression Common Peroneal nerve in severe valgus knee arthroplasty. Materials and MethodsFrom February 2013 to September 2015, 9 severe valgus knee patients(9 knees)using the posterolateral assisted small incision to decompression Common Peroneal nerve in conventional incision total knee arthroplasty,1 man, 8 women. Aged 39-83, mean 64.7±4.9 years. Valgus Angle from 22-39 degrees, mean 29.7±2.1 degrees. 2 patients of Rheumatoid arthritis, 7 patients of osteoarthritis. Before conventional total knee arthroplasty, use 3cm posterolateral assisted small incision to decompression Common Peroneal nerve, exposing and slacking Common Peroneal nerve out-inside, then using conventional skin incision and the medial patellar approach to resect bone and balance gap tissue and install prosthesis. Using straight preferred method for soft-tissue balance, mainly for iliotibial band by cross-cutting, and achieve posterolateral gap balance by means of pie-crusting, and the flexion of the parallel section method. To observe whether appears foot drop and evaluate myodynamia of tibialis anterior and extensor digitorum longus and extensor hallucis longus after the operation. To evaluate the sensation of the first digit and Dorsum of foot and anterior lateral leg. Record the operation time, blood transfusion rate, and HSS knee function score, VAS pain degree, starting walking time, the degree of activity of the knee joint, and alignment of the prosthesis and the stability of the knee joint. ResultsAll patients were not in the presence of foot drop after operation, having good foot's dorsiflexion, and having satisfied myodynamia of tibialis anterior and extensor digitorum longus and extensor hallucis longus, the sensation of the first digit and dorsum of foot and anterior lateral leg without loss and bilateral symmetry. 2 patients use fixed bearing. 7 patients' use mobile bearing and 1 patient use stabilize and reinforced shim. The blood transfusion rate was zero, and the two incisions healed well. In 9 patients, followed up for 2 years, 8 patients were followed up all time, 8 patients had no complications, prosthesis were not loosing and replacement, the HSS knee function score by preoperative increased 20-35 points to the end of the 85-95 points. Knee joint activity follow-up were 98-130 degree. The appearence of the deformity was corrected, and the alignment of the lower limb was satisfied. The followed up valgus Angle(angle of the femur and tibia) mean 11.11±0.68 degrees(8degrees-14 degrees). ConclusionSevere valgus knee deformity use posterolateral assisted small incision to decompression and protect common peroneal nerve in total knee arthroplasty, avoiding the common peroneal nerve palsy when straightening the knee alignment, releasing posterolateral soft-tissue boldly because of the common peroneal nerve protection and decompression, which obtain adequate lateral and medial ligament balance and complete the total knee arthroplasty with normal prosthesis.