Moving a skin incision to lateral side of tibial tubercle reduces the risk of persistent skin numbness compared with a regular midline one: A randomized paired study in bilateral total knee arthroplasty

Abstract

Background

The midline incision during total knee arthroplasty (TKA) is known to damage the infrapatellar branch of the saphenous nerve (IPBSN), leading to lateral flap numbness. The aim was to evaluate the rate of persistent skin numbness (RSN) and area of skin numbness (AON) after a lateral-based skin incision compared with the standard midline incision in bilateral TKA patients.

Methods

Thirty-six patients undergoing bilateral TKA were included and randomly assigned to receive the lateral skin incision (lateral side of the tibial tubercle) on one knee and the standard midline incision on the contralateral. All other surgical steps were identical. Primary outcomes were the RSN at 1 year and the AON at 6 weeks, 3, 6, and 12 months postoperatively. Kneeling ability test (KAT), operative time, and length of incision were also recorded.

Results

The lateral incision had half the RSN at 12 months compared to the midline incision (25% vs 53%; p = 0.01). The median AON at 1-year after surgery was 0 [0–0.5] cm² in lateral incision vs 4 [0–7.5] cm² in midline group (p < 0.001). KAT was minimally better in the lateral group at 110° of kneeling between 6-month to 1-year. Operative time and length of incision were similar between both groups.

Conclusion

The lateral skin incision reduced RSN by approximately 50% compared with the midline incision. The AON in lateral incision was 4 cm² smaller than midline at 1-year after surgery. Moving a skin incision more lateral may be considered to minimize the numbness after TKA.