Effect of J-Shaped Incision After Total Knee Arthroplasty (J-TKA)

Total knee arthroplasty is an effective surgical treatment for advanced knee osteoarthritis; however, peri-incisional numbness is a frequent postoperative finding. This sensory disturbance is commonly attributed to injury of the infrapatellar branch of the saphenous nerve during the standard anterior skin incision. Although peri-incisional numbness is often not regarded as a major complication, it may negatively influence postoperative comfort and patient satisfaction and may also be associated with persistent local pain.

This study was designed to investigate whether a modified J-shaped skin incision could reduce peri-incisional numbness compared with the conventional midline incision in patients undergoing primary TKA. The underlying rationale is that altering the distal course of the skin incision laterally near the tibial tuberosity may help decrease injury to the infrapatellar branch of the saphenous nerve while preserving standard surgical exposure and not increasing operative difficulty or wound-related complications.

In this prospective randomized controlled trial, 62 patients with Kellgren-Lawrence grade 4 varus osteoarthritis scheduled for primary TKA were allocated to one of two groups: a conventional midline incision group or a modified J-shaped incision group. In the modified technique, the distal portion of the incision is curved laterally by approximately 3 cm at the level of the tibial tuberosity. All participants undergo peri-incisional sensory evaluation preoperatively and again at 2 and 6 months postoperatively. Sensory loss is quantified using Semmes-Weinstein 10-g monofilament testing combined with a grid-mapping method to determine the area of numbness.

The primary outcome measure is the area of peri-incisional numbness after surgery. Secondary outcome measures include postoperative pain assessed by visual analog scale (VAS), functional outcomes assessed by The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), Hospital for Special Surgery Knee-Rating Scale (HSS) and Anterior Knee Pain Scale (AKPS) scores, range of motion, estimated blood loss, tourniquet time, and wound-related complications. These measures are intended to determine whether the modified incision provides sensory and pain-related benefits without adversely affecting clinical recovery, surgical efficiency, or wound healing.

Based on the study findings summarized in the abstract, the modified J-shaped incision was associated with a significantly smaller area of postoperative numbness at both 2 and 6 months and with lower pain scores at 6 months, while functional scores, range of motion, blood loss, tourniquet time, and wound-related complications were similar between groups. These findings support the hypothesis that a simple modification of the skin incision may improve postoperative sensory outcomes and comfort after primary TKA without increasing surgical risk.

Inclusion criteria

• Adults undergoing primary total knee arthroplasty
• Diagnosis of Kellgren-Lawrence grade 4 varus knee osteoarthritis
• Planned treatment with primary total knee arthroplasty
• Ability to provide written informed consent
• Ability to comply with postoperative follow-up evaluations

Exclusion criteria

• Valgus knee deformity
• Revision total knee arthroplasty
• Previous surgery on the affected knee
• History of periarticular fracture around the knee
• Pre-existing sensory deficit or neurologic disorder affecting the operative lower extremity
• History of lumbar disc herniation
• Known neuromuscular disease
• Peripheral vascular disease
• Inability to comply with follow-up and postoperative evaluations
• Refusal or inability to provide informed consent