Minimal-Incision Technique With Modified Tracking Pin Placement Versus Standard Robotic-Assisted Total Knee Arthroplasty

The combined Patient and Observer Scar Assessment Scale (POSAS) score is calculated by summing the total Patient Scale score and the total Observer Scale score. Each scale consists of six items rated from 1 to 10, resulting in a score of 6 to 60 for each scale and a combined score ranging from 12 to 120. Higher scores indicate poorer scar quality. The Observer Scale will be completed by an independent outcome assessor blinded to treatment allocation.

The length of the main surgical incision will be measured in centimeters. The initial incision length will be measured immediately after the skin incision with the knee in extension, and the final incision length will be measured before wound closure. The incision length will also be evaluated on postoperative day 1. Separate tracking pin-site incisions will not be included.

The incision stretching index is calculated as the maximum length of the main incision during knee flexion and maximal surgical retraction divided by the initial incision length measured with the knee in extension. A value of 1 indicates no stretching, and higher values indicate greater intraoperative stretching of the incision and surrounding soft tissue.

Postoperative wound oozing will be assessed according to the amount of blood or exudate visible on the surgical dressing using a prespecified ordinal grading scale. Higher grades indicate more extensive wound oozing.

Participants will rate thigh pain at rest using an 11-point numeric rating scale ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain.

Participants will rate thigh pain during active hip flexion while maintaining knee extension and without external resistance. Pain will be assessed using an 11-point numeric rating scale ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain.

Tenderness elicited by palpation at a prespecified standardized anatomical location corresponding to the tracking pin region will be rated using an 11-point numeric rating scale ranging from 0 to 10, where 0 indicates no tenderness and 10 indicates the worst imaginable tenderness.

The participant's ability to independently raise the operated lower extremity while maintaining knee extension will be recorded as a binary outcome: able or unable to perform straight-leg raising. The number and proportion of participants able to perform the test will be compared between groups.

Pain during resisted straight-leg raising will be assessed using a 100-mm visual analog scale, where 0 mm indicates no pain and 100 mm indicates the worst imaginable pain.

Tracking pin sites will be examined for complications, including erythema, swelling, wound drainage, infection, and pin-related fracture. The occurrence of one or more prespecified pin-site complications will be recorded as a binary outcome, and the number and proportion of participants with any complication will be reported.

The Forgotten Joint Score-12 is a 12-item patient-reported questionnaire assessing awareness of the operated knee during daily activities. Scores are transformed to a scale ranging from 0 to 100, with higher scores indicating less awareness of the artificial joint and a better outcome.

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) assesses knee pain, stiffness, and physical function. The 24 items are scored using a 5-point Likert scale, producing a total score ranging from 0 to 96. Higher scores indicate more severe symptoms and poorer physical function.