Transcutaneous oxygen tension in the anterior skin of the knee after minimal incision total knee arthroplasty

Delayed wound healing after total knee arthroplasty (TKA) can lead to devastating complications. The lateral flap is reported to be more hypoxic than the medial flap in conventional TKA. However, the surgical approach significantly affects the cutaneous blood supply. Our hypothesis was that postoperative oxygenation of the skin over the anterior knee would be different in minimal incision TKA.

This prospective observation study included 21 patients who underwent minimal incision TKA. Transcutaneous oxygen tension (TcPO2) was measured perioperatively at four sites around the midline incision: superio-medial, superio-lateral, inferio-medial, and inferio-lateral. The ratio of the regional TcPO2 to the reference TcPO2 was calculated as the regional perfusion index (RPI). We compared the RPI among four sites and evaluated the association between the RPI and wound healing.

At all measurement sites, the RPI significantly decreased after surgery (days 1 and 7; p < 0.01). On day 7, the RPI at inferio-medial and inferio-lateral sites were significantly lower than superio-medial and superio-lateral sites, respectively ( p < 0.05). No significant difference between the medial and lateral sites was observed. In three patients, delayed healing was noted at the inferio-lateral wound edge, where the RPI significantly decreased on day 1.

The distal part of the wound was significantly more hypoxic than the proximal part in minimal incision TKA. Atraumatic wound edge retraction should be carried out especially in the distal part. Although further investigation is necessary, delayed wound healing is potentially associated with regional skin hypoxia on day 1.