CORR Insights^®: The Chitranjan Ranawat Award: Running Subcuticular Closure Enables the Most Robust Perfusion After TKA: A Randomized Clinical Trial

Where Are We Now?

Previous research [1, 3, 7, 9, 10] has supported many different wound closure techniques for use in TKA including staples, interrupted sutures, running barbed subcutaneous sutures, and subcuticular methods. A midline incision is generally used, but medial and lateral incisions have also been advocated to permit better kneeling ability after surgery or for other reasons [2, 6].

Subfacial vessels provide circulation to the skin, which perforate through the subcutaneous tissue layer [10]. Subfacial dissection of skin and subcutaneous tissue flaps preserve skin circulation while dissection into the subcutaneous layer disrupts skin circulation. Circulation to the skin over the knee occurs in a medial to lateral direction [12]. Sensory nerve supply follows the same direction. This is why sensation in the lateral skin flap is often diminished after TKA, and the lateral skin edge is generally more hypoxic than the medial skin edge [5]. Oxygenation of the skin edges is also reduced by knee flexion because this puts greater tension on the wound, while also decreasing to a maximum several days after surgery before returning toward normal [5].

The development of skin necrosis and postsurgery wound healing problems can lead to infection of the prosthetic components. These issues are influenced by many risk factors and comorbidities that are not under the control of the surgeon. Surgical technique, including the method of soft tissue dissection and wound closure, are also important in promoting primary wound healing. However, there is no clear consensus on the best method of wound closure in TKA.

The study by Wyles et al. utilizes a sophisticated fluorescent imaging system following intravenous administration of dye to quantitate skin perfusion. This method is a valuable research tool that is more sensitive than other techniques, and also appears to be useful in clinical practice to help with treatment decisions. The authors found that subcuticular wound closure was associated with more favorable skin perfusion than staple closure. This is likely related to the more uniform distribution of tension across the wound with a running suture placed into the dermis, which has considerably better mechanical integrity than the subcutaneous fatty layer, in comparison to wound tension with staples that is more concentrated on each point of contact at which the stable enters the skin.

Where Do We Need To Go?

Many factors other than the method of wound closure can affect skin perfusion, including the location and length of the incision, method of soft tissue flap elevation, deep surgical approach to the knee, and patient comorbidities such as diabetes, peripheral vascular disease, and immunosuppressive disorders. However, the relative effect of these various factors on skin perfusion and wound healing after TKA is not clear. Since wound healing problems are not common after TKA, and many factors can contribute to skin perfusion, traditional methods to assess the relative value of each of these factors on wound healing would require multivariate analysis of a large patient population.

How Do We Get There?

Most wound healing problems are likely associated with some impairment in skin vascularity, but not all patients with impaired skin vascularity develop a wound healing problem. Studies using in vivo nuclear vascular imaging provide an assessment of soft tissue perfusion, which is a surrogate of wound healing [4, 8, 11]. This is similar to research studies that evaluate deep venous thrombosis rather than pulmonary embolus after TKA to determine the effects of various prophylactic pharmacologic agents on thromboembolic complications. Researchers have performed these types of studies because deep venous thrombosis is more common than pulmonary embolus—although pulmonary embolus is more clinically relevant.

Nuclear vascular imaging techniques have been used in plastic surgery research and clinical practice [4, 11]. It appears that controlled clinical studies with fluorescent imaging following intravenous administration of dye or similar techniques could be employed at institutions other than the Mayo clinic. Since the method used in the study by Wyles et al. is highly sensitive, it could be used in future controlled studies to determine the effect of various patient related factors or differences in surgical technique on skin vascularity with relatively small patient populations. Researchers would need a correlation of the measurements of skin perfusion with clinical outcomes in larger patient populations in order to determine the threshold of skin perfusion that is clinically relevant for wound healing in TKA.