Pretubercular Subcutaneous Thickness Is a Protective Factor for Superficial Wound Complications After Total Knee Arthroplasty in Nonmorbidly Obese Patients.

Background: Anterior knee subcutaneous thickness has been associated with increased risk of early reoperation for surgical site infection after primary total knee arthroplasty (TKA) in morbidly obese patients. However, most patients undergoing TKA are not morbidly obese. The aims of this study were to (1) assess the association between anterior knee subcutaneous thickness and early superficial wound complications and (2) determine a threshold value for anterior knee subcutaneous thickness measures that can assist in preoperative risk stratification in nonmorbidly obese TKA patients.

Methods: Using retrospective analysis, we reviewed 494 primary TKAs performed in patients with a body mass index <40 kg/m at our institution from January 1, 2010 to December 31, 2017. All patients developing a superficial surgical site infection within 90 days of index arthroplasty requiring treatment with antibiotics or reoperation were identified. Prepatellar thickness and pretubercular thickness were measured on preoperative lateral radiographs and associated with 90-day superficial wound complications.

Results: Sixty-two of the 494 patients developed a superficial wound complication within 90 days of index arthroplasty. TKA patients in the superficial wound complication group had significantly less pretubercular thickness (P = .027). Risk of developing 90-day superficial wound complication was 1.85-fold lower when pretubercular thickness was ≥12 mm (P = .028). Prepatellar thickness (P = .895) was not significantly associated with superficial wound complications.

Conclusion: Increased pretubercular thickness is a protective factor for developing superficial wound complications, with 12 mm being an ideal threshold value for preoperative risk stratification in nonmorbidly obese patients undergoing primary TKA surgery.