Although preoperative risk assessment is multifactorial, subcutaneous fat thickness at the incision site has been associated with postoperative complications in studies of total hip arthroplasty (THA) and other procedures. This study compared subcutaneous fat thickness encountered in THA approaches using a lateral hip incision with that of approaches using an anterior incision and examined the relationship between body mass index (BMI) and fat distribution based on sex and age.
Subcutaneous fat measurements were obtained from 2004 patient CT images at positions that correspond with lateral and anterior incision sites for common approaches to THA. A thickness ratio (lateral/anterior) was calculated, and BMI, sex, and age were collected via chart review.
Males and females had significantly different thickness ratio averages at 1.97 and 2.68, respectively. Thickness ratios were not significantly different between BMI groups. Lateral thickness averages were significantly different for males and females, and the interaction between sex and BMI group was significant. The relationship between BMI and the thickness ratio in males aged ≥65 years was significantly different from males of <65 years and females of all ages.
Regardless of BMI, sex, or age, incision site soft tissue thickness was greater for approaches using a lateral hip incision than for those with an anterior incision, and a positive relationship between BMI and both measurements was identified. The predominance of lateral fat was more pronounced in females of all age and BMI groups and less pronounced in obese males aged ≥65 years.