Novel radiographic hip fat thickness ratio correlates with early re-operation following total hip arthroplasty

Abstract

Introduction: Obesity is thought to lead to increased failure rates following total hip arthroplasty (THA). Site-specific fat distribution has been suggested to be a better indicator of risk, compared to body mass index. Fat thickness measurement methods were developed for total knee arthroplasty, however, there is limited data on the methods for THA. The aim of this study was to assess the interobserver and intraobserver reliability of a newly defined radiographic subcutaneous fat thickness ratio and investigate the correlation of this ratio with early failure following THA. Methods: 321 patients who underwent primary THA at a single institution between 2014 and 2017, with at least 1-year of follow-up and a preoperative pelvis anteroposterior x-ray radiograph were included in this study. A high hip fat thickness ratio (HFTR) was arbitrarily defined as ⩾2. Early failure was defined as revision or re-operation for any reason and death related to operation first year following THA. Results: The HFTR was shown to have excellent intraobserver and interobserver reliability. High HFTR was associated with higher risk of early failure following THA (odds ratio 3.8, [95% confidence interval, 1.2–12.1], p < 0.05). The same association persisted when HFTR was analysed as a continuous variable ( p < 0.01) and in multivariate analysis ( p < 0.05). Conclusions: HFTR can be used to assess periarticular soft tissue distribution and may be regarded as a useful and reproducible tool for assessing risk of early failure following THA.

Local Soft-Tissue Thickness vs. Body Mass Index as Predictors of Complications After Total Knee or Hip Arthroplasty

“…The failure rates for the 2 groups were 2.2% (HFTR ,2) and 7.7% (HFTR $2), but not significantly different (p 5 0.03). An HFTR $2 was associated with a higher risk of early failure after THA (OR, 3.8, 95% CI, 1.2-12.1, p , 0.05) 28 . Multivariate analysis demonstrated a significant association between THA failure and HFTR on continuous (OR, 4, 95% CI, 1.5-10.3, p , 0.01) and categorical models (OR, 4.6, 95% CI, 1.2-12.1, p , 0.05).…”

“…Two studies refuted this hypothesis 26,27 . These studies and their results are explained below 17,23-25,28 .…”

“…Sezgin et al conducted a retrospective cohort study but used a hip fat thickness ratio (HFTR) to measure STT and predict failure risk in the first year after primary THA through the anterolateral approach 28 . THA failure was defined as mortality or any visit to the operating room for the same hip.…”

“…Although BMI can be calculated by a simple formula (BMI 5 kg/m 2 ), STT is defined differently between studies. On review of the 7 studies discussing STT and THA complications, 2 studies intraoperatively measured the distance from the most lateral part of the greater trochanter (GT) to the skin, 4 used radiographic lines from different parts of the GT or femoral head to the skin, and 1 created a ratio by measuring the STT laterally on an anterior-posterior (AP) radiograph and dividing it by the femoral diaphyseal diameter 17,[23][24][25][26][27][28] . These measurements are further discussed under the "hips" subsection.…”

“…Five studies revealed that larger STT around the hip is associated with an increased incidence of complications after THA 17,[23][24][25]28 (Table I). Two studies refuted this hypothesis 26,27 .…”