Preoperative femoral abduction angle correlates with initial postoperative lateral hip pain after transcutaneous osseointegrated prosthetic system (TOPS) in transfemoral amputees

Purpose To analyse whether a preoperative femoral abduction angle (FAA) correlates with postoperative initial lateral hip pain (LHP) in above-knee amputees (AKA) treated with transcutaneous osseointegrated prosthetic system (TOPS). Methods Pre- and postoperative long-leg radiographs of eighteen unilateral AKA (mean age 51.55y ± 12.16) were retrospectively measured. FAA was measured on both sides. Pain intensity of LHP was measured by numeric rating scale (NRS) preoperatively and every week for four weeks from the first day of weight loading. Pearson’s r was calculated for correlation. Furthermore, odds ratio for LHP ≥ 5/10 NRS and relative FAA > 13° was calculated. Results FAA significantly decreased in the postoperative period (pre/post. 15.33° ± 4.22; p < 0.001). Median LHP was 0/10 NRS (min.0, max.3) preoperatively and 4/10 NRS (min.2, max. 7, p < 0.001) postoperatively after first loading. Interestingly, it decreased within four weeks to a median of 0.5/10 NRS (min.0, max. 3) without intervention. A strong correlation was seen on the amputated side between preoperative FAA and LHP after loading ( r = 0.835, p < 0.001), as well as the relative FAA to LHP after loading ( r = 0.732, p < 0.001) and between the gap of pre- to postoperative FAA and LHP. Odds ratio for LHP ≥ 5/10 and relative FAA > 13° was 6.4 (95%CI = 0.55; 74.89). Conclusion The preoperative FAA strongly correlates with postoperative LHP. Surgeons should be aware of high risk of LHP that can limit prosthetic training. High preoperative FAAs should be realised in the decision meeting of TOPS implantation and pre-rehabilitative reduction of the FAA should be taken into consideration.