Tapered stems one-third proximally coated have higher complication rates than cylindrical two-third coated stems in patients with high hip dislocation undergoing total hip arthroplasty with step-cut shortening osteotomy

Abstract

Background: The results of cementless stems in total hip arthroplasty (THA) done because of congenital dislocation with step-cut osteotomy is not well known, particularly the influence of the design and therole of extent of porous coating. Therefore we performed a retrospective study to evaluate the mid tolongterm results THA performed with a single type acetabular component and different geometry and fixation type stems with ceramic bearings in the setting of step-cut subtrochanteric osteotomy in high hipdislocated (HHD) patients. We asked if the stem type affect the outcomes in terms of (1) intra and postoperative complication rates (2) radiographic outcomes (3) prosthesis survival in step-cut subtrochanteric shortening osteotomy. Hypothesis: The type of the stem, whether cylindrical or tapered does not affect the outcome if the femoralcanal fit and fill is obtained and the step-cut femoral shortening osteotomy is primarily fixed. Materials and methods: Forty-five hips in 35 patients with a mean follow up of 10 years (range, 7-14years) were evaluated. The single type cementless cup was placed at the level of the true acetabulum, a step-cut shortening femoral osteotomy was performed and reconstruction was performed with two different types of tapered stem in twenty-two hips (Synergy (TM) and Image (TM) proximally coated, Smithand Nephew, Menphis, TN, USA) and one type of cylindrical stem (Echelon (TM) with 2/3 coated, Smith and Nephew, Menphis, TN, USA) in twenty-three hips. Harris hip scores (HHS) and a University of CaliforniaLos Angeles (UCLA) activity scores were calculated for all patients and successive X-rays were evaluatedregarding component loosening and osteolysis, along with complications related to bearing, step-cutosteotomy and stem types. Results: Forty-one hips (91\%) had good and excellent clinical outcome according to HHS. The mean UCLA activity scores improved from 3.2 +/- 0.6 points (range, 2-4) preoperatively to 6.3 points +/- 0.5 (range, 5-7) at the latest follow-up. The mean femoral shortening was 36 +/- 10 mm (range, 20-65 mm). Four (9\%) dislocations were observed. There were five (11\%) intra-operative femoral fractures and three (7\%) cases of non-union, which were observed in tapered stems. Cylindrical stems had superior neutral alignmentprimarily. With any stem revision as the end point, cylindrical stems had a higher survival rate (100\%) than all tapered stems (82\%

95\% confident interval {[}CI] 77-97\%) at ten years. With any revision as the endpoint, the 10-year survival rate for acetabular component (Reflection-Ceramic Interfit) and for femoralcomponents were 98\% (95\% CI, 85-99\%) and 91\% (95\% CI, 78-97\%), respectively. Conclusions: There were more implant related complications in HHD patients undergoing THA when tapered stems with 1/3 proximal coating were used to reconstruct a step cut osteotomized femur, compared to cylindrical stems 2/3 coated. (C) 2017 Elsevier Masson SAS. All rights reserved.