A predictive radiological analysis of short stems versus both shortened and long stems in primary hip replacement: A case-control study of 100 cases of Metha versus ABG II and Omnifit HA at 2–8 years’ follow-up - 07/11/17

Doi : 10.1016/j.otsr.2017.07.014

J.-A. Epinette ^a,^⁎ , M. Brax ^b, Y. Chammaï ^b
^a Clinique Médico-Chirurgicale, 200, rue d’Auvergne, 62700 Bruay-La-Buissière, France
^b Centre Hospitalier, 64, avenue du Professeur-Leriche, 67500 Haguenau, France

^⁎Corresponding author.

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Abstract

Introduction

Short hip stems, intended to conserve bone stock and ensure a more physiological distribution of stress in the femur under loading, are meeting with renewed interest. Radiologic semiology is not known exactly, particularly in relation to conventional implants; we therefore conducted a case-control study of 3 types of implant differing only in stem length: short, shortened or long. The aim was: (1) to compare radiographic aspects, (2) to attempt to systematize medium-term radiologic status for the 3 types, and (3) to assess the impact of radiographic aspect on loosening and revision rates.

Hypothesis

The short Metha stem is better adapted to the recipient bone than longer stems, without sacrificing stability.

Material and methods

A prospective series comprising the first 100 selected cases of hip replacement using the short Metha stem was compared to two other series of 100 “long” (Omnifit HA) and 100 “shortened” (ABG II) stems at comparable follow-up: 4.05±1.44years (range: 2–8years) for Metha, 4.48±0.97years (range: 2–8years) for Omnifit, and 4.75±2.07years (range: 2–8years) for ABG II. Selection criteria in this initial phase were very strict: young age and/or high activity level, with good bone stock and femoral morphology suited to fitting a Metha stem (no “stovepipe” or “champagne-flute” femurs), for which 12.8% of primary hip replacements were selected. Matching was performed by sampling on criteria of age, gender, body-mass index and etiology. Radiographic parameters were compared between the short stem group and the two control groups and classified according to Engh-Massin score (10 points for fixation and 17 for stability).

Results

The short Metha stem provided excellent fixation scores: 7.65/10, versus 7.16 (P=0.003) and 5.92 (P=0.0001) for ABG II and Omnifit, respectively. Likewise, stability was scored 14.23/17 for Metha, vs. 14.51 (NS) and 11.83 (P=0.0001) respectively, and the total score was higher for Metha (21.88/27) than ABG II (21.67; P=0.03) or, more particularly, Omnifit (17.83; P=0.0001). The Metha stem was never associated with thigh pain or periprosthetic fracture. 8-year survival was 100%, without significant difference with respect to ABG II (100%; NS) or Omnifit (98.8%; 95% CI: 0.964-1; NS).

Discussion

The apparent radiologic superiority of the short Metha stem requires long-term confirmation in non-selected series. Meanwhile, Metha can be asserted to have demonstrated optimal compromise between lasting bone anchorage and respect of bone physiology under loading at medium term.