Optimizing Implant Selection: The Critical Role of Objective and Biomechanical Data in Orthopaedic Decision-Making

Commentary Use of a cementless femoral stem in total hip arthroplasty (THA) is the main surgical option to obtain strong femoral fixation and satisfactory implant survivorship in an active and young population1. Nevertheless, implant stability and integration are not guaranteed for every patient2. Several parameters can impact this osseointegration and implant survivorship. These parameters are related to the patient (such as osteoporosis, previous hip surgery, and metabolic diseases), to the quality of the surgery (such as downsizing and malpositioning), or to the implant (such as the shape and the coating of the femoral implant)3,4. The variety of uncemented stems is wide, involving various characteristics: coating types, coating location (complete or metaphyseal only), shape (anatomical or standard), cross-sectional geometry, and collared or collarless. Several criteria influence the implant choice by each surgeon: the surgeon's experience and education, the literature, and the influence of implant companies. The first criterion is based on the clinical and functional outcomes of the patients previous treated by the surgeon. The literature contains mainly functional outcomes and complication and revision rates, based mostly in either heterogeneous or selected cohorts, in the hands of experienced surgeons. The reliability and value of these studies are always tricky to evaluate. Their potential extension to other surgeons and patients worldwide remains uncertain. Moreover, the reported functional outcomes do not provide good discrimination when THAs are being assessed because most patients have good outcomes. As described in the study by Hooper et al., the functional outcomes were similar among the 3 groups. Few strong studies, with a high level of evidence, have assessed the biomechanical impact of the shape and coating of femoral stems. The influence of implant companies is probably the least objective criterion. That is why biomechanical characteristics are often neglected and not considered thoroughly before the implant is chosen by a surgeon. The strength of this study is the objective assessment of femoral stems using a randomized study design with few methodologic biases. The patient selection criteria were strict, excluding all patients with osteoporosis. The randomization allowed the creation of similar patient groups. The 3 stems in this study differed mainly in 2 parameters: the location of the coating and the shape of the stem (standard or anatomical). The stems were otherwise similar, which reduced the risk of confounding by other factors. A well-known standard stem, the Corail stem, was used as a reference against which to compare the results. However, a limitation of this study is the links between the implant companies and the authors. This study indicated that the proximally coated dual-taper wedge stem yielded a greater change in bone mineral density in Gruen zones 2 and/or 7 than the anatomical and Corail stems. The anatomical stem with a proximal coating restored the preoperative bone mineral density more accurately than the other stems did. Contrary to the study hypotheses, no stress riser at the tip of the stem was reported for any of the 3 stems. This objective assessment suggests that a proximally coated non-anatomical stem increases the stress on, and thus the bone mineral density in, the metaphyseal zones, particularly in the calcar. The anatomical shape, matching the typical curvature of the femoral shaft, was able to yield strong fixation in the metaphysis even though the coating did not extend beyond that region. These anatomical implants already have excellent survivorship even in young populations5. The arthroplasty field is currently tending toward personalized surgery: personalized alignment, personalized positioning, and personalized implants. The question of whether to use customized or personalized implants more often should be discussed in orthopaedic societies, while considering all of the constraints and limitations of these implants (availability, cost, need for preoperative imaging, production delay). This robust study raises 2 primary issues: first, the need for objective and honest biomechanical data that surgeons can use to optimize implant selection, reducing the influences of their personal beliefs and of implant companies; and second, the future place of personalized implants in daily practice to continue improving our patient's outcomes, such that their hip becomes a "forgotten joint" equivalent to their other joints.