Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

Abstract

Background Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a metaphyseal anchoring short and standard stem in native biomechanical femora. Methods The subject specific finite element models of biomechanical femora, one native and two with implanted metaphyseal anchoring SHA (Metha, B. Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution. Results Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally. Conclusions Both, short and standard THA, cause unloading of the proximal femur. However, the metaphyseal anchoring SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load patterns implicate a reduced stress shielding proximally for metaphyseal anchoring SHA stems and might be able to translate in a better bone preservation.

Promising medium-term results of anterior approach with an anatomical short stem in primary hip arthroplasty

“…For this reason, the anatomic stem should provide excellent initial stability and reliable bone growth [25][26][27][28]. The three main concerns are (1) the high variability of the femoral canal anatomy in the population, so the stem may not fit one of the other patients; (2) a possible high incidence of periprosthetic fractures due to the posterior arch; and (3) a high incidence of thigh pain due to closed fit [3,8,22]. The short anatomic stem, lacking the portion that fills the first part of the shaft, could theoretically have less primary stability but should result in a lower incidence of thigh pain [8][9][10].…”

“…In general, short stems have a significantly smaller bone contact area than standard stems and, as a result, may have less torsional and axial resistance. A solution proposed in the literature to overcome the problem is to spare the femoral neck, by means of a high osteotomy [3,4,[29][30][31]. The short neck-sparing stems provide additional axial and torsional stability and reduce stress at the bone interface of the implant.…”

“…Among the causes of cortical bone hypertrophy discussed in the literature, the first is the transfer of the distal load by the stem. The abnormal load transmitted from the stem to the bone, in particular overload around the tip of the stem rather than the calcar area, can cause bone resorption in the calcar region and the development of a hypertrophy reaction in the distal region of the stem [ 3 , 4 , 33 ].…”

“…Short stems have been introduced into surgical practice to achieve greater preservation of proximal bone stock and stability than those of conventional stems [1][2][3][4]. In the last decade, the increase in the use of the direct anterior approach to the hip has contributed to the diffusion of short stems in orthopedic surgery.…”

Restoration of Some Anatomical Dimensions By Spiron Short Stem Hip Replacement Applied To Vietnamese People

“…Recent studies have focused the surgeon's interest on short-stem replacement designs. Today, there are many types of short stem implants with little clari cation on the basis of design, xation, surgical technique, and clinical outcome [11,12]. Almost every major implant company now offers short stems and comes in a variety of designs.…”