Does the Implantation of a Short-Stem Hip Prosthesis Change the Lower Limb Alignment?-Comparison of Two Modern Short-Stem Designs

Abstract

Background/Objectives: Limited data exist regarding the influence of total hip arthroplasty (THA) on the alignment of the lower limb. Therefore, the objective of this study was to investigate potential alterations in lower limb alignment (LLA) following total hip arthroplasty, with a focus on the comparison of two different short-stem implant designs. Methods: This retrospective study compares pre- and postoperative hip-knee-ankle angle (HKA), femoral offset, and leg length data of 115 consecutive hips with two different implant types (Mathys Optimys^® stem and Implantec Alpha proxy^® stem). Results: There was not a significant difference between the pre- and postoperative HKA angles regarding the entire study population (p = 0.293), nor after comparing the two short-stem implant designs (p = 0.433). Hip offset almost remained unchanged in the entire study cohort (p = 0.662), as well as when comparing the two short-stem implant designs (p = 0.206). Conclusions: Modern short-stem THA does not significantly affect overall LLA.

Keywords: THA; leg length; limb alignment; offset; short stem.

Figure 1

Stems compared included the Alpha Stem proxy^® (1) and Optimys^® (2).

Figure 2

FMA and TMA measurements were performed on the THA side pre- and postoperatively.

Figure 3

Measurements of FO, AO, HO, and leg length on a preoperative radiograph.

Figure 4

Most frequent functional knee phenotypes of all patients pre- and postoperatively; each phenotype is represented in a separate column, combining HKA, FMA, and TMA measurements. Figure 4 Legend: HKA (NEU: 178.5° to 181.5°; VAR3°: 175.5° to 178.5°; VAL3°: 181.5° to 184.5°), FMA (NEU: 91.5° to 94.5°; VAR3°: 88.5° to 91.5°; VAL3°: 94.5° to 97.5°), TMA (NEU: 85.5° to 88.5°; VAR3°: 82.5° to 85.5°; VAL3°: 88.5° to 91.5°).