Is there a difference in pelvic and femoral morphology in early periprosthetic femoral fracture in cementless short stem total hip arthroplasty via an anterolateral approach?

Background: The pelvic and femoral morphology are associated with the occurrence of early periprosthetic femoral fractures (PFFs) in cementless total hip arthroplasty (THA). Differences exist depending on the performed approach and implanted stem design. Therefore, this study was conducted to analyze the pelvic and femoral morphology in cementless short stem THA via a minimally-invasive (MIS) anterolateral approach.

Methods: A retrospective, single-center, multi-surgeon, comparative propensity-score matched study of a cohort of 1826 short stem THAs was conducted. A total of 39 PFFs within the first 90 days after surgery was matched on a 2:1 ratio to non-fracture patients. The morphology of the proximal femur was analyzed with canal flare index (CFI), canal-calcar ratio (CCR), canal-bone ratio (CBR), morphological cortical index (MCI), and femoral cortical index (CI). The pelvic morphology was analyzed with ilium-ischial ratio (IR), distance anterior superior iliac spine to the tip of the greater trochanter (AGT). Both groups were analyzed regarding several parameters for femoral and pelvic morphology in non-parametric testing and univariate regression analysis.

Results: A significantly higher AGT was detected in the fracture group (104.5 mm ± 18 versus 97.4 mm ± 9.8; p = 0.016). All other femoral and pelvic parameters did not differ between both groups, also when compared depending on the Vancouver type of the PFF.

Conclusions: The morphology of the proximal femur and the pelvis do not differ in several radiological parameters in patients sustaining a PFF in cementless short stem THA via an anterolateral approach compared with matched non-fracture group. The findings are controversial to other studies with different stem types and approaches. Future studies should focus on analyzing the influence of the pelvic geometry and the shape of the proximal femur in the occurrence of PFFs in different approaches with the same stem type and vice versa. Level of Evidence Level III case-controlled study.