Relationship between histological findings of vastus lateralis muscle and function after total hip arthroplasty in patients with hip fracture: a prospective cohort study.

Background and purpose:  We aimed to examine the histological characteristics of vastus lateralis muscles in patients undergoing total hip arthroplasty (THA) following femoral neck fractures and to explore the correlation between muscle fiber types and postoperative functional recovery.

Methods:  34 patients undergoing THA for femoral neck fractures were included. A biopsy of the vastus lateralis muscle was performed during surgery, followed by immunohistochemical staining. Subsequently, image analysis was conducted to measure the average area of muscle fiber types and the number of type I and II muscle fibers, and the ratio of the area and the number of type II muscle fibers. Functional recovery was assessed 2 weeks post-surgery using the Short Physical Performance Battery (SPPB).

Results: A significant positive correlation was observed between type II muscle fibers and SPPB scores. The ratio of type II muscle fiber area and number strongly correlated with the SPPB scores, indicating a robust static association. The average area of type II fibers showed a strong correlation (r = 0.63, P < 0.001), as did the number of type II fibers (r = 0.53, P = 0.001). Moreover, the ratio of type II muscle fiber area and number significantly correlated with SPPB scores (area: r = 0.77, P < 0.001; number: r = 0.51, P = 0.002), indicating that larger and more numerous type II fibers are associated with better physical performance.

Conclusion: The reduction of type II muscle fibers was strongly correlated with a low SPPB postoperative functional recovery in patients who underwent THA following femoral neck fractures.