Changes in the supporting muscles of the fractured hip in elderly women

There is little information concerning the changes in the muscles supporting the fractured hip joint. Morphologic and histochemical examinations of biopsy specimen from the middle gluteal muscles were performed at surgery in 42 elderly women with hip fracture caused by a fall. On the basis of serum 25-hydroxyvitamin D (25-OHD) concentration, the patients were divided into a sufficient group (25-OHD concentration >39 nmol/L, N = 20) and a deficient group (25-OHD concentration <39 nmol/L, N = 22). Reflecting the muscular trauma in the fall-induced hip fracture, the following pathologic changes were common in both the sufficient and deficient groups: degenerating and regenerating fibers; fiber necrosis; and inflammatory reaction. The mean type II fiber diameter in the deficient group (15.4 ± 4.2 μm) was significantly smaller than that in the sufficient group (38.7 ± 8.1 μm) (p< 0.0001). In the deficient group, the mean type II fiber diameter correlated with the serum 25-OHD concentration (r = 0.714, p = 0.0011). This correlation was not observed in the sufficient group. Low physical activity along with vitamin D deficiency prior to the hip fractures may have caused the severe type II fiber atrophy in the deficient group. Such changes may weaken the support of the hip joint and lead to falls. We believe that severe type fiber II atrophy is an independent risk factor for hip fractures and this should be studied in a classic case-control study. Severe type II fiber atrophy may also have contributed to the poor functional outcome in the deficient group. Further research is needed to develop treatments and rehabilitation protocols that might improve gait and body function by attenuating type II fiber atrophy.