Our understanding of the origin of hip pain in degenerative disorders of the hip, including primary osteoarthritis, avascular necrosis and femoroacetabular impingement (FAI), is limited. We undertook a histological investigation of the nociceptive innervation of the acetabular labrum, ligamentum teres and capsule of the hip, in order to prove pain- and proprioceptive-associated marker expression. These structures were isolated from 57 patients who had undergone elective hip surgery (44 labral samples, 33 ligamentum teres specimens, 34 capsular samples; in 19 patients all three structures were harvested). A total of 15 000 histological sections were prepared that were investigated immunohistochemically for the presence of protein S-100, 68 kDa neurofilament, neuropeptide Y, nociceptin and substance P. The tissues were evaluated in six representative areas.

Within the labrum, pain-associated free nerve ending expression was located predominantly at its base, decreasing in the periphery. In contrast, the distribution within the ligamentum teres showed a high local concentration in the centre. The hip capsule had an almost homogeneous marker expression in all investigated areas.

This study showed characteristic distribution profiles of nociceptive and pain-related nerve fibres, which may help in understanding the origin of hip pain.

Cite this article: Bone Joint J 2013;95-B:770–6.

We report the presence of estrogen receptor (ER) in the ligamentum capitis femoris (LCF) and hip capsule. We took 15 LCF and hip capsule biopsies from 15 patients undergoing hip surgery for the Developmental Dysplasia of the hip (DDH) and 15 hip capsules and LCF’s from intrauterine ex fetuses. The mean age of the babies was 10.3 months (6–18 months) at the time of surgery. Total 60 specimens were grouped into two as the DDH group and the control group and each of these groups were further divided into two to generate the groups for the LCF and hip capsules. Full thickness 1 x 1 cm anterior capsule and LCF portions were taken as biopsy specimens. An immunohistochemical study using monoclonal antibody against to estrogen receptors was performed to identify estrogen target cells in the hip capsule and LCF. The positive rates of ER staining in the control group were % 1.6 ± 0.2 for the LCF and % 1.3 ± 0.2 for the hip capsule, in the DDH group positive rates of ER staining were %2.5 ± 0.3 for the LCF and % 2.0 ± 0.3 for the hip capsule. The positive rates of ER staining in LCF and hip capsule of the control group were significantly lower than that in the DDH group in both groups we found ER’s to be significantly lower in the hip capsule than in LCF. The presence of estrogen receptors in the LCF and hip capsule supports the effect of estrogen in etiology of the DDH

We aimed to determine if there are mechanoreceptors in hip joint capsule and ligamentum capitis femoris of the patients with developmental dysplasia of the hip. We took capsule and ligamentum capitis femoris biopsies from 20 hips of 20 patients who were operated because of developmental dysplasia of the hip. Meanage was 10.2 months (ranges 6-20 months) on the time of surgery. There were 12 girls and 8 boys. Teratologic and secondary hip dislocations were not included in this study. 0.5x 0.5 cm full thickness anterior capsule and liga-mentum capitis femoris portions were taken for biopsy specimen. Specimens were stained with hemotoxylin eosin and examined immunohistochemically using poly-clonal antibodyagainst S-100 Protein. In both analysis no mechanoreceptors was found in any samples of capsule and ligamentum capitis femoris. Conclusion: We think that there is a possibility that developmental dysplasia of the hip can be caused from a defect in formation of mechanoreceptors on localized capsule and ligamentum capitis femoris and we emphasize the need for further studies on the subject