Papers of the Week

Persistent symptoms, most commonly pain, may remain after otherwise successful hip replacement surgery. Innervation of fascia and soft tissues has become increasingly important in etiopathogenesis of pain, but the relative importance of the various anatomical structures in the hip region is still not known. Innervation of skin, superficial adipose tissue, superficial fascia, deep adipose tissue, deep fascia, muscles, capsule, capsule ligament, ligamentum teres and tendon in the human hip from 11 patients and 2 cadavers were quantified by staining with anti-S100 antibody for myelin-forming Schwann cells, to obtain the percentage of antibody positivity, density and mean diameter of the nerve fibers. The skin was the most highly innervated (0.73±0.37% of positive area in patients; 0.80±0.28% in cadavers); the tendon was the least innervated (0.07±0.01% in patients, 0.07±0.007% in cadavers). The muscles (vasto-lateral and gluteus medius) were the second most innervated structure according the percentage (0.31±0.13% in living humans, 0.30±0.07% in cadavers), but with only a few nerves, with large diameters (mean diameter 36.4±13.4µm). Instead, the fasciae showed 0.22±0.06% and 0.26±0.05% of positive areas in living humans and cadavers, respectively; they were also invaded by networks of small nerve fibers, revealing a possible role in pain. The superficial fascia was the second most highly innervated tissue after the skin, with a density of 33±2.5/cm , and a mean nerve sizes of 19.1±7.2µm. Lastly, the capsule turned out to be poorly innervated (0.09%), showing that its removal does not necessarily lead to painful consequences. This article is protected by copyright. All rights reserved.