Objective: To describe the histological features of the fascial-periosteal interface at the medial tibial border of patients surgically treated for chronic deep posterior compartment syndrome and to make statistical comparisons with control tissue. Methods: Nineteen subjects and 11 controls were recruited. Subject tissue was obtained at operation, and control tissue from autopsy cases. Tissue samples underwent histological preparation and then examination by an independent pathologist. Samples were analysed with regard to six histological variables: fibroblastic activity, chronic inflammatory cells, vascularity, collagen regularity, mononuclear cells, and ground substance. Collagen regularity was measured with respect to collagen density, fibre arrangement, orientation, and spacing. The observed changes were graded from 1 to 4 in terms of abnormality. Mann-Whitney U test, Spearman correlation coefficients, and intraobserver reliability scores were used. Results: With regard to collagen arrangement, control tissue showed greater degrees of irregularity than subject tissue (p = 0.01). Subjects with a symptom duration of greater than 12 months ( as opposed to less than 12 months) showed greater degrees of collagen irregularity (p = 0.043). Vascular changes approached significance (p = 0.077). With regard to the amount of fibrocyte activity, chronic inflammatory cell activity, mononuclear cells, or ground substance, there were no significant differences between controls and subjects. Good correlation was seen in scores measuring chronic inflammatory cell activity and mononuclear cells (r = 0.649), and moderate correlation was seen between fibrocyte activity and vascular changes (r = 0.574). Intraobserver reliability scores were good for chronic inflammatory cell activity and moderate for vascular changes, but were poor for collagen and fibrocyte variables. Individual cases showed varying degrees of fibrocyte activity, chronic inflammatory cellular infiltration, vascular abnormalities, and collagen fibre disruption. Conclusions: Statistical analysis showed no histological differences at the fascial-periosteal interface in cases of chronic deep posterior compartment syndrome, except for collagen, which showed less irregularity in subject samples. The latter may indicate a remodelling process, and this is supported by greater collagen irregularity in subjects with longer duration of symptoms.
