THE EFFECTS OF ELEVATED COMPARTMENT PRESSURE ON TIBIAL ARTERIOVENOUS FLOW AND RELATIONSHIP OF MECHANICAL AND BIOCHEMICAL CHARACTERISTICS OFFASCIA TO GENESIS OF CHRONIC ANTERIOR COMPARTMENT SYNDROME

Purpose: The purpose of this study is to evaluate the effects of incre ased compartment pressure on anterior tibial arteriovenous flow patter ns and to determine whether mechanical and biochemical properties of f ascia are responsible for compartment pressure abnormalities. Methods: Twenty patients with chronic anterior compartment syndrome (CACS) and 20 age-matched control subjects had compartment pressure measurements and analysis of tibial arterial and venous flow before and after fasc iectomy. Fascia specimens were evaluated for thickness, stress failure , structural stiffness, and total collagen content and prevalence of c ollagen cross-linkage. Results: Pressures were significantly elevated in patients with CACS versus control subjects (23.8 mm Hg vs 6 mm Hg). No significant difference in tibial arterial flow could be detected i n either group (43 cm/sec mean vs 41.9 cm/sec mean). Venous drainage w as severely impaired in patients with CACS but not in control subjects . CACS fascia was thicker and stiffer than control fascia specimens (0 .35 mm +/- 0.12 mm, 109 +/- 65 MN/mm; versus 0.22 mm +/- 0.06 mm; 60.3 +/- 22 MN/mm), Fasciectomy normalized postoperative compartment press ures and improved venous drainage. Collagen content per unit mass was similar for both CACS and control fascia specimens, although collagen cross-linking was significantly lower in the CACS fascia than in the c ontrols. Conclusions: Tibial venous drainage is impaired, but arterial flow is not in patients with CACS. Fascia thickness and structural st iffness can account for increased pressure in CACS compartments. Colla gen content and cross-linkage are unrelated to fascia stiffness or thi ckness. Postoperative improvement in vascular hemodynamics and reducti on in compartment pressure is caused by increased capacitance in the c ompartment after fasciectomy.