BIOCHEMISTRY AND BIOMECHANICS OF HEALING TENDON - PART I - EFFECTS OFRIGID PLASTER CASTS AND FUNCTIONAL CASTS

Purpose: Traditional treatment of surgically repaired Achilles tendons includes complete immobilization of the joint in rigid casts for 6 to 8 wk. We tested the use of functional polyurethane casts as an altern ative to rigid plaster casts after experimental tenotomy and repair of the rabbit Achilles tendon. Methods: After repair the limbs of 15 exp erimental rabbits were immobilized in a functional polyurethane cast f or 15 d, while those of 14 controls were immobilized in traditional ri gid plaster casts for the same period.Results: Functional casting resu lted in a 60% increase in total collagen in the neotendon compared wit h that in rigid casting (P < 0.05). Mature collagen cross-links declin ed 8% in the tendons with functional casts. The biomechanical paramete rs of the tendons changed with functional casting, showing a 20% incre ase in maximum load and 21% increase in maximum stress. Conclusions: T hese changes were noted without any cases of tendon re-rupture in eith er type of cast. Thus, functional casting following surgery of Achille s tendons appears to improve healing without significant risks of re-r upture.