Achilles tendon healing: a correlation between functional and mechanical performance in the rat.
The pathogenesis and treatment of rupture of the Achilles tendon remain a source of controversy. This study presents the results of a biomechanical, functional, and morphological evaluation of a group of rats that had division and repair of the Achilles tendon. A total of 46 rats were used: 18 for biomechanical testing, 18 for functional evaluation, and 10 for histology. Morphological examination revealed an early inflammatory response with loose connective tissue formation that was replaced gradually by fibroblasts and a collagenous matrix. The functional evaluation (Achilles functional index [AFI]) was made from measurements of the hind pawprints of walking rats. Division and repair of the Achilles tendon produced a significant functional impairment (mean [+/- SEM] AFI = -87 +/- 8; p < 0.001), which gradually improved with healing time. The load to failure for the repaired tendons consistently improved with healing time, in a manner similar to the functional recovery. The average deformation (repair/control) varied considerably and was not related to healing time. The stiffness of the repaired tendons increased with healing time and was 60% of the corresponding control side by day 15. The major finding of this study was a strong correlation between the AFI and the failure load of the healing tendon-bone constructs (250-300 g group, r = 0.97, p < 0.001; 325-375 g group, r = 0.96, p < 0.001).
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Division of Orthopaedic Surgery, Duke University Medical Center, Durham, NC 27710.
Collins
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Lilly
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Seaber
A V
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Goldner
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Murrell
G A
GA
D000125:Achilles Tendon / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D001696:Biomechanical Phenomena; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D013997:Time Factors; D014945:Wound Healing