Semitendinosus regrowth: biochemical, ultrastructural, and physiological characterization of the regenerate tendon.
BACKGROUND
Previous studies have suggested that hamstring tendons can regenerate following harvesting for anterior cruciate ligament reconstruction.


OBJECTIVE
This "neo-tendon" is a true, functional tendon, not scar tissue.


METHODS
Controlled laboratory study.


METHODS
Semitendinosus tendons were harvested from 35 New Zealand white rabbits using a standard tendon stripper. The rabbits were sacrificed 9 to 12 months following the index procedure and thoroughly evaluated.


RESULTS
Thirty-one rabbits were available at the time of sacrifice. The neo-tendon was present in 26 rabbits but was highly variable in size and location of its tibial insertion. Histologic and immunohistochemical staining confirmed that the regenerate tissue was indeed tendon with normal cellularity, organization, and immunolocalization of type I collagen. Electron microscopy showed regeneration of organized collagen tissue that simulated native tendon but with a smaller cross-sectional diameter. Functionally, the neo-tendon was able to transmit force across the musculotendinous junction but at a significantly slower rate than the opposite, control leg. Biomechanical properties of the neo-tendon were significantly less than the control side. Biochemical analysis revealed that the neo-tendons contained glycosaminoglycans and collagen, but levels were significantly lower than normal tendons.


CONCLUSIONS
Semitendinosus tendons regenerate with biologically reactive tendinous tissues in an animal model. This tissue has many of the characteristics of a normal tendon but appears to be inferior to the original musculotendinous unit at 9- to 12-month evaluation. Further characterization of the "lizard tail phenomenon" is still needed.


CONCLUSIONS
Hamstring tendon regrowth may have a dramatic impact on postoperative function of patients who undergo anterior cruciate ligament reconstruction with these tendons. Further modulation of this regeneration may further reduce graft harvesting morbidity.
Gill
Sanjitpal S
SS
Department of Orthopaedic Surgery, University of Charlottesville, Charlottesville, VA 22903, USA.
Turner
Maria A
MA
Battaglia
Todd C
TC
Leis
Henry T
HT
Balian
Gary
G
Miller
Mark D
MD
D000818:Animals; D001696:Biomechanical Phenomena; D024042:Collagen Type I / Q000032:analysis / Q000648:ultrastructure; D004594:Electrophysiology; D042783:Endothelial Cells / Q000378:metabolism; D006025:Glycosaminoglycans / Q000032:analysis; D008854:Microscopy, Electron; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000502:physiology; D011817:Rabbits; D012038:Regeneration / Q000502:physiology*; D013194:Staining and Labeling; D013710:Tendons / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure*; D013718:Tensile Strength / Q000502:physiology; D013977:Tibia / Q000601:surgery; D016474:Weight-Bearing / Q000502:physiology
D024042:Collagen Type I; D006025:Glycosaminoglycans