title: Tendon to bone tunnel healing--a study on the time-dependent changes in biomechanics, bone remodeling, and histology in a rat model.
abstract: Tendons and ligaments attach to bone through a transitional connective tissue with complex biomechanical properties. This unique tissue is not regenerated during healing, and surgical reattachment therefore often fails. The present study was designed to evaluate tendon healing in a bone tunnel and to evaluate the utilized rat model. Wistar rats (n = 61) were operated with the Achilles tendon through a bone tunnel in the distal tibia. Healing was evaluated at 2, 3, 4, and 12 weeks by biomechanical testing, bone mineral density and histology. After 2 weeks median (interquartile range) pull-out force was 2.2 N (1.9). The pull-out force increased chronologically, by 12 weeks fivefold to 11.2 N (11.4). Energy absorption, stiffness, and bone mineral density increased similarly. The histological analyses showed inflammation at early stages with increasing callus by time. Our data showed a slow healing response the first 4 weeks followed by an accelerated healing period, favoring that most of the gain in mechanical strength occurred later than 4 weeks postoperatively. These findings support the concern of a vulnerable tendon bone tunnel interface in the early stages of healing.
authors.affiliation: Department of Orthopaedic Surgery, Division of Surgery and Clinical Neuroscience, Oslo University Hospital, Kirkeveien 166, N-0450, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Oslo, Norway.
authors.forename: Geir Aasmund
authors.initials: GA
authors.lastname: Hjorthaug
authors.forename: Jan Erik
authors.initials: JE
authors.lastname: Madsen
authors.forename: Lars
authors.initials: L
authors.lastname: Nordsletten
authors.forename: Finn P
authors.initials: FP
authors.lastname: Reinholt
authors.forename: Harald
authors.initials: H
authors.lastname: Steen
authors.forename: Sigbjorn
authors.initials: S
authors.lastname: Dimmen
mesh_terms: D000125:Achilles Tendon / Q000601:surgery*; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D016723:Bone Remodeling; D005260:Female; D019637:Orthopedic Procedures; D011859:Radiography; D011897:Random Allocation; D017208:Rats, Wistar; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*; D014945:Wound Healing
keywords: biomechanical testing; histology; model; rat; tendon-to-bone healing