title: Nonsurgical treatment and early return to activity leads to improved Achilles tendon fatigue mechanics and functional outcomes during early healing in an animal model.
abstract: Achilles tendon ruptures are common and devastating injuries; however, an optimized treatment and rehabilitation protocol has yet to be defined. Therefore, the objective of this study was to investigate the effects of surgical repair and return to activity on joint function and Achilles tendon properties after 3 weeks of healing. Sprague-Dawley rats (N = 100) received unilateral blunt transection of their Achilles tendon. Animals were then randomized into repaired or non-repaired treatments, and further randomized into groups that returned to activity after 1 week (RTA1) or after 3 weeks (RTA3) of limb casting in plantarflexion. Limb function, passive joint mechanics, and tendon properties (mechanical, organizational using high frequency ultrasound, histological, and compositional) were evaluated. Results showed that both treatment and return to activity collectively affected limb function, passive joint mechanics, and tendon properties. Functionally, RTA1 animals had increased dorsiflexion ROM and weight bearing of the injured limb compared to RTA3 animals 3-weeks post-injury. Such functional improvements in RTA1 tendons were evidenced in their mechanical fatigue properties and increased cross sectional area compared to RTA3 tendons. When RTA1 was coupled with nonsurgical treatment, superior fatigue properties were achieved compared to repaired tendons. No differences in cell shape, cellularity, GAG, collagen type I, or TGF-β staining were identified between groups, but collagen type III was elevated in RTA3 repaired tendons. The larger tissue area and increased fatigue resistance created in RTA1 tendons may prove critical for optimized outcomes in early Achilles tendon healing following complete rupture. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2172-2180, 2016.
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Freedman
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Gordon
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Pankti R
authors.initials: PR
authors.lastname: Bhatt
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.|Department of Kinesiology, Temple University, Philadelphia, Pennsylvania.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Pardes
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.|Department of Kinesiology, Temple University, Philadelphia, Pennsylvania.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Thomas
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.|Department of Biomedical Engineering, Drexel University, Philadelphia, Pennsylvania.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Sarver
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Corinne N
authors.initials: CN
authors.lastname: Riggin
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Jennica J
authors.initials: JJ
authors.lastname: Tucker
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Alexis W
authors.initials: AW
authors.lastname: Williams
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Zanes
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Hast
authors.affiliation: Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Farber
authors.affiliation: Department of Physical Therapy, University of Delaware, Newark, Delaware.
authors.forename: Karin G
authors.initials: KG
authors.lastname: Silbernagel
authors.affiliation: McKay Orthopaedic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Soslowsky
mesh_terms: D000125:Achilles Tendon / Q000293:injuries* / Q000502:physiology / Q000601:surgery; D000818:Animals; D004434:Early Ambulation; D005221:Fatigue / Q000503:physiopathology; D008297:Male; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D013708:Tendon Injuries / Q000601:surgery*
keywords: collagen; fatigue; mechanics; structure-function; ultrasound