Healing characteristics of deep digital flexor tenorrhaphy within the digital sheath of horses

Authors

  • Henry Jann DVM, MS, Diplomate ACVS,

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • Margaret Blaik DVM, Diplomate ACVR,

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • Robert Emerson PhD,

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • Michiko Tomioka DVM,

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • Larry Stein PhD,

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • David Moll DVM, MS, Diplomate ACVS

    1. From the Departments of Veterinary Clinical Sciences, Civil and Environmental Engineering, and Physiological Sciences, Oklahoma State University, Stillwater, OK.
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  • Supported by the Biggs-Oxley Chair for Equine Sports Medicine, OSU Foundation.

  • Address reprint requests to Henry Jann, DVM, Department of Veterinary Clinical Sciences, Oklahoma State University, 001 BVMTH, Stillwater, OK 74078.

Abstract

Objective— To describe the healing characteristics of deep digital flexor tenorrhaphy within the digital sheath.

Study Design— Experimental study.

Animals— Five mature horses.

Methods— Right thoracic limb, deep digital flexor tenorrhaphy was performed within the digital sheath. Limbs were cast in partial flexion using a short limb cast for 6 weeks. Next, extended heel shoes were used for limb support for 14 weeks. Healing was evaluated by sequential ultrasonographic examinations, and limb use was evaluated by force plate analysis. At 26 weeks, mechanical strength and morphologic characteristics of the repair site were evaluated.

Results— Gap (mean, 0.93 cm.) formation was evident in unloaded limbs at 3 weeks. This increased markedly by 6 weeks and was 5 cm at 26 weeks. Demarcation between the deep and superficial flexor tendons decreased as the transected ends adhered to the dorsal surface of the superficial flexor tendon. The intrathecal space was reduced by fibrous tissue. Mean maximum load to failure of the repair tissue was 4,616 ± 3,556 N, with a mean stress of 12.99 ± 2.78 MPa. The repair consistently failed at the adhesion between the transected tendon and the superficial flexor tendon.

Conclusions— Intrathecal tenorrhaphy with external coaptation (in partial limb flexion) for 6 weeks resulted in gap healing, fibrous adhesion between the deep and superficial flexor tendons, fibrous tissue reduction of the intrathecal space, and a pasture-sound horse at 26 weeks.

Clinical Relevance— Without improved methods for immobilizing the deep digital flexor tendon, intrathecal tenorrhaphy is unlikely to result in first intention tendon healing.

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