Spontaneous Rupture of the Proximal Superficial Digital Flexor Tendon: A Clinical Syndrome in Aged Equids

Acute rupture of the proximal superficial digital flexor tendon (SDFT) can occur spontaneously in older horses resulting in severe pain and prolonged lameness. Pasture soundness is achievable but requires long term rest and rehabilitation. Authors’ addresses: Department of Surgical & Radiological Sciences (Vaughan, Whitcomb, Galuppo) and William R. Pritchard Veterinary Medical Teaching Hospital (Shields), School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616; e-mail: mevaughan@ucdavis.edu.

1. Introduction

Injury to the SDFT is a well-documented cause of lameness in horses of all ages and disciplines; however, acute rupture of the SDFT has been infrequently described.

2. Materials and Methods

Records were reviewed for equids presenting for metacarpal ultrasound from August 2003 to July 2013. Cases were included if complete rupture of the SDFT was detected at any location within the carpal canal or metacarpal region.

3. Results

One mule and 13 horses were identified, ranging in age from 15 to 30 years. Affected equids were retired or lightly ridden (10), show jumpers (3), or breeding stock (1). All presented for concurrent swelling and lameness of the affected limb, graded as severe in 12 of 14 cases. SDFT rupture was unilateral (13) or bilateral (1 mule). All ruptures occurred in the carpal canal and proximal metacarpal region. Concurrent carpal sheath effusion (5), superior check ligament desmitis (2), and carpal flexor retinaculum rupture (1) were also noted. Recheck ultrasound revealed substantial improvement in 4 horses. The mule was euthanized after diagnosis. Six horses attained at least pasture soundness, including 3 used for light riding, 1 breeding stallion, and 2 that were retired. Four were retired due to lameness, including 2 that ruptured the contralateral SDFT. One remains in rehabilitation, and 2 were lost to follow-up.

4. Conclusion

Spontaneous rupture of the proximal SDFT should be considered in older horses or mules with severe acute lameness and SDFT swelling. Affected equids have a fair prognosis for pasture soundness after prolonged rehabilitation.

Acknowledgments

Conflicts of Interest

The Authors declare no conflicts of interest.