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ACQUIRED FLEXURAL DEFORMITY OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES: TREATMENT BY DESMOTOMY OF THE ACCESSORY LIGAMENT OF THE DEEP DIGITAL FLEXOR TENDON A Retrospective Study Nicolai Jansson, DVM, PhD~; Hans V. SCnnichsen, DVM, Dr.med.vet.
INTRODUCTION SUMMARY
Hospital records of 29 horses treated by desmotomy of the accessory ligament of the deep digital flexor tendon for correction of acquired flexural deformity of the distal interphalangeal joint in one or both forelimbs were reviewed and evaluated retrospectively. Information on correction of the deformity, cosmetic appearance of the surgery site, and current use of the horses was obtained by interviews with the owners. At the time of surgery, 27 horses were less than one year old and two horses were more than one year old. Eleven months to five years after surgery, 26 horses had normal appearance of the hoof and limb, and 26 horses had acceptable cosmetic appearance of the surgery site due to no or minimal scarring. At the time of interview, all but two of the I I horses more than three years old were in full training. It is concluded that desmotomy of the accessory ligament of the dcep digital flexor tendon is an effective and cosmetically acceptable treatment for acquired flexural deformity of the distal interphalangeal joint in the horse. Authors' Address: Section o1 Large Animal Surgery. Dept. of Clinncal Studies, The Royal Veterinary and Agricultural University, Bulowsvel 13. DK-1870 Frederiksberg C. DENMARK. ~As of September 1, 1995. the address of the first author is: Department of Clinical Sciences, College of Veterinary Medicine. Cornell Unwersaty. Ithaca. New York 14853.
Volume 15, Number 8, 1995
Acquired flexural detbrmities in the horse occur more frequently in the forelimbs, and often both forelimbs are affected. 1.2 The term "contracted tendons" has previously been used to describe the conditions, and subdivisions into involvement of the deep digital flexor tendon, the superficial digital flexor tendon, or both have been made. The term "contracted tendons" should be avoided as the tendons are actually not contracted, rather functionally too short relative to the skeletal structures and this has lead to the term "'flexural deformities" which has now gained general acceptance? ,3 Acquired flexural deformities are subdivided according to the involved region of the limb and two clinical entities are recognized, namely flexural deformity of the distal interphalangeal joint, which eventually leads to the characteristic boxy foot where the dorsal hoof wall and the heel are practically the same length, and flexural deformity of the metacarpophalangeal joint. TM The etiopathogenesis of acquired flexural deformities is complex and not fully understood, 1'3-8 but the main problem is a functional shortening of the involved flexor tcndon or tendons. Classically, flexural dcformity of the distal interphalangeal joint was considered to be a deep digital flexor tendon problem, whereas flexural deformity of the metacarpophalangeal joint was recognized as a superficial digital flexor tendon problem. However, the dccp digital flexor tcndon has been considered to play an 353
important role in the development of metacarpophalangeal joint deformity as well. 4,s Flexural deformity of the distal interphalangeal joint tends to occur early in life, and the condition is primarily seen in foals from six weeks to six months of age. a The treatment for flexural deformity of the distal interphalangeal joint is conservative or surgical according to the duration and severity of the condition. Conservative measures include diet reduction, moderate controlled exercise on a firm surface, corrective trimming and shoeing and, if necessary, judicious use of anti-inflammatory drugs. 1,3-8 Corrective trimming and shoeing are typically achieved by lowering the heels and applying a shoe with a toe extension to prolong breakover, but recently the use of a raised (wedged) heel shoe has been advocated, s Surgical treatment for flexural deformity of the distal interphalangeal joint by desmotomy of the accessory ligament of the deep digital flexor tendon was originally described by Lysholt & SCnnichsen, 1~and this method has since gained widespread use in the surgical management of the condition. 1-3'8'~1-20Transecting the accessory ligament places more load on the deep digital flexor tendon, causing the muscle-tendon unit to lengthen. 1~ Before introducing this technique as a treatment for flexural deformity of the distal interphalangeal joint in foals, it had been described as an adjunct to the management of tendon contracture in adult horses. 21 More severe cases of flexural deformity of the distal interphalangeal joint where the dorsal hoof wall is flexed past vertical have been treated successfully by deep digital flexor tenotomy.22'23 Transection of the deep digital flexor tendon is a radical procedure, but secondary contracture of the joint capsule and periarticular soft-tissue structures may be the reason why this technique does not result in marked elevation of the toe during weight bearing characteristic of traumatic rupture of this tendon. 22 The purpose of the present study is to evaluate the results obtained by desmotomy of the accessory ligament of the deep digital flexor tendon in 29 horses affected with acquired flexural deformity of the distal interphalangea] joint in one or both forelimbs.
MATERIALS AND METHODS
Hospital records of 29 horses with acquired flexural deformity of the distal interphalangeal joint in one or both forelimbs that had been treated by desmotomy of the accessory ligament of the deep digital flexor tendon at the Royal Veterinary and Agricultural University of Copenhagen from 1989 to 1993 were reviewed. In none of the patients, the dorsal hoof wall was flexed past vertical. The age of the patients ranged from two to 14 months (mean, 5.9 months), and 15 were males and 14 were females. The patient group consisted of 22 Warmbloods, 354
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Figure 1. Diagram of the equine foot indicating location of flexor tendons, accessory ligament of the deep digital flexor tendon, and suspensory ligament (from Sonnichsen 1982). five Ponies, one Standardbred, and one Arabian. Nineteen horses were unilaterally affected whereas 10 were bilaterally affected. Information on correction of the deformity, cosmetic appearance of the surgery site, and current use of the horse was obtained by interviews with the owners. Correction of the deformity was regarded as successful when the owner stated that the affected limb was appearing normal with no signs of "boxy foot." Cosmetic appearance of the surgery site was judged to be acceptable when the owner stated that the scarring was either invisible or minimal. Marked scarring and/or white hair growth were considered to be unacceptable cosmetic appearances. Surgical technique
The operation was performed with the horse under general anesthesia and in lateral recumbency, with the affected limb uppermost. A skin incision located at the junction of the middle and proximal thirds of the metacarpus was made on the lateral side of the limb along the dorsal border of the deep digital flexor tendon, the total length of the incision being approximately 5 cm. The underlying fascia and paratenon were incised, hereby revealing the deep digital flexor tendon and the accessory ligament (Fig. 1). Using blunt dissection, the accessory ligament was loosened from its attachments, isolated and transected using a scalpel. By extending the toe and observing a gap in the ligament, it was confirmed that the transection was complete. The fascia was closed with a continuous polyglycolic acid suture and the skin was closed using either an intradermal suture of polyglycolic acid or interrupted nylon sutures. Hereafter, a sterile bandage was applied. In bilaterally affected cases, the horse was turned over on its back and the procedure repeated on the contralateral forelimb. JOURNAL OF EQUINE VETERINARY SCIENCE
Finally, the heels were trimmed and a toe extension established using an acrylic product. Postoperatively, the owners were informed that the horses should receive regular hoof care every three weeks. In the first two weeks after the operation, daily controlled exercise on a firm surface and of at least 20 minutes duration was recommended. Hereafter, free pasture exercise was allowed.
RESULTS
Of the 29 surgeries performed from 1989 to 1993, 26 (90%) were considered to be successful, whereas 2 (7%) were judged to be unsuccessful and one (3%) to be improved. The cosmetic appearance of the surgery site was acceptable due to no or minimal scarring in 26 cases (90%), whereas the scarring was marked in two cases. White hair growth at the surgery site was reported in two cases. Of the 11 horses more than three years old at the time of interview, all but two were in full training. Three horses less than three years old were also in full training. Fourteen of the horses were at the time of interview not yet in training, two horses had died of causes unrelated to the flexural deformity, and one horse was used as a broodmare. Of those horses in training, eight horses were used for pleasure riding, two were used for pleasure driving, one horse competed in 3day events, and one was racing (Standardbred).
DISCUSSION
The results of the present study agree well with those of previous reports. 1~ The high success rate of desmotomy as shown in this study clearly indicates that the operation is an effective treatment for acquired flexural deformity of the distal interphalangeal joint in horses. Excessive scarring at the surgery site in occasional cases have been reported, 137 but generally the cosmetic appearance is acceptable as demonstrated in the present study. Measures to minimize scarring include limited exercise in the first two weeks postoperatively TMand the application of a bandage at the surgery site. A medial approach has been advocated for cosmetic reasons, 3 but this technique is somewhat more difficult due to the medial location of the major palmar vessels. As an important adjunct to surgery, hoof trimming and shoeing by lowering the heels and applying a toe extension have been described, the purpose of this being restoration of normal alignment of the distal interphalangeal joint and establishment of a leverage acting to extend this joint. 1-3 In the present study, all patients received immediate postoperative heel trimming, and an acrylic shoe with a toe extension was applied. Recently, a somewhat different approach to corrective trimming and shoeing of foals with flexural deformity of the distal interphalangeal joint has Volume 15, Number 8, 1995
been recommended. 9 This method involves the use of a raised (wedged) heel shoe to alleviate the pull of the deep digital flexor tendon on the third phalanx. In so doing, it may relieve pain and thereby reduce muscle contracture, a Correction of the deformity is usually observed immediately after recovery from anesthesia but in some cases, however, it may take a few days until correction is observed. Functionally, the accessory ligament of the deep digital flexor tendon prevents strain of the digital flexor muscle belly during weight bearing, e4 but the severance of the ligament to correct a flexural deformity does not seem to be of any significance as to the long-term use of the horse, iF It can be speculated that scar tissue reunites and restores accessory ligament function. Although the present report is not a long-term study, the data show that all but two of the 11 horses, more than three years old at the time of interview, were in full training, clearly indicating the good prognosis of the operation. In cases of severe flexural deformity of the distal interphalangeal joint, deep digital flexor tenotomy has been reported as an effective surgical treatmenc 22 None of the patients included in the present study had an angle between the dorsal hoof wall and the ground of 90 degrees or more and, therefore, tenotomy was not considered necessary. Flexural deformity of the distal interphalangeal joint develops early in life 1,3,7,8,10,15,17and this corresponds well with the age distribution in the present study where only two patients were more than one year old. The patients had often been treated conservatively for some time before admission for surgery and, therefore, the age at presentation was not identical to the age at onset of the condition, This may account for the more than one-year-old horses in the present study. In conclusion, acquired flexural deformity of the distal interphalangeal joint should initially be managed conservatively by diet reduction, moderate controlled exercise on a firm surface, corrective trimming and shoeing, and, if necessary, use of anti-inflammatory drugs. Rapidly developing cases or lack of response to conservative therapy are indications for surgical treatment, and the treatment of choice is desmotomy of the accessory ligament of the deep digital flexor tendon. The operation carries a high success rate as to normal function, normal appearance of the hoof and toe and cosmetic appearance of the surgery site.
REFERENCES 1.
Auer JA: Flexural deformities. In: Auer JA, ed. Equine
surgery. Philadelphia: WB Saunders Co, 1992;957-971. 2. Wagner von Matthiessen P: Case selection and management of flexural limb deformities in horses: Acquired flexural limb deformities, part 1. Equine Pract 1993; 15:51-55. 3. Barr A: Developmental flexural deformities in the horse. tn pract 1994;I6:182-I88. 4. Mcllwraith CW: Acquired flexure deformities. In: Stashak
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TS, ed. Adams'lameness in horses. Philadelphia: Lea & Febiger, 1987;454-462. 5. Owen JM: Abnormal flexion of the corono-pedal joint or "contracted tendons" in unweaned foals. Equine VetJ 1975; 7: 4045. 6. Rooney JR: Forelimb contracture in the young horse. J Equine Med Surg 1977;1:350-351. 7. Gerring EL: Flexural deformities of the limb in foals. Equine Vet Educ 1989;1:39-41. 8. Munroe G: Pathogenesis and treatment of acquired flexure deformities in horses. Equine Vet Educ 1989;1:62-64. 9. Redden RF: A method for treating club feet. Proc Am Assoc Equine Pract, 34th Ann Conv, 1988;321-324. 10. Lysholt B, Sennichsen HV: Senestyltefod hos fol og plage (in Danish with English summary). Nord Vet Med 1969;21:601608. 11. Sennichsen HV, Christiansen FR: Desmotomia capitis tendinei. Proc European Soc Vet Surg, 11th Congr, 1975;1-2. 12. Sonnichsen HV: Desmotomia capitistendinei. VetAnnual 1977;17:133-135. 13. Sennichsen HV: Desmotomia capitis tendinei (in Danish). Proc 13th Nord Vet Congr, 1978;274-277. 14. Sennichsen HV: Subcarpal check ligament desmotomy for the treatment of contracted deep flexor tendon in foals. Equine Vet J 1982;14:256-257. 15. Mcllwraith CW, Fessler, JF: Evaluation of inferior check ligament desmotomy for treatment of acquired flexor tendon contracture in the horse. JAm VetMedAssoc 1978;172:293-298. 16. Fackelman GE: Equine flexural deformities of
9 NORMAN W. RANTANEN, DVM, MS 9 i
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Presents 1995 Fall Equine Ultrasound 2-Day Short Course f o r Veterinarians
developmental origin. Proc Am Assoc Equine Pract, 26th Ann Conv, 1980; 97-105. 17. Wagner PC, Grant BD, Kaneps A J, Waltrous BJ: Longterm results of desmotomy of the accessory ligament of the deep digital flexor tendon (distal check ligament) in horses. J Am Vet Med Assoc 1985; 187:1351-1353. 18. Dietz O: Diagnostik und Therapie des tendogenen Stelzfusses beim Fohlen (in German with English summary). Mh Vet Med 1985;40:838-840. 19. Stick JA, Nickels FA, Williams MA: Long-term effects of desmotomy of the accessory ligament of the deep digital flexor muscle in Standardbreds: 23 cases (1979-1989)9 J Am Vet Med Assoc 1992;200:1131-1132. 20. Tarr S, Butler D, Shideler RK: Successful treatment of a horse with chronic, severe flexural deformity of the distal interphalangeal joint: A case report. J Equine Vet Sci 1993;13: 711-714. 21. Lewandowski M: An attempt at operative treatment of stilted gait of tendon origin by cutting the caput tendineum (in Polish with English summary). Med Wet 1967;23:321-326. 22. Fackelman GE, Auer JA, Orsini J, von Salis B: Surgical treatment of severe flexural deformity of the distal interphalangeal joint in young horses. J Am Vet Med Assoc 1983; 182:949-952. 23. Lloyd-Bauer P, Fretz PB: Correction of acquired flexural deformity by deep digital flexor tenotomy in a miniature horse. Can Vet J 1989;30:585-589. 24. Shively MJ: Functional and clinical significance of the check ligaments. Equine Pract 1983;5:37-42.
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