Minimally invasive desmotomy of the accessory ligament of the deep digital flexor tendon in horses

This retrospective study describes ultrasound guided desmotomy of the accessory ligament of the deep digital flexor tendon in 35 cases, and a modification of this procedure using an adapted surgical instrument. The procedure was successful in 97% of cases. Wound healing was excellent in all except 4 cases. Corrective shoeing prior to surgery contributes to success. The procedure can be performed on the standing horse and offers the advantages of minimally invasive surgery which include: reduced incision length, reduced morbidity and improved cosmetic outcome. The adapted surgical instrument can be an alternative to isolate the ligament under ultrasound guidance.     

Retrospective study of outcome following desmotomy of the accessory ligament of the deep digital flexor tendon for type 1 flexural deformity in Thoroughbreds

Objective Determine the long‐term outcome for Thoroughbreds undergoing desmotomy of the accessory ligament of the deep digital flexor tendon (DAL‐DDFT) for type 1 flexural deformity of the distal interphalangeal joint (DIPJ). Design Retrospective matched cohort study Procedure Medical records were retrieved over a 17‐year period for Thoroughbreds that underwent DAL‐DDFT for type 1 flexural deformity. Long‐term outcome was determined by analysis of race records and comparison with maternal siblings. Comparisons between cases and controls included 2‐year‐old, 3‐year‐old and total career performance data. Results There were 46 cases of DAL‐DDFT. The mean age at surgery was 151 days (median 118, range 2–562); 48% of case horses and 77% of 90 controls started in a race. For case horses that did race, the time to first race, total number of starts and prize money per race were not significantly different to maternal siblings. Age at the time of surgery did not alter the likelihood of starting a race. Conclusion Thoroughbreds undergoing DAL‐DDFT for type 1 flexural deformity of the DIPJ are less likely to race when compared with their maternal siblings. For those that do race, the time to first race, total races and earnings per race are not different from controls. There is no evidence to suggest that age at the time of surgery influences the likelihood of racing.     

Evaluation of a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon in horses

Objective: To develop a tenoscopic approach for desmotomy of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) in horses. Study Design: Experimental. Animals: Cadaveric forelimbs (n=10) and 4 forelimbs from 2 horses anesthetized for terminal teaching procedures, and 12 forelimbs of 6 experimental horses. Methods: Saline distention of the carpal flexor sheath facilitated insertion of an arthroscope into the distal medial aspect of the sheath between the AL‐DDFT and deep digital flexor tendon (DDFT). Location of an instrument portal on the lateral aspect of the metacarpus was identified with a needle. The lateral aspect of the AL‐DDFT was transected and the arthroscope and instrument were switched to transect the remaining fibers on the medial aspect. Cadaveric specimens were dissected for evaluation. Experimental horses were monitored for 30 days postoperatively. Results: Minor complications including incomplete division of the AL‐DDFT and shallow incision into the suspensory ligament were observed in some cadaver specimens. The AL‐DDFT was completely transected in all experimental horses with no suspensory ligament damage. Mean±SD surgical time (incision to skin closure) was 28.3±11.8 minutes. On ultrasonographic examination, transection of the AL‐DDFT was complete in all experimental horses. Minor DDFT fiber disruption was noted in 1 limb during ultrasound examination at day 30. Conclusions: A tenoscopic approach through the carpal flexor sheath provided adequate access for desmotomy of the AL‐DDFT.     

Retrospective analysis of distal limb conformation and lameness in mature horses after desmotomy of the accessory ligament of the deep digital flexor tendon for management of a flexural deformity

Mature horses that present with flexural deformity of the distal interphalangeal joint and lameness isolated to the foot may obtain long‐term benefits from desmotomy of the accessory ligament of the deep digital flexor tendon (ALDDFT). This retrospective analysis of medical records and radiographs included 13 horses, aged ≥2 years, presented for lameness isolated to the hoof region and diagnosed with flexural deformity of the distal interphalangeal joint. Radiographic angles of the hoof and distal interphalangeal joint and lameness scores were compared before and after desmotomy of the ALDDFT. Follow‐up data including the ability to perform the intended use were obtained at least one year after surgery. There was improvement in the angle between the dorsal aspect of the third phalanx and the weightbearing surface of the hoof, improved alignment between the dorsal hoof wall and dorsal aspect of the third phalanx, and improved alignment of the distal interphalangeal joint. Lameness was decreased in 9/13 horses and 10/13 horses were performing at their level of intended use. Evidence of improved hoof conformation and lameness following desmotomy of the ALDDFT in lame horses with flexural deformity of the distal interphalangeal joint would indicate this procedure should be considered in mature horses.     

Electrosurgical tenoscopic desmotomy of the accessory ligament of the superficial digital flexor muscle (proximal check ligament) in horses

Objective: To report a tenoscopic technique using monopolar electrosurgery to transect the accessory ligament of superficial digital flexor muscle (AL‐SDFM) and outcome in 33 horses. Study Design: Case series. Animals: Horses (n=33). Methods: Medical files and surgery video recordings of horses that had AL‐SDFM desmotomy performed by tenoscopy with monopolar electrosurgical electrodes were reviewed. Results: Of 33 horses, 24 were Standardbred racehorses with surgery performed bilaterally for superficial digital flexor tendonitis and 9 horses had flexural deformity. Severe (n=6) and mild (6) intrathecal hemorrhage was the most common intraoperative complication. Large intrathecal vessels including the nutrient artery were successfully electrocoagulated and AL‐SDFM transection was completed. Clear/serosanguinous drainage from skin incisions was observed for 4.3±3.3 days (mean, SD). Protracted wound drainage for >4 days occurred in 10 horses, principally in the group treated for flexural deformities (P=.01). Conclusions: Sixty‐four AL‐SDFM were transected under tenoscopic observation using monopolar electrodes. Electrocoagulation of large intrathecal vessels, including the nutrient artery, was possible in all cases and allowed completion of desmotomy. Postoperative wound care was similar to routine tenoscopy in most (70%) horses. Aseptic protracted wound drainage was observed in 30% of horses (principally those with flexural deformity), and led to a prolonged hospitalization.     

Ultrasonographic anatomy of the accessory ligament of the superficial digital flexor tendon in horses.

The ultrasonographic anatomy of the accessory ligament of the superficial digital flexor tendon (AL-SDFT) in the horse is presented. Comparison between anatomical sections of isolated limbs and ultrasound scans of the distal antebrachium in sound horses enabled the authors to establish the normal reference ultrasonographic images of this structure. The AL-SDFT inserts 7-14 cm above the antebrachiocarpal joint on the palmaromedial aspect of the radius. Ultrasonographically it appears as an uniformly echogenic structure located deep to the median artery. The knowledge of ultrasonographic anatomy is essential for identification of abnormal images and assessment of AL-SDFT damage.     

Two clinical manifestations of desmopathy of the accessory ligament of the deep digital flexor tendon in the hindlimb of 23 horses

REASONS FOR PERFORMING STUDY: Desmopathy of the accessory ligament of the deep digital flexor tendon (ALDDFT) in the hindlimb is an unusual cause of lameness in horses, and reports of the condition are sparse. OBJECTIVES: To describe the clinical and ultrasonographic findings, therapy and outcome of 23 horses treated for desmopathy of the ALDDFT in the hindlimb. METHODS: Records of 23 horses with ultrasonographic evidence of desmopathy of the ALDDFT in one or both hindlimbs from 3 referral centres were reviewed retrospectively. Age, breed, sex, duration and nature of clinical signs, results of clinical and lameness examinations, treatment and outcome were recorded. RESULTS: In 13 horses (Group A), there was an acute onset of unilateral lameness. Ten horses (Group B) had an insidious or sudden onset of postural abnormality. There were 10 cobs, 5 British native-breed ponies and 8 horses of various larger breeds. Twenty horses were used for general purposes, and mean age was 12 years. Enlargement of the ALDDFT in the affected hindlimb(s) was identified in all horses. In 44% of horses, ultrasonographic abnormalities were localised to part of the ALDDFT. Treatment included box-rest and controlled exercise, and 10 horses were subjected to desmotomy or desmectomy of the ALDDFT. Seventy-three percent of horses in Group A returned to full function, while 90% of those in Group B remained lame. CONCLUSIONS: Two distinct clinical conditions are associated with the ALDDFT of the hindlimb. Traumatically induced injury resulting in acute onset lameness appears to have a favourable prognosis, with most horses returning to previous work. However, postural changes, once present, are irreversible and indicate a poor prognosis. POTENTIAL RELEVANCE: Desmopathy of the ALDDFT should be recognised as a potential cause of hindlimb lameness and this study provides clinical and prognostic information. Knuckling and/or semiflexion of the metatarsophalangeal joint may accompany the condition; therefore, if a horse is presented with a flexural deformity of this joint, desmopathy of the ALDDFT should be considered as a primary differential diagnosis.     

Desmotomy of the accessory ligament of the deep digital flexor tendon in the forelimb of 24 horses 2 years and older

Objective: To report outcome after desmotomy of the accessory ligament of the deep digital flexor tendon (ALDDFT) in adult horses (≥2 years) for treatment of desmitis of the ALDDFT or flexural deformity of the distal interphalangeal joint (FDDIJ). Study Design: Case series. Animals: Horses with desmitis of the ALDDFT (n=9) and FDDIJ (n=15). Methods: Records (April 1996–July 2008) of 24 adult horses (mean age, 6.7 years) that had ALDDFT desmotomy were reviewed. Follow‐up data was obtained 12–120 months after desmotomy. Results: Outcome was available for 22 horses; 18 (82%; 6 of 8 horses with desmitis of the ALDDFT and 12 of 14 with FDDIJ) returned to their intended use within 6–24 months (mean, 12 months). Conclusion: In mature horses, ALDDFT desmotomy resulted in successful return to intended use in most horses with ALDDFT desmitis (75%) or FDDIJ (86%).     

Desmotomy of the accessory ligament of the deep digital flexor tendon for treatment of chronic deep digital flexor tendinopathy in three Quarter Horses

Effective treatments for horses diagnosed with severe deep digital flexor (DDF) tendinopathy are limited. In this study, three Quarter Horses diagnosed with severe bilateral DDF tendinopathy underwent bilateral desmotomy of the accessory ligament of the DDF tendon after failing to respond to conservative therapy. Lameness markedly improved in all three horses. Given that severe DDF tendinopathy is typically associated with persistent or recurrent lameness, desmotomy of the accessory ligament of the DDF tendon might be a treatment option to alleviate lameness in horses with DDF tendinopathy. This treatment option appears promising; however, a larger number of cases is necessary to support the results in these three horses.     

Aseptic tenosynovitis of the carpal flexor sheath caused by rupture of the accessory ligament of the deep digital flexor tendon

A mare was evaluated for acute left forelimb lameness with effusion of the carpal flexor sheath. No osseous abnormalities were noted during radiographic examination. Significant disruption of the accessory ligament of the deep digital flexor tendon was seen during ultrasonographic examination. Carpal sheath effusion and lameness resolved after medical treatment.     

Myofibroblasts in the accessory ligament (distal check ligament) and the deep digital flexor tendon of foals

OBJECTIVE: To demonstrate myofibroblasts in the accessory ligament of the deep digital flexor tendon (ie, distal check ligament) and deep digital flexor tendon of clinically normal foals. SAMPLE POPULATION: Tissue specimens from 25 foals that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease. PROCEDURE: The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by immunohistochemical staining specific for alpha-smooth muscle actin (alpha-SMA). RESULTS: Most of the cells in the distal check ligament and deep digital flexor tendon of all foals stained positive for alpha-SMA. CONCLUSION AND CLINICAL RELEVANCE: Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically normal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein alpha-smooth muscle actin could inhibit the myofibroblasts' ability to contract, thus providing a rationale for tetracycline administration as a treatment of distal interphalangeal joint flexor deformity in foals.     

Anatomical, magnetic resonance imaging and histological findings in the accessory ligament of the deep digital flexor tendon of forelimbs in nonlame horses

Reasons for performing the study: Detailed magnetic resonance imaging (MRI) and histological appearances of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) have not been documented previously in detail. Objectives: To: 1) describe anatomical connections between the AL‐DDFT and adjacent structures; 2) describe high‐field and low‐field MRI and histological appearances of the AL‐DDFT in the forelimb of horses with no carpal or proximal metacarpal pain; and 3) assess the relationship between age, breed, gender, height, weight and MRI findings. Methods: Ten forelimbs were dissected to determine anatomical relationships among the AL‐DDFT and adjacent structures. High‐ and low‐field MR images of the AL‐DDFT and related structures from 29 cadaver limbs of nonlame horses were analysed subjectively and objectively. The relationship between age, breed, gender, height, weight and MRI findings was assessed using a Chi‐squared test. Twelve ALs‐DDFT were examined histologically. Histological and MRI findings were compared subjectively. Results: Fibrous bundles were seen between the AL‐DDFT and the lateral aspect of the superficial digital flexor tendon (n = 9) and the DDFT (n = 2). The AL‐DDFT had low to intermediate signal intensity in most limbs in most high‐field and low‐field MRI sequences. In 69% of limbs, oblique bands of higher signal intensity than the rest of the ligament were identified in high‐field images of the AL‐DDFT. The cross‐sectional area of the AL‐DDFT in the proximal 7 cm of the metacarpal region ranged from 68.1–299 mm². There was no significant relationship between age, gender, weight or height and either the cross‐sectional area of the AL‐DDFT or the presence of oblique higher signal intensity bands. Histological examination revealed that the AL‐DDFT had thick collagen bundles arranged in large crimps and sometimes crossing in oblique directions. The cellularity was greater than in the deep digital flexor tendon in all limbs. Conclusion and potential relevance: The large variability in the MRI appearance and size of the AL‐DDFT in nonlame horses should be borne in mind when interpreting MR images of lame horses.     

Desmitis of the accessory ligament of the deep digital flexor tendon: 27 cases (1986-1990).

Desmitis of the accessory ligament of the deep digital flexor tendon (ALDDFT) was diagnosed in 27 horses between September 1986 and December 1990. The first observed clinical sign in four horses was localised swelling in the proximal metacarpus. Twenty horses became lame suddenly during a work period and most developed swelling within 24 h of exercise. The injury was confirmed by ultrasonographic examination. Ten of 13 horses with uncomplicated desmitis of the ALDDFT resumed full work, within three to nine months of the onset of clinical signs, without recurrence of clinical signs in the period of follow-up (nine months to four years). Three horses presented with concurrent acute desmitis of the ALDDFT and superficial digital flexor (SDF) tendonitis and two horses had a history of SDF tendonitis; none of these resumed full work.     

Long-term effects of desmotomy of the accessory ligament of the deep digital flexor muscle in standardbreds: 23 cases (1979-1989).

Desmotomy of the accessory ligament of the deep digital flexor muscle (inferior check desmotomy) permitted Standardbred foals affected with flexural deformities to reach their full athletic potential. Long-term effects of inferior check desmotomy were examined in 23 Standardbreds over a 10-year period. Six of 11 foals that were treated surgically either raced 6 times and obtained a race record or were training sound (if yearlings). All 12 horses with flexural deformity that did not receive an inferior check desmotomy had an unfavorable outcome (no race record). Foals that had surgery performed at a younger age apparently had a better chance of racing or training sound because no foals treated surgically after 8 months of age had a favorable outcome and only 1 foal that was older than 5 months at the time of surgery had a favorable outcome. In 5 foals that had surgery with an unsuccessful outcome, 3 were greater than or equal to 1 year old at the time of surgery and were lame when training was started on the limb(s) with the desmotomy.     

Superior check ligament desmotomy for treatment of superficial digital flexor tendonitis in Thoroughbred and Standardbred horses

Summary Bilateral superior check ligament desmotomy was performed on 31 Thoroughbred and 17 Standardbred horses as the sole method of treatment for superficial digital flexor tendonitis. Horses resumed racing between 6 and 19 months after surgery. Horses that were able to compete in 5 or more races without injury to the tendon again were considered to have had a successful return to racing. Twenty-five Thoroughbreds were suitable for later study and 13 of these (52%) raced on 5 or more occasions. Fifteen Standardbreds were suitable for later study and 10 of these (66%) raced on 5 or more occasions. Within the racing industry it is generally thought that about 20 to 30% of horses with superficial digital flexor tendonitis can return to racing after a prolonged rest. The results of this study suggest that bilateral superior check ligament desmotomy may improve the prognosis for a horse returning to racing after injury to the superficial digital flexor tendon.