Sarah N. Sampson

Desmitis of the Distal Digital Annular Ligament in Seven Horses: MRI Diagnosis and Surgical Treatment

OBJECTIVE (1) To describe the clinical signs and abnormalities observed on magnetic resonance imaging (MRI) in 7 horses with desmitis of the distal digital annular ligament (DDAL); (2) to describe the normal magnetic resonance (MR) appearance and thickness of the DDAL in health; and (3) to describe a tenoscopic surgical technique for treating horses with desmitis of the DDAL. STUDY DESIGN Retrospective study. ANIMALS Horses (n=7) with desmitis of the DDAL. METHODS MR examinations of 20 sound horses were reviewed to determine the normal appearance of the DDAL. Dimensions obtained from these images were compared with MR findings from 7 horses with DDAL desmitis. Desmitis of the DDAL was treated by tenoscopic surgery and outcome assessed. RESULTS Horses with DDAL desmitis had lameness (grade 2-3 out of 5) that improved after a palmar digital nerve block. The affected DDAL was enlarged and had an abnormal signal on MR images of the feet. After tenoscopy and DDAL transection, 5 horses returned to athletic performance, including 2 horses that failed to respond to medical treatment and rest before surgery. CONCLUSION Primary desmitis of the DDAL is a cause of lameness in horses. Transection of the DDAL allowed 5 horses with this injury to return to athletic performance. CLINICAL RELEVANCE DDAL desmitis should be included in the differential diagnoses of horses with lameness that improves after a palmar digital nerve block but have no abnormalities observed on radiographs of the feet. Tenoscopic surgical transection of the DDAL is an effective treatment for some horses.

Response to injection of the navicular bursa with corticosteroid and hyaluronan following high-field magnetic resonance imaging in horses with signs of navicular syndrome: 101 cases (2000–2008)

OBJECTIVE To determine treatment outcome on the basis of pathological changes identified on MRI and lameness duration in horses with navicular syndrome that underwent injection of corticosteroid and hyaluronan into the navicular bursa. DESIGN Retrospective case series. ANIMALS 101 horses with navicular syndrome. PROCEDURES Medical records of horses with signs of navicular syndrome evaluated between January 2000 and December 2008 were reviewed. Data on signalment, use of the horse, history, affected limbs, duration of lameness, findings on lameness examination, radiographic findings, MRI findings, treatment, and outcome were collected from the medical records. Follow-up information was obtained a minimum of 10 months after navicular bursa injection. RESULTS Following navicular bursa injection, 76 of 101 (75%) horses returned to their intended use for a mean of 9.66 months, and 35 (35%) were sound at follow-up. Horses that had been lame for < 6 months before treatment were significantly more likely to return to their intended use, have a longer positive response to treatment, and be sound at follow-up, compared with horses that had a longer lameness history. Horses with primary deep digital flexor (DDF) tendonitis responded best to navicular bursa injection with rest and rehabilitation, followed by horses with navicular bursitis and horses with DDF tendonitis and adhesions to the collateral sesamoidean ligament of the distal sesamoid (navicular) bone. Horses with scar tissue in the proximal portion of the navicular bursa, adhesions from the navicular bone to the DDF tendon, or multiple abnormalities did not respond as well to treatment. CONCLUSIONS AND CLINICAL RELEVANCE Response to navicular bursa injection with corticosteroid and hyaluronan in horses with navicular syndrome was dependent on the disease process detected on MRI and duration of lameness.

MRI FINDINGS IN 232 HORSES WITH LAMENESS LOCALIZED TO THE METACARPO(TARSO)PHALANGEAL REGION AND WITHOUT A RADIOGRAPHIC DIAGNOSIS

Two hundred and thirty-two horses with lameness localized to the metacarpo(tarso)phalangeal (MCP/MTP) region without a radiographic diagnosis were evaluated. All horses had high-field magnetic resonance (MR) imaging of the MCP/MTP region performed for the lame limb and the contralateral limb for comparison. There were 46 horses that had bilateral abnormalities in the forelimbs; 27 of these horses were not lame in the contralateral limb at the time of examination. Bilateral hind limb abnormalities were observed in 37 horses; 22 horses were not lame in the contralateral limb. Soft tissue abnormalities alone were observed in 218 limbs (162 horses). Subchondral bone and articular cartilage abnormalities alone were observed in 43 limbs (34 horses). A combination of soft tissue, subchondral bone, and cartilage abnormalities were observed in 64 limbs (36 horses). The distribution of primary abnormalities was as follows; oblique distal sesamoidean ligament desmitis (73 limbs in 56 horses), straight distal sesamoidean ligament desmitis (44 limbs in 38 horses), chronic subchondral bone injuries (15 limbs in 12 horses), suspensory ligament branch desmitis (14 limbs in 12 horses), collateral ligament desmitis (12 limbs in 12 horses), tendonitis of the superficial and deep digital flexor tendons (10 limbs in 10 horses), osteochondral defects greater than 1 cm (nine limbs in six horses), osteochondral defects less than 1 cm (eight limbs in seven horses), bone marrow lesions (six limbs in five horses), intersesamoidean ligament desmitis (five limbs in four horses). MR imaging is useful in diagnosing bone and soft tissue injuries when radiographs and ultrasound fail to yield a diagnosis.

Medical treatment of horses with deep digital flexor tendon injuries diagnosed with high-field-strength magnetic resonance imaging: 118 cases (2000–2010)

OBJECTIVE To describe the location and severity of deep digital flexor tendon (DDFT) lesions diagnosed by means of high-field-strength MRI in horses and to identify variables associated with return to activity following medical treatment. DESIGN Retrospective case series. ANIMALS 118 horses. PROCEDURES Medical records of horses with DDFT injury diagnosed with MRI over a 10-year period (2000-2010) and treated medically (intrasynovial administration of corticosteroids and sodium hyaluronan, rest and rehabilitation, or both) were reviewed. History, signalment, use, results of lameness examination and diagnostic local anesthesia, MRI findings, and treatment details were recorded. Outcome was obtained by telephone interview or follow-up examination. Horses were grouped by predictor variables and analyzed with logistic regression to identify significant effects. RESULTS Overall, of 97 horses available for follow-up (median time to follow-up, 5 years; range, 1 to 12 years), 59 (61%) returned to activity for a mean duration of 22.6 months (median, 18 months; range, 3 to 72 months), with 25 (26%) still sound at follow-up. Of horses with mild, moderate, and severe injury, 21 of 29 (72%), 20 of 36 (56%), and 18 of 32 (56%), respectively, returned to use. Horses treated with intrasynovial corticosteroid injection and 6 months of rest and rehabilitation returned to use for a significantly longer duration than did horses treated without rest. Western performance horses returned to use for a significantly longer duration than did English performance horses. CONCLUSIONS AND CLINICAL RELEVANCE Results of the present study suggested that outcome for horses with DDFT injuries treated medically depended on injury severity, presence of concurrent injury to other structures in the foot, type of activity, and owner compliance with specific treatment recommendations. Although some horses successfully returned to prior activity, additional treatment options are needed to improve outcome in horses with severe injuries and to improve long-term prognosis.

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%).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%).

Comparison of basilar and axial sesamoidean approaches for digital flexor tendon sheath synoviocentesis and injection in horses

OBJECTIVE To define a method for the basilar sesamoidean approach (BSA) to the digital flexor tendon sheath (DFTS) in horses and compare it with the axial sesamoidean approach (ASA) for DFTS synoviocentesis and injection. DESIGN Evaluation study. ANIMALS 12 healthy adult mares without evidence of abnormalities related to the lower limbs. PROCEDURES Each horse had 1 forelimb and 1 hind limb assigned to each DFTS approach (basilar vs axial, relative to the proximal sesamoid bones) in a Latin square design. The order of horses and of limb injection for each horse was randomly selected. All procedures were performed in standing sedated horses. The number of attempts to place a needle in the DFTS, presence of synovial fluid in the needle hub, time for DFTS injection, and number of accurate injections of sterile contrast material into the DFTS (evaluated by means of radiography) were compared between methods. RESULTS Median time for injection was significantly shorter for the BSA, compared with the ASA. The median number of times the needle was redirected was also significantly less for the BSA. Odds of obtaining synovial fluid via the BSA were 5.7 times as great as for the ASA (95% confidence interval, 1.2 to 278). Successful injection of contrast material into the DFTS did not differ significantly between the BSA (24/24 limbs) and ASA (23/24). CONCLUSIONS AND CLINICAL RELEVANCE The BSA was a useful method for DFTS synoviocentesis in the forelimbs and hind limbs of standing sedated horses and was superior to the ASA in most aspects. This approach to the DFTS should be considered when DFTS injection or synovial fluid retrieval is desired, particularly in horses with minimal DFTS effusion.

Evaluation of a New Surgical Treatment for Equine Hind Limb Proximal Suspensory Desmitis.

OBJECTIVE To evaluate the effects of a new microfracture and ligament splitting procedure on ligament healing and to examine the usefulness of magnetic resonance (MR) imaging for monitoring ligament healing over time using a collagenase model of hind limb proximal suspensory desmitis. STUDY DESIGN Experimental in vivo study. ANIMALS Healthy adult horses (n=6). METHODS Horses were free of lameness with normal hind limb proximal suspensory ligaments (PSL). The origin of both hind limb PSL was injected with collagenase and underwent MR imaging 2 weeks later, followed by the microfracture and ligament splitting procedure on 1 limb, with the opposite limb serving as the sham-operated control. Serial lameness and MR examinations were performed. Horses were euthanatized 210 days after surgery, the PSL harvested, and histology, biochemistry, and gene expression performed on both PSL. RESULTS Collagenase lesions viewed on MR images appeared similar to those seen clinically. Serial MR images demonstrated resolution of abnormal signal intensity and tissue formation in the microfracture sites within the third metatarsal bone. Treated limbs had histologic evidence of connective tissue appearing to originate from the small perforations and blending into the ligament but no statistical differences were identified. Gene expression for cartilage oligomeric matrix protein and decorin were significantly increased in treated compared to control limbs. CONCLUSION The microfracture and ligament splitting procedure did incite a tissue response but further clinical investigation is necessary to determine if this tissue remodeling at the bone-ligament interface translates to improved clinical outcome. MR imaging may be useful to follow healing in horses with hind limb proximal suspensory desmitis.