Use of standing low-field magnetic resonance imaging to assess oblique distal sesamoidean ligament desmitis in three Thoroughbred racehorses

Equine non-septic tenosynovitis: A systematic literature review of site-specific pathological lesions, outcomes and surgical complications

BACKGROUND

Non-septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse.

OBJECTIVES

To review the published literature to determine which tendon sheaths are commonly affected by non-septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non-septic tenosynovitis.

STUDY DESIGN

Systematic review.

METHODS

Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. The inclusion criteria followed a participants, interventions, comparisons, outcome and study design (PICOS) approach. For inclusion, studies had to include live equids with non-septic tenosynovitis of any tendon sheath. Studies were excluded if they only described non-equine species, if they included data only on non-tendon sheath structures, or if they included data exclusively on cases of septic or contaminated tendon sheaths. Determination of non-sepsis relied on the diagnosis of the original authors; however, if non-sepsis was not explicitly specified, then cases that had a history of contamination of the sheath, a wound near the sheath or a positive bacterial culture were excluded from analysis. Data analysed included the distribution of structures affected by non-septic tenosynovitis, the most common pathological lesions identified within each sheath, and the most frequently reported surgical complications of non-septic tenosynovitis. The quality of each study was assessed using a methodological quality analysis.

RESULTS

A total of 85 studies describing non-septic tenosynovitis in the horse were included. Across all 85 studies, there were a total of 2449 tendon sheaths in 2101 horses reported to be affected by non-septic tenosynovitis. The digital flexor sheath was the most reported structure to be diagnosed with non-septic tenosynovitis: 41/85 (48%) studies examined the digital flexor sheath exclusively, followed by the carpal flexor sheath, tarsal flexor sheath, carpal extensor sheaths, tarsal extensor sheaths, and one case of biceps brachii non-septic tenosynovitis. For most tendon sheaths, the most common pathological lesion was an intrathecal tear of a soft tissue structure, including tears of the deep digital flexor tendon and tears of the manica flexoria. Bilateral disease was most common in the carpal flexor sheath, where distal radial physeal exostoses were the most common pathological lesions. Less common causes of non-septic tenosynovitis included neoplasia, fracture of a bone adjacent to a tendon sheath, and mineralisation of an intrathecal tendon. The likelihood of return to previous level of athletic function following non-septic tenosynovitis of most structures was approximately 50%, and the most common complication was persistent effusion following tenoscopy. While iatrogenic infection following surgery was uncommon, it was most likely following tenoscopy of the digital flexor sheath.

CONCLUSION

Non-septic tenosynovitis is commonly reported in equine athletes, with intra-thecal tears of the deep digital flexor tendon, superficial digital flexor tendon and manica flexoria frequently reported. Directions for future research include more thorough assessment of and reporting of complications following non-septic tenosynovitis and correlation of characteristics of intrathecal pathological lesions with clinical outcomes.

Retrospective analysis of oblique and straight distal sesamoidean ligament desmitis in 52 horses

BACKGROUND

Injuries to the oblique (ODSL) or straight (SDSL) distal sesamoidean ligaments are a recognised cause of distal limb lameness in the horse. However, there are only limited publications addressing common diagnostic features and prognosis.

OBJECTIVES

(a) Report findings on ultrasonography and standing low-field magnetic resonance imaging (sMRI) in horses with ODSL or SDSL injury; (b) Identify clinical variables associated with lesion type and (c) Identify factors associated with return to soundness in horses with ODSL or SDSL injury.

STUDY DESIGN

Retrospective case series.

METHODS

Horses with a primary diagnosis of ODSL or SDSL injury confirmed with a combination of diagnostic analgesia and detection of a lesion on imaging (ultrasonographic ± advanced imaging) were included. Return to soundness and performance follow-up data were obtained.

RESULTS

Fifty-one horses were included. SDSL injuries were more common in the forelimb (13/21, 62%), while ODSL injuries had equal frequency in fore- (15/30, 50%) and hindlimbs (15/30, 50%). ODSL injuries were more likely than SDSL injuries to affect the proximal third of the ligament (OR =13; 95% CI 2.3-74.3; p = 0.004) and often presented with periligamentar swelling (20/30;67%) and focal pain (22/28;79%). Lesions were frequently detected using ultrasonography (35/42;83%) and sMRI examination (18/25;72%). Only 27/49 cases (55%) returned to soundness, with only 15/49 (31%) returning to intended use. There were no significant associations between outcome and clinical features or treatment.

MAIN LIMITATIONS

There was no comparative "gold standard" to validate lesions such as high-field MRI or histopathology.

CONCLUSIONS

In contrast to previous studies, ODSL and SDSL injuries were readily identified ultrasonographically using appropriate views, and with sMRI. Given the limited availability, cost and general anaesthetic risks associated with high-field MRI, more focus should be placed on optimising the ultrasonographic examination. Owners of affected horses should be informed of the guarded prognosis for return to full use.

Chronic Collateral Sesamoidean Desmopathy in Draft Horses: Magnetic Resonance Imaging and Histopathological Findings

Desmopathy of the collateral sesamoidean ligament (CSL) is an unusual disorder in draft horses. This study records the magnetic resonance imaging (MRI) features of chronic CSL desmopathy in eight draft horses and confirms these features by histopathology. The recorded chronic CSL desmopathy has usually affected the forelimbs (100%) and commonly bilateral (62.5%). All horses showed positive proximal digital nerve block, positive front digital flexion test, and negative interphalangeal extension test. Radiography revealed no osseous abnormalities in all feet. MRI features of chronic CSL desmopathy included thickening of the ligament with increased moderate intensity in fast low-angle shot, T1 turbo spin echo, and proton density images in the affected part of the ligament. Chronic CSL desmopathy was concomitant with deep digital flexor tendon injury and distal sesamoidean impar desmitis. In most chronic cases of CSL desmopathy, heterogeneous signal intensities were seen with multiple foci of low signal intensities interlaced with increased moderate signal intensities of thickened CSL. Histopathology confirmed the MRI findings and revealed separated bundles and fascicles by septa of less organized and loose connective tissues containing fibroblasts and loose collagen fibers. Multifocal islands of cartilaginous metaplasia, mineralized areas, and dystrophic calcification were observed in the injured ligament. In conclusion, chronic CSL desmopathy may progress to cartilaginous metaplasia and dystrophic calcification. MRI is a beneficial diagnostic and prognostic tool for chronic CSL desmopathy, and histopathology is a gold standard to document the MRI findings associated with CSL dysmopathy in draft horses.

Magnetic resonance imaging and histopathological evaluation of equine oblique sesamoidean ligaments

BACKGROUND

Pathology involving the oblique sesamoidean ligaments (OSLs) is commonly diagnosed during magnetic resonance imaging (MRI) of the equine distal limb. Presence of striations within the ligament and magic angle artefact can result in an incorrect diagnosis of pathological change. No studies have been performed using histopathology, the gold standard, to corroborate their imaging diagnosis.

OBJECTIVES

(a) To determine which MRI characteristics are associated with normal vs abnormal OSLs and (b) to evaluate the ability of MRI to correctly identify abnormal vs normal oblique sesamoidean ligaments using histopathology as the gold standard.

STUDY DESIGN

Observational, cross-sectional study.

METHODS

Cadaver limbs (n = 77) were obtained from horses (n = 21) subjected to euthanasia at the hospital. MRI and histopathology was performed on each of the limbs. MRI scoring was performed for multiple MRI characteristics, and each limb was deemed normal or abnormal. Histopathology scoring was performed to give an overall score of normal or abnormal. Mixed model logistic regression was performed to evaluate which MRI characteristics were associated with normal vs abnormal OSLs using backwards elimination and a significance level of <0.1. Sensitivity and specificity were also calculated.

RESULTS

The sensitivity and specificity of MRI to correctly identify abnormal OSLs was 81% (95% CI 54%-96%) and 90% (95% CI 79%-96%) respectively. Based on logistic regression, increased cross-sectional area at the origin (OR: 26.77, 95% CI 1.1-4640, P = .07), increased ligament hyperintensity (OR: 9.59, 95% CI 1.23-155; P = .04) and reduction in striations (increased hypointensity score) (OR: 7.8, 95% CI 0.72-218, P = .07) were associated with abnormal OSL.

MAIN LIMITATIONS

Lameness exam was not performed on any of the horses prior to euthanasia. Findings can only be applied to chronic, degenerative changes, rather than an acute injury.

CONCLUSIONS

Increased cross-sectional area and changes in the signal intensity are associated with pathology within the OSLs. Medial to lateral size asymmetry and striation pattern variation can occur in histologically normal OSLs and should be interpreted with caution if other signs of pathology are absent.

Characteristic findings of magnetic resonance imaging (MRI) and computed tomography (CT) for severe chronic laminitis in a Thoroughbred horse

A Thoroughbred horse with severe chronic laminitis of both forelimbs was evaluated on the same day with magnetic resonance imaging (MRI) and computed tomography (CT). Both MRI and CT revealed loss of the dorsal aspect of the cortical bone of the 3rd phalanx and sclerosis. CT reflected the status of the horny layer and bone of the affected feet, while MRI depicted inflammation of the laminar corium, together with tendon edema. On the 3-dimensional CT venogram, vessels were visualized in both the right and left forelimbs, although there was a difference in the vasculature of the coronary plexus and circumflex vessels between the right and left forelimbs. A combination of both MRI and CT provides detailed information regarding pathological conditions.