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Summary: The desmotomy of the palmar/plantar annular ligament (PAL) is recommended when it hinders the sliding motion of the flexor tendons in the sesamoidean canal, leading to persistent lameness that often does not improve with conservative treatment. Tenoscopic‐assisted PAL desmotomy can be accomplished with various instruments via an intrathecal approach. However, severe constriction or adhesions within the fetlock canal can restrict manoeuvrability and access of instruments within the sheath, preventing safe and effective transection of the ligament. This case report describes the successful use of a hook knife via a subcutaneous approach to safely transect the PAL under tenoscopic visualisation in a horse where severe constriction of the fetlock canal prohibited the standard intrathecal approach. In similar chronic tenosynovitis cases, a subcutaneous approach to PAL transection at the start of the tenoscopic examination of the digital flexor tendon sheath may minimise iatrogenic injury to intrathecal structures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Digital flexor tendon sheath (DFTS) pathology is an important cause of lameness in horses. The outcome after surgical treatment is variable and depends on the exact diagnosis. Objectives: To (1) describe the prevalence of lesions associated with lameness caused by nonseptic DFTS tenosynovitis in a large population of German sports and pleasure horses; (2) determine the sensitivity and specificity of diagnostic imaging techniques for identifying lesions within the DFTS with tenoscopic diagnosis being the gold standard; (3) explore associations between tenoscopically diagnosed lesions and signalment, purpose, and limb affected; and (4) describe the outcome following DFTS tenoscopy with nonseptic DFTS tenosynovitis in this population. Study design: Retrospective case series. Methods: Medical records of horses admitted for tenoscopic surgery of nonseptic DFTS tenosynovitis between 2011 and 2020 were reviewed. Follow‐up information was obtained via telephone contact. Sensitivity and specificity of ultrasonography and contrast tenography were determined using tenoscopic diagnosis as gold standard and univariable analysis was used to explore associations between signalment, case history, and tenoscopic diagnosis. Results: Medical records from 131 horses were retrieved, of which 8 horses had bilateral disease and 6 horses were presented for tenoscopy on two separate occasions (3 for tenoscopy in the same limb, 3 in a different limb), thus, making a total of 145 limbs. Lesions were most commonly diagnosed in the deep (DDFT; n = 55 limbs) and superficial (SDFT; n = 55 limbs) digital flexor tendons. Manica flexoria (MF) lesions were detected in 44 limbs and palmar/plantar annular ligament (PAL) constriction in 99 limbs. In 36 limbs, only one structure within the DFTS was injured, whereas in 109 limbs a combination of lesions was noted, the most common being the combination of a SDFT lesion with PAL constriction. All affected limbs were examined with diagnostic ultrasonography; contrast tenography was performed in 86 limbs. For diagnosis of MF and DDFT tears, tenography was more sensitive (89% [confidence interval, CI: 65.4%–95.2%]; 72% [CI: 46.4%–89.3%], respectively) than specific (64% [CI: 52.5%–77.6%]; 53% [CI: 42.2%–73.3%], respectively) whereas ultrasonography was more specific (92% [CI: 84.5%–96.3%]; 92% [CI: 83.6%–96.0%]) with lower sensitivity (64% [CI: 47.7%–77.2%]; 54% [CI: 39.5%–67.9%]). For SDFT lesions, ultrasonography was highly specific (94% [CI: 86.9%–97.9%]) with lower sensitivity (66% [CI: 51.3%–77.4%]). Follow‐up information following first surgery was obtained for 118 horses (132 limbs): 18 (15.3%) of 118 horses remained chronically lame, 40 (33.8%) performed at a reduced level and 60 (50.8%) performed at the same or higher level following rehabilitation after tenoscopy. Horses with DDFT lesions had the poorest outcomes with only 36.6% returning to the same or higher level of exercise. Main limitations: Retrospective analysis of clinical records and subjective outcome assessment based on owner follow‐up with potential recall bias. Findings on diagnostic imaging are impacted by many factors including equipment quality and operator expertise and experience. Conclusion: Diagnostic imaging techniques were complimentary and contrast tenography was sensitive and ultrasonography was specific for the diagnosis of MF and DDFT lesions. Following tenoscopic surgery for nonseptic tenosynovitis of the DFTS, approximately half the cases were able to return to preinjury level of exercise. [ABSTRACT FROM AUTHOR]

While MRI is the modality of choice for the diagnosis of longitudinal tears (LTs) of the deep digital flexor tendon (DDFT) of horses, differentiating between various grades of tears based on imaging characteristics is challenging due to overlapping imaging features. In this retrospective, exploratory, diagnostic accuracy study, a machine learning (ML) scheme was applied to link quantitative features and qualitative descriptors to leverage MRI characteristics of different grades of tearing of the DDFT of horses. A qualitative MRI characteristic scheme, combining tendon morphologic features, altered signal intensity, and synovial sheath distention, was used for LT classification with an excellent diagnostic accuracy of the high‐grade tears but more limited accuracy for the detection of low‐grade tears. A quantitative ML approach was followed to measure the contribution of 30 quantitative phenotypic features for characterizing and classifying tendinous tears. Among the 30 imaging features, boundary curvature represented by the standard deviation and maximum had the most significant discriminatory power (P < 0.05) between normal and abnormal tendons and could be used as an aid for classifying the different grades of LTs of DDFTs. Imaging analysis‐based 3D interactive surface plot supports qualitative characterization of different grades of LTs of the DDFT through clearer visualization of the tendon in three dimensions and simple integration of two perspectives features (i.e., margin/distribution and intensity/distribution). A systematic approach combining quantitative features with qualitative analyses using ML was diagnostically beneficial in MRI characterization and in discriminating between different grades of LTs of the DDFT of horses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: A 7‐year‐old Holsteiner gelding was presented with a left common digital extensor sheath effusion of one‐year's duration. Radiographic examination revealed two extra‐articular mineralised bodies adjacent to the dorsolateral carpometacarpal joint. Ultrasonography confirmed an intrathecal location of one mineralised body in the common digital extensor sheath, palmar fraying of the common digital extensor tendon and tenosynovitis. Ultrasound could not confirm whether the second mineralised body was intrathecal or located external to the common digital extensor sheath. Common digital extensor tenoscopy facilitated removal of both mineralised bodies and revealed a fistula communicating with the carpometacarpal joint. The mineralised bodies, initially thought to be synovial osteochondromas, were histologically identified as para‐articular osteochondromas. There are no previously published reports of para‐articular chondroma/osteochondroma in the horse. Despite surgical removal of the para‐articular osteochondromas, concern for future extensor sheath distension remained given the communication between the carpometacarpal joint and common digital extensor sheath. [ABSTRACT FROM AUTHOR]

Summary: Solitary osteochondromas are a relatively infrequent cause of lameness in the horse, most commonly occurring in the caudal distal radial metaphysis, with sparse reports in other locations. Their presence adjacent to a synovial sheath frequently results in intra‐thecal tendinous laceration and resultant synovial effusion. Surgical excision in combination with arthroscopic debridement of the tendinous pathology offers the best prognosis for soundness. This report details the successful treatment of a caudodistal tibial osteochondroma using a combination of open surgical excision and tarsal sheath tenoscopy. [ABSTRACT FROM AUTHOR]

Summary: A 6‐year‐old Highland pony gelding was presented with severe left fore (LF) limb lameness of acute onset. The lameness occurred concomitantly with mild digital flexor tendon sheath (DFTS) effusion and focal painful swelling on the lateral aspect of the LF fetlock region. Clinical examination and diagnostic analgesia localised the lameness to the fetlock region and on ultrasound, a cyst‐like structure filled with anaechoic fluid was detected just proximal to the lateral sesamoid bone, at the proximo‐lateral aspect of the DFTS and adjacent to the lateral neurovascular bundle. Communication between the cyst‐like structure and the DFTS was suspected ultrasonographically and then confirmed with contrast tenography. Tenoscopic examination of the LF DFTS was performed and the communication between the fluid‐filled structure and the synovial cavity was detected. The defect in the DFTS wall was enlarged tenoscopically and the lining of the cyst‐like structure was debrided. The horse recovered well post‐operatively and was back in work with no evident lameness 8 months after surgery. This alternative minimally invasive surgical treatment had an excellent outcome and has the advantage of reducing the risk associated with en bloc resection. [ABSTRACT FROM AUTHOR]

Reasons for performing study The overall rate of sepsis following endoscopic surgery of synovial structures has not previously been documented. Clinical observation has led to the conjecture that tendon sheaths, in particular the carpal flexor tendon sheath, are more prone to post operative synovial sepsis than other synovial structures. Objectives To document and investigate the rate of post operative synovial sepsis following elective endoscopic surgery. Study design Retrospective case series. Methods The medical records of horses that underwent arthroscopy, tenoscopy or bursoscopy at Donnington Grove Veterinary Surgery between January 1999 and July 2012 were reviewed. The signalment, anatomical structure involved, use of electrosurgery, tourniquet or motorised resector, presence of a fracture, whether surgery was performed with the horse standing or under general anaesthesia and the number of structures examined were recorded. Multivariable logistic regression was used to test the association between the selected variables and synovial sepsis. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. Level of significance was P<0.05. Results There were 1670 horses that underwent endoscopic surgery of 3159 synovial structures: 2517 joints, 583 tendon sheaths and 59 bursae. There were 16 cases of post operative sepsis in 16 horses; therefore, the infection rate was one per 100 horses or 5 per 1000 procedures. Carpal sheath tenoscopy was associated with an OR of developing post operative synovial sepsis of 14.9 (95% CI 4.8-45.9, P<0.001) compared to other synovial structures. Tendon sheath endoscopy had an OR of developing post operative synovial sepsis of 5.21 (95% CI 1.24-21.91, P<0.02) compared to other synovial structures. Conclusion Surgeons should be aware that tendon sheaths and the carpal sheath in particular appear to have higher odds of developing sepsis following endoscopic surgery. [ABSTRACT FROM AUTHOR]

Reasons for performing study Tears of the accessory ligament of the superficial digital flexor ( ALSDF) that communicate with the carpal sheath are not reported in the literature. The study describes ultrasonographic techniques for evaluation of the ALSDF and reports clinical, ultrasonographic and endoscopic features associated with intrathecal tears of the ligament. Objectives To investigate whether tearing of the ALSDF can be: 1) intrathecal with respect to the carpal sheath; 2) cause lameness and distension of the carpal sheath; and 3) result in intrathecal haemorrhage by tearing vessels that appear to be direct branches of the median artery, as well as to confirm that these lesions are reliably predicted by ultrasonography. Study design Retrospective case series. Methods Case records and diagnostic images of horses with ALSDF injuries were reviewed retrospectively, and follow-up information was obtained. Results Ultrasonographic examination using a combination of linear and curved array transducers identified 10 cases with intrathecal tears of the ALSDF. This was confirmed in 7 cases that underwent tenoscopy. Tears were consistently in the caudal ALSDF and in 3 cases exposed the median artery. Extruded torn fibres were removed. Of the 7 surgical cases, one horse returned to competitive work, one was back in full training, 2 were retired from racing but performing riding club activities, 2 were convalescing and one was lost to follow-up. Of the 3 cases that did not undergo surgery, one was subjected to euthanasia and the other 2 failed to return to training. Conclusions Tears of the ALSDF can communicate with the carpal sheath, resulting in lameness and intrathecal haemorrhage. The latter appears to result from vessels that are primary branches of the median artery, and tears in the ALSDF can extend to this. These injuries are reliably predicted by multimodal ultrasonography, which also allows assessment of the proximity of tears to the median artery. [ABSTRACT FROM AUTHOR]

Reasons for performing study: Annular ligament desmotomy is commonly performed in horses with chronic tenosynovitis. Previously reported tenoscopic techniques have limitations related to haemorrhage and awkward instrumentation. Radiofrequency (RF) energy affords precision and excellent haemostasis and may be a good alternative to sharp transection of the annular ligament in horses. Objective: To describe a technique for using a RF probe for tenoscopic-guided annular ligament desmotomy and to report the clinical outcome of horses in which it was performed. Methods: Cadaver specimens (n = 14) and live horses undergoing unrelated terminal procedures (n = 2) were used to optimise the tenoscopic-guided RF annular ligament desmotomy technique. Records were examined for all horses undergoing annular ligament desmotomy with an RF probe from 2003 to 2008 for which follow-up of >1 year post operatively was available. Results: The annular ligament was successfully transected in the cadaver and live horse model limbs using 2 different commercially available RF probes. Complete transection was achieved with practice and confirmed on gross dissection. Histopathology did not reveal any collateral damage to surrounding tissue. Follow-up of >1 year was available for 6 of 7 clinical cases. Four of 6 horses returned to work. Owners were satisfied with the outcome in all cases. Conclusions: Desmotomy using a RF probe allows precise tissue transection under tenoscopic guidance without damage to surrounding structures or haemorrhage. With experience, it is an easily performed technique. In clinical patients, an acceptable outcome may be expected. Potential relevance: Tenoscopic-guided RF annular ligament desmotomy offers advantages, including reliable haemostasis and precise tissue transection, over previously reported techniques and is a viable surgical alternative for treating horses with annular ligament desmitis and other complex pathology within the tendon sheath. [ABSTRACT FROM AUTHOR]

Summary Reasons for performing study: Although a well recognised clinical entity, only small numbers of osteochondromata on the caudal distal radius have previously been published and its occurrence in young racing Thoroughbreds has not previously been reported. Identification and management of associated lesions in the deep digital flexor tendon have received scant attention in the literature. Hypothesis: Osteochondromata of the caudal distal radius occur commonly in young racing Thoroughbreds. They vary in size and location, sagittally and proximodistally, but the majority cause impingement damage to the deep digital flexor tendon. Methods: Case records and diagnostic images of horses with osteochondromata of the caudal distal radius were reviewed retrospectively and follow-up information obtained. Results: Twenty-five osteochondromata were identified in 22 horses, 19 of which were Thoroughbreds. All osteochondromata were metaphyseal. Twenty-two were in the middle one-third of the bone and laceration of the adjacent deep digital flexor tendon was identified in 21 limbs. Treatment in all cases consisted of removal of the osteochondroma with debridement of the deep digital flexor tendon when this was affected. All horses returned to work and none exhibited any evidence of recurrence. Conclusion: Osteochondromata of the caudal distal radius occur in young racing Thoroughbreds but are also identified in other horses. They have a consistent metaphyseal location and most are found in the middle one-third of the radius. Size varies, but most cause laceration of the adjacent deep digital flexor tendon. Treatment by removal of the mass and debridement of the tendon is associated with a good prognosis. Potential relevance: Osteochondromata of the caudal distal radius are an important cause of tenosynovitis of the carpal sheath of the digital flexor tendons in young racing Thoroughbreds. When present in the most common location of the middle one-third of the bone, they are likely to cause impingement damage to the deep digital flexor tendon. Tenoscopic surgery offers a good prognosis. [ABSTRACT FROM AUTHOR]