Treatment response and athletic outcome of foals with tarsal valgus deformities: 39 cases (1988-1997)

OBJECTIVE: To evaluate the response to various treatments and long-term outcome of foals with tarsal valgus deformities. DESIGN: Retrospective study. ANIMALS: 39 foals with tarsal valgus deformities. PROCEDURE: Data collected from medical records, included signalment, history, reason for admission, and clinical findings. Radiographic views of the tarsus were evaluated for incomplete ossification of tarsal bones and were classified as normal in appearance, type-I incomplete ossification, or type-II incomplete ossification. Treatment and athletic outcome were documented for each foal. RESULTS: Radiographic assessment revealed that 22 of 39 foals (56%) had concomitant tarsal valgus deformities and incomplete ossification of the tarsal bones. Eight of 19 foals with tarsal valgus deformities that were treated with periosteal stripping responded favorably. Foals < or = 60 days old were significantly more likely to respond to periosteal stripping than older foals. Five of 8 foals with tarsal valgus deformities that were treated with growth plate retardation responded favorably. Eleven of 21 foals with long-term follow-up performed as intended. Compared with foals with type-II incomplete ossification, foals with tarsal bones that had a normal radiographic appearance or type-I incomplete ossification were significantly more likely to perform as intended. CONCLUSIONS AND CLINICAL RELEVANCE: Foals with tarsal valgus deformities should have lateromedial radiographic views of the tarsus obtained to assess the tarsal bones for incomplete ossification, which will affect athletic outcome. Because foals with type-II incomplete ossification of the tarsal bones respond poorly to periosteal stripping alone, treatment by growth-plate retardation is recommended.     

Single transphyseal screws for the correction of moderate to severe angular limb deformities in 28 Thoroughbred foals

This study reports on the effective use of a single transphyseal screw for the treatment of moderate to severe angular limb deformities (ALDs) of the fetlocks and carpi of 28 young Thoroughbred foals. The objective was to evaluate the surgical management of foals with moderate to severe ALDs treated with single transphyseal screws. Evaluation of medical records of 28 Thoroughbred foals treated with single transphyseal screws placed across the distal radial, metacarpal and metatarsal physes was undertaken. The angle of joint deviation was measured prior to implantation and at removal of the implants, and the degree of improvement was calculated. A total of 39 screws were placed: 24 in the distal metacarpus or metatarsus and 15 in the distal radial physis. Varus or valgus deformities in the fetlock improved by 4–5° over a period of 15–30 days. Varus or valgus deformities in the carpi improved by 8–11° in 11–56 days. One case failed to improve adequately due to implant infection. Single transphyseal screws were effective in treating moderate to severe varus and valgus ALD of the fetlocks and carpi in young Thoroughbred foals. Further investigation into their use in the distal radius in young foals is needed. While single transphyseal screws are almost exclusively used by some clinics in the distal metatarsal and metacarpal physes, many clinicians do not use them in the distal radial physis of young foals due to fear of over‐correction, physitis and metaphyseal collapse. This was not observed in any of our cases.     

Standing placement of transphyseal screw in the distal radius in 8 Thoroughbred yearlings

This retrospective study describes placement of distal radial transphyseal screws in Thoroughbred yearlings with carpal varus deformities while standing, and identifes short- and long-term complications following the procedure. Data gathered from 2009 to 2013 identified 8 yearlings that met the inclusion criteria. Horses were sedated intravenously and a single 4.5-mm cortical screw was placed in the distal lateral radial physis following application of local anesthetic and surgical preparation of a pre-placed hole. All horses were evaluated weekly after surgery and screw removal was performed standing and under sedation when correction of the angular limb deformity was achieved. The mean time for screw removal was 46 days. No short- or long-term complications were identified. Findings indicate that placing a single transphyseal screw in the lateral aspect of the distal radial physis with the horse standing is a viable option to treat varus angular limb deformity of the carpus in horses.     

Racing and sales performance after unilateral or bilateral single transphyseal screw insertion for varus angular limb deformities of the carpus in 53 thoroughbreds

Objective: To evaluate the racing and sales performance of Thoroughbred horses with varus angular limb deformities of the carpus treated by unilateral or bilateral single transphyseal screw (STS) placement. Study Design: Case series. Animals: Thoroughbred horses (n=53). Methods: Medical records (January 1, 2005–December 31, 2006) of yearling Thoroughbreds treated for carpal angular limb deformity by transphyseal screw insertion in the distal aspect of the radius were reviewed. Retrieved data were sex, surgery, and screw removal dates, surgical site, appearance, limb(s) affected, type of angular limb deformity, and degree of angular deviation measured by a goniometer. Racing and sales data were collected for analysis from an online racing site for all treated horses and their maternal siblings. Results: No significant differences were identified between treated horses and their maternal siblings in yearling sale price, 2‐year‐olds in training sale price, percent starters, percent winners, and starts, earnings, and earnings/start made during the 2‐ and 3‐year old years. Conclusions: No deleterious effects on sales or racing performance were identified after use of STS in the distal aspect of the radius of Thoroughbreds for the treatment of varus angular limb deformities of the carpus.     

Flexural deformities of the distal interphalangeal joint (clubfeet)

A true clubfoot results from a flexural deformity of the distal interphalangeal joint that is characterised by a shortening of the deep digital flexor tendon musculotendinous unit. Flexural deformities are a problem not only in foals but are also responsible for the clubfoot conformation seen in mature horses. Treatment is most successful when the cause is investigated and therapy initiated as early as possible, and when the biomechanical properties of the foot are thoroughly understood. Flexural deformities in foals and mature horses are addressed through appropriate farriery, often combined with surgery.     

The use of an absorbable bone screw as a transphyseal bridge for the correction of fetlock varus deviations in six foals

This report describes and evaluates the use of a single‐positional absorbable screw (Smart Screw) ¹ as a temporary transphyseal bridge of the lateral aspect of the distal metacarpus in 6 foals with fetlock varus deformities. Using radiographic and visual assessments, an improvement in the severity of the deviation was identified in all cases. There were no complications encountered during screw placement or post operatively. The use of absorbable screws in the treatment of angular limb deformities in foals has potential and offers several advantages over the use of traditional stainless steel implants.     

Nuclear Scintigraphic Evaluation of the Distal Tarsal Region in Normal Horses

Bone-phase scintigraphy is sensitive to the dynamic process of bone modeling and remodeling, which may be adaptive or pathologic. Our knowledge of normal patterns of radiopharmaceutical uptake (RU) is limited, making interpretation of images problematic. It is therefore important to characterize normal patterns of RU at specific sites and relate these to age and exercise, to ensure valid interpretation of images in clinical cases with subtle lesions. This study aimed to characterize patterns of uptake of radiopharmaceutical in the distal tarsal region in clinically normal horses, and to investigate the effects of age and work discipline. Retrospective evaluation of nuclear scintigraphic images of the distal tarsal region of 30 clinically sound, high-level showjumpers and lower-level riding horses was performed. All images were acquired dynamically as a series of 35 two-second frames, which were then motion corrected and summated. The images were assessed using vertical and horizontal profile analysis across the distal tarsal region, and regions of interest comparisons between the distal tarsal region and tibia within each horse. There was a repeatable pattern of RU across the distal tarsal region in both horizontal and vertical directions. There was significantly greater RU on the dorsal compared with plantar aspect, and lateral compared with medial aspect of the distal tarsal region. RU in the right distal tarsal region was significantly greater than in the left. Elite showjumpers had significantly higher RU ratio compared with the lower-level riding horses, but no significant alterations in the pattern of RU were detected.     

Effect of hemi-circumferential periosteal transection and elevation in foals with experimentally induced angular limb deformities

OBJECTIVE: To evaluate the effect of hemi-circumferential periosteal transection and elevation (HCPTE) in foals with, experimentally induced angular limb deformities. DESIGN: Prospective study. ANIMALS: 10 healthy foals. PROCEDURE: When foals were 30 days old, transphyseal bridge implants were placed on the lateral aspects of both distal radial physes. At 90 days of age (or when 15 degrees of angulation had developed), implants were removed, and HCPTE was performed on 1 limb. Foals were confined in small pens after surgery; the front feet of the foals were rasped weekly to maintain medial-to-lateral hoof wall balance. Dorsopalmar radiographic projections of the carpi were obtained before HCPTE and 2, 4, 6, 8, and 48 weeks later. RESULTS: At the time of transphyseal bridge removal and HCPTE, both treated and control limbs were observed to have a significantly greater carpal valgus, compared with the initial degree of angulation at 30 days of age. Following HCPTE or sham surgery, all limbs straightened over the subsequent 2 months of the study. Median angulation was not significantly different between treated and control limbs at any time during the study. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in foals with experimentally induced limb deformities, HCPTE was no more effective than stall confinement and hoof trimming alone for correction of the deformity.     

Periosteal transection and stripping for treatment of angular limb deformities in foals: clinical observations

Correction was attempted in 27 foals (41 limbs) with angular deformities at the carpal region (35 limbs), metatarsophalangeal region (5 limbs) and distal end of the tibia (1 limb) by hemicircumferential transection of the periosteum (HCTP) and periosteal stripping (PS). Successful outcome was determined by straight limbs and soundness, which was achieved in 81.5% of the cases, with 60% of the horses in performance training. Follow-up evaluation for all foals was completed at various times after physiologic closure of the physes. In none of the limbs was the deformity overcorrected. Owners of foals with carpal region deviations corrected by means of HCTP and PS were satisfied with the result. The cosmetic appearance of the surgical site was excellent. The HCTP and PS adequately corrected greater degrees of carpal region deformity and greater degrees of deformity in older foals than previously reported with this or other surgical techniques.     

Alteration of distal tarsal subchondral bone thickness pattern in horses with tarsal pain

REASONS FOR PERFORMING STUDY: Understanding of the development of pathology and source of pain in distal tarsal osteoarthritis is poorly understood. Magnetic resonance imaging is often used in the analysis of human osteoarthritis (OA) because it is sensitive to early changes. HYPOTHESIS: In association with distal tarsal joint (DTJ) pain, there will be an alteration in the characteristic subchondral bone (SCB) thickness pattern of horses with no history of pain when subjected to low-level exercise. METHODS: Sixteen cadaver tarsal joints were collected from 9 mature horses with a history of tarsal pain and radiographic evidence of OA; 3 cadaver tarsi were collected from 2 mature horses with a history of tarsal pain and no radiographic abnormality. Magnetic resonance images were acquired using high-resolution sagittal 3D T1 weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (MT3). RESULTS: In tarsi with radiographic evidence of OA medial and lateral SCB thicknesses were greater than midline on the proximal and distal aspects of CT and T3. Lateral SCB thickness was greater than medial on the proximal aspect of MT3. There was an increase in SCB thickness at the majority of sites compared with normal horses. There were too few joints in the group without radiographic changes to analyse statistically. In painful tarsi SCB thickness was greater medially than laterally at all sites. In horses without tarsal pain all lateral sites had greater SCB thickness, except the proximal aspect of CT. CONCLUSIONS: There is alteration of normal SCB thickness patterns in painful tarsi. Different thickness patterns could represent different types of pathological processes. Potential clinical relevance: Further work is required to elucidate the pathological processes leading to OA of the DTJs.     

Pes varus correction in Dachshunds using a hybrid external fixator

Objective— To describe surgical correction of pes varus deformity in Dachshunds by acute medial opening wedge osteotomy of the distal aspect of the tibia stabilized with a hybrid external skeletal fixator (HESF), and report clinical and radiographic outcomes.
Study Design— Multicenter, retrospective clinical study.
Animals— Immature Dachshunds (n=13) with pes varus deformity.
Methods— Limb function and lameness scores were assigned before and after surgery, and correction was determined visually at surgery. Tibiotarsal joint orientation (TTJO) and medial and lateral tibial cortex lengths, measured on radiographs of deformed and normal (when available) limbs, were compared before correction and after fixator removal.
Results— Pes varus deformities (n=14) were corrected; 93% had good to excellent clinical outcome. None of the dogs had a normal preoperative gait. Mean TTJO of abnormal and normal tibiae before surgery were 29° varus (median, 28°), and 12° valgus (median, 12°). Angular correction ranged from 20° to 51° (mean, 36±8°; median, 36°). M e an TTJO after fixator removal was 7° valgus (median, 7°). Two dogs had minor transient postoperative complications whereas 3 had major complications; only 1 of which was resolved.
Conclusions— Pes varus deformity in Dachshunds can be corrected by acute medial opening wedge osteotomy of the distal aspect of the tibia stabilized by HESF. Technique modifications are needed to improve correction precision.
Clinical Relevance— Visual inspection of limb alignment during surgery resulted in good to excellent clinical outcomes; however, 91% of tibiae were under- or overcorrected (mean, 6°; median, 5°). Limb alignment should be based on evaluation of immediate postoperative TTJO measurements, not solely on intraoperative visual assessment.     

Surgical correction of metacarpophalangeal valgus deformity in an alpaca

A 1-month-old alpaca cria presented with a 13 degree valgus deformity of the left metacarpophalangeal joint. The angular limb deformity was centered on the distal metacarpal physes. Transphyseal bridging of the physes was recommended. Two 2.7 mm cortical bone screws were placed either side of the distal metacarpal physes and a figure of eight wire was placed medially around the screw heads. The screws extended through the medial metacarpus into the axial cortex of the lateral metacarpus. Seven weeks after surgery the limb was straight and the screws and wire were removed. Transphyseal bridging of the distal metacarpal physes can be effectively used for the treatment of metacarpophalangeal valgus in crias with open physes.     

Active tension‐extension splints: A novel technique for management of congenital flexural deformities affecting the distal limb in the foal

A variety of methods are described for managing distal limb flexural deformities in the foal, including intravenous oxytetracycline and splint or cast use. This case series describes a novel technique that creates an ‘active tension‐extension splint’ by wiring the toe into a custom‐made fibreglass splint and therefore into active extension. A dorsal fibreglass splint is made by halving a cast that is set around the affected leg with padding underneath it, so that it is sculpted to a more appropriate anatomical shape. Cerclage wire is placed through the toe and the dorsal aspect of the splint, then tightened to pull the limb into active extension. Foals with distal limb flexural deformities that were treated in this way were followed up by examination of hospital records and telephone questionnaire. Records were examined for 13 foals treated between 2004 and 2010. One foal developed septic osteitis of the distal phalanx due to suspected laminar penetration; other post operative complications seen were bandage sores and minor cosmetic scarring. Out of 10 foals where follow‐up by questionnaire was available, 8 had complete resolution of their deformity following active tension‐extension splinting, one required inferior check ligament desmotomy for complete correction and one had carpal flexural deformities that did not resolve. All that survived to adulthood are sound and have achieved their intended purpose. This previously unpublished technique using a wire through the toe to create an active tension‐extension splint has a high success rate for correction of congenital flexural deformities affecting the distal interphalangeal and metacarpo‐/metatarsophalangeal joints in the foal. The majority of post operative complications are minor and easily managed. This is a simple technique that can improve the management of neonatal distal limb deformities both in a hospital situation and for equine practitioners in the field.     

Congenital bilateral aplasia of the metacarpophalangeal joints in a foal

A 2‐day‐old Warmblood filly was presented for examination of an angular limb deformity of the left front limb and an upright conformation of both metacarpophalangeal joints. Radiological examination revealed bilateral absence of the metacarpophalangeal joint space with fusion of the third metacarpal bone and first phalanx (synostosis). No treatment was undertaken. The filly was readmitted to the clinic 10 weeks later for bilateral front limb lameness. On radiological examination, the synostosis of the front metacarpophalangeal joints was still present. Physitis of the distal growth plate of the right third metacarpal bone and proximal growth plate of the right proximal phalanx, and an avulsion fracture of the palmaromedial and proximal aspect of the left middle phalanx, with a cystic like lesion on the medial aspect of distal first phalanx and proximal middle phalanx were diagnosed. Given the poor prognosis, the foal was subjected to euthanasia. Post mortem examination confirmed the absence of the metacarpophalangeal joint space with a trabecular bony union between the third metacarpal bone and the first phalanx. A rudimentary joint capsule was present at the level of the absent joints as well as a small zone of articular cartilage, which invaginated over a short distance into the dorsal trabecular bone on the right front limb. On the medial aspect of the left proximal interphalangeal joint, a focal defect of articular cartilage with exposure of subchondral bone was observed. This is the first case report of a foal born with congenital aplasia of both metacarpophalangeal joints. Congenital malformations should be considered as differential diagnosis in lame foals or foals born with angular or flexural limb deformities.     

Clinical significance of osseous spurs on the dorsoproximal aspect of the third metatarsal bone

Reasons for performing study: Osseous spurs on the dorsoproximal aspect of the third metatarsal bone (MtIII) are common, but their clinical significance is unknown. Objectives: To verify the sites of insertion of the dorsal metatarsal ligament and the tendons of tibialis cranialis and fibularis tertius in order to determine if periarticular osteophytes and entheseophytes could be differentiated radiologically; and to determine the frequency of occurrence of osseous spurs on the dorsoproximal aspect of MtIII. Hypotheses: The frequency of osseous spurs on the dorsoproximal aspect of MtIII would be higher in lame than in clinically normal horses and higher in horses with distal hock joint pain or proximal suspensory desmitis than in horses with other causes of hindlimb lameness. Methods: A retrospective study of data from the clinical work up and tarsal radiographs of 455 horses was performed. Horses were divided into: Group 1, clinically normal horses; Groups 2–5, according to the diagnosis of hindlimb lameness. Radiographs were examined for the presence of an osseous spur on the dorsoproximal aspect of MtIII; pathology of the distal tarsal joints was graded. The associations between the presence of a spur and lameness, diagnosis group and the grade of distal tarsal joint abnormalities were analysed statistically using Chi‐squared tests. Results: An osseous spur was present in 25% of horses; 13% of horses with bilateral radiographs had bilateral spurs. There was no significant difference in frequency of the presence of a spur between lame and nonlame horses, or between horses with other causes of hindlimb lameness and horses with proximal suspensory desmitis and/or distal tarsal joint pain. The presence of an osseous spur was significantly associated with the grade of radiological abnormality in the distal tarsal joints (tarsometatarsal joint P = 0.018: centrodistal joint P = 0.027). In many horses it was not possible to differentiate accurately between osteophytes and entheseophytes. Conclusions and potential relevance: The presence of an osseous spur on the dorsoproximal aspect of MtIII in the absence of other radiological abnormalities may be an incidental finding. Osseous spurs occur more frequently in hocks with radiological abnormalities in the distal tarsal joints and may be an indicator of distal tarsal joint osteoarthritis. The clinical significance must be established by intra‐articular analgesia.     

Is there a characteristic distal tarsal subchondral bone plate thickness pattern in horses with no history of hindlimb lameness?

REASONS FOR PERFORMING STUDY: Osteoarthritis (OA) is a common cause of distal tarsal pain, but disease development is poorly understood. Awareness of normal tarsal structure and function is important in order to understand the pathogenesis of OA. Thickening of the subchondral bone (SCB) plate has been related to the development of OA, but SCB plate patterns in the equine tarsus have not been documented. HYPOTHESES: There is a repeatable pattern of SCB thickness across the distal tarsal joints, and specifically that thickness would be greatest dorsally and laterally. METHODS: Twenty cadaver tarsi were collected from mature horses that had undertaken low-level exercise only with no history of hindlimb lameness. Magnetic resonance images were acquired using a high-resolution sagittal 3-dimensional T1-weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (Mt3). RESULTS: On the proximal aspect of CT, medial and lateral SCB thickness were significantly greater than midline. On the distal aspect of CT and T3 and proximal Mt3, lateral SCB thickness was significantly greater than medial and midline sites. Dorsal SCB thickness was greatest on the proximal and distal aspects of CT and proximal Mt3. Subchondral bone accounted for a greater proportion of CT and T3 on the dorsal aspect than the plantar. CONCLUSIONS: There is a repeatable pattern of SCB thickness in the distal tarsal bones of horses with no history of hindlimb lameness. This reflects the pattern of loading across the joints. POTENTIAL RELEVANCE: This study provides evidence of a consistent osteochondral pattern in the equine tarsus for reference in identification of osteoarticular pathologies.     

Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 Thoroughbred yearlings

Reasons for performing study: Surgical correction of carpal angular limb deformities by growth retardation is commonly undertaken with a screws and tension band wire loop technique (S&W) or a single transphyseal screw (STS). This study compares complications after S&W and STS bridging in the distal radius of Thoroughbred yearlings. Objective: To compare the prevalence of complications serious enough to require follow‐up radiographs following either S&W or STS surgery for growth manipulation in the distal radius of Thoroughbred yearlings. Methods: Medical records and radiographs from Thoroughbred yearlings (age range 261–457 days) treated for carpal angular limb deformities at a single hospital over 2 years were reviewed. Each of the techniques was used exclusively during a single year. The complication threshold criterion for inclusion was the need for nonroutine radiographs of the operated site anytime after implant insertion or removal. Results: Of 568 horses, 253 received S&W and 315 received STS. Horses were of similar age at the time of surgery for STS and S&W. Single transphyseal screws were left in place for a significantly shorter amount of time (16 days). Sex, the limb(s) treated and medial vs. lateral placement were not significantly different between techniques. Complications included physitis post implant removal, metaphyseal collapse post implant removal, infection, overcorrection and seroma formation severe enough to require radiography. Physitis and metaphyseal collapse occurred significantly more frequently with STS compared with S&W. Infection, overcorrection and seromas were not significantly different between techniques. Conclusion: The STS and S&W techniques are both viable treatment options for correction of carpal angular limb deformities. However, horses treated with the STS technique have a significantly increased risk of developing physitis or metaphyseal collapse. Potential relevance: Horses treated with STS bridging have a significantly increased risk of developing the post correction complications of moderate to severe physitis and metaphyseal collapse compared with horses treated with S&W bridging.     

Periosteal transection of the proximal phalanx in foals with angular limb deformities of the metacarpo/metatarsophalangeal area

Bilateral angular limb deformities of the metacarpo/metatarsophalangeal regions in 2 foals are discussed. Periosteal transection was used to correct the deformity in both foals. In one foal, only the right forelimb was treated because the deformity in the left forelimb did not appear to warrant surgery. Subsequently, an angular limb deformity, which could have been prevented, developed in the left forelimb. A third foal developed a deformity in the proximal phalanx after periosteal transection of the distal third metatarsal bone.     

Use of a three-drill-tract technique for arthrodesis of the distal tarsal joints in horses with distal tarsal osteoarthritis: 54 cases (1990-1999)

OBJECTIVE: To assess the long-term clinical outcome of horses with distal tarsal osteoarthritis (OA) in which a 3-drill-tract technique was used to induce arthrodesis of the affected joints, identify any preoperative or operative factors associated with outcome, and describe any complications associated with the technique. DESIGN: Retrospective study. ANIMALS: 54 horses. PROCEDURE: Medical records were reviewed for information on signalment, use, history, physical and lameness examination findings, surgical technique, and postoperative care. Radiographs were examined, and severity of OA was graded. Follow-up information was obtained through telephone interviews with owners at least 13 months after the procedure. RESULTS: 32 (59%) horses had a successful outcome, 6 (11%) improved but were not sound after surgery, and 16 (30%) did not improve following surgery. Outcome was negatively associated with the previous use of intra-articular injections. Few postoperative complications were evident. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that distal tarsal OA in horses can be successfully treated by means of distal tarsal arthrodesis with a 3-drill-tract technique. Horses with advanced distal tarsal OA are likely to have poorer outcomes, and the procedure will likely be of minimal benefit in horses with concomitant causes of hind limb lameness prior to surgery and in horses with preexisting proximal intertarsal joint disease.     

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.