FEASIBILITY FOR ULTRASOUND‐GUIDED INJECTION OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES

Desmitis of the collateral ligament of the distal interphalangeal joint is a cause of lameness in performance horses. The objective of this prospective, experimental, ex vivo feasibility study was to evaluate the success of ultrasound‐guided injection of the collateral ligaments of the distal interphalangeal joint in the equine forelimb. Seventy‐six ultrasound‐guided dye injections of the collateral ligament of the distal interphalangeal joint were performed on horses’ cadaver limbs. The hooves were sectioned transversely to verify the location of the dye relative to the collateral ligaments and surrounding structures. Evaluations of transverse sections were performed independently by two experienced observers. A scoring system was used to assess injection of the collateral ligament of the distal interphalangeal joint at the proximal, middle, and distal aspect over the length of the ligament. The collateral ligament was injected at any point in 97.4% of cases. The ligament was injected over the entire scored length in 43.2% of cases (32/74), over two scored length areas in 45.9% of cases (34/74), and in one area in 10.8% of cases (8/74). The distal interphalangeal joint and the common digital extensor tendon were also injected in 81.6% (62/76) and 43.4% (33/76) of the cases, respectively. Use of the ultrasound had a positive and negative predictive value of 98% and 9%, respectively. In this study, ultrasound guidance was useful for confirming injection of the collateral ligament of the distal interphalangeal joint but did not prevent injecting the distal interphalangeal joint and the common digital extensor tendon.     

Comparisons of computed tomography, contrast enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 1: anatomic visualisation scores

Reasons for performing study: To date, few reports exist comparing magnetic resonance imaging (MRI) and computed tomography (CT) for imaging of the equine distal limb, yet clinicians are required to decide which modality to use regularly. Objectives: To report and compare anatomic visualisation scores obtained for CT, contrast enhanced CT (CECT) and standing low‐field MRI (LFMRI) in the equine foot. Hypothesis: Anatomic visualisation score discrepancies would exist between CT, CECT and LFMRI. Methods: Images of 22 lame horses (31 limbs) undergoing both CT and LFMRI of the foot were reviewed. When available, CECT images were reviewed. The deep digital flexor tendon (DDFT) was categorised into proximal to distal levels (A–D), structures were assigned visualisation scores (Grades 0–3) and technique comparisons were made using the paired marginal homogeneity test. Results: Computed tomography and LFMRI had similar visibility scores for the navicular bone, middle phalanx, DDFT‐B, collateral ligaments of the distal interphalangeal joint and collateral sesamoidean ligament of the navicular bone. The proximal and distal phalanx had lower visibility scores with LFMRI. The distal DDFT (C–D), distal sesamoidean impar ligament and synovial structures had higher scores with LFMRI. Contrast enhanced CT lowered DDFT and collateral sesamoidean ligament scores and raised distal interphalangeal synovium CT visualisation scores. Conclusions and potential relevance: Visualisation scores differ depending on imaging technique and anatomic structure of interest. This information increases our understanding of the limitations of CT, CECT and LFMRI to visualise anatomy in clinical cases.     

Accuracy of open magnetic resonance imaging for guiding injection of the equine deep digital flexor tendon within the hoof

Lesions of the distal deep digital flexor tendon (DDFT) are frequently diagnosed using MRI in horses with foot pain. Intralesional injection of biologic therapeutics shows promise in tendon healing; however, accurate injection of distal deep digital flexor tendon lesions within the hoof is difficult. The aim of this experimental study was to evaluate accuracy of a technique for injection of the deep digital flexor tendon within the hoof using MRI‐guidance, which could be performed in standing patients. We hypothesized that injection of the distal deep digital flexor tendon within the hoof could be accurately guided using open low‐field MRI to target either the lateral or medial lobe at a specific location. Ten cadaver limbs were positioned in an open, low‐field MRI unit. Each distal deep digital flexor tendon lobe was assigned to have a proximal (adjacent to the proximal aspect of the navicular bursa) or distal (adjacent to the navicular bone) injection. A titanium needle was inserted into each tendon lobe, guided by T1‐weighted transverse images acquired simultaneously during injection. Colored dye was injected as a marker and postinjection MRI and gross sections were assessed. The success of injection as evaluated on gross section was 85% (70% proximal, 100% distal). The success of injection as evaluated by MRI was 65% (60% proximal, 70% distal). There was no significant difference between the success of injecting the medial versus lateral lobe. The major limitation of this study was the use of cadaver limbs with normal tendons. The authors conclude that injection of the distal deep digital flexor tendon within the hoof is possible using MRI guidance.     

Risk of intra‐articular injection with longitudinal ultrasound‐guided injection of collateral ligaments of the equine distal interphalangeal joint

Desmopathy of the collateral ligaments of the distal interphalangeal joint is a common cause of equine foot lameness and carries a poor prognosis with conservative management. Intralesional injections may improve healing, although accuracy of radiographically guided injections is significantly less than when guided by MRI, which requires special needles. Longitudinal ultrasound‐guided injection of the distal collateral ligament has not been evaluated objectively. In this prospective, anatomic study, seven equine cadaver limbs (14 collateral ligaments) were injected with methylene blue dye and radiographic contrast medium using ultrasound to guide the needle longitudinally into the collateral ligaments until contacting bone. The insertion site of the needle proximal to the coronary band was measured on the limb and the needles left in place for radiography and CT to evaluate the needle angulation, location of the contrast medium, and whether the contrast entered the distal interphalangeal joint. The limbs were frozen and sectioned with a band saw to identify the location of the dye. Fifty percentage of injections were in or around the collateral ligaments. However, the percentage of “successful” injections, defined as in the collateral ligament but not in the joint, was only 36%. All legs had dye and contrast in the joint after both ligaments had been injected. There were no significant differences between the needle angle and entry site for “successful” and “unsuccessful” injections. Findings from this study indicates that the success rate is low for injecting the distal portions of the distal interphalangeal joint collateral ligaments using ultrasound guidance alone.     

The collateral ligaments of the distal interphalangeal joint: magnetic resonance imaging and post mortem observations in 25 lame and 12 control horses

Reasons for performing study: Magnetic resonance imaging (MRI) is used with increasing frequency to diagnose injuries of the collateral ligaments (CLs) of the distal interphalangeal (DIP) joint, but the results have not been verified by histology and the mechanism of injury is poorly understood. Hypothesis: Abnormal signal intensity and tissue contour represents change in tissue structure detected on histology. Objectives: To compare results in horses free from and those with chronic lameness and to describe possible progression of lesions. Methods: One or both feet of horses free from lameness (Group N: n = 12) and with foot‐related lameness (Group L: n = 25) were examined using MRI and by gross post mortem examination. The magnetic resonance (MR) images were graded. Sagittal sections from the proximal and distal aspect of each CL were examined histologically and each ligament assigned a score. Scintigraphic images from lame horses were also evaluated. Results: In Group N, 25 CLs were graded normal on both MR images and histology, 2 CLs were grade 1 on MR images, but were histologically normal, and 2 CLs had MR abnormalities verified histologically. However, 2 CLs appeared normal on MR images but were histologically abnormal. In Group L, 18 CLs were deemed normal on both MR images and histology, and 54 CLs had MR abnormalities verified histologically. However, 13 CLs appeared normal on MR images but were graded abnormal histologically. Lesions appeared to be degenerative, characterised by extensive fibrocartilaginous metaplasia and development of multiple, intercommunicating fissures within the degenerate collagen in severe lesions. There was an association between increased radiopharmaceutical uptake and a higher histological score. Conclusions: High‐field MRI is reasonably reliable for detection of lesions of the CLs of the DIP joint, but may underestimate their prevalence. Clinical relevance: Collateral ligament injury appears to be a primary degenerative process, which may explain the poor response to conservative treatment and a need for promotion of regeneration.     

Effect of a collateral ligament sparing surgical approach on mechanical properties of equine proximal interphalangeal joint arthrodesis constructs

Objective: To (1) compare the effect of a collateral ligament sparing surgical approach with an open surgical approach on mechanical properties of proximal interphalangeal joint (PIPJ) arthrodesis, and (2) to determine the percentage of articular cartilage surface removed by transarticular (TA) drilling with different diameter drill bits. Study Design: Randomized paired limb design. Sample Population: Cadaveric equine limbs (n=76). Methods: Cadaveric PIPJ were drilled using a 3.5, 4.5, or 5.5 mm drill bit at 80–84° to the dorsal plane to remove articular cartilage and subchondral bone from the distal articular surface of the proximal phalanx (P1) and the proximal articular surface of the middle phalanx (P2). Bone ends were photographed and the percentage of the projected surface area that was denuded of cartilage was measured. PIPJ arthrodesis constructs (3‐hole dynamic compression plate [DCP], two 5.5 mm TA screws inserted in lag fashion, medial and lateral to the DCP; DCP‐TA) were created using 2 surgical approaches in paired limbs. A conventional open approach was used in 1 limb and a collateral ligament sparing approach used in the other limb. Constructs were tested to failure in single‐cycle 3‐point dorsopalmar/plantar or lateromedial bending. Maximum load, yield load, and composite stiffness were compared between techniques. Results: The 3.5, 4.5, and 5.5 mm drill bits removed 24±4%, 35±5%, and 45±7% of total PIPJ articular cartilage surface, respectively. Constructs with the collateral ligament sparing approach had significantly greater mean yield load (11.3±2.8 versus 7.68±1.1 kN, P=.008) and mean maximum load (13.5±3.1 versus 10.1±1.94 kN, P=.02) under lateromedial bending. Under dorsopalmar/plantar bending there was no significant difference between surgical approaches. The collateral ligament sparing arthrodesis technique had a shorter surgical time (19±3 minutes) compared with the open technique (31±3 minutes). Conclusion: A collateral ligament sparing surgical approach to the PIPJ with removal of articular cartilage by TA drilling and arthrodesis by DCP‐TA was faster and stronger in mediolateral bending than arthrodesis constructs created with an open surgical approach. Clinical Relevance: Preservation of the collateral ligaments and TA drilling for cartilage removal during PIPJ arthrodesis may be a superior approach to the conventional open approach and warrants clinical evaluation.     

ELASTOGRAPHIC EVALUATION OF NATURALLY OCCURING TENDON AND LIGAMENT INJURIES OF THE EQUINE DISTAL LIMB

Compression elastography is an ultrasonographic technique that estimates tissue strain and may have utility in diagnosing and monitoring soft tissue injuries in the equine athlete. Recently, elastography has been proven to be a feasible and repeatable imaging modality for evaluating normal tendons and ligaments of the equine distal forelimb. The purposes of this prospective study were to investigate the ability of elastography to detect spontaneously occurring lesions of equine tendons and ligaments diagnosed with magnetic resonance imaging (MRI) and gray‐scale ultrasound (US) and to characterize the differences in the elastographic appearance of acute vs. chronic injuries. Fifty seven horses with a total of 65 lesions were evaluated. Images were assessed quantitatively and qualitatively. Acute lesions were found to be significantly softer (P < 0.0001) than chronic lesions (P < 0.0001) and the stiffness of lesions increased with progression of healing (P = 0.0138). A negative correlation between lesion hypoechogenicity and softness was appreciated with more hypoechoic lesions appearing softer (P = 0.0087) and more hyperechoic regions harder (P = 0.0002). A similar finding occurred with increased signal intensity on short tau inversion recovery (STIR) and proton density (PD) MRI sequences correlating with increased softness on elastography (P = 0.0164). Using US and MRI as references, commonly encountered soft tissue injuries of the equine distal limb could be detected with elastography. However, elastography was limited for detecting small, proximal injuries of the hindlimb proximal suspensory ligament. Elastographic evaluation of equine tendons and ligaments may allow better characterization of lesion chronicity and severity, and sequential examinations may optimize lesion management, rehabilitation, and return to training.     

Anatomic variations and degenerative changes in the collateral cartilages and middle and distal phalanges of the forelimb in Ardenner colts

The anatomic variations and the degenerative changes in the collateral cartilages and middle and distal phalanges in 6 Ardenner colts were characterized by radiography, scintigraphy, and magnetic resonance imaging (MRI). The radiographic changes were assessed between the ages of 16.5 and 25 months. An anatomic variation of the middle and distal phalanges was demonstrated in some of the colts. MRI examination of the 6 colts revealed an association between the deep digital flexor tendon cross-sectional area and body weight as well as foot circumference. Also, a thin collateral sesamoidean (suspensory navicular) ligament was observed subjectively. The presence of an extensive ossification of the collateral cartilages of the foot was found in these young horses. The ossification was characterized by the existence of 2 separate ossification centers, which had a tendency to unite. The radiographic interphalangeal degenerative lesions seen appear as bone remodeling of the dorsal edges of the middle and distal phalanx, on the insertion sites of collateral ligaments of the distal interphalangeal joint, the digital extensor tendon, and the distal interphalangeal joint capsule.     

RADIOGRAPHIC MEASUREMENTS OF HOOF BALANCE ARE SIGNIFICANTLY INFLUENCED BY A HORSE'S STANCE

Hoof balance radiographs are commonly used as the basis for corrective farriery decision‐making in horses, however there are limited published data quantifying effects of the stance of the horse or the horizontal radiographic beam angle. In this analytical study, the influence of variation of the horse's stance in the craniocaudal and lateromodial plane on hoof balance measurements as well as the influence of variation of the horizontal radiographic beam angle on dorsopalmar hoof balance measurements was examined. Distal left thoracic limb lateromedial radiographs were acquired using a standardized protocol while varying the craniocaudal stance of five horses, each selected to be sound and conformationally normal. Dorsopalmar foot radiographs were acquired while varying the lateromedial stance; and variable angle horizontal beam dorsopalmar foot radiographs were acquired while keeping the limb position constant. Analyses of measurements demonstrated that hoof pastern angle had a linear relationship (R² = 0.89, P < 0.001) with craniocaudal stance of the horse. The relationship of joint angle and stance was greater for the distal interphalangeal joint angle (R² = 0.89, P < 0.001) than the proximal interphalangeal joint angle (R² = 0.65, P = 0.001). The distal phalanx angle did not change with craniocaudal stance variation. The proximal interphalangeal joint width, distal interphalangeal joint width, or distal phalanx height did not change with lateromedial stance variation, nor within a 15 degree dorsolateral to caudomedial and dorsomedial to caudolateral variation from the dorsopalmar axis. Findings indicated that positioning of the thoracic limb needs to be considered during radiographic interpretation and decision‐making for corrective farriery.     

RADIOGRAPHIC AND ULTRASONOGRAPHIC EVALUATION OF THE PATELLAR LIGAMENT FOLLOWING TIBIAL TUBEROSITY ADVANCEMENT

Effect of tibial tuberosity advancement (TTA) on the patellar ligament has not been described. Our purpose was to evaluate the patellar ligament radiographically and ultrasonographically before and after a TTA. Twenty‐one stifles (20 dogs) were evaluated preoperatively (T0), and at six (n=18) (T1) and 16 weeks (n=17) (T2) postTTA. Radiographically, proximal and distal thickness of the patellar ligament was assessed and a ratio to the total length of the ligament was calculated to compensate for the magnification. Ultrasound evaluation included measurements of the transverse thickness and cross‐sectional area at three different levels, as well as a subjective score of ligament changes. In comparison with T0, all radiographic and ultrasonographic measurements increased significantly, 6 weeks postoperatively (P≤0.04), and did not change 16 weeks postoperatively compared with T1. The subjective score worsened significantly from T0 to T1 and T0 to T2 (P<0.0001), and improved significantly from T1 to T2 (P=0.02). Larger cage size was associated with a more severe increase in radiographic proximal thickness to total length ratio and ultrasonographic middle transverse area at both follow‐up examinations (P0.02). Dogs in which arthrotomy was not performed appeared to have ultrasonographically less changes. In conclusion, patellar desmopathy was a common postoperative sequel to TTA. Surgical trauma, arthrotomy, perfusion injury, complete vs. partial cranial cruciate ligament rupture, larger tibial advancement, postoperative activity or altered insertion angle of the patellar ligament at the tibial tuberosity are suggested causes, that should be elucidated in a larger study cohort.     

Collateral desmitis of the distal interphalangeal joint in conjunction with concurrent ossification of the cartilages of the foot in nine horses

The purpose of this study was to describe the frequency of occurrence of severe ossification of the collateral cartilages (sidebone) coexistent with collateral desmitis of the distal interphalangeal joint (DIPJ) in lame horses. Sidebone was diagnosed and graded on standard radiographs and soft tissue injuries of the foot were diagnosed using standing low‐field magnetic resonance imaging (MRI). Of 15 horses with forelimb lameness and severe sidebone, 9 had evidence of concurrent collateral desmitis of the DIPJ. All 15 horses had damage to other structures (including the deep digital flexor tendon, distal sesamoidean impar ligament, collateral sesamoidean ligament, navicular bone and distal phalanx) within the affected feet as identified on MRI. The clinical and pathophysiological significance of concurrent collateral desmitis of the DIPJ and sidebone is currently uncertain. However, this study shows that injuries to multiple structures within the foot are common and that collateral desmitis of the distal interphalangeal joint is frequently seen in lame horses in conjunction with severe ossification of the collateral cartilages.     

Osseous abnormalities associated with collateral desmopathy of the distal interphalangeal joint: Part 1

Reasons for performing study: Osseous abnormalities. associated with collateral ligament (CL) injury of the distal interphalangeal (DIP) joint have been documented using magnetic resonance imaging (MRI) but there is currently limited information about the frequency of osseous pathology associated with CL injury. Objectives: To determine the frequency of occurrence of osseous abnormality coexistent with CL injury of the DIP joint and describe the distribution and character of osseous lesions; and to establish if there was an association between osseous abnormality and increased radiopharmaceutical uptake (IRU). Hypotheses: There would be a higher incidence of osseous abnormality at the insertion of an injured CL than at the origin; and a relationship between the presence of osseous abnormality and duration of lameness. Materials and methods: Magnetic resonance images of 313 feet of 289 horses with foot pain and a definitive diagnosis of collateral desmopathy of the DIP joint were analysed retrospectively for presence and type of osseous abnormality in the middle and distal phalanges. Scintigraphic images were examined and the presence of IRU in the middle or distal phalanges recorded. Results: Osseous abnormalities were detected in 143 (45.7%) feet, 27 (18.8%) of which had osseous and CL injury alone, while the remaining 116 had CL related osseous injury and multiple injuries within the hoof capsule. Entheseous new bone and endosteal irregularity of the middle and distal phalanges were the most frequent types of osseous abnormality. There was a higher incidence of osseous abnormalities medially than laterally and at the ligament insertion than at the origin. There was a significant association between presence of IRU and osseous injury. Conclusions: A variety of osseous lesions of differing severity are associated with CL injury. Normal radiopharmaceutical uptake does not preclude significant osseous pathology associated with CL injury. Clinical relevance: Further studies are necessary in order to determine if osseous abnormalities associated with CL injury influence prognosis for return to performance.     

MAGNETIC RESONANCE IMAGING,GROSS POSTMORTEM,AND HISTOLOGICAL FINDINGS FOR SOFT TISSUES OF THE PLANTAR ASPECT OF THE TARSUS AND PROXIMAL METATARSAL REGION IN NON‐LAME HORSES

Injuries of the plantar soft tissues of the tarsus and proximal metatarsus can be a source of lameness in horses, however published information is lacking on high field MRI characteristics of these tissues. Objectives of the current anatomic study were to (1) describe high‐field MRI features of the plantar tarsal and proximal metatarsal soft tissues; and (2) compare MRI findings with gross and histological appearances of selected structures for a sample of cadaver limbs from non‐lame horses. Single hindlimbs for 42 horses, and right and left hindlimbs for eight horses were scanned using high‐field MRI. The MRI findings were described for the 50 single limbs; and the MRI, gross postmortem and histological findings were compared for the eight pairs of hindlimbs. The superficial digital flexor tendon had uniform low signal intensity, surrounded by the flexor retinaculum of intermediate to high signal intensity on all sequences. The lateral digital flexor tendon had slightly higher signal intensity, enclosed on the plantaromedial aspects by the low signal intensity metatarsocalcaneal ligament. The accessory ligament of the deep digital flexor tendon varied in size and signal intensity. The proximal and distal plantar ligaments, accessory ligament of the suspensory ligament, and calcaneoquartal ligament had low signal intensity. The long plantar ligament comprised a number of related parts, separated by lines of high signal intensity corresponding with fibrous septae seen in gross anatomical specimens. The plantar aspect of the ligament had uniform low signal intensity in all sequences, but the dorsal half was more heterogeneous with multifocal spots or lines of higher signal intensity.     

Standing MRI lesions of the distal interphalangeal joint and podotrochlear apparatus occur with a high frequency in warmblood horses

Foot pain is a common presenting complaint in Warmblood horses. The aim of this retrospective, cross‐sectional study was to determine the spectrum of foot lesions detected by magnetic resonance imaging (MRI) in Warmblood horses used for dressage, jumping, and eventing. The medical records of 550 Warmblood horses with foot pain that were scanned using standing MRI were reviewed and the following data were recorded: signalment, occupation, lameness, diagnostic analgesia, imaging results, treatments, and follow‐up assessments. Associations between standing MRI lesions and chronic lameness following treatment were tested. Abnormalities of the navicular bone (409 horses, 74%), distal interphalangeal joint (362 horses, 65%), and deep digital flexor (DDF) tendon (260 horses, 47%) occurred with the highest frequency. The following abnormalities were significantly associated (P < .05) with chronic lameness following conservative therapy: moderate to severe MRI lesions in the trabecular bone of the navicular bone, mild or severe erosions of the flexor surface of the navicular bone, moderate sagittal/parasagittal DDF tendinopathies, and moderate collateral sesamoidean desmopathies. Also, identification of concurrent lesions of the DDF tendon, navicular bone, navicular bursa, and distal sesamoidean impar ligament was associated with chronic lameness after conservative therapy. Development of effective treatment options for foot lesions that respond poorly to conservative therapy is necessary.     

EFFECTS OF STIFLE FLEXION ANGLE AND SCAN PLANE ON VISIBILITY OF THE NORMAL CANINE CRANIAL CRUCIATE LIGAMENT USING LOW‐FIELD MAGNETIC RESONANCE IMAGING

Low‐field magnetic resonance imaging (MRI) is commonly used to evaluate dogs with suspected cranial cruciate ligament injury; however, effects of stifle positioning and scan plane on visualization of the ligament are incompletely understood. Six stifle joints (one pilot, five test) were collected from dogs that were scheduled for euthanasia due to reasons unrelated to the stifle joint. Each stifle joint was scanned in three angles of flexion (90°, 135°, 145°) and eight scan planes (three dorsal, three axial, two sagittal), using the same low‐field MRI scanner and T2‐weighted fast spin echo scan protocol. Two experienced observers who were unaware of scan technique independently scored visualization of the cranial cruciate ligament in each scan using a scale of 0–3. Visualization score rank sums were higher when the stifle was flexed at 90° compared to 145°, regardless of the scan plane. Visualization scores for the cranial cruciate ligament in the dorsal (H (2) = 19.620, P = 0.000), axial (H (2) = 14.633, P = 0.001), and sagittal (H (2) = 8.143, P = 0.017) planes were significantly affected by the angle of stifle flexion. Post hoc analysis showed that the ligament was best visualized at 90° compared to 145° in the dorsal (Z = ?3.906, P = 0.000), axial (Z = ?3.398, P = 0.001), and sagittal (Z = ?2.530, P = 0.011) planes. Findings supported the use of a 90° flexed stifle position for maximizing visualization of the cranial cruciate ligament using low‐field MRI in dogs.     

Medial collateral ligament desmitis of the distal interphalangeal joint in the hindlimb of a horse: treatment with cast immobilisation

A 12‐year‐old show‐jumping mare was presented for investigation of a chronic hindlimb lameness of 16 weeks duration. Perineural anaesthesia and ultrasonography localised the lesion to the medial collateral ligament of the distal interphalangeal joint of the left hindlimb. Treatment consisted of a heavily padded distal limb cast for 6 weeks, strict box rest and a strictly regulated hand walking program. Serial ultrasonographic examinations were performed throughout the rehabilitation period. Collateral ligament desmitis of the distal interphalangeal joint is a commonly diagnosed condition of the forelimb; however, hindlimb collateral ligament desmitis has been rarely reported. Ultrasonographic examination in this case was an invaluable diagnostic and follow‐up tool. Immobilisation of the foot by means of a heavily padded distal limb cast allowed excellent healing of the ligament and is presented as a novel treatment for collateral ligament desmitis. At the time of writing the mare had returned to her previous level of exercise and was showing no signs of lameness.     

Anatomical considerations of the distal interphalangeal joint of sheep

The ligamentous attachments and the extent of the capsule of the distal interphalangeal joint of sheep was studied using both dissection and radiographic techniques. The distal interphalangeal joint was considered to be most vulnerable to infection and trauma on the axial, or interdigital, aspect where the joint capsule protrudes above the coronary border. In sheep the interdigital ligament and each proximal collateral sesamoidean ligament help to unite the two digits: a role performed in cattle by the cruciate ligament.     

Influence of the position of the foot on MRI signal in the deep digital flexor tendon and collateral ligaments of the distal interphalangeal joint in the standing horse

Reasons for performing study: Hyperintense signal is sometimes observed in ligaments and tendons of the equine foot on standing magnetic resonance examination without associated changes in size and shape. In such cases, the presence of a true lesion or an artifact should be considered. A change in position of a ligament or tendon relative to the magnetic field can induce increased signal intensity due to the magic angle effect. Objectives: To assess if positional rotation of the foot in the solar plane could be responsible for artifactual changes in signal intensity in the collateral ligaments of the distal interphalangeal joint and in the deep digital flexor tendon. Methods: Six isolated equine feet were imaged with a standing equine magnetic resonance system in 9 different positions with different degrees of rotation in the solar plane. Results: Rotation of the limb induced a linear hyperintense signal on all feet at the palmar aspect of one of the lobes of the deep digital flexor tendon and at the dorsal aspect of the other lobe. Changes in signal intensity in the collateral ligaments of the distal interphalangeal joint occurred with rotation of the limb only in those feet where mediolateral hoof imbalance was present. Conclusions: The position and conformation of the foot influence the signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint. Potential relevance: The significance of increased signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint should be interpreted with regard to the position and the conformation of the foot.     

MAGNETIC RESONANCE IMAGING FINDINGS OF DESMOPATHY OF THE COLLATERAL LIGAMENTS OF THE EQUINE DISTAL INTERPHALANGEAL JOINT

We report the use of a low-field magnetic resonance (MR) imaging system for the detection of desmopathy of the collateral ligament of the distal interphalangeal joint and the long-term outcome. Twenty horses were studied and their medical records and MR images were reviewed retrospectively. Long-term follow-up information was obtained by telephonic questionnaires of owners, trainers, or referring veterinarians. Desmopathy of the medial collateral ligament (80%) and enthesopathy of the affected collateral ligament (80%) were common MR imaging features. Treatment consisted of stall rest followed by a rehabilitation period. Additional treatments included shoeing, extracorporeal shock wave therapy, application of a half limb or foot cast, and medication of the distal interphalangeal joint. Twelve (60%) horses returned to their previous level of exercise and maintained their previous level, whereas eight horses had a poor outcome. Low-field MR imaging in the standing patient can be used to detect collateral ligament desmopathy of the distal interphalangeal joint without a need for general anesthesia.     

Osseous abnormalities associated with collateral desmopathy of the distal interphalangeal joint. Part 2: Treatment and outcome

Reasons for performing study: There are currently few long‐term follow‐up data relating to recovery from injury of a collateral ligament (CL) of the distal interphalangeal (DIP) joint and limited information about the effect of associated osseous injury on prognosis. Objectives: To describe long‐term follow‐up results for horses with CL injury, with and without associated osseous injury; and to determine the effect of extracorporeal shock wave therapy (ECSWT) or radial pressure wave therapy (RPWT) on outcome. Hypotheses: Prognosis for return to performance for horses with CL‐related osseous injury would be worse than for horses with CL injury alone. Methods: Magnetic resonance images from 313 feet of 289 horses with foot pain and a definitive diagnosis of collateral desmopathy of the DIP joint were analysed retrospectively for presence of osseous abnormality associated with the ligament origin or insertion and the middle and distal phalanges. Horses were assigned to groups according to the combination of their injuries. Type of treatment was recorded and follow‐up information obtained. Thirty‐two horses with additional sources of lameness were excluded from analysis of outcome. Results: Follow‐up data were available for 182 horses, 55 of which had follow‐up information for up to 2 years after presentation. Twenty‐seven percent of horses with CL injury alone and 34% of horses with CL related osseous injury returned to their previous performance level. Prognosis for a combination of injuries to multiple soft tissue and osseous structures within the hoof capsule was substantially worse. There was no effect of ECSWT or RPWT on outcome. Conclusions: The presence of mild to moderate CL related osseous injury does not appear to influence prognosis compared with CL injury alone. Clinical relevance: Further studies of a larger number of horses are necessary in order to ascertain if specific types of osseous pathology influence return to performance levels.