Disorders of the origin of the suspensory ligament in the horse: a diagnostic challenge

Lameness in horses due to pain originating from the proximal metacarpal/metatarsal region remains a diagnostic challenge. In cases of obvious lameness the pain can be localised to this region by diagnostic anaesthesia. Because a variety of disorders can cause lameness in this region different imaging modalities including radiography, ultrasonography and scintigraphy should be used to arrive at an accurate diagnosis. Even though a precise anatomic-pathologic diagnosis can still be an enigma, because not only bone and joints, but also soft tissue structures including the proximal suspensory ligament, its origin at the proximal metacarpus/ metatarsus, its fascia, the superficial fascia, as well as the intermetacarpal/metatarsal ligaments, the accessory ligament of the deep digital flexor tendon and both digital flexor tendons may be involved. Magnet resonance tomography (MRT) shows a high diagnostic sensitivity in imaging soft tissue structures and bone. In horses MRT is still at the beginning. The MRT appearance of the proximal metacarpal/metatarsal region has not yet been evaluated in detail and there are only few anatomic studies of the origin of the suspensory ligament in horses. The first experiences showed, that more gross and histologic examinations are necessary to fully interpret MRT-images and to differentiate pathologic alterations from clinically not relevant variations.     

MRI FEATURES OF METACARPO(TARSO)PHALANGEAL REGION LAMENESS IN 40 HORSES

Lameness originating from the metacarpo(tarso)phalangeal (MP) joint has a significant effect on the use and athletic competitiveness of a horse. The identification of the cause of lameness originating from the MP joint can be challenging, given the limitations of radiography, ultrasonography, and nuclear scintigraphy. Our purpose was to describe the injury types and incidence in magnetic resonance imaging (MRI) studies from 40 horses with lameness attributable to the MP joint region where it was not possible to reach a clinically plausible diagnosis using other imaging modalities. Horses were examined in a 1.5 T magnet (Siemens Medical Solutions) under general anesthesia. The frequency of occurrence of MR lesions was subchondral bone injury (19), straight or oblique distal sesamoidean desmitis (13), articular cartilage injury and osteoarthritis (eight), suspensory branch desmitis (seven), osteochondral fragmentation (seven), proximal sesamoid bone injury (seven), intersesamoidean desmitis (four), deep digital flexor tendonitis (four), collateral desmitis (three), superficial digital flexor tendonitis (two), enostosis‐like lesions of the proximal phalanx or MCIII (two), desmitis of the palmar annular ligament (one), desmitis of the proximal digital annular ligament (one), and dystrophic calcification of the lateral digital extensor tendon (one). Twenty‐five horses had multiple MR abnormalities. MRI provided information that was complementary to radiography, ultrasonography, and nuclear scintigraphy and that allowed for a comprehensive evaluation of all structures in the MP joint region and a diagnosis in all 40 horses.     

Hindlimb lameness associated with proximal suspensory desmopathy and injury of the accessory ligament of the suspensory ligament in five horses

The accessory ligament of the hindlimb suspensory ligament arises from the plantar aspect of the calcaneus and fourth tarsal bones and blends with the suspensory ligament in the proximal aspect of the metatarsus. The accessory ligament of the suspensory ligament of both hindlimbs of 12 mature horses, with no history of hindlimb lameness, was assessed ultrasonographically. The ligament comprised linear parallel echoes which were consistently shorter than those of the lateral digital flexor tendon; the dorsal and plantar borders were parallel. Lameness associated with injury of the accessory ligament of the suspensory ligament was identified in 6 of 8 lame hindlimbs of 5 horses, unilaterally in 4 horses and bilaterally in one horse. In all horses there was concurrent proximal suspensory desmopathy. There was localised oedematous swelling on the distal medial aspect of the chestnut extending distally in 2 horses. Lameness was best identified when the horses were ridden. Perineural analgesia of the deep branch of the lateral plantar nerve abolished lameness in 3 horses but perineural analgesia of the tibial nerve was required to abolish lameness in the hindlimb with injury of the accessory ligament of the suspensory ligament in 2 horses. Injury of the accessory ligament of the suspensory ligament was characterised by marked decrease in echogenicity of the ligament and loss of parallel alignment of the linear echoes, which were shorter than normal in longitudinal images.     

Use of magnetic resonance imaging identify suspensory desmitis and adhesions between exostoses of the second metacarpal bone and the suspensory ligament in four horses

Four horses were examined because of chronic forelimb lameness. In all horses, the cause of the lameness was localized to the metacarpus by means of physical examination and diagnostic anesthesia, and radiography of the affected limb revealed a small exostosis of the second metacarpal bone. Magnetic resonance imaging revealed suspensory desmitis in the region of this exostosis in all 4 horses. In addition, an abnormal area of low signal intensity, suggestive of an adhesion, was seen between the exostosis and the suspensory ligament. In all horses, an adhesion between the suspensory ligament and the exostosis on the second metacarpal bone was identified and transected at surgery, and the exostosis and distal portion of the second metacarpal bone were removed. All horses were able to return to their previous athletic use following a 6-month rest and rehabilitation program for treatment of the suspensory desmitis. Findings in these horses suggest that adhesions between the suspensory ligament and an exostosis of the second metacarpal bone may be a cause of chronic or recurrent forelimb lameness in horses.     

Concurrent proximal suspensory desmopathy and injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon in forelimbs or hindlimbs in 19 horses

Clinical features of proximal suspensory desmopathy (PSD) and concurrent injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon (ALDDFT) have not been documented. The objectives were to describe clinical signs and diagnosis. This was a retrospective study. Patient details, lame limb(s), response to diagnostic analgesia, and radiographic and ultrasonographic findings were recorded. PSD and injury of the proximal aspect of the ALDDFT were identified in 19 horses, 14 with forelimb lameness (unilateral 5, bilateral 9) and 5 with hindlimb lameness (unilateral 2, bilateral 3). Localising clinical signs were seen in 7/31 lame limbs (subtle thickening in the region of the ALDDFT [n = 3], pain on palpation of the body of the suspensory ligament (SL) [n = 6], heat in the proximal metacarpal or metatarsal region [n = 2]). Forelimb lameness was abolished by perineural analgesia of the palmar metacarpal (subcarpal) nerves in 17/23 limbs. In the remaining limbs intra‐articular analgesia of the middle carpal joint (n = 2) or an ulnar nerve block (n = 4) were required to eliminate the lameness. Hindlimb lameness was abolished by perineural analgesia of the deep branch of the lateral plantar nerve (n = 2) or local infiltration of the proximal plantar aspect of the metatarsus (n = 3); a tibial nerve block resolved lameness in the remaining 3 limbs. Lesions of the SL and of the ALDDFT were characterised ultrasonographically by enlargement, heterogeneous echogenicity and loss of long linear echoes in longitudinal images. In 3 horses adhesions between the ALDDFT and the SL were identified post mortem. Close apposition of these structures seen ultrasonographically may indicate adhesion formation. It was concluded that the clinical features of PSD and concurrent injury of the ALDDFT are similar to those for PSD alone, highlighting the need for comprehensive and systematic ultrasonographic assessment.     

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.     

Magnetic Resonance Imaging Findings in the Proximal Metacarpal Region of 359 Horses and Proximal Metatarsal Region of 64 Horses Acquired Under Standing Sedation

Standing magnetic resonance (MR) images of proximal metacarpal/metatarsal regions are increasingly being acquired. This study aimed at describing ranges of abnormalities detected in sport/racehorses, using retrospective evaluation of magnetic resonance imaging (MRI) reports from horses with lameness isolated to proximal metacarpal/metatarsal regions with images acquired standing. It was hypothesized that MRI features are different between metacarpal and metatarsal regions and between horses doing different sports. Reports from 359 forelimbs and 64 hindlimbs were included. Palmar/plantar metacarpal/metatarsal bone injury and suspensory desmopathy, which often occurred concurrently, were most frequently reported. Third metacarpal abnormalities were more likely at palmar/medial locations, including cortical (86.4%) and trabecular (38.2%) pathology with frequent thickening, irregularity, and periosteal/endosteal abnormalities. Fluid signal was reported in cortical (38.7%) and trabecular (22.6%) bone. Medial intermetacarpal articulation abnormalities were more frequently reported (52.5%) than lateral. Suspensory ligament pathology was reported in 83.8% forelimbs, frequently with cortical (74.1%) or trabecular (32.9%) pathology. Tarsal-joint abnormalities were significantly more likely than carpal-joint abnormalities. Third metatarsal cortical (57.8%) and trabecular (20.3%) pathology was most frequently plantar, but significantly more likely to be dorsal than forelimbs. Metatarsal fluid signal was significantly less likely than metacarpal. Lateral intermetatarsal articulation pathology (23.4%) was more frequent than medial; medial was significantly more likely in forelimbs. Suspensory ligament abnormalities were reported in 64.1% hindlimbs, 39.1% having concurrent cortical pathology. Metacarpal fluid signal was significantly more likely in endurance/racehorses than dressage/show jumping horses. Dressage was overrepresented in hindlimb suspensory origin pathology. These findings indicate different pathology patterns between forelimb/hindlimb and between different sports and may be useful for MRI interpretation.     

CLINICAL, MAGNETIC RESONANCE, AND SONOGRAPHIC IMAGING FINDINGS IN HORSES WITH PROXIMAL PLANTAR METATARSAL PAIN

Sonography is commonly used for diagnosis of desmopathy of the proximal part of the suspensory ligament in horses. However, magnetic resonance (MR) imaging has been stated to be superior for detecting disease and localizing lesions. In this retrospective study of 39 horses or 46 hind limbs with lameness due to proximal plantar metatarsal pain, the clinical and diagnostic findings are discussed and sonography and MR imaging compared for examination of the proximal part of the suspensory ligament. With MR imaging interpreted as the clinical gold standard, desmopathy of the proximal part of the suspensory ligament was diagnosed in 21 hind limbs, proximal plantar metatarsal pain of unknown cause in 12, an osseous injury at the origin of the suspensory ligament in four and a condition unrelated to the suspensory ligament in nine. Based on these findings, sonography had a sensitivity of 0.77 and 0.66 and specificity of 0.33 and 0.31 for diagnosing proximal suspensory desmopathy and for accurately localizing lesions, respectively. MR imaging changes consistent with proximal suspensory desmopathy were signal hyperintensities and an increase in cross-sectional area compared with the contralateral limb. Anesthesia of the deep branch of the lateral plantar nerve is not specific neither for proximal suspensory desmopathy, as conditions unrelated to the suspensory ligament were diagnosed, nor for diagnosis of proximal plantar metatarsal pain, as conditions outside the proximal plantar metatarsal region were also diagnosed.     

MAGNETIC RESONANCE IMAGING FEATURES OF OBLIQUE AND STRAIGHT DISTAL SESAMOIDEAN DESMITIS IN 27 HORSES

Injury to the oblique and straight distal sesamoidean ligaments is becoming recognized as a more common cause of lameness in horses than was previously thought. The purpose of this study was to review the magnetic resonance (MR) imaging findings of 27 horses affected with desmitis of the oblique and/or straight distal sesamoidean ligament and determine long-term prognosis for horses with this diagnosis. Imaging was performed with horses in right lateral recumbency in a high-field 1 T magnet. All horses had lameness localized to the digit or metacarpophalangeal/metatarsophalangeal joint region with diagnostic local anesthetic blocks. Ten horses had forelimb lameness and 17 horses had hind limb lameness. MR imaging revealed abnormalities in the oblique distal sesamoidean ligaments in 18 horses, in the straight distal sesamoidean ligament in three horses, and in both the oblique and straight distal sesamoidean ligament in six horses. Treatment consisted of a 6-month rest and rehabilitation program in all horses. The digital flexor tendon sheath was injected with methylprednisolone acetate and hyaluronic acid in 22 horses to decrease inflammation in the injured ligaments before starting the rest and rehabilitation program. Two horses had ligament splitting performed, one in the oblique distal sesamoidean ligament and one in the straight distal sesamoidean ligament. MR imaging is an effective method for diagnosing injury to the oblique and straight distal sesamoidean ligaments in horses. Treatment, primarily a 6-month rest and rehabilitation program, allowed 76% of the horses to successfully resume performance.     

Mineralization can be an incidental ultrasonographic finding in equine tendons and ligaments

Tendon/ligament mineralization is recognized in horses but information regarding its clinical significance is limited. The aims of this observational study were to report the structures most commonly affected by ultrasonographically detectable mineralization and, for these, determine frequency of diagnosis and key clinical features. Cases presented at our hospital in April 1999–April 2013 and September 2014–November 2015 were included: a total of 27 horses (22 retrospective, five prospective). Mineralizations were most common in deep digital flexor tendons (10) and suspensory ligament branches (eight), representing 10% and 7% (estimated), respectively, of horses diagnosed with injuries to these structures during the study. Two deep digital flexor tendon and three suspensory ligament branch cases showed bilateral mineralization. Deep digital flexor tendon mineralization was restricted to the digital flexor tendon sheath, most commonly in the proximal sheath (±sesamoidean canal), and seven of 10 cases involved hindlimbs. Suspensory ligament branch mineralization was visible in the same ultrasound window as the proximal sesamoid bones in 10/11 limbs and six of eight cases involved forelimbs. Previous corticosteroid medication was a feature of one deep digital flexor tendon and one suspensory ligament branch case. Mineralization was associated with lameness in some but not all limbs. Mineralized foci within the deep digital flexor tendon preceded hypoechoic lesion formation in two limbs. Of the cases with deep digital flexor tendon or suspensory ligament branch injury only, one of three and two of three cases, respectively, became sound. Findings indicated that tendon/ligament mineralization can be associated with lameness in some horses, but can also be an incidental finding.     

Detection of an epidermoid cyst in the foot of a horse by use of magnetic resonance imaging

CASE DESCRIPTION-A 4-year-old Quarter Horse stallion was evaluated because of a 10-month history of moderate (grade 3/5) left forelimb lameness (detectable during trotting over a smooth, hard surface). CLINICAL FINDINGS-No abnormalities were detected in either forelimb via palpation or application of hoof testers; however, lameness was eliminated after administration of a palmar digital nerve block in the left forelimb. Whereas radiography and ultrasonography did not identify any left forelimb foot abnormalities, magnetic resonance (MR) imaging revealed a circumscribed soft tissue mass in the distal aspect of the digital flexor tendon sheath (DFTS) dorsal to the lateral aspect of the deep digital flexor tendon. Subsequently, the left forelimb DFTS was injected with local anesthetic, which resulted in 90% improvement of the horse's lameness. TREATMENT AND OUTCOME-The distal aspect of the left forelimb DFTS was evaluated tenoscopically. The mass was removed under tenoscopic guidance, after which the distal digital annular ligament was transected. The horse received phenylbutazone orally for 10 days, and the left forelimb DFTS was injected with hyaluronic acid and methylprednisolone acetate 7 days after the surgery. Following a rehabilitation program, the horse was returned to full training at 6 months after surgery and competed successfully during a 2-year follow-up period. CLINICAL RELEVANCE-Use of MR imaging should be considered in all lame horses for which a definitive diagnosis cannot be made via radiography, ultrasonography, or other imaging techniques, especially when the lameness has been localized to a specific anatomic region by use of diagnostic anesthesia.     

EFFECT OF PERINEURAL ANESTHESIA ON THE ULTRASONOGRAPHIC APPEARANCE OF EQUINE PALMAR METACARPAL STRUCTURES

The purpose of this study was to describe ultrasonographic changes of the equine palmar metacarpal area attributed to the infiltration of local anesthetic solution and to determine whether these changes were noted immediately or at 24 h. The palmar metacarpal region of one forelimb in each of six horses was examined ultrasonographically with a 10-MHz linear array transducer and a 7.5-MHz curvilinear transducer. Transverse and longitudinal images were recorded at 5-cm intervals distal to the accessory carpal bone. High and low palmar and palmar metacarpal nerve blocks were performed with a 2% mepivacaine hydrochloride solution. Ultrasonographic examinations similar to the initial examination then were performed immediately, 1 h and 24 h postinjection. Cross-sectional area and mean pixel value were determined for the superficial and deep digital flexor tendons, the accessory ligament of the deep digital flexor tendon, the suspensory ligament, and the suspensory branches at each level and time period. Subjective ultrasonographic changes also were noted. No significant difference was noted in the cross-sectional area or mean pixel value of any structure at any level or time period compared to baseline. Subjective changes in the tendons and ligaments were not noted. There was mild hypoechoic swelling of the surrounding soft tissues and gas in the region of the injections. Gas could interfere with the evaluation of the origin of the suspensory ligament and the proximal portion of the accessory ligament of the deep digital flexor tendon within the first hour but was not detectable ultrasonographically at 24 h. Based on these findings, if gas interferes with an ultrasonographic examination performed temporally close to perineural anesthesia, a repeat examination at 24 h is recommended.     

Ultrasound appearance of the palmar metacarpal soft tissues of the horse

Using real-time ultrasound imaging, the normal anatomy of the soft tissues of the palmar aspect of the equine forelimb was examined. Sections of frozen specimens were prepared which correlated well with the ultrasound images. The superficial and deep digital flexor tendons, tendon sheaths, inferior check ligament (accessory ligament of the deep digital flexor tendon), suspensory ligament, contours of the apices of the proximal sesamoids and the intersesamoidean ligament, were identified.     

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

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

The use of computed tomography to diagnose bilateral forelimb tendon pathology in a horse with unilateral lameness

A horse with unilateral forefoot lameness had bilateral deep digital flexor tendon (DDFT) lesions on computed tomography (CT). Venous contrast enhanced CT revealed distal sesamoidean impar desmitis in the lame forelimb. Computed tomography is useful for diagnosis of soft tissue lesions within the hoof capsule and contrast enhancement improves lesion conspicuity.     

SCINTIGRAPHIC EVALUATION OF THE PROXIMAL METACARPAL AND METATARSAL REGIONS OF HORSES WITH PROXIMAL SUSPENSORY DESMITIS

The aim of the study was to characterize radiopharmaceutical uptake patterns in horses with clinical and ultrasonographic evidence of proximal suspensory desmitis. It was hypothesized that radiopharmaceutical uptake in the proximal palmar (plantar) aspect of the third metacarpal (metatarsal) bone would be greater in lame limbs of horses with proximal suspensory desmitis than in sound limbs and that there would be a positive correlation between the severity of ultrasonographic abnormalities and the degree of radiopharmaceutical uptake. Nuclear scintigraphic evaluation of the proximal metacarpal or metatarsal regions of 126 horses with ultrasonographic evidence of proximal suspensory desmitis was performed. In all horses lameness was substantially improved by perineural analgesia of the palmar metacarpal (subcarpal) or plantar metatarsal (subtarsal) nerves. Scintigraphic images were assessed subjectively, by profile analysis and using region of interest analysis. Associations between the degree of ultrasonographic abnormality and radiopharmaceutical uptake ratios and the presence of radiographic abnormalities and radiopharmaceutical uptake ratios were analyzed. Subjectively, the majority of horses had normal radiopharmaceutical uptake. Profile analysis provided little additional information. However with region of interest analysis there was greater radiopharmaceutical uptake ratios in plantar images in the proximal metatarsal regions of lame limbs compared with nonlame limbs. There was no association between radiological abnormalities and radiopharmaceutical uptake ratios. In forelimbs there was no association between ultrasonographic lesion grade and radiopharmaceutical uptake ratios, however in hindlimbs there was a significant relationship between ultrasonographic grade and radiopharmaceutical uptake ratios.     

Anatomical, magnetic resonance imaging and histological findings in the accessory ligament of the deep digital flexor tendon of forelimbs in nonlame horses

Reasons for performing the study: Detailed magnetic resonance imaging (MRI) and histological appearances of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) have not been documented previously in detail. Objectives: To: 1) describe anatomical connections between the AL‐DDFT and adjacent structures; 2) describe high‐field and low‐field MRI and histological appearances of the AL‐DDFT in the forelimb of horses with no carpal or proximal metacarpal pain; and 3) assess the relationship between age, breed, gender, height, weight and MRI findings. Methods: Ten forelimbs were dissected to determine anatomical relationships among the AL‐DDFT and adjacent structures. High‐ and low‐field MR images of the AL‐DDFT and related structures from 29 cadaver limbs of nonlame horses were analysed subjectively and objectively. The relationship between age, breed, gender, height, weight and MRI findings was assessed using a Chi‐squared test. Twelve ALs‐DDFT were examined histologically. Histological and MRI findings were compared subjectively. Results: Fibrous bundles were seen between the AL‐DDFT and the lateral aspect of the superficial digital flexor tendon (n = 9) and the DDFT (n = 2). The AL‐DDFT had low to intermediate signal intensity in most limbs in most high‐field and low‐field MRI sequences. In 69% of limbs, oblique bands of higher signal intensity than the rest of the ligament were identified in high‐field images of the AL‐DDFT. The cross‐sectional area of the AL‐DDFT in the proximal 7 cm of the metacarpal region ranged from 68.1–299 mm². There was no significant relationship between age, gender, weight or height and either the cross‐sectional area of the AL‐DDFT or the presence of oblique higher signal intensity bands. Histological examination revealed that the AL‐DDFT had thick collagen bundles arranged in large crimps and sometimes crossing in oblique directions. The cellularity was greater than in the deep digital flexor tendon in all limbs. Conclusion and potential relevance: The large variability in the MRI appearance and size of the AL‐DDFT in nonlame horses should be borne in mind when interpreting MR images of lame horses.     

Surgical treatment of a second metacarpal bone exostosis with associated desmitis of the body of the suspensory ligament in a horse

This report outlines the diagnosis, surgical treatment and successful outcome following treatment of second metacarpal bone exostosis with concurrent suspensory ligament desmitis, and lameness in a horse. Magnetic resonance imaging was useful in determining the extent of pathology within the suspensory ligament and site of proposed surgical resection. MRI was also utilised as a post-operative tool in determining the timescale for satisfactory healing to enable the horse to return to athletic work.     

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.