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.     

INJURY OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT DIAGNOSED BY MAGNETIC RESONANCE

We describe the clinical, imaging, and necropsy findings of two horses with severe injury of the collateral ligaments of the distal interphalangeal (DIP) joint diagnosed using magnetic resonance (MR) imaging. In MR images it was possible to examine the collateral ligaments of the DIP joint from the origin at the middle phalanx to the insertion on the distal phalanx. Both horses in this report had abnormal high signal intensity within the collateral ligaments of the DIP joint, and one horse had abnormal high signal intensity within the bone of the distal phalanx on short tau inversion recovery (STIR) and T2-weighted imaging sequences. High signal intensity on STIR and T2-weighted images represents abnormal fluid accumulation indicative of inflammation, within ligament, tendon, or bone on these imaging sequences. Abnormalities were confirmed on necropsy in both horses. Injury of the collateral ligaments of the DIP joint should be considered as a source of pain in horses with lameness localized to the foot.     

Shoulder lameness in horses: an analysis of 58 suspected cases

The results of a detailed investigation of 58 horses with suspected shoulder lameness are described. Lameness was found to originate distal to the shoulder region in 22 horses. No diagnosis was reached in five horses. Genuine shoulder problems occurred in 29 horses. The clinical signs of shoulder lameness are described and contrasted with lower limb lameness. The limitations of currently available diagnostic techniques are discussed. Problems identified in the shoulder region included osteochondritis dissecans, subchondral bone cysts, arthrosis, fracture, luxation, septic arthritis and soft tissue damage. Some of the differences between osteochondritis dissecans and subchondral bone cysts are described and it is suggested that these are two separate conditions.     

ULTRASONOGRAPHIC DIAGNOSIS OF COXOFEMORAL SUBLUXATION IN HORSES

The clinical and ultrasonographic features of seven horses with coxofemoral subluxation are presented. Affected horses included five adult geldings (11–20 years), one large pony (6 years) and a 3-month-old filly. All were lame at the walk except for the pony with grade 3/5 lameness. Lameness was acute in all horses, but three horses progressed after initial improvement. Crepitus, muscle atrophy, and pelvic asymmetry were inconsistent findings. Ultrasonographic diagnosis of subluxation required dynamic visualization of femoral head displacement from the acetabulum while placing weight on the affected limb and subsequent replacement into its normal position upon limb resting. Acetabular rim fractures and joint effusion were visible regardless of weight bearing status in six horses each. No fractures were identified in the pony; the only patient with a good outcome. Six horses had a poor outcome with severe chronic lameness, four of which were euthanized. Postmortem ventrodorsal radiographs obtained in two horses confirmed subluxation only on extended limb projections, but not on hip-flexed projections. Acetabular rim fractures were not visible radiographically in either horse but were confirmed at necropsy. Subluxation was due to an elongated but intact ligament of the head of the femur in both horses. Osteoarthrosis was evident ultrasonographically, radiographically, and at necropsy. Dynamic ultrasonography was readily performed in the standing horse and produced diagnostic images with a low frequency curvilinear transducer. The apparent poor prognosis for horses with subluxation and acetabular fracture illustrate the importance of this imaging technique to identify affected horses.     

Quantitative evaluation of subchondral bone injury of the plantaro‐lateral condyles of the third metatarsal bone in Thoroughbred horses identified using nuclear scintigraphy: 48 cases

Reasons for performing study: Increased radio‐isotope uptake (IRU) in the subchondral bone of the plantaro‐lateral condyle of the third metatarsus (MTIII) is a commonly reported scintigraphic finding and potential cause of lameness in UK Thoroughbred racehorses in training and has not been fully documented. Objectives: To characterise lameness attributable to IRU of the subchondral bone of MTIII, compare the scintigraphic findings of these horses with a normal population and evaluate the use of scintigraphy as an indicator of prognosis. Hypothesis: IRU will be in significantly higher in horses with subchondral bone injury and will be related to prognosis and future racing performance. Methods: Data were analysed from 48 horses in which subchondral bone injury of the plantaro‐lateral condyle of MTIII had been diagnosed using nuclear scintigraphy and that met the inclusion criteria. Data recorded included age, sex, trainer, racing discipline, lameness assessment, treatment regimes, radiographic and scintigraphic findings, response to diagnostic analgesia where performed and racing performance pre‐ and post diagnosis. Region of interest (ROI) counts were obtained for the plantar condyle and the mid diaphysis from the latero‐medial view, the ratio calculated and then compared with a control group of clinically unaffected horses. Results: The mean condyle mid‐diaphysis ROI ratio was significantly (P<0.001) higher in the affected population and with positively correlation (P = 0.024) with the level of lameness. The presence of radiographic findings had no significant effect on the ROI ratio. Conclusion: Subchondral bone injury of the plantar lateral condyles of MTIII is a significant cause of lameness in UK Thoroughbred racehorses. Nuclear scintigraphy is a useful diagnostic imaging modality in the detection of affected horses but is a poor indicator of prognosis for the condition. Potential relevance: Better understanding of the clinical manifestations, diagnosis of and prognosis for subchondral bone injury will benefit the Thoroughbred industry in the UK.     

ULTRASONOGRAPHIC FINDINGS IN HORSES WITH FOOT PAIN BUT WITHOUT RADIOGRAPHICALLY DETECTABLE OSSEOUS ABNORMALITIES

Foot pain is an important cause of lameness in horses. When horses with foot pain have no detectable radiographic abnormalities, soft‐tissue assessment remains a diagnostic challenge without magnetic resonance (MR) imaging. Ultrasonography can provide an alternative to MR imaging when that modality is not available but the extent of changes that might be seen has not been characterized. We reviewed the ultrasonographic findings in 39 horses with lameness responding positively to anesthesia of the palmar digital nerves and without radiographically detectable osseous abnormalities. Thirty of the 39 horses had lesions affecting the deep digital flexor tendon (DDFT), 27 had abnormalities in the distal interphalangeal joint of which six had a visible abnormality in the collateral ligament. Ultrasonographic abnormalities were seen in the podotrochlear bursa in 22 horses and in the ligaments of the navicular bone in two horses. Abnormalities of the navicular bone flexor surface were detected in eight horses. In three of the 39 horses, only the DDFT was affected. The other 36 horses had ultrasonographic abnormalities in more than one anatomical structure. Based on our results, ultrasonographic examination provides useful diagnostic information in horses without radiographic changes.     

Subchondral cystic lesions (osteochondrosis) of the femoral heads in a horse

Bilateral subchondral cystic lesions of the femoral head in a horse resulted in lameness. The lesions had resulted in degenerative disease in the left coxofemoral joint. The cause of lameness was confirmed by use of intra-articular anesthesia, joint fluid analysis, and radiography. Subchondral cystic lesions involving the femoral head should be considered in the differential diagnosis of equine lameness localized in the upper portion of the hind limb.     

The use of advanced vs. conventional imaging modalities for the diagnosis of subchondral bone injuries

Damage to the subchondral bone has been associated with a number of orthopaedic diseases. Diagnostic imaging is, therefore, critical in identifying disease and damage of the subchondral bone, not only for the diagnosis of joint and subchondral bone disease causing lameness, but also for identifying early/pre-symptomatic damage. The aims of this Critically Appraised Topic (CAT) were to assess the published evidence for the use of advanced imaging techniques (magnetic resonance imaging [MRI] and computed tomography [CT]) in the diagnosis of subchondral bone disease in the distal limb joints (metacarpo/metatarsophalangeal and interphalangeal joints) of the adult horse, and to compare the diagnostic value of these techniques with radiography. In the studies reviewed in this CAT, advanced imaging modalities (MRI and CT) were superior to routine radiography for the diagnosis of subchondral bone injury of the distal limb joints. In a small percentage of horses, post-MRI reevaluation of the initial radiographs or acquiring further lesion-orientated radiographs allowed the identification of the subchondral bone injury. Extended radiographic examinations, including non-standard views, might increase the sensitivity of radiography to detect subchondral bone injuries, however, currently CT and MRI may be considered the “gold standard” imaging modalities. More studies comparing the identification of subchondral bone lesions on imaging and by histopathological/gross examination would be useful to assess more precisely the sensitivity and specificity of the different modalities.     

Osseous cyst‐like lesions in the feet of lame horses: Diagnosis by standing low‐field magnetic resonance imaging

Osseous cyst‐like lesions (OCLLs) were diagnosed by standing low‐field magnetic resonance (MR) imaging in 9 mature horses (age range 6–17 years). All horses had been subjected to a routine lameness evaluation (including standard foot radiographs) with no diagnosis being reached prior to MR imaging. The duration of lameness ranged from one month to one year. OCLLs were diagnosed in 12 feet. The site of the lesions included the distal phalanx in 11 feet (subchondral bone in 4, insertion of collateral ligaments of the distal interphalangeal joint in 4, insertion of the distal sesamoidean impar ligament in 3) and the subchondral bone of the distal aspect of the middle phalanx in one foot. OCLLs were characterised by discrete spherical or elliptical areas of high or intermediate signal in all MR sequences. In most cases the lesion was surrounded by a rim of bone with abnormally low signal.     

Arthroscopic autologous osteochondral mosaicplasty for the treatment of subchondral cystic lesion in the medial femoral condyle in a horse

An 11-year-old, Hungarian half-bred stallion was presented with a history of mixed left hindlimb lameness of 6 months duration. Subchondral bone cyst of the medial femoral condyle and injury of the medial meniscus were diagnosed. Osteochondral autograft transplantation (mosaic arthroplasty) was performed, taking grafts from the less weight-bearing medial border of the medial femoral trochlea of the affected limb, and transplanting them into the cyst during arthroscopy. The lameness was evaluated prior to and one year after the operation with a motion analysis system during treadmill exercise. Considerable improvement of the lameness and the clinical signs as well as successful transplantation of the grafts, and a new hard joint cartilage surface of the medial femoral condyle could be detected during follow-up arthroscopy. Osteochondral autograft transplantation seems to bee a possible alternative for treating subchondral cystic lesions of the medial femoral condyle in horses. A new technique for the surgical treatment of a subchondral cystic lesion of the medial femoral condyle in the horse is described.     

Osteochondrosis-like lesion of the anconeal process in two horses

A suspected lesion of osteochondrosis dissecans involving the anconeal process of the humeroradial joint (elbow) was found in 2 horses. In horse 1, the lesion was found during routine lameness examination, during which alleviation of the lameness was achieved after intra-articular anesthesia of the elbow. In horse 2, the lesion was found at necropsy. Horse 1 responded satisfactorily to intra-articular treatment with hyaluronic acid. Both horses also had other joints affected with osteochondrosis dissecans.     

OSSEOUS LESIONS IN THE METACARPO(TARSO)PHALANGEAL JOINT DIAGNOSED USING LOW-FIELD MAGNETIC RESONANCE IMAGING IN STANDING HORSES

We report the use of low-field standing magnetic resonance imaging in the standing horse for the diagnosis of osseous lesions in the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint that were not apparent using standard radiography. Thirteen horses were studied and all had thickening of the subchondral bone plate and abnormal signal intensity in the adjacent spongiosa in either the condyles of metacarpal/metatarsal III or the proximal phalanx or both. Abnormalities were characterized by diffuse decreased signal intensity on T1-weighting adjacent to the subchondral bone and within the spongiosa in at least two imaging planes; in the absence of increases in signal intensity in fat-suppressed images, this change was interpreted as bone sclerosis. Nine horses also had a diffuse decreased signal intensity on T2^*-weighting in the same areas and five had a diffuse increase in signal intensity in fat-suppressed images in conjunction with a decrease in signal intensity on T1- and T2^*-weighted images; the increase in signal intensity in fat-suppressed images was interpreted as fluid accumulation. Five horses had a focal area of change in signal intensity within the subchondral bone with apparent loss of definition between the subchondral bone and the articular cartilage. Eleven horses were available for follow up, of which eight were sound and three remained lame. We conclude that lameness originating from the MCP or MTP joint may be associated with osseous damage in horses of any signalment in the absence of radiographic changes.     

Using magnetic resonance imaging to diagnose nondisplaced fractures of the second phalanx in horses

Two horses presented with a history of severe lameness that was localised to the area around the second phalanx (P2) of one forelimb. Radiographs of the second phalanx of both horses were unremarkable, apart from some smooth periosteal new bone production on the dorsum of P2. Magnetic resonance imaging revealed a non-displaced fracture of P2 in both horses. One horse was euthanased because of a poor prognosis for racing, but the second horse was treated conservatively and salvaged for breeding. Magnetic resonance imaging is a newer imaging modality in horses and may be useful in diagnosing cases of obscure lameness.     

Epidural morphine and detomidine decreases postoperative hindlimb lameness in horses after bilateral stifle arthroscopy

OBJECTIVE: To determine whether preoperative epidural administration of morphine and detomidine would decrease postoperative lameness after bilateral stifle arthroscopy in horses. STUDY DESIGN: Prospective clinical controlled study. ANIMALS: Eight adult horses that had bilateral arthroscopic procedures, including drilling of cartilage and subchondral bone within the femoropatellar joints. METHODS: Horses were randomly separated into 2 groups. Preoperatively, 4 horses were administered a combination of epidural morphine (0.2 mg/kg) and detomidine (30 microg/kg), and 4 horses were administered an equivalent volume of epidural saline (0.9% NaCl) solution. Postoperative pain was assessed using 6 video recordings made at hourly intervals of each horse at a walk. Assessments began 1 hour after recovery from anesthesia. The recordings were scrambled out of sequence and evaluated by 3 observers, unaware of treatment groups, who scored lameness from 0 to 4. Lameness scores of the 2 groups of horses were compared using a Wilcoxon's rank sum test. Heart and respiratory rates were also measured at each hourly interval and compared between groups using a repeated-measures ANOVA; statistical significance was set at P <.05. RESULTS: Preoperative administration of epidural morphine and detomidine significantly decreased lameness and heart rates after bilateral stifle arthroscopy. The greatest decrease was detected at hours 1 and 2 after recovery from anesthesia. CONCLUSION: We conclude that horses undergoing a painful arthroscopic procedure of the stifle joint benefit from the administration of preoperative epidural morphine and detomidine. CLINICAL RELEVANCE: Preoperative epidural administration of detomidine and morphine may be useful in decreasing postoperative pain after stifle arthroscopy as well as pain associated with other painful disorders involving the stifle joint, such as septic arthritis and trauma.     

CLINICAL AND DIAGNOSTIC IMAGING CHARACTERISTICS OF LATERAL DIGITAL FLEXOR TENDINITIS WITHIN THE TARSAL SHEATH IN FOUR HORSES

Lateral digital flexor tendonitis is a rarely reported cause of hind limb lameness in performance horses. The purpose of this retrospective study was to describe clinical and diagnostic imaging findings for a group of horses with lateral digital flexor tendinitis within the tarsal sheath. Equine cases with a diagnosis of lateral digital flexor tendonitis and magnetic resonance imaging (MRI) studies of the affected region were retrieved from North Carolina University's medical record database. Recorded data for included horses were signalment; findings from history, physical examination, lameness examination, and all diagnostic imaging studies; treatment administered; and outcome. Four horses met inclusion criteria. Lameness was mild/moderate in severity and insidious in onset in all patients. Responses to flexion tests were variable. All horses showed positive improvement (70–90%) in lameness after tarsal sheath analgesia. Radiographic, scintigraphic, and ultrasonographic findings were inconclusive. For all horses, MRI characteristics included increased T2, PD, and STIR signal intensity within the lateral digital flexor tendon in the area of the tarsal sheath. Tarsal sheath effusion was slight in three horses, and mild/moderate in one horse. With medical treatment, two horses were sound at 6‐month followup, one horse was sound at 1‐year followup, and one horse had a slight persistent lameness (grade 1/5) at 9‐month followup. Findings supported the use of MRI for diagnosing lateral digital flexor tendonitis within the tarsal sheath in horses. Affected horses may have a good prognosis for return to athletic performance following appropriate medical treatment.     

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.     

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.     

Arthroscopic findings in horses with subtle radiographic evidence of osteochondral lesions of the medial femoral condyle: 15 cases (1995-2002)

OBJECTIVE: To determine arthroscopic findings in lame horses with subtle radiographic lesions of the medial femoral condyle. DESIGN: Retrospective study. ANIMALS: 15 horses examined because of lameness that had subtle radiographic evidence of osteochondral lesions involving the medial femoral condyle in at least 1 joint. PROCEDURE: Medical records were reviewed, and results of physical examination, radiography, and arthroscopy were recorded. Follow-up information was obtained through reexamination of the horses or telephone conversations with the referring veterinarians, owners, or trainers. RESULTS: Lameness severity ranged from grade 1 to 3 on a scale from 0 to 5. Radiography and arthroscopy were performed on 28 stifle joints. The 4 unaffected joints in 4 horses with unilateral hind limb lameness that underwent bilateral arthroscopy had no radiographic lesions, but 2 of the 4 had arthroscopic lesions. Of the remaining 24 joints, 20 had radiographic evidence of flattening of the apex of the medial femoral condyle and 4 had minimal subchondral lucency. Lesions were identified arthroscopically in 18 of the 20 joints with flattening of the condyle and in all 4 joints with subchondral lucency. Treatment consisted of abrasion arthroplasty or microfracture. Seven of the 9 horses with focal cartilage lesions and 2 of the 6 horses with generalized cartilage lesions were reportedly sound without any evidence of joint effusion at the time of final follow-up. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that horses with hind limb lameness and subtle radiographic lesions of the medial femoral condyle are likely to have arthroscopically apparent cartilage lesions and subchondral bone defects.     

Intra-articular Anesthesia of the Distal Interphalangeal Joint Alleviates Lameness Associated With the Navicular Bursa in Horses

Objective — To determine if intra-articular anesthesia of the distal interphalangeal joint could alleviate lameness associated with the navicular bursa in horses.
Study Design — Experimental investigation.
Animals — Six clinically normal horses.
Methods — Lameness was induced in each horse by injecting either the left or right front navicular bursa with 5 mg of amphotericin-B. Forty-eight hours later each horse was videotaped walking and trotting before, and 5, 30, and 60 minutes after injecting the distal interphalangeal joint of the treated limb with 5 mL of 2% mepivacaine hydrochloride. All video recordings were then rerecorded onto master tapes in a random sequence. Four clinicians, unaware of the animal identity related to observation time or limb treated, independently viewed these tapes and graded the lamenesses.
Results — There was a significant reduction in lameness 5 and 30 minutes after anesthetic was injected into the distal interphalangeal joint. Lameness scores 60 minutes after anesthetic administration were not significantly different than baseline values. Gross pathological examination confirmed marked inflammation of the treated navicular bursae and normal appearance of the distal interphalangeal joints.
Conclusions — Intra-articular anesthesia of the distal interphalangeal joint can alleviate lameness associated with the navicular bursa.
Clinical Relevance — Intra-articular anesthesia of the distal interphalangeal joint is not specific only for lameness originating in the distal interphalangeal joint.     

Diagnosis and treatment of carpometacarpal desmopathy in a horse

A 9‐year‐old Warmblood gelding underwent magnetic resonance (MR) imaging of the carpal and proximal metacarpal regions for evaluation of prolonged right forelimb lameness. Magnetic resonance findings were indicative of desmopathy of the right lateral carpometacarpal ligament and the interosseous ligament between the third and fourth metacarpal bones. Based on the MR findings and lack of response to conservative therapy, surgery using a drilling technique was performed to facilitate fusion of the right carpometacarpal joint. After surgery and a 6‐month rest and rehabilitation programme, the horse returned to soundness. This case report describes a unique combination of lateral carpal/proximal metacarpal soft tissue injuries that resulted in prolonged lameness and were treated with facilitated arthrodesis of the carpometacarpal joint. These soft tissue injuries should be considered as a differential diagnosis in horses with lameness localised to the proximal metacarpal/distal carpal region.