Observations on the anatomy and pathology of the palmar intercarpal ligaments in the middle carpal joints of thoroughbred racehorses

Morphometric analysis of the intercarpal ligaments of the equine proximal carpal bones during simulated flexion and extension of cadaver limbs

Despite many reported cases of carpal lameness associated with intercarpal ligament injuries in horses, the morphometry, movement pattern and general intrinsic biomechanics of the carpus are largely unknown. Using osteoligamentous preparation of the carpus prepared from 14 equine cadaver forelimbs (aged 9.62 ± 4.25 years), locomotory simulations of flexion and extension movements of the carpal joint were carried out to observed carpal biomechanics and, thereafter, the limbs were further dissected to obtain morphometric measurements of the medial and lateral collateral ligaments (MLC and LCL); medial and lateral palmar intercarpal ligaments (MPICL and LPICL); intercarpal ligaments between radial (Cr) and intermediate (Ci) carpal bones (Cr-Ci ICL); and intercarpal ligaments between Ci and ulnar (Cu) carpal bones (Ci-Cu ICL). The Cr, Ci, Cu and Ca are held together by a series of intercarpal ligaments and move in unison lateropalmarly during flexion, and mediodorsally during extension with a distinguishable proximo-distal sliding movement (gliding) of Cr and Ci against each other during movement. The mean length of MCL (108.82 ± 9.64 mm) was significantly longer (p = 0.042) than LCL (104.43 ± 7.65 mm). The Cr-Ci ICL has a dorsopalmar depth of 37.58 ± 4.14 mm and a midpoint width of 12.05 ± 3.09 mm and its fibres ran diagonally from the medial side of the Ci in a proximo-palmar disto-dorsal direction (i.e. palmarodistally) to the lateral side of the Cr. The specialized movement of the Cr-Ci ICL, which appeared to be further facilitated by a longer MCL suggest a biomechanical function by which carpal damage may be minimized in the equine carpus.

A diagnostic pathologist's guide to carpal disease in racehorses

As a pathologist, postmortem examination of the equine carpus can be daunting. The anatomy is complex and oftentimes, small or subtle lesions have significant impact on lameness and secondary lesions such as catastrophic musculoskeletal fractures and other injuries. In performance horses, particularly racehorses, the carpus is a common site of injury and source of lameness. Given the predisposition of racehorses to developing carpal disease, familiarity with clinically relevant anatomy and common developmental, degenerative, traumatic, and inflammatory processes are imperative for thorough postmortem examination. Our aim is (1) to provide a concise summary of clinically relevant anatomy and function that serves as a guide for postmortem evaluation of the equine carpus, and (2) to review common carpal injuries and diseases in actively training, racing, or retired racehorses, including developmental lesions (incomplete ossification, osteochondromata), infectious and inflammatory lesions (septic arthritis and tenosynovitis), and degenerative and traumatic lesions (degenerative and traumatic osteoarthritis, osteochondral fragmentation, and polyostotic catastrophic "breakdown" fractures). Representative gross and histologic images are presented along with corresponding antemortem and postmortem diagnostic images, and a review of current scientific literature pertaining to the pathogenesis of these equine carpal lesions.

Dorsal Arthroscopic Approach and Intra-Articular Anatomy of the Bovine Antebrachiocarpal and Middle Carpal Joints

OBJECTIVE

To determine arthroscopic approaches to the dorsal synovial compartments of the antebrachiocarpal and middle carpal joints in adult cattle, and to describe the arthroscopic intra-articular anatomy from each approach.

STUDY DESIGN

Ex vivo study.

ANIMALS

Six fresh adult bovine cadavers.

METHODS

Two carpi were injected with latex and dissected to determine the ideal location for arthroscopic portals. Arthroscopy of the antebrachiocarpal and middle carpal joints of 10 carpi was then performed. The dorsolateral approach was made between the extensor carpi radialis and common digital extensor tendons. The dorsomedial approach was made medial to the extensor carpi radialis tendon, midway between the distal radius and proximal row of carpal bones (antebrachiocarpal joint) and midway between the two rows of carpal bones (middle carpal joint), with the joint in flexion.

RESULTS

Arthroscopy of the antebrachiocarpal joint allowed visualization of the distal radius, proximal aspect of the radial, intermediate and ulnar carpal bones, and a palmar ligament located between the radius and the intermediate carpal bone. The approach to the middle carpal joint allowed visualization of the distal aspect of the radial, intermediate, and ulnar carpal bones, the proximal aspect of the fourth and fused second and third carpal bones and an interosseous ligament. The most lateral articular structures (lateral glenoid cavity of the distal radius, ulnar carpal and fourth carpal bones) were difficult to assess.

CONCLUSION

Dorsal approaches to the antebrachiocarpal and middle carpal joints allowed visualization of most intra-articular dorsal structures in adult cattle.

The centrodistal joint interosseous ligament region in the tarsus of the horse: Normal appearance, abnormalities and possible association with other tarsal lesions, including osteoarthritis

REASONS FOR PERFORMING STUDY

There have been no detailed descriptions of the radiological appearance of the centrodistal joint interosseous ligament region in horses with and without distal tarsal joint pain.

OBJECTIVES

To describe the normal radiological appearance of the centrodistal joint interosseous ligament region; to determine the prevalence of mineralisation or ossification of the interosseous ligament; and to describe radiological abnormalities surrounding the interosseous space and concurrent radiological abnormalities in the tarsus. The association between interosseous ligament region abnormalities and radiological evidence of osteoarthritis of the centrodistal joint was assessed.

STUDY DESIGN

Retrospective study.

METHODS

Case records and radiographs of all horses/ponies (n = 700) that underwent radiographic examination of one/both tarsi over 7 years were reviewed. Case history, height, bodyweight and cause(s) of lameness were recorded. Factors associated with abnormalities of the centrodistal interosseous ligament region were assessed using logistic regression analysis.

RESULTS

The normal interosseous space was an oval or circular-shaped radiolucent area bordered proximally and distally by a rim of bone of uniform opacity and thickness, which varied in thickness among animals. Abnormalities of the interosseous ligament region of the lame(r) limb were evident in 121/700 (17.3%; 95% confidence interval 14.5-20.1%) animals. Increasing bodyweight was associated with decreased odds of interosseous ligament region abnormalities. Forty-seven animals (6.7%; 95% confidence interval 4.9-8.6%) had radiological evidence of osteoarthritis of the centrodistal joint. A greater proportion of animals with interosseous ligament region abnormalities (36.4%) had radiological evidence of osteoarthritis of the centrodistal joint, compared to those with normal interosseous ligament regions (0.5%; P<0.001). Interosseous ligament region abnormalities and osteoarthritis of the centrodistal joint were not necessarily associated with distal tarsal joint pain.

CONCLUSIONS

There is an association between abnormalities of the centrodistal joint interosseous ligament region and osteoarthritis. Radiological evidence of abnormalities of the centrodistal intertarsal ligament region alone or in association with osteoarthritis may be present asymptomatically.

Ultrasonography of the medial palmar intercarpal ligament in the Thoroughbred: technique and normal appearance

REASONS FOR PERFORMING STUDY

Tearing of the medial palmar intercarpal ligament (MPICL) has been recognised as a cause of lameness in the Thoroughbred, but diagnosis is difficult due to the nonspecific clinical signs, and can be achieved only by performing arthroscopy on the mid carpal joint (MCJ). It would be beneficial to be able to image the MPICL using ultrasonography to determine whether pathology is present in the ligament in order to aid diagnosis and prognosis.

OBJECTIVES

To determine whether the MPICL could be imaged using ultrasound from the dorsal aspect of the MCJ, and to describe the technique and normal ultrasonographic appearance of the ligament.

METHODS

A pilot study was performed using 2 cadaver carpi. Each carpus in turn had the MPICL imaged simultaneously using arthroscopy and ultrasound, with a metallic probe positioned on the dorsal aspect of the ligament to highlight the position of the MPICL. Six further pairs of carpi had the MPICL imaged ultrasonographically followed by dissection of the carpus to evaluate the ligament and relate its anatomy to the ultrasound images. Finally, 15 Thoroughbreds with no history of lameness isolated to the carpus had their MPICLs assessed and measured ultrasonographically.

RESULTS

The MPICL could be imaged via the dorsal aspect of the MCJ using standard ultrasound equipment. The body and division into medial and lateral branches could be seen as a distinct, moderately dense granular echogenic structure in the palmar aspect of the joint, with clearly defined margins.

CONCLUSIONS

The normal MPICL can be imaged reliably using ultrasound in the Thoroughbred from the dorsal aspect of the MCJ. There is a wide range in the normal width of the lateral aspect of the MPICL, but there is good symmetry between contralateral limbs.

POTENTIAL RELEVANCE

This report of the normal ultrasonographic appearance of the ligament will be beneficial in acting as a reference for the detection of pathology using ultrasound.

Endoscopic assessment and treatment of lesions of the deep digital flexor tendon in the navicular bursae of 20 lame horses

REASONS FOR PERFORMING STUDY

Clinical lesions of the deep digital flexor tendon and navicular bone are being reported with increasing frequency. However, the role of direct visualisation by navicular bursoscopy in the diagnosis and management of such injuries has not been explored.

HYPOTHESIS

Navicular bursoscopy: 1) corroborates information obtained from other, noninvasive imaging modalities; 2) allows direct visualisation of lesions unidentified by other diagnostic modalities; 3) provides further information on morphology of lesions; and 4) permits minimally invasive surgical access to lesions.

METHODS

The case records of all horses that underwent diagnostic navicular bursoscopy for the investigation of lameness admitted to 2 referral clinics (the Royal Veterinary College and Reynolds House Referrals) were evaluated retrospectively. Follow-up information was obtained by telephone questionnaire.

RESULTS

Twenty-three bursae were examined endoscopically in 20 horses. Tears of the deep digital flexor tendon were seen in all horses (22 bursae). In 8 bursae, cartilage lesions were also present and in one bursa this was the only abnormal finding. Computed tomography and low field magnetic resonance imaging predicted tendon lesions in most cases, but failed to identify cartilage damage. Greater than 6 month follow-up information was available for 15 animals of which 11 were sound and 9 had returned to preoperative levels of performance.

CONCLUSION

Lameness localised to the foot may result from tears of the deep digital flexor tendon and/or navicular fibrocartilage loss. Navicular bursoscopy allows comprehensive evaluation of these changes and also permits appropriate lesion management.

POTENTIAL RELEVANCE

The diagnostic information obtained from and therapeutic options offered by bursoscopy justify its use in horses with clinical findings localising lameness to the navicular bursa.

Characterization of the Fatigue Behavior of the Medial Collateral Ligament Utilizing Traditional and Novel Mechanical Variables for the Assessment of Damage Accumulation

Ligaments are regularly subjected to repetitive loading in vivo. Typically, mechanical studies focus on repetitive loading protocols of short duration, while those characterizing damage accumulation over a longer duration (i.e., fatigue studies) are lacking. The aims of this study were as follows: (a) to demonstrate that damage does accumulate in ligament tissue subjected to repetitive loading and (b) to evaluate existing and new methods for characterizing fatigue damage accumulation. It was hypothesized that ligaments would accumulate damage with repetitive loading as evidenced by failure at stresses well below ultimate tensile strength, creep curve discontinuities, and by reductions in stiffness during loading. Eight normal medial collateral ligaments from female New Zealand white rabbits were cycled in tension, between 0 MPa and 28 MPa, to failure or until 259,200 cycles, whichever came first. Medial collateral ligaments that did not fail were subsequently loaded to failure. Displacement rates (dlmax/dt) as well as primary, secondary, and tertiary creeps were monitored as indices of damage accumulation and impending mechanical failure. Additionally, the relative utilities of tangent, secant, and chord stiffness parameters were critically evaluated. Finally, new uses for the second derivative of force-displacement data were explored. Three out of eight ligaments failed during testing, demonstrating that ligaments can fail in fatigue under moderate tensile stress in vitro. The evaluation of displacement rates (dlmax/dt), as well as primary through tertiary creep patterns, were not well suited to predicting failure in normal ligaments until rupture was all but imminent. Tangent stiffness, which was calculated from a mathematically defined start of the “linear region,” was surprisingly constant throughout testing. Secant stiffness dropped in a predictable fashion, providing a global indicator of tissue stiffness, but did not provide any insight into fiber mechanics. Chord stiffness, on the other hand, appeared to be sensitive to fiber recruitment patterns. The second derivative of force-displacement data proved to be a useful means of (a) objectively defining the start of the linear region and (b) inferring changes in fiber recruitment patterns within ligament tissue. Tangent, secant, and chord stiffnesses highlight different attributes of ligament responses to loading; hence these parameters cannot be used interchangeably. Additionally, the second derivative of the force-displacement curve was introduced as a useful descriptive and analytical tool.

Palmar carpal osteochondral fragments in racehorses: 31 cases (1994–2004)

OBJECTIVE

To evaluate records of racehorses with palmar carpal osteochondral fragments and determine whether the fragments were indicators of the severity of pathologic joint changes or prognosis.

DESIGN

Retrospective case series.

ANIMALS

31 racehorses.

PROCEDURES

Medical records, radiographs, and videos of arthroscopic procedures were reviewed. Information gathered included signalment; location, number, and size of the primary lesion; number and size of palmar carpal fragments; and details pertaining to surgical procedures. Outcome variables were obtained from race records.

RESULTS

31 horses met the selection criteria. Multiple palmar fragments were diagnosed in 58% of horses; small fragments (< 3 mm in diameter) were most common (52% of horses). Fifty-two percent of the horses returned to racing, 48% returned to racing and earned money, and 32% had at least 5 more starts. Horses with multiple fragments had significantly less earnings per start and lower performance index values after surgery than those with 1 fragment. Horses with palmar fragments < 3 mm in diameter were significantly less likely to return to racing and have 5 starts or to win money after surgery than horses with larger fragments.

CONCLUSIONS AND CLINICAL RELEVANCE

Palmar carpal osteochondral fragments can be used as an indicator of clinically important joint pathology and as a prognostic indicator in racehorses. Horses with multiple small fragments were less likely to successfully return to racing than horses with only dorsally located carpal fragments or horses with 1 or 2 large palmar fragments. When possible, removal of palmar carpal osteochondral fragments should be considered.

Prevalence and response to surgical treatment of lateral palmar intercarpal ligament avulsion in horses: 37 cases (1990-2001)

OBJECTIVE

To clarify the diagnosis of avulsion of the lateral palmar intercarpal ligament (LPICL), correlate avulsion of this ligament with lameness, determine the prevalence of avulsion of the LPICL in a hospital population, and evaluate the response to surgical removal of the avulsion fragment in horses.

DESIGN

Retrospective study.

ANIMALS

37 horses with avulsion of the LPICL.

PROCEDURE

Medical records and radiographs of horses with avulsion of the LPICL were reviewed; follow-up information was obtained from race records and from owners via a telephone survey.

RESULTS

Of 6,418 horses evaluated for forelimb lameness from March 1, 1990, to December 31, 2001, 37 (0.5%) had avulsion of the LPICL; each horse had a discrete fragment associated with avulsion of the ligament origin from the ulnar carpal bone. Twenty-six horses underwent arthroscopic fragment removal; 20 of 22 (91%) horses for which follow-up information was available returned to work. Of 9 horses treated conservatively, 5 returned to work. Odds ratio calculations indicated that horses treated surgically were 8 times as likely to return to work than those not treated surgically. Twelve horses had LPICL avulsion without concurrent osteochondral fragmentation in the same or additional joints; follow-up information was available for 9 of those horses, of which 8 returned to athletic work.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, discrete avulsion of the LPICL can be a cause of lameness and arthroscopic debridement may be the treatment of choice. Prognosis for return to work of horses with avulsion of the LPICL is good.

RADIOGRAPHIC AND PATHOLOGIC CHARACTERIZATION OF LATERAL PALMAR INTERCARPAL LIGAMENT AVULSION FRACTURES IN THE HORSE

In this study, the radiographic and histologic appearance of lateral palmar intercarpal ligament (LPICL) avulsion in the horse was characterized. Thirty-seven horses with radiographic evidence of avulsion fragments originating from the medial palmar aspect of the ulnar carpal bone were examined. The dorsolateral to palmaromedial projection was useful for evaluating the size and shape of the avulsed bone fragment, and the dorsopalmar projection added information on the relative proximity of the fragment to its fracture bed. Radiographic features that differentiated LPICL avulsion from subchondral cystic lesions of the ulnar carpal bone included a variable-sized osseous opacity adjacent to the lucent concavity of the fracture bed and the consistent location within the palmar transition zone at the confluence of LPICL insertion and hyaline cartilage on the palmar surface of the ulnar carpal bone. All 26 horses having surgical removal of the fragments had arthroscopic confirmation that the fragment was within the LPICL. Histologic examination confirmed the fragments were fracture related rather than developmental or the result of dystrophic mineralization. Many of the fragments had attached remnants of a ligament. This study describes the radiographic, surgical, and histologic features in 37 horses which better characterize LPICL avulsion fracture in the carpus and provide differentiating features to assist in separating this syndrome from true osseous cyst-like lesions within the ulnar carpal bone.

Postoperative performance of racing horses with tearing of the medial palmar intercarpal ligament

OBJECTIVE

To examine the relationship between medial palmar intercarpal ligament (MPICL) tearing and postoperative performance in racing horses.

MATERIALS AND METHODS

The postoperative performance of 42 horses in which the midcarpal joint was examined arthroscopically was followed prospectively. Intra-articular variables examined were the severity of MPICL tearing, subchondral bone damage and articular cartilage damage. Using a scoring system based on the class of race and the position in the race, a mean score was calculated for up to five races before and after surgery. The preoperative score was subtracted from the postoperative score to give a net score. Statistical analysis was by a Mann Whitney U test and multiple linear regression.

RESULTS

Thirty-two (76%) raced postoperatively, 23 (55%) won at least one race and 12 of 26 (46%) performed at the same or higher level. Horses with grades 2 to 4 MPICL tearing had significantly lower net scores than those with grade 1 or no tearing. The severity of subchondral bone damage was the only variable on its own that was significantly correlated with net score (r2 = 0.23, P < 0.05). The addition of the grade of MPICL tearing to bone damage significantly improved the prediction of postoperative performance (P < 0.05). The inclusion of articular cartilage damage had no effect on the prediction of postoperative performance.

CONCLUSION

Tears involving more than one third of the MPICL as observed arthroscopically have a significant detrimental affect on postoperative performance of racing horses.

Tenosynovitis associated with longitudinal tears of the digital flexor tendons in horses: a report of 20 cases

The paper describes a series of cases with longitudinal tears in the superficial or deep digital flexor tendons within the digital flexor tendon sheath. This appears to be a previously unreported condition. Twenty cases are described, one horse was affected bilaterally. Nineteen defects involved the deep digital flexor tendon and in 2 horses the manica flexoria of the superficial digital flexor tendon was torn. All affected horses were lame and there was marked distension of the digital flexor tendon sheaths. Ultrasonography revealed nonspecific signs of chronic tenosynovitis but not the cause. Diagnosis was established by tenoscopy in 9 cases and by open surgical exploration in the remainder. In 7 limbs, the deep digital flexor tendon lesions were treated by removal of the torn fibrils under tenoscopic control. In the remaining cases they were removed and the defects were repaired with absorbable suture material. Wound closure in all open cases included repair of the palmar/plantar annular ligament. Eleven horses became sound and returned to work, 3 improved but were lame on returning to work and 2 horses did not improve following treatment. At the time of reporting, 4 horses are sound and in controlled ascending exercise regimes. It is concluded that longitudinal tears of the digital flexor tendons should be considered in the differential diagnosis of tenosynovitis of the digital flexor tendon sheath. The results presented suggest that accurate diagnosis and specific treatment justify surgical investigation.

Postmortem lesions in the intercarpal ligaments of the equine midcarpal joint

OBJECTIVE

To determine the frequency of damage to the medial palmar intercarpal ligament (MPICL), and the range of sizes of the dorsomedial intercarpal ligament (DMICL) of the midcarpal joint in horses with no history of carpal joint disease.

MATERIALS AND METHODS

Cadaver limbs were collected from 72 horses with no history of carpal joint disease. One hundred and forty-two midcarpal joints were dissected and the MPICL and DMICL were examined. Measurements were made with a digital micrometer.

RESULTS

MPICL tearing was present in 88 of 96 joints from horses 2 years and older. Tears were predominantly of the dorsolateral bundle and complete rupture of the dorsolateral and dorsomedial bundles was not observed. Tearing was not present in foals less than 4 months of age and the severity of tearing increased significantly with age (P < 0.0001). Severity of tearing was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01), but there was no significant difference between racing and non-racing horses. The lateromedial thickness of the DMICL ranged from 0.4 mm to 2.6 mm in horses 2 years and older. Lateromedial thickness increased significantly with age, and was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01). There was no significant difference between racing and nonracing horses.

CONCLUSIONS

Damage confined to the dorsolateral bundle of the MPICL is a common finding in horses over 1 year of age and is probably of little clinical significance. Complete rupture of both dorsolateral and dorsomedial bundles is uncommon in horses with no history of midcarpal joint disease. Variation in size of the DMICL is observed in horses of all ages, but is most marked in 2-year-old horses.

The intercarpal ligaments of the equine midcarpal joint, Part 1: The anatomy of the palmar and dorsomedial intercarpal ligaments of the midcarpal joint

OBJECTIVE

To describe in detail the structure of the medial palmar intercarpal ligament (MPICL), the lateral palmar intercarpal ligament (LPICL), and a dorsomedial intercarpal ligament (DMICL) of the equine midcarpal joint.

STUDY DESIGN

Dissections of equine midcarpal joints. ANIMALS AND SAMPLE POPULATION: Ten carpal joints from eight thoroughbred horses.

METHODS

Detailed dissections of the midcarpal joint were performed, with particular attention paid to the MPICL, the LPICL, and the DMICL. The attachments and dimensions of these structures were recorded, as well as their behavior during joint movement.

RESULTS

The DMICL arose from the dorsomedial surface of the radial carpal bone (CR) and coursed palmarodistally to insert on the dorsomedial aspect of the second carpal bone (C2). The LPICL attached proximally predominantly on the distal part of the palmaromedial surface of the ulnar carpal bone (CU). From here the ligament coursed distomedially and slightly palmarly to the proximal palmarolateral surface of the third carpal bone (C3). The structure of the MPICL was complex. It attached proximally to the distolateral surface of the CR and distally to the proximal palmaromedial surface of C3, and the proximal palmarolateral aspect of the C2. It could be divided into four fiber bundles in all carpi. The predominant direction of fibers was dorsoproximal to palmarodistal, whereas the palmaromedial bundle coursed palmaroproximal to dorsodistal.

CONCLUSIONS

The orientation of their fibers indicate that the MPICL and DMICL primarily resist dorsomedial displacement of CR, whereas the LPICL resists dorsolateral displacement of the CU and intermediate carpal bone.

CLINICAL RELEVANCE

An understanding of the structure of the intercarpal ligaments of the midcarpal joint is important in interpreting their function and the reasons for damage to their structure.

The intercarpal ligaments of the equine midcarpal joint, Part 2: The role of the palmar intercarpal ligaments in the restraint of dorsal displacement of the proximal row of carpal bones

OBJECTIVE

To determine the relative contributions of the palmar intercarpal ligaments in the midcarpal joint to the restraint of dorsal displacement of the proximal row of carpal bones.

STUDY DESIGN

A biomechanical study of cadaver equine carpi.

ANIMALS OR SAMPLE POPULATION

Eight equine forelimbs from six thoroughbred horses.

METHODS

With joints in full extension, the radius was dorsally displaced while midcarpal joint displacement was measured. The restraining force at a joint displacement of 1.5 mm was determined from the load-displacement curve. A ligament or pair of ligaments was then cut and the testing procedure repeated. Their contribution to restraining force was calculated as the percentage change in restraining force after the ligament was sectioned. Relative cross-sectional areas of the ligaments tested were measured at the level of the midcarpal joint.

RESULTS

The collateral ligaments were the major contributors to the restraint of dorsal displacement (P < .001). In all joints, the palmar intercarpal ligaments contributed a greater proportion than the palmar carpal ligament (PCL) (P < .05). The mean percentage (+/-SEM) contributions to the restraint of dorsal displacement were 62.8 +/- 3.4 for the collateral ligaments, 14.5 +/- 1.4 for the PCL, and 22.7 +/- 2.2 for the palmar intercarpal ligaments. Mean cross-sectional area expressed as a percentage (+/-SEM) of the total ligamentous area were 9.0 +/- 0.3 for the palmar intercarpal ligaments, 27.1 +/- 3.0 for the PCL, and 63.8 +/- 2.8 for the collateral ligaments.

CONCLUSIONS

Despite the small size of the palmar intercarpal ligaments, they play an important role in the restraint of dorsal displacement of the proximal row of carpal bones.

CLINICAL RELEVANCE

Interpretation, as well as prevention and treatment of intercarpal ligament tearing requires an understanding of their function.

The intercarpal ligaments of the equine midcarpal joint, Part 3: Clinical observations in 32 racing horses with midcarpal joint disease

OBJECTIVE

To characterize the clinical features of intercarpal ligament pathology and to determine the relationship among palmar intercarpal ligament tearing, dorsomedial intercarpal ligament (DMICL) hypertrophy, and other intraarticular lesions.

STUDY DESIGN

Prospective clinical observations.

ANIMALS OR SAMPLE POPULATION

Twenty-eight thoroughbred and four standardbred race horses.

METHODS

Clinical, radiographic, and arthroscopic examination of 53 midcarpal joints of 32 horses.

RESULTS

Palmar intercarpal ligament tearing was observed in 30 joints of 22 horses. Some tearing of the medial palmar intercarpal ligament (MPICL) was present in 27 joints of 20 horses, and tearing of the lateral palmar intercarpal ligament in 9 joints of 7 horses. There was no correlation between the severity of clinical signs recorded and the degree of MPICL tearing. Joints with grade 2-4 MPICL tearing had significantly less cartilage and bone damage than joints with grade 1 or no ligament damage (P < .05). There was a significant inverse relationship between the number and size of intra-articular fractures, as assessed radiographically, and ligament damage (R = -.31). The DMICL was identified in all joints, and in 18 joints the ligament was enlarged. There was a significant correlation between MPICL damage and hypertrophy of the DMICL (R = .35). There was no correlation between DMICL hypertrophy and articular cartilage damage or subchondral bone damage.

CONCLUSIONS

Severe subchondral bone and MPICL damage rarely occur in the same joint and DMICL hypertrophy may be associated with, rather than a cause of, joint disease.

CLINICAL RELEVANCE

There are no clinical or radiographic findings that will differentiate intercarpal ligament injury from other carpal injuries. Diagnosis is only possible by arthroscopic examination of the midcarpal joint.

Ligaments associated with joints

This article contains a short introduction to the anatomy, physiology, and pathophysiology of ligaments associated with diarthrodial joints. Individual ligaments are discussed on a regional basis as forelimb, distal limb, and hindlimb. Emphasis is placed on the anatomy of the ligaments because this is the key to sound clinical application of their involvement in joint disease. There are few conditions of diarthrodial joints that do not involve their associated ligaments, and this role may be in causative, diagnostic, and therapeutic or convalescent considerations.