Sclerosis of the third carpal bone changes the mechanical properties of bone, and sclerotic bone is brittle and at risk of fracturing. Once the radial fossa becomes completely devoid of trabecular detail and has a ground glass appearance radiologically, the changes are often permanent. In my experience, corner fractures most often occur in the distal radius, in the proximal or distal corners of the radial carpal bone, and in the proximal aspect of the third carpal bone. In such instances, a flexed lateral or flexed lateral oblique can often identify the true location of the injury (Figure 7-21). Diagnosis of third carpal bone subchondral bone pain can be challenging, because many young horses do not develop effusion. The insertion is a long crest of bone on the lateral ulna known as the crista supinatorum. Chip fractures, as the name implies, are small flakes or chunks of bone that are sheared off the upper or lower corners of carpal bones, typically while a horse is racing. The capsular attachment on the humerus extends from the outer margins of the capitulum and trochlea upwards to enclose the olecranon fossa posteriorly and the coronoid fossa and, The third carpal bone and other carpal bones such as the radial carpal bone become sclerotic (model) to withstand the stress of training and racing. This usually leads to or is associated with coexistent secondary sclerosis of the opposing third carpal bone because the load becomes borne by the medullary bone, instead of the weight-bearing pillar of the dorsal cortex. Ideally, the medullary cavity of the ulna is positioned centrally over the intercondylar region to reduce unwanted superimposition (Figure 4-33). Radiological signs include increased radiopacity in the, Scaphoid fractures should be suspected in any patient with wrist pain. A craniocaudal view with the cranial surface of the antebrachium rotated medially 15 degrees (Cr15L-CdMO) allows for better assessment of the medial part of the condyle.
Also important is the fact that, in the craniocaudal view, there is a relatively large portion of the lateral aspect of the proximal articular surface of the radius that does not articulate with the humerus; this is often confused with elbow subluxation (see Figures 4-27 and 4-28). They are the most destabilizing, and thus most serious, of all carpal fractures. Sagittal slab fractures typically occur on the medial aspect of the, a connection between exercise-induced increased bone density in the region of the, The second syndrome, which may include some horses in the first category if training has continued, involves development of more severe sclerosis in the third carpal bone and remodeling of the distal aspect of the radial carpal bone. These radiological abnormalities result from overloading the carpus, leading to bone stiffening, cartilage damage, and secondary OA. These horses probably are suffering from pain produced by concussion of immature cartilage and excessive torsion on untrained ligaments within the carpus, and should be given rest. If conservative measures such as immobilization or steroid injection fail, excision of the fragment will usually result in pain relief. Although removing the spur is logical, it is not curative, and the horse will still require treatment the following season. The lateral and medial parts of the humeral condyle normally fuse by 8 to 12 weeks,1 and no radiographic evidence of a division between the two should be visible after this time (Figure 4-32). In cats, the sesamoid bone is rarely visible in the craniocaudal view and, when present, is most often visible in the lateral view (Figure 4-43, A, B). These horses often have unilateral lameness associated with middle carpal joint effusion. With cheap horses and in yards where money is tight, many horses with mild carpal OA can be treated once by intraarticular medication with hyaluronan and triamcinolone acetonide, followed by 4 to 6 weeks of rest and a graded return to exercise. We use cookies to help provide and enhance our service and tailor content and ads. The limbs are held abducted during the protraction phase, and the carpi are barely flexed. Some surgeons feel there is a correlation between the amount of pain and the duration and displacement of the fragment. Alternatively, arthroscopic evaluation and debridement result in a better outcome than does conservative management.49 Evaluating the joint arthroscopically and then formulating a management plan is a reasonable approach, but certainly surgical management is preferred over rest alone. DeHaan and co-workers identified the radial fossa as the most common site of third carpal injury and furthermore found that sclerosis in this location often predated subsequent injury.14 Most fractures appeared comminuted in the standard projections, a feature that often required a skyline projection to confirm. OTA/AO classification system. Fractures of the scaphoid that are nondisplaced may be treated with cast immobilization. Diagnostic analgesia should be used to establish the authentic source of pain. In Diagnosis and Management of Lameness in the Horse (Second Edition), 2011, The middle carpal joint is the most common site of lameness in young STBs. Posteriorly, the capsule is tight in flexion; anteriorly, the capsule is tight in extension. The medial aspect of the humeral condyle articulates with the trochlear notch of the ulna to form one of the most stable hinge joints in the body (Figure 4-29).
Often the horse has bilateral middle carpal joint effusion and pain on carpal flexion. If any doubt exists about the nature of a lesion affecting the medial aspect of the third carpal bone, arthroscopic examination can be performed to formulate a surgical plan. Sagittal slab fractures of the third carpal bone must be differentiated from corner fractures, subchondral lucency, and other crushing-type injuries that occur in the radial fossa. The frontal view proved the least revealing. Joint congruency, particularly humeroulnar incongruency, is better evaluated in the craniocaudal view where the medial coronoid process of the ulna appears as a sharply marginated shelf of bone subjacent to the medial aspect of the humeral condyle (see Figure 4-27). Surprisingly, few nonunions occur, although healing is usually protracted (Figure 7-36). Accessory carpal bone fractures are most common in Thoroughbred hunter-jumpers and cross-country steeplechasers. This is important with respect to assessing possible osteochondrosis of the medial part of the humeral condyle (see Figure 4-30). Abnormal radiological findings range from complete slab fracture of the third carpal bone to more subtle signs of radiolucency of the, Joint Disease in the Horse (Second Edition), ). These horses are treated using arthroscopic trimming and are given 4 to 6 weeks of stall rest followed by 4 weeks of stall rest with handwalking exercise, and joints are injected with short-acting corticosteroids. However, stability of the elbow should be monitored and tested to identify if any ligamentous injury has occurred after fracture fixation. In addition, as with all complex joints, specifically positioned views are often required to highlight particular aspects of the joint.
The Dissection of Vertebrates (Second Edition), Shoulder and Elbow Trauma and its Complications, Diagnosis and Management of Lameness in the Horse (Second Edition), Sagittal slab fractures of the third carpal bone are much less common than frontal slab fractures, usually involve the medial aspect of the, The elbow joint is a synovial joint. To repair a fracture, I prefer a direct view provided by arthrotomy, because positioning a screw perpendicular to the fracture line using arthroscopic surgery and stereotactic techniques is difficult and because the fracture is closely associated with the second carpal bone. The change in the third carpal bone is seen on a skyline radiograph as increased radiopacity of the, The European and Australasian Standardbreds, Visual inspection from a dorsolateral perspective reveals abnormal contour of the dorsomedial aspect of the carpus. Heat may be present over the dorsal aspect of the carpus, and horses move wide and tend to abduct the limb during advancement (MWC). It has long been theorized that decreased bone density in young racehorses may herald impending fracture. However, no objective studies have characterized this. By continuing you agree to the use of cookies. If pain is still present but x-ray continues to be normal; consider MRI or a bone scan. Charles S. Farrow DVM, DACVRProfessor of Veterinary Medical Imaging, in Veterinary Diagnostic Imaging: The Horse, 2006. In addition to fragmentation and fracture of the carpus, it is not unusual to find subchondral bone sclerosis and lysis that leads to pain, typically in racehorses. Lameness is usually prominent, but in horses with bilateral fracture or substantial OA or osteochondral fragments in the contralateral carpus, diagnostic analgesia may be required. This gives a stiff, rolling action. Focal overloading of the third carpal bone results from a conformational defect (offset carpi with toe in is the worst) or from a mismatch between loading of the limb and time allowed for adaptation.
Horses can be sound enough to race with chronic nonunion fractures, but this is undesirable. If a chip fracture occurs, then removal of the fragments is probably still mandatory. Robert C. Pilsworth, in Diagnosis and Management of Lameness in the Horse (Second Edition), 2011. In the cat, the humerus contains a supracondylar foramen located distomedially, through which the brachial artery and the median nerve pass (Figure 4-31). Usually the response to carpal flexion is positive, and intraarticular analgesia abolishes lameness in most horses. Some fresh corner fractures can be detected only in supplementary tangential views of the affected bone (skyline view), although not all horses with such fractures will tolerate the necessary limb flexion and related pain associated with these projections.
Further incidence data are shown in Table 7-3. One should explain to the owner and trainer, however, that the horse has preexisting OA that will persist after surgery and that further problems should be anticipated the following season. The training programs of young TBs with evidence of third carpal bone sclerosis should be modified, but trainers are often unwilling. The primary ligamentous stabilizers of the elbow are the LCL, MCL, and the anterior and posterior capsule. The lateral aspect of the humeral condyle articulates with the head of the radius. The origin of the MCL is the anteroinferior aspect of the medial epicondyle and the insertion is located on the sublime tubercle (Figure 4.2). Pain is often localized to the volar and ulnar palm, however, many times it will present with dorsal pain over the hamate. The MCL complex consists of an anterior band, posterior band, and a transverse ligament.
Thrall and co-workers reported that in both Thoroughbred and Standardbred horses, the radial carpal bone was injured twice as often as all other carpal bones combined.16 Furthermore, the relative incidence of new bone depositionradial carpal, distal radius, third carpal, and intermediate carpalfollowed the same general pattern as chip fractures. A corner fracture, like a chip fracture, usually originates from either the upper or the lower front corner of a carpal bone (Figure 7-19). The right radial carpal bone was fractured more often than the left.15 Most fractures occurred on the dorsal surface of the carpus and distal radius. These structures are typically not injured after a distal humerus fracture unless they are iatrogenically injured. Carpal fractures that enter two adjacent joints, typically, but not exclusively, one above and one below, are termed slab or biarticular fractures. Figure 4.3. The physes associated with the distal humeral condyle and medial epicondyle can complicate radiographic interpretation in the young patient (Figure 4-39). The change in the third carpal bone is seen on a skyline radiograph as increased radiopacity of the radial fossa. The mere presence of increased radiopacity does not establish a diagnosis because a certain amount of increased radiopacity reflects a normal, adaptive response. Without radiological information, lameness may be the first indicator of sclerosis, which may already be advanced. Diagnostic analgesia is essential for diagnosis. The olecranon process extends proximal to the trochlear notch and typically has two rounded unnamed prominences at its most proximal cranial margin. Some of these horses have mild increased radiopacity of the third carpal bone, seen on a skyline image, but others have no detectable radiological abnormality. However, sagittal slab fractures of the third carpal bone can occur in the intermediate fossa, and fractures can be bilateral. These should not be confused with enthesophytes due to stress remodeling (Figure 4-40). Focal overloading of the third carpal bone results from a conformational defect (offset carpi with toe in is the worst) or from a mismatch between loading of the limb and time allowed for adaptation. Scaphoid fractures pose one of the greatest challenges to orthopedic surgeons owing to both the difficulty in diagnosis and the tenuous blood supply to this bone.
The origin of the LCL complex is the inferior surface of the lateral epicondyle.
Some horses can continue to train and race without obvious impairment even with chip fractures left in situ in this joint. In racing Thoroughbreds, slab fractures occur most often to the third carpal bone (Figure 7-20).12 Even after successful surgical reduction, horses with biarticular fractures of the third carpal bone tend not to perform as well as they before their injuries. Fractures with any degree of displacement are best treated surgically with open reduction and internal fixation (Fig. These so-called kissing lesions are primarily the result of mechanical abrasion, first to the articular cartilage and subsequently to the underlying bone, aided and abetted by the infiltration of synovial fluid laden with inflammatory residue from the damaged tissues. Further training of these horses risks development of a full sagittal fracture (see Figure 107-2).
We should also always be aware that local anesthetic solution in the middle carpal joint can abolish pain arising from the SL, carpal ligaments, and many other structures, and it may be very simplistic to assume a positive middle carpal joint block means we have problems only in the middle carpal joint. One of the most common syndromes is exemplified by a 2-year-old in early training that develops an increasingly short, choppy gait at the trot. The benefits of therapy will be achieved only in conjunction with rest or a substantial reduction in training. These physes are typically closed by 7 to 8 months of age. This is often achieved by rotating the cranial surface of the antebrachium laterally 15 degrees and acquiring a Cr15M-CdLO view.2. A standard radiographic examination of the elbow consists of a neutral lateral view with the brachium and antebrachium at an approximately 90-degree angle, a lateral view with the elbow highly flexed, and a craniocaudal (or caudocranial) view (Figures 4-26 and 4-27). Christopher E. Kawcak, Myra F. Barrett, in Joint Disease in the Horse (Second Edition), 2016. A classically described presentation is pain with palpation of the anatomic snuffbox, or radial fossa. A classically described presentation is pain with palpation of the anatomic snuffbox, or, Atlas of Normal Radiographic Anatomy and Anatomic Variants in the Dog and Cat (Second Edition). The three principal types of carpal fracture are the (1) chip, (2) corner, and (3) slab or biarticular. Response to flexion varies, but in horses with subchondral bone pain, response is often negative. The third carpal bone and other carpal bones such as the radial carpal bone become sclerotic (model) to withstand the stress of training and racing. Authentic sagittal slab fractures of the third carpal bone involve both articular surfaces of the bone and can be best seen radiologically in skyline and DM-PaLO images. The anconeal process of the ulna is best evaluated in a fully flexed lateral view. Few osteochondral fragments or small (chip) or large (slab) fractures of the third carpal bone occur in normal bone. The olecranon fossa is contiguous with the radial fossa, a similar excavation on the cranial aspect of the distal metaphysis of the humerus, via the supratrochlear foramen. A variety of single and multiple distal radial and carpal bone fractures are shown in Figures 7-22 to 7-35. Ligament injuries, especially affecting the medial palmar intercarpal ligament, must be suspected in the absence of radiological abnormalities.18 However, medial palmar intercarpal ligament injuries are rare. These can be difficult to characterize and subtle changes in the angles of the radiographic images may be needed. Chip fractures in STBs most frequently involve the third and radial carpal bones. Opposing articular surfaces need one another, anatomically and physiologically speaking. The capsule of the elbow attaches just proximal to the articular margin both anteriorly and posteriorly, above the respective coronoid, radial, and olecranon fossae. Also, superimposition of the ulna can confound assessment of the intercondylar region when evaluating for the presence of incomplete ossification of the humeral condyle. Laterally, the capsule becomes contiguous with the LCL and annular ligament. Palpation often elicits a painful response over the dorsal aspect of the radial and third carpal bones. Figure 4.2. The radial and intermediate carpal bones are most often chipped, often in conjunction with a similar type fracture to the overlying distal radius. Diagnostic arthroscopy probably is always indicated in these horses but is also often unhelpful in producing a permanent cure.
Comparing extended and flexed lateral radiographs best assessed fragment mobility. Dorsal plane slab fractures of the carpus are often most easily seen on the standing dorsolateral-palmarmedial oblique projection as these fractures will often reduce in a flexed lateral position (Figure 22-13). The incidence of proximal versus distal corner fractures was similar. The second syndrome, which may include some horses in the first category if training has continued, involves development of more severe sclerosis in the third carpal bone and remodeling of the distal aspect of the radial carpal bone.