Arthroscopic approaches to the palmar aspect of the equine carpus

OBJECTIVE: To identify sites for arthroscopic access to the palmar aspects of the antebrachiocarpal (AC) and middle carpal (MC) joints, and describe visible carpal bone surfaces for each approach. STUDY DESIGN: Prospective experimental study. ANIMALS: Equine carpi: 16 cadavers, 8 live horses. METHODS: A latex model was used to identify possible sites for arthroscopic access to the palmar aspects of the AC and MC joints. Carpi (n = 24) were examined arthroscopically and arthroscopic access sites and visible carpal bone surfaces were described. RESULTS: Arthroscopic approaches and instrument portals were developed for the medial and lateral aspects of the palmar pouches of the AC and MC joints. The palmar surface of the radial carpal bone and radius, and the dorsal articular surfaces of the accessory carpal bone, could be viewed using palmar approaches to the AC joint. The palmar aspect of the radial, third and second carpal bones (medially) and ulnar and fourth carpal bones (laterally) could be observed using a palmar approach to the MC joint. CONCLUSIONS: Arthroscopic access, using separate medial and lateral portals to the AC and MC joints, allowed assessment of portions of the caudodistal radius, the palmar surfaces of the radial, ulnar, second, third and fourth carpal bones, and the dorsal aspect of the accessory carpal bone. CLINICAL RELEVANCE: Arthroscopic approaches to the palmar aspect of the carpus could be used to remove fracture fragments, and to assess the medial palmar intercarpal ligaments.     

Polymelia with two extra forelimbs at the right scapular region in a male Korean native calf.

In a male Korean native calf 14 days of age, polymelia (notomelia) was observed macroscopically and radiographically. External features included two normal forelimbs, two normal hindlimbs and two undeveloped extra forelimbs. The extra forelimbs were attached to the caudal regions of the right scapula and devoid of muscular tissues. In the extra forelimbs, a scapula-like bone formed a joint with the incompletely duplicated humerus. The humerus fused with the incompletely duplicated radius. The ulna, carpal bones, metacarpal bones and phalanges were completely duplicated. But one set of the duplicated carpal bones consisted of five bones: radial, accessory, fourth carpal, fused second and third carpal, and fused ulnar and intermediate carpal bones. The hoof and the rudimentary hoof of accessory digit were duplicated.     

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.     

Arthroscopy of the antebrachiocarpal joint in dogs

A technique for arthroscopy of the antebrachiocarpal joint in dogs is described. Both antebrachiocarpal joints in 9 dog cadavers were examined arthroscopically and grossly to refine the technique and determine structures that could be seen. Two arthroscope portals were evaluated in each joint. The antebrachiocarpal synovium, ulnar carpal bone, distal portion of the ulna, medial and lateral collateral ligaments, accessory carpal bone, intercarpal ligament of the radial and ulnar carpal bone, distal portion of the radius, radial carpal bone, palmar process of the radial carpal bone, ligaments of the accessory carpal bone, palmar radiocarpal ligament, and palmar ulnocarpal ligament were visible and accessible to instruments. Arthroscopy was also performed in 5 client-owned dogs, allowing diagnosis of hyperextension injuries (n = 2), septic arthritis (2), and immune-mediated arthropathy (1). Arthroscopy of the antebrachiocarpal joint was found to be a useful adjunct to standard diagnostic modalities.     

Morphometrical variations of the carpal bones in thoroughbreds and ponies

There is scant morphological data for equine carpal bones despite the frequent pathology in Thoroughbreds (TB). This study aimed to identify morphological and morphometrical variations and similarities in carpal bones between and within TB and Ponies (Po). Carpal bones from nine TB and 13 Po were prepared by boiling and drying. Lateromedial width, dorsopalmar depth, proximodistal height, relative density and volume of each bone were measured. Normalized measurements of the radial (Cr) and third (C3) carpal bones were significantly different in all dimensions, and there were significant variations in relative sizes of articular facets of the ulnar (Cu), C3 and fourth (C4) carpal bones between the groups. Bilaterally, the proportionate volume of the intermediate carpal bone (Ci) was significantly greater in Po while that of Cu and C4 were significantly greater in TB. Relative density of most bones was greater in Po. The palmar tuberosity of the proximal surface of Ci and palmar tubercle on the palmar surface of Cu were more prominent and relatively larger in TB. In the second carpal bone (C2), the distal extent of the proximal articular surface on the palmar surface was greater in Po. The inconsistent first carpal bone (C1) was relatively larger in Po. Morphometrical similarities and differences in carpal bones between TB and Po indicate potential effects of selection for body size or fast exercise.     

The morphological characteristics of the antebrachiocarpal joint of the cheetah (Acinonyx jubatus)

A morphological study of the structures of the antebrachiocarpal (AC) joint of the cheetah was carded out by dissection of eight forelimbs obtained from four adult cheetahs culled from the Kruger National Park, Republic of South Africa. The aim was to evaluate the deviations of this joint from the normal feline pattern and to consider their possible relationship to the cheetah's adaptation to speed. Although published data on the AC joint of the other felids show general resemblance to that of the cheetah, there are nevertheless slight, but significant variations and modifications which tend to suggest adaptation to speed. The shafts of the radius and ulna of the cheetah are relatively straight and slender, with poorly developed distal ends. The ulnar notch is reduced to a very shallow concavity while the corresponding ulnar facet is a barely noticeable convexity, separated from the distal ulnar articular facet by an ill-defined groove. The movement of the distal radio-ulnar joint is highly restricted by the presence of a fibro-cartilaginous structure and a strong interrosseous membrane, limiting pronation and supination normally achieved by the rotation of the radius around the ulna. The extensor grooves at the distal extremity of the radius are deep and narrow and are guarded by prominent ridges. A thick extensor retinaculum anchors the strong extensor tendons in these grooves. The distal articular surface of the radius is concave in all directions except at the point where it moves into its stylold process. At this point it is convex in the dorsopalmar direction, with a surface that is rather deep and narrow. The proximal row of carpal bones presents a strongly convex surface, which is more pronounced in the dorsopalmar direction with the greatest convexity on the lateral aspect. Medially, there is a ridge-like concavity across the base of the tubercle, which rocks on the flexor surface of the radius, limiting excessive flexion as well as restricting lateral deviation of the AC joint.     

Congenital malformation of the front limbs in a llama (Lama glama): polydactyly in combination with arthrogryposis

A male, 10 month old llama with malformation of both front limbs was presented. Both front limbs had one more digit located medially. The distal phalanx of this additional digit at the left front limb reached the ground by the tip of the keratinzed pad and the toenail. The accessory digit at the right front limb was bent in a 90 degree angle caudolateraly. Beside the digital bones of the accessory digits the second metacarpal bone and the first carpal bone could be detected in both front limbs by radiological examination. Secondary a bilateral slight carpal valgus deformity could be seen.     

A study of ossification of carpal and tarsal bones in normal and hypothyroid foals

The degree of ossification of carpal and tarsal bones was determined in normal foals of various ages and in hypothyroid and thyroidectomized foals. In normal foals ossification occurred very rapidly in the last few weeks of gestation and less rapidly from birth to 33 days. The ulnar carpal bone was consistently less ossified than other carpal or tarsal bones. Foals with congenital hyperplastic goitre had retarded ossification of the cuboidal bones, especially the central and third tarsal bones. Thyroidectomized foals had retarded ossification of lesser degree.     

Carpal arthrodesis using a minimally invasive approach and locking compression plates: Three cases

Three horses with carpal instability due to comminuted second carpal bone fractures (Cases 1 and 3), fracture of the head of the second metacarpal bone (Case 1) or comminuted fractures of the fourth carpal bone, ulnar and intermediate carpal bones (Case 2) were treated by minimally invasive approach for partial (Cases 1 and 3) or pancarpal (Case 2) joint arthrodesis, using locking compression plates. The joint cartilage was removed by either an arthroscopic approach (middle carpal joint and antebrachiocarpal joint) or a percutaneous drilling technique (carpometacarpal joint). Two or 3 locking compression plates were contoured to the dorsolateral, dorsomedial and dorsoaxial aspects of the carpal joints using a custom‐made tunnelling tool and a minimally invasive tunnelling technique, and the screws were positioned through stab incisions. All cases recovered well, were lame free at the walk, were able to trot and gallop and could be used for leisure and pasture activities (partial carpal arthrodesis) and breeding (pancarpal arthrodesis). Post‐operative x‐rays showed progressive joint fusion after 12 months (Case 1), 5 months (Case 2) and 10 months (Case 3). Case 2 with a pancarpal arthrodesis showed a mechanical lameness at the walk due to the inability to flex the carpus. Carpal flexion after carpometacarpal and middle carpal arthrodesis in Case 1 was calculated to be 42.6° and 44° in Case 3.     

Antebrachial metacarpal arthrodesis for fusion of deranged carpal joints in two dogs

Congenital malformation of the carpal joint in a young dog resulted in a progressive lameness. Traumatic disruption of the carpus in another dog resulted in carpal bone necrosis, infection, and chronic instability. Radial metacarpal arthrodesis was performed in both dogs. The diseased carpal bones were excised, sparing the accessory carpal bone in both dogs. Radial metacarpal arthrodeses were then performed, using bone plate fixation. In the dog with the malformed limb, the gait had improved, but intermittent lameness was still present 8 months later because of an associated malarticulation of the cubital joint. The dog with the traumatized carpus had little or no lameness associated with normal activity for 32 months.     

Arthroscopic landmarks of the equine carpus

The radiocarpal and middle carpal joints of 4 clinically normal horses and 24 necropsy specimens were examined with an arthroscope to describe the topographic anatomy of these joints. The carpal bones of the radiocarpal joint had congruent articular surfaces in extension, but carpal flexion resulted in a stairstep between the radial and intermediate carpal bones. The variable surface anatomy, as well as the restricted synovial space and the technical limitations of the arthroscope, contributed to the need for more than one arthroscopic approach to the radiocarpal joint to ensure a thorough examination. The middle carpal joint's hinge-like biomechanics resulted in a spacious synovial cavity that was more amenable to arthroscopic examination. Careful planning was necessary to ensure that areas of interest were distant from the arthroscope-insertion site to allow the best perspective possible. The lateral approach to the middle carpal joint provided the best viewing of both facets of the intermediate and third carpal bones as well as the dorsal rim of the radial carpal bone. The medial approach did not allow complete inspection of these areas.     

Anatomische und röntgenologische Untersuchungen am Schultergelenk des Geparden (Acinonyx jubatus)

Anatomical structures of shoulder joints of five adult cheetahs were examined by dissection, corrosion casts and radiography. The bones, capsules and auxiliary synovial devices were described, as well as ligaments and adjacent muscles. The cheetah shoulder has many similarities with the shoulder joint of the domestic cat, but also considerable differences. Proper osteological features were the large supraglenoid tubercle, the caudally directed coracoid process and the extension of the articular surface of the scapula to the lateral area of the supraglenoid tubercle. On the proximal end of the humerus the width of the head of humerus, the facet of infraspinatus muscle as a shallow cavity with the insertion of the infraspinatus muscle around it and two raised roughnesses on the proximal end of the tricipital line for the insertions of the lateral glenohumeral ligament and the teres minor muscle were noticeable. The insertion of the joint capsule was mainly on the glenoid labrum, only in part of the articular surface on the lateral area of the supraglenoid tubercle laterally on the scapula. The joint capsule formed a supra- and infraspinatus recess laterally, an intertubercular tendon sheet for the biceps brachii muscle cranially, and a bipartited subscapular recess medially. An extracapsular transverse ligament passing the intertubercular groove, a laterally capsular strengthening—called lateral glenohumeral ligament—and an intracapsular medial glenohumeral ligament could be found. The latter one was joined to the capsule by a mesoligament, dividing the subscapular recess into two pouches.     

MAGNETIC RESONANCE ANATOMY OF THE CARPUS OF THE HORSE DESCRIBED FROM IMAGES ACQUIRED FROM LOW‐FIELD AND HIGH‐FIELD MAGNETS

Cadaver carpi of 30 mature horses with no history of carpal or proximal metacarpal pain were examined using low‐field (0.27 T) and high‐field (1.5 T) magnetic resonance imaging (MRI). Normal MRI anatomy in transverse, sagittal, and dorsal plane images was determined by comparison with anatomical specimens and standard texts. Subchondral bone and cortical bone thickness measurements were obtained from standardised sites. There was variable subchondral bone thickness in the radius and carpal bones; subchondral bone thickness was consistently larger at dorsal compared with palmar sites in the proximal row of carpal bones. The endosteal surface of the subchondral bone was smooth. The shape of the ulnar carpal bone was variable and one or more small osseous fragments were identified palmar to the bone in 5/30 limbs. There was no evidence to suggest that these were pathological fractures or avulsions of the lateral palmar intercarpal ligament. The amount of muscle tissue in the superficial and deep digital flexor tendons in the proximal aspect of the carpus varied, but none was present at the level of the middle carpal joint and distally. Several structures could be evaluated that cannot be imaged using radiography, ultrasonography, or arthroscopy, including the transverse intercarpal ligaments, the radiocarpal ligament, the short palmar carpal ligaments, and the carpometacarpal ligaments. Anatomical variations not previously described were identified, including the layers of the medial aspect of the carpal fascia. Knowledge of the variation in MRI appearance of the carpus of nonlame horses is helpful for interpretation of MR images of lame horses.     

Comminuted fracture of the accessory carpal bone removed via an arthroscopic-assisted arthrotomy

A 16-year-old American paint horse gelding was presented for evaluation of a left forelimb lameness grade III/V. Radiographs and computed tomography revealed a comminuted fracture of the accessory carpal bone involving the entire articulation with the distal radius and the proximal aspect of the articulation with the ulnar carpal bone. Multiple fragments were present in the palmar pouch of the antebrachiocarpal joint. An arthroscopic-assisted open approach was necessary to remove all fractured fragments. Subsequently the horse was re-admitted for lameness and was treated successfully with antibiotics and long-term supportive bandaging.     

Surgical correction of polydactyly in a camel (Camelus dromedarius).

A 2-mo-old, 90-kg, intact male camel (Camelus dromedarius) was admitted for surgical removal of a supernumerary digit associated with the medial aspect of the right carpus and metacarpus. Radiographic views of the carpus and metacarpus revealed the supernumerary digit articulating with the middle carpal joint via an extra carpal bone. The supernumerary digit consisted of three bones. Surgical removal of the supernumerary digit was recommended to restore normal limb conformation, limit the possibility of future lameness, and improve the cosmetic appearance of the limb. Complete surgical removal of the digit was performed by disarticulating the extra carpal bone from its attachments to the second and radial carpal bones. One year after surgery, the leg appeared grossly normal and the camel showed no sign of lameness.     

A Comparison of Methods for Proximal Palmar Metacarpal Analgesia in Horses

Three techniques for inducing analgesia of the proximal metacarpal region were evaluated for the frequency of inadvertent injection into the middle carpal and carpometacarpal joints. Using methylene blue solution as a marker dye and 30 fresh cadaver specimens each, three clinicians performed either 30 infiltrations at the origin of the suspensory ligament (method A), 30 palmar and palmar metacarpal nerve blocks at the proximal end of the metacarpus (method B), or 30 palmar and palmar metacarpal nerve blocks at the distal aspect of the accessory carpal bone (method C). The frequency of inadvertent injection into the distal carpal joints was 37, 17, and 0% for methods A, B, and C, respectively. The association between method and injection into the joints was significant (p less than 0.01). Infiltration of the distal carpal joints occurred with injection distances from the carpometacarpal joint of 1.5 to 4.5 cm. Although there was no joint injection with method C, the carpal synovial sheath was inadvertently infiltrated in 68% of the specimens. Injection into the distal carpal joints can occur when deep injections are made into the proximal palmar aspect of the metacarpus because of the distopalmar outpouchings of the carpometacarpal joint between the axial surfaces of the second and fourth metacarpal bones and the abaxial surface of the suspensory ligament.     

Radiographic changes in Thoroughbred yearlings in South Africa

This study involves the evaluation of pre-purchase radiographic studies of South African Thoroughbred yearlings. Radiographic changes were recorded and compared with similar international studies. The study differs from other studies in that a lower prevalence of pedal osteitis (1.26%), dorsal osteochondral fragmentation of the metatarsophalangeal joint (1.60%), distal metacarpal sagittal ridge changes (15.7%), ulnar carpal bone lucencies (8.33%), carpal osteophytes (1.19%), distal intertarsal and tarsometatarsal joint radiographic changes (9.92%), tarsal osteochondrosis lesions (4.40%) and stifle osteochondrosis lesions (0.4%) was found. The prevalence of dorsal osteochondral fragments in the metacarpophalangeal joint was similar to other studies (1.60%). A higher prevalence of vascular channels as well as irregular borders and lucencies was evident in the proximal sesamoid bones. There was a higher prevalence of palmar metacarpophalangeal and plantar metatarsophalangeal osteochondral fragments (2% and 7.10% respectively). Palmar metacarpal disease, metacarpal supracondylar lysis, proximal sesamoid bone fractures and carpal osteochondral fragmentation were absent in the current study. Additional findings recorded in the current study were proximal interphalangeal joint hyperextension (left front 15.13%, right front 18.91%), the solar angle (right front 2.38 degrees, left front 2.79 degrees), the prevalence of carpal bone 1 (30.95%) and carpal bone 5 (1.59%). Management, nutrition and genetics in the various groups of Thoroughbred yearlings should be further investigated in order to explain the reasons for the differences recorded in the current study.     

Radiographic and scintigraphic evaluation of the third carpal bone of control horses and horses with carpal lameness

We compared the radiographic and scintigraphic findings in the third carpal bone of horses performing different work disciplines and investigated their relationship with lameness. Horses had undergone carpal radiography including acquisition of a dorsoproximal-dorsodistal oblique (DPr-DDiO) image of the distal row of carpal bones and/or scintigraphic examination of the carpi. Cause of lameness, breed, age, and work discipline were recorded. Increased opacity in the third carpal bone was graded, ratio of radiopharmaceutical uptake calculated objectively, and increased radiopharmaceutical uptake graded subjectively. Relationships between radiographic, scintigraphic, and clinical findings were assessed statistically. Increased opacity in the third carpal bone (P = 0.003) and ratio of radiopharmaceutical uptake (P = 0.015) were associated with the work discipline. Increased opacity in the third carpal bone was associated with both increased radiopharmaceutical uptake grade (P = 0.002; rs = 0.59) and ratio of radiopharmaceutical uptake (P = 0.013; rs = 0.46). Increased radiopharmaceutical uptake and increased opacity in the third carpal bone were not always observed concurrently. Lameness related to the middle carpal joint was associated with increased opacity (P < 0.001), ratio of radiopharmaceutical uptake (P = 0.037), and increased radiopharmaceutical uptake grade (P < 0.001). Radiographic and scintigraphic abnormalities were observed in horses performing all disciplines, indicating that high-speed exercise may not be the only factor determining the development of osseous disease in the third carpal bone. Both increased opacity and increased radiopharmaceutical uptake were more likely to be seen in horses with lameness related to the middle carpal joint than in horses with other sources of pain.     

RADIOLOGIC ANATOMIC VARIATION OF THE CARPUS IN HORSES WITH CARPAL LAMENESS AND CONTROL HORSES

Our purpose was to describe the variation of the radiologic appearance of the carpus of horses of different breeds, discipline, and gender with lameness related to the carpus and control horses, with particular reference to the ulnar carpal bone. Two hundred and eighty‐six sets of carpal radiographs from 222 horses were analyzed. Breed, gender, discipline, and cause of lameness were recorded. Chi square tests were used to test for associations between radiologic findings and gender, breed and discipline, to test for associations between different radiologic findings, and to test for associations between radiologic findings and causes of lameness. Bonferroni correction was applied when necessary. The shape of the ulnar carpal bone and most of the anatomic variants, with the exception of the first carpal bone and a radiolucent area in the second carpal bone, were not breed or gender related. Radiolucent areas and associated fragments on the palmaromedial aspect of the ulnar carpal bone can be an incidental finding in horses from all disciplines.