Accessory Carpal Bone Research Articles

Morphological characteristics of rabbits’ carpal tunnel: Evaluation of its potential for carpal tunnel research

This study aimed to define the main anatomic components and describe the normal size and form of the carpal tunnel in rabbits using imaging techniques. It was also aimed to evaluate the potential of rabbits as an animal model for carpal tunnel research. The forelimbs of eight adult New Zealand rabbits were investigated using histology, magnetic resonance, and computed tomography. Two cadavers were used for anatomical dissection to support the findings. The carpal tunnel was examined at proximal and distal levels, and it was found that the flexor retinaculum is two-layered in rabbits. Both vascular nerve bundles, including the median nerve and the ramus palmaris of the ulnar nerve, were within two layers of it and passed through the carpal tunnel. The deep digital flexor, superficial digital flexor, and radial carpal flexor tendons were observed within the carpal tunnel. The flexor pollicis longus tendon is not found in rabbits. The area of the carpal tunnel narrowed towards the distal end in three methods, and its depth decreased in CT and MRI. The length of the accessory carpal bone determined this depth. The study found that rabbits' carpal tunnels are morphologically similar to those of humans compared to dogs. This situation is thought to pave the way for more accurate approaches to carpal tunnel research in rabbits.

Successful surgical management of a Salter-Harris type I fracture of the accessory carpal bone in a dog.

To describe the successful surgical management of a previously unreported Salter-Harris type I fracture of the accessory carpal bone in a dog. An 11-week-old intact female Golden Retriever-Poodle cross presented with a history of a marked left forelimb lameness following a suspected fall from a height. On physical examination, the patient demonstrated a severe left forelimb lameness and pain on palpation and range of motion of the left carpus. Orthogonal radiographs of the distal left forelimb demonstrated a type I Salter-Harris fracture of the accessory carpal bone with proximal displacement of the palmar fragment. The patient underwent open reduction and internal fixation wherein the fracture was reduced and stabilized with two 1.1-mm Kirschner wires. Postoperatively, the patient was initially managed with a carpal flexion bandage for 2 weeks and then a soft padded bandage was maintained until 4 weeks postoperatively. The patient recovered well and was walking and weight-bearing comfortably following removal of the carpal flexion bandage. Repeat radiographs performed 4 and 8 weeks postoperatively demonstrated adequate fracture healing but showed mild proximocaudal implant displacement. Implant removal was not performed, as the patient was doing well at home and the implant migration appeared static and was not causing clinical morbidity. To the authors' knowledge, this was the only reported case of a Salter-Harris fracture of the accessory carpal bone in a dog and the only described case of successful surgical stabilization.

Evaluation of a palmar approach to the carpal flexor tendon sheath

SummaryBackgroundA palmar approach for centesis of the carpal flexor tendon sheath has not been reported.ObjectiveTo determine the feasibility and accuracy of a palmar approach to an undistended carpal flexor tendon sheath.Study designIn vivo and experimental.MethodsBoth forelimbs of six horses were used. A 20‐gauge, 8.9‐ or 7.62‐cm spinal needle was inserted 3–4 cm proximal to the dorsal border of the accessory carpal bone in the space between the ulnaris lateralis and flexor carpi ulnaris muscles and directed sagittally and perpendicular to the long axis of the limb until the needle contacted the radius. The needle was retracted slightly, contrast medium was injected, and a laterally projected radiograph of the carpus and distal aspect of the radius was obtained and examined.ResultsThe technique, when performed on 12 limbs of six horses, was 92% accurate. For one limb, the needle was inadvertently directed slightly ventrally, rather than perpendicular to the long axis of the limb, causing it to contact the radius near its physeal remnant, resulting in centesis of the antebrachiocarpal joint.ConclusionsThe palmar approach to the carpal flexor tendon sheath appears to be highly accurate.

Endoscopic diagnosis of an obstructive fungal ball in the urethra of a dog

AbstractA 1‐year‐old, male, neutered German shepherd dog was presented for a chronic atraumatic non‐healing fracture of the right accessory carpal bone, stranguria and polyuria/polydipsia. Biochemistry and urinalysis showed azotaemia. Ultrasound and computed tomography of the abdomen both demonstrated bilateral renal infarcts with pyelectasia, bilateral ureteral dilation and bladder distension. Cystoscopy of the bladder identified a fungal ball obstructing the pelvic urethral sphincter, which was adhered to the bladder mucosa in the region of the ureterovesicular junction. The obstruction was traversed endoscopically, but could not be removed transurethrally. The combination of elevated serum galactomannan titres (6.4) and Aspergillus terreus cultured from urine, confirmed a diagnosis of disseminated aspergillosis. The dog was euthanased due to poor quality of life, guarded prognosis and lengthy timeframe before an expected medical response. This is the first case report describing Aspergillus fungal balls in a dog causing partial urethral and bilateral ureteral obstruction, identified using cystoscopy.

Adaptação óssea ao exercício em cavalos árabes praticantes de enduro equestre de 120-160 km - análise quantitativa e funcional

ABSTRACT Seeking the improvement of equine sports medicine, the present work aimed to determine quantitative data from different bone structures. Therefore, the objective of this work was to quantify the thickness of the cortex in a comparative way to determine the bone densitometry and also the bone density of the bone trabeculae of the spongy substance of the radius, calcaneus, and metacarpal III bones of horses practicing equestrian enduro long-distance running tests. Six thoroughbred Arabian horses and long-distance competitors (120 and 160km) were evaluated for metacarpal III, calcaneus, and accessory carpal bone. Long bones have a different micro functional structure than short bones. The sites that received and dissipated energy varied in distal, proximal epiphysis, and diaphysis according to the bone. The calcaneus and accessory carpal bone had a lower transverse thickness of the compact substance and greater density of the same, this increase was related to the improvement of local resistance. The density of the spongy substance varied with different bones. Thus, it was concluded that stress directly influenced the quantity and quality of the compact and spongy substance.

180 Effect of leg wraps on skin temperature in exercising horses

Tendon or ligament injuries are common in performance horses and have a negative impact on training time and economics in all equestrian disciplines. There are some factors that increase the risk of tendon and ligament injury including fitness level, overexertion, and tendon core temperature. In vitro studies have shown fibroblast death at tendon core temperatures of 43° to 48°C, suggesting that repeated hyperthermic events may predispose the horse to tendon or ligament injury. The distal limb of the horse houses tendons and ligaments only, and is often covered in boots or polo wraps during exercise to protect the limb from trauma. Previous studies of exercising horses have compared distal limb skin temperature under solid boots, perforated boots, and polo wraps, and found that increased airflow is important to reduce skin temperature and likely tendon core temperature. Currently on the market are several brands of polo wraps that claim to promote airflow and keep the limb cooler during exercise than traditional coverings. The objective of this study was to investigate this claim and compare the distal limb skin temperature under a traditional pair and 2 brands of cooling polo wraps during and after exercise. Using a HOBO TidbiT MX Temperature Data Logger taped on the skin halfway between the ergot and accessory carpal bone, a total of 5horses were used to test a different covering each day: traditional fleece polo wrap, cooling wrap 1, and cooling wrap 2. The temperature under the wraps was recorded during exercise and for an additional 5 min afterward at rest. For all 3 treatment conditions, the median was used as the measure of center for the distributions of average temperature change because the distributions for the cooling wraps were highly right skewed. Because of the small sample size, a Friedman test (P = .05) was conducted to determine if there was a significant difference in the average heat buildup between the 3 treatments. The median of the average temperature change was 4.24°C for the regular fleece polo wrap, 3.50°C for cooling wrap 1 and 2.70°C for cooling wrap 2. There were no statistically significant differences found in the distributions of average temperature across the 3 treatments (P = 0.247). However, the data did show a trend of lower average temperature under the cooling wraps compared with the traditional fleece wraps. These results prompt further study of larger sample size, time to plateau and cool down under the wraps, and temperatures under more rigorous exercise to fully evaluate the difference between treatments.

Pneumatic compression therapy using the EQ Press accelerates lymphatic flow in healthy equine forelimbs as determined by lymphoscintigraphy.

Limb lymphedema in horses can be debilitating and painful. Pneumatic compression therapy has shown significant benefits for people suffering from lymphedema. The objective of this study was to determine the effect of a novel, equine-specific pneumatic compression device on the lymphatic flow of healthy horse forelimbs as determined by Tc-99m sulfur colloid lymphoscintigraphy. 6 healthy Thoroughbreds. In a randomized crossover design, horses underwent bilateral forelimb lymphoscintigraphy following subcutaneous injection of Tc-99m sulfur colloid at the coronary band as untreated control or with pneumatic compression therapy using the EQ Press. Lateral, static images were obtained of the distal limb (time 0 to 60 minutes) and proximal limb (time 30 to 60 minutes) using a standard gamma camera. Lymphatic flow was determined by assigning a score to the time point at which Tc-99m sulfur colloid was first visualized at the level of the accessory carpal bone (1 to 7) in the distal limb and the cubital lymph node (1 to 4) in the proximal limb. EQ Press treatment led to a significantly faster lymphatic flow of Tc-99m sulfur colloid to the predetermined anatomic locations of the accessory carpal bone (P = .002) in the distal limb and the cubital lymph node (P = .001) in the proximal limb. Pneumatic compression therapy as provided by an equine-specific device encouraged lymphatic flow in healthy, nonedematous equine forelimbs. These data support further study of the EQ Press for pneumatic compression therapy in horses clinically affected by lymphedema and lymphatic drainage disorders.

Standing osteosynthesis of an accessory carpal bone fracture in a Warmblood mare with a 6‐hole 3.5 talonavicular fusion plate and 3.5‐mm screws

SummaryA 9‐year‐old Warmblood, high‐level showjumping mare sustained an acute, closed, vertical, comminuted fracture of the left accessory carpal bone (ACB) during a fall. The fracture was repaired under standing sedation and local anaesthesia, using a 6‐hole APTUS® 3.5 TFP and 5 × 3.5‐mm self‐tapping TriLock© screws. The mare recovered from surgery without complications. Upon follow‐up examination 9 months post‐operatively the mare was sound in all gaits and back to full athletic activity. The ACB fracture had completely healed. The displaced dorsoproximal fracture fragment was in a stationary position and there was evidence of mild nonprogressive osteoarthritis of the antebrachiocarpal joint.

Applicability of ARFI elastography in detecting elasticity changes of the equine superficial digital flexor tendon with induced injury.

The objectives of this prospective, experimental study were to describe changes in the stiffness of the equine superficial digital flexor tendon (SDFT) after induced injury, deep digital flexor tendon (DDFT), accessory ligament (AL-DDFT), and suspensory ligament (SL) during 90 days of healing using acoustic radiation force impulse (ARFI) elastography. Eight healthy horses were selected. Preinjury B mode and ARFI evaluations were performed bilaterally in the palmar metacarpal region. Injury was induced only on the left forelimb (G2) by a single injection of collagenase in SDFT, 15 cm distal to the accessory carpal bone. The right forelimb was used as a control (G1). Evaluations were performed at eight timepoints: one before injury (T0) and seven (T1-T7) after injury (3, 15, 30, 40, 60, 75, and 90 days post-induction). Tendinopathies were visualized as hypoechoic areas with loss of parallel tendon fiber pattern. Injured SDFTs presented mainly cool colors (soft) from T1 to T3, and from T4, there was an increase in warm colors (hard), close to the appearance of tendons of G1. In the first four timepoints, there was a decrease in stiffness compared to G1 (P < 0.001). On T1 and T2, a cutoff value <6.21 m/s to determine tendinopathy of the SDFT was established (75.8% sensitivity and 92.03% specificity). Stiffness changes in the DDFT, AL-DDFT, and SL of injured limbs occurred at different timepoints. Tendinopathy significantly altered the stiffness of the injured tendon and the adjacent tissues. ARFI made it possible to detect these changes, helping to monitor the reparation of this injury.

High-Resolution Ultrasonographic Anatomy of the Carpal Tendons of Sporting Border Collies.

Simple SummaryDog agility is a canine sport that has gained popularity among pet owners in recent decades. Because of the high-performance level, injuries to dogs competing in this sport are becoming frequent. The need for better knowledge of the anatomy of the structures involved in athletic movements is an essential starting point for correctly managing agility-related injuries. The aim of this paper was to investigate the ultrasonographic anatomy of the carpal joint, creating a baseline reference for the Border Collie, which is the breed most utilised in agility competitions. The data acquired could be of use in future studies regarding sport-induced injuries in the canine carpus.Recent literature has demonstrated that high-resolution ultrasonographic anatomy of the canine carpus is possible; however, only the structures of the dorsal face were described. The aims of this prospective study were: (1) to describe the normal ultrasonographic appearance of the carpal tendons in sporting Border Collies; (2) to measure the height, length, and thickness of the tendon at the radial ulnar notch level in order to create a baseline reference for the breed, and (3) to describe a standardised protocol to ultrasonographically evaluate the carpal faces and visible tendinous structures. A pilot study based on ten cadaveric front limbs was used to identify the structures. A subsequent clinical phase of the study using twenty-six Border Collies was recorded. The tendons of the Extensor Carpi Radialis, Extensor Digitorum Communis, and Extensor Digitorum Lateralis were identified and followed from the tenomuscular junction to the distal insertion on the dorsal face of the digits. On the lateral face, the tendon of the Extensor Carpi Ulnaris was recognised and followed. On the palmar face, the two heads of the Flexor Carpi Ulnaris tendon ending on the accessory carpal bone, the adjacent Flexor Digitorum Superficialis tendon, and the deep and medially located Flexor Digitorum Profundus tendon were seen and followed. The Flexor Carpi Radialis and the Abductor Pollicis Longus tendons were seen in the medial carpal face. The ulnar notch of the radius was used as the measurement and starting point of the ultrasonography. These data could be used as a standard reference in the case of chronic overuse and trauma-induced changes in the canine carpus.

Arthroscopic removal of palmar intermediate carpal bone fracture fragments in four horses using a transthecal approach through the carpal flexor tendon sheath

ObjectiveTo describe the removal of palmar intermediate carpal bone (ICB) fracture fragments using a transthecal approach through the carpal flexor tendon sheath.Study designCase series.AnimalsFour horses with fractures of the palmar aspect of the ICB.MethodsTwo horses were injured when falling and two during recovery from general anesthesia. Three horses underwent MRI to supplement conventional imaging. Three horses had concurrent fractures of the radial and/or accessory carpal bones. Conventional proximolateral carpal sheath arthroscope and instrument portals were used, supplemented with a medial instrument portal through the carpal flexor retinaculum to access the palmar carpal ligament. Optimized dissection through the latter was facilitated by needle guidance and radiography. The fragment was dissected from the soft tissue attachments and the palmar ICB fragments retrieved through the carpal sheath in all horses. Surgery time was 85 to 142 min.ResultsLimitations of this technique include a long surgery time and the potential for hemorrhage to impair visibility during surgery. All four horses were discharged 3 to 8 days postoperatively. Three horses returned to full athletic work within 9 months postoperatively and one horse was euthanized due to persistent lameness.ConclusionA tenoscopic transthecal carpal flexor tendon sheath approach provides access for removal of palmar ICB fracture fragments but should be viewed as an advanced arthroscopic procedure.Clinical significanceA transthecal approach through the carpal flexor tendon sheath offers an alternative technique for removal of palmar ICB fracture fragments.

Fracture of the accessory carpal bone—conservative or surgical therapy?

Fracture of the accessory carpal bone—conservative or surgical therapy?

Development of Ultrasound-Guided Technique for 4 Points Blockade of Manus in Dromedary Camel: A Cadaveric Investigation

The purposes of this study were to describe the most applicable approach of manus blockade in camel using ultrasound-guided techniques. The study was performed on 40 forelimbs of 20 apparently healthy mature freshly slaughtered camels. Limbs were randomly allocated into 3 phases of the study. Phase-I (n=8 limbs): dissection of both dorsal and palmar aspects to identify the topographical anatomy of the target nerves. Phase-II (n=8 limbs): dissection after US guided needle insertion to confirm the needle insertion position. Phase-III (n=24 limbs): US-guided methylene blue injection using one of three volumes (3, 5, or 7 mL) to establish the ideal injection volume. Our results revealed that the dorsal aspect of manus received its innervation from dorsal common digital nerves II and III (DCDN-II &amp; III) and dorsal common digital nerve IV (DCDN-IV). The palmar aspect of manus was received its innervation from the palmar common digital nerve IV (PCDN-IV) and the median nerve. Under Ultrasonographic guidance, the most applicable approach for blocking the DCDN-II &amp; III is at the dorsomedial aspect at about 8-10 c.m below the carpometacarpal joint (CMJ) and 2 cm medial to CDET. Blocking of the DCDN-IV is performed at the dorsolateral aspect at about 8-10 c.m below the CMJ and 2 cm lateral to CDET. Blocking the PCDN IV was performed at the lateral and palmar aspect at about 10-12 c.m below the accessory carpal bone (ACB) and 5 cm palmar to the imaginary line bisect the forelimb longitudinally from lateral to medial. Blocking the median nerve was performed at the proximal third of medial and palmar aspect of metacarpal bone at about 10-12 c.m below the ACB and about 5 cm palmar to the same imaginary line. In conclusion, four point blockade of the manus region in dromedary cadavers can be achieved by US-guided injection of the DCDN-II, III, DCDN-IV, PCDN-IV, and the median nerve.

Accessory carpal bone fracture repair by means of computer‐assisted orthopaedic surgery in a Warmblood stallion

SummaryA 10‐year‐old, 595 kg Irish Warmblood stallion used for showjumping was presented with a marked right forelimb lameness at walk. The horse sustained a dorsal plane fracture of the accessory carpal bone (ACB) when falling with both carpi in flexion. The fracture was repaired by means of computer‐assisted orthopaedic surgery (CAOS) using two cortex screws placed in lag fashion. In a second CAOS procedure, a dorsoproximal fragment of the ACB was removed after further proximal displacement had become apparent. Both surgical procedures were facilitated by the application of a fibreglass cast to immobilise the carpus in extension and to allow for the placement of the patient tracker distant from the surgical site. One year after surgery, the horse had returned to full athletic activity. Neither the antebrachiocarpal joint nor the carpal sheath were distended. Control radiographs and standing cone beam computed tomography showed complete osseous union of the fracture and osteophyte formation on the caudal aspect of the radius and the proximal border of the ACB.

Fascial plane mapping for superficial tumor resection in dogs. Part II: Forelimb.

To detail the qualitative fascial categories and fascial intersections of the forelimb of the dog to facilitate preoperative planning for superficial cancers. Qualitative anatomical study. Three male and four female mixed breed canine cadavers weighing approximately 20-35 kg. The skin and subcutaneous fat were excised. Fascial planes were incised and elevated to allow exploration of their quality and borders. Fascia was categorized as type I (discrete sheets), type II (tightly adhered to thin muscles), type III (tightly adhered to thick muscles), or type IV (associated with periosteum). Photographs of specimens were digitally modified with overlays to map tissue types. Differences between the cadavers used were largely based on muscle mass and sex, with minimal other subjective differences affecting fascial mapping. The fasciae of the forelimb were largely type II or type III, with type I fascia at the antebrachium and type IV fascia at the olecranon, scapular spine, and accessory carpal bone. Fascial integrity was often questionable or lacking distal to the distal quarter of the antebrachium. The fascial types and integrity of the forelimb varied with anatomic location with thin or absent fascia for surgical use at the elbow, carpus, and manus. This study provides information for preoperative planning and excision of superficial tumors of the forelimb. Knowledge of the potential limitations of fascia to provide a deep margin may influence selection of treatment modalities.

Intratendinous Fibroma of the Superficial Digital Flexor Tendon within the Carpal Sheath of a Horse

A 20-year-old British Warmblood gelding was presented for a progressively worsening right forelimb lameness which developed following an intense dressage training session. Initial ultrasound examination revealed a triangular, intrathecal, hypoechoic region within the superficial digital flexor tendon (SDFT) in the proximal, palmar carpal region distal to the accessory carpal bone (ACB), extending 7cm distally into the proximal metacarpal region. No significant improvement in clinical presentation was observed following an eight-week rehabilitation programme. Repeat ultrasound examination revealed an enlarged cross-sectional area of affected tendon. Due to a poor clinical response to conservative treatment, combined with increasingly marked severity of the lameness, the horse was humanely euthanised and the affected SDFT was submitted for macroscopic and histopathological examination at the University of Liverpool. This revealed an approximately 70mm-elongated, focally extensive mass located within the SDFT. On cross-section, the mass was poorly delineated, irregularly triangular, focally haemorrhagic, firm, 15 × 12mm wide and eccentrically placed towards the palmar aspect of the tendon. Histopathological examination identified a moderately to highly cellular, infiltrative, poorly demarcated mesenchymal neoplasm comprised of streams of moderately atypical spindloid cells including bizarre mitoses. Intratendinous fibroma is an uncommonly recorded human neoplasm and this case represents the third reported case of this entity in the horse, the first in an adult horse and the first to be identified in the SDFT.

The porcine accessory carpal bone as a model for biologic joint replacement for trapeziometacarpal osteoarthritis

Given its complex shape and relatively small size, the trapezium surface at the trapeziometacarpal (TMC) joint is a particularly attractive target for anatomic biologic joint resurfacing, especially given its propensity to develop osteoarthritis, and the limited and sub-optimal treatment options available. For this to advance to clinical translation, however, an appropriate large animal model is required. In this study, we explored the porcine accessory carpal bone (ACB) as a model for the human trapezium. We characterized ACB anatomy, geometry, joint and tissue-scale mechanics, and composition across multiple donors. We showed that the ACB is similar both in size, and in the saddle shape of the main articulating surface to the human trapezium, and that loads experienced across each joint are similar. Using this information, we then devised a fabrication method and workflow to produce patient-specific tissue-engineered replicas based on CT scans, and showed that when such replicas are implanted orthotopically in an ex vivo model, normal loading is restored. Data from this study establish the porcine ACB as a model system in which to evaluate function of engineered living joint resurfacing strategies. Statement of significanceBiologic joint resurfacing, or the replacement of a joint with living tissue as opposed to metal and plastic, is the holy grail of orthopaedic tissue engineering. However, despite marked advances in engineering native-like osteochondral tissues and in matching patient-specific anatomy, these technologies have not yet reached clinical translation. Given its propensity for developing osteoarthritis, as well as its small size and complex shape, the trapezial surface of the trapeziometacarpal joint at the base of the thumb presents a unique opportunity for pursuing a biologic joint resurfacing strategy. This work establishes the porcine accessory carpal bone as an animal model for the human trapezium and presents a viable test-bed for evaluating the function of engineered living joint resurfacing strategies.

Forelimb amputation and long‐term follow‐up in a White Dorper ram

AbstractThis paper aimed to report a successful forelimb amputation and long‐term follow‐up in a White Dorper ram. An 8‐month‐old 45.5 kg White Dorper ram was found standing on the exposed metacarpal bone of the right forelimb. Detailed clinical examination and radiographic evaluation confirmed metacarpophalangeal avulsion. Limb amputation was performed by radiocarpal disarticulation. Postoperative complications included wound infection and dehiscence. Fifteen days post‐surgery, the necrotic accessory carpal bone was retrieved during wound cleaning. After this, the stump healed rapidly by secondary intention within 30 days. During this recovery time, the ram showed good adaptation to walking on three legs, and the owner gave up buying the prosthesis. The ram returned to the flock fully adapted 45 days after surgery. We emphasize that documenting more limb amputations in livestock is critical to obtain conclusions about the prognosis, life expectancy and expected quality of life.

Kinematics of the Feline Antebrachiocarpal Joint from Supination to Pronation.

Cats rely on their forelimb mobility for everyday activities including climbing and grooming. Supination and pronation of the forelimb in cats are considered to primarily involve the antebrachium, rather than the carpus. Therefore, our null hypothesis was that there would be no movement of the carpal bones (radial carpal bone, ulnar carpal bone and accessory carpal bone) relative to the ulna during supination and pronation. Eight feline cadaveric forelimbs were rotated from supination to pronation in a jig and computed tomography was performed in the neutral, supinated and pronated positions. The individual carpal bones were segmented from computed tomography images of the supinated and pronated scans in each of the eight specimens. A feline ulna coordinate system was established and used to quantify the translations and rotations between bones of the proximal carpal row and antebrachium. After the carpus was rotated from the initial supinated position into pronation, there was significant translation (x, y and z axes) and rotation (x and y axes) of the proximal row of carpal bones based on absolute magnitude values. Given the differences in translations and rotations of the proximal row of carpal bones, our null hypothesis was rejected. The proximal row of carpal bones translate and rotate independently from the ulna in the cat during pronation of the antebrachium. This may have future implications in the diagnosis and management of feline carpal injuries involving the antebrachiocarpal joint.

Comparison of the racing performance of Thoroughbreds with versus without osteochondral fragmentation of the accessory carpal bone identified on yearling sales repository radiographs.

OBJECTIVE To evaluate 2- and 3-year-old and career race performance of Thoroughbred racehorse prospects with and without osteochondral fragmentation of the accessory carpal bone (ACB) identified on yearling presale radiographs. DESIGN Retrospective, matched cohort study. ANIMALS 47 nonlame Thoroughbreds with (exposed cohort) and 94 nonlame Thoroughbreds without (unexposed cohort) osteochondral fragmentation of ACB facture identified on yearling sales repository radiographs. PROCEDURES Repository radiographic interpretation reports for September yearling sales of a large Kentucky auction house from 2005 through 2012 were reviewed, and race records were collected and analyzed. Race performance was compared between horses with and without ACB fracture chosen from the same sale to identify associations between racing performance and ACB fracture. RESULTS No significant differences were identified between horses with or without ACB fracture in their incidence of starting a race as a 2- or 3-year-old and the number of races started, earnings, or earnings per start for 2- or 3-year-old or career race performance. There was no significant difference in performance between horses with or without concurrent carpal osteoarthritis, nor did performance differ between horses with ACB fracture alone and those with ACB fracture and other radiographic abnormalities found to be associated with poorer performance in previous studies. CONCLUSIONS AND CLINICAL RELEVANCE ACB fracture with or without carpal osteoarthritic changes identified on repository radiographs of Thoroughbred yearlings was not associated with poorer racing performance or lower likelihood of starting a race as a 2- or 3-year-old, compared with outcomes for unaffected horses.