Radiographic technique to improve diagnosis of sagittal axial sesamoid fracture in racing Thoroughbreds with lateral condylar fracture

The current study identified 124 lateral condylar fractures of the distal metacarpus or metatarsus over a 6-year period. Thirty of 124 lateral condylar fractures were classified as displaced. Eight of 30 displaced lateral condylar fractures and 1/86 incomplete lateral condylar fractures had concurrent sagittal axial fracture of the lateral proximal sesamoid bone. A 20-degree DMPLO view is the most sensitive radiographic projection to identify sagittal axial fracture of the lateral proximal sesamoid bone. A flexed 20-degree DMPLO projection demonstrates displacement of complete sagittal axial sesamoid fractures. Radiographic identification of axial sesamoid fracture is critical to provide the most accurate prognosis for return to racing. Arthroscopic assessment of the axial sesamoid fracture and cartilage injury on the lateral proximal sesamoid bone, as well as post-operative progression, are described in four surgical cases.     

Axial sesamoid injuries associated with lateral condylar fractures in horses

Axial sesamoid injuries were found in 4 of 18 horses with lateral condylar fractures of the metacarpus or metatarsus. The injuries appeared as axial sesamoid fractures or progressive demineralization of the axial border of one of the sesamoids. None of the horses with axial sesamoid injuries returned to performance soundness. Axial sesamoid injury appeared to be an indication of severe fetlock trauma due to condylar fracture. Such injuries appeared to indicate a poor prognosis for return to performance soundness.     

Biomechanical investigation of the association between suspensory ligament injury and lateral condylar fracture in thoroughbred racehorses

Objective-To determine whether partial transection of the medial branch of the suspensory ligament (MBSL) alters equine third metacarpal bone (MC3) condylar surface strains and forelimb, distal joint angles in a manner consistent with promotion of lateral condylar fracture. Study Design-In vitro biomechanical experiment. Sample Population-Right forelimbs from 7 Thoroughbred horse cadavers. Methods-Lateral and medial MC3 condylar, dorsal and abaxial, bone surface strains and distal joint angles were measured both before and after partial transection of the MBSL during in vitro axial limb compression. Dorsal, principal bone strains and abaxial, uniaxial, and proximodistal strains were compared before and after MBSL partial transection at 1,400-, 3,000-, and 5,600-N loads. Results-Bone strains increased in all locations with increasing axial load. All lateral condylar bone strains were significantly higher, and abaxial surface medial condylar bone strain was significantly lower, after partial transection of the MBSL. Respective distal joints became more flexed or extended as axial load increased but were not significantly different after partial transection of the MBSL. Conclusions-Partial transection of the MBSL increases in vitro MC3 lateral condylar bone surface strains. Clinical Relevance-Loss of integrity of the medial branch of the suspensory ligament could increase the risk for lateral condylar fracture in Thoroughbred horses by amplifying bone strain in the lateral condyle.     

Management of proximal sesamoid bone fractures in the horse

The case records of 49 horses with proximal sesamoid bone fracture were studied. The population consisted of 20 Thoroughbreds, 20 Standardbreds, 5 Quarter Horses, 2 Arabians, and 2 grade horses. The fractured bones were classified into 5 categories: apical fractures, basilar fractures, abaxial fractures, middle one-third fractures, and bilateral comminuted-distracted fractures. Apical fractures occurred most frequently in the Standardbred, with the prevalence of medial fracture being equal to that of lateral fracture. Basilar fractures occurred predominantly in the Thoroughbred, with the highest prevalence in the lateral sesamoid bone of the right front fetlock. Bilateral comminuted-distracted fractures also occurred primarily in the right front fetlock. The prognosis following surgical removal of apical fractures appeared to be superior to that for stall rest alone. The prognosis for basilar fractures was poor.     

Risk of fatal distal limb fractures among Thoroughbreds involved in the five types of racing in the United Kingdom

The risk of fatal distal limb fractures in thoroughbreds racing in the UK was calculated and shown to vary considerably between the different types of race. Flat turf racing was associated with the lowest risk (0.4 per 1000 starts) and national hunt flat racing was associated with the highest risk (2.2 per 1000 starts). The types of fracture were classified by detailed radiographic and postmortem examinations of all the cases recorded over two years, and the distribution of the different types of fracture in the five main types of racing was examined. Overall, lateral condylar fractures of the third metacarpus were the most common, and they were also the most common in national hunt-type races (hurdle, steeplechase and national hunt flat races). In all-weather flat racing biaxial proximal sesamoid fractures were most common, and in turf flat racing fractures of the first phalanx were most common. The risk of fractures of more than one bone was greater in national hunt-type races.     

Association between findings on palmarodorsal radiographic images and detection of a fracture in the proximal sesamoid bones of forelimbs obtained from cadavers of racing Thoroughbreds

OBJECTIVE: To determine the distribution for limbs and bones in horses with fractures of the proximal sesamoid bones and relationships with findings on palmarodorsal radiographic images. SAMPLE POPULATION: Proximal sesamoid bones obtained from both forelimbs of cadavers of 328 racing Thoroughbreds. PROCEDURE: Osteophytes; large vascular channels; and fracture location, orientation, configuration, and margin distinctness were categorized by use of high-detail contact palmarodorsal radiographs. Distributions of findings were determined. Relationships between radiographic findings and fracture characteristics were examined by use of chi2 and logistic regression techniques. RESULTS: Fractures were detected in 136 (41.5%) horses. Biaxial fractures were evident in 109 (80%) horses with a fracture. Osteophytes and large vascular channels were evident in 266 (81%) and 325 (99%) horses, respectively. Medial bones typically had complete transverse or split transverse simple fractures, indistinct fracture margins, > 1 vascular channel that was > 1 mm in width, and osteophytes in abaxial wing and basilar middle or basilar abaxial locations. Lateral bones typically had an oblique fracture and distinct fracture margins. Odds of proximal sesamoid bone fracture were approximately 2 to 5 times higher in bones without radiographic evidence of osteophytes or large vascular channels, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Biaxial fractures of proximal sesamoid bones were common in cadavers of racing Thoroughbreds. Differences between medial and lateral bones for characteristics associated with fracture may relate to differences in fracture pathogeneses for these bones. Osteophytes and vascular channels were common findings; however, fractures were less likely to occur in bones with these features.     

Risk factors for proximal sesamoid bone fractures associated with exercise history and horseshoe characteristics in Thoroughbred racehorses

OBJECTIVE: To assess individual and combined associations of high-speed exercise and horseshoe characteristics with risk of forelimb proximal sesamoid bone fractures and proximal sesamoid bone midbody fractures in Thoroughbred racehorses. ANIMALS: 269 deceased Thoroughbred racehorses. PROCEDURES: A case-control study design was used to compare 121 horses with a fracture of at least 1 of 4 forelimb proximal sesamoid bones (75 horses had a midbody fracture) and 148 horses without a forelimb proximal sesamoid bone fracture. Univariable and multivariable logistic regression analyses were used to evaluate potential risk factors for association with proximal sesamoid bone fracture. RESULTS: Compared with horses that died without proximal sesamoid bone fractures, horses that died with proximal sesamoid bone fractures were more likely to be sexually intact males, spend more time in active trainingand racing, complete more events, train and race longer since their last layup, have higher exercise intensities during the 12 months prior to death, and have greater cumulative distances for their career. Horses with proximal sesamoid bone midbody fractures were more likely to be sexually intact males, train and race longer since their last layup, and have higher exercise intensities during the 12 months prior to death. CONCLUSIONS AND CLINICAL RELEVANCE: Limitingexercise intensity and the continuous time spent in activity duringa horse's career may decrease the frequency of forelimb proximal sesamoid bone fractures in Thoroughbred horses.     

Size and geometry of apical sesamoid fracture fragments as a determinant of prognosis in Thoroughbred racehorses

Reason for performing study: Analysis was performed to examine a method for refining the preoperative prognosis for horses that had surgery to remove apical fractures of the proximal sesamoid bones (PSBs). Objectives: To determine if: 1) there was a difference in size or configuration of apical fractures between the different anatomical locations of the PSBs, which have been shown to affect the prognosis; and 2) the size or configuration could predict the prognosis for racehorses with these fractures. Methods: The study included 110 weanlings and yearlings and 56 training racehorses that underwent surgery to remove apical PSB fractures. Radiographs of the fractures were used for measurement of the abaxial and axial proportion and the abaxial to axial ratio, and race records were used to determine average earnings per start (AEPS) and total post operative starts. Analysis of variance and regression statistics were used to compare the fragment sizes between the specific PSBs on each of the limbs and compare size and configuration of the fractures to prognosis. Results: There was a significantly larger abaxial to axial ratio (more transverse fracture) for the forelimb medial sesamoids than for all other sesamoids in untrained racehorses (P = 0.03). There were no other significant differences in size. There was no relationship between fracture size or configuration and AEPS nor total post operative starts. Conclusions: Apical fractures in weanlings and yearlings tend to be more transverse in the forelimb medial PSBs than the other PSBs. Apical fracture size and geometry does not determine prognosis for apical sesamoid fractures. Potential relevance: Horses that undergo surgery to remove larger apical fractures of the PSBs do not have a worse outcome than those horses with smaller fractures.     

Fractures of the proximal sesamoid bones in thoroughbred foals.

Eighteen cases of fractures of the proximal sesamoid bones in Thoroughbred foals are described. Most of the fractures were in foals under 2 months old and all but one occurred in the forelegs. The bones commonly fractured when the foal galloped to exhaustion trying to keep up with its dam in the paddock. The types of fracture varied but a simple fracture of the medial sesamoid was most frequent and the majority were towards the base of the bone. Six foals sustained a fracture of more than one sesamoid bone and one foal fractured all 4 proximal sesamoid bones in its front legs. Treatment included box rest and the surgical removal of the separated piece of sesamoid bone. Only 3 of the foals treated have raced. One of these was treated surgically.     

Effect of Gelatin Hydrogel Sheet Containing Basic Fibroblast Growth Factor on Proximal Sesamoid Bone Transverse Fracture Healing in the Horse

Our objective in this study was to examine the effect of gelatin hydrogel (GH) sheets containing basic fibroblast growth factor (bFGF) on healing of proximal sesamoid bone transverse fractures in the horse. Ten healthy adult Thoroughbreds were used. The lateral proximal sesamoid bone of the left forelimb and the medial proximal sesamoid bone of the right forelimb were osteotomized, while the horses were under general anesthesia, and subsequently repaired by lag screw fixation using a single 4.5-mm cortical screw. A GH sheet containing 100 μg of bFGF was then sutured to the synovial membrane adjacent to the osteotomized proximal sesamoid bone. In the control group, the fracture was fixed with a lag screw, and the articular capsule was sutured. Fracture healing was assessed by radiographic examination once a week for 16 weeks after the operation. Radiographic examination of bone healing revealed significantly lower demineralization of the fracture line in the GH sheet-treated group than in the control group. The rate of demineralization of the fracture line in the GH sheet-treated group was significantly lower than that in the control group at 2, 4, and 8 weeks after the operation. In this study, we demonstrated that the use of a GH sheet containing bFGF promotes healing of proximal sesamoid bone fracture in the horse. Therefore, it is believed that this treatment strategy would be useful for quick recovery from bone fracture in the horse.     

Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age < 2 years: 151 cases (1989--2002)

REASONS FOR PERFORMING STUDY: Studies on arthroscopic removal of apical proximal sesamoid fracture fragments in Thoroughbred (TB) horses age > or = 2 years have reported a high success rate. However, there are no reports documenting the racing prognosis of TB horses that undergo such surgery as weanlings or yearlings. OBJECTIVES: To describe the incidence of apical proximal sesamoid fractures in immature TB horses, age < 2 years and determine probability and quality of racing performance after arthroscopic removal of such fractures in 151 TB weanlings and yearlings. METHODS: The medical records of TB horses age < 2 years that underwent arthroscopic surgery for removal of apical proximal sesamoid fracture fragments were reviewed. Follow-up information was obtained from race records. Student's t tests were used to compare performance variables of operated racehorses to that of their maternal siblings. RESULTS: Ninety-two percent (139/151) of fractures occurred in the hindlimbs and 8% (11/151) in the forelimbs (fracture of both fore- and hindlimb, n = 1). Horses with forelimb fractures had a greatly reduced probability of racing (55%) compared to those with hindlimb fractures (86%). Overall, 84% of the horses raced post operatively and had performance records similar to that of their maternal siblings, 78% (787/1006) of which raced. CONCLUSIONS: Arthroscopic removal of apical proximal sesamoid fracture fragments in TB weanlings and yearlings carries an excellent prognosis for racing in horses with hindlimb fractures and a reduced prognosis in those with forelimb fractures. Medial fractures of the forelimb carry the worst prognosis. POTENTIAL RELEVANCE: The determination of prognosis increases knowledge on apical sesamoid bone fractures and potential for arthroscopic restoration of the ability to race; and enables the value of yearlings for subsequent sale to be established.     

Lag screw and cancellous bone graft fixation of transverse proximal sesamoid bone fractures in horses: 25 cases (1983-1989).

Case records of 25 horses with transverse fractures of the proximal sesamoid bone were reviewed to evaluate the success of treatment. All fractures were repaired by use of lag screw fixation and an autogenous cancellous bone graft because the fracture fragments were considered too large for surgical removal and reconstruction of the suspensory apparatus was necessary. Radiography was performed in all cases, and the fractures were classified into 3 types: (1) proximal midbody fractures, which included all fractures in the proximal aspect of the sesamoid bone that resulted in fragments involving greater than one third but less than one half of the total mass of the sesamoid bone; (2) midbody fractures that divided the bone into 2 equal portions; and (3) distal midbody fractures, which included transverse fractures in the distal aspect of the sesamoid bone that resulted in fragments involving greater than one third but less than one half of the total mass of the sesamoid bone. Of these cases, race records were obtained for 9 Standardbreds and 5 Thoroughbreds. Postoperative performance criteria evaluated were the ability to train and start 1 race, ability to maintain preinjury class of racing, earnings per start, and the number of starts following surgery. In Thoroughbreds, fractures occurred most commonly in the right forelimb; in Standardbreds, the left hind limb was most commonly involved. The midbody fracture was the most common type in both breeds, and the distribution of fracture location within the sesamoid bone was similar for both breeds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum parathyroid hormone and calcitonin levels in racehorses with fracture

Serum parathyroid hormone (PTH) and calcitonin (CT) levels in fractured racehorses were measured by radioimmunoassay. Racehorses with fracture of large bone such as the radius, third metacarpus, third carpus, digital bone or tibia, showed normal PTH level and elevated CT level in the serum. Serum PTH level was slightly higher in racehorses with sesamoid bone fracture compared to that of healthy racehorses, but not statistically significant. Moreover, serum CT level of racehorses with sesamoid bone fracture was significantly higher than that of healthy racehorses. Racehorses with sesamoid bone fracture and large bone fracture might be in different conditions of calcium regulation.     

Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age > or = 2 years: 84 cases (1989-2002)

REASONS FOR PERFORMING STUDY: Studies have shown that surgical removal of apical fracture fragments in Standardbred racehorses carries the best prognosis for return to racing performance, but there are no reports involving mature Thoroughbred (TB) racehorses. OBJECTIVES: To describe the incidence of apical proximal sesamoid fractures in TB racehorses and determine probability and quality of racing performance after arthroscopic removal of such fractures in TB racehorses age > or = 2 years. METHODS: Medical records and pre- and post operative race records of TB racehorses age > or = 2 years that underwent arthroscopic surgery for removal of apical proximal sesamoid fracture fragments were reviewed. RESULTS: Sixty-four percent of fractures occurred in the hindlimbs and 36% in the forelimbs. Horses with forelimb fractures had a reduced probability of return to racing (67%) compared to those with hindlimb fractures (83%), but the majority (77%) of treated horses recovered to return to race post operatively. Horses with medial forelimb fractures raced at only a 47% rate; those with suspensory desmitis at 63%. Unlike Standardbreds, there was no difference in probability of racing post operatively between horses that had, and had not, raced preoperatively. CONCLUSIONS: Data show that arthroscopic removal of apical proximal sesamoid fracture fragments is successful at restoring ability to race in skeletally mature TB horses without evidence of severe suspensory ligament damage. Prognosis for return to racing is excellent (83%) in horses with hindlimb fractures and good (67%) in those with forelimb fractures. Medial fractures of the forelimb have the worst prognosis. POTENTIAL RELEVANCE: The determination of prognosis for differing sites in TB racehorses should increase knowledge of apical proximal sesamoid bone fractures and improve communication from veterinarian to owner, and trainer, on the potential for arthroscopic restoration of the ability to race.     

Risk factors for fatal lateral condylar fracture of the third metacarpus/metatarsus in UK racing

REASONS FOR PERFORMING STUDY: Lateral condylar fractures of the third metacarpus/metatarsus are the most common cause of equine fatality on UK racecourses. Identification of risk factors for such injuries and the subsequent implementation of intervention strategies could significantly reduce the total number of racecourse fatalities. OBJECTIVES: To identify horse-, race- and course-level risk factors for fatal lateral condylar fracture in Thoroughbreds on UK racecourses. METHODS: Case-control study designs were used. Case horses were defined as those that were subjected to euthanasia having sustained an irreparable lateral condylar fracture while racing at any of the 59 UK racecourses. Case races were defined as those in which one or more horses sustained a fatal lateral condylar fracture. Three controls for each case horse were selected at random from the race in which the case was running. Three controls for each case race were selected at random from all races of the same type held in the same year. Ninety-eight cases were included in the study. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have started racing as 3- or 4-year-olds. Fractures were found to be more likely in longer races with a larger number of runners, races in which professional jockeys were not permitted to ride and races in which the going was described as firm or hard. CONCLUSIONS AND POTENTIAL RELEVANCE: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal lateral condylar fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 201 m (1 furlong) and 1609 m (8 furlongs) per week. The association with age at first race requires further investigation for flat and National Hunt racing separately. A reduction in the number of races taking place on very firm going could have an impact on the number of lateral condylar fractures.     

Long incomplete longitudinal fractures of the third metacarpal and metatarsal bone in horses

Five horses with long incomplete longitudinal fractures of the third metacarpal bone and three horses with similar fractures of the third metatarsal bone were examined. In three of the metacarpal fractures a long incomplete fissure extended proximomedially, in association with the more common lateral condylar fracture of the third metacarpal bone, and in the other two cases the fracture originated from the medial aspect of the distal articular surface. In the three horses with fractures of the third metatarsal bone the fractures had a consistent spiral configuration.     

Risk factors for humeral condylar fractures in the dog: A retrospective study

Humeral condylar fractures have fracture lines that extend through the joint surface and through one or both epicondyles. One hundred and eighty-nine dogs with humeral condylar fractures are presented in this study. Lateral condylar fractures were the most frequent (67 per cent), occurring nearly 10 times as often as the medial condylar fracture. Intercondylar fractures represented about 35 per cent of these. Condylar fractures occur as a result of moderate trauma and only rarely due to traffic accidents. The histories and circumstances of the three fracture types are not essentially different. Dogs, three and four months old, were strongly over-represented among the lateral and medial condylar fractures, compared with the age distribution of other types of fractures in the extremities of the dogs. Humeral condylar fractures were recorded in 58 breeds. All dogs are vulnerable to humeral condylar fractures. All sizes and both sexes are equally at risk. Some breeds seem to be more vulnerable to lateral condylar fractures: English and French bulldogs, Yorkshire terriers, miniature schnauzers, Gordon setters and German short-haired pointers. The St Bernard seems to be more vulnerable to medial and intercondylar fractures and the German shepherd dog and beagle to intercondylar fractures. A retrospective case control study does not provide wholly reliable statistical information on risk factors, and the statistics concerning breed and breed size must be judged accordingly. The method was considered to be the best statistical model available for this study.     

Compressive Forces Achieved in Simulated Equine Third Metacarpal Bone Lateral Condylar Fractures of Varying Fragment Thickness with Acutrak Plus Screw and 4.5 mm AO Cortical Screws

Objectives— To compare compression pressure (CP) of 6.5 mm Acutrak Plus (AP) and 4.5 mm AO cortical screws (AO) when inserted in simulated lateral condylar fractures of equine 3rd metacarpal (MC3) bones. Study Design— Paired in vitro biomechanical testing. Sample Population— Cadaveric equine MC3 bones (n=12 pair). Methods— Complete lateral condylar osteotomies were created parallel to the midsagittal ridge at 20, 12, and 8 mm axial to the epicondylar fossa on different specimens grouped accordingly. Interfragmentary compression was measured using a pressure sensor placed in the fracture plane before screw placement for fracture fixation. CP was acquired and mean values of CP for each fixation method were compared between the 6.5 mm (AP) and 4.5 mm (AO) for each group using a paired t‐test within each fracture fragment thickness group with statistical significance set at P<.05. Results— AO screw configurations generated significantly greater compressive pressure compared with AP configurations. The ratio of mean CP for AP screws to AO screws at 20, 12, and 8 mm, were 21.6%, 26.2%, and 34.2%, respectively. Conclusion— Mean CP for AP screw fixations are weaker than those for AO screw fixations, most notably with the 20 mm fragments. The 12 and 8 mm groups have comparatively better compression characteristics than the 20 mm group; however, they are still significantly weaker than AO fixations. Clinical Relevance— Given that the primary goals of surgical repair are to achieve rigid fixation, primary bone healing, and good articular alignment, based on these results, it is recommended that caution should be used when choosing the AP screw for repair of lateral condylar fractures, especially complete fractures. Because interfragmentary compression plays a factor in the overall stability of a repair, it is recommended for use only in patients with thin lateral condyle fracture fragments, as the compression tends to decrease with an increase in thickness.