Incomplete Longitudinal Fracture of the Proximal Palmar Cortex of the Third Metacarpal Bone in Horses

Seven horses, 2 to 4 years of age, were examined because of moderate-to-severe forelimb lameness, mild effusion of the middle carpal joint (3 horses), and pain on palpation of the origin of the suspensory ligament (4 horses). The lameness was abolished by anesthetic infiltration of the middle carpal joint in six horses. In four of them, a high palmar nerve block also abolished the lameness. A linear radiolucency in the proximal end of the third metacarpal bone (McIII) was interpreted as an incomplete longitudinal fracture. In one horse, distinct intramedullary sclerosis limited to the palmar cortex was indicative of an incomplete fracture confined to the palmar cortex. No osteoproliferative lesions were identified on the dorsal cortex of any of the horses. Surgical treatment with cortical screws in lag fashion accompanied by a rest period was successful in one horse. In four horses, rest for at least 3 months resulted in clinical soundness. In two horses, a shorter rest period resulted in recurrence of the lameness even though the horses were sound when put back into training. Careful clinical and radiographic examinations helped differentiate incomplete longitudinal fractures from lesions involving the carpus and proximal aspect of the suspensory ligament.     

Osteostixis for Incomplete Cortical Fracture of the Third Metacarpal Bone: Results in 11 Horses

Eleven horses with acute or chronic incomplete cortical fractures of the left or right third metacarpal bone (McIII) were treated with surgical puncture (osteostixis). The fractures were diagnosed by physical examination and radiography. Four to eight holes, 2.7 or 3.5 mm in diameter, were drilled in the fractured bone. Radiographically, the fractures were healed by month 3, and the drill holes were inapparent by month 7. Nine horses (82%) returned to race competition, and two horses were retired, one the result of a surgical complication. The mean time between surgery and the first race was 9.4 months. None of the bones refractured within 24 months of surgery. Osteostixis was not technically difficult and a second operation for implant removal was not necessary.     

The Histological Appearance of the Proximal Aspect of the Dorsal Condylar Sagittal Ridge of the Third Metacarpal and Metatarsal Bone in Young Warmblood Horses: Normal Appearance and Correlation with Detected Radiographic Variations

The objective of this study is to describe the normal histological appearance of the dorsoproximal aspect of the sagittal ridge of the third metacarpal/metatarsal bone in young Warmblood horses, and to compare it to the different radiographic variations (irregular, indentation, lucency, notch) described at this level. A total of 25 metacarpo/metatarsophalangeal joints of 12 Warmblood horses were used. Five samples of each radiographically described group were selected for histological processing. Each category was compared with the normal control group. Each group showed a bone cortex, covered by hyaline cartilage and longitudinally aligned collagen fibres covered by loosely organized connective tissue proximally. The normal and irregular group showed a smooth bone cortex. In the indentation and lucency group, a depression in the cortex was detected. The notch group presented an expansion of the cortex. The collagen fibres and connective tissue were located in the depression in the indentation group whereas the location varied in the lucency and notch group. The radiologic detected differences are translated into detectable histological differences. Further research is warranted to determine whether these variations are developmental or congenital and to evaluate their potential influence on the joint function during hyperextension.     

A Lateral Approach for Screw Repair in Lag Fashion of Spiral Third Metacarpal and Metatarsal Medial Condylar Fractures in Horses

Objective— To describe a lateral approach for screw fixation in lag fashion of simple spiral medial condylar fractures of the third metacarpus/metatarsus (MC3/MT3).
Study Design— Case series.
Animals— Thoroughbred racehorses (n=9).
Methods— Nondisplaced medial MC3/MT3 condylar fractures (3 thoracic, 6 pelvic limbs), with mean length 126 mm (range, 91–151 mm) were repaired by internal fixation, under general anesthesia, using multiple 4.5 mm cortical screws inserted in lag fashion from the lateral aspect of the limb, using radiographic or fluoroscopic guidance. Horses were recovered from anesthesia in half-limb casts; 7 unassisted and 2 using a rope-recovery system. Horses had 2 months box rest, 1 month in-hand walking, and follow-up radiographic examination at 3 months.
Results— Horses recovered uneventfully from anesthesia. Five horses raced; 1 returned to training, was persistently lame, and was retired to stud; 2 were retired directly to stud; and 1 horse was lost to follow-up.
Conclusions— MC3/MT3 medial condylar fractures were successfully repaired by screws inserted n lag fashion form the lateral aspect.
Clinical Relevance— Use of a lateral approach to medial condylar MC3/MT3 fractures allows screw insertion perpendicular to the fracture plane without interference with palmar/plantar soft tissue structures or from the splint bones. Although repair was performed under general anesthesia, the technique should be adaptable to application in standing horses.     

Scintigraphic Appearance of the Dorsal Cortex of the Third Metacarpus and Third Metatarsus in the Horse

The lack of "standard uptake pattern" to refer to when interpreting scintigraphic images poses a problem to anyone working with skeletal scintigraphy. An article written by Koblik et al. stated that in the normal scintigraphic image of older horses, the dorsal cortex of the metacarpus and metatarsus is not identifiable, whereas it can be identified in younger horses. In this retrospective study we evaluated the association between the age of a horse and visibility of the dorsal cortex of the metacarpus and metatarsus. We found that dorsal cortical uptake can be seen in the normal adult horse. The population in the study consisted of 139 horses scanned under general anesthesia in lateral recumbency. Scintigraphic images of 202 limbs were examined visually and by using a profile image tool. In almost all limbs the dorsal cortex was identifiable (82%); only 7% of the dorsal cortices were not identifiable; and 11% of the scintigraphic images were not interpretable.     

Surgical Repair of Metacarpal Condylar Fractures with Palmar Osteochondral Comminution in Two Thoroughbred Horses

Complete displaced lateral condylar fractures of the metacarpus with triangular osteochondral fragments at the palmar articular surface occurred in two Thoroughbred horses. The condylar fractures were repaired with cortical bone screws following removal of the osetochondral fragments via a dorsal arthrotomy and distraction of the condyles. One horse raced successfully after surgery, and the other is being used successfully as an English pleasure mount.     

Radiographic Calibration for Analysis of Bone Mineral Density of the Equine Third Metacarpal Bone

Digital radiography represents the primary diagnostic tool the veterinarian uses to diagnose skeletal injuries in the horse. Advances in digital radiography have provided the veterinarian with opportunities to make simple radiographic assessments from calibrated digital radiographs such as dimensional analyses; however, more complex variables such as radiographic opacity have yet to be standardized. Therefore, we investigated the quantification of bone mineral density (BMD) via computed radiographic absorptiometry at various radiographic exposure intensities (kV), times (sec), and milliamps (mA) in the third metacarpal in the horse. By developing a brightness/darkness index (BDI), the grayscale of radiographs, calibrated with an aluminum (Al) marker of various known thicknesses and uniform densities, can be compared to the average BMD of a region of interest at various radiographic exposures. Al BDI was a significant predictor of bone BDI (r² = 0.960, P < .001) and BMD (r² = 0.971, P < .001). This method of calibration can be used for quantitative noninvasive bone mineral analysis and allows direct comparison of radiographs taken under different exposure settings.     

A Lateral Approach to the Repair of Propagating Fractures of the Medial Condyle of the Third Metacarpal and Metatarsal Bone in 18 Racehorses

Objectives— To report the technique, observations on fracture configurations and results of treatment by fixation lag screw following the fracture plane determined by an approach to the third metacarpal/metatarsal bone (MC3/MT3) that begins laterally over the metacarpo(metatarso)phalangeal joint and extends dorsally over the diaphysis of the bone.
Study Design— Case series.
Animals— Thoroughbred horses (n=18) with propagating fractures of the medial condyle of MC3/MT3.
Methods— Retrospective analysis of case records of horses with fractures of the medial condyle of MC3/MT3 that propagated sagittaly or in a spiral configuration into the diaphysis, repaired surgically under general anesthesia by screw fixation in lag fashion through a lateral approach with periosteal reflection.
Results— Fractures were readily identified at surgery, enabling screw fixation in lag fashion following the fracture plane. Fracture configurations varied and could be classified as sagittal and spiral fractures with fractures within each group generally following a similar course. All horses recovered relatively uneventfully from general anesthesia and surgery, and all fractures healed well. Thirteen horses returned to training; 5 subsequently raced.
Conclusions— Repair of propagating sagittal and spiral fractures of the medial condyle of MC3/MT3 with diaphyseal involvement, through a lateral approach with periosteal reflection permits stable fixation with minimal complications. In this series there were no catastrophic failures.
Clinical relevance— Fractures of the medial condyle of MC3/MT3 that propagate either sagittaly or in a spiral configuration into the diaphysis can be successfully repaired with screw fixation in lag fashion using a lateral approach with periosteal reflection.     

Lag Screw Fixation of a Sagittal Fracture of the Third Carpal Bone in a Horse

A sagittal fracture of the third carpal bone of a Standardbred racehorse was repaired with lag screw fixation. Healing of the fracture was uncomplicated, and the horse made a successful return to racing. It was concluded that selected sagittal fractures of the third carpal bone may be treated successfully with lag screw fixation. Criteria for selection of cases include fragment size and orientation of the fracture plane.     

The Effect of Hole Diameter on the Torsional Mechanical Properties of the Equine Third Metacarpal Bone

The torsional monotonic structural material properties of equine metacarpi with or without, either a 5/16 inch or 3/8 inch diameter bicortical lateromedial middiaphyseal hole were assessed to determine the effect of a hole on metacarpal strength. Torsional stiffness was not significantly effected by the presence of a bicortical hole, whereas yield and failure angles, torques and energies of metacarpi with a hole were 51% to 97% of those of intact bones. Significant differences were not apparent for yield and failure mechanical properties between metacarpi with a 5/16 inch diameter hole and metacarpi with a 3/8 inch diameter hole; however, postyield mechanical properties were lower for metacarpi with a 3/8 inch hole. Whereas some metacarpi with a 5/16 inch hole were capable of plastic deformation before failure, metacarpi with a 3/8 inch diameter hole appeared to have sufficient stress concentration to propagate complete fracture on structural yield.     

Use of Bone Plate for Treatment of an Open Third Metacarpal Fracture in a Foal

A 7-month-old, 180-kg, female foal was presented with open diaphyseal fracture of the left third metacarpal bone. The fractured limb was stabilized preoperatively with external coaptation. Open reduction and internal fixation were done using 4.5-mm broad dynamic compression plate, which was applied in a neutralization manner. Postoperatively, external support with padded bandage reinforced with gutter splint made of fiber glass was provided. The incisional infection and the contaminated wound on medial aspect of the metacarpal were managed with regular dressing. Complete radiographic union and functional recovery were noticed by 4 months postoperatively. Open diaphyseal fractures can be managed by proper preoperative fracture stabilization, wound management, and fixation methods using bone plate and external coaptation.     

Surgical Repair of Mid‐body Proximal Sesamoid Bone Fractures in 25 Horses

Objective— To describe the characteristics of unilateral mid‐body proximal sesamoid bone (PSB) fractures, to determine factors associated with the outcome of horses after surgical repair, and to describe a technique for arthroscopically assisted screw fixation in lag fashion. Study Design— Retrospective case series. Animals— Horses (n=25) with unilateral mid‐body PSB fracture. Methods— Medical records (1996–2006), radiographs, and arthroscopic videos of horses with surgically repaired unilateral mid‐body PSB fractures were reviewed. Retrieved data included signalment, affected limb and PSB, fracture characteristics, and surgical technique. Outcome was established by radiographic assessment of healing and race records; categorical data were analyzed using Fisher's Exact test. Results— Medial forelimb PSBs were most commonly affected (80%). Surgical technique and degree of reduction were significantly associated with outcome; 44% of horses with screw repair and none of the horses with wire fixation raced (P=.047). Factors that may have influenced this outcome were differences in fracture reduction (improved reduction in 22% wire repairs and 88% screw repairs, P=.002) and use of external coaptation (22% wire repair and 88% lag screw repair, P=.002). None of the horses with unimproved reduction raced after surgery. Conclusions— Only 28% of horses with mid‐body PSB fractures raced after surgery. Compared with wire fixation, screw fixation in lag fashion resulted in good reduction and is seemingly a superior repair technique. Clinical Relevance— For mid‐body PSB fractures, arthroscopically assisted screw fixation in lag fashion and external coaptation for anesthesia recovery and initial support provides the best likelihood of return to athletic use.     

Circumferential Wiring of Mid-body and Large Basilar Fractures of the Proximal Sesamoid Bone in 15 Horses

Circumferential wiring was used to repair 12 mid-body fractures and four large basilar fractures of proximal sesamoid bones in 15 horses. Eighteen-gauge stainless steel wire was placed around both fragments in five horses, and through the proximal fragment and around the distal fragment in 10 horses. The horses were returned to work when they were clinically sound and fracture healing was evident radiographically. Eleven horses resumed athletic performance, three horses were used as breeding animals, and one horse was retired. Five horses performed at an athletic level equal to or better than their previous levels, and six horses performed at a lower level.     

Large Experimental Fistula of the Right Dorsal Colon in Horses

Studies in horses with experimental gastrointestinal fistulas may lead to rapid advancements in equine nutrition, as well as prevention and treatment of diseases such as colic and laminitis. The aim of this study was to devise a technique and a cannula to create a large fistula in the right dorsal colon (RDC). A total of 13 horses with normal gastrointestinal tract were used. After the administration of sedatives and local anesthetics, a segment of the right 16th rib was removed, a circular defect was created in the muscular wall, and the RDC was sutured to the muscular wall. The subcutaneous tissue and skin were closed over the attached RDC in eight horses (closed technique), or removed to expose the serosa of the colon sutured to the abdominal wall in five horses (open technique). A full thickness circular incision was made 2 to 6 weeks later to create a fistula. A cannula (diameter, 5 cm) made of natural rubber or silicon was inserted in the fistula. The open surgical technique was easier to perform and resulted in fewer complications. The cannula made of silicon resulted in less pruritus. One horse had a large colon torsion around the colopexy before fistula creation. One of the 12 fistulated horses had a large colon displacement 43 days after cannula insertion. These observations suggest that pexis of the RDC may predispose the horse to large colon displacement or volvulus. The open technique for the colopexy and the cannula made of silicon can be used for creation of a RDC fistula.     

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.     

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.     

Holding Power of Orthopedic Screws in Equine Third Metacarpal and Metatarsal Bones: Part I. Foal Bone

The holding power of orthopedic screws in the third metacarpal and metatarsal cadaver bones of foals that were aged from 1 to 14 days was tested. Comparative trials between screws inserted at the same site in contralateral bones from the same foal were performed to compare the holding power of 5.5 mm cortical and 6.5 mm cancellous screws in the metaphysis, and the holding power of 5.5 and 4.5 mm cortical screws in the diaphysis. A MTS servohydraulic tensile testing machine was used to perform screw pullouts at a displacement rate of 19 mm/sec. There was no significant difference between maximum holding power of 5.5 mm cortical screws and 6.5 mm cancellous screws in the metaphysis when expressed as kg per mm of bone width at the screw insertion site (p = 0.097) or as kg per mm of screw thread engaged in the bone (p = 0.17). There was no significant difference in holding power of 5.5 and 6.5 mm screws in the proximal versus distal metaphysis (p = 0.10). The 5.5 mm screws had significantly greater holding power than the 4.5 mm screws in the diaphysis (p = 0.0097). Fixation failure at screw pullout was always due to bone shear. In internal fixation in foal bone, the 5.5 mm screws may be a suitable alternative to 6.5 mm screws in the metaphysis. Use of 5.5 mm rather than 4.5 mm screws is recommended in the diaphysis because of greater holding power.     

Use of Intraoperative Ultrasonography in Six Horses

Intraoperative ultrasonography was used in six horses to aid localization and removal of bone fragments (3 horses) and foreign bodies (3 horses). The ultrasound transducer was enclosed in a sterile sleeve containing sterile aqueous gel and the examination was performed after aseptic preparation of the surgical site. Using ultrasound guidance a needle was placed in contact with the bone fragment or foreign body and an incision was made along the path of the needle to expose and remove the object. This technique resulted in decreased operative time and minimal tissue dissection.