Biomechanical comparison of canine median sternotomy closure using suture tape and orthopedic wire cerclage

OBJECTIVE

To compare the mechanical properties of suture tape and orthopedic wire cerclage in an ex vivo canine median sternotomy model.

STUDY DESIGN

Ex vivo.

ANIMALS

Twelve large-breed canine cadaveric sternums.

METHODS

Median sternotomies were performed, leaving the manubrium intact. The specimens were randomly assigned to group W (20-gauge stainless steel orthopedic wire cerclage in a figure-of-eight pattern) or group ST (suture tape in a figure-of-eight pattern). Each specimen was laterally distracted until failure using an electrodynamic materials-testing system.

RESULTS

No differences were observed for displacement, yield load, maximum load, implant failure between the groups. The orthopedic wire construct was stiffer than the suture tape construct.

CONCLUSION

Suture tape was biomechanically similar to orthopedic wire cerclage for sternotomy closure in dogs, although wire constructs were stiffer.

CLINICAL SIGNIFICANCE

Suture tape may represent an alternative to cerclage wire for sternotomy closure in dogs. Additional studies evaluating its clinical use are needed.

Evaluation of a 3-D printed drill guide to facilitate fluoroscopic-assisted Kirschner wire placement for minimally invasive iliosacral screw placement in dog cadavers

OBJECTIVE

To evaluate the ease and accuracy of using a 3-D printed (3-DP) drill guide to insert Kirschner wires through the ilium and into the sacral body in preparation for minimally invasive iliosacral screw placement in dog cadavers.

ANIMALS

10 dog cadavers weighing 20 to 30 kg (mean ± SD, 24.5 ± 5 kg).

METHODS

Kirschner wires were placed using a limited approach to the lateral ilium. Fluoroscopy was used in freehand and 3-DP drill guide application groups to facilitate the placement of a 1.0-mm Kirschner wire that was over-drilled using a 2.5-mm cannulated drill bit. Kirschner wires were placed using a 3-DP drill guide on 1 hemipelvis and freehand wire placement was done on the contralateral hemipelvis. Postprocedural CTs were obtained, and 2-D and 3-D analyses were performed. The Student t-test and Wilcoxon rank sum test were used to compare groups. A Pearson correlation coefficient was performed to evaluate the in-group correlation.

RESULTS

Likert scores that assessed the ease of the procedure were significantly greater (P = .04) and the incision length was significantly shorter (P = .016) in the 3-DP drill guide group compared with the freehand group. The time of the procedure, the number of attempts to obtain accurate Kirschner wire placement, and fluoroscopy images did not differ (P > .05) between application groups. Drill tracks were primarily confined to the sacral body, with minor projected screw thread cortical breeches occurred in 1 cadaver in the freehand group and 2 cadavers in the 3-DP drill guide group.

CLINICAL RELEVANCE

The 3-DP drill guide simplified appropriate iliosacral Kirschner wire placement through a smaller incision compared with freehand drilling and would appear to be an efficient, practical instrument to facilitate accurate fluoroscopic-assisted screw placement when stabilizing sacroiliac luxations in dogs.

Biomechanical evaluation of three fixation methods in a feline transverse patella fracture model

OBJECTIVES

This study aimed to compare the biomechanical properties of three stabilisation techniques in feline patella transverse fractures and select the strongest method with potentially minimal complications.

METHODS

Patella fracture was simulated in 27 feline cadaveric pelvic limbs (mean weight of the cadavers 3.78 kg), and the limbs were randomly grouped to be stabilised with one of the three stabilisation methods. The modified tension band wiring technique with a single Kirschner wire (0.9 mm) and figure-of-eight wiring (20 G) was applied to group 1 (n = 9). Group 2 (n = 9) was stabilised with a combination of circumferential and figure-of-eight wiring techniques with orthopaedic wire (20 G). Group 3 (n = 9) was stabilised with the same technique as group 2, but with #2 FiberWire. The knee joints were positioned and fixed in the neutral standing angle (135°) and tested by applying tensile force. The loads at gap formations of 1, 2 and 3 mm were recorded, and the maximum failure load was measured in each group.

RESULTS

In all the loads at displacement (1, 2 and 3 mm), group 3 was significantly stronger than groups 1 and 2, respectively (P <0.017). Group 3 (261.0 ± 52.8 N) showed significantly stronger fixation in the maximum load compared with group 1 (172.9 ± 45.6 N) (P <0.017). No significant difference was observed between groups 1 and 2 (204.9 ± 68.4 N) or between groups 2 and 3.

CONCLUSIONS AND RELEVANCE

This study shows that the combination of circumferential and figure-of-eight techniques with FiberWire is more resistant to displacement than metal wire in this ex vivo feline patella fracture model.

Traumatic physeal fractures in cats: a review of 36 cases (2010-2020)

OBJECTIVES

The aim of this study was to describe the demography, aetiology, location and classification of physeal fractures in cats, and to describe their management and outcomes.

METHODS

Clinical records and radiographs of cats referred for management of physeal fractures were retrospectively reviewed. Fractures of the proximal femoral physis were excluded. Descriptive statistics were used to describe signalment, cause of injury, presence of concurrent injuries, fracture description, treatment modality, complications, follow-up, physeal closure, implant removal and outcome.

RESULTS

Thirty-four cats with 36 fractures were included, of which 17 affected the distal femur, 11 the distal tibia and fibula, five the distal radius and ulna, two the proximal tibia and one the distal humerus. Salter-Harris classification was type I in 14, type II in 16, type III in two and type IV in four fractures. Thirty-four fractures were treated with primary fixation, and the most common method was crossed Kirschner wires (24/34 fractures). Complications were observed in 14 fractures, of which 12 were minor. At radiographic follow-up, physeal closure was reported in 23 fractures, of which 15 were considered premature. Implant removal was performed in three fractures. Outcome was good in 28, fair in four and poor in two fractures.

CONCLUSIONS AND RELEVANCE

Fracture of the distal femoral physis was the most common physeal fracture seen. Cats presenting with physeal fractures may be skeletally immature or mature with delayed physeal closure. The rate of physeal closure after fracture repair was relatively high but without apparent impact. The frequency of implant removal was very low, indicating that despite having a physeal fracture repair, most cats did not require a second procedure to remove implants. Overall, internal fixation provided a good outcome in most fractures.

Rostral mandibular fracture repair in a pet bearded dragon (Pogona vitticeps)

CASE DESCRIPTION A 2-year-old male bearded dragon (Pogona vitticeps) was evaluated because of a traumatic mandibular fracture. CLINICAL FINDINGS An open comminuted fracture of the rostral aspect of the right mandible was evident, with a fragment of bone exposed and dorsally displaced. Whole-body radiography revealed no evidence of additional injury. Other findings were unremarkable, except for moderate anemia (PCV, 19%). TREATMENT AND OUTCOME The fracture fragments were stabilized with 2 crossed 36-gauge interfragmentary wire loops. An external fixator device was fashioned from four 25-gauge needles inserted at alternating angles through the fracture fragments; plastic IV fluid line tubing filled with dental acrylic was used as a connecting bar. One day after surgery, the lizard had regained its typical activity level and appetite. Body weight was measured and the external fixator was inspected 1 week after surgery and monthly thereafter. Three months after initial injury, the fracture was stable, radiography revealed bony callus formation at the fracture site, and the external fixator was removed. Recheck radiography performed 5.5 months after initial injury revealed complete osseous union of the fracture fragments, and the interfragmentary wires were removed. CLINICAL RELEVANCE Surgical management of the traumatic comminuted mandibular fracture in this bearded dragon by means of a combination of internal and external fixation resulted in complete healing of the mandible and restoration of function. Management of this complicated fracture was achieved with the aid of readily available and inexpensive supplies in a clinical setting, which may be useful to other clinicians in the management of similar cases.

Complete longitudinal patellar fracture in a cat: A rare case

Longitudinal patellar fractures in cats are extremely rare with only 1 other report of a comminuted longitudinal fracture for which pins and wires were placed in the patella for stabilization. This report describes the surgery and outcome of a strictly longitudinal patellar fracture in a cat.

Proximal tibial epiphysiodesis to reduce tibial plateau slope in young dogs with cranial cruciate ligament deficient stifle

The purpose of this study was to evaluate the ability of proximal tibial epiphysiodesis to reduce the tibial plateau slope in young dogs with cranial cruciate ligament (CCL) deficient stifles. Of the 14 treated dogs, eight had a bilateral injury, for a total of 22 joints. After physical and radiographical examination and measurement of tibial plateau slope, all of the dogs underwent surgery. Insertion of the screw was placed in the most proximal part of the tibial plateau, in its medio-lateral centre, aiming to the tibial shaft and using a K wire predriven as a guide; correct position of the screw was confirmed with intraoperative fluoroscopy or radiography. In all of the dogs the tibial slope was decreased at the time of physis fusion and the degree of change depended on the age and the breed of the dog at the time of surgery. The minimum change was 4 degrees and the maximum was 24 degrees. There was a statistically significant difference between tibial slope measured before surgery compared to tibial slope measured at the last follow-up visit after surgery. This study shows that the partial proximal tibial fusion in dogs with ACL injuries was effective in reducing the tibial slope during the residual growing time to such an extent to stabilize the joint, provided that the surgery had been carried out when there was still residual growing potential. The technique appeared to be mini-invasive and malalignment complications could be avoided by correct and precise insertion of the screw.

Surgical correction of metacarpophalangeal valgus deformity in an alpaca

A 1-month-old alpaca cria presented with a 13 degree valgus deformity of the left metacarpophalangeal joint. The angular limb deformity was centered on the distal metacarpal physes. Transphyseal bridging of the physes was recommended. Two 2.7 mm cortical bone screws were placed either side of the distal metacarpal physes and a figure of eight wire was placed medially around the screw heads. The screws extended through the medial metacarpus into the axial cortex of the lateral metacarpus. Seven weeks after surgery the limb was straight and the screws and wire were removed. Transphyseal bridging of the distal metacarpal physes can be effectively used for the treatment of metacarpophalangeal valgus in crias with open physes.

Mandibular fracture repair in a harbor seal

A 30-year-old captive female harbor seal (Phoca vitulina) bit down upon a metal ring within a hoop-net normally used to assist in securing the seal for routine physical examination. Radiographic examination performed under general anesthesia revealed a unilateral closed fracture of the rostral left mandible between the first and second premolar teeth. The rostral fragment was displaced ventrally and slight laxity of the mandibular symphysis was noted. The fracture was repaired surgically using an oral dental acrylic splint incorporating circumferential mandibular cerclage wire. The mandibular symphysis was stabilized using interdental wire between the right and left canine teeth. The fixation device was removed following evaluation of radiographs that showed signs of bony union 12-months postoperatively.

Intramedullary pinning of metacarpal and metatarsal fractures in cats using a simple distraction technique

OBJECTIVE

To describe a simple technique of intramedullary (IM) pinning for open reduction and internal fixation of metacarpal and metatarsal fractures in cats and evaluate outcome.

STUDY DESIGN

Retrospective study.

ANIMALS

Cats (n=17).

METHODS

Medical records of cats with metacarpal and metatarsal fractures treated by a specific IM pinning method with Kirschner wires were reviewed. Types of fractures and number of pins used were recorded. Pre- and postoperative radiographs were evaluated. Outcome was assessed based on clinical examination, evaluation of radiographs, and owner questionnaire.

RESULTS

Seventeen questionnaires were evaluated. Thirteen cats had a final recheck and radiographic assessment. Eight cats were lost to follow-up. Sixteen owners (94%) reported no obvious change in their cat's gait after treatment. One owner reported excellent function in her cat despite a slightly abnormal gait because of bent implants.

CONCLUSIONS

IM pinning after distraction of bone fragments is a reliable technique for treatment of metacarpal and metatarsal fractures in cats. Complications associated with fracture healing may or may not be associated with lameness.

CLINICAL RELEVANCE

IM pinning used in conjunction with appropriate bandaging for 4 weeks yields excellent functional outcome for treatment of metacarpal and metatarsal fractures in cats. Metacarpo- and metatarsophalangeal joint damage is prevented using this technique.

Biomechanical comparison of dual interlocking single loop and double loop tension band techniques to the classic AO tension band technique for repair of olecranon osteotomies in dogs

OBJECTIVE

To compare olecranon fragment stability between the classic tension band wire (TBW) technique with the wire placed either in contact with (Arbeitsgemeinschaft für Osteosynthesefragen [AO]), or not in contact with, a Kirschner (K)-wire (AOW) to 2 novel wire patterns: a dual interlocking single loop (DISL) and a double loop (DL).

STUDY DESIGN

Ex vivo mechanical evaluation on cadaveric bones.

SAMPLE POPULATION

Canine ulnae (n=40) with olecranon osteotomies repaired with 2 K-wires and 1 of 4 TBW constructs.

METHODS

Single load to failure applied through the triceps tendon. Displacement was measured from images captured from digital video. Techniques were compared based on the load resisted when the olecranon fragment was displaced 0.5, 1, and 2 mm.

RESULTS

At 0.5 mm of displacement, the DISL construct resisted more load than the AOW construct (505 versus 350 N; P=.05). AO and DL constructs resisted an intermediate load (345 and 330 N, respectively). There was no significant difference between groups at 1 mm of displacement. At 2 mm of displacement, DL (785 N) resisted more load than AO (522 N, P=.01) and AOW (492 N, P=.03) groups.

CONCLUSIONS

DISL constructs provided similar stability to classic TBW constructs whereas DL constructs were more stable at higher loads.

CLINICAL RELEVANCE

The DL construct is easy to perform, less bulky, and provides comparable fragment stability to standard TBW techniques at functional loads. Surgical method is important for optimal performance of all TBW constructs.

Internal fixation of a femur fracture in an American bullfrog

CASE DESCRIPTION

An adult male American bullfrog (Rana catesbeiana) was evaluated by the North Carolina State University College of Veterinary Medicine's Turtle Rescue Team following vehicular trauma.

CLINICAL FINDINGS

A fracture of the left femur was suspected on examination and palpation of the hind limbs, but no other injuries or abnormalities were detected. While the bullfrog was sedated, whole-body radiographic views were obtained, which revealed a closed midshaft comminuted fracture of the left femur.

TREATMENT AND OUTCOME

The fracture was repaired by use of an internal fixation technique that included Kirschner wires, a positive-profile pin secured along the femur with encircling sutures, and polymethylmethacrylate molded around the entire apparatus. There were no major complications during the postoperative rehabilitation period. One year after surgery, radiography revealed complete fracture healing and the bullfrog was released back into the wild.

CLINICAL RELEVANCE

Presently, there are no widely accepted methods for fracture fixation in amphibians. Factors associated with their aquatic environment and lengthy fracture healing time must be addressed when planning fracture fixation strategies. In the bullfrog of this report, the applied internal fixation method provided effective long-term stabilization of the femur, allowed for normal movement, and enabled the bullfrog to be housed in an aquatic environment immediately after surgery.

Cranial cruciate ligament rupture in large and giant dogs. A retrospective evaluation of a modified lateral extracapsular stabilization

Forty-two dogs weighing between 30 and 87 kg (mean body weight of 49 kg) with cranial cruciate ligament ruptures (CCLR) were treated with a modified lateral extra-capsular stabilization using braided polyester prosthetic ligament-suture anchor technique. Clinical and radiographic outcomes of 48 stifles were retrospectively evaluated with a mean follow-up of 18 months. Ten dogs had pulled out their bone anchors with no clinical relevance. Draining tracts did not appear. Despite mild radiographic progression of osteoarthritis, all of the dogs regained acceptable function of the operated limb.

Tension band stabilisation of acetabular physeal fractures in four kittens

The surgical repair of acetabular physeal fractures in four kittens using a screw and tension band technique is reported. This was an appropriate method for restoring articular congruency and improving pelvic alignment. All cases had an excellent outcome and full limb use following fracture repair. In kittens younger than 12 weeks, there is a possibility of premature fusion of the acetabular bone resulting in development of a deformed, shallow acetabulum and hip subluxation. However, surgery is still justified when there is pelvic canal narrowing to decrease the risk of future defecatory problems. Early implant removal in such young kittens may decrease the severity of deformity caused by premature physeal closure. In kittens of 16 weeks or older, the prognosis is good for normal acetabular development and implant removal is not necessary.

Mechanical evaluation of pin and tension-band wire factors in an olecranon osteotomy model

OBJECTIVE

To evaluate the effect of altering pin and wire diameter, wire position and configuration, and osteotomy angle on applied load and absorbed strain energy in a pin and tension-band wire (PTBW) fixation model.

STUDY DESIGN

In vitro mechanical study.

SAMPLE POPULATION

Delrin models (n=96).

METHODS

PTBW was applied to Delrin olecranon osteotomy models. A control configuration was defined and then altered, 1 variable (wire diameter, pin diameter, wire-hole position, wire configuration, osteotomy angle) at a time, to create 11 test configurations. Tensile force was applied and displacement at the caudal aspect of the osteotomy was measured. Fixation strength, in terms of tensile load and strain energy, was compared between control and each test configuration at 4 osteotomy displacements.

RESULTS

Models with larger wire, pins, or combined figure-of-eight/lateral wires were stronger than control, whereas those with smaller wire, pins, or a solitary lateral wire were weaker. The superior strength of the larger wire was apparent for all assessed osteotomy displacement.

CONCLUSIONS

PTBW fixation strength increases as implant diameter is increased, with wire diameter having greatest effect. Lateral wire configuration is weaker than figure-of-eight, but can be added to figure-of-eight configuration to increase strength. Wire-hole position and osteotomy angle have little effect on PTBW strength.

CLINICAL RELEVANCE

Wire diameter is the key determinant of PTBW strength, whereas pin diameter is somewhat less critical. Wire passage through an additional hole proximally provides equivalent strength and may avoid soft-tissue entrapment and subsequent loosening.

Median Sternotomy Closure in Dogs: A Mechanical Comparison of Technique Stability

OBJECTIVE

To evaluate the mechanical properties of canine median sternotomy closure using double-loop cerclage compared with other commonly used cerclage sternotomy closure patterns.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Forty canine cadaveric sternal segments.

METHODS

Median sternotomy-wire constructs were loaded to failure in a materials testing machine. Each construct was radiographed before and after testing. Specific wire configurations tested were: 2 single twist cerclage centered on the sternebrae, single twist figure of 8 pattern centered on the sternal synchondrosis, double twist figure of 8 pattern centered on the sternal synchondrosis, 2 double-loop cerclage centered on the sternebrae, and 1 double-loop cerclage centered on the sternal synchondrosis. Wire configurations were compared by craniocaudal translation of sternabrae on pre-test radiographs, and displacement during loading, and mode of failure, based on analysis of test video, and post-test radiographs.

RESULTS

Double-loop cerclage did not provide superior mechanical stabilization of median sternotomy. Both figure of 8 patterns had the least displacement at higher loads. Two single twists that were centered on sternebrae were least able to prevent displacement at higher loads, caused the most craniocaudal translation before testing, and fractured more often at loads < or = 200 N compared with other configurations.

CONCLUSION

Sternal wiring techniques stabilizing sternal synchondroses had the least displacement. Overall, figure of 8 cerclage appeared most suitable because they minimized displacement at high loads and facilitated accurate reduction during tensioning.

CLINICAL RELEVANCE

In closing canine sternotomy, figure of 8 cerclage may be most suitable. Double-loop cerclage centered on the sternal synchondrosis should be avoided because of wire failure at high loads.

Extensive nasal septum resection in horses using a 3-wire method

OBJECTIVE

To describe a surgical technique for, and report outcome after, extensive nasal septum resection in horses with congenital or acquired septal diseases.

STUDY DESIGN

Retrospective study.

ANIMALS

Horses (5) with nasal septal deformity.

METHODS

Under general anesthesia, obstetrical wires were preplaced around the ventral, caudal, and dorsal aspects of the nasal septum by combinations of manual guidance (ventral and caudal wires) and use of a trephine hole on the dorsal mid-line (dorsal and caudal wires). The rostral part of the septum was incised with a scalpel and the ventral, dorsal, and caudal septal incisions were made with the preplaced wires. After septum removal, the nasal cavity packed with a tampon and a temporary tracheotomy was performed.

RESULTS

The diseased nasal septum was completely removed in all horses. It was possible to direct the caudal cut at a sufficient angle so that the remaining stump was in a wide part of the nasal passage, where it would have minimal effect on airflow. Four horses healed, and returned to intended use but continued to make a slight respiratory noise during exercise. At 13 months after surgery, 1 horse with a concurrent wry nose was retired from race training after 2 additional surgeries failed to relieve exercise intolerance at high speed.

CONCLUSIONS

The 3 wire-cut method of nasal septum resection was technically easy to perform and safe, allowed return to function in most horses, and produced an excellent cosmetic appearance.

CLINICAL RELEVANCE

This technique for nasal septum resection allows removal of a large portion of the nasal septum and provides a safe alternative to conventional techniques of nasal septum resection in the horse.

Multiple Rib Fracture in a Neonatal Foal Using a Nylon Strand Suture Repair Technique

OBJECTIVES

To report rib fracture repair using the Securos Cranial Cruciate Ligament Repair System (SCCLRS; Securos Veterinary Orthopedics, Charlton, MA) in a neonatal foal.

STUDY DESIGN

Case report.

ANIMALS

A 1-day-old Standardbred foal with fracture of left ribs 2-9.

METHODS

Four days after admission the foal was anesthetized and rib fractures were repaired using open reduction and the SCCLRS.

RESULTS

Rib fractures were successfully stabilized and the foal was discharged 7 days postoperatively without further complications.

CONCLUSIONS

The SCCLRS provided a straightforward, effective method of rib fracture repair in neonatal foals.

CLINICAL RELEVANCE

Effective rib fracture repair in neonatal foals can be achieved with the SCCLRS.

Surgical repair of rib fractures in 14 neonatal foals: case selection, surgical technique and results

REASONS FOR PERFORMING STUDY

Fractured ribs are encountered quite frequently in newborn Thoroughbred foals, often with fatal outcome. Surgical repair of fractures therefore requires consideration as a means of reducing mortality.

OBJECTIVES

To evaluate the repair of rib fractures using internal fixation techniques in foals at 2 different equine hospitals following similar diagnostics and case selection.

METHODS

The records of 14 foals that underwent internal fixation of fracture ribs were reviewed. Subject details, clinical presentation, diagnosis, surgical technique, post operative care and complications were recorded. Follow-up information was obtained in 7 foals.

RESULTS

The fractured ribs were reduced and stabilised using reconstruction plate(s), self-tapping cortical screws and cerclage wire in 12 cases, Steinmann pins and cerclage wires in 1 case and both techniques in 1 case. Not every rib was reduced on each case. Surgical reduction was performed on an average of 2 ribs, range 1-3 ribs in each foal. At the time of writing, 4 foals had been sold, one age 2 years was in training and 2 others died from unrelated causes.

CONCLUSIONS

Our data support the use of surgical stabilisation utilising reconstruction plates, self-tapping cortical screws and cerclage wire for selected cases of thoracic trauma in neonatal foals. The use of Steinmann pins may be suboptimal due to cyclic failure, implant migration and the potential for iatrogenic internal thoracic trauma.

POTENTIAL RELEVANCE

Foals with existing extensive internal thoracic trauma resulting from rib fracture(s), or the potential for such trauma, previously considered to have a guarded to poor prognosis for survival, may be successfully managed with internal fixation of selected fracture sites.

Bilateral fixation of Y-T humeral condyle fractures via medial and lateral approaches in 29 dogs

OBJECTIVES

To describe bilateral fixation of Y-T fractures of the humeral condyle via combined medial and lateral approaches, and to determine the technique's clinical and radiographic short-term outcomes.

METHODS

Details of 30 consecutive fractures in 29 dogs were reviewed. These included signalment, method of fixation, complications, and follow-up limb function and range of elbow joint motion.

RESULTS

The age of the dogs ranged from three months to nine years, and bodyweight ranged from 1.9 to 48 kg. The humeral condyle was reattached to the shaft using medial and lateral bone plates in 18 fractures, a medial plate and lateral Kirschner wire(s) in six fractures, and medial and lateral Kirschner wire(s) in six fractures. Major complications were recorded in four fractures and minor complications in two fractures. Limb function at follow-up was graded as excellent in 12, good in 15 and fair in three fractures. The range of elbow flexion was normal in seven, mildly reduced in 18, moderately reduced in four and severely reduced in one fracture.

CLINICAL SIGNIFICANCE

In contrast to the caudal approach, combined medial and lateral approaches decrease the extent of periarticular soft tissue dissection, avoid complications associated with olecranon osteotomy and enable exposure of the entire humeral diaphysis for fixation. Bilateral fixation is likely to be better at counteracting bending and torsional forces compared with unilateral fixation.

Comparison of anatomical tibial plateau angle versus observer measurement from lateral radiographs in dogs

This study was conducted to compare the anatomical tibial plateau angle (TPA) with that measured by observers from a lateral radiograph of the limb, the hypothesis being that there would not be any statistically significant differences between the observer measured TPA and the true anatomical TPA. Twelve pelvic limbs from skeletally mature greyhound cadavers, without any clinical or radiographic evidence of stifle pathology, were used in this study. The radiographs were taken of each limb in a lateral position with the primary beam centered over the tibial eminences and collimated to include the stifle and tarso-crural joints. For subsequent radiographs, Kirschner wires were inserted to enable identification of the tibial plateau. The TPA was then measured, by three observers, from the plain radiographs and by one observer from the marked radiographs. The mean observer TPA was 24.4 degrees (range 17-30 degrees) and the mean anatomical TPA was 23.8 degrees (range 15-31 degrees). The mean and median discrepancy between the anatomical TPA and the observer TPA was negative and very small (- 0.64 degrees and 0 degrees). The magnitude of the discrepancy between individual measurements made by the observers tended to overestimate small angles and underestimate the large ones, and this trend is statistically significant. These results suggest that the measurements made by observers accurately represent the anatomical slope of the tibial plateau. Therefore, observer TPA is suitable for the planning and assessment of TPLO procedures. However, as the anatomical TPA moves away from a median angle (23.25 degrees) the magnitude of error in the measurement increases.

Fixation of a proximal femoral physeal fracture in a dog using a ventral approach and two Kirschner wires

A Salter-Harris type I proximal femoral physeal fracture was diagnosed in a six-month-old Norfolk Terrier. The fracture was reduced using a ventromedial approach to the hip joint and fixation with two small Kirschner wires applied from the joint surface and countersunk below the cartilage. The ventromedial approach minimizes soft-tissue and vascular damage and affords direct visualization of the fracture, facilitating reduction and fixation. The two-year postoperative outcome was considered satisfactory in this case.

The use of a circular external skeletal fixation device for the management of long bone osteotomies in large ruminants: an experimental study

The study was undertaken to evaluate the feasibility of a simple, inexpensive model of circular external fixator (CEF) for use in large ruminants. A simple model of CEF frames consisting of four full rings (13-19 cm diameter, 4 cm wide and 4 mm thick with 18-24 holes) connected by threaded rods (8 mm diameter, 10-15 cm long) and nuts was developed using mild (low carbon) steel and were nickel-plated. In the first phase of the study, three male cow calves were utilized to study the feasibility of application of the fixators in the metatarsus, tibia and radius, in reference of adaptation and tolerance by animals. In the second phase, the fixators were tested in osteotomized bones. Six bull calves of 1.5-2 years of age weighing about 200-250 kg were utilized for this purpose. After preparing the area for aseptic surgery, under xylazine (at 0.1 mg/kg, i.m.)-ketamine (i.v. till effect) general anaesthesia, the test bone (metatarsus, radius and tibia in two animals each) was approached through the medial surface and an osteotomy was created with a saw and chisel at the mid-diaphysis. The pre-constructed 4-ring CEF was mounted on the limb around the test bone in such a way that it formed a cylinder with the axis of the limb at the centre. Each ring was then fixed to the bone with a pair of beaded wires (316 SS) of 3.5 mm diameter. During the post-operative period, the animals were observed for any change in behaviour, tolerance of the fixators, the weight bearing on the test limb, the status of the fixator, and the level of reduction of the osteotomy, alignment and healing at different intervals. The fixation of CEF was easier in the metatarsus and radius than in the tibia. The inner ring diameters found adequate for metatarsus, radius and tibia were 13-15 cm, 15-17 cm and 17-19 cm, respectively. The fixators applied to different bones were well-tolerated, and the animals could lay down, stand and walk freely with the fixator without any problems. All the animals showed good weight bearing in the immediate post-operative period. Weight bearing, however, slightly reduced in the inflammatory period and showed improvement after about 4 weeks. Wire tract infection was seen in all the animals, which was more on proximal wire tracts on lateral aspect of limbs. Circular fixators were well-tolerated by all the animals, and there was no breaking/bending of connecting rods, slotted bolts or the rings at any stage of observation. Slight bowing of some wires was noticed in cases of tibia and radius (in phase II) and bending of some wires was noticed from first week in two animals one each in radius and tibia. Bone fragments were well maintained until healing occurred (appearance of bridging periosteal callus) at 60-70 days. The functional results were good in all but one case of tibia, where a mal-union was recorded. From this study, it can be concluded that CEF are well-tolerated by large ruminants and can be used to treat long bone fractures. The fixator assembly using mild steel is sufficiently strong to maintain fracture fixation and is inexpensive. The simple design of the CEF appears to be sufficient to treat simple diaphyseal fractures of the metatarsus and radius. Improvement in the technique of fixation and design-like coupling of linear and circular fixator components into hybrid constructs may help to provide greater rigidity in treating tibial and open long bone fractures.

Surgical reduction and stabilization for repair of femoral capital physeal fractures in cats: 13 cases (1998–2002)

OBJECTIVE

To evaluate anatomic reduction and surgical stabilization of femoral capital physeal fractures in cats.

DESIGN

Retrospective study.

ANIMALS

13 cats.

PROCEDURE

Medical records of cats with unilateral or bilateral femoral capital physeal fractures evaluated from 1998 to 2002 were reviewed. Age and weight of cats at the time of surgery; breed; sex; concurrent injuries; severity of lameness before and 1, 2, 4, 6, and 8 weeks after surgery; the amount of fracture reduction achieved and number of Kirschner wires (K-wires) used; degree of degenerative joint disease of the hip joint and lysis of the femoral neck and head observed after surgery; whether K-wires were removed after surgery; and complications after surgery were evaluated.

RESULTS

Thirteen cats with 16 capital physeal fractures were identified. There was significant improvement in the severity of clinical lameness in all cats from weeks 1 through 4 after surgery. There was no correlation between the scores of the individuals who evaluated radiographs for fracture reduction and placement of K-wires.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that surgical stabilization and repair of femoral capital physeal fractures facilitate a short recovery period and a good prognosis for return to normal function in cats.

Outcomes and Complications Associated With Ventral Screws, Pins, and Polymethyl Methacrylate for Atlantoaxial Instability in 12 Dogs

Clinical outcomes and complications of a technique used for atlantoaxial stabilization were evaluated in a group of 12 dogs. At surgery, the atlantoaxial joint was realigned and rigidly fixated using cortical bone screws, K-wire, and polymethyl methacrylate. Results in nine dogs were graded as excellent. Results in two dogs were judged as good. One dog was euthanized 17 months after surgery for recurrent cervical pain. Eight dogs had no postoperative complications. The surgical technique described provided an adaptable method for the correction of atlantoaxial instability.

Dorsal tarsal instability in three racing greyhounds

Rupture of the dorsal ligaments of the tarsus in the greyhound is a rare racing injury. This case report describes dorsal tarsal instability in three greyhounds. A stumble and somersault were observed in two cases and were thought to have caused the injury. Previous reports advocate partial intertarsal arthrodesis as the preferred treatment for dorsal instability of the proximal intertarsal joint, but not all dogs returned to successful racing. In these three cases, stability was restored by the insertion of a wire tension band anchored to two bone screws, allowing the development of periarticular fibrosis. The dogs raced again with no loss of form.

Circular External Skeletal Fixation Stabilization of Antebrachial and Crural Fractures in 25 Dogs

Fracture stabilization using circular external skeletal fixation was evaluated in 14 dogs with antebrachial fractures and 11 dogs with crural fractures. Most dogs were consistently weight bearing on the stabilized limb by 3 days following surgery. Although all dogs developed minor wire/pin tract inflammation and eight dogs developed major wire/pin tract inflammation, postoperative lameness was not consistently associated with wire/pin tract complications. Fractures in 23 dogs achieved radiographic union (mean±standard deviation [SD], 61±21 days; median, 57 days) without additional surgery; two dogs required restabilization of their fractures with linear fixators. Twenty of the 21 owners that could be contacted felt their dog had no (n=15) or only a mild (n=5) intermittent lameness at the time of final, long-term (mean±SD, 37±17 months; median, 42 months) assessment.

Biomechanical comparison of a circular external skeletal fixator construct to pin and tension band wire fixation for the stabilization of olecranon osteotomies in dogs: a cadaveric study

OBJECTIVE

To compare anatomic reduction and the biomechanical properties of a circular external skeletal fixator (CESF) construct to pin and tension band wire (PTBW) fixation for the stabilization of olecranon osteotomies in dogs.

STUDY DESIGN

Cadaveric study.

ANIMALS

Forelimbs from 12 skeletally mature mixed-breed dogs, weighing 23 to 28 kg.

METHODS

An olecranon osteotomy was stabilized with either a CESF construct or PTBW fixation. A single distractive load to failure was applied to each specimen through the triceps tendon. Osteotomy reduction and biomechanical properties were compared between fixation groups.

RESULTS

Reduction was not significantly different (gap: P =.171; malalignment: P =.558) between fixation groups. Osteotomies stabilized with the CESF had greater stiffness (P <.0001) and maximum load sustained (P <.0001) compared to PTBW fixation. There was no significant difference for yield load (P =.318) or for load at 1 mm of axial displacement (P =.997) between fixation groups. Failure of fixation occurred by bending of the intramedullary Steinmann pin and the fixation wires in the CESF specimens and by untwisting of the tension band wire knot with pullout and bending of the Kirschner wires in the PTBW specimens.

CONCLUSIONS

Specimens stabilized with the CESF construct had similar reduction and yield load, greater stiffness and maximum load sustained, and less elastic deformation than specimens stabilized with PTBW fixation.

CLINICAL RELEVANCE

The CESF construct may provide a biomechanically favorable alternative to PTBW fixation for stabilization of olecranon osteotomies in dogs, and its application warrants clinical investigation.

Fixation technique influences the monotonic properties of equine mandibular fracture constructs

OBJECTIVE

To determine the optimal fixation technique for equine interdental space fractures by evaluating the biomechanical characteristics of 4 fixation techniques.

STUDY DESIGN

In vitro randomized block design.

SAMPLE POPULATION

Twenty-seven adult equine mandibles.

METHODS

Mandibles with interdental osteotomies were randomly divided into 4 fixation groups (n = 6/group). Fixation techniques were the following: (1) dynamic compression plates (DCP), (2) external fixator (EF), (3) external fixator with interdental wires (EFW), and (4) intraoral splint with interdental wires (ISW). Three intact (nonosteotomized) mandibles were tested as controls. Mandibles were subjected to monotonic cantilever bending until failure. Angular displacement data (radians) were derived from continuously recorded gap width measurements provided by extensometers placed across the osteotomy site. Osteotomy gap width data (mm) at 50 and 100 Nm were selected for standardized comparison of gap width before the yield point and failure point, respectively of all constructs tested. Stiffness (Nm/radian), yield strength (Nm), and failure strength (Nm) were determined from bending moment-angular displacement curves and were compared using ANOVA with appropriate post hoc testing when indicated. Radiographs were obtained prefixation, postfixation, and posttesting.

RESULTS

Bending stiffness, yield, and ultimate failure loads were greatest for intact mandibles. Among osteotomized mandibles, stiffness was greatest for DCP constructs (P <.05) and was not significantly different among EF, EFW, and ISW constructs. Yield load was greatest for ISW constructs (P <.05) and was not significantly different among DCP and EFW constructs. Yield and ultimate failure loads were lowest (P <.05) and osteotomy gap width at 50 and 100 Nm were greatest for EF constructs (P =.09 and P <.05, respectively). There was no significant difference in failure loads and osteotomy gap widths among DCP, EFW, and ISW constructs (P <.05). Failure occurred through the screw-bone interface (DCP), acrylic splint (ISW), acrylic connecting bar and/or pin-bone interface (EF, EFW), and wire loosening (EFW). All 3 intact mandibles fractured through the vertical ramus at its attachment to the testing apparatus.

CONCLUSIONS

Among osteotomized mandibles, DCP fixation had the greatest stiffness under monotonic bending to failure; however, the relatively low yield value may predispose it to earlier failure in fatigue testing without supplemental fixation. Techniques using tension-band wiring (EFW and ISW) were similar to DCP constructs in yield, failure, and osteotomy displacement, whereas EF constructs were biomechanically inferior to all other constructs.

CLINICAL RELEVANCE

DCP fixation is most likely the most stable form of fixation for comminuted interdental space fractures. However, for simple interdental space fractures, ISW fixation may provide adequate stability with minimal invasiveness and decreased expense. Tension-band wiring significantly enhances the strength of type II external skeletal fixators and should be used to augment mandibular fracture repairs.

Influence of bolt tightening torque, wire size, and component reuse on wire fixation in circular external fixation

OBJECTIVES

To evaluate the effects of bolt torque, wire size, and component reuse on the ability to maintain wire tension in 3 external skeletal fixation systems.

STUDY DESIGN

Biomechanical study.

METHODS

Yield strength in tension of 1.0-, 1.2-, 1.5-, and 1.6-mm-diameter wires, and yield strength in torque of Hofmann Small Bone Fixation (SBF) cannulated and slotted bolts and IMEX regular and miniature bolts were determined on a testing machine. The minimum bolt tightening torque needed to prevent wire slippage at clinically recommended wire tensions was determined. Components were tested 10 times, and loads at slippage were recorded.

RESULTS

The IMEX system required a mean of 8 Nm of bolt tightening torque to maintain 900 N (1.6-mm wires). The SBF system required a mean of 3 Nm bolt torque to maintain 300 N (1.0-mm wires) and 5 Nm to maintain 600 N (1.2-mm wires). The SBF cannulated bolt required 9 Nm of torque to maintain 900 N (1.5-mm wires). The SBF slotted bolts could only maintain 800 N before yield. The IMEX miniature system required a mean bolt torque of 1.1 Nm to maintain 300 N. The cannulated and slotted bolts from both manufacturers failed to maintain 70% of initial wire tension after 7 and 4 uses, respectively.

CONCLUSIONS

The IMEX systems and the SBF system using 1.0- and 1.2-mm wires could maintain clinically recommended wire tension safely. Only the IMEX system could maintain clinically recommended wire tension safely using 1.5- or 1.6-mm wires.

CLINICAL RELEVANCE

The SBF system using 1.0- and 1.2-mm wires and the IMEX system using all wire sizes can maintain clinically relevant wire tension. The SBF system using 1.5-mm wires could not. Cannulated and slotted bolts should not be used more than 6 and 3 times, respectively. Nuts should not be reused.

Removal of infected canine cemented total hip prostheses using a femoral window technique

OBJECTIVE

To evaluate a femoral window technique for retrieval of cemented total hip prostheses.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Twelve dogs with infection of a cemented modular total hip prosthesis.

METHODS

Implant removal was performed by an extended craniolateral approach to the hip and proximal femur without trochanteric osteotomy. The femoral cement mantle was fragmented and removed with simple orthopedic instrumentation by a lateral femoral window that was repaired using cerclage wires. Surgical technique, intraoperative and postoperative complications, bacterial culture results, histopathologic findings, and completeness of cement removal were recorded. Follow-up radiographs were taken 5 to 9 weeks postoperatively. Long-term follow-up information was obtained by client questionnaire. Functional outcome was assessed by scoring ability to stand, sit, walk, run, play, climb stairs, and get into a car.

RESULTS

Prosthesis retrieval was performed 2 to 41 months after implantation (median, 14 months). Complete removal of femoral cement was achieved in 10 dogs. A nondisplaced femoral fissure, extending proximally from the window, was an intraoperative complication in 2 dogs. Staphylococcus spp was most commonly isolated (6 dogs) from interfacial membrane samples. Systemic antibiotic therapy, dependent on susceptibility testing, was administered for 3 to 10 weeks postoperatively. There was radiographic evidence of osteotomy healing at 5- to 9-week reassessment. Recurrence of osteomyelitis was not observed. Long-term functional outcome was considered mildly abnormal.

CONCLUSIONS

The lateral window was an effective technique for retrieval of retained femoral cement.

CLINICAL RELEVANCE

Removal of an infected prosthesis using this technique generally resulted in a clinical outcome comparable to that with ab initio femoral head and neck excision.

Closure of median sternotomy in dogs: suture versus wire

Twenty normal, large-breed dogs underwent median sternotomy. Median sternotomies were closed with 20-gauge orthopedic wire in 10 dogs and no. 2 polybutester in 10 dogs. Closure with suture was faster than with wire (6.7 +/- 1.8 minutes versus 9.1 +/- 1.9 minutes, respectively). Significant differences were not observed in degree of postoperative pain or wound complication rates. Sternotomies closed with wire showed a trend to be more stable and had significantly less displacement on radiographic evaluation at 28 days. All sterna closed with wire examined histopathologically showed evidence of chondral or osteochondral bridging, while sterna closed with suture only showed fibrous union.

A comparison of ultra-high-molecular weight polyethylene cable and stainless steel wire using two fixation techniques for repair of equine midbody sesamoid fractures: an in vitro biomechanical study

OBJECTIVE

To compare the monotonic tensile and fatigue strength of 16-gauge stainless steel wire (SSW) to ultra-high-molecular weight polyethylene (UHMWPE) cable using a transfixed cerclage technique in an in vitro midbody sesamoid osteotomy model. Endoscopic modifications to Martins transfixed cerclage technique were developed. A new suture technique of fixation was compared with the transfixed cerclage technique by measuring gap formation after cyclic testing.

STUDY DESIGN

An in vitro biomechanical paired equine cadaver limb study.

SAMPLE POPULATION

Twenty-one paired cadaveric adult equine forelimbs.

METHODS

Uniaxial medial midbody sesamoid osteotomies were created in paired adult equine forelimbs. Monotonic tensile strength was measured on 10 forelimbs repaired by a transfixed cerclage technique using wire or cable. Fatigue testing to failure was performed on 4 forelimbs repaired using the transfixed cerclage technique by cycling the limbs between 500 N and 2,000 N. The limbs were initially repaired with wire, cycled until the wire broke, then repaired with cable and cycled again to failure. Fatigue testing for gap displacement was performed on 8 limbs repaired with either the transfixed cerclage technique or the suture technique. Limbs were cycled between 500 N and 2,000 N for 10,000 cycles. The limbs were repaired with wire initially, tested, and then repaired with cable and tested again. Twenty-two limbs were used for mechanical testing. The remaining limbs (20) were used to develop and practice the endoscopic transfixed cerclage (10 limbs) and suture (10 limbs) techniques.

RESULTS

Ultimate tensile strength (UTS) of UHMWPE cable constructs was 34% greater than the UTS of SSW constructs. Fatigue strength was 2 to 20 times greater for UHMWPE cable constructs than SSW constructs. Separation of fragments was 153% less for limbs repaired by the suture technique compared with those repaired by the transfixed cerclage technique.

CONCLUSIONS

UHMWPE cable shows promise for this clinical application because of its greater tensile and fatigue strength. The newly described suture technique significantly reduced gap formation compared with the transfixed cerclage technique. Osteotomy gap formation occurred early in cycling, suggesting that rigid support in the form of a cast may be needed during the early postoperative period for wiring techniques.

CLINICAL RELEVANCE

Clinical testing of UHMWPE cable should eliminate problems of wire breakage seen with SSW. The endoscopic transfixed cerclage technique can be used by surgeons familiar with arthroscopic surgery. However, the suture technique needs to be tested in vivo to determine whether there is a clinical advantage compared with the transfixed cerclage technique.

Avascular necrosis of the femoral heads in a red panda (Ailurus fulgens fulgens): possible Legg-Calve-Perthes disease

A 17-mo-old captive-born female red panda (Ailurus fulgens fulgens) presented with a sudden onset of lameness in its left hind leg was diagnosed radiographically as having possible severe, bilateral Legg-Calve-Perthes disease with fracture of the great trochanter of the left femur. Surgical repair of the fracture was performed using pins and a tension band wire through a lateral approach to the hip. This is the first case reported at Madrid Zoo-Aquarium, where 63 individuals have been bred over 15 yr.

Complication rate and factors affecting outcome of olecranon osteotomies repaired with pin and tension-band fixation in dogs

The objective of this study was to determine the complication rate and evaluate factors affecting the outcome of olecranon osteotomy in dogs. Medical records were searched to identify dogs that had undergone olecranon osteotomy (stabilized with 2 Kirschner wires and a figure-of-8 wire) during internal fixation of a supracondylar or condylar humeral fracture. Signalment, description of the fracture, parameters regarding the osteotomy and its repair, and radiographic outcome were recorded. A logistic regression model compared patient and technical parameters with the osteotomy outcome. Of the 19 dogs, 7 (37%) had complications of the osteotomy, including osteomyelitis, loss of reduction, and improper placement and migration of the Kirschner wires. Olecranon osteotomy is associated with a high complication rate in dogs; however, there was no correlation between patient-related or technical parameters and the development of complications. Further clinical and biomechanical investigations are warranted to improve the results of olecranon osteotomy and its repair.

Evaluation of tension obtained by use of three knots for tying cerclage wires by surgeons of various abilities and experience

OBJECTIVE

To compare tension of 3 cerclage wire knots tied by surgeons of various abilities and experience.

DESIGN

Cross-sectional study.

SAMPLE POPULATION

Participants and faculty at a postgraduate course in veterinary orthopedics.

PROCEDURE

Subjects tied a cerclage of their choice on an instrumented tying stand that displayed the tension on a computer. Mean tensions in cerclage wires tied with twist, single loop, or double loop knots were compared. The relationship between level of surgeon experience and tension achieved was examined.

RESULTS

29 twist, 30 single loop, and 16 double loop wires were analyzed. Mean +/- SD tension for twist knots was significantly less than for single loop knots (82.3+/-46.1 vs 166.6+/-42.2 N, respectively). Double loop knots achieved significantly greater tension (392.0+/-116.6 N) than twist and single loop knots did, even though few participants had ever tied this knot previously. There was no correlation with experience of the participant. For twist knots, wiggling the wire during cutting and pushing the twist over to flatten it to the bone further reduced tension.

CONCLUSIONS AND CLINICAL RELEVANCE

Cerclage applied with a twist knot does not compress fracture fragments as effectively as cerclage applied with single loop or double loop techniques. Because greater compression of fragments will improve the stability of a fracture, a surgeon should strive to maximize the tension in the cerclage that they use. Experience and abilities of the surgeon are not associated with ability to tie cerclage wires tightly.

Radiographic features of a lateral extracapsular wire suture in the canine cranial cruciate deficient stifle

Radiographs of 74 dogs (84 stifles) presented with a cranial cruciate ligament rupture and surgically treated using a lateral extracapsular wire (LEW) were reviewed. A strand of orthopaedic wire was surgically placed caudally around the lateral fabella and through a predrilled hole in the tibial crest. At six week follow-up, the LEW was broken at least once in 26 of 33 stifles, predominantly in the area of the lateral fabella. In five stifles, the LEW had slipped off the fabella and was displaced distally along the gastrocnemius muscle. Six months after surgery, the LEW was often broken at several sites. LEW migration was rare. Osteolysis and sclerosis at the site of LEW penetration through the tibial crest occurred in about two-thirds of the stifles examined.

Oral and maxillofacial reconstruction in a cat using wire and acrylic

A 15-month-old DSH cat was presented with facial deformity secondary to multiple oral and maxillofacial fractures after being struck by an automobile. Multiple wires and dental acrylics were used for fracture repair.

Evaluation of four interfragmentary Kirschner wire configurations as a component of screw/wire/polymethylmethacrylate fixation for acetabular fractures in dogs

The biomechanical contribution of the interfragmentary Kirschner wire as a component of composite fixation for acetabular fracture repair was subjectively and objectively evaluated. Acetabular osteotomies were repaired using the screw/wire/polymethylmethacrylate (SWP) composite fixation with or without one of three configurations of Kirschner wire in 32 hemipelves obtained from 16 dogs. Reduction, assessed objectively and subjectively, was unaffected by Kirschner wire placement. Hemipelves repaired with Kirschner wire(s) were subjectively more stable prior to application of polymethylmethacrylate when manually assessed in multiple planes. Consistent incremental increases in stiffness, yield load, and maximum load sustained that were observed during biomechanical testing were not significant, with the exception that hemipelves repaired with two Kirschner wires had significantly greater yield loads than hemipelves repaired without Kirschner wires. The subjective results of this study support the use of at least one interfragmentary Kirschner wire to maintain reduction prior to polymethylmethacrylate application; however, fracture configuration and location may dictate the number and pattern of interfragmentary Kirschner wires used to maintain reduction prior to application of the polymethylmethacrylate. The objective results and observations made during biomechanical testing suggest that use of one or more interfragmentary Kirschner wires may enhance stability after polymethylmethacrylate application.

In vitro biomechanical properties of 2 compression fixation methods for midbody proximal sesamoid bone fractures in horses

OBJECTIVE

To evaluate 2 methods of midbody proximal sesamoid bone repair--fixation by a screw placed in lag fashion and circumferential wire fixation--by comparing yield load and the adjacent soft-tissue strain during monotonic loading.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

10 paired equine cadaver forelimbs from race-trained horses.

METHODS

A transverse midbody osteotomy of the medial proximal sesamoid bone (PSB) was created. The osteotomy was repaired with a 4.5-mm cortex bone screw placed in lag fashion or a 1.25-mm circumferential wire. The limbs were instrumented with differential variable reluctance transducers placed in the suspensory apparatus and distal sesamoidean ligaments. The limbs were tested in axial compression in a single cycle until failure.

RESULTS

The cortex bone screw repairs had a mean yield load of 2,908.2 N; 1 limb did not fail when tested to 5,000 N. All circumferential wire repairs failed with a mean yield load of 3,406.3 N. There was no statistical difference in mean yield load between the 2 repair methods. The maximum strain generated in the soft tissues attached to the proximal sesamoid bones was not significantly different between repair groups.

CONCLUSIONS

All repaired limbs were able to withstand loads equal to those reportedly applied to the suspensory apparatus in vivo during walking.

CLINICAL RELEVANCE

Each repair technique should have adequate yield strength for repair of midbody fractures of the PSB immediately after surgery.

An in vitro biomechanical comparison of two fixation methods for transverse osteotomies of the medial proximal forelimb sesamoid bones in horses

OBJECTIVE

This study compared the mechanical properties of the normal intact suspensory apparatus and two methods of fixation for repair of transverse, midbody fractures of the proximal sesamoid bones of adult horses: transfixation wiring (TW) and screws placed in lag fashion (LS).

STUDY DESIGN

An in vitro, paired study using equine cadaver limbs mounted in a loading apparatus was used to test the mechanical properties of TW and LS.

ANIMAL OR SAMPLE POPULATION

Seventeen paired (13 repaired, 4 normal) equine cadaver limbs consisting of the suspensory apparatus third metacarpal bone, and first and second phalanges.

METHOD

The two methods of repair and normal intact specimens were evaluated in single cycle-to-failure loading. Yield failure was defined to occur at the first notable discontinuity (>50 N) in the load-displacement curve, the first visible failure as evident on the videotape, or a change in the slope of the moment-fetlock angle curve. Ultimate failure was defined to occur at the highest load resisted by the specimen. Corresponding resultant force and force per kg of body weight on the suspensory apparatus, fetlock joint moment, and angle of fetlock dorsiflexion were calculated by use of specimen dimensions and applied load. These were compared along with specimen stiffness, and ram displacement.

RESULTS

Load on the suspensory apparatus, load on the suspensory apparatus per kg of body weight, moment, applied load, and angle of fetlock dorsiflexion at yield failure were significantly greater for the TW-repaired than for the LS-repaired specimens. A 3 to 5 mm gap was observed before yield failure in most TW-repaired osteotomies.

CONCLUSIONS

Transfixation wiring provided greater strength to yield failure than screws placed in lag fashion in single cycle load-to-failure mechanical testing of repaired transverse osteotomized specimens of the medial proximal forelimb sesamoid bone.

Internal fixation. Intramedullary pins, cerclage wires, and interlocking nails

IM pins, cerclage wires, and ILNs are valuable tools for repairing long bone fractures. Successful bone healing is readily achieved with these tools but also requires aseptic technique, attention to preserving soft tissues, and proper application procedures.

Fractures of the rostral portion of the mandible and maxilla in horses: 89 cases (1979-1997)

OBJECTIVE

To compare fracture locations, repair methods, complications, and outcomes of horses with fractures of the rostral portions of the mandible and maxilla.

DESIGN

Retrospective study.

ANIMALS

89 horses with fractures of the rostral portions of the mandible and maxilla.

PROCEDURE

Medical records and radiographs were reviewed. Fractures were categorized by fracture location and stability. Postoperative complications and long-term outcome were determined by clinical examination and telephone interviews with horse owners.

RESULTS

4 fracture types were recognized. Fractures involving just the alveolar plate (33%) and those involving the alveolar plate and the body of the bone (32%) were most common and were often repaired by interdental wiring. Unilateral fractures of the mandible (11%) were managed without surgery if stable. Unstable fractures were repaired with wires, a U-shaped bar (U-bar), or a bone plate. Bilateral fractures (24%) were often repaired with orthopedic wires in foals or with a U-bar, acrylic splint, wires, or bone plate in adult horses. In 2 horses, bilateral fractures were managed conservatively. Short-term complications developed in 24 of 89 (27%) horses. Soft tissue infections and wire loosening or failure were the most common short-term and long-term complications. Wire replacement was not required in any horses after release from hospital. Persistent draining tracts were most often associated with bone sequestration. Long-term functional and cosmetic outcomes were favorable for all fracture types and repair methods.

CLINICAL IMPLICATIONS

Although complications in horses with fractures of the mandible and maxilla are common, long-term prognoses for functional and cosmetic outcome are favorable.

A biomechanical comparison of screw and wire fixation with and without polymethylmethacrylate re-enforcement for acetabular osteotomy stabilization in dogs

OBJECTIVE

Compare the biomechanical characteristics of screw and wire fixation with and without polymethylmethacrylate (PMMA) re-enforcement for acetabular osteotomy stabilization in dogs.

ANIMALS

Pelves removed from 8 adult mixed breed dogs weighing between 25 and 30 kg.

PROCEDURE

The pubic symphysis of each pelvis was split and a central transverse acetabular osteotomy was performed. One hemipelvis from each dog was stabilized with the composite fixation (interfragmentary Kirschner wire, two screws and a figure-of-eight orthopedic wire with PMMA). The contralateral hemipelves was stabilized with an interfragmentary Kirschner wire, two screws, and a figure-of-eight orthopedic wire without PMMA. All hemipelves were tested in bending by using a materials testing machine at a cross head speed of 5 mm/min. An extensometer was placed on the dorsomedial surface of the hemipelves centered over acetabular osteotomy to record distraction of the osteotomy during loading. A load/deformation curve and a load/distraction curve was produced for each hemipelvis. The slope for the initial linear portion of the load/deformation curve and the load/distraction curve, yield load and maximum load sustained were compared between repair groups using a paired t-test with P < .05 considered significant.

RESULTS

The slope of the load/deformation curve was significantly greater (P = .001) for hemipelves stabilized with the composite fixation (mean +/- SD: 69 +/- 18 N/mm) compared with hemipelves stabilized without PMMA (mean +/- SD: 39 +/- 8 N/mm). There was no significant difference (P = .593) between repair groups in the slope of the load/distraction curves as measured on the extensometer. Yield load was significantly greater (P = .0002) for hemipelves stabilized with the composite fixation (mean +/- SD: 184 +/- 25 N) compared to hemipelves stabilized without PMMA (mean +/- SD: 74 +/- 12 N). Maximum load sustained was also significantly greater (P = .013) for hemipelves stabilized with the composite fixation (mean +/- SD: 396 +/- 71 N) compared to hemipelves stabilized without PMMA (mean +/- SD: 265 +/- 94 N). Failure of hemipelves stabilized with the composite fixation occurred primarily by ventrolateral bending of the cranial and caudal pelvic segments at the osteotomy site. Failure of hemipelves stabilized without PMMA occurred by ventrolateral bending of the cranial and caudal pelvic segments at the osteotomy site with pronounced concurrent ventrolateral rotation of the cranial pelvic segment.

CONCLUSION

PMMA improves the mechanical characteristics of acetabular fracture fixation, at least in part by neutralization of rotational forces. The results of this study justify use of PMMA as a component of the composite fixation when repairing acetabular fractures.

Interlocking nail treatment of diaphyseal long-bone fractures in dogs

OBJECTIVE

To determine results of using interlocking nails (IN) for fixation of diaphyseal long bone fractures in dogs.

DESIGN

Multi-center prospective clinical trial.

ANIMALS

134 dogs with diaphyseal fractures of the femur (n = 92), tibia (23), or humerus (19); 11 had previous unsuccessful treatments, and 103 had comminuted fractures of which 70 were classified as unstable.

PROCEDURE

All fractures were stabilized with 6- or 8-mm-diameter IN with 3.5- or 4.5-mm screws, respectively. Cerclage wires and an autogenous bone graft were used at the surgeon's discretion. Participating surgeons provided information on age, sex, weight, and breed of the dog, details of the surgery, details of any intra- or postoperative complications, fracture healing time, and limb function.

RESULTS

Eight dogs were lost to follow-up evaluation. In 105 of the remaining 126 dogs (83%), fractures healed without complications. For these 105 dogs, limb function was excellent (n = 90), good (12), fair (2), and poor (1). Complications developed for 21 dogs (17%); limb function after additional treatment was excellent (n = 10), good (2), fair (5), poor (1), or unreported (3). Interlocking nails broke in 9 dogs; breakage was attributed to fatigue failure because of use of too small an IN or because of insertion of the IN so that a screw hole was positioned at the fracture site.

CLINICAL IMPLICATIONS

The high success rate and low complication rate suggest that IN can be used to stabilize diaphyseal fractures in dogs. Good technique is necessary for optimal results.