Numerical evaluation of internal femur osteosynthesis based on a biomechanical model of the loading in the proximal equine hindlimb

Femoral fractures are often considered lethal for adult horses because femur osteosynthesis is still a surgical challenge. For equine femur osteosynthesis, primary stability is essential, but the detailed physiological forces occurring in the hindlimb are largely unknown. The objective of this study was to create a numerical testing environment to evaluate equine femur osteosynthesis based on physiological conditions. The study was designed as a finite element analysis (FEA) of the femur using a musculoskeletal model of the loading situation in stance. Relevant forces were determined in the musculoskeletal model via optimization. The treatment of four different fracture types with an intramedullary nail was investigated in FEA with loading conditions derived from the model. The analyzed diaphyseal fracture types were a transverse (TR) fracture, two oblique fractures in different orientations (OB-ML: medial-lateral and OB-AP: anterior-posterior) and a "gap" fracture (GAP) without contact between the fragments. For the native femur, the most relevant areas of increased stress were located distally to the femoral head and proximally to the caudal side of the condyles. For all fracture types, the highest stresses in the implant material were present in the fracture-adjacent screws. Maximum compressive (-348 MPa) and tensile stress (197 MPa) were found for the GAP fracture, but material strength was not exceeded. The mathematical model was able to predict a load distribution in the femur of the standing horse and was used to assess the performance of internal fixation devices via FEA. The analyzed intramedullary nail and screws showed sufficient stability for all fracture types.

Stabilisation of femoral capital physeal fractures using transcervical pinning in cats: 19 cases (2014-2022)

OBJECTIVES

To report the short-term clinical and radiographic outcomes in cats with femoral capital physeal fractures stabilised with transcervical pinning.

MATERIALS AND METHODS

Medical records of cats diagnosed with femoral capital physeal fractures and treated with transcervical pinning were reviewed. The collected data included signalment, weight, time from lameness to surgery, reported trauma, affected side, concomitant orthopaedic injuries, radiographs, osteoarthritis, femoral neck osteolysis, proximal femoral epiphysis to femoral neck ratio, fracture reduction, implants, complications and clinical evaluation results. An owner questionnaire was used for long-term follow-up.

RESULTS

Nineteen cats with a total of 21 fractures met the inclusion criteria. Fifteen of the 19 cats showed no signs of lameness at the 1-month follow-up. Major and catastrophic complications occurred in 9.5% and 23.8% of the fractures, respectively. All catastrophic complications occurred in fractures with a high preoperative osteolysis grade (2 or 3).

CLINICAL SIGNIFICANCE

In our study, transcervical pinning was found to be a reliable fixation method for the treatment of femoral capital physeal fractures in cats with minimal preoperative femoral neck osteolysis. High rates of implant failure with loss of fracture reduction were observed in cats with high-grade preoperative osteolysis.

Repair of femoral fractures in calves via external skeletal fixator with intramedullary pin tie-in

OBJECTIVE

To describe the success rate and associated complications of external skeletal fixator/intramedullary pin tie-in for calf femoral fracture fixation.

STUDY DESIGN

Clinical retrospective.

ANIMALS

Ten calves, less than 30 days old, with diaphyseal/metaphyseal femoral fractures.

METHODS

Medical records were reviewed from the University of Wisconsin from 2000 to 2020. Fractures were repaired using open reduction and fixation. An intramedullary Steinman pin was placed, exiting near the greater trochanter, and utilized for fracture reduction. Bicortical transfixation pins were placed distal and proximal to the fracture site. Poly(methyl methacrylate) (PMMA)-filled tubing connected the transfixation pins and proximal intramedullary pin, creating a Type 1a external skeletal fixator (ESF) tie-in. Follow up was obtained via medical records and phone interviews.

RESULTS

Short-term survival rate was 7/10 (70%). Postanesthetic death occurred once. Postoperative complications occurred in all remaining cases. The most common findings were transfixation pin tract lucency and lameness (6/9 cases), implant dysfunction (5/9 cases), and infection (4/9 cases). Three of five cases with long-term follow up survived; all went on to productive careers.

CONCLUSION

Although patients were prone to postoperative complications, short-term survival was comparable to previous reports.

CLINICAL SIGNIFICANCE

The external skeletal fixator/intramedullary (ESF/IM) pin tie-in is less expensive and offers comparable success rates to other methods, providing a lower cost option for calf femoral fracture repair.

Closed reduction and fluoroscopic-guided percutaneous pinning of femoral capital physeal or neck fractures: Thirteen fractures in 11 dogs

OBJECTIVES

To report the short-term clinical outcome and complications in dogs that underwent surgical repair of femoral capital physeal or neck fractures via fluoroscopic-guided percutaneous pinning (FGPP).

STUDY DESIGN

Retrospective case series.

ANIMALS

Client owned dogs (n = 11) with femoral capital physeal or neck fractures (n = 13).

METHODS

Records (July 2018-July 2021) of dogs that underwent surgery for femoral capital physeal or neck fracture repair with FGPP from two hospitals were reviewed. Data collected included signalment, age, weight, preoperative lameness severity, fracture factors (etiology, Salter-Harris classification, time from injury to surgery, radiographic displacement), surgical factors (surgery time, number/size of implants, reduction quality) and outcome (follow-up examination findings, radiographic findings, complications).

RESULTS

Most fractures (11/13) occurred secondary to trauma. The median time from injury to surgery was 5.5 days. There was mild radiographic displacement preoperatively in 10/13 fractures. Satisfactory fracture healing and limb function was achieved in 10/13 femurs. Complications occurred in 5/11 cases and included intra-articular implants, implant failure/nonunion, implant migration (2), and malunion. Of these five complications, two resolved with implant removal, and a salvage procedure was recommended in the remaining cases. Of the three cases requiring salvage procedures, two originally presented with radiographic evidence of fracture chronicity.

CONCLUSIONS

FGPP can be used to successfully treat femoral head and neck fractures with appropriate case selection and precise surgical technique.

Minimally invasive plate osteosynthesis of femoral fractures with 3D-printed bone models and custom surgical guides: A cadaveric study in dogs

OBJECTIVE

Assess the accuracy and efficiency of reduction provided by application of plates precontoured to 3-dimensional (3D)-printed femoral bone models using a custom fracture reduction system (FRS) or intramedullary pin (IMP) to facilitate femoral minimally invasive plate osteosynthesis (MIPO) in dogs.

STUDY DESIGN

Experimental cadaveric study.

SAMPLE POPULATION

Seven dog cadavers.

METHODS

Virtual 3D femoral models were created using computed tomographic images. Simulated, virtual mid-diaphyseal femoral fractures were created and reduced. Reduced femoral models were 3D-printed and a plate was contoured. Custom drill guides for plate screw placement were designed and 3D-printed for the FRS. Mid-diaphyseal simulated comminuted fractures were created in cadavers, and fractures were aligned using FRS or IMP and stabilized with the precontoured plates. Number of fluoroscopic images acquired per procedure and surgical duration were recorded. Computed tomographic scans were repeated to assess femoral length and alignment.

RESULTS

Compared to the preoperative virtual plan, median change in femoral length and frontal, sagittal, and axial alignment was less than 3 mm, 2°, 3°, and 3° postoperatively, respectively, in both reduction groups. There was no difference in length or alignment between reduction groups (P > .05). During FRS, fewer fluoroscopic images were taken (P = .001), however, surgical duration was longer than IMP procedures (P = .011).

CONCLUSION

Femoral alignment was accurate when using plates precontoured to 3D printed models, regardless of reduction method.

CLINICAL SIGNIFICANCE

Accurate plate contouring using anatomically accurate models may improve fracture reduction accuracy during MIPO applications. Custom surgical guides may reduce fluoroscopy use associated with MIPO.

Determination of the insertion position of implants for the cross-pin fixation of distal femoral physis fractures

The cross-pin technique for the treatment of distal femoral physis fractures (specifically, Salter-Harris Type I fractures) was investigated using femurs collected from beagle cadavers. The pin was inserted from the medial surface of the femur at an inclination of approximately 30 to 45° relative to the long axis of the femur in the anteroposterior direction; the pin exit was set proximal to the origin of the long digital extensor tendon. Digital and radiographic images of the femur in the anteroposterior and lateral directions were obtained. In both types of images, the insertion angle of the pin relative to the long axis was measured. Results suggest that when inserting a pin proximal to the fracture line, the ideal position can be achieved by inclining the pin approximately 20° cranially relative to the long axis of the lateral direction of the femur, in addition to the previously described criteria.

Arthroscopic removal of an intra-articular screw causing joint impingement after distal femoral fracture repair in a dog

The use of lag screws to treat femoral condyle fractures is common, and their placement in surgery is technically demanding. Intra-articular screw impingement is a serious complication that may occur during surgical treatment of femoral condyle fractures. Here, we describe the case of a 3-year-old 40-kg dog which experienced recurrent lameness 6 mo after successful surgical treatment of a comminuted medial femoral condyle fracture due to an intra-articular non-loosening screw causing joint impingement. Removal of the conflicting screw was performed arthroscopically, based on its ability to offer minimally invasive access to the stifle joint. Six months after removal of the screw, the dog had full recovery without limitations to range of motion or stifle pain. To our knowledge, this is the first report on the use of arthroscopy to remove an intra-articular screw causing joint impingement after distal femoral fracture repair in a dog.

Outcome following surgical stabilization of distal diaphyseal and supracondylar femoral fractures in dogs

Signalment, clinical features, fixation techniques, complications, and outcome for dogs presenting with distal diaphyseal and supracondylar femoral fractures were retrospectively reviewed. A total of 45 dogs with unilateral femoral fractures were included. Supracondylar femoral plates were the most popular method of fixation. However, various fixation techniques resulted in favorable outcomes in most dogs with 19/45 cases achieving full function and 22/45 achieving acceptable function. Degree of fracture comminution did not appear to affect complication rate or be a surrogate for worse clinical outcome.

A case of bone fracture with callus on the right femur of a chicken (Gallus gallus domesticus, L. 1758) from the ancient site of Dharih, Jordan

Archaeozoology provides bones, which quite regularly present traces of fractures. These fractures are more or less at an advanced level of healing and bear witness to traumas or pathologies. These cases of palaeopathology are not always the subject of publications, which further restricts our knowledge about them. This short note allows the scientific community to be aware of an original case from an archaeological context in Jordan of a fracture on a hen's femur, consolidated by a callus and with displacement of the distal ends. Beyond the "anecdotal" aspect, and without imagining the circumstances in which the fracture occurred, the animal survived.

Surgical management of long bone fractures in cats using cortical bone allografts preserved in honey

This report describes comminuted fractures in 2 cats repaired by stabilization with cortical bone allografts that had been preserved in honey. Both cats exhibited appropriate post-operative weight-bearing. Preservation of bone in honey is a simple and widely available alternative for bone banking. This is the first report of a bone defect in cats repaired with bone preserved in honey.

Rapamycin facilitates fracture healing through inducing cell autophagy and suppressing cell apoptosis in bone tissues

OBJECTIVE

To investigate the changes in cell autophagy and the molecular mechanism of rapamycin affecting the fracture healing.

MATERIAL AND METHODS

Sprague-Dawley (SD) rats were used to establish the right femoral shaft fracture models, and then underwent immunofluorescence assay to detect the autophagy level in bone tissues. After model establishment, SD rats were divided into two groups, the control group and the rapamycin group (1 mg/kg/d). Respectively, at the 2nd, 4th, and 6th week, rats were randomly selected from each group for X-ray and Micro-computed tomography (Micro-CT) examinations to determine callus growth, immunofluorescence assay to detect the protein expression of light chain 3 II (LC3 II), immunohistochemistry to evaluate the autophagy level through detecting the expression of Beclin1 in rats, Western blotting assay to detect cell apoptosis in tissues, hematoxylin and eosin staining (HE staining) to evaluate the osteoblastic activity through count of osteoblast in bone tissue at the end of fracture, and measure the expression of vascular endothelial growth factors (VEGF).

RESULTS

Significant increases were seen in protein expression of cells in bone tissues at the end of fracture. In rapamycin group, callus formation and calcification level in rats were all higher than those in control group; compared with control group, for rats in rapamycin group, cell autophagy was significantly elevated in bone tissues, while cell apoptosis at the end of fracture was reduced with a significant increase in osteoblastic activity. The expression of VEGF in rapamycin group was higher than that in control group.

CONCLUSIONS

Rapamycin can facilitate fracture healing through inducing cell apoptosis and suppressing cell apoptosis in bone tissues.

Biomechanical comparison of a 3.5-mm conical coupling plating system and a 3.5-mm locking compression plate applied as plate-rod constructs to an experimentally created fracture gap in femurs of canine cadavers

OBJECTIVE To compare stiffness and resistance to cyclic fatigue of two 3.5-mm locking system plate-rod constructs applied to an experimentally created fracture gap in femurs of canine cadavers. SAMPLE 20 femurs from cadavers of 10 mixed-breed adult dogs. PROCEDURES 1 femur from each cadaver was stabilized with a conical coupling plating system-rod construct, and the contralateral femur was stabilized with a locking compression plate (LCP)-rod construct. An intramedullary Steinmann pin was inserted in each femur. A 40-mm gap then was created; the gap was centered beneath the central portion of each plate. Cyclic axial loading with increasing loads was performed. Specimens that did not fail during cyclic loading were subjected to an acute load to failure. RESULTS During cyclic loading, significantly more LCP constructs failed (6/10), compared with the number of conical coupling plating system constructs that failed (1/10). Mode of failure of the constructs included fracture of the medial or caudal aspect of the cortex of the proximal segment with bending of the plate and pin, bending of the plate and pin without fracture, and screw pullout. Mean stiffness, yield load, and load to failure were not significantly different between the 2 methods of stabilization. CONCLUSIONS AND CLINICAL RELEVANCE Both constructs had similar biomechanical properties, but the conical coupling plating system was less likely to fail than was the LCP system when subjected to cyclic loading. These results should be interpreted with caution because testing was limited to a single loading mode.

Physeal Fractures in Foals

Physeal fractures are common musculoskeletal injuries in foals and should be included as a differential diagnosis for the lame or nonweightbearing foal. Careful evaluation of the patient, including precise radiographic assessment, is paramount in determining the options for treatment. Prognosis mostly depends on the patient's age, weight, and fracture location and configuration.

Diagnosis and Treatment Considerations for Nonphyseal Long Bone Fractures in the Foal

Many long bone fractures that are not considered repairable in the adult horse are repairable in the foal. This is largely because of reduced patient size and more rapid healing in the foal. When there is no articular communication, the long-term prognosis for athletic function can be very good. Emergency care and transport of the foal with a long bone fracture is different than the adult.

In vitro biomechanical comparison of a newly designed interlocking nail system to a standard DCP. Testing of cat femora in an osteotomy gap model

OBJECTIVE

To describe a newly designed interlocking nail system (Targon® Vet System, TVS) tested in a model of diaphyseal femoral fractures in cats.

MATERIAL AND METHODS

Introduction of the TVS and presentation of the system components. Evaluation of application range and biomechanical testing of the TVS in cadaver bones under cyclic loading until fatigue failure occurred. The first two test groups compared the influence of implantation and immediate removal of the TVS locking bolts and six holes created by 2.0 mm cortical screws on the stability of feline femora. In the third group the two fixation systems were compared to each other with implants in place in an osteotomy gap model. The failure mode was statistically compared for each group (p < 0.05).

RESULTS

Femora after implantation and removal of the bolts of the TVS were significantly stiffer than after implantation and removal of the six 2.0 mm cortical screws. In the osteotomy gap model, femora with the TVS in place failed some- what later, but not statistically significant, than the opposite femur of the same cat with the 2.0 8-hole DCP in place.

CONCLUSION AND CLINICAL RELEVANCE

Using this testing method, stability of the TVS seems to be biomechanically comparable to conventional osteosynthesis plate systems. Therefore the TVS may be an encouraging alternative to conventional osteosynthesis systems in diaphyseal fractures, offering several advantages without the need for extensive specialized equipment.

[Calcium deficiency: a problem in growing and adult dogs: two case reports]

Two case reports demonstrate the consequences of a deficient calcium supply in dogs. The first case describes an adult dog with a history of food allergy. The dog had been fed with an unbalanced elimination diet (no minerals and vitamins supplemented) over many years and was referred with the diagnosis of osteomalacia (rubber jaw) for optimization of his ration. The second case refers to a puppy which was fed a homemade diet without supplementing the missing minerals and vitamins and suffered a femur fracture after moderate physical impact. In both cases, the computer-aided ration calculation showed a suboptimal to severely deficient supply for several minerals and vitamins, in particular calcium whereas serum calcium levels were normal. Both dogs recovered after being fed a complete and balanced diet. In conclusion, a survey of the feeding using ration calculation is essential especially in the case of potential nutrition-related skeletal disorders. Serum calcium levels cannot be used as a tool to diagnose nutritional calcium deficiency.

Tubular anomalous bones found in both thighs of a long-tailed macaque (Macaca fascicularis)

Tubular anomalous bones were found in both thighs of a 6-year-old male long-tailed macaque (Macaca fascicularis) bred in captivity. The bones had jagged ends and protruded from the skin. Radiographs showed that they developed in the femurs at the middle and elongated. They were removed with surgery under anesthesia. Histological analysis revealed that these bones had the same histological structure as the femur, though they were composed of primary and secondary osteon regions. This finding indicated that the new bones developed from the old bone piece(s), acquired a tubular shape, and elongated. It is suggested that the anomalous bones were produced not by the congenital deformity but by regeneration from fragments of the fractured femur that were embedded in the bone marrow; these acquired a tubular pattern and elongated.

[Treatment of long bone fractures in 125 newborn calves. A retrospective study]

OBJECTIVES

Retrospective study of the causes, location, configuration, treatment and outcome of long bone fractures in newborn calves.

MATERIAL AND METHODS

The medical records of 125 calves presented during a 16-year period because of fracture of the humerus (3 calves), radius/ulna (14), femur (50) or tibia (58) were evaluated. The majority of calves (61.6%) sustained the fractures during assisted delivery. Of 125 calves, 107 were treated and 18 were euthanized because of concurrent diseases. Conservative treatment was used in 16 calves and surgical treatment in 91. Four of the latter were euthanized because of muscle contraction which prevented fracture reduction, and five others died in surgery.

RESULTS

Fracture healing occurred after conservative treatment in 10 of 16 calves and after surgical treatment in 44 of 82 calves. The outcome was better in calves with plate and clamp-rod internal fixation (37/58 healed) than with intramedullary pinning (4/16 healed) or external fixation (3/8 healed). There were significant associations (chi2-test, p<0.01) between concurrent diseases and choice of therapy and fracture healing. Of 67 calves that developed complications, only 26 could be cured. Common complications were implant loosening and instability, which were often followed by osteomyelitis and sepsis. Implants were removed in 39 of 44 surgically treated calves that survived up to 6 months postoperatively. Long-term follow up (> 6 months postoperatively) by clinical and radiographic re-examination (25 calves) or telephone inquiry (29 calves) revealed that 54 animals were sound and had returned to their intended use.

CONCLUSIONS AND CLINICAL RELEVANCE

The treatment of long bone fractures in newborn calves remains difficult because of a high incidence of complications. These are most likely attributable to trauma during delivery, which results in insufficient colostrum intake and predisposes to concurrent diseases. In addition, the characteristics of juvenile bones do not provide sufficient physical strength for implants. Therefore, professional and diligent assistance during forced extraction, particularly in presentations with "stifle lock" or "hip lock", is required to minimize the incidence of long bone fractures in newborn calves. Most cases require surgical fixation, which is time consuming, expensive and carries a guarded prognosis.

Pathologic fracture of the femur due to endometrial adenocarcinoma metastasis in a female pet rabbit (Oryctolagus cuniculi)

This case report describes the clinical, pathomorphological and histopathological findings in a 12-year-old female pet rabbit with a pathologic fracture of the femur due to a metastasising endometrial adenocarcinoma. The animal was presented due to a history of right hindlimb lameness and inappetence. A fracture of the right femur with adjacent lyric bone lesions was detected by clinical and X-ray examination. Necropsy and histopathology revealed an endometrial adenocarcinoma with metastasis to the right femoral bone, resulting in the pathologic fracture. In both locations, tumour cells were immunohistochemically positive for pan-cytokeratin. Additionally, the animal suffered from an Encephalitozoon cuniculi infection which manifested itself in a multifocal granulomatous encephalitis and bilateral chronic inflammatory lesions in the kidneys.The report shows that in case of bone fractures in female pet rabbits the possibility of a pathologic fracture due to metastasising endometrial adenocarcinoma has to be considered.

Epidemiological investigation of femoral fractures in market pigs and the associated economic implications

The cause of an increased number of femoral fractures in market pigs from a single producer is described. Blood chemical, bone ash, radiographic, and feed analyses revealed that the fractures were caused by insufficient calcium in the diet. Associated economic and welfare implications are discussed.

Evaluation of a short glass fibre-reinforced tube as a model for cat femur for biomechanical testing of orthopaedic implants

The biomechanical testing of tubes made of third generation short glass fibre-reinforced (SGFR) material approximating cat femurs was performed in order to determine their suitability as cat femur surrogates for the biomechanical testing of orthopaedic implants. The tubes were tested in compression, three-point bending, notch testing, and screw pullout. Thin walled (B1-tubes) had a 13% lower maximum load to failure, a 19% higher maximum strength and a 13% lower elastic modulus compared to cat femurs tested in compression. B1-tubes maximum load to failure in three-point bending and screw pullout strength were considerably lower compared to cat femurs (29% and 63%, respectively). Notch testing was not performed on B1-tubes due to low bending strength. Thicker walled (B2-tubes) had a 23% higher maximum load to failure, a 10% higher maximum strength and a 21% lower elastic modulus compared to cat femurs tested in compression. The comparison of B2-tubes and cat femurs in three-point bending revealed a 7% increase in maximum load to failure for the B2-tubes. Drilled B2-tubes (notch testing) were weaker with a 30% lower load to failure compared to cat femurs. A screw pullout comparison of B2-tubes and cat femurs revealed a 2% increase in maximum load to failure for the B2-tubes. These tubes were intended to provide a model as a suitable surrogate for cat femurs for testing the bending strength of various orthopaedic constructs involving plates and screws. Testing revealed that third generation SGFR tubes were not suitable for these purposes and emphasizes the need to carefully evaluate the suitability of any model.

Use of extensible internal device in the femur of young dogs

An extensible internal device (EID) was developed to preserve growth plate during the treatment of fracture complications or segmental bone loss from tumour resection in children. Since this type of extensible, transphyseal, internal fixation device has only been used in a few paediatric cases; the aim of this study was to evaluate an in vivo canine study, a surgical application of this device, and its interference with longitudinal growth of the non-fractured distal femur. Ten clinically healthy two- to three-month-old poodles weighing 1.5-2.3 kg were used. Following a medial approach to the right distal femur, one extremity of the EID, similar to a T-plate, was fixed in the femoral condyle with two cortical screws placed below the growth plate. The other extremity, consisting of an adaptable brim with two screw holes and a plate guide, was fixed in the third distal of the femoral diaphysis with two cortical screws. The EID was removed 180 days after application. All of the dogs demonstrated full weight-bearing after surgery. The values of thigh and stifle circumferences, and stifle joint motion range did not show any difference between operated and control hindlimbs. The plate slid in the device according to longitudinal bone growth, in all but one dog. In this dog, a 10.5% shortening of the femoral shaft was observed due to a lack of EID sliding. The other dogs had the same longitudinal lengths in both femurs. The EID permits longitudinal bone growth without blocking the distal femur growth plate if appropriately placed.

Unifocal internal and external bone lengthening with circular external skeletal fixator in 5 dogs

The purpose of this study was to investigate the effectiveness of treatment of long bone defects and extremity shortness in 5 dogs using circular external skeletal fixator. In one case a bone necrosis and osteomyelitis shortened radius by 7.0 cm; however in others extremity shortening between 3.0 and 6.0 cm affected radius-ulna or tibia. 2 or 3 rings of 80.0-100.0 mm diameters, and 3 rods were used as a circular external skeletal fixator. The distractions at the rate of 0.5 mm X 2 times/day were performed following a latent period of 3 days after the corticotomy. Unifocal internal lengthening for case 1 and unifocal external lengthening for the others were performed. Distraction was performed between 30 and 70 days (mean 50 days). It was noted that the circular external skeletal fixator was well-tolerated in all cases. The first usages of limbs in all cases were on postoperative day between 8 and 43 (mean 22 days). The radiographic follow-up examinations revealed a complete consolidation on postoperative day between 35 and 75 (mean 55.6 days). The fixators were removed on the postoperative day between 45 and 85 (mean 65 days). The treatment was successful in restoring the appropriate length of the limbs. After removing the fixator, functional and cosmetic results were graded as excellent in 3 cases, good in one case and fair in one case.

Comparison of analgesic efficacy of preoperative or postoperative carprofen with or without preincisional mepivacaine epidural anesthesia in canine pelvic or femoral fracture repair

OBJECTIVE

To compare analgesic efficacy of preoperative versus postoperative administration of carprofen and to determine, if preincisional mepivacaine epidural anesthesia improves postoperative analgesia in dogs treated with carprofen.

STUDY DESIGN

Blind, randomized clinical study.

ANIMALS

Dogs with femoral (n=18) or pelvic (27) fractures.

METHODS

Dogs were grouped by restricted randomization into 4 groups: group 1 = carprofen (4 mg/kg subcutaneously) immediately before induction of anesthesia, no epidural anesthesia; group 2 = carprofen immediately after extubation, no epidural anesthesia; group 3 = carprofen immediately before induction, mepivacaine epidural block 15 minutes before surgical incision; and group 4 = mepivacaine epidural block 15 minutes before surgical incision, carprofen after extubation. All dogs were administered carprofen (4 mg/kg, subcutaneously, once daily) for 4 days after surgery. Physiologic variables, nociceptive threshold, lameness score, pain, and sedation (numerical rating scale [NRS], visual analog scale [VAS]), plasma glucose and cortisol concentration, renal function, and hemostatic variables were measured preoperatively and at various times after surgery. Dogs with VAS pain scores >30 were administered rescue analgesia.

RESULTS

Group 3 and 4 dogs had significantly lower pain scores and amount of rescue analgesia compared with groups 1 and 2. VAS and NRS pain scores were not significantly different among groups 1 and 2 or among groups 3 and 4. There was no treatment effect on renal function and hemostatic variables.

CONCLUSIONS

Preoperative carprofen combined with mepivacaine epidural anesthesia had superior postoperative analgesia compared with preoperative carprofen alone. When preoperative epidural anesthesia was performed, preoperative administration of carprofen did not improve postoperative analgesia compared with postoperative administration of carprofen.

CLINICAL RELEVANCE

Preoperative administration of systemic opioid agonists in combination with regional anesthesia and postoperative administration of carprofen provides safe and effective pain relieve in canine fracture repair.

Ultrasonographic assessment of fracture healing after plate osteosynthesis

The goals of this study were to assess the ability of ultrasonography (US) to assess uncomplicated fracture healing and to establish normal images. Twenty-two dogs, ranging in age from 6 to 180 months were studied. Body weight ranged from 2.2 to 60 kg. All fractures were treated by plate osteosynthesis. US (B-mode and power Doppler) and radiography were performed until both were consistent with complete healing. B-mode US was performed in all dogs, and power Doppler US in 14. Fracture healing was judged to be complete based on US earlier than when based on radiography. The tissue immediately adjacent to the plate appeared vascularized on power Doppler images at a time when the tissue at the fracture site had a negative power Doppler exam. US appears useful for assessment of primary fracture healing and power Doppler was useful for detecting vascularization at the fracture site in nonhealed fractures. Power Doppler interrogation should be performed away from any metal implant, as a result from an interrogation adjacent to an implant will not reflect actual vascularization at the fracture site.

Retrograde placement of a novel 3.5 mm titanium interlocking nail for supracondylar and diaphyseal femoral fractures in cats

Twenty-four simple or comminuted supracondylar and diaphyseal femoral fractures in cats, which had been treated by retrograde insertion of a new 3.5 mm titanium interlocking nail (IN) from the intercondylar notch, were evaluated between June 2000 and October 2004 at the Ecole Nationale Vétérinaire d'Alfort. Patient data (species, breed, weight, and age), fracture characteristics, details of the surgery, post-operative complications and radiographic follow-up were recorded. The mean body weight was 3.75 kg and the cats ranged in age between four and 66 months (mean 29 months). The IN had a diameter of 3.5 mm and a length of 100, 109 or 119 mm, and were all fixed in a static position (two screws in seven cats, three screws in 10 cats and four screws in seven cats). Cerclage wires were used in seven cats and an autogenous bone graft was used in two cats. Screw or nail breakage were not recorded. Nineteen fractures healed without any complications, three cats died during the post-operative period from unknown causes, and two cats showed delayed bone healing. Twenty cats were considered to have an excellent limb function at one month. One cat with a sciatic injury was non-weight bearing for several months. Radiographic signs of degenerative joint disease of the stifle joint were not observed except in the cat with the sciatic nerve injury. The results of this study suggest that this new 3.5 mm titanium IN can be introduced from the intercondylar notch and be used in static fixation mode to stabilize supracondylar and diaphyseal femoral fractures in cats.

Management of fractures of the long bones of eight cats using external skeletal fixation and a tied-in intra-medullary pin with a resin-acrylic bar

CASE HISTORY AND CLINICAL FINDINGS

Eight feline patients with fractures of the femur, tibia or humerus were presented non-weight-bearing, with varying degrees of soft tissue and concurrent injury. Five fractures were comminuted, two were open fractures and there was one malunion.

TREATMENT

Fracture repair was performed in each case using a low-cost resin-acrylic external skeletal fixator (ESF). An open, limited open, or 'open but do not touch' (OBDNT) approach allowed intra-medullary (IM) pinning of the major fragments, establishing axial alignment and countering bending stress. Application of a unilateral, uniplanar (Type IA) ESF using small diameter half-pins provided stabilisation against rotational and compressive forces. The half-pins and IM pin (tied-in) were incorporated into a composite bar with the resin-acrylic. The single humeral construct incorporated a transcondylar pin into a Type I-II design.

RESULTS

Seven cats, including all five comminuted fractures, had uncomplicated fracture healing. Median time to complete removal of the construct was 7 (range 5-12) weeks. In the eighth cat, an open fracture developed into a non-union, which required revision with a plate and bone graft. This cat and six others available for follow-up (median 6 months) were reported by their owners to enjoy normal activity. Two had a mild, intermittent lameness, one had a mild but persistent lameness, and four were sound. Six out of seven owners rated the appearance of their pet's limb as normal.

CLINICAL RELEVANCE

The resin-acrylic ESF/tied-in IM pin construct was versatile and lightweight and allowed even highly comminuted non-load-sharing fracture configurations to be stabilised successfully using a biological strategy. Failure of the pin/acrylic interface did not occur and the frames provided sufficient strength as evidenced by healing without failure of the bar in these cases. A resin-acrylic ESF construct is inexpensive and affords the occasional orthopaedist the means to provide rotational stability when IM pinning has been used as the primary mode of fracture repair for short-oblique and transverse fractures. An extensive and costly clamp/bar inventory is not required, and there is greater flexibility for the orientation and placement of fixation pins than allowed by traditional linear bar systems.

Clinical application of recombinant human bone morphogenetic protein-2 in 4 dogs

OBJECTIVE

To describe outcome in dogs with insufficient bone healing treated with recombinant human bone morphogenetic protein-2 (rhBMP-2).

STUDY DESIGN

Retrospective study.

ANIMALS

Four dogs clinically affected with delayed union or nonunion bone healing.

METHODS

Medical records were reviewed for signalment, clinical problem, treatment, and outcome.

RESULTS

Four dogs that had delayed- or nonunion of bone fracture, osteotomy, or arthrodesis were treated with either minimally invasive, fluoroscopically guided, percutaneous administration or direct surgical application of rhBMP-2. Doses used ranged from 0.2 to 1.6 mg of rhBMP-2. In 3 dogs, a calcium phosphate matrix (CPM) carrier was used whereas in 1 dog commercially prepared rhBMP-2 impregnated in an absorbable collagen sponge (INFUSE Bone Graft) was used. This latter dog had osteomyelitis associated with implant infection before rhBMP-2 administration. Rapid radiographic union was noted in all dogs with excellent long-term outcome. Adverse effects were minimal and included transient worsening of lameness after percutaneous administration of rhBMP-2 in 2 dogs.

CONCLUSIONS

rhBMP-2 stimulated rapid bone formation at delayed- or nonunion sites resulting in radiographic bone union with minimal adverse effects and excellent long-term outcome in 4 dogs.

CLINICAL RELEVANCE

Direct intraoperative administration or fluoroscopically guided, minimally invasive delivery of rhBMP-2 may be an effective treatment modality for bone delayed- or nonunions and could potentially be used to stimulate new bone production in a variety of orthopedic surgical conditions in dogs.

Surgical repair of femoral fractures in New World camelids: five cases (1996?2003)

Five New World camelids were admitted to the Western College of Veterinary Medicine between 1996 and 2003 for evaluation of femoral fractures. There were three alpacas and two llamas. Four of the animals were female and three were less than 3 months of age. Fracture configurations consisted of distal physeal fractures (three), a comminuted diaphyseal/metaphyseal fracture, and a transverse diaphyseal fracture. Fractures were diagnosed with a combination of physical examination and radiographs in all cases. All five fractures were repaired with internal fixation and three animals were discharged from the hospital with fractures that healed. One cria underwent successful internal fixation but died from pulmonary oedema during recovery from anaesthesia. Postoperative complications were rare and limited to inadequate fracture stability in one alpaca and prolonged recovery to weight bearing in another. One llama with a comminuted metaphyseal fracture, repaired with a 4.5 mm dynamic compression plate, subsequently had catastrophic failure of the bone 17 days after surgery. Overall the clients were pleased with the outcome of discharged animals. Although femoral fractures are considered rare, they pose a unique opportunity for the large animal veterinarian to successfully achieve fracture union with the aid of internal fixation.

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.

Suspect osteogenesis imperfecta in a male kitten

A 4.5-month-old, male domestic shorthair was presented with bilateral femoral fractures after falling from a low height. Radiographs revealed reduced radio-opacity and thin cortices of all long bones. A presumptive diagnosis of osteodystrophy, secondary to osteogenesis imperfecta, was made on postmortem examination.

Treatment of femoral and tibial fractures in puppies by elastic plate osteosynthesis. A review of 17 cases

Seventeen puppies, two to four months old, with a femoral (n = 12) or tibial (n = 5) diaphyseal fracture were treated by elastic plate osteosynthesis with a Veterinary Cuttable Plate (VCP) or straight plate. In one case of femoral fracture treated with a VCP, plate bending due to an excessive elasticity of the implant was observed three days after the osteosynthesis and surgical revision was required. Two cases of femoral overgrowth and one case of slight femoral head and neck retroversion were identified during the radiographic follow-up but without any clinical consequences. Bone healing was obtained for all fractures four to eight weeks (5.64 +/- 0.88 weeks) after the surgical procedure, and functional results were excellent in all cases. Our study confirms that elastic plate osteosynthesis with either a VCP or straight plate can be used to treat femoral diaphyseal fractures in medium and large breed puppies less than four months old, but that modification of implant elasticity or rigid osteosynthesis use is required when such puppies reach four months. The same technique can also be used successfully to treat tibial fractures in puppies younger than four months old.

Comminuted long bone fractures in cats caused by pneumatic gun shot and repaired using the external fixator "tie-in" technique

Five cats with femoral fractures caused by pneumatic gun shot wounds were treated using intramedullary pin/external skeletal fixation "tie-in" (IM/ESF tie-in) technique between 1997 and 2005. Clinical and radiographical examinations were used to assess bone healing, limb function recovery and complications. Clinical results as well as fracture healing were excellent in all five cats. The study showed that the IM/ESF tie-in technique can be used in cats for the treatment of comminuted femoral fractures caused by pneumatic bullets.

Rod-through-plate fixation of canine diaphyseal fractures

Efficacy of the rod-through-plate fixation for fracture repair was evaluated in six clinical cases of canine long bone fractures. This fixation incorporates principles of intramedullary and extramedullary osteosynthesis for transverse and short oblique fractures of long tubular bones. The plate-through-rod device is comprised of one pair of curved rods, a connecting plate and two bone screws. The connecting plate has both a hole and a channel on each end. Curved rods have a long curved part and a straight part with a hole in it for screw fixation. All components are made up of medical stainless steel. Clinical and radiographical examinations were performed from week seven to18 months after the operation. Functional abnormalities were not observed at this period in five patients and all fractures were healed. In one patient screw stripping in the proximal fragment of the femur was detected radiologically and minimal implant dislocation was noted at seven weeks after the initial repair. The rod-through-plate fixation method gives strong fixation of bone fragments with minimal traumatization of soft tissue during the operation. The design of the rod-through-plate is intended to reduce pressure of the plate on the cortex in the area of the fracture, whereas the dynamic fixation provided by the intramedullary rods may allow micromotion, thus stimulating callus formation and avoiding implant-induced osteoporosis.

CLINICAL RELEVANCE

The rod-through-plate fixator has a simple construction and its use expands the treatment possibilities for diaphyseal fractures of long bones.

Clinical evaluation of the CRIF 4.5/5.5 system for long-bone fracture repair in cattle

OBJECTIVE

To report clinical evaluation of the clamp rod internal fixator 4.5/5.5 (CRIF 4.5/5.5) in bovine long-bone fracture repair.

STUDY DESIGN

Retrospective study.

ANIMALS

Cattle (n=22) with long-bone fractures.

METHODS

Records for cattle with long-bone fractures repaired between 1999 and 2004 with CRIF 4.5/5.5 were reviewed. Quality of fracture repair, fracture healing, and clinical outcome were investigated by means of clinical examination, medical records, radiographs, and telephone questionnaire.

RESULTS

Successful long-term outcome was achieved in 18 cattle (82%); 4 were euthanatized 2-14 days postoperatively because of fracture breakdowns. Two cattle had movement of clamps on the rod. Moderate to severe callus formation was evident in 11 cattle 6 months postoperatively.

CONCLUSIONS

Movement of clamps on the rod was recognized as implant failure unique to the CRIF. This occurred in cattle with poor fracture stability because of an extensive cortical defect. The CRIF system may not be ideal to treat metacarpal/metatarsal fractures because its voluminous size makes skin closure difficult, thereby increasing the risk of postoperative infections.

CLINICAL RELEVANCE

CRIF cannot be recommended for repair of complicated long-bone fractures in cattle.

Ex vivo comparison of one versus two distal screws in 8 mm model 11 interlocking nails used to stabilize canine distal femoral fractures

OBJECTIVE

To compare the structural properties of an 8 mm model 11 interlocking nail (IN) with 2 proximal and 2 distal screws (2/2) to 2 proximal and 1 distal screws (2/1) in an unstable canine fracture model.

STUDY DESIGN

Ex vivo biomechanical investigation.

SAMPLE POPULATION

Eight pairs of adult canine femurs.

METHODS

A simple transverse distal metaphyseal femoral fracture with a 1 cm gap was created. The unstable fracture in 1 femur was repaired with a nail with 2 distal and 2 proximal screws and the paired femur with a nail with 1 distal and 2 proximal screws. Cyclic mechanical testing in torsion was performed to assess fatigue life, peak torque, stiffness, and mode of failure.

RESULTS

All 2/1 IN-femoral constructs, but only 2 of eight 2/2 constructs, failed before completion of 50,000 loading cycles. The 2/2 constructs had significantly greater peak torque to failure (P = .002) and longer fatigue life (P = .00003) compared with 2/1 constructs. There were no significant differences in stiffness between 2/2 and 2/1 constructs when the non-failed constructs were compared (P > .5). All constructs failed by screw deformation.

CONCLUSIONS

An 8 mm model 11 IN used for fixation of unstable canine distal femoral fractures has a longer fatigue life and is stronger under torsional loads when 2 rather than 1 distal screws are placed.

CLINICAL RELEVANCE

When repairing unstable canine distal femoral fractures with an IN system, 2 distal screws should be inserted to avoid catastrophic implant failure before bone healing is achieved.

Power Doppler assessment of the neovascularization during uncomplicated fracture healing of long bones in dogs and cats

The aims of this prospective study were to test the feasibility of assessing neovascularization with power Doppler ultrasonography and to investigate its usefulness to follow fracture healing of long bones in dogs and cats. A total of 51 patients (44 dogs and seven cats) were followed. Fracture types differed from simple to comminuted. Therapy ranged from external coaptation to plate osteosynthesis. Patients were followed with radiography, B-mode real time and power Doppler ultrasonography every 2-4 weeks until the fracture was healed. All fractures healed uneventfully. A semi-quantitative numerical score based on signal intensity, vessel area, and number of Doppler signals was assigned and the mean value was used to compare patients and examinations. Time postoperatively was divided into periods of 10 days. No Doppler signal was present during the first 10 days. The mean of the scores was highest between 11 and 20 days postoperatively and the median of the scores peaked between 21 and 30 days. A gradual decrease was seen thereafter. The mean of the scores was zero at 71-80 days and the median at 51-0 days postoperatively for the grouped results. In all positive power Doppler examinations, signals were present in and close to the callus. In seven patients (five dogs and two cats) signals were also present in the peripheral soft tissues in one of the follow up examinations. The normal healing process of fractured bones can be visualized using power Doppler ultrasonography and follows a distinctive time-dependent pattern.

Experimental use of polyamide bands in combination with intramedullary pinning for repair of oblique femoral fractures in rabbits

OBJECTIVE

To evaluate the use of polyamide bands, manufactured for securing electrical cables, for repair of oblique femoral fractures in rabbits.

STUDY DESIGN

Experimental study.

ANIMALS

Twelve nulliparous, 21-25-week-old, California female rabbits.

METHODS

Rabbits were divided into 3 groups (n=4) and studied for 14, 28, or 56 days. A Z-shaped mid-diaphyseal femoral osteotomy was repaired with a 2.5 mm intramedullary pin and a polyamide 6.6 cerclage band. Healing was evaluated at intervals by physical examination, limb use, femoral radiographs, and callus histology.

RESULTS

Rabbits had early limb use with good wound healing. From the 1st day, movement of the hip and stifle joints was satisfactory. Radiographically, fractures were healed at 28 days. Histologically, there was no foreign body reaction and bone healing was normal.

CONCLUSION

Nylon cerclage band application was accomplished easily, maintained reduction, and resulted in good healing and limb use.

CLINICAL RELEVANCE

Sterilized nylon bands, manufactured for electrical use, can be used for cerclage in rabbits.

Ultrasonographic and Radiographic Assessment of Uncomplicated Secondary Fracture Healing of Long Bones in Dogs and Cats

OBJECTIVES

To evaluate the use of ultrasonography (US) to detect bone healing in uncomplicated diaphyseal fractures of dogs and cats, and to compare these observations with detection of healing by radiography (RG).

STUDY DESIGN

Clinical study.

ANIMALS

Dogs (33) and cats (11).

METHODS

RG and brightness mode US were used to follow uncomplicated secondary fracture healing. Fractures were examined at admission and then every 2-4 weeks until healed or implant removal. Temporal differences in definitive detection of healed fracture by imaging technique were examined by species, patient age, bone, and fracture type.

RESULTS

US images obtained during uncomplicated secondary fracture healing were consistent with images of fracture healing described in humans. Mean time to US diagnosis of a healed fracture (mean 46 days) was significantly shorter than by RG (mean 66 days). Mean time until diagnosis of a healed fracture (US and RG) did not differ significantly between open and closed treatment. Patients </=7 months (n=9) healed significantly faster (P<.05) than animals aged 7-36 months (n=24) and animals >36 months (n=11), but there was no significant difference between the latter 2 groups. Diagnosis of a healed simple fracture by US was significantly quicker than for a comminuted fracture (P<.05), but no difference was noted when using RG.

CONCLUSIONS

US can be used to evaluate secondary fracture healing in biologically treated fractures in dogs and cats. US permits detection of a healed fracture earlier than RG.

CLINICAL RELEVANCE

Earlier diagnosis of a healed fracture by US can prevent unnecessarily long limb immobilization and allow earlier dynamization.

[Placebo-controlled blinded study of postoperative pain therapy with carprofen and levomethadone in dogs with fractures]

It was the aim of this placebo-controlled study to evaluate the analgesic efficacy of the NASAID carprofen and the pure m-agonist levomthadone over a five-day postoperative evaluation period in dogs with fractures of the humerus or the femur (n = 30). Pain and sedation evaluation was carried out with a visual analogues system (VAS) and with the aid of a numerical estimation scale(NRS). The degree of lameness, the pain treshhold, the glucose and cortisol concentration curves as well as the respiration and heart rate and the systolic blood pressure were used as further pain indicators and to identify drug side effects. The levomethadon group displayed the lowest degree of pain on postoperative examination on the first day. On days 2 to 5, the carprofen group showed the lowest degree of pain in comparison to the placebo group. The levomethadon- and the carprofen group showed no statistically proven differences from day 2 on. Due to great variations in the pain scores and comparatively high median pain score especially on the first day of this study, the efficacy of all analgesics evaluated here must be regarded as insufficient in many cases. Only the parameter nociceptive pain treshhold showed a little, the degree of lameness, the glucose and cortisol levels showed no close correlation to the VAS and NRS pain scores and were therefore of little usefulness as postoperative pain indicators. No relevant clinical side effects caused by the used analgesics were detected in the kidney, the liver, the gastrointestinal tract and the circulatory system in this study. Rather, traumatically induced elevation of enzyme levels improves or normalised until the 5th day of the study. In addition, no negative effect on wound healing was noted, especially for carprofen. Therefore, the evaluated analgesics seems to be adequate for postoperative pain therapy also in fracture patients (trauma patients). However, the efficacy of all analgesics evaluated here must be regarded as insufficient in many cases.

Biomechanical evaluation of a veterinary suture anchor in the canine cadaver pelvis and femur

A commercially available veterinary suture anchor was tested in the acetabula and femurs of canine cadavers. Size #2 suture anchor constructs were compared to a traditional screw and Teflon spiked washer constructs in a model of coxofemoral luxation repair. The screw/washer constructs failed at a higher maximum load than the #2 anchor constructs. In the acetabulum, significant differences in strength were also found in the position of the implant and in the direction of pull. The constructs in a more caudal position, and constructs pulled 90 degrees to the axis of insertion, failed at higher loads. The predominant mode of failure of the constructs was a suture failure. In the femur, size #5 suture anchors were used in a model of cranial cruciate ligament repair and collateral ligament repair. The anchor constructs failed predominantly by anchor pull-out in the distal femur. The constructs pulled 90 degrees to the axis of insertion were stronger than construcs pulled at 0 degrees to the axis of insertion. Varying the location of the implant in the femur did not affect the maximum load to failure.

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.

Interlocking nail treatment of long-bone fractures in cats: 33 cases (1995-2004)

A retrospective study between 1995 and 2004 of fracture repair in cats (n = 46) using interlocking nails (ILN) was made. Only the cases in which clinical and radiographic examination of bone healing were available are included. Five humeral and twenty eight femoral fractures were reviewed. Multiple-hole interlocking nails (MH-ILN) were used in 22 fractures, with the four-hole model (FH-ILN) in the remaining cases. In three of the cases, the FH-ILN was transformed to a three-hole model by cutting the nail between the two most distal holes. The average length of humeral ILN was 78.8 mm, and the femoral ILN was 97.2 mm. Static fixation was performed in 27 cases, with dynamic fixation in the remaining. The medullary canal filling was 100% in both radiographic views in 16 cases. Intra-operative complications were encountered in two cases. A total number of 76 screws were inserted, with 5.26% of them being malpositioned. Malunion, in a deformed femur, and partial unscrewing of one screw were the only radiographic complications observed at the time of follow-up. The clinical outcome, as well as fracture healing, were excellent in all of the cases. The results of this study indicate that the 4.0 and 5.0 mm MH-ILN and FH-ILN can be used to repair simple or comminuted humeral and femoral fractures in cats.

Evaluation of healing in feline femoral defects filled with cancellous autograft, cancellous allograft or Bioglass

Cancellous bone grafting is a widely accepted technique in human and veterinary orthopaedic surgery. However, the use of autogenous bone graft is limited by the additional surgical time required to harvest the graft, the morbidity associated with the donor site, and the limited availability of cancellous bone, especially in feline patients. Various allografts and bone graft substitutes are available commercially but have not been fully evaluated for efficacy in the cat. The purpose of this study was to compare the incorporation of autogenous and allogenous cancellous bone graft and Bioglass, a synthetic bone graft substitute, in femoral defects in cats. Four (4.0 mm diameter) defects were created in the lateral diaphyseal cortex of the left femur with an orthopaedic drill. In each femur, one of the cortical defects was filled with autogenous cancellous graft (harvested from the tibia), one was filled with allogenic cancellous graft, and one was filled with Bioglass. The fourth defect remained unfilled. Graft incorporation within the femoral defects was evaluated by radiographic evaluation every two weeks. Six weeks after the grafting procedure, the cats were euthanatized and high detailed radiography, dual energy X-ray absorptiometry (DEXA), histopathology and histomorphometry of the defects were performed. Satisfactory bone healing was observed within all of the defects.

Slipped capital femoral epiphysis in dogs

In a retrospective review of 43 femoral fractures, three dogs had separation of the femoral capital epiphysis from the metaphysis in the absence of trauma. Two of these dogs also had evidence of pathology in the contralateral femoral neck including, in one dog, displacement of the capital epiphysis in relation to the metaphysis without actual separation. The case histories, radiographic features and histopathological findings of these cases were reviewed and compared with previous cases of slipped capital femoral epiphysis (SCFE) reported in dogs and also with SCFE in children. Pre-slip, acute, chronic and acute-on-chronic slips were Identified. Based on the cases reviewed, the authors advise internal fixation of stable slipped epiphyses in dogs. This may also be appropriate for unstable separations, although resorption of the femoral neck may preclude stable fixation and necessitate femoral head and neck excision.

An In Vitro Biomechanical Comparison of the Insertion Variables and Pullout Mechanical Properties of AO 6.5-mm Standard Cancellous and 7.3-mm Self-Tapping, Cannulated Bone Screws in Foal Femoral Bone

OBJECTIVE

To compare screw insertion variables and pullout mechanical properties between AO 6.5-mm cancellous and 7.3-mm cannulated bone screws in foal femoral bone.

STUDY DESIGN

A paired, in vitro mechanical study.

SAMPLE POPULATION

Seven pairs of femora from immature (1-7 months) foals.

METHODS

The 6.5 cancellous and 7.3-mm cannulated screws were inserted at standardized proximal and distal metaphyseal, and mid-diaphyseal locations. Insertion torque, force, and time to drill, tap (6.5-mm cancellous), guide wire insertion (7.3-mm cannulated), and screw insertion were measured. Screw pullout properties (yield and failure load, displacement, and energy, and stiffness) were determined from mechanical tests. The effects of screw type and location on insertion variables and pullout properties were assessed with repeated measures ANOVA. Pairwise comparisons were examined with post hoc contrasts. Significance was set at P<.05 for all comparisons.

RESULTS

Insertion torques for the 7.3-mm cannulated screws were significantly greater than for the 6.5-mm tap, but significantly lower than for the 6.5-mm cancellous screws. Total screw insertion times were similar. Pullout properties of both screws were similar at each femoral location. The holding power of both screws was significantly greater in the mid-diaphysis than in either metaphyseal location. Pullout failure occurred by bone shearing at the bone-screw interface in all specimens.

CONCLUSIONS

The 6.5-mm cancellous and 7.3-mm cannulated screws vary in insertion properties, but have similar pullout properties in the mid-diaphysis, proximal, and distal metaphysis of foal femora. Both screw types have greater holding power at the mid-diaphyseal location compared with metaphyseal locations. Based on overall similar holding powers of 6.5-mm cancellous and 7.3-mm cannulated screws, it is unlikely that increasing the screw diameter beyond 6.5 mm will provide increased holding power in foal femoral bone.

CLINICAL RELEVANCE

Use of the 7.3-mm cannulated screw should be considered for foal femoral fracture repair when greater accuracy is needed, or when bone threads for the 6.5-mm cancellous screw have been stripped.

Two Techniques for Supplementing Interlocking Nail Repair of Fractures of the Humerus, Femur, and Tibia: Results in 12 Dogs and Cats

OBJECTIVE

To describe 2 devices for improving stabilization of inadequately stabilized interlocking nail (ILN) repairs of the humerus, tibia, and femur in dogs and cats.

STUDY DESIGN

Prospective study.

ANIMALS

Twelve client-owned dogs and cats.

METHODS

Two devices to further stabilize ILN repair of inadequately stabilized diaphyseal fractures were developed. Device 1 was an axial extension for the ILN that was connected to a conventional type I external skeletal fixator (ESF) with a short connecting bar. Device 2 had hybrid ILN bolt/ESF pins that were used to lock the ILN and serve as the pins for a type I ESF. Devices were used at the initial surgery when the stability of ILN repair was considered inadequate based on palpable fracture segment movement, insufficient medullary canal filling of the ILN at the fracture site, or when the ILN was used in a buttress mode. Outcome was obtained by recheck examinations, radiography, and telephone interview.

RESULTS

Device 1 was applicable to fractures of the humerus and femur, but was not used for fractures of the tibia because the ILN extension would have interfered with the stifle. No gross loosening of the ILN/ESF extension connection to the ILN occurred. Device 2 was easily placed and used in the humerus, femur, and tibia. Device 2 allowed removal of the ILN interlock to one or both main fracture segments non-invasively. Clinically, both devices added stability compared with ILN repair alone. Both devices facilitated controlled destabilization of the fracture repair as healing progressed. Complications of pin tract infection, and premature hybrid bolt/ESF pin loosening resulting in premature ESF removal each occurred in 1 patient. Four of 28 hybrid ILN/ESF pins were grossly loose at 4- or 6-week postoperative recheck examinations. Outcomes were excellent (9), good (1), fair (1), and poor (1).

CONCLUSIONS

Inadequately stabilized ILN repair of fractures can be stabilized by use of either device, both of which also permit controlled destabilization of the repair during healing. Device 2 can be used when non-invasive removal of the ILN interlock is desired during healing.

CLINICAL RELEVANCE

These 2 devices should be considered as alternative methods for stabilization of inadequately stabilized ILN repairs in dogs and cats, or when controlled destabilization of an ILN fracture repair is desired.

Orthopedic clinical techniques femur fracture repair

Femur fractures occur commonly in cats and dogs following substantial trauma. Fractures of the femur may be categorized as capital physeal, femoral neck, trochanteric, subtrochanteric, diaphyseal, supracondylar or condylar or distal physeal. Most femur fractures are closed due to the heavy overlying muscle, unless due to a penetrating injury such as a gunshot wound. Femur fractures are generally not amenable to conservative repair, and some kind of internal fixation is generally required. Implant systems suitable for repair of femur fractures include bone plates, interlocking nails, plate-rod construct, lag screws, pins and wires and external fixators. Fractures may be repaired using anatomic reduction and rigid fixation or using the principles of biologic osteosynthesis. Biologic osteosynthesis is particularly effective for highly comminuted fractures because vascular supply and soft tissue attachments to bone fragments are preserved, speeding the formation of bone callus. Articular fractures should be anatomically reduced and rigidly stabilized to reduce the chance of progressive osteoarthritis.