Effect of Tibial Plateau Levelling Osteotomy on Cranial Tibial Subluxation in the Feline Cranial Cruciate Deficient Stifle Joint: An Ex Vivo Experimental Study.

OBJECTIVES: This study evaluated the effects of tibial plateau levelling osteotomy on cranial tibial subluxation and tibial rotation angle in a model of feline cranial cruciate ligament deficient stifle joint. METHODS: Quadriceps and gastrocnemius muscles were simulated with cables, turnbuckles and a spring in an ex vivo limb model. Cranial tibial subluxation and tibial rotation angle were measured radiographically before and after cranial cruciate ligament section, and after tibial plateau levelling osteotomy, at postoperative tibial plateau angles of +5°, 0° and -5°. RESULTS: Cranial tibial subluxation and tibial rotation angle were not significantly altered after tibial plateau levelling osteotomy with a tibial plateau angle of +5°. Additional rotation of the tibial plateau to a tibial plateau angle of 0° and -5° had no significant effect on cranial tibial subluxation and tibial rotation angle, although 2 out of 10 specimens were stabilized by a postoperative tibial plateau angle of -5°. No stabilization of the cranial cruciate ligament deficient stifle was observed in this model of the feline stifle, after tibial plateau levelling osteotomy. CLINICAL SIGNIFICANCE: Given that stabilization of the cranial cruciate ligament deficient stifle was not obtained in this model, simple transposition of the tibial plateau levelling osteotomy technique from the dog to the cat may not be appropriate.

Effect of tibial tuberosity advancement on cranial tibial subluxation in the feline cranial cruciate deficient stifle joint: An ex vivo experimental study.

The effects of Tibial Tuberosity Advancement (TTA) on Cranial Tibial Subluxation (CTS) and Tibial Rotation Angle (TRA) were evaluated in a model of feline Cranial Cruciate Ligament (CrCL)-deficient stifle joint. Ten hindlimbs of adult cats were used. Quadriceps and gastrocnemius muscles were simulated using cables, turnbuckles and a spring. An axial load of 30% body weight was applied. The stifle and talocrural joint angles were adjusted to 120°. Patellar tendon angle (PTA), CTS and TRA were measured radiographically before and after CrCL section, after TTA and after additional advancement by 1 and 2mm. CrCL section resulted in a CTS of 8.1±1.5mm and a TRA of 18.4±5.7 °. After TTA, PTA was significantly decreased from 99.1±1.7° to 89.1±0.7°; CTS and TRA did not change significantly (7.8±1.0mm and 15.9±5.7° respectively). Additional advancement of the tibial tuberosity by 1mm did not significantly affect CTS and TRA. Additional advancement of the tibial tuberosity by 2mm significantly reduced the PTA to 82.9±0.9°. A significant decrease of CTS (6.9±1.3mm) and TRA (14.7±3.6°) was also observed. A lack of stabilization of the CrCL deficient stifle was observed after TTA in this model of the feline stifle. Even though the validity of the model can be questioned, simple transposition of the technique of TTA from the cat to the dog appeared hazardous.

Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model. Two screws versus three screws per fragment.

OBJECTIVES: The number of locking screws required per fragment during bridging osteosynthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion. METHODS: Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure. RESULTS: The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing. CLINICAL SIGNIFICANCE: Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model.

OBJECTIVES: To compare the mechanical properties of locking compression plate (LCP) and limited contact dynamic compression plate (LC-DCP) constructs in an experimental model of comminuted fracture of the canine femur during eccentric cyclic loading. METHODS: A 20 mm mid-diaphyseal gap was created in eighteen canine femora. A 10-hole, 2.4 mm stainless steel plate (LCP or LC-DCP) was applied with three bicortical screws in each bone fragment. Eccentric cyclic loadings were applied at 10 Hertz for 610,000 cycles. Quasistatic loading / unloading cycles were applied at 0 and 10,000 cycles, and then every 50,000 cycles. Structural stiffness was calculated as the slope of the linear portion of the load-displacement curves during quasistatic loading / unloading cycles. RESULTS: No bone failure or screw loosening occurred. Two of the nine LCP constructs failed by plate breakage during fatigue testing, whereas no gross failure occurred with the LC-DCP constructs. The mean first stiffness of the LCP constructs over the course of testing was 24.0% lower than that of constructs stabilized by LC-DCP. Construct stiffness increased in some specimens during testing, presumably due to changes in bone-plate contact. The first stiffness of LC-DCP constructs decreased by 19.4% and that of locked constructs by 34.3% during the cycling period. A biphasic stiffness profile was observed: the second stiffness was significantly greater than the first stiffness in both groups, which allowed progressive stabilization at elevated load levels. CLINICAL SIGNIFICANCE: Because LCP are not compressed to the bone, they may have a longer working length across a fracture, and thus be less stiff. However, this may cause them to be more susceptible to fatigue failure if healing is delayed.

Dual mobility canine total hip prosthesis: implant characteristics and surgical procedure.

Prosthetic dislocation is one of the most common complications after canine hip replacement. The use of dual mobility acetabular components has been shown to reduce the rate of dislocation in first intent hip replacement in human patients who are at high risk for dislocation. In such implants, a mobile polyethylene liner articulates on one side with a metallic acetabular component and on the other side with a metallic prosthetic head. A dual mobility cemented acetabular component has been designed for use in dogs, and is available for use in association with a previously designed modular femoral component. This report describes the characteristics and the procedure for implantation of this implant combination.

Outcome and complications after dual mobility total hip replacement: fifty cases with a minimum of six months clinical and radiographic follow-up.

OBJECTIVES: To report the clinical and radiographic outcome of a canine total hip prosthesis with a dual mobility acetabular component, with a minimum of six months follow-up. METHODS: The outcome of dogs that underwent primary cemented unilateral dual mobility hip prosthesis surgery by one of the authors for hip dysplasia or trauma, and which had a minimum of six months clinical and radiologic follow-up, was evaluated. RESULTS: Fifty dogs were included in the study. Follow-up ranged from six to 38 months (mean 14.4 months). Perioperative complications were acetabular collapse (n = 1) and greater trochanter fracture (n = 1), both of which were successfully managed perioperatively. Postoperative complications were aseptic loosening of the acetabular component (n = 2; both surgically revised), implant sepsis (n = 3; all explanted), acetabular fracture (n = 1; conservatively managed), greater trochanter fracture (n = 1; conservatively managed) and sciatic neurapraxia (n = 1). No cases of postoperative luxation or femoral implant aseptic loosening were encountered. Outcome was poor for three cases (3 implant sepsis), fair for three cases (including 1 acetabular component loosening and 1 acetabular fracture), and good or excellent for 44 cases (88%). CLINICAL SIGNIFICANCE: There were not any cases of postoperative coxofemoral luxation observed in this series of 50 dogs with dual mobility hip prosthesis. Studies with more patients and longer follow-up are needed to confirm the satisfactory results observed to date with this implant.

Effective mechanical properties of diaphyseal cortical bone in the canine femur.

The effective elastic modulus, yield strength, yield strain, ultimate strength, ultimate strain, strain energy density at yield and strain energy density at ultimate failure of femoral diaphyseal cortical bone were investigated on canine femurs. Four femurs representative of the canine population were selected from four statistically-determined clusters based on increasing size and weight comprising the Toy poodle (5 kg), Poodle (12 kg), German shorthaired pointer (25 kg) and Doberman (50 kg). The zones of interest were the lateral, medial, cranial, and caudal quadrants of the mid-diaphysis. Effective mechanical properties were measured using quasi-static three-point bending tests on strips. The averages ± SD were 15.6 ± 2.6 GPa for effective elastic modulus, 174.3 ± 32.1 MPa for yield strength, 0.012 ± 0.003 for yield strain, 251.0 ± 49.1 MPa for ultimate strength, 0.021 ± 0.005 for ultimate strain, 10.7 ± 4.0J m(-3) × 10(5) for strain energy density at Yield and 33.0 ± 14.1 Jm(-3)× 10(5) for strain energy density at ultimate failure. Significant differences were found between dogs and the effective elastic modulus increased with breed weight and size (13.9 GPa for the Toy poodle to 17.2 GPa for the Doberman). The ultimate strength σ(u) and strain energy density at ultimate failure U(u) were significantly lower in the Toy poodle than in the Poodle and German shorthaired pointer indicating that the cortical bone material in the Toy poodle differed from that of the other dogs. Examination of the zones of interest revealed that the cranial quadrant showed the greatest stiffness, whereas strength was highest at the medial site. The caudal cortex was less stiff and strong than the cranial cortex.

Type IV Monteggia fracture in a cat.

A one-year-old neutered male cat was referred for a grade IIIA open radius and ulna fracture. The mid-diaphyseal radial and ulnar fractures were associated with lateral radio-humeral and radio-ulnar dislocations. From these abnormalities, a diagnosis of type IV Monteggia fracture was made. The annular ligament was found to be intact on examination and the radial head was correctly positioned and stable after fracture reduction and plate fixation. Eighteen months postoperatively, the cat did not exhibit any signs of lameness or any signs of pain on palpation and mobilisation. Signs of mild osteoarthritis were present on radiographs. Type IV Monteggia fractures are very rare in animals. The combination of a radial head dislocation with an intact annular ligament is uncommon. This pattern allowed a single reconstruction with two plates without a radio-ulnar screw.

Long-term efficacy and safety of firocoxib in the treatment of dogs with osteoarthritis.

Thirty-nine client-owned dogs with osteoarthritis were treated with 5 mg/kg firocoxib administered orally, once a day for 52 weeks. Veterinary examinations were performed on approximately days 0, 15, 90, 180, 270 and 360. Twenty-five dogs completed the study. The withdrawal rate associated with gastrointestinal side effects was low (5.1 per cent of dogs). Based on the owners' assessment, 82 per cent of the dogs had improved at day 15, 84 per cent of the 32 remaining dogs had improved at day 90, and 96 per cent of the 25 dogs that completed the trial had improved at day 360. During this trial, 12 (48 per cent) of the 25 remaining dogs showed an improvement in their lameness from day 90 to day 360 (P<0.05).

A case of stifle osteochondrosis treated by osteochondral autogenous grafting. One month morphological follow-up.

OBJECTIVE: To describe the one-month morphological appearance of autogenous osteochondral grafting in a dog with stifle osteochondrosis. METHOD: Osteochondral autografting was performed in one stifle of an eight-month-old dog with spontaneously occurring bilateral osteochondrosis. RESULT: Histopathological analysis performed one month after surgery confirmed partial integration of the grafts and osteochondral survival. CLINICAL SIGNIFICANCE: Autogenous osteochondral grafting in stifle osteochondrosis results in acceptable graft survival postoperatively and is worthy of further evaluation.

A case of bilateral patellar osteochondrosis and fracture in a cat. Clinical and histological findings.

Fracture of the patella associated with bilateral osteochondrosis of the superior pole of the patella in a 14-week-old cat is reported with histological findings. Patellar osteochondrosis has been described in humans, horses, pigs, and dogs and is characterised by incomplete union of the ossification centres related to an abnormal process of endochondral ossification. However this disease has not yet been described in cats. Macroscopically, two main fragments separated by interposed tissue were identified on the left patella. In contrast, no fracture but only a fissuration of the articular cartilage was observed on the right patella. Bilateral partial patellectomy was performed. Histological examination of the excised fragments from the left patella revealed two main areas of trabecular bone separated by a wide irregular band of hyaline cartilage. The microscopic aspect of the right patella was similar to that of the left. Serial sections showed the initial appearance of an area of necrosis in the central band of hyaline cartilage, and that this hyaline cartilage was subsequently replaced by fibrovascular connective tissue. These findings indicate that some patellar fractures may be due to patellar osteochondrosis.

Spontaneous recovery of experimental valgus deformity in lambs.

INTRODUCTION: Angular deformity in the growing skeleton of animals, especially in the radius and ulna, is occasionally seen in clinical practice. The mechanism of spontaneous correction of these angular deformities however remains to be elucidated. The purpose of our experiment was to explore the ability of a growth plate to correct an induced valgus deformity, and to study the mechanism of correction. METHODS: Before beginning the study, valgus deformity of the distal radius had been induced in lambs by the application of a device that causes asymmetrical compression of the growth plate. The study began after removal of the device and spontaneous correction of the induced deformity was observed weekly for 20 weeks. The angles of the deformity and longitudinal growth on the medial and lateral portions of the growth plate were respectively measured on craniocaudal and mediolateral radiographs. RESULTS AND CONCLUSIONS: Spontaneous correction of the valgus deformity occurred during the first 16 weeks. It resulted from asymmetrical growth characterised by restricted activity of the medial portion of the growth plate (14.8%) in comparison to the lateral portion of the experimental radius, and also in comparison to the medial portion of the control radius.

A case of dorso-medial luxation of the radial carpal bone in a dog.

Luxation of the radial carpal bone is an uncommon injury in the dog and cat. Previous clinical cases have reported palmaro-medial luxation with injury to the short radial collateral ligament. In this study a case of dorsomedial luxation of the radial carpal bone in a 10-year-old female Gordon Setter is described. A closed reduction of the luxation was performed and a conservative treatment was carried out. Thirteen months after the reduction, the dog had a satisfactory limb function, despite the presence of degenerative joint disease of the carpus. A pathogenic hypothesis for this dorso-medial luxation of the radial carpal bone is proposed reproducing the luxation on canine cadavers.

Management of traumatic urethral rupture in 11 cats using primary alignment with a urethral catheter.

OBJECTIVE: To assess the management of traumatic urethral ruptures using a systematic attempt at urethral catheterisation. METHODS: Eleven cats that had been diagnosed with a traumatic urethral rupture over a five-year period were included in this study. Rupture was assessed by positive-contrast retrograde urethrography. An attempt was made to manage these ruptures by placing an indwelling urethral catheter. RESULTS: The placement of an indwelling urethral catheter, could be performed in 10 out of 11 cats, which indicated a partial rupture. In one cat, catheterisation was not possible because of complete urethral rupture. A urethral catheter was placed into the urinary bladder via the urethra in five animals. In the other five animals, urethral catheterization required cystotomy using a modified 'inside to outside' technique. Urethral catheter removal occurred between five and 14 days after placement. Urethral healing was accomplished in all cases of catheterisation with a good outcome in eight of the 10 cats. Two cats showed clinical signs related to stricture formation during the follow-up period (seven to 72 months). Retrograde urethrography provided a definitive diagnosis of partial rupture in only six of the 10 cases of partial rupture. CLINICAL SIGNIFICANCE: Results suggested that primary alignment with the placement of a urethral catheter should be attempted for the management of traumatic urethral ruptures in cats. Gentle urethral catheterisation seems to be an effective procedure for diagnosing and dealing with partial urethral rupture in cats. Clinical stricture formation can occur, but the risk does not seem to be high. Further studies are warranted in order to define the ideal duration for maintenance of an indwelling urethral catheter in cases of traumatic partial urethral rupture.

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.

The point of view of the veterinary surgeon: bone and fracture.

It is important to understand the biomechanics of fractures if the morphological characteristics of fracture, fracture treatment and fracture healing are to be understood. Because of the mechanical properties of bone, which is stronger in compression than in tension, a fracture line is initiated perpendicular to the direction of tension or in shear. The mechanical properties of bone are also time-dependent (viscoelasticity). Subsequently, when the load is applied at a higher load range, a greater amount of energy is stored within the bone, resulting in a more severe fracture (high energy fractures). There are five types of fracture: tension, compression, torque, bending, and shear, with typical morphologies: transverse fractures in tension, fracture line at 45 degrees to the long axis of the bone in compression, spiral fracture in torsion, combined transverse and butterfly fracture in bending, shear line when the overload is applied eccentrically. These different morphological types are shown on radiographs.

Osseointegration of composite calcium phosphate bioceramics.

The resistance of macroporous calcium phosphate ceramics to compressive strength generally is low and depends on, among other factors, porosity percentage and pore size. A compromise always is adopted between high porosity, required for a good integration, and mechanical strength, which increases with material density. We improved the strength of macroporous calcium phosphate ceramics of interconnected porosity by filling the pores with a highly soluble, self-setting calcium phosphate cement made of TCP and DCPD. Cylinders of the resulting material were implanted in sheep condyles and subjected to histological analysis after 20, 60, and 120 days. Microradiographs were made of the histological sections. The control material consisted of ceramic that had not been loaded with cement. Progressive ingrowth of bone into the ceramic pores occurred as the cement was degraded during the first implantation period. Marked degradation of the cement was apparent after 2 months, with fragmentation of the cement in most of the pores and the presence of bone tissue between the fragments. All the cement had been replaced by bone after 4 months. Some fragments of cement still were embedded in the newly formed bone. There was no significant difference between the integration of loaded and nonloaded ceramics. Filling the macroporous ceramic pores with a calcium phosphate cement significantly improved the mechanical strength of these ceramics without modifying their integration in the healing bone.

Accuracy and precision of in vivo bone mineral measurements in sheep using dual-energy X-ray absorptiometry.

We evaluated the precision and accuracy of in vivo measurements of spine bone mineral density (BMD) and bone mineral content (BMC) in five ewes using dual-energy X-ray absorptiometry (DXA, Lunar DPX-L). The short-term in vivo reproducibility expressed as the coefficient of variation (CV) varied from 0.9 to 1.6% for spine BMD and from 1 to 3.1% for spine BMC. The ex vivo measurements, performed in 20 cm of water to simulate soft tissue thickness, correlated closely with the in vivo measurements, yielding an r value of 0.98 and 0.97 for spine BMD and BMC, respectively. The accuracy was determined by comparing the total BMC of each vertebra measured in vivo with the corresponding ash weight. The correlation coefficient between the two measurements was r = 0.98, with an accuracy error of 5.6%. We concluded that the DXA allows a precise and accurate measurement of spine bone mineral in live ewes using the methodology designed for humans.

Histological integration of allogeneic cancellous bone tissue treated by supercritical CO2 implanted in sheep bones.

UNLABELLED: Different chemical or physical methods of bone processing have been developed to decrease the antigenicity of allogeneic bone which may delay or prevent graft integration. We have developed a method based on delipidation and deproteination of the bone with a supercritical fluid and hydrogen peroxide. Cylinders of cancellous allogeneic bone treated in this way were implanted for four weeks, four months or eight months in holes drilled in sheep condyles or tibial plateau. Histological sections were then processed and analysed qualitatively and quantitatively using an image analysis software coupled to a light microscope. Measurements were made of the trabecular bone surface (BS/TS), the relative osteoid surface (OS/BS), the active osteoid surface (OS/BS), active resorption surface (Oc.S/BS) and the relative surface of newly formed bone. After four weeks, the control cylinders (non-treated allogeneic bone) had been invaded by cellular tissue composed of lymphocytes and plasmocytes surrounding remnants of the donor bone marrow tissue. The processed cylinders showed osteoid apposition at the surface of their external trabeculae. The trabecular bone and osteoid surfaces were significantly higher in the processed bone sections than in the control bone sections. After four months, most of the control material had been osteolysed and replaced by connective tissue containing lymphocyte islets, while the processed materials showed a large amount of bone synthesized at the surface of implant trabeculae which appeared fragmented and disseminated within the newly formed bone. All the histomorphometric parameters measured were significantly different from those of the control. By eight months, most of the control material had been totally osteolysed with very little bone ingrown in the implantation site. Only one control implant had been integrated. The processed cylinders were difficult to discern from the bone in which they were implanted. The parameters measured on the processed cylinders were significantly higher than those measured on the control sections. IN CONCLUSION: the treatment applied to the bone enhanced allogeneic bone integration and could provide a new kind of tissue treatment for bone banking.