Femoral medullary infarction secondary to canine total hip arthroplasty

OBJECTIVE: To evaluate the prevalence of femoral intramedullary infarction after total hip arthroplasty (THA) and to determine whether any specific femoral morphology predisposes to bone infarction. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: All dogs from our hospital population undergoing THA between 1984 and 1997 with radiographic follow-up available at 1 year or more postoperatively. METHODS: A case control study was conducted within the THA group to determine risk factors predisposing to femoral infarction after THA. Medical records and radiographs were reviewed. Data were collected on clinical parameters, femoral morphology, prosthesis, and bone changes. Radiographic diagnosis was confirmed using histopathology in 11 femora. Radiographs of 50 age-matched control dogs weighing more than 20 kg with coxofemoral degenerative joint disease were randomly chosen to determine the prevalence of bone infarction in nonoperated dogs. RESULTS: Ninety-one dogs with 110 THA were included in the study. Fifteen of the 110 femora with THA had radiographic evidence of infarction (14%). Infarction was not present in any femora in the control group. There was no significant difference in the prevalence of infarction between dogs that received cemented or uncemented prostheses. Clinical signs were not reported in any patient that developed femoral infarction. Young age (P = .03) and a distance between the greater trochanter and nutrient foramen greater than 79 mm (P = .008) predisposed dogs to femoral infarction. Over time, three infarcts decreased in size radiographically, five remained unchanged, and three expanded. An osteosarcoma developed at the site of a bone infarct in one dog. CONCLUSION: Femoral intramedullary infarction occurred in 15 of 110 THA. Young age at the time of THA and a greater distance between the greater trochanter and the nutrient foramen predisposed to infarction. CLINICAL RELEVANCE: Intramedullary infarction occurs after canine THA. These bone infarcts do not appear to cause clinical signs; however, they may present a diagnostic challenge. Malignant transformation could potentially result from medullary infarction.     

Short-term evaluation of dorsal acetabular augmentation in 10 canine total hip replacements

OBJECTIVE: To report the use of dorsal acetabular augmentation (DAA) in canine total hip arthroplasty (THA) and to evaluate the clinical and radiographic outcome after a minimum of 1 year follow-up. STUDY DESIGN: Clinical study. ANIMALS: Nine dogs that had THA. METHODS: Ten hips requiring acetabular augmentation for optimum acetabular cup implantation for THA were evaluated retrospectively. The excised femoral head and neck was used as the corticocancellous bone graft for index THA surgeries, and the dorsal crest of the ipsilateral ilial wing was used as the bone graft in 1 dog that had a revision surgery. Clinical and radiographic follow-up examinations were performed at approximately 8 weeks and 1 year postoperatively. Long-term radiographic examinations included use of a standing dorsal acetabular rim (DAR) projection for assessment of graft-recipient boundary. Functional clinical outcome was assessed using direct patient evaluation and telephone interview. RESULTS: One dog failed to regain limb function after surgery. Suspected aseptic loosening of the acetabular cup was observed on radiographs approximately 12 weeks postoperatively. Excluding this single explantation, follow-up physical and radiographic examinations indicated good implant and graft positioning and normal function for all dogs. CONCLUSIONS: Acetabular augmentation permitted implantation of an appropriately sized acetabular cup while maintaining complete DAR coverage of the prosthesis. Nine out of 10 hips had a successful outcome with minimal radiographic and no functional abnormalities. Further follow-up is necessary to determine the long-term outcome of DAR augmentation in canine THA. CLINICAL RELEVANCE: Acetabular augmentation with an autogenous corticocancellous bone graft constructed from the femoral head and neck can provide complete DAR coverage to permit use of an appropriately sized acetabular cup in THA.     

Radiographic Assessment of a Canine Uncemented Porous-Coated Anatomic Total Hip Prosthesis

Thirty uncemented porous-coated anatomic total hip prostheses in 24 dogs were evaluated radiographically at 6 months, 12 months, or 18 months after arthroplasty. All dogs were fully weight bearing and free of lameness at the time of follow-up. Radiographs were assessed for prosthetic component alignment, percentage of femoral canal fill, resorptive and formative bony changes, and changes at the implant bone interface. No evidence of infection, loosening, or failure of component fixation was seen. Settling of the acetabular component and subsidence of the femoral stem was seen early after surgery. Cortical atrophy was seen in all femurs and was the most significant bony remodeling change. Early results of clinical and radiographic evaluation of uncemented total hip arthroplasty in dogs have been encouraging.     

Extraosseous cement granuloma associated with total hip replacement in 6 dogs

OBJECTIVE: To report the clinical, radiographic, and pathologic features of extraosseous cement granuloma (ECG), a low occurrence, long-term complication of total hip replacement (THR). STUDY DESIGN: Retrospective clinical study. Sample Population-Six client-owned dogs. METHODS: Medical records for 6 dogs that had a cemented modular THR and developed ECG were reviewed for the clinical, radiologic, and histopathologic findings of ECG. Morphologic and elemental analyses of retrieved particles were conducted in 2 dogs using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). RESULTS: Three golden retrievers and 3 Labrador retrievers had progressive lameness in the operated limb 4 to 7 years after THR and developed ECG. Other clinical features included an acute deterioration to non-weight bearing associated with pathologic fracture of the proximal femur in 2 dogs, and obstipation in 1 dog. In 5 dogs, there was a large caseous mass surrounding the proximal femur. Obstipation in 1 dog was caused by a similar mass adjacent to bone cement used for fixation of the acetabular cup. Radiographic changes included a multilobular soft tissue mass, containing irregular mineral densities, in the gluteal mass surrounding the proximal femur, THR interface deterioration, osteolysis, new bone formation, and implant subsidence were consistent with chronic aseptic loosening. The histopathologic diagnosis was sterile granuloma associated with a massive heterogeneous particulate burden, which was assumed to have resulted from severe wear of all prosthesis components. CONCLUSIONS: ECG is a manifestation of severe aseptic loosening of cemented total hip replacement, with the generation of wear debris probably responsible for granuloma formation. CLINICAL RELEVANCE: Because revision can offer a good prognosis in early aseptic femoral loosening, yearly radiographic monitoring of the recipients is recommended.     

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

OBJECTIVE: To evaluate a femoral window technique for retrieval of cemented total hip prostheses. STUDY DESIGN: Retrospective clinical study. ANIMALS: Twelve dogs with infection of a cemented modular total hip prosthesis. METHODS: Implant removal was performed by an extended craniolateral approach to the hip and proximal femur without trochanteric osteotomy. The femoral cement mantle was fragmented and removed with simple orthopedic instrumentation by a lateral femoral window that was repaired using cerclage wires. Surgical technique, intraoperative and postoperative complications, bacterial culture results, histopathologic findings, and completeness of cement removal were recorded. Follow-up radiographs were taken 5 to 9 weeks postoperatively. Long-term follow-up information was obtained by client questionnaire. Functional outcome was assessed by scoring ability to stand, sit, walk, run, play, climb stairs, and get into a car. RESULTS: Prosthesis retrieval was performed 2 to 41 months after implantation (median, 14 months). Complete removal of femoral cement was achieved in 10 dogs. A nondisplaced femoral fissure, extending proximally from the window, was an intraoperative complication in 2 dogs. Staphylococcus spp was most commonly isolated (6 dogs) from interfacial membrane samples. Systemic antibiotic therapy, dependent on susceptibility testing, was administered for 3 to 10 weeks postoperatively. There was radiographic evidence of osteotomy healing at 5- to 9-week reassessment. Recurrence of osteomyelitis was not observed. Long-term functional outcome was considered mildly abnormal. CONCLUSIONS: The lateral window was an effective technique for retrieval of retained femoral cement. CLINICAL RELEVANCE: Removal of an infected prosthesis using this technique generally resulted in a clinical outcome comparable to that with ab initio femoral head and neck excision.     

Orthogonal view analysis for evaluating the femoral component position of total hip implants in dogs using postoperative radiographs

OBJECTIVE: To show the ability to obtain repeatable, accurate, quantitative data to assess the position of the femoral component of canine total hip implants using postoperative radiographs. STUDY DESIGN: Cadaveric study and clinical trial. ANIMALS: Five cadaveric canine femurs and 4 patients. METHODS: Femoral implants were placed into 5 cadaveric canine femurs in predetermined locations. Orthogonal radiographs were taken of each femur at 10 degrees intervals as they were moved through a natural range of hip motion. An assessment of implant position was made with each set of radiographs and analyzed to observe significant inconsistencies in the values obtained when the femur was repositioned. Three investigators positioned and radiographed the hips of 4 client-owned dogs that had total hip arthroplasty (THA). Each investigator obtained a set of orthogonal radiographic views from which implant position was measured. The measurements obtained from each investigator's set of radiographs were statistically analyzed to evaluate for interobserver differences. RESULTS: The methods described indicate that consistent data regarding femoral implant placement can be obtained from postoperative radiographs of THA patients. Under most circumstances, change in position of the femur did not significantly affect femoral implant measurements. There were no significant differences noted among values obtained by different investigators. CONCLUSIONS: Measurements based on the femoral and implant axes obtained from orthogonal radiographic views of the femur provide a means for obtaining accurate and consistent quantitative data regarding femoral implant position using postoperative radiographs of canine THA patients. CLINICAL RELEVANCE: Acquisition of quantitative information about femoral implant position using postoperative radiographs will facilitate development of a readily available data source. This information, attainable in a clinical setting, may help identify elements of implant position that are important in determining the clinical outcome of THA in dogs.     

Effect of conformation of the distal portion of the femur and proximal portion of the tibia on the pathogenesis of cranial cruciate ligament disease in dogs

OBJECTIVE: To evaluate mediolateral radiographic views of stifle joints to identify conformational differences between athletically sound dogs and dogs with cranial cruciate ligament disease (CCLD). SAMPLE POPULATION: Radiographic images of 50 stifle joints of 43 dogs with surgically confirmed CCLD and 50 stifle joints of 38 dogs without clinical signs of stifle joint disease. PROCEDURES: Mediolateral radiographic views of stifle joints were obtained, and long axes of the femur, tibia, and femoral condyles were measured. Angles between long axes of the femur and femoral condyle and between long axes of the femur and tibia were measured. Circles were drawn representing the joint surface of femoral condyles (circle 1), area of contact on the tibial plateau (circle 2), and femoral trochlea (circle 3). Radii of circles 1, 2 (line F), and 3 were measured. Distances between midpoints of circles 1 and 2 (line K) and between midpoint of circle 2 and most cranial aspect of the tibial tuberosity (line G) were measured. To evaluate differences in conformation that could lead to CCLD, quotients derived from measurements were created for comparison; angles were compared between dog groups. RESULTS: Significant differences were found in the quotients created by the lengths of lines G and F and lines G and K between dogs with and without CCLD. CONCLUSIONS AND CLINICAL RELEVANCE: No anatomic differences were detected in the distal portion of the femur between dogs with and without CCLD. Development of the tibial tuberosity and shape (convexity) of tibial condyles may be relevant in the pathogenesis of CCLD.     

Radiologic and gross anatomic evaluation of bone healing in the dog.

Bone healing associated with 3 techniques of midshaft femoral fracture fixation in 36 young adult Beagle-type dogs was evaluated in radiographic and gross pathoanatomic studies. A serrated transverse fracture was surgically and aseptically created on the midshaft of either the left or the right femur of each dog. The fixation devices used were intramedullary (IM) pin, IM pin and 1/2 Kirschner device, and tension bone plates. The radiographic evaluation was done in series. The first radiographs were taken during surgery. Radiographs were then taken immediately after surgery, to record the status of reduction, alignment, and fixation. Radiographs were taken at the 4th and 10th postoperative weeks, to monitor healing. All dogs were euthanatized at the 10th week. Both the normal femur and the healing femur were removed from all dogs, all soft tissue was removed from the bone, and each femur was examined grossly. Each type of fixation was associated with a distinct mode of osteogenesis. Bony union and clinical union (that stage in the healing process when fixation can be removed) were defined as a successful conclusion to each case. Malunion and nonunion were defined as unsuccessful conclusions. Delayed union was defined as neither successful nor unsuccessful. The IM pin cases had a 64.2% success rate and a 14.2% failure rate. The IM pin and 1/2 Kirschner cases had a 100% success rate. The bone plate cases were 91% successful, with 0% failure. A problem identified with IM pinning was axial rotation (6 of 14 or 42% of the cases). It was concluded that IM pins should not be used alone for the fixation of femoral fractures in adult dogs.     

Vascular and Morphologic Changes in Canine Femora after Uncemented Hip Arthroplasty

The effects on femoral remodeling of medullary reaming and insertion of a porous endopros-thesis in uncemented hip arthroplasty (UHA) were measured. A unilateral hip hemiarthroplasty (HA) was performed in 12 dogs, with six dogs receiving full-sized and six dogs receiving undersized femoral endoprostheses. A prosthetic head and neck, or acetabular cup, was not implanted. A control group of six dogs underwent femoral head and neck excision (FHNE) only. All dogs were killed 4 weeks after the surgical procedure. Porosity, vascularity, and bone formation were quantified in each femur of the dogs that had been operated on and in each femur of two unoperated dogs. Full-sized did not differ from undersized HA bones in vascularity, porosity, or bone formation. Femurs in which hemiarthroplasties had been performed (full-sized and undersized) had a three-fold increase in porosity, vascularity, and bone formation compared to the contralateral and the FHNE femurs. Changes in porosity and vascularity were greatest (p < .05) at the metaphyseal level and in the medial and caudal quadrants. There was a strong correlation (R² 0.77 to 0.93, and p − .0001) between the increase in porosity and vascularity. These results support the hypothesis that medullary reaming followed by uncemented prosthetic stem implantation contribute to remodeling of the proximal portion of the femur after UHA.     

Determination of Pelvic Limb Alignment in the Large‐Breed Dog: A Cadaveric Radiographic Study in the Frontal Plane

Objectives— To report a method for radiographic determination of the mechanical axis of the canine pelvic limb and its relationship to the joints and bone axes. To report reference ranges for the relationships between the axes of the pelvic limb and for joint position relative to the pelvic limb axis. Study Design— Cadaveric radiographic anatomic study. Animals— Pelvic limbs (n=101) from normal midsized to large breed dogs; tibiae (n=105) from dogs with cranial cruciate ligament disease (previous study). Methods— Extended full‐limb radiography was performed and images analyzed to determine: mechanical joint reference angles (femur, tibia), pelvic limb axis, tibiofemoral and metatarsotibial angle, mechanical axis—femur/metatarsus angle, and mechanical axis deviation (MAD) of the stifle/tarsus. Results— Mean mechanical angles were: lateral proximal femoral (103.7°±5.4°), lateral distal femoral (98.6°±2.5°), medial proximal tibial (92.2°±1.8°), medial distal tibial (95.9°±2.2°), tibiofemoral (9.1° varus ±2.8°), metatarsotibial (0.6° valgus ±2.1°). Mean mechanical axis—femur and—metatarsus angles were 5.6° (±1.7°) and 2.9° (±1.5°), respectively. Mean MAD of the stifle and tarsus were 3.6% (±1.1%) and 1.2% (±0.6%), respectively. Tibial angles were not different between dogs with and without cranial cruciate ligament disease. Conclusions— Mechanical axes of the canine pelvic limb and their relationship to the joints can be determined by full‐limb radiography. Clinical Relevance— Techniques and reference ranges may be useful for diagnosis, surgical planning, and postoperative assessment of pelvic limb deformities.     

Use of veterinary interlocking nails for diaphyseal fractures in dogs and cats: 121 cases

OBJECTIVE: To report clinical outcome after use of an interlocking nail (veterinary interlocking nail [VIN]) for stabilization of diaphyseal fractures in dogs and cats. STUDY DESIGN: Retrospective study. Animals: Seventy-eight dogs and 43 cats with diaphyseal fractures of the femur (n = 96), tibia (n = 14), or humerus (n = 11). METHODS: Interlocking nails (4 mm diameter [n = 72], 6 mm [n = 25] or 8 mm [n = 24]), were used in static (n = 106) or dynamic (n = 15) fixation mode. Cerclage wires also were used in 63 (52%) cases. Data about the patient (species, breed, weight, age), characteristics of the fracture, and details of the surgery and perioperative complications were recorded. The surgeon evaluated functional outcome, and fracture healing was quantified 6 weeks (W6) and 3 months (M3) after surgery with a radiographic index. RESULTS: Twelve cases had been unsuccessfully treated by another technique. Of 106 comminuted fractures, 60 were classified as unstable. Only 112 animals were evaluated at W6; 86 (77%) healed without complication and had a functional outcome considered excellent (n = 80, 93%), good (n = 5, 4%), or fair (n = 1). Twenty-six complications were noted: 16 (14%) patients did not require additional surgery and had a good or excellent outcome, whereas 10 (8%) patients needed surgical intervention to CONCLUSIONS: VINs can be used to repair diaphyseal fractures of the femur, tibia, and humerus in dogs and cats provided the implants are appropriately sized for the fractured bone. The high healing rate (even with unstable fractures), associated with a functional outcome, and low complication rate support the use of VINs for these fracture types. However, a period of training and the application of basic principles are necessary to ensure successful results. CLINICAL RELEVANCE: VINs should be considered as alternative technique for management of selected diaphyseal fractures of the femur, tibia, and humerus in dogs and cats.     

Risk Factors for Femoral Fracture after Canine Press‐Fit Cementless Total Hip Arthroplasty

Objective: To evaluate risk factors for femoral fracture after porous‐coated cementless total hip arthroplasty (THA). Study Design: Case series. Animals: Dogs (n=74) that had cementless THA (n=84). Methods: Medical records of dogs from 2 referral hospitals were reviewed for occurrence of postoperative femoral fracture. Patient and operative (age, breed, sex, weight, and canal flare index [CFI], indication for arthroplasty, intraoperative fissure, cerclage usage, and implant sizes) factors were analyzed. Assessment of implant positioning and canal fill was performed on immediate postoperative radiographs. Femoral fractures (n=11) were evaluated and compared with 73 cases without fracture that met the inclusion criteria. Results: Mean (±SEM) age was 7.30±0.69 years for dogs with, and 4.77±0.37 years for dogs without femoral fracture. Age was positively associated with fracture (P=.022). Mean (±SEM) CFI was 1.80±0.09 for dogs with, and 1.98±0.04 for dogs without fracture. CFI was negatively associated with fracture (P=.045). Body weight, intraoperative fissure, cerclage use, implant size, position, and canal fill did not influence the occurrence of femoral fracture. Conclusions: Older dogs and dogs with lower CFI may be at increased risk for femoral fracture after porous‐coated cementless THA. Clinical Relevance: Risk factors exist for femoral fracture after cementless THA using porous‐coated implants, and should be critically evaluated during the patient selection. These risks should be weighed against the benefits of the system, and measures to minimize femoral fracture in at‐risk patients studied.     

Zurich Cementless Total Hip Replacement: Retrospective Evaluation of 2nd Generation Implants in 60 Dogs

Objective— To evaluate the results of application, and identify complications, of the 2nd generation of Zurich Cementless Total Hip Replacement (ZCTHR).
Study Design— Case series.
Animals— Client-owned dogs (n=60) that had ZCTHR (n=65).
Methods— Dogs with ZCTHR (2001–2003) with a minimum follow-up ≥6 months were evaluated. Data included signalment, cup position, longest follow-up, complications, management of complications and outcome.
Results— Mean follow-up was 22.68 months. Eleven cases (17%) had postoperative complications: femoral fracture (n=1; 1.5%), prosthesis luxation (7; 11%), cup loosening (2; 3%), and implant failure (1; 1.5%); 9 cases were successfully revised. Explantation of implants was performed in 1 case because of infection, and 1 dog was euthanatized after reluxation.
Conclusions— ZCTHR can restore function in dogs affected by disabling diseases of the coxofemoral joint. The press-fit fixation of the cup allowed for corrections in cases of incorrect positioning. Cases with aseptic loosening were revised successfully by impacting larger cups. Newer stems of this generation are shot peening treated to increase their resistance to breakage. In our cases, infection is a disastrous event, leading to implant removal. After resolution of complications, a successful final outcome was achieved in 97% of THR.
Clinical Relevance— ZCTHR offers a reliable alternative for treating dogs with disabling diseases of the hip joints.     

Femur fractures associated with canine total hip replacement

OBJECTIVE: To report femur fracture as a complication of canine total hip replacement (THR) and to report the incidence, predisposing factors, treatment options, and outcome. STUDY DESIGN: Prospective clinical study. ANIMALS: Twenty-two client-owned dogs with 24 femoral fractures occurring during or after THR. METHODS: Cemented THR (BioMedtrix, Boonton, NJ) was performed. Medical records and radiographs were used to identify dogs that had femur fracture and to identify risk factors. Follow-up was obtained until dog death or study end. RESULTS: The overall incidence of femur fracture after THR was 2.9%. Femoral fractures occurred intraoperatively, immediately postoperatively, and up to 2196 days after THR. In 17 dogs, fractures resulted from a traumatic event. Osteopathy was present at THR in 5 dogs; all developed femoral fissures during reaming. Three dogs had fractures associated with cortical thinning secondary to aseptic loosening. Fracture treatment included euthanasia (1 dog), strict confinement (3 dogs), full cerclage wires on long oblique fractures (3 dogs), or plate and screw fixation (10 with, and 7 without, cerclage wires). All fractures extended near the distal tip of the femoral stem and all aggressively treated fractures healed. CONCLUSIONS: Predisposing risk factors for femur fracture after THR include osteopathy and iatrogenic fissures created during reaming. Trauma, excessive load concentration, and increased torque can lead to mid-diaphyseal fracture near the end of the femoral stem. Fracture did not disrupt THR implants. Cement fracture exposing the tip of the femoral stem did not affect fracture healing or rehabilitation. Immediate plate and screw fixation resulted in the most favorable outcome; healing occurred in 6-10 weeks. CLINICAL RELEVANCE: Femur fractures that occur after THR should be repaired using plate and screw fixation augmented with cerclage wire when needed. Forces on fissures should be neutralized to prevent propagation and fracture. Owners of high-risk patients (old dogs with osteopathies or previous hip surgery) should be counseled before THR. The prognosis is excellent when fractures are treated correctly.     

Effects of femur position on radiographic assessment of completeness of femoral head and neck excision in medium- to large-breed dogs

OBJECTIVE: To determine the effect of femur positioning on radiographic assessment of completeness of excision after femoral head and neck excision (FHNE) in medium to large breed dogs. SAMPLE POPULATION: 10 femurs from canine cadavers (body weight > 20 kg). PROCEDURE: Complete FHNE was performed on 5 canine femurs. Excision consisting of inadequate removal of the medial distal aspect of the femoral neck was performed on the remaining 5 femurs. Each femur was positioned with predetermined amounts of internal and external rotation about the long axis and radiographed. Investigators evaluated a set of 8 radiographic views of each femur. Sensitivity (SE), specificity (SP), positive predictive value, negative predictive value, and completeness of excision assessment accuracy were estimated for each of the femur positions. RESULTS: Craniocaudal radiographic views of the femur positioned with external rotation of 15 degrees, 30 degrees, and 45 degrees as a group had the highest SE, SP, and completeness of excision assessment accuracy relative to other radiographic views. The SE, SP, and accuracy of assessment were higher when the degree of external rotation was increased from 15 degrees to 30 degrees or 45 degrees. CONCLUSIONS AND CLINICAL RELEVANCE: Craniocaudal radiographic views of the femur positioned in external rotation (15 degrees, 30 degrees, and 45 degrees) improved the ability to detect adequacy of excision relative to standard craniocaudal and lateromedial radiographic views. Evaluation of craniocaudal radiographic views of the femur positioned in external rotation may increase the ability to assess FHNE adequacy in medium- to large-breed dogs.     

Osteosarcoma at the site of bone infarction associated with total hip arthroplasty in a dog

OBJECTIVE: To report the occurrence of medullary bone infarction in both femoral canals after bilateral total hip arthroplasty (THA) and the subsequent unilateral development of an osteosarcoma at the site of bone infarction. STUDY DESIGN: Clinical report. ANIMAL POPULATION: An 8-month-old neutered male Samoyed dog. METHODS: Serial physical and radiographic examinations performed at 1, 2, 3, and 5 years after THA. Bone biopsy specimens of the right distal femoral metaphysis were taken 5 years after THA, and a complete necropsy was performed at the time of euthanasia. RESULTS: Bilateral medullary bone infarction was visible in the femoral canals 1 year after THA and remained visible on subsequent evaluations. An osteosarcoma developed in the right distal femoral metaphysis at the site of infarction, 5 years after THA, and was found to have metastasized widely throughout the body. CONCLUSION: Bone infarction may occur in the femoral canal after canine THA. CLINICAL RELEVANCE: Bone infarction may be a predisposing factor for the development of osteosarcoma in the femora of dogs with THAs.     

The influence of age on patellar reflex response in the dog

The patellar tendon reflex is a clinical parameter commonly used to assess neurological status. Factors such as quadriceps muscle fiber composition, femur length, and patient age have been reported to influence total and fractionated reflex times in human beings. The purpose of this blinded, cross-sectional study was to examine the effect of age on the patellar reflex in the dog. Eighty-six dogs without evidence of neurological impairment or orthopedic disease of the stifle (eg, patellar luxation or cranial cruciate ligament rupture) were assigned to 1 of 2 groups on the basis of age: group 1, <10 years old (n = 72); or group 2, > or =10 years old (n = 14). Patellar reflexes were elicited in both pelvic limbs by a reflex hammer while the dog was in lateral recumbency. The reflex was scored as present or absent by a blinded individual. Two dogs in group I had reflexes absent in both limbs, 3 dogs in group 2 had reflexes absent in both limbs, and 1 dog in group 2 lacked a response in 1 limb. The proportion of dogs with absent patellar reflexes in group 2 (4 of 14, 95% CI, 8-58%) was significantly higher than the proportion of dogs with absent patellar reflexes in group 1 (2 of 72, 95% CI, 0-10%) (P < .006). Furthermore, dogs lacking at least 1 patellar reflex were older than those having both reflexes present (P = .04). Weight was not related to the presence of both reflexes (P = .49). These findings suggest that neurologically normal dogs may have an age-dependent decline in patellar reflex magnitude or a prolongation of total reflex time (TRT).     

Management of femoral fractures in dogs with unilateral semicircular external skeletal fixators

Objective: To report use of semicircular external skeletal fixators (ESF) for management of femoral fractures in dogs. Study Design: Prospective clinical study. Animals: Dogs (n=16) with femoral fractures (n=18). Methods: A semicircular ESF system composed of 6‐hole 45° or 5‐hole 40° carbon‐fiber arches, 6 mm threaded rods, half pin fixation bolts, 6 mm nuts, and negative profile end‐threaded half pins were used for open repair of femoral fractures. ESF configuration, complications, limb use, fixator removal time, and functional outcomes were evaluated. Outcome was graded as excellent, good, fair, or poor. Results: Seventeen fractures with sufficient follow‐up healed. Eight dogs started using the limb immediately after waking up from anesthesia whereas initial limb use was 1–4 days after repair in the other dogs. Time to fixator removal ranged from 28 to 63 days (mean, 38 days). Functional outcome was excellent in 13 cases, good in 4, and poor in 1 nonunion. Conclusion: Semicircular ESF combined with open surgical reduction can be used to successfully repair metaphyseal and diaphyseal femoral fractures in young growing dogs.     

Results of Screw/Wire/Polymethylmethacrylate Composite Fixation for Acetabular Fracture Repair in 14 Dogs

Objective- To assess the clinical results in dogs with acetabular fractures stabilized using a screw-wire-polymethylmethacrylate (SWP) composite fixation.
Study Design- A retrospective study of client-owned dogs with acetabular fractures.
Animals- Fourteen dogs ranging in age from 4 to 95 months (mean, 34 ±25 months; median, 25 months) and body weight from 8 to 39 kg (mean, 25 ±6 kg; median, 27 kg).
Methods- Medical records and radiographs were retrospectively evaluated to determine location of the fracture, presence of preexisting degenerative joint disease, accuracy of fracture reduction and complications associated with surgery. Long-term results were evaluated by subjective assessment of lameness, elicitation of pain and/or crepitus on manipulation of the coxofemoral joint, measurements of pelvic limb circumference, coxofemoral joint goniometric measurements, and radiographic evaluation.
Results- Fracture reduction was considered anatomic in 13 dogs. At the time of the last follow-up evaluation (mean, 347 ±261 days; median, 380 days) 10 dogs were sound on the affected limb, three dogs had a subtle weight-bearing lameness of the affected limb, and the remaining dog had a consistent non-weight-bearing lameness of the affected limb. Mild (n = 10) or moderate (n = 1) degenerative changes of the affected coxofemoral joint attributed to the acetabular fracture and its repair were noted on the follow-up radiographs in 11 dogs. Limb circumference of the affected limb ranged from -8.2% to +10.8% (mean, -0.8 ±4.2%; median, -0.7%) of the contralateral limb.
Conclusions- The SWP composite fixation consistently maintained anatomic reduction, was associated with few complications, and yielded satisfactory clinical results.
Clinical Relevance- The SWP composite fixation technique would seem to be an acceptable means of stabilizing acetabular fractures in dogs.