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.     

Coxofemoral arthroscopy and total hip arthroplasty for management of intermediate grade fibrosarcoma in a dog

OBJECTIVE: To report the use of arthroscopy and total hip arthroplasty (THA) for management of intermediate grade fibrosarcoma of the femoral head in a dog. STUDY DESIGN: Clinical case report. ANIMAL: A 6-year-old spayed female Rottweiler presented for evaluation of acute-onset of lameness of the right pelvic limb of approximately 10 days duration. METHODS: Coxofemoral arthroscopy was performed to obtain fine needle aspiration and Jamshidi biopsy of a lytic lesion of the femoral head. A cemented THA was performed removing as much of the femoral neck and proximal femur as possible while not compromising implant or joint stability. RESULTS: Histologic evaluation of specimens from the femoral head and neck remnants confirmed an intermediate grade fibrosarcoma. Fifteen months after THA, subjectively there was normal use of the right limb with only limited decrease in range of motion and mild muscular atrophy. Radiographs demonstrated stationary positioning of the THA implants. CONCLUSIONS: Arthroscopy of the coxofemoral joint is an effective diagnostic tool for evaluation of disease of the articular structures and canine total hip replacement may be an appropriate means of limb salvage in rare cases of disease of the femoral head. CLINICAL RELEVANCE: This case provides support for the use of coxofemoral arthroscopy as a diagnostic tool as well as an aid in acquiring representative intraarticular tissue samples. Additionally, the case presented demonstrates the potential use of THA as a limb sparing technique in cases of disease affecting the femoral head of dogs.     

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.     

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.     

Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases

OBJECTIVE: To evaluate the long-term clinical and radiographic results of a canine uncemented porous-coated anatomic (PCA) total hip arthroplasty (THA). STUDY DESIGN: Prospective study of consecutive clinical patients using survival analysis. ANIMALS: Forty-one dogs that underwent PCA THA; nine had bilateral PCA THA (50 prostheses). METHODS: Gait observation, orthopedic examination, and radiographic assessment were conducted before THA, 6 months after THA, and yearly thereafter. A zonal analysis system was used to document osseous changes in the femur and the acetabulum. Acetabular cup and femoral stem subsidence and migration, femoral canal fill, and implant orientation were measured. Survival analysis of the procedure was conducted. RESULTS: Long-term follow-up was available for 37 dogs (46 prostheses). The median follow-up was 63 months. Limb function was normal for 37 limbs and abnormal for 9 limbs because of dislocation (n = 3), lumbosacral disease (n = 2), degenerative myelopathy (n = 1), autoimmune disease (n = 1), brain tumor (n = 1), or osteosarcoma of the femur (n = 1). All prosthetic stems and cups were fixed by bone ingrowth fixation. Osteolysis was not observed. Bone infarction occurred in five femoral canals (four dogs). The 6-year survival rate for the procedure was 87% (95% confidence interval, 72%-96%). CONCLUSIONS: Long-term fixation of the uncemented PCA acetabular cup and stem is successful in dogs, and long-term clinical function is excellent.     

Retrospective analysis of canine miniature total hip prostheses

OBJECTIVE: To determine the practicality and clinical outcome of miniature total hip replacement (THR) in dogs. STUDY DESIGN: Retrospective study. Sample Population- Seventeen client-owned dogs that had miniature THR. METHODS: Patient data surveyed included signalment, body weight, diagnosis, implant size, surgical technique, and intraoperative and postoperative complications. Radiographic evaluation included angle of lateral opening of the acetabular component, implant positioning, cement mantle quality, and femoral displacement measurement and ratio. Client questionnaire and orthopedic examination were used to obtain long-term follow-up information. RESULTS: Miniature THR was performed to address hip dysplasia and secondary osteoarthritis. In 1 dog, a staged bilateral procedure was performed. Mean body weight was 19 kg (range, 12 to 25 kg). Penetration or fissure of the femoral cortex was the most common intraoperative complication and occurred in 3 dogs. In 3 dogs, there was excessive coxofemoral laxity after reduction of the prosthesis. This instability was addressed specifically in 2 dogs by capsulorrhaphy or capsular prosthesis. Postoperative convalescent complications (craniodorsal luxation, 2 dogs; acetabular cup displacement, 1 dog) were related to surgical errors. Aseptic loosening of the femoral implant was diagnosed in 1 dog at 18 months. Mean follow-up time was 17 months (range, 4 to 42 months). Fifteen of 18 (83%) miniature THRs had good or excellent outcomes. CONCLUSIONS: Miniature THR should be considered a satisfactory alternative to femoral head and neck ostectomy in medium-size dogs affected by hip dysplasia and secondary osteoarthritis. The population of medium-size dogs that might derive more benefit from THR than FHO has yet to be defined. CLINICAL RELEVANCE: Miniature THR is a viable treatment option in medium-size dogs with hip dysplasia.     

Use of the cumulative summation technique to quantitatively assess a surgical learning curve: canine total hip replacement

Objective: To quantitatively assess a surgical “learning curve” using the cumulative summation (CUSUM) score technique. Study Design: Application of a CUSUM technique to a consecutive series of surgical cases. Animals: Consecutive primary cemented total hip replacement (THR; n=116) in 106 dogs. Methods: Records of all dogs that had primary canine THR were reviewed. Data retrieved included date of surgery, postoperative complications, and duration of follow‐up. The 12‐week outcome was analyzed graphically and with a CUSUM technique. Results: One hundred and one (87%) procedures were “successful” and 15 (13%) developed major complications within 12 weeks (failures). The CUSUM chart clearly demonstrated an initial “learning curve” of ～44 THR. Conclusion: The CUSUM technique can be used to demonstrate the learning curve for canine THR surgery.     

Augmentation of the transverse acetabular ligament in canine caudoventral hip luxation.

Open surgical fixation was performed on four hip joints in three dogs who were suffering from caudoventral hip luxations for which closed reduction had previously failed. Stabilization of the joint was achieved with a ventral coxofemoral approach, which augmented the function of the transverse acetabular ligament using a sling implant through a bone tunnel (n = 1), a sling implant around two pelvic screws (n = 1), or an internal fixator plate (n = 2). Transverse acetabular ligament augmentation resulted in successful joint stabilization in all cases, and should be considered for the surgical reduction of caudoventral hip luxations in dogs. The use of an internal fixator plate, while preserving soft-tissue blood supply and resulting in minimal to no long-term arthritic changes, may provide an optimal outcome.     

Radiographic evaluation of the Zurich cementless total hip acetabular component

OBJECTIVE: To radiographically evaluate the Zurich cementless total hip (ZCTH) cup and correlate lucency with clinical signs of implant instability, time since surgery, and implant generation, using zonal analysis. STUDY DESIGN: Retrospective study. ANIMALS: Client-owned dogs (n = 53). METHODS: Radiographs of dogs that had ZCTH arthroplasty (>1 year) were evaluated using zonal analysis, for lucency surrounding the cup-bone interface (number of zones, length, area). Dogs were examined for clinical signs of implant instability (lameness, hip pain). Lucency was correlated with lameness, time after surgery, and implant generation. RESULTS: Radiographs of 68 implants (18 generation I, 50 generation II) were evaluated. Eight dogs were lame (11.8%). Dogs with lameness were more likely to have lucency in > or =2 zones of analysis (per view), have >2 times the average curvilinear length of lucency, and have >4 times the average area of lucency surrounding the implant compared with non-lame dogs. A weak relationship was observed between time after surgery and implant generation; however, there was no relationship between time after surgery and lucency. CONCLUSIONS: Dogs with lameness after ZCTH arthroplasty were more likely to have lucency at the cup-bone interface. Lucency was better evaluated by radiographic projection than zonal analysis. Temporal progression of lucency was weakly correlated with implant generation. CLINICAL RELEVANCE: Dogs with lucency in > or =2 zones of analysis should be evaluated more frequently for clinical signs of implant loosening. Further investigation of serial radiographs after ZCTH arthroplasty is warranted.     

Micro Total Hip Replacement for Dogs and Cats: Surgical Technique and Outcomes

Objective: To describe the surgical technique for the micro total hip replacement (Micro THR) system and report clinical outcomes. Study Design: Prospective study. Animals: Dogs (n=49) and cats (n=8) with coxofemoral arthropathy. Methods: Small breed dogs and cats with coxofemoral arthritis were enrolled for Micro THR. Patient data were recorded. Implant positioning and cement mantle quality were evaluated radiographically. Orthopedic examinations and client interviews were used to assess outcome. Results: Micro THR was performed unilaterally (40 dogs, 8 cats) and staged bilaterally (9 dogs) to resolve pain associated with osteoarthritis or trauma. Mean body weight was 7.2 kg. Postoperative complications included prosthesis luxation (9), cup aseptic loosening (1), and sciatic neurapraxia (1). Mean radiographic follow up was 96.1 weeks; 10 joints were followed for ≥3.0 years. Sixty of the 66 (91%) Micro THRs had excellent outcomes. Two dogs (<2.75 kg) were too small for the prosthesis and 4 dogs with unmanageable luxation had explantation. Conclusions: Micro THR is considered a satisfactory procedure for management of small breed dogs and cats with coxofemoral disease unresponsive to medical management. Clinical Relevance: Micro THR is a viable option to treat disabling disorders of the hip. More than 170 cat and small dog breeds, and many mixed breeds, could benefit from Micro THR surgery.     

Evaluation of risk factors for luxation after total hip replacement in dogs

OBJECTIVE: To identify risk factors for luxation after canine total hip replacement (THR). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: 256 client-owned dogs that underwent THR. METHODS: Patient data surveyed included signalment, body weight, diagnosis, prior hip surgery, implant size, intraoperative complications, and angle of lateral opening of the acetabular component. RESULTS: Postoperative complications were recorded in 20 cases (7.8%). The most common complication was dorsal luxation which occurred in 12 dogs (4.7%). The interval between joint replacement and luxation ranged from 1 to 116 days (mean, 44 days). In 1 case, luxation was attributable to failure of the repair of an intraoperative fracture of the greater trochanter. Excluding this case, the mean angle of lateral opening in those dogs that sustained luxation was 62 degrees (range, 46 degrees - 75 degrees). The mean angle of lateral opening overall was 48 degrees (range, 18 degrees - 76 degrees). The angle of lateral opening was the only factor that had a statistically significant effect on whether luxation occurred (P = .035). Acetabular revision, performed primarily to reduce the angle of lateral opening, was performed in 8 dogs and successfully prevented subsequent luxation. CONCLUSION: Luxation of the prosthesis is substantially under the control of the surgeon. It is recommended that the acetabular cup be inserted at an angle of lateral opening of 35 degrees to 45 degrees. In those cases of THR luxation in which an inappropriate angle of lateral opening is identified, acetabular revision arthroplasty generally results in a good clinical outcome.     

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.     

Owner assessment of the outcome of total hip arthroplasty in dogs

OBJECTIVE: To evaluate owners' perceptions of the outcomes of dogs that have undergone total hip arthroplasty (THA). DESIGN: Survey. SAMPLE POPULATION: Owners of 145 dogs that had undergone THA. PROCEDURE: Surveys were mailed to owners of 353 dogs that underwent THA between 1982 and 1996. Owners were asked to answer multiple-choice questions and provide written comments. RESULTS: The response rate was 41%. For owners who responded to the survey, time from surgery to completion of the questionnaire ranged from 6 months to 11 years. Overall, 122 respondents (84.1%) rated results of THA in their dog as excellent or good. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that owners are generally satisfied with the results of THA in their dogs.     

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.     

Total hip arthroplasty for treatment of canine hip dysplasia.

Cemented THA is an established procedure for treating arthropathies of the hip in large, healthy mature dogs. CHD with secondary osteoarthritis is the most common indication. Although comparative studies between THA and excision arthroplasty have not been reported, our experience with both procedures and studies in the literature support THA as the best available treatment for crippling degenerative joint disease secondary to CHD in large, mature dogs. Negative aspects of the procedure include high cost, the potential of significant complications, and the sophisticated surgical technique required. Improvements in patient selection, design of implants, surgical technique, and postoperative care have decreased the incidence of complications and improved the success rate to over 90%. However, concerns in human applications about cement disease and the desire to increase the functional life of the prosthesis have renewed interest in cementless systems. Advantages of cementless THA are fixation via bony ingrowth and avoidance of problems associated with PMMA. Important technical aspects of cementless THA relate to optimal fit and fill so that the prosthesis is stable, bone ingrowth is promoted, and weight-bearing forces are transferred to the proximal femur physiologically. Problems recognized with cementless systems include fissure fracture, bone resorption, and excessive motion between the implant and bone. Currently, investigations are being conducted to develop prosthetic materials that more closely match the stiffness of bone, stem designs that provide optimal fit and maintain normal strain patterns in the bone, and coating materials that promote permanent fixation by bone ingrowth. Early clinical results in humans and research results in dogs have been encouraging but have not withstood the test of time. Results of cementless techniques must be compared to the standards set by cemented THA over the last 20 years in humans and the last 10 years in dogs.     

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.     

Total hip arthroplasty in the horse: Overview,technical considerations and case report

A total hip arthroplasty was performed in a small equine patient with a history of traumatic subluxation of the coxofemoral joint during infancy resulting in severe degenerative changes to the femoral head and acetabulum. The transtrochanteric surgical approach used to expose the joint, as well as the technique and technology to replace the joint, is described. The patient was weightbearing within 24 h of surgery and walking successfully without sling support 4 days post operatively. On the fifth post operative day, the patient abruptly deteriorated and succumbed to multiple pulmonary thromboemboli and a jejunal infarction. Despite the systemic complications in this case, the initial short‐term success of this treatment option indicate its potential to be considered in the management of equine coxofemoral joint disease/lesions.     

Additional kinematic variables to describe differences in the trot between clinically normal dogs and dogs with hip dysplasia

OBJECTIVE: To describe the abnormal gait of dogs with hip dysplasia by use of kinematic gait analysis. ANIMALS: 19 large-breed dogs with moderate to severe clinical and radiographic evidence of hip dysplasia and 10 clinically normal dogs (controls). PROCEDURE: Kinematic and force plate data were collected, and degree of coxofemoral joint abduction-adduction, mediolateral foot movement, distance between hind feet, maximum hind foot elevation, mediolateral pelvic movement, and coxofemoral joint angular acceleration were calculated. Essential Fourier coefficients were determined and used to reconstruct mean angular acceleration curves. Fourier coefficients and foot and pelvic movement data were compared between groups. RESULTS: Dogs with hip dysplasia had a greater degree of coxofemoral joint adduction and range of abduction-adduction and greater lateral pelvic movement, compared with controls. Foot movement variables did not differ significantly between groups. Coxofemoral joint angular acceleration was greater in the middle to end of the stance phase, whereas deceleration was greater in the late stance to early swing phase and middle to end of the swing phase in dogs with hip dysplasia, compared with controls. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in degree of coxofemoral joint abduction-adduction, amount of mediolateral pelvic movement, and coxofemoral joint angular acceleration between clinically normal dogs and dogs with hip dysplasia may indicate a compensation in gait of affected dogs as a result of discomfort or biomechanical effects attributable to hip dysplasia and degenerative joint disease. Information gained from kinematic and kinetic gait analyses may be useful in evaluating treatments for hip dysplasia in dogs.     

Effect of anaesthesia and stress on the radiographic evaluation of the coxofemoral joint

A pelvic radiographic examination was performed on 15 large breed dogs without history and clinical sign of hip dysplasia. The effect of anaesthesia and of two stress-radiographic methods on the coxofemoral subluxation was evaluated. With anaesthesia a mild coxofemoral subluxation was seen in 31 per cent of the dogs, which all appeared radiographically normal when sedated. The Norberg angle was significantly decreased in anaesthetised dogs (P < 0–05). When dogs with a radiographically normal coxofemoral joint conformation were submitted to a stress-radiographic examination there was a shift towards an increased coxofemoral subluxation. Subluxation was seen in 70 per cent of the dogs when the knee fixation method of positioning was applied and in 100 per cent of the dogs when the wedge method was used. Correspondingly the Norberg angle decreased significantly when the coxofermoral joints were stressed (P_kneefix < 0–00003; P_wedge= 0–000008). The study concludes that the currently used procedure for evaluation of the hip joints does not necessarily disclose whether or not a dog has hip dysplasia.     

Treatment of coxofemoral luxation in a mature Welsh pony by femoral head ostectomy: Long‐term outcome

A 233 kg, 4‐year‐old Welsh pony stallion presented with a unilateral coxofemoral luxation and a history of previous upward fixation of the patella. This condition was surgically managed by femoral head ostectomy using a craniodorsal approach to the luxated coxofemoral joint, without greater trochanteric osteotomy. Immediate improvement in weightbearing was observed after surgery and primary intention healing was recorded. Long‐term outcome, 4 years after surgery, was assessed by radiographic, ultrasonographic and lameness examination. The pony was in good body condition and the initial weight of this patient was restored. Despite fetlock hyperlaxity of the contralateral hindlimb, amyotrophy and mechanical lameness of the affected hindlimb, the pony showed evident comfort without apparent signs of pain and was able to trot and gallop. Bone callus was observed at imaging examination.