Cortical allograft and endoprosthesis for limb-sparing surgery in dogs with distal radial osteosarcoma: a prospective clinical comparison of two different limb-sparing techniques

OBJECTIVE: To compare surgical and oncologic outcome in dogs with osteosarcoma (OSA) of the distal aspect of the radius treated with limb-sparing surgery, using either a cortical allograft or endoprosthesis, and postoperative chemotherapy; and to evaluate predictive factors for outcome. STUDY DESIGN: Prospective cohort study. ANIMALS: Dogs (n = 20) with spontaneous, non-metastatic OSA of the distal aspect of the radius. METHODS: Dogs were prospectively randomized for limb-sparing surgery with either a cortical allograft (n = 10) or endoprosthesis (10) and full-course adjuvant chemotherapy using single or dual agent protocols of cisplatin, carboplatin, and/or doxorubicin. Surgical (intraoperative findings, postoperative infection, construct failure) and oncologic (local tumor recurrence, metastasis, survival) outcomes were compared. The influence of intraoperative and postoperative variables on surgical and oncologic outcome were evaluated. RESULTS: No clinically significant differences in surgical and oncologic outcome were detected between groups. The percentage of radius replaced by the implant was significantly greater in the endoprosthesis group (60.9% compared with 48.6%, P = .008). Median survival time (MST) for dogs with construct failure, regardless of implant type, was 685 days and significantly greater than MST of dogs without construct failure (322 days, P = .042; hazard ratio [HR] 16.82). Median metastasis-free interval and MST (685 days versus 289 days; P = .034, HR 24.58) were significantly greater in dogs with postoperative infection. Disease-free and overall limb-salvage rates were 70% and 85%, respectively. Overall MST was 430 days. CONCLUSIONS: For dogs with OSA of the distal aspect of the radius, a cortical allograft or endoprosthesis can be used for limb-sparing surgery. Construct failure and postoperative infection significantly improve survival time regardless of implant type. CLINICAL RELEVANCE: An endoprosthesis is an attractive alternative to cortical allografts for limb-salvage of the distal aspect of the radius in dogs because surgical and oncologic outcomes are similar, but the endoprosthesis is an immediately available off-the-shelf implant which is not complicated by the bone harvesting and banking requirements associated with cortical allografts. Mechanisms whereby postoperative infection improves survival time requires further investigation and, if elucidated, may provide the opportunity to improve the outcome of dogs and humans with OSA.     

Intercalary bone grafts for joint and limb preservation in 17 dogs with high-grade malignant tumors of the diaphysis

OBJECTIVE: To evaluate postoperative complications, limb function, and tumor control after intercalary resection and reconstruction for preservation of limb and joint function in dogs with high-grade malignant tumors of diaphyseal bone. STUDY DESIGN: Retrospective study. ANIMALS: Seventeen client-owned dogs. METHODS: The bone tumor database and medical records were reviewed (1986-2002) for dogs with diaphyseal tumors treated with intercalary resection and reconstruction with either an allograft or irradiated autograft. Clinical presentation, diagnostic findings, surgical management, and outcome were determined from medical records and telephone interviews with veterinarians and owners. Statistical analyses included chi2 to test associations between intra- and postoperative variables with complications, and Kaplan-Meier survival analysis for disease-free interval, metastasis-free interval (MFI), and median survival time. RESULTS: Intercalary limb-sparing surgery was performed in 17 dogs with diaphyseal tumors: osteosarcoma (OSA) (15), histiocytic sarcoma (1), and solitary metastasis from a pulmonary adenocarcinoma (1). One dog was excluded from further analysis when the spared limb was amputated 4 days postoperatively because of incomplete tumor resection. In 16 dogs, limb function was good to excellent. Complications occurred in 5 dogs (31.3%) and included superficial infection in 2 dogs (12.5%) and implant failure in 4 dogs (25%). All implant failures occurred in the ulna and there was a significant association between implant failure and non-cemented allografts (P=.042). Non-union of 1 or both osteotomies was diagnosed in 10 dogs (83.3%) and, despite lack of clinical signs in all cases, was significantly associated with the use of intracavitary locally released cisplatin (P=.046) and cemented intercalary grafts (P=.046). Local tumor recurrence was diagnosed in 1 dog (6.3%) and metastatic disease in 12 dogs (75.0%), including 10 dogs with OSA. The median MFI was 137 days. The local disease-free and overall limb-salvage rate was 94% and 100%, respectively. Overall median survival time was 393 days and the median survival time for dogs with OSA was 449 days. CONCLUSION: Intercalary limb-sparing surgery results in better postoperative limb function with fewer and less severe complications than historical reports of dogs treated with non-intercalary limb-sparing surgery. CLINICAL RELEVANCE: In dogs with diaphyseal tumors, intercalary limb-sparing surgery preserves normal joint function and results in good to excellent limb use with few complications and good local tumor control.     

Pasteurized tumoral autograft and adjuvant chemotherapy for the treatment of canine distal radial osteosarcoma: 13 cases

OBJECTIVE: To report outcome in 13 dogs with distal radial osteosarcoma, without evidence of metastasis, treated by a combination of adjuvant chemotherapy and a pasteurized autograft limb-sparing procedure. STUDY DESIGN: Prospective clinical study. ANIMALS: Thirteen dogs with distal radial osteosarcoma. METHODS: Limb-sparing procedure was performed using an autograft from the excised tumoral segment, pasteurized at 65 degrees C for 40 minutes. Adjuvant chemotherapy (cisplatin or cisplatin and doxorubicin) was administered in all dogs. RESULTS: Mean and median survival times were 531 and 324 days, respectively (range, 180 to 1,868 days). Overall survival was 100% at 6 months, 50% at 12 months, 44% at 18 months, and 22% at 24 months. Lung metastasis occurred in 5 (38%) dogs. Observed complications were local recurrence (2 dogs, 15%), allograft infection (4 dogs, 31%), and implant failure (3 dogs, 23%). Limb function was good in 12 dogs (92%) and fair in 1 dog. CONCLUSIONS: Pasteurized bone autograft derived from the tumoral bone segment was an effective alternative to cortical bone allograft for limb sparing in canine distal radial osteosarcoma, in terms of feasibility, pattern of healing, complications, and survival. CLINICAL RELEVANCE: Use of a pasteurized bone autograft eliminates the need for a canine bone allograft bank and has the added advantage of good fit to the recipient site.     

Long-term outcome of distal femoral osteotomy for treatment of combined distal femoral varus and medial patellar luxation: 12 cases (1999-2004)

OBJECTIVE: To determine long-term outcome of distal femoral osteotomy as a component of treatment for distal femoral varus and medial patellar luxation in large-breed dogs. DESIGN:Retrospective case series. ANIMALS: 12 dogs (16 stifle joints). PROCEDURES: Medical records and radiographs were reviewed to identify large-breed dogs with medial patellar luxation (grade > or = 2) and femoral varus angle > or = 12 degrees treated with distal femoral osteotomy, with a minimum follow-up (by a veterinarian) of 18 months. Signalment, weight, medial patellar luxation and lameness grade, pre- and postoperative femoral varus angle, surgical technique, time to radiographic bone union, and complications were recorded. Follow-up with owners via questionnaire was performed > 18 months after surgery. RESULTS: 16 corrective distal femoral osteotomies were performed with ancillary medial patellar luxation procedures in 12 dogs; 4 dogs had staged bilateral procedures. Mean +/- SD preoperative and postoperative femoral varus angles were 16.3 +/- 4.3 degrees and 3.9 +/- 2.5 degrees , respectively. Mean +/- SD time to radiographic union of the distal femoral osteotomy was 52.6 +/- 13 days. One dog had Kirschner wire migration from the tibial tuberosity. Patellar luxation was not detected after surgery in any dog. Mean +/- SD follow-up by a veterinarian was 1,335 +/- 410 days and by use of an owner questionnaire was 1,497 +/- 464 days. All 10 variables of owner-observed patient comfort and function were significantly improved. CONCLUSIONS AND CLINICAL RELEVANCE: Distal femoral osteotomy in combination with traditional treatment provided predictable osteotomy healing, patellar stabilization, and long-term improvement in patient comfort and function when used to treat combined distal femoral varus and medial patellar luxation in large-breed dogs.     

Total Hip Replacement in an Alpaca Using a Cementless Implant

Objective— To report use of a cementless total hip prosthesis in an alpaca.
Study Design— Case report.
Animals— Alpaca (n=1) with chronic craniodorsal coxofemoral luxation.
Methods— A 2.5-year-old Suri alpaca, 3 months pregnant, was admitted for evaluation of acute onset severe left hind limb lameness (grade 4/5) of 6 weeks duration. After diagnosis of craniodorsal luxation of the left femoral head, total hip replacement (THR) using a cementless implant was performed because of the poor prognosis for reduction of a chronic luxation.
Results— A press-fit prosthesis was used and the alpaca delivered a live cria 8 months later. Persistent mild mechanical lameness remained after surgery, with moderate reduction in mobility of the coxofemoral joint. The prosthesis was stable and correctly positioned at 7 weeks and at 9 months. There was mild exostosis surrounding the proximal aspect of the femur at 9 months, and Steinmann pins used to repair the trochanteric osteotomy were removed because of migration. At 1 year, the alpaca has a slight gait abnormality, remains with the herd on pasture and has been re-bred.
Conclusion— Chronic coxofemoral luxation in an alpaca can be managed by THR.
Clinical Relevance— THR is a viable treatment option in alpacas with severe coxofemoral disease.     

Treatment of medial patellar luxation by femoral closing wedge ostectomy using a distal femoral plate in four dogs

This case report describes the treatment of recurrent medial patellar luxation associated with varus deformity of the distal femur by distal femoral ostectomy stabilised using a distal femoral plate. Four dogs (five affected limbs) were included in the study. All cases had received previous surgery for medial patellar luxation but remained significantly lame. All were treated by femoral ostectomy to correct distal femoral varus deformity with application of a distal femoral bone plate. All cases improved following surgery. An excellent outcome was recorded in four of five cases. Lameness persisted in one case despite satisfactory patellar stability as a result of concurrent cranial cruciate ligament deficiency. One case suffered implant failure. Femoral ostectomy is an effective treatment for medial patellar luxation associated with femoral varus deformity. The distal femoral plate provides a convenient method by which to stabilise the ostectomy. Care should be exercised when the 2 mm distal femoral plate is applied.     

Proximodistal alignment of the canine patella: radiographic evaluation and association with medial and lateral patellar luxation

Objectives— To evaluate the contribution of proximodistal alignment of the patella to patellar luxation, and to evaluate the structures contributing to proximodistal alignment of the patella relative to the femoral trochlea.
Study Design— Retrospective study using a convenience sample.
Animals— Medium to giant breed dogs (n=106).
Methods— Medical records and stifle radiographs of 106 dogs were reviewed. Radiographic measurements evaluated the proximodistal alignment of the patella with respect to the femoral trochlea, distal aspect of the femur, and proximal aspect of the tibia. Measurements were compared between dogs with clinically normal stifles (controls; n=51 dogs, 66 stifles), and dogs with a clinical diagnosis of medial patellar luxation (MPL, n=46 dogs, 65 stifles) or lateral patellar luxation (LPL, n=9 dogs, 11 stifles) using ANOVA.
Results— In dogs with MPL, the ratio of patellar ligament length (PLL) to patellar length (PL) was increased, as was the ratio of the distance from the proximal aspect of the patella to the femoral condyle (A) to PL ( P <.0001). Dogs with LPL had a decreased A:PL ( P =.003) and an increased ratio of the proximal tibial length (PTL) to distal tibial width (DTW; P =.009).
Conclusions— MPL is associated with a relatively long patellar ligament and patella alta in medium to giant breed dogs. LPL is associated with a relatively long proximal tibia and patella baja. Values for PLL:PL>2.06 and A:PL>2.03 are suggestive of the presence of patella alta, whereas a value for A:PL<1.92 is suggestive of patella baja.
Clinical Relevance— Measurements of both PLL:PL and A:PL are recommended in dogs with patellar luxation, and surgical correction should be considered in those with abnormal values.     

Loss of implant-bone interface following distal radial locking-plate endoprosthesis limb-sparing surgery in a dog

An eight-year-old, neutered female Rottweiler was presented with lameness of seven days duration. Radiographs were consistent with a distal radial bone tumour. Limb-sparing surgery was performed using a commercially available endoprosthesis with a locking bone plate. Histopathological examination of the resected bone revealed an intraosseous fibrosarcoma, and postoperative adjuvant chemotherapy was initiated three weeks after surgery. Despite initial satisfactory limb function, lameness worsened four months after surgery. Radiographs revealed large areas of bone lysis around the proximal and distal screws, leading to significant resorption of the radius and radial carpal bone with subsequent construct failure. Further treatment was declined by the owner and the dog was subsequently euthanased. This case illustrates that implant failure is not necessarily averted by the use of locking (compared with non-locking) implants combined with an endoprosthesis to treat distal radial tumours in dogs.     

Ipsilateral vascularised ulnar transposition autograft for limb-sparing surgery of the distal radius in 2 dogs with osteosarcoma

Canine osteosarcoma is the most commonly diagnosed primary bone tumour in the dog, affecting mainly large and giant breed dogs with the predilection site being the metaphysis of long bones, specifically the distal radius, proximal humerus, distal femur and proximal tibia and fibula. Treatment options are either palliative or curative intent therapy, the latter limb amputation or limb-sparing surgery together with chemotherapy. This article describes the use of an ipsilateral vascularised ulnar transposition autograft as well as chemotherapy in 2 dogs with osteosarcoma of the distal radius. Both dogs showed minimal complications with the technique and both survived over 381 days following the surgery. Complications seen were loosening of the screws and osteomyelitis. The procedure was well tolerated with excellent limb use. This technique is indicated for use in cases with small tumour size that have not broken through the bone cortex.     

Osteosarcoma at the Site of a Cortical Bone Allograft in a Dog

An osteosarcoma developed in the proximal femur of a 9-year-old female Great Dane. The femur had been fractured 5 years previously and was stabilized with plate fixation with the incorporation of a frozen cortical bone allograft. The dog recovered without complications after the surgery and had normal use of the leg before the osteosarcoma developed. The tumor had metastasized to the lungs, spleen, and ipsilateral popliteal lymph node.     

Pasteurized tumoral autograft as a novel procedure for limb sparing in the dog: A clinical report

OBJECTIVE: To evaluate use of a pasteurized tumoral autograft prepared from the resected primary bone neoplasm for limb sparing in a dog with distal radial osteosarcoma (OSA). STUDY DESIGN: Clinical case report. ANIMALS: A 9-year-old male Maremma shepherd dog. METHODS: After right distal radial OSA removal, the tumoral autograft was pasteurized. The excised bone segment was placed in a sterile watertight box containing sterile saline solution preheated to 65 degrees C in a water bath. The box was kept immersed in the water bath at 65 degrees C for 40 minutes to kill the tumor cells. The autograft was then fixed in the host with a plate and screws based on standard AO/ASIF technique for carpal arthrodesis. Three doses of cisplatin (70 mg/m(2) intravenously) were administered, 3 weeks apart; the initial dose was administered the day after surgery. RESULTS: The autograft was incorporated in a manner comparable to an allograft, and after 708 days, the metallic implants were removed. A 1-month activity restriction as well as spoon splint to protect the leg from a full loading were used thereafter. Limb function was fair to good, and the dog remains disease free after 56 months. CONCLUSIONS: A pasteurized autograft consisting of the resected primary bone neoplasm is a valid alternative to a cortical bone allograft for limb sparing in dogs with appendicular OSA in terms of feasibility and pattern of healing. CLINICAL RELEVANCE: This procedure can be an alternative method of limb sparing when difficulties are encountered in establishing and maintaining a canine bone allograft bank.     

Experimental Coxofemoral Replacement Hemiarthroplasty in the Pony

For the in vivo evaluation of hip joint prostheses that are developed for man, the suitability of the pony as an animal model has been studied. Human and custom made prostheses were implanted into 1 femur in each of 7 ponies to replace the femoral head. The surgical approach was through a caudolateral incision. The prosthesis was fixed in the femur with bone cement. Because of errors in the implantation technique and resulting lack of sufficient fixation 2 ponies as well as 1 control animal with an excision arthroplasty were unwilling or unable to stand. Rigid fixation of the implant was achieved in 3 ponies. They were returned to pasture after 8 days. A full return to a normal gait did not occur within an observation period of up to 3 months. All 3 ponies developed a dorsolateral coxofemoral luxation and pseudarthrosis within the first 10 days. A mismatch between the equine anatomy and human prosthesis geometry was thought to be the cause. We, therefore, believe that the pony does not provide a suitable model for the testing of human femoral joint implants. The results, however, indicate that coxofemoral surgery can be performed in the adult pony. For clinical reconstruction of joint function, a custom made total artificial hip joint might provide better results.     

Femoral bone adaptation to unstable long-term cemented total hip arthroplasty in dogs

OBJECTIVE: To evaluate femoral adaptation after unstable long-term cemented total hip arthroplasty (cTHA) in dogs. STUDY DESIGN: Clinical study. ANIMALS: Four dogs. METHODS: Paired femurs were examined from client-owned dogs that were donated to a retrieval program after death from causes unrelated to their cTHA. Mean (+/-SEM) dog age was 10.0+/-1.5 years and implant duration was 6.0+/-1.4 years. Implanted femurs had radiographic changes associated with implant loosening and gross mechanical instability at femur retrieval. Femurs were evaluated at 3 levels relative to implant length. Cortical area and medullary area were measured at each level, and cortical porosity was assessed at each level in 4 quadrants and in 3 regions. Implanted femurs were compared with the contralateral non-implanted femurs. RESULTS: Cortical area and cortical porosity were increased at all levels in femurs with unstable implants. Implanted femurs had increased porosity in all quadrants and regions at the proximal 2 levels, and increased porosity in only the cranial quadrant and mid-cortical area at the distal level, when compared with contralateral non-implanted femurs. Corresponding medullary areas were not different. CONCLUSIONS: Significant histomorphometric changes occur in femurs after unstable cTHA. The patterns of periosteal bone formation and endosteal bone resorption support mechanisms of stress shielding and wear debris-mediated osteolysis as factors that may contribute to femoral adaptation and implant loosening. CLINICAL RELEVANCE: Despite popularity and excellent return to function with cTHA, aseptic loosening remains a serious long-term complication. Substantial net bone loss and unfavorable environment with unstable cTHA may make revision surgery less successful.     

Use of a condylar screw plate for repair of a Salter-Harris type-III fracture of the femur in a 2-year-old horse

A 2-year-old sexually intact male Paint horse weighing 427 kg (940 lb) was admitted for examination and treatment of intermittent non-weight-bearing lameness of the right hind limb of 1 week's duration. Radiography revealed a displaced Salter-Harris type-III fracture of the right femoral condyle with the sagittal component of the fracture line located in the intercondylar space and the transverse component exiting on the medial aspect of the femur. The fracture was repaired with a condylar screw plate designed for repair of femoral condylar fractures in humans. The owner reported by telephone 9 months after surgery that the horse was sound. To our knowledge, use of this particular implant system for fixation of a Salter-Harris type-III fracture on the medial side of the femur in a horse has not been described. Results in this horse suggest that this implant can be successfully used for repair of femoral condylar fractures in selected adult horses.     

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.     

Bone allografts and adjuvant cisplatin for the treatment of canine appendicular osteosarcoma in 18 dogs

The results achieved in 18 dogs following the use of frozen bone cortical allografts for limb-sparing resection of non-metastatic canine appendicular osteosarcoma are presented. Three to five cisplatin doses (70 mg/m2) were administered, starting the day after surgery. The mean and median survival times were 478 and 266 days (range 80 to 2,611 days), respectively. The survival rate was 94 per cent at three months, 78 per cent at six months, 35 per cent at 12 months, 23 per cent at 18 months and 19 per cent at 24 months; the disease-free interval was 80 to 1,246 days (mean 365 days, median 266 days). Lung metastasis developed in 55 per cent of the dogs within one year. Complications were observed in 14/18 dogs (78 per cent), comprising local recurrence (28 per cent), allograft infection (39 per cent) and implant failure (11 per cent). Despite complications, limb sparing is a useful alternative to amputation in selected cases of appendicular osteosarcoma.     

Subluxation/luxation of the second carpal bone in two racing greyhounds and a Staffordshire bull terrier

Subluxation of the second carpal bone (C2) in two racing greyhounds, and luxation associated with other carpal injuries in a Staffordshire bull terrier, were diagnosed as causes of thoracic limb lameness. The clinical signs of subluxation were subtle, with local soft tissue swelling and a pain reaction on digital pressure over the dorsal aspect of C2. In contrast, the dog with a complete luxation was very lame, having marked soft tissue swelling with carpal hyperextension and valgus. Diagnosis was made by radiography. Subluxation of C2 was seen as a small, dorsally displaced opacity between the proximal and distal rows of carpal bones on the mediolateral view and, on the oblique view taken in only one case, as a marked dorsal displacement of one-third of the proximal joint surface of C2. In the case of luxation, C2 appeared on the mediolateral view lying dorsal to the radial carpal bone. There was also fracture of C4. Both greyhounds were treated by internal fixation and returned to racing. The Staffordshire bull terrier was treated by pancarpal arthrodesis with a successful outcome.     

Intraoperative extracorporeal irradiation for limb sparing in 13 dogs

OBJECTIVE: To evaluate extracorporeal intraoperative radiation therapy (IORT) as a treatment method for limb and joint sparing in dogs with appendicular sarcomas in sites other than the distal aspect of the radius. STUDY DESIGN: Retrospective study. ANIMALS: Thirteen client-owned dogs. METHODS: The bone tumor database and medical records (1998-2002) were reviewed for dogs with primary appendicular bone tumors treated with IORT limb-sparing surgery and adjuvant chemotherapy. The segment of bone containing the tumor was isolated from adjacent soft tissue and an osteotomy performed distant to the tumor. The bone segment was exteriorized, irradiated (70 Gy single fraction), and then stabilized with internal fixation. Adjuvant chemotherapy was administered. Lameness was graded and local and distant tumor control was determined. Associations between intra- and postoperative variables with complications and Kaplan-Meier survival analysis for median disease-free interval and survival time were calculated. RESULTS: Limb function was good or excellent in 10 dogs (77%). Postoperative complications (9 dogs, 69%) included deep infection, fracture of the irradiated bone, and implant failure. Surgical failure was more likely if a single implant was used to stabilize the osteotomized bone and if deep infection developed postoperatively. In 3 dogs, tumors recurred locally within bone in the radiation field. The disease-free and overall success rates of extracorporeal IORT for limb and joint preservation were 46% and 54%, respectively. CONCLUSIONS: Extracorporeal IORT provides a novel alternative to traditional techniques for preservation of joint and limb function in dogs with primary appendicular sarcomas. A minimum of 2 implants and intramedullary bone cement should be used to stabilize the osteotomized bone to minimize postoperative complications. Extracorporeal IORT should be used with caution in dogs with tumors of the distal tibia because of a high complication rate. Dogs with tumors in areas of good soft-tissue coverage, such as the humerus and femur, may be good candidates for limb and joint-sparing surgery using extracorporeal IORT. CLINICAL RELEVANCE: Extracorporeal IORT is a surgical technique that can be used for limb and joint salvage in dogs with primary appendicular sarcomas in sites usually not amenable to traditional limb-sparing techniques.     

Unilateral limb enlargement in a dog with a malignant peripheral nerve sheath tumor

A 3- to 4-month-old female Golden Retriever dog presented with right hind limb enlargement. Physical examination of the limb and radiographic findings initially included soft tissue swelling with elongation, bowing, and cortical irregularity of the femur and tibia. During a period of approximately 7 months, pathology in the limb progressed to include tarsal laxity, muscle atrophy, avulsion of the gastrocnemius muscle, and luxation of the patella. During surgical intervention to shorten the limb and repair the patellar luxation, a large soft tissue cyst was identified along the caudal aspect of the femur and stifle. The limb was later amputated, and a final diagnosis of malignant peripheral nerve sheath (PNS) tumor of the sciatic nerve and surrounding soft tissues was made. The unilateral limb enlargement in this dog appears to have been because of the development and progression of a malignant PNS tumor. The presentation and associated pathologic changes in the limb are unusual for canine PNS tumor but have similarities with neurofibromatosis in the limbs of humans.     

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.