Intraoperative Extracorporeal Irradiation for Limb Sparing in 13 Dogs

Updates in Surgical Oncology

New knowledge and data can influence the treatment options of dogs and cats affected by neoplasms. Partial limb amputation with the use of a prosthesis is possible in dogs. Newer studies attempt to define better and understand the complications and limb function associated with this approach. Limb sparing is an alternative to amputation, and three-dimensional printing allows the manufacturing of personalized endoprostheses. Finally, the recommended approach for the excision of cutaneous mast cell tumors (MCTs) is with proportional margins. In dogs, grade shifting might have occurred when removing a recurrent MCT or soft tissue sarcoma.

Nanocarriers in Veterinary Medicine: A Challenge for Improving Osteosarcoma Conventional Treatments

In recent years, several nanocarrier-based drug delivery systems, such as polymeric nanoparticles, solid lipid nanoparticles, metallic nanoparticles, liposomes, and others, have been explored to target and treat a wide variety of diseases. Their employment has brought many benefits, not only to human medicine but also to veterinary medicine, albeit at a slower rate. Soon, the use of nanocarriers could revolutionize the animal health sector, and many veterinary therapies will be more effective as a result. The purpose of this review is to offer an overview of the main applications of nanocarriers in the veterinary field, from supplements for animal health and reproduction to nanovaccines and nanotherapies. Among the major pathologies that can affect animals, special attention is given to canine osteosarcoma (OSA): a comparison with human OSA is provided and the main treatment options are reviewed emphasizing the benefits that nanocarriers could bring in the treatment of this widespread disease.

Personalized endoprostheses for the proximal humerus and scapulohumeral joint in dogs: Biomechanical study of the muscles’ contributions during locomotion

Osteosarcoma represents one of the most common bone tumours in dogs. It commonly occurs in the proximal humerus, the most affected anatomic site. Until recently, amputation or limb-sparing surgery leading to an arthrodesis coupled with chemotherapy were the only available treatments, but they often lead to complications, reduced mobility and highly impact dog’s quality of life. Prototypes of both articulated and monobloc (no mobility) patient-specific endoprostheses have been designed to spare the limb afflicted with osteosarcoma of the proximal humerus. This study focuses on the biomechanical effects of endoprostheses and shoulder muscle kinematics. For each of the endoprosthesis designs, a minimal number of muscles needed to ensure stability and a certain degree of joint movement during walking is sought. A quasi-static study based on an optimization method, the minimization of the sum of maximal muscle stresses, was carried out to assess the contribution of each muscle to the shoulder function. The identification of the most important muscles and their impact on the kinematics of the prosthetic joint lead to an improvement of the endoprosthesis design relevance and implantation feasibility.

Outcome and prognosis for canine appendicular osteosarcoma treated with stereotactic body radiation therapy in 123 dogs

Canine appendicular osteosarcoma is commonly treated with limb amputation; however, limb-sparing options are frequently desired or necessary for a subset of patients. We evaluated 123 patients and 130 sites treated with stereotactic body radiation therapy (SBRT). Eighty-two out of 98 dogs (84%) had maximum lameness improvement at a median of 3 weeks for a median of 6 months duration. Histopathologic evaluation of available samples from amputation or necropsy revealed >80% tumor necrosis in 50% of limbs consistent with local disease control. Of evaluable patients, 41% fractured and 21% pursued an amputation after treatment. Fine needle aspirate (n = 52) and needle core biopsy (n = 28) did not result in increased fracture risk compared to those without tumor sampling (n = 50). Median survival time (MST) was 233 days and time to first event was 143 days. Gross tumor volume and planned target volume were significantly inversely associated with survival and tumor location was significantly associated with survival. Dogs with salvage amputation had a significantly longer MST compared to those without (346 vs 202 days; P = .04). The presence of metastatic disease at the time of treatment in 15 dogs did not significantly impact survival time (200 vs 237 days without metastasis; P = .58). Skin side effects correlated significantly with dose with 33% of patients with acute grade 3 effects developing consequential late grade 3 effects. While SBRT improves lameness in most patients, further investigation is needed to identify candidates with minimal early fracture risk prior to initiating therapy.

Personalized 3D-printed endoprostheses for limb sparing in dogs: Modeling and in vitro testing

Osteosarcoma is the most common type of bone cancer in dogs, treatable by amputation or limb-sparing surgery. For the latter, commercially available plate - endoprosthesis assemblies require contouring, to be adapted to the patient's bone geometry, and lead to sub-optimal results. The use of additively-manufactured personalized endoprostheses and cutting guides for distal radius limb-sparing surgery in dogs presents a promising alternative. Specialized software is used for the bone structure reconstruction from the patient's CT scans and for the design of endoprostheses and cutting guides. The prostheses are manufactured from a titanium alloy using a laser powder bed fusion system, while the cutting guides are manufactured from an ABS plastic using a fused deposition modeling system. A finite element model of an instrumented limb was developed and validated using experimental testing of a cadaveric limb implanted with a personalized endoprosthesis. Personalized endoprostheses and cutting guides can reduce limb sparing surgery time by 25-50% and may reduce the risk of implant failure. The numerical model was validated using the kinematics and force-displacement diagrams of the implant-limb construct. The model indicated that a modulus of elasticity of an implant material ranging from 25 to 50 GPa would improve the stress distribution within the implant. The results of the current study will allow optimization of the design of the personal implants in both veterinary and human patients.

Limb-sparing in dogs using patient-specific, three-dimensional-printed endoprosthesis for distal radial osteosarcoma: A pilot study

Limb-sparing for distal radial osteosarcoma has a high rate of complications. Using personalized three-dimensional (3D)-printed implants might improve outcome. The goals of this study were to optimize use of patient-specific, 3D-printed endoprostheses for limb-sparing in dogs in the clinical environment and to report the outcome. This was a pilot study where five client-owned dogs were enrolled. Computed tomography (CT) of the thoracic limbs was performed, which was used to create patient-specific endoprostheses and cutting guides, and repeated on the day of surgery. Intra-arterial (IA) carboplatin was introduced in the clinical management. Limb-sparing was performed. Outcome measures were time required to produce the endoprosthesis and cutting guide, fit between cutting guide and endoprosthesis with host bones, gait analysis, size of the tumour, percent tumour necrosis, complications, disease-free interval (DFI) and survival time (ST). Four dogs received IA carboplatin. Excessive tumour growth between planning CT and surgery did not occur in any dog. The interval between the CT and surgery ranged from 14 to 70 days. Fit between the cutting-guide and endoprosthesis with the host bones was good to excellent. At least one complication occurred in all dogs. Two dogs were euthanized with STs of 192 and 531 days. The other dogs were alive with a follow up of 534 to 575 days. IA chemotherapy is a promising strategy to minimize the risk of excessive tumour growth while waiting for the endoprosthesis and cutting-guide to be made. The design of the cutting-guide was critical for best fit of the endoprosthesis with host bones.

Efficacy of frozen autograft treated with liquid nitrogen in limb-sparing surgery in feline scapular osteosarcoma: A case report

In recent years, a novel technique of limb preservation has been used in human medicine that involves frozen autograft treated with liquid nitrogen. In this case, frozen autograft treatment along with shoulder joint reconstruction was performed in an 11-year-old cat with osteosarcoma of the distal scapula. Surgical site infection, shoulder dislocation, local recurrence, and pulmonary metastases were not reported for 24 months after surgery. Moreover, the patient was able to bear weight on the operated limb after 2 months of surgery, and excellent limb function without lameness was demonstrated after 15 months. The frozen autograft technique is advantageous because it is inexpensive, simple, and retains its initial strength after treatment, and could be a novel treatment in feline osteosarcoma.

Prognostic value of fluorine18 flourodeoxyglucose positron emission tomography/computed tomography in dogs with appendicular osteosarcoma

Background

Factors indicative of a negative prognosis for appendicular osteosarcoma (OSA) in dogs are visible metastatic disease, location, and size of lesion. In human medicine maximum standard uptake value (SUV_max), as measured on a fluorine¹⁸ flourodeoxyglucose positron emission tomography/computed tomography (¹⁸F‐FDG PET/CT), is prognostic for survival for several tumor types.

Objective

Determine if SUV_max is associated with progression‐free interval (PFI) and determination of survival in dogs with appendicular OSA.

Animals

Sixty‐two dogs with untreated appendicular OSA that had been staged with ¹⁸F‐FDG PET/CT.

Methods

Retrospective analysis of the ¹⁸F‐FDG PET/CT was performed. Dogs were excluded from the study if they did not receive definitive intent treatment for their primary OSA and adjuvant chemotherapy with carboplatin, or had visible metastatic disease on initial imaging. A region of interest (ROI) was created around the primary tumor to measure SUV_max. Univariable and multivariable Cox proportional hazards analysis was performed to evaluate for associations between variables including SUV_max and outcome of PFI and overall survival (OS).

Results

Maximum standard uptake value of the primary tumor was significantly associated with the OS (P = .04) with adjustment for treatment type and monocyte count. The overall median survival time (OST) was 284 days (range, 39‐1293 days) with the OST of dogs having an SUV_max of ≥7.4 of 254 days (range, 98‐428 days) and dogs with an SUV_max of <7.4 of 680 days (range, 108‐811 days, P = .01).

Conclusions and Clinical Importance

Maximum standard uptake value as measured via ¹⁸F‐FDG PET/CT is significantly associated with survival in dogs with appendicular OSA with a high SUV_max being an indicator of a negative prognosis.

New clinical application of three-dimensional-printed polycaprolactone/β-tricalcium phosphate scaffold as an alternative to allograft bone for limb-sparing surgery in a dog with distal radial osteosarcoma

Limb-sparing surgery is one of the surgical options for dogs with distal radial osteosarcoma (OSA). This case report highlights the novel application of a three-dimensional (3D)-printed patient-specific polycaprolactone/β-tricalcium phosphate (PCL/β-TCP) scaffold in limb-sparing surgery in a dog with distal radial OSA. The outcomes evaluated included postoperative gait analysis, complications, local recurrence of tumor, metastasis, and survival time. Post-operative gait evaluation showed significant improvement in limb function, including increased weight distribution and decreased asymmetry. The implant remained well in place and increased bone opacity was observed between the host bone and the scaffold. There was no complication due to scaffold or surgery. Significant improvement in limb function and quality of life was noted postoperatively. Local recurrence and pulmonary metastasis were identified at 8 weeks postoperatively. The survival time from diagnosis of OSA to death was 190 days. The PCL/β-TCP scaffold may be an effective alternative to cortical allograft in limb-sparing surgery for bone tumors.

Orthogonal bone plate stabilization for limb-sparing surgery

This report describes limb-sparing surgery in a 35 kg, six-year-old Hungarian Vizsla with a distal radial lytic bone lesion. Preoperative biopsy had suggested a bone cyst, however histopathology on the excised bone segment was indicative of an osteosarcoma. Following excision of the tumour, the bone defect was filled with a composite bone graft and stabilized with a custom-made dorsal 3.5/2.7 mm pancarpal arthrodesis plate and an orthogonally positioned medial 2.7 mm compression plate. This technique has not previously been described for limb-sparing procedures. No complications were encountered, and despite the owners declining adjunctive chemotherapy, the dog was alive 34 months postoperatively with near normal limb function.

Mechanical properties of canine osteosarcoma-affected antebrachia

OBJECTIVE

To determine the influence of neoplasia on the biomechanical properties of canine antebrachia.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Osteosarcoma (OSA)-affected canine antebrachia (n = 12) and unaffected canine antebrachia (n = 9).

METHODS

Antebrachia were compressed in axial loading until failure. A load-deformation curve was used to acquire the structural mechanical properties of neoplastic and unaffected specimens. Structural properties and properties normalized by body weight (BW) and radius length were compared using analysis of variance (ANOVA). Modes of failure were compared descriptively.

RESULTS

Neoplastic antebrachia fractured at, or adjacent to, the OSA in the distal radial diaphysis. Unaffected antebrachia failed via mid-diaphyseal radial fractures with a transverse cranial component and an oblique caudal component. Structural mechanical properties were more variable in neoplastic antebrachia than unaffected antebrachia, which was partially attributable to differences in bone geometry related to dog size. When normalized by dog BW and radial length, strength, stiffness, and energy to yield and failure, were lower in neoplastic antebrachia than in unaffected antebrachia.

CONCLUSIONS

OSA of the distal radial metaphysis in dogs presented for limb amputation markedly compromises the structural integrity of affected antebrachia. However, biomechanical properties of affected bones was sufficient for weight-bearing, as none of the neoplastic antebrachia fractured before amputation. The behavior of tumor invaded bone under cyclic loading warrants further investigations to evaluate the viability of in situ therapies for bone tumors in dogs.

Outcomes of Limb-Sparing Surgery Using Two Generations of Metal Endoprosthesis in 45 Dogs With Distal Radial Osteosarcoma. A Veterinary Society of Surgical Oncology Retrospective Study

OBJECTIVE

To report outcomes in dogs with distal radial osteosarcoma (OSA) treated with metal endoprosthesis limb-sparing surgery and compare outcomes between 2 generations of endoprosthesis.

STUDY DESIGN

Multi-institutional retrospective case series.

ANIMALS

Forty-five dogs with distal radial OSA treated with endoprosthesis and chemotherapy.

METHODS

Data of dogs treated with either first-generation endoprosthesis (GEN1) or second-generation endoprosthesis (GEN2) were sourced from medical records and radiographs. Surgical outcomes included postoperative lameness assessment and the presence, severity, and time to onset of complications. Oncologic outcomes included presence of local recurrence or metastasis, time to onset of local recurrence, metastasis-free interval (MFI), and survival time. Results for surgical and oncologic outcomes were compared between GEN1 and GEN2.

RESULTS

Twenty-eight dogs received GEN1 and 17 dogs received GEN2. There were 39 complications (96%, 14 minor, 29 major) including infection (78%), implant-related complication (36%), and local recurrence (24%). Metastatic frequency was 67% and median MFI was 188 days (95% confidence interval [CI]: 126-250 days). Survival time ranged from 34 days to 6.1 years with a median of 289 days (95% CI: 207-371 days). There was no significant difference in complication severity, frequency, time to complication, MFI, or survival time between dogs receiving GEN1 and GEN2.

CONCLUSION

There was no significant difference in outcomes between dogs receiving GEN1 and GEN2 for limb-sparing surgery of the radius. Metastatic frequency and survival time for metal endoprosthesis were similar to that of amputation with curative intent chemotherapy.

Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology

Osteosarcoma (OSA) is the most common form of malignant bone cancer in children and dogs, although the disease occurs in dogs approximately 10 times more frequently than in people. Multidrug chemotherapy and aggressive surgical techniques have improved survival; however, new therapies for OSA are critical, as little improvement in survival times has been achieved in either dogs or people over the past 15 years, even with significant efforts directed at the incorporation of novel therapeutic approaches. Both clinical and molecular evidence suggests that human and canine OSA share many key features, including tumor location, presence of microscopic metastatic disease at diagnosis, development of chemotherapy-resistant metastases, and altered expression/activation of several proteins (e.g. Met, ezrin, phosphatase and tensin homolog, signal transducer and activator of transcription 3), and p53 mutations, among others. Additionally, canine and pediatric OSA exhibit overlapping transcriptional profiles and shared DNA copy number aberrations, supporting the notion that these diseases are similar at the molecular level. This review will discuss the similarities between pediatric and canine OSA with regard to histology, biologic behavior, and molecular genetic alterations that indicate canine OSA is a relevant, spontaneous, large animal model of the pediatric disease and outline how the study of naturally occurring OSA in dogs will offer additional insights into the biology and future treatment of this disease in both children and dogs.

Stereotactic radiosurgery and fracture fixation in 6 dogs with appendicular osteosarcoma

OBJECTIVE

To evaluate clinical outcome of dogs with appendicular osteosarcoma (OSA) treated with stereotactic radiosurgery (SRS) and subsequent internal fixation of a pathologic fracture.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs with spontaneous-occurring appendicular OSA (n = 6).

METHODS

Medical records (May 2002-January 2008) of dogs that had SRS for appendicular OSA were reviewed. Dogs were included if they had a pathologic fracture either before or after SRS and were treated with internal fixation. Signalment, history, physical examination findings, clinicopathologic data, diagnostic imaging findings, biopsy results, surgical complications, number of surgeries, adjuvant therapy, development of metastatic disease and cause of death were recorded.

RESULTS

Six dogs met the inclusion criteria. Two dogs had a pathologic fracture at admission and 4 dogs developed a fracture after SRS with a mean ± SD time to fracture development of 6.25 ± 1.65 months. The first 3 fractures were repaired using an open approach and the latter three using minimally invasive percutaneous osteosynthesis (MIPO). Infection occurred in 5 dogs and implant failure in 3. Limb function was subjectively assessed as good in all dogs when the implants were stable and infections were subclinical. Survival times ranged from 364-897 days; 1 dog was lost to follow-up.

CONCLUSIONS

Fracture repair using internal fixation should be considered a viable limb-sparing alternative for pathologic fractures that have been treated with SRS.

Use of irradiated autologous bone in joint sparing endoprosthetic femoral replacement tumor surgery

BACKGROUND

Joint preservation is usually attempted in cases of bone tumors, though insufficient bone following tumour resection may prevent fixation of conventional joint sparing prosthesis. To preserve the hip joint in skeletally immature patients, we have combined autologous proximal femoral irradiation and intercalary re-implantation with custom made distal femoral replacements.

MATERIALS AND METHODS

A retrospective cohort study of four patients (aged 4-12 years); in whom irradiated autologous bone was combined with an extendable distal femoral endoprostheses was performed. There were three cases of osteosarcoma and one case of Ewing's sarcoma.

RESULTS

At a mean follow-up of 70.5 months (range 26-185 months), all four patients were alive without evidence of local recurrence. There was no evidence of metastatic disease in three patients while one patient showed chest metastatic disease at presentation. In all cases, the irradiated segment of bone united with the proximal femur and demonstrated bone ongrowth at the prosthetic collar. There were no cases of loosening or peri-prosthetic fracture. One implant was revised after 14 years following fracture of the extending component of the endoprosthesis.

CONCLUSIONS

We report encouraging results utilizing irradiated autologous proximal femoral bone combined with distal femoral replacement in skeletally immature patients.

Percutaneous cementoplasty in the palliative, multimodal treatment of primary bone tumors of the distal aspect of the radius in four dogs

OBJECTIVE

To (1) evaluate the analgesic effect of percutaneous cementoplasty (PC) in dogs with primary bone tumor (PBT) of the distal aspect of the radius and (2) evaluate the impact on the course of disease by adding PC to a palliative, multimodal treatment protocol in these dogs.

STUDY DESIGN

Prospective pilot study.

ANIMALS

Dogs (n=4) with PBT of the distal aspect of the radius.

METHODS

Tumor lesions were filled percutaneously with polymethylmethacrylate under fluoroscopic guidance. Pamidronate was administered once in a week before PC. Radiotherapy and chemotherapy were initiated 2 and 6 weeks after PC, respectively. Force plate analysis was performed immediately before 2, and 6 weeks after PC. Survival time was defined from PC to euthanasia.

RESULTS

Two dogs had a significant increase in peak vertical force 2 weeks after PC (P=.043) and remained free of lameness for 18 and 20 weeks, respectively. One dog had an acute relapse after an initially lame-free period of 10 days. The remaining dog failed to improve (P=.686). Three dogs developed at least 2 complications including transient worsening of the lameness after PC, cement leakage, wound infection and suspected thromboembolism in combination with cough and anemia. Median survival was 4.8 months (range, 1-5.7 months).

CONCLUSIONS

PC in combination with pamidronate significantly improved lameness in 2 dogs; however, PC is not risk-free. Deep wound infection, intraarticular cement leakage, and venous thrombosis were the main complications.

CLINICAL RELEVANCE

PC might be a useful addition to established palliative, multimodal treatment protocols in dogs with PBT; however, because of the complications encountered PC warrants further study before routine use can be considered.

Extracorporeal irradiation for pelvic reconstruction in Ewing’s sarcoma

We review the treatment of pelvic Ewing’s sarcoma by the implantation of extracorporeally-irradiated (ECI) autografts and compare the outcome with that of other reported methods.

We treated 13 patients with ECI autografts between 1994 and 2004. There were seven males and six females with a median age of 15.7 years (interquartile range (IQR) 12.2 to 21.7). At a median follow-up of five years (IQR 1.8 to 7.4), the disease-free survival was 69% overall, and 75% if one patient with local recurrence after initial treatment elsewhere was excluded. Four patients died from distant metastases at a mean of 17 months (13 to 23). There were three complications which required operative intervention; one was a deep infection which required removal of the graft. The functional results gave a mean Musculoskeletal Tumor Society score of 85% (60% to 97%), a mean Toronto extremity salvage score of 86% (69% to 100%) and a mean Harris hip score of 92 (67 to 100).

We conclude that ECI grafting is a suitable form of treatment for localised and resectable pelvic Ewing’s sarcoma.

Intraoperative Radiation for Limb Sparing of the Distal Aspect of the Radius Without Transcarpal Plating in Five Dogs

OBJECTIVES

To evaluate intraoperative irradiation (IORT) as a method of limb spare with preservation of the radiocarpal joint.

STUDY DESIGN

Prospective case series.

ANIMALS

Dogs (n=5) with stage II sarcoma of the distal aspect of the radius.

METHODS

A bone segment containing the tumor was isolated surgically, treated by IORT, reimplanted, and secured by internal fixation. In 1 dog, the postradiation tumor bed was curetted and filled with bone cement. Dogs were administered alternating adriamycin and carboplatin starting 2 weeks after IORT and monitored at regular intervals.

RESULTS

Four dogs had osteosarcoma and 1 had undifferentiated sarcoma. Implant failure (n=3), deep tissue infection (3), and pathologic fracture (3) resulted in amputation (3) or pancarpal plating (2). The dog with undifferentiated sarcoma was euthanatized because of suspected tumor recurrence 4 months postoperatively. Osteotomy healing was documented by radiography (1), histopathology (2), or by direct observation (2).

CONCLUSIONS

A technique for limb-sparing surgery of the distal portion of the radius in dogs using IORT had advantages include healing of the autograft and a source for a perfectly fitting autograft but did not appear to offer any advantage with respect to infection rate. Long-term preservation of the radiocarpal joint was not successful.

CLINICAL RELEVANCE

It was not possible to preserve the function of the radiocarpal joint and so this technique cannot be recommended currently. Further study is needed to evaluate whether or not IORT can be considered in combination with pancarpal plating and possibly curettage and cementation of the tumor to prevent subchondral bone collapse.

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.

Cortical Bone Graft and Endoprosthesis in the Distal Radius of Dogs: A Biomechanical Comparison of Two Different Limb-Sparing Techniques

OBJECTIVE

To compare the biomechanical properties of cortical bone and surgical steel endoprosthesis for limb-sparing surgery of the distal radius in dogs and evaluate the role of the ulna in providing stability to the reconstructed limb.

STUDY DESIGN

Cadaveric biomechanical study.

ANIMALS

Twelve pairs of normal canine thoracic limbs.

METHODS

Paired limbs were divided into 4 groups: endoprosthesis and cortical bone graft, with and without preservation of the ulna. In each limb pair, the distal segment of the radius resected from the limb to be reconstructed with an endoprosthesis was used as the cortical bone graft in the contralateral limb. The ulna was resected en bloc with the radius and at the same level as the radial osteotomy in limbs where the ulna was not preserved. Limbs were tested in axial loading until failure. The load-deformation curve was used to acquire the biomechanical properties of each construct, which were compared using 2-way ANOVA. Failure modes were compared descriptively.

RESULTS

Limbs reconstructed with the endoprosthesis had significantly greater yield load, energy at yield, and ultimate load compared with limbs reconstructed with a cortical bone graft. There were no significant differences in either energy to failure or stiffness between the 2 constructs. Preservation of the ulna did not significantly improve any of the biomechanical properties tested with either endoprosthesis or cortical bone graft constructs. The modes of failure in all 4 groups were variable and inconsistent.

CONCLUSIONS

Limbs reconstructed with an endoprosthesis were biomechanically superior to limbs reconstructed with a cortical bone graft in axial loading to failure. Preservation of the ulna is not required to improve the stability in axial compression after limb-sparing surgery of the distal radius.

CLINICAL RELEVANCE

The endoprosthesis may provide another option for limb-sparing surgery of the distal radius in dogs. It has potential advantages when compared with cortical bone grafts, including better biomechanical performance and resistance to implant failure in axial compression, immediate availability, and no requirement for bone banking facilities. The ulna can be resected en bloc with the radius without having a negative impact on construct stability. En bloc resection of the ulna and radius may decrease the risk of local tumor recurrence after limb-sparing surgery.

Common malignant musculoskeletal neoplasms of dogs and cats

Malignancies of the musculoskeletal system in dogs and cats can be categorized as either primary or metastatic within the bony or soft structures that comprise the musculoskeletal system. By far, the most common tumor that affects the musculoskeletal system in dogs is osteosarcoma. The most common tumors that affect the musculoskeletal system in cats are injection site sarcomas. These tumors are locally infiltrative; whereas up to 25% metastasize, most animals die from our inability to control local disease. The aim of this article is to provide a brief review of the biologic behavior of and treatment recommendations for common tumors of the musculoskeletal system, excluding the oral and nasal cavities.

Limb-Sparing Surgery in a Dog with Osteosarcoma of the Proximal Femur

OBJECTIVE

To report successful limb-sparing surgery in a dog with a proximal femoral osteosarcoma (OSA) using a composite allograft-prosthetic technique.

STUDY DESIGN

Case report.

ANIMAL

Client-owned dog.

METHODS

A stage IIB OSA of the proximal aspect of the femur was resected in accordance with oncologic and limb-sparing principles. The osseous defect was reconstructed with a proximal femoral allograft and cemented, long-stemmed femoral prosthesis. Soft tissue reconstruction was achieved by suturing host tendons to their respective allogeneic tendons on the allograft. Coxofemoral joint function was preserved using standard total hip arthroplasty techniques.

RESULTS

Limb-sparing surgery of the proximal aspect of the femur using a composite allograft-prosthetic technique resulted in excellent limb function. Postoperative complications included aseptic loosening of the femoral composite graft and allograft nonunion, which required revision, traumatic implant luxation, and local tumor recurrence. Limb function was excellent after surgical stabilization of the allograft nonunion but deteriorated after implant luxation 270 days postlimb-sparing surgery. Pulmonary and skeletal metastases were diagnosed and local tumor recurrence suspected 596 and 650 days postoperatively, respectively. The dog was euthanatized 688 days after limb-sparing surgery as a result of progressive local and metastatic disease.

CONCLUSIONS AND CLINICAL RELEVANCE

Limb-sparing surgery for dogs with primary bone tumors of the proximal aspect of the femur is feasible with good functional results.