Osteosarcoma following total hip arthroplasty in a dog

Radiographic and CT features of metallosis in a lame dog after total hip replacement: the cloud sign

A 2-year-old female American Akita was referred for CT of the pelvis and hindlimbs due to a left hindlimb lameness after a left total hip replacement. Referral radiographs and CT images demonstrated amorphous soft-tissue and mineral opacities surrounding the proximal femur and the prosthetic stem, consistent with the "cloud sign" reported as a characteristic of metallosis in humans. Dorsomedial displacement of the prosthetic head, multiple foci of geographic osteolysis alongside the "cloud sign", presumed pseudotumor lesions, and medial iliac lymphadenopathy were also identified with CT. Metallosis was confirmed based on ultrasound-guided cytology, revision surgery, and histopathology.

Indications for the removal of implants after fracture healing: A comparison between human and veterinary medicine

Indications for implant removal after fracture healing are still under debate in both human and veterinary medicine. Although hardware removal is a common procedure, it should not be undertaken lightly. Intra and post-operative complications are common and a thorough evaluation of the risks and benefits should be performed. This review aimed to collect and summarise published data on the indications for implant removal in small animals, compare the collected data with human and equine medicine, and investigate the existence of guidelines for this purpose. There is no international consensual agreement for implant removal after fracture healing, neither in small animals nor in human orthopaedics. Decision-making processes are still controversial in some scenarios, thus clear evidence-based protocols for implant removal are needed.

Canine Idiopathic Arteriopathy, Appendicular Bone Infarcts, and Neoplastic Transformation of Bone Infarcts in 108 Dogs (Canis lupus familiaris)

Osteosarcoma (OSA) is the most common primary bone tumor in both dogs and humans. The dog is an important research model for OSA, yet dogs have much higher prevalence of bone tumors than do humans, a disparity that has yet to be explained. Neoplastic transformation of cells within or adjacent to bone infarcts into primary bone tumors has been described in humans but only sparsely characterized in the veterinary literature. In this study, 653 cases of canine bone infarcts were received through a referral veterinary osteopathology service over a 14-y period. We identified an idiopathic disorder affecting the nutrient artery, termed canine idiopathic arteriopathy (CIA), which to our knowledge has no direct counterpart in human medicine. This disorder was documented alongside ischemic necrosis of the medullary cavity in 114 bone infarcts in 108 dogs. We hypothesize that CIA precipitated an ischemic environment, resulting in development of a bone infarct down- stream of the abnormal artery. In 52% (59 of 114) of cases, bone infarcts demonstrated evidence of repair (termed reparative bone infarcts [RBI]), while in 48% (55 of 114) of infarcts, a bone tumor was also present, including pleomorphic sarcoma, OSA, fibrosarcoma, and chondrosarcoma. In some cases, a spectrum of tumors was present. We hypothesize that the ischemic infarct environment provoked bone marrow mesenchymal stem cells (MSCs) to attempt repair of the stroma, and in approximately half of cases, MSCs underwent neoplastic transformation (BINT) to produce tumors. The most common sites of bone infarcts were the distal femur, distal radius, proximal humerus, and distal tibia, coinciding with common sites of canine OSA. The authors propose that CIA leading to bone infarcts and infarct-derived tumors, in combination with possible underdiagnosis of canine bone infarcts and misdiagnosis of some RBI as neoplasia, may contribute to the higher reported proportion of bone tumors in dogs compared with humans.

The occurrence of osteosarcoma after tibial fracture repair in a dog

Background:

There are few detailed reports on implant-associated sarcoma in dogs; however, loose implants, metal type, and infection have not been shown as specific risk factors for this condition.

Case Description:

A 14-year-old spayed female Labrador retriever was referred to our hospital with a main complaint of chronic right hind lameness after previous tibial fracture repair. On radiographs, rupture of the bone plate and screws with swelling of the surrounding soft tissue was observed, and osteosarcoma (OSA) was diagnosed after histopathological examinations. During amputation surgery, a plastic band was found associated with the implant.

Conclusion:

Veterinary surgeons should be aware of implant-associated OSA and refrain from using non-medical materials in the implants. Furthermore, they should recommend the removal of orthopedic implants after fracture repair.

Risk Factors for Development of Canine and Human Osteosarcoma: A Comparative Review

Osteosarcoma is the most common primary tumor of bone. Osteosarcomas are rare in humans, but occur more commonly in dogs. A comparative approach to studying osteosarcoma has highlighted many clinical and biologic aspects of the disease that are similar between dogs and humans; however, important species-specific differences are becoming increasingly recognized. In this review, we describe risk factors for the development of osteosarcoma in dogs and humans, including height and body size, genetics, and conditions that increase turnover of bone-forming cells, underscoring the concept that stochastic mutational events associated with cellular replication are likely to be the major molecular drivers of this disease. We also discuss adaptive, cancer-protective traits that have evolved in large, long-lived mammals, and how increasing size and longevity in the absence of natural selection can account for the elevated bone cancer risk in modern domestic dogs.

Association of tibial plateau leveling osteotomy with proximal tibial osteosarcoma in dogs

OBJECTIVE To assess for any association between a history of tibial plateau leveling osteotomy (TPLO) and subsequent development of proximal tibial osteosarcoma in dogs. DESIGN Matched case-control study. ANIMALS 34 client-owned dogs in which proximal tibial osteosarcoma was diagnosed between January 2005 and December 2012 (cases) and 79 dogs without osteosarcoma, matched 3:1 to cases (when possible) by age, breed, and initial examination date (controls). PROCEDURES Information on each case and control was collected from the medical records and other sources regarding date of birth, sex and neuter status, body weight, breed, and whether TPLO had been performed ≥ 1 year ago. A multivariable conditional logistic regression model was constructed to evaluate associations of body weight and history of TPLO with the outcome of proximal tibial osteosarcoma in dogs. RESULTS After adjusting for body weight in the multivariable model, dogs with a history of TPLO were 40 times as likely to develop proximal tibial osteosarcoma as were dogs with no history of TPLO. In addition, each 1-kg (2.2-lb) increase in body weight was associated with an 11% increase in the odds of proximal tibial osteosarcoma. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that dogs with a history of TPLO were at increased risk of developing osteosarcoma of the proximal region of the tibia relative to dogs with no such history. Therefore, it is important for proximal tibial osteosarcoma to be included among the differential diagnoses for new or worsening hind limb lameness in dogs that underwent TPLO ≥ 1 year previously.

Implant-associated neoplasia in dogs: 16 cases (1983-2013)

OBJECTIVE

To characterize clinical and pathological features of implant-associated neoplasms in dogs.

DESIGN

Retrospective case-control study.

ANIMALS

16 dogs with implant-associated neoplasia and 32 control dogs with osteosarcoma without implants. Procedures: Medical records of dogs with tumors associated with metallic implants (cases) treated between 1983 and 2013 were reviewed. Two dogs with naturally occurring osteosarcoma (controls) were matched to each case on the basis of tumor location, age, and sex.

RESULTS

Median time from implant placement to diagnosis of neoplasia was 5.5 years (range, 9 months to 10 years). Pelvic limbs were most frequently affected, including the tibia (8/16) and femur (5/16), with 1 neoplasm involving both the femur and pelvis. Implant: associated tumors most commonly affected the diaphysis (15/16), with osteosarcomas significantly more likely to involve the long bone diaphysis in case dogs than in control dogs with naturally occurring osteosarcomas. Osteosarcoma was the most common tumor, accounting for 13 of 16 implant-associated tumors. For 7 of these osteosarcoma cases, review of histopathology results enabled subclassification into osteoblastic nonproductive (n = 3), chondroblastic (2), osteoblastic productive (1), and fibroblastic (1) groups. Three case dogs had a diagnosis of histiocytic sarcoma, fibrosarcoma, and spindle cell sarcoma.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study highlighted important anatomic differences between spontaneous and implant-associated neoplasia in dogs.

Total hip arthroplasty-related osteogenic osteosarcoma: case report and review of the literature

BACKGROUND

Orthopedic implant-related sarcoma is an exceedingly rare, but a known complication of total hip arthroplasty (THA).

CASE PRESENTATION

The authors describe clinical and radiologic features, histologic appearance, and treatment of osteogenic osteosarcoma located in the proximal femoral diaphysis associated with an unstable femoral prosthesis following THA in a 65-year-old male patient. The patient with HLA-B27 positive ankylosing spondylitis underwent arthroplasty 15 years ago.

CONCLUSIONS

The neoplastic process may be considered as an extraordinary complication of THA and might just be coincidental or the result of some derangement of the healing process in host tissue with no definitely proven hypothesis that the implants or their by-products are carcinogenic. The soluble chemical substances from the implanted prosthetic material are, at least in animals, suspected to play a vital role in the pathogenesis of the neoplastic transformation of the bone tissue. The presented case shall alert orthopedic surgeons to clinical, radiologic, and macroscopic similarities between a malignant tumor and benign lesions caused by wear debris at THA sites. At the examination of plane X-rays of patients with THA loosening, the differential diagnosis should always include osteogenic sarcoma, as well. To our knowledge, there have been only nine cases of THA-related osteogenic osteosarcomas described in the English-language literature.

Risk of Osteosarcoma in Dogs After Open Fracture Fixation

OBJECTIVE

To critically evaluate whether open fracture fixation is a significant risk factor for latent osteosarcoma development.

STUDY DESIGN

Case-control study.

SAMPLE POPULATION

Dogs undergoing open fracture repair and dogs diagnosed with osteosarcoma.

METHODS

Records were retrieved from the Veterinary Medical Database VMDB (1970-2000) for dogs undergoing surgical repair of a fracture and dogs diagnosed with osteosarcoma. Dogs with open reduction of joint luxation, dogs diagnosed with bacterial cystitis, and dogs diagnosed with urinary bladder transitional cell carcinoma (UBTCC) were queried as comparison populations. Relative risk for osteosarcoma development was determined.

RESULTS

From a population of 19,041 fractures treated surgically, 15 of those dogs subsequently appeared in the VMDB with osteosarcoma affecting the same bone. The relative risk of a fracture repair and associated orthopedic implants and osteosarcoma occurrence was equivalent to the relative risk of open joint reduction and osteosarcoma occurrence (95% confidence interval; 0.998-1.00). The relative risk of having bacterial cystitis and appearing again in the VMDB with UBTCC was higher than the risk of open fracture repair and a subsequent diagnosis of osteosarcoma (P < .02).

CONCLUSION

The incidence of fracture-related osteosarcoma may be significantly less than previously estimated based on cases queried from the VMDB. Although possible cases of implant-associated osteosarcoma were identified, their occurrence was rare. Elective implant removal for the purpose of reducing the risk of osteosarcoma after fracture repair may not be warranted and merits further investigation.

Osteosarcoma following tibial plateau leveling osteotomy in dogs: 29 cases (1997-2011)

OBJECTIVE

To determine the signalment, tibial plateau leveling osteotomy (TPLO) plate type, clinical staging information, treatment, and oncological outcome in dogs that developed osteosarcoma at the proximal aspect of the tibia following TPLO and to calculate the interval between TPLO and osteosarcoma diagnosis.

DESIGN

Multi-institutional retrospective case series.

ANIMALS

29 dogs.

PROCEDURES

Medical records from 8 participating institutions were searched for dogs that developed osteosarcoma (confirmed through cytologic or histologic evaluation) at previous TPLO sites. Signalment, TPLO details, staging tests, treatment data, and outcome information were recorded. Descriptive statistics were calculated, and disease-free intervals and survival times were evaluated by means of Kaplan-Meier analysis.

RESULTS

29 dogs met the inclusion criteria. The mean age was 9.2 years and mean weight was 45.1 kg (99.2 lb) at the time of osteosarcoma diagnosis. Most dogs had swelling over the proximal aspect of the tibia (17/21) and lameness of the affected limb (28/29). The mean interval between TPLO and osteosarcoma diagnosis was 5.3 years. One type of cast stainless steel TPLO plate was used in most (18) dogs; the remaining dogs had received plates of wrought stainless steel (n = 4) or unrecorded type (7). Twenty-three of 29 dogs underwent treatment for osteosarcoma. Median survival time for 10 dogs that underwent amputation of the affected limb and received ≥ 1 chemotherapeutic treatment was 313 days.

CONCLUSIONS AND CLINICAL RELEVANCE

Results supported that osteosarcoma should be a differential diagnosis for dogs with a history of TPLO that later develop lameness and swelling at the previous surgical site. Oncological outcome following amputation and chemotherapy appeared to be similar to outcomes previously reported for dogs with appendicular osteosarcoma.

Modified cementless total coxofemoral prosthesis: development, implantation and clinical evaluation

The aim of this study was to modify canine coxofemoral prostheses and the clinical evaluation of the implantation. Fifteen canine hips and femora of cadavers were used in order to study the surface points of modification in prostheses and develop a perforation guide. Femoral stems and acetabular components were perforated and coated with biphasic calcium phosphate layer. Twelve young adult male mongrel dogs were implanted with coxofemoral prostheses. Six were operated upon and implanted with cemented canine modular hip prostheses, establishing the control group. The remaining six were implanted with a novel design of cementless porous tricalcic phosphate-hydroxyapatite coated hip prostheses. Clinical and orthopedic performance, complications, and thigh muscular hypotrophy were assessed up to the 120th post-operatory day. After 120 days, animals with cementless prostheses had similar clinical and orthopedic performance compared to the cemented group despite the increased pain thigh hypotrophy. Animals that underwent cementless hip prosthesis evidenced more pain, compared to animals with cemented hip prosthesis that required longer recuperation time. No luxations, two fractures and two isquiatic neurapraxies were identified in the course of the study. Using both the cemented and the bioactive coated cementless model were suitable to dogs, showing clinical satisfactory results. Osseointegration and biological fixation were observed in the animals with the modified cementless hip prosthesis.

Osteosarcoma at the site of a triple pelvic osteotomy in a dog

An osteosarcoma (OSA) involving the right pelvis was diagnosed in a 12-year-old golden retriever 11 years after triple pelvic osteotomy (TPO) surgery. The dog was presented with a 12-week history of nonweight-bearing lameness of the right hind limb. Radiographs demonstrated an aggressive bone lesion of the right ilium with profound periosteal proliferation and punctate lysis that extended along the ilium caudally and into the right ischium, with its epicenter at the level of the right TPO plate. Necropsy revealed that the entire right hemipelvis, especially the ischium, was markedly thickened and firm with irregular margins. Histopathology was consistent with a diagnosis of OSA.

Microchemical and surface evaluation of canine tibial plateau leveling osteotomy plates

OBJECTIVE

To determine the microchemical and surface composition of tibial plateau leveling osteotomy (TPLO) plates before and after explantation.

SAMPLE POPULATION

7 TPLO plates surgically removed from host dogs 6 to 54 months after implantation; 2 raw unpolished-and-unpassivated 316L TPLO plates; and 2 heat-treated, polished-and-passivated, and cleaned 316L TPLO plates.

PROCEDURES

Samples were removed by use of standard techniques to ensure the plate surface was not damaged. Sample pieces were dissolved and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to determine bulk elemental composition. Other sample pieces were investigated by use of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS) for determination of sample morphology, near-surface elemental composition, and surface elemental composition, respectively. To investigate the possibility of corrosion in situ, some samples were chemically corroded and analyzed.

RESULTS

ICP-MS confirmed that elemental composition of samples was consistent with 316L stainless steel. The SEM and EDS analyses revealed trace amounts of polishing materials and a nonuniform carbonaceous biofilm on < 1% of the surface area of samples removed from the host dogs. The XPS analysis indicated an increase in the chromium-to-iron ratio on passivated surfaces, with no difference between passivated samples before implantation and after explantation.

CONCLUSIONS AND CLINICAL RELEVANCE

Composition of the TPLO plates was consistent with 316L stainless steel. No chemical or topographic changes were detected in TPLO plates that had been implanted in dogs for up to 54 months. A small amount of biofilm was evident on the surface of 2 plates.

Total joint replacement in the dog

Total joint replacement has evolved over the past 50 years from a concept that was first attempted in people suffering from osteoarthritis to a commonly applied practice in veterinary medicine. Although many questions have been answered, several controversies still exist, with many implant and technical options being explored. Currently, total hip and elbow replacement are commercially available options viable for use in dogs. These options are detailed in this article. Joint replacement for other canine joints (ie, knee, hock, shoulder) that develop osteoarthritis likely will be developed in the near future.

Osteosarcoma of the Humeral Head Associated With Osteochondritis Dissecans in a Dog

A 6-year-old, male Labrador retriever was presented for lameness of the right forelimb. The lameness occurred 5 years after the dog was surgically treated for osteochondritis dissecans (OCD) of the caudal right humeral head. Radiographs revealed an expansile, osteolytic lesion occupying the entire caudal half of the right humeral head, and biopsy confirmed the diagnosis of osteosarcoma. Forelimb amputation was performed. Histopathology of the lesion and associated articular cartilage revealed neoplastic osteoblasts extensively infiltrating the marrow space adjacent to scar tissue associated with the previous OCD lesion. This is the first report of an epiphyseal osteosarcoma in the area of a previous OCD lesion in a dog.