The knowledge of the paleopathologies that affected large mammals during the Pleistocene of South America has increased in the last years, but most of the reported cases belong to the endemic clade Xenarthra. On the contrary, almost no case of diseases is known among representatives of other clades, such as Carnivora. Here we present and describe an inflammatory lesion in a left metacarpal IV assigned to the saber tooth Smilodon populator (Felidae) from the Late Pleistocene (ca. 100 ka; MIS 5) of Northeastern Argentina. The macroscopic and radiologic analyses reveal features consistent with chronic osteomyelitis, which in turn represents the first accurate record of an infectious process in a limb of this predator. This injury presumably caused lameness and loss of toe flexion, and considerably reduced the hunting abilities of this top predator, which used its robust forelimbs, particularly wide forepaws, and powerful back muscles to catch and bring down large prey.

Bone pathologies have great potential to provide information on the palaeobiology of fossil organisms. Some were likely related to inter/intraspecific fighting behaviors. Among the iconic and conspicuous Late Pleistocene armored mammals, Panochthus Burmeister, 1866 is notable for being one of the largest, most abundant, and diversified genera. A particular feature of Panochthus species is the presence of a caudal armor including a solid bony structure known as a caudal tube that would have played an important role in intra/interspecific contests. In this contribution, we report and describe a caudal vertebra of Panochthus that shows strong evidence of pathologies that may be related to the performance of strong tail movements that could correspond to offensive/defensive behaviors. The specimen (MFA-G-PV 1740) was recovered from Late Pleistocene deposits (MIS 5–3 cycles) cropping out in the cliffs of Northern Salado River, Santa Fe Province, Argentina. Based on morphological and radiological features, the lesions observed are related to a traumatic lesion that would have affected the ligamentum flavum and probably the articular capsule of the postzygapophysis, generating a severe enthesopathy and related septic arthritis. The involvement of this ligament in particular is crucial because it connects adjacent vertebral laminae and restricts mobility, offering resistance to extreme vertebral flexion and protecting the remaining vertebral structures when confronted with large forces. Although it is challenging to determine the exact way in which this species performed fighting tail movements, the joints with the greatest range of movement correspond to the most anterior caudal vertebrae. This also implies that any strong impact would have directly affected these vertebrae and associated soft tissues, including ligaments. Based on this evidence, we consider that the pathology described here represents strong evidence to support the idea of an active use of the caudal tube in Panochthus.

Biodegradable, shape memory polymer (SMP) scaffolds based on poly(ε-caprolactone) (PCL) offer unique advantages as a regenerative treatment strategy for critical-sized bone defects. In particular, a conformal fit may be achieved following exposure to warm saline, thereby improving osseointegration and regeneration. Advancing the clinical translation of these SMP scaffolds requires establishment of efficacy not only in non-loading models, but also load-bearing or load-sharing models. Thus, the present study evaluated the biocompatibility and bone regeneration potential of SMP scaffolds in a rabbit distal femoral condyle model. Two distinct SMP scaffold compositions were evaluated, a "PCL-only" scaffold formed from PCL-diacrylate (PCL-DA) and a semi-interpenetrating network (semi-IPN) formed from PCL-DA and poly(L-lactic acid) (PCL:PLLA). Semi-IPN PCL:PLLA scaffolds possess greater rigidity and faster rates of degradation versus PCL scaffolds. In vivo biocompatibility was assessed with a rat subcutaneous implantation model, whereas osseointegration was assessed with a 4 mm × 8 mm rabbit distal femoral condyle defect model. Both types of SMP scaffolds exhibited excellent biocompatibility marked by infiltration with fibrous tissue and a minimal inflammatory response. When implanted in the rabbit distal femur, both SMP scaffolds supported bone ingrowth. Collectively, these results demonstrate that the SMP scaffolds are biocompatible and integrate with adjacent host osseous tissues when implanted in vivo in a load-sharing environment. This study provides key proof-of-concept data necessary to proceed with large animal translational studies and clinical trials in human subjects.

Objective: To report a capital physeal fracture as the result of a bone infarction with subsequent neoplastic transformation 4 years following total hip replacement. Study design: Case report. Animals: Five-year-old female spayed golden retriever. Methods: The dog was initially presented for evaluation of a 2 week history of spontaneous right hind-limb lameness. Pelvic radiographs demonstrated a displaced capital epiphysis and proximal femur changes consistent with a bone infarction. A cementless total hip replacement was performed, and limb function returned to normal until 51 months after surgery. A radiolucency adjacent to the femoral stem at the greater trochanter, partial calcar resorption, and stable implants were present on pelvic radiographs acquired 52 months after surgery. Surgical exploration of the surgical site for tissue collection for histopathology and bacteria culture was performed 58 months following surgery. No bacterial growth occurred and histologic findings were nonspecific. A right hind-limb amputation was performed 61 months after total hip replacement due to the dog's progression to a non-weight-bearing lameness, Additional tissue samples were taken from the femur for histopathologic examination. Results: Histopathologic examination was consistent with a pleomorphic sarcoma. No metallic or polyethylene particulate debris was present. Nine months after surgery there was evidence of regional and distant spread of the neoplasia. Conclusion: In similar cases, submitting the femoral head for histopathologic examination should be considered at the time of the hip replacement surgery. If bone infarction is diagnosed as a causative agent, given the possibility of malignant transformation, long-term serial radiographic monitoring should be given serious consideration.

A 2.5-year-old, 2.9 kg, neutered, male domestic rabbit presented for sudden onset of sneezing and wheezing of 2-day duration. Upon physical examination, there was mild dyspnoea characterised by mild to moderate increased inspiratory effort and audible wheeze, without evidence of ocular or nasal discharge. An aggressive expansile lytic mass lesion of the right caudal maxilla extending into the zygomatic arch was identified on skull radiographs. Computed tomography confirmed a large heterogeneously contrast enhancing soft tissue mass associated with the lytic lesion, likely originating from the right alveolar bulla, extending into the zygomatic arch. Histopathological diagnosis was osteosarcoma with areas of osteogenic and fibroblastic patterns. Diseases of the nasal cavity are common in rabbits; while infectious rhinitis remains the most common diagnosis, increasing number of cases of neoplasms involving the maxilla and nasal cavity should remind clinicians to include it in the differential diagnosis list.

Proliferative tenosynovitis (PT) is an inflammatory and proliferative disorder of the synovial membrane of the tendon sheath that is rare in animals. The histological alterations are characterized by multinodular neovascularization, with infiltration of histiocytic and multinucleated giant cells and haemosiderin deposition. We reviewed necropsy and biopsy records of horses submitted to the Setor de Anatomia Patológica of the Universidade Federal Rural do Rio de Janeiro from January 2017 to December 2020 to select cases of PT. We identified PT in three adult Brazilian Mangalarga Marchador horses with nodular lesions on the metacarpophalangeal, metatarsophalangeal or carpal joints. The three horses were under 6 years of age and presented with lameness and pain on palpation. There were recurrences in two horses after surgical removal. Radiographic and ultrasound examinations detected masses in the flexor or extensor tendons and subtendinous bursa. Histological study of synovial membrane and tendon sheath revealed an increased number of vessels, fibroplasia, osseous metaplasia and infiltration of lymphocytes, plasma cells and siderophages. This is the first description of PT in horses, which should be included as an orthopaedic differential diagnosis, especially in Mangalarga Marchador horses with lameness.

A 6-year-old neutered male bloodhound dog was presented for surgical evaluation of an intraoral hard palate mass noted during a routine dental cleaning performed by the primary veterinarian. Computed tomography (CT) of the skull revealed a well-defined, multilobular, mineralized mass with a coarse, granular appearance, centered along the palatomaxillary suture extending into both the nasal and oral cavities. Bilateral caudal maxillectomy was performed for curative-intent resection of the tumor. The histopathology of the mass was consistent with a completely excised palatomaxillary multilobular tumor of bone (MLTB). This is apparently the 1st successful report of surgical excision of an MLTB associated with the palatomaxillary suture line. Key clinical message: Our findings emphasized that MLTB should be considered as a differential diagnosis for masses arising in the location of cranial sutures, and a definitive diagnosis can be made postoperatively with histopathology of the mass.

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.

A 9-year-old, entire, male miniature schnauzer with a history of chronic right hindlimb lameness was presented to a referral orthopaedic surgery practice for acute nonweight bearing and suspected cranial cruciate ligament rupture. Radiographs revealed polyostotic bone infarcts, characterised by stippled medullary densities, and an aggressive osteolytic infarct in the right proximal tibia. Histopathology of the amputated limb revealed an arteriopathy of the nutrient artery and a zonal histologic pattern of neoplastic transformation: at the infarct apex, mesenchymal stromal cells (MSCs) were engaged in repair. As the cells proliferated towards the centre of the infarct within an environment of chronic ischaemia, cell features became consistent with low-grade sarcoma, then nascent (early) osteosarcoma. This zonal progression has been described in humans, but not in dogs. It is unknown whether nascent osteosarcoma has the same biologic activity as long-standing osteosarcoma. Veterinarians should be aware of canine bone infarcts and their potential sequelae.

This case report describes a rare form of malignant bone tumor in an 8-year-old Labrador retriever. This dog initially presented for evaluation of a right distal humeral mass. Radiographs of the right elbow and thorax were performed, revealing a smooth mineralized mass adjacent to the lateral aspect of the distal humerus and a 5mm pulmonary nodule. Computed tomography (CT) of the humerus and thorax showed a smooth mineralized lesion adjacent to the lateral humeral epicondyle, and a right cranial lung lobe nodule with a thin mineral rim. Surgical biopsies of both lesions were diagnostic for parosteal osteosarcoma (POSA). The dog was then treated with stereotactic body radiation therapy (SBRT) which controlled the dog's discomfort for 14 months until he became progressively painful and subsequently had his right forelimb amputated. This case report is the first to document the CT imaging characteristics of a metastatic appendicular POSA in a dog and the first dog described with POSA treated with SBRT. The dog lived for 623 days after histopathologic diagnosis and 849 days after initial presentation with pulmonary metastatic disease.

This case report details a previously undescribed malignancy of the tendon sheath in a golden retriever. This dog originally presented with lameness of the left forelimb, at which point radiographs revealed a monostotic, lytic lesion of the distal radius with overlying soft-tissue swelling. A fine-needle aspirate was performed, and cytology was compatible with a sarcoma, with the primary differential being an osteosarcoma. After amputation, the leg was submitted for histopathology, which revealed inconsistencies with a typical osteosarcoma lesion, including lack of osteoid deposition. Second opinion histopathology showed a fibrosarcoma that appeared to have originated in the tendon sheath of an extensor tendon and then secondarily invaded the radius. At the time of publication, ∼17 mo after amputation, the dog continues to do well without any evidence of recurrent or metastatic disease.

SummaryA 7‐year‐old Holsteiner gelding was presented with a left common digital extensor sheath effusion of one‐year's duration. Radiographic examination revealed two extra‐articular mineralised bodies adjacent to the dorsolateral carpometacarpal joint. Ultrasonography confirmed an intrathecal location of one mineralised body in the common digital extensor sheath, palmar fraying of the common digital extensor tendon and tenosynovitis. Ultrasound could not confirm whether the second mineralised body was intrathecal or located external to the common digital extensor sheath. Common digital extensor tenoscopy facilitated removal of both mineralised bodies and revealed a fistula communicating with the carpometacarpal joint. The mineralised bodies, initially thought to be synovial osteochondromas, were histologically identified as para‐articular osteochondromas. There are no previously published reports of para‐articular chondroma/osteochondroma in the horse. Despite surgical removal of the para‐articular osteochondromas, concern for future extensor sheath distension remained given the communication between the carpometacarpal joint and common digital extensor sheath.

SummaryA primary ossifying fibroma was found at necropsy in a 5‐year‐old Welsh pony cross mare that was humanely subjected to euthanasia for an intractable severe left hindlimb lameness. Antemortem radiographs of the left hind pastern were characterised by articular, subchondral and cortical areas of lysis. Primary ossifying fibroma is a rare lesion of the distal limb but should be considered when there is extensive lysis extending into the medulla and proximal cortical bone.

OBJECTIVE To describe the radiographic appearance of benign bone infarcts and bone infarcts associated with neoplasia in dogs and determine the utility of radiography in differentiating benign and malignancy-associated bone infarcts. SAMPLE 49 dogs with benign (n = 33) or malignancy-associated (16) infarcts involving the appendicular skeleton. PROCEDURES A retrospective cohort study was performed by searching a referral osteopathology database for cases involving dogs with a histologic diagnosis of bone infarction. Case radiographs were anonymized and reviewed by 2 board-certified veterinary radiologists blinded to the histologic classification. Radiographic features commonly used to differentiate aggressive from nonaggressive osseous lesions were recorded, and reviewers classified each case as likely benign infarct, likely malignancy-associated infarct, or undistinguishable. RESULTS Only 16 (48%) of the benign infarcts and 6 (38%) of the malignancy-associated infarcts were correctly classified by both reviewers. Medullary lysis pattern and periosteal proliferation pattern were significantly associated with histologic classification. Although all 16 (100%) malignancy-associated lesions had aggressive medullary lysis, 23 of the 33 (70%) benign lesions also did. Eight of the 16 (50%) malignancy-associated infarcts had aggressive periosteal proliferation, compared with 7 of the 33 (21%) benign infarcts. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that radiography was not particularly helpful in distinguishing benign from malignancy-associated bone infarcts in dogs.

Nature gave the horse a fibro-cartilaginous or elastic union to particular bones, so that all its motions might be bounding and graceful.... High action, however, especially that kind of action the horse is taught to exemplify, soon deranges the system. It breeds inflammation in the fibro-cartilaginous tissues, upon which its chief strain is felt. The union between the splint bones and the cannon, or between the shin bone and the accessories, one on either side, speedily becomes converted into osseous matter.... The Illustrated Horse Doctor Edward Mayhew 1850

Background Reports of osteoblastic tumours are limited to a few case reports in veterinary medicine. Osteoblastoma-like osteosarcoma has been accepted by the World Health Organization as an intermediate form between an osteosarcoma and osteoblastoma. This type of tumour indicates an osteosarcoma, that may resemble osteoblastoma clinically, histologically, and radiologically and have the capability for metastasis. Osteoblastoma-like osteosarcoma has not been described in veterinary medicine so far. Case presentation An eight-year old cat was presented due to progressive ataxia and paraparesis of the pelvic limbs. Imaging confirmed a well-defined, extradural mass originating from the spinous process of the second thoracic vertebra (T2) leading to severe compression of the spinal cord. Decompressive cytoreduction was achieved by removal of the mass after dorsal laminectomy of T1. After recovering from an acute worsening 3.5 weeks after surgery, the cat had an improved neurological status and the dorsal compression was resolved at follow-up 8 months later. A focal contrast enhancing lesion was still evident at the base of T2 spinous process and lung metastasis was additionally suspected. Based on histopathological, radiographic, and clinical features, an “osteoblastoma-like osteosarcoma” was suspected. Conclusions To the best of our knowledge, this is the first description of this tumour in veterinary medicine. In addition, this case report highlights the difficulty in the diagnosis and definition of osseous neoplasia in cats and provides a literature review.