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EQUINE VETERINARY EDUCATION / AE / MARCH 2015
Fig 1: Nuclear scintigraphic images of left (a) and right (b) femora. Both images are lateral projections and cranial is to the left. Notice the severe increased radiopharmaceutical uptake in the proximal femur of the right hindlimb between the femoral neck and third trochanter.
did not elicit a response. Flexion tests of the right hindlimb revealed a moderate to severely positive response to the stifle flexion, moderately positive response to full limb flexion and a mildly positive response to distal limb flexion. Flexion tests of the left hindlimb were negative. Pelvic ultrasound (rectal and transcutaneous) was performed and did not reveal any abnormalities in the sacroiliac region, coxofemoral joint, ilium or ischium. Due to the significant lameness, nuclear scintigraphy of the spine and hindlimbs was scheduled. Further evaluation of the ventral abdominal oedema
included complete blood count (CBC) and serum biochemistry profile. The results revealed a mild hyperfibrinogenaemia (5.0 g/l: reference interval 1.0–4.0 g/l) and mild thrombocytopenia (76 × 109/l; reference interval 125–300 × 109/l). Examination of his penis revealed local inflammation at the distal aspect along with multifocal 1–3mm nodules, which according to the owner were unchanged since the earlier biopsy. Serum protein electrophoresis was performed and the results were normal. Corynebacterium pseudotuberculosis serum haemolysin inhibition test was negative. Transrectal palpation did not reveal any abnormalities aside from some mild irregularity on the visceral surface of the spleen. Transabdominal ultrasound was unremarkable. Nuclear scintigraphy of the thoracolumbar spine
and hindlimbs revealed severe focal increased radiopharmaceutical uptake (IRU) within the right proximal femur between the femoral neck and third trochanter (Fig 1). There was mild focal IRU within the right calcaneus, specifically the tuber calcanei, and mild generalised IRU within the proximal right fourth metatarsal bone. Based upon the results of scintigraphy, caudocranial radiographic projections of the right femur and standard views of the right tarsus were performed. There were no radiographic abnormalities identified on the right femur, but there was moderate osteoarthritis of the tarsometatarsal and distal intertarsal joints. Ultrasound of the proximal femur was performed and revealed an irregular periosteal surface with an adjacent hypoechoic region on the lateral aspect of the proximal femur adjacent to the third trochanter (Fig 2), consistent with reactive periosteum
© 2014 EVJ Ltd
Fig 2: Ultrasound image (long axis view) of the third trochanter of the right femur (right image) and the contralateral normal left femur (left image). The bracket marks indicate irregular periosteum and the arrow points to a hypoechoic region, which indicates subperiosteal oedema or haemorrhage. None of these changes were detected on the left femur. LT = left; RT = right.
with possible subperiosteal haemorrhage, oedema and/or necrosis. There was no evidence of muscle trauma or haematoma formation in the area.
Treatment/outcome
Based upon the findings of diagnostic imaging a definitive diagnosis could not be determined, but fracture (incomplete/nondisplaced) of the femur, or a neoplastic process was suspected. A bone biopsy was considered; however, due to the potential risk of catastrophic fracture and lack of treatment options for either suspected diagnosis, the owner elected conservative management. The horse was discharged from the hospital with instructions for strict stall confinement for 3 months until recheck examination. The horse was placed on a 2 week course of firocoxib (Equioxx)1 (0.09 mg/kg bwt per os, once daily). Four weeks following hospital discharge, the horse
became unable to raise his head without pain and progressively was unable to elevate his neck. During this time the horse also became more dull and lethargic. The horse presented to a local veterinary clinic where it was treated with anti-inflammatory medications for a few days. Based upon his general condition and lack of response to this treatment, his owner elected humane euthanasia and a post mortem examination was performed.
Post mortem examination
Gross necropsy findings revealed moderate ventral abdominal oedema similar to that observed in the clinical examination. The musculature in the region of the right proximal femur was mildly atrophied and contained multifocal streaks of pallor. Transection of the femur revealed a proliferative, firm, tan, irregular mass circumferentially expanding the proximal cortex up to 20 times its normal thickness. Multifocally, the medullary cavity of the proximal femoral cortex was effaced by similarly firm and tan masses (Fig 3a,b). No fractures were observed in the proximal femur. Gross examination of the spleen, and the superficial and deep inguinal and medial iliac lymph nodes were within normal
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