Enostosis‐like lesions in the long bones of 10 horses: scintigraphic and radiographic features

Abstract

Summary Ten horses admitted for lameness evaluation including bone scintigraphy had enostosis‐like lesions, described scintigraphically as focal or multifocal areas of intense increased radioisotope uptake within the medullary cavity of one or more long bones, and radiographically as one or multiple round to irregularly shaped radiopacities within the medullary cavity, often in close proximity to the nutrient foramen. There were 6 Thoroughbreds, one male, one female and 4 geldings, 3 Standardbreds, all geldings and one Appaloosa gelding; age 3–10 years. Enostosis‐like lesions were seen in the tibia (5 horses), radius (3 horses), humerus (one horse) and third metatarsal bone (MT‐III) (4 horses). The number of affected bones in each horse was 1–3. Of 16 affected limbs, there were 9 hindlimbs and 7 forelimbs. Enostosis‐like lesions were considered a possible cause of lameness in 5 horses, but were considered incidental findings in the other horses. Lesions thought to cause lameness were seen in the tibia (2 horses), MT‐III (one horse) and in the radius (4 horses). Lameness resolved after horses were rested (2–6 months) and given nonsteroidal anti‐inflammatory drugs (4 horses). Follow‐up scintigraphic examination in 3 horses (2, 6 and 9 months later, respectively) revealed normal radioisotope uptake in the affected areas.

Enigma of enostosis‐like lesions in the horse

“…The latter radiological appearance is more typical of the lesions seen in canine panosteitis. The similarities between ELLs and panosteitis have been discussed previously (Bassage and Ross 1998). …”

“…This coincides with focal increased radiopharmaceutical uptake (IRU) of variable intensity. However, in many horses these lesions appear to be incidental abnormalities and were considered to be unrelated to lameness in 29 per cent (O'Neill and Bladon 2011), 50 per cent (Bassage and Ross 1998), 51 per cent (Ahern and others 2010) and 67 per cent (Ramzan 2002) of 21, 10, 79 and 12 horses respectively.…”

“…Moreover, in some horses follow-up scintigraphic and radiological examination reveals resolution of lesions, whereas in others the lesions persist or new lesions become apparent, with or without clinical signs of lameness. The presence of coexistent lesions likely to be contributing to pain and lameness makes it difficult to interpret the descriptions of the character and degree of lameness, which has ranged from mild to severe (Bassage and Ross 1998, Ramzan 2002, Stieger-Vanegas and others 2009, Ahern and others 2010, O'Neill and Bladon 2011). …”

Imaging Diagnosis—enostosis‐like Lesion in the Femur of a Horse

“…Enostosis‐like lesions most commonly involve long bones. All enostosis‐like lesions described in horses have affected the appendicular skeleton 1–3 . None of the lesions described previously involved the femur.…”

“…In horses, the degree of lameness secondary to an enostosis-like lesion is variable. 1,2,6 In this horse the enostosis-like lesion was considered as the cause for the severe lameness. Pain can be an indicator that a lesion is growing.…”