Enostosis-like lesionsKatie Phillips

Hanzaccession 147214

• 12 yr old warmblood gelding

• Used for dressage• 2 week history of lameness• Presented for evaluation of

a sore back.• 3/5 Lame RF & LH. • No change with flexion• Could not be blocked

Hanz RF

Differentials: enostosis-like lesion, or less likely fracture, osteomyelitis, bone infarct, osteonecrosis. VRUS 2009

Hanz RH

Enostosis• Scintigraphically as focal

or multifocal areas of intense increased radioisotope uptake within the medullary cavity of long bones.

• Radiographically as one or multiple round to irregular shaped opacities within the medullary cavity.

• A mass of proliferating bone within a bone. –Stedman

• A morbid bony growth developed within the cavity of a bone or on the internal surface of the bone cortex. -Dorland

Hanz radiographs

Hanz radiographsWell circumscribed intramedullary sclerosis with no apparent involvement of the cortex.

Enostosis-like lesions in the literature

• Case reports and clusters of case reports, only.

• All describe similar scintigraphy and radiographic findings.

• Etiology is unknown• Often considered incidental• If no other cause of lameness is identified

they are considered the cause. • O’Neil 2011 – report 15/21 cases where

enostosis-like lesions were considered the cause of lameness.

Features

• Multiple breeds and disciplines described.• May be single or multiple lesions, often multiple

limbs.• Frequently associated with dorsal endocortex

directly across from nutrient foramen. • Lameness and lesions resolve with time.

SpeculationSimilarities to Canine Panosteitis• Radiopharmacutical uptake &

medullary sclerosis• Nidus in vicinity of nutrient

foramen• Radiographic changes don’t

always correlate with lameness.• Similar temporal changes• Histologically the same• But… case reports are all horses

in work (skeletally mature).

Human enostosis• AKA bone islands• Typically not scintigraphically

active• Asymptomatic, static, solitary• Usually metaphyseal or

epiphyseal

Bone Infarct• Case report in horse- showed colic like pain, then lameness.•Time line is different for scintigraphy changes and radiographic lag.

IMAGING DIAGNOSIS—ENOSTOSIS-LIKE LESION IN THE FEMUROF A HORSE

SUSANNE M. STIEGER-VANEGAS, HEGE KIPPENES-SKOGMO, EBBA NILSSON Veterinary Radiology & Ultrasound, Vol. 50, No.

5, 2009, pp 509–512.

• Case report 15yr WB• Only case in literature with

histology!!• 4/5 lame LH localization was not

possible.• Histo: No inflammatory cells, no

thrombus, no evidence of bone necrosis. Similar to panosteitis of young dogs.

• No histological involvement of endosteum.

References Stieger-Vanegas, Kippenes-Skogmo, Nilsson. Imaging

diagnosis- Enostosis-like lesion in the femur of a horse. 2009.VRUS.50(5) 509-512

Bassage, Ross. Enostosis-like lesions in the long bones of 10 horses:scintigraphic and radiographic features. 1998.Equine vet j. 30(1) 35-42

• Ramzan.Equine enostosis-like lesions:12 cases 2002 EVE14(3) 143-148.

• Jones & McDiarmid. Case report:Multiple enostosis-like lesions in a racing thoroughbred. 2005.eve. 17(2 92-95

• O’Neil & Bladon.Retrospective study of scintigraphic and radiological findings in 21 cases of enostosis-like lesions in horses. 2011 veterinary record. 168:326

MRI – Travis 147695

There are regions of intense medullary T2-hyperintensity in the third metatarsal bone at the level of the nutrient artery. This appearance is consistent with enostosis but hematogenous osteomyelitis could also have this appearance.

Hanz – follow up

• One dose IV Tildren• 2 months rest• Re-check: grade 1/5

lame RF, mildly positive to flexion LH.