Cauda equina syndrome presentation of sacral insufficiency fractures.

INTRODUCTION: Sacral insufficiency fractures are a well recognised cause for low back, buttock and groin pain in the elderly. However, over a 4 year period, four patients have presented with symptoms of cauda equina syndrome, who were found on investigation to have acute sacral insufficiency fracture without any other aetiological spinal abnormality. PATIENTS AND METHOD: Four patients who presented to the spinal surgeons of our institution with symptoms of cauda equina syndrome were referred for spinal MR. Sagittal and axial T1 and T2 weighted turbo spin echo sequences of the lower thoracic and lumbar spine were performed on all patients. Subsequent studies included MR of the sacrum supplemented where appropriate by CT and technetium MDP bone scintigraphy. RESULTS: No evidence of a compressive lesion of the lower thoracic or lumbar spine was present in any of the four patients. Dedicated MR examination of the sacrum in these patients revealed unilateral acute insufficiency fractures involving zone 1 from S1 to S3 extending from the sacro-iliac joint to the lateral margin of the sacral foramen. There was no evidence of compression of the sacral nerve roots. The possible mechanism for the symptomatic presentation is discussed. CONCLUSION: Sacral insufficiency fractures should be excluded in elderly or osteoporotic patients presenting with cauda equina syndrome who have no evidence of compression in the thoraco-lumbar MR studies.

Primary synovial osteochondromatosis presenting as constrictive capsulitis.

Primary synovial chondromatosis of the joints can present as capsular constriction with peri-articular osteopenia. This rare presentation is highlighted in three cases (two hips and one shoulder). The diagnosis in all the patients was made on arthrography and/or MRI/CT and was confirmed histologically. Synovial chondromatosis should be considered in patients with this presentation. Arthrography is the best imaging modality to confirm the cause (synovial chondromatosis) and effect (constrictive capsulitis).

Subperiosteal ganglion associated with Paget's disease of bone.

Tumoral lesions related to Paget's disease may be classified as malignant, benign or pseudotumoral. While sarcomatous degeneration is the most feared complication, awareness of benign and pseudotumoral lesions is essential for assisting in accurate histological interpretation of the biopsy sample, which may avoid unnecessary repeat biopsies. We present the first case of a juxta-articular subperiosteal ganglion associated with Paget's disease, with classic imaging characteristics, especially on CT examination. The well-defined soft tissue mass at the medial aspect of the obturator rim, adjacent to a small fracture in pagetic quadrilateral plate, showed an ossified rim and internal gas lucencies, these being the hallmarks of a juxta-articular subperiosteal ganglion. On MRI, the lesion was of intermediate signal intensity on T1-weighted sequences, increased signal intensity on T2-weighted sequences, with rim enhancement after gadolinium contrast injection and preservation of fatty marrow signal of the underlying pagetic bone. Identification of the entity avoided an unnecessary biopsy or surgical intervention.