LAUSR

A 56-year-old female presented with symptoms of flatback syndrome, including poor posture, back pain, and difficulty mobilizing. She had a lumbar epidural steroid injection several years previously for ‘sciatica’. On examination, the patient demonstrated positive sagittal imbalance despite increased pelvic retroversion, and exaggerated knee flexion. Neurological exam was normal. T1and T2-weighted magnetic resonance imaging (MRI) unexpectedly demonstrated calcification of the cauda equina, most dramatically at L4/5 (Fig. 1(a)—(d)). Computed tomography (CT) showed ankylosis resulting in reversal of normal lumbar lordosis and confirmed calcifications in the lumbar region of the spinal canal, most pronounced at L4/5 (Fig. 1(e) and (f)), likely Type III arachnoiditis ossificans (AO). A three-column osteotomy was offered as a surgical intervention. However, the patient declined after full disclosure of surgical risk. Additionally there is no evidence to support a safe osteotomy in the presence of AO and furthermore, Type III AO does not have any specific surgical treatment. AO is a generally a cause of chronic, progressive myelopathy or radiculopathy and results in replacement of spinal arachnoid by bone. Usually the consequence of prior trauma or procedures, it is possible that the previous epidural injection was the cause in this case. The three types of AO include semicircular (Type I), circular (Type II), and englobing the caudal fibres (Type III). AO is more common and severe in the thoracic spine where arachnoid cells are more concentrated and the