Bertolotti first described articulation of the L5 transverse process with the sacrum as a cause of back pain in 1917. Since then little attention has been payed to these atypical articulations despite their high reported incidence. Here we describe our early experience of surgical treatment and propose a validated CT based classification of lumbosacral segment abnormalities (LSSA). 400 lumbosacral CT scans were reviewed (NBT), a classification devised and incidence of abnormalities recorded. 40 patients were selected and 4 independent observers classified each scan. Case notes for all patients (C&V) who received steroid injections into or surgical excision of LSSAs were reviewed. Results as follows: 5 types of abnormality were identified. Type 0 - normal Type 1 - asymmetrical shortening of the iliolumbar ligament Type 2 - transverse process of L5 within 2mm of the sacrum Type 3 - diarthrodial joint (3A: no evidence of degeneration 3B: degenerative change) Type 4 - transverse process and sacrum have fused Type 5 - extends to L4 54.5% of patients had abnormalities. The kappa values for the intra-observer results were 0.69 to 0.88 and the inter-observer ratings gave a combined score of over 0.7 indicating substantial agreement. Our CT classification of LSSAs is both straight forward to use and repeatable. The incidence of these abnormalities is higher in our population of CT scans compared to previous published series using plain radiographs. All patients treated with surgical excision of established articulations (Type 3A or above) reported good or excellent outcomes following excision.
