Although interlaminar endoscopic lumbar discectomy (IELD) is considered to be less invasive than microscopic lumbar discectomy (MLD) in treatment of lumbar herniated nucleus pulposus, the radiologic change of multifidus muscles by each surgery has rarely been reported. The aim of the present study was to compare the quantitative and qualitative changes of multifidus muscles between two surgical approaches and to analyze the correlation between various parameters of multifidus muscles and long term surgical outcome. 21 patients who received MLD and 18 patients who received IELD in a single tertiary hospital were enrolled and their preoperative, postoperative (≤15 days), and follow-up (≥6 months) MRIs were analyzed. The cross-sectional area (CSA) and fatty degeneration rate (FD) were quantitatively estimated at the level of surgery. The correlations among CSA, FD, body mass index, follow-up visual analogue scale(VAS) and Oswestry Disability Index(ODI) were assessed. Mean intervals of postoperative MRI and follow-up MRI from surgery were 3.0±3.7 days and 14.5±10.7 months, respectively. During the follow-up period, VAS was improved from 7.1±1.3 to 2.1±1.8 in MLD and from 8.2±1.4 to 2.2±1.8 in IELD. In cases of MLD, comparing with preoperative MRI, ipsilateral CSA was significantly increased in postoperative MRI (795.6mm. 2. vs. 906.5mm. 2. , p<0.01), but it was not significantly different in follow-up MRI (795.6mm. 2. vs. 814.4mm. 2. , p=1.00). However, in case of IELD, the ipsilateral CSAs in preoperative, postoperative, and follow-up periods were 892.0 mm. 2. , 909.3 mm. 2. , and 900.3 mm. 2. , respectively. These changes were not significant over time (p=0.691). The ipsilateral FDs were not significantly changed between preoperative and follow-up periods in both MLD (21.4% vs. 20.9%, p=0.81) and IELD groups (23.5% vs. 21.8%, p=0.19). The increment of ipsilateral CSA had significant correlations with follow-up ODI (r=−0.368, p=0.02). Comparing with IELD, MLD induced more surgical trauma on multifidus muscle in postoperative period, but the muscular damage was recovered in follow-up period. IELD can minimize surgical trauma on multifidus muscle showing similar pain relief as MLD. Favorable surgical outcome in follow-up period may be related to increment of multifidus muscle volume. Figure 1. (A-C) The multifidus muscles in preoperative, postoperative, and follow-up periods, respectively, in patient with MLD. Comparing with preoperative period, the CSA of right multifidus muscle (ipsilateral side) was increased in postoperative period, but recovered in follow-up period. (D-F) The multifidus muscle in preoperative, postoperative, and follow-up periods, respectively, in patient with IELD. The CSA of left multifidus muscles (ipsilateral side) was not significantly changed over time. Comparing preoperative MRIs with follow-up MRIs, the FDs of multifidus muscles were not significantly changed regardless of surgical technique. Figure 2. The CSA was measured by marking region of interest (ROI) and FD was measured by calculating the rate of pixels beyond the threshold in ROI. All measurements were performed using ImageJ software (version 1.52a, National Institutes of Health, Bethesda, Maryland, USA). For any figures or tables, please contact the authors directly

Background. Low back-related leg pain (LBLP) is clinically diagnosed as referred leg pain or sciatica. Within the spectrum of LBLP there may be unrecognised subgroups of patients. This study aimed to identify and describe clusters of LBLP patients using latent class analysis (LCA). Methods. The study population were 609 LBLP primary care consulters. Variables from clinical assessment were included in the LCA. Characteristics of the statistically identified clusters were described and compared to the clinically defined groups of LBLP patients. Results. A five cluster solution was optimal. Cluster one (n=104) had mild leg pain severity, no clinical signs suggestive of sciatica and more anxiety. Cluster two (n=122), three (n=188) and four (n=69) represented mild, moderate and severe sciatica in terms of response to clinical assessment items, pain severity and impact on function. Cluster five (n=126) was more difficult to define based on response to clinical assessment items (below knee pain and possible neural tension) and had a similar severe profile to cluster four in terms of high pain, disability, psychosocial factors, work impact and risk of poor outcome; but had longer duration pain and more comorbidities. Cluster three consistently mirrored the profile of the overall group of patients with a clinical diagnosis of sciatica. Cluster one mirrored the referred leg pain group. Conclusion. This is the first study that used LCA to classify LBLP patients, including sciatica. These clusters could represent more homogenous groups that may require different treatment approaches. Further work will describe the clinical course and longer term outcomes of these clusters. No conflicts of interest. S Stynes is supported by an NIHR/CNO Clinical Doctoral Research Fellowship (CDRF-2010-055). Dr Konstantinou is supported by a HEFCE/NIHR Senior Clinical Lectureship. Professor Hay is a NIHR Senior Investigator

Background. Rotatory subluxation of the atlantoaxial joint has been thoroughly documented in children. However, pure traumatic atlantoaxial rotatory subluxation (TAARS) is a rare injury in adults with only a few cases reported in the English literature. Aim. To report two cases of TAARS in adults. Methods. A case note, clinical and radiological review. Results. Both patients were female. There was a history of a motor vehicle collision in both cases. There was no neurological impairment at presentation in either case. The injury in both cases was identified by plain X-ray and confirmed by CT scan. Both were managed by conservative treatment, initially with halo traction, followed by immobilisation in a rigid collar. Final clinical reviews occurred at 7 years and 2.5 years following injury. Neither patient had signs of C1-C2 instability or impaired neurology. Both patients, however, suffered headaches and occipital neuralgia, with stiffness and reduction in cervical spine movement. Conclusion. Traumatic rotatory subluxation in adults is a rare injury. It can pose a diagnostic challenge and CT scanning is mandatory for a correct evaluation of the C1-2 complex. Reduction and stability can be achieved through conservative treatment. However, it is evident from this short series that even early diagnosis and prompt reduction may not necessarily result in a good long term outcome in adult patients with TAARS