Several studies have evaluated the risk of peroneal nerve (PN) injuries in all-inside lateral meniscal repair using standard knee magnetic resonance imaging (MRI) with the 30 degrees flexed knee position which is different from the knee position during actual arthroscopic lateral meniscal repair. The point of concern is “Can the risk of PN injury using standard knee MRIs be accurately determined”. To evaluate and compare the risk of PN injury in all-inside lateral meniscal repair in relation to both borders of the popliteus tendon (PT) using MRIs of the two knee positions in the same patients. Using axial MRI studies with standard knee MRIs and figure-of-4 with joint fluid dilatation actual arthroscopic lateral meniscal repair position MRIs, direct lines were drawn simulating a straight all-inside meniscal repair device from the anteromedial and anterolateral portals to the medial and lateral borders of the PT. The distance from the tip of each line to the PN was measured. If a line touched or passed the PN, a potential risk of iatrogenic injury was noted and a new line was drawn from the same portal to the border of the PN. The danger area was measured from the first line to the new direct line along the joint capsule. In 28 adult patients, the closest distances from each line to the PN in standard knee MRI images were significantly shorter than arthroscopic position MRI images (all p-values < 0.05). All danger areas assessed in the actual arthroscopic position MRIs were included within the danger areas as assessed by the standard knee MRIs. We found that the standard knee MRIs can be used to determine the risk of peroneal nerve injury in arthroscopic lateral meniscal repair, although the risks are slightly overestimated

Aims

Treatment of high-grade limb bone sarcoma that invades a joint requires en bloc extra-articular excision. MRI can demonstrate joint invasion but is frequently inconclusive, and its predictive value is unknown. We evaluated the diagnostic accuracy of direct and indirect radiological signs of intra-articular tumour extension and the performance characteristics of MRI findings of intra-articular tumour extension.

Aims

The aims of this study were first, to determine if adding fusion to a decompression of the lumbar spine for spinal stenosis decreases the rate of radiological restenosis and/or proximal adjacent level stenosis two years after surgery, and second, to evaluate the change in vertebral slip two years after surgery with and without fusion.

Aims. Classifying trochlear dysplasia (TD) is useful to determine the treatment options for patients suffering from patellofemoral instability (PFI). There is no consensus on which classification system is more reliable and reproducible for the purpose of guiding clinicians’ management of PFI. There are also concerns about the validity of the Dejour Classification (DJC), which is the most widely used classification for TD, having only a fair reliability score. The Oswestry-Bristol Classification (OBC) is a recently proposed system of classification of TD, and the authors report a fair-to-good interobserver agreement and good-to-excellent intraobserver agreement in the assessment of TD. The aim of this study was to compare the reliability and reproducibility of these two classifications. Methods. In all, six assessors (four consultants and two registrars) independently evaluated 100 axial MRIs of the patellofemoral joint (PFJ) for TD and classified them according to OBC and DJC. These assessments were again repeated by all raters after four weeks. The inter- and intraobserver reliability scores were calculated using Cohen’s kappa and Cronbach’s α. Results. Both classifications showed good to excellent interobserver reliability with high α scores. The OBC classification showed a substantial intraobserver agreement (mean kappa 0.628; p < 0.005) whereas the DJC showed a moderate agreement (mean kappa 0.572; p < 0.005). There was no significant difference in the kappa values when comparing the assessments by consultants with those by registrars, in either classification system. Conclusion. This large study from a non-founding institute shows both classification systems to be reliable for classifying TD based on axial MRIs of the PFJ, with the simple-to-use OBC having a higher intraobserver reliability score than that of the DJC. Cite this article: Bone Jt Open 2023;4(7):532–538

The relationship of degeneration to symptoms has been questioned. MRI detects apparently similar disc degeneration and degenerative changes in subjects both with and without back pain. We aimed to overcome these problems by re-annotating MRIs from asymptomatic and symptomatic groups onto the same grading system. We analysed disc degeneration in pre-existing large MRI datasets. Their MRIs were all originally annotated on different scales. We re-annotated all MRIs independent of their initial grading system, using a verified, rapid automated MRI annotation system (SpineNet) which reported degeneration on the Pfirrmann (1-5) scale, and other degenerative features (herniation, endplate defects, marrow signs, spinal stenosis) as binary present/absent. We compared prevalence of degenerative features between symptomatics and asymptomatics. Pfirrmann degeneration grades in relation to age and spinal level were very similar for the two independent groups of symptomatics over all ages and spinal levels. Severe degenerative changes were significantly more prevalent in discs of symptomatics than asymptomatics in the caudal but not the rostral lumbar discs in subjects < 60 years. We found high co-existence of degenerative features in both populations. Degeneration was minimal in around 30% of symptomatics < 50 years. We confirmed age and disc level are significant in determining imaging differences between asymptomatic and symptomatic populations and should not be ignored. Automated analysis, by rapidly combining and comparing data from existing groups with MRIs and information on LBP, provides a way in which epidemiological and ‘big data’ analysis could be advanced without the expense of collecting new groups

In current practice in the UK there are three main approaches to investigating suspected scaphoid fractures not seen on initial plain film x-rays. Early MRI of all cases. Review all cases in clinic at two weeks with repeat x-rays. Hybrid model. Virtual Fracture Clinic (VFC) triage to reduce those who are seen in clinic at two weeks by:. ∘. Organising early MRI for those with high-risk presentation. ∘. Discharging those with an alternative more likely diagnosis. Our unit uses the VFC model. We aimed to evaluate its efficiency, safety, clinical outcomes and economic viability. All patients attending the emergency department with either a confirmed or suspected scaphoid fracture between March and December 2020 were included (n=305). Of these 297 were referred to the VFC: 33 had a confirmed fracture on x-ray and 264 had a suspected fracture. Of the suspected fractures reviewed in VFC 14% had an MRI organised directly owing to a high-risk presentation, 79% were brought for fracture clinic review and 17% discharged with an alternative diagnosis such as osteoarthritis. Of those subsequently reviewed in fracture clinic at two weeks: 9% were treated as scaphoid fractures (based on clinical suspicion and repeat x-rays), 17% had MRI or CT imaging organised, 5% did not attend and 69% were discharged. Overall, 17% of cases initially triaged, had further imaging – 41 MRIs and 5 CTs. MRI detected: 5% scaphoid fracture, 17% other fracture, 24% bone contusion, complete ligament tear 10%, partial ligament tear 39% and normal study 10%. The results of MRI minimally affected management. 3 patients were taken out of plaster early, 1 patient was immobilized who was not previously and no patients underwent operative management. In the following 12-month period one patient re-presented with a hand or wrist issue. This approach avoided 218 MRIs, equating to £24000 and 109 hours of scanner time. VFC triage and selective use of MRI scanning is a safe, efficient and cost-effective method for the management suspected scaphoid fractures. This can be implemented in units without the resource to MRI all suspected scaphoid fractures from the emergency department

Introduction. Nucleus replacement surgery has the potential to be an early treatment option for chronic lower back pain. The surgery involves removal (nuclectomy) and replacement of the native degenerated nucleus with a material designed to restore the disc's physiological properties. Multiple techniques have been considered to perform a nuclectomy, however the advantages and disadvantages of each are not well understood. The aim of this study was to quantitatively compare three nuclectomy techniques: automated-shaver, rongeurs, and laser. Methods and results. Fifteen human vertebra-disc-vertebra lumbar specimens were split into three groups. Before and after nuclectomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen. Using the automated-shaver and rongeur similar volumes of disc material were removed (2.51±1.10% and 2.76±1.39% of the total disc volume, respectively), whilst considerably less material was removed when using the laser (0.12±0.07%). Using the automated-shaver and rongeur significantly reduced the toe-region stiffness, while the linear region stiffness was significantly reduced only in the rongeur group. From the MRIs, more homogeneous cavities were seen in the center of the disc when using the automated shaver compared to rongeur, whilst laser ablation resulted in small, localized cavities. Conclusion. Results suggest that the current laser parameters are not suitable for removal of large volumes of material unless the technique is optimised for this application. Both rongeurs and automated-shavers can be used to remove large volumes of material but the reduced risk of collateral damage to surrounding tissues suggests that an automated-shaver may be more suitable. Conflicts of interest: No conflicts of interest. Sources of funding: Part of this work was funded by an Imperial College Research Fellowship for NN and an EPSRC DTP CASE Conversion Studentship for TR (EP/R513052/1)

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

Patellar dislocation is a common presentation with a clear management pathway. Sometimes, however, what a patient experiences as the patella dislocating may, in fact, be ACL insufficiency. We reviewed case notes and imaging of 315 consecutive ACL reconstructions, collecting data on the date and mechanism of injury, time to MRI, and reconstruction. We noted cases initially diagnosed as patellar dislocation. 25 of 315 (7.9%) patients were initially diagnosed with a patellar dislocation. Subsequently, however, MRI scans revealed no evidence of patellar dislocation and instead showed ACL rupture with pathognomonic pivot-shift bony oedema. The false patella dislocation group were 32% female and had an average age of 25; the rest of the group average age was 27.1 and there were a lower proportion of females; 21%. The false patella instability patients had a median waiting time of 412 days from injury to operation (range: 70-2445 days), compared to 392 days (range: 9 – 4212 days) for rest of the patients. 5 of the remaining 290 had MRIs showing patella oedema with medial patello-femoral ligament injury in addition to their ACL rupture. From our literature search this is a new finding which shows that ACL rupture can present with symptoms suggestive of patellar dislocation. These findings raise the risk that there are a group of people who have been diagnosed with patellar instability who instead have ACL insufficiency and so are at risk of meniscal and chondral damage. Further research should analyse those diagnosed with patellar instability to quantify missed ACL injuries

Aim. Our collaborative study aims to demonstrate that acute partial Achilles Tendon Tears (ATTs) are not separate diagnostic entities from full ATTs. and should be thought of as a continuum rather than binary partial or full. Methods. We pooled anonymised data from four hospitals, identifying patients with acute partial ATTs on USS reports from 2019–2021. Patients were only included if they had an acute injury and no previous background Achilles tendinopathy. Results. 91 patients had acute partial ATTs reported on USS. 74/91 (81%) of patients had clinical findings in keeping with a full ATT (positive Simmonds test, palpable gap). 88/91 (97%) of patients were managed according to local full ATT protocols. 2 patients had MRIs – one showed no tear, the other showed a full rupture. 2 patients underwent surgical repair and both intra-operatively were found to have full ATTs. Conclusion. Our regional data suggests that a significant proportion (81%) of USS diagnosed partial ATTs may in fact be misdiagnosed full ATTs. All injuries clinically suspicious for an ATT should be managed according to local Achilles Protocol. USS is useful to diagnose the presence or absence of a tear but is not good at differentiating partial vs full tear. There is significant tendon end fibrillation and overlap on USS of an acute full ATT, which can give the impression of a partial ATT. More research is needed into whether any threshold exists to support the current distinction of “partial” and “full” as relates to management and outcomes

Femoroacetabular impingement is a prearthritic deformity frequently associated with early chondral damage. Several techniques exist for restoring larger cartilage defects. While AMIC proved to be an effective treatment in knee and ankle, there are only short-term data available in hip. This study aimed to investigate the mid-term clinical outcome of patients with chondral lesions treated by AMIC and evaluate the quality of repair tissue via MRI. This retrospective, single center study includes 18 patients undergoing surgical hip dislocation for FAI between 2013 and 2016. Inclusion criteria were: cam or pincer-type FAI, femoral or acetabular chondral lesions > 1 cm. 2. , (IRCS III-IV). Due to exclusion criteria and loss-to-follow-up 9 patients (10 hips) could be included. Patient reported outcome measures included Oxford Hip Score (OHS) & Core Outcome Measure Index (COMI)). MRIs were evaluated using the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score. None of the patients underwent revision surgery except screw removals from the greater trochanter. Followup data indicate a satisfactory to good hip function at 5 years: PROMS improved from pre- to postop at 5 years: OHS from 38.1 to 43.4, COMI from to 1.8 and UCLA from 4 to 8.1 respectively. MOCART score was 67.5 postoperatively. Subgrouping showed slightly better results for acetabular defects (Ø 69.4) compared femoral defects (Ø 60). Based on the reported mid-term results, we consider AMIC as a valuable treatment option for larger chondral defects of the hip

Demand for total knee arthroplasty (TKA) is increasing as it remains the gold-standard treatment for end-stage osteoarthritis (OA) of the knee. While magnetic-resonance imaging (MRI) scans of the knee are not indicated for diagnosing knee OA, they are commonly ordered prior to the referral to an orthopaedic surgeon. The purpose of this study was to determine the proportion of patients who underwent an MRI in the two years prior to their primary TKA for OA. Secondary outcomes included determining patient and physician associations with increased MRI usage. This is a population-based cohort study using billing codes in Ontario, Canada. All patients over 40 years-old who underwent a primary TKA between April 1, 2008 and March 31, 2017 were included. Statistical analyses were performed using SAS and included the Cochran-Armitage test for trend of MRI prior to surgery, and predictive multivariable regression model. Significance was set to p<0.05. There were 172,689 eligible first-time TKA recipients, of which 34,140 (19.8%) received an MRI in the two years prior to their surgery. The majority of these (70.8%) were ordered by primary care physicians, followed by orthopaedic surgeons (22.5%). Patients who received an MRI were younger and had fewer comorbidities than patients who did not (p<0.001). MRI use prior to TKA increased from 15.9% in 2008 to 20.1% in 2017 (p<0.0001). Despite MRIs rarely being indicated for the work-up of knee OA, nearly one in five patients have an MRI in the two years prior to their TKA. Reducing the use of this prior to TKA may help reduce wait-times for surgery

Knee pain is common, representing a significant socioeconomic burden. Caused by a variety of pathologies, its evaluation in primary-care is challenging. Subsequently, an over-reliance on magnetic resonance imaging (MRI) exists. Prior to orthopaedic surgeon referral, many patients receive no, or incorrect, imaging. Electronic-triage (e-triage) tools represent an innovative solution to address this problem. The primary aim of this study was to ascertain whether an e-triage tool is capable of outperforming existing clinical pathways to determine the correct pre-hospital imaging based on knee pain diagnosis. Patients ≥18 years with a new presentation of knee pain were retrospectively identified. The timing and appropriateness of imaging was assessed. A symptom-based e-triage tool was developed, using the Amazon LEXbotplatform, and piloted to predict five common knee pathologies and suggest appropriate imaging. 1462 patients were identified. 17% of arthroplasty patients received an ‘unnecessary MRI’, whilst 28% of arthroscopy patients did not have a ‘necessary MRI’, thus requiring a follow-up appointment, with a mean delay of three months (SD 2.6, range 0.2-20.2). Using NHS tariffs, a wasted cost through unnecessary/necessary MRIs and subsequent follow-up appointments was estimated at £45,816. The e-triage pilot was trialled with 41 patients (mean age:58.4 years, 58.5% female). Preliminary diagnoses were available for 34 patients. Using the highest proportion of reported symptoms in the corresponding group, the e-triage tool correctly identified three of the four knee pathologies. The e-triage tool did not correctly identify anterior cruciate ligament injuries (n=3). 79.2% of participants would use the tool again. A significant number of knee pathology patients received incorrect imaging prior to their initial hospital appointment, incurring delays and unnecessary costs. A symptom-based e-triage tool was developed, with promising pilot data and user feedback. With refinement, this tool has the potential to improve wait-times and referral quality, whilst reducing costs

This study investigates the relationships between Intervertebral Disc (IVD) morphology and biomechanics using patient-specific (PS) finite element (FE) models and poromechanical simulations. 169 3D lumbar IVD shapes from the European project MySpine (FP7-269909), spanning healthy to Pfirrmann grade 4 degeneration, were obtained from MRIs. A Bayesian Coherent Point Drift algorithm aligned meshes to a previously validated structural FE mesh of the IVD. After mesh quality analyses and Hausdorff distance measurements, mechanical simulations were performed: 8 and 16 hours of sleep and daytime, respectively, applying 0.11 and 0.54 MPa of pressure on the upper cartilage endplate (CEP). Simulation results were extracted from the anterior (ATZ) and posterior regions (PTZ) and the center of the nucleus pulposus (CNP). Data mining was performed using Linear Regression, Support Vector Machine, and eXtreme Gradient Boosting techniques. Mechanical variables of interest in DD, such as pore fluid velocity (FLVEL), water content, and swelling pressure, were examined. The morphological variables of the simulated discs were used as input features. Local morphological variables significantly impacted the local mechanical response. The local disc heights, respectively in the mid (mh), anterior (ah), and posterior (ph) regions, were key factors in general. Additionally, fluid transport, reflected by FLVEL, was greatly influenced (r2 0.69) by the shape of the upper and lower cartilage endplates (CEPs). This study suggests that disc morphology affects Mechanical variables of interest in DD. Attention should be paid to the antero-posterior distribution and local effects of disc heights. Surprisingly, the CEP morphology remotely affected the fluid transport in NP volumes around mid-height, and mechanobiological implications shall be explored. In conclusion, patient-specific IVD modeling has strong potential to unravel important correlations between IVD phenotypes and local tissue regulation. Acknowledgments: European Commission: Disc4All-MSCA-2020-ITN-ETN GA: 955735; O-Health-ERC-CoG-2021-101044828

Introduction. Osteochondral lesions (OCLs) of the talus are a challenging and increasingly recognized problem in chronic ankle pain. Many novel techniques exist to attempt to treat this challenging entity. Difficulties associated with treating OCLs include lesion location, size, chronicity, and problems associated with potential graft harvest sites. Matrix associated stem cell transplantation (MAST) is one such treatment described for larger lesions >15mm2 or failed alternative therapies. This cohort study describes a medium-term review of the outcomes of talar lesions treated with MAST. Methods. A review of all patients treated with MAST by a single surgeon was conducted. Preoperative radiographs, MRIs and FAOS outcome questionnaire scores were conducted. Intraoperative classification was undertaken to correlate with imaging. Postoperative outcomes included FAOS scores, return to sport, revision surgery/failure of treatment and progression to arthritis/fusion surgery. Results. 58 MAST procedures in 57 patients were identified in this cohort. The mean follow up was 5 years. There were 20 females and37males, with a mean age of 37 years (SD 9.1). 22 patients had lateral OCLS were and 35 patients had medial OCLs. Of this cohort 32patients had previous surgery and 25 had this procedure as a primary event. 15 patients had one failed previous surgery, 9 patients had two, four patients had three previous surgeries and three patients had four previous surgeries. 12 patients had corrective or realignment procedures at the time of surgery. In terms of complications 3 patients of this cohort went on to have an ankle fusion and two of these had medial malleolar metal work taken out prior to this, 5 patients had additional procedures for arthrofibrotic debridements, 1 patient had a repeat MAST procedure, 1 additional patients had removal of medial malleolar osteotomy screws for pain at the osteotomy site, there were 2 wound complications one related to the ankle and one related to pain at the iliac crest donor site. Conclusion. MAST has demonstrated positive results in lesions which prove challenging to treat, even in a “ failed microfracture” cohort. RCT still lacking in field of orthobiologics for MAST. Longer term follow up required to evaluate durability

Traditionally, sports Injuries have been sub-optimally managed through Emergency Departments (ED) in the public health system due to a lack of adequate referral processes. Fractures are ruled out through plain radiographs followed by a reactive process involving patient initiated further follow up and investigation. Consequently, significant soft tissue and chondral injuries can go undiagnosed during periods in which early intervention can significantly affect natural progression. The purpose of this quality improvement project was to assess the efficacy of an innovative Sports Injury Pathway introduced to detect and treat significant soft tissue injuries. A Sports Injury Pathway was introduced at Fiona Stanley Hospital (WA, Australia) in April 2019 as a collaboration between the ED, Physiotherapy and Orthopaedic Departments. ED practitioners were advised to have a low threshold for referral, especially in the presence of a history of a twisting knee injury, shoulder dislocation or any suggestion of a hip tendon injury. All referrals were triaged by the Perth Sports Surgery Fellow with early follow-up in our Sports Trauma Clinics with additional investigations if required. A detailed database of all referrals was maintained, and relevant data was extracted for analysis over the first 3 years of this pathway. 570 patients were included in the final analysis. 54% of injuries occurred while playing sport, with AFL injuries constituting the most common contact-sports injury (13%). Advanced Scope Physiotherapists were the largest source of referrals (60%). A total of 460 MRI scans were eventually ordered comprising 81% of total referrals. Regarding Knee MRIs, 86% identified a significant structural injury with ACL injuries being the most common (33%) followed by isolated meniscal tears (16%) and multi-ligament knee injuries (11%). 95% of Shoulder MRI scans showed significant pathology. 39% of patients required surgical management, and of these 50% were performed within 3 months from injury. The Fiona Stanley Hospital Sports Injury Pathway has demonstrated its clear value in successfully diagnosing and treating an important cohort of patients who present to our Emergency Department. This low threshold/streamlined referral pathway has found that the vast majority of these patients suffer significant structural injuries that may have been otherwise missed, while providing referring practitioners and patients access to prompt imaging and high-quality Orthopaedic sports trauma services. We recommend the implementation of a similar Sports Injury Pathway at all secondary and tertiary Orthopaedic Centres

Background. In vivo evaluation of IVD strains is crucial to better understand normal and pathological IVD mechanics, and to evaluate the effectiveness of treatments. This study aimed to 1) develop a novel in vivo technique based on 3T MRI and digital volume correlation (DVC) to measure strains within IVDs and 2) to use this technique to resolve 3D strains within IVDs of healthy volunteers during extension. Methods. This study included 40 lumbar IVDs from eight healthy subjects. The optimal MR sequence to minimise DVC uncertainties was identified by scanning one subject with four different sequences: CISS, T1VIBE, T2SPACE, and T2TSE. To assess the repeatability of the strain measurements in spines with different anatomical and morphological variations four subjects were scanned with the optimal sequence, and uncertainties of the strain measurements were quantified. Additionally, to calculate 3D strains during extension, MRIs were acquired from six subjects in both the neutral position and after full extension. Results. Measurement errors were lowest when using the T2TSE sequence (precision=0.33 ± 0.10%, accuracy=0.48 ± 0.11%). The largest average maximum tensile and shear strains were seen at the L2-L3 level in all volunteers (7.2 ± 1.5% and 6.8 ± 1.1%, respectively), while the L5-S1 level experienced the lowest average tensile and shear strains (3.5 ± 1.0% and 3.9 ± 0.7%, respectively). Conclusion. The findings of this study establish clinical MRI-based DVC (MRI-DVC) as a new tool for in vivo strain measurement within human IVDs. MRI-DVC successfully provided internal strain distributions within IVDs and has great potential to be used for a wide range of clinical applications. Conflict of interest: No conflicts of interest. Source of funding: This work was supported by the EPSRC, New Investigator Award, EP/V029452/1

Background. The anatomy of the human body has been studied for centuries. Despite this, recent articles have announced the presence of a new knee ligament- the anterolateral ligament. It has been the subject of much discussion and media commentary. Previous anatomical studies indicate its presence, and describe its location, origin, course and insertion. Magnetic resonance imaging (MRI) is the best and most commonly used investigation to assess the ligamentous structure of the knee. To date, most MRI knee reports make no mention of the anterolateral ligament. The aim of this study was to assess for the presence of the anterolateral ligament using MRI, and to describe the structure if visualised. Methods. All right knee MRIs performed on a Siemens Magnetom Espree 1.5 Tesla scanner in Merlin Park Hospital over a 4 year period were retrospectively analysed. Patients born before 1970, or with reported abnormalities were excluded. The normal MRIs were then analysed by a consultant radiologist specialising in musculoskeletal imaging. Measurements on origin, insertion, course and length were noted. Results. 942 right knee MRIs were performed in the time period. 62 were classed as normal, and within the specified age range. 10 were randomly sampled. Of these the ligament was visible on all 10 MRIs, best viewed in the coronal plane. The average length (visible in 8/10) was 28.88mm +/− 5.14mm. The origin (visible in all 10) was 2.25mm +/− 0.39mm. The insertion (visible in 9/10) was 1.93mm +/− 0.424. The mid thickness was 1.87mm +/− 0.2mm. Conclusions. This study indicates that the ALL is a discrete, visible structure on MRI. This furthers the evidence of the presence of the ALL and also provides information that may be beneficial in future studies, and assessment of knee injuries. Level of evidence. 4

Introduction. The direct anterior approach (DAA) and the posterior approach (PA) are 2 common total hip arthroplasty (THA) exposures. This prospective study quantitatively compared changes in periarticular muscle volume after DAA and PA THA. Materials. Nineteen patients undergoing THA were recruited from the practices of 3 fellowship-trained hip surgeons. Each surgeon performed a single approach, DAA or PA. Enrolled patients underwent a preoperative MRI of the affected hip and two subsequent postoperative MRIs, averaging 9.6 and 24.3 weeks after surgery. Clinical evaluations were done by Harris Hip Score at each follow-up interval. Results. MRIs for 10 DAA and 9 PA patients were analyzed. Groups did not differ significantly with regard to BMI, age, or pre-operative muscle volume. 1 DAA patient suffered a periprosthetic fracture and was excluded from the study. DAA hips showed significant atrophy in the obturator internus (−37.3%) muscle at early follow-up, with persistent atrophy of this muscle at the final follow-up. PA hips showed significant atrophy in the obturator internus (−46.8%) and externus (−16.0%), piriformis (−8.12%), and quadratus femoris muscles (−13.1%) at early follow-up, with persistent atrophy of these muscles at final follow-up. Loss of anterior capsular integrity was present at final follow-up in 2/10 DAA hips while loss of posterior capsular integrity was present in 5/9 PA hips. There was no difference in clinical outcomes. Discussion. This study provides objective evidence that, regardless of surgical approach, a muscle whose tendon is detached from its insertion is likely to demonstrate persistent atrophy 6 months following THA. Although the study was not powered to compare clinical outcomes, it should be noted that no significant difference in patient outcomes were observed. For any tables or figures, please contact the authors directly

Introduction. The current recommendation by the AAOS in the 2010 clinical practice guidelines for the use of MRI to diagnose a periprosthetic joint infection (PJI) is “inconclusive” given the lack of evidence to support its use. The purpose of this study was to determine the utility of MRI with metal reduction artifact sequencing in diagnosing a periprosthetic joint infection (PJI) after total hip arthroplasty (THA). Methods. 176 patients who underwent MRI with multi-acquisition variable resonance image combination (MAVRIC) to reduce metal artifact for a painful THA between the years of 2009–2013 were retrospectively evaluated. All MRIs were read by one of four radiologists with extensive experience in interpreting MRIs after THA. All MRIs were performed using a 1.5 Tesla magnet. Of the 176 patients examined, 16 patients were found to have a deep periprosthetic joint infection using Musculoskeletal Infection Society (MSIS) criteria after the MRI was performed. MRI reads were classified as either positive (read as “evidence of active infection” or “suspicious for infection”) or negative (read as no evidence of infection). Only one patient who had a positive MRI read was excluded because of loss to followup after the MRI was performed. Results. Of the 160 aseptic patients, only one patient was read as suspicious for infection (false positive rate = 0.6%, specificity=99.4%, negative predictive value (NPV)=98.8%). Of the 16 patients with an infected THA, 14 patients were read as positive for infection (false negative rate=12.5%, sensitivity = 87.5%, positive predictive value (PPV)=93%). Conclusion. MRI with metal reduction artifact sequence is a highly specific test to diagnose or rule out a PJI with a low false positive rate and excellent PPV and NPV however, given its lower sensitivity than published for the serum C-reactive protein, is not recommended as a general “screening” test for all patients with pain after THA to rule out infection