Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group.

Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Research Program Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing magnetic resonance imaging (MRI) acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.

Midterm Follow-Up and Assessment of Cartilage Thickness by Arthro-Magnetic Resonance Imaging After Arthroscopic Cam Resection, Labral Repair, and Rim Trimming Without Labral Detachment.

PURPOSE: To evaluate the clinical and radiological outcome, sum of acetabular and femoral cartilage thickness, and rate of failure in the midterm after arthroscopic treatment of femoroacetabular impingement (FAI) syndrome with femoral osteoplasty, labral repair, and rim trimming without labral detachment. METHODS: This retrospective case series included patients with FAI syndrome who had undergone hip arthroscopy from January 2009 to December 2010 by a single surgeon, with a minimum follow-up of 55 months. Data from patients who had undergone arthroscopic hip procedures with labral repair, rim trimming, and femoral osteoplasty were analyzed pre- and postoperatively. Clinical outcome (nonarthritic hip score [NAHS], Short Form 36 [SF-36]), range of motion, progression of osteoarthritis (Tönnis grade), radiological parameters (α angle, lateral center-edge angle [LCEA], Tönnis angle), femoral and acetabular cartilage thickness (using magnetic resonance imaging [MRI]), and intraoperative findings were evaluated. RESULTS: Of 148 hip arthroscopies performed, 97 included rim trimming, labral refixation, and femoral osteoplasty. Ten cases were lost to follow-up, leaving 87 hips. Arthroscopic revision was performed on 4 hips and total hip replacement on 4 hips, and 1 hip underwent both arthroscopic revision and total hip replacement. Excluding these 9 cases of revision, for which follow-up was not possible (retrospective study), the remaining 78 hips were followed up for a minimum of 55 months (77 ± 11.4, mean ± SD; range 55 to 124). Mean NAHS (65 to 88, P < .001), SF-36 physical subscale (65 to 85, P < .001), and the numerical pain rating scale (NRS) (5 to 1, P < .001) improved significantly. Outcome scores of minimal clinical importance (NAHS) were achieved in 67.6% of the patients. Mean range of movement improved significantly in flexion (109 to 122, P < .001) and internal rotation (10 to 22.7, P < .001). NAHS was positively associated with flexion of the hip postoperatively (r = 0.307, P = .011). In 16 cases, microfracture was performed (15 acetabular and 1 femoral). Preoperative α angles (anteroposterior and modified Dunn) were significantly higher in this cohort (P < .001, 95% confidence interval 8.9 to 25.2, P = .001). Twenty hips (28 %) progressed to worse Tönnis grades. Initial Tönnis grades were grade 0, 38; grade 1, 48; grade 2, 8. Pre- or postoperative Tönnis grades did not show any correlation with pre- or postoperative NAHS and NRS. MRI measurements at the latest follow-up (69 patients) of the femoral and acetabular cartilage thickness did not reveal any significant reduction at the 12 o'clock position. CONCLUSION: Arthroscopic cam resection, rim trimming, and labral repair without detachment of the labrum provides good or excellent outcome in 77.1% of hips based on NAHS in the midterm. Higher range of motion in flexion is associated with higher NAHS postoperatively. Arthroscopic cam resection, rim trimming and labral repair without detachment of the labrum is a successful method for the treatment of FAI syndrome in the midterm. LEVEL OF EVIDENCE: IV, retrospective case series.

Measuring and reporting of vertebral endplate bone marrow lesions as seen on MRI (Modic changes): recommendations from the ISSLS Degenerative Spinal Phenotypes Group.

PURPOSE: The positive association between low back pain and MRI evidence of vertebral endplate bone marrow lesions, often called Modic changes (MC), offers the exciting prospect of diagnosing a specific phenotype of chronic low back pain (LBP). However, imprecision in the reporting of MC has introduced substantial challenges, as variations in both imaging equipment and scanning parameters can impact conspicuity of MC. This review discusses key methodological factors that impact MC classification and recommends guidelines for more consistent MC reporting that will allow for better integration of research into this LBP phenotype. METHODS: Non-systematic literature review. RESULTS: The high diagnostic specificity of MC classification for a painful level contributes to the significant association observed between MC and LBP, whereas low and variable sensitivity underlies the between- and within-study variability in observed associations. Poor sensitivity may be owing to the presence of other pain generators, to the limited MRI resolution, and to the imperfect reliability of MC classification, which lowers diagnostic sensitivity and thus influences the association between MC and LBP. Importantly, magnetic field strength and pulse sequence parameters also impact detection of MC. Advances in pulse sequences may improve reliability and prove valuable for quantifying lesion severity. CONCLUSIONS: Comparison of MC data between studies can be problematic. Various methodological factors impact detection and classification of MC, and the lack of reporting guidelines hinders interpretation and comparison of findings. Thus, it is critical to adopt imaging and reporting standards that codify acceptable methodological criteria. These slides can be retrieved under Electronic Supplementary Material.

Comparison of interscalene block, general anesthesia, and intravenous analgesia for out-patient shoulder reduction.

PURPOSE: Shoulder dislocation is often associated with intense pain, and requires urgent pain therapy and reduction. Interscalene block, general anesthesia, or intravenous analgesia alone are applied procedures that facilitate shoulder reduction by the surgeon and ease patients' pain. This study was conducted to compare procedure times, patient satisfaction, side-effects, and clinical outcome of these clinical procedures. METHODS: Retrospective chart analysis was performed for all patients treated at the Emergency Department of a primary care hospital. In addition, standardized telephone interviews were conducted. Subjective clinical outcome and patient satisfaction (SF-36, Quick-DASH, ZUF-8) were measured with the standardized questionnaires. RESULTS: The shortest overall procedure time [67.5 min (48.8-93.5 min), P = 0.003] was found in patients with interscalene block. The advantage of general anesthesia was the shortest anesthesia induction time [10 min (7.8-10 min), P < 0.0001]; reduction time [6 min (4.3-6 min), P = 0.039]; and time to discharge [90 min (67.5-123.8 min), P = 0.0001] were significantly prolonged in comparison to interscalene block [5 min (1-5 min) and 45 min (2-67.5 min)]. The longest reduction time [11 min (10-13.5 min), P = 0.0008] was seen in patients in the intravenous analgesia group. Overall, patient satisfaction was greater in patients with regional as compared to general anesthesia [measured by ZUF-8: 12 (9-15) vs. 17 (12-24), P = 0.03]. Subjective clinical outcome (SF-36, DASH) was comparable among the three groups. There was one immediately identified esophageal intubation in the general anesthesia group. CONCLUSIONS: Out-patient shoulder reduction can be accomplished no matter whether general anesthesia, regional anesthesia, or intravenous analgesia alone was administered. Clinical outcome as measured by SF-36 and DASH was comparable among the three groups, but the shortest overall procedure time and greater patient satisfaction were found in patients with interscalene block.

The intervertebral disc, the endplates and the vertebral bone marrow as a unit in the process of degeneration.

OBJECTIVES: The association of disc degeneration (DD) and vertebral endplate degeneration (EPD) is still not well understood. This study aimed to find segmental predictive risk factors for DD and EPD and to illuminate associations of the disc, endplate and bone marrow changes in the process of degeneration. METHODS: After institutional review board approval, 450 lumbar levels, followed up with MRI for at least 4 years, were retrospectively graded for DD according to Pfirrmann (PFG), for EPD according to the endplate score (EPS) and according to the presence, extension and type of Modic changes (MC). Clustered logistic regression and multivariate analysis was applied in nested, matched case-control subgroups to evaluate potential local risk factors for progression. RESULTS: An EPS score of ≥4 was identified as an independent risk factor for progression of DD (OR = 2.32, 95%CI:1.07-5.01,p = 0.03) and MC (OR = 5.49,95%CI:2.30-13.10,p < 0.001). Progression of DD was significantly accompanied by progression or evolution of MC (OR = 12.25,95%CI:1.49-100.6,p = 0.02) and with progression of EPS (OR = 1.71, 95%CI:1.00-1.05, p = 0.01). Once advanced DD has occurred, it becomes a risk factor for progression in EPS (OR = 2.24,95%CI:1.23-4.12,p < 0.01). CONCLUSIONS: The degenerative processes in the disc, endplate and bone marrow are highly associated. An EPS ≥ 4 is an independent risk factor for DD and MC progression in a population with low back pain. KEY POINTS: • The degenerative processes in the disc, endplate and bone marrow are associated. • An endplate score ≥4 is a risk factor for DD and MC progression. • Modic changes are last to occur in the development of segmental intervertebral degeneration. • A new segmental grading system is suggested.

Merits of different anatomical landmarks for correct numbering of the lumbar vertebrae in lumbosacral transitional anomalies.

PURPOSE: Anatomical landmarks and their relation to the lumbar vertebrae are well described in subjects with normal spine anatomy, but not for subjects with lumbosacral transitional vertebra (LSTV), in whom correct numbering of the vertebrae is challenging and can lead to wrong-level treatment. The aim of this study was to quantify the value of different anatomical landmarks for correct identification of the lumbar vertebra level in subjects with LSTV. METHODS: After IRB approval, 71 subjects (57 ± 17 years) with and 62 without LSTV (57 ± 17 years), all with imaging studies that allowed correct numbering of the lumbar vertebrae by counting down from C2 (n = 118) or T1 (n = 15) were included. Commonly used anatomical landmarks (ribs, aortic bifurcation (AB), right renal artery (RRA) and iliac crest height) were documented to determine the ability to correctly number the lumbar vertebrae. Further, a tangent to the top of the iliac crests was drawn on coronal MRI images by two blinded, independent readers and named the 'iliac crest tangent sign'. The sensitivity, specificity and the interreader agreement were calculated. RESULTS: While the level of the AB and the RRA were found to be unreliable in correct numbering of the lumbar vertebrae in LSTV subjects, the iliac crest tangent sign had a sensitivity and specificity of 81 % and 64-88 %, respectively, with an interreader agreement of k = 0.75. CONCLUSION: While anatomical landmarks are not always reliable, the 'iliac crest tangent sign' can be used without advanced knowledge in MRI to most accurately number the vertebrae in subjects with LSTV, if only a lumbar spine MRI is available.

Is the iliolumbar ligament a reliable identifier of the L5 vertebra in lumbosacral transitional anomalies?

OBJECTIVE: Sufficiently sized studies to determine the value of the iliolumbar ligament (ILL) as an identifier of the L5 vertebra in cases of a lumbosacral transitional vertebra (LSTV) are lacking. METHODS: Seventy-one of 770 patients with LSTV (case group) and 62 of 611 subjects without LSTV with confirmed L5 level were included. Two independent radiologists using coronal MR images documented the level(s) of origin of the ILL. The interobserver agreement was analysed using weighted kappa/kappa (wκ/κ) and a Fischer's exact test to assess the value of the ILL as an identifier of the L5 vertebra. RESULTS: The ILL identified the L5 vertebra by originating solely from L5 in 95 % of the controls; additional origins were observed in 5 %. In the case group, the ILL was able to identify the L5 vertebra by originating solely from L5 in 25-38 %. Partial origin from L5, including origins from other vertebra was observed in 39-59 % and no origin from L5 at all in 15-23 % (wκ = 0.69). Both readers agreed that an ILL was always present and its origin always involved the last lumbar vertebra. CONCLUSION: The level of the origin of the ILL is unreliable for identification of the L5 vertebra in the setting of an LSTV or segmentation anomalies. KEY POINTS: • The origin of the ILL is evaluated in subjects with an LSTV. • The origin of the ILL is anatomically highly variable in LSTV. • The ILL is not a reliable landmark of the L5 vertebra in LSTV.

Is an annular tear a predictor for accelerated disc degeneration?

PURPOSE: It is questionable whether an annular tear (AT) is a predictor for accelerated degeneration of the intervertebral discs. The aim of the present study was to answer this question via a matched case-control study design that reliably eliminates potential confounders. MATERIALS: Presence or absence of AT, defined as a hyperintense lesion within the annular fibrosus on T2-weighted non-contrast MRI images, was documented in 450 intervertebral lumbar discs of 90 patients who could be followed up for at least 4 years with MRI. Discs with an AT (n = 36) were matched 1:1 to control discs according to the level, degree of initial disc degeneration on MRI (both Pfirrmann grade median 4, range 3-4), age (59.5 ± 15.0 versus 59.3 ± 14.6 years), BMI (26.7 ± 4.4 versus 26.9 ± 4.4 kg/m(2)) and interval to the follow-up MRI (4.8 ± 0.9 versus 5.1 ± 0.8 years). The degree of disc degeneration after a minimum of 4 years was graded on the follow-up MRI in both groups according to the Pfirrmann classification. RESULTS: One-fourth (25%) of the 36 discs with an AT on the initial MRI exam progressed in degeneration. This was similar to the rate of the matched control discs with no AT, in which also around one-fourth (22%) showed a progression of degeneration (p = 1.00), also without any difference in the degree of degeneration. CONCLUSION: Discs with a Pfirrmann grade >2 with an AT, defined by a hyperintense signal intensity on MRI, are not prone to accelerated degeneration if compared to discs without an AT. Therefore, the presence of an AT per se does not predict accelerated disc degeneration.

Determinants of evolution of endplate and disc degeneration in the lumbar spine: a multifactorial perspective.

PURPOSE: Evolution and progression of disc and endplate bone marrow degeneration of the lumbar spine are thought to be multifactorial, yet, their influence and interactions are not understood. The aim of this study was to find association of potential predictors of evolution of degeneration of the lumbar spine. METHODS: Patients (n = 90) who underwent two lumbar magnetic resonance imaging (MRI) exams with an interval of at least 4 years and without any spinal surgery were included into the longitudinal cohort study with nested case-control analysis. Disc degeneration (DD) was scored according to the Pfirrmann classification and endplate bone marrow changes (EC) according to Modic in 450 levels on both MRIs. Potential variables for degeneration such as age, gender, BMI, scoliosis and sagittal parameters were compared between patients with and without evolution or progression of degenerative changes in their lumbar spine. A multivariate analysis aimed to identify the most important variables for progression of disc and endplate degeneration, respectively. RESULTS: While neither age, gender, BMI, sacral slope or the presence of scoliosis could be identified as progression factor for DD, a higher lordosis was observed in subjects with no progression (49° ± 11° vs 43° ± 12°; p = 0.017). Progression or evolution of EC was only associated with a slightly higher degree of scoliosis (10° ± 10° vs 6° ± 9°; p = 0.04) and not to any of the other variables. CONCLUSION: While a coronal deformity of the lumbar spine seems associated with evolution or progression of EC, a higher lumbar lordosis is protective for radiographic progression of DD. This implies that scoliotic deformity and lesser lumbar lordosis are associated with higher overall degeneration of the lumbar spine.

Improving the Reliability of Peer Review Without a Gold Standard.

Peer review plays a crucial role in accreditation and credentialing processes as it can identify outliers and foster a peer learning approach, facilitating error analysis and knowledge sharing. However, traditional peer review methods may fall short in effectively addressing the interpretive variability among reviewing and primary reading radiologists, hindering scalability and effectiveness. Reducing this variability is key to enhancing the reliability of results and instilling confidence in the review process. In this paper, we propose a novel statistical approach called "Bayesian Inter-Reviewer Agreement Rate" (BIRAR) that integrates radiologist variability. By doing so, BIRAR aims to enhance the accuracy and consistency of peer review assessments, providing physicians involved in quality improvement and peer learning programs with valuable and reliable insights. A computer simulation was designed to assign predefined interpretive error rates to hypothetical interpreting and peer-reviewing radiologists. The Monte Carlo simulation then sampled (100 samples per experiment) the data that would be generated by peer reviews. The performances of BIRAR and four other peer review methods for measuring interpretive error rates were then evaluated, including a method that uses a gold standard diagnosis. Application of the BIRAR method resulted in 93% and 79% higher relative accuracy and 43% and 66% lower relative variability, compared to "Single/Standard" and "Majority Panel" peer review methods, respectively. Accuracy was defined by the median difference of Monte Carlo simulations between measured and pre-defined "actual" interpretive error rates. Variability was defined by the 95% CI around the median difference of Monte Carlo simulations between measured and pre-defined "actual" interpretive error rates. BIRAR is a practical and scalable peer review method that produces more accurate and less variable assessments of interpretive quality by accounting for variability within the group's radiologists, implicitly applying a standard derived from the level of consensus within the group across various types of interpretive findings.

Comparison of a fluoroscopic 3-dimensional imaging system and conventional CT in detection of pars fractures in the cadaveric lumbar spine.

STUDY DESIGN: Cadaveric Study. OBJECTIVE: To compare a fluoroscopic imaging system with computed tomography (CT) and radiographs in detection of spondylolysis and radiation exposure in a cadaver model. SUMMARY OF BACKGROUND DATA: Lumbar spondylolysis is defined as a defect or fracture of the pars interarticularis and occurs with or without anterior spondylolisthesis. CT scan is the gold standard imaging study for spondylolysis but is limited by the supine position, which may cause reduction of anterolisthesis and by ionizing radiation, which limits the frequency of follow-up scans. METHODS: Thirteen intact cadaveric lumbar spine segments with 26 pars were randomized to be left intact or to undergo simulated fracture using a 1.3 mm oscillating microsurgical saw. Fifteen pars underwent simulated fracture and 11 pars were left intact. Lumbar spine segments were imaged using plain radiographs, multiplanar fluoroscopic imaging, and conventional CT scan. The images were interpreted by 3 observers blinded to the number and location of defects. Radiation exposure and doses were recorded from all imaging units. RESULTS: Average radiation doses were 0.0025 mSv for each radiograph, 0.23 mSv (low dose) and 0.47 mSv (high dose) for fluoroscopic imaging, and 1.5 mSv for conventional CT imaging (pediatric dose setting). Evaluation of radiographs for spondylolysis had sensitivity of 98% and specificity of 97%. Evaluation using low-dose fluoroscopic images, high-dose fluoroscopic images, and CT scan images correctly identified the status of all pars based on multiplanar images; sensitivity and specificity were 100%. Kappa analysis demonstrated a value of 0.89 for radiographic interpretation indicating excellent agreement. Kappa values describing agreement for image interpretation for fluoroscopic imaging and CT scan were equal to 1.0, representing perfect agreement. CONCLUSIONS: Three-dimensional fluoroscopic imaging provides comparable diagnostic imaging with CT scan in an experimental cadaveric model of spondylolysis using up to 85% less radiation than conventional CT scan.

Anatomy of the psoas muscle and lumbar plexus with respect to the surgical approach for lateral transpsoas interbody fusion.

Lateral transpsoas interbody fusion (LTIF) is a minimally invasive technique that permits interbody fusion utilizing cages placed via a direct lateral retroperitoneal approach. We sought to describe the locations of relevant neurovascular structures based on MRI with respect to this novel surgical approach. We retrospectively reviewed consecutive lumbosacral spine MRI scans in 43 skeletally mature adults. MRI scans were independently reviewed by two readers to identify the location of the psoas muscle, lumbar plexus, femoral nerve, inferior vena cava and right iliac vein. Structures potentially at risk for injury were identified by: a distance from the anterior aspect of the adjacent vertebral bodies of <20 mm, representing the minimum retraction necessary for cage placement, and extension of vascular structures posterior to the anterior vertebral body, requiring anterior retraction. The percentage of patients with neurovascular structures at risk for left-sided approaches was 2.3% at L1-2, 7.0% at L2-3, 4.7% at L3-4 and 20.9% at L4-5. For right-sided approaches, this rose to 7.0% at L1-2, 7.0% at L2-3, 9.3% at L3-4 and 44.2% at L4-5, largely because of the relatively posterior right-sided vasculature. A relationship between the position of psoas muscle and lumbar plexus is described which allows use of the psoas position as a proxy for lumbar plexus position to identify patients who may be at risk, particularly at the L4-5 level. Further study will establish the clinical relevance of these measurements and the ability of neurovascular structures to be retracted without significant injury.

Arthroscopic treatment of femoroacetabular impingement of the hip: a new technique to access the joint.

UNLABELLED: Femoroacetabular impingement has been established as an important cause of groin pain and limitation of range of motion in young, active patients and a possible cause for early osteoarthritis of the hip. Open surgery is a well-recognized approach for treatment and probably the standard for most surgeons, but recent reports regarding arthroscopic treatment procedures suggest comparable results. We present a technique that provides a way to securely penetrate the joint capsule and evaluate the clinical results of this technique in patients with femoroacetabular impingement. Between 2004 and 2007, we prospectively followed a cohort of 105 hips (88 patients; 60 males, 28 females) who underwent surgery for symptomatic cam or mixed femoroacetabular impingement. All patients were evaluated for the Nonarthritic Hip Score, clinical parameters, visual analog scale pain score, initial radiographic degenerative changes, and alpha angle. At a minimum followup of 1.3 years (average, 2.3 years; range, 1.3-4.1 years), all clinical outcome measures improved. The Nonarthritic Hip Score improved from 56.7 points (range, 15-92.5 points) to 84.6 points (range, 47.5-100 points). Nine patients (8.6%) underwent THA during followup. The outcome measures after arthroscopic therapy for femoroacetabular impingement seem comparable to those reported after open procedures. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Arthroscopic treatment of femoral acetabular impingement in patients with preoperative generalized degenerative changes.

PURPOSE: The aim of this study was to evaluate the short-term results after arthroscopic femoroacetabular impingement (FAI) correction combined with additional procedures addressing labral and chondral damages in patients who showed generalized severe cartilage lesions intraoperatively. METHODS: Between 2004 and 2007, 20 patients (16 men and 4 women) could be included in the study. Clinical parameters, the pain score on a visual analog scale, initial radiologic degenerative changes, the alpha angle, and the Nonarthritic Hip Score were prospectively documented. The study endpoint was the implantation of a total hip arthroscopy or the latest follow-up. RESULTS: At a mean follow-up of 3.0 years, 10 patients (50%) had undergone, or planned to undergo, total hip replacement. The remaining patients showed a significant improvement in pain, Nonarthritic Hip Score, and hip flexion and internal rotation. CONCLUSIONS: In patients with already marked generalized chondral lesions, arthroscopy does not have any effect beyond the short-term pain relief resulting from debridement. The study underlines the fact that FAI with advanced osteoarthrosis, particularly Tönnis grade III, is not an indication for arthroscopic FAI correction. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Magnetic resonance imaging (MRI) versus single photon emission computed tomography (SPECT/CT) in painful total hip arthroplasty: a comparative multi-institutional analysis.

OBJECTIVE: To investigate the value of MRI in comparison to single photon emission computed tomography (SPECT)/CT in patients with painful hip arthroplasties. METHODS: A prospective, multi-institutional study was performed. Therefore, 35 consecutive patients (21 female, 14 male, mean age 61.8 ± 13.3 years) with 37-painful hip arthroplasties were included. A hip surgeon noted the most likely diagnosis based on clinical examination and hip radiographs. Then, MRI and SPECT/CT of the painful hips were acquired. MRI and SPECT/CT were assessed for loosening, infection, fracture, tendon pathology and other abnormalities. Final diagnosis and therapy was established by the hip surgeon after integration of MRI and SPECT/CT results. The value of MRI and SPECT/CT for diagnosis was assessed with a 3-point scale (1 = unimportant, 2 = helpful, 3 = essential). RESULTS: Loosening was observed in 13/37 arthroplasties (6 shaft only, 6 cup only, 1 combined). Sensitivity, specificity, positive predictive value and negative predictive value for loosening of MRI were 86%/88%/60%/100% and of SPECT/CT 93%/97%/90%/100%, respectively. MRI and SPECT/CT diagnosed infection correctly in two of three patients and fractures in two patients, which were missed by X-ray. MRI detected soft tissue abnormalities in 21 patients (6 bursitis, 14 tendon lesions, 1 pseudotumor), of which only 1 tendon abnormality was accurately detected with SPECT/CT. All 5 arthroplasties with polyethylene wear were correctly diagnosed clinically and with both imaging modalities. MRI and SPECT/CT were judged as not helpful in 0/0%, as helpful in 16%/49% and essential in 84%/51%. CONCLUSION: In patients with painful hip arthroplasty SPECT/CT is slightly superior to MR in the assessment of loosening. MRI is far superior in the detection of soft tissue, especially tendon pathologies. ADVANCES IN KNOWLEDGE: To our knowledge this is the first prospective, multiinstitutional study which compares MRI with SPECT/CT in painful hip arthroplasties. We found that MRI is far superior in the detection of soft tissue pathologies, whereas SPECT/CT remains slightly superior regarding loosening.

Lumbar spine: reliability of MR imaging findings.

PURPOSE: To characterize the inter- and intraobserver variability of qualitative, non-disk contour degenerative findings of the lumbar spine at magnetic resonance (MR) imaging. MATERIALS AND METHODS: The case accrual method used to perform this institutional review board-approved, HIPAA-compliant retrospective study was the random selection of 111 interpretable MR examination cases of subjects from the Spine Patient Outcomes Research Trial. The subjects were aged 18-87 years (mean, 53 years +/- 16 [standard deviation]). Four independent readers rated the cases according to defined criteria. A subsample of 40 MR examination cases was selected for reevaluation at least 1 month later. The following findings were assessed: spondylolisthesis, disk degeneration, marrow endplate abnormality (Modic changes), posterior anular hyperintense zone (HIZ), and facet arthropathy. Inter- and intraobserver agreement in rating the data was summarized by using weighted kappa statistics. RESULTS: Interobserver agreement was good (kappa = 0.66) in rating disk degeneration and moderate in rating spondylolisthesis (kappa = 0.55), Modic changes (kappa = 0.59), facet arthropathy (kappa = 0.54), and posterior HIZ (kappa = 0.44). Interobserver agreement in rating the extent of Modic changes was moderate: kappa Values were 0.43 for determining superior anteroposterior extent, 0.47 for determining superior craniocaudal extent, 0.57 for determining inferior anteroposterior extent, and 0.48 for determining inferior craniocaudal extent. Intraobserver agreement was good in rating spondylolisthesis (kappa = 0.66), disk degeneration (kappa = 0.74), Modic changes (kappa = 0.64), facet arthropathy (kappa = 0.69), and posterior HIZ (kappa = 0.67). Intraobserver agreement in rating the extent of Modic changes was moderate, with kappa values of 0.54 for superior anteroposterior, 0.60 for inferior anteroposterior, 0.50 for superior craniocaudal, and 0.60 for inferior craniocaudal extent determinations. CONCLUSION: The interpretation of general lumbar spine MR characteristics has sufficient reliability to warrant the further evaluation of these features as potential prognostic indicators.

Evaluation of a computed tomography-based navigation system prototype for hip arthroscopy in the treatment of femoroacetabular cam impingement.

PURPOSE: The purpose of this study was to investigate the impact of a new computed tomography-based computer navigation system on the accuracy of arthroscopic offset correction in patients with cam type femoroacetabular impingement (FAI), and to evaluate if the accuracy of offset restoration compromises the early clinical outcome. METHODS: We prospectively treated 50 patients (25 navigated and 25 non-navigated) by hip arthroscopy and arthroscopic offset restoration for cam FAI. The patients were a mean age 42.9 years, and the average follow-up was 26.7 months, with no patients lost to follow-up. Magnetic resonance imaging scans were performed preoperatively and 6 weeks postoperatively. A postoperative alpha angle of less than 50 degrees or a reduction of the alpha angle of more than 20 degrees was considered to be successful offset restoration. Outcomes were measured with a visual analogue scale for pain, range of motion, and the nonarthritic hip score. RESULTS: The mean alpha angle improved from 76.5 degrees (range, 57 degrees to 110 degrees) to 54.2 degrees (range, 40 degrees to 84 degrees). In both the navigated and the non-navigated groups, 6 patients (24%) showed insufficient offset correction. Range of motion, visual analogue scale for pain scores, and nonarthritic hip scores significantly improved in all subgroups. Statistical analysis showed no significant difference regarding the clinical outcome between patients with sufficient and insufficient correction of the alpha angle. CONCLUSIONS: In this series, a significant percentage of patients (24%) showed an insufficient correction of the alpha angle after hip arthroscopy for cam FAI. This study shows that the presented navigation system could not improve this rate and that the insufficient accuracy of reduction of the alpha angle does not appear to compromise the early clinical outcome. LEVEL OF EVIDENCE: Level II, prospective comparative study.

The position of anterior cruciate ligament in frontal and sagittal plane and its relation to the inner side of the lateral femoral condyle.

The position of the anterior cruciate ligament (ACL) is one of the anatomical factors that lead to its injury. We evaluated 66 patients divided in two groups: 33 patients in the examined group with a diagnosed ACL lesion, and 33 patients in the control group with diagnosed patellofemoral pain. The patients were matched by age, sex, type of lesion (whether it was profession related) and whether the lesion was left or right sided. Measurements were carried out by radiography and MRI. The following positions of angles were measured: the angle of ACL in sagittal and frontal plane, the angle of the inner side of lateral condyle in frontal and horizontal plane and the angle between the course of ACL and the inner side of lateral condyle. In our study there is a significant difference (P < 0.05) in the degree of the ACL angles in the frontal plane between the examined group (74.5 degrees) and the control group (70.6 degrees). Also, there was a significant difference (P < 0.05) in the degree of the ACL angle in the sagittal plane between the examined group (48 degrees ) and the control (50.4 degrees). The angle between the inner side of the lateral condyle of the femur and the ACL of the examined group (32.9 degrees) differs significantly (P < 0.01) from the same angle of the control group (40.6 degrees ). According to the results of our study it appears that the increment of the ACL angle in the frontal plane, the decrement of the ACL angle in the sagittal plane and the decrement of the angle between the ACL and the inner side of the lateral condyle in the frontal plane are associated with the rupture of the ACL.

Arthroscopic offset restoration in femoroacetabular cam impingement: accuracy and early clinical outcome.

PURPOSE: The purpose of this study was to determine the accuracy of arthroscopic restoration of femoral offset as well as the early clinical outcome of arthroscopic debridement and femoral offset restoration and whether there is a correlation between accuracy and outcome. METHODS: Twenty-two patients with symptomatic femoroacetabular cam impingement underwent arthroscopic correction of the femoral offset and debridement. The alpha angle was measured with magnetic resonance imaging preoperatively and postoperatively for quantification of the offset, and the clinical status was determined by documenting the impingement sign, range of motion, intensity of pain on a visual analog scale, Nonarthritic Hip Score, and complications preoperatively and 6 months postoperatively. RESULTS: The alpha angle improved from a mean of 75 degrees to 54 degrees. Internal rotation increased from a mean of 5 degrees to 22 degrees, flexion increased from a mean of 107 degrees to 124 degrees, and the pain score decreased from a mean of 5.8 to 1.4. The Nonarthritic Hip Score increased from a mean of 49 to 74 points. No major complications were encountered. Patients with early osteoarthritis did substantially worse than those without it. The alpha angle did not correlate with any clinical outcome measure. CONCLUSIONS: The femoral offset can be precisely restored via an arthroscopic technique in the treatment of femoroacetabular cam impingement. The early clinical outcome of arthroscopic offset restoration and debridement is good in patients with no or only mild osteoarthritis. The accuracy of correction is not correlated with the early clinical outcome. LEVEL OF EVIDENCE: Level IV, therapeutic case series.