Patellar articular overlap is better associated with patellar alignment during weight-bearing than traditional measures of patellar height.

BACKGROUND: A consequence of a high riding patella is reduced osseous stability and malalignment of the patella (i.e., lateral patellar tilt and displacement). Although quantification of patellar height is a routine part of the radiographic examination of the patellofemoral joint, it is not clear which measure of patellar height is best associated with patella alignment. HYPOTHESIS/PURPOSE: To determine if patellar articular overlap (PAO) is better associated with lateral patellar tilt and lateral patellar displacement compared to traditional measures of patellar height. STUDY DESIGN: Cross-sectional. METHODS: Magnetic resonance images were obtained from 50 female participants (21 with patellofemoral pain and 29 healthy controls) under loaded conditions (25-35% bodyweight) at 15-20 degrees of knee flexion. Measurements of lateral patellar tilt and displacement as well as the PAO, Insall-Salvati ratio (ISV), Caton Deschamps-index (CD-index), or the Blacburn Peel-index (BP-index) were obtained from sagittal and axial plane images. RESULTS: The PAO was found to significantly correlated with lateral patellar tilt (r = -0.77, p < 0.001). In contrast, the ISV, CD-index, or the BP-index were not found to be associated with lateral patellar tilt (r = 0.13, p = 0.34; r = -0.14, p = 0.33; r = -0.08, p = 0.56, respectively). Both the PAO and ISV were found to be significantly correlated with lateral patellar displacement (r = -0.52, p < 0.001; r = 0.43, p = 0.002, respectively). Conversely, the CD-index and BP-index were not found to be associated with lateral patellar displacement (r = 0.03 p = 0.83; r = 0.05 p = 0.74, respectively). CONCLUSION: Of the measures of patellar height evaluated, the PAO was found to provide the greatest association with lateral patellar tilt and displacement.

Managing Patients With Unlabeled Passive Implants on MR Systems Operating Below 1.5 T.

The standard of care for managing a patient with an implant is to identify the item and to assess the relative safety of scanning the patient. Because the 1.5 T MR system is the most prevalent scanner in the world and 3 T is the highest field strength in widespread use, implants typically have "MR Conditional" (i.e., an item with demonstrated safety in the MR environment within defined conditions) labeling at 1.5 and/or 3 T only. This presents challenges for a facility that has a scanner operating at a field strength below 1.5 T when encountering a patient with an implant, because scanning the patient is considered "off-label." In this case, the supervising physician is responsible for deciding whether to scan the patient based on the risks associated with the implant and the benefit of magnetic resonance imaging (MRI). For a passive implant, the MRI safety-related concerns are static magnetic field interactions (i.e., force and torque) and radiofrequency (RF) field-induced heating. The worldwide utilization of scanners operating below 1.5 T combined with the increasing incidence of patients with implants that need MRI creates circumstances that include patients potentially being subjected to unsafe imaging conditions or being denied access to MRI because physicians often lack the knowledge to perform an assessment of risk vs. benefit. Thus, physicians must have a complete understanding of the MRI-related safety issues that impact passive implants when managing patients with these products on scanners operating below 1.5 T. This monograph provides an overview of the various clinical MR systems operating below 1.5 T and discusses the MRI-related factors that influence safety for passive implants. Suggestions are provided for the management of patients with passive implants labeled MR Conditional at 1.5 and/or 3 T, referred to scanners operating below 1.5 T. The purpose of this information is to empower supervising physicians with the essential knowledge to perform MRI exams confidently and safely in patients with passive implants. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.

Xenograft bone-patellar tendon-bone ACL reconstruction: a case series at 20-year follow-up as proof of principle.

PURPOSE: ACL reconstruction has a significant failure rate. To address the need for inexpensive strong tissue, a treatment process to "humanize" porcine tissue was developed and tested in primates and humans. This report describes the long-term outcomes from the first human clinical trial using a porcine xenograft ACL reconstruction device. METHODS: The study was performed with Z-Lig™ xenograft ACL device in 2003 as a pilot clinical feasibility study. This device was processed to slow its immune-mediated destruction by enzymatic elimination of α-gal epitopes and by partial crosslinking to slow the infiltration of macrophages into the biotransplant. RESULTS: Ten patients underwent reconstruction with the Z-Lig™ device. Five of 10 patients failed due to subsequent trauma (n = 3), arthrofibrosis (n = 1), and surgical technical error (n = 1). One patient was lost to follow-up after the 12-year evaluation. Each remaining patient reported a stable fully athletic knee. Physical exams are consistent with a score of less than one on the ACL stability tests. MRIs demonstrate mature remodeling of the device. There is no significant degradation in patient-reported outcome scores, physical exams, or MRI appearance from 12 to 20-year follow-ups. CONCLUSIONS: The studies in a small group of patients have demonstrated that implantation of porcine ligament bioprosthesis into patients with torn ACLs can result in the reconstruction of the bioprosthesis into autologous ACL that remains successful over 20 years. The possibility of humanizing porcine tissue opens the door to unlimited clinical material for tissue reconstructions if supported by additional clinical trials. LEVEL OF EVIDENCE: IV, case series.

Variations of magnetic resonance imaging findings in asymptomatic elbows.

BACKGROUND: Magnetic resonance imaging (MRI) findings in asymptomatic patients have been described for hips, knees, ankles, shoulders, and intervertebral disks. No such description exists for the elbow. METHODS: MRI scans of 189 asymptomatic elbows divided into 3 groups by age (group 1, 20-39 years; group 2, 40-59 years; and group 3, ≥60 years) were evaluated for abnormalities within 13 anatomic structures using a novel classification system. RESULTS: At least 1 variation was found in all elbows. Of the 13 structures, 8 showed an increase in the prevalence and intensity of signal changes with aging, 2 remained the same, and 2 showed a decrease. One anatomic structure showed no variations in any elbow. CONCLUSIONS: Elbow MRI variations may be seen regardless of symptoms. These changes appear to increase in prevalence and intensity with age. Results from this study can be used to help guide the clinician in interpreting MRI findings of the elbow. We hope this study helps provide a contextual background for discussing MRI findings with patients and differentiating age-related variations from true pathology.

Magnetic Resonance Imaging for Patellofemoral Chondromalacia: Is There a Role for T2 Mapping?

BACKGROUND: Patellofemoral pain is common, and treatment is guided by the presence and grade of chondromalacia. PURPOSE: To evaluate and compare the sensitivity and specificity in detecting and grading chondral abnormalities of the patella between proton density fat suppression (PDFS) and T2 mapping magnetic resonance imaging (MRI). STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 25 patients who underwent MRI of the knee with both a PDFS sequence and T2 mapping and subsequently underwent arthroscopic knee surgery were included. The cartilage surface of the patella was graded on both MRI sequences by 2 independent, blinded radiologists. Cartilage was then graded during arthroscopic surgery by a sports medicine fellowship-trained orthopaedic surgeon. Reliability, sensitivity, specificity, and accuracy were determined for both MRI methods. The findings during arthroscopic surgery were considered the gold standard. RESULTS: Intraobserver and interobserver agreement for both PDFS (98.5% and 89.4%, respectively) and T2 mapping (99.4% and 91.3%, respectively) MRI were excellent. For T2 mapping, the sensitivity (61%) and specificity (64%) were comparable, whereas for PDFS there was a lower sensitivity (37%) but higher specificity (81%) in identifying cartilage abnormalities. This resulted in a similar accuracy for PDFS (59%) and T2 mapping (62%). CONCLUSION: Both PDFS and T2 mapping MRI were reliable but only moderately accurate in predicting patellar chondromalacia found during knee arthroscopic surgery.

Identifying Hidden Zones of the Far Posterior Cartilage of the Femoral Condyles Not Visible During Knee Arthroscopy.

OBJECTIVE: The purpose of this study was to compare standard knee arthroscopic and MRI findings and measurements for visualization of the femoral condyle articular cartilage. The hypothesis was that certain posterior cartilage defects identified with MRI may not be accessible with routine arthroscopy. MATERIALS AND METHODS: Six cadaveric knees were examined by routine arthroscopy through standard inferomedial and inferolateral portals. Suture anchors were inserted into the femoral condyles at 30°, 60°, 90°, and 120° of flexion as markers of the cartilage surface at the most posterior aspect of the condyle that could be accessed at each degree of flexion. Each specimen was then examined with 3-T MRI and gross dissection. Measurements were obtained and compared. RESULTS: During arthroscopy at 90° of knee flexion, only 5.83 mm of the medial femoral condyle and 6.83 mm of the lateral femoral condyle were visualized posterior to the anchor placed at 90° of flexion. These arthroscopic measurements were statistically significant underestimates of the actual amount of cartilage identified posterior to the 90° anchor at gross dissection (medial condyle, 44.20 mm; lateral condyle, 37.50 mm) and MRI (medial, 41.33 mm; lateral, 38.87 mm). This indicates that 85.9% of the medial and 81.8% of the lateral posterior articular cartilage of the femoral condyle seen at MRI were not visualized during arthroscopy. CONCLUSION: More than 80% of the articular cartilage proximal to the menisci seen at MRI is not visible during routine arthroscopy. This far posterior articular cartilage should be called the hidden zone.

Osteochondral grafting for failed knee osteochondritis dissecans repairs.

BACKGROUND: Revision of failed surgical treatments of osteochondritis dissecans (OCD) lesions remains a challenge without an obvious solution. The aim of this study was to evaluate seven consecutive patients undergoing osteochondral grafting of a failed OCD repair. METHODS: The mean time from surgery to the latest evaluation was 7.0 years. IKDC, WOMAC, Tegner, and MRI studies were collected both preoperatively and during follow-up. Evaluation of the graft was assessed using the magnetic resonance observation of cartilage repair tissue (MOCART) grading system. RESULTS: Over the course of the study period, five patients required additional surgery with a study median of one additional surgery (range, zero to 3). At most recent follow-up, there was significant improvement from preoperative values in median IKDC (p=0.004), WOMAC (p=0.030), and Tegner (p=0.012). Complete cartilage fill and adjacent tissue integration of the paste graft were observed by MRI evaluation in five of the seven (71.4%) patients. Definitive correlation between clinical outcomes and MRI scores was not observed. CONCLUSIONS: This study shows promising results of osteochondral grafting as a viable option for the revision of failed OCD lesion repairs; however, more patients are needed to fully support its efficacy in these challenging failed revision cases.

Clinical and magnetic resonance imaging findings associated with Little League elbow.

BACKGROUND: Valgus overload in the skeletally immature elbow can lead to medial epicondyle apophysitis, or Little League elbow. The skeletal manifestations have been well described through radiographic studies. The involvement of surrounding structures, including the ulnar collateral ligament, remains unclear. The purpose of this study is to better characterize the involvement and relationship of medial elbow structures in Little League elbow through magnetic resonance (MR) imaging. METHODS: Institutional review board approval was obtained. Nine Little Leaguers, 8 to 13 years, with clinical diagnosis of Little League elbow were enrolled. Play history questionnaire (including age, position, pitching history, duration of symptoms, and Kerlan Jobe Orthopedic Clinic shoulder elbow score), clinical examination, radiograph, and MRI of both elbows were obtained for analysis. Evaluation of radiographs and MRIs were performed by 2 radiologists blinded to clinical findings. RESULTS: A majority of the players reported compliance with pitch count recommendations. Four out of 9 players, however, were throwing breaking pitches at an average age of 11 years. Radiographic abnormalities were present in 4 players. MRI abnormalities were present in 6 players. All patients demonstrated normal ulnar collateral ligament (UCL) on MRI. The distance from UCL origin to the medial epicondyle physis were measured in both injured and healthy elbows. No significant differences were found. This distance ranged from 0 to 4 mm. CONCLUSIONS: MRI of Little League elbow demonstrated more abnormalities compared with radiographs. The increased number of findings, however, does not change clinical management. MR evaluation of the ulnar collateral ligament demonstrates no role for reconstruction in Little League elbow. In addition, given the close proximity of the ligament to the physis, any surgical procedure involving the UCL origin should be performed with caution. LEVEL III: Diagnostic study.

A quantitative approach to sequence and image weighting.

Weighting is the term most frequently used to describe magnetic resonance pulse sequences and the concept most commonly used to relate image contrast to differences in magnetic resonance tissue properties. It is generally used in a qualitative sense with the single tissue property thought to be most responsible for the contrast used to describe the weighting of the image as a whole. This article describes a quantitative approach for understanding the weighting of sequences and images, using filters and partial derivatives of signal with respect to logarithms of tissue property values. Univariate and multivariate models are described for several pulse sequences including methods for maximizing weighting and calculating both sequence and image weighting ratios. The approach provides insights into difficulties associated with qualitative use of the concept of weighting and a quantitative basis for assessing the signal, contrast, and weighting of commonly used sequences and images.

Bone marrow edema is the most specific finding for rheumatoid arthritis (RA) on noncontrast magnetic resonance imaging of the hands and wrists: a comparison of patients with RA and healthy controls.

OBJECTIVE: To evaluate the sensitivity and specificity of magnetic resonance imaging (MRI) in detecting erosions, bone edema, and synovitis in the metacarpophalangeal and wrist joints for rheumatoid arthritis (RA). METHODS: MRI scans of bilateral hands and wrists of 40 healthy subjects and 40 RA patients were performed using 0.2 T extremity-MRI and read blindly using a modified RA MRI (RAMRIS) system (no contrast injection, imaging in 1 plane only). To determine interreader reliability, images of 10 randomly selected subjects were read independently by a musculoskeletal radiologist. RESULTS: A total of 3360 bones were evaluated. Patients with RA had significantly more erosions as well as higher scores for bone edema and synovitis than healthy subjects. Age had a significant effect on the number of erosions in both groups. However, when disease duration was factored in, age became insignificant in RA patients. Erosion number correlated with positive rheumatoid factor and higher C-reactive protein values. The intraclass correlation coefficient between the 2 readers was 0.76 for individual joints and 0.88 for total scores. When having a single erosion was used as a positive test for RA, the sensitivity of this test was 90%, but the specificity was only 35%. Presence of bone edema provided 65% sensitivity and 82.5% specificity. Eliminating the lunate from scoring for bone edema increased the specificity to 87.5% while decreasing the sensitivity to 62.5%. CONCLUSION: While MRI is a highly sensitive tool for identifying and tracking the progression of erosions, erosions detected by MRI with measures commonly used in a rheumatologist's office (no contrast, imaging in 1 plane) provide low specificity for RA. Bone marrow edema is the most specific MRI lesion for RA in this setting.

Complexities of MRI and false positive findings.

MRI is a robust technology that allows for superior contrast of muscles, tissues, and bones within the body, which enables visualization of soft tissue pathology that cannot be seen with CT or plain film radiography. In order to appreciate the subtle (and sometimes not so subtle) intricacies of MRI, one must have a basic knowledge of the MRI physics involved to acquire an image, which leads to better recognition and a clearer understanding of some of the more important artifacts seen with MRI, including incomplete fat suppression, chemical shift, magnetic susceptibility, magic angle, partial volume, wraparound, and motion artifact. There are, however, many complexities and pitfalls in imaging the rheumatoid wrist. Normal anatomy such as capsular insertion sites and nutrient vessels can mimic erosion sites. The magic angle phenomenon can mimic tendon tears. Alignment abnormalities can be simulated based on wrist positioning. By having a solid understanding of the physics of magnetic resonance, anatomy, and the disease processes involved, many of these pitfalls can be avoided.

Technical considerations and potential advantages of musculoskeletal imaging at 3.0 Tesla.

High field magnetic resonance imaging at 3.0 T is rapidly gaining clinical acceptance as the preferred platform for magnetic resonance (MR) imaging. This is spurred in part because advances in the manufacture of magnet technology have brought the cost of 3.0-T magnets into the range of previous 1.5-T machines, as well as ongoing research demonstrating numerous advantages of 3.0 T over 1.5 T in neurological imaging. Many factors are responsible for improved imaging at higher field strength, including increased signal-to-noise and contrast-to-noise ratios. The impact of 3.0-T imaging of the musculoskeletal system has been less dramatic because its optimization is more complicated in the musculoskeletal system than in the brain. Many issues must be considered beyond what might be expected from simply doubling the field strength, including hardware design, protocol modifications because of changes in tissue characteristics at higher fields, artifact reduction, and safety. This article addresses many of these concerns, focusing on techniques to optimize high field MR imaging of the musculoskeletal system.

Repair site integrity after arthroscopic transosseous-equivalent suture-bridge rotator cuff repair.

BACKGROUND: Successful healing after arthroscopic rotator cuff repair remains a challenge. Earlier studies have shown a relatively high rate of failure. New surgical techniques may improve healing potential. The purpose of this study was to provide an objective evaluation of repair site integrity after arthroscopic transosseous-equivalent suture-bridge rotator cuff repair. HYPOTHESIS: Rotator cuff tears repaired using the transosseous-equivalent suture-bridge technique will show a higher intact rate on postoperative magnetic resonance imaging (MRI) evaluation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: The first 25 patients who underwent arthroscopic rotator cuff repair using the transosseous-equivalent suture-bridge technique underwent MRI evaluation of the postoperative shoulder. Minimum follow-up was 1 year. Demographic, clinical, and surgical factors, including tear size, were evaluated. RESULTS: Postoperative MRI demonstrated intact surgical repair sites in 22 of 25 patients (88%). Tears limited to the supraspinatus tendon were intact in 16 of 18 patients (89%). Tears of the supraspinatus involving part or all of the infraspinatus showed an 86% intact rate (6 of 7 patients). Of these tears, 3 were considered massive (complete 2-tendon or greater). These demonstrated an intact cuff on MRI. CONCLUSIONS: The transosseous-equivalent suture-bridge technique demonstrates a high healing rate on imaging studies at 1 year. Of the first 25 patients repaired with the technique, 88% had an intact rotator cuff repair on MRI evaluation. This indicates excellent cuff healing, as judged by the intact repair sites, compared with most standard arthroscopic rotator cuff repair series. In this early report of the technique, a persistent tear could not be correlated with age or initial tear size; however, this may be due to the relatively small sample size.

Ironman triathletes: MRI assessment of the shoulder.

OBJECTIVE: The objective of this paper was to demonstrate the prevalence of shoulder magnetic resonance imaging (MRI) abnormalities, including abnormal bone marrow signal at the acromioclavicular (AC) joint in symptomatic and asymptomatic Ironman Triathletes. MATERIALS AND METHODS: The shoulders of 23 Ironman Triathletes, seven asymptomatic (group I) and 16 symptomatic (group II), were studied by MRI. A separate, non-triathlete group was evaluated specifically for AC joint marrow signal abnormalities to compare with the Ironman Triathletes. RESULTS: Partial thickness tears of the rotator cuff, rotator cuff tendinopathy, and AC joint arthrosis were common findings in both groups of triathletes. Tendinopathy was the only finding that was more prevalent in the symptomatic group, but this was not a statistically significant difference (p = 0.35). There were no tears of the glenoid labrum seen in group I or II subjects. Of note is that 71% (5/7) of group I subjects and 62% (10/16) of group II subjects had increased signal changes in the marrow of the AC joint (p = 0.68). The comparison group showed a lower prevalence (35%, p = 0.06) of this finding. CONCLUSIONS: No statistically significant difference was found among the findings for group 1, group 2, or the comparison group, although the difference between the comparison group and Ironman Triathletes approached statistical significance when evaluating for AC joint abnormal signal. Shoulder MRI of Ironman Triathletes should be interpreted with an appreciation of the commonly seen findings in asymptomatic subjects.

Meniscal sizing based on gender, height, and weight.

PURPOSE: Successful meniscus transplantation may depend on accurate sizing. Meniscal sizing is currently determined by measuring a combination of bony landmarks and soft-tissue insertion points through images obtained radiographically or by magnetic resonance imaging (MRI). The literature widely reports inaccuracy in sizing resulting from radiographic errors in magnification, erroneous identification of bony landmarks, and difficulty in differentiating between the soft-tissue and bone interface. In our meniscus transplantations we have observed that when the height and weight of the recipient matched those of the donor, the meniscal size appeared to be a match at surgical implantation; we designed this study to confirm this observation. METHODS: The MRI-based meniscal sizing of 111 patients (63 male and 38 female patients; mean age, 44 years [range, 15 to 76 years]), totaling 147 menisci (87 lateral and 60 medial), was compared with the height, weight, gender, and body mass index (BMI) of each patient. MRI scans were obtained with a 1.0-Tesla MRI system (ONI Medical Systems, Wilmington, MA). Sizing was performed by an independent musculoskeletal MRI radiologist as established by the literature. Statistical methods include nonparametric Pearson correlation (r) between MRI-based lateral meniscal width, lateral meniscal length, medial meniscal width, medial meniscal length, total tibial plateau width, and patient height, weight, gender, and BMI. Significance at the P = .05 level was used. RESULTS: Height was found to have a linear relationship to total tibial plateau, which has a good predictive correlation with meniscal dimensions of r > 0.7. Female patients generally present with smaller dimensions than male patients. High-BMI groups present with significantly larger meniscal dimensions than low-BMI groups at any given height. CONCLUSIONS: Height, weight, and gender are easily obtained variables and are proportional to meniscal tissue dimensions. These exploratory statistics establish correlations between height, weight, gender, total tibial plateau width, and meniscal size. CLINICAL RELEVANCE: Height, weight, and gender should be considered by both tissue banks and surgeons as fast and cost-effective variables by which to predict meniscal dimensions.

Open-label, pilot protocol of patients with rheumatoid arthritis who switch to infliximab after an incomplete response to etanercept: the opposite study.

OBJECTIVE: To incorporate a new trial design to examine clinical response, cytokine expression and joint imaging in patients with rheumatoid arthritis (RA) switching from etanercept to infliximab treatment. METHODS: A randomised, open-label, clinical trial of 28 patients with an inadequate response to etanercept was conducted. Eligible patients received background methotrexate and were randomised 1:1 to discontinue etanercept and receive infliximab 3 mg/kg at weeks 0, 2, 6, 14 and 22, or to continue etanercept 25 mg twice weekly. Data were analysed for clinical response, serum biomarker levels, radiographic progression, MRI and adverse events. RESULTS: At week 16, 62% of infliximab-treated patients achieved American College of Rheumatology 20% criteria for improvement in RA (ACR20) responses compared with 29% of etanercept-treated patients. A 30.8% decrease from baseline in Disease Activity Score 28 was observed in patients receiving infliximab, compared with a 16.0% decrease in patients receiving etanercept. ACR20 and American College of Rheumatology 50% criteria for improvement in RA responses correlated at least minimally with intracellular adhesion molecule-1 and interleukin 8 in patients receiving infliximab. 38% of patients who were switched to infliximab showed reductions in Health Assessment Questionnaire scores (>0.4), compared with 0% of patients receiving etanercept. MRI analyses were inconclusive. Both drugs were well tolerated; 54% of infliximab-treated patients and 50% of etanercept-treated patients reported adverse events. CONCLUSIONS: In this exploratory, open-label trial (with single-blind evaluator), patients were randomised to continue with etanercept or switch to infliximab. The small sample size of this hypothesis-generating study was underpowered to show statistical differences between groups. There was a numerical trend favouring patients who switched to infliximab, therefore warranting further study with a more rigorous design.

Low-field musculoskeletal MRI.

Since it was first introduced in the field of medical imaging in the early 1980s, MRI has become essential for the diagnosis and treatment of musculoskeletal conditions. Most imaging in the United States is performed on high-field (>1.0T), whole-body scanners. However, for reasons discussed below, imaging at low (<0.5T) and medium (0.5-1.0T) field strengths using small, low-cost, easily installed scanners in imaging centers and physicians' offices is gaining increasing popularity. Such scanners can be very useful for imaging the upper and lower extremities, from the shoulder to the fingers and the hips to the toes. In this review we provide an overview of the different available extremity scanners and their advantages and disadvantages, briefly review the literature regarding their use, and discuss our experience in using low-field extremity scanners to evaluate joints.