Beneficial Effect of Calcium Treatment for Hyperkalemia Is Not Due to "Membrane Stabilization".

OBJECTIVES: Hyperkalemia is a common life-threatening condition causing severe electrophysiologic derangements and arrhythmias. The beneficial effects of calcium (Ca 2+ ) treatment for hyperkalemia have been attributed to "membrane stabilization," by restoration of resting membrane potential (RMP). However, the underlying mechanisms remain poorly understood. Our objective was to investigate the mechanisms underlying adverse electrophysiologic effects of hyperkalemia and the therapeutic effects of Ca 2+ treatment. DESIGN: Controlled experimental trial. SETTING: Laboratory investigation. SUBJECTS: Canine myocytes and tissue preparations. INTERVENTIONS AND MEASUREMENTS: Optical action potentials and volume averaged electrocardiograms were recorded from the transmural wall of ventricular wedge preparations ( n = 7) at baseline (4 mM potassium), hyperkalemia (8-12 mM), and hyperkalemia + Ca 2+ (3.6 mM). Isolated myocytes were studied during hyperkalemia (8 mM) and after Ca 2+ treatment (6 mM) to determine cellular RMP. MAIN RESULTS: Hyperkalemia markedly slowed conduction velocity (CV, by 67% ± 7%; p < 0.001) and homogeneously shortened action potential duration (APD, by 20% ± 10%; p < 0.002). In all preparations, this resulted in QRS widening and the "sine wave" pattern observed in severe hyperkalemia. Ca 2+ treatment restored CV (increase by 44% ± 18%; p < 0.02), resulting in narrowing of the QRS and normalization of the electrocardiogram, but did not restore APD. RMP was significantly elevated by hyperkalemia; however, it was not restored with Ca 2+ treatment suggesting a mechanism unrelated to "membrane stabilization." In addition, the effect of Ca 2+ was attenuated during L-type Ca 2+ channel blockade, suggesting a mechanism related to Ca 2+ -dependent (rather than normally sodium-dependent) conduction. CONCLUSIONS: These data suggest that Ca 2+ treatment for hyperkalemia restores conduction through Ca 2+ -dependent propagation, rather than restoration of membrane potential or "membrane stabilization." Our findings provide a mechanistic rationale for Ca 2+ treatment when hyperkalemia produces abnormalities of conduction (i.e., QRS prolongation).

Beneficial Effect of Calcium Treatment for Hyperkalemia Is Not Due to "Membrane Stabilization".

OBJECTIVES: Hyperkalemia is a common life-threatening condition causing severe electrophysiologic derangements and arrhythmias. The beneficial effects of calcium (Ca 2+ ) treatment for hyperkalemia have been attributed to "membrane stabilization," by restoration of resting membrane potential (RMP). However, the underlying mechanisms remain poorly understood. Our objective was to investigate the mechanisms underlying adverse electrophysiologic effects of hyperkalemia and the therapeutic effects of Ca 2+ treatment. DESIGN: Controlled experimental trial. SETTING: Laboratory investigation. SUBJECTS: Canine myocytes and tissue preparations. INTERVENTIONS AND MEASUREMENTS: Optical action potentials and volume averaged electrocardiograms were recorded from the transmural wall of ventricular wedge preparations ( n = 7) at baseline (4 mM potassium), hyperkalemia (8-12 mM), and hyperkalemia + Ca 2+ (3.6 mM). Isolated myocytes were studied during hyperkalemia (8 mM) and after Ca 2+ treatment (6 mM) to determine cellular RMP. MAIN RESULTS: Hyperkalemia markedly slowed conduction velocity (CV, by 67% ± 7%; p < 0.001) and homogeneously shortened action potential duration (APD, by 20% ± 10%; p < 0.002). In all preparations, this resulted in QRS widening and the "sine wave" pattern observed in severe hyperkalemia. Ca 2+ treatment restored CV (increase by 44% ± 18%; p < 0.02), resulting in narrowing of the QRS and normalization of the electrocardiogram, but did not restore APD. RMP was significantly elevated by hyperkalemia; however, it was not restored with Ca 2+ treatment suggesting a mechanism unrelated to "membrane stabilization." In addition, the effect of Ca 2+ was attenuated during L-type Ca 2+ channel blockade, suggesting a mechanism related to Ca 2+ -dependent (rather than normally sodium-dependent) conduction. CONCLUSIONS: These data suggest that Ca 2+ treatment for hyperkalemia restores conduction through Ca 2+ -dependent propagation, rather than restoration of membrane potential or "membrane stabilization." Our findings provide a mechanistic rationale for Ca 2+ treatment when hyperkalemia produces abnormalities of conduction (i.e., QRS prolongation).

Clinical Outcomes of Hip Arthroscopy in Patients With Systemic Inflammatory Diseases Compared With Matched Controls at a Minimum of 2-Year Follow-Up.

PURPOSE: To evaluate postoperative outcomes and preoperative risk factors for patients with underlying systemic inflammatory disorders after hip arthroscopy. METHODS: A retrospective analysis of patients who had undergone hip arthroscopy, with a history of systemic inflammatory disease, was performed. This included patients with a diagnosis of lupus, a positive antinuclear antibody test, rheumatoid arthritis, psoriatic arthritis, sarcoidosis, inflammatory bowel disease, Reiter syndrome, and mixed connective tissue disease. These cases were 1:2 matched to a control group of patients with no history of systemic inflammatory disease based on age and sex. An a priori power analysis was conducted and A 1:2 case-control ratio was selected to increase study power. Inclusion criteria included all skeletally mature patients with hip pain refractory to nonoperative management who underwent hip arthroscopy for labral tears and femoroacetabular impingement. Skeletally immature patients, those with Tönnis grades of 2 or more (less than 2 mm of joint space), hip dysplasia, patients undergoing revision hip arthroscopy, and patients whose pain failed to improve after intra-articular injection were excluded. The primary outcome was rate of revision hip arthroscopy or total hip arthroplasty 24 months after surgery. Secondary outcomes included 2 patient-reported outcome scores, the modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS). RESULTS: Twenty patients (21 hip arthroscopy procedures) and 42 controls were included. There was no significant difference in proportion of patients who met failure criteria (28.6% vs 16.7%, P = .271) or 2-year survivorship (76.2% vs 83.3%, P = .496) between the systemic inflammatory disorder and control groups, respectively. Both groups had a significant improvement in mHHS and NAHS at 24 months compared with baseline; however, there was no significant difference in mHHS (P = .28) or NAHS (P = .22) at 24 months between the 2 groups. CONCLUSIONS: Patients with underlying inflammatory conditions have similar 2-year outcomes after hip arthroscopy for intra-articular pathology compared with patients with no history of inflammatory disease. LEVEL OF EVIDENCE: III, retrospective comparative study.

Skilled Nursing Facility Partnerships May Decrease 90-Day Costs in a Total Joint Arthroplasty Episode Under the Bundled Payments for Care Improvement Initiative.

BACKGROUND: The Bundled Payments for Care Improvement initiative was developed to reduce costs associated with total joint arthroplasty through a single payment for all patient care from index admission through a 90-day post-discharge period, including care at skilled nursing facilities (SNFs). The aim of this study is to investigate whether forming partnerships between hospitals and SNFs could lower the post-discharge costs. We hypothesize that institutionally aligned SNFs have lower post-discharge costs than non-aligned SNFs. METHODS: A cohort of 615 elective, primary total hip and knee arthroplasty subjects discharged to an SNF under the Bundled Payments for Care Improvement from 2014 to 2016 were included in our analysis. Patients were grouped into one of the 3 categories of SNF alignment: group 1: non-partners; group 2: agreement-based partners; group 3: institution-owned partners. Demographics, comorbidities, length of stay (LOS) at SNF, and associated costs during the 90-day post-operative period were compared between the 3 groups. RESULTS: Mean index hospital LOS was statistically shortest in group 3 (mean 2.7 days vs 3.5 for groups 1 and 2, P = .001). SNF LOS was also shortest in group 3 (mean 11 days vs 19 and 21 days in groups 2 and 1 respectively, P < .001). Total SNF costs and total 90-day costs were both significantly lower in group 3 compared with groups 1 and 2 (P < .001 for all), even after controlling for medical comorbidities. CONCLUSION: Institution-owned partner SNFs demonstrated the shortest patient LOS, and the lowest SNF and total 90-day costs, without increased risk of readmissions, compared with other SNFs.

Accuracy of palpation-directed intra-articular glenohumeral injection confirmed by magnetic resonance arthrography.

PURPOSE: The aim of this study was to determine the accuracy of anatomic palpation-directed injections in the office setting. METHODS: Two hundred twenty-six shoulders in 208 patients were studied using a 0.2-Tesla extremity scanner after the injection of gadolinium-diethylene triamine pentaacetic acid-saline. All patients were injected in a sterile fashion by a single board-certified shoulder surgeon using an anterior approach by palpating the rotator interval anterior to the acromioclavicular joint and angling the needle 45° lateral and 45° caudad. All injections, successful or otherwise, were single injections. Magnetic resonance (MR) arthrograms were retrospectively read by 2 musculoskeletal fellowship-trained, board certified radiologists to determine whether the injection was in the glenohumeral joint. RESULTS: Two hundred one of the 226 injections were successful (88.9%). Of the 25 unsuccessful injections, the contrast material extravasated out of the capsule in 5 cases and into the subscapularis tendon in 10 cases. The contrast material was injected into the subacromial space in 9 cases, into the rotator interval fat in 9 cases, and into extracapsular tissue in 6 cases. There was insufficient volume of contrast material in 10 cases. The accuracy rate was 88.9%. There were no complications. CONCLUSIONS: The palpation-directed rotator interval anterior approach technique for intra-articular glenohumeral MR arthrogram injections performed by a single surgeon was 88.9% accurate. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Intersurgeon Consistency of Ulnar Collateral Ligament Repair With Internal Brace: A Biomechanical Analysis.

Background: Injury to the ulnar collateral ligament (UCL) of the medial elbow has been treated successfully with ligament repair augmented with internal brace. Previous work has shown that this procedure does not overconstrain the ulnohumeral joint; however, the procedures were conducted by a single surgeon, which controlled for anchor placement and graft tensioning. Purpose/Hypothesis: Our purpose was to evaluate the reproducibility of contact mechanics and joint torque after UCL repair with internal brace as performed by different surgeons compared with repair by a single surgeon. It was hypothesized that there would be no significant difference in elbow contact mechanics, valgus torque, or torsional stiffness between the 2 groups. Study Design: Controlled laboratory study. Methods: Nine pairs of fresh-frozen cadaveric elbows were tested biomechanically under 3 conditions: UCL-intact (UCL-I), UCL-deficient (UCL-D), and UCL-repaired with internal brace augmentation (UCLR-IB). For each pair, 1 elbow was repaired by a single surgeon, and the contralateral elbow was repaired by 1 of 9 other surgeons. Testing consisted of valgus torsion between 0° and 5° with the elbow positioned at 90° of flexion. Ulnohumeral contact mechanics and overall joint torque and stiffness were measured and compared between surgeon groups. Results: There were no statistically significant differences between the single-surgeon and multiple-surgeon groups regarding contact area (P = .83), contact force (P = .27), peak pressure (P = .26), or peak force (P = .30); however, contact pressure was significantly affected (P = .02) by surgeon group. Compared with UCL-I, both UCL-D and UCLR-IB conditions had a significant overall effect on contact area (P = .004) and contact force (P = .05); however, contact pressure (P = .56), peak pressure (P = .27), and peak force (P = .24) were not affected by injury condition. Measurements of elbow torque (P = .28) and stiffness (P = .98) were not significantly different between surgeon groups. Conclusion: UCL repair with internal brace provided consistent results among several surgeons when compared with a single surgeon. The procedure did not lead to joint overconstraint while also returning the ligament to near-intact levels of resisting valgus stress. Clinical Relevance: UCL repair with internal brace augmentation is a reproducible surgical technique that has good clinical outcomes in the literature.

Performance and return to sport after injury in professional mixed martial arts.

BACKGROUND: Mixed Martial Arts (MMA) is an increasingly popular combat sport incorporating striking and grappling that results in a high incidence of injuries. OBJECTIVES: The purpose of this study was to analyze the impact of injuries on the return to sport and post-injury performance of professional MMA athletes. We hypothesize that increased age is associated with lower probability of return to sport and diminished post-injury performance. METHODS: Publicly available data (obtained from ESPN.com/MMA, UFC.com, Rotowire.com/MMA) from professional MMA fighters who resigned from fight cards due to injury from 2012 to 2014 were analyzed. Injury history, match history and outcomes, and duration of time to return to professional fighting were recorded and compared to a cohort consisting of uninjured opponents. RESULTS: 454 fighters were included in the analysis. The mean age at the time of injury was 30.0±3.9 years. 94.4% of injured athletes were able to return to professional MMA, and athletes required a mean duration of 6.8±6.7 months between injury and their next professional fight (range 0.3-58 months). There was no significant difference in winning percentage in the post-injury period between the injured group and the uninjured group (p = 0.691). Increased age at the time of injury was associated with the odds of being able to return to professional fighting after injury (OR = 0.822, p = 0.001). CONCLUSION: In this analysis of publicly available injury data on MMA fighters, there was a high rate of return to professional sport and no evidence of an associated decline in performance following major injury requiring withdrawal from a fight card. Older age at the time of injury was associated with decreased odds of being able to return to professional fighting. With increasing popularity of combat sports, sport-specific prognostic information will help guide and treat specific injuries associated with MMA participation.

Complication of the use of a radiofrequency device in arthroscopic shoulder surgery: second-degree burn of the shoulder girdle.

Radiofrequency ablation (RF) energy devices are increasingly being used in arthroscopic surgery. This is a case report of a 53-year-old man who had second-degree burns of the shoulder and chest wall as a result of fluid overheating due to RF. During an extensive arthroscopic bursal dissection of the left shoulder, the suction device on the RF wand and the valve was left open, allowing fluid to drip onto the chest and arm of the patient. Three days after his surgery, on his first postoperative visit, the dressings were removed, and the patient was noted to have severe blistering on the lateral aspect of his arm and on the anterolateral aspect of his left chest wall. One year after the surgery, he still had residual scarring that was only mildly intermittently pruritic. The use of RF during arthroscopic surgery is very useful clinically; however, it is important to have a strict understanding of the potential hazards the thermal energy can cause to the surrounding soft tissue.

The Evolution of Arthroscopy A Historical Perspective.

The Hospital for Joint Disease was constructed in 1924, ushering in a new generation of orthopedic leaders in research and clinical care. One such surgeon, Michael S. Burman, helped pioneer the early advancement and development of arthroscopy in North America. Arthroscopic surgery, now a vital component of orthopedic surgery, has many connections to the Hospital for Joint Diseases (now the NYU Langone Orthopedic Hospital). This manuscript will review the history of arthroscopy from its roots in endoscopy, through its development in Europe, and early growth in Japan and North America. The first published reports of endoscopy from Europe inspired Dr. Burman to travel to Germany to learn more. After, he brought his newly acquired knowledge back to the Hospital for Joint Diseases, where he carried out some of the seminal experiments on arthroscopy. Dr. Masaki Watanabe, now known as the father of arthroscopy, ultimately transitioned the early experiments into a viable surgical technique. The first generation of surgeons from Canada and the US visited Dr. Watanabe in Japan, brought these techniques back to North America in the late 1960s and early 1970s, and helped to teach and revolutionize this new type of surgery. Arthroscopy has further evolved over the next 50 years, but to continually improve we must look back and acknowledge those who helped create what we have today.

Effect of Amiodarone and Hypothermia on Arrhythmia Substrates During Resuscitation.

Background Amiodarone is administered during resuscitation, but its antiarrhythmic effects during targeted temperature management are unknown. The purpose of this study was to determine the effect of both therapeutic hypothermia and amiodarone on arrhythmia substrates during resuscitation from cardiac arrest. Methods and Results We utilized 2 complementary models: (1) In vitro no-flow global ischemia canine left ventricular transmural wedge preparation. Wedges at different temperatures (36°C or 32°C) were given 5 µmol/L amiodarone (36-Amio or 32-Amio, each n=8) and subsequently underwent ischemia and reperfusion. Results were compared with previous controls. Optical mapping was used to measure action potential duration, dispersion of repolarization (DOR), and conduction velocity (CV). (2) In vivo pig model of resuscitation. Pigs (control or targeted temperature management, 32-34°C) underwent ischemic cardiac arrest and were administered amiodarone (or not) after 8 minutes of ventricular fibrillation. In vitro: therapeutic hypothermia but not amiodarone prolonged action potential duration. During ischemia, DOR increased in the 32-Amio group versus 32-Alone (84±7 ms versus 40±7 ms, P<0.05) while CV slowed in the 32-Amio group. Amiodarone did not affect CV, DOR, or action potential duration during ischemia at 36°C. Conduction block was only observed at 36°C (5/8 36-Amio versus 6/7 36-Alone, 0/8 32-Amio, versus 0/7 32-Alone). In vivo: QTc decreased upon reperfusion from ischemia that was ameliorated by targeted temperature management. Amiodarone did not worsen DOR or CV. Amiodarone suppressed rearrest caused by ventricular fibrillation (7/8 without amiodarone, 2/7 with amiodarone, P=0.041), but not pulseless electrical activity (2/8 without amiodarone, 5/7 with amiodarone, P=0.13). Conclusions Although amiodarone abolishes a beneficial effect of therapeutic hypothermia on ischemia-induced DOR and CV, it did not worsen susceptibility to ventricular tachycardia/ventricular fibrillation during resuscitation.

Excision of Prominent Bony Mass due to Skeletal Fluorosis: A Case Report.

CASE: A 72-year-old man presented for evaluation of bony prominences over extremities. Radiographic imaging demonstrated masses of varying sizes extending from the cortical surfaces without medullary continuity. The patient had a history of Freon inhalation abuse and was diagnosed with skeletal fluorosis due to elevated serum fluoride levels. He underwent an uncomplicated excision of a left fibular mass that was threatening skin breakdown. CONCLUSIONS: This is the first reported surgical case of skeletal fluorosis demonstrating continued enlargement of bony prominences throughout the body. Skeletal fluorosis not only causes diffuse mineralization but may also lead to protruding lesions throughout the body.

Total Hip Arthroplasty for Femoral Neck Fracture in the Setting of Challenging Extraction of an Intramedullary Femoral Nail: A Case Report.

INTRODUCTION: Performing total hip arthroplasty (THA) for femoral neck fracture in the setting of a pre-existing intramedullary nail can be technically challenging, particularly if nail extraction is not feasible. CASE REPORT: A 76-year-old male presented with a with a displaced femoral neck fracture in the setting of a previously placed antegrade intramedullary nail with a healed femoral shaft fracture. After failed nail extraction, a novel technique was used to remove the proximal portion of the nail to allow for hybrid THA with implantation of a cemented femoral stem. CONCLUSION: This is the first reported surgical technique of using a cortical window technique for partial intramedullary nail resection and cemented stem implantation in the setting of challenging intramedullary femoral nail extraction.

Effect of Shoulder Stabilization on Career Length and Performance in National Basketball Association Athletes.

PURPOSE: Untreated episodes of shoulder instability can have major consequences on athletic careers. Operative shoulder stabilization reduces the rate of recurrent instability and allows for high rates of return to sport (RTS). Basketball players who experience an episode of instability have high rates of recurrence, though little is known about postoperative player performance. The purpose of this study was to identify the impact of shoulder instability and surgical stabilization on player performance and career lengths in the National Basketball Association (NBA). METHODS: NBA players who had episodes of shoulder instability between 1994-2014 were identified using the NBA Injury Surveillance and Analytics Database. Players were stratified according to operative versus nonoperative treatment of shoulder instability. Two demographic- and performance-matched controls were chosen for each test subject. Univariate analyses were used to compare pre- and postoperative player performance metrics. Survival analysis was used to assess the effect of shoulder surgery on postoperative career lengths. RESULTS: Fifty athletes were identified, 46 (92.0%) returned to play in the NBA. Compared to controls, there was no significant difference in postoperative performance according to either 1- or 3-year averages. Survival analysis demonstrated no significant difference in postoperative career lengths between athletes with a history of shoulder surgery for instability and matched controls. CONCLUSION: NBA players return to professional basketball in high numbers following orthopedic surgery for shoulder instability. Shoulder instability may not be a career-altering event, as there are highly effective methods of shoulder stabilization available to athletes.

Robot-Assisted Medial Compartment Arthroplasty Following Remote Patellectomy: A Case Report.

INTRODUCTION: Total patellectomies are uncommon procedures that are reserved as salvage treatment for severely comminuted fractures of the patella. Due to the alteration of normal joint mechanics, these patients present later on in life with degenerative cartilage damage to the femorotibial joint and altered extensor mechanism. There are very few reports of unicondylar knee arthroplasties following previous patellectomy and none that specifically address robot-assisted unicompartmental knee arthroplasty. A recent case report by Pang et al. described the use of minimally invasive fixed-bearing unicondylar knee arthroplasty in a patellectomized patient with moderate medial compartment osteoarthritis. Our report details a case with more significant chondral loss along with patellar tendon subluxation. CASE REPORT: This is a case report of a patient with severe medial compartment osteoarthritis after a patellectomy following a motor vehicle collision. After failing conservative treatment, the patient underwent a medial MAKOplasty with complete resolution of arthritic pain. CONCLUSION: Significant pain relief and improved knee function can be achieved with MAKOPlasty partial knee resurfacing system in a previously patellectomized patient with severe medial compartment osteoarthritis.

Rotating hinge prosthesis for complex revision total knee arthroplasty: A review of the literature.

INTRODUCTION: The rotating hinge prosthesis was originally used and designed as a primary total knee arthroplasty implant, but was hampered due to poor outcomes and catastrophic failures. Newer rotating hinge implants can be utilized in complex revision total knee arthroplasties when appropriately indicated, but their outcome data is very difficult to interpret due to the strict and varied indications for use and subsequently small number of procedures performed. The goal of this review is to evaluate the current evidence on large cohort, rotating hinge knee prostheses used in the revision setting, in order to provide a clearer understanding of the indications, outcomes and complications. METHODS: The PubMed database was utilized to search the available literature regarding "hinged knee," or "rotating hinge" devices. Exclusion criteria included papers focusing on primary arthroplasty, revision for oncologic issues, one-stage revision for infection or studies with less than fifty cases. RESULTS: Review of 115 abstracts after initial search, led to ten studies in the literature that met our inclusion and exclusion criteria. The data shows that rotating hinge knee implants have good survivorship ranging from 51% to 92.5% at 10 years post-operatively. Complication rates range from 9.2% to 63% with infection and aseptic loosening as the most common complications. CONCLUSION: Rotating hinge knee prostheses are most commonly indicated for infection, aseptic loosening, instability and bone loss in the literature. They have good outcome scores and survivorship, but continue to have high complication and revision rates. The implant is a good option when utilized appropriately for patients that are not candidates for less constrained devices.

Interobserver Agreement in the Classification of Partial-Thickness Rotator Cuff Tears Using the Snyder Classification System.

BACKGROUND: At present, there is no widely accepted classification system for partial-thickness rotator cuff tears, and as a result, optimal treatment remains controversial. PURPOSE: To examine the interobserver reliability and accuracy of classifying partial rotator cuff tears using the Snyder classification system. We hypothesized that the Snyder classification would be reproducible with high reliability and accuracy. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Twenty-seven orthopaedic surgeons reviewed 10 video-recorded shoulder arthroscopies. Each surgeon was provided with a description of the Snyder classification system for partial-thickness rotator cuff tears and was then instructed to use this system to describe each tear. Interrater kappa statistics and percentage agreement between observers were calculated to measure the level of agreement. Surgeon experience as well as fellowship training was evaluated to determine possible correlations. RESULTS: A kappa coefficient of 0.512 indicated moderate reliability between surgeons using the Snyder classification to describe partial-thickness rotator cuff tears. The mean correct score was 80%, which indicated "very good" agreement. There was no correlation between the number of shoulder arthroscopies performed per year and fellowship training and the number of correct scores. CONCLUSION: The Snyder classification system is reproducible and can be used in future research studies in analyzing the treatment options of partial rotator cuff tears.

Sensitivity of magnetic resonance imaging in the diagnosis of mobile and nonmobile L4-L5 degenerative spondylolisthesis.

BACKGROUND CONTEXT: Lumbar degenerative spondylolisthesis (LDS) is often diagnosed by conventional supine magnetic resonance imaging (MRI). Numerous studies have shown, however, that the degree of spondylolisthesis can be reduced or disappears when the patient is supine as compared with standing lateral and flexion-extension (SLFE) radiographs. PURPOSE: To compare the sensitivity of supine MRI with SLFE radiographs in patients with L4-L5 LDS. STUDY DESIGN: A retrospective imaging study. PATIENT SAMPLE: Included patients diagnosed with L4-L5 LDS with both SLFE films and supine MRI. METHODS: Lumbar degenerative spondylolisthesis was defined radiographically as a slip greater than 4.5 mm. Mobile LDS was defined as a difference of greater than 3% in slip percentage between lateral radiographs and sagittal MRIs. Additional measurements included L4-L5 facet effusion diameter on axial MRIs. Measurements were performed by two independent examiners. The kappa coefficient was used to assess the interobserver agreement. RESULTS: Of 103 patients assessed, 68% were women and the average age was 66 years. Lumbar degenerative spondylolisthesis was seen on 101 (98%) lateral films and 80 (78%) MRIs. Average slip was 10.0 mm for lateral standing radiographs and 6.6 mm on MRI (p<.0001). Fifty (48%) patients were identified with mobile LDS. The positive predictive value of facet joint effusion for mobile LDS increased from 52% for effusions greater than 1 mm to 100% for effusions greater than 3.5 mm. CONCLUSIONS: This study found that MRI had a sensitivity of 78% for detecting L4-L5 LDS compared with 98% for lateral standing films. We also identified facet effusion size as a marker to predict mobile LDS. These findings suggest that, particularly in the setting of facet effusions, the complete workup of patients in whom LDS is possible should include standing radiographs.

Analysis of Low-Field MRI Scanners for Evaluation of Shoulder Pathology Based on Arthroscopy.

BACKGROUND: Many studies have compared the diagnostic capabilities of low-field magnetic resonance imaging (MRI) scanners to high-field MRI scanners; however, few have evaluated the low-field MRI diagnoses compared with intraoperative findings. PURPOSE: To determine the accuracy and sensitivity of low-field MRI scanners in diagnosing lesions of the rotator cuff and glenoid labrum. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Over a 2-year period, MRI examinations without intra-articular contrast were performed on 79 patients for shoulder pathologies using an in-office 0.2-T extremity scanner. The MRI examinations were read by board-certified, musculoskeletal fellowship-trained radiologists. All patients underwent shoulder arthroscopy performed by a single sports fellowship-trained orthopaedic surgeon within a mean time of 56 days (range, 8-188 days) after the MRI examination. The mean patient age was 54 years (range, 18-81 years). Operative notes from the shoulder arthroscopies were then retrospectively reviewed by a single blinded observer, and the intraoperative findings were compared with the MRI reports. RESULTS: For partial-thickness rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 85%, 89%, 79%, and 92%, respectively. For full-thickness rotator cuff tears, the respective values were 97%, 100%, 100%, and 98%. For anterior labral lesions, the values were 86%, 99%, 86%, and 99%, and for superior labral anterior-posterior (SLAP) lesions, the values were 20%, 100%, 100%, and 79%, respectively. CONCLUSION: Low-field MRI is an accurate tool for evaluation of partial- and full-thickness rotator cuff tears; however, it is not effective in diagnosing SLAP lesions. More information is needed to properly assess its ability to diagnose anterior and posterior labral lesions.