Magnetic resonance imaging evaluation of muscle usage associated with three exercises for rotator cuff rehabilitation.

PURPOSE: Methods of determining muscle usage for exercises involving rotator cuff muscles are limited. Therefore, this investigation used magnetic resonance imaging (MRI) to evaluate the effect of three different exercises used for rehabilitation of the rotator cuff. METHODS: Five normal volunteer subjects (3 men, 2 women, mean age 31.4 yr) were studied. The exercises were scaption with internal rotation (SIR), military press (MP), and side-lying 45 degrees abduction (SLA). MR imaging was performed immediately before and after exercise using a "fast" spin echo STIR sequence and oblique coronal plane imaging. Changes in signal intensity pre- and post-exercise were measured at comparable section locations for the MR images of the supraspinatus, infraspinatus, teres minor, subscapularis, deltoid, and trapezius. RESULTS: The SLA showed the greatest increase in signal intensity in all the muscles (percent change, P < 0.01) except for the trapezius, which was used more by the MP and SIR. None of the exercises activated the teres minor (percent change, P = not significant). CONCLUSION: These findings have important implications in efficacy of physical rehabilitation of the rotator cuff and avoidance of subacromial impingement exercise motions.

Spinal imaging and intervention: 1998.

Imaging of the lumbar spine is the most common application of magnetic resonance (MR) imaging in many radiologic practices. MR imaging has replaced computed tomography (CT) and CT myelography as the primary mode of spinal imaging and has relegated myelography to a secondary role in the evaluation of lumbar spinal disorders. At the same time, however, it has become evident that the correlation between gross anatomic findings as depicted on MR images and the clinical signs and symptoms detected by the clinician may be lacking. Defining the precise anatomic source of patients' complaints on the basis of imaging studies must be approached judiciously because a significant proportion of the population has disc disease as depicted on imaging studies, yet many have no clinical findings.

MR imaging of miscellaneous disorders of the shoulder.

During the course of routine MR imaging of the shoulder, a wide variety of abnormalities may be encountered owing to the technique's broad soft-tissue contrast resolution and multiplanar tomographic capability. In this article, the authors provide an overview of the lesions that might be encountered in this setting.

Imaging of stress injuries to bone. Radiography, scintigraphy, and MR imaging.

Although conventional radiographs continue to be used as a primary method for the diagnosis of stress fractures, the limitations of radiography in early detection have been increasingly recognized. Advanced imaging techniques, including radionuclide methods, and more recently, MR imaging, have increasingly been employed in the assessment of stress fractures, and have provided valuable insights into the spectrum of stress-related changes to bone. This article reviews the diagnostic methods available to the clinician for detection of stress injuries to bone.

Percutaneous lumbar discectomy. Preoperative and postoperative magnetic resonance imaging.

We evaluated magnetic resonance imaging studies of thirty patients before and after a contained herniation of a lumbar disc was treated with a percutaneous lumbar discectomy. The imaging studies were evaluated to determine whether the preoperative appearance of the herniated disc was predictive of the outcome of percutaneous discectomy and also to determine a possible mechanism of action of the procedure in the relief of symptoms. The index operation was successful in seventeen (57 per cent) of the thirty patients. The preoperative imaging studies showed no differences in the appearance of the discs that went on to have a successful result and those that went on to have an unsuccessful result. Imaging studies made four to six weeks after the operation showed no measurable changes in the morphology of the disc. Imaging studies made a mean of fourteen months after the operation showed no changes in the morphology of the disc in twenty-four (80 per cent) of the patients, irrespective of the clinical outcome. Only three of the seventeen patients who had a successful result had a reduction of more than two millimeters in the size of the herniated segment, and two of the thirteen patients who had an unsuccessful result had an increase of more than one millimeter in the size of the herniated segment. We found that preoperative imaging studies cannot predict the clinical outcome of percutaneous lumbar discectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a newly designed patellar realignment brace on patellofemoral relationships.

The effect of applying a newly developed patellar realignment brace to a patient with lateral subluxation of the patella was evaluated using active movement, loaded kinematic magnetic resonance (MR) imaging. The brace corrected the lateral displacement of the patella as shown on the kinematic MR imaging study. The patient underwent physical rehabilitation in conjunction with the use of the patellar realignment brace and has had resolution of her painful symptoms for the past 4 months.

Effect of a patellar realignment brace on patellofemoral relationships: evaluation with kinematic MR imaging.

The effect of a newly developed patellar realignment brace was evaluated in 21 patellofemoral joints (19 patients) with patellar subluxation (13 joints with lateral subluxation and eight with medial subluxation) by using active-movement, loaded kinematic magnetic resonance (MR) imaging. Sixteen patellofemoral joints (76%) demonstrated a qualitative correction of or improvement in patellar subluxation (ie, centralization of the patella or a decrease in the displacement of the patella) after application of the brace. Four of the five "failures" occurred in patellofemoral joints that had patella alta and/or dysplastic bone anatomy. These results indicate that the patellar realignment brace was able to counteract patellar subluxation in the majority of patellofemoral joints studied, as shown by active-movement, loaded kinematic MR imaging. This brace appears to be useful for conservative treatment of patients with patellofemoral joint pain secondary to patellar malalignment and maltracking.

Prior lateral patellar dislocation: MR imaging findings.

PURPOSE: To illustrate the constellation of magnetic resonance (MR) findings that suggest prior patellar dislocation. MATERIALS AND METHODS: A computer search of all MR examinations of the knee with a coded diagnosis of patellar dislocation performed between February 1988 and October 1990 disclosed 22 cases (11 male and 11 female patients, aged 1-70 years). RESULTS: Eighteen cases (82%) demonstrated hemarthrosis, medical retinacular disruption, and contusion of the lateral femoral condyle. In 11 cases, the patella was displaced from the trochlear sulcus, but in no patient was there complete dislocation at the time of imaging. Axial short-inversion-time inversion-recovery (STIR) images demonstrated subtle subchondral and cancellous signal intensity abnormalities that were often poorly appreciated on T2-weighted images. In 11 cases, patellar dislocation was not suspected before MR imaging. CONCLUSION: Hemarthrosis, medial patellar and lateral femoral contusion, and retinacular disruption suggest prior lateral patellar dislocation. Because of its sensitivity to subtle intraosseous signal abnormality, axial STIR imaging is a valuable adjunct in the evaluation of the acutely injured knee.

Adverse reaction to intravenous gadoteridol.

Moderate and severe anaphylactoid reactions--while extremely rare--have been reported in association with intravenous administration of gadopentetate dimeglumine. There has been no similar experience related to use of the newly released magnetic resonance (MR) imaging contrast agent gadoteridol. The authors describe a case of vasovagal response and anaphylactoid reaction during intravenous administration of gadoteridol. MR users should be aware of the potential for adverse effects to occur in association with use of gadoteridol and be prepared by implementing appropriate observation procedures for patients receiving this as well as other MR contrast agents. In addition, physiologic monitoring devices and resuscitation equipment should be readily available in the clinical MR setting for proper treatment of patients who may experience moderate to severe adverse reactions.

Magnetic resonance imaging of miscellaneous disorders of the shoulder.

The ability to simultaneously and comprehensively evaluate both articular and extra-articular structures represents a distinct advantage for MR imaging over all other diagnostic methods. This article reviews how the technique can demonstrate a wide spectrum of abnormalities in and around the shoulder, with an emphasis on abnormalities encountered during MR imaging that were clinically unsuspected at the time of examination.

Patellofemoral joint: identification of abnormalities with active-movement, "unloaded" versus "loaded" kinematic MR imaging techniques.

A positioning device was used to apply a "load" to stress the patellofemoral joint during active-movement, kinematic magnetic resonance (MR) imaging. Twenty-three symptomatic patellofemoral joints were studied by using "unloaded" versus "loaded" techniques. With the unloaded technique, seven joints were normal, nine had lateral subluxation, three had lateral tilt, and four had medial subluxation. With the loaded technique, one was normal, 13 had lateral subluxation, four had lateral tilt, and five had medial subluxation. The active-movement, loaded kinematic MR imaging technique provides improved ability to identify patellofemoral joint abnormalities.

Lumbar spine following successful surgical discectomy. Magnetic resonance imaging features and implications.

In an attempt to determine the expected long-term appearance of the lumbar spine in patients who have undergone successful lumbar discectomy, follow-up magnetic resonance (MR) examinations were performed on 23 patients (26 levels). All patients in the study had undergone at surgery at least one year prior to the study. All patients met rigorous criteria for a successful outcome. In nine cases, the postoperative study indicated a virtually total resolution of the previously identified disc herniations. In 13 cases, the study noted moderate, persistent posterior contour defects in the disc that contributed to persistent mass effect on the thecal sac or corresponding nerve root. In the remaining four cases, the postoperative study indicated virtually no change in the apparent contour of the posterior disc margin. Gadolinium contrast examinations demonstrated enhancement of the persistent contour abnormalities in 18 of 19 disc levels, suggesting the common presence of fibrosis, which was at times "mass-like," in these successful patients. These findings suggest that localized discal contour abnormalities morphologically simulating recurrent disc herniations and variably contributing to mass effect, may be commonly encountered in long-term follow-up imaging studies of successful discectomy patients.

Kinematic MR imaging of the patellofemoral joint: comparison of passive positioning and active movement techniques.

Thirteen patients underwent magnetic resonance (MR) imaging of the patellofemoral joint in an evaluation of passive positioning and active movement kinematic MR imaging techniques. Sixteen joints were symptomatic, and 10 were not. Delineation of normal and abnormal patellar alignment and tracking was similar with the two techniques, but kinematic MR imaging performed with active movement allowed a substantial reduction in examination time while permitting evaluation of the contribution of associated activated muscles and soft-tissue structures to patellofemoral joint function.

MR imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact.

Magnetic resonance (MR) imaging is contraindicated for patients with certain ferromagnetic implants, primarily because of potential risks related to movement or dislodgment of the devices. An additional problem with metallic implants is the potential image distortion that may affect the interpretation of the MR study. Since MR imaging is frequently useful for the evaluation of postoperative anterior cruciate ligament (ACL) reconstruction, the ferromagnetic qualities and artifacts associated with MR imaging were determined for five metallic orthopedic implants commonly used for this surgery. Only the Perfix interference screw displayed a substantial deflection force and caused extensive signal loss. Images of the knee of one patient with two Perfix screws in place were not interpretable because of the image distortion caused by these implants. Therefore, alternative nonferromagnetic implants should be considered for reconstruction of the ACL.

The postoperative knee.

Magnetic resonance (MR) has established itself as the gold standard for noninvasive imaging of the knee. As in arthroscopy, assessment of injuries to the menisci, articular surfaces, synovium, and cruciate ligaments can be made. Additionally, MR has an advantage over arthroscopy in being able to assess the para articular soft tissues and cortical and medullary bony compartments. Until recently, the role of MR in the postoperative knee has been less clear. New information, however, suggests that MR is capable of assessing the status of the partially resected meniscus, the adjacent articular surfaces, and subchondral medullary lesions that frequently occur. There has been recent interest in reestablishment of the stabilizing function of a previously torn anterior cruciate ligament by means of autogenous or allogenous materials. MR permits the surgeon to assess the isometry and possible sites of graft impingement that may occur following cruciate ligament reconstruction. The purpose of this article is to define the current status of MR in the assessment of the postoperative knee.

Hematopoietic bone marrow hyperplasia: high prevalence on MR images of the knee in asymptomatic marathon runners.

In a prior study of marathon runners, we noticed that MR scans of the knee frequently showed hyperplasia of red (i.e., hematopoietic) bone marrow. Because the frequency of this finding in various populations is unknown, the purpose of this study was to determine the relative prevalences of hematopoietic bone marrow hyperplasia on MR examinations of the knees of healthy volunteers (n = 74), patients with symptoms of knee disorders (n = 54), and asymptomatic marathon runners (n = 23). The prevalence of hematopoietic bone marrow hyperplasia was 3% (2/74) for the healthy volunteers, 15% (8/54) for the patients, and 43% (10/23) for the marathon runners. The difference in prevalence between each of the three groups was statistically significant at p less than .05 in each case with hematopoietic bone marrow hyperplasia, the distal femur was the only area affected, while the epiphysis and proximal tibia were uninvolved. This pattern of affected bone marrow with hyperplasia of the hematopoietic marrow may be useful for the differential diagnosis. We postulate that the high prevalence of hematopoietic bone marrow hyperplasia in marathon runners may develop as a response to "sports anemia", which is commonly found in highly conditioned, aerobically trained athletes. Furthermore, this is considered to be a normal variant when found in the pattern described here.

Do asymptomatic marathon runners have an increased prevalence of meniscal abnormalities? An MR study of the knee in 23 volunteers.

Excessive repetitive musculoskeletal loads and stresses associated with intense physical activity may lead to deterioration of the menisci of the knee. Therefore, MR imaging was performed on the knees of 23 asymptomatic marathon runners (eight men, 15 women; average age, 40 years; average number of years training, 10; average training distance per week, 41 miles) to determine the prevalence of meniscal signal abnormalities. None of the runners had previous knee injuries or surgery and each of them regularly competes in 26-mile, 50-mile, or 100-mile marathon races. T1-weighted coronal MR images and proton density-weighted and T2-weighted sagittal images were obtained with a 1.5-T MR system and a transmit/receive extremity coil. The medial and lateral menisci were divided into four portions, or horns, and a total of 92 horns were evaluated (i.e., four horns per knee: medial posterior, medial anterior, lateral posterior, and lateral anterior). Two meniscal horns (2%) had grade 3 signal (grade 3 indicates a meniscal tear), 12 (13%) had grade 2 signal, 29 (32%) had grade 1 signal (grades 1 and 2 are indicative of meniscal degeneration), and 49 (53%) had grade 0 signal (grade 0 is normal). Overall, the prevalence of meniscal tears was 9% (two meniscal tears found in 23 runners). This is lower than the prevalence of MR signal abnormalities indicative of meniscal tears reported for asymptomatic, nonrunner athletes (20% of 20 athletes) and for asymptomatic nonathletes (16% of 74 subjects). Fifty-three percent of the meniscal horns of the nonrunner athletes had grade 1 or 2 signal, indicative of meniscal degeneration. Our results indicate that the prevalence of meniscal tears in marathon runners is no higher than the prevalence reported for sedentary persons, and the runners have the same amount of meniscal degeneration as do nonrunner athletes.

Tendon injuries of the lower extremity: magnetic resonance assessment.

MR is rapidly establishing itself as a premiere imaging modality for the assessment of musculoskeletal trauma. Its utility in the evaluation of the menisci and ligaments of the knee is well known, but there is far less known about the use of MR for evaluation of the tendons. MR, by virtue of its unmatched soft tissue resolution capability, can determine not only the contour of an affected tendon, but the tendon sheath and internal signal alterations that accompany tendonitis, partial and complete ruptures. Injuries to the Achilles tendon are well known to the athlete and the imager alike; however, abnormalities of the posterior tibial tendon, peroneal tendon, and flexor hallucis longus also result in significant clinical symptoms, as well as imaging abnormalities.