Paul C. Hajek

Carpal tunnel syndrome: Morphologic changes after release of the transverse carpal ligament

We describe the morphologic changes that follow division of the transverse carpal ligament in patients with carpal tunnel syndrome. Fifteen hands in 12 patients with carpal tunnel syndrome were studied with magnetic resonance imaging before operation and for 6 weeks after operation. Eight hands were studied at 8 months after operation. Carpal arch width, anterior displacement of the carpal canal contents, and carpal canal volume were measured by use of multiplanar reformation and three-dimensional reconstruction of magnetic resonance images. There was a 24.2 +/- 11.6% increase in carpal canal volume 6 weeks after carpal tunnel release (p less than 0.001). This difference persisted at 8-month follow-up. There was an anterior displacement of carpal canal contents 3.5 +/- 1.9 mm from its original position 6 weeks after operation (p less than 0.001). This palmar displacement persisted at the 8-month follow-up. There was no statistically significant increase in carpal arch width 8 months after carpal tunnel release. We believe that division of the transverse carpal ligament restores median nerve function by increasing the volume of the carpal canal. This volumetric increase results from an anterior displacement of the newly formed transverse carpal ligament and not from a widening of the bony carpal arch.

Carpal tunnel volume determination by magnetic resonance imaging three-dimensional reconstruction

Three-dimensional computer reconstruction of magnetic resonance images (MRI) of ten cadaveric specimens was used to determine carpal tunnel volume and carpal arch width. Magnetic resonance images-acquired data were compared with direct measurement of cadaveric carpal canal volume by means of a silicone-injection technique. Mean MRI three-dimensional reconstruction volume was 5.84 ml +/- 1.24 ml. Mean silicone-mold volume was 4.73 +/- 1.01 ml. A correction factor of 0.8161 was used to accurately calculate carpal tunnel volume from MRI-acquired data. There was no significant difference between calculated carpal tunnel volumes and silicone-mold volumes (p = 0.623), and there was a linear relationship between MRI-acquired volumes and silicone-mold volumes (correlation coefficient r = 0.97). Differences in MRI-volume determinations between observers were not significant (0.25 greater than or equal to p greater than 0.1). MRI three-dimensional reconstruction, a valid and reproducible technique for measuring carpal tunnel volume and dimensions, has considerable research potential for the evaluation of the relationship between the carpal canal and its contents before and after carpal tunnel release.

Magnetic resonance imaging of the lower vertebral column in patients with multiple myeloma.

Eighteen patients with multiple myeloma (clinical stages 1-3) and a control group of 21 persons underwent magnetic resonance imaging (MRI) studies of the lower thoracic and lumbar spine. This was done to determine the potential benefit of MRI in addition to conventional radiographs, tomograms, computed tomography and nuclear scans. In addition to focal fatty replacement of normal hematopoietic marrow, which presented as focal hyperintense lesions on T1-weighted images (T1-WI) and on T2-weighted images (T2-WI), two types of myelomatous lesions were found: (1) focal areas with reduced signal intensity when compared with normal bone marrow on T1-WI and enhanced signal intensity on T2-WI, mainly found in untreated myelomas; and (2) focal areas of decreased signal intensity on T1-WI and on T2-WI, which were predominantly detected after previous radiation therapy. MRI surpassed conventional radiography in detecting abnormal focal marrow infiltration in 41 of 247 vertebrae. Radiographs identified only 11 of the 41 as pathologic, based on shape and structure of the vertebral bodies; however, 15 other collapsed vertebrae showed no signal abnormalities of the marrow on MR images. Discrimination of normals and abnormals by statistical analysis of intensity measurements of the bone marrow was not possible.

The effect of intra-articular gadolinium-DTPA on synovial membrane and cartilage.

This investigation evaluated the potential effect of gadolinium (Gd)-DTPA-dimeglumine on synovial membrane and joint cartilage, using macroscopic, microscopic, and x-ray fluorescent spectroscopic techniques. Thirteen New Zealand white rabbits (26 knees) were used in this study, ten receiving 500 micromolar injections of Gd-DTPA-dimeglumine in their right knees; the remainder of the knees served as controls. One injected knee had minimal joint effusion and one had mild hyperemia. Microscopically four knees exhibited mild focal hyperplasia of the synovium, another three minimal focal mononuclear cell infiltration. X-ray fluorescent spectroscopy demonstrated no evidence of Gd-DTPA-dimeglumine in the synovium or articular cartilage. Neither macroscopic nor microscopic evaluation detected any Gd-DTPA-dimeglumine related effects. Gd-DTPA-dimeglumine was found to be safe for intra-articular injection in this animal model.

High-resolution magnetic resonance imaging of the wrist: normal anatomy.

Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms, TE 25 ms) were most useful because of short imaging times, satisfactory image quality, and the absence of motion artifacts. The coronal plane provided the clearest definition of important structures. Potential diagnostic limitations exist due to the inability of MRI ot clearly delineate articular cartilage, joint capsules, and small interosseous ligmaents. The presence of intra-articular fluid in both living subjects and cadaveric specimens, however, allowed for fine depiction of these structures on T2 weighted images.

Magnetic resonance imaging of glenohumeral joint diseases

Through the application of oblique planes and flexible surface coil techniques, magnetic resonance imaging (MRI) promises to be of great clinical value in the evaluation of a variety of pathologic conditions affecting the shoulder. In patients with joint effusions, the tendinous portion of the rotator cuff, glenoid labrum, and bicipital tendon can be readily visualized. This capability has particular relevance in patients with inflammatory disease and traumatic conditions. Rotator cuff atrophy and impingement of the coracoacromial arc upon the supraspinatus muscle and tendon can also be demonstrated. MRI is also useful in the evaluation of shoulder instability.

High-resolution magnetic resonance imaging of the ankle: normal anatomy

An imaging-anatomic correlative study of ankle anatomy based upon six healthy adults and six fresh cadaveric specimens was performed to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI). Optimal pulsing sequences and imaging planes for various structures of interest were established. MRI afforded exquisite depiction of anatomic detail, particularly the diagnostically important collateral ligaments. Limitations in the ability to delineate the joint capsule and articular cartilage were documented, with the former detectable only on T2 weighted images in the presence of synovial fluid.

Detection of Testicular Torsion by Magnetic Resonance Imaging in a Rat Model

Testicular torsion is one of the most common pediatric urological emergencies. Incorrect or delayed diagnosis contributes significantly to morbidity. We previously have shown that magnetic resonance displays scrotal contents with great detail using hydrogen concentration weighted and T2 weighted images. Sprague-Dawley rats underwent either unilateral 720-degree testicular torsion or a sham procedure. Magnetic resonance images were obtained at intervals with a 3 or 5-inch surface coil. Scans after surgical torsion showed a characteristic spiral distortion of the fascial planes of the spermatic cord, not seen in the sham animals, as well as a decrease in testicular size with prolonged torsion.