Jacob Zeiss

Carpal tunnel changes and median nerve compression during wrist flexion and extension seen by magnetic resonance imaging

Magnetic resonance imaging was done on the wrists of 14 volunteer subjects with the wrists in the neutral position, then flexed and extended at 45 degrees. Computer enhanced cross-sectional areas were measured on each subject at the level of the hook of the hamate. In the neutral position the distance between confining structures around the median nerve is 2.0 +/- 0.2 mm in the anteroposterior direction, and the mean cross-sectional area of the carpal tunnel is 1.52 cm2. With the wrist in the extended position the distance available for the median nerve measures 2.2 +/- 0.4 mm and the cross-sectional area increases to 1.75 cm2. When the wrist is flexed, the distance available for the median nerve between the flexor tendons and transverse carpal ligament decreases to 1.1 +/- 0.4 mm, and the cross-sectional tunnel area decreases to 1.36 cm2. Flexion of the wrist and/or fingers both produces a palmar rearrangement of the flexor tendons creating potential compression of the median nerve. The nerve responds to these forces by becoming interposed in various positions between the superficial flexor tendons.

MRI of suprascapular neuropathy in a weight lifter.

Suprascapular neuropathy results from abnormal compression of the suprascapular nerve, typically at the suprascapular or spinoglenoid notch. This may be produced by either mass effect such as ganglion cyst or by certain repetitive shoulder motions producing wide scapular excursion (e.g., hyperabduction), which causes traction upon the nerve. Certain sports activities such as weight lifting predispose to this type of neuropathy. The clinical presentation is frequently not specific and the patient may be sent for MR evaluation to rule out rotator cuff tear or other more common shoulder abnormalities. This entity should be suspected if MR images demonstrate selective atrophy of the spinatus muscles with a structurally intact rotator cuff.

MR demonstration of anomalous muscles about the volar aspect of the wrist and forearm

Magnetic resonance (MR) examination of 42 normal wrists was performed for evaluation of anomalous musculature. A total of 23 muscle variations were found. An accessory abductor digiti minimi was found in 10 wrists (24%), an absent palmaris longus was found in seven wrists (16%), a muscular palmaris longus tendon was found in three wrists (7%), a muscular flexor digitorum superficialis was found in two wrists (5%), and an aberrant lumbrical muscle originating from within the carpal tunnel was found in one wrist (2.4%). Such muscle variations can be distinguished by MR from other mass lesions at the wrist and a knowledge of their frequency, appearance, and location can be of help in this regard.

Comparison of bone contusion seen by MRI in partial and complete tears of the anterior cruciate ligament.

Objective Bone contusions are frequently found in association with complete tears of the anterior cruciate ligament (ACL) and can be a helpful secondary sign in diagnosis. We compare the frequency, location, and significance of bone contusions in complete and partial ACL tears. Materials and Methods Twenty-nine patients with complete and 42 patients with incomplete tears of the ACL were examined by MRI for the presence of accompanying bone contusions within 1 month of injury. Results Bone contusions were found in 72% of the complete ACL tears but in only 12% of the partial tears. Of the partial ACL tears with accompanying contusions, 80% were high grade injuries that eventually went on to complete rupture within 6 months. Only 16% of the partial ACL injuries without bone contusion progressed to complete rupture at 1–2 year follow-up. There was no difference between the bone contusions of partial and complete tears in terms of general appearance and location. They were predominantly in the lateral compartment (90%) and had a specific predilection for the mid portion of the lateral femoral condyle and the posterior portion of the lateral tibial plateau, often occurring in tandem. Conclusion Bone contusions occur with much less frequency in partial ACL tears than in complete tears but their presence in partial rupture favors a high grade tear that is likely to become complete.

MR demonstration of an anomalous muscle in a patient with coexistent carpal and ulnar tunnel syndrome. Case report and literature summary.

An aberrant muscle is demonstrated by magnetic resonance (MR) imaging in a patient presenting with focal wrist swelling and compression neuropathy of median and ulnar nerves following 4 months of carpentry work. The muscle originated from the palmaris longus tendon and ulnar antebrachial fascia at the lower half of the forearm as a single belly, then diverged medially from palmaris longus tendon and bifurcated. Both portions of the split muscle extended into the distal ulnar tunnel or Guyons canal. One segment joined with the abductor digiti minimi muscle and the other with the flexor retinaculum. MR was able to clearly delineate this hypertrophied, symptomatic muscle anomaly. It may be helpful when mass effect is suspected in either tunnel, or in patients with atypical work-related carpal tunnel syndrome with evidence of significant ulnar neuropathy for evaluation of underlying anomalous musculature. Normal MR images of the wrist are included for comparison and the literature is reviewed.

Magnetic resonance imaging for ineffectual tarsal tunnel surgical treatment.

Tarsal tunnel syndrome (TTS) is an entrapment neuropathy caused by compression of the posterior tibial nerve beneath the ankle flexor retinaculum. Treatment of TTS consists of surgical release of the retinaculum. The failure rate is 10%-20%. Magnetic resonance (MR) imaging was used to evaluate a patient with an unsatisfactory response. MR imaging demonstrated incompleteness of the surgical release of the flexor retinaculum.

Chronic bursitis presenting as a mass in the pes anserine bursa : MR diagnosis

A case of chronic, nonspecific synovial inflammation presenting as a mass in the pes anserine bursa is demonstrated by MRI. The lesion was well demarcated and surrounded by a low intensity rim. On spin echo images it was homogeneous and of intermediate signal intensity, whereas on T2-weighted images it showed scattered areas of high signal producing a heterogeneous pattern. It is contrasted with a typical example of acute pes anserine bursitis, presenting as simple fluid within the bursa. The differential considerations vary accordingly between the acute and chronic forms of pes anserine bursitis, with the latter requiring differentiation from other forms of synovitis, synovial hemangioma, and synovial sarcoma. The MR features of these entities are reviewed as an aid in differential diagnosis.

Titanium hip implants for improved magnetic resonance and computed tomography examinations

The value of magnetic resonance imaging (MRI) for assessment of the hip has been demonstrated, particularly in cases of avascular necrosis. Magnetic resonance imaging can be used to provide anatomic evaluation of the femoral head, acetabulum, hip joint, joint fluid, and the surrounding structures. MR examinations of two patients with hip fractures fixed with stainless steel hip implants were compared with nine patients with hip fractures fixed with titanium hip implants, one of which showed avascular necrosis of the femoral head. The titanium implants resulted in less MRI artifacts, allowing for improved depiction of the femoral head and surrounding soft tissue. For this reason titanium fixation devices are recommended as a substitute for stainless steel in the hip joint region in a patient who may need future MR examination.

Magnetic resonance imaging in the diagnosis of anterior tibialis muscle herniation

Magnetic resonance imaging (MRI) can be employed to successfully image the fascial compartments of the leg. Herniated muscle tissue and fascial discontinuity can each be unequivocally identified. Both the extent of fascial splitting and the size of the muscle herniation can be demarcated and quantified. MRI is favored over computed tomography because of its superior ability to distinguish soft-tissues structures, making it possible to see both muscle and fascia separately.

Normal Magnetic Resonance Anatomy of the Tarsal Tunnel

Images of five cadaver ankles and three normal volunteers were obtained in an attempt to delineate magnetic resonance (MR) anatomy of the tarsal tunnel. Multiplanar T1-weighted (TE 20 msec, TR 600 msec) scans were obtained of the cadaver specimens while T1 and T2 weighted (TE 20, 80 msec, TR 2000 msec) scans were obtained of the volunteer ankles. After imaging, the cadaver ankles were frozen, sectioned, photographed, and compared to the MR images in the transverse plane. The anatomical structures seen on the MR images correlated closely with the cadaver sections. The bony and soft tissue boundaries and contents of the tarsal tunnel could be imaged with detail easily sufficient to delineate all the major structures within it, including the posterior tibial nerve and its branches