Joel Rubenstein

Kinematics of the distal radioulnar joint

The kinematics of the normal distal radioulnar joint (DRUJ) in five fresh frozen cadavers were investigated by means of computerized tomography (CT). Rotation of the radius about the ulna is accompanied by translation so that in supination the ulna is somewhat palmar, and in pronation the ulna is more dorsal relative to the radius. The average ranges of motion of the hand and DRUJ were 260 degrees and 190 degrees, respectively. Significant carpal and metacarpal rotation occurred with pronation-supination of the hand. The DRUJ has both rotational and translational components of movement and does not have a single center of rotation. The pathway of the instantaneous centers of rotation, or centrode, of the DRUJ has a characteristic pattern. The centrode moves in a direction opposite that of the DRUJ movement and is located near the center of the ulnar head. A prosthetic joint for the DRUJ should not have a fixed axis of rotation but should allow the normal translatory motion of the ulna and radius if early joint failure is to be prevented.

Computerized tomography of the distal radioulnar joint: Correlation with ligamentous pathology in a cadaveric model

The kinematics of the normal distal radioulnar joint (DRUJ) and the stabilizing function of various structures about the DRUJ were investigated in a study involving six fresh frozen cadavers. Sequential division of the supporting structures was correlated with abnormalities detected by computerized tomography (CT). The infratendinous portion of the extensor carpi ulnaris is a major restraint against dorsal and palmar subluxation. Division of the radioulnar ligaments and triangular fibrocartilage alone produced only minor changes. Lateral displacement was controlled by the interosseous membrane and the pronator quadratus. CT is a useful method of gaining objective and quantifiable information regarding incongruity of the DRUJ. Three scans--one each in pronation, neutral, and supination--would be optimal. The pronation scan is likely to detect palmar subluxation, while the neutral scan is sensitive for dorsal subluxation and DRUJ diastasis. The supination view should confirm reduction of any subluxation. An important observation of this study was the spontaneous reduction of palmar, dorsal, and lateral displacement in supination. This suggests that immobilization in supination may be indicated in cases of acute DRUJ injury.

Adenocarcinoma of the lung metastatic to the psoas muscle

Abstract Hematogenous metastasis to the psoas muscle is rare, and the resulting clinical symptoms may mimic psoas abscess or hemorrhage. When the clinical history is not specific, CT is important in documenting the presence of a psoas mass and providing biopsy guidance for histologic diagnosis. Only three previously reported cases have been related to a primary carcinoma of the lung.

The Role of Plain Radiographs in Management of Bone Metastases

Approximately 50% of patients with cancer will develop skeletal metastases, which often lead to significant pain. When a patient complains of pain, a bone scan and/or plain x-rays are ordered as investigations. X-rays necessitate a 1-cm diameter mass and 50% bone mineral loss at minimum for detection. Up to 40% of lesions will be unidentified by x-rays, presenting false-negative results. Computed tomography (CT) scans can recognize a bony metastatic lesion up to 6 months earlier than an x-ray. However, plain x-rays can also lead to rare false-positive results. We present a case with a false-positive result in a patient with lung cancer.

Radiographic definition of the dorsal and palmar edges of the distal radius

The dorsal and palmar edges of the distal radius, as well as the concavity of the articular surface were labeled with wire and radiographs taken from neutral to 30 degrees of added dorsal tilt. The dorsal edge was identified as the structure that protrudes distally in neutral. The palmar edge was found to overlap with the sclerotic subchondral bone of the radius in neutral. With increasing dorsal tilt the profile of the palmar edge appeared as it protruded distal to the sclerotic subchondral line of the radius. The profile of the palmar edge could be distinguished from that of the dorsal edge on the anteroposterior view. The wire, which was placed midway between the dorsal and palmar edges and the concavity of the articular surface corresponded to the prominent sclerotic subchondral bone line of the distal radius. This did not change in position with increasing dorsal tilt. This clarification of the radiologic anatomy is helpful in extending the use of the anteroposterior radiograph for the interpretation of fractures and malunions of the distal radius.

False-normal bone imaging in spinal tuberculosis.

Tc-99m MDP bone imaging in spinal tuberculosis usually shows increased radioactivity at the sites of involvement. Uncommonly, the bone scan can be normal if the infection is low grade, indolent, or severely destructive. Two cases of spinal tuberculosis with normal bone imaging are reported. A normal bone image does not exclude tuberculous spondylitis. If there is clinical suspicion of this disease, further investigations, including tissue specimens, should be obtained.

Correlation of Computed Tomography Imaging Features With Pain Response in Patients With Spine Metastases After Radiation Therapy

PURPOSE To correlate computed tomography (CT) imaging features of spinal metastases with pain relief after radiotherapy (RT). METHODS AND MATERIALS Thirty-three patients receiving computed tomography (CT)-simulated RT for spinal metastases in an outpatient palliative RT clinic from January 2007 to October 2008 were retrospectively reviewed. Forty spinal metastases were evaluated. Pain response was rated using the International Bone Metastases Consensus Working Party endpoints. Three musculoskeletal radiologists and two orthopaedic surgeons evaluated CT features, including osseous and soft tissue tumor extent, presence of a pathologic fracture, severity of vertebral height loss, and presence of kyphosis. RESULTS The mean patient age was 69 years; 24 were men and 9 were women. The mean worst pain score was 7/10, and the mean total daily oral morphine equivalent was 77.3 mg. Treatment doses included 8 Gy in one fraction (22/33), 20 Gy in five fractions (10/33), and 20 Gy in eight fractions (1/33). The CT imaging appearance of spinal metastases included vertebral body involvement (40/40), pedicle involvement (23/40), and lamina involvement (18/40). Soft tissue component (10/40) and nerve root compression (9/40) were less common. Pathologic fractures existed in 11/40 lesions, with resultant vertebral body height loss in 10/40 and kyphosis in 2/40 lesions. At months 1, 2, and 3 after RT, 18%, 69%, and 70% of patients experienced pain relief. Pain response was observed with various CT imaging features. CONCLUSIONS Pain response after RT did not differ in patients with and without pathologic fracture, kyphosis, or any other CT features related to extent of tumor involvement. All patients with painful spinal metastases may benefit from palliative RT.

Case report 766

A 30-year -o ld w o m a n presen ted wi th a h i s to ry o f ins id ious onse t o f pa in and swell ing over the do r sa l r ad ia l aspec t o f her r ight midd le f inger for a p p r o x i m a t e l y 1 year. She h a d no prev ious h i s to ry o f ma l i gnancy or systemic illness and could recal l no t r a u m a to the finger. Phys ica l e x a m i n a t i o n revea led diffuse swell ing over the do r sa l r ad i a l aspect o f the p r o x i m a l p h a l a n x o f the r ight m idd l e finger. N o nodules were pa lpab l e a n d the swell ing was n o t mobi le . L a b o r a t o r y examina t i ons were wi th in n o r m a l l imits. A r a d i o g r a p h o f the r ight midd le f inger was a b n o r m a l (Fig. 1), and bone scan showed increased u p t a k e only in the c o r r e s p o n d i n g p r o x i m a l pha lanx . Subsequen t ly c o m p u t e d tom o g r a p h y (Fig. 2) and magne t i c resonance imag ing (Fig. 3) o f the f inger were car r ied out. A b iopsy o f the r ight midd le f inger was pe r fo rmed .

Impact of Magnetic Resonance Imaging on Gross Tumor Volume Delineation in Non-spine Bony Metastasis Treated With Stereotactic Body Radiation Therapy

PURPOSE This study investigates the inter-observer variability of contouring non-spine bone metastases using the planning CT alone vs. the addition of MRI T1 and T2 imaging sequences. METHODS AND MATERIALS 10 cases of non-spine bone metastases treated with SBRT at our institution were selected. The gross tumor volume (GTV) for each case was delineated by six SBRT radiation oncologists (RO) and one diagnostic radiologist (DR) on the treatment planning CT. After a minimum of three months, each case was re-contoured on the CT fused with a MRI T1 sequence followed by a MRI T2 sequence. STAPLE consensus contours were created from the RO volumes and inter-observer variability was measured using both κ agreement and the Dice coefficient (DSC). RESULTS In total, 180 RO contours were analyzed within three datasets (CT, CT + MRI T1 and CT + MRI T1 + MRI T2). The mean GTV was 16.95 cm3 (range, 0.12-269.6 cm3). The RO κ agreement was 0.6129 based on CT alone, and significantly increased to 0.7045 in the CT + MRI T1 (P = .042) dataset and 0.7017 in the CT + MRI T1 + MRI T2 dataset (P = .048). The mean DSC in the CT alone dataset was 0.7047, and significantly increased to 0.7628 in the CT + MRI T1 dataset (P < .001) and 0.7544 in the CT + MRI T1 + MRI T2 dataset (P = .001). There were no statistical differences in RO κ agreement (P = .948) or mean DSC (P = .573) when comparing the CT + MRI T1 and CT + MRI T1 + MRI T2 datasets. The DSC agreement between DR and RO volumes was lowest (0.6887) in the CT alone dataset and significantly increased to 0.7398 in the CT + MRI T1 dataset (P = .003) and 0.7342 in the CT + MRI T1 + MRI T2 dataset (P = .008). CONCLUSIONS The fusion of MRI T1 images to CT significantly reduced inter-observer variability amongst ROs in delineating non-spine bone metastases, and improved agreement between GTVs delineated by the RO to the DR.

Imaging of Arthritis and Metabolic Bone Disease

Barbara N. Weissman MD. . Philadelphia: Saunders/Elsevier, 2009, pages,