The effects of tibial component inclination on bone stress after unicompartmental knee arthroplasty.

Unlike the case with total knee arthroplasty, the femorotibial angle (FTA) after unicompartmental knee arthroplasty (UKA) does not directly depend on the inclination of the tibial component when the height of the joint line is maintained. This study analyzed the effects of the inclination of the tibial component in the coronal plane on the contact pressure of the implant-bone surface and the stresses on the proximal tibia. A two-dimensional, coronal plane model of the proximal tibia was subjected to finite-element analysis. Sixteen patterns of finite-element models of equal FTA were developed in which the inclination of tibial components ranged from 5 degrees valgus to 10 degrees varus in increments of 1 degrees. Stress concentration at the proximal medial diaphyseal cortex gradually increased as the inclination changed from valgus to varus. Maximum contact pressure on the metal-bone interface similarly changed and shifted from the lateral edge to the medial edge of the implant as the inclination changed to varus. It was found that even without changing FTA, the inclination of the tibial component might affect stress concentration and contact pressure in the proximal tibia after UKA. The results suggested that slight valgus inclination of the tibial component might be preferable to varus and even to 0 degrees (square) inclination so far as the stress distribution is concerned.

Evaluation of the risk of instrumentation as a foreign body in spinal tuberculosis. Clinical and biologic study.

The risk of persistence and recurrence of infection in posterior spinal instrumentation surgery for spinal tuberculosis was studied clinically and microbiologically. Eleven patients with thoracic, thoracolumbar, and lumbar spinal tuberculosis treated by debridement, anterior fusion, and combined posterior instrumentation surgery were analyzed. Seven patients had tuberculosis in both anterior and posterior spinal elements. There were no cases of persistence or recurrence of infection after surgery, and instrumentation provided immediate stability and protected against development of kyphotic deformity. The adherence properties of Mycobacterium tuberculosis to stainless steel (SUS 316) was evaluated experimentally. The results showed that posterior instrumentation surgery was not a hazard to spinal tuberculosis infection when combined with radical debridement and intensive anti-tuberculosis chemotherapy.

Atlantoaxial subluxation associated with ossification of posterior longitudinal ligament of the cervical spine.

STUDY DESIGN: Two case reports. OBJECTIVE: To demonstrate two rare cases of atlantoaxial subluxation associated with ossification of the posterior longitudinal ligament of the cervical spine, in which spastic quadriplegia developed. SUMMARY OF BACKGROUND DATA: There are only two reports of an association of diffuse idiopathic skeletal hyperostosis with atlantoaxial subluxation. This condition often accompanies ossification of the posterior longitudinal ligament of the cervical spine, but there is nothing in the literature about the association of ossification of the posterior longitudinal ligament with atlantoaxial subluxation. METHODS: Clinical and radiographic findings of these two cases were demonstrated. In both cases laminoplasty of the cervical spine was performed with occipitoaxial arthrodesis. RESULTS: The spastic quadriplegia of these two patients caused by myelocompression improved after surgical intervention. CONCLUSION: Ossification of the posterior longitudinal ligament of the cervical spine may cause atlantoaxial subluxation.

Painful snapping in rheumatoid knees.

Painful snapping caused by a solitary intra-articular nodular mass was found in 11 knee joints of 8 patients with rheumatoid arthritis. The masses were characteristically situated in the anterolateral aspect of the lateral femoral condyle of each joint, and appeared to jump and slip in and out of the patellofemoral articulation during flexion and extension. The snapping caused by the solitary mass was noticed as the joint flexed from 15 degrees to 30 degrees in 9 knees and from 50 degrees to 60 degrees in 3. Histopathological examination of the masses revealed typical findings of a rheumatoid nodule in 4 knee joints and myxomatous degeneration and collagen necrosis in 7.

Grafted bone used in acetabular reconstruction: assessment by SPECT scintigraphy.

OBJECTIVE: To investigate incorporation of the grafted bone used for acetabular reconstruction. DESIGN: Single photon emission computed tomography (SPECT) was carried out at the 1st, 6th, and 12th month after the operation and the uptakes on serial SPECT scintigrams were normalized. The horizontal histogram of scintigraphic activity at the level of the central grafted bone in the coronal image was designated the profile curve. PATIENTS: Seven patients who had undergone bipolar hip arthroplasty for osteoarthritis of the hip were randomly selected. RESULTS AND CONCLUSION: Five of seven profile curves obtained at the 1st month demonstrated a single peak at the host-graft junction. The profile curve obtained at the 6th month showed two peaks at the host-graft junction and the periphery of the grafted bone in all patients. The profile curve at the 12th month showed slightly increased activity in the center of the grafted bone. This preliminary study demonstrates that comparison of the serial profile curves on SPECT is valuable in evaluating the progress of incorporation of the grafted bone in hip arthroplasty.

MR appearance of paraganglioma of the cauda equina. Case reports.

PURPOSE: To investigate the value of MR imaging for preoperative diagnosis of paraganglioma of the cauda equina. MATERIAL AND METHODS: A retrospective review of 2 cases of paraganglioma of the cauda equina examined with MR imaging was undertaken. Features assessed included the homogeneity of the lesions, presence or absence of serpiginous flow void and thin hypointense margins. RESULTS: In case 1, the tumor was hyperintense on the postcontrast examination and serpiginous flow void suggested vessels in the upper pole of the tumor. In case 2, the tumor was encapsulated by a thin hypointense margin on both T1- and T2-weighted images, which suggested hemosiderin. CONCLUSION: The MR appearance may be of great value in the preoperative diagnosis of paraganglioma of the cauda equina.

Delayed paraplegia caused by the gradual collapse of an infected vertebra.

A case of delayed paraplegia caused by a gradual and progressive collapse of a vertebra after healing of pyogenic spondylitis is reported. A 73-year-old man was treated for a hematogenously seeded pyogenic spondylitis of the first lumbar vertebra. Magnetic resonance imaging showed a high signal intensity of the involved vertebra and adjacent discs and a paravertebral abscess without disc space narrowing. Eight months after healing of the infection, the patient had muscle weakness and paresthesia of the lower extremities, which gradually increased. The plane radiographs revealed a kyphotic deformity of 36 degrees with a collapse of the first lumbar vertebra.

[The signification of total elbow replacement in the treatment of rheumatoid arthritis].

The purpose of this paper is to emphasis the signification of total elbow replacement in the treatment of rheumatoid arthritis. Total elbow replacement were performed in twenty elbows in fourteen patients who had rheumatoid arthritis from 1982 to 1990. The follow-up period ranged from 2 to 9 years. Pain relief was complete in twelve patients. Preoperation flexion averaged 119 degrees, increasing to 127 degrees. Preoperation extension averaged -34 degrees, increasing to -24 degrees postoperation. There were no infection and fracture postoperatively. Radiolucent lines were seen in four humeral components, in one ulnar component. Proximal subsidence of the humeral component were found in two elbows. Posterior dislocation occurred in three elbows. In two cases, reduction was successful by three weeks immobilization in a plaster cast with the elbow in the flexion position. Transient ulnar nerve palsy was evident in two elbows. Revision surgeries were performed in two cases, which occurred dislocation and progressive subsidence. Multiple replacements of major joints were performed in ten patients. Two joints were replaced in two patients, three joints were replaced in six patients, four joints were replaced in two patients. Four total elbow replacements were performed accompanied with other joints replacement in the same anesthesia. We recommended two joint replacements in the same anesthesia in patient with good general condition. All patients had functional improvements after total elbow replacement, especially reaching of the arm. Four patients improved the walking by being able to use stich after total elbow replacement.

Extraosseous calcified plasmacytoma causing thoracic myelopathy.

We report on a rare, calcified, plasma cell tumor of the spine causing progressive myelopathy. Other unusual features were the lack of an osseous lesion at the site of the mass, considerable calcified amyloid within the mass but no identifiable amyloid elsewhere, and normal serum immunoelectrophoresis.