RF testbed for thermoacoustic tomography.

Thermoacoustic signal excitation is a function of intrinsic tissue properties and illuminating electric field. De-ionized (DI) water is a preferred acoustic coupling medium for thermoacoustics because acoustic and electromagnetic waves propagate in DI water with very little loss. We have designed a water-filled testbed propagating a controlled electric field with respect to pulse shape, power, and polarization. Directional coupler line sections permit measurement of incident, reflected, and transmitted powers. Both S-parameters and E(y) measurement show that the electric-field distribution is relatively uniform in testbed. Comparing baseline power measurements to those taken with a test object in place yields power loss in the object, which should correlate to thermoacoustic signal strength. Moreover, power loss--and therefore thermoacoustic computerized tomography signal strength--is sensitive to the orientation of the object to the polarization of the electric field. This testbed will enable quantitative characterization of the thermoacoustic contrast mechanism in ex vivo tissue specimens.

Cyst of the ligamentum flavum.

STUDY DESIGN: A patient with sciatica resulting from a hemorrhagic cyst of the ligamentum flavum is reported. Surgical removal of the cyst relieved the patient of her sciatic symptoms. SUMMARY OF BACKGROUND DATA: Cyst of ligamentum flavum is an uncommon cause of radiculopathy. There are 13 cases in the literature. CONCLUSIONS: The differential diagnosis of benign interspinal extradural mass lesions includes spinal synovial cysts, ligamentum flavum cysts, perineural cysts, dermoid cysts, and parasitic cysts.

Anterior and posterior internal fixation of vertical shear fractures of the pelvis.

A laboratory study was undertaken to evaluate the effectiveness of alternative methods of fixation of unilateral vertical shear fractures of the pelvis. Prior to experimental testing, a biomechanical analysis was performed to estimate the forces that displace the hemipelvis in the presence of two different patterns of injury: an interforaminal sacral fracture and a disruption of the sacroiliac joint. These lesions were then experimentally created in five unembalmed human pelvises and sequentially fixed with an external Hoffmann frame alone, a Hoffmann frame with sacral bars, or sacral bars with either one or two bone plates placed across the symphysis pubis. Each pelvis/fixator system was mechanically tested by loading along the direction of the resultant muscle force predicted by the biomechanical analysis. During loading the proximal migration of the ilium was continuously recorded with a transducer. At intervals during loading, the three-dimensional displacement of the detached hemipelvis at the pubic symphysis was also measured using a stereophotographic technique. With both the sacral fracture and the sacroiliac disruption, the addition of posterior sacral rods substantially increased the strength and rigidity of fixation provided by the Hoffmann fixation frame alone (p less than 0.01). In specimens with a sacral fracture, the use of anterior plates with posterior rods restored 65-71% of the strength of the intact pelvis, in comparison with 46% observed with the combination of sacral rods with an anterior Hoffmann frame (p less than 0.01). All of the methods of fixation evaluated in this study were less successful in stabilizing the sacroiliac disruption.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterior discectomy, microscopic decompression, and fusion: a treatment for cervical spondylotic radiculopathy.

A consecutive series of 47 patients with cervical radiculopathy secondary to spondylosis were treated with complete discectomy, root decompression accomplished by microscopic foraminotomy on the affected side(s), and iliac graft fusion at the involved interspace(s). Forty of the 47 patients were contacted with an average follow-up of 15 months. Eighty-three percent of the patients were judged as having good results. Fusion of the involved interspace(s) occurred in 87% of cases, although this did not appear to correlate with the clinical results.

Unstable fractures of the pelvis treated by external fixation.

Forty-five patients with an unstable fracture of the pelvic ring, for whom the conventional treatment would have been bed rest with skeletal traction or with a pelvic sling, were treated with the Hoffmann external-fixation apparatus. In eighteen fractures of the lateral compression type and fourteen fractures of the anteroposterior compression type, the treatment was successful. Proximal migration of the hemipelvis occurred in four of the eleven patients with a fracture of the unilateral shear type. There were two deaths from associated injuries.

External fixation use in the management of massive upper extremity trauma.

Immobilization of fractures associated with instability and comminution by an external skeletal device facilitates wound care, skin coverage, and ultimate reconstructive surgery. External skeletal fixation was applied in 20 patients who sustained complex open injuries of the upper extremity. All injuries were associated with extensive soft tissue and skin defects. Associated neurovascular injuries included 14 nerve injuries and five major vascular injuries. The Hoffman fixation device was used in the majority of cases. Skin coverage was obtained in all patients by an appropriate method of skin grafts, pedicle flaps, and a free myocutaneous flap. Primary bone union was achieved in five of 16 patients. Ten of 16 patients required secondary procedure to obtain union in cases of delayed union or nonunion, and one case remained with a nonunion. Pin tract infection in three patients and osteomyelitis in two patients were effectively treated with antibiotics and appropriate surgery. The initial treatment goals of limb salvage, skin coverage, and bone stabilization without drainage or persistent osteomyelitis can be accomplished by the use of external skeletal fixation devices.

Subtrochanteric fractures of the femur treated with nail-plate devices: a retrospective study.

Fifty-four cases of nonpathologic subtrochanteric fractures of the femur were treated by fixation with nail-plate devices. Of the 48 final cases, 42 patients (88%) united successfully after a single operative procedure. Six patients (12.5%) developed a non-union and required further surgery, an experience similar to that of other authors. Ten per cent appears to be the expected non-union rate with nail-plate devices. At this time the Jewett nail and the compression screw should be regarded as part of the the orthopedist's armamentarium in the treatment of comminuted subtrochanteric fractures of the femur.