Faculty Bibliography

Laboratory measurement of the tensile forces on the plate fixation screws of the sliding hip nail demonstrated that most of the force is borne by the proximal three screws in an intertrochanteric fracture model. Testing of an intact femur, which simulate a healed femur, demonstrated a proximal shift of the screw forces. Four screws appear adequate for fixation if screw torque is controlled

Cyclic loading of Ti-6-4 and Co-Cr-Mo (cast) test samples with grit-blasted or waffle-textured surfaces coated with a plasma-sprayed 50-mum HA layer was performed in air, Ringer's solution (5% dextrose), 0.9% NaCl (Tris buffer, pH 7.40), and balanced Hank's solution. Maximum interfacial stresses in bending of 40 ksi (280 MPa) and 20 ksi (140 MPa) were utilized, and the specimens tested to 10 6 cycles at 5 Hz with a MTS servohydraulic machine. Tested samples were examined by optical microscopy to determine coating integrity and thickness and by scanning electron microscopy (electron backscatter mode and EDAX) to determine surface morphology and chemical changes. The following observations were made: (1) Samples cyclically tested in solutions showed a general thinning of the coating, accentuated in the higher-stressed regions. (2) Samples tested with an equivalent static load in the solutions did not show this centralization. (3) Bare metal interface surfaces were noted on most of the edges of highly stressed central specimen regions, in several entire central regions, and on the upper surfaces of some of the waffled samples. (4) The specimens tested in Ringer's solution (pH 4.70 initially) demonstrated the most dramatic coating deterioration. (5) The coatings on titanium appeared more stable than these on Co-Cr as tested in all solution environments for both surface types. The HA coating evaluated in this experiment demonstrated increased instability when cyclically loaded in in vitro solutions of lowered pH and depleted cations (Ca 2+) at stress levels of 280 MPa.(ABSTRACT TRUNCATED AT 250 WORDS)

Early onset osteoarthritis of the hip associated with osteopetrosis has been described in the literature. The surgical management of these patients has been difficult and fraught with complications. We describe a case in which a custom resurfacing hip arthroplasty was performed in a patient with osteopetrosis and severe osteoarthritis of the hip.

A case of a dissociation of a metal-backed patellar component with a resultant metallic synovitis is presented. The mechanism of failure is discussed and an analysis of patellar component design is reviewed.

An acrylic-headed prosthesis was removed after 30 years and analyzed for material deterioration. Although the acrylic head showed some wear and minor corrosion of the cobalt-chromium stem was found, tissue responses were not significant, indicating that use of these materials is consistent with the long-time survival of a prosthesis

Aortitis with associated aortic insufficiency is a well-known extra-articular manifestation of ankylosing spondylitis and other HLA-B27 associated spondyloarthropathies in adults. The cardiovascular histopathology is distinct from other forms of inflammatory and degenerative valve disease. Clinical cardiac involvement may be slowly progressive or fulminant and life-threatening. Mitral valve involvement associated with juvenile onset ankylosing spondylitis has rarely been reported. This article discusses a case of juvenile onset spondylitis in which associated aortic, and possibly mitral, valve disease dominated the clinical course for many years before axial joint disease required total replacement of the right hip

Marked bending prior to fatigue failure of the femoral component of a total hip arthroplasty points out the necessity for proper valgus placement of the prosthesis in the femoral shaft, especially in large active patients. This failure also indicates the need for limiting activities in such a patient.