Medialization of the patella in total knee arthroplasty.

Patellar complications of total knee arthroplasty remain the most common cause of pain and reoperation. Laboratory studies have suggested that medialization of the patella will improve tracking of the patella on the trochlea of the femoral component. The purpose of this study was to determine if clinical medialization of the patellar component on the patellar bone would improve tracking of the patella as demonstrated radiographically. Sixty-two knees were randomized so that 31 knees had a centrally placed patellar component and 31 had the patellar component placed on the medial two thirds of the patellar bone. There was no difference between the two groups with respect to either clinical or radiographic results in the first year after surgery. There was no improvement compared with previous reports in the incidence of tilt and displacement. The one improvement was a reduction in the incidence of lateral release. Thus, consequences of lateral release such as postoperative morbidity, avascular necrosis of the patella, and stress fracture of the patella can be avoided. It is recommended that the patellar component be placed on the medial two thirds of the patella to reduce the occurrence of lateral release. Tracking of the patella during surgery can be assessed using a single suture placed at the superior pole of the patella, and this technique in combination with the no-thumbs test provides an additional means of evaluation for patellar tracking.

Failure mechanisms of anatomic porous replacement I cementless total hip replacement.

The APR-I Hip System was designed for metaphyseal bone attachment by proximal patch porous coating and the acetabular component was a hemisphere fixed with screws. The results of 100 consecutive primary total hip arthroplasties performed with the APR-I were studied in patients still alive after an average of 6.7 years. The selection of hips for implantation of this hip system was limited to those patients in whom a satisfactory intraoperative fit could be obtained. This resulted in a distribution of patients such that 75% were younger than age 65 years and only 15% had osteoporotic bone. The revision rate was 16% with a mechanical failure rate of 11%. Seventy percent of hips had progressive loss of fixation. loss of femoral component fixation was correlated with younger patient age, higher patient activity level, metaphyseal fill of less than 90%, and increased polyethylene wear and osteolysis. Eighty-nine percent of hips maintained femoral neck contact with the porous coated collar. The acetabular component was well fixed in 97% of hips. The failure rate of the APR-I stem is unacceptably high and this stem is no longer used by the authors.

Visual versus quantified digital radiographic determination of bone density.

Quantitative digital radiography (QDR) was used to assess the ability of physicians to determine bone mineral density (BMD) loss from a series of plain radiographs. Twenty-four spinal cord injured patients underwent QDR of the left knee. Seven of the 24 were selected, each of whom had bone mineral loss from 10-70% in 10% increments as assessed by comparison to average BMD of age-matched controls, and a standardized AP radiograph of the left knee was performed. Twenty-five independent examiners (orthopaedic surgeons and residents) were then asked to view the randomly arranged radiographs and visually determine the amount of BMD loss for each radiograph as compared to a control radiograph at 100%. Chi square analysis of the data revealed that the distribution of responses was significantly different than expected at the p less than .01 level. Taking into account that responses may have erred by +/-10%, the distribution of responses was again found to be significant at the p less than .01 level. An accurate determination of BMD loss was achieved only at 10% bone loss and 70% bone loss. The results of this study suggest that the visual determination of bone loss based on plain radiographs is accurate only at very low or very high levels of bone loss. Using standardized techniques, only near normal radiographs or radiographs with at least 70% BMD loss can be assessed accurately.

Complete posterior sternoclavicular epiphyseal separation. A case report and review of the literature.

A review of the literature shows that fractures of the medial clavicular physis rarely occur. Fractures of the medial clavicular physis was diagnosed in a 14-year-old boy. Bony closure of this physis may not be complete until as late as 25 years of age. Complete fracture-separations of this physis, with posterior displacement into the mediastinum, should be included in the differential diagnosis of children and any young adult patients with an apparent posterior sternoclavicular dislocation.

Routine use of magnetic resonance imaging in idiopathic scoliosis patients less than eleven years of age.

The purpose of this study was to determine the incidence of intraspinal pathology presenting as idiopathic scoliosis in children less than 11 years of age and otherwise neurologically normal. Twenty-six consecutive patients (5 boys, 21 girls) with idiopathic scoliosis measuring at least 15 degrees were studied with magnetic resonance imaging. Five children (19.2%) were diagnosed by magnetic resonance imaging to have Chiari-I malformations with hydromyelia (two patients), syringomelia (one patient), intramedullary tumor (one patient) and terminal lipoma (one patient). Only two of the five patients had left thoracic curves. Intramedullary spinal cord pathology can present as scoliosis without neurologic signs. Scoliosis can be the initial neurologic sign suggesting intraspinal pathology, and magnetic resonance imaging is indicated in routine evaluation of children less than 11 years of age.