Hypercholesterolemia: an association with osteonecrosis of the femoral head.

To determine whether hypercholesterolemia is an associated factor for idiopathic avascular necrosis, serum cholesterol levels were measured in all patients presenting with idiopathic avascular necrosis of the femoral head from December 1987 to December 1995. Of 77 patients, with 114 affected hips, presenting with avascular necrosis of the femoral head, 58 patients, with 81 affected hips, were excluded for known associated risk factors. Of the remaining 19 patients (33 hips) who were diagnosed with idiopathic avascular necrosis, 16 had serum cholesterol levels that were statistically elevated (mean value, 254 mg/dL) compared with accepted age-matched control standards (P < 0.0031). Four of the 16 patients were taking cholesterol-lowering medications at the time of initial evaluation and testing. In addition, 12 of the 16 patients had bilateral avascular necrosis, suggesting that the systemic effect of hypercholesterolemia may be involved in the pathophysiology of osteonecrosis. These results suggest an association between elevated serum cholesterol levels and idiopathic avascular necrosis of the femoral head.

External fixation of pediatric femoral fractures.

Fifteen pediatric femoral fractures in 14 patients were treated with external fixation using the EBI Orthofix unilateral external fixator. The average patient age was 8.5 years (range, 3-13 years). There were 7 children with multiple injuries and 7 with isolated fractures. The average duration in the fixator was 63 days; average followup was 34 months. All 15 fractures healed without additional operative intervention. Average angulation at the fracture site was 4.4 degrees in the anteroposterior plane (range, 0 degrees-10 degrees) and 4.6 degrees in the lateral plane (range, 0 degrees-11 degrees). There were 5 pin tract infections, all of which resolved with systemic antibiotics. There was 1 case of refracture in a boy with muscular dystrophy. Ten patients had clinically equal leg lengths, 3 patients had < 1 cm of inequality, and 1 patient had a 1.5 cm discrepancy. External fixation is a well-proven technique for managing pediatric femoral fractures in the child with multiple injuries. It is also an effective means of treating isolated femoral fractures in the pediatric population.

Clinical evaluation of crossed-pin versus lateral-pin fixation in displaced supracondylar humerus fractures.

The radiographs and patient charts of 47 children treated with closed reduction and percutaneous pin fixation of displaced supracondylar humerus fractures were reviewed. Twenty-seven fractures were fixed with crossed medial and lateral pins. Twenty fractures were treated with two parallel laterally placed pins. Baumann's angle on the anteroposterior elbow film and the humerocapitellar angle on the lateral elbow film were independently measured by the three authors on initial postoperative films and on films taken at the time of pin removal. No statistically significant differences regarding maintenance of reduction were found when comparing the two fixation groups. There were two complications in the medial pin group (one cubitus varus and one ulnar nerve injury) and none in the lateral-pin group. We conclude that crossed-pin fixation offers no clinically significant advantage over two laterally placed pins in the treatment of supracondylar humerus fractures.

Type X collagen in fracture callus and the effects of experimental diabetes.

Studies of fracture repair in diabetes have shown decreased mechanical strength and total collagen in the callus. Type I and Type II collagen are synthesized by bone and cartilage cells, respectively, while Type X collagen is synthesized by hypertrophic chondrocytes in endochondral ossification. A standardized fracture model was chosen to investigate extracellular matrix changes during fracture healing of normal and diabetic rats. Histological examination of the fracture callus in both normal and diabetic animals showed progression from a fibrous tissue to cartilage to bone. An antiserum to Type X collagen was prepared, and immunostaining was observed in the matrix surrounding the hypertrophic chondrocytes. Fracture calluses from streptozotocin induced diabetic rats had similar histology and immunostaining to controls. Radiolabelled proteins were extracted from the calluses of normal and diabetic rats to measure Type X collagen. Type X collagen expression in the fracture callus of normal rats reached a maximum at day fourteen and was decreased by between 54% and 70% in the fracture callus of diabetic rats. The decrease in Type X collagen synthesis may have a role in the defect of fracture healing in diabetes.