In vitro analysis of periprosthetic strains following total knee arthroplasty.

Clinical case studies have disclosed certain risk factors associated with periprosthetic fracture in elderly patients. How the mechanical strength of the distal femur is changed by total knee arthroplasty (TKA) has not been elucidated. Using elderly cadaveric femora, this study evaluated both periprosthetic strains and associated fracture patterns arising from an in vitro simulation of a fall onto the distal femur. The data showed a significant increase in anterior and posterior mechanical strain following TKA. Neither stemless nor stemmed versions of two cemented Howmedica prostheses (Rutherford, NJ) reduced distal femur strains to baseline values. However, neither produced a disproportionate frequency of periprosthetic fractures. Although not formally evaluated herein, bone geometry/density may contribute more profoundly to the occurrence of periprosthetic fracture than the implants tested.

Single bone straight line graphs for the lower extremity.

Valuable information about growth and growth prediction in the lower extremity has been provided in the past by Anderson and Green, Moseley, and Menelans. Greater patient expectations and advanced techniques for lower extremity lengthening require more precise information regarding the growth characteristics of each long bone. A simple method for predicting growth is presented for the femur and tibia. Straight line graphs similar to one described previously by Moseley for the entire lower extremity have been drawn separately for the femur and tibia. Information from a contemporary population and new knowledge about growth plate activity have been included to provide more accurate predictions. By superimposing identically scaled growth remaining graphs on these single bone straight line graphs, a simple and accurate estimate is obtained for the timing and effect of epiphysiodeses or lengthening procedures.

Straight-line graphs for the prediction of growth of the upper extremities.

A simple graphic method was used for the prediction of growth and the determination of when a corrective procedure should be performed to equalize the lengths of the upper extremities. Straight-line graphs, similar to those described by Moseley for the lower extremities, were constructed for the radius, ulna, and humerus. The data for the current study were derived from a multidisciplinary, longitudinal study of growth in 244 healthy children (123 boys and 121 girls)--from infancy to skeletal maturity--and from previously constructed graphs depicting remaining growth. The use of this method can simplify the planning of an equalization procedure for an upper extremity.

Degenerative symptomatic lumbar scoliosis.

Scoliosis with progressive deformity can develop late in life. The authors studied 200 patients older than age 50 years with back pain and recent onset of scoliosis. Seventy-one percent of patients were women, and no patient had undergone spinal surgery. The curves involved the area from T12 to L5 with the apex at L2 or L3 and did not exceed 60 degrees. Degenerative facet joint and disc disease always were present, and the curves were associated with a loss of lumbar lordosis. Forty-five patients with severe pain and neurologic deficits were studied using myelography. Indention of the column of contrast medium was seen at several levels but was most severe at the apex of the curve. It was least severe at the lumbosacral joint. The curves progressed an average of 3 degrees per year over a 5-year period in 73% of patients. Grade 3 apical rotation, a Cobb angle of 30 or more, lateral vertebral translation of 6 mm or more, and the prominence of L5 in relation to the intercrest line were important factors in predicting curve progression.

Tobramycin-impregnated cement in total hip replacements.

The clinical effect of adding 1.2 g of tobramycin powder to each 40-g pack of powdered polymethylmethacrylate used in hip replacement surgery was investigated. Fifteen patients underwent total hip replacement in which a cemented femoral prosthesis and a cementless acetabular prosthesis were used. Postoperatively, the tobramycin levels in the blood and in the wound drainage fluid were measured. The serum tobramycin concentrations were low, whereas the wound drainage fluid contained highly effective antibacterial concentrations. There was no evidence of reaction or toxicity to the antibiotic-impregnated bone cement.

Knee replacement in morbidly obese women.

Sixty-six total knee replacements in 50 morbidly obese women with osteoarthritis were performed. The results in these patients were compared with 64 knee replacements in 50 nonobese women and with 50 obese women who did not have knee replacement operations. All obese patients were advised by a physician to lose weight and were counseled by a dietician. Five obese patients with six replaced knees and four nonobese patients were lost prior to follow-up study. Follow-up examinations were performed after 24 to 60 months, with mean of 33 months, in the remaining patients. No significant sustained weight loss occurred in the obese patients who had knee replacement operations or in obese patients who did not have surgical treatment. Eighty-six per cent of nonobese patients had excellent or good results from knee replacement surgical treatment. Fifty-seven per cent of morbidity obese patients had excellent or good results. There were two infections and two revision operations in morbidly obese patients and no infections and one revision in nonobese patients. Total knee replacement is safe and reasonably effective in the morbidly obese. However, the results are not comparable with those achieved in nonobese patients, and knee replacement should not be expected to facilitate weight loss.

Total hip replacement after central fracture dislocation of the acetabulum.

We performed total hip replacement (THR) for traumatic arthritis following central fracture dislocation of the acetabulum in 19 patients (15 men and four women). This situation is significantly challenging, as most patients have scarring, contractures, and unequal leg length. The average age was 49 years, and all patients were followed for a minimum of 2 years. A two-piece cementless acetabular component and a cemented or cementless femoral component were utilized. In each patient, prophylactic low-dose irradiation was administered to discourage heterotopic ossification, and gentamicin with either cefazolin or vancomycin were given as prophylaxis for infection. Overall, the results were excellent. The mean Harris hip score after surgery was 84. No infections, dislocations, or significant heterotopic ossification occurred. Limb length was within 1 cm in each patient. No revision surgeries were performed, and no components were roentgenographically loose. There was one case of transient nerve palsy. We conclude that THR after central fracture dislocation of the acetabulum is a safe and effective procedure.