RESUMEN
Cemented fixation of the femoral stem is the gold standard for patients older than 60 years. The importance of reliably achieving an adequate cement mantle has been shown in many studies. Currently, inspection and grading of plain radiographs is the accepted method for study of the cement mantle. However, the reliability of plain radiographs for this purpose has been questioned. In addition, the interobserver agreement of current grading systems has been shown to be limited. A new in vitro method of cement mantle analysis is described. Plastic replicas of six contemporary stems were implanted into femurs from cadavers. The specimens were imaged with a computed tomography scanner. Detailed, computer-assisted analysis of mantle thickness was done. Comparisons were made between designs. A subset was compared with standard radiographs. Plain radiographs overestimated thickness and underestimated the deficiencies. There was significant variability in the mantle produced by the different designs. Commonly used designs had deficiencies in their mantles by standard criteria despite proper surgical technique. The importance of being fully acquainted with the particular implant one uses is emphasized by these results. This is a valuable technique for investigation of the effects on the cement mantle of implant design, surgical technique, and patient anatomy.
Asunto(s)
Artroplastia de Reemplazo de Cadera , Cementos para Huesos , Prótesis de Cadera , Imagenología Tridimensional , Tomografía Computarizada por Rayos X/métodos , Distinciones y Premios , Ortopedia , Diseño de PrótesisRESUMEN
OBJECTIVE: To determine the prevalence of heterotopic bone formation in cemented versus noncemented total hip joint replacement. DESIGN: A prospective randomized controlled trial. Follow-up ranged from 2 to 6 years (mean 4 years). SETTING: A university hospital. PATIENTS: Two hundred and twenty-six patients who had primary or secondary osteoarthrosis of the hip were stratified according to type of fixation, surgeon and age. Patients were randomized within strata: 112 received noncemented total hip prostheses and 114 received cemented prostheses. The 2 groups were similar with respect to age and sex. INTERVENTION: Primary total hip arthroplasty. A cemented (methylmethacrylate) or noncemented prosthesis was inserted by a lateral surgical approach. MAIN OUTCOME MEASURE: The Brooker classification was used to grade heterotopic bone formation from postoperative radiographs. RESULTS: Overall, 148 (66%) hips had no heterotopic ossification, 56 (25%) were Brooker class I, 14 (6%) were class II, 8 (3%) were class III and none were class IV. In the noncemented group of patients, 76 (68%) hips had no heterotopic ossification, 25 (22%) were Brooker class I, 7 (6%) were class II, 4 (4%) were class III and none were class IV. In the cemented group of patients, 72 (63%) hips had no heterotopic ossification, 31 (27%) hips were Brooker class I, 7 (6%) were class II, 4 (4%) were class III and none were class IV. CONCLUSION: There was no significant difference in the prevalence of heterotopic ossification between cemented and noncemented total hip replacements in patients with osteoarthrosis.