ELSEVIER Chicul Biomechunics Vol. 12, No. 7/X, pp. 482-490. 1YY7 0 lYY7 Elscvicr Science Ltd. All rights reserved Printed in Great Britain 02%W33197 $17.00 +O.OO PII: SO268-0033(97)00032-6 New concepts - biomechanical studies of a newly designed femoral prosthesis (cervico- trochanter prosthesis) ChumHsiung Shihl, Weng-Pin Chen*, Ching-Lung Tail, Rong-Fu Kuo3, Chi-Chuan Wu’, Chih-Hwa Chenl ‘Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Taoyuan, Taiwan, Republic of China; 2Department of Biomedical Engineering, Chung-Yuan Christian University, Taoyuan, Taiwan, Republic of China; 30rthopedic Research Laboratory, Veterans General Hospital, Taipei, Taiwan, Republic of China Abstract Objective. A newly designed stemless (cervico-trochanter) prosthesis was developed for the purpose of reducing the incidence of the stress-shielding effect caused by the traditional stem-type prosthesis. Design. Both mechanical test and three-dimensional finite element analysis were performed for comparing the differences of strain and stress distributions between the intact, C-T and PCA prosthetic femora. Background. The stress-shielding effect and polyethylene (PE) wear debris were thought to be the main factors that resulted in local bone loss after the implantation of stem-type prostheses. In this study, we developed the new C-T prosthesis, which aimed to resolve the above-mentioned problems. Methods. Six pairs of femora taken from human male cadavers were used to compare the strain magnitudes of intact (n = 12), C-T (n = 12) and PCA (n = 4) prosthetic femora in specific positions. Failure load tests of C-T (n = 8) and PCA (n = 12) prosthetic femora were also carried out from the load-displacement curve. The analysis of variance (ANOVA) test was used for statistical analysis. In addition, three-dimensional finite element stress analyses were performed using a commercial package, ANSYS, on a Convex 3810 computer. Results. Both mechanical test and finite element results showed that the C-T prosthetic femora has a lower stress-shielding tendency than the PCA prosthetic femora (P<O.OOl). The C-T prosthetic femora also withstood an average bearing load of 6312 N, which is greater than that of the PCA prosthesis at 5358 N (P<O.Ol). Conclusions. The C-T prosthetic femur could withstand a higher failure load than the PCA prosthesis, which effectively reduced the incidence of the stress-shielding effect. Moreover, the particular design of the C-T prosthesis also reduced localized osteolysis because of the overall coverage of the neck-trochanteric area. Relevance Several significant findings were identified in this study for clinical purposes. The new concept of the C-T prosthesis may prove to be useful in future prosthesis design. 0 1997 Elsevier Science Ltd. All rights reserved Key words: Proximal femoral strains, stemless prosthesis, finite element analysis, stress shielding Clin. Biomech. Vol 12, No. 718, 482-490, 1997 Introduction patients, and an increase in the types of prostheses The popularization of hip arthroplasty has brought about a decrease in the average age of operated which are available’-5. Despite improvements in surgical techniques which aim to prevent complica- tions, the loosening of the femoral stem during the Received: 1 October 1996;Accepted: 17 April 1997 long-term follow-up period still remains a threat to patientP9. Complicated revision surgeries are Correspondence and reprint requests to: Dr Chun-Hsiung Shih, Department of Orthopedic Surgery, Chang Gung Memorial Hospital, No. 5 Fu-Hsin St. 333, Kweishan, Taoyuan, Taiwan, R.O.C. Tel: +886 3 3281200 (ext. 2163); Fax: +886 3 3285818 usually required. During the initial stages of the development of hip arthroplasty, surface replacement was once widely