Norimasa Iwasaki

Normal hip joint contact pressure distribution in single-leg standing--effect of gender and anatomic parameters.

A practical and easy-to-use analysis technique that can study the patients hip joint contact force/pressure distribution would be useful to assess the effect of abnormal biomechanical conditions and anatomical deformities on joint contact stress for treatment planning purpose. This technique can also help to establish the normative database on hip joint contact pressure distribution in men and women in different age groups. Twelve anatomic parameters and seven biomechanical parameters of the hip joint in a normal population (41 females, 15 males) were calculated. The inter-parameter correlations were investigated. The pressure distribution in the hip joint was calculated using a three-dimensional discrete element analysis (DEA) technique. The 3D contact geometry of the hip joint was estimated from a 2D radiograph by assuming that the femoral head and the acetabular surface were spherical in shape. The head-trochanter ratio (HT), femoral head radius, pelvic height, the joint contact area, the normalized peak contact pressure, abductor force, and the joint contact force were significantly different between men and women. The normalized peak contact pressure was correlated both with acetabular coverage and head-trochanter ratio. Change of abductor force direction within normal variation did not affect the joint peak contact pressure. However, in simulated dysplastic conditions when the CE angle is small or negative, abductor muscle direction becomes very sensitive in joint contact pressure estimation. The models and the results presented can be used as the reference base in computer simulation for preoperative planning in pelvic or femoral osteotomy.

Limb Replantation in the Rat

Replantation of amputated parts of the body by microvascular techniques has become a fairly common clinical procedure. To improve the success rate of this procedure, a considerable number of basic studies have been performed using experimental models of various animals [1–4].The rat hind limb amputation and replantation model has been especially widely used because rats are inexpensive and easy to handle, and because the diameter of their femoral vessels approximates that of the human finger and of various subcutaneous island flaps.

Allograft of Composite Tissues: Experimental Model in the Rat

Early experimental studies of vascularized joint and whole-limb allografts were performed using large animal models [1-6]. However, in some studies, a lack of defined major histo compatibility complex (MHC) barriers in these animals yielded variable allograft rejection and did not permit syngeneic controls. On the other hand, the rat is most suitable for studies of organ allogeneic transplantation, because a variety of inbred strains are available. In addition, with the development of microsurgical technique, the size of this animal is sufficient to permit a vascular anastomosis to be performed.