Kinematics and stabilizing roles of capsuloligamentous structures in index metacarpophalangeal joint

Abstract

s 369 KINEMATICS AND STABILIZING ROLES OF CAPSULOLICAMESTOUS STRUCTURES 1s ISDEX METACARPOPHALAN’GEAL JOIST AKIO MINAW. KAI-NAN As, WILLIAM P. COOKEY III. ROS.ALD L. LINSCHEID and EDMUND Y. S. CHAO. Gross examination of the metacarpophalangeal collateral ligaments of human cadaver specimens demonstrated that the ligaments were separated into two layers, one superficial and the other deep. The distances between origin and insertion of the collateral ligaments were measured with biplanar radiographic technique throughout the range of joint flexion. Dorsal and volar portions of both collateral ligaments were found to be under tension in flexed and extended positions, respectively. The relative contribution of the collateral ligaments to joint stability was studied by using stiffness tests on an MTS machine. The results of sequential sectioning of the ligaments indicate that the radial collateral ligament contributed to constraint of pronation and adduction, while the ulnar collateral ligament mainly contributed to constraint of supination and abduction. The volar plate was important in preventing dorsal displacement, while the dorsal capsule was found generally insignificant. MATHEMATICAL MODEL OF THE HIP CAPSULE IN CONGENITAL HIP DISEASE GEORGE T. RAB (Department of Orthopaedic Surgery, Universi!y of California, Davis, CA, U.S.A.) A three-dimensional mathematical model of the hip capsule in bony structures has been devised to allow study of the elfect of femoral position on capsular tightness in intra-articular stability. The model has been used to investigate factors in stability of congenitally dislocated hips. Common positions clinically in use for immobilization of the hip are successful because they twist the capsule, eliminating redundancy. Clinically observed persistent instability after capsulotomy is quantitated and confirmed. The capsule is also found to be important in procedures which have been generally thought of as bony; namely, Salter osteotomy and varus derotation osteotomy. AN ANALYTICAL STEREOPHOTOGRAMMETRIC METHOD TO iMEASURE THE THREEDIMENSIONAL GEOMETRY OF ARTICULAR SLRFACES R. HUISKES and A. DE LANGE (Biomechanics Section, Laboratory of Experimental Orthopaedics, University of Nijmcgen, 6500 HB, The Netherlands) Accurate description of the three-dimensional geometry of articular surfaces in skeletal joints have become essential information in several kinds of biomechanical investigations. To measure these data a technique was deveioped, based on analytical stereophotogrammetry, which, as compared to other methods reported, is believed to be a good cost-efficient compromise between accuracy and simplicity. Tests were performed on known curved surfaces,and a total accuracy (95 % confidence interval) between about 0. I and I.5 mm in the threedimensional position of a surface point was found to be possible, depending on the equipment and conditions chosen. This method was applied to measure the geometry of knee-joint surfaces and to evaluate the locationdependent thickness of the cartilage. COMPUTER MODELLING OF PROXIMAL FEMUR OSTEOTOMIES D. R. PEDERSEN and R. A. BRAND (Orthopaedic Biomechanics Laboratory, University of Iowa Hospitals and Clinics, Iowa City, IA, U.S.A.) We have developed techniques to predict mechanical effects of musculo-skeletal operations on joint loads and muscle force distribution. Biological effects are not addressed. This study investigates 10, 20 and 30’ intertrochanteric varus-valgus osteotomies and ante-retroversion rotations of the proximal femur. Assuming surgical intervention is to help the patient achieve a normal gait pattern, these anatomic changes were introduced into our gait analysis model with normal data. While littleeffect was seen on peak hip, knee and patello-femoral resultants, the femoral head experienced 59 % to 1707; of normal anterior force in the 30’ retro-anteversion simulations. Anteversion of 30’ caused 19% and 10 TtA increases in the gluteus minimus and medius and a 22 y0 decrease from normal in the gluteus maximus. Thirty degree retroversion elicited 21%. 20% and 60 % increases in these same three muscles. The rectus femoris and tensor fascia latae experienced a 33 % increase after 30” anteversion and a 33 % decrease after femoral retroversion. These muscles remained within 10% of normal after varus-valgus displacement, except the gluteus minimus at 150% of physiologic in 30’ valgus.