Effects of patellar tendon adhesion to the anterior tibia on knee mechanics.

The effects of patellar tendon adhesion on the knee extensor mechanism and on the kinematics and contact areas for both the patellofemoral and tibiofemoral joints were determined for five cadaveric knees in an open kinetic chain testing configuration. Patellar tendon adhesion decreased the distance from the inferior patellar pole to the tibial tuberosity, effectively creating patella infera. When compared with the controls, knees with adhesion had medial and distal translation of the patella, as well as increased patellar flexion.

Topography of the osteoarthritic thumb carpometacarpal joint and its variations with regard to gender, age, site, and osteoarthritic stage.

The articular topography of 46 osteoarthritic thumb carpometacarpal joints was quantitatively analyzed, as well as variations with regard to gender, age, site, and anatomic osteoarthritic stage. It was found that for osteoarthritic thumb carpometacarpal joints, (1) the opposing articular surfaces of elder and severely degenerated joints are more congruent than those of middle-aged and minimally or moderately degenerated joints, although the articular contact area is not significantly different when accounting for thinning of the cartilage layer with age or disease; (2) significant changes in joint topography due to osteoarthritis only occur in severely degenerated joints; (3) joints in women are less congruent, have smaller contact areas, and are likely to experience higher contact stresses than joints in men for similar activities of daily living that involve similar joint loads; and (4) osteoarthritic changes are less severe on the dorsoulnar aspect of the trapezium and the dorsal aspect of the metacarpal, which are known to be low load-bearing regions.

Finite deformation biphasic material properties of bovine articular cartilage from confined compression experiments.

In 1990, Holmes and Mow [Journal of Biomechanics 23, 1145-1156] developed a hyperelastic biphasic theory to describe finite deformation behaviors of articular cartilage. To date, however, no experimental finite deformation studies have been made to assess the ability of this constitutive model to describe its finite deformation behaviors (e.g.

The normal stress effect and equilibrium friction coefficient of articular cartilage under steady frictional shear.

During creep or stress relaxation, articular cartilage exhibits a time-dependent friction coefficient which has been shown to reach an equilibrium value, mu eq, as the tissue deformation equilibrates. This study investigates the frictional properties of articular cartilage explants under steady frictional shear and constant compressive strain after the tissue reaches stress-relaxation equilibrium. The two parameters measured are the normal force and frictional torque, from which the friction coefficient was then calculated.

Anatomy of the human patellofemoral joint articular cartilage: surface curvature analysis.

Articular cartilage surfaces of 49 human patellae and 24 distal femora were characterized by identifying distinctive features with surface curvature analysis. Paired specimens from the same donor generally exhibited natural symmetry, so only results from nonpaired specimens were considered (39 patellae and 19 femora). In 23 of 39 patellae, proximal median and lateral transverse ridges extended to form an oblique ridge resembling a skewed lambda (lambda).

A theoretical formulation for boundary friction in articular cartilage.

A theoretical boundary friction model is proposed for predicting the frictional behavior of articular cartilage, including its time-dependent, velocity-dependent, and load-dependent responses. This theoretical model uses the framework of the biphasic theory for articular cartilage, and provides a mathematical formulation for the principle that interstitial fluid pressurization contributes significantly to reduction of the effective friction coefficient. Several examples of the application of this theory are provided, which demonstrate that a variety of experimentally observed cartilage frictional behaviors can now be theoretically predicted.

Rolling resistance of articular cartilage due to interstitial fluid flow.

A mechanism which may contribute to the frictional coefficient of diarthrodial joints is the rolling resistance due to hysteretic energy loss of viscoelastic cartilage resulting from interstitial fluid flow. The hypothesis of this study is that rolling resistance contributes significantly to the measured friction coefficient of articular cartilage. Due to the difficulty of testing this hypothesis experimentally, theoretical predictions of the rolling resistance are obtained using the solution for rolling contact of biphasic cylindrical cartilage layers [Ateshian and Wang].

A theoretical solution for the frictionless rolling contact of cylindrical biphasic articular cartilage layers.

Previous studies have shown that interstitial fluid pressurization plays an important role in the load support mechanism of articular cartilage under normal step loading. These studies have demonstrated that interstitial fluid pressurization decreases with time if the applied load is maintained constant. In the present study, a theoretical solution is obtained for another common loading of articular cartilage, namely the contact of surfaces in rolling motion.

Contact areas in the thumb carpometacarpal joint.

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar-ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint.

An asymptotic solution for the contact of two biphasic cartilage layers.

This study addresses the hypothesis that interstitial fluid plays a major role in the load support mechanism of articular cartilage. An asymptotic solution is presented for two contacting biphasic cartilage layers under compression. This solution is valid for identical thin (i.

Computer simulation of glenohumeral and patellofemoral subluxation. Estimating pathological articular contact.

Analytic stereophotogrammetry and an interactive computer graphics program were used to obtain first order assessments of joint contact patterns in patellofemoral and glenohumeral joints, simulating normal and abnormal articulations. Precise (90 microns accuracy) computer graphic representations of the humeral head, glenoid, patella, and femoral articular surfaces were obtained from cadaver knees and shoulders. These surface representations were then manipulated into an articulated position, and joint contact areas computed by a proximity criterion.

A stereophotogrammetric method for determining in situ contact areas in diarthrodial joints, and a comparison with other methods.

Determination of contact areas in diarthrodial joints is necessary for understanding the state of stress within the articular cartilage layers and the supporting bony structures. The present study describes the use of a stereophotogrammetry (SPG) system [Huiskes et al., J.

A B-spline least-squares surface-fitting method for articular surfaces of diarthrodial joints.

The B-spline least-squares surface-fitting method is employed to create geometric models of diarthrodial joint articular surfaces. This method provides a smooth higher-order surface approximation from experimental three-dimensional surface data that have been obtained with any suitable measurement technique. Akima's method for surface interpolation is used to provide complete support to the B-spline surface.

Biomechanics of diarthrodial joints: a review of twenty years of progress.

A survey of some of the advances made over the past twenty years in understanding diarthrodial joint biomechanics is presented. Topics covered in this review include: biotribology (i.e.

Quantitation of in situ contact areas at the glenohumeral joint: a biomechanical study.

Glenohumeral arthritis may result from abnormal articular mechanics, and shoulder reconstructive procedures often rely implicitly on the belief that the restoration of normal articular mechanics is required to obtain satisfactory clinical results. Despite this, limited knowledge of normal or pathologic glenohumeral joint articular mechanics and contact is available. This study uses a stereophotogrammetry technique to determine contact areas in normal cadaver glenohumeral joints with intact ligaments and capsule through a large range of motion using simulated forces of the four rotator cuff muscles and three deltoid heads.

Curvature characteristics and congruence of the thumb carpometacarpal joint: differences between female and male joints.

Three-dimensional geometric models of the articular surfaces of the thumb carpometacarpal (CMC) joint were constructed using precise data obtained from stereophotogrammetry (SPG). It was demonstrated that by using a least-squares surface-fitting technique, the SPG data on the surface can accurately be described by a single parametric biquintic spline function. From this mathematical description, curvature maps of the surfaces were calculated for 13 CMC joints (eight females, average 64 yr old, five males, average 70 yr old).

Quantitation of articular surface topography and cartilage thickness in knee joints using stereophotogrammetry.

An analytical stereophotogrammetry (SPG) technique has been developed based upon some of the pioneering work of Selvik [Ph.D. thesis, University of Lund, Sweden (1974)] and Huiskes and coworkers [J.