V Wright

Changes in joint laxity occurring during pregnancy.

We have studied changes in peripheral joint laxity occurring during pregnancy in 68 females using both the finger hyperextensometer to quantify laxity at the metacarpophalangeal joint of the index finger and Beighton et al.s modification of the Carter and Wilkinson scoring system. Although the latter system recorded no change, the more sensitive hyperextensometer demonstrated a significant increase in joint laxity during the last trimester of pregnancy (0.02 greater than p greater than 0.01) over the readings from the same individuals after parturition. When primigravidae and multigravidae were compared, a highly significant increase in laxity was found in women having their second baby over those having their first (0.01 greater than p greater than 0.001), though no further increase in laxity occurred in subsequent pregnancies.

Transient Elastohydrodynamic Lubrication Models for the Human Ankle Joint

An equivalent bearing was proposed to represent the normal human ankle joint. The geometry was based on measurements of dissected ankle joints and tissue properties were obtained from the work of previous investigators. Theoretical models were developed to estimate the cyclic variation in lubricant film thickness and coefficient of friction during repetitive activities such as walking. Solutions were obtained for various combinations of input parameters. For the conditions representing the walking cycle, film thicknesses of about 0.7 μm were calculated. Although this value was smaller than most previous measurements of the rms roughness of cartilage, it was not much smaller and suggested that transient elastohydrodynamic lubrication played a role in synovial joint lubrication. The possibility of full fluid film lubrication was supported only when a very high input viscosity was employed, based on values estimated from the previous experimental studies of the boosted lubrication mechanism. Also, an attempt...

Some new evidence on human joint lubrication.

Theoretical consideration has been given to the use of pendulum machines which are used to examine the frictional properties of human joints by incorporating them as fulcra. As a result, a new type of pendulum machine has been built which incorporates the facility to apply sudden loads to the joint on starting the swinging motion, and also the ability to measure directly the frictional torque experienced by the joint. The results obtained from natural hip joints indicate the presence of squeeze film lubrication under conditions of sudden loading of a joint. In addition, a self-generated fluid film process was observed at low loads while at higher loads boundary lubrication appeared to be important. These results have been used to describe the lubrication regimens occurring in a normal activity such as walking. A single experiment carried out on a hip from a patient suffering from severe rheumatoid arthritis has also been reported and the frictional resistance was seen to be increased fifteenfold compared to a normal hip.

Behaviour of synovial fluid on surfaces of articular cartilage. A scanning electron microscope study.

Much attention has been given to the mechanics of synovial joints from a descriptive aspect and to studies relating to joint lubrication. The synovial fluid has been analysed and details of its composition are known (Ropes and Bauer, 1953). The principal constituent is hyaluronic acid-protein complex, the acid molecule having been shown to be a non-branched chain of repeating units with hydroxyl end-groups on each unit (Meyer, 1931). The acid-protein complex is responsible for the viscous properties of the synovial fluid (Negami, 1964; Davies, 1966) and it is fairly certain that it plays an important function in protecting the cartilage surfaces. A reasonably good picture has been obtained of the structure of articular cartilage, which is understood to consist of bundles of collagen fibres in a ground substance, chondroitin sulphate, with a high water content. The collagen bundles on the surface are believed to lie parallel to it. Those below are randomly or perpendicularly orientated to the surface depending upon the age and condition of the cartilage. (Benninghoff, 1930; Martin, 1953; Little, Pimm, and Trueta, 1958.) The remarkable lubrication characteristics of joints have been found to be due to the combination of properties of synovial fluid and articular cartilage. From experiments using a reciprocating friction machine and by measuring the topography of the surfaces of cartilage with stylus equipment, it has been concluded that the cartilage surfaces are prevented from contacting primarily because of the formation of trapped pools of lubricant (Dowson, Longfield, Walker, and Wright, 1969). Furthermore, it has been shown that, under some conditions,

Dimensions of the knee. Radiographic and autopsy study of sizes required by a knee prosthesis.

Increasing interest is developing in the design of a knee prosthesis (British Orthopaedic Association, 1970). Some prostheses have used the principle of a hinge (Walldius, 1957; Shiers, 1960). Others have tried a prosthesis of a closer geometry to that of the natural joint (Platt and Pepler, 1969). The prosthesis developed in Leeds (Fig. 1) has two components: a metallic shell that has almost the same geometry as the natural femoral condyles, and a plastic disc with a slot

Survey of satisfaction with care in a rheumatology outpatient clinic.

Consumer satisfaction is increasingly recognised by hospital administrators and health care providers as an important aspect of health care. A study was undertaken to investigate the satisfaction with care among patients with rheumatoid arthritis (RA) attending a rheumatology outpatient clinic at Leeds General Infirmary. The Leeds satisfaction questionnaire was developed and rigorously tested for reliability (Cronbachs alpha) and stability (test/retest). The Leeds satisfaction questionnaire was then completed by 70 patients with RA who had attended the Leeds General Infirmary on at least three previous occasions. The results showed that patients were, in general, satisfied with the care they received. The highest satisfaction scores were obtained on the scale for technical quality and competence of health professionals. The least satisfaction was accredited to the difficulty of unscheduled access to the clinic and the lack of continuity with the providers of care. The time spent in the waiting area before consultation was highlighted as the one aspect which caused the greatest dissatisfaction.

An Evaluation of the Ratio between the Tensions along the Quadriceps Tendon and the Patellar Ligament

An experiment was devised whereby physiological loads could be applied to the quadriceps tendon of cadaveric knee joints so that the ratio of tensions in the quadriceps tendon and the patellar ligament could be determined. On two knee joints, radiographs were taken before testing, so that the theoretical ratio of the tensions could be evaluated and compared with the experimental results. As the knee was flexed, the ratio of the tensions, frequently assumed to be unity, reduced by up to fifty per cent.

A comparison of clinical assessments of disease activity in rheumatoid arthritis.

Six clinical assessments of disease activity, including a new summated change scale (SCS), have been compared in a group of 30 patients with rheumatoid arthritis seen on 8 separate occasions during their first 6 months of therapy with either D-penicillamine or hydroxychloroquine. Articular index and grip strength correlate best with erythrocyte sedimentation rate and C-reactive protein, pain score and early morning stiffness less well, and summated change score and joint circumference least well. Articular index and grip strength also correlated well with the other clinical parameters and are therefore judged to be the best clinical indices of change in treatment with these drugs.

Mode of aggregation of hyaluronic acid protein complex on the surface of articular cartilage.

There is a great deal of experimental evidence that the frictional forces between sliding cartilage surfaces lubricated with synovial fluid are very low under normal conditions. Considering coefficient of friction as the meaningful measure of friction (i.e. tangential force resisting sliding divided by the normal load forcing the sliding surfaces together), typical values for cartilage on glass have been found to be 0-002 to 0-01 (McCutchen, 1962; Walker, 1969). A similar range was found for the ankle joints of dogs (Linn, 1968). However, under certain conditions, the coefficient of friction can be much higher than the range quoted. For instance, a test on a dog ankle joint was run for up to 6 hours under conditions of starved lubrication (Linn, 1968), and the coefficient of friction was found to be 0 1. For cartilage on glass, even higher figures have been obtained (Walker, Dowson, Longfield, and Wright, 1968).

Quantitative study of stiffness in the knee joint.

Data from a knee arthrograph, which imparts a passive sinusoidal motion to the joint and measures the resistive torque and displacement, have been shown to be reproducible. Tests carried out on joints (from 49 males, 21 females) showed that the energy loss per cycle of the joint increased with age for both sexes but the peak to peak torque (elastic stiffness) did not vary with age. Muscle bulk had a large influence on the stiffness (both dissipative and elastic) of the knee as did the size of the joint itself. Womens knee joints exhibited lower values of dissipative energy loss and peak to peak torque than mens for all ages and sizes of joints.