Association between changes in knee load and effusion-synovitis: evidence of mechano-inflammation in knee osteoarthritis using high tibial osteotomy as a model.

OBJECTIVE: Although mechanically-induced inflammation is an appealing explanation linking different etiologic factors in osteoarthritis (OA), clinical research investigating changes in both biomechanics and joint inflammation is limited. The purpose of this study was to evaluate the association between change in surrogate measures of knee load and knee effusion-synovitis in patients with medial compartment knee OA undergoing high tibial osteotomy (HTO). METHODS: Thirty-six patients with medial compartment knee OA and varus alignment underwent 3D gait analysis and 3T magnetic resonance imaging (MRI) preoperatively and 1 year after medial opening wedge HTO. Primary outcome measures were the change in the external knee adduction moment impulse during walking and change in knee suprapatellar effusion-synovitis volume manually segmented on MRI by one blinded assessor. RESULTS: Mean (SD) knee adduction moment impulse [24.0 (6.5) Nm•s] and knee effusion-synovitis volume [8976.7 (8016.9) mm3] suggested substantial preoperative medial knee load and inflammation. 1-year postoperative changes in knee adduction moment impulse [-10.1 Nm•s (95%CI: -12.7, -7.4)], and knee effusion-synovitis volume [-1856 mm3 (95%CI: -3830, 117)] were positively correlated [r = 0.60 (95% CI 0.34, 0.78)]. Simple linear regression suggested a 448 mm3 (95%CI: 241, 656) reduction in knee effusion-synovitis volume per 1 Nm•s reduction in knee adduction moment impulse. Change in knee adduction moment impulse explained 36% (R2 = 0.36) of the variance of change in knee effusion-synovitis volume. CONCLUSIONS: Reduction in medial knee load is positively associated with reduction in knee inflammation after HTO, suggesting the phenomenon of mechano-inflammation in patients with knee OA.

Some early dental extraction instruments including the pelican, bird or axe?

This paper is the result of the cataloguing, preparation for exhibition and the study of some early dental extraction instruments. The artefacts included elevators, pelicans, keys, forceps and pincers produced by unidentified makers or known firms. An evolutionary process is demonstrated from the simplest instrument leading to those used today. The naming of the artefacts follows a path relating to their method of use and to their appearance in regard to common everyday objects and animals or their parts. All were found to exhibit this association except the pelican which did not fit its long held position.

Mandibular movement in lateral excursions.

Mandibular movement during lateral articulatory movements was studied in young subjects with no apparent dental disease or malocclusion. A closed circuit television movement detector was used. Signals of each vector of movement were combined in pairs to provide envelopes of movement in three planes, mutually at right angles. Symmetry of movement was not as common as expected and sudden small changes in direction were frequently observed. Maximum displacement in each vector of movement was not always coincident. It is postulated that treatment factors, such as simple restoration of teeth, are initiating factors which cause variation in mandibular movement from the normal.

An analysis of tooth position on initial tooth contact.

A closed circuit television movement detector was used to study mandibular movement in the form of tooth tapping, in subjects with no apparent dental disease or malocclusion. The velocity and form of various phases of movement was studied, in the transverse, sagittal and coronal planes, from measurements made on u.v. charts and X-Y recordings. It was shown that closing movements were more direct and faster than opening movements; that initial contact on closing is in a well-defined contact area, followed by a sliding of cusps over each other to a final centric position and that the closing path of the mandible in tapping movements is in the form of a smooth curve showing simple axis rotation through distances normally greater than those accepted clinically. It was also shown that microphone signals can be detected at times other than when normally expected, indicating displacement with tooth contact, at times other than at the fully intercuspated position.

In vitro strength of the human periodontal ligament.

The tensile properties of the human periodontal ligament were studied by direct loading and compression experiments. It was found that the ligament behaved in an elastic manner up to an elastic limit after which rupture occurred. The values obtained for the tensile strength of the ligament are in general agreement with those of other workers for similar tissues.

Research into mastication.

An electronic method of recording displacement was used to study mandibular movement during mastication. The technique enables the parameters of muscle activity, the sound of tooth contact, the force developed between opposing teeth, and the displacement of the mandible to be recorded at the same time on a single U/V chart. Previous reports on mandibular movement using cine-photographic techniques were confirmed in relation to mastication, but additional information was obtained in relation to muscle activity in the final closing movements. It appears that tooth contact initiates a latent-silent period in masseter and temporalis which occurs before movement is arrested in the final intercuspal position. It is considered that the kinetic energy of the mandible on closing is reduced by the cessation of activity in these two muscles during the silent period and finally absorbed by the crushing of food during the terminal intercuspal slide to rest. A description of mastication is given and a theory advanced that this may be controlled by a central clock mechanism.