Intra-articular Pressure in the Distal Radioulnar Joint: A Biomechanical Study.

PURPOSE: The aim of the study was to use cadaveric models to assess the effect of loading the forearm muscles in different forearm rotations, with or without disruption to the stabilizing components, on the intra-articular pressure of the distal radioulnar joint (DRUJ). METHODS: Ten forearms with no severe osteoarthritis or injury to the DRUJ stabilizers were used. They were placed in a vertical support, and pressure sensors measured pressure within the DRUJ in 5 forearm rotations (neutral, pronation, supination, extension, and flexion) under the following 6 conditions: 1) no loading; 2) loading (at 1/5 of the load per cross-sectional area) with no disruption; 3) loading with disruption of the triangular fibrocartilage complex (TFCC); 4) loading with disruption of the TFCC and ulnar ligaments (ULs); 5) loading with disruption of the TFCC, ULs and interosseous membrane (IM); and 6) loading with disruption of the TFCC, ULs, IM, and pronator quadratus (PQ). RESULTS: Under the no disruption-no load, no disruption-loaded, and disrupted TFCC conditions, the highest intra-articular pressures were recorded in supination. Compared with the no-load condition, pressure was greater in the no disruption-loaded condition with a mean difference (MD) of 1.57 kg/cm2 in a neutral position. In flexion, pressure was greater with a disrupted TFCC (MD, 4.3 kg/cm2). In supination, pressure was only greater with a disrupted TFCC (MD, 3.3 kg/cm2), and pressure decreased in the other disruption conditions. The pressures recorded did not differ from the no disruption-no load condition in pronation or extension. CONCLUSIONS: Pressures within the DRUJ changed with forearm rotations. In the no disruption-no load, no disruption-loaded, and disrupted TFCC conditions, intra-articular pressure was highest in supination. In flexion and supination with load and disruption of stabilizers, intra-articular pressure only increased significantly in the disrupted TFCC condition compared with no load. CLINICAL RELEVANCE: Based on our findings, exercises in supination should be avoided during the first phase of rehabilitation of TFCC injuries given the increased pressure on the DRUJ.

The loads developed by epicondylar and epitrochlear muscles across the elbow joint. A dynamic simulated model.

The radio-humeral joint has traditionally been believed to support most of the loads transmitted through the elbow. Load transfer through the elbow has been a controversial issue since the publication of the first biomechanical studies on the subject, most of which were based on extrinsic forces acting on the extended joint. The present study analyzes load distribution across the six different compartments in the elbow while the joint is flexed, as well as the intrinsic forces generated in the epicondylar and epitrochlear muscles. Ten cadaveric elbows were positioned at 90° of flexion, forearm in a neutral position and wrist at 0°. Tekscan sensors were used for measuring intraarticular pressures. Forces generated by epitrochlear muscles results in a series of loads that affect mainly the anteromedial facet (40%), followed by the posterolateral facet (34%) of the ulnohumeral joint, with the flexor carpi ulnaris generating the heaviest loads (43% on the anteromedial and 38% on the posterolateral facets). Conversely, the forces generated by the epicondylar muscles, similar in behavior but with an opposite direction, convey heavier loads to the elbow's anterolateral facet (45%), followed by the radiohumeral joint (26%) with the extensor carpi ulnaris generating the heaviest loads (54% on the anterolateral facet and 17% on the radiohumeral joint). Our results indicate that the elbow joint exhibits a characteristic load distribution pattern that depends on the muscles, as intrinsic forces are generated by the epicondylar and epitrochlear muscles. The anterior portion of the ulnohumeral joint is the area bearing the heaviest loads.

Study of intraarticular pressures in the elbow joints.

The purpose of this study was to describe pressure originating in the six elbow articular compartments after muscular contractions. Ten cryopreserved cadaveric arms were dissected and the insertional tendons and capsuloligamentous tissues were preserved. The specimens were placed in a custom-made device. Elbow position was established at 90° flexion with the forearm in a neutral position and the wrist extended at 0°. Tekscan sensors sere used for measuring intraarticular pressures. Without loading the elbow, the humeroradial joint received the lowest pressure, and, among the humeroulnar joints, the highest pressure was found in the anterolateral compartment. After loading the epitrochlear muscles to the maximum (5.0 kg), the pressure increased in the anteromedial joint (0.6 kg to 3.3 kg) and decreased in the posteromedial and anterolateral joints (4.2 kg to 0.3 kg and 4.2 kg to 0.9 kg, respectively). After the same loading in the epicondylar muscles, the pressure increased in the anterolateral and humeroradial joints (4.2 kg to 8.2 kg and 0.2 kg to 1.0 kg respectively), but decreased in the posterolateral joint (3.4 kg to 1.0 kg). The pressure distribution patterns among the humeroulnar compartments depend on the muscle geometries and their origins. Understanding these patterns can be useful in applying physiotherapeutic treatments for reinforcement of different muscular groups in order to decrease pressure in certain articular compartments.