Effect of simulated muscle activity on distal radioulnar joint loading in vitro

Abstract

This study investigated the relationship between simulated forearm muscle loads and the joint reaction force in the distal radioulnar joint using an in vitro model. Seven fresh frozen cadaveric specimens were mounted in an upper extremity joint simulator capable of applying pneumatic loads to various (muscle) tendons while restraining the forearm in the three positions of pronation, supination, and neutral rotation. Loads were applied to model four forearm muscles (biceps, pronator teres, pronator quadratus, and supinator) in 10 N increments ranging from 10 N to 80 N for the biceps and pronator teres and in 10 N increments from 10 N to 50 N for the pronator quadratus and the supinator. Distal ulnar arthroplasty was performed on each specimen with a custom instrumented ulnar head replacement implant that quantified loads (via strain gauge instrumentation). The relationship between increasing muscle load and joint load was found to be positive and quasilinear in most cases. The biceps had the greatest influence on the distal radioulnar joint reaction force with a joint force in the range of 8% to 33% of the applied muscle load. The pronator teres, supinator, and pronator quadratus were less influential with a joint reaction force ranging between 6% to 19%, 4% to 9% and 2% to 10% of the applied muscle load, respectively.

Isoelastic Distal Ulnar Head Prosthesis: An In Vitro Joint Simulator Study

“…11,12 Therefore, during wear testing, 10 N of normal force should be sufficient. However, to quantify the worst-case scenario, we chose a force 11 times greater than that predicted and consistently used 110 N for both friction measurements and the wear test.…”

“…com; Vashon, WA). A specialized fixture with a built-in spring that generated 110 N (25 lb) of normal (perpendicular) force 11,12 was mounted to the fixture housing the synthetic bone counterface (Fig. 1).…”

A Nondestructive, Reproducible Method of Measuring Joint Reaction Force at the Distal Radioulnar Joint

“…7–11,13,14,28 However, prior methods have all involved major disruptions of periarticular soft tissues, which likely altered normal joint mechanics. In addition, methods that involve capsulotomy for sensor insertion result in loss of negative intra-articular pressure and its stabilizing suction effect.…”

“…The periarticuar soft tissue dissection required in these studies altered the normal mechanics of the DRUJ. 13,14 …”

The effect of elbow joint centre displacement on force generation and neural excitation

“…Specifically, changes in both muscle force and moment arms have been demonstrated. Altered muscle forces may lead to an altered joint reaction force, which is an important consideration in implant design [11]. Joint reaction force plays a crucial role in joint stability, counterbalancing the forces transmitted across the joint surface due to body weight, muscle contraction and other applied loads [2].…”