Dynamometric measurement of the grasp strength is commonly used in wrist assessment. On the other hand measurement of the pronation-supination (PS) strength has been few studied. The longitudinal forearm rotation needs integrity of the two radioulnar joints and of the antebrachial interosseous membrane. The strength developed during PS assesses also trophicity of pronator and supinator muscles. A PS dynamometer (Baseline ®, AREX) is now available for such measurements. The aims of this study were: 1) to study the best way to neutralize the shoulder movements of abduction-adduction, 2) to find the values of PS Strength in a healthy population, and 3) to study correlations between this PS force and several biometric items. A first series of measurements des PS strength was performed thanks to the Baseline dynamometer in 8 people, in association with two devices neutralizing the shoulder movements of abduction-adduction, in repeated campaigns allowed the authors to determine and keep the better one for optimal measurements following campaigns. To assess the normal values of PS Strength in a healthy population, 38 healthy volunteers from both genders and different ages, classified according their age class, from three different forearm position: neutral, from 90 ° of supination and 90 ° of pronation. Finally, statistical analysis looked for correlations between PS strength and some biometric data. Manipulations beginning from a neutral position of forearm were the most reliable. The mean strength within the whole studied sample (76 wrists, 17 male, 21 female) was 10.6 N.m (standard deviation SD 3.26) for the supination and 13.9 N.m (standard deviation 4.19) for the supination. The dominant side exhibited a PS strength superior by 7.5% to that of the non-dominant side. Male gender, the height and weight of the body, forearm circumference displayed positive relationships with PS strength. Mean values of PS strength, measured from a neutral forearm rotation and with the best device to neutralize the shoulder movements, in a healthy population of 38 volunteers, allowed the authors establishing reference values. They will allow precise comparisons between the values found in patients suffering from forearm and/or wrist pathology and the healthy population, taking into account the age, gender and hand dominance.
In rheumatoid arthritis (RA), non constrained or semi-constrained prostheses can be used. The authors used the Kudo III, IV or V or iBP prostheses 54 times from 1994 to 2003. After initial satisfactory results, they had to change one or both implants for several reasons: humeral stem fracture (5 cases), unipolar humeral loosening (1 case), ulnar loosening without laxity (8 cases), polyethylene wear (11 cases), due to progressive ulnar collateral ligament lengthening and progressive valgus deformity, without or with metallosis, due to contact between Cr-Co humeral component and titanium alloy ulnar component, chronic infection (1 case). When the local conditions were satisfactory (bone stock, ligament balance), the fractured or loosened component was changed. When the conditions were bad (poor bone stock, ligament misbalance, metallosis), both implants were removed; posterior humeral and/or medial or lateral ulnar window were used to removed the uncemented stems still osteointegrated. All the bipolar operations used the Coonrad-Morrey prosthesis, but the last case a Discovery prosthesis. The operative tricks are described, the management of the extensor apparatus is discussed, the clinical outcomes (especially the extensor apparatus function, most often weak) and the radiographic outcomes are presented.
