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Objectives and questions: Arthrosis of the trapeziometacarpal joint is the most common arthrosis of the hand. 20–30% occurs bilaterally, more females than males are affected. Aim of the study is to compare strength and primary stability in a biomechanical model after performing a modified Eppingplasty with biotenodesis screw, using a MiniTightRope and two more surgical prcedures for resectionssuspesionsarthroplasty, on one side an abductor pollicis longus transfer and on the other side a flexor carpi radialis transfer.

Material and methods: A physiological key pinch was performed in 48 fresh-frozen below-elbow arms, the trapezial space high got documented by x-ray and a polyaxial sensor. Fixation in the testing frame was in neutralposition, movements in the carpometacarpal joint were free. Instead of the Index, a polyaxial sensor was placed, target values were 12,5–25 Newton for a physiological key pinch. Defined muscles were charged, the muscles vectors were reconstructed in eyelets in the metacarpale II, os hamatum, os capitatum. X-rays were taken in anterior posterior view and 30° to define the trapezial high before, after trapecectomy and after resections-arhtroplasty. The Key Pinch were performed frequently, three times in a row, to the defined times, preoperative, after trapezectomy and after performing the defined surgical method. The area of the trapecial high got calculated.

Results: The key pinch was reproducibly performed without significant differences. There was also no significant difference between anterior-posterior and 30° x-rays. There was a significant difference between the both surgical procedures, the MiniTightRope has a trapezial space high from 130 percent without a load, extensor load 83 percent and 47 percent of the original trapezial space high in performing a maximal key pinch. The intra-rater-reliability was 96% and the inter-rater-reliability was 97%. The MiniTightRope was superior to the other methods.

Discussion and conclusions: The MiniTightRope had a higher primary stability in comparison to three methods. One reason could be a reduced tendon quality. On the other side the measurements of the trapezoid area shows higher results for the biotenodesis screw than the results of the trapezial space high. The physiological movements of the thumb changes after different surgical procedures. The MiniThightRope is a great tool to recreate the jointline between the base of metacarpale I and the base of metacarpale II and for revisions.