Comparison of Strength, Weight Bearing, Proprioception, Reaction Time and Function in Scapholunate Instability

Plain-language summary

Scapholunate (SL) instability is the most common type of instability seen in the wrist, resulting from SLI injury or excessive mobility \[1,2\]. It usually occurs after trauma and can range from mild injury to severe malalignment \[3\]. Symptoms include dorsal pain, clicking sound, limited movement, increased pain with weight-bearing, and weakness \[4,5\]. Pain reduces joint movement and grip strength, limiting daily activities \[6\]. If there is no dislocation, conservative treatment (education, exercise, splinting) is applied \[7\]. The wrist absorbs and transfers load through ligaments. During flexion-extension, the scaphoid and lunate follow the capitate \[10\]. SLIL injuries alter forearm muscle activation. EKRL, EKRB, APL, and FKR are "scapholunate-friendly" muscles; EKU is not recommended due to its pronator effect \[12-15\]. SLIL mechanoreceptors enhance dynamic stability \[11,19\]. There are no studies objectively measuring the strength of these muscles. Isokinetic muscle assessment has not been performed in SL instability. These measurements objectively determine muscle strength and imbalances, personalizing treatment. Weight transfer capacity, reaction time, and proprioception have also not been studied. However, weight transfer is an indicator of stability, proprioception is critical for functionality, and reaction time reflects neuromuscular response speed \[23-27\]. The aim of this study is to compare forearm isokinetic muscle strength, grip strength, weight transfer, proprioception, reaction time, and functionality in individuals with SL instability with those in healthy individuals.

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