Scapholunate Instability: Proprioception and Neuromuscular Control

Abstract

From a kinetic point of view, the wrist is considered stable when it is capable of resisting load without suffering injury. Several prerequisites are necessary for the wrist to be kinetically stable: bone morphology, normal articulating surfaces, ligaments, the sensorimotor system, the muscles crossing the wrist, and all nerves connecting to ligaments and muscles. Failure of any one of these factors may result in carpal instability. The terms ?scapholunate (SL) dissociation? and ?SL instability? refer to one of the most frequent types of wrist instability, resulting from rupture or attenuation of the SL supporting ligaments. From a radiologic point of view, SL instability may be dynamic or static. Unlike static instabilities, which tend to be painful and dysfunctional, a good proportion of dynamic SL instabilities remain asymptomatic and stable for prolonged periods of time. Such a lack of symptoms suggests that a ligament rupture, in itself, is not enough for a joint to become unstable. Certainly, the process of achieving stability is multifactorial and involves normal joint surfaces, ligaments, muscles, and a complex network of neural connections linking all these elements. In this article, we will review the neuromuscular stabilization of the SL joint and the proprioceptive mechanisms that contribute to the dynamic carpal stabilization.

The composite extensor retinaculum cutaneous flap: an anatomical cadaveric study

“…16 The terminal PIN sends proprioceptive and nociceptive branches to the distal radioulnar joint and scapholunate ligament. [17][18][19] The significance of this sensory input on wrist stability has been disputed by some study groups. [17][18][19] Nonetheless, efforts should be taken to extensor tendon injuries, which has the potential to allow early rehabilitation and recovery.…”

Optimal management of scapholunate ligament injuries

“…Afferent information is collected at the ligaments of the wrist when stretched, and results in reflex motor control stabilizing the wrist joint via the secondary muscular stabilizers 19,20. In-vivo studies using electromyography have shown that denervation of the anterior or posterior interosseous nerves can lead to dysfunction of the stabilizing reflex pathways of the wrist joint 21,22…”

Concepts and Artistry in the Treatment of Scapholunate Ligament Injuries

“…Maintaining intracarpal supination maintains the reduction of the scaphoid to the lunate and prevents widening of the SL gap and SL malalignment. 34 Elbow flexion and extension are permitted, but forearm rotation is blocked for a total of 8 weeks. After 8 weeks, patients are transitioned into a volar wrist splint and supination and pronation exercises begin.…”