Proprioception of the wrist joint: a review of current concepts and possible implications on the rehabilitation of the wrist.

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Es un resumen preparado por Sandra Hall, Dip Phys (Otago), PGD (Hand and Upper Limb Therapy), Registered Hand Therapist (NZAHT) sobre la publicación realizada por Hagert en 2010.

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Hagert E (2010): Proprioception of the wrist joint: A review of current concepts and possible implications on the rehabilitation of the wrist. Journal of Hand Therapy 23: 2-1 7. (Abstract prepared by Sandra Hall)

Background: Over the past two decades the notion that ligaments are mere static stabilisers of a joint has been questioned. The differing types and distribution of mechanoreceptors in ligaments implies a variable functionality of their sensory role in the regulation of muscle activity around a joint and contribution to dynamic joint stability. With the majority of studies based around the knee, ankle and shoulder it has only been over the past five years that research has focused on the proprioceptive sensory influence of wrist ligaments. In order to adequately rehabilitate wrist injuries an understanding of these influences is essential.

Aim: The main aims of this review were to (i) Summarise the scientific evidence on wrist joint proprioception, and (ii) Relate this evidence to wrist proprioceptive rehabilitation.

Study Design: Narrative review. Information regarding the proprioception of the wrist joint is summarised under the broad headings of joint mechanoreceptors, proprioceptive reflexes and pathways, and proprioception senses and therapeutic applications.

Conclusion: Research on the sensorimotor function and neuromuscular control of the wrist joint is still in its infancy. Further basic science studies of proprioceptive reflexes and the effect of neuromuscular actions on wrist stability are required, as is clinical research into proprioceptive rehabilitation of the wrist joint and the development of neuromuscular rehabilitation programmes.

Commentary

Elisabeth Hagert draws on what has been identifed about the wrist joint, along with the knowledge gained from studies about the knee, ankle and shoulder joints, to present proprioceptive therapeutic concepts that can be incorporated into clinical rehabilitation of the wrist.

Evidence of wrist proprioceptive reflexes was demonstrated in a recently published article (Hagert, 2009). By electrically stimulating the scapholunate ligament (SLL) during wrist flexion-extension and radioulnar deviation, the immediate reflex response was consistently observed in the antagonist muscle for each position (joint protection), followed by coactivation (global stability). An interesting observation in this study was the consistent reflex inhibition of the extensor carpi ulnaris (ECU) during ulnar deviation, differing greatly from co-contractions that were seen in the other wrist positions. Correlating this finding with studies performed on the role of muscles on carpal stability, Hagert (2010) postulates why ECU was inhibited during this motion. Contraction of ECU has been found to increase the pronation tendency of the distal row of the carpus, which results in widening of the scapholunate interval and tension of the SLL.

Obscured by the historical vision of carpal kinematics of the wrist moving through sagittal and coronal planes, exercises of this joint have primarily focused on rehabilitation in the orthogonal moments of flexion-extension and radioulnar deviation. In fact, the most common plane of wrist rotation in activities of daily living, aligning with minimal muscle force and normal carpal kinematics, is that of an oblique motion from radial extension to ulnar deviation (the dart-throwing motion [DTM]). It is suggested therefore that any training should follow this arc. This is particularly pertinent in patients with a SLL injury whereby using the DTM, the activity of the stabilising flexor carpi ulnaris (FCU) and extensor carpi radialis longus is enhanced, whilst the activity of the potentially harmful ECU is demoted.

Based primarily on injuries to the knee or shoulder joints, the types of exercises advocated in neuromuscular training include isokinetic, isometric, eccentric, co-activation and unconscious reactive muscle activation. Some examples are provided as they apply to the wrist:

1. Isometric activation of pronator quadratus in supination and neutral wrist position can serve to stabilise the distal radioulnar joint (both pre-and postoperatively). Isometric exercise of the FCU will act to compress the pisiform against the volar aspect of the triquetrum, thus contributing to stability in the presence of an ulnar midcarpal instability pattern. However, with instability of the SLL, isometric exercise can either be beneficial or detrimental depending on the degree of ligament injury. If the SLL is intact, flexor carpi radialis (FCR) is thought to be an important dynamic stabiliser of the scaphoid, possibly due to its compression action at the scaphotrapezial-trapezoid joint. In a complete lesion however, cadaver studies of FCR have revealed a significant increase in its moment arm and subsequent increase in the load distributed through the radial carpus, thus enhancing the scaphoid displacement.

2. Designed to strengthen the muscle while it is lengthening, and commonly used to relieve pain and build tendon strength in tendonopathies, a secondary benefit of eccentric exercise in rehabilitation of the wrist has been suggested to lie in the coactivation of the antagonist muscles (Leger and Milner 2001).

3. Akin to the balance plate exercises used in ankle instabilities, which have been shown to improve proprioception and co-activation around the ankle joint, Hagert (2010) suggests slow and controlled motion of a ball on a table.

4. A recent study on subjects with no wrist dysfunction, using a Powerball [R] gyroscope demonstrated a significant increase in muscle endurance, which was sustained for an extended period after not using the device (Balan and Garcia-Elias 2008). Because this device generates random, multidirectional forces, the muscles are forced to react in an unpredictable manner and the resultant unconscious reactive muscle activation would likely stimulate more efficient neuromuscular control about the wrist. The authors suggest that this device may be beneficial in those patients with hyperlaxity acquired as a result of poor neuromuscular control. They warn however that this device should be used with caution as the muscular control that is required to counteract the centrifugal forces is likely an eccentric exercise, thus predisposing the patient to a possible increase in pain and damage to the neuromuscular structures.

Hagert (2010) also proposes the use of visual infuences, cutaneous infuences and the conscious awareness of limb movement and position to complement the aforementioned techniques. Shown to enhance both sensory and motor recovery after hand injury (Altschuler and Hu 2008, Rosen and Lundborg 2005), mirror therapy creates an illusion of the damaged hand and as a consequence there has been shown to be activation of its representative areas in the cortex. In summary, this paper challenges the clinician treating the wrist to consider proprioceptive rehabilitation as an integral part of our treatment armamentarium.

REFERENCES

Altschuler EL and Hu J (2008): Mirror therapy in a patient with a fractured wrist and no active wrist extension. Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 42: 110-111.

Balan SA and Garcia-Elias M (2008): Utility of the powerball in the invigoration of the musculature of the forearm. Hand Surgery 13: 79-83.

Hagert E, Persson JKE, Werner M and Ljung B-O (2009): Evidence of wrist proprioceptive reflexes elicited after stimulation of the scapholunate interosseous ligament. Journal of Hand Surgery (American) 34: 642-651.

Leger AB and Milner TE (2001): Muscle function at the wrist after eccentric exercise. Medicine and Science in Sports and Exercise 33: 612-620.

Rosen B and Lundborg G (2005): Training with a mirror in rehabilitation of the hand. Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 39: 104-108.

Routine blood results explained (2nd Edition). A. Blann, 2007 M & K Publishing, Cumbria, UK. ISBN 978-905539-38-3. Soft cover, 151 pages.