Splints Acting on the Wrist and Forearm

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Chapter Outline

ARTICULAR WRIST AND FOREARM SPLINTS

Wrist Splints

Immobilization Splints

Mobilization Splints

Mobilization/Restriction Splints

Restriction Splints

Torque Transmission Splints

Wrist, Finger Splints

Mobilization Splints

Wrist, Thumb Splints

Restriction/Immobilization Splints

Wrist: Finger Splints

Torque Transmission Splints

Wrist: Finger, Thumb Splints

Torque Transmission/Immobilization Splints

Forearm Splints

Immobilization Splints

Mobilization Splints

Forearm, Finger Splints

Mobilization/Restriction Splints

Forearm, Wrist, Thumb Splints

Mobilization Splints

NONARTICULAR FOREARM SPLINTS

SUMMARY

This chapter follows the expanded ASHT ESCS format by first dividing splints into articular or nonarticular categories. In the articular category, splints are next grouped according to the primary joint or joints they influence. Splints in the nonarticular category are defined by the anatomical segments upon which they are based.

Once articular splints are grouped according to their primary joints, they are further defined by direction of force application and then divided according to one of four purposes: immobilization, mobilization, restriction, or torque transmission. Splints with more than one primary purpose are designated by dualpurpose categories (e.g., mobilization/restriction or immobilization/mobilization). In this chapter, force direction (e.g., flexion, extension, supination, etc.) for wrist and forearm splints is included in the purpose groupings. Purpose categories are further subdivided by type. Type identifies the number of secondary joint levels included in splints. Note: Type refers to the number of secondary joint levels, not the total number of secondary joints in a splint. While not all categories and/or subcategories are represented in this chapter, the expanded SCS is sufficiently flexible to accommodate additional groupings as needed.

Wrist and forearm articulations are key elements to upper extremity function in that they fine-tune positioning of the distally sited hand, providing proficiency in self-care, work, and leisure activities. Essential to normal hand function, the wrist and forearm refine motion of more proximal upper extremity joints through progressive, proximal-to-distal summation of intercalated joint motion. When integrated with selective joint stabilization, this cumulative joint motion allows the hand to be positioned in a seemingly infinite number of attitudes, further maximizing its capacity for interaction within the environment. With powerful extrinsic tendon systems traversing the wrist and inserting in the hand and digits, hand strength, digital posture, and fine finger/thumb motions are dependent on the integrity and positioning of wrist and forearm joints.

The ulna and radius, connected by a fibrous interosseous membrane, create two articulations: the proximal radioulnar joint (PRUJ) and the distal radioulnar joint (DRUJ). Together the proximal and distal radioulnar joints form a bicondylar joint with the radial head rotating axially and the distal ulna head fixed regarding rotation.7-9,17 These integrated osseous and ligamentous forearm components provide critical rotational movement to the entire distal portion of the upper extremity open kinematic chain. With an axis of motion that travels proximally through the head of the radius and distally through the head of the ulna, the radius rotates in relation to the ulna. The two bones are positioned parallel to each other in supination, and the radius crosses over the ulna in pronation. One may consider the forearm as a two-part unit with the hand and radius being the mobile unit and the ulna and humerus as the fixed unit about which the radius-hand unit rotates. As the radius rotates, the ulna moves volarly in supination and dor-sally in pronation. The ulna head glides in the sigmoid notch of the radius from the dorsal pronation position to the volar supination position. The interosseous membrane, although not considered an anatomical joint of the forearm, is an important structure in that it binds the radius and ulna together and limits extremes of forearm rotation.

Following the arc of the radius, the hand may be rotated approximately 180°. Combined, the radioul-nar joints allow a single arc of transverse rotational motion—pronation-supination—and form a uniaxial joint with 1° of freedom of movement. Coalescence of forearm and wrist motion results in hand positioning in the sagittal, coronal, and transverse planes. Normally, axial load is shared between the radius and ulna with the radius accepting 82% of the workload and the ulna 18%, with the triangular fibrocartilage complex (TFCC) stabilizing the distal RU joint.17 Disruption of the PRUJ, DRUJ, and/or interosseous membrane may compromise forearm rotation, causing substitution patterns of shoulder internal or external rotation to compensate for limited forearm pronation or supination.

The osseous anatomy of the wrist consists of the distal radius and ulna and eight carpal bones. The wrist is classified as a condylar diarthrosis with a wide range of motion resulting from its many small internal joints. Intrinsic stability is provided by a complex ligamentous arrangement. As the most proximal segment in the intercalated chain of hand joints, the wrist is the key to function at the more distal joint levels. The wrist is vulnerable to a wide assortment of injuries and diseases, thus making it subject to acute or secondary patterns of deformity, instability, or collapse that may significantly interfere with hand performance.

The collective carpal bones form the anteriorly concave proximal transverse arch, whose functional position directly influences the kinetic interaction of structures composing the longitudinal arch. It appears that the once widely held concept of the wrist carpus as two transverse four-bone rows is a substantial oversimplification of its complex dynamic motion patterns. Taleisnik,18,20 in refining the work of Navarro, defines the carpal scaphoid as the lateral or mobile column of the wrist, with the triquetrum serving as the medial or rotation column and the remaining six bones comprising the central or flexion-extension column. Taleisnik notes that the anatomic positioning of the wrist ligaments, particularly on the palmar side, permits these intricate columnar movements and provides a sound rationale for understanding the dynamic anatomy of the wrist, its function, and its behavior during injury. Garcia-Elias and Dobyns5 describe six compartment articulations with interdependent kinematic behaviors. These include distal radioulnar joint, radiocarpal joint, midcarpal joint, pisotriquetral joint, trapeziometacarpal joint, and common CMC joint. These joints provide stability of grip and a wide range of motion for fine prehension.

Direct or adjacent trauma, particularly when accompanied by crushing or prolonged edema, may result in fibrotic changes in the tightly articulated wrist joints, resulting in limited range of motion. The obligatory immobilization of fracture, tendon, or ligament injuries in this area increases the possibility of motion loss. Conversely, ligamentous rupture or attenuation secondary to inflammatory disease processes may result in wrist instability and collapse patterns that can compromise digital performance to an even greater extent than that produced by wrist stiffening. Surgical intervention may include partial wrist fusions to decrease pain and increase wrist stability. Injuries commonly referred to therapists for splinting include diagnoses ranging from repetitive strain injuries to scaphoid and lunate fractures. Close communication between referring surgeons and therapists is critical because wrist pathology and surgical intervention is often esoteric and highly individualized. Knowledge of anatomic idiosyncrasies is also important. For example, the poor blood supply to carpal bones such as the scaphoid and lunate may delay healing and necessitate splinting to stabilize the wrist and prevent movement.

The wrist serves as the key joint to distal hand function and influences both digital strength and dexterity. It is therefore important to give very careful consideration to proper joint positioning and protection, as well as the restoration and preservation of a satisfactory range of motion. A program that integrates splinting and exercise often provides the essential elements to maintain wrist function.

It is also important that the effect of wrist position be thoroughly considered in the preparation of any hand splint. Wrist dorsiflexion tightens extrinsic flexor tendons and permits the synergistic wrist extension-strong finger flexion function employed in power grasp. Wrist palmar flexion tightens the long extrinsic extensor tendons, allowing the hand to open automatically, while greatly reducing digit flexion efficiency. Splints designed either to relax or protect extensor tendons or to promote active digital flexion should support the wrist in an appropriate degree of dorsiflexion as determined by the presenting pathology. Conversely, splinting the wrist in a flexed attitude enhances active digital extension or allows protection for flexor tendon healing. One must take care, however, to avoid positioning the wrist in either excessive palmar flexion or dorsiflexion, which could lead to attenuation of delicate soft tissue structures or cause pressure on the median nerve as it passes through the carpal canal. Understanding and careful application of these kinetic mechanisms will aid healing and motion programs in the hand.

The purpose of this chapter is to discuss splinting of the wrist and forearm with regard to anatomic, kinesiologic, and mechanical factors. It is much more common to use wrist and forearm splints for immobilization purposes. With the limited exception of splints designed to correct deformation, the majority of splints in the preceding list require immobilization techniques.

I ARTICULAR WRIST AND FOREARM SPLINTS

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