Low-Temperature Thermoplastic Splints/Orthoses Made by Therapists: An Overview of Current Practice

Therapists who treat patients with hand problems frequently use low-temperature thermoplastic materials for the construction of hand splints/orthoses ^1-9 . Splints/orthoses are used by therapists to meet many different clinical goals and are altered frequently in response to changes in motion, edema, strength, or joint mobility in the hand. The use of splints/orthoses is an integral part of the therapy process and the construction and fitting of splints is a skill required of therapists to help the patient regain functional use of the hand.

NOTE: Since therapists commonly use the term "splint" and orthotists commonly use the term "orthosis" when referring to custom-fitted devices molded to the hand, this article will use these terms interchangeably. Previous authors have advocated these terms be used synonymously ^4,10,11 .

History

Prior to the advent of low-temperature thermoplastic materials in the 1970s, therapists used plaster of Paris, leather, metal, and high-temperature plastics to construct hand splints/orthoses. The use of these materials required significant construction time after measurements and/or molds were taken of the patient. Multiple patient visits and fittings were usually required. Adjustments and modifications were cumbersome and time-consuming. With the introduction of low-temperature thermoplastic materials, the splint/orthosis could be molded directly to the patient and completed in one patient visit while other therapeutic intervention occurred. Modifications and adjustments to the orthosis could also be completed quickly and efficiently. At the same time as the advent of low-temperature thermoplastic materials, the specialties of hand surgery and hand therapy rapidly developed in the United States. The growth of these specialties greatly expanded the use of custom-fitted low-temperature splints/orthoses with hand patients.

This article intends to serve as an overview of the current state of the art use of low-temperature thermoplastic splints/orthoses in the treatment of hand patients.

Splinting for Protection and Mobilization: Early Motion

Following injury to the hand, maintaining joint motion and glide of tissue layers is required to maintain the complex mobility of the hand. The therapist's job is to thoroughly understand the anatomy, the injury, and the surgical repair in order to create a balance of protecting healing structures while safely maintaining as much movement as possible ¹² .

Figure 1. This custom molded splint/orthosis protects the healing 5th metacarpal fracture from external forces. The patient works actively to maintain proximal and distal interphalangeal joint motion while in the splint and periodically removes it to gently, actively flex and extend the metacarpophalangeal joint.

The striking beneficial effects of early motion following injury have led to immediate post-operative involvement of the therapist even in the most severe trauma patients ^13-18 . For example, standard treatment of stable fractures of the hand often consists of a custom-molded removable splint/orthosis, which allows early motion while providing protection to the healing fracture during use of the hand. (See figure 1). Additionally, management of repaired flexor or extensor tendon injuries is now often begun on an immediate protected active motion protocol, which includes a protective splint/orthosis ¹⁹ . (See figure 2).

Figure 2. Following a complex open crush injury to the dorsum of the hand that included laceration of all extensor digitorum communis (EDC) tendons, this dynamic splint allows limited metacarpophalangeal (MP) joint flexion but assists with MP joint extension. This splint/orthosis permits safe early active motion by the patient, maximizing glide of the EDC tendons while protecting them from excessive force.

The purposes of the splint/orthosis become intertwined with the goals of therapy, and at each therapy visit the splint/orthosis and its use is reevaluated. As tendon healing proceeds or bony union is achieved, the patient is weaned from the splint/orthosis. During this weaning period, the splint/orthosis may undergo numerous adjustments, freeing up joints to allow additional motion, repositioning joints for better tendon glide, or refitting the splint/orthosis may occur to accommodate edema reduction or change of contour of a wound area.

Splints/orthoses are also used to immobilize selected anatomical areas when inflammation of a ligament, tendon, or nerve is apparent. Immobilization via an external device imposes rest to the inflamed tissues. This rest, coupled with oral or local anti-inflammatory medications, usually allows most inflammation to subside without surgical intervention.

Splinting for Scar Management

Figure 3. Following the initial period of healing, mobilization splints/orthoses are used to slowly coax the stiff joints into the desirable position. This patient sustained a complex injury resulting in multiple fractures and soft tissue injuries. In this example the molded piece on the volar aspect of the replanted thumb maintains thumb abduction and extension in the face of the contracting soft tissue scar while the dynamic portion regains joint motion.

All traumatic hand injuries create the potential for scar to limit joint motion and tendon gliding. Large surface injuries including skin avulsions, burns, and crush/mangle injuries require many months of vigilant attention to assure motion is maintained in the face of contractile scar. Complex surgical reconstruction may include full and/or partial skin grafts as well as sophisticated flaps, which include blood vessels and nerves. As these grafts heal and contract, tissue length and mobility is maintained by prolonged positioning of the affected part by an immobilization splint/orthosis.

The contouring of healing tissue with positioning and the positive pressure of the splint/orthosis is achieved by multiple splints/orthoses, which are changed as the scar matures. Invariably, joint stiffness (see below) accompanies these complex injuries and the concurrent goal of regaining motion is balanced with the need to maintain scar length and tissue elasticity. (See figure 3).

Treatment of burns to the hand or other parts of the body requires attentive positional splinting for many months to encourage the scar tissue to mature in a lengthened position. (See figure 4).

Figure 4. This child sustained bilateral burns when he grasped his sister's hot curling iron. Many months of molded positional splinting regained joint motion and prevented the need for surgical release. The before and after of the left hand is shown.

Splinting to Regain Muscle Strength and Tendon Glide

Injury to one or more of the three major peripheral nerves of the upper extremity begins a long period of recovery. Following surgical repair of the nerve, it may be months or years before the maximum sensory and motor return is achieved. During this time, the use of a splint/orthosis keeps denervated muscles from remaining in an over-stretched position, prevents joint contractures from developing, prevents development of strong muscle substitution patterns, and maximizes the functional use of the hand ²⁰ . Although isolated nerve injuries can occur, many nerve injuries are combined with injury to other anatomical structures. Months of therapy may be required to reestablish joint and tendon motion before a splint/orthosis for the peripheral nerve muscle imbalance is required. As motor power returns to the muscle/s, the splint/orthosis is altered to maintain the best balance possible for the remaining denervated muscles. (See figure 5).

Figure 5. A patient with an injury to the ulnar nerve at the wrist exhibits the classic claw position. The small unobtrusive splint/orthosis prevents the denervated interosseous muscles from remaining in an over-stretched position, prevents proximal interphalangeal joint contractures, averts the development of muscle substitution patterns, and maximizes the functional use of the hand while awaiting nerve return.

The greatest challenge in reestablishing tissue glide and functional sensory and motor regeneration is in patients who have undergone replantation of an amputated part. Depending on the level of amputation, remarkable functional results can be achieved with months of individualized therapy, which includes numerous splints/orthoses. Initially the splint/orthosis supports and protects the healing tissue. As tissue healing progresses, the splint/orthosis directs the tendon gliding, maintains soft tissue length, or mobilizes stiff joints.

Splinting to Alleviate Joint Stiffness

One of the most common uses of the splints/orthoses is to regain joint motion following injury and the subsequent joint stiffness. Mobilization splints/orthoses are used to apply a gentle prolonged force to effect tissue elongation. These mobilization splints/orthoses can either be static splints that are remolded to position the joint/s in a new position; static progressive splints that allow the patient to adjust the position of the splint/orthosis as the joint motion changes; or a dynamic splint/orthosis that provides a continual elastic force.

Custom splints/orthoses can be constructed to increase joint motion of any joint in the upper extremity in any plane of motion desired. Exercises to strengthening muscles and reestablish maximum tendon glide must accompany the use of any splinting/orthotic program so passive motion gained by the splint/orthosis can be maintained by the patient.

Splinting to Support an Unstable Joint

A supportive immobilization splint/orthosis may be used to protect a healing ligament following injury and/or surgical repair. This splint/orthosis is worn until healing is complete. The patient is weaned from the splint/orthosis as physical activity is increased.

Arthritis or trauma can diminish the normal joint stability provided by the ligaments. In such circumstances, the patient may require an external device to support the joint when muscle force is transmitted across the joint during functional use. (See figure 6). If the patient is not a surgical candidate, or has multiple other joints involved, the splint/orthosis may be worn indefinitely and replaced many times.

Figure 6. This patient with long standing rheumatoid arthritis has developed an unstable wrist joint, making it difficult to transmit force to her fingers. A custom molded splint/orthosis with a dorsal neoprene strap provides support to the wrist to maximize hand use.

Conclusion

Splints/orthoses made of low-temperature thermoplastic materials can be fitted directly to the patient and easily changed. They have become an integral part of the therapy process when regaining motion or function in the hand. Each splint/orthosis has a specific goal and, as the therapeutic goal/s change, the design and/or use of the orthosis evolves. Although many splints/orthoses may be worn long term, many are also worn only during the post-injury/post-surgical period. Examples are shown which introduce the reader to a variety of low-temperature thermoplastic splints/orthoses.

Judy C. Colditz is a licensed occupational therapist, certified hand therapist, and a Fellow in the American Occupational Therapy Association with more than 30 years of clinical experience in hand therapy. She has written numerous articles, chapters, and papers on hand splinting and therapy as well as co-authored the CD-ROM: The Interactive Hand-Therapist's Edition along with an accompanying home study-guide published by the American Occupational Therapy Association. In the last five years, Ms. Colditz has been a three-time recipient of the best clinical paper award at the American Society of Hand Therapists Annual Meeting. She has taught courses, workshops, and lectures throughout the United States and Canada and in 24 countries outside North America. Contact: JColditz@HandLab.com

References

1. Benaglia P, Sartorio F, Franchignoni F. A new thermoplastic splint for proximal interphalangeal joint flexion contractures. J Sports Med Phys Fitness 1999;39:249-52.

2. Colditz JC. The biomechanics of a thumb CMC immobilization splint: design and fitting. Jour of Hand Ther 2000;13:228-35.

3. Van Lede P, Van Veldhoven G. Therapeutic hand splints-A rational approach. Volume I: Mechanical and biomechanical considerations. Antwerp, Belgium: Provan bvba; 1998.

4. Van Lede P, Van Veldhoven G. Therapeutic hand splints-A rational approach. Volume II: Practical applications. Knokke-Heist, Belgium: Provan bvba; 2004.

5. Wilton J. Hand splinting. London: W.B. Saunders Company, Ltd.; 1997.

6. Coppard BM, Lohman H. Introduction to splinting-A clinical-reasoning & problem-solving approach. Second edition ed. St. Louis: Mosby; 2001.

7. Hogan L, Uditsky T. Pediatric splinting-selection, fabrication, and clinical application of upper extremity splints. San Antonio, Texas: Therapy Skill Builders; 1998.

8. McKee P, Morgan L. Orthotics in rehabilitation. Philadelphia: F.A. Davis Company; 1998.

9. Jacobs ML, Austin N. Splinting the hand and upper extremity: principles and process. Baltimore: Lippincott Williams & Wilkins; 2003.

10. American Society of Hand Therapists: Position statement on the use of orthotics in hand therapy. June 2003.

11. Fess EE. A history of splinting: To understand the present, view the past. J Hand Ther 2002;15(2):97-132.

12. Colditz JC. Therapist's management of the stiff hand. In: Mackin EJ, Callahan A, Skirven T, Schneider LH, Osterman AL, editors. Rehabilitation of the hand and upper extremity. 5 ed. St. Louis: Mosby, Inc.; 2002. p. 1021-49.

13. Akeson WH, Amiel D, Mechanic GL, Woo SLY, Harwood FL, Hamer ML. Collagen cross-linking alterations in joint contractures: changes in the reducible cross-links in periarticular connective tissue collagen after nine weeks of immobilization. Conn Tis Res 197

14. Akeson WH, Amiel D, Abel MF, Garfin SR, Woo SL-Y. Effects of immobilization on joints. Clin Ortho Rel Res 1987;219:28-37.

15. Akeson WH. An experimental study of joint stiffness. J Bone Joint Surg 1961;43-A(7):1022-34.

16. Amiel D, Woo SL-Y, Harwood FL, Akeson WH. The effect of immobilization on collagen turnover in connective tissue: A biochemical-biomechanical correlation. Acta Orthop Scand 1982;53:325-32.

17. Woo SL-Y, Matthews P, Akeson WH, Amiel D, Convery FR. Connective tissue response to immobility: Correlative Study of biomechanical measurements of normal and immobilized rabbit knees. Arthritis and Rheu 1975;18(3):257-64.

18. Arem AJ, Madden JW. Effects of stress on healing wounds: I. intermittent noncyclical tension. J Surg Res 1976;20:93-102.

19. Pettengill KMS, van Strien G. Postoperative management of flexor tendon injuries. In: Mackin EJ, Callahan A, Skirven T, Schneider LH, Osterman AL, editors. Rehabilitation of the hand and upper extremity. 5 ed. St. Louis: Mosby, Inc.; 2002. p. 431-56.

20. Colditz JC. Splinting the hand with a peripheral nerve injury. In: Mackin EJ, Callahan A, Skirven T, Schneider LH, Osterman AL, editors. Rehabilitation of the hand and upper extremity. 5th ed. St. Louis: Mosby; 2002. p. 622-34.