Upper Limb Orthoses: Functions, Types, and Applications

What is the function of the upper limb orthosis?

Upper limb orthoses are external devices applied to the arm, hand, or shoulder designed to support, immobilize, protect, correct, or assist the limb, thereby improving function, reducing pain, and facilitating the healing process or independence.

Understanding Upper Limb Orthoses

An orthosis (plural: orthoses) is an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. When applied to the upper limb, these devices range from simple slings and braces to complex custom-fabricated splints and dynamic assistive devices. They are prescribed and designed by qualified healthcare professionals, including orthotists, physical therapists, occupational therapists, and physicians, based on a thorough assessment of the patient's condition, goals, and anatomical needs.

Upper limb orthoses can generally be categorized into two main types:

• Static Orthoses: These devices have no moving parts and are primarily used for immobilization, support, protection, or to apply a sustained stretch to soft tissues.
• Dynamic Orthoses: These devices incorporate elastic components, springs, or other moving parts to provide a controlled, assistive force to a joint, facilitating movement or providing resistance for exercise.

Primary Functions of Upper Limb Orthoses

The functions of upper limb orthoses are diverse and critically important in rehabilitation, injury management, and long-term care.

• Support and Stabilization: Orthoses provide external support to weakened or injured structures, enhancing stability. This is crucial in cases of ligamentous instability, muscle weakness, or after reconstructive surgery, helping to maintain proper anatomical alignment and reduce stress on healing tissues.
• Immobilization: A primary function is to restrict or prevent unwanted movement of a joint or limb segment. This is essential for pain management, protection of healing fractures (e.g., post-operative bone fusion), and resting inflamed tissues (e.g., tendinitis).
• Protection: Orthoses shield vulnerable areas from external forces or further injury. This can include protecting a healing wound, a newly repaired tendon, or a joint prone to dislocation. Custom sports orthoses also fall into this category, preventing injury during athletic activity.
• Correction of Deformity: By applying sustained, gentle forces, orthoses can gradually stretch contracted tissues, correct joint malalignment, and improve range of motion. This is particularly relevant in conditions leading to joint contractures, such as neurological disorders or severe burns.
• Prevention of Deformity: In chronic conditions, especially those involving neurological impairment (e.g., stroke, spinal cord injury), orthoses can maintain joints in a functional position, preventing the development of contractures, secondary deformities, and skin breakdown.
• Assistance with Movement/Facilitation: Dynamic orthoses can assist weak muscles in performing movements, provide a gentle stretch to increase range of motion, or act as a substitute for lost muscle function. This enables individuals to engage in activities they might otherwise be unable to perform.
• Pain Reduction: By limiting painful movements, offloading stress from an injured area, or providing compression, orthoses can significantly alleviate pain, allowing for better participation in rehabilitation and daily activities.
• Improved Function/Performance: Ultimately, many orthoses aim to enhance a person's ability to perform activities of daily living (ADLs), occupational tasks, or recreational pursuits. This can involve improving grip strength, increasing reach, or stabilizing a limb for better control.

Key Anatomical Regions and Common Applications

Orthoses are designed specifically for different parts of the upper limb, each with unique biomechanical considerations.

• Shoulder and Arm:
  • Applications: Rotator cuff injuries, shoulder dislocations, brachial plexus injuries, humeral fractures, post-surgical immobilization.
  • Examples: Slings, shoulder immobilizers, abduction pillows, humeral fracture braces.
• Elbow and Forearm:
  • Applications: Epicondylitis (tennis/golfer's elbow), elbow fractures, cubital tunnel syndrome, post-surgical elbow reconstruction.
  • Examples: Counterforce forearm straps, elbow immobilizers, range-of-motion (ROM) elbow braces.
• Wrist and Hand:
  • Applications: Carpal tunnel syndrome, wrist fractures, sprains, De Quervain's tenosynovitis, rheumatoid arthritis, stroke, nerve injuries.
  • Examples: Wrist cock-up splints, carpal tunnel braces, thumb spica splints, resting hand splints, wrist-driven flexor hinge orthoses.
• Fingers and Thumb:
  • Applications: Mallet finger, trigger finger, Boutonnière deformity, swan neck deformity, collateral ligament injuries (e.g., Gamekeeper's thumb), fractures of phalanges.
  • Examples: Mallet finger splints, stack splints, dynamic finger extension splints, custom-molded digit splints.

Biomechanical Principles at Play

The effectiveness of upper limb orthoses relies on fundamental biomechanical principles:

• Leverage and Force Application: Orthoses utilize lever arms to apply forces efficiently. A longer lever arm requires less force to achieve the desired effect, reducing pressure on the skin and improving comfort.
• Three-Point Pressure System: Many orthoses work by applying three points of pressure: two forces acting in one direction (e.g., proximal and distal to a joint) and a third, opposing force acting between them (e.g., directly over the joint). This system effectively controls movement, corrects alignment, or provides stabilization.
• Joint Alignment and Kinematics: Orthoses are designed to influence the natural motion and position of joints. By controlling degrees of freedom or guiding movement along physiological planes, they can optimize joint health and function.

Considerations for Effective Orthotic Use

For an upper limb orthosis to be effective, several factors must be carefully considered:

• Proper Fit and Customization: An ill-fitting orthosis can cause pressure sores, discomfort, or fail to achieve its intended purpose. Custom fabrication or precise fitting by a trained professional is often crucial.
• Patient Compliance and Education: The patient must understand the purpose of the orthosis, the wear schedule, and proper care instructions. Without compliance, even the best-designed orthosis will be ineffective.
• Integration with Rehabilitation: Orthoses are rarely a standalone solution. They are typically an integral part of a comprehensive rehabilitation program, including physical therapy, occupational therapy, and home exercises, to maximize functional outcomes.

Conclusion

Upper limb orthoses are indispensable tools in the management and rehabilitation of a wide array of conditions affecting the arm, hand, and shoulder. By strategically applying biomechanical principles, these devices can support healing, prevent secondary complications, alleviate pain, and significantly improve an individual's functional capacity and quality of life. Understanding their diverse functions and proper application is paramount for healthcare professionals and individuals seeking to optimize upper limb health and performance.