Orthotics

Definition

An orthosis is a device that applies externally to a body segment and improves function by supporting, correcting, or compensating for deformity or weakness.

Ideal Characteristics of an Orthotic

  • Ease of use
  • Light weight
  • Cosmetic appeal
  • Cost-effective
  • Durable
  • Washable
  • Comfortable
  • Free of pressure areas

Functional Characteristics of Orthotics

  1. 3 Point Pressure: Provides a force that can correct or support a deformity.
  2. End Point Control: Limits motion at the end range of a joint.
  3. Total Contact: Ensures full contact with the body to distribute forces evenly.
  4. Kinaesthetic Reminder: Serves as a reminder to the patient about the position and movement of their body.

Examples of Orthotics

  • Provide Support:
    • TLSO for an osteoporotic spine.
  • Limit Motion:
    • KO (Knee Orthosis) to prevent knee hyperextension.
  • Correct Deformity:
    • Ponseti boots and bars for clubfoot correction.
  • Combination:
    • KAFO (Knee Ankle Foot Orthosis) in polio rehabilitation.

Biomechanics of Orthoses

Orthoses influence moments and forces around a joint in four ways:

  1. Control of Bending Moments:
    • The most common reason for prescription.
    • Limits motion in a certain plane using 3-point pressure.
    • Allows movement in other planes (e.g., KO for MCL injury).
  2. Control of Translation:
    • Limits shear force causing translation (e.g., KO in PCL rupture prevents transverse plane translation).
    • Requires 4-point contact.
  3. Control of Axial Force:
    • Works by sharing the load with the joint, beneficial for painful joints.
  4. Control of Line of Ground Reaction Force (GRF):
    • Alters the line of GRF, influencing the force across the joint indirectly.
    • Example: A lateral heel wedge moves load laterally and offloads the painful medial compartment.

Materials Used in Orthotics

  • Traditional Materials: Metals, leather, and rubber.

  • Common Materials: Plastics, categorized as follows:

    Thermosetting Plastics:

    • Rigid after heating; do not return to their original shape.
    • Commonly used in prosthetics for increased rigidity.

    Thermoforming Plastics:

    • Can be reshaped upon reheating.
    • Vary in the temperature needed for reshaping.
    • High-temperature thermoplastics are used for AFOs; low-temperature types can be molded directly onto the patient with a hair dryer.

    Polyurethane Foam:

    • Poured into a mold and allowed to harden.
    • Can be molded directly onto patients.
    • Examples include neoprene braces, cushions, and corsets.

Commonly Used Orthoses

Foot Orthoses

  • Insoles:
    • Simple: Off-the-shelf with little biomechanical value.
    • Total Contact: Thermoplastic molds to match the patient; most common type.
    • Functional: Corrects deformity; the foot is held in a corrected position during molding (e.g., UCBL for flexible deformities).
    • Types:
      • Rigid: Limits movement and corrects deformity.
      • Semi-rigid: Limits movement in a certain plane (e.g., ankle brace).
      • Soft: Provides a shock-absorbing role to ease pressure areas.

Shoe Alterations

  • Can be made internally or externally to the sole and/or heel.
  • UCBL Insert: Corrects valgus hindfoot and pronation; useful for tibialis posterior insufficiency.
  • Heel Raises: Corrects leg length discrepancy or equinus contracture.
  • Rocker Bottom: Convex structure that moves the roll-over point from MT head to MT shaft; offloads distally, helpful for ulcer healing.
  • Metatarsal Bar: Flat bar posterior to MT head that offloads MT heads.
  • Heel Wedges: Promote supination or pronation by correcting hindfoot alignment (e.g., medial wedge corrects valgus and pronation).
  • Arch Supports: Support medial arch and promote supination and heel varus.

Custom-Made Shoes

  • Accommodative: For fixed deformities (e.g., Hallux valgus).
  • Corrective: For supple deformities (e.g., CTEV).

Ankle Foot Orthoses

  • Position of the ankle directly affects knee position during gait and reduces energy consumption in conditions like polio and CP.
  • Types:
    • Posterior Leaf Spring: Compensates for weak dorsiflexors; prevents excessive plantarflexion, no medio-lateral support.
    • Ground Reaction AFO (GRAFO): Wraps around the shin to prevent knee hyperextension by utilizing GRF.
    • Dynamic AFO (DAFO): Provides extensive support over most of the foot; effective in CP.
    • Metal-Plastic AFO: Attaches to shoe or foot with ankle hinge, stops, and springs; controls motion in all directions but is bulky.

Knee Ankle Foot Orthoses

  • Extension of AFO with bars and a thigh band plus a mechanical knee joint.
  • Prevents knee instability; useful for individuals with paraplegia.

Patella Tendon Bearing Orthoses

  • Reduces weight bearing below the knee, used in fracture healing, ulcer treatment, and neuropathic joints & prosthetic sockets for BKA.

Hydrostatic Orthoses

  • E.g., Sarmiento humeral brace, which uses soft tissue circumferential pressure to create hydrostatic force, preventing fracture motion.

Complications of Orthoses

  • Psychosocial or Physical Complications:
    • Compression Phenomena: May cause pain, neuropathy, or venous congestion.
    • Heat and Skin Problems: Can lead to maceration of the skin and secondary infections.
    • Dependence: Reliance on a prosthesis even when it may not provide biomechanical benefits.
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