Anatomic and Biomechanical principles related to splinting

Anatomic location Arm: area from shoulder to elbow (humerus) Antecubital fossa: depression at the bend of the elbow Forearm: area from elbow to wrist Carpal: wrist or carpal bones Fingers: thumb, index, middle, ring, little Numbering fingers: I, II, III, IV, V (thumb) Palmar = volar: ant aspect of hand and forarm Radial : thumb side / Ulnar: little finger side

Muscles and function nerve supply Study table 4-4 on page 59

Arches of the hand 1. longitudinal arch 2. Distal transverse arch 3. Proximal transverse arch Functional significance Never splint the hand flat .. Creates deformity Specially with tendon and nerve injury

Creases of the hand Three main palmar creases: distal, proximal and thenar creases The distal palmar crease extends from the fifth MCP joint to a point midway between the second and third MCP joints. This is important for allowing motion of the MCP’s for a wrist immobilization splint

Creases of the hand Important for landmarks when making splint pattern and molding Figure 4-11 When splinting to immobilize a join, the crease should be included in the splint When mobilizing a joint? What happens with: Edema Paralysis disuse

Biomechanical principles of splinting Correct Biomechanics of Splint Design Splints are simply machines and levers that work together. Optimal client outcomes rely on biomechanics Weak muscles are supported, and the pull of stronger muscles is counteracted. Reduces risk of skin irritation due to pressure Ultimately may lead to patient comfort, compliance, and function Splint is an external force acting on the hand

Biomechanical principles of splinting three point pressure Mechanical advantage (F1*D1 = F2*D2) Torque Pressure and stress 1. degree 2. duration 3. repetition 4. direction Splint is an external force acting on the hand

Degree and Duration of Stress The skin is the least tolerating tissue to stress Skin becomes ischemic as load increases Even low stress can cause capillary damage and lead to ischemia Splints may do that, this is why it is advised to distribute pressure over a larger area of skin

Repetitive stress It could lead to inflammation and skin breakdown You have to remember that some diseases (lymph and vascular involvement) leads to an altered sense of tolerance Small and sharp edges lead to stress

Direction of Stress You have to remember that there are three directions of stress: Compression Tension Shear Pressure = Total Force/ Area of force application

Questions?