ABC CPO cheat sheet

Transtibial socket biomechanics: patellar tendon-bearing (PTB) design loads the patellar tendon and medial tibial flare while relieving the tibial crest and fibular head.

Transfemoral socket designs: quadrilateral socket uses ischial seat and anteroposterior loading; ischial containment (CAT-CAM) seats the ischium within the socket medially and laterally.

K-level classification: K0 no potential for ambulation; K1 household ambulator; K2 limited community ambulator; K3 community ambulator with variable cadence; K4 high-activity, high-impact user.

Energy-storing-and-return (ESR) feet store energy in keel deflection during stance and return it at push-off; effectiveness increases with walking speed and body weight.

Prosthetic knee stance-control mechanisms: weight-activated friction brake, geometric (polycentric) locking, and hydraulic stance control; swing-phase control uses pneumatic or hydraulic resistance.

Medicare functional levels drive component selection: microprocessor knees are typically justified at K3-K4, and microprocessor feet at K3-K4.

Residual limb volume fluctuates with fluid shifts; shrinking is managed with progressively tighter socket fit or liner ply adjustments rather than permanent socket enlargement.

Upper-limb body-powered prostheses use cable-and-harness control: figure-of-nine harness with dual control for elbow and terminal device; Bowden cable transmits force.

Myoelectric control uses surface EMG from residual muscle; proportional control maps signal amplitude to speed and grip force, while digital (on-off) control gives fixed output.

Ankle-foot orthosis (AFO) trim lines determine stiffness: a wider, more anteriorly extended proximal trim increases resistance to dorsiflexion and improves toe clearance.

Ground reaction AFO (GRAFO) applies a posterior shell and anterior proximal strap so the tibia is restrained from forward progression, compensating for quadriceps weakness.

Knee-ankle-foot orthosis (KAFO) with locked knee provides stance stability but increases energy cost of gait and requires compensatory hip hiking or circumduction.

Toronto and Milwaukee spinal orthoses treat scoliosis: Milwaukee is a cervico-thoraco-lumbo-sacral design for high thoracic curves; Boston is a thoraco-lumbo-sacral design for lower curves.

Foot orthosis posting: forefoot posting controls forefoot varus/valgus; rearfoot posting controls calcaneal eversion/inversion; total posting equals forefoot plus rearfoot correction.

AFO hinge types: solid ankle resists all motion; free-motion hinge permits unrestricted sagittal motion; plantarflexion stop prevents dropfoot; dorsiflexion stop limits anterior tibial progression.

Orthotic three-point pressure system: a force applied at the apex of a deformity is counterbalanced by two forces on the opposite side to correct alignment.

Reciprocating gait orthosis (RGO) couples hip flexion on one side to hip extension on the other via cables, enabling a reciprocating swing-through pattern in paraplegia.

Shoe modifications: rocker-bottom sole assists push-off and reduces forefoot pressure; medial heel wedge controls rearfoot valgus; metatarsal pad relieves metatarsal head pressure.