6.5 Assistive Devices & Orthotics Refresher
Key Takeaways
- Axillary crutch height is adjusted so the axillary pad sits 2-3 finger widths (about 1-1.5 inches) below the axilla with hand grips at the level of the greater trochanter and the elbow flexed about 20-30 degrees.
- Standard canes are used on the side OPPOSITE the involved lower extremity; the cane and the involved limb advance together to widen the base of support and reduce hip abductor demand.
- Three-point gait (involved limb partially or non-weight-bearing) uses crutches or a walker; four-point and two-point gaits require bilateral devices and are used with bilateral lower-extremity involvement.
- Standard manual wheelchair seat width equals the widest hip measurement plus about 2 inches; seat depth equals the posterior thigh from buttock to popliteal fossa minus about 2 inches; footrest clearance from the floor should be about 2 inches.
- Common prosthetic gait deviations include lateral trunk lean (often a short prosthesis or weak hip abductors), vaulting (often a prosthesis that is too long), circumduction (often a long prosthesis or limited knee flexion), and excessive knee flexion at heel strike (heel cushion too firm or socket flexed too much).
Assistive Devices and Orthotics Refresher
This section integrates equipment-and-devices content the PTA uses during nearly every clinical encounter. Each device has a small set of measurement rules and selection criteria the NPTE-PTA tests directly. Devices are ranked roughly from most to least stable: parallel bars, walker, axillary crutches, forearm crutches, hemi walker, quad cane, single-point cane.
Crutches
| Crutch | Use | Fitting cues |
|---|---|---|
| Axillary | Short-term lower-extremity injury, post-op weight-bearing restrictions | Pad 2-3 finger widths (~1-1.5 in) below axilla, hand grip at greater trochanter, elbow 20-30 degrees flexion |
| Forearm (Lofstrand) | Longer-term use, paraplegia, more upper-body strength | Forearm cuff 1-1.5 in below olecranon, hand grip at greater trochanter, elbow 20-30 degrees flexion |
| Platform | Inability to bear weight through wrist or hand (e.g., rheumatoid arthritis) | Forearm horizontal on platform with elbow at 90 degrees |
Weight should be borne through the hands, not the axilla; axillary pressure can compress the brachial plexus and cause crutch palsy (a transient radial-nerve neuropraxia).
Walkers and Canes
- Standard walker: picked up and advanced about 6-12 inches with each step; requires upper-extremity strength but provides maximum stability.
- Front-wheeled (rolling) walker: lower energy cost than a standard walker; the patient pushes the device with a continuous gait rather than lifting it.
- Hemi walker: one-handed walker for patients with hemiparesis who cannot manage two crutches but need more support than a quad cane.
- Quad cane: four-point base for more lateral stability than a single-point cane; the wide-base side faces away from the patient and is held opposite the involved lower extremity.
- Standard cane: held opposite the involved lower extremity; reduces hip abductor (gluteus medius) demand on the stance limb and broadens the base of support.
Cane and walker height: adjust so the hand grip is at the patient's greater trochanter (or roughly at the wrist crease when the arm hangs at the side) with the elbow at 20-30 degrees of flexion.
Gait Patterns
| Pattern | Sequence | Indication |
|---|---|---|
| Two-point | One crutch and the opposite lower extremity move together, then the other pair | Bilateral involvement, partial weight-bearing both legs; faster than four-point |
| Four-point | Right crutch, left lower extremity, left crutch, right lower extremity (each moves separately) | Bilateral involvement requiring maximum stability; slow but very stable |
| Three-point | Both crutches and involved limb advance together, then the uninvolved limb steps through | Non-weight-bearing (NWB) or partial weight-bearing on one lower extremity |
| Modified three-point | Like three-point but the involved limb bears partial weight | Touch-down or partial weight-bearing single-limb injuries |
| Swing-to | Both crutches forward; both legs swing to the crutches | Limited lower-extremity function (e.g., paraplegia) |
| Swing-through | Both crutches forward; both legs swing past the crutches | More advanced; higher energy cost |
For stairs, the standard memory cue is "up with the good, down with the bad and the crutch." The uninvolved limb leads on ascent; the involved limb and the assistive device lead on descent.
Wheelchair Measurements
A poorly fitted wheelchair causes skin breakdown, postural deformity, and pain. Standard measurements:
| Measure | Rule | Reason |
|---|---|---|
| Seat width | Widest hip measurement + ~2 in | Allows clothing and weight shifts without trochanteric pressure |
| Seat depth | Posterior thigh (buttock to popliteal fossa) - ~2 in | Prevents popliteal pressure and forward sliding |
| Seat height / footrest clearance | Footrest at least 2 in off the floor | Prevents catching and allows curb clearance |
| Back height | Inferior angle of scapula for active users; higher for trunk support | Balances mobility and stability |
| Arm rest height | Elbow flexed 90 degrees with the forearm resting comfortably | Supports the upper body without elevating the shoulders |
For pressure relief, an independent user shifts weight every 15-30 minutes (push-up, side lean, or forward lean) for at least 1-2 minutes.
Lower-Extremity Orthoses
| Orthosis | Common use | Key feature |
|---|---|---|
| Ankle-foot orthosis (AFO) | Foot drop after stroke or peroneal nerve injury | Controls dorsiflexion and plantarflexion at the ankle |
| Solid AFO | Non-functional ankle; maximal plantarflexion control | Fully restricts ankle motion |
| Posterior leaf spring (PLS) | Mild foot drop | Allows some dorsiflexion and assists toe clearance |
| Knee-ankle-foot orthosis (KAFO) | Quadriceps weakness, knee instability | Adds knee control |
| Hip-knee-ankle-foot orthosis (HKAFO) | Bilateral lower-extremity paralysis | Adds hip control |
| Reciprocating gait orthosis (RGO) | Paraplegia, ambulation training | Cable linkage produces reciprocal stepping |
Common Prosthetic Gait Deviations
For lower-limb amputees, the PTA observes and reports gait deviations; the PT decides on socket or component changes.
| Deviation | Common causes |
|---|---|
| Lateral trunk lean toward prosthesis | Prosthesis too short, abductor weakness, painful socket |
| Vaulting (sound-side toe rise) | Prosthesis too long, inadequate suspension, locked knee |
| Circumduction | Prosthesis too long, locked or stiff knee, weak hip flexors |
| Hip hike | Prosthesis too long, locked knee |
| Excessive knee flexion at heel strike | Heel cushion too firm, socket flexed too much, weak quadriceps |
| Inadequate knee flexion (extension thrust) | Heel cushion too soft, socket flexed too little, knee too stable |
| Foot slap at heel strike | Plantarflexion bumper too soft |
A classic NPTE-PTA item shows a transfemoral amputee who leans laterally toward the prosthetic side. High-yield reasoning: think first about whether the prosthesis is too short, then about weak hip abductors on the prosthetic side, then about socket comfort. The PTA documents the deviation specifically and reports it back to the supervising PT for adjustment.
A 70-year-old patient is non-weight-bearing on the right lower extremity after open reduction and internal fixation of a right ankle fracture. The PT's plan of care calls for axillary crutches and an appropriate gait pattern. Which pattern is correct?
A PTA is fitting a standard manual wheelchair. The patient's widest hip measurement is 16 inches and the distance from posterior buttock to the popliteal fossa is 18 inches. Which seat dimensions are most appropriate?
During gait training with a left transfemoral prosthesis, the PTA observes that the patient leans the trunk laterally over the prosthetic (left) side during mid-stance on the prosthesis. Which is the MOST common cause to report to the supervising PT?