5.1 Equipment, Devices & Technologies
Key Takeaways
- Assistive device progression (least to most support): cane → forearm crutch → axillary crutch → standard walker → rolling walker → platform walker
- Cane fitting: elbow flexion 20-30 degrees when holding the cane; top of cane at greater trochanter or wrist crease
- Canes are held on the OPPOSITE side of the affected lower extremity to reduce joint forces and improve gait pattern
- Axillary crutch fitting: 2-3 finger widths below the axilla; weight borne on handgrips, NOT on axillary pads (axillary nerve/brachial plexus compression risk)
- Walker types: standard (pick-up), front-wheeled, four-wheeled (rollator); rollators allow fastest gait but least stability
- Weight-bearing status: NWB (0%), TDWB (toe touch only), PWB (up to 25-50%), WBAT (as tolerated), FWB (100%)
- Wheelchair measurements: seat width = widest point of hips + 2 inches; seat depth = posterior buttock to popliteal fossa - 2 inches; footrest clearance = minimum 2 inches from ground
- TENS (Transcutaneous Electrical Nerve Stimulation) uses the gate control theory of pain; conventional TENS uses high frequency (50-150 Hz), low intensity for pain modulation
The non-systems domain covers equipment selection, fitting, and training that spans across all clinical settings. This section focuses on assistive devices, wheelchairs, and electrotherapy modalities.
Assistive Devices
Canes
Fitting:
- Top of cane at the level of the greater trochanter or wrist crease when standing upright
- Elbow flexion of 20-30 degrees when holding the cane
- Held on the OPPOSITE side of the affected lower extremity
Why opposite side? Holding the cane contralateral to the affected leg reduces the compressive force on the affected hip joint by creating a counterbalancing moment arm. This also promotes a more normal reciprocal gait pattern.
Cane Types:
| Type | Support Level | Indications |
|---|---|---|
| Single-point (straight) cane | Minimal support | Mild balance deficit, slight weight-bearing assist |
| Small-base quad cane (SBQC) | Moderate support | Moderate balance deficit; freestanding |
| Large-base quad cane (LBQC) | Greater support | Significant balance deficit; provides most stability |
| Hemi-walker | Maximum support (cane category) | Hemiplegia, maximal stability needed from one-hand device |
Crutches
Axillary Crutch Fitting:
- 2-3 finger widths (approximately 2 inches) below the axilla
- Handgrips positioned for 20-30 degrees of elbow flexion
- Critical safety point: Weight must be borne on the handgrips, NOT the axillary pads. Leaning on axillary pads compresses the axillary nerve and brachial plexus, potentially causing "crutch palsy" (radial/axillary nerve injury)
Forearm (Lofstrand) Crutches:
- Cuff encircles the forearm below the elbow
- Allows hand release without dropping the crutch
- Preferred for long-term crutch users (better energy efficiency)
- Common in patients with lower extremity paralysis, bilateral involvement
Crutch Gait Patterns
| Pattern | Description | Weight-Bearing Status |
|---|---|---|
| 2-point | Right crutch + left foot, then left crutch + right foot | PWB to FWB bilateral |
| 3-point | Both crutches + affected leg, then unaffected leg | NWB, TDWB, PWB on one leg |
| 4-point | Right crutch, left foot, left crutch, right foot (one at a time) | PWB bilateral, slowest/most stable |
| Swing-to | Both crutches forward, swing feet to crutches | NWB bilateral, paraplegia |
| Swing-through | Both crutches forward, swing feet past crutches | NWB bilateral, fastest, most energy |
Walkers
| Type | Characteristics | Best For |
|---|---|---|
| Standard (pick-up) walker | Must be lifted with each step; most stable | Maximum support, poor balance, limited endurance for crutches |
| Front-wheeled walker | Two front wheels, two rear tips; push forward | Patients who cannot lift standard walker (weakness, coordination) |
| Four-wheeled (rollator) | All four wheels, brakes, often with seat | Community ambulation, endurance training, patients who need periodic rest |
Wheelchair Fitting
| Measurement | Guideline |
|---|---|
| Seat width | Widest part of hips/thighs + 2 inches |
| Seat depth | Posterior buttock to popliteal fossa - 2 inches (prevents pressure on posterior knee) |
| Seat height | Allows 2+ inches clearance between footrests and ground |
| Back height | Below the inferior angle of the scapula (standard); higher for trunk support if needed |
| Armrest height | Shoulders relaxed, elbows flexed 90 degrees |
Common Wheelchair Problems
| Problem | Likely Cause |
|---|---|
| Pressure on posterior knees | Seat depth too long |
| Difficulty reaching wheels for propulsion | Seat width too wide |
| Trunk lean to one side | Seat too wide, scoliosis, weak trunk muscles |
| Skin breakdown at ischial tuberosities | Inadequate pressure relief, poor cushion |
Electrotherapy Modalities
TENS (Transcutaneous Electrical Nerve Stimulation)
| Mode | Frequency | Intensity | Duration | Mechanism |
|---|---|---|---|---|
| Conventional | High (50-150 Hz) | Low (sensory level) | 30-60 min; can use continuously | Gate control theory (large fiber activation blocks pain signals) |
| Acupuncture-like | Low (1-10 Hz) | High (motor level, visible contraction) | 20-30 min | Endorphin release (endogenous opioid system) |
| Brief-intense | High (100-150 Hz) | High (highest tolerable) | 15 min | Gate control + counterirritant |
NMES (Neuromuscular Electrical Stimulation)
- Used to produce muscle contraction for strengthening, motor relearning, or preventing atrophy
- Frequency: 35-80 Hz
- On:Off ratio: 1:3 to 1:5 (to prevent fatigue), progressing to 1:1
- Common applications: Quad strengthening post-TKA, dorsiflexor activation for foot drop, shoulder subluxation post-stroke
Interferential Current (IFC)
- Uses two medium-frequency currents (e.g., 4000 Hz and 4100 Hz) that interfere to produce a low-frequency (100 Hz) current at depth
- Deeper penetration than conventional TENS
- Used for deep pain, edema, and muscle spasm
Ultrasound (Therapeutic)
| Parameter | Thermal Effects | Non-Thermal Effects |
|---|---|---|
| Frequency | 1 MHz (deep, 3-5 cm) or 3 MHz (superficial, 1-2 cm) | Same |
| Duty cycle | Continuous (100%) | Pulsed (20% typical) |
| Intensity | 1.0-2.0 W/cm2 | 0.5-1.0 W/cm2 |
| Effects | Increases tissue temperature, extensibility, blood flow | Cavitation, acoustic streaming, tissue healing |
| Indications | Joint contracture, chronic inflammation | Acute inflammation, wound healing |
Weight-Bearing Status and Device Selection
Selecting and progressing devices requires fluency with weight-bearing (WB) terminology, which is physician-ordered and dictates the appropriate device and gait pattern:
| Status | Definition |
|---|---|
| NWB (non-weight bearing) | 0% — no contact of the limb with the floor |
| TTWB / TDWB (toe-touch) | Foot rests for balance only (~10-15% or "as if on eggshells") |
| PWB (partial weight bearing) | A defined percentage, commonly 25-50% |
| WBAT (as tolerated) | Patient self-limits by comfort |
| FWB (full weight bearing) | 100% as tolerated |
NWB and TTWB statuses generally require a 3-point gait with axillary or forearm crutches (a walker can also be used). As the patient progresses to FWB and improved balance, the device is downgraded from walker to crutches to cane, and finally to no device — always advancing the cane on the side opposite the involved limb.
NMES, FES, and Biofeedback
Neuromuscular electrical stimulation (NMES) elicits a muscle contraction for strengthening and atrophy prevention; functional electrical stimulation (FES) times stimulation to a functional task, such as stimulating the dorsiflexors during the swing phase of gait for foot drop. A 1:5 on:off ratio limits early fatigue and is progressed toward 1:1.
Russian current (a 2500 Hz medium-frequency burst) targets strengthening of healthy muscle, while high-volt pulsed current (HVPC) is used for edema and wound healing. EMG biofeedback converts muscle electrical activity into visual or auditory signals, helping patients up-train weak muscles (e.g., quadriceps post-TKA) or down-train overactive muscles (e.g., upper trapezius, pelvic floor).
Robotics, Body-Weight Support, and Emerging Technology
Contemporary rehabilitation technology appears on the exam in concept. Body-weight-supported treadmill training (BWSTT) unloads a percentage of body weight via a harness to enable task-specific gait practice in patients with stroke, spinal cord injury, or Parkinson disease. Robotic exoskeletons and end-effector devices provide repetitive, high-dose movement practice consistent with motor-learning principles.
Tilt tables progressively reintroduce upright tolerance for patients with orthostatic intolerance after prolonged bed rest, and continuous passive motion (CPM) machines maintain joint range after surgery such as total knee arthroplasty. In every case, technology is an adjunct that should reinforce active, task-specific practice rather than replace it.
A cane should be held on which side relative to the affected lower extremity?
When fitting axillary crutches, the pad should be positioned:
A patient is non-weight bearing on the right lower extremity. Which crutch gait pattern is MOST appropriate?
Match each wheelchair measurement to its correct guideline.
Match each item on the left with the correct item on the right
Conventional TENS uses which parameters to achieve pain relief via the gate control mechanism?
A therapeutic ultrasound frequency of 1 MHz penetrates to a depth of approximately _____ cm, while 3 MHz penetrates to 1-2 cm.
Type your answer below