MPT Electrophysiology and Wound Care 1 — Questions and Answers

Question 1: Which type of electrical stimulation is most appropriate for denervated muscle to maintain muscle bulk and prevent atrophy?

High-volt pulsed current (HVPC)
Russian stimulation (medium frequency AC)
Low-frequency direct current using long pulse durations (Correct answer)
Interferential current (IFC)

Correct answer: Low-frequency direct current using long pulse durations

Denervated muscle requires longer pulse durations (greater than 10 ms) and lower frequencies to produce a twitch response, as it lacks functional motor nerve fibers and cannot respond to normal NMES parameters.

Normal NMES stimulates intact motor nerves using short pulse durations (0.1-0.3 ms). Denervated muscle has lost its motor nerve and must be directly stimulated with long pulse durations (10-300 ms) and low frequencies (0.5-5 Hz) to produce a visible twitch. The strength-duration curve for denervated muscle shifts markedly rightward (higher rheobase and longer chronaxie). Despite limited clinical evidence for efficacy, this approach is used to maintain muscle bulk during nerve regeneration, typically after peripheral nerve injury awaiting reinnervation.

Question 2: In wound healing, the proliferative phase is characterized by which cellular process?

Platelet aggregation and hemostasis
Fibroblast activity, collagen synthesis, and angiogenesis (Correct answer)
Macrophage debridement of necrotic tissue
Collagen cross-linking and scar remodeling

Correct answer: Fibroblast activity, collagen synthesis, and angiogenesis

The proliferative phase (days 3-21) is characterized by fibroblast proliferation, type III collagen synthesis, angiogenesis (new blood vessel formation), and epithelialization.

Wound healing progresses through four overlapping phases: hemostasis (seconds to hours), inflammation (days 1-5), proliferation (days 3-21), and remodeling (weeks to years). During proliferation, fibroblasts migrate into the wound and synthesize type III collagen (later replaced by stronger type I collagen during remodeling). Angiogenesis provides the new blood supply needed for healing tissue. Epithelialization covers the wound surface. PT interventions during proliferation include appropriate wound care and modalities to support healing.

Question 3: High-volt pulsed current (HVPC) used for wound healing is best described as:

Alternating current with frequency greater than 1000 Hz
Monophasic twin-peaked pulses with peak voltages greater than 100V and very short pulse durations (Correct answer)
Biphasic balanced waveform for pain control only
Low-voltage direct current with continuous flow

Correct answer: Monophasic twin-peaked pulses with peak voltages greater than 100V and very short pulse durations

HVPC delivers monophasic twin-peaked pulses at high peak voltages (greater than 100V) but very short durations and low average current, making it safe for wound care application.

HVPC uses monophasic (unidirectional) twin-peaked pulses. The high peak voltage overcomes skin impedance to reach deep tissues, but the extremely short pulse duration (less than 100 microseconds) keeps the average current and charge per pulse low, minimizing risk of chemical burns. For wound healing, the negative pole is typically used initially to promote inflammation resolution and bacteriostasis, then the positive pole to promote epithelialization. Evidence supports HVPC for chronic wound management including pressure ulcers and diabetic foot ulcers.

Question 4: According to the Wagner classification, a Grade 2 diabetic foot ulcer is defined as:

Superficial ulcer without subcutaneous involvement
Deep ulcer penetrating to tendon, capsule, or bone (Correct answer)
Localized gangrene
Full-thickness ulcer with exposed bone and osteomyelitis

Correct answer: Deep ulcer penetrating to tendon, capsule, or bone

Wagner Grade 2 describes a deep diabetic foot ulcer penetrating to tendon, joint capsule, or bone, without frank infection or osteomyelitis.

The Wagner Ulcer Classification System grades diabetic foot ulcers from 0-5. Grade 0: intact skin, pre-ulcerative lesion. Grade 1: superficial ulcer, skin only. Grade 2: deep ulcer to tendon, capsule, or bone. Grade 3: deep ulcer with abscess, osteomyelitis, or joint sepsis. Grade 4: localized gangrene (toes or forefoot). Grade 5: gangrene of entire foot. PTs use this classification to guide wound care decisions, referrals, and off-loading prescriptions. Grade 2 and above requires urgent referral to a wound care specialist or vascular surgeon.

Question 5: Which electrophysiological finding is most characteristic of carpal tunnel syndrome (median nerve compression)?

Decreased sensory nerve conduction velocity across the wrist (Correct answer)
Increased motor conduction velocity of the ulnar nerve
Normal distal motor latency with absent H-reflex
Fibrillation potentials in the APB with normal sensory conduction

Correct answer: Decreased sensory nerve conduction velocity across the wrist

Carpal tunnel syndrome characteristically shows prolonged or slowed sensory nerve conduction velocity (NCV) of the median nerve across the wrist, as sensory fibers are more sensitive to compression than motor fibers.

In carpal tunnel syndrome, median nerve sensory fibers are affected first due to their smaller diameter and greater susceptibility to ischemic compression. The classic electrophysiological finding is increased median sensory distal latency or decreased sensory NCV across the wrist. Motor involvement (prolonged APB distal motor latency) occurs with more severe compression. EMG may show fibrillations and positive sharp waves in the APB with severe or chronic cases. PTs use this information to stage severity and guide conservative management (splinting, neural mobilization, tendon gliding) versus surgical referral.

Question 6: Which color of wound tissue indicates healthy granulation tissue and suggests the wound is progressing toward healing?

Yellow (slough)
Red (granulation) (Correct answer)
Black (eschar)
Green (infected exudate)

Correct answer: Red (granulation)

Red, beefy, moist granulation tissue indicates healthy wound healing with good vascularization. It represents new connective tissue and blood vessels filling the wound bed.

Wound bed preparation uses the color-coded system: Red means granulating and healing (maintain moist environment, protect); Yellow is slough or fibrinous exudate (remove or debride); Black is necrotic eschar (debride unless contraindicated, as with dry stable heel eschar). Green indicates infection requiring antimicrobial treatment and possible culture. PTs performing wound care must recognize these tissue types to select appropriate dressings. Healthy granulation tissue should not be disturbed with aggressive cleaning.

MPT Electrophysiology and Wound Care 1

Which type of electrical stimulation is most appropriate for denervated muscle to maintain muscle bulk and prevent atrophy?