AAOS Comprehensive Orthopaedic Review

Section 2 - General Knowledge

Chapter 21. Orthoses, Amputations, and Prostheses

I. Lower Limb Orthoses

A. Terminology

 

1. Orthosis (or orthotic device) is the medical term for a brace or splint. Orthoses generally are named according to body region.

 

2. The basic types are static and dynamic devices.

 

a. Static—Rigid devices used to support the weakened or paralyzed body parts in a particular position.

 

b. Dynamic—Used to facilitate body motion to allow optimal function.

 

3. Standard abbreviations include FO (foot orthosis), AFO (ankle-foot orthosis), KAFO (knee-ankle-foot orthosis), HKAFO (hip-knee-ankle-foot orthosis), and THKAFO (trunk-hip-knee-ankle-foot orthosis).

 

B. Principles

 

1. Orthoses are used for management of a specific disorder, including a painful joint, muscle weakness, or joint instability or contracture.

 

2. Orthotic joints should be aligned at the approximate anatomic joints.

 

3. Orthoses should be simple, lightweight, strong, durable, and cosmetically acceptable.

 

4. Considerations for orthotic prescription

 

a. Three-point pressure control system

 

b. Static or dynamic stabilization

 

c. Tissue tolerance to compression and shear force

 

5. Construction materials include metal, plastic (most commonly polypropylene), leather, synthetic fabric, or any combination thereof.

 

C. Foot orthoses

 

1. Shoes are a type of FO and can be modified to accommodate deformities or to provide support to the limb during walking.

 

a. A cushioned or negative heel is often used with a rigid ankle to reduce the knee flexion moment.

 

b. Medial and lateral wedges can be added to the heel or sole of a shoe to accommodate fixed varus or valgus foot deformities. These wedges also influence the varus and valgus forces on the knee.

 

c. Medial and lateral flares can be added to the heel or sole of a shoe to widen the base of support for the foot.

 

d. Rocker soles help to transfer the body weight forward while walking, but they may destabilize the knee by transferring body weight forward too rapidly.

 

e. An extra deep shoe allows additional room for deformities and inserts.

 

2. An FO placed inside the shoe can provide support, control motion, stabilize gait, reduce pain, correct flexible deformities, and prevent progression of fixed deformities.

 

a. Heel cup

 

i. A heel cup is a rigid plastic insert.

 

ii. It covers the plantar surface of the heel and extends posteriorly, medially, and laterally up the side of the heel.

 

iii. Heel cups are used to prevent lateral calcaneal shift in the flexible flatfoot.

 

b. University of California Biomechanics Laboratory (UCBL) FO (

Figure 1).

 

i. The UCBL FO is constructed of plastic and is fabricated over a cast of the foot held in maximal manual correction.

 

ii. It encompasses the heel and midfoot with rigid medial, lateral, and posterior walls.

 

c. Arizona brace

 

i. The Arizona brace combines the UCBL orthosis with a laced ankle support.

 

ii. It provides more rigid hindfoot support.

 

[Figure 1. The UCBL foot orthosis encompasses the heel and midfoot. It has medial, lateral, and posterior walls.]

D. Ankle-foot orthoses (

Table 1 and

Figure 2)

 

1. AFOs are prescribed for weakness or muscle overactivity of ankle dorsiflexion, plantar flexion, inversion, and eversion.

 

2. AFOs are used to prevent or correct deformities.

 

3. The ankle position indirectly affects knee stability, with ankle plantar flexion providing a knee extension force and ankle dorsiflexion providing a knee flexion force.

 

4. All AFOs consist of a footplate with stirrups, uprights, and a calf band, regardless of the materials used for construction.

 

5. Nonarticulated AFOs

 

a. Nonarticulated AFOs are more cosmetically acceptable.

 

b. They place a flexion force on the knee during weight acceptance.

 

c. The trim lines of plastic AFOs determine the degree of flexibility during late stance and are described as having maximal, moderate, or minimal resistance to ankle dorsiflexion.

 

d. Nonarticulated AFOs may be constructed of plastic, composite materials, or leather and metal.

 

e. Thermoplastic AFOs must be used with care in patients with fluctuating edema and lack of sensation.

 

f. Nonarticulated AFOs are described according to the amount of rigidity of the brace, which depends on the thickness and composition of the plastic, as well as the trim lines and shape.

 

i. Posterior leaf spring

 

ii. Minimal resistance to ankle dorsiflexion

 

iii. Moderate resistance to dorsiflexion

 

iv. Maximal resistance to dorsiflexion

 

[Table 1. Types of Ankle Motion allowed by Orthotic Ankle Joints and the Effect on Gait]

6. Articulated AFOs

 

a. Articulated AFOs allow a more natural gait pattern and adjustment of plantar and dorsiflexion.

 

b. They can be designed to provide dorsiflexion assistance to clear the toes during swing.

 

c. Adjustable ankle joints can be set to the desired range of ankle dorsiflexion or plantar flexion.

 

d. Mechanical ankle joints

 

i. These joints can control or assist ankle dorsiflexion or plantar flexion by means of stops (pins) or assists (springs).

 

ii. They also control medial-lateral stability of the ankle joint.

 

iii. Limits on ankle motion affect knee stability: Unrestricted plantar flexion allows normal weight acceptance in early stance; plantar flexion stop causes a knee flexion moment during weight acceptance; dorsiflexion stop provides a knee extension moment during the later part of stance.

 

[Figure 2. Examples of ankle-foot orthoses (AFOs). A, Posterior leaf-spring AFO. B, Floor reaction AFO. C, Carbon fiber composite AFO. D, Clamshell AFO for neuropathic arthropathy. E, Articulated AFO with simple joint. F, Dynamic dorsiflexion AFO.]

7. Types of AFO designs

 

a. Free motion ankle joints—Allow unrestricted ankle dorsiflexion and plantar flexion motion, provide only medial-lateral stability, and are useful for ligamentous instability.

 

b. Unrestricted (free) plantar flexion—Allows normal weight acceptance in early stance.

 

c. Unrestricted (free) dorsiflexion—Allows calf muscle strengthening and stretching of the plantar flexors (Achilles tendon).

 

d. Limited motion ankle joints—Can be adjusted for use in ankle weakness affecting all muscle groups.

 

e. Plantar flexion stop ankle joint

 

i. These joints are used in patients with weakness of dorsiflexion during swing phase.

 

ii. The plantar flexion stop limits a dynamic (flexible) equinus deformity.

 

iii. These joints provide a knee flexion moment during weight acceptance. They should not be used in patients with quadriceps weakness.

 

f. Dorsiflexion stop ankle joint

 

i. In the setting of mild equinus, this joint can be used to promote a knee extension moment

 

[

Figure 3. Examples of knee-ankle-foot orthoses (KAFOs). A, KAFO. B, KAFO with bail knee lock joint. C, Posterior knee joint and drop lock for a KAFO. D, Combined prosthesis for ankle disarticulation and KAFO for quadriceps weakness.]

   during the loading response to prevent buckling of the knee.

 

ii. Limited ankle dorsiflexion provides a knee extension moment in the later part of stance.

 

iii. These joints are useful for stabilizing the knee during the later part of stance in the presence of quadriceps or ankle plantar flexion weakness.

 

g. Locked ankle joint—Limits motion for multiplanar instability or ankle pain.

 

h. Dorsiflexion assist spring joint—Provides dynamic ankle dorsiflexion during swing phase and corrects a flexible foot drop during swing.

 

8. Varus or valgus correction straps (T-straps)

 

a. When used for valgus correction, this type of device contacts the skin medially and circles the ankle until buckled on the outside of the lateral upright.

 

b. When used for varus correction, this type of device contacts the skin laterally and is buckled around the medial upright.

 

E. Knee-ankle-foot orthoses

 

1. Construction

 

a. KAFOs consist of an AFO with metal uprights, a mechanical knee joint, and two thigh bands (Figure 3).

 

b. They can be made of metal-leather and metal-plastic or plastic and plastic-metal.

 

2. Principles of operation

 

a. KAFOs can be used in quadriceps paralysis or weakness to maintain knee stability and control flexible genu valgum or varum.

 

b. They are used to limit the weight bearing of the thigh, leg, and foot with quadrilateral or ischial containment brim.

 

c. A KAFO is more difficult to don and doff than an AFO.

 

d. KAFOs are not recommended for patients who have moderate to severe cognitive dysfunction.

 

3. Types of KAFO designs

 

a.

Double upright metal KAFO (most common)

 

i.

This type of KAFO comprises an AFO with two metal uprights extending proximally to the thigh to control knee motion and alignment.

 

ii.

It consists of a mechanical knee joint and two thigh bands between two uprights.

b.

Scott-Craig orthosis

 

i.

The Scott-Craig orthosis includes a cushioned heel with a T-shaped foot plate for mediolateral stability, an ankle joint with anterior and posterior adjustable stops, double uprights, a pretibial band, a posterior thigh

 

[

Table 2. Designs of Orthotic Knee Joints and Their Uses]

 

 

band, and a knee joint with pawl locks and bail control.

 

ii.

Hip hyperextension allows the center of gravity to fall behind the hip joint and in front of the locked knee and ankle joint.

 

iii.

With 10° of ankle dorsiflexion alignment, a swing-to or swing-through gait with crutches is possible.

 

iv.

The Scott-Craig orthosis is used for standing and ambulation in patients with paraplegia as a result of a spinal cord injury.

c.

Supracondylar plastic orthosis

 

i.

The ankle is immobilized in slight plantar flexion to produce a knee extension moment in stance to help eliminate the need for a mechanical knee lock.

 

ii.

This orthosis resists genu recurvatum and provides medial-lateral knee stability.

d.

Plastic shell and metal upright orthosis—Posterior leaf spring AFO with double metal uprights that extend up to a plastic shell in the thigh with an intervening knee joint.

 

4. Knee joints (Table 2)

 

a. Single-axis knee joints—The axis of rotation of the joint is aligned with the rotational axis of the anatomic knee joint.

 

i. The single-axis knee joint is useful for knee stabilization.

 

ii. The arc of knee motion can be full or limited.

 

iii. A free motion knee joint allows unrestricted knee flexion and extension with a stop to prevent hyperextension; it is used for patients with recurvatum but good strength of the quadriceps to control knee motion.

 

b. Posterior offset knee joint—The axis of rotation of the orthotic joint is aligned posterior to the rotational axis of the anatomic knee joint.

 

i. The posterior offset knee shifts the weight-bearing axis provided by the center of mass (COM) more anterior to the anatomic knee joint.

 

ii. At initial contact and during weight acceptance, the ground reaction force is anterior to the flexion axis of the anatomic knee. This extends the knee and results in great stability during early stance.

 

iii. It provides a knee extension moment during stance.

 

iv. The knee can flex freely during swing phase.

 

c. Polycentric joint

 

i. This joint allows limited multiplanar motion during flexion and extension.

 

ii. It is useful for patients with knee arthritis.

 

d. Dynamic knee extension joint

 

i. This type of joint provides active knee extension, usually by means of a coiled spring within the joint.

 

ii. It is helpful for patients with quadriceps weakness but full knee extension.

 

5. Types of knee joint locking mechanisms—Orthotic knee joints can be modified to allow locking of the joint for stability during stance.

 

a. Drop ring lock knee joint

 

i. This is the most commonly used knee lock to prevent knee flexion while walking.

 

ii. Rings drop over the joint to lock the knee joint while the knee is in extension.

 

iii. The knee is stable, but gait is stiff without knee motion.

 

iv. This type of lock is appropriate for patients

 

[

Figure 4. Dynamic knee extension orthosis.]

   with severe quadriceps weakness or gross ligamentous instability.

 

v. Extensions may be added to the rings to allow the patient to unlock the joint for sitting without the need to bend forward.

 

b. Pawl lock with bail release knee joint

 

i. A semicircular bail attaches to the knee joint posteriorly, and the patient can unlock both joints easily by pulling up the bail or backing up to sit down in a chair.

 

ii. A major drawback is that the knee can accidentally unlock, such as while the patient is pulling up his or her pants or if bumped on a chair.

 

c. Adjustable knee lock joint (dial lock)

 

i. This serrated adjustable knee joint allows knee locking at different degrees of flexion.

 

ii. This type of lock is used for patients with knee flexion contractures that are improving gradually with stretching.

 

6. Additional potential modifications of a KAFO

 

a. Anterior knee pad—Can be placed over the patella to prevent knee flexion.

 

b. Medial strap or pad—Controls a valgus knee deformity.

 

[

Figure 5. Hip-knee-ankle-foot orthosis (HKAFO).]

c. Lateral strap or pad—Controls a varus knee deformity.

 

d. Ischial weight bearing—Upper thigh band cuff is brought up above the ischium to provide a weight bearing surface.

 

F. Knee orthoses—KOs provide support or control to the knee only, not the foot and ankle (Figure 4).

 

1. KOs for patellofemoral disorders—These types of KOs supply medial-lateral knee stability, control patellar tracking during knee flexion and extension, and generally include an infrapatellar strap.

 

2. KOs for knee control in the sagittal plane—These KOs control genu recurvatum with minimal medial-lateral stability and include a Swedish knee cage and a three-way knee stabilizer.

 

3. KOs for knee control in the frontal plane—This type of KO consists of thigh and calf cuffs joined by sidebars with mechanical knee joints, is usually polycentric, and closely mimics the anatomic joint motion.

 

4. KOs for axial rotation control—These KOs can provide angular control of flexion-extension and medial-lateral planes, control axial rotation, and are used mostly in the management of sports injuries of the knee.

 

G. Hip-knee-ankle-foot orthoses

 

1. HKAFOs consist of an AFO with metal uprights, a mechanical knee joint, thigh uprights, a thigh socket, a hip joint, and waist band (Figure 5).

 

2. The hip joint can be adjusted in two planes to control flexion and extension and to control abduction and adduction.

 

a. Single-axis hip joint with lock

 

i. This is the most common hip joint with flexion and extension.

 

ii. It may include an adjustable stop to control hyperextension.

 

b. Two-position lock hip joint

 

i. This type of hip joint can be locked at full extension and 90° of flexion.

 

ii. It is used for hip spasticity control in a patient who has difficulty maintaining a seated position.

 

c. Double-axis hip joint

 

i. The double-axis hip joint has a flexion-extension axis to control these motions.

 

ii. It also has an abduction-adduction axis to control these motions.

 

3. The orthotic hip joint is positioned with the patient sitting upright at 90°, whereas the orthotic knee joint is centered over the medial femoral condyle.

 

4. Pelvic bands

 

a. Pelvic bands complicate dressing after toileting unless the orthosis is worn under all clothing.

 

b. Pelvic bands also increase energy demands for ambulation.

 

H. Trunk-hip-knee-ankle-foot orthoses

 

1. THKAFOs consist of a spinal orthosis in addition to an HKAFO to control trunk motion and spinal alignment.

 

2. THKAFOs are indicated in patients with paraplegia.

 

3. They are very difficult to don and doff.



II. Lower Limb Amputations

A. Demographics

 

1. Approximately 130,000 new amputations are performed annually in the United States.

 

2. Causes and levels of amputations performed are listed in

Table 3.

 

B. Goals of lower limb amputation

 

1. General goals

 

a. Remove diseased, injured, or nonfunctioning limb in a reconstructive procedure

 

b. Restore function to the level of patient need

 

c. Preserve length and strength

 

d. Balance the forces of the remaining muscles to provide a stable residual limb

 

[Table 3. Causes and levels of Lower Limb Amputations]

2. Goals for ambulatory patients

 

a. Restore a maximum level of independent function

 

b. Ablate diseased tissue

 

c. Reduce morbidity and mortality

 

3. Goals for nonambulatory patients

 

a. Achieve wound healing while minimizing complications

 

b. Improve sitting balance

 

c. Facilitate position and transfers

 

C. Preoperative evaluation

 

1. The preoperative evaluation should include an assessment of skin integrity and sensation, joint mobility, and muscle strength.

 

2. Vascular status (to determine the viable level of amputation) should also be evaluated. Several assessment techniques are used.

 

a. Doppler ultrasound

 

i. Ankle/brachial index >0.45 correlates with 90% healing.

 

ii. Advantages—Readily available, noninvasive.

 

iii. Disadvantages—Arterial wall calcification can give misleadingly elevated readings.

 

3. Toe systolic blood pressure

 

a. The minimum requirement for distal healing is 55 mm Hg.

 

b. Advantages—Noninvasive, readily available, and inexpensive.

 

4. Transcutaneous oxygen tension

 

a. Po2 >35 is necessary for wound healing.

 

b. Advantages—Noninvasive, highly accurate in assessing wound healing.

 

c. Disadvantages—Results may be altered by skin disorders such as edema or cellulitis.

 

5. Skin blood flow measurement

 

a. Xenon 133 clearance has been used in the past.

 

b. Expensive and time consuming

 

6. Fluorescence studies have been used but provide unreliable results.

 

7. Arteriography

 

a. Advantage—Visualize the patency of vessels.

 

b. Disadvantages—Invasive and unreliable in determining successful wound healing.

 

D. Assessment of nutrition and immune competence

 

1. Total lymphocyte count of > 1,500/mL

 

2. Serum albumin ≥ 3 g/dL

 

E. Psychological preparation

 

1. Viewing amputation as a step in recovery, not a failure

 

2. Early plan for prosthetic fitting and return to function

 

3. Preoperative counseling for the patient and family

 

4. Referral to amputee support groups

 

F. Surgical principles

 

1. Blood and soft-tissue considerations

 

a. Use a tourniquet to minimize blood loss if there is no significant vascular disease.

 

b. Plan soft-tissue flaps for mobile and sensate skin.

 

c. Balance muscle forces across the residual joints.

 

2. Bone considerations

 

a. Bevel the bone ends to minimize skin pressure and maximize weight-bearing capacity of the residual limb.

 

b. Avoid periosteal stripping to preserve bone viability and to minimize the likelihood of heterotopic bone formation.

 

3. Surgical procedure

 

a. Myodesis is the technique in which distal muscle is sutured directly to bone or tendon, covering the distal bone end and maximizing the weight-bearing capacity of the residual limb.

 

b. Divide nerves proximally and sharply to avoid painful neuromas.

 

c. Close the wound with minimal tension and place a drain to decompress the underlying tissue.

 

4. Postoperative management

 

a. Apply a compressive dressing to protect the wound and control edema.

 

b. A splint or cast also may be applied to limit edema and prevent contractures.

 

G. Complications

 

1. Failure of the wound to heal properly occurs as the result of insufficient blood supply, infection, or errors in surgical technique.

 

2. Infection may develop postoperatively without widespread tissue necrosis or flap failure, especially if active distal infection was present at the time of the definitive amputation or if the amputation was done near the zone of a traumatic injury.

 

3. Postoperative edema is common, but rigid dressings help reduce this problem.

 

4. Phantom sensation

 

a. The feeling that all or a part of the amputated limb is still present

 

b. Common in nearly everyone who undergoes amputation but usually diminishes over time

 

5. Phantom pain

 

a. A bothersome painful or burning sensation in the part of the limb that is missing

 

b. Unrelenting phantom pain occurs in only a minority of patients.

 

6. Joint contractures

 

a. Usually develop between the time of amputation and prosthetic fitting

 

b. Treatment is difficult and often unsuccessful.

 

c. Prevention with adequate pain control and the initial use of casts or splints is paramount.

 

7. Dermatologic problems

 

a. The residual limb and prosthetic socket must be kept clean, rinsed well to remove all soap residue, and thoroughly dried.

 

b. Shaving increases problems with ingrown hairs and folliculitis.

 

c. Epidermoid cysts commonly occur at the prosthetic socket brim. The best approach is to modify the socket and relieve pressure over the cyst.

 

d. Verrucous hyperplasia is a wartlike overgrowth of skin that can occur on the distal end of the residual limb. It is caused by a lack of distal contact and failure to remove normal keratin.

 

e. Contact dermatitis is caused by contact with acids, bases, or caustics and frequently results from failure to rinse detergents and soaps from prosthetic socks.

 

f. Candidiasis and other dermatophytoses present with scaly, itchy skin, often with vesicles at the border and clearing centrally. Dermatophytoses are diagnosed with a potassium hydroxide preparation and treated with topical antifungal agents.



III. Levels of Amputation

A. Foot

 

1. Hallux amputation

 

a. Save the base of proximal phalanx to preserve push-off strength.

 

b. Stabilize the sesamoid bones by performing tenodesis of flexor hallucis brevis tendon.

 

2. Lesser toes can be amputated through the interphalangeal joint, metatarsophalangeal joint, or the phalanx.

 

a. Can use side-to-side or plantar dorsal flaps

 

b. Save the base of the proximal phalanx to provide better stability and push-off strength.

 

3. Ray amputations are best done on the border rays; central ray resections take longer to heal.

 

4. Transmetatarsal amputations can be performed through the metatarsals or Lisfranc joints.

 

a. Bevel bone cuts on plantar surface to prevent skin pressure.

 

b. Create a cascade from medial to lateral side of the foot.

 

c. Consider Achilles lengthening to prevent equinus.

 

5. Hindfoot

 

a. Chopart amputation is done through the transverse tarsal joints.

 

i. Preserves the talus and calcaneus

 

ii. Equinus deformity can result.

 

iii. Rebalance the muscle forces by lengthening the Achilles tendon and reattaching the tibialis anterior and extensor hallucis longus tendons to the anterior talus.

 

b. Boyd amputation—Combines a talectomy with calcaneotibial arthrodesis.

 

c. Pirogoff amputation—The distal end of the calcaneus is excised, then rotated and fused to tibia.

 

d. Both the Boyd and Pirogoff amputations prevent migration of the heel pad and provide a stable distal weight-bearing surface.

 

B. Ankle disarticulation (Syme)

 

1. Provides superior mechanics compared with transtibial amputation

 

2. Surgical procedure

 

a. A long posterior flap is preferred to sagittal flaps.

 

b. Preserve the length of the residual tibia.

 

c. Bevel the tibia cut and perform a myodesis to protect the distal end of the limb.

 

d. Distal limb is covered by heel pad and plantar skin, and the fascia is sutured.

 

3. Postoperative management includes a rigid dressing or cast to control edema, protect the skin from pressure, and prevent knee flexion contracture.

 

C. Knee disarticulation

 

1. Indicated for ambulatory patients who cannot have a transtibial amputation and nonambulatory patients

 

2. Retains the length of femur for good sitting balance

 

3. Prosthetic fitting is more challenging because the knee joint is distal to the opposite leg.

 

4. Longer limb length provides better leverage for use of prosthesis.

 

D. Transfemoral amputation

 

1. Usually done with equal anterior-posterior flaps

 

2. Muscle stabilization is critical (

Figure 6).

 

3. Abduction and flexion forces must be balanced, even in nonambulatory patients.

 

4. Without an adductor myodesis, the femur can migrate to a subcutaneous position even within a well-fitted prosthetic socket.

 

E. Hip disarticulation—Rarely done.

 

1. Ambulation with prosthesis requires more energy than a swing-through gait with crutches.

 

2. A lateral approach is preferred for several reasons:

 

a. Anatomy is more familiar to orthopaedic surgeons.

 

b. Dissection is simplified.

 

[Figure 6. Transfemoral prostheses. A, Transfemoral prosthesis with a microprocessor knee joint. B, Radiograph shows abducted femur within the socket of a transfemoral prosthesis.]

c. Few perforating vessels are encountered.

 

d. Results in a quick procedure with minimal blood loss.

 

e. Preserves femoral and gluteal circulation.

 

3. Mortality varies with the underlying disease process.



IV. Lower Limb Prostheses

A. Overview

 

1. Goals

 

a. Comfortable to wear

 

b. Easy to don and doff

 

c. Lightweight

 

d. Durable

 

e. Cosmetically pleasing

 

f. Must function well mechanically

 

g. Must have reasonably low maintenance requirements

 

2. Major advances in lower limb prostheses

 

a. Development of new lightweight structural materials

 

b. Incorporation of elastic response ("energy-storing") designs

 

c. Use of computer-assisted design and computer-assisted manufacturing technology for sockets

 

d. Microprocessor control of the prosthetic knee joint

 

3. Major components include the socket, suspension mechanism, knee joint, pylon, and terminal device.

 

B. Socket—The connection between the residual limb and the prosthesis; the socket must protect the residual limb but also must transmit the forces associated with standing and ambulation.

 

1. Preparatory (temporary) socket

 

a. The preparatory socket must be adjusted several times as the volume of the residual limb stabilizes.

 

b. It can be created by using a plaster mold of the residual limb as a template.

 

2. The most common socket used in a transtibial amputation is a patellar tendon-bearing prosthesis.

 

C. Suspension mechanism—Attaches the prosthesis to the residual limb using belts, wedges, straps, suction, or a combination thereof.

 

1. Suction suspension—The two types are standard suction and silicon suspension.

 

a. Standard suction—Form-fitting rigid or semirigid socket into which the residual limb is fitted (

Figure 7).

 

b. Silicon suction—Uses a silicon-based sock that slips onto the residual limb, which is then inserted into the socket. The silicon helps to form an airtight seal that stabilizes the prosthesis (

Figure 8).

 

D. Knee (articulating) joint (if needed)

 

1. The knee joint has three principal functions:

 

a. To provide support during stance phase.

 

b. To produce smooth control during swing phase.

 

c. To maintain unrestricted motion for sitting and kneeling.

 

[Figure 7. Transtibial prosthesis with standard socket and supracondylar suspension strap.]

[Figure 8. Transfemoral prosthesis with silicone suspension system.]

[

Figure 9. Transfemoral prosthesis with a microprocessor knee joint.]

2. Two types of axis

 

a. A single axis with a simple hinge and a single pivot point

 

b. A polycentric axis with multiple centers of rotation

 

3. Microprocessor control systems have been applied to the knee units for transfemoral amputees (Figure 9).

 

a. The microprocessor alters resistance of the knee unit to flexion or extension appropriately by sensing the position and velocity of the shank relative to the thigh.

 

b. Current microprocessor-controlled knee units do not provide power for active knee extension, which would assist the amputee in rising from the sitting position or going up stairs and would provide power to the amputee's gait.

 

c. The new microprocessor-controlled, "intelligent" knee units do offer superior control when walking at varied speeds, descending ramps and stairs, and walking on uneven surfaces.

 

E. Pylon—A simple tube or shell that attaches the socket to the terminal device.

 

1. This component has progressed from simple static shells to dynamic devices that allow axial rotation and absorb, store, and release energy.

 

2. The pylon can be an exoskeleton (soft foam contoured to match the other limb with a hard laminated shell) or an endoskeleton (internal metal frame with cosmetic soft covering).

 

F. Terminal device—Typically a foot, but it may take other specialized forms, as for water or other sports activities.

 

1. Ankle

 

a. Ankle function usually is incorporated into the terminal device.

 

b. Separate ankle joints can be beneficial in heavy-duty industrial work or in sports, but the additional weight requires more energy expenditure and more limb strength to control the additional motion.

 

2. Foot—The prosthetic foot has five basic functions: To provide a stable weight-bearing surface, absorb shock, replace lost muscle function, replicate the anatomic joint, and restore cosmetic appearance.

 

a. Non-energy-storing feet

 

i. Solid ankle/cushioned heel (SACH) foot—Mimics ankle plantar flexion, which allows for a smooth gait. It is a low-cost, low-maintenance foot for a sedentary patient who has had a transtibial or a transfemoral amputation.

 

ii. Single-axis foot—Adds passive plantar flexion and dorsiflexion, which increase stability during stance phase.

 

b. Energy-storing feet

 

i. Multiaxis foot—Adds inversion, eversion, and rotation to plantar flexion and dorsiflexion; handles uneven terrain well and is a good choice for the individual with a minimal-to-moderate activity level.

 

ii. Dynamic-response foot—This top-of-the-line foot is commonly used by young active individuals and athletic individuals with amputations.

 

G. Prosthetic prescription—Includes the type of prosthesis and its components. Considers the patient's functional level.

 

1. Functional level 1—Has the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at a fixed cadence.

 

2. Functional level 2—Has the ability or potential for ambulation with the ability to traverse low-level environmental barriers such as curbs, stairs, or uneven surfaces.

 

3. Functional level 3—Has the ability or potential for ambulation with a variable cadence.

 

4. Functional level 4—Has the ability or potential for prosthetic ambulation that exceeds the basic ambulation skills, exhibiting high impact, stress, or energy levels.

 

H. Prosthetic training

 

1. Basics of prosthesis care

 

a. How to don and doff the prosthesis

 

b. How to inspect the residual limb for signs of skin breakdown; should be checked daily

 

c. How to perform safe transfers

 

2. Skills training—The end goal is for the patient to safely ambulate on all usual surfaces without adaptive equipment. Training includes:

 

a. Weight bearing with the prosthesis

 

b. Ambulation on level surfaces with a walker or other assistive device

 

c. Training on stairs, uneven surfaces, and ramps/inclines

 

I. Problems with prosthesis use

 

1. Choke syndrome

 

a. Venous outflow can be obstructed when the proximal part of the socket has too snug a fit on the residual limb. When combined with an empty space more distally in the socket, swelling can occur until that empty space is filled.

 

b. With acute choke syndrome, the skin is red and indurated and may have an orange-peel appearance with prominent skin pores.

 

c. If the constriction is not resolved, chronic skin changes with hemosiderin deposits and venous stasis ulcers can develop.

 

2. Dermatologic problems

 

a. Contact dermatitis—The usual culprits are the liner, socks, and suspension mechanism, with the socket a less likely cause. Treatment consists of removal of the offending item and symptomatic treatment with topical diphenhydramine or cortisone creams.

 

b. Cysts and excessive sweating—Can be signs of excessive shear forces and components that are improperly fitted.

 

c. Scar management—Focuses on massaging and lubricating the scar to obtain a well-healed result without dog ears or adhesions.

 

3. Painful residual limb

 

a. Prosthesis-related pain—Possible causes:

 

i. Excessive pressure over anatomic bony prominences

 

ii. Excessive pressure over heterotopic ossification

 

iii. Excessive friction between the skin and prosthetic socket from a poor fit

 

b. Residual limb-related pain—Possible causes:

 

i. Insufficient soft-tissue coverage over bony prominences

 

ii. An unstable residual limb from lack of myodesis to balance muscle forces (eg, no adductor myodesis in a transfemoral amputation leads to unopposed hip abductor force)

 

iii. Unstable soft-tissue pad over the distal residual limb

 

iv. Neuroma formation in a superficial location

 

4. Prosthetic gait—The ability to walk with a prosthesis is related to the mechanical quality of the prosthesis and the physiologic quality of the residual limb. The physiologic quality of the residual limb is related to passive joint mobility and muscle strength.

 

a. Transtibial amputation

 

i. The demands of weight acceptance require heightened muscle control and strength.

 

ii. The increased muscle demand results from insufficient knee flexion and persistent ankle dorsiflexion of the prosthesis.

 

iii. A knee flexion contracture >10° is the most significant obstacle to walking with a transtibial prosthesis.

 

b. Transfemoral amputation

 

i. Walking is an arduous task for the transfemoral amputee, requiring significant functional contributions from the trunk and intact limb.

 

ii. Residual limb function is hampered by the loss of musculature, the lack of direct contact between the thigh and the prosthetic knee joint, and limitations of the prosthetic foot, which ideally should provide increased flexibility without loss of stance stability.

 

J. Energy requirements of prosthetic gait (

Table 4)

 

1. The increase in energy requirements can be the limiting factor in ambulation.

 

2. An individual who has a lower limb amputation and requires a walker or crutches to ambulate uses 65% more energy than someone with a normal gait.

 

[Table 4. Metabolic Cost of Ambulation per Level and Nature of Amputation]

3. Increased levels of energy consumption (percentage above normal)

 

a. Below-knee unilateral amputation: 10% to 20%

 

b. Below-knee bilateral amputation: 20% to 40%

 

c. Above-knee unilateral amputation: 60% to 70%

 

d. Above-knee bilateral amputation: >200%

 

4. Energy consumption is actually less with a transtibial prosthesis than ambulating with crutches. Ambulating with a transfemoral prosthesis, however, requires more energy, which makes the cardiopulmonary status of the patient more significant.



V. Upper Limb Amputations

A. Traumatic amputation

 

1. Overview—The initial management of traumatic amputations often occurs at centers that do not have the expertise to replant the amputated body part or appropriately treat the amputee. It is important for the physicians involved in the initial care of the patient to understand the indications for replantation as well as proper care of the patient, the residual limb, and the amputated limb segment. Knowledge of the basics of initial care and management of the residual limb and amputated body part is crucial.

 

B. Replantation

 

1. Indications—The decision whether to replant depends on patient factors (eg, age, comorbidities) and the condition of the residual limb and amputated body part.

 

2. Common replantations—The most commonly replanted parts are the thumb, multiple digits in adults, and amputated digits in children.

 

3. Initial patient management

 

a. Initial management of the trauma patient includes stabilization of the patient and evaluation for other conditions that may supersede the amputation.

 

b. Life-threatening injuries always take precedence over amputation or replantation.

 

c. Consultation with a hand center helps to determine whether a replantation is indicated. The goal is to expedite patient transfer to a hand center if a replantation is possibly needed.

 

4. Initial management of the amputated body part

 

a. The amputated part should never be placed directly on ice because direct exposure of the amputated part to ice or ice water will result in tissue damage.

 

b. Wrap the amputated body part in moist gauze, place inside a plastic bag, and place the bag on ice.

 

5. Preoperative management for replantation

 

a. Patient should be placed on nothing-by-mouth (NPO) status, and tetanus prophylaxis, antibiotic therapy, and intravenous fluids should be administered.

 

b. Other emergent medical conditions should be treated.

 

c. Radiographs of both the residual limb and the amputated part should be obtained.

 

d. Delay in treatment should be minimized because the likelihood of success of the replantation decreases with prolonged tissue ischemia.

 

6. Contraindications to replantation

 

a. Replantation of a single digit may result in a stiff, painful, and nonfunctional finger. Ray resection may be more useful.

 

b. In patients with factors that contraindicate single-digit replantation (eg, advanced age, diabetes mellitus, smoking), revision amputation is indicated.

 

c. Amputations of the distal thumb or fingers can be shortened and closed primarily.

 

C. Surgical amputation

 

1. Indications for amputation—Irreparable loss of the blood supply or tissue of a diseased or injured upper limb is the only absolute indication for amputation regardless of all other circumstances.

 

a. Vascular compromise or occlusion—Patients present very differently, depending on the etiology.

 

b. Trauma—Most cases of involve significant avulsion and crush components.

 

c. Thermal burns and frostbite—These cases rarely require amputation proximal to the hand.

 

d. Neglected compartment syndromes

 

e. Systemic sepsis—Amputations may be necessary to control an otherwise rampant infection.

 

f. Malignant tumors

 

2. Incidence

 

a. Published estimates of the annual incidence of upper limb amputations in the United States vary significantly, from 20,000 to 30,000 new amputations per year.

 

b. Prevalence—350,000 to 1,000,000 persons with all types of amputations in the United States.

 

3. Goals of upper limb amputation surgery

 

a. Preservation of functional length

 

b. Durable skin and soft-tissue coverage

 

c. Preservation of useful sensation

 

d. Prevention of symptomatic neuromas

 

e. Prevention of adjacent joint contractures

 

f. Controlled short-term morbidity

 

g. Early prosthetic fitting

 

h. Early patient return to work and recreation

 

4. Levels of amputation

 

a. Ray resection—A digital ray resection (eg, index or little finger) may be preferable to a digital replantation if the result of the replantation would be a stiff, useless, or painful digit.

 

b. Transcarpal amputation

 

i. Advantages—Preserves supination and pronation of the forearm and limited flexion and extension of the wrist. The long lever arm increases the ease and power with which a prosthesis can be used.

 

ii. Disadvantages—Prosthetic fitting is more difficult than with a wrist disarticulation.

 

iii. Surgical technique—Long full-thickness palmar and shorter dorsal flap should be created in a ratio of 2:1. The finger flexor and extensor tendons should be transected. The wrist flexors and extensors should be anchored to the remaining carpus in line with their insertions to preserve active wrist motion.

 

c. Wrist disarticulation

 

i. Indications—Wrist disarticulation is the procedure of choice in children because it preserves the distal radial and ulnar physes. It also provides a longer lever arm for strength in both adults and children.

 

ii. Advantages—Preserves the distal radioulnar joint to preserve pronation and supination.

 

iii. Surgical technique—The prominent styloid processes should be rounded off. The radial styloid flare should be preserved to improve prosthetic suspension.

 

d. Transradial amputation

 

i. Advantages—Despite resection of the distal radioulnar joint, some degree of pronation and supination is preserved.

 

ii. Surgical technique—Amputation at the junction of the distal and middle third of the forearm appears to provide a good compromise between adequate functional length and adequate wound healing. If amputation at this level is not possible, a shorter residual limb is still preferable to a transhumeral amputation. Detaching the biceps tendon and reattaching it proximally to the ulna at a position approximating its resting length is advisable to facilitate prosthetic fitting. Distal reattachment may cause a flexion contracture at the elbow.

 

e. Transhumeral amputation

 

i. Efforts should be made to retain as much of the bone length that has suitable soft-tissue coverage as possible.

 

ii. Even if only the humeral head remains and no functional length is salvageable, an improved shoulder contour and cosmetic appearance results.

 

iii. Myodesis helps preserve biceps and triceps strength, prosthetic control, and myoelectric signals.

 

f. Shoulder disarticulation

 

i. Incidence and indications—Shoulder disarticulations are performed only rarely, usually in cases of cancer or severe trauma.

 

ii. Disadvantages—Results in a loss of the normal shoulder contour and causes the patient difficulty because clothing does not fit well.

 

iii. Surgical considerations—The humeral head should be saved if possible because this can improve the contour of a shoulder disarticulation tremendously.

 

D. Postoperative management of upper limb amputations

 

1. A soft compressive dressing is applied.

 

2. An elastic bandage is applied to prevent edema.

 

3. If a drain is used, it is removed within 24 to 48 hours.

 

4. If no contraindications exist, anticoagulation may be administered for deep venous thrombosis prophylaxis.

 

5. Immediate active range of motion of the shoulder and elbow (and wrist) is implemented to prevent joint contractures.

 

E. Immediate or early postoperative prosthetic fitting

 

1. Advantages include decreased edema, postoperative pain, and phantom pain; accelerated wound healing; improved rehabilitation; and shorter hospital stays.

 

2. Benefits are less pronounced at amputation levels above the elbow.



VI. Upper Limb Prostheses

A. Overview

 

1. Terminology

 

a. Relief—A concavity within the socket designed for pressure-sensitive bony prominences.

 

b. Buildup—A convexity designed for areas tolerant to high pressure.

 

c. Terminal device—Most distal part of the prosthesis used to do work (eg, hand).

 

d. Myodesis—Direct suturing of muscle or tendon to bone.

 

e. Myoplasty—Suturing of muscle to periosteum.

 

f. Prehensile—Designed for grasping.

 

2. Considerations for upper limb prostheses

 

a. Amputation level

 

b. Expected function of the prosthesis

 

c. Cognitive function of the patient

 

d. Vocation of the patient (desk job versus manual labor)

 

e. Avocational interests of the patient

 

f. Cosmetic importance of the prosthesis

 

g. Financial resources of the patient

 

B. Types of upper limb prostheses

 

1. Body-powered prostheses

 

a. Advantages

 

i. Moderate cost and weight

 

ii. Most durable prostheses

 

iii. Have higher sensory feedback

 

b. Disadvantages

 

i. Less cosmetically pleasing than a myoelectric unit

 

ii. Require more gross limb movement

 

2. Myoelectric prostheses—Function by transmitting electrical activity that the surface electrodes on the residual limb muscles detect to the electric motor.

 

a. Advantages

 

i. Provide more proximal function

 

ii. Better cosmesis

 

b. Disadvantages

 

i. Heavy and expensive

 

ii. Less sensory feedback

 

iii. Require more maintenance

 

c. Types of myoelectric units

 

i. 2-site/2-function device—Has separate electrodes for flexion and extension.

 

ii. 1-site/2-function device—Has one electrode for both flexion and extension. The patient uses muscle contractions of different strengths to differentiate between flexion and extension (eg, a strong contraction opens the device, and a weak contraction closes it).

 

C. Prosthesis characteristics by amputation level

 

1. Transradial (below-elbow)

 

a. Voluntary opening split hook

 

b. Friction wrist

 

c. Double-walled plastic laminate socket

 

d. Flexible elbow hinge, a single-control cable system

 

e. Biceps or triceps cuff

 

f. Figure-of-8 harness

 

2. Transhumeral (above-elbow)—Similar to transradial, with several differences

 

a. Substitutes an internal-locking elbow for the flexible elbow hinge

 

b. Uses a dual-control instead of single-control cable

 

c. No biceps or triceps cuff

 

D. Components

 

1. Terminal devices

 

a. Passive terminal devices

 

i. Advantages—The main advantage of a passive terminal device is its cosmetic appearance. With newer advances in materials and design, a device that is virtually indistinguishable from the native hand can be manufactured.

 

ii. Disadvantages—Passive terminal devices usually are less functional and more expensive than active terminal devices.

 

b. Active terminal devices

 

i. Active terminal devices usually are more functional than cosmetic.

 

ii. Active devices can be divided into two main categories: hooks and prosthetic hands with cables, and myoelectric devices.

 

c. Grips—Five types

 

i. Precision grip (pincer grip)

 

ii. Tripod grip (palmar grip, 3-jaw chuck pinch)

 

iii. Lateral pinch (key pinch)

 

iv. Hook power grip (carrying a briefcase)

 

v. Spherical grip (turning a doorknob)

 

d. Considerations for choice of terminal device (prehension device)

 

i. Handlike devices—These devices are composed of a thumb and an index and long finger. The thumb and fingers are oriented to provide palmar prehension. The fingers are coupled as one unit with the thumb in a plane perpendicular to the axis of the finger joints. The device may be covered with a cosmetic silicone glove simulating the appearance of an intact hand. Often the device of choice for a person working in an office environment.

 

ii. Non-hand prehension devices—Hooks or two-finger pincer designs with parallel surfaces. Good for work situations that require higher prehension force. May be fitted with quick release mechanisms to attach task-specific tools for both vocational and avocational activities. Often used in an environment requiring physical labor.

 

iii. Externally powered myoelectric devices—Use force-sensing resistors. Offer freedom from a control suspension harness. Provide stronger prehension. Can be used only in a non-hostile environment, free from dirt, dust, water, grease, or solvents.

 

iv. Many upper extremity amputees have both a body-powered and a myoelectric prosthesis to use for specific activities.

 

e. Terminal device mechanisms

 

i. Voluntary opening mechanism—The terminal device is closed at rest. This type of mechanism is more common than a voluntary closing mechanism. The patient uses the proximal muscles to open a hook-based device against the resistive force of rubber bands or cables. Relaxation of the proximal muscles allows the terminal device to close around the desired object. In a myoelectric device, contraction of the proximal muscles activates the electric motor.

 

ii. Voluntary closing mechanism—The terminal device is open at rest. The patient uses the residual forearm flexors to grasp the desired object. These devices are usually heavier and less durable than a voluntary opening mechanism.

 

2. Wrist units

 

a. Quick-disconnect wrist unit—Allows easy swapping of terminal devices with specialized functions.

 

b. Locking wrist unit—Prevents rotation during grasping and lifting.

 

c. Wrist flexion unit—In a patient with bilateral upper limb amputations, a wrist flexion unit can be placed on the longer residual limb (regardless of premorbid hand dominance) to allow midline activities such as shaving or manipulating buttons.

 

3. Elbow units—Chosen based on the level of the amputation and the amount of residual function.

 

a. Rigid elbow hinge—When a patient cannot achieve adequate pronation and supination but does have adequate native elbow flexion, such as in a short transradial amputation, a rigid elbow hinge provides additional stability.

 

b. Flexible elbow hinge—When a patient has sufficient voluntary pronation and supination as well as elbow flexion and extension, such as in a wrist disarticulation or a long transradial amputation, a flexible elbow hinge usually works well.

 

4. Prostheses for amputations about the shoulder

 

a. When an amputation is required at the shoulder or forequarter level, function is very difficult to restore because of the weight of the prosthetic components as well as the increased energy expenditure necessary to operate the prosthesis.

 

b. For this reason, some individuals with this level of amputation choose a purely cosmetic prosthesis to improve body image and the fit of their clothes.

 

E. Problems associated with upper limb prostheses

 

1. Dermatologic problems

 

a. Contact dermatitis—The usual culprits are the liner, socks, and suspension mechanism, with the socket a less likely cause. Treatment consists of removal of the offending item and symptomatic treatment with topical diphenhydramine or cortisone creams.

 

b. Cysts and excessive sweating—Can be signs of excessive shear forces and components that are improperly fitted.

 

c. Scar management—Focuses on massaging and lubricating the scar to obtain a well-healed result without adhesions.

 

2. Painful residual limb

 

a. Prosthesis-related pain—Possible causes:

 

i. Excessive pressure over anatomic bony prominences

 

ii. Excessive pressure over heterotopic ossification

 

iii. Excessive friction between the skin and prosthetic socket from a poor fit

 

b. Residual limb-related pain—Possible causes:

 

i. Insufficient soft-tissue coverage over bony prominences

 

ii. An unstable residual limb from lack of myodesis to balance muscle forces.

 

iii. An unstable soft-tissue pad over the distal residual limb

 

iv. Neuroma formation in a superficial location



Top Testing Facts

1. Articulated AFOs allow a more natural gait pattern and allow adjustment of plantar and dorsiflexion. The joints can be designed to provide stability in terminal stance and to provide dorsiflexion assistance to clear the toes during swing.

 

2. A KAFO can be used in quadriceps paralysis or weakness to maintain knee stability and control flexible recurvatum, valgus, or varus.

 

3. A polycentric knee joint allows limited multiplanar motion during flexion and extension that decreases specific areas of joint contact forces. This is helpful for persons with osteoarthritis.

 

4. Lower limb amputation is a reconstructive procedure with the goals of preserving length and strength and balancing the forces of the remaining muscles to provide a stable residual limb.

 

5. The Syme ankle disarticulation provides superior mechanics and is the most common level of amputation in the foot.

 

6. The major advances in lower limb prostheses include (a) the development of new lightweight structural materials; (b) the incorporation of elastic response ("energy-storing") designs; (c) the use of computer-assisted design and computer-assisted manufacturing technology in sockets; and (d) microprocessor control of the prosthetic knee joint.

 

7. Increased levels of energy (percentage over normal) are associated with amputations: below-knee, 10% to 20%; bilateral below-knee, 20% to 40%; above-knee, 60% to 70%.

 

8. Patient management for replantation includes the following: emergent medical conditions should be treated; radiographs of both the residual limb and the amputated part should be obtained; the patient should be made NPO; and tetanus prophylaxis, antibiotic therapy, and intravenous fluids should be administered. The amputated part should be wrapped in wet gauze and placed in a plastic bag on ice.

 

9. Goals of upper limb amputation surgery include preservation of functional length, durable skin and soft-tissue coverage, preservation of useful sensation, prevention of symptomatic neuromas, prevention of adjacent joint contractures, controlled short-term morbidity, early prosthetic fitting, and early patient return to work and recreation.

 

10. A voluntary opening mechanism (the terminal device is closed at rest) is commonly used for the hand.



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Goel A, Navato-Dehning C, Varghese G, Hassanein K: Replantation and amputation of digits: User analysis. Am J Phys Med Rehabil 1995;74:134-138.

Martin C, Gonzalez del Pino J: Controversies in the treatment of fingertip amputations: Conservative versus surgical reconstruction. Clin Orthop Relat Res 1998;353:63-73.

Potter BK, Scoville CR: Amputation is not isolated: An overview of the us army amputee patient care program and associated amputee injuries. J Am Acad Orthop Surg 2006;14: S188-S190.

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Wilkinson MC, Birch R, Bonney G: Brachial plexus injury: When to amputate? Injury 1993;24:603-605.

Wright TW, Hagen AD, Wood MB: Prosthetic usage in major upper extremity amputations. J Hand Surg [Am] 1995;20: 619-622.