Amputations and Rehabilitation

Todd Borenstein, Gregory R. Waryasz, and Roman Hayda

I. Gait and Amputation

• Just prior to heel rise in terminal stance, the posterior tibial tendon fires, which inverts the hindfoot and locks the transverse tarsal joint.

• Windlass mechanism

After heel rise, the plantar fascia is tightened as the metatarsophalangeal (MTP) joints extend and the longitudinal arch is accentuated, helping to further lock the transverse tarsal joint into a rigid platform.

▪ Swing phase: 40% of gait cycle

• Initial swing: hip flexed, knee flexed, ankle dorsiflexed (single-limb support)

• Mid-swing: knee extends, hip and ankle stay flexed

• Terminal swing: hamstrings decelerate the leg, and hip and ankle stay flexed as walker transitions to heel strike

▪ Normal gait prerequisites

• Stance phase stability

• Swing phase ground clearance

• Foot position before initial contact

• Energy-efficient step length and speed

♦ Gait dynamics

▪ Energy-efficient gait lessens the excursion of the center of gravity.

• Reference for moment arm to the center of the joint under consideration, can be used to calculate joint forces

Line of gravity passes anterior to hip joint and posterior to the knee joint, the weight of the body hyperextends these joints, which are resisted by the iliofemoral ligament at the hip and the ligamentous apparatus of the knee

♦ Determinants of gait: six factors that help minimize excursion of the body’s center of gravity

▪ Pelvic rotation: occurs horizontally about a vertical axis

• Lessens the center of mass deviation

• Reduces impact on floor contact

▪ Knee flexion in stance: stance phase limb is flexed to 15 degrees at loading

• Dampen impact at loading

• Lowers the center of gravity to decrease energy expenditure

▪ Foot and ankle motion: impact of loading is dampened through ankle plantarflexion

• Increased stability at midstance

• Increased efficiency during push-off

▪ Knee motion: knee extends while ankle plantarflexes after midstance to restore limb length

• Diminishes fall of pelvis at contralateral heel strike

▪ Lateral pelvic displacement: displacement of the center of gravity over the stance limb

• Increases stance-phase stability

♦ Muscle action

▪ Agonists and antagonists work together during the gait cycle.

▪ Eccentric contraction of an antagonist muscle dampens the activity of an agonist causing deceleration, and lengthening the muscle during active resistance of an opposing force.

• Eccentric contraction is associated with highest tensile forces on muscle tendon unit and is associated with tears of major tendons.

▪ Concentric muscle contraction shortens the muscle to move a joint through space.

▪ During swing phase the limb is advanced forward by concentric contraction of the hip flexors and decelerated during terminal swing by eccentric contraction of the hip extensors.

▪ Neurologic conditions may affect gait by producing muscle weakness, loss of balance, and reduced coordination between agonists and antagonists with or without joint contracture.

• Steppage gait: foot drop

Equinus and varus foot and back-set knees; result of the loss of tibialis anterior and peroneal muscles (peroneal nerve)

• Knee hyperextension: spasticity of ankle plantar flexor or knee extensors during stance phase; may also be the result of quadriceps weakness to prevent knee buckling with weight bearing

• Hip scissoring: overactive hip adductors

• Knee flexion contracture: hamstring spasticity

• Flatfoot gait: weak gastrocnemius from posterior tibial nerve injury or muscle tear

• Stroke: equinovarus, spastic gastrocnemius/soleus ± tibialis anterior and tibialis posterior

Split anterior tibial tendon transfer and gastrocnemius recession to correct

▪ Antalgic gait: shortened stance phase on a painful limb; contralateral swing phase is more rapid

▪ Hemiplegia: prolonged stance and double-limb support

• Gait impairments as a result of excessive plantarflexion, weakness, and balance problems

Associated with ankle equinus, limitation of knee flexion, increased hip flexion

▪ Leg length discrepancy

• Increased mechanical work by long leg

• Increased stance time and step length on longer leg

• Overall walking velocity is slower

• Increased ground reaction forces on long leg

▪ Crutches and canes ameliorate instability and pain.

• Crutches increase stability.

To be touchdown weight bearing, a patient must use double axillary crutches.

• A cane shifts the center of gravity to the affected side when used in the contralateral hand.

Decreases the joint reactive force by decreasing the moment arm between the center of gravity and the femoral head

▪ Arthritis: forces across the knee may be four to seven times body weight

• 70% through the medial compartment

▪ Water walking: decreases joint contact forces as result of the effect of buoyancy

2. Amputations

• Treatment of peripheral vascular disease, trauma, tumor, infection or a congenital anomaly

• Metabolic cost of amputee gait

a. Metabolic cost of walking is increased with proximal-level amputations.

◦ Inversely proportional to length of the residual limb and number of preserved joints

b. Most predictive factor for successful wound healing

c. > 40 mm Hg good wound healing, < 20 mm Hg poor wound healing

d. Ideally > 45 mm Hg

• Hemoglobin > 10 g/dL

• Doppler pressure > 70 mm Hg

a. Minimum inflow pressure to support wound healing

• Toe pressure > 40 mm Hg

• Ischemic index > 0.5

a. Ratio of Doppler pressure at the level compared with the brachial systolic pressure

b. An index of > 1 can be falsely elevated due to vascular calcifications.

2. Nutritional and immune status

• Serum albumin > 3.0 g/dL

a. < 3.0 g/dL indicates a patient is malnourished

• Total lymphocyte > 1,500/mm³

a. Total lymphocyte < 1,500/mm³ indicates immune deficiency

• High rate of wound failure in patients with malnutrition or immune deficiency

• Should delay amputation until nutritional parameters can be improved by nutritional support

• Pediatric amputations

a. Usually performed for congenital limb deficiencies, trauma, or tumors

b. Congenital amputations are the result of failure of formation.

◦ Amputations are rarely indicated for upper extremity congenital limb deficiencies; even rudimentary appendages can be useful.

◦ In the lower extremity, amputation of an unstable segment may allow for direct load transfer and improved walking.

♦ Absent fibula: Syme amputation

♦ Absent tibia: knee disarticulation

c. Overgrowth is the most common complication in transosseous pediatric amputations, most commonly at the humerus

◦ Also seen in diaphyseal amputations of fibula, tibia, and femur

◦ Best method to predictably resolve this is surgical revision with adequate resection of bone

◦ Osteochondral stump capping has unpredictable results.

◦ Disarticulation is the only reliable measure to prevent overgrowth and subsequent revision surgeries.

♦ Maintain maximum residual limb length by preserving growth plates

d. Prosthetic fitting

◦ Upper limb: at 4–6 months of age (sitting), 2–3 years for active device

◦ Lower limb: at 8–12 months of age

• Amputations in the trauma patient

a. There are grading scales for evaluating mangled extremities that act as guidelines to determine if a limb is salvageable

◦ LEAP (Lower Extremity Assessment Project): severe soft tissue injury most important factor in decision making

◦ MESS (Mangled Extremity Severity Score): takes into consideration age, shock, limb ischemia, and energy of skeletal soft tissue injury

♦ Helpful as guide, but not proven to be sufficiently sensitive

◦ Physiological, psychological, social, economic resources (self-efficacy); substance abuse history

◦ May sway decision in “gray area” scenarios

c. Indications for immediate amputation

◦ Grade IIIB and IIIC tibial injuries with uncontrollable hemorrhage

♦ Typically from multiple levels of arterial/venous injury

♦ Life versus limb: patients in extremis or very critically ill

◦ Crush injury with warm ischemia time > 6 hours

◦ Incomplete traumatic amputations with significantly injured distal segment

d. “Gray area” indications with high risk for prolonged reconstruction with complications and resulting in poor function

◦ Significant segmental bone or muscle loss

◦ Open tibia fractures associated with open foot injuries

◦ Significant nerve injury

♦ Lack of plantar sensation on exam is not a reliable clinical indicator of significant nerve injury; may be neurapraxia

▪ Exploration of tibial nerve required

e. Amputation level

◦ Amputate at most distal, viable level followed by open wound management

♦ Closure or coverage when patient condition is stable and soft tissue stabilized

◦ Amputation through the zone of injury caused by a blast mechanism predictive for the development of heterotopic ossification

♦ Role of limb salvage in the trauma patient

▪ Used in “gray area” scenarios when patient factors sway decision to limb salvage

▪ SIP (Sickness Impact Profile) and return to work not significantly different at 2 and 7 years between limb salvage and amputation in severe limb threatening injuries

• A salvaged lower limb that is insensate on the weight-bearing surface with associated functional muscle and bone loss is unlikely to provide a durable weight-bearing surface.

▪ Lifetime costs incurred are thought to be higher with amputation than with limb salvage.

• Western society: costs associated with prosthetics

▪ Complication rates

• Severe open tibia fractures managed by limb salvage have high rates of complications, including increased hospitalizations, infection, multiple surgeries

• Musculoskeletal tumors

a. The goal of surgery is to remove the tumor with negative margins.

b. Limb salvage versus amputation

◦ Based on expected functional outcome if acceptable margins can be obtained with limb salvage

◦ There is controversy regarding the outcomes of limb salvage versus amputation.

◦ Limb salvage patients tend to be more sedentary.

◦ Amputees tend to be more active.

a. Skin flaps should be full thickness.

b. Periosteal stripping helps minimize regenerative bone overgrowth.

c. Wounds should not be closed under tension.

d. Muscle should be secured to bone (myodesis) at resting tension as opposed to secured to antagonist muscle (myoplasty).

◦ Especially adductor in transfemoral amputation

e. Stable residual limb mass reduces atrophy and provides a stable soft tissue envelope over bone.

f. All transected nerves form neuromas.

◦ The nerve end should be far away from potential pressure areas.

g. Compressive dressings postoperatively help with swelling and pain.

h. Early prosthetic fitting is done at 5–21 days.

• Complications

a. Pain

◦ Phantom limb sensation occurs in most adults

◦ Phantom dysesthesia in the absent limb

◦ Complex regional pain syndrome is a common cause of residual pain.

♦ May be treated with α-blocking agents

b. Edema

◦ Postoperative edema may prevent wound healing.

◦ Rigid dressings and compression help reduce edema.

◦ Chronic swelling can cause verrucous hyperplasia.

♦ Should be treated with total contact casting

c. Joint contractures

◦ Hip and knee flexion contractures occur if the respective muscles are anchored with the joints in a flexed position during surgery.

◦ Avoided with correct positioning during recovery (keeping knee fully extended and prone lying for the hip)

d. Wound failure to heal

◦ Most often in diabetics

◦ If not amenable to local care, excision of a wedge of soft tissue and bone with tension-free soft tissue closure is preferred.

• Upper limb amputations

a. Benefits of limb salvage

◦ Sensation is crucial for function in the upper limb.

◦ A partially sensate, partially functional salvaged limb is often more functional than an insensate prosthesis.

b. Wrist disarticulation

◦ Advantages

♦ Preserves more forearm rotation because preserves distal radioulnar joint (DRUJ) compared with transradial

♦ Flare of distal radius helps suspend prosthesis

◦ Disadvantages

♦ Cosmetic issues

▪ Prosthesis is longer than contralateral limb

▪ Motor and battery of myoelectric components cannot be hidden

▪ Transradial amputation and elbow disarticulation

• A nonfunctioning hand and forearm is best treated with a transradial amputation or elbow disarticulation.

Myoelectric components can be hidden.

• Length and shape of elbow disarticulation provides improved lever arm; epicondyles can enhance suspension.

▪ Transhumeral amputation

• Often limited prosthetic use due to discomfort and difficulty using prosthesis—elbow (flexion/extension) and hand functions (hand open/close) performed sequentially. Patients adapt using single upper extremity.

• Lower limb amputations

a. Toe and ray amputations

◦ Patients with ischemia do well after toe amputations because they ambulate with a propulsive gait pattern.

◦ Great toe should be amputated distal to the flexor hallucis brevis (FHB) insertion

◦ Isolated second-toe amputations are performed distal to the proximal phalanx metaphyseal flare to prevent late hallux valgus.

◦ Single outer ray amputations function well in shoes.

◦ Resection of more than one ray creates a narrow forefoot, leading to difficulty in shoe fitting.

◦ Central ray amputations have wound healing issues:

♦ Rarely gets better results than midfoot amputations

b. Transmetatarsal and midfoot amputations (Lisfranc and Chopart)

◦ Long plantar flap is myocutaneous and the preferred flap

◦ Transmetatarsal amputations should be through proximal metaphyses to help prevent ulcer formation.

♦ May bevel metatarsals on plantar surface and medial and lateral border

◦ Achilles tendon lengthening should be performed to help prevent equinus or equinovarus.

♦ Result of overpull from gastrocnemius and posterior tibialis and short lever arm of absent forefoot

◦ Equinovarus can be corrected with tibialis anterior transfer to the neck of the talus.

♦ Insertion site of the peroneus brevis and tertius at the base of the fifth metatarsal should be preserved.

♦ Act as antagonists to posterior tibial tendon to prevent supination/inversion of the foot

◦ Avoid hindfoot amputations in patients with diabetes and vascular disease.

c. Ankle disarticulation (Syme)

◦ Allows direct load transfer, rarely has issues with ulcers and tissue breakdown

◦ Provides stable gait pattern

◦ Despite being more proximal, is more energy efficient than midfoot amputations such as Lisfranc or Chopart amputations

◦ Less energy efficient than a transmetatarsal amputation

◦ Posterior tibial artery supplies the heel pad and must be patent

♦ Patients with an ankle-brachial index (ABI) < 0.5 in the posterior tibial artery have decreased healing rates.

◦ Remove malleoli and metaphyseal flares.

♦ Avoid hypermobile heel pad to ensure good results.

d. Transtibial amputation (below knee)

◦ The soft tissue envelope is created using a long posterior myocutaneous flap.

♦ “Dog ears” at the edge of a long posterior flap are left intact because of the risk of injury to the saphenous and sural arteries. Flap necrosis is also a risk.

◦ Optimum bone length is at least 12 cm below the joint line but longer is better; provides soft tissue cover and room for prosthetic components

◦ Posterior muscle secured to beveled anterior tibia by myodesis

◦ Cylindrical shape preferred

◦ Rigid dressings are used in the early postoperative period.

◦ Early prosthesis fitting in 5–21 days depending on wound healing and if the residual limb is able to transfer load.

◦ Ertl modification, in which a bone bridge between the fibula and the tibia is created, was proposed to create a more stable platform for load transfer by enlarging the stable surface area.

e. Knee disarticulation

◦ Use long posterior flap with gastrocnemius as end padding

◦ The patella is sutured to the cruciate ligaments, leaving the patella on the anterior femur.

◦ Findings from the LEAP study suggest this to be the level of slowest walking speed and least self-reported satisfaction.

♦ May be due to amputation through zone of injury in LEAP study and shorter follow-up (24 month)

◦ Patients report less pain compared with transtibial and transfemoral amputations.

◦ Usually used in nonambulatory patients

◦ Entails a muscle balanced amputation with a stable weight-bearing platform; allows direct load transfer

◦ Can use polycentric knee; maintains the knee center close to the anatomic joint line

f. Transfemoral amputation (above knee)

◦ Increases energy cost of walking

◦ Patients with transfemoral amputations and peripheral vascular disease usually do not ambulate well.