Amputations and Rehabilitation

11


Amputations and Rehabilitation


Todd Borenstein, Gregory R. Waryasz, and Roman Hayda


I. Gait and Amputation


1. Gait (Fig. 11.1)


• Walking


a. Definitions


Cycle: initial heel contact to initial contact (same foot)


Cadence: steps per minute


Single-limb support: phase of gait in which body weight is supported by one leg


Double-limb support: period when both feet are in contact with the ground (not present in running)


Step: the distance from initial contact of one foot to initial contact of contralateral foot


Stride: the distance from initial contact to initial contact of the same foot


♦ One stride = two steps (Fig. 11.1)


♦ Running


▪ Free-float phase: period when neither limb is in contact with the ground (not present in walking)


♦ Gait phases


▪ Stance phase: 60% of gait cycle



• Initial contact, Loading response, Midstance, Terminal stance, Pre-Swing; mnemonic: “I Like My Tea Pre-Sweetened”


• Initial contact: heel touches ground, hip is flexed, knee is extended, ankle is dorsiflexed


• Load response: foot contacts floor, knee flexes slightly, and ankle plantar flexes to absorb energy while dorsiflexors eccentrically fire; quadriceps fire to stabilize flexed knee as limb accepts all body weight (contralateral leg comes off the ground)


• Midstance: single limb support; hip extended and quadriceps concentrically fire to straighten the leg and progress body forward; calf muscles begin to fire as weight transitions anterior to leg and ankle begins to plantarflex


• Terminal stance: heel rises (opposite foot is in heel strike); toes dorsiflex and toe flexors are active


• Pre-swing: second time both limbs are on the ground; body weight transferred to other side (contralateral side in loading response), hip flexors fire to advance the limb forward; knee flexed and ankle plantar flexed



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



• Hindfoot inversion in terminal stance locks the transverse tarsal joint, making the foot rigid and increasing the length of the lever arm of the Achilles tendon. This inversion optimizes heel rise/push off. Posterior tibial tendon insufficiency prevents this from happening efficiently.


• Windlass mechanism


images 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 (toe off), limb acceleration to Mid-swing, limb deceleration to Terminal swing; mnemonic: “In My Teapot”


• 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.


▪ Center of gravity (Fig. 11.2)


• Located anterior to T10, average of 33 cm above the hip


• Vertical displacement: 5 cm; follows sinusoidal curve


• Lateral displacement, transfer of body weight to limb: 6 cm; also follows sinusoidal curve


▪ Line of gravity (Fig. 11.2)


• Passes anterior to S2



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


images 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


▪ Pelvic tilt: the non–weight-bearing side drops 5 degrees to reduce superior deviation


▪ 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.



• Achilles, patellar, and quadriceps tendon tears are often associated with eccentric muscle contractions, such as occur during deceleration from a jump or preventing a fall.


▪ 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.


▪ Muscle contraction forces at the ankle during stance (Fig. 11.3):


• During initial contact dorsiflexors (tibialis anterior) eccentrically contract to slow ankle plantarflexion and prevent the foot from slapping the floor.


images Maximum electrical activity of tibialis anterior during initial contact


• Then plantar flexors eccentrically contract during stance to slow ankle dorsiflexion.


• Concentric contraction by plantar flexors for heel; off at end of stance phase


♦ Pathological gait (Table 11.1)


▪ Muscle weakness decreases the ability to move a joint normally through space.


▪ Grading of motor weakness (Table 11.2)


• Walking patterns develop based on the specific muscle weakness and the ability of the individual to acquire a substitution pattern.


• Example: abductor lurch (Trendelenburg) gait (weak hip abductors)


images Superior gluteal nerve (L4,5) or muscle injury


images Contralateral pelvis drops; as a result the trunk lurches to the weakened side to maintain balance (Fig. 11.4).



▪ 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


images 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


images 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


Table 11.1 Gait Alteration Patterns from Muscle Weakness






















Abnormal Gait


Muscle Weakness


Abductor lurch (Trendelenburg)


Gluteus medius


Hip hyperextension/lurch


Gluteus maximus


Back knee gait


Quadriceps


Flatfoot


Gastrocnemius/soleus


Steppage gait/foot drop


Tibialis anterior


Table 11.2 Grading of Muscle Weakness

























Grade


Description


0/5


No contraction


1/5


Muscle flicker, no movement


2/5


Movement with gravity eliminated


3/5


Movement against gravity


4/5


Movement against some resistance


5/5


Movement against full resistance/normal strength



▪ Hemiplegia: prolonged stance and double-limb support


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


images 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.


images 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.


images 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


Table 11.3 Energy Expenditure for Ambulation
































Amputation Level


Energy Above Baseline (%)


Speed (m/min)


Long transtibial


10


70


Average transtibial


25


60


Short transtibial


40


50


Bilateral transtibial


41


50


Transfemoral


65


40


Wheelchair


0–8


70


b. Energy expenditure compared with normal limb (Table 11.3):


Transfemoral, 65% more


Transfemoral in vascular patient, 100% more


Bilateral transtibial, 40% more


Short transtibial, 25% more


Long transtibial, 10% more



Note: a unilateral transfemoral amputation entails a higher energy expenditure than a bilateral transtibial amputation.


• Load transfer


a. The soft tissue envelope acts as an interface between the bone of the residual limb and the prosthetic socket.


Ideally composed of a secure muscle mass covering the bone end and full-thickness skin that can tolerate direct pressure


A mobile nonadherent soft tissue envelope decreases shear forces.


b. Load transfer occurs either directly or indirectly


Direct load transfer: occurs in knee or ankle disarticulations


♦ Load transferred directly through terminal weight-bearing surface


♦ Intimacy of prosthetic device is necessary only for suspension


Indirect load transfer: occurs when the amputation is through a long bone, i.e., transfemoral or transtibial


♦ Load is transferred indirectly by total contact method


♦ Must have intimate fit of the prosthetic socket


• Amputations in the dysvascular patient


a. Patients with diabetes and peripheral vascular disease


Special wound healing and soft tissue considerations


♦ Peripheral neuropathy most important risk factor


♦ Total contact casts can reduce pressure and shear stress on wounds


♦ May perform myoplasty instead of myodesis


▪ Avoid further compromise of blood supply to muscle



Myoplasty: suturing muscle directly to muscle to cover bone end


Myodesis: suturing muscle or tendon directly to bone end


• Amputations commonly for nonhealing wounds and infections


II. Wound Healing Considerations


1. Vascular supply


• Transcutaneous oxygen tension > 40 mm Hg (gold standard)


a. Measure of oxygenation and vascular supply


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


b. Patient factors always a consideration:


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.


• Technical considerations


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.


• Optimum length of transradial amputation is at junction of middle and distal thirds.


images 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.


The heel pad should be secured to the tibia either anteriorly with drill holes or posteriorly using the Achilles tendon.


♦ 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.



Transfemoral amputees may use close to maximum energy expenditure and may not regain the capacity to walk, especially the elderly and dysvascular patient.

Jun 28, 2018 | Posted by in ORTHOPEDIC | Comments Off on Amputations and Rehabilitation
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