Limb Deficiency and Prosthetic Management. 1. Decision Making in Prosthetic Prescription and Management

1.1 Clinical Activity: To discuss the management of a 1-year-old child with a congenital complete transverse radial limb deficiency 

APPROXIMATELY 60% OF LIMB deficiencies in children are congenital, according to the Association of Children’s Prosthetic and Orthotic Clinics (ACPOC).1 This number may not represent true prevalence, because the data are collected from specialized clinics that do not serve the entire population of children with limb deficiencies. Congenital limb deletions occur during the third to eighth weeks of gestation. It is estimated that 32% have no known cause, 30% are genetic, 34% are vascular, and 4% are caused by a teratogenic agent.2 The ratio of upper- to lower-extremity limb deletions is 2:1, with 40% of all congenital deletions being left transverse radial.

The short left transverse radial limb deficiency is the most common congenital limb deficiency after missing digits. This is typically an isolated lesion, although infrequently it may be associated with the following syndromes: thrombocytopenia and absent radius (TAR syndrome), heart defect and absent radius (Holt-Oram syndrome), anemia and absent radius (Fanconi syndrome), and vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal defects, and limb defects (VACTERL syndrome).3

A child with transverse radial limb deficiency generally has normal development and movement of the humerus and shoulder joint. The elbow is frequently hypermobile, but the forearm has normal pronation and supination. Often, there are vestiges of fingers, which are nonfunctional. Sensation is intact and skin is normal in the residual limb.

Various classification systems have been devised to describe congenital limb deletions and malformations. The International Standards Organization/International Society of Prosthetists and Orthotists (ISO/ISPO) system is the standard for classifying congenital limb deficiency, although its clinical application is inconsistent, and older classification systems are frequently used (Fig 1, Fig 2, Fig 3).2, 4, 5, 6 In the ISO/ISPO system, transverse deficiencies are named at the segment where the limb terminates. Longitudinal deficiencies are named for the bones partially or totally affected and the fraction missing.

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Fig 1. ISO/ISPO designation of levels of transverse deficiencies of upper and lower limbs. Note that the skeletal elements marked with an asterisk are used as adjectives in describing transverse deficiencies; for example, transverse carpal total deficiency. A total absence of the shoulder or hemipelvis (and all distal elements) is a transverse deficiency. If only a portion of the shoulder or hemipelvis is absent, the deficiency is of the longitudinal type. Reprinted with permission.2

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Fig 2. Description of longitudinal deficiencies of the upper limb using the ISO/ISPO system. *Digits of the hand are sometimes referred by name: 1, thumb; 2, index; 3, middle; 4, ring; 5, little (or small). Reprinted with permission.2

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Fig 3. Description of longitudinal deficiencies of the lower limb using the ISO/ISPO system. *The great toe, or hallux. Reprinted with permission.2

Older systems include the Saint-Hilaire (1837), Frantz-O’Rahilly (1951), and Frantz-O’Rahilly revised (1961). Appendix 1 offers a comparison between classification systems.3

The commonly accepted management of infants and children with unilateral transverse radial limb deficiency in child amputee clinics and among members of ACPOC is that these children should be “fit to sit,” meaning fitted by the age of 6 (six) months with an initial prosthesis that has a passive terminal device. Application of an active terminal device is appropriate at 12 to 15 months.3, 7 Large long-term studies comparing functional outcomes of children fitted early and those fitted at a later age or never fitted with a prosthesis have not been reported. Thus, at this time “expert opinion” guides clinical practice.

Children with unilateral congenital transverse radial limb deficiency typically develop normally, except they may never crawl. Walking may be mildly delayed because of the lack of 2 arms for balance in early walking. These children generally can do most age-appropriate activities with or without their prostheses, although some activities may be done in an atypical manner. They may use the elbow, chin, or knee to assist with bimanual activities. It remains controversial whether toddlers should be fitted with a body-powered prosthesis versus a myoelectric prosthesis. Initial prescription of a body-powered prosthesis with subsequent conversion to a myoelectric prosthesis at the age of 3 to 5 years is the common practice.

Prescription of a body-powered prosthesis for this child may include the following components. (1) Suspension/harness: commonly a figure-of-8 harness is used for suspension. This component enables the child to control a cable to activate the terminal device. A flexible elbow with triceps cuff further secures the prosthesis to the child. (2) Socket: a double-walled socket with a removable growth liner accommodates growth and extends the life of the prosthesis. (3) Control system: a cable controls opening and closing of the terminal device. (4) Terminal device: a child-sized hook or a mechanical hand may be voluntary opening or closing. The terminal device should be selected with input from the prosthetist, physician, and parents.

Later prescription of a myoelectric prosthesis might include the following elements: (1) Suspension: supracondylar suspension (no harness necessary) is recommended, (2) Socket: a custom-molded socket with electrode contacts and a growth liner is recommended, (3) Control system: a single-site control system is recommended if the child is fitted under about 3 years of age; 2-site control is appropriate if the child is fitted at 3 years or older, (4) Terminal device: this component is typically an electric hand that is comparable in size to the other hand. Specialized devices like the Greifer are not currently available in children’s sizes.

To decrease weight in either prosthesis, typically no wrist unit is used. The myoelectric prosthesis may be operated by an external battery attached by cable to the prosthesis to reduce the weight of the prosthesis.

As children grow, their prostheses may require socket and harness adjustments every 3 to 6 months. Replacement of the entire prosthesis is often necessary every 1 to 2 years. Of children with congenital limb deletions or amputations, 10% to 30% develop bony overgrowth that must be surgically addressed.2 This overgrowth initially presents with pain or poor socket fit. Initial management is socket revision, but if the bony overgrowth is too prominent or protrudes through the skin, it must be removed surgically. Various surgical techniques have been tried to prevent further bony overgrowth, but results have not been favorable.2

Most children with congenital unilateral arm or leg amputations can be fully functional, but they may need help with problem-solving on how to do some activities such as bicycle riding or playing on playground equipment. For example, a child may need a prosthetic or equipment adaptation to activate the gear shift or grip the handlebar on a bicycle. The child and/or family may need psychologic support. School and daycare personnel should be educated about what to expect and how to care for the prosthesis. As children grow up, they may choose to participate in sports. There are many “sport prostheses” available such as the swimming leg or a terminal device that facilitates a golf swing, but many children choose to do sports without their prostheses.

1.2 Clinical Activity: To design a rehabilitation program for a 21-year-old male construction worker with a traumatic knee disarticulation 

Patients who sustain amputations from trauma often have irregularly shaped residual limbs and often have large skin wounds or grafted skin. A rigid removable dressing or elastic compressive garment should be used to reduce edema and promote proper shaping. These patients may experience surgical and neuropathic pain after traumatic amputation. Surgical pain may require use of opioids with subsequent transition to non-narcotic pain medications. Neuropathic pain is typically managed with topical agents, antidepressants, and/or anticonvulsants. Levy et al8 have presented a thorough review of pain management. A comprehensive approach should include attention to sleep and attention to psychologic adjustment, with pharmacologic agents used as indicated. Counseling should be provided to address adjustment to disability, depression, and posttraumatic stress disorder.

There are advantages and disadvantages of knee disarticulation compared with a transfemoral amputation. Knee disarticulations allow end-weight bearing on the condyles and offer more stability than transfemoral amputations. In children, the tendency for bony overgrowth is minimized with disarticulation, because the preservation of the articular cartilages prevents bony overgrowth. The energy cost of walking is midway between transtibial and transfemoral amputation levels, which may be important in older amputees or in people with coexisting medical conditions. The major disadvantage of knee disarticulation is the unfavorable appearance and limited prosthetic knee options.

Therapy should begin as soon as possible after the amputation, with an emphasis on reducing residual limb edema, increasing hip range of motion, enhancing mobility, and improving activities of daily living. Timing of prosthetic fitting will depend on many factors including closure and healing of the residual limb, presence of other injuries, and comorbidities. An immediate postoperative prosthesis (IPOP) with early weight bearing may be considered, particularly for patients with healthy residual limb tissue and a high level of cognitive functioning. For selected patients with more fragile residual limb tissue, an IPOP may be prescribed if there is strict monitoring of skin integrity and gentle progressive weight bearing. An early postsurgical fitting (EPSF) prosthesis may be prescribed 1 to 4 weeks after the amputation. Both the IPOP and the EPSF have a removable, molded, cast-like socket and may include a pylon and foot, which facilitate early, controlled ambulation. These early prostheses are training intensive and generally require a comprehensive amputee program.9

Knee disarticulation may pose prosthetic design problems; design of the prosthesis is essential for success of ambulation. Patients who can tolerate distal condylar weight bearing have sockets that end at the upper-thigh region. If the patient is unable to bear weight on the distal end of the femur, redistribution of weight bearing proximally may be necessary, similar to that used for transfemoral amputations. Those with osteotomy reduction of the condyles may have intolerance of distal end-weight bearing and require these modifications. The socket may require a removable component or adaptation to allow the larger femoral condyles to pass through the proximal socket comfortably. Padding of the socket around the medial condyle provides both comfort and suspension.10 Suspension may be achieved with a supracondylar design (preferred), suction, or even an accessory waist belt. Including the prosthetic knee joint poses challenges in the extra length added to the femoral component of the prosthesis. Which prosthetic knee to use depends on the distance between the end of the socket and the anatomic knee center. The 3 major designs are (1) external (outside) knee joints, (2) traditional transfemoral components, and (3) polycentric knees specifically developed for knee disarticulations. External hinges allow the prosthetic knee joint to most closely match the normal knee center and are the most financially economical. Disadvantages include compromised appearance and the wear they exert on clothing. Transfemoral knee joints will result in a lower knee center, which is cosmetically undesirable but not mechanically problematic. Many varieties of knees are available, including single-axis, constant-friction, stance control, manual lock, polycentric knees not designed for disarticulation, and microprocessor-controlled knees. Knee disarticulation polycentric knees will provide a more anatomic knee center of rotation, stance-phase stability, and durability. They tend to be more expensive, require more maintenance, and be heavier than external hinges.10, 11 Foot and ankle components should be selected according to the same criteria used for transfemoral amputations.

Timing of return to work or school varies, depending on the extent of injuries, adaptation to prosthetic fitting and training, and psychologic adjustment. Many patients must first complete the mourning process before they are able to resume work or school. Patients who need to change occupations should be referred to their state vocational rehabilitation agency and other available public or private resources for assistance. For people who do return to their jobs, assistance should be offered in designing necessary workplace adaptations. This patient would benefit from vocational evaluation, training, job placement, and workplace modifications. Some young adults with isolated lower-extremity amputations may be able to return to even heavy physical jobs, if effective adaptations are made.

1.3 Educational Activity: To contrast how the initial prosthetic prescription may differ for 33-year-old and 71-year-old patients with traumatic transtibial amputations 

Older people with traumatic amputations will take longer to recover and may not recover as completely as younger people. The following factors may affect recovery and should be considered in prosthetic prescription and rehabilitation: comorbidities (eg, heart disease, diabetes, chronic lung disease, peripheral vascular disease, cancer), premorbid activity level, vocation, leisure pursuits, skin integrity, energy level, and strength and conditioning before the injury. Physicians must be cautious in assuming activity levels based solely on age. A full evaluation of a patient should include a history with an emphasis on functional abilities and a physical examination that emphasizes the neurologic, musculoskeletal, and vascular systems and the skin in the affected and unaffected limbs. Cardiopulmonary disease that prevents the patient from participating in vigorous activity will dictate differences in prosthetic design. Activity levels are defined as K levels (table 1).12 Assuming the 33-year-old patient is at a K4 level and the 71-year-old patient is at a K2 level, the prosthetic prescriptions will differ in design, socket and suspension system, and foot and/or ankle components.

Table 1. Medicare Guidelines for Prostheses, by Activity (K) Level

	K Level	Description	Medicare-Covered Prosthesis
	K0	Nonambulatory	None
	K1	Household ambulator	Constant-friction knee
	K2	Limited community ambulator	Constant-friction knee
	K3	Unlimited community ambulator	Fluid-control knee
	K4	Very active	Fluid-control knee

Source: Region B Medicare Supplier Bulletin.12

Prosthesis Prescription for a K4 Amputation 

Design: An exoskeletal design is more rugged for use by an active person.

Socket/suspension: Initially a fiberglass socket will be used. Subsequently this device will be replaced with a definitive total-contact patellar weight-bearing (PTB) socket. A silicone sleeve should be used until the volume of the residual limb has stabilized. The advantage of this sleeve is that additional stump socks can be added as the residual limb volume shrinks. After the residual limb’s volume has stabilized, differential pressure or suction suspension may be prescribed for the most secure suspension and greatest range of knee motion.

Foot/ankle: Although a new amputee will not be as active as he/she will be later, anyone expected to ultimately function at an optimum level should be provided with a dynamic response foot (eg, the Seattle Light Foota or Flex-Footb) for greatest responsiveness during vigorous activity. An articulated dynamic response foot with multiaxial ankle may be used where more dynamic response and accommodation are desired.

Prosthesis Prescription for a K2 Amputation 

Design: An endoskeletal design is lighter weight and may be preferred.

Socket/suspension: The most secure system of suspension that the amputee can use should be prescribed. If the patient can independently don and doff a total-contact PTB with a silicone sleeve, this should be prescribed.

Foot: A solid-ankle, cushion heel (SACH) foot or a stationary-ankle, flexible-endoskeleton foot with no ankle joint should be prescribed to provide the most stability.

For more detailed discussion of prosthetic options, see also Jamieson and Davis,11 Romo,13 or Huang et al.14

Average walking speed for most healthy adults is from 60 to 100m/min, with men typically walking faster than women. Rate of oxygen consumption at this speed does not vary significantly between adults in the 20- to 59-year age group or those aged 60 to 80 years (12.1 and 12.0mL·kg−1·min−1, respectively). For sedentary people, the percentage of maximal oxygen consumption (V̇o2max) during ambulation is 32% for the younger group and 48% for the older group. For active people, V̇o2max across the age groups is the same. Fast walking speed, however, is slower in the older group (90m/min vs 106m/min), and the rate of oxygen consumption is lower (15.4mL·kg−1·min−1 vs 18.4mL·kg−1·min−1). Studies of velocity and energy expenditure of unilateral amputees show slower self-selected velocity and lower rate of oxygen consumption at all ages.15, 16 Studies of vascular amputees show even lower velocity and oxygen consumption at the same amputation level. Although age can influence functional outcomes, prosthetic prescriptions are primarily based on anticipated functional levels.

1.4 Clinical Activity: To analyze the gait deviations in a 33-year-old man with a traumatic transtibial amputation who complains of buckling at the knee and anterior knee pain 

The gait cycle consists of stance and swing phases with approximately 60% of the cycle in stance. The time when both feet are in stance is the period of double support. A person with a lower-extremity amputation will expend more energy than a person without impairment walking at the same speed. Rather than maintaining the same velocity, most amputees will walk more slowly and have a shortened stride length. A person who has a higher amputation level will have a slower velocity than a person who has a lower amputation level.16 Gait in amputees is affected by many components of the prosthesis and the individual person. There are major differences in the duration of heel support during stance among prosthetic foot types. The SACH foot has the longest duration of heel support (27% of gait cycle), and the single-axis foot the shortest (17% of gait cycle). Dynamic response feet such as the Seattle Light Foot (21%) and the Flex-Foot (19%) fall between these ranges. Peak knee flexion with a trans-tibial prosthesis is decreased (6°–10° vs 18°) and occurs later in the gait cycle (20% vs 12%) compared with that of a person without impairment. Hip flexion during the gait cycle in a person with a transtibial amputation is increased about 10° during swing, and hip extension is 10° less in stance.17

There are many reasons why one may deviate from the “typical” transtibial amputee gait (table 2). Faulty suspension may cause excessive knee flexion or unequal stride length. Excessive knee flexion and buckling may also be caused by a knee flexion contracture. Uncontrolled knee flexion may be caused by a weak quadriceps muscle, the socket being too flexed, the foot being too posteriorly placed, or the heel on the shoe being too high.18 All of these can be diagnosed by observational gait analysis (OGA), but only computerized gait analysis can provide quantifiable results. After OGA, observed problems with the prosthesis can be corrected. If the problems are caused by muscle weakness or contractures, physical therapy can focus on strengthening or stretching of the appropriate muscle groups. A fixed knee contracture, however, may require a surgical release.

Table 2. Transtibial Gait Deviations

	Gait Cycle Phase	Deviation	Possible Causes
	Initial contact (heel strike)	Knee is fully extended	■Suspension is faulty (does not maintain knee in 5° to 10° of flexion) ■Preflexion of the socket is insufficient ■Foot is too anterior
		Knee is excessively flexed (>10°)	■Suspension is faulty (maintains knee in >10° of flexion) ■Possible flexion contracture is present
		Length is unequal stride	■Suspension is faulty (may limit knee range of motion) ■Poor gait pattern is present
	Heel strike to foot flat (loading response)	Knee flexion is not smooth or controlled, may look “jerky”	Quadriceps are weak
		Knee flexion is abrupt and uncontrolled	■Foot is too posterior ■Socket is too flexed (foot is excessively dorsiflexed) ■Heel on shoe is too high ■Plantarflexion bumper or heel wedge in foot is too firm ■Shoe does not allow heel cushion to compress sufficiently
		Knee remains extended and patient “rides” the heel through to midstance	■Foot is too anterior ■Socket flexion is insufficient (foot plantarflexed) ■SACH heel is too soft (if >.95cm [in]) ■Heel on shoe is too low ■Poor gait pattern is present (excessive use of knee extensors)
		Piston action occurs. Patient may be dropping too deeply into the socket (best viewed in the coronal plane as patient walks away from observer)	■Suspension is too loose ■Not enough prosthetic socks are used ■Socket modifications are faulty (not enough support under mediotibial flare or patellar tendon)
	Midstance	Pylon leans medially	■The socket has too much adduction ■Foot may be outset
		Pylon leans laterally	■The socket has too little adduction ■Foot may be inset
		1.27-cm [½-in] varus moment is not apparent (for some patients this may be desirable to reduce torque)	■Foot is relatively outset
		Varus moment is excessive (>1.27cm [½in] is never desirable)	■Foot is too inset ■Mediolateral socket dimension is too wide
		There are <5.08cm (2in) between feet at midstance	■Foot is inset (narrow base gait)
		There are >10.16cm (4in) between feet at midstance	■Foot is too outset
		Lateral trunk bends to the prosthetic side at midstance	■Prosthesis is too short ■Because of residual limb pain, patient leans laterally to reduce torque ■Prosthesis is too long ■Foot is too outset
	Terminal stance (heel-off)	Heel-off occurs early and abruptly. The patient appears to “drop off” the foot at the end of stance phase	■Because of excessive posterior position of the foot, toe lever arm is too short ■Foot may be excessively dorsiflexed (socket is in too much flexion)
		Heel-off is delayed. The patient’s knee may tend to hyperextend. The patient may describe a feeling of “walking uphill”	■Because of excessive anterior placement of the foot, toe lever arm is too long ■The foot may be plantarflexed (insufficient socket flexion)
	Preswing (toe-off)	“Drop off” occurs. The patient appears to fall too quickly to the sound side	■Foot is too posterior ■Foot is too dorsiflexed (excessive socket flexion)
		Socket drops away from residual limb (evident when the anterior socket gaps or the posterior proximal socket rim drops distally in relation to the popliteal region)	■Suspension is too loose (for supracondylar sockets) or indentation is located too high above the femoral condyles (for patellar tendon–bearing supracondylar-suprapatellar sockets) ■Patient may not be wearing enough prosthetic socks
	Swing	Foot “whips” medially or laterally during initial swing	■Cuff suspension tabs are not aligned evenly ■Prosthetic socket is rotated medially or laterally with respect to the line of progression
		Prosthetic foot touches the floor during midswing	■Prosthesis is too long ■Suspension is too loose ■Knee flexion may be limited by the socket or suspension system ■Patient may have muscle weakness or lack of gait training

Source: Adapted from Kapp18 with permission.

Anterior knee pain may be caused by improper fit of the socket, faulty suspension, or knee flexion contracture. Improper socket fit may cause pistoning if the socket is too loose or if not enough support is provided under the medial tibial flare or patellar tendon. Improving socket fit, either by adjusting sock ply or by changing the insert’s shape, can address these issues. Additional therapies can address knee flexion contractures. Stretching and splinting may decrease or eliminate contractures. If these modalities are not effective, surgical release should be considered to improve gait.