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Chapter 35A - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles Lower-Limb Deficiencies: Surgical ManagementLeon M. Kruger, M.D.
BASIC PRINCIPLES
The physiologic differences between children and adults have already been discussed, as have general surgical considerations and planning for the care of the juvenile amputee. Emphasis should be placed on early prosthetic fitting and rehabilitation whenever possible. In general, it can be stated that the child with a unilateral lower-limb transverse deficiency can and should be fitted when he shows any tendency to stand. One should anticipate that the child will become ambulatory promptly, whether the deficiency is distal or proximal. By the same token, in unilateral longitudinal limb deficiency, in which it is likely that surgical revision will be necessary, a treatment plan should be developed so that, if possible, all surgical procedures can be carried out in one stage. The child should be brought to independent walking as early as possible, with surgical intervention and resultant scarring kept to a minimum and with the best physiologic restoration available.
Surgical intervention on the limb-deficient child, particularly on those with longitudinal deficiencies, should be undertaken only by the experienced orthopaedic surgeon and preferably in those centers that are accustomed to dealing with these children. By their very nature and fortuitously, these deformities occur infrequently and therefore are not likely to be seen on any recurring basis in the office practice or general hospital.
While in the past, limb lengthening for congenital longitudinal deficiencies has been considered and largely abandoned (with the possible exception of the congenital short femur), the introduction of the Ilizarov technique of limb lengthening by callus distraction has once again appealed to some orthopaedic surgeons. It should be pointed out that prior to discussing limb lengthening for longitudinal deficiency of the femur or fibula, the total predicted discrepancy must be calculated in advance, and the impact that this choice will have on the childhood of the patient must be considered. The family must recognize that when the child is just beginning to walk, a lift will be required until the child is old enough for lengthening; that at least 9 to 12 months will be required, during which period the patient will be either in the lengthening apparatus or immobilized or braced after healing; and that if over-lengthened he will require a lift on the normal side. This cycle will probably be repeated as he approaches the teenage years until definitive equalization can be attempted. In effect, this path would occupy the entire childhood. Prior to embarking on such an ambitious surgical program, the family must completely understand the difficulties they will face. This problem will be further discussed under the individual deficiencies where lengthening may be an option.
Surgical intervention on these children requires that certain basic principles be understood and applied: (1) early communication and explanation of treatment concepts to the parents as well as to the pediatrician; (2) maintenance of muscular development in the residual limb; (3) prevention of progressive deformity, especially in joints proximal to the deficiency; and (4) retention of all long-bone growth plates.
Early Communication With Parents and Pediatricians
Those clinics caring for limb-deficient children should attempt to establish rapport with pediatricians and obstetricians so that when such a child is born, the clinic chief will have the opportunity to examine the child in the newborn nursery. Recognition of the shock, grief, and guilt experienced by the new parents of a child with one or more deficient limbs dictates the physician's responsibility to assuage these feelings by presenting to the parents not just the diagnosis or anatomic description of the deficiency, but a positive approach to the child's immediate status and future capabilities as well. The physician should emphasize the remaining normal limbs, absence of brain damage, and expectations of the child's physical development. The new parents should be assured of the child's potential for ambulation, independence of daily living, and normal mental development. Assistance in these discussions may be sought from the social worker and pediatrician. If there is a problem with the parents, psychological or psychiatric consultations may be indicated.
Many parents, on visiting a limb deficiency clinic, are impressed with the athletic accomplishments of children with limb deficiencies. These parents should be encouraged to raise their child as "a normal child," and they should encourage normal physical activity, including any sports activity that the child is capable of carrying out and in which he is interested. Competitive sports should not be prohibited for a child with a limb deficiency but, in fact, should be encouraged. Experience has shown that a child who is missing a leg can play competitive football, basketball, and tennis or, for that matter, any other sport (Fig 35A-1.,A and B). Even when an individual is missing a hand, baseball, basketball, and golf are not outside his abilities.
It is particularly important to stress to the family that most limb deficiencies occur sporadically and are not genetically transmitted. Genetic consultation is important, however. In those instances in which there is a known heritable defect such as deficiency of the tibia, genetic consultation is mandatory. Should pregnancy occur, parents should also be encouraged to advise the obstetrician of the history and to be certain that a sonographic study is carried out in the early stages of the pregnancy.
Once out of the hospital, and particularly if surgical conversion of the limb deficiency is anticipated, the parents should be invited to the "clinic.'' There they should be encouraged to observe older children with the same or similar deficiencies, and particularly to discuss the child's physical and social development with the parents of these older children. They should be encouraged to ask questions about the child's participation not only in family activity at home but also in social, play, and school activities. Concerns about social acceptance of the deficiency and, particularly, of indicated prosthetic restoration may subconsciously prejudice a parent against any recommended treatment program. Airing their concerns to parents of other children with the same problems eases new parents through this difficult transition period and assimilates them into the clinic team. They become integral members in the planning and implementation of the program to habilitate their child. Such "group therapy" enables the parents to comprehend the need for and accept the recommendation to proceed with ablative surgery when it is indicated. Without this open communication between parents and clinic team, the more complicated problems of the limb-deficient child may be insoluble.
Maintenance of Muscular Development in the Residual Limb
A congenital limb deficiency may not be simply the absence of a long bone or the peripheral joint distal to the deficiency; it may also include inadequacy of the proximal musculature and deficits in the skin, nails, and nerves. Torode and Gillespie as well as Johansson and Aparisi have reported on the missing cruciate ligaments in patients with congenital short femur and fibula deficiency. Recognizing the deficits in the proximal musculature at the initial evaluation is important if progressive deformity is to be prevented. To this end a program must be developed that includes not only institutional physical therapy but also education for the parents in the techniques of development and maintenance of muscle strength. The parents should be brought into the physical therapy department for instruction by the therapist in setting up a home program.
Prevention of Progressive Deformity
Prevention of deformity in the child with a lesser deficiency may pose no problem. In fact, even with a major deficiency such as an amelia, there is no concern with progressive deformity. However, in the more complicated limb deficiency such as proximal femoral focal deficiency (PFFD) and longitudinal deficiency of the tibia and fibula, an exercise program for strengthening or stretching of the remaining musculature may be inadequate to prevent deformity of the remaining joints. Orthotic management for the control of foot, ankle, and knee deformities can be pursued until the child is ready for definitive surgical conversion (Fig 35A-2.). In many patients, particularly those with PFFD, orthotic management without revision may be indicated until the optimal time for surgical intervention is reached.
Prevention of progressive deformity is an important ingredient of the long-range planning for these patients. When surgical intervention is considered, plans should be laid out in such a manner as to anticipate the result in terms of the adult patient. To this end we must consider the many facets of surgical intervention, including the retention of all long-bone epiphyses as indicated. On occasion, as in carrying out a knee fusion in the patient with PFFD, it can be anticipated that the amputation level will leave one with a prosthetic knee joint that is below the level of the knee joint on the normal side. In such a case, appropriately planned, the epiphyses may be destroyed. We should also think in terms of the preservation of functional proximal joints, stabilization of proximal joints where necessary (i.e., knee fusion), and the judicious use of skin grafting when necessary.
Retention of All Long-Bone Growth Plates
The percent contributions to the longitudinal growth of the distal femoral, proximal tibial, and distal tibial growth plates have been determined (Fig 35A-3.). Unnecessary sacrifice of any of these three longitudinal growth centers in the infant or very young child may result in major prosthetic problems in adult life. In some instances, the sacrifice of such an epiphysis in the very young child can be catastrophic. As an example, the patient with a longitudinal deficiency of the tibia should be treated by disarticulation at the knee level, with the distal femoral epiphysis left intact. Assuming normal growth in the distal and proximal femoral growth plates, in adult life the patient would have a slightly shortened knee disarticulation, which is ideal for prosthetic fitting. Should the surgeon elect to carry out a transfemoral (above-knee) amputation with sacrifice of the distal femoral growth plate, it would deprive the child of 70% of the eventual length of the femur, and in adult life the patient would have a very short transfemoral residual limb. Disarticulation ensures a long residual limb with all of its advantages in adult life.
Similarly, in a longitudinal deficiency of the tibia, it is important to determine by ultrasound or magnetic resonance imaging (MRI) the possibility of a nonossified proximal epiphysis of the tibia, which would indicate a partial deficiency. In such a case, disarticulation should not be carried out so that the below-knee segment of the limb can be preserved.
Preservation of Proximal Joints
Particularly in transverse deficiencies of the leg in the upper quarter or higher, preservation of the knee joint is important. Functional restoration of the trans-tibial (below-knee) amputee is far superior to what can be expected of the transfemoral amputee. The sacrifice of a knee joint in the small child may severely limit his ability to climb stairs, manage ramps, and take part in many physical and sports activities. By the same token, efforts to preserve such a very short tibial segment (Fig 35A-4.) may be rewarded in adult life with a competent, functional knee joint and a good, sturdy, sufficiently long transtibial stump.
Patients with classes A and B PFFD are recognized as having a hip joint at birth. It is not possible at the time of birth to be sure of the integrity or the stability of that joint. Although Lloyd-Roberts and Stone had recommended early exploration of all of these joints, they later conceded that it may not be necessary and that early exploration may damage the joint.
Stabilization of Proximal Joints Where Necessary
Stabilization of proximal joints is particularly applicable to patients with PFFD. Steel et al. have described iliofemoral fusion for PFFD-fusing the femoral segment to the pelvis so that the femoral segment will be parallel to the floor. The knee is thereby flexed at a right angle when the patient stands. Extending the knee would then, in effect, flex the hip. We have not used this procedure. When hip instability is present due either in type A to the subtrochanteric defect or in type B to the lack of contact between the head, neck, and shaft fragments, osteotomy and bone grafting or osteosynthesis between the two fragments will stabilize the hip. In Aitken types C and D, when the femoral segment is quite short, knee fusion may be necessary in order to have a good prosthetic result. These procedures will be described in more detail in the section on PFFD.
Bilateral Limb Deficiencies
These decisions will be somewhat altered with regard to the bilateral limb-deficient child, but in general an effort should be made to fit prostheses as early as possible, based on the team evaluation of the child. Emphasis must be placed on the therapist's evaluation of the child's muscular coordination and ability to manage prosthetic devices. Prosthetic fitting may have to be staged or delayed until surgical intervention can reasonably be accomplished. The physiologic and, particularly, psychological differences between the child with bilateral limb deficiencies and the adult with a bilateral amputation must be recognized when contemplating the bilateral fitting. When bilateral surgical conversion or a revision procedure is planned, rehabilitation goals for the infant or juvenile should take these differences into consideration. The child who requires bilateral Syme ankle disarticulation should be expected to walk independently without crutches or canes (Fig 35A-5.). He should be expected to take part in all normal activities, including athletics, and should be able to don and doff the prostheses independently early in life. Similarly, the child with a bilateral transtibial fitting should have very high rehabilitation goals (Fig 35A-6.). Even as the levels of amputation go higher, one should anticipate that as long as the child has functional upper limbs with which to improve balance, he should be independently ambulatory. It is generally appreciated that the adult bilateral transfemoral amputee, if he is to walk, will require crutches or canes. The child, on the other hand, can be expected to walk independently when properly trained. Early fitting and appropriate training can be a very rewarding experience in such a patient. In the very young child, as in the very old patient with bilateral transfemoral amputations, initial fitting with stubbies is recommended. Stubbies are modified sockets with either a rocker or rubber-soled bottom. The use of stubbies permits the patient to develop balance in the erect position. When independent walking has been accomplished, the stubbies may be lengthened, thereby increasing the child's height and confidence in the erect position. The final prescription is for articulated limbs (Fig 35A-7.). Ambulation without crutches or other external aids should be expected.
The parents of the bilateral lower-limb-deficient child must be made aware of the importance of weight control. Instruction and dietary regulation should be available to the family and their responsibility at home stressed (Fig 35A-8.).
Although the problem of the patient with bilateral PFFD will be dealt with later in this chapter, it cannot be repeated often enough that this is the one situation in which any consideration of amputation of the feet should be deferred.
Skin Grafting
Skin grafting in the child is very well tolerated. Split-thickness skin grafts on the residual limbs of children will mature and withstand the shearing or frictional forces of socket contact. Denuding of a short transtibial residual limb is no indication to proceed with higher amputation in a child. Instead, skin grafting should be carried out. The resurfaced limb should then be toughened up in anticipation of prosthetic application.
The surgeon should keep this philosophy in mind when dealing with the limb-deficient child. If preservation of a knee joint requires a posterior release and skin is a problem, split-thickness grafting may be carried out. The surgeon should not hesitate to use a skin graft to preserve an epiphysis where there is a deficiency of skin. Split-thickness grafting in weight-bearing areas may ultimately require revision and/or a pedicle graft (Fig 35A-9.), but most split-thickness grafts mature and tolerate prosthetic wear well. Newer improved materials for sockets have been developed to reduce shear forces at the stump-socket interface and lessen the possibility of breakdown of grafted surfaces.
Selection of a donor site for a skin graft in the lower-limb amputee should not be casually undertaken. Consideration must be given to the ultimate amputation level and the type of prosthesis that the patient will ultimately wear. No area should be chosen as a donor site if there is the possibility that it may later interfere with prosthetic wear. As an example, the ipsilateral thigh should not be chosen as the donor site for skin grafting for a transtibial stump. There may subsequently be the need for a thigh corset, in which case the scarred thigh would be a problem. In a transfemoral amputation, the pelvic brim area should never be chosen as a donor site for skin grafts since a pelvic belt or Silesian bandage may be necessary for suspension, in which case this would be directly over the scarred area.
When there is a need for a pedicle or flap graft, the operating surgeon should take into consideration the patient's ultimate amputation level. These procedures should be planned so that there will be no unnecessary scarring in areas of weight bearing or in areas where a strap or stump-socket interface may occur. Such scarred stumps require special attention from the pros-thetist; with appropriate prescription and prosthetic restoration, the skin graft will mature and be able to withstand the stress of a socket.
TRANSVERSE DEFICIENCIES
Phalangeal Deficiencies
Transverse deficiencies of the phalanges, whether partial or total, do not usually require revision surgery. If associated with congenital constriction bands, surgical intervention should be directed at the constriction bands. Occasionally, proximal amputation of the toes will be necessary.
Partial or Complete Metatarsal Deficiencies
As in transverse deficiencies of the phalanges, revision surgery is not usually necessary for metatarsal deficiencies. Occasionally, it is necessary to remove vestigial phalanges that have either no bony component or insufficient bony component for functional value. These may present not only cosmetic and hygienic problems but also a serious problem in shoe insert fitting. The vestigial phalanges may become irritated and even ulcerate. With such problems, excision is recommended. When the residual metatarsal elements are extremely small, whether short or atrophied, shoe fitting problems are the major concern. If there is insufficient residual foot on which to fit a shoe with an insert, consideration must be given to other prosthetic restoration. Those patients with very short remaining metatarsal elements and those with complete transverse metatarsal deficiencies must be treated as though they have a tarsal deficiency.
Complete or Partial Tarsal Deficiencies
For the patient with a complete transverse tarsal deficiency (apodia or congenital ankle disarticulation), the deficit may be managed by prosthetic restoration. No surgical intervention is necessary.
Partial tarsal deficiencies with a normal distal tibial epiphysis and no length discrepancy may require conversion surgery. In the very early years, these children may walk with a high-top laced shoe. Prosthetic devices are available, but function and cosmesis are less than ideal (Fig 35A-10.). Proximal revision for functional as well as cosmetic reasons will be considered (Fig 35A-11.), with Syme ankle disarticulation as the procedure of choice. This procedure is frequently referred to as a modified Syme's amputation because the articular cartilage is left intact. The Boyd amputation may also be considered as an alternative to disarticulation. In the very small child, up to 3 years of age, the malleoli may be left intact and will present no problem in prosthetic fit or restoration. In the older child, the malleoli may be transversely sectioned at the level of the tibial articular surface to provide a broad, flat, end-bearing stump. Care must be taken not to damage the distal tibial epiphysis in this procedure. In an older child in whom the epiphyses have closed, one may have to model the stump or shave the malleoli to achieve acceptable cosmetic result in a Syme-type prosthesis. Patients so treated are left with an end-bearing stump that is the most functional type. The patient may walk without the prosthesis. There is no concern for the phenomenon of bony overgrowth so frequently observed when transtibial amputation is performed.
Procedure for Syme Ankle Disarticulation
The procedure for Syme ankle disarticulation should be carried out with tourniquet control. The incision starts anteriorly at the tip of the medial malleolus and is carried directly across the ankle joint to the lateral side. The second half of the incision is then carried from these two points across the plantar surface of the foot in a slight arc to carry the incision just distal to the calcaneocuboid level (Fig 35A-12.). The anterior part of the incision is carried down through the subcutaneous tissue and the superficial vessels clamped and ligated. The anterior tibial tendon and toe extensors are divided and held with a clamp or suture for later attachment. The dissection is carried medially, and the posterior tibial vessel and nerve are identified and traced distal-ward to preserve the circulation of the plantar flap. The anterior ankle capsule is opened, and the medial and lateral ligaments are divided. The plantar portion of the incision is carried directly down to the bone and the plantar flap dissected off the inferior aspect of the os calcis by sharp and blunt dissection. With the foot pulled forward, the posterior capsule is divided and the heel cord dissected off the superior aspect of the os calcis. The dissection is completed by separating the os calcis from the plantar flaps and care taken not to puncture the skin posteriorly. All major bleeders are ligated, the tourniquet released, and bleeding controlled. The heel cord is now sutured to the posterior capsule. The anterior tibial tendon is sutured to the anterior capsule, and the plantar flap is brought forward. The heel pad is stabilized with a Kirschner wire or Steinmann pin through the heel pad and the articular surface and across the epiphysis. The plantar fascia flap is sutured to the anterior capsule. Drainage may be accomplished with a soft-tissue drain or suction drainage if desired. The skin is closed with loose interrupted sutures. Dressing may be done by using either the rigid dressing or dry compression technique. Drainage is discontinued at 48 hours.
Transverse Deficiency of the Leg, Partial
Upper Third
A partial transverse leg deficiency (congenital transtibial amputation, partial transverse hemimelia) may occur as a true deficiency or in association with Street-er's dysplasia (congenital constriction band syndrome). When it is associated with Streeter's dysplasia, surgical attention to other constriction bands may be necessary, either above the level of amputation or on other limbs. In those true deficiencies, vestigial digits may be present, and these may require surgical removal. Such appendages may range from one metacarpal or metatarsal ray to five vestigial digits.
The deficiency is apparent at the time of birth, and attention should be directed to the maintenance of range of motion in the proximal joints, particularly the knee joint. If the child is born with a flexion contracture of the knee joint, it may be necessary to surgically relieve this condition prior to considering prosthetic restoration. If the knee joint extends completely at the time of birth, implementation of a range-of-motion program should be maintained until the child is ready for the prosthesis.
Until recently it was thought that these congenital amputations were not subject to the phenomenon of bony overgrowth. Pellicore et al. have now reported the observation of bony overgrowth in the remaining tibia of these children; this phenomenon has been observed through the period of symptomatic overgrowth until surgical revision was required.
Children with transverse deficiencies of the leg in the proximal portion will demonstrate good standing balance on their sound limb somewhere between 9 and 15 months of age. They are ready for prosthetic restoration at this time (Fig 35A-13.).
Transverse Deficiency of the Leg, Total and Transverse Deficiency of the Thigh, Lower Third
Transfemoral deficiencies occur less frequently in children than do transtibial deficiencies. Surgical intervention is seldom if ever indicated. Management is prosthetic restoration (Fig 35A-7.).
Transverse Deficiency of the Thigh, Total (Amelia)
Children with total transverse deficiency of the thigh (amelia) (Fig 35A-14.) should be fitted with their first prosthesis as soon as they are standing independently on the normal opposite side. As with other deficiencies, there may be a vestigial digit attached. This usually is not a problem since the vestige has no rigidity and, hence, can be incorporated into the socket without difficulty. Surgical intervention is seldom indicated.
The infant with bilateral amelia will require a plastic "bucket-type" socket fitted to a firm base to achieve sitting or "standing" balance. As he grows older, he may progress to the swivel walker. If the child has normal upper limbs, bilateral articulated hip disarticulation prostheses may be prescribed at about 4 or 5 years of age.
LONGITUDINAL DEFICIENCIES
Longitudinal Deficiency of the Fibula, Partial
Partial longitudinal deficiency of the fibula may take on many forms, from a shortening of the fibula, which will frequently be associated with a ball-and-socket ankle, to almost complete absence of the fibula with only a small segment present. In between, there may be a very hypoplastic short fibula, which will be associated with a leg length discrepancy. The very small remaining segment of the fibula will frequently be treated as a total longitudinal deficiency of the fibula, whereas the full-length fibula with shortening is treated primarily as a length discrepancy problem.
Longitudinal Deficiency of the Fibula, Total
Because of the frequency of its occurrence,longitudinal deficiency of the fibula has received a great deal of attention in the literature. The titles are varied- congenital absence of the fibula, fibular deficiency, paraxial fibular hemimelia, dysgenesis, etc. O'Rahilly reported on 296 cases of this deficiency that he had reviewed in the literature prior to 1935. Since that time several hundred cases have been reported. In 1952, Coventry and Johnson reported 29 cases of congenital absence of the fibula and mentioned amputation as a form of treatment but stressed the reconstructive approach. Since Aitken's report of 1959, most authors have emphasized amputation and prosthetic restoration. Although O'Rahilly was able to find only 296 cases in the literature prior to 1935, by 1991 there were over 2,200 cases in the Shriners Hospitals for Crippled Children. Our experience at the Springfield Unit increased from 60 patients in 1961 to 120 in 1991.
Clinical Picture
As with other longitudinal limb deficiencies, one is impressed by the fact that fibular deficiency is a true limb deficiency, not simply the absence of a single bone (fibula). The tibia may be bowed and usually has an abnormality of the distal epiphysis. There may be a minimal shortening of the femur or coexistent PFFD. A congenitally short femur may be present. Deficiency also exists in the muscles, tendons, nerves, and even the skin, as evidenced by the dimpling frequently present over the deformed tibia. Hootnick et al. described a midline metatarsal dysplasia associated with an absent fibula in addition to the deficiency of the lateral rays. The classic clinical picture is a foreshortened limb with an equinovalgus foot, with or without absence of the metatarsal rays and tarsal anomalies (Fig 35A-15.). For the patient with total unilateral longitudinal deficiency of the fibula, progressive length discrepancy is the major clinical problem. In the patient with bilateral fibular deficiency, this problem translates to a failure to attain normal height.
Definitive treatment of patients with fibular deficiency will depend on two major considerations: (1) is it associated with PFFD, and (2) is it unilateral or bilateral? Patients with longitudinal deficiency of the fibula and associated ipsilateral PFFD must be treated primarily as having a PFFD, with the fibular deficiency as a secondary consideration. The patient with unilateral fibular deficiency and PFFD on the contralateral side is an exception to this.
Treatment of Unilateral Longitudinal Fibula Deficiency, Total
Leg length discrepancy is the major problem in the patient with total unilateral longitudinal deficiency of the fibula. Experience has shown that this is a progressive discrepancy and that the progress of this discrepancy can be predicted on growth charts. Efforts at equalizing the discrepancy by tibial lengthening have generally been unsatisfactory.
With the advent of the Ilizarov technique of lengthening by callus distraction, there has been a reappearance of interest in preserving the foot and lengthening these limbs. As mentioned earlier, if, in fact, an effort is made to lengthen the tibia in such a child, he will have to wear a lift to compensate for his discrepancy until he is old enough for his limb to be lengthened. He then has a protracted period of wearing the lengthening apparatus and protecting the limb, and this process will probably have to be repeated a second time in order to obtain adequate equalization. Efforts at equalizing discrepancies in excess of 7.5 cm (3 in.) by contralateral growth arrest or shortening are contraindi-cated because this amount of loss in overall height of the patient is too great a price to pay. Therefore, it would appear that only in the unusual patient can leg length equalization, by a combination of lengthening and growth arrest, be accomplished. To consider an effort at leg length equalization the patient should have a straight tibia with no anterior bow, as well as a normal or near-normal foot and a length discrepancy that is not expected to exceed 7.5 cm. In our experience, if the child has a 5-cm length discrepancy at birth and an abnormal foot, with or without shortening of the femoral segment, then the treatment of choice remains ankle disarticulation (Syme type) and prosthetic restoration. Reconstruction has been recommended but, in our opinion, is not optimal. Therefore, it is recommended that early conversion be carried out (Fig 35A-16.)-between 9 and 12 months of age, or as soon as the child is able to stand and indicates a readiness to commence walking.
Indications for early amputation and prosthetic restoration may then be summed up as (1) length discrepancy in excess of 5 cm (2 in.) and progressing, (2) foot deformity, and (3) a normal femur. It is important that the procedure be a Syme ankle disarticulation or Boyd amputation, never transtibial amputation. Trans-tibial amputation is contraindicated for two major reasons: (1) loss of longitudinal growth at the distal tibial growth plate and (2) bony overgrowth at the amputation site.
The distal tibial epiphysis contributes 20% of the growth of the limb as a whole and 45% of the growth of the tibia itself. Even if it is known that the distal tibial epiphysis may not be normal, it is still important to appreciate that if this epiphysis is sacrificed at 1 year of age, the child will be left with a short transtibial residual limb when he attains full growth. On the other hand, if the growth plate is retained, one may anticipate that there will be, at worst, a long transtibial stump or, at best, a good Syme-type ankle disarticulation. The disarticulation procedure also provides an end-bearing stump on which the child may walk without the prosthesis.
Prior to 8 years of age, transtibial amputation is accompanied by a high incidence of bony overgrowth at the amputation site (Fig 35A-17.). Much has been written about bony overgrowth, its prevention, and treatment. When symptomatic, revision of the amputation is necessary.
In summary, most children with unilateral fibular deficiency require ankle disarticulation and prosthetic restoration. During the operation the articular cartilage should be left on the distal portion of the tibia and the heel pad fixed to it. One should also look for the presence of an anterior tibial bow. This has been described as a kyphoscoliotic tibia and becomes a problem in prosthetic fit. It may be a result of contracture of a lateral band but is more appropriately recognized as a central defect of the tibia. One sees dimpling of the skin over this anterior bow. When indicated, this anteriorly bowed or kyphoscoliotic tibia should be corrected by rhomboid resection of bone (Fig 35A-18.). The presence of a lateral band should also be taken into consideration. Excision of this lateral band, which may be a deforming force, can be carried out at the same time as the rhomboid resection and straightening of the tibial bow. The procedure for ankle disarticulation has been described.
In the older child, consideration should be given to modification of the disarticulation procedure. Many of these children have already undergone triple arthrodesis or other surgical procedures in an attempt to restore a functional foot. Length discrepancy is progressive and is the indication for amputation. In these patients, fusion of the ankle joint and amputation through the mid-tarsal level, or a modified Boyd procedure, retains the extra length and normal attachment of the heel pad to the os calcis. The broad stump contour does require a more bulky prosthetic socket and is cosmetically less desirable. The procedure is therefore usually reserved for boys, in whom cosmesis is not so important (Fig 35A-19.). Ankle disarticulation is the procedure of choice for girls.
Bilateral Longitudinal Fibula Deficiency, Total
There are two major considerations for patients with complete bilateral longitudinal deficiency of the fibula and a normal femur: (1) the condition of the feet and (2) the anticipated overall height of the patient.
Patients with five-rayed feet that are reasonably aligned beneath the tibia will have no problem in shoe wear. On the other hand, those patients with a three-or four-rayed foot and associated severe equinus and valgus may require considerable surgery to align the foot plantigrade, Even after repeated surgical procedures, normal shoe wear may be precluded by the shape and deformity of the foot. Severe foot deformity may then be an indication for amputation and prosthetic restoration.
With fibular deficiency there may be a deficiency of the distal end of the tibia and its growth plate. When the tibia at birth is disproportionately short as compared with the femur or when there is a severe anterior bow in the tibia, one can anticipate that the discrepancy will be progressive. In these patients early ankle disarticulation at the age of 1 year to 18 months is indicated.
A retrospective study of a small group of unampu-tated patients at Shriners Hospital in Springfield, Massachusetts, concluded that 50% should have had amputation (Fig 35A-20.) and prosthetic restoration to provide normal stature. When length discrepancy between the tibia and femur is sufficiently great to make this decision at an early age, it is desirable to introduce parents to the limb deficiency clinic. There they can see similar children with prosthetic restoration and have an opportunity to talk with the parents of these children rather than having to rely completely on the recommendation of the clinic chief.
If the discrepancy in proportional length of the tibia and femur is small and there is a good foot, consideration of amputation should be deferred, but growth charts should be maintained for the patient. If the discrepancy is a progressive one and it is apparent that the patient is going to be unduly short in adult life, bilateral ankle disarticulation and prosthetic restoration may be recommended prior to school age (Fig 35A-21.). As the child grows older, and particularly if he has been permitted to enter his early teens without surgical intervention, the child himself should enter into the decision making concerning such ablative surgery and prosthetic restoration.
Longitudinal Deficiency of the Tibia
Longitudinal deficiency of the tibia may occur either unilaterally or bilaterally, and it may be either partial or complete. Its occurrence is much less frequent than fibular deficiency. There have been several reports of the association of longitudinal deficiency of the tibia with deficiency of the first metacarpal (absent thumb), as well as with Polydactyly. Although Eaton and Mc-Kusick in reporting their four cases stated that "no familial cases have been recorded," Clark has cited 13 case reports of familial occurrence of tibial deficiency that she found in the literature. She added to it her report of a patient with nine affected descendants in three generations.
The characteristic clinical picture of tibial deficiency can usually be recognized at birth (Fig 35A-22.). Gross instability of the knee is evident, with or without flexion contracture and lateral displacement of the fibula. Severe varus of the foot is present, with the sole of the foot facing toward the opposite leg or even toward the knee or perineum. The knee joint is so unstable that the foot can almost be brought up against the medial portion of the thigh. Length discrepancy is the most obvious part of this deficiency. Several patients have an exostosis or osteochondroma of the femur (Fig 35A-23.). The deficiency may be total or partial, but at birth it is difficult to be sure of this differential diagnosis. A pterygium may be present.
Partial Tibial Deficiency
Since the presence or absence of a proximal segment of the tibia is crucial in the treatment decision, it is important to ascertain this knowledge early in life (Fig 35A-24.). If there is a suggestion that a proximal tibial segment is present, even though it is not visualized on a radiograph, it is important to rely on the clinical examination. Ossification of a proximal tibial segment may not occur for months or even up to 2 years of age. In such patients, arthrography and other techniques may be of assistance in making a diagnosis. Grissom et al. have described the use of sonography in the management of tibial deficiencies since ultrasound examination can define the cartilaginous anlage of the proximal tibial segment that cannot be visualized radiographi-cally at birth. MRI may also be used, but ultrasound is a simpler and less expensive examination and does not require the sedation necessary for the small child who is to have an MRI examination. Partial deficiency of the tibia should be treated with an orthosis or an orthopros-thesis until one is certain of the ossification of the proximal fragment and of the presence of the knee joint.
Having established the presence of a proximal fragment and knee joint, the size of this tibial fragment is the next concern. If the tibial segment is short, less than one third the length of the normal tibia, the procedure of choice is synostosis of the fibula to the tibia and disarticulation of the foot (Fig 35A-25.). This produces a long transtibial residual limb. On occasion, the fibula may migrate proximally above the knee joint (Fig 35A-26.). In our experience, this has occurred in only one patient. Resection of the proximal half of the fibula was carried out, and stability of the knee joint was maintained. Tibiofibular synostosis should prevent this from occurring if it is done early enough.
Procedure for Tibiofibular Synostosis
The proximal tibial segment is exposed through an elliptical incision between it and the fibula. The distal portion of this tibial segment is dissected subperi-osteally and completely exposed. The fibula is now exposed subperiosteally at a level opposite the remaining tibia. With a sharp gouge, the medial surface of the fibula is turned proximalward, and the lateral aspect of the tibia is turned distalward. Bone graft is then packed into the defect between the two. The fascia is not sutured. The subcutaneous tissue and skin are closed in layers. Disarticulation at the ankle is then accomplished in the usual fashion. Marquardt has described implantation of the fibula into the os calcis to create an end-bearing stump. This procedure may be employed instead of simple disarticulation at the ankle. The limb is immobilized in a long-leg plaster cast with the knee in full extension for 8 weeks, or until there is evidence of firm cross-union between the tibia and fibula.
If the proximal segment of the tibia is sufficiently long, tibiofibular synostosis is not necessary. Syme ankle disarticulation or a modified procedure (Boyd type) and fitting with a transtibial-type prosthesis may be carried out early in life. When the proximal tibial fragment is very small, one must wait until adequate ossification occurs and then attempt to implant the fibula into the tibial segment to create a one-bone leg. After this is done, the os calcis can be implanted into the distal end of the fibula and amputation carried out, thus treating the patient as a Syme disarticulate (Fig 35A-27.).
Longitudinal Deficiency of the Tibia, Complete
With complete longitudinal deficiency of the tibia, the clinical picture is the same as just described.
In 1965, Brown first reported his experience with construction of a knee joint in patients with complete longitudinal deficiency of the tibia. His experience dated back to 1957, when he first implanted the fibula beneath the femur and disarticulated the foot. The residual limb was fitted into a "transtibial" socket with outside hinges. A limb deficiency that had always been considered for transfemoral amputation was converted into a "transtibial" prosthetic restoration. Since that time, many of these procedures have been accomplished. However, at a long-term review,[*Cooperative Clinic Chief's Meeting, Seattle, 1975.] the high incidence of recurrent deformity and the need for repeated operative intervention was such that only a few centers continue to perform this procedure. On occasion, the picture is altered by the presence of a pterygium between the femur and the fibula. This pterygium may determine the incision location for surgical intervention.
The treatment of choice is disarticulation at the knee. Resection of the fibula may also be necessary when there is a severe pterygium. In those patients with unilateral deficiency, this procedure may be considered as soon as the individual is standing on the normal limb. Prosthetic restoration and good functional rehabilitation should be anticipated.
Procedure for Knee Disarticulation
In the procedure for knee disarticulation, a skin incision is marked out with a long anterior flap, which is also wide at its distal portion, and carried to well below the level of the femoral condyles. The posterior portion of the incision should be marked out at or just below the popliteal crease. The anterior incision is made and carried down through the subcutaneous tissues. The anterior capsular structures are divided to enter the knee joint. There may not be a patellar tendon. Posteriorly, the incision is made and deepened, and the hamstring tendons, if identifiable, are divided somewhat long and tagged for later suture. The great vessels are clamped and doubly ligated and the nerves drawn distally, divided, and allowed to retract. The gastrocnemius origin (if discernible) is severed from the femoral condyles. The capsule and ligaments are divided and the limb removed. At this point, the tourniquet is released and all bleeding controlled. The hamstring tendons are sutured to the capsule or ligamentous structure as available. If a patella and its tendon are present, the patella is left in place, and the tendon is sutured to the hamstring tendons or posterior capsule. The capsule is closed over the cartilage of the femoral condyles. Drainage with either a soft-tissue drain or suction is instituted, and the closure is completed. It should be noted that the long anterior flap provides good coverage of the femoral condyles and good weight-bearing skin for subsequent prosthetic wear. The postoperative care may be with rigid dressing or soft dressing according to the surgeon's preference.
Disarticulation in the presence of a pterygium may pose a surgical dilemma for placement of the incision. We have resolved this problem by making an L-shaped incision from the base of the pterygium down to the "knee joint." The fibula is then filleted out extraperi-osteally and removed and the L incision closed to leave a good end-bearing cover of the femoral condyles. A lateral scar is also left, which may be bulky proximally but shrinks down rapidly thereafter (Fig 35A-28.).
As the patient grows older, a length discrepancy of the remaining femur may occur that will permit use of a knee joint other than the outside hinge. If this discrepancy does not occur, distal femoral epiphysiodesis may be considered when the child is 10 to 12 years of age. If the child is seen when it is considered too late for epiphysiodesis and spontaneous differential femoral shortening has not occurred, the distal end of the femur may be modified to allow for a more cosmetic prosthetic fitting. This can include distal shortening of 2.5 to 3.0 cm, partial condylar ostectomies medially and posteriorly, and patellectomy. Femoral shortening may be considered. Newer design of joints for the knee disarticulation prosthesis may render this option unnecessary.
Longitudinal Deficiency Femur, Partial (Proximal Femoral Focal Deficiency [PFFD])
In 1939, Langston described a "congenital defect of the shaft of the femur." Aitken recognized "the existence of a group of partial deficiencies of the proximal femur involving the iliofemoral joint" and, since no appropriate terminology existed, used the designation "proximal femoral focal deficiency." Amstutz has defined PFFD as the "absence of some quality or characteristic of completeness of the proximal femur, including stunting or shortening of the entire femur." Aitken described four classes (Fig 35A-29.). In class A there is an acetabulum. The head of the femur is within the acetabulum, and there is a subtrochanteric deficit. Class B presents with an acetabulum and a capital fragment within the acetabulum. There is a short shaft fragment with no bony connection between the two. In class C there is no acetabulum. One finds a short femoral fragment with a tuft on top. In Class D there is also no acetabulum. A very short triangular femoral segment is present. Amstutz further expanded this classification and developed five types. His type 1 included those patients with what has been described by Aitken as a congenital short femur or coxa vara with bowing. His other four types approximate the Aitken classes A, B, C, and D. These morphologic classifications offer assistance in treatment decision primarily with regard to the hip.
Most reports of PFFD have included only small numbers of cases. Prior to Jan 1, 1968, the Area Child Amputee Center in Grand Rapids, Michigan, had only 35 cases. In his report, King was able to review over 100 cases of PFFD collected from various juvenile amputee clinics throughout the United States. In 1968, Westin and Gunderson were able to gather 165 cases collectively recorded from Shriners hospitals. More recent reports have included a larger number of patients.
Westin and Gunderson reported a 65% incidence of other defects, with 50% of the patients having deficiency of the fibula in the same limb. Amstutz and Ait-ken noted a high incidence of fibular deficiencies in the same limb, as well as other skeletal deficiencies.Kruger and Rossi reported 31 of 38 patients to have other limb abnormalities, with fibular deficiency in 50% of their patients. Koman et al. described their 50-year experience in the management of PFFD. Sen-Gupta and Gupta reported four patients with PFFD in one family and stated, "In the absence of a history of maternal diabetes; premature child birth; exposure to known teratogenic factors such as irradiation, toxic chemicals, and drugs; mechanical trauma; or maternal viral infection, the defects appear to be genetic in origin." Only male members were affected.
Shatz and Kopits reported that "A review of radiographs obtained on one patients maternal great aunt showed that she had a PFFD with absence of the ipsilateral fibula." Hillmann et al. reported that a review of 49 patients showed no genetic basis for the diagnosis. Steel et al. in 1987 suggested iliofemoral fusion for stabilization of the hip in PFFD. |
