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This is Section 2 of 5 from PFFD: A Congenital Anomaly, National Academy of Sciences, 1969.
RICHARD E. KING, M.D.
Whenever a large sample of chaotic elements is taken in hand and marshalled in order of their magnitude, an unsuspected and most beautiful form of regularity proves to have been latent all along.
-GALTON..,Natural Inheritance, 1889
By definition, the term "proximal femoral focal deficiency" implies that
the proximal femur is lacking in completeness. That this incompleteness is
only part of the problem was made clear by the study of many x-rays in an
attempt to cull true cases of this type from the morass of what has been
frequently classified as proximal femoral focal deficiency. A study of the
past literature has also revealed that not uncommonly cases of congenital
short femur, epiphyseal coxa vara, and phocomelia have been included with
the PFFD group (3, 18. 20, 25, 31, 45, 48, 51, 52 59).
CLASSIFICATION OF TYPES
It remained for Aitken (1) to present a workable classification that is easily
understood and that can serve as a background for the surgical correction
of this condition (Figure 1). As seen in Figure 2, Types A and B show elements
of the Proximal femur, i.e., acetabulum and head; whereas Types C and D show
no evidence of acetabulum and consequently no head or neck of the femur.
These four types all present clinically with a thigh that has the appearance
of a ship's funnel and is almost always flexed, abducted, and externally
rotated (Figure 3). It is not uncommon for the ankle on the affected side
to lie at the level of the knee joint on the normal side. Complete absence
of the fibula on the affected side is frequently associated with proximal
femoral focal deficiencies. Nilsonne (45) reports a 50 percent incidence,
Aitken (1) 70 percent, and Amstutz (2) 80 percent.
EMBRYOLOGY
Ossification is commonly delayed in congenital deformities, and this delay
is seen in proximal femoral focal deficiency also.
Because of the delayed ossification of the femoral head, ingenious attempts
to attain pelvi-femoral stability by bone graft from the shaft of the femur
to the acetabulum have been described in the literature (35, 50, 52).
Lloyd-Roberts (38) performed arthrography in two cases in order to outline
the process of delayed femoral head ossification, which was present in both
of his cases.
Much of this confusion can be resolved when we realize that the ilium and proximal femur develop from a common cartilage anlage. The elements of head and neck of the femur are actually hewn from this common block of cartilage, and the hip joint appears as a cleft between the head of the femur and what is later the acetabulum (19,30,32,36,47,56,57).
Laurenson (36) states that the head of the femur and the acetabulum gradually separate from each other by formation of a cleft and then formation of a definitive joint cavity. At nine weeks the embryonic hip joint resembles the general form of the adult.
Figure 4-A represents a 17-mm embryo and shows the approximate size of the limb bud. The development of the hip joint at this stage is shown in Figures 4-B and 4-C. The ilium, ischium, and pubis still consist of precartilage, and the acetabulum shows little increase in its concavity. By this time the head of the femur is slightly rounded, and while the acetabulum is not much more concave than in younger specimens, there is nevertheless a slight depression more marked medially which contains loose tissue and indicates a primitive acetabular fossa (19, 56, 57).
At 22 mm (Figures 5-A, 5-B, and 5-C), the acetabulum deepens medially. Both trochanters are now well defined, but the neck of the femur is short. Note the beginning of cavitation at the periphery of the interzone where dissolution is occurring to form the acetabular cleft. As chondrification proceeds in the blastemal anlage, the portion of the blastema between femur and acetabulum remains unchondrified to form a disc or interzone. However, at 20 mm its middle portion becomes lighter in staining density and a three layered arrangement is evident (19,56,57).
At 30 mm (Figures 6-A through 6-D), the acetabular cavity is well developed, but obliterated at the center. Figures 7-A through 7-E trace embryological development in fetuses from 73 to 270 mm. Figure 7-A shows the acetabular fossa, fovea capitis femoris, and early vascularization at the femoral neck and near the glenoid lip at 73 mm. In Figure 7-B, at 106 mm, vascularization is considerably advanced and ligaments are well defined. Figure 7-C shows increased ossification and vascularization at 180 mm. Figure 7-D, at 250 mm, depicts the proximal extent of diaphyseal ossification. At 270 mm, the fovea capitis, filled with vascular tissue sharply demarcated from cartilage, is shown in Figure 7-E (19,56,57).
A composite of fetuses from 44 mm to 126 mm is shown in Figure 8 to indicate the relative external appearance of the lower extremity.
Since the lower limb develops in a proximodistal direction, and in view of the embryological development described above, may we not infer that if an acetabulum is visualized at birth a femoral head will appear? Conversely, may we not assume that if no acetabulum is present at birth no elements of proximal femur will appear?
This conclusion has been corroborated in our review of x-rays on over 100 cases of proximal femoral focal deficiency collected from various juvenile amputee clinics throughout the United States. When we establish that a femoral head is present, although delayed in ossification, our attempts at surgical correction can be initiated earlier and without confusion as to whether or not a femoral head is present (33, 34).
We can only postulate that the cause of this error of development is some type of insult sustained by the embryonic lower extremity at the time that the cleft which later represents the hip joint is being formed. Whether this insult is some transient physical or chemical trauma to the limb bud at this stage, we are not prepared to say (61, 62). It is significant that Duraiswami (15), injecting insulin into the yolk sac on the sixth day of the developing chick embryo, was able to produce some deficiency of the proximal femur (Figures 9-A and 9-B).
TREATMENT
CONSERVATIVE
The nonstandard prosthesis typically fitted to all types of patients with uncorrected proximal femoral focal deficiency usually includes a wide-mouthed socket, a platform for support of the foot, and outside knee joints (Figures 10-A and 10-B). Functionally and cosmetically this prosthesis leaves much to be desired.
SURGICAL
General Principles
Because of dissatisfaction with the results of conservative management, an attempt has been made to convert surgically the existing elements of the femur to a single skeletal lever so that a standard conventional prosthesis could be used.
The usual deformity presented is one of external rotation, flexion, and abduction of the proximal portion of the femur. The surgery performed usually does not require that special attention be directed to these contractures, i.e., surgery directed toward completion and achievement of an intact skeletal lever usually is sufficient to correct the contracture about the hip area.
Analysis of the skin, nerves, bone, joint, and musculature of a proximal femoral focal deficiency reveals that a single skeletal lever with adequate skin, no disturbance of the nerves or circulation, adequate bone, good joint function, and musculature sufficient to move the skeletal lever can be achieved surgically. In providing a skeletal lever, every effort should be made to provide pelvi-femoral stability also.
It cannot be emphasized too frequently or strongly that each individual case requires careful analysis if an appropriate solution to this formidable problem is to be found. Also, the surgeon must be aware that if an acetabulum is present at birth, elements of a femoral head will eventually develop Awareness of this developmental sequence will obviate unnecessary attempts at obtaining pelvi-femoral stability by such means as bifurcation, osteotomies, and bone grafts (34,50,52).
Specific Surgical Techniques for Each of the Four Types of
Proximal Femoral Focal Deficiency in the Aitken Classification
Type A Type A proximal femoral focal deficiency can be realigned by osteotomy for better mechanical leverage. This procedure should be done at the subtrochanteric level, and the osteotomy site can be held by internal fixation, pins, etc. A case in point is that of B.B., who was first seen at the age of nine months. X-rays revealed a Type A proximal femoral focal deficiency (Figure 11-A). At eighteen months x-rays revealed developing varus with bending occurring at the subtrochanteric level (Figure 11-B). An osteotomy was done at the subtrochanteric level and fixed at 90 deg in a spica cast. Subsequent healing is shown in Figure 11-C. When the patient was last seen, in May 1968, x-rays revealed complete remodeling of the proximal femur (Figure 11-D). Clinical photographs of the stump and of the patient in his prosthesis were made at this time (Figures 11-E and 11-F).
Type B Type B proximal femoral focal deficiency requires realignment of the fragments to create a skeletal lever. Two case reports demonstrate a planned approach to the achievement of this end.
P.M., initially seen at the age of 2 1/2 years, presented the flexion, external rotation, and abduction of hip deformities typical of proximal femoral focal deficiency (Figures 12-A and 12-B). This patient had never walked because of lack of stability in the hip area. An attempt was made to align the skeletal fragments over an intramedullary rod.
The area of pseudarthrosis between the neck of the femur and the elements of the distal femur and its epiphysis was removed (Figure 13). This was good cartilage in a dormant state of endochondral ossification, and mere realignment of the fragments in a semblance of weight-bearing position was sufficient to awaken it so that normal endochondral ossification could ensue (Figure 14) (8,51,52,59).
Figure 15 shows the fragments of the proximal and distal femur fixed over an intramedullary rod, with the rod presented distally in the region of the foot.
A knee arthrodesis was performed, concomitant with the realignment of the femoral segments (Figure 16).
Figure 17 shows the final realignment of knee fusion and seudarthrosis to make a single skeletal lever.
Approximately two months later a disarticulation at the ankle was performed. The knee fusion was solid and the intramedullary rod was removed at the time of the disarticulation (Figure 18). This procedure retains intact the epiphyses of the distal femur and proximal and distal tibia. It is noteworthy that the ankle disarticulation at this age provides a stump the distal end of which is level with the opposite knee for a cosmetic prosthetic application (Figures 19-A, 19-B, and 19-C).
With the skeletal lever stabilized, the range of motion and strength available for prosthetic control is quite impressive (Figures 20-A, 20-B, and 20-C). The patient was fitted with a conventional thigh-corset prosthesis with hip control (Figures 21 -A and 21 -B).
At present, this patient plays on a soccer team and is active in every phase of everyday childhood life. Sufficient time has not yet elapsed for proper evaluation of the epiphyses of the distal femur and proximal and distal tibia. However, the latest x-rays on this boy, taken in January 1967, still show the epiphyses to be open, and 2 cm of growth have occurred in the single skeletal segment (Figure 22).
P.D. was initially seen shortly after her birth on September 19, 1960, and was followed through the Georgia Crippled Children's Service. The child's thigh had the typical ship's funnel appearance, with the usual flexion, external rotation, and abduction contractures (Figure 23-A). The patient was fitted with an extension brace and ambulation was permitted., The child was referred to the Juvenile Amputee Clinic in February 1965, at which time x-rays revealed a Type B proximal femoral focal deficiency (Figure 23-B).
In April 1965, an attempt was made to place the sharpened spike of the distal femur into a mortise in the femoral head (25,35,52). At the same time a knee fusion was performed. The sequence of procedures was as follows: a 6-mm intramedullary Kuntcher rod was driven retrograde through the tibia and out of the foot. The femur was then threaded onto this rod to complete the knee fusion. The rod was driven proximally into the femur. At this time the sharp spike of the femur was placed into the mortise in the femoral head. However, the upper end of the femur was bowed, and the intramedullary rod came out laterally. Therefore, the entire limb was held in 90-deg abduction, and the rod was driven into the anterior inferior spine of the ilium, thus stabilizing the femoral-tibial segments in this position, as well as offering a supporting strut to the epiphyseal-diaphyseal fusion (femoral head to the femoral shaft). The patient was placed in a double spica cast with the affected extremity in 90-deg abduction.
Sections from the proximal femur showed viable cartilage (Figure 24), and sections from the epiphysis of the femoral head showed a viable but somewhat disorganized epiphyseailline (Figure 25). On July 7, 1965, the spica was removed, and x-rays revealed a thin spicule of bone from femur to femoral head (Figure 26). It was felt that this spicule represented a precarious attachment, and another spica was applied for an additional month. When this cast was removed on August 11, 1965, x-rays were made in adduction and abduction, and it was believed that the femur and femoral head moved as a single unit.
By February 15, 1966, the patient had been putting some weight on the foot, and x-rays revealed that the thin spicule of bone had hypertrophied and was now the thickness of a thumb (Figure 27). The knee also appeared to be solid. The intramedullary rod was removed and at the same time a Syme's amputation was performed (Figure 28).
On Much 23, 1966, the patient was found to have a stable hip with no flexion contracture (Figure 29). Satisfactory stump abduction, flexion, and extension were present (Figures 30-A through 30-D). On this date the patient was fitted with a plastic funnel-shaped socket with an ischial seat, metal hip control, single-axis knee, and SACH foot (Figures 31-A, 31 -B, and 31 -C).
The patient received prosthetics training and is now ambulating well. When seen in July of 1966, x-rays revealed further apparent hypertrophy of the proximal femur with a suggestion of increased growth of the femoral head. The patient had developed an inexplicable line of translucency in the femoral shaft (Figure 32). Perhaps this zone represented an area through which bending may occur to cause a subsequent coxa vara. If necessary, osteotomy to realign this bending could be performed later and should cause this zone to close. However, x-rays taken in March 1967 showed this translucent zone to be closing with use of the prosthesis (Figure 33).
Type C Patients with Type C proximal femoral focal deficiency can only be offered a knee fusion to achieve a skeletal lever since no pelvi-femoral stability exists or can be provided. Since the femur usually presents as a long segment, the ankle joint lies at a level below the knee joint of the normal leg. An example of this type of case is A.R., who was seen shortly after birth (Figures 34-A and 34-B). Subsequent x-rays show surgical fusion of the knee. A below-knee amputation at the level of the opposite knee was done after the knee fusion was solid (Figures 35-A and 35-B). Follow-up two years after amputation has shown no evidence of overgrowth.
Amputation of the affected leg will be at the below-knee level rather than through the ankle in order to bring the prosthetic knee level with the normal knee joint.
Since the distal tibial epiphysis is removed, this amputation should be done as near growth completion as possible to decrease the chance of overgrowth of tibia and fibula.
TYPE D Type D proximal femoral focal deficiency presents a formidable problem, and we can only offer our contemplated plans for surgical conversion. Pelvi-femoral stability can be achieved by a preliminary Chiari tmnsirmominate osteotomy. Then the element of the distal femur can be fixed to the pelvic shelf to allow the knee joint to serve as a hip joint. Later a disarticulation of the ankle can be done so that a conventional prosthesis may be worn. We have not as yet tried this procedure, but we feel that sufficient musculature is present to flex and extend the knee joint so that it could be made to act as an effective hip joint (Figures 36-A and 36-B).
CONCLUSIONS
An attempt has been made to use a classification system for proximal femoral focal deficiency developed by Aitken that allows us to proceed to a planned surgical approach for each of the four types identified. Each case should be treateded separately, and the type of surgical conversion best suited to the elements of the proximal femur present should be performed. It has not been found necessary to correct the contractures present by a separate procedure. In the conversions described in this paper, the contractures of flexion, abduction, and external rotation are probably released through the soft tissue dissection and femoral shortening associated with the knee fusion which is done at the same time. The principle of establishing a single skeletal lever by alignment of fragments over an intmmedullary rod has so far proven sound. It has provided pelvi-femoral and skeletal stability of the femoral segment upon which existing musculature can act to operate a prosthesis. Although this is a preliminary report based on six cases of surgical conversion, we have not as yet noticed any closure of epiphyseal lines due to the central penetration of epiphyseal plates by an intramedullary rod. These thoughts are presented in the hopes of stimulating others to an awareness that reasonable function, comfort, and cosmesis result from this approach to these formidable deformities.
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This is Section 2 of 5 from PFFD: A Congenital Anomaly, National Academy of Sciences, 1969.