Follow-Up Findings on the Skeletal Lever in the Surgical Management of Proximal Femoral Focal Deficiency

RICHARD E. KING, M.D.RICHARD E. KING, M.D. THOMAS W. MARKS, M.D


In the treatment of those classes of proximal femoral focal deficiency in which surgical intervention appears warranted one of the basic concepts that has guided us has been the establishment of a single skeletal lever. A second has been the establishment of pelvifemoral stability 3,4 . These conditions are essential for optimal motivation of the prosthetic appliance. As described in the referenced publications, these objectives have been pursued in different ways according to the type of PFFD involved. However, in all cases it has been found that sufficient musculature, skeletal foundation, skin, nerves and vascular supply were present to make the skeletal lever a functional organ.

In the process of creating the skeletal lever it also became apparent that it was not necessary to relieve the flexion, abduction and extension rotation contractures that existed about the hip.

The implementation of these concepts has produced results which have borne the test of time. Time has also brought forth some unforeseen developments. It is now becoming apparent that the skeletal lever, given an opportunity to experience normal functional stresses, has assumed its role with a voracious appetite. The results have been particularly spectacular in the surgical-prosthetic management of Class B* PFFD. Some of the outcomes that have been noted are:

  1. The achievement of a negative Trendelenburg gait, indicating a tremendous increase in the flexor and abductor strength of the muscles about the hip.

  2. The development of a suggestive trochanteric apophysis. This development suggests that the pelvifemoral muscle unit has responded to the demands placed upon it ( Fig. 1 , Fig. 2 , and Fig. 3 ).

  3. Gradual loss of the ship's-ventilator appearance of the stump. Some of our patients have successfully made the transition from a nonconventional ship's-ventilator-type socket with a rigid hip control and a pelvic band to a quadrilateral closed-end total-contact socket with a Silesian bandage; and finally to a total-contact quadrilateral socket with suction.

Fusion of the knee to create the skeletal lever in PFFD Classes B and C has been accomplished easily through the use of an 8 mm. Küntscher intramedullary rod. So far there has been no closure of the epiphyses about the knee and distal tibia attributable to penetration by the nail. In all cases fusion of the knee has occurred in 3-4 weeks.

We have been much surprised by the gradual development of flexion in the fused knee segment with the passage of time and increased use of the prosthesis. This flexion begins about 3-5 years after fusion and the beginning of prosthetic use. Initially it was felt that flexion was a result of growing out of the prosthesis with resultant mechanical bending of the fused knee segment ( Fig. 4 ). However, as additional cases that did not grow out of their prostheses were encountered it was felt that perhaps the lifting of the weight of the prosthesis in walking was the causative factor ( Fig. 5 ).

Literature on Knee Arthrodesis

It was of interest to review the literature on arthrodesis of the knee in children to see whether flexion of the fused knee was a complication. Toumey7 was of the opinion that in children the knee should be fused in extension. He felt that with time a dislocation of the distal femoral epiphysis would occur and he reported an approximate incidence of eleven per cent. This then was his explanation of the flexion that eventually occurred in the fused knees of children with tuberculosis. Green et al.1 agreed with Toumey's observations. It is of interest that no examples of dislocated distal femoral epiphyses were given in either article. However, in reviewing his series Green1 reported two children who developed excessive flexion deformity of the knee. One child subsequently required an osteotomy of the femur for correction. The other was lost to follow-up.

Hueter-Volkmann's Law

It is our contention that flexion of the fused knee in children is an example of the Hueter-Volkmann law of epiphyseal growth. In 1862, Hueter2 noted the relatively greater growth of bone structures which were under diminished compression. Seven years later Volkmann8 referred to the observation of Hueter and added that abnormal differences of compression caused unequal, asymmetrical growth with retardation on the side where pressure was abnormally elevated. Stinchfield5, in response to a recent inquiry, stated that the x-rays of Toumey's series which was reported as covering a period from 1915 to 1936 had been destroyed. Hence, they could not be checked for this phenomenon. He agreed that this complication probably represents an example of the Hueter-Volkmann law of epiphyseal growth and not a slippage of the distal femoral epiphysis as was thought by Toumey.

We believe that this flexion phenomenon is initiated by tight hamstrings resulting in unequal pressure on the distal femoral and proximal tibial epiphyses as the skeletal lever grows. (Increased hamstring pressure causes compression of the posterior parts of the epiphyseal plates of the distal femoral and proximal tibial epiphyses.)

Thompson 6 stated that neither he nor Bosworth had ever seen a dislocated distal femoral epiphysis in a child who had had his knee fused for tuberculosis. He also stated that Bosworth had never seen bending, as the child grew, in a knee that was fused in an extended position. However, if the knee were fused in a flexed position the flexion increased with growth.

In recent correspondence Green1 also stated that he had never seen a dislocation of the distal femoral epiphysis in a child but felt that the bending at the fusion site was the result of hamstring tightening with growth of the limb. Since it is important to have a functioning skeletal lever, it is a simple matter to os-teotomize either the distal femur or the proximal tibia, or both, to obtain the necessary correction ( Fig. 6 ). This procedure has been followed on two patients using the 8 mm. intramedullary nail for fixation. As yet no premature closure of these epiphyses has occurred.

Summary

Since the concept of a single skeletal lever created by knee fusion is an integral part of the surgical management of several types of proximal femoral focal deficiencies, it is necessary to be aware that the skeletal segment has a tendency to flex in the area of fusion. This flexion is felt to result from the operation of the Hueter-Volkmann law of unequal epiphyseal growth rather than represent a dislocation of the distal femoral epiphysis, as was formerly thought. Correction is easily obtained by osteotomy of the distal femur or the proximal tibia, or both, using an 8 mm. intramedullary nail for fixation. Perhaps sectioning of the hamstrings at the time of osteotomy to correct the flexion might prevent recurrence of this flexion deformity.

* Aitken's classification is used

Juvenile Amputee Clinic Atlanta, Georgia

References:
1. Green, D. P., J. C. Parkes, II, and F. E. Stinchfield, Arthrodesis of the knee. J. Bone and Joint Surg., 49-A:6:1065-1078, Sept. 1967.
2. Hueter, C, Anatomische Studien an den Extremitätengelenken Neugeborener und Erwachsener. Virchow's Arch. f. Path Anat., 25:572-599, 1862.
3. King, R. E., Some concepts of proximal femoral focal deficiency, in Proximal femoral focal deficiency, G. T. Aitken, Ed., National Academy of Sciences, Washington, D.C., 1969, pp. 23-49.
4. Sage, F. P., Congenital anomalies, Chapt. 25, in Campbell's operative orthopaedics, Vol. 2, A. H. Crenshaw, Ed., C. V. Mosby Co., St Louis, 1971, pp 1942-1944.
5. Stinchfield, F. E., Personal communication.
6. Thompson, F. R., Personal communication.
7. Toumey, J. W., Knee joint tuberculosis; two-hundred and twenty-two patients treated by operative fusion. Surg., Gynec , and Obst, 68:1029 1037, June 1939.
8. Volkmann, Richard, Die Krankheiten der Bewegungsorgane, in Handbuch der allgemeinen und speciellen Chirurgie, v. Pitha and Billroth, Eds., Bd. 2, Abt. A, Ferdinand Enke, Stuttgart, 1882, S. 694.