Correction of Angulation Deformity in the Below-Knee Amputation Stump

A. Kritter, M.D. E. Grossenbacher, M.D.


Angulation deformity of the below-knee stump has been a problem in two cases at the Milwaukee Children's Hospital Congenital Amputee and Limb Deficiency Center. These two deformations occurred in a small series of 11 below-knee amputees. The problem presents unique prosthetic fitting difficulties during the development of the angular deformity since a deformity below and at the knee-joint level will produce improper stresses on this hinge joint. In the growing child these stresses will produce further deformity, and if the deformity is allowed to persist it will produce a degenerative joint disease in adult life.

The Milwaukee Clinic has treated two cases, one of genu varus and the other of genu valgus, by epiphyseal stapling with prompt correction of the deformity. This procedure has provided good control of the deformity by adding a dimension of reversibility which is important in the growing child. The correction provides a good solution for the prosthetic fitting problems posed by a severe varus or valgus with subsequent poor cosmesis. It produces a more normal alignment for the growing knee joint as the child approaches skeletal maturity.

The operative control of bone growth has had an interesting history. Oilier6 was probably the first to attempt surgical retardation of growth when, in 1888, he resected the remaining portion of the distal tibial epiphysis to correct a traumatic varus of the ankle. In 1914 Lane5 reported the development of genu varum after internal fixation of a fracture of the distal femoral epiphysis with three staples on the medial side. In 1933 Phemister7 reported the operative arrest of longitudinal bone growth for correction of leg-length discrepancies in which he curetted and grafted the epiphyseal plate. Interest in temporary arrest in epiphyseal growth was stimulated by the experiments of Haas3 in 1945 in which growth was arrested by circling the epiphyseal plate in dogs with a wire loop.

Milwaukee Children's Hospital has had a special interest in epiphyseal arrest since Blount and Clark1 in 1949 proposed a simplified method for temporary epiphyseal arrest by inserting a metal staple or staples across the epiphyseal line. Growth can be retarded up to 90 per cent depending upon the number of staples inserted and the stage in the child's growth life at which the staples are inserted.

Case Reports

Case No. 1-M.A., a 13-year-old boy, was involved in a pedestrian-train accident in June 1966, at which time he suffered severe soft tissue and bone injury to the right tibia, treated initially by debridement, skin grafting, and cast immobilization. Eight months following the injury a below-knee amputation which preserved 12 cm. of tibia and fibula was performed. The patient was seen initially at the Milwaukee Children's Amputee Clinic at two years postinjury. At that time he had not had a prosthetic fitting. Records were not available to determine if any epiphyseal fracture had occurred at the time of the original injury. However, no fracture deformity of the epiphysis was evident on x-ray two years after the injury, although 12 deg. of genu varus had developed (Fig. 1 ). The prosthetic prescription was for a patellar-tendon-bearing hard-socket prosthesis with a condylar strap and a silastic end pad. Prosthetic alignment was complicated by the 12 deg. of genu varus present, and the cosmesis of the prosthesis was unsatisfactory (Fig. 2 ). Because of the increasing genu varum, a Phemister-type epiphysiodesis of the proximal fibular epiphysis and a stapling of the lateral proximal tibial epiphysis (two staples) were performed in May 1968 (Fig. 3 ). Prompt correction of the angular deformity occurred (Fig. 4-A and Fig. 4-B ) and the presence of the staples were tolerated without incident with full use of the prosthesis. The staples were removed in December 1968, seven months after placement, when full correction had been obtained (Fig. 5 ). A new PTB prosthesis with a hard socket and a silastic end pad was then fabricated (Fig. 6 ). Good correction was maintained at 18 months following stapling and epiphysiodesis, and the patient was comfortable in his prosthesis. No loss of correction or rebound effect has occurred following removal of the staples (Fig. 7 ).

As the authors were concerned about possible retardation of the linear growth of the stapled bone, bone markers2,4 were inserted in both tibiae at the time of the stapling of the right proximal tibial epiphysis. X-ray measurements since the time of the stapling have shown that the right proximal tibial epiphysis has grown 7 mm. and the left proximal tibial epiphysis 26 mm. This disparity in growth is thought to derive primarily from the amputation and secondarily from the stapling of the lateral side of the proximal tibial epiphysis.

Case No. 2-P.B. is a 14-year-old male born with a left paraxial fibular hemimelia and a kyphotic tibia. The father reports that the child underwent surgery nearly every year for the first six years of his life for "straightening and stimulation of the tibia." The patient reported that all of his life he had worn a long-leg brace without any knee motion. Amputation at the below-knee level was performed at the age of six years and the patient was fitted with a below-knee, open-end, wood socket with a thigh lacer and knee joint.

When the child was first examined at the Milwaukee Amputee Clinic, he had a marked valgus (18 deg.) of the left knee (Fig. 8 ). The below-knee stump was in good condition. The tibia measured 10 cm. and the fibula was absent with relative underdevelopment of the knee joint and patella. A new below-knee prosthesis consisting of a total-contact hard socket, supracondylar strap, SACH foot, and silastic end pad was prescribed. On April 22, 1969, when the boy was 13 years of age, a stapling of the left proximal medial tibial epiphysis was done (Fig. 9 ). The patient returned to full use of the prosthesis ten days post stapling. Correction of the deformity to 13 deg. of valgus occurred in seven months (Fig. 10 ), and at one year the deformity had decreased to 5 deg. (Fig. 11 ). Staples were removed on July 13, 1970, and the patient had full use of his prosthesis ten days later. With correction of the deformity (Fig. 12 ), the prosthesis was refabricated with the now normal alignment of the tibia and knee joint (Fig. 13 ). In this case the authors were in a dilemma as to whether to staple the femur or the tibia. They decided that the tibia was the site of the deformity, and that this epiphysis should be stapled. The possibility that the femur should have been stapled in order to keep the joint interval level with the ground is still under consideration (Fig. 14 ). This knee joint will be watched carefully with eventual final alignment achieved by either stapling of the femoral epiphysis or osteotomy at maturity.

Summary

(1) Stapling of the epiphysis for correction of angular deformity in the below-knee amputation stump of a growing child is an effective method of obtaining correction with a built-in safeguard against over correction.

(2) Stapling as an alternative to osteotomy produces far less morbidity and allows prompt continued full use of the prosthesis while correction is being obtained.

(3) The angular deformity is corrected with minimal alteration of linear bone growth as illustrated by the bone marker measurements taken in Case No. 1. Some of the discrepancy noted might well be due to atrophy of disuse arising from the amputation.

(4) In both cases reported the staples have been well tolerated while the patients were wearing PTB prostheses.

(5) The method is applicable only in the growing child where there is potential for growth.

(6) The authors are unable to explain the presence of genu varus in the acquired amputation of Case No. 1 without apparent epiphyseal injury. The genu valgus in the second case is probably associated with the previous paraxial fibular hemimelia. The authors have found no reference in the literature to angular deformities in the below-knee juvenile amputee.

(7) The authors are of the opinion that, if the progressive angular deformity in the below-knee amputee is well controlled before skeletal maturity is reached, the overall development of the knee will be enhanced. Thus, when the child completes final linear and condylar growth about the knee at skeletal maturity, a more normal knee is assured during adult life.

Congenital Amputee and Limb Deficiency Center Children's Hospital, Milwaukee, Wisconsin

References:
1. Blount, W. P., and D. R. Clark, Control of bone growth by epiphyseal stapling; a preliminary report, J. Bone and Joint Surg., 31-A 464-468, 1949. 
2. Blount, W. P., Septieme Congr. Soc. Internat. Chir. Orthop., 378-408, 1957. 
3. Haas, S. L., Retardation of bone growth by a wire loop, J. Bone and Joint Surg., 27:25-36, 1945. 
4. Kritter, A. E., and W. P. Blount, A study of the growth of human epiphyses of the tibia and femur, Surgical Forum-45th Clinical Congress, Vol. 10, 1959. 
5. Lane, A., Operative treatment of fractures, second edition, p. 133, London: Medical Publishing Co., 1914. 
6. Oilier, L., Traite des resections et des operations conservatrices qu'on peut practiquer sur le systeme oxxeus, fifth edition, Vol. II, p. 473, Paris: V. Mas-son, 1888. 
7. Phemister, D. B., Operative arrestment of longitudinal growth of bones in the treatment of deformities, J. Bone and Joint Surg., 15:1-15, 1933.