Rotary-Mower Foot Amputation in Children and the Slipper Prosthesis

A. Kritter, M.D. R. G. Bidwell, C.P.O. D. Morfey, C.P.


Because of the great popularity of the rotary mower, young children are exposed to a new hazard to their limbs. Amputations from this cause are becoming increasingly frequent. Typically these amputations occur when children are playing in the yard where the rotary mower is being used and one of them falls in front of the machine and is cut before the operator can stop the motor. Amputations occurring in this way are particularly traumatic psychologically in that the operator of the mower is usually a member of the immediate family. The children suffer a variety of unusual amputations through the foot or leg that present all the problems of an open amputation and test the acumen and judgment of the attending surgeon in preserving the utmost function and in obtaining primary healing with little morbidity.

At the Milwaukee Clinic these amputations have been treated by thorough debridement, primary closure if there were no question of tissue viability, closed suction drainage for a minimum of 36 hr., an antibiotic umbrella, routine protection against gas gangrene and tetanus, and the use of a rigid, total-contact, immediate portsurgical dressing. Prosthetically, the children have been fitted with a slipper- or Syme's-type prosthesis.

If there is any question as to the viability of the soft tissues, a delayed open-flap amputation, preferably with skin traction, should be carried out with secondary closure at a later date. In the author's experience this procedure has not been required in foot amputations but has been necessary in open below-knee amputations.

Case Presentation

Case No. 1-J.P., a four-year-old male, was seen in May 1965 after suffering a traumatic open amputation of the left foot in a rotary-lawn-mower accident (Figs. 1 and 2 ). At surgery a thorough debridement of devitalized tissues was performed and the amputation revised at the talonavicular and calcaneal-cuboid joint level. The anterior tibial tendon and common toe extensors were slung beneath the neck of the talus to correct the pronounced plantar attitude of the remainder of the foot. A wafer of bone was removed from the anteroinferior portion of the calcaneus to allow primary closure of the wound. Closed suction drainage was used, a Steinmann pin was placed to position the os calcis in a neutral position (Fig. 3 ), and a rigid total-contact postsurgical dressing was fitted. The patient went on to primary healing (Figs. 4 and 5 ). A follow-up rigid total-contact cast with walking heel was applied until stump maturity was obtained. The child had a good weight-bearing stump without a prosthesis but the stump was too bulbous to be fitted in a conventional Syme's prosthesis. It was, of course, desirous not to go above the ankle joint in prosthetic fitting, and one of our own prosthetists (R.G.B.) solved the problem by fabricating a slipper-type prosthesis which proved adequate suspension from the os calcis and dorsum of the very short stump (Figs. 6 and 7 ). Despite the initial pin fixation and the provision of a sling beneath the neck of the talus, posterior displacement of the plantar portion of the os calcis continued (Fig. 8 ). Leg-length measurements taken 2 1/2 years after the amputation (Nov. 7, 1967) showed the right tibia to be 11 mm. shorter than the left. At follow-up five years after surgery the child enjoyed full activity in the slipper-type prosthesis.

Case No. 2-M.K., a five-year-old girl, was seen in July 1970 at Milwaukee Children's Hospital Amputee Clinic after suffering injury from a rotary mower in May 1970. She had had a complete debridement and primary closure with excellent healing. Examination revealed a traumatic amputation of the right foot at the level of the neck of the talus, with a residual of 10 deg. of motion in the dorsiflexion and plantar flexion (Fig. 9 and Figs. 10 and 11 ). The calcaneus tended to be displaced posteriorly. X-rays showed amputation through the neck of the talus with the calcaneus remaining (Fig. 12 ). The patient was fitted with a slipper-type prosthesis (Figs. 13 and 14 , and Figs. 15 and 16 ).

Case No. 3-J.D. In 1960, at the age of three years, this patient sustained a partial avulsion injury of the left os calcis and plantar skin from a rotary mower. After debridement, primary healing was obtained with split-thickness grafts on the plantar surface. This patient was first seen in the Milwaukee Children's Hospital Amputee Clinic in June 1969 because of continued breakdown of the split-thickness grafts on the plantar surface. The area had been the repeated focus of infection with frequent episodes of loss of time from school and the need to use crutches for extended periods three or four times a year. The patient walked on the remaining metatarsal heads and lacked pushoff power and adequate heel strike (Fig. 17 ). A Syme's type of amputation was recommended, using the remaining anterior and dorsal skin of the foot which was free of scar. It was realized that there were attendant risks in using this skin. However, it was judged that its use to allow a Syme's amputation, with its advantages, would be worth the risk in preference to going to a below-knee amputation. It was the senior author's opinion that a Chopart-type amputation with an eventual slipper-type prosthesis would not be satisfactory because of the inadequate weight-bearing skin. The Syme's amputation with an anterior skin flap healed nicely (Figs. 18 and 19 ) and the patient was fitted satisfactorily with a Syme's prosthesis with a medial window (Figs. 20, 21, and 22 ). In the year since the Syme's amputation the thin anterior skin flap over the stump has functioned well without any evidence of breakdown and the child has enjoyed full activity. It is anticipated that, after the child has reached maturity, the malleoli can be shaved to allow the fitting of a Syme's prosthesis without the window.

Fabrication of Slipper-Type Prosthesis

A jeltrate cast of the stump is taken with the patient in the standing position with one half of his weight on the amputated side. All bony prominences, scar tissue, and other areas which may be a problem in fitting, are marked and reliefs are then built up on the plaster mold. If the stump has enough of the cuneiform, navicular, and cuboid bones remaining, one or two socks and a balloon may be put on in taking the cast. This will extend the adjustability available to accommodate for growth of the stump. A flexible socket is made of laminae resin consisting of 80 per cent 4134 and 20 per cent 4110. Heavy dacron felt and six layers of nylon stockinette are used as filler. Extra dacron felt is added to the anterior wall for flaring purposes and small patches are attached in the areas between the malleoli and the Achilles tendon. The socket is then trimmed and attached to a wood foot which has a sole of rubber belting material. The prosthesis can be finished either by laminating or by covering with horsehide. An elastic strap is attached to the top anterior portion of the socket if the suspension is otherwise inadequate. The minor problems with the prosthesis have been replacement of the elastic strap and repair of the anterior portion of the socket.

Discussion

  1. In order to obtain consistent primary healing of the open amputation with the minimum of morbidity, proven concepts of treatment must be carefully adhered to.
  2. The rigid total-contact dressing is applicable to this amputation and provides advantages of edema prevention, early stump maturation, and the relative serenity afforded the patient and the family by early ambulation.
  3. The slipper prosthesis used for cases one and two has been particularly satisfactory for the active growing child. Prosthetically this slipper has the advantage of terminating below the ankle instead of extending almost to the knee as in a Syme's prosthesis, thus retaining some ankle motion.
  4. Slinging the anterior tibial and long extensor tendons beneath the neck of the talus in Case No. 1 has been effective in maintaining the stump in a moderate degree of plantar flexion and limited posterior displacement of the talus and os calcis. At five years postamputation the stump does not present any problems as far as prosthetic fitting, pain, or unsatisfactory deformity are concerned.
  5. The Syme's-type amputation using an anterior skin flap, in Case No. 3, has functioned extremely well.

Summary

Rotary-mower injuries, because of wide variations in the tarsal area of the foot in the growing child, present a challenging problem to the surgeon seeking to obtain primary healing with a minimum of morbidity and to provide a functional stump that will not drift into uncompromising deformity as the child completes his growth. Prosthetic fitting of these amputations is a challenging problem and the slipper prosthesis has proved to be a useful adjunct to the armamentarium of the treating physician for these Chopart-type amputations.

Juvenile Amputee Clinic, Children's Hospital Milwaukee, Wisconsin

A. Kritter is Clinic Chief.