GAIT KINETICS AND KINEMATICS IN CHILDREN WITH VAN NES ROTATION-PLASTY:

May Fong, B.Sc.P.T.


INTRODUCTION:

This is a pilot case study of three children with osteosarcoma of the distal femur who were all surgically treated with rotation-plasty and chemotherapy protocols. The children all wore their prostheses full-time, from morning until bedtime and all walked independently, without any external aids.

PURPOSE:

The purpose of this study was to analyze gait patterns of these children, using kinetic and kinematic parameters. These data were compared with the measurements of those in the normal population. (M.P. Kadaba et al).

DEFINITION:

Van Nes rotation-plasty is a procedure traditionally used for children with congenital defect of the femur, later adopted to children with bone tumours in the distal femur. In our three cases, all their surgical procedures involved resection of the distal femur, knee joint, the proximal tibia and fibula, then the remaining tibia was rotated approximately 180 deg. And fused to the femur. A special prosthesis was fitted with the rotated foot inserted into the shank segment of the prosthesis. The rotated ankle flexed and extended the prosthetic knee.

METHODS:

Three-dimensional data were collected using a video system with four cameras (120 Hz motion Analysis Corp), twelve reflective markers to determine joint angles of hips, knees and ankles.

Kinetic data were collected as vertical ground reaction forces from the force plate, (Kistler).

Three patients walked at their comfortable walking speeds and at a fact-walking speed at approximately 1.3 m/second. They did five trials on each leg and at each speed on a 15 metre walkway.

Subjects: case age post-op full-time wear
  #1 12 2 years 1 year
  #2 14 6.5 years 5.5 years
  #3 17 3.5 years 2.5 years

Case #1 had a poor-follow up due to rural community and non-compliance.

Case #2 had a good follow program with good co-operation and the most experienced.

RESULTS:

Kinematic similarities in stance phase:

Child with leg prostheses

  1. Hip-level - on the prosthetic side, hip joints were kept in relative abduction throughout the stance phase as compared to those of the normal; whereas the hips on the side were kept in relative adduction at stance phase, compared to those of the normal.
  2. Knee level- on the prosthetic side, case #1 and case #2 kept knee locked in extension at stance phase. In case #3, knee sank more into flexion at stance phase.
    Both patterns were due to weak gastrocnemius control. For the knees on normal side, joint motions were all similar to those of the normal.

Kinetic similarities and differences: In vertical group reaction force, case #1 was different from the others as she had a two-inch lengthening on the day of the testing. In case #2 and #3, we found low acceptance force (Fl), on the prosthetic side and low push-off force (F2) on the normal side.

SUMMARY

We found increased hip abduction on the prosthetic leg and decreased hip adduction on the normal leg, with absence of or excessive knee flexion a the prosthetic knee. For vertical ground reaction force we found low push-off force (F2) on normal leg and low acceptance force (Fl) on prosthetic leg.

DISCUSSION:

The continuing factors might be due to the poor muscle control at hips and knees, causing poor balance onto the prosthetic side during one-limb support; therefore reluctance to weight-shift to the prosthetic side. With the centre of gravity remaining on the normal leg, the prosthetic hip is more abducted and the normal hip is more adducted.

For the experienced patients, they seemed to demonstrate a "guarded loading" onto the prosthetic leg. This might reflect the low acceptance force (Fl) on the prosthetic leg with a low push-off force (F2) on the normal leg.

We also found that the patient who had the poor rehabilitation follow-up program had the worst finding. We like to emphasize that rehabilitation is not over when the patient is able to walk independently with the prosthesis. A lot of fine-tuning is still needed to improve muscle strength, balance and gait.

CONCLUSION:

In this pilot study we sound a lot of interesting observations which indicate further research is needed.

Alberta Childrens Hospital Calgary, Alberta