KNEE JOINT POSIITION SENSE IN CONGENITAL BELOW KNEE AMPUTEES

James A. Hardner B.Sc.,M.D., FRCSĀ©, Mei Fong B.Sc, P.T., Alberta Children's Hospital, Calgary, Alberta, Canada


Introduction

Many studies have evaluated knee joint proprioception in different conditions and populations. We have found only two studies for the below knee amputee population. Both studies involved adult traumatic and vascular amputees. Variability of joint proprioceptive awareness may have profound affect on performance. For children who have congenital lower limb deficiency, is joint proprioception different in the abnormal leg? Does wearing the prosthesis improve knee joint position sense?

In this study, knee joint position sense was evaluated in nine congenital below-knee amputees, and nine age-matched normal control subjects. Knee joint position sense was assessed by reproduction of passive positioning of the knee.

Hypothesis

  1. Knee joint position sense of the congenitally abnormal leg is decreased.
  2. The shorter the congenitally abnormal side is compared to the normal side, the less accurate is the joint position sense of the knee.
  3. Joint position sense through the knee joint of the congenitally abnormal side is improved with wearing the prosthesis.

Subjects

Patients were drawn from the Juvenile Amputee Clinic at the Alberta Children's Hospital. Nine patients participated in the study. They all had congenital absence of fibula and cruciate ligaments, with symes amputation prior to ambulating. Nine age matched normal volunteers were chosen to participate in the study as control.

Methods and Materials

  1. Kin Com Chair which allowed the waist and thighs to be strapped to the chair.
  2. The "Angle Finder" was strapped onto the anterior border of the tibia on the test leg.
  3. The subject's vision was obscured from the leg while sitting on a Kin Com chair with the knees in a free hanging position of 90°, back of the knees were 5 cm away from the edge of the chair.
  4. Knee flexion was tested in 30, 45 and 60. Each tested leg was positioned at a predetermined angle (i.e., 30°, 45°or 60°) randomly selected. The leg was held in this position for 2 - 4 seconds, subject was asked to concentrate on that position, and then the leg was returned to the starting position of 90. The subject was then asked to return the tested leg to that position. Two people recorded the angle position. Three trails were done.
  5. Both legs of the normal subjects and the amputees were tested.
  6. For amputees, the prosthetic leg was tested with the prosthesis on and off.
  7. Stump length was also measured to compare to the non- prosthetic side.

Data analysis

The data was analyzed by multi-variant analysis of variants. This analysis was by groups, by limb position, and using the two recorders and the three trials. A separate analysis was use to assess the joint position sense with and without the prostheses, and stump length.

The discrepancies between the tested angles and the subjects reproduced angles were calculated over two recorders and three trials. The paired t-test was used to compare the average angle discrepancies away from the tested angles.

Results on mean angle discrepancies

Knee joint position sense in reproduction of passive positioning

  1. In the control group
    No statistical significant difference was found between the dominant and the non-dominant knee.
  2. In the amputees
    No statistical significant difference was found between the prosthetic and the non-prosthetic knee, and the control. It was the same with prosthesis on and with prosthesis off.
  3. No statistical significant difference was found with the stump length and the knee joint position sense using linear regression.

Clinical observations

Even thought we found no significant difference in all groups. We observed two clinical trends

  1. The mean angle discrepancy was small-which meant the children in both groups were very accurate in reproducing the passive position of the knee.
  2. At 60 degrees of knee flexion, the standard deviation was greatest with the prosthesis off. This suggested that the congenital amputees had more difficulties reproducing the tested angles with their prostheses off. With their prostheses on, their prosthetic knees performed better than their good knees.

    This might suggest that the prosthesis does provide sensory feedback to the leg to enhance knee joint position sense of the congenital knee.

Discussion

Variability of joint position sense in congenital limb deficiency will have an impact on:

  1. Early rehabilitation and gait training.
  2. Later ñ effective use of the prosthesis.

In order to maximize efficient prosthetic, wear the rehabilitation team will benefit by having prior knowledge of decreased position sense. Since we found no decreased knee position sense in our congenital amputees. We concluded that the below knee amputees performed equally well on both knees in-spite of their abnormalities. However at knee flexion of 60 degrees, these children performed better with their prostheses on than off.

Even though we found no relationship between the stump length and the knee position sense, clinically adequate stump length is critical for good prosthetic fitting which enable amputees to function effectively.

Impacts on therapeutic training

The following need to be involved:

  1. Early fitting to ensure normal gross motor development, to enhance body awareness with prosthesis [joint position sense, the kinesthetic awareness]
  2. Extending a soft elastic sleeve above the knee to improve sensation during movement.
  3. Being assured that the prosthesis fits well and applies pressure to the entire residual limb to achieve total contact.
  4. In sports, knee support is needed to protect the unstable knee.

Conclusion

Our sample size was very small, we might not able to detect any decreased in the congenital knee joint. We will continue to collect data to get a bigger sample as an ongoing study.