The effect of muscle contraction on kinaesthesia

Active Joint Position Sense in Children With Unilateral Cerebral Palsy

Objective

The aim of the study was to examine the differences in joint position sense at the elbow joint between 15 children with unilateral cerebral palsy (CP) and 15 typically developing (TD) controls without neurological or other health deficits.

Methodology

Joint position sense, a major proprioceptive component, was evaluated actively using a Kin Com 125 AP isokinetic dynamometer (Chattanooga Group, Chattanooga, TN).

Results

A significant interaction was found (p<0.05) between disability and side, with respect to the active reproduction movement scores. Post-hoc independent t-tests, with Bonferroni adjustments, revealed significant differences for the dominant (t=-3.63, p=0.001) and non-dominant sides respectively (t=-6.19, p=0.000). Repeated measures t-test revealed wider errors with the non-dominant (affected side) in the active reproduction test, compared to the dominant (nonaffected) side for the CP group of children (t=-4.73, p=0.000). A positive correlation was evident between the level of spasticity and joint position sense (Rho=0.71, p=0.003).

Conclusions

Based on our findings, joint position sense is impaired at the elbow joint in children with spastic hemiplegia. The proprioceptive deficit is present at both the affected and unaffected sides and is related to the level of spasticity.

Proprioception 3 years after shoulder arthroplasty in 3D motion analysis: a prospective study

BACKGROUND

This prospective study evaluated the development of proprioception over the course of 3 years after shoulder arthroplasty.

METHODS

Twenty-one patients were enrolled who underwent total shoulder arthroplasty (n = 10) or hemiarthroplasty (HEMI) (n = 11) for shoulder osteoarthritis. All patients were examined 1 day before the operation, 6 months and 3 years after surgery in a motion analysis study with an active angle-reproduction (AAR) test.

RESULTS

Overall proprioception measured by the AAR deteriorated significantly 3 years after surgery [from 6.6° (SD 3.1) to 10.3° (SD 5.7); p = 0.017] and was significantly worse than in the control group [10.3° (SD 5.7) vs. 7.8° (SD 2.3); p = 0.030). In the HEMI subgroup, 3 years after shoulder replacement, there is a significant deterioration of proprioception at 30° of external rotation [from 3.1° (SD 3.5) to 12.8° (SD 10.7); p = 0.031]. On average, in the TSA subgroup proprioception deteriorated from 7.1° (SD 3.1) to 8.6° (SD 1.4) and in the HEMI subgroup from 6.1° (SD 2.1) to 12.4° (SD 8.3). The comparison of postoperative impairment of proprioception between the TSA and HEMI subgroup showed significantly worse proprioception for the HEMI subgroup at 30° of external rotation [9.8° (SD 10.1) vs. 1.6° (SD 6.3) in the TSA group; p = 0.046].

CONCLUSION

In conclusion, proprioception that was measured by an AAR test remained unchanged or deteriorated 3 years after shoulder arthroplasty. The postoperative deterioration of proprioception was more distinctive in HEMI than in TSA group.

Vibration sensitivity of human muscle spindles and golgi tendon organs

The responses of the various muscle receptors to vibration are more complicated than a naïve categorization into stretch (muscle spindle primary ending), length (muscle spindle secondary endings), and tension (Golgi tendon organs) receptors. To emphasize the similarity of responses to small length changes, we recorded from 58 individual muscle afferents subserving receptors in the ankle or toe dorsiflexors of awake human subjects (32 primary endings, 20 secondary endings, and six Golgi tendon organs). Transverse sinusoidal vibration was applied to the distal tendon of the receptor-bearing muscle, while subjects either remained completely relaxed or maintained a weak isometric contraction of the appropriate muscle. In relaxed muscle, few units responded in a 1:1 manner to vibration, and there was no evidence of a preferred frequency of activation. In active muscle the response profiles of all three receptor types overlapped, with no significant difference in threshold between receptor types. These results emphasize that when intramuscular tension increases during a voluntary contraction, Golgi tendon organs and muscle spindle secondary endings, not just muscle spindle primary endings, can effectively encode small imposed length changes.