The purpose of our study was to prospectively evaluate the effectiveness of Botulinum toxin in patients with involuntary positional instability who had failed a specific rehabilitation programme.

Patients with Involuntary Positional Instability present with a muscle patterning problem that results in active dislocation of the glenohumeral joint. Botulinum toxin is used to inhabit the patterning muscle and therefore facilitate rehabilitation of optimal movement patterns.

Materials and Method: 14 patients referred to a tertiary referral unit were included. All patients had failed rehabilitation, reported multiple recurrent dislocations, repeated surgical interventions (Range 2 – 6) and mean duration of symptoms 5 years (Range 2 – 9). Patients were assessed with Constant and ASES scores, psychological scores (HADS and DRAM) and the Ashworth muscle tone scale. Botulinum Toxin was injected into the muscle dominating movement (identified with clinical assessment and EMG) and patients were re-entered into the rehabilitation programme post-injection.

Results: At an average of 2 years follow-up (8/12 – 4.1) 11 out of 14 patients demonstrated a statistically significant improvement in all parameters. 1 patient required a repeat injection at 4 months but at 2 years remains asymptomatic. Of the 2 patients who failed both demonstrated the highest scores on psychological screening and 1 of them had a severe connective tissue disorder.

Conclusion: Our early experience of Botulinum suggests that it is an effective tool in patients with involuntary positional instability resistant to rehabilitation. Psychological scores may be a useful tool to aid patient selection.