The subscapularis muscle is the key muscle in shoulder pain. It is strong and pulls the shoulder up to impinge “better”. It is a principle muscle involved in frozen shoulder. The best trigger / Botox injection would perhaps hit the most motor points (where the nerve ends into the muscle). A block with phenol has recently been shown to help spastic shoulders in cervical injury patients.
Spinal Cord. 2008 Sep 30. [Epub ahead of print] Subscapularis motor point block for spastic shoulders in patients with cervical cord injury. Uchikawa K, Toikawa H, Liu M. abstract
This study used 0.2- 0.3 ml 5% phenol. A coated 100 mm coated needle and a stimulator was used.
Subscapularis phenol injection dropped pain VAS from 6 to 3.4 p<0.05 and improved ROM.
A study was done to see where the motor points where in the subscapularis:
Archives of Physical Medicine and Rehabilitation Volume 88, Issue 3, March 2007, Pages 295-297
Motor Points for the Neuromuscular Blockade of the Subscapularis Muscle
Tim P. Harrison MBBS, BSca, Anna Sadnicka MBChB, BSca and Deborah M. Eastwood MB, FRCSb
The motor points were distributed in brown dot areas (blue just a marker of scapula spine edge)
On average, a person would have 3-6 (average 5) motor points.
From that they concluded a posterior fold injection aimed for mid portion upper scapula:
It would seem that would be the most suitable place to get subscapularis block/Botox as well. I have one patient with cervical disc disease that tightens up the scapula muscles so it rubs underneath. I have found he gains relief from injection through the medial approach. This approach would be better and Botox worthwhile now that I know where best to put it.
Anyone had any experience with this?
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