Shouldering narrowing surgery is based on a straightforward premise of shortening the length of the clavicle on each side. Besides the length of the clavicle bone removed the success of the procedure is bases on satisfactory bone healing. Like bone fractures elective bone osteotomies can successfully heal if the two bone ends are held rigidly together long enough that ossification occurs in the narrow gap between them.
Plate and screw fixation is what holds the two bone ends together and being able to successfully do so depends onto numerous biomechanics factors. First and foremost the plate must be strong enough to resist bending or breaking when exposed to certain arm motions. In clavicle fractures 3.5mm thick plates are typically used but in elective osteotomies 2.7mm plates are adequate due to the two blunt ends of bone in such close proximity.
Because the plates used in shoulder narrowing are not long, unlike those used in fractures (due to the good quality of bone and the use of a very small incision), I will usually place two plates (longer superior and shorter anterior) to optimally resist different vectors of arm motion. (extension and rotation) Together they account for 9 or 10 holes for screw placement.
The often overlooked factor in clavicle osteotomy plate placement is the screws used to hold it. Anatomically the clavicle is not a solid bone. It has a fairly large central marrow space. This means it is important to have screw placement that engages both sides of the cortical bone to optimally resists screw pullout. (bicortical screw placement) To ensure that the screws are of adequate length the segment of bone removed can be used as a screw length measuring method. Screw lengths needs can be anywhere from 12 to 18mms.
Every shoulder narrowing patient now gets a one day postoperative x-ray to document the bone alignment as well as to check screw lengths. Such x-rays provide a basis for comparison should there be a concern in the recovery period about alignment and security of the fixation devices.
Dr. Barry Eppley
Indianapolis, Indiana