Background: The collarbones are very visible in both male and females but little regard is paid to their actual shape and size. The size of the clavicles is typically perceived as how prominent they are but that is not a reflection of their actual length and thicknesses. Rather that is a function more of how thick the overlying soft tissues are and the patient’s body habitus.
The length and cross-sectional thickness of the clavicles is well known to be influenced by patient size and gender. The taller the patient is the longer the clavicle is. The larger the body habitus the thicker or increased cross-sectional diameter it has. There is some correlation between height and cross-sectional thickness but is more related to gender and body size. The cross-sectional thickness of the bone is important as the screw lengths used need to fully engage the cortex on both sides of the bone.
When performing shoulder narrowing surgery, regardless of the length of bone removed, the two reapposed ends are never similar in cross-sectional diameter. The outer segment is always about 1/3 smaller than the inner segment. This is because of the location of resection. Being done closure to the inner third of the clavicle due to the more favorable incision location, the inner segment is at the thickest part of the bone. With the removal of a mid-shaft segment of bone the thinner outer segment is pulled to the inner segment resulting in the size differences across the osteotomy site.
Case Study: This female desired shoulder narrowing surgery with a bideltoid distance of 52.5cms. Her clavicle length from sterno-clavicular joint head to the acromioclavicular joint was 17.75cms.
Under general anesthesia 3cm bone length segments were removed from the largest clavicle I have seen to date. Large is defined as cross-sectional thickness with a very flat top surface of the bone. Double plates and screw fixation was applied needing 24mm long screws on the inner segment and 20mm screws on the outer segment.
Her 2 day result show the improvement in her shoulder shape both in the front and back views.
Her postop x-rays show good bicortical screw engagement on both sides of the bones.
The cross-sectional diameter of the clavicle has an important consideration in both the execution and success of the procedure. Screws must be of adequate length to fully engage both cortices to resist postoperative pullout and ensure good fixation stability. The large the clavicle is in cross-sectional diameter the longer the screws must be to do so. While 20mm lengths are usually adequate for the inner segment in most patients in larger clavicles those lengths must be increased up to 24mms.
Key Points:
1) Large clavicles can be as successfully reduced as well as smaller clavicles and require slightly longer lengths of resection to do so.
2) The larger the clavicle is in cross-sectional diameter the longer the bicortical screws need to be on the superior plate.
3) Cross-sectional size differences between the reappposed bone ends will always occur regardless of the original size of the clavicles or the amount of bone removed.
Dr. Barry Eppley
World-Renowned Plastic Surgeon