Stephanie Muh, MD
The development of postoperative scapular spine or acromial base fractures remains a difficult problem to treat. With a reported incidence of 1-10% in the literature, there has been no consensus on the best treatment, and most authors report poor post-fracture functional outcomes.1-3 Both operative and nonoperative management of these fractures have been advocated with variable outcomes.2,3
This retrospective study presents data from a large cohort of patients with a single prosthetic design (Grammont style with medialized center of rotation and medialized humerus with inlay prosthesis). The authors found an overall prevalence of 1.3% scapular fractures in 1,953 implants. This seems to correlate with other literature where the incidence ranged from 1-10%. 1-4 When evaluating the functional results with a minimum of five years follow-up, 19 fractures were identified with an overall improved range of motion and Constant score. It is important to note, however, the patients with fractures did not improve as greatly as those without fractures. While the postoperative Constant score improved from 25.6 to 47 postoperatively, the authors note the average postoperative Constant score in a non-fracture group is 70. They did not directly compare the fracture group range of motion to non-fracture group which I think would have added valuable information. It would have been interesting if the authors presented initial improvement postoperatively and compared this to post-fracture outcomes and commented if there was function.
Another reported outcome in this study looked at radiographic results including a nonunion rate of 58%. Identified fractures were treated nonoperatively in an abduction sling for six weeks; and of the fractures that healed, all had a residual downward tilt resulting in loss of acromial-tuberosity height. This is an important point as the loss of acromial-tuberosity height likely alters deltoid length and tensioning which could result in loss of motion.
This is an important point as the loss of acromial-tuberosity height likely alters deltoid length and tensioning which could result in loss of motion.
While comparing inlay versus onlay prosthesis design, the authors note that there appears to be a four-to-five-times higher rate of scapular fractures with the onlay prosthesis. At face value, it may appear that an inlay prosthesis has a lower fracture rate. However, Kennon et al.5 demonstrated that an onlay design with an initial fracture rate of 4.4% was decreased to 0% when the superior screw for the baseplate was not utilized. It should be noted that the authors also reported a 44% potential link between screw position and fracture line. Additionally, Teusink et al.1 reported a 3.3% fracture rate with an inlay design prosthesis. It is likely that complete understanding of prosthesis design and scapular fracture has not been fully understood.
I agree with the authors conclusion that postoperative scapular fractures are a detrimental turning point in the postoperative course after RSA with worse functional outcome. There are limited options for treatment with overall guarded and variable results. It is clear that more research needs to be done to determine if implant design, surgeon technique (baseplate screw position), or patient factors (osteoporosis, AC joint arthritis, etc.) influence the development of postoperative scapular spine fractures.
- Teusink, et al. What is the effect of postoperative scapular fracture on outcomes of reverse shoulder arthroplasty? J Shoulder Elbow Surg. 2014 Jun;23(6):782-90. doi: 10.1016/j.jse.2013.09.010
- Crosby, et al. Scapula fractures after reverse total shoulder arthroplasty: classification and treatment. Clin Orthop Relat Res. 2011 Sep;469(9):2544-9. doi: 10.1007/s11999-011-1881-3.
- Cagle, et al. Acromial spine fracture after reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2019 Apr;28(4):792-801. doi: 10.1016/j.jse.2018.08.033.
- Zumstein, et al. Problems, complications, reoperations, and revisions in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2011 Jan;20(1):146-57. doi: 10.1016/j.jse.2010.08.001
- Kennon, et al. Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes. J Shoulder Elbow Surg. 2017 Jun;26(6):1023-1030. doi: 10.1016/j.jse.2016.10.018
Stephanie Muh, MD, is deputy chief of service in the department of orthopaedics at Henry Ford Hospital West Bloomfield where she specializes in shoulder and elbow reconstruction, rotator cuff repair and arthritis. Dr. Muh completed her residency in orthopaedic surgery at the Henry Ford Hospital and shoulder and elbow fellowship at Case Western Reserve University/University Hospitals of Cleveland.