Coracoid Fracture After Reverse Total Shoulder Arthroplasty: A Report of 2 Cases

On presentation, her active forward flexion, abduction, and external rotation were 40°, 30°, and 10°, respectively. She had full passive range of motion and pain with active and passive shoulder motion. Radiographic imaging showed superior migration of the humeral head with evidence of glenohumeral arthropathy suggestive of rotator cuff arthropathy (Seebauer type IIA⁸). After thorough discussion of options, risks, and benefits, the decision was made to proceed with RTSA. She underwent the procedure without complications. A DePuy Delta Xtend prosthesis was used with a cemented humeral stem, polyethylene, and glenosphere, sizes of 8, +3, and 38, respectively. The glenosphere component, positioned inferiorly to avoid scapular notching, was secured with 4 screws, and the stem was placed in neutral version. Her shoulder was reduced, ranged, and noted to be stable, allowing for supple passive range of motion without evidence of excessive tightness. She was placed in a sling with the shoulder positioned in neutral alignment. Her postoperative radiographs revealed satisfactory implantation of the reverse total shoulder prosthesis. Her postoperative course was uneventful. She was taken out of her shoulder immobilizer 4 weeks after surgery and began home-based physical therapy.

At 1 year after surgery, the patient had minimal shoulder pain with active forward flexion, external rotation, and abduction of 135°, 20°, and 85°, respectively. She presented to our clinic 15 months after RTSA with acute onset of pain about her anterior shoulder. She denied any recent trauma or infectious exposures. On examination, her motion was unchanged from prior examinations. However, she was tender on palpation of the coracoid. Radiographs at that time were unchanged (Figures 3A, 3B). Laboratory tests (erythrocyte sedimentation rate, C-reactive protein, and complete blood count with differential) that were subsequently ordered to rule out an occult infection were within normal limits. Computed tomography, which was ordered for further assessment and to ensure that the implant was stable with no loosening, showed satisfactory alignment of the prosthesis without loosening. However, a lucency was noted in the midportion of the coracoid that was suggestive of a fracture (Figures 4A, 4B). A conservative plan of treatment was advised with sling immobilization for 3 weeks and follow-up visits. The patient responded satisfactorily to this treatment approach, and, at her latest follow-up, 8 months after presenting with a coracoid fracture, she was pain-free. At the 5-year postoperative follow-up, her visual analog scale, American Shoulder and Elbow Surgeons score, and Simple Shoulder Test score were 1-2, 78, and 75, respectively. 

Discussion

The reverse prosthesis, a semi-constrained ball-and-socket device, provides satisfactory functional outcomes when used in carefully selected patients with rotator cuff arthropathy and pseudoparalysis, failed shoulder arthroplasty, and fracture sequelae.^1,9-11 By the traditional Grammont principles of medializing the center of rotation and lowering the humerus, shear forces about the glenoid are reduced and the deltoid muscle is tensioned, allowing for adequate torque generation, required to facilitate shoulder motion.^12,13 While long-term outcomes  concerning durability and survivorship are pending, some studies have attempted to improve our understanding of implant and functional longevity. Guery and colleagues¹⁴ noted an implant survival of 91% at 120 months. However, increased pain and decreased function were seen at the 6-year mark.¹⁴ A more recent study by Cuff and colleagues¹⁵ revealed 94% implant survivorship and sustained improvement in range of motion and pain at 5 years. 

Despite considerable success, RTSA can be associated with a myriad of complications. The most common complications of RTSA include scapular notching (44%-96%), glenoid side failure (5%-40%), instability (2.4%-31%), and infection (1%-15.3%).^2,3 In the setting of inflammatory arthropathy, there is an increased risk for intraoperative and postoperative fractures.^16,17 To date, there are only 2 reported cases of coracoid process fractures after RTSA.^18,19 In the case by Nolan and colleagues,¹⁸ conservative management with a sling for 6 weeks led to successful resolution of symptoms. Although little information is provided on the management of these rare fractures, literature on the slightly more common scapular (0.9%-7.2%) and acromial (0.9%-4.9%) fractures suggest that periscapular fractures are on the rise, may increase the risk for revision surgery, and can lead to inferior outcomes when compared with patients without fractures.^5,20,21

Acromial fractures after RTSA have been reported to occur at a rate of 0.9% to 4.9%.^5,21 This is a concern because of RTSA reliance on a functional deltoid.^5,6 The cause of these fractures remains to be fully elucidated. Wahlquist and colleagues⁶ in 2011 reported the cases of 5 patients that sustained acromial base fractures after RTSA. All 5 patients were noted to have unsatisfactory functional results despite achieving union (3 were treated with open reduction and internal fixation, and 2 were treated nonoperatively). Acromial fractures tend to present with pain within 6 months of surgery, which may indicate excessive constraint about the scapula, eventually leading to fracture. Furthermore, disruption of this bony structure can lead to devastating results because the acromial base serves as a fulcrum for the deltoid.