John MP 2nd, Wilson JT, Mesa L, Simon P, Frankle MA. Revision reverse shoulder arthroplasty for the management of baseplate failure: an analysis of 676 revision reverse shoulder arthroplasty procedures. J Shoulder Elbow Surg. 2024 Mar;33(3):707-714. doi: 10.1016/j.jse.2023.06.039. Epub 2023 Aug 4. PMID: 37543279.
This study is a look at a relatively uncommon complication of reverse shoulder arthroplasty: glenoid-sided baseplate failure.
Out of 676 primary reverse arthroplasties, 46 (6.8%) required revision for aseptic glenoid loosening over a 15-year study period. The take-home message of the study is that correcting the failed baseplate with revision reverse arthroplasty was a reliable option with low repeat failure rate (3 of 46 patients or 6.5% required re-revision) with a modest improvement in outcome scores at 1 and 2 years postoperatively. The relative success of the revision surgery was attributed to several technical factors, including the use of locking screws on the baseplate, allograft bone grafting, osteoinductive stimulation (BMP-2), larger glenospheres, and alternative baseplate positioning where the baseplate was aligned with alternative spine line, instead of the axis of the native glenoid. The authors should be commended for reporting on a difficult problem in shoulder arthroplasty, improving our ability to care for these patients.
While at first glance, it may seem that revision surgery is overall a major success and these patients did just fine, but a closer examination of this cohort may be appropriate. Patients undergoing revision surgery for aseptic failure of a glenoid implant can be a challenging population to manage. Many of these patients postpone surgical intervention sometimes for years, often only electing to have surgery when radiographs reveal clear lucency around the implant or when the pain becomes unbearable. Patients may be several years older than they were during the primary operation, sometimes having developed medical or social problems that make revision surgery suboptimal. Stated differently, examining a cohort of patients having surgery for a failed baseplate may not adequately capture the full extent of the morbidity and treatment challenges posed by glenoid component loosening after reverse arthroplasty.
It becomes clear that prevention of glenoid component loosening after the primary arthroplasty becomes paramount. Surgical factors including fixation and positioning of the baseplate should be optimized with careful surgical execution and planning, with use of intraoperative tools such as navigation (ie, Exactech GPS) where necessary. Could there be factors unique to the design of the primary reverse glenoid implant that could contribute to loosening? I would hypothesize yes, as the location of the center of rotation (CoR) of the glenoid implant is directly related to shear forces on the baseplate, with more lateral CoR designs (such as the DJO prosthesis) placing far higher shear forces on the glenoid-bone interface. In this present John et al. study, the DJO implant comprised the majority of baseplate failures (25), more than the other 6+ manufacturers combined (Exactech had just 4). In fact, initial designs of the lateral CoR DJO prosthesis had even higher rates of baseplate failure(1) prior to design modifications made on the central post and peripheral locking screws which improved, but did not eliminate the problem.
If one were to assume the surgical execution of the implant is perfect, is there a variable in the design of the implant that could optimize longevity of the glenoid implant? The Exactech Equinoxe design focuses on a medial CoR, where the CoR is just off (lateral to) the native glenoid. This substantially limits shear forces on the baseplate, and may be one important factor in long term follow up data that demonstrates superior survivorship. To compare, a recent large cohort of 492 patients treated with the Exactech Equinoxe Reverse prosthesis demonstrated a rate of aseptic glenoid loosening of just 1% (5/492) followed for up to two years(2). The comparatively low rates of baseplate failure in this cohort likely relate to a difference in implant design that may improve the rates of revision surgery for this difficult clinical problem.
References:
- Holcomb JO, Cuff D, Petersen SA, Pupello DR, Frankle MA. Revision reverse shoulder arthroplasty for glenoid baseplate failure after primary reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2009 Sep-Oct;18(5):717-23. doi: 10.1016/j.jse.2008.11.017. Epub 2009 Mar 17. PMID: 19278872.
- Flurin PH, Tams C, Simovitch RW, Knudsen C, Roche C, Wright TW, Zuckerman J, Schoch BS. Comparison of survivorship and performance of a platform shoulder system in anatomic and reverse total shoulder arthroplasty. JSES Int. 2020 Jul 27;4(4):923-928. doi: 10.1016/j.jseint.2020.07.001. PMID: 33345236; PMCID: PMC7738444.