Moby Parsons, MD
3D imaging technology has led to a much better understanding of glenoid morphology and how it is affected by the wear process in shoulder arthritis. The pathologic triad as described by Matsen1 (1. posterior humeral subluxation; 2. increased glenoid retroversion; 3. biconcave glenoid) is encountered in many arthritic shoulders. Other wear patterns like superior erosion may also commonly occur in certain conditions like cuff tear arthropathy. One of the principle goals of shoulder replacement, whether anatomic or reverse, is to recognize and correct pathologic glenoid deformity as failure to do so may risk premature loosening of the glenoid implant due to abnormal loading mechanics.
Unfortunately, even experienced shoulder surgeons do a poor job in correcting glenoid erosion. A meta-analysis by Sadoghi et al demonstrated an average error in glenoid correction of +/- 11 degrees2. Other research by Iannotti et al showed an angular variability of 10 degrees in pin placement using a free-hand technique3.
Advanced CT imaging has allowed surgeons to preoperatively plan the placement of the glenoid component with the goal of correcting pathologic version, minimizing bone loss and preventing penetration of the glenoid vault.
This lack of precision is no longer acceptable given today’s technology. Advanced CT imaging has allowed surgeons to preoperatively plan the placement of the glenoid component with the goal of correcting the pathologic version, minimizing bone loss and preventing penetration of the glenoid vault. As many systems now offer augmented glenoid implants, such systems also allow selection of the optimal implant for each given case. Research looking at the ability of surgeons to recreate a preoperative plan using conventional, free-hand instruments compared to surgical navigation has been performed. The results demonstrate that even with planning, a surgeon’s ability to execute that plan remains very inaccurate. The scatter plot above shows the range of implantation variability without navigation in blue compared to with navigation in orange. These results clearly show that eye-balling it in the operating room is no longer acceptable with today’s technology.
Stephanie Muh, MD
Read complete study: Radiographic changes and clinical outcomes associated with an adjustable diaphyseal press-fit humeral stem in primary reverse shoulder arthroplasty
The use of press-fit humeral components for reverse shoulder arthroplasty has become more common in shoulder replacement surgery. Historically, humeral fixation was achieved with cementation techniques. However, due to increased operating time for cementation and added difficulty with higher complications in revisions during humeral component removal, surgeons have increasingly transitioned to press-fit humeral stems.
This article is a retrospective review of primary reverse shoulder replacements implanted with a modular diaphyseal press-fit humeral stem. Total hip literature has shown that distal press-fit stems obtain control through the medullary canal. The torsional stress is then transferred to proximal fixation and leads to increased stress shielding proximally with corresponding bone loss. This seems to be demonstrated in this study as well. With only a short-term follow-up, the authors found minimal radiolucent lines around distal fixation. However, 97% of radiographs demonstrated radiolucent lines around the smooth metaphyseal component. Additionally, the authors found progression of these radiolucent lines during the first two years. The authors claim the radiolucent line progression stabilizes after two years, however their mean follow up was 42 months (three and a half years). I do not believe this is sufficient time to truly access whether evidence of radiolucent lines has stabilized.
The evidence of proximal humeral bone loss is concerning and brings up an interesting clinical question. How do we revise shoulders with massive proximal bone loss? Continue reading
Thomas Wright, MD
Read complete study: Risk of insufficient internal rotation after bilateral reverse shoulder arthroplasty: clinical and patient reported outcome in 57 patients.
This study focused on the effects and risks of bilateral reverse shoulder arthroplasty (rTSA) on internal rotation (IR) in 57 patients. Data was recorded up to two years after the second surgery. The study found that only 15 percent of patients had insufficient IR in both shoulders after 12 months and 5 percent after 24 months. Patients who had insufficient baseline IR in their second shoulder and insufficient IR 12 month post op after their first shoulder had a 100 percent risk of having insufficient IR in both shoulders. The conclusion of this article is a recommendation to use staged bilateral rTSA over the use of a hemiathroplasty. The authors found that the majority of patients would undergo the surgery again, as it does provide benefits, like reduction in pain, regardless of the issues with IR.
The authors of this study focused on the risks of staged bilateral rTSA on internal rotation. I agree with their concern, as bilateral decreased IR could result in difficulties with toileting. In my practice, I stage my bilateral cases; however the timing is up to the patient. I will proceed with the second surgery no sooner than 12 weeks, but I do not recommend waiting as long as a year. In 2014, we published an article on bilateral rTSA1 in which we found all patients eventually had enough IR to allow toileting with at least one shoulder. I agree with the authors and do not recommend using a hemiarthroplasty in the second shoulder, based on the positive results that we had with rTSA.
Although the article showed a 100 percent failure rate in achieving sufficient IR in the second shoulder when it comes to patients who have both insufficient baseline IR and insufficient IR 12 months post op in their first shoulder, we have not noted that to be a problem.
One example is a 79 year old male with symptomatic cuff tear arthropathy on the right and a failed total shoulder arthroplasty (TSA) on the left due to rotator cuff insufficiency.Because of the predictable nature of performing an rTSA as a primary, the right side was addressed first. At three months post-op he had IR to L5.
79 year old male, cuff tear arthropathy on the right side, 3 months post op