The Technique for Assessing and Correcting Glenoid Inclination May Be Implant-Specific

Moby Parsons, MD

Read complete study: The reverse shoulder arthroplasty angle: a new measurement of glenoid inclination for reverse shoulder arthroplasty

There is ample support in the literature that superior inclination of the glenoid baseplate in reverse total shoulder arthroplasty (rTSA) can lead to a higher risk of instability and premature implant failure. This is because a superiorly inclined baseplate experiences a greater shear vector imparted by the action of the deltoid muscle. Because cuff deficient arthritic shoulders often develop superior glenoid erosion, shoulder surgeons must carefully assess preoperative glenoid inclination when planning rTSA to avoid implant malposition. Preoperative planning platforms now allow surgeons virtually correct glenoid deformity while also optimizing implant fixation, backside contact with host bone, and avoidance of bone impingement such as scapular notching.

Boileau et al recently described a new measurement of glenoid inclination called the Reverse Shoulder Angle (RSA). Their contention is that referencing the more traditional ß-angle (the angle formed by a line connecting the superior and inferior glenoid face with a perpendicular to a line along the floor of the supraspinatus fossa) may inadvertently cause surgeons to superiorly incline small, flat-backed reverse baseplates when placed on the inferior half of the glenoid. Therefore, the RSA angle measures only the inferior half of the glenoid rather than the full glenoid face. This results in an average measured inclination of 25° + 8°, which is a 10° + 5° compared to the ß-angle. The authors note that Favard E1 glenoids with central erosion are at risk for baseplate malposition.

If the goal of rTSA is correction of glenoid inclination to neutral, then according to this paradigm a vast majority of baseplates would require a bonegraft to correct over 20° of superior inclination when using the RSA angle and a small, inferiorly-positioned implant. While this may be true for this specific implant design, it does not necessarily translate to all other baseplates, such as those with a curved back. Curved-backed implants fit the natural curvature of the glenoid bone and require less bone removal as they do not convert a curved surface to a flat surface.

Furthermore, an oval-shaped implant with an offset central peg can allow inferior shift of the glenosphere without having to exaggerate the baseplate position on the inferior half of the glenoid. The combination of these design features with 10° superior augmentation allows even severely eroded glenoids to achieve neutral inclination correction with less bone loss, better host bone contact, and no need for additional bone grafting such as in the BIO-RSA.

While the RSA angle does shed important light on the necessity of carefully considering the impact of erosion on the assessment of glenoid inclination, the clinical applicability of this angle may not be generalizable across implant systems. Prior to adopting the RSA over other methods of inclination measurement such as the ß-angle, Friedman axis or glenoid centerline, surgeons need to understand the relationship of implant design and implant options to correction of glenoid deformity. The RSA angle would suggest that all glenoids have considerable superior inclination and would require the establishment of a new Gaussian distribution of normal values. According to this paradigm, measurement of normal glenoids without wear could result in an RSA angle > 10°. To correct such glenoids to neutral (assuming this is defined as perpendicular to the floor of the supraspinatus fossa), may result in over-correction. This, in turn, may have unintended consequences such as further distalization and lateralization of the implant.

The varied methods of measuring inclination, each with its range of normal values, invites further efforts to define consensus on establishing optimal implant position with respect to fixation stability, joint biomechanics, and mitigation of complications such as instability and bone impingement. Our efforts to correlate implant position with clinical outcomes using the ExactechGPS® shoulder navigation platform will ultimately help us to establish guidelines through machine-learning applied to large clinical data sets.

Moby Parsons, MD, is in private practice in New Hampshire. He completed his internship and residency at University of Pittsburgh and fellowships at the University of Washington, Southern California Orthopaedic Institute and the University of Sydney. His work has produced multiple published articles and international presentations.

Computer Navigation in Shoulder Arthroplasty: The Learning Curve is Short

Kaveh R. Sajadi, MD, FAAOS

Read complete study: Computer navigation of the glenoid component in reverse total shoulder arthroplasty: a clinical trial to evaluate the learning curve.

Accurate placement of the glenoid component in reverse total shoulder arthroplasty (rTSA) is important to reduce component loosening, scapular notching, instability and to maximize impingement-free range of motion. Initial stability of the implant is critical for bony in-growth and is dependent upon optimal screw placement and maximizing screw length. Glenoid exposure and anatomy can be difficult, and in the presence of glenoid wear or deformity, placement of the implant and screws may be challenging.

Computer navigation has been shown to improve the ability to place the central glenoid post/cage fully within the glenoid vault and to optimize screw placement and length (Nashikkar et al). Computer navigation has also been shown to improve accuracy in achieving correct version and inclination of the glenoid component (Nguyen et al; Verborgt et al; Kircher et al). Some surgeons may be concerned about the perception of increased surgical time associated with computer navigation as well as any learning curve that comes with adopting a new procedure. This study by Wang et al investigated the learning curve of computer navigated rTSA, the accuracy of implant placement, and the effect on surgical time.

This well-designed study was a prospective case-series of a single experienced shoulder surgeon evaluating his first 24 consecutive navigated rTSAs. Although he had extensive experience with the arthroplasty system, his only prior experience with this navigation system was a sawbone workshop, a single cadaveric case, and a single clinical case to allow himself and his surgical team to be familiar with the setup and workflow. All cases underwent preoperative planning using Blue Ortho CT protocol (Blue Ortho, Grenoble, France). The goal of planning was to attain a glenoid implant version as close to 00 as possible using reaming or augments, attain 00 of inferior inclination, maximize bone-implant contact, and keep the glenoid central cage fully contained in the glenoid vault. Preoperative planning took 3-5 minutes per patient, a step I would argue should be done whether navigation is planned or not.

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Screw Length vs Quantity in rTSA

Jay J. King, MD

Read complete study: Impact of screw length and screw quantity on reverse total shoulder arthroplasty glenoid fixation for 2 different sizes of glenoid baseplates

Even though reverse total shoulder arthroplasty (rTSA) is becoming an increasingly commonly performed procedure throughout the world, studies are still needed in order to understand how we can maximize outcomes and minimize complications. While lack of glenoid baseplate fixation is not a common problem, loosening can occur1,2  and can lead to inferior outcomes and revision surgery.  In addition, scapular spine stress fractures have been associated with glenoid screw placement in rTSA and also lead to inferior clinical outcomes.3,4  Understanding complications such as these are important for future surgeons so that they can be avoided.

Roche et al in their recent article in JSES Open Access entitled “Impact of screw length and screw quantity on reverse total shoulder arthroplasty glenoid fixation for 2 different sizes of glenoid baseplates” evaluated how the number and length of screws affect baseplate fixation in an osteoporotic bone-substitute model using the Exactech standard and the Exactech small glenoid baseplates. They evaluated shear and compressive cyclic loading in a biomechanical model looking at constructs with two, four, and six screws with different screw lengths (18, 30, 46mm). All scenarios tested showed that the baseplates remained well-fixed after cyclical loading of 10,000 cycles without catastrophic failure, but there was a difference in displacement between the constructs. Baseplate displacement was less for the constructs with four screws compared to the constructs with two screws. The addition of six screws in the large baseplate did not make a difference in displacement. In addition, constructs with the longest screws had the lowest amount of baseplate displacement after cyclical loading. Short screws (18mm) showed the most displacement in both the small and standard baseplates.

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Clinical Studies Validate the Accuracy of GPS in Targeting Implant Placement in Anatomic and Reverse Shoulder Arthroplasty

Moby Parsons, MD

Read complete study: Computer navigation re-creates planned glenoid placement and reduces correction variability in total shoulder arthroplasty: an in vivo case-control study

The incidence of shoulder arthroplasty continues to increase, and this has brought continued innovation in preoperative planning and implant design. Concurrently, with improved imaging techniques, our understanding of pathologic changes that affect the joint have begun to elucidate strategies to address glenoid wear. Durability of the glenoid implant remains the weak link of shoulder arthroplasty,2,10 and both clinical and biomechanical studies have demonstrated that excessive residual retroversion or inclination,7,9 excessive corrective reaming,4,5 recurrent humeral subluxation6 and insufficient implant contact1 with bone are all risk factors for component loosening or failure. While augmented anatomic and reverse glenoid implants are now widely available, their use remains fairly limited relative to the frequency of pathologic wear. Guidelines on their use have also yet to be established, and a surgeon’s ability to accurately place such implants in cases with significant to extreme glenoid wear are uncertain. Prior cadaveric studies examined surgeon accuracy in recreating a preoperative plan using conventional instruments with free-hand techniques. The studies demonstrated significant variability and an average error of + 6-10° relative to the planned correction.11 This indicates that “eyeballing” glenoid implant placement may lead to significant variation from the plan. Particularly in cases of moderate to severe pathologic wear, such as the Walch B2 or B3 glenoid. This inaccuracy can be the difference between long-term durability and mid-term failure.

CT-based preoperative planning is now widely available and increasingly popular as it allows surgeons to virtually plan implant selection and placement and optimize parameters such as correction of inclination and version, peg placement in the glenoid vault, backside contact and amount of corrective reaming. While this can provide a very quantitative method of glenoid reconstruction, planning alone does not guarantee proper bone preparation or implant placement without additional technology to assist surgeons in replicating the plan. While patient-specific instrumentation (PSI) can improve the accuracy of implant placement over free-hand techniques, it still has a margin of error of + 4° on average.3,12 As studies have shown increased stresses in the cement mantle over 10° of residual version, this amount of error could potentially lead to pathologic implant malposition. Furthermore, PSI does not allow surgeons to adjust the plan intraoperatively if needed.

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Is patient-specific instrumentation better than standard instruments in shoulder arthroplasty?

Stephanie Muh, MD

Read complete study: Accuracy of patient-specific instrumentation in shoulder arthroplasty: a systematic review and meta-analysis

One of the most difficult aspects of shoulder arthroplasty remains the ability to correct glenoid deformity with accurate reaming and positioning of the glenoid implant. Even with experienced surgeons, it remains a challenge to appreciate how much version and inclination is corrected intra-operatively. The success of patient-specific instrumentation (PSI) in total hip and knee arthroplasty has naturally led to the surge of growth of PSI in shoulder arthroplasty. However, the key question of whether PSI is better than standard instrumentation is unknown.

21 of the 22 articles required the assistance of a physical PSI component to be manufactured prior to surgery. It took an average of 10 days to 5 weeks for production once the preoperative plan was completed.

This meta-analysis attempts to determine whether PSI significantly improves implantation accuracy during shoulder arthroplasty. The authors review all the available literature on PSI in shoulder arthroplasty including both cadaveric and clinical studies looking at a variety of available industry manufactured components. A total of 22 articles were compared and all preoperative planning programs were predetermined with a goal of 0 degrees of version and 0 degrees of inclination for total shoulder arthroplasty (TSA) and 5-10 degrees of inferior inclination for rTSA. 21 of the 22 articles required the assistance of a physical PSI component to be manufactured prior to surgery. It took an average of 10 days to 5 weeks for production once the preoperative plan was completed. The authors found that in 91% of articles, the postoperative errors were found to be less than 5 degrees with the assistance of PSI compared to preoperative plans. However, there was only 18% of articles that found PSI significantly reduced glenoid component malposition compared to standard instrumentation. Meta-analysis that directly compared PSI to standard instrumentation was only available for 7 articles (2 clinical, 5 cadaveric). While analysis did demonstrate an improvement in accuracy with PSI, it did not demonstrate any significant difference in accuracy when comparing PSI to standard instruments when looking at differences in version error (3 degrees), inclination error (1 degree) and offset (0.22mm).

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Opioid-Free Shoulder Arthroplasty: Are We There Yet?

Thomas Obermeyer, MD

Read complete study: Opioid-free shoulder arthroplasty: a prospective
study of a novel clinical care pathway

As the evolution of shoulder arthroplasty permits progressively shorter lengths of hospital stay and performance of these procedures in the ambulatory setting, pain management continues to receive increased attention from patients and physicians. Pain management is critical for timing of discharge, patient participation in early physical therapy, and is highly correlated with patient satisfaction. For some time, opioids have been a cornerstone of pain management, despite the opioid problem in the United States having achieved “epidemic” proportions with use, misuse and diversion. As a result, there is increased awareness of the benefits of limiting opioid exposure in the perioperative period surrounding elective orthopedic surgery. The authors of the study, “Opioid-Free Total Shoulder Arthroplasty” by Van Doren et al, reported on a series of properly selected patients undergoing total shoulder arthroplasty (TSA) who had satisfactory pain management using a multimodal pain approach without opioids. The study was an important demonstration that all providers performing shoulder replacement can make even minor modifications to pain protocols to move closer to eliminating the requirement for opioids, making these procedures increasingly safer for patients.

The study was an important demonstration that all providers performing shoulder replacement can make even minor modifications to pain protocols to move closer to eliminating the requirement for opioids…

The study was a prospective nonrandomized look at 65 patients with a mean age of 71 years undergoing a mix of primary and reverse arthroplasty; one group received opioid medications and the other group did not. Important exclusions were history of prior surgery, renal or liver disease (contraindicating NSAIDs), fractures, and inability to undergo regional anesthesia in the form of an interscalene nerve block. The observation group received interscalene block, intraoperative fentanyl and routine postoperative opioid medications with over the counter NSAIDs when recommended as needed. The intervention group received interscalene block, preoperative gabapentin and celecoxib, intraoperative acetaminophen, periarticular injection of liposomal bupivacaine, in-hospital use of ketorolac (Toradol), and post-discharge oral gabapentin and celecoxib prescriptions with oral acetaminophen as needed.

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The Effect of Glenoid Component Lucency on Outcomes

Kaveh Sajadi, MD

Read complete study: Glenoid component lucencies are associated with poorer patient-reported outcomes following anatomic shoulder arthroplasty

The volume of shoulder replacements performed has grown exponentially in the last decade due to its success in relieving pain and improving function with modern techniques and implants, but concerns regarding its longevity remain. The most common reason for failure in the long-term is loosening of the glenoid component. Progression of radiolucent lines is a worrisome sign that may suggest glenoid component loosening. However, the presence of radiolucent lines, as noted in the article, have been reported between 0-100% of the time with the lines frequently present on immediate postoperative radiographs. The presence of lines does appear to increase with longer follow up. The significance of these lines, aside from concern for loosening, is debated.

The authors of this study performed a retrospective review of all total shoulder arthroplasties (TSAs) over an 11-year period with all-polyethylene pegged or keeled glenoid components with a minimum 2-year followup. A multi-center research database was utilized. Glenoid lines were graded by the Lazarus scale, which grades lines on a scale from 0 (no lucency) to 5 (gross loosening or shift in component position). Demographic data was collected as well as patient-reported outcome (PRO) measures, including ASES score, Constant score, UCLA score, Simple Shoulder Test score, and Shoulder Pain and Disability Index score. Patients’ active range of motion was recorded as well. The authors only examined traditional all-polyethylene cemented implants, specifically excluding patients with a central in-growth peg as a previous study by Grey SG, et al, showed significantly reduced radiolucent lines with this prosthesis. This was recently confirmed in the study by Friedman RJ, et al, which showed a rate of lucent lines in 9% of patients with the hybrid cage glenoid versus 37.6% in all polyethylene pegged glenoids (p < .0001).

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Navigated Ream and Run Procedure with ExactechGPS

Moby Parsons, MD

The Ream and Run shoulder replacement is a great option for younger patients with shoulder arthritis who have failed conservative treatment yet wish to maintain a high level of activity. Because the weak link in shoulder replacement is the plastic socket implant, avoiding the insertion of this reduces the risk of failure, particularly for patients who intend to subject their shoulder to moderate stress over a long period of time. The Ream and Run resurfaces the ball, removes the bone spurs, releases the contracted tissues and reshapes the worn socket to a smooth and conforming concavity to mate with the ball.

While partial shoulder replacement (hemiarthroplasty) has historically gotten a bad reputation for having inferior results to total shoulder replacement, the results cannot be generalized to all cases. Many glenoids (socket) have substantial wear and erosion from the arthritic process. If such wear is not addressed at the time of hemiathroplasty, patients are at high risk of continued pain and abnormal joint mechanics. The Walch classification shows the different patterns of wear with the B1, B2 and B3 being both common and problematic. In these patterns, the ball shifts to the back of the arthritic socket and results in progressive erosion of the posterior glenoid. Failure to recenter and reshape the head into a single concavity will result in failure of hemiarthroplasty.

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PRP: Should I Be Using It?

Kaveh Sajadi, MD

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PRP, platelet-rich plasma, is touted by some to be a revolutionary treatment with the potential to heal or alleviate any number of ailments, from arthritis to tendinopathies to tendon tears or ruptures. The idea is to use the body’s own “healing” system to repair damaged tissue by amplifying it–increasing the concentration of platelets and their accompanying growth factors, which is then injected into the diseased or injured area.

Platelets are typically activated when a blood vessel is damaged. When the platelet is activated to clot, it also releases many growth factors which are contained within the alpha granules in the platelet. The growth factors present include PDGF (platelet-derived growth factor), important in wound healing, VEGF (vascular endothelial growth factor), which recruits the body to form new blood vessels, as well as many other signaling factors and cytokines.

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Stress Fractures After rTSA. Not Every Onlay is Created Equal.

Ian Byram, MD

Read complete study: Increased scapular spine fractures after reverse shoulder arthroplasty with a humeral onlay short stem: an analysis of 485 consecutive cases

Since its FDA clearance in 2003, reverse shoulder arthroplasty (RSA) has become increasingly utilized for the treatment of arthritis, fractures, and rotator cuff failures in the United States. Initial reports demonstrated a high rate of complications, including instability, impingement, scapular notching, and subsequent implant failure.Many implant designs have been successfully modified to minimize these problems. While scapular notching seen with the initial Grammont style prosthesis has decreased with modern lateralized implant designs, scapular spine fractures have become more prevalent.

The authors of this study analyzed a series of RSA cases utilizing a short stem, 145° neck-shaft inclination prosthesis hoping to shed light on implant features that may lead to scapular spine fractures. In a retrospective review of 485 consecutive arthroplasties, they reported 21 (4.3%) scapular spine fractures that were diagnosed at a mean of 8.6 months after surgery. Comparing those patients with matched controls, patients with fractures demonstrated significantly worse Constant scores and forward flexion. They concluded that utilization of a lateralized “onlay” convertible humeral design creates increased stress on the deltoid and acromion, resulting in an undesirable rate of scapular spine and acromial fractures.

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