Treatment of displaced intra-articular glenoid malunion deformity with reverse total shoulder arthroplasty guided by augmented reality-assisted computer navigation

The position of the glenoid component in total shoulder arthroplasty is important for maximizing postoperative function and long-term survivorship.13Matsen F.A. Clinton J. Lynch J. Bertelsen A. Richardson M.L. Glenoid component failure in total shoulder arthroplasty.J Bone Joint Surg Am. 2008; 90: 885-896https://doi.org/10.2106/JBJS.G.01263Crossref PubMed Scopus (250) Google Scholar Proper baseplate alignment allows optimal range of motion, minimizes impingement, and decreases stress on the bone-prosthesis interface.7Iannotti J.P. Spencer E.E. Winter U. Deffenbaugh D. Williams G. Prosthetic positioning in total shoulder arthroplasty.J Shoulder Elbow Surg. 2005; 14: S111-S121https://doi.org/10.1016/j.jse.2004.09.026Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar Glenoid malposition is associated with higher rates of implant loosening, instability, early failure, and poor clinical outcomes, and is one of the most common complications of reverse shoulder arthroplasty.14Nyffeler R.W. Werner C.M.L. Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis.J Shoulder Elbow Surg. 2005; 14: 524-528https://doi.org/10.1016/j.jse.2004.09.010Abstract Full Text Full Text PDF PubMed Scopus (358) Google Scholar Abnormal glenoid morphology, bone loss, or post-traumatic deformity can further complicate the intraoperative implant positioning process. In these scenarios, it is often difficult to determine native glenoid version, inclination and medialization, and the amount of required correction is not always clearly defined.12Kwon Y.W. Powell K.A. Yum J.K. Brems J.J. Iannotti J.P. Use of three-dimensional computed tomography for the analysis of the glenoid anatomy.J Shoulder Elbow Surg. 2005; 14: 85-90https://doi.org/10.1016/j.jse.2004.04.011Abstract Full Text Full Text PDF PubMed Scopus (256) Google Scholar Traditional preoperative planning methods and surgical techniques do not provide a standardized approach to correct moderate to severe glenoid deformity.6Iannotti J.P. Greeson C. Downing D. Sabesan V. Bryan J.A. Effect of glenoid deformity on glenoid component placement in primary shoulder arthroplasty.J Shoulder Elbow Surg. 2012; 21: 48-55https://doi.org/10.1016/j.jse.2011.02.011Abstract Full Text Full Text PDF PubMed Scopus (140) Google Scholar The development of new technology within the field of shoulder arthroplasty offers novel solutions to solve complex surgical problems. This case highlights the opportunity for and implementation of a novel navigation system, assisted by augmented reality (AR) images superimposed on the surgical field, allowing precise replication of a complex preoperative three-dimensional plan. The patient is a 64-year-old right hand dominant male laborer who sustained a right comminuted intra-articular glenoid and scapular body fracture after involvement in a motorcycle accident (Figure 1). After failing to progress with 10 weeks of non-operative management, the patient underwent open reduction internal fixation (ORIF) at an outside institution through a posterior Judet approach. This ultimately resulted in a displaced intra-articular malunion, and was associated with severe pain, restricted passive range of motion, and weakness in both posterosuperior rotator cuff and deltoid musculature one year after his ORIF. On exam, the patient demonstrated active and passive range of motion limited to 60° forward flexion, 10° external rotation, and internal rotation to the level of his SI joint. Radiographs and computed tomography (CT) scan obtained 12 months from date of surgery demonstrated malunion of the intra-articular glenoid fracture and intra-articular screw penetration from the posterior plate (Figure 2). Infection workup in the form of WBC, ESR, and CRP was negative, and EMG of suprascapular and axillary nerves demonstrated adequate conduction potential. Given persistent pain, activity-limiting stiffness, and weakness, the patient was indicated for removal of hardware and conversion to reverse total shoulder arthroplasty.Figure 2Grashey XR, axial CT, and CT 3D reconstructions demonstrate glenoid malunion with intra-articular extension of multiple screws.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Due to the malunion of both the glenoid and the scapular body, it was clear that the standard visual and tactile reference techniques used during reverse total shoulder arthroplasty would be difficult to apply at the time of surgery, making intraoperative determination of baseplate version, inclination, and medialization imprecise. We decided to utilize 3D planning software to optimize the position of the baseplate to maximize impingement-free range of motion and baseplate fixation (Figure 3). The preoperative plan identified a large posterosuperior glenoid defect with step-off. This defect was too large to correct simply by reaming the inferior glenoid, which would have resulted in excess medialization of the construct. Using the planning software, we determined that a bone autograft would fill the defect nicely and provide structural support to the glenoid construct while still allowing at least 50% of the backside of the baseplate to rest on native bone. We specified the precise graft thickness and angulation using the software and incorporated this into the plan. In order to precisely execute this plan, we chose to proceed with intra-operative computer-navigated implant placement assisted by augmented reality glasses. Using a posterior incision, full thickness medial and lateral skin flaps were developed until the inferior border of the deltoid fascia was encountered. This fascia was opened and the deltoid retracted superiorly. The interval between infraspinatus and teres minor was then identified and incised, exposing the previously placed hardware. The plate and screws were removed, and assessment of the fracture site demonstrated bony union. A standard deltopectoral incision was utilized to approach the glenohumeral joint. The rotator cuff was inspected, revealing a fibrotic and thin subscapularis and high-grade partial-thickness tear of both supraspinatus and anterior infraspinatus tendons with 90% exposed greater tuberosity. Posterior infraspinatus and teres minor tendons appeared normal. Using bone graft harvesting instrumentation matched to the preop planning software, the humeral head guide was centered and secured with a bicortical guidewire. The reamer was then utilized to match the radius of curvature of the glenoid baseplate. The central piston guide and trephine construct were then used to core a graft of the planned thickness. According to the preoperative plan, the graft was cut at 20 degrees and of a thickness to allow 50% of the baseplate to contact the native inferior glenoid. (Figure 3). The humeral shaft was reamed and broached until rotational stability was obtained. The glenoid was exposed, taking care to identify and protect the axillary nerve. The extent of malunion was examined and found to be significant, as anticipated (Figure 4). For this case, we utilized NextAR navigation (Medacta, Castel San Pietro, Switzerland) with Medacta Reverse TSA implants (Medacta, Castel San Pietro, Switzerland). The navigation tracker was secured to the coracoid using two small pins (Figure 5). The scapula was then registered to the navigation software using 15 points of reference on the glenoid and 15 on the coracoid. This allowed real-time calibration between the preoperative CT scan, the patient's scapula, and the software.Figure 5Intraoperative photo depicting NextAR tracker secured to coracoid to allow for calibration between NextAR instruments and preoperative CT scan.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The optimal start point target was superimposed onto the surgical field and directly visualized through the augmented reality glasses, and the guidewire was advanced to match the templated version and inclination and the glenoid was then reamed to the appropriate depth. (Figure 6). Once the planned reaming depth was achieved, primarily on the inferior malunion fragment, the long peg center hole was drilled. In order to maximize the likelihood of graft fusion, the superior aspect of the malunited glenoid joint surface graft site was roughened with a bur and the graft was placed superiorly. The baseplate was then impacted into position over the bone graft, and optimal rotation was achieved with AR/navigation assistance (Figure 7). Excellent press-fit peg fixation was obtained, and additional compression of the graft was provided by variable angle locking screws, also directed with navigation and visualized on CT DICOM images in real-time (Figure 8). A 39mm glenosphere was rotated under navigation to the offset position maximizing impingement-free range of motion as determined on the preoperative plan.Figure 7CT scans with superimposed glenoid baseplate, where green represents templated position and blue represents implanted position. This color code is also used to compare preoperative and postoperative measurements (inclination, retroversion, reaming depth, and baseplate rotation).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 8Baseplate fully seated and secured using navigation-assisted screw fixation.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The humeral component was press-fit and trialed through full range of motion with various polyethylene sizes and neck-shaft angles until the optimal tension, stability, and impingement-free range of motion was achieved. The patient's immediate postoperative course was uneventful, and radiographs demonstrated satisfactory position of bone graft and implants (Figure 9). At 6 weeks he began formal physical therapy, and by 12 weeks his motion had improved to 150° forward flexion and 30° external rotation; internal rotation remained to the level of the SI joint. Interval radiographs obtained at 3 and 12 months demonstrated maintained implant alignment (Figure 10). At 1 year from surgery, the patient remained satisfied with the cosmesis, range of motion, strength, and lack of pain associated with his reverse total shoulder arthroplasty (Figure 11).Figure 10AP and axillary radiographs obtained at 3 (A, B) and 12 (C, D) months from date of surgery demonstrate maintained implant alignment without evidence of complication.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 11Clinical photographs obtained 1 year from date of surgery demonstrate well-healed surgical scars, 150° forward flexion, and 30° external rotation.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The importance of glenoid positioning has been well described in the shoulder arthroplasty literature, with malalignment resulting in premature failure and poor clinical outcomes.14Nyffeler R.W. Werner C.M.L. Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis.J Shoulder Elbow Surg. 2005; 14: 524-528https://doi.org/10.1016/j.jse.2004.09.010Abstract Full Text Full Text PDF PubMed Scopus (358) Google Scholar In cases of significant glenoid deformity, identifying and executing optimal implant positioning in terms of peg position, version, inclination, medialization, and glenosphere offset/rotation represents a significant challenge. Traditional techniques to accurately implant the glenoid baseplate rely on the surgeon identifying visual and tactile landmarks intra-operatively and comparing those to a preoperative 2D or 3D imaging of the scapula. These conventional techniques have been found to result in a higher rates of glenoid component malposition when compared to patient specific instrumentation and computer navigation.1Burns D.M. Frank T. Whyne C.M. Henry P.D. Glenoid component positioning and guidance techniques in anatomic and reverse total shoulder arthroplasty: A systematic review and meta-analysis.Shoulder Elbow. 2019; 11: 16-28https://doi.org/10.1177/1758573218806252Crossref PubMed Scopus (39) Google Scholar Computer-based 3D preoperative planning has become widespread in shoulder arthroplasty and is especially useful for complex glenoid deformity cases. Standard three-dimensional templating tools reconstruct the scapula to provide a plan that matches patient anatomy with implants to optimize implant size and orientation.8Iannotti J.P. Weiner S. Rodriguez E. Subhas N. Patterson T.E. Jun B.J. et al.Three-Dimensional Imaging and Templating Improve Glenoid Implant Positioning.J Bone Joint Surg Am. 2015; 97: 651-658https://doi.org/10.2106/JBJS.N.00493Crossref PubMed Scopus (143) Google Scholar These images can then be displayed in the operating room for visualization during surgery, but do not provide any specific guidance or real-time feedback.9Jacquot A. Gauci M.O. Chaoui J. Baba M. Deransart P. Boileau P. et al.Proper benefit of a three dimensional pre-operative planning software for glenoid component positioning in total shoulder arthroplasty.Int Orthop. 2018; 42: 2897-2906https://doi.org/10.1007/s00264-018-4037-1Crossref PubMed Scopus (34) Google Scholar When intraoperative landmarks are difficult to discern, execution of the preoperative 3D plan can be improved by using additional intra-operative aids such as patient-specific guides, computer navigation, or, as in this case, navigation assisted by augmented reality. Patient-specific instrumentation (PSI) has been designed with the goal of improving glenoid component position, decreasing deviation from preoperative plan, and achieving improved version.2Elsheikh A.A. Galhoum M.S. Mokhtar M.A. Roebuck M.M. Wood A. Yin Q. et al.Patient-specific Instrumentation Versus Standard Surgical Instruments in Primary Reverse Total Shoulder Arthroplasty: A Retrospective Comparative Clinical Study.J Shoulder Elb Arthroplast. 2022; 6247154922210754https://doi.org/10.1177/24715492221075449Crossref Google Scholar,3Gauci M.O. Boileau P. Baba M. Chaoui J. Walch G. Patient-specific glenoid guides provide accuracy and reproducibility in total shoulder arthroplasty.Bone Joint J. 2016; 98-B: 1080-1085https://doi.org/10.1302/0301-620X.98B8.37257Crossref PubMed Scopus (103) Google Scholar There is evidence to suggest that use of PSI results in less likelihood for deviation in highly deformed glenoids.4Heylen S. Van Haver A. Vuylsteke K. Declercq G. Verborgt O. Patient-specific instrument guidance of glenoid component implantation reduces inclination variability in total and reverse shoulder arthroplasty.J Shoulder Elbow Surg. 2016; 25: 186-192https://doi.org/10.1016/j.jse.2015.07.024Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar While PSIs are thought to optimize glenoid component placement, the degree of improvement and impact on clinical outcomes is still unclear. Recent literature examined patient reported outcomes (PROs), active range of motion, and strength, and compared values between patients having undergone glenoid guide pin placement with standard guides vs patient specific instrumentation. Though patients in the PSI cohort achieved greater improvement in postoperative strength, there were no significant differences in PROs.5Hwang S. Werner B.C. Provencher M. Ardebol J. Denard P.J. Short-term functional outcomes of reverse shoulder arthroplasty following three-dimensional planning is similar whether placed with a standard guide or patient-specific instrumentation.J Shoulder Elbow Surg. 2023; 32: 1654-1661https://doi.org/10.1016/j.jse.2023.02.136Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar The development of AR-assisted intraoperative navigation software and instrumentation to aid in reverse total shoulder arthroplasty offers a promising solution to expand upon previously utilized technologies. CT scans have become commonplace for preoperative planning,12Kwon Y.W. Powell K.A. Yum J.K. Brems J.J. Iannotti J.P. Use of three-dimensional computed tomography for the analysis of the glenoid anatomy.J Shoulder Elbow Surg. 2005; 14: 85-90https://doi.org/10.1016/j.jse.2004.04.011Abstract Full Text Full Text PDF PubMed Scopus (256) Google Scholar and this technology offers the ability to directly merge preoperative plans with computer navigation software, which can then be paired with augmented reality hardware.10Kriechling P. Loucas R. Loucas M. Casari F. Fürnstahl P. Wieser K. Augmented reality through head-mounted display for navigation of baseplate component placement in reverse total shoulder arthroplasty: a cadaveric study.Arch Orthop Trauma Surg. 2023; 143: 169-175https://doi.org/10.1007/s00402-021-04025-5Crossref PubMed Scopus (15) Google Scholar,11Kriechling P. Roner S. Liebmann F. Casari F. Fürnstahl P. Wieser K. Augmented reality for base plate component placement in reverse total shoulder arthroplasty: a feasibility study.Arch Orthop Trauma Surg. 2021; 141: 1447-1453https://doi.org/10.1007/s00402-020-03542-zCrossref PubMed Scopus (29) Google Scholar AR truly excels in its ability to aid navigation through providing real-time feedback via calibration between instruments and the patient's intra-operative 3D imaging. This allows for image-guided glenoid pin placement, reaming, bone grafting, and baseplate seating. While PSI provides a single, predetermined implant position, AR allows for an infinite number of subtle adjustments as needed. Additionally, the instrumentation included in the NextAR set is not patient-specific, removing the need for production of custom instruments or physical templates that require additional preoperative processing time. Finally, the precision provided by real-time feedback allows for optimal implant positioning even in the presence of residual soft tissue or severe deformity.10Kriechling P. Loucas R. Loucas M. Casari F. Fürnstahl P. Wieser K. Augmented reality through head-mounted display for navigation of baseplate component placement in reverse total shoulder arthroplasty: a cadaveric study.Arch Orthop Trauma Surg. 2023; 143: 169-175https://doi.org/10.1007/s00402-021-04025-5Crossref PubMed Scopus (15) Google Scholar This case demonstrates the successful application of AR-assisted navigation in the treatment of a badly displaced glenoid malunion deformity with reverse total shoulder arthroplasty. The integration of preoperative planning software, non-specific instrumentation, and real-time AR-guided navigation assistance makes this a promising technology with the potential to improve then execution of shoulder arthroplasty, particularly in challenging cases with severe glenoid deformity.