Faculty Bibliography

In this article, we present clinical results of primary total shoulder arthroplasty for osteoarthritis using an implant that provides dual eccentricity and variable neck and version angles for reconstruction of proximal humeral anatomy. Two hundred one patients with symptomatic osteoarthritis underwent 218 total shoulder arthroplasties with a fourth-generation anatomical shoulder and a replicator plate at 4 centers between August 1, 2006, and December 31, 2010. Fourth-generation implants allow for varying humeral neck and version angles and have dual eccentricity so as to be consistently able to cover the humeral head cut. At a mean follow-up of 3 years (minimum, 2 years), there was an 81% follow-up rate. At final follow-up, 3 objective measures were significantly (P < .05) improved over preoperative levels: average active elevation (preoperative, 92°; postoperative, 137°), active external rotation (pre, 15°; post, 42°), and active internal rotation (pre, S3; post, L2). The functional outcome scores that were significantly (P < .05) improved at final follow-up were Constant normalized (pre, 39; post, 79), Shoulder Pain and Disability Index (pre, 86; post, 20), Simple Shoulder Test (pre, 3.3; post, 10), UCLA Shoulder Rating Scale (pre, 13; post, 31), and American Shoulder and Elbow Surgeons Shoulder Assessment (pre, 33; post, 85). Complications were noted in 11% of the shoulders. The most common complications were rotator cuff failure (13, 6%) and infection (5, 2%).

INTRODUCTION: Achieving glenoid fixation with posterior bone loss can be challenging. The purpose of this study was to quantify the impact of two different sizes of posterior glenoid defects (10 degrees and 20 degrees ) on reverse shoulder arthroplasty (rTSA) glenoid baseplate fixation and determine if utilizing different sizes of posterior augmented baseplates (8 degrees and 16 degrees ) with off-axis reaming provides comparable fixation to using a standard baseplate with different amounts of eccentric reaming. METHODS: We quantified the impact of 10 degrees and 20 degrees posterior glenoid defects on rTSA baseplate fixation in composite scapulae using the ASTM F2028-14 rTSA glenoid loosening test method. Forty-two total implants (N = 7 for each size defect and for each type of baseplate) were tested at 750 N for 10,000 cycles. Baseplate displacement was measured before and after cyclic loading in the superior-inferior and anterior-posterior directions. Statistical analysis was performed with a two-tailed unpaired Student's t-test (significance defined as p < 0.05) to compare prosthesis displacements relative to each scapula (10 degrees and 20 degrees posterior defects for each type of baseplate versus the non-defect control) before and after cyclic loading. RESULTS: All glenoid baseplates remained well-fixed after cyclic loading in composite scapulae without a defect and in scapulae with posterior defects. Increased pre- and post-cyclic displacement was observed with increased posterior defect size and differences in displacement were observed between standard and augmented baseplates. Augmented baseplates were observed to remove significantly less bone than standard baseplates when correcting posterior defects, regardless of size. DISCUSSION: Both standard baseplates with eccentric reaming and two different sizes of augmented baseplates with off-axis reaming successfully maintained fixation following cyclic loading in composite scapula with corrected 10 degrees and 20 degrees posterior glenoid defects. Augmented glenoids may be more advantageous long-term from a fixation perspective as they preserve more subchondral glenoid bone due to the minimal reaming occurring by the off-axis method. Mid and long-term clinical follow-up comparisons of outcomes are necessary between these two techniques.

INTRODUCTION: Paul Grammont's hemispherical gleno sphere concept medializes the center of rotation (CoR) to the glenoid face to increase deltoid abductor moment arms and improve muscle efficiency. Reducing glenosphere thickness to less than half its spherical radius further medializes the CoR and offers the potential for even greater improvements in efficiency. To that end, this study quantifies deltoid abducttor moment arms for six different rTSA prostheses during scapular abduction from 0 degrees to 140 degrees . METHODS: A 3D computer model was developed in Uni graphics to quantify deltoid moment arms during scapular abduction for the normal anatomic shoulder, the 36 mm Grammont Delta III (Depuy, Inc.), 36 mm BIO-RSA (R) (Tornier, Inc.), the 32 mm RSP(R) (DJO, Inc.), and the Equinoxe(R) rTSA (Exactech, Inc.) with three different glenosphere geometries: 38 mm x 21 mm, 46 mm x 25 mm, and the novel 46 mm x 21 mm. Each muscle was simulated as three lines from origin to insertion as the arm was elevated; positional data was exported to Matlab where the abductor moment arms were calculated for the anterior, middle, and posterior deltoid from 0 degrees to 140 degrees humeral abduction in the scapular plane using a 1.8:1 scapular rhythm. RESULTS: The 46 mm x 21 mm glenosphere had the larg est average abductor moment arms and also the largest efficiency for all three heads of the deltoid, having a 4.8% to 40.7% increase in the average deltoid efficiency relative to all other designs tested. The glenosphere design with the next most efficient deltoid was the 36 mm Delta III, which had the next most medialized CoR. The two least efficient designs were the BIO-RSA (R) and the DJO RSP(R) , which had the most lateral CoR. DISCUSSION: These results provide new biomechanical insights on the impact of glenosphere geometry on deltoid abductor moment arms and demonstrate that subtle changes in rTSA prosthesis design can result in dramatic improvements. Increasing glenosphere diameter while also decreasing thickness to be less than half its spherical radius may minimize the muscle forces required to perform activities of daily living. Clinical follow-up is necessary to demonstrate a reduction in complications related to joint over-loading and also demonstrate greater increases in range of motion for patients with weak musculature.

Multiple different reverse total shoulder arthroplasty (rTSA) prosthesis designs are available in the global marketplace for surgeons to perform this growing procedure. Subtle differences in rTSA prosthesis design parameters have been shown to have significant biomechanical impact and clinical consequences. We propose an rTSA prosthesis design classification system to objectively identify and categorize different designs based upon their specific glenoid and humeral prosthetic characteristics for the purpose of standardizing nomenclature that will help the orthopaedic surgeon determine which combination of design configurations best suit a given clinical scenario. The impact of each prosthesis classification type on shoulder muscle length and deltoid wrapping are also described to illustrate how each prosthesis classification type impacts these biomechanical parameters.

Body Mass Index (BMI) is one of the metrics used to assess overall health and has been implicated in having predictive value in many aspects of health, including outcomes after shoulder replacement surgery. Outcome data from a multi- institutional database with an average follow-up period of 39.8 months (minimum 24-months) demonstrated that all patients, regardless of BMI, improved significantly after treatment with anatomic total shoulder arthroplasty (aTSA) or reverse total shoulder arthroplasty (rTSA). Improvements in outcomes were stratified and compared based upon BMI in three groups: less than 25, 25 to 35, and greater than 35. Comparing these measures demonstrated that aTSA patients with higher BMI were generally associated with lower functional postoperative outcome metric scores than aTSA patients with lower BMI, though the preoperative to postoperative gains were generally equivalent regardless of BMI. Interestingly, postoperative outcome metric scores with rTSA patients were equivalent regardless of BMI as were the pre-to-postoperative gains. Additionally, differences in the magnitude of pre-to-postoperative improvement of range of motion (ROM) measurements between patients of BMI less than 25 and BMI greater than 35 were noted for forward flexion, internal rotation, and active and passive external rotation. The actual clinical significance of these differences is unknown. Finally, patients with lower BMI appeared to have a higher incidence of low-grade scapular notching.

Total hip arthroplasty (THA) is considered one of the mosteffective treatments for hip arthritis, but the decision toperform simultaneous bilateral THA versus staged bilateralTHA remains a source of controversy based primarily on theanalysis of the risks and benefits of each approach. Manysurgeons are reluctant to consider simultaneous total hiparthroplasty even though the procedure is associated witha shorter total hospitalization, shorter recovery and rehabilitationtime, and decreased cost. However, in this review,we find that despite higher blood loss in the simultaneousgroup, there are no significant differences in terms of cardiopulmonarycomplications, thromboembolic events, stroke,surgical site infection, and rate of allogeneic transfusionbetween simultaneous and staged procedures. In addition,careful patient selection (ASA 1 and 2) can further minimizethe risks of simultaneous bilateral total hip arthroplasty andincrease the likelihood of consistent successful outcomes.

Patients with significant gouty arthritis can develop disablingjoint pain secondary to monosodium urate (MSU)articular deposition. We report a case of white, chalky MSUcrystal deposition covering the articular surfaces of the kneeas discovered by total knee arthroplasty. A 65-year-old malewith a history of gout presented with bilateral knee pain.His radiographic imaging was negative for gouty tophi, andhe elected to undergo left total knee arthroplasty. Intraoperativelya distinct chalky, white paste consistent with MSUdeposition was observed covering the articular surfaces ofthe knee consistent with the diagnosis of gouty arthritis.Gout is the most common inflammatory arthritisaffecting more than 3 million people in the USA.1The inflammation results from the phagocytosisof monosodium urate crystals (MSU) and the release ofinflammatory cytokines within the joint.2 Gout progressesfrom acute to chronic over many years and frequentlycauses chronic arthropathy.3 When significant knee pain anddisability is associated with gouty arthropathy, total kneearthroplasty is certainly an option.The pathological appearance of gouty joints is characteristic.Macroscopic examination of joints affected bygout reveals a nodular, white, chalky appearance. Polarizedmicroscopy of gout demonstrates negative birefringentneedle-shaped MSU crystals.3 In this case report, we describethe characteristic chalky, white MSU deposit that covers thearticular surfaces of a knee joint in a patient with a historyof gout undergoing total knee arthroplasty. The investigatorshave obtained the patient's informed written consent for printand electronic publication of the case report.

BACKGROUND: Shoulder arthroplasty is now used to treat an expanding variety of glenohumeral disorders. METHODS: This study assessed the demographic patterns and utilization rates of shoulder hemiarthroplasty (HA) and anatomic or reverse total shoulder arthroplasty (TSA) within New York State (NYS) from 1991 to 2010. Using the New York Statewide Planning and Research Cooperative System database, all shoulder arthroplasty procedures that occurred within NYS during the study period were retrospectively identified and analyzed. RESULTS: During the 20-year period, 24,040 shoulder arthroplasty procedures were performed. During the second decade (2001-2010), there was a 393% increase in utilization of TSA with a 98% increase in HA. This disproportionate increase is likely due to the introduction and expanding indications of reverse TSA as an effective procedure in place of HA for the treatment of proximal humerus fractures and rotator cuff arthropathy, as rotator cuff arthropathy as a primary indication for HA was significantly less prevalent in period 2. Also notable was an identifiable disparity in race; whites represented approximately 80% of the shoulder arthroplasty procedures in both decades, whereas African Americans made up <5%. This is significantly different from the general racial demographics of NYS during both periods analyzed. DISCUSSION: It is clear that the volume of shoulder arthroplasty procedures performed in NYS is increasing, mirroring the national experience. This trend reflects the expanding indications, the general success of these procedures, the aging demographic of our population, and a greater desire and willingness of patients to consider operative management to maintain or to improve quality of life.

BACKGROUND: The reverse total shoulder arthroplasty (RTSA) has been used in the treatment of complex shoulder problems. The incidence of aseptic loosening of the humeral component has not been previously reported. METHODS: This is a multicenter, retrospective, blinded, case-control radiographic review of 292 patients to determine the rate of humeral stem loosening. There were 177 cemented and 115 press-fit humeral components. Radiographs were critiqued for radiolucent lines adjacent to the humeral stem based on the method described by Gruen et al. RESULTS: The overall rate of loosening was 0.74%. No radiographic loosening occurred in the press-fit group (115 stems). In the cemented group (177 stems), 2 shoulders (1.18%) were identified with radiographically loose stems. No loosening occurred in the press-fit group. No statistically significant difference was found in humeral stem loosening when the press-fit group and the cemented group were compared (P = .198). DISCUSSION: Our study indicates the cemented or press-fit RTSA system will result in a low incidence of radiolucent lines and radiographic loosening. Compared with historical survivorship of conventional anatomic total shoulder arthroplasty, RTSA shows a lower rate of radiographic stem loosening at a mean of 38.46 months. CONCLUSIONS: The RTSA has a low incidence of humeral stem loosening at midterm. These results underscore the importance of careful selection of patients to provide the benefits of this surgical technique. Press-fit fixation may provide a lower risk to stem loosening.