Bone support correlation of X-Ray and CT for a new PE-glenoid.

INTRODUCTION: The radiographic evaluation of novel cementless anatomic polyethylene (PE) glenoid components featuring a titanium-coated back is still unclear. This study explores potential radiolucent lines (RLL) between the radiopaque titanium layer and sclerotic convex reamed bone in an intermodal comparison analysis with computed tomography (CT) scans. MATERIALS AND METHODS: Eight RM pressfit vitamys glenoids (Mathys®) were implanted into cadaveric scapulae. In the CT scans, glenoids were quantified by evaluating ideal complete bony support (NO GAP) and gap between bone and titanium coating (GAP). X-rays were in perfect 0-degree projection and tilted in ± 10° and ± 20° mediolateral (ml) and craniocaudal (cc) directions. Radiographs evaluated were graded as NO RLL, RLL (gap > 1 mm) or DL (double line, gap < 1 mm) in an intermodal comparison of CT and X-ray findings. RESULTS: The inter-rater (Cohen's = 0.643) and intra-rater reliability (Cohen's = 0.714) were good. The overall evaluation showed a significant agreement between (NO) RLL on X-ray and (NO) GAP on CT (p < 0.001). The - 10-degree ml projection showed good agreement between CT and X-ray (Cohen's = 0.628). Adequate agreement was shown at 0 degrees (Cohen's = 0.386), + 10 degrees ml (Cohen's = 0.338), and + 20 degrees cc (Cohen's = 0.327). Compared to the scenario DL = NO RLL, the true a.p. view showed better sensitivity when the DL is classified as RLL. Conversely, the true a.p. view demonstrated both better specificity and significant agreement between the X-ray and CT findings in scenario when DL = No RLL. CONCLUSION: Standard true a. p. projections are reliable in ruling out gaps when no RLL or DL is visible and the detection of RLL shows high intermodal agreement. Varying agreement across tilting angles emphasizes the importance of a comprehensive approach in evaluating bone support and CT is indispensable for a scientifically reliable assessment. LEVEL OF EVIDENCE: Level III Treatment Study.

Primary and revision reverse total shoulder arthroplasty using a patient-matched glenoid implant for severe glenoid bone deficiency.

BACKGROUND: Severe glenoid bone loss in the setting of both primary and revision reverse total shoulder arthroplasty (rTSA) continues to remain a significant challenge. The purpose of this study was to report on radiographic and clinical outcomes of primary and revision rTSA using a patient-matched, 3-dimensionally printed metal glenoid implant to address severe glenoid bone deficiency. This is a follow-up study to previously reported preliminary results. METHODS: A retrospective review was performed on 62 patients with severe glenoid bone deficiency who underwent either primary or revision rTSA using the Comprehensive Vault Reconstruction System (VRS) (Zimmer Biomet) at a single institution. Preoperative and postoperative values for the Disabilities of the Arm, Shoulder and Hand (DASH), Constant, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), Simple Shoulder Test (SST), Single Assessment Numeric Evaluation (SANE), and visual analog scale (VAS) pain scores as well as active range of motion (ROM) were collected and compared using the Wilcoxon signed rank test with the level of statistical significance set at P < .05. The percentage of patients achieving minimal clinically important difference (MCID) and substantial clinical benefit (SCB) was also calculated. RESULTS: Fifty-five of 62 shoulders (88.7%) were able to be contacted at a minimum of 2 years postoperatively, with 47 of 62 (75.8%) having complete clinical and radiographic follow-up with a mean age of 67.5 years (range, 48-85 years) and follow-up of 39.2 months (range, 25-56 months). There were 19 primary and 28 revision rTSAs. Significant improvements were seen in mean active forward flexion (63.1° ± 30.3° to 116.8° ± 35°), abduction (48.1° ± 16.1 to 76.2° ± 13.4°) (P < .001), external rotation (16° ± 23.7° to 32.1° ± 24.5°) (P < .005), DASH (59.9 ± 17.7 to 35.7 ± 24.3), Constant (23.4 ± 13.1 to 53.1 ± 17.4), ASES (27.8 ± 16.2 to 69.1 ± 25.2), SST (3.3 ± 2.5 to 7.6 ± 3.5), SANE (28.9 ± 18.3 to 66.7 ± 21.2), and VAS pain (7.1 ± 2.4 to 1.8 ± 2.6) scores (P < .001). MCID and SCB was achieved in a majority of patients postoperatively. The overall complication rate was 29.1%, with only 1 baseplate failure. CONCLUSION: This study demonstrates promising evidence that the VRS implant can be used as a viable option to achieve clinically important improvement in a majority of patients treated for severe glenoid bone deficiency with rTSA in both the primary and revision setting.

Temporary Protective Shoulder Implants for Revision Surgery with Bone Glenoid Grafting.

This article describes the development of a temporary protective glenoid prosthesis placed between the augmentation and humeral head prosthesis during the healing phase of shoulder prosthesis revision with necessary reconstruction of the bony structure of the glenoid. The glenoid protection prosthesis ensures the fixation of the augmentation material and protects the screws from contact with the metallic humeral head prosthesis. Another approach of the development is a reduction of the resorption of the augmentation by targeted mechanical stimulation of the tissue. The aim should be to achieve significantly improved conditions for the implantation of a new glenoid component at the end of the healing phase of the augmentation material in comparison to the current standard method. The development of the protective prosthesis was carried out according to specific needs and includes the collection of requirements and boundary conditions, the design and technical detailing of the implant, the verification of the development results as well as the validation of the design. For the verification, FEM simulations (Finite Element Analysis) were performed to estimate the mechanical stability in advance. Mechanical tests to confirm the stability and abrasion behavior have been carried out and confirm the suitability of the protective implant. The result of the present work is the detailed technical design of two variants of a glenoid protective prosthesis "GlenoProtect" for use in revision procedures on shoulder joints-with large-volume defects on the glenoid-treated by arthroplasty and the necessity of augmenting the glenoid, including a description of the surgical procedure for implantation.

Effects of conform, non-conform, and hybrid conformity toward stress distribution at the glenoid implant and cement: A finite element study.

Glenoid conformity is one of the important aspects that could contribute to implant stability. However, the optimal conformity is still being debated among the researchers. Therefore, this study aims to analyze the stress distribution of the implant and cement in three types of conformity (conform, non-conform, and hybrid) in three load conditions (central, anterior, and posterior). Glenoid implant and cement were reconstructed using Solidwork software and a 3D model of scapula bone was done using MIMICS software. Constant load, 750 N, was applied at the central, anterior, and posterior region of the glenoid implant which represents average load for daily living activities for elder people, including, walking with a stick and standing up from a chair. The results showed that, during center load, an implant with dual conformity (hybrid) showed the best (Max Stress-3.93 MPa) and well-distributed stress as compared to other conformity (Non-conform-7.21 MPa, Conform-9.38 MPa). While, during eccentric load (anterior and posterior), high stress was located at the anterior and posterior region with respect to the load applied. Cement stress for non-conform and hybrid implant recorded less than 5 MPa, which indicates it had a very low risk to have cement microcracks, whilst, conform implant was exposed to microcrack of the cement. In conclusion, hybrid conformity showed a promising result that could compromise between conform and non-conform implant. However, further enhancement is required for hybrid implants when dealing with eccentric load (anterior and posterior).

Two-year results of a multi-centre, randomized controlled trial comparing a second-generation uncemented trabecular metal-backed versus cemented polyethylene glenoid component in total shoulder arthroplasty.

AIMS: To report early (two-year) postoperative findings from a randomized controlled trial (RCT) investigating disease-specific quality of life (QOL), clinical, patient-reported, and radiological outcomes in patients undergoing a total shoulder arthroplasty (TSA) with a second-generation uncemented trabecular metal (TM) glenoid versus a cemented polyethylene glenoid (POLY) component. METHODS: Five fellowship-trained surgeons from three centres participated. Patients aged between 18 and 79 years with a primary diagnosis of glenohumeral osteoarthritis were screened for eligibility. Patients were randomized intraoperatively to either a TM or POLY glenoid component. Study intervals were: baseline, six weeks, six-, 12-, and 24 months postoperatively. The primary outcome was the Western Ontario Osteoarthritis Shoulder QOL score. Radiological images were reviewed for metal debris. Mixed effects repeated measures analysis of variance for within and between group comparisons were performed. RESULTS: A total of 93 patients were randomized (46 TM; 47 POLY). No significant or clinically important differences were found with patient-reported outcomes at 24-month follow-up. Regarding the glenoid components, there were no complications or revision surgeries in either group. Grade 1 metal debris was observed in three (6.5%) patients with TM glenoids at 24 months but outcomes were not negatively impacted. CONCLUSION: Early results from this RCT showed no differences in disease-specific QOL, radiographs, complication rates, or shoulder function between uncemented second-generation TM and cemented POLY glenoids at 24 months postoperatively. Revision surgeries and reoperations were reported in both groups, but none attributed to glenoid implant failure. At 24 months postoperatively, Grade 1 metal debris was found in 6.5% of patients with a TM glenoid but did not negatively influence patient-reported outcomes. Longer-term follow-up is needed and is underway. Cite this article: Bone Jt Open 2021;2(9):728-736.

Is preoperative glenoid bone mineral density associated with aseptic glenoid implant loosening in anatomic total shoulder arthroplasty?

BACKGROUND: Aseptic loosening of glenoid implants is the primary revision cause in anatomic total shoulder arthroplasty (aTSA). While supported by biomechanical studies, the impact of glenoid bone quality, more specifically bone mineral density (BMD), on aseptic glenoid loosening remains unclear. We hypothesized that lower preoperative glenoid BMD was associated with aseptic glenoid implant loosening in aTSA. METHODS: We retrospectively included 93 patients (69 females and 24 males; mean age, 69.2 years) who underwent preoperative non-arthrographic shoulder computed tomography (CT) scans and aTSA between 2002 and 2014. Preoperative glenoid BMD (CT numbers in Hounsfield unit) was measured in 3D using a reliable semi-automated quantitative method, in the following six contiguous volumes of interest (VOI): cortical, subchondral cortical plate (SC), subchondral trabecular, and three successive adjacent layers of trabecular bone. Univariate Cox regression was used to estimate the impact of preoperative glenoid BMD on aseptic glenoid implant loosening. We further compared 26 aseptic glenoid loosening patients with 56 matched control patients. RESULTS: Glenoid implant survival rates were 89% (95% confidence interval CI, 81-96%) and 57% (41-74%) at 5 and 10 years, respectively. Hazard ratios for the different glenoid VOIs ranged between 0.998 and 1.004 (95% CI [0.996, 1.007], p≥0.121). Only the SC VOI showed significantly lower CTn in the loosening group (622±104 HU) compared with the control group (658±88 HU) (p=0.048), though with a medium effect size (d=0.42). There were no significant differences in preoperative glenoid BMD in any other VOI between patients from the loosening and control groups. CONCLUSIONS: Although the preoperative glenoid BMD was statistically significantly lower in the SC region of patients with aseptic glenoid implant loosening compared with controls, this single-VOI difference was only moderate. We are thus unable to prove that lower preoperative glenoid BMD is clearly associated with aseptic glenoid implant loosening in aTSA. However, due to its proven biomechanical role in glenoid implant survival, we recommend extending this study to larger CT datasets to further assess and better understand the impact of preoperative glenoid BMD on glenoid implant loosening/survival and aTSA outcome.

Baseplate Options for Reverse Total Shoulder Arthroplasty.

PURPOSE OF REVIEW: Baseplate fixation has been known to be the weak link in reverse total shoulder arthroplasty (RTSA). A wide variety of different baseplates options are currently available. This review investigates the recent literature to present the reader with an overview of the currently available baseplate options and modes of fixation. RECENT FINDINGS: The main elements that differentiate baseplates are the central fixation element, the size of the baseplate, the shape, the backside geometry, whether or not an offset central fixation exists, the number of peripheral screws, and the availability of peripheral augmentation. The wide array of baseplate options indicates that no particular design has proven superiority. As such, surgeons should be aware of their options and choose an implant that the surgeon is comfortable with and one that best suits the individual patient anatomy. With the growing number of RTSA procedures and registries with long-term follow-up, future investigations will hopefully delineate the ideal baseplate design to optimize survivorship.

Early results of reverse total shoulder arthroplasty using a patient-matched glenoid implant for severe glenoid bone deficiency.

BACKGROUND: Reverse total shoulder arthroplasty (rTSA) in the presence of significant glenoid bone loss remains a challenge. This study presents preliminary clinical and radiographic outcomes of primary and revision rTSA using a patient-matched, 3-dimensionally printed custom metal glenoid implant to address severe glenoid bone deficiency. METHODS: Between September 2017 and November 2018, 19 patients with severe glenoid bone deficiency underwent primary (n = 9) or revision rTSA (n = 10) using the Comprehensive Vault Reconstruction System (VRS) (Zimmer Biomet, Warsaw, IN, USA) at a single institution. Preoperative and postoperative values for the Disabilities of the Arm, Shoulder and Hand score, Constant score, American Shoulder and Elbow Surgeons score, Simple Shoulder Test score, Single Assessment Numeric Evaluation score, and visual analog scale pain score and active range of motion were compared using the Wilcoxon signed rank test with the level of statistical significance set at P < .05. RESULTS: Complications occurred in 4 patients (21%), including a nondisplaced greater tuberosity fracture treated conservatively in 1, intraoperative cortical perforation during humeral cement removal treated with an allograft strut in 1, and recurrent instability and hematoma formation treated with humeral component revision in 1. One patient with an early periprosthetic infection was treated with component removal and antibiotic spacer placement at an outside facility and was subsequently lost to follow-up. Eighteen patients with 1-year minimum clinical and radiographic follow-up were evaluated (mean, 18.2 months; range, 12-27 months). Significant improvements were noted in the mean Disabilities of the Arm, Shoulder and Hand score (57.4 ± 16.5 vs. 29.4 ± 19.5, P < .001), mean Constant score (24.6 ± 10.2 vs. 60.4 ± 14.5, P < .001), mean American Shoulder and Elbow Surgeons score (32 ± 18.2 vs. 79 ± 15.6, P < .001), mean Simple Shoulder Test score (4.5 ± 2.6 vs. 9.3 ± 1.8, P < .001), mean Single Assessment Numeric Evaluation score (25.4 ± 13.7 vs. 72.2 ± 17.8, P < .001), mean visual analog scale pain score (6.2 ± 2.9 vs. 0.7 ± 1.3, P < .001), mean active forward flexion (53° ± 27° vs. 124° ± 23°, P < .001), and mean active abduction (42° ± 17° to 77° ± 15°, P < .001). Mean external rotation changed from 17° ± 19° to 32° ± 24° (P = .06). No radiographic evidence of component loosening, scapular notching, or hardware failure was observed at last follow-up in any patient. CONCLUSION: The preliminary results of rTSA using the VRS to manage severe glenoid bone deficiency are promising, but longer follow-up is necessary to determine the longevity of this implant.

Reduction of scapulohumeral subluxation with posterior augmented glenoid implants in anatomic total shoulder arthroplasty: Short-term 3D comparison between pre- and post-operative CT.

BACKGROUND: Failure rates in anatomic total shoulder arthroplasty (aTSA) are higher in case of asymmetric glenoid bone loss secondary to posterior wear, and in persistent static posterior subluxation of the humeral head (PSH). HYPOTHESIS: This study aimed to test the hypothesis that the combined use of posterior augmented glenoid (PAG) implants with three-dimensional (3D) surgical planning and patient-specific instrumentation (PSI) guides helps reduce short-term PSH after aTSA in patients with type B2-B3 glenoids. PATIENTS AND METHODS: We included nine consecutive patients with primary glenohumeral osteoarthritis and type B2 or B3 glenoids, who underwent aTSA with cemented keeled PAG implants (posterior augments of 15, 25, or 35 degrees). All patients underwent preoperative shoulder computed tomography (CT) scans, with 3D surgical planning coupled to PSI at the time of surgery. Postoperative shoulder CT scans were performed at an average of 14 weeks (range, 10-21 weeks). Scapulohumeral subluxation and glenoid version and inclination were measured in 3D, on both pre- and post-operative CT scans, using the same reliable quantitative method. RESULTS: There was a significant decrease in scapulohumeral subluxation from 49±12% preoperatively to 22±17% postoperatively (p=0.0039), with a large effect size (Cohen's d=1.89). Preoperative glenoid version was corrected from -17.3±9.4 degrees to -5.2±7.5 degrees postoperatively. The absolute difference between the postoperative and surgically planned version and inclination was 5.4±3.6 degrees and 3.3±2.0 degrees, respectively. DISCUSSION: The combined use of PAG implants with 3D preoperative planning and PSI results in a significant decrease in short-term PSH and glenoid version in patients with asymmetric posterior glenoid wear. We suggest that such implants should not be limited to posterior augmentation, because glenoid deficiency can also be observed in other glenoid sectors. LEVEL OF EVIDENCE: IV, Basic science study.

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

BACKGROUND: Intraoperative computer navigation has been introduced recently to assist with placement of the glenoid component. The aim of this study was to evaluate the learning curve of a single surgeon performing computer navigation of glenoid implant placement in primary reverse total shoulder arthroplasty (RTSA). METHODS: Following training with the intraoperative computer navigation system, we conducted a prospective case-series study of the first 24 consecutive patients undergoing a primary RTSA with navigation performed by a single surgeon. Surgical times, complications, and accuracy of glenoid positioning compared with the preoperative plan were evaluated. Surgical times were compared with the preceding non-navigated series of 24 consecutive primary RTSA cases. Postoperative 3-dimensional computed tomography scans were performed to evaluate glenoid component version and inclination compared with the preoperative plan. RESULTS: The total surgical time was 77.3 minutes (standard deviation [SD], 11.8 minutes) in the navigated RTSA cohort and 78.5 minutes (SD, 18.1 minutes) in the non-navigated series. A significant downward trend in the total surgical time was observed in the navigated cohort (P = .038), which flattened after 8 cases. No learning curve was observed in deviation of glenoid version or inclination from the preoperative plan. The mean deviation of achieved version from planned version was 3° (SD, 2°), and the mean deviation of achieved inclination from planned inclination was 5° (SD, 3°). CONCLUSION: Findings from this study suggest that intraoperative computer navigation will not require substantially increased operating times compared with standard surgical techniques. With prior surgeon training, approximately 8 operative cases are required to achieve proficiency in intraoperative computer navigation of the glenoid component.

Biomechanical comparison of glenoid implants with adaptable and fixed backside curvatures in anatomic total shoulder arthroplasty.

BACKGROUND: We evaluated the biomechanical effects and potential advantages of glenoid implants with adaptable backside curvature radii and compared them with standard implants having fixed backside curvatures in anatomic total shoulder arthroplasty (aTSA) for primary glenohumeral osteoarthritis with uniconcave glenoids. METHODS: A glenoid implant with adaptable backside curvatures (Aequalis PerFORM, Tornier SAS, Montbonnot, France) was compared with its previous model having a fixed curvature radius. Virtual aTSAs were performed in 24 patients from preoperative shoulder computed tomography data sets, using both implants in each patient. For all 48 simulated aTSAs, we first measured the glenoid bone reaming depth, subchondral bone quality after reaming, and implant backside surface and then the predicted cement stress, bone-cement interfacial stress, and bone strain at 60° of arm abduction. These biomechanical quantities were tested for differences between adaptable and fixed implants and for correlations between preoperative measurements and postoperative predictions. RESULTS: Adaptable glenoid implants induced a significant decrease in cement stress (P = .008), bone-cement interfacial stress (P = .045), and bone strain (P = .039), particularly for glenoids with curvature radii larger than 40 mm. However, these biomechanical effects were not significantly correlated with an increase in subchondral glenoid bone quality. CONCLUSIONS: Our study confirms the presumed biomechanical advantages of adaptable glenoid implants, even though the effects were not directly due to the adaptation of the backside curvature radius. Benefits were more pronounced for glenoids with large curvature radii. Our initial biomechanical findings should now be corroborated with large-scale clinical studies.

A comparison of onlay versus inlay glenoid component loosening in total shoulder arthroplasty.

BACKGROUND: Glenoid component loosening is common in total shoulder arthroplasty (TSA), often resulting from the mechanical interaction of glenohumeral components. This cadaveric study was performed to evaluate and to compare commercially available onlay and inlay glenoid prosthetic designs with respect to loading characteristics and loosening. METHODS: Sixteen prescreened cadaveric shoulders (8 matched pairs) underwent either onlay or inlay TSA. We created a custom glenohumeral loading model and used cycles of 5 mm anterior-posterior humeral translation to simulate a rocking-horse loosening mechanism for all testing. Articular TekScan measurements were performed with 9.1 kg (88.9 N) of glenohumeral compression before and after TSA. Fatigue testing was performed with 34.0 kg (333.6 N) of glenohumeral compression using high-definition video to document gross glenoid loosening. Testing ended with gross loosening or a maximum of 4000 cycles. Mean contact area, pressure, and joint reaction force were used to compare the 2 glenoid designs. RESULTS: In both implant types, contact area decreased and pressure increased after TSA (P < .0001). Force increased at the onlay component edge only (P = .0012) compared with native glenoid testing. Force was greater in the onlay vs. the inlay implants (P < .0001). During fatigue testing, all onlay glenoid components exhibited gross loosening at a mean of 1126 cycles (range, 749-1838), whereas none of the inlay glenoid components exhibited gross loosening (P < .0001). CONCLUSION: The inlay glenoid implant exhibited biomechanical characteristics favoring stability and decreased loosening compared with the onlay glenoid implant in this cadaveric model.

Peri-implant stress correlates with bone and cement morphology: Micro-FE modeling of implanted cadaveric glenoids.

Aseptic loosening of cemented joint replacements is a complex biological and mechanical process, and remains a clinical concern especially in patients with poor bone quality. Utilizing high resolution finite element analysis of a series of implanted cadaver glenoids, the objective of this study was to quantify relationships between construct morphology and resulting mechanical stresses in cement and trabeculae. Eight glenoid cadavers were implanted with a cemented central peg implant. Specimens were imaged by micro-CT, and subject-specific finite element models were developed. Bone volume fraction, glenoid width, implant-cortex distance, cement volume, cement-cortex contact, and cement-bone interface area were measured. Axial loading was applied to the implant of each model and stress distributions were characterized. Correlation analysis was completed across all specimens for pairs of morphological and mechanical variables. The amount of trabecular bone with high stress was strongly negatively correlated with both cement volume and contact between the cement and cortex (r = -0.85 and -0.84, p < 0.05). Bone with high stress was also correlated with both glenoid width and implant-cortex distance. Contact between the cement and underlying cortex may dramatically reduce trabecular bone stresses surrounding the cement, and this contact depends on bone shape, cement amount, and implant positioning.

Multi-patient finite element simulation of keeled versus pegged glenoid implant designs in shoulder arthroplasty.

This study investigates the mechanical behaviour of keeled and pegged implant designs used in shoulder arthroplasty for the first time using multiple 3D models. Thus, this study should provide valuable insights into the preferable use of either of these two controversial implant designs. Three-dimensional models of a scapula were derived from the CT scans of five patients, and an inter-patient-specific finite element analysis with special attention to bone density and boundary conditions was carried out. A distinct decrease in the investigated parameters was evident with the pegged implant in all of the patients, specifically for the implant and the bone cement. The relevance of the stress reduction within the bone is minor, whereas the reduction in the stress of the bone cement contributes to an increase in the bone cement survival. The particular construction of the pegged implant provides better stability and therefore supports bone ingrowth. The large variations between the patients show the necessity of patient-specific simulations and the use of multiple models to derive valuable results. In the conducted inter-patient-specific FEA, the pegged glenoid implants were found to exhibit superior behaviour compared with keeled implants. The results confirm the general clinical findings and demonstrate the FEA as a valuable tool in prosthetic and orthopaedic problems.