Fixation of the glenoid component is critical to the outcome of total shoulder arthroplasty. In an in vitro study, we analysed the effect of surface design and thickness of the cement mantle on the pull-out strength of the polyethylene pegs which are considered essential for fixation of cemented glenoid components. The macrostructure and surface of the pegs and the thickness of the cement mantle were studied in human glenoid bone. The lowest pull-out forces, 20 ± 5 N, were for cylindrical pegs with a smooth surface fixed in the glenoid with a thin cement mantle. The highest values, 425 ± 7 N, were for threaded pegs fixed with a thicker cement mantle. Increasing the diameter of the hole into which the peg is inserted from 5.2 to 6.2 mm thereby increasing the thickness of the cement mantle, improved the mean pull-out force for the pegs tested

Introduction and Objective. In recent years, along with the extending longevity of patients and the increase in their functional demands, the number of annually performed RSA and the incidence of complications are also increasing. When a complication occurs, the patient often needs multiple surgeries to restore the function of the upper limb. Revision implants are directly responsible for the critical reduction of the bone stock, especially in the shoulder. The purpose of this paper is to report the use of allograft bone to restore the bone stock of the glenoid in the treatment of an aseptic glenoid component loosening after a reverse shoulder arthroplasty (RSA). Materials and Methods. An 86-years-old man came to our attention for aseptic glenoid component loosening after RSA. Plain radiographs showed a complete dislocation of the glenoid component with 2 broken screws in the neck of glenoid. CT scans confirmed the severe reduction of the glenoid bone stock and critical bone resorption and were used for the preoperative planning. To our opinion, given the critical bone defect, the only viable option was revision surgery with restoration of bone stock. We planned to use a bone graft harvested from distal bone bank femur as component augmentation. During the revision procedure the baseplate with a long central peg was implanted “on table” on the allograft and an appropriate osteotomy was made to customize the allograft on the glenoid defect according to the CT-based preoperative planning. The Bio-component was implanted with stable screws fixation on residual scapula. We decided not to replace the humeral component since it was stable and showed no signs of mobilization. Results. The new bio-implant was stable, and the patient gained a complete functional recovery of the shoulder. The scheduled radiological assessments up to 12 months showed no signs of bone resorption or mobilization of the glenoid component. Conclusions. The use of bone allograft in revision surgery after a RSA is a versatile and effective technique to treat severe glenoid bone loss and to improve the global stability of the implant. Furthermore, it represents a viable alternative to autologous graft since it requires shorter operative times and reduces graft site complications. There are very few data available regarding the use of allografts and, although the first studies are encouraging, further investigation is needed to determine the biological capabilities of the transplant and its validity in complex revisions after RSA

The computational modelling and 3D technology are finding more and more applications in the medical field. Orthopedic surgery is one of the specialties that can benefit the most from this solution. Three case reports drawn from the experience of the authors’ Orthopedic Clinic are illustraded to highlight the benefits of applying this technology. Drawing on the extensive experience gained within the authors’ Operating Unit, three cases regarding different body segments have been selected to prove the importance of 3D technology in preoperative planning and during the surgery. A sternal transplant by allograft from a cryopreserved cadaver, the realization of a custom made implant of the glenoid component in a two-stage revision of a reverse shoulder arthroplasty, and a case of revision on a hip prosthesis with acetabular bone loss (Paprosky 3B) treated with custom system. In all cases the surgery was planned using 3D processing software and models of the affected bone segments, printed by 3D printer, and based on CT scans of the patients. The surgical implant was managed with dedicated instruments. The use of 3D technology can improve the results of orthopedic surgery in many ways: by optimizing the outcomes of the operation as it allows a preliminary study of the bone loss and an evalutation of feasibility of the surgery, it improves the precision of the positioning of the implant, especially in the context of severe deformity and bone loss, and it reduces the operating time; by improving surgeon training; by increasing patient involvement in decision making and informed consent. 3D technology, by offering targeted and customized solutions, is a valid tool to obtain the tailored care that every patient needs and deserves, also providing the surgeon with an important help in cases of great complexity

The purpose of this study is to report the clinical and radiological outcomes of patients undergoing primary or revision reverse total shoulder arthroplasty using custom 3D printed components to manage severe glenoid bone loss with a minimum of 2-year follow-up. After ethical approval (reference: 17/YH/0318), patients were identified and invited to participate in this observational study. Inclusion criteria included: 1) severe glenoid bone loss necessitating the need for custom implants; 2) patients with definitive glenoid and humeral components implanted more than 2 years prior; 3) ability to comply with patient reported outcome questionnaires. After seeking consent, included patients underwent clinical assessment utilising the Oxford Shoulder Score (OSS), Constant-Murley score, American Shoulder and Elbow Society Score (ASES), and quick Disabilities of the Arm, Shoulder, and Hand Score (quickDASH). Radiographic assessment included AP and axial projections. Patients were invited to attend a CT scan to confirm osseointegration. Statistical analysis utilised included descriptive statistics (mean and standard deviation) and paired t test for parametric data. 3 patients had revision surgery prior to the 2-year follow-up. Of these, 2/3 retained their custom glenoid components. 4 patients declined to participate. 5 patients were deceased at the time of commencement of the study. 21 patients were included in this analysis. The mean follow-up was 36.1 months from surgery (range 22–60.2 months). OSS improved from a mean 16 (SD 9.1) to 36 (SD 11.5) (p < 0.001). Constant-Murley score improved from mean 9 (SD 9.2) to 50 (SD 16.4) (p < 0.001). QuickDASH improved from mean 67 (SD 24) to 26 (SD 27.2) (p = 0.004). ASES improved from mean 28 (SD 24.8) to 70 (SD 23.9) (p = 0.007). Radiographic evaluation demonstrated good osseointegration in all 21 included patients. The utility of custom 3D-printed components for managing severe glenoid bone loss in primary and revision reverse total shoulder arthroplasty yields significant clinical improvements in this complex patient cohort

Background. While total shoulder arthroplasty (TSA) is a generally successful procedure, glenoid loosening remains a common complication. Though the occurrence of loosening was related to patient-specific factors, biomechanical factors related to implant features may also affect the fixation of the glenoid component, in particular increased glenohumeral mismatch that could result in eccentric loads and translations. In this study, a novel test setup was used to quantify glenohumeral pressures for different motion patterns after TSA. Methods. Six cadaveric human shoulders were implanted with total shoulder replacements (Exactech, Inc., USA) and subjected to cyclic internal-external, flexion-extension and abduction-adduction rotations in a passive motion testing apparatus. The system was coupled to a pressure sensor system (Tekscan, Inc., USA) to acquire joint loads and to a Zebris system (Zebris Medical, GmbH, Germany) to measure joint kinematics. The specimens were subjected to a total of 2160 cycles and peak pressures were compared for each motion pattern. Results. It was shown that during abduction the contact area between the humeral head and the glenoid component shifts from a posterior to an anterior position, while also moving inferiorly. For internal-external rotation a mean peak pressure of 8.37 ± 0.22 MPa was registered, while for flexion-extension a pressure of 9.37 ± 0.38 MPa and for abduction-adduction a pressure of 9.88 ± 0.07 MPa were obtained. Conclusion. This study showed how glenohumeral pressures after TSA vary during simulated internal-external, flexion-extension and abduction-adduction rotations in a cyclic testing setup. It showed that peak loads are mainly obtained in abduction, and that these occurred mainly near the anterior part of the glenoid. Future steps involve implantation of other type of anatomical glenoid components to obtain different levels of glenohumeral mismatch and relating the 3D measurements of motion patterns to contact pressures

Summary Statement. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide. Introduction. Today's techniques for total or reverse shoulder arthroplasty are limited when dealing with severe glenoid defects. The available procedures, for instance the use of bone allografts in combination with available standard implants, are technically difficult and tend to give uncertain outcomes (Hill et al. 2001; Elhassan et al. 2008; Sears et al. 2012). A durable fixation between bone and implant with optimal fit and implant positioning needs to be achieved. Custom-made defect-filling glenoid components are a new treatment option for severe glenoid defects. Despite that the patient-specific implants are uniquely designed to fit the patient's bone, it can be difficult to achieve the preoperatively planned position of the component, resulting in less optimal screw fixation. We hypothesised that the use of a patient-specific guide would improve implant and screw positioning. The aim of this study was to evaluate the added value of a newly developed patient-specific guide for implant and screw positioning, by comparing glenoid implantations with and without such guide. Patients & Methods. Large glenoid defects, representative for the defects encountered in clinical practice, were created in ten cadaveric shoulders. A CT scan of each cadaver was taken to evaluate the defects and to generate three-dimensional models of the scapular bones. Based on these models, custom glenoid components were designed. Furthermore, a newly developed custom guide was designed for five randomly selected shoulders. New CT scans were taken after implantation to generate 3D models of the bone and the implanted component and screws. This enabled to compare the experimentally achieved and preoperatively planned reconstruction. The location and orientation of the glenoid component and screw positioning were determined and differences with the optimal preoperative planning were calculated. Results. An excellent component positioning (difference in location: 1.4±0, 7mm; difference in orientation: 2, 5±1, 2°) was achieved when using the guide compared to implantations without guidance (respectively 1, 7±0, 5mm; 5, 1±2, 3°). The guide improved component orientation significantly (P<0.1). After using the guide, all screws were positioned inside the scapular bone whereas 25% of the screws placed without guidance were positioned outside the scapular bone. Discussion/Conclusion. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide

Abstract. Shoulder replacements have evolved and current 4th generation implants allow intraoperative flexibility to perform anatomic, reverse, trauma, and revision shoulder arthroplasty. Despite high success rates with shoulder arthroplasty, complication rates high as 10–15% have been reported and progressive glenoid loosening remains a concern. Objectives. To report medium term outcomes following 4th generation VAIOS® shoulder replacement. Methods. We retrospectively analysed prospectively collected data following VAIOS® shoulder arthroplasty performed by the senior author between 2014–2020. This included anatomical (TSR), reverse(rTSR), revision and trauma shoulder replacements. The primary outcome was implant survival (Kaplan-Meier analysis). Secondary outcomes were Oxford Shoulder Scores (OSS), radiological outcomes and complications. Results. 172 patients met our inclusion criteria with 114 rTSR, 38 anatomical TSR, and 20 hemiarthroplasty. Reverse TSR- 55 primary, 31 revision, 28 for trauma. Primary rTSR- 0 revisions, average 3.35-year follow-up. Revision rTSR-1 revision (4.17%), average 3.52-year follow-up. Trauma rTSR- 1 revision (3.57%), average 4.56-year follow-up OSS: Average OSS improved from 15.39 to 33.8 (Primary rTSR) and from 15.11 to 29.1 (Revision rTSR). Trauma rTSR-Average post-operative OSS was 31.4 Anatomical TSR38 patients underwent primary anatomical TSR, 8 were revisions following hemiarthroplasty. In 16/38 patients, glenoid bone loss was addressed by bone grafting before implantation of the metal back glenoid component. Mean age at time of surgery was 68.3 years (53 – 81 years). Mean follow-up was 34 months (12 – 62 months). The average Oxford shoulder score improved from 14 (7–30) to 30 (9–48). There were 3 revisions (7.8%); two following subscapularis failure requiring revision conversion to reverse shoulder replacement and one for glenoid graft failure. Conclusions. The medium-term results of the VAIOS® system suggest much lower revision rates across multiple configurations of the system than previously reported, as well as a low incidence of scapular notching. This system allows conversion to rTSR during primary and revision surgery

Introduction and Objective. The aim of this study was to evaluate whether CT-based pre-operative planning, integrated with intra-operative navigation could improve glenoid baseplate fixation and positioning by increasing screw length, reducing number of screws required to obtain fixation and increasing the use of augmented baseplate to gain the desired positioning. Reverse total shoulder arthroplasty (RSA) successfully restores shoulder function in different conditions. Glenoid baseplate fixation and positioning seem to be the most important factors influencing RSA survival. When scapular anatomy is distorted (primitive or secondary), optimal baseplate positioning and secure screw purchase can be challenging. Materials and Methods. Twenty patients who underwent navigated RSA (oct 2018 and feb 2019) were compared retrospectively with twenty patients operated on with a conventional technique. All the procedures were performed by the same surgeon, using the same implant in cases of eccentric osteoarthritis or complete cuff tear. Exclusion criteria were: other diagnosis as proximal humeral fractures, post-traumatic OA previously treated operatively with hardware retention, revision shoulder arthroplasty. Results. The NAV procedure required mean 11 (range 7–16) minutes more to performed than the conventional procedure. Mean screw length was significantly longer in the navigation group (35.5+4.4 mm vs 29.9+3.6 mm; p . .001). Significant higher rate of optimal fixation using 2 screws only (17 vs 3 cases, p . .019) and higher rate of augmented baseplate usage (13 vs 4 cases, p . .009) was also present in the navigation group. Signficant difference there is all in function outcomes, DASH score is 15.7 vs 29.4 and constant scale 78.1 vs 69.8. Conclusions. The glenoid component positioning in RSA is crucial to prevent failure, loosening and biomechanical mismatch, coverage by the baseplate of the glenoid surface, version, inclination and offset are all essential for implant survival. This study showed how useful 3D CT-based planning helps in identifying the best position of the metaglena and the usefulness of receiving directly in the operation theater real-time feedback on the change in position. This study shows promising results, suggesting that improved baseplate and screw positioning and fixation is possible when computer-assisted implantation is used in RSA comparing to a conventional procedure

Introduction. Glenoid loosening, still a main complication for shoulder arthroplasty, was suggested to be related implant design, surgical aspects, and also bone quality. However, typical studies of fixation do not account for heterogeneity in bone morphology and density which were suggested to affect fixation failure. In this study, a combination of cyclic rocking horse tests on cadaver specimens and microCT-based finite element (microFE) analysis of specimens of a wide range of bone density were used to evaluate the effects of periprosthetic bone quality on the risks of loosening of anatomical keeled or pegged glenoid implants. Methods. Six pairs of cadaveric scapulae, scanned with a quantitative computer tomography (QCT) scanner to calculate bone mineral density (BMD), were implanted with either cemented anatomical pegged or keeled glenoid components and tested under constant glenohumeral load while a humeral head component was moved cyclically in the inferior and superior directions. Edge displacements were measured after 1000, 4000 and 23000 test cycles, and tested for statistical differences with regards to changes or implant design. Relationships were established between edge displacements and QCT-based BMD below the implant. Four other specimens were scanned with high-resolution peripheral QCT (82µm) and implanted with the same 2 implants to generate virtual models. These were loaded with constant glenohumeral force, varying glenohumeral conformity and superior or inferior load shifts while internal stresses at the cement-bone and implant-cement interfaces were calculated and related to apparent bone density in the periprosthetic zone. Results. Mean displacements at the inferior and superior edges showed no statistical difference between keeled and pegged designs (p>0.05). Compression and distraction were however statistically different from the initial reference measurement at even 1000 and 4000 cycles for both implant designs (p<0.05). For both implant designs, superior and inferior distractions were generally highest at each measurement time in specimens where BMD below the lifting edge was lower, showing a trend of increased distraction with decreased BMD. Moreover, the microFE models predicted higher bone and cement stresses for specimens of lower apparent bone density. Finally, highest peak stresses were located at the cement-bone interface, which seemed the weaker part of the fixation. Discussion. With this combined experimental and numerical study, it was shown that implant distraction and stresses in the cement layer are greater in glenoids of lower bone density for both implant designs. This indicates that fixation failure will most likely occur in bone of lower density, and that fixation design itself may play a secondary role. These results have important impact for understanding the mechanisms of glenoid component failure, a common complication of total shoulder arthroplasty

Total shoulder arthroplasty is a well-tested procedure that offers pain relief and restores the joint function. However, failure rate is still high, and glenoid loosening is pointed as the main reason in orthopedic registers. In order to understand the principles of failure, the principal strain distributions after implantation with Comprehensive® Total Shoulder System of Biomet® were experimental and numerically studied to predict bone behavior. Fourth generation composite left humerus and scapula from Sawbones® were used. These were implanted with Comprehensive® Total Shoulder System (Biomet®) with a modular Hybrid® glenoid base and Regenerex® glenoid and placed in situ by an experienced surgeon. The structures were placed in order to simulate 90º abduction, including principal muscular actions. Muscle forces used were as follows: Deltoideus 300N, Infraspinatus 120N, Supraspinatus 90N, Subscapularis 225N. All bone structures were modeled considering cortical and the trabecular bone of the scapula. The components of prosthesis were placed in the same positions than those in the in vitro models. Geometries were meshed with tetrahedral linear elements, with material properties as follows: Elastic modulus of cortical bone equal to 16 GPa, elastic modulus of trabecular bone equal to 0.155 GPa, polyethylene equal to 1GPa and titanium equal to 110 GPa. The assumed Poisson's ratio was 0.3 in all except for polyethylene where we assumed a value of 0.4. The prosthesis was considered as glued to the adjacent bone. The finite element model was composed of 336 024 elements. At the glenoid cavity, the major influence of the strain distributions was observed at the posterior-superior region, in both cortical and trabecular bone structures. The system presents critical region around holes of fixation in glenoid component. At the trabecular bone, the maximum principal strains at the posterior-superior region ranged from 2250 µε to 3000 µε. While at the cortical bone, the maximum principal strains were 300 µε to 400 µε. The results observed evidence some critical regions of concern and the effect of implant in the bone strains mainly at the posterior-superior region of the glenoid cavity is pronounced. This indicates that this region is more affected by the implant if bone remodeling is a concern and it is due to the strain-shielding effect, which has been connected with loosening of the glenoid component

Proximal humerus fractures (PHF) are the third most common fractures in the elderly. Treatment of complex PHF has remained challenging with mechanical failure rates ranging up to 35% even when state-of-the-art locked plates are used. Secondary (post-operative) screw perforation through the articular surface of the humeral head is the most frequent mechanical failure mode, with rates up to 23%. Besides other known risk factors, such as non-anatomical reduction and lack of medial cortical support, in-adverse intraoperative perforation of the articular surfaces during pilot hole drilling (overdrilling) may increase the risk of secondary screw perforation. Overdrilling often occurs during surgical treatment of osteoporotic PHF due to minimal tactile feedback; however, the awareness in the surgical community is low and the consequences on the fixation stability have remained unproved. Therefore, the aim of this study was to evaluate biomechanically whether overdrilling would increase the risk of cyclic screw perforation failure in unstable PHF. A highly unstable malreduced 3-part fracture was simulated by osteotomizing 9 pairs of fresh-frozen human cadaveric proximal humeri from elderly donors (73.7 ± 13.0 ys, f/m: 3/6). The fragments were fixed with a locking plate (PHILOS, DePuy Synthes, Switzerland) using six proximal screws, with their lengths selected to ensure 6 mm tip-to-joint distance. The pairs were randomized into two treatment groups, one with all pilot holes accurately predrilled (APD) and another one with the boreholes of the two calcar screws overdrilled (COD). The constructs were tested under progressively increasing cyclic loading to failure at 4 Hz using a previously developed setup and protocol. Starting from 50 N, the peak load was increased by 0.05 N/cycle. The event of initial screw loosening was defined by the abrupt increase of the displacement at valley load, following its initial linear behavior. Perforation failure was defined by the first screw penetrating the joint surface, touching the artificial glenoid component and stopping the test via electrical contact. Bone mineral density (range: 63.8 – 196.2 mgHA/cm3) was not significantly different between the groups. Initial screw loosening occurred at a significantly lower number of cycles in the COD group (10,310 ± 3,575) compared to the APD group (12,409 ± 4,569), p = 0.006. Number of cycles to screw perforation was significantly lower for the COD versus APD specimens (20,173 ± 5,851 and 24,311 ± 6,318, respectively), p = 0.019. Failure mode was varus collapse combined with lateral-inferior translation of the humeral head. The first screw perforating the articular surface was one of the calcar screws in all but one specimen. Besides risk factors such as fracture complexity and osteoporosis, inadequate surgical technique is a crucial contributor to high failure rates in locked plating of complex PHF. This study shows for the first time that overdrilling of pilot holes can significantly increase the risk of secondary screw perforation. Study limitations include the fracture model and loading method. While the findings require clinical corroboration, raising the awareness of the surgical community towards this largely neglected risk source, together with development of devices to avoid overdrilling, are expected to help improve the treatment outcomes

Wear of polymeric glenoid components has been identified as a cause of loosening and failure of shoulder implants1,2 in vivo. A small number of shoulder joint simulators have been built for in vitro wear testing, however none have been capable of testing with physiological motion patterns in three axes and with physiological loading. The Newcastle Shoulder Wear Simulator was designed with three axes of motion, which are programmable so that different activities of daily living might be replicated. The simulator uses three pneumatic cylinders with integral position encoders to move five shoulder prostheses simultaneously in the flexion-extension, abduction-adduction, and internal-external rotation axes. Axial loading is applied with pneumatic cylinders supplied from a pneumatic proportional valve via a manifold, which also supplies a sixth static control station. In order to establish if that the machine can actually perform as intended, commissioning trials were conducted replicating lifting a 0.5 Kg weight to head height as a daily living activity. During the commissioning trials JRI Orthopaedics Reverse VAIOS shoulder prostheses were tested in 50% bovine serum at ambient temperature. The results show that the shoulder joint wear simulator can satisfactorily reproduce a daily living activity deliberately selected for having a large range of motion and loading. Other daily activities, such as drinking from a mug, are less demanding in the ranges of motion and loading and represent no difficulty in being reproduced on the simulator. Now successfully commissioned, this new multi-station shoulder wear simulator can wear test current and new designs of shoulder prosthesis in vitro

Wear of polyethylene is associated with aseptic loosening of orthopaedic implants and has been observed in hip and knee prostheses and anatomical implants for the shoulder. The reversed shoulder prostheses have not been assessed as yet. We investigated the volumetric polyethylene wear of the reversed and anatomical Aequalis shoulder prostheses using a mathematical musculoskeletal model. Movement and joint stability were achieved by EMG-controlled activation of the muscles. A non-constant wear factor was considered. Simulated activities of daily living were estimated from in vivo recorded data.

After one year of use, the volumetric wear was 8.4 mm³ for the anatomical prosthesis, but 44.6 mm³ for the reversed version. For the anatomical prosthesis the predictions for contact pressure and wear were consistent with biomechanical and clinical data. The abrasive wear of the polyethylene in reversed prostheses should not be underestimated, and further analysis, both experimental and clinical, is required.

This study compared the effect of a computer-assisted and a traditional surgical technique on the kinematics of the glenohumeral joint during passive abduction after hemiarthroplasty of the shoulder for the treatment of fractures. We used seven pairs of fresh-frozen cadaver shoulders to create simulated four-part fractures of the proximal humerus, which were then reconstructed with hemiarthroplasty and reattachment of the tuberosities. The specimens were randomised, so that one from each pair was repaired using the computer-assisted technique, whereas a traditional hemiarthroplasty without navigation was performed in the contralateral shoulder. Kinematic data were obtained using an electromagnetic tracking device.

The traditional technique resulted in posterior and inferior translation of the humeral head. No statistical differences were observed before or after computer-assisted surgery.

Although it requires further improvement, the computer-assisted approach appears to allow glenohumeral kinematics to more closely replicate those of the native joint, potentially improving the function of the shoulder and extending the longevity of the prosthesis.