The emerging role of the non-cemented glenoid in total shoulder arthroplasty

In an effort to address the relatively high rate of glenoid component lucent lines, loosening and failure, tantalum/trabecular metal glenoid implant fixation has evolved as it has in hip and knee arthroplasty. Trabecular metal-anchored glenoid implants used in this consecutive patient case series has demonstrated a lower failure rate than traditional all-polyethylene cemented glenoids. Although the radiographs of some patients demonstrated small focal areas of lucency, none have become loose, and only one has actually demonstrated glenoid component failure due to a fracture 6 years after the index procedure. One with glenoid loosening was due to poly wear from a massive cuff tear occurring 8 years after the index procedure. Most patients experienced significant improvements in shoulder range of motion and reduction in pain. Trabecular metal glenoids when carefully implanted do not produce excessive failure rates, but rather result in functional improvements while decreasing operative time.     

Hemiarthroplasty versus total shoulder prosthesis: results of cemented glenoid components

In this retrospective study, we compared the results of 705 total shoulder arthroplasties (TSAs) with 469 hemiarthroplasties (HSAs), all having been performed with the Aequalis shoulder prosthesis. Each group, both TSA and HSA, was comparable by age (mean, 63.9 years) and sex (853 men and 321 women). Each group had comparable dominance and preoperative Constant scores (mean, 29 points). The length of follow-up averaged 43 months (range, 24-110 months) in both groups. The postoperative functional outcome and subjective assessment demonstrated the superiority of TSA over HSA independent of age or rotator cuff status (Constant score, 65.7 vs 56.3 points). The analysis of the radiographs showed a disturbing 68% of cases with radiolucent lines developing around the glenoid component and their subsequent progression with time. We saw an adverse effect on functional outcome by the presence of these radiolucent lines. This review would suggest that TSA is superior to HSA in most cases with chronic pathologic entities. HSA remains a satisfactory solution in specific cases. In the future, we need to optimize the designs of the glenoid implant and develop a better implantation technique to avoid the problems associated with glenoid replacement.     

Arthroscopic glenoid removal for aseptic loosening in total shoulder arthroplasty

BackgroundGlenoid loosening is the most common long-term complication of total shoulder arthroplasty (TSA) and frequently necessitates revision. Though arthroscopic glenoid removal is an accepted treatment option for glenoid loosening, there is a paucity of outcomes literature available. The purpose of this study was to report the long-term clinical and radiographic outcomes of arthroscopic glenoid removal for failed or loosened glenoid component in TSA. We hypothesized that arthroscopic glenoid removal would produce acceptable clinical and patient-reported outcomes while limiting the need for further revisions.MethodsThis was a retrospective analysis of 11 consecutive patients undergoing 12 arthroscopic glenoid removals for symptomatic glenoid loosening by a single orthopedic surgeon between March 2005 and March 2018. Indication for arthroscopic glenoid removal included symptomatic glenoid loosening with radiographic evidence of a 1-2 mm radiolucent line around the glenoid. Shoulder range of motion, functionality (American Shoulder and Elbow Surgeons, Simple Shoulder Test), and pain (visual analog scale [VAS]) were evaluated. Radiographs were assessed for glenohumeral subluxation, humeral superior migration, and glenohumeral offset following glenoid removal.ResultsThe mean follow-up period since arthroscopic glenoid removal was 55 months (range, 20-172 months). Glenoid component removal significantly reduced forward elevation, with a mean decrease from 147 ± 13° preoperatively to 127 ± 29° postoperatively (P= .031). However, there was no significant change in external rotation (44 ± 9° vs. 43 ± 19°; P= .941) or internal rotation (L4 vs. L4; P= .768). Importantly, glenoid removal significantly decreased VAS pain scores from 7 ± 3 preoperatively to 5 ± 3 postoperatively (P= .037). Additionally, improvement in ASES approached statistical significance, increasing from 33 ± 25 preoperatively to 53 ± 28 postoperatively (P= .055). With regard to radiographic outcomes, there was no evidence of glenohumeral subluxation and humeral superior migration developed in 1 patient. However, there was significant medialization of the greater tuberosity relative to the acromion, with a mean lateral offset of 6 ± 7 mm preoperatively and −2 ± 4 mm postoperatively (P= .002). Two patients required conversion to reverse TSA for persistent pain. There were no complications.DiscussionThese findings suggest that arthroscopic glenoid removal for symptomatic glenoid loosening is a viable option to improve pain while limiting the need for additional reoperations and decreasing the risks associated with revision arthroplasty. However, continual follow-up to monitor medialization is recommended.Level of EvidenceLevel IV; Case Series; Treatment Study     

The case for the metal-backed glenoid design in total anatomical shoulder arthroplasty

After 38 years of unchallenged reign of cemented full polyethylene glenoid implants, the main problem of anatomical shoulder arthroplasty is still glenoid loosening, also the main cause of failure. A certain concern regarding uncemented metal back components in total anatomical shoulder arthroplasty has developed, due to problems evoked in the literature. This work is a comprehensive bibliographical review of the different clinical and biomechanical studies of noncemented glenoid implants. Those publications often showed a high rate of failure of uncemented glenoid implants, but their arguments appeared often theoretical or based on old and/or nonadapted devices. In conclusion, the authors emphasise that research on new designs of metal back components needs to go on.     

Stress analyses of glenoid components in total shoulder arthroplasty

Finite element analysis was used to characterize the local stresses at the bone-implant interface of 2 different types of glenoid components presently used in unconstrained total shoulder arthroplasty. A series of 2-dimensional finite-element meshes was developed to model the glenoid in 2 mutually perpendicular planes with and without implanted components. One of the implants modeled was a cemented all-polyethylene component, and the second was an uncemented metal-backed component. A variety of parameters were studied including the resultant loading direction (concentric versus eccentric), keel geometry, subchondral bone integrity, and cement mantle size. Results of the analyses show that the cemented all-polyethylene design demonstrated an overall stress pattern that was closer to that of the intact glenoid. When the effects of concentric and eccentric loading conditions were compared, the overall stress magnitudes in the subchondral bone were found to be much lower with the uncemented metal-backed component than with its cemented all-polyethylene counterpart. This finding suggests that some degree of stress shielding may be associated with the metal-backed component. In addition, under both the concentric and eccentric loading conditions, extremely high stress regions were found within the polyethylene near the polyethylene-metal interface of the uncemented metal-backed component.