Loosening performance of cemented glenoid prosthesis design pairs

Implant breakage after shoulder arthroplasty: a systematic review of data from worldwide arthroplasty registries and clinical trials

BACKGROUND

Implant breakage after shoulder arthroplasty is a rare complication after aseptic loosening, infection or persistent pain, resulting in malfunction of the components requiring revision surgery. This correlates with a high burden for the patient and increasing costs. Specific data of complication rates and implant breakage are available in detailed arthroplasty registries, but due to the rare occurrence and possibly underestimated value rarely described in published studies. The aim of this systematic review was to point out the frequency of implant breakage after shoulder arthroplasty. We hypothesized that worldwide arthroplasty registry datasets record higher rates of implant breakage than clinical trials.

METHODS

PubMed, MEDLINE, EMBASE, CINHAL, and the Cochrane Central Register of Controlled Trials database were utilized for this systematic review using the items "(implant fracture/complication/breakage) OR (glenoid/baseplate complication/breakage) AND (shoulder arthroplasty)" according to the PRISMA guidelines on July 3rd, 2023. Study selection, quality assessment, and data extraction were conducted according to the Cochrane standards. Case reports and experimental studies were excluded to reduce bias. The breakage rate per 100,000 observed component years was used to compare data from national arthroplasty registries and clinical trials, published in peer-reviewed journals. Relevant types of shoulder prosthetics were analyzed and differences in implant breakage were considered.

RESULTS

Data of 5 registries and 15 studies were included. Rates of implant breakage after shoulder arthroplasty were reported with 0.06-0.86% in registries versus 0.01-6.65% in clinical studies. The breakage rate per 100,000 observed component years was 10 in clinical studies and 9 in registries. There was a revision rate of 0.09% for registry data and 0.1% for clinical studies within a 10-year period. The most frequently affected component in connection with implant fracture was the glenoid insert.

CONCLUSION

Clinical studies revealed a similar incidence of implant failure compared to data of worldwide arthroplasty registries. These complications arise mainly due to breakage of screws and glenospheres and there seems to be a direct correlation to loosening. Periprosthetic joint infection might be associated with loosening of the prosthesis and subsequent material breakage. We believe that this analysis can help physicians to advise patients on potential risks after shoulder arthroplasty.

LEVEL OF EVIDENCE

III.

Mid- to long-term outcomes of a cemented, all-polyethylene pegged glenoid component in anatomic total shoulder arthroplasty

BACKGROUND

The primary aim of this study was to evaluate mid- to long-term survival of an all-polyethylene pegged glenoid component used in anatomic total shoulder arthroplasty (TSA). The secondary aim was to review clinical and radiologic outcomes.

METHODS

A retrospective analysis of a prospectively collected local arthroplasty register of consecutive patients undergoing TSA with an all-polyethylene pegged glenoid between January 2009 and December 2018 was undertaken. In total, 108 TSAs using this implant were performed in our unit in 98 patients (18 men and 80 women), with 10 patients undergoing bilateral TSA. The mean age at the time of the operation was 71.3 years (range, 44-87 years). The mean follow-up period was 5.1 years (range, 2-10.6 years). In addition to survival analysis, clinical evaluation included the postoperative Oxford Shoulder Score, Constant score, and visual analog scale (VAS) pain score, as well as range-of-motion assessment. Radiologic outcomes included an assessment of radiolucency based on the Lazarus grade.

RESULTS

Kaplan-Meier survival analysis revealed a 6-year survival estimate of 94.1% for all-cause revision. Revision was required in 6 patients: 4 for cuff failure and 2 for instability. At follow-up, the mean Oxford Shoulder Score was 38.2 (standard deviation [SD], 12.3); mean Constant score, 59.3 (SD, 17.0); and mean VAS pain score, 1.8 (SD, 2.5). Mean forward elevation at final follow-up was 111⁰ (SD, 26.6⁰); mean abduction, 102⁰ (SD, 34.0⁰). Clinical outcomes were maintained at long-term follow-up (>8 years), with the exception of the VAS pain score, which increased by 2.1 points (P = .034). Radiologic assessment revealed that 28 patients had radiolucency consistent with Lazarus grade ≥ 3 with clinical outcomes not being affected.

CONCLUSIONS

Mid- to long-term follow-up indicates a low revision rate and good clinical survivorship for cemented, all-polyethylene glenoid components. No patients, so far, have undergone revision for glenoid loosening, but radiographic follow-up has shown that 36% of these implants have signs of radiolucency. Further follow-up is required to determine longer-term survivorship.

Encouraging outcomes of stemless ceramic head anatomic shoulder arthroplasty in severe primary osteoarthritis (Walch type B glenoids)

Background: We report the radiological and functional outcomes at five years in patients with severe osteoarthritis of the glenohumeral joint and a Walch type B glenoid who have undergone stemless anatomic total shoulder replacement. Methods: A retrospective analysis of case notes, computed tomography scans and plain radiographs of patients undergoing anatomic total shoulder replacement for primary glenohumeral osteoarthritis were performed. Patients were grouped by the severity of their osteoarthritis using the modified Walch classification, glenoid retroversion and posterior humeral head subluxation. An evaluation was made using modern planning software. Functional outcomes were assessed using the American shoulder and elbow surgeons score, shoulder pain and disability index and visual analogue scale. Annual Lazarus scores were reviewed as regard to glenoid loosening. Results: Thirty patients were reviewed at 5 years. Analysis of all patient-reported outcome measures demonstrated significant improvement at 5-year review, American shoulder and elbow surgeons (p = <0.0001), shoulder pain and disability index (p = 0.0001), visual analogue scale (p = 0.0001). Radiological associations between Walch scores and Lazarus scores were not statistically significant (p = 0.1251) at 5 years. There were no associations between features of glenohumeral osteoarthritis and patient-reported outcome measures. Discussion: The severity of osteoarthritis did not show any association with glenoid component survivorship or with patient-reported outcome measures at 5 years review. Level of evidence: IV.

A comparison of pegged and keeled glenoid clinical outcomes at long-term follow-up after total shoulder arthroplasty

Background

The two main glenoid types used in total shoulder arthroplasty (TSA) are the pegged and keeled glenoid designs. We aimed to determine if a pegged glenoid is superior to a keeled glenoid at long-term follow-up as measured by range of motion (ROM), patient reported outcomes (PROs), and radiographic glenoid loosening.

Methods

We retrospectively reviewed all patients undergoing TSA by a single surgeon at an urban, academic hospital. The cohort was stratified into two groups based on glenoid type - one group consisting of keeled implants and a second group consisting of pegged implants. For each patient, forward elevation (FE), internal rotation (IR), external rotation (ER), visual analog scale (VAS), American Shoulder and Elbow Surgeons (ASES) shoulder score, and simple shoulder test (SST) scores were collected preoperatively and at the most recent follow-up visit. Radiographic variables included acromiohumeral interval (AHI) and glenoid loosening.

Results

After applying exclusion criteria, 144 TSAs were included in our study. Of these, 42 (29.2%) had keeled glenoids and 102 (70.8%) had pegged glenoids. Patients with a pegged glenoid implant were older (67.4 vs. 60.7 years; p < 0.001) and had a shorter follow-up time (9.3 vs. 14.4 years; p < 0.001) than patients with a keeled glenoid implant. At the most recent follow-up visit, there were no significant differences among postoperative FE, ER, AHI, or PROs. However, pegged glenoid implants provided significantly more internal rotation (T11 vs. L1; p = 0.010) and were less likely to show evidence of radiographic glenoid loosening (16.7% vs. 42.9%; p=<0.001). Revision rates were not significantly different between the pegged and keeled groups (6.9% vs. 14.3%; p = 0.158).

Conclusion

Although a pegged design correlated with superior internal rotation and less radiographic glenoid loosening, both pegged and keeled glenoid designs offered favorable long-term clinical outcomes following TSA over the long-term.

Improved mechanical fixation of an all-polyethylene glenoid reduces postoperative radiolucent lines

BACKGROUND

The rationale for advances in implant design is to improve performance in comparison to their predecessors. The purpose of this study was to compare a newer, self-pressurizing peripheral peg glenoid to a traditional polyethylene pegged glenoid through biomechanical evaluation and a retrospective radiographic and clinical review.

METHODS

Three testing conditions (uncemented, partially cemented, and fully cemented) were chosen to assess the 2 component designs in a foam block model. The number of hammer hits to seat the component, amount of time to seat the component, and resistance-to-seat were collected. The implants were then cyclically loaded following ASTM F2028-17 testing standard. Clinically, postoperative radiographs of patients with a self-pressurized glenoid component (n = 225 patients) and traditional glenoid component (n = 206 patients) were evaluated for radiolucent lines and glenoid seating at various timepoints. Clinical outcomes (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, Simple Shoulder Test, and visual analog scale pain scores) and complications were recorded. The presence of radiolucent lines at the bone-cement interface was evaluated using the Modified Franklin Grade and the Lazarus grade.

RESULTS

The self-pressurizing glenoid design required significantly more hammer hits than traditional glenoid designs in all groups tested (P < .029). Moreover, the self-pressurizing design had significantly more resistance-to-seat than traditional components in both the uncemented and partially cemented group (P < .002). No difference in resistance-to-seat was found between designs in the fully cemented group. The uncemented and partially cemented groups did not survive the full 50,000 cycles; however the self-pressurizing design had significantly less motion than the traditional design (P < .001). No differences between component designs were found in the fully cemented group at 50,000 cycles. The self-pressurizing glenoid component had 0.005% radiographic radiolucent lines, and the traditional glenoid component had 45% radiographic radiolucent lines, with 38% of the radiolucencies in the traditional glenoid component group being defined as grade E. There were no progressive radiolucencies, differences in clinical outcomes, or complications at 2 years postoperatively.

CONCLUSION

In the fully cemented condition, the 2 component designs had comparable performance; however, the differences in designs could be better observed in the uncemented group. The self-pressurizing all-polyethylene design studied has superior biomechanical stability. Clinically, the improved stability of the glenoid component correlated with a reduction of radiolucent lines and will likely lead to a reduction in glenoid component loosening.

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).

Radiographic performance depends on the radial glenohumeral mismatch in total shoulder arthroplasty

BACKGROUND

Optimal radii of curvature of the articulating surfaces of the prosthetic components are factors associated with the longevity of cemented glenoid components in anatomical total shoulder arthroplasty. It was the purpose of this study, to evaluate the radiographic and clinical performance of an anatomical glenoid component of a total shoulder arthroplasty (TSA) with respect to radial mismatch of the glenoid and humeral component.

METHODS

In a retrospective study 75 TSA were analyzed for their clinical and radiographic performance with computed tomography by independent examiners using an established methodology. The study group was divided in two groups, one with mismatch < 4.5 mm (n:52) the others with mismatch ≥4.5 mm (n:23) and analyzed for confounding variables as indication, primary or revision surgery, age, gender, glenoid morphology and implant characteristics.

RESULTS

The mean glenohumeral radial mismatch was 3.4 mm (range 0.5-6.9). At median follow-up of 41 months (range 19-113) radiographic loosening (defined as modified Molé scores ≥6) was present in 7 cases (9.3%). Lucencies around the glenoid pegs (defined as modified Molé score ≥ 1) were present in 34 cases (45%). Radiolucencies were significantly associated with a radial mismatch < 4.5 mm (p = 0.000). The pre- to postoperative improvements in Subjective Shoulder Value and absolute Constant Score were significantly better in the group with a mismatch ≥4.5 mm (p = 0.018, p = 0.014).

CONCLUSION

A lower conformity of the radii of humerus and glenoid seems to improve the loosening performance in TSA. Perhaps cut-off values regarding the recommended mismatch need to be revalued in the future.

In silico study of glenoid perforation during total shoulder arthroplasty: the effects on stress & micromotion

Glenoid perforation is not the intended consequence of the surgery and must be avoided. The analysis on biomechanical aspect of glenoid vault perforation remains unknown. The purpose of this study is to determine the impact of glenoid perforation towards stress distribution and micromotion at the interfaces. Eight glenoid implant models had been constructed with various size, number and type of fixation. A load of 750 N was applied to centre, superior-anterior and superior-posterior area. Implant perforation had minimal impact on stress distribution and micromotion at the interfaces. However, cement survival rate for implant without perforation was the highest with a difference of up to 37% compared to other perforated models. Besides that, implant fixation and high stresses at the implant had more of an impact on implant instability than implant perforation. As a conclusion, glenoid perforation did not influence the stress distribution and micromotion, but, it reduced cement survival rate and increase the stress critical volume.

A comparison of pegged vs. keeled glenoid components regarding functional and radiographic outcomes in anatomic total shoulder arthroplasty: a systematic review and meta-analysis

Background

The number of total shoulder arthroplasties (TSAs) performed is increasing annually, with a continued effort to improve outcomes using new techniques and materials. In anatomic TSAs, the main options for glenoid fixation currently involve keeled or pegged components. The aim of this review was to determine which fixation option provides optimal long-term functional outcomes with decreased rates of revision surgery and radiolucency.

Methods

The MEDLINE, Embase, PubMed, and Cochrane databases were searched from 2007 to July 10, 2017, for all articles that examined TSAs using either pegged or keeled glenoid fixations. All studies were screened in duplicate for eligibility. Two separate analyses were completed examining noncomparative and comparative studies independently.

Results

A total of 7 comparative studies and 25 noncomparative studies were included in the final analysis. Included in the analysis were 4 randomized (level I) studies, 1 level II study, 8 level III studies, and 19 level IV studies. Meta-analysis of the comparative studies demonstrated a higher rate of revision surgery with keeled fixations compared with pegged fixations (odds ratio, 6.22; 95% confidence interval [CI], 1.38-28.1; P = .02). No significant difference was found with respect to functional outcomes, such as the American Shoulder and Elbow Surgeons score (mean difference, 9.54; 95% CI, –8.25 to 27.34; P = .29) and Constant score (mean difference, 5.31; 95% CI, –12.28 to 22.89; P = .55), as well as radiolucency rates (odds ratio, 1.89; 95% CI, 0.56−6.39; P = .30).

Conclusion

Pegged glenoid fixation may result in a decreased risk of revision TSAs, but no significant differences in patient-reported outcomes have been identified to date.

Journey of the glenoid in anatomic total shoulder replacement

Anatomic total shoulder arthroplasty (TSR) has been shown to generate good to excellent results for patients with osteoarthritis and a functioning rotator cuff. Many studies have reported that the glenoid component loosening and failure remain the most common long-term complication of total shoulder arthroplasty. The approach to glenoid component is critical because a surgeon should consider patient-specific anatomy, preserving bone stock and joint line restoration, for a good and durable shoulder function. Over the years, different glenoid design and materials have been tried in various configurations. These include cemented polyethylene, uncemented metal-backed and hybrid implants. Although advances in biomechanics, design and tribology have improved our understanding of the glenoid, the journey of the glenoid component in anatomic total shoulder arthroplasty has not yet reached its final destination. This article attempts to describe the evolution of the glenoid component in anatomic TSR and current practice.

Does the cement mantle thickness influence the glenoid loosening in anatomic total shoulder arthroplasty? An experimental study

BACKGROUND

Glenoid component loosening is the most frequent failure mode. Few data are available on the effect of thickness of cement on glenoid loosening. The purpose of this study is to determine if the cement mantle thickness influences the mode and localization of loosening. Our hypotheses are: 1) failure is caused by traction stresses generated within the cement mantle and 2) a thicker cement mantle amplifies the rocking horse effect.

METHODS

Using bone substitute, an experimental protocol was designed to compare loosening of a keeled glenoid prosthesis in axial traction and off-centered-load, to recreate the rocking-horse effect (1.000.000 cycles). Different standardized mantle of cement between the back of the glenoid and the foam were tested (0-1 - 2-3 mm). The displacement of the polyethylene was assessed with an LVDT (Linear Variable Differential Transformer) gauge when the prosthetic humeral head loaded the opposite part of the implant.

RESULTS

The loosening took place within the keel of the implant, and at the polyethylene-cement interface in traction if there was cement at the back of the polyethylene. For cycling loading, we observed a loosening at this interface, with associated fracture of the cement, only for cement 2 and 3 mm thick.

CONCLUSION

This experimental study suggests that the cement mantle should be as thin as possible between the back of the implant and the sub-chondral bone but should be optimized around the keel of the implant.

LEVEL OF EVIDENCE

Basic Science Study.

Survival of the pegged glenoid component in shoulder arthroplasty: part II

BACKGROUND

Loosening of the glenoid component is a primary reason for failure of an anatomic shoulder arthroplasty. Pegged glenoids were designed in an effort to outperform keeled components. This study evaluated the midterm clinical and radiographic survival of a single implant design with implantation of an in-line pegged glenoid component and identified risk factors for radiographic loosening and clinical failure.

MATERIALS AND METHODS

There were 330 total shoulder arthroplasties that had been implanted with a cemented, all-polyethylene, in-line pegged glenoid component evaluated with an average clinical follow-up of 7.2 years. Of these shoulders, 287 had presurgical, initial postsurgical, and late postsurgical radiographs (mean radiographic follow-up, 7.0 years).

RESULTS

At most recent follow-up, 30 glenoid components had been revised for aseptic loosening. This translated to a rate of glenoid component survival free from revision for all 330 shoulders of 99% at 5 years and 83% at 10 years. Of 287 glenoid components, 120 were considered loose on the basis of radiographic evaluation. Four humeral components were considered loose. Component survival (Kaplan-Meier) free from radiographic failure at 5 and 10 years was 92% and 43%. Severe presurgical glenoid erosion (Walch A2, B2, C) and patient age <65 years were risk factors for radiographic failure. Late humeral head subluxation was associated with radiographic failure.

CONCLUSION

Despite the predominant thinking that pegged glenoid components may be superior to keeled designs, midterm radiographic and clinical failure rates were high with this pegged component design, particularly after 5 years. Advanced presurgical glenoid erosion and younger patient age are risk factors for radiographic loosening. Revision rates underestimate radiographic glenoid loosening.

Treatment of the Fixation Surface Improves Glenoid Prosthesis Longevity in vitro

Many commercial cemented glenoid components claim superior fixation designs and increased survivability. However, both research and clinical studies have shown conflicting results and it is unclear whether these design variations do improve loosening rates. Part of the difficulty in investigating fixation failure is the inability to directly observe the fixation interface, a problem addressed in this study by using a novel experimental set-up. Cyclic loading-displacement tests were carried out on 60 custom-made glenoid prostheses implanted into a bone substitute. Design parameters investigated included treatment of the fixation surface of the component resulting in different levels of back-surface roughness, flat-back versus curved-back, keel versus peg and more versus less conforming implants. Visually-observed failure and ASTM-recommended rim-displacements were recorded throughout testing to investigate fixation failure and if rim displacement is an appropriate measure of loosening. Roughening the implant back (R_a>3µm) improved resistance to failure (P<0.005) by an order of magnitude with the rough and smooth groups failing at 8712±5584 cycles (mean±SD) and 1080±1197 cycles, respectively. All other design parameters had no statistically significant effect on the number of cycles to failure. All implants failed inferiorly and 95% (57/60) at the implant/cement interface. Rim-displacement correlated with visually observed failure. The most important effect was that of roughening the implant, which strengthened the polyethylene-cement interface. Rim-displacement can be used as an indicator of fixation failure, but the sensitivity was insufficient to capture subtle effects.

LEVEL OF EVIDENCE

Basic Science Study, Biomechanical Analysis.

No correlation between radiolucency and biomechanical stability of keeled and pegged glenoid components

Background

The purpose of this study was to examine biomechanical properties and the degree of radiolucency of two cemented basic glenoid designs for total shoulder arthroplasty. Our hypothesis was that a component with increased micro-motion in the laboratory at time zero would also exhibit a greater amount of radiolucency in patients at a minimum of 2 years post total shoulder arthroplasty.

Methods

Thirty cadaveric shoulders were divided into 2 groups (keel vs. peg). The glenoid components were first loaded with a single axial eccentric force of 196 N in all orientations and then with a transversal load of 49 N to simulate in vivo loads with abduction. Displacement of the glenoid component was determined with four different linear variable-differential transducers. In the second phase, 56 antero-posterior x-rays of 52 patients with either the same keeled (n = 24) or pegged (n = 32) glenoid component with a minimum of 24 months follow-up were evaluated for radiolucency.

Results

Biomechanically the pegged glenoid showed a significant increase in micro-motion during eccentric axial loading as well as during combined loading in the anterior, posterior, and inferior position as compared to the keeled glenoid (p < 0.05). In contrast all results were significant with greater radiolucency for the keeled glenoid component (p = 0.001).

Conclusion

While the pegged component exhibited a greater amount of micro-motion during biomechanical testing, radiolucency was greater in patients with a keeled component. These findings provide support for both components from different perspectives and highlight the need for well-constructed studies to determine whether glenoid design has an effect on clinical outcome, because influences are multifactorial and biomechanical forces may not recreate forces seen in vivo.

Porous metals and alternate bearing surfaces in shoulder arthroplasty

Total shoulder arthroplasty (TSA) provides an effective solution for the treatment of glenohumeral arthritis. However, long-term outcomes have been limited by glenoid component aseptic loosening and polyethylene (PE) wear. Previous attempts to improve glenoid fixation with metal-backed glenoids resulted in inferior results. Newer component designs that contain porous metal allow for biological ingrowth of the prosthesis, potentially improving longevity and overall outcomes. Porous metal can also improve humeral component fixation, obviating the need for cement and simplifying revision surgery. Advances such as highly cross-linked polyethylene (HXLPE), vitamin E-doped HXLPE, and alternate bearing surfaces like ceramics and pyrolytic carbon have proven to provide superior wear characteristics in other joint replacements and may prove beneficial in the shoulder as well.

Inferior tilt fixation of the glenoid component in reverse total shoulder arthroplasty: A biomechanical study

BACKGROUND

Glenoid component fixation with an inferior tilt has been suggested to decrease scapular notching, but this remains controversial. We aimed here to evaluate the effect of glenoid component inferior tilt in reverse total shoulder arthroplasty (RSA) on micromotion and loss of fixation of the glenoid component by biomechanical testing.

HYPOTHESIS

Increased inferior reaming of the glenoid for inferiorly tilted implantation of the glenoid component will decrease glenoid bone stock and compromise the fixation of RSA.

MATERIALS AND METHODS

The micromotions of the glenoid components attached to 14 scapulae from fresh frozen cadavers were measured and compared between neutral and 10° inferior tilts in 0.7- and 1-body weight cyclic loading tests using digital-image analysis. The incidence of bone breakage or loss of fixation was assessed in the 1-body weight fatigue-loading test.

RESULTS

Micromotion was higher with a 10° inferior tilt than with a neutral tilt during both the 0.7-body weight (36 ± 11 μm vs. 22 ± 5 μm; P = 0.028) and 1-body weight (44 ± 16 μm vs. 28 ± 9 μm; P = 0.045) cyclic loading. The incidence of bone breakage or loss of fixation was 17% and 60% with a neutral and 10° inferior tilt, respectively.

DISCUSSION

Glenoid component inferior tilt fixation in RSA may reduce primary stability and increase mechanical failure of the glenoid component, thereby reducing longevity of the prosthesis. Accordingly, we recommend careful placement of the glenoid component when an inferior tilt is used.

A novel dynamic mechanical testing technique for reverse shoulder replacements

In vitro mechanical testing of orthopedic implants provides information regarding their mechanical performance under simulated biomechanical conditions. Current in vitro component stability testing methods for reverse shoulder implants are based on anatomical shoulder designs, which do not capture the dynamic nature of these loads. With glenoid component loosening as one of the most prevalent modes of failure in reverse shoulder replacements, it is important to establish a testing protocol with a more realistic loading regime. This paper introduces a novel method of mechanically testing reverse shoulder implants, using more realistic load magnitudes and vectors, than is currently practiced. Using a custom made jig setup within an Instron mechanical testing system, it is possible to simulate the change in magnitude and direction of the joint load during arm abduction. This method is a step towards a more realistic testing protocol for measuring reverse shoulder implant stability.

Fully uncemented glenoid component in total shoulder arthroplasty

BACKGROUND

Loosening of the glenoid component remains the most common problem in total shoulder arthroplasty. It has been described that the round-backed, all-polyethylene components with cemented peg fixation perform better biomechanically and clinically than flat-backed, metal-backed, or keeled components. However, side effects of cementing have been described. We hypothesized that cementing of a specific type of all-polyethylene glenoid component with 3 peripheral pegs and 1 central anchor peg is not necessary to obtain good clinical and radiologic results.

MATERIALS AND METHODS

Thirty-four shoulders (34 patients), with a mean follow-up of 28.3 months, were evaluated clinically with the Constant-Murley score and the SF-12 Health Survey score. The fixation of the glenoid component was evaluated with computed tomography scan.

RESULTS

The Constant-Murley score increased from 40.2 points (range, 13-73 points) preoperatively to 72 points (range, 54-93 points) postoperatively. The SF-12 Physical Component Summary score was 45, and the SF-12 Mental Component Summary score was 50. No signs of loosening were seen around the pegs or glenoid in 30 shoulders. Signs of loosening were seen around the central anchor peg and the peripheral pegs in 4 shoulders. There was no statistical difference between the clinical outcome of patients with and without signs of loosening.

CONCLUSION

The clinical and radiologic evaluation of an uncemented all-polyethylene glenoid is promising, with good clinical results and with no signs of loosening in 88% of the patients on computed tomography scans.

Glenoid morphology affects the incidence of radiolucent lines around cemented pegged polyethylene glenoid components

PURPOSE

Radiolucent lines (RLL) are frequent findings around cemented all-polyethylene glenoid implants. The present study evaluates the frequency, extend and the clinical impact of RLL around a cemented two-pegged glenoid implant with special focus on the influence of preoperative glenoid morphology. Our hypothesis was that glenoid morphology does not affect clinical outcome and RLL in the investigated setting.

METHODS

Between 2003 and 2008, a total of 113 cases of total shoulder arthroplasties (Affinis, Mathys Ltd Bettlach, Switzerland) were performed in three surgical centres using a pegged cemented polyethylene glenoid component. A total of 90 cases could be evaluated clinically and radiographically. Clinical outcome was analysed using the constant score (CS) and range of motion assessment. Radiographic evaluation was performed in true anterior-posterior and axial views with special focus on loosening and RLL. Further, preoperative glenoid morphology was documented and its correlation to radiolucent lines and clinical outcomes was evaluated.

RESULTS

At a mean of 58.8 (range 31.2-92.5)-month follow-up the CS improved from 21.5 points preoperatively to 62.3 points postoperatively. Radiolucent lines were found in 76.6 % of cases. If present, RLL were located at the backside of the implant (74.4 %) in the majority of the cases not around the pegs (10 %). There was no significant correlation between RLL and clinical outcome or follow-up time. The amount and extend of RLL were correlated to glenoid morphology with significantly higher values for glenoid types B2 and C according to Walch in comparison to glenoid types A1, A2 and B1.

CONCLUSIONS

RLL did not affect clinical outcome and did not correlate with the follow-up time. Patients with glenoid morphology types B2 and C showed significantly worse radiographic results.

LEVEL OF EVIDENCE

Level IV case series study.

Glenoid implant orientation and cement failure in total shoulder arthroplasty: a finite element analysis

BACKGROUND

To minimize glenoid implant loosening in total shoulder arthroplasty (TSA), the ideal surgical procedure achieves correction to neutral version, complete implant-bone contact, and bone stock preservation. These goals, however, are not always achievable, and guidelines to prioritize their impact are not well established. The purpose of this study was to investigate how the degree of glenoid correction affects potential cement failure.

METHODS

Eight patient-specific computer models were created for 4 TSA scenarios with different permutations of retroversion correction and implant-bone contact. Two bone models were used: a homogeneous cortical bone model and a heterogeneous cortical-trabecular bone model. A 750-N load was simulated, and cement stress was calculated. The risk of cement mantle fracture was reported as the percentage of cement stress exceeding the material endurance limit.

RESULTS

Orienting the glenoid implant in retroversion resulted in the highest risk of cement fracture in a homogeneous bone model (P < .05). In the heterogeneous bone model, complete correction resulted in the highest risk of failure (P = .0028). A positive correlation (ρ = 0.901) was found between the risk of cement failure and amount of exposed trabecular bone.

CONCLUSIONS

Incorporating trabecular bone into the model changed the effect of implant orientation on cement failure. As exposed trabecular bone increased, the risk of cement fracture increased. This may be due to shifting the load-bearing support underneath the cement from cortical bone to trabecular bone.

Fracture risk and initial fixation of a cementless glenoid implant: the effect of numbers and types of screws

The initial fixation of an anatomical cementless glenoid component, provided by different numbers and types of screws, and the risk of bone fracture were evaluated by estimating the bone-implant interface micromotions and the principal strains around the prosthesis. Four different fixation configurations using locking or compression screws were tested. Estimation of the micromotions at the bone-implant interface was performed both experimentally, using an in vitro model, and computationally, using a numerical model. Principal bone strains were estimated using the numerical model. Subject variability was included by modelling two different bone qualities (healthy and rheumatoid bone). For the fixation configurations that used two screws, experimental and modelling results found that the micromotions at the bone-implant interface did not change with screw type. However, screw type had a significant effect on fixation when only one screw was used; in this case, a locking screw resulted in less micromotion at the bone-implant interface compared with the compression screw. Bone strains were predicted by the numerical model, and strains were found to be independent of the screw type; however, the predicted strain levels calculated in rheumatoid bone were larger than the strain levels that may cause bone damage for most considered arm positions. Predicted bone strain in healthy bone did not reach this level. While proper initial component fixation that allows biological fixation can be achieved by using additional screws, the risk of bone failure around the screws must be considered, especially in cases of weak bone.

[Differential indications for current endoprosthesis systems of the shoulder]

Modern shoulder prostheses adapt to the size, inclination, posterior offset and retrotorsion of the shoulder anatomy. Typical implants are cup prostheses for surface replacement, stemless prostheses that anchor in metaphyseal bone, anatomical prostheses using stems of different lengths, and last but not least reverse prostheses. The main reasons for implantation of shoulder prostheses are primary osteoarthritis, posttraumatic and rheumatoid arthritis, avascular necrosis, arthritis of instability and cuff defect arthropathy.Anatomical hemiprostheses should be used only if the glenoid is intact as total prostheses are functionally better as soon as the arthritis involves the glenoid. Conventional stems are cemented most of the time and cemented glenoids that are convex on the back are standard. Stemless prostheses were developed for posttraumatic indications and can often replace stemmed designs if the bone quality is good. Reverse prostheses were developed for the treatment of cuff tear arthropathies but if used as a revision implant complication rates rise and survival time is shorter.

Glenoid or not glenoid component in primary osteoarthritis

The optimal choice for the treatment of end-stage primary glenohumeral osteoarthritis remains controversial, with alternatives including total shoulder replacement (TSR) and humeral head replacement (HHR). The objective of this review is to analyze the effect of TSR compared with HHR on rates of pain relief, range of motion, patient satisfaction and revision surgery in patients with primary glenohumeral osteoarthritis. Compared with HHR, TSR provided significantly greater pain relief, gain in forward elevation, and gain in external rotation and patient satisfaction. Furthermore, TSR required significantly less revision surgery glenoid component loosening than patients undergoing HHR (progression of osteoarthritis changes with subchondral sclerosis, joint space narrowing and glenoid subsidence). A convex-back pegged glenoid component with a modern instrumented cement pressurization technique achieves risk of loosening. For 10 years, a high interest regarding new designs of un-cemented metal back glenoid components has developed with promising results, because they allow glenoid bone graft in case of glenoid erosion or dysplasia and a one-stage glenoid bone reconstruction in case of revision surgery.

EXPERIMENTAL EVALUATION OF THE TESTING CONDITIONS INFLUENCE ON SHOULDER PROSTHESES SUBLUXATION AND EDGE DISPLACEMENT DURING ASTM F2028-05 TESTING

Glenoid failure is one of the major indications for revision in total shoulder arthroplasty. Glenoid components should be carefully designed to improve the reliability of the prostheses, and mechanical testing can be a key tool to compare the performances of different designs. The most relevant guidelines for mechanical testing of glenoid prostheses are included in the ASTM F2028-05 Standard. The Standard refers to glenoid subluxation tests, designed to evaluate the intrinsic stability of the prosthesis system, and to glenoid edge displacement tests, which estimate the risk of micro-motions at the bone-glenoid interface. However, some indications given by the Standard are not mandatory, leaving the possibility to choose some parameters of the testing set-up and procedure. The main goal of this study was to investigate how different testing parameters (i.e. loads, velocities and bone-glenoid conformity) may affect the test results. In order to reach this target an experimental apparatus was developed and mechanical tests were performed on a keeled glenoid. The study showed that the applied load and the bone-glenoid conformity have a significant effect on the tests results, because of bone and glenoid deformation. Contrarily, the testing velocity was not found to be an influencing testing parameter.

Mechanical characteristics of a novel posterior-step prosthesis for biconcave glenoid defects

BACKGROUND

Posterior glenoid defects increase the risk of glenoid component loosening after total shoulder arthroplasty (TSA). The goal of this work was to evaluate the mechanical performance of a novel posterior-step glenoid prosthesis, designed to compensate for biconcave (type B2) glenoid defects. Two prototypes ("Poly-step" and "Ti-step") were constructed by attaching polyethylene or titanium step-blocks onto standard (STD) glenoid prostheses. We hypothesized that the mechanical performance of the experimental prostheses in the presence of a B2 defect would be similar to that of an STD prosthesis in the absence of a defect.

METHODS

Fifteen normal shoulder specimens were consistently loaded under simulated muscle activity while peri-glenoid bone strains were measured. In 5 specimens, arthroplasty was performed with an STD glenoid prosthesis. In the remaining 10 specimens, a 20° B2 glenoid defect was created before arthroplasty was performed with the Poly-step or Ti-step prosthesis.

RESULTS

Load-induced peri-glenoid strains after TSA with either the STD or Poly-step prosthesis did not show statistical differences as compared with the native joints (P > .05). A posterior defect decreased superior glenoid strain as compared with the intact specimens (P < .05). The change in strains after Poly-step prosthesis implantation in the presence of a biconcave glenoid defect was not different than the change induced by STD prosthesis implantation in the absence of a defect. In contrast, strains after Ti-step prosthesis implantation were statistically different from those induced by the STD and Poly-step prostheses (P < .05).

CONCLUSIONS

The Poly-step prosthesis may be a viable option for treating posterior glenoid defects.

A ten-year radiologic comparison of two-all polyethylene glenoid component designs: a prospective trial

BACKGROUND

Aseptic glenoid component loosening remains a common problem in total shoulder arthroplasty (TSA). This study presents long-term prospective follow-up of 2 cemented all-polyethylene glenoid components with different backside design geometry and the effect on the presence and progression of radiolucent lines (RLLs).

MATERIALS AND METHODS

Fifty-six TSAs were performed for primary osteoarthritis. Two surgeons used an identical technique to implant 32 flat-back and 24 convex-back glenoids. In particular, the glenoid components were cemented after a minimal reaming and bone compaction. Standardized postoperative radiologic and clinical follow-up was at 2 and 10 years. Three independent observers evaluated the x-ray images for RLLs around the base plate and keel. The results were analyzed for progression and influencing factors.

RESULTS

At 10 years, progression of RLL was seen in both components, but there was no difference between the 2 glenoid designs (P = .16). Younger patient age (P = .03), hand dominance (P = .017), and presence of early RLLs (P = .018) were significant factors for progression of RLLs. Constant scores deteriorated with progression of RLLs (P = .006). The glenoid revision rate at 10 years was 5%.

CONCLUSION

At 10 years there was no difference in the presence or progression of RRLs between a flat-back and a convex-back glenoid all-polyethylene design. Young age, hand dominance, and poor implantation technique influence glenoid RLLs and affect the clinical result of TSA.

The glenoid in total shoulder arthroplasty

Management of glenohumeral arthrosis with a total shoulder prosthesis is becoming increasingly common. However, failure of the glenoid component remains one of the most common causes for failure. Our understanding of this problem has evolved greatly since the first implants were placed in the 1970's. However glenoid failure remains a challenging problem to address and manage. This article reviews the current knowledge regarding the glenoid in total shoulder arthroplasty touching on anatomy, component design, implant fixation, causes of implant failure, management of glenoid failure and alternatives to glenoid replacement.

Total shoulder arthroplasty with an uncemented soft-metal-backed glenoid component

BACKGROUND

Loosening associated with cemented polyethylene glenoid components is a major concern following total shoulder arthroplasty (TSA). The purpose of this study was to investigate the clinical and radiographic results associated with use of a novel uncemented soft-metal-backed glenoid component (SMBG), with a minimum follow-up of 2 years.

MATERIALS AND METHODS

Twenty-two patients (19 women) underwent TSA using a uncemented SMBG. The mean age was 68.5 years (range, 49-84). Mean follow-up was 50 months (range, 24-89). Indications for TSA were primary osteoarthritis (10), post-traumatic osteoarthritis (8), steroid-induced avascular necrosis (2), crystalline arthropathy (1), and arthritis secondary to systemic lupus erythematodes (1). Subjective and objective parameters were assessed. Loosening and polyethylene wear were evaluated.

RESULTS

Mean absolute Constant scores improved from 29.1 to 65.9 points (P < .001), age- and sex-adjusted Constant scores improved from 40.1 to 87.7% (P < .001), and subjective shoulder values improved from 35% to 75.2% (P < .001). Mean pain scores improved from 4.2 points to 13.1 (P < .001). Three cases had a fractured glenoid component. Only these 3 had a definite loosening. Polyethylene wear was found in 2 cases.

CONCLUSION

Use of an uncemented SMBG component yields controversial results. Osteointegration appears possible and loosening signs have virtually not been observed. Conversely, the current implant can be associated with a high failure rate (13.6%) because of implant fractures despite short follow-up. As loosening seems absent or minimal but implant stability insufficient, design changes need to be performed and tested in view of solving the implant failure problem while preserving the actually excellent bone-implant interface characteristics.

Radiographic comparison of pegged and keeled glenoid components using modern cementing techniques: a prospective randomized study

BACKGROUND

Modern cementing techniques have improved glenoid fixation, reduced glenoid lucency seen with keeled components, and may eliminate differences attributable to glenoid design. The purpose of this study was to determine the effect of glenoid design on immediate and follow-up radiographic lucency of pegged and keeled glenoid components, using modern cementing techniques.

MATERIAL AND METHODS

Fifty-three total shoulder arthroplasties were performed in patients with primary glenohumeral osteoarthritis. Patients were randomized prospectively to receive either a pegged or keeled glenoid component. Three raters graded radiographic glenoid lucencies.

RESULTS

On immediate radiographs, there was no significant difference in the rate of glenoid lucency between pegged (0%) and keeled (15%) glenoid components (P = .128). However, after an average of 26 months, the rate of glenoid lucency was significantly higher in patients with keeled components (46%) compared to patients with pegged components (15%) (P = .003).

CONCLUSION

Even with modern cementing techniques, pegged glenoid components remain radiographically superior to keeled glenoid components.

Glenoid loosening after total shoulder arthroplasty: an in vitro CT-scan study

Glenoid fixation failure has only been grossly characterized. This lack of information hinders attempts to improve fixation because of a lack of methodologies for detecting and monitoring fixation failure. Our goal was twofold: to collect detailed data of glenoid fixation fracture, and to investigate computed tomography (CT)-scanning as a tool for investigations of fixation failure. Six cadaver scapulas and six bone-substitute specimens were cyclically loaded and CT-scanned at clinical settings after 0, 1,000, 5,000, 10,000, 30,000, 50,000 and 70,000 load cycles. The fixation status was evaluated by inspection of the scans. After 70,000 cycles, the specimens were sectioned, and the fixation inspected by microscopy. The results of the microscopy analysis were compared to the CT-scan analysis. Fracture of the glenoid fixation initiated at the edge of the glenoid rim and propagated towards and around the keel of the implant. The entire process from initiation to complete fracture took place at the polyethylene implant-cement interface, while the cement, the adjacent bone, and the cement-bone interface remained intact. Thus, strengthening the polyethylene-cement interface should improve glenoid fixation. Microscopy results validated the CT methodology, suggesting that the CT technique is reliable.

The SMR reverse shoulder prosthesis in the treatment of cuff-deficient shoulder conditions

BACKGROUND

Reverse total shoulder arthroplasty (RSA) is a relatively recent concept that provides further options in the management of cuff-deficient shoulder disorders. While early results utilizing the Delta III prosthesis (DePuy, Warsaw, IN) have been promising, there is limited data in the literature on outcomes utilizing differing prosthetic designs. We report on the outcomes of Reverse total shoulder arthroplasty (RSA) utilizing a previously unreported prosthesis, the SMR Modular Shoulder System (Systema Multiplana Randelli, Lima-LTO, Italy).

MATERIAL AND METHODS

49 arthroplasties in 48 patients who underwent Reverse Shoulder Arthroplasty with the SMR prosthesis were available for follow up. There were 10 males and 38 females with a mean age of 78.9 years (55-94) at time of operation. The most common indications were cuff tear arthropathy and osteoarthritis with cuff deficiency (66%), followed by fracture and fracture sequelae (16%).

RESULTS

At a mean 38 months follow up, 89% of patients rated their outcome as good or excellent. The mean American Shoulder and Elbow Surgeon Score was 70.1 (range 3-100), and the mean Oxford Shoulder Score 22.0 (12-47). The mean active anterior elevation was 122 degrees (range 45-180) and the mean external rotation 14.7 degrees (25-75). Inferior glenoid notching was seen in 24% of patients. There was no radiological evidence of component loosening and no reoperations.

CONCLUSION

Modern RSA designs give encouraging results in the treatment of cuff deficient shoulder conditions. Our early experience with the SMR RSA shows favourable outcomes and a low rate of complications.

LEVEL OF EVIDENCE

Level 4 Retrospective case series, no control group.

Consequences of scapular anatomy for reversed total shoulder arthroplasty

The reverse total shoulder prosthesis provides successful functional outcome in many patients with rotator cuff tear arthropathy. However, scapular notching, a direct consequence of mechanical impingement between the humeral prosthesis and the glenoid, remains a major concern. We presumed a better knowledge of the anatomy of the scapula would enable design or placement modifications to minimize this phenomenon. After establishing a uniform spatial reference system using easy locatable surgical reference points and planes, we analyzed 200 dry bony scapulae and defined the glenoid and infraglenoid anatomy relative to the reference system. The bony rim of the two inferior quadrants of the glenoid forms a semicircle the center of which can be used perioperatively as an easy locatable bony reference point. The infraglenoid tubercle varies in width and length, and can interfere with the humeral part of the reverse prosthesis, creating scapular notching. To avoid notching, we suggest using a convex base plate with a smaller radius than currently used, placing it as low as possible with a 42-mm glenosphere eccentrically assembled to create a posterior offset. If prosthetic overhang cannot be obtained, we suggest removing part of the infraglenoid tubercle.

Validation of three-dimensional models of in situ scapulae

A principal challenge in creating accurate models of in situ scapulae is delineating bone from surrounding soft tissues. Computed tomography scans were obtained of both shoulders of 20 embalmed cadavers. Each shoulder was rescanned after repositioning of the cadavers to test for rescan reliability. After scans were complete, all scapulae were excised and stripped of all soft tissue. Thresholding, region growing, and manual processing were used to create computer-generated 3-dimensional (3D) models. Seven anatomic measurements were performed on each scapula and 3D model. Mean differences between corresponding measurements of specimen and model were small (<3 mm). Intraobserver and interobserver reliability for cadaveric measurements and rescan and interobserver reliability for model measurements were all excellent (R(2) = 0.99). Patient positioning was not a significant source of error in obtaining measurements from 3D models. Results from this work verify that accurate and reproducible 3D models can be created from in situ scapulae by use of effective segmentation.

Glenoid resurfacing: what are the limits to asymmetric reaming for posterior erosion?

Eccentric posterior glenoid erosion is a common condition in osteoarthritis. No limits have ever been placed on the degree of eccentric erosion that can be corrected while still maintaining sufficient bone stock to implant a glenoid securely. Five cadaveric scapulae were dissected. Posterior glenoid erosion was created to simulate retroversion of 15 degrees or more. A computed tomography (CT) scan confirmed the degree of glenoid retroversion. The glenoid was then reshaped to correct the glenoid retroversion to neutral, and a glenoid component with central and peripheral pegs was inserted. A second CT scan confirmed the correction to neutral and also evaluated the fit of the component into the glenoid. In all 5 experimental cases, at least 1 of the 4 pegs penetrated the glenoid vault. In 1 case, there was a fracture of the anterior rim. Glenoid retroversion of 15 degrees or more cannot be satisfactorily corrected simply by reaming to lower the anterior edge of the glenoid and restore neutral version when using a glenoid component with peripheral pegs.

Nonprosthetic glenoid arthroplasty with humeral hemiarthroplasty and total shoulder arthroplasty yield similar self-assessed outcomes in the management of comparable patients with glenohumeral arthritis

The risk of glenoid component failure has led us to explore nonprosthetic glenoid arthroplasty coupled with humeral hemiarthroplasty, the "ream and run" (R&R) procedure, for the management of glenohumeral arthritis in active patients. We hypothesized that patients having a R&R procedure would have outcomes comparable with those of similar patients having a total shoulder arthroplasty (TSA). A case-matched control study compared 35 consecutive patients (32 men, 3 women) with an average age of 56 years, after R&R with matched controls having TSA. The respective Simple Shoulder Test (SST) scores for the R&R and TSA groups were 4.5 and 4.0 before surgery, 7.8 and 9.6 at 12 months, 8.3 and 10.2 at 18 months, 8.9 and 9.4 at 24 months, 9.4 and 9.6 at 30 months, and 9.5 and 10.0 at 36 months. The "ream and run" procedure can offer similar functional recovery to patients with total shoulder arthroplasty, although the time to recovery may be longer.

Developments in shoulder arthroplasty

Indications for shoulder arthroplasty are numerous, mainly owing to glenohumeral osteoarthritis, rheumatoid arthritis, or fracture of the proximal humerus. However, the anatomy and the biomechanics of the shoulder are complex and shoulder arthroplasty has evolved significantly over the past 30 years. This paper presents the main recent evolutions in shoulder replacement, the questions not answered yet, and the main future areas of research. The review focuses firstly on the design, positioning, and fixation of the humeral component, secondly on the design, positioning, and fixation of the glenoid implant, and thirdly on other concepts of shoulder arthroplasty such as the reversed prosthesis, the cementless surface replacement arthroplasty, and the bipolar arthroplasty. This review demonstrates that more research is needed. Although, in the long term, large randomized trials are needed to settle the fundamental questions of what type of replacement and which kind of fixation should be used, biomechanical research in the laboratory should be focused primarily on the comprehension of glenoid loosening, which is a major cause of total shoulder arthroplasty failure, and the significance of radiolucent lines which are often seen but with no clear understanding about their relation with failure.

Schulterendoprothetik

The design of shoulder prostheses has been developed through four generations which mirror adaptation to our increasing knowledge of the biomechanics of the shoulder joint. Modern shoulder prostheses are adapted to the size, inclination, posterior offset, and retrotorsion of the shoulder. The main reasons for implantation of a shoulder prosthesis are primary osteoarthritis, posttraumatic and rheumatoid arthritis, avascular necrosis, instability arthritis and cuff defect arthropathy. Typical implants are cup prostheses for surface replacement, anatomical stem prostheses, and reverse prostheses. Total prostheses are functionally better as soon as the arthritis involves the glenoid, whereas hemiprostheses should be preferred as long as the glenoid is intact. The stem is mostly cemented, whereas in younger patients with good bone quality a cementless stem may be used. Cemented glenoids may be considered as standard.

The effect of cementing technique on structural fixation of pegged glenoid components in total shoulder arthroplasty

Although loosening of cemented glenoid components is one of the major complications of total shoulder arthroplasty, there is little information about factors affecting initial fixation of these components in the scapular neck. This study was performed to assess the characteristics of structural fixation of pegged glenoid components, if inserted with two different recommended cementing techniques. Six fresh-frozen shoulder specimens and two types of glenoid components were used. The glenoids were prepared according to the instructions and with the instrumentation of the manufacturer. In 3 specimens, the bone cement was inserted into the peg receiving holes (n = 12) and applied to the back surface of the glenoid component with a syringe. In the other 3 specimens, the cement was inserted into the holes (n = 15) by use of pure finger pressure: no cement was applied on the backside of the component. Micro-computed tomography scans with a resolution of 36 microm showed an intact cement mantle around all 12 pegs (100%) when a syringe was used. An incomplete cement plug was found in 7 of 15 pegs (47%) when the finger-pressure technique was used. Cement penetration into the cancellous bone was deeper in osteopenic bone. Application of bone cement on the backside of the glenoid prosthesis improved seating by filling out small spaces between bone and polyethylene resulting from irregularities after reaming or local cement extrusion from a drill hole. The fixation of a pegged glenoid component is better if the holes are filled with cement under pressure by use of a syringe and if cement is applied to the back of the glenoid component than if cement is inserted with pure finger pressure and no cement is applied to the back surface of the component.