Glenoid cementing may generate sufficient heat to endanger the surrounding bone

An experimental study on the impact of prosthesis temperature on the biomechanical properties of bone cement fixation

PURPOSE

To investigate the effect of the femoral component and tibial plateau component temperature on the strength of cement fixation during total knee arthroplasty (TKA).

METHODS

Femoral prosthesis, tibial plateau prosthesis, and polypropylene mold base were used to simulate TKA for bone cement fixation. Pre-cooling or pre-warming of femoral and tibial plateau components at different temperatures (4 °C, 15 °C, 25 °C, 37 °C, 45 °C), followed by mixing and stirring of bone cement at laboratory room temperature (22 °C), were performed during research. The prosthesis and the base adhered together, and the bone cement was solidified for 24 h at a constant temperature of 37 °C to verify the hardness of the bone cement with a push-out test.

RESULTS

The push-out force of the femoral prosthesis after fixation was higher than that of the tibial plateau prosthesis, and with the increase of the prosthesis temperature, the push-out force after fixation of the bone cement also increased linearly and the porosity of the prosthetic cement in the tibia and femur decreased as the temperature increased.

CONCLUSION

Without changing the mixing temperature and solidification temperature, the fixation strength of the femoral prosthesis is higher than that of the tibial plateau prosthesis. Properly increasing the temperature of the prosthesis can increase the push-out force of the fixation strength.

Glenoid Prosthesis Design Considerations in Anatomic Total Shoulder Arthroplasty

Total shoulder arthroplasty is an increasingly popular option for the treatment of glenohumeral arthritis. Historically, the effectiveness of the procedure has largely been determined by the long-term stability of the glenoid component. Glenoid component loosening can lead to clinically concerning complications including pain with movement, loss of function, and accumulation of debris which may require surgery to revise. In response, there has been a push to optimize the design of the glenoid prosthesis. Traditional contemporary glenoid components use pegs for fixation and are made entirely of polyethylene. Variations on the standard implant include keeled, metal-backed, hybrid, augmented, and inlay designs. There is a wealth of biomechanical and clinical studies that report on the effectiveness of these different designs. The purpose of this review is to summarize existing literature regarding glenoid component design and identify key areas for future research. Knowledge of the rationale underlying glenoid design will help surgeons select the best component for their patients and optimize outcomes following TSA.

Clinical and radiographic outcomes of total shoulder arthroplasty with a partially cemented all-polyethylene pegged bone-ingrowth glenoid component: a systematic review

BACKGROUND

Several articles have been published reporting on the clinical performance of a novel pegged, all-polyethylene glenoid component design which features a central peg, circumferentially fluted, interference-fit peg for tissue integration and three small peripheral pegs for cementing. However, no systematic review exists to this date.

METHODS

The US National Library of Medicine (PubMed/MEDLINE), EMBASE, and the Cochrane Database of Systematic Reviews were queried for publications up to May 2020.

RESULTS

Overall, 13 articles were included for analysis (560 operated shoulders, range of mean follow-up: 2-6 years). The survival rate was 98.2% (550 out of 560 cases), while the rate of aseptic loosening was 0.2% (1 out of 560 cases). There were 139 cases (out of 399 reported; 34.1%) with peri-glenoid radiolucency, and 35 cases (out of 223 reported; 15.7%) of asymptomatic central peg osteolysis, with 1 of them undergoing revision.

CONCLUSIONS

There was fair quality of evidence to show that partially cemented all-polyethylene pegged bone-ingrowth glenoid components produce promising results, with a low revision rate in the short- to medium-term follow-up. Nevertheless, this analysis showed high rates of both radiolucency of the glenoid component and osteolysis around the central peg which raise concern for potential failure of this glenoid component in the long-term follow-up.

LEVEL OF EVIDENCE

Systematic review, IV.

Medium-term rates of radiolucency after primary total shoulder arthroplasty using a cementless metal-backed pegged polyethylene glenoid

BACKGROUND

Total shoulder arthroplasty is an established treatment with the commonest cause of failure loosening of the glenoid component. Hydroxyapatite metal-backed glenoid components could offer better survivorship due to improved fixation. The aim of this study was to investigate periprosthetic radiolucency rates associated with an uncemented, metal-backed polyethylene glenoid component with medium-term results.

METHODS

A single centre retrospective study examining radiological outcomes of the Epoca metal-backed glenoid component. Radiographs were analysed for post-operative adequacy of glenoid seating and radiographs at follow-up assessed for periprosthetic lucencies and any revision procedures were recorded.

RESULTS

Forty-one patients were followed up with a mean follow-up time of 5.5 years (3-8 years). Primary indication for total shoulder arthroplasty was osteoarthritis (80%). Mean age was 69 years (53-86 years). Ninety-five per cent of glenoid components were completely seated. At follow-up six patients had undergone revision (14.6%). Thirty of the remaining patients (86%) did not demonstrate any radiolucency on follow-up radiographs. Complete glenoid seating post-operatively was associated with lower rate of subsequent radiolucency and revision (P < 0.01).

CONCLUSION

Low rates of radiolucency at medium-term follow-up with an uncemented metal-backed glenoid, however significant rates of revision. Complete seating of the glenoid component was associated with lower rates of radiolucency and revision.

The study of 2-dimensional computed tomography scans of the glenoid anatomy in relation to reverse shoulder arthroplasty in the Southern Chinese population

Background

Reverse shoulder arthroplasty is becoming an increasingly common surgical procedure in Hong Kong, as well as in many other countries worldwide. The aim of this study is to describe the glenoid anatomy in the Southern Chinese population. We are interested to know whether commercially available glenoid implants are suitable for this population and whether there are any steps or precautions we can take during surgery to optimize the clinical outcome for these patients.

Method

A total of 244 shoulders of Southern Chinese patients were analyzed using 2-dimensional computed tomography, formatted to align along the scapular axis. The anatomic parameters analyzed included the shape, axial configuration, maximum width, maximum height, version, and presence of bone defect.

Results

In our study, 76.6% of glenoids were pear-shaped, 23.0% were elliptical, and only 0.4% were inverted pear in shape. Of all glenoids, 95.1% of glenoids had posterior-prominent axial configuration, whereas 4.9% had neutral axial configuration. The mean maximum glenoid height for both genders was 33.8 mm, whereas the mean maximum glenoid height was 32.2 mm for women and 36.6 mm for men. The mean maximum glenoid width for both genders was 25.8 mm, whereas the mean maximum glenoid width was 24.8 mm for women and 27.3 mm for men. The differences in measurements between genders were statistically significant. Of all glenoids, 46.3% of the glenoids were retroverted, whereas 53.7% of the glenoids were anteverted. The mean version for both genders was 0.77 degrees anteversion. The mean version was 1.16 degrees anteversion for women and 0.10 degrees anteversion for men. Of the 244 glenoids, 4 had bone defects. In our study, 39.8% of patients had mean maximum glenoid widths that were less than 25 mm, which is the smallest size available for most conventional glenoid baseplates.

Conclusion

A significant portion of the Southern Chinese population has glenoid widths that are smaller than the smallest commercially available glenoid baseplates. Understanding the glenoid anatomy is crucial in the case of reverse shoulder arthroplasty, as it has significant implications in implant design, operative planning, and surgical outcomes.

Short-term rates of radiolucency after primary total shoulder arthroplasty using a cementless metal-backed pegged polyethylene glenoid

BACKGROUND

Total shoulder arthroplasty has shown good clinical efficacy in treating primary and secondary degenerative conditions of the glenohumeral joint. Glenoid loosening, however, remains the commonest cause of failure. The purpose of this study was to investigate the rate of radiographic periprosthetic lucency associated with the use of an uncemented, pegged, metal-backed polyethylene glenoid component.

MATERIALS AND METHODS

A retrospective, single-centre study using the Epoca (Synthes, Paoli, Pennsylvania) metal-backed glenoid component. Operations were performed by two experienced consultant upper limb surgeons. Radiographs were analysed for immediate post-operative component seating and periprosthetic radiolucent lines at predefined regular post-operative intervals. Intra- and inter-observer reliability was assessed to improve validity of results.

RESULTS

Mean age and follow-up was 72 (48-91) years and 2.5 years (2-5), respectively. Main indications for total shoulder arthroplasty were primary osteoarthritis, rheumatoid arthritis, revision for failed hemi-arthroplasty and acute fracture. Ninety-six per cent of components were completely seated post-operatively. Fifty-four (95%) of the 57 shoulders had no periprosthetic radiolucent lines at most recent follow-up. Complete post-operative glenoid seating was significantly associated with the absence of later periprosthetic radiolucency (p < 0.01).

CONCLUSION

This study reports low early radiolucency rates with the pegged, uncemented, metal-backed polyethylene glenoid prosthesis used. Excellent post-operative glenoid seating is associated with a significantly lower rate of radiolucency. Longer follow-up data are required to confirm these early promising results.Level of evidence: Therapeutic, level IV.

Integração óssea e prevalência de linhas radiotransparentes ao redor dos pinos de componentes glenoidais minimamente cimentados na artroplastia total de ombro

Objectives  Glenoid component failure is the main cause of total shoulder arthroplasty (TSA) revision, and component design seems to influence the failure rate. The aim of the present study was to clinically and radiographically (through X-rays and computed tomography scan) evaluate the results of TSA using a minimally cemented glenoid component.

Methods  Total should arthroplasties performed using the minimally cemented Anchor Peg (DuPuy Synthes, Warsaw, IN, USA) glenoid component between 2008 and 2013 were evaluated. University of California at Los Angeles (UCLA) scores were calculated, and standardized plain film and computed tomography images were obtained, at a minimum follow-up of 24 months. The presence of bone between the fins of the central component peg, which indicates its integration, was assessed on the images, as well the presence of radiolucent lines around the glenoid component.

Results  Nineteen shoulders in 17 patients were available for evaluation. According to the UCLA score, clinical results were satisfactory in 74% of cases and fair in 21% of cases. One patient had a poor result. Component integration was found in 58% of patients (total in 42% and partial in 16%). Radiolucent lines were observed in 52% of cases. No relationship was detected between component integration and clinical results.

Conclusion  Satisfactory clinical results were achieved in most patients undergoing TSA using a minimally cemented glenoid component. Radiolucent lines around the glenoid component are common, but do not interfere with the clinical results.

Level of evidence IV; Case series; Treatment study.

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.

Cementless versus cemented glenoid components in conventional total shoulder joint arthroplasty: analysis from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

Glenoid loosening is a common mode of failure after total shoulder arthroplasty (TSA). Newer cementless glenoid components have been introduced to promote biological fixation with the aim to decrease glenoid loosening. Limited data are available comparing revision rates between cemented and cementless glenoid fixation in TSA. The study aim was to compare the revision rates of cemented and cementless design glenoid components used in conventional TSA performed for the diagnosis of osteoarthritis. The secondary aim was to compare various subclasses of glenoid components.

METHODS

Data were obtained between April 16, 2004, and December 31, 2016, from the Australian Orthopaedic Association National Joint Replacement Registry. Within the study period, 10,805 primary conventional TSAs were identified. The analysis was undertaken for the diagnosis of osteoarthritis, which represented 95.8% of all conventional TSA procedures.

RESULTS

At 5 years, in patients with primary TSA procedures, those with cemented glenoids had a lower revision rate than those with cementless glenoids: 3.7% versus 17.9% (hazard ratio for entire period, 4.77). The most common revision diagnosis for primary conventional TSA with cementless glenoid fixation was rotator cuff insufficiency (4.4% for cementless vs 0.4% for cemented), instability and/or dislocation (3.8% for cementless vs 0.8% for cemented), and loosening and/or lysis (1.1% for cementless vs 1.1% for cemented).

CONCLUSIONS

Cementless glenoid components in conventional TSA had a significantly higher revision rate than cemented glenoid components. The loosening rates between cemented and cementless glenoid components were similar. Glenoid design and fixation are important considerations when selecting a prosthesis for TSA.

Stability of small pegs for cementless implant fixation

Most glenoid implants rely on large centrally located fixation features to avoid perforation of the glenoid vault in its peripheral regions. Upon revision of such components there may not be enough bone left for the reinsertion of an anatomical prosthesis. Multiple press-fit small pegs would allow for less bone resection and strong anchoring in the stiffer and denser peripheral subchondral bone. This study assessed the fixation characteristics, measured as the push-in (P_in ) and pull-out (P_out ) forces, and spring-back, measured as the elastic displacement immediately after insertion, for five different small press-fitted peg configurations manufactured out of UHMWPE cylinders (5 mm diameter and length). A total of 16 specimens for each configuration were tested in two types of solid bone substitute: Hard (40 PCF, 0.64 g/cm³ , worst-case scenario of P_in ) and soft (15 PCF, 0.24 g/cm³ , worst-case scenario of spring-back and P_out ). Two different diametric interference-fits were studied. Geometries with lower stiffness fins (large length to width aspect ratio) were the best performing designs in terms of primary fixation stability. They required the lowest force to fully seat, meaning they are less damaging to the bone during implantation, while providing the highest P_out /P_in ratio, indicating that when implanted they provide the strongest anchoring for the glenoid component. It is highlighted that drilling of chamfered holes could minimize spring-back displacements. These findings are relevant for the design of implants press-fitted pegs because primary fixation has been shown to be an important factor in achieving osseointegration and longevity of secondary fixation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2765-2772, 2017.

Total shoulder replacement using a bone ingrowth central peg polyethylene glenoid component: a prospective clinical and computed tomography study with short- to mid-term follow-up

AIM OF THE STUDY

To assess the clinical and computed tomography (CT) outcomes of shoulder replacement with a novel bone ingrowth all-polyethylene glenoid component (APGC).

METHODS

Twenty-eight patients (30 shoulders) with osteoarthritis, mean age 62.3 years (range, 45-75), were implanted with the novel component between 2011 and 2013. Patients were evaluated by active range of motion (ROM), Constant-Murley score (CMS), simple shoulder test (SST), X-rays, and multidetector CT at two months and at a mean follow-up of 31 months (range, 24-39). Early and late follow-up CT scans were available for 21/30 shoulders.

RESULTS

Median ROM increased from 105 to 160° for anterior elevation, from 100 to 160° for lateral elevation, from 20 to 40° for external rotation, and from 2 to 10 points for internal rotation (all p < 0.001). CMS rose from 30 to 80.5 points and SST from 2.5 to 11 (both p < 0.0001). None of the glenoid components migrated. Progressive radiolucency was seen in 28/30 shoulders. There was a strong correlation between greater bone ingrowth (median Arnold score: 7) and lower radiolucency score (median Yian score: 2) at the last follow-up (p < 0.001). Osteolysis around the central peg was seen in two shoulders. There was no correlation between clinical scores and CT findings (p >0.05).

DISCUSSION

The partially cemented glenoid component for TSR assessed in this study resulted in satisfactory shoulder function at an early follow-up. The glenoid prosthesis was stable, with few radiolucent lines and good central peg bone ingrowth.

CONCLUSIONS

The satisfactory bone ingrowth documented on CT is encouraging and supports the use of the new prosthesis. Long-term follow-up studies can confirm if this device represents a rational alternative to fully cemented polyethylene glenoids.

Observation of initial postoperative radiolucent lines using a modern pegged-glenoid design

PURPOSE

Glenoid component loosening remains a common mode of failure for total shoulder arthroplasty and has inspired improvements in implant design, instrumentation, and surgical technique. The purpose of this manuscript was to evaluate the incidence of radiolucent lines and glenoid seating on initial postoperative radiographs using a modern pegged-glenoid design, instrumentation, and surgical technique.

MATERIALS AND METHODS

We performed a retrospective analysis of a consecutive series of 100 pegged-glenoid total shoulder replacements. In cases of excessive glenoid version, the glenoid was asymmetrically reamed to recreate more normal version. Initial postoperative radiographs were evaluated for the presence of radiolucent lines and completeness of glenoid seating. The preoperative glenoid version measured on axial computed tomography (CT) scans was used to compare differences in version among those with complete and incompletely seated glenoids.

RESULTS

The rate of radiolucent lines observed on postoperative radiographs was 0%. Complete glenoid seating (Grade A) was observed in 81 patients (observer 1) and 82 patients (observer 2). Measurements of preoperative CT scans found a higher percentage of abnormal glenoid version for incompletely seated glenoids (47%) than completely seated glenoids (34%) but no significant difference (P = 0.327). The mean preoperative glenoid retroversion for incompletely seated glenoids was 12.1° and 9.1° for completely seated glenoids (P = 0.263).

CONCLUSIONS

Modern surgical techniques, surgical instrumentation, and peg glenoid design have facilitated the ability to eliminate radiolucent lines on initial postoperative radiographs with high rates of complete seating of glenoid components. Incomplete seating may be related to incomplete correction of glenoid version.

Radiographic and clinical outcomes of total shoulder arthroplasty with an all-polyethylene pegged bone ingrowth glenoid component: prospective short- to medium-term follow-up

BACKGROUND

Glenoid components often cause total shoulder arthroplasty failure. This study examines short-term to midterm radiographic and clinical results of a hybrid glenoid component with 3 cemented peripheral pegs and a central peg, which allows biologic fixation with use of native humeral head autograft.

METHODS

In 4 years, 80 glenoid components were implanted during primary total shoulder arthroplasty with at least 2-year follow-up data. Within 12 months, 4 shoulders were revised and excluded from final analyses. Seven patients did not complete their questionnaires. Outcomes data included the American Shoulder and Elbow Surgeons (ASES) questionnaire, Constant score, and satisfaction score. A shoulder and elbow fellowship-trained surgeon, not involved in the care of these patients, analyzed radiographs for radiolucent lines, glenoid seating, and radiodensity in between the flanges of the central peg.

RESULTS

Only 1 of 80 shoulders was revised for aseptic glenoid loosening. At final follow-up, 81.6% had a radiolucency grade of 0 or 1. Nearly 90% had a glenoid seating grade of A or B. Grade 2 or 3 bone around the central peg was seen in 88.2%. No statistical association existed between Walch glenoid types and radiolucency grades, bone grades around the central peg, perfect radiolucency grade, seating grade, and grade 3 bone around the central peg. There was significant improvement in mean ASES score, adjusted ASES pain score, Constant score, and satisfaction score as well as in forward flexion, abduction, and external rotation.

CONCLUSIONS

The hybrid glenoid can produce stable radiographic and clinical outcomes at short- to medium-term follow-up.

No differences in early results of a hybrid glenoid compared with a pegged implant

BACKGROUND

Glenoid component loosening after total shoulder arthroplasty is one of the most common causes of failure. A hybrid glenoid that uses peripherally cemented pegs and a central press-fit post may improve implant longevity.

QUESTIONS/PURPOSES

We asked, compared with polyethylene pegged glenoid implants, do hybrid glenoid implants with a titanium post provide (1) better ingrowth with fewer radiolucencies, (2) better outcome and pain scores, and (3) lower risk of complications and revisions?

METHODS

Between 2009 and 2010, 126 patients underwent primary total shoulder arthroplasty for osteoarthritis. Patients were included in this retrospective study if they consented for inclusion in a shoulder arthroplasty registry, had complete baseline and 2-year data, and had complete radiographs. Eighty-three (67%) were available at an average followup of 3.2 years (range, 24-45 months). Forty received a conventional all-polyethylene pegged glenoid and 43 received a hybrid component. During the period in question, four of the participating surgeons used only one implant, and four used only the other; there was one high-volume surgeon in each of the study groups. Radiographs were taken at the 2-year followup and analyzed for radiolucent lines. CT scans were obtained randomly for 10 patients with hybrid glenoid implants to assess bone ongrowth. American Shoulder and Elbow Surgeons score, VAS score, complications and revisions were recorded.

RESULTS

At final followup, radiolucent lines between the two study groups were not different (hybrid, 1.0 ± 0.4; pegged, 1.6 ± 0.3; mean difference, 0.6; 95% CI, 0.85-1.72; p = 0.323). Final VAS pain scores were not different (hybrid, 1.2 ± 0.2; pegged, 1.5 ± 0.3; p = 0.056). Change in American Shoulder and Elbow Surgeons scores were not different (hybrid, 33.7 ± 7.3; pegged, 35.5 ± 8.2; p = 0.283). There were no differences in complication risk (hybrid, one of 43 [2.3%]; pegged, three of 40 [7.5%]; relative risk, 2.3; 95% CI, 0.82-3.12; p = 0.061).

CONCLUSIONS

With the numbers available and at early followup, there were no differences between the hybrid and pegged glenoids in terms of fixation, functional outcome, pain scores, and complications. CT scans confirmed bone ongrowth on the porous titanium post in a small subcohort of patients. Further studies are needed to determine how this new implant will perform with time. Until then, its use should be initiated with caution.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Five- to ten-year follow-up with a partially cemented all-polyethylene bone-ingrowth glenoid component

BACKGROUND

Although total shoulder arthroplasty has demonstrated better clinical outcomes than hemiarthroplasty, glenoid component loosening is a common complication. Recently, a novel partially cemented all-polyethylene fluted central peg bone-ingrowth component was introduced.

METHODS

Forty-two consecutive total shoulder arthroplasties from 2003 to 2007 performed by a single surgeon were evaluated radiographically and clinically with American Shoulder and Elbow Surgeons (ASES) scores and range of motion.

RESULTS

The average follow-up was 80 months (63-114); the average forward elevation improved from 107° to 137°, and external rotation improved from 30° to 37° at the latest follow-up. The average ASES score improved from 50 to 84. There was a strong correlation with the mean peripheral peg lucent line score (Lazarus score), which was 0.81, with the mean anchor peg lucent line score, which was 0.50 (P < .001). An analysis of polyethylene before and after cross-linking revealed a strong correlation between components with cross-linking and the Lazarus scores and the central fluted peg scores. Overall, there was 97% survivorship at 80 months. On radiographs, 81% of the central fluted pegs had complete incorporation with no lucent lines. These lucent lines correlated with lower ASES scores, suggesting that loosening of the glenoid decreases functional outcome.

CONCLUSION

Care should be taken in preparing the central fluted peg as perforation of the vault can lead to central flute peg lucent line formation, whereas perforation of the peripheral pegs does not seem to negatively affect the outcome.

Bone Graft Substitute Provides Metaphyseal Fixation for a Stemless Humeral Implant

Stemless humeral fixation has become an alternative to traditional total shoulder arthroplasty, but metaphyseal fixation may be compromised by the quality of the trabecular bone that diminishes with age and disease, and augmentation of the fixation may be desirable. The authors hypothesized that a bone graft substitute (BGS) could achieve initial fixation comparable to polymethylmethacrylate (PMMA) bone cement. Fifteen fresh-frozen human male humerii were randomly implanted using a stemless humeral prosthesis, and metaphyseal fixation was augmented with either high-viscosity PMMA bone cement (PMMA group) or a magnesium-based injectable BGS (OsteoCrete; Bone Solutions Inc, Dallas, Texas) (OC group). Both groups were compared with a control group with no augmentation. Initial stiffness, failure load, failure displacement, failure cycle, and total work were compared among groups. The PMMA and OC groups showed markedly higher failure loads, failure displacements, and failure cycles than the control group (P<.01). There were no statistically significant differences in initial stiffness, failure load, failure displacement, failure cycle, or total work between the PMMA and OC groups. The biomechanical properties of magnesium-based BGS fixation compared favorably with PMMA bone cement in the fixation of stemless humeral prostheses and may provide sufficient initial fixation for this clinical application. Future work will investigate the long-term remodeling characteristics and bone quality at the prosthetic-bone interface in an in vivo model to evaluate the clinical efficacy of this approach.

The glenoid component in anatomic shoulder arthroplasty

Ideal management of the glenoid in anatomic shoulder arthroplasty remains controversial. Glenoid component loosening remains a common source of clinical concern and, in young, active patients, implantation of a glenoid prosthesis is often avoided. Efforts to decrease glenoid loosening have resulted in changes to prosthetic design and implantation techniques. Currently, a wide variety of glenoid component options are available, including metal-backed or all-polyethylene, bone ingrowth or ongrowth, inset, and augmented designs. Additionally, several alternatives are available for the young, active patient, including hemiarthroplasty, nonprosthetic resurfacing, and tissue interposition. Many recent clinical and biomechanical studies have examined these implant options. A thorough knowledge of glenoid anatomy, pathology, implant options, indications, and principles of implantation is necessary to optimize the outcome following anatomic shoulder arthroplasty.

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.

Thermal damage during humeral reaming in total shoulder resurfacing

INTRODUCTION

Total shoulder resurfacing (TSR) provides a reliable solution for the treatment of glenohumeral arthritis. It confers a number of advantages over traditional joint replacement with stemmed humeral components, in terms of bone preservation and improved joint kinematics. This study aimed to determine if humeral reaming instruments produce a thermal insult to subchondral bone during TSR.

PATIENTS AND METHODS

This was tested in vivo on 13 patients (8 with rheumatoid arthritis and 5 with osteoarthritis) with a single reaming system and in vitro with three different humeral reaming systems on saw bone models. Real-time infrared thermal video imaging was used to assess the temperatures generated.

RESULTS

Synthes (Epoca) instruments generated average temperatures of 40.7°C (SD 0.9°C) in the rheumatoid group and 56.5°C (SD 0.87°C) in the osteoarthritis group (P = 0.001). Irrigation with room temperature saline cooled the humeral head to 30°C (SD 1.2°C). Saw bone analysis generated temperatures of 58.2°C (SD 0.79°C) in the Synthes (Epoca) 59.9°C (SD 0.81°C) in Biomet (Copeland) and 58.4°C (SD 0.88°C) in the Depuy Conservative Anatomic Prosthesis (CAP) reamers (P = 0.12).

CONCLUSION

Humeral reaming with power driven instruments generates considerable temperatures both in vivo and in vitro. This paper demonstrates that a significant thermal effect beyond the 47°C threshold needed to induce osteonecrosis is observed with humeral reamers, with little variation seen between manufacturers. Irrigation with room temperature saline cools the reamed bone to physiological levels and should be performed regularly during this step in TSR.

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.

Pressurisation leads to better cement penetration into the glenoid bone: a cadaveric study

The aim of this study was to compare a third-generation cementing procedure for glenoid components with a new technique for cement pressurisation. In 20 pairs of scapulae, 20 keeled and 20 pegged glenoid components were implanted using either a third-generation cementing technique (group 1) or a new pressuriser (group 2). Cement penetration was measured by three-dimensional (3D) analysis of micro-CT scans. The mean 3D depth of penetration of the cement was significantly greater in group 2 (p < 0.001). The mean thickness of the cement mantle for keeled glenoids was 2.50 mm (2.0 to 3.3) in group 1 and 5.18 mm (4.4 to 6.1) in group 2, and for pegged glenoids it was 1.72 mm (0.9 to 2.3) in group 1 and 5.63 mm (3.6 to 6.4) in group 2. A cement mantle < 2 mm was detected less frequently in group 2 (p < 0.001). Using the cement pressuriser the proportion of cement mantles < 2 mm was significantly reduced compared with the third-generation cementing technique.

Heat generated with pegged or keeled glenoid components fixed with defined amounts of cement

Glenoid component loosening is a common complication of total shoulder arthroplasty and has been associated with the progression of radiolucent lines at the glenoid bone-cement interface. Generation of heat during the exothermic reaction of cement curing may cause osteonecrosis of bone, potentially leading to the development of radiolucent lines. The purpose of this study was to measure the heat generated with various defined amounts of cement used for glenoid component fixation.Ten fresh-frozen cadaver scapulas were randomized to receive a keeled or pegged component with 1, 2, 3, 5, or 7 g of cement for fixation. An infrared camera was used to record the surface temperature generated during the cement curing process to an accuracy of ±2.0°C. Computed tomography was used to evaluate the cement mantle. The maximum temperatures generated did not exceed the critical value for osteonecrosis (56°C) in any of the specimens. The 4 specimens without a complete mantle were those fixed with a smaller quantity of cement (1, 2, or 3 g), and the largest cement mantle thicknesses were observed with the use of 7 g of cement.Up to 7 g of cement can be used without significant concern for thermal necrosis. Incomplete cement mantles were observed when ≤3 g of cement was used for fixation. Our results suggest that surgeons should use >3 g of cement to avoid incomplete cement mantles and that up to 7 g of cement can safely be used for glenoid fixation.

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.

Vacuum assist glenoid fixation: does this technique lead to a more durable glenoid component?

INTRODUCTION

This was a prospective random study to determine if suction applied to the glenoid vault through the coracoid process would facilitate deeper penetration of cement into the vault, and if deeper penetration would lead to a more durable glenoid component.

MATERIALS AND METHODS

A group of 96 patients were randomly assigned to 1 of 2 pathways for glenoid fixation. One was cemented using modern "third generation" cementing techniques, while the second group utilizes these same steps as well as a vacuum assist (weep-hole) technique. We measured the "amount" of cement that penetrated the vault around either a pegged or keeled component as a function of the area of the cement noted on the fluoroscopic AP film that was taken 35.1 months postoperatively. We were able to determine the area of this irregular shape by using a program that was specifically written for the study. The films were evaluated by the senior author, as well as 2 musculoskeletal trained radiologists blind to the technique.

RESULTS

The area of the cement mantle was found to be significantly larger (P < .005) in the group with the vacuum assist technique. There was a positive relationship between the durability of the cement mantle as determined by the presence and the extent of radiolucent lines and the size of the cement mantle (P < .001).

CONCLUSION

If a cement technique is chosen to implant a glenoid component, the vacuum assist weep-hole technique is the most effective cementing technique to achieve durable fixation.

Bone presence between the central peg's radial fins of a partially cemented pegged all poly glenoid component suggest few radiolucencies

BACKGROUND

Cement penetration problems and/or cement-induced bone necrosis may contribute to glenoid component failures. An all polyethylene component was developed that promotes biologic fixation between radial fins of its central peg and utilizes minimal cement fixation for its peripheral pegs, but it has little published data. We hypothesized better bone presence between the radial fins would be associated with less overall radiolucencies. This study's purpose was to utilize computed tomography (CT) and plain films to assess for bone between the central peg's radial fins and to assess overall component radiolucencies.

MATERIALS AND METHODS

Thirty-five of 48 consecutively performed total shoulder arthroplasties (TSA) for primary glenohumeral osteoarthritis were in patients able to participate a minimum 2 years after surgery. All had reamed humeral head bone packed between radial fins of the central peg and minimal cement for the peripheral pegs. Thin cut (0.625 mm) CT scans, standardized plain films, Simple Shoulder Tests (SST), and Constant scores were obtained. A musculoskeletal radiologist calculated Yian CT scores, bone presence between fins on CT, and Lazarus radiolucency scores.

RESULTS

At a mean of 43 months, by CT: 1) better Yian scores correlated with more bone between fins, and 2) bone was present in 6/6 inter-fin compartments in 23/35 shoulders, averaging 4.5/6 overall. Mean Lazarus radiolucency score was 0.45. Mean SST and Constant scores were 10.3 and 81.3, respectively.

CONCLUSION

TSA utilizing autologous bone in inter-fin compartments of the central peg and minimal peripheral peg cement maintained bone presence a minimum 2 years post-op. More bone imparted fewer overall component radiolucencies.

Thermal effects of glenoid reaming during shoulder arthroplasty in vivo

BACKGROUND

Glenoid component loosening is a common cause of failure of total shoulder arthroplasty. It has been proposed that the heat generated during glenoid preparation may reach temperatures capable of producing osteonecrosis at the bone-implant interface. We hypothesized that temperatures sufficient to induce thermal necrosis can be produced with routine drilling and reaming during glenoid preparation for shoulder arthroplasty in vivo. Furthermore, we hypothesized that irrigation of the glenoid during reaming can reduce this temperature increase.

METHODS

Real-time, high-definition, infrared thermal video imaging was used to determine the temperatures produced by drilling and reaming during glenoid preparation in ten consecutive patients undergoing total shoulder arthroplasty. The maximum temperature and the duration of temperatures greater than the established thresholds for thermal necrosis were documented. The first five arthroplasties were performed without irrigation and were compared with the second five arthroplasties, in which continuous bulb irrigation was used during drilling and reaming. A one-dimensional finite element model was developed to estimate the depth of penetration of critical temperatures into the bone of the glenoid on the basis of recorded surface temperatures.

RESULTS

Our first hypothesis was supported by the recording of maximum surface temperatures above the 56°C threshold during reaming in four of the five arthroplasties done without irrigation and during drilling in two of the five arthroplasties without irrigation. The estimated depth of penetration of the critical temperature (56°C) to produce instantaneous osteonecrosis was beyond 1 mm (range, 1.97 to 5.12 mm) in four of these patients during reaming and one of these patients during drilling, and two had estimated temperatures above 56°C at 3 mm. Our second hypothesis was supported by the observation that, in the group receiving irrigation, the temperature exceeded the critical threshold in only one specimen during reaming and in two during drilling. The estimated depth of penetration for the critical temperature (56°C) did not reach a depth of 1 mm in any of these patients (range, 0.07 to 0.19 mm).

CONCLUSIONS

Temperatures sufficient to induce thermal necrosis of glenoid bone can be generated by glenoid preparation in shoulder arthroplasty in vivo. Frequent irrigation may be effective in preventing temperatures from reaching the threshold for bone necrosis during glenoid preparation.

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.

Polymethylmethacrylate: properties and contemporary uses in orthopaedics

Polymethylmethacrylate (PMMA) has been used in orthopaedics since the 1940s. Despite the development and popularity of new biomaterials, PMMA remains popular. Although its basic components remain the same, small proprietary and environmental changes create variations in its properties. PMMA can serve as a spacer and as a delivery vehicle for antibiotics, and it can be placed to eliminate dead space. Endogenous and exogenous variables that affect its performance include component variables, air, temperature, and handling and mixing. PMMA is used in hip arthroplasty and vertebral augmentation, notably, vertebroplasty and kyphoplasty. Cardiopulmonary complications have been reported.

In vitro measurement of temperature changes during implantation of cemented glenoid components

BACKGROUND AND PURPOSE

It is unclear whether the increase in temperature during cement curing may cause osteonecrosis, leading to loosening of the glenoid component in shoulder arthroplasty. We therefore analyzed the temperature during implantation of cemented glenoid implants.

METHODS

8 keeled and 8 pegged glenoids were implanted in standardized fashion in 8 pairs of scapulas. Temperature and pressure sensors were implanted at the bone-cement interface in the glenoid. Real-time measurements were made of temperature and pressure within the glenoid vault.

RESULTS

In no case was the temperature reached high enough to endanger the surrounding bone. The mean increase in temperature was 5 degrees (0.5-6.9) in the keeled group and 2.7 degrees (1.7-3.6) in the pegged group. The mean maximum pressure in the keeled group was 50 kPa (20-100) and in the pegged group it was 113 kPa (60- 181). Both differences were statistically significant.

INTERPRETATION

The temperatures that occur during implantation of cemented components are low and probably not high enough to cause osteonecrosis in the surrounding bone.

The glenoid in shoulder arthroplasty

Total shoulder arthroplasty is a common treatment for glenohumeral arthritis. One of the most common failure modes of total shoulder arthroplasty is glenoid loosening, causing postoperative pain, limitation of function, and potentially, the need for revision surgery. The literature has devoted considerable attention to the design of the glenoid component; efforts to better understand the biomechanics of the reconstructed glenohumeral joint and identify factors that contribute to glenoid component loosening are ongoing. This article reviews the current state of knowledge about the glenoid in total shoulder arthroplasty, summarizing the anatomic parameters of the intact glenoid, variations in component design and fixation, the mechanisms of glenoid loosening, the outcomes of revision surgery in the treatment of glenoid component failure, and alternative treatments for younger patients.

The incidence of early radiolucencies about a pegged glenoid component using cement pressurization

Glenoid component loosening is the most common early mode of failure of total shoulder arthroplasty (TSA) We hypothesised that the use of a pegged glenoid component with a modern glenoid reaming system and an instrumented cement pressurization technique would achieve a low prevalence of early radiolucent lines. Of 81 patients having TSA with a cemented, all polyethylene, 3-peg glenoid component for primary glenohumeral osteoarthritis, 69 had high quality radiographs available for analysis. All preoperative and initial postoperative radiographs were reviewed and graded in a blinded manner using previously established criteria. When the radiolucency grade of cement fixation was converted to a numeric scale of 0 (no radiolucency) to 5 (grossly loose), the mean cementing score was 0.14 + 0.06. Of the 69 shoulders, 62 (90%) had no radiolucencies. These techniques to improve glenoid fixation resulted in a low incidence of early radiolucencies about the glenoid component in patients having TSA for primary glenohumeral osteoarthritis.

Glenoid component failure in total shoulder arthroplasty

Glenoid component failure is the most common complication of total shoulder arthroplasty. Glenoid components fail as a result of their inability to replicate essential properties of the normal glenoid articular surface to achieve durable fixation to the underlying bone, to withstand repeated eccentric loads and glenohumeral translation, and to resist wear and deformation. The possibility of glenoid component failure should be considered whenever a total shoulder arthroplasty has an unsatisfactory result. High-quality radiographs made in the plane of the scapula and in the axillary projection are usually sufficient to evaluate the status of the glenoid component. Failures of prosthetic glenoid arthroplasty can be understood in terms of failure of the component itself, failure of seating, failure of fixation, failure of the glenoid bone, and failure to effectively manage eccentric loading. An understanding of these modes of failure leads to strategies to minimize complications related to prosthetic glenoid arthroplasty.

Evaluation of the mechanical and architectural properties of glenoid bone

Successful glenoid fixation in shoulder arthroplasty is partly dependent on the properties of the underlying bone. Therefore, mapping of the glenoid surface and locating the bone with the highest quality, in terms of mechanical properties and morphology, is a key requirement in ensuring effective fixation. To this end, an investigation was undertaken to study the relationship between indentation behavior and the quality of the glenoid bone. Nineteen embalmed glenoids were obtained from human cadavers (mean age at death, 82 years). Each specimen was tested using a cylindrical indentor at 11 predetermined points to investigate load-displacement behavior. Microcomputed tomography analysis was performed to ascertain the bone volume (BV)/total volume (TV) fraction of the trabecular bone and the subchondral thickness. Statistical analysis showed that both strength and modulus varied with indentation position. Significant relationships were found between either strength or modulus and BV/TV or subchondral thickness, although the explained variance was relatively low.

Shoulder arthroplasty: the socket perspective

Although much attention has been directed to the development of the humeral components used in shoulder arthroplasty, the major unsolved challenge lies on the glenoid side of the articulation. This challenge arises from difficulties resisting eccentric loading and providing adequate implant-bone fixation. Current glenoid component designs use polyethylene and polymethyl methacrylate and are prone to loosening, plastic deformation, particulate debris, and third-body wear. Metal-backed components present further challenges, and results have generally been disappointing. There is interest in biologic resurfacing procedures, including the interposition of fascia, capsule, or meniscal allograft and nonprosthetic glenoid arthroplasty, or what has become known as the "ream-and-run" procedure. Despite encouraging results, important questions remain unanswered about these procedures. However, each may warrant further exploration with a goal of providing an effective and durable approach to glenoid arthritis that avoids the risks associated with polymethyl methacrylate and polyethylene.

Development and characterization of a porous poly(methyl methacrylate) scaffold with controllable modulus and permeability

Functional restoration following extensive bone injury often requires bone grafting. The primary source of graft material is either autograft or allograft. The use of both material sources is well established, however both suffer limitations. In response, grafting alternatives are being investigated. This manuscript presents the development of a highly porous scaffold with controllable elastic modulus and permeability for use in tissue grafting and tissue engineering applications that is manufactured from FDA approved poly(methyl methacrylate) (PMMA). Fifteen protocol variations based on the commonly used porogen leaching technique for porous scaffold fabrication were employed to control scaffold pore size, pore interconnectivity, and structural strength. Scaffolds were tested for porosity, permeability, elastic modulus, cell culture compatibility, and fatigue tested in compression. Scaffold permeability ranged from 6.6 x 10(-16) m(2) to 1.4 x 10(-10) m(2), and elastic modulus was adjustable between 14 and 322 MPa; data similar to cancellous bone specimens from a variety of species and anatomic locations. Fatigue evaluations revealed 65% strength maintenance after 80,000 loading cycles, and in vitro culture with marrow-derived stromal cells show no cytotoxic effects based on Live/Dead assay. The scaffolds detailed herein will help broaden the spectrum of available orthopaedic tissue scaffolds for research in this evolving field. , 2007.

The pillars of the scapula

Total shoulder replacement has been shown to provide predictable pain relief and functional improvement in patients with glenohumeral arthritis. Loosening of the glenoid component remains the most frequent indication for revision surgery at long-term follow-up. The component most widely used is an all-polyethylene keeled or pegged design cemented to the glenoid cavity of the scapula. The glenoid is small and its cup-shaped morphology allows only a restricted site for limited fixation devices. This is particularly so in revision surgery where there are often large bony defects of the glenoid. In an anatomical study, we investigated the scapula in order to identify substantial bony pillars for better component fixation. Forty cadaveric shoulders (mean age 86, range 67-101) were dissected, the glenoids were denuded from cartilage, and the subchondral and cancellous bone was removed. Two bony pillars approaching the glenoid were consistently identified in all scapulae investigated. These pillars were outlined by three cortices and orientated to the circle formed by the rim of the inferior quadrants of the glenoid. One pillar is directed inferiorly near the margo lateralis and the other pillar is directed superiorly into the spine of the scapula. We defined these pillars in length and direction, and three-dimensionally located them in relation to the joint surface. This study demonstrated two bony pillars as important anatomical landmarks in the scapula. They were constant in presence, surgically accessible, and have not been described before. These results can be used as a guideline in the development of prosthetic designs to improve the fixation of glenoid components.

A study of the micromovement of pegged and keeled glenoid components compared using radiostereometric analysis

In a prospective, randomized study between 2000 and 2004, 20 patients with primary osteoarthritis of the shoulder had a total shoulder arthroplasty with radiostereometric analysis, 10 with keeled and 10 with pegged glenoid components. The relative movement of the glenoid component with respect to the scapula was measured over a 24-month period. Three keeled and five pegged glenoids needed reaming for erosion. The largest translations occurred along the longitudinal axis (mean of 1.35 mm for keeled eroded components) (P = .017 for keeled vs pegged components and P = .013 for eroded vs non-eroded components). Both of the other translation axes showed no significant differences. The highest maximum total point movement at 24 months was 2.57 mm for keeled eroded components and 1.64 mm for pegged eroded components (P = .029 for keeled vs pegged components and P = .023 for eroded vs non-eroded components). The largest rotation was anteversion, with mean values of 5.5 degrees for keeled eroded components and 4.8 degrees for pegged eroded components (P = .658 for keeled vs pegged components and P = .90 for eroded vs non-eroded components). The mean varus tilt was 4.5 degrees for keeled eroded components compared with 2.3 degrees for pegged eroded components (P = .004 for keeled vs pegged components and P = .016 for eroded vs non-eroded components), and finally, anterior-posterior rotation mean values were 3.5 degrees for keeled eroded components and 1.1 degrees for pegged eroded components (P = .022 for keeled vs pegged components and P = .04 for eroded vs non-eroded components). In conclusion, whereas all components moved, radiostereometric analysis revealed increased migration with keeled components, exacerbated by glenoid erosion. Furthermore, a distinctive pattern of migration was identified over the 2-year period.