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

Short-term radiographic and clinical outcomes of patients treated with anatomic total shoulder arthroplasty using a modern-generation implant with a metal-backed glenoid component

BACKGROUND

A leading cause of anatomic total shoulder arthroplasty failure continues to be glenoid component loosening. Historically, metal-backed glenoids (MBGs) have shown decreased performance compared with polyethylene-backed glenoid (PEG) components. Previous studies have shown that MBG components have higher revision rates and shorter time to prosthetic failure compared with PEG components. However, the negative outcomes of many of these studies may have been linked to an examination of older generations of MBG implants, and do not account for newer technology. Thus, our study aims to assess the short-term radiographic and clinical outcomes of patients treated with anatomic total shoulder arthroplasty using the current and more modern generation of implants with a universal metal-backed glenoid component.

METHODS

We conducted a retrospective chart review of patients who had their primary anatomic shoulder replacement performed from 2017 to 2022 by a single surgeon, and used one of 2 currently available implants that incorporated a metal-backed glenoid component with a convertible baseplate. After the exclusion of those lost to follow-up, we included 26 patients in this study, 3 of whom underwent bilateral shoulder replacement surgery at staggered time intervals. The primary outcome measure was evidence of radiographic change via in-office X-ray reports. Analysis of radiographic changes was conducted for each postoperative visit, which was aimed for 2 weeks, 6 weeks, 12 weeks, 1 year, and annually thereafter. Secondary analysis tracked clinical progression and used Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH) scores, range of motion evaluation, strength testing, and instability examination using evidence of apprehension and sulcus signs at each time interval.

RESULTS

In our study, radiographic changes at each time interval and the longest follow-up appointment demonstrated no evidence of hardware loosening of either the glenoid or the humeral component and no evidence of periprosthetic fracture or hardware failure of any kind for MBG implants. There were no revisions performed because of polyethylene wear. The overall average range of motion, strength, and DASH scores were improved at each postoperative visit.

CONCLUSION

Previous studies have suggested that TSA implants with MBG components may be inferior to PEG implants. However, the results of many of these studies may not be as representative of the current implant designs available today. Although additional studies are necessary to assess the long-term survivability of the implant and its effects on glenoid bone stock, our findings suggest that university MBG components have minimal complications, do not demonstrate loosening, and have acceptable outcomes in short-term follow-up.

Arthroplasty-Related Pseudotumor of the Scapula: Case Report and Review of the Literature

Arthroplasty-related pseudotumors are nonneoplastic and noninfectious inflammatory masses that are typically associated with adverse reaction to metal debris. Pseudotumors most commonly occur in the setting of metal-on-metal joint replacements at the hip. However, the presentation of pseudotumor at the shoulder is exceedingly rare. In this article, we reported a case of arthroplasty-related pseudotumor of the scapula. Clinical history, radiologic signs, and tissue analysis are described. Knowledge of this rare diagnosis will support clinical decision making for teams of radiologists, pathologists, oncologists, and orthopaedic surgeons who provide care for patients presenting with suspicious shoulder masses.

Hypoxic acclimatization training improves the resistance to motion sickness

Objective

Vestibular provocation is one of the main causes of flight illusions, and its occurrence is closely related to the susceptibility of motion sickness (MS). However, existing training programs have limited effect in improving the resistance to motion sickness. In this study, we investigated the effects of hypoxia acclimatization training (HAT) on the resistance to motion sickness.

Methods

Healthy military college students were identified as subjects according to the criteria. MS model was induced by a rotary chair. Experimental groups included control, HAT, 3D roller training (3DRT), and combined training.

Results

The Graybiel scores were decreased in the HAT group and the 3DRT group and further decreased in the combined training group in MS induced by the rotary chair. Participants had a significant increase in blood pressure after the rotary chair test and a significant increase in the heart rate during the rotary chair test, but these changes disappeared in all three training groups. Additionally, LFn was increased, HFn was decreased, and LF/HF was increased accordingly during the rotary chair test in the control group, but the changes of these three parameters were completely opposite in the three training groups during the rotary chair test. Compared with the control group, the decreasing changes in pupillary contraction velocity (PCV) and pupillary minimum diameter (PMD) of the three training groups were smaller. In particular, the binocular PCV changes were further attenuated in the combined training group.

Conclusion

Our research provides a possible candidate solution for training military pilots in the resistance to motion sickness.

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.

Effects of rest interval and training intensity on jumping performance: a systematic review and meta-analysis investigating post-activation performance enhancement

Background: There is no clear agreement regarding the ideal rest interval and training intensity to optimize post-activation performance enhancement (PAPE) after barbell squat (BS). Therefore, the aim of this study was to investigate the effects of rest interval and training intensity on jumping performance due to PAPE. Methods: Searches were performed in PubMed, Web of Science, and EBSCO databases. We included studies that satisfied the following criteria: (1) eligible studies should be randomized controlled trials; (2) eligible studies should investigate the acute effect of barbell squat-induced PAPE on jump performance; (3) eligible studies should use countermovement jump, squat jump, or vertical jump as the outcome measure. Results: From 2518 search records initially identified, 19 studies were eligible for meta-analysis. Our meta-analysis results showed that BS had no significant effect on improving jumping performance due to PAPE (Cohen's d = 0.09, p = 0.08). Subgroup analysis showed that rest interval between 0-1 min was detrimental to jumping performance (Cohen's d = -0.33, p < 0.01), while rest intervals between 4-7 min (Cohen's d = 0.31, p < 0.01) and 8-9 min (Cohen's d = 0.26, p = 0.02) provided favorable jumping performance outcomes. In addition, low-intensity and moderate-intensity BS had no significant effect on jump performance, while high-intensity BS showed results consistent with rest interval. Conclusion: Our study indicated that both low-intensity and moderate-intensity BS failed to induce PAPE, and it is recommended that future studies use high-intensity BS to induce PAPE. A rest interval of 4-9 min had a beneficial impact on jump height, and an interval range of 4-7 min seems to be the best rest interval between conditioning activity and jumping performance.

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 Radiologic Outcomes after Anatomical Total Shoulder Replacement Using a Modular Metal-Backed Glenoid after a Mean Follow-Up of 5.7 Years

Background: Glenoid wear is a common complication of anatomical total shoulder arthroplasty (aTSA) with a metal-backed glenoid (MBG), and the clinical and radiological results of historical implants are poor. The aim of this work was to evaluate the clinical and radiological results of 25 participants as well as the longevity after implantation of an anatomic shoulder prosthesis with a recent, modular cementless flat metal-backed glenoid component after a mean follow-up of 5.7 years. Methods: Clinically, the Simple Shoulder Test (SST), UCLA Activity Score (UCLA), and Constant Murley Score (CMS) were evaluated. Radiographically, the radiolucent lines (RLs), humeral head migration (HHM), and lateral glenohumeral offset (LGHO) were assessed. Survival was calculated with Kaplan−Meier curves and life-table analysis. Results: The mean CMS at follow-up was 46.2 points (range: 14−77; SD: 19.5). In terms of the SST score, the average value was 6.5 points (range: 1−10; SD: 3.5). The UCLA activity score showed a mean value of 5.9 points (range: 1−9; SD: 2.1). There were 17 revisions after a mean follow-up of 68.2 months (range: 1.8−119.6; SD: 27.9). HHM occurred in every patient, with a mean measurement of 6.4 mm (range: 0.5−13.4; SD: 3.9; p < 0.0001). The mean LGHO between the initial postoperative and follow-up images was 2.6 mm (range: 0−4.0; SD: 1.5; p < 0.0001). RLs were found in 22 patients (88%) around the glenoid and in 21 patients (84%) around the humeral head prosthesis. Conclusion: The clinical and radiographic outcomes after metal-backed glenoids were poor at 2.2 to 8.4 years of follow-up. We determined devastating survival in the majority of cases (68%), with mostly inlay wear (71%) as the main reason that led to revision surgery. The use of metalback genoids cannot be recommended based on the data of this study.

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.

Hybrid Glenoid Designs in Anatomic Total Shoulder Arthroplasty: A Systematic Review

BACKGROUND

Hybrid glenoid components in total shoulder arthroplasty (TSA) utilize both polyethylene and metal components to provide short-term stability and long-term biologic fixation through bone ingrowth.

QUESTIONS/PURPOSE

We sought to systematically review the literature for studies that assessed outcomes of TSA performed using hybrid glenoid components.

METHODS

PubMed, Medline, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Embase were searched systematically for articles measuring clinical and patient-reported outcomes and rates of complication and revision following TSA using a hybrid glenoid component.

RESULTS

Seven studies with 593 shoulders were included in this review. The mean age of patients was 65 ± 1 years, and 46% of the population was male. Mean follow-up was 50 months (4.2 years). The overall complication rate was 7% and rate of revision was 2.5%; glenoid radiolucency was present in 33% of shoulders at mean follow-up of 50 months. Mean improvements in forward elevation, external rotation, internal rotation score, and abduction were 49°, 28°, 2 points, and 42°, respectively. Mean improvements in Constant, American Shoulder and Elbow Surgeons (ASES), and University of California, Los Angeles (UCLA) scores were 36 points, 52 points, and 17 points, respectively.

CONCLUSION

Our review found that TSA using hybrid glenoid components results in low rates of complication and revision at early follow-up. Long-term studies are warranted to understand more fully the role of hybrid glenoid components in TSA.

Conversion of anatomic total shoulder arthroplasty to reverse shoulder arthroplasty using a unique hybrid glenoid component: technique and preliminary results

Background

Degenerative arthritis of the shoulder is a common condition that is successfully treated with anatomic total shoulder arthroplasty (TSA). Rotator cuff disease has evolved as a leading cause of failure of anatomic TSA, requiring revision to reverse shoulder arthroplasty (RSA). This revision procedure can be extremely complex, particularly if removal of a well-fixed glenoid component is necessary. This case series outlines the technique and preliminary clinical results of conversion of anatomic TSA to RSA utilizing both modular humeral and hybrid glenoid components.

Methods

From July 2017 to December 2019, the senior author (PMC) performed 84 consecutive anatomic TSA procedures utilizing a modular humeral arthroplasty system and a unique hybrid glenoid component. Three cases (3/84, or 3.6%) required conversion from anatomic TSA to RSA because of postoperative traumatic rotator cuff failure. All modular revision cases were performed without humeral stem removal and with utilization of the existing, well-fixed hybrid glenoid central titanium peg as the foundation for glenoid component revision. Preoperative and postoperative American Shoulder and Elbow Surgeons scores, visual analog scale pain scores, forward flexion, and patient satisfaction were analyzed in this modular revision group. In addition, several perioperative variables including operative time, blood loss, and length of stay were compared between this modular revision group and a nonmodular anatomic TSA to RSA revision comparative cohort.

Results

At an average follow-up of 24 months, average active forward flexion, postoperative American Shoulder and Elbow Surgeons scores, and visual analog scale pain scores improved significantly compared with preoperative scores in the modular revision group. All three patients were satisfied with their outcome. The average total operative time (109 minutes vs. 154 minutes, P = .02), blood loss (183 cc vs. 500 cc, P = .08), and length of hospital stay (26.3 hours vs. 36.6 hours P < .05) were lower in the modular revision group than those in a nonmodular revision cohort.

Conclusion

Revision of anatomic TSA to RSA utilizing a modular humeral system and a convertible hybrid glenoid component that does not require removal of a well-fixed central titanium peg which serves as the foundation for glenoid component revision was performed efficiently, safely, and successfully in three cases. This technique results in significantly improved clinical outcomes when revision to RSA is needed while potentially decreasing perioperative complications in the revision setting.

Radiographic and clinical outcomes of second generation Trabecular Metal™ glenoid components in total shoulder arthroplasty

BACKGROUND

Total shoulder arthroplasty with second generation porous tantalum glenoid implants (Trabecular Metal™) has shown good short-term outcomes, but mid-term outcomes are unknown. This study describes the clinical, radiographic, and patient-rated mid-term outcomes of total shoulder arthroplasty utilizing cemented Trabecular Metal™ glenoid components.

METHODS

Patients who underwent anatomic total shoulder arthroplasty with cemented Trabecular Metal™ glenoid components for primary osteoarthritis were identified for minimum five-year follow-up. The primary outcome measure was implant survival; secondary outcome measures included patient-rated outcome scores, shoulder range of motion findings, and radiographic analysis.

RESULTS

Twenty-seven patients were enrolled in the study. Twenty-one patients had full radiographic follow-up. Mean follow-up was 6.6 years. There was 100% implant survival. Shoulder range of motion significantly improved and the mean American Shoulder and Elbow Society score was 89.8. There was presence of metal debris radiographically in 24% of patients. Twenty-nine percent of patients had evidence of radiolucency. Fourteen percent of patients had moderate superior subluxation.

CONCLUSION

Total shoulder arthroplasty with second generation cemented Trabecular Metal™ glenoid components yielded good outcomes at mean 6.6-year follow-up. Metal debris incidence and clinical outcomes were similar to short-term findings. The presence of metal debris did not significantly affect clinical outcomes. Continued observation of these patients will elucidate longer-term implant survival.

Complications After Anatomic Shoulder Arthroplasty: Revisiting Leading Causes of Failure

For practicing shoulder arthroplasty surgeons, it is advisable to consider a breadth of data sources concerning complications and outcomes. Although published series from high-volume centers are the primary source of data, these results may not be generalizable to a wide range of practice settings. National or health system-specific registry and medical device databases are useful adjuncts to assess the changing complication profile of shoulder arthroplasty, as well as to understand the complications specific to certain implants or implant types. To reduce the risk of postoperative complications, surgeons must have a clear understanding of the most common modes of failure.

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 Clinical Application of Porous Tantalum and Its New Development for Bone Tissue Engineering

Porous tantalum (Ta) is a promising biomaterial and has been applied in orthopedics and dentistry for nearly two decades. The high porosity and interconnected pore structure of porous Ta promise fine bone ingrowth and new bone formation within the inner space, which further guarantee rapid osteointegration and bone-implant stability in the long term. Porous Ta has high wettability and surface energy that can facilitate adherence, proliferation and mineralization of osteoblasts. Meanwhile, the low elastic modulus and high friction coefficient of porous Ta allow it to effectively avoid the stress shield effect, minimize marginal bone loss and ensure primary stability. Accordingly, the satisfactory clinical application of porous Ta-based implants or prostheses is mainly derived from its excellent biological and mechanical properties. With the advent of additive manufacturing, personalized porous Ta-based implants or prostheses have shown their clinical value in the treatment of individual patients who need specially designed implants or prosthesis. In addition, many modification methods have been introduced to enhance the bioactivity and antibacterial property of porous Ta with promising in vitro and in vivo research results. In any case, choosing suitable patients is of great importance to guarantee surgical success after porous Ta insertion.

Prospective midterm results of a new convertible glenoid component in anatomic shoulder arthroplasty: a cohort study

PURPOSE

The purpose of our study was to evaluate the clinical and radiological results of a new anatomic convertible cementless glenoid component.

METHODS

Forty-eight patients with a mean age of 67.3 years were clinically and radiologically followed-up with a mean of 49 months. Indications for glenoid replacement were A2 glenoid wear in 21.7%, B1 glenoid wear in 28.3%, B2 glenoid wear in 28.3%, B3 glenoid wear in 13%, D glenoid wear in 2.2%, and glenoid component loosening in 6.5%.

RESULTS

The Constant-Murley score improved significantly (p < 0.0001) from 50% pre-OP to 103% post-OP. Patients with a B3 glenoid type according to Walch achieved a significant (p = 0.044) lower Constant-Murley Sscore post-OP compared to patients with a B1 glenoid type (88% vs 106%). The mean subluxation index changed significantly (p < 0.0001) from 0.54 pre-OP to 0.46 post-OP. At the metal-back bone interface an incomplete radiolucent line < 1 mm was observed in two cases (4.2%) and an incomplete radiolucent line < 2 mm was observed in another two cases (4.2%). PE dissociation occurred in two cases. No glenoid loosening was observed. The implant related revision rate was 4.2% (2 cases). All components (n = 612.5%) requiring conversion to reverse were converted without any further complications or loosening.

CONCLUSION

Good functional results can be achieved in cases with a B1 and a B2 glenoid after anatomic shoulder arthroplasty using the described metal back glenoid. A conversion from an anatomic to a reverse glenoid component were possible in all cases without any further complications. Conversion of the anatomic glenoid component to a reverse system alleviates revision surgery.

Cement pressurizing reduces radiolucent lines at glenoid: A randomized, multicentric study

BACKGROUND

The hypothesis of this study is that cement pressurization into the glenoid reduces the rate of radiolucent lines in total shoulder arthroplasty in the mean 25.5 months after the operation.

METHODS

To examine this effect, a multicentric prospective randomized study (level of evidence 1) was initiated: one group (group P, n = 24) received intraoperative pressurization of cement into the cancellous bone of the glenoid, the other cement without pressure (group NoP, n = 27). Inclusion criteria were an osteoarthritis with glenoid erosion <15° and an intact rotator cuff.

RESULTS

There were no significant differences preoperatively between the groups regarding age (mean age 66 ± 10 years (range 44-81)), gender, range of motion, scores and pathomorphology. Both groups had a significant improvement of the scores, strength, motion and satisfaction 25.5 months after the intervention. The scores were similar between the groups (ns). However, cement pressurization at the glenoid side significantly reduced the incidence of radiolucent lines (p < 0.027).

CONCLUSION

This supports the use of this simple technique to improve long-term survival of total shoulder arthroplasty.Level of evidence: 1.

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.

Do Modern Designs of Metal-Backed Glenoid Components Show Improved Clinical Results in Total Shoulder Arthroplasty? A Systematic Review of the Literature

Background:

Despite the increased popularity of reverse total shoulder arthroplasty, total shoulder arthroplasty is the standard treatment for advanced shoulder arthritis in young adult patients. Conventional metal-backed glenoid (MBG) designs result in more loosening and revision surgery compared with cemented polyethylene glenoid components. However, modern MBG designs have been recently devised to overcome such drawbacks.

Purpose:

To compare the radiolucency, loosening, and failure rates of modern MBG designs with those of conventional designs.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A search for relevant articles was carried out using the PubMed, Cochrane Library, and Embase databases using MeSH (Medical Subject Headings) terms and natural keywords. A total of 362 articles were screened. We descriptively analyzed numerical data between the groups and statistically analyzed categorical data, such as the presence of loosening, failure, and revision surgery. The main outcome was the rate of revision surgery or failure. Subgroup analysis according to follow-up duration was performed to reduce heterogeneity.

Results:

A total of 25 articles (2036 shoulders) were included; 15 articles (1579 shoulders) involved a conventional MBG design, and 10 (457 shoulders) involved a modern design. The mean age of the patients was 64.2 and 66.5 years in the conventional and modern design groups, respectively, with a mean follow-up duration of 102.0 and 56.1 months, a mean gain of forward elevation of 35.1° and 61.7°, and a mean gain of external rotation of 24.2° and 39.2°. The rate of radiolucency was 48.0% and 16.7%, the rate of loosening was 11.2% and 4.9%, and the rate of revision was 15.9% and 2.4%, for the conventional and modern design groups, respectively. Subgroup analysis according to follow-up duration showed that the rates of loosening and revision were significantly lower in the modern design group (P < .001).

Conclusion:

Our findings suggest that modern MBG designs showed significantly lower loosening and failure rates than conventional designs. The overall results of the comparison, including loosening, failure, change in range of motion, and clinical scores, indicate that modern MBG designs are promising. More long-term follow-up studies on modern MBGs should be conducted.

The Biomaterials of Total Shoulder Arthroplasty: Their Features, Function, and Effect on Outcomes

The materials that are used in total shoulder arthroplasty (TSA) implants have been carefully chosen in an attempt to minimize hardware-related complications. The 2 main metal alloys used in TSA implants are Ti-6Al-4V (titanium-aluminum-vanadium) and CoCrMo (cobalt-chromium-molybdenum). Ti alloys are softer than CoCr alloys, making them less wear-resistant and more susceptible to damage, but they have improved osseointegration and osteoconduction properties. Although controversial, metal allergy may be a concern in patients undergoing TSA and may lead to local tissue reaction and aseptic loosening. Numerous modifications to polyethylene, including cross-linking, minimizing oxidation, and vitamin E impregnation, have been developed to minimize wear and reduce complications. Alternative bearing surfaces such as ceramic and pyrolytic carbon, which have strong track records in other fields, represent promising possibilities to enhance the strength and the durability of TSA prostheses.

Loosening and revision rates after total shoulder arthroplasty: a systematic review of cemented all-polyethylene glenoid and three modern designs of metal-backed glenoid

BACKGROUND

Several modern designs of metal-backed glenoids (MBG) have been devised to overcome flaws such as loosening and a high failure rate. This review aimed to compare rates of complications and revision surgeries between cemented polyethylene glenoid (PEG) and three examples of modern MBG designs.

METHODS

Literature search was carried out using PubMed, Cochrane Library, EMBASE, and Google Scholar using MeSH terms and natural keywords. A total of 1186 articles were screened. We descriptively analyzed numerical data between the groups and statistically analyzed the categorical data, such as the presence of radiolucent line, loosening, and revision surgery (failure). Articles were divided into three groups based on follow-up duration: < 36-month, 36-72-month, and > 72-month subgroups.

RESULTS

This study included 35 articles (3769 shoulders); 25 on cemented PEG and ten on the modern MBG. Mean age was 66.4 (21-93) and 66.5 years (31-88). The mean duration of follow-up was 73.1 (12-211) and 56.1 months (24-100). Overall, the rate of the radiolucent line was 354/1302 (27%) and 47/282 (17%), the loosening rate was 465/3185 (15%) and 22/449 (5%), and the failure rate was 189/3316 (6%) and 11/457 (2%), for PEG and MBG, respectively. The results of < 36-month and 36-72-month subgroups showed lower rates of radiolucency and loosening in the cemented PEG group, but there was no significant difference in failure rate (P = 0.754 and 0.829, respectively). In the > 72-month subgroup, MBG was better in terms of loosening (P < 0.001) and failure rates (P = 0.006).

CONCLUSIONS

The modern MBG component, especially TM glenoid, seems to be a promising alternative to cemented PEGs, based on subgroup revision rates according to the follow-up duration and overall results of ROM and clinical scores. All polyethylene glenoids tend to increase loosening and failure over time. Three modern MBG designs seem to have no difference in failure, at least in the < 36-month and 36-72-month subgroups compared to the cemented PEG. More long-term follow-up studies on modern MBG should be ultimately conducted.

LEVEL OF EVIDENCE

Level IV, systematic review.

Clinical and radiographic comparison of a hybrid cage glenoid to a cemented polyethylene glenoid in anatomic total shoulder arthroplasty

BACKGROUND

This study reports the clinical and radiographic outcomes of a hybrid cage glenoid compared with an age-matched, sex-matched, and follow-up-matched cohort of cemented all-polyethylene peg glenoids in patients undergoing anatomic total shoulder arthroplasty with 2 years' minimum follow-up.

MATERIALS AND METHODS

We reviewed 632 primary anatomic total shoulder arthroplasty patients from an international multi-institutional database; 316 patients received hybrid cage glenoids and were matched for age, sex, and follow-up with 316 patients with cemented all-polyethylene peg glenoids. Each cohort received the same humeral component. Scoring was performed in all patients preoperatively and at latest follow-up using 5 outcome scoring metrics and 4 active range-of-motion measurements. A Student 2-tailed unpaired t test identified differences in outcomes; P < .05 denoted a significant difference.

RESULTS

Cage glenoid patients had significantly lower rates of radiolucent glenoid lines (9.0% vs. 37.6%, P < .0001) and radiolucent humeral lines (3.0% vs. 9.1%, P = .0088) than all-polyethylene peg glenoid patients. In the cage glenoid cohort, 4 cases of aseptic glenoid loosening (1.3%) and 4 cases of articular surface dissociation (1.3%) occurred. In the all-polyethylene peg cohort, 12 cases of aseptic loosening (3.8%) occurred. Cage glenoid patients had a significantly lower revision rate than all-polyethylene peg glenoid patients (2.5% vs. 6.9%, P = .0088).

CONCLUSION

At 50 months' mean follow-up, cage glenoids demonstrated equally good clinical outcomes to all-polyethylene peg glenoids. Cage glenoids had significantly fewer radiolucent lines around both the glenoid and humeral components and a lower revision rate. Longer-term follow-up is required to confirm these promising short-term results.

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.

The subchondral bone layer and glenoid implant design are relevant for primary stability in glenoid arthroplasty

BACKGROUND

Clinical studies suggest that reaming of the subchondral bone layer to achieve good implant seating is a risk factor for glenoid loosening. This study aims to evaluate (1) the importance of the subchondral bone layer and (2) the influence of the design of the glenoid component.

METHODS

Different techniques for preparation of an A1 glenoid were compared: (1) preserving the subchondral bone layer; (2) removal of the subchondral bone layer; (3) implantation of a glenoid component that does not adapt to the native anatomy. Artificial glenoid bones (n = 5 each) were used with a highly standardized preparation and implantation protocol. Biomechanical testing was performed during simulated physiological shoulder motion. Using a high-resolution optical system, the micromotions between implant and bone were measured up to 10,000 motion cycles.

RESULTS

At the 10,000 cycle measuring point, significantly more micromotions were found in the subchondral layer removed group than in the subchondral layer preserved group (p = 0.0427). The number of micromotions in the nonadapted group was significantly higher than in the subchondral layer preserved group (p = 0.0003) or the subchondral layer removed group (p = 0.0207).

CONCLUSION

Conservative reaming proved important to diminish the micromotions of the glenoid component. Implantation of a glenoid component that matches with the bony underlying glenoid can help to preserve the subchondral bone layer without sacrificing proper implant seating.

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post

BACKGROUND

To determine the effectiveness of hybrid glenoid components in reducing the frequency of glenoid component loosening, we evaluated clinical and radiographic outcomes at a minimum 5-year follow-up in 45 shoulders that underwent total shoulder arthroplasty (TSA) using a system with a central porous titanium post to augment the cemented peripheral pegs.

METHODS

Function and pain were evaluated with the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment score, visual analog scale, active shoulder range of motion, and strength. Postoperative radiographs were analyzed for radiolucent lines, progressive loosening, and at-risk signs.

RESULTS

The mean American Shoulder and Elbow Surgeons score improved from 40.4 to 83.7 (P < .0001) and the mean visual analog scale from 5.9 to 0.8 (P < .0001). Forward elevation improved from 113° to 151° (P < .001), internal rotation from 49° to 60° (P = .035), and mean external rotation from 36° to 50° (P = .0006). Radiographs showed glenoid component radiolucency in 29 shoulders. Radiolucencies were confined to the area under the glenoid faceplate in 6 and were only around the central post in 13. Nine TSAs (20%) demonstrated 2 or more columns of involvement but were not judged to be at-risk. One implant (2.2%) had glenoid component failure and was revised to a hemiarthroplasty.

CONCLUSION

Anatomic TSA using a hybrid glenoid component with a central porous titanium post demonstrated a low rate of mechanical failure and a rate of radiolucent lines comparable to reports of all polyethylene implants. Further evaluations are needed to demonstrate the long-term durability of these implants and to determine the significance and fate of the radiolucent lines, particularly relative to the central post.

Short-term radiographic results of a cemented polyethylene keeled glenoid component with varying backside radiuses of curvature

BACKGROUND

This study analyzed the radiographic results of a cemented all-polyethylene keeled glenoid component available in different sizes and multiple backside radiuses of curvature.

METHODS

The study group consisted of 118 cases (114 patients). There were 63 women and 51 men. Mean age at the time of arthroplasty was 68 years (range, 51-85 years). True anterior-posterior radiographs obtained postoperatively and at the final follow-up were analyzed for implant seating and the occurrence of radiolucent lines. Glenoid morphology and fatty infiltration of the rotator cuff muscles were examined using computed tomography scans. Mean follow-up was 38 months (range, 24-70 months).

RESULTS

The mean radiolucent line score after surgery was 0.54 points (range, 0-3 points), and 90% had no or only 1 radiolucent line. At the final follow-up, the mean score was 1.06 points (range, 0-3 points), and 74% had no or only 1 radiolucent line. The score increased significantly over time (P < .001). No component was at risk for loosening. No correlation was found between patient age, sex, hand dominance, glenoid morphology, or fatty infiltration of the rotator cuff muscles and the occurrence of radiolucent lines.

CONCLUSION

In the short-term, the glenoid component analyzed in this study showed promising radiographic results, with a low number of radiolucent lines without failure. However, the mean radiolucent line score increased significantly over time, and long-term observations are necessary to confirm a possible advantage compared with older component designs.

Improving the surface properties of an UHMWPE shoulder implant with an atmospheric pressure plasma jet

Insufficient glenoid fixation is one of the main reasons for failure in total shoulder arthroplasty. This is predominantly caused by the inert nature of the ultra-high molecular weight polyethylene (UHMWPE) used in the glenoid component of the implant, which makes it difficult to adhesively bind to bone cement or bone. Previous studies have shown that this adhesion can be ameliorated by changing the surface chemistry using plasma technology. An atmospheric pressure plasma jet is used to treat UHMWPE substrates and to modify their surface chemistry. The modifications are investigated using several surface analysis techniques. The adhesion with bone cement is assessed using pull-out tests while osteoblast adhesion and proliferation is also tested making use of several cell viability assays. Additionally, the treated samples are put in simulated body fluid and the resulting calcium phosphate (CaP) deposition is evaluated as a measure of the in vitro bioactivity of the samples. The results show that the plasma modifications result in incorporation of oxygen in the surface, which leads to a significant improved adhesion to bone cement, an enhanced osteoblast proliferation and a more pronounced CaP deposition. The plasma-treated surfaces are therefore promising to act as a shoulder implant.

Outcomes of Trabecular Metal-backed glenoid components in anatomic total shoulder arthroplasty

BACKGROUND

As glenoid failure is one of the primary causes of failure of anatomic total shoulder arthroplasty (TSA), Trabecular Metal-backed glenoid components have become popular. This study reports implant survival and clinical outcomes of patients who received a Trabecular Metal-backed glenoid component during primary anatomic TSA.

METHODS

Patients who underwent TSA with a Trabecular Metal-backed glenoid component by a single surgeon were identified and reviewed for clinical, radiographic, and patient-reported outcome measures with a minimum of 2 years' follow-up.

RESULTS

Of 47 patients identified, radiographic and clinical follow-up was available on 36 patients (77%). Average age was 66.36 years (range, 50-85 years), and the average follow-up 41 months (range, 24-66 months). Three patients showed signs of osteolysis, 4 had radiographic evidence of metal debris, and 1 patient had a catastrophic failure after a fall. Of the 47 TSAs, 5 (11%) were revised to a reverse TSA for subscapularis failure and pain. Visual analog scale for pain scores improved by an average of 4.4. At final follow-up, the average Single Assessment Numeric Evaluation score was 72.4; Penn satisfaction score, 7.5; Penn score, 70.35; and American Shoulder and Elbow Surgeons score, 69.23. Outcome scores were similar in the 7 patients with osteolysis or metal debris compared to those without.

CONCLUSION

Trabecular Metal-backed glenoids had a 25% rate of radiographic metal debris and osteolysis at a minimum 2-year follow-up in this series with one catastrophic failure. This implant should be used with caution, and patients followed closely.

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.

Survivorship of Trabecular Metal Anchored Glenoid Total Shoulder Arthroplasties

Trabecular metal anchored glenoids (TMAGs) were developed to counter the pervasive problem of component loosening at the bone-cement interface in total shoulder arthroplasty. Increased failure rates associated with the glenoid component have been previously reported due to increased rates of glenoid failures. Our hypothesis was that in our patients, the failure rate of TMAG implants is similar to or less than reported failure rates of traditional all polyethylene glenoid components. A medical chart review of 66 consecutive patients treated with a TMAG total shoulder replacement was conducted including clinical and radiographic follow-up. Paired t test analyses were used to compare the patients' preoperative and postoperative shoulder range of motion. Patients on average had 50.2 months of clinical follow-up available. Although the radiographs of several patients demonstrated focal areas of lucency, none of the patients demonstrated evidence of glenoid loosening. Glenoid component failure was a rare occurrence, happening only once in the 66 patients (1.5%). The patient with a glenoid fracture sustained that complication 6 years after her index total shoulder replacement. She was the only patient in the series who required revision surgery. Most patients experienced significant improvements in their shoulder range of motion, improving forward flexion from 73.7 to 144.2 degrees (P<0.0001), internal rotation from L5 to T8 (P<0.0001), and external rotation 12.8 to 48.9 degrees (P<0.0001). With improved implant design and meticulous surgical technique, recent iterations of TMAG components do not produce excessive failure rates but result in significant functional improvements.

Parametric analysis of glenoid implant design and fixation type

Common post-operative problems in shoulder arthroplasty such as glenoid loosening and joint instability may be reduced by improvements in glenoid design, shape, material choice, and fixation method. A framework for parametric analysis of different implant fixation configurations was developed in order to efficiently sift through potential glenoid component designs. We investigated the influence of design factors such as fixation type, component thickness, and peg position, number, diameter, and length in a multi-factorial design investigation. The proposed method allowed for simultaneous comparison of the mechanical performance of 344 different parametric variations of 10 different reference geometries with either large central fixation features or small peripheral pegs, undergoing four different worst-case scenario loading conditions, and averaging 64.7 s per model. The impact of design parameters were assessed for different factors responsible for post-operative problems in shoulder arthroplasty, such as bone volume preservation, stresses in the implant, central displacement or fixation stability, and the worst performing geometries all relied on conventional central fixation. Of the remaining geometries, four peripheral fixation configurations produced von Mises stresses comfortably below the material's yield strength. We show that the developed method allows for simple, direct, rapid, and repeatable comparison of different design features, material choices, or fixation methods by analyzing how they influence the bone-implant mechanical environment. The proposed method can provide valuable insight in implant design optimization by screening through multiple potential design modifications at an early design evaluation stage and highlighting the best performing combinations according to the failure mechanism to mitigate. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:775-784, 2017.

Clinical and radiologic outcomes of the second-generation Trabecular Metal™ glenoid for total shoulder replacements after 2-6 years follow-up

BACKGROUND

A porous tantalum glenoid component for total shoulder replacements was introduced in 2003 to promote biologic ingrowth. However, reports of component failure prompted design modifications. The purpose of this study is to present the largest series to date, of TSR with the second-generation Trabecular Metal™ glenoid component.

METHOD

A radiologic and clinical evaluation of the second-generation TM glenoid was conducted in consecutive cases of 76 shoulders (66 patients) with a mean follow-up of 43.2 months (range 24-72 months). Pre-operative VAS score, patient self-assessed ASES score, active shoulder range of motion, and radiologic assessment were recorded. Patients were recalled for latest follow-up clinical and radiologic evaluation.

RESULTS

On latest follow-up, the mean VAS scores (pre-op: 6.4-latest: 0.9) and ASES scores (pre-op: 36.9-latest: 88.5) improved. Active range of motion improved in all planes. There was no report of glenoid component migration, loosening, or humeral stem subsidence. The incidence of non-progressive radiolucency in the glenoid was 6.6 % (Franklin 1: 3 cases, Franklin 2: 2 cases). Post-operative complications involved dislocation (n = 2) which were reduced in ED, post-operative stiffness (n = 1), transient axillary nerve neuropraxia (n = 1), and supraspinatus tear which underwent arthroscopic repair at 16 months post-op. There were no revision surgeries for implant loosening nor glenoid component fracture at the peg-base plate junction.

CONCLUSIONS

The modifications established in the second-generation TM glenoid resulted to improve early to mid-term survivorship and clinical outcomes in TSR, with promise of long-term implant stability through bony ingrowth.

LEVEL OF EVIDENCE

Level IV, case series, treatment study.

Metallosis in shoulder arthroplasty: an integrative review of literature

Shoulder arthroplasty has gained popularity as an efficient means of achieving pain relief and improved function in a variety of complex shoulder disorders. Despite promising reports, given the increasing number of shoulder arthroplasty procedures, various causes that may contribute to failure of a well-functioning arthroplasty are being increasingly recognized. One such disastrous condition is metallosis, a subject which has not been much talked off with reference to shoulder arthroplasty. This article besides reviewing the existing literature intends to discuss the possible causes that contribute to metallosis and devise a protocol for its timely diagnosis and management.

Early Debris Formation with a Porous Tantalum Glenoid Component: Radiographic Analysis with 2-Year Minimum Follow-up

BACKGROUND

Porous tantalum has been used effectively in hip, knee, and reverse shoulder arthroplasty implants. However, a first-generation porous tantalum glenoid component for use in anatomic shoulder arthroplasty previously demonstrated failure, with failure usually preceded by the appearance of intra-articular metallic debris. After redesign, the component was reintroduced in 2009. The purpose of the current study was to evaluate the radiographic and clinical outcomes of the redesigned glenoid component.

METHODS

Sixty-eight patients undergoing total shoulder arthroplasty received a Trabecular Metal porous tantalum glenoid component (73 components; 5 patients underwent staged bilateral procedures). No polymethylmethacrylate cement was used (off-label usage in the U.S.). A grading system to assess metallic debris formation was developed using radiographs of the previous generation of porous tantalum glenoid components that failed. Radiographs from the current series were independently reviewed by 2 shoulder arthroplasty specialists, and their results were compared. Glenoid components were evaluated for signs of bone ingrowth and metallic debris formation.

RESULTS

Sixty-six (90%) of the 73 components were evaluated at a minimum of 2 years of follow-up (mean radiographic follow-up of 50.8 months; range, 24 to 68 months). Of these, 92.4% demonstrated minimal or no glenoid radiolucency. Overall, the prevalence of metallic tantalum debris formation was 44% (29 of 66). Sequential radiograph review demonstrated that the incidence of metallic debris formation increased for each year of follow-up, with radiographs from 2, 3, 4, and ≥5 years of follow-up demonstrating a metallic debris incidence of 23%, 36%, 49%, and 52%, respectively. Additionally, the severity of metallic debris formation increased with follow-up duration. There was no component dissociation or revision due to implant breakage in this series.

CONCLUSIONS

The porous tantalum glenoid component studied had excellent short-term component fixation. However, the development of metallic debris, increasing in both overall incidence and degree of severity over time, raises concern for potential failure of this glenoid component. Longer follow-up is required.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Regression forest-based automatic estimation of the articular margin plane for shoulder prosthesis planning

In shoulder arthroplasty, the proximal humeral head is resected by sawing along the cartilage-bone transition and replaced by a prosthetic implant. The resection plane, called articular margin plane (AMP), defines the orientation, position and size of the prosthetic humeral head in relation to the humeral shaft. Therefore, the correct definition of the AMP is crucial for the computer-assisted preoperative planning of shoulder arthroplasty. We present a fully automated method for estimating the AMP relying only on computed tomography (CT) images of the upper arm. It consists of two consecutive steps, each of which uses random regression forests (RFs) to establish a direct mapping from the CT image to the AMP parameters. In the first step, image intensities serve as features to compute a coarse estimate of the AMP. The second step builds upon this estimate, calculating a refined AMP using novel feature types that combine a bone enhancing sheetness measure with ray features. The proposed method was evaluated on a dataset consisting of 72 CT images of upper arm cadavers. A mean localization error of 2.40mm and a mean angular error of 6.51° was measured compared to manually annotated ground truth.

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.

Catastrophic failure of a low profile metal-backed glenoid component after total shoulder arthroplasty

Context:

The longevity of the glenoid component in total shoulder arthroplasty (TSA) continues to be problematic. All polyethylene glenoid components have been most widely used, but loosening rates with time and the need for revision has resulted in high-profile metal-backed components with the potential for a more stable prosthesis bone interface and liner exchange. High revision rates in the high profile metal backed designs led us to evaluate a low profile metal backed component.

Aims:

To examine the rate and mode of failure of a TSA in a single surgeon consecutive series that has been identified by the Australian National Joint Replacement Registry to have a higher than anticipated rate of revision.

Materials and Methods:

This is a single surgeon retrospective consecutive series of 51 arthroplasties undertaken in 50 patients (18 males and 32 females) with an average age of 70.4 ears (range 51-90) and mean follow-up of 5.5 years (range 3.7-8.1).

Results:

We observed a very high (29%) rate of revision of the metal-backed glenoid components in this series. The primary mode of failure was glenoid baseplate nonintegration which with a well-fixed central cage screw led to bone resorption and implant breakage or disassembly.

Conclusion:

Analysis of the mode of failure of implants identified by robust registries is essential for the development of new prostheses and the pursuit of prosthesis longevity. This low profile metal backed prosthesis has been withdrawn, but without a published mechanism of failure. We feel that any prosthesis withdrawal should be accompanied by appropriate published mechanisms to prevent future component design errors based on similar design problems.

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.

Metal-backed glenoid implant with polyethylene insert is not a viable long-term therapeutic option

BACKGROUND

The aims of this study were to determine the survival of anatomic total shoulder arthroplasty with uncemented metal-backed (MB) glenoid components with a polyethylene (PE) insert in primary osteoarthritis, to assess the reasons for revision surgery, and to identify patients and diagnostic factors that influence failure rates.

METHODS

Between 1994 and 1999, 165 patients (mean age, 68 years) with primary osteoarthritis were treated with anatomic total shoulder arthroplasty using an uncemented MB/PE glenoid component. Outcomes were assessed both clinically and radiologically with a minimum of 2 years of follow-up. A prosthetic survival curve was constructed with the end point defined as either partial or complete revision, using 100% confidence intervals.

RESULTS

Survival rate free of revision was 46% (100% confidence interval, 32%-54%) at 12 years. At a mean follow-up of 8.5 years (range, 2-16 years), revision was required in 61 patients (37%); 80% of shoulders undergoing revision (49 of 61) had evidence of PE wear. Glenoid loosening (because of osteolysis secondary to wear debris), soft tissue deficiency, and prosthetic instability were the most common modes of failure. Younger patients and biconcave glenoids (with posterior humeral subluxation) have a negative effect on implant survival. Proximal humerus osteolysis was significantly more frequent in shoulders with PE wear. Exchange of the PE insert (with conservation of the MB tray) was possible in only 3% of the revised shoulders.

CONCLUSION

Uncemented MB glenoid resurfacing is not a viable long-term therapeutic option because of accelerated PE wear leading to early revision surgery. Conservation of the MB tray with reinsertion of a new PE insert is rarely possible because of glenoid bone loss, implant loosening, soft tissue deficiency, and prosthetic instability. Younger patients and biconcave glenoids have a negative effect on implant survival.

Kinematic analysis of reaching movements of the upper limb after total or reverse shoulder arthroplasty

Studies have analyzed three-dimensional complex motion of the shoulder in healthy subjects or patients undergoing total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (RSA). No study to date has assessed the reaching movements in patients with TSA or RSA. Twelve patients with TSA (Group A) and 12 with RSA (Group B) underwent kinematic analysis of reaching movements directed at four targets. The results were compared to those of 12 healthy subjects (Group C). The assessed parameters were hand-to-target distance, target-approaching velocity, humeral-elevation angular velocity, normalized jerk (indicating motion fluidity), elbow extension and humeral elevation angles. Mean Constant score increased by 38 points in Group A and 47 in Group B after surgery. In three of the tasks, there were no significant differences between healthy subjects and patients in the study groups. Mean target-approaching velocity and humeral-elevation angular velocity were significantly greater in the control group than in study groups and, overall, greater in Group A than Group B. Movement fluidity was significantly greater in the controls, with patients in Group B showing greater fluidity than those in Group A. Reaching movements in the study groups were comparable, in three of the tasks, to those in the control group. However, the latter performed significantly better with regard to target-approaching velocity, humeral-elevation angular velocity and movement fluidity, which are the most representative characteristics of reaching motion. These differences, that may be related to deterioration of shoulder proprioception after prosthetic implant, might possibly be decreased with appropriate rehabilitation.

Metallosis following a dual coat porous hydroxyapatite shoulder hemiarthroplasty

We report a case of metallosis following a shoulder hemiarthroplasty with a humeral component resurfacing shoulder replacement.

Short stem shoulder replacement

Context:

It is agreed that it is important to anatomically reproduce the proximal humeral anatomy when performing a prosthetic shoulder replacement. This can be difficult with a long stemmed prosthesis, in particular if there is little relationship of the metaphysis to the humeral shaft. The ‘short stem’ prosthesis can deal with this problem.

Aims:

A prospective study assessed the results of total shoulder arthroplasty using a short stem humeral prosthesis, a ceramic humeral head, and a pegged cemented polyethylene glenoid.

Materials and methods:

Patients with primary shoulder osteoarthritis were recruited into this prospective trial and pre-operatively had the ASES, Constant, SPADI, and DASH scores recorded. The patients were clinically reviewed at the two weeks, eight weeks, one year, and two year mark with completion of a data form. Radiological evaluation was at the eight week, one year and two year follow-up. At the one and two year follow-up the satisfaction rating, the range of passive and active motion, Constant, ASES, SPADI, DASH and pain results were recorded and analysed with SPPS 20.

Results:

During the study period 97 short stem, ceramic head total shoulder replacements were carried out. At the time of follow-up 12 were two years from operation and 38 one year from operation. Active elevation was overall mean 160 degrees. Constant scores were 76 at 1 year, and 86 at 2 years, ASES 88 and 93, and satisfaction 96% and 98% respectively at one and 2 year follow up. There were no problems during insertion of the humeral prosthesis, or any radiolucent lines or movement of the prosthesis on later radiographs.

Conclusion:

The short stem prosthesis had no complications, and on follow up radiographs good bone fixation. These fairly short term clinical results were overall good.

Metal-Backed Glenoid Components Have a Higher Rate of Failure and Fail by Different Modes in Comparison with All-Polyethylene Components: A Systematic Review

BACKGROUND

Glenoid component failure is a common and serious complication of total shoulder arthroplasty. The purpose of this study was to evaluate published evidence on whether metal backing lessens the rate of glenoid component failure.

METHODS

A comprehensive systematic review yielded twenty-one studies on radiolucency, radiographic failure, and revision after arthroplasty with metal-backed glenoid components and twenty-three studies with all-polyethylene components. Our analysis included data on 1571 metal-backed and 3035 all-polyethylene components. The mean duration of follow-up was 5.8 years in the studies with metal-backed components and 7.3 years with all-polyethylene components.

RESULTS

All-polyethylene components had a 42.5% rate of radiolucency compared with 34.9% for metal-backed components (p = 0.0026) and a 21.1% rate of radiographic loosening or failure compared with 16.8% for metal-backed components (p = 0.0005). However, the rate of revision was more than three times higher with metal-backed components (14.0%) than with all-polyethylene components (3.8%, p < 0.0001). Although 77% of the revisions of all-polyethylene components were for loosening, 62% of the revisions of metal-backed components were for other reasons, such as component fracture, screw breakage, component dissociation, polyethylene wear, metal wear, and rotator cuff tear (p < 0.0001).

CONCLUSIONS

The published evidence indicates that metal-backed glenoid components require revision at a significantly higher rate and for different reasons in comparison with all-polyethylene components.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effect of glenoid cementation on total shoulder arthroplasty for degenerative arthritis of the shoulder: a review of the New Zealand National Joint Registry

BACKGROUND

Despite the lack of literature showing improved results compared with cemented designs, uncemented glenoid components are still commonly used in total shoulder arthroplasty (TSA). Most studies comparing cemented with uncemented glenoids involve small numbers or include patients with inflammatory arthritis.

METHODS

New Zealand National Joint Registry data was used to compare the outcomes of uncemented and cemented glenoids in TSA performed for degenerative arthritis. Measured variables were the revision rate and the Oxford Shoulder Score (OSS).

RESULTS

Data were retrieved on 1596 patients, with a mean follow-up 3.5 years (range 2-10.7 years), 1065 of whom had a cemented glenoid. There were no significant differences in any preoperative factors between the 2 groups. The revision rate for uncemented glenoids was 4.4 times higher than for cemented glenoids (1.92 vs. 0.44 revisions per 100 component-years, P < .001). Age <55 years was an independent risk factor for revision (P < .001). The most common reason for revision was rotator cuff wear (35.5%) in the uncemented glenoids and loosening (36.3%) in the cemented glenoids. The difference in the mean OSS between the 2 groups was less than 1 point at 6 months (P = .109) and at 5 years (P = .377).

CONCLUSION

Uncemented glenoids had a markedly higher revision rate. Patients aged <55 years have the highest revision rate regardless of glenoid fixation method. The higher revision rate in the uncemented glenoid group persisted when the effect of young age was corrected for. There was no clinically or statistically significant difference in the OSS results for clinical outcome between the two groups.

LEVEL OF EVIDENCE

Level III, retrospective cohort, treatment study.

The evaluation of the failed shoulder arthroplasty

As the incidence of shoulder arthroplasty continues to rise, the orthopedic shoulder surgeon will be increasingly faced with the difficult problem of evaluating a failed shoulder arthroplasty. The patient is usually dissatisfied with the outcome of the previous arthroplasty as a result of pain, but may complain of poor function due to limited range of motion or instability. A thorough and systematic approach is necessary so that the most appropriate treatment pathway can be initiated. A comprehensive history and physical examination are the first steps in the evaluation. Diagnostic studies are numerous and include laboratory values, plain radiography, computed tomography, ultrasound imaging, joint aspiration, nuclear scans, and electromyography. Common causes of early pain after shoulder arthroplasty include technical issues related to the surgery, such as malposition or improper sizing of the prosthesis, periprosthetic infection, neurologic injury, and complex regional pain syndrome. Pain presenting after a symptom-free interval may be related to chronic periprosthetic infection, component wear and loosening, glenoid erosion, rotator cuff degeneration, and fracture. Poor range of motion may result from inadequate postoperative rehabilitation, implant-related factors, and heterotopic ossification. Instability is generally caused by rotator cuff deficiency and implant-related factors. Unfortunately, determining the cause of a failed shoulder arthroplasty can be difficult, and in many situations, the source of pain and disability is multifactorial.

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.

Midterm results of a total shoulder prosthesis fixed with a cementless glenoid component

BACKGROUND

The aim of this study was to evaluate the midterm results and complications of a total shoulder arthroplasty implanted with a metal-backed, bone-ingrowth glenoid component.

MATERIALS AND METHODS

In total, 62 patients (65 shoulders) diagnosed with primary osteoarthritis were treated with total shoulder arthroplasty with a cementless glenoid component. The mean age was 66 years (range, 54-85 years). Fifty-three patients were evaluated after a mean of 64 months (range, 26-85 months). Functional results were documented by use of the age- and sex-adjusted Constant score. Radiolucent line (RLL) assessment of the glenoid component was performed by use of true anteroposterior and axillary views.

RESULTS

The Constant score improved significantly from 49% preoperatively to 89.8% postoperatively (P < .0001). Active range of motion improved significantly for flexion (from 118° to 146°), abduction (from 87° to 133°), and external rotation (from 21° to 44°) (P < .0001). In 3 cases (5.7%), RLLs of 1 mm or less were present, and 1 case (1.8%) had an RLL of 2 mm or less in 1 zone. Glenoid component loosening occurred in 5 cases (9.4%) because of breakage of the cage screw. Four of these patients presented preoperatively with a type B1 glenoid and one patient with type A2. Two of the patients who underwent revision also had a complete tear of the rotator cuff. The revision rate was 11.3% (6 patients) after a mean of 68 months.

CONCLUSION

After midterm follow-up, clinical outcomes of patients operated on with a cementless, metal-backed glenoid implant improved significantly. However, an unacceptable rate of complications and revisions was found. Glenoid loosening predominantly occurred in patients with preoperative eccentric glenoid morphology and was also related to cranial migration of the proximal humerus during the follow-up period.