Elucidating trends in revision reverse total shoulder arthroplasty procedures: a retrieval study evaluating clinical, radiographic, and functional outcomes data

Long-term outcomes of hemiarthroplasty using a smaller head combined with rotator cuff reconstruction in patients with cuff-tear arthropathy

Background

Hemiarthroplasty (HHR) using a smaller head with rotator cuff reconstruction is a treatment option for cuff-tear arthropathy, offering advantages like facilitating rotator cuff-tear closure, increasing the lever arm of deltoid, and restoring function in irreparable cuff tears. This study aimed to evaluate the long-term outcomes of this procedure.

Methods

A retrospective analysis was conducted for 91 shoulders undergoing HHR using a smaller head with rotator cuff reconstruction between May 2005 and September 2012. Surgery involved reducing the size of humeral head and performing rotator cuff reconstruction based on the site of the deficient rotator cuff. The study analyzed University of California, Los Angeles shoulder scores, Japanese Orthopaedics Association shoulder scores, range of motion, and postoperative radiographs.

Results

Twenty-eight patients, divided into an elderly group (14 women, 2 men, mean age 74.5 ± 3.8 years) and a younger group (6 women, 6 men, mean age 63.5 ± 3.1 years) were followed up for a mean of 133.2 ± 14.1 months. No complications were reported. The clinical scores and range of motion significantly improved postoperatively and remained over 10 years. Radiographs revealed high incidence of glenoid wear (82.1%), bone resorption (43%) and cranial humeral head migration (54%), with no prosthesis loosening.

Conclusion

We believe that HHR using a smaller head with rotator cuff reconstruction is a surgical technique that can maintain stable long-term outcomes in both elderly and younger individuals with cuff-tear arthropathy.

Evaluating trunnionosis in modular anatomic shoulder arthroplasties: a retrieval study

BACKGROUND

Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems.

METHODS

Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information.

RESULTS

In this series, 158 of explants were from female patients (male = 107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P < .001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P < .001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P < .001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P = .002).

CONCLUSION

In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings.

Disparities in arthroplasty utilization for rotator cuff tear arthropathy

BACKGROUND

Rotator cuff tear arthropathy (CTA) carries a significant symptomatic burden for patients. Reverse shoulder arthroplasty (RSA) is an effective treatment intervention for CTA. Disparities in musculoskeletal medicine are well documented; however, there is a paucity of literature on how social determinants of health affect utilization rates. The purpose of this study is to determine how social determinants of health affect the utilization rates of RSA.

METHODS

A single-center retrospective review was conducted for adult patients diagnosed with CTA between 2015 and 2020. Patients were divided by those who underwent RSA and those who were offered RSA but did not undergo surgery. Each patient's zip code was used to determine the most specific median household income in the US Census Bureau database and compared to the multistate metropolitan statistical area median income. Income levels were defined by the US Department of Housing and Urban Development's (HUD's) 2022 Income Limits Documentation System and the Federal Reserve's (FED's) Community Reinvestment Act. Because of numeric restrictions, patients were grouped into racial cohorts of Black, White, and all other races.

RESULTS

Patients of other races had significantly lower odds of continuing to surgery compared with White patients in models controlled for median household income (odds ratio [OR] 0.38, 95% confidence interval [CI] 0.18-0.81, P = .01), HUD's 3 income levels (OR 0.36, 95% CI 0.18-0.74, P = .01), and FED's income levels (OR 0.37, 95% CI 0.17-0.79, P = .01). There was no significantly different odds of going on to surgery between FED income levels and median household income levels, but when compared with those with low HUD income, those below median had significantly lower odds of going on to surgery (OR 0.43, 95% CI 0.23-0.80, P = .01).

CONCLUSION

Although contradictory to reported health care utilization for Black patients, our study supports reported disparities in utilization for other ethnic minorities. These findings may suggest that improvements in utilization efforts targeted Black-identifying patients but not necessarily other ethnic minorities. The findings of this study can help providers understand how social determinants of health play a role in the utilization of care for CTA and direct mitigation efforts to reduce disparities in access to adequate orthopedic care.

Larger-diameter trunnions and bolt-reinforced taper junctions are associated with less tribocorrosion in reverse total shoulder arthroplasty

BACKGROUND

Morse taper junction tribocorrosion is recognized as an important failure mode in total hip arthroplasty. Although taper junctions are used in almost all shoulder arthroplasty systems currently available in the United States, with large variation in design, limited literature has described comparable analyses of taper damage in these implants. In this study, taper junction damage in retrieved reverse total shoulder arthroplasty (RTSA) implants was assessed and analyzed.

METHODS

Fifty-seven retrieved RTSAs with paired baseplate and glenosphere components with Morse taper junctions were identified via database query; 19 of these also included paired humeral stems and trays or spacers with taper junctions. Components were graded for standard damage modes and for fretting and corrosion with a modified Goldberg-Cusick classification system. Medical records and preoperative radiographs were reviewed. Comparative analyses were performed assessing the impact of various implant, radiographic, and patient factors on taper damage.

RESULTS

Standard damage modes were commonly found at the evaluated trunnion junctions, with scratching and edge deformation damage on 76% and 46% of all components, respectively. Fretting and corrosion damage was also common, observed on 86% and 72% of baseplates, respectively, and 23% and 40% of glenospheres, respectively. Baseplates showed greater moderate to severe (grade ≥ 3) fretting (43%) and corrosion (27%) damage than matched glenospheres (fretting, 9%; corrosion, 13%). Humeral stems showed moderate to severe fretting and corrosion on 28% and 30% of implants, respectively; matched humeral trays or spacers showed both less fretting (14%) and less corrosion (17%). On subgroup analysis, large-tapered implants had significantly lower summed fretting and corrosion grades than small-tapered implants (P < .001 for both) on glenospheres; paired baseplate corrosion grades were also significantly lower (P = .031) on large-tapered implants. Factorial analysis showed that bolt reinforcement of the taper junction was also associated with less fretting and corrosion damage on both baseplates and glenospheres. Summed fretting and corrosion grades on glenospheres with trunnions (male) were significantly greater than on glenospheres with bores (female) (P < .001 for both).

CONCLUSIONS

Damage to the taper junction is commonly found in retrieved RTSAs and can occur after only months of being implanted. In this study, tribocorrosion predominantly occurred on the taper surface of the baseplate (vs. glenosphere) and on the humeral stem (vs. tray or spacer), which may relate to the flexural rigidity difference between the titanium and cobalt-chrome components. Bolt reinforcement and the use of large-diameter trunnions led to less tribocorrosion of the taper junction. The findings of this study provide evidence for the improved design of RTSA prostheses to decrease tribocorrosion.

The Evolution of Reverse Total Shoulder Arthroplasty-From the First Steps to Novel Implant Designs and Surgical Techniques

Purpose of Review: The purpose of this review is to summarize recent literature regarding the latest design modifications and biomechanical evolutions of reverse total shoulder arthroplasty and their impact on postoperative outcomes. Recent findings: Over the past decade, worldwide implantation rates of reverse total shoulder arthroplasty have drastically increased for various shoulder pathologies. While Paul Grammont’s design principles first published in 1985 for reverse total shoulder arthroplasty remained unchanged, several adjustments were made to address postoperative clinical and biomechanical challenges such as implant glenoid loosening, scapular notching, or limited range of motion in order to maximize functional outcomes and increase the longevity of reverse total shoulder arthroplasty. However, the adequate and stable fixation of prosthetic components can be challenging, especially in massive osteoarthritis with concomitant bone loss. To overcome such issues, surgical navigation and patient-specific instruments may be a viable tool to improve accurate prosthetic component positioning. Nevertheless, larger clinical series on the accuracy and possible complications of this novel technique are still missing.

Backside polyethylene wear in reverse shoulder arthroplasty

BACKGROUND

Aseptic loosening from implant-associated osteolysis in reverse shoulder arthroplasty (RSA) may contribute to premature implant failure. Although articular side polyethylene (PE) damage has been well documented in the literature, no studies to date have investigated backside wear in RSA. The aims of this investigation were to (1) document and compare the damage between the backside and articular surface in explanted RSA components, (2) assess whether certain quadrants have a greater propensity for damage, and (3) report the most common mode(s) of backside PE damage.

METHODS

Twenty-one RSA humeral liners retrieved during revision procedures between 2005 and 2014 were included for analysis. The mean time between implantation and extraction was 16 months (10 days-88 months). Diagnoses at the time of revision included dislocation (10), infection (4), mechanical failure (3), loosening (2), and unknown (2). Liners were examined under light microscopy (×10-30 magnification) and damage on the articular and backside of the liner surface was graded using the modified Hood score. The location and damage modality were compared between the articular side and backside of the implant.

RESULTS

Damage was noted on the articular surfaces of all 21 liners and on the backside surface of 20 liners. The total damage in all the quadrants was higher on the articular surface than on the backside of the component, with a mean difference in total quadrant damage scores of 11.74 ± 3.53 (P < .001). There was no difference in damage among the quadrants on the backside (P = .44) or the articular surface (P = .08). The articular side exhibited greater scratching, abrasion, and surface deformation than the backside (P < .001).

CONCLUSIONS

This short-term retrieval study demonstrated that backside PE damage occurs on the humeral component of RSA implants. There was greater damage to the articular side of the liner but wear to the backside was present in almost all liners. The clinical importance of backside wear in RSA and its overall contribution to PE particulate disease and osteolysis needs further investigation.

Reverse shoulder arthroplasty for proximal humeral fracture in the elderly. Cemented or uncemented stem?

OBJECTIVE

The purposes of this study were to compare functional outcomes, radiographic stem changes and complication rate in patients with proximal humeral fractures operated with cemented or uncemented RSA.

METHODS

Retrospective review of 68 primary RSAs in PHF, 45 cemented/23 uncemented. Functional outcomes were evaluated according to constant, ASES scales and the range of motion (ROM). Radiographic assessment was performed at a minimum of two years post-operatively.

RESULTS

The mean follow-up cemented/uncemented was 37.8/26.5 months (p = .04) and the mean age 78/80 years old (p = .09). The functional outcome and range of movement were equivalent in the two groups except for the forward flexion that was significantly higher in the cemented group (p = .03). Stress shielding was seen in 30.4% of uncemented group and none in the cemented. Anatomic tuberosity healing was significantly higher with uncemented components compared with cemented components (64% vs 91%, p = .02). Cemented stems had radiolucent lines with a width of 2 mm or more in three or more Gruen zones in 9% vs 0% in the uncemented group and an evident change in the stem position was present in 4% vs 0% in the non-cemented group.

CONCLUSION

At mid-term follow-up, no differences in functional outcomes were detected depending on the stem fixation technique. Cemented stems, however, have a complication rate (including stem loosening) significantly higher than press-fit stems.

Reverse shoulder arthroplasty used for revision of reverse shoulder arthroplasty: a systematic review

Background

As reverse shoulder arthroplasty (RSA) cases increase, so too will the need to revise subsequent failures. Many of the complications associated with revising anatomic total shoulder and hemiarthroplasty have been adequately addressed by RSA including glenoid bone deficiency, instability, and functional outcomes. However, the risk for complication when revising a failed reverse prosthesis may be more pronounced with increased bone and soft tissue deficiency. The ability for the reversed prosthesis to accommodate these insufficiencies following a prior reversed prosthesis is unclear.

Methods

PubMed, Embase, and Google Scholar were queried for articles which fit the inclusion criteria of a reversed prosthesis used to revise a failed primary reverse prosthesis with a minimum follow-up of 12 months and clinical outcome reporting.

Results

After exclusions, 9 studies reporting on 242 reverse shoulders with a mean follow-up of 40.29 months were analyzed. The differences between preoperative and postoperative weighted means were not significant for Constant (P = .26), American Shoulder and Elbow Surgeons Shoulder score (P = .61), SSV (P = .57), and visual analog scale for pain (P = .48). Functional improvements in elevation (74°-102°) and external rotation (18°-21°) were consistent with those reported for primary reverse procedures, although differences in preoperative and postoperative measures were not statistically significant. Patient satisfaction was 89% with a major complication rate of 25%.

Discussion

The reverse shoulder prosthesis has proven satisfactory in revising hemiarthroplasty and anatomic total shoulder arthroplasty. The current results indicate RSA is also a satisfactory treatment option when revising a prior reverse prosthesis. Inherent to revision shoulder surgery is the obstacle of humeral and glenoid bone loss, an attenuated soft-tissue envelope, and instability. The reverse prosthesis may adequately address these commonly confronted difficulties with its inherent design characteristics. RSA provides a secure glenoid fixation for bone grafting, the ability to increase construct stability with component sizing, and a reliance on the deltoid for function. As our learning about revision of RSA improves, so will our ability to preemptively address potential issues which may lead to decreased complications in these cases. Despite the 25% rate of major complication, patients reported satisfaction of 89% which demonstrates the improvements in function and pain relief that are provided by the reverse prosthesis.

Outcome and complications following revision shoulder arthroplasty : a systematic review and meta-analysis

AIMS

It is important to understand the rate of complications associated with the increasing burden of revision shoulder arthroplasty. Currently, this has not been well quantified. This review aims to address that deficiency with a focus on complication and reoperation rates, shoulder outcome scores, and comparison of anatomical and reverse prostheses when used in revision surgery.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) systematic review was performed to identify clinical data for patients undergoing revision shoulder arthroplasty. Data were extracted from the literature and pooled for analysis. Complication and reoperation rates were analyzed using a meta-analysis of proportion, and continuous variables underwent comparative subgroup analysis.

RESULTS

A total of 112 studies (5,379 shoulders) were eligible for inclusion, although complete clinical data was not ubiquitous. Indications for revision included component loosening 20% (601/3,041), instability 19% (577/3,041), rotator cuff failure 17% (528/3,041), and infection 16% (490/3,041). Intraoperative complication and postoperative complication and reoperation rates were 8% (230/2,915), 22% (825/3,843), and 13% (584/3,843) respectively. Intraoperative and postoperative complications included iatrogenic humeral fractures (91/230, 40%) and instability (215/825, 26%). Revision to reverse total shoulder arthroplasty (TSA), rather than revision to anatomical TSA from any index prosthesis, resulted in lower complication rates and superior Constant scores, although there was no difference in American Shoulder and Elbow Surgeons scores.

CONCLUSION

Satisfactory improvement in patient-reported outcome measures are reported following revision shoulder arthroplasty; however, revision surgery is associated with high complication rates and better outcomes may be evident following revision to reverse TSA. Cite this article: Bone Jt Open 2021;2(8):618-630.

Wear and damage in retrieved humeral inlays of reverse total shoulder arthroplasty-where, how much, and why?

BACKGROUND

Polyethylene (PE) wear and material degradation have been reported as complications in reverse total shoulder replacements (rTSAs). In this regard, scapular notching is associated with more clinical complications. Therefore, the purposes of the study were to quantify the linear and volumetric wear, as a measure for the amount of removed material, and to qualitatively assess the PE damage modes to describe the material degradation in retrieved rTSA humeral PE inlays that contribute to failure of shoulder replacements. Furthermore, this study aimed to evaluate the effect of scapular notching on PE wear and rim damage of the humeral components.

METHODS

The total study population of 39 humeral inlays contains 2 cohorts that were used for the damage mode analysis and for the wear analysis, respectively. The extent and presence of wear damage modes in 5 defined zones were assessed by a grading system for all PE joint replacements. For quantitative wear analysis the most frequent design (n = 17) was chosen. Using a coordinate-measuring machine and postprocessing software, volumetric wear measurements for the retrieved humeral PE inlays were undertaken. Furthermore, prerevision radiographs were analyzed for scapular notching. Finally, retrieval findings were correlated with clinical and radiographic data to consider the effect of notching and to identify risk of failures for these prostheses.

RESULTS

Damage on the rim of the humeral PE inlays was more frequent and severe than on the intended articulation surface. Irrespective of the damage mode, the inferior rim zone sustained the greatest amount of wear damage followed by the posterior zone. Burnishing, scratching, pitting, and embedded particles are most likely to occur in the articular surface area, whereas surface deformation, abrasion, delamination and gross material degradation are predominantly present in the inferior and posterior rim zones. The retrieved inlays exhibited a mean volumetric wear rate of 296.9 mm³/yr ± 87.0 mm³/yr. However, if the notched and non-notched components were compared, a significant higher volumetric wear rate (296.5 ± 106.1 mm³/yr) was found for the notched components compared to the non-notched group (65.7 ± 7.4 mm³/yr). Generally, there was a significantly greater incidence of damage and greater amount of wear if scapular notching occurred.

CONCLUSION

The notched components showed a 5-fold increase in PE wear rate. Therefore, scapular notching has a strong effect on PE damage and wear. If scapular notching can be clinically avoided, the PE wear performance is in a similar magnitude as found for hip and knee replacements.

Humeral osteolysis after reverse shoulder arthroplasty using cemented or cementless stems comparative retrospective study with a mean follow-up of 9 years

INTRODUCTION

The cause of proximal humeral osteolysis after reverse shoulder arthroplasty (RSA) remains controversial. The primary objective of our study was to compare the radiographic outcomes of Grammont-type RSA when a cemented stem is used versus when a cementless stem is used. The secondary objective was to identify the cause of these radiographic changes, especially for the cementless stems.

HYPOTHESIS

More proximal humerus bone loss occurs when a cementless humeral stem is used.

METHODS

With a minimum follow-up of 5 years, two paired cohorts were compared retrospectively: 70 RSA with cemented stem and 70 RSA with cementless stem. Using the radiographs made at the final follow-up visit, we looked for tuberosity resorption, signs of stress shielding, the presence of periprosthetic radiolucent lines and scapular notching.

RESULTS

At a mean follow-up of 9 years (5.0-20.6), the RSA revision rate was 1.8% in the cemented group and 3.6% in the cementless group (p=1). Tuberosity resorption was twice as common in the cementless group: 59% versus 30% (p<0.001). Signs of stress shielding such as osteopenia were only present in the cementless group. In both groups, tuberosity resorption was often associated with scapular notching. In the shoulders with tuberosity resorption, stage≥3 scapular notching was more common in the cementless group (p=0.001).

DISCUSSION

For the cementless stems, proximal humeral osteolysis can in part be attributed to stress shielding. The relationship between notching and tuberosity resorption in the two groups also suggests a secondary biological cause.

LEVEL OF EVIDENCE

III; Comparative retrospective study.

Press-fit vs. cemented humeral stem fixation for reverse shoulder arthroplasty: functional outcomes at a mean follow-up of 9.5 years

BACKGROUND

Reverse shoulder arthroplasty (RSA) is a reliable, long-term treatment option for degenerative shoulder pathology. However, the functional outcomes degrade around the fifth year postoperation, particularly for internal and external rotation. Long-term radiographic changes have been reported around the humeral stem, depending on the fixation method.

OBJECTIVES

The primary objective was to compare the clinical outcomes of RSAs by fixation method-cemented vs. press-fit-after a minimum follow-up of 5 years. We hypothesized that proximal humeral osteolysis impacts the functional outcomes.

DESIGN AND METHODS

Our study compared 2 matched cohorts: 56 RSAs with cemented stems and 56 RSAs with press-fit stems. We evaluated all the patients using the Constant-Murley score (CMS) and range of motion (ROM), which we measured preoperatively and at the final follow-up visit. We evaluated radiographs from the final follow-up visit to look for proximal humeral osteolysis with tuberosity resorption, signs of stress shielding, periprosthetic radiolucent lines, and scapular notching.

RESULTS

At a mean follow-up of 9.5 years (5-21), regardless of the fixation method, the RSA procedure helped to improve the CMS and active joint ROM postoperatively, except for internal and external rotation with elbow at side in the press-fit group. Shoulder ROM was significantly better in the group with cemented stems for anterior elevation (P < .001), abduction (P = .006), and external (P = .02) and internal rotation with elbow at side (P = .02). The CMS did not differ between groups. The presence of tuberosity resorption or scapular notching had no effect on the CMS and active ROM in either group. Osteopenia, which was more prevalent in the press-fit group, had no impact on the functional outcome.

CONCLUSION

There was no significant difference between groups in the CMS, although the active shoulder ROM was significantly worse in the press-fit group. This difference could be attributed to more frequent tuberosity resorption in this group.

Analysis of the surface topography of retrieved metal-on-polyethylene reverse shoulder prostheses

Despite the encouraging short- and medium-term clinical results and increased usage of reverse shoulder replacements, a higher revision rate is documented compared with other major joint arthroplasties. Adverse reaction to polyethylene wear debris is still an important factor which may influence the long-term survival of reverse shoulder arthroplasty. To date, only a small number of retrieval studies of reverse shoulder arthroplasty have reported the different damage modes on polyethylene components, but none have quantified the ex vivo surface roughness on both articulating surfaces. The main purpose of this study was to assess, for the first time, the surface roughness of 13 retrieved metal-on-polyethylene reverse shoulder replacements using a white light profilometre with nanometre resolution. Although no significant relationship was observed between the surface roughness values and patient variables, it was noted that half of the polyethylene components still showed their original machining marks, indicating little change in vivo and that the metallic humeral components in the reversed design configuration showed low values of surface roughness after their time in vivo.

The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part I

Background

Globally, reverse shoulder arthroplasty (RSA) has moved away from the Grammont design to modern prosthesis designs. The purpose of this 2-part study was to systematically review each of the most common complications of RSA, limiting each search to publications in 2010 or later. In this part (part I), we examined (1) scapular notching (SN), (2) periprosthetic infection (PJI), (3) mechanical failure (glenoid or humeral component), and (4) neurologic injury (NI).

Methods

Four separate PubMed database searches were performed following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Overall, 113 studies on SN, 62 on PJI, 34 on mechanical failure, and 48 on NI were included in our reviews. Univariate analysis was performed with the χ² or Fisher exact test.

Results

The Grammont design had a higher SN rate vs. all other designs combined (42.5% vs. 12.3%, P < .001). The onlay humeral design had a lower rate than the lateralized glenoid design (10.5% vs. 14.8%, P < .001). The PJI rate was 2.4% for primary RSA and 2.6% for revision RSA. The incidence of glenoid and humeral component loosening was 2.3% and 1.4%, respectively. The Grammont design had an increased NI rate vs. all other designs combined (0.9% vs. 0.1%, P = .04).

Conclusions

Focused systematic reviews of the recent literature with a large volume of RSAs demonstrate that with the use of non-Grammont modern prosthesis designs, complications including SN, PJI, glenoid component loosening, and NI are significantly reduced compared with previous studies. As the indications for RSA continue to expand, it is imperative to accurately track the rates and types of complications to justify its cost and increased indications.

Delta Xtend reverse shoulder arthroplasty - Results at a minimum of five years

BACKGROUND

Reverse shoulder arthroplasty provides predictable pain relief and improvements in function, but concerns remain regarding complication rates and there is little long-term outcome data. The aim of this study was to review the clinical and radiographic outcomes of the Delta Xtend reverse shoulder arthroplasty at a minimum of five years.

METHODS

Ninety-six Delta Xtend reverse shoulder arthroplasty procedures were performed in 93 patients. There were 41 males and 52 females with an average age of 74.9 years. All available patients returned for clinical and radiographic analysis, including completion of patient reported outcome measures.

RESULTS

The complication rate was 9.4%. There were three revisions (3.1%) and two other reoperations (2.1%). Fifty-nine shoulders were available for review at an average of 81 months. Average forward flexion was 142°. Average American Shoulder and Elbow Assessment Score improved from 27.6 to 78.5 (p<0.001). Radiolucent lines and/or proximal bone resorption was seen in 35.4%. Scapula notching was observed in 69.1%, with Grade III or IV notching in 20%. These findings had no effect on patient reported outcome measures.

DISCUSSION

This study confirms the clinical benefits of reverse shoulder arthroplasty, with improvements maintained out to 10 years. The high rate of scapula notching remains a concern. Further study is needed to fully understand the clinical significance of notching, as well as the potential benefits of newer implant designs.

Humeral-sided Radiographic Changes Following Reverse Total Shoulder Arthroplasty

Background

We sought to characterize humeral-sided radiographic changes at a minimum of 2 years after reverse shoulder arthroplasty (RSA) to determine their association with specific implantation techniques.

Methods

The immediate and most recent postoperative anteroposterior radiographs of 120 shoulders with primary RSA and a minimum of 2-years of radiographic follow-up were analyzed (mean follow-up 35.2 months). Stress shielding was evaluated by measuring cortical thickness at 4 different locations. Three independent examiners evaluated radiographs for humeral osteolysis, radiolucent lines, stress shielding, stem loosening, and scapular notching.

Results

The cortical diameter, marker of external stress shielding, significantly decreased from initial to most recent measurement (P<0.001), but did not differ between cemented and uncemented groups. Cemented stems had significantly more osteolysis and radiolucent lines; uncemented stems had significantly more internal stress shielding (P<001). The presence of scapular notching was significantly correlated with the presence of humeral osteolysis (P<0.001). Three (2.5%) stems were deemed "at risk" for loosening and 2 (1.7%) were loose.

Conclusion

Cemented humeral stems were associated with an increased rate of radiolucent lines and osteolysis, whereas uncemented stems were associated with more internal stress shielding. Humeral cortical thickness significantly decreased over time regardless of fixation. There was an association between scapular notching and increased humeral osteolysis.

Risk Factors and Complications for Revision Shoulder Arthroplasty

BACKGROUND

Revision shoulder arthroplasty has become increasingly common as primary arthroplasty has become more widespread.

QUESTIONS/PURPOSES

We sought to answer two questions: What are the risks factors for revision shoulder arthroplasty? What are the complications associated with revision shoulder arthroplasty?

METHODS

A retrospective search of a national insurance database from the years 2013 to 2016 was undertaken for billing codes of patients undergoing revision shoulder arthroplasty. The odds ratios for revision of various patient demographic characteristics and comorbidities were determined. The incidences of various complications within 90 days of revision were determined.

RESULTS

A total of 824 cases of revision shoulder arthroplasty were found. Eighty-seven patients (10.5%) had infections prior to revision and 133 patients (16.1%) had dislocations prior to revision. Of the risk factors examined, smoking status was associated with the highest odds ratio for revision (8.1). Additionally, depression, Charlson Comorbidity Index (CCI), male gender, renal failure, and diabetes were significant risks factors for revision. The most common complication of revision shoulder arthroplasty was found to be surgical site infection, affecting 10.9% of patients. In the time period studied, 89 patients underwent more than one revision shoulder arthroplasty.

CONCLUSION

Despite limitations inherent in database studies, this data may have utility for surgeons in pre-operative counseling of patients on their risk.

Analysis of Retrieved Unicompartmental Knee Implants and Tissue: Third-Body Wear as a Potential Contributor to Progression of Arthritis to Adjacent Compartments

Unicompartmental knee arthroplasty (UKA) for the treatment of single-compartment osteoarthritis has been associated with polyethylene wear and progression of osteoarthritis into adjacent compartments, leading to revision. In this study, damage and clinical failure modes of retrieved UKA implants were investigated and protein expression profiles between articular cartilage adjacent to UKA and primary osteoarthritic cartilage were compared. Fifty retrieved UKA implants were analyzed for various damage. Records review and radiographic analysis were performed to collect clinical data and implant characteristics. Cartilage harvested from revision UKA and primary total knee arthroplasty surgeries was characterized with a proteome profiling array detecting levels of 36 different cytokines, chemokines, and acute phase inflammatory proteins. Progression of osteoarthritis (n=18, 36%) and component loosening (n=17, 34%) were the most common reasons for revision. Liners exhibited the highest frequency of damage modes. Progression of arthritis positively correlated with radiographic presence of extruded bone cement and burnishing of liner components. A protein-level profile between revision UKA and primary total knee arthroplasty cartilage showed 12 differentially expressed cytokines. Failure of UKA may be secondary to the effects of wear debris particulate migration into the adjacent compartment, suggesting an additional pathway of cartilage damage manifesting as traditional clinical symptoms. [Orthopedics. 2019; 42(3):149-157.].

The effect of combined loading cycles on the wear of reverse shoulder joint replacements

Wear of polyethylene is a current limitation in the long-term survival of reverse shoulder arthroplasties (RSAs). The purpose of this study was to investigate, for the first time, the influence of a combination of clinically relevant activities of daily living (ADLs) as patterns of motion and loading on the wear of ultra-high molecular-weight polyethylene (UHMWPE) in RSA. This physiological combined cycle, termed "repeated-motion-load", was applied on four new samples of a commercially available reverse shoulder prosthesis for five million cycles using the unique Newcastle Shoulder Wear Simulator. This resulted in a mean wear rate of 12.0 ± 3.9 mm³/million cycles for the UHMWPE components in combination with metallic glenospheres, while the average articulating UHMWPE surface roughness reduced from 692 ± 132 nm Sa to 42 ± 29 nm Sa.

Quantitative evaluation of retrieved reverse total shoulder arthroplasty liner surface deviation and volumetric wear

Polyethylene wear is a known complication in total joint arthroplasty, however, in vivo wear rates in reverse total shoulder arthroplasty (RTSA) remain largely unknown. This study aimed to quantify volumetric and surface deviation changes in retrieved RTSA humeral liners using a novel micro-computed tomography (μCT)-based technique. After IRB-approval, 32 humeral liners (single manufacturer and model) with term-of-service greater than 90 days were analyzed. Clinical demographics and surgical data were collected via chart review. Unworn liners were used as geometric controls. Retrieved and unworn liners underwent μCT scanning. Retrieved liner volumes were isolated, co-registered to controls of matching geometry, and surface deviations of the articulation surface and rim were computed. Differences in total volume loss (TVL), volumetric wear rate (VWR), and surface deviation were reported. Semi-quantitative grading evaluated rim damage presence and severity. Mean term-of-service for all liners was 2.07 ± 1.33 years (range: 0.30-4.73). Mean TVL and VWR were 181.3 ± 208.2 mm³ and 114.5 ± 160.3 mm³ /year, respectively. Mean articulation and rim surface deviations were 0.084 ± 0.065 and 0.177 ± 0.159 mm, respectively. Articulation surface deviation was positively correlated to term-of-service. Rim damage was present on 63% of liners and correlated significantly to rim surface deviation. This study reports in vivo wear rates of retrieved RTSA implants. Our results demonstrate volumetric and articulation surface wear in select RTSA liners that is correlated to term-of-service. Calculation of in vivo wear rates can help bridge the gap between clinical outcomes and experimental models such as wear simulations and computational models. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2007-2014, 2018.

Fretting and Corrosion Damage in Retrieved Metal-on-Polyethylene Modular Total Hip Arthroplasty Systems: What Is the Importance of Femoral Head Size?

BACKGROUND

Fretting and corrosion at the modular femoral head-femoral neck (taper) interface have been reported in retrieved total hip arthroplasty (THA) prostheses. This study investigated associations among implant design, radiographic factors, and patient factors with corrosion and fretting at the taper interface in retrieved metal-on-polyethylene modular THA prostheses.

METHODS

Ninety-two retrieved primary metal-on-polyethylene THA implants were evaluated and graded for fretting, corrosion, and damage at the taper interface, including the femoral stem trunnion and femoral head. Preoperative radiographs were assessed for osteolysis and femoral stem alignment; and medical records were reviewed for demographic data.

RESULTS

Male patients had greater head corrosion (P = .037), patient age at revision had a weak, negative correlation with trunnion corrosion (ρ = -0.20, P = .04), and both body mass index and duration of implantation had weak, positive correlations with head fretting (ρ = 0.26, P = .01 and ρ = 0.33, P = .001, respectively). A weak, negative correlation was found between femoral head size and both head fretting and head corrosion (ρ = -0.26, P = .007 and ρ = -0.21, P = .028, respectively), and a weak, positive correlation was found between head offset and trunnion fretting (ρ = 0.23, P = .030). Varus femoral stem alignment was associated with greater head fretting (P = .038).

CONCLUSION

Larger femoral head sizes were correlated with less severe head corrosion and head fretting, with 28-mm heads exhibiting more moderate-to-severe damage. Other factors, such as head-taper engagement and geometry, rather than head size, may affect rates of corrosion and fretting damage at the taper interface.

Neer Award 2017: wear rates of 32-mm and 40-mm glenospheres in a reverse total shoulder arthroplasty wear simulation model

BACKGROUND

Larger glenosphere diameters have been used recently to increase prosthesis stability and impingement-free range of motion in reverse total shoulder arthroplasty. The goal of this study was to evaluate the rate of polyethylene wear for 32-mm and 40-mm glenospheres.

METHODS

Glenospheres (32 mm and 40 mm, n = 6/group) and conventional polyethylene humeral liners underwent a 5-million cycle (MC) wear simulation protocol. Abduction-adduction and flexion-extension motion profiles were alternated every 250,000 cycles. At each interval, mass loss was determined and converted to volume loss and wear rate. At 0, 2.5 MC, and 5 MC, liners were imaged using micro-computed tomography to determine surface deviation. White light interferometry was performed on liners and glenospheres at 0 and 5 MC to quantify surface roughness. Wear particle morphology was characterized by environmental scanning electron microscopy.

RESULTS

Total volume loss was significantly higher in 40-mm liners from 1.5 MC onward (P < .05). Overall, volumetric wear rate was significantly higher in 40-mm liners compared with 32-mm glenospheres (81.7 ± 23.9 mm³/MC vs. 68.0 ± 18.9 mm³/MC; P < .001). However, micro-computed tomography surface deviation results demonstrated increased linear penetration on 32-mm glenospheres compared with 40-mm glenospheres (0.36 ± 0.03 µm vs. 0.28 ± 0.01 µm; P = .002). Surface roughness measurements showed no difference for liners; however, increased roughness was noted for 40-mm glenospheres at 5 MC compared with 32 mm (P < .05).

CONCLUSION

Larger glenospheres underwent significantly greater polyethylene volume loss and volumetric wear rates, whereas smaller glenospheres underwent greater polyethylene surface deviations. The enhanced stability provided by larger glenospheres must be weighed against the potential for increased polyethylene wear.

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.

Effect of size and dimensional tolerance of reverse total shoulder arthroplasty on wear: An in-silico study

Although huge research efforts have been devoted to wear analysis of ultra-high molecular weight polyethylene (UHMWPE) in hip and knee implants, shoulder prostheses have been studied only marginally. Recently, the authors presented a numerical wear model of reverse total shoulder arthroplasties (RTSAs), and its application for estimating the wear coefficient k from experimental data according to different wear laws. In this study, such model and k expressions are exploited to investigate the sensitivity of UHMWPE wear to implant size and dimensional tolerance. A set of 10 different geometries was analysed, considering nominal diameters in the range 36-42mm, available on the market, and a cup dimensional tolerance of +0.2, -0.0mm (resulting in a diametrical clearance ranging between 0.04-0.24mm), estimated from measurements on RTSAs. Since the most reliable wear law and wear coefficient k for UHMWPE are still controversial in the literature, both the Archard law (AR) and the wear law of UHMWPE (PE), as well as four different k expressions were considered, carrying out a total of 40 simulations. Results showed that the wear volume increases with the implant size and decreases with the dimensional tolerance for both the wear laws. Interestingly, different trends were obtained for the maximum wear depth vs. clearance: the best performing implants should have a high conformity according to the AR law but low conformity for the PE law. However, according to both laws, wear is highly affected by both implant size and dimensional tolerance, although it is much more sensitive to the latter, with up to a twofold variation of wear predicted. Indeed, dimensional tolerance directly alters the clearance, and therefore the lubrication and contact pressure distribution in the implant. Rather surprisingly the role of dimensional tolerance has been completely disregarded in the literature, as well as in the standards. Furthermore, this study notes some important issues for future work, such as the validation of wear laws and predictive wear models and the sensitivity of k to implant geometry.