Development of superlattice CrN/NbN coatings for joint replacements deposited by high power impulse magnetron sputtering

The demand for reliable coating on medical implants is ever growing. In this research, enhanced performance of medical implants was achieved by a CrN/NbN coating, utilising nanoscale multilayer/superlattice structure. The advantages of the novel high power impulse magnetron sputtering technology, namely, its unique highly ionised plasma, were exploited to deposit dense and strongly adherent coatings on CoCr implants. Transmission electron microscopy analysis revealed coating superlattice structure with bi-layer thickness of 3.5 nm. CrN/NbN deposited on CoCr samples showed exceptionally high adhesion, critical load values of LC2 = 50 N in scratch adhesion tests. Nanoindentation tests showed high hardness of 34 GPa and Young's modulus of 447 GPa. Low coefficient of friction (μ) 0.49 and coating wear coefficient (K C) = 4.94 × 10(-16) m(3) N(-1) m(-1) were recorded in dry sliding tests. Metal ion release studies showed a reduction in Co, Cr and Mo release at physiological and elevated temperatures (70 °C) to almost undetectable levels (<1 ppb). Rotating beam fatigue testing showed a significant increase in fatigue strength from 349 ± 59 MPa (uncoated) to 539 ± 59 MPa (coated). In vitro biological testing has been performed in order to assess the safety of the coating in biological environment; cytotoxicity, genotoxicity and sensitisation testing have been performed, all showing no adverse effects.

Anatomic stemless shoulder arthroplasty and related outcomes: a systematic review

BACKGROUND

The latest generation of shoulder arthroplasty includes canal-sparing respectively stemless designs that have been developed to allow restoration of the glenohumeral center of rotation independently from the shaft, and to avoid stem-related complications. The stemless prosthesis design has also recently been introduced for use in reverse arthroplasty systems.

METHODS

We systematically reviewed the literature for studies of currently available canal-sparing respectively stemless shoulder arthroplasty systems. From the identified series, we recorded the indications, outcome measures, and humeral-sided complications.

RESULTS

We identified 11 studies of canal-sparing respectively stemless anatomic shoulder arthroplasty implants, published between 2010 and 2016. These studies included 929 cases, and had a mean follow-up of 26 months (range, 6 to 72 months). The rates of humeral component-related complications ranged between 0 and 7.9 %. The studies reported only a few isolated cases of complications of the humeral component. Some arthroplasty systems are associated with radiological changes, but without any clinical relevance.

CONCLUSIONS

All of the published studies of canal-sparing respectively stemless shoulder arthroplasty reported promising clinical and radiological outcomes in short to midterm follow-up. Long-term studies are needed to demonstrate the long-term value of these kind of implants.

Avanta Versus Swanson Silicone Implants in the MCP Joint—A Prospective, Randomized Comparison of 30 Patients Followed for 2 Years

The results of Swanson and Avanta metacarpophalangeal joint arthroplasties in rheumatoid patients were compared in a prospective, randomized study of 30 patients (120 implants). At 2-year follow-up, grip strength was measured, hand function was assessed with the Sollerman test and the subjective outcome was determined with visual analogue scores. With both implants ulnar deviation and flexion deformities decreased, and there was no difference between the groups. The increase in range of motion was 7° greater with Avanta implants than with Swanson implants. Grip strength and hand function were unaltered but the visual analogue scales showed decreased pain levels and subjective improvements in hand function, grip strength and cosmesis. Twenty-four of 30 patients were satisfied. Fracture of the silicone spacer occurred with 12 Avanta (20%) and eight Swanson implants (13%), with a higher fracture frequency in men.

A Comparative Study of Outcome between the Neuflex and Swanson Metacarpophalangeal Joint Replacements

This prospective double blind trial compares the clinical findings of Swanson and Neuflex metacarpophalangeal joint replacements in patients with rheumatoid arthritis, up to 2 years follow-up. There were 37 joints (10 patients) in the Swanson group and 40 joints (12 patients) in the Neuflex group. Assessments of range of movement, grip strength and hand function were undertaken in a double blind fashion, preoperatively and up to 2 years following implantation. The mean and standard deviation of the data were calculated. A two-tailed student’s t-test was used when comparing groups of data. An X-ray analysis was also undertaken to identify any implant failure.

There was no significant difference between the two groups with respect to flexion and extension before surgery. At follow-up there was also no significant difference in the extensor lag, with mean extension lags of 19° and 16° for the Swanson and Neuflex implants, respectively. However, there was a significant difference in flexion, with mean active flexion values of 59° and 72° for the Swanson and Neuflex implants, respectively. There were no differences between the two groups in respect to arc of metacarpophalangeal joint motion, ulnar deviation, grip strength or the SODA function test at follow-up. At this early stage there was no evidence of any case of implant failure.

In conclusion, patients who underwent Neuflex metacarpophalangeal joint replacements obtained greater flexion than those who underwent a Swanson replacement.

Long term results after bipolar radial head arthroplasty

Radial head fractures are common injuries, occurring mostly in active young people 85%. Treatment of the more complex radial head fractures (Mason type III and IV), appear to be challenging and remain a subject of controversy. Replacement of the radial head with a metal prosthesis imitates the stabilizing role of the radial head and has been considered as the treatment of choice. However, long-term results are scarce. We report our mid to long-term (mean 9.4 year) clinical and radiographic results after insertion of a Judet Bipolar Radial Head prosthesis. 34 patients were treated with the Judet Bipolar Head prosthesis between 2000 and 2008. In this study, 21 patients were re-examined after a mean period of 113 months (range, 174-84), ie, 9.4 years (range, 14.5-7). Follow-up examinations included both the Mayo Elbow Performance Index (MEPI) and Dis- abilities of the arm, shoulder and hand (DASH) score. Range of motion was measured with a hand goniometer. X-rays were evaluated for peri-articular ossifications, radiolucent lines and signs of proximal erosion, capitellar erosion. Mean Mayo Elbow Performance Index was 88.6 (Range 100-50). According to the MEPI score we had 14 excellent, 1 good, 5 fair results and one poor result. One patient reported severe pain, 3 patients reported moderate pain, one patient reported mild pain and 16 patients reported no pain at all. Difference between pronation-suppination range was noted between primary or secondary indication of the radial head, no other significant differences were found. Mean DASH score was 23.1° (Range 0-63) without difference between primary and secondary indication. Mean flexion was 121.8° (Range : 110-140), mean extension deficit was 24.8° (Range 15-40), mean pronation was 62.4° (Range : 50-80) and suppination 58.8° (Range : 45-80). Ten patients showed signs of ulnohumeral joint degenerative arthritis. One patient developed symptomatic ulna plus. One patient showed radiolucent lines surrounding the prosthesis with proximal bone erosion. There were no reports of dislocations of the prosthesis. One case of radiological signs of overlenghtening was noted. Mainly good clinical results are achieved with the -Judet bipolar radial head implant. Functional results after long term follow-up are, however less optimistic then the excellent results achieved after short- to mid-term follow-up. No clear link between radiological signs and functional results can be found.

Update on calcium pyrophosphate deposition

Calcium pyrophosphate crystal deposition (CPPD) associates with ageing, osteoarthritis (OA), uncommon metabolic diseases, mutations and polymorphisms in the ankylosis human gene (ANKH). CPPD is frequently polyarticular, occurs due to a generalised articular predisposition, and the association between CPPD and OA is joint specific, for example CPPD associates with knee OA, but not with hip OA. Other recently identified associations include knee malalignment (knee CC), low cortical BMD and soft-tissue calcification. CPPD is generally asymptomatic. A recent study reported that knees with OA plus CC at the index joint, or at distant joints (in absence of index joint CC), were more likely to have attrition. CPPD can cause acute CPP crystal arthritis, chronic CPP crystal inflammatory arthritis, and is frequently present in joints with OA. Joint aspiration remains the gold standard for diagnosing CPPD, although other promising techniques are emerging. Patients with polyarticular or young onset CPPD should be screened for underlying metabolic abnormalities, however, such testing can be unrewarding. The treatment of CPPD is symptomatic. Acute CPP crystal arthritis is treated with rest, local application of ice-packs, joint aspiration, colchicine and/or intra-articular corticosteroid injection (once infection is excluded). Colchicine, low-dose corticosteroids, hydroxychloroquine and radiosynovectomy are recommended for the treatment of chronic or recurrent acute CPP crystal arthritis. Recent RCTs did not confirm any benefit from methotrexate, and although there is increasing interest in the use of anti-IL1 agents for acute or chronic CPP crystal arthritis, their efficacy has not been formally examined. Unlike gout, currently there are no treatments to eliminate CPP crystal deposits.

Quantitative assessment and characterization of glenoid bone loss in a spectrum of patients with glenohumeral osteoarthritis

PURPOSE

Eccentric posterior bone loss and associated glenoid retroversion represent challenges to glenoid placement during total shoulder arthroplasty. This bone loss can lead to poor stability and perforation of the glenoid during arthroplasty. The purpose of this study was to evaluate the morphology of glenoid bone loss for a spectrum of osteoarthritis patients using 3D computed tomography imaging and simulation software.

METHODS

This study included 29 patients with glenohumeral osteoarthritis treated with shoulder arthroplasty. Three-dimensional reconstruction of preoperative CT images was performed. Glenoid bone loss was measured at ten, vertically equidistant axial planes along the glenoid surface at four distinct anterior-posterior points on each plane. The images were fitted with modeled pegged glenoid implants to predict glenoid perforation.

RESULTS

The 3D maps demonstrated greatest average bone loss posteriorly in the AP plane at the central axis of the glenoid in the SI plane. The average amount of bone loss was 3.85 mm. Walch A2 and B1 shoulders showed more central bone loss, while Walch B2 shoulders displayed more posterior and inferior bone loss. Patients with predicted peg perforation displayed significantly greater bone loss than those without predicted peg perforation (p = 0.037). Peg perforation was most common in Walch B2 shoulders occurring in the posterior direction involving the central and posterior-inferior peg.

CONCLUSIONS

These data demonstrate an anatomic pattern of glenoid bone loss for different classes of glenohumeral arthritis. These findings can be used to develop various models of glenoid bone loss to guide surgeons, predict failures, and develop better glenoid implants. This study has been approved by the Cleveland Clinic IRB: Number 6235.

The Etiology of Improved Outcomes at High Volume Centers Learning Theory and the Case of Implant Flashing

Increased volume has been shown to be associated with improved outcomes for many orthopaedic procedures. For individual surgeons, the concepts of learning curves and volume effects have been well established in the literature. For institutions, high-volume hospitals have also been shown to have better outcomes for orthopaedic procedures such as total joint replacements. However, exactly how hospital volume mediates this improvement is not well understood. Learning theory states that learning occurs as a result of accumulated experience, not based on time. We compared our institution's curve representing our implant flashing rates to other institutional data sets that exhibit learning and continuous quality improvement, including airline near misses, coal mining accidents, and others. Development of expertise is based on volume and rate of errors, and therefore higher volume is conducive to faster learning.

Does exchange arthroplasty of an infected shoulder prosthesis provide better eradication rate and better functional outcome, compared to a permanent spacer or resection arthroplasty? a systematic review

BACKGROUND

The best surgical modality for treating chronic periprosthetic shoulder infections has not been established, with a lack of randomised comparative studies. This systematic review compares the infection eradication rate and functional outcomes after single- or two-stage shoulder exchange arthroplasty, to permanent spacer implant or resection arthroplasty.

METHODS

Full-text papers and those with an abstract in English published from January 2000 to June 2014, identified through international databases, such as EMBASE and PubMed, were reviewed. Those reporting the success rate of infection eradication after a single-stage exchange, two-stage exchange, resection arthroplasty or permanent spacer implant, with a minimum follow-up of 6 months and sample size of 5 patients were included.

RESULTS

Eight original articles reporting the results after resection arthroplasty (n = 83), 6 on single-stage exchange (n = 75), 13 on two-stage exchange (n = 142) and 8 papers on permanent spacer (n = 68) were included. The average infection eradication rate was 86.7 % at a mean follow-up of 39.8 months (SD 20.8) after resection arthroplasty, 94.7 % at 46.8 months (SD 17.6) after a single-stage exchange, 90.8 % at 37.9 months (SD 12.8) after two-stage exchange, and 95.6 % at 31.0 months (SD 9.8) following a permanent spacer implant. The difference was not statistically significant (p = 0.650). Regarding functional outcome, patients treated with single-stage exchange had statistically significant better postoperative Constant scores (mean 51, SD 13) than patients undergoing a two-stage exchange (mean 44, SD 9), resection arthroplasty (mean 32, SD 7) or a permanent spacer implant (mean 31, SD 9) (p = 0.029). However, when considering studies comparing pre- and post-operative Constant scores, the difference was not statistically significant.

CONCLUSION

This systematic review failed to demonstrate a clear difference in infection eradication and functional improvement between all four treatment modalities for established periprosthetic shoulder infection. The relatively low number of patients and the methodological limitations of the studies available point out the need for well designed multi-center trials to further assess the best treatment option of peri-prosthetic shoulder infection.

Scapular Notching

Developed in 1985, the Grammont-style reverse total shoulder arthroplasty offered a biomechanical advantage for the deltoid muscle as well as predictably reduced pain and improved shoulder function in rotator cuff-deficient shoulders. Despite favorable outcomes, reverse total shoulder arthroplasty is associated with a unique set of complications, one of which is scapular notching. Scapular notching is believed to be a result of mechanical impingement of the humeral component on the lateral scapular pillar. Although it appears that scapular notching progresses with time, its effect on implant survivorship and clinical outcomes is unknown. Factors associated with scapular notching are categorized into several groups, including patient-specific risk factors, surgical approach and technique, and prosthetic design. Surgical strategies to reduce the rate of scapular notching include inferior positioning of the glenosphere, inferior tilting of the glenosphere, and increasing the size of the glenosphere. A lateralized center of rotation and a decreased humeral shaft-neck angle also decrease the incidence of scapular notching. As the indications for reverse total shoulder arthroplasty expand, it is important for orthopaedic surgeons to understand the etiology and incidence, predictive factors, and clinical relevance of scapular notching as well as strategies to avoid it.

Biomechanics of Reverse Shoulder Arthroplasty: Current Concepts

The evolution of reverse shoulder arthroplasty has provided surgeons with new solutions for many complex shoulder problems. A primary goal of orthopaedics is the restoration or re-creation of functional anatomy to reduce pain and improve function, which can be accomplished by either repairing injured structures or replacing them as anatomically as possible. If reconstructible tissue is lacking or not available, which is seen in patients who have complex shoulder conditions such as an irreparable rotator cuff-deficient shoulder, cuff tear arthropathy, or severe glenoid bone loss, substantial problems may arise. Historically, hemiarthroplasty or glenoid grafting with total shoulder arthroplasty yielded inconsistent and unsatisfactory results. Underlying pathologies in patients who have an irreparable rotator cuff-deficient shoulder, cuff tear arthropathy, or severe glenoid bone loss can considerably alter the mechanical function of the shoulder and create treatment dilemmas that are difficult to overcome. A better biomechanical understanding of these pathologic adaptations has improved treatment options. In the past three decades, reverse total shoulder arthroplasty was developed to treat these complex shoulder conditions not by specifically re-creating the anatomy but by using the remaining functional tissue to improve shoulder balance. Reverse total shoulder arthroplasty has achieved reliable improvements in both pain and function. Initial implant designs lacked scientific evidence to support the design rationale, and many implants failed because surgeons did not completely understand the forces involved or the pathology being treated. Implant function and clinical results will continue to improve as surgeons' biomechanical understanding of shoulder disease and reverse shoulder arthroplasty implants increases.

Reverse Shoulder Arthroplasty for Trauma: When, Where, and How

Reverse shoulder arthroplasty has become increasingly popular for the treatment of complex shoulder injuries, including proximal humerus fractures and fixed glenohumeral dislocation, in the elderly population. The early to midterm results of reverse shoulder arthroplasty for the treatment of proximal humerus fractures are promising compared with the results of unconstrained humeral head replacement, and patients may have more predictable improvement with less dependence on bone healing and rehabilitation. However, long-term follow-up is needed, and surgeons must be familiar with various complications that are specific to reverse shoulder arthroplasty. To achieve optimal patient outcomes for the management of traumatic shoulder injuries, surgeons must have a comprehensive understanding of the current implant options, indications, and surgical techniques for reverse shoulder arthroplasty.

Emerging Indications for Reverse Shoulder Arthroplasty

Historically, reverse shoulder arthroplasty was reserved for older, low-demand patients in whom rotator cuff arthropathy was diagnosed. Other common indications included sequelae of previously treated proximal humerus fractures, failed anatomic total shoulder arthroplasty, tumor resection, and rheumatoid arthritis in the elderly population. Unpredictable implant durability and high complication rates have limited the use of reverse shoulder arthroplasty to a narrow group of patients. Over the past decade, however, research has led to an improved understanding of the biomechanics behind reverse shoulder prostheses, which has improved implant design and surgical techniques. Consequently, orthopaedic surgeons have slowly begun to expand the indications for reverse shoulder arthroplasty to include a wider spectrum of shoulder pathologies. Recent studies have shown promising results for patients who undergo reverse shoulder arthroplasty for the treatment of acute proximal humerus fractures, massive rotator cuff tears without arthropathy, primary osteoarthritis, and chronic anterior dislocation, as well as for younger patients who have rheumatoid arthritis. These data suggest that, with judicious patient selection, reverse shoulder arthroplasty can be an excellent treatment option for a growing patient cohort.

Shoulder Arthroplasty: Key Steps to Improve Outcomes and Minimize Complications

Advances in shoulder replacement surgery have allowed for the successful treatment of various shoulder conditions. As the elderly population increases and the surgical indications for shoulder replacement surgery continue to expand, the number of shoulder replacements performed annually will continue to increase. Accordingly, the number of complications also will be expected to increase. Successful shoulder replacement outcomes require surgeons to have a thorough understanding of the surgical indications, surgical technique, and potential complications of the procedure. By reviewing the key aspects of shoulder replacement surgery and focusing on the surgical technique and common complications for both anatomic and reverse total shoulder arthroplasty, surgeons can help improve outcomes and minimize complications.

[Alloplastic Materials and their Propensity to Bacterial Colonisation]

PURPOSE OF THE STUDY The alloplastic materials currently used for protective surface layers on implants were tested in vitro under microbiological laboratory conditions by contamination with microbial agents most frequently found in deep infection of total joint replacements. The objective was to find out how the resistance to bacterial colonisation was related to different surface finishes. MATERIAL AND METHODS Each of 14 samples of alloplastic material currently used in the manufacture of orthopaedic implants was inoculated with each of the group of microorganisms most frequently infecting joint replacements; these were Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Enterococcus faecalis and Escherichia coli. At 24 hours of incubation, biofilms produced on sample surfaces were collected, stained with crystalline violet and assessed by spectrophotometry. The average value of biofilm absorbances (AV595) for the group of microorganism tested was taken as a basic characteristic of each material sample indicating its sensitivity to bacterial. RESULTS Of the metal materials with smooth surface finish, Vitalium (AV595, 0.368) showed the lowest affinity to microbial colonisation; next was titanium (AV595, 0.459) and steel (AV595, 0.505). A significant increase in sensitivity to bacterial colonisation was recorded in all types of surface finish of steel (AV595, 0.571) and in titanium alloy with a rough surface texture (AV595, 0.737 to 1.676); p < 0.05. Porous titanium surfaces significantly increased material affinity to colonisation. DISCUSSION Our study had certain limitations concerning in vitro evaluation of porous surfaces that have high affinity to bacterial colonisation. Porous titanium, and its hydroxyapatite layer in particular, considerably promotes osteoblast colonisation of the surface as well as implant osseointegration in the bone bed. Microorganisms therefore have no room for surface colonisation. Problematic may remain the surface parts outside contact with bone that keep their affinity to bacterial colonisation. CONCLUSIONS The material of choice for cemented implants is Vitalium which, of all metal surfaces, has the lowest sensitivity to bacterial colonisation. The materials of choice for cementless implants are titanium alloys. However, an osteoactive surface not in contact with bone remains a problem. On the one hand, its roughness and porosity are crucial to good osseointegration, on the other hand, its affinity to bacterial colonisation is high.

KEY WORDS

alloplastic material, biofilm, joint replacement infection.

Correlation Between Clinical Outcomes and Anatomic Reconstruction with Anatomic Total Shoulder Arthroplasty

Many glenohumeral studies have demonstrated how anatomy varies across the population. Third and fourth generation shoulder prosthesis designs were developed to provide greater modularity and size ranges to better reproduce this anatomy and thus achieve better results in terms of shoulder function. This study quantifies the quality of anatomic reconstruction and compares that to long-term clinical outcomes using one fourth generation platform shoulder system.

METHODOLOGY

One hundred and forty primary total shoulder arthroplasties were performed by one experienced single surgeon between 2001 and 2009, using the same fourth generation modular prosthesis. Pre- and postoperative clinical assessments were quantified with the Constant, ASES, SPADI, SST, and UCLA scores, and active range of motion was measured. Five anatomic parameters were defined, measured, and compared pre- and postoperatively on the anterior-posterior (AP) radiographs: Humeral Head Height (HHH), Humeral Head Centering (HHC), Humeral Head Medial Offset (HHMO), Humeral Head Diameter (HHD), and Humeral Neck Angle (HNA). The differences between each of the parameters were then calculated and rated from 0 to 2 and then summed for each patient to obtain the Anatomic Reconstruction Index (ARI), which objectively quantifies and assesses the quality of the anatomic reconstruction. Patients were sorted based upon their ARI score into two groups (ARI 5 to 7 and ARI 8 to 10), and their latest follow-up outcomes were compared using the Mann-Whitney test to identify differences in preoperative and postoperative results, where p < 0.05 denoted a significant difference.

RESULTS

Of the 140 primary prostheses performed, 78 patients were lost to follow-up, and 13 were excluded for complications that were not related to the anatomic reconstruction. Forty-nine patients (75.8 yrs., 31F/18M) were included with an average follow-up of 9.1 years. The average score for HHH was 1.9 ± 0.4, 1.8 ± 0.5 for HHC, 1.7 ± 0.5 for HHMO, 1.7 ± 0.5 for HHD, and 1.5 ± 0.7 for HNA. Thus, all reconstructions were rated good to excellent with 86% of very good/excellent reconstruction (ARI 8 to 10) and 14% good reconstruction (ARI 5 to 7). A comparison of radiographic anatomic parameters was performed for these two cohorts: HHC (< 0.0001), HNA (0.000), and ARI (<0.0001) were significantly greater for the ARI 8 to 10 cohort. Four of five postoperative clinical outcome metrics for the ARI 8 to 10 cohort were significantly greater than the mean values for the ARI 5 to 7 cohort. Additionally, mean postoperative pain on a daily basis and shoulder function for the ARI 8 to 10 cohort were significantly greater than that for the ARI 5 to 7 cohort.

DISCUSSION

The relatively small number of good reconstructions (14%) compared to very good/excellent reconstructions (86%) and the absence of fair/poor reconstructions limited the ability for any strong linear correlations between anatomical reconstruction and clinical parameters. Despite this, patients with larger mean ARI scores were associated with significantly better outcomes for some measures. This study is limited by the use of 2D assessments from standard AP radiographs; this method can be further refined by the use of 3D quantitative assessment of each parameter.

CONCLUSION

This study confirmed that an improved anatomic reconstruction results in better postoperative clinica outcomes. The fourth generation prosthesis used for this study allows continuous in-situ adjustment of the humeral head orientation through use of the spherical taper on the replicator plate and also a double adjustment of offset through the use of the offset humeral head and offset taper on the replicator plate.

A Comparison and Correlation of Clinical Outcome Metrics in Anatomic and Reverse Total Shoulder Arthroplasty

INTRODUCTION

Indications for anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty are well defined and dependent on the function of the rotator cuff; however, indications for rTSA have gradually extended to complex fractures, revisions, and primary arthritis in very elderly patients. The risk of secondary rupture of a weakened or degenerative rotator cuff is difficult to assess and can lead the orthopaedic surgeon to hesitate between aTSA or rTSA. It, therefore, seems appropriate to compare these two types of prostheses in terms of pain, functional, clinical outcome metric scores, and complications, despite suspected differences between populations and the respective diseases.

METHODOLOGY

1,145 patients (69.2 ± 8.9 years) were treated by 12 orthopaedic surgeons in France and in the USA, using either aTSA or rTSA with one platform shoulder system. Five hundred twenty-eight patients received aTSA (66.2 ± 9.0 years; 283 female, 245 male) for treatment of degenerative arthritis, and 617 patients received rTSA (71.8 ± 8.0 years; 392 female, 225 male) for treatment of cuff tear arthroplasty, rotator cuff tear, and osteoarthritis. Each patient was scored preoperatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics; active range of motion was also measured. The average follow-up for all patients was 39.7 ± 18.7 months (aTSA: 42.7 ± 21.9 months; rTSA: 37.1 ± 15.1 months). Improvements in outcome using each metric score were normalized on a 100 point scale, correlated, and compared. A Student's two-tailed, unpaired t-test was used to identify differences in preoperative, postoperative, and pre-to-postoperative improvements, where p < 0.05 denoted a significant difference.

RESULTS

Preoperatively, rTSA patients had significantly lower mean outcome scores and significantly lower mean active range of motion as compared to aTSA patients. Post-operatively, rTSA and aTSA patients showed no significant difference in active forward flexion or in mean outcome scores as measured by four of the five metrics. rTSA patients had significantly lower active abduction, internal rotation, and active and passive external rotation than aTSA patients. However, they had significantly better strength (9.7 vs. 7.3 lbs, p < 0.0001). Preoperative to postoperative mean improvements were compared between both cohorts. rTSA patients were associated with significantly larger improvements in outcomes and also had significantly better improvements in active forward flexion and strength. Conversely, aTSA patients had significantly better improvement in active and passive external rotation and active internal rotation. Analysis of complications demonstrated a very similar rate between cohorts, with aTSA patients associated with a slightly lower rate (6.6 vs. 7.3%).

CONCLUSION

This retrospective analysis of prospectively acquired data from 1,145 patients who received either a primary aTSA or rTSA prosthesis demonstrates that each device provides significant improvements with very similar mean results. In fact, the mean clinical outcomes associated with the reverse shoulder prostheses approach that of the "gold standard" anatomic device for their respective indications. Furthermore, the complication rates in this series are very similar and also favorable relative to the clinical literature. Findings, such as these, may at some point extend the indications of the reverse prosthesis to patients for whom an anatomical prosthesis could lead to a premature deterioration of the result.

Role of Subscapularis Repair on Muscle Force Requirements with Reverse Shoulder Arthroplasty

Concomitant repair of the subscapularis with reverse shoulder arthroplasty (rTSA) is controversial. To evaluate the biomechanical impact of subscapularis repair with rTSA, a cadaveric shoulder controller quantified the muscle forces required to elevate the arm during scapular abduction with the elbow flexed at 90°. The results of this study demonstrate that concomitant subscapularis repair with rTSA creates a biomechanically unfavorable condition during arm elevation. Specifically, repair of the subscapularis significantly increased the force required by the deltoid and posterior rotator cuff and also significantly increased the joint reaction force relative to when the subscapularis was not repaired. These results also demonstrated that both the 42 mm Grammont and 42 mm Equinoxe® rTSA prostheses significantly decreased the mean force required by the posterior rotator cuff and also significantly decreased the mean joint reaction force over the range of motion relative to the native joint with a rotator cuff tear (supraspinatus). As the posterior rotator cuff is often compromised in patients undergoing rTSA, patients may not be able to sustain these elevated forces in the infraspinatus and teres minor required to counteract the adduction and internal rotation moments generated by the subscapularis during activities of daily living. Similarly, the elevated posterior deltoid force and joint reaction loads could be deleterious to the long-term life of the prosthesis and can also increase the risk of loosening and fractures. For all these reasons, rTSA functional outcomes may be compromised if the subscapularis is repaired.

Optimization of Cemented Glenoid Peg Geometry. A Comparison of Resistance to Axial Distraction

INTRODUCTION

Glenoid loosening is one of the most common complications of anatomic total shoulder arthroplasty (aTSA). Numerous glenoid pegged designs exist within the market place; however, little effort has been made to optimize peg geometry, and as a result, there is no consensus regarding the superiority of one design over another. The aim of this study was to determine the impact of peg design on the fixation strength by comparing the force and displacement associated with five different geometries of cemented glenoid components when each is axially displaced from two different densities of polyurethane bone substitute substrates.

METHODS

An axial pull-out test was conducted on five different cemented peg geometries in both low- and high- density polyurethane bone-substitute blocks. All substrates were prepared utilizing a drill, which created a 7.3 mm diameter hole to a depth of 26.8 mm. Cemex ® brand bone cement was prepared and used to cement all pegs. After cementation of each peg, an electromechanical load frame applied a linear ramp displacement of 10 mm/minute axially to each peg while the polyurethane block was fully con strained. Load and displacement of each peg was sampled at 100 Hz until failure and axial distraction of each peg where the peak pull-out force and associated displacement were recorded. The average load to failure and associated displacement for each peg geometry were compared utilizing the Student's t-test where a p-value < 0.05 determined significance.

RESULTS

Cemented peg design #3 was associated with the greatest axial load to failure (675.3 N ± 18.8 N in low density and 707.3 N ± 11.7 N in high density) for both densities of bone-substitute blocks. Peg designs #5 and #2 were associated with the next highest axial loads to failure in both low and high density blocks. Finally, peg designs #1 and #4 were associated with the lowest axial loads to failure in both low and high density blocks. Only design #3 had a statistically significant difference between peak pull-out forces between the low- and high-density bone substitute blocks, as compared to all other designs.

CONCLUSIONS

The results of this study demonstrate that glenoid peg geometry can significantly influence the resistance to axial distraction where the continuous threaded geometry exemplified by peg design #3 demonstrated significantly superior cemented fixation relative to the other peg designs. It can be concluded that overall macrostructure and design of the peg itself plays a key role in pull-out force; however, performance in a clinical setting is required to confirm these biomechanical results.

Analysis of Glenoid Fixation with Anatomic Total Shoulder Arthroplasty in an Extreme Cyclic Loading Scenario

INTRODUCTION

ASTM F2028-14 was adopted to recom mend a cyclic eccentric glenoid edge loading test that simulates the rocking horse loading mechanism beleived to cause aTSA glenoid loosening. While this method accurately simulates that failure mechanism, the recommended 750 N load may not be sufficient to simulate worst-case loading magnitudes, and the recommended 100,000 cycles may not be sufficient to simulate device fatigue-related failure modes. Finally, if greater loading magnitude or a larger number of cycles is performed, the recommended substrate density may not be sufficiently strong to support the elevated loads and cycles. To this end, a new test method is proposed to supplement ASTM F2028-14.

METHODS

A series of cyclic tests were performed to evaluate the long-term fixation strength of two different hybrid glenoid designs in both low (15 pcf) and high (30 pcf) density polyurethane blocks at elevated loads relative to ASTM F2028-14. To simulate a worst case clinical condition in which the humeral head is superiorly migrated, a cyclic load was applied to the superior glenoid rim to induce a maximum torque on the fixation pegs for three different cyclic loading tests: 1. 1,250 N load for 0.75 M cycles in a 15 pcf block, 2. 1,250 N load for 1.5 M cycles in a 30 pcf block, and 3. 2,000 N load for 0.65 M cycles in a 30 pcf block.

RESULTS

All devices completed cyclic loading without failure, fracture, or loss of fixation regardless of glenoid design, polyurethane density, loading magnitude, or cycle length. No significant difference in post-cyclic displacement was noted between designs in any of the three tests. Post-cyclic radiographs demonstrated that each device maintained fixa - tion with the metal pegs within the bone-substitute blocks with no fatigue related failures.

DISCUSSION

These results demonstrate that both cemented hybrid glenoids maintained fixation when tested according to each cyclic loading scenario, with no difference in post-cyclic displacement observed between designs. The lack of fatigue-related failures in these elevated load and high cycle test scenarios are promising, as are the relatively low displacements given the extreme nature of each test. This cyclic loading method is intended to supplement the ASTM F2028-14 standard that adequately simulates the rocking horse loading mechanism but may not adequately simulate the fatigue-related failure modes.

Impact of Posterior Wear on Muscle Length with Reverse Shoulder Arthroplasty

The use of reverse total shoulder arthroplasty (rTSA) in patients with posterior glenoid wear can be challenging. Implanting a baseplate in the correct version may require significant eccentric reaming, which further medializes the joint line and results in greater rotator cuff muscle shortening. To restore the joint line, bone graft may be required, though it is associated with additional risks. As an alternative solution, augmented glenoid baseplates offer the potential to restore the joint line and improve rotator cuff muscle tensioning without the need for eccentric reaming or supplemental bone graft. To that end, this computer analysis quantifies the rotator cuff muscle length for standard and augmented rTSA when used in a normal and posteriorly worn glenoid. These results demonstrate that shortening of the rotator cuff occurred for both the standard and posterior augmented reverse shoulder designs with additional muscle shortening occurring in scapula with posteriorly worn glenoids. More anatomic rotator cuff muscle tensioning was observed with augmented glenoid baseplates. The use of posterior augmented glenoid baseplates has the potential to improve stability and better restore active internal and external rotation, a current limitation of rTSA. However, clinical follow-up is necessary to confirm these favorable biomechanical results.

Rate of Improvement in Clinical Outcomes with Anatomic and Reverse Total Shoulder Arthroplasty

INTRODUCTION

The rate of clinical improvement has never been studied after anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty. This study quantifies the rate of improvement after aTSA and rTSA using five different scoring metrics for 1,641 patients.

METHODS

We evaluated 1,641 (69 ± 9.3 years old) patients treated by 14 orthopaedic surgeons using either aTSA or rTSA with a single platform shoulder system. Seven hundred twenty-nine patients received aTSA, and 912 patients received rTSA. Each patient was scored preoperatively and at various follow-up intervals (2 weeks, 6 weeks, 3 months, 6 months, annually, etc.) with a maximum follow-up time of 139 months using the SST, UCLA, ASES, Constant, and SPADI metrics. In addition, range of motion was measured. The rate of improvement was analyzed using a 40-point moving filter treadline over the entire range of follow-up.

RESULTS

All metrics improved in a majority of patients with less than 5% worsening after 6 months. While gains in motion were present in the majority of patients after aTSA, a higher incidence of patients failed to experience improvement in range of motion after rTSA. Clinical worsening was seen in up to 10% and 20% of the visits for active flexion and abduction and external rotation, respectively. The majority of clinical improvement after aTSA and rTSA was noted in the first 6 months with full improvement noted by 12 to 24 months. During the first 12 months, the rate of improvement associated with rTSA patients was generally 30% larger than that of aTSA patients.

DISCUSSION

The results of this large-scale database analysis demonstrate the reliability of improvements in outcomes and motion achieved with both aTSA and rTSA for various indications. For both aTSA and rTSA, less than 5% of patients reported worsening in each of the five clinical metrics after 6 months postoperative follow-up time. This study is significant because it quantifies how patient outcomes improve with time following treatment with both aTSA and rTSA. These results can be used to establish realistic patient expectations regarding the typical follow-up time required for pain to be reduced and function restored following surgical treatment with a total shoulder prosthesis.

Bone Grafting the Glenoid Versus Use of Augmented Glenoid Baseplates with Reverse Shoulder Arthroplasty

BACKGROUND

Large glenoid defects are a difficult reconstructive problem for surgeons performing reverse shoulder arthroplasty (rTSA). Options to address glenoid defects include eccentric reaming, bone grafting, and augmented glenoid baseplates. Augmented glenoid baseplates may provide a simpler, cost-effective, bone-preserving option compared to other techniques. No studies report the use of augmented baseplates to correct glenoid deformity in rTSA relative to the use of glenoid bone graft.

MATERIALS AND METHODS

We retrospectively reviewed 80 patients that received a primary rTSA and received either a structural bone graft or an augmented glenoid baseplate to address a significant glenoid defect. There were 39 patients in the augmented baseplate cohort and 41 patients in the bone graft cohort. The augmented baseplate cohort contained 24 8° posterior augment implants and 15 10° superior augment baseplates. The bone graft cohort consisted of 36 autograft humeral heads and 5 allograft femoral heads. The average follow-up for rTSA patients with an augmented baseplate was 28.3 ± 5.7 months, and the average follow-up for rTSA patients with glenoid bone graft was 34.1 ± 15.0 months. Each patient was scored preoperatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics. Range of motion data was obtained as well.

RESULTS

All patients demonstrated significant improvements in pain, ROM, and functional scores following treatment with rTSA using either augmented baseplates or glenoid bone graft to correct glenoid defects. The database contained no complications for the augmented glenoid baseplate cohort, and six complications (14.6%) for the glenoid bone graft cohort (including two glenoid loosenings and graft failures). Additionally, the augmented baseplate cohort showed a lower scapular notching rate of 10% as compared to the bone graft cohort which had a notching rate of 18.5%.

DISCUSSION

The results of this study suggest that either augmented glenoid baseplates or glenoid bone graft can be used to address large glenoid defects during rTSA with significant improvement in outcomes. Augmented glenoid baseplates may achieve a lower complication and scapular notching rate, but additional and longer-term clinical follow-up is required to confirm these results.

Assessment of the Anatomic Neck as an Accurate Landmark for Humeral Head Resurfacing Implant Height Placement

INTRODUCTION

Humeral head resurfacing has been described as a more anatomic replacement alternative for proximal humerus arthroplasties when compared to conventional stemmed implants. However, not all studies show that humeral head resurfacing is better at reproducing the proximal humeral anatomy with overstuffing of the joint being a common complication. The purpose of this study was to assess the use of the anatomic neck as a landmark for proper placement of humeral head replacements.

METHODS

Sixty-six cadaveric shoulder CT scans were reconstructed using Mimics to create 3D models of the humerus. After 3D reconstruction, each bone model was analyzed in Rapidform to establish the anatomic neck plane, the humeral head average radius of curvature, and anatomic center of rotation (CoR) using a best fit sphere over the articular surface. Humeral head resurfacing implants (Equinoxe®, Exactech, Inc.) were assembled onto the 3D humeral models, selected by matching the closest implant size available with the anatomic radius of curvature. Implants were constrained to match the anatomic neck angle and version and were spaced 2 mm away from the anatomic neck. The 3D distances between the anatomic center of rotation and the implant CoR and the implanted head thickness deviations were measured using Unigraphics to observe anatomic reproduction with the resurfacing implants.

RESULTS

When placing all resurfacing implants 2 mm from the anatomic neck, the average implant CoR offset from the anatomic CoR was determined to be 1.03 mm ± 0.75 mm. The average implant Humeral Head Thickness (HHT) deviation from the anatomic HHT was determined to be -0.36 mm ± 0.84 mm. There were no significant differences in CoR offset or HHT offset between implant sizes used.

DISCUSSION

Newer generation resurfacing implant designs allow for more anatomic reproduction of the humeral articular surface. Depth of reaming and resurfacing implant height placement are potential pitfalls in humeral head replacement and have been shown to have negative effects on reproducing the CoR and HHT. Using the anatomic neck as a landmark for the depth of reaming has been observed to closely reproduce anatomic HHT and CoR. Further work aims to validate the use of the anatomic neck as a consistent landmark in cadaveric studies and to investigate if these findings are clinically relevant.

Preliminary Results of a Novel Hybrid Cage Glenoid Compared to an All-Polyethylene Glenoid in Total Shoulder Arthroplasty

INTRODUCTION

The aim of this study was to evaluate the preliminary outcomes of a hybrid cage glenoid design in comparison to pegged all-polyethylene glenoid components in anatomic total shoulder arthroplasty (aTSA).

MATERIALS AND METHODS

Ninety-two patients undergoing primary anatomic total shoulder arthroplasty with minimum two-year follow-up were reviewed. Forty-six patients had an ultra-high molecular weight polyethylene (UHMWPE) cemented pegged glenoid component, and 46 had a hybrid cage glenoid component. Patient data was retrospectively reviewed from prospectively acquired data in a multi-institutional IRB approved database. These age, gender, and follow-up matched patients were evaluated and scored preoperatively and a latest follow-up using the SST, UCLA, ASES, Constant, and SPADI scoring metrics. Additional measures included active abduction, elevation, and external rotation. Radiolucent line assessment of the glenoid was performed by use of a Grashey and axillary radiograph at latest follow-up. A Student's two tailed, unpaired t-test was used to identify differences in preoperative and postoperative results, where p < 0.05 denoted a significant difference.

RESULTS

All patients demonstrated significant improvements in pain and function following treatment with the primary aTSA. The database contained three complications for the aTSA patients with a cage glenoid, and three complications for patients with a UHMWPE pegged glenoid. Radiographic data was available for 37 of 46 cage glenoid patients and 29 of 46 UHMWPE pegged glenoid patients. Five of 37 cage glenoid patients had a radiolucent line (13.5%) with an average radiographic line score of 0.22. Eight of 29 UHMWPE peg glenoid patients had a radiolucent line (27.6%) with an average radiographic line score of 0.57. Cage aTSA patients were associated with significantly less blood loss than aTSA UHMWPE pegged glenoid patients (avg. blood loss = 242 vs. 337; p = 0.022).

CONCLUSION

At minimum two-year follow-up, hybrid cage aTSA components show equal clinical outcomes to UHMWPE pegged glenoids. However, the hybrid cage components had significantly fewer radiolucent lines and less intra-operative blood loss. Additional and longer-term clinical and radiographic follow-up is necessary to confirm these promising early results.