In vitro comparison of wear characteristics of PyroCarbon and metal on bone: Shoulder hemiarthroplasty

Pyrocarbon hemiarthroplasty and the shoulder: biomechanical and clinical results of an emerging treatment option

While shoulder hemiarthroplasty is still used to treat young patients with shoulder pathology, the use of this procedure has substantially declined in recent years due to its significant complication profile. Glenoid wear with arthrosis is one of the major postoperative complications following shoulder hemiarthroplasty, and efforts to prevent this complication led many scientists to explore alternative weight-bearing surfaces on arthroplasty implants to decrease joint wear and improve patient outcomes. Pyrolytic carbon, or pyrocarbon, is a material that has better biocompatibility, survivorship, strength, and wear resistance compared to the materials used in traditional shoulder hemiarthroplasty. Pyrocarbon implants have been used in orthopedics for over 50 years; recently, their utility in shoulder hemiarthroplasty has garnered much interest. The purpose behind the use of pyrocarbon in shoulder hemiarthroplasty is to decrease the risk of progressive glenoid wear, especially in young active patients in whom joint preservation is important. Promising survivorship and outcomes have been demonstrated by recent studies, including limited glenoid wear following pyrocarbon hemiarthroplasty. Nevertheless, these clinical studies have been limited to relatively small case series with limited long-term follow-up. Accordingly, additional research and comparative studies need to be conducted in order to properly assess the therapeutic efficacy and value of pyrocarbon hemiarthroplasty.

Pyrocarbon humeral heads for hemishoulder arthroplasty grant satisfactory clinical scores with minimal glenoid erosion at 5-9 years of follow-up

BACKGROUND

Hemishoulder arthroplasty (HSA) is a more conservative alternative to total shoulder arthroplasty for young and active patients with minimal glenoid erosion or deformity. Pyrocarbon humeral heads were introduced as an alternative to metallic humeral heads, which were associated with glenoid erosion in 28%-43%. The purpose of this study was to evaluate the progression of glenoid erosion and clinical scores of HSA using pyrocarbon humeral heads from short- (2-4 years) to midterm (5-9 years).

METHODS

We retrieved the records of 45 consecutive patients who underwent HSA with pyrocarbon humeral heads from 2013 to 2017. Patients were evaluated radiographically and clinically at a first follow-up (2-4 years) and a second follow-up (5-9 years). Preoperative glenoid morphology was assessed using computed tomography scans, and glenoid erosion was assessed using plain radiographs according to Sperling et al. The Constant score (CS), American Shoulder and Elbow Surgeons (ASES) score, and Subjective Shoulder Value (SSV) score were assessed by an independent observer.

RESULTS

From the initial cohort of 45 patients, 2 underwent revision surgery (4.4%) due to persistent pain (without signs of rotator cuff pathology or glenoid erosion) and 6 were lost to follow-up (13%), leaving 37 for outcome assessment (82%). At the first follow-up of 2.2 ± 0.4 years, all clinical scores improved substantially (CS from 29.3 ± 13.5 to 76.7 ± 14.4, ASES from 23.7 ± 15.6 to 87.0 ± 16.0, and SSV from 25.3 ± 12.2 to 84.1 ± 15.2), and at the second follow-up of 6.2 ± 1.2 years, good clinical scores were maintained (CS from 76.7 ± 14.4 to 80.8 ± 16.0, ASES from 87.0 ± 16.0 to 92.3 ± 15.0, and SSV from 84.1 ± 15.2 to 82.8 ± 18.3). At the second follow-up, glenoid erosion was moderate in 9 (24%) and severe in 3 (8.1%). When comparing with immediate postoperative radiographs, 10 shoulders exhibited progression of glenoid erosion by 1 grade (n = 9) or 2 grades (n = 1).

CONCLUSION

Pyrocarbon humeral heads for HSA grant satisfactory clinical scores with minimal glenoid erosion.

Pyrocarbon hemiprostheses show little glenoid erosion and good clinical function at 5.5 years of follow-up

BACKGROUND

The success of traditional shoulder hemiarthroplasty (HA) with cobalt-chromium heads is limited by painful glenoid erosion with problematic bone loss. Hemiprostheses with pyrolytic carbon (PyC) heads have shown reduced glenoid erosion in experimental laboratory studies. Few in vivo data are available.

METHODS

We performed a single-center consecutive cohort study of 31 of 34 patients (91%) who underwent PyC HA between September 2013 and June 2018. In 11 of these patients, concentric glenoid reaming was additionally performed. The mean follow-up period was 5.5 years (range, 3.5-7 years). Standardized radiographs were taken, and clinical function (Constant score) and pain (visual analog scale score) were recorded. Anteroposterior radiographs were analyzed according to an established method by 2 independent observers: A line parallel to the superior and inferior glenoid rim was translated to the most medial point of the glenoid surface. A further parallel line was placed on the spinoglenoid notch. The distance between these 2 lines was measured. Measurements were scaled using the known diameter of the implanted humeral head component. To assess eccentric erosion, anteroposterior and axial images were classified according to Favard and Walch, respectively.

RESULTS

Mean medial glenoid erosion measured 1.4 mm at an average of 5.5 years of follow-up. In the first year, 0.8 mm of erosion was observed, significantly more than the average erosion per year of 0.3 mm (P < .001). Mean erosion per year was 0.4 mm in patients with glenoid reaming vs. 0.2 mm in those without reaming (P = .09). An evolution of glenoid morphology was observed in 6 patients, of whom 4 had a progression of the erosion grade. The prosthesis survival rate was 100%. The Constant score improved from 45.0 preoperatively to 78.0 at 2-3 years postoperatively and 78.8 at latest follow-up (5.5 years postoperatively) (P < .001). The pain score on a visual analog scale decreased from 6.7 (range, 3-9) preoperatively to 2.2 (range, 0-8) at latest follow-up (P < .001). There was a weak correlation (r = 0.37) between erosion and pain improvement (P = .039) and no correlation between erosion and change in Constant score (r = 0.06).

CONCLUSION

PyC HA caused little glenoid erosion and a sustained improvement in clinical function in our cohort at mid-term follow-up. PyC demonstrates a biphasic development of glenoid erosion, with a reduced rate after the first year. PyC HA should therefore be considered as an alternative to cobalt-chromium HA and to anatomical total shoulder arthroplasty for patients with a high risk of glenoid component complications.

Pyrolytic carbon head shoulder arthroplasty: CT scan glenoid bone modeling assessment and clinical results at 3-year follow-up

Background

The aim of this study is to report the radiological glenoid modifications and clinical outcomes at 3 years mean follow-up of hemi shoulder arthroplasty (HA) with pyrocarbon (PYC) humeral head. Our hypothesis was that the PYC implants would provide good outcomes without major glenoid erosion. Additionally, we hypothesized that HA-PYC allowed for remodeling of the bone.

Methods

Patients underwent HA with PyC humeral head for treatment of primary or secondary osteoarthritis, excluding post-traumatic cases. All patients had a Constant Score assessed preoperatively and at the last follow-up. Preoperative and postoperative computed tomography scans at the last follow-up were performed to achieve 3-dimensional reconstructions of the scapulae. Deformities of the glenoid surface were analyzed as a distance differential between postoperative and preoperative to investigate potential bone remodeling vs. glenoid erosion. The subluxation index (SLI) was measured.

Results

We included 41 patients implanted with a HA-PYC. Average age at the time of implant was 63.8 (40 to 79 years). All patients were followed for ≥2 years with an average follow-up of 36.3 months (24 to 60 months). Constant Scores increased from 34 at baseline to 80 at the last follow-up points on average (P < .01). Return to work rate was 100% and 96% had resumed their physical activity. Ten (77%) of the 13 patients with posterior head subluxation had normalized their SLI. Furthermore, no significant differences were detected between the individuals having corrected their posterior subluxation and the others (preoperative SLI between 0.45 and 0.55). Glenoid wear is less than 0.6 mm at 3 years mean follow-up, ie, 5 times less than metallic implants. A tendency to recenter the head in the anteroposterior plane was found in type B glenoid, without increased erosion of the glenoid, with very good clinical results. We did not find any difference according to age or glenoid type for clinical and radiological results.

Conclusion

HA-PYCs give, in the short term, excellent clinical results in terms of pain and function. The development of a precise and objective measurement method has made it possible to demonstrate that the glenoid surface is the site of modifications that may be part of bone remodeling or progression of the osteoarthritis disease.

Survivorship of shoulder arthroplasty in young patients with osteoarthritis: an analysis of the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

The treatment of shoulder osteoarthritis in the young patient remains challenging. The higher functional demands and higher expectations of the young patient cohort are often coupled with increased failure and revision rates. Consequently, shoulder surgeons are faced with a unique challenge with implant selection. The aim of this study was to compare the survivorship and reasons for revision of 5 classes of shoulder arthroplasty in patients aged <55 years with a primary diagnosis of osteoarthritis by use of data from a large national arthroplasty registry.

METHODS

The study population included all primary shoulder arthroplasty procedures undertaken for osteoarthritis in patients aged <55 years and reported to the registry between September 1999 and December 2021. Procedures were grouped into the following classes: total shoulder arthroplasty (TSA), hemiarthroplasty resurfacing (HRA), hemiarthroplasty stemmed metallic head (HSMH), hemiarthroplasty stemmed pyrocarbon head (HSPH), and reverse total shoulder arthroplasty (RTSA). The outcome measure was the cumulative percent revision, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios (HRs) were calculated from Cox proportional hazards models, adjusting for age and sex, to compare revision rates among groups.

RESULTS

There were 1564 shoulder arthroplasty procedures in patients aged <55 years, of which 361 (23.1%) were HRA, 70 (4.5%) were HSMH, 159 (10.2%) were HSPH, 714 (45.7%) were TSA, and 260 (16.6%) were RTSA. HRA had a higher rate of revision than RTSA after 1 year (HRA = 2.51 (95% CI 1.30, 4.83), P = .005), with no difference prior to that time. In addition, HSMH had a higher rate of revision than RTSA for the entire period (HR, 2.69 [95% confidence interval, 1.28-5.63], P = .008). There was no significant difference in the rate of revision for HSPH and TSA when they were compared with RTSA. Glenoid erosion was the most common cause of revision for HRA (28.6% of revisions) and HSMH (50%). Instability/dislocation was the leading cause of revision for RTSA (41.7%) and HSPH (28.6%), and for TSA, the majority of revisions were for either instability/dislocation (20.6%) or loosening (18.6%).

CONCLUSION

These results should be interpreted within the context of the lack of availability of long-term data on RTSA and HSPH stems. RTSA outperforms all implants regarding revision rates at mid-term follow-up. The high early dislocation rate associated with RTSA, as well as the lack of revision options available to address this, indicates that careful selection of patients and a greater appreciation of anatomic risk factors are needed in the future.

Short to Early-Mid Term Clinical Outcomes and Survival of Pyrocarbon Shoulder Implants: A Systematic Review and Meta-Analysis

Background

The appropriate surgical treatment option for young and active patients undergoing shoulder arthroplasty for arthritis remains questionable. Pyrolitic carbon (pyrocarbon) has been shown to improve implant longevity and decrease wear when in contact with cartilage or bone. The present systematic review aimed to evaluate clinical and radiological outcomes as well as the survivorship of pyrocarbon shoulder implants.

Methods

The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. A systematic search was performed using the MEDLINE, EMBASE and Cochrane Library databases. All the studies dealing with the use of pyrolitic shoulder implants were pooled, data of interest were extracted and statistically analyzed through meta-analysis.

Results

A total of 9 studies were included for a total of 477 shoulders treated. The overall mean rate of survival of the implants was 93.4 ± 5.8% and 80% ± 26.5% at 2 years and final follow up, respectively, while resulting 82.4% ± 22.1% and 92.3% ± 3.5% for PISA (pyrocarbon interposition shoulder arthroplasty) and hemi-arthroplasty/hemi-resurfacing, respectively.

Conclusions

Pyrolitic carbon shoulder implants showed good survivorship and clinical outcomes at an early to early-midterm follow-up. More studies and better-designed trials are needed in order to enrich the evidence on long-term outcomes and comparison with other shoulder replacement options for young and active patients.

Level of Evidence

IV.

Pyrocarbon hemiarthroplasty of the shoulder: a systematic review and meta-analysis of clinical results

BACKGROUND

Hemiarthroplasty is often considered in the setting of preserved glenoid cartilage given the high risk of revision associated with total shoulder arthroplasty. Pyrocarbon (PyC) has been used as an implant material that theoretically allows for formation of a neo-membrane that would act like cartilage to reduce glenoid wear. The purpose of this study was to evaluate the clinical outcomes, radiographic outcomes, revision rates, and complication rates in the existing literature on shoulder hemiarthroplasty using PyC.

METHODS

The MEDLINE, Embase, and Scopus databases were searched for articles relating to shoulder hemiarthroplasty using the terms "pyrocarbon" or "pyrolytic carbon." Abstracts and articles were screened against predefined inclusion and exclusion criteria, with a minimum of 24 months' follow-up required. Data on patient demographic characteristics, clinical outcome scores, complications, revision rates, and radiographic findings were recorded. Where appropriate, meta-analysis was performed.

RESULTS

Twelve studies were selected for final inclusion, with a total of 536 patients. Among the studies reporting preoperative and postoperative range of motion (ROM), an overall improvement in ROM was observed. The mean Constant score was 70.9 points postoperatively, with a mean improvement of 36.2 points (n = 359, 9 studies). Radiographically, 22.8% of patients (n = 536, 8 studies) had evidence of glenoid erosion, 10.4% had changes in implant positioning, and 9.9% had tuberosity thinning. In addition, 1.5% of patients had radiographic subacromial space reduction, whereas 0.7% had an increase in tuberosity thickness. Across all studies, there was an 8.6% complication rate, with the most common cause being glenoid erosion (2.6%, n = 14). There was an overall 7.7% revision rate (n = 41), with 63% of revisions (n = 26) undergoing conversion to reverse or total shoulder arthroplasty.

CONCLUSION

PyC hemiarthroplasty shows overall improvements in ROM and patient-reported outcomes for patients. However, there remains concern for glenoid erosion on radiographic evaluation at minimum 2-year follow-up. Although preliminary studies have shown encouraging results, this systematic review emphasizes the need for longer-term follow-up studies with further radiographic evaluation of the severity of glenoid erosion and the association with functional outcomes and failure risk.

Survivorship of anatomic press-fit short-stem radial head replacement with a pyrocarbon bearing

BACKGROUND

Restoring the radial head as a stabiliser of the elbow is considered important in cases where there is an associated bony or ligamentous injury. A variety of radial head prostheses are available. There are no reports of the survivorship of a short-stem press-fit radial head prostheses with pyrocarbon bearing.

PATIENTS AND METHODS

With institutional review board approval, a retrospective case-note analysis was performed of a consecutive single-surgeon case series of the Integra LifeScience pyrocarbon radial head prostheses (Carbon Modular Radial Head) from October 2010 to October 2019 in a tertiary referral centre. The series was divided into acute trauma and salvage cohorts. Kaplan-Meier survivorship analysis was conducted.

RESULTS

36 patients were included, 23 (64%) for acute injuries and 13 (36%) for failed initial treatment. Of the acute injuries, 20 (87%) had a Wrightington type-C elbow fracture-dislocation. Reoperation was performed in 4 (11%) patients; 10 (28%) had possible loosening on radiographs. The implant survival rate was 94% at shortest follow-up of 17 months (mean 70 months).

DISCUSSION

Treatment of complex radial head fractures using a pyrocarbon-bearing, anatomic press-fit design provides satisfactory short-term survivorship in this case series. The implant should be used with caution in salvage cases, due to higher rates of loosening seen in this cohort.

Innovations in Shoulder Arthroplasty

Innovations currently available with anatomic total shoulder arthroplasty include shorter stem designs and augmented/inset/inlay glenoid components. Regarding reverse shoulder arthroplasty (RSA), metal augmentation, including custom augments, on both the glenoid and humeral side have expanded indications in cases of bone loss. In the setting of revision arthroplasty, humeral options include convertible stems and newer tools to improve humeral implant removal. New strategies for treatment and surgical techniques have been developed for recalcitrant shoulder instability, acromial fractures, and infections after RSA. Finally, computer planning, navigation, PSI, and augmented reality are imaging options now available that have redefined preoperative planning and indications as well intraoperative component placement. This review covers many of the innovations in the realm of shoulder arthroplasty.

Mid-term outcomes of pyrolytic carbon humeral resurfacing hemiarthroplasty compared with metal humeral resurfacing and metal stemmed hemiarthroplasty for osteoarthritis in young patients: analysis from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

The optimal surgical management of glenohumeral osteoarthritis in young patients remains an unsolved problem. Humeral resurfacing hemiarthroplasty and stemmed hemiarthroplasty using metallic heads are 2 surgical options that avoid the complications of loosening or wear of the glenoid component seen in total shoulder arthroplasty. Despite the potential benefits, improvement in survivorship has not been demonstrated from joint registry studies or other studies at mid-term follow-up. This is predominantly because of glenoid erosion and pain that occur when the metal resurfaced head articulates with the native glenoid. The use of pyrolytic carbon (pyrocarbon) as a resurfacing material has been proposed as an alternative bearing surface thought to reduce glenoid erosion owing to a marked reduction in wear rates in vitro. This study aimed to compare the survivorship of shoulder hemi-resurfacing using pyrocarbon with shoulder hemi-resurfacing and stemmed hemiarthroplasty using metallic heads.

METHODS

Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) were analyzed for all patients aged <55 years who had undergone a primary shoulder replacement for osteoarthritis from April 16, 2004, to December 31, 2019. The outcomes of shoulder procedures using pyrocarbon hemi-resurfacing were compared with procedures using metal hemi-resurfacing and metal stemmed hemiarthroplasty. The reasons for revision in each arthroplasty class were analyzed. The analyses were undertaken using Kaplan-Meier estimates of survivorship and hazard ratios (HRs) from Cox proportional hazards models.

RESULTS

We analyzed 393 primary shoulder procedures, of which 163 were pyrocarbon hemi-resurfacing procedures, 163 were metal hemi-resurfacing procedures, and 67 were metal stemmed hemiarthroplasties.The cumulative percentage of revision at 6 years was 8.9% for pyrocarbon hemi-resurfacing, 17.1% for metal hemi-resurfacing, and 17.5% for metal stemmed hemiarthroplasty. Pyrocarbon hemi-resurfacing prostheses had a statistically lower revision rate than other hemi-resurfacing prostheses (HR, 0.41; 95% confidence interval, 0.18-0.93; P = .032). Pain, prosthesis fracture, and infection were the key reasons for revision. No pyrocarbon hemi-resurfacing cases were revised for glenoid erosion. In male patients, pyrocarbon humeral resurfacing had a lower cumulative percentage of revision compared with metal stemmed hemiarthroplasty (HR, 0.32; 95% confidence interval, 0.11-0.93; P = .037).

CONCLUSION

Pyrocarbon humeral resurfacing arthroplasty had statistically lower revision rates at mid-term follow-up in patients aged <55 years compared with other hemi-resurfacing procedures.

Retrospective review of pyrocarbon radial head replacement

Background

Radial head arthroplasty is the preferred surgical management for complex, unreconstructable radial head fractures. There has been increasing use of pyrocarbon prostheses, with potential tribology and modulus advantages over metallic counterparts. This study aims to assess clinical and radiological outcomes for radial head replacement after trauma using a modular, uncemented pyrocarbon prosthesis.

Materials and Methods

Between September 2009 and March 2020, a consecutive series of 22 trauma cases were available for review. Patients underwent radial head arthroplasty using a pyrocarbon prosthesis (Ascension Modular Radial Head System, Austin, TX). Recorded outcomes included clinical assessment, radiological evaluation, and patient-reported outcome measures specific to elbow function.

Results

Twenty-two patients (7 male, 15 female) with an average age of 51 years (range 21-64) were analyzed with a minimum 12 months of follow-up. All patients had complex radial head fractures, categorized as a Mason 3 or 4 injury. At follow-up, mean elbow range of motion included flexion 130° (range 100°-150°), extension 19° (0-50°), pronation 73° (30°-90°), and supination 70° (10°-90°). The mean Mayo Elbow Performance Index score was 83 (55-100), and Disabilities of the Arm, Shoulder and Hand score was 22 (2.5-60). Radiological evaluation showed 14 patients with asymptomatic proximal neck resorption and two patients with radiological stem loosening. In total, 3 of 22 implants were revised-2 were excised, and 1 revised to a long stem for traumatic implant fracture.

Conclusion

Pyrocarbon radial head arthroplasty provided reliable functional results for patients after unreconstructable radial head fracture. The unique potential for fracture of the prosthesis should be considered in long-term follow-up, with appropriate activity advice to patients.

Pyrocarbon Humeral Head in a Shoulder Hemiarthroplasty: Preliminary Results at 3 Years Follow-Up and Review of the Current Literature

Shoulder hemiarthroplasty is a viable option in young patients with an intact rotator cuff in order to preserve the native glenoid. To avoid the dreaded and expected wear of the glenoid in very active shoulders, implants with humeral head coated with a high resistant and elastic material—pyrolytic carbon—are now an option. The authors present the first pyrocarbon coated hemishoulder arthroplasty performed at our Orthopedic Department in a patient with osteonecrosis of the humeral head. At three years of follow-up, the patient is pain free and without limitations in his daily work. The Constant score was applied pre- and postoperatively, and an improvement of 32 points was reported. Larger cohorts with long-term follow-up are required to confirm our promising results.

Pyrocarbon interposition shoulder arthroplasty in young arthritic patients: a prospective observational study

BACKGROUND

We evaluated survival and midterm results of pyrocarbon interposition shoulder arthroplasty (PISA) in arthritic patients younger than 65 years.

METHODS

Fifty-eight PISAs (InSpyre; Tornier-Wright, Bloomington, MN, USA), implanted in 56 patients between 2010 and 2015, were prospectively observed. The mean age at surgery was 52 ± 13 years. The cause was primary osteoarthritis (18), fracture sequelae (16), post-instability arthritis (15), aseptic necrosis (3), inflammatory disease (2), and failed hemiarthroplasty (4); 34 shoulders (61%) had previously undergone surgery. Glenoid erosion was assessed in 4 grades according to the Sperling classification. Humeral erosion was also assessed in 4 grades. Multivariate analysis was used to determine predisposing risk factors for both humeral and glenoid erosion.

RESULTS

At a mean follow-up of 47 ± 15 months, survival rate was 90%. Six patients (10%) required conversion to reverse total shoulder prosthesis for painful glenoid erosion (n = 2) and humeral erosion with greater tuberosity stress fractures (n = 4). The mean Constant score and subjective shoulder value significantly increased from 36 ± 14 points to 70 ± 15 points and 32% ± 14% to 75% ± 19%, respectively (P < .001). Humeral medialization was observed in 78% of the cases with increased pain score. Uncorrected anteroposterior implant subluxation (12 cases) was associated with lower Constant score (50 points vs. 72 points; P = .02) and lower subjective shoulder value (53% vs. 78%; P = .002). On multivariate analysis, no risk factors for glenoid or humeral erosion were found.

CONCLUSION

At midterm follow-up, PISA does not protect from progressive glenoid erosion and can lead to greater tuberosity erosion and stress fractures. Longer follow-up is required to see whether PISA survival will be superior to that of hemiarthroplasty.