Wear resistant performance of highly cross-linked and annealed ultra-high molecular weight polyethylene against ceramic heads in total hip arthroplasty

Rate of revision and wear penetration in different polyethylene liner compositions in total hip arthroplasty: a Bayesian network meta-analysis

The present Bayesian network meta-analysis compared different types of polyethylene liners in total hip arthroplasty (THA) in terms of wear penetration (mm/year) and rate of revision. The type of liners compared were the crosslinked ultra-high molecular weight polyethylene (CPE/UHMWPE), Vitamin E infused highly cross-linked polyethylene (HXLPE-VEPE), modified cross-linked polyethylene (MXLPE), highly cross-linked polyethylene (HXLPE), Cross-linked polyethylene (XLPE). This study was conducted according to the PRISMA extension statement for reporting systematic reviews incorporating network meta-analyses of healthcare interventions. In June 2024, PubMed, Scopus, Embase, Google Scholar, and Cochrane databases were accessed. A time constraint was set from January 2000. All investigations which compared two or more types of polyethylene liners for THA were accessed. Only studies that clearly stated the nature of the liner were included. Data from 60 studies (37,352 THAs) were collected. 56% of patients were women. The mean age of patients was 60.0 ± 6.6 years, the mean BMI was 27.5 ± 2.0 kg/m2. The mean length of follow-up was 81.6 ± 44.4 months. Comparability was found at baseline between groups. XLPE and HXLPE liners in THA are associated with the lowest wear penetration (mm/year) and the lowest revision rate at approximately 7 years of follow-up.

Head, acetabular liner composition, and rate of revision and wear in total hip arthroplasty: a Bayesian network meta-analysis

Total hip arthroplasty (THA) is a common procedure for patients suffering from hip pain e.g. from osteoarthritis, osteonecrosis, or hip fractures. The satisfaction of patients undergoing THA is influenced by the choice of implant type and material, with one key factor being the selection of the appropriate material combination for the bearing surface. In this Bayesian network meta-analysis, we investigated the impact of material combinations for the bearing surface on the longevity of hip implants. The wear penetration rate per year and the total wear penetration in the liner resulting from different material combinations, as well as the survival rate at last follow-up, were examined. We analyzed a total of 663,038 THAs, with 55% of patients being women. Mean patient age was 59.0 ± 8.1 years and mean BMI 27.6 ± 2.6 kg/m2. The combination of an aluminium oxide (Al2O3) head and an Al2O3 liner demonstrated the lowest wear penetration at last follow-up and the lowest rate of wear penetration per year. Additionally, the combination of a crosslinked polyethylene (XLPE) liner and a zircon oxide (ZrO2) head demonstrated the lowest rate of revision at last follow-up. These findings underscore the importance of careful material selection for hip implant bearing surfaces to optimize their longevity and patient satisfaction after THA.

Risk factors for liner wear and head migration in total hip arthroplasty: a systematic review

Total hip arthroplasty (THA) is a successful orthopaedic surgical procedure, and its longevity depends on bearing components and implant fixation. Optimizing polyethylene and ceramics has led to improved wear parameters and contributed to improved long-term outcomes. The present systematic review investigated whether time span from implantation, patient characteristics and performance status exert an influence on liner wear and head migration in THA. This study was conducted in conformity to the 2020 PRISMA guidelines. All the clinical investigations which reported quantitative data on the amount of liner wear and head migration in THA were considered. Only studies which reported quantitative data at least on one of the following patient characteristics were suitable: mean age, mean BMI (kg/m2), sex, side, time span between the index THA and the last follow-up (months) were eligible. A multiple linear model regression analysis was employed to verify the association between patient characteristics and the amount of liner wear and/or head migration. The Pearson Product-Moment Correlation Coefficient was used to assess the association between variables. Data from 12,629 patients were considered. The mean length of the follow-up was 90.5 ± 50.9 months. The mean age of patients at surgery was 58.4 ± 9.4 years, and the mean BMI was 27.2 ± 2.5 kg/m2. 57% (7199 of 12,629 patients) were women, and in 44% (5557 of 12,629 patients) THAs were performed on the left. The mean pre-operative Harris hip score was 46.5 ± 6.0 points. There was evidence of a moderate positive association between the amount of liner wear and the time elapsed between the index surgery to the follow-up (P = 0.02). There was evidence of a moderate positive association between the amount of head migration and the time elapsed between the index surgery to the follow-up (P = 0.01). No further statistically significant association was found. The time elapsed between the index surgery to the follow-up was the most important factor which influence the head migration and liner wear in THA. Patients' characteristics and preoperative physical activity did not influence the amount of head migration and liner wear.

Encouraging outcomes of stemless ceramic head anatomic shoulder arthroplasty in severe primary osteoarthritis (Walch type B glenoids)

Background: We report the radiological and functional outcomes at five years in patients with severe osteoarthritis of the glenohumeral joint and a Walch type B glenoid who have undergone stemless anatomic total shoulder replacement. Methods: A retrospective analysis of case notes, computed tomography scans and plain radiographs of patients undergoing anatomic total shoulder replacement for primary glenohumeral osteoarthritis were performed. Patients were grouped by the severity of their osteoarthritis using the modified Walch classification, glenoid retroversion and posterior humeral head subluxation. An evaluation was made using modern planning software. Functional outcomes were assessed using the American shoulder and elbow surgeons score, shoulder pain and disability index and visual analogue scale. Annual Lazarus scores were reviewed as regard to glenoid loosening. Results: Thirty patients were reviewed at 5 years. Analysis of all patient-reported outcome measures demonstrated significant improvement at 5-year review, American shoulder and elbow surgeons (p = <0.0001), shoulder pain and disability index (p = 0.0001), visual analogue scale (p = 0.0001). Radiological associations between Walch scores and Lazarus scores were not statistically significant (p = 0.1251) at 5 years. There were no associations between features of glenohumeral osteoarthritis and patient-reported outcome measures. Discussion: The severity of osteoarthritis did not show any association with glenoid component survivorship or with patient-reported outcome measures at 5 years review. Level of evidence: IV.

Squatting After Total Hip Arthroplasty: Patient-Reported Outcomes and In Vivo Three-Dimensional Kinematic Study

BACKGROUND

Squatting is an important function for many daily activities, but has not been well documented after total hip arthroplasty (THA). This study investigated the participation rate of squatting and in vivo kinematics during squatting.

METHODS

A survey questionnaire about squatting was mailed to patients who underwent primary THA and 328 patients returned acceptable responses. Additionally, 32 hips were evaluated for dynamic 3-dimensional kinematics of squatting using density-based image-matching techniques. Multivariate analyses were applied to determine which factors were associated with anterior liner-to-neck distance at maximum hip flexion.

RESULTS

Patients who could easily squat significantly increased this ability postoperatively (23.5% vs 46%, P < .01). In 29.5% of the patients there was still no ability to squat after THA; the main reason was anxiety of dislocation (34.2%). Kinematic analysis revealed that maximum hip flexion averaged 80.7° ± 12.3° with 12.8° ± 10.7° of posterior pelvic tilt and 9.7 ± 3.0 mm of anterior liner-to-neck distance. Neither liner-to-neck, bone-to-bone, nor bone-to-implant contact was observed in any of the hips. Larger hip flexion and smaller cup anteversion were negatively associated with the anterior liner-to-neck distance at maximum hip flexion (P < .05).

CONCLUSION

Postoperatively, approximately 70% of patients squatted easily or with support. Anxiety of dislocation made patients avoid squatting after THA. In vivo squatting kinematics suggest no danger of impingement or subsequent dislocation, but excessively large hip flexion and small cup anteversion remain as risks.

Wear analysis of the first-generation cross-linked polyethylene at minimum 10 years follow-up after THA: no significant effect of sports participation

The impact of sports on long-term wear of highly cross-linked polyethylene (XLPE) after total hip arthroplasty (THA) is not fully understood. We investigated (1) the wear performance of the first-generation XLPE, and (2) whether sports participation influences the steady wear rate of XLPE. The femoral head penetration into the cup was measured digitally on radiographs of hips undergoing THA with XLPE. We retrospectively reviewed data that included age, gender, body mass index, follow-up period, preoperative diagnosis, types of XLPE, ball diameter, head material, inclination of the cup, physical function score, and sports participation. Statistical analyses were applied to determine whether sports affect the wear of XLPE and which factors were associated with the steady wear rate. Creep and steady wear rate were found to be 0.18 mm and 0.005 mm/year, respectively. Sports participation, regardless of impact, provided no significant difference in the steady wear rate. Multiple regression analysis demonstrated that sports did not increase the steady wear rate. Our findings showed excellent wear performance of the first-generation XLPE at a minimum of ten years after THA, without significant effect of sports participation on the liner wear.

Wear Risk Prevention and Reduction in Total Hip Arthroplasty. A Personalized Study Comparing Cement and Cementless Fixation Techniques Employing Finite Element Analysis

The wear rate on Total Hip Arthroplasty (THA) entails a heavy burden for patients. This becomes more relevant with increased wear risk and its consequences such as osteolysis. In addition, osteolysis has been described in cemented and uncemented acetabular implants, and nowadays, controversy remains as to whether or not to cement the acetabular component. A personalized theoretical study was carried out to investigate which parameters have an influence on wear risk and to determine the best fixation method. Liner wear risk was assessed for two different types of fixation (cemented vs uncemented) through Finite Elements Analysis (FEA). The intraoperative variables used to determine the wear risk (cervical-diaphyseal angle, Center of Rotation positioning -COR-, head material, head size, and liner thickness) are vital parameters in surgical planning. Two types of tridimensional liner models of Ultra High Molecular Weight Polyethene (UHMWPE) were simulated through finite element analysis (FEA-over 216 cases were the core of this research). A significant relationship was found between the cervical-diaphyseal angle and wear risk (p < 0.0001), especially in valgus morphology. The acetabular fixation technique (p < 0.0001) and liner thickness (p < 0.0001) showed a significant relationship with wear risk. According to our study, using a cemented fixation with a thick liner in the right center of rotation appears to be the proper stratagy for preventing polyethylene liner wear.

Pathogenesis, Evaluation, and Management of Osteolysis Following Total Ankle Arthroplasty

Periprosthetic osteolysis is a common occurrence after total ankle arthroplasty (TAA) and poses many challenges for the foot and ankle surgeon. Osteolysis may be asymptomatic and remain benign, or it may lead to component instability and require revision or arthrodesis. In this article, we present a current and comprehensive review of osteolysis in TAA with illustrative cases. We examine the basic science principles behind the etiology of osteolysis, discuss the workup of a patient with suspected osteolysis, and present a review of the evidence of various management strategies, including grafting of cysts, revision TAA, and arthrodesis.Level of Evidence: Level V, expert opinion.

Minimum 10-Year Follow-Up of Cementless Total Hip Arthroplasty With a 32-mm Cobalt-Chromium Head on Highly Cross-Linked Polyethylene and a Tapered, Fiber Metal Proximally Coated Femoral Stem

BACKGROUND

The clinical and radiographic results of cementless total hip arthroplasty using a 32-mm cobalt-chromium head on remelted highly cross-linked polyethylene (HXLPE) and a tapered, fiber metal proximally coated femoral stem were evaluated at a mean follow-up of 12 years.

METHODS

A total of 57 cementless total hip arthroplasties using remelted HXLPE combined with a 32-mm cobalt-chromium head, and a tapered, fiber metal proximally coated femoral stem were performed from October 2004 to December 2006. Clinical evaluation was performed using the Merle d'Aubigné and Postel scoring system. Standardized anteroposterior and lateral radiographs of the pelvis and femur without weight-bearing were analyzed. Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up.

RESULTS

The mean Merle d'Aubigné and Postel score improved significantly from 10.7 points preoperatively to 15.6 postoperatively (P < .001). No osteolysis was found around the implant. Stem fixation in all cases showed stable bone ingrowth. Third-degree stress shielding was found in 46% of all stems. The total head penetration rate was 0.05 mm/y, and the steady-state wear rate was 0.01 mm/y. The Kaplan-Meier survivorship with the end point of revision was 95% (95% confidence interval, 85%-98%) at 12 years.

CONCLUSION

A 32-mm cobalt-chromium head on remelted HXLPE demonstrated low wear properties, and a tapered, fiber metal proximally coated femoral stem showed good results at long-term follow-up.

Prospective Study Showing Results of Large-Diameter Femoral Heads After Cementless Total Hip Replacement

Introduction Large-diameter femoral heads (≥36 mm) were introduced to decrease instability and improve the range of motion of the hip. We hypothesized regarding the clinical outcome and complications (dislocation, implant survivorship, and functional scores) following total hip replacement (THR) surgery in an Indian population who have smaller acetabulum compared to the western population. Methodology A prospective study was conducted at a tertiary hospital from November 2011 to July 2013. A total of 70 patients with hip pathology were operated by a senior surgeon for THR using the anterolateral approach. The Harris Hip Scores were recorded pre and postoperatively in all patients. Postoperatively, radiographs were taken to check for evidence of implant loosening or osteolysis. The patients were followed up till a mean follow-up of 86.52 months (range: 74 to 108 months) in our cohort. Detailed clinical and radiographic results were available for 59 patients, while six died (three died of myocardial infarction (MI), two had cerebrovascular accident (CVA), and one patient died of pulmonary embolism) and five patients were lost to follow-up. Results Of the 59 hips, majority (76%) had acetabular inclination of 46-55 degrees. Ninety percent of the stems were in the central position and 10% were in the varus position. The average preoperative Harris Hip Score was 38.8 ± 5.7 (range: 24-46), which increased to 90.4 ± 7.3 (range: 78-94) at the last follow-up. A total of six patients died (four died of MI and two of CVA) and two patients had infection which was treated with antibiotics. Three cases of dislocation were observed; one following a fall one year after surgery and revision total hip arthroplasty was done and two cases while getting up from the bed which were managed with closed reduction and abduction brace for six weeks. Two cases of periprosthetic fracture were observed which were managed with plating. Conclusion Lower dislocation rate and better range of movement reinforces the advantage of large-diameter femoral head during THR in the Indian population.

Thirteen-year results of cementless total hip arthroplasty with zirconia heads on highly cross-linked polyethylene

OBJECTIVES

Zirconia ceramic was introduced for femoral heads because of its mechanical strength and fracture toughness. Highly cross-linked polyethylene has been shown to achieve wear reduction compared to conventional polyethylene. The purpose of this study was to investigate the long-term results of cementless total hip arthroplasty with zirconia femoral heads on highly cross-linked polyethylene.

METHODS

Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method (PolyWare) in 93 hips at a mean follow-up of 13 years. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up.

RESULTS

The mean Merle d'Aubigné and Postel score had improved significantly from 10.9 points preoperatively to 15.3 postoperatively (p < 0.001). Osteolysis was not found around the implant, and no zirconia heads had fractures. The total head penetration rate was 0.04 mm/year, and the steady-state wear rate was 0.02 mm/year. Kaplan-Meier survivorship with the endpoint of revision was 97% (95% confidence interval [CI], 92% to 99%) at 10 years.

CONCLUSION

Zirconia on highly cross-linked polyethylene demonstrated extremely low wear properties at long-term follow-up.

Recent update on crosslinked polyethylene in total hip arthroplasty

More than two decades after their clinical introduction, crosslinked polyethylenes (XLPE) have been widely adopted. Though concerns were initially raised regarding oxidation and brittleness, on a large scale, the first generation of XLPE continues to be highly effective 15 years after the surgery, even in a young and active population. Remelted XLPE might display lower wear rates than annealed XLPE. Second generation XLPEs, not only including sequentially irradiated and annealed but also associated with antioxidants, demonstrate encouraging short- to mid-term results. Registry data support clinical trial reports. Even in less favorable settings (lipped liners, dual mobility cups, revision surgery, hip resurfacing) results are promising. However, failures (fractures) have already been described. Therefore, a high level of surveillance remains crucial.

Dual mobility total hip arthroplasty: should everyone get one?

Hip instability following total hip arthroplasty (THA) remains a major challenge and is one of the main causes of revision surgery.

Dual mobility (DM) implants have been introduced to try to overcome this problem. The DM design consists of a small femoral head captive and mobile within a polyethylene liner.

Numerous studies have shown that DM implants reduce the rate of dislocation compared to fixed-bearing inserts.

Early designs for DM implants had problems with wear and intra-prosthetic dislocations, so their use was restricted to limited indications.

The results of the latest generation of DM prostheses demonstrate that these problems have been overcome. Given the results of these studies presented in this review, surgeons may now consider DM THA for a wider patient selection.

Cite this article: EFORT Open Rev 2019;4:541-547. DOI: 10.1302/2058-5241.4.180045

In vivo kinematic analysis of replaced hip during stationary cycling and computer simulation of optimal cup positioning against prosthetic impingement

BACKGROUND

Dynamic hip kinematics during stationary cycling after total hip arthroplasty (THA) have been unclear. Furthermore, no computer simulation of optimal cup position based on in vivo kinematics has yet been assessed.

METHODS

This study consisted of 7 patients who underwent unilateral primary THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, continuous radiographs were obtained during stationary cycling. We analyzed the three-dimensional replaced hip kinematics from the top to the bottom position of the crank using image-matching techniques and quantified minimum liner-to-stem neck distance. Simulation analyses with in vivo kinematics were performed to examine patient-specific optimal cup placement against prosthetic impingement.

FINDINGS

During stationary cycling, pelvis showed 27.1° of posterior tilt on average without significant change. Hip flexed by 59.4° and 19.3° on average at the top and bottom positions, respectively. Minimum liner-to-neck distance was 8.8 mm on average at the bottom position. Liner-to-neck, bone-to-bone, or bone-to-component impingement was not observed at any positions in any hips. Simulation analysis of cup placement showed that larger cup anteversion, inclination, and use of elevated liner significantly decreased the minimum distance between posterior liner and stem neck. Cup anteversion of more than 30° with elevated liner could cause posterior liner-to-neck impingement at bottom position.

INTERPRETATION

Stationary cycling after THA provides no excessive hip range of motion or liner-to-neck contact. Cup placement and use of elevated liner significantly influence the minimum liner-to-neck distance, in some cases simulating posterior prosthetic impingement.

Is Oxidized Zirconium Femoral Head Superior to Other Bearing Types in Total Hip Arthroplasty? A Systematic Review and Meta-Analysis

BACKGROUND

Oxidized zirconium (OxZi) is a relatively new type of material that combines the strength of a metal with the surface/wears properties of a ceramic. Our aim was to investigate whether OxZi femoral heads lead to lower polyethylene wear, higher survival rate, and better clinical outcomes than the other bearing types in patients treated with total hip arthroplasty (THA).

METHODS

Two reviewers independently conducted a systematic search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews. These databases were queried with the terms: a. "oxidized" AND "zirconium" AND "total" AND "hip" AND "arthroplasty"; b. "oxinium" AND "total" AND "hip" AND "arthroplasty". The primary outcome measures were the survival rate of the bearing surfaces as well as the polyethylene wear.

RESULTS

The vast majority (85.7%) of the studies, which reported the mean polyethylene wear rate, showed that there was not any significant difference between OxZi and cobalt-chrome (CoCr) femoral heads (rate ratio: 0.836; 95% confidence interval: 0.362-1.928; P = .674). All studies comparing the survival rate of OxZi and CoCr femoral heads illustrated almost excellent survivorship with both implants.

CONCLUSION

OxZi femoral heads did not lead to lower polyethylene wear rate or higher survival rate, when compared with CoCr femoral heads in patients treated with THA. On the basis of these results and taking into account the higher cost of these implants, we would not recommend the routine use of OxZi femoral heads in primary THAs.

LEVEL OF EVIDENCE

Systematic review and meta-analysis of therapeutic studies I-III.

Do component position and muscle strength affect the cup-head translation during gait after total hip arthroplasty?

INTRODUCTION

This study examined whether the component position or muscle strength affects the cup-head translation under in vivo weight-bearing conditions after total hip arthroplasty (THA). We hypothesized that there was a correlation between the hip offset or abductor strength and cup-head translation during gait.

MATERIALS AND METHODS

We prospectively evaluated 31 patients undergoing unilateral cementless primary THA. The cup height, cup/stem offset, and limb length discrepancy were measured on anterior-posterior bilateral hip radiographic images. The isometric muscle strength of the lower limbs was quantified using a handheld dynamometer. Continuous radiographic images were recorded during gait, and cup-head translation was analysed using a computer-assisted method.

RESULTS

The average cup height, cup/stem offset, and limb length discrepancy were - 3.8 ± 5.1 mm, 1.2 ± 5.2 mm/- 0.7 ± 7.7 mm, and - 2.1 ± 5.2 mm, respectively. The average hip abductor/flexor and knee extensor strength were 86% ± 18%/85% ± 17% and 88% ± 17% of the contralateral healthy hip, respectively. The average cup-head translation during swing phase of gait was - 0.003 ± 0.31 mm. Multiple regression analyses found no significant independent predictors of cup-head translation (p > 0.05).

CONCLUSIONS

The component position or muscle strength did not significantly influence cup-head translation during gait after well-positioned primary THA.

Dynamic hip kinematics during squatting before and after total hip arthroplasty

Background

The difference in in vivo kinematics before and after total hip arthroplasty (THA) for the same subjects and the clearance between the liner and neck during squatting have been unclear. The purpose of the present study was to clarify (1) the changes in the in vivo kinematics between prosthetic hips and osteoarthritis hips of the same subjects and (2) the extent of the liner-to-neck clearance during squatting under weight-bearing conditions.

Methods

This study consisted of 10 patients who underwent unilateral THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, we obtained continuous radiographs during squatting. We analyzed the hip joint’s movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also quantified the minimum distance at maximum flexion and extension, and the minimum angle at maximum flexion between the liner and stem neck.

Results

The maximum hip flexion angles post-THA (80.7° [range, 69.4–98.6°]) changed significantly compared with the pre-THA values (71.7° [range, 55.2°–91.2°]). The pelvic tilt angle (posterior +, anterior−) at the maximum hip flexion post-THA (10.4° [range, − 6.7° to 26.9°]) was significantly smaller than that at pre-THA (16.6° [range, − 3° to 40.3°]). The minimum anterior and posterior liner-to-neck distances averaged 10.9 and 8.0 mm, respectively, which was a significant difference. The minimum liner-to-neck angle at maximum flexion averaged 34.7° (range, 20.7°–46.3°). No liner-to-neck contact occurred in any of the hips.

Conclusion

THA increased the range of hip joint motion and the pelvis tilted anteriorly more after than before THA, with sufficient liner-to-neck clearance during squatting. These data may be beneficial for advising patients after THA regarding postoperative activity restrictions in daily life.

Wear performance of cobalt chromium, ceramic, and oxidized zirconium on highly crosslinked polyethylene at mid-term follow-up

Patients with THA using a ceramic head and using an OxZr head were each matched to patients with a CoCr head. Mean implantation time was 5 years. There was no difference in steady state wear rate between the ceramic (0.066 ± 0.050 mm/year) and CoCr match groups (0.052 ± 0.041 mm/year), or between the OxZr (0.022 ± 0.029 mm/year) and CoCr match groups (0.048 ± 0.071 mm/year). Follow-up into the second decade will be necessary before any changes in THA wear rate from using ceramic or OxZr bearings may be appreciated clinically with available imaging techniques.

Sports Participation in Patients After Total Hip Arthroplasty vs Periacetabular Osteotomy: A Propensity Score-Matched Asian Cohort Study

BACKGROUND

No studies have compared sports participation between total hip arthroplasty (THA) and periacetabular osteotomy (PAO) in matched Asian cohorts. We investigated sports participation and activity levels in Asian THA cohort, and compared them between THA and PAO cohorts.

METHODS

Multivariate analyses were applied to determine which factors were associated with postoperative sports participation and University of California-Los Angeles (UCLA) activity score in (1) 524 THA patients and (2) 487 acetabular dysplasia patients (295 THA patients and 192 PAO patients). In addition, postoperative sports participation and UCLA score were compared between 62 THA and 62 PAO patients after adjusting for baseline characteristics with propensity score matching.

RESULTS

Sports participation and UCLA score significantly increased after THA (P < .001 in both analyses). Preoperative sports participation was the factor most associated with both postoperative sports participation and UCLA score in both 524 THA patients and 487 acetabular dysplasia patients (P < .001 in all analyses). Multivariate analysis in 487 acetabular dysplasia patients demonstrated that THA, compared with PAO, was negatively associated with postoperative sports participation (P < .001), but not postoperative UCLA score (P = .22). THA patients showed significantly lower rate of postoperative sports participation (32.3% and 51.6%, respectively, P = .046), but not postoperative UCLA score (5.0 ± 1.6 and 5.2 ± 1.9, respectively, P = .47) compared with matched PAO patients.

CONCLUSION

THA significantly increased both sports participation and activity levels. Both multivariate and propensity score-matched analyses showed that postoperative activity levels were comparable between THA and PAO cohorts.

Bearing Surfaces for Total Hip Arthroplasty

Metal-on-highly cross-linked polyethylene is considered the preferred bearing surface for conventional total hip arthroplasty because of its safety profile and excellent results in the first 10 to 15 years of use. However, with younger patient age, activity expectations increase, and the life expectancy of patients with total hip arthroplasty also has increased, so interest remains in other bearing couples. These other options include the use of various ceramic composites for the femoral head on highly cross-linked polyethylene, the so-called second-generation antioxidant polyethylenes, and ceramic acetabular liners. Several of these bearing couples have shown excellent wear rates in vitro, and short-term clinical studies have demonstrated favorable wear and safety results. It is uncertain whether any of these bearing couples should be adopted at present. Understanding the unique properties and possible complications of these bearing couples is critical for appropriate implant selection.

Wear of XLPE liner against zirconium heads in cementless total hip arthroplasty for patients under 40 years of age

INTRODUCTION

Total hip arthroplasty (THA) in the young is challenging. The purpose of this study was to retrospectively determine the clinical, radiographic, and polyethylene wear rate of relatively young patients.

METHODS

We evaluated the outcome of consecutive patients receiving primary THA who were under 40 years of age with a minimum 10-year follow-up. Indications for THA in these patients were osteoarthritis due to developmental dysplasia of the hip joint (9 hips), osteonecrosis of the femoral head (7 hips), juvenile idiopathic arthritis (2 hips), and osteoarthritis due to Perthes disease (1 hip). All THA were performed with a cross-linked ultra-high-molecular-weight polyethylene (XLPE) liner against zirconium heads with cementless implants.

RESULTS

The average Japanese Orthopaedic Association hip score significantly improved from 42 to 93 points at the latest follow-up. The mean steady wear was 0.015 mm/year (maximum 0.033 mm/year), and the mean creep wear was 0.111 mm (maximum 0.4 mm). Osteolysis was observed around 1 acetabular component and 2 stems. 1 femoral component had subsidence over 5 mm. All of the femoral components achieved fixation with an optimal interface with spot welds at the latest follow-up. Stress shielding was observed in all hips.

CONCLUSIONS

THA using an XLPE liner against zirconium heads appeared to have improved THA longevity. However, the imaging findings in some cases were suggestive of wear debris. A rigorous continual follow-up is required for relatively young patients undergoing THA.

Highly Cross-linked Polyethylene Liner Dissociation from a Cement-less Modular Acetabular Shell: Two Case Reports

Liner dissociation of polyethylene from a cementless acetabular socket following total hip arthroplasty (THA) is a rare complication. Cross-linked polyethylene liner dissociation from AMS-HA shell (KYOCERA Med, Osaka, Japan) occurred in 2 out of the 4153 (0.04%) cases approximately 10 years after undergoing surgery at our institute. First case was an 80-year-old female who underwent right THA along with subtrochanteric femoral shortening osteotomy due to complete dislocation hip, and second case was a 72-year-old male, who underwent right THA due to coxarthrosis. A 26 mm femoral head and CPE liner were used in both cases and the inclination degree of the acetabular socket was within 50°.There was no implant loosening in both cases. There was partial damage in the elevated rim on the alternative side and scratches on the back side in the both extracted CPE liner. It was surmised that liner dissociation was caused due to a problem in the liner fixing format of the push in type of the present model.

Dynamic Hip Kinematics During the Golf Swing After Total Hip Arthroplasty

BACKGROUND

Although most surgeons allow their patients to play golf after total hip arthroplasty (THA), the effect on the implant during the golf swing is still unclear.

PURPOSE

To evaluate hip kinematics during the golf swing after THA.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Eleven hips in 9 patients who underwent primary THA were analyzed. All patients were right-handed recreational golfers, and these 11 hips included 6 right hips and 5 left hips. Periodic radiographic images of the golf swing were taken using a flat-panel x-ray detector. Movements of the hip joint and components were assessed using 3-dimensional-to-2-dimensional model-to-image registration techniques. Liner-to-neck contact and translation of the femoral head with respect to the acetabular cup (cup-head translation) were examined. Hip kinematics, orientation of components, and maximum cup-head translation were compared between patients with and without liner-to-neck contact.

RESULTS

On average, the golf swing produced approximately 50° of axial rotation in both lead and trail hips. Liner-to-neck contact was observed in 4 hips with elevated rim liners (2 lead hips and 2 trail hips) at maximum external rotation. Neither bone-to-bone nor bone-to-implant contact was observed at any phases of the golf swing in any of the hips. Four hips with liner-to-neck contact had significantly larger maximum external rotation (37.9° ± 7.0° vs 20.6° ± 9.9°, respectively; P = .01) and more cup anteversion (26.5° ± 6.1° vs 10.8° ± 8.9°, respectively; P = .01) than hips without liner-to-neck contact. No significant differences between hips with and without contact were found for cup inclination (42.0° ± 2.5° vs 38.1° ± 5.5°, respectively; P = .22), combined anteversion (45.3° ± 8.9° vs 51.4° ± 7.9°, respectively; P = .26), or maximum cup-head translation (1.3 ± 0.3 mm vs 1.5 ± 0.4 mm, respectively; P = .61).

CONCLUSION

In this analysis, the golf swing did not produce excessive hip rotation or cup-head translation in any hips. However, liner-to-neck contact during the golf swing was observed in 36% of the hips, with unknown effects on the long-term results.

CLINICAL RELEVANCE

Golf is an admissible sport after THA because dynamic hip stability was observed. However, the implant position, especially cup anteversion and the use of elevated rim liners, promoted liner-to-neck contact.

The Absence of Hydroxyapatite Coating on Cementless Acetabular Components Does Not Affect Long-Term Survivorship in Total Hip Arthroplasty

BACKGROUND

Hydroxyapatite (HA) has been applied to joint prostheses as a bioactive coating to prolong their durability. However, HA benefits for cup survival in total hip arthroplasty (THA) remain controversial. In this study, we compared the survival of cups with and without HA coating during a minimum follow-up of 18 years.

METHODS

In total, 183 THA cases in 163 patients were analyzed, including 73 cups with HA coating (HA(+) group) and 110 without HA coating (HA(-) group); otherwise, the cups had identical titanium-sprayed rough surfaces and were fixed with screws. In both groups, the same conventional polyethylene liners were applied. Zirconia and alumina ceramic heads were used in the HA(+) and HA(-) groups, respectively. We retrospectively analyzed cup survival based on cup revision for any reason or aseptic loosening as end points.

RESULTS

In total, 7 and 8 revisions were performed in the HA(-) and HA(+) groups with survival rates of 86.3% and 90.1%, respectively. Among them, 3 cups in the HA(-) group and 1 cup in the HA(+) group were revised for aseptic loosening in 20 years (survival rates 94.1% and 98.7%, respectively). No significant difference was detected in cup survival rates between the groups based on both end points. There were no stem revisions during the observation period.

CONCLUSION

The results suggested that HA coating did not have either beneficial or adverse effects on the long-term cup survival in primary cementless THA.

Porous metals and alternate bearing surfaces in shoulder arthroplasty

Total shoulder arthroplasty (TSA) provides an effective solution for the treatment of glenohumeral arthritis. However, long-term outcomes have been limited by glenoid component aseptic loosening and polyethylene (PE) wear. Previous attempts to improve glenoid fixation with metal-backed glenoids resulted in inferior results. Newer component designs that contain porous metal allow for biological ingrowth of the prosthesis, potentially improving longevity and overall outcomes. Porous metal can also improve humeral component fixation, obviating the need for cement and simplifying revision surgery. Advances such as highly cross-linked polyethylene (HXLPE), vitamin E-doped HXLPE, and alternate bearing surfaces like ceramics and pyrolytic carbon have proven to provide superior wear characteristics in other joint replacements and may prove beneficial in the shoulder as well.

Mid-term survivorship and clinical outcomes of cobalt-chrome and oxidized zirconium on highly crosslinked polyethylene

BACKGROUND

The choice of bearing articulation for total hip arthroplasty in younger patients is amenable to debate. We compared mid-term patient-reported outcomes and survivorship across 2 different bearing articulations in a young patient cohort.

METHODS

We reviewed patients with cobalt-chrome or oxidized zirconium on highly crosslinked polyethylene who were followed prospectively between 2004 and 2012. Kaplan-Meier analysis was used to determine predicted cumulative survivorship at 5 years with all-cause and aseptic revisions as the outcome. We compared patient-reported outcomes, including the Harris hip score (HHS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Short-form 12 (SF-12) scores.

RESULTS

A total of 622 patients were followed during the study period. Mean follow-up was 8.2 (range 2.0-10.6) years for cobalt-chrome and 7.8 (range 2.1-10.7) years for oxidized zirconium. Mean age was 54.9 ± 10.6 years for cobalt-chrome and 54.8 ± 10.7 years for oxidized zirconium. Implant survivorship was 96.0% (95% confidence interval [CI] 94.9%-97.1%) for cobalt-chrome and 98.7% (95% CI 98.0%-99.4%) for oxidized zirconium on highly crosslinked polyethylene for all-cause revisions, and 97.2% (95% CI 96.2%-98.2%) for cobalt-chrome and 99.0% (95% CI 98.4%-99.6%) for oxidized zirconium for aseptic revisions. An age-, sex- and diagnosis-matched comparison of the HHS, WOMAC and SF-12 scores demonstrated no significant changes in clinical outcomes across the groups.

CONCLUSION

Both bearing surface couples demonstrated excellent mid-term survivorship and outcomes in young patient cohorts. Future analyses on wear and costs are warranted to elicit differences between the groups at long-term follow-up.

Comparison of 10-year clinical wear of annealed and remelted highly cross-linked polyethylene: A propensity-matched cohort study

No previous studies comparing the clinical wear rates of the two different kinds of cross-linked ultra-high-molecular-weight polyethylene (XLPE), annealed and remelted, are available. We compared the creep and steady wear rates of 36 matched pairs (72 hips in total) adjusting for baseline characteristics with propensity score matching techniques. Zirconia femoral heads with 26-mm diameter were used in all cases. The femoral-head cup penetration was measured digitally on radiographs. Significantly greater creep (p=0.006) was detected in the remelted (0.234mm) than annealed (0.159mm) XLPE. However, no significant difference (p=0.19) was found between the steady wear rates (0.003 and 0.008mm/year, respectively) of the annealed and remelted XLPE. Multiple regression analyses showed that remelted XLPE is significant independent variable (p<0.001) that is positively associated with creep. However, the patient age and body weight, cup size, the liner thickness, cup inclination, follow-up periods, and postoperative Merle d'Aubigné hip score had no significant effects (p>0.05) on the steady wear rates. No patients exhibited above the osteolysis threshold of 0.1mm/year, progressive radiolucencies, osteolysis, or polyethylene fracture. This　propensity-matched cohort study document no significant difference in wear resistant performances of annealed and remelted XLPE over an average period of 10 years.

Metal ions as inflammatory initiators of osteolysis

Osteolysis and aseptic loosening currently contribute 75 % of implant failures. Furthermore, with over four million joint replacements projected to be performed in the United States annually, osteolysis and aseptic loosening may continue to pose a significant morbidity. This paper reviews the osteolysis cascade leading to osteoclast activation and bone resorption at the biochemical level. Additionally, the metal ion release mechanism from metallic implants is elucidated. Even though metal ions are not the predominating initiator of osteolysis, they do increase the concentration of key inflammatory cytokines that stimulate osteoclasts and prove to be a contributor to osteolysis and aseptic loosening. Osteolysis is a competitive mechanism among a number of biological reactions, which includes debris release, macrophage and osteoclast activation, an inflammatory response as well as metal ion release. Pharmacological therapy for component loosening has also been reviewed. A non-surgical treatment of osteolysis has not been found in the literature and thus may become an area of future research. Even though this research is warranted, comprehensively understanding the immune response to orthopedic implants and their metallic ions, and thus, creating improved prostheses appears to be the most cost-effective approach to decrease the morbidity related to osteolysis and to design implants with greater longevity. The ionic forms, cytokines, toxicity, gene expression, biological effects, and hypersensitivity responses of metallic elements from metal implants are summarized as well.

No difference in clinical outcome, bone density and polyethylene wear 5-7 years after standard navigated vs. conventional cementfree total hip arthroplasty

INTRODUCTION

The purpose of this investigation was to compare clinical outcome, component loosening, polyethylene cup wear and periprosthetic bone mineral density between "cup first" navigated and conventional cementless total hip arthroplasty (THA) 5-7 years after surgery.

MATERIALS AND METHODS

Fifty patients who received THA with (n = 25) or without (n = 25) the use of an image-free navigation system by a single surgeon were investigated after a mean follow-up of 6.4 (4.8-7.4) years. The Hip Osteoarthritis Outcome Score (HOOS) and the Harris Hip Score (HHS) were obtained; range-of-motion (ROM) was evaluated by a blinded examiner. Radiographic cup inclination, signs of radiographic loosening and polyethylene wear were analysed with the help of digital analysis software on anterio-posterior radiographs by a blinded examiner. Acetabular and femoral periprosthetic bone density was evaluated with the help of dual-energy X-ray absorptiometry.

RESULTS

We were unable to find any statistical significant or clinically relevant difference for the HOOS, HHS, ROM and polyethylene wear between the navigated and the conventional THA group 5-7 years after surgery. Cup inclination was more precise in the navigated THA group in relation to the target value of 45°.

CONCLUSIONS

Standard "cup first" THA navigation does not improve mid-term functional outcome, bony ingrowth and/or polyethylene wear. New concepts in computer-assisted THA, considering cup and stem as coupled biomechanical partners are needed to justify the effort of navigation in routine operations.

Wear rates of highly cross-linked polyethylene humeral liners subjected to alternating cycles of glenohumeral flexion and abduction

BACKGROUND

Although short-term outcomes of reverse total shoulder arthroplasty have been promising, long-term success may be limited due to device-specific complications, including scapular notching. Scapular notching has been explained primarily as mechanical erosion; however, the generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching.

METHODS

A 12-station hip simulator was converted to a reverse total shoulder arthroplasty wear simulator subjecting conventional and highly cross-linked ultra-high-molecular-weight polyethylene humeral liners to 5 million cycles of alternating abduction-adduction and flexion-extension loading profiles.

RESULTS

Highly cross-linked polyethylene liners (36.5 ± 10.0 mm(3)/million cycle) exhibited significantly lower volumetric wear rates compared with conventional polyethylene liners (83.6 ± 20.6 mm(3)/million cycle; P < .001). The flexion-extension loading profile exhibited significantly higher wear rates for conventional (P < .001) and highly cross-linked polyethylene (P < .001) compared with the abduction-adduction loading profile. Highly cross-linked wear particles had an equivalent circle diameter significantly smaller than wear particles from conventional polyethylene (P < .001).

CONCLUSIONS

Highly cross-linked polyethylene liners significantly reduced polyethylene wear and subsequent particle generation. More favorable wear properties with the use of highly cross-linked polyethylene may lead to increased device longevity and fewer complications but must be weighed against the effect of reduced mechanical properties.

Results at a minimum of 10 years of follow-up for AMS and PerFix HA-coated cementless total hip arthroplasty: impact of cross-linked polyethylene on implant longevity

PURPOSE

The purpose of this study was to report results at a minimum of 10 years for hydroxyapatite (HA) coating on the titanium arc-sprayed cementless total hip arthroplasty (THA) and to evaluate the impact of cross-linked polyethylene (XLPE) on implant longevity.

METHODS

A total of 131 consecutive primary THAs in 123 patients using an AMS acetabular cup and a PerFix HA stem were retrospectively reviewed. Conventional PE was used for 62 hips (CPE group) and cross-linked PE for 69 hips (XLPE group), with mean follow-up periods of 13 and 11.5 years, respectively. These patients were reviewed using the Japanese Orthopaedic Association (JOA) Hip Score and evaluated in terms of PE wear, osteolysis, and implant survival.

RESULTS

The JOA score improved from 42.6 to 83.9 points at the final follow-up. The mean wear rate of 0.12 mm/year in the CPE group was significantly greater than that of XLPE at 0.007 mm/year. In the CPE group, ten (16.1 %) and two (3.2 %) hips, respectively, underwent PE exchange due to severe wear and acetabular revision due to loosening associated with osteolysis. Three patients had revision in the XLPE group: one cup for aseptic loosening, one PE for recurrent dislocation, and one stem for neck fracture. No evident osteolysis was seen in the XLPE group. Kaplan-Meier survivorship with any revision as the end point shows that the 12-year survival rate was 97.7 % for cups, 93.8 % for PE liners, and 99.2 % for stems. Multivariate analysis revealed that the use of XLPE significantly reduced the risk of revision, with the odds ratio (OR) of 4.3.

CONCLUSIONS

AMS and PerFix HA components in this series show excellent implant fixation; however, high rates of PE wear and subsequent osteolysis were limiting factors in long-term success. Low wear rates with XLPE suggest improved implant longevity.

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

PURPOSE

The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup.

METHODS

We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(-)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips.

RESULTS

One hip (0.4%) had a dislocation in the CA(+) group, whereas ten hips (2.5%) had a dislocation in the CA(-) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(-) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0%) achieved the intended CA.

CONCLUSIONS

Although the manual placement of the cup resulted in 27% of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.