Metal-backed acetabular components with conventional polyethylene: a review of 9113 primary components with a follow-up of 20 years

Long-term follow-up and survival of delayed total hip arthroplasty following acetabular fracture: a matched cohort study of 552 cases from the Norwegian Arthroplasty Register

BACKGROUND

Operative treatment of acetabular fractures generally yields good results, but several authors report up to 15-20% of patients developing post-traumatic osteoarthritis (OA). Previous studies have shown that total hip arthroplasty (THA) following post-traumatic OA have inferior results compared to THA for primary OA. The aim of this study was to report on long-term outcome of THA following acetabular fracture, compared to primary OA.

MATERIALS AND METHODS

We performed a matched cohort study with data from the Norwegian Arthroplasty Register (NAR). All patients receiving THA following an acetabular fracture between 1987 and 2018 were identified. A 3:1 matched cohort consisting of patients treated for primary OA with THA was selected using propensity scores and matched for age, gender and year of surgery. Survival analysis was performed with revision of any cause as endpoint. Cox regression was used to identify factors associated with risk of revision surgery.

RESULTS

552 cases were identified, 397 men and 155 women. Mean age was 58.8 (11-91) years. 224 had previously been operated for the acetabular fracture, 328 had been treated non-operatively. Mean follow up time was 8.7 (1-29) years. Implant survival at 10 years was 79.7% (75.6-83.3) and at 20 years 62.4% (55.5-69.3). The hazard ratio for revision was 1.38 (1.07-1.77, p < 0.001) compared to the OA cohort, regardless of operative or non-operative treatment of the index acetabular fracture. Uncemented acetabular components had an increased risk of revision with hazard ratio for revision 1.61 (p = 0.012).

CONCLUSIONS

THA following an acetabular fracture can be performed with acceptable results regarding implant survival, however, we report an increased risk for revision when compared to primary OA. Our results indicate that previous operative fracture treatment does not increase the risk for THA revision compared to cases treated non-operatively.

Early unrestricted vs. partial weight bearing after uncemented total hip arthroplasty: a systematic review and meta-analysis

Background

The choice of postoperative weight bearing protocol after uncemented total hip arthroplasty (THA) remains controversial. The aim of this study was to assess the efficacy and safety of immediate unrestricted weight bearing (UWB) compared with partial weight bearing (PWB) in patients undergoing uncemented THA.

Methods

Relevant articles were retrieved from electronic databases. Both randomized controlled trials (RCTs) and non-RCTs were included but analyzed separately. All functional and clinical outcomes with at least 2 independent study outcomes were meta-analyzed.

Results

A total of 17 studies were investigated. No adverse effect was found regarding micromotion of the femoral stem with immediate UWB following uncemented THA. There was also no correlation between immediate UWB and failure of ingrowth fixation and higher risks of femoral stem subsidence and surgical revision in RCTs. Harris hip score was better in patients with immediate UWB than those with PWB at 1 year post surgery, but the difference was not statistically significant.

Conclusions

Immediate UWB did not have extra harm compared with PWB in patients undergoing uncemented THA. UWB was not superior to PWB. Considering the improvement of Harris score and the compliance of patients, UWB can be encouraged in THA rehabilitation.

How Does Implant Survivorship Vary with Different Corail Femoral Stem Variants? Results of 51,212 Cases with Up to 30 Years Of Follow-up from the Norwegian Arthroplasty Register

BACKGROUND

The Corail® cementless stem (DePuy Synthes) has been used in Norway since 1987 and is one of the most frequently used stems in THA worldwide. Although the published survival results of the standard Corail stem have been good, little is known about the long-term (more than 20 years) survival of other stem design variants. Further, some changes were made to the extramedullary part of the stem in 2003, and the effect of these changes on survival is unknown.

QUESTIONS/PURPOSES

(1) What is the survival up to 30 years of the standard collarless Corail femoral stem, and were extramedullary changes (slimmer, polished and rectangular neck, shorter taper) associated with differences in survivorship? (2) How does the 10-year survival and the risk of revision of other Corail stem variants, including the standard collared stem, coxa vara collared stem, and high offset collarless stem, compare with those of the standard collarless stem? (3) Which factors are associated with an increased risk of revision of the Corail stem, and are there any differences in those factors among the four stem variants?

METHODS

Data for this study were drawn from the Norwegian Arthroplasty Register. Since 1987, THAs have been registered in the Norwegian Arthroplasty Register with completeness of data greater than 97% for primary THAs and 93% for revisions. To study survivorship with up to 30 years of follow-up (1987 to 2018; median 7.7-year follow-up), and to compare the original stem with stems with extramedullary modifications, we included 28,928 standard collarless Corail stems in 24,893 patients (mean age at time of implantation 62 years; 66% [16,525 of 24,893] were women). To compare the newer stem variants with the standard collarless stem (2008 to 2018), we included 20,871 standard collarless, 10,335 standard collared, 6760 coxa vara collared, and 4801 high offset collarless stems. Survival probabilities were estimated using the Kaplan-Meier method with endpoints of stem revision, revision due to aseptic stem loosening, and periprosthetic fracture. The endpoint of all noninfectious causes of THA revision (including cup revision) was additionally analyzed for the long-term comparison. The proportion of patients who died was limited, and there was no difference in death rate between the groups compared. Therefore, we believe that competing events were not likely to influence survivorship estimates to a large degree. To compare different stem variants and evaluate factors that could be associated with the risk of revision, we calculated hazard ratios using Cox regression analyses with adjustments for gender, age group, surgical approach, diagnosis, and stem size.

RESULTS

The 30-year Kaplan-Meier survival of the standard collarless stem was 88.4% (95% confidence interval 85.4% to 91.4%), 93.3% (95% CI 91.1% to 95.5%), and 94.4% (95% CI 92.0% to 96.8%) using stem revision for any noninfectious cause, aseptic loosening, and periprosthetic fracture of the femur as endpoints, respectively. There was no difference in survival between the original stem and the modified stem. The 10-year Kaplan-Meier survivorship free of stem revision (all causes including infection) was 97.6% (95% CI 97.2% to 98.0%) for the standard collarless stem, 99.0% (95% CI 98.8% to 99.2%) for the standard collared stem, 97.3% (95% CI 96.3% to 98.3%) for the coxa vara collared stem, and 95.0% (95% CI 93.6% to 96.4%) for the high offset collarless stem. Compared with the standard collarless stem, the standard collared stem performed better (HR 0.4 [95% CI 0.3 to 0.6]; p < 0.001) and the high offset collarless stem performed more poorly (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.006) with any stem revision as the endpoint, and similar results were found with revision for aseptic stem loosening and periprosthetic fracture as endpoints. Controlling for the noted confounders, the standard collared stem had a lower revision risk. The high offset collarless stem had an increased stem revision risk for any reason (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.006) and aseptic loosening (HR 1.6 [95% CI 1.1 to 2.3]; p = 0.022). Other factors associated with an increased risk of stem revision for all stem variants were being a man (HR 1.7 [95% CI 1.4 to 2.0]; p < 0.001), age 70 to 79 years and 80 years and older compared with the age group of 50 to 59 years (HR 1.6 [95% CI 1.2 to 2.0]; p < 0.001 and HR 1.9 [95% CI 1.4 to 2.6]; p < 0.001, respectively), the anterior approaches (direct anterior Smith-Petersen and anterolateral Watson-Jones combined) compared with the posterior approach (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.005), as well as a preoperative nonosteoarthritis diagnosis (HR 1.3 [95% CI 1.0 to 1.6]; p = 0.02) and small stem sizes (sizes 8-11) compared with the medium sizes (sizes 12-15) (HR 1.4 [95% CI 1.1 to 1.6]; p = 0.001). The very small sizes (8 and 9) were associated with a 2.0 times higher risk of revision (95%. CI 1.4 to 2.6; p < 0.01) compared with all other sizes combined.

CONCLUSION

When using the uncemented Corail stem, surgeons can expect good results with up to 30 years of follow-up. Our results should be generalizable to the typical surgeon at the average hospital in a comparable setting. From our results, using a collared variant would be preferable to a collarless one. Due to an increased risk of periprosthetic fracture, caution with the use of the uncemented Corail stem in patients older than 70 years, especially in women, is warranted. Poorer stem survival should also be expected with the use of small stem sizes. The risk of periprosthetic fractures for the Corail uncemented stem versus cemented stems in different age categories has not been extensively examined, nor has the use of a collar for different age groups and genders, and both should be subjects for further investigation.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Cemented or uncemented acetabular fixation in combination with the Exeter Universal cemented stem

AIMS

To compare long-term survival of all-cemented and hybrid total hip arthroplasty (THA) using the Exeter Universal stem.

METHODS

Details of 1,086 THAs performed between 1999 and 2005 using the Exeter stem and either a cemented (632) or uncemented acetabular component (454) were collected from local records and the New Zealand Joint Registry. A competing risks regression survival analysis was performed with death as the competing risk with adjustments made for age, sex, approach, and bearing.

RESULTS

There were 61 revisions (9.7%; 0.82 revisions/100 observed component years, (OCYs)) in the all-cemented group and 18 (4.0%; 0.30/100 OCYs) in the hybrid group. The cumulative incidence of revision at 18 years was 12.1% for cemented and 5.2% for hybrids. There was a significantly greater risk of revision for all-cemented compared with hybrids (unadjusted sub-hazard ratio (SHR) 2.44; p = 0.001), and of revision for loosening, wear, or osteolysis (unadjusted SHR 3.77; p < 0.001). After adjustment, the increased risk of all-cause revision did not reach significance at age 70 years and above. The advantage for revision for loosening, wear, and osteolysis remained at all ages.

CONCLUSION

This study supports the use of uncemented acetabular fixation when used in combination with the Exeter stem with improved survivorship for revision for aseptic loosening, wear, and osteolysis at all ages and for all-cause revision in patients less than 70 years. Cite this article: Bone Joint J 2020;102-B(4):414-422.

Fixation, sex, and age: highest risk of revision for uncemented stems in elderly women - data from 66,995 primary total hip arthroplasties in the Norwegian Arthroplasty Register

Background and purpose - There is no consensus on best method of fixation in hip arthroplasty. We investigated different modes of fixation in primary total hip arthroplasty (THA) and the influence of age and sex, to assess need for a differentiated approach.Patients and methods - The study was based on data from the Norwegian Arthroplasty Register in the period 2005-2017. Included were all-cemented, all-uncemented, reverse hybrid (uncemented stem and cemented cup), and hybrid (cemented stem and uncemented cup) THA designs that were commonly used, contemporary and well documented, using different causes of revision as endpoints.Results - From the included 66,995 primary THAs, 2,242 (3.3%) were revised. Compared with all-cemented THAs, all-uncemented had a higher risk of revision due to any cause (RR 1.4; CI 1.2-1.6), mainly due to an increased risk of periprosthetic fracture (RR 5.2; CI 3.2-8.5) and dislocation (RR 2.2; CI 1.5-3.0). Women had considerably higher risk of revision due to periprosthetic fracture after all-uncemented THA (RR 12; CI 6-25), compared with cemented. All-uncemented THAs in women of age 55-75 years (RR 1.3; CI 1.0-1.7) and over 75 years of age (RR 1.8; CI 1.2-2.7), and reverse hybrid THAs in women over the age of 75 (RR 1.5; CI 1.1-1.9) had higher risk of revision compared with cemented. Hybrid THAs (RR 1.0; CI 0.9-1.2) and reverse hybrid THAs (RR 1.0; CI 0.7-1.3) had similar risk of revision due to any cause as cemented THAs.Interpretation - Uncemented stems (all-uncemented and reverse hybrid THAs) had increased risk of revision in women over 55 years of age, mainly due to periprosthetic fracture and dislocation, and should probably not be used in THA in these patients.

Low wear rate at 6-year follow-up of vitamin E-infused cross-linked polyethylene: a randomised trial using 32- and 36-mm heads

BACKGROUND

Free radicals formed in the cross-linking process may over time alter the mechanical properties of highly cross-linked polyethylene. Vitamin E-infused highly cross-linked polyethylene was therefore developed to achieve low wear-rate and good mechanical properties in the long term.

AIM

To present 6-year results from the initial randomised controlled trial.

PATIENTS AND METHODS

We measured wear and periacetabular bone remodelling in cementless total hip arthroplasty; 32- or 36-mm Biolox Delta heads and vitamin E-infused highly cross-linked polyethylene (E-Poly) were used. Markerless radiosterometric analysis measured the in vivo wear and dual energy x-ray absorptiometry was used to analyse bone remodelling in 40 hips at 6-year follow-up.

RESULTS

In the proximal direction the wear for 32- and 36-mm heads was 0.15 mm (95% confidence interval [CI], 0.08-0.21) and 0.06 mm (95% CI, -0.002-0.12), respectively (p = 0. 015). However, between 3 months and 6 years (excluding the period of "bedding in"), the proximal wear for 32- and 36-mm heads was 0.10 mm (95% CI, 0.05-0.15) and 0.05 mm (95% CI, -0.01-0.11), respectively (p = 0.12). The annual proximal wear rate for 32- and 36-mm heads from 3 months to 6 years was 0.02 mm and 0.01 mm, respectively. There was no difference in bone remodelling around the cup from baseline to 6 years for the total material and no differences between study groups.

CONCLUSION

Wear of this vitamin E-infused highly cross-linked polyethylene is still low at 6-year follow-up, with no significant difference in wear from 3 months to 6 years between 32- and 36-mm heads.

Impact of hip arthroplasty registers on orthopaedic practice and perspectives for the future

Total hip arthroplasty (THA) registers are established in several countries to collect data aiming to improve the results after THA. Monitoring of adverse outcomes after THA has focused mainly on revision surgery, but patient-reported outcomes have also been investigated.Several surgery-related factors influencing the survival of the THA have been thoroughly investigated and have changed clinical practice. These factors include surgical approach, specific implants, the size of the components, type of fixation and different bone cements.Register data have been used to examine the risk of venous thromboembolism and bleeding after THA. These investigations have resulted in shorter duration of thromboprophylaxis and a reduced frequency of blood transfusion.Registers may provide specific information to surgeons on the outcome of all THAs that they have performed with a detailed analysis of revisions rates and reasons for the revisions.A number of other stakeholders can use register data to provide benchmarks. The National Joint Registry for England, Wales, Northern Ireland and the Isle of Man supplies data to the Orthopaedic Device Evaluation Panel (ODEP), which provides benchmarks at 3, 5, 7, 10, and 13 years graded from A*, A, B and C.Future perspectives: National registers have to play a major role in documenting the quality of THA in order to describe best practice and report implant outliers. The registers have to be used for research and post-market surveillance and register data may be a source for intelligent decision tools. Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180091.

Model-based roentgen stereophotogrammetric analysis using elementary geometrical shape models: 10 years results of an uncemented acetabular cup component

Background

Non-cemented acetabular cup components demonstrated different clinical performance depending on their surface texture or bearing couple. However, clinical osseointegration needs to be proved for each total joint arthroplasty (TJA) design. Aim of this study was to detect the in vivo migration pattern of a non-cemented cup design, using model-based roentgen stereophotogrammetric analysis with elementary geometrical shape models (EGS-RSA) to calculate early cup migration.

Methods

Interchangeable applicability of the model-based EGS-RSA method next to gold standard marker-based RSA method was assessed by clinical radiographs. Afterwards, in vivo acetabular cup migration for 39 patients in a maximum follow up of 120 months (10 years) was calculated using model-based EGS-RSA.

Results

For the axes with the best predictive capability for acetabular cup loosening, mean (±SD) values were calculated for migration and rotation of the cup. The cup migrated 0.16 (±0.22) mm along the cranio-caudal axis after 24 months and 0.36 (±0.72) mm after 120 months, respectively. It rotated − 0.61 (±0.57) deg. about the medio-lateral axis after 24 months and − 0.53 (±0.67) deg. after 120 months, respectively.

Conclusions

Interchangeable applicability of model-based EGS-RSA next to gold standard marker-based RSA method could be shown. Model-based EGS-RSA enables an in vivo migration measurement without the necessity of TJA specific surface models. Migration of the investigated acetabular cup component indicates significant migration values along all the three axes. However, migration values after the second postoperative year were within the thresholds reported in literature, indicating no risk for later aseptic component loosening of this TJA design.

The Morscher Press-Fit Acetabular Component: An Independent Long-Term Review at 18-22 Years

BACKGROUND

There are relatively few 20-year results of uncemented acetabular components, and most of these are modular designs. This study reports the 20-year results of a monoblock press-fit acetabular component.

METHODS

A total of 122 total hip arthroplasties (111 patients) using the Morscher cup were reviewed at a mean of 19.7 years. The average age at implantation was 57.3 years (range, 36-74 years), and 81 (66%) were men.

RESULTS

Twenty-two patients (25 hips) had died. Seven hips were revised, including 5 acetabular revisions. Six patients (6 hips) declined to participate but were known not to have been revised. The mean Oxford hip score was 41.1 (range, 22-48), and the mean reduced Western Ontario and McMaster Universities Osteoarthritis Index score was 5.7/48 (range, 0-24). Eccentric wear was seen in 13 (15.7%) and major osteolysis in 14 (17%) of 82 surviving hips with radiographs. The all-cause revision rate was 0.32 per 100 observed component years (95% confidence interval [CI], 0.13-0.66). The 20-year Kaplan-Meier survival was 93.4% (CI, 86.6-96.8) for all-cause revisions, 95.5% (CI, 89.4-98.1) for any acetabular revision, and 97.1% (CI, 91.2-99.1) for acetabular aseptic loosening, wear, or osteolysis.

CONCLUSION

The Morscher acetabular component has continued to perform well at 20 years despite using conventional polyethylene with results that match or surpass other cementless acetabulae.

Outcome in design-specific comparisons between highly crosslinked and conventional polyethylene in total hip arthroplasty

Background and purpose - Most registry studies regarding highly crosslinked polyethylene (XLPE) have focused on the overall revision risk. We compared the risk of cup and/or liner revision for specific cup and liner designs made of either XLPE or conventional polyethylene (CPE), regarding revision for any reason and revision due to aseptic loosening and/or osteolysis. Patients and methods - Using the Nordic Arthroplasty Register Association (NARA) database, we identified cup and liner designs where either XLPE or CPE had been used in more than 500 THAs performed for primary hip osteoarthritis. We assessed risk of revision for any reason and for aseptic loosening using Cox regression adjusted for age, sex, femoral head material and size, surgical approach, stem fixation, and presence of hydroxyapatite coating (uncemented cups). Results - The CPE version of the ZCA cup had a risk of revision for any reason similar to that of the XLPE version (p = 0.09), but showed a 6-fold higher risk of revision for aseptic loosening (p < 0.001). The CPE version of the Reflection All Poly cup had an 8-fold elevated risk of revision for any reason (p < 0.001) and a 5-fold increased risk of revision for aseptic loosening (p < 0.001). The Charnley Elite Ogee/Marathon cup and the Trilogy cup did not show such differences. Interpretation - Whether XLPE has any advantage over CPE regarding revision risk may depend on the properties of the polyethylene materials being compared, as well as the respective cup designs, fixation type, and follow-up times. Further research is needed to elucidate how cup design factors interact with polyethylene type to affect the risk of revision.

A case control study of cemented acetabular total hip arthroplasty components in patients less than 50 with 5-year minimum follow-up

BACKGROUND

This study investigates the outcomes of cemented sockets in young patients (<50 years) requiring a total hip replacement (THR) compared to older patients (>50 years) having the same procedure, under the same surgeon between June 2005 and May 2009.

METHODS

Prosthesis survivorship rates, patient outcomes and radiological findings were compared between a consecutive series of 56 young patients (mean 42, range 25-49) and 56 older patients (mean 69, range 53-81) that underwent a primary THR using a cemented Stryker® Exeter™ Contemporary™ flanged cup. The minimum follow-up was 5 years.

RESULTS

No significant difference was observed between the groups' Oxford Hip Scores (p = 0.078) or satisfaction scores (p = 0.67). Worst case scenario analysis for revision, failure or lost to follow-up showed 94.6% survival in the <50 year olds and 92.9% survival in the >50 year olds at 5 years. This study demonstrates no significant difference in patient outcomes, survivorship or radiographic findings at a minimum of 5 years between patients <50 years old and those >50 years old undergoing THR with a cemented socket.

CONCLUSIONS

We believe the current trend towards uncemented cups may be driven by marketing rather than by evidence of improved outcomes. Cemented sockets provide very good outcomes for patients of all ages.

THE DETERMINATION OF THE VOLUMETRIC WEAR FOR SURGICALLY RETRIEVED HIP IMPLANTS BASED ON CMM

The effects of wear mechanisms on the long-term survivorship of artificial hip implants emphasized the importance of determining the 3D volumetric wear in retrieved hip replacements. Traditional methods for determining the volumetric wear on acetabular cups require reference surface from a pre-worn model, which is not feasible for clinical retrieved implants. In this study, a methodology based on co-ordinate measuring machine (CMM) measurement is proposed to reconstruct the reference surface by applying a mathematical model on those selected unworn regions of the acetabular liners. For validation purposes, three polyethylene liners from 5-million-cycle hip simulator testing were employed, whose wear volume at different measurement points was determined by applying the developed method and the results were compared to those determined via traditional approaches. Volumetric loss estimated by the developed method was found to correlate well with the results estimated by the traditional methods ([Formula: see text]). Moreover, two surgically retrieved inserts were analyzed using the developed methodology. The wear volume estimated from the two retrieved liners was also found to agree well with the observation from X-ray photograph. Results demonstrated that the proposed method is effective in determining the volumetric wear for retrieved components providing viable unworn regions on the liner.

Backside Wear Is Not Dependent on the Acetabular Socket Design in Crosslinked Polyethylene Liners

BACKGROUND

Although it is understood that backside damage occurs in polyethylene acetabular liners, the effect of highly crosslinked polyethylene, which has completely replaced conventional polyethylene, has yet to be examined.

QUESTIONS/PURPOSES

The purpose of this study was to answer the following questions: (1) With conventional polyethylene (CPE), did the acetabular design make a difference in backside wear? (2) Is there a difference in backside damage between CPE and crosslinked polyethylene (XLPE) liners? (3) With XLPE, is the difference in backside wear between designs still present? (4) Is there any difference in backside damage in various zones on backside of individual liners?

METHODS

This single-institution retrieval analysis involved visual damage scoring on the backside of 233 polyethylene liners implanted between 2002 and 2011. The liners were retrieved from either polished/dovetail cups (PD) or roughened/wire cups (RW) made by two different manufacturers. The inserts were divided into four groups: PD-CPE (n = 105), PD-XLPE (n = 16), RW-CPE (n = 99), and RW-XLPE (n = 13). Aseptic loosening and polyethylene wear were the predominant reasons for revision of CPE liners, whereas instability and infection were the common reasons for revision of XLPE liners. The time in situ (TIS) was shorter for the XLPE liners as compared with the CPE liners (PD-CPE: 8.5 years [SD 4.4]; RD-CPE: 9.5 [SD 4.8]; PD-CPE: 3.8 [SD 3.7]; RD-XLPE: 4.0 [SD 4.3]). The backside of each liner was divided into five zones and graded initially from a scale of 0 to 3 for seven different damage modes by one observer. There was substantial interobserver (kappa 0.769) and intraobserver (0.736) reliability on repeat scoring. To compare the effects of crosslinking, a subset of the conventional polyethylene liners was matched to the crosslinked liners based on TIS, resulting in 16 per group for the two PD types and 13 per group for the two RW types.

RESULTS

Total damage scores in the RW-CPE (19 ± 7) group were greater (p < 0.001) than the PD-CPE group (8 ± 4). Damage was reduced with XLPE (p = 0.02) only for the RW-XLPE (9 ± 9) versus RW-CPE-type sockets (4 ± 4). There was no difference (p = 0.16) between the RW-XLPE group and the PD-XLPE group. Damage scores in the peripheral zone of the locking mechanisms were higher for RW-CPE (4 ± 3) compared with PD-CPE (1.4 ± 1.0, p < 0.001) and RW-XLPE (1.3 ± 1.3, p = 0.02). Damage was greater (p < 0.001) within the superior zones (7 ± 4) compared with the inferior zones (3.0 ± 2.8) of all liners.

CONCLUSIONS

The current study shows greater backside damage for CPE in the roughened, wire lock cups. XLPE was shown to be more resistant to backside damage for both socket designs.

CLINICAL RELEVANCE

Although the polished/dovetail cups seem to cause less backside damage in the CPE liners than roughened/wire cups, the use of XLPE liners has been shown to protect the liner from backside damage in either cup design. If an acetabular shell has a functional locking mechanism, surgeons should not worry about cup design when undertaking isolated liner revision using XLPE liners.

Long-term results with the Atlas IIIp elastic cementless acetabular component in total hip replacement

PURPOSE

Modular cementless elastic acetabular systems have advantages over cemented and hard shell cementless acetabular systems. There are few reports on the medium-term and long-term follow up of this particular type of implant. This study describes our experience with the Atlas IIIp modular acetabular system, which is a thin shell cementless elastic acetabular implant for total hip replacement commercialized under this name in many countries.

METHODS

We prospectively followed 244 patients treated with Atlas IIIp acetabular system between 2001 and 2004. Minimum ten year follow up was available for 148 hips (139 patients) from the original cohort of 263 hips (244 patients). One hundred five patients had died from unrelated causes and were excluded from the results. Post-operative and follow up radiographs of patients were assessed; and Harris hip scores were used as clinical outcome. Revision for any reason was defined as the end point for survivorship analysis.

RESULTS

The mean pre-operative Harris hip score was 48 (S.D. 16) and the average post-operative score was 82 (S.D. 12). The mean follow up in our series was 11.5 years, ranging from ten to 13.5 years. Thirteen hips required further surgery in our cohort; of which ten cases required cup revision. The 13-years cumulative implant survival was 91.2 % and the risk of implant revision was 8.8 % at 13 years in 148 hips (139 patients). Kaplan-Meier analysis showed the implant survival rate of 95.2 % at ten years for revision for any reason and 99.4 % for aseptic loosening.

CONCLUSIONS

Our clinical experience with this acetabular cup suggests good long-term survival rates that are similar to other cups on the market. The clinical experience in this study shows long-term survival rates that are consistent, acceptable and good results achieved with a low revision rate.

LEVEL OF EVIDENCE

Therapeutic III; therapeutic study.

E-vitamin infused highly cross-linked polyethylene: RSA results from a randomised controlled trial using 32 mm and 36 mm ceramic heads

BACKGROUND

Polyethylene wear has been a major cause of revision of cementless total hip replacements. Highly cross-linked polyethylene has been developed to increase mechanical resistance to wear. However, cross-linking from irradiation of the polyethylene generates free radicals and these can oxidise in vivo and might over time alter the initial mechanical properties. Vitamin-E infused highly cross-linked polyethylene has been developed to reduce the amount of free radicals without compromising the mechanical properties.

PURPOSE

To measure wear of vitamin E infused highly cross-linked polyethylene and compare wear between 2 different head sizes.

METHODS

In a prospective randomised study between 32 mm and 36 mm Biolox® delta heads in 50 hips we analysed the in vivo wear of the E-poly™ with markerless radiostereometry.

RESULTS

Mean (95% CI) wear for the total material was 0.041 mm (0.015-0.066) in the vertical direction and 0.177 mm (0.155-0.200) in the total 3D direction. After the anticipated period of bedding-in we found no statistically significant differences in wear from three months to 2 years in vertical and total 3D directions. Although statistical significant differences between 32 mm and 36 mm heads were found in the total 3D direction we cannot conclude that there are significant clinical important differences in wear comparing these head sizes.

CONCLUSIONS

This study shows promising early results with very low wear, even for 36 mm heads, but long term follow-up is necessary to evaluate if this polyethylene will provide low wear and good mechanical properties in the long-term.

Distributed analysis of hip implants using six national and regional registries: comparing metal-on-metal with metal-on-highly cross-linked polyethylene bearings in cementless total hip arthroplasty in young patients

BACKGROUND

The regulation of medical devices has attracted controversy recently because of problems related to metal-on-metal hip implants. There is growing evidence that metal-on-metal implants fail early and cause local and systemic complications. However, the failure associated with metal-on-metal head size is not consistently documented and needs to be communicated to patients and surgeons. The purpose of this study is to compare implant survival of metal on metal with that of metal on highly cross-linked polyethylene.

METHODS

Using a distributed health data network, primary total hip arthroplasties were identified from six national and regional total joint arthroplasty registries (2001 to 2010). Inclusion criteria were patient age of forty-five to sixty-four years, cementless total hip arthroplasties, primary osteoarthritis diagnosis, and exclusion of the well-known outlier implant ASR (articular surface replacement). The primary outcome was revision for any reason. A meta-analysis of survival probabilities was performed with use of a fixed-effects model. Metal-on-metal implants with a large head size of >36 mm were compared with metal-on-highly cross-linked polyethylene implants.

RESULTS

Metal-on-metal implants with a large head size of >36 mm were used in 5172 hips and metal-on-highly cross-linked polyethylene implants were used in 14,372 hips. Metal-on-metal total hip replacements with a large head size of >36 mm had an increased risk of revision compared with metal-on-highly cross-linked polyethylene total hip replacements with more than two years of follow-up, with no difference during the first two years after implantation. The results of the hazard ratios (and 95% confidence intervals) from the multivariable model at various durations of follow-up were 0.95 (0.74 to 1.23) at zero to two years (p = 0.698), 1.42 (1.16 to 1.75) at more than two years to four years (p = 0.001), 1.78 (1.45 to 2.19) at more than four years to six years (p < 0.001), and 2.15 (1.63 to 2.83) at more than six years to seven years (p < 0.001).

CONCLUSIONS

We conducted a comparison of large-head-size, metal-on-metal implants and metal-on-highly cross-linked polyethylene implants in younger patients with uncemented fixation. We found consistent and strong evidence worldwide that large-head-size, metal-on-metal implants were associated with increased risk of revision after two years compared with metal-on-highly cross-linked polyethylene implants, with the effect becoming more pronounced over time.

Empirical support for radiographic review: a follow-up study of total hip arthroplasty

Routine post surgery surveillance of total hip arthroplasty (THA) is widely recommended to identify asymptomatic failure but inclusion of an x-ray adds to service costs. Evidence is needed to support orthopaedic opinion in order to identify what should be included in surveillance. An investigation was conducted to establish whether an x-ray is needed in addition to patient reported outcome measures. One hundred and fifty-four THA had been assessed at 3 years and were reviewed again at 6 to 9 years (mid-term) when radiographic signs of deterioration commonly appear. Data were explored for associations between radiographic changes and changes in the participants' Oxford Hip Score, age, EuroQol 5-D score or comorbidities. Hierarchical multiple regression analysis showed that the number of radiographic changes could not be predicted by any of the other variables. This supports the inclusion of an x-ray in THA surveillance and suggests that the state of the THA cannot be determined by the use of patient reported outcome measures alone. This has implications for future arthroplasty surveillance.

10-year results of the uncemented Allofit press-fit cup in young patients

BACKGROUND AND PURPOSE

Uncemented acetabular components in primary total hip arthroplasty (THA) are commonly used today, but few studies have evaluated their survival into the second decade in young and active patients. We report on a minimum 10-year follow-up of an uncemented press-fit acetabular component that is still in clinical use.

METHODS

We examined the clinical and radiographic results of our first 121 consecutive cementless THAs using a cementless, grit-blasted, non-porous, titanium alloy press-fit cup (Allofit; Zimmer Inc., Warsaw, IN) without additional screw fixation in 116 patients. Mean age at surgery was 51 (21-60) years. Mean time of follow-up evaluation was 11 (10-12) years.

RESULTS

At final follow-up, 8 patients had died (8 hips), and 1 patient (1 hip) was lost to follow-up. 3 hips in 3 patients had undergone acetabular revision, 2 for deep infection and 1 for aseptic acetabular loosening. There were no impending revisions at the most recent follow-up. We did not detect periacetabular osteolysis or loosening on plain radiographs in those hips that were evaluated radiographically (n = 90; 83% of the hips available at a minimum of 10 years). Kaplan-Meier survival analysis using revision of the acetabular component for any reason (including isolated inlay revisions) as endpoint estimated the 11-year survival rate at 98% (95% CI: 92-99).

INTERPRETATION

Uncemented acetabular fixation using the Allofit press-fit cup without additional screws was excellent into early in the second decade in this young and active patient cohort. The rate of complications related to the liner and to osteolysis was low.

A comparative study of four bearing couples of the same acetabular and femoral component: a mean follow-up of 11.5 years

We present a retrospective evaluation of 1369 hip arthroplasties performed using the Bicon-Plus cups and SL-Plus stems, differing only in the bearing combination. Four bearing combination groups were used: metal-on-polyethylene (MoP) group with 587 hips, ceramic-on-polyethylene (CoP) group with 161 hips, metal-on-metal (MoM) group with 322 hips and ceramic-on-ceramic (CoC) group with 299 hips. The mean follow-up was 11.5 years (4.1 to 15.0). Radiological evaluation was performed on implants failed due to aseptic loosening. The survival for prosthesis with revision for any reason at ten years was 96.1% (95% confidence interval (CI) 94.3 to 97.9) for MoP, 98.1% (CI 95.9 to 100) for CoP, 90.2% (CI 86.8 to 93.6) for MoM, and 95.6% (CI 93.0 to 98.2) for CoC. Survival for aseptic loosening was also determined.

[Aseptic, simultaneous and bilateral mobilisation due to an acetabular shell fracture in a 43 year-old patient]

The acetabular shell mobilization is the main long-term complication in total hip replacement. Metal-back fracture has also to be considered among the possible causes of shell mobilization. A case is presented of bilateral acetabular shell mobilization due to the trabecular covering de-soldering from the metal-back in a 43 year-old patient, 13-14 years after the first surgery.

Accelerated polyethylene wear and early failure of the uncemented Reflection acetabular component: a ten to fifteen-year follow-up study

PURPOSE

The Reflection® second-generation uncemented acetabular component was designed to address increased rates of failure observed with the early acetabular designs. However, the reported survivorship of this acetabular component has been conflicting. The aim of this study was to describe the ten to 15-year survivorship and polyethylene wear rate for the uncemented Reflection® acetabular component performed as part of a primary total hip replacement.

METHODS

One hundred and four consecutive Reflection® uncemented acetabular components in 97 patients were identified from a prospective arthroplasty database with a minimum of ten years of follow-up. No patient was lost to follow-up. Mean cohort age was 59.1 years.

RESULTS

There were 24 revisions of the acetabular component. The all-cause survival rate at ten years was 77.2% [95% confidence interval (CI) 73.9-80.5]. Mean linear wear was 0.20 mm [standard deviation (SD) 0.08] per year and the volumetric wear was 106.2 mm(3) per year. At final follow-up, more than half the patients had osteolysis identified around the femoral component. The mean Oxford Hip Score was 35.6 (SD 9.8) at a mean follow-up of 11.9 years, with six (11.1%) excellent, 26 (48.1%) good, 17 (31.5%) fair and five (9.3%) poor outcomes. Despite the fact that more than a third had a fair or poor outcome, only four (7.4%) were not satisfied with their hip.

CONCLUSIONS

Due to the high rate of relatively asymptomatic polyethylene wear and osteolysis associated with this acetabular component, in our department, we now review all surviving patients both clinically and radiographically on an annual basis.

New polyethylenes in total hip replacement: A ten- to 12-year follow-up study

Between 1999 and 2001, 90 patients underwent total hip replacement using the same uncemented acetabular and femoral components with a 28 mm metallic femoral head but with prospective randomisation of the acetabular liner to either Durasul highly cross-linked polyethylene or nitrogen-sterilised Sulene polyethylene. We assessed 83 patients at a minimum follow-up of ten years. Linear penetration of the femoral head was estimated at six weeks, six and 12 months and annually thereafter, using the Dorr method, given the non-spherical shape of the acetabular component. There was no loosening of any component; only one hip in the Sulene group showed proximal femoral osteolysis. The mean penetration of the femoral head at six weeks was 0.08 mm (0.02 to 0.15) for the Durasul group and 0.16 mm (0.05 to 0.28) for the Sulene group (p = 0.001). The mean yearly linear penetration was 64.8% lower for the Durasul group at 0.05 mm/year (sd 0.035) for the Sulene group and 0.02 mm/year (sd 0.016) for the Durasul (p < 0.001). Mean linear femoral head penetration at ten years was 61% less in the Durasul than Sulene group. Highly cross-linked polyethylene gives excellent results at ten years.

Is there evidence for accelerated polyethylene wear in uncemented compared to cemented acetabular components? A systematic review of the literature

Joint arthroplasty registries show an increased rate of aseptic loosening in uncemented acetabular components as compared to cemented acetabular components. Since loosening is associated with particulate wear debris, we postulated that uncemented acetabular components demonstrate a higher polyethylene wear rate than cemented acetabular components in total hip arthroplasty. We performed a systematic review of the peer-reviewed literature, comparing the wear rate in uncemented and cemented acetabular components in total hip arthroplasty. Studies were identified using MEDLINE (PubMed), EMBASE and the Cochrane Central Register of Controlled Trials. Study quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. The search resulted in 425 papers. After excluding duplicates and selection based on title and abstracts, nine studies were found eligible for further analysis: two randomised controlled trials, and seven observational studies. One randomised controlled trial found a higher polyethylene wear rate in uncemented acetabular components, while the other found no differences. Three out of seven observational studies showed a higher polyethylene wear in uncemented acetabular component fixation; the other four studies did not show any differences in wear rates. The available evidence suggests that a higher annual wear rate may be encountered in uncemented acetabular components as compared to cemented components.

Revision total hip replacement using the cement-in-cement technique for the acetabular component

The technique of femoral cement-in-cement revision is well established, but there are no previous series reporting its use on the acetabular side at the time of revision total hip replacement. We describe the technique and report the outcome of 60 consecutive acetabular cement-in-cement revisions in 59 patients at a mean follow-up of 8.5 years (5 to 12). All had a radiologically and clinically well-fixed acetabular cement mantle at the time of revision. During the follow-up 29 patients died, but no hips were lost to follow-up. The two most common indications for acetabular revision were recurrent dislocation (46, 77%) and to complement femoral revision (12, 20%).

Of the 60 hips, there were two cases of aseptic loosening of the acetabular component (3.3%) requiring re-revision. No other hip was clinically or radiologically loose (96.7%) at the latest follow-up. One hip was re-revised for infection, four for recurrent dislocation and one for disarticulation of a constrained component. At five years the Kaplan-Meier survival rate was 100% for aseptic loosening and 92.2% (95% CI 84.8 to 99.6), with revision for any cause as the endpoint.

These results support the use of cement-in-cement revision on the acetabular side in appropriate cases. Theoretical advantages include preservation of bone stock, reduced operating time, reduced risk of complications and durable fixation.

Is routine mid-term total hip arthroplasty surveillance beneficial?

BACKGROUND

Routine followup of patients after primary or revision THA is commonly practiced and driven by concerns that delays in identifying early failure will result in more complicated or more costly surgical interventions. Although mid-term followup (4-10 years) has been performed to follow cohorts of patients, the benefit of observing individual patients regardless of symptoms has not been established.

QUESTIONS/PURPOSES

We determined (1) the reasons patients with THA return for mid-term followup, (2) the treatment recommendations and interventions occurring as a result of mid-term followup, and (3) how frequently revision surgery is recommended for asymptomatic and symptomatic patients at mid-term followup.

METHODS

We retrospectively identified 501 patients (503 hips) who returned for followup at least 4 years (mean, 5 years; range, 4-10.9 years) after their primary or revision THA. We recorded their reasons for followup and treatment recommendations, including those for revision surgery, at mid-term followup.

RESULTS

Fifty-three percent of patients returning for routine followup had no symptoms, 31% reported an unrelated musculoskeletal concern, and 19% had symptoms from their primary THA (15%) or revision THA (32%). Sixty-nine percent of symptomatic patients and 10% of asymptomatic patients received treatment recommendations, with physical therapy as the most frequent intervention (74%). Revision surgery was recommended for 6% of symptomatic and 0.6% of asymptomatic patients.

CONCLUSIONS

Although routine surveillance may identify rare, asymptomatic patients with arthroplasty failure, it is much more likely to result in recommendations for nonoperative management during early followup.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Head material influences survival of a cemented total hip prosthesis in the Norwegian Arthroplasty Register

BACKGROUND

High prosthesis survival is reported for total hip prostheses with metal and alumina heads, but direct comparisons of a single prosthesis design with one of two different head materials has seldom been studied. Prostheses with zirconia heads are less commonly used than metal and alumina heads, and the few reports suggest variable results with zirconia heads.

QUESTIONS/PURPOSES

We therefore asked: (1) Would metal heads provide better survival of a cemented total hip arthroplasty (THA) than alumina heads? (2) Would metal heads provide better survival of a cemented THA than zirconia heads?

METHODS

We searched in the Norwegian Arthroplasty Register for cemented primary THA cup/stem combinations that simultaneously had been used with different head materials. The only THA that fulfilled these inclusion criteria was the cemented Reflection All-Poly/Spectron EF (cup/stem) that had during 2001 to 2006 been used both with alumina (n = 448) and cobalt-chromium (n = 5229) heads; that implant had also been used with zirconia (n = 275) and cobalt-chromium heads (n = 3195) during 1997 to 2003, and we included patients with this THA from these two time intervals in the study. All cups were conventional polyethylene. We estimated prosthesis survival and relative revision risks adjusting for age, sex, and diagnosis. The followup in the two study materials was until December 2010.

RESULTS

The survival at 8 years of the Spectron EF/Reflection THAs, inserted with alumina and cobalt-chromium heads during 2001 to 2006, was 92.3% and 94.0%, respectively. The Reflection/Spectron EF THA had inferior survival with zirconia heads compared with cobalt-chromium heads (relative risk, 1.7). At 12 years, the survival rate was 88.1% with cobalt-chromium heads and 74.8% with zirconia heads.

CONCLUSIONS

Alumina femoral heads provided no advantage over cobalt-chromium heads on midterm prosthesis survival. THAs with zirconia heads had inferior survival.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Cup press fit in uncemented THA depends on sex, acetabular shape, and surgical technique

BACKGROUND

Uncemented press-fit cups provide bone fixation in primary THA, but the use of screws is sometimes necessary to achieve primary stability of the socket. However, it is unclear whether and when screws should be used.

QUESTION/PURPOSES

We analyzed the factors related to screw use with a press-fit uncemented cup and assessed whether screw use is associated with the same rates of loosening and revision as a press-fit technique.

METHODS

We retrospectively reviewed 248 patients who underwent THA using the same prosthetic design. Eighty-eight hips had screws to achieve primary cup fixation (Group 1), and 189 did not (Group 2). Mean age was 50 years (range, 14-73 years). We analyzed factors related to the patient, acetabular type, and reconstruction of the rotation center of the hip. Minimum followup was 5 years (mean, 8.9 years; range, 5-12 years).

RESULTS

We found higher screw use in women, patients with less physical activity, Acetabular Types A or C, and a distance from the center of the prosthetic femoral head to the normal center of rotation of more than 3 mm. There were four revisions in Group 1 and five in Group 2. Eight hips had radiographic loosening in Group 1 and nine in Group 2. Cups with a postoperative abduction angle of more than 50° had a higher risk for loosening.

CONCLUSIONS

Press fit was achieved less frequently in women and patients with Acetabular Types A or C and less physical activity; a closer distance to the normal center of rotation decreased screw use. Screw use to augment fixation achieved survival similar to that of a press-fit cup.

LEVEL OF EVIDENCE

Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

Successful long-term fixation and progression of osteolysis associated with first-generation cementless acetabular components retrieved post mortem

BACKGROUND

Primary cementless acetabular reconstruction has shown durable long-term fixation. Late failures secondary to aseptic loosening are rare but may occur in patients with previously well-fixed components. In the present study, the histopathological characteristics of postmortem specimens were correlated with wear damage and radiographic data in an attempt to better understand the long-term events in the periacetabular tissue around well-functioning devices.

METHODS

Seventeen primary cementless Harris-Galante I acetabular components with adjacent tissues were harvested after a mean of eleven years (range, four to twenty-five years) from patients whose implants were well functioning at the time of death. Undecalcified and paraffin sections were used to quantify the extent of bone and soft tissues within the porous coating and at the interface between the coating and the surrounding bone. Wear particles were identified with use of polarized light microscopy and energy-dispersive x-ray analysis. Bearing-surface volumetric wear and backside wear damage of the polyethylene liner were assessed.

RESULTS

All of the components were fixed by bone ingrowth (mean extent, 33% ± 21%). Particle-induced granulomas were present in the porous coating and along the interface and progressed through screw holes, ballooning into the retroacetabular bone in the longer-term specimens. Particles of femoral and acetabular origin were identified in the granulomas. Bearing-surface volumetric wear (mean, 41.6 mm3/year) increased with duration and correlated with increasing extent of granuloma in the porous coating and the increasing size of pelvic granulomas. Radiolucencies on radiographs correlated with the extent of bone and fibrous tissue ingrowth. Of the six pelvic granulomas that were identified histologically, only one was apparent on routine radiographs.

CONCLUSIONS

Acetabular fixation by bone ingrowth can be successful into the third decade after implantation. Osteolysis and secondary replacement of bone with particle-induced granuloma are commonly seen in the presence of excellent clinical function. Strategies designed to minimize bearing-surface wear and backside damage are important to maintain long-term bone ingrowth fixation.

Survival of uncemented acetabular monoblock cups: evaluation of 210 hips in the Swedish Hip Arthroplasty Register

BACKGROUND AND PURPOSE

Monoblock acetabular cups represent a subtype of uncemented cups with the polyethylene liner molded into a metal shell, thus eliminating-or at least minimizing-potential backside wear. We hypothesized that the use of monoblock cups could reduce the incidence of osteolysis and aseptic loosening, and thus improve survival compared to modular designs.

PATIENTS AND METHODS

We identified all 210 primary total hip arthroplasty (THA) procedures in the Swedish Hip Arthroplasty Register that used uncemented monoblock cups during the period 1999-2010. Kaplan-Meier and Cox regression analyses with adjustment for age, sex, and other variables were used to calculate survival rates and adjusted hazard ratios (HRs) of the revision risk for any reason. 1,130 modular cups, inserted during the same time period, were used as a control group.

RESULTS

There was a nearly equal sex distribution in both groups. Median age at the index operation was 47 years in the monoblock group and 56 years in the control group (p < 0.001). The cumulative 5-year survival with any revision as the endpoint was 95% (95% CI: 91-98) for monoblock cups and 97% (CI: 96-98) for modular cups (p = 0.6). The adjusted HR for revision of monoblock cups compared to modular cups was 2 (CI: 0.8-6; p = 0.1). The use of 28-mm prosthesis heads rather than 22-mm heads reduced the risk of cup revision (HR = 0.2, CI: 0.1-0.5; p = 0.001).

INTERPRETATION

Both cups showed good medium-term survival rates. There was no statistically significant difference in revision risk between the cup designs. Further review of the current patient population is warranted to determine the long-term durability and risk of revision of monoblock cup designs.

Total hip arthroplasty: to cement or not to cement the acetabular socket? A critical review of the literature

The optimal method for acetabular socket fixation remains controversial. We present a critical analysis of the current evidence from a systemic literature review of comparative studies, long-term case series, prior literature reviews, meta-analysis, and national arthroplasty registry data for cemented and uncemented acetabular components to determine the respective survivorship rates, overall risk of re-operation, dislocation rates, and wear-related complications. Using contemporary techniques, both cemented and uncemented sockets can yield good long-term results, but our evaluation suggests that the overall/all cause re-operation risk is lower for cemented fixation. Until and unless crosslinked polyethylene (PE) liners or alternative bearings can prove to yield superior outcome in the future, the cemented PE cup remains the gold standard, in all age groups, by which every acetabular component should be compared.

High survival in young patients using a second generation uncemented total hip replacement

Purpose

Whilst excellent long-term results with contemporary uncemented stems have been reported for total hip arthroplasty in young patients, the survival rates for the whole reconstruction are often compromised by high failure rates on the acetabular site due to peri-acetabular osteolysis and accelerated wear.

Methods

In patients 60 years old or younger, we retrospectively reviewed the results at a minimum of ten years of 89 consecutive uncemented total hip replacements in 88 patients using the press-fit Fitmore acetabular component in combination with the CLS Spotorno stem and a 28-mm Metasul metal-on-metal articulation or a 28-mm alumina ceramic on conventional polyethylene bearing. The mean age at the time of surgery was 49 years (range, 25–60). The mean clinical and radiological follow-up was 12 years (range, 10–15).

Results

Six patients (six hips) died and two patients (two hips) were lost to follow-up. Five hips were revised: one for deep infection, one for peri-prosthetic femoral fracture, and one for aseptic stem loosening. In two hips an isolated revision of the acetabular liner was performed (one for recurrent dislocation and one for unexplained pain). No revision was performed for accelerated wear, osteolysis or aseptic loosening of the acetabular shell. We could not detect peri-acetabular osteolysis visible on plain radiographs in those hips evaluated radiographically. The Kaplan-Meier survival with revision for any reason as the endpoint was 94% (95% confidence interval, 86–97) at 12 years.

Conclusions

The survival rates and the radiological outcomes with this implant combination in this young and active patient group are encouraging when compared to the results reported for other uncemented cups in this age group.

Metal-on-metal or metal-on-polyethylene for total hip arthroplasty: a meta-analysis of prospective randomized studies

BACKGROUND

There has been recent concern regarding the increased use of metal-on-metal total hip arthroplasty (MOM-THA) as an alternative to contemporary metal-on-polyethylene total hip arthroplasty (MOP-THA), and the choice remains controversial. We performed a meta-analysis to evaluate and compare metal ion concentrations, complications, reoperation rates, clinical outcomes and radiographic outcomes of MOM-THA and MOP-THA.

METHODS

We performed a systematic review of English and non-English articles identified from MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, PreMEDLINE and HealthSTAR. Metal ion concentrations, complications, reoperation rates and other outcomes of MOM bearings were compared with MOP bearings in THA based on relative risks, mean differences and standardized mean difference statistics.

RESULTS

Eight prospective randomized trials were identified from 1,075 citations. Our results demonstrated significantly elevated erythrocyte, serum and urine levels of metal ions (cobalt and chromium) among patients who received MOM-THA. No significant differences in titanium concentrations or total complication or reoperation rates were found between MOM-THA and MOP-THA. Clinical function scores and radiographic evaluations were similar between the two groups.

CONCLUSIONS

This analysis found insufficient evidence to identify any clinical advantage of MOM-THA compared with MOP-THA. Although cobalt and chromium concentrations were elevated after MOM-THA, there were no significant differences in total complication rates (including all-case mortality) between the two groups in the short- to mid-term follow-up period. The MOM bearing option for THA should be used with caution.

Less wear with aluminium-oxide heads than cobalt-chrome heads with ultra high molecular weight cemented polyethylene cups: a ten-year follow-up with radiostereometry

PURPOSE

Wear is a major contributor to osteolysis and aseptic loosening of total hip replacements (THR). Both alumina (Al(2)O(3)) and cobalt-chrome (CoCr) femoral heads are commonly used. We investigated wear comparing alumina heads to cobalt-chrome heads against conventional cemented polyethylene (PE) cups for up to ten years.

METHODS

Linear wear was measured with radiostereometry (RSA). Our material was derived from two prospective randomised trials that investigated fixation of femoral stems, not wear, and was evaluated retrospectively (Level III).

RESULTS

The mean (95% CI) proximal head penetration was 0.96 mm (0.68-1.23) in the cobalt-chrome group and 0.42 mm (0.30-0.53) in the alumina group at ten years (P = 0.001). The mean (95% CI) 3D penetration was 1.07 mm (0.79-1.35) and 0.53 mm (0.38-0.63), respectively, at ten years (P = 0.001).

CONCLUSION

Alumina heads performed better than cobalt-chrome heads in this study after ten-year follow-up.

Statistical analysis of arthroplasty data. II. Guidelines

It is envisaged that guidelines for statistical analysis and presentation of results will improve the quality and value of research. The Nordic Arthroplasty Register Association (NARA) has therefore developed guidelines for the statistical analysis of arthroplasty register data. The guidelines are divided into two parts, one with an introduction and a discussion of the background to the guidelines (Ranstam et al. 2011a, see pages x-y in this issue), and this one with a more technical statistical discussion on how specific problems can be handled. This second part contains (1) recommendations for the interpretation of methods used to calculate survival, (2) recommendations on howto deal with bilateral observations, and (3) a discussion of problems and pitfalls associated with analysis of factors that influence survival or comparisons between outcomes extracted from different hospitals.

In vivo polyethylene wear of bilateral total hip replacements - cemented versus uncemented modular sockets

We assessed polyethylene wear and osteolysis in 15 patients (30 hips) undergoing staged bilateral total hip arthroplasties, who had a cemented arthroplasty on one side and a hybrid arthroplasty on the other. All factors apart from mode of acetabular component fixation were matched. Wear was measured radiographically using Livermore's technique. The mean clinical and radiological follow-up was 11.2 years for the cemented and 10.7 years for the hybrid arthroplasties. Mean annual linear wear rate was 0.09mm/year in the cemented sockets and 0.14mm/year in the uncemented sockets. This difference was statistically significant (p=0.03), confirming previous reports that the rate of polyethylene wear is increased in uncemented sockets. No periacetabular osteolysis was noted. Femoral osteolysis in zone 7 occurred in 3 hybrid arthroplasties. It appears not all patients are equally affected. These results are further discussed.