Porous-coated cups fixed with screws: a 12-year clinical and radiostereometric follow-up study of 50 hips

Bone ingrowth observed in a cup removed during revision surgery for early dislocation after primary THA: A case report

Introduction and importance

Recently cementless total hip arthroplasty (THA) has shown good long-term results with excellent stability resulted from the porous coating of the implant. A hydroxyapatite-tricalcium phosphate (HA-TCP) coating on the porous surface is expected to promote bone ingrowth and to improve initial fixation of the implant. Here we report a case of bone ingrowth observed in a cup removed during revision surgery for early dislocation, 37 days after primary THA using a porous coating cup with HA-TCP.

Case presentation

A 61-year-old woman who has bilateral osteoarthritis underwent same-day bilateral THA. Both sides used porous coating cups with HA-TCP. Line-to-line technique and screw fixation were utilized. Anterior dislocation of the left hip occurred on days 27 and 31, and we performed cup revision on day 37 after surgery. We noted bone-like tissue on the posterior surface of the cup and in a vacant screw hole. Bone tissue was also confirmed in pathological findings.

Clinical discussion

Studies in animals have confirmed early bone ingrowth about 4 weeks after surgery with HA-TCP coated implants. In humans, the earliest report of bone ingrowth in cups is for a cup without HA-TCP coating, detected 5 weeks after surgery. In the present case, we used a porous coating cup with HA-TCP, and bone ingrowth was confirmed at approximately the same time as for the previous case.

Conclusion

Early clinical bone ingrowth was confirmed in an HA-TCP coated cup, occurring at about the same time after surgery as in previous reports.

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Cementless THA shows excellent long-term results for porous coating of implant.

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HA-TCP coating promotes bone ingrowth of mesenchymal cells.

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Post-THA revision showed good initial fixation with porous coating cup and HA-TCP.

Acetabular screws do not improve early revision rates in primary total hip arthroplasty. An instrumented registry analysis

BACKGROUND

Initial stability of uncemented acetabular components in total hip arthroplasty (THA) is important for osseointegration and potentially enhanced by screw fixation. We used Australian Orthopaedic Association National Joint Replacement Registry data to determine whether screw usage influences uncemented acetabular component survival.

METHODS

Primary THA with uncemented acetabular components performed for osteoarthritis from 1999 to 2018 was included. Survivorship was calculated using Kaplan-Meier estimates of cumulative percent revision (CPR). Comparisons used Cox proportional hazards method. An instrumental variable analysis adjusted for surgeon preference for screws as a confounding factor was used.

RESULTS

Three hundred thirty thousand one hundred ninety-two THAs were included (31.8% with screws, 68.2% without). Two hundred twenty thousand six hundred seven were included in the instrumental variable analysis. Revision rate of acetabular components (all causes) was higher with screws during the first six years (hazard ratio (HR) = 1.45 (95% CI 1.34, 1.57), p < 0.001) and lower thereafter (HR = 0.81 (95% CI 0.67, 0.98), p = 0.027). Revision rate of acetabular components for loosening was higher with screws over the entire study period (HR = 1.73 (95% CI 1.51, 1.98), p < 0.001). Overall THA revision rate was higher with screws during the first six years (HR = 1.20 (95% CI 1.15, 1.26), p < 0.001) but lower thereafter (HR = 0.89 (95% CI 0.81, 0.98), p = 0.020). Revision rate for dislocation was higher with screws over the entire period (HR = 1.16 (95% CI 1.06, 1.26), p < 0.001). Instrumental variable analysis revealed higher revision rates with acetabular screws in the first six years. (HR = 1.18 (95% CI 1.09-1.29), p < 0.001).

CONCLUSION

Screws did not confer a protective effect against acetabular loosening and were not associated with long-term negative consequences.

Relationship between use of screws and acetabular cup stability in total hip arthroplasty: a meta-analysis

Objective

The relationship between the use of screws and acetabular cup stability in total hip arthroplasty (THA) remains controversial. We evaluated cup stability in THA with and without the use of screws.

Methods

We performed a systematic literature search to identify studies on cup stability relative to the use of screws in patients undergoing THA before October 2018. Methodological quality assessment and data collection were performed by two individual reviewers. Meta-analysis was performed using Review Manager version 5.3.5.

Results

We included seven trials involving 1402 patients (1469 THAs): 767 patients (809 THAs) with screws and 635 patients (660 THAs) without screws. The findings of meta-analysis indicated that uncemented acetabular component fixation with the use of additional screws was not correlated with migration of the cup, migration on roentgen stereophotogrammetry, or reoperation after THA. Moreover, operation time was not significantly different according to whether screws were used. There was no relationship between use of additional screws and osteoporosis or Harris Hip Score; however, THA with or without the use of screws might be related to bone sclerosis in the C1 region.

Conclusion

Currently, limited evidence shows that the use of screws during THA may not improve cup stability.

Results of a randomized controlled trial with five-year radiostereometric analysis results of vitamin E-infused highly crosslinked versus moderately crosslinked polyethylene in reverse total hip arthroplasty

Aims

Vitamin E-infused highly crosslinked polyethylene (VEPE) has been introduced into total hip arthroplasty (THA) with the aim of further improving the wear characteristics of moderately and highly crosslinked polyethylenes (ModXLPE and HXLPE). There are few studies analyzing the outcomes of vitamin E-infused components in cemented arthroplasty, though early acetabular component migration has been reported. The aim of this study was to measure five-year polyethylene wear and acetabular component stability of a cemented VEPE acetabular component compared with a ModXLPE cemented acetabular component.

Methods

In a prospective randomized controlled trial (RCT), we assessed polyethylene wear and acetabular component stability (primary outcome) with radiostereometric analysis (RSA) in 68 patients with reverse hybrid THA at five years follow-up. Patients were randomized to either a VEPE or a ModXLPE cemented acetabular component.

Results

Mean polyethylene wear in the proximal direction was 0.17 mm (SD 0.15) for the VEPE group and 0.20 mm (SD 0.09) for the ModXLPE group (p = 0.005) at five years. Annual proximal wear rates were 0.03 mm/year (VEPE) and 0.04 mm/year (ModXLPE). Total 3D wear was 0.21 mm (SD 0.26) and 0.23 mm (SD 0.10) for the VEPE and ModXLPE groups, respectively (p = 0.009). Total 3D cup translation was 0.72 mm (SD 0.70) (VEPE) and 0.50 mm (SD 0.44) (ModXLPE) (p = 0.409).

Conclusion

At five years, there was less polyethylene wear in the VEPE group than in the ModXLPE group. Both VEPE and ModXLPE cemented components showed low annual wear rates. Component stability was similar in the two groups and remained constant up to five years. Whether these results will equate to a lower long-term revision rate is still unknown. Cite this article: Bone Joint J 2020;102-B(12):1646–1653.

Minimum ten-year follow-up of a randomized trial comparing acetabular component fixation of two porous in-growth surfaces using radiosteriometric analysis

Aims

To compare the in vivo long-term fixation achieved by two acetabular components with different porous ingrowth surfaces using radiostereometric analysis (RSA).

Methods

This was a minimum ten-year follow-up of a prospective randomized trial of 62 hips with two different porous ingrowth acetabular components. RSA exams had previously been acquired through two years of follow-up. Patients returned for RSA examination at a minimum of ten years. In addition, radiological appearance of these acetabular components was analyzed, and patient-reported outcome measures (PROMs) obtained.

Results

In all, 15 hips were available at ten years. There was no statistically significant difference in PROMS between the two groups; PROMs were improved at ten years compared to preoperative scores. Conventional radiological assessment revealed well-fixed components. There was minimal movement for both porous surfaces in translation (X, Y, Z, 3D translation in mm (median and interquartile range (IQR)), StikTite (Smith and Nephew, Memphis, Tennessee, USA): 0.03 (1.08), 0.12 (0.7), 0.003 (2.3), 0.37 (0.30), and Roughcoat (Smith and Nephew): -0.6 (0.59),–0.1 (0.49), 0.1 (1.12), 0.48 (0.38)), and rotation (X, Y, Z rotation in degrees (median and IQR), (Stiktite: -0.4 (3), 0.28 (2), -0.2 (1), and Roughcoat: - 0.4 (1),–0.1 (1), 0.2 (2)). There was no statistically significant difference between the two cohorts (p-value for X, Y, Z, 3D translation - 0.54, 0.46, 0.87, 0.55 and for X, Y, Z rotation - 0.41, 0.23, 0.23 respectively) at ten years. There was significant correlation between two years and ten years 3D translation for all components (r = 0.81(p =< 0.001)).

Conclusion

Both porous ingrowth surfaces demonstrated excellent fixation on plain radiographs and with RSA at ten years. Short-term RSA data are good predictors for long-term migration data.

Routine Use of Radiostereometric Analysis in Elective Hip and Knee Arthroplasty Patients: Surgical Impact, Safety, and Bead Stability

BACKGROUND

Radiostereometric analysis (RSA) accurately assesses arthroplasty implant performance and is routinely used for research purposes. Because of its efficacy in detecting implant failure in research subjects, we deployed the use of RSA beads for routine surveillance in all elective total hip and total knee arthroplasty patients.

METHODS

We retrospectively compared 143 patients who received RSA beads intraoperatively with 343 patients who did not receive RSA beads. Using RSA images, we assessed bead stability at 6 weeks and 1 year postoperatively.

RESULTS

There were no intraoperative complications in the RSA group and two in the control group. No differences were found between groups for the surgical time and the expected blood loss. At 6 weeks, 99.5% of beads were considered to be stable, with stability increasing to 99.7% of beads at 1 year.

CONCLUSION

The routine use of RSA bead insertion is a safe procedure and may provide the ability to assess implant fixation in clinical practice.

R3 Cup Does Not Have a High Failure Rate in Conventional Bearings: A Minimum of 5-Year Follow-Up

BACKGROUND

The R3 cementless acetabular system was first marketed in Australia and Europe in 2007. Previous papers have shown high failure rates of the R3 cup with up to 24% with metal-on-metal bearing. There are currently no medium term clinical results on this cup. The aim of the study is to review our results of the R3 acetabular cup with conventional bearings with a minimum of 5-year follow-up.

METHODS

Patients who were implanted with the R3 acetabular cup were identified from our center's arthroplasty database. A total of 293 consecutive total hip arthroplasties were performed in 286 patients. The primary outcome was revision. The secondary outcomes were the Oxford Hip Scores (OHS) and radiographic evaluation.

RESULTS

The mean age of the patients was 69.4 years. The mean preoperative OHS was 23 (range 10-34) and the mean OHS was 40 (range 33-48) at the final follow-up. Radiological evaluation showed an excellent ARA score in all patients at 5 years. None of the R3 cups showed osteolysis at the final follow-up. There were 3 revisions in our series, of which 2 R3 cups were revised. The risk of revision was 1.11% at 5 years.

CONCLUSION

Our experience of using the R3 acetabular system with conventional bearings showed high survivorship and is consistent with the allocated Orthopaedic Data Evaluation Panel rating of 5A* as rated in 2015 in the United Kingdom.

Wear rate and medium-term survival of a cemented, moderately cross-linked polyethylene acetabular prosthesis

INTRODUCTION

The moderately cross-linked Depuy Marathon® cemented acetabular component was introduced into the UK in 2007. The wear rate for the previously introduced Marathon® uncemented acetabular component has been reported to range from 0.06 to 0.01 mm/year. The aim of this study was to present the medium-term results and wear rate of the Marathon® cemented prosthesis used in primary total hip arthroplasty.

METHODS

103 Marathon® cemented acetabular components were implanted between 2008 and 2009 in primary arthroplasty, who were eligible for this study. All patients received a metal 28-mm head. Mean age was 68 years (range 27-87). Mean clinical follow-up was 55 months (range 50-61). Mean radiological follow-up was 46 months (range 24-57). Wear was calculated on AP radiographs using computer-assisted uni-radiographic technique.

RESULTS

The mean wear was 0.37 mm (range 0.0-0.78 mm). The wear rate was calculated as 0.03 mm/year (95% confidence interval 0.02-0.06). Postoperative complications included deep vein thrombosis (2%) and dislocation (0.8%); there were no deep infections. There were no revisions for failure of the Marathon® cemented acetabular component.

CONCLUSIONS

The Marathon® cemented acetabular component demonstrates satisfactory wear rates and survivorship at medium-term follow-up.

Screws are not needed when secure interference fit of uncemented acetabular components is adequate: a 5- to 15-year follow-up with clinical and radiological analysis

PURPOSE

Even with good surgical preparation, adequate primary stability of the acetabular component is not always achieved after primary total hip replacement (THR). We hypothesise that adequate bone preparation for appropriate cortical loading would allow us to avoid screw use.

METHODS

A total of 791 uncemented cups were analysed to compare the need for screws to obtain primary fixation in 5 different designs. Arthritic hips with inflammatory arthritis or severe congenital hip disease were excluded. A press-fit technique was first tried in all hips and screws were only used when strictly needed. Radiological acetabular shape and postoperative cup position were assessed in all hips. The mean follow-up was 9.6 (5-15) years.

RESULTS

Screws were required in 155 hips (19.6%). We could not detect any difference in the percentage of screw use between designs. We found that female patients (odds ratio [OR] 2.06; 95% confidence interval [CI], 1.41-3.02) and cups with a greater distance to the hip rotation centre on the postoperative radiograph (OR 1.69; 95% CI, 1.17-2.45) had a higher risk for screw use. A greater anteversion of the cup had a lower risk for screw use (OR 0.96; 95% CI, 0.94-0.99). At latest follow-up no hips had needed revision for aseptic loosening.

CONCLUSIONS

Good intraoperative technique is not enough to avoid screw use since more accurate cup position and reconstruction of the hip rotation centre are required for an adequate interference fit. A press-fit technique can provide similar mid-term results to screw use in hips without severe deformities.

Increased migration of uncemented acetabular cups in female total hip arthroplasty patients with low systemic bone mineral density. A 2-year RSA and 8-year radiographic follow-up study of 34 patients

BACKGROUND AND PURPOSE

Low bone mineral density (BMD) may jeopardize the initial component stability and delay osseointegration of uncemented acetabular cups in total hip arthroplasty (THA). We measured the migration of uncemented cups in women with low or normal BMD.

PATIENTS AND METHODS

We used radiostereometric analysis (RSA) to measure the migration of hydroxyapatite-coated titanium alloy cups with alumina-on-alumina bearings in THA of 34 female patients with a median age of 64 (41-78) years. 10 patients had normal BMD and 24 patients had low systemic BMD (T-score ≤ -1) based on dual-energy X-ray absorptiometry (DXA). Cup migration was followed with RSA for 2 years. Radiographic follow-up was done at a median of 8 (2-10) years.

RESULTS

Patients with normal BMD did not show a statistically significant cup migration after the settling period of 3 months, while patients with low BMD had a continuous proximal migration between 3 and 12 months (p = 0.03). These differences in cup migration persisted at 24 months. Based on the perceived risk of cup revision, 14 of the 24 cases were "at risk" (proximal translation of 0.2 to 1.0 mm) in the low-BMD group and 2 of the 10 cases were "at risk" in the normal-BMD group (odds ratio (OR) = 8.0, 95% CI: 1.3-48). The radiographic follow-up showed no radiolucent lines or osteolysis. 2 cups have been revised for fractures of the ceramic bearings, but none for loosening.

INTERPRETATION

Low BMD contributed to cup migration beyond the settling period of 3 months, but the migrating cups appeared to osseointegrate eventually.

Preliminary analysis on the MD-4® plasma-sprayed titanium acetabular component

Objectives

To evaluate the short-term performance of a type of implant manufactured in Brazil.

Methods

This study analyzed a cohort of 60 patients who underwent implantation of MD-4^® acetabular components during primary hip arthroplasty procedures performed between January 1, 2010, and August 1, 2012. The patients were studied retrospectively with regard to clinical behavior, stability and radiological osseointegration. The patients were followed up for a minimum of 12 months and a maximum of 42 months (mean: 27) and were evaluated by means of the Harris Hip Score, SF-36 questionnaire and serial conventional radiographs.

Results

All the components were radiologically stable, without evidence of migration or progressive radiolucency lines. On average, the Harris Hip Score evolved from 36.1 to 92.1 (p < 0.001) and the SF-36 showed significant increases in all its domains (p < 0.001). No differences were observed among patients with osteoarthrosis, osteonecrosis, hip dysplasia or other conditions.

Conclusions

The short-term results showed clinical and radiological signs of stability and osseointegration of the implants, which may represent a predictive factor regarding medium-term survival of this acetabular component.

Bone loss around a stable, partly threaded hydroxyapatite-coated cup: a prospective cohort study using RSA and DXA

STUDY PURPOSE

Aseptic loosening of the acetabular component is the most common reason for revision after primary THA, and periprosthetic demineralisation has been described as a potential cause for this process. The trabeculae-oriented pattern (TOP)-cup is a flat, hydroxyapatite (HA)-coated titanium shell with a threaded rim that was developed in order to minimise periprosthetic bone loss. We hypothesised that this cup provides good primary stability and improves preservation of periprosthetic bone mineral density (BMD).

BASIC PROCEDURES

A prospective cohort study on 30 patients receiving the TOP cup was carried out. Preoperative total hip BMD and postoperative periprosthetic BMD in five periprosthetic regions of interest were investigated by dual energy radiographic absorptiometry (DXA), cup migration was analysed by radiostereometry (RSA), and the Harris hips score (HHS) was determined.

MAIN FINDINGS

Mean HHS increased from 49 (24-79) preoperatively to 99 (92-100) after two years. DXA after one year demonstrated substantial BMD loss in the proximal periprosthetic zones 1 (-18%), zone 2 (-16 %) and zone 3 (-9%, all p<0.001 when compared with baseline BMD determined immediately postoperatively). The bone loss in these regions did not recover after two years. RSA (performed on 16 patients) showed that only very limited micromotion of the implant occurred: Mean cranial migration was 0.01 mm (95% confidence interval (CI): -0.09-0.12) and mean inclination decreased by 0.02º (CI: -0.43-0.39) after two years.

CONCLUSION

We conclude that the TOP cup provides good primary stability in the short-term. However, substantial BMD loss in proximal periprosthetic areas indicates that the design of this cup cannot prevent periprosthetic bone loss that has also been observed around other uncemented cups.

Higher wear-rate of third-generation metal-backed Reflection cups with eto-sterilised UHMWPE at a mean 13 years follow-up

Polyethylene (PE) wear and osteolysis is a recognised problem with non-cross linked PE liners and first generation modular cup designs. Wear particles induce osteolysis leading to aseptic loosening. We retrospectively compared the linear PE wear and implant survival and revision rates of the Reflection Cup and the Duraloc 300. After a mean clinical follow-up of 13 years (range 11-15 years), the 2D linear PE wear-rate of the Reflection liner (n = 68) was 0.23 mm/year, with a mean total wear of 3.14 mm (1.04-7.36), SD 1.45. The wear-rate of the Duraloc 300 cups (n = 32) was 0.14 mm/year, with a mean total wear of 1.84 mm (0.55-4.63), SD 1.07. The difference in PE wear-rate as well as mean total wear was highly significant (p = 0.0001). There was a positive correlation between wear-rate and both Oxford Hip Score and Harris Hip Score (p = 0.02). Large acetabular cup size (>54 mm), HA coating on the stem and age <50 years did not influence PE wear. The higher wear-rate in the Reflection liners could be related to the EtO sterilisation. Intermediate and long-term follow-up is advisable.

A titanium plasma-sprayed cup with and without hydroxyapatite-coating: a randomised radiostereometric study of stability and osseointegration

We present a prospective, two-centre radiostereometric analysis (RSA) regarding the stability of a flattened pole titanium press-fit cup (EP-FIT PLUS), and whether additional hydroxyapatite coating leads to faster bone ingrowth into the porous coating. Forty-two postmenopausal female patients (44 hips) undergoing total hip arthroplasty for primary osteoarthritis, selected to avoid hormonal factors influencing bone metabolism, were randomised to receive this cup with a titanium-plasma-sprayed surface with or without an additional hydroxyapatite coating. RSA was used to measure cup translation and rotation along three cardinal axes with respect to the host bone at the following time points: immediately postoperatively, at 6 weeks, and at 3, 6, 12, and 24 months. The most pronounced translation was proximal (0.11 mm) and posterior tilt (-0.27°). No difference in translation and rotation could be detected between the two groups. With the exception of one cup with an isolated radiolucent line <2 mm in zone 1, all cups showed complete osseointegration on conventional radiographs. The flattened pole cup provided excellent early stability and no advantage could be detected with additional hydroxyapatite coating.

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines. A systematic review

BACKGROUND AND PURPOSE

Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.

METHODS

We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.

RESULTS

153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000-2005) and 92 after the guidelines were introduced (2006-2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.

INTERPRETATION

The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.

A randomized trial comparing acetabular component fixation of two porous ingrowth surfaces using RSA

Several new porous ingrowth surfaces for acetabular component fixation have recently been developed. The purpose of this study was to compare the in vivo fixation achieved by two different porosity ingrowth surfaces using radiostereometric analysis (RSA). Sixty-two patients undergoing primary total hip arthroplasty (THA) were randomized to receive a cementless acetabular component with either a 61% high porosity asymmetric titanium porous surface (StikTite, Smith and Nephew, TN, USA) or a 45% low porosity sintered bead porous surface (Roughcoat, Smith and Nephew, TN, USA). RSA and clinical follow-up examinations were done post-operatively, 6-weeks, 3-months, 6-months, 1-year and 2-years. Both the high porosity StikTite and lower porosity Roughcoat surfaces provided excellent biologic fixation.

Center index method-an alternative for wear measurements with radiostereometry (RSA)

Radiostereometry (RSA) is considered to be the most precise and accurate method for wear-measurements in total hip replacement. Post-operative stereoradiographs has so far been necessary for wear measurement. Hence, the use of RSA has been limited to studies planned for RSA measurements. We compared a new RSA method for wear measurements that does not require previous radiographs with conventional RSA. Instead of comparing present stereoradiographs with post-operative ones, we developed a method for calculating the post-operative position of the center of the femoral head on the present examination and using this as the index measurement. We compared this alternative method to conventional RSA in 27 hips in an ongoing RSA study. We found a high degree of agreement between the methods for both mean proximal (1.19 mm vs. 1.14 mm) and mean 3D wear (1.52 mm vs. 1.44 mm) after 10 years. Intraclass correlation coefficients (ICC) were 0.958 and 0.955, respectively (p<0.001 for both ICCs). The results were also within the limits of agreement when plotted subject-by-subject in a Bland-Altman plot. Our alternative method for wear measurements with RSA offers comparable results to conventional RSA measurements. It allows precise wear measurements without previous radiological examinations.

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.

A cementless, elastic press-fit socket with and without screws

BACKGROUND

The acetabular component has remained the weakest link in hip arthroplasty regarding achievement of long-term survival. Primary fixation is a prerequisite for long-term performance. For this reason, we investigated the stability of a unique cementless titanium-coated elastic monoblock socket and the influence of supplementary screw fixation.

PATIENT AND METHODS

During 2006-2008, we performed a randomized controlled trial on 37 patients (mean age 63 years (SD 7), 22 females) in whom we implanted a cementless press-fit socket. The socket was implanted with additional screw fixation (group A, n = 19) and without additional screw fixation (group B, n = 18). Using radiostereometric analysis with a 2-year follow-up, we determined the stability of the socket. Clinically relevant migration was defined as > 1 mm translation and > 2º rotation. Clinical scores were determined.

RESULTS

The sockets without screw fixation showed a statistically significantly higher proximal translation compared to the socket with additional screw fixation. However, this higher migration was below the clinically relevant threshold. The numbers of migratory sockets were not significantly different between groups. After the 2-year follow-up, there were no clinically relevant differences between groups A and B regarding the clinical scores. 1 patient dropped out of the study. In the others, no sockets were revised.

INTERPRETATION

We found that additional screw fixation is not necessary to achieve stability of the cementless press-fit elastic RM socket. We saw no postoperative benefit or clinical effect of additional screw fixation.

Effects of hydroxyapatite coating of cups used in hip revision arthroplasty

BACKGROUND AND PURPOSE

Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision.

METHODS

We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening.

RESULTS

71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0-24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9-2.0) or due to aseptic loosening (RR = 1.1, 0.6-1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01-3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05-4.2).

INTERPRETATION

We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.

No adverse effects of submelt-annealed highly crosslinked polyethylene in cemented cups: an RSA study of 8 patients 10 yaers after surgery

BACKGROUND AND PURPOSE

Highly crosslinked polyethylene (PE) is in standard use worldwide. Differences in the crosslinking procedure may affect the clinical performance. Experimenatal data from retrieved cups have shown free radicals and excessive wear of annealed highly crosslinked PE. We have previously reported low wear and good clinical performance after 6 years with this implant, and now report on the 10-year results.

PATIENTS AND METHODS

In 8 patients, we measured wear of annealed highly crosslinked PE prospectively with radiostereometry after 10 years. Activity was assessed by UCLA activity score and a specifically designed activity score. Conventional radiographs were evaluated for osteolysis and clinical outcome by the Harris hip score (HHS).

RESULTS

The mean (95% CI) proximal head penetration for highly crosslinked PE after 10 years was 0.07 (-0.015 to 0.153) mm, and the 3D wear was 0.2 (0.026 to 0.36) mm. Without creep, proximal head penetration was 0.02 (-0.026 to 0.066) mm and for 3D penetration was 0.016 (-0.47 to 0.08) mm. This represents an annual proximal wear of less than 2 µm. All cups were clinically and radiographically stable but showed a tendency of increased rotation after 5 years.

INTERPRETATION

Wear for annealed highly crosslinked PE is extremely low up to 10 years. Free radicals do not affect mechanical performance or lead to clinically adverse effects. Creep stops after the first 6 months after implantation. Highly crosslinked PE is a true competitor of hard-on-hard bearings.

Second-generation modular acetabular components provide fixation at 10 to 16 years

BACKGROUND

First-generation modular titanium fiber-metal-coated acetabular components had high rates of wear, pelvic osteolysis, and liner dissociation. Second-generation components were designed to reduce the incidence of these problems but it is unclear whether the changes achieved these goals.

QUESTIONS/PURPOSES

We asked the following questions: (1) Is the risk of revision surgery for loosening, wear, or liner dissociation low with the second-generation acetabular component? (2) Is the rate of pelvic osteolysis low? (3) Can the liner be exchanged without bone cement?

METHODS

We retrospectively reviewed prospectively collected data from 99 patients (118 hips) undergoing THAs with one second-generation modular titanium acetabular component with routine screw fixation and conventional polyethylene. The minimum followup was 10 years (mean, 12 years; range, 10-16 years). We obtained Harris hip scores and examined radiographs for loosening and osteolysis.

RESULTS

At last followup, all acetabular components were well fixed and no titanium shell had been revised or removed. No liner had dissociation. At most recent followup, the mean Harris hip score was 89. We observed pelvic osteolysis in eight hips (7%). There were three reoperations for dislocation (head-liner exchange only) and three loose femoral components revised. Two liners (at 11 and 14 years) were exchanged for wear-pelvic osteolysis.

CONCLUSIONS

This second-generation modular titanium fiber-metal-coated acetabular component with screw fixation had no loosening, no liner dissociation, and a low rate of pelvic osteolysis at 10 to 16 years. Liner exchange is practical without use of cement. We continue to use this component with highly crosslinked polyethylene liners.

LEVEL OF EVIDENCE

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

Management of polyethylene wear associated with a well-fixed modular cementless shell during revision total hip arthroplasty

We identified 128 revision total hip arthroplasties from 1993 to 2005 involving a well-fixed Harris-Galante Porous (HGP)-I or HGP-II acetabular component with minimum 2-year post-revision follow-up. Three treatment cohorts were identified. Of the hips that underwent modular liner exchange at revision, 14 hips (25%) required re-revision of the acetabular component, 8 for liner dislodgement, 3 for osteolysis and poly-wear, 2 for dislocation, and 1 for aseptic loosening. Of the hips that underwent revision of the well-fixed shell, 4 (15%) required subsequent re-revision of the acetabular component; 2 for dislocation and 2 for aseptic loosening. Six hips (27%) in the cemented liner group were re-revised; 4 for dislocation and 2 for loosening. Complete revision of a well-fixed HGP acetabular component is more reliable than liner exchange or liner cementation.

Comparison of trabecular metal cups and titanium fiber-mesh cups in primary hip arthroplasty: a randomized RSA and bone mineral densitometry study of 50 hips

BACKGROUND

Trabecular metal has shown promising results in experimental studies of bone ingrowth. Several clinical studies support these results. However, until now, no randomized clinical radiostereometric analysis (RSA) studies have been published. In this randomized RSA trial, we compared a new acetabular cup with a surface made of tantalum trabecular metal and a cup with a titanium fiber-mesh surface.

PATIENTS AND METHODS

Between 2004 and 2006, we operated 60 patients with noninflammatory hip arthritis. The patients were randomized to receive either an uncemented cup with a titanium fiber-mesh surface (Trilogy cup) or a cup with a trabecular tantalum surface (Monoblock cup). After 2 years, 50 patients had completed the study. The primary endpoint was cup migration within the first 2 years after surgery; the secondary endpoints were change in bone mineral density and Harris hip score at 3 months.

RESULTS

Both cup types showed excellent fixation. RSA revealed minimal translation and rotation at 2 years. There was no statistically significant difference between the cup types with regard to translation. However, less rotation along the transverse axis was seen in the trabecular metal cups than in the fiber mesh cups: mean -0.01º (95% CI: -0.11 to 0.12) for trabecular metal cups and -0.60º (-0.72 to -0.48) for fiber-mesh cups (p = 0.04). The degree of periprosthetic bone loss was similar between the cup types in any of the regions of interest at 2 years of follow-up. 3 months postoperatively, we found a similar increase in Harris hip score in both groups: from around 50 to over 90.

INTERPRETATION

We found promising early results concerning fixation of trabecular metal components to the acetabular host bone. However, we recommend a longer observation period to evaluate the outcome of this new cup design.

The Harris-Galante cementless THA: a 19- to 25-year follow-up study

The goal of this study was to evaluate the long-term survivorship of primary cementless total hip arthroplasty (THA) using Harris-Galante porous I acetabular and Harris-Galante porous femoral components. From July 1985 to December 1991, we performed primary cementless THA on 76 hips (70 patients). Twenty-nine patients (31 hips) died due to causes unrelated to the THA, and 6 patients (7 hips) were lost to follow-up. Of 76 hips (70 patients) studied, 38 hips (35 patients) were available for follow-up at a mean 22.5 years (range, 19-25 years) postoperatively. Mean patient age at index procedure was 51.2 years (range, 42-65 years). Average Harris Hip Score was 40.5 points preoperatively and 85.8 points at final follow-up. No patient had an early or late postoperative deep infection. Radiographically, the acetabular component fixation was stable in all 38 hips. The femoral component was bone-ingrown in 26 hips, stable-fibrous in 10, and unstable in 2. One unstable hip required revision of the femoral component. Dissociation of the polyethylene liner occurred in 3 hips without fractures of the metal locking tines and required revision of the polyethylene liner and the articular head. A total of 4 hips had documented revision, and 1 femoral component failed radiographically. The survival rate with the endpoint defined as revision surgery and radiographic loosening was 86.8% at 22.5 years of follow-up. Mean polyethylene wear was 0.085 mm/year (range, 0.031-0.15 mm). This study found that the Harris-Galante porous I acetabular and Harris-Galante porous femoral components produce excellent long-term results.

Increased risk of revision of acetabular cups coated with hydroxyapatite

BACKGROUND

Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival.

METHODS

All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision.

RESULTS

HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3-2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening.

INTERPRETATION

Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening-resulting in revision surgery.

Uncemented and cemented primary total hip arthroplasty in the Swedish Hip Arthroplasty Register

BACKGROUND AND PURPOSE

Since the introduction of total hip arthroplasty (THA) in Sweden, both components have most commonly been cemented. A decade ago the frequency of uncemented fixation started to increase, and this change in practice has continued. We therefore analyzed implant survival of cemented and uncemented THA, and whether the modes of failure differ between the two methods of fixation.

PATIENTS AND METHODS

All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 who received either totally cemented or totally uncemented THA were identified (n = 170,413). Kaplan-Meier survival analysis with revision of any component, and for any reason, as the endpoints was performed. Cox regression models were used to calculate risk ratios (RRs) for revision for various reasons, adjusted for sex, age, and primary diagnosis.

RESULTS

Revision-free 10-year survival of uncemented THA was lower than that of cemented THA (85% vs. 94%, p < 0.001). No age or diagnosis groups benefited from the use of uncemented fixation. Cox regression analysis confirmed that uncemented THA had a higher risk of revision for any reason (RR = 1.5, 95% CI: 1.4-1.6) and for aseptic loosening (RR = 1.5, CI: 1.3-1.6). Uncemented cup components had a higher risk of cup revision due to aseptic loosening (RR = 1.8, CI: 1.6-2.0), whereas uncemented stem components had a lower risk of stem revision due to aseptic loosening (RR = 0.4, CI: 0.3-0.5) when compared to cemented components. Uncemented stems were more frequently revised due to periprosthetic fracture during the first 2 postoperative years than cemented stems (RR = 8, CI: 5-14). The 5 most common uncemented cups had no increased risk of revision for any reason when compared with the 5 most commonly used cemented cups (RR = 0.9, CI: 0.6-1.1). There was no significant difference in the risk of revision due to infection between cemented and uncemented THA.

INTERPRETATION

Survival of uncemented THA is inferior to that of cemented THA, and this appears to be mainly related to poorer performance of uncemented cups. Uncemented stems perform better than cemented stems; however, unrecognized intraoperative femoral fractures may be an important reason for early failure of uncemented stems. The risk of revision of the most common uncemented cup designs is similar to that of cemented cups, indicating that some of the problems with uncemented cup fixation may have been solved.

Polyethylene wear and osteolysis with a new modular titanium acetabular component: results at 7 to 13 years

The first-generation and second-generation modular titanium fiber-metal acetabular components were notable for high rates of pelvic osteolysis and liner dislodgment. This is a prospective, consecutive study of 111 new modular titanium-fiber metal acetabular components with a novel polyethylene locking mechanism at a mean follow-up of 9.5 years (range, 7-13 years). The polyethylene was gamma-irradiated in air in 58 hips and gamma-irradiated in nitrogen in 54 hips. No acetabular component migrated, none were revised, and there was no liner dislodgment. Pelvic osteolysis was seen in only 2 hips. The mean linear wear rate was 0.085 mm/y (range, 0.001-0.3 mm/y). There was a significantly lower rate of wear with polyethylene liners sterilized by gamma-irradiation in nitrogen (P = .0001). The high rate of success and low rate of polyethylene wear and pelvic osteolysis at this length of follow-up may be related to the new design features of this modular acetabular component.