Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty

Accepted Manuscript Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty I. Laaksonen, MD, PhD, V. Galea, BA, J.W. Connelly, BA, S. Matuszak, BA, O. Muratoglu, PhD, H. Malchau, MD, PhD PII:

S0883-5403(17)30765-9

DOI:

10.1016/j.arth.2017.08.042

Reference:

YARTH 56072

To appear in:

The Journal of Arthroplasty

Received Date: 5 May 2017 Revised Date:

25 August 2017

Accepted Date: 30 August 2017

Please cite this article as: Laaksonen I, Galea V, Connelly J, Matuszak S, Muratoglu O, Malchau H, Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty, The Journal of Arthroplasty (2017), doi: 10.1016/j.arth.2017.08.042. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Inferior Radiographic and Functional Outcomes with

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Modular Stem in Metal-on-Metal Total Hip Arthroplasty

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Laaksonen I, MD, PhD a, b, Galea V, BA a, Connelly JW, BA a, Matuszak S, BA a, Muratoglu O, PhD a, b, Malchau H, MD, PhD a, b

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Harvard Medical School, Department of Orthopaedic Surgery 25 Shattuck St. Boston, MA 02115 USA

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Harris Orthopaedic Laboratory Massachusetts General Hospital 55 Fruit St. GRJ 1231 Boston, MA 02114 USA

Henrik Malchau, M.D., Ph.D., Orthopaedic Department,

Massachusetts General Hospital 55 Fruit Street, GRJ 1126 Boston, Massachusetts 02114-2696 E-mail: [email protected] Tel: 617.726.3866 Fax: 617.726.3883

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Inferior Radiographic and Functional Outcomes with

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Modular Stem in Metal-on-Metal Total Hip Arthroplasty

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Abstract

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Background. Data on the association between stem type and metal-on-metal (MoM) total hip

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arthroplasty (THA) performance are limited. The aim of this study was to investigate the effect

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of stem type on the prevalence of osteolysis and radiolucency, blood metal ion levels, and

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functional outcomes in patients with Articular Surface Replacement THA (ASR XL), a type of

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MoM THA.

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Methods. We analyzed 539 unilateral MoM THAs coupled with either Summit (48%), Corail

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(35%), or S-ROM (17%) hip stems at a mean follow-up of 6.4 years. Fifty-four percent were

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male, and the mean age was 60 years. We studied radiographs, patient reported outcome

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measures (PROMs), and ion levels.

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Results. Patients with S-ROM hip stems were 3.8 times more likely to have osteolysis (p=0.003)

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and 7.6 times more likely to have radiolucency (p<0.001) than those treated with Summit hip

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stems. In addition, patients treated with S-ROM hip stems scored worse than those with Summit

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hip stems in four out of five PROMs: Harris Hip Score, VAS pain, UCLA activity, and EQ-5D

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index. All of these differences were statistically significant and ranged from 5% to 10%, which is

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clinically significant.

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Conclusion. Patients with S-ROM hip stems had inferior functional and radiographic results

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compared to patients with Summit hip stems. Retrieval studies on large diameter head MoM

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THA and close follow up of these patients with hip stems are needed to understand the

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mechanism causing the differences in outcomes between these stem types.

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Keywords. total hip arthroplasty, hip stem, metal-on-metal, patient-reported outcome measure,

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osteolysis, blood metal ion level

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Introduction More than one million metal-on-metal (MoM) total hip arthroplasties (THA) were implanted prior to multiple reports of high revision rates and subsequent widespread

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recommendations to avoid their use. [1–3] Many of these MoM failures are due to adverse local

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tissue reactions (ALTR), which are associated with elevated metal ions levels secondary to

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implant wear. [4] MoM implant wear is associated mainly with the debris released from the

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bearing surface. [5] Metal ion release secondary to corrosion from the head-neck junction is

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another mechanism that may cause ALTR. [6] MoM hip resurfacing arthroplasty (HRA)

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implants do not have trunnions, which might explain why higher ALTR rates have been

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observed in MoM THA when compared to MoM HRA. [7] The majority of MoM THA implants

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are still in-situ, but with consistently high revision rates, there is a definite need for continuous

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clinical follow-up. This includes the Articular Surface Replacement (ASR) Hip System (DePuy

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Synthes, Warsaw, IN), which has two MoM versions, the MoM HRA (ASR) and the MoM THA

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(ASR XL). The ASR and the ASR XL were recalled in 2010 by the manufacturer, DePuy

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Orthopaedics (Warsaw, IN).

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Studies have shown varying results when different stem types are used with the ASR XL. For example, there has been an increased revision risk associated with patients who have fully-

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coated Corail stems (CORAIL® Total Hip System, DePuy Synthes, Warsaw, IN), and those

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patients also have a higher risk for ALTR compared to patients with proximally porous-coated

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Summit stems (SUMMIT® Tapered Hip System, DePuy Synthes, Warsaw, IN). [8,9] The S-

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ROM stem (S-ROM® Modular Hip System, DePuy Synthes, Warsaw, IN) is another stem type

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often coupled with the ASR XL, and it has excellent long-term results in non-MoM THA

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[10,11]. However, limited data have been published on the S-ROM stem and MoM THA

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outcomes. The S-ROM stem, clinically available for 32 years, is a modular stem that has a

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porous coated proximal sleeve part. This is an additional MoM interface from which metal ions

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may emanate.

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Our hypothesis was that MoM THA modular stems would be associated with inferior

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long-term implant fixation, elevated blood metal ions, and poorer functional outcomes when

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compared to non-modular MoM THA stems. We investigated this hypothesis using the ASR XL

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implant coupled with three different stems, one of which was the modular S-ROM.

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Material and Methods

The study population consisted of 539 unilateral MoM THAs. This study was based on a subset of patients from a prospective, multicenter, global follow-up study of the ASR Hip

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System, the methods of which have been described previously. [7,12] For the current study, we

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considered all ASR XL patients who had complete data at enrollment. This data included basic

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demographics, whole blood chromium (Cr) and cobalt (Co) levels, and five different patient-

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reported outcome measures (PROMs) used to evaluate functional outcomes: Harris Hip Score

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(HHS), UCLA activity score, EuroQol five dimensions questionnaire (EQ-5D) to indicate health

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related quality of life, Visual Analogue Scale (VAS) for pain, and VAS for satisfaction. The

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presence of both osteolysis and radiolucency were evaluated also. Four independent orthopedic

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physicians validated in evaluating plain radiographs for osteolysis from anteroposterior (AP) and

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shoot-through lateral (STL) radiographs. The inter- and intra-observer reliability were high. The

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mDesk™ software (RSA Biomedical, Umeå, Sweden) was used in the evaluation. Any areas of

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osteolysis ≥2 mm and any areas of radiolucency ≥0.5 mm were recorded (Figures 1, 2, and 3).

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The only stems included were those that had been used in 30 or more cases. No bilateral patients

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were included. All patients signed an informed consent. The study was approved by the

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institutional review board (IRB) for each site and at the data coordinating center.

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The stem used most often in this cohort was Summit (260 patients, 48%) and therefore

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used as the reference implant in the statistical analysis. Corail was used in 188 patients (35%),

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and S-ROM in 91 patients (17%). There was no difference in the prevalence of adapter sleeve

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use between the three stem groups (p = 0.490). The total cohort consisted of 290 (54%) male,

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and the mean age was 60 years (range, 23–94) (Table 1). The mean time from index surgery was

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6.4 years (range, 3–11 years). Binary logistic regression analysis was used to evaluate the

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association of stem type on the development of osteolysis and radiolucency. A general linear

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model was used to evaluate the association of stem type on blood metal ion levels and PROM

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scores. The following were included as possible confounding factors to both analyses: age at the

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index surgery, sex, geographic region, high metal ion levels (Co or Cr ≥5 ppb), preoperative

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diagnosis, time from the index surgery, and femoral head size. A p-value of <0.05 was

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considered statistically significant. All statistical analyses were performed with SPSS version

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24.0.

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Results

Patients with S-ROM stems were 3.8 times more likely to have osteolysis (p=0.003) and

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7.6 times more likely to have radiolucency (p<0.001) than patients with Summit stems. Patients

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with Corail stems were 2.5 times more likely to have osteolysis and 4.7 times more likely to have

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radiolucency (p<0.001) than patients with Summit stems (p=0.024) (Tables 2 and 3).

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Patients with S-ROM stems also reported significantly worse functional health outcomes

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in four of the five PROMs when compared to those with Summit stems. S-ROM patients scored

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5.1 points lower in HHS (0-100) (p = 0.023), 0.75 points higher in VAS for pain (0-10)

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(p=0.003), 0.66 points lower in UCLA Activity Score (0-10) (p=0.022), and 0.101 points lower

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in EQ-5D Index score (0-1) (p=0.001). S-ROM patients did not show any statistically significant

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difference in VAS for satisfaction. The patients treated with Corail stem had inferior results in

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VAS satisfaction compared to patients with Summit stems (-0.6 points, p=0.028), UCLA (-0.8

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points, p=0.000), and EQ-5D Index (-0.046 points, p=0.049) (Tables 2 and 4).

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We found blood Co level above 5 ppb to be associated with inferior HHS and EQ-5D Index (p=0.038 and p=0.017, respectively) for all patients (Table 4). Stem type did not have an

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association with blood Co level, although patients with Corail stems had higher Cr level than

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patients with Summit stems (mean 4.1 ppb vs 2.5 ppb, p=0.030). There was no statistically

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significant difference in revision risk among these three stem types, and there were no other

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significant predictors for revision beyond those described here. Blood Co ion level below 5 ppb

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was associated with a slightly lower revision risk for all stem types (HR=0.94, p<0.001).

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Discussion

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ALTR has been found in THAs with non-MoM bearings; therefore, corrosion in the taper

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junction area is thought to be only one possible source of metal wear and ion release. [13]

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However, data published on the effect of stem type on the outcome of MoM THAs is limited.

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We hypothesized that MoM THA modular stems would be associated with inferior long-term

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implant fixation, elevated blood metal ions, and poorer functional outcomes when compared to

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non-modular MoM THA stems. Our main aim was to analyze the radiographic findings and ion

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levels for three commonly used stem types when each was used with the ASR XL. Our

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secondary aim was to evaluate functional outcome differences between these stem types by using

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PROM data.

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Patients treated with S-ROM stems had significantly higher risk for osteolysis and

radiolucency than patients treated with Summit stems. This increased risk might be related to the

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modularity of S-ROM stems. Although modularity provides greater adaptability to patient

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variation, it also creates an additional metal junction. Modular neck-stems reportedly have a high

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prevalence of wear and ALTR. [6,14] The S-ROM stem is not directly comparable to these

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modular devices because the modularity of the S-ROM stem is unique. It consists of a proximal

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sleeve that is implanted inside of the femur and allows for adjustable femoral rotation. In fact,

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earlier studies have reported excellent survival for patients treated with S-ROM stems and non-

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MoM bearings in both primary and revision settings. [10,11,15]

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There has been some discussion that metal particles and ions existing locally within the hip joint might be more likely to cause ALTR than the circulating metal ions we measured would

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be. In our study, patients with Corail stems were more likely to have higher Cr levels than

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patients with Summit stems, but there were no significant differences Cr levels for patients with

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S-ROM stem or in Co levels between all stem types. It is possible that patients with S-ROM

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stems might have had a higher concentration of local metal particles, although we found no

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increase in blood metal ion levels. This might explain the higher osteolysis rate and inferior

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functional scores in patients treated with S-ROM stems even though there was no difference in

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blood metal ion levels between stem types.

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MoM THA is generally associated with higher blood metal ion levels when compared to MoM HRA. [16] One possible explanation for this is that metal wear debris and corrosion

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products can be generated by both the taper-neck junction and the metal bearing. The S-ROM

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stem has a smoother and longer neck-taper compared to the taper of Summit and Corail stems.

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[17] One recent study analyzed retrieval data from Summit, Corail, and S-ROM stems paired

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with Pinnacle cups (PINNACLE® Acetabular Hip System, DePuy Synthes, Warsaw, IN) and

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patients treated with S-ROM stems had less corrosion in the trunnion than those treated with

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Corail or Summit stems. [18] The authors suggested that the shorter, rougher tapers of the

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Summit and Corail stems might predispose those stems to trunnion problems. However, their

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model, which included stem type and three other variables, explained 29% of all trunnion wear.

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Therefore, there remain factors affecting trunnion wear that we are not aware of. This may

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include possible corrosion from the stem modularity of the S-ROM which was not measured.

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Moreover, all femoral heads in that study were size 36 mm in diameter. [18] This is significantly

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smaller than head size in our cohort where smallest head size was 39 mm (mean = 48 mm).

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Patients with S-ROM stems had inferior functional outcomes compared to patients with Summit stems in four of the five PROMs included in our study. Parameter estimates in these

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PROM scores were 5% to 10% worse than those for patients with Summit stems, which is

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clinically significant. There was no difference in revision rate between stem types, even though

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functional scores for patients with S-ROM stems were inferior. Patient selection is one possible

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explanation for the inferior PROM scores of patients with S-ROM stems. The modularity of the

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S-ROM stem allows more variations based on individual anatomy, and S-ROM stems have been

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used often for patients with more complex anatomy, such as arthritis due to developmental

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dysplasia of the hip (DDH). [11] In our study population, DDH was a more common

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preoperative diagnosis in the S-ROM group than in the Summit or Corail groups (23%, 0.4%,

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and 0.5%, respectively). We included preoperative diagnosis in the general linear model in order

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to minimize its confounding effect. The diagnosis of DDH did not have an effect on the

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association between stem type and PROM score. Osteolysis and implant loosening might be

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another possible explanation for inferior functional scores and increased pain. However, we were

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not able to directly correlate either osteolysis or radiolucency with pain, functional scores, or ion

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levels.

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Data on osteolysis in patients treated with MoM THA is limited. [19] In general

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uncemented stem fixation is a durable option especially among younger patients. [20] All three

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stems included into this study have a porous coating to improve osseointegration. Corail stems

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are coated with hydroxyapatite (HA) for full length and S-ROM and Summit can have HA

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coating on top of proximal porous titanium bead coating. However, in our material both fully

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coated Corail stem and proximally coated S-ROM stem had higher osteolysis and radiolucency

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prevalence than proximally coated Summit stem, which indicates that the length of the coating is

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not the explaining factor.

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We acknowledge that our study has a number of limitations. First, we were not able to perform magnetic resonance imaging (MRI) on all hips in the cohort. MRIs might have provided

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additional information about any underlying ALTR. Secondly, our follow up started from the

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enrollment date of the study and not from the date of the primary surgery. Therefore, we have no

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information on revisions prior to study initiation, which makes our data regarding revision rates

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incomplete. Third, even though to our knowledge this is the largest study assessing modular

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stems in MoM THA our number of patients was limited. Due to this we could not include all

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collected data to our multiple regression model in order to keep the calculation reliable. Finally,

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our material included only ASR XL THAs. Extrapolation to other MoM THAs should be done

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with caution because of other confounding variables associated with cup design.

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Conclusions

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Patients with S-ROM stems had significantly higher osteolysis prevalence and poorer functional

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outcomes than other stem types used frequently in ASR XL THA. Patients who have large head

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MoM THAs coupled with S-ROM stems require detailed follow-up with regular clinical

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controls, radiographic imaging, and blood metal ion measurements.

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References

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[1]

Medical Device Alert (Draft) http://www.mhra.gov.uk/home/groups/dtsbs/documents/medicaldevicealert/con155767.pdf [Accessed August 18, 2017]

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[2]

FDA. FDA Medical Device Alert: Metal-on-Metal Hip Implants n.d. http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProstheti cs/MetalonMetalHipImplants/ucm241667.htm#3. [Accessed August 18, 2017]

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[3]

Huang DCT, Tatman P, Mehle S, Gioe TJ. Cumulative revision rate is higher in metal-onmetal THA than metal-on-polyethylene THA: Analysis of survival in a community registry. Clin Orthop Relat Res 2013;471:1920–5.

220 221 222

[4]

Munro JT, Masri BA, Duncan CP, Garbuz DS. High complication rate after revision of large-head metal-on-metal total hip arthroplasty. Clin Orthop Relat Res. 2014;472(2):523– 8.

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[5]

Hart AJ, Muirhead-Allwood S, Porter M, Matthies A, Ilo K, Maggiore P, et al. Which factors determine the wear rate of large-diameter metal-on-metal hip replacements? Multivariate analysis of two hundred and seventy-six components. J Bone Joint Surg Am 2013;95:678–85.

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[6]

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[7]

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[8]

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Higgs GB, Hanzlik JA, MacDonald DW, Gilbert JL, Rimnac CM, Kurtz SM. Is increased modularity associated with increased fretting and corrosion damage in metal-on-metal total hip arthroplasty devices? A retrieval study. J Arthroplasty 2013;28:2–6. Madanat R, Hussey DK, Donahue GS, Potter HG, Wallace R, Bragdon C, et al. Early Lessons From a Worldwide, Multicenter, Followup Study of the Recalled Articular Surface Replacement Hip System. Clin Orthop Relat Res 2016;474:166–74. Reito A, Elo P, Puolakka T, Pajamäki J, Eskelinen A. Femoral diameter and stem type are independent risk factors for ARMD in the Large-headed ASR THR group. BMC Musculoskelet Disord 2015;16:118.

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[9]

Reito A, Puolakka T, Elo P, Pajamäki J, Eskelinen A. High prevalence of adverse reactions to metal debris in small-headed ASRTM hips. Clin Orthop Relat Res 2013;471:2954–61.

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[10]

Tudor FS, Donaldson JR, Rodriguez-Elizalde SR, Cameron HU. Long-Term Comparison of Porous Versus Hydroxyapatite Coated Sleeve of a Modular Cementless Femoral Stem (SROM) in Primary Total Hip Arthroplasty. J Arthroplasty 2015;30:1777–80.

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[11]

Imbuldeniya AM, Walter WK, Zicat BA, Walter WL. The S-ROM hydroxyapatite proximally-coated modular femoral stem in revision hip replacement: Results of 397 hips at a minimum ten-year follow-up. Bone Joint J 2014;96 B:730–6.

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[12]

Hussey DK, Madanat R, Donahue GS, Rolfson O, Muratoglu OK, Malchau H. Worse health-related quality of life and hip function in female patients with elevated chromium levels. Acta Orthop 2016;3674:1–7.

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[13]

Matharu GS, Pandit HG, Murray DW JA. Adverse reactions to metal debris occur with all types of hip replacement not just metal-on-metal hips: a retrospective observational study of 3340 revisions for adverse reactions to metal debris from the National Joint Registry for England, Wales, Northe. BMC Musculoskelet Disord 2016;17:495.

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[14]

Bernstein DT, Meftah M, Paranilam J, Incavo SJ. Eighty-six Percent Failure Rate of a Modular-Neck Femoral Stem Design at 3 to 5 Years. J Bone Joint Surg 2016;98:e49.

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[15]

Cameron HU, Keppler L, McTighe T. The role of modularity in primary total hip arthroplasty. J Arthroplasty 2006;21:89–92.

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[16]

Lainiala OS, Moilanen TPS, Hart AJ, Huhtala HSA, Sabah SA, Eskelinen AP. Higher Blood Cobalt and Chromium Levels in Patients With Unilateral Metal-on-Metal Total Hip Arthroplasties Compared to Hip Resurfacings. J Arthroplasty 2016;31:1261–6.

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[17]

Munir S, Walter WL, Walsh WR. Variations in the trunnion surface topography between different commercially available hip replacement stems. J Orthop Res 2015;33:98–105.

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[18]

Hothi HS, Eskelinen AP, Berber R, Lainiala OS, Moilanen TPS, Skinner JA, et al. Factors Associated With Trunnionosis in the Metal-on-Metal Pinnacle Hip. J Arthroplasty 2017:286–90.

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[19]

Renner L, Schmidt-Braekling T, Faschingbauer M BF. Do cobalt and chromium levels predict osteolysis in metal-on-metal total hip arthroplasty? Acta Orthop Trauma Surg 2016;136:1657–62.

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Delaunay CP, Putman S, Puliero B, Begin M, Migaud H, Bonnomet F. Cementless Total Hip Arthroplasty With Metasul Bearings Provides Good Results in Active Young Patients: A Concise Followup. Clin Orthop Relat Res 2016;474:2126–33.

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Acknowledgements We would like to thank the Harris Orthopedic Laboratory and DePuy Orthopedics for enabling

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this study. This study was supported by DePuy Orthopedics (Warsaw, IN). We would also like to thank Dr. Ola Rolfson for his advice on PROM measurements. One of the authors (IL) has

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received funding from the Orion Research Foundation sr.

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Figure Legend Figure 1. Plain radiographs of S-ROM stem. Well-integrated stem shown on left, stem with radiolucency in center, and with osteolysis on right.

stem with radiolucency in center, and with osteolysis on right.

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Figure 2. Plain radiographs of Corail stem. Well-integrated stem shown on left,

Figure 3. Plain radiographs of Summit stem. Well-integrated stem shown on left,

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stem with radiolucency in center, and with osteolysis on right.

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Table 1. Demographic data. OA = osteoarthrosis, DDH = developmental dysplasia of the hip, AVN = avascular necrosis, RA = rheumatoid arthrosis. Summit

SROM

Corail

N Age (range) Gender

539 60.1 (23 – 94)

260 60.2 (23 -94)

91 56 (28 – 82)

188 61.9 (36 – 84)

Male (%) Female (%) Follow up time (range) Headsize (range) Adapter sleeve use Diagnosis n(%) OA DDH Post-traumatic arthrosis AVN RA Country 0 (%) 1 (%) 2 (%) 3 (%) 4 (%) 5 (%) Abduction (range) Anteversion (range) ASA (mean)

290 (54) 249 (46) 6.4 (3 – 11) 48.4 (39 – 59) 533 (98.9%)

150 (58) 110 (42) 6.5 (4 – 10) 49.3 (41 – 57) 260 (100%)

46 (51) 45 (49) 6.7 (4-11) 46.6 (39-59) 91 (100%)

94 (50) 94 (50) 6.3 (3-10) 48.0 (41-59) 185 (97.9%)

478 (89) 23 (4) 13 (2) 23 (4) 2 (0)

241 (93) 1 (0.4) 3 (1) 14 (5) 1 (0.4)

56 (62) 21 (23) 8 (9) 5 (6) 1 (1)

181 (96) 1 (0.5) 2 (1) 4 (2) 0

60 (66) 0 1 (1) 0 30 (33) 0 42.7 (21-61) 25.2 (0-54) 2.0

79 (42) 44 (23) 13 (7) 47 (25) 0 5 (3) 43.6 (19-75) 28.3 (1-49) 1.5

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301 (56) 109 (20) 43 (8) 47 (9) 34 (6) 5 (1) 43.6 (19 – 75) 29.2 (0 – 54)) 1.7

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All

Summit

SROM

Corail

Radiolucency*

85 (15.8%)

15 (5.8%)

27 (29.7%)

43 (22.9%)

Osteolysis*

67 (12.4%)

15 (5.8%)

30 (33.0%)

22 (11.7%)

Cobalt (ppb)†

3.1 (0.0-142.9)

2.5 (0.0-142.9)

2.5 (0.0-56.1)

4.8 (0.0-58.9)

Chromium (ppb)†

1.7 (0.0-55.1)

1.4 (0.0-55.1)

1.5 (0.0-32.7)

2.4 (0.0-51.9)

210 (39.0%)

93 (35.8%)

25 (27.5%)

92 (48.9%)

91 (6-100)

93 (6-100)

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Table 2. Summary of clinical visit findings given for the whole study cohort and by stem type.

89 (35-100)

90 (19-100)

0.5 (0.0-8.0)

1.0 (0.0-10.0)

0.5 (0.0-10.0)

0.5 (0.0-9.0)

1.0 (0.0-10.0)

1.0 (0.0-10.0)

6 (1-10)

6 (2-10)

6 (2-10)

1.0 (0.0-1.0)

0.8(0.1-1.0)

0.8 (0.0-1.0)

Blood metal ion levels

Either Co or Cr > 5ppb*

HHS† VAS Pain (mm)†

0.5 (0.0-10.0)

VAS Satisfaction (mm)†

0.5 (0.0-10.0)

UCLA†

6 (1-10)

EQ-5D Index†

0.8 (0.0-1.0)

M AN U

PROMs

EP

TE D

* Values given as N (%). † Values given as median (range).

AC C

RI PT

Radiographic Grading

ACCEPTED MANUSCRIPT

Table 3. P values for independent variables inserted into binary logistic regression models assessing radiolucency, osteolysis, and revision rate. OA = osteoarthrosis, DDH = developmental dysplasia of the hip, PTA = post-traumatic arthrosis, AVN = avascular necrosis, RA = rheumatoid arthrosis.

Preoperative diagnosis

(ref = 0) 1 2 3 4 5 OA (ref) DDH PTA AVN

0.930 0.124 0.808 0.101 0.252 0.000 (0.940) a 0.100

0.594 0.562 0.302 0.297 0.534

0.507 0.845 0.092 0.553 0.833

0.007 (2.584) a 0.297 0.108 0.997 0.886

0.755

0.505

0.998

0.300

0.068

0.365

0.180

0.388

0.693

0.326

0.999

0.999

EP

P value deemed significant, hazard ratio listed in parenthesis.

AC C

a

0.003 (3.788) a 0.024 (2.458) a 0.727 0.855 0.296 0.855 0.438

TE D

RA

<0.001 (7.622) a <0.001 (4.729) a 0.853 0.522 0.137 0.487 0.898

RI PT

Male Gender Age at Surgery Head Size Cobalt less than 5 ppb Chromium less than 5 ppb Country

Revision

SC

(ref = Summit) S-ROM Corail

Osteolysis

M AN U

Stem

Radiolucency

ACCEPTED MANUSCRIPT

Table 4. General linear model. OA = osteoarthrosis, DDH = developmental dysplasia of the hip, PTA = post-traumatic arthrosis, AVN = avascular necrosis, RA = rheumatoid arthrosis. HHS = Harris Hip Score, Co = Cobalt, Cr = Chromium. VAS Satisfactio n

0.003 a (0.749) 0.119

0.236

(ref = Summit)

Stem

0.023 (a 5.111) 0.072

S-ROM

0.028 a (0.602)

Corail 0.268

0.935

0.369

0.916

0.730

0.594

0.524

0.589

0.553

0.013 (a 0.209) 0.186

0.038 (3.213)

0.176

0.092

4

a

P value

0.766

0.400

0.114

0.030 (1.284) a

0.460

0.470

0.264

0.174

0.509

0.196

0.430

0.381

0.175

0.319

0.382

0.263

0.017 a (0.052) 0.108

0.033 (a 3.926) 0.628

0.563

0.459

0.470

0.684

0.226

0.315

0.032 a (0.623) 0.113

0.607

0.148

0.215

0.743

0.310

0.073

0.798

0.945

0.535

0.296

0.241

0.061

0.201

0.564

0.022 (1.187) a

0.252

<0.001 (10.286)

<0.001 (4.791)

a

a

0.873

0.286

0.880

0.044 a (1.778)

0.595

0.922

0.677

DDH

0.364

0.188

0.056

0.544

0.879

0.012

0.559

PTA

0.209

0.137

0.091

0.327

0.650

0.770

AVN

0.562

0.404

0.002 a (2.264) 0.654

0.741

0.759

0.275

0.519

RA

0.716

0.706

0.716

0.507

0.417

0.258

0.622

5 OA (ref)

AC C

Preoperative diagnosis

0.001 (a 0.101) 0.049 (a 0.046)

0.017 (a 1.313) 0.369

EP

3

0.022 (a 0.661) 0.000 (a 0.832)

0.021 (a 2.288) 0.487

0 (ref)

2

Cr

0.028 a (0.053) 0.213

a

1

Co

0.004 a (0.632) 0.000 (a 0.038) 0.731

TE D

Head Size Cobalt < 5 ppb Chromium <5 ppb Country

EQ-5D Index

M AN U

0.514 Male Gender Age at Surgery Time from surgery

UCLA

RI PT

VAS Pain

SC

HHS

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT