A Prospective, Randomized Clinical Study Comparing Marathon Polyethylene and Enduron Polyethylene Acetabular Liners Used in Total Hip Arthroplasty at Long-Term Follow-up
Phase: NA
Conditions: Osteoarthritis, Arthritis, Joint Diseases, Musculoskeletal Diseases, Rheumatic Diseases
Sponsor: Anderson Orthopaedic Research Institute

Research Protocol 
 
 
 
 
 
 
 
 
A Prospective, Randomized Clinical Study Comparing 
Marathon Polyethylene and Enduron Polyethylene 
Acetabular Liners Used in Total Hip Arthroplasty 
at Long-Term Follow-up 
 
Date: January 15, 2014 
 
 
 
 
 
Sponsor: 
 
Partial funding for this study will be provided by DePuy Orthopaedics, a Johnson & 
Johnson company. 
 
Principal Investigator: 
 C. Anderson Engh, Jr., MD 
 
Anderson Orthopaedic Research Institute 
2501 Parker’s Lane, Suite 200 
Alexandria, VA  22306 
(703) 619-4411 
 
2445 Army-Navy Drive 
Arlington, VA 22206 
(703) 619-4411 

Background and Purpose 
 
 
In 1999, the Anderson Orthopaedic Research Institute (AORI) initiated a 
prospective, Institutional Review Board-approved study to compare the clinical outcome 
of total hip arthroplasty (THA) patients who were randomized to either crosslinked 
Marathon or non-crosslinked Enduron polyethylene liners.  During an 18-month 
enrollment period, 226 patients who received 236 THAs consented to participate in the 
study.  Six patients (6 THAs) were excluded intra-operatively, leaving 230 THAs 
implanted with a Duraloc acetabular shell (DePuy) coupled with a 28-mm cobalt-chrome 
femoral head (DePuy).  At 5-year outcome, we found that crosslinked Marathon 
polyethylene liners were wearing 95% less than the non-crosslinked Enduron liners [1].  
In fact, the Marathon wear rates were so low at 5-year follow-up that the mean was not 
statistically different than zero.  Several other institutions have also reported very low 
wear rates with highly crosslinked polyethylene based on early clinical outcome data [2-
8].  However, since osteolysis typically appears after 5-year follow-up, the reduction in 
the incidence and extent of periprosthetic bone loss among THA patients with Marathon 
liners, compared to those with Enduron liners, was not as dramatic as the wear reduction 
[9].  Despite the substantial reduction in wear that we observed at 5-year follow-up, the 
patients' perceptions of their outcomes remained similar among the Marathon and 
Enduron groups [1].  At an average follow-up interval of at least 10-years (using outcome 
data for individual study participants obtained at a minimum of 9-year follow-up), we 
anticipated that the reduction in wear associated with Marathon polyethylene would be 
associated with significant reductions in periprosthetic osteolysis. Our findings [10] 
confirmed this hypothesis and indicated that the wear rate of Marathon polyethylene 
remained substantially lower than conventional Enduron polyethylene through 10-year 
follow-up. 
 
Because crosslinking is accompanied by a reduction in the ultimate tensile 
strength, fatigue strength, and elongation to failure of ultra high molecular weight 
polyethylene [11-13], characterizing the long-term clinical performance of Marathon 
polyethylene is also important.  Concerns have been expressed about the potential for the 
liner fracture, in vivo polyethylene oxidation or accelerated wear at long-term follow-up, 
the effects of femoral head roughening over time and the bioreactivity of crosslinked 
polyethylene debris particles [14-23].  Ultimately, the best way to address these concerns 
is in the context of well-controlled, long-term clinical outcome studies.  As part of our 
efforts to follow patients throughout their lives to obtain long-term outcome data, we will 
continue to obtain routine follow-up at 5-year intervals from the date of surgery for each 
patient.  Because we anticipate that the reduced incidence of wear and osteolysis will 
result in a lower incidence of revision surgery among the patients randomized to 
Marathon liners, implant revision for reasons related to wear will be our primary outcome 
measure at long-term follow-up.  
 
 
 
 
 
 

Primary Hypothesis: 
 Primary THAs prospectively randomized to Marathon liners will demonstrate a 
lower rate of revision for wear-related complications and higher survivorship 
compared to primary THAs randomized to Enduron liners. 
Additional Hypotheses: 
 Primary THAs prospectively randomized to Marathon liners will demonstrate 
substantially reduced polyethylene wear compared to primary THAs 
randomized to Enduron liners. 
 THAs prospectively randomized to Marathon liners will demonstrate a reduced 
incidence of clinically important osteolysis with an area of at least 1.5 square 
centimeters compared to primary THAs prospectively randomized to Enduron 
liners. 
 THAs prospectively randomized to Marathon liners will demonstrate higher rates 
of patient satisfaction and better Harris Hip Scores compared to primary THAs 
randomized to Enduron liners. 
 All the THAs prospectively randomized to Marathon and Enduron liners will 
demonstrate constant wear rates over time. 
 
 
Study Population 
 
Inclusion criteria 
 Patient consented to participate in this study 
 Implanted on the acetabular side with a Duraloc 100 cup incorporating a 4-mm 
lateralized polyethylene liner that was randomized to either Marathon or 
Enduron 
 Implanted on the femoral side with an extensively porous-coated 
(AML/Solution or Prodigy) stem with a 28-mm cobalt-chrome femoral head 
Exclusion criteria 
 Intra-operative considerations related to implant stability, leg length correction 
or bone quality led to the implantation of THA components other than a 
Duraloc 100 cup, 4-mm lateralized liner, extensively porous-coated stem 
and 28-mm cobalt-chrome femoral head 
 Patient refused reconsent for continued follow-up 
Anticipated Study Population Size 
 
The 230 THAs randomized to a Marathon or Enduron polyethylene liner will 
comprise the study population for our survivorship analyses.  Based on our previously 
published data, we found 9 THAs among deceased patients at a mean follow-up of 5.7 
years [1] and 32 THAs among deceased patients at a mean follow-up of 10 years [10].  
Based on this data, we anticipate that approximately 12% of the patients enrolled in the 
study will pass away every five years.  

 
Material and Methods: 
 Patients due for routine 15-year follow-up will be contacted by Anderson 
Orthopaedic Institute personnel who will schedule follow-up appointments.  
Attempts will be made to obtain follow-up for all enrolled patients who have 
not had a follow-up evaluation at the Anderson Clinic within one year before 
the 15-year anniversary of their original surgery date.  This procedure will be 
repeated at five-year intervals (20 years, 25 years, etc.). 
 
Study interval 
Minimum follow-up date 
for study interval  
End date 
15-year 
DOS + 14 years 
DOS + 19 years -1 day 
20-year 
DOS + 19 years 
DOS + 24 years -1 day 
25-year 
Continue every 5 
years  
DOS + 24 years, etc. 
DOS + 29 years -1 day, etc. 
 
 At the initial follow-up visit associated with this long-term study, the subjects will 
be informed of changes to the protocol and asked to sign a reconsent. 
 At the time of each follow-up visit, patients will complete the clinic patient 
questionnaire per current protocols and the physician will complete a 
standardized evaluation.   
 Standardized x-rays will be obtained during follow-up visits per current standard 
of care. 
 Subjects who have already come to the clinic for a routine follow-up visit within 
one year preceding each 5-year anniversary and have not yet signed a reconsent 
for this long-term follow-up study will be sent a copy of the reconsent in the 
mail.  Designated research personnel will call the subject to review the consent 
when the subject is able to read along, answer any questions, and ask the subject 
to send back the signed form if the subject is willing to reconsent. 
 Subjects unable to return to the Anderson Clinic for follow-up will be asked to 
complete the clinic patient questionnaire and a prescription for x-rays will be 
sent to them after a reconsent has been obtained by telephone as outlined above. 
 If a subject does not request to be withdrawn from this study but a fully executed 
reconsent cannot be obtained (potentially because the subject cannot be 
contacted), a waiver of informed consent and HIPAA Authorization is requested 
from the IRB to use the subject’s existing medical records for the purposes of 
this study. 
 Serial anteroposterior (AP) pelvic x-rays will be analyzed to evaluate femoral head 
penetration into the polyethylene liner for each THA using a computer-assisted, 
validated software application (Hip Analysis Suite, Chicago, IL) [24].  A least-

squares linear regression analysis based on the head penetration versus time in 
situ will be used to calculate a wear rate for each THA [25].  The Hip Analysis 
Suite software will also be used to calculate the volumetric wear of the 
polyethylene liner based on the femoral head penetration data.  Wear rates 
among the Marathon and Enduron groups will be compared using an 
Independent samples t-test or Mann-Whitney U, depending on the normality of 
the data. 
 Serial x-rays for each THA will be analyzed to identify regions of femoral and 
acetabular osteolysis.  The area of each osteolytic region will be measured on 
the AP pelvic x-ray with Martell's Hip Analysis Suite software.  The incidence 
of osteolysis will be compared using a chi-square or Fisher's Exact test, 
depending on the cell counts.  The size of osteolytic lesions will be compared 
using an Independent samples t-test or Mann-Whitney U, depending on the 
normality of the data.  X-rays will also be used to evaluate radiographic 
complications such as periprosthetic fracture and implant loosening.  The 
incidence of radiographic complications among the Marathon and Enduron 
groups will be compared using a chi-square or Fisher's Exact test, depending on 
the cell counts. 
 Kaplan-Meier survivorship analysis will be used to compare the outcome of the 
Marathon and Enduron groups using revision for any reason as an endpoint.  
Survivorship analyses using revision for specific diagnoses, such as wear and 
osteolysis or implant loosening, will also be performed. 
 Clinical outcome data among the Marathon and Enduron groups will queried from 
AORI's institutional database and compared based on the nature and distribution 
of the data.  Specifically, we anticipate that patient satisfaction will be 
compared with a Fisher's Exact test and Harris Hip scores will be compared 
with the use of a Mann-Whitney U. 
 A manuscript summarizing the results of this study will be submitted for 
publication in a peer-reviewed orthopaedic journal. The results of this study will 
also be presented at orthopaedic meetings and conferences. 
 Subjects will continue to be followed for life. 
Source of Funding 
 
Partial funding for this study will be provided by DePuy Orthopaedics.  Study 
costs in excess of the funding provided by DePuy will be supported internally by the 
Anderson Orthopaedic Research Institute.  
 
 
 
 
 
 
 
 

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