Clinical Outcomes of Primary Cementless Total Hip Arthroplasty Using the Collarless Actis Stem

September 14, 2026 updated by: Young-Kyun Lee, Seoul National University Bundang Hospital

Prospective Cohort Study of Primary Cementless Total Hip Arthroplasty Using Actis Stems

This study looks at how well a hip replacement using the collarless Actis stem works over five years.

Total hip replacement is a common operation for people whose hip joint has been damaged by arthritis, by loss of blood supply to the hip bone, or by a broken hip. During the operation, the damaged parts of the hip are replaced with artificial parts. The Actis stem is the part that is fitted into the thigh bone. It is designed to bond directly with the bone, without the use of bone cement.

The Actis stem is already used in many countries, and early results have been good. However, almost all of those results come from Western patients, and most studies used a version of the stem that has a small collar. Very little is known about how the collarless version performs in Asian patients, who tend to be younger at the time of surgery and more often have the operation because of loss of blood supply to the hip bone.

People aged 18 years or older who are already scheduled for a hip replacement at this hospital may take part. Everyone who takes part has the same operation, with the same set of artificial parts. No extra tests are done for research purposes.

After surgery, participants return to the clinic at 6 weeks, 3 months, and 12 months, and then once a year until 5 years have passed. These are the same visits that patients would have anyway. At each visit, the study team checks for any problems with the new hip, takes routine X-rays, and asks participants to fill in questionnaires about their hip pain, their daily activities, and their overall health.

The main question the study asks is how many participants have a problem with the new hip within five years, such as the hip coming out of place, an infection, a break in the bone around the implant, or the implant becoming loose.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

The collarless Actis stem is a cementless femoral component featuring a proximal DUOFIX hydroxyapatite coating and a triple-tapered geometry, intended to enhance proximal bone remodeling, promote favorable load distribution, and limit stress shielding. Favorable short-term outcomes have been reported by the manufacturer and in registry-based analyses, and a comparative series has shown results similar to those of the Corail stem. These data, however, derive almost entirely from Western populations, and the majority of published series have evaluated the collared version of the implant. No study has reported the outcomes of the collarless Actis stem in an East Asian population, in whom osteonecrosis of the femoral head is a more frequent indication for arthroplasty and the mean age at the time of surgery is lower than in Western cohorts.

All participants undergo primary cementless ceramic-on-ceramic total hip arthroplasty using the collarless Actis femoral stem and the Pinnacle acetabular cup, with a fourth-generation BIOLOX delta ceramic head and liner. Hybrid use of implants or ceramic bearings is precluded in order to avoid bias. All procedures are performed through a posterior approach with the patient in the lateral decubitus position. Component positioning follows a combined anteversion technique using anatomical landmarks, with a target cup anteversion of 37.3 degrees minus 0.7 times the stem anteversion.

At the routine preoperative medical clearance, participants are assessed for age, sex, body mass index, ambulatory function graded by the Koval classification, diagnosis, comorbidities, and operative risk according to the American Society of Anesthesiologists classification. Preoperative imaging comprises a three-dimensional computed tomography scan of the hip for planning, together with hip anteroposterior, hip cross-table lateral, pelvis lateral, and lumbosacral spine radiographs. Operative data include operative time, type of anesthesia, estimated blood loss, implant fixation, cup position, intraoperative complications, and length of hospital stay.

Postoperative mobilization begins on the first or second day after surgery, and participants ambulate with partial weight bearing using a walking aid for six weeks. Follow-up is scheduled at 6 weeks, 3 months, and 12 months after surgery and annually thereafter until 5 years, corresponding to the institution's routine postoperative schedule. No additional examinations are performed for research purposes beyond those obtained in routine care.

Serial hip anteroposterior and cross-table lateral radiographs are assessed for implant fixation, ceramic wear, osteolysis, implant loosening, and heterotopic ossification according to previously established criteria. Radiographic evaluation is performed by two independent observers who did not participate in the operations, with the six-week radiographs serving as the baseline for comparison. Patient-reported outcome measures are obtained preoperatively and at one year postoperatively and annually thereafter, and comprise the modified Harris Hip Score, the Hip Disability and Osteoarthritis Outcome Score, the EQ-5D, the University of California Los Angeles activity score, and the Forgotten Joint Score, the last of which is acquired postoperatively only.

The target enrollment of 210 hips was derived from an a priori power analysis. Assuming a complication rate of 6.5 percent, based on the investigators' previously reported 10- to 12-year outcomes of fourth-generation ceramic-on-ceramic total hip arthroplasty using the Pinnacle cup, 178 hips were required to detect a 2 percent difference with 80 percent power at a two-sided alpha of 0.05. Allowing for a 15 percent dropout rate, enrollment was set at 210 hips.

Data are recorded in an electronic case report form using a web-based REDCap platform and are monitored every six months for safety and data quality. Categorical data are summarized as counts and percentages and continuous data as means with standard deviations. Implant survivorship is analyzed using the Kaplan-Meier method with reoperation or revision as the endpoint.

Study Type

Interventional

Enrollment (Estimated)

210

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • South Korea
    • Gyeonggi-do
      • Seongnam-si, Gyeonggi-do, South Korea, 13620
        • Recruiting
        • Seoul National University Bundang Hospital
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age 18 years or older
  • Scheduled to undergo primary total hip arthroplasty for one of the following: osteoarthritis of the hip, developmental dysplasia of the hip, rheumatoid arthritis, non-rheumatoid inflammatory arthritis, post-traumatic arthritis, osteonecrosis of the femoral head, or displaced femoral neck fracture
  • Willing and able to provide written informed consent

Exclusion Criteria:

  • Age under 18 years
  • Total hip arthroplasty performed with a femoral stem other than the collarless Actis stem
  • Severe medical comorbidity precluding participation
  • Unwilling to participate in the study

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Actis
Participants undergo primary cementless total hip arthroplasty using the collarless Actis femoral stem with a Pinnacle acetabular cup and a fourth-generation ceramic-on-ceramic bearing, performed through a posterior approach with the patient in the lateral decubitus position.
Device: Collarless Actis femoral stem
Primary cementless total hip arthroplasty using the collarless Actis femoral stem and Pinnacle acetabular cup (DePuy Synthes, Warsaw, IN, USA) with a fourth-generation BIOLOX delta ceramic head and liner (CeramTec, Plochingen, Germany).

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of orthopedic complications
Time Frame: Up to 5 years after the index total hip arthroplasty
Number of participants with any orthopedic complication, defined as dislocation, periprosthetic joint infection, aseptic loosening, or periprosthetic fracture.
Up to 5 years after the index total hip arthroplasty

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Reoperation rate
Time Frame: Up to 5 years after the index total hip arthroplasty
Number of participants undergoing any reoperation or revision of the index hip for any reason.
Up to 5 years after the index total hip arthroplasty
Implant survivorship
Time Frame: Up to 5 years after the index total hip arthroplasty
Kaplan-Meier survivorship of the implant with reoperation or revision for any reason as the endpoint.
Up to 5 years after the index total hip arthroplasty
Modified Harris Hip Score
Time Frame: Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
Modified Harris Hip Score, a measure of hip pain and function ranging from 0 to 100, with higher scores indicating better hip function.
Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
Hip Disability and Osteoarthritis Outcome Score (HOOS)
Time Frame: Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
HOOS, a patient-reported measure scored from 0 to 100 in each subscale, with higher scores indicating fewer symptoms and better function.
Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
EQ-5D index score
Time Frame: Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
EQ-5D health-related quality of life index, with higher scores indicating better health status.
Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
University of California Los Angeles (UCLA) activity score
Time Frame: Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
UCLA activity score, ranging from 1 to 10, with higher scores indicating a higher level of physical activity.
Preoperatively and at 1, 2, 3, 4, and 5 years after surgery
Forgotten Joint Score (FJS)
Time Frame: 1, 2, 3, 4, and 5 years after surgery
Forgotten Joint Score, ranging from 0 to 100, with higher scores indicating greater ability to forget the artificial joint in everyday life. Acquired postoperatively only.
1, 2, 3, 4, and 5 years after surgery
Radiographic findings
Time Frame: 6 weeks to 5 years after surgery
Number of participants with radiographic evidence of implant loosening, osteolysis, ceramic wear, or heterotopic ossification on serial hip anteroposterior and cross-table lateral radiographs, assessed by two independent observers who did not participate in the operations. Six-week radiographs serve as the baseline for comparison.
6 weeks to 5 years after surgery
Incidence of medical complications
Time Frame: Up to 5 years after the index total hip arthroplasty
Number of participants with deep vein thrombosis, pulmonary embolism, major adverse cardiac events, or death.
Up to 5 years after the index total hip arthroplasty

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Seoul National University Bundang Hospital

Collaborators

Johnson & Johnson Medical Korea Ltd

Investigators

  • Principal Investigator: Young-Kyun Lee, MD, Seoul National University Bundang Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 18, 2025

Primary Completion (Estimated)

June 30, 2031

Study Completion (Estimated)

December 31, 2031

Study Registration Dates

First Submitted

September 14, 2026

First Submitted That Met QC Criteria

September 14, 2026

First Posted (Actual)

September 18, 2026

Study Record Updates

Last Update Posted (Actual)

September 18, 2026

Last Update Submitted That Met QC Criteria

September 14, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • B-2504-966-307
  • DPS-Joints-2024-036 (Other Grant/Funding Number: Johnson and Johnson Medical Korea Ltd.)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data are the property of the sponsor institution and are subject to confidentiality obligations under the research support agreement. There is no plan to share individual participant data.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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