Early stability of the Delta-TT cup with Polyethylene insert compared to the Delta-TT cup with Ceramic insert. A RSA study.

Rationale: Roentgen
Stereophotogrammetric Analysis (RSA) is a very accurate measurement technique used to obtain micromotion of the implants relative to inserted tantalum markers in the surrounding bone. Using RSA, long-term predictions of prosthetic loosening can be made based on a two years follow-up. Therefore, it is recommended to analyse all (new) prosthetic components by means of RSA.

Objective: The goal of this study is to study in a randomised trial the stability of the Delta-TT cup with polyethylene insert and the Delta-TT cup with ceramic insert both combined with the H-MAX femoral stem by means of RSA to assess whether the differences in stiffness of the cup will have an influence on incorporation and mechanical stability. It is hypothesized that there will be more micromotion on the short-term (<2 years) in the patients with the ceramic insert because of the higher stiffness, however, all components will be considered stable on the short and long-term. Secondary goal is to compare the stability of the C2 femoral stem, to the H-MAX femoral stem as well as to compare it to relevant migration results of similar stems from the literature. These RSA results will contribute to knowledge about the early stability and long-term prosthetic loosening of these cementless stems.

Study design: A Prospective Randomized Single Centre RSA Study (Group A and B) combined with a non-randomised treatment group (Group C)

Study duration: 18 months enrolment period + up to 5 year follow-up = 6.5 years total duration.

Study population: Primary total hip replacement
Number of patients: 65 patients

Study Devices: Delta-TT cup in combination with a polyethylene insert or a ceramic insert; H-MAX femoral stem; C2 femoral stem.

Intervention: Group A: 25 patients will be randomised to receive the H-MAX femoral stem and the Delta-TT cup with polyethylene insert. Group B: 25 patients will be randomised to receive the H-MAX femoral stem and the Delta-TT cup with ceramic insert. Group C: 15 patients will receive the C2 femoral stem and the Delta-TT cup with ceramic insert (non-randomised).
Main study parameters/endpoints: The main study parameter is the early stability of the Delta-TT cup with Polyethylene insert, the Delta-TT cup with Ceramic insert and the H-MAX femoral stem by means of RSA. The RSA data of the components will be described in terms of translational and rotational movements.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness: In addition to the benefits from the primary hip arthroplasty procedure e.g. reduced pain, improved range of motion, there is no guarantee that patients will personally benefit from inclusion in this study. Patients may undergo more thorough screening and follow-up than non-study patients and may benefit from this increased surveillance. The additional annual radiation dose is negligible if the natural annual exposure of 2 mSv is considered and will do the patient no harm.

It is hypothesized that there will be more micromotion on the short-term (<2 years) in the patients with a Delta-TT cup and ceramic insert as compared to a polyethylene insert, because of the higher stiffness, however, all components will be considered stable on the short and long-term.

Pre-operative, discharge, 6 weeks, 3, 6, 12 months, 2 and 5 years.

Randomized trial:

• Group A: 25 patients will receive the H-MAX femoral stem and the Delta-TT cup with polyethylene insert.

• Group B: 25 patients will receive the H-MAX femoral stem and the Delta-TT cup with ceramic insert.

Non-randomised group:

• Group C: 15 patients will receive the C2 femoral stem and the Delta-TT cup with ceramic insert. Group C will be included when inclusion of group A and B is completed.