Comparison of Functional Results of ADM X3-MoP Cup (Stryker) and a CoC Cup (Zimmer) in Young Patients

A Single-Center Randomized, Patient-Blinded, Prospective Five-Year Study to Compare the Functional Results after Insertion of ADM X3-MoP Cup (Stryker) and a CoC Cup (Zimmer) in Primary THA. 60 patients will be enrolled during a 2 year period. At surgery tantalum beads will be inserted into predrilled holes of the polyethylene rim for assessment of motion of the large mobile poly in the ADM Trident Cup by use of RSA. Patients will be followed by functional examinations as well as PROM assessment.

With Metal-on-Metal (MoM) articulations leaving the marked the THA bearing choice for younger patients is currently debated and overall the choice stands between CoC and MoP. New HXLPE is wear-resistant and safe and clinical HXLPE wear (RSA) hardly exceed the wear measured in retrieval CoC implants. For CoC articulations stripe wear on edge loading is a reported problem leading to increased wear in examined retrieval components and CoC wear is dependent on component position. Although the risk is very small, CoC bearings are at still at risk of fracture, and functional squeaking is a complication that adversely affects the quality of life in about 1% of CoC THA patient. Dual mobility MoP cups were designed for reducing hip dislocations in older patients treated with THA after medial hip fractures. The concept provides good stability and mobility and may also be an optimal solution for younger and active patients; however, dual mobility MoP has not previously been documented for use in younger patients. The anatomical dual mobility (ADM) cup design (Stryker) is soft tissue sparing (iliopsoas tendon) potentially leading to lesser groin-pain and squeaking is not a concern. It is currently unknown if the outer-articulation of the dual mobility PE liner keeps moving over time or could impinge in the joint capsule in an undesirable position and result in unwanted edge loading and higher wear-rates. Metal ions are produced even in MoP bearings and even though in dual-articulation MoP bearings most (90%) of the motion is believed to occur between the head and liner (ceramic-polyenthylene), the metal ion levels may be higher than expected for MoP hips (large poly contact in metal shell), while expectedly there will be no metal ions in CoC THA.

Eligibility Criteria:
Inclusion Criteria:

* primary hip osteoarthritis
* sufficient bone quality for total hip arthroplasty
* age 40 through 65 years of age
* informed and written consent
* patient can only enter the project with one hip

Exclusion Criteria:

* neuromuscular or vascular disease in the affected leg
* patients with osteoporosis
* fracture sequelae or previous extensive hip surgery
* patients with metabolic bone disease including rheumatoid arthritis
* non-Danish citizenship
* patients who do not comprehend the Danish language
* senile dementia
* alcoholism and drug abuse
* major psychiatric disease
* current metastatic cancer disease and on-going treatment with radiation therapy/chemotherapy
* severe systemic disease affecting gait
* contralateral knee, hip and/or spine disease
* on-going case regarding industrial injury insurance of the hip
* patients with very poor dental status