The goal of this clinical trial is to evaluate the safety and effectiveness of the Polymotion Hip Resurfacing (PHR) System compared to total hip arthroplasty, for adults who require hip resurfacing arthroplasty due to 1) non-inflammatory arthritis (degenerative joint disease) such as osteoarthritis, traumatic arthritis, or 2) mild dysplasia/developmental dislocation of the hip (DDH) up to Crowe Grade 1.

The PHR® System is a single-use device consisting of a Cobalt Chromium, bone-cemented femoral head component, and a cementless acetabular component comprising of a Vitamin E polyethylene (Vit E-XPE) bearing with a titanium coating.

The PHR® System is intended for patients who, due to their relatively younger age (under 65) and increased activity level, may not be suitable for traditional total hip arthroplasty due to an increased possibility of requiring future ipsilateral hip joint revision.

Hip Resurfacing Arthroplasty (HRA) is a surgery that has been developed as an alternative to Total Hip Arthroplasty (THA), especially for younger, more active patients. Studies done on past designs of HRA demonstrate the following noteworthy benefits of the HRA procedure when compared with THA: bone conservation, improved gait, higher activity levels, lower rates of dislocations, reduced thigh pain, and reduced alteration in leg length. Hip resurfacing restores the natural shape of the joint meaning better stability, longevity, and higher levels of activity than a traditional hip replacement.

In Total Hip Replacement, the femoral head and neck (ball joint of the hip) is removed and replaced by a long, stemmed device. The procedure is highly successful; however, in some cases the replacement hip joint has the potential to wear out much more quickly in younger, more active patients, leading to revision surgery being required. With the PHR® procedure, your surgeon removes less bone from the femoral head of the femur and retains the femoral neck. The femoral head is shaped to accept a low-wear metal cap. This spherical cap closely matches your anatomy, reducing the risk of dislocation, and offering a broad range of movement and excellent stability. The acetabular socket (cup joint of the hip) is then fitted with a corresponding polyethylene component, significantly reducing potential reactions to metal ions associated with historic Metal-on-Metal hip resurfacing devices.

A comprehensive range of sizes is offered to address the needs of most patients. Both components are designed to be implanted, to achieve reconstructive and functional replacement of the hip joint. The PHR® System is intended to offer the traditional benefits of hip resurfacing over total hip arthroplasties, such as bone conservation and restoration of natural biomechanics, without a metal-on-metal articulating surface.

In order to be eligible to participate in this study, subjects must meet all of the following criteria:

1. Requires primary hip resurfacing arthroplasty due to:

   1. non-inflammatory arthritis (degenerative joint disease) such as osteoarthritis, traumatic arthritis, or
   2. mild dysplasia/developmental dislocation of the hip (DDH) up to Crowe Grade 1.

2. Harris Hip Score < 70 points.

3. Skeletally mature, age ≥21 and <65 years.

4. Physically and mentally able and willing to comply with the Protocol, including the ability to read and complete required forms and willing and able to adhere to the scheduled follow-up visits and requirements of the Protocol.

Subjects who meet any of the following criteria will be excluded from participating in this study:

1. Inadequate bone stock or bone quality to support the device based on a Canal-Bone Ratio (CBR-7) of >0.45.0F

2. Severe osteopenia, a medical history or increased risk of severe osteoporosis or severe osteopenia, a history of fragility fracture, and other conditions that lead to increased bone resorption

3. Osteonecrosis or avascular necrosis (AVN)

4. Multiple cysts of the femoral head (> 1cm) or cysts crossing the head-neck junction

5. Metabolic disorders which may impair bone formation (e.g., osteomalacia, osteogenesis imperfecta, parathyroid disease, rickets, etc.)

6. Severe femoral head deformities that will prevent fixation of the prosthetic resurfacing femoral head

7. Inflammatory arthritis such as rheumatoid arthritis (RA)

8. Severe proximal femoral rotational deformity in whom appropriate combined anteversion of femoral-acetabular construct is unachievable

9. Severe acetabular dysplasia/development dislocation of the hip, defined as Crowe Grade ≥ 2

10. Previous surgical intervention on index hip (e.g., treatment of hip fracture, arthroscopy)

11. Severe medical comorbidities, including:

    1. severe cardiopulmonary disease,
    2. congestive heart failure,
    3. severe liver or kidney dysfunction,
    4. end-stage renal disease,
    5. severe uncontrolled diabetes,
    6. history of IV drug use,
    7. history of hypercoagulable state or pulmonary embolism,
    8. severe lumbar spinal stenosis,
    9. vascular insufficiency, muscular atrophy, or neuromuscular disease severe enough to compromise implant stability or post-operative recovery,
    10. neuropathic arthropathy (Charcot joint),
    11. immunosuppression or other immunodeficiency disorders, e.g., diseases such as Acquired Immune Deficiency Syndrome (AIDS) or post-organ transplant and on high doses of corticosteroids.

12. Incompetent or deficient soft tissue surrounding the joint (e.g., hip abductor muscle deficiency)

13. BMI > 40

14. Active or suspected infection in or around the hip joint

15. Known or suspected metal sensitivity (e.g., jewelry) or allergy to any implant materials

16. Pregnant or plan to become pregnant during the study duration

17. Current smoker