Safety and Efficacy of the Oxford Cementless Partial Knee System

The objective of this clinical investigation is to evaluate the safety and effectiveness of the Oxford® Cementless Partial Knee System. The Oxford® Cementless Partial Knee System is intended to help the patients diagnosed with osteoarthritis or avascular necrosis gain mobility and decrease pain. All of the risks common to a conventional joint replacement are possible with this device as certain risks are associated with any invasive procedures. The study is designed to document and compare the clinical and radiographic results of the Oxford® Cementless Partial Knee System to those of the cemented Oxford® Partial Knee System (control treatment).

Prospectively controlled, randomized Investigational study. Patients are asked to come in pre-operatively, surgery, 6 weeks, 6 months, 1 year, 2 years and annually until the last patient reaches their 2 year visit. Product has not been cleared for use.

Eligibility Criteria:
Inclusion Criteria:

* Patients with a preoperative Knee Society Assessment Score of \<70
* Patients undergoing primary partial knee arthroplasty as unilateral arthroplasty or bilateral arthroplasty, simultaneously or otherwise
* Patients diagnosed with osteoarthritis or avascular necrosis limited to the medial compartment of the operative knee joint
* Male or female patients who are at least 21 years of age at the time of surgery
* Patients with full thickness cartilage loss, with or without bone loss in the medial compartment
* Patients with functionally intact Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL)
* Patients who needs to obtain relief of pain and/or improved function in their knee
* Patients with fixed flexion deformity \<15 degrees
* Patients who are able to follow postoperative care instructions
* Patients who are willing and able to return for scheduled follow-up evaluations
* Patients in which natural alignment can be restored
* Patients who have completed a valid, Institutional Review Board (IRB) approved Informed Consent Form
* Patients with child-bearing potential who voluntarily agree to prevent pregnancy for 2 years following device implantation

Exclusion Criteria:

* Patients with a preoperative Knee Society Assessment Score of greater than or equal to 70
* Patients in which the device would be used to revise a failed prosthesis
* Patients who are less than 21 years of age, at the time of surgery
* Disease or damage to the lateral part of the knee that in the investigator's opinion contraindicates a partial knee replacement
* Patients diagnosed with rheumatoid arthritis or other forms of inflammatory joint disease
* Patients diagnosed with a failed upper tibial osteotomy in the operative knee
* Patients diagnosed with post-traumatic arthritis after tibial plateau fracture
* Patients who have had a patellectomy
* Patients with a flexion deformity \> 15 degrees
* Patients with a fixed varus deformity \> 15 degrees
* Patients who have rapid joint destruction, marked bone loss or bone resorption apparent on roentgenogram
* Patients with a fused knee on operative side(s)
* Patients who have active or suspected infection, local or systemic that, in the opinion of the investigator, may put patients at undue risk
* Patients with pre-existing condition(s) that may interfere with the survival of the implants or their outcomes, including:

  * Sickle Cell Anemia
  * Lower extremity muscular atrophy
  * Neuromuscular disease
  * Vascular insufficiency
  * Metabolic Disorders which impair bone formation
  * Paget's Disease
  * Charcot's Disease
  * Osteomalacia
  * Severe Osteoporosis
* Patients with clinical conditions that may limit follow-up (in the opinion of the investigator) including:

  * Immunocompromised conditions (i.e. HIV)
  * Hepatitis
  * Tuberculosis
  * Neoplastic disease such as cancer of the prostate, lung, stomach, cervix, etc.
* Chronic renal failure
* Organ transplant (i.e. heart, liver, lung, etc.) recipients
* Known disease process that in the opinion of the investigator may limit long term (4 year) follow-up (i.e. multiple sclerosis, leukemia, lymphoma, etc.)
* Patients diagnosed with Parkinson's or Alzheimer's Disease
* Patients who have had an above-knee amputation in the contralateral leg
* Instability or deformity of the ligaments and/or surrounding soft tissue, which would preclude stability of the prostheses
* Patients with a known metal allergy
* Prisoners or, individuals who are known to be abusing drugs or alcohol or are mentally incompetent
* Patients who have received systemic steroids within the past 6 months or steroid injections into the affected knee within the previous 6 weeks prior to enrollment
* Patients who are pregnant
* Patients with severe valgus or varus knees (valgus or varus angulation of more than 20 degrees) where collateral ligament, iliotibial band, or popliteal release is required
* Patients who refuse to sign the IRB approved Informed Consent Form
* Participation in an interventional clinical research study procedure, other than a bilateral knee arthroplasty in this study, within the past 12 months
* Patients with a history of osteomyelitis or sepsis of the index knee
* Patients who require patellar resurfacing
* Patients who are not skeletally mature
* Patients who have had a total hip replacement procedure \< 18 months prior to entering the study
* Patients who have had a contralateral non-study knee replacement procedure \< 18 months prior to entering the study
* Patients who are found intraoperatively to have inadequate bone stock or other conditions that contraindicate a partial knee replacement