Enrollment goals not being met.

The purpose of this study is to compare the 10-year Knee Society Score (KSS) functional results of the Triathlon PKR Unicondylar Knee to the 10-year Knee Society Score (KSS) functional results of the Triathlon Cruciate Retaining (CR) Total Knee.

Inclusion Criteria:

• The subject is a male or non-pregnant female 21-75 years of age at the time of enrollment.
• The subject requires a primary cemented unicompartmental knee replacement.
• The subject has a diagnosis of osteoarthritis (OA) or posttraumatic arthritis (TA).
• The subject has clinically intact cruciate and collateral ligaments and no ligamentous instability is present.
• The subject has less than 10 degrees of flexion contracture and greater than 90 degrees of flexion.
• The subject's preoperative mechanical alignment is less than 15 degrees of varus and 15 degrees of valgus.
• The subject has signed the Institutional Review Board (IRB) approved study specific Informed Patient Consent Form.
• The subject is willing and able to comply with postoperative scheduled clinical and radiographic evaluations and rehabilitation.

Exclusion Criteria:

• The subject has inflammatory arthritis or avascular necrosis(AVN).
• The subject is obese, BMI > 35.
• The subject has a history of total or unicompartmental (contralateral compartment and/or patellofemoral joint) reconstruction of the affected joint.
• The subject has a history of anterior cruciate ligament (ACL) reconstruction.
• The subject has had a high distal femoral, or proximal tibial osteotomy.
• The subject has a mental, neuromuscular or neurosensory disorder, which would create an unacceptable risk of prosthesis instability, prosthesis fixation failure, or complications in post-operative care and/or limit the ability to assess the performance of the device.
• The subject has a systemic or metabolic disorder leading to progressive bone deterioration that the surgeon feels would affect the overall outcome of the study.
• The subject is immunologically suppressed, or is receiving chronic steroids (>30 days duration).
• The subject has a known sensitivity to device materials.
• The subject's bone stock is compromised by disease and/or infection which cannot provide adequate support and/or fixation to the prosthesis.
• The subject's bone stock is compromised by a prior implantation which cannot provide adequate support and/or fixation to the prosthesis.
• The subject has an active or suspected latent infection in or about the knee joint.
• The subject is a prisoner.

This study required that all operative site adverse events, regardless of seriousness, and serious systemic events, be reported from enrollment to the 10-year postoperative time interval.

The date of occurrence, date diagnosed, type of complication/adverse event and treatment were collected.

After 13-years the enrollment goal was not met. This led to a protocol amendment to include retrospective cases. These cases were combined with the initial prospective cases and followed prospectively for the planned observation time. This study does not compare prospective to retrospective cases. The retrospectively enrolled cases were followed prospectively and there were no retrospective cases that reached the 10-year time point, only 12 prospective cases had 10-year data.