Cemented Versus Cementless Unicompartmental Knee Arthroplasty

Not Applicable

Completed

Conditions: Osteoarthritis, Knee

Registration Number: NCT05935878

Lead Sponsor: Oxford University Hospitals NHS Trust

Brief Summary: Unicompartmental knee replacement for selected cases of osteoarthritis is less invasive than total knee replacement. It gives better range of movement; patients stay for shorter time in the hospital and have a more natural feel than total knee replacement. Usually, the implant is fixed in the bone using bone cement. However, there are potential disadvantages of using bone cement. The operation takes longer; cement can get squeezed out into the surrounding tissues and may interfere with function. To avoid these problems, the implant can be fixed without cement. Cementless components have a special coating to encourage bone in-growth and fixation. Although the investigators believe cementless fixation will be at least as good as cemented fixation, there is a risk that it could be worse and might result in loosening.

The aim of this study is therefore to compare the outcome of cemented and cementless unicompartmental knee replacement.

Detailed Description: Design: A prospective, randomised trial to compare the outcome of cemented and cementless unicompartmental knee replacement.

Size: 40 subjects in total will be recruited with 20 in each arm.

Methods: Patients will be recruited from the routine waiting list for unicompartmental knee replacement at the Nuffield Orthopaedic Centre. All subjects will have the procedure explained and be fully consented prior to the procedure.

Randomisation: Patients will be randomly allocated to receive either a cemented or cementless Oxford Unicompartmental Knee Replacement. This will be performed using a randomisation program based on optimisation (Minim). Subjects will be stratified according to sex and age.

Operation: All subjects will undergo the same surgical approach. 0.8mm Tantalum marker balls will be placed at standardised sites on the femur and tibia in all cases. All cemented components will be secured using the same cement. Cementless components have a hydroxy-appatite coating to facilitate bone ingrowth.

Follow-up: All patients will be followed up at 0, 3, 6, 12, 24, 60, and 120 months with clinical and radiological assessment. Clinical assessment will involve documentation with the Oxford Knee Score. Patients will undergo radiostereometric analysis and fluoroscopy to study implant migration and occurence of radiolucency, respectively.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 47

Inclusion Criteria

Healthy Subjects with osteoarthritis of knee fulfilling the standard indications for an Oxford Unicompartmental Knee Replacement.
American Society of Anaesthesiologists (ASA) Score of 1 to 3.

Exclusion Criteria

Subjects with severe limiting systemic illness (i.e. ASA > 3).
Subjects who are too large for radiostereometric analysis to be carried out.
Subjects who have had previous open surgery or anterior cruciate ligament (ACL) reconstruction on the same knee.

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Radiostereometric Analysis Examination - Translations	Patients will be examined 120 months post surgery.	Patients will have weight-bearing stereoradiographs. These stereoradiographs will be analysed using model-based radiostereometric analysis which will allow the migration of the components relative to the bone to be determined. Three-dimensional translations will be measured in millimetres. The component position at the post-operative timepoint was used as the baseline for measurement of migration. Migration can be interpreted as: * X translation: Positive (+ve) = Medial; Negative (-ve) = Lateral * Y translation: Positive (+ve) = Superior; Negative (-ve) = Inferior * Z translation: Positive (+ve) = Anterior; Negative (-ve) = Posterior
Radiostereometric Analysis Examination - Rotations	Patients will be examined at 120 months post surgery.	Patients will have weight-bearing stereoradiographs. These stereoradiographs will be analysed using model-based radiostereometric analysis which will allow the migration of the components relative to the bone to be determined. Three-dimensional rotations will be measured in degrees.The component position at the post-operative timepoint was used as the baseline for measurement of migration. Migration can be interpreted as: * For the Femoral Component\* X Rotation: Positive (+ve) = Increased Flexion; Negative (-ve) = Decreased Flexion Y Rotation: Positive (+ve) = Internal Rotation; Negative (-ve) = External Rotation Z Rotation: Positive (+ve) = Valgus; Negative (-ve) = Varus * For the Tibial Component\* X Rotation: Positive (+ve) = Reduced Slope; Negative (-ve) = Increased Slope Y Rotation: Positive (+ve) = Internal Rotation; Negative (-ve) = External Rotation Z Rotation: Positive (+ve) = Valgus; Negative (-ve) = Varus
Radiostereometric Analysis Examination - Maximum Total Point Motion	Patients will be assessed at 6 months post surgery.	Patients will have weight-bearing stereoradiographs. These stereoradiographs will be analysed using model-based radiostereometric analysis which will allow the migration of the components relative to the bone to be determined. Maximum Total Point Motion (MTPM - defined as the length of the translation vector of the point of the component model that has migrated the most) will be measured in millimetres.
Radiographic Examination	Patients will be examined at 120 months post surgery.	Fluoroscopic imaging will be used to study the occurence of radiolucencies beneath the components. Anteroposterior radiographs will be analysed to assess the presence and position of radiolucencies. Radiolucencies will be graded as either 'no radiolucency present', 'partial radiolucency', or 'complete radiolucency'.
Clinical Assessment	Patients will be assessed at 120 months post surgery.	Clinical assessment will involve documentation with the Oxford Knee Score. The score will be calculated on a scale of 0 (worst) to 48 (best).