Unicompartmental Knee Arthroplasty - Wheeless' Textbook of Orthopaedics

- Discussion:
    - unicompartmental arthroplasty serves a specific nitch for knees that are too severe for arthroscopic management of medial DJD (see mosaicplasty)
            but are not severe enough for total knee replacement;

- Technical Goals:
     - balance the flexion and extension gaps;
     - balance the forces between the medial and lateral compartments (in both flexion and extension)
     - maintain anatomic alignment;
     - references:
           - Alignment Influences Wear in the Knee after Medial Unicompartmental Arthroplasty.
           - Unicompartmental knee arthroplasty for DJD of the knee. Remaining postoperative flexion contracture affecting overall results.
           - Lateral tibiofemoral compartment narrowing after medial unicondylar arthroplasty.
           - Alignment influences wear in the knee after medial unicompartmental arthroplasty.
           - The effect of leg alignment on the outcome of unicompartmental knee replacement

     - surgical exposure:
           - minimal elevation of MCL

     - tibial component:
           - many systems base alignment of the femoral component off of the tibial component;
           - tibial component must be aligned in the true AP plane (no internal rotation, no varus);
           - sizing: tibial component needs to cover the entire tibial peripheral cortex;

           - references:
                 - Stress fracture of the medial tibial plateau after minimally invasive unicompartmental knee arthroplasty. A Report of 2 Cases
                 - Rapid Poly Failure of Unicondylar Tibial Components Sterilized w/ Gamma Irradiation in Air and Implanted After a Long Shelf Life.
                 - Posterior Slope of the Tibial Implant and the Outcome of Unicompartmental Knee Arthroplasty.
                 - Influence of the tibial slope on tibial translation and mobility of non-constrained total knee prosthesis
                 - Patient, implant, and alignment factors associated with revision of medial compartment unicondylar arthroplasty.
                 - Proximal tibial meniscal slope: a comparison with the bone slope

     - femoral component:
           - must be positioned on adequate base of bleeding subchondral bone;
                    - potential conflict in need to mill deep enough to get down to subchondral bone, while maintaining flexion and extension balance;
           - must be position anterior enough for adequate coverage in full extension, while avoiding patellar impingement;
           - must be centered over native anatomy of the medial femoral condyle;
           - must have maximal congruent contact with tibial component in full flexion and extension;
           - avoid tendency to internally rotate the femoral component;
                    - with the knee in flexion, slight internal rotation may not seem important, but with knee extension the femur will further internally rotate,
                               (tibia externally rotates) which will cause the femoral component to be non congruent over the tibia component;
                    - anatomy and kinematics of the knee joint
           - references:
                 - Influence of rotatory malposition of femoral implant in failure of unicompartimental medial knee prosthesis
                 - Patellar Impingement Following Unicompartmental Arthroplasty.
                 - Relative positions of the contacts on the cartilage surfaces of the knee joint
                 - The influence of presence and severity of pre-existing patellofemoral degenerative changes on outcome of Oxford medial UKR.

     - cement technique:
           - the cement technique needs to be as optimal as with total knee.
           - consider extending the "trough" for the tibial component anteriorly;

           - Posteromedial compartment cement extrusion after unicompartmental knee arthroplasty treated by arthroscopy: a case report.

Three cases of pseudogout complicated with unicondylar knee arthroplasty.

Minimally invasive unicondylar arthroplasty: eight-year follow-up.

Unicompartmental knee arthroplasty: long-term results.

Minimally invasive unicondylar arthroplasty: eight-year follow-up.

Medial Unicompartmental Knee Arthroplasty with the Miller-Galante Prosthesis.

Unicompartmental knee arthroplasty. 2- to 12-year results in a community hospital.

Results of Unicompartmental Knee Arthroplasty at a Minimum of Ten Years of Follow-up.

- Vanguard Biomet Knee

- Repicci Unicondylar Replacement

Alternatives to Total Knee Replacement: Autologous Hamstring Resurfacing Arthroplasty

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