Constrained Condylar Knee (CCK) Revision Arthroplasty

A constrained condylar knee (CCK) — also called a varus-valgus constrained (VVC) implant — is the intermediate articulation on the revision constraint ladder. It is chosen when the collateral ligaments cannot provide coronal stability and a posterior-stabilised (PS) implant will not balance the gaps, but the deficiency is not severe enough to justify a rotating hinge. Move up the ladder one rung at a time — cruciate-retaining, then posterior-stabilised, then CCK, then rotating hinge, then fixed hinge — selecting the lowest constraint that solves the instability pattern.

Setup. Supine on a radiolucent table with a bump under the ipsilateral hip, the leg draped free and a tourniquet high on the thigh. A sterile bump or triangle holds the knee at 90 degrees of flexion for most of the procedure, with the ability to extend for gap measurement. Plan the exposure and fixation beforehand on full-length standing radiographs and a CT for bone loss assessment.

The goal is to remove the failed components without harming the extensor mechanism, reconstruct the metaphyseal bone loss, confirm that the instability or gap mismatch genuinely requires a constrained articulation, and implant a stemmed CCK with metaphyseal cones. The exposure — a deep medial parapatellar arthrotomy with an extensile option — is the foundation of a safe revision and is laid out as the first steps below.

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Rehabilitation | Phase | Timing | Weight-bearing | Therapy goals | |-------|--------|----------------|---------------| | 1 | 0–6 weeks | Protected 20–50 percent with crutches or walker; hinged brace locked in extension for ambulation, unlocked for ROM | Passive and active-assisted ROM from day 1, aiming for 0–90 degrees by week 2; quadriceps sets and straight-leg raises | | 2 | 6–12 weeks | Progressive as tolerated once radiographic metaphyseal integration; brace weaning | Stationary cycling, pool therapy, progressive strengthening; independent ambulation by 12 weeks | | 3 | 3–6 months | Full weight-bearing | Advanced strengthening and proprioception; return to low-impact activities (walking, swimming, cycling); high-impact activities discouraged permanently | Radiographic surveillance at 6 weeks, 3 months, 1 year, 2 years, 5 years and 10 years monitors for component migration, osteolysis and post wear. Complications

The CCK articulation. The constrained condylar knee features a tall, rectangular tibial post that engages a deepened femoral box. Post height and box geometry limit varus-valgus angulation to approximately 2 to 4 degrees and restrict rotation to approximately 5 to 8 degrees. This provides coronal stability when the collaterals are incompetent while still allowing some rotation, which reduces torsional stress at the fixation interfaces compared with a fixed hinge. Why stems and metaphyseal fixation are mandatory. The constrained post-box articulation transmits coronal shear and torsional moments to the implant-bone interface. Without stems and metaphyseal cones or sleeves these forces cause early aseptic loosening. Every CCK revision therefore includes cemented or cementless diaphyseal stems (minimum 100 to 150 mm), porous metaphyseal cones or sleeves in both tibia and femur when AORI type 2 or 3 bone loss is present, and highly cross-linked polyethylene inserts when available to reduce post wear. Bone loss — the AORI classification. The Anderson Orthopaedic Research Institute (AORI) classification guides metaphyseal reconstruction, and CCK revisions almost always involve type 2 or 3 defects that necessitate cones or sleeves.

Relevant anatomy in the revision setting. The MCL originates from the medial epicondyle and inserts on the proximal tibia approximately 5 to 7 cm distal to the joint line; in revision it is often attenuated, avulsed or scarred from prior surgery or instability. The LCL runs from the lateral epicondyle to the fibular head and is frequently incompetent in valgus deformity or after multiple revisions. The extensor mechanism — the patellar tendon insertion on the tibial tubercle — is the structure most at risk during tibial component extraction. Key evidence. Long-term single-centre series and registry data show solid survivorship for CCK revision TKA when stems and cones are used, with polyethylene post wear the dominant mid-term concern. Posterior-stabilised articulations show superior survivorship when the ligaments can be balanced, which reinforces reserving CCK for genuine collateral incompetence or irreducible gap mismatch. The full references are listed below.