Tibial cut and knee prosthesis: respecting anatomy
Dr. Vallotton discusses the importance of the tibial cutting angle in partial knee replacement surgery. He advocates for respecting the natural obliquity of the joint space, allowing for better implant stability and avoiding subluxations. This is a technical but essential procedure to ensure the success of the surgery.
Doctors
Topics
Treatments
Advice
- Dr Jacques Vallotton
- Definition of the tibial angle
- Custom tibial cut
- Risks of standardized cuts
- Unicompartmental prosthesis
- Respect for the joint axis
- Respect the patient's anatomy
- Measure the tibial varus angle
- Follow the joint space
Unicompartmental prosthesis: respecting anatomy for stability
In unicompartmental knee replacement, the quality of the result depends first of all on respecting the anatomy. The tibio-femoral joint space is often oblique in varus knees; imposing a 90° tibial cut on the mechanical axis can disrupt this natural geometry. By following the patient's own obliquity, the implant remains wedged, the menisco-prosthetic interface functions without parasitic sliding and the tibia does not tend to subluxate.
This logic prioritizes function and stability, conditions for smooth recovery and lasting satisfaction.
Understanding tibial joint line obliquity
The more pronounced the varus curvature, the more oblique the knee joint space. The tibial cut should not align with the wear cup, but with the opposite healthy cartilage. It is this anatomical reference that guides the orientation of the prosthetic bearing surface. By respecting the patient's own angle, the implant follows the native mechanics of the joint, avoiding abnormal constraints and tilting phenomena.
The goal is simple: to reproduce the physiology of the preserved knee rather than imposing an artificial geometry.
Respect for anatomy is the guarantee of the absence of subluxation.
Measuring the tibial varus angle: a simple and reproducible method
The approach consists of tracing the mechanical axis of the tibia (from the tibial spines to the center of the ankle), then the line exactly following the healthy cartilage of the opposite compartment. The perpendicular to this line, crossing the mechanical axis, defines the tibial varus angle to be respected during the cut. This reproducible measurement aligns the implant with the actual functional joint space of the patient's knee.
A cut faithful to this angle stabilizes the prosthetic plate and limits the constraints on the spine mass.
Risks of a 90° cut: slippage and subluxation
Cutting perpendicular to the mechanical axis on a varus knee accentuates the gap between the prosthesis and the anatomical joint space. In the medium term, the spine mass can come into conflict with the edge of the implant, causing slippage, wear, and instability. In historical series, these "surprises" have led to changes in the design of the implants; the best response remains to respect the native obliquity.
Aligning the prosthesis with the patient's joint space reduces the risk of subluxation and preserves kinematics.
It is essential to follow the natural obliquity of the joint space.
What this changes for the patient: mobility without instability
A prosthetic support parallel to the joint space makes kinematics more fluid: flexion is free, medial stability is better preserved and the sensation of "catching" disappears. Rehabilitation then focuses on strengthening and proprioception, without having to compensate for an orientation error. This biomechanical coherence results in more confident walking and activities resumed more calmly.
Planning and monitoring: integrating anatomy into each step
3D planning and surgical templates help reproduce the angle determined preoperatively. Postoperatively, clinical and radiological analysis verifies alignment, while physiotherapy consolidates function. Respecting anatomy is not a dogma: it is a concrete strategy to achieve stability, comfort, and longevity of the implant.
Français 
English (UK)