Biomechanical Analysis of the Rebar Technique for Tibial Defects in Total Knee Arthroplasty

Background

Tibial defects in total knee arthroplasty require appropriate fixation for stability. Smaller defects are treated with cement or a screw and cement construct (rebar technique), while larger defects may require augments. Prior studies validate screws and cement for small defects but caution against use beyond 5 mm. This study compares the stiffness and subsidence of cement-only vs rebar techniques in larger contained and uncontained defects.

Methods

Thirty-two proximal tibial composite bone analogs were divided into 2 groups: (1) Cemented and (2) Rebar, with subgroups for contained and uncontained defects (8 each). Tibial defects mimicked Anderson Orthopaedic Research Institute Bone Defect Classification T1 and T2A classifications. Tibial baseplates were implanted using either cement alone or with a rebar technique (2 6.5 mm cancellous screws). Samples were mounted to a testing fixture simulating heel strike and underwent 10,000 cycles at 1 Hz. Tracking points were placed on each sample to measure displacement. Load and displacement data from the test frame were also collected.

Results

In the contained defect subgroup, rebar showed higher stiffness than cement alone, but the difference was not statistically significant (P = .349) and both groups had similar micromotion (P = .989). In uncontained defects, cement-only showed slightly higher stiffness than rebar (P = .655), with no statistical difference in micromotion (P = .893). Uncontained defects exhibited significantly more micromotion than contained defects (P = .0018, P = .0055).

Conclusions

Rebar and cement-only techniques demonstrated similar biomechanical performance in tibial defects up to 1 cm. The cement and screw technique remains a viable option but may not be necessary in primary and revision total knee arthroplasty.