Avoiding neurologic and vascular injuries with screw fixation of the tibial component in total knee arthroplasty.

This investigation determined the position of neurologic and vascular structures at risk during screw fixation of an uncemented tibial component in total knee arthroplasty relative to the cut surface of the tibial plateau. Sixteen anatomic specimens of the lower extremities were studied by systematically placing screws about the tibial plateau followed by computed tomographic scanning with three-dimensional reconstruction and anatomic dissection. The structures at risk during screw preparation and placement were the tibial nerve, popliteal artery, popliteal vein, anterior tibial artery, and common peroneal nerve with its superficial and deep branches. The application of a clock system to the cut surface of the tibial plateau with the six o'clock position defined as directly anterior and the three o'clock position defined as lateral identified the entire region between the 11 o'clock and three o'clock positions as a location where potential injury to vital structures can occur during screw placement. The risk of injury to these structures may be minimized by directing screws radially inward to avoid violation of the tibial cortex. Any penetration of the cortex between the 11 o'clock and three o'clock positions may have potentially devastating consequences because of the close proximity of neurologic and vascular structures.