Very low-dose computed tomography for planning and outcome measurement in knee replacement

TLDR

Surgeons require accurate three‑dimensional measurements for knee‑replacement planning, but conventional CT delivers higher radiation than long‑leg standing radiographs, and dose variability across centres demands tighter control. We refined the CT protocol to lower the effective dose to that of a single long‑leg standing radiograph. The reduced dose increases patient acceptability of CT and enables surgeons to precisely assess how implant positioning affects outcomes.

Abstract

Surgeons need to be able to measure angles and distances in three dimensions in the planning and assessment of knee replacement. Computed tomography (CT) offers the accuracy needed but involves greater radiation exposure to patients than traditional long-leg standing radiographs, which give very little information outside the plane of the image. There is considerable variation in CT radiation doses between research centres, scanning protocols and individual scanners, and ethics committees are rightly demanding more consistency in this area. By refining the CT scanning protocol we have reduced the effective radiation dose received by the patient down to the equivalent of one long-leg standing radiograph. Because of this, it will be more acceptable to obtain the three-dimensional data set produced by CT scanning. Surgeons will be able to document the impact of implant position on outcome with greater precision.