Table 1. Summary of parametric differences, advantages and disadvantages between the three published methods for JSW measurement: CLG (11), LYN (12), and SFR (13).

JSW method	Joint space definition			Distance transform
	Dilation	Erosion		Function	Advantages	Disadvantages
CLG	25**	25**		/dt_background	/close function faster than /dilation & /erosion sequence but limited to similar amplitudes	Same as SFR
LYN	25	31		/dt_object	Conservative definition of joint space via larger erosion than dilation reduces sensitivity to joint angle (see Figure 1)	/dt_object function sensitive to boundary conditions. Values on boundary of joint space may be truncated
SFR	20	20		/dt_background	/dt_background function reduces sensitivity to boundary effects; dilation/erosion of similar amplitudes create a joint space volume that looks closer to intuitive definition	Larger joint space definition induces more sensitivity of DT to joint alignment/angle in DT at boundaries (see Figure 1)
Spectra consensus	20	26		/dt_spacing*	Conservative joint definition less sensitive to joint alignment/placement: new function /dt_spacing less sensitive to boundary conditions

*, indicates function available since 2018 in the manufacturer’s Image Processing Language IPL v5.42; **, indicates use of a single-step closing function in place of separate dilation/erosion steps. JSW, joint space width; SFR, University of California San Francisco; CLG, University of Calgary; LYN, University of Lyon.