TABLE V.

Gap Progression at the 1 and 2-Year Follow-ups^*

Comparison	PTC†			PPS‡
	Filled	Persistent	Progressed	Filled	Persistent	Progressed
A. Between postop. and 1-year radiographs
Zone 1	3	0	0	0	0	0
Zone 2	2	1	0	2	0	0
Zone 3	0	0	0	1	2	0
Total	5	1	0	3	2	0
B. Between postop. and 2-year radiographs
Zone 1	3	0	0	0	0	0
Zone 2	2	0	1	2	0	0
Zone 3	0	0	0	2	0	0
Total	5	0	1	4	0	0

^*PTC = porous titanium coating, and PPS = porous plasma spray. The values are given as the number of gaps.

^†6 zones in 6 patients.

^‡5 zones in 4 patients for A; 4 zones in 3 patients for B.