Slocum originally used a a closing wedge osteotomy as his Tibial Plateau Levelling Osteotomy. He later decided that just rotating the articular surface produced a better cosmetic result as shown by the 'sit test' and the resulting repaired osteotomy was more stable than the closing wedge. There is little or no evidence that clinical outcomes are better using a radial cut over a closing wedge. Cynics might argue that the radial cut osteotomy required a patented saw and a patented plate which resulted in better financial outcomes than the closing wedge procedure.
It is certainly the case that the Radial Cut Slocum TPLO is the single most common form of tibial plateau geometry altering surgery. Since the patent expired on the Slocum plate there has been something of a 'feeding frenzy' by manufacturers offering new plates.