G2138 HCPCS - BACK PAIN AS MEASURED BY THE VISUAL ANALOG SCALE (VAS) OR NUMERIC PAIN SCALE AT ONE YEAR (9 TO 15 MONTHS) POSTOPERATIVELY WAS LESS THAN OR EQUAL TO 3.0 OR BACK PAIN MEASURED BY THE VISUAL ANALOG SCALE (VAS) OR NUMERIC PAIN SCALE WITHIN THREE MONTHS PREOPERATIVELY AND AT ONE YEAR (9 TO 15 MONTHS) POSTOPERATIVELY DEMONSTRATED AN IMPROVEMENT OF 5.0 POINTS OR GREATER