Table 3.

Serum level creatine phosphokinase before surgery (CPK1) and 1 day after surgery (CPK2)

Creatine phosphokinase	Tubular discectomy (N = 110)	Conventional microdiscectomy (N = 106)	P-value
CPK1 (IU/l)	105.8 ± 65.5	107.1 ± 59.8	0.88
CPK2 (IU/l)	255.7 ± 209.8	268.1 ± 242.4	0.69
CPK ratio	2.75 ± 2.26	2.65 ± 2.23	0.74
Log (CPK ratio)	0.33 ± 0.31	0.31 ± 0.32	0.65

The CPK ratio (CPK2/CPK1) represents the difference within one patient. Because CPK1 and CPK2 were not normally distributed and slightly skewed, the log transform of the CPK ratio was also performed. Plus-minus values are means ± standard deviations

CPK creatine phosphokinase