OBJECTIVETo compare the clinical effects of isthmic spondylolisthesis by a single cage or double cages interbody fusion combined with pedicle screw fixation.

METHODSThe clinical data of 172 patients with isthmic spondylolisthesis underwent surgery from March 2000 to August 2008 were retrospectively analyzed. All cases underwent posterior pedicle screw fixation and interbody fusion, 89 cases with single cage fusion and 83 cases with double cages fusion. In single cage group, there were 56 males and 33 females, aged from 18 to 63 years old with an average of(41.60±8.20) years;25 cases were in L4 segment and 64 cases were in L5;according to the Meyerding standard, 32 cases were I degree, 46 cases were II degree and 11 cases were III degree. In double cage group, there were 49 males and 34 females, aged from 20 to 65 years old with an average of(43.30±6.39) years;21 cases were in L4 and 62 cases were in L5;according to the Meyerding standard, 25 cases were I degrees, 45 cases were II degree, and 13 cases were III degree. The operative time, intraoperative blood loss, postoperative drainage volum, bone fusion rate, intervertebral space height and the improvement of clinical symptoms were compared between two groups.

RESULTSAll the operations were successful and all patients were followed up for 18 to 83 months with an average of 4 years and 3 months. The operative time, intraoperative blood loss, postoperative drainage volume in single cage group were less than of double cage group(<0.05). Two weeks after operation, the intervertebral space height was significantly increased in two groups(<0.05), and there was no significant difference at the last follow-up between two groups. At 16 months after operation, all bone grafts of patients got bony fusion by X-rays. At the last follow-up, there were no statistically significant difference in JOA, ODI and VAS score between two groups, no pedicle screw loosening and breaking were found.

CONCLUSIONSSingle cage interbody fusion combined with pedicle screw fixation is as effective as with double cages interbody fusion in treatment of isthmic spondylolisthesis, it has the advantages of short operative time and less blood loss.