The Effect of Posterior Lumbar Interbody Fusion After Posterolateral Fusion in Degenerative Spondylolisthesis

Nah, Ki Ho; Shin, Jae Hyuk; Choi, Nam Yong; Lee, Yong Sun; Ha, Kee Yong

Abstract

PURPOSE
To determine the necessity of an additional posterior lumbar interbody fusion (PLIF) after a posterolateral fusion (PLF) for the treatment of degenerative spondylolisthesis (DS). MATERIALS AND METHODS: A retrospective study, after a minimum follow-up of 2 years was conducted on forty patients who underwent a single level decompression and instrumented fusion for DS with spinal stenosis at the L4-5 level. A PLF was performed in 21 patients, and a circumferential fusion (CF) with an additional PLIF in 19 patients. According to the fusion methods and preoperative segmental mobility, the patients were divided into four groups; s-PLF group (PLF in the stable group, n=13), s-PLIF group (CF in the stable group, n=11), u-PLF group (PLF in the unstable group, n=8), and u-PLIF group (CF in the unstable group, n=8). Clinical and radiographic comparisions between the PLF and PLIF groups were performed. RESULTS: The mean decrements of Oswestry Disability Index (Visual Analog Scale) scores were 29% (5.5), 29% (5.9), 22% (2.6) and 42% (5.9) respectively for the s-PLF, s-PLIF, u-PLF and u-PLIF groups, and a statistical difference was found only between the u-PLF and u-PLIF groups (ODI: p=0.032, VAS: p=0.004). Fusion rates were 92%, 100%, 88% and 100% respectively. The mean slip angle increments were serially 2.5 degrees, -3.1 degrees, -1.5 degrees and -0.3 degrees, and the mean percent slip decrements were 6.7%, 8.7%, 5.1% and 3.7%, and the mean disc height increments were -0.4 mm, 1.8 mm, 0.5 mm and 3.0 mm, and the mean lumbar lordosis increments were 8.6 degrees, 4.7 degrees, -1.9 degrees and 1.9 degrees and the mean sacral tilt increments were 3.8 degrees, 3.4 degrees, -1.3 degrees and 0.9 degrees. Statistical differences were found only between the s-PLF and s-PLIF groups in slip angle increments (p=0.029) and between the s-PLF and s-PLIF groups (p=0.043) and between the u-PLF and u-PLIF groups (p=0.042) in disc height increments. CONCLUSION: PLF alone provided successful clinical outcome in stable group, but CF provided better clinical outcomes in the unstable groups. This study suggests that preoperative segmental mobility may be a criterion to determine whether or not an additional PLIF is necessary in the treatment of lumbar DS.