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Fusion Rates and Subsidence of Morselized Local Bone Grafted in Titanium Cages in Posterior Lumbar Interbody Fusion Using Quantitative Three-Dimensional Computed Tomography Scans

Lee, Jae Hyup MD, PhD*†; Jeon, Do-Whan MD‡; Lee, Suk-Jae MD‡; Chang, Bong-Soon MD, PhD*‡; Lee, Choon-Ki MD, PhD*‡

doi: 10.1097/BRS.0b013e3181c4baf5
Clinical Case Series

Study Design. Prospective, controlled study.

Objective. To determine fusion rates, cage to bone contact area ratios, and subsidences using titanium cages filled with a local bone graft for posterior lumbar interbody fusion (PLIF).

Summary of Background Data. PLIF using decompressed local bone inserted in titanium cages combined with pedicle screw fixation is a popular procedure for treating lumbar spine degeneration. There is no report about cage to bone contact area ratios using titanium cages filled with a local bone graft for PLIF.

Methods. PLIF using a titanium cage filled with excised laminar and facet joint bone with pedicle screw fixation was performed in 54 (78 levels) consecutive patients. Mean age at the time of surgery was 62.5 years. Radiographic assessments of posterior and anterior disc heights were performed. Three-dimensional thin-section computed tomography assessments of cage subsidences, fused area ratios of local bone inside cages, and overall fusion rates were analyzed.

Results. Mean values of anterior and posterior disc heights at 1 year after surgery were significantly greater than mean preoperative disc heights. The fusion rate of cages over both upper and lower segment endplates was 96.2%. The ratios of fused areas of local bone inside cages exposed to upper and lower segment endplates were 46.7% and 52.2% in the coronal plane and 46.4% and 49.9% in the sagittal 3-dimensional computed tomography plane, respectively. And, subsidences of titanium cages at upper and lower segment endplates were 1.26 mm and 0.72 mm in the coronal plane and 1.04 mm and 0.53 mm in the sagittal plane, respectively.

Conclusion. The ratio of fused area of local bone inside cages at regions exposed to endplates was <50%, which is insufficient for physiologic load transmission. The authors recommend that additional bone should be grafted into the disc space or new bone bonding interbody spacer should be considered.

The ratio of fused area of local bone inside cages at regions exposed to endplates was <50% in PLIF, which is insufficient for physiological load transmission. The authors recommend that additional bone should be grafted or new bone bonding interbody spacer should be considered.

From the *Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul, Korea; †SMG-SNU Boramae Medical Center, Seoul, Korea; and ‡Seoul National University Hospital, Seoul, Korea.

Acknowledgment date: October 28, 2008. Revision date: September 2, 2009. Acceptance date: September 11, 2009.

The device(s)/drug(s) is/are FDA-approved or approved by the corresponding national agency for this indication.

No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Institutional Review Board approval was obtained before beginning the study.

Address correspondence and reprint requests to Choon-Ki Lee, MD, PhD, Department of Orthopaedic Surgery, Seoul National University Medical College, Seoul National University Hospital, 28 Yoengon-Dong, Jongno-Gu, Seoul 110-744, Korea; E-mail: choonki@plaza.snu.ac.kr.

© 2010 Lippincott Williams & Wilkins, Inc.