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Mismatch Between Proximal Rod Contouring and Proximal Junctional Angle: A Predisposed Risk Factor for Proximal Junctional Kyphosis in Degenerative Scoliosis

Yan, Peng MD, PhD; Bao, Hongda MD, PhD; Qiu, Yong MD; Bao, Mike BS; Varghese, Jeffrey J. BS; Sun, Xu MD, PhD; Liu, Zhen MD, PhD; Zhu, Zezhang MD, PhD; Qian, Bangping MD, PhD; Zheng, Minghao PhD; Zhu, Feng MD, PhD

doi: 10.1097/BRS.0000000000001883

Study Design. A retrospective study.

Objective. To investigate whether the mismatch between proximal junctional angle (PJA) and the proximal rod contouring contributed to the occurrence of postoperative proximal junctional kyphosis (PJK) in degenerative scoliosis.

Summary of Background Data. PJK is one of the complications in the treatment of degenerative scoliosis, the postoperative PI-LL mismatch and the increased rod stiffness are supposed to be the etiology of PJK. However, the impact of rod contouring on PJK has not been fully illustrated.

Methods. A retrospective study was performed on 27 consecutive degenerative scoliosis patients (three males and 24 females) who underwent corrective surgery with more than 2-year follow-up. Radiographic parameters included proximal rod contouring angle (PRCA) and PJA at the three time-points. The subjects were divided into two groups: PJK group and non-PJK group with the definition of PJK as a PJA more than 10°. The mismatch between PRCA and post-op PJA, defined as the difference between PRCA and postop PJA of more than 5°, was then compared with PJK and non-PJK group.

Results. The patients’ mean age was 60.48 ± 6.47 years old with a mean Cobb angle of 40.89 ± 14.33°. Twelve patients, with a mean PJA of 18.67 ± 5.31° at the last followup, were stratified into the PJK group, while the remaining 15 patients, with a mean PJA of 5.33 ± 2.47, were placed into the non-PJK group. A significant difference in the mismatch between post-op PJA and PRCA was observed between PJK and non-PJK group (8.83 ± 5.07° vs. 4.07 ± 2.91°, P = 0.005). Meanwhile the difference of mismatch between preop PJA and PRCA showed no statistical significance (5.16 ± 4.24° vs. 3.00 ± 2.48°, P = 0.109).

Conclusion. Mismatch between rod contouring and postoperative proximal spinal curve may be a predisposed risk factor for PJK in degenerative scoliosis.

Level of Evidence: 4

*Department of Spine Surgery, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China

Geisel School of Medicine, Dartmouth College, Hanover, NH

Spine Service, Hospital for Special Surgery, New York, NY

§School of Surgery, Orthopeadic Research, University of Western Australia, Perth, Australia.

Address correspondence and reprint requests to Feng Zhu, MD, Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Zhongshan Road 321, Nanjing 210008, China; E-mail:

Received 22 February, 2016

Revised 14 May, 2016

Accepted 10 June, 2016

The manuscript submitted does not contain information about medical device(s)/drug(s).

Jiangsu Peek projects for talents (Grant No. WSW-005) funds were received in support of this work.

No relevant financial activities outside the submitted work.

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