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Proximal Junctional Kyphosis in Primary Adult Deformity Surgery: Evaluation of 20 Degrees as a Critical Angle

Bridwell, Keith H. MD*; Lenke, Lawrence G. MD*; Cho, Samuel K. MD; Pahys, Joshua M. MD§; Zebala, Lukas P. MD*; Dorward, Ian G. MD*; Cho, Woojin MD, PhD*; Baldus, Christine RN, MHS*; Hill, Brian W. MD∥,¶; Kang, Matthew M. MD

doi: 10.1227/NEU.0b013e31828bacd8
Research-Human-Clinical Studies

BACKGROUND: Multiple studies have reported on the prevalence of proximal junctional kyphosis (PJK) following spinal deformity surgery; however, none have demonstrated its significance with respect to functional outcome scores or revision surgery.

OBJECTIVE: To evaluate if 20° is a possible critical PJK angle in primary adult scoliosis surgery patients as a threshold for worse patient-reported outcomes.

METHODS: Clinical and radiographic data of 90 consecutive primary surgical patients at a single institution (2002-2007) with adult idiopathic/degenerative scoliosis and 2-year minimum follow-up were analyzed. Assessment included radiographic measurements, but most notably sagittal Cobb angle of the proximal junctional angle at preoperation, between 1 and 2 months, 2 years, and ultimate follow-up.

RESULTS: Prevalence of PJK ≥20° at 3.5 years was 27.8% (n = 25). Those with PJK ≥20° at ultimate follow-up were older (mean 56 vs 46 years), had lower number of levels fused (median 8 vs 11), and were proximally fused to the lower thoracic spine more often than upper thoracic spine (all P < .001). PJK ≥20° was associated with significantly higher body mass index and fusion to the sacrum with iliac screws (P < .016, P < .029, respectively). Scoliosis Research Society outcome score changes were lower for PJK patients, but not significantly different from those in the non-PJK group.

CONCLUSION: PJK ≥20° in primary adult idiopathic/degenerative scoliosis does not lead to revision surgery for PJK, but is univariately associated with older age, shorter constructs starting in the lower thoracic spine, obesity, and fusion to the sacrum. The negative results, supported by Scoliosis Research Society outcome data, provide important guidance on the postoperative management of such PJK patients.

ABBREVIATIONS: BMI, body mass index

LIV, lowest instrumented vertebrae

ODI, Oswestry Disability Index

PJ, proximal junctional

PJK, proximal junctional kyphosis

SRS, Scoliosis Research Society

UIV, upper instrumented vertebra

*Department of Orthopaedic Surgery, Washington University Medical Center, St. Louis, Missouri;

Department of Orthopedics, Mount Sinai School of Medicine, New York, New York;

§Department of Orthopedic Surgery, Albert Einstein Medical Center, Philadelphia, Pennsylvania;

Department of Orthopaedic Surgery, Regions Hospital, University of Minnesota, St. Paul, Minnesota

Neurosurgery Department, Regions Hospital, Saint Paul, Minnesota

Correspondence: Matthew M. Kang, MD, Regions Hospital, Department of Neurosurgery, Mail stop 11503G, 640 Jackson St, St Paul, MN 55101. E-mail:

Received September 05, 2012

Accepted January 29, 2013

Copyright © by the Congress of Neurological Surgeons