Proximal Junctional Kyphosis and Proximal Junctional Failure

Proximal junctional failure (PJF) should be distinguished from proximal junctional kyphosis, which is a recurrent deformity with limited clinical impact. PJF includes mechanical failure, and is a significant complication following adult spinal deformity surgery with potential for neurologic injury and increased need for surgical revision. Risk factors for PJF include age, severity of sagittal plane deformity, and extent of operative sagittal plane realignment. Techniques for avoiding PJF will likely require refinements in both perioperative and surgical strategies.

Key points

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Proximal junctional failure should be distinguished from proximal junctional kyphosis, which is a recurrent deformity with limited clinical impact.
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Proximal junctional failure is a significant complication following adult spinal deformity surgery with potential for neurologic injury and increased need for surgical revision.
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Risk factors for proximal junctional failure include age, severity of sagittal plane deformity, and extent of operative sagittal plane realignment.
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Techniques for avoiding proximal junctional failure will likely require multiple refinements in perioperative and surgical strategies.

Background and definitions

Proximal junctional kyphosis (PJK) is a recognized complication for patients undergoing posterior segmental instrumented fusion for spinal deformity. However, descriptions of criteria for defining PJK, its incidence and clinical impact, and the basis for its development vary in the literature. Measured radiographically with a sagittal view, PJK has traditionally been defined by a 10° or greater increase in kyphosis at the proximal junction as measured by the Cobb angle from the caudal endplate of the uppermost instrumented vertebrae (UIV) to the cephalad endplate of the vertebrae 2 segments cranial to the UIV. This was the measurement used by Glattes and colleagues and proved reliable in a study by Sacramento-Dominguez and colleagues testing the reproducibility of different methods of measuring PJK.

Several investigators have reported that PJK according to the definition mentioned earlier does not generate significant clinical or quality-of-life issues. In general, PJK is often well tolerated and does not lead to revision surgery in most cases. Yagi and colleagues reported that 4 of 32 PJK patients underwent additional surgery because of local pain but found no significant differences in Scoliosis Research Society (SRS) or Oswestry Disability Index (ODI) scores at final follow-up. Kim and colleagues found no significant differences in clinical outcomes with SRS scores except in the self-image domain when PJK was greater than 20°. Similarly, no differences in clinical outcomes were found among PJK patients in the studies of Glattes and colleagues and Hyun and Rhim. Collectively, these reports support the idea that PJK defined radiographically amounts really to recurrent deformity, which is both infrequently associated with revision surgery and has a limited impact on clinical outcomes ( Fig. 1 ).