Proximal junctional kyphosis (PJK) is a commonly encountered clinical and radiographic phenomenon after pediatric and adolescent spinal deformity surgery that may lead to post-operative deformity, pain, and dissatisfaction. Understanding the risk factors of PJK can be useful for pre-operative informed consent as well as to identify any potential preventative strategies.
We performed a systematic review and critical analysis following the PRISMA statement in July 2019 by searching the PubMed, Scopus, and Embase databases, including all prior published studies. We included articles with data on PJK in patients with operative pediatric and adolescent scoliosis and those that detailed risk factors and/or preventative strategies for PJK. Levels of evidence were determined based on consensus. Findings were summarized and grades of recommendation were assigned by consensus. This study was registered in the PROSPERO database; 202,457.
Six hundred and thirty five studies were identified. Thirty-seven studies met criteria for inclusion into the analysis. No studies including neuromuscular scoliosis met inclusion criteria. No findings had Grade A evidence. There were 4 findings found to contribute to PJK with Grade B evidence in EOS: higher number of distractions, disruption of posterior elements, greater sagittal plane correction. There was no difference in incidence noted between etiology of the curvature. Five findings with Grade B evidence were found to contribute to PJK in AIS populations: higher pre-operative thoracic kyphosis, higher pre-operative lumbar lordosis, longer fusion constructs, greater sagittal plane correction, and posterior versus anterior fusion constructs.
Greater sagittal plane correction has Grade B evidence as a risk factor for PJK in both EOS and AIS populations. In EOS patients, an increased number of distractions and posterior element disruption are Grade B risk factors. In AIS patients, longer fusion constructs, higher pre-operative thoracic kyphosis and lumbar lordosis, and posterior (as opposed to anterior) constructs also contributed to PJK with Grade B evidence. These findings can guide informed consent and surgical management, and provide the foundation for future studies.
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SP thanks the National Institute of Health for support (R21AR075971-02).
No funds, grants, or other support was received.
Conflict of interest
R. Justin Mistovich serves as a paid consultant to OrthoPediatrics and Philips Healthcare Companies. Keith D. Baldwin owns stock in Pfizer. Mehmet Erkilinc and Saba Pasha have no financial interest.
Systematic review. No patient information was accessed for this manuscript. IRB exempt.
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EOS findings with inconclusive evidence
Coronal plane curve magnitude
Pre-operative cervical lordosis
Rationale: one Level 3 study found that patients who developed PJK had higher pre-operative cervical lordosis .
Malpositioned screw at UIV
Rationale: one Level 3 study reported that 6/7 patients who developed PJK had ≥ 1 malpositioned screw .
Longer fusion constructs
Selection of UIV influences the rate of PJK
Rationale: one level 3 study reported that UIV distal to T2 (hazard ratio = 5.474; P = 0.044) were found to be independent risk factors of PJK in the multivariate analyses .
Selection of LIV influences the rate of PJK
Rationale: one Level 3 study described LIV at or cranial to L3 as a risk factor for PJK .
AIS findings with inconclusive evidence
High lordosis/pelvic incidence ratio
Rationale: one Level 2 study reported higher pre-op and post-op lumbar lordosis/PT ratios in patients who developed PJK .
Disruption of posterior elements
Rationale: one Level three study reported a greater frequency of disrupted junctional ligaments in the PJK group , and another study reported a single case of posterior ligamentous failure in a patient with PJK .
Rationale: a Level 3 study found no difference in PJK risk between titanium and cobalt chrome rods . Another Level 3 study reported that significantly higher risk with cobalt chromium (28%), compared to titanium and stainless steel (12%) (p < 0.0001) .
Bone graft material
Rationale: a single Level 3 study described autologous bone graft as a risk factor for PJK .
Use of distraction
Rationale: a single Level 3 study described distraction during deformity correction as a risk factor .
Body mass index
Rationale: one Level 2, one Level 3 and one Level 4 study found no significant difference in BMI between PJK and non-PJK cohorts [26, 33, 38]. A level 3 study reported a significantly increased BMI in the PJK group .
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Erkilinc, M., Baldwin, K.D., Pasha, S. et al. Proximal junctional kyphosis in pediatric spinal deformity surgery: a systematic review and critical analysis. Spine Deform (2021). https://doi.org/10.1007/s43390-021-00429-w
- Proximal junctional kyphosis
- Adolescent idiopathic scoliosis
- Early-onset scoliosis