Time to development, clinical and radiographic characteristics, and management of proximal junctional kyphosis following adult thoracolumbar instrumented fusion for spinal deformity.

STUDY DESIGN: A retrospective review. OBJECTIVE: To study time to development, clinical and radiographic characteristics, and management of proximal junctional kyphosis (PJK) following thoracolumbar instrumented fusion for adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: PJK continues to be a common mode of failure following ASD surgery. Although literature exists on possible risk factors, data on management remain limited. METHODS: A retrospective review of medical records of 289 consecutive ASD patients who underwent posterior segmental instrumentation incorporating at least 5 segments was conducted. PJK was defined as proximal kyphotic angle >10 degrees. RESULTS: PJK occurred in 32 patients (11%) at a mean follow-up of 34 months (range, 1.3-61.9±19 mo). Sixteen (50%) patients were revised (mean, 1.7 revisions; range, 1-3) at a mean follow-up of 9.6 months (range, 0.7-40 mo); primary indications for revision were pain (n=16), myelopathy (n=6), instability (n=4), and instrumentation protrusion (n=2). Comparison of preindex and postindex surgery radiographic parameters demonstrated significant improvement in mean lumbar lordosis (24 vs. 42 degrees, P<0.001), pelvic incidence-lumbar lordosis mismatch (30 vs. 11 degrees, P<0.001), and pelvic tilt (29 vs. 23 degrees, P<0.011). The mean T5-T12 kyphosis worsened (30 vs. 53 degrees, P<0.001) and the mean global sagittal spinal alignment failed to improve (9.6 vs. 8.0 cm, P=0.76). There was no apparent relationship between the absolute PJK angle and revision surgery (P>0.05). CONCLUSIONS: The patients in this series who developed PJK had substantial preoperative positive sagittal malalignment that remained inadequately corrected following surgery, likely resulting from a combination of inadequate surgical correction and a significant compensatory increase in thoracic kyphosis. In the absence of direct relationship between a greater PJK angle and worse clinical outcome, clinical symptoms and neurological status rather than absolute reliance on radiographic parameters should drive the decision to pursue revision surgery.