Analysis of the incidence and risk factors for the progression of proximal junctional kyphosis following surgical treatment for lumbar degenerative kyphosis: minimum 2-year follow-up.

BACKGROUND CONTEXT. Proximal junctional kyphosis (PJK) following surgical treatment of lumbar degenerative kyphosis (LDK) is one of the critical complications leading to the failure of instrumentation and additional extensive surgery. However, most previous studies have focused on idiopathic scoliosis resulting from variable surgical techniques. LDK usually differ from other scoliotic deformities in terms of patient characteristics and disease mechanisms. PURPOSE. Identification of the prevalence of PJK after the surgical treatment of LDK and searching for the predictable value for the progression of PJK. Study design. Retrospective comparative study. Patient sample (must be included in clinical studies). Forty-seven consecutive patients who underwent surgical correction of a sagittal imbalance due to LDK, from January 2005 to December 2008 in a single spine clinic, were evaluated with a minimum 2 years follow-up (mean 3.8 years). METHODS. Patients were divided into 2 groups: with or without the occurrence of PJK, and three categorized factors according to patient characteristics, surgical variables, and the radiographic spinopelvic parameters were evaluated. RESULTS. PJK had occurred in 29 of 47 patients (61.7%). Among variable factors, old age, upper-instrumented vertebra below L2, lumbar lordosis to PI ratio, and the sum of lumbar lordosis, and the sacral slope related to PI were found to be statistically significant. CONCLUSIONS. The overall incidence of PJK following surgical treatment of LDK patients was higher than expected. Spinal biomechanics may be changed after long instrumented fusion surgery. Thorough consideration of these factors is needed in the treatment strategy of LDK patients. A long-term follow-up study should be conducted.