Risk factor analysis of proximal junctional kyphosis after posterior fusion in patients with idiopathic scoliosis
Introduction
In the past, thoracolumbar and lumbar idiopathic scoliosis have been treated by anterior spinal instrumentation and fusion, however, such treatment was associated with loss of fixation, high pseudoarthrosis rates, and kyphogenic effect at the instrumented level.12, 15 Posterior spinal fusion with segmental fixation provides better control of the lordosis and reduces the need for postoperative immobilization.18 However, the incidence of proximal junctional kyphosis (PJK) caused by the accelerated degeneration of the joint capsule and smaller articular processes in the proximal junctional region has attracted the attention of many scholars.3, 5, 7, 8, 9, 13, 18
In the past, the incidence of proximal junctional kyphosis and its associated risk factors varied greatly according to the reporting institution (ranging from 9.2% to 46%). Lee et al.13 first reported PJK as a complication, with an incidence as high as 46%. Their data showed that preoperative proximal junctional kyphosis greater than 5° is an important predictive factor for the development of postoperative PJK. However, Kim et al.8, 9 conducted two large studies of PJK and found the incidence of PJK ranged from 26% to 28%. Their data showed that different types of internal fixation and the degree of preoperative thoracic kyphosis were the dominant factors affecting the PJK occurrence. The latest data from Hollenbeck et al.7 were obtained from a 4.9-year follow-up study on idiopathic scoliosis (n = 174). He found that only 9.2% patients showed increased postoperative proximal kyphosis.
There are many reasons for the aforementioned differences in the reported results including the definition of the proximal junction zone, the method used to measure the angle, surgical strategies, and the orthopaedic approach chosen.
According to the Lenke et al. classification,14 there are a large proportion of patients with types 1–4 and type 6 idiopathic scoliosis. The surgical strategy for those patients requires fusion to the upper thoracic vertebra to prevent the postoperative superposition effect of physiological stress in the proximal junctional region, which will greatly affect the occurrence and development of kyphosis.
This study included adolescents with idiopathic scoliosis (n = 150) who received posterior fusion at our hospital from 2000 to 2005 and were assessed for changes in their proximal junctional kyphosis angle during follow-up of at least 2 years. The objectives of this study were to observe the incidence of postoperative proximal junctional kyphosis in this group of patients and to compare our data with the data reported in the literature. In addition, we systemically analysed the risk factors associated with the development of PJK in order to modify the current operational strategy at our institution.
Section snippets
Subjects
We performed a retrospective analysis of 150 patients with idiopathic scoliosis who underwent orthopaedic surgery at Shanghai Changhai Hospital from 2000 to 2005. All the patients were citizens of mainland China. The postoperative follow-up time for all patients was more than 2 years with an average of 3.5 years. The selected patients were further screened to meet the following inclusion criteria:
- (1)
The type of scoliosis was adolescent idiopathic scoliosis.
- (2)
The surgical approach was simple
Results
Among the 150 patients, 123 patients met the screening criteria. Among 27 patients excluded, 3 patients had previous anterior surgery, 4 patients were excluded due to postoperative internal fixation-related complications, and 20 patients were excluded due to incomplete imaging data. Among the remaining 123 patients, 35 patients experienced PJK during the follow-up period with an incidence of 28%. We divided all patients into 2 groups according to whether PJK occurred or not. In the PJK group,
What is the underlying aetiology of PJK?
Although the posterior fusion technique for idiopathic scoliosis in adolescents has been adopted by the majority of spine surgeons, the potential development of junctional kyphosis after posterior spinal fusion for idiopathic scoliosis is not well understood.3 According to recent studies, proximal junctional kyphosis may be attributable to a weakening effect caused by muscle dissection and disruption of posterior ligaments or may be secondary to loss of lumbar lordosis.2, 18
Alternatively, since
Conflict of interest statement
The authors declare no conflict of interest exists.
Acknowledgement
No funding support was provided for this research.
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These authors contributed equally to the article.