Postoperative progressive spinal deformity has been reported as an important complication following intracanal tumors resection. Deformity may develop progressively within many years after surgery and affect the final outcomes of patients . However, opinions varied about the risk factors for postoperative progressive spinal deformity[5, 6]. Since first described in 1976, laminoplasty has gradually replaced laminectomy for the less damages to the structure of the vertebral body and lower incidence of postoperative complications, such as incisional CSF leak. However, some studies reported that laminoplasty was not associated with improvement in postoperative deformity after tumor resection[8, 10]. Here, we analyzed the risk factors for postoperative spinal deformity following intracanal tumors resection, hoping to arouse the attention of the surgeons to reduce the occurrence of such complication. For those patients who had more risk factors of progressive spinal deformity, spinal fusion surgery may be seriously considered, and close follow-up should be given to those who did not undergo this procedure.
In this research, 272 patients with resection of intracanal tumors were presented and risk factors of progressive spinal deformity were evaluated. After an average of 21.8 months of follow-up, the overall incidence of postoperative progressive spinal deformity was 15.8%, which was comparable to previously reported incidence. We included the current most factors to analyze. Our research revealed that age ≤ 18 years (p = 0.027), vertebral levels of tumor involvement (p = 0.019) and preoperative spinal deformity (p=0.008) was the independent risk factors (p < 0.05), increasing the odds of postoperative progressive spinal deformity by 3.94- , 0.69- and 27.11-fold, respectively. Meanwhile, the patients with progressive spinal deformity had a trend of increased postoperative median MMS score at last follow-up (p= 0.199) and neurologic complications. To date, this is the largest reported risk factor analysis case series in this field. Not only does it contain the largest number of cases, but also the factors. Moreover, it involved intramedullary and extramedullary tumors.
Papagelopoulos et al.[13, 14] reported that the incidence of spinal column deformity was 33% in children and adolescents while 8% in young adults. Recently, Wei Shi et al. reported that patient age ≤ 25 was the main significant predictive risk factor for postoperative spinal deformity. These data were consistent with our results that pediatric patients (≤ 18 years of age) were more likely to suffer from postoperative progressive spinal deformity than the older adults (> 18 years of age). We speculated that the pediatric patient's immature skeletal system as well as surgery itself may change the mechanics of the spine, contributing to this phenomenon. In additionbecause the growth rate of bone growth in children was greater than the spinal cord, adhesions in the postoperative area may cause a phenomenon similar with tethered cord syndrome, which caused related muscle neurotrophic decline that contributed to the development of spinal deformity.
Many previous studies demonstrated that extent of surgery resection (no. of spinal levels) was related to progressive spinal deformity. Katsumi et al.revealed that age at operation, preoperative curvature in neutral position, number of removed laminas, C2 laminectomy, and destruction of facet joints are the risk factors that are involved in the pathogenetic mechanism of cervical instability. However, in our research, our data showed that not the extent of surgery resection, but the vertebral levels of tumor involvement may cause instability of the spine. The study revealed the average level of tumor involvement was 3.4 in patients who had progressive spinal deformity, comparing with 2 who had not. The risk factor of the vertebral levels of tumor involvement increased the odds of postoperative progressive spinal deformity by 0.69- fold. The more levels of tumor involvement, the more severe compression of the spinal cord, which may led to neurotrophic decline that aggravated the occurrence of spinal deformity.
Preoperative spinal deformity was independently associated with development of postoperative spinal deformity. Similarly, Kaptain GJ et al.[14, 17] reported that the presence of preoperative spinal deformity was the factor most significantly related to the risk of developing progressive spinal deformity. Our research drawed the same conclusion. Preoperative spinal deformity even increased the odds of postoperative progressive spinal deformity by 27.11-fold, and it was the biggest risk factor in the occurrence of postoperative spinal deformity. We speculated that it may result from the spinal cord compression of spinal cord from by the intracanal tumors, especially involving the anterior horn cells, which in turn led to neurotrophic disorders of the paravertebral muscles of at the corresponding segments. The imbalance of paravertebral muscle caused a decrease in the stability of the spine. Eventually it led to progressive deformity. These asymmetrical loads of the spine were still present after surgery, and even more severe because of the damage caused by surgery to the spine, which would further aggravate the degree of spinal deformity.
Riseborough et al. reported that the greater amount of irradiation could lead to more severe deformity of the spine. Although the prior radiotherapy was not analyzed because of few relevant cases in our study, we found the patients with spinal deformity were more likely to suffer from preoperative puncture or biopsy, which might destroy the stability of the spine to some extent. Moreover, in the univariate analysis, extent of surgery resection involvement was also significantly higher in patients with spinal deformity than that without spinal deformity. However, in subsequent multivariate analysis, we found that compared with younger age and preoperative spinal deformity, the extent of surgery resection involvement contributed little to postoperative progressive spinal deformity. Many previous studies revealed that number of laminae resected played a role in the development of postoperative spinal deformity. Here, we recommended that when encountering the tumors involved in multiple segments, under the premise of ensuring complete resection, minimize the number of laminae resected to minimize the loss of spinal stability.
Furthermore, the pathology of the tumors, location of tumor and the surgeons may influence the development of postoperative spinal deformity[16, 19]. Our research also showed this trend (pathology, p=0.085; surgeon, p= 0.078), but they did not reach statistical significance. In addition, our study showed that methods(laminectomy or laminoplasty, p= 0.746) didn’t affect the occurrence of postoperative progressive spinal deformity.