PD patients have been shown to have more postoperative surgical complications due to various musculoskeletal problems. Studies have investigated high rates of perioperative and postoperative complications following hip and knee surgery in PD patients using a nationwide inpatient database [18, 19]. Furthermore, other surgical studies on the PD population have suggested high rates of postoperative medical complications such as pneumonia, delirium, and sepsis [5]. However, few case series have examined the relationship between PD and complications following corrective surgery for ASD. Furthermore, few studies have focused on postoperative loss of correction of radiographic parameters in PD patients. Thus, we retrospectively analyzed both postoperative complications and radiographic parameters in this multicenter database of ASD patients and compared PD patients with non-PD patients matched for age, sex, and BMI with at least 2-years’ follow-up.
The results of this study demonstrated that the rate of delirium was significantly higher, and the rates of PE and DVT tended to be higher in the PD(+) group. In addition, Watanabe et al. previously reported that postoperative delirium was more common in patients with PD (23.1%) than in the controls (3.4%) [20]. This higher rate of delirium is possibly due to the use of antidopaminergic drugs and neurodegeneration in PD patients. Although delirium is a reversible condition, it is necessary to avoid additional complications due to falls or movement beyond the limits of restriction. For thrombotic events, PE is known to be a possible adverse reaction to antidopaminergic drugs, such as levodopa [21]. Yamane et al. reported a higher incidence (20%) of DVT in PD patients with a postural abnormality [22]. Since the correction surgery for ASD itself has a high risk for PE due to its long surgical time and large blood loss, it is assumed that the risk of PE of this surgery in PD patients is very high. In fact, in this study, the incidence of PE in PD patients was 7 times higher and that of DVT was about 2 times higher than in non-PD patients. Surgeons should thus consider PE in patients who develop chest pain and dyspnea after surgery.
In this study, we found significantly higher preoperative SVA and larger correction of SVA in the PD(+) group. We also found higher SVA at the final follow-up and higher loss of correction in SVA, even though longer fusion was performed in the PD(+) group. This finding suggests that the deformities in the PD(+) group were mostly flexible and largely corrected by the surgery. However, the corrected alignment could not be well maintained in this group, suggesting that a larger correction can lead to a higher rate of loss of correction. In addition, the progressive stooping posture of PD patients can pose a risk for loss of correction of global sagittal alignment, and this may be one of the causes for the poorer outcome in PD patients. Kawaguchi et al. reported that longer fusion until T4 yielded a good clinical outcome in a PD patient after corrective surgery for L1 to S1 was unsuccessful [23]. Watanabe et al. reported on 8 surgically treated ASD patients with PD who demonstrated poor clinical outcomes with a high non-union rate and adjacent segment disease [24]. Thus, it is crucial to consider possible prevention strategies, including longer fusion.
Previous studies reported that PD patients have a higher rate of osteoporotic vertebral fracture and lower BMD [1, 20]. However, we found no significant difference in BMD in this study even though the rates of previous vertebral fractures were significantly higher in the PD group. We assumed that the postural abnormality in the PD(+) group added greater burden on the vertebral body than on that of a healthy person and resulted in vertebral fracture. Thus, caution should be exercised when considering the risk of PJK type fracture in PD patients. Yagi et al. reported that teriparatide treatment started immediately after surgery resulted in a decrease in rates of PJK-type bone fracture [25]. If BMD is low, then administration of osteoporotic drugs such as teriparatide could be a viable option to decrease the risk of complications, as suggested in the previous study.
This study showed that the revision rate due to mechanical complications was 33.3%, which was almost two times higher in the PD(+) group than in the PD(−) group. Similar to our study, Sheu et al. investigated 66 PD patients who underwent thoracolumbar or lumbar instrumented surgery due to degeneration or deformity; 29% of them needed revision surgery due to mechanical complications [13]. Bouyer et al. reported a high revision rate of 42% in 48 ASD patients with PD, 89% of which were due to mechanical complications [16]. In terms of each complication, PJK has been reported to be significantly higher in PD patients. In contrast, a history of PD had no significant impact on the PJK rate in this study. Instead, rates of pseudarthrosis and rod failure were higher in the PD(+) group. This was probably because a longer fusion was performed in the PD(+) group, possibly as a result of the surgeon’s decision considering the severe deformity with higher SVA. Long-segment fixation may lower the risk of PJK but the stress on the rod and the mobile segment of the spine can be higher and may have caused rod fracture and pseudarthrosis.
Several studies have investigated risk factors for revision surgery in PD patients. Schroeder et al. reported that an HY stage > 2, diabetes mellitus, treatment for osteoporosis, and a combined anterior and posterior approach were risk factors for revision surgery in 94 lumbar spine surgeries [12]. According to Sheu et al., HY stage > 2, cancer history, osteoporosis, and three column osteotomy were risk factors for revision surgery [13]. In our study, PD duration was significantly longer in the revision subgroup, even though they were younger. HY stage can be affected by symptoms of sagittal malalignment and imbalance in ASD patients, and thus the stage itself may not reflect the exact severity of PD in ASD patients. However, the HY stage also tended to be higher in the revision subgroup. As the previous study indicated, poorly controlled PD negatively impacts the incidence of revision surgery. Thus, it is vital to consider duration and severity of PD when performing surgical treatment in ASD patients.
There are several limitations to this study. First, there was a selection bias in which the surgeon could change their choice of a surgical procedure because of the patient’s PD status. Second, our study was retrospective in nature. Studies with more appropriate study designs and a larger sample size are needed. Despite these limitations, our study demonstrated surgical outcomes in patients with PD compared with patients without PD using a large database with a sufficient follow-up period.