Lumbar Spinal Surgery in Patients With Parkinson Disease
A Multicenter Retrospective Study
Kimura, Hiroaki MD, PhD*; Fujibayashi, Shunsuke MD, PhD*; Otsuki, Bungo MD, PhD*; Takemoto, Mitsuru MD, PhD*; Shikata, Jitsuhiko MD, PhD†; Odate, Seiichi MD†; Matsushita, Mutsumi MD, PhD‡; Kusuba, Akira MD‡; Kim, Youngwoo MD, PhD§; Sakamoto, Takeshi MD, PhD∥; Watanabe, Kei MD∥; Ota, Masato MD, PhD¶; Izeki, Masanori MD, PhD¶; Tsubouchi, Naoya MD#; Matsuda, Shuichi MD, PhD*
Author InformationAbstract
Parkinson disease (PD) is a degenerative disorder of the central nervous system that occurs in an older population, the cardinal features of which are resting tremor, rigidity, bradykinesia, and gait disorder/postural instability. Skeletal deformities, such as scoliosis, kyphosis, and kyphoscoliosis as the result of muscular dysfunction are often seen in PD patients.1,2 In PD patients, vertebral compression fractures caused by poor bone quality and falls because of the disturbed postural reflex accelerate kyphotic deformity.3,4 In addition, camptocormia, defined as an abnormal, severe, and marked anteroflexion of the thoracolumbar spine, has been reported since 1995.5,6 These significant spinal deformities not only prevent PD patients from standing or walking because of trunk imbalance and inclination, but also confine them to wheelchairs.
Only a few studies, which were case series with <25 patients, have looked at spinal surgery in PD patients, and these reported a high rate of complications, including multiple reoperations and construct failure, or poor surgical outcomes.7–9 Although spine surgeons recognize the difficulties involved in surgical treatment for PD patients, we frequently encounter PD patients who suffer from pain or severe postural impairment because of spinal canal stenosis, vertebral fracture, or significant spinal deformity, and who need surgical treatment. Because the data concerning spinal surgery in PD patients are inadequate, there is no consensus as to the guidelines for their surgical treatment. Postoperative progression of sagittal deformity, which occurs after both instrumentation surgery and decompression surgery, considerably affects the surgical results in PD patients.7,10 Therefore, the purpose of this study was to use the data from 67 PD patients with various spinal disorders, to identify the factors that affect postoperative progression of sagittal deformity, and to clarify the surgical strategy for treating lumbar disorders in PD patients.
MATERIALS AND METHODS
This is a multicenter, retrospective review of PD patients who underwent lumbar spinal surgery between 2006 and 2013. This study was approved by the ethics review boards of all 7 participating institutions. All radiographic and clinical data were sent to and compiled by H.K. and B.O. Inclusion criteria were patients who underwent lumbar surgery because of persistent symptomatic lumbar degenerative diseases, vertebral fracture–related disorders, or gait disturbance because of postural imbalance, and who could be evaluated 1.5 years after the surgery. Surgeries involving the thoracic spine were included. Exclusion criteria were patients with secondary parkinsonism. At each institution, surgical procedures were selected depending on the indication. Sex, age, follow-up period, surgical data, PD status, and the mean duration of PD were evaluated. PD status was defined according to the Hoehn and Yahr (H-Y) stage.11
Anteroposterior and lateral plain radiographs obtained before surgery, immediately following surgery, and at the most recent follow-up were analyzed retrospectively. Measurements of the coronal curves and lumbar lordotic angle (LL; upper endplate of L1–S1) were performed using the Cobb method. To evaluate the sagittal balance, the C7 sagittal vertical axis was measured when whole-spine radiographs were available.12 Implant failures, including pedicle screw loosening, rod fracture, and cage migration, and postoperative fracture were assessed from radiographs or computed tomography.
The patients were divided into 3 groups: those who underwent laminectomy (Laminectomy; 12 patients) or posterior fusion surgery (Fusion; 24 patients) for lumbar canal stenosis, and corrective surgery for spinal deformity (Deformity; 31 patients), as shown in Table 1. The Fusion group was mainly selected for patients with severe degeneration, spondylolisthesis, or instability, and the Laminectomy group was for patients who suffered from leg pain without the radiographic finding of deformity or instability. The Deformity group included patients with spinal deformity, defined as degenerative scoliosis (Cobb angle >30 degrees) or kyphosis (sagittal vertical axis >100 mm or LL<0 degree), and patients with fracture-related disorders, and was treated with instrumented fusion surgery. During the periods of follow-up, surgery-related complications, as listed in Table 2, were assessed. Severe progression of deformity was defined as a postoperative radiologic change in LL (LL immediately after surgery−LL at the most recent follow-up >20 degrees), and mild progression was defined as a change in LL (5 degrees <LL immediately after surgery−LL at the most recent follow-up <20 degrees). A failure of the initial surgery was defined as severe progression of deformity or a requirement for reoperation for progression of deformity, implant failure, or fracture around fusion sites. Implant failure such as pedicle screw loosening/pullout, rod fracture, or cage migration/sinking, and postoperative fracture frequently caused severe progression of deformity, a failure of the initial surgery, in PD patients.
Statistical Analysis
Statistical analyses were performed using SPSS software version 22 for Windows (IBM Japan Ltd, Tokyo, Japan). Continuous data were described as mean±SD, if normally distributed, or median and interquartile range if not normally distributed. Differences in categorical variables were analyzed using Fisher exact test. Differences in continuous variables were analyzed using 1-way ANOVA, followed by independent t test with Bonferroni correction, or Kruskal-Wallis test, followed by Mann-Whitney U test with Bonferroni correction for multiple comparisons. To investigate the factors associated with failure of the initial surgery, a Cox proportional hazards model was fitted to the data. Variables were included in the likelihood forward selection multivariate model if their univariate analysis P-value <0.2. A P-value <0.05 was considered significant in all analyses.
RESULTS
There were 67 patients (24 men and 43 women) with an average age of 70.7 years (range, 56–81 y). The average duration of follow-up was 2.8 years (range, 1.5–7 y). Table 1 shows the demographics of all 67 patients. The H-Y stage was significantly higher in the Deformity group and lower in the Laminectomy group (P=0.019, Laminectomy vs. Fusion; P<0.001, Laminectomy vs. Deformity; P=0.029, Fusion vs. Deformity). The number of fusion levels in the Deformity group was significantly greater than that in the Fusion group (P<0.001). The preoperative LL in the Deformity group was significantly lower than those in the Laminectomy and Fusion groups (P=0.032, Laminectomy vs. Deformity; P=0.004, Fusion vs. Deformity).
Table 2 lists the postoperative complications. The rates of implant failure in the Fusion and Deformity groups were high (33.3% and 38.7%, respectively). For 19 of 20 patients in the Fusion and Deformity groups who experienced implant failure, this occurred within a year after surgery. Six (28.6%) patients in the Fusion group and 2 (22.2%) in the Deformity group experienced cage migration/sinking with pedicle screw loosening/pullout at the most caudal disk level, as shown in Figure 1. Thirteen patients (41.9%) in the Deformity group experienced postoperative vertebral fractures, most of which occurred at the most caudal instrumented vertebra, as shown in Figure 2. In all of the 15 patients in the Fusion and Deformity groups who experienced postoperative vertebral fracture, this occurred within a year after surgery. These complications caused postoperative progression of deformity. Overall, 37 patients developed postoperative deformity at last follow-up, and the rates of postoperative deformity in the Laminectomy, Fusion, and Deformity groups were all high (41.7%, 50.0%, and 64.5%, respectively). One patient in the Laminectomy group, 7 patients in the Fusion group, and 7 patients in the Deformity group required reoperation (Table 3). The percentages of patients who experienced failure of the initial surgery were 33.3% in the Laminectomy group, 45.8% in the Fusion group, and 67.7% in the Deformity group.
In the Deformity group, 14 of 19 patients with preoperative fracture and 7 of 12 patients without preoperative fracture experienced failure of the initial surgery. Notably, 8 of 11 patients who underwent posterior instrumentation with vertebroplasty for vertebral fracture experienced failure of the initial surgery; most of these involved pedicle screw pullout at the caudal fusion site or vertebral fracture around the fusion segment, leading to the progression of kyphosis. Of 17 patients in the Deformity group with severe postoperative deformity, 13 experienced failure of the most caudal fixation (Fig. 2) and 3 experienced rod fracture at the pedicle subtraction osteotomy (PSO) site (Fig. 3). None of the 4 patients in the Deformity group for whom iliac screws were used experienced failure of the initial surgery, despite the high rate of failure in the Deformity group (Fig. 4). In addition, lumbar lordosis was maintained in all 4 patients who underwent reoperation using iliac screws (Table 3).
Twelve patients were diagnosed with PD after surgery because their symptoms did not improve after surgery. Two of these patients developed kyphoscoliosis progressively after single-level posterior lumbar interbody fusion (Fig. 5).
The results of the Cox proportional hazards models to identify risk factors for failure of the initial surgery are shown in Table 4. Univariate analysis demonstrated that preoperative LL (per −1 degree), preoperative fracture, and preoperative deformity were associated with failure of the initial surgery (P=0.003, 0.012, and 0.012, respectively). Multivariate analysis found that preoperative LL (per −1 degree) was associated with failure of the initial surgery (P=0.003). Each decrease of 1 degree in the preoperative LL increased the risk of failure of the initial surgery by 1.024 times, indicating that a smaller preoperative LL increased the risk for failure of the initial surgery (95% confidence interval, 1.008–1.04).
DISCUSSION
Previous studies reported a high complication rate for spinal surgery in patients with PD. Babat et al7 reported that 12 of 14 patients (86%) required additional surgery, undergoing 31 reoperations. Koller et al8 reported that 52.2% and 33% of 23 PD patients with sagittal imbalance had surgical complications and revision surgery, respectively. In the present study of 67 PD patients, 36 patients (53.7%) experienced failure of the initial surgery and 15 patients (22.4%) underwent reoperation. We found that fusion failure and vertebral fracture, which occurred frequently at the most caudal site within a year after surgery, caused the progression of kyphosis. We demonstrated that a small preoperative LL is a risk factor for failure of the initial surgery in PD patients. However, because the data concerning spinal surgery in PD patients are inadequate, there are neither guidelines for treatment nor sufficient information regarding spinal surgery in PD patients.
Surgery for Lumbar Spinal Canal Stenosis Without Deformity
Babat et al7 stated that the only patients who avoided failure of the index surgical procedure were those treated with single-level decompression followed by instrumented spinal fusion, and that all patients who underwent decompression surgery went on to failure because of postoperative occurrence of spondylolisthesis or deformity. Upadhyaya et al10 suggested that short-segmental fusion be recommended for PD patients with spinal canal stenosis causing radiculopathy or myelopathy, and that long-segmental fusion procedures should be performed sparingly because of the very high complication rate. There are no reports that recommend decompression surgery for PD patients. In contrast to previous reports, 8 of the 12 patients (66.7%) in the Laminectomy group did not experience failure of the initial surgery. This is perhaps because surgeons select fusion surgery for patients with severe degeneration, spondylolisthesis, instability, or malalignment, and select decompression for patients without these pathologies. Considering the results of the multivariate analysis, which showed that a smaller preoperative LL is a risk factor for failure of the initial surgery, decompression may be effective for patients with less degeneration, larger LL, and a stable spine.
Fusion surgery is indicated in cases of severe degeneration, spondylolisthesis, or instability. Notably, 6 patients in the Fusion group experienced cage-related complications including migration and sinking, which may be caused by poor bone quality and the strong tendency of PD to bend the body forward. Considering that a smaller preoperative LL is a risk factor for failure of the initial surgery, and that patients with implant failures often developed postoperative kyphosis, rigid interbody fusion surgery to attain and maintain appropriate lumbar lordosis may be necessary in these cases.
It should be noted that PD itself causes a walking impairment that resembles the symptoms of lumbar canal stenosis, as Moon et al13 described from their experience that only 1 of 20 cases had a satisfactory outcome from lumbar fusion surgery (1–3 levels) despite a 75% fusion rate. Indeed, we encountered 12 PD patients who were diagnosed as PD after surgery, and who did not improve their walking impairment. Surgery for lumbar canal stenosis in PD patients should be indicated only when the possibility that the condition is a symptom of PD is excluded with high probability based on strict medical examination and radiographic findings.
Surgery for Spinal Deformity
Oh et al14 reported that greater severity of PD is associated with sagittal spinopelvic malalignment, which is consistent with our observation that H-Y stage was significantly higher in the Deformity group. Koller et al8 recommended multilevel fusion for reconstruction of the skeletal deformity, and obtained satisfactory results despite high rates of complications and revision surgery. Bourghli et al9 reported spinal fusion from T2 to pelvis with an L5/S1 transforaminal lumbar interbody fusion for 12 PD patients with deformities, and obtained satisfactory outcomes, although 6 patients underwent revision surgery. In our series, the complication rate for the correction of deformities was high (67.7%). In particular, the extremely poor bone quality and the strong tendency to bend forward in patients with preoperative vertebral fracture frequently caused implant failures, including pedicle screw pullout or vertebral fracture.
To our knowledge, no reports have described the treatment for fracture-related disorders in PD patients. Several authors have recommended posterior fixation with vertebroplasty for osteoporotic vertebral fractures with neurological deficits because it is a less-invasive procedure and produces satisfactory results.15,16 In our study, 8 of 11 patients treated with posterior instrumentation with vertebroplasty for a fracture-related disorder had subsequent fusion failure, most of which involved pedicle screw pullout at the caudal fusion site followed by the progression of kyphosis. This suggests that anterior reconstruction or rigid caudal fixation might be required when treating a fracture-related disorder in PD patients.
In the Deformity group, pedicle screw pullout and instrumented vertebral fracture at the caudal site occurred frequently, and these complications accelerated progression of postoperative postural imbalance. However, the 4 patients in the Deformity group who were treated using an L5/S interbody cage and iliac screw fixation did not experience failure of the initial surgery, and sagittal alignment was maintained in 4 patients who underwent reoperation using iliac screw fixation. These results suggest that iliac screw fixation, which is becoming the standard for performing long fusions in adult deformity, might be adequate to resist the pressure to bend forward, especially when used for deformity-correction surgery as described by Bourghli and colleagues.9,17
As Koller et al8 and Bourghli et al9 suggested, in deformity-correction surgery the reconstruction of the spinopelvic balance with a focus on lumbar lordosis and global sagittal alignment is required. After attaining the proper sagittal alignment, the maintenance of the alignment is also important, because we found that caudal fixation failure, rod fracture at the PSO site, and adjacent segmental degeneration caused postoperative progression of kyphosis.
Patients with preoperative vertebral fracture frequently experienced failure of the initial surgery. Vertebroplasty with posterior instrumentation might not be indicated for the treatment of vertebral fracture in PD patients because of the risk of caudal PS pullout, followed by the progression of kyphosis. Long fusion to the pelvis to attain a rigid caudal fixation and lumbar lordosis may be indicated. Short fusion with anterior reconstruction with posterior instrumentation may be an option. This procedure was performed in a patient in the present series, and this patient did not experience failure of the initial surgery.
Recommendations
Regrettably, we could not statistically analyze the risk factors for failure of the initial surgery in each subgroup (Laminectomy, Fusion, and Deformity) because of the small patient numbers. Combining our results and those of previous reports, we can make several recommendations for the treatment of spinal disorders in PD patients.
Decompression surgery for lumbar canal stenosis may be effective for the patient with less degeneration, greater LL, and a stable spine, whereas fusion surgery is indicated in cases of severe degeneration, spondylolisthesis, or instability. Rigid interbody fusion surgery with thicker pedicle screws and the appropriate cage size is advisable to attain and maintain appropriate lumbar lordosis, because fusion with malalignment and fusion failure cause the progression of kyphosis.
In deformity-correction surgery, the reconstruction of the sagittal balance and its maintenance is imperative.8,9 We recommend iliac screw fixation to avoid caudal fixation failure, and the installment of an interbody cage above and below the PSO site and the use of thick rods or multiple rods to avoid rod fracture.
Patients with preoperative vertebral fracture frequently experienced failure of the initial surgery. Vertebroplasty with posterior instrumentation might not be indicated for the treatment of vertebral fracture in PD patients because of the risk of caudal PS pullout, followed by the progression of kyphosis. Long fusion to the pelvis to attain a rigid caudal fixation and lumbar lordosis may be indicated. Short fusion with anterior reconstruction with posterior instrumentation may be an option if appropriate lumbar lordosis can be attained.
The severity of PD and the bone quality considerably affect the surgical results. Therefore, medical control of PD by neurologists and control of osteoporosis are required. Because Ohtori et al18 demonstrated that teriparatide accelerates lumbar posterolateral fusion in women with postmenopausal osteoporosis, administration of teriparatide as osteoporosis medication may be desirable before treatment with fusion surgery in PD patients.
Limitations
The retrospective nature of our multicenter study resulted in several limitations. First, operative indications, including indications for reoperation, and surgical techniques differed between institutions. Second, whole-spine radiographs to assess spinopelvic alignment by measuring spinopelvic parameters including pelvic incidence and pelvic tilt12 were not available. However, an excessively reduced LL, which is often seen in PD patients, leads to sagittal imbalance because of the limited ability to compensate by pelvic retroversion.14 Therefore, we measured the LL to assess the aggravation of sagittal imbalance after surgery. Third, the present data do not include standardized measures of health-related quality of life. Because the most frustrating problem in surgical treatment of PD patients is the postoperative implant-related complications and deformity, we evaluated the radiographic results. Fourth, our study population was heterogenous because of the rarity of spinal surgery in PD patients. A well-designed prospective multicenter study is necessary to establish guidelines for surgical treatment of PD patients. Despite these limitations, the present study, which included 67 patients, is the largest reported, and will help spine surgeons to treat PD patients.
CONCLUSIONS
The rates of failure of the initial surgery and postoperative deformity were high in all groups. We found that a small preoperative LL was a risk factor for failure of the initial surgery in PD patients. Implant failure and postoperative fracture, which occurred frequently at the most caudal site within a year after surgery, caused progression of kyphosis. These findings suggest that attaining and maintaining proper lumbar lordosis with rigid fixation, especially at the most caudal site, may be necessary in PD patients with a small preoperative LL.
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