ASD is an increasing public health concern, people of any age and gender may suffer from the spinal deformity. Patients who undergo spinal corrective surgery may improve their quality of life. The rate of complications reported in the literature varies widely, ranging from 26.8–42%.[10–15] Urgent and severe complications may require UIROR. UIROR during hospitalization is an unexpected outcome, causing psychological, physical, and financial burden on patients with ASD. Nearly half of the UIROR patients because of postoperative severe lower limbs radiating pain caused by implants deviation.
As ASD patients grow older, the severity of the spinal deformity may also increase. Previous literature has proven that the incidence of complications in elderly patients has increased.[17–19] In this study, the age of the UIROR group was slightly older than that of the non-UIROR group, it didn’t reach statistical significance (34.5 ± 14.95 years vs 31.5 ± 12.2, P = .385). The duration of the history of spinal deformity in the UIROR group was significantly longer than that in the non-UIROR group (26.2 ± 15.32 years vs 18.9 ± 12.6 years, P = .040), but there was no significant statistical difference in multivariate analysis (P = .470). Some previous studies have reported the relationship between obesity and long-term outcomes and complications after ASD corrective surgery.[20, 21] Pull ter Gunne et al found that the incidence of wound infection in obese patients increased. It is speculated that the amount of subcutaneous fat that needs to be retracted, leading to more cell necrosis, and therefore the infection rate is higher. Similarly, Soroceanu et al found that obese patients had a higher rate of major complications and wound infections, but this did not affect the number of minor complications or the necessity of reoperation. In our case series, obese patients have a higher risk of UIROR during hospitalization with statistical difference (OR = 11.766; P = .023).
As the predictor, preoperative high AVR (> Grade Ⅱ) were found to be significant risk factors in this study (OR = 9.534; P = .005). In the preoperative standing 36-in posteroanterior spine radiographs, eight of the patients with congenital deformity had high AVR, and the other were 2 patients with NFS and 1 with PPS. ASD may be long-standing and a stretch of evolvable deformity from primary disease, lending to increased scoliosis, kyphosis, vertebral rotation. In the univariate analysis, the proportion of patients with congenital deformity in UIROR group was significantly more than in non-UIROR group (73.3% vs 41.3%, p = .026), but no statistical difference among the two groups (p = .064). There are no significant differences in the preoperative coronal and sagittal imaging parameters such as the cobb angle and flexibility of the main curve in our study (p > .05). We considered that the greater rotary vertebrae generally lead to angular torsion of the spinal cord, which increases the risk of postoperative neurologic complications, also increases the rate of UIROR. Future research should pay attention to this key point.
In term of the surgical factors. The implant-related complications occurred in 9 patients (60%) of UIROR group, two-thirds patients present implant-related low limb neurologic deficit. Soroceanu et al performed a multicenter, prospective study involving eleven institutions of 245 patients who underwent ASD surgery, 13.8% patients with implant-related complications and more than half of them (52.6%) required reoperation within 2 years. Faloon et al compared the complications of primary and revision surgeries for 134 consecutive ASD patients treated with long fusions to the sacropelvis, the rate of return to the OR was 27.6%. In our study, three patients underwent spinal corrective and fusion from the thoracic spine to the sacrum in UIROR group, eight patients in non-UIROR group, without significant statistical difference (20% vs 6.34% P = .096). Lee et al reported a National Surgical Quality Improvement Project (NSQIP) study based on 5803 patients, 150 (2.8%) patients unintended return to the OR due to short-term postoperative complications, the significant surgery-related predictors included long fusion (OR = 1.3, P = .002), posterior fusion (OR = 3.6, P < .0001), combined approach (OR = 3.3, P < .0001), pelvic fusion (OR = 1.9, P < .0001), osteotomy (OR = 2.1, P < .0001), and operative time > 4 hours (OR = 3.5, P < .0001). The above factors were not statistically significant in the univariate analysis in our series. However, there are differences between our study and the above literature, which may be caused by the different time points of the clinical observation results.
Postoperative neurological complication is one of the reasons for UIROR. In a multicenter, prospective, worldwide observational study, Lenke et al found a higher rate of postoperative neurologic deficit in patients with a preoperative neurologic deficit compared with patients without preoperative deficit. (25.76% vs 22.17%, P < .0001). Kim et al reviewed 233 patients with ASD who underwent posterior vertebral resection, the preoperative neurologic deficit significantly increased complications (OR = 5.55, P = .0004). In this study, previous lower limbs neurological symptom is also an essential preoperative predictor (OR = 7.748; P = .003).
The finding of the current study can be presented in the following case examples. Patient A (Fig. 2) was a 52-year-old woman with complex congenital kyphoscoliosis. She is obese (BMI = 30.4). She had neurologic deficits more than 20 years. Preoperative standing posteroanterior spine radiograph showed the AVR is grade Ⅳ. She underwent spinal fusion from T9 to S1 and L1/L2 vertebral column resection (VCR), with an operative duration of 320 minutes and estimated blood loss of 600 milliliters. On the postoperative day 4, she developed severe left lower limb radiating pain, postoperative CT scan demonstrated that left L2 pedicle screw deviation. UIROR was performed on postoperative day 5. Patient A’s radiating pain was significantly relieved after implant adjustive and decompressive surgery.
There are still some limitations for our study. First, this is a retrospective single-institution study and thus the results may not be generalizable to other institutions. The relatively small sample size may have reduced the statistical significance to some extent, but all surgeries were performed by the same experienced surgeon and it shows predictors for UIROR in ASD surgery. We should expand the sample size in future work. Future study should consider the psychological, physical burden and cost analysis which would improve our standing of the mental and financial impact of UIROR on ASD patients.