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Purpose: Spinal fusion surgery is often performed with pelvic fixation to prevent distal junctional kyphosis. The inclusion of spinopelvic fixation has been reported to induce progression of hip joint arthropathy in a radiographic follow-up study. However, its biomechanical mechanism has not yet been elucidated. This study aimed to compare the changes in hip joint moment before and after spinal fusion surgery., Methods: This study was an observational study and included nine patients (eight women and one man) who were scheduled to undergo spinopelvic fusion surgery. We calculated the three-dimensional external joint moments of the hip during gait, standing, and climbing stairs before and 1 year after surgery., Results: During gait, the maximum extension moment was 0.51 ± 0.29 and 0.63 ± 0.40 before and after spinopelvic fusion surgery (p = 0.011), and maximum abduction moment was 0.60 ± 0.33 and 0.83 ± 0.34 before and after surgery (p = 0.004), respectively. During standing, maximum extension moment was 0.76 ± 0.32 and 1.04 ± 0.21 before and after spinopelvic fusion surgery (p = 0.0026), and maximum abduction moment was 0.12 ± 0.20 and 0.36 ± 0.22 before and after surgery (p = 0.0005), respectively. During climbing stairs, maximum extension moment was - 0.31 ± 0.30 and - 0.48 ± 0.15 before and after spinopelvic fusion surgery (p = 0.040), and maximum abduction moment was 0.023 ± 0.18 and - 0.02 ± 0.13 before and after surgery (p = 0.038), respectively., Conclusion: This study revealed that hip joint flexion-extension and abduction-adduction moments increased after spinopelvic fixation surgery in the postures of standing, walking, and climbing stairs. The mechanism was considered to be adjacent joint disease after spinopelvic fusion surgery including sacroiliac joint fixation., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: This study aimed to evaluate the progression of hip pathology and risk factors after ASD surgery., Methods: This case-control study enrolled 123 patients (246 hips); seven hips underwent hip arthroplasty were excluded. We measured the center-edge (CE) angle, joint space width (JSW), and Kellgren-Lawrence (KL) grade. We defined a CE angle˂25° as developmental dysplasia of the hip (DDH). We evaluated S2 alar-iliac (AI) screw loosening at final follow-up., Results: The annual decrease in the JSW was 0.31 mm up to 1 year, and 0.13 mm after 1 year (p = 0.001). KL grade progression occurred in 24 hips (10.0%; group P), while no progression occurred in 215 (90.0%; group N) hips. Nonparametric analysis between groups P and N revealed that significant differences were observed in sex, DDH, KL grade, ratio of S2AI screw fixation at baseline, and ratio of S2AI screw loosening at final follow-up. Multiple logistic regression analysis revealed that DDH (p = 0.018, odds ratio (OR) = 3.0, 95%CI = 1.2-7.3), baseline KL grade (p < 0.0001, OR = 37.7, 95%CI = 7.0-203.2), and S2AI screw fixation (p = 0.035, OR = 3.4, 95%CI = 1.1-10.4) were significant factors. We performed sub-analysis to elucidate the relationship between screw loosening and hip osteoarthritis in 131 hips that underwent S2AI screw fixation. Non-loosening of the S2AI screw was a significant factor for KL grade progression (p < 0.0001, OR = 8.9, 95%CI = 3.0-26.4)., Conclusion: This study identified the prevalence and risk factors for the progression of hip osteoarthritis after ASD surgery. Physicians need to pay attention to the hip joint pathology after ASD surgery., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Recently, the number of adult spinal deformity surgeries including sacroiliac joint fixation (SIJF) by using an S2 alar iliac screw or iliac screw has increased to avoid the distal junctional failure. However, we occasionally experienced patients who suffered from hip pain after a long instrumented spinal fusion. We hypothesized that long spinal fusion surgery including SIJF influenced the hip joint as an adjacent joint. The aim of this paper was to evaluate the association between spinal deformity surgery including SIJF and radiographic progression of hip osteoarthritis (OA)., Methods: This study was retrospective cohort study. In total, 118 patients who underwent spinal fusion surgery at single center from January 2013 to August 2018 were included. We measured joint space width (JSW) at central space of the hip joint. We defined reduction of more than 0.5 mm/year in JSW as hip OA progression. The patients were divided into two groups depending on either a progression of hip osteoarthritis (Group P), or no progression (Group N)., Results: The number of patients in Group P and Group N was 47 and 71, respectively. Factor that was statistically significant for hip OA was SIJF (p = 0.0065, odds ratio = 7.1, 95% confidence interval = 1.6-31.6). There were no other significant differences by the multiple logistic regression analysis., Conclusion: This study identified spinal fixation surgery that includes SIJF as a predictor for radiographic progression of hip OA over 12 months. We should pay attention to hip joint lesions after adult spinal deformity surgery, including SIJF.

Purpose: Although psychological factors are assumed to be the primary cause of stress-related back pain, there have been no studies of the relationships between stress and low back pain in an animal model. The purpose of this study was to examine the influence of specific alternation of rhythm in temperature (SART) stress on gait abnormality using the CatWalk method in a rat model of low back pain caused by lumbar facetectomy., Methods: Sixty rats were divided into three groups: the control, sham and experimental groups. Each group was then divided into non-SART stress and SART stress subgroups. We evaluated the behavioral changes 7 weeks postoperatively using the von Frey test and the CatWalk method., Results: Threshold values for the hind paw in the SART stress subgroups were significantly lower than those in the non-SART stress subgroups. In the experimental group, significant changes by CatWalk in step cycle, stand time and average speed were observed under non-SART stress conditions, but SART stress resulted in additional significant changes in not only these parameters, but in other parameters including the duty cycle and swing time, compared with those in the control and sham groups., Conclusions: The demonstration by CatWalk analysis may indicate that SART stress enhanced gait disturbance. In this animal model, we demonstrated for the first time that stress may be a factor involved in worsening of low back pain.

Purpose: Intervertebral disc degeneration is thought to contribute to low back pain. However, the pathophysiological mechanisms remain controversial. In a previous study, we developed an animal model that showed delayed gait disturbance after lumbar facetectomy in the rat. We believe that this gait disturbance was caused by low back pain, although the mechanisms of this gait abnormality remain unknown. The purpose of this study was to evaluate structural changes of the lumbar spine after facetectomy in the rat utilizing three-dimensional micro-computed tomography (3DμCT) compared to histology., Methods: Thirty male SD rats were divided into three groups. In the Sham group (n = 13), only exposure of bilateral facet joints at the L4-5 level was performed. In the Experimental group (n = 13), complete resection of bilateral L4-5 facet joints was achieved. Naïve rats (n = 4) were used for controls. At 7-week postoperative, 3DµCT and histological analyses were performed., Results: On 3DµCT images, increased disc height and endplate irregularities at the L4-5 segment and decreased disc height at adjacent segments were observed in the Experimental group. Histological scores were also higher in the Experimental group than the Sham Group., Conclusions: Degenerative changes were observed at the facetectomy level. These may correspond with the previously reported delayed gait disturbance after facetectomy. This animal model may be useful to create mechanically induced disc degeneration without direct tissue damage to the disc.

Purpose: A bipolar sealer using Transcollation ® technology, a combination of radiofrequency energy and saline, can provide hemostasis at 100 °C, which is lower than that used in standard electrocautery. Previous studies of joint arthroplasty have shown that use of the bipolar sealer reduces blood loss and tissue damage during the operation. However, it is unknown whether a bipolar sealer reduces blood loss and tissue damage in lumbar posterolateral fusion (PLF) surgery. The purpose of this study was to analyze the efficacy of this device in limiting blood loss during exposure of the lumbar spine in the treatment of PLF and postoperative pain., Methods: Fifty patients who underwent PLF were prospectively enrolled between October 2011 and March 2013. Twenty-five patients were randomized to the bipolar sealer group (BS group) and 25 patients to the standard electrocautery group (control group). Operative time and blood loss during exposure of posterior bony elements including the transverse process for PLF, visual analog scale (VAS) to quantify postoperative pain, and the interval from the surgery to hospital discharge were compared., Results: Operative time and blood loss expressed per level of exposure were significantly lower in the BS group than in the control group. There was a tendency toward a lower VAS at postoperative week 1 in the BS group. The duration of hospitalization was 15 and 26 days in the BS and control groups, respectively., Conclusions: A large randomized control trial adjusted for the number of fusion levels and body mass index is required to confirm the novelty value of this new bipolar sealers.

Purpose: Spinal instability of the lumbar spine causes various clinical symptoms. Among them, spinal instability is thought to contribute to low back pain, but the pathophysiological mechanisms are controversial. Although experimental animal models of spinal instability have been reported, it is unknown whether these models produce pain and whether spinal instability affects walking ability. We used the CatWalk system to investigate whether lumbar facetectomy causes gait abnormalities and low back pain., Methods: Thirty male Sprague-Dawley rats were divided into three experimental groups. In the sham group, only the bilateral L4-L5 facet joints were exposed. In the experimental group, rats underwent complete resection of the bilateral L4-L5 facet joints without neural tissue injury. The control group comprised naïve rats. The CatWalk system was used to analyze gait in postoperative weeks 3, 4.5, 6, and 7. Radiological and histological analyses were also performed., Results: At 7 weeks postoperatively, the rats in the experimental group showed the gait abnormalities seen in low back pain and neuropathic pain models. Radiological examination of the same rats revealed spinal instability with histological evidence of intervertebral disc degeneration., Conclusions: These results suggest that spinal instability and/or intervertebral disc degeneration induce gait abnormalities and low back pain. This experimental model may be useful for elucidating the mechanisms underlying clinical symptoms, such as low back pain, in patients with spinal instability.

Background: Surgical site infection (SSI) after spinal surgery is a devastating complication. Various methods of skin closure are used in spinal surgery, but the optimal skin-closure method remains unclear. A recent report recommended against the use of metal staples for skin closure in orthopedic surgery. 2-Octyl-cyanoacrylate (Dermabond; Ethicon, NJ, USA) has been widely applied for wound closure in various surgeries. In this cohort study, we assessed the rate of SSI in spinal surgery using metal staples and 2-octyl-cyanoacrylate for wound closure., Methods: This study enrolled 609 consecutive patients undergoing spinal surgery in our hospital. From April 2007 to March 2010 surgical wounds were closed with metal staples (group 1, n = 294). From April 2010 to February 2012 skin closure was performed using 2-octyl-cyanoacrylate (group 2, n = 315). We assessed the rate of SSI using these two different methods of wound closure. Prospective study of the time and cost evaluation of wound closure was performed between two groups., Results: Patients in the 2-octyl-cyanoacrylate group had more risk factors for SSI than those in the metal-staple group. Nonetheless, eight patients in the metal-staple group compared with none in the 2-octyl-cyanoacrylate group acquired SSIs (p < 0.01). The closure of the wound in length of 10 cm with 2-octyl-cyanoacrylate could save 28 s and $13.5., Conclusions: This study reveals that in spinal surgery, wound closure using 2-octyl-cyanoacrylate was associated with a lower rate of SSI than wound closure with staples. Moreover, the use of 2-octyl-cyanoacrylate has a more time saving effect and cost-effectiveness than the use of staples in wound closure of 10 cm in length.