Posterior Lumbar Spine Surgery Research Articles

Wound Closure After Posterior Multi-level Lumbar Spine Surgery: An Anatomical Cadaver Study and Technical Note

Meticulous attention to wound closure in posterior lumbar spine surgery is an important principle in reducing surgical site infections. We detail standardized wound closure used for posterior lumbar spine surgery at a tertiary care referral center and illustrate this as a step-by-step cadaveric dissection. The lumbar spine of a cadaveric specimen (male, 73 years at death) was used for dissection. Standardizing wound closure in posterior lumbar spine surgery may help limit wound complications and infection. Some key points of our technique, as demonstrated on a cadaveric specimen, include separating fascial compartments, avoiding suture abscesses, and creating a tension-free wound.

Ascorbic Acid Attenuates Multifidus Muscles Injury and Atrophy After Posterior Lumbar Spine Surgery by Suppressing Inflammation and Oxidative Stress in a Rat Model.

A rat model of multifidus muscles injury and atrophy after posterior lumbar spine surgery. We determined the effect of ascorbic acid (AA) on the postoperative multifidus muscles in rat model. Previous studies show oxidative stress and inflammation are two main molecular mechanisms in multifidus muscle injury and atrophy after posterior lumbar surgery. AA may have a protective effect in postoperative multifidus muscles. Rats were divided into sham surgery, control surgery, and surgery plus AA groups. Multifidus muscles of the control and AA groups were excised from the osseous structures. The muscles were retracted continuously for 2 hours. In the sham and AA groups, AA was administered via oral gavage daily in the first week. In each group, the oxidative stress was evaluated by measuring malondialdehyde (MDA) and Total superoxide dismutase (T-SOD). The inflammation, fat degeneration, or fibrosis of multifidus muscle were evaluated by quantitative real-time polymerase chain reaction (q-PCR), histology, or immunohistochemical analysis. T-SOD activity was significantly lower in the control group than that in the AA group in the first week. MDA levels were significantly higher in the AA group. Interleukin-6 and tumor necrosis factor-α in multifidus muscles also showed significant differences when treated with AA. The inflammation score on histology was significantly lower in the AA group postoperatively in the first week. In the long run, marker genes for fibrosis and fat degeneration, and fibrosis and fat degeneration scores, were significantly lower in the AA than the control group on days 14 and 28 postoperatively. In conclusion, AA attenuated the oxidative stress and inflammation response in the postoperative multifidus muscles, and remarkable differences were observed from the histological assessment and related marker genes expression. Our results provided important insight into the anti-inflammatory and anti-oxidative effects of AA in the postoperative multifidus muscles. N/A.

Factors Influencing Postoperative Urinary Retention Following Elective Posterior Lumbar Spine Surgery: A Prospective Study.

Study DesignProspective observational study.PurposeTo determine the incidence of postoperative urinary retention (POUR) in patients undergoing elective posterior lumbar spine surgery and identify the risk factors associated with the development of POUR.Overview of LiteraturePOUR following surgery can lead to detrusor dysfunction, urinary tract infections, prolonged hospital stay, and a higher treatment cost; however, the risk factors for POUR in spine surgery remain unclear.MethodsA prospective, consecutive analysis was conducted on patients undergoing elective posterior lumbar surgery in the form of lumbar discectomy, lumbar decompression, and single-level lumbar fusions during a 6-month period. Patients with spine trauma, preoperative neurological deficit, previous urinary disturbance/symptoms, multiple-level fusion, and preoperative catheterization were excluded from the study. Potential patient- and surgery-dependent risk factors for the development of POUR were assessed. Univariate analysis and a multiple logistical regression analysis were performed.ResultsA total of 687 patients underwent posterior lumbar spine surgery during the study period; among these, 370 patients were included in the final analysis. Sixty-one patients developed POUR, with an incidence of 16.48%. Significant risk factors for POUR were older age, higher body mass index (BMI), surgery duration, intraoperative fluid administration, lumbar fusion versus discectomy/ decompression, and higher postoperative pain scores (p<0.05 for all). Sex, diabetes, and the type of inhalational agent used during anesthesia were not significantly associated with POUR. Multiple logistical regression analysis, including age, BMI, surgery duration, intraoperative fluid administration, fusion surgery, and postoperative pain scores demonstrated a predictive value of 92% for the study population and 97% for the POUR group.ConclusionsPOUR was associated with older age, higher BMI, longer surgery duration, a larger volume of intraoperative fluid administration, and higher postoperative pain scores. The contribution of postoperative pain scores in the multiple regression analysis was a significant predictor of POUR.

The Effect of Pressure Controlled Ventilation on Pulmonary Mechanics in Prone Patients Undergoing Elective Spine Surgeries: Comparative Study with Volume Controlled Ventilation

Abstract Background: As patients turned into prone position expe-rienced more decrease in lung compliance than those on supine position, this prospective, randomized study was designed to compare the effect of PCV and volume-controlled ventilation (VCV) on lung mechanics and heamodynamics in the prone position using the Wilson frame during elective lumbar spine surgery.Patients and Methods: Sixty patients scheduled for elective lumbar spine surgery were randomly allocated to receive mechanical ventilation using either the VCV (n=30) or PCV (n=30) mode. Respiratory variables (peak airway pressure, mean airway pressure, shunt fraction, alveolar-arterial oxygen gradient). Dynamic compliance (Cdyn) of the respiratory system was calculated as VT/ (Ppeak-PEEP). The alveolar dead space-to-tidal volume ratio (VD/VT) will be estimated using the Hardman and Aitkenhead equation: VD/VT=1. 135– (PaCO2-ETCO2)/(PaCO2-0. 005). Results: The Ppeak in the PCV group was lower than that in the VCV group throughout the study period (p-value=0.961 and 0. 0.109 at supine position and prone position, respectively) and was increased at prone position compared with supine position in both groups. Cdyn was decreased from supine to prone position in both groups. However, the Cdyn in the PCV group was higher than that in the VCV group during the study period however it is only statistically significant after 1.5 and 2hrs. The arterial oxygen tension was comparable between the 2 groups during the study period.Conclusions: PCV provides lower Ppeak compared with VCV when the ventilator is set to deliver the same tidal volume and variable respiratory rate to maintain a constant end-tidal carbon dioxide tension in patients undergoing pos-terior lumbar spine surgery in the prone position using the Wilson frame.

The impact of prophylactic intraoperative vancomycin powder on microbial profile, antibiotic regimen, length of stay, and reoperation rate in elective spine surgery

Background ContextThere is growing concern that the microbial profile of surgical site infection (SSI) in the setting of prophylactic vancomycin powder may favor more resistant and uncommon organisms. PurposeTo demonstrate the impact of prophylactic intraoperative vancomycin powder on microbial profile, antibiotic regimen, length of stay (LOS), and reoperation rate in spine surgical site infection. Study Design and/or SettingRetrospective cohort study. Patient Sample: the study included 115 postoperative spine patients who were required to return to the operating room for SSI. Outcome MeasuresThe outcome measures were microbial profile, reoperation rate, antibiotic regimen, and LOS for patients with postoperative spine infection who either did (treated) or did not (untreated) receive prophylactic vancomycin powder during their index procedure. MethodsA retrospective review of patients who underwent posterior thoracic and/or lumbar spine surgery between 2010 and 2017 was conducted. Those undergoing surgical treatment of SSI were identified, and patients were divided into two groups - those who were treated with intraoperative vancomycin (treated) and those who were not (untreated). The organism profile for each group was compared. The average LOS, reoperation rate, and number of patients requiring more than 1 antibiotic were calculated for each patient in both groups. ResultsThere were 5,909 procedures performed. One hundred and fifteen SSIs were identified, resulting in a 1.9% infection rate. Prophylactic vancomycin powder was used in the index procedure for 42 of those cases. 23.8% of cultures in the vancomycin group were polymicrobial and 16.7% were gram-negative compared with 9.6% (p=0.039) and 4.1% (p=0.021) in the untreated group, respectively. In the vancomycin-treated group, 26.1% of patients underwent repeat irrigation and debridement compared with 38.4% in the untreated group (p=0.184). The percentage of patients in the treatment and untreated group who required more than 1 antibiotic was 26.0% and 26.1%, respectively (p=0.984). Mean LOS in the treatment group was 8.0 versus 7.9 for the untreated group (p=0.945) ConclusionsIn this series, vancomycin powder was associated with a higher prevalence of gram-negative and polymicrobial organisms in patients that ultimately developed postoperative SSI. However, this did not adversely affect the need for multiple reoperations, antibiotic regimen, or LOS for these patients.

Risk Factors for Surgical Site Infection After Posterior Lumbar Spinal Surgery.

A retrospective study. The purpose of this study was to identify the independent risk factors for postoperative surgical site infection (SSI) after posterior lumbar spinal surgery based on the perioperative factors analysis. SSI is one of the most common complications after spinal surgery. Previous studies have identified different risk factors for postoperative SSI after lumbar spinal surgery. However, most of the studies were focused on the patient and procedure-related factors. Few studies reported the correlation between laboratory tests and postoperative SSI. A retrospective study was carried out in a single institution. Patients who underwent posterior lumbar spinal surgery between January 2010 and August 2016 were included in this study. All patients' medical records were reviewed and patients with postoperative SSI were identified. Perioperative variables were included to determine the risk factors for SSI by univariate and multivariate regression analysis. A total of 2715 patients undergoing posterior lumbar spinal surgery were included in this study. Of these patients, 64 (2.4%) were detected with postoperative SSI, including 46 men and 18 women. Diabetes mellitus (P = 0.026), low preoperative serum level of calcium (P = 0.009), low preoperative and postoperative albumin (P = 0.025 and 0.035), high preoperative serum glucose (P = 0.029), multiple fusion segments (P < 0.001), increased surgical time and estimated blood loss (P = 0.023 and 0.005), decreased postoperative hemoglobin (P = 0.008), and prolonged drainage duration (P = 0.016) were found to be the independent risk factors for SSI. Multilevel fusion and a history of diabetes mellitus were the two strongest risk factors (odds ratio = 2.329 and 2.227) for SSI. Based on a large population analysis, previous reported risk factors for SSI were confirmed in this study while some new independent risk factors were identified significantly associated with SSI following lumbar spinal surgery, including preoperative low serum level of calcium, decreased preoperative and postoperative albumin, and decreased postoperative hemoglobin. 4.

Point-of-View: Risk Factors for Surgical Site Infection After Posterior Lumbar Spinal Surgery.

Point-of-View: Risk Factors for Surgical Site Infection After Posterior Lumbar Spinal Surgery.

Anatomical and technical factors associated with superior facet joint violation in lumbar fusion.

OBJECTIVE The aim of this study was to evaluate the anatomical and surgical risk factors for screw-related facet joint violation at the superior level in lumbar fusion. METHODS The authors conducted a retrospective review of a consecutive series of posterior lumbar instrumented fusions performed by a single surgeon. Inclusion criteria were primary lumbar fusion of 1 or 2 levels for degenerative disorders. The following variables were analyzed as possible risk factors: surgical technique (percutaneous vs open screw placement), depth of surgical field, degree of anterior slippage of the superior level, pedicle and facet angle, and facet degeneration of the superior level. Postoperative CT scans were evaluated by 2 independent reviewers. Axial, sagittal, and coronal views were reviewed. Pedicle screws were graded as intra-articular if they clearly interposed between the superior and inferior facet joints of the superior level. Multivariate logistic regression analyses were conducted to assess the factors associated with this complication. RESULTS One hundred thirty-one patients were included. Interobserver reliability for facet joint violation assessment was high (κ = 0.789). The incidence of superior facet joint violation was 12.59% per top-level screw (33 of 262 proximal screws). The rate of facet violation was 28.0% in the percutaneous technique group (14 of 50 patients) and 12.3% in the open surgery group (10 of 81 patients) (OR 2.26, 95% CI 1.09-4.21; p = 0.024). In multivariate logistic regression analysis, independent predictors of facet violation were percutaneous screw placement (adjusted OR 3.31, 95% CI 1.42-7.73; p = 0.006), right-side pedicle screw (adjusted OR 3.14, 95% CI 1.29-7.63; p = 0.011), and facet angle > 45° (adjusted OR 10.95, 95% CI 4.64-25.84; p < 0.0001). CONCLUSIONS The incidence of facet joint violation was higher in percutaneous minimally invasive than in open technique for posterior lumbar spine surgery. Also, coronal orientation of the facet joint is a significant risk factor independent of the surgical technique.

Treatment of delayed deep infection after spinal fixation

Objective To explore the efficacy of early aggressive debridement with implant retention, primary wound closure, closed suction drain without irrigation and antibiotic therapy for the treatment of delayed deep infection after spinal fixation. Methods 4 057 patients were underwent dorsal spinal fixation from January 2010 to June 2014. Among them, 42 cases of delayed deep infection after operation were included in the study. There were 25 males and 17 females, with an average age of 68.6±8.1 years (ranged from 53 to 83 years). The diagnosis of delayed deep infection was based on the time of onset, clinical symptoms and signs, imaging and laboratory findings. Surgical debridement was performed immediately after diagnosis of infection. In addition, devitalized and necrotic tissue and biofilms which adhered to the surface of the implant were removed meticulously and thoroughly. Primary wound closure was performed in each patient, and closed suction drains were maintained for about 7-10 d without irrigation. Routine sensitive antimicrobial drugs was applied for 3 months after operation. Results 42 cases were all followed up for 24 to 72 months with an average of 46 months. Among the 42 infected patients, 3 patients were underwent posterior cervical spine surgery and 39 patients were underwent posterior lumbar spine surgery. There were 13 cases of staphylococcus aureus infection, 7 cases of escherichia coli infection, 3 cases of ESBL escherichia coli infection, 3 cases of enterobacter cloacae infection, 2 cases of MRSA, 2 cases of acinetobacter baumannii infection, 2 cases of klebsiella pneumoniae infection, 1 case in enterococcus faecium and pseudomonas aeruginosa and staphylococcus haemolyticus, respectively. There were still 7 patients with negative bacterial culture. 41 cases retained their implant, whereas 1 staphylococcus aureus infection patient had the implants removed because of loosening during debridement. Nevertheless, primary wound healing was found in all patients, and stitches were removed 2 to 3 weeks after debridement. Infections were effectively controlled with no recurrence of infection during the follow-up. The average erythrocyte sedimentation rate was (65.76±20.08) mm/h preoperative, (41.43±14.65) mm/h 1 month postoperative, (10.81±2.72) mm/h 6 months postoperative, and (8.10±5.46) mm/h 12 months postoperative, respectively, the differences were statistically significant. The average C reactive protein was (40.55±16.91) mg/L preoperative, (6.50±2.46) mg/L 1 month postoperative, (4.31±1.26) mg/L 6 months postoperative, and (3.83±1.50) mg/L 12 months postoperative, respectively, the differences were statistically significant. The average procalcitonin was (0.47±0.28) ng/ml preoperative, (0.08±0.06) ng/ml 1 month postoperative, (0.06±0.03) ng/ml 6 months postoperative, and (0.05±0.00) ng/ml 12 months postoperative, respectively, and the differences were statistically significant. Conclusion A timely diagnosis, aggressive and meticulous debridement, high vacuum closed-suction drain, routine and adequate use of antibacterial agents are keys to successfully resolving infection and maintaining implant retention in the treatment of delayed deep infection after spinal fixation. Key words: Infection; Reoperation; Debridement

Incidence and risk factors for symptomatic spinal epidural haematoma following lumbar spinal surgery

Spinal epidural haematoma (SEH) is a common complication after lumbar spinal decompression surgery, and symptomatic SEH usually causes devastating neurological deficits. Although different risk factors for post-operative SEH have been reported, few studies focused on patients' laboratory tests. The purpose of this study was to analyze the incidence of symptomatic SEH following lumbar spinal surgery, as well as identify the risk factors for it. Patients who underwent posterior lumbar spinal decompression surgery between January 2010 and August 2016 were included in this study and their medical records were retrospectively reviewed. Those who developed post-operative symptomatic SEH after the surgery were identified. The risk factors for SEH were analyzed by univariate and multivariate regression analysis. In total, 2715 patients were included in this study and 31 (1.14%) were identified with post-operative symptomatic SEH. Of these patients, 19 were males and 12 were females, with an average age of 59.39±11.66years. After multivariate logistic regression analysis, low serum calcium level (P=0.025), blood type A (P=0.04), increased estimated blood loss (P=0.032), prolonged surgical duration (P=0.018), and decreased post-operative globulin (P=0.016) were identified as the independent risk factors for post-operative SEH following lumbar spinal surgery. Furthermore, prolonged surgical duration (odds ratio=3.105) was the strongest risk factor for SEH. Based on a large population investigation, the incidence of symptomatic SEH following lumbar spinal decompression surgery was 1.14%. Blood type A, increased estimated blood loss, and prolonged surgical duration were identified as the independent risk factors for post-operative SEH while two new risk factors, including low serum calcium level and decreased post-operative globulin, were firstly identified in this study.

171 Psychiatric Comorbidities - What to Expect Post Spine Surgery

Abstract INTRODUCTION Improved life expectancy and elderly population has significantly increased the co-morbid conditions encountered by spine surgeons. One of the comorbidities include mood disorder patients requiring spine surgery. It is important to understand the short term outcome in these patients after spine surgery as it is known to impact the outcome. In this study, we detail outcomes for first 30days in patients with mood disorders. METHODS A retrospective database of 550 patients who underwent posterior lumbar spine surgery (between 2015 and 2016) was analyzed. We collected data including demographics, surgical technique, outcomes and complications. A multivariate regression analyses were performed assessing differences in outcomes and morbidity in the mood disorder (anxiety and depressive) versus non-mood disorder groups. RESULTS &gt;275 included patients were stratified into mood disorder (n = 24) and Non-mood disorder (n = 251) groups. The average age was 59.1 ± 14.6 years old with 48% patients being male. There was higher incidence of 30-day readmission in mood disorder group (12.5% vs 6%, P = 0.462). In regards to surgical outcome, patients with mood disorder tend to have higher mean VAS (4.5 vs 3.7, P = 0.089), higher mean ODI (24.2 vs 16.8, P &lt; 0.001), slightly lower mean EQ-50 (0.67 vs 0.77, P = 0.004) CONCLUSION Our study is provides detail estimate of short term outcome in patients with mood disorder. Our study patients operated at our institution and significantly differ from the online commercial database analysis. Spine surgeons also have to be aware of the outcomes and prepare to optimize the peri-operative condition. Patient education significantly reduces the expectation vs reality post spine surgery.

Influence of Obesity on Complications, Clinical Outcome, and Subsidence After Anterior Lumbar Interbody Fusion (ALIF): Prospective Observational Study.

The complications associated with obesity have been well described for posterior lumbar spinal surgery. However, the influence of obesity on anterior lumbar interbody fusion (ALIF) is not well established. We aimed to compare complication risks, functional outcomes, and subsidence rates in normal-weight, overweight, and obese patients who underwent ALIF. A total of 137 consecutive patients undergoing ALIF surgery from 2012 to 2014 were followed prospectively. Patients were categorized into 3 groups according to their body mass index (BMI). Patients were evaluated preoperative and postoperatively. Outcome measures included Short Form-12, Oswestry Disability Index, surgical complications, and subsidence. There was no significant difference between the BMI groups in terms of baseline age, proportion of men, levels operated, smoking status, diabetes status, or anterior, posterior, or average disc height. There was no difference in operative duration, blood loss, or hospital stay. At 12-month follow-up, no difference was found in terms of total complications, change in Short Form-12 mental or physical component scores, or Oswestry Disability Index scores. Average disc height was significant lower for the obese group (11.3 mm) compared with the normal-weight (14.4 mm) group. Fusion rate was also significantly lower for patients who were obese (60%) compared with normal-weight (88.2%) and overweight patients (76%) (P= 0.014). Delayed subsidence rates also were similar between normal-weight and overweight patients. There were no differences in functional outcomes or complications in patients with elevated BMI compared with normal-weight patients. Fusion rates were lower for patients were obese. Obesity should not be considered a contraindication to surgery in patients with appropriate indication to undergo ALIF.

Safety and effectiveness of argatroban versus heparin for preventing venous thromboembolism after lumbar decompressive surgery

BackgroundTo evaluate the safety and effectiveness of argatroban for the prevention of venous thromboembolism (VTE) after posterior lumbar decompressive surgery. MethodsIncluded in this retrospective study were 556 patients who underwent posterior lumbar decompressive surgery for trauma and degenerative diseases. They were divided into two groups: argatroban group (n = 274), and low molecular weight heparin (LMWH) group (n = 282). The occurrence of postoperative venous thrombosis and complications including hemorrhage and allergic reaction was compared between the two groups. Neurological and clinical outcomes in terms of Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI) were assessed before operation and at 6 and 12 months after operation. ResultsPostoperative venous thromboembolism (VTE) occurred in seven patient. No pulmonary embolism (PE) occurred in any patient. Thrombosis occurred in 3 cases (1.0%) and bleeding in 1 case (0.04%) in argatroban group vs. 4 (1.4%) and 4 (1.4%) in LMWH group, showing no significant between the two groups (P > 0.05). There was significant reduction in the severity of back and leg pain (VAS P < 0.05) and significant improvement in the patient quality of life (ODI, P < 0.05) 6 months and 1 year after operation, showing no significant difference between the two groups (P > 0.05). ConclusionsArgatroban proved to be equally effective as LWMH for anticoagulation therapy. Both drugs exhibited a similar preventive effect against postoperative VTE after posterior lumbar spine surgery, without increasing the risk of postoperative bleeding. The neurological and clinical outcomes are satisfactory and similar between the two pharmacological methods.

Meralgia paresthetica following prone position in posterior lumbar spinal surgery: Case series and review of the literature

Meralgia paresthetica following prone position in posterior lumbar spinal surgery: Case series and review of the literature

Vascular Injury in Posterior Lumbar Spinal Surgery

Vascular Injury in Posterior Lumbar Spinal Surgery

Use of liposomal bupivacaine in the postoperative management of posterior spinal decompression.

OBJECTIVE The aim in this paper was to evaluate the efficacy of long-acting liposomal bupivacaine in comparison with bupivacaine hydrochloride for lowering postoperative analgesic usage in the management of posterior cervical and lumbar decompression and fusion. METHODS A retrospective cohort-matched chart review of 531 consecutive cases over 17 months (October 2013 to February 2015) for posterior cervical and lumbar spinal surgery procedures performed by a single surgeon (J.J.) was performed. Inclusion criteria for the analysis were limited to those patients who received posterior approach decompression and fusion for cervical or lumbar spondylolisthesis and/or stenosis. Patients from October 1, 2013, through December 31, 2013, received periincisional injections of bupivacaine hydrochloride, whereas after January 1, 2014, liposomal bupivacaine was solely administered to all patients undergoing posterior approach cervical and lumbar spinal surgery through the duration of treatment. Patients were separated into 2 groups for further analysis: posterior cervical and posterior lumbar spinal surgery. RESULTS One hundred sixteen patients were identified: 52 in the cervical cohort and 64 in the lumbar cohort. For both cervical and lumbar cases, patients who received bupivacaine hydrochloride required approximately twice the adjusted morphine milligram equivalent (MME) per day in comparison with the liposomal bupivacaine groups (5.7 vs 2.7 MME, p = 0.27 [cervical] and 17.3 vs 7.1 MME, p = 0.30 [lumbar]). The amounts of intravenous rescue analgesic requirements were greater for bupivacaine hydrochloride in comparison with liposomal bupivacaine in both the cervical (1.0 vs 0.39 MME, p = 0.31) and lumbar (1.0 vs 0.37 MME, p = 0.08) cohorts as well. None of these differences was found to be statistically significant. There were also no significant differences in lengths of stay, complication rates, or infection rates. A subgroup analysis of both cohorts of opiate-naive versus opiate-dependent patients found that those patients who were naive had no difference in opiate requirements. In chronic opiate users, there was a trend toward higher opiate requirements for the bupivacaine hydrochloride group than for the liposomal bupivacaine group; however, this trend did not achieve statistical significance. CONCLUSIONS Liposomal bupivacaine did not appear to significantly decrease perioperative narcotic use or length of hospitalization, although there was a trend toward decreased narcotic use in comparison with bupivacaine hydrochloride. While the results of this study do not support the routine use of liposomal bupivacaine, there may be a benefit in the subgroup of patients who are chronic opiate users. Future prospective randomized controlled trials, ideally with dose-response parameters, must be performed to fully explore the efficacy of liposomal bupivacaine, as the prior literature suggests that clinically relevant effects require a minimum tissue concentration.

Rectangular Tubular Retractor for Microendoscopic Lumbar Decompression.

Background A cylindrical working tube with a diameter of 16 mm has been used for endoscopic posterior lumbar spinal surgery. However, intraoperative muscle resection is significant when using the current conventional tubular retractor. Objective To describe a novel tubular retractor for microendoscopic surgery and to analyze the outcomes of lumbar decompressive laminotomy using this retractor. Materials and Methods We devised a novel tubular retractor by changing the medial and lateral sides of the conventional 16-mm cylindrical tubular retractor to planes with a mediolateral dimension of 10 mm (rectangular tubular retractor hereafter). The amount of muscle resection, osteotomy angle on the approach side, and operating time were compared between 25 intervertebral levels treated by bilateral decompression through a unilateral approach using the rectangular tubular retractor and 31 intervertebral levels treated with the same surgery using a 16-mm cylindrical tubular retractor. Results Due to the short mediolateral dimension, muscle resection decreased by 86%. The rectangular tubular retractor also decreased early postoperative wound pain. Because the craniocaudal dimension of the tubular retractor was maintained, surgical difficulty did not increase, resulting in only a slight increase in operating time. The facet joint on the approach side could be sufficiently preserved. Conclusions The rectangular tubular retractor reduced surgical invasiveness without increasing surgical difficulty.

Effect of pure muscle retraction on multifidus injury and atrophy after posterior lumbar spine surgery with 24weeks observation in a rabbit model.

To evaluate the effect of pure muscle retraction on multifidus injury and atrophy. Sixty-three adult New Zealand white rabbits were divided evenly into three groups: 1-h retraction (group R1), 2-h retraction (R2), and sham surgery (C). The multifidus muscle was evaluated using magnetic resonance imaging (MRI) and histology after 3 and 48h, and 1, 3, 6, 12, and 24weeks after surgery. Multifidus muscle injury and atrophy were not observed in group C, but were obvious in groups R1 and R2. Edema, necrosis, and inflammation mainly occurred in the first week postoperatively, and were more severe in R2 than in R1 (P<0.01). Muscle fiber regeneration began at week 1, fibrotic changes mainly occurred at weeks 3 and 6, and fat degeneration became obvious at weeks 12 and 24 postoperatively. The fibrosis and fat degeneration scores of R2 were higher than those of R1 (P<0.01). Decreased acetylcholine activity and granular degeneration of the neuromuscular junction were observed in both retraction groups, but was more severe in R2 than in R1 (P<0.01). Muscle retraction was an important factor not only for multifidus injury, but also for long-term multifidus atrophy after posterior lumbar surgery; a longer retraction time caused more severe multifidus injury and atrophy. Muscle fibers can be regenerated postoperatively, and denervation might be the reason for muscle atrophy.

Prospective multicenter surveillance and risk factor analysis of deep surgical site infection after posterior thoracic and/or lumbar spinal surgery in adults

Surgical site infection is a serious and significant complication after spinal surgery and is associated with high morbidity rates, high healthcare costs and poor patient outcomes. Accurate identification of risk factors is essential for developing strategies to prevent devastating infections. The purpose of this study was to identify independent risk factors for surgical site infection among posterior thoracic and/or lumbar spinal surgery in adult patients using a prospective multicenter surveillance research method. From July 2010 to June 2012, we performed a prospective surveillance study in adult patients who had developed surgical site infection after undergoing thoracic and/or lumbar posterior spinal surgery at 11 participating hospitals. Detailed preoperative and operative patient characteristics were prospectively recorded using a standardized data collection format. Surgical site infection was based on the definition established by the Centers for Disease Control and Prevention. A total of 2,736 consecutive adult patients were enrolled, of which 24 (0.9%) developed postoperative deep surgical site infection. Multivariate regression analysis indicated four independent risk factors. Preoperative steroid therapy (P = 0.001), spinal trauma (P = 0.048) and gender (male) (P = 0.02) were statistically significant independent patient-related risk factors, whereas an operating time ≥3 h (P < 0.001) was a surgery-related independent risk factor. Preoperative steroid therapy, spinal trauma, male gender and an operating time ≥3 h were independent risk factors for deep surgical site infection after thoracic and/or lumbar spinal surgery in adult patients. Identification of these risk factors can be used to develop protocols aimed at decreasing the risk of surgical site infection.

Patient and surgical factors associated with postoperative urinary retention after lumbar spine surgery.

Retrospective case series. The objectives of this study were to (1) determine the rate of postoperative urinary retention (POUR) in a series of patients undergoing lumbar spine surgery, (2) compare length of hospital stay between patients who developed POUR and patients who did not, and (3) identify the patient and surgical factors associated with the development of POUR. Although POUR is a common complication in many surgical subspecialties, sparse literature is present regarding development of POUR after posterior lumbar surgical procedures. A retrospective review was conducted of all posterior lumbar surgery cases performed at single institute from July 2008 to July 2012. Data collected included demographic variables (age, sex, body mass index), length of stay, comorbid medical conditions, and surgical data. The Wilcoxon rank sum test with continuity correction was used to compare length of hospital stay between patients who developed POUR and patients who did not. A multivariate logistic regression model was created using all patient and surgical factors and systematically pruned of variables not improving overall predictive power. A total of 647 patients (291 decompression, 356 decompression and fusion) were included in the study. Of 647 patients, 36 had urinary retention after lumbar spine surgery (5.6%). Patients who developed POUR had a longer length of stay than patients who did not develop POUR (3.94 d vs. 2.34 d; P=0.005). Male sex, benign prostatic hyperplasia, age, diabetes, and depression were significantly associated with development of POUR (odds ratio=3.05, 9.82, 1.04, 3.32, and 2.51, respectively). Smoking was inversely associated with the development of POUR (odds ratio=0.45). The risk of developing POUR after posterior lumbar spine surgery is approximately 5%. Male sex, benign prostatic hyperplasia, age, diabetes, and depression were significantly associated with the POUR group. Patients who developed POUR had a greater length of hospital stay. 4.