Four-Level Cervical Disc Arthroplasty.

BACKGROUND: Multilevel anterior cervical discectomy and fusion inevitably yields a higher chance of pseudarthrosis or require more reoperations than single-level procedures. Therefore, multilevel cervical disc arthroplasty (CDA) could be an alternative surgery for cervical spondylosis, as it (particularly 3- and 4-level CDA) could preserve more functional motility than single-level disc diseases. This study aimed to investigate the clinical and radiological outcomes of 4-level CDA, a relatively infrequently indicated surgery. METHODS: The medical records of consecutive patients who underwent 4-level CDA were retrospectively reviewed. These highly selected patients typically had multilevel disc herniations with mild spondylosis. The inclusion criteria were symptomatic cervical spondylotic myelopathy, radiculopathy, or both, that were medically refractory. The clinical outcomes were assessed. The radiographic outcomes, including global and individual segmental range of motion (ROM) at C3-7, and any complications were also analyzed. RESULTS: Data from a total of 20 patients (mean age: 56 ± 8 years) with an average follow-up of 34 ± 20 months were analyzed. All patients reported improved clinical outcomes compared with that of preoperation, and the ROMs at C3-7 were not only preserved but also trended toward an increase (35 ± 8 vs 37 ± 10 degrees, pre- vs postoperation, P = 0.271) after the 4-level CDA. However, global cervical alignment remained unchanged. There was one permanent C5 radiculopathy, but no other neurological deteriorations or any reoperations occurred. CONCLUSION: For these rare but unique indications, 4-level CDA yielded clinical improvement and preserved segmental motility with low rates of complications. Four-level CDA is a safe and effective surgery, maintaining the ROM in patients with primarily disc herniations and mild spondylosis. CLINICAL RELEVANCE: For patients with mild spondylosis, whose degeneration at the cervical spine is not so severe, CDA is more suitable.

Assessing Range of Motion Gap in Circumferential Surgery for Cervical Myelopathy due to Ossification of the Posterior Longitudinal Ligament.

OBJECTIVE: Only a few studies have investigated the gap range of motion (gROM) in cervical myelopathy or deformity caused by ossification of the posterior longitudinal ligament (OPLL). The aim of this study is to investigate the correlation between the individual gROM and the postoperative clinical outcomes of patients with OPLL. METHODS: Consecutive patients of cervical myelopathy caused by OPLL were analyzed retrospectively. The clinical outcomes were evaluated using Visual Analogue Scale scores of the neck and arm pain and the Japanese Orthopaedic Association scores. Radiologic measurements included flexion ROM (fROM), which was defined as the difference of cervical lordosis in flexion and neutral positions, extension ROM (eROM), defined as the difference between neutral and extension positions, and gROM, defined as the difference between fROM and eROM. Patients were grouped by the values of gROM, and comparisons of all outcomes were made between the groups. RESULTS: A total of 42 patients underwent surgery. The patients with greater gROM did not differ from those with smaller gROM by demographic characteristics. During follow-up (mean 45.8 months), both groups had similar improvements, but the C5 palsy rates were higher in the greater gROM group than in the smaller gROM group (71% and 22%, P < 0.05). CONCLUSIONS: Simultaneous circumferential decompression and fixation is an effective surgical option for patients with cervical myelopathy caused by OPLL. A higher rate of postoperative C5 palsy was observed in the patients with greater gROMs after surgery, although all patients presented with similar clinical improvements.

Comparison of intraoperative cone-beam CT versus preoperative fan-beam CT for navigated spine surgery: a prospective randomized study.

OBJECTIVE: This prospective randomized study aimed to investigate the accuracy, radiation exposure, and surgical workflow optimization of a novel intraoperative spinal navigation system using preoperative fan-beam (FB) CT versus the classic intraoperative cone-beam (CB) CT in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). METHODS: In this two-arm, single-center, randomized study, the authors evaluated the safety and clinical outcomes of a novel navigation system for pedicle screw placement in spine surgery. RESULTS: The accuracy of pedicle screw placement in the experimental group (FB group) was 94.38%, while it was 94.55% in the control group (CB group). Notably, the intraoperative radiation exposure to patients in the FB CT group (mean 0.361 ± 0.261 mSv) was significantly lower than that in the CB CT group (mean 6.526 ± 13.591 mSv) (p < 0.0001). Furthermore, the intraoperative preparation time for screw placement in the FB group (mean 10.6 ± 5.62 minutes) was significantly lower than that in the CB group (mean 17.6 ± 5.59 minutes) (p = 0.0004). No significant differences were observed for blood loss during surgery, total radiation exposure to surgeons, mean time for inserting a single pedicle screw, revision surgery rate, patients' reported outcomes, and length of postoperative hospital stay between the two groups. Significant differences were observed for intraoperative radiation exposure to patients and the preparation time for pedicle screw placement. CONCLUSIONS: The preoperative FB CT-based intraoperative spinal navigation system demonstrated comparable accuracy and safety when compared with the intraoperative CB CT-based system. Moreover, the FB CT-based system had a shorter time for screw placement and reduced intraoperative radiation exposure to patients. These findings support the potential benefits of adopting this novel navigation system to enhance surgical precision and reduce radiation-related risks in MIS-TLIF procedures.

Cervical disc arthroplasty for magnetic resonance-evident cervical spondylotic myelopathy: comparison with anterior cervical discectomy and fusion.

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) is a standard surgical approach for cervical spondylotic myelopathy (CSM) caused by disc herniations. Although cervical disc arthroplasty (CDA) has become, in the past decade, a viable alternative to ACDF in selected patients, the differences among patients with CSM treated with CDA and ACDF remain elusive. The effectiveness of motion preservation devices in CSM is also unclear. METHODS: Adult patients who underwent 1- or 2-level CDA or ACDF between 2007 and 2021 were retrospectively reviewed. Patients whose preoperative T2-weighted MRI demonstrated increased intramedullary signal intensity (IISI) were included and analyzed for the following: comparison of the length of IISI on pre- and postoperative MR images as well as range of motion (ROM) at the indexed levels between the CDA and ACDF groups. Measurement for clinical outcomes included the visual analog scale (VAS) of the arm and neck, the Neck Disability Index, and modified Japanese Orthopaedic Association scores. Perioperative clinical data were also compared between the two groups. RESULTS: A total of 122 patients were allocated to the CDA group and 108 to the ACDF group, with mean follow-ups of 46.6 and 39.0 months, respectively. Patients in the CDA group were younger than those in the ACDF group (47.64 ± 12.40 vs 61.73 ± 12.25 years, p < 0.001) (mean ± SD). The ACDF group had more 2-level surgery compared to the CDA group (p = 0.002). Both groups had significant regression of IISI on postoperative MRI compared to that of preoperative imaging (CDA: 1.23 ± 0.84 to 0.28 ± 0.39 cm; ACDF: 1.07 ± 0.60 to 0.37 ± 0.42 cm; both p < 0.001). The decrease in the length of IISI was similar between the two groups (p = 0.058). The postoperative ROM was well preserved in the CDA group (superior to ACDF, which yielded minimal ROM postoperatively). Both the CDA and ACDF groups demonstrated improvement in Neck Disability Index and modified Japanese Orthopaedic Association scores at 24 months postoperatively. The CDA group had significant improvements on VAS scores, whereas the improvement did not reach significance for the ACDF group at 24 months postoperatively. CONCLUSIONS: Significant shortening of IISI on T2-weighted MRI was demonstrated after both CDA and ACDF. At 24 months postoperatively, all clinical outcomes demonstrated improvement after both strategies, except that the VAS score was not significantly improved for ACDF. Therefore, CDA is a safe and effective option for patients with MR-evident CSM.

Nature or nurture: a latent ossification of the posterior longitudinal ligament after atlantoaxial fusion. Illustrative case.

BACKGROUND: The natural history of ossification of the posterior longitudinal ligament (OPLL) remains poorly understood and multiple etiologies have been reported. However, most have focused on the characteristics of the patient rather than alternation of mechanical stress after spinal fusion. OBSERVATIONS: This report describes, for the first time, a de novo OPLL found at the subaxial cervical spine 7 years after an atlantoaxial fusion surgery. A 57-year-old female initially required atlantoaxial arthrodesis for os odontoideum and stenosis that caused myelopathy. The posterior fusion surgery went smoothly without complications and the patient had good recovery of neurological functions. There was no associated instability, trauma, or reoperations during the follow-up. Seven years later, the patient presented with slight neck pain and a newly developed OPLL at C3-4 caudal to the C1-2 fusion construct. LESSONS: Conflicting with the conventional concept that OPLL is common in elderly men with genetic or hormonal factors, or associated spondyloarthropathies, OPLL could develop in women even after solid C1-2 fusion. The adjacent subaxial cervical spine is not free of risks for subsequent development of OPLL and cervical spondylotic myelopathy. This case illustration extends the scope of etiologies of OPLL within the present literature.

Revision Surgery for Adjacent Segment Degeneration After Fusion for Lumbar Spondylolisthesis: Is there a Correlation with Roussouly Type?

STUDY DESIGN: Retrospective study. OBJECTIVE: The aim of this study was to investigate whether there is an association between revision surgery rates for adjacent segment degeneration (ASD) and Roussouly type after L4-5 transforaminal lumbar interbody fusion (TLIF) for spondylolisthesis. SUMMARY OF BACKGROUND DATA: Revision surgery for ASD is known to occur after spinal fusion; however, it is unclear whether rates of ASD are associated with certain Roussouly types. METHODS: Patients who underwent L4-5 TLIF for spondylolisthesis at the University of California San Francisco from January 2006 to December 2016 with minimum 2-year follow-up were retrospectively analyzed by Roussouly type. Revision surgery for ASD was noted and correlated by Roussouly type. Spinopelvic parameters were also measured for correlation. A value of P < 0.05 was significant. RESULTS: There were 174 patients who met inclusion criteria, (59 males and 115 females). The average age was 62.3 (25-80) years. A total of 132 patients had grade I spondylolisthesis, and 42 had grade II. Mean follow-up was 45.2 months (24-497). A total of 22 patients (12.6%) underwent revision surgery for ASD after L4-5 TLIF. When classified by Roussouly type, revision surgery rates for ASD were: 1, 14.3%; 2, 22.6%; 3, 4.9%; and 4, 15.6% (P = 0.013). Type 3 spines with normal PI-LL (8.85°â€Š±â€Š6.83°) had the lowest revision surgery rate (4.9%), and type 2 spines with PI-LL mismatch (11.06°â€Š±â€Š8.81°) had the highest revision surgery rate (22.6%), a four-fold difference (P = 0.013). The PI-LL mismatch did not change significantly in each type postoperatively (P > 0.05). CONCLUSION: We found that there may be a correlation between Roussouly type and revision surgery for ASD after L4-5 TLIF for spondylolisthesis, with type 2 spines having the highest rate. Spinopelvic parameters may also correlate with revision surgery for ASD after L4-5 TLIF.Level of Evidence: 4.

Cortical Bone Trajectory-Based Dynamic Stabilization.

BACKGROUND: Cortical bone trajectory (CBT) screws have demonstrated similar biomechanical strength and fusion rates as conventional pedicle screws for short-segment lumbar fusion. However, very few studies have verified the viability of CBT screws in dynamic stabilization. In the present study, we compared the clinical outcomes of CBT-based Dynesys dynamic stabilization (CBT-DDS) with standard minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). METHODS: Consecutive patients who had undergone CBT-DDS or MI-TLIF at L4-L5 or L3-L5 were retrospectively reviewed. All the radiological and clinical outcomes were compared between the 2 groups. The patient-reported outcomes included the visual analog scale scores for back and leg pain, Japanese Orthopaedic Association scores, and Oswestry disability index. The pre- and postoperative radiological evaluations were also reviewed. RESULTS: A total of 60 patients (20 patients in the CBT-DDS and 40 in the MI-TLIF groups) were analyzed. The MI-TLIF group had required a longer operation time (P = 0.010) than the CBT-DDS group but had had a similar estimated blood loss (P = 0.484). The perioperative complications, including screw loosening, wound infection, and radiculopathy, were similar in both groups (P > 0.05 for all). The degree of decreased range of motion after surgery was similar between the 2 groups (P = 0.781), and no pseudarthrosis developed in the MI-TLIF group. CONCLUSIONS: Because the clinical and radiological outcomes of CBT-DDS were similar to those of MI-TLIF in patients with L4-L5 or L3-L5 spondylosis and spondylolisthesis, CBT-DDS appears to be a viable and effective alternative to MI-TLIF, with a shorter operation time and similarly limited segmental motility.

Measurement of Deformity at the Craniovertebral Junction: Correlation of Triangular Area and Myelopathy.

OBJECTIVE: Diseases of the craniovertebral junction (CVJ) are commonly associated with deformity, malalignment, and subsequent myelopathy. The misaligned CVJ might cause compression of neuronal tissues and subsequently clinical symptoms. The triangular area (TA), measured by magnetic resonance imaging/images (MRI/s), is a novel measurement for quantification of the severity of compression to the brain stem. This study aimed to assess the normal and pathological values of TA by a comparison of patients with CVJ disease to age- and sex-matched controls. Moreover, postoperative TAs were correlated with outcomes. METHODS: Consecutive patients who underwent surgery for CVJ disease were included for comparison to an age- and sex-matched cohort of normal CVJ persons as controls. The demographics, perioperative information, and pre- and postoperative 2-year cervical MRIs were collected for analysis. Cervical TAs were measured and compared. RESULTS: A total of 201 patients, all of whom had pre- or postoperative MRI, were analyzed. The TA of the CVJ deformity group was larger than the healthy control group (1.62 ± 0.57 cm2 vs. 1.01 ± 0.18 cm2, p < 0.001). Moreover, patients who had combined anterior odontoidectomy and posterior laminectomy with fixation had the greatest reduction in the TA (1.18 ± 0.58 cm2). CONCLUSION: In CVJ deformity, the measurement of the cervical TA could indicate the severity of brain stem compression. After surgery, the TA had a varying degree of improvement, which could represent the efficacy of surgery.

Cranio-Vertebral Junction Triangular Area: Quantification of Brain Stem Compression by Magnetic Resonance Images.

(1) Background: Most of the currently used radiological criteria for craniovertebral junction (CVJ) were developed prior to the popularity of magnetic resonance images (MRIs). This study aimed to evaluate the efficacy of a novel triangular area (TA) calculated on MRIs for pathologies at the CVJ. (2) Methods: A total of 702 consecutive patients were enrolled, grouped into three: (a) Those with pathologies at the CVJ (n = 129); (b) those with underlying rheumatoid arthritis (RA) but no CVJ abnormalities (n = 279); and (3) normal (control; n = 294). TA was defined on T2-weighted MRIs by three points: The lowest point of the clivus, the posterior-inferior point of C2, and the most dorsal indentation point at the ventral brain stem. Receiver operating characteristic (ROC) analysis was used to correlate the prognostic value of the TA with myelopathy. Pre- and post-operative TA values were compared for validation. (c) Results: The CVJ-pathology group had the largest mean TA (1.58 ± 0.47 cm2), compared to the RA and control groups (0.96 ± 0.31 and 1.05 ± 0.26, respectively). The ROC analysis calculated the cutoff-point for myelopathy as 1.36 cm2 with the area under the curve at 0.93. Of the 81 surgical patients, the TA was reduced (1.21 ± 0.37 cm2) at two-years post-operation compared to that at pre-operation (1.67 ± 0.51 cm2). Moreover, intra-operative complete reduction of the abnormalities could further decrease the TA to 1.03 ± 0.39 cm2. (4) Conclusions: The TA, a valid measurement to quantify compression at the CVJ and evaluate the efficacy of surgery, averaged 1.05 cm2 in normal patients, and 1.36 cm2 could be a cutoff-point for myelopathy and of clinical significance.

Combined Anterior and Posterior Decompression With Fusion for Cervical Ossification of the Posterior Longitudinal Ligament.

OBJECTIVE: Cervical myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) is not uncommon among Asian ethnic groups. Despite reports comparing the pros and cons of anterior- and posterior-only approaches, the optimal management remains debatable. This study aimed to evaluate the outcomes of patients who underwent a combined anterior and posterior approach, simultaneous circumferential decompression and fixation, for cervical OPLL. METHOD: The study retrospectively reviewed patients with OPLL and who underwent circumferential decompression and fixation, combined anterior corpectomy and posterior laminectomy. The clinical outcomes were evaluated by the Visual Analog Scale of neck and arm pain, the Japanese Orthopedic Association scores, Neck Disability Index, and Nurick scores at each time-point of evaluation. Radiological evaluations included plain and dynamic radiographs and computed tomography for every patient within 2 years post-operation. Subgroup analyses were further performed between the groups, with and without intra-operative cerebrospinal fluid (CSF) leakage. RESULTS: A total of 41 patients completed the follow-up for more than 2 years (mean = 39.8 months) and were analyzed. Continuous-type OPLL was the most common (44%), followed by segmental (27%), mixed (22%), and localized types (7%) in the cohort. Myelopathy and all other functional outcomes improved significantly at 2 years post-operation (all p < 0.05). There were 13 (32%) patients who had intra-operative CSF leakage. At 2 years post-operation, there were no differences in the demographics, functional outcomes, and complication rates between the CSF-leakage and no-leakage groups. The CSF-leakage group had more patients with continuous-type OPLL than the no-leakage group (77 vs. 29%, p = 0.004 < 0.05). During the follow-up, there was no secondary or revision surgery for pseudomeningocele, pseudarthrosis, or other surgery-related complications. CONCLUSIONS: Simultaneous circumferential decompression and fixation combine the surgical benefits of sufficient decompression by the posterior approach and direct decompression of OPLL by the anterior approach. It is an effective surgical option for patients with cervical myelopathy caused by OPLL, given that myelopathy unanimously improved without neurological complications in this study. The fusion rates were high, and reoperation rates were low. Despite higher rates of CSF leakage, there were no related long-term sequelae, and minimal wound complications.

Supine anterior lumbar interbody fusion versus lateral position oblique lumbar interbody fusion at L5-S1: A comparison of two approaches to the lumbosacral junction.

INTRODUCTION: At L5-S1, anterior access can be performed with a supine anterior lumbar interbody fusion (ALIF) or lateral position oblique lumbar interbody fusion (LOLIF). We compared clinical and radiographic features of both approaches. METHODS: A retrospective study of L5-S1 ALIF and LOLIF patients (2013-2018) by 3 spine surgeons and a vascular surgeon at our hospital was performed. Inclusion criteria were patients undergoing L5-S1 anterior surgery only without other anterior or lateral fusion levels, and data collected were patient demographics, cage parameters, perioperative variables, and radiographic parameters. 58 patients were included (33 ALIF and 25 LOLIF). RESULTS: The average surgical time was 211.94 min for ALIF and 154.86 min for LOLIF (p < 0.001). The average blood loss was 214 ml for ALIF and 74 ml for LOLIF (p < 0.001). The average number of days to solid food was 2.55 for ALIF and 0.8 for LOLIF (p < 0.001). The average anterior L5-S1 disc height increase was 8.52 mm for ALIF and 5.02 mm LOLIF (p = 0.018), and the average posterior L5-S1 disc height increase was 3.34 mm for ALIF and 1.30 mm for LOLIF (p = 0.034). The average L5-S1 segmental lordosis increase was 6.82 degrees for ALIF and 7.63 degrees for LOLIF (p = 0.638). CONCLUSION: The LOLIF is a feasible option for L5-S1 anterior access compared to ALIF. However, supine ALIF afforded larger cages to be placed, resulting in greater postoperative disc height. There did not appear to be a significant difference in postoperative L5-S1 segmental lordosis between the two approaches.

Minimally invasive dynamic screw stabilization using cortical bone trajectory.

BACKGROUND: The conventional pedicle-screw-based dynamic stabilization process involves dissection of the Wiltse plane to cannulate the pedicles, which cannot be undertaken with minimal surgical invasion. Despite some reports having demonstrated satisfactory outcomes of dynamic stabilization in the management of low-grade spondylolisthesis, the extensive soft tissue dissection involved during pedicle screw insertion substantially compromises the designed rationale of motion (muscular) preservation. The authors report on a novel method for minimally invasive insertion of dynamic screws and a mini case series. METHODS: The authors describe innovations for inserting dynamic screws via the cortical bone trajectory (CBT) under spinal navigation. All the detailed surgical procedures and clinical data are demonstrated. RESULTS: A total of four (2 females) patients (mean age 64.75 years) with spinal stenosis at L4-5 were included. By a combination of microscopic decompression and image-guided CBT screw insertion, laminectomy and dynamic screw stabilization were achieved via one small skin incision (less than 3 cm). These patients' back and leg pain improved significantly after the surgery. CONCLUSION: This innovative dynamic screw stabilization via the CBT involved no discectomy (or removal of sequestrated fragment only), no interbody fusion, and little muscle dissection (not even of the Wiltse plane). As a minimally invasive surgery, CBT appeared to be a viable alternative to the conventional pedicle-screw-based dynamic stabilization approach.

Crossing the Cervicothoracic Junction During Posterior Cervical Fusion for Myelopathy Is Associated With Superior Radiographic Parameters But Similar Clinical Outcomes.

BACKGROUND: For laminectomy and posterior spinal fusion (LPSF) surgery for cervical spondylotic myelopathy (CSM), the evidence is unclear as to whether fusions should cross the cervicothoracic junction (CTJ). OBJECTIVE: To compare LPSF outcomes between those with and without lower instrumented vertebrae (LIV) crossing the CTJ. METHODS: A consecutive series of adults undergoing LPSF for CSM from 2012 to 2018 with a minimum of 12-mo follow-up were identified. LPSF with subaxial upper instrumented vertebrae and LIV between C6 and T2 were included. Clinical and radiographic outcomes were compared. RESULTS: A total of 79 patients were included: 46 crossed the CTJ (crossed-CTJ) and 33 did not. The mean follow-up was 22.2 mo (minimum: 12 mo). Crossed-CTJ had higher preoperative C2-7 sagittal vertical axis (cSVA) (33.3 ± 16.0 vs 23.8 ± 12.4 mm, P = .01) but similar preoperative cervical lordosis (CL) and CL minus T1-slope (CL minus T1-slope) (P > .05, both comparisons). The overall reoperation rate was 3.8% (crossed-CTJ: 2.2% vs not-crossed: 6.1%, P = .37). In adjusted analyses, crossed-CTJ was associated with superior cSVA (ß = -9.7; P = .002), CL (ß = 6.2; P = .04), and CL minus T1-slope (ß = -6.6; P = .04), but longer operative times (ß = 46.3; P = .001). Crossed- and not-crossed CTJ achieved similar postoperative patient-reported outcomes [Visual Analog Scale (VAS) neck pain, VAS arm pain, Nurick Grade, Modified Japanese Orthopedic Association Scale, Neck Disability Index, and EuroQol-5D] in adjusted multivariable analyses (adjusted P > .05). For the entire cohort, higher postoperative CL was associated with lower postoperative arm pain (adjusted Pearson's r -0.1, P = .02). No postoperative cervical radiographic parameters were associated with neck pain (P > .05). CONCLUSION: Subaxial LPSF for CSM that crossed the CTJ were associated with superior radiographic outcomes for cSVA, CL, and CL minus T1-slope, but longer operative times. There were no differences in neck pain or reoperation rate.

Lower Hounsfield units on CT are associated with cage subsidence after anterior cervical discectomy and fusion.

OBJECTIVE: A consequence of anterior cervical discectomy and fusion (ACDF) is graft subsidence, potentially leading to kyphosis, nonunion, foraminal stenosis, and recurrent pain. Bone density, as measured in Hounsfield units (HUs) on CT, may be associated with subsidence. The authors evaluated the association between HUs and subsidence rates after ACDF. METHODS: A retrospective study of patients treated with single-level ACDF at the University of California, San Francisco, from 2008 to 2017 was performed. HU values were measured according to previously published methods. Only patients with preoperative CT, minimum 1-year follow-up, and single-level ACDF were included. Patients with posterior surgery, tumor, infection, trauma, deformity, or osteoporosis treatment were excluded. Changes in segmental height were measured at 1-year follow-up compared with immediate postoperative radiographs. Subsidence was defined as segmental height loss of more than 2 mm. RESULTS: A total of 91 patients met inclusion criteria. There was no significant difference in age or sex between the subsidence and nonsubsidence groups. Mean HU values in the subsidence group (320.8 ± 23.9, n = 8) were significantly lower than those of the nonsubsidence group (389.1 ± 53.7, n = 83, p < 0.01, t-test). There was a negative correlation between the HU values and segmental height loss (Pearson's coefficient -0.735, p = 0.01). Using receiver operating characteristic curves, the area under the curve was 0.89, and the most appropriate threshold of HU value was 343.7 (sensitivity 77.1%, specificity 87.5%). A preoperative lower HU is a risk factor for postoperative subsidence (binary logistic regression, p < 0.05). The subsidence rate and distance between allograft and polyetheretherketone (PEEK) materials were not significantly different (PEEK 0.9 ± 0.7 mm, allograft 1.0 ± 0.7 mm; p > 0.05). CONCLUSIONS: Lower preoperative CT HU values are associated with cage subsidence in single-level ACDF. Preoperative measurement of HUs may be useful in predicting outcomes after ACDF.

Effects of smoking on pedicle screw-based dynamic stabilization: radiological and clinical evaluations of screw loosening in 306 patients.

OBJECTIVE: Cigarette smoking has been known to increase the risk of pseudarthrosis in spinal fusion. However, there is a paucity of data on the effects of smoking in dynamic stabilization following lumbar spine surgery. This study aimed to investigate the clinical outcomes and the incidence of screw loosening among patients who smoked. METHODS: Consecutive patients who had lumbar spondylosis, recurrent disc herniations, or low-grade spondylolisthesis that was treated with 1- or 2-level surgical decompression and pedicle screw-based Dynesys dynamic stabilization (DDS) were retrospectively reviewed. Patients who did not complete the minimum 2 years of radiological and clinical evaluations were excluded. All screw loosening was determined by both radiographs and CT scans. Patient-reported outcomes, including visual analog scale (VAS) scores of back and leg pain, Japanese Orthopaedic Association (JOA) scores, and Oswestry Disability Index (ODI), were analyzed. Patients were grouped by smoking versus nonsmoking, and loosening versus intact screws, respectively. All radiological and clinical outcomes were compared between the groups. RESULTS: A total of 306 patients (140 women), with a mean age of 60.2 ± 12.5 years, were analyzed during an average follow-up of 44 months. There were 34 smokers (9 women) and 272 nonsmokers (131 women, 48.2% more than the 26.5% of smokers, p = 0.017). Postoperatively, all the clinical outcomes improved (e.g., VAS back and leg pain, JOA scores, and ODI, all p < 0.001). The overall rate of screw loosening was 23.2% (71 patients), and patients who had loosened screws were older (61.7 ± 9.6 years vs 59.8 ± 13.2 years, p = 0.003) and had higher rates of diabetes mellitus (33.8% vs 21.7%, p = 0.038) than those who had intact DDS screws. Although the patients who smoked had similar clinical improvement (even better VAS scores in their legs, p = 0.038) and a nonsignificantly lower rate of screw loosening (17.7% and 23.9%, p = 0.416), the chances of secondary surgery for adjacent segment disease (ASD) were higher than for the nonsmokers (11.8% vs 1.5%, p < 0.001). CONCLUSIONS: Smoking had no adverse effects on the improvements of clinical outcomes in the pedicle screw-based DDS surgery. For smokers, the rate of screw loosening trended lower (without significance), but the chances of secondary surgery for ASD were higher than for the nonsmoking patients. However, the optimal surgical strategy to stabilize the lumbar spine of smoking patients requires future investigation.

Comparison of Radiation Exposure Between O-Arm Navigated and C-Arm Guided Screw Placement in Minimally Invasive Transforaminal Lumbar Interbody Fusion.

BACKGROUND: Instrumentation in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is highly dependent on image guidance. Guidance with fluoroscopy (C-arm) and cone-beam computed tomography (O-arm) with navigation are common options. The intraoperative radiation exposure to patients with the different image modalities has not been compared, however. The present study aimed to compare the radiation exposure of the C-arm guidance and O-arm navigation techniques during MIS-TLIF surgery. METHODS: Ninety consecutive patients who underwent MIS-TLIF for degenerative lumbar pathologies were retrospectively reviewed. The patients were divided into the C-arm guided (CG) and the O-arm navigated (ON) groups (45 patients in each group), and the radiation dosage reports were analyzed for comparison of radiation exposure. RESULTS: The ON group had a higher average effective radiation dose (1.99 ± 0.4 mSv vs. 0.91 ± 0.3 mSv). For patients with more than 2 interbody fusion levels (≥6 pedicle screws), the effective dose per screw was similar in the CG and ON groups (0.22 ± 0.08 mSv vs. 0.23 ± 0.05 mSv). As the body mass index increased, the per-screw effective dose of the CG group showed a significant positive trend, compared with a nonsignificant negative trend in the ON group. CONCLUSIONS: For level 1 MIS-TLIF (4 percutaneous screws), patients in the ON group had almost double the radiation exposure as those in the CG group. For level ≥2 (≥6 screws) or obese patients, the O-arm with navigation has the advantage of similar radiation exposure to the patient and less (almost no) radiation to the operating room staff.

Spinal column shortening versus revision detethering for recurrent adult tethered cord syndrome: a preliminary comparison of perioperative and clinical outcomes.

OBJECTIVE: Recurrent tethered cord syndrome (TCS), believed to result from tension on the distal portion of the spinal cord, causes a constellation of neurological symptoms. Detethering surgery has been the traditional treatment for TCS. However, in cases of recurrent TCS, there is a risk of new neurological deficits developing, and subsequent retethering is difficult to prevent. Spinal column shortening has been proposed as an alternative technique to reduce the tension on the spinal cord without incurring the morbidity of revision surgery on the spinal cord. The authors compared the perioperative outcomes and morbidity of patients who were treated with one or the other procedure. METHODS: The medical records of 16 adult patients with recurrent TCS who were treated between 2005 and 2018 were reviewed. Eight patients underwent spinal column shortening, and 8 patients underwent revision detethering surgery. Patient demographics, clinical outcomes, and perioperative factors were analyzed. The authors include a video to illustrate their technique of spinal column shortening. RESULTS: Within the spinal column shortening group, no patients experienced any complications, and all 8 patients either improved or stabilized with regard to lower-extremity and bowel and bladder function. Within the revision detethering group, 2 patients had worsening of lower-extremity strength, 3 patients had worsening of bowel and bladder function, and 1 patient had improvement in bladder function. Also, 3 patients had wound-related complications. The median estimated blood loss was 731 ml in the shortening group and 163 ml in the revision detethering group. The median operative time was 358 minutes in the shortening group and 226 minutes in the revision detethering group. CONCLUSIONS: Clinical outcomes were comparable between the groups, but none of the spinal column shortening patients experienced worsening, whereas 3 of the revision detethering patients did and also had wound-related complications. Although the operative times and blood loss were higher in the spinal column shortening group, this procedure may be an alternative to revision detethering in extremely scarred or complex wound revision cases.

Navigated oblique lumbar interbody fusion for adult spinal deformity.

Adult spinal deformity (ASD) is an increasing disease entity as the population ages. An emerging minimally invasive surgery (MIS) option for the treatment of ASD is the oblique lumbar interbody fusion (OLIF), which allows indirect foraminal decompression of stenosis as well as segmental deformity correction (DiGiorgio et al., 2017). The authors utilize computer-assisted navigation with OLIF to reduce radiation exposure and improve time efficiency. The authors present a video of navigated oblique lumbar interbody fusion at L3-5 followed by open posterior screw-rod fixation. The video can be found here: https://youtu.be/zKDT7PhMYf8.

Effect of Tracheal Intubation Mode on Cuff Pressure During Retractor Splay and Dysphonia Recovery After Anterior Cervical Spine Surgery: A Randomized Clinical Trial.

MINI: This randomized clinical trial showed different intubation mode in anesthesia did not affect the increase of endotracheal cuff pressure caused by the retractor splay in anterior cervical spine surgery. However, nasotracheal intubation improved postoperative dysphonia recovery after anterior cervical spine surgery. STUDY DESIGN: Prospective, randomized, double-blinded trial. OBJECTIVE: The aim of this study was to investigate whether the mode of tracheal intubation affects intraoperative endotracheal tube cuff pressure on retractor splay and post-anterior cervical spine surgery (ACSS) voice outcome. SUMMARY OF BACKGROUND DATA: The combination of endotracheal tube (ETT) and cervical retractors has been implicated in recurrent laryngeal nerve compression and neuropraxia after ACSS. The asymmetric position of the oroETT within the larynx, as being fixed distally by the cuff and proximally by taping on one side of the mouth, may contribute to unilateral vocal palsy. METHODS: Adult patients undergoing ACSS were randomized to receive either nasotracheal or orotracheal intubation under anesthesia. The primary endpoint was the maximal endotracheal tube cuff pressure (ETCP) when the retractors were set up. After the maximal ETCPs were recorded, then ETCPs were controlled to less than 25 mmHg. Secondary endpoints were self-assessed hoarseness, pitch, and loudness of voice on postoperative days (PODs) 1, 2, 7, and 30. RESULTS: We equally allocated 110 patients to nasotracheal and orotracheal intubation. The maximal ETCP during retractor splay did not differ for both the means and distributions of pressure range. After the surgery, more patients in the nasotracheal intubation group reported none or mild change of voice than did the orotracheal intubation group on PODs 1 and 2, in terms of hoarseness, pitch, and loudness (P = 0.001, 0.001, and 0.005, respectively, on POD 1; P = 0.002, 0.003, and 0.011, respectively, on POD 2). Mixed model analysis demonstrated that patients with nasotracheal intubation had significantly lower dysphonia scores after surgery (estimate treatment effect: -1.62, P < 0.0001). Statistics was adjusted to exclude interaction with ETT sizes. CONCLUSION: The tracheal intubation modes did not affect ETCP during retractor splay. However, nasotracheal intubation had a beneficial effect on dysphonia recovery after ACSS. LEVEL OF EVIDENCE: 2.

Prospective, randomized, double-blinded trial. The aim of this study was to investigate whether the mode of tracheal intubation affects intraoperative endotracheal tube cuff pressure on retractor splay and post-anterior cervical spine surgery (ACSS) voice outcome. The combination of endotracheal tube (ETT) and cervical retractors has been implicated in recurrent laryngeal nerve compression and neuropraxia after ACSS. The asymmetric position of the oroETT within the larynx, as being fixed distally by the cuff and proximally by taping on one side of the mouth, may contribute to unilateral vocal palsy. Adult patients undergoing ACSS were randomized to receive either nasotracheal or orotracheal intubation under anesthesia. The primary endpoint was the maximal endotracheal tube cuff pressure (ETCP) when the retractors were set up. After the maximal ETCPs were recorded, then ETCPs were controlled to less than 25 mmHg. Secondary endpoints were self-assessed hoarseness, pitch, and loudness of voice on postoperative days (PODs) 1, 2, 7, and 30. We equally allocated 110 patients to nasotracheal and orotracheal intubation. The maximal ETCP during retractor splay did not differ for both the means and distributions of pressure range. After the surgery, more patients in the nasotracheal intubation group reported none or mild change of voice than did the orotracheal intubation group on PODs 1 and 2, in terms of hoarseness, pitch, and loudness (P = 0.001, 0.001, and 0.005, respectively, on POD 1; P = 0.002, 0.003, and 0.011, respectively, on POD 2). Mixed model analysis demonstrated that patients with nasotracheal intubation had significantly lower dysphonia scores after surgery (estimate treatment effect: −1.62, P < 0.0001). Statistics was adjusted to exclude interaction with ETT sizes. The tracheal intubation modes did not affect ETCP during retractor splay. However, nasotracheal intubation had a beneficial effect on dysphonia recovery after ACSS. Level of Evidence: 2.