Pseudarthrosis and Rod Fracture Rates After Transforaminal Lumbar Interbody Fusion at the Caudal Levels of Long Constructs for Adult Spinal Deformity Surgery.

BACKGROUND: Interbody fusion at the caudal levels of long constructs for adult spinal deformity (ASD) surgery is used to promote fusion and secure a solid foundation for maintenance of deformity correction. We sought to evaluate long-term pseudarthrosis, rod fracture, and revision rates for TLIF performed at the base of a long construct for ASD. METHODS: We reviewed 316 patients who underwent TLIF as a component of ASD surgery for medical comorbidities, surgical characteristics, and rate of unplanned reoperation for pseudarthrosis or instrumentation failure at the TLIF level. Fusion grading was assessed after revision surgery for pseudarthrosis at the TLIF level. RESULTS: Rate of pseudarthrosis at the TLIF level was 9.8% (31/316), and rate of rod fractures was 7.9% (25/316). The rate of revision surgery at the TLIF level was 8.9% (28/316), and surgery was performed at a mean of 20.4 ± 16 months from the index procedure. Current smoking status (odds ratio 3.34, P = 0.037) was predictive of pseudarthrosis at the TLIF site. At a mean follow-up of 43 ± 12 months after revision surgery, all patients had achieved bony union at the TLIF site. CONCLUSIONS: At 3-year follow-up, the rate of pseudarthrosis after TLIF performed at the base of a long fusion for ASD was 9.8%, and the rate of revision surgery to address pseudarthrosis and/or rod fracture was 8.9%. All patients were successfully treated with revision interbody fusion or posterior augmentation of the fusion mass, without need for further revision procedures at the TLIF level.

Clinical outcomes and safety of the SpineJack vertebral augmentation system for the treatment of vertebral compression fractures in a United States patient population.

The SpineJack implant system was recently FDA approved for treatment of vertebral compression fractures (VCF), however United States-based outcomes data is lacking. We sought to examine the safety and clinical outcomes following vertebral augmentation using the SpineJack implant for treatment of VCF in a U.S. patient population. An IRB-approved, retrospective study of SpineJack implants used in vertebral augmentation was performed from 11/2018 to 2/2020. Outcome objectives included pain improvement, vertebral body height (VH) restoration, improvement in local kyphotic angle (LKA), and incidence of adjacent level fractures (ALF). Complications were reviewed to assess safety of the procedure. Thirty patients with VCF (60% female; mean [SD] age of 62.7 [±12.8] years) underwent a total of 53 vertebral augmentations with 106 SpineJack implants. Worst pain scores decreased significantly from 8.7 to 4.3 (95%CI of the change [Δ]: 4.3-4.4; p < 0.001). Middle and anterior VH significantly increased from 13.1 ± 0.2 to 15.9 ± 0.2 mm (95%CI Δ: 2.6-2.9 mm; p < 0.001) and 15.6 ± 0.2 to 16.8 ± 0.2 mm (95%CI Δ: 1.1-1.4 mm; p < 0.001), respectively. LKA was significantly decreased from 10.0 ± 2.1 to 7.4 ± 2.1 degrees (95%CI Δ: 2.4-2.8 degrees; p < 0.001). Four patients (13%) sustained ten ALF over a median (IQR) follow up period of 94 (17.5-203) days. There were no major adverse events during the follow up period. To summarize, vertebral augmentation with SpineJack implants of patients with VCF resulted in significantly decreased pain, restored VH, and improved LKA, without major adverse events. However, 13% of patients sustained ALF during a median follow up period of 3 months.

Deep Learning Application in Spinal Implant Identification.

STUDY DESIGN: Retrospective observational study. OBJECTIVE: To demonstrate the clinical usefulness of deep learning by identifying previous spinal implants through application of deep learning. SUMMARY OF BACKGROUND DATA: Deep learning has recently been actively applied to medical images. However, despite many attempts to apply deep learning to medical images, the application has rarely been successful. We aimed to demonstrate the effectiveness and usefulness of deep learning in the medical field. The goal of this study was to demonstrate the clinical usefulness of deep learning by identifying previous spinal implants through application of deep learning. METHODS: For deep learning algorithm development, radiographs were retrospectively obtained from clinical cases in which the patients had lumbar spine one-segment instrument surgery. A total of 2894 lumbar spine anteroposterior (AP: 1446 cases) and lateral (1448 cases) radiographs were collected. Labeling work was conducted for five different implants. We conducted experiments using three deep learning algorithms. The traditional deep neural network model built by coding the transfer learning algorithm, Google AutoML, and Apple Create ML. Recall (sensitivity) and precision (specificity) were measured after training. RESULTS: Overall, each model performed well in identifying each pedicle screw implant. In conventional transfer learning, AP radiography showed 97.0% precision and 96.7% recall. Lateral radiography showed 98.7% precision and 98.2% recall. In Google AutoML, AP radiography showed 91.4% precision and 87.4% recall; lateral radiography showed 97.9% precision and 98.4% recall. In Apple Create ML, AP radiography showed 76.0% precision and 73.0% recall; lateral radiography showed 89.0% precision and 87.0% recall. In all deep learning algorithms, precision and recall were higher in lateral than in AP radiography. CONCLUSION: The deep learning application is effective for spinal implant identification. This demonstrates that clinicians can use ML-based deep learning applications to improve clinical practice and patient care.Level of Evidence: 3.

Determining the Difference in Clinical and Radiologic Outcomes Between Expandable and Nonexpandable Titanium Cages in Cervical Fusion Procedures: A Systematic Review and Meta-Analysis.

BACKGROUND: Expandable cages have been increasingly used in cervical and lumbar reconstructions; however, there is a paucity in the literature on how they compare with traditional nonexpandable cages in the cervical spine. We present a systematic review and meta-analysis, comparing the clinical and radiologic outcomes of expandable versus nonexpandable corpectomy cage use in the cervical spine. METHODS: A database search identified studies detailing the outcomes of expandable and nonexpandable titanium cage use in the cervical spine. These studies were screened using the PRISMA protocol. Fixed-effects and random-effects models were used with a 95% confidence interval. Two analyses were carried out for each outcome: one including all studies and the other including only studies reporting on exclusively 1-level and 2-level cases. RESULTS: Forty-one studies were included. The mean change in segmental lordosis was significantly greater in expandable cages (all, 6.72 vs. 3.69°, P < 0.001; 1-level and 2-level, 6.81° vs. 4.31°, P < 0.001). The mean change in cervical lordosis was also significantly greater in expandable cages (all, 5.71° vs. 3.11°, P = 0.027; 1-level and 2-level, 5.71° vs. 2.07°, P = 0.002). No significant difference was found between the complication rates (all, P = 0.43; 1-level and 2-level, P = 0.94); however, the proportion of revisions was significantly greater in expandable cages (all, 0.06 vs. 0.02, P = 0.03; 1-level and 2-level, 0.08 vs. 0.01, P = 0.017). CONCLUSIONS: The use of expandable cages may carry a modest improvement in radiologic outcomes compared with nonexpandable cages in the cervical spine; however, they may also lead to a higher rate of revisions based on our analyses.

Incidence and risk factors of proximal junctional kyphosis after internal fixation for adult spinal deformity: a systematic evaluation and meta-analysis.

To investigate the factors associated with proximal junctional kyphosis (PJK). A systematic search was performed. The weighted mean difference (WMD) was pooled for continuous variables, and the odds ratio (OR) was calculated for dichotomous variables. The PJK group had higher values for age (WMD = 2.53, 95%CI = 1.38 ~ 3.68, P < 0.001), female gender (OR = 1.56, 95%CI = 1.29 ~ 1.87, P < 0.001), and diagnosed osteoporosis (OR = 1.58, 95%CI = 1.11 ~ 2.26, P = 0.01). Preoperatively, significant differences were detected in sagittal vertical axis (SVA) (WMD = 19.29, 95%CI = 16.60 ~ 21.98, P < 0.001), pelvic incidence minus lumbar lordosis (PI-LL) (WMD = 2.71, 95%CI = 0.25 ~ 5.18, P = 0.03), pelvic tilt (PT) (WMD = 2.64, 95%CI = 1.38 ~ 3.90, P < 0.001), lumbar lordosis (LL) (WMD = - 1.76, 95%CI = - 2.73 ~ -0.79, P < 0.001), and sacral slope (SS) (WMD = - 2.80, 95%CI = - 5.57 ~ -0.04, P = 0.001). At follow-up, the following were higher in the PJK group: thoracic kyphosis (TK) (WMD = 5.51, 95%CI = 2.23 ~ 8.80, P < 0.001), proximal junctional angle (PJA) (WMD = 9.07, 95%CI = 4.21 ~ 13.92, P < 0.001), and PT (WMD = 1.51, 95%CI = 0.31 ~ 2.72, P = 0.01). However, there was no significant difference in SS (P = 0.49), and SVA (P = 0.11) between groups. Fusion to S1 or pelvis significantly increased the risk of PJK (OR = 2.08, P < 0.001). Ligament augmentation reduced the risk of PJK (OR = 0.34, 95%CI = 0.21 ~ 0.53, P < 0.001) better than the use of laminar hook (OR = 0.46, P < 0.001). Although no difference was detected for preoperative SRS-22 score (P = 0.056), a lower score (WMD = - 0.24, 95%CI = - 0.35 ~ -0.14, P < 0.001) was detected in PJK group at follow-up. The elderly female ASD patients were more susceptible to PJK, especially for those with osteoporosis, high preoperative SVA, low LL, large PT, and LIV extended to pelvis. The use of laminar hook and ligament reinforcement at the proximal end might prevent PJK.

Does interbody cage lordosis impact actual segmental lordosis achieved in minimally invasive lumbar spine fusion?

OBJECTIVE: In an effort to prevent loss of segmental lordosis (SL) with minimally invasive interbody fusions, manufacturers have increased the amount of lordosis that is built into interbody cages. However, the relationship between cage lordotic angle and actual SL achieved intraoperatively remains unclear. The purpose of this study was to determine if the lordotic angle manufactured into an interbody cage impacts the change in SL during minimally invasive surgery (MIS) for lumbar interbody fusion (LIF) done for degenerative pathology. METHODS: The authors performed a retrospective review of a single-surgeon database of adult patients who underwent primary LIF between April 2017 and December 2018. Procedures were performed for 1-2-level lumbar degenerative disease using contemporary MIS techniques, including transforaminal LIF (TLIF), lateral LIF (LLIF), and anterior LIF (ALIF). Surgical levels were classified on lateral radiographs based on the cage lordotic angle (6°-8°, 10°-12°, and 15°-20°) and the position of the cage in the disc space (anterior vs posterior). Change in SL was the primary outcome of interest. Subgroup analyses of the cage lordotic angle within each surgical approach were also conducted. RESULTS: A total of 116 surgical levels in 98 patients were included. Surgical approaches included TLIF (56.1%), LLIF (32.7%), and ALIF (11.2%). There were no differences in SL gained by cage lordotic angle (2.7° SL gain with 6°-8° cages, 1.6° with 10°-12° cages, and 3.4° with 15°-20° cages, p = 0.581). Subgroup analysis of LLIF showed increased SL with 15° cages only (p = 0.002). The change in SL was highest after ALIF (average increase 9.8° in SL vs 1.8° in TLIF vs 1.8° in LLIF, p < 0.001). Anterior position of the cage in the disc space was also associated with a significantly greater gain in SL (4.2° vs -0.3°, p = 0.001), and was the only factor independently correlated with SL gain (p = 0.016). CONCLUSIONS: Compared with cage lordotic angle, cage position and approach play larger roles in the generation of SL in 1-2-level MIS for lumbar degenerative disease.

Lumbar disc height and vertebral Hounsfield units: association with interbody cage subsidence.

OBJECTIVE: Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) cages can result in loss of lordosis and foraminal height, and potential recurrence of nerve root impingement. The objectives of this study were to determine factors associated with TLIF cage subsidence. Specifically, the authors sought to determine if preoperative disc height compared to cage height could be used to predict TLIF interbody cage subsidence, and if decreased postoperative vertebral Hounsfield units (HUs) predisposed to cage subsidence. METHODS: The authors retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. The preoperative disc height was measured for the operative and adjacent-level disc on MRI. The difference between cage and disc heights was measured and compared between the subsidence and nonsubsidence groups. The average HUs of the L1 vertebral body were measured on CT scans. RESULTS: Eighty-nine patients were identified with complete imaging and follow-up information. Forty-five patients (50.6%) had evidence of interbody cage subsidence on follow-up CT. The average cage subsidence was 5.5 mm (range 2.2-10.8 mm). The average implant height was significantly higher in the subsidence group compared to the nonsubsidence group (12.6 vs 11.2 mm). Additionally, the difference between cage height and preoperative adjacent-level disc height was also significantly larger in the subsidence group (3.8 vs 1.2 mm). First lumbar vertebral body (L1) HUs were significantly higher in the nonsubsidence versus the subsidence group (167.8 vs 137.71 HUs, p = 0.002). Multivariate logistic regression analysis identified suprajacent disc height and L1 HUs to be independent predictors of interbody cage subsidence. Receiver operating characteristic curves identified a suprajacent to cage height difference > 1.3 mm to have a 93.3% sensitivity for cage subsidence. CONCLUSIONS: This study is the first of its kind to demonstrate the association between vertebral body HUs and suprajacent disc height with the development of interbody cage subsidence after TLIF. The authors found that patients with lower HUs in the L1 vertebral body were more likely to experience subsidence, regardless of surgical level. Additionally, the study demonstrated that interbody cage height > 1.3 mm above the height of the suprajacent level is an independent risk factor for cage subsidence, with 93.3% sensitivity. These findings suggest that these factors may be utilized to create a template preoperatively for intraoperative cage selection.

The Titanium-coated PEEK Cage Maintains Better Bone Fusion With the Endplate Than the PEEK Cage 6 Months After PLIF Surgery: A Multicenter, Prospective, Randomized Study.

STUDY DESIGN: A multicenter, randomized, open-label, parallel-group trial. OBJECTIVE: To investigate interbody bone fusion rates in titanium-coated polyetheretherketone (TiPEEK) and polyetheretherketone (PEEK) cages after posterior lumbar interbody fusion (PLIF) surgery. SUMMARY OF BACKGROUND DATA: Previous clinical studies have not revealed any significant difference in bone fusion rates between TiPEEK and PEEK cages. METHODS: During one-level PLIF surgery, 149 patients (84 men, 65 women, mean age 67 yr) were randomly allocated to use either a TiPEEK cage (n = 69) or PEEK cage (n = 80). Blinded radiographic evaluations were performed using computed tomography and assessed by modified intention-to-treat analysis in 149 cases and per-protocol analysis in 143 cases who were followed for 12 months. Clinical outcomes were assessed using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and the Oswestry Disability Index. RESULTS: The interbody union rate at 12 months after surgery was 45% owing to a very strict definition of bone fusion. The rates of bone fusion were significantly higher at 4 and 6 months after surgery in the TiPEEK group than in the PEEK group in the unadjusted modified intention-to-treat analysis and were significantly higher at 6 months in the unadjusted per-protocol analysis. Binary logistic regression analysis adjusted for sex, age, body mass index, bone mineral density, and surgical level showed that using a TiPEEK cage (odds ratio, 2.27; 95% confidence interval: 1.09-4.74; P = 0.03) was independently associated with bone fusion at 6 months after surgery. Japanese Orthopaedic Association Back Pain Evaluation Questionnaire and Oswestry Disability Index results improved postoperatively in both groups. CONCLUSION: Using the TiPEEK cage for PLIF enabled the maintenance of better bone fusion to the endplate than using the PEEK cage at 6 months after the surgery. Our findings suggest the possibility of an earlier return to rigorous work or sports by the use of TiPEEK cage. LEVEL OF EVIDENCE: 1.

Does zero-profile anchored cage accompanied by a higher postoperative subsidence compared with cage-plate construct? A meta-analysis.

BACKGROUND: The zero-profile anchored cage (ZP) has been widely used for its lower occurrence of dysphagia. However, it is still controversial whether it has the same stability as the cage-plate construct (CP) and increases the incidence of postoperative subsidence. We compared the rate of subsidence after anterior cervical discectomy and fusion (ACDF) with ZP and CP to determine whether the zero-profile device had a higher subsidence rate. METHODS: We performed a meta-analysis of studies that compared the subsidence rates of ZP and CP. An extensive and systematic search covered the PubMed and Embase databases according to the PRISMA guidelines and identified ten articles that satisfied our inclusion criteria. Relevant clinical and radiological data were extracted and analyzed by the RevMan 5.3 software. RESULTS: Ten trials involving 626 patients were included in this meta-analysis. The incidence of postoperative subsidence in the ZP group was significantly higher than that in the CP group [15.1% (89/588) versus 8.8% (51/581), OR = 1.97 (1.34, 2.89), P = 0.0005]. In the subgroup analysis, we found that the definition of subsidence did not affect the higher subsidence rate in the ZP group. Considering the quantity of operative segments, there was no significant difference in the incidence of subsidence between the two groups after single-level fusion (OR 1.43, 95% CI 0.61-3.37, P = 0.41). However, the subsidence rate of the ZP group was significantly higher than that of the CP group (OR 2.61, 95% CI 1.55-4.40, P = 0.0003) after multilevel (≥ 2-level) procedures. There were no significant differences in intraoperative blood loss, JOA score, NDI score, fusion rate, or cervical alignment in the final follow-up between the two groups. In addition, the CP group had a longer operation time and a higher incidence of dysphagia than the ZP group at each follow-up time. CONCLUSION: Based on the limited evidence, we suggest that ZP has a higher risk of postoperative subsidence than CP, although with elevated swallowing discomfort. A high-quality, multicenter randomized controlled trial is required to validate our results in the future.

Radiographic Fusion Rates Following a Stand-alone Interbody Cage Versus an Anterior Plate Construct for Adjacent Segment Disease After Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Case-control. OBJECTIVES: The aim of this study was to evaluate fusion rates and compare a stand-alone cage construct with an anterior-plate construct in the setting revision anterior cervical discectomy and fusion (ACDF) for adjacent segment disease. SUMMARY OF BACKGROUND DATA: Anterior cervical discectomy and fusion are considered the criterion standard of surgical treatment for cervical myelopathy and radiculopathy. One common consequence is adjacent segment disease. Treatment of adjacent segment disease is complicated by the previous surgical implants, which may make application of an additional anterior cervical plate difficult. Stand-alone cage constructs obviate the need for removal or revision of prior implants in the setting of adjacent segment disease. METHODS: All patients undergoing surgery for adjacent segment disease in a 2-year period were identified and separated into groups based on implant construct. A control group of patients undergoing primary, single-level ACDF were selected from during the same 2-year period. Demographic variables, fusion rate, and reoperation rate were compared between groups. Continuous variables were compared using Student t test, fusion, and revision rates were compared using Pearson χ test. RESULTS: Patients undergoing primary ACDF had lower age and American Society of Anesthesia score as well as shorter operative time. Fusion rate was higher for primary ACDF compared to all patients who underwent ACDF for adjacent segment disease (95% vs. 74%). When compared to primary ACDF, patients with a stand-alone cage construct had significantly lower fusion rate (69% vs. 95%) and higher reoperation rate (14% vs. 0%). There were no significant differences in anterior plate construct versus stand-alone cage construct in terms of fusion and reoperation. CONCLUSION: Symptomatic adjacent segment disease can be managed surgically with either revision anterior plating or a stand-alone cage constructs, although our results raise questions regarding a difference in fusion rates that requires further investigation. LEVEL OF EVIDENCE: 3.

Surface Technologies in Spinal Fusion.

Patients with symptomatic instability of the spine may be treated surgically with interbody fusion. Cost and complexity in this procedure arises owing to the implanted materials involved with facilitating fusion such as titanium or polyetheretherketone. Surface modifications have been developed to augment these base materials such as plasma-spraying polyetheretherketone with titanium or coating implants with hydroxyapatite. Although some evidence has been gathered on these novel materials, additional study is needed to establish the true efficacy of surface modifications for interbody fusion devices in improving long-term patient outcomes.

Clinical and Short-Term Radiographic Outcomes of Minimally Invasive Transforaminal Lumbar Interbody Fusion With Expandable Lordotic Devices.

BACKGROUND: Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is a well-accepted procedure for the treatment of degenerative lumbar disease. However, its ability to restore lumbar lordosis has been limited. Development of expandable lordotic interbody devices has challenged this limitation, furthering the scope of minimally invasive surgery. OBJECTIVE: To evaluate the radiographic and clinical effects of expandable lordotic interbody devices placed through an MIS-TLIF approach. METHODS: We conducted a retrospective review of 32 1-level and 18 2-level MIS-TLIFs performed using lordotic expandable interbody devices. Lumbar radiographic measurements, Oswestry Disability Index scores (ODI), and Visual Analogue Scale scores (VAS) were obtained at preoperative, 6 wk follow up, and last follow up time points. Last follow up occurred at a mean of 11.5 ± 7.6 mo (mean ± SD). RESULTS: At 6-wk follow-up, segmental lordosis, disc height, and foraminal height increased by an average of 3.4°, 6.4 mm, and 4.4 mm, respectively. Only the 2-level group showed a significant increase in lumbar lordosis of 5.8°. No significant changes occurred in sacral slope, pelvic tilt, or pelvic incidence. Average ODI and VAS decreased by -12.0 and -4.5, respectively. Postoperative lumbar lordosis inversely correlated with preoperative lordosis in patients with an initial Pelvic Incidence to Lumbar Lordosis mismatch (PI-LL) of >10°, (r = -0.5, P = .009). CONCLUSION: When applied across 2-levels, MIS-TLIF using expandable lordotic interbody devices produced a significant increase in lumbar lordosis. Preoperative lumbar lordosis was found to be a predictor of postoperative lumbar lordotic change in patients with sagittal imbalance.

Long-Term Treatment Effect and Predictability of Spinopelvic Alignment After Surgical Correction of Adult Spine Deformity With Patient-Specific Spine Rods.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To evaluate the short- and long-term treatment effect (TE) of spinopelvic parameters after surgical correction of adult spine deformity (ASD) utilizing preoperative planning and patient-specific spine rods (PSSRs), and to assess the correspondence between planned and real outcomes. SUMMARY OF BACKGROUND DATA: PSSR have been used in ASD correction for the last decade. However, a TE and predictability of spinopelvic alignment at long-term follow-up has not been studied. METHODS: Inclusion criteria: male or female; age more than 20 years; correction of ASD with PSSR; 24-month follow-up (or revision surgery). Studied parameters: sagittal vertical axis; lumbar lordosis (LL); pelvic tilt (PT); sacral slope; pelvic incidence (PI); and PI-LL. The measurement error, TE (the differences between postoperative and preoperative values), standardized TE, and predictability of the studied parameters assessed. The variables included categorical (optimal/nonoptimal) and continuous obtained by direct measurements and weighted by individual optimal values. Statistical significance was set at P ≤ 0.05. RESULTS: Thirty-four patients were included: 56% women; the mean age, 63.4 (standard deviation, 12.7); at each follow-up: 32 at 1 to 3 months, 34 at 11 to 13, and 14 at 23 to 25 with 9 followed to the revision surgery. Strong or moderate TE was shown for sagittal vertical axis, LL, and PI-LL. The TE of PT and sacral slope was less significant and lower than planned. PI was not stable in 18%. The changes of continuous variables were more prominent and statistically significant then categorical. The mean values did not show significant differences between planned and postoperative outcomes except for PT. However, the individual deviations were substantial for all parameters. Significant predictability was shown only for LL and PI. CONCLUSION: Use of PSSR showed strong and relatively stable TE in ASD during 2 postoperative years. However, improvement of the planning accuracy may contribute to further enhancement of the method's efficacy. LEVEL OF EVIDENCE: 4.

A longitudinal investigation of the endplate cystic lesion effect on oblique lumbar interbody fusion.

OBJECTIVE: To determine longitudinal effects of changes in endplate cystic lesions on oblique lumbar interbody fusion (OLIF), the relationship between bone healing and endplate cystic lesion changes, and clinical significance of cyst formation. PATIENTS AND METHODS: A total of 107 segments in 67 patients who underwent OLIF between January 2013 and July 2016 were examined in this retrospective study. Using computed tomography, radiographic examinations of endplate cystic lesion, positive or negative cyst formation, cage subsidence, and fusion status were performed. Clinical outcomes were measured using visual analogue scale (VAS) pain scores, Oswestry disability index (ODI), and modified Macnab criteria. Outcomes were compared with preoperatively and postoperatively. A logistic regression analysis was performed to evaluate the relationship between measurements for endplate cysts. RESULTS: The fusion rate after OLIF was 94.4% at 2-year follow-up, with 86% of cases reporting satisfactory outcome (based on modified Macnab criteria). A significantly higher (P <  0.01) VAS score for back pain was observed in the cystic lesion group than non-cystic lesion group at 6-month follow-up. Cage subsidence significantly increased the risk of non-union (odds ratio [OR]: 17.24; 95% confidence interval [CI]: 1.67-178.09). Positive cyst sign was a significant risk factor for cage subsidence (OR: 8.52; 95% CI: 2.73-26.62) while cage subsidence was also a significant risk factor for positive cyst formation (OR: 8.37; 95% CI: 2.71-25.89). CONCLUSIONS: Cystic lesion may increase back pain in the early postoperative period. However, the preoperative cystic lesion does not aggravate a positive cyst formation or affect the final clinical result. Positive cyst formation was a significant risk factor for cage subsidence. In addition, cage subsidence was a significant predictor of non-union. Thus, the authors can speculate that positive cyst sign was potentially an indirect predictor of non-union.

Sagittal alignment correlates with the C1-C2 fixation angle and functional outcome after posterior atlantoaxial fixation for traumatic atlantoaxial instability.

The C1-C2 angle has been shown to correlate with subaxial alignment under various conditions. The aim of this study was to evaluate the correlation between the C1-C2 fixation angle and subaxial sagittal alignment as well as the impact of the sagittal vertical axis (SVA) on functional outcomes in traumatic atlantoaxial (A-A) instabilities. The data of 36 patients who underwent posterior C1-C2 fixation for traumatic A-A instability between December 2005 and September 2015 were retrospectively reviewed. Radiographic parameters, including the C1-C2 angle, occipitocervical angle, C2-C7 angle, and C2-C7 SVA, were measured before surgery and at 1-year follow-up. Clinical outcomes were measured using the visual analogue scale (VAS) and Neck Disability Index (NDI). The preoperative and postoperative relationships between parameters were analyzed. In preoperative and postoperative radiographs, the C1-C2 angle correlated with the C2-C7 angle (r = -0.347, p = 0.038, and r = -0.339, p = 0.043, respectively) and the C2-C7 SVA (r = 0.648, p < 0.001, and r = 0.436, p = 0.008, respectively). The postoperative C2-C7 SVA was directly proportional to the preoperative C2-C7 SVA and postoperative C1-C2 angle (postoperative C2-C7 SVA = 0.72 + 0.669 × [preoperative C2-C7 SVA] + 0.555 × [postoperative C1-C2], r2 = 0.677, p < 0.001). The postoperative C2-C7 SVA correlated with postoperative VAS (rs = 0.382, p = 0.021) and NDI (rs = 0.476, p = 0.003). The postoperative C2-C7 SVA was affected by the preoperative C2-C7 SVA and the postoperative C1-C2 angle and showed significant positive correlation with postoperative NDI. The C1-C2 fixation angle and the preoperative C2-C7 SVA should be carefully considered to avoid postoperative sagittal imbalance.

Morphological changes of contralateral intervertebral foramen induced by cage insertion orientation after unilateral transforaminal lumbar interbody fusion.

BACKGROUND: This study was performed to investigate the morphological changes of contralateral intervertebral foramen (IVF) based on computed tomography images of patients with lumbar spinal stenosis after unilateral transforaminal lumbar interbody fusion (TLIF) and to compare the influence of different orientation of cage insertion on these changes. METHODS: This is a retrospective cohort study. Sixty-nine patients with lumbar spinal stenosis who had undergone single-level unilateral TLIF were retrospectively analyzed. The patients were divided into two groups according to the cage insertion orientation: the oblique group (o-group, 39 cases) and the transverse group (t-group, 30 cases). The morphological parameters of contralateral IVF were measured before and 6 months after the operation. Changes in these parameters were compared and analyzed between the two groups. The 6-month clinical outcomes of the two groups were also collected and analyzed. RESULTS: There was a significant difference in the rate of increase in the segmental angle (p < 0.01) between the two groups, the mean value of segmental angle increased by an average of 29.08% ± 14.93% in the o-group and 48.63% ± 12.01% in the t-group. Overall, the posterior disc height had a significant positive correlation with the foraminal height and area. In the o-group, however, an increase in the segmental angle resulted in a decrease in the foraminal area. No significant difference in clinical outcomes was found between the two groups. CONCLUSIONS: Compared with oblique cage insertion, transverse cage insertion could achieve greater restoration of segmental lumbar lordosis without decreasing contralateral foraminal dimensions.

Cages in ACDF are Associated With a Higher Nonunion Rate Than Allograft: A Stratified Comparative Analysis of 6130 Patients.

STUDY DESIGN: A retrospective database review. OBJECTIVE: The purpose of this study was to analyze the rate of nonunion in patients treated with structural allograft and intervertebral cages in anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Existing literature consists primarily of single-center studies with inconsistent findings. METHODS: We performed a retrospective analysis of 6130 patients registered in the PearlDiver national database through Humana Insurance from 2007 to 2016. All ACDF patients with anterior plating who were active in the database for at least 1 year were included in the study. Patients with a fracture history within 1 year of intervention, past arthrodesis of hand, foot, or ankle, or a planned posterior approach were excluded from the study. Patients were stratified by number of levels treated, tobacco use, and diabetic condition. Nonunion rates of structural allograft and intervertebral cage groups after 1 year were compared using Chi-squared analyses. RESULTS: Four thousand sixty-three patients were included in the allograft group, while 2067 were included in the cage group. Overall nonunion rates were significantly higher in the cage group (5.32%) than in allograft group (1.97%) (P < 0.01). When controlling for confounders, increased rates of nonunion were consistently observed in the cage group, achieving statistical significance in 25 of the 26 analyses. CONCLUSION: The increased rate of nonunion associated with intervertebral cages may suggest the superiority of allograft over cages in ACDF. LEVEL OF EVIDENCE: 3.

Cage Subsidence and Fusion Rate in Extreme Lateral Interbody Fusion with and without Fixation.

OBJECTIVE: To examine the subsidence rate in patients undergoing extreme lateral interbody fusion (XLIF) using data from a 2-year retrospective study to assess the effect of supplemental fixation on the stand-alone procedure. METHODS: Demographic and perioperative data for all patients who underwent XLIF for degenerative lumbar disorders between June 2012 and January 2016 were collected and divided into 4 groups: the stand-alone (SA), lateral fixation, unilateral pedicle screw, and bilateral pedicle screw (BPS) groups. The disk height (DH), lumbar lordotic (LL) angle, and segmental lordotic (SL) angle were measured preoperatively and 3 days, 3 months, 1 year, and 2 years postoperatively. Clinical outcomes were evaluated using Japanese Orthopaedic Association (JOA) and visual analog scale (VAS) scores. Fusion was defined according to computed tomography scan. RESULTS: There were 126 vertebrae in 107 patients treated. SL angle, LL angle, and DH significantly increased postoperatively in all groups. Although the preoperative and 2-year postoperative DHs in the SA group were similar, the other measures showed significant differences from baseline at each follow-up visit. No significant effects on SL angle or DH were found in any of the groups. A significant difference in the LL angle was found in the BPS group compared with the other groups. At the last follow-up, high-grade subsidence was found in 26.89% of all cases, the fusion rate was 85.71%, and the VAS and JOA scores were significantly improved in all groups. CONCLUSIONS: Supplemental fixation did not significantly influence cage subsidence or SL angle. Only BPS fixation significantly improved the LL angle. The 2-year fusion rate was satisfactory.

Radiographic outcomes of transosseous intradiscal screw fixation in lumbar reconstruction-Imaging results of an experience with an alternative in fixation of the unexpectedly osteopenic spine.

OBJECTIVE: To present the results of a new alternative in the technique lumbar pedicle screw reconstruction in osteopenic bone. Pedicle screw fixation is compromised in osteopenic bone and adjunct fixation commonly requires incremental technology that can increase cost and risk, and which may not commonly be available. Readily available low cost techniques are desirable. PATIENTS AND METHODS: This is a retrospective review of a prospectively accumulated case series of all patients presenting to the senior author's (DAB) practice for elective lumbar reconstruction at a tertiary spine referral center. All consecutive patients treated by the senior author 2002-2012 who were unexpectedly found to be severely osteopenic at surgery are reported. RESULTS: In seventy-four cases with imaging and clinical information available at an average of five years after surgery there was no screw lucency or accelerated disc degeneration observed despite these screws purposefully projecting into the suprajacent disc space within the limits of the construct. No patient had presented for instrumentation-related revision surgery of any sort. CONCLUSION: Transosseous intradiscal screw fixation is a potentially viable alternative in surgical stabilization of the unexpectedly osteopenic lumbar spine.

Stand-Alone Anterolateral Interbody Fusion Versus Extended Posterior Fusion for Symptomatic Adjacent-Segment Degeneration: A Retrospective Study of 2 Years' Follow-up.

OBJECTIVE: To evaluate the clinical and radiologic outcome of stand-alone anterolateral lumbar interbody fusion (ALLIF) using self-locked cages in comparison with extended posterior lumbar interbody fusion (PLIF) for symptomatic adjacent-segment degeneration (ASD) after posterior lumbar fusion. METHODS: This retrospective study enrolled 40 symptomatic patients with ASD who were treated with ALLIF (n = 13) or extended PLIF (n = 27) between January 2011 and January 2015. Evaluations were performed preoperatively, at 3, 12, and 24 months postoperatively. Clinical outcome measurements included visual analog scale scores for low-back and leg pain, Oswestry Disability Index score for function assessment, Short-Form 36 Questionnaire for quality of life, and modified Macnab criteria for patient satisfaction. Radiologic outcome measurements included fusion rate, cage subsidence, disc height, and lumbar lordosis. RESULTS: There were no significant differences in the baseline data for the ALLIF and PLIF groups (P > 0.05). Mean operative time, blood loss, and length of hospital stay were significantly decreased for the ALLIF group (P < 0.05). Postoperatively, low back and leg pain was relieved, function and quality of life were improved in both groups (P < 0.05), whereas disc height and lumbar lordosis were restored (P < 0.05). At 24-month follow-up, fusion was observed in 13 of 13 patients (100%), with 3 of 13 (23.1%) patients developing cage subsidence in the ALLIF group. CONCLUSIONS: Stand-alone ALLIF could achieve satisfactory safety and efficacy for the treatment of symptomatic ASD with less trauma and faster recovery, and it may serve as an alternative surgical treatment for symptomatic ASD with appropriate indication.