Biomechanical analysis of complications following T10-Pelvis spinal fusion: A population based computational study.

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are challenging complications of long fusion constructs for the treatment of adult spinal deformity. The objective of this study is to understand the biomechanical stresses proximal to the upper instrumentation of a T10-pelvis fusion in a large patient cohort. The pre-fusion models were subject-specific thoracolumbar spine models that incorporate the height, weight, spine curvature, and muscle morphology of 250 individuals from the Framingham Heart Study Multidetector CT Study. To create post-fusion models, the subject-specific models were further modified to eliminate motion between the intervertebral joints from T10 to the pelvis. OpenSim analysis tools were used to calculate the medial lateral shear force, anterior posterior shear force, and compressive force on the T9 vertebra during the static postures. Differences between pre-fusion and post-fusion T9 biomechanics were consistent between increased segmental mobility and unchanged segmental mobility conditions. For all static postures, compression decreased (p < 0. 0005). Anterior-posterior shear force significantly increased (p < 0. 0005) during axial twist and significantly increased (p < 0. 0005) during trunk flexion. Medial lateral shear force significantly increased (p < 0. 0005) during axial twist. This computational study provided the first use of subject-specific models to investigate the biomechanics of long spinal fusions. Patients undergoing T10-Pelvis fusion were predicted to have increased shear forces and decreased compressive force at the T9 vertebra, independent of change in segmental mobility. The computational model shows potential for the investigation of spinal fusion biomechanics to reduce the risk of PJK or PJF.

Comparison of clinical outcomes in patients undergoing one- and two-level minimally invasive lumbar microdiscectomy.

OBJECTIVE: Herniated nucleus pulposus (HNP) is one of the most common lumbar spine conditions treated surgically, often through a minimally invasive surgery (MIS) microdiscectomy approach. This technique attempts to reduce damage to the paraspinal muscular-ligamentous envelope. However, there are currently limited data regarding comparative outcomes using patient-reported outcome measures (PROMs) for one- and two-level MIS discectomies. The aim of this study was to quantify comparative clinical outcomes in patients undergoing one-level and two-level MIS lumbar microdiscectomy for HNP using PROMs. METHODS: The authors performed a retrospective review of patients undergoing MIS lumbar microdiscectomy between 2004 and 2019 for the primary diagnosis of HNP at a single academic institution. All patients had a minimum 1-year follow-up. Patient demographics and comorbidities were collected to establish baselines between cohorts. PROMs and minimal clinically important differences (MCIDs) were used to examine the patient's perception of operative success. Bivariate and multivariate linear/logistic regression analyses were used to compare one- and two-level discectomies. The bivariate analysis included the t-test and chi-square test, which were used to assess continuous and categorical variables, respectively. Statistical significance was established at p < 0.05. RESULTS: A total of 293 patients underwent one-level (n = 250) or two-level (n = 43) MIS discectomies. The mean follow-ups for the one- and two-level cohorts were 50.4 (SD 35.5) months and 61.6 (SD 39.8) months, respectively. Fewer female patients underwent two-level discectomies, and BMI and operative duration were higher in the two-level group (p < 0.001). Recurrent herniation requiring reoperation was recorded at rates of 6.80% and 11.6% in the one- and two-level groups, respectively (p = 0.270). Pre- and postoperative PROMs were largely similar between the cohorts; however, patients undergoing one-level discectomy had greater improvement in leg pain, and a significantly greater proportion of these patients achieved MCID for the leg pain visual analog scale score (p < 0.001). CONCLUSIONS: At the 1-year clinical follow-up, patients who underwent two-level discectomy had significantly less improvement in leg pain scores with lower achievement of MCID for leg pain improvement than patients undergoing one-level procedures. At the 1-year follow-up, there were no other significant differences in PROMs between the two cohorts. Given these findings, patients should be counseled regarding the anticipated outcomes to better manage expectations. Further studies are warranted to examine the long-term clinical outcomes associated with single- and multilevel MIS discectomy.

Short-term and Long-term Complications of Cervical Disc Arthroplasty.

STUDY DESIGN: A narrative review. OBJECTIVE: This review discusses the short and long-term complications associated with cervical disc arthroplasty (CDA). SUMMARY OF BACKGROUND DATA: CDA is a safe and effective motion-sparing alternative to fusion for the treatment of cervical disc pathology in patients with cervical radiculopathy or myelopathy. Although CDA offers advantages over fusion within a narrower set of indications, it introduces new technical challenges and potential complications. METHODS: A systematic search of several large databases, including Cochrane Central, PubMed, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry, was conducted from January 2005 to August 2023 to identify published studies and clinical trials evaluating cervical disc replacement complications and outcomes. RESULTS: Short-term complications are primarily related to surgical approach and include dysphagia reported as high as ~70%, laryngeal nerve injury ~0%-1.25%, Horner syndrome ~0.06%, hematoma ~0.01%, gross device extrusion ~0.3%, whereas long-term complications include adjacent segment disease reported at ~3.8%, osteolysis ~44%-64%, heterotopic ossification ~7.3%-69.2%, implant failure ~3.3%-3.7%, and implant wear, which varies depending on design. CONCLUSIONS: Approaches for mitigating complications broadly include meticulous dissection, intraoperative techniques, and diligent postoperative follow-up. This review emphasizes the need for a comprehensive understanding and management of complications to enhance the safety, reproducibility, and success of CDA. As CDA continues to evolve, there remains a critical need for ongoing research to delve deeper into evaluating risk for complications and long-term patient outcomes.

The Effect of Changes in Segmental Lordosis on Global Lumbar and Adjacent Segment Lordosis After L5-S1 Anterior Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective Cohort Study. OBJECTIVE: Restoration of lordosis in lumbar fusion reduces low back pain, decreases adjacent segment degeneration, and improves postoperative outcomes. However, the potential effects of changes in segmental lordosis on adjacent-level and global lordosis remain less understood. This study aims to examine the relationships between segmental (SL), adjacent-level, and global lumbar lordosis following L5-S1 Anterior Lumbar Interbody Fusion (ALIF). METHODS: 80 consecutive patients who underwent single-level L5-S1 ALIF were divided into 3 groups based on the degree of change (∆) in index-level segmental lordosis: <5° (n = 23), 5°-10° (n = 29), >10° (n = 28). Radiographic parameters measured included global lumbar, segmental, and adjacent level lordosis, sacral slope, pelvic tilt, pelvic incidence, and PI-LL mismatch. RESULTS: Patients with ∆SL 5°-10° or ∆SL >10° both showed significant increases in global lumbar lordosis from preoperative to final follow-up. However, patients with ∆SL >10° showed statistically significant losses in adjacent level lordosis at both immediate postoperative and final follow-up compared to preoperative. When comparing patients with ∆SL >10° to those with ∆SL 5-10°, there were no significant differences in global lumbar lordosis at final follow-up, due to significantly greater losses of adjacent level lordosis in these patients. CONCLUSION: The degree of compensatory loss of lordosis at the adjacent level L4-L5 correlated with the extent of segmental lordosis creation at the index L5-S1 level. This may suggest that the L4 to S1 segment acts as a "harmonious unit," able to accommodate only a certain amount of lordosis and further increases in segmental lordosis may be mitigated by loss of adjacent-level lordosis.

Increased cage angle effects on radiographic outcomes after stand-alone anterior lumbar interbody fusion.

OBJECTIVE: Anterior lumbar interbody fusion (ALIF) is a well-accepted surgical technique used to treat various lumbar degenerative pathologies. Recently, hyperlordotic cages have been introduced to create higher degrees of lordosis to the lumbar spine. There are little data currently available to define the radiographic benefits that these cages provide with stand-alone ALIF. The goal of the present study was to assess the effect of increasing cage angles on postoperative subsidence, sagittal alignment, and foraminal and disc height in patients who underwent single-level stand-alone ALIF surgery. METHODS: A retrospective cohort study was performed of consecutive patients who underwent single-level ALIF by a single spine surgeon. Radiographic analysis included global lordosis, operative level of segmental lordosis, cage subsidence, sacral slope, pelvic tilt, pelvic incidence, pelvic incidence-lumbar lordosis mismatch, edge loading, foraminal height, posterior disc height, anterior disc height, and adjacent-level lordosis. Multivariate linear and logistic regressions were performed to analyze the relationship between cage angle and radiographic outcomes. RESULTS: Seventy-two patients were included in the study and divided into three groups based on cage angle: < 10° (n = 17), 10°-15° (n = 36), and > 15° (n = 19). Within the entire study cohort, there were significant improvements in disc and foraminal height, as well as segmental and global lordosis, at the final follow-up after single-level ALIF. However, when stratified by cage angle groups, patients with > 15° cages did not have any additional significant changes in global or segmental lordosis compared with those patients with smaller cage angles, but patients with > 15° cages showed greater risk of subsidence while also having significantly less improvements in foraminal height, posterior disc height, and average disc height compared with the other groups. CONCLUSIONS: Patients with < 15° stand-alone ALIF cages showed improved average foraminal and disc (posterior, anterior, and average) height without sacrificing improvements in sagittal parameters or increasing risk of subsidence when compared to patients with hyperlordotic cages. The use of hyperlordotic cages > 15° did not provide spinal lordosis commensurate with the lordotic angle of the cage and had a greater risk of subsidence. Although this study was limited by a lack of patient-reported outcomes to correlate with radiographic results, these findings support the judicious use of hyperlordotic cages in stand-alone ALIF.

Rates of Postoperative Complications and Approach-related Neurological Symptoms After L4-L5 Lateral Transpsoas Lumbar Interbody Fusion Compared With Upper Lumbar Levels.

STUDY DESIGN: This was a retrospective comparative study. OBJECTIVE: To compare the likelihood of approach-related complications for patients undergoing single-level lateral lumbar interbody fusion (LLIF) at L4-L5 to those undergoing the procedure at upper lumbar levels. SUMMARY OF BACKGROUND DATA: LLIF has been associated with a number of advantages when compared with traditional interbody fusion techniques. However, potential risks with the approach include vascular or visceral injury, thigh dysesthesias, and lumbar plexus injury. There are concerns of a higher risk of these complications at the L4-L5 level compared with upper lumbar levels. MATERIALS AND METHODS: A retrospective cohort review was completed for consecutive patients undergoing single-level LLIF between 2004 and 2019 by a single surgeon. Indication for surgery was symptomatic degenerative lumbar stenosis and/or spondylolisthesis. Patients were divided into 2 cohorts: LLIF at L4-L5 versus a single level between L1 and L4. Baseline characteristics, intraoperative complications, postoperative approach-related neurological symptoms, and patient-reported outcomes were compared and analyzed between the cohorts. RESULTS: A total of 122 were included in analysis, of which 58 underwent LLIF at L4-L5 and 64 underwent LLIF between L1 and L4. There were no visceral or vascular injuries or lumbar plexus injuries in either cohort. There was no significant difference in the rate of postoperative hip pain, anterior thigh dysesthesias, and/or hip flexor weakness between the cohorts (53.5% L4-L5 vs. 37.5% L1-L4; P =0.102). All patients reported complete resolution of these symptoms by 6-month postoperative follow-up. DISCUSSION: LLIF surgery at the L4-L5 level is associated with a similar infrequent likelihood of approach-related complications and postoperative hip pain, thigh dysesthesias, and hip flexor weakness when compared with upper lumbar level LLIF. Careful patient selection, meticulous use of real-time neuromonitoring, and an understanding of the anatomic location of the lumbar plexus to the working corridor are critical to success.

High-Intensity Zones on MRI of the Cervical Spine in Patients: Epidemiology and Association With Pain and Disability.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: This study aimed to address the prevalence, distribution, and clinical significance of cervical high-intensity zones (HIZs) on magnetic resonance imaging (MRI) with respect to pain and other patient-reported outcomes in the setting of patients that will undergo an anterior cervical discectomy and fusion (ACDF) procedure. METHODS: A retrospective cohort study of ACDF patients surgically treated at a single center from 2008 to 2015. Based on preoperative MRI, HIZ subtypes were identified as either traditional T2-hyperintense, T1-hypointense ("single-HIZs"), or combined T1- and T2-hyperintense ("dual-HIZs"), and their level-specific prevalence was assessed. Preoperative symptoms, patient-reported outcomes, and disc degeneration pathology were assessed in relation to HIZs and HIZ subtypes. RESULTS: Of 861 patients, 58 demonstrated evidence of HIZs in the cervical spine (6.7%). Single-HIZs and dual-HIZs comprised 63.8% and 36.2% of the overall HIZs, respectively. HIZs found outside of the planned fusion segment reported better preoperative Neck Disability Index (NDI; P = .049) and Visual Analogue Scale (VAS) Arm (P = .014) scores relative to patients without HIZs. Furthermore, patients with single-HIZs found inside the planned fusion segment had worse VAS Neck (P = .045) and VAS Arm (P = .010) scores. In general, dual-HIZ patients showed no significant differences across all clinical outcomes. CONCLUSIONS: This is the first study to evaluate the clinical significance of HIZs in the cervical spine, noting level-specific and clinical outcome-specific variations. Single-HIZs were associated with significantly more pain when located inside the fusion segment, while dual-HIZs showed no associations with patient-reported outcomes. The presence of single-HIZs may correlate with concurrent spinal pathologies and should be more closely evaluated.

Reasons for revision following stand-alone anterior lumbar interbody fusion and lateral lumbar interbody fusion.

OBJECTIVE: Anterior lumbar interbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) are alternative and less invasive techniques to stabilize the spine and indirectly decompress the neural elements compared with open posterior approaches. While reoperation rates have been described for open posterior lumbar surgery, there are sparse data on reoperation rates following these less invasive procedures without direct posterior decompression. This study aimed to evaluate the overall rate, cause, and timing of reoperation procedures following anterior or lateral lumbar interbody fusions without direct posterior decompression. METHODS: This was a retrospective cohort study of all consecutive patients indicated for an ALIF or LLIF for lumbar spine at a single academic institution. Patients who underwent concomitant posterior fusion or direct decompression surgeries were excluded. Rates, causes, and timing of reoperations were analyzed. Patients who underwent a revision decompression were matched with patients who did not require a reoperation, and preoperative imaging characteristics were analyzed to assess for risk factors for the reoperation. RESULTS: The study cohort consisted of 529 patients with an average follow-up of 2.37 years; 40.3% (213/529) and 67.3% (356/529) of patients had a minimum of 2 years and 1 year of follow-up, respectively. The total revision rate was 5.7% (30/529), with same-level revision in 3.8% (20/529) and adjacent-level revision in 1.9% (10/529) of patients. Same-level revision patients had significantly shorter time to revision (7.14 months) than adjacent-level revision patients (31.91 months) (p < 0.0001). Fifty percent of same-level revisions were for a posterior decompression. After further analysis of decompression revisions, an increased preoperative canal area was significantly associated with a lower risk of further decompression revision compared to the control group (p = 0.015; OR 0.977, 95% CI 0.959-0.995). CONCLUSIONS: There was a low reoperation rate after anterior or lateral lumbar interbody fusions without direct posterior decompression. The majority of same-level reoperations were due to a need for further decompression. Smaller preoperative canal diameters were associated with the need for revision decompression.

Preoperative Risk Factors for Postoperative Urinary Tract Infection After Primary Total Hip and Knee Arthroplasties.

BACKGROUND: Establishing clear risk factors for complications such as urinary tract infection (UTI) after arthroplasty procedures helps guide clinical practice and provides more information to both surgeons and patients. This study aims to assess selected preoperative patient characteristics as risk factors for postoperative UTI after primary total hip and knee arthroplasties (THA and TKA). METHODS: This was a retrospective analysis using current procedural terminology codes to investigate the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database for patients who underwent THA or TKA from 2010 to 2017. Patients were classified for UTI by NSQIP guidelines. Patient samples with all possible covariates were included for multivariate logistic regression analysis and assessed for independent associations. RESULTS: In a cohort of 983 identified patients (983 of 119,096; 0.83%): ages 57+ years, preoperative red blood cell (RBC) transfusion, perioperative RBC transfusion, bleeding disorders, operative time 110+ minutes, preoperative steroid use, diabetes, pulmonary comorbidities, body mass index 30+ kg/m2 were independent risk factors for postoperative UTI after THA. In a cohort of 1503 identified patients (1503 of 189,327; 0.8%): ages 60+ years, preoperative RBC transfusion, perioperative RBC transfusion, anemia, platelets less than 150k, preoperative steroid use, diabetes, and body mass index 30+ kg/m2 were independent risk factors for postoperative UTI after TKA. Male sex was associated with a decreased risk of UTI in both THA and TKA. CONCLUSION: This study provides novel evidence on risk factors associated with the development of UTI after THA or TKA. Clinicians should be aware of risk factors in the manifestation of postoperative UTI after primary THA or TKA procedures.

Cervical Spine Endplate Abnormalities and Association With Pain, Disability, and Adjacent Segment Degeneration After Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: A retrospective study with prospectively-collected data. OBJECTIVE: To determine how type, location, and size of endplate lesions on magnetic resonance imaging (MRI) may be associated with symptoms and clinical outcomes after anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Structural endplate abnormalities are important, yet understudied, phenomena in the cervical spine. ACDF is a common surgical treatment for degenerative disc disease; however, adjacent segment degeneration/disease (ASD) may develop. METHODS: Assessed the imaging, symptoms and clinical outcomes of 861 patients who underwent ACDF at a single center. MRI and plain radiographs of the cervical spine were evaluated. Endplate abnormalities on MRI were identified and stratified by type (atypical, typical), location, relation to operative levels, presence at the adjacent level, and size. These strata were assessed for association with presenting symptoms, patient-reported, and postoperative outcomes. RESULTS: Of 861 patients (mean follow-up: 17.4 months), 57.3% had evidence of endplate abnormalities, 39.0% had typical abnormalities, while 18.2% had atypical abnormalities. Patients with any endplate abnormality had greater odds of myelopathy irrespective of location or size, while sensory deficits were associated with atypical lesions (P = 0.016). Typical and atypical abnormalities demonstrated differences in patient-reported outcomes based on location relative to the fused segment. Typical variants were not associated with adverse surgical outcomes, while atypical lesions were associated with ASD (irrespective of size/location; P = 0.004) and reoperations, when a large abnormality was present at the proximal adjacent level (P = 0.025). CONCLUSION: This is the first study to examine endplate abnormalities on MRI of the cervical spine, demonstrating distinct risk profiles for symptoms, patient-reported, and surgical outcomes after ACDF. Patients with typical lesions reported worsening postoperative pain/disability, while those with atypical abnormalities experienced greater rates of ASD and reoperation. This highlights the relevance of a degenerative spine phenotypic assessment, and suggests endplate abnormalities may prognosticate clinical outcomes after surgery. LEVEL OF EVIDENCE: 3.