Biomechanics of the spine. Part I: spinal stability

Quantitatively assessing the effect of cervical sagittal alignment on dynamic intervertebral kinematics by video-fluoroscopy technique

BACKGROUND

Cervical sagittal alignment is crucial for distributing the head load to lower cervical segments and maintaining normal cervical spine function, but its biomechanical effect on the cervical spine was not fully elucidated.

OBJECTIVE

To investigate the effect of cervical sagittal alignment on dynamic intervertebral kinematics.

DESIGN

Cross-sectional study.

METHODS

Healthy participants without neck pain were recruited and divided into lordosis, straight and kyphosis groups according to the C2-C7 Cobb angle at the neutral position. The anti-directional and total joint motions were extracted across 10 epochs of dynamic cervical flexion and extension movements.

RESULTS

/findings: The overall anti-directional joint motion during flexion is larger in the kyphosis group when compared with the lordosis group (p = 0.021), while the range of flexion is smaller in the kyphosis group than that in the lordosis group (p = 0.017). The C2/C3 anti-directional joint motion during extension in the straight group is larger than that in the lordosis group (p = 0016). The range of extension in the kyphosis group (p < 0.001) and the straight group (p = 0.002) are larger than that in the lordosis group. The increased range of extension in the kyphosis and straight groups were mainly from the C3/C4, C4/C5, and C5/C6 joints(p < 0.05).

CONCLUSION

Changes in cervical sagittal alignment alter both the quality and quantity of the individual joint motions. More adjustments are required by the cervical joints to complete neck movements with the loss of lordosis. The lordotic curvature is a relatively effort-saving mode for the cervical spine from a biomechanical perspective.

The Emerging Role of the Mitochondrial Respiratory Chain in Skeletal Aging

Maintenance of mitochondrial homeostasis is crucial for ensuring healthy mitochondria and normal cellular function. This process is primarily responsible for regulating processes that include mitochondrial OXPHOS, which generates ATP, as well as mitochondrial oxidative stress, apoptosis, calcium homeostasis, and mitophagy. Bone mesenchymal stem cells express factors that aid in bone formation and vascular growth. Positive regulation of hematopoietic stem cells in the bone marrow affects the differentiation of osteoclasts. Furthermore, the metabolic regulation of cells that play fundamental roles in various regions of the bone, as well as interactions within the bone microenvironment, actively participates in regulating bone integrity and aging. The maintenance of cellular homeostasis is dependent on the regulation of intracellular organelles, thus understanding the impact of mitochondrial functional changes on overall bone metabolism is crucially important. Recent studies have revealed that mitochondrial homeostasis can lead to morphological and functional abnormalities in senescent cells, particularly in the context of bone diseases. Mitochondrial dysfunction in skeletal diseases results in abnormal metabolism of bone-associated cells and a secondary dysregulated microenvironment within bone tissue. This imbalance in the oxidative system and immune disruption in the bone microenvironment ultimately leads to bone dysplasia. In this review, we examine the latest developments in mitochondrial respiratory chain regulation and its impacts on maintenance of bone health. Specifically, we explored whether enhancing mitochondrial function can reduce the occurrence of bone cell deterioration and improve bone metabolism. These findings offer prospects for developing bone remodeling biology strategies to treat age-related degenerative diseases.

Anatomy and mobility in the adult cadaveric craniocervical junction

Genetic diseases with craniofacial malformations can be associated with anomalies of the craniocervical joint (CCJ). The functions of the CCJ are thus impaired, as mobility may be either limited by abnormal bone fusion causing headaches, or exaggerated in the case of hypermobility, which may cause irreparable damage to the spinal cord. Restoring the balance between mobility and stability requires surgical correction in children. The anatomy and biomechanics of the CCJ are quite unique, yet have been overlooked in the past decades. Pediatric evidence is so scarce, that investigating the adult CCJ is our best shot to disentangle the form-function relationships of this anatomical region. The motivation of the present study was to understand the morphological and functional basis of motion in the CCJ, in the hope to find morphological features accessible from medical imaging able to predict mobility. To do so, we have quantified the in-vitro kinematics of the CCJ in nine cadaveric asymptomatic adults, and estimated a wide range of mobility variables covering the complexity of spinal motion. We compared these variables with the shape of the occipital, the atlas and the axis, obtained using a dense geometric morphometric approach. Morphological joint congruence was also quantified. Our results suggest a strong relationship between bone shape and motion, with the overall geometry predicting best the primary movements, and the joint facets predicting best the secondary movements. We propose a functional hypothesis stating that the musculoligamental system determines movements of great amplitude, while the shape and congruence of joint facets determine the secondary and coupled movements, especially by varying the geometry of bone stops and the way ligaments are tensioned. We believe this work will provide valuable insights in understanding the biomechanics of the CCJ. Furthermore, it should help surgeons treating CCJ anomalies by enabling them to translate objectives of functional and clinical outcome into clear objectives of morphological outcome.

Biomechanical comparison of a new undercut thread design vs. the V-shape thread design for pedicle screws

BACKGROUND CONTEXT

Thread shape is regarded as an important factor influencing the fixation strength and osseointegration of bone screws. However, commercial pedicle screws with a V-shaped thread are prone to generating stress concentration at the bone-screw interface, thereby increasing the risk of screw loosening. Thus, modification of the pedicle-screw thread is imperative.

PURPOSE

This study aimed to investigate the fixation stability of pedicle screws with the new undercut thread design in comparison to pedicle screws with a V-shaped thread.

STUDY DESIGN

In vitro cadaveric biomechanical test and finite element analysis (FEA).

METHODS

Pedicle screws with the undercut thread (characterized by a flat crest feature and a tip-facing undercut feature) were custom-manufactured, whereas those with the V-shaped thread were procured from a commercial supplier. Fixation stability was assessed by the cyclic nonpullout compressive biomechanical testing on cadaveric female osteoporotic vertebrae. The vertical displacement and rotation angle of the 2 types of pedicle screws were calculated every 100 cycles to evaluate their resistance to migration and rotation. FEA was conducted to investigate the stress distribution and bone damage at the bone-screw interface for both types of pedicle screws.

RESULTS

Biomechanical testing revealed that the pedicle screws with the undercut thread exhibited significantly lower vertical displacement and rotation angles than the pedicle screws with the V-shape thread (P < 0.05). FEA results demonstrated a more uniform stress distribution in the bone surrounding the thread in the undercut design than in the V-shape design. Additionally, bone damage resulting from the pedicle screw was lower in the undercut design than in the V-shape design.

CONCLUSIONS

Pedicle screws with an undercut thread are less prone to migration and rotation and thus more stable in the bone than those with a V-shape thread.

CLINICAL SIGNIFICANCE

The undercut thread design may reduce the incidence of pedicle-screw loosening.

Reference Data for Diagnosis of Spondylolisthesis and Disc Space Narrowing Based on NHANES-II X-rays

Robust reference data, representing a large and diverse population, are needed to objectively classify measurements of spondylolisthesis and disc space narrowing as normal or abnormal. The reference data should be open access to drive standardization across technology developers. The large collection of radiographs from the 2nd National Health and Nutrition Examination Survey was used to establish reference data. A pipeline of neural networks and coded logic was used to place landmarks on the corners of all vertebrae, and these landmarks were used to calculate multiple disc space metrics. Descriptive statistics for nine SPO and disc metrics were tabulated and used to identify normal discs, and data for only the normal discs were used to arrive at reference data. A spondylolisthesis index was developed that accounts for important variables. These reference data facilitate simplified and standardized reporting of multiple intervertebral disc metrics.

Comparison of the effects of core stability and whole-body electromyostimulation exercises on kyphosis angle and core muscle endurance of inactive people with hyper kyphosis: A quasi-experimental pre-post study

OBJECTIVE

Restoring the degree of kyphosis to be consistent with good sagittal alignment of the spine is a key concern. This study aimed to compare the effect of core stability exercises (CSE) versus whole-body electromyostimulation (WB-EMS) and a combined program (PLUS) on kyphosis angle and core muscle endurance in sedentary individuals with hyperkyphosis.

DESIGN

A quasi-experimental single group pre-post study.

SETTINGS

Laboratory of corrective exercise.

PARTICIPANTS

seventy-five untrained men (28.9 ± 5.3 years) with thoracic hyperkyphosis.

MAIN OUTCOME MEASURES

A flexible ruler was used to measure the angle of kyphosis and McGill's test was used to evaluate core stability.

RESULTS

The results of the post hoc test demonstrated that the kyphosis angle was improved in the WB-EMS and PLUS groups compared to that in the CG (P < 0.05), but no significant difference was observed among the three groups(P > 0.05). In the post-test, core stability was significantly improved in CSE, WB-EMS and PLUS groups compared to that in the CG.

CONCLUSIONS

The WB-EMS and PLUS protocols as new training methods seem to be effective in changing posture parameters and correcting postural deformities, including kyphosis. Therefore, these protocols along with other rehabilitation programs can be used to correct kyphosis and improve core muscle endurance.

Lumbar muscle involvement in the occurrence of osteoporotic vertebral fracture

Objective

To determine if a lumbar musculature deficiency (paravertebral - PVM - and psoas - PM - muscles) is associated with a higher prevalence of vertebral fractures in osteoporotic patients.

Methods

To constitute the fracture group, data were collected retrospectively from patients with one or more recent osteoporotic vertebral fractures between T10 and L5 such as non-injected computerized tomography (CT), dual-energy X-ray absorptiometry (DXA). A control group was made by matching the patients on age, bone mineral density measured by DXA and gender. We analyzed PM and PVM atrophy based on cross-sectional area (CSA) adjusted to the body area as well as fatty infiltration on a 3-level scale and the average muscle density in Hounsfield units (HU).

Results

One hundred seventeen patients were included in each group. The fracture group had a lower PVM CSA than the control group (2197.92 ± 460.19 versus 2335.20 ± 394.42 mm2.m-2, respectively p = 0.015), but there was no significant difference in the PM (746.92 ± 197.89 versus 731.74 ± 215.53 mm2.m-2, respectively p = 0.575). The fracture group had a higher grade of fatty infiltration than the control group (PM: 1.3 ± 0.46 versus 1.07 ± 0.25, p < 0.001; PVM: 1.93 ± 0.5 versus 1.74 ± 0.5, p = 0.003) and a lower average muscle density (PM: 26.99 ± 12.83 versus 33.91 ± 8.12 HU, p < 0.001; PVM: 3.42 ± 21.06 versus 12.94 ± 18.88 HU, p < 0.001).

Conclusion

This study shows an association between a lack of axial musculature and the occurrence of osteoporotic vertebral fractures. Preventive strengthening exercises could be proposed to osteoporotic patients.

Comparison of Outcomes Between Endoscopic Transforaminal Lumbar Interbody Fusion and Minimally Invasive Transforaminal Lumbar Interbody Fusion in Patients With Single-Level Lumbar Degenerative Disease: A Retrospective Study

OBJECTIVE

The objective of this study was to compare the clinical and radiological outcomes of endoscopic transforaminal lumbar interbody fusion (Endo-TLIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

METHODS

This retrospective study included 110 patients with single-level lumbar degenerative disease who underwent Endo-TLIF or MIS-TLIF between January 2019 and December 2021. Patients were divided into Endo-TLIF (n = 55) and MIS-TLIF groups (n = 55). Perioperative, clinical, and radiological outcomes were assessed.

RESULTS

The Endo-TLIF group had significantly lower blood loss and shorter hospital stay. However, the operation time was significantly longer and there was more x-ray exposure than in the MIS-TLIF group. There were no significant differences in complications between the groups. The Endo-TLIF group showed significantly lower creatine kinase levels than the MIS-TLIF group at 3 days postoperatively (P < 0.05), but not at 7 days postoperatively (P > 0.05). Oswestry Disability Index and visual analog scale scores were significantly reduced in both groups at different time points postoperation compared to preoperation. The visual analog scale score in the Endo-TLIF group was lower than that in the MIS-TLIF group at 3 days postoperatively. Moreover, no significant differences were found in fusion rates, lumbar lordosis, and lumbar segmental lordosis between the 2 groups (P > 0.05).

CONCLUSIONS

Endo-TLIF might be considered as an effective and reliable treatment option for single-level lumbar degeneration. It results in less trauma and faster postoperative recovery, but a longer operative time and more x-ray exposure than MIS-TLIF. Endo-TLIF has effects on clinical and radiological outcomes that are comparable to those of MIS-TLIF.

Preoperative Adjacent Facet Joint Osteoarthritis Is Associated with the Incidence of Adjacent Segment Degeneration and Low Back Pain after Lumbar Interbody Fusion

STUDY DESIGN

A retrospective cohort study.

PURPOSE

To analyze the association between preoperative adjacent facet joint osteoarthritis (FJOA) and outcomes of lumbar interbody fusion (LIF).

OVERVIEW OF LITERATURE

Whether preoperative adjacent FJOA is associated with the incidence of radiological adjacent segment degeneration (RASD) and low back pain (LBP) relief after lumbar fusion remains unknown.

METHODS

The study included patients who underwent LIF. The demographic characteristics and radiographic and surgical data were collected and evaluated. The included patients were divided into control group and FJOA group based on the preoperative adjacent facet joint Pathria grade. Preoperative and last follow-up LBP Visual Analog Scale (VAS) score, leg pain (LP) VAS, Oswestry Disability Index (ODI) and RASD were evaluated and compared. The improvement rates in VAS and ODI were calculated and compared between the two groups. Logistic regression was used to analyze the risk factors of LBP relief and incidence of RASD.

RESULTS

In total, 197 patients (control group, 86; FJOA group, 111) were included, and the median follow-up was 46 months. The VAS and ODI in both groups significantly improved after surgery. At the last follow-up, the FJOA group had higher VAS and lower VAS improvement rates of LBP than the control group (p<0.05). However, no significant difference in the LP VAS and ODI was found between the two groups. The incidence of RASD in the FJOA group was significantly higher than that in the control group (48.6% vs. 30.2%, p=0.034). Multivariate logistic regression analysis showed that preoperative adjacent FJOA was significantly associated with LBP relief (odds ratio [OR], 0.691; 95% confidence interval [CI], 0.498-0.958) and the postoperative incidence of RASD (OR, 1.406; 95% CI, 1.020-1.939).

CONCLUSIONS

The preoperative FJOA in the adjacent segments was significantly associated with LBP following LIF. Patients with preoperative FJOA were more likely to have RASD following lumbar fusion surgery.

How Sagittal Spinal Parameters Predict Anterolateral Spinal Ossification Severity: A Study Based on CT Classification

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

The purpose of this study was to establish a CT classification system of anterolateral spinal ossification and analyze the effects of sagittal spinal parameters on ossification.

SUMMARY OF BACKGROUND DATA

Patients with diffuse idiopathic skeletal hyperostosis often present with anterolateral ossification of the spine. Few reports consider anterolateral spinal ossification at each spinal level or explore the influence of sagittal alignment.

MATERIALS AND METHOD

One hundred and twenty patients (79 males and 41 females) over 60 years old who underwent whole spinal CT scans from October 2018 to November 2021 were analyzed. Volume rendering technique images were used to assess the degree of anterolateral spinal ossification in each intervertebral space, and a classification system was established. Sagittal parameters, such as thoracic kyphosis, lumbar lordosis (LL), cervical lordosis, sacral slope, and thoracolumbar junction angle of the patients were measured. Multifactor stepwise linear regression analysis and ordered logistic regression analysis were used to study the effects of the sagittal parameters on ossification grades.

RESULTS

The median age of the study population was 67 years (63-72 IQR). The new classification system classifies the severity of anterolateral spinal ossification in each intervertebral space into grades 0 to 3 with an intra-observer intraclass correlation coefficient value of 0.909 and inter-observer intraclass correlation coefficient value of 0.900. Multivariate stepwise linear regression analysis showed that age (OR=1.30, P <0.001), weight (OR=1.23, P =0.013), and cervical lordosis (OR=1.19, P <0.001) were significantly correlated with total ossification grade. Multifactor ordered logistic regression analysis showed that there was a statistically significant correlation between cervical lordosis and the ossification grades of each intervertebral space of T1~T4 ( P ≤0.005), between thoracic kyphosis and each intervertebral space in T4~T12 ( P ≤0.019), and between thoracolumbar junction angle and each intervertebral space in T10~L3 ( P ≤0.025). LL was significantly and positively correlated with the ossification grades of each intervertebral space in T7~T11 ( P ≤0.041). LL and sacral slope were significantly negatively correlated with the ossification grades of each intervertebral space in L3~S1 ( P ≤0.047).

CONCLUSION

Our new classification scheme demonstrated good accuracy and reliability for the evaluation of the severity of anterolateral spinal ossification. The effect of sagittal parameters on anterolateral spinal ossification was position-specific. The greater the kyphosis or the smaller the lordosis of a spinal region, the more severe the degree of ossification in the corresponding region.

LEVEL OF EVIDENCE

3.

Minimally invasive fenestration for decompression of C2-C3 spinal stenosis

Conventional techniques in neurosurgery such as laminectomy have been extensively displaced by minimally invasive types, owing to the character of complexity of cervical spinal region. Spinal canal stenosis at C2-C3 level is documented in the literature with the majority being caused by intervertebral disc herniations.This case reports a patient who presented with classical myelopathy symptoms and significant thickening of ligamentum flavum, while minimal spondylosis was detected at C2-C3 level. The decompression was performed from posterior approach and limited to the removal of ligamentum flavum with minimal resection of adjacent laminae, no fixation and no disc evacuation. After surgery, there was a significant improvement with preserved spinal stability.Although the anterior approach is more common for cervical spine, universal access site has not been defined in literature. We suggest that minimal decompression produces desirable effects with no need for fusion and preserving adequate stability of spinal complex.

Fat infiltration of the posterior paraspinal muscles is inversely associated with the fat infiltration of the psoas muscle: a potential compensatory mechanism in the lumbar spine

BACKGROUND

The function of the paraspinal muscles and especially the psoas muscle in maintaining an upright posture is not fully understood. While usually considered solely as a hip flexor, the psoas muscle and its complex anatomy suggest that the muscle has other functions involved in stabilizing the lumbar spine. The aim of this study is to determine how the psoas muscle and the posterior paraspinal muscles (PPM; erector spinae and multifidus) interact with each other.

METHODS

A retrospective review including patients undergoing posterior lumbar fusion surgery between 2014 and 2021 at a tertiary care center was conducted. Patients with a preoperative lumbar magnetic resonance imaging (MRI) scan performed within 12 months prior to surgery were considered eligible. Exclusion criteria included previous spinal surgery at any level, lumbar scoliosis with a Cobb Angle > 20° and patients with incompatible MRIs. MRI-based quantitative assessments of the cross-sectional area (CSA), the functional cross-sectional area (fCSA) and the fat area (FAT) at L4 was conducted. The degree of fat infiltration (FI) was further calculated. FI thresholds for FIPPM were defined according to literature and patients were divided into two groups (< or ≥ 50% FIPPM).

RESULTS

One hundred ninetypatients (57.9% female) with a median age of 64.7 years and median BMI of 28.3 kg/m2 met the inclusion criteria and were analyzed. Patients with a FIPPM ≥ 50% had a significantly lower FI in the psoas muscle in both sexes. Furthermore, a significant inverse correlation was evident between FIPPM and FIPsoas for both sexes. A significant positive correlation between FATPPM and fCSAPsoas was also found for both sexes. No significant differences were found for both sexes in both FIPPM groups.

CONCLUSION

As the FIPPM increases, the FIPsoas decreases. Increased FI is a surrogate marker for a decrease in muscular strength. Since the psoas and the PPM both segmentally stabilize the lumbar spine, these results may be indicative of a potential compensatory mechanism. Due to the weakened PPM, the psoas may compensate for a loss in strength in order to stabilize the spine segmentally.

Degenerative L4-L5 spondylolisthesis and stenosis surgery: does over-level flavectomy technique influence clinical outcomes and rates of cranial adjacent segment disease?

BACKGROUND

One of the most dreaded long-term complications related to L4-L5 lumbar arthrodesis is the onset of adjacent segment disease, which most frequently occurs at the cranial level. Few studies have compared the rates of cranial adjacent segment disease (CASD) in patients undergoing lumbar fusion associated with total laminectomy at the same level with those undergoing partial laminectomy. No study has examined the role of selective over-level flavectomy (OLF; i.e., L3-L4).

METHODS

A total of 299 patients undergoing posterolateral arthrodesis (PLA) for L4-L5 degenerative spondylolisthesis were retrospectively analyzed with a 5-year follow-up. 148 patients underwent PLA + L4-L5 flavectomy + L4 partial laminectomy (control group), while 151 underwent PLA + L4-L5 flavectomy + total L4 laminectomy + L3-L4 flavectomy (OLF group). Rates of reoperations due to CASD were examined utilizing Cox proportional hazard models, while clinical improvement at follow-up (measured in ODI) was analyzed using generalized linear models (GLMs). Adjustments for potential confounders were made (grade of lumbar lordosis, age, sex, BMI, intervertebral disc degeneration, and presurgical cranial spinal stenosis).

RESULTS

At 5 years from the operation, 16 patients (10.8%) in the control group had undergone revision surgery for CASD compared to 5 patients (3.3%) in the OLF group (p = 0.013). Survival analysis and GLM demonstrated that the OLF group had a significantly lower incidence of CASD and presented more favorable clinical outcome. There were no differences in the rate of discal degeneration or the onset of Meyerding's grade I degenerative spondylolisthesis at the adjacent segment. BMI was the only other significant predictor of ODI improvement and of the incidence of CASD.

CONCLUSIONS

In patients with L4-L5 degenerative spondylolisthesis and stenosis, the OLF technique may lower rates of CASD and improve clinical outcomes by preventing cranial spinal stenosis without increasing iatrogenic instability or accelerating intervertebral disc degenerative changes.

Biomechanical Effects of Different Sitting Postures and Physiologic Movements on the Lumbar Spine: A Finite Element Study

This study used the finite element method(FEM) to investigate how pressure on the lumbar spine changes during dynamic movements in different postures: standing, erect sitting on a chair, slumped sitting on a chair, and sitting on the floor. Three load modes (flexion, lateral bending, and axial rotation) were applied to the FEM, simulating movements of the lumbar spine. Results showed no significant difference in pressure distribution on the annulus fiber and nucleus pulposus, representing intradiscal pressure, as well as on the cortical bone during movements between standing and erect sitting postures. However, both slumped sitting on a chair and sitting on the floor postures significantly increased pressure on the nucleus pulposus, annulus fibrosus, and cortical bone in all three movements when compared to standing or erect sitting on a chair. Notably, sitting on the floor resulted in even higher pressure on the nucleus pulposus and annulus fibers compared to slumped sitting on a chair. The decreased lumbar lordosis while sitting on the floor led to the highest increase in pressure on the annulus fiber and nucleus pulposus in the lumbar spine. In conclusion, maintaining an erect sitting position with increased lumbar lordosis during seated activities can effectively reduce intradiscal pressure and cortical bone stress associated with degenerative disc diseases and spinal deformities.

Factors Predisposing to The Formation of Degenerative Spondylolisthesis-A Narrative Review

The relationship between various factors predisposing to the formation of spondylolisthesis, including degenerative spondylolisthesis, has been analyzed by many authors. However, not all observations are consistent. In this review, we identified factors whose impact on the prevalence of spondylolisthesis was most often mentioned in the literature. These included gender, age, bone mineral density, ethnic origin, and oophorectomy. The results were inclusive in terms of physical activity, pregnancy status, and use of hormone replacement therapy. Associations between diabetes and smoking were very poorly marked. The literature so far has identified a number of factors significantly affecting the incidence of degenerative spondylolisthesis. These include age, gender, body weight, ethnic origin, bone mineral density, and hormonal balance. Radiological parameters, which include iliac crest, pelvic tilt, pelvic incidence, sacral slope, and lumbar lordosis, may also be of great importance for assessing changes in the occurrence and progression. However, the authors do not agree on the real significance of individual factors. The aim of this review was to identify the factors predisposing to the formation of degenerative spondylolisthesis, the importance of which has been suggested in the current literature. The systematization of knowledge in this field can allow a more accurate adjustment of the treatment plan for each patient affected by this condition.

Type IIB urethral duplication in adult: A case report

Urethral duplication are rare anomalies of the lower urinary tract consisting of partial or complete development of an accessory urethra that common in males than female. The exact embryological mechanism for this condition remain unclear, it is thought to relate to a disruption of development of the lateral folds of Rathke during hindgut development. There are 3 types based on Effman's classification. Diagnosis of urethral duplication, a genital examination has to performed and confirmed by micturating cytourethrography and retrograde urethrography. The authors presented a case of 67-year-old man complaining of dysuria, who was diagnosed with urethral duplication Effman Classification type IIB accompanied by bulbar urethral stricture and diverticula and multiple bladder diverticula after performing retrograde urethrography and micturating cystourethrography. This is an extremely rare type of duplication of the urethra (type IIB) with late presentation. Further study may be required regarding the surgical management.

Anatomical and imaging measurements of the angle between the axis of the lumbar pedicle and lateral isthmus margin and its clinical significance

BACKGROUND

This study aims to explore the measurement of the angle between the axis of the pedicle and the lateral margin of the isthmus on the lumbar spine, and investigate its clinical significance.

METHODS

The angle was measured on 120 normal adults' X-ray and 25 dry anatomical specimens. 60 screws were placed by junior residents on 6 wet specimens through the freehand technique. 30 screws were placed on one side with their original experience. After learning the techniques mentioned in the study, 30 screws were placed on the other side. The specimens were examined by X-ray and CT, and the angles of the screw paths and the integrity of the pedicle were evaluated.

RESULTS

The angles of 120 subjects and 25 anatomical specimens show a gradually increasing trend. The differences among each segment were statistically significant (P < 0.05), but the difference in the same segment between the X-ray and the anatomical specimens was not statistically significant (P > 0.05). Furthermore, the differences in L1, L2, and L3 between the two genders were not statistically significant (P > 0.05). However, the angles were larger in female group than in male group in L4 and L5, and the differences were statistically significant (P < 0.05). The difference in the deviation rate of screw placement before and after the learning was statistically significant only in the L5 segment (P < 0.05). The difference in overall excellence rate was statistically significant (P < 0.05).

CONCLUSIONS

The measurement of the angle between the axis of the pedicle and the lateral margin of the isthmus on the lumbar can improve the accuracy of the lumbar sagittal screw angle.

The difference and clinical application of modified thoracolumbar fracture classification scoring system in guiding clinical treatment

OBJECTIVE

This study aimed to evaluate the feasibility of the modified thoracolumbar injury classification and severity score system in guiding clinical treatment.

METHODS

A retrospective study was conducted on a cohort of 120 patients with thoracolumbar fractures who were admitted to the Department of Spinal Surgery at Ningbo Sixth Hospital between December 2019 and June 2021. The study population consisted of 68 males and 52 females, with an average age of 36.7 ± 5.7 years. The severity of the fractures was assessed based on comprehensive scores incorporating fracture morphology, neurological function, posterior ligament complex integrity, and disc injury status. The evaluation was performed using the total score T, which guided the formulation of the clinical treatment strategy. Furthermore, the study compared the treatment options, imaging data, and clinical efficacy between two classification systems.

RESULTS

The analysis of 120 patients revealed no statistically significant difference in the total score or treatment method between the TLICS system and the modified TLICS system. However, the operation rate for the modified TLICS system (73.3%) was slightly lower compared to the TLICS system (79.2%). All patients were followed up for a mean duration of 19.2 ± 4.6 months, ranging from 11 to 27 months. At the last follow-up, the visual analogue scale score was 1.94 ± 0.52, and the modified Japanese Orthopaedic Association score was 28.8 ± 4.5, indicating a significant improvement compared to the scores obtained prior to treatment. The neurological status exhibited varying degrees of improvement. Notably, the anterior vertebral height ratio was 87.10 ± 7.17%, the sagittal index was 90.35 ± 7.72%, and the Cobb angle was 3.05 ± 0.97 degrees at the last follow-up. All these measurements demonstrated statistically significant differences compared to the values observed prior to treatment (P < 0.05). Additionally, two cases of pedicle screw breakage and seven cases of pedicle screw wear and cutting in the vertebral body were observed at the last follow-up, resulting in varying degrees of low back pain. However, no instances of rod breakage were reported.

CONCLUSION

The modified TLICS system is a practical tool for the classification and assessment of thoracolumbar fractures. It has guiding significance for clinical treatment, and the operation rate was slightly lower than that of TLICS system.

An Approach to Managing Disorders Affecting the Craniovertebral Junction

The craniovertebral junction (CVJ), or the "first junction," can be affected by a variety of pathological states. Some of these conditions could represent a gray area in that they can be treated by general neurosurgeons or such specialists as skull base or spinal surgeons. However, some conditions are best managed with a multidisciplinary approach. The importance of in-depth knowledge of the anatomy and biomechanics of this junction cannot be overemphasized. Identifying what represents clinical stability or instability is key to successful diagnosis and, hence, treatment. In this report, the second in a 3-article series, we describe our approach to managing CVJ pathologies in a case-based fashion to illustrate key concepts.

Relationship between Isokinetic Trunk Muscle Strength and Return to Sports Competition after Conservative Therapy in Fresh Cases of Lumbar Spondylolysis: A Retrospective Observational Study

This study aimed to clarify the relationship between isokinetic trunk muscle strength and return to sporting activities in fresh cases of lumbar spondylolysis treated with conservative therapy. Patients included a total of ten men (age: 13.5 ± 1.7) who were instructed by their attending physicians to stop exercising and who met the eligibility criteria. Isokinetic trunk muscle strength was measured immediately after exercising for the first time (First) and one month (1M). Flexion and extension and maximum torque/body weight ratio were significantly lower First compared to 1M at all angular velocities (p < 0.05). Maximum torque generation time was significantly lower for First at 120°/s and 180°/s than at 1M (p < 0.05). Correlations with the number of days to return to sports competition were detected at 60°/s for maximum torque generation time (p < 0.05, r = 0.65). Following conservative treatment for lumbar spondylolysis, it was considered necessary to focus on trunk flexion and extension muscle strength and contraction speed of trunk flexors at the beginning of the exercise period. It was suggested that trunk extension muscle strength in the extension range might be one of the critical factors for returning to sports.

Association of Hallux Valgus with Degenerative Spinal Diseases: A Population-Based Cohort Study

Background: Although hallux valgus is known to cause lower-back pain, the association between hallux valgus and spinal degenerative disease remains unclear. Methods: A retrospective cohort study was conducted between 1 January 2000 and 31 December 2015 using data from the Longitudinal Health Insurance Database in Taiwan. After propensity score matching for age, sex, and some potential comorbidities, 1000 individuals newly diagnosed with hallux valgus were enrolled in the study group, while 1000 individuals never diagnosed with hallux valgus served as the control group. Both groups were followed up until 2015 to evaluate the incidence of hallux valgus. Kaplan-Meier analysis was used to determine the cumulative incidence of hallux valgus, while the Cox proportional hazard model was adopted to estimate the hazard ratio (HR) and adjusted hazard ratio (aHR) with 95% confidence intervals (CIs). Results: The incidence densities of spinal degeneration in the hallux valgus and non-hallux valgus groups were 73.10 and 42.63 per 1000 person-years, respectively. An increased risk of spinal degenerative changes was associated with hallux valgus (adjusted HR = 1.75, 95% CI = 1.50−2.05). Age- and sex-stratified analyses showed a significantly higher risk of spinal degeneration in the hallux valgus group. Moreover, sub-outcome evaluations revealed significantly higher risks of spondylosis (aHR = 2.01, 95% CI = 1.55−2.61), intervertebral disorder (aHR = 2.27, 95% CI = 1.62−3.17), and spinal stenosis (aHR = 1.24, 95% CI = 1.47−1.76). There was also an increased risk of spinal degenerative change in those with hallux valgus without surgical intervention (aHR = 1.95, 95% CI = 1.66−2.99, p < 0.001). Conclusions: Hallux valgus was associated with increased risk of degenerative spinal changes and other spinal disorders.

Facet joint degeneration—An initial procedure of the cervical spine degeneration

Objective

This study aims to emphasize the initiating role of facet joint (FJ) degeneration in the process of cervical spine degeneration induced by tangential load, and we further validate it in a novel cervical spine degeneration animal model.

Methods

The characteristics of cervical degeneration in patients of different ages were summarized through case collection. In the rat models, Hematoxylin-Eosin, Safranin O staining, and micro-computed tomography were used to show the histopathological changes and bone fiber structure of FJ and the height of intervertebral disc (IVD) space. The ingrowth of nociceptive sensory nerve fibers was observed by immunofluorescence staining.

Results

FJ degeneration without IVDs degeneration was more common in people with cervical spondylosis in young patients. The obvious degeneration phenotypes of the FJs preceded the IVDs at the same cervical segment in our animal model. The SP⁺ and CGRP⁺ sensory nerve fibers were observed in the articular subchondral bone of degenerated FJs and porous endplates of degenerated IVDs.

Conclusion

The FJ degeneration may act as the major contributor to cervical spine degeneration in young people. The dysfunction of functional unit of spine, not a certain part of IVD tissue, results in the occurrence of cervical degeneration and neck pain.

A biomechanical study shows the direction of compression influences the amount of lordosis gained in lumbar fusion

STUDY DESIGN

Biomechanical model study.

BACKGROUND

Lumbar lordosis is usually lost in the degenerative process, and when lumbar fusion is required, its restoration is one of the modern metrics of a successful operation. We sought to investigate the hypothesis that changing direction of compression during surgical fusion, would gain more lordosis.

METHODS

Using a biomechanical Sawbones™ model we inserted polyaxial pedicle screws from S1 to L4. A rod was placed in the screws without requiring reduction. Markers were attached to the spinous processes to allow photographic analysis of lordosis. Two methods were compared. Method A - caudal screws were locked first and compression proceeded in a cranial direction prior to locking. Method B - cranial screws were locked first and compression proceeded caudally. Increasing levels of surgical invasiveness were tested; intact, interbody cage, inferior facet resection, and Ponte resection and using different rods including: lordotic, hyperlordotic and straight.

FINDINGS

Method B demonstrated to be consistently superior to Method A, regardless of the type of rod used and for every level of surgical invasiveness performed. (P < 0.001).

INTERPRETATION

locking the top screws first was a consistently superior method of compression, gaining more lordosis. To explain this finding we suggest the following: During posterior compression of pedicle screws along a fixed rod, screw motion is limited by the conflict between the fixed lordotic rod position, and the need for the moving screw to move in a kyphotic arc which is determined by the cage which acts as a pivot point.

Degenerative Lumbar Spine Disease: Imaging and Biomechanics

Chronic low back pain (CLBP) is one of the most common diagnoses encountered when considering years lived with disability. The degenerative changes of the lumbar spine include a wide spectrum of morphological modifications visible on imaging, some of them often asymptomatic or not consistent with symptoms. Phenotyping by considering both clinical and imaging biomarkers can improve the management of CLBP. Depending on the clinical presentation, imaging helps determine the most likely anatomical nociceptive source, thereby enhancing the therapeutic approach by targeting a specific lesion. Three pathologic conditions with an approach based on our experience can be described: (1) pure painful syndromes related to single nociceptive sources (e.g., disk pain, active disk pain, and facet joint osteoarthritis pain), (2) multifactorial painful syndromes, representing a combination of several nociceptive sources (such as lumbar spinal stenosis pain, foraminal stenosis pain, and instability pain), and (3) nonspecific CLBP, often explained by postural (muscular) syndromes.

Neck Pain: Do We Know Enough About the Sensorimotor Control System?

Neck pain is a worldwide health problem. Clarifying the etiology and providing effective interventions are challenging for the multifactorial nature of neck pain. As an essential component of cervical spine function, the sensorimotor control system has been extensively studied in both healthy and pathological conditions. Proprioceptive signals generated from cervical structures are crucial to normal cervical functions, and abnormal proprioception caused by neck pain leads to alterations in neural plasticity, cervical muscle recruitment and cervical kinematics. The long-term sensorimotor disturbance and maladaptive neural plasticity are supposed to contribute to the recurrence and chronicity of neck pain. Therefore, multiple clinical evaluations and treatments aiming at restoring the sensorimotor control system and neural plasticity have been proposed. This paper provides a short review on neck pain from perspectives of proprioception, sensorimotor control system, neural plasticity and potential interventions. Future research may need to clarify the molecular mechanism underlying proprioception and pain. The existing assessment methods of cervical proprioceptive impairment and corresponding treatments may need to be systematically reevaluated and standardized. Additionally, new precise motor parameters reflecting sensorimotor deficit and more effective interventions targeting the sensorimotor control system or neural plasticity are encouraged to be proposed.

Vertebral stabilisation for thoracolumbar vertebral instability associated with cranial and caudal articular process anomalies in pugs: Seven cases (2010-2019)

OBJECTIVES

To describe the diagnostic findings, surgical technique and outcomes in seven pugs with thoracolumbar vertebral instability due to articular process anomalies.

MATERIALS AND METHODS

Records (2010 to 2019) of pugs with thoracolumbar vertebral instability associated with articular process anomalies that underwent decompressive laminectomy and vertebral stabilisation were reviewed. Data on preoperative and postoperative neurologic status, diagnostic findings, surgical techniques and outcomes were retrieved.

RESULTS

Seven dogs were presented with ambulatory or non-ambulatory paraparesis. Caudal articular process anomalies (three dogs) and concomitant cranial and caudal articular process anomalies (four dogs) were noted. Myelography (six dogs) or magnetic resonance imaging (one dog) showed none to severe spinal cord compression. Dynamic myelography in six dogs demonstrated nine distinct sites of spinal cord dimension reduction positioned in extension and/or flexion (mean reduction: 16.0%, range: 8.5 to 24.0%). These dynamic compressions were located at sites with articular process anomalies (seven sites) and sites with no articular process anomalies (two sites). Vertebral instability was confirmed by intraoperative spinal manipulation in all dogs. All dogs remained ambulatory with improved (five dogs) or static (two dogs) neurological deficits at the last follow-up (median: 16 months; range: 1.5 to 66 months).

CLINICAL SIGNIFICANCE

Dynamic myelography and/or intraoperative spinal manipulation demonstrated vertebral instabilities at sites with or without articular process anomalies on imaging. Decompressive laminectomy with vertebral stabilisation resulted in long-term neurological improvement in most dogs.

Biomechanical Evaluation of an Oblique Lateral Locking Plate System for Oblique Lumbar Interbody Fusion: A Finite Element Analysis

OBJECTIVE

The oblique lateral locking plate system (OLLPS) is a novel internal fixation with a locking and reverse pedicle track screw configuration designed for oblique lumbar interbody fusion (OLIF). The OLLPS is placed in a single position through the oblique lateral surgical corridor to reduce operative time and complications associated with prolonged anesthesia and prone positioning. The purpose of this study was to verify the biomechanical effect of the OLLPS.

METHODS

An intact finite element model of L1-S1 (intact) was established based on computed tomography images of a healthy male volunteer. The L4-L5 intervertebral space was selected as the surgical segment. The surgical models were established separately based on OLIF surgical procedures and different internal fixations: 1) stand-alone OLIF (SA); 2) OLIF with a 2-screw lateral plate; 3) OLIF with a 4-screw lateral plate; 4) OLIF with OLLPS; and 5) OLIF with bilateral pedicle screw fixation (BPS). After validation of the intact model, physiologic loads were applied to the superior surface of L1 to simulate motions such as flexion, extension, left bending, right bending, left rotation, and right rotation. The evaluation indices included the L4/5 range of motion, the L4 maximum displacement, and the maximum stresses of the superior and inferior end plates, the cage, and the supplemental fixation.

RESULTS

During OLIF surgery, the OLLPS provided multiplanar stability similar to that provided by BPS. Compared with 2-screw lateral plate and 4-screw lateral plate, OLLPS had better biomechanical properties in terms of enhancing the instant stability of the surgical segment, reducing the stress on the superior and inferior end plates of the surgical segment, and decreasing the risk of cage subsidence.

CONCLUSIONS

With a minimally invasive background, the OLLPS can be used as an alternative to BPS in OLIF and it has better prospects for clinical promotions and applications.

Comparison of Oblique Lateral Interbody Fusion (OLIF) and Minimally Invasive Transforaminal Lumbar Interbody Fusion (MI-TLIF) for Treatment of Lumbar Degeneration Disease: A Prospective Cohort Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To assess the differences in the clinical and radiological outcomes between oblique lateral interbody fusion (OLIF) and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF).

SUMMARY OF BACKGROUND DATA

Nowadays, there is still a controversy regarding whether OLIF is superior to MI-TLIF in the management of degenerative lumbar disease.

METHODS

Between August 3, 2019 and February 3, 2020, 137 patients were assigned to OLIF or MI-TLIF at their request and the surgeon's discretion: 71 in the OLIF group and 66 in the MI-TLIF group. The perioperative data, patient-reported outcomes, radiographic outcomes, and complications were compared between the two groups.

RESULTS

The OLIF group showed shorter operation time (110.5 vs.183.8 minutes, P < 0.001), lesser estimated blood loss (123.1 vs. 232.0 mL, P < 0.001), shorter length of hospital stay (5.5 vs. 6.7 days, P < 0.001), and lower serum creatine kinase (CK) (1 day postoperatively) (376.0 vs. 541.8 IU/L, P < 0.01) than that of MI-TLIF group. Both groups showed no significant differences in the visual analog scale (VAS) scores of lower back and leg pain and the Oswestry Disability Index (ODI) scores preoperatively and at 1, 3, and 12 months postoperatively, respectively (P > 0.05). Compared with the MI-TLIF group, the OLIF group showed better restoration of disc height (DH) (4.7/4.6/4.7 vs. 3.7/3.7/3.7 mm, P < 0.01) and lumbar lordosis angle (LLA) (10.5°/10.8°/11.1° vs. 5.8°/5.7°/5.3°, P < 0.001), but not the value of segmental lordosis angle (SLA) (P > 0.05) at 1 day, 1 month, and 1 year postoperatively, respectively. The complication rate of OLIF was higher than that of MI-TLIF (29.4% vs. 9.7%, P < 0.01).

CONCLUSION

Compared with MI-TLIF, OLIF showed similar results in terms of patient-reported outcomes, restoration of SLA and fusion rate, and superior results with respect to restoration of DH and LLA, operation time, estimated blood loss, length of hospital stay, and serum CK levels (1 day postoperatively). Even though the complication rate of OLIF is higher than that of MI-TLIF, it does not bring persistent and substantial damage to the patients.Level of Evidence: 3.

Computer-Aided Diagnosis for Determining Sagittal Spinal Curvatures Using Deep Learning and Radiography

Analyzing spinal curvatures manually is time-consuming and tedious for clinicians, and intra-observer and inter-observer variability can affect manual measurements. In this study, we developed and evaluated the performance of an automated deep learning-based computer-aided diagnosis (CAD) tool for measuring the sagittal alignment of the spine from X-ray images. The CAD system proposed here performs two functions: deep learning-based lateral spine segmentation and automatic analysis of thoracic kyphosis and lumbar lordosis angles. We utilized 322 datasets with data augmentation for learning and fivefold cross-validation. The segmentation model was based on U-Net, which has multiple applications in medical image processing. Here, we utilized parameter equations and trigonometric functions to design spinal angle measurement algorithms. The kyphosis (T4-T12) and lordosis angle (L1-S1, L1-L5) were automatically measured to help diagnose kyphosis and lordosis. The segmentation model had precision, sensitivity, and dice similarity coefficient values of 90.53 ± 4.61%, 89.53 ± 1.8%, and 90.22 ± 0.62%, respectively. The performance of the CAD algorithm was also verified with the Pearson correlation, Bland-Altman, and intra-class correlation coefficient (ICC) analysis. The proposed angle measurement algorithm exhibited high similarity and reliability during verification. Therefore, CAD can help clinicians in reaching a diagnosis by analyzing the sagittal spinal curvatures while reducing observer-based variability and the required time or effort.

Impact of sarcopenia and sagittal parameters on the residual back pain after percutaneous vertebroplasty in patients with osteoporotic vertebral compression fracture

Objective

The objective of this study was to explore the impact of sarcopenia and sagittal parameters on the residual back pain (RBP) after percutaneous vertebroplasty (PVP) for treatment of osteoporotic vertebral compression fracture (OVCF).

Methods

This retrospective study included elderly patients (age range 60–90 years) with OVCF treated with PVP from January 2015 and December 2020 in our hospital. The skeletal muscle mass index (SMI) was calculated by dividing the T12 pedicle level muscle cross-sectional area by the square of body height from chest CT to diagnose sarcopenia. The radiological parameters for measuring the sagittal alignment were included: C7-sagittal vertical axis (SVA), T1 pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI).

Result

According to whether the VAS score > 4, patients were divided into RBP group (56 patients) and Control group (100 patients). There was no difference in age, gender, body mass index, BMD, surgical segment, bone cement usage between the groups (P > 0.05). The SMI in RBP group (27.3 ± 5.1) was significantly lower compared to that in Control group (36.8 ± 3.2) (P < 0.05). Sarcopenia was present in 19 patients (20.3%) in RBP group, which was significantly more than that in Control group (P < 0.05). C7-SVA and TPA was significantly larger in the RBP group than in the Control group (P < 0.05). PI and LL was significantly smaller in the RBP group compared to the Control group (P < 0.05). However, no significant differences between the two groups with respect to TK, SS and PT (P > 0.05).

Conclusion

Poor sagittal parameters and sarcopenia in OVCF patients after PVP were more prone to residual back pain. Larger C7-SVA, TPA and PI-LL mismatch could increase the incidence of RBP in elderly patients with single-segment osteoporotic compression fractures.

Reconstruction of the cervical lateral mass using 3D-printed prostheses

Objective

This study aimed to investigate the outcome of using 3-dimensional (3D)-printed prostheses to reconstruct a cervical lateral mass to maintain cervical stability.

Methods

We retrospectively analyzed data of 7 patients who underwent cervical lateral mass reconstruction using a 3D-printed prosthesis, comprising axial and subaxial lateral mass reconstruction in 2 and 5 patients, respectively. Bilateral mass was reconstructed in 1 patient and unilateral mass in the remaining 6 patients.

Results

Using a 3D-printed lateral mass prosthesis, internal fixation was stable for all 7 patients postoperatively. No implant-related complications such as prosthesis loosening, displacement, and compression were observed at the last follow-up.

Conclusion

Reconstruction of the lateral mass structure is beneficial in restoring load transfer in the cervical spine under physiological conditions. A 3D-printed prosthesis can be considered a good option for reconstruction of the lateral mass as fusion was achieved, with no subsequent complications observed.

Laser Marking of Spine Rods Is Strongly Associated With Risk of Clinical Rod Failure

INTRODUCTION

What is overlooked in clinical studies are the possibilities of manufacturing and design aspects of the instrumentation that could initiate rod fracture. Although revision because of hardware fracture is a small fraction of the overall revision rates (12.1% to 13.7%), there are sufficient numbers of revision cases where hardware removed can undergo a thorough metallurgic analysis. This study is unique in that rod characteristics, such as alloy, surface markings, and fracture type, seen at fracture surfaces are considered in the analysis.

METHODS

This work was conducted under both a retrospective and prospective IRB. Patients considered for this study were between the ages of 18 and 85 years who underwent or were undergoing revision spine surgery with previous instrumentation in the cervical, thoracic, or lumbar region and evidence of at least one of the following: catastrophic hardware failure, pseudarthrosis, implant loosening, or nonfusion. Inclusion criteria were determined through radiographic and medical records review.

RESULTS

Fifty-six patients who had revision procedures because of different indications were included; 101 rods were removed, tested for fracture, and included in the analysis. Laser marking is significantly (P < 0.0001) associated with rod fracture. Detailed analysis showed notable surface and subsurface changes as the result of the marking, such as surface melting, cracking, and notching, creating locations to initiate a fracture. The three most informative variables to clinical rod fracture using multiple regression modeling were body mass index, presence or absence of laser mark (yes/no), and length of posterior fusion (≤2 spinal levels/>2 spinal levels). It was found that the relative risk of rod fracture is 23 times higher during 20 postoperative years than in cases with this index <0.4.

DISCUSSION

For a patient with a given body mass index, if they require a multilevel fixation greater than two levels and rods with laser marks are used, the risk of early rod fracture increases by 40%.

Subaxial lateral mass prosthesis for posterior reconstruction of cervical spine

PURPOSE

To obtain the relevant morphometry of the lateral mass of the subaxial cervical spine (C3-C7) and to design a series of lateral mass prostheses for the posterior reconstruction of the stability of cervical spine.

METHODS

The computed tomography (CT) scans of healthy volunteers were obtained. RadiAnt DICOM Viewer software (Version 2020.1, Medixant, Poland) was used to measure the parameters of lateral mass, such as height, anteroposterior dimension (APD), mediolateral dimension (MLD) and facet joint angle. According to the parameters, a series of cervical lateral mass prostheses were designed. Cadaver experiment was conducted to demonstrate its feasibility.

RESULTS

23 volunteers with an average age of 30.1 ± 7.1 years were enrolled in this study. The height of lateral mass is 14.1 mm averagely. Facet joint angle, APD and MLD of lateral mass averaged 40.1 degrees, 11.2 mm and 12.18 mm, respectively. With these key data, a lateral mass prosthesis consists of a bone grafting column and a posterior fixation plate was designed. The column has a 4.0 mm radius, 41 degrees surface angle and adjustable height of 13, 15, or 17 mm. In the cadaver experiment, the grafting column could function as a supporting structure between adjacent facets, and it would not violate exiting nerve root (NR) or vertebral artery (VA).

CONCLUSION

This study provided detailed morphology of the lateral mass of subaxial cervical spine. A series of subaxial cervical lateral mass prostheses were designed awaiting further clinical application.

Influence of Axial Load and a 45-Degree Flexion Head Position on Cervical Spinal Stiffness in Healthy Young Adults

Background: Neck pain is a major cause of disability worldwide. Poor neck posture such as using a smartphone or work-related additional cervical axial load, such headgear of aviators, can cause neck pain. This study aimed at investigating the role of head posture or additional axial load on spinal stiffness, a proxy measure to assess cervical motor control. Methods: The posterior-to-anterior cervical spinal stiffness of 49 young healthy male military employees [mean (SD) age 20 ± 1 years] was measured in two head positions: neutral and 45-degree flexed head position and two loading conditions: with and without additional 3 kg axial load. Each test condition comprised three trials. Measurements were taken at three cervical locations, i.e., spinous processes C2 and C7 and mid-cervical (MC). Results: Cervical spinal stiffness measurements showed good reliability in all test conditions. There was a significant three-way interaction between location × head position × load [F(2, 576) = 9.305, p < 0.001]. Significant two-way interactions were found between measurement locations × loading [F(2, 576) = 15.688, p < 0.001] and measurement locations × head position [F(2, 576) = 9.263, p < 0.001]. There was no significant interaction between loading × head position [F(1, 576) = 0.692, p = 0.406]. Post hoc analysis showed reduction of stiffness in all three measurement locations in flexion position. There was a decrease in stiffness in C2 with loading, increase in stiffness in C7 and no change in MC. Discussion: A flexed head posture leading to decreased stiffness of the cervical spine might contribute to neck pain, especially if the posture is prolonged and static, such as is the case with smartphone users. Regarding the additional load, stiffness decreased high cervical and increased low cervical. There was no change mid cervical. The lower spinal stiffness at the high cervical spine might be caused by capsular ligament laxity due to the buckling effect. At the lower cervical spine, the buckling effect seems to be less dominant, because the proximity to the ribs and sternum provide additional stiffness.

Posterior Ligamentous Complex Injuries of the Thoracolumbar Spine: Importance and Surgical Implications

The soft tissues surrounding the spine play a primordial role in its stability, the most important of which are located posteriorly and are deemed the posterior ligamentous complex (PLC). Injuries to the PLC in the setting of thoracolumbar trauma are often dreaded and little attention has been given to them in the management protocols of thoracolumbar trauma. This review aims to summarize and contextualize current concepts in PLC injuries of the thoracolumbar spine with the aim to provide a clear guide for clinical management. Injuries to the PLC may be suspected on the clinical exam but are often missed, leading to serious complications, including instability and neurological compromise. The diagnosis is often made indirectly by spinal radiographs and CT-scanning or by direct visualization of soft tissues via magnetic resonance imaging. The latter remains the standard imaging modality and is mandatory for patients with a high suspicion of PLC injury. PLC injuries are associated with vertebral fractures and follow a progressive pattern of severity, depending on the mechanism of injury and extent of trauma. Surgical management is warranted, as PLC damage renders the spine unstable. Although fusion was once the standard of care and remains applicable for certain patients, recent endeavors of temporary spinal fixation without fusion are increasingly gaining traction in patients with PLC injuries. In conclusion, PLC injuries are challenging as they are often missed, poorly understood, and are not easily managed. Proper diagnosis and management are crucial to avoid long-standing complications such as spinal instability. Considering the paucity of available data on such an important topic in thoracolumbar trauma, this review article aims to contextualize current concepts in PLC injuries in order to demystify this sparsely covered subject.

Dual lesion spinal cord injury in a polytrauma patient: a case report

INTRODUCTION

Dual lesion spinal cord injury (SCI) is the presence of two distinct regions of injury to the spinal cord, which can occur simultaneously or as a sequela of initial injury. Dual lesion SCI appears to be a rather rare occurrence with a paucity of cases described. As such, there is limited information available regarding presentation, evaluation, long-term rehabilitation management, and prognostication of these patients.

CASE PRESENTATION

Presented is a case of a 25-year-old woman with a gunshot wound injury to the T5 vertebra with associated cord damage, initially classified as T6 ASIA Impairment Scale (AIS) B. A subsequent cervical spinal stroke, in the setting of cord edema, resulted in a motor incomplete cervical SCI. As such, she underwent additional functional decline.

DISCUSSION

Patients with dual lesion SCI present with unique challenges in evaluation and management. This case highlights key factors for the acute care and rehabilitation teams to consider when addressing these challenges.

Effects of increasing axial load on cervical motor control

To investigate the effects of increasing axial load on cervical motor control. Surrogates of cervical motor control were active cervical range of motion (C-ROM) and joint position error (JPE) assessed in flexion, extension, lateroflexion and rotation directions in 49 healthy young men (mean age: 20.2 years). All measurements were executed with 0-, 1-, 2-, and 3-kg axial loads. Linear mixed models were used to assess the effects of axial loading and cervical movement-direction on C-ROM and JPE. Post-hoc analysis was performed to compare load levels. Axial loading (p = 0.045) and movement direction (p < 0.001) showed significant main effects on C-ROM as well as an interaction (p < 0.001). C-ROM significantly changed with 3-kg axial load by decreaseing extension (− 13.6%) and increasing lateroflexion (+ 9.9%). No significant main effect was observed of axial loading on JPE (p = 0.139). Cervical motor control is influenced by axial loading, which results in decreased C-ROM in extension and increased C-ROM lateroflexion direction.

Novel Distributed Loading Technique Using Multimaterial, Long-Segment Spinal Constructs to Prevent Proximal Junctional Pathology in Adult Spinal Deformity Correction-Operative Technique and Radiographic Findings

BACKGROUND

Proximal junctional kyphosis (PJK) and proximal junction failure are common and costly complications after long-segment adult spinal deformity (ASD) correction. Although much research has focused on the concept of "softening the landing" to prevent proximal junction pathologies, long-segment constructs largely deviate from the force-deformation curve of the physiologic spine. Our novel distributed loading technique for ASD correction is described using multimaterial, long-segment constructs to create a biomechanically sound, yet physiologic, decremental stiffness toward the rostral end.

METHODS

Operative steps detail the custom-designed constructs of dual-headed pedicle screws and varied rod diameters and materials (cobalt chromium or titanium) for an initial 20 patients (mean 66.6 ± 4.8 years). Standing scoliosis films were obtained preoperatively and at regular intervals postoperatively to assess for PJK.

RESULTS

No patient had evidence of PJK or proximal junction failure at latest radiographic follow-up (mean 17.9 months, range 13-25 months). Radiographic findings for sagittal vertical axis averaged 11.2 ± 5.6 cm preoperatively and 3.6 ± 2.3 cm postoperatively. Compared with preoperative parameters, postoperative reductions in pelvic incidence-lumbar lordosis mismatch averaged 28.7 ± 12.9 degrees, and sagittal vertical axis averaged 7.6 ± 5.2 cm while PJA was essentially unchanged.

CONCLUSIONS

Preliminary results suggest that the distributed loading technique is promising for prevention of PJK with stiffness gradients that mimic the force-deformation curve of the physiologic posterior tension band. Our technique may optimize the degree of stress at the proximal junction without overwhelming the anterior column bony while remodeling and mature arthrodesis takes place.

Calibration and validation of a novel hybrid model of the lumbosacral spine in ArtiSynth-The passive structures

In computational biomechanics, two separate types of models have been used predominantly to enhance the understanding of the mechanisms of action of the lumbosacral spine (LSS): Finite element (FE) and musculoskeletal multibody (MB) models. To combine advantages of both models, hybrid FE-MB models are an increasingly used alternative. The aim of this paper is to develop, calibrate, and validate a novel passive hybrid FE-MB open-access simulation model of a ligamentous LSS using ArtiSynth. Based on anatomical data from the Male Visible Human Project, the LSS model is constructed from the L1-S1 rigid vertebrae interconnected with hyperelastic fiber-reinforced FE intervertebral discs, ligaments, and facet joints. A mesh convergence study, sensitivity analyses, and systematic calibration were conducted with the hybrid functional spinal unit (FSU) L4/5. The predicted mechanical responses of the FSU L4/5, the lumbar spine (L1-L5), and the LSS were validated against literature data from in vivo and in vitro measurements and in silico models. Spinal mechanical responses considered when loaded with pure moments and combined loading modes were total and intervertebral range of motions, instantaneous axes and centers of rotation, facet joint contact forces, intradiscal pressures, disc bulges, and stiffnesses. Undesirable correlations with the FE mesh were minimized, the number of crisscrossed collagen fiber rings was reduced to five, and the individual influences of specific anatomical structures were adjusted to in vitro range of motions. Including intervertebral motion couplings for axial rotation and nonlinear stiffening under increasing axial compression, the predicted kinematic and structural mechanics responses were consistent with the comparative data. The results demonstrate that the hybrid simulation model is robust and efficient in reproducing valid mechanical responses to provide a starting point for upcoming optimizations and extensions, such as with active skeletal muscles.

Predictive risk factors for recollapse of cemented vertebrae after percutaneous vertebroplasty: A meta-analysis

BACKGROUND

As one of the most common complications of osteoporosis, osteoporotic vertebral compression fracture (OVCF) increases the risk of disability and mortality in elderly patients. Percutaneous vertebroplasty (PVP) is considered to be an effective, safe, and minimally invasive treatment for OVCFs. The recollapse of cemented vertebrae is one of the serious complications of PVP. However, the risk factors associated with recollapse after PVP remain controversial.

AIM

To identify risk factors for the recollapse of cemented vertebrae after PVP in patients with OVCFs.

METHODS

A systematic search in EMBASE, MEDLINE, the Cochrane Library, and PubMed was conducted for relevant studies from inception until March 2020. Studies investigating risk factors for the recollapse of cemented vertebrae after PVP without additional trauma were selected for analysis. Odds ratios (ORs) or standardized mean differences with 95% confidence interval (CI) were calculated and heterogeneity was assessed by both the chi-squared test and the I-squared test. The methodological quality of the included studies was assessed according to the Newcastle-Ottawa Scale.

RESULTS

A total of nine case-control studies were included in our meta-analysis comprising 300 cases and 2674 controls. The significant risk factors for the recollapse of cemented vertebrae after PVP in OVCF patients were fractures located at the thoracolumbar junction (OR = 2.09; 95%CI: 1.30 to 3.38; P = 0.002), preoperative intravertebral cleft (OR = 2.97; 95%CI: 1.93 to 4.57; P < 0.00001), and solid lump distribution pattern of the cement (OR = 3.11; 95%CI: 1.91 to 5.07; P < 0.00001). The analysis did not support that age, gender, lumbar bone mineral density, preoperative visual analogue scale score, injected cement volume, intradiscal cement leakage, or vertebral height restoration could increase the risk for cemented vertebra recollapse after PVP in OVCFs.

CONCLUSION

This meta-analysis suggests that thoracolumbar junction fractures, preoperative intravertebral cleft, and solid lump cement distribution pattern are associated with the recollapse of cemented vertebrae after PVP in OVCF patients.

Numerical Evaluation of Spinal Stability after Posterior Spinal Fusion with Various Fixation Segments and Screw Types in Patients with Osteoporotic Thoracolumbar Burst Fracture Using Finite Element Analysis

The aim of this study was to analyze the spinal stability and safety after posterior spinal fusion with various fixation segments and screw types in patients with an osteoporotic thoracolumbar burst fracture based on finite element analysis (FEA). To realize various osteoporotic vertebral fracture conditions on T12, seven cases of Young’s modulus, namely 0%, 1%, 5%, 10%, 25%, 50%, and 100% of the Young’s modulus, for vertebral bones under intact conditions were considered. Four types of fixation for thoracolumbar fracture on T12 (fixed with T11-L1, T10-T11-L1, T11-L1-L2, and T10-T11-L1-L2) were applied to the thoracolumbar fusion model. The following screw types were considered: pedicle screw (PS) and cortical screw (CS). Using FEA, four motions were performed on the fixed spine, and the stress applied to the screw, peri-implant bone (PIB), and intervertebral disc (IVD) and the range of motion (ROM) were calculated. The lowest ROM calculated corresponded to the T10-T11-L1-L2 model, while the closest to the intact situation was achieved in the T11-L1-L2 fixation model using PS. The lowest stress in the screw and PB was detected in the T10-T11-L1-L2 fixation model.

Spinal trauma in DISH and AS: is MRI essential following the detection of vertebral fractures on CT?

BACKGROUND

Both ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH) cause a rigid spine, but through different pathophysiology. Recent data has shown that characteristic fracture patterns may also differ following trauma since the posterior osseous and soft tissue elements are often spared in DISH. CT and MRI are important in diagnosing spine injury, but given the differences between AS and DISH, the utility of obtaining both studies in all patients warrants scrutiny.

PURPOSE

To assess the prevalence of posterior element injury on CT and MRI in DISH and AS patients with known vertebral body injury detected on CT; to determine whether MRI demonstrates additional injuries in neurologically intact patients presumed to have isolated vertebral body injuries on CT.

STUDY DESIGN

Multicenter, retrospective, case-control study.

PATIENT SAMPLE

DISH and AS patients presenting after spine trauma between 2007 and 2017.

OUTCOME MEASURES

Review of CT and MRI findings at the time of presentation.

METHODS

One hundred sixty DISH and 85 AS patients presenting after spine trauma were identified from 2 affiliated academic hospitals serving as level 1 trauma and tertiary referral centers. A diagnosis of DISH or AS was verified by a board-certified emergency radiologist with 3 years of experience. Age, gender, mechanism of injury, fracture type, spine CT and MRI imaging findings, surgical intervention, and neurologic deficit were recorded. The CT and MRI studies were reviewed by the same radiologist for fracture location and type using the AO spine classification. No funding source or conflict of interest was present.

RESULTS

Median age was 72 and 79 years old for the AS and DISH groups, respectively. Both were predominantly male (81%) and most presented after a low energy mechanism of injury (74% and 73%). Type C AO spine injuries were seen in 52% of AS patients but only 4% of DISH patients. In patients with known vertebral body injury on CT, additional injury to the posterior elements on CT or MRI in DISH patients was 51% versus 92% in AS patients. However, in patients with an isolated vertebral body fracture on CT and no neurological deficit, MRI identified posterior element injury in only 4/22 (18%) DISH patients compared to 5 of 7 (71%) AS patients. None of the MRI findings in the DISH patients were considered clinically important while all 5 AS patients eventually underwent operative treatment despite having no neurological deficit. Epidural hematoma on MRI was seen in 43% of AS patients as opposed to 5% of DISH patients.

CONCLUSION

Based on our small sample size, CT alone may be adequate in DISH patients with isolated vertebral body fractures and no neurologic deficit, but an additional MRI should be considered in the presence of an unclear neurological exam or deficit. MRI should be strongly considered for any AS patient regardless of neurologic status.

Effectiveness of Rehabilitative Intervention on Pain, Postural Balance, and Quality of Life in Women with Multiple Vertebral Fragility Fractures: A Prospective Cohort Study

Patients with vertebral fragility fractures often experience chronic pain, postural and balance disorders, and poor quality of life (QoL). Although several studies have investigated the role of rehabilitation in severe osteoporosis, the effectiveness of this intervention in patients with multiple vertebral fractures is poorly known. The aim of our longitudinal cohort study is to evaluate the effectiveness of rehabilitation, including postural training, resistance exercises, and visual stabilization exercises, for a 7-week period, on the pain, postural balance, and QoL of subjects with at least two vertebral fragility fractures receiving denosumab and vitamin D. We investigated, before (T0) and after (T1, at 7 weeks) rehabilitation, the following outcome measures on 28 patients: pain (Numerical Rating Scale (NRS)), self-perceived QoL (36-Item Short Form Survey (SF-36) and Mini-Osteoporosis Quality of Life Questionnaire (Mini-OQOL)), dizziness (Dizziness Handicap Inventory (DHI-I)), mobility (Timed-Up and Go (TUG) test), and instrumental posturographic assessment (FreeMed posturography system). At the end of the treatment, improvements of pain and QoL were recorded. Pain relief was highly obtained in patients with more than two vertebral fractures. Moreover, a significant functional improvement (TUG test) was found in those with two vertebral fractures, without any statistically significant change reported for other outcomes. Our findings suggest that combined intervention, including anti-osteoporotic drugs and postural rehabilitation, should be proposed to osteoporotic patients with multiple vertebral fractures.

A Preoperative Predictive Model of Lower Lumbar Spine Instability Based on Three-Dimensional Computed Tomography: A Retrospective Case-Control Pilot Study

OBJECTIVE

This study aimed to build a predictive model of lower lumbar instability.

METHODS

This retrospective study included 199 patients. Patients were divided into the lower lumbar instability group (LLIG) (n = 98) and lower lumbar stability group (LLSG) (n = 101). All participants of LLIG were recruited over a 2-year period (2015-2017) from the patients who accept lumbar surgery at the First Hospital of Jilin University. The LLSG was selected from outpatients who had underwent lumbar spine computed tomography (CT) and Flexion and extension radiographs (FER) at the First Hospital of Jilin University from 2015 to 2017. Several lower lumbar parameters were measured, including Lordosis angle (LA), intervertebral height (IH), ratio of anterior height to posterior height (APR), angle between endplate and anterior edge of vertebral body (AEPVa), sagittal slip ratio (SSR), and angle between the upper endplate and z-axis on sagittal plane (AUEZS). These parameters were keyed into the SPSS software to create a predictive model for classification. Sensitivity, specificity, predictive accuracy, and Kappa value were used to evaluate the predictive model.

RESULTS

Compared with LLSG, the LA of LLIG decreased by 3.49° (126.54° vs 130.3°). Similarly, the IH of LLIG decreased by 1.23°mm, 1.66°mm, and 0.71°mm at L3-4, L4-5, and L5-S1. Compared with LLSG, the SSR of LLIG is higher at L3-4, L4-5, and L5-S1 (0.54 vs 0.51, 0.57 vs 0.46, and 0.59 vs 0. 47). Moreover, the APR of LLIG is higher than those of LLSG at L3-4, L4-5, and L5-S1 (1.97 vs 1.81, 2.40 vs 1.97, and 2.69 vs 2.26). The LLIG has bigger AEPVa than LLIG at L3-4, L4-5, and L5-S1. Compared with LLSG, the AUEZS of LLIG is bigger at L3-4 (91.75° vs 90.81°) and smaller at L4-5 and L5-S1(84.63° vs 85.85° and 73.27° vs 75.01°). The SSR (L4) show highest predictive accuracy (83%) when every parameter was fed to LDA classifier to generate a univariate model. All parameters represent a statistically significant difference (P < 0.05) between LLSG and LLIG. The model including LA, APR (L5-S1), IH (L4-5), SSR (L5), AUEZS (L5) has highest predictive accuracy of 88.2%. The sensitivity, specificity, and Kappa value are 88.7%, 93.1%, and 0.77.

CONCLUSION

The predictive model has good classification performance and can be an auxiliary tool for clinicians to evaluate lumbar instability in preoperative patients with severe pain aggravated by lumbar movement.

Analysis of translation and angular motion in loaded and unloaded positions in the lumbar spine

Background Context

Abnormalities in intervertebral rotation and translation are important to diagnosis and treatment planning for common spinal disorders. Tests that do not sufficiently load the spine can result in mis-diagnosed motion abnormalities. Upright flexion and extension x-rays are commonly used despite known limitations. Additional evidence is needed in support of preliminary studies suggesting that the change from standing to supine may sufficiently stress the spine to diagnose motion abnormalities.

Purpose

Compare intervertebral translation between flexion and extension to translation between upright and supine positions in a representative clinical population.

Study Design/Setting

Prospective analysis of images retrospectively collected from routine clinical practices.

Methods

After obtaining IRB approval for analysis of previously obtained images, patients were identified via chart reviews where a neutral-lateral x-ray and an MRI or CT exam were obtained for diagnosis of a spinal disorder and where flexion-extension x-rays had been obtained to help diagnose abnormal intervertebral motion. The mid-sagittal slice from the MRI or CT exam was paired with the neutral-lateral radiograph. Intervertebral translation at the L4-L5 and L5-S1 levels between supine and standing and between flexion and extension were measured from the images using previously validated methods. The translations were classified as normal or abnormal with reference to a previously obtained database of intervertebral motion in radiographically normal and asymptomatic volunteers.

Results

At the L5-S1 level in particular, there tended to be greater translation between the supine and standing than between upright flexion and extension. On average, translations were below that found in asymptomatic volunteers. No abnormal translations were detected from flexion-extension radiographs whereas approximately 7% of levels had abnormal translations between supine and upright positions.

Conclusions

Intervertebral translations between supine and standing, measured using the mid-sagittal slice from a MRI or CT exam and a lateral x-ray with the patient standing can help to identify abnormal motion. This would be particularly valuable for patients with limited flexion and extension. This study thereby adds to the evidence in support of measuring intervertebral motion between the supine and upright positions to detect abnormal intervertebral motion.

Aged Lumbar Extension Strength of Chronic Low Back Pain in Korean Population of 10-80 Years

Background:

The purpose of this study was to find the basic data of medical and exercise therapy by indexing lumbar extension muscle strength of low back pain (LBP) patients.

Methods:

In this cross-sectional study, 3078 chronic LBP participants from The J hospital, Seoul, Republic of Korea, from 2003 to 2010 were enrolled. Maximum muscle strength was measured at maximum flexion angle and maximum extension angle according to range of motion (ROM) results. For each isometric test, participants were seated and secured in the MEDX (medx lumbar extension machine, Ocala, FL, USA) machine.

Results:

The relative ROM (P=0.012) differed significantly among the aged groups in all participants. In addition, mean of strength (P<0.001), maximal of strength (P<0.001), mean of strength %BW (P<0.001) and maximal of strength %BW (P<0.001) are significant differences in all participants. The results of multiple regression analysis was the ‘model A’, maximal of strength for 32.1% of the variance in weigh, body mass index and range of motion. In addition, ‘model B’ was 30.4%, ‘model C’ was 28.8%, ‘model D’ was 28.5%, ‘model E’ was 21.7%, and ‘model F’ was 23.5% of the variance in weigh, body mass index and range of motion.

Conclusion:

We found the three predictor (weight, BMI, and ROM) variables accounted for 32.1% of the variance in maximal of strength %BW, the highest in < 29 yr groups. Our data indicate the basic data of medical and exercise therapy by indexing lumbar extension muscle strength of LBP patients.

Assessment of load-sharing thoracolumbar injury: A modified scoring system

BACKGROUND

Many classification systems of thoracolumbar spinal fractures have been proposed to enhance treatment protocols, but none have achieved universal adoption.

AIM

To develop a new patient scoring system for cases with thoracolumbar injury classification and severity score (TLICS) = 4, namely the load-sharing thoracolumbar injury score (LSTLIS).

METHODS

Based on thoracolumbar injury classification and severity score, this study proposes the use of the established load-sharing classification (LSC) to develop an improved classification system (LSTLIS). To prove the reliability and reproducibility of LSTLIS, a retrospective analysis for patients with thoracolumbar vertebral fractures has been conducted.

RESULTS

A total of 102 cases were enrolled in the study. The scoring trend of LSTLIS is roughly similar as the LSC scoring, however, the average deviation based on the former method is relatively smaller than that of the latter. Thus, the robustness of the LSTLIS scoring method is better than that of LSC. LSTLIS can further classify patients with TLICS = 4, so as to assess more accurately this particular circumstance, and the majority of LSTLIS recommendations are consistent with actual clinical decisions.

CONCLUSION

LSTLIS is a scoring system that combines LSC and TLICS to compensate for the lack of appropriate inclusion of anterior and middle column compression fractures with TLICS. Following preliminary clinical verification, LSTLIS has greater feasibility and reliability value, is more practical in comprehensively assessing certain clinical circumstances, and has better accuracy with clinically significant guidelines.

Characterization of biomaterials intended for use in the nucleus pulposus of degenerated intervertebral discs

Biomaterials for regeneration of the intervertebral disc must meet complex requirements conforming to biological, mechanical and clinical demands. Currently no consensus on their characterization exists. It is crucial to identify parameters and their method of characterization for accurate assessment of their potential efficacy, keeping in mind the translation towards clinical application. This review systematically analyses the characterization techniques of biomaterial systems that have been used for nucleus pulposus (NP) restoration and regeneration. Substantial differences in the approach towards assessment became evident, hindering comparisons between different materials with respect to their suitability for NP restoration and regeneration. We have analysed the current approaches and identified parameters necessary for adequate biomaterial characterization, with the clinical goal of functional restoration and biological regeneration of the NP in mind. Further, we provide guidelines and goals for their measurement. STATEMENT OF SIGNIFICANCE: Biomaterials intended for restoration of regeneration of the nucleus pulposus within the intervertebral disc must meet biological, biomechanical and clinical demands. Many materials have been investigated, but a lack of consensus on which parameters to evaluate leads to difficulties in comparing materials as well as mostly partial characterization of the materials in question. A gap between current methodology and clinically relevant and meaningful characterization is prevalent. In this article, we identify necessary methods and their implementation for complete biomaterial characterization in the context of clinical applicability. This will allow for a more unified approach to NP-biomaterials research within the field as a whole and enable comparative analysis of novel materials yet to be developed.