[Risk factors for venous thromboembolic complications in elderly and senile patients with diabetes mellitus planned for spinal surgery.]

The search for literature sources in domestic and foreign databases showed the absence of works devoted to the study of risk factors for venous thromboembolic events (VTE) in patients of the older age group with diabetes mellitus who are planned to undergo surgical interventions on the spine, which was the impetus for this study. The aim of the study was to study the risk factors for VTE in elderly and senile patients with diabetes mellitus who are scheduled for spinal surgery. A single-center retrospective study included 119 elderly and senile patients (64 men, 55 women, mean age 74,2±6,5 years) who underwent various surgical interventions on the spinal column. According to the binary logistic regression model, the following parameters are statistically significantly associated with the development of VTEC in the studied group of respondents: age of patients over 75 years (p=0,048), HbA1C levels over 7,5% (p=0,007) and D-dimer over 0,5 mg /l FEU (p=0,034), as well as high risk (5 points or more) of VTE according to Caprini scale (p=0,012). In order to reduce the incidence of VTE in elderly and senile patients with diabetes mellitus who are planned to perform surgical interventions on the spine, it is necessary to verify the above clinical and laboratory parameters in the early stages of hospitalization.

[Facet joint distraction as a risk factor for poor clinical outcomes in older patients after anterior cervical discectomy and fusion.]

The search for literature sources in domestic and foreign databases showed the absence of works devoted to the study of the influence of the degree of distraction of the facet joints in elderly and senile patients who underwent anterior cervical discectomy and fusion (ACDF). The purpose of the study was to study the effect of the degree of facet joint distraction on clinical outcomes in patients of the older age group who underwent ACDF. A single-center retrospective study included 47 elderly and senile patients who underwent ACDF for radiculopathy due to degenerative diseases of the cervical spine. A statistically significant correlation was found between the differences in the value of the interfacet distance and the severity of pain in the cervical spine according to VAS (p<0,01). Patients with X-ray semiotics of facet distraction more than 0,55 mm 12 months after the operation were significantly more likely to experience increased pain in the cervical spine according to VAS (p=0,028) and significantly limited daily activities due to pain in the neck NDI (p=0,043). The choice of indications for ACDF in patients of the older age group should be based on a rigorous analysis of facet distraction, cervical sagittal parameters in combination with the functional status of patients.

[Decompression fusion surgery and minimally invasive microsurgical decompression in patients with single-segment lumbar spinal stenosis]. / Sravnitel'nyi analiz rezul'tatov primeneniya metodik dekompressii so stabilizatsiei i minimal'no invazivnoi mikrokhirurgicheskoi dekompressii u patsientov s monosegmentarnym poyasnichnym spinal'nym stenozom.

There are few studies comparing clinical efficacy of decompression/fusion surgery (transforaminal lumbar interbody fusion (TLIF) + transpedicular interbody fusion) and minimally invasive microsurgical decompression (MMD) in patients with single-segment lumbar spinal stenosis. OBJECTIVE: To compare the results of TLIF + transpedicular interbody fusion and MMD in patients with single-segment lumbar spinal stenosis. MATERIAL AND METHODS: A retrospective observational cohort study included medical records of 196 patients (100 (51%) men, 96 (49%) women). Age of patients ranged from 18 to 84 years. Mean postoperative follow-up period was 20.1±6.7 months. Patients were divided into 2 groups: group I (control) included 100 patients who underwent TLIF + transpedicular interbody fusion, group II (study) included 96 patients who underwent MMD. We analyzed pain syndrome and working capacity using visual analogue scale (VAS) and Oswestry Disability Index (ODI), respectively. RESULTS: Analysis of pain syndrome in both groups after 3, 6, 9, 12 and 24 months clearly demonstrated stable relief of pain syndrome (VAS score) in the lower extremities. In group II, VAS score of lower back and leg pain was significantly higher in long-term follow-up period (after 9 months or more) compared to the 1st group (p<0.05). In long-term follow-up period (after 12 months), there was significant decrease in degree of disability (ODI score) in both groups (p<0.001) without between-group differences. We assessed achievement of treatment goal in 12 and 24 months after surgery in both groups. The result was significantly better in the 2nd group. At the same time, some respondents failed to achieve the final clinical goal of treatment in both groups (group I - 8 (12.1%), group II - 2 (3%) patients). CONCLUSION: Analysis of postoperative outcomes in patients with single-segment degenerative lumbar spinal stenosis revealed similar clinical effectiveness of TLIF + transpedicular interbody fusion and MMD regarding decompression quality. However, MMD was associated with less traumatization of paravertebral tissues, blood loss, fewer unwanted phenomena and earlier recovery.

[Intramedullary cervical abscess: a case report and literature review]. / Intramedullyarnyi abstsess sheinogo otdela spinnogo mozga: klinicheskii sluchai i obzor literatury.

Intramedullary abscesses of the spinal cord are the rarest form of infectious lesions of the central nervous system. We report surgical treatment of a patient with intramedullary cervical abscess caused by L. monocytogenes. Features of this case are absence of primary purulent focus and atypical infectious agent. The patient underwent surgical treatment for intramedullary cervical abscess and subsequent antimicrobial therapy. Subtotal regression of neurological symptoms was noted in early postoperative period. The authors emphasize strict collegial decision-making regarding diagnosis of this disease and choice of optimal treatment strategy.

[Minimally invasive microsurgical decompression in patients with monosegmental lumbar spinal stenosis]. / Rezul'taty primeneniya minimal'no invazivnoi mikrokhirurgicheskoi dekompressii u patsientov s monosegmentarnym poyasnichnym stenozom.

Surgical treatment of degenerative lumbar spinal stenosis is an actual problem of modern spinal surgery and orthopedics. OBJECTIVE: To analyze the results of minimally invasive microsurgical decompression (MI-MD) in patients with monosegmental lumbar spinal stenosis. MATERIAL AND METHODS: A retrospective observational cohort study was performed. We analyzed medical records of patients who underwent MI-MD for monosegmental degenerative lumbar spinal stenosis. Clinical and objective results of MI-MD, as well as the types and prevalence of adverse clinical events were studied. RESULTS: The study included 96 medical records (50 (52%) males and 46 (48%) females aged 18-84 years). Analysis of pain in lower back and lower extremities in 3, 6, 9, 12 and 24 months after MI-MD showed a significant decrease of this indicator (p<0.001). There was significant improvement of capacity according to ODI score up to 5-12% in 72.9% of patients in early postoperative period (p=0.055). In delayed postoperative period, we also observed significant improvement of working capacity according to ODI score and gradual decrease in disability index (p<0.001). Adverse clinical events occurred in 6 (6.2%) patients. CONCLUSION: MI-MD is a highly effective surgical method for monosegmental lumbar spinal stenosis with minimal incidence of adverse clinical events.

[Benign extramedullary spinal cord tumors at the level of craniovertebral junction: a systematic review]. / Dobrokachestvennye ekstramedullyarnye opukholi spinnogo mozga na urovne kraniovertebral'nogo perekhoda: sistematicheskii obzor.

Extramedullary spinal cord tumors at the level of craniovertebral junction are a rare group of neoplasms with their own characteristics. Taking into account the peculiarities of clinical course and complex anatomy of craniovertebral complex, these tumors present a complex diagnostic and surgical problem. A systematic review of literature data on epidemiology, clinical picture, diagnostic methods and dorsal minimally invasive methods of surgical treatment of patients with extramedullary spinal cord tumors of craniovertebral junction was performed.

[A validated new classification for intervertebral disk degeneration]. / Novaya validizirovannaya klassifikatsiya klassov degeneratsii mezhpozvonkovykh diskov.

OBJECTIVE: To develop a new validated classification of intervertebral disc degeneration. MATERIAL AND METHODS: A retrospective observational single-center study included medical records of patients with and without degenerative disease of lumbar intervertebral discs. The interval values of apparent diffusion coefficient (ADC) of intervertebral discs were grouped into degeneration classes. RESULTS: The study included medical records of 100 patients. A quantitative analysis of data showed that mean ADC has a significant correlation with severity of lumbosacral disc degeneration according to classification by Pfirrmann et al. Lumbar intervertebral discs with degeneration grade 3-4 were less homogeneous compared to grade 2-3. Among discs with degeneration grade 4, mean ADC was significantly higher in case of hernia (p=0.01). Conversely, mean ADC was significantly higher in the absence of hernia for discs grade 3 (p=0.04). Combination of all data is presented as original classification of lumbosacral disc degeneration based on mean ADC. CONCLUSION: The developed classification can be recommended for radiologists, neurologists and neurosurgeons.

[Risk factors of unsatisfactory outcomes after percutaneous laser decompression of lumbar intervertebral discs]. / Faktory riska neudovletvoritel'nykh rezul'tatov posle chreskozhnoi lazernoi dekompressii poyasnichnykh mezhpozvonkovykh diskov.

OBJECTIVE: To study the risk factors of unsatisfactory clinical results after percutaneous laser decompression of the lumbar intervertebral disc (PLDD). MATERIAL AND METHODS: A retrospective observational single-center study included medical records of patients who underwent lumbar PLDD for degenerative spine disease. We analyzed clinical and instrumental parameters potentially affecting the results of lumbar PLDD. RESULTS: Clinical study included 82 patients who underwent PLDD for lumbar intervertebral disc degenerative disease. Mean postoperative follow-up period was 30.8±13.3 months. In 22 (26%) patients, unsatisfactory clinical outcomes were observed. According to binary logistic regression model, comorbidities (p=0.03), duration of disease over 12 months (p=0.03), low preoperative quality of life according to ODI score (more than 50%) (p=0.04), high body mass index (over 25 kg/m2) (p=0.02), severe intervertebral disc (p=0.04) and facet joint degeneration (p=0.01) and intervertebral disc height decrease more than 50% (p=0.01) were significantly associated with unsatisfactory clinical outcomes after lumbar PLDD for degenerative spine disease. CONCLUSION: Identification of these risk factors of unsatisfactory clinical outcomes is important stage of preoperative preparation in patients scheduled for lumbar PLDD.

[Risk factors of adverse clinical outcomes in the elderly and senile patients with stroke-associated pneumonia.]

In the domestic and foreign specialized literature, there are no studies devoted to the study of risk factors of mortality in the older age patients with stroke-associated nosocomial pneumonia. The purpose of the study was to study the risk factors of adverse clinical outcomes in elderly and senile patients with stroke-associated nosocomial pneumonia. The study included 247 elderly and senile patients (139 men, 108 women, mean age -- 74,1±6,3 years) who were hospitalized with signs of ischemic or hemorrhagic stroke. According to the binary logistic regression model, the following parameters are statistically significantly associated with adverse clinical outcomes in the studied group of respondents: age over 75 years (p=0.011), degree of disability according to mRS ≥3 (p=0,009), and C-reactive protein levels over 100 mg/l (p=0,023) and urea more than 7 mmol/l (p=0,044). In order to reduce the incidence of adverse clinical outcomes in patients of the older age group with stroke-associated nosocomial pneumonia, it is necessary to verify the above clinical and laboratory parameters at the early stages of hospitalization.

[Effect of renin-angiotensin-aldosterone system inhibitors on functional activity of the spinal cord and nerve roots in patients with degenerative lumbar spine diseases]. / Vliyanie blokatorov renin-angiotenzin-al'dosteronovoi sistemy na funktsional'nuyu aktivnost' spinnogo mozga i ego koreshkov u patsientov s degenerativnymi zabolevaniyami poyasnichno-kresttsovogo otdela pozvonochnika.

High neuroprotective activity of renin-angiotensin-aldosterone system (RAAS) inhibitors in patients with vascular diseases of the brain and spinal cord has been confirmed. OBJECTIVE: To evaluate the effect of renin-angiotensin-aldosterone system inhibitors on functional activity of the spinal cord and nerve roots in patients with degenerative lumbar spine diseases. MATERIAL AND METHODS: A retrospective observational cohort study was performed. We evaluated clinical and radiological parameters (gender, age of patients, type of antihypertensive drug, concomitant diseases, ODI (6) and SF-36 (7) scores of patient quality of life), functional recovery, increase of signal intensity and its area in T2WIs, localization and maximum spinal canal stenosis, as well as maximum spinal cord and nerve root compression. RESULTS: The study included 117 medical records of respondents (88 men and 29 women aged 56.9±13.2 years) who underwent lumbar spine surgery for degenerative diseases. Arterial hypertension was verified in 68 (58.1%) patients, diabetes mellitus in 22 (18.8%) respondents. Age (p=0.002), diabetes mellitus (p=0.007), arterial hypertension (p=0.015) and antihypertensive therapy (p=0.023) were significantly associated with worse clinical and neurological status of patients. Binary logistic regression model demonstrated that only arterial hypertension was significantly associated with low preoperative quality of life (p=0.002). CONCLUSION: Intake of AT II-1 receptor blockers and angiotensin converting enzyme inhibitors for arterial hypertension is a significant predictor of decrease in signal intensity of the spinal cord and its roots according to T2WIs.

[Smoking as a risk factor of advanced heterotopic ossification in patients after lumbar total disk arthroplasty]. / Kurenie kak faktor riska uvelicheniya skorosti formirovaniya ochagov geterotopicheskoi ossifikatsii u patsientov posle vypolneniya total'noi artroplastiki poyasnichnykh mezhpozvonkovykh diskov.

Smoking is an obvious risk factor of adverse events in early and long-term postoperative period after spine surgery including lumbar total disk arthroplasty. Objective. To study the effect of smoking on clinical and radiological outcomes after lumbar total disk arthroplasty. MATERIAL AND METHODS: A single-center retrospective observational cohort study was performed. We have analyzed medical records of patients who underwent single-level lumbar total disk arthroplasty for degenerative disease. RESULTS: The study included 57 medical records of respondents. The examined medical records were divided into two groups - smokers (n=26) and non-smokers (n=31). There were no significant between-group differences in clinical outcomes. Incidence of adverse events was similar too. Kaplan-Meier event-free survival was similar in both groups. There were no significant between-group differences in X-ray data. Development of heterotopic ossification after lumbar total disk arthroplasty was more active in smokers. CONCLUSION: Smoking has no significant effect on clinical and radiological outcomes in patients after single-level after lumbar total disk arthroplasty. On the other hand, smoking significantly increases formation of heterotopic ossification after lumbar total disk arthroplasty.

[The effectiveness of local application of vancomycin powder in the prevention of surgical site infections in spine surgery: a meta-analysis]. / Effektivnost' lokal'nogo primeneniya poroshka vankomitsina v profilaktike infektsii oblasti khirurgicheskogo vmeshatel'stva v spinal'noi khirurgii: metaanaliz.

OBJECTIVE: To perform a meta-analysis of studies examining the effectiveness of the local application of vancomycin powder for the prophylaxis of surgical site infections (SSIs) in spine surgery. MATERIAL AND METHODS: Retrospective cohort studies and prospective randomized clinical trials were searched for in the Pubmed, EMBASE, Cochrane Library and eLibrary databases published from 2008 to December 2018. For the resulting variables, the odds ratio and 95% confidence interval were calculated using random and fixed effects models. Estimation of the degree of heterogeneity is estimated using the coefficient I2. Statistically significant differences were considered differences p<0.05. RESULTS: The meta-analysis included 28 clinical studies that included the results of the local application of vancomycin powder in 17,469 patients after performing various spinal surgical interventions. Two publications had a prospective, randomized, controlled study design. Topical application of vancomycin powder reduces the incidence of SSIs after spine surgery (p<0.0001). The use of vancomycin powder reduces the incidence of SSIs in patients operated on with stabilizing implants (p=0.004). On the other hand, the topical application of vancomycin powder did not affect the prevalence of SSIs in respondents who were operated on without the use of stabilizing implants (p=0.12) or due to deformities of the spine (p=0.06). CONCLUSION: Topical application of vancomycin powder is highly effective in preventing the development of SSIs in patients after spinal surgical interventions.

[Risk factors for adverse clinical events after carotid arteries stenting in elderly and senile patients.]

The safety of the use of carotid arteries stenting (CAS) in elderly and senile patients remains a controversial issue. The reasons for the development of adverse events in this group of patients after CAS surgical procedure are unknown. The purpose of this study was to evaluate the risk factors for the development of adverse clinical events after CAS surgical procedure in elderly patients group. The study included 147 patients (94 men, 53 women, average age -- 72,1±3,5 years) of elderly and senile patients hospitalized to perform CAS for stenosis of the carotid arteries. According to the constructed model of binary logistic regression, the following parameters are statistically significantly associated with the development of complications after CAS: the presence of stroke in the anamnesis (p=0,013), symptomatic stenosis of the carotid arteries (p=0,011) and the degree of disability according to mRS (Modified Rankin Scale) ≥3 (p=0,002). In order to identify the identified risk factors and minimize the incidence of complications in elderly patients who underwent CAS surgery, a detailed preoperative assessment of their somatic status is necessary with an emphasis on the state of the cardiovascular system.

[Prevalence of Vitamin D Deficiency in Elderly Patients Planned for Spine Surgery.]

A decrease in bone mineral density is the most common cause of complications in the long-term period of postoperative observation. The purpose of the study was to study the prevalence of vitamin D deficiency in elderly patients who are planning to perform spine surgical procedures. The study included 63 elderly patients hospitalized in spine surgical clinics in order to perform planned surgical procedures for degenerative diseases of the cervical and lumbar spine (34 women, 29 men, average age 63,6±3,2 years). The construction of a binary logistic regression model showed that the following parameters are reliably associated with a deficiency of the active form of vitamin D in patients who are planning to perform surgical interventions on the spine: male gender, age (over 65 years), body mass index (more than 30 kg/m2) and diabetes. The identification of risk factors associated with the presence of vitamin D deficiency and the study of markers of bone metabolism represent the most important stage in the preoperative preparation of older patients who are planning to perform surgical interventions on the spine.

[Local administration of vancomycin powder in posterior lumbar fusion surgery]. / Éffektivnost' mestnogo primeneniia vankomitsina pri zadnikh dekompressivno-stabiliziruiushchikh operativnykh vmeshatel'stvakh na poiasnichno-kresttsovom otdele pozvonochnika.

AIM: To evaluate an efficacy of local administration of vancomycin powder in posterior lumbar fusion surgery for prevention of local infection. MATERIAL AND METHODS: The study included 214 patients. All patients were divided into 2 groups: I group (control) and II (experimental). Patients of the first group underwent conventional antibiotic prophylaxis of wound infections, in group II traditional antibiotic prophylaxis was supplemented by local administration of vancomycin powder 1 g prior to wound closure. RESULTS: There were 12 cases of wound infection in group I and 5 cases in group II. There were significant differences in overall incidence of wound infection and wound infections caused by S. aureus (p=0.035; p=0.044, respectively). Significant risk factors of local infection were determined in group II: obesity, diabetes mellitus, arterial hypertension, coronary artery disease, length of hospital-stay and previous lumbosacral spinal surgery. Multivariate analysis revealed following risk factors of wound infection: diabetes mellitus, arterial hypertension, coronary artery disease, the number of involved spinal segments and previous lumbosacral spinal surgery. CONCLUSION: Local application of vancomycin powder in posterior lumbar fusion surgery significantly reduces the incidence of wound infection.

[Comparison of the long-term outcomes of total arthroplasty and anterior spinal fusion in the treatment of cervical degenerative disc disease: a metaanalysis]. / Sravnenie otdalennykh rezul'tatov primeneniia total'noi artroplastiki i perednego spondilodeza v lechenii degenerativnogo zabolevaniia sheinykh mezhpozvonkovykh diskov: metaanaliz.

AIM: The study aim was to perform a meta-analysis based on the results of randomized clinical trials comparing long-term outcomes of total intervertebral disc arthroplasty (TA) and anterior cervical spinal fusion (ACSF) in the surgical treatment of cervical degenerative disc disease. MATERIAL AND METHODS: We searched Pubmed, EMBASE, ELibrary, and Cochrane Library databases for randomized clinical trials reported between 2008 and August 2018. The relative risk and 95% confidence interval were calculated for dichotomous variables; for continuous variables, we used the standardized mean difference and their 95% CI with application of a random effects model. RESULTS: The metaanalysis involved 9 randomized controlled clinical trials including the long-term outcomes of surgical treatment in 2,439 patients. A pooled analysis of the data showed that regression of neurological symptoms (p<0.00001), improvement in the quality of life of patients (Neck Disability Index), and lower pain severity (visual analogue scale for upper extremities) were significantly more often observed (p=0.02) in the group of TA patients. In addition, the TA technique was characterized by a statistically significantly lower rate of re-surgery (p<0.0005) and degeneration of the superjacent segment (p<0.0001), with the rate of adverse events being slightly increased (p=0.04). CONCLUSION: Compared to anterior cervical spinal fusion, TA of cervical intervertebral discs is characterized by significantly better clinical efficacy in patients with cervical degenerative disc disease in the long-term postoperative follow-up.

[Comparison of open and minimally invasive techniques in the surgical treatment of intradural extramedullary spinal tumors in elderly and senile patients.]

With an increase in the average life expectancy of the population, some histological types of symptomatic IEMT are more common in elderly and senile patients. Of the 45 patients included in the study, 27 (60%) patients underwent a microneurosurgical resection of the tumor tissue using minimally invasive techniques (minimally invasive group) and 18 (40%) to patients using the classical open method (open group). The duration of operative intervention in both cohorts of respondents is comparable and is 245,4±117,1 min and 261,1±108,6 min for open and minimally invasive groups, respectively (p=0,71). The volume of blood loss in the minimally invasive group of patients (139,6±44,6 ml) was statistically significantly lower than in the open technique group (539,2±127,5 ml) (p<0,01). The total degree of resection of tumor tissue was achieved in 97,4% of patients in the open group and 92,8% in the minimally invasive group (p=0,81). The incidence of recurrence of IEMT in the study cohort of patients was 6,6%. At the same time, in 1 case the relapse of IEMT was verified in an open group of patients and in 2 cases in patients of the minimally invasive group. The average duration of hospitalization of patients of the minimally invasive group was 9,6±2,7 days, and the open group 13,5±3,1 (p<0,01). The comparison of the incidence of adverse events between the two groups of patients did not show significant differences (p=0,61).

[The use of apparent diffusion coefficient in diagnosis of lumbar intervertebral disk degeneration in patients with middle and old age by diffusion-weighted MRI.]

The most common cause of low back pain is the intervertebral disk (IVD) degeneration. Standard modes of MRI (T1 and T2-modes) do not allow quantifying the degree of IVD degeneration. Diffusion-weighted MRI (DW MRI) is able to analyze the state of IVD structures by the diffusion of water molecules. The degree of diffusion can be estimated using the apparent diffusion coefficient (ADC). In this paper, a quantitative assessment of the degree of IVD degeneration was made by ADC calculating. 281 IVD were studied in 57 elderly and senile patients with the definition of body mass index (BMI). ADC values and degree of C.W.Pfirmann degeneration were measured. For each of the five IVDs, reliable differences in mean ADC values were determined. Between age and mean ADC values noted inverse relationship. Between the degree of IVD degeneration, BMI and ADC values, a reliable inverse relationship noted also. Age, BMI values and the degree of IVD degeneration are the most significant factors affecting the ADC value. Thus, the DW MRI technique can be recommended, as a modern non-invasive method for diagnosing the degree of IVD degeneration in elderly and senile patients.

[Molecular biology of brain meningiomas].

Meningiomas are by far the most common tumors arising from the minges. A myriad of aberrant signaling pathways involved with meningioma tumorigenesis, have been discovered. Understanding these disrupted pathways will aid in deciphering the relationship between various genetic changes and their downstream effects on meningioma pathogenesis. An understanding of the genetic and molecular profile of meningioma would provide a valuable first step towards developing more effective treatment for this intracranial tumor. Chromosomes 1, 10, 14, 22, their associated genes, have been linked to meningioma proliferation and progression. It is presumed that through an understanding of these genetic factors, more educated meningioma treatment techniques can be implemented. Future therapies will include combinations of targeted molecular agents including gene therapy, si-RNA mediation, proton therapy, and other approaches as a result of continued progress in the understanding of genetic and biological changes associated with meningiomas.

Complex Analysis of Diffusion Transport and Microstructure of an Intervertebral Disk.

We studied the relationship between diffusion transport and morphological and microstructural organization of extracellular matrix of human intervertebral disk. Specimens of the lumbar intervertebral disks without abnormalities were studied ex vivo by diffusion-weighed magnetic resonance imaging, histological and immunohistochemical methods, and electron microscopy. Distribution of the diffusion coefficient in various compartments of the intervertebral disk was studied. Significant correlations between diffusion coefficient and cell density in the nucleus pulposus, posterior aspects of annulus fibrosus, and endplate at the level of the posterior annulus fibrosus were detected for each disk. In disks with nucleus pulposus diffusion coefficient below 15×10-4 mm2/sec, collagens X and XI were detected apart from aggrecan and collagens I and II. The results supplement the concept on the relationship between the microstructure and cell composition of various compartments of the intervertebral disk and parameters of nutrient transport.