Tag: posture

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The human craniospinal venous system and its influence on postural intracranial pressure: a review

J Neurosurg 141:1484–1493, 2024

The cerebral and spinal venous systems have similar functions but unique anatomical and physiological properties. CSF occupies space in the cranial and spinal vaults, is continuously produced, and has many roles, including maintaining a favorable environment for CNS structures. The influence of the cerebrospinal venous system on CSF dynamics has been theorized since the 1940s. Newer studies suggest venous outflow pattern alterations in response to changes in body position. However, the relationship of postural cerebrospinal venous outflow shifts with and their influence on CSF homeostasis is not well understood.

METHODS The authors searched the published literature related to the anatomy and function of vertebral venous plexus (VVP), CSF, and positional cerebral venous flow characteristics. A comprehensive collection of literature was compiled and reviewed, and the relationship between cerebrospinal and venous system changes and alterations in body positions, with an emphasis on the craniocervical system, is discussed.

RESULTS The VVP is a network of valveless veins extending from the sacrum to the cranium that are interconnected with the cranial dural sinuses. The internal VVP occupies space within the extradural spinal canal and functions to return spinal venous blood to the heart, but it has additional properties, including the capability of bidirectional venous flow, an intraspinal dilatory capacity, and a role in cerebral venous outflow. When one rises to the upright position, CSF shifts toward the spinal canal and force vectors change, leading to reduced intracranial CSF pressure; simultaneously, cerebral venous outflow shifts from the jugular vein to the VVP outflow pathway. The venous outflow shift mechanism and its purpose are poorly understood. The authors review the known physiology of the system, identify gaps in knowledge to direct future research, and propose an interpretation of these data, concluding that position-dependent CSF and cerebrospinal venous shifts are part of a complementary positional craniospinal pressure regulation system that must be kept in balance for optimal CNS function.

CONCLUSIONS Current knowledge of the cerebrospinal venous anatomy, dynamic flow characteristics in response to gravity, and the venous system’s influence on CSF suggests that the VVP plays a role in influencing CSF pressure, and the authors hypothesize that it plays a role in supporting intracranial pressure in the upright body posture. Further research is needed to better characterize the functional relationship of the VVP to CSF dynamics as well as identify potentially related disease states.

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Spine surgery is kyphosing to spine surgeon

Acta Neurochirurgica (2020) 162:967–971

Spine surgery is a demanding surgical specialty which requires surgeons to operate for hours on end, often compromising good posture. Sustained poor posture in the operating room (OR) can be the source of many adverse health effects on spine surgeons. This study will analyze posture of a spine surgeon in different types of spine surgery cases.

Methods Posture of a surgeon was measured using the UPRIGHT Posture Training Device. The device was worn by the surgeon in the OR through a wide variety of spine surgery cases.

Results The percent time spent slouched while performing cervical, adult deformity, and lumbar spine surgeries is 39.9, 58.9, and 38.6, respectively. For all surgeries recorded, the percent time slouched is 41.6. The average procedure time was 145.3 min, with adult deformity cases on average being the longest (245.6 min) followed by cervical (152.9 min) and then lumbar (122.5 min).

Conclusion Poor posture while operating is very likely to occur for many spine surgeons regardless of case type. This poor posture is maintained for long periods of time given the average spine surgery procedure recorded in the study was roughly 2.5 h long. Spine surgeons should be aware of the tendency for poor posture while operating, and they should try using postureimproving techniques to maintain good spine health.

 

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Comparison of anti-siphon devices—how do they affect CSF dynamics in supine and upright posture?

Acta Neurochir (2017) 159:1389–1397

Three different types of anti-siphon devices (ASDs) have been developed to counteract siphoning induced overdrainage in upright posture. However, it is not known how the different ASDs affect CSF dynamics under the complex pressure environment seen in clinic due to postural changes. We investigated which ASDs can avoid overdrainage in upright posture best without leading to CSF accumulation.

Methods Three shunts each of the types Codman Hakim with SiphonGuard (flow-regulated), Miethke miniNAV with proSA (gravitational), and Medtronic Delta (membrane controlled) were tested. The shunts were compared on a novel in vitro setup that actively emulates the physiology of a shunted patient. This testing method allows determining the CSF drainage rates, resulting CSF volume, and intracranial pressure in the supine, sitting, and standing posture.

Results The flow-regulated ASDs avoided increased drainage by closing their primary flow path when drainage exceeded 1.39 ± 0.42 mL/min. However, with intraperitoneal pressure increased in standing posture, we observed reopening of the ASD in 3 out of 18 experiment repetitions. The adjustable gravitational ASDs allow independent opening pressures in horizontal and vertical orientation, but they did not provide constant drainage in upright posture (0.37 ± 0.03 mL/min and 0.26 ± 0.03 mL/min in sitting and standing posture, respectively). Consequently, adaptation to the individual patient is critical. The membrane-controlled ASDs stopped drainage in upright posture. This eliminates the risk of overdrainage, but leads to CSF accumulation up to the volume observed without shunting when the patient is upright.

Conclusions While all tested ASDs reduced overdrainage, their actual performance will depend on a patient’s specific needs because of the large variation in the way the ASDs influence CSF dynamics: while the flow-regulated shunts provide continuous drainage in upright posture, the gravitational ASDs allow and require additional adaptation, and the membrane-controlled ASDs show robust siphon prevention by a total stop of drainage.

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Total Sagittal Spinal Alignment in Patients With Lumbar Canal Stenosis Accompanied by Intermittent Claudication

Spine 2010;35:E344–E346

Study Design. Cross-sectional study of total sagittal spinal alignment in lumbar spinal canal stenosis (LCS) patients with and without intermittent claudication.

Objective. To evaluate total sagittal spinal alignment in LCS. Summary of Background Data. The sagittal spinal alignment is an important factor in the management of lumbar degenerative diseases and lower back pain. Patients with LCS accompanied by intermittent claudication adopt a forward-bending posture during walking. However, few studies have quantitatively assessed the abnormal posture in LCS in relation to clinical symptoms.

Methods. This study analyzed 93 patients with LCS. They were divided into two groups according to the presence of neurogenic intermittent claudication; patients of the Claudicant group had intermittent claudication of the cauda equina (n  53; mean age, 66.7) and those of the Nerve root group had no claudication (n  40; mean age, 67.0). The following parameters were measured on the lateral whole-spine standing radiographs: the distance between the C7 plumb line and the posterior superior corner on the superior margin of S1 (sagittal vertical axis), the angle between the superior margin of the first lumbar vertebra and the first sacral vertebra (L1S1), lumbar lordotic angle, pelvic tilting angle (PA), and pelvic morphologic angle (PRS1).

Results. The sagittal vertical axis of the Claudicant group (57.6  37.5 mm) was significantly larger than that of the Nerve root group (40.3  42.3 mm) and was larger in both groups compared with the standard values. Lumbar lordotic angle was smaller (18.8°  13.2°) and pelvic tilting angle was larger (27.2°  8.3°) in patients with the Claudicant group than those with the Nerve root group (22.4°  14.0° and 22.7°  7.2°, respectively).

Conclusion. Patients of the Claudicant group exhibited forward bending of the trunk and pelvis backtilt, compared with those of the Nerve root group.


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