Spine Surgery in Space

Microgravity-Induced Spinal Changes

Across the 32 biomechanical papers, prolonged weightlessness was consistently associated with spinal elongation (astronauts gain ∼3–5 cm in height), intervertebral disc swelling, paraspinal muscle atrophy, and reduced bone density in vertebrae.^10–12 A large retrospective cohort further documented a 4.3-fold increase in herniated nucleus pulposus among astronauts within the first postflight months compared with terrestrial controls.¹³ Cephalic fluid redistribution, documented by ultrasound and MRI, straightens lumbar lordosis and adds to disc swelling, reinforcing these structural changes.^10,14

Therapeutic Considerations

There were 23 papers which addressed treatment and recovery. Collectively, they show that microgravity impairs wound and bone healing.^15–17 Multimodal countermeasures, such as peri-mission bisphosphonate therapy,¹⁸ targeted nutrition, resistance exercise, and telemetric monitoring, are required to support postoperative recovery. There is a broad consensus that early supervised rehabilitation and continuous physiological surveillance are essential for restoring spinal stability and function.^15,19 Several studies recommend cardiovascular support, including graded re-ambulation, lower-body negative pressure, compression garments, and judicious fluid loading, to counter postflight orthostatic intolerance during early mobilization.^4,19

Surgical Feasibility and Technology

A total of 22 publications evaluated surgical feasibility. The literature reflects that no actual spine surgeries have been done in space to date, but there is extensive discussion of potential techniques. All cited environmental hurdles include sterility maintenance, free-floating fluids, and restricted workspace.^20–22 Surgical simulation studies, including animal models on shuttle missions, demonstrate that minor procedures are technically feasible in microgravity (Drudi et al.).^22,23 Most authors identified image-guided robotics, augmented-reality navigation, and telemedicine as critical enablers for future space surgeries.^21,24,25 The spaceMIRA experiment in 2024 provided the first on-orbit demonstration of Earth-controlled robotic surgical tasks, validating the mechanical feasibility of tele-operation in microgravity.²⁶ Five studies further noted that total intravenous anesthesia and restrained airway management are preferred options to mitigate equipment float and altered pharmacokinetics in weightlessness.²⁷

Together, the literature reveals predictable microgravity-induced spine degeneration, highlights targeted countermeasures for postoperative recovery, and suggests that emerging imaging and robotic systems offer a plausible pathway toward safe spine surgery during future long-duration missions.

Impact of Microgravity on Spine Health

The impact of microgravity on the musculoskeletal system, specifically the spine, is essential for mitigating the adverse effects of space travel on astronaut health and operational efficiency.²⁸ In microgravity, the absence of Earth’s gravitational pull results in diminished axial loading on the spinal intervertebral discs, allowing these discs to expand and contributing to increased spinal length.^29–31 MRI studies have shown that astronauts can experience spinal elongation of up to 5 cm following prolonged spaceflights.⁶ This elongation, which leads to a straightening of the natural spinal curvature, is thought to be driven by changes in fluid distribution within the discs, tissue hydration shifts, and microgravity-induced adaptations in spinal biomechanics.³² Furthermore, microgravity affects the structure and function of intervertebral discs. The reduction in gravitational forces facilitates disc hydration shifts and swelling, resulting in alterations in disc height and mechanical properties.¹⁰ Variations in disc metabolism and nutrient exchange have also been speculated to exacerbate disc degeneration, potentially increasing susceptibility to herniation and degenerative disc disease.^33,34

CT studies have demonstrated persistent decreases in bone mineral density, paraspinal muscle cross-sectional area, and muscle density in astronauts, even after a year of readaptation to Earth’s gravity.¹¹ This decline was corroborated by Bailey et al., who found reduced flexion-extension range of motion and decreased muscle mass following long-duration spaceflights.¹²

The lack of normal mechanical loading in microgravity also leads to muscle disuse and atrophy, particularly affecting the paraspinal muscles essential for spinal stabilization and posture maintenance, thus increasing the risk of musculoskeletal injuries.^6,35 Concurrently, microgravity disrupts the balance between bone formation and resorption, leading to accelerated bone loss, especially in weight-bearing bones such as the vertebrae. This can result in osteopenia and osteoporosis, conditions characterized by weakened bones and an increased fracture risk. Notably, astronauts often experience significant losses in bone mass while in space, particularly in the hip and spine regions.³⁶ Understanding these microgravity-induced spinal changes is crucial for surgical planning. Surgeons must anticipate that astronauts might present with degenerative changes or injury postflight, and that bone fragility or muscle atrophy could impact surgical stability and healing.

Challenges in Spine Surgery After Extended Time in Space

Performing spine surgery on individuals who have spent extended periods in space presents unique challenges that require innovative solutions and adaptations to current guidelines to ensure safe and effective procedures. These challenges stem from logistical constraints, altered biomechanical behavior, and resource limitations inherent to space missions.^6,37

The rigorous planning and stringent scheduling of space missions offer limited windows for medical interventions, necessitating the alignment of surgical procedures with mission timelines, crew availability, and operational constraints.^27,38,39 The remote nature of space missions, coupled with potential delays in communication with mission control, exacerbates these logistical difficulties, necessitating a higher degree of autonomous decision-making and the possible reliance on telemedicine support.⁴⁰

Prolonged exposure to microgravity significantly affects the biomechanical behavior of the spine, resulting in reduced gravitational loading, changes in tissue properties, and shifts in mechanical responses.^31,41,42 Additionally, deteriorated bone quality increases the risk of complications such as screw loosening or failure of spinal constructs, complicating surgical care. Surgeons may need to adapt their plans to accommodate altered tissue and intraoperative dynamics.⁴³ To address these complexities, precise instrumentation, advanced imaging techniques, and vigilant monitoring throughout procedures will be crucial in navigating the challenges posed by the absence of gravitational force.^40,44,45

Anesthetic management in microgravity presents its own set of challenges. Traditional inhalational anesthesia is problematic in a closed spacecraft environment, as anesthetic gases can diffuse unpredictably and are difficult to scavenge in weightlessness.²² A more promising approach is total intravenous anesthesia,²² which avoids gas leakage issues; however, microgravity-induced fluid shifts and reduced blood volume can alter pharmacokinetics and drug efficacy. Securing the airway for general anesthesia requires restraining both the patient and the equipment to prevent movement and ensure stability. Endotracheal intubation must be performed with the patient and operator securely anchored to prevent the tube from dislodging. Special endotracheal tube holders are necessary to keep the tube in place during surgery. Regional anesthesia (nerve blocks) can mitigate some risks by avoiding intubation and minimizing cardiovascular depression; however, performing these blocks in microgravity is challenging due to the lack of gravitational reference points and the floating of both the patient and the ultrasound needle, which can complicate needle guidance.⁴⁶

Additionally, microgravity affects intraoperative physiology. Due to the high surface tension of blood, cohesive fluid domes or streams adhere to the wound surface rather than dispersing as free-floating droplets.⁴⁷ Although these are typically manageable with sponges and suction, causing minimal obstruction in small surgical fields, larger or arterial bleeds produce high-velocity streams that pose a greater challenge in microgravity and require immediate control.⁴⁷ Altered fluid dynamics in microgravity also compromise drainage systems, as standard drains may clog or fail due to surface tension and capillary action resisting fluid flow, necessitating redesigned drainage systems such as shorter, larger-bore tubing or self-contained drainage units .⁴⁷ A sealed surgical enclosure has been proposed to further enhance visualization and prevent cabin contamination .⁴⁷ Hemodynamic regulation is also more precarious as astronauts often have blunted baroreceptor responses and diminished cardiac output after adaptation to microgravity,⁴⁸ raising concern for hypotension when surgical anesthesia is induced. These anesthetic and physiological challenges underscore that developing spine surgery capability for space is not solely about the surgical technique, but also about ensuring the patient’s homeostasis can be maintained in a radically altered environment.

The constraints imposed by spacecraft, including limited spatial allowance, weight restrictions, and resource availability, pose substantial logistical challenges for conducting spine surgery.⁴³ Surgeons must operate within restricted workspaces with minimal access to equipment and supplies, necessitating continued innovation of compact, lightweight surgical instruments and the optimization of surgical workflows.^49,50 Current innovations include the development of an instrument called the spaceMIRA, a microwave-sized device that can mimic human movement using two different robotic arms. In February of 2024, the spaceMIRA successfully remotely simulated several surgical techniques on the International Space Station, representing an advancement in the current standard of surgery in space with implications for future space travel.²⁶ Further development and implementation of streamlined, space-efficient surgical tools and methods will likely be essential to overcoming the spatial and resource constraints in extraterrestrial environments; however, these advancements may be limited in scope due to costs and the limited demand for innovation.⁵¹

Therapeutic Considerations for Spine Surgery

To protect astronauts’ bone health during and after space missions, a multidisciplinary approach involving space medicine, biomechanics, and surgical innovation is essential.^20,52,53 Ensuring adequate intake of nutrients such as calcium, vitamin D, and proteins is crucial to counteract the bone demineralization and muscle atrophy induced by microgravity.^20,54 Nutritional strategies should focus on mitigating these effects. Regular exercise regimens, including resistance training, are also essential for stimulating bone growth and muscle strength, thereby reducing the risks of osteoporosis and muscle atrophy prevalent under microgravity conditions. A study by Leblanc et al. supports the peri-mission administration of alendronate and bisphosphonates to attenuate bone loss in the spine, hip, and pelvis, with significant implications for both preventative and surgical care.¹⁸ Additionally, emerging pharmacological agents, such as receptor activator of nuclear factor kappa-Β ligand (RANKL) antibodies and proteasome inhibitors, have shown promise in reducing bone resorption and promoting bone formation in microgravity conditions.⁵⁵ However, alterations in tissue healing processes due to microgravity-induced changes in cellular behavior^17,56 and reduced mechanical loading may impede surgical site healing.^15,16,57 Minimally invasive surgical approaches, including endoscopic and laparoscopic techniques, are preferred for their reduced tissue trauma and enhanced visualization capabilities.^45,58 The integration of these methods, alongside advanced robotic technologies, offers effective solutions that improve postoperative outcomes and recovery times, which are critical for astronauts fulfilling mission objectives.^40,59,60

Beyond musculoskeletal rehabilitation, clinicians must manage the broader physiological changes associated with spaceflight during the postoperative period. Fluid shifts due to microgravity, such as cephalic fluid redistribution, can contribute to facial edema and potentially increase intracranial pressure.^14,61,62 When returning to Earth’s gravity, this can reverse and lead to orthostatic intolerance. There is also evidence that microgravity may alter the endothelial glycocalyx, the protective carbohydrate layer on blood vessels that regulates permeability.⁶³ Disruption of the glycocalyx could exacerbate fluid leakage into tissues and impair vascular function during recovery. As a result, astronauts might experience more tissue edema or difficulties in volume regulation after surgery.

Moreover, long-duration missions lead to cardiovascular deconditioning, characterized by reduced plasma volume, cardiac muscle atrophy, and diminished baroreflexes.⁴⁸ In the immediate postflight period, astronauts often suffer orthostatic hypotension.^4,48 A postoperative patient with such issues is at risk for fainting or inadequate perfusion of the spinal cord when ambulating. Postoperative care protocols should therefore include cardiovascular support, such as gradual reambulation under monitoring, fluid loading, compression garments, or lower-body negative pressure to counteract orthostatic effects.^4,48 Close monitoring of hemodynamics, in addition to neurological status, is critical.

Effective postoperative care is vital in managing microgravity-induced alterations in the spine and musculoskeletal system. Rehabilitation programs that focus on muscle strengthening, range-of-motion exercises, and proprioceptive training are essential for promoting spinal stability and functional recovery, while mitigating the risk of musculoskeletal deconditioning in astronauts.⁶⁴ Continuous monitoring of postoperative outcomes is crucial, as the deconditioned spine and altered physiology may increase the risk of chronic pain, delayed wound healing, and impaired neurological function.^15,19

Interventions to enhance tissue repair may include optimizing nutritional intake to ensure adequate protein and vitamin levels, coupled with pharmacological agents that promote collagen synthesis and wound healing.⁶⁵ Similarly, fluid and blood pressure management, and possibly pharmacological support to protect vascular integrity, are warranted. Employing robust telemedicine support is helpful for effective postoperative recovery management and promptly addressing complications that may arise following space missions.⁶⁶

Adaptations and Innovations in Spine Surgery for Astronauts in Space

Addressing the challenges of maintaining spinal health in space necessitates the integration of advanced imaging technologies and surgical techniques, including remote surgery, augmented reality, and robotic systems. These innovations are essential to ensure the safety and efficacy of surgical procedures performed on astronauts who may require intervention before returning to Earth. One promising strategy involves using image-guided navigation systems that combine real-time imaging data with precise location tracking to enhance surgical accuracy while minimizing radiation exposure. This is particularly advantageous considering that astronauts are already exposed to elevated baseline levels of radiation, which can exacerbate the residual effects of prolonged space exposure.⁶⁷

MRI offers high-quality three-dimensional visualization of anatomical structures without the use of ionizing radiation. Despite challenges such as strong static magnetic fields and confined spaces, MRI-compatible robotic systems are being developed to assist with intraoperative MRI. This real-time guidance is crucial for patients whose musculoskeletal systems have been affected by long-duration spaceflight.⁶⁸ Additionally, intraoperative ultrasound is valuable due to its cost-effectiveness, efficiency, and real-time visualization capabilities. Intraoperative ultrasound is particularly useful for visualizing soft tissues and pathologies during surgery, especially in scenarios involving intradural lesions that microgravity-induced changes may exacerbate.^69,70

Augmented reality could aid visualization and navigation during spine surgery by allowing surgeons to view three-dimensional anatomical structures directly while observing the surgical field. This technology improves accuracy and reduces operating time, making it particularly beneficial for addressing anatomical changes resulting from prolonged space habitation.⁷¹ This adaptation is particularly relevant for the unique challenges astronauts face after extended missions.⁷² Robotic-assisted surgery provides enhanced precision and control, which is crucial for patients who have experienced the musculoskeletal impacts of microgravity.⁷³ Robotic systems improve surgical accuracy and dexterity, reduce surgeon fatigue, and can incorporate advanced imaging technologies such as intraoperative CT or fluoroscopy for real-time navigation.^21,24,25 Platforms like the da Vinci Surgical System and the Mazor Robotics Renaissance System, which have demonstrated success on Earth, hold promise for adaptation to the unique challenges caused by spaceflight.⁴⁰

Future Directions and Recommendations for Spine Health

Interdisciplinary cooperation among neurosurgeons, engineers, and space scientists is crucial for refining surgical techniques and technologies tailored to the needs of astronauts following long-duration space missions. Ground-based analogs, such as bed rest studies or innovative analogs like hyper-buoyancy flotation, can provide insights into spinal unloading and reloading mechanisms.⁷⁴ Continued investigation in this focus informs the development and implementation of effective countermeasures to spinal muscle atrophy and spinal instability during space missions. Evaluating the efficacy of regular axial loading exercises is crucial for maintaining spinal health.⁵³

Technological innovations, including intraoperative image guidance, robotics, and augmented reality, have significantly enhanced spine surgery on Earth but require rigorous validation for application in space. Investment in advanced neurosurgical technologies, such as machine learning, augmented reality, and virtual reality, is pivotal for enhancing diagnostic accuracy, reducing complications, and improving surgical outcomes. Training programs using these technologies can equip surgeons to address the unique challenges of spine surgery on astronauts, thereby enhancing surgical skills and minimizing the risk of complications. Wearable sensors have been proposed as a solution to monitor spinal and muscle activity under microgravity conditions, providing longitudinal data on the efficacy and reliability of interventions in space.^75,76 Despite extensive advancement of technology, a more intentional evaluation of its use in a microgravity environment is required to mitigate potential risks.⁵⁰ Additionally, policies and infrastructure must support the provision of surgical care during and after space missions, ensuring the availability of trained medical personnel, necessary surgical equipment, and telemedicine capabilities for remote guidance and support.²² Addressing these domains will enable policymakers, space agencies, and healthcare providers to advance spine surgery capabilities for astronauts more effectively, ultimately enhancing their health and safety during and after space missions.²⁰

Ethical and Legal Implications of Space Healthcare

Legal frameworks and regulatory standards are pivotal in ensuring patient safety, maintaining medical ethics, and addressing liability issues in space medicine. International space law, including key treaties like the Outer Space Treaty and the Agreement on the Rescue of Astronauts, delineates the principles that govern space activities, emphasizing cooperation, mutual assistance, and shared responsibility for astronaut health and safety.⁷⁷ However, as surgical interventions in space are contemplated, these regulations will need to evolve to address consent, autonomy, and liability in the off-Earth context.

National space agencies, including NASA, the European Space Agency, and Roscosmos, have formulated specific regulations that govern medical procedures in space.⁷⁸ These regulations encompass preflight assessments, in-flight care, and postflight monitoring, including medical standards that exist for low Earth orbit spaceflight. There also exists a medical checklist, written in both English and Russian, on the International Space Station for potential standard medical procedures, as well as a standard of care for the process of stabilizing and transporting a crewmember in case of injury or medical emergency.⁷⁹ As of December 2016, NASA’s Office of the Chief Health and Medical Officer integrated a NASA procedural requirement (NPR 8900.1B) based on the framework of medical ethics developed by the Institute of Medicine’s Aerospace Medicine and Medicine in Extreme Environments Committee in an effort to further expand guidelines governing medical ethics and procedures in space.⁷⁸ While the European medical ethics guidelines have not been publicly announced, agencies are striving to collaborate closely with regulatory authorities and medical experts to ensure adherence to safety and ethical standards during spaceflight.⁸⁰

Spinal Surgery in Space

While spine surgery in space may be possible in the near future, there remain considerable challenges at present that have been presented by the existing literature. Lajczak et al. highlight several limitations of conventional manual surgical techniques in their review, finding major drawbacks in accuracy, size, and invasiveness of procedures, exposure to radiation, and surgical efficiency.²¹ These challenges are further amplified in the setting of microgravity during space missions and may limit the application of conventional means to emergency or extremely narrow circumstances.^20,81 Robotic surgery could reduce these limitations and may be an effective solution for performing spine surgery in space.^21,25

A unique challenge accompanied by using robotics surgery in space derives from communication delays between Earth and the space crew. Although the speed at which information travels may be negligible in low Earth orbit, missions that span beyond this region are subject to latency or communication delays that range from minutes to hours, compromising the performance of telesurgery and telemonitoring.⁴⁰ The limitations of current technology suggest that long-duration space missions may require flight surgeons to accompany the crew to provide definitive care for injuries that exceed the training and technical capabilities of the crew medical officer, a crewmember without a medical background who has received 60 h of medical training.^40,82 Others have proposed artificially intelligent autonomous systems capable of performing a selection of preset surgeries to assist the crew and crew medical officer.^51,60,83 Although the literature on the topic of robotics surgery for space applications has emphasized a completely autonomous system with cognitive capabilities for active decision-making,^51,60,83 a fully autonomous and cognitive system has not received FDA (Food and Drug Administration) clearance nor, to our knowledge, has been developed.⁸⁴ Such an ambitious feat is beyond what is capable with today’s technology; however, augmenting the surgical methods to accompany human decision-making through the use of preplanned robotics movements may fill the technological gap until these advanced surgical systems are developed. While patient-specific prerecorded surgeries may be feasible, it would require a perfect overlap of the surgical field in the prerecorded robotics surgery and the surgical field erected during the mission. Moreover, it is possible that with high-precision scans of the affected crewmember and an even more robust virtual simulation system, surgeons may be able to perform surgeries on a virtual copy of the patient before sending the virtual recording to the flight crew, who then prepare the surgical robot and the patient to replay the surgery from space as if it was occurring in real-time. This, of course, would require an extensive and highly delicate calibration cycle to minimize the risk of invading unintended tissue or bone during spine surgery.

The spaceMIRA device represents an advancement in the current status of technology and surgical abilities in space.²⁶ While there were limitations stemming from the signal latency, the spaceMIRA was able to complete several basic surgical tasks. Regarding the future of spinal surgery, a device similar to the spaceMIRA with the additional ability to perform the surgery in augmented reality portrays potential future devices that could be used to perform spinal surgery in space. The spaceMIRA, in this example, would be classified as a remote-controlled robot, in contrast with an on-site-controlled robot that would have to be controlled on the International Space Station.⁸⁵ Using remote-controlled robots in surgery provides an opportunity for a myriad of different surgeons to perform a multitude of surgeries, including spinal surgeries, based on the needs of the patient in space. Furthermore, robots are currently in use during spine surgery and relocating a similar robotic device to the International Space Station could provide further opportunities and new directions for spinal surgery in space.

Effective spine surgery during and after space travel requires a comprehensive approach to address the physiological changes induced by microgravity. Prolonged exposure significantly affects bone density, muscle mass, and disc health, necessitating targeted interventions upon return to Earth. A holistic strategy that includes rehabilitation, pharmacological support, and surgical solutions is essential for maintaining spinal integrity. Notably, this review identifies novel methodologies, such as teleoperated robotic surgical systems, advanced imaging guidance, and augmented reality navigation, as promising avenues to enable safe spinal surgery beyond Earth. These technologies, alongside rigorous astronaut training and telemedical support, represent new frontiers in surgery and future directions of study that can mitigate the limitations imposed by microgravity. Continued research and innovation are crucial to overcoming these challenges and ensuring the safety and effectiveness of spine surgeries for astronauts. By developing space-adapted surgical techniques and supportive care protocols, we can protect the long-term health of astronauts. As we venture further into space, our commitment to astronauts’ well-being will empower future missions, ensuring that those who lead humanity into the cosmos return intact and thriving.