question: When you break a bone in space does it repair like it would on earth or is it altered because of Zero Gravity?
comment: Proper bone is composed of these long, interlocking, concentric tubes called [osteons]( URL_0 ). Osteons are formed by repeatedly tunneling and rebuilding. You have these cells called osteoclasts which are the tunnelers. They form a circle and go in a straight line, eating up matrix. Behind them are osteoblasts. They're the builders. They follow in this tunnel made by the osteoclasts and lay down new matrix. Over months to years, this results in the overlapping, concentric tubular structure you see in that picture above. When you break a bone, these rings are broken and the process is needed to rebuild the bone back to its original structure. It takes months to years to do this. Here's the thing: the osteoblasts only know which way to go based on the forces applied to the bones. In particular, they run perpendicular to applied forces. This is how martial artists can train their hand bones to break strong bricks, because by repeatedly smacking things with their hand in that fashion, over time, the whole bone remodels to absorb that kind of force. Gravity is one of the primary forces acting on you, and it's how your bones know how to build themselves. In space, they just tunnel around willy nilly, laying down very weak and disorganized bones. This is one of the big problems with long space flights.
passages: Bone remodels in response to stress in order to maintain constant strain energy per bone mass throughout. To do this, it grows more dense in areas experiencing high stress, while resorbing density in areas experiencing low stress. On Mars, where gravity is about one-third that of earth, the gravitational forces acting on astronauts' bodies would be much lower, causing bones to decrease in mass and density.
  
  Average bone loss of 1-2% was recorded in astronauts on Mir each month. This is in comparison to 1–1.5% bone loss in the elderly "per year", and 2–3% in postmenopausal women.
  
  Section::::Countermeasures.
   Some people who experience increased bone resorption and decreased bone formation are astronauts. Due to the condition of being in a zero-gravity environment, astronauts do not need to work their musculoskeletal system as hard as when on earth. Ossification decreases due to a lack of stress, while resorption increases, leading to a net decrease in bone density.
  
  Section::::Alcoholism.
   Another scientist is testing a new glue that fixes fractured bone and stabilizes the seal between metal hardware and bones. The researcher found that when the bone was glued back together on Earth, the materials eventually converted to new bone over time. The researcher is now testing the glue in space to see if it accelerates the formation of new bone.
  
  This scientist believes that surgeries on fractured bone could become a lot less complicated if bone glue were used instead of metal plates, screws and rods.
  
  Section::::Research.:Life Sciences.:Research examples.:Analyzing Bacterial Growth.
   Typical examples of the influence of maximum forces and the resulting elastic deformations on bone growth or bone loss are extended flights of astronauts and cosmonauts as well as patient with paraplegia due to an accident. Extended periods in free fall do not lead to loss of bone from the skull, providing support to the idea that its bone is maintained by a genetic not a mechanical influence. (Skull bone often increases in long term space flights, something thought to be related to fluid shifts within the body.) 
   Bone loss has been observed during spaceflight since at least as early as Gemini in the 1960s. Although most early measurements of the amount of bone loss were not reliable, they did show bone loss in Gemini, Soyuz 9, Apollo, Skylab, Salyut 7, Mir, and the International Space Station. William E. Thornton, an astronaut and physician, was one of the biggest proponents of exercise as a way of preventing bone loss.
  
  Section::::Cause.
   Bone metabolism also changes. Normally, bone is laid down in the direction of mechanical stress. However, in a microgravity environment there is very little mechanical stress. This results in a loss of bone tissue approximately 1.5% per month especially from the lower vertebrae, hip and femur. Due to microgravity and the decreased load on the bones, there is a rapid increase in bone loss, from 3% cortical bone loss per decade to about 1% every month the body is exposed to microgravity, for an otherwise healthy adult. The rapid change in bone density is dramatic, making bones frail and resulting in symptoms which resemble those of osteoporosis. On Earth, the bones are constantly being shed and regenerated through a well-balanced system which involves signaling of osteoblasts and osteoclasts. These systems are coupled, so that whenever bone is broken down, newly formed layers take its place—neither should happen without the other, in a healthy adult. In space, however, there is an increase in osteoclast activity due to microgravity. This is a problem, because osteoclasts break down the bones into minerals that are reabsorbed by the body. Osteoblasts are not consecutively active with the osteoclasts, causing the bone to be constantly diminished with no recovery. This increase in osteoclasts activity has been seen particularly in the pelvic region, because this is the region which carries the biggest load with gravity present. A study demonstrated that in healthy mice, osteoclasts appearance increased by 197%, accompanied by a down-regulation of osteoblasts and growth factors that are known to help with the formation of new bone, after only sixteen days of exposure to microgravity. Elevated blood calcium levels from the lost bone result in dangerous calcification of soft tissues and potential kidney stone formation. It is still unknown whether bone recovers completely. Unlike people with osteoporosis, astronauts eventually regain their bone density. After a 3–4 month trip into space, it takes about 2–3 years to regain lost bone density. New techniques are being developed to help astronauts recover faster. Research on diet, exercise and medication may hold the potential to aid the process of growing new bone.
   Spaceflight osteopenia is the bone loss associated with human spaceflight. After a 3–4 month trip into space, it takes about 2–3 years to regain lost bone density. New techniques are being developed to help astronauts recover faster. Research in the following areas holds the potential to aid the process of growing new bone:
  
  BULLET::::- Diet and Exercise changes may reduce osteoporosis.
  
  BULLET::::- Vibration Therapy may stimulate bone growth.
  
  BULLET::::- Medication could trigger the body to produce more of the protein responsible for bone growth and formation.
  
  Section::::Effects of space-travel.:Loss of muscle mass.
   From a medical perspective, long duration space flight also has physiological impacts on astronauts. Accelerated bone decalcification, similar to osteopenia and osteoporosis on Earth, is just one such condition. Study of these effects is useful not only in advancing methods for safe habitation of and travel through space, but also in uncovering ways to more effectively treat the related terrestrial ailments.
   Spaceflight osteopenia
  
  Spaceflight osteopenia refers to the characteristic bone loss that occurs during spaceflight. Astronauts lose an average of more than 1% bone mass per month spent in space. There is concern that during long duration flights, excessive bone loss and the associated increase in serum calcium ion levels will interfere with execution of mission tasks and result in irreversible skeletal damage.
  
  Section::::History.
   In simple cases healing may be evident within 3 months. Gavriil Ilizarov revolutionized the treatment of recalcitrant nonunions demonstrating that the affected area of the bone could be removed, the fresh ends "docked" and the remaining bone lengthened using an external fixator device. The time course of healing after such treatment is longer than normal bone healing. Usually there are signs of union within 3 months, but the treatment may continue for many months beyond that.
  
  Section::::Treatment.:Bone stimulation.
   The same year, the Duchess of Cornwall wrote to British astronaut Tim Peake, thanking him for his help in osteoporosis research during his time in space. The work undertaken was designed to help researchers develop interventions to prevent bone loss and to help future space travellers as well as people living with osteoporosis on Earth. 
   From the time of Hippocrates it has been known that bone has considerable potential for regeneration and repair. Nicholas Senn, a surgeon at Rush Medical College in Chicago, described the utility of antiseptic decalcified bone implants in the treatment of osteomyelitis and certain bone deformities. Pierre Lacroix proposed that there might be a hypothetical substance, osteogenin, that might initiate bone growth.
   Section::::Life and work.:Bone experiments.
  
  Ilizarov's residency was carried out in orthopedic surgery, during which he developed an external fixator system (1951). He discovered that by carefully severing a bone without severing the periosteum around it, one could separate two halves of a bone slightly and fix them in place, and the bone would grow to fill the gap. He also discovered that bone regrows at a fairly uniform rate across people and circumstances.
   Bone fracture, which is a complete or partial break in the bone, is a very common condition that has more than three million US cases per year. Human bones have the ability to regenerate themselves by cycle of bone resorption and bone formation. The cell responsible for bone resorption is osteoclast, while the cell responsible for bone formation is osteoblast. That being said, the human body can regenerate fractured bone. However, if damage to bone is caused by a disease or severe injury, it becomes difficult for the body to repair itself. When the human body is unable to regenerate the lost bone tissue, surgeons come in and replace the missing bone using autografts, allografts, and synthetic grafts (artificial bone). When compare artificial bone to autograft and allograft, it is less invasive and more biocompatible since it avoids the risk of unknown viral infections.
   In the 1950s, Gavriil Ilizarov of Kurgan, Soviet Union, devised and developed a new method for treating fractures, deformities and other bone defects. A metal frame that encircles the limb is attached to the underlying bone by crossing (X) pins inserted through the bone and limb. The external rings are linked to each other by threaded rods and hinges that allow to move the position of the bone fragments without opening the fracture site, then the fragments can be fixed in rigid position until complete healing.
  
  Section::::Types.
  
  BULLET::::- Ilizarov apparatus
  
  BULLET::::- Taylor Spatial Frame
  
  Smart Correction
  
  Section::::See also.
   If x-rays show that the capitate fracture fragments are out of alignment, surgery is indicated. A surgeon can use small compression screws or K-wires to unite the two pieces of bone. The headless compression screw has advantage over the K-wire as it provides compression across the fracture site and allows early motion. It may be the case that the ligament between the сapitate and the scaphoid bone is also injured; if so, this would be repaired at the same time.
   Facial implants that are left immobilised and that create pressure against bone can cause bone resorption. For example, chin implants that are immobilised create pressure on the anterior mandible which can cause an increase in bone resorption. Facial implants that are placed in a supraperiosteal plane centrally and subperiosteal plane laterally minimise bone resorption. The supraperiosteal plane placement of the implant minimises the degree of contact to the bone as the implant is immobilised and the subperiosteal plane has lateral pockets that fixate the implant. Chin implants can also be fixated and equally remove pressure from bone through the use of screw fixation.
   Once diagnosed and located, surgery is the most common treatment for a malunion. The surgery consists of the surgeon re-breaking the bone and realigning it to the anatomically correct position. There are different types and levels of severity for malunions which helps determine the treatment. Most often, either screws, plates or pins are used secure the new alignment. In some cases, the bone may be trimmed to allow full orientation at the fractured spot. It is also possible that a bone graft could be used to help with healing.
   For example, scientists are using microgravity's unique ability to accelerate bone deterioration to study rodent bone loss in space. The experiment involves studying how NELL-1, a molecule in humans that has the ability to grow new bone, works as a treatment for preventing bone loss in mice in space. The findings could lead to the development of treatments in bone restoration, bone loss prevention and bone grafting.
  
  Section::::Research.:Remote Sensing.
   Implants utilizing a plateau-root form design (or screw-root form implants with a wide enough gap between the pitch of the screws) undergo a different mode of peri-implant ossification. Unlike the aforementioned screw-root form implants, plateau-root form implants exhibit de novo bone formation on the implant surface. The type of bone healing exhibited by plateau-root form implants is known as intramembranous-like healing.
   The basis of osteogenic loading stems from Wolff's law, which shows that the force or loading on bone through its axis, can stimulate the bone's natural function of increasing in density. Further study has shown that greater loads on bone can stimulate a greater effect of the body to respond and increase the density of bone, and can show immediate effects in the body via blood testing showing bone turnover markers This high level of loading on bone would typically be seen in high-impact activity, which is not practical for therapy given the risk of injury potential.
   Section::::Reception.
   Section::::Types.:Acquired.
  
  Post-traumatic cases are most likely to develop following surgery for a forearm fracture, this is more common with high-energy injuries where the bones are broken into many pieces (comminuted). It can also develop following soft tissue injury to the forearm where there is haematoma formation.
  
  Section::::Treatment.
  
  It is sometimes possible to correct the problem with surgery, though this has high failure rates for treatment of post-traumatic radioulnar synostosis. Indication for the surgical treatment of congenital radioulnar synostosis include severe disability due to bilateral disorder or hyperpronation ≥90 
   In healthy adults, bone is undergoing constant repair and renewal. New bone is deposited by osteoblast cells and resorbed or destroyed by osteoclast cells. This addition and subtraction of bone usually yields no net change in the overall mass of the skeleton, but the turnover process can be significantly affected by pH.
  
  Section::::Amino Acid Metabolism.:Bone Mineral Density.
   BULLET::::- Bisphosphonates as a Countermeasure to Space Flight Induced Bone Loss (Bisphosphonates)
  
  BULLET::::- Commercial Biomedical Testing Module: Effects of Osteoprotegerin on Bone Maintenance in Microgravity (CBTM)
  
  BULLET::::- Commercial Biomedical Test Module - 2 (CBTM-2)
  
  BULLET::::- Foot Reaction Forces During Space Flight (Foot)
  
  BULLET::::- Effects of Altered Gravity on Spinal Cord Excitability (H-Reflex)
  
  BULLET::::- Hand Posture Analyzer (HPA)
  
  BULLET::::- Renal Stone Risk During Spaceflight: Assessment and Countermeasure Validation (Renal_Stone)
  
  BULLET::::- Spinal Elongation and its Effects on Seated Height in a Microgravity Environment (Spinal_Elongation)
  
  BULLET::::- Subregional Assessment of Bone Loss in the Axial Skeleton in Long-term Space Flight (Subregional_Bone)
  