(1) Systemic factors
① Age: healing speed is closely related to age; the younger the age, the faster the fracture heals, and the older the age, the slower the fracture heals.
(2) Health status: Strong body and vigorous qi and blood will result in faster fracture healing; conversely, weak body or patients with chronic wasting diseases, such as diabetes, tuberculosis, severe malnutrition, calcium metabolism disorders, osteochondrosis, and serious complications after fracture will have delayed fracture healing.
(iii) Hormonal effects: Studies have proven that cortisone can affect the rate of fracture healing. Certain experimental studies have proven that growth hormone, thyroxine, calcitonin, insulin, vitamin A, vitamin D, and anabolic hormones can promote fracture healing, but there have not been a large number of case reports in clinical practice.
④ Exercise and local stress state of the fracture: The slow healing of fractures in limbs with nerve damage is thought to be related to reduced stress stimulation at the fracture end. Functional exercise accelerates fracture healing, which is thought to be a result of stress perpendicular to the interfracture stimulating the osteogenic process.
(2) Local factors
(1) Degree of fracture injury: generally fractures with large bone defects, or severe soft tissue injury, large hematoma at the fracture end, and severe periosteal injury result in slower fracture healing. If the soft tissue injury is light and the hematoma is small, or if the fracture displacement is small and the periosteal injury is light, the fracture will heal faster.
②The size of the contact area of the fracture: generally speaking, a large contact area of the fracture is easy to heal, while a small contact area of the fracture is more difficult to heal. In this case, the fractures with good alignment heal faster after revision, while those with poor alignment heal slower. Oblique and spiral fractures heal faster than transverse fractures.
(iii) Tightness of fracture contact: The tightness of fracture contact is also related to the healing speed. The tighter the contact, the easier it is to heal, e.g., an embedded fracture is easier to heal than one with a gap or significant separation at the fracture end. Poor rectification, or any inappropriate internal or external fixation, so that the fracture end is still angulated, displaced, or separated, can cause non-union or delayed healing, especially when using traction fixation or internal fixation, so that the fracture end fails to make contact, even if there is only a 1 mm gap, delayed healing of the fracture can occur.
④Type of fracture: cancellous bone fractures, due to their large contact surface and good blood flow, heal faster, while the healing process of cortical bone is more complex and takes longer to heal if it is poorly rectified, poorly aligned, and unreasonably fixed.
⑤ Special violence: When a fracture occurs by special violence such as a high-voltage electric shock or a gunshot wound, the soft tissue at the fracture end is badly necrotic due to the strong current or high temperature, resulting in non-healing or delayed healing of the fracture.
(6) Premature activity and loading: After fracture repositioning, the patient is prematurely engaged in unreasonable activities or premature weight-bearing on the affected part, which is also not conducive to fracture healing.
(7) Soft tissue entrapment: If soft tissue such as muscle or tendon is entrapped between the fracture ends, it will make the fracture healing difficult or non-healing.
(8) Infection: Infection can cause long-term local congestion and decalcification, and the ossification process can only start after the infection stops and the congestion disappears. If the infection is not controlled for a long time, the fracture healing will be delayed or not healed, and in serious cases, it will cause osteonecrosis, which will lead to limb disability.
⑨ Blood supply to the fractured end: regeneration of the local tissue of the fracture requires adequate blood supply. The parts with good blood supply heal faster; conversely, healing is slow, and even delayed healing, non-healing or ischemic osteonecrosis occurs.
⑩Pathological fractures: Pathological fractures caused by bone diseases and tumors are usually healable, but when fractures occur in patients with malignant tumors, the prognosis is often poor.
(3) Medical factors
(1) Improper treatment: Incorrect treatment measures, such as rough or repeated multiple manipulation, unnecessary surgical incision and repositioning, and inappropriate peeling of the periosteum during surgery, can damage the blood circulation at the bone end and affect the healing of the fracture.
(ii) Excessive traction: excessive traction force causes separation of the bone ends, which is not conducive to fracture healing.
Improper fixation: Improper fixation methods, such as small splint fixation tied too tightly and loosely, insufficient fixation range of splint or cast, or poor internal fixation, or too short fixation time, can affect fracture healing.
④Inappropriate activities: incorrect exercises, such as starting some functional exercises too early, too strong activities, or improper activities, can affect fracture healing.
⑤ Postoperative infection: Infection and septicemia after surgery, incomplete debridement, improper use of drugs, failure to control infection in time, resulting in long-term non-healing of the wound, or wrong debridement method, improper debridement, excessive removal of viable bone fragments in debridement and formation of bone defects, resulting in crawling and filling of bone scabs, can affect fracture healing.