Introduction
Anatomy
Cause
Symptoms
Diagnosis
Non-surgical treatment
Surgical treatment
Rehabilitation
Prevention
不論大家是否專業的運動員,亦有機會受到這種創傷。不過,無疑長跑選手、籃球員、芭蕾舞蹈員及軍人是較為「高危」的一族。
While the bone, being a living tissue, has the ability to repair, regenerate and remodel itself in situations where external stress is exerted on it, a stress fracture occurs when the external force exceeds the bone’s built-in mechanical strength. In other words, if a there is repeated stress of a bone due to overuse, the chances of a stress fracture is significantly increased.
Stress fractures most commonly occur in the bones of the leg (tibia and fibula) and the foot (tarsal and metatarsal). Among these bones, the second to the fourth metatarsal bones account for 50% of the cases. The posterior spinal arch (lumbar) and the femoral neck (top of thigh) are other potential sites for stress fractures.
If you live a sedentary lifestyle and suddenly increase the amount of exercise at an unreasonable rate, you run the risk of having stress fracture. Other circumstances under which a person can get a stress fracture are:
athletic training plans that are too intensive;
fatigue of muscles, which decrease their ability to absorb shock;
hormonal and dietary imbalance, especially among adolescents, which may affect normal bone metabolism.
What is deceptive about stress fractures is that the force of the external stress causing the injury is actually much smaller than that which causes common bone fractures. But given enough repetition, the stress eventually exceeds the ability of the bone to heal itself.
Pain over the affected site when performing an activity is the usual symptom for stress fractures. However, the pain reduces if the affected area is not in exertion or bearing weight (i.e. when the involved limb or bone is resting).
Because stress fractures develop over time due to repeated stress to the bone, they are difficult to detect. In fact, in its early stages, the injury is usually undetected by X-ray. Diagnosis therefore depends on other methods, such as experience of excess pain by the patient during exercise; careful physical examination by the doctor to look for local tenderness; and the use of CT, MRI or bone scans.
Besides using pain killers and physical therapy to lessen the pain, the treatment options for lower limb stress fractures are conservative methods for most patients, such as using plastic orthosis for proper weight support or casting to allow the bone to heal. The total healing time will be around three months, which is similar to other common fractures.
For selected patients, such as those suffering from displaced fractures (fractures in which the two ends of the broken bone are separated from one another) surgery using bone screws and bone grafting may be necessary. To enhance the healing process, electromagnetic or ultrasonic bone stimulators or intravenous injection of bisphosphonate may be used in addition to the surgery.
It usually takes a fractured bone around three months to heal after the operation. Protected weight-bearing of the operated site is necessary in the early post-operative phase. Physical therapy is recommended as soon as the fracture is stable enough for mobilization. This enables an early restoration of the normal range of motion and flexibility of the adjacent joint.
To a certain extent, stress fractures can be prevented through the following measures:
For people with a sedentary lifestyle, set a reasonable goal for training.
For athletes, avoid excessive training programmes.
For runners, the distance covered should be increased by no more than 10% per week.
When sport shoes are worn out, get a new pair.
Regular training of muscles, including the foot muscles, can improve the body’s shock-absorbing mechanism during weight-bearing exercises.
Increase dietary intake of calcium and vitamin D.
Correct any hormonal imbalance, especially in adolescent girls.
Look out for intrinsic risk factors, such as a hereditarily shorter big toe metatarsal bone, which may transfer stress to the other foot bones or cause misalignment of the foot architecture. In such a case, wear proper insoles in shoes.
Dr. NGAI, Wai-kit