Posts Tagged ‘fracture’

Metatarsal Stress Fractures

November 9, 2013

Image

Metatarsal Stress Fractures

A teenage girl presents complaining of pain in her forefoot. The pain first started 2 weeks ago and has gradually worsened. She noticed swelling over the top of her foot a couple days ago. She recently started long distance running and started training for a half-marathon. She states that her pain worsens the longer she runs and gets somewhat better when she is off her feet. What could be the cause of her pain?

What is a Stress Fracture?

Our bones undergo stresses everyday. Every time we take a step, stress is applied to the bones in our feet. The human body has developed ways to lessen these forces by using muscles in the foot that help decrease the load applied to the bones. Additionally, the ability of the bone to repair itself when minor damage occurs prevents the development of a full fracture. A stress fracture is an injury that occurs because of repeated low-grade stress that is applied to the bone over a prolonged period of time, which overpowers this ability for the bone to repair itself. The slow, progressive nature of this injury causes symptoms to occur gradually and worsen with continued exertion.

Our feet endure stresses when we walk, jump or even stand. A change in normal routine or increased level of activity introduces new stresses to the bones of the foot and can result in a stress fracture. An area commonly affected by these types of injuries is the metatarsals, which are the long bones of the forefoot.

Metatarsal Stress Fractures

Stress fractures affecting the metatarsals are a common occurrence, especially in sports that involve running such as track and field and basketball, especially when played on a hard floor [1].

There are five metatarsals in each foot. It is important to note the function of the individual metatarsals in order to understand which bones are likely to be affected. The first and fifth metatarsals are unique in that they have their own independent range of motion apart from the other middle three metatarsals. This means that they have the liberty to move upward when forces from the ground are applied to them. This helps prevent injury to these two bones, making stress fractures of the first and fifth metatarsals relatively rare.

The central three metatarsals (referred to as #2, #3, #4), on the other hand, are more rigid. This is important because their immobility provides stability to the forefoot. However, this anatomical configuration makes the central metatarsals more likely to develop stress fractures. The second metatarsal is particularly susceptible because it is the longest of the five metatarsals. The term “March” fracture has been applied to stress fractures of the second and third metatarsals because of their increased incidence in military personnel. In fact, metatarsal stress fractures were first described in Prussian soldiers in 1855 [2].

Clinical Presentation

Metatarsal stress fractures typically present as pain in the forefoot that increases with weight bearing activity. The pain can be generalized in the front part of the foot or localized to a certain area in advanced cases.  The pain usually subsides when the inciting activity is ceased. Over time, however, if left untreated the pain can remain even when at rest. Since the pain usually slowly worsens, the patient may not be able to indicate a specific time when an injury took place. Swelling over the site of injury is very common.

What are the Risk Factors?

The patient should be asked if they recently changed their level of physical activity. Stress fractures commonly occur when people abruptly increase their level of activity.

Biomechanical abnormalities in the foot can also lead to development of a fracture.

Other risk factors include corticosteroid use, smoking and disorders of Vitamin D (rickets, osteomalacia).  Also, smoking can affect bone healing .

Physical Examination

Visual examination of the patient may reveal swelling in the forefoot. The affected metatarsal can be identified by pushing the metatarsal heads to elicit pain over the site of the fracture. Placing a vibrating tuning fork over the suspected metatarsal may also elicit pain.

Imaging

X-ray imaging is always obtained.  However, they may not reveal a visible fracture line early in the course of metatarsal stress fractures. Usually, the diagnosis of stress fracture is made based on the clinical history, even when the radiographs look normal.

MRI scans are useful to visualize a stress fracture, but are not always required especially if the fracture is clearly seen on the x-ray film.  These scans can rule out other suspected causes of pain because of the level of detail it reveals. Bone scanning is another method that can be used and involves injection of technetium-99 isotope to visualize uptake of the agent in the area of injury.

Treatment of Metatarsal Stress Fracture

Metatarsal stress fractures can usually be treated non-surgically, especially if the symptoms are addressed early in the course of the disease. The activity that caused the injury must be discontinued until the fracture is healed. The patient should also elevate the injured limb.  Crutches may be needed for ambulation to relieve stress. The affected limb may require immobilization with a CAM walker. NSAIDs such as ibuprofen (Motrin) can be used as needed to alleviate pain. When someone chooses to ignore symptoms of a stress fracture and refuses to rest, the injury can progress to a full fracture that could require surgical intervention. Surgery may also be necessary if the injury fails to heal properly or heals in a poor position. Once the patient feels comfortable and the fracture appears healed on imaging physical activity can be resumed. After healing the fracture, return to activity should start off slowly and modified to reduce chances of recurring injury.

Source Material

1. Iwamoto and Takeda. Stress fractures in athletes: Review of 196 cases. J Orthop Sci 2003; 8: 273 – 275.

2. Gehrmann and Renard. Current Concepts Review: Stress fractures of the foot. Foot and Ankle Int 2006; 27:250