Crush Injuries

An injury caused by a crushing blow to the foot is different from all other injuries in the amount and unpredictability of the damage that is caused, the amount of scar tissue and the time required for healing.

Crush injuries are usually caused by a large heavy object falling on top of the foot or by a car tire rolling over it. Occasionally the foot is caught between two moving objects such as a boat that is coming in to dock. Often times these are work-related injuries but occur commonly enough in the garage at home when a car slides off an unstable jack. In the same way that some ankle sprains are worse than a fracture, so it is with crush injuries because the soft tissue damage tends to be so extensive.

Complications and Initial Treatment

Concurrent injuries such as open fractures, dislocations and wounds that may occur at the same time is beyond the scope of this article. Suffice it to say that open wounds, with or without fracture or dislocation require immediate institution of antibiotics within six hours, if possible, the so called golden window for antibiotic treatment. Immediate stabilization of fractures and measures aimed at reduction of swelling may be needed to preclude cutting off circulation and allowing the continuous delivery of oxygen to the injured tissues. Occasionally, the injury is accompanied by a stripping away of the skin when torque is applied during the injury. Microfractures not apparent at first may become more obvious after a week or two or with more advanced imaging. Further imaging studies after the initial X-rays may include MRI, diagnostic ultrasound or bone scan to look for less apparent components of the initial injury.

Following the institution of first aid measures, the damage caused to the soft tissues by the crush injury remains. Within the soft tissue are the muscle and subcutaneous tissue compartments which contain a separate circulatory system that drains fluid back to the heart called the lymphatic system. The lymphatic system of drainage exists in the microscopic world outside of the capillary beds and collects the bloodless fluid that bathes each cell back to the heart. This system, along with the lymph nodes located behind the knees and at the front of the groin, drains this clear fluid back to the heart through the lymphatic duct which empties into the right atrium, completely separate from the large veins that return blood back to the heart. These microscopic lymphatic channels proliferate scar tissue in response to a crush injury and get clogged such that they don’t drain fluid away from the injured foot properly resulting in what I call “perma-swelling.” This perma-swelling must be treated with compression, lymphatic massage and physical therapy to heal properly and more quickly than would otherwise be the case. Because crushed soft tissue doesn’t heal normally but instead “reorganizes” over greater lengths of time such as six to eighteen months following injury, the healing of a crush injury proceeds very slowly.

Consider a clean laceration made with a sharp object such as a sharp surgical blade. The wound edges are tightly closed and hopefully the surgeon has done his best to handle the soft tissues encountered with gentleness and has closed each layer using suture. This type of wound is surgical, exact and heals from side to side a few millimeters across at the most. Healing is complete within a relatively short and predictable period of time. The skin takes about 14 days and the deeper tissues a little longer. Bone healing takes about six weeks. Generally, the more gentle and meticulous the surgery, the shorter the healing time. Not so with a crush injury.

In addition to the crushing damage sustained to the tissue layers that contain lymphatics, crush injury to the small nerve branches within the damaged soft tissue cause ongoing pain and numbness that takes 12 to 24 months to heal and may not heal completely for much longer. Nerve healing proceeds from the spinal cord at a rate of 1-2mm per day under ideal circumstances. Each nerve cell that goes to the foot is very long, extending from the lower spine to the foot. These are the longest cells in the body, about three feet long. Each nerve cell goes through an insulatory “microtubule.” The microtubule is left intact while a new nerve cell regrows down the tube. If the tubes at the site of injury remain crushed then the nerve can never heal completely and an area limited hopefully to just numbness will persist. Often the final determinant of how completely a crush injury will heal is the ability of these peripheral nerves to reconstitute themselves.

Follow Up Treatment of Crush Injuries

  1. Compression – By applying a layered external compression the lymphatic drainage is encouraged to heal in a more compact fashion. Compression is best alternated with lymphatic massage and physical therapy.
  2. Physical therapy – Moving the muscles against resistance is called active motion and simply moving a muscle that is not contracted is called passive motion. Both are needed to help healing of the muscle and its lymphatic drainage. The alternation of heat and cold applied to the injured area increases blood flow which delivers oxygen and nutrients for rebuilding damaged muscle cells.
  3. Lymphatic massage – Massage following a crush injury should be done toward the heart which is therefore in the direction that the lymph fluid should be flowing. This is done by fingertip touch using something like a Jergen’s hand lotion or any other lubricant so that the fingers go smoothly over the surface of the skin using enough pressure to cause indentation and compression of the deeper tissues. By moving the fluid out of the damaged tissues there is less pressure and distention encouraging a more compact healing and stimulating blood flow as well.

The final ingredient and the least predictable is time. It is safe to say that healing will take much longer than a clean incision even under the best of treatment regimens because reorganization and remodeling of soft tissue is a much slower process that simple side to side healing of a laceration.

Look at it this way; while the laceration only has to heal a few millimeters to heal, the crush injury has to heal over the entire width affected by the crush. It is certain that when the patient is returned to his or her usual level of activity that healing is not complete and will occur only over a long period of time. Hopefully, perma-swelling and the resultant pain and loss of function will not be a major long term or permanent final component of the injury.

Posted by Mark A. Kuzel, DPM, FACFAS on May 6, 2012