What Every Surgeon Should Know About Knee InjuriesKnee dislocations are known to cause severe ligament damage with knee joint instability. If the blood vessels and local nerves in the area are damaged, the risk of losing the leg is much higher. The authors of this article report that such damage can occur even with a single ligament rupture in the knee. And what appears to be minor trauma (e.g., sports injury, fall from standing) can also cause serious damage to the blood vessels. Without early diagnosis and treatment, loss of limb is a definite possibility.
To prevent this from happening, surgeons and other physicians must be aware of the types of common neurovascular injuries that can occur with knee injury. An understanding of anatomy and mechanism of injury will guide the surgeon in planning the most optimal course of treatment for each patient.
The authors of this article review types of injuries (e.g., knee dislocation, vascular injury, compartment syndrome, nerve injury). They describe diagnostic tests for each one and recommended treatment. Timing of ligament repairs, new technology for treatment of arteries and veins, and classification of nerve injuries are presented and discussed in detail.
The authors suggest that whether one, two, or multiple ligaments are damaged in a knee injury, the surgeon should evaluate as if a total dislocation with neurovascular complications have occurred. In this way, difficult to detect damage will be recognized quickly with better final results.
The examiner should keep these key points in mind:
Diagnosis begins with the patient interview, clinical tests, and imaging studies. X-rays can help show any fractures that might be present. A neurologic exam can reveal nerve damage. A quick screen for pulses can help identify vascular injury. This test should be done before and after any treatment to reduce a dislocated knee. Damage to even small blood vessels can result in local hemorrhaging and loss of vital blood supply.
Testing pulses is a very accurate clinical test. Pulses must be checked every two hours for up to 48 hours. More specific vascular studies (arterial-pressure index, Doppler ultrasound, arteriography) can be ordered if there is any sign of vascular compromise. Restoring circulation quickly (within six to eight hours) is absolutely vital in saving the leg. Most experts agree that treatment for known or suspected vascular injury should not be delayed by doing additional imaging studies.
Surgery to restore blood flow involves repairing the damaged blood vessels while reconstructing the torn ligaments. If the damage to the blood vessel is more than a minor or small tear, then vein grafting is done. The authors describe all types of vascular repairs including balloon angioplasty, stent placement, and fasciotomy for compartment syndrome.
Once the blood supply has been restored, then the ligaments are repaired. This may be done in the same procedure, but more often, the surgeon waits two to six weeks. This gives time for healing of the blood vessel(s). Without adequate blood supply, repairing or reconstructing the ligament won't be successful.
Other injuries such as disruption of the peroneal nerve or tibial nerve may be present with knee dislocation. The force of the injury is enough to cause traction or stretching to the nerve(s). Anyone with avulsion fracture of the fibula (smaller bone in the lower leg) is at increased risk for peroneal nerve damage.
The surgeon must look for such injuries and address them in treatment. Even with treatment, the risk of sensory and motor damage is high. Difficulty walking because of a foot drop can lead to permanent disability. Physical therapy is often advised to prevent joint contractures (loss of joint motion), deformity, and altered gait (walking) patterns. Electrical stimulation may be used to restore muscle function and strength.
With all of these injuries, the patient must be followed carefully. It can take some time before the extent of recovery can be determined. With nerve damage, it takes about one month after injury for the nerve to start to recover. Peripheral nerves can regrow about one millimeter per day. The surgeon uses this time frame to watch for signs of recovery before performing additional surgery. If recovery is too slow or not occurring, nerve repair, nerve grafting, and/or tendon transfer may be needed.
In summary, prognosis is varied and guarded when knee injury results in nerve and/or blood vessel damage. The surgeon must remain alert and perform serial (frequent) examinations of the patient. This must be done until the patient is clearly on the road to recovery. The early detection and management of neurovascular injuries is essential to a good outcome.
Michael E. Johnson, MD, et al. Neurologic and Vascular Injuries Associated with Knee Ligament Injuries. In The American Journal of Sports Medicine. December 2008. Vol. 36. No. 12. Pp. 2448-2462.
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