Getting a finger smashed in the car door (or other similar crush injuries) is a fairly common injury and can be very problematic. The best way to treat these injuries is a matter of opinion and conjecture. Deformity and loss of finger function can be very serious consequences of this injury.
Without proper treatment, more problems and complications can develop. Blood trapped under the nail bed known as a subungual hematoma can prevent normal healing. Other injuries that occur at the same time (e.g., fractures, fingertip amputation, nail matrix laceration) must be treated as well.
There was a recent article in The Journal of Hand Surgery written by hand surgeons from Vanderbilt University Medical Center in Nashville, Tennessee that may be helpful. They addressed the complexities and controversies in the treatment of nail bed injuries. They focused primarily on nail plate injuries and what to do about them. The nail plate covers the nail matrix, which is divided into two matrices: germinal and sterile.
The nail matrix (also known as matrix unguis) is formed by these two layers of cells at the base of the fingernail (or toenail). This tissue consists of rapidly dividing skin cells that soon fill with the protein keratin. The matrix of finger nails consists of the most rapidly dividing skin cells in the body. The matrix is involved in growth and position of the nail plate.
A crush injury such as you described compresses the nail matrix between the nail plate and the bone. Damage to the nail bed can lead to the formation of scar tissue and misalignment of matrices and nail plate. However, in the acute phase (right now immediately after the injury), the more immediate problem is the subungual hematoma.
A decision-formula for determining whether or not to remove the nail and repair the nail bed when there is a subungual hematoma has not been developed. Most surgeons depend on their own experience and expertise in making treatment decisions regarding these hematomas. Some surgeons make the decision based on how much of the nail bed (e.g., more than 25 to 50 per cent) is compromised by the hematoma.
Others suggest that removing a circular piece of the nail (the procedure you mentioned called trephination) to take pressure off the nail bed is all that’s needed. Surgical removal of the nail and nail bed repair is advised by some experts in the case of bone fracture along with more than 50 per cent of the nail bed affected by a hematoma. The nail plate is removed, the nail bed is examined for deep cuts, the area is debrided (cleansed), and any lacerations (cuts) are repaired with sutures.
Studies where only trephination was performed for subungual hematoma (with or without fracture) report equally good results as when surgery is done. This type of minimal approach (i.e., trephination) aids in preventing infection and post-injury nail abnormalities. One other consideration is the cost of each treatment. Trephination can be done at one-tenth the cost of the more involved surgery.
The authors point out the need for further research to provide evidence-based treatment protocols for nail bed crush injuries. All indications are (from currently available studies) that trephination works well even for subungual hematomas with fracture. More involved surgery may only be needed when the bone fracture is unstable or when the nail matrix is trapped or embedded in the nail matrix. Trephination is also a cost savings!