Subungual hematomas are injuries of the nail bed in which bleeding develops under the nail. Patients usually complain of pain and discoloration of the nail. The damage is caused by a direct blow or a crush injury to the distal phalanx, for example, getting a finger pinched in a doorway. As blood enters the space it applies painful pressure to the nail-bed. The injury may also be accompanied by distal phalanx fractures, nail avulsion, or finger-tip avulsions. Most subungual hematomas can be relieved with simple trephination, a procedure which involves making a small hole in the nail.
The provider should examine the entire nail structure for disruption of the nail fold and the whole finger for motor function, sensation, and evaluation of circulation. The extensor mechanism of the distal interphalangeal joint (DIP) should be evaluated by holding the middle phalange and testing the strength of extension by providing resistance to the motion. A decrease in strength compared to the contralateral side indicates a mallet finger injury. Circulation can be tested by capillary refill distal to the injury. In some patients, such as small children, practitioners may be required to perform digital nerve block to examine the injury.
Three-view radiograph should be obtained to evaluate for underlying fracture as distal tuft fractures are common. Point of care ultrasound (POCUS) can be used to identify nail bed laceration and underlying distal tuft fractures that may indicate a more involved repair.
The complete nail structure is called the perionychium. It is composed of the nail fold, the paronychium (the dorsal skin of the fingertip), the hyponychium (the keratinized distal end of the nail bed which is in contact with the skin of the fingertip), nail bed (composed of the germinal and sterile matrices) and nail. The germinal matrix is located on the ventral floor of the proximal nail fold and produces 90% of the nail cells. It extends to the lunula, the crescent-shaped lighter portion of the nail. The sterile matrix is highly vascularized and located on the ventral floor of the distal nail bed and adds layers of cells responsible for attaching the nail to the nail bed.
Current recommendations for drainage of acute (less than 48 hours) subungual hematomas advocate for trephination, a procedure where a hole is made in the nail to drain the hematoma. Previous recommendations were to remove the nail for any hematoma greater than 50% of the nail or greater than 25% of the nail in the presence of a fracture. Several studies have shown that trephination has an equal cosmetic outcome and similar complication rates for the majority of cases.
There are no absolute contraindications to trephination; however, in some situations, patients may have better cosmetic outcomes with nail removal and nail bed repair. Subungal hematoma with associated avulsion of the nail, a displaced distal phalanx fracture, a proximal fracture involving the germinal matrix may require a surgical consult for removal of the nail and nail bed repair. In the event of the nontraumatic development of subungual hematoma, the patient may not benefit from trephination. Examples of nontraumatic subungual hematoma include a variety of tumors including a junctional nevus or melanoma or splinter hemorrhages.
If you have no other supplies available, a heated paperclip can do in a pinch.
Clean the digit with chlorhexidine, betadine or povidone/iodine solution.
Patient with distal phalanx fractures may benefit from a digital block. However, this is frequently more painful than the procedure.
Obtain consent before the procedure. Discuss with the patient that they can expect to bleed from trephination site and complications include loss of the nail, re-accumulation of hematoma, and infection.
Once a hole is created it is expected that blood will drain out from the hematoma resolving most of the patient's pain. It may take more than one trephination to decompress the hematoma completely. Take care when advancing through the nail to avoid damage to the nail bed. Bandage site with sterile gauze in instruct patient to keep digit clean and dry.
Follow-up instructions should be given to the patient with advisement not to soak the finger as this can cause an introduction of bacteria. Also, inform the patient that blood may continue to ooze from the hole in the nail for 1 to 2 days. Instructions for re-evaluation should be given in the event of signs of infection such as warmth, redness, increasing swelling and fever, and reaccumulation of the hematoma with pain. Non-displaced distal phalanx fractures should be splinted in an extension splint for 4 weeks, and the patient should follow-up with a hand specialist. The patient should be informed that the hematoma should advance distally over the next several weeks. If the hematoma is not advancing, they should see a dermatologist for further evaluation of the hematoma due to the possibility of abnormally growing tissue such as melanoma or a nevus. There is no current consensus on post-procedure antibiotics, and they are currently not recommended due to a small observational study which evaluated 47 patients and found no benefit for antibiotics.
This injury is a frequent complaint in both the pediatric and adult populations. It is also seen in austere environments. Having multiple strategies including low-tech ones will be beneficial to promptly and adequately treat patients.
Management of a subungual hematoma is often done by the emergency department physician, nurse practitioner, primary care provider or surgeon, typically with the assistance of a nurse stabilizing the finer. The key is to ensure that the hematoma is not older than 48 hours. In most cases, the hematoma can be drained with a large needle without any complications. Follow up of patients is recommended to ensure that there is no infection and the hematoma has resolved.
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