Flexor tendon injuries in children are often missed or delayed.
The most difficult aspect of caring for flexor tendon injuries in children is the rehabilitation.
Priorities in management are a wound that heals without infection, restoration of sensory function, and reconstruction of functioning tendons.
With a partial tendon laceration of less than 60% to 75% of the cross-sectional area, the digit should be immobilized and protected from excessive stress for 3 to 4 weeks.
With an old injury, it may be preferable to delay reconstruction until the child is able to cooperate and the structures are larger, except in the case of concomitant nerve injury.
Immobilization after flexor tendon repair in children leads to better outcomes and decreased chance of rupture; immobilization should not exceed 4 weeks.
A flexor tendon injury is a difficult condition to treat in the best of circumstances, and a flexor tendon injury in a child can never be considered the best of circumstances.
The evaluation and treatment of flexor tendon injuries in children have been recognized as needing special care, with some authors recommending primary tendon grafting rather than end-to-end repair within zone 2.
Flexor tendon injuries in children are often missed or their diagnosis delayed, either because the examination is difficult or because the child does not report a functional loss. A small child presents a number of challenges, not the least of which is the challenge of handling the smaller anatomy with surgical dexterity. Scar formation may be unpredictable in the very young child.
By far, the most difficult aspect of caring for flexor tendon injuries in children is the rehabilitation needed for a good result. It is an arduous process to take a compliant adult through the rehabilitation protocols that balance the natural tendency to heal with scar against the desire to allow early controlled gliding of the tendon within the sheath. It is usually impossible to use early movement protocols with children of any age.
Another factor making this a difficult problem is that a large number of children “fall through the cracks” in any health-care system, and attention is delayed beyond the window of a primary tendon repair. If a primary repair is difficult in a small child, a two-stage tendon reconstruction can be completely daunting.
There are similarities in caring for flexor tendon injuries in children and adults. Decision making in both groups incorporates the variables of location and nature of the injury and time since injury. Primary repair of flexor tendon injuries no matter what zone is desirable. Postoperative rehabilitation must be appropriate to the patient.
Decision making about what to do and when to do it takes judgment. The priorities for the child are a wound that heals without infection, restoration of sensory function, and finally reconstruction of functioning tendons. The home environment must enter into decision making about how to accomplish these goals.
Examination of the injured hand in a child is difficult at best. No conscious toddler will actively participate in an evaluation of his or her injured hand. Topographical anticipation , a term used to describe knowing what to assess based on the location of the injury, is critical in the child.
Mechanism of Injury
A sharp laceration will create less soft tissue disruption and preserve a good bed for tendon repair. Crush or avulsion injuries create a larger zone of injury and are more likely to be associated with skeletal injury or loss of soft tissue coverage. Radiographs should be obtained to look for retained foreign bodies as well as skeletal injury.
The collateral arterial supply in a child’s finger is excellent, and the finger will usually remain viable even if both digital arteries are transected. Injury to the digital nerves is a larger problem that may be inferred by loss of sweat in the finger tip on the side of the nerve injury compared with a normal digit. This is often not apparent in the child who is too young or too scared to cooperate with a sensory evaluation. Wrinkling of the finger when it is soaked in water is not an accurate test for neural integrity because an amputated fingertip will also wrinkle if soaked in water. If there is doubt about the status of the digital nerves in a wound, they should be visualized by someone capable of assessing them before skin closure. This means by either a competent emergency department physician or by the surgeon who is consulted to care for the child. Assessment of digital nerve injury may require a general anesthetic for exploration if there is any question about nerve function and integrity. Injury to the digital nerves will result in impaired function and a progressive growth discrepancy, the mechanism of which is not fully understood.
The flexor tendon injury may be obvious by the altered stance of the finger or loss of normal digital cascade, with the finger lying in extension when both tendons are cut, and out of phase when only one is injured ( Fig. 129-1 ). The more difficult assessment is in the child with a partial injury or the “nick in the sheath.” Partial lacerations risk rupture when subjected to unprotected and excessive stress. When these children are identified in the emergency department, the percentage of laceration should be ascertained. Although it has been reported that as much as a 75% laceration may be treated with immobilization alone, it is tempting to place a suture into those tendons with less than 40% of the diameter in continuity. If the corresponding “nick” in the tendon is less than 60% to 75% of the cross-sectional area, the digit should be immobilized and protected from excessive tension until healing occurs or approximately 3 to 4 weeks ( Fig. 129-2 ).