Flexor Tendon Injury

Flexor tendons are the cord-like structures that extend from the muscles in the forearm to the thumb and fingers on the volar, or palm side, of the forearm and hand. These tendons play a crucial role in allowing the flexion or bending of the thumb and fingers, enabling us to make a fist, grasp objects, and perform various tasks. The thumb has one major flexor tendon (flexor pollicis longus or abbreviated as “FPL”) and the four fingers typically each have two flexor tendons (flexor digitorum superficialis and flexor digitorum profundus or abbreviated as “FDS” and “FDP”). Flexor tendon injuries can be quite debilitating, as they compromise hand function and dexterity.

Flexor tendon injuries commonly result from sharp lacerations that sever the tendon, such as accidents with knives or glass. However, tendon or pulley ruptures can also occur due to forceful pulling on the finger, such as during rock climbing, or as a consequence of "jersey finger" in sports like rugby or football. Depending on the severity and location of the injury, it may be classified as a Zone 1, 2, 3, 4, or 5 injury. Zone 2 injuries, which are located in the finger, previously were known as being in “no man’s land” due to being notoriously challenging to treat. These injuries should be evaluated and treated by an experienced hand surgeon.

These injuries typically necessitate surgical intervention and should ideally be treated within 7-10 days of the injury to maximize recovery potential and achieve optimal results. Delays in treatment will compromise the final outcome. The prognosis for flexor tendon injuries varies, with factors such as age, occupation, the extent of the injury, and adherence to rehabilitation protocols influencing the outcome.

Diagnosing a flexor tendon injury begins with a thorough medical history and physical examination by an experienced hand surgeon. The surgeon will assess the range of motion, strength, and sensation in the affected hand and fingers. Complete flexor tendon injuries or lacerations result in an inability to bend one or more joints on the affected finger. In cases of partial injuries, you might still be able to bend your finger, but you could experience pain or a catching sensation during the movement.

Associated nerve injuries will be assessed and addressed if present. Nerve injuries can manifest as numbness, tingling, or weakness in the affected hand and fingers. In case of an accompanying artery injury that compromises blood flow to the finger, immediate attention at an emergency room may be warranted to assess whether replantation or revascularization is needed..

Rarely, additional imaging with ultrasound or MRI may be necessary to visualize the extent of the injury and plan the surgical approach. If a jersey finger injury is suspected, x-rays are required to evaluate any avulsion fractures.

Complete flexor tendon injuries generally will not heal without surgical intervention to repair the two ends of the tendon. This process may require additional incisions within the hand to retrieve the severed tendon ends. Delicate dissection and a strong repair technique are essential to minimize scarring and optimize recovery.

In some cases, grafts or tendon transfers may be considered if the tendon ends cannot be brought together or if the injury is chronic. Tendon grafts involve using a portion of a tendon from another area of the hand or body to bridge the gap between the severed tendon ends. Tendon transfers involve re-routing a nearby tendon to compensate for the loss of function in the injured tendon. In other situations, a two stage technique is required with placement of silicone rods known as “Hunter rods” before a second stage operation months later with placement of tendon grafts.

After the tendon repair, your hand surgeon may also address any associated nerve or blood vessel injuries, as well as repair any damaged pulleys that guide the tendon through the finger.

After surgery, hand therapy plays a critical role in the recovery process. You will be placed into a splint immediately following your surgery to provide support and protection. This splint typically immobilizes the wrist and affected finger(s) in a slightly flexed position to minimize tension on the repair site. Your surgeon will let you know when to begin hand therapy, but often this is within several days of surgery. Thus, it is important to begin planning your hand therapy appointments at the same time that you are scheduling your surgery.

Your hand therapist will remove the splint soon after surgery to initiate a "range of motion protocol," which involves carefully moving your fingers to minimize scarring between the flexor tendon and the surrounding tissue, which results in stiffness. This protocol aims to optimize your hand function and overall outcome. Passive and active range of motion exercises will be introduced in stages with the guidance and supervision of your hand therapist.

However, hand therapy and the motion protocol must be balanced with the delicate nature of the tendon repair, as there is a risk of rupturing the repair during the early stages of healing. It is imperative to adhere to the instructions and limitations provided by your hand surgeon and hand therapist. Gradually, your therapist will introduce strengthening exercises and functional activities to help you regain your pre-injury level of function.

Keep in mind that even with optimal healing, full recovery may take several months, and patience and dedication to your rehabilitation program are crucial for achieving the best possible outcome. Factors such as age, overall health, the severity of the injury, and commitment to rehabilitation will influence the final outcome.

Be sure to see an experienced surgeon to treat this condition. Our fellowship-trained specialists at The Buncke Clinic in San Francisco treat patients with flexor tendon injuries from across the Bay Area and Northern California. Contact us to schedule a consultation.

Below are links for third party resources

American Society for Surgery of the Hand

American Academy of Orthopaedic Surgeons