What is Flexor Tendon Lacerations?
Since doctors started repairing tendons as early as the 1960s, our understanding of tendons — the fibrous tissue that connects muscle to bone — has greatly improved. Today, not only do we know more about the basic nature of tendons, but we also better understand how they respond to injuries and the best ways to fix them. Recent research has improved surgical techniques and aftercare, which in turn has improved the success rates of tendon repair surgeries, reducing the need for multiple operations. The overall goal of these surgeries is to carefully reconnect the severed tendon ends, apply a protocol after surgery that helps the tendon glide smoothly, avoid the forming of scar tissue, restore the surface of the tendon to stimulate healing, and ultimately, restore strength to allow early movement of the finger.
The Flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), and flexor pollicis longus (FPL) are the muscles responsible for bending the fingers and thumb. These muscles have tendons that follow a particular path. Understanding the specific paths of these tendons is important for successfully treating tendon injuries.
The FDS tendons, for example, help to bend the first joint from the tip of your finger. These tendons come from the inner side of your elbow, pass through the front of your forearm, and attach to the bone in the middle of your finger. They get their blood supply mainly from the radial and ulnar arteries, which are the main arteries of your forearm and hand, and their function is controlled by the median nerve.
The FDP tendons are responsible for bending the last joint of your finger. These tendons are also controlled by nerves, specifically the anterior interosseous branch of the median nerve for the index and middle fingers, and the ulnar nerve for the ring and little fingers. The blood supply to FDP is mainly from the ulnar artery.
The FPL muscle bends the thumb. It originates from the top of your forearm and attaches to the base of your thumb. The FPL function is controlled by the median nerve, and its blood supply mainly comes from the radial artery.
All these tendons lay within a tendon sheath, a layer that is further strengthened by areas known as pulleys, which keep the tendons close to the bones of the fingers as they move. These pulleys make the movement of the tendons more efficient and enhance the overall function of the hand. This system is made up of five annular (A) pulleys and three cruciate (C) pulleys. Injuries to these structures can cause the tendons to deviate from their path during bending, which is called “bowstringing”. Specifically, injuries to the A2 and A4 pulleys are most problematic for the proper function of the hand.
Doctors use a standard system, called Verdan’s zones, to categorize the different areas along the length of these tendons. This system helps doctors decide on the best way to repair the tendon in the event of an injury, as techniques and outcomes may differ depending on the area of the tendon that has been damaged.
What Causes Flexor Tendon Lacerations?
About 20% of visits to the emergency room are due to hand injuries. Injuries to the flexor tendon, which is the part of your hand that helps you bend your fingers and thumb, often happen because of cuts or lacerations. This could be due to a sharp object like glass or a knife, or from a forceful impact that occurs in sports like football, basketball, or wrestling. Workplace accidents in developed and industrialized countries often cause these injuries, while in low-income areas, they may occur more frequently due to cuts from knives or glass during disputes.
Depending on the severity of the injury, patients might experience a loss of ability to bend their fingers, or sort of a pinching sensation when they try to do so. There could also be a decrease in the sensation or the strength of the fingers. If the injury is a closed one (where the skin hasn’t been broken), it might result in a loss of movement in the joints at the tips of the fingers. In cases where the tendon is torn off (known as tendon avulsion), you could feel a painful lump in the region where the tendon has retracted. These injuries are most common in the part of your hand where your fingers join your palm, and are frequently seen in the index or the little finger.
Risk Factors and Frequency for Flexor Tendon Lacerations
Flexor tendon injuries, which are injuries to the tendons in your hand that help you bend your fingers, aren’t fully understood. What we do know is that they’re a leading cause of physical disability among working-age men (ages 20 to 45), who are especially prone to these injuries. Flexor tendon injuries often involve damage to the nerves and usually affect the hand you use most, which is your dominant hand. These injuries can happen when you’re handling sharp objects or trying to catch something that’s falling.
- Flexor tendon injuries often occur in young men between the age of 20 and 45.
- They usually affect the dominant hand.
- They tend to happen when handling sharp objects or catching falling items.
- Between 30 to 42 out of every 100,000 people will have a flexor tendon injury.
- In the United States alone, these injuries cost between $240 to $409 million each year due to medical expenses and lost productivity.
Signs and Symptoms of Flexor Tendon Lacerations
When someone injures their hand, it’s essential to get a detailed history and physical examination. This examination should happen before anyone gives local anesthesia or sedation — this is the best way to spot any possible injuries to the nerves or blood vessels. The history should cover things like the patient’s age, their primary hand, their job, how the injury happened (including the hand’s position when it was injured), when the injury occurred, any previous treatments, whether they use tobacco, and if they’re up-to-date on their tetanus shots.
The physical examination should note the location and depth of any wounds, the hand’s resting position, the blood supply to the injured finger, and a neurological test. If it’s hard to feel the pulses, a handheld Doppler probe can help. It’s also useful to know the position of the finger during the injury. This can give clues about the distal tendon’s location – that’s the tendon at the furthest end of the finger. If the finger was bent during the injury, the tendon injury would be further than the skin cut. But if the finger was straight, the tendon injury will be close to the skin cut.
Testing for Flexor Tendon Lacerations
To thoroughly assess any medical concerns, a full body examination is necessary. This includes checking your skin, muscles, nerves and blood vessels.
Examining the skin: Your doctor will check the overall condition of your skin to potentially identify or rule out other related injuries. It is important to document each skin lesion or abrasion that’s found.
Checking the Muscles & Bones: If any obvious irregularities in the shape or rotation of your fingers are found, your doctor may conduct more thorough examinations to detect possible fractures or ligament injuries. They might correct misalignments before checking the flexor tendons (the connective tissues that help bend your fingers) or any possible impacts on nerves or blood vessels.
If a flexor tendon is fully cut, your finger might not bend fully at the middle and end joints. Additionally, each tendon in every finger will need to be checked. The tendons that allows your end finger joint to bend is examined by keeping the middle finger joint from bending and seeing if the end joint can still bend. The tendon that bends your middle finger joint is inspected by stopping the other fingers from bending and seeing if the middle joint on the examined finger can still bend. Loss of ability to bend your fingers and the usual downward bending shape when the wrist is extended tends to suggest a fully severed tendon. Pain while bending fingers might be due to a partially injured tendon.
Checking the nerves: Before using any local anesthetic, your doctor will conduct tests to check your sense of touch. After a deep cut, any loss of sensation might suggest a severed nerve until further tests prove otherwise.
Evaluating Blood circulation: The doctor will check the return of blood flow on the pads of your fingers and on the nail bed. If these tests show delayed blood flow return or weak skin elasticity, the doctor might suspect a cut in the digital artery or blood vessel running through your fingers. In such cases, additional tests might be done.
Your doctor will also ask about your tetanus vaccination history and when you last had a booster shot.
X-rays will be taken from different angles to check for possible fractures or leftover pieces of foreign objects. If it’s not clear whether a flexor tendon is still intact or to assess a potential partial cut, an ultrasound might be considered. Based on the findings during the surgery, detailed X-ray images might be taken.
In general, the results from the physical examination will typically suggest whether there’s a flexor tendon injury, which will be correlated with the depth of the cut, the condition of the skin around the cut, and how the injury happened. This information will be useful to decide if surgical exploration and potential repair are necessary. After a full examination of the skin, skeleton, tendons, nerves and the blood vessels, a confident decision can be made regarding the need, timing, and the type of surgery that might be needed.
Treatment Options for Flexor Tendon Lacerations
If our hands suffer a deep cut, it might damage what are called the flexor tendons. These are the tough fibers which link our muscles to our bones in the hands and fingers and enable us to bend our fingers and thumbs, kind of like the strings on a puppet. When these gets cut, it can limit our ability to move our fingers and even cause them to curl up. Despite this, not every tendon cut needs immediate surgery. Here’s what typically happens in these situations:
When you go to a health clinic, urgent care, or emergency department with a cut hand, they usually won’t rush you right off to surgery. Instead, they’re likely to give you an antibiotic through an injection, clean the wound thoroughly, and remove any foreign bits that may be in the wound. They might also assess how well the surrounding tissues are doing. They’ll then close the wound loosely, put a splint on your hand to prevent further damage to the tendon, and educate you about the importance of coming back for follow-up visits.
The preferred treatment for most cases of flexor tendon laceration is to repair it within 24 hours, if possible. However, if the wound is severely contaminated, if the damage came from a human bite, if there’s clear evidence of infection, or if the skin around the area isn’t healthy enough, immediate repair might not be the best option.
Instead, doctors might opt for what’s called a delayed primary repair. This is where they’d repair the tendon between 24 hours to 2 weeks after the injury. This is often a reasonable approach for heavily contaminated wounds, and the results are generally comparable with immediate repair.
If the repair is delayed further, it would fall into the category of secondary repair. This can happen anywhere from 2 to 5 weeks after the injury (early secondary repair) or more than 5 weeks after the injury (late secondary repair). However, the longer the delay, the greater the risk of infection and swelling.
For injuries to the tendons at the tips of our fingers (zone 1 injuries), treatment may vary depending on the kind of injury and how much of the tendon end is still available. Surgeries to repair these injuries can either involve stitching the tendon back together (primary tendon repair) or reattaching the tendon to the bone using small devices called suture anchors. Studies have shown that using suture anchors can result in better outcomes for patients, including a greater range of motion in the finger and a quicker return to work.
In contrast, injuries in zone 2, known as “no man’s land” because of their difficult complication rate are treated differently. The gold standard is to repair the crucial tendons known as FDP and FDS if more than 60% of its overall area has been damaged. In severe cases, the “repair” might just consist of the FDP. If the wound isn’t repaired immediately, it should be cleaned out and the skin loosely stitched shut. A tetanus shot and antibiotics should be given to prevent infection.
Zone 3 to 5 injuries, which are injuries to the tendons in the hand and wrist rather than the fingers, are also typically repaired surgically. However, the prognosis for these injuries also depends on whether nerve damage is part of the problem. Nerve damage that affects how well the hand works can reduce the effectiveness of the tendon repair process.
The most effective initial treatment for damaged flexor tendons is to repair them immediately after the injury. However, in severe cases where prompt repair isn’t possible, such as when there’s significant nerve, muscle or circulatory damage, doctors may consider alternative treatments like tendon grafting or tendon transfers.
Overall, repairing flexor tendon injuries can be a complicated process that involves delicate surgery and careful recovery. The patient’s commitment to a therapy program after the surgery is key to regaining movement in the hand and fingers. It’s also important to bear in mind that these treatments, like all medical procedures, can carry risks and it’s always best to discuss the process and the risks thoroughly with your doctor.
What else can Flexor Tendon Lacerations be?
Commonly, injuries to the flexor tendon occur alongside cuts on the palm-facing surface of the fingers and hand. These injuries can be further classified into:
- Partial cuts to the tendon
- Complete cuts to the tendon
- Tendon being torn away from its attachment (avulsion injuries)
What to expect with Flexor Tendon Lacerations
The results after fixing a damaged flexor tendon (a tendon that helps in bending your fingers) can vary greatly. This is because they are influenced by several factors like the nature of the disease, how the patient’s body responds to the injury, the time it took to get treated, the method of repair used, and how well the patient sticks to their post-surgery recovery program.
Good functional results usually happen when the tendon repair is satisfactory and the patient follows their aftercare program fully. Starting the recovery exercises soon after surgery helps the tendon to heal naturally, strengthens it, reduces swelling and scarring, and helps the tendon move more smoothly, which all contribute to a better outcome.
The most common issue after surgery is stiffness in the fingers. In rare circumstances, the repair site can tear, which usually suggests that the patient might not be following their recovery exercises correctly.
Various factors affect how well the flexor tendon heals. These include the patient’s age, whether they speak the same language as their doctors, whether they smoke, the extent of the injury, any other injuries they have, where the injury is, how long it took to get surgery, the type of surgery, the recommended post-surgery exercises, and whether they are sticking to these exercises.
Some patients might not heal as well as others, especially if they lack resources, get an infection after the surgery, or are less educated about the condition and treatment. Getting an infection in the hospital can particularly affect recovery, especially in hospitals with limited resources.
In places where lots of hand surgeries are done, patients are likely to get surgery faster after the injury compared to places that do fewer surgeries. This could mean that patients do better after surgery in these high-volume facilities. However, if there are language barriers, patients might struggle to understand their instructions after surgery and may struggle with their recovery exercises, which could negatively affect their healing.
Lastly, if the injury happens in a specific area called ‘Zone 2’, that could cause poorer results due to the complex anatomy of that area, which contains both the FDS (Flexor Digitorum Superficialis) and FDP (Flexor Digitorum Profundus) tendons within a narrow sheath (a protective layer).
Possible Complications When Diagnosed with Flexor Tendon Lacerations
Despite advances in treatment for hand injuries involving the flexor tendon, complications still happen, and they can significantly affect hand function long term.
- Ruptures are a bit more common in the flexor pollicis longus tendon, happening in about 5% of all complete surgeries. Ruptures call for immediate checking and fixing again before scarring and retraction prevent successful second fixing. If rupture happens again, the best treatment could be secondary tendon reconstruction, tendon transfer, or arthrodesis.
- The best way to prevent ruptures at the repair site is through a well-executed multistrand core suture, along with a simultaneous running encircling repair and early commencement of high-quality hand therapy.
Studies have shown that repair methods using only two strands are not strong enough for controlled active movement or early use of the hand after an operation, with an 11.7% rupture rate. The WALANT approach to flexor tendon repair helps to identify and repair gaps in the tendon before the skin closure, reducing the rupture rate by 7%. This approach, combined with complete fist flexion and extension testing during surgery, gives the team confidence to adhere to active movement-based therapy protocols after surgery.
Adhesions, which are bands of scar tissue that can limit movement, may form because of scarring after surgery or injury. They are more likely to happen after long periods of non-movement or severe injuries, acting as the culprit of adhesion formation between the tendon and its surrounding fibro-osseous sheath. In fact, adhesions with resultant digital stiffness remain one of the most common complications after flexor tendon repair.
- Reports suggest that adhesion formation with following restriction of tendon movement, prompting the need for tenolysis, has been reported in rates varying from 12-47%.
- About 3-6 months after successful but still intact tendon surgery, tenolysis can be considered if the active range of motion is significantly less than the passive range of motion, or there has been no significant improvement in the range of motion despite aggressive hand therapy.
About 17% of tendon surgeries lead to contraction of a muscle or a part; their primary prevention is via splinting, with surgical treatment proceeding to either open or closed capsulotomy for stubborn cases.
- Only after nearly complete restoration of PROM, patients should be considered for tenolysis to secondarily improve AROM.
Other possible complications following surgery for flexor tendon injuries include infection, skin flap necrosis, mechanical failure of an implant (if used), pulley disruption, swan neck deformity, infection, and synovitis. In cases of staged tendon reconstruction, other complications may include disruption of the distal implant junction after stage one, rupture of the graft, a graft that is too loose or too tight, development of an intrinsic plus phenomenon, reflex dystrophy, nail deformity, scar sensitivity, triggering, and flexion deformities.
Recovery from Flexor Tendon Lacerations
Doctors would typically put on extension block-splints to position your wrist in a certain way after flexor tendon repairs, this is to reduce the chances of the repaired tendon snapping. The flexion of the joints is carefully controlled and after two weeks, the stitches are usually taken out.
Research nowadays shows that rehab that slowly introduces movement early on is better than keeping the tendon completely still. Starting therapy early can help speed up healing, increase the strength of the tendon, and improve the movement of the tendon, leading to more flexible joints, fewer curve contractions and improved function of the hand. The rehab program should be designed to improve the function of the entire hand while accommodating for the injuries to the soft tissues. As all patients are unique, each therapy program has to be personalised. This process therefore requires a knowledgeable and experienced hand therapist. Passive rehabilitation methods, where the hand is kept still, have been mostly replaced by methods where controlled movement is introduced early.
Protocols usually recommend passive movement of a certain range and how the hand exercises should be performed with variations in these protocols. One such protocol is the Saint John Protocol. This protocol starts 3-5 days after the flexor tendon repair when active flexion of the fingers is initiated. The decrease in swelling and flexion work during the waiting period minimizes the chance of the repaired tendon snapping. This protocol then proceeds with passive flexion of all fingers after warming up before proceeding to active flexion. This method of flexion prevents joint flexion contraction. From the 4th day to the 2nd week, active flexion is increased daily. After the 2nd week, the program moves into a synergistic exercise program working towards half to full active fist position while continuing joint extension. Ideally, a full fist position should be achieved in six weeks. Generally, six weeks is also when patients move onto lighter activities.
Scientific studies have shown that starting therapy within the first week after tendon repair showed benefits with the same complication rate, tendon rupture risk, or secondary surgery rate regardless of when therapy is initiated. There was specific benefit seen for zone 2 injuries.
When the hand is immobilized, the repaired area becomes weaker with time, specifically, 50% weaker after a week, and the strength can decrease further by 30% after three weeks. However, when following a protocol which introduces movement early, the strength of the repaired site can increase two-fold or more from 4-6 weeks after the operation. Usually, after 3-4 months, patients would have recovered around 90% of the motion range they had before the operation.
It is also essential to start a rehabilitation plan that gradually introduces more movement as soon as possible. This should be done under the supervision of a professional therapist while wearing a protective splint and carrying out certain wrist movements to improve the mobility of the repaired site. The therapists usually monitor the patient’s progress closely by scheduling therapy sessions twice weekly for the first 6-8 weeks. Both the injury and the patient’s ability to respond to physical stimuli affect recovery. Patients can usually return to their full activities after 4-6 months post-operation, provided they follow the post-operation routines diligently.
Tech advancements in flexor tendon repair and therapy have led to changes in how patients are rehabbed. There has been a shift from passive to active methods that are controlled and initiated early, but ultimately, the surgery and therapy need to be customized to suit each patient’s unique needs for the best results.
Preventing Flexor Tendon Lacerations
The success of rehabilitation after surgery depends largely on the patient’s willingness to follow the care plan. While there are common guidelines used in every treatment, these plans are adjusted faster or slower based on how the individual follows and responds to their prescribed therapy. Getting back to work can take several months. It’s worth noting that about 10% of patients might need additional surgeries due to complications. Therefore, it’s very important for patients to stick to their post-surgery therapy plan. This can significantly help to improve their recovery rate and final outcomes.
