Tendons are cord-like extensions, which connect muscles to bone. As the muscles tighten, the attached tendons will pull on certain bones and elicit motion. Tendon anatomy in the hand is delicate and intricate and so is the surgery required to restore it after injury.

Tendon injuries are common. Our hands are constantly involved in daily activities and relatively superficial location of tendons in the hand, especially in the fingers, renders them susceptible to trauma.

In brief, the palm and inner side of the forearm contain tendons which bend (flex) fingers and wrist (flexor tendons). On the back of the hand and forearm lie tendons which straighten (extend) fingers and wrist (extensor tendons). Most of these long muscles originate at the elbow and forearm regions, turning into tendons just past the middle of the forearm, and attach to the bones of the fingers and palm. In the finger, flexor tendons pass through very narrow tunnels (“flexor sheaths”) which keep them close to the bones and facilitate their action and gliding (Picture 1; Gallery below).

Only partially divided tendons (less then 50% of the tendon diameter) can just about heal spontaneously. A completely cut tendon can rarely heal without surgery. The severed ends separate from each other due to inherent tension present in all tendons. An injury that appears simple on the outside can be much more complex on the inside.

It is important to repair these injuries early (within few days from an accident) in order to facilitate good long term results. Specialist expertise in dealing with these sophisticated structures, as well as dedicated hand therapy help such goal.

Many tendon injuries are not associated with breach in the skin (Pictures 2-5; Gallery below). Tendon insertions onto the bones can be disrupted during forceful twists, pulls and blunt trauma imposed onto the fingers. Not surprisingly, such closed injuries are associated with delayed referral and diagnosis  making surgical treatment even more difficult and treatment outcomes often compromised. Inability to fully straighten or bend your finger(s) should alarm you to seek specialist advise as soon as possible. Photo Gallery below illustrates fingertip injuries resulting in avulsion of either extensor (Pictures 2,3) or flexor tendon insertion (Pictures 4,5) which require instant diagnosis and treatment, as most of tendon injuries. Treatment can be a simple, just splintage as demonstrated in Picture 3 or specialist surgery. Either one needs to be delivered early in order to prevent complicated, less predictable interventions required for missed injuries (please see below).

After an extensor tendon repair you should predictably have well working finger or thumb. The outcome is often better when the injury is a clean cut to the tendon, rather than one that involves crushing or damage to the bones and joints.

A flexor tendon injury is generally more difficult to manage as those structures function under more strain than extensors and have particularly intricate anatomy. Good function of flexor tendon system in the hand, especially fingers, is based on intactness of a fascinatingly complex, smart, gliding mechanism (Picture 1). Any scarring (inevitably associated with either injury or surgery) interferes adversely with this fine physiology so will need to be managed promptly and adequately from the beginning. Specialist input from the start should provide the best chances for good recovery.

It always helps to plan things in advance of surgery and adjust work and life activities accordingly. Therefore, please consider the following issues prior to your operation:

• Please make sure that you arrange to be collected from the hospital as you will not be able to drive after the surgery
• Plan your time off school / work / sports
• Allow at least few weeks after surgery before considering holiday

Tendon surgery is carried out on a day care basis.

Extensor tendons are easier to reach, so repairing them is relatively straightforward. Many can be done under local anaesthetic, but more extensive ones will require general or regional anaesthesia. The simplest and smallest extensor tendon cuts can sometimes even be fixed in the Accident and Emergency department.

Repairing flexor tendons is more challenging because the flexor tendon system is more complex and responds worse to consequences of injury and scarring. Flexor tendon repair usually needs to be carried out under either general or regional anaesthesia, ideally by an experienced hand surgeon for variety of reasons (see below).

Tendons ends need to be stitched together in a very particular way: repair must be robust enough to withstand future strong forces, but also neat and elegant not to compromise gliding of the tendon within the narrow tunnel. At the end of operation hand is bandaged and splinted from the tip of the fingers up to the elbow.

Tendons which bend our fingers (flexor tendons) act as elastic cords suspended under gentle tension between muscle bellies in the forearm and fine finger bones. When severed completely or detached from the bone by strong avulsion force, tendon ends will therefore, tend to spread apart to lesser or greater degree, pending exact action and position of the fingers at the time of accident (Picture 6; Gallery below). Within the first few days of injury, it is easy to retrieve retracted tendon, overcome the gap between their ends and repair tendon directly as described above. However, as the time passes, elasticity of muscle and tendon becomes compromised by scarring so it becomes progressively more difficult to approximate tendon ends after 7-10 days after injury. After 4-5 weeks, such task is often impossible – scarring and stiffness prevails over tendon elasticity and fine gliding mechanism. More complicated operations have to be used, often involving tendon grafting, to restore function. Successful outcome rate of such interventions, even in the most experienced surgical hands, drops dramatically in comparison to simple, early, direct tendon repair.

Two particular pato-physiological problems exist in old (over 3-4 weeks) flexor tendon injuries: 1) a creation of gap between tendon ends and 2) disappearance of a fine, protective finger tunnel in which intact flexor tendon glides. Both of these issues require additional surgical input, often via more than one operation, if the flexor tendon function is to be restored.

The gap between tendon ends is best overcome by use of the tendon graft which is harvested from the forearm (Picture 7; Gallery below) or leg, pending individual anatomical circumstances. One of the less important tendons needs to be sacrificed for this, but hand surgeons know well which of those would lead to no functional impairment. Graft also needs to be placed within the fine, protective, lubricated tunnel in order to glide freely and transmit the pull between the muscle and bone/distal tendon end. If injury is to be addressed within the first 4-8 weeks, it might just be possible to use existing flexor tunnel, before it collapses completely. Beyond 8 weeks from injury, such tunnel is expected to be replaced by scarring completely, so a new one will have to be created first. At least two operations are therefore required, several months apart.

During the first operation, a special, off the shelf, silicon rod is inserted into the finger first and left in place for 3-6 months (Picture 8). In expected and physiological reaction to the foreign body, tissues around silicone rod will create a specialised, smooth scar tissue layer which will act as a new tendon tunnel.

After 3-6 months of supervised hand therapy, second operation can be carried out whereby the silicone rod is pulled out and tendon graft inserted instead in well established, new tendon tunnel (Picture 9). Another 6-12 months of intense rehabilitation is required after this intervention.

Brief and simplified description above will hopefully exemplify well how important is to recognise and treat hand injuries early. Timely management is simpler, less time consuming and with ultimately, much better outcome.

Unfortunately, complications are common after tendon surgery, especially flexor mechanism. Please note below the commonest complications:

• Infection and wound breakdown
• Repair failure/ rupture (5-15% cases) requiring additional surgery
• Adhesions/scarring around tendon repair requiring further surgery
• Stiffness (reduced range of motion)
• Complex Regional Pain Syndrome (CRPS) – rarely people are sensitive to hand surgery and their (seen in 5% of surgery) hand may become very swollen, painful and stiff after any operation.
• Scar sensitivity

Rehabilitation most commonly includes wearing a custom made splint for minimum of 6 weeks. During that time fingers however have to be mobilised to stop repaired tendons sticking to nearby tissues i.e. prevent adhesions around tendon which can compromise tendon gliding and ideal outcome. Specialist hand therapist guidance is indispensible in conducting this process.

It takes 6-8 weeks for repaired tendon ends to bond together and another 6-8 weeks for that repair to regain full biomechanical strength. During those 3 months hand therapy is essential yet demanding, but without compliance and dedications with therapy there is no successful recovery from tendon surgery. Naturally, delayed repairs and reconstructions indicated for missed tendon injuries require considerablymore time, patient’s compliance and expertise.

Return to work will depend on your job and exact injury details, but tendon injury and its surgery (especially flexor tendon repairs) can affect your work for a considerable length of time. Light activities can often be resumed after 6-8 weeks and heavy activities and sport after 10-12 weeks.