Extensor Tendon Injuries

Introduction

Extensor tendon injuries refer to disruptions of the tendons that straighten the fingers, thumb, or wrist. These injuries are common and often occur from lacerations, jamming injuries, or trauma to the dorsal (back) side of the hand. Unlike flexor tendons (which bend the fingers), extensor tendons lie just beneath the thin skin on the dorsum, making them vulnerable to injury. They are organized into specific zones (I–VIII) along the finger, hand, and forearm to describe injury location (e.g. zone I at the fingertip, zone III at the middle joint, zone V at the knuckle, etc.). This zonal classification helps predict which structures are involved and guides treatment emedicine.medscape.com emedicine.medscape.com. Common patterns include mallet finger (zone I injury causing inability to extend the fingertip), boutonnière deformity (zone III injury causing a bent middle joint and hyperextended fingertip), and sagittal band rupture (zone V injury at the knuckle leading to extensor tendon subluxation to one side). Early recognition and proper management are critical, as chronic extensor tendon injuries can lead to permanent deformity and functional deficits emedicine.medscape.com. In the following sections, we review the relevant anatomy, typical presentations, diagnostic workup, and evidence-based management of extensor tendon injuries in the hand, wrist, and forearm – key knowledge for the FESSH exam.

Key takeaways

• Extensor tendon zones: There are 8–9 extensor tendon zones from the fingertip (zone I) to the forearm (zone VIII/IX). Injuries in each zone have characteristic deformities (e.g. zone I – mallet finger; zone III – boutonnière; zone V – sagittal band injury).

• Mechanism of injury: Extensor tendons are thin and superficially located, making them prone to lacerations and avulsions. Closed injuries like mallet finger (jammed fingertip) and boutonnière (forced flexion of a bent PIP joint) can be subtle initially but lead to significant deformities if untreated.

• Clinical exam & imaging: Look for extensor lag at each joint. Always examine each finger individually – juncturae tendinum (inter-tendon connections) can mask a tendon rupture by allowing neighboring tendons to extend the finger. Obtain X-rays to detect avulsion fractures or foreign bodies. Ultrasound is highly sensitive for detecting extensor tendon lacerations, often outperforming MRI in acute injuries pmc.ncbi.nlm.nih.gov.

• Management approach: Many extensor tendon injuries can be managed nonoperatively with splinting if criteria are met (e.g. closed mallet finger without large fracture, acute sagittal band rupture). Operative repair is indicated for open lacerations, complete ruptures, large bony avulsions, or injuries that fail conservative treatment. Early controlled mobilization (e.g. with a relative motion splint) after repair can improve outcomes by reducing stiffness pubmed.ncbi.nlm.nih.gov.

• Outcomes: With appropriate treatment and hand therapy, most extensor tendon injuries regain good function. Evidence suggests that for certain injuries like mallet finger, well-managed splinting yields outcomes comparable to surgery pubmed.ncbi.nlm.nih.gov. However, poor compliance or delayed treatment can result in complications such as swan-neck deformity, chronic extensor lag, or joint contractures.

Anatomy & Pathophysiology

The extensor tendons of the hand originate from muscles in the forearm (primarily the lateral epicondyle of the humerus and proximal forearm) and course down the dorsal wrist and hand to the fingers emedicine.medscape.com. At the wrist, they are organized into six dorsal extensor compartments, numbered from radial (thumb) to ulnar side emedicine.medscape.com. Each compartment contains specific tendons, for example: compartment 1 holds the abductor pollicis longus and extensor pollicis brevis (thumb extensors), compartment 3 holds the extensor pollicis longus, and compartment 4 contains the extensor digitorum communis (EDC) tendons to the fingers and extensor indicis emedicine.medscape.com. The extensor tendons are secured at the wrist by the extensor retinaculum. As they pass over the dorsum of the hand, the EDC tendons to the index through small finger are interconnected by fibrous bands called juncturae tendinum, which help coordinate finger extension.

In the fingers, the extensor tendons form a complex extensor mechanism (extensor hood). Over the back of the proximal phalanx, the EDC tendon broadens into a fibrous hood that receives contributions from the lumbrical and interosseous muscles. At the level of the proximal interphalangeal (PIP) joint, the extensor mechanism divides into a central slip (inserting on the base of the middle phalanx) and two lateral bands that run along the sides and reunite to attach at the distal phalanx. This arrangement allows the extensor muscles to extend both the PIP and distal interphalangeal (DIP) joints.

Injury Zones: Extensor tendon injuries are classified by zones (I through VIII) numbered from distal to proximal emedicine.medscape.com emedicine.medscape.com. Each zone has unique anatomical features and injury patterns:

• Zone I: Terminal extensor tendon over the DIP joint. Injury (often a sudden forceful flexion of an extended fingertip) can avulse the tendon from its insertion, causing a mallet finger – the DIP droops into flexion and cannot be actively extended. If the injury avulses a piece of bone, it’s a bony mallet. Loss of the terminal extensor disrupts the extensor-extensor balance, and over time, the PIP joint may hyperextend (swan-neck deformity) due to volar plate laxity emedicine.medscape.com.

• Zone II: Tendon over middle phalanx. Injuries here are usually lacerations. Complete laceration behaves like a zone I injury (loss of DIP extension) because the distal tendon attachment is lost emedicine.medscape.com. If the oblique retinacular ligament is intact, there may be minimal acute deformity emedicine.medscape.com.

• Zone III: Central slip over PIP joint. Disruption (from laceration or a jammed finger) leads to inability to extend the PIP. The lateral bands slip volarly, causing the classic boutonnière deformity (PIP flexion with DIP hyperextension) emedicine.medscape.com. This deformity may develop over 1–3 weeks rather than immediately. A simple way to test for a zone III injury is the Elson test (bend the PIP 90° over a table edge and ask the patient to extend the finger – inability to extend or weak extension with a rigid DIP indicates central slip tear).

• Zone IV: Proximal phalanx. Injuries may involve the extensor hood. Lacerations here often also disrupt the central slip or lateral bands. Clinical exam might show an extensor lag at the PIP.

• Zone V: MCP joint (knuckle) region. The common injury is a sagittal band rupture, often from a punch (called a “boxer’s knuckle”). The sagittal band normally centers the EDC tendon over the MCP. A tear (usually of the radial sagittal band of the middle or ring finger) allows the extensor tendon to sublux ulnarward off the MCP pubmed.ncbi.nlm.nih.gov. The patient cannot fully extend the MCP and may feel the tendon “snap” to the side. If the injury is due to a human bite over the knuckle (fight bite), the wound is considered contaminated and prone to infection. In such cases, the extensor tendon is often partially lacerated. (Notably, any laceration over an MCP joint should raise concern for a fight bite with joint penetration.)

• Zone VI: Dorsal hand. These injuries involve the extensor tendons between the juncturae and wrist. Because of the interconnections, an isolated EDC laceration in the hand may not cause obvious finger drop – adjacent tendons via the juncturae can extend the finger to some degree emedicine.medscape.com. This can mask the injury on exam. Multiple tendons can be injured by deeper lacerations (e.g. from glass or knives) across the dorsum of the hand.

• Zone VII: Dorsal wrist (extensor retinaculum). Injuries here may involve the retinaculum itself in addition to tendons. A complete laceration causes the tendon to retract proximally, often beneath the cut retinaculum. If repairing a tendon at this level, surgeons often perform a Z-lengthening of the retinaculum to prevent constriction of the repair emedicine.medscape.com.

• Zone VIII: Distal forearm. Tendon or muscle-tendon junction injuries in the forearm can result from trauma or even attrition (e.g. extensor pollicis longus can rupture after a distal radius fracture). In the forearm, the extensor tendons are rounder and begin to transition into muscle; lacerations here are usually repaired with core suture techniques similar to flexor tendon repairs emedicine.medscape.com. If the muscle belly is injured, direct repair may be difficult and tendon transfer might be required in chronic cases (for example, using the extensor indicis proprius tendon to restore extensor pollicis longus function in a chronic EPL rupture emedicine.medscape.com).

Pathophysiology: When an extensor tendon is cut or avulsed, the ability to actively extend the associated joint(s) is lost. The degree of functional deficit and deformity depends on the zone and whether other supporting structures remain intact. For instance, terminal tendon avulsion (zone I) leads to unopposed flexion at the DIP (mallet finger). A central slip tear (zone III) initially causes a PIP extensor lag; subsequently, the imbalance of forces (lateral bands dropping volarly) produces the boutonnière posture (PIP flexed, DIP hyperextended) emedicine.medscape.com. In sagittal band injuries (zone V), the extensor tendon slips out of alignment, so the MCP cannot be actively extended even though the tendon itself is intact. Partial lacerations of extensor tendons can be tricky – if more than ~30–50% of the tendon is cut, the remaining fibers may not sustain extension, or they may “trigger” (catch) on the injury site emedicine.medscape.com. Incomplete tears can also progress to full rupture if stressed.

Additionally, because extensor tendons lack the bulky synovial sheaths and pulleys of the flexor side, they are more prone to adhesion formation during healing. This can lead to stiffness if rehabilitation is not optimized. On the other hand, the blood supply to extensor tendons is somewhat better, and they can tolerate immobilization in extension (which places less tension on the repair) better than flexors can. These factors influence management strategies, as discussed later.

Clinical Presentation

Patients with extensor tendon injuries may present with an obvious laceration or a more subtle loss of finger motion. Key aspects of the clinical presentation include:

• Visible Wound: In open injuries (e.g. cuts from a knife, glass, or a bite), there may be a laceration over the dorsal hand or finger. The patient might notice immediate loss of the ability to straighten the affected finger or thumb. For example, a laceration over the dorsal MCP joint that results in the extensor tendon slipping off will present as the finger staying flexed at that knuckle. In the case of a human bite over the knuckle, there may be a small puncture wound with surrounding redness – clinicians should suspect a septic joint or tendon involvement in these “fight bite” injuries.

• Extensor Lag: In closed injuries, the patient may not have a cut, but will have difficulty actively extending one or more joints. A classic example is the mallet finger – often resulting from a ball striking the fingertip. The patient cannot straighten the DIP joint, which droops (~45°) into flexion. They can usually still extend the PIP joint normally. There may be mild pain and swelling at the DIP. If a fragment of bone was avulsed, the DIP joint can also be slightly misaligned. Another example is an acute boutonnière injury: initially, the PIP joint may be painful and swollen, with limited extension, but not yet fixed in a bent position. Over 1–2 weeks, if untreated, the boutonnière deformity manifests more clearly as the PIP contracts into flexion and the DIP hyperextends. Patients might present later with this fixed deformity if the central slip injury was missed early.

• “Snapping” or Subluxation: Patients with sagittal band rupture (extensor hood injury at the MCP) often describe that the extensor tendon “pops” to one side of the knuckle when they try to extend the finger. They may have pain and swelling at the MCP. On exam, the MCP of the involved finger (commonly the middle finger) will droop slightly, especially when the fist is made, and the patient has difficulty initiating extension at that joint. You might palpate the extensor tendon slipping off the knuckle. This injury can be tested by having the patient slightly flex the MCP 10–15° and extend against resistance – in radial sagittal band tears, the tendon will dislocate ulnarly and the finger will not extend.

• Multiple Tendon Injury: High-energy trauma (e.g. crush or extensive laceration) can injure several extensor tendons. Patients will have a combined loss of extension in multiple fingers or the wrist. For instance, a dorsal wrist laceration could cut the extensor tendons to the fingers and thumb, as well as the extensor carpi tendons – the patient then presents with an inability to extend the wrist and fingers (a flail wrist/drop finger posture). If the posterior interosseous nerve was injured (in proximal forearm injuries), there may be a complete inability to extend the fingers and thumb despite intact tendons.

On examination, important steps include inspecting for wounds or deformities, and testing active extension of each joint of each finger and the wrist. The examiner should support the adjacent joints to isolate the extensor function. For example, to test the central slip (zone III) in a suspected boutonnière, the wrist and MCP are flexed (to neutralize the long extensor) and the patient tries to extend the PIP – an extensor lag or inability indicates central slip disruption emedicine.medscape.com. Similarly, to test a suspected sagittal band injury, observe the extensor tendon position during finger motion; an ulnar subluxation of the tendon on a flexed MCP that corrects when the MCP is extended is pathognomonic.

Neurological and vascular exam of the hand is also necessary, as dorsal injuries can sometimes coincide with nerve or vessel damage (though palm-sided neurovascular structures are usually uninjured in isolated dorsal lacerations). In cases of fight bites, look carefully for signs of infection (redness, warmth, purulent discharge) and assess if the joint capsule is violated (which often it is).

Diagnosis

Most extensor tendon injuries are diagnosed clinically by history and physical exam. Key diagnostic considerations include:

• Physical Examination: The cornerstone of diagnosis is the exam of active and passive range of motion. If a patient cannot actively extend a joint but passive extension is full, an extensor tendon injury is likely. For closed injuries, special tests like the Elson test (for central slip) help detect partial tears before deformity appears. Comparing to the opposite hand can be useful for subtle deficits. Pain with resisted extension may indicate a partial tear. In the case of sagittal band injuries, observing the tendon position relative to the MCP (with the fist clenched versus fingers extended) is diagnostic.

• Imaging – X-ray: Plain radiographs should be obtained for virtually all significant extensor tendon injuries (especially zone I and III injuries, or any with trauma) emedicine.medscape.com. X-rays can reveal avulsion fractures (e.g. bony mallet finger where a fragment of the distal phalanx is avulsed emedicine.medscape.com, or a small fragment from the dorsal base of the middle phalanx in a central slip injury). In a mallet injury, if the bony fragment is large (>30% of the joint surface) or the DIP joint is subluxed, this influences management (often requiring pinning) emedicine.medscape.com. X-rays also detect foreign bodies (like glass) or gas in tissues (infections). In fight bites, an x-ray may show a chipped metacarpal head or foreign material from the tooth.

• Ultrasound (US): Bedside high-frequency ultrasound is an excellent tool for evaluating tendon integrity in the hand. It can directly visualize extensor tendons and detect discontinuity or a partial tear. Studies have shown ultrasound to be very accurate for acute extensor tendon lacerations – one cadaveric study demonstrated near 100% sensitivity and specificity for detecting extensor tendon injuries with dynamic ultrasound emedicine.medscape.com. In clinical series, ultrasound has outperformed MRI for diagnosing extensor tendon injuries, especially in delayed presentations. In a 2023 study of missed hand tendon injuries, ultrasound had ~84% sensitivity and accuracy for extensor tendon tears, whereas MRI had only ~44% sensitivity pmc.ncbi.nlm.nih.gov. Ultrasound is quick, can be done in the emergency setting, and also allows dynamic assessment (e.g. seeing the tendon ends move with finger motion). It is operator-dependent, but even surgeons with brief training have been shown to locate extensor tendon ends with ultrasound reliably pmc.ncbi.nlm.nih.gov.

• MRI: MRI is generally not first-line for acute extensor tendon injuries. It may be used in ambiguous cases or chronic injuries to assess tendon retraction or scar. As noted, MRI is very sensitive for flexor tendon issues, but for extensor side injuries ultrasound tends to be more practical. MRI might be considered if there are concurrent ligament or bone injuries (for example, in a complex dorsal hand trauma with suspected ligamentous injury or chronic boutonnière to evaluate the soft tissue). However, given the accessibility of ultrasound and the superficial location of extensor tendons, MRI is often unnecessary.

• Other: If infection is suspected (fight bite), lab tests (WBC, CRP) and possibly joint aspiration may be indicated. For complex injuries, surgical exploration can be diagnostic as well as therapeutic.

Combining the clinical exam with appropriate imaging usually yields the diagnosis. For example, in a mallet finger, the triad of mechanism (jammed finger), exam (DIP extensor lag), and X-ray (ą avulsion fragment) confirms the diagnosis. In partial tendon lacerations, imaging can help quantify the extent of the cut. It’s important to document the exam findings carefully, as this guides treatment choice (operative vs nonoperative).

Treatment Options

Management of extensor tendon injuries depends on the zone of injury, whether the injury is open or closed, the presence of fractures, and the chronicity. Broadly, options range from splinting (nonoperative) to surgical repair, and each has variations. Early consultation with a hand surgeon is recommended for significant injuries. Below we outline treatment approaches by injury type, followed by a comparison table of options:

Zone I (Mallet Finger): The standard treatment for a closed mallet finger (no large fracture) is strict immobilization of the DIP in extension using a stack splint or custom thermoplastic splint for about 6–8 weeks emedicine.medscape.com. The PIP joint is left free. This allows the torn tendon end to heal to the bone. Patient compliance is crucial – the splint must be worn continuously, as even a brief lapse can re-gap the healing tendon emedicine.medscape.com. If after 6–8 weeks the patient has no extensor lag, gentle motion is started; if lag >0–10° remains, additional splint time or nighttime splinting is done. Closed mallet injuries do very well with splinting in most cases (success rates ~85-90%). Surgery is usually reserved for mallet injuries with a large bony avulsion (>30% of joint surface) or volar subluxation of the DIP joint emedicine.medscape.com, or for open mallet injuries. Surgical options include percutaneous pinning of the DIP joint in extension (often with a Kirschner wire) or an “extension block” pin technique for bony mallets. A recent comparative study by Nagura et al. (2020) found that in purely tendinous mallet injuries, patients treated with oblique K-wire fixation of the DIP had a significantly smaller residual extensor lag (mean ~2°) compared to those treated with splinting (~14° lag) pubmed.ncbi.nlm.nih.gov. However, splinted patients who were compliant also achieved good outcomes, and a 2023 systematic review (meta-analysis) concluded that overall there is no high-level evidence of superiority of surgery over splinting for mallet fingers – both methods can provide similar excellent results in most cases pubmed.ncbi.nlm.nih.gov. Surgery carries risks such as pin track infection, nail bed injury, or skin necrosis from dorsal tension. Thus, the consensus is to splint uncomplicated mallets and reserve surgery for specific indications or failed conservative treatment pubmed.ncbi.nlm.nih.gov. In an open mallet (laceration causing tendon detachment), surgical repair of the terminal tendon is indicated (often with a pull-out suture or anchor), typically supplemented by temporary DIP pinning or continuous splinting emedicine.medscape.com. Chronic mallet deformities (>3 months old) are harder to treat; if the fingertip can still passively straighten, a trial of splinting may still improve it emedicine.medscape.com, but fixed deformities might ultimately need DIP arthrodesis (fusion) for a stable, functional finger.

Zone III (Boutonnière): For an acute closed central slip injury (boutonnière), initial treatment is splinting the PIP joint in full extension for about 6 weeks, with the DIP joint free to move emedicine.medscape.com. This allows the torn central slip to heal. During this period, DIP flexion exercises are encouraged to prevent lateral band adhesions and to help restore them dorsal to the axis. If a small avulsion fracture is present but the PIP is congruent, this is treated similarly (or with a brief period of pin fixation if the fragment is large enough to significantly affect joint stability). If the boutonnière injury is open (laceration of the central slip), surgical repair of the central slip is performed, usually with the PIP pinned or splinted in extension for 4–6 weeks post-operatively emedicine.medscape.com. After splinting, careful therapy is started to regain flexion. Established boutonnière deformities (weeks to months old) are challenging – if the PIP joint is stiff in flexion, therapy or surgical releases are needed to regain extension before attempting tendon reconstruction emedicine.medscape.com. Chronic cases might require procedures such as lateral band mobilization or central slip reconstruction (e.g. Fowler tenotomy, or dorsal tenotomy of the extensor to balance extension). Early management is therefore critical to avoid these complex surgeries. In rheumatoid arthritis patients, chronic boutonnière often coexists with joint disease and may be managed with ring splints or arthrodesis if severe. Fortunately, most acute boutonnière injuries that are treated with extension splinting heal well, and motion can be regained gradually with hand therapy.

Zone V (MCP/Sagittal Band): Sagittal band (extensor hood) injuries can often be managed nonoperatively if acute. The recommended treatment for an acute sagittal band rupture is splinting the involved MCP joint in full extension (or using a relative motion extension splint that holds the affected finger slightly extended relative to the others) for about 3–4 weeks pubmed.ncbi.nlm.nih.gov. This allows the torn sagittal band to scar down and the extensor tendon to remain centralized. A systematic review by Wu et al. (2021) found that acute (<3 weeks) sagittal band injuries were successfully treated with extension splinting in most cases, with low rates of persistent subluxation pubmed.ncbi.nlm.nih.gov. During splinting, the patient is encouraged to move the PIP and DIP joints to prevent stiffness. If the injury is chronic (tendon subluxation already persistent, or injury neglected for >3 weeks) or if the nonoperative treatment fails (continued instability of the tendon after splinting), then surgical repair is indicated pubmed.ncbi.nlm.nih.gov. Surgical treatment involves either direct repair of the sagittal band (suturing the torn ends, often through bone tunnels or with suture anchors) or a reconstruction using a slip of nearby tendon to reconstruct the sling. Postoperatively, the MCP is usually immobilized in extension for ~3 weeks, similar to the nonoperative protocol. Notably, if a sagittal band injury is due to a rheumatoid subluxation (common in RA, where chronic synovitis attenuates the sagittal bands), the approach may differ (often requiring synovectomy and tendon centralization, and treating the underlying rheumatoid disease). Fight bite lacerations over the MCP (which often partially injure the extensor tendon and sagittal band) deserve special mention: due to the high risk of infection from human oral flora, these injuries are managed with urgent irrigation, debridement, and antibiotics. Tendon repair is usually delayed until the infection is controlled and wound is clean emedicine.medscape.com. During that interim, the finger is splinted in extension. Once it’s safe, the extensor tendon and sagittal band can be formally repaired (often 1–2 weeks later). This staged approach prevents trapping bacteria inside a repaired tendon. If the extensor tendon was completely severed by the bite, sometimes a tendon graft is needed at the time of delayed repair if ends are retracted or deficient.

Zones VI–VIII (Dorsal hand/wrist/forearm): Open lacerations in these zones generally require surgical repair. In zone VI (dorsum of hand), because multiple tendon slips or juncturae may be involved, all divided structures should be repaired to restore full extension of each finger emedicine.medscape.com. The repair is typically done with a figure-of-8 or horizontal mattress suture in the thin, flat tendon material emedicine.medscape.com. If the extensor retinaculum (zone VII) is cut, it should be repaired (often lengthened) to prevent bowstringing of tendons across the wrist. Zone VIII injuries (distal forearm) are repaired with core sutures (e.g. 4-strand core stitch, similar to flexor tendon technique) since the tendons are rounder here emedicine.medscape.com. In the forearm, if a muscle belly is transected, direct repair may be attempted but under tension it might not hold; sometimes a tendon transfer is planned later if function is lost. After surgical repair of zones V–VIII injuries, the wrist and digits are usually immobilized in extension to protect the repairs. A common position is wrist ~40–45° extension, MCP joints 0° (full extension), and IP joints slight flexion (to relax the lateral bands) in a cast or splint for about 3–4 weeks.

Partial Lacerations: Partial cuts to extensor tendons present a management dilemma. For small partial tears (often <30% of tendon width) that do not significantly affect extension strength, one can treat with splinting (or even just buddy taping/support) for a short period to allow healing emedicine.medscape.com. The tendon often scars and remodels. However, larger partial lacerations (>50% of the tendon diameter, or those causing obvious extensor weakness/triggering) are usually best treated by surgical repair (trimming and suturing the partial tear) emedicine.medscape.com. If left untreated, a significant partial tear can catch on adjacent tissue and eventually rupture or cause painful snapping with motion emedicine.medscape.com. A recent systematic review (Dickson et al. 2023) noted that high-quality evidence on partial extensor laceration management is limited, with practice varying; generally, most surgeons use the 50% rule as a guideline (repair if more than half the tendon is injured) pubmed.ncbi.nlm.nih.gov. Intraoperatively, if a partial injury is found, the surgeon will often complete the laceration and then repair it (because a clean cut repair will heal better than a ragged partial tear).

Rehabilitation and Early Motion: A critical aspect of extensor tendon injury management is the post-treatment rehabilitation. Historically, repaired extensor tendons were immobilized in extension for about 4 weeks to ensure healing, since extending (stretching) a repaired tendon too soon risked pulling the repair apart. While this protective immobilization prevents rupture, it can result in joint stiffness and adhesions. Modern approaches often favor early controlled motion protocols for extensor tendon repairs in certain zones, to improve final range of motion. One popular method is the use of a relative motion orthosis (RMO) – a splint that holds the injured finger’s MCP in slight extension relative to the adjacent fingers. This allows the patient to gently flex and extend the fingers within a safe range almost immediately after surgery. Early motion under controlled conditions can stimulate tendon healing and prevent adhesion. Recent developments, including performing tendon repair under WALANT (Wide Awake Local Anesthesia No Tourniquet), even allow the surgeon to have the patient actively move the finger during the repair to fine-tune tension pubmed.ncbi.nlm.nih.gov. For example, Merritt et al. (2020) highlight that beginning protected movement at 3-5 days post-op with a relative motion extension splint can lead to faster return to activities and excellent outcomes in zone V–VI repairs pubmed.ncbi.nlm.nih.gov pubmed.ncbi.nlm.nih.gov. Many hand therapy protocols (e.g. the Evans or Merritt protocol) incorporate early motion using either dynamic extension splints or yoke splints. The balance is to avoid excessive tension on the repair while preventing stiffness. Typically, for zones V–VI, an RMO is used along with a wrist splint (wrist in slight extension) for the first few weeks, and the patient performs limited active flexion-extension within the orthosis. Zones VII–VIII (tendons under the retinaculum) are often managed with slightly longer immobilization due to risk of bowstringing. Regardless, close follow-up with a hand therapist is essential. After 4–6 weeks, strengthening and endurance exercises are added. Most patients achieve near full extension, but a mild extensor lag (especially at the PIP or DIP) is not uncommon despite optimal care.

The following table compares common treatment modalities for extensor tendon injuries, with their pros/cons and relevant evidence:

After treatment (whether splint or surgery), hand therapy is essential. Therapists will gradually mobilize the affected joints, monitor extensor lags, and sometimes fabricate custom splints (e.g. dynamic extension outriggers or relative motion splints). Typical total rehabilitation time for an extensor tendon injury is about 8–12 weeks of progressive therapy. Common complications to watch for include residual extensor lag (if the tendon heals lengthened or scarred) and extensor adhesions limiting flexion (if scar binds the tendon, requiring possible tenolysis later). Balanced, evidence-based management helps optimize outcomes and is a key focus of board examinations like FESSH.

Practice Questions – True/False

Question 1: A 30-year-old male presents after injuring his right long finger playing basketball. He reports the fingertip was forcibly “jammed” into flexion while his finger was extended. On exam, the DIP joint of the long finger rests in about 45° of flexion and the patient is unable to actively extend it. The rest of the finger’s motion is normal. X-ray shows a small dorsal avulsion fragment involving 20% of the distal phalanx articular surface without subluxation. Regarding this injury (mallet finger), which of the following statements are true or false?

This injury is classified as an extensor zone I injury.

The preferred initial treatment is continuous splinting of the DIP in extension for about 6 weeks.

An avulsion involving 20% of the joint surface with an intact, congruent joint can be managed nonoperatively.

Without proper treatment, this injury can lead to a swan-neck deformity of the finger.

Surgical pinning of the DIP joint has been shown to result in less extensor lag than splinting in some studies.

Question 2: A 25-year-old boxer strikes a wall and injures his right hand. He now notes his ring finger knuckle is painful and the finger tends to “give out” when trying to extend. On exam, there is slight extensor lag at the ring finger MCP joint. The extensor tendon over that MCP is observed to sublux ulnarly when he flexes the finger. The tendon recentralizes when the MCP is extended. There is no gross instability of the PIP or DIP joints. He has a small 1 cm longitudinal laceration over the dorsal MCP (no signs of infection). Concerning this extensor mechanism injury, identify each statement as true or false:

The clinical scenario is most consistent with a sagittal band (extensor hood) rupture of the ring finger.

The extensor tendon is subluxing in an ulnar direction at the MCP joint.

Initial management should consist of surgical exploration and primary repair within 24–48 hours, as acute sagittal band injuries require urgent surgery.

Splinting the MCP joint in full extension for 3–4 weeks is a recognized treatment for acute sagittal band injuries.

This injury corresponds to extensor zone V.

References

1. Peng C, Huang RW, Chen SH, et al. Comparative outcomes between surgical treatment and orthosis splint for mallet finger: a systematic review and meta-analysis. J Plast Surg Hand Surg. 2023;57(1-6):54-63. pubmed.ncbi.nlm.nih.gov (Open Access)

2. Wu K, Masschelein G, Suh N. Treatment of sagittal band injuries and extensor tendon subluxation: a systematic review. Hand (NY). 2021;16(6):854-860. pubmed.ncbi.nlm.nih.gov (Open Access)

3. Nagura S, Suzuki T, Iwamoto T, et al. A comparison of splint versus pinning the distal interphalangeal joint for acute closed tendinous mallet injuries. J Hand Surg Asian Pac Vol. 2020;25(2):172-176. pubmed.ncbi.nlm.nih.gov*

4. Merritt WH, Wong AL, Lalonde DH. Recent developments are changing extensor tendon management. Plast Reconstr Surg. 2020;145(3):617e-628e. pubmed.ncbi.nlm.nih.gov *

5. Bezirgan U, Acar E, Erdoğan Y, et al. The diagnostic value of ultrasonography and MRI in missed hand tendon injuries. Ulus Travma Acil Cerrahi Derg. 2023;29(5):677-684. pmc.ncbi.nlm.nih.gov (Open Access)

6. Dickson K, Mantelakis A, Reed AJM, et al. The management of partial extensor tendon lacerations of the hand and forearm: a systematic review. J Plast Reconstr Aesthet Surg. 2023;85:34-43. *

7. Elzinga K, Chung KC. Managing swan neck and boutonnière deformities. Clin Plast Surg. 2019;46(3):329-337. *

8. James N, Farrell N, Mauck B, Calandruccio J. Sagittal band injury and extensor tendon realignment. Orthop Clin North Am. 2022;53(3):319-325. pubmed.ncbi.nlm.nih.gov *

Disclaimer

This content is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for medical concerns.