Overview
Definition:
Zone II of the flexor tendon system in the hand, often termed "no man's land", extends from the distal palmar crease to the insertion of the flexor digitorum superficialis
Injuries in this zone are complex due to the tight space, lack of mesotenon, and the presence of vital structures, making tendon repair and subsequent rehabilitation critically important for functional recovery.
Epidemiology:
Flexor tendon injuries are common, particularly in younger, active individuals
Zone II injuries constitute a significant proportion of these
Factors like type of injury (laceration, avulsion), mechanism, and patient compliance influence outcomes.
Clinical Significance:
Successful repair and meticulous rehabilitation in Zone II are paramount to restore full digital motion and prevent long-term disability
Adhesions are a major concern, leading to restricted motion and functional impairment, directly impacting a patient's quality of life and ability to perform daily activities and work
Early and coordinated management is key.
Clinical Presentation
Symptoms:
Inability to actively flex the injured finger at the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints
Pain at the site of injury
Palpable defect or gap if the tendon is completely severed
Bleeding may be present depending on the wound
Loss of passive extension of the PIP joint can suggest a "buttonhole" deformity if the flexor digitorum profundus (FDP) is retracted proximally.
Signs:
Loss of active flexion at the PIP joint and DIP joint
Inability to make a fist
Passive flexion may be possible but limited
Tenderness over the palmar aspect of the finger
Visible wound or scar
A positive "lag" of the finger when attempting to flex the adjacent fingers (indicating FDP rupture).
Diagnostic Criteria:
Diagnosis is primarily clinical, based on the mechanism of injury, patient history, and physical examination findings of loss of active flexion
If the wound is complex or the diagnosis is unclear, imaging may be considered, though direct visualization during exploration is definitive.
Diagnostic Approach
History Taking:
Detailed history of the injury mechanism (e.g., sharp laceration, crush injury, avulsion)
Time since injury
Patient's occupation and dominant hand
Previous hand surgeries or injuries
Assessment of tetanus immunization status
Evaluation of sensation and vascular status distal to the injury.
Physical Examination:
Careful assessment of all digits for tendon injuries
Assess active and passive range of motion of all finger joints (MCP, PIP, DIP)
Assess sensation (light touch, two-point discrimination)
Assess vascularity (capillary refill, pulse)
Evaluate for concomitant nerve or vessel injury.
Investigations:
Radiographs are primarily used to rule out bony injury (fractures, dislocations) or foreign bodies
Ultrasound may sometimes be used to assess tendon integrity and extent of injury preoperatively, but it is not routinely necessary
The definitive diagnosis and assessment of tendon status are made during surgical exploration.
Differential Diagnosis:
Extensor tendon injury
Nerve injury (digital nerve laceration)
Vascular injury
Joint capsule injury
Contusion or sprain
Fracture-dislocation
Skin and soft tissue loss.
Management
Initial Management:
Thorough wound irrigation and debridement
Assess for tendon, nerve, and vascular integrity
If tendon is injured, ensure adequate visualization
Gentle splinting to protect the repaired tendon, typically in a position of slight flexion
Tetanus prophylaxis if indicated
Antibiotic prophylaxis is often administered
Urgent surgical consultation is required.
Surgical Management:
Surgical repair is indicated for complete flexor tendon injuries in Zone II
Primary repair aims to approximate tendon ends with minimal tension
Techniques include modified Kessler, Savage, or epitendinous suture techniques using fine, non-absorbable monofilament sutures (e.g., 4-0, 5-0, 6-0 Prolene or Nylon)
Avoidance of excessive knots or bulky suture material within the tendon sheath is crucial to minimize adhesion formation
Repair should ideally be done within 7-10 days of injury, though delayed repairs are possible
Consideration for tendon grafting if the gap is too large for primary repair or if there is significant tendon loss
Nerve repair should be performed concurrently if digital nerves are severed
Consideration for vascular repair if indicated.
Rehabilitation Protocol:
Postoperative rehabilitation is critical and typically involves a structured protocol
It starts with immobilisation in a protective splint (e.g., volar splint or dynamic splint)
Passive range of motion exercises are initiated early (often within 3-5 days), followed by controlled active motion and tendon gliding exercises
A common protocol includes: 1
Early passive flexion and extension (within splint limitations)
2
Tendon gliding exercises (e.g., hook fist, straight fist, full fist)
3
Gentle active flexion exercises
4
Progressive strengthening
This phased approach aims to prevent adhesions while allowing tendon healing
Supervision by a trained hand therapist is essential.
Supportive Care:
Pain management with analgesics
Edema control with elevation and compression
Wound care and monitoring for signs of infection
Patient education on splint wear, exercise regimen, and danger signs.
Complications
Early Complications:
Tendon rupture during rehabilitation
Infection
Wound dehiscence
Stiffness due to premature adhesion formation
Extensor lag due to inadvertent injury to extensor mechanism
Nerve injury during repair
Volar plate subluxation.
Late Complications:
Persistent stiffness
Adhesions causing restricted motion
Triggering of the digit
Tendon bowstringing
Malunion or non-union of bony fragments if associated fracture
Chronic pain
Loss of grip strength.
Prevention Strategies:
Meticulous surgical technique to minimize trauma and knotting
Early and diligent adherence to a structured rehabilitation protocol
Close supervision by a hand therapist
Appropriate splinting
Patient compliance with exercises and activity restrictions
Prophylactic antibiotics and tetanus immunization.
Prognosis
Factors Affecting Prognosis:
Zone of injury (Zone II is most challenging)
Type and extent of injury
Quality of tendon repair
Patient age and health status
Strict adherence to postoperative rehabilitation protocol
Presence of concomitant nerve or vessel injury
Surgeon's experience
Avoidance of infection.
Outcomes:
With optimal repair and rehabilitation, good to excellent functional outcomes can be achieved, including full or near-full range of motion
However, some degree of stiffness or limitation may persist, especially with challenging injuries or poor compliance
Full return to pre-injury level of function, particularly for manual laborers, may take several months
Poor outcomes are characterized by significant stiffness, limited motion, and chronic pain.
Follow Up:
Regular follow-up with the hand surgeon and hand therapist is crucial
Typically, initial follow-up is at 1-2 weeks post-op for suture removal and assessment of wound healing
Subsequent visits monitor progress of rehabilitation, range of motion, and to adjust the protocol as needed
Long-term follow-up may be required for several months to ensure sustained functional recovery and address any emerging issues.
Key Points
Exam Focus:
Zone II is "no man's land" due to high adhesion risk
Meticulous surgical repair and early, structured rehabilitation are key
The goal is to achieve tendon healing without excessive scarring
Tendon gliding exercises are fundamental
Know the different phases of rehabilitation and common complications like stiffness and rupture.
Clinical Pearls:
Use fine monofilament non-absorbable sutures for repair
Avoid bulky knots and excessive tension
A circumferential epitendinous suture provides optimal strength
Early passive motion is vital to prevent adhesions
If passive motion is possible but active is not, suspect tendon injury
Concurrent digital nerve repair is often necessary.
Common Mistakes:
Aggressive early active motion leading to rupture
Insufficient or delayed rehabilitation leading to adhesions and stiffness
Inadequate surgical repair technique causing gapping or instability
Ignoring concomitant neurovascular injuries
Poor patient education regarding the importance of rehabilitation compliance.