Flexor Tendon Injuries

Topic updated on 06/30/16 6:02am
  •  Injuries commonly result from volar lacerations
    • concomitant neurovascular injury is prevalent
  • Injury to the flexor tendons is classified by the zone of injury (see table below)
  • Basic concepts in repair are similar for different zones of injury 
  • Location of a tendon laceration directly affects healing potential
Phases of Tendon Healing
cellular proliferation none
fibroblastic proliferation with disorganized collagen increasing
linear collagen organization will tolerate controlled active motion 
  • Muscles
    • flexor digitorum profundus (FDP)  
      • functions as a flexor of the DIP joint
      • assists with PIP and MCP flexion
      • shares a common muscle belly in the forearm
    • flexor digitorum superficialis (FDS)  
      • functions as a flexor of the PIP joint
      • assists with MCP flexion
      • individual muscle bellies exist in the forearm
        • FDS to the small finger is absent in 25% of people
    • flexor pollicis longus (FPL) 
      • located within the carpal tunnel as the most radial structure
    • flexor carpi radialis (FCR) 
      • primary wrist flexor
      • inserts on the base of the second metacarpal
      • closest flexor tendon to the median nerve 
    • flexor carpi ulnaris (FCU) 
      • primary wrist flexor
      • inserts on the pisiform, hook of hamate, and the base of the 5th metacarpal
  • Blood supply
    • 2 sources exist
      • diffusion through synovial sheaths
        • occurs when flexor tendons are located within a sheath  
        • it is the more important source proximal to the MCP joint
      • direct vascular supply
        • nourishes flexor tendons located outside of synovial sheaths 
  • Campers chiasm 
    • located at the level of the proximal phalanx where FDP splits FDS 
  • Pulley system  
    • digits 1-4 contain
      • 5 annular pulleys (A1 to A5)
      • 3 cruciate pulleys (C1 to C3)  
        • A2 and A4 are the most important pulleys to prevent flexor tendon bowstringing
    • thumb contains
      • 2 annular pulley
      • interposed oblique pulley (most important)  
Distal to FDS insertion  Jersey finger 
FDS insertion to distal palmar crease

Zone is unique in that FDP and FDS in same tendon sheath (both injured within the flexor retinaculum) 

Direct repair of both tendons followed by early ROM (Duran, Kleinert). Be sure to preserve A2 and A4 pulley. This zone historically had very poor results but results have improved due to advances in postoperative motion protocols


Often associated with neurovascular injury which carries a worse prognosis

Direct tendon repair. Good results from direct repair can be expected due to absence of retinacular structures (if no neurovascular injury)

Carpal tunnel

Often complicated by postoperative adhesions due to close quarters and synovial sheath of the carpal tunnel

Direct tendon repair. Transverse carpal ligament should be repaired in a lengthened fashion

Wrist to forearm

Often associated with neurovascular injury which carries a worse prognosis

Direct tendon repair

Outcomes different than fingers. Early motion protocols do not improve long-term results and there is a higher re-rupture rate than flexor tendon repair in fingers

Direct end-to-end repair of FPL is advocated. Try to avoid Zone III to avoid injury to the recurrent motor branch of the median nerve. Oblique pulley is more important than the A1 pulley; however both may be incised if necessary. Attempt to leave one pulley intact to prevent bowstringing

  • Symptoms
    • loss of active flexion strength or motion of the involved digit(s)
  • Physical exam
    • inspection
      • observe resting posture of the hand and assess the digital cascade
      • evidence of malalignment or malrotation may indicate an underlying fracture
      • assess skin integrity to help localize potential sites of tendon injury
      • look for evidence of traumatic arthrotomy
    • range of motion
      • passive wrist flexion and extension allows for assessment of the tenodesis effect
        • normally wrist extension causes passive flexion of the digits at the MCP, PIP, and DIP joints
        • maintenance of extension at the PIP or DIP joints with wrist extension indicates flexor tendon discontinuity
      • active PIP and DIP flexion is tested in isolation for each digit
    • neurovascular exam
      • important given the close proximity of flexor tendons to the digital neurovascular bundles
  • Nonoperative
    • wound care and early range of motion
      • indications
        • partial lacerations < 60% of tendon width
      • outcomes
        • may be associated with gap formation or triggering
  • Operative
    • flexor tendon repair and controlled mobilization 
      • indications
        • lacerations > 60% of tendon width   
      • outcomes
        • depends on zone of injury
    • flexor tendon reconstruction and intensive postoperative rehabilitation
      • indications
        • failed primary repair
        • chronic untreated injuries
      • outcomes
        • subsequent tenolysis is required more than 50% of the time
Surgical Technique
  • Flexor Tendon Repair of Complete Lacerations
    • approach
      • incisions should always cross flexion creases transversely or obliquely to avoid contractures (never longitudinal)
    • timing of repair
      • perform repair within three weeks of injury (2 weeks ideal)
      • waiting longer leads to difficulty due to tendon retraction
    • technique
      • # of suture strands that cross the repair site is more important than the number of grasping loops
        • linear relationship between strength of repair and # of sutures crossing repair
        • 4-6 strands provide adequate strength for early active motion  
        • high-caliber suture material increases strength and stiffness and decreases gap formation
        • locking-loops decrease gap formation
        • ideal suture purchase is 10mm from cut edge 
        • core sutures placed dorsally are stronger
        • meticulous atraumatic tendon handling minimizes adhesions
      • circumferential epitendinous suture
        • improves tendon gliding
        • improves strength of repair (adds 20% to tensile strength)
        • allows for less gap formation (first step in repair failure)
        • simple running suture is recommended
      • sheath repair is controversial
        • theoretically improves tendon nutrition through synovial pathway
        • clinical studies show no difference with or without sheath repair
        • most surgeons will repair if it is easy to do
      • pulley management
        • critical to preserve A2 and A4 pulleys in digits and oblique pulley in thumb
      • FDS repair 
        • in zone 2 injuries, repair of one slip alone improves gliding when compared to repair of both slips
    • outcomes
      • repair failure
        • tendon repairs are weakest between postoperative day 6 and 12
        • repair usually fails at suture knots
  • Flexor Tendon Repair of Partial Lacerations
    • indications
      • >75% laceration
      • ≥50-60% laceration with triggering
        • epitendinous suture at the laceration site is sufficient  
        • no benefit of adding core suture
  • Wide-Awake Flexor Tendon Repair   
    • performed under tumescent local anesthesia using lidocaine with epinephrine
      • dosing
        • usually epinephrine 1:100,000 and 7mg/kg lidocaine
        • from 1:400,000 to 1:1000 is safe
        • if <50cc is needed
          • 1% lidocaine with 1:100,000 epi for a 70kg person
        • if 50-100cc is needed
          • dilute with saline (50:50) to get 0.5% lidocaine, 1:200,000 epi
        • if 100-200cc is needed for large fields (tendon transfer, spaghetti wrist)
          • dilute with 150cc saline to get 0.25% lidocaine and 1:400,000 epi
        • for longer surgery >2h 
          • add 10cc of 0.5% bupivacaine with 1:200,000 epi
      • location
        • proximal and middle phalanges, use 2ml
        • distal phalanx, use 1ml
        • palm, use 10-15ml
    • no tourniquet, no sedation
    • 4 advantages
      • allows intraoperative assessment for repair gaps by getting awake patient to actively flex digit
      • reduces need for postop tenolysis by allowing intraoperative assessment of whether repair will fit through pulleys
        • allows on-the-spot debulking of bunched repairs
        • allows division of A4 pulley and venting (partial division) of A2 pulleys
      • allows repair of tendons inside tendon sheaths as patients can demonstrate that the inside of the sheath has not been inadvertently caught
      • facilitates postop early active motion
        • immobilize for 3 days
        • begin active midrange motion after day 3 (form a partial fist with 45 degree flexion at MP, PIP and DIP joints, or "half a fist 45/45/45 regime")
  • Reconstruction Technique 
    • requirements
      • supple skin
      • sensate digit
      • adequate vascularity
      • full passive range of motion of adjacent joints
    • techniques
      • Hunter-Salisbury two-stage procedure
        • Stage I - silicone rod is placed to create a favorable tendon bed
        • Stage II (3-4 months) - retrieve SR and pass a tendon graft through the mesothelium lined pseudosheath
        • only perform a single-stage reconstruction if the flexor sheath is pristine and the digit has full ROM
        • pulvertaft weave proximally and end-to-end tenorrhaphy distally
      • Paneva-Holevich two-stage technique  
        • Stage I - SR is placed in the flexor sheath, pulleys are reconstructed (as needed), and a loop between the proximal stumps of FDS and FDP is created in the palm
        • Stage II - SR is retrieved, FDS is cut proximally and reflected distally through pseudosheath and attached directly to FDP stump/or secured with button 
        • advantages
          • graft (FDS) size is known at the time of silicone rod selection
            • less graft diameter-rod diameter mismatch
          • FDS graft is intrasynovial (fewer adhesions than extrasynovial grafts)
          • only relying on 1 tenorrhaphy site (distal or proximal) to heal at any one time (vs Hunter technique where 2 tennoprhaphy sites are healing simultaneously)
        • disadvantage
          • graft tensioning is at the distal end during stage II
            • the proximal end has already healed after stage I
    • graft choices
      • palmaris longus (absent in 15% of population)
        • most common
      • plantaris (absent in 19%)
        • indicated if longer graft is needed
      • long toe extensor
    • pulley reconstruction 
      • one pulley should be reconstructed proximal and distal to each joint
      • methods include belt loop method and FDS tail method
  • Tenolysis
    • indications
      • localized tendon adhesions with minimal to no joint contracture and full passive digital motion 
      • may be required if a discrepancy between active and passive motion exists after therapy
    • timing of procedure
      • wait for soft tissue stabilization (> 3 months) and full passive motion of all joints
    • technique
      • careful technique to preserve A2 and A4 pulleys
    • postoperative care
      • follow with extensive therapy
Postoperative Rehabilitation
  • Postoperative controlled mobilization has been the major reason for improved results with tendon repair
    • especially in zone II
    • leads to improved tendon healing biology
    • limits restrictive adhesions and leads to increased tendon excursion
  • Early active motion protocols
    • moderate force and potentially high excursion
    • dorsal blocking splint limiting wrist extension
    • perform “place and hold” exercises with digits
  • Early passive motion protocols
    • Duran protocol
      • low force and low excursion
      • active finger extension with patient-assisted passive finger flexion
    • Kleinert protocol
      • low force and low excursion
      • active finger extension, dynamic splint-assisted passive finger flexion
    • Mayo synergistic splint  
      • low force and high tendon excursion
      • adds active wrist motion which increases flexor tendon excursion the most
  • Immobilize children and noncompliant patients
    • Children should be immobilized following repair 
    • Casts or splints are applied with the wrist and MCP joints positioned in flexion and the IP joints in extension
  • Tendon adhesions
    • most common complication following flexor tendon repair
  • Rerupture 
    • 15-25% rerupture rate
    • treatment
      • if <1cm of scar is present, resect the scar and perform primary repair
      • if >1cm of scar is present, perform tendon graft
        • if the sheath is intact and allows passage of a pediatric urethral catheter or vascular dilator, perform primary tendon grafting
        • if the sheath is collapsed, place Hunter rod and perform staged grafting
  • Joint contracture
    • rates as high as 17%
  • Swan-neck deformity  
  • Trigger finger 
  • Lumbrical plus finger  
  • Quadrigia 


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Qbank (15 Questions)

(OBQ13.225) A 28-year-old man sustained a complete laceration of the flexor digitorum profundus of his index finger while cutting a watermelon 3 days ago. A clinical photograph is shown in Figure A. The surgeon plans to repair the tendon using a 4-strand core suture technique. Which method of tendon repair will give him the best results in terms of load to failure and gliding resistance? Topic Review Topic
FIGURES: A          

1. Repair with core suture purchase 5mm from the cut edge only. No epitendinous suture
2. Repair with core suture purchase 10mm from the cut edge only. No epitendinous suture
3. Repair with core suture purchase 5mm from the cut edge. Circumferential simple running epitendinous suture.
4. Repair with core suture purchase 10mm from the cut edge. Circumferential Silfverskiold epitendinous suture.
5. Repair with core suture purchase 10mm from the cut edge. Circumferential simple running epitendinous suture.

(OBQ12.182) Which of the following statements is true regarding zone II flexor tendon injuries? Topic Review Topic

1. At this level, FDS and FDP are located within separate tendon sheaths
2. FDS repair has not been shown to improve outcomes
3. Improved gliding is seen with repair of 1 slip of FDS compared to repairing both slips
4. Repairing FDS does not affect post-operative digit strength
5. FDP repair has not been shown to improve outcomes

(OBQ10.170) A 24-year-old male cuts his left middle finger with a knife while chopping vegetables. Physical exam reveals a zone 2 flexor tendon laceration. He undergoes a 2-strand core suture repair with epitendinous suture. This particular repair is strong enough for each of the following rehabilitation protocols EXCEPT: Topic Review Topic

1. Kleinert protocol
2. Duran protocol
3. Synergistic motion protocol
4. Low force and low tendon excursion passive range of motion
5. Early digit active range of motion protocol

(OBQ09.97) You are seeing a 26-year-old man after he was involved in a knife fight. He has pain when flexing and extending his index finger. You explore a 2 centimeter wound in zone 2 and find his flexor tendons to the index are 40% lacerated. What is the preferred method of treatment? Topic Review Topic

1. Trim the frayed tendon edges and begin early range of motion
2. Trim the frayed tendon edges and cast in an intrinsic positive position for 2 weeks
3. Peritendinous 6/0 and Core 4/0 suture repair
4. Core 4/0 suture repair
5. Core 6/0 suture repair

(OBQ08.165) The median nerve lies immediately ulnar to which of the following structures at the level of the distal radioulnar joint? Topic Review Topic

1. Flexor carpi radialis
2. Flexor carpi ulnaris
3. Radial artery
4. Flexor digitorum profundus
5. Pronator teres

(OBQ08.227) Flexor tendons of the fingers within Zone 2 receive their primary nutritional supply from: Topic Review Topic

1. Vinculae
2. Phalangeal periosteum
3. Musculotendon junction
4. Tendon insertion
5. Diffusion from the synovial sheath

(OBQ06.274) A 32-year-old male sustains a 100% tear of his flexor tendon in the Zone 2 region after cutting his finger with a knife. You plan a one-stage repair of the flexor tendon. Which of the following variables has the greatest effect on increasing the strength of the tendon repair? Topic Review Topic

1. The size of the core suture
2. Number of core strands crossing the repair site
3. Use of epitendinous suture
4. Active range of motion during the immediate postoperative period
5. Repair of the flexor tendon sheath

(OBQ05.21) A 34-year-old man sustains a finger flexor tendon laceration and undergoes operative repair. Which of the following statements best describes the tendon motion rehabilitation protocol as depicted in Figures A where the splint holds the wrist at 45 degrees of flexion? Topic Review Topic
FIGURES: A          

1. Low force and low excursion
2. Moderate force and potentially high tendon excursion
3. Low force and high tendon excursion
4. High force and high tendon excursion
5. High force and low tendon excursion

(OBQ05.103) A 4-year-old boy sustains a flexor tendon laceration in Zone 2 of his 4th digit when he attempts to grab a knife. Optimal surgical management and postoperative rehabilitation consists of: Topic Review Topic

1. 2 strand core suture technique and gentle active flexion and extension exercises with wrist in extension
2. 2 strand core suture technique and cast immobilization for 8 weeks
3. 4 strand core suture technique and gentle active flexion and extension exercises with wrist in extension
4. 4 strand core suture technique and cast immobilization for 4 weeks
5. 4 strand core suture technique and cast immobilization for 8 weeks

(OBQ04.10) A 23-year-old presents with a knife laceration in the flexor zone 2 of the hand. Examination of the wound is performed and a laceration of the flexor tendon one-half the width of the tendon is identified. There is no triggering present as the patient's finger is passively extended and flexed fully. The most appropriate treatment is: Topic Review Topic

1. No tendon repair with early protected range of motion
2. No tendon repair with splint immobilization for 2 weeks
3. Tendon repair with 2 strand repair and early protected range of motion
4. Tendon repair with 2 strand repair with splint immobilization for 2 weeks
5. Tendon repair with 4 strand repair and early active range of motion

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