Updated: 7/13/2019

Flexor Tendon Injuries

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https://upload.orthobullets.com/topic/6031/images/flexor_zones.jpg
https://upload.orthobullets.com/topic/6031/images/campers chiasm.jpg
Introduction
  • Overview
    • flexor tendon injuries are a traumatic condition classified by the zone of injury (see table below)
      • basic concepts in repair are similar for different zones 
      • location of laceration directly affects healing potential
  • Epidemiology
    • incidence
      • rare
      • occurs in 4.83 per 100,000
  • Pathophysiology
    • mechanism of injury
      • commonly results from volar lacerations and may have concomitant neurovascular injury
    • pathophysiology
      • tendon healing
        • occurs via 2 pathways
          • intrinsic
            • produced by tenocytes within the tendon
          • extrinsic
            • stimulated by surrounding synovial fluid and inflammatory cells
            • implicated in the formation of scarring and adhesions
        • occurs in 3 phases
Phases of Tendon Healing
Phase
Days
Histology
Strength
Inflammatory
0-5
cellular proliferation none
Fibroblastic
5-28
fibroblastic proliferation with disorganized collagen increasing
Remodeling
>28
linear collagen organization will tolerate controlled active motion 
 
Anatomy
  • 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
      • has dual innervation
        • index and long fingers are innervated by the AIN of the median nerve
        • ring and small fingers are innervated by the ulnar nerve
    • 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
      • innervated by the median nerve
    • flexor pollicis longus (FPL) 
      • located within the carpal tunnel as the most radial structure
      • innervated by the AIN of the median nerve
    • flexor carpi radialis (FCR) 
      • primary wrist flexor
      • inserts on the base of the second metacarpal
      • closest flexor tendon to the median nerve 
      • innervated by the median nerve
    • flexor carpi ulnaris (FCU) 
      • primary wrist flexor
      • inserts on the pisiform, hook of hamate, and the base of the 5th metacarpal
      • innervated by the ulnar nerve
  • Camper 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)
        • thicker and stiffer than cruciate pulleys
        • A2 and A4 arise from the periosteum
          • most important pulleys to prevent flexor tendon bowstringing
        • A1, A3, and A5 arise from the volar plate
      • 3 cruciate pulleys (C1 to C3)  
        • collapsible and flexible
          • allows the annular pulleys to approximate each other during digital flexion
    • thumb contains
      • 2 annular pulleys
      • 1 interposed oblique pulley
        • most important pulley to prevent flexor tendon bowstringing
  • Blood supply
    • 2 sources exist
      • diffusion through synovial sheaths
        • occurs when flexor tendons are located within a sheath  
        • it is the more important source distal to the MCP joint
      • direct vascular perfusion
        • nourishes flexor tendons located outside of synovial sheaths 
        • supplied by the vincular system, osseous bony insertions, reflected vessels from the tendon sheath, and longitudinal vessels from the palm
Classification 
 
Zone
Definition
Introduction
Treatment
I
distal to FDS insertion  Jersey finger 
II
FDS insertion to distal palmar crease/proximal A1 pulley

Zone is unique in that FDP and FDS in same tendon sheath (both can be injured within the flexor retinaculum). Tendons can retract if vincula are disrupted.

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

III
palm (A1 pulley to distal aspect of carpal ligament)

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). May require A1 pulley release to avoid impingement of the repaired tendon on the pulley.

IV
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 if tendon bowstringing is present.

V
carpel tunnel to forearm

Often associated with neurovascular injury which carries a worse prognosis.

Direct tendon repair
Thumb
TI, TII, TIII

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

 
Presentation
  • 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
    • 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 
      • important given the close proximity of flexor tendons to the digital neurovascular bundles
Imaging
  • Radiographs
    • may have associated fracture
  • Ultrasound
    • used to assess suspected lacerations
Treatment
  • 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   
    • flexor tendon reconstruction and intensive postoperative rehabilitation 
      • indications
        • failed primary repair
        • chronic untreated injuries
    • FDS4 transfer to thumb
      • single stage procedure
      • indications
        • chronic FPL rupture
Techniques
  • Flexor tendon repair
    • indications
      • > 75% laceration
      • ≥ 50-60% laceration with triggering
        • epitendinous suture at the laceration site is sufficient  
        • no benefit of adding core suture
    • fundamentals of repair
      • easy placement of sutures in the tendon
      • secure suture knots
      • smooth juncture of the tendon ends
      • minimal gapping at the repair site
      • minimal interference with tendon vascularity
      • sufficient strength throughout healing to permit application of early motion stress to the tendon
    • timing of repair
      • perform repair within three weeks of injury (2 weeks is ideal)
        • delayed treatment leads to difficulty due to tendon retraction
    • approach
      • incisions should always cross flexion creases transversely or obliquely to avoid contractures (never longitudinal)
      • meticulous atraumatic tendon handling minimizes adhesions
    • technique
      • core sutures
        • # 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
      • circumferential epitendinous suture
        • improves tendon gliding by reducing the cross-sectional area
        • improves strength of repair (adds 20% to tensile strength)
        • allows for less gap formation (first step in repair failure)
        • simple running suture is recommended
          • produces less gliding resistance than other techniques
      • sheath repair 
        • theoretically improves tendon nutrition through synovial pathway
        • controversial
          • clinical studies show no difference with or without sheath repair
          • most surgeons will repair if it is easy to do
      • pulley management
        • historically believef to be critical to preserve A2 and A4 pulleys in digits and oblique pulley in thumb
        • recent biomechanical studies have shown that 25% of A2 and 100% of A4 can be incised with little resulting functional deficit
      • FDS repair 
        • in zone 2 injuries, repair of one slip alone improves gliding
        • 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
        • repair site gaps > 3mm are associated with an increased risk of repair failure
      • adhesion formation
        • increased risk with zone 2 injuries
  • Wide-awake flexor tendon repair   
    • anesthesia
      • 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 > 2 hours 
            • 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")
  • Flexor tendon reconstruction
    • requirements
      • supple skin
      • sensate digit
      • adequate vascularity
      • full passive range of motion of adjacent joints
    • techniques
      • single-stage procedures
        • only perform if the flexor sheath is pristine and the digit has full ROM
      • two-stage procedures
        • Hunter-Salisbury 
          • Stage I - SR is placed to create a favorable tendon bed
          • Stage II (3-4 months) - SR is retrieved and a tendon graft is placed through the mesothelium-lined pseudosheath
            • pulvertaft weave proximally and end-to-end tenorrhaphy distally
        • Paneva-Holevich  
          • 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 the pseudosheath and either attached directly to FDP stump or secured with a 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
            • relies on only 1 tenorrhaphy site (distal or proximal) to heal at any one time (vs. Hunter technique where 2 tennoprhaphy sites are healing simultaneously)
          • disadvantages
            • graft tensioning is at the distal end during stage II
              • the proximal end has already healed after stage I
      • graft selection
        • palmaris longus (absent in 15% of population)
          • most common
        • plantaris (absent in 19%)
          • indicated if longer graft is needed
        • extensor digitorum longus to 2nd-4th toes
        • extensor indicis proprius
        • flexor digitorum longus to 2nd toe
        • FDS
      • pulley reconstruction 
        • one pulley should be reconstructed proximal and distal to each joint
        • pulley reconstruction should occur first if a tendon graft is being used
        • methods
          • belt loop method
          • FDS tail method
    • outcomes
      • subsequent tenolysis is required more than 50% of the time
  • 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
  • Protocols
    • Immobilization
      • indicated for children and non-compliant patients
      • casts/splints are applied with the wrist and MCP joints positioned in flexion and the IP joints in extension
    • Early passive motion 
      • Duran protocol
        • low force and low excursion
        • active finger extension with patient-assisted passive finger flexion and static splint
      • Kleinert protocol
        • low force and low excursion
        • active finger extension with 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
    • Early active motion
      • moderate force and potentially high excursion
      • dorsal blocking splint limiting wrist extension
      • perform “place and hold” exercises with digits
Complications
  • Tendon adhesions
    • most common complication following flexor tendon repair
    • higher risk with zone 2 injuries
    • treatment
      • physical therapy
      • tenolysis
        • perform if 4-6 months after tendon repair and significant loss of excursion
  • 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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Questions (22)
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(OBQ13.75) A 27-year-old male sustains the injury shown in Figure A. He is taken to the operating room and the lesion is repaired primarily. Two months later, he feels a "pop" while using his hand and is no longer able to flex the distal phalanx of the involved digit. He is taken to the operating room for surgical exploration where 1.8 cm of scar tissue between the tendon ends is identified. The tendon sheath is found to be intact and allows smooth passage of a pediatric urethral catheter. What is the next step in management? Review Topic

QID: 4710
FIGURES:
1

Resection of scar and primary repair of tendon ends.

6%

(154/2594)

2

Resection of scar and adjacent 1cm of tendon, placement of Hunter rod for staged reconstruction.

21%

(548/2594)

3

Debulking of scar, partial excision of 25% of the A2 and A4 pulleys.

2%

(40/2594)

4

Resection of scar, harvest of ipsilateral palmaris longus tendon for tendon reconstruction.

69%

(1781/2594)

5

Resection of scar and proximal tendon, tendon transfer from adjacent digit.

2%

(50/2594)

ML 3

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PREFERRED RESPONSE 4

(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? Review Topic

QID: 4860
FIGURES:
1

Repair with core suture purchase 5mm from the cut edge only. No epitendinous suture

2%

(103/4673)

2

Repair with core suture purchase 10mm from the cut edge only. No epitendinous suture

3%

(159/4673)

3

Repair with core suture purchase 5mm from the cut edge. Circumferential simple running epitendinous suture.

20%

(936/4673)

4

Repair with core suture purchase 10mm from the cut edge. Circumferential Silfverskiold epitendinous suture.

12%

(573/4673)

5

Repair with core suture purchase 10mm from the cut edge. Circumferential simple running epitendinous suture.

61%

(2872/4673)

ML 4

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PREFERRED RESPONSE 5

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

QID: 4542
1

At this level, FDS and FDP are located within separate tendon sheaths

11%

(280/2636)

2

FDS repair has not been shown to improve outcomes

10%

(264/2636)

3

Improved gliding is seen with repair of 1 slip of FDS compared to repairing both slips

70%

(1838/2636)

4

Repairing FDS does not affect post-operative digit strength

4%

(118/2636)

5

FDP repair has not been shown to improve outcomes

4%

(112/2636)

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(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: Review Topic

QID: 3263
1

Kleinert protocol

3%

(59/2112)

2

Duran protocol

4%

(86/2112)

3

Synergistic motion protocol

5%

(113/2112)

4

Low force and low tendon excursion passive range of motion

5%

(107/2112)

5

Early digit active range of motion protocol

82%

(1727/2112)

ML 2

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PREFERRED RESPONSE 5

(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? Review Topic

QID: 2910
1

Trim the frayed tendon edges and begin early range of motion

74%

(1943/2627)

2

Trim the frayed tendon edges and cast in an intrinsic positive position for 2 weeks

7%

(186/2627)

3

Peritendinous 6/0 and Core 4/0 suture repair

14%

(360/2627)

4

Core 4/0 suture repair

3%

(90/2627)

5

Core 6/0 suture repair

1%

(37/2627)

ML 2

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PREFERRED RESPONSE 1
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(OBQ08.227) Flexor tendons of the fingers within Zone 2 receive their primary nutritional supply from: Review Topic

QID: 613
1

Vinculae

31%

(655/2143)

2

Phalangeal periosteum

1%

(26/2143)

3

Musculotendon junction

1%

(22/2143)

4

Tendon insertion

1%

(13/2143)

5

Diffusion from the synovial sheath

66%

(1407/2143)

ML 3

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PREFERRED RESPONSE 5

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

QID: 551
1

Flexor carpi radialis

76%

(1511/1983)

2

Flexor carpi ulnaris

2%

(46/1983)

3

Radial artery

4%

(86/1983)

4

Flexor digitorum profundus

15%

(297/1983)

5

Pronator teres

1%

(23/1983)

ML 2

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PREFERRED RESPONSE 1

(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? Review Topic

QID: 285
1

The size of the core suture

1%

(28/2281)

2

Number of core strands crossing the repair site

92%

(2091/2281)

3

Use of epitendinous suture

3%

(72/2281)

4

Active range of motion during the immediate postoperative period

2%

(36/2281)

5

Repair of the flexor tendon sheath

2%

(38/2281)

ML 1

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PREFERRED RESPONSE 2

(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: Review Topic

QID: 989
1

2 strand core suture technique and gentle active flexion and extension exercises with wrist in extension

4%

(106/2599)

2

2 strand core suture technique and cast immobilization for 8 weeks

1%

(33/2599)

3

4 strand core suture technique and gentle active flexion and extension exercises with wrist in extension

24%

(625/2599)

4

4 strand core suture technique and cast immobilization for 4 weeks

61%

(1578/2599)

5

4 strand core suture technique and cast immobilization for 8 weeks

9%

(225/2599)

ML 3

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PREFERRED RESPONSE 4

(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? Review Topic

QID: 58
FIGURES:
1

Low force and low excursion

46%

(971/2129)

2

Moderate force and potentially high tendon excursion

5%

(96/2129)

3

Low force and high tendon excursion

40%

(854/2129)

4

High force and high tendon excursion

2%

(34/2129)

5

High force and low tendon excursion

7%

(153/2129)

ML 4

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PREFERRED RESPONSE 1

(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: Review Topic

QID: 121
1

No tendon repair with early protected range of motion

71%

(947/1327)

2

No tendon repair with splint immobilization for 2 weeks

6%

(82/1327)

3

Tendon repair with 2 strand repair and early protected range of motion

9%

(124/1327)

4

Tendon repair with 2 strand repair with splint immobilization for 2 weeks

3%

(46/1327)

5

Tendon repair with 4 strand repair and early active range of motion

9%

(117/1327)

ML 2

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PREFERRED RESPONSE 1
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