ANATOMY AND PHYSIOLOGY 
From where do tendons receive their nourishment?
In the forearm, from vessels in the paratenon.
In the hand, from the vincular vessels (intrinsic system) and from the synovial fluid (extrinsic system) within the tendon sheath.
Which source is more important to the tendons in the hand?
Synovial fluid.
What are the vincula?
Folds of mesotendon containing blood vessels. Each tendon (Flexor digitorum superficialis [FDS] and Flexor digitorum profundus [FDP]) has two vincula, a short vinculum distally and a long vinculum proximally, that enter the dorsal surface of the tendons.
What are the source vessels of the vincula?
The transverse digital arteries, which enter the fibro-osseous tunnel at the levels of the cruciate pulleys.
How is the short vinculum of the superficialis tendon related to the long vinculum of the profundus tendon?
They cross each other at the distal P1 level.
How many pulleys are there in the fingers?
Eight (five annular and three cruciate).
What effect do the pulleys have?
They prevent bowstringing of the flexor tendons in flexion, increasing the effective excursion of the tendons and thus the degree of finger flexion. Theoretically, a finger with bowstringing flexor tendons will actually flex with greater strength because the force vector is farther from the joint axis, but will not be able to flex fully.
Which pulleys are the most important in the fingers, and where are they located?
• A2, at the proximal part of the proximal phalanx
• A4, at the middle part of the middle phalanx
The interval between which annular ligaments has no cruciate ligament?
Between A1 and A2. The first cruciate ligament lies between A2 and A3.
How many pulleys are there in the thumb?
Three:
• A1 at the MP level
• Oblique at the P1 level
• A2 at the IP level
The oblique and A2 pulleys are the most important in the thumb.
What comprises the floor of the fibro-osseous tunnel?
The periosteum of the phalanges and the volar plates of the MP and PIP joints.
What lies immediately volar to the volar plate of the PIP joint?
FDS tendon.
Describe the orientation of the FDS tendons within the carpal tunnel.
The tendons of the index and small fingers are dorsal to the tendons of the long and ring fingers.
FLEXOR TENDONS 
Describe the boundaries of the five flexor zones of the fingers.
Zone I: Distal to the insertion of FDS on P2.
Zone II: Within the fibro-osseous tunnel (from the A1 pulley to the FDS insertion).
Zone III: The area of the palm between the carpal tunnel and the fibro-osseous tunnel.
Zone IV: Within the carpal tunnel.
Zone V: Proximal to the carpal tunnel.
What are the two main deficits resulting from zone I tendon laceration?
Loss of DIP flexion and diminution of grip strength.
What provides the stronger repair in zone I injuries—suturing of tendon ends together or anchoring of tendon end directly to bone?
Anchoring directly to bone.
What is the farthest the FDP tendon should be advanced to achieve direct anchoring to bone?
1 cm.
What is a jersey finger?
Avulsion of the FDP tendon from its insertion on P3 (an injury that might occur when a football player reaches out to grab an opponent’s jersey).
What finger is most commonly affected, and why?
The ring finger, because:
1. It has the weakest FDP insertion.
2. It is the most protruding finger when the hand is in the grasping position.
3. The juncturae tendinae prevent independent extension of the ring finger (much more so than the other fingers).
4. The common muscle belly of FDP prevents independent relaxation of the FDP tendon.
Describe the four types of FDP avulsion injuries.
Type I: Tendon retracts into palm.
Type II: Tendon retracts to level of PIP.
Type III: Tendon avulsed with large bony fragment, which catches at A4.
Type IV: Large bony fragment, with avulsion and retraction of tendon from fragment.
Which type of FDP avulsion is most common? Which has the best prognosis? The worst?
Most common: type II.
Best prognosis: type III.
Worst prognosis: type I and type IV.
What is the lumbrical plus deformity?
If an injured FDP tendon retracts into the palm (type I avulsion), the lumbrical (which originates on the FDP tendon) will be under tension, creating an extension force on the IP joints. When one attempts to make a fist, the FDP tendon will place even greater tension on the lumbrical, paradoxically extending the finger. This can also happen if an FDP tendon in the finger is reconstructed with a tendon graft that is too long.
Why must type I FDP avulsion be repaired without significant delay?
Because both the vincular and synovial nutritional supplies have been disrupted.
What holds the FDP tendon at the level of the PIP in a type II FDP avulsion?
The vincula.
A heavy laborer sustained a type I FDP avulsion 1 month ago. What treatment should be considered?
DIP fusion, if the joint is symptomatically unstable or painful. Attempt at repair would likely result in worse stiffness.
Where is a zone II flexor tendon laceration usually located with respect to the skin laceration?
Distal (the finger is usually flexed at the time of injury).
If the vinculum is ruptured in a zone II injury, to where will the tendon usually retract?
To the palm, held in place by the lumbrical.
How can the tendon be retrieved from the palm?
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