1. Flexor Tendon Injuries
Applied Anatomy & Examination
Tendon Healing
Management

2. Flexor Tendon Injuries
no subject in hand surgery has sparked more interest and discussion.

4. Applied Anatomy

5. Anatomy Musculotendinous units Synovial sheaths & Fibrosseous canals
Pulleys
Vascular supply
Zones

6. Tendon Structure
Composite material consisting of collagen fibrils embedded in a matrix of proteoglycans
Type I collagen (95%)
Type III and IV collagen (5%)
Tenocytes are arranged in parallel rows between bundles

7. Tendon Structure
The ligament or tendon then is split into smaller entities called fascicles. The fascicle contains the basic fibril of the ligament or tendon, and the fibroblasts, which are the biological cells that produce the ligament or tendon. There is a structural characteristic at this level that plays a significant role in the mechanics of ligaments and tendons: the crimp of the fibril. The crimp is the waviness of the fibril; we will see that this contributes significantly to the nonlinear stress strain relationship for ligaments and tendons and indeed for bascially all soft collagenous tissues.

8. Tendon Structure Endotenon circumscribes each fascicle
Permits fascicular gliding
Epitenon surrounds the tendon
Contains capillary blood supply

9. Tendon Structure
Epitenon
Paratenon
Endotenon

10. Tendon Structure
Paratenon is the adventitia that covers the flexor tendon in the palm
Consists of visceral & parietal layer
Continuous with synovial mesotenon
Supplies tendon nutrients
Allows tendon gliding

11. Applied Anatomy
FDS
FDP
FPL
N & V

12. FDS
The flexor digitorum superficialis arises from multiple origins on the volar surface of the humerus, ulna, and radius and is interconnected by a fibrous aponeurosis that overlies the median nerve and the ulnar vascular bundle in the forearm 49 . In the midpart of the forearm, the superficialis muscle belly divides into four bundles, which separate into a superficial and a deep layer; the superficial layer sends tendons to the long and ring fingers, and the deep layer sends tendons to the index and small fingers. The flexor digitorum superficialis tendon to the small finger may not be present in all individuals

13. FDP
The common muscle belly of the flexor digitorum profundus originates from the anterior-medial aspect of the ulna and interosseous membrane and remains dorsal to the flexor digitorum superficialis in the volar aspect of the forearm. The four flexor digitorum profundus tendons usually arise from a common muscle belly; however, the flexor digitorum profundus to the index finger exhibits a high degree of independence, often originating from an individual muscle belly.

14. FPL FDP
Anterior surface of radius and adjacent interosseous membrane. Inserts on the base of distal phalanx of thumb. Flexes phalanges of 1st digit (thumb). Anterior interosseous nerve from median nerve (C8 and T1)

15. Verdan Zones
Kleinert and Verdan divided the flexor tendon into five anatomic zones

16. Zone 5
Zone V extends from the muscle-tendon junction to the entrance of the carpal canal,

17. Zone 5/4
Zone V extends from the muscle-tendon junction to the entrance of the carpal canal, and Zone IV lies deep to the transverse carpal ligament, where the flexor digitorum superficialis tendons to the long and ring fingers lie directly palmar to those of the index and small fingers and the flexor digitorum profundus tendons travel deep. As the tendons emerge from the carpal canal, the lumbrical muscles take origin from the flexor digitorum profundus tendons and travel distally to insert into the radial lateral bands of the digits.

18. Zone 4

19. Zone 3
Zone III is the region from the distal edge of the transverse carpal ligament to the proximal aspect of the digital fibro-osseous sheath at the palmar crease.

20. Zone 1/2
Zone II begins at the origin of the fibro-osseous flexor sheath in the distal aspect of the palm, and it extends to the distal aspect of the insertion of the flexor digitorum superficialis tendon. Zone I is distal to the insertion of the flexor digitorum superficialis.

21. Zone 2 – Campers Chiasma
At the level of the A1 pulley, the superficialis tendon flattens out and bifurcates, allowing the deeper profundus tendon to pass distal to its insertion at the base of the distal phalanx. The two limbs of the superficialis tendon rotate away from the midline and wrap around the profundus tendon, with half of the fibers crossing on the palmar surface of the phalanx to insert dorsal to the profundus tendon on the palmar surface of the proximal half of the middle phalanx. The remaining fibers insert as radial and ulnar slips on the diaphysis of the middle phalanx.

22. Tendon Nutrition Longitudinal vessels from the palm supply
proximal portion of tendon within the sheath
2) Vincula system - folds of mesotenon carry
blood to both FDP and FDS in distal portion of sheath.
3) Vascular input from bony insertion site
There is a single avascular zone within the intrasynovial portion of the flexor digitorum superficialis tendon; it lies over the proximal phalanx and under the A2 pulley. There are two avascular zones within the intrasynovial portion of the flexor digitorum profundus tendon; the first lies over the proximal phalanx deep to the A2 pulley, and the second is located over the middle phalanx, typically under the A4 pulley.
one short and one long vinculum supply each FDS & FDP tendon;     - vincula receive their blood vessels thru transverse communicating             branches of the common digital artery located on the dorsal             surface of the flexor tendons;     - vincula provide the blood supply that participates in early healing             of flexor tendons and that also serves as a checkrein to limit             proximal retraction of a lacerated tendon;

23. Nutrient Supply Dual Source via Perfusion and Diffusion
A. Perfusion from blood supplied by longitudinal vessels as well as the vincula system.
B. Diffusion within the sheath is via synovial fluid.
Diffusion is more important within the digital sheath. (Lundborg 1978, 1980)

24. Vascular Supply
Studies of the physiology of intrasynovial flexor tendons have demonstrated the importance of both intrinsic and extrinsic sources of nutrition, from local vascular networks and from the synovial fluid environment.
intrinsic healing occurs without direct blood flow to the tendon;
extrinsic healing is known to occur by proliferation of fibroblasts             from the peripheral epitendon;             - fibrous proliferation froms tenoma around the periphery of                   cut tendon ends and also invades space between tendon ends;             - adhesions occur because of extrinsic healing of the tendon and                   limit tendon gliding within fibrous synovial sheaths;

25. Synovial Sheaths
The flexor tendons are covered by a thin visceral layer of adventitia, or paratenon. The tendons enter a synovium-lined fibro-osseous tunnel at the base of each digit that provides both a biomechanical advantage (on the basis of the pulley system) and a source of tendon nutrition (from the parietal and visceral layers of paratenon) 51

26. Digital Sheaths Analogous to paratenon
Visceral layer surrounds tendons
Parietal layer contains thickenings that comprise the flexor sheath and pulley system
Contains synovial fluid

27. Pulleys Pulley System - thickened areas within flexor sheath
The A1, A3, and A5 pulleys originate from the palmar plates of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints, respectively. The A2 and A4 pulleys are continuous with the periosteum of the proximal aspect of the proximal phalanx and of the middle third of the middle phalanx, respectively. The cruciform pulleys are thin and compliant; they are located between the A2 and A3 pulleys (C1), between the A3 and A4 pulleys (C2), and between the A4 and A5 pulleys (C3)

28. Pulleys- A2 & A4 Annular Pulley
Prevent tendon bow string during finger flexion
A2 and A4 pulleys most important
A1 and oblique pulleys most important in thumb
Cruciform Pulley
Give sheath the ability to conform to the position of flexion by allowing the Annular pulleys to approximate each other

29. Biomechanics Moment arm-pulleys
Loss of pulleys increase excursion necessary for desired flexion
Strickland OCNA 1983
Condensations of the synovial sheaths form at strategic points along the digit and work in conjunction with the palmar aponeurosis pulley and the transverse carpal ligament to maximize the efficiency of joint rotation and force transmission

30. Biomechanics Forces generated during tendon function
Passive flexion 2-4 N
Active with mild resistance 10N
Active with moderate resistance 17N
Strong grasp 70N
Tip pinch 120N
Power grip 200N
(FDS 30% < FDP, loads increased by edema/scar) Schiund et al JHS 1992

31. Biomechanics
9 cm of tendon excursion is required for composite wrist & digital flexion
2.5 cm for full digital flexion with wrist stabilized
Tendon excursion and joint rotation are controlled by pulley system

32. Summary Intrasynovial flexor tendon repair- leave sheath intact
Preservation of A2 & A4 pulleys
Digital arterial ladder branch is identified and preserved

33. Summary Thick skin flaps retracted with sutures
Create windows in the membranous portion of the flexor tendon sheath
Blind passage of instruments into the tendon sheath should be avoided

34. Management of Flexor tendon Lacerations
History
Physical Examination
Surgical Repair
Rehabilitation

36. Examination Colour, Capillary Refill, Temperature
Compare to non-injured hand

37. Circulation

38. Nerves - Sensory

39. Diagnosis of Flexor Injury
Posture of Hand/ Normal cascade
Passive tenodesis test
Forearm compression test
Independent testing of FDS & FDP
Partial damage
When both flexor tendons of a finger are severed, the finger lies in an unnatural position of hyperextension, especially when compared with uninjured fingers. Flexor tendon injuries may be tentatively confirmed by several passive maneuvers. Passive extension of the wrist does not produce the normal ‘‘tenodesis’’ flexion of the fingers. If the wrist is flexed, even greater unopposed extension of the affected finger is produced. Gentle compression of the forearm muscle mass will at times demonstrate concomitant flexion of the joints of the uninvolved fingers, whereas the injured finger will not demonstrate this related flexion, indicating
separation of the tendon ends. Gently pressing the fingertip of each digit will reveal loss of normal tension in the injured finger.

40. Normal Flexion Cascade

42. Flexor Tendon Testing
With the proximal interphalangeal joint stabilized, the flexor digitorum profundus is presumed
severed if the distal interphalangeal joint cannot be actively flexed (Figure 66-3). If neither the proximal nor the distal interphalangeal joint can be actively flexed with the metacarpophalangeal joint stabilized, both flexor tendons probably are severed. The method used to demonstrate the transection of a flexor digitorum sublimis tendon with an intact flexor
profundus tendon involves maintaining the adjacent fingers in complete extension, anchoring the profundus tendon in the extended position, and removing its influence from the proximal interphalangeal joint. Thus, when a sublimis tendon has been severed and the two adjacent fingers are held in maximum extension, flexion of the interphalangeal joint usually is not possibleThe obvious exception to this evaluation is the result of the independent function of the index finger flexor digitorum profundus; a technique advocated by Lister is helpful in evaluating an isolated injury to this tendon. In this examination, the patient is requested to pinch and pull a sheet of paper with each hand, using the index fingers. In the intact finger, this function is accomplished by the flexor sublimis with the flexor digitorum profundus relaxed, allowing hyperextension of the distal interphalangeal joint so that maximum pulp contact occurs with the paper. In the injured finger, the distal interphalangeal joint will hyperflex and the proximal interphalangeal joint will assume an extended position.

43. FPL