Zone II Flexor Injuries : Wheeless' Textbook of Orthopaedics

- Discussion:
- see flexor tendon repair
- see FDP lacerations: FDS and FDP
- almost all tendon injuries in zone 2 are due to lacerations;
- this is where 2 tendons enter fibro-osseuous tunnel at mid-palm level;
- once the FDS and FDP tendons enter flexor tendon sheath, the FDS separates into 2 segments, which pass around FDP tendon, and which
then reunite at Camper's chiasma (dorsal to the FDP);
- hences zone II lacerations will injure the FDP prior to injuring the two slips of the FDS tendon;
- note: that even in the best of hands, digital motion following Zone II injuries will be about 80% of the uninjured digits;
- evaulation:
- examiner should have the patient flex at the DIP joint to assess FDP function and at PIP joint, while holding adjacent digits in full
extension, to assess FDS function;
- digital nerve and arterial injuries are noted; (see nerve and artery repair)
- arterial injuries can be assessed by applying a "pulse oximeter" and then applying a digital allen's test;
- primary repair:
- primary repair of both tendons is performed only under ideal conditions;
- wound must be clean and well debrided of all crushed tissue;
- tendon sheath should be atleast partially intact;
- see:
- FDS laceration
- FDP laceration
- partial tendon lacerations
- delayed repair:
- even at 1 month following initial injury, end to end suture of both tendons is possible;
- neglected zone II injuries will require staged tendon grafting:
- controversies: should both flexor tendons be repaired?
- in zone II injuries in which both FDS and FDP are lacerated, both tendons should be repaired - expect up to 90% good or excellent results;
- the main complication of repair, is formation of adhesions to the flexor tendon sheaths;
- advantages of superficialis repair:
- repaired FDS increases digit strength;
- improved flexion at PIP joints
- preserves short vincula which provides blood supply to FDP and improves healing potential;
- acts as pulley for repaired profunda that provides improved excursion and strength;
- intact FDS prevents PIP hyperextension and DIP hyperflexion;
- ref: Work of Flexion Related to Different Suture Materials After FDP and FDS Tendon Repair in Zone II: A Biomechanical Study

- Exposure:
- see: phalangeal incisions:
- note: if both digital nerves are injured (which implies concomitant digital vessel injury) then it will be essential to carefully consider the incision so as not to create an avascular flap;
- digital wounds are extended both proximally and distally;

- Management of Flexor Tendon Sheath:
- see: anatomy of sheath and pulley reconstruction;
- small portion of the fibroosseous canal may need to be opened, but as much of A2 and A4 pulleys as possible are left intact;
- it is not usually possible to close annular ligaments, once they are cut;
- in order to avoid impingment of flexor tendons with in flexor sheath, consider removal of a portion of flexor tendon sheath around tendon repair;
- one good option is to make a "Z" step cut incision into the pulley sheath;
- following the tendon repair, the pulley sheath is closed over the pulley, with assurance that the closure is not constrictive;
- another technique is to open sheath and then use a slip of extensor retinaculum in order to augment repair and to achieve a water tight closure;
- small longitudinal incisions can be made between the annular pulleys, which allows visualization of the flexor tendons;
- typically the surgeon will open the C1 or the C2 pulleys;
- the tendon repair will be completed in these annular windows;
- references:
- Effect of pulley integrity on excursions and work of flexion in healing flexor tendons
           - A2 pulley incision or one slip of the superficialis improves flexor tendon repairs.
- Flexor tendon pulley V-Y plasty: an alternative to pulley venting or resection.
           - "Venting" or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries.
           - Use of vein graft as a tendon sheath substitute following tendon repair: an innovative technique in tendon surgery .
           - Results of primary tendon repair with closure of the tendon sheath .
           - Flexor tendon repair and rehabilitation in zone II open sheath technique versus closed sheath technique.
- Biomechanical and histologic evaluation of tendon sheath management.
           - Flexor sheath closure during delayed primary tendon repair

- Tendon Retreival:
- distal tendon edge:
- if fingers are flexed during the injury, the distal end of the tendon may retract 1 cm distal to the tendon sheath wound;
- DIP is flexed (and PIP if needed) to bring tendon edge into optimal position within the cruciate window;
- proximal tendon edge:
- Morris and Martin (1993)
- single pronged skin hook is carefully inserted into sheath, and at least one tendon edge is secured;
- withdrawl of the hook should retrieve both tendons;
- Sourmelis and McGrouther (1987);
- a small catheter is passed into the sheath and is delivered proximally into a small wound in the palm, just proximal to the A1 pulley;
- if the tendons have retracted proximal to the synovial sheath, the relative positions of the tendons must be restored;
- i.e., the FDP must pass from dorsal to volar through Camper's chiasma;
- catheter is sutured to both tendons 2 cm proximal to A1 pulley, which is then pulled distally to deliver tendons into synovial windon;
- tendon ends are held in place with 25 gauge needle inserted thru annular pulleys;
- if more than 1 cm of tendon edge can be exposed then the core suture can be inserted thru a single synovial window;
- references:
- A simple tendon retrieval method.
- A further tendon retrieval trick.
- The use of skin hooks and hypodermic needles in tendon surgery.
- Retrieval of the retracted flexor tendon.
- Retrieving tendon ends in zone II flexor tendon injuries.
- A simple, semirigid, and surgeon-friendly tendon retriever and flexor sheath dilator.
- The reversed Esmarch tourniquet technique for the retrieval of cut flexor tendons

- Tendon Repair: (tendon repair technique)
- consider use of the tenofix device;
- ref: Device for Zone-II Flexor Tendon Repair. A Multicenter, Randomized, Blinded, Clinical Trial.
- only on rare occassions do tendon edges require debridement;
- traumatizing the outer surface of the tendon with instruments may cause additional adhesions;
- instead, press cut end of tendon against against adjacent tissues / blunt end of forceps, and then pass suture;
- FDS tendon slips are repaired initially;
- when the laceration occurs near the FDS insertion, consider repairing both slips w/ figure of 8 sutures;
- avoid constriciton of the FDS tendon slips over the FDP repair (will inhibit gluiding):
- in report by Zhao C, et al (2002), authors examined effect of releasing 1 slip of FDS w/ FDP lacerations;
- after FDP repair the gliding resistance after modified Kessler repair increased 247% with FDS intact, 132% with one slip of
FDS present, and 103% with FDS entirely removed;
- references:
- Resection of the flexor digitorum superficialis reduces gliding resistance after zone II flexor digitorum profundus repair in vitro.
- Flexor Digitorum Superficialis Repair Outside the A2 Pulley After Zone II Laceration: Gliding and Bowstringing

- FDP is then repaired end to end using 4-O Ethibond suture w/ reinforcing peripheral sutures;
- core sutures are placed, using two separate double armed needles;
- ideally the core suture will contain at least 4 strands crossing the repair;
- core suture may be placed the primary window, but if exposure is not sufficient the surgeon can utilize the
more proximal or distal cruciate window (C1 and C2) w/ care taken to preserve the A3 pulley;
- this allows the the needle to move out of and into the tendon as the core stitch is being created;
- - management of repair impingement / indications for FDS sacrifice:
- when tendon repair requires sacrifice of pulleys
- when both tendons are lacerated & need to be immobilized at same level;
- as an alternative, consider staged tendon reconstruction:
- resection of one slip of the FDS to facilitate gluiding:
- in the report by Zhao C, et al (2002), authors examined effect of releasing 1 slip of FDS w/ FDP lacerations;
- after FDP repair the gliding resistance after modified Kessler repair increased 247% with FDS intact, 132% with one slip of FDS present, and 103% with FDS entirely removed;
- references:
- Resection of the flexor digitorum superficialis reduces gliding resistance after zone II flexor digitorum profundus repair in vitro.
- Pulley plasty versus resection of one slip of the flexor digitorum superficialis after repair of both flexor tendons in zone II: a biomechanical study.
- Impact of flexor digitorum superficialis on gliding function of the flexor digitorum profundus according to regions in zone II.
- Flexor sheath closure during delayed primary tendon repair
- “Venting” or partial lateral release of the A2 and A4 pulleys after repair of zone 2 flexor tendon injuries

- Tendon Sheath Repair: (see tendon sheath reconstruction)
- prior to extending digit, the sheath is closed w/ a running 6-0 monofilament;
- following tendon sheath repair, the digit is extended which delivers the tendon repair site distally;
- cautions:
- adequate tendon sheath repair is not only necessary to prevent bowstringing but it is also important to prevent flexion contractures;

- Post Operative Care