Key notes on plastic surgery/Adrian M. Richards

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36 GENERAL PRINCIPLES
• Verdan described five zones of flexor tendon injury.
• Zone 1: distal to the insertion of flexor digitorum superficialis (FDS).
• Zone 2: between the proximal end of the flexor sheath and the insertion of FDS.
• Zone 3: between the distal edge of the flexor retinaculum and the proximal end
of the flexor sheath.
• Zone 4: under the flexor retinaculum.
• Zone 5: proximal to the flexor retinaculum.
• Zone 2 was described as ‘no man’s land’ by Bunnell because of the poor results
of flexor tendon repair at this site.
• Tendon repair in this area is complicated by the fact that the superficial and deep
flexors are in close approximation within a tight sheath.
• Extensor tendons are subdivided into eight zones.
• Zone 1: over the distal interphalangeal joint (DIPJ).
• Zone 2: between the proximal interphalangeal joint (PIPJ) and the DIPJ.
• Zone 3: over the PIPJ.
• Zone 4: between the metacarpophalangeal joint (MCPJ) and the PIPJ.
• Zone 5: over the MCPJ.
• Zone 6: between the MCPJ and the extensor retinaculum.
• Zone 7: under the extensor retinaculum.
• Zone 8: between the extensor retinaculum and the musculotendinous junction.
• The odd-numbered zones are located over the joints.
• The first five zones are in the finger.
Mechanisms of tendon healing
Extrinsic healing
• Extrinsinc healing is dependent on fibrous attachments forming between the
tendon sheath and the underlying tendon.
• Historically this was believed to be the sole mechanism by which tendons healed.
• This led to the development of post-operative protocols which immobilized the
tendons in the mistaken belief that this maximized tendon repair.
Intrinsic healing
• Intrinsic tendon healing is dependent on:
• Bloodflow though the long and short vinculae.
• Diffusion from the synovial fluid.
• Lunborg showed that tendons heal when wrapped in a semipermeable membrane
and placed in the knee joint of a rabbit.
• Enclosing the tendons in semipermeable membrane stimulates intrinsic healing
as it permits the passage of nutrients but not cells.
• Awareness of the ability of tendons to heal by intrinsic mechanisms has led to the
development of post-operative protocols which include early mobilization.
Phases of tendon healing
These are similar to those of wound healing.