EXTENSOR EXPANSION PPT BY DR. SHUBHANSHU GAURAV.pptx

Anatomy of extensor expansion

1. Extensor Expansion Anatomy Dr. Shubhanshu Gaurav Department of Plastic Surgery K.E.M. Hospital, Mumbai

2. Extensor Expansion

3. definition Translucent, fibrous expansion on the dorsum of proximal phalanx of each digit An aponeurotic extension of the extensor digitorum tendons (EDC,EI,EDM) Triangular structure, forms a hood over MCP and Proximal phalynx

4. The EDC tendon attaches by a tendinous slip to proximal Phalanx, through which it extends the MCP joint. The central tendon (or Slip) proceeds dorsally to attach the base of middle phalanx where tension can extend the PIP joint. Lateral bands extends DIP joint - inserts to the distal phalynx Lumbricals, extensor indicis , palmer and dorsal interossei inserts on lateral bands

5. Interosseous slip  ±  Lumbrical (radial) slip =  Lateral band Lateral band + Lateral slip of EDC =  Conjoined lateral band 2 Conjoined lateral bands converge at dorsal distal phalanx base =  Terminal extensor tendon

6. The lateral bands proceed on either side of dorsal midline and rejoin before attaching the distal phalanx The extensor hood surrounds the MCP joint laterally, medially and dorsally ; and receives tendinous fibers from the lumbricals and interossei

7. Tendon of EDC blends with the expansion along its central axis and separated from the MCP joint by small bursa. Base – connects it to the interosseous muscle on each side Stabilized by numerous transverse fibers and by links that extend to the deep transverse metacarpal ligaments – Which separates the phalangeal attachment of dorsal interosseus from the rest of muscle and also palmar interosseus from the lumbricals

8. Deep transverse metacarpal ligament Function: prevents metacarpal heads from splaying apart (abduction) allows some dorsal-volar translation Anatomic components connects 2nd to 5th metacarpal heads together at volar plate of the MCP joint

9. Sagittal bands Function keep extensor mechanism tracking in the midline during flexion of MP joint Anatomy    origin: palmar plate insertion: extensor mechanism (curves around radial and ulnar side of MP joint)

10. Triangular ligament (Triangle of stack) Function counteracts pull of oblique retinacular ligament, preventing lateral subluxation of the common extensor mechanism Anatomy Triangular in shape  located on dorsal side of extensor mechanism, distal to PIP joint

11. Oblique retinacular ligament of Landsmeer (ORL) attach at the sides of the proximal phalanx to distal tendon sheaths and proceed to distal portion of lateral bands. Thus, the ORL’s line of application is volar to the PIP joints’ lateral axis and dorsal to the DIP joints’ lateral axis.(Retraction leads to Boutonniere deformity ) Transverse retinacular ligament:  Connect the lateral bands to PIP joint volar plate (prevent hyperextension of PIP joint – complete disruption leads to  swan-neck deformity )

12. Muscles that transmits force to the otherwise non-contractile extensor mechanism

13. Lumbricals (4) Attachments proximally tendon of flexor digitorum profundus and distally to extensor mechanism on radial side at the level of the lateral bands. Pass on the volar side of the transverse metacarpal ligament If they act alone, produce MCP Flexion. Also PIP and DIP extension when they introduce tension into the extensor mechanism

14. The lumbricals permit a dynamic interaction between flexors and extensors. This attachments transmit their force to both the FDP tendon and extensor mechanism. Increases passive tension in the extensor mechanism Decreases passive tension in FDP tendons distal portion

15. Palmar INTEROSSEI (4) Attach proximally to a metacarpal and distally to the same digit’s proximal phalanx and /or its extensor Mechanism They produce MCP adduction and in certain instances, MP flexion . They also produce PIP and DIP extension when they introduce tension into extensor mechanism.

16. Dorsal interossei (4) Attaches proximally between adjacent metacarpals and distally to proximal phalnyx Produce MCP abduction and in certain instances, MCP flexion. Also they attach to the extensor mechanism, produces PIP and DIP extension.

17. How does the extensor Mechanism work ? Extensor Mechanism’s fibers are tendinous, and therefore incapable of producing active force, they transmit force to their attachments

18. The extensor mechanism’s fibers have Lines of Application that are always dorsal to the lateral axes of the PIP and DIP joints. Therefore, activity in the intrinsic muscles that attach to the extensor mechanism always produces DIP and PIP extension. Passive flexion of the MP joint elongates the extensor mechanism and extends the PIP and DIP joints there.

19. MCP in flexion : flexes the MP joint and distal shift in the extensor hood. MCP in extension : extends the MP joint, also pulls the extensor mechanism ( including the hood) proximally.

20. Thanks