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https://upload.orthobullets.com/topic/6003/images/ORL strauch 300_moved.jpg
https://upload.orthobullets.com/topic/6003/images/obretlig..jpg
https://upload.orthobullets.com/topic/6003/images/Cleland's_moved.jpg
https://upload.orthobullets.com/topic/6003/images/cleland-grayson.jpg
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https://upload.orthobullets.com/topic/6003/images/Extensor hood_moved.jpg
Extensor Ligaments
  • Lumbrical tendon passes volar to transverse metacarpal ligament 
  • Interossei tendons pass dorsal to transverse metacarpal ligament 
Retinacular Ligaments 
  • Function  
    • retain and position common extensor mechanism during PIP and DIP flexion 
    • similar to sagittal band function 
  • Anatomic Components
    • oblique band (oblique retinacular ligament of Landsmeer)
      • function
        • links motion of DIP and PIP
          • lies volar to axis of PIP, but dorsal to axis of DIP
      • anatomy
        • origin: from lateral volar aspect of proximal phalanx, 
        • insertion: to lateral terminal extensor dorsally (crosses collateral ligaments)
      • biomechanics
        • with PIP flexion, ligament relaxes to allow DIP flexion
        • with PIP extension, ligament tights to facilitate DIP extension
      • pathology
        • contracture causes volar displacement of lateral bands and a resulting Boutonniere Deformity 
        • reconstruction of oblique retinacular ligament used to treat swan neck deformity
        • if ORL is tight
          • resting finger position is DIP extended, PIP flexed
          • unable to flex DIP if PIP is extended
          • able to flex DIP only after PIP is flexed
            • contrast this with intrinsic tightness, where there is decreased PIP flexion when the MCP is extended, and improved PIP flexion when the MCP is flexed
            • contrast this with extrinsic tightnes (extensor tendon tightness), where there is increased PIP flexion when MCP is extended, and decreased PIP flexion when MCP is flexed
    • transverse band 
      • function
        • with PIP flexion, pull lateral bands volarly over PIP
        • with PIP extension, prevents excessive dorsal translation of lateral bands 
      • anatomy
        • origin: from edge of flexor tendon sheath at PIP
        • insertion: lateral border of conjointed lateral bands
      • pathology
        • attenuation leads to dorsal translation of lateral bands and a resulting swan neck deformity 
        • contracture (with attenuation of triangular ligament) leads to volar translation of lateral bands and resulting boutonniere deformity
Digital Cutaneous Ligaments
  • Function
    • tether skin to deeper layers of fascia and bone to prevent excessive mobility of skin and improve grip 
    • stabilize the digital neurovascular bundle with finger flexion and extension
  • Anatomic Components
    • Cleland's ligaments (remember "C" for ceiling)   
      • dorsal to digital nerves
      • not involved in Dupuytren's disease
    • Grayson's ligament (remember "G" for ground)    
      • volar to digital nerves
Expansion Hood
  • Function
    • works to extend PIP and DIP joint
  • Anatomic Components
    • central slip 
      • functions to extend PIP
      • inserts into base of middle phalanx
    • lateral band 
      • functions to extend DIP
      • inserts into distal phalanx
        • lumbricals, extensor indicis, dorsal and palmar interossei insert on lateral band
MCP Joint Collateral Ligaments
  • Function
    • stabilize MCP joint during motion
      • MCP joint "cam" nature leads to inconstant arc of motion because of joint asymmetry 
        • caused by "snoopy head" configuration of metacarpal head
      • collaterals looser in extension, tighten during increasing flexion
        • as MP joint flexes, proximal phalanx moves further away from metacarpal head, tightening all the ligaments
  • Anatomic Components
    • radial collateral ligaments (RCL) are more horizontal than ulnar collateral ligaments (UCL)
    • RCL and UCL have 2 parts each: proper and accessory ligaments 
      • accessory ligament 
        • fan shaped 
        • more volar
          • tight in extension
        • attachment
          • from metacarpal head at center of rotation
          • to palmar plate and deep transverse metacarpal ligament
        • clinical test
          • adduction/abduction stress in extension
      • proper ligament 
        • cord like
        • more dorsal
          • tight in 30 degrees of flexion
        • attachment
          • from posterior tubercle of metacarpal head  (dorsal to mid axis)
          • to proximal phalanx base
        • clinical test
          • adduction/abduction stress in 30 degrees flexion to isolate proper ligaments
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 MP joint   
Natatory Ligament (Superficial Transverse Metacarpal Ligament)
  • Function
    • resists abduction
  • Anatomic components
    • most superficial MP joint ligament  
    • origin: from distal to the MP joint
    • insertion:  proximal phalanx of all 5 fingers (runs in the web space)
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)
Triangular ligament
  • 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
  • Pathology
    • contracture leads to swan neck deformity
Volar Plate 
  • Function
    • prevent hyperextension
  • Anatomy
    • thickening of joint capsule volar to the MP joint  
    • in the thumb, sesamoid bones are located here
    • origin: metacarpal head
    • insertion: periarticular surface of proximal phalanx , via checkrein ligaments 
  • Biomechanics
    • loose in flexion
      • folds into metacarpal neck during flexion
    • tight in extension
 

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