Extensor Ligaments Lumbrical tendon passes volar to transverse metacarpal ligament Interossei tendon passes 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