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MUN ORTHOPEDICS Wrist Biomechanics and Carpal Instability.

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Presentation on theme: "MUN ORTHOPEDICS Wrist Biomechanics and Carpal Instability."— Presentation transcript:

1 MUN ORTHOPEDICS Wrist Biomechanics and Carpal Instability

2 MUN ORTHOPEDICS Wrist Biomechanics Anatomy Kinematics Force transmission

3 MUN ORTHOPEDICS Anatomy 8 bones Complex interlocking shapes Intrinsic and extrinsic ligaments

4 MUN ORTHOPEDICS

5 Wrist ligaments

6 MUN ORTHOPEDICS Wrist ligaments Volar stronger than dorsal Double V shape with weak area ; space of Poirier Important interosseous ligaments are SLIL and LTIL Dorsal ligaments tend to converge on triquetrum

7 MUN ORTHOPEDICS Kinematics Three axes of motion –FEM 90 – 70 degrees –Flex/ext split between radiocarpal & midcarpal –RUD 20 – 50 degrees –PSM 90 – 90 degrees

8 MUN ORTHOPEDICS Axes of Motion

9 MUN ORTHOPEDICS Kinematics Rows Columns (Navarro) Oval ring Longitudinal columns (Weber) “Link Joint”

10 MUN ORTHOPEDICS Link Joint

11 MUN ORTHOPEDICS Kinematics Rows –Proximal and Distal with scaphoid as a bridge –Motion within and between rows Columns –Central(flex/ext) lunate,capitate,hamate –Lateral (mobile) scaphoid,trapezoid,trapezium –Medial (rotation) triquetrum

12 MUN ORTHOPEDICS

13 Kinematics Center of rotation : head of capitate

14 MUN ORTHOPEDICS Kinematics Radial deviation : scaphoid flexes proximal pole goes dorsal “pulling” lunate into palmar flexion Ulnar deviation : scaphoid extends proximal pole goes volar pulling lunate into dorsiflexion

15 MUN ORTHOPEDICS Kinematics Triquetrohamate helicoid joint Ulnar deviation : “low” position distal and dorsiflexed pulling lunate into dorsiflexion Radial deviation : “high”position proximal and palmar flexed pulling lunate into palmar flexion

16 MUN ORTHOPEDICS Force Transmission Principal force transmission is through capitate lunate and proximal pole of scaphoid 75% radius 25% ulna

17 MUN ORTHOPEDICS Classification of Carpal Instability CID (dissociative) –DISI –VISI CIND (non-dissociative) –Radiocarpal,Midcarpal,Ulnar transloc’n CIC (complex) –Perilunate Dislocation

18 MUN ORTHOPEDICS Progressive periLunate Instability Stage I – scapholunate instability Stage II – capitate dislocation Stage III – triquetral dislocation Stage IV – lunate dislocation Spectrum of injury

19 MUN ORTHOPEDICS PLI

20 MUN ORTHOPEDICS Mechanism of injury Impact on thenar side of wrist causes hyperextension, ulnar deviation and intercarpal supination Progressive damage around lunate Bony or ligamentous

21 MUN ORTHOPEDICS Normal wrist

22 MUN ORTHOPEDICS Volar Intercalated Segment Instability

23 MUN ORTHOPEDICS Dorsal Intercalated Segment Instability

24 MUN ORTHOPEDICS Gilula lines

25 MUN ORTHOPEDICS Carpal Angles

26 MUN ORTHOPEDICS Carpal Height L2/L1 = 0.54 New ratio L2/capitate = 1.57

27 MUN ORTHOPEDICS Scapholunate Instability Most common form Rarely diagnosed acutely Local tenderness Scaphoid shift(Watson) Associated with other injuries eg distal radius

28 MUN ORTHOPEDICS Scapholunate Instability: Classification Type 1 – dynamic –Neg Xray;+ve Watson:+ve cine Type 2 – static – +ve plain films Type 3 – degenerative Type 4 – secondary –Kienbock’s ; SNAC

29 MUN ORTHOPEDICS Scapholunate Instability: Radiographs Scapholunate gap >2mm Foreshortened scaphoid Cortical ring sign Taliesnik,s “V” sign Lack of parallelism?

30 MUN ORTHOPEDICS Scapholunate Instability

31 MUN ORTHOPEDICS DISI

32 MUN ORTHOPEDICS Scapholunate Instability

33 MUN ORTHOPEDICS

34

35 Scapholunate Instability: Treatment Acute (0-3 wks) : open repair vs arthroscopically-assisted PCP x 8wks Chronic (>4 wks) : repair + reconstruction –STT –Blatt –SLC

36 MUN ORTHOPEDICS Scapholunate instability

37 MUN ORTHOPEDICS Acute repair SLIL

38 MUN ORTHOPEDICS Blatt Capsulodesis

39 MUN ORTHOPEDICS STT Fusion

40 MUN ORTHOPEDICS STT Arthrodesis

41 MUN ORTHOPEDICS Scapholunate Instability: Arthrosis SLAC PRC Arthrodesis RSL

42 MUN ORTHOPEDICS Triquetrolunate instabliity Limited understanding of ulnar side TL or TH ?? Ulnar pain post injury Click +ve ballottement test Beware ulnar impaction syndrome Conservative Rx; rarely need limited fusion

43 MUN ORTHOPEDICS VISI

44 MUN ORTHOPEDICS Perilunate Dislocation Perilunate & Lunate are same basic injury Still missed in ER Rx of choice : open reduction & repair of ligaments/bones Dorsal and volar approach Late: fusion or PRC

45 MUN ORTHOPEDICS Lesser and Greater arcs

46 MUN ORTHOPEDICS Perilunate Dislocation

47 MUN ORTHOPEDICS Perilunate repair

48 MUN ORTHOPEDICS Ulnar Translocation Rare Difficult to treat Non-traumatic causes : RA,Madelung’s

49 MUN ORTHOPEDICS Ulnar Translocation

50 MUN ORTHOPEDICS

51 Carpal Instability: Unresolved Issues Role of arthroscopy Method of reconstruction SLIL eg bone- tendon-bone Ulnar side pathomechanics Role of MRI

52 MUN ORTHOPEDICS Grade III

53 MUN ORTHOPEDICS Grade IV


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