The Ligaments of the Wrist

1. The Ligaments of the Wrist Reviewed by: K. Ikram, D.O. February 23, 2001

2. Introduction • Few things are more confusing than the overwhelming number of wrist ligaments and the variance of nomenclature. • The wrist is divided into 3 major jt regions: distal radioulnar, radiocarpal, and midcarpal • Carpal bones divided into prox and distal rows

3. Prox row is composed of scaphoid, lunate, and triquetrum • Distal row is comprised of trapezium, trapezoid, capitate, and hamate. • Distal radioulnar jt (DRUJ) is composed of head of ulna, sigmoid notch region of distal radius, DRUJ capsule, and triangular fibrocart complex (TFCC)

4. Distal Radioulnar Jt • Composed of 2 lig • Dorsal radioulnar lig • Palmar radioulnar lig • Dorsal Radioulnar lig • Blends with dorsal radiocarpal lig • Is the dorsal limit of TFC • Dorsal fibers separate to form ECU tendon • Action is to stabilize distal ulna from subluxing ant during supination

5. Palmar radioulnar lig • Forms the palmar limit of the TFC. • Interdigitates with the DRU lig • Forms the bulk of the prox attachment of the ulnolunate and ulnotriquetral lig • Fxn to stabilize DRUJ by preventing dorsal subluxation of ulna relative to the radius in pronation.

6. Palmar Radiocarpal Jt • The ligaments are part of the palmar jt. capsule • 4 palmar RC lig, best viewed from intraarticular perspective • Radioscaphocapitate • Long radiolunate • Radioscapholunate • Short radiolunate

7. Radioscaphocapitate Lig • Large capsular ligament • Courses distally and ulnarly to form the radial wall of the radiocarpal jt capsule • Majority of fibers pass ant to scaphoid to form palmar capsule of midcarpal jt • Remaining fibers arc around the distal margin of palmar horn of lunate and interdigitate with fibers from UC and TC lig to form the arcuate ligament • RSC separated from LRL by interligamentous sulcus • It is a weak link of capsule and divides to form “space of Poirier” in a perilunate dislocation

8. Functions include: • Formation of radial collateral lig of wrist • Constraint against radiocarpal pronation • Constraint against ulnocarpal translocation • Stabilizes distal pole of scaphoid

9. Long Radiolunate ligament • Also called palmar radiolunotriquetral or palmar radiotriquetral lig • Just deep to RSC ligament • Separated by interligamentous sulcus • Fxn • Constraint against ulnar translocation of lunate • May constrain distal translation without interfering in palmar/dorsiflexion of lunate

10. Radioscapholunate lig • Also called ligament of Testut • Found b/n LRL and SRL • Considered the intra-articular fat pad • Composed largely of arterioles, venules, and small nerves • The vessels originate from the radial carpal arch • Nerve fibers are terminal branches of ant interosseous nerve. • Little data showing mech contribution by this structure

11. May serve as a mechanoreceptor • Also a likely source for synovial filtration, producing synovial fluid and possibly resorbing metabolic waste.

12. Short Radiolunate Lig • Forms the palmar radiocarpal jt capsule b/n the lunate fossa of the distal radius and the lunate • Immediately adj to RSL lig and is directly contiguous with UL ligament.

13. Ulnocarpal Joint • Represents the interface b/n the carpus and the forearm • The UC lig maintain the stability of the UC jt and guide the motion of the lunate and triquetrum. • 3 lig here are UL, UT, and UC

14. Ulnolunate Ligament • Found directly contiguous with SRL lig, continuing the palmor jt capsule just ulnar to the lunate fossa. • Precise fxn is unknown • It mirrors the fxn of the SRL, proximally stabilizing the luante during all phases of wrist motion • No direct bony attachment.

15. Ulnotriquetral Ligament • Divided into medial and lateral bands • Separated by an orifice leading to the pisotriquetral jt • Lat band arises immediately medial to UL lig, from fibers in PRU lig • lies in the same plane as the SRL and UL ligaments • Forms palmar floor of UC jt and constrains triquetrum. • Med band arises from DRU ligament • Forms ulnar and dorsal wall of UC jt and deep surface of ECU • Serves as ulnar coll lig of wrist, constrains distal translation of triquetrum, and reinforces ECU sheath.

16. Ulnocapitate Ligament • Different from UL and UT lig • Has a distinctly bony origin from ulnar head • Not visible from an intra-articular perspective • Courses around the distal margin of palmar horn of the lunate forming an “arcuate” lig that is the palmar midcarpal jt capsule. • Fxn unsure but may reinforce ulnocarpal jt capsule and LT jt.

17. Dorsal Radiocarpal Joint • Reinforced by a single lig – the DRC lig • The radial half of DRC jt is devoid of lig reinforcement

18. Dorsal Radiocarpal Lig • Broad zone from Listers tubercle to sigmoid notch • Shares insertion with dorsal intercarpal lig • Reinforces dorsal region of LT interosseous lig and constrains ulnar translocation of carpus

19. Palmar Midcarpal Jt • Appears as an S from frontal perspective • 4 palmar midcarpal capsular lig • Scaphotrapezium-trapezoid (STT) • Scaphocapitate (SC) • Triquetrocapitate (TC) • Triquetrohamate (TH)

20. Scaphotrapezium-trapezoid lig • Attaches prox to the distal half of the palmar cortex of the tubercle of the scaphoid • Fxn • Stabilize the distal pole of the scaphoid, trapezium, and trapezoid. • When dissociation occurs, most common clinical sign is abnormally dorsiflexed scaphoid

21. Scaphocapitate Ligament • A strong band • Functions as a stabilizer of the distal pole of the scaphoid • Also constrains midcarpal pronation

22. Triquetrocapitate ligament • A strong ligament • Exact fxn unknown but when disrupted, lead to non dissociative instability

23. Triquetrohamate ligament • Ulnar most lig of palmar midcarpal jt • Fxn unknown but critical in preventing midcarpal dissociative instability and constraining midcarpal supination

24. Palmar Scaphotriquetral Lig • Recently described as a band spanning the midcarpal jt • A part of the midcarpal arcuate lig formed by the RSC and UC lig.

25. Dorsal Midcarpal Joint • These ligaments are long capsular ligaments, spanning several bones. • 2 bands • Dorsal intercarpal lig • Dorsal scaphotriquetral lig

26. Dorsal Intercarpal Ligament • A strong capsular lig that attaches to DRC ligament • Some fibers continue to form the deep fascia of the midhand, enveloping the radial art in the anatomic snuffbox.

27. Dorsal Scaphotriquetral Lig • Forms a labral like extension of the SL and LT lig over the prox aspect of the midcarpal jt • May fxn as a labrum for the head of the capitate and prox pole of hamate. • Also stabilizes SL and LT interosseous ligaments

28. Prox Row Interosseous Jts • SL and LT jts formed by mutual articulation of bones of prox carpal row. • SL and LT lig are C shaped • Midcarpal jt normally isolated from communication with radiocarpal jt.

29. Scapholunate Ligament • SL ligament is a 3-part structure with dorsal, palmar, and proximal regions. • Dorsal region is thickest • Contiguous with DST ligament • RSL lig interrupts prox and palmar regions • Dorsal region most critical for resistance to palmar-dorsal translation • Palmar region critical for constraint of palmar/dorsiflexion.

30. Lunotriquetral Ligament • Divided into 3 regions: dorsal, palmar, and proximal regions • Prox is fibrocartilage, other 2 are true ligaments • Palmar region is thick, interdigitating with UC ligament • Palmar region most critical in constraining mutual translation of lunate and triquetrum • Dorsal region constrains palmar/dorsiflexion.

31. Will get volar intercalated segmental instability if both the LT and DRC ligaments are compromised.

32. Distal Row Interosseous Lig • Represent a heterogeneous group of articulations • With 4 bones in distal row, 3 interposed joints • Trapezium-trapezoid (TT) • Trapezocapitate • Capitatohamate.

33. Trapeziotrapezoid Ligament • Composed of dorsal and palmar regions • Dorsal region forms floor for ECRL and for deep branch of radial art

34. Trapeziocapitate Ligament • Composed of dorsal, palmar, and deep regions • Deep region situated entirely within the joint space • High energy impact with radial sided axial dissociation causes disruption

35. Capitohamate Ligament • Divided into 3 regions: dorsal, palmar, and deep • Contributes substantially to transverse stability of distal row and entire carpal arch system

36. Conclusions • The list of ligaments may be intimidating to the new student of wrist anatomy. However, there is no way to simplify these ligaments.