Biomechanics of Wrist and Hand Complex- Dr Gurjant Singh (PT)

Easy notes for physiotherapy students

1. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR BIOMECHANICS OF WRIST & HAND COMPLEX

2. THE WRIST COMPLEX Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

3. The wrist complex consist of 2 joints – Radiocarpal joint Midcarpal joint RADIOGRAPHIC REPRESENTATION SCHEMATIC REPRESENTATION Dr. Gurjant Singh (PT), MPT, ( Ph.D ) Assistant Professor, MMIPR

4. Normal varying ranges of wrist joint are – The 2 joint rather than single joint complex provides – Large ROM with less exposed articular surfaces & tighter joint capsule Less tendency for structural pinch at extreme ranges F la t t e n e d m u l t ij o i n t s u r fa c e s t h a t a r e m o r e c ap a b l e o f w i t h s t a n d i n g imposed pressures Flexion 65° - 85° Extension 60° - 85° Radial deviation 15° - 21° Ulnar deviation 20° - 45° Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

5. RADIOCARPAL JOINT STRUCTURE Formed by radius & radioulnar discs as a part of triangular fibrocartilage complex (TFCC) proximally & scaphoid, lunate & triquetrum distally. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

6. PROXIMAL & DISTAL SEGMENTS OF RC JOINT Proximal joint surface consist of : TFCC (triquetrum & little with lunate in neutral position) Distally: scaphoid , lunate , triquetrum P r o x i m a l r ad io c a r p a l j o i n t s u r fa c e i s o b li q u e& a ng l e d sl ig h t l y v o l a r l y & ulnarly . Average inclination of radius is 23° & tilted 11° volarly. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

7. Average inclination of radius is 23° & tilted 11° volarly . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

8. Triangular Fibrocartilage complex Consist of radioulnar disc & various fibrous attachments providing support to distal radioulnar joint. The disc is connected medially via 2 dense, fibrous connective tissue laminae. Upper laminae include dorsal & volar radioulnar ligament whereas lower laminae has connections to sheath of ECU tendon, triquetrum, hamate & base of 5 th metacarpal through ulnar collateral ligament. Meniscus homolog – region of irregular connective tissue (part o f lower laminae) traverse volarly & ulnarly from dorsal radius to insert on the triquetrum. Overall TFCC functions at wrist as an extension of distal radius. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

9. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

10. Scaphoid , lunate & triquetrum – proximal carpal row. B on e s a r e i n t e r c onn e c t e d b y 2 li ga m e n t s i e . S c apho l un a t e interosseous & lunotriquetral interosseous ligaments. Proximal carpal row & ligaments together appears as a single biconvex cartilage covered joint surface that can change shape to accommodate to the demands of space between forearm & hand. In radiocarpal joint distal surface is sharper than proximal both in coronal & sagittal plane – makes joint incongruent. This causes greater range of flexion than extension & greater ulnar deviation than radial deviation. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

11. A s t h e c u r v a t u r e & i n cli n a t i o n o f t h e r ad i o c a r pa l s u r f a c e s a f f e ct s function , the length of ulna in relation to radius also affects it. Ulnar negative variance - shorter ulna than radius at the distal end. Ulnar positive variance - longer distal ulna than distal radius. P o s i t i v e v a r i a n c e i s a s s o ci a t e d w i t h c han g e s i n T F C C t h i c k n e s s - potential for impingement of TFCC between ulna & triquetrum . Negative variance – abnormal force distribution at radiocarpal joint – potential degeneration – avascular necrosis of lunate ( kienbock’s disease). Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

12. RADIOCARPAL CAPSULE & LIGAMENTS Has strong but somewhat loose capsule & reinforced by capsular & intracapsular ligaments. Most ligaments & muscles crossing radiocarpal joint also contributes to midcarpal joint stability Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

13. MIDCARPAL JOINT STRUCTURE Ar t i c u l a t i o n b e t w e e n s c aph o i d , l un a t e & t r i qu e t r u m p r ox i m al l y & trapezium , trapezoid, capitate & hamate distally. Functional unit rather than an anatomical unit. Has separate fibrous capsule & synovial lining that is continuous with each intercarpal articulation & some with CMC joint. Complex as it has overall reciprocally concave convex configuration . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

14. Functionally distal carpal row moves as a fixed unit. Union of distal carpals also results in equal distribution of loads across scaphoid -trapezium-trapezoid, scaphoid - capitate , lunate-capitate & triquetrum-hamate articulations Distal row contributes to 2 degrees of freedom to wrist complex with varying amounts of ulnar /radial deviation & flexion/extension. Distal carpal row lads to the foundation of transverse & longitudinal arches of hand. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

15. LIGAMENTS OF THE WRIST COMPLEX The ligamentous structure of carpus is responsible for articular stability as well as guiding & checking motions between & among the carpals. In general, dorsal ligaments are thin & numerous volar ligaments are thicker & stronger. Ligaments Extrinsic Connects carpals to radius ulna proximally or metacarpals distally I n tri n s ic Interconnects the carpals Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

16. PROPERTIES EXTRINSIC LIGAMENTS INTRINSIC LIGAMENTS CONNECTION Carpals to radius ulna proximally & metacarpals distally Interconnect carpals (intercarpals / inrterosseous) Nutrition Contiguous vascularized tissue Through synovial fluid Risk of injury High Low Healing Fast Slow Accept forces first Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

17. VOLAR CARPAL LIGAMENTS Organized into 2 groups : radiocarpal & ulnocarpal ligaments – composite volar radiocarpal ligaments. Has 3 distinct bands – the radioscaphocapitate (radiocapitate); short & long radiolunate & radioscapholunate ligaments. Radioscapholunate – stabilizes scaphoid – disruption causes scaphoid instability. Radial collateral ligament – extension of volar radiocarpal ligaments & capsule. Ulnocarpal ligament complex – composed of TFCC including articular disc & meniscus homolog; ulnolunate ligament & ulnar collateral ligament. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

18. 2 Volar intrinsic ligaments - important in wrist function. Scapholunate interosseous ligament - maintains scaphoid stability & so wrist stability. L u n o tr i q u e tr a l i n t e r o s s eou s li g a m e n t - m a i n t a i n s s t ab i l i t y b e t w ee n lunate & triquetrum Stretched while wrist extension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

19. DORSAL CARPAL LIGAMENTS Dorsal radiocarpal ligament Dorsal intercarpal ligament Together forms a horizontal ‘V’ that contributes to radiocarpal stability; notably stabilizes scaphoid during wrist ROM. Taut with wrist flexion. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

20. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

21. FUNCTIONS OF WRIST COMPLEX Movements of radiocarpal & midcarpal joints :- Proximal carpals acts as mechanical link between radius & distal carpals & metacarpals to which the muscular forces are directly applied – intercalated segment. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

22. Flexion / extension of the wrist – In 3 proximal carpal bones, scaphoid has greatest motion & lunate moves least. The movements of complex from complete flexion to extension are – distal carpal row moves on proximal carpal row → scaphoid & distal carpals moves on lunate & triquetrum → carpals as a unit move over radius & TFCC. Extension to flexion – reverse process. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

23. Radial / ulnar deviation – In radial deviation, carpals slide ulnarly over radius with simultaneous flexion of proximal carpals & extension of distal carpals. The opposite occurs in ulnar deviation. in full radial deviation, both the radiocarpal & midcarpal joints are in closed packed position. Ranges vary according to the wrist position – more to less – neutral → fully flexed → fully extended. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

24. MUSCLES OF WRIST COMPLEX Primary role – T o p r o vi d e a st ab l e b a s e f o r han d w h i l e p e r m i t t i n g p o s i t i o na l adjustments & allow for optimal length tension relationships . Muscles Volar (cause flexion) PL,FCR,FCU FD S ,FD P ,FPL Dorsal (cause extension) ECRL, ECRB,ECU E D C,EI P ,EDM,EPL,EP B ,APL

25. THE HAND COMPLEX Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

26. Hand complex consist of 5 digits – 4 fingers & one thumb . Each finger has 1 CMC, 1 MCP & 2 IP (proximal & distal) joints whereas thumb has 1 CMC, 1 MCP & ONLY 1 IP joint . Overall there are 19 bones & 19 joints distal to the carpals. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

27. CARPOMETACARPAL JOINTS OF FINGERS Articulation between distal carpal row with 2 nd to 5 th bases of metacarpals (MC). The 2 nd MC articulates primarily with trapezoid & secondarily with trapezium & capitate; 3 rd MC with capitate; 4 th with capitate & hamate & 5 th MC articulates with only hamate. Supported by strong transverse & weaker longitudinal ligaments . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

28. Deep transverse metacarpal ligament covers 2 nd to 4 th MC volarly – tethers together the MC heads & prevents excessive abduction which contributes to CMC stability . Proximal transverse (carpal) arch – affects CMC & hand function but not the wrist function. It is formed by trapezium, trapezoid, capitate & hamate (distal carpal row) – which is concave volarly. This concavity is maintained by transverse carpal ligament & intercarpal ligament. This forms carpal tunnel which contains median nerve & 9 extrinsic flexor tendons. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

29. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

30. CMC JOINT RANGE OF MOTION In the articulating surface more range is available at MC heads. The mobility increases from radial to ulnar side of hand. 2 nd to 4 th CMC joints are plane synovial joints having only 1° of freedom (flexion/extension) whereas 5 th CMC joint is saddle joint with 2° of freedom. (flexion/extension, abduction/adduction & limited opposition ) 2 nd & 3 rd C M C j o i n t s c ons i de r e d to have 0° of freedom – as it provides fixed & stable axis for 1 st , 4 th & 5 th MC heads Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

31. PALMAR ARCHES Th e f unc t i o n o f f i ng e r s C M C j o i n t s & t he i r seg m en t i s to contribute to palmar arch system. Proximal transverse arch – concavity formed by carpal bones. Distal transverse arch – formed by 1 st , 4 th & 5 th MC heads & is relatively mobile. Longitudinal arch – traverse length of the digits from proximal to distal. Deep transverse MC ligament contributes to stability of mobile arches during grip functions. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

32. PALMAR ARCHES Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

33. Allows the palm & digits to conform optimally to the shape of the object being held – allowing maximum surface contact, enhance stability & increase sensory feedback. Muscles crossing CMC joint contributes to palmar cupping – hollowing of palm accompanies finger flexion & relative flattening of palm accompanies finger extension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

34. METACARPOPHALANGEAL JOINTS OF FINGERS C onve x m e t aca r pa l hea d p r ox i m a ll y & concav e ba s e o f 1 st phalanx distally. C ondy l o i d j o i n t wi t h 2 ° o f f r eed o m ( f l ex i o n / e x t ens i o n & abduction/adduction ) In sagittal plane, MC head has 180° of articular surface (predominant portion lying volarly ), opposed to 20° of articular surface on 1 st phalanx. In frontal plane there is less but more congruent frontal plane . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

35. S u r r ounde d b y a capsu l e - l a x i n ex t ens i o n – a ll o w s s o m e passive axial rotation of phalanx. C o ll a t e r a l li g a m en t a t t h e vo l a r l y l o c a t e d dee p t r a n sv e r s e MC ligament - enhances joint stability. Volar plates - accessory joint structure to enhance joint stability. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

36. VOLAR PLATES Also called as palmar plates Increases joint congruence; provides stability to MCP joints (limits hyperextension) Composed of fibrocartilage & is firmly attached to base of proximal phalanx. Becomes membranous proximally to blend with volar capsule at MC heads. During MCP extension, the plate adds up the amount of surface in contact with large MC heads. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

37. Fibrocrtilage composition resist both tensile stresses (MCP hyperextension) & compressive forces (to protect MC heads from objects held in palm) During flexion – glides proximally - prevents pinching of long flexor tendons in MCP joint. Also blends with & are interconnected superficially by deep transverse MC ligament. sagittal bands (dorsal to deep transverse MC ligaments) - stabilizes volar plates. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

38. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

39. COLLATERAL LIGAMENT The radial & ulnar collateral ligaments of MCP joints are composed of 2 parts: collateral ligament proper (cordlike) & accessory collateral ligament. Tension in collateral ligament at full MCP joint flexion (closed pack position) - limits MCP abduction in full flexion. Provides stability throughout the MCP joint ROM Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

40. RANGE OF MOTION ROM at each joint varies; flexion/extension increases radially to ulnarly with index finger (90°) & little finger (110°). Hyperextension - consistent between fingers but varies among individuals. Range of passive hyperextension is used to assess flexibility. Abduction/adduction is maximal in MCP extension & restricted in flexion. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

41. INTERPHALANGEAL JOINTS OF FINGERS E ac h p r ox i m a l & d i s t a l I P j o i n t s i s c o m pose d o f hea d o f t h e phalanx & the base of the phalanx distal to it. True synovial hinge joint with 1° of freedom (flexion/extension), a joint capsule, a volar plate & 2 collateral ligaments. Structure similar to MCP joint but with little posterior articular surface (permits hyperextension) Volar plates - reinforce each IP joint capsule, enhances stability & limits hyperextension. Similar to MCP joint plates except no connection with deep transverse ligament. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

42. Collateral ligaments - cord like, similar to MCP joint, provides stability. Injuries to proximal IP joint collateral ligament are common in sports & at workplace (radial > ulnar collateral) Flexion/extension of IP joints of index finger – proximal (100°- 110°) > distal (80°). Range of PIP & DIP joint flexion increases ulnarly with 5 th PIP & DIP having flexion ranges of 135° & 90° respectively. Additional range to ulnarly fingers - favors angulation of fingers towards scaphoid & opposition with thumb. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

43. EXTRINSIC FINGER FLEXORS Muscles of fingers & thumb having proximal attachment above wrist. 2 m usc l e s con t r i bu t i n g t o f i ng e r f l e x i o n – f l ex o r d i g i t o r u m superficialis (FDS) & flexor digitorum profundus (FDP). FDS - Flexes proximal IP joint & MCP joint. Produces more torque than FDP. Crosses fewer joints & superficial to FDP at MCP joint. Greater moment arm for MCP joint. FDP - Flexes MCP, PIP, DIP joints - more active. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

44. During finger flexion with wrist flexion – FDS & FDP works together. At the proximal phalanx (proximal to PIP), FDP emerges through split in FDS (camper’s chiasma) & FDS attaches to base of middle phalanx. Both FDS & FDP are dependent on wrist position for optimal length tension relationship. Counterbalancing extensor torque at wrist is provided by extensor carpi radialis brevis (ECRB) or sometimes by extensor digitorum communis (EDC). Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

45. MECHANISM OF FINGER FLEXION Optimal function of FDS & FDP depends on - Stabilization by wrist musculature Intact flexor gliding mechanism Gliding mechanism consist of – Flexor retinacula Bursae Digital tendon sheaths Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

46. The fibrous retinacular structures (proximal flexor retinacula, transverse carpal ligament, & extensor retinaculum) tethers the long flexor tendons to hand – prevents bowstringing of tendons. Bursae & tendon sheaths facilitate friction free excursion of tendons on retinacula. FDS & FDP tendons – crosses wrist – pass beneath proximal flexor retinaculum – through carpal tunnel – ulnar bursa (all 8 tendons). Flexor pollicis longus (FPL) – pass through carpal tunnel with FDS & FDP – then radial bursa encases it. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

47. FDS & FDP tendons of each finger pass through a fibroosseous tunnel which comprises 5 transversely oriented annular pulleys (vaginal ligaments) & 3 obliquely oriented cruciate pulleys. Annular pulleys – A1 – at head of MC A2 – volar midshaft of proximal phalanx A3 – distal most part of proximal phalanx A4 – centrally on the middle phalanx A5 – base of the distal phalanx Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

48. The base of each pulley is longer than the roof superficially & roof has slight concavity volarly. This prevents the pulleys from pinching each other at extremes of flexion & minimizes the pressure on the tendon when it is under tension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

49. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

50. The cruciate pulleys – C1 – between A2 & A3 C2 – between A3 & A4 C3 – between A4 & A5 A4, A5 & C3 contains only FDP tendon & no FDS. Thumb has different pulley system. Function of annular pulleys – To keep the flexor tendons close to the bone T o a ll o w on l y a mi n i m u m a m ou n t o f bo w s tr i n g i n g & m i g r a t i o n volarly from the joint axes. Enhances tendon excursion efficiency & work efficiency of long tendons Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

51. EXTRINSIC FINGER EXTENSORS Extrinsic finger extensors are extensor digitorum communis (EDC), extensor indicis proprius (EIP) & extensor digiti minimi (EDM). Passes from forearm – beneath extensor retinaculum that maintains proximity of tendons to the joints & improves excursion efficiency. At MCP joint level EDC tendon of each finger merges with broad aponeurosis known as dorsal hood or extensor hood. EIP & EDM tendons inserts into EDC tendon of index & little finger at or just proximal to extensor hood. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

52. I Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

53. EDC, EIP & EDM - extension of MCP joints of fingers via connection to extensor hood & sagittal band; also causes wrist extension. Distal to the extensor hood, tendon splits into 3 bands, as - Central tendon (inserts on base of middle halanx) 2 lateral bands – rejoins as terminal tendon (inserts into base of distal phalanx) Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

54. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

55. EXTENSOR MECHANISM Formed by EDC, EIP, EDM, extensor hood, central tendon, & the lateral bands that merge into terminal tendon. Passive components are - triangular ligaments (helps stabilize the bands on the dorsum of fingers) & sagittal bands (connects volar surface of hood to volar plates & deep transverse MC ligament – prevents bowstringing of extensor tendons ). The dorsal interossei (DI), volar interossei (VI) & lumbrical (intrinsic musculature) are active components of extensor mechanism. Passive element – oblique retinacular ligament (ORL ) Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

56. INTRINSIC FINGER MUSCULATURE With all attachments distal to radiocarpal joint. Dorsal & volar interossei muscles :- Arise between the MC & are important part of extensor mechanism. 4 DI & 3-4 VI muscles DI & VI are alike in their locations & some of their actions; characterized by their ability to produce MCP joint abduction & adduction respectively. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

57. The interossei muscle fibers join extensor expansion in 2 locations; some fibers attach proximally to the proximal phalanx & to extensor hood; some attach more distally to lateral bands & central tendons. 1 st D I ha s m o s t cons i s t en t a tt ac h m en t- i n t o bon y bas e of proximal phalanx & extensor hood. 2 nd & 3 rd DI have both proximal & distal attachments. 4 th DI – not actually present – abductor digiti minimi (ADM) plays that role Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

58. 3 VI muscles – have distal attachment only (lateral band / central tendon). Proximal interossei have predominant effect on MCP joint only, but distal interossei will produce their predominant action at IP joints & some effect on MCP joints. All DI & VI muscles pass dorsal to transverse MC ligament but volar to axis of MCP joints flexion/extension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

59. Role of interossei at MCP joint in Extension :- Effective stabilizers & prevent clawing due to flexion torque. Balances passive tension in the extrinsic extensors at MCP joint at rest. Interossei muscles are effective abductors & adductors at MCP joint when MCP joint is in extension. P r o x i m a l i n s e r t i o n m usc l e s a r e m o r e e f fe c t i v e t ha n d i s t a l insertion muscles. So abduction is stronger than adduction . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

60. Role of interossei at MCP joint in flexion :- From extension to flexion – tendons & action lines of interossei muscles migrate volarly away from coronal axis of MCP joint – increases moment arm for MCP flexion – action line being nearly perpendicular to moving segment. Increases the flexion torque at MCP joint as it approaches to full flexion. The volar migration of interossei is restricted by deep transverse MC ligament – prevents loss of active tension & serves as anatomical pulley. In full MCP flexion, abduction/adduction is restricted due to – tight collateral ligaments, shape of condyles on MC heads & active insufficiency of fully shortened interossei muscles.

61. Role of interossei at IP joint in IP extension:- Ability to cause IP extension is influenced by its attachments. IP joint extension produced by distal interossei is stronger than MCP abduction/adduction during MCP extension. Index & little finger has weaker IP extension than middle & ring fingers (fewer distal interossei muscles). Overall, proximal components are effective in MCP flexion & distal component in IP extension. So most consistent activity of interossei is when MCP joints are flexed & IP joints are extended – advantage of optimal biomechanics for both DI & VI. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

62. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

63. Lumbrical muscles:- O n l y m usc l e s i n t h e bo d y t ha t a t t ac h e s t o t end o n s o f o t h e r muscles. Each muscle originates from tendon of FDP muscle in the pal m- volar to d eep transverse MC ligament - attaches to lateral band of extensor mechanism on radial side. Crosses MCP joint volarly & IP joints dorsally. Difference in interossei & lumbricals is - more distal insertion of lumbricals, origin at FDP & great contractile range of lumbricals . Effective IP extensors than MCP joint position. Deep transverse MC ligament prevents lumbricals migration dorsally & loosing tension as MCP & IP extends .

64. L u m br i c a l con t r ac t i o n i nc r ease s ten s i o n i n l at e r a l ban d & F D P tendon too. Acts as both agonist & synergist for IP extension. As lumbricals activate to cause IP extension, there is effective release of passive tension in FDP tendon. Also assist FDP indirectly during hand closure. F unc t i on a l l y M C P j o i n t f l e x i o n i s weake r i n l u m b r i c a l s tha n interossei. L a r g e r ang e o f l u m b r i c a l s , p r event s ac t i v e i nsu f f i c i enc y whe n shortening over MCP & IP joints. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

65. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

66. THE THUMB Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

67. C a r p o m e t a c a r p a l ( C MC ) or tr ape z i o m e t a c a r pa l ( T M ) j o i n t - between trapezium & base of 1 st metacarpal head . Saddle j o i n t w i t h 2 ° of freedom- flexion/extension, abduction/adduction ; permits s o m e a xi a l r o t a t i o n - n e t e f fe c t be i n g c i r c u m d u c t i o n called “opposition ” - permits tip of thumb to oppose tips of fingers . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

68. CARPOMETACARPAL JOINT OF THUMB Saddle shaped portion of trapezium is concave in sagittal plane ( abdu c t i on / a dduc t i on ) & conve x i n f r o n t a l p l an e (flexion/extension). Spherical portion on trapezium – convex in all directions. Base of 1 st MC has reciprocal shape to the trapezium. F l ex i on / e x t ens i o n & abduc t i on / adduc ti o n occ u r s on sadd l e surface but axial rotation at spherical surface. MOVEMENT PLANE AXIS Flexion/extension Sagittal Oblique AP axis Abduction/adduction Frontal Oblique coronal axis

69. Capsule of 1 st CMC joint is relatively lax but is reinforced by radial, ulnar, volar & dorsal ligaments. Intermetacarpal ligament – helps to tether the base of 1 st & 2 nd MC, prevents extremes of radial & dorsal displacement of base of 1 st MC joint. Dorsoradial & anterior oblique ligaments – key stabilizers of CMC joint . OA changes with aging are common at 1 st CMC joint, may be due to cartilage thinning in high load areas imposed on this joint by pinch & grasps across incongruent surfaces . Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

70. Unique range & direction of motion . Closed pack position – extremes of both abduction & adduction O ppos i t i o n i s sequen t i a l abduc t i on , f l ex i o n & adduc t i o n o f 1 st MC with simultaneous rotation. The functional significance of 1 st CMC joint is appreciated in all forms of prehension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

71. MCP & IP JOINTS OF THUMB MCP joint :- Between head of 1 st MC & base of proximal phalanx. C ondy l o i d j o i n t w i t h 2 ° o f f r eedo m - f l ex i o n / ex t ens i on & abduction/adduction . The joint capsule, volar plates & collateral ligaments are similar to other MCP joints. Func t i o n - t o p r o v i d e a dd i t i ona l f l e x i o n r ang e t o t hu m b in opposition & to allow thumb to grasp & contour to objects. Though structure is same flexion/extension ranges are half of the other fingers. Abduction/adduction is extremely limited.

72. IP joints :- Between head of proximal phalanx & base of distal phalanx. Similar to other IP joints of the fngers. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

73. MUSCULATURE Extrinsic thumb muscles :- The 4 extrinsic thumb muscles are - Flexor pollicis longus (FPL) Extensor pollicis longus (EPL) Extensor pollicis brevis (EPB) Abductor pollicis longus (APL) Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

74. FPL – Inserts on distal phalanx Correlates to FDP At wrist, invested by radial bursa which is continuous with its digital tendon sheath. U n i qu e ; Fu n c t i on s i ndependen t l y ; on l y m u s c l e r e spons i b l e f o r thumb flexion at IP joint. Si t s be t w ee n t h e ses a m o i d bone s - de r i ve s s o m e p r o t e c t i o n from the bones. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

75. Other 3 muscles are located dorsoradially. EP B & AP L - co m m o n c ou r s e - d o r s a l f o r e a r m - 1 st d o r s a l c ompartment-radial aspect of wrist . ABL inserts on base of MC joint. EPB inserts on base of proximal p halanx - abducts CMC joint , slight radial deviation of wrist. EBP- extension of MC joint EPL-inserts on base on base of distal phalanx- at proximal phalanx EPL is joined by expansion from APB, 1 st volar interossei & adductor pollicis (ADP)-extends thumbs IP joint to neutral but no hyperextension, extends and adducts 1 st CMC joint Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

76. Intrinsic thumb muscles :- 5 thenar muscles - originates from carpal bones and flexor retinaculum. Opponens pollicis (OP)- only intrinsic muscle having distal attachment on 1 st MC on the lateral side – very effective in positioning the MC in an abducted, flexed and rotated posture APB , FPB , AdP & 1 st volar interossei inserts on proximal phalanx. FPB has two heads of insertion. Large lat. h ead attaches to ABL- abduction . Medial head attaches to AdP-adduction

77. 1 st dorsal interossei- though not consider as a thenar muscle con t r i bu t e s t o t hu m b f u nc t i o n - C M C j o i n t d i s t r a c t i on , a s s i s t thumb adduction. Thenar muscles- active in most grasping activities A c t i v i t y o f e x t r i ns i c t h u m b m usc l e i n g r as p i s p a r t i a ll y f un c t i o n o f he l p i n g t o pos i t i o n t h e M C P an d I P j o i n t s, m a i n f un c t i o n being returning the thumb to extension from its position Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

78. PREHENSIO N Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

79. Prehension activities involves grasping or taking hold of an object between any 2 surfaces of hand. Thumb paticipate in most but not all the prehension activities. Prehension Power grip (full hand prehension) Precision handling (finger thumb prehension) Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

80. POWER GRIP PRECISION Forceful act resulting in flexion of all finger joints. The thumb acts as a stabilizer to the object held in fingers or palm. Skillful placement of an object between fingers or between finger & thumb. No involvement of palm. Phases Opening of hand Positioning the fingers Bringing the fingers to the object Maintaining the static phase Opening of hand Positioning the fingers Bringing the fingers to the object Object is grasped to move through space by some proximal joints Fingers & thumb grasps the object to manipulate it within the hand Thumb is generally adducted. Thumb is generally abducted.

81. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

82. POWER GRIP Fingers function to clamp on or hold an object into the palm. Fingers sustain flexion position that varies in degree with size, shape & weight of the object; palmar arches around it. Thumb - serves as additional surface to finger palm by adducting against the object. Different power grips – Cylindrical grip Spherical grip Hook grip Lateral prehension

83. Involves use of all finger flexors FDP works predominantly I n t e r o s s e i m u s cl e s – p r im a r y M C P flexors, abductors/adductors F P L & t hena r m u s cl e s - f l e xi o n & adduction of thumb . Hypothenar eminence-flex & abduct MCP joint. T y p i c a ll y w i t h w r i s t i n ne u t r a l/ extension & slight ulnar deviation. E.g . turning a door knob . CYLINDRICAL GRIP Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

84. Most respect to cylindrical grip but greater spread of fingers to encompass the object. More activity of interosseus for e.g. holding a ball. SPHERICAL GRIP Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

85. Specialised form of prehension- function primarily of fingers. Major activity of FDP & FDS . Load – more distally FDP, proximally (FDS) Thu m b - m ode r a t e t o f u l l extension. E.g . - carrying a briefcase. HOOK GRIP Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

86. Contact between two fingers. MCP & IP joint- in extension as contigious MCP joint simultaneously abduct & adduct Extensor musculature pre dominates. E.g. holding a paper LATERAL PREHENSION Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

87. PRECISION HANDLING Require much finer motor control & more dependent on intact sensation. In “two – jaw chuck”,one jaw is thumb ( abducted & rotated) & 2 nd jaw is by distal tip, the pad or the side of finger . 3 varieties of prcesion are – Pad to pad prehension Tip to tip prehension Pad to side prehension. Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

88. Involves opposition of pad or pulp of thumb to pad or pulp of finger. The pad has greatest concentration of tactile corpuscles. MCP & proximal IP joint of the finger – partially flexed Distal IP joint- extended or slightly flexed. PAD TO PAD PREHENSION Thumb- CMC flexion, abduction & rotation; MCP & IP joint partially flexed or extended. E.g. holding a foreceps Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

89. Muscle activity almost same to pad to pad prehension with some key differences like IP joint of the fingers & the thumb have range & force to create full flexion. MCP joint of opposing finger deviates ulnarly. E.g. holding a pen. TIP TO TIP PREHENSION Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

90. Key grip or lateral pinch. Between thumb & side of index finger Thumb-more adducted & less rotated least precise form of precesion handling. SIDE TO SIDE PREHENSION Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

91. FUNCTIONAL POSITION OF WRIST & HAND The functional position is – Wrist complex in slight extension (20°) & slight ulnar deviation (10°) Fingers moderately flexed at MCP joint (45°) & proximal ip joint (30°) & slightly flexed at distal IP joint Dr. Gurjant Singh (PT), MPT, (Ph.D) Assistant Professor, MMIPR

92. THANK YOU