The Crpometcrpl Joint of the Thumb: Stbility, Deformity, nd Therpeutic Intervention Donld A. Neumnn, PT, PhD 1 Teri Bielefeld, PT, CHT 2 Journl of Orthopedic & Sports Physicl Therpy The crpometcrpl (CMC) of the thumb is sddle joint tht permits wide rnge of motion nd is lrgely responsible for the chrcteristic dexterity of humn prehension. This joint, locted t the very bse of the thumb, is subject to lrge physicl stresses throughout life. Osteorthritis (posttrumtic or idiopthic), rheumtoid rthritis, nd postmenopusl lxity of the cpsulr ligments cn predispose structurl instbility nd impirment of this importnt joint. The instbility is chrcterized by vrying nd often progressive disloction of the joint surfces, resulting in displced xis of rottion nd bnorml ctions of thumb muscles. The min consequence of the instbility is most often pin nd wekness, most notbly during pinch nd grsping ctions. This pper is conceptully divided into 2 sections. The first section describes the ntomic structures tht mintin stbility in the norml CMC joint of the thumb nd how disese or trum cn cuse instbility nd ultimte deformity. The second section describes both nonsurgicl nd surgicl interventions tht re most often used to tret n unstble CMC joint. This pper is intended primrily s n overview for the physicl therpist who does not specilize in the tretment of the hnd, lthough desires bsic informtion on this importnt topic. J Orthop Sports Phys Ther 2003;33:386 399. The thumb is the most importnt digit of the hnd nd gretly mgnifies the complexity of humn prehension. Functionlly, the most importnt joint of the thumb is the crpometcrpl (CMC) joint, locted t the very bse of the digit. This pper focuses on instbility nd the subsequent loss of function of this importnt joint. This joint is considered unstble when it exhibits gross bnorml lignment, which is often combined with excessive nd berrnt mobility. An unstble joint my, over time, become fixed nd deformed. Instbility of the CMC joint is often cused by osteorthritis or rheumtoid rthritis. Osteorthritis develops reltively frequently t the CMC joint of the thumb, often s result of thletic injury or cumultive trum ssocited with n rduous occuption or hobby. Synovitis ssocited with rheumtoid rthritis my eventully erode nd soften the ligments tht protect the rticulr surfces. 23 Severl other conditions my led to instbility of the CMC joint of the thumb. These conditions include bnorml shpe of the rticulr surfces, cute 1 Associte Professor, Physicl Therpy Deprtment, Mrquette University, Milwukee, WI. 2 PT Clinicl Specilist, Physicl Therpy Deprtment, Zblocki VA Medicl Center, Milwukee, WI. Send correspondence to Donld A. Neumnn, Mrquette University, Physicl Therpy Deprtment, Schroeder Helth Complex, PO Box 1881, Milwukee, WI 53201-1881. E-mil: donld.neumnn@mrquette.edu trum (such s hyperextension nd hyperbduction sprins, or frctures of the proximl bse of the thumb metcrpl 52 ), nd idiopthic or hormonl-bsed lxity of the ligments. Persons who require medicl ttention for instbility of the thumb CMC joint often present with combintion of symptoms, which typiclly involves ligmentous lxity nd resultnt instbility, pin, nd functionl limittions. These symptoms my be precursors to osteorthritis t the joint 6,56 or my be prt of the rthritic process itself. When the disese hs dvnced, osteorthritis of the bse of the thumb is chrcterized by mrked pin, especilly excerbted by pinch or grsping ctions, wekness, reduced motion, osteophyte formtion, swelling, subluxtion, nd crepittion. 17,28,37 Osteorthritis of the thumb CMC joint occurs with disproportionlly greter frequency in femles, typiclly in their fifth nd sixth decde. 8,38,54 This gender-relted propensity is likely ssocited with postmenopusl induced lxity in the joint s ligments. 3 Although rthritis of the interphlngel joint of the thumb occurs with greter frequency, rthritis of the CMC joint is usully more severe nd more likely to cuse greter pin nd functionl impirment. 1,19 386 Journl of Orthopedic & Sports Physicl Therpy
Hnd therpists nd surgeons frequently collborte in the tretment of n unstble CMC joint. 59 Surgicl nd therpeutic interventions typiclly focus on reducing pin nd improving motion nd function. Effective therpeutic intervention requires tht the clinicin understnd the structurl nd functionl reltionships tht exist t this complex joint nd, in prticulr, how these reltionships ffect joint stbility. The first prt of this pper reviews the bsic structure nd function of the CMC joint of the thumb, with n emphsis on the structures tht nturlly stbilize the rticultion. This is followed by n exmple of how loss in restrint within the perirticulr connective tissues cn initite deforming process throughout the entire digit. This informtion underscores the importnce of effective therpeutic intervention for the CMC joint, the focus of the second prt of this pper. Although instbility t the CMC joint cn be cused by severl fctors, this pper will focus primrily on the effects of osteorthritis. Journl of Orthopedic & Sports Physicl Therpy STABILITY Structurl nd Functionl Considertions The CMC joint of the thumb consists of the rticultion between the bse of the first metcrpl nd the distl side of the trpezium (Figure 1). Three other djcent rticultions re functionlly relted to this joint, which include the joints between the trpezium nd the scphoid, the trpezium nd the trpezoid, nd the bse of the first metcrpl nd the rdil side of the bse of the second metcrpl. As set, the 4 synovil rticultions re referred to s the bsl joint complex. The CMC joint, the focus of this pper, is referred to s the bsl joint of the thumb, reflecting its proximl loction within the digit. The CMC joint of the thumb is sddle joint. 48 The chrcteristic feture of sddle joint is tht ech rticulr surfce is concve in one dimension nd convex in the other. Within the CMC joint of the thumb, the longitudinl dimeter of the rticulr surfce of the trpezium is generlly concve from plmr-to-dorsl direction. This surfce is nlogous to the front-to-rer contour of horse s sddle (Figure 1). The trnsverse dimeter on the rticulr surfce of the trpezium is generlly convex long medil-to-lterl direction, nlogous to the side-toside contour of horse s sddle. The proximl rticulr surfce of the metcrpl hs reciprocl shpe to tht of the trpezium. Studies suggest tht the trpezium bone of women is shllower, less congruent, nd is lined with thinner lyer of rticulr crtilge thn tht of men. 36,49,60,74 These FIGURE 1. The crpometcrpl of the right thumb is opened to expose the shpe of the sddle joint. The drker gry re highlighted on the surfce of the trpezium mrks the region of higher contct stress during lterl key pinch (see text for further explntion). Modified slightly nd reprinted from Neumnn, 48 with permission from Elsevier. fctors my contribute to the higher incidence of instbility nd subsequent CMC joint rthritis in women. One of the most importnt functionl spects of the thumb is its extensive mobility. The primry motions t the CMC joint re plmr bduction nd dduction, which occur bout the joint s medillterl xis, nd flexion nd extension, which occur bout the joint s nterior-posterior xis. The xes of rottion for these biplnr motions re directed generlly through the convexity of the joint; 34 the xis pierces the bse of the metcrpl during bduction nd dduction, nd the trpezium during flexion nd extension. The ultimte kinemtic expressions of the thumb re opposition nd reposition. These re composite motions bsed on the other primry biplnr motions. Strting from the ntomic position, opposition involves wide rc of motion, combining elements of plmr bduction nd flexion (the ltter movement being strongly linked to medil rottion [prontion] of the metcrpl). The motion of reposition returns the thumb to the ntomic position, motion tht incorportes elements of dduction with extension nd lterl rottion (supintion) of the metcrpl. The opponens pollicis muscle is specificlly designed to produce the kinemtics of opposition. By CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 387
Journl of Orthopedic & Sports Physicl Therpy ttching long the rdil border of the first metcrpl, this muscle flexes nd medilly rottes the thumb, helping to guide the rticulr surfce of the metcrpl through groove on the trnsverse rticulr surfce of the trpezium. 75 Although mximl in opposition, only 53% of the surfce re of the trpezium is in contct with the metcrpl. 45 Full opposition incorportes t lest 45 to 60 of medil rottion of the thumb. Axil rottion of the thumb s whole occurs primrily t the CMC joint, but lso through lesser mounts (in the form of ccessory motions) t the metcrpl nd interphlngel joints. Observtion of fluoroscopy during full opposition shows tht full-rnge opposition is ssocited with slight twisting of the trpezium reltive to the scphoid nd the trpezoid. This motion mplifies the full extent of the metcrpl rottion. Full opposition llows the tip of the thumb to mke pulp-to-pulp contct with the 4 fingers. This interction between the opposing thumb nd the fingers llows the hnd to conform to n extrordinry number of shpes nd sizes, thereby gretly enhncing the security nd dexterity of humn prehension. The shpe of the CMC joint of the thumb fvors mobility, n essentil prerequisite for full opposition. The curved surfces within the joint provide only limited intr-rticulr stbility, s the primry source of stbility is gined from the ligments embedded within the joint cpsule. 51 Ligments not only stbilize the joint but lso, in conjunction with the pssive tension in muscles, set the limits of motion. Cpsule nd Ligments The cpsule surrounding the CMC joint of the thumb is reltively lrge nd loose to ccommodte Trnsverse crpl ligment Plmr view M e t c r p l 2nd R d i l s u r f c e 1st metcrpl Intermetcrpl ligment Ulnr collterl ligment Posterior oblique ligment Anterior oblique ligment Rdil collterl ligment Abductor pollicis longus Flexor crpi rdilis Extensor crpi rdilis longus lrge rnge of motion. The cpsule is reinforced by t lest 5 ligments (Figure 2). 33,51 The primry ligments t the CMC joint re essentil to mintining sttic nd dynmic stbility between the metcrpl nd trpezium. These ligments hve 3 functions: (1) to control the extent nd direction of joint motion, (2) to help mintin norml lignment of the joint, nd (3) to help control nd dissipte forces produced by ctivted muscles. Excessive lxity of the ligments, either through chronic synovitis, inflmmtion, or repetitive injury, is primry cuse of instbility t this joint or cn be precursor to degenertion of the rticulr crtilge. 54 Mny investigtors hve studied the ntomy nd function of the ligments of the CMC joint. 8 An understnding of the function of the ligments hs been complicted by lck of greement on nomenclture. Much of this confusion is relted to the fct tht the first metcrpl is ligned bout 90 reltive to the other metcrpl bones nd to the trpezium. In the relxed rest position of the hnd, the thumb is reltively bducted, with its plmr flexor surfce directed in n ulnr (medil) direction. This lignment fcilittes pinch nd other interctions with the fingers. 15 This present rticle will refer to the ligments of the CMC joint bsed on their ttchments to the surfces of the trpezium, not to the surfces of the thumb metcrpl. The ttchments of the ligments nd motions tht increse their tension re listed in Tble 1. The tendon of the bductor pollicis longus lso provides stbility to the joint. This tendon inserts into the dorsl-rdil corner of the extreme bse of the metcrpl. When stretched during movement, tension in the ligments of the CMC joint provides n essentil D o r s l s u rf c e Lterl view M e t c r p l 2nd FIGURE 2. Plmr nd lterl views of the ligments of the crpometcrpl joint of the right thumb. Note the distl ttchment of the bductor pollicis longus into the cpsule of the crpometcrpl joint of the thumb. Reprinted from Neumnn, 48 with permission from Elsevier. 388 J Orthop Sports Phys Ther Volume 33 Number 7 July 2003
TABLE 1. Ligments tht support the crpometcrpl joint of the thumb. Nme Proximl Attchment Distl Attchment Motions Tht Increse Ligment Tensions Anterior oblique* Plmr tubercle on trpezium Plmr bse of thumb metcrpl Abduction, extension, nd opposition Ulnr collterl Trnsverse crpl ligment Plmr-ulnr bse of thumb metcrpl Intermetcrpl Dorsl side of bse of second metcrpl Plmr-ulnr bse of thumb metcrpl (with ulnr collterl) Posterior oblique Posterior surfce of trpezium Plmr-ulnr bse of thumb metcrpl Rdil collterl Rdil (lterl) surfce of trpezium * Described s 2 heds: superficil nd deep ( bek ) fibers. Also clled dorsl-rdil ligment. Dorsl surfce of thumb metcrpl Abduction, extension, nd opposition Abduction nd opposition Abduction nd opposition All movements to vrying degrees, except extension Journl of Orthopedic & Sports Physicl Therpy source of stbility to the joint. 8,23,51 In generl, extension, bduction, nd opposition (which includes vrying mounts of flexion, medil rottion, nd plmr bduction) elongte most of the thumb s ligments. The nterior oblique, rdil collterl, nd ulnr collterl ligments hve been described s primry dynmic stbilizers of the thumb, especilly during pinch nd opposition of the thumb. 8 The nterior oblique ligment plys prticulrly importnt role in 2 functions: (1) to pssively guide the medil xil rottion of the metcrpl during full flexion, nd (2) to restrin the extent of rdil (lterl) trnsltion of the metcrpl reltive to the trpezium. 54 This rdil trnsltion is driven, in prt, by the line-of-force of the intrinsic flexor muscles of the thumb when the digit is fully flexed nd dducted; these motions re intimtely ssocited with key pinch. 8 Ateshin et l 4 provide evidence tht the forces produced by lterl pinch re generlly concentrted t the sme region where crtilge thinning is most often observed in cdvers. This lends support to the ide tht stress is significnt precursor to degenertion of the CMC joint. Muscle Function Any muscle tht exerts force on the thumb must lso exert force cross the CMC joint. Tble 2 lists the ctions performed by these muscles. The mount of force produced by contrction of the thumb flexors, for instnce, is severl times greter thn the contct forces (between the thumb nd n object) experienced t the more distl regions of the thumb. 14 The difference reflects the disprity between the smll internl moment rms vilble to the muscles compred to the much lrger externl moment rms ssocited with the contct forces. (The internl moment rm is the distnce between TABLE 2. Primry ctions of muscles tht cross the crpometcrpl joint of the thumb. Flexion: Adductor pollicis Flexor pollicis longus Opponens pollicis Flexor pollicis brevis Abduction: Abductor pollicis brevis Abductor pollicis longus Opposition: Opponens pollicis Flexor pollicis brevis Abductor pollicis brevis Flexor pollicis longus Abductor pollicis longus Extension: Extensor pollicis brevis Extensor pollicis longus Abductor pollicis longus Adduction: Adductor pollicis Extensor pollicis longus First dorsl interosseus Reposition: Extensor pollicis longus the muscle force nd xis of rottion t the CMC joint; the externl moment rm is the distnce between the externl contct force nd the sme xis of rottion. 48 ) A reltively lrge muscle force results in reltively lrge force cross the rticulr surfces of the joint. Cooney nd Cho 14 hve estimted 12-fold greter compression force within the CMC joint s compred to the contct forces pplied t the distl end of the thumb. This disprity is typiclly relized while producing key pinch between the thumb nd index finger. Even reltively low-stress ct such s brushing the teeth would, in theory, plce significnt lod cross the joint. When the thumb is ctively flexed nd dducted during key pinch, compression forces concentrte on the plmr nd ulnr surfces of the trpezium nd on the djcent surfces of the bse of the metcrpl. 54 This region is highlighted on the trpezium in Figure 1, t loction djcent to the proximl ttchment of the CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 389
Journl of Orthopedic & Sports Physicl Therpy nterior oblique ligment. This limited surfce re for contct cn crete lrge nd potentilly dmging pressure within the joint. The strength (torque) potentil of the thumb musculture is gretest for the motions of flexion nd dduction, reflecting the need for strong key pinch. Figure 3 shows the reltive torque potentil nd ctions of 7 thumb muscles, bsed on dt from cdver specimens. 63 The loction of the dot ssocited with ech muscle indictes the ctions of ech muscle. For exmple, the dductor pollicis (oblique hed) is shown producing combined dduction nd flexion torque cross the CMC joint. This plot lso shows tht the oblique hed of the dductor pollicis is theoreticlly cpble of producing the gretest torque of ll the thumb muscles. It is importnt to relize tht the musculr forces tht produce the torque for thumb strength nd movement lso stbilize the bse of the metcrpl cross the trpezium. Tension in ligments help direct nd control the ctions of these muscles. As will be described hed, excessive lxity or wekness 4 Flexion ADPo 3 ADPt 2 1 OPP FPB APB Adduction 2 1 EPL -1-2 Abduction EPB -2 Extension Outline of trpezium APL FIGURE 3. Digrm showing the torque potentil of 7 muscles tht cross the crpometcrpl joint of the right thumb. Note the trpezium outlined t the bse of the thumb. The length of ech line ssocited with ech muscle is proportionl to the torque potentil of the muscle, which considers both moment rm nd crosssectionl re of the muscle. The orienttion of ech line reltive to the x nd y xes shows the direction of the muscle s pull nd subsequent muscle ction. The units used on the x-y scle re Nm. (Abbrevitions: ADPo, dductor pollicis, oblique hed; ADPt, dductor pollicis, trnsverse hed; OPP, opponens pollicis; FBP, flexor pollicis brevis; APB, bductor pollicis brevis; APL, bductor pollicis longus; EPB, extensor pollicis brevis; EPL, extensor pollicis longus.) The digrm is drwn bsed on dt plotted by Smutz et l. 63-1 in the ligments cn lter the ctions of muscles, thereby contributing to joint instbility nd possible deformity. DEFORMITY As described bove, reltively lrge demnds re routinely plced on the CMC joint of the thumb. The combintion of lrge compression nd sher forces cn crete potentilly stressful environment t the joint. Proof of this stressful environment is evident by the high rte of mechnicl filure of silicone implnts t the CMC joint. 57 In most persons, the CMC joint functions well throughout lifetime of reltively lrge imposed stress. Force t the joint is prtilly bsorbed nd resisted by helthy, strong ligments. In ddition, intct nd helthy rticulr crtilge cn help dissipte forces tht cross the joint. Unfortuntely, however, in the cse of trum or disese, ligments my lose their bility to stbilize the joint. As will be described, loss of stbility t the bsl joint of the thumb cn led to rthritic chnges within the joint, s well s compenstory deformities in the more distl joints. In 1968, Nlebuff 47 outlined system for clssifying deformities of the thumb. Although the deformities were originlly described in the context of rheumtoid rthritis, they cn result from ny disese or injury tht wekens the surrounding ligments nd cpsule. Nlebuff s clssifiction scheme typiclly includes 4 deformities (Tble 3), lthough, more recently, other uthors hve described 6 clssic deformities of the thumb. 65 As noted in Tble 3, the CMC joint is significntly involved in the pthomechnics of 3 of the 4 clssic thumb deformities. Chronic synovitis ssocited with rheumtoid rthritis wekens the cpsule nd the supporting ligments of the CMC joint. Altered congruity between the joint surfces typiclly increses stress on the rticulr crtilge due to reduced surfce re vilble to disperse the forces. 54 In cses of osteorthritis, the CMC joint is frequently ffected long with degenertion of other rticultions within the bsl joint complex, especilly between the trpezium nd second metcrpl. 25 In either rheumtoid rthritis or osteorthritis, eventul subluxtion of the CMC joint often initites kinetic imblnce in the other more distl joints of the thumb. This phenomenon is nicely exemplified in the pthomechnics ssocited with the type III deformity. As depicted in Figure 4, the clssic type III deformity is chrcterized by CMC joint flexion nd dduction, metcrpophlngel (MCP) joint hyperextension, nd interphlngel (IP) joint flexion. This deformity is reltively common in the thumb with rheumtoid rthritis nd is typiclly progressive if untreted. 7 The following sequence of 390 J Orthop Sports Phys Ther Volume 33 Number 7 July 2003
TABLE 3. Nlebuff s 47 originl system for clssifying deformities of the thumb. Type Description Comments I Flexion of the metcrpophlngel (MCP) joint nd hyperextension of the interphlngel (IP) joint (lso clled boutonnière deformity of the thumb). Most common deformity of the thumb; typiclly strts with synovitis of the MCP joint. The crpometcrpl (CMC) joint is not significnt fctor in the pthomechnics. II III IV Flexion of the MCP joint nd hyperextension of the IP joint, with dduction t the CMC joint. Hyperextension of the MCP joint nd flexion of the IP joint (lso clled swn neck deformity). Adduction t the CMC joint with mrked bduction t the MCP joint. Reltively uncommon; synovitis nd subluxtion of the CMC joint re significnt precipitting fctors in the pthomechnics. Reltively common; synovitis nd subluxtion of the CMC joint re significnt precipitting fctors in the pthomechnics. Synovitis of both the MCP nd CMC joints re significnt precipitting fctors in the pthomechnics. The deformity is often ssocited with rupture or ttenution of the ulnr collterl ligment of the MCP joint. Journl of Orthopedic & Sports Physicl Therpy Extensor pollicis longus Dislocted crpometcrpl joint Tut flexor pollicis longus Overstretched plmr plte t the metcrpophlngel joint Ruptured ligments FIGURE 4. Plmr view showing the pthomechnics of common zigzg deformity of the thumb due to rheumtoid rthritis. The thumb metcrpl disloctes lterlly t the crpometcrpl joint, cusing hyperextension t the metcrpophlngel joint. The interphlngel joint remins prtilly flexed due to the pssive tension in the stretched nd tut flexor pollicis longus. Note tht the bowstringing of the tendon of the extensor pollicis longus cross the metcrpophlngel joint cretes lrge extensor moment rm, thereby mgnifying the mechnics of the deformity. 63 Reprinted from Neumnn 48 with permission from Elsevier. events is one likely scenrio tht cn led to type III deformity. Ligments tht normlly reinforce the medil (ulnr) side of the CMC joint (such s the nterior oblique, ulnr collterl, nd intermetcrpl ligments) cn become wek nd/or prtilly ruptured due to chronic synovitis. The ligments re no longer ble to resist the previling rdilly directed forces tht nturlly occur with thumb pinch. Subsequently, the bse of the first metcrpl slides rdilly, or rdil-dorslly, reltive to the trpezium. 53 Potentilly dmging sher forces my concentrte ner the plmr spect of the trpezium, djcent to the ttchments of the nterior oblique ligment. 54 Intrinsic muscles, such s the dductor pollicis, my become fibrotic nd permnently contrcted, thereby mintining the deformity t the CMC joint nd nrrowing of the first web spce. In ddition, prtilly subluxed or dislocted CMC joint ffects the moment rms of the muscles tht cross the region. Dt from cdver study suggests tht the chnges in muscle leverge my bis rdil-dorsl migrtion of the metcrpl. 50 Instbility of the bsl joint of the thumb fvors instbility nd zigzg deformities of the more distl joints. The term zigzg describes collpse of multiple interconnected joints in lternting directions. In the exmple of the type III deformity shown in Figure 4, ttempts of extending the thumb wy from the plm my overstretch nd cuse creep in the plmr plte t the MCP joint, especilly if synovitis is involved. A compenstory hyperextension deformity my therefore result t the MCP joint. Bowstringing of the tendons of the extensor pollicis brevis nd longus cross the hyperextended MCP joint my increse their leverge s extensors nd thereby contribute to the hyperextension deformity. The interphlngel joint my be bised in flexed position due to the pssive tension in the stretched nd excessively tut flexor pollicis longus. The pthomechnics ssocited with the deformity displyed in Figure 4 demonstrte the importnce of stbility or blnce t the CMC joint. The principles behind most common forms of nonsurgicl nd surgicl intervention for instbility of the CMC joint re described in the remining sections of this pper. CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 391
Journl of Orthopedic & Sports Physicl Therpy THERAPEUTIC INTERVENTION As described in the Introduction, severl coexisting fctors cn cuse instbility nd resulting deformity t the CMC joint. Tretment of the instbility includes both reltively conservtive nonsurgicl intervention nd more progressive surgicl intervention. Nonsurgicl Intervention Nonsurgicl intervention of the unstble CMC joint typiclly begins by crefully ssessing the ptient s hnd function while considering the underlying pthology or cuse of the instbility. The more common forms of conservtive intervention for CMC joint instbility include splinting, pin control, exercise, nonsteroidl nti-inflmmtory drugs (NSAIDS), corticosteriod injections, nd teching principles of joint protection. Joint protection is defined s the ct of eliminting or minimizing stress plced upon the joint during the performnce of ctivities of dily living. Idelly these principles re instructed nd understood before the joint becomes mrkedly unstble or deformed. Tble 4 shows set of stndrd gols for nonsurgicl hnd therpy, ech directly ssocited with set of common therpeutic interventions. Splinting The gols of splinting the CMC joint of the thumb re to increse stbility, reduce pin, decrese inflmmtion, improve function, nd reduce the mechnicl stress tht my be cusing the instbility. Instbility of the CMC joint is typiclly cused by n intrinsic wekness of the cpsulr structures. Wering splint only provides extrinsic support to the joint; once removed, it no longer hs therpeutic effect. A sttic splint is typiclly indicted for the CMC joint tht is becoming progressively hypermobile or unstble. A sttic splint is generlly not indicted, however, for joint with fixed deformity. Sttic splinting is designed to mintin optiml joint lignment nd to reduce the forces tht my led to further joint deteriortion or deformity. 13,44,59,66,71 In cses of rpidly progressive rthritis, splinting generlly will not prevent joint deformity, but cn provide needed rest nd support. 43 Figure 5A shows n exmple of hnd of person who is good cndidte for sttic splint. The rounded hump t the bse of the thumb is typicl of erly stges of ensuing instbility nd osteorthritis of the CMC joint. In this cse, the CMC joint is pinful, especilly during pinch. The cpsulr ligments re likely lx nd wekened nd therefore not ble to resist rdil-dorsl trnsltion of the bse of the thumb metcrpl reltive to the trpezium. The choice of the type of sttic splint depends on the specific joints of the thumb tht need to be immobilized. Regrdless of specific design, sttic splint typiclly positions the bse of the thumb in reltive plmr bduction, which incorportes slight flexion-nd-medil rottion. This position helps to mintin the web spce, but lso increses the nturl stbility of the joint by incresing the congruity or fit of the joint surfces. 25,35,72 The most trditionl sttic splint is clled the long opponens splint, more descriptively known s the wrist- CMC immobiliztion splint (Figure 5B). 2 The splint supports multiple joints, ffording mximl protection to the entire thumb region, which is n especilly desired effect for pinful thumb in very ctive person. As depicted in Figure 5B, this splint supports both the wrist nd hnd nd typiclly immobilizes the wrist in 10 to 20 of extension, the CMC joint in reltive plmr bduction, the MCP joint in 30 of flexion, with the IP joint remining unconstrined. Moulton et l, 46 using cdver mteril, showed tht the center of pressure within the CMC joint shifted dorslly when the MCP joint ws rigidly immobilized in 30 of flexion. This shift TABLE 4. Stndrd gols nd their ssocited interventions for nonsurgicl tretment of pthology involving the crpometcrpl joint of the thumb. X indictes the interventions tht re directly ssocited with prticulr gol. Interventions Gols Splinting Pin Control Light to Moderte Exercise* NSAIDS Corticosteroid Injections Joint Protection Decrese pin X X X X X X Allevite inflmmtion X X X X X Mintin stbility or mobility X X X X X X Mintin or increse strength X X X Mintin or increse function X X X X X X Reduce mechnicl loding X X Mintin first web spce X X * See text for further clrifiction. Nonsteroidl nti-inflmmtory drugs. 392 J Orthop Sports Phys Ther Volume 33 Number 7 July 2003
Journl of Orthopedic & Sports Physicl Therpy B A FIGURE 5. (A) A dorsl view showing erly stges of instbility of the crpometcrpl joint secondry to osteorthritis. The rrow points to the rounded hump t the bse of the thumb, which shows tht the bse of the metcrpl hs dislocted slightly in rdil nd dorsl direction. (B) The long opponens splint is shown for the person described in A. Note tht the wrist joint nd the crpometcrpl nd metcrpophlngel joints of the thumb re ll incorported into the splint. prtilly unlods the plmr region of the CMC joint, which hs been shown to be susceptible to degenertion. 54,55 A second type of sttic splint is the short opponens splint, more descriptively clled the CMC-MCP immobiliztion splint. This hnd-bsed splint is similr to the long opponens splint in fbriction with the exception tht the wrist is not constrined (Figure 6A). A third type of splint, designed by Colditz, 13 is modifiction of the short opponens splint (Figure 6B). This splint mintins the CMC joint in ner extension while llowing the MCP joint the freedom to flex nd extend. Active contrction of the thenr muscles during pinch tends to compress the bse of the thumb ginst the inside of the plmr surfce of the splint. This compression provides dditionl stbility to the CMC joint. Tble 5 summrizes the dvntges nd disdvntges of these 3 splints. A review of the literture hs shown some body of reserch on the effectiveness of sttic splinting for primry CMC joint instbility. Weiss et l 71 studied the effectiveness of the long opponens splint (Figure 5B) versus the much less confining CMC immobiliztion splint (Figure 6B). 71 Both splints similrly reduced pin, lthough neither resulted in n increse in pinch strength, or decrese in pin during pinch. The reltively unconstrined feture of the CMC immobiliztion splint is desirble feture in terms of comfort. The study found tht the ptients who wore the CMC immobiliztion splint reported tht 93% of their ctivities of dily living were either esier or the sme s not wering splint. One potentil disdvntge of this smller splint is tht the CMC joint is the only joint immobilized, which my concentrte more wer on the MCP joint. Pin Control Pin is usully the primry fctor tht directs the course of tretment of the unstble CMC joint of the thumb. The ptient my complin of pin even in the bsence of typicl pin-relted symptoms such s wrmth, erythem, or edem. Pin in the unstble joint cn be cused by impingement of the loose cpsule, ttenution of the joint cpsule over n osteophyte, mucous cysts, or secondry muscle ching nd spsm. 44 A pinful thumb cn drmticlly limit the performnce of ctivities of dily living. Pin typiclly increses following ctivities such s repetitive pinching, grsping (holding book), twisting (turning key), prehension, nd forceful pounding with the thenr eminence. Most of these ctivities re performed with the CMC joint flexed nd dducted. Pin-free stbility t the bsl joint of the thumb is essentil for norml hnd function. Becuse rest nd immobiliztion re often effective t reducing pin, splinting is often the primry tretment. In ddition to splinting, pproprite use of medicines nd ltering stressful use ptterns pper to be the most effective blend of interventions to reduce pin. CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 393
Journl of Orthopedic & Sports Physicl Therpy A B FIGURE 6. Two forms of the short opponens splint. (A) The clssic short opponens splint is shown immobilizing the crpometcrpl (CMC) nd metcrpophlngel (MCP) joints. (B) A modified short opponens splint is shown immobilizing the CMC joint only. This smller splint keeps the CMC joint in ner extension, while llowing the MCP nd interphlngel (IP) joints to be unconstrined. Both splints stbilize the CMC joint in vrying degrees of plmr bduction, llowing lterl pinch nd tip-to-tip pinch. Both splints re lso hnd-bsed, which mrks mjor difference between these nd the long opponens splint. Exercise Strengthening nd flexibility exercises my be n pproprite form of tretment for instbility of the CMC joint of the thumb, but only in certin circumstnces. If musculr wekness is n issue, exercises should be prescribed only in the erly stges of instbility, generlly in the bsence of inflmmtion nd mrked pin. As generl principle, mrkedly unstble or inflmed joint requires rest nd support through splinting nd nti-inflmmtory medicine; exercises re more pproprite either when the joint is not inflmed nd reltively pinless, or s prt of postsurgicl rehbilittion progrm. If exercises re deemed pproprite, they re generlly prescribed within the light-to-moderte intensity rnge. Flexibility exercises re intended to mintin the plibility of the surrounding soft tissues. In generl, prticulr ttention must be plced on preventing n dduction contrcture with loss of the first web spce. 59 The gols of resistive exercises re to promote musculr-bsed stbility bout the bse of the thumb nd mintin the strength required for the performnce of functionl ctivities. Reserch hs demonstrted tht exercise is n effective mens for incresing grip strength nd reducing morning stiffness in persons with rheumtoid rthritis. 31 The specific type of exercise progrm will vry bsed on the severity of the joint instbility, the nture of the underlying pthology or mechnicl disturbnce, nd the clinicl judgment nd experience of the therpist nd physicin. Isometric exercises re generlly indicted for the nonpinful joint. Flexibility exercises should be limited only to the reltively stble, pin-free rnge of the joint s motion. Exercise, regrdless of the type, should not cuse pin tht persists for more thn 2 hours fter the ctivity. If pproprite, one should consider the need to strengthen the muscles of the thenr eminence, the bductor pollicis longus, nd the extensor pollicis longus s mens to offset the potentil deforming flexion-dduction forces of the dductor pollicis. 56,59 As discussed previously, bduction combined with slight medil rottion nd flexion of the CMC joint increses the nturl stbility of the bse of the thumb. Strengthening of muscles tht ssist with opposition my encourge joint stbility. Exercises tht strengthen the extensor pollicis longus in isoltion should be voided becuse they my enhnce lterl rottion nd dduction, thereby incresing the subluxtion potentil of the CMC joint. 59 Nonsteroidl Anti-inflmmtory Drugs Nonsteroidl nti-inflmmtory drugs (NSAIDS) re routinely utilized to reduce pin, inflmmtion, synovitis, nd effusion ssocited with rthritis of the CMC joint of the thumb. Numerous nti-inflmmtory medictions re vilble which generlly hve similr phrmcologic properties. Clinicl trils hve shown tht no one NSAID is more effective in treting 394 J Orthop Sports Phys Ther Volume 33 Number 7 July 2003
TABLE 5. The dvntges nd disdvntges of 3 trditionl sttic splints for the CMC joint of the thumb. See text for further detils. Nme Description Advntges Disdvntges Long opponens (wrist-cmc immobiliztion) splint Short opponens (CMC-MCP immobiliztion) splint Modified short opponens (CMC immobiliztion) splint Immobilizes the wrist, CMC, nd MCP joints; IP joint is free to move. Immobilizes the CMC nd MCP joints; wrist nd IP joints re free to move. Immobilizes CMC joint only. Abbrevitions: CMC, crpometcrpl; MCP, metcrpophlngel; IP, interphlngel. Provides mximum support nd protection cross entire thumb nd wrist region. Wrist not incorported in splint, however it still provides dequte support to the MCP nd CMC joints. Provides mximl freedom of movement. Immobilizes the wrist, which cn be restrictive during ctivities of dily living. My not provide dequte immobiliztion nd protection to entire wrist nd thumb region. My not provide dequte immobiliztion nd protection to the entire thumb region. Journl of Orthopedic & Sports Physicl Therpy rthritis thn nother. 10 Although NSAIDS re vluble for reducing inflmmtion nd pin, their effects re only pllitive. This is vluble, however, becuse the functionl level of ptients tends to be inversely relted to their pin level. Corticosteroid Injections If the synovitis nd inflmmtion of the CMC joint re not effectively controlled by NSAIDS, then corticosteroid injections my be recommended. Similr to nti-inflmmtory medictions, intr-rticulr injections my provide short-term pin relief. Reducing inflmmtion my help retrd the destruction of the cpsulr structures surrounding the bse of the thumb. Intr-rticulr injections in the re of the CMC joint must be performed without dmging the superimposed superficil sensory brnches of the rdil nerve. Combining corticosteroid injections with splinting of the thumb is n effective wy to decrese inflmmtion of the CMC joint. 44 The ultimte gol of this combined tretment is to postpone surgery. Steroid injections into the bse of the thumb re performed reltively infrequently s compred to injections into the lrger weight-bering joints of the lower extremity. Joint Protection Ptients with joint disese re commonly educted in principles to protect their joints from further destruction. 16,44 In this context, destruction typiclly refers to microtrum of rticulr crtilge nd djcent subchondrl bone nd n overdistension of the supporting ligments nd cpsule. Principles of joint protection re usully imed to reduce pin nd inflmmtion, improve function, nd to mintin structurl stbility of the joint. For the CMC joint of the thumb, these principles re implemented by: voiding stressful ctivities, such s lterl pinching nd gripping; mintining pin-free functionl strength nd flexibility; nd prcticing energy conservtion (optiml ctivity versus rest cycles) by dividing stress mong multiple joints or extremities nd using ssistive devices or splints. Mny of the ssistive devices commonly vilble on the mrket re designed to reduce the pinch nd grip forces ssocited with given functionl tsk. These ssistive devices my include jr openers, doorknob turners, modified eting utensils, key holders, pen grips, nd spring ction scissors. Performing most necessry ctivities of dily living requires t lest 9.9 kg (20 lb) of grip force nd 2.3 to 3.2 kg (5 to 7 lb) of thumb pinch force. 58 Certin ctivities tht likely exceed these levels re cutting with scissors, opening bottle or jr, or turning key in lock. An ctivity such s cutting with scissors, for exmple, cn be modified by using spring ction scissors, which require hlf the strength of conventionl scissors. Regrdless of the specific methods to protect the CMC joint, the underlying objective is to void unnecessry stress to the bse of the thumb. Due to the lrge functionl demnds nturlly plced on this region, these methods my be difficult to implement in prctice. Effective ptient eduction nd chnging long-lerned behviors re keys to the success of joint protection progrms. It is impertive tht ptients ssume n ctive role in structured, gol-oriented eductionl progrm, nd tht they thoroughly understnd the rtionle behind the principles. 29 Studies of persons with osteorthritis or rheumtoid rthritis of the hnd hve shown very positive outcomes from joint protection progrms. 29,64 Improvements hve been shown in grip strength, globl hnd function, pin mngement, stiffness, nd functionl sttus. It is worth noting tht Hmmond nd Freemn 29 were not ble to show significnt retrding of the deforming process in the hnds of persons with rheumtoid rthritis, lthough the study showed very good results in most other res. Surgicl Intervention Surgicl intervention is typiclly used when conservtive therpy is unble to retrd the progression of instbility. Surgery is especilly considered when the instbility is ssocited with uncontrollble pin nd loss of function. The gols of surgery re essentilly similr to those of conservtive intervention for the CMC joint. Selection of the specific surgicl proce- CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 395
Journl of Orthopedic & Sports Physicl Therpy dure is bsed on physicl ssessment nd the rdiogrphic findings of the CMC joint. 56,59 The following presents brief explntion of 3 reltively common surgicl procedures for instbility of the CMC joint. A textbook by Hentz nd Chse 30 should be consulted for more detils on these nd other surgicl procedures. Additionl less common surgicl procedures will lso be briefly reviewed. Arthroplsty Using Ligment Reconstruction With or Without Tendon Interposition Severl types of rthroplsties my be performed on the unstble CMC joint to improve thumb function nd reduce instbility nd ssocited subluxtion of the metcrpl bse. 12,23,32,40,69 In generl, these procedures reconstruct the ligments nd cpsule of the joint, nd my use tendon s spcer inserted into the joint (typiclly referred to s tendon interposition). Two of the most common procedures involve (1) reconstruction of the nterior oblique ligment utilizing donor tendon, nd (2) combining the ligment reconstruction with tendon interposition (LRTI). LRTI significntly relieves pin nd preserves motion of the bse of the thumb nd is the preferred procedure for end stge instbility of the thumb CMC joint. 12,18,26,27,53,61,67,68,70 This procedure typiclly divides the tendon of the flexor crpi rdilis in hlf nd uses hlf to replce the nterior oblique ligment nd the remining hlf s n interpositionl spcer to help fill the void creted by completely or prtilly removing the trpezium. To promote heling, the thumb metcrpl is fixed to the index metcrpl by Kirschner wire nd cst in thumb spic. 69 Tble 6 outlines typicl postopertive therpy progrm for the LRTI. Becuse this progrm will vry considerbly cross clinicl settings, it is ment only s generl guide. One importnt clinicl feture of this surgery is tht the CMC joint must be held immobilized in the thumb spic cst for 4 weeks. Hemirthroplsty A CMC hemirthroplsty most commonly describes the insertion of n llogrft costochondrl crtilge between the prtilly resected trpezium nd the bse of the thumb metcrpl. Originlly developed by Littler in 1984, 22,30,69 this surgery ws termed the lifesver technique due to the coiled shpe of the donted costochondrl crtilge. This procedure is generlly indicted for persons with mrked rthritis nd ssocited instbility tht is limited primrily to the bse of the thumb in contrst to the entire digit. An expected outcome of this surgery is often pin-free nd stble thumb tht functions well in reltively low-stress environment. The CMC joint is typiclly stbilized by weving the tendon of the flexor crpi rdilis through the trpezium nd donted crtilge, then nchoring it to the proximl thumb metcrpl. This surgery provides very stble reconstruction of the CMC joint without the long-term fixtion required for the LRTI. 69 Arthrodesis As mentioned for the hemirthroplsty, n rthrodesis of the CMC joint of the thumb is most typiclly performed on person with posttrumtic rthritis or joint destruction tht is limited to the bse of the thumb. Becuse the surgery rigidly fuses the bse of the thumb to the trpezium, it is generlly indicted for the person whose voction requires extensive physicl use with the hnds, such TABLE 6. A typicl postsurgicl therpy progrm following ligment reconstruction tendon interposition (LRTI). Approximte Timetble Postopertive d 1 through wk 4 Postopertive wk 4 through wk 8 Postopertive wk 8 Postopertive wk 12 Postopertive wk 13 through wk 16 Postopertive wk 16 through wk 24 Therpeutic Intervention Apply thumb spic cst Instruct in continuous elevtion of upper extremity Perform ctive rnge of motion (ROM) to nonimmobilized digits Remove cst, fbricte wrist-crpometcrpl (CMC) immobiliztion splint; to be worn t ll times except during exercise Perform ctive ROM to ll joints of the wrist nd hnd, except the thumb CMC joint Perform pssive ROM to the CMC joint; include bduction nd extension only Flexion nd dduction must be voided to protect the surgiclly incised dorsl side of the cpsule Progress exercise to include ctive thumb plmr bduction, opposition, nd circumduction Perform isometric thenr strengthening in the direction of plmr bduction Progress strengthening exercise to include nonisometric thenr bduction nd lterl pinch Remove splint for light ctivities only Discontinue wrist-cmc immobiliztion splint s indicted Continue thenr bduction nd key pinch strengthening exercises Return to work with light duty restrictions Engge in moderte functionl ctivities Resume voctionl or voctionl ctivities 396 J Orthop Sports Phys Ther Volume 33 Number 7 July 2003
Journl of Orthopedic & Sports Physicl Therpy s n utomobile mechnic. Although the fusion limits mobility, it does offer secure, stble, nd often pin-free bse for the thumb. The LRTI is generlly not pproprite for this popultion becuse the tendon used for the rthroplsty would likely overstretch nd weken due to the lrge forces pplied to the thumb over mny yers. The CMC joint is fused such tht the distl phlnx of the thumb rests on the middle phlnx of the index finger when the hnd is fully fisted. On verge, bduction nd dduction motions of the thumb re reduced by 72%, nd flexion nd extension movements re reduced by 61%. 5,20 Postsurgiclly, persons my report difficulties mnipulting the hnd into restricted res (such s pnts pocket) or plce the hnd on flt surfces. Individuls often compenste for the rigid hypomobility t the CMC joint by developing incresed rnge of motion t other juxtposed joints, such s the scphotrpezil joint proximlly, or the MCP joint distlly. As consequence, individuls generlly do not report significnt functionl deficits following the fusion. 22 The min complictions with this procedure re nonunion in 13% of the cses nd occsionlly lte secondry degenertion in the overtxed scphotrpezil nd MCP joints. 5 Postopertive mngement requires tht the thumb be immobilized in thumb spic cst with the CMC nd MCP joints stbilized nd the IP joint left free to move. Immobiliztion is continued for 3 to 4 months, until rdiogrphic results indicte evidence of trbeculr bridging cross the CMC joint. 5 Less Common Surgicl Procedures There re severl less common surgicl procedures for the tretment of instbility of the CMC joint. A thumb metcrpophlngel joint volr cpsulodesis 39 nd n bductor pollicis longus tenodesis 24 my be performed in conjunction with the 3 surgicl procedures previously discussed. Either performed seprtely or together, these 2 procedures serve to reinforce the cpsules of the MCP nd CMC joints, respectively. In the 1960s, CMC joint rthroplsty ws first performed tht replced the trpezium with silicone implnt. 9 Numerous techniques hve been devised since, however, reports indicte mixed results. 57 Two min resons for filure of this surgery re silicone implnt frcture over time nd silicone synovitis. Finlly, the extension osteotomy of the thumb metcrpl 73 nd rthroscopy of the first CMC joint re reltively new surgeries, without significnt reserch on their long-term outcomes. SUMMARY The gol of this clinicl commentry is to provide n overview for the generl prctitioner of physicl therpy on the fundmentl issues pertining to the therpeutic mngement of instbility of the CMC joint of the thumb. The first prt of this pper described the ntomic nd functionl considertions tht mintin the stbility of the norml CMC joint of the thumb. The section concluded by focusing on how disese or trum t the bse of the thumb cn predispose instbility, often leding to deformity nd reduced function. The second section of this pper describes common nonsurgicl nd surgicl interventions for the unstble CMC joint. Nonsurgicl interventions included sections on splinting, pin control, exercise, use of nonsteroidl nti-inflmmtory drugs, corticosteroid injections, nd joint protection. Nonsurgicl interventions included brief review of the rtionle for severl surgeries nd guide to postsurgicl therpeutic mngement. REFERENCES 1. Acheson RM, Chn YK, Clemett AR. New Hven survey of joint diseses. XII. Distribution nd symptoms of osteorthrosis in the hnds with reference to hndedness. Ann Rheum Dis. 1970;29(3):275 286. 2. Americn Society of Hnd Therpists. Splint Clssifiction System. 1st ed. Chicgo, IL: Americn Society of Hnd Therpists; 1992. 3. Armstrong AL, Hunter JB, Dvis TR. The prevlence of degenertive rthritis of the bse of the thumb in post-menopusl women. J Hnd Surg [Br]. 1994;19(3):340 341. 4. Ateshin GA, Ark JW, Rosenwsser MP, Pwluk RJ, Soslowsky LJ, Mow VC. Contct res in the thumb crpometcrpl joint. J Orthop Res. 1995;13(3):450 458. 5. Bmberger HB, Stern PJ, Kiefhber TR, McDonough JJ, Cntor RM. Trpeziometcrpl joint rthrodesis: functionl evlution. J Hnd Surg [Am]. 1992;17(4):605 611. 6. Brron OA, Glickel SZ, Eton RG. Bsl joint rthritis of the thumb. J Am Acd Orthop Surg. 2000;8(5):314 323. 7. Belt E, Krel K, Lehtinen J, Kutiinen H, Kuppi M, Lehto MU. When does subluxtion of the first crpometcrpl joint cuse swn-neck deformity of the thumb in rheumtoid rthritis: 20-yer follow-up study. Clin Rheumtol. 1998;17(2):135 138. 8. Bettinger PC, Linscheid RL, Berger RA, Cooney WP, 3rd, An KN. An ntomic study of the stbilizing ligments of the trpezium nd trpeziometcrpl joint. J Hnd Surg [Am]. 1999;24(4):786 798. 9. Bezwd HP, Suer ST, Hnkins ST, Webber JB. Longterm results of trpeziometcrpl silicone rthroplsty. J Hnd Surg [Am]. 2002;27(3):409 417. 10. Brooks PM, Dy RO. Nonsteroidl ntiinflmmtory drugs differences nd similrities. N Engl J Med. 1991;324(24):1716 1725. 11. Burton RI, Pellegrini VD, Jr. Surgicl mngement of bsl joint rthritis of the thumb. Prt II. Ligment reconstruction with tendon interposition rthroplsty. J Hnd Surg [Am]. 1986;11(3):324 332. CLINICAL COMMENTARY J Orthop Sports Phys Ther Volume 33 Number 7 July 2003 397