The Teleology of the Thumb: On Purpose and Design
2018; Elsevier BV; Volume: 43; Issue: 3 Linguagem: Inglês
10.1016/j.jhsa.2018.01.002
ISSN1531-6564
Autores Tópico(s)Elbow and Forearm Trauma Treatment
ResumoThe Andrew J. Weiland Medal is presented by the American Society for Surgery of the Hand to a midcareer researcher dedicated to advancing patient care in the field of hand surgery. The Weiland Medal for 2017 was presented to the author at the annual meeting of the American Society for Surgery of the Hand. The purpose of this article is to present current evidence on how biomechanics and morphology influence the pathophysiology of thumb carpometacarpal joint osteoarthritis. The Andrew J. Weiland Medal is presented by the American Society for Surgery of the Hand to a midcareer researcher dedicated to advancing patient care in the field of hand surgery. The Weiland Medal for 2017 was presented to the author at the annual meeting of the American Society for Surgery of the Hand. The purpose of this article is to present current evidence on how biomechanics and morphology influence the pathophysiology of thumb carpometacarpal joint osteoarthritis. Evolutionary development of the brain has afforded the accomplishment and possibility of the human hand.1Wilson F.R. The Hand: How Its Use Shapes the Brain, Language, and Human Culture. Pantheon Books, New York1998Google Scholar, 2Marzke M.W. Evolutionary development of the human thumb.Hand Clin. 1992; 8: 1-8Abstract Full Text PDF PubMed Google Scholar, 3Pellegrini Jr., V.D. The ABJS 2005 Nicolas Andry Award: osteoarthritis and injury at the base of the human thumb: survival of the fittest?.Clin Orthop Relat Res. 2005; 438: 266-276Crossref PubMed Scopus (48) Google Scholar, 4Ladd A.L. Thoughts on the accomplishment and possibility of the human hand: Sterling Bunnell traveling fellow report 2000–2001.J Am Soc Surg Hand. 2003; 3: 117-128Abstract Full Text Full Text PDF Scopus (1) Google Scholar, 5Ladd A.L. Upper-limb evolution and development: skeletons in the closet. Congenital anomalies and evolution's template.J Bone Joint Surg Am. 2009; 91: 19-25Crossref PubMed Scopus (6) Google Scholar, 6Ladd A.L. Crisco J.J. Hagert E. Rose J. Weiss A.P. The 2014 ABJS Nicolas Andry Award: the puzzle of the thumb: mobility, stability, and demands in opposition.Clin Orthop Relat Res. 2014; 472: 3605-3622Crossref PubMed Scopus (31) Google Scholar In turn, the hand and thumb serve the human brain—the actuator and receiver to perform simple activities of daily living and, to the artist or athlete, highly coordinated movement. The teleology of the trapeziometacarpal joint—the thumb carpometacarpal (CMC) joint—represents the inextricable relationship of function to form. The CMC's unique saddle shape represents a complex design that accommodates similarly complex demands: mobility, to produce precision pinch and firm grasp, and stability to manipulate or position an object.7Marzke M.W. Tocheri M.W. Steinberg B. et al.Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins.Am J Phys Anthropol. 2010; 141: 38-51PubMed Google Scholar, 8Marzke M.W. Tocheri M.W. Marzke R.F. Femiani J.D. Three-dimensional quantitative comparative analysis of trapezial-metacarpal joint surface curvatures in human populations.J Hand Surg Am. 2012; 37: 72-76Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar The paradox of motion arguably drives the design. The conventional wisdom regarding the etiology of CMC joint osteoarthritis (OA) implicates ligamentous laxity, postmenopausal hormonal imbalance, and the wear and tear of daily life. Despite being the most common site for surgical treatment in the hand,9Van Heest A.E. Kallemeier P. Thumb carpal metacarpal arthritis.J Am Acad Orthop Surg. 2008; 16: 140-151Crossref PubMed Scopus (108) Google Scholar controversy exists regarding the varying roles of these factors as primary, secondary, or interrelated contributors.3Pellegrini Jr., V.D. The ABJS 2005 Nicolas Andry Award: osteoarthritis and injury at the base of the human thumb: survival of the fittest?.Clin Orthop Relat Res. 2005; 438: 266-276Crossref PubMed Scopus (48) Google Scholar, 6Ladd A.L. Crisco J.J. Hagert E. Rose J. Weiss A.P. The 2014 ABJS Nicolas Andry Award: the puzzle of the thumb: mobility, stability, and demands in opposition.Clin Orthop Relat Res. 2014; 472: 3605-3622Crossref PubMed Scopus (31) Google Scholar, 10Ladd A.L. Weiss A.P. Crisco J.J. et al.The thumb carpometacarpal joint: anatomy, hormones, and biomechanics.Instr Course Lect. 2013; 62: 165-179PubMed Google Scholar, 11Wolf J.M. Cannada L. Van Heest A.E. O'Connor M.I. Ladd A.L. Male and female differences in musculoskeletal disease.J Am Acad Orthop Surg. 2015; 23: 339-347Crossref PubMed Scopus (34) Google Scholar Compelling research on systemic OA suggests a more intricate balance of joint homeostasis, with pathomechanics considered the driving force to upregulate inflammatory markers and injure the surrounding soft tissue structures of the joint itself.12Felson D.T. Osteoarthritis as a disease of mechanics.Osteoarthritis Cartilage. 2003; 21: 10-15Abstract Full Text Full Text PDF Scopus (353) Google Scholar, 13Griffin T.M. Guilak F. The role of mechanical loading in the onset and progression of osteoarthritis.Exerc Sport Sci Rev. 2005; 33: 195-200Crossref PubMed Scopus (315) Google Scholar, 14Chu C.R. Andriacchi T.P. Dance between biology, mechanics, and structure: a systems-based approach to developing osteoarthritis prevention strategies.J Orthop Res. 2015; 33: 939-947Crossref PubMed Scopus (61) Google Scholar With the premise of OA as an organ system gone awry, we review current evidence that thumb CMC joint OA reflects its teleology—its purpose and design. The thumb ray, in the neutral state, is out of plane to the rest of the hand but opposes the fingers, ever ready for digital communication. Three tasks representing the breadth of thumb CMC stability, mobility, and demands in opposition include lateral key pinch, grasp, and torsional grip such as a jar twist.6Ladd A.L. Crisco J.J. Hagert E. Rose J. Weiss A.P. The 2014 ABJS Nicolas Andry Award: the puzzle of the thumb: mobility, stability, and demands in opposition.Clin Orthop Relat Res. 2014; 472: 3605-3622Crossref PubMed Scopus (31) Google Scholar, 10Ladd A.L. Weiss A.P. Crisco J.J. et al.The thumb carpometacarpal joint: anatomy, hormones, and biomechanics.Instr Course Lect. 2013; 62: 165-179PubMed Google Scholar In pinch, the thumb pad engages another finger and, in grasp, acts in concert with the fingers to close around an object. Fine motor intrinsic muscles stabilize the joint for key pinch. Grasp—prehension—typically requires forceful isometric load to accommodate a larger spherical or cylindrical shape, actively engaging intrinsic and extrinsic muscles. Opening a jar adds a torsional or shear load to the grasp position. The CMC joint carries extraordinary load in these routine tasks, and cadaveric biomechanical studies indicate that grasp produces a 10-fold increase in stress at the CMC joint compared with pinch.15Cooney III, W.P. Chao E.Y. Biomechanical analysis of static forces in the thumb during hand function.J Bone Joint Surg Am. 1977; 59: 27-36Crossref PubMed Scopus (432) Google Scholar What is the in vivo evidence of force generation and motion, supporting laboratory studies? The answer lies in analyzing the interdependent joint motion of the trunk and extremities as well as discrete motion at the CMC joint. The hand is the terminus of coordinated, integrated movement of the upper extremity. Like the early hominins, good trunk and leg support, freeing a mobile shoulder, permits 3-dimensional, spherical opportunity for the hand. This linkage creates powerful mechanical coupling for hand manipulation. Examining abnormal motion best elucidates normal coordinated function. We have examined the hand, upper limb, and trunk in purposeful motion of reach and grasp of an object as well as pinch, grasp, and jar opening with marker-based kinematic analysis.16Butler E.E. Ladd A.L. Lamont L.E. Rose J. Temporal-spatial parameters of the upper limb during a Reach & Grasp Cycle for children.Gait Posture. 2010; 32: 301-306Crossref PubMed Scopus (56) Google Scholar, 17Butler E.E. Ladd A.L. Louie S.A. Lamont L.E. Wong W. Rose J. Three-dimensional kinematics of the upper limb during a Reach and Grasp Cycle for children.Gait Posture. 2010; 32: 72-77Crossref PubMed Scopus (71) Google Scholar, 18Luker K.R. Aguinaldo A. Kenney D. Cahill-Rowley K. Ladd A.L. Functional task kinematics of the thumb carpometacarpal joint.Clin Orthop Relat Res. 2014; 472: 1123-1129Crossref PubMed Scopus (30) Google Scholar Like with abnormal gait, an errant golf swing,19Meister D.W. Ladd A.L. Butler E.E. et al.Rotational biomechanics of the elite golf swing: benchmarks for amateurs.J Appl Biomech. 2011; 27: 242-251Crossref PubMed Scopus (44) Google Scholar or the contracted space of a spastic upper limb,16Butler E.E. Ladd A.L. Lamont L.E. Rose J. Temporal-spatial parameters of the upper limb during a Reach & Grasp Cycle for children.Gait Posture. 2010; 32: 301-306Crossref PubMed Scopus (56) Google Scholar, 17Butler E.E. Ladd A.L. Louie S.A. Lamont L.E. Wong W. Rose J. Three-dimensional kinematics of the upper limb during a Reach and Grasp Cycle for children.Gait Posture. 2010; 32: 72-77Crossref PubMed Scopus (71) Google Scholar compensatory motion that is phasic in nature can be quantified. In each study, subjects with abnormal motion took longer to complete a task, used substitutions, and had compromised efficiency. For hand tasks, typical substitutions include shoulder abduction with elbow flexion to improve mechanical advantage. The adducted, arthritic thumb dynamically compensates with increased metacarpophalangeal abduction and extension.18Luker K.R. Aguinaldo A. Kenney D. Cahill-Rowley K. Ladd A.L. Functional task kinematics of the thumb carpometacarpal joint.Clin Orthop Relat Res. 2014; 472: 1123-1129Crossref PubMed Scopus (30) Google Scholar Our quantification of complex interactive hand and thumb motion in both normal and abnormal states provides target zones for emulating functional activity. We propose that this serves as a basis for creating training tools for rehabilitation, in both the nonsurgical and the perisurgical setting. We have analyzed the functional tasks of key pinch, cylindrical grasp, and jar twist (Fig. 1) in asymptomatic, healthy subjects without radiographic disease, compared with those with early symptomatic arthritis (modified Eaton 0/120Ladd A.L. Messana J.M. Berger A.J. Weiss A.P. Correlation of clinical disease severity to radiographic thumb osteoarthritis index.J Hand Surg Am. 2015; 40: 474-482Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar). The cylindrical grasp demonstrated weakness in the early OA population when adjusting for age, sex, and handedness. Standard gross grasp dynamometer measurements in these subjects showed no difference in comparison with asymptomatic controls.21Coughlan M.J. Bourdillon A. Crisco J.J. Kenney D. Weiss A.P. Ladd A.L. Reduction in cylindrical grasp strength is associated with early thumb carpometacarpal osteoarthritis.Clin Orthop Relat Res. 2017; 475: 522-528Crossref PubMed Scopus (10) Google Scholar In addition, key, tripod, and tip pinch diminished in the early OA population compared with controls, with key pinch the most robust predictor of OA.22McQuillan T.J. Kenney D. Crisco J.J. Weiss A.P. Ladd A.L. Weaker functional pinch strength is associated with early thumb carpometacarpal osteoarthritis.Clin Orthop Relat Res. 2016; 474: 557-561Crossref PubMed Scopus (32) Google Scholar This suggests sensitive measurements exist for early, symptomatic disease, which may complement and refine nonsurgical joint protection and strengthening protocols. The discrete and complex nature of the CMC joint poses a challenge to define during purposeful, coordinated motion. Micromotion at a discrete joint may be analyzed with computed tomography (CT), with markerless motion analysis protocols adopted from large joint (hip and knee) kinematic analysis, as well as the wrist dart-thrower's motion.23Marai G.E. Laidlaw D.H. Crisco J.J. Super-resolution registration using tissue-classified distance fields.IEEE Trans Med Imaging. 2006; 25: 177-187Crossref PubMed Scopus (47) Google Scholar, 24Crisco J.J. Coburn J.C. Moore D.C. Akelman E. Weiss A.P. Wolfe S.W. In vivo radiocarpal kinematics and the dart thrower's motion.J Bone Joint Surg Am. 2005; 87: 2729-2740Crossref PubMed Scopus (186) Google Scholar Our 10-year longitudinal, multi-institutional investigation of the thumb CMC joint examines age, sex, and radiographic disease and CT kinematics of the 3 functional tasks performed at 80% effort as measured by positioning jigs with an embedded load cell (Fig. 1). Defining neutral with a thumb orthosis adjusted for the subject's hand size, we have measured position based on segmented joint morphology for neutral, extension, flexion, abduction, and adduction as well as loaded and unloaded pinch, jar twist, and grasp.25Halilaj E. Moore D.C. Patel T.K. et al.Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities.Conf Proc IEEE Eng Med Biol Soc. 2014; 2014: 4354-4357PubMed Google Scholar Analysis of the asymptomatic, disease-free subjects has revealed surprising results. Isometric loading of the CMC joint in 46 asymptomatic subjects (22 men and 24 women), with no radiographic OA and matched in 2 age cohorts (age 18–25 years and age 40–75 years), revealed motion patterns unique to the 3 tasks. This motion, however, did not differ between men and women of either age cohort.26Halilaj E. Rainbow M.J. Got C. et al.In vivo kinematics of the thumb carpometacarpal joint during three isometric functional tasks.Clin Orthop Relat Res. 2014; 472: 1114-1122Crossref PubMed Scopus (52) Google Scholar Motion patterns differed with age, although not consistently across tasks (Fig. 2). The directions of coupled CMC joint motion included flexion, internal rotation, and volar translation during key pinch (Fig. 3A); external rotation, abduction, ulnar, distal, and volar translation during jar grasp (Fig. 3B); and proximal translation during jar twist (Fig. 3C).26Halilaj E. Rainbow M.J. Got C. et al.In vivo kinematics of the thumb carpometacarpal joint during three isometric functional tasks.Clin Orthop Relat Res. 2014; 472: 1114-1122Crossref PubMed Scopus (52) Google Scholar Furthermore, internal rotation and ulnar translation were coupled with flexion,27Crisco J.J. Halilaj E. Moore D.C. Patel T. Weiss A.P. Ladd A.L. In vivo kinematics of the trapeziometacarpal joint during thumb extension-flexion and abduction-adduction.J Hand Surg Am. 2015; 40: 289-296Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar indicating a potentially stabilizing screw-home mechanism, as proposed by Edmonds's cadaveric descriptive study.28Edmunds J.O. Current concepts of the anatomy of the thumb trapeziometacarpal joint.J Hand Surg Am. 2011; 36: 170-182Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar This complex coupled motion, in concert with rotation, recalls the stabilizing effect of knee extension.29McLeod W.D. Moschi A. Andrews J.R. Hughston J.C. Tibial plateau topography.Am J Sports Med. 1977; 5: 13-18Crossref PubMed Scopus (25) Google ScholarFigure 3A The trapezium and metacarpal bones from segmented surface CT scans. B Congruency represented by topography. C Polar coordinate systems of the 3-dimensional histograms.(Image reproduced from Halilaj E, Moore DC, Patel TK, et al. Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities. Conf Proc IEEE Eng Med Biol Soc. 2014;2014:4354–4357.25Halilaj E. Moore D.C. Patel T.K. et al.Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities.Conf Proc IEEE Eng Med Biol Soc. 2014; 2014: 4354-4357PubMed Google Scholar)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Joint congruency, considered a mark of a stable joint in a ball-and-socket articulation, is more difficult to interpret in the normal CMC joint. Based on joint position and polar histograms of curvature (Fig. 3), we found that the joint was most congruent in the neutral position, that congruency differed between the tasks, but that there was no statistical difference between men and women in how the joint was positioned.25Halilaj E. Moore D.C. Patel T.K. et al.Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities.Conf Proc IEEE Eng Med Biol Soc. 2014; 2014: 4354-4357PubMed Google Scholar This analysis included 68 asymptomatic subjects, again age-matched (16 men, 17 women, ages 18–25 years; and 16 men, 19 women, ages 45–75 years). In contrast, 87 subjects with modified Eaton stage 1 and 2 arthritis,20Ladd A.L. Messana J.M. Berger A.J. Weiss A.P. Correlation of clinical disease severity to radiographic thumb osteoarthritis index.J Hand Surg Am. 2015; 40: 474-482Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar ages 45 to 75 years (39 men, average age 60 years; 48 women, average age 52 years), joint congruency was consistently lower in all positions.25Halilaj E. Moore D.C. Patel T.K. et al.Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities.Conf Proc IEEE Eng Med Biol Soc. 2014; 2014: 4354-4357PubMed Google Scholar, 26Halilaj E. Rainbow M.J. Got C. et al.In vivo kinematics of the thumb carpometacarpal joint during three isometric functional tasks.Clin Orthop Relat Res. 2014; 472: 1114-1122Crossref PubMed Scopus (52) Google Scholar, 27Crisco J.J. Halilaj E. Moore D.C. Patel T. Weiss A.P. Ladd A.L. In vivo kinematics of the trapeziometacarpal joint during thumb extension-flexion and abduction-adduction.J Hand Surg Am. 2015; 40: 289-296Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar Joint stability assessment produced more surprising results. Stability was measured by metacarpal translation during the various tasks, with the most translation found in key pinch compared with other tasks. This did not differ between men and women or between asymptomatic (44 subjects) and early arthritic (modified Eaton 1, 76 subjects) individuals.30Halilaj E. Moore D.C. Patel T.K. Ladd A.L. Weiss A.P. Crisco J.J. Early osteoarthritis of the trapeziometacarpal joint is not associated with joint instability during typical isometric loading.J Orthop Res. 2015; 33: 1639-1645Crossref PubMed Scopus (21) Google Scholar Beighton and Horan hypermobility scores31Beighton P.H. Horan F.T. Dominant inheritance in familial generalised articular hypermobility.J Bone Joint Surg Br. 1970; 52: 145-147Crossref PubMed Google Scholar did not correlate with translation, although scores trended toward lowering with increasing age. As noted, weaker key pinch most correlated with early symptomatic arthritis independent of age, sex, and body mass index.21Coughlan M.J. Bourdillon A. Crisco J.J. Kenney D. Weiss A.P. Ladd A.L. Reduction in cylindrical grasp strength is associated with early thumb carpometacarpal osteoarthritis.Clin Orthop Relat Res. 2017; 475: 522-528Crossref PubMed Scopus (10) Google Scholar, 22McQuillan T.J. Kenney D. Crisco J.J. Weiss A.P. Ladd A.L. Weaker functional pinch strength is associated with early thumb carpometacarpal osteoarthritis.Clin Orthop Relat Res. 2016; 474: 557-561Crossref PubMed Scopus (32) Google Scholar Based on the in vivo biomechanics of purposeful movement, we have thus far challenged the concept that women have intrinsic laxity that makes them more susceptible to wearing out the CMC joint. Where else can we look? Further analysis of anatomy and pathoanatomy contributes to inferred function in normal and pathological shape. The biaxial "saddle joint" described by Gray and Lewis as an "articulation by reciprocal reception,"32Gray H. Lewis W.H. Anatomy of the Human Body. 20th ed. Lea & Febiger, Philadelphia1918: 1936Google Scholar bears morphology like no other: the first metacarpal-trapezial surface is largely convex in the volar-dorsal plane and concave in the radial-ulnar plane, with a curved complement, although more loosely so, on the metacarpal surface (Fig. 4). Furthermore, the radial side is elongated, and extra-articular protuberances for ligaments and draping muscles preclude a perfect double saddle.6Ladd A.L. Crisco J.J. Hagert E. Rose J. Weiss A.P. The 2014 ABJS Nicolas Andry Award: the puzzle of the thumb: mobility, stability, and demands in opposition.Clin Orthop Relat Res. 2014; 472: 3605-3622Crossref PubMed Scopus (31) Google Scholar, 33Ladd A.L. Lee J. Hagert E. Macroscopic and microscopic analysis of the thumb carpometacarpal ligaments: a cadaveric study of ligament anatomy and histology.J Bone Joint Surg Am. 2012; 94: 1468-1477Crossref PubMed Scopus (70) Google Scholar The CMC joint lacks the stable bony configuration of a ball-and-socket joint such as the hip, and its loosely reciprocal, eccentric configuration lends to differential joint congruity that supports the screw-home mechanism of the knee.6Ladd A.L. Crisco J.J. Hagert E. Rose J. Weiss A.P. The 2014 ABJS Nicolas Andry Award: the puzzle of the thumb: mobility, stability, and demands in opposition.Clin Orthop Relat Res. 2014; 472: 3605-3622Crossref PubMed Scopus (31) Google Scholar, 25Halilaj E. Moore D.C. Patel T.K. et al.Thumb carpometacarpal joint congruence during functional tasks and thumb range-of-motion activities.Conf Proc IEEE Eng Med Biol Soc. 2014; 2014: 4354-4357PubMed Google Scholar, 28Edmunds J.O. Current concepts of the anatomy of the thumb trapeziometacarpal joint.J Hand Surg Am. 2011; 36: 170-182Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar, 29McLeod W.D. Moschi A. Andrews J.R. Hughston J.C. Tibial plateau topography.Am J Sports Med. 1977; 5: 13-18Crossref PubMed Scopus (25) Google Scholar, 30Halilaj E. Moore D.C. Patel T.K. Ladd A.L. Weiss A.P. Crisco J.J. Early osteoarthritis of the trapeziometacarpal joint is not associated with joint instability during typical isometric loading.J Orthop Res. 2015; 33: 1639-1645Crossref PubMed Scopus (21) Google Scholar In contrast to previous reports,34Xu L. Strauch R.J. Ateshian G.A. Pawluk R.J. Mow V.C. Rosenwasser M.P. Topography of the osteoarthritic thumb carpometacarpal joint and its variations with regard to gender, age, site, and osteoarthritic stage.J Hand Surg Am. 1998; 23: 454-464Abstract Full Text PDF PubMed Scopus (86) Google Scholar, 35Ateshian G.A. Rosenwasser M.P. Mow V.C. Curvature characteristics and congruence of the thumb carpometacarpal joint: differences between female and male joints.J Biomech. 1992; 25: 591-607Crossref PubMed Scopus (131) Google Scholar, 36Pellegrini Jr., V.D. Smith R.L. Ku C.W. Pathobiology of articular cartilage in trapeziometacarpal osteoarthritis. I. Regional biochemical analysis.J Hand Surg Am. 1994; 19: 70-78Abstract Full Text PDF PubMed Scopus (28) Google Scholar we found no difference in the shape of the trapezium and first metacarpal between men and women in 50 healthy, age-matched, asymptomatic subjects. With shape-modeling analysis, the only difference encountered between men and women was size.37Schneider M.T. Zhang J. Crisco J.J. et al.Men and women have similarly shaped carpometacarpal joint bones.J Biomech. 2015; 48: 3420-3426Crossref PubMed Scopus (31) Google Scholar We additionally identified older healthy subjects, compared with healthy young subjects, as having higher curvature in concave and lower curvature in convex directions of the trapezial and metacarpal reciprocating surfaces.38Halilaj E. Moore D.C. Laidlaw D.H. et al.The morphology of the thumb carpometacarpal joint does not differ between men and women, but changes with aging and early osteoarthritis.J Biomech. 2014; 47: 2709-2714Crossref PubMed Scopus (45) Google Scholar Subjects with early OA (modified Eaton 1/220Ladd A.L. Messana J.M. Berger A.J. Weiss A.P. Correlation of clinical disease severity to radiographic thumb osteoarthritis index.J Hand Surg Am. 2015; 40: 474-482Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar, 39Eaton R.G. Littler J.W. Ligament reconstruction for the painful thumb carpometacarpal joint.J Bone Joint Surg Am. 1973; 55: 1655-1666Crossref PubMed Scopus (672) Google Scholar, 40Eaton R.G. Glickel S.Z. Trapeziometacarpal osteoarthritis. Staging as a rationale for treatment.Hand Clin. 1987; 3: 455-471Abstract Full Text PDF PubMed Google Scholar, 41Berger A.J. Momeni A. Ladd A.L. Intra- and interobserver reliability of the Eaton classification for trapeziometacarpal arthritis: a systematic review.Clin Orthop Relat Res. 2014; 472: 1155-1159Crossref PubMed Scopus (40) Google Scholar) had significantly different metacarpal and trapezial articular shapes from healthy subjects of the same age. These findings suggest that aging and OA affect the articular shape of the CMC joint, but challenge current concepts that inherent sex differences based on shape are responsible for the higher incidence of CMC OA in women.42Halilaj E. Moore D.C. Patel T.K. et al.Older asymptomatic women exhibit patterns of thumb carpometacarpal joint space narrowing that precede changes associated with early osteoarthritis.J Biomech. 2015; 48: 3634-3640Crossref PubMed Scopus (15) Google Scholar Furthermore, utilizing our standardized CT segmentation technique, we identified decreasing subchondral bone distance, indicating cartilage wear, in early OA subjects with absent or minimal x-ray changes (modified Eaton 0/120Ladd A.L. Messana J.M. Berger A.J. Weiss A.P. Correlation of clinical disease severity to radiographic thumb osteoarthritis index.J Hand Surg Am. 2015; 40: 474-482Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar) (Fig. 5). A change in center of pressure—the "centroid"—occurs with each loaded and unloaded position in women.42Halilaj E. Moore D.C. Patel T.K. et al.Older asymptomatic women exhibit patterns of thumb carpometacarpal joint space narrowing that precede changes associated with early osteoarthritis.J Biomech. 2015; 48: 3634-3640Crossref PubMed Scopus (15) Google Scholar The larger joint space area, representing diminished cartilage distance, was also encountered in older asymptomatic female subjects without radiographic arthritis (Fig. 6). This suggests that joint space narrowing precedes radiographic arthritis in women, supporting the concept of female predisposition to develop OA.42Halilaj E. Moore D.C. Patel T.K. et al.Older asymptomatic women exhibit patterns of thumb carpometacarpal joint space narrowing that precede changes associated with early osteoarthritis.J Biomech. 2015; 48: 3634-3640Crossref PubMed Scopus (15) Google Scholar Our preliminary analysis of progression in the early OA cohort magnifies this effect, with half of subjects progressing 1 modified Eaton stage by 3 years.Figure 6Healthy (left) and arthritic (right) CMC joints, in which the color intensity represents bone-to-bone distance between the trapezium (TPM) and the metacarpal (MC1), in a resting key pinch position. The joint is closer (narrower joint space) in OA subjects than in healthy controls. The joint space area is defined as the area where the bone-to-bone distance is less than or equal to 1.5 mm (yellow). The joint space centroid (black) is the distance-weighted centroid of the joint space area.(Image reproduced from Halilaj E, Moore DC, Patel TK, et al. Older asymptomatic women exhibit patterns of thumb carpometacarpal joint space narrowing that precede changes associated with early osteoarthritis. J Biomech. 2015;48[13]:3634–3640.42Halilaj E. Moore D.C. Patel T.K. et al.Older asymptomatic women exhibit patterns of thumb carpometacarpal joint space narrowing that precede changes associated with early osteoarthritis.J Biomech. 2015; 48: 3634-3640Crossref PubMed Scopus (15) Google Scholar)View Large Image Figure ViewerDownload Hi-res image Download (PPT) At the other end of the spectrum from our in vivo early OA cohort, we have also focused on advanced arthritis. The accessible population is surgical patients, by definition a symptomatic population with end-stage clinical disease, regardless of radiographic staging. With micro-CT, we have identified that the volar ulnar trabecular bone in 16 explanted trapezia has greater trabecular number and connectivity compared with 13 trapezia without arthritis.43Lee A.T. Williams A.A. Lee J. Cheng R. Lindsey D.P. Ladd A.L. Trapezium trabecular morphology in carpometacarpal arthritis.J Hand Surg Am. 2013; 38: 309-315Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar This increase in bone density suggests preferential loading in the volar ulnar quadrant, supporting the concept of concentrated force loading with degeneration. In addition, surgically excised trapezia display 3 reproducible patterns of wear: (1) retained saddle configuration with minimal osteophyte formation; (2) reversal of the volar-dorsal convexity into 1 large concave "dish" with extensive rimming osteophytes, especially beneath the abductor pollicis longus radially and the flexor carpi radialis ulnarly; and (3) a volar concave neofacet encountered in the corresponding region of the volar metacarpal beak, similar to a glacier "cirque" (Fig. 7).44Van Nortwick S. Berger A. Cheng R. Lee J. Ladd A.L. Trapezial topography in thumb carpometacarpal arthritis.J Wrist Surg. 2013; 2: 263-270Crossref PubMed Google Scholar Whereas a retained saddle typically represents "early" or "mild" radiographic disease, no correlation exists between "advanced" sev
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