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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Instr Course Lect. Author manuscript; available in PMC 2014 February 26.
Published in final edited form as:
Instr Course Lect. 2013; 62: 165–179.
PMCID: PMC3935621
NIHMSID: NIHMS552273

The Thumb Carpometacarpal Joint: Anatomy, Hormones, and Biomechanics

Abstract

Although there are many surgical options to treat thumb carpometacarpal (CMC) arthritis, a precise etiology for this common disorder remains obscure. To better understand the physiology of the thumb CMC joint and treat pathology, it is helpful to examine the biomechanics, hormonal influences, and available surgical treatment options, along with the evolutionary roots of the thumb; its form and function, its functional demands; and the role of supporting ligaments based on their location, stability, and ultrastructure. It is important to appreciate the micromotion of a saddle joint and the role that sex, age, and reproductive hormones play in influencing laxity and joint disease. Minimally invasive surgery is now challenging prevailing treatment principles of ligament reconstruction and plays a role in thumb CMC joint procedures.

A Marvelous Piece of Machinery

Stability and mobility represent the functional paradox of the thumb carpometacarpal (CMC) joint. The thumb requires a breadth of motion to perform tasks that are uniquely human, from forceful grasp to fine pinch. The joint morphology of the metacarpal on the trapezium affords this functional spectrum. Although in circumduction it behaves like a ball and socket, providing close lateral pinch to the index finger or wide prehension of large objects within the palm, its configuration is more complex. The concavo-convex saddle design, described as “articulation by reciprocal reception” in Gray’s seminal anatomy textbook,1 imparts arcs of motion in flexion-extension and abduction-adduction. Pronation-supination represents composite rotation and translation of this joint based on morphology and muscular activity in planes out of phase with the fingers. The metacarpal base is concave dorsovolarly and convex radioulnarly. Conversely, the trapezial concave arc is radioulnar, and the convex arc is dorsovolar. The trapezial and metacarpal articular surfaces have disparate radii of curvature that are congruous only at the extremes of motion25 (Figure 1). The concavity of each articular surface is shallow, so the skeleton affords little intrinsic stability. The ligaments and muscles play varying roles in stability, laxity, and proprioception of this complex joint.610

Figure 1
Topography of the distal trapezial joint surface, redrawn from a CT surface rendering of a normal right hand. The CMC-I motion arcs of the metacarpal on the trapezium are flexion-extension and abduction-adduction. Pronation-supination represents composite ...

The evolutionary demands for prehension and manipulative activity accompanied the ability of hominid species to stand upright, freeing the torso and upper limbs. These demands and capabilities coevolved with a larger brain and neurologic complexity.11,12 Bipedalism and club wielding in Homo sapiens are closely associated; other primates and their ancestors use the comparatively hypoplastic thumb as a post, given its shorter, stiffer configuration and absence of intrinsic muscular development.13,14

Biomechanical studies have shown that forces increase exponentially from the tip of the thumb to the CMC joint with grasp and forceful pinch. The joint reactive force at the base of the thumb is 12 times greater than that generated at the tip of the thumb with lateral pinch, and compressive forces of as much as 120 kg may occur at the trapeziometacarpal joint with forceful grasp.8 Cadaver biomechanical studies have suggested that most of the force in pinch is transmitted proximally and dorsoradially.8 The precise position of the metacarpal on the trapezium during these activities in live subjects can be visualized with various imaging techniques (Figures 2 and and3),3), although correlating the force generated in these positions has yet to be quantified. The functional importance of the thumb is underscored by its effect on disability; loss of thumb function imparts a 40% to 50% rate of impairment to the upper extremity because of its central role in nearly all grasping and handling maneuvers.3

Video 14.1: Animation of Grasp, Jar Opening, and Pinch. Amy L. Ladd, MD (30 sec)

Figure 2
A cine radiograph of the hand during functional, loaded grasp. The position of the metacarpal on the trapezium demonstrates apparent abduction; however, the two-dimensional nature and image overlap prevent precise location and relationship of the two ...
Figure 3
Surface three-dimensional rendering from CT (depicted here as a two-dimensional image) permits quantifying the position of the trapezium and the metacarpal relative to each other in functional grasp. The shading and coloring are added for clarity. (Courtesy ...

CMC joint osteoarthritis is traditionally viewed as a disease endemic in postmenopausal women.4,15,16 Demographic radiographic studies show a 6:1 female-to-male incidence of arthrosis of the trapeziometacarpal joint, although this difference decreases with age, with the incidence in women and men at age 75 years of 40% and 25%, respectively.17,18 The surgical literature and the institutional experience of one of this chapter’s authors (AL) indicates that the average age of patients at the time of surgery for CMC osteoarthritis is 60 years, and the incidence of men undergoing surgery is higher than the radiographic incidence.4,1822 One of this chapter’s authors (AL) reported on her consecutive surgical experience in 2010 to 2011 with articular wear in 39 trapezia in 37 patients (average age, 62 years). The incidence of female and male specimens in this study was 69% and 31%, respectively.23 The roles of sex, ethnicity, age, and hand use likely contribute to both the incidence of arthritis and the decision for surgical treatment. Future improvements in surgical treatment will rely on a better understanding of the pathomechanics of the disease.

Thumb CMC Kinematics and Osteoarthritis Progression

Despite the prevalence of thumb CMC joint osteoarthritis, there is little definitive understanding of how altered joint biomechanics relate to the natural history of the disease. Basic science and clinical studies have correlated increases in general joint laxity with the development of CMC osteoarthritis.24 Radial subluxation of the metacarpal on the trapezium has been noted with functional activities.25

In an attempt to further define the kinematic factors that influence the development of thumb osteoarthritis, a state-of-the-art, markerless bone registration (MBR) technique was used for three-dimensional in vivo kinematic analysis in normal individuals and in an ongoing study evaluating patients with early CMC osteoarthritis. Data on thumb CMC kinematics were obtained over several years.26 Key pinch, progressing from unloaded to loaded, in 12 asymptomatic men (age, 38.7 ± 11.7 years) and 12 women (age, 43.2 ± 15.8 years) was evaluated. These normal individuals demonstrated metacarpal volar translation, internal rotation, and flexion on the distal trapezial surface in key pinch (Figure 4). In object grasp, progressing from unloaded to loaded, the metacarpal bone undergoes ulnar translation, flexion, and abduction relative to the distal trapezial surface (Figure 5). There appears to be a definite functional coupling of flexion-extension and abduction-adduction (statistical significance, P < 0.001) from the neutral position on performing each task (Figure 6). Extension of the thumb metacarpal relative to the trapezium couples with adduction, and flexion couples with abduction. These studies provide a solid framework to further analyze the kinematics of patients with early thumb osteoarthritis and determine whether changes in motion over time (abnormal motion or laxity) can predict osteoarthritis progression in symptomatic patients with little evidence of radiographic disease.

Figure 4
Illustration of MBR kinematic analysis of loaded key pinch. The thumb metacarpal undergoes volar translation, internal rotation, and flexion relative to the trapezium. (Courtesy of Arnold-Peter C. Weiss, MD, Providence, RI.)
Figure 5
Illustration of MBR kinematic analysis of loaded object grasp. The thumb metacarpal undergoes ulnar translation, flexion, and abduction relative to the trapezium.(Courtesy of Arnold-Peter C. Weiss, MD, Providence, RI.)
Figure 6
A specific CMC functional coupling occurs in multiple tasks. Coupling occurs with extension/adduction and flexion/abduction. Ab = abduction, deg = degrees, ext = extension, flex = flexion. (Courtesy of Arnold-Peter C. Weiss, MD, Providence, RI.)

CMC Ligament Anatomy: New Evidence to Change Old Ideas

Although the first accounts of basal thumb ligament anatomy date back to the mid 18th century, an accurate description and reproducible measurements of thumb CMC ligament anatomy remain elusive.27 As few as 3 and as many as 16 ligaments have been identified. Volar, dorsal, and ulnar ligaments have been named as primary stabilizers of the CMC joint.7,14,2830

Ligaments play an important role in the static stability and the dynamic neuromuscular control of a joint. Studies of knee, shoulder, ankle, and wrist joints have established the concept of proprioception, in which nerve endings within the joint capsule and the ligaments contribute afferent information to the spinal cord for efferent control of periarticular muscles.3135 The Hilton law states that “any nerve innervating a joint will also innervate the muscles moving that joint.”36 The thumb CMC joint receives innervation from the dorsal sensory radial nerve and the volar thenar median nerve branches, but the innervation of the ligaments has not been delineated.3739

To better understand thumb CMC stability and function, a study of CMC ligament morphometry, histology, and neuroanatomy (to investigate the anatomy and proprioceptive role of the CMC ligaments) was performed.9,10,39 Some of the main findings include those associated with the volar anterior oblique ligament, the dorsal deltoid ligament, and CMC ligament innervation.

Volar Anterior Oblique Ligament

The volar anterior oblique ligament is consistently described but variably situated in anatomic studies of the CMC joint (Figure 7). Pieron40 described it as a curtain-like structure covering the volar joint surface, which was later affirmed by other studies.7,10 Bettinger et al7 and Pellegrini19 described a deep, intra-articular ligament (the so-called beak ligament), but this finding was not confirmed in a study of low-arthritic cadaver specimens.10 Morphometric data revealed that the volar anterior oblique ligament is a thin, capsular structure with a mean thickness of 0.71 mm (SD = 11) and variable width.10 Histomorphometric analysis, including hematoxylin-eosin and 4',6'-diamidino-2-phenylindole (DAPI) staining to determine morphology and cellularity, also support the notion that the volar anterior oblique ligament is primarily a capsular structure consisting of disorganized connective tissue.

Figure 7
The volar thumb CMC ligaments from a right hand, showing the attenuated volar anterior oblique ligament (AOL) and ulnar collateral ligament (UCL), which course from the trapezial ridge (Tz) onto the volar base of metacarpal 1 (MC1). Also seen are the ...

Dorsal Deltoid Ligament

In contrast to the volar anterior oblique ligament, the dorsal deltoid ligament in the cadaver study by Ladd et al10 consisted of three stout ligaments, all emanating from the dorsal tubercle of the triquetrum and inserting fan shaped onto the dorsal base of the first metacarpal (Figure 8). These ligaments were consistently found in the same location, had a mean thickness of 1.85 mm (SD = 0.14), and showed histologic findings consistent with a stout ligament with grouped collagen bundles.10 Macroscopic findings were consistent with articles purporting that the dorsal ligaments are the primary stabilizers of the thumb CMC joint,7,30 and a recent study comparing the arthroscopic and macroscopic appearance of the thumb CMC ligaments.41

Figure 8
The dorsal thumb CMC ligaments from a right hand showing the dorsal deltoid ligament complex consisting of the dorsal radial ligament (DRL), dorsal central ligament (DCL), and posterior oblique ligament (POL), all emanating from the dorsal tubercle of ...

CMC Ligament Innervation

A new, triple-stain immunofluorescent technique was used to investigate the innervation patterns of the three dorsal and two volar thumb CMC ligaments9 (Figure 9). Sensory nerve endings, so-called mechanoreceptors, were identified and classified according to Freeman and Wyke.42 Ordinal grading of the nerve endings showed that the dorsal deltoid ligament complex was consistently innervated with mechanoreceptors and free nerve endings, with a predominance of nerve endings located close to the insertion into bone and, significantly (P < 0.05) more often, closer to the mobile metacarpal insertion than the stable triquetral insertion.39 The most common mechanoreceptor type was the Ruffini ending, which is known for its ability to monitor joint position and kinesthesia.

Figure 9
A, Ruffini ending from a dorsal radial ligament, as seen in an immunofluorescent protein gene product 9.5 stain. B, The Ruffini ending is superimposed on the collagen fibers in the DAPI stain, which highlights the nuclei of fibrocytes. (Courtesy of Amy ...

Influence of Laxity and Hormones on Basilar Thumb Arthritis

The prevalence in women of both symptomatic and radiographic CMC osteoarthritis has led to speculation that reproductive hormones or joint laxity are responsible for this disparity between the sexes.17,42 Sodha et al17 reviewed the radiographs of 615 patients with distal radius fractures. The authors reported a 6:1 female-to-male ratio of radiographic trapeziometacarpal arthritis and found the disorder increases in prevalence with advancing age in both sexes.

Joint Laxity

Joint hypermobility is defined as greater than normal motion at multiple joints. Patients with this condition are often characterized as double jointed because of the hyperextensibility of various joints.43 In patients with joint laxity, studies have shown a higher correlation with anterior cruciate ligament (ACL) tears, shoulder instability, and ankle sprains.44,45 Joint laxity is also associated with a higher rate of knee arthritis, implying that greater joint mobility leads to abnormal biomechanical stresses on the joint.46

Studies in subjects with extremes of joint laxity, as well as normative populations, have suggested that joint laxity affects the thumb CMC joint. Gamble et al47 reported thumb CMC joint subluxation and dislocation in more than 75% of a cohort of 24 young patients with Ehlers-Danlos syndrome, with radiographic evidence of CMC arthritis in 16% (Figure 10). Jónsson et al24 noted a higher prevalence of CMC osteoarthritis in Icelandic patients with joint laxity compared with those without hypermobility. Another study showed a significant correlation between the radiographic stress ratio at the trapeziometacarpal joint and the Beighton score of generalized joint laxity.48,49

Figure 10
Radiograph showing trapeziometacarpal joint dislocation in a patient with intrinsic ligament laxity after a minor fall. (Courtesy of Jennifer M. Wolf, MD, Farmington, CT.)

Hormonal Influences

The sex differences in multiple musculoskeletal diseases have led to theories that differences in reproductive hormones may account for these disparities. More women than men sustain ACL tears playing soccer and basketball.50 Women also have shown less anterior shoulder stiffness and greater shoulder hypermobility than men.45 In studies of the effect of hormones in these joints, it has been shown that ACL tears occur most frequently during the ovulatory phase in menstruating women.51 Focusing on the hand joints, Cooley et al52 reported a higher rate of overall hand osteoarthritis in women who had an earlier onset of menarche and later menopause, implying greater exposure to reproductive hormones.

There is some evidence that reproductive hormones affect various joints. Estrogen and relaxin receptors have been described in the ACL in both women and men.53 Kapila et al54 reported that estrogen and relaxin caused dose-dependent matrix degradation of temporomandibular fibro-cartilage explants, an effect attenuated by the addition of progesterone.

Relaxin, a hormone produced by the corpus luteum during pregnancy, loosens the pelvic ligaments in preparation for childbirth.55 It has been proposed as a specific hormone target in the development of trapeziometacarpal arthritis because of attenuation of the supporting joint ligaments. Relaxin is a member of the insulin superfamily that is produced both in pregnant and nonpregnant women and in men.56,57 Its mechanism of action is mediated through upregulation of matrix metalloproteases and suppression of tissue inhibitors of metalloproteases within the extracellular matrix.58

In a prospective study, Dragoo et al59 demonstrated that serum relaxin levels were higher in female collegiate athletes who sustained ACL tears compared with noninjured athletes. In the basilar thumb joint, Lubahn et al60 performed an immunohistochemical evaluation of surgically sampled anterior oblique ligaments and showed the presence of relaxin receptors, indicating that relaxin may affect the trapeziometacarpal joint. Fifty anterior oblique ligaments were sampled, RNA was extracted, and reverse-transcriptase polymerase chain reaction analyses were performed (JM Wolf, MD, unpublished data, 2011). A significant correlation was shown between serum relaxin and the presence of relaxin receptors and matrix metalloproteases-1 in the anterior oblique ligament (P = 0.02 and 0.05, respectively).

The relaxin knockout mouse model shows progressive fibrosis with interstitial collagen deposition in the lungs, kidney, and heart.61 These findings suggest that relaxin is a naturally occurring inhibitor of collagen deposition. The effect of relaxin on the supporting ligaments of the CMC joint may involve attenuation of the ligaments or inhibition of repair, potentially during the peak of a woman’s reproductive potential.

Reconstructing the Joint: Restoring the Anatomy

Because the skeletal architecture of the trapeziometacarpal joint affords little intrinsic bony stability, the ligaments are critically important for resisting the natural tendency to subluxate with pinch and grasp maneuvers (Figure 11). There is no consensus about which ligament or ligaments are most important in preventing the metacarpal from shifting with load. Biddulph62 focused on the intermetacarpal ligament and Eaton and Littler63 emphasized the volar or anterior oblique ligament. They pointed out that in a Bennett fracture, the stable fragment is the volar fragment of the metacarpal that is attached to the anterior oblique ligament. By cutting cadaver ligaments, Strauch et al64 reported that the primary restraint to dorsal subluxation of the trapeziometacarpal joint is the dorsoradial ligament; however, the anterior oblique ligament had to subperiosteally strip off the volar cortex of the metacarpal to dislocate the joint. Arguably, stability of the basal joint is provided by the additive and synergistic effect of each ligament.

Figure 11
View of a left thumb: The CMC joint is a biconcavo-convex saddle in which the longitudinal axes of the trapezial and metacarpal articular surfaces are perpendicular to each other. The (primarily) concave surface of the metacarpal and the convex surface ...

A series of studies has provided compelling evidence to support the hypothesis that the degeneration of the anterior oblique ligament is the precursor of basal joint degenerative disease.3,19,65 Based on cadaver studies, the volar part of the trapezial articular surface is considered the primary contact area during flexion adduction and, particularly, with key pinch. Degeneration and subsequent detachment of the anterior oblique ligament potentially creates magnified shear forces volarly and dorsal translation of the contact area, predisposing the patient to progressive degeneration of the joint. One study indicted that severely degenerated joints had a nonfunctional anterior oblique ligament.65

In 1949, Gervis66 reported good initial results in a series of 18 trapezium excisions for basal joint osteoarthritis. In 1960, Murley67 reviewed 39 trapeziectomies and reported that surgery usually relieved pain, but there was a high incidence of loss of strength and decreased range of motion in abduction. Because of the loss of grip strength, he believed that the procedure was most appropriate for less active patients and was not suitable for “men doing heavy work.” In a study by Weilby,68 17 patients were treated with excision of the trapezium. He reported that five patients had symptoms of weakness, painful spasms, and difficulty holding objects, which were attributed to joint instability. In general, patients regained 75% of their motion, but strength was materially reduced.

Persistent weakness after simple trapeziectomies was likely an impetus for the development of methods to stabilize and resurface or eliminate the trapeziometacarpal joint to provide a more physiologic reconstruction by attempting to restore normal anatomy. Froimson69 cited the problem of metacarpal subsidence and weakness after trapeziectomy and recommended interposition of a tendon spacer between the metacarpal and the scaphoid. Other investigators pursued the approach of stabilizing the metacarpal with a ligament reconstruction that would tether the metacarpal base (usually to the adjacent index metacarpal). The rationale was to prevent subluxation, prevent metacarpal subsidence in the absence of all or part of the trapezium, and fix the relationship of the thumb metacarpal to the index metacarpal by suspension.

Eaton and Littler63 and Eaton et al70 reported that idiopathic hypermobility of the basal joint caused pain, particularly in young women, and also predisposed the joint to progressive degeneration. They developed a method of volar ligament reconstruction using half of the distally based flexor carpi radialis (FCR) tendon, which is passed through a volar-to-dorsal hole in the base of the thumb metacarpal.63 The tendon is tensioned and sutured to the adjacent periosteum. It is then passed deep to the abductor pollicis longus (APL) tendon, to which it is sutured, and again volarly where it previously passed under the intact part of the FCR tendon and back dorsally where it is again sutured. It was theorized that the reconstruction restored the function of the lax volar ligament and reinforced the thin radial capsule. This reconstruction supported the joint in two planes, rendering it more stable than uniplanar reconstruction. In the initial study reported in 1973, volar ligament reconstruction was used to treat patients with all four stages of basal joint disease.63 Eaton and Littler63 reported good or excellent results in 16 of 18 patients and 2 fair results, which occurred in patients with stage IV basal joint disease. In 38 patients who were followed for approximately 7 years, 32 (84%) had good or excellent results, and 6 (16%) had fair results.70 After segregating the results of 19 patients with stage I or II disease, for whom the procedure is most appropriate, 95% good or excellent results were reported. A 14.7-year average follow-up study of 19 patients treated with volar ligament reconstruction showed no pain in 7, mild pain with strenuous use in 13, and pain with activities of daily living in 4.71 This reconstructive procedure achieves good but not ideal results, which may in part be related to the fact that seven patients advanced one stage of disease and two patients advanced two disease stages. Volar ligament reconstruction also was used to stabilize the metacarpal after partial trapeziectomy and tendon interposition in patients with stage II or III basal joint disease.63,70,71

Burton and Pelligrini72 popularized the procedure that has become known as ligament reconstruction tendon interposition (LRTI), extending the volar ligament reconstruction to combine it with partial and complete trapeziectomies (Figures 12 through through14).14). The concept is similar to that of volar ligament reconstruction except that the tendon is routed obliquely through the base of the thumb metacarpal and exits dorsally approximately 1 cm distal to the articular surface and perpendicular to the plane of the thumbnail. The remaining tissue is folded and interposed into the space created by the trapezial excision. The reconstruction is stabilized with Kirschner wire fixation. Initially, half of the FCR tendon was used for reconstruction and, more recently, the entire tendon has been used, thus providing more tissue for interposition. A 2-year postoperative review of 25 thumbs treated with LRTI for basal joint laxity showed that the thumb metacarpal subsided proximally 11% of the arthroplasty space, and subluxation was limited to 7%.71 Ninety-two percent of the patients had pain relief and were satisfied with the procedure. In a 9-year follow-up study of 24 of the patients, Tomaino et al73 reported little change in metacarpal subsidence (13%) and subluxation (11%) and continued satisfaction and pain relief (95%). Strength increased and grip improved 93%, key pinch improved 34%, and tip pinch improved 65%. LRTI is arguably the most commonly used procedure to treat arthritis of the basal joint. The technique of LRTI includes interposition of the tendon not used for the reconstruction into the space created by the trapezial excision.

Figure 12
The volar ligament reconstruction (left thumb) reconstructs the lax or incompetent volar anterior oblique ligament complex, with the routing of the tendon dorsally to volarly and back dorsally, thus reinforcing the dorsal ligament complex. Intraoperative ...
Figure 14
The remainder of the FCR tendon is rolled or folded and interposed in the space created by excision of the trapezium. (Courtesy of Steven Z. Glickel, MD, New York, NY.)

Several alternative procedures to LRTI use different rerouting pathways for the FCR tendon (with or without bone tunnels) or use different tendons to tether the thumb to the index metacarpal. The suspensionplasty uses part of the APL tendon to stabilize the thumb metacarpal. The procedure was originated by Thompson74 as a means of salvaging failed arthroplasties with Silastic implants after trapeziectomy for basal joint osteoarthritis. Because the procedure was effective, the indications were extended to include the primary treatment of stage II to IV basal joint disease. The technique uses part of the APL tendon divided just distal to the musculotendinous junction, mobilizing it from proximal to distal, and leaving it attached to the dorsal base of the thumb metacarpal. An oblique hole is made in the thumb metacarpal base, similar to the hole used for LRTI. The hole starts dorsally approximately 1 cm distal to the articular surface and exits proximally just volar to the center of the base of the metacarpal. A second hole is made dorsally to volarly 1 cm distal to the base of the index metacarpal. Using wire, suture, or a tendon passer, the slip of the APL is passed through the base of the thumb metacarpal and then volarly to dorsally in the index metacarpal. After appropriate tension is set, the APL is fixed dorsally by weaving it into the adjacent extensor carpi radialis longus tendon. Thompson74 described the technique but did not report results. Soejima et al75 reported on 18 patients (21 thumbs) treated with suspensionplasty and followed for an average of 33 months. No pain was reported in 13 thumbs, 5 had mild pain with strenuous use, and 3 had mild pain with light use. Metacarpal subsidence was 15% of the arthroplasty space. Radial and palmar abduction were both 56°. These results are comparable to those of LRTI, as reported by Burton and Pellegrini.72

Comparing Treatment Options

When nonsurgical measures fail to definitively treat a patient’s pain from disabling arthritis of the thumb CMC joint, many treatment options exist. Gervis66 was the first to champion simple excision of the trapezium to remove the bone-on-bone pain generator created by the thumb metacarpal articulating with the trapezium without the benefit of an interposed layer of articular cartilage (Figure 15). Subsequent procedures have emphasized height retention and reconstruction of ligament support, with the LRTI procedures, APL suspensionplasty, allograft and other interposition procedures, implant arthroplasty, unloading osteotomy, and arthrodesis.76,77

Figure 15
Radiograph of the thumb after a simple trapeziectomy. (Courtesy of Jeffrey Yao, MD, Palo Alto, CA.)

Ligament reconstruction is believed to be important based on the theory that attenuation and incompetence of the anterior oblique ligament is the fundamental cause of thumb CMC joint degeneration. LRTI and APL suspensionplasty techniques are usually performed to reinforce or reconstruct important ligaments; however, simple trapeziectomy with hematoma distraction without ligament reconstruction has recently regained popularity because of the results of medium-term and long-term follow-up studies by Kuhns and Meals78 and Gray and Meals.79 Their results challenge the need for more elaborate and time-consuming procedures for reconstructing the anterior oblique ligament.

Outcome studies support the benefits of both reconstructive procedures and excisional arthroplasty. Because comparable pain relief and improvements in range of motion and strength have been reported, it is unclear if any one surgical option is superior to the others.76,77 In 2005, Wajon et al76 evaluated 384 patients from seven studies treated with five different techniques. The authors found no significant differences among the techniques in regard to postoperative pain levels, physical function, patient global assessment, range of motion, and strength. However, they reported 16% fewer complications in the patients treated with trapeziectomy alone. In a follow-up study in 2009, Wajon et al77 reported on 477 patients from nine studies treated with seven different techniques. The authors again found no differences in outcome variables, except fewer complications were again found in the cohort treated with trapeziectomy alone. In a comparison of three techniques (LRTI, costochondral allograft interposition, and trapeziectomy alone), Gray and Meals79 found no differences in pinch and grip strength and subjective patient-reported outcome using Disability of the Arm, Shoulder and Hand scores. However, surgical time was substantially increased for LRTI procedures when compared with costochondral allograft interposition and trapeziectomy.22 The conclusions of these three recent studies suggest that any of the described surgical techniques for managing arthritis of the thumb CMC will adequately treat symptoms with comparable subjective and objective outcomes. In contrast, secondary outcomes measures, including overall procedural costs (including surgical time), complications, shorter recovery times, and time off work, influence the treatment choices. A recent publication with long-term follow-up further supports the “less is more” concept over reconstruction of the anatomy.80

More recently, arthroscopic management of thumb CMC arthritis has gained popularity. First described by Berger81 and Menon,82 arthroscopy is an accepted method for treating the thumb CMC joint (Figure 16). Either hemitrapeziectomy or complete trapeziectomy can be performed arthroscopically, with or without interposition of material within the newly created space (Figure 17). The benefits of arthroscopy include smaller incisions, less dissection, and, theoretically, faster healing of the CMC joint capsule. Minimal capsular violation with the arthroscopic technique supports the concept of less painful and more rapid recovery for patients. Short- and medium-term results are similar to those seen with open techniques.8187

Figure 16
Clinical photograph of thumb CMC joint arthroscopy. (Courtesy of Jeffrey Yao, MD, Palo Alto, CA.)
Figure 17
Radiograph of the CMC joint following arthroscopic hemitrapeziectomy. (Courtesy of Jeffrey Yao, MD, Palo Alto, CA.)

With rising medical costs and the emphasis on cost containment, improving short-term quality of life parameters, and expediting a patient’s return to work, secondary outcomes measures have an undoubtable influence on the selection of surgical options. The literature supports a spectrum of surgical procedures for treating thumb CMC arthritis. Because the well-accepted reconstructive procedures are linked to longer recovery periods and higher costs and complication rates, less extensive and invasive procedures may be preferred by many surgeons. Currently, however, the literature is not sufficiently robust to compare the spectrum of anatomic reconstructive procedures focused on ligament reconstruction with minimally invasive procedures that emphasize arthroscopy and excisional arthroplasty.

The ideal surgical procedure expands beyond trapeziectomy. Trapeziectomy, the root treatment in current CMC arthritis surgery, predictably achieves pain relief. The ideal surgical procedure will achieve versatile mobility, with strength and precise docking in the myriad of positions required for fine and gross motor function. This versatility is not currently achieved with any single popular surgical technique. Surgical options that combine a basic science approach and clinical relevance that address strength, mobility, stability, and proprioception, either through emulation (soft-tissue reconstruction), or re-creation (implant arthroplasty), will constitute the ideal surgical procedure.

Summary

The CMC joint, with its complex demands of both stability and mobility, is prone to arthritis for a variety of reasons: evolutionary pressure for a less constrained joint, intricate kinematics and compressive loads with functional activity, and hormonal influences related to sex and age. The joint is primarily stabilized by stout dorsal ligaments that are richly innervated with mechanoreceptors and nerve endings. The volar aspect of the joint has a thin capsular tissue, intimately connected to the thenar muscles, which provide volar muscular stability of the joint. The dynamic proprioceptive function of the joint is the subject of continuing investigations.

Surgical procedures that provide CMC joint pain relief are universal, but the precise combination of treatments to restore stability and strength is yet to be determined. Reconstructive ligament stabilizing procedures are currently being challenged by simpler, less invasive techniques. Improved characterization of the CMC joint as it relates to anatomy, function, and genetic influences will expand and clarify future treatments for CMC arthritis.

Figure 13
At the completion of the LRTI procedure, the correct tension is set on the FCR tendon that is sutured to the adjacent periosteum. (Courtesy of Steven Z. Glickel, MD, New York, NY.)

Acknowledgments

Dr. Ladd or an immediate family member serves as a board member, owner, officer, or committee member of the Ruth Jackson Orthopaedic Society; has received royalties from Extremity Medical and Orthohelix; has received research or institutional support from the National Institutes of Health (NIAMS and NICHD) and OREF; and owns stock or stock options in Articulinx, Extremity Medical, Illuminoss Medical, and OsteoSpring Medical. Dr. Weiss or an immediate family member serves as a board member, owner, officer, or committee member of the American Society for Surgery of the Hand; has received royalties from DePuy, Extremity Medical, and Medartis; serves as a paid consultant to or is an employee of Illuminoss Medical; and owns stock or stock options in Articulinx, Illuminoss Medical, and OsteoSpring Medical. Dr. Crisco or an immediate family member serves as a board member, owner, officer, or committee member of the American Society of Biomechanics; has received royalties from Extremity Medical; serves as a paid consultant to or is an employee of Extremity Medical and Illuminoss Medical; and has received research or institutional support from Extremity Medical. Dr. Hagert or an immediate family member serves as an unpaid consultant to Osteomed. Dr. Wolf or an immediate family member serves as a board member, owner, officer, or committee member of the American Association for Hand Surgery, the American Society for Surgery of the Hand, and the American Academy of Orthopaedic Surgeons. Dr. Glickel or an immediate family member serves as a board member, owner, officer, or committee member of the American Society for Surgery of the Hand, the American Orthopaedic Association, and the Dupuytren Foundation. Dr. Yao or an immediate family member serves as a board member, owner, officer, or committee member of the American Society for Surgery of the Hand and the Arthroscopy Association of North America; has received royalties from Arthrex; is a member of a speakers’ bureau or has made paid presentations on behalf of Arthrex; and serves as a paid consultant to or is an employee of Smith & Nephew, Arthrex, and Axogen.

The section titled “Thumb CMC Kinematics and Osteoarthritis Progression” was funded by the American Foundation for Surgery of the Hand and National Institutes of Health AR059185. The section titled “CMC Ligament Anatomy: New Evidence to Change Old Ideas” was funded by the Williams Charitable Trust and the Orthopaedic Research Education Foundation/Ruth Jackson Orthopaedic Society/DePuy Career Development Award.

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Video Reference

14.1. Ladd AL. Animation of Grasp, Jar Opening, and Pinch. Palo Alto, CA: 2012. Video.