A biomechanical assessment of ligaments preventing dorsoradial subluxation of the trapeziometacarpal joint

Ultrastructure and innervation of thumb carpometacarpal ligaments in surgical patients with osteoarthritis

BACKGROUND

The complex configuration of the thumb carpometacarpal (CMC-1) joint relies on musculotendinous and ligamentous support for precise circumduction. Ligament innervation contributes to joint stability and proprioception. Evidence suggests abnormal ligament innervation is associated with osteoarthritis (OA) in large joints; however, little is known about CMC-1 ligament innervation characteristics in patients with OA. We studied the dorsal radial ligament (DRL) and the anterior oblique ligament (AOL), ligaments with a reported divergent presence of mechanoreceptors in nonosteoarthritic joints.

QUESTIONS/PURPOSES

This study's purposes were (1) to examine the ultrastructural architecture of CMC-1 ligaments in surgical patients with OA; (2) to describe innervation, specifically looking at mechanoreceptors, of these ligaments using immunohistochemical techniques and compare the AOL and DRL in terms of innervation; and (3) to determine whether there is a correlation between age and mechanoreceptor density.

METHODS

The AOL and DRL were harvested from 11 patients with OA during trapeziectomy (10 women, one man; mean age, 67 years). The 22 ligaments were sectioned in paraffin and analyzed using immunoflourescent triple staining microscopy.

RESULTS

In contrast to the organized collagen bundles of the DRL, the AOL appeared to be composed of disorganized connective tissue with few collagen fibers and little innervation. Mechanoreceptors were identified in CMC-1 ligaments of all patients with OA. The DRL was significantly more innervated than the AOL. There was no significant correlation between innervation of the DRL and AOL and patient age.

CONCLUSIONS

The dense collagen structure and rich innervation of the DRL in patients with OA suggest that the DRL has an important proprioceptive and stabilizing role.

CLINICAL RELEVANCE

Ligament innervation may correlate with proprioceptive and neuromuscular changes in OA pathophysiology and consequently support further investigation of innervation in disease prevention and treatment strategies.

Carpometacarpal dislocation of the thumb associated with fracture of the trapezium

Carpometacarpal dislocation (CMC) of the thumb associated with fracture of trapezium is an extremely rare injury, with only 12 cases that sustained similar injuries reported in the literature. In this article, another patient with this rare injury was reported, and all previously published cases were extensively reviewed. The presented case and all previously published cases had a longitudinally oriented trapezium fracture, which is naturally unstable and almost always associated with dislocation of the CMC joint. In contrast to previous descriptions, we believe that CMC joint dislocation and trapezium fracture are not two distinct pathologies that occur simultaneously by chance but share cause and consequence.

The carpometacarpal joint of the thumb: MR appearance in asymptomatic volunteers

PURPOSE

To prospectively characterize the MR appearance of the carpometacarpal (CMC) joint of the thumb in asymptomatic volunteers.

MATERIALS AND METHODS

Thirty-four asymptomatic volunteers (17 women, 17 men, mean age, 33.9 ± 9.2 years) underwent MR imaging of the thumb after approval by the local ethical committee. Two musculoskeletal radiologists independently classified visibility and signal intensity (SI) characteristics of the anterior oblique (AOL/beak ligament), the posterior oblique (POL), the intermetacarpal (IML), and the dorsoradial ligaments (DRL) on a three-point Likert scale. The thickness of all ligaments, cartilage integrity, and presence of joint fluid were assessed. The alignment of the first metacarpal base with the trapezium was quantified on sagittal and coronal planes.

RESULTS

The ligaments of the CMC joint were constantly visible in all volunteers for the POL and IML, and in all but one for the AOL and DRL. On intermediate-weighted fat-saturated images the POL (65 %/74 % reader 1/reader 2) and DRL (58 %/64 %) were commonly of increased SI, while the IML had a striated appearance in 91 %/76 % of subjects. The AOL showed a variable SI (36 %/42 % low, 27 %/27 % increased, 36 %/30 % striated). The IML was the thickest ligament with a mean of 2.9 mm/3.1 mm and the DRL the thinnest (1.2 mm/1.4 mm). There was a mean dorsal subluxation of 1.8 mm/2.0 mm and radial subluxation of 2.8 mm/3.4 mm of the metacarpal base. The AOL was significantly thicker in men (1.7 mm) than in women (1.2 mm; p = 0.02). Radial subluxation was significantly larger in men (3.4 mm) than in women (2.2 mm; p = 0.02). No subluxation in palmar or ulnar direction was seen.

CONCLUSIONS

Radial and dorsal subluxation of the CMC joint can be a normal finding in a resting position at MR imaging. The CMC ligaments showed a considerable variability of signal intensity with a typically striated IML; thickness of the AOL is typically less than 2.2 mm, of the POL typically less than 2.9 mm.

Thumb carpometacarpal ligaments inside and out: a comparative study of arthroscopic and gross anatomy from the robert a. Chase hand and upper limb center at stanford university

Purpose We propose to identify and correlate arthroscopic internal ligaments with external ligaments, providing an accurate roadmap for arthroscopic ligament and joint anatomy. Ligamentous laxity is considered an important risk factor in developing the common basilar arthritis of the thumb. Controversy exists as to the precise ligamentous anatomy of the thumb carpometacarpal (CMC) joint (CMC-I); description of the internal arthroscopic anatomy is limited. Methods We performed CMC-I joint arthroscopy using the 1-Ulnar (1U) and thenar portals in five cadavers, seeking to identify the following seven ligaments arthroscopically: the superficial anterior oblique ligament (sAOL), deep anterior oblique ligament (dAOL), ulnar collateral ligament (UCL), dorsal trapeziometacarpal ligament (DTM-1), posterior oblique ligament (POL), dorsal central ligament (DCL), and dorsal radial ligament (DRL). After grading articular changes of the trapezium, we passed Kirschner wires (K-wires) (0.028) outside-in to mark the arthroscopic insertion of each ligament on the trapezium. Gross dissection was performed to confirm the wire placement; the anatomic identity and position of joint stabilizing ligaments, and the location of frequently used portals. Results The volar ligaments-the sAOL, dAOL, and UCL-were highly variable in their arthroscopic appearance and precise location. The sAOL is a thin veil of membranous tissue that variably drapes across the anterior joint capsule. The reported dAOL and UCL, in our study, correlated to a thickened portion of this veil around the volar beak and was not consistently identified with gross dissection. In contrast, the arthroscopic appearance and location of the dorsal ligaments-DTM-I, POL, DCL, and DRL-were consistent in all specimens. Conclusion Our study further defines and correlates the arthroscopic and external ligamentous anatomy of the CMC-I joint.

Dorsoradial capsulodesis for trapeziometacarpal joint instability

We describe an alternative method for treating chronic trapeziometacarpal (TM) joint instability after acute injury or chronic repetitive use of the thumb by performing a dorsoradial capsulodesis procedure. The procedure is done by imbricating the redundant TM joint dorsoradial ligament and capsule after reducing the joint by pronating the thumb. The dorsoradial capsulodesis is a reasonable reconstructive option for chronic TM joint instability and subluxation.

Macroscopic and microscopic analysis of the thumb carpometacarpal ligaments: a cadaveric study of ligament anatomy and histology

BACKGROUND

Stability and mobility represent the paradoxical demands of the human thumb carpometacarpal joint, yet the structural origin of each functional demand is poorly defined. As many as sixteen and as few as four ligaments have been described as primary stabilizers, but controversy exists as to which ligaments are most important. We hypothesized that a comparative macroscopic and microscopic analysis of the ligaments of the thumb carpometacarpal joint would further define their role in joint stability.

METHODS

Thirty cadaveric hands (ten fresh-frozen and twenty embalmed) from nineteen cadavers (eight female and eleven male; average age at the time of death, seventy-six years) were dissected, and the supporting ligaments of the thumb carpometacarpal joint were identified. Ligament width, length, and thickness were recorded for morphometric analysis and were compared with use of the Student t test. The dorsal and volar ligaments were excised from the fresh-frozen specimens and were stained with use of a triple-staining immunofluorescent technique and underwent semiquantitative analysis of sensory innervation; half of these specimens were additionally analyzed for histomorphometric data. Mixed-effects linear regression was used to estimate differences between ligaments.

RESULTS

Seven principal ligaments of the thumb carpometacarpal joint were identified: three dorsal deltoid-shaped ligaments (dorsal radial, dorsal central, posterior oblique), two volar ligaments (anterior oblique and ulnar collateral), and two ulnar ligaments (dorsal trapeziometacarpal and intermetacarpal). The dorsal ligaments were significantly thicker (p < 0.001) than the volar ligaments, with a significantly greater cellularity and greater sensory innervation compared with the anterior oblique ligament (p < 0.001). The anterior oblique ligament was consistently a thin structure with a histologic appearance of capsular tissue with low cellularity.

CONCLUSIONS

The dorsal deltoid ligament complex is uniformly stout and robust; this ligament complex is the thickest morphometrically, has the highest cellularity histologically, and shows the greatest degree of sensory nerve endings. The hypocellular anterior oblique ligament is thin, is variable in its location, and is more structurally consistent with a capsular structure than a proper ligament.

Modified Eaton-Littler's Reconstruction for Traumatic Dislocation of the Carpometacarpal Joint of the Thumb-A Case Report and Review of Literature

Isolated traumatic dislocation of the carpometacarpal joint of the thumb is an uncommon injury. Left untreated, resulting mechanical instability of this joint interferes with normal function of the hand and can lead to articular degeneration of the joint. Most are amenable to closed reduction with or without supplementary pinning. We present a case of a 21 year old female patient with continual instability of the carpometacarpal joint of her right thumb, following closed reduction and pinning. Surgical stabilization was achieved by anterior oblique ligament reconstruction using a Modified Eaton- Littler's technique. At 1 year follow-up evaluation the patient was pain free with no clinico-radiological evidence of instability.

Innervation patterns of thumb trapeziometacarpal joint ligaments

PURPOSE

The human thumb trapeziometacarpal (TM) joint is a unique articulation that allows stability during pinch and grip and great degrees of mobility. Because the saddle-shaped articulating surfaces of the TM joint are inherently unstable, joint congruity depends on the action of restraining ligaments and periarticular muscles. From other joints, it is known that proprioceptive and neuromuscular joint stability depend on afferent information from nerve endings within ligaments. We hypothesize that the TM joint ligaments may similarly be innervated, indicating a possible proprioceptive function of the joint.

METHODS

We harvested 5 TM joint ligaments in entirety from 10 fresh-frozen cadaver hands with no or only minor signs of osteoarthritis and suture-marked them for proximal-distal orientation. The ligaments harvested were the dorsal radial, dorsal central, posterior oblique, ulnar collateral, and anterior oblique ligaments. After paraffin-sectioning, we stained the ligaments using a triple-antibody immunofluorescent technique and analyzed them using immunofluorescence microscopy.

RESULTS

Using the triple-stain technique, mechanoreceptors could be classified as Pacinian corpuscles, Ruffini endings, or Golgi-like endings. The 3 dorsal ligaments had significantly more nerve endings than the 2 volar ligaments. Most of the nerve endings were close to the bony attachments and significantly closer (P = .010) to the metacarpal insertion of each ligament. The anterior oblique ligament had little to no innervation in any of the specimens analyzed.

DISCUSSION

The TM joint ligaments had an abundance of nerve endings in the dorsal ligaments but little to no innervation in the anterior oblique ligament. The Ruffini ending was the predominant mechanoreceptor type, with a greater density in the mobile metacarpal portion of each ligament.

CLINICAL RELEVANCE

Presence of mechanoreceptors in the dorsal TM joint ligaments infers a proprioceptive function of these ligaments in addition to their biomechanical importance in TM joint stability.

Arthroscopic hemiresection for stage II-III trapeziometacarpal osteoarthritis

Trapeziometacarpal osteoarthritis is a common problem, due to the anatomy of the first ray and the forces applied to the trapeziometacarpal joint throughout activities of daily living. Numerous treatment options exist, and continue to be developed, for this problem. The current goal is to eliminate pain and restore function and strength in a timely manner. New advances allow for earlier return to function with minimally invasive techniques. Arthroscopic hemitrapeziectomy combined with interposition arthroplasty and/or suspensionplasty is a treatment option for Stage II and III trapeziometacarpal arthritis that uses a minimally invasive technique and allows for earlier return of function.

In vivo length and changes of ligaments stabilizing the thumb carpometacarpal joint

PURPOSE

To investigate the lengths and changes of selected ligaments stabilizing the thumb carpometacarpal (CMC) joint during thumb motion in vivo.

METHODS

We obtained serial computed tomography scans of the thumb CMC joints of 6 healthy volunteers during thumb flexion, abduction, and opposition. We reconstructed the 3-dimensional structures of the bones of the thumb CMC joint using customized software and modeled the paths of fibers of 5 principal ligaments--deep anterior oblique (beak), dorsoradial, posterior oblique, intermetacarpal, and dorsal intermetacarpal--at each of the CMC joint positions studied. We estimated the virtual lengths of these ligaments in neutral position, flexion, abduction, and opposition of the CMC joint by measuring the distances between the origin and the insertion of individual ligaments, and statistically analyzed the length changes.

RESULTS

The estimated length of the CMC joint ligaments underwent significant changes during thumb motion in vivo. Thumb flexion led to the greatest changes in ligament lengths. During flexion, all the ligaments lengthened significantly (p < .05 or p < .01), except for the beak ligament, which shortened significantly (p < .001). The lengths of the ligaments changed similarly during thumb abduction and opposition, except for the dorsoradial ligament. In both motions, the posterior oblique and dorsal intermetacarpal ligaments lengthened and the beak ligament shortened significantly (p < .05 or p < .01). During the 3 thumb motions, the beak ligament underwent marked shortening, while the other measured ligaments lengthened to varied extent.

CONCLUSIONS

The estimated lengths of principal ligaments stabilizing the CMC joint change substantially during thumb motions in vivo. Thumb flexion causes the greatest changes of the ligament lengths; abduction and opposition result in similar changes in the ligament lengths. The beak ligaments shorten while the other ligaments lengthen. This in vivo study suggests that thumb motions expose the CMC joint ligaments to different tensions at these thumb positions, and that the ligaments are under lower tension during thumb opposition and abduction than during flexion.

Current concepts of the anatomy of the thumb trapeziometacarpal joint

This review article describes the anatomy of the thumb trapeziometacarpal joint. In the final phase of opposition screw home torque rotation of the volar beak of the thumb metacarpal in the pivot area of the trapezium recess and tension on the dorsal ligament complex create stability for power pinch and power grip. The resulting compressive shear forces can lead over time to trapeziometacarpal joint osteoarthritis.

Unusual pattern of dislocation of the trapeziometacarpal joint with avulsion fracture of the trapezium: case report

Dislocation of the trapeziometacarpal joint is a rare injury. We report an unusual pattern of dorsal dislocation of the trapeziometacarpal joint with an avulsion fracture of the dorsoradial tubercle of the trapezium. Simultaneous ligament rupture with an avulsion fracture of the thumb metacarpophalangeal joint was associated. The trapeziometacarpal joint was reduced and disrupted ligaments with avulsed fragments of both joints were surgically repaired.

The carpometacarpal stress view radiograph in the evaluation of trapeziometacarpal joint laxity

PURPOSE

Hypermobility at the thumb carpometacarpal (CMC) joint has been proposed as an explanation for abnormal loading and subsequent development of osteoarthritis. Radiographic evaluation of this joint is difficult owing to the obliquity of the articulation. We modified a previously described technique to obtain a bilateral stress radiograph of the thumbs to measure CMC joint laxity. The purpose of this study was to present the details of this modified technique and evaluate its reproducibility in a group of volunteer subjects. We hypothesized that this technique would be reliable and reproducible.

METHODS

A posteroanterior radiograph was obtained after asking volunteer subjects to press their thumbs together using a foam hand support. Three measurements were performed: radial subluxation of the first metacarpal base, first metacarpal articular width, and the distance between the ulnar articular facet of the trapezium and the ulnar metacarpal edge (uncovered edge). Using digital calibration on a picture archiving and communication system radiology server, a radiologist, radiology resident, orthopedic surgeon, and orthopedic resident performed measurements at 2 time points. To evaluate consistency among the raters, intraclass correlation coefficients were calculated. Test-retest bivariate analyses were performed to assess intra-rater reliability.

RESULTS

A total of 69 volunteers (39 women and 30 men) were imaged. Women showed significantly greater radial subluxation compared to men (p < .01). Inter-rater reliability coefficients for radial subluxation and articular width initially and at 2 weeks showed high agreement, as did test-retest reliability coefficients. For the uncovered edge measurement, inter-rater reliability coefficients were low, with wide variation in reliability.

CONCLUSIONS

The modified thumb CMC stress view radiograph evaluates laxity and joint abnormalities of the trapeziometacarpal articulation. The details of the radiographic technique are straightforward, and the inter- and intra-observer reliability of radial subluxation and first metacarpal width are high. The ratio of the 2 measurements provides an accurate measure of the radiographic subluxation of the first metacarpal from the trapezium. This measurement is most specific to radial subluxation under simulated active loading, in the plane of the hand. The medial uncovered edge of trapezium measurement does not have high inter-observer reliability and varies widely, and it should not be included in laxity measurements.

Anatomy and pathomechanics of the thumb

The prehensile thumb provides the human mind an outlet for coordinated activity through its fine motions of prehension, opposition, and circumduction. A comprehensive understanding of the anatomy and biomechanics of the thumb provides a foundation on which functional disorders may be recognized and effectively treated.

Thumb carpal metacarpal arthritis

The thumb carpometacarpal (CMC) joint is the most common site of surgical reconstruction for osteoarthritis in the upper extremity. In patients older than age 75 years, thumb CMC osteoarthritis has a radiographic prevalence of 25% in men and 40% in women. The thumb CMC joint obtains its stability primarily through ligamentous support. A diagnosis of thumb CMC arthritis is based on symptoms of localized pain, tenderness and instability on physical examination, and radiographic evaluation. A reproducible radiographic classification for disease severity is based on the four-stage system described by Eaton. Nonsurgical treatment options include hand therapy, splinting, and injection. Surgical treatment is tailored to the extent of arthritic involvement and may include ligament reconstruction, metacarpal extension osteotomy, arthroscopic partial trapeziectomy, implant arthroplasty, and trapeziectomy with or without ligament reconstruction and tendon interposition.

Traumatic thumb carpometacarpal joint dislocations

Isolated traumatic dislocation of the thumb carpometacarpal joint, also called the trapeziometacarpal joint, is a rare injury. Controversy still exists concerning which ligaments are the true key stabilizers for the joint and therefore need to be damaged to result in dislocation, and optimal treatment strategies for thumb carpometacarpal joint dislocations are the subject of continuing debate. We give a review of the literature concerning traumatic dislocations of the carpometacarpal joint of the thumb and propose a treatment algorithm.

Arthroscopy of the trapeziometacarpal and metacarpophalangeal joints

Indications for small joint arthroscopy in the hand remain poorly understood. This is due to a paucity of articles discussing these techniques in the literature, as well as inadequate hands-on training in the pearls and pitfalls regarding this application within the routine "scope" of hand surgery. Despite the fact that small joint arthroscopes have been available for more than a decade, hand surgeons have been slow to adopt this technique for the treatment of both traumatic and degenerative conditions involving the thumb and the digital metacarpophalangeal joints. An arthroscopic classification for basal joint osteoarthritis provides additional clinical information and can direct further treatment depending on the stage of disease. This article will also review the brief history of trapeziometacarpal arthroscopy and provide insight as to how this technique can be incorporated into a treatment algorithm in managing this common affliction. Metacarpophalangeal joint arthroscopy is even less commonly utilized, while traumatic and overuse injuries are frequently seen in the thumb and constitute ideal indications in certain scenarios. Painful conditions affecting the metacarpophalangeal joints of the fingers are less commonly seen, yet the small joint arthroscope presents a much clearer picture of the pathology compared with other imaging techniques or even open, potentially deleterious surgery. The application of this technology to the smaller joints will soon make the treating surgeon realize that a myriad of pathologies are readily visible and can augment treatment, as well as diagnosis. Similar to the wrist, small joint arthroscopy may one day supplant imaging techniques such as magnetic resonance imaging or computed tomography for establishing an accurate diagnosis.

Effects of the deep anterior oblique and dorsoradial ligaments on trapeziometacarpal joint stability

PURPOSE

Osteoarthritis of the trapeziometacarpal (TMC) joint of the thumb affects as many as 25% of postmenopausal women and 5% of middle-aged men. This study investigated the relative contribution of the dorsoradial ligament (DRL) and the deep anterior oblique ligament (dAOL) to the stability of the TMC joint. This knowledge will improve our understanding of the pathomechanics of osteoarthritis at the base of the thumb and may help to design novel reconstructive surgical procedures.

METHODS

Seventeen intact cadaver hands were dissected to reveal the DRL and dAOL. Either the DRL or dAOL was transected randomly, physiologic muscle loads were applied to simulate lateral key pinch or thumb opposition, or a 3-dimensional magnetic tracking system was used to record the position of the thumb metacarpal relative to the trapezium. The differences in the 3-dimensional positions between the control and transected states were determined.

RESULTS

In lateral pinch, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.3 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.6 mm. Statistically significant 2-dimensional findings in lateral pinch after transecting the DRL or dAOL included an increased palmar subluxation of 0.3 mm and 0.2 mm, an increased radial (1.0 mm) and ulnar (0.3 mm) translation, and an increased pronation of 4.1 degrees and 2.4 degrees, respectively. In thumb opposition, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.0 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.5 mm.

CONCLUSIONS

In most degrees of freedom of metacarpal movement relative to the trapezium, the DRL is relatively more important than the dAOL in providing stability to the TMC joint.

Arthroscopie des articulations trapézométacarpienne et métacarpophalangienne : installation, voie d'abord et exploration

Indications for small joint arthroscopy in the hand remain poorly understood. This is due to a paucity of papers discussing this technique in the literature, as well as inadequate hands on training in the pearls and pitfalls regarding this application within the commonly used "scope" of arthroscopy. Despite the fact that small joint arthroscopes have been available for over a decade, hand surgeons have been slow to adopt this technique within their treatment armamentarium for the treatment of both traumatic and degenerative conditions involving the thumb and the digital metacarpophalangeal joints. A proposed arthroscopic classification for basal joint osteoarthritis provides additional clinical information and can direct further treatment depending on the stage of disease. This chapter will also review the brief history of trapeziometacarpal arthroscopy and provide insight as to how this technique can be incorporated into a treatment algorithm in managing this common affliction. Metacarpophalangeal joint arthroscopy is even less commonly used, while traumatic and overuse injuries are frequently seen in the thumb, and present an ideal indication in certain scenarios. Painful conditions affecting the metacarpophalangeal joints of the fingers are less commonly seen, yet the small joint arthroscope presents a much clearer picture of the present pathology compared to other imaging techniques or even open, and potentially deleterious, surgery. The application of this technology to the smaller joints will soon make the treating surgeon realize that a myriad of pathologies are readily visible and can augment treatment, as well as diagnosis. Similar to the wrist, small joint arthroscopy may one day supplant imaging techniques such as MRI or CT in establishing an accurate diagnosis.

Three-dimensional analysis of the ligamentous attachments of the first carpometacarpal joint

PURPOSE

To show the ligamentous locations and attachments of the first carpometacarpal (CMC) joint on a 3-dimensional (3-D) surface model.

METHODS

Ten fresh-frozen cadaver wrists were used to dissect and identify the first CMC ligaments. Their ligamentous attachments and whole bone surfaces were digitized 3-dimensionally and their areas were calculated. The attachments of each ligament were represented in a model combining 3-D computed tomography surfaces overlaid by a digitized 3-D surface and also were shown visually by a specific color on 3-D bone images. The superimposed outlines of the ligamentous attachments on both the radial and ulnar base of the first metacarpal (MC) also are described.

RESULTS

Seven ligaments of the first CMC joint were identified: the dorsoradial ligament, the posterior oblique ligament, the superficial anterior oblique ligament, the deep anterior oblique ligament, the ulnar collateral ligament, the dorsal first MC ulnar base-second MC radial base intermetacarpal ligament, and the volar first MC ulnar base-second MC radial base intermetacarpal ligament. The detailed locations and areas of the ligamentous attachments of the first CMC joint were determined. The average locations of the centroid of the ligamentous attachments of the ulnar collateral and the dorsoradial ligaments were located ulnovolar and dorsoradial on the first MC base, respectively.

CONCLUSIONS

The anatomic 3-D attachment sites of the first CMC ligaments were shown qualitatively and their areas were quantified. The results of this study improve the knowledge and understanding of the normal anatomy and its impact on the mechanics of the first CMC joint. This should help in making an accurate assessment of radiographic images and treating injuries and degenerative changes in the first CMC joint by ligament reconstruction, repair, and arthroscopy.

Trapeziometacarpal arthroscopy: a classification and treatment algorithm

Arthroscopic assessment of the CMC joint allows direct visualization of all components of the joint, including synovium, articular surfaces, ligaments, and the joint capsule. It also allows for the extent of joint pathology to be evaluated and staged with intraoperative management decisions made based on this information. The author recommends this arthroscopic staging to ensure better judgment of this condition in order to provide the most adequate treatment option to patients who have this disabling condition. Future studies assessing the clinical long term results using arthroscopy will likely ensure its place in the treatment armamentarium for trapeziometacarpal osteoarthritis.

Thumb by metacarpal extension osteotomy: rationale and efficacy for Eaton Stage I disease

This article describes the rationale and results of a "biomechanical" strategy to restore trapeziometacarpal (TM) stability when symptomatic Eaton Stage I disease exists. Though the author has performed TM arthroscopy, synovectomy, and capsular shrinkage for such cases in 10 patients, the author has been dissatisfied with the outcomes, particularly pain relief. The author currently relies exclusively on extension osteotomy as treatment for this subset of patients. Thumb metacarpal extension osteotomy remains an effective treatment alternative for the hypermobile TM joint consistent with Eaton Stage I disease. This procedure alters forces, shifts load away from the volar compartment, and further engages the dorsoradial ligament. Clinical outcomes are favorable, and no bridges are burned should arthritic changes develop in the future.

Trapeziometacarpal joint instability after Bennett's fracture-dislocation

BACKGROUND

Investigation of trapeziometacarpal joint instability was undertaken following Bennett's fracture-dislocation.

METHODS

We treated six patients who were experiencing trapeziometacarpal joint instability following Bennett's fracture-dislocation. The average age of the patients at the initial visit was 22.2 years. There were four men and two women. All six patients complained of trapeziometacarpal joint pain and instability preoperatively. Fluoroscopy confirmed that the beak fragment moved with the shaft fragment. The length of time from injury to surgery ranged from 1 to 29 months (average 10.7 months). Ligament reconstruction based on Eaton's method was performed on five patients, and in one patient the fracture site was osteotomized and reduced and the dorsoradial ligament repaired.

RESULTS

Over an average follow-up observation period of 20 months, none of the patients complained of severe joint pain or instability.

CONCLUSIONS

When treating Bennett's fracture-dislocation, it is necessary to pay careful attention not only to accurate anatomic reduction of the joint surface but also to joint instability.

Anatomie et physiologie de l’articulation trapézométacarpienne humaine

Biomechanics of the trapeziometacarpal joint (TMJ) are controversial, because of differences between its normal anatomical description and theories of its pathophysiology. The aim of this article is to explain the mechanisms underlying trapeziometacarpal osteoarthritis by means of the anatomy and physiology of the TM joint. Having described the main ligaments and their roles in the physiology of the joint, it is then difficult to understand why trapezectomy usually improves patients with TMO, when the ligaments are destroyed or only partially repaired by tendinoplasty. Different explanations of TMO are detailed but it seems, according to the literature, that TMO can be explained more by genetic considerations than anatomic dysfunction. The theory of Zancolli is not verified by facts, and other concepts such as ligament theory, and dysplasia of the caudal aspect of the trapezial bone are not sufficient to understand this disease. The same discussion is engaged with regard to explaining the automatic rotation of the thumb in the TM joint. The cantilever bending principle is described as proposed by Bettinger and al.

Trapeziometacarpal joint instability affects the moment arms of thumb motor tendons

This study measured the changes in moment arm length of thumb motor tendons after simulated ligamentous instability and subsequent reconstruction of the trapeziometacarpal joint. Excursions of thumb motor tendons were measured simultaneously with the trapeziometacarpal joint angulation during flexion to extension and abduction to adduction motion. Tendon moment arms were calculated based on joint and tendon displacement techniques in the intact joint, after sequential sectionings of the capsuloligamentous restraints, and after the reconstruction procedure of Eaton and Littler. The results showed that moment arms of the abductor pollicis longus and extensor pollicis brevis tendons increased significantly as compared with those for normal joints during flexion to extension motion after sectioning the palmar capsuloligamentous components. After the ulnopalmar structures were cut, the moment arm of the extensor pollicis longus tendon had a statistically significant increase during abduction to adduction motion, and those of the extensor and flexor pollicis longus tendons decreased significantly during flexion to extension motion. Changed moment arms were restored to a normal level after the ligamentous reconstruction. These results indicate that ligamentous disruptions alter the mechanical balance of thumb motor tendons, which may contribute to joint deformities observed in trapeziometacarpal joint arthritis. Restoring joint stability is important to correct mechanical imbalance of the tendons.

An anatomic study of the stabilizing ligaments of the trapezium and trapeziometacarpal joint

We provide a detailed and comprehensive anatomic description of the ligaments stabilizing the trapezium and trapeziometacarpal joint. Sixteen ligaments were identified. Fourteen ligaments inserted onto the trapezium and 2 others attached independently to the thumb metacarpal. The ligaments inserting onto the trapezium were the superficial anterior oblique, deep anterior oblique (beak ligament), dorsoradial, posterior oblique, ulnar collateral, dorsal trapezio-trapezoid, volar trapezio-trapezoid, dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, trapezio-third metacarpal, volar scaphotrapezial, radial scaphotrapezial, transverse carpal, and trapezio-capitate ligaments. The remaining 2 ligaments attach onto the thumb metacarpal and are the proper intermetacarpal and the dorsal intermetacarpal. The dorsoradial and deep anterior oblique ligaments play a substantial role in stabilizing the trapeziometacarpal joint, and the deep anterior oblique ligament may function as a pivot for the first metacarpal during palmar abduction to allow rotation (pronation). The dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, and trapezio-third metacarpal ligaments function as tension bands and are required to prevent instability from cantilever bending forces on the trapezium.