Importance of the posteromedial trapezometacarpal ligamentous complex

Pronation and supination of the human thumb has both a practical and a symbolic importance. In supination the thumb caresses but in pronation it grasps. The articular surfaces of the trapezium and first metacarpal are not congruent enough in themselves to assure pronation and supination, but their reciprocal saddle shape causes them to have two distinct orthogonal "fundamental" axes of rotation, and hence two "privileged" planes of rotation. The one corresponds to the movements of the lateral pinch grip and the other to opposition and counter-opposition of the thumb. The important ligaments are situated on both sides of the trapeziometacarpal joint. The posteromedial ligamentous complex is composed of the posterior oblique ligament, the anterior oblique ligament, the intermetacarpal ligament, and a fourth or more anteromedial ligament which we have called the retinaculometacarpal ligament by reason of its proximal insertion. It plays an essential role in suspending and anchoring the base of the first metacarpal. By its action it induces two types of motion: 1) a discrete translation of the metacarpal along the articular concavity of the trapezium in lateral pinch grip; 2) a more important motion characterised by a prosupination of 90 degrees during its rotation in the plane of opposition. The anterolateral ligament's action is restricted to strengthening the action of the posteromedial ligaments in the extreme positions of closing of lateral pinch and thumb opposition. In cases of trapeziometacarpal subluxation it prevents a complete dislocation. These various observations have significant clinical and therapeutic implications.     

Simulated extension osteotomy of the thumb metacarpal reduces carpometacarpal joint laxity in lateral pinch

PURPOSE: To assess the effect of an extension osteotomy of the thumb metacarpal on thumb carpometacarpal (CMC) joint laxity with respect to the lateral pinch position. METHODS: Seven fresh-frozen specimens were dissected. The metacarpal, trapezium, and trapezoid were removed en bloc and rigidly fixed proximally and distally. The laxity of each specimen was measured by cyclically loading the CMC joint in a custom-built laxity testing device designed to allow relative movement of the trapezium and first metacarpal in 4 directions. The position of the CMC joint in lateral pinch was used as the baseline joint position. An extension osteotomy then was simulated by flexing the metacarpal base 30 degrees, thus placing the joint in the relationship it would assume if an extension osteotomy was performed and the specimen was positioned in lateral pinch. Laxity measurements then were repeated. RESULTS: The simulated extension osteotomy reduced laxity in all directions tested: dorsal-volar (40% reduction), radial-ulnar (23% reduction), distraction (15% reduction), and pronation-supination (29% reduction). CONCLUSIONS: The beneficial clinical effects of a thumb metacarpal extension osteotomy may be partially due to reduced joint laxity in the position of lateral pinch.     

An in vitro analysis of ligament reconstruction or extension osteotomy on trapeziometacarpal joint stability and contact area

PURPOSE: Painful instability of the minimally osteoarthritic thumb carpometacarpal (CMC) joint can be treated successfully by either ligament reconstruction or metacarpal extension osteotomy. The purpose of this study was to measure the laxity of cadaveric thumb CMC joints and to determine the influence of ligament reconstruction and metacarpal osteotomy on joint laxity and contact area. METHODS: The baseline laxity of CMC joints from 25 fresh-frozen human cadaveric specimens (average age, 42 y; range, 18-55 y) was measured in the position of lateral pinch on a custom-designed CMC joint laxity tester. Joint laxity was measured again after 2 surgical simulations consisting of either a metacarpal extension osteotomy (at 10 degrees and 15 degrees) or a simulated Eaton-Littler ligament reconstruction (including total, volar, and dorsal ligament reconstructions relative to the plane of the thumbnail). Contact area between the thumb metacarpal and trapezium during testing was determined using stereophotogrammetry. RESULTS: The 15 degrees extension osteotomy significantly reduced CMC joint laxity in the radial-ulnar, dorsal-volar, pronation-supination, and distraction directions in the position of lateral pinch. The 10 degrees osteotomy reduced laxity only in the dorsal-volar direction. The total ligament reconstruction significantly reduced joint laxity in the radial-ulnar, dorsal-volar, and pronation-supination directions. The dorsal ligament reconstruction reduced laxity in the dorsal-volar direction only; the volar ligament reconstruction reduced laxity in both dorsovolar and radioulnar directions. The 10 degrees and 15 degrees osteotomies produced a dorsal shift of the weighted centroid of contact on the metacarpal and trapezium, whereas the ligament reconstruction did not produce such an effect. CONCLUSIONS: In the position of lateral pinch the 15 degrees osteotomy and total ligament reconstruction significantly reduced laxity of the thumb CMC joint in all directions tested. The isolated dorsal or volar ligament reconstructions both reduced dorsal-volar laxity. Metacarpal extension osteotomy may stabilize the thumb CMC joint in lateral pinch to a degree similar to that of a standard ligament reconstruction.     

Contact area of the trapeziometacarpal joint.

Eighteen cadaver hands were studied to determine the contact area of the trapeziometacarpal joint by using silicone rubber casts. Casting material was introduced into the trapeziometacarpal joint during several motions of the thumb and the contact location was observed. The ratios of the contact area to the total joint area were calculated. The contact locations in opposition were the radial, volar, and ulnar segments of the trapezium and the dorsal, radial, and volar segments of the metacarpal. On average, 53% of the trapezium was in contact with 53% of the metacarpal in opposition, while 28% of the trapezium was in contact with 28% of the metacarpal in palmar abduction and 25% of the trapezium was in contact with 25% of the metacarpal in radial abduction. The contact area was the largest in opposition. The trapeziometacarpal joint is stable in opposition and facilitates a strong pinch.     

Material properties of the trapezial and trapeziometacarpal ligaments

Destabilization of the trapezium from its normal orientation with respect to the trapezoid, second metacarpal, and thumb metacarpal leads to incongruity at the trapeziometacarpal (TMC) joint. Abnormal shear forces may eventually result in TMC joint arthritis. By determining the relative stiffness and strength of the ligaments that stabilize this joint, one may infer their role in providing stability to the TMC joint. This study addresses the material properties of the ligaments stabilizing the trapezium and TMC joint to better understand the mechanics and kinematics of this joint. Fresh-frozen cadaveric hands (10 males and 10 females) were used to obtain bone-ligament-bone complexes from the dorsal and volar trapeziotrapezoid ligaments, dorsal and volar trapezio-second metacarpal ligaments, anterior oblique ligament, dorsoradial ligament, and trapezio-third metacarpal (T-III MC) ligament. The following material properties were derived from our data: ultimate load, ultimate stress (normalized failure load), ultimate strain (percent elongation), stiffness, toughness (energy to failure), and hysteresis. The dorsoradial ligament demonstrated the greatest ultimate load and toughness (energy to failure). The T-III MC ligament demonstrated the greatest ultimate stress (normalized failure load) and stiffness. The anterior oblique ligament demonstrated the least stiffness and the greatest hysteresis. The material properties of capsuloligamentous structures may be a good indicator of their importance to joint stability. Using these criteria we conclude that the T-III MC and dorsoradial ligaments are important stabilizers of the trapezium and TMC joint, respectively. These two ligaments were found to be the strongest, stiffest, and toughest ligaments, while the anterior oblique ligament was relatively weak and compliant. The dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, and T-III MC ligaments were all relatively strong and are anatomically aligned to function as tension bands to restrain the trapezium against cantilever bending forces applied to it by the thumb during key or tip pinch.     

In Vivo Pilot Study Evaluating the Thumb Carpometacarpal Joint During Circumduction

Background

Analysis of arthrokinematics may have clinical use in the diagnosis of dynamic instability of the thumb and wrist. Recent technological advances allow noninvasive, high-resolution imaging of skeletal (thumb and carpal bones) structures during motion.

Questions/purposes

The primary purpose of this study is to define the arthrokinematics, estimated joint contact patterns, and distribution ratios of the carpometacarpal joint of the thumb using four-dimensional CT (three-dimensional CT + time) and registration algorithms. The second purpose is to validate the accuracy of the approach.

Methods

Four-dimensional CT scans were obtained using a nongated sequential scanning technique. Eighteen image volumes were reconstructed over a 2-second cycle during thumb circumduction in one healthy volunteer. Using a registration algorithm, serial thumb motions as well as estimated joint contact areas were quantified. To evaluate the accuracy of our approach, one cadaveric hand was used.

Results

During circumduction, the ranges of motion of the thumb carpometacarpal joint were: flexion-extension, 27.3°; adduction-abduction, 66.9°; and pronation-supination, 10°. The magnitude of the translation of the center of the estimated joint contact area of the metacarpal was 4.1, 4.0, 1.0, and 1.5 mm when moving from the initial key pinch position to adduction, adduction to palmar abduction, palmar abduction to opposition, and opposition to the initial key pinch position, respectively. The maximum estimated contact area on the trapezium and on the metacarpal was in palmar abduction; the minimum was in adduction. Dominant central-volar contact patterns were observed on both the trapezium and the metacarpal bone except in adduction. This analysis approach had an average rotational error of less than 1°.

Conclusions

During circumduction, the estimated joint contact area was concentrated on the central-volar regions of both the trapezium and the metacarpal bones except when the thumb was adducted.

Clinical Relevance

This tool provides quantification of estimated joint contact areas throughout joint motion under physiological dynamic loading conditions; this tool may, in future studies, help to clarify some of the ways that joint mechanics might or might not predispose patients to arthritis.     

Early osteoarthritis of the trapeziometacarpal joint is not associated with joint instability during typical isometric loading

The saddle‐shaped trapeziometacarpal (TMC) joint contributes importantly to the function of the human thumb. A balance between mobility and stability is essential in this joint, which experiences high loads and is prone to osteoarthritis (OA). Since instability is considered a risk factor for TMC OA, we assessed TMC joint instability during the execution of three isometric functional tasks (key pinch, jar grasp, and jar twist) in 76 patients with early TMC OA and 44 asymptomatic controls. Computed tomography images were acquired while subjects held their hands relaxed and while they applied 80% of their maximum effort for each task. Six degree‐of‐freedom rigid body kinematics of the metacarpal with respect to the trapezium from the unloaded to the loaded task positions were computed in terms of a TMC joint coordinate system. Joint instability was expressed as a function of the metacarpal translation and the applied force. We found that the TMC joint was more unstable during a key pinch task than during a jar grasp or a jar twist task. Sex, age, and early OA did not have an effect on TMC joint instability, suggesting that instability during these three tasks is not a predisposing factor in TMC OA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1639–1645, 2015.     

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.     

The effects of transection and reconstruction of the ulnar collateral ligament complex on the position of the proximal phalanx of the thumb during simulated tip pinch

Injuries to the ulnar collateral ligament (UCL) of the metacarpophalangeal joint of the thumb are common and may result in functional instability of the joint. Eight cadaveric hands were studied. Physiologic levels of muscle loads were applied to the extrinsic flexor tendon of the thumb to simulate tip pinch of the thumb. We investigated the effects of transection of the UCL and accessory UCL (UCL complex) with and without transection of the dorsal capsule and volar plate and of reconstruction of the UCL, for 2 surgical techniques, on the position of the proximal phalanx with respect to the thumb metacarpal. The spatial positions of the metacarpal and proximal phalanx were measured with a 6 degrees of freedom digitizing system for flexion angles from 0 degrees to 60 degrees in 15 degrees increments. Transection of the UCL complex, dorsal capsule, and volar plate (ulnar capsuloligamentous structures) of the metacarpophalangeal joint did not affect radioulnar deviation or radioulnar shift, but did produce significant increases in supination by 8 degrees and volar translation by 2 mm at 45 degrees and 60 degrees compared with those found for the intact joint. The UCL was reconstructed with a tendon graft using the autogenous extensor digiti quinti. The first surgical technique, a traditional technique, and the second surgical technique, a technique based on anatomy, returned the position of the proximal phalanx on the metacarpal head to normal, with the exceptions of volar translation of the proximal phalanx at 60 degrees and trends toward abnormal supination of the proximal phalanx for flexion angels of 45 degrees and 60 degrees.     

Sequential wear patterns of the articular cartilage of the thumb carpometacarpal joint in osteoarthritis

PURPOSE: The thumb carpometacarpal (CMC) joint is a primary location for osteoarthritis (OA) in the body; however, articular cartilage thickness distribution during progression of OA in the joint has not been reported previously. Determining the cartilage wear patterns within the joint is important in understanding the etiology and treatment of thumb CMC joint OA. This study used cadaveric specimens to investigate the wear patters of the articular surfaces of the trapezium and thumb metacarpal. METHODS: A total of 104 fresh-frozen thumb CMC joints were radiographed, disarticulated, and visually staged for OA. Cartilage thickness maps of the trapezium and metacarpal were determined for each joint by using stereophotogrammetry. Average cartilage thickness maps for the trapezium and metacarpal were generated from all specimens for each of 4 stages of OA, showing the progression of cartilage thickness changes with disease. RESULTS: In normal joints, the surface-wide mean thickness of the articular layers is 0.8 +/- 0.2 mm for the trapezium and 0.7 +/- 0.2 mm for the metacarpal. The average thickness maps were analyzed by anatomic quadrant (dorsal-radial, dorsal-ulnar, volar-radial, volar-ulnar) within the 4 stages of OA. Corresponding quadrants also were compared across the increasing stages of OA. Results show that cartilage degradation is initiated in the radial quadrants of the metacarpal and progresses to the volar quadrants of the articular surface, while significant wear is seen on the dorsal-radial quadrant of the trapezium and progresses to the volar quadrants in late-stage osteoarthritis. CONCLUSIONS: These quantitative results on cartilage thinning agree with previous investigators' reports of high load bearing and low load bearing areas in the CMC joint during functional pinch and grasp positions. Understanding the progression of OA in the thumb CMC joint may aid in the surgical treatment of this disease.     

Tendon interposition arthroplasty versus arthrodesis for the treatment of trapeziometacarpal arthritis: a retrospective comparative follow-up study

Long-term subjective and objective outcomes of 24 tendon interposition arthroplasties in 17 patients and 32 trapeziometacarpal (TMC) arthrodeses in 26 patients were compared retrospectively in a standardized manner. Tendon interposition arthroplasty led to complications less often (27%) than TMC arthrodesis (39%). Patients in the tendon interposition arthroplasty group reported significantly less pain, less temperature intolerance, and better thumb mobility and were more satisfied with pain symptoms than patients in the arthrodesis group. Patients undergoing tendon interposition arthroplasty had better thumb opposition, interphalangeal joint mobility, and radial and palmar TMC joint range of motion. No statistically significant differences were found in tip pinch, key pinch, and grip strength between the 2 groups. Proximal first metacarpal collapse occurred in the tendon interposition patients without affecting subjective or objective outcome. Seven of 25 patients with TMC arthrodesis had pseudarthrosis. Tendon interposition arthroplasty seems to be preferable to TMC joint arthrodesis for the treatment of TMC arthritis.     

Contact areas in the thumb carpometacarpal joint

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar-ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint. These contact areas were assessed relative to the observed sites of cartilage thinning. Eight hands from cadavers of women and five from cadavers of men were tested in vitro with the thumb under a 25 N load in the lateral pinch position, and under small muscle loads (0–5 N) with the thumb in flexion, extension, abduction, adduction, and neutral positions. Contact areas of articular surfaces of the thumb carpometacarpal joint were determined for these positions using a stereophotogrammetric technique. The lateral pinch position produced contact areas predominantly on the central, volar, and volar-ulnar regions of the trapezium and the metacarpal. In three specimens, contact areas were distinctly separated between the dorsoradial and volar-ulnar regions, and in one specimen, from a man, contact occurred exclusively on the dorsoradial region of the trapezium. Using stereophotogrammetry, maps of cartilage thickness also were determined for a subset of nine specimens. The volar-ulnar, ulnar, and dorsoradial regions of the trapezium were the most common sites of thin cartilage, and these may be sites of cartilage wear. The results of this study indicate that the lateral pinch position produced stresses in the same regions where cartilage thinning was observed; this lends support to the hypothesis that high stresses can lead to osteoarthritis in this joint.     

A quantitative method to measure maximal workspace of the trapeziometacarpal joint--normal model development.

INTRODUCTION: A reliable and quantitative method for measuring motion of the thumb is lacking. In particular, review of the previous methods of motion analysis of the thumb joints shows that there is no objective method for clinicians to assess the impairment of the thumb trapeziometacarpal (TMC) joint. Based on the concept of the three-dimensional (3-D) space within which the first metacarpal can move relative to the trapezium (a concept of defining and measuring the workspace of the TMC motion), we present a quantitative method for measuring motion and impairment (loss of function) of the TMC joint. METHODS: Twenty normal subjects were recruited in this study. An electromagnetic device was placed over the thumb metacarpal and long finger metacarpal, the 3-D relationship between them previously established. We measured the position and orientation of the TMC motion in space. Maximum movements of the thumb TMC joint in circumduction, flexion-extension and abduction-adduction were used to construct the 3-D maximal workspace of the TMC joint. Mathematical methods were used to verify the model and calculate the maximal workspace. RESULTS: The results of this study demonstrate accurate and repeatable measurement of 3-D TMC motion with high statistical reliability and low variability of the maximal TMC workspace. A statistically significant linear correlation between the maximal surface area and the square of the first metacarpal length was obtained. CONCLUSION: We conclude that a quantitatively comparative measurement of the range of motion of the TMC joint can be obtained with potential to measure motion in joints affected by arthritis or trauma and measured in both dynamic and static positions of the thumb.     

Trapezial tilt: a radiographic correlation with advanced trapeziometacarpal joint arthritis

Trapeziometacarpal (TMC) joint arthritis is a common and debilitating condition of the hand. We defined a radiographic measure of trapezial inclination (trapezial tilt) and found a positive correlation between an increased trapezial tilt and severity of TMC joint arthritis. Radiographs (Robert's views) were obtained from 50 pairs of normal hands to evaluate the trapezial tilt to assess radial inclination of the trapezium with respect to the second metacarpal. The trapezial tilt was also measured in 65 hands from 43 patients with various stages of TMC joint arthritis and compared with the normal value. The trapezial tilt for hands without arthritis was 42 degrees +/- 4 degrees, Eaton stages I and II was 42 degrees +/- 4 degrees, and Eaton stages III and IV was 50 degrees +/- 4 degrees. Trapezial tilt angles from the Eaton III and IV group were significantly greater than those of the normal and Eaton I and II groups. Advanced TMC joint arthritis (Eaton III and IV) is associated with an increased trapezial tilt. Mild TMC joint arthritis with an increased trapezial tilt may be treated surgically. We speculate that a trapezio-trapezoid and trapezio-II metacarpal arthrodesis, or an opening wedge osteotomy of the trapezium might arrest the progression of TMC joint arthritis by resetting the slope of the trapezium and decreasing the shear stress within the TMC joint.     

In vivo kinematics of the thumb during flexion and adduction motion: Evidence for a screw‐home mechanism

The thumb plays a crucial role in basic hand function. However, the kinematics of its entire articular chain have not yet been quantified. Such investigation is essential to improve our understanding of thumb function and to develop better strategies to treat thumb joint pathologies. The primary objective of this study is to quantify the in vivo kinematics of the trapeziometacarpal (TMC) and scaphotrapezial (ST) joints during flexion and adduction of the thumb. In addition, we want to evaluate the potential coupling between the TMC and ST joints during these tasks. The hand of 16 asymptomatic women without signs of thumb osteoarthritis were CT scanned in positions of maximal thumb extension, flexion, abduction, and adduction. The CT images were segmented and three‐dimensional surface models of the radius, scaphoid, trapezium, and the first metacarpal were created for each thumb motion. The corresponding rotations angles, translations, and helical axes were calculated for each sequence. The analysis shows that flexion and adduction of the thumb result in a three‐dimensional rotation and translation of the entire articular chain, including the trapezium and scaphoid. A wider range of motion is observed for the first metacarpal, which displays a clear axial rotation. The coupling of axial rotation of the first metacarpal with flexion and abduction during thumb flexion supports the existence of a screw‐home mechanism in the TMC joint. In addition, our results point to a potential motion coupling between the TMC and ST joints and underline the complexity of thumb kinematics. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1556–1564, 2017.

     

Interposition arthroplasty using trapezium tendon ball for osteoarthritis of the carpometacarpal joint of the thumb

Carpometacarpal (CM) joint arthroplasty of the thumb using a trapezium tendon ball was performed in 11 hands of 9 patients with osteoarthritis. After a total dissection of the trapezium, the palmaris longus was wrapped around the trapezium, with the surfaces of both the CM joint and the scaphotrapezial joint tightly covered. Grafted trapezium was repositioned, and a congruency of the CM joint was confirmed. All patients were relieved from pain, with the radial abduction angle, grip strength, and the pinch strength increased 5 years after surgery. Radiographically, the mean width of the CM joint space increased, and a central migration of the first metacarpal bone was not found. This procedure would be available for the osteoarthritis in both the CM joint and the scaphotrapezial joint.     

Tendon interposition arthroplasty of carpometacarpal joint of the thumb

Osteoarthritis of the thumb carpal metacarpal joint is effectively managed by complete excision of the trapezium or excision of the distal half of the trapezium with maintenance of the space by insertion of interposition tendinous material from palmaris longus or flexor carpi radialis. The more recent modification of partial trapezium excision has improved pinch strength and maintenance of thumb length and so has enhanced the final results. Carpal metacarpal ligament reconstruction is demonstrated because it is occasionally necessary.     

Effects of the adductor pollicis and abductor pollicis brevis on thumb metacarpophalangeal joint laxity before and after ulnar collateral ligament reconstruction

PURPOSE: The intrinsic muscles and ulnar capsuloligamentous structures (UCLS), which consist of the ulnar collateral ligament (UCL), accessory UCL, dorsal capsule, and volar plate of the thumb metacarpophalangeal (MCP) joint are important for controlling the motion and stability of the MCP joint during pinch. The purpose of this cadaveric study was to determine the effects of the adductor pollicis (AdP) and abductor pollicis brevis (APB) on the 3-dimensional MCP joint laxity before transection of the UCLS and after reconstruction of the UCL and repair of the dorsal capsule. METHODS: Loads were applied to the flexor pollicis longus (FPL) alone, to the AdP and FPL in combination, and to the APB and FPL in combination in 11 cadavers. This was done in the intact joint after the UCLS were transected and after the UCL was reconstructed for flexion angles of 0 degrees, 15 degrees, 30 degrees, and 45 degrees. The spatial positions of the proximal phalanx and the metacarpal of the MCP joint were measured with a 6-degrees-of-freedom digitizing system. RESULTS: In the intact joint combined loading of the AdP and FPL did not affect the position of the proximal phalanx. Combined loading of the APB and FPL changed the position of the phalanx from an ulnar to a radial shift and from an ulnar to a radial deviation and it increased pronation. After transection of the UCLS combined loading of the FPL and AdP increased supination of the MCP joint and combined loading of the FPL and APB increased radial shift, radial deviation, and pronation of the joint. Reconstruction of the UCL restored normal laxity to the MCP joint. CONCLUSIONS: The AdP failed to affect MCP joint motion. The ABP produced a radial shift and radial deviation of the MCP joint and increased pronation of the thumb. Transection of the UCLS increased joint laxity for each of the combined loadings and reconstruction of the UCL restored normal laxity to the MCP joint.     

Traumatic dislocations and instability of the trapeziometacarpal joint of the thumb

The surgeon treating traumatic injuries to the TMC joint should be aware of the fundamental misconceptions and pervasive axiomatic myths perpetuated in the medical literature: namely that the volar beak ligament is the prime stabilizer, that the dorsal ligament complex plays no significant role in TMC joint function, and that the APL is a deforming force in Bennett fractures. On the contrary, stability of the TMC joint in power pinch and power grasp depends on the TMC joint's two prime stabilizers, the volar beak of the thumb metacarpal and the dorsal radial ligament complex; and the APL is not a deforming force in a Bennett fracture. Screw-home-torque occurs in the final phase of opposition; the acute Bennett fracture can be treated closed and percutaneously fixed if the screw-home-torque technique is used to anatomically reduce the fracture. After soft tissue interposition, if a semi-acute Bennett fracture is diagnosed late, it should be treated open with a volar approach, the screw-home-torque reduction technique, and screw or pin fixation. Rolando multipart fractures of the thumb metacarpal into the TMC joint are best treated closed, with traction in opposition with pin fixation; pure dislocations of the TMC joint that tear the dorsal ligament complex and Bennett fractures with an associated dorsal ligament complex tear (as diagnosed by the screw-home-torque technique) require open reduction and dorsal ligament complex repair. The current literature is so replete with myths and folklore regarding the anatomy that a conscientious surgeon treating a traumatic dislocation or in-stability of the TMC joint should return to the cadaver room and carefully review and understand TMC joint anatomy.     

Treatment of Eaton stage I trapeziometacarpal disease with thumb metacarpal extension osteotomy

The current benchmark for the treatment of Eaton stage I disease of the trapeziometacarpal (TMC) joint includes palmar oblique ligament reconstruction and reflects its primary role in providing stability during lateral pinch. This study prospectively evaluates the efficacy of an alternative extra-articular approach using a 30 degrees extension osteotomy of the thumb metacarpal to redistribute trapeziometacarpal contact area and load, obviating the need for ligament reconstruction. Preoperative and postoperative subjective and objective data are reported for 12 patients enrolled in the study between 1995 and 1998. Trapeziometacarpal arthrotomy allowed accurate intra-articular assessment and verified palmar oblique ligament incompetence in each case. The average follow-up period was 2.1 years (range, 6-46 months). All osteotomies healed at an average of 7 weeks. Eleven patients were satisfied with outcome. Grip and pinch strength increased an average of 8.5 and 3.0 kg, respectively. Thumb metacarpal extension osteotomy is an effective biomechanical alternative to ligament reconstruction in the treatment of Eaton stage I disease of the trapeziometacarpal joint.