Kinematics of the normal trapeziometacarpal joint

MAÏA Trapeziometacarpal Joint Arthroplasty: Clinical and Radiological Outcomes of 76 Patients With More Than 10 Years of Follow-Up

PURPOSE

Trapeziometacarpal (TMC) joint replacement has become a valid option in the therapeutic arsenal of TMC joint osteoarthritis in Europe. Good mid-term results of the MAÏA TMC joint prosthesis suggested that it is a reliable procedure. This study aimed to assess the long-term results of this modular uncemented ball-and-socket hydroxyapatite-coated implant.

METHODS

This single-center retrospective study evaluated 92 MAÏA TMC joint prostheses in 76 patients with a minimum of 10 years of follow-up. Indications for the procedure were painful TMC joint osteoarthritis both at rest and during activity, despite nonsurgical treatment for more than six months. Pre- and postoperative clinical and radiographic outcomes were compared.

RESULTS

Mean follow-up was 134 months (range: 120-158 months). Mean age at the time of surgery was 67 years (range: 53-84 years). The cohort comprised 86.8% of women (n = 66). The mean Quick Disabilities of the Arm, Shoulder, and Hand score improved from 61.3 ± 17.1 to 19.6 ± 16. Range of motion was restored, and postoperative mobility was comparable with that of the contralateral side. Final Kapandji opposition score was almost normal (9.2 ± 0.7). Final key pinch and grip strength improved by 26% and 39%, respectively. Eight implants were surgically revised, six for trapezium cup loosening and two for instability because of polyethylene wear. Three cases of traumatic fracture of the trapezium in older patients were successfully treated with a cast for eight weeks. Five of 26 (20.8%) cases of preoperative-reducible z-deformity were not totally corrected after surgery. The Kaplan-Meier survival over 10 years was 88% (95% confidence interval: 84-93) versus 93% (95% confidence interval: 87-98) over 5 years.

CONCLUSIONS

MAÏA TMC joint prosthesis is a reliable long-term surgical procedure for TMC joint osteoarthritis, improving overall function beyond 10 years.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The Female Thumb Carpometacarpal Joint: Motion and Force Changes Due to Arthritis and Surgical Intervention

Thumb carpometacarpal (CMC) osteoarthritis (OA) has been one of the most common locations of hand OA. CMC OA disproportionately occurs in females over males. In severe cases, surgical intervention may be needed. However, to determine the effects of surgical treatment, normative, pre-, and postsurgery function must be understood. The goals of this work were to compare the thumb motion and force abilities of older healthy (OH) females without CMC OA to those of females with CMC OA and who received ligament reconstruction with tendon interposition (LRTI) surgery at time points presurgery, 3- and 6-months postsurgery. On average, CMC OA participants 3- and 6-months postsurgery showed 35.6% and 32.9% less overall metacarpal motion compared to presurgery, 31.9% and 29.1% less than OH, and exhibited altered motion. Metacarpal flexion/extension and abduction/adduction ranges were 51.9 deg and 43.4 deg for OH, 52.9 deg and 40.3 deg presurgery, 39.9 deg and 33.5 deg at 3-months, and 42.6 deg and 32.7 deg at 6-months postsurgery. On average, participants had increased force generation at 6-months postsurgery compared to presurgery, and 20% of participants returned to the level of OH females. These data sets highlight changes in thumb metacarpal movement and thumb force generation due to disease and surgical intervention. This work has the ability to support both surgeons and patients through improved outcome assessments as well as additional data to inform the decision process on intervention.

The passive biomechanics of the thumb carpometacarpal joint: An in vitro study

The thumb carpometacarpal (CMC) joint facilitates multidirectional motion of the thumb and affords prehensile power and precision. Traditional methods of quantifying thumb CMC kinematics have been largely limited to range-of-motion (ROM) measurements in 4 orthogonal primary directions (flexion, extension, abduction, adduction) due to difficulties in capturing multidirectional thumb motion. However, important functional motions (e.g., opposition) consist of combinations of these primary directions, as well as coupled rotations (internal and external rotation) and translations. Our goal was to present a method of quantifying the multidirectional in vitro biomechanics of the thumb CMC joint in 6 degrees-of-freedom. A robotic musculoskeletal simulation system was used to manipulate CMC joints of 10 healthy specimens according to specimen-specific joint coordinate systems calculated from computed tomography bone models. To determine ROM and stiffness (K), the first metacarpal (MC1) was rotated with respect to the trapezium (TPM) to a terminal torque of 1 Nm in the four primary directions and in 20 combinations of these primary directions. ROM and K were also determined in internal and external rotation. We found multidirectional ROM was greatest and K least in directions oblique to the primary directions. We also found external rotation coupling with adduction-flexion and abduction-extension and internal rotation coupling with abduction-flexion and adduction-extension. Additionally, the translation of the proximal MC1 was predominantly radial during adduction and predominantly ulnar during abduction. The findings of this study aid in understanding thumb CMC joint mechanics and contextualize pathological changes for future treatment improvement.

In-vivo kinematics of the trapeziometacarpal joint in dynamic pinch motion using four-dimensional computed tomography imaging

OBJECTIVE

CT imaging precisely and quantitatively analyzes the kinematics of the carpal bones to evaluate the etiology of related osteoarthritis. Previous studies have investigated the kinematics of the trapeziometacarpal joint using static CT scans of various postures including the pinch position. This study analyzed the in-vivo kinematics of the trapeziometacarpal joint during dynamic pinch motion in young healthy volunteers using four-dimensional CT.

MATERIALS AND METHODS

Twelve healthy young volunteers participated in this study. Each participant held the pinch meter between their thumb and index finger and pinched it with maximum force for a period of 6 s. This series of movement was recorded using a four-dimensional CT. The surface data of the trapezium and first metacarpal of all frames were reconstructed, and bone movement at the trapeziometacarpal joint was calculated using sequential three-dimensional registration. The instantaneous pinch force of each frame was measured using a pointer on a pinch meter that was reconstructed from the CT data.

RESULTS

The first metacarpal was abducted (15.9 ± 8.3°) and flexed (12.2 ± 7.1°) relative to the trapezium, and significantly translated to the volar　(0.8 ± 0.6 mm) and ulnar directions (0.9 ± 0.8 mm) with maximum pinch force. This movement consistently increased with the pinch force.

CONCLUSION

This study successfully employed 4D-CT to precisely demonstrate changes in rotation and translation at the trapeziometacarpal joint during pinch motion for various instantaneous forces.

Usability of curved keyboard design on the large smartphone: An empirical study

The curved design is ubiquitous, with a vast user base due to its similarity with in shape to human physiological structure. The curved QWERTY keyboard layout was proposed for one-handed usage on smartphones with ambiguous effects. This study evaluated whether the curved QWERTY could optimize the user experience and input performance on large smartphones better than the traditional straight QWERTY layout. Eight measurements were used to evaluate the usability of each design, six suggesting curved QWERTY failed to achieve outstanding typing performance or subjective user experience, while the other two indicators showed that curved QWERTY had advantages in touch dispersion and touching offset, indicating the possible higher usability it could reach. The results also investigated the potential application of curved designs and provided insights into the optimization methods.

Partial Trapeziotrapezoid Resection and Thumb Range of Movement After Trapeziometacarpal Joint Fusion-A Biomechanical Study

PURPOSE

Trapeziometacarpal (TMC) joint arthrodesis is an effective treatment for stage III osteoarthritis. Although this procedure alleviates thumb pain and restores grip power and pinch strength, persistent limitation of thumb movement is inevitable. This biomechanical study aimed to investigate the altered kinematics of thumb circumduction motion after TMC joint arthrodesis and subsequent excision of the trapeziotrapezoid (TT) and trapezio-second metacarpal (T-2MC) joint spaces.

METHODS

Eight cadaver upper extremities were mounted on a custom testing apparatus. The hand and carpal bones were fixed to the apparatus, except for the first metacarpal bone, trapezium, and trapezoid. A 50-g load was applied at the tip of the first metacarpal head to generate passive thumb circumduction. An electromagnetic tracking system measured the angular and rotational displacement of the first metacarpal. All specimens were tested in 4 conditions: intact, after simulated TMC joint fusion, after subsequent excision of 3 mm of bone at the TT joint space, and after additional 3 mm resection at the T-2MC joint space.

RESULTS

After simulated TMC arthrodesis, the range of angular motion of thumb circumduction decreased to 25% that of the intact thumb. Subsequent resections at the TT and T-2MC joint spaces increased circumduction ranges to 49% (TT joint) and 73% (TT plus T-2MC joints) that of the intact thumb. The range of thumb rotational motion showed a similar trend.

CONCLUSIONS

Trapeziometacarpal arthrodesis decreased the range of both angular and rotational motion during thumb circumduction. Subsequent resections at the paratrapezial space increased the range of thumb motion, suggesting that hypermobility of the paratrapezial joints increases thumb mobility after TMC joint fusion.

CLINICAL RELEVANCE

Patients with hypermobile paratrapezial joints may have larger thumb movement after TMC joint fusion. Additional resections of the TT and T-2MC joint spaces may further mobilize the thumb in patients who complain of stiffness after TMC fusion.

An overview of robotic/mechanical devices for post-stroke thumb rehabilitation

PURPOSE

This article aims to clarify the current state-of-the-art of robotic/mechanical devices for post-stroke thumb rehabilitation as well as the anatomical characteristics and motions of the thumb that are crucial for the development of any device that aims to support its motion.

METHODS

A systematic literature search was conducted to identify robotic/mechanical devices for post-stroke thumb rehabilitation. Specific electronic databases and well-defined search terms and inclusion/exclusion criteria were used for such purpose. A reasoning model was devised to support the structured abstraction of relevant data from the literature of interest.

RESULTS

Following the main search and after removing duplicated and other non-relevant studies, 68 articles (corresponding to 32 devices) were left for further examination. These articles were analyzed to extract data relative to (i) the motions assisted/permitted - either actively or passively - by the device per anatomical joint of the thumb and (ii) mechanical-related aspects (i.e., architecture, connections to thumb, other fingers supported, adjustability to different hand sizes, actuators - type, quantity, location, power transmission and motion trajectory).

CONCLUSIONS

Most articles describe preliminary design and testing of prototypes, rather than the thorough evaluation of commercially ready devices. Defining appropriate kinematic models of the thumb upon which to design such devices still remains a challenging and unresolved task. Further research is needed before these devices can actually be implemented in clinical environments to serve their intended purpose of complementing the labour of therapists by facilitating intensive treatment with precise and repeatable exercises. Implications for Rehabilitation Post-stroke functional disability of the hand, and particularly of the thumb, significantly affects the capability to perform activities of daily living, threatening the independence and quality of life of the stroke survivors. The latest studies show that a high-dose intensive therapy (in terms of frequency, duration and intensity/effort) is the key to effectively modify neural organization and recover the motor skills that were lost after a stroke. Conventional therapy based on manual interaction with physical therapists makes the procedure labour intensive and increases the costs. Robotic/mechanical devices hold promise for complementing conventional post-stroke therapy. Specifically, these devices can provide reliable and accurate therapy for long periods of time without the associated fatigue. Also, they can be used as a means to assess patients? performance and progress in an objective and consistent manner. The full potential of robot-assisted therapy is still to be unveiled. Further exploration will surely lead to devices that can be well accepted equally by therapists and patients and that can be useful both in clinical and home-based rehabilitation practice such that motor recovery of the hand becomes a common outcome in stroke survivors. This overview provides the reader, possibly a designer of such a device, with a complete overview of the state-of-the-art of robotic/mechanical devices consisting of or including features for the rehabilitation of the thumb. Also, we clarify the anatomical characteristics and motions of the thumb that are crucial for the development of any device that aims to support its motion. Hopefully, this?combined with the outlined opportunities for further research?leads to the improvement of current devices and the development of new technology and knowledge in the field.

The Envelope of Physiological Motion of the First Carpometacarpal Joint

Much of the hand's functional capacity is due to the versatility of the motions at the thumb carpometacarpal (CMC) joint, which are presently incompletely defined. The aim of this study was to develop a mathematical model to completely describe the envelope of physiological motion of the thumb CMC joint and then to examine if there were differences in the kinematic envelope between women and men. In vivo kinematics of the first metacarpal with respect to the trapezium were computed from computed tomography (CT) volume images of 44 subjects (20M, 24F, 40.3 ± 17.7 yr) with no signs of CMC joint pathology. Kinematics of the first metacarpal were described with respect to the trapezium using helical axis of motion (HAM) variables and then modeled with discrete Fourier analysis. Each HAM variable was fit in a cyclic domain as a function of screw axis orientation in the trapezial articular plane; the RMSE of the fits was 14.5 deg, 1.4 mm, and 0.8 mm for the elevation, location, and translation, respectively. After normalizing for the larger bone size in men, no differences in the kinematic variables between sexes could be identified. Analysis of the kinematic data also revealed notable coupling of the primary rotations of the thumb with translation and internal and external rotations. This study advances our basic understanding of thumb CMC joint function and provides a complete description of the CMC joint for incorporation into future models of hand function. From a clinical perspective, our findings provide a basis for evaluating CMC pathology, especially the mechanically mediated aspects of osteoarthritis (OA), and should be used to inform artificial joint design, where accurate replication of kinematics is essential for long-term success.

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.

In Vivo kinematics of the trapeziometacarpal joint during thumb extension-flexion and abduction-adduction

PURPOSE

The primary aim of this study was to determine whether the in vivo kinematics of the trapeziometacarpal (TMC) joint differ as a function of age and sex during thumb extension-flexion (Ex-Fl) and abduction-adduction (Ab-Ad) motions.

METHODS

The hands and wrists of 44 subjects (10 men and 11 women with ages 18-35 y and 10 men and 13 women with ages 40-75 y) with no symptoms or signs of TMC joint pathology were imaged with computed tomography during thumb extension, flexion, abduction, and adduction. The kinematics of the TMC joint were computed and compared across direction, age, and sex.

RESULTS

We found no significant effects of age or sex, after normalizing for size, in any of the kinematic parameters. The Ex-Fl and Ab-Ad rotation axes did not intersect, and both were oriented obliquely to the saddle-shaped anatomy of the TMC articulation. The Ex-Fl axis was located in the trapezium and the Ab-Ad axis was located in the metacarpal. Metacarpal translation and internal rotation occurred primarily during Ex-Fl.

CONCLUSIONS

Our findings indicate that normal TMC joint kinematics are similar in males and females, regardless of age, and that the primary rotation axes are nonorthogonal and nonintersecting. In contrast to previous studies, we found Ex-Fl and Ab-Ad to be coupled with internal-external rotation and translation. Specifically, internal rotation and ulnar translation were coupled with flexion, indicating a potential stabilizing screw-home mechanism.

CLINICAL RELEVANCE

The treatment of TMC pathology and arthroplasty design require a detailed and accurate understanding of TMC function. This study confirms the complexity of TMC kinematics and describes metacarpal translation coupled with internal rotation during Ex-Fl, which may explain some of the limitations of current treatment strategies and should help improve implant designs.

The 2014 ABJS Nicolas Andry Award: The puzzle of the thumb: mobility, stability, and demands in opposition

BACKGROUND

The paradoxical demands of stability and mobility reflect the purpose and function of the human thumb. Its functional importance is underscored when a thumb is congenitally absent, injured, or afflicted with degenerative arthritis. Prevailing literature and teaching implicate the unique shape of the thumb carpometacarpal (CMC) joint, as well as its ligament support, applied forces, and repetitive motion, as culprits causing osteoarthritis (OA). Sex, ethnicity, and occupation may predispose individuals to OA.

QUESTIONS/PURPOSES

What evidence links ligament structure, forces, and motion to progressive CMC disease? Specifically: (1) Do unique attributes of the bony and ligamentous anatomy contribute to OA? (2) Can discrete joint load patterns be established that contribute to OA? And (3) can thumb motion that characterizes OA be measured at the fine and gross level?

METHODS

We addressed the morphology, load, and movement of the human thumb, emphasizing the CMC joint in normal and arthritic states. We present comparative anatomy, gross dissections, microscopic analysis, multimodal imaging, and live-subject kinematic studies to support or challenge the current understanding of the thumb CMC joint and its predisposition to disease.

RESULTS

The current evidence suggests structural differences and loading characteristics predispose the thumb CMC to joint degeneration, especially related to volar or central wear. The patterns of degeneration, however, are not consistently identified, suggesting influences beyond inherent anatomy, repetitive load, and abnormal motion.

CONCLUSIONS

Additional studies to define patterns of normal use and wear will provide data to better characterize CMC OA and opportunities for tailored treatment, including prevention, delay of progression, and joint arthroplasty.

Effect of carpometacarpal joint osteoarthritis, sex, and handedness on thumb in vivo kinematics

PURPOSE

To investigate the influence of trapeziometacarpal (TMC) osteoarthritis (OA) on the 3-dimensional motion capability of the TMC and thumb metacarpophalangeal (MCP) joints. In order to examine other factors affecting the thumb's motion kinematics, we further aimed to address the influence of sex and handedness on the motion capability of normal TMC and MCP joints.

METHODS

We included 18 healthy subjects (9 women, 9 men; 8 dominant hands, 10 nondominant hands) and 18 women with stage II/III TMC OA. A motion analysis system using surface markers was used to quantify the thumb's 3-dimensional opposition-reposition kinematics. The range of motion of the thumb's TMC and MCP joints in flexion-extension, abduction-adduction, and pronation-supination were determined.

RESULTS

TMC OA led to a loss in abduction-adduction in the TMC joint (38° in controls, 26° in TMC OA subjects), although neither flexion-extension nor pronation-supination were affected. At the MCP joint, the TMC OA subjects showed a 48% reduction in abduction-adduction (32° controls, 16° TMC OA subjects) and 42% reduction in pronation-supination (34° in controls, 20° in TMC OA subjects) than the healthy controls. Ranges of motion of the healthy TMC and MCP joints were similar in dominant and nondominant hands as well as in women and men.

DISCUSSION

The study demonstrated that stage II/III TMC OA restricts the motion of the TMC joint in abduction-adduction and of the MCP joint in abduction-adduction and pronation-supination. Thumb motion capability was unaffected by sex and handedness.

CLINICAL RELEVANCE

Osteoarthritis-induced loss of TMC motion did not reflect a generalizable clinical parameter, rather, it seemed to distinctly affect the TMC and the MCP joints and their motion planes and directions. As neither sex nor handedness influenced the motion capabilities of the healthy thumb, kinematic factors contributing to TMC OA may develop at a later age.

In vivo analysis of trapeziometacarpal joint arthrokinematics during multi-directional thumb motions

BACKGROUND

The investigation of the joint arthrokinematics of the trapeziometacarpal joint is critical to comprehend the causative mechanism underlying this common form of osteoarthritis. Therefore, the purpose of this study is to evaluate the arthrokinematics of the trapeziometacarpal joint during thumb postures in vivo.

METHODS

Fifteen healthy participants were enrolled in this study. Static computed tomography images of the 1st metacarpal bone and trapezium were taken at specific thumb postures during thumb flexion-extension, abduction-adduction, and circumduction motions. Images were analyzed to examine the joint gliding, expressed as displacement of the centroid of the articular surface of the 1st metacarpal bone, relative to the trapezium. The gliding ratio, defined as joint gliding in each direction normalized to the dimension of the trapezium joint surface in the given direction, was computed and compared between different thumb motions.

FINDINGS

The results indicate that thumb motions influenced joint gliding. The centroids of the articular surface of the 1st metacarpal bone were primarily located at the central and dorsal-radial regions while executing these motions. The maximum joint gliding of the 1st metacarpal bone occurred in the radial-ulnar direction when performing abduction-adduction, and in the dorsal-volar direction while performing flexion-extension and circumduction, with the gliding ratio values of 42.35%, 51.65%, and 51.85%, respectively.

INTERPRETATION

Activities that involved abduction-adduction in the trapeziometacarpal joint caused greater joint gliding in the ulnar-radial direction, while flexion-extension resulted in greater joint gliding in the dorsal-volar and distal-proximal directions. Understanding normal joint kinematics in vivo may provide insights into the possible mechanism leading to osteoarthritis of the trapeziometacarpal joint, and help to improve the design of implants.

In vivo analysis of trapeziometacarpal joint kinematics during pinch tasks

This study investigated how the posture of the thumb while performing common pinch movements and the levels of pinch force applied by the thumb affect the arthrokinematics of the trapeziometacarpal joint in vivo. Fifteen subjects performed the pinch tasks at the distal phalange (DP), proximal interphalangeal (PIP) joint, and metacarpophalangeal (MP) joint of the index finger with 0%, 50%, and 80% of maximal pinch forces by a single-axis load cell. 3D images of the thumb were obtained using the computed tomography. The results show that the reference points moved from the central region to the dorsal-radial region when changing from pinching the DP to the MP joint without pinching force being applied. Pinching with 80% of the maximum pinching force resulted in reference points being the closest to the volar-ulnar direction. Significant differences were seen between 0% and 50% of maximum pinch force, as well as between 0% and 80%, when pinching the MP joint in the distal-proximal direction. The effects of posture of the thumb and applied pinch force on the arthrokinematics of the joint were investigated with a 3D model of the trapeziometacarpal joint. Pinching with more than 50% of maximum pinch force might subject this joint to extreme displacement.

In vivo kinematics of the thumb carpometacarpal joint during three isometric functional tasks

BACKGROUND

The thumb carpometacarpal (CMC) joint is often affected by osteoarthritis--a mechanically mediated disease. Pathomechanics of the CMC joint, however, are not thoroughly understood due to a paucity of in vivo data.

QUESTIONS/PURPOSES

We documented normal, in vivo CMC joint kinematics during isometric functional tasks. We hypothesized there would be motion of the CMC joint during these tasks and that this motion would differ with sex and age group. We also sought to determine whether the rotations at the CMC joint were coupled and whether the trapezium moved with respect to the third metacarpal.

METHODS

Forty-six asymptomatic subjects were CT-scanned in a neutral position and during three functional tasks (key pinch, jar grasp, jar twist), in an unloaded and a loaded position. Kinematics of the first metacarpal, third metacarpal, and the trapezium were then computed.

RESULTS

Significant motion was identified in the CMC joint during all tasks. Sex did not have an effect on CMC joint kinematics. Motion patterns differed with age group, but these differences were not systematic across the tasks. Rotation at the CMC joint was generally coupled and posture of the trapezium relative to the third metacarpal changed significantly with thumb position.

CONCLUSIONS

The healthy CMC joint is relatively stable during key pinch, jar grasp, and jar twist tasks, despite sex and age group.

CLINICAL RELEVANCE

Our findings indicate that directionally coupled motion patterns in the CMC joint, which lead to a specific loading profile, are similar in men and women. These patterns, in addition to other, nonkinematic influences, especially in the female population, may contribute to the pathomechanics of the osteoarthritic joint.

Trapezium trabecular morphology in carpometacarpal arthritis

PURPOSE

In thumb carpometacarpal osteoarthritis, current evidence suggests that degenerative, bony remodeling primarily occurs within the trapezium. Nevertheless, the pathomechanics involved and the most common sites of wear remain controversial. Quantifying structural bone morphology characteristics with high-resolution computed tomography CT (micro-CT) infer regions of load transmission. Using micro-CT, we investigated whether predominant trabecular patterns exist in arthritic versus normal trapeziums.

METHODS

We performed micro-CT analysis on 13 normal cadaveric trapeziums and 16 Eaton stage III to IV trapeziums. We computationally divided each specimen into 4 quadrants: volar-ulnar, volar-radial, dorsal-radial, and dorsal-ulnar. Measurements of trabecular bone morphologic parameters included bone volume ratio, connectivity, trabecular number, and trabecular thickness. Using analysis of variance with post hoc Bonferroni/Dunn correction, we compared osteoarthritic and normal specimen quadrant measurements.

RESULTS

No significant difference existed in bone volume fraction between the osteoarthritic and normal specimens. Osteoarthritic trapeziums, however, demonstrated significantly higher trabecular number and connectivity than nonosteoarthritic trapeziums. Comparing the volar-ulnar quadrant of osteoarthritis and normal specimens collectively, this quadrant in both consistently possessed significantly higher bone volume fraction, trabecular number, and connectivity than the dorsal-radial and volar-radial quadrants.

CONCLUSIONS

The significantly greater trabecular bone volume, thickness, and connectivity in the volar-ulnar quadrant compared with the dorsal-radial and dorsal-ulnar quadrants provides evidence that the greatest compressive loads at the first carpometacarpal joint occur at the volar-ulnar quadrant of the trapezium, representing a consistently affected region of wear in both normal and arthritic states.

CLINICAL RELEVANCE

These findings suggest that trapezial trabecular morphology undergoes pathologic alteration. This provides indirect evidence that changes in load transmission occur with thumb carpometacarpal joint arthritis development.

A thumb carpometacarpal joint coordinate system based on articular surface geometry

The thumb carpometacarpal (CMC) joint is a saddle-shaped articulation whose in vivo kinematics can be explored more accurately with computed tomography (CT) imaging methods than with previously used skin-based marker systems. These CT-based methods permit a detailed analysis of the morphology of the joint, and thus the prominent saddle geometry can be used to define a coordinate system that is inherently aligned with the primary directions of motion at the joint. The purpose of this study was to develop a CMC joint coordinate systems that is based on the computed principal directions of curvature on the trapezium and the first metacarpal. We evaluated the new coordinate system using bone surface models segmented from the CT scans of 24 healthy subjects. An analysis of sensitivity to the manual selection of articular surfaces resulted in mean orientation differences of 0.7±0.7° and mean location differences of 0.2±0.1mm. Inter-subject variability, which mostly emanates from anatomical differences, was evaluated with whole bone registration and resulted in mean orientation differences of 3.1±2.7° and mean location differences of 0.9±0.5mm. The proposed joint coordinate system addresses concerns of repeatability associated with bony landmark identification and provides a robust platform for describing the complex kinematics of the CMC joint.

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.

LIGAMENT LENGTH DURING CIRCUMDUCTION OF THE TRAPEZIOMETACARPAL JOINT AFTER LIGAMENT SECTIONING

Thumb motion and stability were examined after sequential division of support ligaments of the trapeziometacarpal (TMC) to simulate the pathologic condition of ligament laxity. The motion obtained with passive circumduction was measured with a magnetic tracking system. The lengths of the TMC joint ligaments were approximated by measuring the distance between origin and insertion of each ligament. The change in this apparent interorigin distance of the ligaments was measured before and after ligament sectioning. The anterior oblique ligament (AOL) and the ulnar collateral ligament (UCL) had the greatest effect on TMC joint stability during circumduction of the thumb. Division of the first intermetacarpal ligament (IML) did not produce a change in apparent length of other ligaments. We conclude that small changes in ligament length affect thumb stability and alter the path of circumduction. Neither the IML or posterior oblique ligaments were major stabilizers of the TMC joint during circumduction, prehensile grasp, or tip pinch. Reconstruction of the AOL and UCL ligaments should be considered for treatment of the initial stages of TMC instability.

Method for the estimation of a double hinge kinematic model for the trapeziometacarpal joint using MR imaging

In this paper, we propose a method to estimate the parameters of a double hinge model of the trapeziometacarpal joint (TMC) by MRI-based motion analysis. The model includes two non-orthogonal and non-intersecting rotation axes accounting for flexion-extension (F-E) and adduction-abduction (A-A). We evaluated the quality of the estimated model parameters in the prediction of the relative motion of the first metacarpal bone with respect to the trapezium. As a result, we obtained that: (a) the estimated location and orientation of the F-E and A-A axes were in agreement with previous in vitro studies, (b) the motion of the first metacarpal predicted by the 2 degrees of freedom (2DoF) model exhibits a maximum surface distance error in the range of about 2 mm and (c) four thumb postures at the boundary of the TMC range of motion are sufficient to provide a good estimation of the 2DoF TMC kinematic model and good reproducibility (~1.7 mm) of the real thumb motion at TMC level.

Basal metacarpal osteotomy for osteoarthritis of the thumb

Thumb metacarpal extension osteotomy provides effective treatment for the hypermobile trapeziometacarpal joint consistent with Eaton stage 1 disease. This procedure is a useful alternative to Eaton ligament reconstruction. Clinical outcomes are favorable and, should symptoms persist, the procedure does not jeopardize satisfactory execution of trapezial resection arthroplasty in the future.

The three-dimensional analysis of three thumb joints coordination in activities of daily living

BACKGROUND

Presently, the angular movements of the three thumb joints during activities of daily living are limited as a result of their static position and lack of the required thumb range of motion information during motion. The purpose of this study was to investigate the three thumb joints' motion required in activities of daily living.

METHODS

Sixteen healthy subjects were recruited for this study. A three-dimensional motion analysis system was used, with 14 retroreflective markers attached to each subject's thumb for motion data collection. Three joints including interphalangeal joint, metacarpophalangeal joint and carpometacarpal joint of the thumb were analyzed. The distal segment orientation relative to the proximal segment was defined the joint angle. The styloid process of radial bone orientation when quantifying the carpometacarpal joint movement was indirectly calculated from the third metacarpal bone.

FINDINGS

The results showed that each type of activity involved significant interphalangeal flexion. The metacarpophalangeal joint mainly showed abduction motion, cylinder grip and spherical grip with the largest angle. For the carpometacarpal joint, the cylinder grip and spherical grip showed a relatively larger rotational range of motion. The interphalangeal joint in the three thumb joints was primary in flexion.

INTERPRETATION

These results may provide more information to precisely describe the thumb function in daily life activities and also provide a reference when assessing thumb impairment or for constructing an index used for evaluating the recovery of an injured thumb in clinic. It also could help in designing hand-related instruments for use in activities of daily life.

In vivo kinematics of the first carpometacarpal joint after trapezectomy

First carpometacarpal osteoarthitis is frequent and surgery may be necessary if medical treatment is not efficient. Trapeziometacarpal arthroplasty, trapeziometacarpal arthrodesis and trapezectomy may be proposed. These surgical solutions may modify the carpometacarpal kinematics of the thumb. However, no clinical tools are currently available to assess these modifications. The goal of our study is to assess the TM kinematics, with an optoelectronic system, in patients after trapezectomy. Ten women, average age 53 (range 45 to 67) underwent trapezectomy with ligamentoplasty for trapeziometacarpal osteoarthritis. An optoelectronic device (Polaris(®)) was used to analyse postoperative range-of-motion of the thumb. Splints were used in order to isolate the trapeziometacarpal joint and retroreflective markers were placed both on the splints and on the thumb. Mean flexion-extension, abduction-adduction, axial rotation and circumduction were calculated.

RESULTS

The mean range-of-motion of trapeziometacarpal joint was 50 degrees for flexion-extension, 47 degrees for abduction-adduction and 11 degrees for axial rotation. The mean angle between rotation axes was 90 degrees and the mean distance d between the axes was 3 millimeters. Comparisons between patients and healthy subjects showed no significant differences in flexion-extension, abduction-adduction and axial rotation. Circumduction in patients was reduced compared to healthy subjects. No significant differences were noted between the operated side and the contralateral side.

DISCUSSION AND CONCLUSION

Our study showed that this protocol can be used in the postoperative follow-up of patients after trapezectomy. We did not find any significant differences compared to the contralateral side. However, circumduction after trapezectomy was reduced compared to healthy subjects.

Quantitative evidence of kinematics and functional differences in different graded trigger fingers

BACKGROUND

Clinical diagnosis and classification of trigger fingers is traditionally based on physical examinations and certain obvious symptoms. However, it might lack quantitative evidence to describe the different graded trigger digits. This study provides quantitative evidence of kinematics and functional differences among different graded trigger fingers based on Froimson's classification.

METHODS

Forty-seven patients with fifty-five trigger fingers and graded twenty-three, eleven, and twenty-one fingers as grades II, III, and IV, respectively. The QuickDASH questionnaire evaluated the subject's self-perception of hand symptoms and functions. The study measured maximal workspace of the fingertip motion and range of motion of the finger joints during an assigned tendon-gliding task using an electromagnetic tracking device. In addition, R(alpha), defined as the ratio range of angular acceleration during finger extension to the range during finger flexion of each joint, quantified the triggering effect.

FINDINGS

The QuickDASH score results show that functional performances have significant differences among three grades (P<0.05). Workspace, range of motion of proximal interphalangeal joint and R(alpha) of proximal interphalangeal and distal interphalangeal joint of trigger fingers also significantly differ among three grades (P<0.05). These findings quantitatively show that trigger fingers in different impairment levels have different kinematics and functional performances.

INTERPRETATION

The results serve as evidence-based knowledge for clinics. The more practical and immediate application of this study would be to facilitate the assessment, design and execution of rehabilitation for patients with trigger fingers.

Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins

Comparisons of joint surface curvature at the base of the thumb have long been made to discern differences among living and fossil primates in functional capabilities of the hand. However, the complex shape of this joint makes it difficult to quantify differences among taxa. The purpose of this study is to determine whether significant differences in curvature exist among selected catarrhine genera and to compare these genera with hominin fossils in trapeziometacarpal curvature. Two 3D approaches are used to quantify curvatures of the trapezial and metacarpal joint surfaces: (1) stereophotogrammetry with nonuniform rational B-spline (NURBS) calculation of joint curvature to compare modern humans with captive chimpanzees and (2) laser scanning with a quadric-based calculation of curvature to compare modern humans and wild-caught Pan, Gorilla, Pongo, and Papio. Both approaches show that Homo has significantly lower curvature of the joint surfaces than does Pan. The second approach shows that Gorilla has significantly more curvature than modern humans, while Pongo overlaps with humans and African apes. The surfaces in Papio are more cylindrical and flatter than in Homo. Australopithecus afarensis resembles African apes more than modern humans in curvatures, whereas the Homo habilis trapezial metacarpal surface is flatter than in all genera except Papio. Neandertals fall at one end of the modern human range of variation, with smaller dorsovolar curvature. Modern human topography appears to be derived relative to great apes and Australopithecus and contributes to the distinctive human morphology that facilitates forceful precision and power gripping, fundamental to human manipulative activities.

A simulating analysis of the effects of increased joint stiffness on muscle loading in a thumb

BACKGROUND

The development of osteoarthritis (OA) in the hand results in increased joint stiffness, which in turn affects the grip strength. The goal of the present study is to theoretically analyze the muscle forces in a thumb in response to the increased joint stiffness.

METHODS

The thumb was modeled as a linkage system consisting of a trapezium, a metacarpal bone, a proximal and a distal phalanx. Nine muscles were included in the model: flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), abductor pollicis longus (APL), flexor pollicis brevis (FPB), abductor pollicis brevis (APB), the transverse head of the adductor pollicis (ADPt), the oblique head of the adductor pollicis (ADPo), and opponens pollicis (OPP). Numerical tests were performed using an inverse dynamic approach. The joints were prescribed to an angular motion at one degree-of-freedom (DOF) each time with all other DOFs of the joints being mechanically constrained, while the muscle forces in response to the joint motions were predicted. The normal joint stiffness was assumed to be 0.05, 0.10, and 0.15 N m/rad for interphalangeal (IP), metacarpophalangeal (MCP), and carpometacarpal (CMC) joint, respectively. The joint stiffness was assumed to increase by 50% and 100%, simulating the biomechanical consequences of OA.

RESULTS

Our simulations indicated that the increase in joint stiffness induced substantial increases in muscle forces, especially in the EPL and FPL muscles in response to IP, MCP, or CMC extension/flexion motions.

CONCLUSIONS

Because the strength of the muscles in the fingers is limited, the muscles will not be able to overcome joint resistance if joint stiffness is increased to its limit due to OA. This may contribute to the reduced range of motion typically seen in OA.

A joint coordinate system proposal for the study of the trapeziometacarpal joint kinematics

The International Society of Biomechanics (ISB) has recommended a standardisation for the motion reporting of almost all human joints. This study proposes an adaptation for the trapeziometacarpal joint. The definition of the segment coordinate system of both trapezium and first metacarpal is based on functional anatomy. The definition of the joint coordinate system (JCS) is guided by the two degrees of freedom of the joint, i.e. flexion-extension about a trapezium axis and abduction-adduction about a first metacarpal axis. The rotations obtained using three methods are compared on the same data: the fixed axes sequence proposed by Cooney et al., the mobile axes sequence proposed by the ISB and our alternative mobile axes sequence. The rotation amplitudes show a difference of 9 degrees in flexion-extension, 2 degrees in abduction-adduction and 13 degrees in internal-external rotation. This study emphasizes the importance of adapting the JCS to the functional anatomy of each particular joint.

Effects of age and gender on the movement workspace of the trapeziometacarpal joint

While researchers have suggested that joint mobility would probably be affected by age and gender, research findings often present discrepancies. Little research has been performed on the factors which effect mobility of the trapeziometacarpal (TMC) joint. The purpose of this study was to address the effects of age and gender on the ranges of motion of the normal TMC joint. Eighty normal subjects divided into four age groups participated in this study. The TMC joint motions were recorded using an electromagnetic tracking system. In order to achieve a maximal range of TMC joint motion which was defined as the maximal workspace, each subject was asked to perform actively maximal circumduction, flexion-extension, and abduction-adduction of the TMC joint. Numerical and statistical methods were used to compute the TMC workspace and to detect significant differences. A workspace-to-length ratio was determined as an index to examine the effects of the age and gender on the joint mobility. The results demonstrated that age and gender had significant influences on the TMC workspace among the groups studied. The understanding of TMC joint mobility under different age and gender conditions is achieved through this study. The findings can be used to report clinical measures in the determination of the extent of impairment of osteoarthritis as well as the outcomes between pre- and post-surgical (or non-surgical) interventions.

Prediction of fingers posture using artificial neural networks

Predicting the hand and fingers posture during grasping tasks is an important issue in the frame of biomechanics. In this paper, a technique based on neural networks is proposed to learn the inverse kinematics mapping between the fingertip 3D position and the corresponding joint angles. Finger movements are obtained by an instrumented glove and are mapped to a multichain model of the hand. From the fingertip desired position, the neural networks allow predicting the corresponding finger joint angles keeping the specific subject coordination patterns. Two sets of movements are considered in this study. The first one, the training set, consisting of free fingers movements is used to construct the mapping between fingertip position and joint angles. The second one, constructed for testing purposes, is composed of a sequence of grasping tasks of everyday-life objects. The maximal mean error between fingertip measured position and fingertip position obtained from simulated joint angles and forward kinematics is 0.99+/-0.76 mm for the training set and 1.49+/-1.62 mm for the test set. Also, the maximal RMS error of joint angles prediction is 2.85 degrees and 5.10 degrees for the training and test sets respectively, while the maximal mean joint angles prediction error is -0.11+/-4.34 degrees and -2.52+/-6.71 degrees for the training and test sets, respectively. Results relative to the learning and generalization capabilities of this architecture are also presented and discussed.

In vivo validation of a realistic kinematic model for the trapezio-metacarpal joint using an optoelectronic system

This article analyzes a realistic kinematic model of the trapezio-metacarpal (TM) joint in the human thumb that involves two non-orthogonal and non-intersecting rotation axes. The estimation of the model parameters, i.e. the position and orientation of the two axes with respect to an anatomical coordinate system, was carried out by processing the motion of nine retroreflective markers, externally attached to the hand surface, surveyed by a video motion capture system. In order to compute the model parameters, prototypical circumduction movements were processed within an evolutionary optimization approach. Quality and reproducibility in assessing the parameters were demonstrated across multiple testing sessions on 10 healthy subjects (both left and right thumbs), involving the complete removal of all markers and then retesting. Maximum errors of less than 5 mm in the axis position and less than 6 degrees in the orientation were found, respectively. The inter-subject mean distance between the two axes was 4.16 and 4.71 mm for right and left TM joints, respectively. The inter-subject mean relative orientation between the two axes was about 106 and 113 degrees for right and left TM joints, respectively. Generalization properties of the model were evaluated quantitatively on opposition movements in terms of distance between measured and predicted marker positions (maximum error less than 5 mm). The performance of the proposed model compared favorably with the one (maximum error in the range of 7-8 mm) obtained by applying a universal joint model (orthogonal and intersecting axes). The ability of in vivo estimating the parameters of the proposed kinematic model represents a significant improvement for the biomechanical analysis of the hand motion.

Joint kinematics after thumb carpometacarpal joint reconstruction: an in vitro comparison of various constructs

PURPOSE

Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint causes pain and limits thumb motion. Different surgical procedures exist to treat thumb CMC OA; however, kinematic analyses of thumb reconstructions are limited. The purpose of this study was to evaluate kinematic changes of the thumb CMC joint as the result of different thumb reconstruction procedures.

METHODS

Fifteen cadaveric forearms were prepared and instrumented with an electromagnetic tracking device to measure the motion of the thumb metacarpal with respect to the trapezium (thumb trapeziometacarpal joint). Kinematics of the intact thumb and the thumb after trapeziectomy under passive motion were recorded. Specimens then had joint reconstruction consisting of either a ligament reconstruction with tendon interposition (LRTI), Weilby arthroplasty, or Thompson arthroplasty. The kinematic data collection analysis was repeated. The radius of joint motion and 3-dimensional (3D) work area were calculated for each surgery and were used for statistical analysis.

RESULTS

The type of surgical treatment significantly affected the joint radius of motion and the 3D work area. The Thompson and LRTI techniques produced a larger joint radius of motion than the other techniques (Weilby technique and total trapezial resection) and was similar to that of the intact joint. The Weilby and LRTI techniques produced a 3D work area similar to those of the intact joint and trapeziectomy and was also larger than that of the Thompson reconstruction.

CONCLUSIONS

Kinematic analysis of the thumb CMC joint is effective in differentiating surgical treatments used for end-stage of OA. Only the LRTI reconstruction produced a joint radius of motion and a 3D work area similar to the those of an intact thumb. Additional research is needed to define the optimal surgical techniques to treat the end-stage OA thumb CMC joint.

Coordination of thumb joints during opposition

Thumb opposition plays a vital role in hand function. Kinematically, thumb opposition results from composite movements from multiple joints moving in multiple directions. The purpose of this study was to examine the coordination of thumb joints during opposition tasks. A total of 15 female subjects with asymptomatic hands were studied. Three-dimensional angular kinematics of the carpometacarpal (CMC), metacarpophalangeal (MCP) and interphalangeal (IP) joints were obtained by a marker-based motion analysis system. Thumb opposition revealed coordination among joints in a specific direction (inter-joint coordination) and among different directions within a joint (intra-joint coordination). In particular, linear couplings existed between the flexion and pronation at the CMC joint, and between the flexion of the CMC joint and flexion of the MCP joint. Principal component analysis showed that only two principal components adequately represented the thumb opposition data of seven movement directions. A term functional degrees of freedom by virtue of principal component analysis was proposed to uncover the extent of movement coordination in functional tasks.

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.

A normative database of thumb circumduction in vivo: center of rotation and range of motion

This article reports a systematic research effort aimed at establishing a normative database of thumb circumduction range of motion (ROM) and related kinematic characteristics in vivo while examining the effects of anthropometry, gender, and direction of rotation. Twenty-eight (14 men, 14 women) anthropometrically diverse participants performed maximum voluntary thumb circumductions as the trajectories of the surface markers placed on their thumb landmarks were recorded by an optoelectronic motion capture system. A globographic representation method was employed to model the measured marker trajectories, determining the center of rotation and central reference axes for thumb circumduction. Thumb ROM was quantified using (a) the joint sinuses expressing the thumb orientation change with respect to the reference axes and (b) cone volumes circumscribed by the thumb at the distal phalangeal, interphalangeal, and metacarpophalangeal levels. Data analyses resulted in statistical summaries of the derived kinematic and ROM measures with significant effects identified and regression equations predicting the cone volumes. Potential applications of this research include ergonomic design of hand-operated controls or devices and evaluation of thumb impairments or disorders.

A kinematic method to calculate the workspace of the trapeziometacarpal joint

The specific aim of this study was to develop a quantitative method and a kinematic method to evaluate the maximal workspace of the trapeziometacarpal (TM) joint. Six fresh-frozen human cadaver hands were disarticulated 4 cm proximal to the wrist joint and used in this experiment. The three-dimensional motion data of the TM joint was collected by an electromagnetic tracking device at 30 Hz. The workspace was reconstructed according to a complete set of motion data included circumduction, flexion-extension and abduction-adduction. A spherical fitting technique was used to obtain a sphere encompassing all the motion trajectories and estimating the centre of the sphere. The surface area of the maximal TM workspace, located on the one part of the sphere surface, was calculated by surface integration. The interclass correlation coefficient values for the reliability estimation of the repeated measurements of the radius and surface area of all specimens were 0.91 and 0.98 respectively. The mean coefficients of variance of the measured radius and the surface area were 2.04 per cent and 3.65 per cent respectively. The results also showed that using a spherical model to calculate the maximal workspace as an index for assessing TM joint impairment is practical.

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.

Comparative in vivo kinematic analysis of normal and osteoarthritic trapeziometacarpal joints

PURPOSE

Although extensive studies have been conducted on the trapeziometacarpal (TM) joint, there have been few quantitative studies on its in vivo kinematics. The purposes of this study are to quantitatively evaluate the in vivo kinematics of the TM joint with a fluoroscope and to determine the difference between normal and arthritic joints.

METHODS

Fourteen healthy hands and 8 symptomatic hands with idiopathic osteoarthritis were included in this study. The healthy subjects were divided into 2 groups: a younger control group aged under 50 years (n = 7) and an older control group aged 51 years or older (n = 7). Radial and dorsal translations of the center of rotation (COR) were quantified in active abduction-adduction and active flexion-extension. In addition, volar tilt of the metacarpal facet of the TM joint was measured on the lateral view.

RESULTS

The CORs in flexion-extension translated more dorsally in the patient group than those in the 2 control groups whereas the CORs in abduction-adduction did not differ significantly between the patient group and the control groups. There was no significant difference in the translation of COR between the 2 control groups in either abduction-adduction or flexion-extension. The average volar tilt in the patients with osteoarthritis increased significantly compared with those in the control groups.

CONCLUSIONS

Dorsal translation of the COR in flexion-extension but not radial translation in abduction-adduction is the kinematic characteristic of the arthritic TM joint. We suggest that increased volar tilt is a predisposition to the dorsal translation of COR in the patient group.

Feasibility of using surface markers for assessing motion of the thumb trapeziometacarpal joint

OBJECTIVE

The purposes of the present study were to investigate the feasibility of using a skin sensor to represent the first and third metacarpal bone, to verify that there was no significant relative motion between the skin of the third metacarpal bone and trapezium bony segment and to measure thumb metacarpal motion with respect to the hand (third metacarpal).

DESIGN

Eight hands from fresh-frozen human cadavers were disarticulated 4 cm proximal to the wrist joint and used in this experiment.

BACKGROUND

Recently, magnetic-tracking systems have been developed for the measurement of joint kinematics. Based on the concept of the three-dimensional space within which the thumb metacarpal bone can move, the current study proposes a 3D method for evaluating the relationship between the skin and bony segment.

METHODS

An electromagnetic tracking system was used to provide quantitative measurement and evaluation of the relationship between the skin and bony segment while moving the trapeziometacarpal joint.

RESULTS

The adjusted coefficient of multiple determination, R(a)(2), values of the kinematic waveforms between the sensors were larger than 0.84. The angular differences and displacements of the center of sensors between the skin and bony sensors were less than 4.9 degrees and 2.8 mm.

CONCLUSION

These data revealed that the similarities of the two sensors throughout the motion cycle were high. The differences between the two sensors were also within the clinically allowable range of +/-5 degrees. Therefore, it is feasible to collect motions of the first metacarpal by attaching the skin sensors at the metacarpal head to measure the bony segment.

The carpometacarpal joint of the thumb: stability, deformity, and therapeutic intervention

The carpometacarpal (CMC) of the thumb is a saddle joint that permits a wide range of motion and is largely responsible for the characteristic dexterity of human prehension. This joint, located at the very base of the thumb, is subject to large physical stresses throughout life. Osteoarthritis (posttraumatic or idiopathic), rheumatoid arthritis, and postmenopausal laxity of the capsular ligaments can predispose structural instability and impairment of this important joint. The instability is characterized by varying and often progressive dislocation of the joint surfaces, resulting in a displaced axis of rotation and abnormal actions of thumb muscles. The main consequence of the instability is most often pain and weakness, most notably during pinch and grasping actions. This paper is conceptually divided into 2 sections. The first section describes the anatomic structures that maintain stability in the normal CMC joint of the thumb and how disease or trauma can cause instability and ultimate deformity. The second section describes both nonsurgical and surgical interventions that are most often used to treat an unstable CMC joint. This paper is intended primarily as an overview for the physical therapist who does not specialize in the treatment of the hand, although desires basic information on this important topic.

Influence of metacarpophalangeal joint position on basal joint-loading in the thumb

BACKGROUND

Conventional wisdom holds that hyperextension of the metacarpophalangeal joint of the thumb is secondary to degenerative subluxation of the trapeziometacarpal joint as occurs in osteoarthritis. We propose that a hypermobile metacarpophalangeal joint may have a causative role in the development of primary osteoarthritis at the base of the thumb by concentrating forces on the palmar aspect of the trapeziometacarpal joint.

METHODS

Twenty fresh-frozen cadaveric forearm specimens were obtained post mortem from donors with no history of connective-tissue disease. Each specimen was categorized by its passive range of metacarpophalangeal joint motion. Testing was conducted with Fuji ultra-low-pressure-sensitive film while the hand was in the lateral-pinch mode with the metacarpophalangeal joint in each of the following positions: unrestrained, pinned in neutral, pinned in 30 degrees of flexion, and pinned in maximal hyperextension. Quantitative analysis of the trapezial contact surface at each of the metacarpophalangeal joint positions was performed, and the center of pressure was determined. Each specimen was then classified according to the extent of arthritic disease (nonarthritic, moderately arthritic, or affected by end-stage arthritis).

RESULTS

In specimens affected by end-stage osteoarthritis, the center of pressure on the trapeziometacarpal joint moved dorsally by 56.8% of the length of the trapezial surface with metacarpophalangeal joint flexions of 30 degrees (p < 0.01), whereas the corresponding values were 28.2% and 40.9% in the hyperextended and neutral metacarpophalangeal joint positions, respectively. In specimens with moderate osteoarthritis, 30 degrees of metacarpophalangeal joint flexion also produced the most dorsal trapeziometacarpal center of pressure (44.8%); however, this center of pressure was not significantly different from the centers of pressure at the other metacarpophalangeal joint positions. In nonarthritic specimens, the center of pressure was again significantly more dorsal with metacarpophalangeal joint flexion of 30 degrees than it was at the other positions (p < 0.01).

CONCLUSION

Metacarpophalangeal joint flexion effectively unloaded the most palmar surfaces of the trapeziometacarpal joint regardless of the presence or severity of arthritic disease in this joint.

[In vivo cinematic study of the trapezometacarpal joint]

The aim of this study was to assess the trapeziometacarpal joint kinematics from in vivo measurements, both quantifying the ranges of motion and suggesting a suitable joint model. A motion analysis system has been used to collect the spatial trajectories of markers, glued respectively on the thumb and on the hand's palm. A rigorous protocol was set up to make sure of the trapezoid bone's fixity relatively to the hand, and then to be able to characterize the movement of the first metacarpus with respect to the trapezium. The ranges of motion have been measured on two distinct movements: circumduction and flexion-extension, and different types of joints: healthy, pathological and prosthetic. The joint axes of rotation (for flexion-extension and ante-retroposition movements) have been determined on healthy subjects. The computation of rotation amplitudes and positions of joint axes was based upon the finite helical axis concept, which degenerates into finite rotation axis when translations can be neglected. Both the measurement protocol and the calculation method have been validated by comparing the computed joint center with that measured on a radiography, in the case of a spherical prosthesis. The ranges of motion obtained on the healthy subject series were consistent with values published by other authors. Comparisons have been realized between these reference joints and different cases: arthrodesis, arthrosis and prosthesis. The determination of rotation axes of a normal joint has lead to a generalized cardan joint, i.e. two non perpendicular converging rotation axes.

[Total trapezometacarpal prostheses: concepts and classification study]

This paper is an attempt to classify the different types of trapezio-metacarpal total prostheses according to their bio-mechanical principle and to compare the bio-mechanics of these prostheses to that of the normal trapeziometacarpal joint. The trapeziometacarpal joint has two approximate centres of rotation (one in the proximal metacarpal, one in the trapezium), two degrees of freedom and two arc of mobility about 70 degrees. The mechanical model of the trapeziometacarpal joint is a universal-joint called "cardan" with three constraint forces (one axial compression force, and two shear forces, radial and posterior) and one constraint moment around the longitudinal axis. The trapeziometacarpal prostheses may be classified in two main categories: the most frequently used are the "ball and socket" prostheses. Several prostheses, including the surface replacement prostheses have the mechanical characteristics of an universal joint (cardan). Ball and socket prostheses have one centre of rotation, 3 degrees of freedom, three constraint forces in three directions and no constraint moment when "cardan" or surface prostheses have two centres of rotation and 2 degrees of freedom; three constraint forces and one constraint moment. Trapeziometacarpal prostheses may also be classified according to their arc of mobility, or according to their mode of primary fixation (cemented, non-cemented), "press-fit", expansion and to their secondary fixation (hydroxyapatite).

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.

Biomechanical analysis of the trapeziometacarpal joint after surface replacement arthroplasty

A biomechanical analysis of the trapeziometacarpal joint was performed in 7 fresh-frozen normal human cadaveric hands to compare the kinematics of the trapeziometacarpal joint before and after surface total joint replacement. Using a 3-space magnetic Isotrak system (Polhemus, Colchester, VT), which provides a 3-dimensional analysis of motion of joints as well as translation, we found that kinematics and stability of the trapeziometacarpal joint could be duplicated by joint surface replacement arthroplasty provided that normal ligament tensions were present.

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

Degenerative arthritis of the trapeziometacarpal joint is commonly associated with ligament laxity and joint subluxation. Specifically, key pinch in an affected joint often results in dorsoradial joint subluxation. This study examined the role the 4 ligaments of the trapeziometacarpal joint play in preventing dorsoradial subluxation. Six fresh-frozen cadaver hands were dissected of all soft tissue to expose the joint capsule and ligaments of the trapeziometacarpal joint. Serial random sectioning of the intermetacarpal ligament, anterior oblique ligament, palmar oblique ligament, and dorsoradial collateral ligament (RCL) was performed. Dorsoradial displacement of the metacarpal shaft in relation to the trapezium was measured using a linear variable dimension transformer. In all 6 specimens, sectioning of the RCL resulted in the greatest dorsoradial subluxation of the metacarpal. The mean displacement due to sectioning of the RCL was 1.4 mm, compared with 0.08 mm for the intermetacarpal ligament, 0.06 mm for the anterior oblique ligament, and 0.2 mm for the palmar oblique ligament. The importance of the RCL in preventing dorsoradial subluxation may have clinical significance. This study suggests that repairing or reconstructing the RCL during ligament reconstruction of the trapeziometacarpal joint should be considered.