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

Kinematic Investigation of Healthy, Arthritic, and Postsurgery Thumbs: Is the Metacarpophalangeal Joint the Gateway to Carpometacarpal Arthritis?

The thumb carpometacarpal (CMC) joint is one of the most likely joints to develop osteoarthritis (OA). If conservative treatments fail to alleviate symptoms, surgery may be pursued. Kinematic outcomes of CMC surgery techniques have been described, but current tools have limitations in capturing motion abilities. The goals of this study were (1) develop a new and robust set of kinematic outcome measures, and apply them to (2) a cohort of younger and older control individuals without CMC OA to determine age and sex-related changes, and (3) a cohort of participants with CMC OA before, 3 months, and 6 months after undergoing thumb ligament reconstruction with tendon interposition surgery to detect the impacts of surgery. 52 (26 males, 26 females) control and 18 (3 males, 15 females) surgical participants were tested. Kinematics were investigated using motion capture by mapping the three-dimensional motion space of the whole thumb, and two-dimensional motion boundaries of the metacarpal (MC) and proximal phalange (PP). Visual analog pain score was recorded. Older control participants had shifted regions of motion compared to younger participants (p ≤ 0.027), suggesting asymptomatic CMC wear. Control females had 31% more metacarpophalangeal (MCP) motion than control males (p = 0.013), which could alter loading paths through the CMC joint and increase OA risk. Pain at 6 months postsurgery was 72% less than presurgery (p < 0.001), but motion abilities were 20-28% less than presurgery (p ≤ 0.074) and 24-40% less than control participants (p ≤ 0.066). These techniques have the possibility of identifying presymptomatic motion changes, including those at the metacarpophalangeal joint in CMC OA progression.

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.

De Quervain tendinitis after total trapeziometacarpal joint arthroplasty: Biomechanical evaluation of tendon excursion in the first extensor tendon compartment

De Quervain's tenosynovitis is the most common complication after total trapeziometacarpal joint replacement. Etiology is unclear. Implantation of a ball-in-socket implant changes the biomechanics of the normal trapeziometacarpal saddle joint and increases its range of motion. The present study demonstrates that this procedure also significantly increases excursion of the abductor pollicis longus and extensor pollicis brevis tendons during thumb flexion-extension, and not during thumb abduction-adduction. Increased tendon gliding under the retinaculum of the first extensor tendon compartment could predispose to the development frictional tenosynovitis and play a role in the development of de Quervain's syndrome after total trapeziometacarpal joint replacement. LEVEL OF EVIDENCE: Not applicable (laboratory study).

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.

Complex motions embedded in a hand exercise regimen - effects on thumb function in participants with carpometacarpal osteoarthritis: A pilot study

Objective

The goal of this pilot study was to identify changes associated with completion of a unique six-week hand exercise program in persons with carpometacarpal osteoarthritis.

Methods

Twenty-four individuals, aged 55-80, with doctor-diagnosed carpometacarpal osteoarthritis participated in the study. Movement data from standard clinical motions and complex multi-planar motions were obtained using a motion capture system at three-time points: an initial visit, after two weeks of hand exercises, and after completion of the six-week exercise program.

Results

This exercise program produced trends of improvement in complex multi-planar motions. Specifically, joint angle changes were seen during opposition and the formation of an "okay sign" that was included as part of the exercise program.

Conclusion

Through the use of motion capture, changes were identified in thumb joint function after exercise. Specifically, motions associated with the more complex multi-planar tasks showed changes in individual joint contributions following the six-week exercise intervention. The results suggest that further exploration of this exercise program, particularly the inclusion of complex multi-planar tasks during osteoarthritis treatment and associated evaluations, should be considered in future clinical studies.

Dorsal Subluxation of the First Metacarpal During Thumb Flexion is an Indicator of Carpometacarpal Osteoarthritis Progression

BACKGROUND

Measurable changes in patients with progression of thumb carpometacarpal (CMC) osteoarthritis (OA) include joint space narrowing, osteophyte formation, subluxation, and adjacent-tissue changes. Subluxation, an indication of mechanical instability, is postulated as an early biomechanical indicator of progressing CMC OA. Various radiographic views and hand postures have been proposed to best assess CMC subluxation, but 3D measurements derived from CT images serve as the optimal metric. However, we do not know which thumb pose yields subluxation that most indicates OA progression.

QUESTIONS/PURPOSES

Using osteophyte volume as a quantitative measure of OA progression, we asked: (1) Does dorsal subluxation vary by thumb pose, time, and disease severity in patients with thumb CMC OA? (2) In which thumb pose(s) does dorsal subluxation most differentiate patients with stable CMC OA from those with progressing CMC OA? (3) In those poses, what values of dorsal subluxation indicate a high likelihood of CMC OA progression?

METHODS

Between 2011 and 2014, 743 patients were seen at our institutions for trapeziometacarpal pain. We considered individuals who were between the ages of 45 and 75 years, had tenderness to palpation or a positive grind test result, and had modified Eaton Stage 0 or 1 radiographic thumb CMC OA as potentially eligible for enrollment. Based on these criteria, 109 patients were eligible. Of the eligible patients, 19 were excluded because of a lack of interest in study participation, and another four were lost before the minimum study follow-up or had incomplete datasets, leaving 86 (43 female patients with a mean age of 53 ± 6 years and 43 male patients with a mean age of 60 ± 7 years) patients for analysis. Twenty-five asymptomatic participants (controls) aged 45 to 75 years were also prospectively recruited to participate in this study. Inclusion criteria for controls included an absence of thumb pain and no evidence of CMC OA during clinical examination. Of the 25 recruited controls, three were lost to follow-up, leaving 22 for analysis (13 female patients with a mean age of 55 ± 7 years and nine male patients with a mean age of 58 ± 9 years). Over the 6-year study period, CT images were acquired of patients and controls in 11 thumb poses: neutral, adduction, abduction, flexion, extension, grasp, jar, pinch, grasp loaded, jar loaded, and pinch loaded. CT images were acquired at enrollment (Year 0) and Years 1.5, 3, 4.5, and 6 for patients and at Years 0 and 6 for controls. From the CT images, bone models of the first metacarpal (MC1) and trapezium were segmented, and coordinate systems were calculated from their CMC articular surfaces. The volar-dorsal location of the MC1 relative to the trapezium was computed and normalized for bone size. Patients were categorized into stable OA and progressing OA subgroups based on trapezial osteophyte volume. MC1 volar-dorsal location was analyzed by thumb pose, time, and disease severity using linear mixed-effects models. Data are reported as the mean and 95% confidence interval. Differences in volar-dorsal location at enrollment and rate of migration during the study were analyzed for each thumb pose by group (control, stable OA, and progressing OA). A receiver operating characteristic curve analysis of MC1 location was used to identify thumb poses that differentiated patients whose OA was stable from those whose OA was progressing. The Youden J statistic was used to determine optimized cutoff values of subluxation from those poses to be tested as indicators of OA progression. Sensitivity, specificity, negative predictive values, and positive predictive values were calculated to assess the performance of pose-specific cutoff values of MC1 locations as indicators of progressing OA.

RESULTS

In flexion, the MC1 locations were volar to the joint center in patients with stable OA (mean -6.2% [95% CI -8.8% to -3.6%]) and controls (mean -6.1% [95% CI -8.9% to -3.2%]), while patients with progressing OA exhibited dorsal subluxation (mean 5.0% [95% CI 1.3% to 8.6%]; p < 0.001). The pose associated with the most rapid MC1 dorsal subluxation in the progressing OA group was thumb flexion (mean 3.2% [95% CI 2.5% to 3.9%] increase per year). In contrast, the MC1 migrated dorsally much slower in the stable OA group (p < 0.001), at only a mean of 0.1% (95% CI -0.4% to 0.6%) per year. A cutoff value of 1.5% for the volar MC1 position during flexion at enrollment (C-statistic: 0.70) was a moderate indicator of OA progression, with a high positive predictive value (0.80) but low negative predictive value (0.54). Positive and negative predictive values of subluxation rate in flexion (2.1% per year) were high (0.81 and 0.81, respectively). The metric that most indicated a high likelihood of OA progression (sensitivity 0.96, negative predictive value 0.89) was a dual cutoff that combined the subluxation rate in flexion (2.1% per year) with that of loaded pinch (1.2% per year).

CONCLUSION

In the thumb flexion pose, only the progressing OA group exhibited MC1 dorsal subluxation. The MC1 location cutoff value for progression in flexion was 1.5% volar to the trapezium , which suggests that dorsal subluxation of any amount in this pose indicates a high likelihood of thumb CMC OA progression. However, volar MC1 location in flexion alone was not sufficient to rule out progression. The availability of longitudinal data improved our ability to identify patients whose disease will likely remain stable. In patients whose MC1 location during flexion changed < 2.1% per year and whose MC1 location during pinch loading changed < 1.2% per year, the confidence that their disease would remain stable throughout the 6-year study period was very high. These cutoff rates were a lower limit, and any patients whose dorsal subluxation advanced faster than 2% to 1% per year in their respective hand poses, were highly likely to experience progressive disease.

CLINICAL RELEVANCE

Our findings suggest that in patients with early signs of CMC OA, nonoperative interventions aimed to reduce further dorsal subluxation or operative treatments that spare the trapezium and limit subluxation may be effective. It remains to be determined whether our subluxation metrics can be rigorously computed from more widely available technologies, such as plain radiography or ultrasound.

The biomechanics of osteoarthritis in the hand: Implications and prospects for hand therapy

BACKGROUND

The unique anatomy of the human hand makes it possible to carefully manipulate tools, powerfully grasp objects, and even throw items with precision. These apparent contradictory functions of the hand, high mobility for manual dexterity vs high stability during forceful grasping, imply that daily activities impose a high strain on a relatively instable joint. This makes the hand susceptible to joint disorders such as osteoarthritis. Both systemic (eg, genetics, hormones) and mechanical factors (eg, joint loading) are important in the development of osteoarthritis, but the precise pathomechanism remains largely unknown. This paper focuses on the biomechanical factors in the disease process and how hand therapists can use this knowledge to improve treatment and research.

CONCLUSION

Multiple factors are involved in the onset and development of osteoarthritis in the hand. Comprehension of the biomechanics helps clinicians establish best practices for orthotics intervention, exercise, and joint protection programs even in de absence of clear evidence-based guidelines. The effect and reach of hand therapy for OA patients can be expanded substantially when intervention parameters are optimized and barriers to early referrals, access reimbursement, and adherence are addressed. Close and early collaboration between hand therapists and primary care, women's health, rheumatology, and hand surgery providers upon diagnosis, and with hand surgeons pre and postoperatively, combined with advances in the supporting science and strategies to enhance adherence, appear to be a promising way forward.

Optimal Center of Rotation for Ball-And-Socket Thumb Carpometacarpal Arthroplasty Identified Using Three-Dimensional Kinematic Analysis: A Pilot Study

Total joint arthroplasty is one of the surgical option for thumb carpometacarpal (CMC) joint arthritis, however the optimal position the center of rotation (COR) has not been quantified. The purpose of this study is to identify ideal ball-and-socket thumb carpometacarpal joint implants and the optimal position of the COR. We obtained eight right thumb computed tomography images each from ten healthy men, comprising four images each of thumbs at various angles of flexion-extension and abduction-adduction. We reconstructed 3D bone models on 3D CAD, created virtual ball-and-socket implants with three variables (neck offset, implant height, neck rotation), and found the optimal COR where the position change in the COR was smallest across various thumb positions. When the offset was 4.5 mm, neck rotation angle was 130.6° from the radial side to the palmar side of the first metacarpal, and implant height from the distal end of the metacarpal was 43.6 mm, we could restore almost normal kinematics. This study could serve as a reference for implant development and surgical technique guidelines.

Trapeziometacarpal joint mobility in gibbons (fam. Hylobatidae) and rhesus macaques (Macaca mulatta)

OBJECTIVES

The purpose of this study is to investigate the differences in 3D kinematics of the trapeziometacarpal (TMC) joint between gibbons (fam. Hylobatidae) and macaques (Macaca mulatta), two non-human primate groups with a distinct locomotor behavior. Gibbons are highly arboreal species, while macaques are quadrupeds. Here, we investigate the mobility and structural constraints of the TMC joint in both these primates and evaluate the hypothesis that differences in locomotor mode are reflected in joint structure and function.

MATERIALS AND METHODS

We have developed an innovative software suite allowing for the quantification of in situ 3D kinematics based on medical imaging of the primate TMC joint using a unique sample of eight gibbons and seven macaques. These analyses are further supported by detailed dissection of the surrounding ligaments.

RESULTS

The data demonstrate distinct differences in TMC joint mobility between gibbons and macaques, with wide ranges of motion in the gibbon TMC joint and restricted movement in macaques. Furthermore, the dissections show little dissimilarity in ligament anatomy that could be associated with the differences in TMC joint capabilities.

CONCLUSION

We conclude that gibbons possess a highly mobile TMC joint and the ball-and-socket morphology allows for large ranges of motion. This type of morphology, however, does not offer much inherent stabilization. Lack of structural joint reinforcement suggests that gibbons may have difficulty in performing any type of power grasp with high loads. Macaques, on the other hand, are shown to have a considerably reinforced TMC joint, which is likely related to the habitual loading of the thumb during locomotion.

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.

Update on Thumb Basal Joint Arthritis Surgery

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Comprehend anatomy and biomechanics of the normal and arthritic trapeziometacarpal joint. 2. Evaluate best evidence for diagnosis and for operative and nonoperative treatment of thumb osteoarthritis. 3. Understand treatment pitfalls of basilar joint arthritis and complication avoidance.

SUMMARY

Articular and ligamentous anatomy of the trapeziometacarpal joint enables complex motions. Disability from arthritis, common at the trapeziometacarpal joint, is debilitating. Furthering the understanding of how trapeziometacarpal arthritis develops can improve treatment. The authors provide current best evidence for diagnosis and treatment of basilar joint arthritis. Pitfalls in treatment are discussed.

Stress distribution in the bonobo (Pan paniscus) trapeziometacarpal joint during grasping

The primate thumb plays a central role in grasping and the basal trapeziometacarpal (TMC) joint is critical to its function. The TMC joint morphology varies across primates, yet little is known about form-function interaction within in the TMC joint. The purpose of this study was to investigate how stress distributions within the joint differ between five grasping types commonly employed by bonobos (Pan paniscus). Five cadaveric bonobo forearms were CT scanned in five standardized positions of the hand as a basis for the generation of parametric finite element models to compare grasps. We have developed a finite element analysis (FEA) approach to investigate stress distribution patterns in the TMC joint associated with each grasp type. We hypothesized that the simulated stress distributions for each position would correspond with the patterns expected from a saddle-shaped joint. However, we also expected differences in stress patterns arising from instraspecific variations in morphology. The models showed a high agreement between simulated and expected stress patterns for each of the five grasps (86% of successful simulations), while partially (52%) and fully (14%) diverging patterns were also encountered. We identified individual variations of key morphological features in the bonobo TMC joint that account for the diverging stress patterns and emphasized the effect of interindividual morphological variation on joint functioning. This study gives unprecedented insight in the form-function interactions in the TMC joint of the bonobo and provides an innovative FEA approach to modelling intra-articular stress distributions, a valuable tool for the study of the primate thumb biomechanics.

Anatomy and biomechanics of healthy and arthritic trapeziometacarpal joints

Understanding the biomechanics of the trapeziometacarpal (TMC) or first carpometacarpal (CMC1) joint, the pathophysiology of basal thumb arthritis, the design and performance of surgical procedures require a solid anatomical basis. This review of literature summarizes the most recent data on the descriptive, functional, and comparative anatomy of healthy and arthritic TMC joints.

Gyroscope Sensor Based In Vivo Finger Axes of Rotation Identification Using Screw Displacement

This paper presents a low-cost, efficient, and portable in vivo method for identifying axes of rotation of the proximal interphalangeal and distal interphalangeal joints in an index finger. The approach is associated with the screw displacement representation of rigid body motion. Using the matrix exponential method, a detailed derivation of general spatial displacement of a rigid body in the form of screw displacement including the Rodrigues' formulae for rotation is presented. Then, based on a gyroscope sensor, a test framework for determining axes of rotation of finger joints is established, and experiments on finding the directions of joint axes of the PIP and DIP joints are conducted. The results obtained highly agree with those presented in literature through traditional but complex methods.

The effect of orthoses on the kinematics of the trapeziometacarpal, scaphotrapeziotrapezoidal, and radioscaphoid joints

The in vivo effect of four different types of thumb and thumb-wrist orthoses on the three-dimensional kinematics of the trapeziometacarpal (TMC), scaphotrapeziotrapezoidal (STT) and radioscaphoid joints was quantified using computed tomography (CT). Eighteen healthy female volunteers were recruited. The dominant hand of each subject was scanned in four thumb and wrist positions, each in three conditions: without orthosis, with a thumb orthosis (Push Ortho and immediate fitting, IMF) and with a thumb-wrist orthosis (Ligaflex Manu and IMF). CT images were analyzed and rotations relative to the more proximal bone were expressed in a joint-specific coordinate system. Without orthosis, the largest STT rotations were observed during radioulnar deviation of the wrist and the STT range of motion (ROM) was significantly lower during wrist flexion-extension. All tested orthoses caused a significant reduction of the ROM at each joint compared to free motion. Significant differences in movement reduction were observed between prefabricated and IMF orthoses.The IMF thumb-wrist outperformed the Ligaflex Manu in terms of immobilization of the radioscaphoid joint. In addition, the IMF thumb orthosis immobilized the TMC joint significantly better during thumb abduction and adduction than the Push Ortho. We found that different types of thumb and thumb-wrist orthotics are effective in reducing joint mobility. While this reduction tends to be higher using IMF compared to prefabricated orthoses, this effect is only significant for the radioscaphoid and TMC joint. The finding that thumb movements do not induce large STT rotations suggests that the thumb does not need to be immobilized in case of isolated STT osteoarthritis.

Radial and palmar active range of motion measurement: reliability of six methods in healthy adults

The current study aims to assess the reliability of 6 range-of-motion measurement methods for the thumb carpometacarpal joint: Pollexograph-thumb, Pollexograph-metacarpal, radius-metacarpal goniometry, intermetacarpal goniometry, intermetacarpal distance, and thumb-distal-interphalangeal distance. A senior hand surgeon, an experienced resident, and a less experienced research fellow evaluated the dominant hands of 29 healthy subjects. All 6 methods were performed for radial adduction, radial abduction, and palmar abduction, but only distance methods were measured for palmar adduction. Intrarater and interrater reliability were computed using intraclass correlation coefficient, standard error of measurement, and smallest detectable difference. Pollexograph-thumb method showed the highest active range of movement for radial adduction (12°) and abduction (71°), while all the other angular methods resulted in approximately 20° for radial adduction and 50° for radial abduction. Distance methods showed comparable mean results for radial and palmar range of motion (adduction/abduction): intermetacarpal distance (50 mm/60 mm) and thumb-distal-interphalangeal distance (50 mm/120 mm). Interrater reliability using the results of the intraclass correlation coefficient demonstrates that Pollexograph-thumb and Pollexograph-metacarpal showed excellent reliability for radial adduction and abduction, whereas Pollexograph-thumb method revealed the best reliability for palmar abduction. Moreover, thumb-distal-interphalangeal distance also showed excellent reliability for radial and palmar abduction. Conventional goniometry showed a large variety of reliability results, ranging from poor to excellent. No clinical benefit can be derived from assessing the palmar adduction. We found that the Pollexograph-thumb showed excellent reliability results throughout all measurements. Thumb-distal-interphalangeal-joint distance is especially valuable for assessing radial and palmar abduction.

Trapeziometacarpal total joint arthroplasty: The effect of capsular release on range of motion

It has been suggested that trapeziometacarpal total joint arthroplasty be combined with complete release of the joint capsule to prevent ligament tethering and implant dislocation. Our goal was to evaluate the consequences of capsular release on range of motion. Trapeziometacarpal joint motion was measured with a 3D motion tracking system in seven fresh frozen human cadaver hands before and after capsular release and total joint arthroplasty with subsequently longer neck lengths. Relative to the native trapeziometacarpal joint with intact joint capsule, mean flexion-extension was significantly increased after the arthroplasty with released capsule and lengthening up to 6 mm. Mean abduction-adduction did not increase significantly. Total joint replacement combined with capsular release increases the trapeziometacarpal joint's range of motion, but not beyond the limits of most trapeziometacarpal implant designs. Lengthening of the implant neck progressively decreases the excess motion.

Maximum Palmar Abduction Angle of the Trapeziometacarpal Joint in Healthy Subjects Can Be Evaluated Accurately Using a Radiograph-Based Measurement Technique

In carpal tunnel syndrome, the abductor pollicis brevis, which is the primary muscle for the palmar abduction of the thumb, is almost inevitably impaired. The active palmar abduction of the thumb may be a better indicator of thumb disability. The authors aimed to establish a simple and accurate method to measure the angle of active palmar abduction of the thumb and to determine the maximum angle values in healthy women. Twenty-five women 20 to 21 years old with no disorder of the hand participated in this study voluntarily. Three measurement methods were tested. The first method was designed according to the Japanese Orthopaedic Association and the second method was designed according to the American Society of Hand Therapists; both use photographs to perform measurement calculations. In the third method, 2 orthopedic surgeons measured the same angle as that described in the second method on hand radiographs. Intra- and interobserver reliability were assessed for each method and described as interclass correlation coefficients. The first and third methods had strong inter- and intraobserver reliability. The second method had strong intraobserver reliability but medium interobserver reliability. The measurement obtained with the first method was significantly different from the values obtained by the second and third methods (almost double). Therefore, the authors regarded the third method as the most appropriate approach for measuring active palmar abduction of the thumb, which, in healthy individuals, yielded maximum values of 45.3°±6.4° and 44°±7° for the left hand and the right hand, respectively. [Orthopedics. 2020; 43(2):e95-e101.].

Complex thumb motions and their potential clinical value in identifying early changes in function

BACKGROUND

Early diagnosis and treatment of osteoarthritis of the thumb allows for early interventions that may mitigate osteoarthritis progression and decrease severity later in life. Early identification of motion changes is limited by the clinical reliance on single planar measurements using goniometry. Multi-planar measurements using motion capture can provide insights into joint function and pathophysiology that cannot be obtained from single-plane goniometry measurements. Thus, the goals of this research were 1) to determine differences in thumb motions across three groups of participants (young healthy (n = 23), older healthy (n = 11), and those with carpometacarpal osteoarthritis (n = 24)) and 2) to determine if multi-planar motions provided additional movement information in comparison to standard planar measures.

METHODS

In this study, a motion capture system was used to collect standard clinical ranges of motion and complex multi-planar tasks. Differences in motion patterns due to aging and osteoarthritis were identified. Motions tested included palmar adduction-abduction, radial adduction-abduction, metacarpophalangeal flexion-extension, interphalangeal flexion-extension, functional adduction-abduction, opposition, and circumduction.

FINDINGS

Results indicated that motion capture was capable of detecting changes in carpometacarpal mobility that were not detected using standard approaches. Our results suggested that use of multi-planar measurements have the potential to identify changes that are indicators of early stages of osteoarthritis.

INTERPRETATION

Early indicators are clinically useful as they will enhance patient treatment by permitting the application of treatment approaches sooner, potentially leading to reduced overall functional deficits.

Scoring of radiographic cortical healing with the radiographic humerus union measurement predicts union in humeral shaft fractures

PURPOSE

The purpose of this study is to determine if the radiographic humerus union measurement (RHUM) is predictive of union in humeral shaft fractures treated nonoperatively.

METHODS

All patients with long bone fracture nonunion presenting to a single surgeon were enrolled in a prospective registry. This registry was queried to identify patients with humeral shaft fractures treated nonoperatively and developed nonunion. The nonunion cohort was matched to a three to one gender- and age-matched control group that were treated nonoperatively for a humeral shaft fracture and achieved union. Two fellowship-trained orthopedic traumatologists blinded to eventual union scored radiographs obtained 12 weeks after injury using the RHUM. A binomial logistic regression determined the effect of the RHUM on the likelihood of developing union.

RESULTS

Nine patients with humeral shaft fractures treated nonoperatively with radiographs 12 weeks after injury that developed nonunion were identified. These patients were matched to 27 controls. Logistic regression demonstrated the RHUM was a significant predictor of healing 12 weeks after humeral shaft fracture treated nonoperatively (p = 0.014, odds ratio 9.434, 95% CI for OR 1.586-56.098). All patients with RHUM below 7 went on to nonunion. All patients with RHUM above 8 healed. Three of seven patients (43%) with RHUM of 7 or 8 healed.

CONCLUSION

The RHUM demonstrated an increased likelihood of achieving union 12 weeks after injury. Orthopedic surgeons can counsel patients that fractures with RHUM scores of 6 or below are in danger of developing nonunion and can target interventions appropriately.

The effect of cup orientation on stability of trapeziometacarpal total joint arthroplasty: a biomechanical cadaver study

It has been suggested that the cup of a trapeziometacarpal total joint replacement should be positioned parallel with the proximal articular surface of the trapezium to align it with the centre of motion. This would diminish the chance of dislocation. The goal of this study was to test this idea biomechanically. A linked trapeziometacarpal prosthesis was implanted in seven cadaver hands and combined with three-dimensional printed trapezium cups in 17 different orientations. For every combination, stability of the prosthesis was assessed through its entire passive range of motion. Dorsal inclination of the cup relative to the proximal articular surface increased the risk of dislocation with thumb flexion and opposition. The risk of dislocation was also increased with lateral or medial inclination of the cup exceeding 20°. Our results demonstrate that cup orientation is an important factor in prosthetic joint stability. Cup placement parallel to the proximal articular surface is ideal.

Osteophyte growth in early thumb carpometacarpal osteoarthritis

OBJECTIVE

Osteophyte formation is a critical part of the degeneration of a joint with osteoarthritis (OA). While often qualitatively described, few studies have succeeded in quantifying osteophyte growth over time. Using computed tomography (CT) image data from a longitudinal, observational study of thumb carpometacarpal (CMC) OA, our aim was to quantify osteophyte growth volume and location over a three-year period in men and women.

METHOD

Ninety patients with early thumb OA were recruited and assessed at baseline, 1.5 years, and 3 years with CT imaging. Osteophyte volume and location on the trapezium and first metacarpal were determined using a library of 46 healthy subjects as a nonarthritic reference database.

RESULTS

There was a significant increase in osteophyte volume for women and men over the three-year follow-up in the trapezium (86.8 mm³-120.5 mm³ and 165.1 mm³-235.3 mm³, means respectively) and in the proximal metacarpal (63 mm³-80.4 mm³, and 115.8 mm³-161.7 mm³, respectively). The location of osteophyte initiation and growth was consistent across subjects and was located in non-opposing regions on the trapezium and first metacarpal. Osteophyte growth occurred about the radial and ulnar margins of the trapezial facet, while on the proximal metacarpal, growth occurred principally about the volar and dorsal margins of the facet.

CONCLUSION

Osteophyte growth occurred in early thumb osteoarthritis over three years. Growth was localized in specific, non-opposing regions on the trapezium and metacarpal, raising intriguing questions about the triggers for their formation, whether the mechanisms are mechanical, biological or a combination of both.

Three-dimensional functional workspace of thumb prehension

BACKGROUND

Clinical assessment of thumb motion is challenging, due to the complex anatomy and motion of the thumb. It is especially difficult to measure hand movement during activity, and to measure the effects of surgery that changes the morphology of the thumb. A three-dimensional model of the hand may enable clinicians to better assess prehension and thumb motion at baseline, and following surgical intervention.

METHODS

A kinematic model of the hand was developed to measure thumb and finger position during functional tasks, enabling the calculation of the volume of space in which prehension could occur. This method was validated by application to a mechanical model of the hand, and then applied to ten adult participants, using three-dimensional motion analysis with a marker array developed for the purpose of this study.

FINDINGS

This method can be used to accurately measure three-dimensional thumb joint range of motion (RoM) and predicted functional workspace during functional activities. The thumb carpometacarpal joint was predominantly responsible for thumb position during functional tasks. Predicted functional workspace is proportional to hand morphometric measurements.

INTERPRETATION

A kinematic model of the hand measures thumb RoM and predicts functional workspace during functional activities.

Ligamento-Muscular Reflex Patterns Following Stimulation of a Thumb Carpometacarpal Ligament: An Electromyographic Study

PURPOSE

The dorsoradial ligament (DRL) is essential for stability of the first carpometacarpal joint (CMC1) and is innervated with nerve endings and mechanoreceptors known to contribute to joint proprioception. The influence of these nerve endings on the neuromuscular stability of CMC1 is not yet known. This study investigated whether a ligamento-muscular reflex pathway is present between the DRL and CMC1 muscles.

METHODS

Ten healthy subjects (5 women and 5 men, mean age 28 years; range, 24-37 years) were included. Four primary CMC1 stabilizing muscles were investigated: the extensor pollicis longus, abductor pollicis longus (APL), abductor pollicis brevis, and first dorsal interosseous. Needle electrodes were inserted into each muscle and a fine-wire electrode was inserted into the DRL. The DRL was stimulated at 200 MHz while EMG activities in the muscles were recorded during isometric tip, key, and palmar pinch. Average EMG values were analyzed to compare prestimulus (t₁) with post-stimulus (t₂) activity.

RESULTS

Poststimulus changes were observed in all 4 muscles and 3 positions tested. During tip pinch we observed mass inhibition with a decrease in all muscle amplitudes. In key pinch we observed a rapid co-contraction response. Rapid inhibitory response of antagonistic musculature was observed during palmar pinch. The APL was the only muscle to react within 20 ms after stimulation.

CONCLUSIONS

We identified CMC1 ligamento-muscular reflexes. The mass inhibition of activity observed during tip pinch indicated a protective ligamento-muscular relation that affects all 4 muscles. The co-contractions observed promote joint stability. The fast response in the APL, coupled with its neuroanatomical proximity to the DRL, indicate a particular role in CMC1 proprioception.

CLINICAL RELEVANCE

Proper ligamentous support and retained innervation is likely important for adequate joint function; their innate functions ought to be considered when planning surgical or orthotic treatments.

Trapeziometacarpal stabilization through dorsoradial ligament reconstruction: An early post-surgery in vivo biomechanical analyses

Ligament reconstruction can provide pain relief in patients with a painful, unstable, pre-arthritic trapeziometacarpal (TMC) joint. Imbrication of the dorsoradial ligament (DRL) has been proposed as a minimal invasive stabilization technique. It requires less invasive surgery than an Eaton-Littler technique and shows promising long-term clinical outcome. We used dynamic CT to objectively review the effects of the imbrication. Four patients with pain and laxity at the TMC joint, but without radiographic signs of osteoarthritis, were recruited. Dynamic CT scans were made during active thumb abduction-adduction, flexion-extension, and two functional grip tasks using a radiolucent jig. Scans of the patients were acquired before and 3 to 6 months after DRL reconstruction. Motion of each bone in the articular chain of the thumb was quantified. In addition, we mapped changes in the contact patterns between the articular facets during the entire thumb motion. After DRL imbrication, we found no overall decrease in MC1 movement in three out of four patients. Furthermore, no increase in TMC joint congruency, defined as proximity area size, was found for three out of four patients. Pre- and post-operative differences in congruency across different tasks were patient-dependent and relatively small. We demonstrated that, from a biomechanical perspective, there is high variability in post-operative outcome between patients that undergo identical surgical procedures performed by the same surgeon. A post-operative decrease in range of motion, increase in joint congruency or decrease in proximity area shift during thumb motion is not omnipresent. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2851-2864, 2018.

Axial Rotation Test for Trapeziometacarpal Joint Hypermobility in the Normal Population

Background: The objective was to quantify joint laxity in healthy volunteers by measuring the passive axial rotation of the trapeziometacarpal joint using the axial rotation test.

Methods: Eighty volunteers (34 men and 46 women) were subjected to the axial rotation shear test and the degree of total rotational motion (TRM) was assessed. Volunteers were divided into Group I with a range of 18–50 years old and Group II for 51 years and older. Statistical analysis was performed.

Results: The average TRM in Group I was 32.3 mm for women, and 27.4 mm, for men (p = 0.04). The average TRM in women of Groups I and II, was 32.3 and 21.6 mm respectively, (p < 0.001). The average TRM in men of Groups I and II, was 27.4 and 19.4 mm (p < 0.001). In Group II the average TRM of women was 21.6 mm, and for men was 19.4 mm, which was not significantly different.

Conclusions: Young women have greater degree of rotational laxity in the TM joint compared to men of the same age group and to older women. The axial rotation test can quantify the degree of rotational laxity of the TM joint.

Early morphologic changes in trapeziometacarpal joint bones with osteoarthritis

OBJECTIVE

Characterising the morphological differences between healthy and early osteoarthritic (EOA) trapeziometacarpal (TMC) joints is important for understanding osteoarthritis onset, and early detection is important for treatment and disease management. This study has two aims: first, to characterise morphological differences between healthy and EOA TMC bones. The second aim was to determine the efficacy of using a statistical shape model (SSM) to detect early signs of osteoarthritis (OA).

METHODS

CT image data of TMC bones from 22 asymptomatic volunteers and 47 patients with EOA were obtained from an ongoing study and used to generate a SSM. A linear discriminant analysis (LDA) classifier was trained on the principal component (PC) weights to characterise features of each group. Multivariable statistical analysis was performed on the PC to investigate morphologic differences. Leave-one-out classification was performed to evaluate the classifiers performance.

RESULTS

We found that TMC bones of EOA subjects exhibited a lower aspect ratio (P = 0.042) compared with healthy subjects. The LDA classifier predicted that protrusions (up to 1.5 mm) at the volar beak of the first metacarpal were characteristic of EOA subjects. This was accompanied with widening of the articular surface, deepening of the articular surface, and protruding bone growths along the concave margin. These characteristics resulted in a leave-one-out classification accuracy of 73.9% (95% CI [61.9%, 83.8%]), sensitivity of 89.4%, specificity of 40.9%, and precision of 75.9%.

CONCLUSION

Our findings indicate that morphological degeneration is well underway in the EOA TMC joint, and shows promise for a clinical tool that can detect these features automatically.

Can surgical guidelines minimize complications after Maïa® trapeziometacarpal joint arthroplasty with unconstrained cups?

The most important complications of trapeziometacarpal arthroplasty are dislocation and component loosening. Incorrect cup position is often a contributing factor. Intra-operative guidelines to optimize cup orientation have recently been described. We evaluated the functional and radiological outcome of 50 Maïa® trapeziometacarpal prostheses that were implanted according to these guidelines. The minimum follow-up was 56 months. No constrained cups were used. Functional outcome was good to excellent. No spontaneous dislocations occurred. No radiological signs of loosening were observed. There was one case of premature wear. The survival rate was 96% (95% confidence interval 85 to 99%) at a mean of 65 months, with two prosthesie removed for posttraumatic trapezial fractures. This study shows that correct implant position can lead to reliable medium-term results after trapeziometacarpal joint arthroplasty.

LEVEL OF EVIDENCE

IV.

Impact of Osteoarthritis and Total Joint Arthroplasty on the Kinematics of the Trapeziometacarpal Joint: A Pilot Study

PURPOSE

To quantify the effect of osteoarthritis (OA) and total trapeziometacarpal (TMC) joint replacement on thumb kinematics during the primary physiological motions of the thumb.

METHODS

We included 4 female patients with stage III TMC OA. A computed tomography-based markerless method was used to quantify the 3-dimensional thumb kinematics in patients before and after TMC joint replacement surgery with the Arpe implant.

RESULTS

Trapeziometacarpal OA led to a marked decrease of internal rotation and abduction of the first metacarpal (MC1) during thumb flexion and a decrease of MC1 adduction during thumb adduction. As a compensatory phenomenon, the trapezium displayed increased abduction. The absence of MC1 translation in the ball-and-socket implant seems to induce a decrease of MC1 adduction as well as a decrease of trapezium adduction during thumb adduction, compared with OA and healthy joints. Implant replacement displayed an unchanged MC1 flexion during thumb flexion and seemed to slightly increase MC1 axial rotation during thumb flexion and adduction. Abduction and adduction of the MC1 are limited and compensated by this somewhat increased axial rotation, allowing more efficient thumb opposition.

CONCLUSIONS

The study highlights that advanced TMC OA mainly restricts the MC1 mobility. We also showed that, whereas total joint arthroplasty is able to restore thumb function, it cannot fully replicate the kinematics of the healthy TMC joint.

CLINICAL RELEVANCE

The quantification of TMC joint kinematics in OA and implanted patients is essential to improve our understanding of TMC OA as well as to enhance the functionality of implant designs.

The Teleology of the Thumb: On Purpose and Design

The Andrew J. Weiland Medal is presented by the American Society for Surgery of the Hand to a midcareer researcher dedicated to advancing patient care in the field of hand surgery. The Weiland Medal for 2017 was presented to the author at the annual meeting of the American Society for Surgery of the Hand. The purpose of this article is to present current evidence on how biomechanics and morphology influence the pathophysiology of thumb carpometacarpal joint osteoarthritis.

In Vivo 3-Dimensional Kinematics of Thumb Carpometacarpal Joint During Thumb Opposition

PURPOSE

This study primarily aimed to demonstrate the screw-home rotation of the thumb carpometacarpal (CMC) joint and the function of surrounding ligaments during thumb oppositional motion.

METHODS

A 3-dimensional kinematic analysis of the thumb CMC joint was conducted using data derived from computed tomography of 9 healthy volunteers. Scans were obtained in the neutral forearm and wrist position and the thumb in maximum radial abduction, maximum palmar abduction, and maximum opposition. The movements of the first metacarpal and the palmar and dorsal bases on the trapezium during thumb oppositional motion from radial abduction through palmar abduction were quantified using a coordinate system originating on the trapezium. In addition to the kinematic analyses, the length of virtual ligaments, including the anterior oblique, ulnar collateral, dorsal radial, dorsal central (DCL), and posterior oblique ligament (POL), were calculated at each thumb position.

RESULTS

From radial abduction to opposition of the thumb through palmar abduction, the first metacarpal was abducted, internally rotated, and flexed on the trapezium. The palmar base of the first metacarpal moved in the palmar-ulnar direction, and the dorsal base moved in the palmar-distal direction along the concave surface of the trapezium. Although the DCL and POL lengthened, the lengths of other ligaments did not change significantly.

CONCLUSIONS

During thumb oppositional motion, internal rotation of the first metacarpal occurred, with the palmar base rotating primarily with respect to the dorsal base. The DCL and POL may be strained in thumb functional positions.

CLINICAL RELEVANCE

Kinematic variables indicated a screw-home rotation of the thumb CMC joint and the contribution of the dorsal ligaments to the stability of the rotation on the pivot point.

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.

Trapeziometacarpal joint contact varies between men and women during three isometric functional tasks

Trapeziometacarpal (TMC) joint osteoarthritis (OA) affects women two to six times more than men, and is influenced by stresses and strains in the cartilage. The purpose of this study was to characterise sex and age differences in contact area and peak stress location of the healthy TMC joint during three isometric tasks including pinch, grasp and jar twist. CT images of the hand from 50 healthy adult men and women were used to create a statistical shape model that was used to create finite element models for each subject and task. Force-driven simulations were performed to evaluate cartilage contact area and peak stress location. We tested for sex and age differences using Principal Component Analysis, linear regression, and Linear Discriminant Analysis. We observed sex differences in peak stress location during pinch (p = .0206), grasp (p = .0264), and jar twist (p = .0484). The greatest sex differences were observed during jar twist, where 94% of peak stresses in men were located in the centre compared with 50% in the central-volar region in women. These findings show that peak stress locations are more variable in women during grasp and jar twist than men, and suggest that women may employ different strategies to perform these tasks.

In vivo biomechanical behavior of the trapeziometacarpal joint in healthy and osteoarthritic subjects

BACKGROUND

The contact biomechanics of the trapeziometacarpal joint have been investigated in several studies. However, these led to conflicting results and were mostly performed in vitro. The purpose of this study was to provide further insight on the contact biomechanics of the trapeziometacarpal joint by in vivo assessment of healthy and osteoarthritic subjects.

METHODS

The hands of 16 healthy women and 6 women with trapeziometacarpal osteoarthritis were scanned in positions of maximal thumb extension, flexion, abduction and adduction during three isometric tasks (lateral key pinch, power grasp and jar twist) and in thumb rest posture (relaxed neutral). Three-dimensional surface models of the trapezium and first metacarpal were created for each thumb configuration. The articular surface of each bone was measured in the neutral posture. A computed tomography-based proximity mapping algorithm was developed to calculate the distance between opposing joint surfaces, which was used as a surrogate for intra-articular stress.

FINDINGS

Distinct proximity patterns were observed across tasks with a recurrent pattern reported on the volar aspect of the first metacarpal. The comparison between healthy and arthritic subjects showed a significantly larger articular area, in parallel with a significant joint space narrowing and an increase in proximity area in arthritic subjects. We also observed severe articular deformations in subjects with late stage osteoarthritis.

INTERPRETATION

This study has increased our insight in the contact biomechanics of the trapeziometacarpal joint during tasks and positions of daily life in healthy and arthritic subjects, which might contribute to a better understanding of the occurrence mechanisms of degenerative diseases such as osteoarthritis.

Developments in trapezium Replacements

The purpose of this update is to report on a variety of topics related to trapezium implants that have been investigated during the past three years. The keyword trapezium implant was utilized to query the PubMed database of the U.S. National Library of Medicine. From the resulting list, papers published from the beginning of January 2012 through the beginning of April 2015 were reviewed. The twenty-three studies identified are reviewed here and referenced at the end of the review. Based on level of evidence criteria for therapeutic studies as adopted by the American Academy of Orthopedic Surgeons, the most frequent level of evidence for reviewed clinical studies was Level IV (13/19 studies), followed by Level III (4/19), and Levels II (1/19) and I (1/19).

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.

Trapezium anatomy as a radiographic reference for optimal cup orientation in total trapeziometacarpal joint arthroplasty

In trapeziometacarpal arthroplasty, correct implant position may be necessary to prevent complications such as dislocation, component loosening and premature wear. The metacarpal stem more easily fits anatomically. However, the cup in the trapezium is not anatomical and guidelines for its orientation are not uniformly defined. We determined the centre of the range of motion of the trapeziometacarpal joint in 30 healthy patients on postero-anterior and lateral radiographs and its relationship to the proximal articular surface of the trapezium. Our study suggests that in thumb carpo-metacarpal total joint arthroplasty, the prosthetic cup in the trapezium should be placed parallel to the proximal articular surface of the trapezium and combined with a metacarpal neck with 7° palmar offset. This should optimize arthroplasty ranges of motion and may minimize the risk of postoperative complications. Our study provides a reference for the surgeon to check correct cup alignment intra-operatively with fluoroscopy.

Subject-specific thumb muscle activity during functional tasks of daily life

BACKGROUND

The trapeziometacarpal joint is subjected to high compressive forces during powerful pinch and grasp tasks due to muscle loading. In addition, muscle contraction is important for stability of the joint. The aim of the present study is to explore if different muscle activation patterns can be found between three functional tasks.

METHODS

Isometric forces and fine-wire electromyographic (fEMG) activity produced by three intrinsic and four extrinsic thumb muscles were measured in 10 healthy female volunteers. The participants performed isometric contractions in a lateral key pinch, a power grasp and a jar twist task. The tasks were executed with and without EMG recording to verify if electrode placement influenced force production.

RESULTS

A subject-specific muscle recruitment was found which remained largely unchanged across tasks. Extrinsic thumb muscles were significantly more active than intrinsic muscles in all tasks. Insertion of the fEMG electrodes decreased force production significantly in all tasks.

CONCLUSION

The thumb muscles display a high variability in muscle activity during functional tasks of daily life. The results of this study suggest that to produce a substantial amount of force, a well-integrated, but subject-specific, co-contraction between the intrinsic and extrinsic thumb muscles is necessary.

Improving Kinematic Accuracy of Soft Wearable Data Gloves by Optimizing Sensor Locations

Bending sensors enable compact, wearable designs when used for measuring hand configurations in data gloves. While existing data gloves can accurately measure angular displacement of the finger and distal thumb joints, accurate measurement of thumb carpometacarpal (CMC) joint movements remains challenging due to crosstalk between the multi-sensor outputs required to measure the degrees of freedom (DOF). To properly measure CMC-joint configurations, sensor locations that minimize sensor crosstalk must be identified. This paper presents a novel approach to identifying optimal sensor locations. Three-dimensional hand surface data from ten subjects was collected in multiple thumb postures with varied CMC-joint flexion and abduction angles. For each posture, scanned CMC-joint contours were used to estimate CMC-joint flexion and abduction angles by varying the positions and orientations of two bending sensors. Optimal sensor locations were estimated by the least squares method, which minimized the difference between the true CMC-joint angles and the joint angle estimates. Finally, the resultant optimal sensor locations were experimentally validated. Placing sensors at the optimal locations, CMC-joint angle measurement accuracies improved (flexion, 2.8° ± 1.9°; abduction, 1.9° ± 1.2°). The proposed method for improving the accuracy of the sensing system can be extended to other types of soft wearable measurement devices.

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.

Long-Term Outcomes of Radial Osteotomy for the Treatment of Kienböck Disease

Background Kienböck disease is an aseptic necrosis of the lunate of unknown etiology, prevalent in young adults. Treatment aims to lower forces on the lunate, decrease pain and improve function. We conducted a retrospective evaluation of the 10-year clinical and radiological outcomes of radial osteotomy as a treatment for Kienböck disease. Materials and Methods We analyzed pain, grip strength, wrist range of motion (ROM), radiological carpal geometry, and staging of osteoarthritic changes over a 10-year period, postosteotomy, for 18 patients. The Mayo wrist score was used as an overall measure of outcome. Technique Outcomes for two types of osteotomies were included, a step-cut osteotomy with fixed screws and an updated technique of two linear transverse osteotomies with volar locking plates. For cases with negative ulnar variance, resection of the radius was included to obtain a final ulnar variance of -1 to 0 mm. For positive ulnar variance, the goal was to obtain a correction of radial inclination of 10 to 15 degrees. Results Improvements in pain, ROM, and grip strength were maintained over the 10-year follow-up, without radiological improvement in geometry (carpal height ratio and Stahl index). Mild osteoarthritic changes were identified in 33% of patients, with no effect on clinical results. Degree of cartilage damage determined postoperative grip strength improvement. The Mayo wrist score at the final follow-up was excellent in one patient, good in nine, and fair in eight. Conclusions Radial osteotomy provides reasonable and long-term clinical benefits. Preoperative arthroscopic evaluation of cartilage damage can inform treatment decisions.

Postoperative Therapy for Chronic Thumb Carpometacarpal (CMC) Joint Dislocation

Surgical arthroplasty of thumb carpometacarpal (CMC) joint osteoarthritis is commonly performed. Postoperative therapeutic protocols aim to improve range of motion and function of the revised thumb. We describe a case in which the thumb CMC joint had been chronically dislocated before surgery, with shortening of the soft-tissue dynamic and static stabilizers of the joint. The postoperative protocol addressed the soft tissues using splinting and exercises aimed at lengthening and strengthening these structures, with good results. It may be beneficial to evaluate soft-tissue tension and the pattern of thumb use after surgery for thumb CMC joint osteoarthritis to improve postoperative functional results.