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Introduction Osteoarthritis of the first carpometacarpal joint is a common pathology of the hand, which may show an increasing prevalence in Germany due to the demographic development. In recent years, not only the current gold standard - the resection arthroplasty of the thumb saddle joint - has been used, but also therapeutic thumb saddle joint arthroscopy. In addition to the patient’s clinical complaints, radiographic diagnostics have been used to decide on treatment, although it has not been proven whether there is a correlation between imaging and clinical complaints. Materials and methods Between 2020 and 2022, 20 articular surfaces of the thumb saddle joint undergoing resection arthroplasty for symptomatic basal thumb osteoarthritis were prospectively examined, mapped and compared with preoperative conventional radiographs. Results The evaluation of the corresponding articular surfaces showed a higher cartilage destruction at the articular surfaces of the trapezium compared to the first metacarpal. No correlation was found between the stage of osteoarthritis and the Eaton-Littler classification. Conclusions Overall, there is a patient-specific heterogeneity of the cartilage damage of the articular surface of the trapezium bone, as well in the metacarpal bone I base in relation to the radiographic diagnosis. Furthermore, an inhomogeneity of the radiographic stage of osteoarthritis of the carpometacarpal joint according to Eaton and Littler in relation to the intraoperatively assessed cartilage damage. The statistical significance of the surgically assessed cartilage damage in relation to the conventional radiographs could not be demonstrated. Thus, the treatment of symptomatic osteoarthritis of the carpometacarpal joint should primarily address the patient’s individual complaints. The radiographic classification according to Eaton and Littler can be used as an additional factor to decide on the surgical procedure but should not delay the therapeutic treatment. Level of evidence III.

Background The complex configuration of the thumb carpometacarpal (CMC-1) joint relies on musculotendinous and ligamentous support for precise circumduction. Ligament innervation contributes to joint stability and proprioception. Evidence suggests abnormal ligament innervation is associated with osteoarthritis (OA) in large joints; however, little is known about CMC-1 ligament innervation characteristics in patients with OA. We studied the dorsal radial ligament (DRL) and the anterior oblique ligament (AOL), ligaments with a reported divergent presence of mechanoreceptors in nonosteoarthritic joints. Questions/purposes This study’s purposes were (1) to examine the ultrastructural architecture of CMC-1 ligaments in surgical patients with OA; (2) to describe innervation, specifically looking at mechanoreceptors, of these ligaments using immunohistochemical techniques and compare the AOL and DRL in terms of innervation; and (3) to determine whether there is a correlation between age and mechanoreceptor density. Methods The AOL and DRL were harvested from 11 patients with OA during trapeziectomy (10 women, one man; mean age, 67 years). The 22 ligaments were sectioned in paraffin and analyzed using immunoflourescent triple staining microscopy. Results In contrast to the organized collagen bundles of the DRL, the AOL appeared to be composed of disorganized connective tissue with few collagen fibers and little innervation. Mechanoreceptors were identified in CMC-1 ligaments of all patients with OA. The DRL was significantly more innervated than the AOL. There was no significant correlation between innervation of the DRL and AOL and patient age. Conclusions The dense collagen structure and rich innervation of the DRL in patients with OA suggest that the DRL has an important proprioceptive and stabilizing role. Clinical Relevance Ligament innervation may correlate with proprioceptive and neuromuscular changes in OA pathophysiology and consequently support further investigation of innervation in disease prevention and treatment strategies.

Purpose Total joint arthroplasty (TJA) has often been used to treat thumb carpometacarpal (CMC) osteoarthritis (OA). However, guidelines for the CMC prosthesis shape remain unclear. This study aimed to identify the effective shape of a ball-and-socket prosthesis in restoring the range of thumb motion after TJA. Methods The participants were 10 healthy young adult men (22–32 years; 26.8 ± 3.57 [mean ± SD]). CT scans were performed in eight static limb positions during abduction and flexion. We defined three design variables (offset R , height H , and neck rotation angle Φ ) as the variables that determine the basic shape of the ball-and-socket prosthesis. The ideal values of these design variables were examined based on the results of a 3D motion analysis, which evaluated the change in the posture of the first metacarpal ( r , h , and φ corresponding to R , H , and Φ , respectively) relative to the center of rotation (COR) during abduction and flexion. We also simulated the effect of these design variables on the range of thumb motion after TJA using 3D CAD. Results We found that the values of r and h averaged over all limb positions were 6.92 ± 1.60 mm and 51.02 ± 1.67 mm, respectively, showing that these values remained constant regardless of limb position. In contrast, φ changed significantly. The simulation results indicated that Φ affected the range of thumb motion after TJA, and Φ  = 0° relatively reproduced all limb positions compared to other values. Conclusion Our results suggested that the desirable values of R and H were the average of r and h over several limb positions and that Φ  = 0° was effective in restoring the range of thumb motion after TJA. Our results will provide surgeons with new guidelines for selecting a prosthesis.

Thumb motion is a key outcome metric for assessing disease progression or treatment efficacy. A literature review found nearly 25 % of recent papers incorrectly described their motion measurements as those of the first carpometacarpal (CMC) joint, when in fact their technology was only capable of measuring thumb motion. The aim of this manuscript is to clarify the importance of the accurate terminology and to rigorously examine the potential error by comparing thumb motion and CMC joint motion. Computed tomography (CT) images from 46 healthy subjects were analyzed using 3D markerless bone registration techniques to compute thumb rotation (first metacarpal (MC1) relative to the radius) and CMC joint rotation (MC1 relative to trapezium). We found thumb rotation was a poor measure of CMC joint rotation. For example, at thumb rotations of 20°, the true CMC joint rotations ranged from 3° to 30°. On average, thumb rotation over predicted CMC rotation by approximately 10°, with 95 % Limits of Agreement ranging from 30° (over estimating CMC joint motion) to −11° (underestimating CMC joint motion). Importantly, the character of the data demonstrated that CMC motion cannot be predicted from thumb motion. 3D CMC joint motion can only be assessed with skeletal imaging technologies; goniometers and skin-based markers can, at best, only measure thumb motion. Referring to goniometer and skin marker measurements as CMC joint motion is incorrect. It is critical that investigators be precise in their reporting of thumb motion versus CMC joint motion, especially when reporting interventions for thumb pathologies.

Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint is prevalent and debilitating, marked by substantial loss of range of motion (ROM) and overall function. CMC OA is associated with osteophyte growth, but the impact of this growth on CMC ROM has not been systematically characterized. Our goal was to determine whether osteophytes decrease CMC ROM and, if so, whether these decreases are direction-dependent. A robotic musculoskeletal simulation system was used to manipulate 18 CMC specimens with a range of joint health following three test protocols: (1) Rotational ROM in flexion, extension, abduction, adduction, and 20 combined directions, (2) Internal/External Rotation (IR/ER), and (3) Translational ROM in volar, dorsal, radial, ulnar, and 4 combined directions. Osteophyte volume (OV) was computed in total and by volar, dorsal, radial, and ulnar quadrants, and correlations with ROM were computed by direction and in total. We found that an increase in overall trapezial OV was associated with a reduction in overall rotational ROM and IR/ER, but not with translational ROM. We found decreased extension was associated with increased ulnar, volar, and radial OV, and decreased abduction was associated with increased volar OV. Decreased internal rotation was associated with increased ulnar, volar, and radial OV. The proposed method and findings of this pilot study will lay the groundwork for a larger investigation into the relationship between pathological structure and function in the CMC joint.

Carpometacarpal osteoarthritis is a common condition that leads to declines in hand dexterity. The Corbett Targeted Coin Test measures dexterity with palm-to-finger translation and proprioceptive target placement, but lacks established norms for the carpometacarpal osteoarthritis population and post carpometacarpal osteoarthritis suture suspension arthroplasty. To determine the Corbett Targeted Coin Test norms for patients with carpometacarpal osteoarthritis that are surgical candidates, as well as Corbett Targeted Coin Test norms and outcomes following carpometacarpal osteoarthritis suture suspension arthroplasty. Clinical measurement of a retrospective cohort. Subjects were diagnosed with carpometacarpal osteoarthritis and had carpometacarpal suture suspension arthroplasty. Outcome measures that were collected included Corbett Targeted Coin Test, Active Range of Motion, Patient-Rated Wrist/Hand Evaluation, Kapandji, Quick Disabilities of Arm, Shoulder, and Hand (QuickDASH), Numeric Pain Rating Scale, Grip, and Pinch Strength. Prior to surgery, the patients with carpometacarpal osteoarthritis that were surgical candidates demonstrated a mean Corbett Targeted Coin Test quality of performance score of 53.4 (range 28-90). A total of 31 participants (22 females, nine males) underwent thumb carpometacarpal suture suspension arthroplasty. On average, there were 7.1 therapy visits (range 4-10) and the average age was 66.6years (51-81years). Outcome measures following suture suspension arthroplasty 12weeks postoperatively demonstrated both statistically and clinically significant improvements in pain reduction (Numeric Pain Rating Scale), QuickDASH scores, and Patient-Rated Wrist/Hand Evaluation scores. There was also a clinically significant improvement in grip strength. Corbett Targeted Coin Test scores improved with a mean quality of performance score of 47.3 (range 20-73) but did not correlate with other outcome measures. Patients with carpometacarpal osteoarthritis had higher quality of performance scores, indicating a slower and/or less accurate dexterity performance compared with the normal population. At 12weeks post suture suspension arthroplasty, the Corbett Targeted Coin Test scores improved 11.4%, and there were statistically and clinically significant improvements in pain reduction (Numeric Pain Rating Scale), QuickDASH, Patient-Rated Wrist/Hand Evaluation, and a clinically significant improvement in grip strength. •Patients with carpometacarpal osteoarthritis were slower and less accurate when completing the Corbett Targeted Coin Test (CTCT).•At 12weeks post suture suspension arthroplasty (SSA), the CTCT scores improved 11.4%.•There were significant improvements in outcome measures at 12weeks post SSA.

Background Analysis of arthrokinematics may have clinical use in the diagnosis of dynamic instability of the thumb and wrist. Recent technological advances allow noninvasive, high-resolution imaging of skeletal (thumb and carpal bones) structures during motion. Questions/purposes The primary purpose of this study is to define the arthrokinematics, estimated joint contact patterns, and distribution ratios of the carpometacarpal joint of the thumb using four-dimensional CT (three-dimensional CT + time) and registration algorithms. The second purpose is to validate the accuracy of the approach. Methods Four-dimensional CT scans were obtained using a nongated sequential scanning technique. Eighteen image volumes were reconstructed over a 2-second cycle during thumb circumduction in one healthy volunteer. Using a registration algorithm, serial thumb motions as well as estimated joint contact areas were quantified. To evaluate the accuracy of our approach, one cadaveric hand was used. Results During circumduction, the ranges of motion of the thumb carpometacarpal joint were: flexion-extension, 27.3°; adduction-abduction, 66.9°; and pronation-supination, 10°. The magnitude of the translation of the center of the estimated joint contact area of the metacarpal was 4.1, 4.0, 1.0, and 1.5 mm when moving from the initial key pinch position to adduction, adduction to palmar abduction, palmar abduction to opposition, and opposition to the initial key pinch position, respectively. The maximum estimated contact area on the trapezium and on the metacarpal was in palmar abduction; the minimum was in adduction. Dominant central-volar contact patterns were observed on both the trapezium and the metacarpal bone except in adduction. This analysis approach had an average rotational error of less than 1°. Conclusions During circumduction, the estimated joint contact area was concentrated on the central-volar regions of both the trapezium and the metacarpal bones except when the thumb was adducted. Clinical Relevance This tool provides quantification of estimated joint contact areas throughout joint motion under physiological dynamic loading conditions; this tool may, in future studies, help to clarify some of the ways that joint mechanics might or might not predispose patients to arthritis.

Thumb carpometacarpal joint space changes when the surrounding soft tissues including the capsule, ligaments, and tendons are stretched or pulled away. When at rest, joint forces originate from passive contraction of muscles and the involvement of joint capsule and ligaments. Previous biomechanical models of hand and finger joints have mostly focused on the assessment of joint properties when muscles were active. This study aims to present an experimental-numerical biomechanical model of thumb carpometacarpal joint to explore the contribution of tendons, ligaments, and other soft tissues in the passive forces during distraction. Five fresh cadaveric specimens were tested using a distractor device to measure the applied forces upon gradual distraction of the intact joint. The subsequent step involved inserting a minuscule sensor into the joint capsule through a small incision, while preserving the integrity of tendons and ligaments, in order to accurately measure the fundamental intra-articular forces. A numerical model was also used to calculate the passive forces of tendons and ligaments. Before the separation of bones, the forces exerted by tendons and ligaments were relatively small compared to the capsule force, which accounted for approximately 92% of the total applied force. Contribution of tendons and ligaments, however, increased by further distraction. The passive force contribution by tendons at 2-mm distraction was determined less than 11%, whereas it reached up to 74% for the ligaments. The present study demonstrated that the ligament-capsule complex plays significant contribution in passive forces of thumb carpometacarpal joint during distraction.

Background The female predominance in thumb carpometacarpal (CMC) joint arthritis has led to speculation that reproductive hormones or hypermobility are responsible. Evidence shows that patients with pathologic laxity have a higher rate of thumb CMC arthritis. Relaxin hormone increases laxity in the pelvic ligaments through upregulation of matrix metalloproteases (MMPs). It is thus a hormone of interest in the development of thumb CMC arthritis. Questions/purposes Our goals were to identify demographic and hormonal factors associated with joint laxity in patients with CMC arthritis and to evaluate the relationship among serum relaxin, relaxin receptors, and MMPs in the anterior oblique ligament (AOL) of the thumb. We hypothesized that serum relaxin was correlated with joint laxity as well as with relaxin receptors and MMPs in the AOL. Methods Forty-nine patients undergoing thumb CMC arthroplasty underwent laxity examination, blood draw, and AOL sampling. Ligaments were analyzed for relaxin receptor and MMPs 1 and 3 using quantitative reverse-transcriptase polymerase chain reaction. Results Women demonstrated more joint laxity than men (p < 0.001). RNA analysis confirmed relaxin receptors in the AOL as well as MMPs 1 and 3. There was a significant correlation between serum relaxin and MMP-1 (p = 0.04). Detectable serum relaxin was negatively correlated with relaxin receptors in the AOL (p = 0.02). Conclusions Further studies are needed to evaluate the role of laxity and sex hormones in thumb CMC arthritis. Clinical Relevance Relaxin hormone may play a role in the development of arthritis at the thumb CMC joint. Level of Evidence Level I, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

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.