The Etiology of Thumb Carpometacarpal Osteoarthritis: Early Indications from In Vivo Joint Contact Mechanics

The thumb carpometacarpal (CMC) joint is frequently affected by osteoarthritis (OA). The prevalence of thumb CMC OA greatly increases with age and has disproportional predominance in postmenopausal women. However, so far the etiology of thumb CMC OA remains unclear, and no conclusion has been achieved regarding the selection of the optimal surgical procedure. Joint contact mechanics can be an important aspect in understanding the mechanism of thumb CMC OA development. The contact pressure distribution on the articular surface directly affects the cartilage condition. This study quantitatively compared the in vivo thumb CMC joint contact mechanics between 4 males and 4 females using finite element modeling (FEM), and also evaluated the accuracy of a time-efficient surface-based contact modeling (SCM) procedure for possible clinical application. Although a sufficient statistical power cannot be achieved with the small number of subjects, the contact patterns were substantially different between male and female groups. Contact area, force and peak contact pressure showed a trend of increase in the older female subjects. Compared with FEM, the contact parameter values from SCM may be somewhat less accurate, but SCM produced contact distribution patterns similar to FEM. In addition, SCM was able to distinguish the different contact patterns between normal and osteoarthritic thumb CMC joints with much less data processing. Therefore, SCM has clear potential for future clinical diagnosis and the evaluation of treatment efficacy for thumb CMC OA

Statistical shape modelling of the first carpometacarpal joint reveals high variation in morphology

The first carpometacarpal (CMC) joint, located at the base of the thumb and formed by the junction between the first metacarpal and trapezium, is a common site for osteoarthritis of the hand. The shape of both the first metacarpal and trapezium contributes to the intrinsic bony stability of the jointandvariability in the morphology of both these bones can affect the joint’s function. The objectivesof this study wereto quantify the morphological variation of the complete metacarpal and trapeziumand determine anycorrelation between anatomical features ofthese two components of the first CMC joint. A multi-object statistical shape modelling pipeline, consisting of scaling, hierarchical rigid registration, non-rigid registration and projection pursuit principal component analysis, was implemented. Four anatomical measureswere quantified from the shape model, namely the first metacarpal articular tilt and torsion angles and the trapeziumlength and width.Variationsin the first metacarpal articulartilt angle (-6.3°<θ<12.3°) and trapezium width (10.28mm <<11.13mm)wereidentified in the firstprincipal component. In the second principal component, variationsin the first metacarpal14torsion angle (0.2°<α<14.2°), first metacarpal articular tilt angle (1.0°<θ<6.4°) and trapezium length (12.25mm <ℓ<17.33mm)weredetermined. Due to their implications for joint stability, the first metacarpal articular tilt angle and trapezium width maybe important anatomical features which couldbe used toadvance early detectionand treatment offirst CMC joint osteoarthritis

Bridging the gap between clinical service and academic education of hand-splinting practice: Perspectives and experiences of Thai occupational therapists

A gap in knowledge about current splinting practice exists between the educational program and clinical service. To bridge this gap, we investigated the perspectives and experiences of Thai occupational therapists regarding contemporary hand splinting practices in clinical use. A mixed-method study was designed. An explanatory sequential mixed methods design was used. In the first quantitative phase, a survey questionnaire was mailed to occupational therapists. The questions were regarding contemporary hand splinting practices in clinical use at seven hospitals in the capital city of Bangkok and outskirt areas. In the second phase, semi-structured interviews were completed to explore expert occupational therapists\u27 perspectives on practice in the same hospital settings. Transcripts were analyzed using thematic analysis. The results showed that most conditions receiving splints were nerve injuries, orthopedics, and stroke, which represented the service frequency of splint types: functional resting (100 %), cock-up (93.3 %), and thumb spica splints (80 %). Bone and joint deformity prevention ranked first with muscle contracture prevention being ranked second, and the third-ranked was maintaining range of motion. Three themes emerged from the interviews: starting with the patient condition; effective function and value; knowledge and experiential skills. Perspectives and experiences of occupational therapists in splinting practice contribute to education based on the reality of practice. Integrated numerical and textual data of professional skills and knowledge in actual splinting practice can be reflected through splints and orthoses program revisions to meet future learning outcomes

Trabecular variation in the first metacarpal and manipulation in hominids

Objectives: The dexterity of fossil hominins is often inferred by assessing the comparative manual anatomy and behaviors of extant hominids, with a focus on the thumb. The aim of this study is to test whether trabecular structure is consistent with what is currently known about habitually loaded thumb postures across extant hominids. Materials and methods: We analyze first metacarpal (Mc1) subarticular trabecular architecture in humans (Homo sapiens, n = 10), bonobos (Pan paniscus, n = 10), chimpanzees (Pan troglodytes, n = 11), as well as for the first time, gorillas (Gorilla gorilla gorilla, n = 10) and orangutans (Pongo sp., n = 1, Pongo abelii, n = 3 and Pongo pygmaeus, n = 5). Using a combination of subarticular and whole‐epiphysis approaches, we test for significant differences in relative trabecular bone volume (RBV/TV) and degree of anisotropy (DA) between species. Results: Humans have significantly greater RBV/TV on the radiopalmar aspects of both the proximal and distal Mc1 subarticular surfaces and greater DA throughout the Mc1 head than other hominids. Nonhuman great apes have greatest RBV/TV on the ulnar aspect of the Mc1 head and the palmar aspect of the Mc1 base. Gorillas possessed significantly lower DA in the Mc1 head than any other taxon in our sample. Discussion: These results are consistent with abduction of the thumb during forceful “pad‐to‐pad” precision grips in humans and, in nonhuman great apes, a habitually adducted thumb that is typically used in precision and power grips. This comparative context will help infer habitual manipulative and locomotor grips in fossil hominins

Limits to temporal synchronization in fundamental hand and finger actions

Coordinated movement is critical not only to sports technique and performance but to daily living and as such represents a fundamental area of research. Coordination requires being able to produce the right actions at the right time and has to incorporate perception, cognition, and forceful neuro-muscular interaction with the environment. Coordinated movements of the hands and fingers are some of the most complex activities undertaken where continuous learning and adaptation take place, but the temporal variability of the most basic movement components is still unknown. This thesis investigates the extent of temporal variability in the execution of four different simple hand and finger coordination tasks, with the purpose to find the various intrinsic temporal variability which limit the ability to coordinate the hands in space and time. Study one showed that in a synchronized bi-lateral two finger tapping test (<<1 cm movement to target) the best participant had a temporaltiming variability of 4.8 ms whereas the largest time variability could be as high as 24.8 ms. No obvious improvement was found after transfer practice, whereas the average time variability for asynchronized tapping decreased from 62.1 ms to 30.3 ms after instructed practice indicating a likely change in task grouping. Study two showed that in a unilateral thumb-index finger pinch and release test, the largest mean timing variability was 12 ms for pinching irrespective of performing the task in a slow alert manner or at a faster speed. However, the mean temporal variability for release was only 6.3 ms when the task was performed in a more alert manner and indicates that release is more accurately controlled temporally than grip. Study three suggested that in a unilateral sagittal plane throwing action of the lower arm and hand, that elbow and wrist coordination for dynamic index finger tip location was better with a radial-ulnar deviation, darts-type, throwing action than a wrist flexor-extensor type action, basketball free throw type action (the mean variability was 37.5 ms and 27.2 ms, respectively). Study four compared the variability in bi-lateral finger tapping between voluntary tapping and involuntary finger contraction tapping. Electrically stimulated neural contractions had significantly lower force onset variability than voluntary or direct magnetic stimulation of muscles (6 ms, 9.5 ms, and 10.3 ms for electrically stimulated, voluntary and Transcranial Magnetic Stimulation stimulated contraction). This work provides a comprehensive analysis of the temporal variability in various fundamental digital movement tasks that can aid with the understanding of basic human coordination in sporting, daily living and clinical areas

The impact of thumb carpometacarpal osteoarthritis and the effectiveness of splinting

Background: Thumb carpometacarpal (CMC) osteoarthritis (OA) is a common, disabling condition, affecting substantial numbers of working and older-age people. It is the single commonest site affected by OA yet its unique characteristics, distinct from general hand OA, have received little individual attention – far less than hip and knee OA. In particular, little is known from patients’ perspectives about the impact of thumb CMC OA. Furthermore, international guidelines recommend splinting as a non-surgical, non- pharmacological treatment option for CMC OA; however, evidence supporting splinting in people with thumb CMC OA is sparse and inconsistent. The aims of this research were to: 1) explore the impact of thumb CMC OA from the perspective of people living with the condition; 2) investigate the effectiveness of splinting interventions for thumb CMC OA. Methods: Three main studies were conducted: 1) a pragmatic qualitative study exploring the impact of thumb CMC OA in 30 individual interviews of people with the condition; 2) a systematic review with meta-analyses of previous studies reporting on the effectiveness of splinting for thumb CMC OA; 3) a feasibility study for a future fully-powered randomised controlled trial (RCT) investigating the effectiveness of a soft splint intervention combined with standardised best practice usual care vs best practice usual care alone comparator intervention. Design of the feasibility study was based on the findings from the qualitative study and the systematic review. Results: The qualitative study identified five main themes representing five inter-related levels of health impact: negative experience of symptoms, functional limitations, restricted social activities and roles, negative thoughts and feelings, and altered sense of self. Pain, including pain at night, was the major concern. CMC OA impact was influenced by: dominant hand involvement; cold climate; people’s financial, social, and societal support; and attitudes to the condition. Many areas of impact are unidentified and missing in currently recommended patient-reported outcomes. The study found a strong desire for access to high-quality information about self-management and effective non-surgical, non-pharmacological treatment options. All evidence for splinting was of low quality. Splints cause a moderate-to-large reduction in pain (SMD -0.7 [95% CI -1.04, -0.35], < 0.0001) and small-to-moderate improvement in function (SMD -0.42 [-0.77, -0.08], p = 0.02) in the medium-term (3-12 months). No effect exists in the short-term. The review identified: variability in self-reported outcomes, case definitions, and rationale for splinting; low and variable splint dosage; lack of standardised usual care; unassessed QoL; and inappropriate study designs. In the feasibility study, all primary outcomes surpassed the a priori thresholds for feasibility. Of thirty enrolled participants, 29 (97%) were retained at the 4-week and 6-month follow-ups. Interventions were acceptable and safe. Preliminary clinical findings suggested greater improvements in pain in the splint group vs comparator intervention in the short-term. Conclusions: Thumb CMC OA has a profound impact on a person’s health and well-being. Splinting is an acceptable and promising intervention although good quality evidence to support its use is lacking. A full RCT of splinting in addition to standardised best practice usual care for thumb CMC OA pain is feasible but should be preceded by exploration of dose effect and optimisation of outcome measures

Trabecular bone patterning across the human hand

Hand bone morphology is regularly used to link particular hominin species with behaviors relevant to cognitive/technological progress. Debates about the functional significance of differing hominin hand bone morphologies tend to rely on establishing phylogenetic relationships and/or inferring behavior from epigenetic variation arising from mechanical loading and adaptive bone modeling. Most research focuses on variation in cortical bone structure, but additional information about hand function may be provided through the analysis of internal trabecular structure. While primate hand bone trabecular structure is known to vary in ways that are consistent with expected joint loading differences during manipulation and locomotion, no study exists that has documented this variation across the numerous bones of the hand. We quantify the trabecular structure in 22 bones of the human hand (early/extant modern Homo sapiens) and compare structural variation between two groups associated with post-agricultural/industrial (post-Neolithic) and foraging/hunter-gatherer (forager) subsistence strategies. We (1) establish trabecular bone volume fraction (BV/TV), modulus (E), degree of anisotropy (DA), mean trabecular thickness (Tb.Th) and spacing (Tb.Sp); (2) visualize the average distribution of site-specific BV/TV for each bone; and (3) examine if the variation in trabecular structure is consistent with expected joint loading differences among the regions of the hand and between the groups. Results indicate similar distributions of trabecular bone in both groups, with those of the forager sample presenting higher BV/TV, E, and lower DA, suggesting greater and more variable loading during manipulation. We find indications of higher loading along the ulnar side of the forager sample hand, with high site-specific BV/TV distributions among the carpals that are suggestive of high loading while the wrist moves through the ‘dart-thrower's’ motion. These results support the use of trabecular structure to infer behavior and have direct implications for refining our understanding of human hand evolution and fossil hominin hand use

A Clearer Picture of Musculoskeletal Disorders of the Knee and Thumb Through the Lens of Image-Based Finite Element Analysis

The first goal of this work was to understand the contributions of intra-cyst fluid pressure to the growth of subchondral bone cysts (SBCs). The equine stifle joint provides a natural animal model for studying SBCs. Finite element models were used to examine three cyst sizes of approximately 0.03 cm3 (C1), 0.5 cm3 (C2), and 1 cm3 (C3) in the equine stifle joint. Fluid pressure was simulated by using a soft solid filling or empty-cysts with uniform pressure loads. The models suggest that shear stresses due to joint loading, not pressurized fluid, are likely the cause of damage to the subchondral bone. The second goal of this work was to develop a modular MRI-compatible micropipette simulator that could be used for MRI-based FEA of the basilar thumb joint. A modular MRI-compatible micropipette simulator addresses several limitations of pipetting studies, and it can be used to isolate micropipette design features to understand how they affect basilar thumb joint contact mechanics. A micropipette simulator with a cylindrical handle (length 127 mm, diameter 25 mm) was used with one subject to demonstrate the system’s feasibility. Contact area, pressure, and location were similar to previously published data of basilar thumb joint models in power grasp and lateral pinch. The simulator’s modularity will allow future studies to examine handle design parameters such as handle diameter, cross-sectional shape, and other features. The third goal of this work was to utilize the modular MRI-compatible micropipette simulator to analyze the effects of three handle diameters (12 mm, 25 mm, and 40 mm) and finger rest inclusion on basilar thumb joint contact mechanics. All contact measures decreased with increasing handle diameter. Contact area and force were higher with a finger rest. We expected contact measures to decrease with the presence of a finger rest. The unexpected outcome may have been due to non-randomized test order and fatigue during testing

Morphological integration and shape covariation between the trapezium and first metacarpal among extant hominids

Objectives: The shape of the trapezium and first metacarpal (Mc1) markedly influence thumb mobility, strength, and the manual abilities of extant hominids. Previous research has typically focused solely on trapezium‐Mc1 joint shape. Here we investigate how morphological integration and shape covariation between the entire trapezium (articular and non‐articular surfaces) and the entire Mc1 reflect known differences in thumb use in extant hominids. Materials and Methods: We analyzed shape covariation in associated trapezia and Mc1s across a large, diverse sample of Homo sapiens (n = 40 individuals) and other extant hominids (Pan troglodytes, n = 16; Pan paniscus, n = 13; Gorilla gorilla gorilla, n = 27; Gorilla beringei, n = 6; Pongo pygmaeus, n = 14; Pongo abelii, n = 9) using a 3D geometric morphometric approach. We tested for interspecific significant differences in degree of morphological integration and patterns of shape covariation between the entire trapezium and Mc1, as well as within the trapezium‐Mc1 joint specifically. Results: Significant morphological integration was only found in the trapezium‐Mc1 joint of H. sapiens and G. g. gorilla. Each genus showed a specific pattern of shape covariation between the entire trapezium and Mc1 that was consistent with different intercarpal and carpometacarpal joint postures. Discussion: Our results are consistent with known differences in habitual thumb use, including a more abducted thumb during forceful precision grips in H. sapiens and a more adducted thumb in other hominids used for diverse grips. These results will help to infer thumb use in fossil hominins