Variation in palmaromedial articulations of carpometacarpal joints in Thoroughbred and Standardbred racehorses.

Background: Carpal conformation is an important factor in relation to joint soundness. The equine carpometacarpal joint (CMCJ) was reported to have variations in its three palmaromedial articulations. Lacking one or more of these articulations has not been radiographically evaluated in Thoroughbred (TB) and Standardbred (SB) racehorses. Aim: The study aimed to identify the prevalence of the variation in the palmaromedial articulation of the carpometacarpal joint (PM-CMCJ) in TB and SB horses. Additionally, to detect the probability of having each of the three articulations within and between the breeds. Finally, to establish an anatomical description for the different patterns of the articulations in these horses. Methods: 313 dorsopalmar radiographs from 174 horses (117 TB and 57 SB) were used. Three articulations at PM-CMCJ were evaluated based on their presence or absence: the articulations between the second and third carpal bones (C2-C3), the second carpal-second metacarpal (C2-Mc2), and the second and third metacarpal (Mc2-Mc3) bones. The probability of each articulation was determined in the breeds. Depending on the presence/absence of one or more of these articulations in each horse, each group of horses that had the same patterns of articulation was gathered into one category. Results: Prevalence of variation in articulations of PM-CMCJ was identified in about 28% of the horses. SB showed a higher variation than TB throughout the comparisons. C2-C3 articulation was significantly the most common articulation, especially in TB (98%). The most common pattern of articulations (73%) was found in category I, which had three articulations whereas three horses grouped in category VI had no palmaromedial articulations. Conclusion: The variations in the articulations of PM-CMCJ in TB and SB racehorse might show a breed association. C2-C3 articulation was considerably the most frequent feature and category I was the common pattern of articulations in PM-CMCJ. The potential clinical effects of the varied patterns of the articulations require investigation.

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 joint, and variability in the morphology of both these bones can affect the joint's function. The objectives of this study were to quantify the morphological variation in the complete metacarpal and trapezium and determine any correlation between anatomical features of these 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 measures were quantified from the shape model, namely the first metacarpal articular tilt and torsion angles and the trapezium length and width. Variations in the first metacarpal articular tilt angle (- 6.3° < θ < 12.3°) and trapezium width (10.28 mm < [Formula: see text] < 11.13 mm) were identified in the first principal component. In the second principal component, variations in the first metacarpal torsion angle (0.2° < α < 14.2°), first metacarpal articular tilt angle (1.0° < θ < 6.4°) and trapezium length (12.25 mm < [Formula: see text] < 17.33 mm) were determined. Due to their implications for joint stability, the first metacarpal articular tilt angle and trapezium width may be important anatomical features which could be used to advance early detection and treatment of first CMC joint osteoarthritis.

The Flexor Pollicis Longus Tendon Does Not Lie Parallel to the Thumb Metacarpal.

BACKGROUND: Repair of the flexor pollicis longus (FPL) tendon by tendon retriever can be challenging because of uncertainty of the optimal direction. This study aims to describe the FPL tendon path in the thenar eminence. METHODS: In 18 hands of 9 cadavers, the angle of the FPL tendon was, after dissection, measured in relation to the axis formed between the metacarpophalangeal (MCP) joint of the thumb and the dorsal carpometacarpal joint (MC1-axis) and the axis formed between the second MCP joint and the distal edge of the trapezium (MC2-axis). RESULTS: The FPL does not follow the angle of the thumb metacarpal. The FPL runs ulnarly from the MC1-axis at a median of 32.5° in abduction and 30.6° in adduction. In relation to the MC2-axis, it runs at a median of 47.5° in abduction and 25° in adduction. CONCLUSIONS: The FPL tendon path can be preoperatively marked using: (1) the MC1-axis from which it runs ulnarly approximately at an angle of 30° in both abduction and adduction; or (2) the MC2-axis from which it runs radially at an angle of 47.5° in abduction and at an angle of 25° in adduction. We conclude that the FPL tendon path can be preoperatively marked using these axes and does not parallel the metacarpal axes of the thumb.

A Cadaveric Study of the Mean Distance of the Radial Artery During the Approach to the First Carpometacarpal Joint.

Multiple surgical procedures have been described to treat first carpometacarpal (CMC) arthritis. Although the superiority of one procedure over the others continues to be a controversial topic, they all approach the trapezium and require careful attention to the surrounding structures. One potential complication is injury to the radial artery, which lies in close proximity to the trapezium and is often encountered during surgical approach. Using cadaveric specimens, the authors dissected to identify and isolate the radial artery as it travels in the forearm, wrist, and hand while being careful not to disturb its native course. The authors then measured the shortest distance interval from the radial artery to the first CMC joint and from the radial artery to the scaphotrapeziotrapezoidal joint. Descriptive statistics were calculated from these measurements and averaged over the various specimens. The mean distance of the radial artery to the closest segment of the volar CMC joint was 11.6±2.5 mm. The mean distance of the radial artery to the closest segment of the volar scaphotrapeziotrapezoidal joint was 1.6±1.8 mm. A precise understanding of nearby anatomy is paramount to a successful surgical treatment for first CMC arthritis and to avoid iatrogenic complications. The authors describe the mean distance from the radial artery to 2 major landmarks used during surgical treatment and provide insight to surgeons who perform these CMC reconstruction procedures to decrease the risk of intraoperative radial artery injury. [Orthopedics. 2018; 41(4):e541-e544.].

Evaluation of the pulley function of the hamulus of the hamate for the flexor tendons.

PURPOSE: The aim of this study was to measure the curvature radii of the finger flexor tendons on CT acquired using tendon conditions to examine whether the hamulus of the hamate functions as a pulley of the flexor tendon. METHODS: The subjects were 20 healthy volunteers (40 hands) (14 males and 6 females, mean age: 27.5 years old). Their hands were imaged in extension and flexion of the fingers on CT. The curvature radii of the little and middle finger flexor tendons at the hamulus of the hamate were calculated. RESULTS: The curvature radii of the little and middle finger flexor tendons were 24.8 ± 7.3 and 327.1 ± 343.9 mm in finger extension, respectively, and 21.3 ± 5.3 and 265.1 ± 202.9 mm in finger flexion, respectively. The curvature radius of the little finger flexor tendon was significantly smaller than that of the middle finger flexor tendon in both finger extension and flexion (P < 0.01). CONCLUSIONS: Our study suggested that the hamulus of the hamate functions as a pulley for the little finger flexor tendon.

Comparison of Computed Tomography Articular Surface Geometry of Male Versus Female Thumb Carpometacarpal Joints.

BACKGROUND: Given the predilection of first carpometacarpal (CMC) joint osteoarthritis in women compared with men, we aim to determine the differences in first CMC joint surface geometry and congruence between young healthy males and females. METHODS: Wrist computed tomographic scan data of 11 men and 11 women aged 20 to 35 years were imported into 3-dimensional software programs. The first metacarpal and the trapezium were aligned in a standardized position according to landmarks at key points on Gaussian and maximum curvature maps. Measurements of joint congruence and surface geometry were analyzed, including joint space volume, distance between the bones at the articular surface edges, area of the joint space, and radii of curvature in the radial-ulnar and volar-dorsal planes. RESULTS: The mean thumb CMC articular space volume was 104.02 ± 30.96 mm3 for females and 138.63 ± 50.36 mm3 for males. The mean first metacarpal articular surface area was 144.9 ± 10.9 mm2 for females and 175.4 ± 25.3 mm2 for males. After normalizing for size, the mean thumb CMC articular space volume was 119.4 ± 24.6 mm3 for females and 117.86 ± 28.5 mm3 for males. There was also no significant difference for the articular space volume, articular surface distances, articular space, and mean radii of curvatures. CONCLUSIONS: This study found that there are sex differences in the first CMC joint articular volume without normalizing for size; however, there are no sex differences in first CMC joint articular volume, curvature characteristics, or joint congruence of young, healthy patients after normalizing for joint size.

Incidence and anatomical distribution of hand tumours: a Singapore study.

INTRODUCTION: Hand tumours are frequently encountered in clinical practice. A list of differential diagnoses of the most common hand tumours based on anatomical location would be helpful for clinicians. We aimed to determine the anatomical distribution of hand tumours seen at a hand surgery practice in Singapore. METHODS: The medical records of 50 men and 65 women (mean age 41.7 [range 17-74] years) who underwent excision of hand tumours between 1 June 2010 and 31 December 2012 were reviewed. The histological diagnoses and anatomical locations of the tumours were analysed. The locations were divided into three main groups: (a) distal to the metacarpophalangeal joints (MCPJs); (b) between the MCPJs and carpometacarpal joints (CMCJs); and (c) between the CMCJs and the radiocarpal joint (RCJ). RESULTS: Overall, the most common tumours excised from the hand were ganglions (n = 66/116, 56.9%) and giant cell tumours of the tendon sheath (GCTTSs; n = 11/116, 9.5%). However, distal to the MCPJs, GCTTSs (n = 11/39, 28.2%) were more common than ganglions (n = 7/39, 17.9%). Most of the ganglions (n = 59/66, 89.4%) arose from between the CMCJs and RCJ. CONCLUSION: Most hand tumours were benign. Ganglions were the most common tumours between the CMCJs and RCJ, while GCTTSs were the most common tumours distal to the MCPJs.

The thumb carpometacarpal joint: curvature morphology of the articulating surfaces, mathematical description and mechanical functioning.

PURPOSE: The purpose is to present a mathematical model of the function of the thumb carpometacarpal joint (TCMCJ) based on measurements of human joints. In the TCMCJ both articulating surfaces are saddle-shaped. The aim was to geometrically survey the shapes of the articulating surfaces using precise replicas of 28 TCMCJs. METHODS: None of these 56 articulating surfaces did mathematically extend the differential geometrical neighbourhood around the main saddle point so that each surface could be characterised by three main parameters: the two extreme radii of curvature in the main saddle point and the angle between the saddles' asymptotics (straight lines). RESULTS: The articulating surfaces, when contacting at the respective main saddle points, are incongruent. Hence, the TCMCJ has functionally five kinematical degrees of freedom (DOF); two DOF belong to flexion/extension, two to ab-/adduction. These four DOF are controlled by the muscular apparatus. The fifth DOF, axial rotation, cannot be adjusted but stabilized by the muscular apparatus so that physiologically under compressive load axial rotation does not exceed an angle of approximately ±3°. CONCLUSIONS: The TCMCJ can be stimulated by the muscular apparatus to circumduct. The mechanisms are traced back to the curvature incongruity of the saddle surfaces. Hence we mathematically proved that none of the individual saddle surfaces can be described by a quadratic saddle surface as is often assumed in literature. We derived an algebraic formula with which the articulating surfaces in the TCMCJ can be quantitatively described. This formula can be used to shape the articulating surfaces in physiologically equivalent TCMCJ-prostheses.

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.

Men and women have similarly shaped carpometacarpal joint bones.

Characterizing the morphology of the carpometacarpal (CMC) joint bones and how they vary across the population is important for understanding the functional anatomy and pathology of the thumb. The purpose of this paper was to develop a statistical shape model of the trapezium and first metacarpal bones to characterize the size and shape of the whole bones across a cohort of 50. We used this shape model to investigate the effects of sex and age on the size and shape of the CMC joint bones and the articulating surface area of the CMC joint. We hypothesized that women have similar shape trapezium and first metacarpal bones compared to men, following scaling for overall size. We also hypothesized that age would be a significant predictor variable for CMC joint bone changes. CT image data and segmented point clouds of 50 CMC bones from healthy adult men and women were obtained from an ongoing study and used to generate two statistical shape models. Statistical analysis of the principal component weights of both models was performed to investigate morphological sex and age differences. We observed sex differences, but were unable to detect any age differences. Between men and women the only difference in morphology of the trapezia and first metacarpal bones was size. These findings confirm our first hypothesis, and suggest that the women have similarly shaped trapezium and first metacarpal bones compared to men. Furthermore, our results reject our second hypothesis, indicating that age is a poor predictor of CMC joint morphology.

Elliptical morphology of the carpal tunnel cross section

Although the carpal tunnel is known for its anatomical constituents, its morphology is not well recognized. The aim of this study was to investigate the morphometric properties of the carpal tunnel and its surrounding structures. Magnetic resonance and cross-sectional images of the distal carpal tunnel were collected from eight cadaveric hands. Morphological analyses were performed for the cross sections of the carpal tunnel, interior carpus boundary, and exterior carpus boundary. The specimens had a carpal arch width and height of 23.9 ± 2.9 mm and 2.2 ± 0.9 mm, respectively. The carpal tunnel, interior carpus boundary, and exterior carpus boundary had perimeters of 54.8 ± 4.5 mm, 68.5 ± 7.0 mm, and 130.6 ± 11.8 mm, respectively, and areas of 183.5 ± 30.1 mm2, 240.7 ± 40.2 mm2, and 1002.3 ± 183.7 mm2, respectively. The cross sections were characterized by elliptical fitting with aspect ratios of 1.96 ± 0.15, 1.96 ± 0.19, and 1.76 ± 0.19 for the carpal tunnel, interior carpus boundary, and exterior carpus boundary, respectively. The major axis of the boundaries increased in pronation angle, relative to the hamate-trapezium axis, for the exterior carpus (6.0 ± 3.0º), interior carpus (8.2 ± 3.2º), and carpal tunnel (15.9 ± 2.2º). This study advances our understanding of the structural anatomy of the carpal tunnel, and the morphological information is valuable in the identification of structural abnormality, assistance of surgical planning, and evaluation of treatment of effects

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Comparison of the anatomical dimensions and mechanical properties of the dorsoradial and anterior oblique ligaments of the trapeziometacarpal joint.

PURPOSE: The respective roles of the dorsoradial (DRL) and anterior oblique (AOL) ligaments in stability of the highly mobile trapeziometacarpal (TMC) joint remain disputed. Earlier publications have pointed to the AOL as the key stabilizing structure; yet, more recent publications have challenged the stabilizing role of the AOL, favoring the DRL as the main TMC joint stabilizer. We executed an anatomical study of the ligaments, including detailed dissection to quantify the length, width, and thickness of the AOL and DRL and tested the material properties of these ligaments. METHODS: Thirteen fresh frozen cadaveric thumbs from 9 specimens were used. Length, width, and thickness of the AOL and DRL were measured on magnetic resonance imaging and/or after dissection. Next, the first metacarpal and trapezium were isolated together with both ligaments, and both bones were cut sagittally to isolate a first metacarpal-AOL-trapezium and first metacarpal-DRL-trapezium complex from each thumb. These samples were subjected to cyclic loading in displacement-controlled tests. The obtained force-displacement curves were used to calculate stiffness and hysteresis of each sample. RESULTS: Our results showed that the DRL is significantly shorter and thicker than the AOL, which is thin and ill-defined. Our results also indicate that the DRL has a higher stiffness than the AOL, making it a more likely candidate to provide joint stability. CONCLUSIONS: Although the AOL has been asserted to be the primary restraint to dorsoradial subluxation, this view has been challenged over the past 10 years by several studies. These studies have shown the AOL to be relatively weak and compliant compared with the intermetacarpal and dorsoradial ligaments and have demonstrated that the DRL is the strongest and stiffest ligament of the TMC joint. Our studies confirm these findings. CLINICAL RELEVANCE: This study indicates that the DRL is relatively stiff and thick, suggesting it should be repaired or reconstructed when disrupted to restore stability of the TMC joint.

Dorsoradial ligament imbrication for thumb carpometacarpal joint instability.

UNLABELLED: Dorsoradial ligament imbrication is a direct and effective alternative to ligament reconstruction or metacarpal osteotomy in patients with symptomatic thumb carpometacarpal (CMC) joint instability. This procedure is performed by imbricating either the trapezial or the metacarpal attachment of the dorsoradial ligament with the use of a suture anchor. The procedure is indicated in the setting of chronic hyperlaxity or instability of the thumb CMC joint. Significant arthritic changes in the thumb CMC joint are a contraindication for this procedure. We present our technique along with an anatomic dissection to demonstrate the ligament and surgical procedure on an anatomic specimen. We also present results from 3 patients who underwent this technique with images and clinical results for 3 patients with long-term follow-up. LEVEL OF EVIDENCE: Level IV-Therapeutic.

Possibility of the hamatum carpometacarpal joint as a new joint donor site for interphalangeal joint restoration.

OBJECTIVE: This research investigates the anatomic basis for the repair and reconstruction of hand joints using transposition of the carpometacarpal (CMC) joint of the hamatum. METHODS: The morphology and structure of the CMC joints of the hamatum and the base joints of the middle phalanx were observed on 22 freshly frozen wrist specimens at Shanghai 6th People's Hospital Research Institute of Microsurgery. The volar dorsal dia, radioulnar dia, depth of concave, and area of the joints were measured. Data were obtained through statistical analysis, and the resemblance of joints was compared in terms of morphology, structure, area, length, and diameter. RESULTS: The radioulnar dia of the CMC joints of the hamatum (13.54 ± 1.15 mm) did not exhibit any evident differences in the middle phalanx of the forefinger, middle finger, and ring finger, and in the distal phalanx of the thumb. The volar dorsal dia of the CMC joints of the hamatum (10.71 ± 0.93 mm) exhibited an evident difference in the middle phalanx of the ring finger. In all fingers, the depth of the ulnar and radial concave of the CMC joints of the hamatum (1.30 ± 0.08 and 0.95 ± 0.05 mm, respectively) and the area of the CMC joints of the hamatum (139.89 ± 5.44 mm(2)) showed an evident difference. CONCLUSION: The CMC joint of the hamatum could be considered a new and viable joint donor site that could be used to repair and reconstruct the base joints of the middle phalanx.

The carpometacarpal joint of the thumb: MR appearance in asymptomatic volunteers.

PURPOSE: To prospectively characterize the MR appearance of the carpometacarpal (CMC) joint of the thumb in asymptomatic volunteers. MATERIALS AND METHODS: Thirty-four asymptomatic volunteers (17 women, 17 men, mean age, 33.9 ± 9.2 years) underwent MR imaging of the thumb after approval by the local ethical committee. Two musculoskeletal radiologists independently classified visibility and signal intensity (SI) characteristics of the anterior oblique (AOL/beak ligament), the posterior oblique (POL), the intermetacarpal (IML), and the dorsoradial ligaments (DRL) on a three-point Likert scale. The thickness of all ligaments, cartilage integrity, and presence of joint fluid were assessed. The alignment of the first metacarpal base with the trapezium was quantified on sagittal and coronal planes. RESULTS: The ligaments of the CMC joint were constantly visible in all volunteers for the POL and IML, and in all but one for the AOL and DRL. On intermediate-weighted fat-saturated images the POL (65 %/74 % reader 1/reader 2) and DRL (58 %/64 %) were commonly of increased SI, while the IML had a striated appearance in 91 %/76 % of subjects. The AOL showed a variable SI (36 %/42 % low, 27 %/27 % increased, 36 %/30 % striated). The IML was the thickest ligament with a mean of 2.9 mm/3.1 mm and the DRL the thinnest (1.2 mm/1.4 mm). There was a mean dorsal subluxation of 1.8 mm/2.0 mm and radial subluxation of 2.8 mm/3.4 mm of the metacarpal base. The AOL was significantly thicker in men (1.7 mm) than in women (1.2 mm; p = 0.02). Radial subluxation was significantly larger in men (3.4 mm) than in women (2.2 mm; p = 0.02). No subluxation in palmar or ulnar direction was seen. CONCLUSIONS: Radial and dorsal subluxation of the CMC joint can be a normal finding in a resting position at MR imaging. The CMC ligaments showed a considerable variability of signal intensity with a typically striated IML; thickness of the AOL is typically less than 2.2 mm, of the POL typically less than 2.9 mm.

Feasibility for mapping cartilage t1 relaxation times in the distal metacarpus3/metatarsus3 of thoroughbred racehorses using delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC): normal cadaver study.

Osteoarthritis of the metacarpo/metatarsophalangeal joints is one of the major causes of poor performance in horses. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) may be a useful technique for noninvasively quantifying articular cartilage damage in horses. The purpose of this study was to describe dGEMRIC characteristics of the distal metacarpus3/metatarsus3 (Mc3/Mt3) articular cartilage in 20 cadaver specimens collected from normal Thoroughbred horses. For each specimen, T1 relaxation time was measured from scans acquired precontrast and at 30, 60, 120, and 180 min post intraarticular injection of Gd-DTPA(2-) (dGEMRIC series). For each scan, T1 relaxation times were calculated using five regions of interest (sites 1-5) in the cartilage. For all sites, a significant decrease in T1 relaxation times occurred between precontrast scans and 30, 60, 120, and 180 min scans of the dGEMRIC series (P < 0.0001). A significant increase in T1 relaxation times occurred between 60 and 180 min and between 120 and 180 min post Gd injection for all sites. For sites 1-4, a significant increase in T1 relaxation time occurred between 30 and 180 min postinjection (P < 0.05). Sites 1-5 differed significantly among one another for all times (P < 0.0001). Findings from this cadaver study indicated that dGEMRIC using intraarticular Gd-DTPA(2-) is a feasible technique for measuring and mapping changes in T1 relaxation times in equine metacarpo/metatarsophalangeal joint cartilage. Optimal times for postcontrast scans were 60-120 min. Future studies are needed to determine whether these findings are reproducible in live horses.

The thumb carpometacarpal joint: anatomy, hormones, and biomechanics.

Although there are many surgical options to treat thumb carpometacarpal (CMC) arthritis, a precise etiology for this common disorder remains obscure. To better understand the physiology of the thumb CMC joint and treat pathology, it is helpful to examine the biomechanics, hormonal influences, and available surgical treatment options, along with the evolutionary roots of the thumb; its form and function, its functional demands; and the role of supporting ligaments based on their location, stability, and ultrastructure. It is important to appreciate the micromotion of a saddle joint and the role that sex, age, and reproductive hormones play in influencing laxity and joint disease. Minimally invasive surgery is now challenging prevailing treatment principles of ligament reconstruction and plays a role in thumb CMC joint procedures.