Thumb Metacarpophalangeal Joint Research Articles

Novel figure-of-eight reconstruction with free tendon graft for unrepairable collateral ligament of the thumb metacarpophalangeal joint

ObjectivesThis study aimed to report surgical technique and clinical outcomes for a novel figure-of-eight collateral ligament reconstruction technique using palmaris longus autograft for chronic irreparable collateral ligament injury of the thumb metacarpophalangeal joint. Material and methodsThe Jobe elbow collateral ligament reconstruction method was adapted for thumb metacarpophalangeal joint collateral ligament reconstruction. Sixteen reconstructions (7 ulnar collateral ligament, 9 radial collateral ligament) using palmaris longus autograft were reviewed retrospectively. Surgery was performed at a mean 12 months post-injury. All 16 patients were followed up for more than 1 year. Metacarpophalangeal joint radial and ulnar deviation, metacarpophalangeal and interphalangeal joint range of motion, key pinch and grip strength, Glickel functional grade and QuickDASH score were evaluated. ResultsPreoperative radial or ulnar deviation improved from 19.3° to 5.3° postoperatively. Metacarpophalangeal range of motion improved from 31.5° to 46.6°, and interphalangeal range of motion from 48.4° to 65.6°. Preoperative key pinch and grip strength were respectively 49% and 81% of contralateral values and improved to 82% and 87%. On Glickel grade, 9 cases were excellent and 7 good. ConclusionThe novel Jobe-like figure-of-eight reconstruction technique using palmaris longus graft was useful for reconstructing irreparable thumb metacarpophalangeal joint instability without an incision on the opposite side or an additional implant. Level of evidenceTherapeutic study, level IV.

Radial Collateral Ligament Laxity of Thumb Metacarpophalangeal Joint Following Trapeziometacarpal Arthrodesis

Trapeziometacarpal (TM) arthrodesis may increase adduction motion of the thumb metacarpophalangeal (MCP) joint, causing radial collateral ligament laxity. Stability of the MCP joint is important to the long-term functional outcome after TM arthrodesis. This study assessed preoperative and postoperative radial collateral ligament laxity using dynamic radiographs to confirm whether laxity was exacerbated after surgery and examined whether there is a relationship between the fixation angle of arthrodesis and the degree of laxity. Forty-four thumbs in 33 patients who underwent TM arthrodesis and were followed for at least 5 years were studied. Dynamic radiographs in radial adduction-abduction and palmar adduction-abduction were obtained. We defined the midpoint of arc of motion as the fixation angle of arthrodesis in the radial and palmar planes. We measured the intersection angle between longitudinal axis of the first metacarpal (M1) and that of thumb proximal phalanx (P1). P1M1 angle in a palmar adduction view of dynamic radiographs reflected radial collateral ligament laxity in palmar adduction (adduction P1M1 angle). We subtracted a preoperative adduction P1M1 angle from a postoperative adduction P1M1 angle and defined its value as an exacerbated adduction P1M1 angle. Adduction P1M1 angle increased from 9° ± 5° to 18° ± 10°. The median exacerbated adduction P1M1 angle was 7°. Ten thumbs (23%) developed ulnar subluxation of MCP joint in the palmar adduction view of dynamic radiographs. Among them, two thumbs developed osteoarthritis of MCP joint (5%). Fixation angle of the arthrodesis was a mean of 35° ± 7° and 32° ± 9° in the radial arc and palmar arc planes, respectively. There was a positive correlation between increasing adduction P1M1 angle and TM arthrodesis in an increasingly palmarly abducted position. Radial collateral ligament laxity of thumb MCP joint was exacerbated after TM arthrodesis. Greater fixation angle in palmar abduction resulted in more laxity of the joint. Prognostic IV.

Biological Versus Nonbiological Reconstruction of the Ulnar Collateral Ligament of the Thumb Metacarpophalangeal Joint: A Retrospective Study

The purpose of this study was to compare clinical and radiologic outcomes of biological ligament reconstruction (BLR) versus nonbiological ligament reconstruction (NBLR) for chronic injuries involving the ulnar collateral ligament of the thumb's metacarpophalangeal joint. Forty-two patients who underwent static BLR (n= 24) or NBLR (n= 18) were included in this retrospective analysis. Preoperative, postoperative, and contralateral thumb measurements (clinical evaluation, radiographs, and subjective outcome questionnaires) were compared over a mean of 38 months of follow-up. Average postoperative thumb metacarpophalangeal and interphalangeal joint ranges of motion were 2° to 54° and 0 to 71°, respectively, for BLR and 0° to 58° and 0° to 71°, respectively, for NBLR. Average grip and pinch strengths, relative to the unaffected hand, were 102% and 84% versus 103% and 89%, respectively. All patients demonstrated stability with a firm end point, compared with the unaffected thumb. The average Quick Disabilities of the Arm, Shoulder, and Hand score among all patients was 12 for the disability/symptom module, 0 for the sports module, and 17 for the work module. Stiffness was reported among four patients, and no patient sustained wound-related issues or other complications. Nonbiological ligament reconstruction of the thumb ulnar collateral ligament generates short-term outcomes comparable with those of BLR, potentially allowing for expedited recovery and rehabilitation. Therapeutic IV.

Atypical Cleft Hand: Surgical Technique for Grasping Improvement

Introduction: We present 6 cases of children with atypical cleft hand and discuss a surgical technique. Clinically, participants presented with a lack of pulp-to-pulp pinch due to metacarpophalangeal ligament insufficiency and difficulty grasping large objects because of the narrowed first web. Materials and Methods: Second metacarpal resection and Z-plasty, creating a wide first web. The second extensor digitorum communis tendon was transferred to improve the thumb metacarpophalangeal joint stability. Conclusions: The surgical technique presented in this paper did improve function in oligodactyly or type-IIA atypical cleft hand.

The Application of Sesamoid Position in Diagnosing Thumb Metacarpophalangeal Joint Dorsal Dislocation: A Retrospective Study.

The position of sesamoid of thumb metacarpophalangeal (MCP) joint changed clearly when the joint was dislocated dorsally. However, the significance of sesamoid location in diagnosing joint dislocation was unclear. The present study aimed to explore the positional relationship between sesamoid bone and thumb metacarpophalangeal joint in normal and dorsal dislocation joints. Between January 2018 and August 2023, we collected 60 isometric plain films from sixty outpatients and reviewed 56 anisometric plain films from twenty-eight emergency patients with dorsal dislocation of thumb MCP joint at Tianjin Hospital, then took measurements on the hand X-ray images. The sesamoid length on its longitudinal axis was defined as DP, the distance between the distal edge of sesamoid and thumb MCP joint was defined as DJ, and the ratio of DJ and DP was R. An independent-samples t-test and paired-samples t-test was utilized to analyze difference among data groups. The 60 isometric images were from 30 male and 30 female outpatients with normal bone structure in their hands, and the 56 anisometric images of the 28 emergency patients included both preoperative and postoperative materials. Among the outpatients, the actual distance between the distal edge of sesamoid and thumb MCP joint space (DJ) was 2.09 mm and 1.40 mm in males and females, respectively. The authentic average length of sesamoid (DP) was 4.46 mm in males and 4.22 mm in females. The average value of R (the ratio of DJ and DP) in males and females was 0.49 and 0.34, respectively. There were gender-related statistical differences in DJ (p < 0.01) and R (p=0.01), but no statistical difference in DP (p > 0.05). For the 28 emergency patients, the mean value of R was -0.47 before joint reduction and 0.58 after joint reduction, with statistical difference between them (p < 0.01). There was significant difference in the relative position between sesamoid and thumb MCP joint when joint dislocation and joint reduction. The distal edge of sesamoid beyond thumb MCP joint could be an evidence in diagnosing joint dorsal dislocation. The distal edge of sesamoid below thumb MCP joint could be an evidence of joint reduction.

High Fracture Rate of AVANTA Silicone Implant Following Arthroplasty of the Thumb MCP Joint of Rheumatoid Arthritis Patients with Boutonniere Deformities.

We retrospectively investigated the mid-term outcomes of arthroplasty using the AVANTA silicone implant for thumb metacarpophalangeal (MCP) joints with boutonniere deformity in patients with rheumatoid arthritis (RA). This study involved 36 thumbs of 33 RA patients with a mean follow-up period of 5.1 years (range, 2.0-13.3). Postoperatively, the mean extension was significantly increased and the mean flexion was significantly decreased (p<0.001, p<0.001, respectively), resulting in the mean arc of range of motion (ROM) shifting in the direction of extension after surgery. Implant fracture was observed in 10 thumbs (28%), and 4 of these (11%) underwent revision surgery. The survivorship with implant fracture and revision surgery as endpoints were 73.4% and 91.8% at 5 years, respectively. The preoperative arc of ROM and the postoperative flexion range of the implant-fracture group were significantly greater than those in the no-implant-fracture group (p=0.039, 0.034, respectively). These results suggest the importance of patient education and careful rehabilitation to prevent excessive flexion. Overall, the AVANTA silicone implant showed a relatively high rate of implant fracture at our institute.

Complications and Unplanned Reoperation After Thumb Metacarpophalangeal Arthrodesis

Arthrodesis of the metacarpophalangeal (MCP) joint of the thumb is a common procedure to treat arthritis or instability. Studies reporting hardware complications and nonunion rates after thumb MCP joint arthrodesis report on small sample sizes. We aimed to describe the hardware complication rate, the nonunion rate, and the number of thumbs that achieve union among patients undergoing thumb MCP joint arthrodesis. A database spanning 5 urban hospitals in a single metropolitan region in the United States was searched for patients who underwent thumb MCP joint arthrodesis between January 1, 2004 and January 1, 2020. After reviewing patient records, we identified 122 thumbs that underwent MCP joint arthrodesis and had a minimum follow-up of 90 days. The primary outcome was unplanned reoperation after hardware complications and nonunion. Second, the number of thumbs that achieved radiographic union was reported for the tension band and screw fixation arthrodesis group. Twenty-two (18%) out of 122 thumbs had hardware complications after thumb MCP joint arthrodesis, and 11 (9%) out of 122 thumbs developed a nonunion. Patients who underwent screw fixation arthrodesis had no events of hardware complications and subsequent hardware removal. The nonunion rate was 9/65 (14%) in the tension band arthrodesis group and 2 (4%) of 45 in the screw fixation arthrodesis group. Of the thumbs that had available radiographs to assess the healing of the arthrodesis, 34 (81%) of 42 were radiographically united in the tension band arthrodesis group and 29 (91%) of 32 in the screw fixation group. Our data suggest that screw fixation has fewer hardware complications and a lower reoperation rate than tension band arthrodesis. Prognosis IV.

MRI spectrum of injuries to the thumb metacarpophalangeal joint ulnar collateral ligament with a proposed expanded classification of injuries in American football players.

Injuries to the ulnar collateral ligament of the thumb metacarpophalangeal joint are of both historic and modern interest for athletes and non-athletes alike. The thumb metacarpophalangeal joint requires stability in both flexion and extension utilizing a combination of static and dynamic stabilizers. This article reviews the magnetic resonance imaging categorization of thumb ulnar collateral ligament injuries and proposes two additional injury patterns seen in high-level and professional athletes who play American football. In addition to the direct magnetic resonance imaging findings in collateral ligament tears, secondary findings of rotation and subluxation can be seen at the thumb metacarpophalangeal joint due to the altered physiologic forces on the joint. Internal brace augmentation via suture tape of a traditional ulnar collateral ligament repair is a novel surgical technique that provides protection during initial healing and the ensuing remodeling phase following repair or reconstruction, resulting in a faster return to play.

Thumb pronation efficacy of Camitz tendon transfer with insertion on the ulnar capsule of the metacarpophalangeal joint: a cadaver study.

Several studies have indicated that Camitz transfer for severe carpal tunnel does not adequately restore thumb opposition. The aim of this study was to determine whether modification of the distal insertion of the transferred palmaris longus tendon could provide more effective opposition. We used 12 fresh-frozen upper extremity specimens. For spatial analysis, we used a three-dimensional motion-tracking device. At 0 N and 5 N of traction force, the pronation angle was significantly larger for the modified procedure than for the conventional procedure. There was no significant difference in the palmar abduction angle between the two groups. The modified palmaris longus tendon insertion on the ulnar side of the thumb metacarpophalangeal joint provides more effective thumb pronation than conventional Camitz opponensplasty in a cadaver model.    .

Thumb Metacarpophalangeal Joint Kinematics and Elongation of the Ulnar Collateral Ligament

The purpose of the study was to determine if the sphericity of the thumb metacarpophalangeal (MCP) joint influences the joint's rotational axis (RA) and elongation patterns of the ulnar collateral ligament (UCL). Ulnar collateral ligament origins and attachments of 28 fresh-frozen cadaveric thumbs were marked with a radiopaque marker. Lateral radiographs were obtained in neutral and 20°, 40°, and 60° of flexion. The dorsal and palmar joint gap and the length of four different UCL portions were digitally measured in all flexion states. The RA was determined by the intersection of the midshaft axis of the proximal phalanx in neutral and flexion states. Sphericity of the MCP joint was assessed using morphometric parameters. Joints were grouped as round or flat. Differences in all measured parameters between groups were analyzed. During flexion, the dorsal joint gap increased by 322% in flat joints and 163% in round joints. The palmar joint gap decreased to 45% in flat joints and to 87% in round joints. The RA was at 29% of metacarpal height and 96% of metacarpal length in flat joints and at 40% of height and 86% of length in round joints. Maximum UCL elongation (111%) was noted at 40° flexion in the dorsal proper UCL in flat joints and at 60° flexion in the accessory UCL (117%) in round joints. In flat MCP joints, the RA is more dorsal and distal in the metacarpal head compared to round joints, resulting in a hinged flexion motion. Elongation of the UCL is highest at end flexion in round joints and highest at midflexion in flat joints. The different kinematics of flat and round MCP joints may contribute to the understanding of the pathophysiology of UCL ruptures. The propensity of this injury and the position in which they occur may be affected by the MCP joint morphology.

Management of Hand and Wrist Injuries in NCAA Division I Football Players From a Single Institution: Factors Associated With Epidemiology, Surgical Intervention, and Return to Play

Background: Upper extremity injuries account for approximately 16.9% of football injuries in the National Collegiate Athletic Association (NCAA). Purpose: To determine the epidemiology, management, and outcomes of hand/wrist injuries in collegiate football athletes so as to identify factors associated with surgical intervention and delayed return to play (RTP). Study Design: Descriptive epidemiology study. Methods: We retrospectively reviewed hand/wrist injuries that occurred within a single NCAA Division I football team from January 1, 2003, to December 31, 2020. Data analyzed included player position, college seniority, injury characteristics, injury management, surgical procedures performed, and timing of RTP. A univariate analysis was performed to identify factors associated with increased risk for surgical intervention and delayed (&gt;21 days) RTP after hand and wrist injury in this cohort. Results: Overall, 124 patients with 168 hand/wrist injuries were identified (9.9 wrist/hand injuries per year). Sprain of the thumb metacarpophalangeal (MCP) joint ulnar collateral ligament (UCL) was the most common diagnosis (19.6%). Surgery was required in 22% of injuries, with injury of the UCL of the thumb MCP joint (8/37) being the most common indication. Injuries occurring during competitive games (odds ratio = 4.29; 95% CI, 1.2-15.9) were associated with an increased risk for surgery. Most (70%) injuries did not lead to time missed from football, whereas the remaining 30% resulted in an average of 33 ± 36 days missed. Conclusion: Over 17 athletic seasons, the annual incidence of hand and wrist injury in these NCAA Division I football players was 9.9 injuries per year, with 22% requiring surgical treatment. Injury to the UCL of the thumb MCP joint was the most common injury and indication for surgery, and 30% of injuries resulted in approximately 1 month lost. Injuries sustained in games were associated with operative management and delayed RTP.

Ultrasound versus MRI in the evaluation of the thumb metacarpophalangeal joint.

An intricate and unique combination of ligamentous, fibrocartilaginous, and osseous structures stabilize the thumb metacarpophalangeal joint. Both ultrasound and high-resolution magnetic resonance imaging are extremely useful in evaluating these critical structures. This article reviews common injuries of the thumb metacarpophalangeal joint, while highlighting the merits, limitations, and pitfalls of the two imaging modalities. A clear appreciation of each method, paired with anatomic knowledge, will lend greater confidence and accuracy to diagnosing impactful injuries and guiding intervention.

Surgical Interventions for Chronic Ulnar Collateral Ligament Injuries of the Thumb: A Systematic Review.

Background: There is no consensus for the appropriate surgical management of symptomatic chronic ulnar collateral ligament (UCL) injuries of the thumb. The aim of this study is to systematically review the treatment of chronic thumb metacarpophalangeal (MCP) joint UCL injuries to determine the optimal approach to treatment. Methods: A systematic review of PubMed, Medline, Embase and ePub Ahead of Print was performed in accordance with Preferred Reporting of Items in Systematic Review and Meta-Analysis (PRISMA) guidelines. Results: Data from 11 studies using various surgical techniques in 245 thumbs were heterogenous and meta-analysis of results not possible. These data were qualitatively assessed. Direct repair, reconstruction with free tendon grafts and arthrodesis all demonstrated favourable outcomes with patient-reported outcome measures (PROMs). Conclusions: Direct repair can be safely performed more than 2 months following injury. Arthrodesis may be considered in heavy manual labourers or those with osteoarthrosis. Tendon grafting is safe, yet the optimal type and configuration are yet to be determined for reconstructive methods. Level of Evidence: Level III (Therapeutic).

Return to Sport and Performance After Thumb Metacarpophalangeal Joint Collateral Ligament Surgery in the National Basketball Association.

Introduction Basketball players are at increased risk of thumb collateral ligament injury (ulnar collateral ligament (UCL) and radial collateral ligament (RCL)). Methods The National Basketball Association (NBA) players with thumb collateral ligament surgery were identified using publicly available data. Performance statistics, ligament injuries (UCL or RCL), return to sport (RTS) time, laterality, and injury dates were recorded. Cases were matched 1:1 with controls based on age (±1 year), body mass index (BMI), NBA experience (±1 year), and performance statistics prior to the index date. RTS was defined as playing in one NBA game postoperatively. Career longevity was evaluated. Summary statistics were calculated, and Student's t-tests (ɑ = 0.001) were performed. Results All 47 players identified with thumb collateral ligament surgeries returned to sport. Thirty-three players (age: 26.9 ± 3.0) had one year of postoperative NBA experience for performance analysis. Career length (case: 9.6 ± 4.1, control: 9.4 ± 4.3, p > 0.001) was not significantly different from controls (p > 0.001). The same season time to RTS (n = 20) was 7.1 ± 2.4 weeks. Off-season or season-ending surgery (n = 13) RTS time was 28.4 ± 18.7 weeks. Neither thumb collateral ligament (UCL, n = 7; RCL, n = 10; unknown, n = 16) had an identifiable difference between the groups when evaluating career length. Career length, games/season, and performance were not different for players who underwent surgery on their dominant thumb (63.6%, 21/33) compared to controls (p > 0.001). Conclusion RTS rate is high in NBA athletes undergoing thumb collateral ligament surgery. Players do not experience decreased performance or career length due to thumb collateral ligament surgery, regardless of a dominant or non-dominant thumb injury.

Satisfactory thumb metacarpophalangeal joint stability after ligament reconstruction with flexor digitorum superficialis in children with radial longitudinal deficiency.

We investigated thumb joint stability and patient-reported and functional outcomes a minimum of 1 year after flexor digitorum superficialis opponensplasty and ligament reconstruction in 23 thumbs of 20 consecutive children with radial longitudinal deficiency. In total, 15 thumbs had preoperative multidirectional instability in the metacarpophalangeal joint. We reconstructed 22 ulnar and 16 radial collateral ligaments. At follow-up, all the metacarpophalangeal joints were stable ulnarly. Seven metacarpophalangeal joints were unstable radially despite ligament reconstruction but had no related complaints. We recommend the flexor digitorum superficialis opponensplasty as a safe and reliable procedure in hypoplastic thumbs to create stability and augment thumb strength.Level of evidence: IV.

Implant-free anatomical reconstruction of thumb metacarpophalangeal joint chronic ulnar collateral ligament injuries.

A technique is described to treat chronic instability of the metacarpophalangeal joint of the thumb caused by rupture of the ulnar collateral ligament using a palmaris longus tendon graft without implants. Good results were obtained in eight patients.

Opponensplasty for Severe Carpal Tunnel Syndrome with the Transfer of the Palmaris Longus Tendon to the Rerouted Extensor Pollicis Brevis Tendon.

The authors describe a novel opponensplasty for severe carpal tunnel syndrome that uses the palmaris longus (PL) tendon transferred to the rerouted extensor pollicis brevis (EPB) tendon with pulley reconstruction using a portion of the PL tendon simultaneously with the carpal tunnel release. Like the Camitz opponensplasty, this technique utilises the PL as the motor source, does not require special postoperative treatment and enables fast functional recovery even in older patients. Compared with the Camitz procedure, this technique can easily acquire thumb rotation without tendon bowstringing. Furthermore, because the function of the EPB tendon is preserved, the tendency of flexion in the thumb metacarpophalangeal (MP) joint is not observed after surgery, and improvement can be expected in patients with preoperative MP joint extension lag. This technique is a useful alternative to the Camitz procedure, as it overcomes the disadvantages of the Camitz procedure while preserving the advantages. Level of Evidence: Level V (Therapeutic).

Inter- and Intra-observer Agreement of Visual Estimation, Goniometric and Radiographic Measurement of Passive Thumb Metacarpophalangeal Joint Hyperextension.

Background: Reliable methods for measuring range of motion is important for hand therapists. Currently, there is no gold standard for the measurement of thumb metacarpophalangeal joint (MCPJ) hyperextension. We hypothesised that visual and goniometric measurements of thumb MCPJ hyperextension vary greater than 10° from radiographic measurements, and between observers. Methods: Twenty-six fresh-frozen hands were measured by a senior orthopaedic resident and fellowship trained hand surgeon. Passive thumb MCPJ hyperextension was measured by visual estimation, goniometry and axis measurement on a lateral thumb radiograph. Raters were blinded to each other's and their own prior measurements. Descriptive statistics were recorded for measurement type and inter-observer agreement using a two-way intra-class correlation coefficient (ICC). Intra-observer agreement was calculated using concordance correlation coefficient (CCC). Bland-Altman plots identified trends, systemic differences or potential outliers. Results: Mean measurements for both raters were similar for visual estimation and radiographic measurements. Mean goniometric measurements were twice as high for Rater B, and closer to radiographic measurements. For both raters, mean radiographic measurements were 10° greater than the other two methods. For inter-rater agreement, measurements were within 10° most frequently with radiographic measurement, then visual estimates, and least by goniometer measurements. Rater B had better agreement comparing visual and goniometric to radiographic measurements. Conclusions: Radiographic measurement has the best inter-observer agreement and precision for evaluating passive thumb MCPJ hyperextension, especially considering adjunct corrective procedures when performing a soft-tissue basal joint arthroplasty. Rater experience improves precision, but there is still poor agreement between visual estimates and goniometer measurements compared to radiographic measurements, as the former two underestimate hyperextension by 10°. Development of a standard method of clinical measurement is needed to improve reliability.

Thumb metacarpophalangeal joint morphology and reconstruction of the ruptured ulnar collateral ligament.

Studies on graft reconstruction techniques for ruptured thumb metacarpophalangeal (MCP) ulnar collateral ligaments (UCL) do not consider the variety of MCP joint morphology. Optimal reconstruction method for flat MCP joints is therefore unclear. Twenty-four fresh-frozen, human thumbs were tested for flexion, extension and valgus stability of the MCP joint. After resection of the UCL, four reconstruction methods, differing in the metacarpal origin and phalangeal attachment, were performed on each specimen, which were then tested again in the same way. Specimens were grouped as 'round' or 'flat' depending on morphometric parameters and group differences were analysed. In flat joints, only the non-anatomical Glickel reconstruction and a modified Fairhurst reconstruction maintained normal mobility and stability. In round joints, only the Glickel reconstruction maintained normal mobility and stability. The original Fairhurst method and a modification with the origin palmar in the metacarpus were disadvantageous in both flat and round joints.

Histology of the volar plate of the thumb metacarpophalangeal joint

BackgroundThe aim of the study was to describe the histology of the thumb MCPJ volar plate. MethodsFive fresh-frozen thumbs were dissected. The volar plates were harvested from the thumb MCPJ. Histological analyses were performed using 0.04% Toluidine blue and counterstained with 0.005% Fast green. ResultsThe thumb MCPJ volar plate comprised two sesamoids, dense fibrous tissue and loose connective tissue. The two sesamoids were connected by dense fibrous tissue, with collagen fibers oriented transversely (perpendicular to the long axis of the thumb). In contrast, the collagen fibers within the dense fibrous tissue on the lateral sides of the sesamoid were oriented longitudinally in line with long axis of the thumb. These fibers blended with the fibers of the radial and ulnar collateral ligaments. The collagen fibers in the dense fibrous tissue distal to the sesamoids ran transversely, perpendicular to the long axis of the thumb. The proximal aspect of the volar plate showed only loose connective tissue. The volar plate of the thumb MCPJ was largely uniform with no division of layers from the dorsum to the palmar surface. There was no fibrocartilaginous component in the thumb MCPJ volar plate. ConclusionsThe histology of the volar plate of the thumb MCPJ differs significantly from the conventional understanding of the volar plate, based on the volar plate of finger proximal interphalangeal joints. The difference is likely due to the presence of the sesamoids, which confer additional stability, reducing the need for a specialized trilaminar fibrocartilaginous structure with the lateral check-rein ligaments found in the volar plate of finger proximal interphalangeal joints to confer additional stability.