Anatomy and Biomechanics of the Thumb Carpometacarpal Joint

The trapeziometacarpal screw home torque mechanism as a clinical indicator of the posterior joint ligament complex integrity: A cadaveric investigation

BACKGROUND

To date, no clinical test provides specific objective information on the integrity of key ligamentous support of the trapeziometacarpal (TMC) joint.

PURPOSE

To examine the potential of the TMC joint screw home torque mechanism (SHTM) in estimating the integrity of the posterior ligament complex in older adult population. STUDY DESIGN: Cross-sectional laboratory-based study.

METHODS

Twenty cadaver hands presenting with various degrees of TMC joint degradation ranging from none to severe osteoarthritis (OA) were radiographed in multiple positions to establish their degeneration status, joint mobility, and amount of dorsal subluxation at rest and with the application of the SHTM. Comparisons and correlations between degeneration status, joint mobility, subluxation reduction and ligament status obtained from dissection were calculated.

RESULTS

No significant statistical correlation was demonstrated with the subluxation reduction ratio of the SHTM and the combined ligament complex value however, a moderate negative correlation was found with dorsal central ligament injury at 21 Nm (τb = -0.46, p < 0.05) and 34 Nm (τb = -0.45, p < 0.05). A statistically significant reduction of radial subluxation of the TMC joint was observed between the subluxation at rest (M = 5.2, SD = 1.9) and subluxation with SHTM of 21 Nm (M = 4.4, SD = 2.4), t (19) = 3.2, p = 0.01, 95% CI [0.3, 1.4] and subluxation with SHTM of 34 Nm (M = 4.3, SD = 2.6), t (19) = 2.6, p = 0.02, 95% CI [0.2, 1.5].

CONCLUSION

Our results did not support the SHTM as indicator of the TMC posterior ligament complex integrity however, it demonstrated 100% stabilization effect with non-arthritic TMC population.

Using a finite element model of the thumb to study Trapeziometacarpal joint contact during lateral pinch

BACKGROUND

Finite element (FE) analysis is widely used in different fields of orthopaedic surgery, however, its application to the trapeziometacarpal joint has been limited due to the small size, complex biconcave-convex joint geometry, and complex musculature. The goal of this study was to improve upon existing models by creating a muscle-driven FE thumb model and use the model to simulate the biomechanical effect of hand therapy exercises and ligament reconstructive surgeries.

METHODS

Bone and cartilage geometry were based on a CT dataset of a subject performing a static lateral pinch task. A previously validated musculoskeletal model was utilized to extract electromyography (EMG)-driven muscle forces. Five ligaments with biomechanical significance were modeled as springs using literature values and attached according to their anatomical landmarks.

FINDINGS

The biomechanical consequence of various interventions was proxied as a change in the maximum cartilage stress. The result shows tightening the dorsal ligament complex (dorsal radial ligament, dorsal central ligament, posterior oblique ligament) is the most effective, achieving a stress reduction of 4.8%. Five exercises used in hand therapies were modeled, among which thenar eminence strengthening showed the most prominent stress reduction of 4.0%. Four ligament reconstructive surgeries were modeled, with Eaton-Littler reconstruction showed the most significant stress reduction of 25.0%.

INTERPRETATION

Among the routinely utilized treatment options for early thumb osteoarthritis, we found that three methods: dorsal ligament imbrication, thenar eminence exercise, and the Eaton-Littler method may confer biomechanical advantages cartilage loading. These advantages align with the clinically observed favorable outcomes.

Anatomy and Biomechanics of the Thumb Carpometacarpal Joint

This review discusses the anatomy and biomechanics of the thumb carpometacarpal (CMC) joint. This articulation between the trapezium and first metacarpal is integral for opposition and other complex movements necessary for pinch and grasp maneuvers. Fortunately, this joint is well equipped to handle the extreme forces imposed by these movements, as it is stabilized by an elaborate arrangement of ligaments and muscles. Without this stability, thumb subluxation would occur with loading during pinch and grasp, and human prehension would be impossible. Understanding the interactions occurring within this joint is essential for adequately treating pathology arising in this crucial joint.

Do Relaxin Levels Impact Hip Injury Incidence in Women? A Scoping Review

PURPOSE

The aim of this review is to assess the current evidence regarding the impact of relaxin on incidence of soft tissue hip injuries in women.

METHODS

A trained research librarian assisted with searches of PubMed, Embase, CINAHL, and SPORTDiscus, with a preset English language filter. The review was completed per the Joanna Briggs Institute (JBI) Manual for Evidence Synthesis methodology. Included studies required assessment of relaxin effects on musculoskeletal health, pelvic girdle stability, or hip joint structures in human subjects. Letters, texts, and opinion papers were excluded.

RESULTS

Our screen yielded 82 studies. Molecularly, relaxin activates matrix metalloproteinases (MMPs) including collagenases MMP-1/-13 and gelatinases MMP-2/-9 to loosen pelvic ligaments for parturition. However, relaxin receptors have also been detected in female periarticular tissues, such as the anterior cruciate ligament, which tears significantly more often during the menstrual cycle peak of relaxin. Recently, high concentrations of relaxin-activated MMP-9 receptors have been found on the acetabular labrum; their expression upregulated by estrogen.

CONCLUSIONS

Menstrual cycle peaks of relaxin activate MMPs, which locally degrade collagen and gelatine. Women have relaxin receptors in multiple joints including the hip and knee, and increased relaxin correlates with increased musculoskeletal injuries. Relaxin has paracrine effects in the female pelvis on ligaments adjacent to hip structures, such as acetabular labral cells which express high levels of relaxin-targeted MMPs. Therefore, it is imperative to investigate the effect of relaxin on the hip to determine if increased levels of relaxin are associated with an increased risk of acetabular labral tears.

Failed Trapeziectomy Treated by Thumb Metacarpal Base Arthrodesis: A Case Series

Trapeziometacarpal joint arthritis is a prevalent condition with a preponderance to women. Most cases are asymptomatic, but typical symptoms are pain, reduced dexterity, and functional decline. Trapeziectomy is the most common surgical treatment in the United Kingdom for patients who remain significantly symptomatic despite nonoperative measures, and this generally produces acceptable outcomes; however, a proportion of patients remain significantly symptomatic. The authors present a case series of 4 patients who underwent successful thumb metacarpal base to index metacarpal base arthrodesis with either distal radial or iliac crest bone grafting. Three of these patients had persisting symptoms after a primary trapeziectomy and 1 patient had gross subluxation of the thumb related to rheumatoid arthritis. Technically, this is a simple procedure to perform. All patients had improved symptoms with satisfactory functional outcomes and an improved cosmetic appearance of the hand.

Suture Suspensionplasty Using Abductor Pollicis Longus and Flexor Carpi Radialis for Advanced Thumb Carpometacarpal Joint Arthritis

PURPOSE

Current operative treatment for advanced thumb carpometacarpal (CMC) joint arthritis mainly constitutes complete trapeziectomy with or without additional stabilizing procedures. However, it is unclear whether the additional procedures influence overall clinical outcomes. Therefore, the purpose of this study was to evaluate the effectiveness of our posttrapeziectomy suture suspensionplasty technique, performed using the abductor pollicis longus and flexor carpi radialis tendons, in patients with advanced thumb CMC arthritis.

MATERIALS AND METHODS

We evaluated 36 thumbs of 35 patients with advanced thumb CMC arthritis treated with combined operative excision of trapezium followed by a suture suspensionplasty using flexor carpi radialis and abductor pollicis longus tendons. We used a minimal volar approach to create a sling construct with a nonabsorbable suture material, which could support the thumb metacarpal base without pin fixation or tendon transfer. For radiographic evaluation, we used the ratio of the radial metacarpal subluxation to metacarpal articular width, estimated from the bilateral stress-view radiographic images of the thumb, and calculated the trapezial space ratio by dividing the trapezial space height by the proximal phalangeal length. The clinical outcomes were evaluated using the visual analog scale and disabilities of the arm, shoulder, and hand scores, along with evaluation of the improvement in both postoperative range of motion and strength recovery.

RESULTS

The mean duration of follow-up was 26 months (range, 18-60 months). The average visual analog scale and disabilities of the arm, shoulder, and hand scores decreased from 5.9 to 0.4 and from 51.6 to 27.0, respectively. The range of motion during palmar abduction and opposition of the metacarpophalangeal joint improved with an increase in mean value from 49.1 degrees to 54.1 degrees, and from 7.8 to 9.3 Kapandji score, respectively. The grip and key pinch strengths showed no significant changes from mean preoperative values of 13.3 kg and 3.8 kg to 13.2 kg and 3.2 kg, respectively, as measured at the 18-month follow-up.

CONCLUSIONS

Our suture suspensionplasty technique has several advantages including minimal invasive approach, short operative time, cost-effectiveness, and early mobilization. We suggest that it can be used as an effective, alternative stabilization method after a complete trapeziectomy.

Artificial-Hand Technology—Current State of Knowledge in Designing and Forecasting Changes

The subject of human-hand versatility has been intensively investigated for many years. Emerging robotic constructions change continuously in order to mimic natural mechanisms as accurately as possible. Such an attitude is motivated by the demand for humanoid robots with sophisticated end effectors and highly biomimic prostheses. This paper provides wide analysis of more than 80 devices that have been created over the last 40 years. It compares both the mechanical structure and various actuators from conventional DC motors and servomechanisms, through pneumatic muscles, to soft actuators and artificial muscles. Described measured factors include angles, forces, torques, tensions, and tactiles. Furthermore, the appropriate statistics of kinematic configuration, as well as the type or number of drive units and sensory systems, show not only recent problems, but also trends that will be followed in the future.

Subtraction hemiarthroplasty in basal joint arthritis: A case report

BACKGROUND

Basal joint arthritis is a common disease which is especially present in post-menopausal women. A variety of procedures have been described once conservative treatment has failed. The purpose of our study is to present a novel surgical technique based on a clinical case with three-year follow-up which is highly effective, even after failure of previous procedures.

CASE SUMMARY

We present a case of a 39 year-old-woman who suffered from recurring, persistent, sharp left thumb pain for several years. After two operative procedures, she presented again with intolerable, sharp pain over the trapeziometacarpal joint, and wished to proceed with a pain relieving procedure or arthroplasty. Intraoperatively, the articular surfaces appeared well, without any bare areas of bone or eburnation, resulting in the decision to perform a “subtraction hemiarthroplasty”. A shortening osteotomy of the os trapezium was performed by removing a slice of 8-9 mm bone, without damaging the joint cartilages. The osteotomy was stabilized using two screws, the ligament and capsular tissue was suture imbricated, and a cut down on the translation and a dorsal radial ligament reconstruction were performed. Three years after the final procedure, a long-term follow-up demonstrates excellent results, pain free with full range-of-motion.

CONCLUSION

Subtraction hemiarthroplasty with ligament tightening imbrication and reconstruction of the radial ligament led to excellent results in motion and pain.

Relaxin and fibrosis: Emerging targets, challenges, and future directions

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.