Thumb Sesamoid Pain: Causes & Treatment

The intricate anatomy of the hand includes small bones known as sesamoids, and the sesamoid bone on thumb plays a crucial role in thumb function. The American Academy of Orthopaedic Surgeons recognizes that pain arising from these sesamoid bones, a condition often referred to as sesamoiditis, can significantly impair an individual's ability to perform everyday tasks. Biomechanical imbalances within the foot can indirectly affect the mechanics of the hand, potentially predisposing individuals to thumb sesamoid issues. Treatment options, which range from conservative measures to surgical interventions performed by hand specialists like those utilizing the Mayo Clinic's protocols, depend on the underlying cause and severity of the sesamoid bone on thumb pathology.

Sesamoid bones, small nodules of bone embedded within tendons, are found throughout the body, playing a crucial role in biomechanics. These often-overlooked structures act as biological pulleys, enhancing muscle force and reducing friction at joints.

Defining Sesamoids: More Than Just Tiny Bones

Unlike most bones connected at joints, sesamoids are uniquely positioned within tendons. This arrangement offers several biomechanical advantages.

They improve the angle of muscle action, increasing leverage and efficiency.

Furthermore, they protect the tendon from stress and the underlying joint surfaces from compressive forces. The patella (kneecap) is perhaps the most well-known example, but the thumb also relies on these small, yet powerful, bones.

The Thumb's Sesamoids: Vital for Dexterity and Strength

Within the thumb, two sesamoid bones reside within the tendons of the Flexor Pollicis Brevis and Adductor Pollicis muscles, near the metacarpophalangeal (MCP) joint at the base of the thumb.

These sesamoids are integral to the thumb's complex movements, including grasping, pinching, and opposition.

They enhance the force generated by the thumb muscles, distributing loads evenly across the MCP joint and preventing excessive stress on specific areas.

This balanced distribution of force is essential for maintaining joint stability and preventing early wear and tear.

Sesamoid Injuries: A Significant Impact on Hand Function

Injuries to the thumb sesamoids, while not as common as other hand injuries, can significantly impair hand function and overall quality of life. Sesamoiditis (inflammation of the sesamoids), fractures, and dislocations can cause pain, swelling, and limited range of motion.

These conditions often affect individuals who engage in activities that place repetitive stress on the thumb, such as athletes, manual laborers, and even frequent smartphone users.

The impact of sesamoid injuries extends beyond physical limitations. Chronic pain can interfere with daily tasks, reduce work productivity, and limit participation in recreational activities.

Early diagnosis and appropriate management are, therefore, crucial for restoring optimal thumb function and preventing long-term complications. Understanding the role of these small bones is a critical first step in addressing related pain and dysfunction.

Anatomy of the Thumb Sesamoids: A Detailed Overview

Sesamoid bones, small nodules of bone embedded within tendons, are found throughout the body, playing a crucial role in biomechanics. These often-overlooked structures act as biological pulleys, enhancing muscle force and reducing friction at joints.

Defining Sesamoids: More Than Just Tiny Bones

Unlike most bones connected at joints, sesamoids are embedded within tendons.

In the thumb, two sesamoid bones are typically located within the tendons that surround the metacarpophalangeal (MCP) joint, at the base of the thumb.

These small bones significantly influence the thumb's movement and stability.

The Metacarpophalangeal (MCP) Joint: A Key Articulation

The MCP joint, where the thumb's metacarpal bone meets the proximal phalanx, is essential for thumb function.

It allows for flexion, extension, abduction, adduction, and circumduction, enabling a wide range of hand movements.

The sesamoid bones reside on the palmar (palm-facing) side of this joint, acting as a critical component of its intricate mechanics.

Muscle Influence: The Flexor Pollicis Brevis

The Flexor Pollicis Brevis (FPB) muscle, one of the thenar muscles, plays a significant role in positioning and stabilizing the sesamoid bones.

The FPB's tendon splits, with each part enveloping a sesamoid bone before inserting onto the base of the proximal phalanx.

This unique arrangement allows the FPB to directly influence the sesamoids' alignment and function, enhancing its ability to flex the MCP joint.

Adductor Pollicis: Power and Stability

The Adductor Pollicis muscle contributes significantly to the thumb's power grip.

Its oblique and transverse heads converge to insert onto the base of the proximal phalanx and the ulnar sesamoid bone.

This insertion provides a strong adduction force and further stabilizes the sesamoid complex during forceful pinching and gripping activities.

Abductor Pollicis Brevis: Thumb Abduction

The Abductor Pollicis Brevis (APB), another key thenar muscle, is primarily responsible for thumb abduction – moving the thumb away from the hand.

While its primary insertion is on the radial aspect of the proximal phalanx, its influence extends to the sesamoid bones through its proximity and interaction with the surrounding soft tissues.

This coordinated action is essential for precision movements and overall hand dexterity.

Tendons Around the MCP Joint: Guiding the Sesamoids

Several tendons surround the MCP joint, including those of the Flexor Pollicis Longus (FPL), which passes between the sesamoid bones.

These tendons act as dynamic stabilizers, ensuring smooth and controlled movement of the thumb.

Their precise insertion points and coordinated action contribute to the sesamoids' function as a gliding mechanism, reducing friction and enhancing force transmission.

Ligamentous Support: Stability is Key

The MCP joint and sesamoid bones are supported by a complex network of ligaments, including the collateral ligaments and the palmar plate.

These ligaments provide static stability, preventing excessive movement and protecting the joint from injury.

The palmar plate, a fibrocartilaginous structure, connects the sesamoid bones and reinforces the joint capsule, providing crucial support against hyperextension.

Cartilage: A Protective Layer

Cartilage lining the articular surfaces of the MCP joint and the sesamoid bones reduces friction and facilitates smooth movement.

This hyaline cartilage acts as a shock absorber, protecting the underlying bone from wear and tear.

Damage to this cartilage can lead to pain and dysfunction, highlighting its importance in maintaining joint health.

Blood Supply: Nourishing the Bones

Adequate blood supply is crucial for sesamoid bone health and healing.

Small blood vessels penetrate the sesamoid bones, providing essential nutrients and oxygen.

Compromised blood flow, such as in avascular necrosis (AVN), can lead to bone tissue death and significant pain and disability.

Nerves: Sensing Pain and Position

Nerves surrounding the MCP joint and sesamoid bones transmit sensory information, including pain and proprioception (position sense).

The digital nerves provide innervation to the thumb, allowing for fine motor control and sensory feedback.

Damage or compression of these nerves can result in pain, numbness, and tingling, affecting the thumb's function and overall hand dexterity.

Pathologies Affecting the Thumb Sesamoids: From Inflammation to Fracture

The intricate anatomy of the thumb sesamoids renders them vulnerable to a spectrum of pathologies, ranging from inflammatory conditions to traumatic injuries. Understanding these conditions—their origins, manifestations, and diagnostic nuances—is crucial for effective management and optimal patient outcomes.

Sesamoiditis: The Overuse Injury

Sesamoiditis refers to the inflammation of the sesamoid bones and the surrounding soft tissues. It is primarily an overuse injury, commonly seen in athletes or individuals engaging in repetitive activities that place excessive stress on the thumb's MCP joint.

Causes and Symptoms

The main causes include repetitive activities, trauma, and improperly fitted footwear.

Symptoms typically include:

• Gradual onset of pain in the ball of the thumb.
• Tenderness to palpation over the sesamoid bones.
• Swelling and inflammation around the MCP joint.
• Pain that worsens with activity and improves with rest.

Diagnostic Criteria

Diagnosis relies on a combination of clinical findings and imaging studies. Physical examination reveals point tenderness over the sesamoid bones. X-rays may be normal or show subtle changes. MRI can be helpful in identifying soft tissue inflammation and ruling out other causes of pain.

Sesamoid Fracture: Acute and Chronic Breaks

Sesamoid fractures can be categorized as acute fractures, resulting from a single traumatic event, or stress fractures, developing gradually due to repetitive stress.

Types and Mechanisms

Acute fractures typically occur due to direct impact or a sudden forceful contraction of the muscles attached to the sesamoid bones.

Stress fractures are more insidious, arising from repetitive loading and insufficient time for bone remodeling.

Diagnostic Imaging

X-rays are usually the first-line imaging modality for suspected sesamoid fractures. However, stress fractures may be difficult to visualize on plain radiographs, requiring advanced imaging such as MRI or bone scan for confirmation.

Dislocation/Subluxation: Joint Instability

Dislocation or subluxation of the thumb sesamoid bones refers to the displacement of the sesamoids from their normal anatomical position within the MCP joint.

Causes and Symptoms

These injuries are often caused by trauma, such as a direct blow to the thumb or a hyperextension injury. Ligamentous laxity, either congenital or acquired, can also predispose individuals to sesamoid instability.

Symptoms include:

• Pain and tenderness around the MCP joint.
• Instability or a feeling of giving way in the thumb.
• Visible deformity or malalignment in severe cases.

Bipartite Sesamoid Bone: A Common Anatomic Variant

A bipartite sesamoid bone refers to a sesamoid bone that is divided into two distinct fragments. This is a congenital condition and is often asymptomatic.

Differentiation from Fracture

It is crucial to differentiate a bipartite sesamoid from a fractured sesamoid bone. Bipartite sesamoids typically have smooth, well-corticated edges, while fractures often exhibit irregular, jagged margins. Comparison views of the contralateral thumb can be helpful, as bipartite sesamoids are often bilateral.

Avascular Necrosis (AVN): Bone Death

Avascular necrosis (AVN), also known as osteonecrosis, occurs when the blood supply to the sesamoid bone is disrupted, leading to bone cell death.

Causes, Symptoms, and Diagnosis

This can be a complication of a fracture, dislocation, or prolonged compression of the blood vessels supplying the sesamoid. Symptoms include:

• Deep, aching pain in the thumb.
• Stiffness and limited range of motion.
• Pain that worsens with activity.

Diagnosis is typically made with MRI, which can detect early changes in bone marrow edema and loss of vascularity.

Tendonitis/Tenosynovitis: Inflammation and Pain

Inflammation of the tendons (tendonitis) or their surrounding sheaths (tenosynovitis) around the thumb can indirectly impact the sesamoid bones, leading to pain and dysfunction.

Impact on Sesamoid Bones

The close proximity of the tendons to the sesamoid bones means that inflammation and swelling can exert pressure on the sesamoids, causing pain and limiting their normal movement.

Osteoarthritis: Degenerative Joint Disease

Osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of cartilage in the MCP joint.

Implications for Sesamoids

The sesamoids, being integral components of the MCP joint, are affected by the structural changes associated with OA. Cartilage loss and bone remodeling can lead to pain, stiffness, and reduced range of motion, further exacerbating pain around the sesamoid bones.

Diagnostic Methods: Identifying the Root Cause of Thumb Pain

Pathologies Affecting the Thumb Sesamoids: From Inflammation to Fracture The intricate anatomy of the thumb sesamoids renders them vulnerable to a spectrum of pathologies, ranging from inflammatory conditions to traumatic injuries. Understanding these conditions—their origins, manifestations, and diagnostic nuances—is crucial for effective management. This section explores the array of diagnostic methods employed to pinpoint the source of thumb pain, ranging from meticulous physical examinations to advanced imaging techniques.

Physical Examination: The First Line of Inquiry

A thorough physical examination is often the first step in diagnosing thumb sesamoid problems. This involves a careful assessment of the thumb's functionality and an attempt to pinpoint the source of the patient’s pain.

Range of Motion and Stability Assessment

The examiner will evaluate the thumb’s range of motion, checking for any limitations or painful movements. Restricted movement can indicate inflammation, arthritis, or mechanical blockage caused by a displaced sesamoid fragment.

Stability is assessed by applying gentle stress to the metacarpophalangeal (MCP) joint. Excessive movement can signify ligamentous laxity or instability of the sesamoid bones themselves.

Palpation and Pain Localization

Palpation, or feeling the area, is crucial. The examiner will carefully palpate around the MCP joint to identify the specific location of the pain. Tenderness directly over the sesamoid bones is a strong indicator of sesamoiditis or fracture.

Provocative maneuvers, such as applying pressure while moving the thumb, can help reproduce the patient’s pain and confirm the diagnosis.

Imaging Techniques: Visualizing the Unseen

When physical examination findings are inconclusive, or to confirm a suspected diagnosis, imaging techniques are essential. These modalities allow clinicians to visualize the sesamoid bones and surrounding structures.

X-ray: Detecting Fractures and Dislocations

X-rays, or radiographs, are often the first-line imaging study used to evaluate thumb pain. They are particularly effective in identifying fractures of the sesamoid bones and detecting dislocations or malalignment of the MCP joint.

Weight-bearing X-rays, taken while the patient is applying pressure to the thumb, can sometimes reveal subtle instability that is not apparent on standard non-weight-bearing images. It's also important to compare the images to the uninjured hand.

MRI (Magnetic Resonance Imaging): A Detailed Look at Soft Tissues

MRI provides detailed images of soft tissues, including tendons, ligaments, cartilage, and bone marrow. It is invaluable for diagnosing sesamoiditis, ligament injuries, and early stress fractures that may not be visible on X-rays.

MRI can also detect avascular necrosis (AVN), a condition in which the sesamoid bone loses its blood supply, leading to bone death.

Ultrasound: Assessing Tendons and Inflammation

Ultrasound uses sound waves to create real-time images of soft tissues. It is particularly useful for evaluating tendons around the thumb, such as the flexor pollicis brevis and adductor pollicis.

Ultrasound can detect tendonitis (inflammation of the tendon) and tenosynovitis (inflammation of the tendon sheath). It can also be used to guide injections of corticosteroids or other medications into the affected area.

Diagnostic Injection: Pinpointing the Pain Generator

In some cases, it can be challenging to determine the exact source of thumb pain. A diagnostic injection involves injecting a local anesthetic into the suspected area.

If the injection temporarily relieves the patient’s pain, it suggests that the injected area is indeed the source of the problem. This can be particularly helpful in differentiating between pain arising from the sesamoid bones and pain from surrounding structures, such as tendons or ligaments.

This diagnostic tool helps guide treatment decisions by confirming the specific pain generator.

Treatment Strategies: Conservative and Surgical Approaches

Pathologies Affecting the Thumb Sesamoids: From Inflammation to Fracture

The intricate anatomy of the thumb sesamoids renders them vulnerable to a spectrum of pathologies, ranging from inflammatory conditions to traumatic injuries. Understanding these conditions—their origins, manifestations, and diagnostic pathways—is crucial. But effective management is the ultimate goal. Treatment strategies encompass both conservative and surgical approaches. Selection depends on the specific diagnosis, severity, and individual patient factors.

Conservative Management: A Foundation for Healing

Conservative treatments form the cornerstone of managing most thumb sesamoid issues. These non-operative approaches aim to reduce pain, inflammation, and promote healing. They can often restore function without resorting to surgery.

Rest and Activity Modification

Rest is paramount in the initial stages of treatment. This involves avoiding activities that aggravate the condition. Modifying hand use to minimize stress on the thumb sesamoids. This can allow inflammation to subside.

RICE Protocol

The RICE protocol is a fundamental component of conservative management:

• Ice: Applying ice packs for 15-20 minutes at a time, several times a day, helps to reduce inflammation and pain.

• Compression: Using a bandage or splint to provide support and minimize swelling.

• Elevation: Elevating the hand above heart level can further reduce swelling.

NSAIDs

Nonsteroidal anti-inflammatory drugs (NSAIDs) can be effective in managing pain and inflammation. These medications are available over-the-counter or by prescription. They provide symptomatic relief.

Thumb Spica Splint

Immobilization with a thumb spica splint is often necessary, especially for fractures or dislocations. The splint restricts movement, allowing the sesamoid bones to heal properly. The duration of immobilization varies based on the injury.

Orthotics

Custom or over-the-counter orthotics can help redistribute pressure away from the sesamoid bones. These devices provide support and cushioning. Orthotics are particularly useful for sesamoiditis and related conditions.

Physical Therapy

Once the acute inflammation has subsided, physical therapy plays a crucial role. Physical therapy focuses on improving strength, range of motion, and function. Exercises may include gentle stretching, strengthening exercises, and proprioceptive training.

Corticosteroid Injections

In some cases, corticosteroid injections may be considered to reduce inflammation around the sesamoid bones. Injections can provide temporary relief. There are potential side effects, repeated injections are generally avoided.

Surgical Interventions: When Conservative Measures Fail

Surgical intervention is typically reserved for cases where conservative treatments have failed to provide adequate relief. Or in situations involving significant instability, displaced fractures, or other severe pathology.

Sesamoidectomy

Sesamoidectomy involves the surgical removal of the sesamoid bone. This procedure may be considered when other treatments have not been successful. It can alleviate pain and improve function.

Indications for sesamoidectomy include:

• Chronic pain unresponsive to conservative measures.

• Significantly displaced or fragmented fractures.

• Severe sesamoiditis with persistent symptoms.

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There are also Risks and Benefits*.

• Benefits: Relief from pain, improved thumb function.

• Risks: Potential for altered biomechanics, weakness, nerve injury, scar tissue formation.

Careful patient selection and surgical technique are essential to minimize complications and optimize outcomes.

Other Treatments: Emerging Therapies

Platelet-Rich Plasma (PRP) Therapy

Platelet-rich plasma (PRP) therapy is an emerging treatment option for thumb sesamoid issues. PRP involves injecting a concentrated solution of platelets, derived from the patient's own blood, into the affected area.

PRP injections aim to promote healing by delivering growth factors to the injured tissues. While the evidence for PRP therapy is still evolving, some studies suggest it may be beneficial for certain conditions. This includes sesamoiditis and non-union fractures.

Medical Professionals Involved in Treatment: Building Your Care Team

The journey to recovery from thumb sesamoid issues often requires a collaborative effort from a diverse team of medical professionals. Each specialist brings unique expertise and skills, contributing to accurate diagnosis, effective treatment, and comprehensive rehabilitation.

Understanding the roles of these individuals is crucial for patients seeking optimal care and navigating the complexities of the healthcare system. Building a strong and well-coordinated care team is paramount for a successful outcome.

Core Specialists

Several medical specialties are central to the diagnosis and management of thumb sesamoid problems. Orthopedic surgeons and hand surgeons often lead the medical team.

Orthopedic Surgeons

Orthopedic surgeons are medical doctors specializing in the diagnosis and treatment of musculoskeletal conditions. Their expertise encompasses a wide range of bone and joint problems, including fractures, arthritis, and sports-related injuries.

In the context of thumb sesamoid issues, orthopedic surgeons can evaluate the extent of the injury, recommend appropriate treatment strategies (both conservative and surgical), and perform surgical procedures when necessary.

Hand Surgeons

Hand surgeons possess specialized training in the intricate anatomy and function of the hand and upper extremity. This specialized knowledge makes them particularly well-suited to manage complex conditions affecting the thumb, including sesamoid injuries.

Hand surgeons are skilled in performing intricate surgical procedures to repair damaged tendons, ligaments, and bones. Their expertise extends to non-surgical management techniques such as injections and splinting.

Allied Health Professionals

Beyond surgeons, allied health professionals play a vital role in patient care and rehabilitation.

Physical Therapists

Physical therapists are movement specialists dedicated to restoring function and reducing pain through exercise, manual therapy, and patient education.

They are integral to the rehabilitation process following thumb sesamoid injuries, guiding patients through personalized exercise programs to improve strength, range of motion, and dexterity. Physical therapists also provide valuable education on injury prevention and proper hand mechanics.

Radiologists

Radiologists are medical doctors who specialize in interpreting medical images, such as X-rays, MRI scans, and ultrasound. Their expertise is essential for accurately diagnosing thumb sesamoid injuries.

Radiologists can identify fractures, dislocations, and other abnormalities that may not be apparent on physical examination alone. They provide crucial information to the medical team, guiding treatment decisions and monitoring the healing process.

Other Contributing Professionals

Depending on the specific nature of the thumb sesamoid issue, other healthcare providers may also be involved in the care team.

Rheumatologists may be consulted to evaluate and manage inflammatory conditions affecting the joints of the hand. Pain management specialists can help manage chronic pain associated with sesamoid injuries.

Ultimately, effective communication and collaboration among all members of the care team are critical to ensuring patients receive comprehensive, coordinated, and patient-centered care. The best possible outcome can only be achieved with the right level of care.

So, if you're experiencing pain around the base of your thumb and suspect it might be thumb sesamoid pain, don't just tough it out! Listen to your body, try some of the remedies mentioned, and if the pain persists, definitely consult a healthcare professional. Taking care of that tiny sesamoid bone on thumb can make a big difference in your hand function and overall comfort.