Central Slip Injury

What is a central slip injury?

A central slip injury is a type of hand injury that affects the extensor tendon. This tendon is responsible for straightening the middle joint of a finger (the proximal interphalangeal joint, or PIP joint). The “central slip” refers to the central portion of the extensor tendon (the extensor tendon runs along the back of the finger. It attaches to the middle phalanx bone). When this slip is torn or ruptured, the finger may become difficult to straighten at the PIP joint, leading to a characteristic deformity known as a “boutonnière deformity.”

Anatomy and Function

Understanding the extensor mechanism and central slip

The extensor mechanism has several components, each of which plays a distinct role in finger movement. It involves:

1. Extensor Digitorum Communis (EDC): The primary muscle that extends each finger. This muscle splits into tendons that travel along the back of each finger.
2. Dorsal Hood: A fibrous structure around the metacarpophalangeal (MCP) joint (knuckle), which stabilises the tendons and facilitates finger extension.
3. Lateral Bands: Two tendons that run along the sides of each finger and contribute to extending both the PIP and distal interphalangeal (DIP) joints.
4. Central Slip: The central portion of the extensor tendon that attaches to the middle phalanx (the bone in the middle of each finger) and directly straightens the PIP joint.

Function of the Central Slip

The central slip is key to the coordinated function of the extensor mechanism. Its main roles are:

• Extending the PIP Joint: When the extensor digitorum contracts, the central slip pulls on the middle phalanx, allowing the finger to straighten at the PIP joint.
• Balancing the Extensor Mechanism: The central slip stabilises the lateral bands, which then work in concert to extend both the PIP and DIP joints.
• Preventing Boutonnière Deformity: When the central slip is intact, it holds the PIP joint in line, preventing the finger from collapsing into a bent position (flexion) at the PIP joint with hyperextension at the DIP joint.

Types of Central Slip Injuries

Acute vs. chronic central slip injuries

Central slip injuries can be classified into two main types: acute and chronic. 

Acute Central Slip Injuries

An acute central slip injury occurs immediately after a direct trauma or significant force is applied to the finger, often during sports or an accident. This type of injury may involve a partial or complete tear of the central slip tendon at the PIP joint.

Chronic Central Slip Injuries

A chronic central slip injury results from an untreated or inadequately managed acute injury. When the injury goes unrecognised or untreated, it can lead to structural changes in the extensor mechanism over time, resulting in a permanent boutonnière deformity.

Prevalence

How common are central slip injuries?

Central slip injuries are relatively uncommon compared to other finger injuries. They are often underdiagnosed, as they can easily be mistaken for minor sprains or simple joint injuries, especially if the injury isn’t severe or if there is only a partial tear.

Prevalence and Context

• Sports-Related Injuries: Central slip injuries are more common among athletes in sports that involve direct impact to the hands, such as basketball, volleyball, and rock climbing. These sports carry a higher risk because fingers are often extended and vulnerable to jamming or impact.
• Occupational Risk: Individuals in occupations with frequent hand use, such as construction, manufacturing, or work involving machinery, are also at a higher risk, although central slip injuries still remain rare in these fields compared to more common hand injuries like fractures or cuts.

Summary

While central slip injuries aren’t among the most common hand injuries, they are significant because they can easily lead to long-term complications if undiagnosed or untreated. Being aware of this injury, especially in sports and high-risk jobs, can improve timely diagnosis and treatment, which is crucial for recovery. Access Ortho offers urgent orthopaedic care for finger injuries in our fracture clinic. Contact Access Ortho for a rapid appointment to minimise the risk of complications. Access Ortho provides emergency care for injuries and follow-up orthopaedic care. 

Symptoms and Causes

What Causes of Central Slip Injuries

Central slip injuries are primarily caused by trauma to the extensor mechanism on the back of the finger, particularly at the proximal interphalangeal (PIP) joint. This trauma can disrupt the central slip tendon, which is crucial for straightening the PIP joint.

Common Causes Include:

1. Direct Impact or Trauma: A forceful impact to the dorsal (back) side of an extended finger can tear the central slip. This often happens in sports like basketball, volleyball, or rock climbing, where fingers are frequently exposed to high-impact forces.
2. Forced Flexion of an Extended Finger: If the PIP joint is suddenly bent while the finger is extended, it can overstretch or tear the central slip. This is common in situations where a ball or other object jams a straightened finger.
3. Laceration or Cut: Sharp trauma, such as a cut to the back of the finger, can sever the central slip tendon.
4. Joint Dislocation: Dislocation of the PIP joint can lead to a central slip injury due to the force and misalignment involved in dislocation.

Risk Factors for Central Slip Injuries

Certain activities and conditions increase the likelihood of a central slip injury:

1. Sports Participation: Athletes, particularly those in sports like basketball, volleyball, rugby, and rock climbing, face a higher risk due to frequent finger impacts, forced flexion, and risk of jamming injuries.
2. Occupational Hazards: Jobs that involve heavy hand use, handling machinery, or exposure to sharp tools (e.g., construction, manufacturing, culinary professions) can put individuals at higher risk of traumatic injuries to the hands and fingers.
3. Inadequate Protection or Precaution: Lack of protective gear or techniques, especially in high-risk sports and occupations, can increase the chance of traumatic injuries to the hands and fingers.
4. Previous Finger Injuries: Individuals with a history of hand or finger injuries, especially to tendons or joints, may be at greater risk due to weakened structures or altered movement patterns.
5. Age and Joint Health: Older individuals or those with joint instability or ligament laxity might be more susceptible to tendon injuries, including central slip injuries.

Complications of Untreated Central Slip Injuries

If a central slip injury goes undiagnosed and untreated, complications may occur that will affect finger function and overall hand mobility. The most common complications include:

1. Boutonnière Deformity: The hallmark complication, a boutonnière deformity, develops when the central slip injury disrupts the extensor mechanism. Over time, the lateral bands of the extensor tendons migrate, causing the PIP joint to bend (flex) and the distal interphalangeal (DIP) joint to hyperextend. This deformity is both functional and aesthetic, making the finger appear “buttonhole” shaped and limiting its mobility.
2. Loss of PIP Joint Extension: Due to the tendon injury, the finger may lose the ability to fully straighten at the PIP joint, reducing the hand’s functional range and fine motor capabilities.
3. Stiffness and Joint Contracture: If untreated, the joint may become stiff and develop contractures (permanent tightening of muscles, tendons, or skin), further limiting finger mobility.
4. Weak Grip Strength: With a boutonnière deformity or limited extension, the finger loses leverage, which can reduce grip strength and affect tasks requiring pinch or grip force.
5. Chronic Pain and Swelling: Long-standing deformities and untreated injuries may cause persistent pain, swelling, or discomfort, especially with hand use.

Summary

Untreated central slip injuries can lead to long-term deformities, functional limitations, and chronic pain, underscoring the importance of early diagnosis and intervention. Promptly recognising the risk factors and symptoms can help prevent these complications and support optimal hand function. Access Ortho offers care for orthopaedic injuries, such as injuries to the fingers. As specialists in orthopaedic care, our staff will provide comprehensive assessments, treatment plans, and follow-up care.

Diagnosis and Assessment

Diagnosis of Central Slip Injuries

Diagnosing a central slip injury requires a careful clinical assessment, as the symptoms can be subtle, especially with partial tears. Early diagnosis is essential to prevent complications like boutonnière deformity and to initiate proper treatment. It is important to seek care by medical staff trained in orthopaedics. 

Steps in Diagnosis Include:

1. Patient History: The medical team begins by taking a detailed history of the injury, including how it occurred, any immediate symptoms (like pain and swelling), and the patient’s ability to move the finger.
2. Physical Examination: A thorough physical assessment is performed to look for any visible deformity, swelling, bruising, tenderness, and range of motion at the PIP joint. The inability to extend the PIP joint is a strong indicator of a central slip injury.
3. Observation of Finger Posture: The natural posture of the finger is examined for signs of boutonnière deformity, even if it’s not yet pronounced.

Tests Used to Evaluate Central Slip Injuries

To confirm the diagnosis, specific clinical tests and imaging studies are used:

1. Elson’s Test:
   1. Purpose: The most commonly used and reliable test for diagnosing central slip injuries.
   2. Method: The patient is asked to bend the injured finger over the edge of a table (PIP joint flexed to 90°) while the examiner holds the finger in this position. The patient then attempts to extend the middle phalanx.
   3. Positive Result: If the central slip is intact, the patient will feel resistance while trying to straighten the finger. If the central slip is injured, the patient will not be able to produce much force or resistance, and the distal joint may droop slightly.
2. Bunnell’s Test:
   1. Purpose: Assesses the integrity of the extensor mechanism.
   2. Method: The finger is placed in slight flexion, and the examiner gently pushes down on the DIP joint while observing the PIP joint’s response.
   3. Positive Result: In a central slip injury, the PIP joint may flex further while attempting to control the DIP joint, indicating weakness in the central slip.
3. Isolated PIP Extension Test:
   1. Purpose: Helps evaluate extensor tendon function at the PIP joint.
   2. Method: The examiner holds the other fingers in flexion and asks the patient to extend only the PIP joint of the injured finger.
   3. Positive Result: An inability to extend the PIP joint or a limited range indicates potential central slip damage.
4. Imaging:
   1. X-rays: Used primarily to rule out fractures, particularly if there was a high-impact injury.
   2. MRI or Ultrasound: These imaging methods visualise soft tissue. They can confirm the extent of the central slip injury or detect partial tears, which are harder to diagnose with clinical tests alone.

Specific Considerations for Boutonnière Deformity

A boutonnière deformity is the most common complication of untreated or chronic central slip injuries. Diagnosing and assessing boutonnière deformity involves:

1. Physical Examination:
   1. Finger Position: In a boutonnière deformity, the PIP joint is flexed (bent), and the DIP joint is hyperextended (over-straightened). If the central slip injury goes untreated, the deformity often becomes more apparent over time.
   2. Tenderness: There is usually tenderness over the dorsal side of the PIP joint.
2. Functional Assessment:
   1. Range of Motion (ROM): Boutonnière deformities can severely limit ROM in both the PIP and DIP joints. This assessment can help gauge the impact on hand function and plan the treatment.
   2. Strength Tests: The strength of the extensor mechanism is tested to determine the degree of weakness or functional limitation.
3. Differentiating from Other Conditions:
   1. A boutonnière deformity can sometimes resemble other conditions, such as arthritis-related deformities or swan-neck deformities. Accurate diagnosis ensures that treatment targets the correct underlying problem.
4. Imaging Considerations:
   1. MRI or Ultrasound: These can confirm tendon migration or show the exact positioning of the lateral bands if surgery is being considered.
   2. Dynamic Imaging: In some cases, clinicians may use imaging while the patient moves the joint to better understand tendon alignment.

Summary

Accurate diagnosis of central slip injuries relies on a combination of clinical tests, imaging, and careful assessment of the injured finger’s functional abilities. Early identification is critical to avoid boutonnière deformity, which requires more complex management. The staff at Access Ortho are trained in the care and management of orthopaedic injuries. Expert care ensures accurate diagnosis and treatment.

Management and Treatment

Conservative Treatment Options for Central Slip Injuries

For central slip injuries that are diagnosed early, especially if they involve partial tears, conservative treatment is typically the first approach.

Conservative Treatment Options Include:

1. Splinting:
   • Method: A splint is used to immobilise the PIP joint in full extension while the DIP joint is left free to move.
   • Duration: The splint is worn continuously for 4-6 weeks, depending on the injury and the healing response. During this period, it’s essential to avoid any bending of the PIP joint to allow the tendon to heal correctly.

Types of Splints: Common options include stack splints, custom moulded splints, or dynamic splints designed specifically for extensor tendon injuries.

2. Edema Management:
   • Swelling control is crucial in the early stages. Elevation, ice application, and gentle massage may be recommended to reduce swelling and improve circulation, which supports healing.
3. Avoiding Certain Movements:
   • Activities to avoid are those that involve gripping, heavy lifting, or direct pressure on the injured finger, as these movements can disrupt the healing process.

Effectiveness: Conservative treatment is generally effective for partial tears or small avulsions (when a small piece of bone is torn off with the tendon). Compliance with splinting and avoiding stress on the finger are critical to successful healing. Access Ortho can fit splints as required, or for more complex injuries, a referral will be made to a skilled hand therapist.

Surgical Interventions for Central Slip Repairs

When the central slip is completely ruptured, conservative treatment fails, or the injury is diagnosed too late and has progressed to a boutonnière deformity, surgery may be necessary.

Surgical Options Include:

1. Primary Repair:
   • Indication: Used in cases of acute, complete rupture or significant avulsion injuries.
   • Procedure: The surgeon reattaches the tendon directly to the bone at the middle phalanx or repairs the torn central slip using sutures.
   • Outcome: Primary repair is generally effective if performed soon after the injury, allowing a good chance of restoring full function.
2. Tendon Grafting or Transfer:
   • Indication: If the injury is chronic or the tendon is irreparable, a tendon graft (using a portion of tendon from elsewhere in the body) or a tendon transfer (redirecting an adjacent tendon to take over the function of the central slip) may be performed.
   • Procedure: Tendon grafts are carefully attached to the bone and the extensor mechanism to restore proper function and movement.
   • Outcome: This approach can restore some degree of movement but may not fully replicate the original function, especially in long-standing injuries.
3. Lateral Band Realignment:
   • Indication: For cases with boutonnière deformity where lateral bands have migrated.
   • Procedure: The surgeon repositions the lateral bands, which are misaligned due to the central slip injury, to improve extension at the PIP joint.
   • Outcome: Realignment can reduce the deformity and improve the finger’s appearance and function.
4. Joint Fusion (Arthrodesis):
   • Indication: In severe, chronic cases where deformity and joint damage are extensive, and restoring movement is not feasible.
   • Procedure: The PIP joint is surgically fused in a functional position, eliminating movement at that joint but stabilising the finger.
   • Outcome: Fusion can relieve pain and provide stability, though it sacrifices mobility at the fused joint.

Rehabilitation Protocol Summary for Central Slip Injuries

Rehabilitation is essential for restoring finger function, preventing stiffness, and minimising the risk of re-injury. The protocol should be personalised and carried out under professional supervision.

1. Early Mobilisation:
   • Timing: Begins around 4-6 weeks post-injury or surgery.
   • Exercises: Gentle range-of-motion movements for PIP and DIP joints, starting with passive exercises and progressing to active ones as healing advances.
2. Strengthening Exercises:
   • Timing: Introduced at 8-12 weeks, when the repair site is stable.
   • Exercises: Light resistance exercises (using bands or putty) to strengthen the extensor mechanism and restore PIP joint extension.
3. Scar Management (Post-Surgery):
   • Techniques: Massage, silicone sheeting, or ultrasound therapy to reduce scar tissue and support smooth tendon movement.
4. Joint Flexibility and Mobility:
   • Goal: Maintain full range of motion through active and passive stretching exercises, preventing stiffness and contractures.
5. Functional Activities:
   • Goal: Rebuild everyday hand functions like gripping and pinching, boosting coordination and confidence in finger use.

Rehabilitation Duration: Full recovery may take 8-16 weeks or longer, depending on injury severity and treatment. Your treating doctor can provide details of your expected recovery timeline. 

Summary

Effective management of central slip injuries requires a comprehensive approach, starting with early diagnosis and, where possible, conservative splinting. Surgical interventions are reserved for more severe or chronic cases, while a structured rehabilitation protocol supports optimal recovery, mobility, and functionality. A rapid orthopaedic assessment helps minimise complications. Access Ortho offers urgent appointments for acute injuries.

Prevention

Prevention Strategies for Central Slip Injuries

Preventing central slip injuries involves protective measures, especially in sports and high-risk occupations. Key strategies include:

1. Protective Gear: Using finger splints, gloves, or tape in activities like sports or manual work can help reduce the chance of direct trauma to the fingers.
2. Proper Technique: Learning and practising correct finger positioning in sports, such as avoiding hyperextension, can minimise injury risk.
3. Strength and Flexibility Training: Regular strengthening and stretching exercises for the hands and fingers improve resilience and reduce the likelihood of injury under stress.
4. Awareness and Caution: Being mindful of finger positioning and avoiding forceful contact with extended fingers, especially in high-contact situations, can prevent injury.

By incorporating these strategies, individuals can lower their risk of central slip injuries and protect hand function.

Prognosis and Recovery

Prognosis and Recovery for Central Slip Injuries

If diagnosed early and treated properly, central slip injuries generally have a good prognosis. The expected recovery and outcomes depend on the severity of the injury, the treatment type, and the adherence to rehabilitation protocols.

What to Expect After a Central Slip Injury

• Restoration of Function: With appropriate treatment, many people regain near-full function of the injured finger. However, chronic or untreated injuries may lead to a permanent boutonnière deformity or limited range of motion.
• Potential Complications: Without timely intervention, the risk of joint stiffness, scar tissue formation, and weakened extension at the PIP joint increases, which may impact hand dexterity and grip strength.

Recovery Timeline

• Initial Healing: Immobilisation with a splint typically lasts 4-6 weeks to allow the central slip tendon to heal.
• Rehabilitation Phase: After immobilisation, gentle range-of-motion exercises start, progressing to strengthening and flexibility exercises over 8-12 weeks.
• Full Recovery: Most patients reach full function by 3-4 months, though some may require additional time, this is more likely after surgery or severe injury.

Overall, individuals can expect a good recovery with early diagnosis and consistent rehabilitation, often returning to normal daily activities within a few months.

When to Seek Medical Attention

When to Seek Medical Attention for Central Slip Injuries

It is important to seek medical attention promptly if you experience any of the following signs after a finger injury that may indicate a central slip injury:

1. Inability to Extend the PIP Joint: If you cannot straighten the middle joint (PIP) of your finger, it may indicate a central slip injury.
2. Visible Deformity: Any noticeable changes in the alignment or shape of the finger, such as drooping at the PIP joint or a pronounced boutonnière deformity.
3. Severe Pain or Swelling: Intense pain that does not subside or significant swelling around the finger that limits movement.
4. Numbness or Tingling: Sensations of numbness, tingling, or weakness in the finger or hand that may suggest nerve involvement.
5. Open Wounds or Lacerations: Cuts or abrasions on the finger, especially if they are deep or exposing underlying structures.
6. Persistent Symptoms: Any ongoing discomfort, stiffness, or loss of function in the finger that does not improve with rest or basic home care after a few days.

If you experience any of these signs, it is important to get immediate medical attention to ensure a proper diagnosis and timely treatment to prevent complications and ensure optimal recovery. Access Ortho is an urgent injuries clinic that treats only orthopaedic injuries. We offer rapid appointments and orthopaedic follow-up care.

The Role of Hand Therapy

The Role of Hand Therapy in Central Slip Injury Recovery

Specialised hand therapy plays a crucial role in the recovery from central slip injuries. A hand therapist provides targeted rehabilitation to restore range of motion, strengthen the extensor mechanism, and improve function. They design customised exercise programs, facilitate scar management, and educate patients on protective techniques to prevent re-injury. Early intervention with hand therapy significantly enhances recovery outcomes, reduces complications, and supports a return to daily activities, ultimately promoting optimal hand function and quality of life.

Access Ortho will refer you to a hand therapist if they feel your injury will benefit from this care. Access Ortho works closely with expert therapists to ensure rapid appointments and quality care.

Commonly Asked Questions

What is the difference between a central slip injury and a mallet finger?

A central slip injury involves the rupture or tear of the central slip tendon that extends the PIP joint, leading to a potential boutonnière deformity. In contrast, mallet finger is an injury to the extensor tendon at the distal phalanx, causing the inability to extend the DIP joint.

Can I still bend my finger with a central slip injury?

It may be difficult or painful to bend the PIP joint properly due to instability. Attempting to bend the finger might lead to further injury or pain, so seeking medical advice is essential.

How long does it take for a central slip injury to heal?

Healing time can vary, but most central slip injuries typically take about 4-6 weeks for initial healing, followed by an additional 2-4 months of rehabilitation to restore full function.

Will I need surgery for my central slip injury?

Surgery is usually required for complete ruptures or chronic injuries. A specialist orthopaedic opinion is required to assess the extent of the injury to determine the appropriate treatment approach.

What exercises can I do to prevent central slip injuries?

Exercises to help with hand and finger strength and flexibility, such as squeezing a stress ball or performing gentle stretches, can help prevent injuries. Focusing on proper technique in sports and activities is also crucial.

Are certain sports or activities more likely to cause central slip injuries?

Yes, sports that involve gripping, throwing, or high-impact activities (such as basketball, rugby, or gymnastics) are more likely to result in central slip injuries due to the risk of direct trauma to the fingers.

How can I differentiate between a central slip injury and other finger injuries?

Key indicators of a central slip injury include an inability to extend the PIP joint and the presence of swelling or pain in that area. In contrast, mallet finger presents as drooping at the DIP joint. It is important to consult a healthcare professional skilled in orthopaedics for a proper diagnosis.

What is the long-term outlook for patients with central slip injuries?

The long-term outlook is generally positive with appropriate treatment. Most patients regain significant function and mobility, though some may experience residual stiffness or weakness if the injury is severe or chronic.

Can a central slip injury lead to permanent deformity?

If left untreated or not managed properly, a central slip injury can lead to a boutonnière deformity, which may result in permanent changes in finger appearance and function.

Are there any home remedies for central slip injuries?

While home remedies should not replace medical treatment, rest, ice application, and elevation may help reduce pain and swelling. Always consult with a medical professional before starting any home treatments.