What is the cause of impaired distal finger flexion?

From the Guidelines

Distal finger flexion is primarily controlled by the flexor digitorum profundus (FDP) muscle, which allows us to bend the fingertips at the distal interphalangeal (DIP) joints. To test distal finger flexion, hold the middle joint (PIP) stable and ask the person to bend just the fingertip. Normal function allows approximately 80-90 degrees of flexion at this joint. Injuries to the FDP tendon, such as jersey finger (when the tendon tears from its attachment on the distal phalanx), can prevent active distal finger flexion. Treatment depends on the injury severity, ranging from splinting for partial tears to surgical repair for complete ruptures. Rehabilitation typically involves protected motion protocols starting 3-5 days after repair, with gradual progression to strengthening exercises after 6-8 weeks. The FDP muscle originates from the anterior forearm and inserts on the distal phalanx of each finger, making it the only muscle that can flex the DIP joint. Understanding distal finger flexion is important for diagnosing hand injuries and planning appropriate treatment to restore full hand function, as hand osteoarthritis can affect the DIP joints and cause pain and stiffness, as noted in the EULAR evidence-based recommendations for the management of hand osteoarthritis 1. Key factors to consider in the management of hand osteoarthritis include the localization of OA, risk factors, type of OA, presence of inflammation, severity of structural change, level of pain, disability, and restriction of quality of life, as well as comorbidity and co-medication 1. Some of the recommended treatments for hand OA include education concerning joint protection, exercise regimens, local application of heat, and splints for thumb base OA and orthoses to prevent or correct lateral angulation and flexion deformity 1. It is also important to consider the differential diagnosis for hand OA, as other conditions such as psoriatic arthritis, rheumatoid arthritis, gout, and haemochromatosis can also affect the hands 1. Plain radiographs can provide the gold standard for morphological assessment of hand OA, and blood tests may be required to exclude coexistent disease 1. Overall, a comprehensive approach to diagnosing and managing hand injuries and osteoarthritis is necessary to restore full hand function and improve quality of life. Some key points to consider when managing hand OA include:

• The importance of individualized treatment plans that take into account the patient's specific needs and circumstances 1
• The use of non-pharmacological and pharmacological treatment modalities, such as education, exercise, and local heat application 1
• The potential benefits and risks of different treatments, such as oral NSAIDs and SYSADOAs 1
• The need for regular monitoring and assessment of disease progression and treatment response 1.

From the Research

Distal Finger Flexion

• Distal finger flexion is related to the function of the extensor mechanism at the base of the distal phalanx, and injuries to this area can result in flexion deformity of the finger, also known as mallet finger 2, 3.
• Mallet finger usually results from forced flexion of an extended finger, and treatment can be difficult as patient compliance is essential to prevent permanent deformity 2.
• The condition is characterized by a flexion deformity of, and inability to actively extend, the distal interphalangeal joint, and can be managed with a strict extension or hyperextension immobilisation splint for 8 weeks 2.
• In some cases, surgery may be necessary, such as when there is a fracture involving more than 30% of the articular surface, or when conservative management fails 2, 3.
• Other deformities of the finger joints, such as swan neck deformity, can also result from an imbalance of the tendons and ligaments in the fingers, and treatment depends on the underlying cause 4.

Related Conditions

• Nerve compression syndromes, such as carpal tunnel syndrome, can also affect the function of the fingers and hands, and may be related to distal finger flexion 5, 6.
• The pathophysiology of nerve compression involves both ischemic and mechanical factors, and treatment may include conservative management, physical therapy, or surgery 5, 6.