Key points

Introduction

Motion of the finger requires bony stability, sensibility, muscle integrity, tendon gliding, and flexible joints. Full range of motion in the finger joints is the precondition of good function of the finger. The term stiff finger refers to a reduction in the range of motion in the finger. Almost all injuries of the fingers can cause finger stiffness, even when the joint is not directly involved in the initial injury. Furthermore, many diseases such as Dupuytren disease, rheumatoid arthritis, gout, and diabetes mellitus result in loss of motion of the finger. In addition, congenital stiffness of fingers without definite cause had been reported. Although the stiff finger has a similar clinical manifestation to joint contracture, different causative factors contribute to the stiffness. Both bone and soft tissue are what ultimately provide mechanical blocks to motion, resulting in finger stiffness. This article focuses on the soft-tissue causes of the injury by reviewing the anatomy, classification, precautions and nonoperative and operative intervention.

Introduction

Motion of the finger requires bony stability, sensibility, muscle integrity, tendon gliding, and flexible joints. Full range of motion in the finger joints is the precondition of good function of the finger. The term stiff finger refers to a reduction in the range of motion in the finger. Almost all injuries of the fingers can cause finger stiffness, even when the joint is not directly involved in the initial injury. Furthermore, many diseases such as Dupuytren disease, rheumatoid arthritis, gout, and diabetes mellitus result in loss of motion of the finger. In addition, congenital stiffness of fingers without definite cause had been reported. Although the stiff finger has a similar clinical manifestation to joint contracture, different causative factors contribute to the stiffness. Both bone and soft tissue are what ultimately provide mechanical blocks to motion, resulting in finger stiffness. This article focuses on the soft-tissue causes of the injury by reviewing the anatomy, classification, precautions and nonoperative and operative intervention.

Anatomy and classification

The anatomy of the MCP joint and PIP joint are complicated and intricate. The MCP and PIP joints share some structural similarities but have significant structural differences.

The base of the proximal phalanx and metacarpal head are the bony foundations of the MCP joint. The soft-tissue boundaries of the joint are made up of the articular capsule and ligaments. The collateral ligaments originate from the tubercle of the metacarpal head and run diagonally in a ladder-shape to the base of proximal phalanx. The length of the collateral ligament changes as the joint flexes and extends. The bilateral accessory collateral ligaments (ACLs) originate slightly proximal and volar to the collateral ligaments. The distal fibers of the ACL attach to the edge of the volar plate and flexor sheath. The volar or palmar plate is a fibrocartilaginous structure that constitutes the base of the MCP joint ( Fig. 1 ). The extensor and flexor tendons, sagittal band, and lumbrical and interosseous muscles embrace the joint and these ligaments. The MCP joint is a condylar joint that has 2 axes of freedom including flexion/extension and radial/ulnar deviation.

Anatomy of the MCP joint. The collateral ligaments arise from the metacarpal head to the base of the proximal phalanx. Proximal and volar to the collateral ligament is the accessory collateral ligament (ACL). The volar plate is directly palmar to the joint.

The head of the proximal phalanx and base of the middle phalanx constitute the bony structures of the PIP joint. The PIP joint is a simple hinge joint that can only move along the flexion/extension axis. The origin and insertion of the collateral ligament, ACL, and volar plate are similar to the MCP joint. The dorsal extensor apparatus, flexor tendons, and their sheath embrace the joint ( Fig. 2 ). The tension in the collateral ligament changes little as the PIP joint moves. Similar to the MCP joint, the volar plate of the PIP joint is composed of 2 portions: a fibrous and a membranous portion. The volar plates of PIP joints are thinner than at the MCP level for most fingers. On each side of the volar plate, it is reinforced by a checkrein ligament that attaches onto the periosteum of the proximal phalanx ( Fig. 3 ). The collateral ligaments and volar plate are composed of a 3-dimensional ligament-box complex that plays a major role in providing the stability of the PIP joint.

Anatomy of the PIP joint. The collateral ligaments and volar plate of the PIP joint are similar to that of the MCP joint. The extensor apparatus and flexor tendons embrace the joint. FDP, flexor digitorum profundus.

Anatomy of volar plate of the PIP joint. The volar plate is composed of fibrous and membranous portion, and it is reinforced by 2 checkrein ligaments proximally.

The distal interphalangeal (DIP) joint is a hinge joint that is composed of the middle phalanx head and distal phalanx base. The DIP joint has flexion, extension, and hyperextension motion. The capsule is reinforced by the collateral ligaments, volar plate, terminal extensor tendon and flexor digitorum profundus tendon.

Stiff fingers are categorized into flexion and extension deformities according to the fixed posture of the joint. Stiff finger deformities can also be classified into 4 categories according to the involved tissues: (1) skin and fascia-related problems, (2) muscle and tendon injuries or lesions, (3) capsule and ligament of joint contractures, and (4) damage of articular bone. The common causes are listed in Table 1 . Some structures result in only one type of deformity, but others can initiate either flexion deformities or extension deformities in different conditions. For example, the collateral ligament contracture is a common reason for flexion contracture of the PIP joint, but rarely, the collateral ligament contracture may also cause an extension deformity.

Information from the patient’s history may be used to discover the cause of joint stiffness. Examination of joint motion is also helpful for a surgeon to identify whether the musculotendinous structures are involved or the contracture is limited to the capsuloligamentous and articular structures. Decrease in active movement more than in passive movement is more likely to be caused by a musculotendinous problem. However, when active and passive motion are limited to the same degree, joint contracture or bone block is the likely cause. Knowledge of the specific patterns of joint deformities (eg, boutonnière deformity, mallet deformity, swan neck deformity) can also be helpful in identifying the cause of the stiff finger. Nevertheless, it may be difficult to determine precisely which structures are involved in some complicated cases.

Precaution

As discussed earlier, the stiff finger is a challenge to treat for many reasons. Stiff fingers may occur in fingers that are not directly injured. For example, an avulsed index finger may result in a stiff small finger if the small finger is not considered during therapy. Prevention of a stiff finger is based on the principle of early joint motion. Therefore, treatment of original diseases and injuries of hands should reduce the duration of immobilization so that finger stiffness can be prevented. Minimizing bleeding, pain, and edema can reduce the inflammation response after injury or operation, which in turn permits hand motion earlier and prevents finger stiffness from developing.

To thwart finger stiffness, the recommended position of immobilization of the hand for any reason is the safe position. In the safe position, the wrist is in 30° of extension, the MCP joint is in 70° to 90° flexion position, and the PIP joint is in full extension ( Fig. 4 ). The opposed position of the MCP and PIP joints can make most portions of the collateral ligament of the MCP lengthened and the volar plate of the PIP joint straightened to minimize the contracture. Furthermore, the PIP joint should be immobilized in extension. This is because it is easier to restore flexion than extension after a PIP joint contracture.

Safe position of the hand. The wrist is in 30° of extension, the MCP joint is in 70° to 90° flexion position, and the PIP joint is in full extension.

Nonoperative intervention

The goal in treating the stiff finger is to provide patients with a pain-free, movable, and stable joint. Nonoperative interventions are effective for most patients who have lost motion. In a large trial study, Weeks and colleagues reported that 87% stiff joints responded sufficiently to exercise and dynamic splinting so that surgeries were not required.

Some investigators believe that patients should accept a certain program of nonoperative therapy before operative intervention is considered. Curtis concluded that if the PIP joint passively flexes to 75°, then patients should undergo physical therapy and splinting to achieve additional flexion rather than operative intervention.

Nonoperative treatment of stiff fingers includes exercise, joint mobilization, continuous passive motion, casting, and splinting. Joint motion loss occurs because the ligaments and capsule of the stiff joint have shortened. Splints are applied to provide stress to stimulate the shortened soft tissues to grow, hence improving the passive range of motion.

Various splints are applied in treating hand disease and injuries, and some are designed to position the MCP or interphalangeal joints in their available end range position. These splints are classified into static, serial static, static progressive, or dynamic splints. Static progressive and dynamic splints have been widely used in recent years. Dynamic splinting applies a passive constant force to maintain the stiff joint in a lengthened position using energy-storing or elastic materials. Static progressive splinting concentrates a force to the stiff joint to statically position at the maximal stretch, using inelastic components. Static progressive splints require adjustment of the inelastic components as the range of joint motion improves. Although these 2 types of splints are different in principle, the current literature suggests that both are effective to treat the stiff finger.

Force of joint distraction and time duration of stretching are 2 important parameters in applying a splint or cast. Flowers introduced his guidelines about how to choose the splint parameters according to the level of joint stiffness. However, the objective recommended force ranges for splinting to a stiff finger remain unknown. The soft tissues of finger joints have viscoelastic behaviors, and excessive force causes tissue inflammatory response. Overload causes extreme discomfort, pain, and edema because of tissue tearing and dislocation. Consequently, the range of motion should be applied with a low load within tissue tolerance.

Because force is limited to a low level, treatment may be improved by adjusting the time spent in the splint. Some investigators agreed that improvement in passive range of motion of a stiff joint was proportional to the time spent in a splint. In 1994, Flowers and LaStayo studied the outcomes of 15 patients with 20 PIP flexion contractures. Patients were randomly assigned to one of 2 groups. All subjects originally had their finger placed in the casts, with the finger positioned at target end range. The researchers measured passive range of motion for group A at 6 days and passive range of motion for group B at 3 days. The results showed that the passive range of motion gained during 6 days was almost twice as much as in 3 days for all subjects. These results were supported by a study by Prosser who investigated the outcome of 20 patients with PIP flexion contracture treated with splinting. Similar to Flower and LaStayo’s study, the statistical analysis showed that the time spent in a splint was also proportional to the final extension angle.

In 2003, Glasgow and colleagues conducted a prospective study of patients with hand joint contractures. One group used splinting for less than 6 hours per day, and the other group used splint for 6 to 12 hours per day. Analysis showed a statistically significant motion gain for the group with the longer daily total end range time. However, when comparing the effect of daily splint total end range time of 6 to 12 hours with 12 to 16 hours, Glasgow found there was no significant difference in extension range of motion between these 2 groups. Most patients had difficulty wearing splints more than 12 hours.

To explore the long-term relationship between the duration of treatment using dynamic splints and contracture resolution in stiff PIP joints, Glasgow and colleagues studied 41 participants with the PIP joint contracture treated with a dynamic splint for 12 weeks. They concluded that the number of weeks of treatment is also significantly associated with the extent of contracture resolution.