Prioritize proximal interphalangeal joint extension, a cadaver study clarifying PIPJ neutral position and joint capsular behavior.

Abstract

Background: Dysmobility of the proximal interphalangeal joint (PIPJ) often arises following trauma, inflammation, or surgery, leading to joint stiffness and reduced range of motion. This condition results from capsular shortening and the development of arthrofibrosis, which restricts mobility and contributes to contracture formation.

Purpose: This study investigates the influence of joint position on capsular space volume distribution in the PIPJ, hypothesizing that the mid-flexion position maximizes capsular space, contributing to ligament shortening and arthrofibrosis. This study investigates the influence of joint position on capsular space volumen distribution in PIPJ, hypothesizing that the mid- flexion position maximizes capsular space, contributing to ligament shortening and arthrofibrosis.

Study design: A cadaveric study examining capsuloligamentous dynamics of the PIPJ across various joint positions.

Methods: Fifteen fingers from five fresh frozen cadaver specimens were evaluated through three studies: RESULTS: 1. The PIPJ demonstrated close-packed positions at full flexion and extension, with maximum capsular space volume observed in the mid-flexion position (30°-40° flexion). 2. Silicone injection consistently held the joint in a mid-flexion position, indicating maximal capsular volume. 3. Latex distribution varied with joint position, concentrating dorsally in extension, spreading equally volar-dorsal in mid-flexion and shifting volarly in flexion.

Conclusions: We propose call to call the mid-flexion position (of 30º-40º flexion) the "neutral" position. This position maximizes capsular space volume, facilitating ligament shortening and arthrofibrosis. Extension minimizes volar capsularspace volume and may be essential for preventing flexion contractures. Clinically, immobilizing the proximal interphalangeal joint in extension with dorsal compression may help prevent contracture and reduce edema, while manual therapy should target the mid-flexion position to enhance joint mobilization.