Influence of generalized joint hyperlaxity on volar plate configuration and its interaction with the FDP tendon in the proximal interphalangeal joint: an MRI study

OBJECTIVES: The volar plate (VP) is critical for stabilizing the proximal interphalangeal joint (PIPJ) during flexion. However, its in vivo behaviour in individuals with generalized joint hyperlaxity (GJH) remains unclear. This study aimed to quantitatively assess VP displacement and its spatial relationship with the flexor digitorum profundus (FDP) tendon in individuals with/without GJH during PIPJ flexion and grasping conditions. METHODS: MRI scans of 64 index fingers (32 participants: 16 with GJH, 16 controls) were acquired at 5 PIPJ flexion angles (0°, 30°, 60°, 90°, full fist) under 2 standardized loading conditions (grasping and forceful grasping). Measured parameters included distances from VP insertions to the PIPJ centre of rotation (CoR), between VP and FDP tendon, and between CoR and FDP. İnter-rater reliability was assessed via ICCs. Group × position effects were analysed using 2-way repeated measures ANOVA with Greenhouse-Geisser correction, and correlations were examined for significant interactions. RESULTS: Most morphometric measures showed excellent reliability (ICC ≥ 0.76). CoR-VPTip and VP-FDP distances were significantly greater in the GJH group at specific angles, indicating altered VP dynamics (interaction P < .05). CoR-VPLip and VPLip-VPTip distances showed no group differences. VP-FDP correlation was weak to moderate (r = 0.41) during forceful grasping. CONCLUSIONS: These findings suggest that GJH primarily modulates the deformation and positional dynamics of the VP's proximal portion and alters its interaction with the flexor tendon during PIPJ flexion. ADVANCES IN KNOWLEDGE: This MRI-based study reveals region-specific VP adaptations in GJH, emphasizing the clinical relevance of segmental soft tissue evaluation.