Casting Position for Distal Radius Fractures Changes Radiocarpal Joint Forces: A Cadaveric Study.

Area of Science:

• Orthopedic surgery
• Biomechanics
• Radiocarpal joint mechanics

Background:

• Nonsurgical treatment of distal radius fractures necessitates immobilization.
• Classical methods propose various cast positions for optimal healing.
• The impact of cast position on articular cartilage forces and pressures is not fully understood.

Purpose of the Study:

• To investigate the effect of short arm cast position on forces and pressures within the scaphoid and lunate fossae of the radiocarpal joint.
• To compare the biomechanical effects of neutral wrist alignment versus a flexed and ulnarly deviated (FUD) position.

Main Methods:

• Utilized ten fresh-frozen cadaveric specimens with standardized extra-articular distal radius fractures.
• Applied force sensors to the articular cartilage of the scaphoid and lunate fossae.
• Measured forces and pressures under a standard load with the wrist in neutral and FUD positions within a short arm cast.

Main Results:

• Both neutral and FUD casts significantly reduced overall radiocarpal joint forces and pressures compared to no cast.
• The FUD cast resulted in significantly greater force on the volar and dorsal lunate fossa and greater pressure on the dorsal lunate fossa compared to the dorsal scaphoid fossa.
• The volar lunate fossa experienced significantly greater relative force in the FUD cast compared to the neutral cast.

Conclusions:

• Casting effectively decreases forces and pressures in the radiocarpal joint for distal radius fractures.
• A flexed and ulnarly deviated (FUD) wrist position in a cast exacerbates forces and pressures on the lunate fossa compared to the scaphoid fossa.
• A neutral cast position is recommended to avoid increased pressure on the lunate fossa.