Biomechanical analysis of four-strand extensor tendon repair techniques

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Hand Surgery

Background:

• Flexor tendon repair experience suggests the augmented Becker (MGH) technique provides superior strength, toughness, and gap resistance.
• Extensor tendon injuries, particularly in Verdan's zone VI, require robust repair techniques to withstand early motion.

Purpose of the Study:

• To biomechanically compare the MGH technique with modified Bunnell and Krackow-Thomas four-strand repairs for extensor tendons in zone VI.
• To evaluate the gap resistance, strength, and toughness of these extensor tendon repair methods.

Main Methods:

• Three four-strand extensor tendon repair techniques (modified Bunnell, modified Krackow-Thomas, MGH) were performed on fresh human cadaver limbs.
• Repairs were conducted in Verdan's zone VI.
• Repaired tendons were subjected to distraction testing until rupture, with continuous monitoring of load and distraction to assess gap formation and ultimate strength.

Main Results:

• The MGH repair demonstrated significantly greater resistance to gap formation compared to the Bunnell and Krackow-Thomas repairs (p < .02).
• No significant differences were observed between the techniques regarding repair performance at metacarpophalangeal (MP) joint extension or at complete rupture.
• The MGH technique exhibited superior toughness and strength in resisting gap formation.

Conclusions:

• The MGH technique is biomechanically superior in terms of gap resistance for four-strand extensor tendon repairs in Verdan's zone VI.
• The MGH repair is recommended for zone VI extensor tendon injuries, especially when early postoperative motion is planned.