INTRINSIC RISK FACTORS FOR THE DEVELOPMENT OF ACHILLES TENDON OVERUSE INJURY: A PROSPECTIVE STUDY

Background: Achilles tendon overuse injuries are common but the precise intrinsic risk factors for these injuries has not been well studied in prospective cohort studies.

Research question/s: What are the intrinsic risk factors for Achilles tendon overuse injuries?

Methodology:Subjects: 69 male military recruits (age 18.4 ± 1.3 years).

Experimental procedure: Each subject was evaluated for anthropometrical characteristics, isokinetic ankle muscle strength, ankle joint range of motion, Achilles tendon stiffness, explosive strength, and leisure and sports activity. Subjects were then followed during a 6-week basic military training programme for the development of Achilles tendon overuse injuries (diagnosed using history and clinical examination). Ten recruits (14.5%) sustained an Achilles tendon overuse injury.

Measures of outcome: Intrinsic risk factors.

Main finding/s:

• There was a tendency (p  =  0.76) for an increased dorsiflexion excursion with the knee extended in the Achilles tendon injury group (15.2 ± 5.35 deg) compared with the non-injured group (12.95 ± 5.39 deg).

• The cutoff value of the plantar flexor strength at 85% sensitivity was 50.0 Nm (with 4.5% specificity).

• The cutoff value of the dorsiflexion range of motion at 85% sensitivity was 9.0^o (with 24.2% specificity).

Conclusion/s: In a prospective cohort study, reduced plantar flexor strength (<50 Nm) and increased ankle dorsiflexion range of motion (>9.0^o) are significant predictors of Achilles tendon overuse injury.