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Hamstring muscle activation and morphology are significantly altered 1-6 years after anterior cruciate ligament reconstruction with semitendinosus graft
Messer, Daniel J. Shield, Anthony J. Williams, Morgan D. Timmins, Ryan Gregory Bourne, Matthew N.
Messer, Daniel J.
Shield, Anthony J.
Williams, Morgan D.
Timmins, Ryan Gregory
Bourne, Matthew N.
Abstract
Purpose
Harvest of the semitendinosus (ST) tendon for anterior cruciate ligament reconstruction (ACLR) causes persistent hypotrophy of this muscle even after a return to sport, although it is unclear if hamstring activation patterns are altered during eccentric exercise. It was hypothesised that in comparison with contralateral control limbs, limbs with previous ACLR involving ST grafts would display (i) deficits in ST activation during maximal eccentric exercise; (ii) smaller ST muscle volumes and anatomical cross-sectional areas (ACSAs); and (iii) lower eccentric knee flexor strength.
Methods
Fourteen athletes who had successfully returned to sport after unilateral ACLR involving ST tendon graft were recruited. Median time since surgery was 49 months (range 12–78 months). Participants underwent functional magnetic resonance imaging (MRI) of their thighs before and after the Nordic hamstring exercise (NHE) and percentage change in transverse (T2) relaxation time was used as an index of hamstring activation. Muscle volumes and ACSAs were determined from MRI and distal ST tendons were evaluated via ultrasound. Eccentric knee flexor strength was determined during the NHE.
Results
Exercise-induced T2 change was lower for ST muscles in surgical than control limbs (95% CI − 3.8 to − 16.0%). Both ST muscle volume (95% CI − 57.1 to − 104.7 cm3) and ACSA (95% CI − 1.9 to − 5.0 cm2) were markedly lower in surgical limbs. Semimembranosus (95% CI 5.5–14.0 cm3) and biceps femoris short head (95% CI 0.6–11.0 cm3) volumes were slightly higher in surgical limbs. No between-limb difference in eccentric knee flexor strength was observed (95% CI 33 N to − 74 N).
Conclusion
ST activation is significantly lower in surgical than control limbs during eccentric knee flexor exercise 1–6 years after ACLR with ST graft. Lower levels of ST activation may partially explain this muscle’s persistent hypotrophy post ACLR and have implications for the design of more effective rehabilitation programs.
Level of evidence
IV.
Keywords
Imaging, Magnetic resonance, Physical therapy, Rehabilitation, Injury prevention
Date
2019
Type
Journal article
Journal
Knee Surgery, Sports Traumatology, Arthroscopy
Book
Volume
27
Issue
Page Range
Article Number
ACU Department
School of Behavioural and Health Sciences
Faculty of Health Sciences
Faculty of Health Sciences
Relation URI
Source URL
Event URL
Open Access Status
Published as green open access
License
File Access
Open
Open
Open
Open
Open
Controlled
Open
Open
Open
Open
Open
Open
Controlled
Open
Open