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Outcome of medial hamstring lengthening in children with spastic paresis: A biomechanical and morphological
Helga Haberfehlner1, Richard T Jaspers1, Erich Rutz2
1Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Amsterdam Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Insights
Semitendinosus tendon lengthening in children with spastic paresis improves knee extension but decreases muscle function. Further research is needed to optimize surgical outcomes and post-operative care for improved gait.
Area of Science:
- Orthopaedic Surgery
- Pediatric Gait Analysis
- Muscle Physiology
Background:
- Spastic paresis, common in cerebral palsy, often requires surgical intervention like semitendinosus muscle lengthening to improve gait.
- Reported side effects include hamstring muscle weakening and gait overcorrections, with unclear links to muscle morphology.
Purpose of the Study:
- To investigate the effects of semitendinosus tendon lengthening on knee joint mechanics, muscle morphology, and gait kinematics in children with spastic paresis.
- To understand the relationship between surgical changes and resulting gait alterations.
Main Methods:
- Bilateral medial hamstring lengthening via single-event multilevel surgery (SEMLS) was performed on six children.
- Measurements of knee joint mechanics, semitendinosus muscle morphology (belly length, tendon length, volume), and gait kinematics were taken pre- and post-surgery (approximately one year).
Main Results:
- Post-surgery, popliteal angle decreased, and knee moment-angle curves shifted towards knee extension.
- Semitendinosus muscle belly length decreased by ~30%, while tendon length increased by ~80%.
- Muscle volume decreased, suggesting reduced physiological cross-sectional area, leading to increased knee extension during stance and pelvic anterior tilt during gait.
Conclusions:
- Surgical lengthening of the semitendinosus tendon promotes knee extension but reduces muscle belly extensibility and cross-sectional area.
- Post-surgical strategies focusing on maintaining muscle belly length and physiological cross-sectional area may enhance treatment outcomes for medial hamstring lengthening.
Abstract:
To improve gait in children with spastic paresis due to cerebral palsy or hereditary spastic paresis, the semitendinosus muscle is frequently lengthened amongst other medial hamstring muscles by orthopaedic surgery. Side effects on gait due to weakening of the hamstring muscles and overcorrections have been reported. How these side effects relate to semitendinosus morphology is unknown. This study assessed the effects of bilateral medial hamstring lengthening as part of single-event multilevel surgery (SEMLS) on (1) knee joint mechanics (2) semitendinosus muscle morphology and (3) gait kinematics. All variables were assessed for the right side only. Six children with spastic paresis selected for surgery to counteract limited knee range of motion were measured before and about a year after surgery. After surgery, in most subjects popliteal angle decreased and knee moment-angle curves were shifted towards a more extended knee joint, semitendinosus muscle belly length was approximately 30% decreased, while at all assessed knee angles tendon length was increased by about 80%. In the majority of children muscle volume of the semitendinosus muscle decreased substantially suggesting a reduction of physiological cross-sectional area. Gait kinematics showed more knee extension during stance (mean change ± standard deviation: 34±13°), but also increased pelvic anterior tilt (mean change ± standard deviation: 23±5°). In most subjects, surgical lengthening of semitendinosus tendon contributed to more extended knee joint angle during static measurements as well as during gait, whereas extensibility of semitendinosus muscle belly was decreased. Post-surgical treatment to maintain muscle belly length and physiological cross-sectional area may improve treatment outcome of medial hamstring lengthening.
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