title: Regeneration of hamstring tendons after anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  Primary aim of the study was analysis of hamstring tendon regeneration after anterior cruciate ligament reconstruction (ACLR). Secondary aim was analysis of isokinetic muscle strength in relation to hamstring regeneration. The hypothesis was that regeneration of hamstring tendons after ACLR occurs and that regenerated hamstring tendons contribute to isokinetic hamstring strength with regeneration distal to the knee joint line.
  
  
  METHODS
  Twenty-two patients scheduled for ACLR underwent prospective MRI analysis of both legs. MRI parameters were tendon regeneration and morphology, muscle retraction and muscle cross-sectional area. A double-blind, prospective analysis of isokinetic quadriceps and hamstrings strength was performed.
  
  
  RESULTS
  Regeneration of the gracilis tendon after ACLR occurred in all patients. Regeneration of the semitendinosus tendon occurred in 14 patients. At 1 year, the surface area of the semitendinosus and gracilis muscle decreased compared to both preoperatively (P < 0.01) and the contralateral leg (P < 0.01). The cross-sectional area of the semitendinosus muscle decreased in the absence of tendon regeneration (P = 0.05). The cross-sectional area of the gracilis muscle was greater in case of regeneration distal to the joint line (P = 0.01). Muscle retraction of the semitendinosus muscle was increased in case of nonregeneration (P = 0.02). There was no significant relationship between isokinetic flexion strength and tendon regeneration.
  
  
  CONCLUSIONS
  Hamstring tendons regenerated after harvest of both semitendinosus and gracilis tendons for ACLR. There was no relation between isokinetic flexion strength and tendon regeneration.
authors: Orthopaedic Center Máxima, Máxima Medical Center, Postbus 90052, 5600 PD, Eindhoven, The Netherlands. r.janssen@mmc.nl
authors: Rob P A
authors: RP
authors: Janssen
authors: Maria J F
authors: MJ
authors: van der Velden
authors: Huub L M
authors: HL
authors: Pasmans
authors: Harm A G M
authors: HA
authors: Sala
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D011446:Prospective Studies; D012038:Regeneration; D013710:Tendons / Q000033:anatomy & histology* / Q000502:physiology* / Q000637:transplantation; D055815:Young Adult