title: Physiological Achilles tendon length and its relation to tibia length.
abstract: OBJECTIVE
  The optimal intraoperative Achilles tendon length (ATL) adjustment is crucial for the physiological functioning of the musculotendinous unit. To date, the resting ATL and its relation to tibia length (TL) have never been defined in healthy subjects. We thus performed metric measurements of the ATL and TL.
  
  
  METHODS
  Case series.
  
  
  METHODS
  Clinical and radiological measurements.
  
  
  METHODS
  Fifty-two subjects placed in a 3-T magnetic resonance imaging with the ankle in neutral position.
  
  
  METHODS
  Unilateral ATL measured from the calcaneal insertion to the beginning of the medial gastrocnemius muscle, TL measured from the intercondylar eminence to the center of the ankle, and qualitative tendon parameters in T2 sequences and human parameters were noted; results were correlated with age, gender, body height, weight, body mass index (BMI), and side of the AT and TL.
  
  
  RESULTS
  The mean ATL was 180.6 ± 25.0 mm and the mean TL was 371.9 ± 25.4 mm with an ATL:TL ratio of 49 ± 5%. Achilles tendon length correlated significantly with body height (R = 38%, P < 0.0001) and with TL (R = 41%, P < 0.0001) but did not correlate with age, BMI, and side of the AT. Tibia length correlated with body height (R = 83%, P < 0.0001) and in multivariate linear regression, TL was the only independent predictor of ATL following the algorithm, ATL (mm) = 0.6 × TL (mm) - 53 (R = 41%).
  
  
  CONCLUSIONS
  We defined a new way to measure the ATL in a consistent way in healthy subjects and showed correlations between ATL, TL and body height and defined an algorithm of ATL based on TL. The ATL and the ATL-algorithm might be important in patients with impaired tendons such as AT ruptures.
authors.affiliation: Orthopaedic Department, University Hospital Basel, University of Basel, Basel, Switzerland. claudio.rosso@unibas.ch
authors.forename: Claudio
authors.initials: C
authors.lastname: Rosso
authors.forename: Philipp
authors.initials: P
authors.lastname: Schuetz
authors.forename: Caroline
authors.initials: C
authors.lastname: Polzer
authors.forename: Lukas
authors.initials: L
authors.lastname: Weisskopf
authors.forename: Ulrich
authors.initials: U
authors.lastname: Studler
authors.forename: Victor
authors.initials: V
authors.lastname: Valderrabano
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D000328:Adult; D000465:Algorithms; D000886:Anthropometry / Q000379:methods*; D001827:Body Height; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D009929:Organ Size; D011859:Radiography; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging