title: The cross-sectional shape of the fourfold semitendinosus tendon is oval, not round.
abstract: BACKGROUND
  The looped side of the semitendinosus tendon (ST) graft (i.e., the side inserted into the femoral tunnel during anterior cruciate ligament reconstruction) appears to be oval rather than round. The purpose of this study was to investigate the cross section of the fourfold semitendinosus tendon graft and, more specifically, the differences in pressure exerted by a rounded rectangular tunnel versus a round femoral tunnel.
  
  
  METHODS
  Seven STs were harvested from cadaveric knees and a fourfold ST graft was made. Aluminum cubes with round or rectangular tunnels containing four-way pressure-sensitive conductive sensors (vertically and bilaterally) were used. The area of both cubes was the same. The graft was inserted into the tunnels 15 mm from the looped edge. After measuring pressure, the graft was fixed using ultraviolet-curing acrylic resin and was cut at 7.5 mm and 15 mm from the lapel edge. The area, axes for the best fitting ellipse of the cross-section, and ellipticity of the axes were measured.
  
  
  RESULTS
  In the round tunnel, the mean contact pressure was 287.0 ± 136.7 gf at the bilateral sensor; there was no contact pressure detected by the vertical sensor. In the rounded rectangular tunnel, the mean contact pressure was 260.9 ± 186.4 gf at the bilateral sensor and 352.9 ± 49.5 gf at the vertical sensor. Ellipticity was 1.25 ± 0.13 at 7.5 mm, and 1.17 ± 0.07 at 15 mm from the lapel edge of the graft.
  
  
  CONCLUSIONS
  The cross-sectional shape of the fourfold ST graft was not round, but oval. Moreover, the rounded rectangular tunnel was more fitted to the graft than the round tunnel.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Oshima
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan. nakase1007@yahoo.co.jp.
authors.forename: Junsuke
authors.initials: J
authors.lastname: Nakase
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Hitoaki
authors.initials: H
authors.lastname: Numata
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Takata
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsuchiya
keywords: Anterior cruciate ligament reconstruction; Cross-sectional shape; Fourfold semitendinosus tendon; Rounded rectangular tunnel