title: Does simulated walking cause gapping of meniscal repairs?
abstract: BACKGROUND
  The objective of rehabilitation following meniscal repair is to promote healing by limiting stresses on repairs, while simultaneously preserving muscle strength and joint motion. Both protective protocols limiting weight bearing and accelerated which do not, have shown clinical success. This study assesses the effects of physiologic gait loading on the kinematic behavior of a repaired medial meniscus.
  
  
  METHODS
  The medial menisci of eight fresh cadaveric knees were implanted with arrays of six 0.8-1.0 mm beads. Pneumatic actuators delivered muscle loads and forces on the knee as each specimen was subjected to a simulated stance phase of gait. Meniscus motion was measured at loading response, mid stance, and toe-off positions. Measurements were performed using biplanar radiography and RSA, with each knee: (a) intact, (b) with posterior longitudinal tear, and (c) after inside-out repair.
  
  
  RESULTS
  The tissue spanning the site of the longitudinal tear underwent compression rather than gapping open in all states (intact [I], torn [T] and repaired [R] states). Average compression at three sites along the posterior half of the meniscus was: posterior horn -0.20 ± 0.08 mm [I], -0.39 ± 0.10 mm [T], and -0.20 ± 0.06 mm [R] (p = 0.15); junction of posterior horn and body -0.11 ± 0.12 mm [I], -0.21 ± 12 mm [T], -0.17 ± 0.09 mm [R] (p = 0.87); and adjacent to the medial collateral ligament -0.07 ± 0.06 mm [I], -0.29 ± 0.13 mm [T], -0.07 ± 0.17 mm [R] (p = 0.35). The entire meniscus translated posteriorly from mid-stance to toe off. Displacement was greatest in the torn state compared to intact, but was not restored to normal levels after repair.
  
  
  CONCLUSIONS
  The edges of a repaired longitudinal medial meniscal tear undergo compression, not gapping, during simulated gait.
authors.affiliation: Methodist Center for Sports Medicine, Houston Methodist Hospital, Houston, TX, USA. pcmcculloch@houstonmethodist.org.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: McCulloch
authors.affiliation: Institute of Orthopedic Research & Education, Houston, TX, USA.
authors.forename: Hugh L
authors.initials: HL
authors.lastname: Jones
authors.affiliation: Methodist Center for Sports Medicine, Houston Methodist Hospital, Houston, TX, USA.|Spectrum Health Medical Group, Grand Rapids, MI, USA.
authors.forename: Kendall
authors.initials: K
authors.lastname: Hamilton
authors.affiliation: Institute of Orthopedic Research & Education, Houston, TX, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hogen
authors.affiliation: Institute of Orthopedic Research & Education, Houston, TX, USA.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Gold
authors.affiliation: Institute of Orthopedic Research & Education, Houston, TX, USA.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Noble