title: Clinical and biomechanical outcome of minimal invasive and open repair of the Achilles tendon.
abstract: BACKGROUND
  With evolutions in surgical techniques, minimally invasive surgical (MIS) repair with Achillon applicator has been introduced. However, there is still a lack of literature to investigate into the clinical merits of MIS over open surgery. This study aims to investigate the correlation between clinical outcome, gait analysis and biomechanical properties comparing both surgical methods.
  
  
  METHODS
  A single centre retrospective review on all the consecutive operated patients between January 2004 and December 2008 was performed. Twenty-six patients (19 male and 7 female; age 40.4 ± 9.2 years) had experienced a complete Achilles tendon rupture with operative repair. Nineteen of the patients, 10 MIS versus 9 open repairs (13 men with a mean age of 40.54 ± 10.43 (range 23-62 yrs) and 6 women with a mean age of 45.33 ± 7.71 (range 35-57 yrs) were further invited to attend a thorough clinical assessment using Holz's scale and biomechanical evaluation at a mean of 25.3 months after operation. This study utilized the Cybex II isokinetic dynamometer to assess the isokinetic peak force of plantar-flexion and dorsiflexion of both ankles. The patients were also invited to return to our Gait Laboratory for analysis. The eight-infrared camera motion capture system (VICON, UK) was utilized for the acquisition of kinematic variables. Their anthropometric data was measured according to the Davis and coworkers' standard.
  
  
  RESULTS
  The mean operative time and length of hospital stay were shorter in the MIS group. The operative time was 54.55 ± 15.15 minutes versus 68.80 ± 18.23 minutes of the MIS group and Open group respectively (p = 0.045), whereas length of stay was 3.36 ± 1.21 days versus 6.40 ± 3.70 days respectively (p = 0.039). There is statistically significant decrease (p = 0.005) in incision length in MIS group than the open surgery group, 3.23 ± 1.10 cm versus 9.64 ± 2.55 cm respectively. Both groups attained similar Holz's scores, 11.70 ± 0.95 versus 12.0 ± 1.50 respectively (p = 0.262). The mean percentage stance time of the injured leg for MIS patient was 58.44% while the mean percentage stance time of the injured leg for patients with open repair was 56.57%. T-test has shown there were no significance differences between the results of the two groups of patients. The loss of peak torque and total work done with respect to the injured side were similar between the MIS and open group.
  
  
  CONCLUSIONS
  MIS using Achillon method can achieve smaller incisions, shorter operative time and hospital stay. There is no statistical significance difference in clinical outcome, the stance time to strike time ratio and biomechanical properties on the leg receiving Achilles tendon repair using MIS method and open surgery.
authors.affiliation: Department of Orthopaedics and Traumatology, Prince of Wales Hospital, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China. dfong@ort.cuhk.edu.hk.
authors.forename: Alexander Pak-Hin
authors.initials: AP
authors.lastname: Chan
authors.forename: Yue-Yan
authors.initials: YY
authors.lastname: Chan
authors.forename: Daniel Tik-Pui
authors.initials: DT
authors.lastname: Fong
authors.forename: Pamela Yuet-Kam
authors.initials: PY
authors.lastname: Wong
authors.forename: Hoi-Yan
authors.initials: HY
authors.lastname: Lam
authors.forename: Chun-Kwong
authors.initials: CK
authors.lastname: Lo
authors.forename: Patrick Shu-Hang
authors.initials: PS
authors.lastname: Yung
authors.forename: Kwai-Yau
authors.initials: KY
authors.lastname: Fung
authors.forename: Kai-Ming
authors.initials: KM
authors.lastname: Chan