title: The effect of screw position and number on the time to union of arthroscopic ankle arthrodesis.
abstract: OBJECTIVE
  This study aimed to investigate the factors that influence the time to union after arthroscopic ankle arthrodesis.
  
  
  METHODS
  From June 2005 to October 2010, 46 patients (50 ankles) underwent arthroscopic ankle arthrodesis with 6.0-mm cannulated cancellous screws. There were 22 men and 24 women (mean age, 63 years). Medical records and radiographs were retrospectively reviewed. Screw configurations used were as follows: 3 transmedial and translateral malleolar screws (ML3) in 12 ankles (24%), 2 transmedial and translateral malleolar screws (ML2) in 4 ankles (8%), 3 transmedial malleolar screws (M3) in 23 ankles (46%), and 2 transmedial malleolar screws (M2) in 11 ankles (22%).
  
  
  RESULTS
  Radiographic fusion was achieved in 46 (92%) of the 50 ankles. The mean time to fusion was 11.0 ± 4.5 weeks for ML3, 13.1 ± 3.3 weeks for ML2, 9.7 ± 2.7 weeks for M3, and 12.5 ± 3.5 weeks for M2 (P < .05). The mean American Orthopaedic Foot & Ankle Society scores were 81.3 ± 2.2 for ML3, 83.5 ± 4.4 for ML2, 88.3 ± 1.5 for M3, and 85.3 ± 2.2 for M2. The mean time until radiographic fusion was 10.2 ± 3.4 weeks for correction angles of less than 10° and 13.2 ± 3.4 weeks for angles of 10° or greater (P < .01). In obese patients a significant difference in ankle fusion time was observed (12.6 ± 3.5 weeks for patients with body mass index ≥25 v 9.4 ± 2.9 weeks for patients with body mass index <25, P < .01).
  
  
  CONCLUSIONS
  Overall, this study showed that arthroscopic ankle arthrodesis achieves a high rate of union, with fastest union achieved with 3 parallel screws placed medially from the distal tibia into the talus. Care should be taken when one is designing treatment strategies for obese patients and/or patients with large correction angles.
  
  
  METHODS
  Level IV, retrospective case series.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University, Fukuoka, Japan. ichiroy@cis.fukuoka-u.ac.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yoshimura
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kanazawa
authors.forename: Akinori
authors.initials: A
authors.lastname: Takeyama
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ida
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Hagio
authors.forename: Chayanin
authors.initials: C
authors.lastname: Angthong
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Naito
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D001174:Arthrodesis / Q000295:instrumentation* / Q000379:methods; D001182:Arthroscopy; D015992:Body Mass Index; D001863:Bone Screws; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D011859:Radiography; D012189:Retrospective Studies; D013997:Time Factors; D014945:Wound Healing / Q000502:physiology*