title: The migration of a BioScrew as a differential diagnosis of knee pain, locking after ACL reconstruction: a report of two cases.
abstract: BACKGROUND
  Problems with the initial fixation strength and widening of the femoral and tibial canal after ACL reconstruction using a triple or quadruple semitendinosus autograft have led to the introduction of the so-called Hybrid fixation with the additional use of interference screws. Pain and intraarticular migration have been reported with metal interference screws requiring implant removal (Am J Knee Surg 11:32-34, 2000, Arthroscopy 11:289-291, 1995) but not yet with bioabsorbable screws.
  
  
  METHODS
  We report on two cases were the intraarticular position of a bioabsorbable interference screw possibly due to migration in the early postoperative period lead to symptoms, the need for further surgery, and implant removal.
  
  
  RESULTS
  A preoperative MRI revealed the diagnosis. After removal of the tibial interference screw both knees were settling down, albeit with residual instability and only a moderate clinical result.
  
  
  CONCLUSIONS
  Despite the attractiveness of bioabsorbable screws due to the very fact that they are being reabsorbed over time, there is a slight risk of migration in the first month after the operation. In any suspicious case an MRI will easily clarify the diagnosis.
authors.affiliation: Orthopädische Klinik, Medizinisches Zentrum Kreis Aachen, Mauerfeldchen 25, 52080 Aachen, Germany. fkrappel@Yahoo.com
authors.forename: Ferdinand Anton
authors.initials: FA
authors.lastname: Krappel
authors.forename: Eberhardt
authors.initials: E
authors.lastname: Bauer
authors.forename: Ulrich
authors.initials: U
authors.lastname: Harland
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001863:Bone Screws / Q000009:adverse effects*; D003287:Contrast Media; D003937:Diagnosis, Differential; D005548:Foreign-Body Migration / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010146:Pain / Q000175:diagnosis*; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D012086:Reoperation
chemical_list: D003287:Contrast Media