title: Hook plate fixation for acromioclavicular joint separations restores coracoclavicular distance more accurately than PDS augmentation, however presents with a high rate of acromial osteolysis.
abstract: BACKGROUND
  Hook plate fixation of acromioclavicular (AC) joint separations carries the disadvantage of compulsory implant removal, occasional implant fatigue and secondary loss of reduction. This study compares the clinical and radiological outcome of a new polyaxial angular stable hook plate (HP) with absorbable polydioxansulfate (PDS) sling.
  
  
  METHODS
  Between 2002 and 2009, out of a consecutive series of 81 patients with symptomatic Rockwood type V lesions 52 patients received clinical and radiographic follow-up (HP: n = 27; PDS: n = 25). HP patients were prospectively analyzed and retrospectively compared with the PDS group. Radiological follow-up included comparative coraco- and acromioclavicular distance (CCD/ACD) measurements as percentage of the uninjured shoulder. For clinical follow-up a standardized functional shoulder assessment with Constant Score, DASH Score, Taft Score and a self-report questionnaire including the visual analog scale (VAS) was carried out.
  
  
  RESULTS
  Direct postoperative radiographs showed an overcorrection of CCD in the HP group (-4.4% of the uninjured side) and failure of anatomic correction in the PDS group (+11.0%). After implant removal, CCD increased in the HP group extensively to 16.7% (overall loss of reduction: 21.1%) and 23.9% in the PDS group. Redisplacement (100% increase of CCD) occurred in five cases (HP: 2, PDS: 3) and partial loss of reduction in four cases of each group. Comparing functional results no differences could be seen between both the groups (Constant-Score HP: 91.2 points, PDS: 94.6 points; Taft-Score HP: 9.4 points, PDS: 10.0 points). The DASH-Score revealed better results for PDS group (3.4 points, HP: 8.0 points). Signs of acromial osteolysis appeared in five cases (18.5%) in HP group. There was no case of implant failure. The X-rays of six patients (HP: 4, PDS: 2) showed AC-joint-osteoarthritis.
  
  
  CONCLUSIONS
  Hook plate fixation employing a polyaxial angular stable plate finally restores the coracoclavicular distance more accurately than augmentation with a PDS sling. Although in HP group no implant failure occurred, major disadvantages are initial overcorrection and acromial osteolysis. Both have no influence on final functional results.
authors.affiliation: Department of Trauma and Reconstructive Surgery, University of Rostock, Schillingallee 35, 18057 Rostock, Germany. anica.eschler@med.unirostock.de
authors.forename: Anica
authors.initials: A
authors.lastname: Eschler
authors.forename: Georg
authors.initials: G
authors.lastname: Gradl
authors.forename: Philip
authors.initials: P
authors.lastname: Gierer
authors.forename: Thomas
authors.initials: T
authors.lastname: Mittlmeier
authors.forename: Markus
authors.initials: M
authors.lastname: Beck
mesh_terms: D020341:Absorbable Implants; D000173:Acromioclavicular Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D000328:Adult; D000368:Aged; D001178:Arthroplasty / Q000295:instrumentation* / Q000379:methods; D001860:Bone Plates; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000209:etiology; D010014:Osteolysis / Q000209:etiology; D016687:Polydioxanone; D011183:Postoperative Complications; D011859:Radiography; D020127:Recovery of Function; D057566:Self Report; D016896:Treatment Outcome
chemical_list: D016687:Polydioxanone