Morphological analysis of acromion and hook plate for the fixation of acromioclavicular joint dislocation

  • Jong Pil Yoon
  • Yeon Soo Lee
  • Geun Soo Song
  • Joo Han Oh



Acromioclavicular (AC) joint dislocation is a common sports injury. Hook plate fixation is currently widely used to treat this injury, as it can promote the natural healing of the ligament with good clinical outcomes. However, subacromial erosion and impingement are frequently observed post-operatively. It was hypothesized that the morphology and the contact characteristics between the hook portion and the acromion are the main causes of complications after hook plate fixation with the currently available commercial designs.


Three-dimensional reconstructed models of the AC joint obtained from the computed tomographic scans of 23 male and 23 female patients (mean age, 61.1 ± 6.3 years) were evaluated, and multiple anatomical parameters were measured. For the subacromial positioning of the hook plate, an actual hook plate (Synthes Inc., West Chester, PA, USA) was scanned, and the contact between the hook plate and the acromion was estimated.


The thicknesses of the acromion and distal clavicle were 9.7 ± 1.5 mm (10.7 mm in men; 8.6 mm in women) and 11.3 ± 1.6 mm (11.6 mm in men; 10.0 mm in women), respectively. The width of the acromion was 28.5 ± 3.6 mm. The mean inclination angle between the hook plate and the acromion was 29.3° ± 9.7° (27.9° in men; 30.6° in women). The hook plate made a point contact with the acromion at 9.2 ± 3.3 mm (31.5 %) from the lateral end of the acromion.


The results revealed that the hook made a pinpoint contact with the undersurface of the acromion, and this might explain why complications commonly occur after hook plate fixation. The force concentration phenomenon associated with the hook plate of existing designs results from cases of morphological mismatch, such as excessive inclination and improper occupation of the subacromial space.


Acromion Morphology Acromioclavicular joint Hook plate 



This work was supported by Biomedical Research Institute Grant, Kyungpook National University Hospital (2015).

Compliance with ethical standards

Ethical board review

This study was approved by the International Review Board of Kyung Pook National University Hospital, No. 2014-03-008.


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2016

Authors and Affiliations

  • Jong Pil Yoon
    • 1
  • Yeon Soo Lee
    • 2
  • Geun Soo Song
    • 2
  • Joo Han Oh
    • 3
  1. 1.Department of Orthopaedic Surgery, School of MedicineKyung Pook National UniversityDaeguSouth Korea
  2. 2.Department of Biomedical Engineering, College of Medical ScienceCatholic University of DaeguGyeongsan-SiSouth Korea
  3. 3.Department of Orthopaedic Surgery, Seoul National University College of MedicineSeoul National University Bundang HospitalSeoulSouth Korea

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