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

• Published in: Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA Vol. 25; no. 3; pp. 980 - 986
• Main Authors: Yoon, Jong Pil, Lee, Yeon Soo, Song, Geun Soo, Oh, Joo Han
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2017; Springer Nature B.V
• Subjects: Acromioclavicular Joint - diagnostic imaging; Acromioclavicular Joint - injuries; Acromioclavicular Joint - pathology; Acromioclavicular Joint - surgery; Acromion - diagnostic imaging; Acromion - pathology; Acromion - surgery; Bone Plates; Clavicle - diagnostic imaging; Clavicle - pathology; Equipment Design; Female; Humans; Imaging, Three-Dimensional; Joint Dislocations - diagnostic imaging; Joint Dislocations - pathology; Joint Dislocations - surgery; Knee; Male; Medical imaging; Medicine; Medicine & Public Health; Middle Aged; Morphology; Orthopedics; Shoulder; Sports injuries; Surgery; Tomography, X-Ray Computed; United States > US; South Korea; Hook plate; Acromioclavicular joint; Morphology; Acromion
• ISSN: 0942-2056; 1433-7347
• DOI: 10.1007/s00167-016-3987-3

Purpose 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. Methods 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. Results 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. Conclusions 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.