The Position and Number of Screws Influence Screw Perforation of the Humeral Head in Modern Locking Plates: A Cadaver Study

*Department of Orthopaedic Surgery, Cantonal Hospital St. Gallen, St. Gallen, Switzerland †Fremantle Orthopaedic Unit, University of Western Australia, Fremantle, Western Australia, Australia ‡Department of Orthopaedic Surgery, Cantonal Hospital St. Gallen, St. Gallen, Switzerland.
Journal of orthopaedic trauma (Impact Factor: 1.54). 02/2012; 26(10):e188-92. DOI: 10.1097/BOT.0b013e31823db922
Source: PubMed

ABSTRACT : Screw perforation of the humeral head in locking plate osteosynthesis occurs in up to 30% of cases. The current study compared different fixation possibilities (eg, number and position of screws) to reduce screw perforation in the humeral head.
: A humeral head fracture with a missing medial support was created in 30 fresh-frozen cadavers and fixed with a polyaxial locking plate (NCB PH; Zimmer, Warsaw, IN). The constructs were loaded with increasing force and the number of cycles until screw perforation was recorded. Four different fixation methods were tested: group 1 five screws with fixed angle, group 2 five screws in polyaxial position according to bone strength, group 3 three screws, and group 4 five screws with 1 as an inferomedial support screw.
: More screws in the humeral head significantly increased the number of cycles before screw perforation. An inferomedial support screw further increased the number of cycles. Polyaxial screw placement compared with fixed-angle placement had no effect on the screw perforation phenomenon.
: We recommend to position an inferomedial support screw, and at least 5 screws in the head fragment, when using a locking plate in proximal humerus fractures with disrupted medial hinge.

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    ABSTRACT: Introduction: In recent years, new angle-stable plate implants with polyaxial screw direction were developed with the aim of an improved treatment of displaced 3- and 4-part fractures of the proximal humerus. There are only a few studies available about polyaxial implants in the treatment of 3- and 4-part proximal humerus fractures. Therefore, the aim of this study was to evaluate clinical results and complications of open reduction and internal fixation of displaced 3- and 4-part fractures using a polyaxial plate. Patients and Methods: Within 51 months, 105 patients with a displaced 3- or 4-part fracture of the proximal humerus were treated with a polyaxial locking plate. The complications were evaluated and the Constant & Murley score was assessed and correlated with patient satisfaction ("very satisfied" to "not satisfied"). Additionally, the results were compared with those of monoaxial plates from the literature. Furthermore, the operative experience of the surgeons at the time of surgery was correlated with the objective results of the patients. Results: 65 patients (average age: 71.3 ± 11.4 years; average follow-up: 19,6 ± 9,8 month [10-44 month]) with a displaced 3- or 4-part fracture were re-examined retrospectively (female: n = 54; male: n = 11). Overall, there were 27 3-part fractures and 38 4-part fractures. The Constant and Murley Score was on average 62.1 ± 16.5 points and the complication rate was 26 %. The most frequent complication was screw perforation through the humeral head. Patient satisfaction with clinical outcome was high within the whole study group. 40 % of the patients were "very satisfied" with their shoulder function, 29 % were "satisfied" ("fair": 12 %, "not satisfied": 19 %). Additionally, the operative experience of the surgeons influenced the final clinical result. Conclusion: In comparison to the literature we could not delineate better clinical outcomes or lower complication rates with polyaxial implants compared to monoaxial plates in 3- and 4-part fractures. Nevertheless, the majority of patients were satisfied with the clinical result in the context of age-related shoulder function. In addition, a close correlation could be detected between the degree of satisfaction and the objectively measured shoulder function. A high level of operative experience is required to avoid typical complications and to achieve a good clinical result. Georg Thieme Verlag KG Stuttgart · New York.
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