Biomechanical comparison of screw-based zoning of PHILOS and Fx proximal humerus plates

Background Treatment of proximal humerus fractures with locking plates is associated with complications. We aimed to compare the biomechanical effects of removing screws and blade of a fixed angle locking plate and hybrid blade plate, on a two-part fracture model. Methods Forty-five synthetic humeri were divided into nine groups where four were implanted with a hybrid blade plate and the remaining with locking plate, to treat a two-part surgical neck fracture. Plates’ head screws and blades were divided into zones based on their distance from fracture site. Two groups acted as a control for each plate and the remaining seven had either a vacant zone or blade swapped with screws. For elastic cantilever bending, humeral head was fixed and the shaft was displaced 5 mm in extension, flexion, valgus and varus direction. Specimens were further loaded in varus direction to investigate their plastic behaviour. Results In both plates, removal of inferomedial screws or blade led to a significantly larger drop in varus construct stiffness than other zones. In blade plate, insertion of screws in place of blade significantly increased the mean extension, flexion valgus and varus bending stiffness (24.458%/16.623%/19.493%/14.137%). In locking plate, removal of screw zones proximal to the inferomedial screws reduced extension and flexion bending stiffness by 26–33%. Conclusions Although medial support improved varus stability, two inferomedial screws were more effective than blade. Proximal screws are important for extension and flexion. Mechanical consequences of screw removal should be considered when deciding the number and choice of screws and blade in clinic

The use of a new locking 90° blade plate in the treatment of atrophic proximal humerus nonunions

This level IV case series study prospectively evaluated patients with atrophic proximal humerus nonunions stabilised with a locking 90° blade plate. All patients were women with an average age of 69 years (range 56–78). Time from trauma to nonunion treatment averaged 23 months. Five patients had had previous surgical treatments. Two patients had a history of infection and one patient with active infection was reconstructed in two stages. Follow-up averaged 22 months (range 18–36); union was achieved in all seven cases after an average of 5.85 months. The DASH score at the last follow-up averaged 25 points and Constant score averaged 72.7 points. No patient required additional procedures. At the last follow-up all patients were free of infection, and there were no cases of avascular necrosis. The results with locked 90° blade plates in atrophic nonunions of the proximal humerus in adults were favourable in this series

Biomechanical in vitro assessment of fixed angle plating using a new concept of locking for the treatment of osteoporotic proximal humerus fractures

Locked plating attempts to improve mechanical stability via better anchorage of the screws in the bone. In 22 paired osteoporotic humeri an AO/ASIF 11-B 1 fracture was created. Locked and conventional plating using the same device of the latest generation was performed. Torsional loading around three axes (x = varus/valgus, y = flexion/extension, z = axial rotation) with an increasing moment (2, 3.5, 5 and 7.5 N·m) was applied. Interfragmentary motion within the locked group was lower for all three axes with higher cumulative survival rates (p < 0.05). The typical mode of failure was loss of fixation in the humeral head occurring earlier in the conventional group. The locking mechanism investigated provides more ultimate strength in an osteoporotic proximal humerus fracture model. Correlation with BMD suggests that this device may especially be suitable for use in osteoporotic bone

Second generation locked plating of proximal humerus fractures—A prospective multicentre observational study

Surgical treatment of most displaced proximal humerus fractures is challenging due to osteoporosis. Locking plates are intended to provide superior mechanical stability. In a prospective multicentre study 131 patients were treated with second generation locked plating (NCB-PH, Zimmer, Inc.). The open procedure (n = 78) was performed using a deltopectoral approach; the minimally invasive technique (n = 53) involved percutaneous reduction and an anterolateral deltoid split approach. Clinical and radiological follow-up was obtained. Improvement in function (ROM) was statistically significant. Fracture type (AO) had the most significant impact on the incidence of complications. The most frequent complications detected were intra-articular screw perforation (15%) and secondary displacement (8%). Complication rate and functional outcome of the NCB-PH are comparable to reports in the literature. Not all problems are likely to be solved by this new generation of implants, i.e. secondary dislocation still occurred in 8% of our patients

Fraturas da extremidade proximal do úmero: estudo comparativo entre dois métodos de fixação Proximal humerus fractures: comparative study of two different fixation methods

OBJETIVO: Comparar o resultado do tratamento das fraturas da extremidade proximal do úmero. osteossíntese com a placa em t de pequenos fragmentos (grupo a), promovendo uma estabilização relativa, em contraposição à placa com parafusos bloqueados (grupo b). MÉTODOS: São alocados de forma aleatória 18 pacientes e avaliados prospectivamente, segundo critérios clínicos, escala funcional e parâmetros radiográficos da redução obtida. RESULTADOS: Pela escala analógica de dor a média aos seis meses de evolução foi 2,1 para o grupo a e 2,2 para o grupo b, a amplitude de elevação no grupo a foi de 140ºe de 143ºno grupo b e a pontuação na escala funcional da ucla foi respectivamente 30 e 31. Nas radiografias avaliadas; no grupo a, três pacientes obtiveram ângulos medidos após a estabilização entre 0º e 10º de desvio em relação à anatomia normal e seis entre 11º e 40º, no grupo b sete pacientes com ângulos entre 0º e 10º e dois entre 11º e 20º. CONCLUSÕES: Nos resultados precoces e tardios não ocorreram diferenças clínicas e funcionais nos dois grupos, prevalecendo uma alta incidência de bons resultados. as medidas radiográficas das reduções obtidas ficaram mais próximas do anatômico no grupo tratado com placas bloqueadas.<br>OBJECTIVES: The present study compares results of the treatment of patients with proximal humerus fractures using two different fixation methods: the t plate (group a) for small segments that provides a relative stabilization is compared to the locking screw plate that promotes a rigid fixation. METHODS: eighteen patients were randomly divided into two groups and evaluated prospectively according to clinical aspect, functional score and radiographic parameters of displacement after fixation. RESULTS: using the visual analogue scale - vas, the mean pain at six months of follow-up was 2.1 for group a and 2.2 for group b. the mean range of forward elevation was 140º in group a and 143º in group b. the mean ucla functional scale scores were 30 and 31, respectively. On the radiographic evaluation, the fractures of three patients in group a had between 0 and 10 degrees of displacement after stabilization and six patients had displacement between 11 and 40 degrees; for group b, seven patients had displacement between 0 and 10 degrees and three between 11 and 40 degrees. CONCLUSION: no early or late differences were found between groups in clinical and functional evaluations. in both groups, the prevalence of good results was observed. the reduction of the anatomical neck angles of the proximal humerus was closer to normal in the blocking screw group