Femoral neck osteosynthesis using interfragmentary compression or position screw in synthetic bones. What are the mechanical differences?

PURPOSE: We aim to compare interfragmentary compression with the position osteosynthesis in the fixation of different femoral neck fractures (FN) in synthetic bones subjected to vertical load. METHODS: Forty-two synthetic femurs were subjected to neck fractures and separated into 3 groups according to the Pauwels classification: Pauwels I had 6 units (PI); Pauwels II, 24 units, with and without comminution (PII); and Pauwels III, 12 units, with and without comminution (PIII). After, they were fixed with 2 different ways: three 7, 0 mm cannulated lag screws (CSs) versus three 6, 5 mm solid fully threaded screws (SSs). Screws positioning was oriented by the Pauwels classification: inverted triangle or crossed screws. All specimens were submitted to vertical loading until failure. RESULTS: The average force was 79.4 ± 22.6 Kgf. The greatest one was recorded in model 1 (135.6 Kgf), and the lowest in model 41 (39.6 Kgf). CSs and SSs had similar resistance until failure (p = 0.2). PI showed heightened resistance and PIII showed a worse response (p < 0,01). CSs had better performance in PIII (p = 0.048). Comminution and screws orientation caused no difference on peak force (p = 0.918 and p = 0.340, respectively). CONCLUSIONS: In synthetic bones, the resistance of a femoral neck fracture osteosynthesis using a 7, 0 mm cannulated lag screw or 6, 5 mm solid fully threaded screw are similar. There was no loss of efficiency with comminution in the femoral neck. Osteosynthesis resistance decreased with the verticalization of the fracture line and, in the more vertical ones, interfragmentary compression with CSs was more resistant than positional osteosynthesis with SSs.

Supra-acetabular fixation and sacroiliac screws for treating unstable pelvic ring injuries: preliminary results from 20 patients.

OBJECTIVE: To analyze the treatment results from 20 patients who underwent an alternative osteosynthesis method as definitive treatment for pelvic ring fractures. METHODS: A retrospective analysis was conducted on a series of 20 patients with pelvic ring fractures (Tile type C) and a high risk of postoperative infection, who were treated at Santa Casa de Misericórdia de São Paulo between August 2004 and December 2012. The patients underwent percutaneous supra-acetabular external fixation in association with cannulated 7.0 mm iliosacral screws. RESULTS: The patients' mean age was 40 years (range 22-77 years) and the mean length of follow-up was 18.5 months (range 3-69 months). At the end of the treatment, ten patients (50%) were classified as having good results, nine patients (45%) had fair results and one patient (5%) did not have any improvement. Six patients presented complications, and paresthesia of the lateral femoral cutaneous nerve was the most frequent of these (two patients). CONCLUSION: Supra-acetabular external fixation in association with iliosacral percutaneous osteosynthesis is a good definitive treatment method for patients with a high risk of postoperative infection.

OBJETIVO: Avaliar os resultados do tratamento de 20 pacientes que usaram como tratamento definitivo um método de osteossíntese opcional para fraturas do anel pélvico. MÉTODOS: Foi feita uma análise retrospectiva da série de 20 casos de pacientes com fratura do anel pélvico tipo C de Tile, portadores de alto risco de infecção pós-operatória, tratados na Santa Casa de Misericórdia de São Paulo entre agosto de 2004 e dezembro de 2012, submetidos a fixação externa supra-acetabular percutânea associada com parafusos canulados iliossacrais de 70 mm. RESULTADOS: A média de idade dos pacientes foi de 40 anos (mínimo de 22; máximo de 77) e o tempo médio de seguimento foi de 18,5 meses (mínimo de três; máximo de 69). Após o término do tratamento dez pacientes (50%) foram classificados com bons resultados, nove (45%) tiveram desfecho regular e um (5%) não apresentou melhoria alguma. Seis apresentaram complicações. A parestesia do nervo cutâneo femoral lateral foi a mais frequente (dois pacientes). CONCLUSÃO: A fixação externa supra-acetabular associada a osteossíntese percutânea iliossacral é um bom método de tratamento definitivo para os pacientes com alto risco de infecção pós-operatória.

What is the real angle of deviation of metacarpal neck fractures on oblique views? A radiographic study.

OBJECTIVE: The aim of this study was to establish an indirect, easy-to-use, predictable and safe means of obtaining the true degree of displacement of fractures of the neck of the fifth metacarpal bone, through oblique radiographic views. METHODS: An anatomical specimen from the fifth human metacarpal was dissected and subjected to ostectomy in the neck region. A 1-mm Kirschner wire was fixed to the base of the fifth metacarpal bone, perpendicular to the longitudinal axis of the bone and parallel to the ground. Another six Kirschner wires of the same diameter were bent over and attached to the ostectomized bone to simulate fracture displacement. Axial rotation of the metacarpus was used to create oblique radiographic views. Radiographic images were generated with different angles and at several degrees of rotation of the bone. RESULTS: We deduced a mathematical formula that showed the true displacement of fractures of the neck of the fifth metacarpal bone by means of oblique radiographs. CONCLUSIONS: Oblique radiographs at 30̊ of supination provided the best view of the bone and least variation from the real value of the displacement of fractures of the fifth metacarpal bone. The mathematical formula deduced was concordant with the experimental model used.

OBJETIVO: Estabelecer uma forma indireta, fácil, previsível e segura na obtenção do valor real do desvio da fratura do colo do quinto metacarpo a partir de radiografias oblíquas. MÉTODOS: Uma peça anatômica de quinto metacarpo humano foi dissecada e submetida à ostectomia na região do colo. Um fio de Kirschner de 1 mm foi fixado perpendicular ao eixo longitudinal do osso e paralelo ao solo. Outros seis fios de Kirschner do mesmo diâmetro foram dobrados e presos ao osso ostectomizado para simular o desvio das fraturas. Rotação axial do metacarpo foi usada para criar as radiografias nas incidências oblíquas. Imagens radiográficas foram obtidas com diferentes ângulos e em vários graus de rotação do osso. RESULTADOS: Deduzimos uma equação matemática que demonstra o real desvio da fratura do colo do quinto metacarpo por meio de radiografias oblíquas. CONCLUSÕES: A radiografia oblíqua com 30̊ de supinação apresenta melhor visualização do osso e menor variação do valor real do desvio da fratura do colo do quinto metacarpo. A fórmula matemática deduzida foi concordante com o modelo experimental usado.