Medial minimally invasive helical plate osteosynthesis of the distal femur - a new technique.

INTRODUCTION: The goal of this study was to evaluate distal femoral minimally invasive plate osteosynthesis (MIPO) from a distal medial approach by use of a pre-bent helical implant. MATERIAL & METHODS: A total of 18 lower extremities was evaluated. A 29.6 cm steel plate was constructed and pre-bent on bone specimens with a torsion of 55.7° A 5 cm incision was performed from the tip of the medial epicondyle alongside its centre in a proximal direction. The medial border of the vastus medialis was retracted anteriorly. The level of the proximal skin incision was determined using the length of the pre-bent plates. The proximal incision was performed at a length of 4 cm at the described height at a line between the lateral epicondyle and the tip of the greater trochanter. A raspatory was advanced beneath the vastus medialis in a proximal direction to create an extraperiosteal tunnel for plate insertion. The plate was fixed to the bone at its proximal and distal portion via screws. Following dissection, the distance between the nearest perforator to the proximal plate end was evaluated. The vertical distances between the medial border of the plate and the femoral artery and femoral nerve were measured at the level of the proximal plate end and at the level of the proximal margin of the vastoadductor membrane. RESULTS: The most proximal perforating artery was located at a mean distance of 20.15 mm starting from the proximal plate margin. The mean interval between the medial border of the plate at the level of its proximal tip and the femoral artery was 51.9 mm. The average distance between the femoral nerve and the medial border of the proximal part of the plate was 42.3 mm. Regarding the interval between the medial border of the plate and the femoral artery, this was at a mean of 40.5 mm at the level of the proximal margin of the vastoadductor membrane. During dissection, none of the specimens showed any lesions of the adjacent anatomical characteristics. CONCLUSION: Our results indicate MIPO of the distal femur from a medial approach as a safe technique.

The 2-2-2-20-20 concept for supraacetabular schanz screw insertion without additional radiography.

PURPOSE: Application of supraacetabular Schanz screws is usually performed under image intensifier guidance. The aim of this study was to perform it without imaging, with the hypothesis that, respecting anatomical landmarks, pre- and intraoperative fluoroscopy can be avoided. MATERIAL & METHODS: Insertion of the supra-acetabular Schanz screws was performed by two trauma surgery residents in a study sample of 14 human adult cadavers which had been embalmed by use of Thiel`s method. With cadavers placed in supine position, the anterior superior iliac spine (ASIS) was palpated. Starting from this landmark, 2 cm were measured in a distal and 2 cm in the medial direction. At this point, a 2 cm long oblique skin incision was performed. Through this approach, 150 mm Schanz screws were drilled bilaterally into the supra-acetabular corridor with an angulation of 20° to distal as well as 20° to medial. Following screw application, combined obturator oblique-outlet views (COOO) were taken bilaterally in each specimen by use of an Arcadis© Orbic 3D C-arm to prove the screw position. Six of the specimens underwent a 3D-CT-scan. Images were evaluated concerning correct screw positioning by a further traumatologist. Skin and subcutaneous tissues were removed in the ilioinguinal region and possible lesions to the lateral femoral cutaneous nerve (LFCN) or to the joint capsule were evaluated. RESULTS: The sample consisted of eight pelves from female and six pelves from male cadavers. During radiographic evaluation of the COOO-scans (14 specimens) and the 3D-scans (6 specimens), the Schanz screws were placed inside the supra-acetabular corridor in all specimens (14/14). During dissections, no intracapsular screw placements or LFCN lesions were found. CONCLUSION: According to the described anatomical data, we defined a 2-2-2-20-20 concept, starting with a 2 cm skin incision 2 cm distal and 2 cm medial to the ASIS with a drill angulation of 20° inferior and 20° lateral orientation. Using this technique, all Schanz screws could be sufficiently inserted without intraprocedural x-ray imaging.