Biomechanical comparison of locked versus non-locked symphyseal plating of unstable pelvic ring injuries.

PURPOSE: Locked symphyseal plates are utilized to provide higher levels of construct stiffness than non-locked plates. The current biomechanical study was performed to compare stiffness at the pubic symphysis between locked and non-locked plating systems. METHODS: Synthetic models were utilized to represent injury to the pelvis and symphyseal plating combined with a sacro-iliac screw. Seven models were evaluated with plates and locking screws, and seven were evaluated with non-locking screws. Single limb stance was simulated, with all models loaded for 1000 cycles with 350 N applied at the sacrum. Two pairs of markers crossing the symphysis were tracked with a video-based tracking system. A coordinate system was developed to quantify motion between the pairs in three directions: medial-lateral gap, anterior-posterior shear translation, and superior-inferior shear translation. Significant differences between the plating systems were identified with t tests (p < 0.05). RESULTS: Anterior-posterior shear translation varied significantly between the two plating systems. From cycles 100 to 1000, average shear translation for the non-locked and locked systems was ~0.7 and 0.3 mm, respectively, at the markers closest to the plate and 2.2 and 1.4 mm, respectively, at the markers further from the plate. Motion in the other two directions did not differ significantly between locked and non-locked models. CONCLUSIONS: Locked symphyseal plating systems can provide better stability than non-locked systems for anterior-posterior shear translation. More stability could potentially reduce the risk of failure of the plate or screws.

Biomechanical comparison of three second-generation reconstruction nails in an unstable subtrochanteric femur fracture model.

The purpose of this study is to determine if a biomechanical difference exists in dynamic stiffness, fatigue life, and fracture site displacement by comparing three cephalomedullary reconstruction nails. An examination was made of the Biomet Uniflex reconstruction nail, the Biomet Vector nail, and the Stryker Howmedica Long Gamma nail in the fixation of an unstable subtrochanteric femur fracture model, using a synthetic bone model. Mean stiffness for each nail was initially determined in control specimens (i.e. no fracture and no instrumentation). The nail stiffness values were 1764.0 N/mm (controls), 373.61 N/mm (Uniflex), 294.27 N/mm (vector), and 656.36 N/mm (Gamma). The Gamma was statistically stiffer than the Uniflex and Vector (p < 0.002). Mean fatigue life measurements were: Uniflex at 52,891 cycles, failing at the most distal of the proximal two screw holes; Vector at 45,344 cycles, failing in the nail at the level of the fracture site; Gamma at 88,748 cycles failing at the lag screw hole. The p value between the Gamma and Vector was less than 0.01 and between Gamma and Uniflex was less than 0.05. The mean maximal axial displacement at the fracture site was 2.448 mm, 2.305 mm, and 0.790 mm for the Uniflex, Vector and Gamma, respectively. The p value between the Gamma and the other nails was < 0.01. The mean maximal transverse displacement at the fracture site was 1.223 mm, 1.197 mm, and 0.280 mm respectively. The p value between the Long Gamma and the other two nails was < 0.01. In conclusion, the Long Gamma nail demonstrated statistically significant fixation superiority in stiffness, resistance to fatigue, and fracture site displacement compared to the Uniflex and Vector nails. This biomechanical information may aid in choosing implants for fixation of unstable, subtrochanteric femur fractures.

[Laparoscopic tumor nephrectomy]. / Laparoskopische Tumornephrektomie.

Initially, laparoscopic surgery in urology was restricted to the treatment of benign diseases, whereas its role in the management of malignant disease was restricted to purely diagnostic procedures. Only recently has laparoscopy been introduced for the treatment of low stage renal cell carcinoma (RCC), and the data on both surgical efficiency and oncologic efficacy are very promising. Therefore, we present our experience with laparoscopic radical nephrectomy and data from literature. The technique of the transperitoneal approach is described in detail. Retroperitoneoscopy is a good alternative, however. Intact removal of the specimen within an organ bag to avoid tumor spillage is an important detail of our technique. Our experience amounts to radical nephrectomy in 121 patients. The indication was clinical stage T1-T2. Mean operative time and blood loss was 2.4 h and 154 ml, respectively. The rate of minor or major complications was 5% and 4%, respectively. There was no conversion to open surgery in any patient. Mean postoperative hospital stay was 6.1 days. Data on tumor control are available for 73 patients with a mean follow-up of 13.3 months. There was no recurrence within this period. Radical nephrectomy for low-stage RCC is associated with low morbidity and great surgical efficiency. The rates for local recurrences and metastases are low, tumor-specific survival is high. However, there is still a lack of long-term data on large series of patients. Despite this fact, laparoscopy is already widely accepted for this indication, and it is quite likely that it will become the standard treatment.