Forces required to dynamize sliding screws in gamma nail and selfdynamizable internal fixator.

BACKGROUND: Single limb support phase of the gait-cycle in patients who are treated for a pertrochanteric fracture is characterized by transversal loads acting on the lag screw, tending to block its dynamization. If the simultaneous axial force overcomes transversal loads of the sliding screw, the dynamization can still occur. METHODS: Biomechanical investigation was performed for three types of dynamic implants: Gamma Nail, and two types of Selfdynamizable Internal Fixators (SIF) - SIF-7 (containing two 7 mm non-cannulated sliding screws), and SIF-10 (containing one 10 mm cannulated sliding screw). Contact surface between the stem and the sliding screws is larger in SIF implants than in Gamma Nail, as the stem of Gamma Nail is hollow. A special testing device was designed for this study to provide simultaneous application of a controlled sliding screws bending moment and a controlled transversal load on sliding screws (Qt) without using of weights. Using each of the implants, axial forces required to initiate sliding screws dynamization (Qa) were applied and measured using a tensile testing machine, for several values of sliding screws bending moment. Standard least-squares method was used to present the results through the linear regression model. RESULTS: Positive correlation between Qt and Qa was confirmed (p < 0.05). While performing higher bending moments in all the tested implants, Qa was higher than it could be provided by the body weight. It was the highest in Gamma Nail, and the lowest in SIF-10. CONCLUSIONS: A larger contact surface between a sliding screw and stem results in lower forces required to initiate dynamization of a sliding screw. Patients treated for a pertrochanteric fracture by a sliding screw internal fixation who have longer femoral neck or higher body weight could have different programme of early postoperative rehabilitation than lighter patients or patients with shorter femoral neck.

[Minimally invasive treatment of bilateral femoral shaft fractures in polytrauma patient using selfdinamisibile internal fixator. A case report].

Proper timing and surgical method in management of femur fractures in polytrauma patients can greatly reduce the mortality, morbidity and disability. The aim of this paper is to present the treatment of bilateral femoral fractures in polytrauma patient with dominant chest trauma by selfdynamisable internal fixator Mitkovic (SIF) as a definitive method of fractures treatment. A 23 years old female was injured in a traffic accident. After resuscitation and treatment of the dominant chest injuries, surgical treatment of bilateral femur fractures performed on the fourth day after the injury. Length of surgery was 65 minutes. There was not blood substitution during the intervention and blood loss through the operative wounds drainage. There was no worsening of the pulmonary function after orthopaedic surgery. The patient discharged from hospital postoperative day ten. Postoperative follow-up was 9 months. The fractures healed with an excellent functional result. Application of selfdynamisable internal fixator (SIF) with minimally invasive technique for the treatment of bilateral femoral fractures in polytrauma patients is a good operative method because poses minimally additional operative trauma and provides excellent biomechanical conditions for fracture healing.

[Dynamic forces of Mitkovic self-dinamysible trochanteric Internal fixators (SIF)].

Dynamic trochanteric fractures implants allow fracture fragments to be compressed. Dynamisation can be realized if the axial pin force overcome friction force between pin and body of the implant. Examination of sliding iniciation forces in Mitkovic Selfdinamysible Trochanteric Internal Fixator (SIF). SIF was attached for angle block in the position with vertical orientation of pins. The transversal load of 5 kg was connected to pins by a rope. A dynamometer was used to measure force during the movement of angle block in up direction. Regression coefficients were a1 = 4,052 i b1 = 0,623 for SIF with 2 sliding screws with diameter of 7mm and a2 = 4,534 i b2 = 0,422 for SIF with 1 screw with diameter of 10 mm. Coefficients of determination were: r12 = 0,470 and r22 = 0,123. Sliding of SIF pins can be achieved for each analysed body weight of patient (50-130 kg). Early bearing of operated leg is significant for sliding initiation of SIF sliding screws.

Single centre experience of the upper limb replantation and revascularisation.

Replantation is defined as reattachment of the amputated limb using the neurovascular and musculoskeletal structures in order to obtain the recovery of the limb. Fortunately, injuries causing limb amputation are rare. Adequate treatment within the optimal time scale can provide successful rehabilitation of the shape and function of the replanted part. We report the experience of our Clinical Centre (regional replantation centre) in the replantation of five forearms/hands and revascularisation of six hands between 1997 and 2001. The most frequent site of injury was the distal part of the forearm, while the major cause of injuries was a wood processing machine. The surgical procedures were performed under general anaesthesia within 2-6 hours after injury. Vascular anastomoses, nerve repair and muscle repair were performed following the external bone fixation. All patients were given anticoagulation treatment postoperatively. Thrombosis in the anastomotic site developed as an early complication in two patients who underwent thrombectomy; one of these patients developed gangrene and underwent amputation. Late postoperative results were good in 10 patients. One patient developed acral epidermolysis. Postoperative results after revascularisation were good in all patients.