Purpose: Little has been written about the size of bone defect that could be restored with one-stage lengthening over a reamed intramedullary nail. The aim of this study was to investigate the mechanical properties of the callus created at gaps of various sizes in sheep tibiae treated with reamed intramedullary nailing.

Material-Methods: Sixteen adult female sheep were divided into four main groups: a simple osteotomy group (group I) and three segmental defect groups (1, 2, and 3 cm gap; groups I to III). One intact left tibia from each group was also used as the non-osteotomized intact-control group (group V). In all cases the osteotomy was fixed with an interlocked Universal Humeral Nail after 7 mm reaming. The osteotomized site was closed in layers including the periosteum without additional bone grafting and the limb was protected with long soft cast for 5 weeks postoperatively. Healing of the osteotomies was evaluated after 16 weeks by biomechanical testing. The examined parameters were torsional stiffness, shear stress and angle of torsion at the time of fracture.

Results: Samples with a simple osteotomy or 1 cm gap were fractured distally to the callus zone, whereas samples with 2 and 3 cm gaps were fractured at the callus zone or at distal metaphysis. The regenerate bone obvious in the x-rays in the group of 1 cm and 2 cm gap had considerable mechanical properties. Torsional stiffness in these two groups was nearly similar and its value was about 60% of the stiffness of the simple osteotomy group. A gradually decreased stiffness was observed as the osteotomy gap increased. There was a decrease in maximum shear stress from simple osteotomy to osteotomy with a fracture gap of 3 cm. No significant differences were found among the angles of torsion at fracture for the various osteotomies or the intact bone. Our results showed that the group of 1 cm gap had the 65% of the shear stress at failure of the simple osteotomy group.

Conclusion: We believe that there is evidence indicating that intramedullary nailing would be a reasonable option when one-stage lengthening of a long bone of 1 or 2 cm is contemplated.

Aim: Periprosthetic fractures are usually difþcult to be stabilized using plates and screws because of the presence of the underlying intramedullary stem, PMMA cement and thin periprosthetic femoral cortex. Modern techniques using cerclages and bands may be useful. Material & Methods: This study compares Ç in vitro È the mechanical performance of þve different osteosynthesis techniques applied on a oak femoral model obliquely oscillated to mimic a short oblique fracture: (a) double stainless steel wiring, (b) two 4.5 mm lag screws, © combination of one 4.5 mm cortical screw and one stainless steel wire, (d) one titanium cerclage CCG (Compression Cerclage Gudolf) combined with one 4.5 mm screw, and (e) double CCG Cerclage. The þve þxation constructs were subjected to a non-cyclic destructive axial compression and torsional loading. Results: The highest torque stiffness showed the double CCG and the double screw constructs, followed by and combination of CCG-screw and double wire constructs. The mode of failure in torque was a longitudinal crack close to screw tip and loosening of CCG and wire. The double screw, double CCG and screw- CCG constructs provided the highest stiffness in axial compressive forces. The mode of failure under compression was either loosening of CCG and wire or bending of the screw. Conclusions: This comparative study showed that double CCG can used in the treatment of oblique periprosthetic femoral fractures with the advantages of the simple technique, biocompatibility of titanium, no interference in modern imaging techniques and avoidance of stripping of muscles and degloving of bone surfaces as in platting often happens.

Introduction-Aim: The fractures which occurred at the midshaft of the femur, in which there is a prosthesis, are difficult to stabilize using free screws or plates, because of the presence of the underlying intramedullary stem, PMMA cement and thin periprosthetic femoral cortex. Although the periprosthetic fractures are usually oblique with a big contact surface between the pieces of the fracture and with the datum of the intramedullary presence of the femoral stem of the prosthesis, which increases the stability, this study compares five different types of internal fixation a rather unstable «worst case scenario» oblique midshaft fracture of the femur.

Material & Methods: We compared «in vitro» the mechanical performance of five different ïsteosynthesis techniques applied on a oak femoral model obliquely oscillated to mimic a short oblique 60o fracture. We compared the following kind of osteosynthesis: (a) double stainless steel wiring, (b) two 4.5 mm lag screws, (c) combination of one 4,5 mm cortical screw and one stainless steel wire, (d) double CCG cerclage, and (e) one titanium cerclage CCG (Compression Cerclage Gudolf) combined with one 4.5 mm screw. The five fixation constructs were subjected to a noncyclic destructive axial compression and torsional loading.

Results: The highest torque stiffness showed the double CCG and the double screw constructs, followed by the combination of CCG-screw and double wire constructs. The mode of failure in torque was a longitudinal crack close to the screw tip and loosening of CCG and wire. The double screw, double CCG and screw-CCG constructs provided the highest stiffness in axial compressive forces. The mode of failure in compression was loosening of CCG and wire and bending of screw.

Conclusions: The advantages of using the CCG is the simple technique, biocomptability of titanium, no interference in modern imaging techniques and avoidance of stripping of muscles. The method with the CCG titanium band proved biomechanically so stable as the system with the double 4,5 mm screw and recommend an alternative solution for the osteosynthesis of the distal periprosthetic fractures of the femur, especially for the cases with periprosthetic osteoporosis.