Biomechanical analysis of nonreamed tibial intramedullary nailing after simulated transverse fracture and fibulectomy

The healing stages of an intramedullary implanted tibia: A stress strain comparative analysis of the calcification process

AIMS

The extended usage of unreamed tibial nailing resulted in reports of an increased rate of complications, especially for the distal portion of the tibia. Unreamed nailing favours biology at the expense of the achievable mechanical stability, it is therefore of interest to define the limits of the clinical indications for this method. Extra-articular fractures of the distal tibial metaphysis, meta-diaphyseal junction, and adjacent diaphysis are distinct in their management from impaction derived ''pilon'' type fractures and mid-diaphyseal fractures. The goals of this work were to gain a thorough understanding of the load-sharing mechanism between unreamed nail and bones in a fractured tibia. With this purpose a complete model of the human leg was realised, simulating a mid-diaphyseal fracture, classified as A2 type 1, according to the AO classification. The analysis of the entire chain allows to have a complete picture of the stress distribution and of the most stressed bones and soft tissues, but, more importantly can overcome problems connected with boundary conditions imposed at single bony components.

METHODS

Model consists of six bony structures: pelvis, femur, patella, fibula, tibia, and a simplified lump of the feet, configured in a standing up position. Their articular cartilage layers, were simulated by 3D membranes of opportune stiffness connecting the different segments. Moreover an unreamed intra-medullary nail Expert Tibial Nail (DePuy Synthes(®)) stabilized the fractured tibia. A load of 700 N has been applied at the top of pelvis and a part the feet, at the tip, was rigidly fixed. Five different contact interfaces have been imposed at the different bony surfaces in contact.

RESULTS

Three different conditions were analysed: the initially healthy tibia, the A2 type 1 fractured tibia with the Expert tibial nail implanted, and the follow up stage after complete healing of tibia. Non-linear finite element analysis of the models were performed with Abaqus version 5.4 (Hibbitt, Karlsson and Sorensen, Inc., Pawtucket, RI) using the geometric non linearity and automatic time stepping options.

CONCLUSION

The obtained results reveal interesting consequences deriving by taking into account how the stress shielding can influence the integrity and resistance of bones, in order to identify the mechanical reasons for the unfavourable clinical results, and to identify borderline indications due to biomechanical factors. The evolution of treatment options for these fractures has been closely linked to developments in implant technology and surgical technique. Further developments in this area, particularly with respect to minimally invasive plating techniques and nail design are ongoing.

Distal tibial metaphyseal fractures: does blocking screw extend the indication of intramedullary nailing?

Aim. To evaluate the clinical use of blocking screws as a supplement to stability in distal tibial metaphyseal fractures treated with statically locked intramedullary nail. Main Outcome Measurement. Alignment and reduction preoperatively, postoperatively, and at healing were the main outcome measured with an emphasis on maintenance of initial reduction on followup. Patients and Methods. This was a prospective study of 20 consecutive cases of distal tibial metaphyseal fractures treated with statically locked intramedullary nailing with supplementary blocking screw between August 2006 and September 2007 with a maximum followup of 3 years. Medullary canal diameter was measured at the levels of fracture and isthmus. Results. The mean diameter of tibia at the level of isthmus was 11.9 mm and at the fracture site was 22.9 mm. Mean length of distal fracture segment was 4.6 cm. Mean varus/valgus alignment was 10.3 degrees preoperatively and 1.7 degrees immediatly postoperatively and was maintained till union. Using Karlstrom-Olerud score the outcome was excellent to good in 90%. Conclusion. We conclude that the use of blocking screw as a supplement will aid in achieving and maintaining the reduction of distal tibial metaphyseal fractures when treated with intramedullary nailing thereby extending the indication of intramedullary nailing.

Exchange reamed nailing compared to augmentation compression plating leaving the inserted nail in situ in the treatment of aseptic tibial non-union: a two-centre study

BACKGROUND

A remarkable number of investigations are available treating tibial non-unions by exchange reamed nailing (ERN). Only few authors reported positive results after augmentation compression plating (ACP) for the same entity. To our knowledge no systematic study is published comparing ERN vs. ACP, so that this trial compares ACP leaving the already inserted un-reamed nail in situ against ERN in the treatment of aseptic tibial non-union, analysing success rate, time for union and operation time.

PATIENTS AND METHODS

Forty-eight patients with aseptic hypertrophic diaphyseal tibial non-union treated previously by un-reamed nailing were included retrospectively in this two-centre study. Group A consisted of 25 patients with ERN and group B of 23 patients with ACP leaving the underlying un-reamed nail in situ.

RESULTS

Mean follow-up was 3.8 years. Union was achieved in 24 out of 25 cases (96 %) for group A and in 22 out of 23 cases (95.6 %) for group B. Time needed for union varied; an average of 29 weeks for group A and 14 weeks for group B. The mean operation time for group A was 99 min, while it was 65 min for group B.

CONCLUSIONS

ERN and ACP with remaining pre-existing nail in situ are both safe and straightforward surgical procedures with equivalent high success rates of about 95 %. ACP has the advantage of less time for union and operating time in this series, but is associated with the disadvantage of requiring an additional incision and complaints associated to the plate requiring implant removal.

Do fibula nonunions predict later tibia nonunions?

OBJECTIVES

The purpose of this study was to evaluate the validity of fibula nonunion as a method for predicting tibia nonunion in the tibiofibula shaft fracture.

DESIGN

Retrospective study.

SETTING

University hospital.

MATERIALS AND METHODS

From March 1998 to October 2008, 224 patients were enrolled. Among 224 patients, 153 patients were treated with intramedullary nail, 34 patients were treated with external fixator, 32 patients with plate and screws. The remaining 5 patients were treated nonsurgically with cast or brace. Patients followed up at 1, 2, 3, 6, 9, 12, and 18 months postoperatively. Multivariate analysis of the relationship between fibula and tibia union was conducted.

RESULTS

Among the 224 patients, 169 patients were included in the fibula union group and 55 patients were in the fibula nonunion group. Mean age was 49 years (19-89 yrs); follow-up period was more than 18 months (18-109 mo). In the fibula union group, there were 21 patients (12.4%) with a tibia nonunion. In the fibula nonunion group, 21 patients (56.3%) had tibia nonunion. Fibula nonunion was significantly statistically associated with tibia nonunion (P = 0.002). Union time between the tibia and the fibula was statistically significant (P = 0.002).

CONCLUSION

Fibula nonunion is a good predictor of tibia nonunion in patients with tibiofibula shaft fractures.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Exchange reamed nailing for aseptic nonunion of the tibia

BACKGROUND

Exchange reamed nailing of the tibia is a common procedure in the treatment of an aseptic tibial nonunion. However, reports in the literature supporting this technique are limited.

METHODS

Forty patients with a tibial nonunion after initial unreamed intramedullary nailing were retrospectively assessed after an exchange reamed nailing. The main outcome measurements included radiographic and clinical union as well as time from exchange reamed nailing to union.

RESULTS

Thirty-eight patients achieved union of their fracture (95%). The average time from exchange nailing to union was 29 +/- 21 weeks. Complications included one deep vein thrombosis (2.5%) and two hardware failures (5%).

CONCLUSION

Exchange reamed nailing for nonunions of the tibia results in a high union rate and is associated with a low complication rate. This technique is recommended as a standard procedure for aseptic tibial nonunions after initial unreamed intramedullary nailing.

Mechanical boundary conditions of fracture healing: borderline indications in the treatment of unreamed tibial nailing

Unreamed nailing favors biology at the expense of the achievable mechanical stability. It is therefore of interest to define the limits of the clinical indications for this method. The extended usage of unreamed tibial nailing resulted in reports of an increased rate of complications, especially for the distal portion of the tibia. The goals of this work were to gain a thorough understanding of the load-sharing mechanism between unreamed nail and bone in a fractured tibia, to identify the mechanical reasons for the unfavorable clinical results, and to identify borderline indications due to biomechanical factors. In a three-dimensional finite element model of a human tibia, horizontal defects were stabilized by means of unreamed nailing for five different fracture locations, including proximal and distal borderline indications for this treatment method. The loading of the bone, the loading of the implant and the inter-fragmentary strains were computed. The findings of this study show that with all muscle and joint contact forces included, nailing leads to considerable unloading of the interlocked bone segments. Unreamed nailing of the distal defect results in an extremely low axial and high shear strain between the fragments. The results suggest that mechanical conditions are advantageous to unreamed nailing of proximal and mid-diaphyseal defects. Apart from biological reasons, clinical problems reported for distal fractures may be due to the less favorable mechanical conditions in unreamed nailing. From a biomechanical perspective, the treatment of distal tibial shaft fractures by means of unreamed nailing without additional fragment contact or without stabilizing the fibula should be carefully reconsidered.