Session IX - Tibia
Effect of Surgical Approach on Fracture Healing: Comparison of Minimal Invasive Approach (MIS) to Conventional Open Reduction and Internal Fixation Technique (ORIF) in a Sheep Tibial Shaft
Michael Schütz, MD; Arno Schmeling, MD; Max Kääb, MD; Ronald Wieling, PhD; Keito Ito, PhD, Dept. of Trauma and Reconstructive Surgery, Charité Campus Virchow-Klinikum Humboldt-University, Berlin, Germany
Purpose: It has been suggested that minimal invasive surgical approaches for internal fixation of fractures is beneficial for fracture healing because of reduced soft tissue damage and osseous perfusion disturbance. The goal of this study was to examine the effect of a minimal invasive approach (MIS) in comparison to that with conventional open reduction internal fixation (ORIF) with regard to fracture healing.
Methods: 12 sheep were bilaterally operated on the hind limbs as a paired comparison in randomized order (right/left to MIS/ORIF). To every sheep leg a high-speed reproducible closed soft-tissue injury (Tscherne GII) was induced on the lateral tibial compartment. Then a simple transverse shaft fracture (AO 42-A3) was created with a specially designed 4pt bending impact device. In both approaches, a point contact fixator (PC-Fix II, Synthes) was used for stabilization. For the MIS technique, the fracture device and the internal fixator were applied on the periosteum through two 2-cm medial longitudinal skin incisions. For the ORIF technique a 12-cm medial longitudinal skin incision was made, and the fracture was reduced with a bone clamp prior to stabilization.
Fracture healing was monitored with radiographs every two weeks, and weight bearing on each leg was measured weekly with specially designed pressure sensing shoe insoles. Fluorochrome-labeling was done in biweekly intervals to monitor bone formation. Six sheep were euthanised at 6 weeks and another six at 12 weeks. After hardware removal, the tibiae were biomechanically tested for stiffness (torsion and 4pt bending) and strength (4pt bending) and then prepared for histological analysis. Statistics were calculated using a paired t-test with a significance level of p<0.05.
Results: No statistically significant difference was found between MIS and ORIF groups in regard to the biomechanical properties of the sheep tibiae at 6 or 12 weeks (see Table). All tibiae of the 6-week group and all except five tibia of the 12-week group failed through the original fracture site (the exceptions failed through a screw hole). There was no significant difference of weight bearing between the MIS and ORIF treated legs, except in one sheep (p<0.005). This sheep received a second operation due to screw pull-out and loss of reduction at 2 weeks post-fixation. Hence, weight bearing of the opposite leg was preferred, but the mechanical properties of both tibiae at 12 weeks were similar to the other sheep.
6 weeks |
12 weeks | |||||
ORIF (mean ±S.E.) |
MIS (mean ±S.E.) |
p value |
ORIF (mean ±S.E.) |
MIS (mean ±S.E.) |
p value | |
Tor. Stiff. [Nm/deg] |
7.0 ±0.7 |
6.8 ± 0.5 |
0.9 |
7.8 ±1.6 |
7.6 ± 0.8 |
0.5 |
Bnd. Stiff. [Nm/deg] |
10.4 ±0.7 |
10.1 ±1.1 |
0.3 |
11.6 ±1.6 |
11.8 ±1.8 |
0.2 |
Bnd. Strength [Nm] |
49.3 9.9 |
44.2 8.3 |
0.2 |
86.3 23.6 |
81.6 14.1 |
0.5 |
Discussion and Conclusion: These biomechanical data did not show a statistical significant difference in fracture healing. One reason for this may be that our model is not sensitive enough to show these differences (insufficient soft tissue injury or fracture severity, inappropriate anatomy or accelerated fracture healing in sheep). On the other hand these results may reflect an overestimation of MIS benefits on osseous healing, since it is a more technically demanding procedure than that with ORIF.
Acknowledgements: This work has been supported by a grant of the AO ASIF Research Commission (Grant Number 99-S20)