Abstract
Objectives
Malrotation after surgical treatment of femoral shaft fractures is a common problem and often leads to follow-up procedures with uncertain outcome. The aim of this study is the validation of a new device (Rotational Fixator) to perform the correction safely and accurately.
Methods
In an in-vitro study, we tested the Rotational Fixator on 21 corpse bones against a commercially available standard goniometer for measurement inaccuracies. For this purpose, we varied the rotation width from 10 to 30° in inside and outside rotation.
Results
We found a small measurement inaccuracy of 1–2° with increasing rotation. The smallest differences are found at 10° IR with 0.9524° (SD ± 1.0713; p = 0.001) difference and 10° ER with at 0.5952° (SD ± 0.6823; p = 0.001) difference and increase up to 30° (IR 1.6667°, SD ± 1.7121, p < 0.000/ER 1.5000°, SD ± 1.0488, p < 0.000).
Conclusions
The measurement results of the device show a constant deviation from the gold standard but are constant in the measurement error and slightly in relation to the desired correction range, so that a further review of the device and further testing in in vivo studies makes sense.
Levels of evidence
Level 3.
Keywords: Malrotation, Femoral shaft fractures, Femoral nailing
1. Introduction
Long bone fractures are common in polytraumatized patients1 and often present significant problems in setting correct rotation during reduction.2,3 In rubble zones or involvement of both sides, a reference is often no longer given. For the treatment of these injuries, the intramedullary nailing is a recognized method.4,5 But postoperatively, a rotational difference is evident from 17% up to 43% of cases with more than 10° rotation error.6, 7, 8 More than 15 ° were found in 19%–28%.8,9 in postoperative CT-measurements for the femoral antetorsion.
This postoperative complication is suggested to be corrected in differences over 15°8 by a new surgical procedure, in which the surgeon is reducing the rotation by clinical means due to the preoperative planning with a permanent risk of another rotational error.
The goal is a method that is quick and easy to use, while being easy to apply. Fixator systems are frequently used in the initial care of seriously injured patients in the context of damage control surgery. The Pins used here provide an ideal point of application for setting the rotation.
In the following, we will introduce a device that allows control of the rotation via the Schanz screws or other pins and enables a correct rotational position by direct means.
2. Material and methods
In this study, the validity of the device (Fig. 1) is examined using 21 corpse bones. 12 left-sided and 9 right-sided bones were cut using an oscillating bone saw (Fig. 2).
Fig. 1.
Rotational fixator.
Fig. 2.
Femur in cross-section with inserted pins.
We used a fixator to set the internal rotation (IR) of the distal bone fragment exactly to 10° and controlled this with a calibrated commercially goniometer (gold standard). Now it was possible to read which angle change was indicated by the rotational fixator. We proceeded in the same way with an internal rotation of 20° and 30°, as well as for an external rotation (ER) of 10°, 20° and 30°. For the statistical analysis we used the paired student t-test and the significance level was set to p < 0.05. This study was approved by our ethic committee. No concerns were raised.
3. Results
In comparison of the 10° internal rotation position between goniometer and fixator, the difference on average is −0.9524° (p = 0.001, CI-1.4400 to −0.4647). For 20° internal rotation, an average difference of −1.0476° (p < 0.000, CI-1.4907 to −0.6045) is shown and indicated for 30° internal rotation on average −1.6667° (p < 0.000; CI -2.4463 to −0.8871). Comparable results are shown in the analysis for the external rotation pairings. For 10° external rotation a mean difference of −0.5952° (p = 0.001, CI -0.9058 to −0.2847), for external rotation of 20°–1.8095° (p < 0.000, CI -2.2560 to −1.3631) and for 30° External rotation −1.5000° (p < 0.000, CI -1.0226 to −6.555).
The mean values of the differences show significant differences for all test pairs.
4. Discussion
In this pilot study, we tested the validity of the device in in vitro experiments on the basis of 21 corpse bones. Gender or ethnic differences were not included. The deviations between the calibrated goniometer and the rotational fixator increased according to the degree of rotation. The smallest differences are found at 10° IR with an 0.9524° (SD ± 1.0713; p = 0.001) difference and 10° ER with an 0.5952° (SD ± 0.6823; p = 0.001) difference and increase up to 30° (IR 1.6667°'; SD ± 1.7121; p < 0.000/ER 1.5000°; SD ± 1.0488; p < 0.000) (Fig. 3).
Fig. 3.
Boxplot IR/ER rotational fixator.
The data show that all the differences found were significant, but low in their severity.
The data thus shows a relatively small but constant deviation over all measurements and thus even an increase in the error with increasing rotation. This shows a systematic measurement error which indicates a device immanent measurement inaccuracy. From the authors' point of view, the deviation can be reduced to an insignificant minimum through better calibration measures and a more precise production. Furthermore, clinically relevant deviations are to be treated with rotational errors more than 15°,8 which corresponds approximately to 10 times the measurement inaccuracy of the rotational fixator. For this reason, the use of the device seems to allow a safe correction into an acceptable range.
The aim of this in vitro study was to check only the technical applicability and validity of the device. The results cannot be directly transferred to an in vivo application.
The question of the influence of axial deviation, a repositioning obstruction by involved soft tissue or debris cannot be answered by this study. Nevertheless, this method seems to be a promising application to solve the problem. From the authors' point of view, further technical improvements need to be made in order to increase the precision of the device, and practical application in clinical practice should be further tested.
5. Conclusion
The measurement results of the device show a constant deviation from the gold standard but are constant in the measurement error and slightly in relation to the desired correction range, so that a further review of the device and further testing in in vivo studies makes sense.
Ethics committee
Ethics Committee of the MHH: An assessment by the ethics committee. No concerns were raised.
Declaration of competing interest
The authors declare that there is no conflict of interest regarding the publication of this article.
Contributor Information
T. Omar Pacha, Email: OmarPacha.Tarek@mh-hannover.de.
A. Khalifa, Email: Khalifa.Ahmed@mh-hannover.de.
T. Graulich, Email: Graulich.Tilman@mh-hannover.de.
H. Alaidarous, Email: Dr.hasanalaidarous@gmail.com.
M. Omar, Email: Omar.Mohamed@mh-hannover.de.
C. Krettek, Email: Krettek.Christian@mh-hannover.de.
T. Stubig, Email: Stuebig.Timo@MH-Hannover.de.
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