Intraoperative Correction of Femoral Rotational Deformity Using a Conventional Navigation System and a Smartphone: A Novel Technique

Measurement of Lag-Screw Anteversion With an iPhone During Trochanteric Fracture Surgery

Introduction  A useful way to easily evaluate femoral rotation during surgery for trochanteric fractures is not known. Hence, this pilot study aimed to develop an intraoperative indicator to evaluate anteversion in femoral trochanteric fractures. Material and methods Prospectively, from June 2021 to January 2022, all patients with femoral trochanteric fractures (Orthopaedic Trauma Association classification: 31A1-3) treated using a cephalo-medullary nail with a lag-screw neck-shaft angle of 125° were included in this study. During surgery, lag-screw anteversion (LS-AV) was measured using the goniometer application in an iPhone with the fractured femur table-top-plane level with the traction table floor. Accuracy was analyzed by comparing axial-projected lag-screw anteversion (AxP-LS-AV) and three-dimensional computed tomography lag-screw anteversion (3DCT-LS-AV) measurements after surgery. Results Fifty patients (14 males and 36 females) were included in the study. The mean age was 87 (range; 69-98) years; the Orthopaedic Trauma Association classifications were A1 (28 patients), A2 (18 patients), and A3 (4 patients). The mean LS-AV was 10.7° ± 6.9°, the mean AxP-LS-AV was 12.8° ± 8.3°, and the mean 3DCT-LS-AV was 13.1° ± 8.6°. The median difference between AxP-LS-AV and 3DCT-LS-AV was 3.0° (range: 0°-12°), and 40 (80%) patients had differences of ≤5° (Bland-Altman plot: inside of limit of agreement = 86%, paired t-test p = 0.7, Pearson correlation coefficient r = 0.817, p <0.001). Conclusion Femur malrotation is defined as a deformity of >15° relative to the normal contralateral limb. Intraoperative LS-AV iPhone measurement on table-top-plane standard had sufficient accuracy as an indicator of anteversion in femoral trochanteric fractures.

Femoral shaft fractures treated by antegrade locked intramedullary nailing: EOS stereoradiographic imaging evaluation of rotational malalignment having a functional impact

INTRODUCTION

The standard treatment of femoral shaft fractures is intramedullary nailing. One of the most frequent complications is femoral malrotation. Our study sought to: 1) use EOS imaging to determine the amount of rotational malalignment after intramedullary nailing that has an impact on 6-month functional results; 2) determine the incidence of femoral malrotation based on EOS imaging; 3) determine the risk factors for postoperative femoral malrotation that impacts the 6-month functional results. The hypothesis was that EOS imaging can be used to determine the amount of femoral malrotation that has a functional impact in patients treated by percutaneous femoral intramedullary nailing.

MATERIAL AND METHODS

We performed a prospective, single-center study between September 2017 and February 2020. Patients who had suffered a femoral shaft fracture treated with antegrade intramedullary nailing were included in this study. Femoral anteversion was measured at 6 months with an EOS stereoradiographic imaging system. Patients were assessed at 6 months with the WOMAC, Oxford, Harris and MDP functional scores. The SF-12 quality of life score was also determined.

RESULTS

Thirty patients were evaluated at 6 months postoperatively, 15 women (50%) and 15 men (50%) who were 47 years old on average [16; 94]. The average anteversion was 19.9°C [-23°; 75°]. The functional scores (Oxford and Harris) were altered when there was 14° or more difference in femoral torsion between the operated side and the healthy side with a sensitivity of 0.88 and a specificity of 0.77. The risk factors for femoral malrotation were age under 35 years (p=0.01), urgent surgical management (p=0.008), location in middle third of femoral shaft (p=0.05), and short spiral fracture (p=0.02).

CONCLUSION

The use of EOS imaging allowed us to demonstrate that functional hip outcomes are altered at 6 months postoperatively when greater than 14° femoral malrotation is present compared to the contralateral side after femoral intramedullary nailing. The risk factors that contributed to intraoperative rotational malalignment were age less than 35 years, urgent surgical management, mid-shaft femoral fracture and short spiroid fractures.

LEVEL OF EVIDENCE

II.

EOS stereographic assessment of femoral shaft malunion after intramedullary nailing. A prospective series of 48 patients at 9 months' follow-up

INTRODUCTION

The aim of the present study was to assess femoral shaft malunion following anterograde intramedullary nailing, using low-dose EOS stereoradiography. The study hypothesis was that our surgical technique is associated with radiological rotation disorder rates equivalent to those reported in the literature.

METHODS

All patients with unilateral femoral shaft fracture treated by anterograde nailing between January 2014 and December 2016 and followed up in our structure were included in a single-center prospective study. The main endpoint was≥15° transverse malrotation compared to the contralateral side as measured on EOS stereoradiography. Correlations between malrotation and Harris Hip and SF12 functional scores were assessed, as were risk factors for onset of shaft malunion in rotation. Forty-eight patients with a mean age of 31.4 years were analyzed at a mean 9.3 months' follow-up.

RESULTS

Stereoradiographic malrotation was found in 29.2% of patients. Mean anteversion was 18.5±13.8°. In 2.1% of patients, symptomatic rotation disorder required revision surgery. No correlations emerged between transverse malrotation and functional scores (p>0.05). Risk factors for malrotation comprised multi-site fracture (p=0.04), surgeon's inexperience (p=0.04), and open reduction (p=0.01).

CONCLUSION

The present radiologic malrotation rate was comparable to those reported in the literature, using the EOS stereoradiographic system, which provides precise assessment of rotation disorder following closed nailing of femoral shaft fracture.

LEVEL OF EVIDENCE

III; prospective study without control group.

Development of an intraoperative 3D C-arm technique for torsion control of femur fractures: a cadaver study

AIM

This study aims to test the accuracy and feasibility of a measurement of femoral torsion of a 3D C-arm system (Linea aspera method) in a cadaver setting.

MATERIALS AND METHODS

A total of 11 intact femora were used. Schanz screws were inserted in the femoral bone in a parallel manner with the help of a fixed drill sleeve. Femur bones were then fractured in a controlled manner and three different internal and external torsion angles were fixed with the help of a Goniometer. After that, a 3D scan was performed. The 3D data set was analyzed using a radiologic software (Visage 7, Visage Imaging Inc, USA). Measurements were then compared in the two methods with a dependent t test.

RESULTS

Specific measurements for different angles did not show any differences between those two utilities.

CONCLUSION

Intraoperative estimation of femoral antetorsion using a 3D C-Arm system and the Linea aspera method seems to be an accurate and feasible method. Nevertheless, more studies with higher patient numbers, comparison to CT seems to be the next step and can be recommended.

Evaluation of the smartphone for measurement of femoral rotational deformity

BACKGROUND

A novel measurement technique has been designed to assess femoral rotation deformation. The purpose of this study was to evaluate smartphone-aided measurement, including measurement software, intra-observer differences and the occurrence frequency of the unacceptable outliers.

METHODS

Five positions (intact bone, external and internal rotations of 20° and 40° of the distal blocks after dividing the femoral shafts using a saw) were used in each of the five artificial femora. Guide wires were separately inserted into the proximal and distal ends of the model femora with a navigation system and the intersection angles between the guide wires were measured with a smartphone. The values obtained by two measurement software packages (Smart Tools and Super Swiss Army Knife) were compared with that measured on the overlapped computed tomography images.

RESULTS

There were no significant differences between the intersection angles measured by smartphone and that measured on the overlapped images (P = 0.24). The mean absolute difference between pairs of measurements of the two software packages for all guide wire angles was 2.33 ± 2.34°, without statistically significant difference (P = 0.33). There was a significant correlation (r = 0.99) between the first and second (1 week apart) measurements with the same measurement tool. The values of offset capability index of the Smart Tools and the Super Swiss Army Knife measurement tools were 1.62 and 1.13, respectively.

CONCLUSION

Smartphone-aided measurement technique could reliably assess femoral rotation deformation with more accurate angle measurement for software with zero calibration function.