Concept for General Improvements in the Treatment of Femoral

Shaft Fractures with an Intramedullary Nail

Finn Siegel

, Christian Buj

, Ralf Schwanbeck

, Andreas Petersik

, Ulrich Hoffmann

Jakob Kemper

, Frank Hildebrand

, Philipp Kobbe

, Jörg Eschweiler

, Johannes Greven

Ricarda Merfort

, Christian Freimann

, Astrid Schwaiger

and Frerk Müller-von Aschwege

OFFIS e.V. – Institute for Information Technology, Escherweg 2, Oldenburg, Germany

Stryker, Schönkirchen, Germany

Universitätsklinikum Aachen, Aachen, Germany

OnCare GmbH, München, Germany

Keywords: Femur Fracture, Intramedullary Nailing, Intraoperative, Malrotation, Rehabilitation, Medical Data Security.

Abstract: The gold standard for femoral shaft fracture treatment is intramedullary (IM) nailing. This principle has gained

acceptance because of the good fracture healing rate and the rapid return to full weight-bearing of the leg.

Nevertheless, a significant number of patients suffer from impairments in everyday life years after treatment.

This paper discusses various causes and presents possible solutions: a) Improving the IM nailing procedure

by developing a new intraoperative assistance system to precisely restore length and rotation angle of the

injured femur. b) Improving rehabilitation after IM nailing treatment, through home monitoring. c) Increasing

data safety, standardization, and centralization along the entire patient pathway, enabling analytics to

statistically verify improvements in IM nailing treatments.

1 INTRODUCTION

Thanks to modern medicine, a femoral shaft fracture

can be treated with few complications. Nevertheless,

20% of patients still suffer from after-effects three

years post-treatment, reducing their quality of life.

These include pain in the lower limbs or an altered

gait pattern. One identified cause is an incorrect

reconstruction of the rotation angle or length of the

femur during surgery. This relationship and possible

improvements are presented in more detail below.

Treatment Challenges

Intramedullary (IM) nailing is the most successful

treatment for a femur shaft fracture in adults, due to

high healing rates with low complication (Rommens

& Hessmann, 2015). During treatment with an IM

nail, the soft tissue is minimally affected, enabling

rapid healing (Fantry et al., 2015). In addition,

https://orcid.org/0000-0002-9319-4304

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https://orcid.org/0000-0003-2856-4804

interlocking with screws provides rotational and

longitudinal stability and thus ensuring the conditions

for an early return to full weight bearing and a high

likelihood of fracture union (Jaarsma & van Kampen,

2004; Paterno & Archdeacon, 2009). Nevertheless, it

is still a surgical procedure that carries risks, such as

infection or neurovascular injury. Another

disadvantage of the minimally invasive procedure is

the difficulty to ensure anatomical realignment under

direct vision, which leads to less control of rotation

and length compared to the classical method of plate

fixation (Jaarsma et al., 2004). Deviations from the

original position, greater than 5° in frontal or sagittal

plane, 15° in the axial plane and 2 cm in length, are

regarded to be deformities (Ricci et al., 2008). It

originates from a poor choice of nail entry point or

incorrect positioning of nail fixation during surgery.

The occurrence varies between 22.7 - 28% of the

cases (28% (Jaarsma & van Kampen, 2004), 26%

360

Siegel, F., Buj, C., Schwanbeck, R., Petersik, A., Hoffmann, U., Kemper, J., Hildebrand, F., Kobbe, P., Eschweiler, J., Greven, J., Merfort, R., Freimann, C., Schwaiger, A. and Aschwege, F.

Concept for General Improvements in the Treatment of Femoral Shaft Fractures with an Intramedullary Nail.

DOI: 10.5220/0011679100003414

In Proceedings of the 16th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2023) - Volume 5: HEALTHINF, pages 360-367

ISBN: 978-989-758-631-6; ISSN: 2184-4305

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

(Strecker et al., 1996), 22.7% (Rommens &

Hessmann, 2015), 25% (Papachristos, 2019)). In

general, a not correctly reconstructed femur leads to

arthritis and pain of back, hip and knee, limping,

restrictions in range of motion and daily life. These

complications scale with the severity of the

malalignment. (Jaarsma & van Kampen, 2004;

Papachristos, 2019). In summary, developing a way

to correctly restore the rotation (also known as

(ante-) version or (ante-) torsion) and the length of the

femur, malalignments could be reduced and therefore

the patient’s quality of life improved. Common

techniques used by surgeons to correctly restore the

anteversion angle of the fractured femur are based on

determining the anteversion angle of the uninjured leg

at beginning of surgery. This angle is used as

reference for the injured leg. One well known method

to determine a reference for the anteversion is the

lesser trochanter method (Deshmukh et al., 1998).

Alternatively, the anteversion angle can be measured

by using the inclination scale of the C-arm to measure

the C-arm angle between the positions required for

taking a true lateral image of the knee and a true

lateral image of the femoral head-neck junction

(Tornetta et al., 1995). Other possible methods for

assessing femoral rotation are the cortical step sign

method (Langer et al., 2010) and computer

tomography (CT) based navigation (Weil et al.,

2014). Although several different methods for

measuring anteversion exist none of the methods is

widely accepted. The fluoroscopy-based methods

significantly increase the number of necessary x-ray

images and the time needed for surgery (Deshmukh

et al., 1998; Tornetta et al., 1995). Additionally, these

methods have limited accuracy (Ju et al., 2021). The

cortical step sign method has limited value for

patients with comminuted fractures, and CT-based

navigation causes high costs and long setup time. In

conclusion, a widely accepted method to control for

anteversion and length of the femur is needed.

Rehabilitation

The following common impairments after IM nailing

are identified: Hip abduction and knee extensor

weakness, knee and hip pain, decreased hip

movement, decreased walking endurance, and gait

abnormalities, especially Trendelenburg gait pattern.

Rehabilitation focuses on reversing these through

physical exercises improving range of motion,

strength, weight bearing and gait. However, it is

described in literature that 20% of the patients could

not return to normality 3 years after surgery (Paterno

& Archdeacon, 2009; Noor, 2019). Therefore, it is

important to consider follow-up issues caused by

malrotation. Researchers found that up to 72% of a

present malrotation could be compensated (Jaarsma

et al., 2004). However, day-to-day monitoring of the

musculoskeletal system and its mobility is necessary

to assess individual stress caused by a given

malrotation. The collection and analysis of the

monitoring data can enable individual therapy

interventions, to improve patient’s healing in a

sustainable way. In addition, interventions can be

made comparable, and their success evaluated.

Lastly, new information about the compensation can

be gathered, for example when it sets in or how it

progresses. Physiotherapy could start directly at this

point and support with targeted training.

2 METHODS AND

PRELIMINARY RESULTS

Within the Secur-e-Health project (Secur-e-Health,

2021) the German subproject Smart Fracture Care

funded by the German Federal Ministry of Education

and Research (BMBF) is focusing on a new approach

for dealing with femur shaft fractures. The main

project goals are:

1. Improving the IM nailing procedure by

developing a new intraoperative assistance system

to precisely restore length and rotation angle of

the injured femur.

2. Improving rehabilitation after IM nailing

treatment, through home monitoring.

3. Increasing data safety, standardization, and

centralization along the entire patient pathway.

This will enable Big Data analytics to statistically

verify improvements in IM nailing treatments.

2.1 Intraoperative Assistance System

There is no widely accepted method controlling

anteversion and length of the femur shaft.

To address this issue, we propose a computer

aided surgery system that allows intraoperative

reconstruction of the 3D shape of the uninjured femur

using a small number of fluoroscopic images

recorded before surgery. The mirrored 3D shape is

used as a reference for restoring the rotation and

length of the injured femur.

The Length Alignment Rotation (LAR) system

consists of a tablet computer with built-in frame

grabber and touch screen. The tablet computer is

placed in the sterile field close to the surgeon

allowing interaction with the LAR software. It also

obtains fluoroscopic images using a frame grabber

Concept for General Improvements in the Treatment of Femoral Shaft Fractures with an Intramedullary Nail

361

Figure 1: Placing (left) and radiographic image (right) of reference bodies attached to the patient, used for the LAR system.

and a connection to the C-arm. Additionally,

reference bodies are attached to the patient (see

Figure 1). These markers are based on polymer-

bodies with small, embedded steel beads. Using

computer vision software, the viewing orientation of

fluoroscopic images can be computed by analysing

the pattern of the projected beads in the image.

The reference Image is created at the beginning

of the surgery. The LAR system is used to compute

the 3D shape of the unaffected femur by the following

steps:

1. A reference body spanning the length of the femur

is placed on the unaffected limb.

2. Two fluoroscopic images of the proximal area of

the unaffected femur are taken.

3. Two fluoroscopic images of the distal area of the

unaffected femur are taken.

4. The LAR system computes a 3D approximation

of the unaffected femur from the images taken in

step 2 and 3.

For rotation and length control of the injured

femur, the approximation of the 3D shape of the

unaffected bone can be used as reference for the

injured bone. For this, the following workflow step

are required:

1. A reference body spanning the length of the femur

is placed on the affected limb.

2. Two fluoroscopic images of the proximal area of

the affected femur are taken.

3. The LAR system computes a 3D approximation

of the proximal part of the affected femur.

4. The mirrored 3D shape of the unaffected femur

is matched to the proximal part of the 3D shape of

the affected femur.

5. The contour and axes of the mirrored unaffected

femur will be presented as an overlay on top of the

fluoroscopic images of the affected femur. This

can be used as a reference by the surgeon (see

Figure 2).

6. Using two images of the distal area, the system

can also reconstruct the entire 3D shape of the

affected femur. Now angle and length of the

affected femur can be directly compared to the

unaffected femur (see Figure 2).

One of the main technical challenges in the LAR

system is the reconstruction of the 3D shape of the

femur from 2D fluoroscopic images. To compute the

3D shape of the femur, first the relative orientation of

the fluoroscopic images is computed using the

projections of the reference body beads in the

fluoroscopic images. A convolutional neural network

(CNN) for 3D segmentation is used to compute an

approximation of the proximal and distal femur shape

from the fluoroscopic images. The network

architecture used for this is similar to the architecture

described in (Milletari et al., 2016). The proximal and

distal approximation of the femur are fused into an

overall shape by fitting a 3D active shape model

(Cootes et al., 1995) to the distal and proximal

approximations.

An early version of the LAR system has been

tested in a cadaver lab on two specimen and in several

sawbone labs. The tests showed that the system can

be used to obtain a 3D reconstruction of a femur bone

from 2D images. The accuracy of the estimated

angles was ± 8 degree and ± 4 mm in length, when

compared to the ground truth obtained from a CT

scan. The objectives of further research are to

improve the workflow, to facilitate the work with

reference bodies and to enhance the robustness of the

3D reconstruction.

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Figure 2: Tablet computer showing the LAR system.

2.2 Rehabilitation Improvement

The healing process is determined either in sessions

with the physiotherapist or by patient self-reports. In

the first case, only a small insight into the treatment

progression is generated and not a continuous picture.

In the second case, documentation is often inaccurate

due to the patients’ tendency to misjudge themselves

(Komaris et al., 2022). Therefore, an objective,

continuous measurement method may be helpful to

obtain a more accurate picture of the patient’s healing

progress to further customize treatment. In addition,

such system could enable intercomparability,

allowing treatment methods to be compared. number.

2.2.1 Concept for Improvements

To overcome the difficulties described above, we

propose the usage of a sensor array, which can be

worn during rehabilitation in a wearable. Used for

this purpose are Force Sensing Resistors (FSRs),

inertial measurement units (IMUs) and

Electromyography (EMG) sensors. Collected data is

then processed and statements about the course of

healing can be made.

To improve individual treatment and to create the

possibility of easy intercomparability, the following

objectives are established:

a) Check for the common residual impairments after

IM nailing, hip abduction weakness, decreased

hip and knee movement, knee extensor weakness,

pain, gait abnormalities, decreased walking

endurance. If these are identified, targeted

countermeasures can be taken during

rehabilitation.

Since hip abduction and knee extension weakness

affect the patient’s gait pattern and daily routine,

they can be detected by combining a specific

questionnaire and a gait analysis. The range of

motion (ROM) can be measured allowing to

conclude about mobility. Which in turn allows

deductions about hip and knee joint movements.

Pain is a subjective perception and needs to be

assessed by questionnaires. Information about

changes in walking endurance can be obtained in

a trend analysis.

b) Collecting information about ROM and pain

tolerable load on the leg in everyday life. This

additional information can be used by the physical

therapist to customize exercises or to properly

assess the use of assistive devices.

c) A malrotation of the femur is followed by a

compensation mechanism of the body. This effect

is well known and documented, but information

about the onset of compensation is not yet

available. Continuous measurements could

provide further knowledge.

d) Visualization of the healing process. A visibly

positive progression could motivate the patient to

continue or even intensify the exercising and thus

accelerate the healing.

To meet these objectives (a-d), information about

the status of mobility, ROM, gait, activity,

malrotation, compensation, status of demanding

activity, pain, managing everyday life and the

before surgery state must be generated from

collected patient data. This will be accomplished

using wearable sensors as well as patient self -

assessments e.g., filling out questionnaires (about

pre-surgical status, pain and satisfaction with

healing).

2.2.2 Sensor Systems

In the following, three sensor systems (EMG, IMU

and FSR) proposed in chapter 2.2.1 for integration

into a wearable are described. After a functional

introduction, the data evaluation methods to generate

relevant information are described.

Electromyography (EMG) can be used to measure

the onset of a muscle activation. Surface electrodes

can measure the electronical potential differences,

which are due to the activation of muscles. The EMG-

signal changes in amplitude and frequency depending

on the induced motion (Wang et al., 2021). The

following information must be determined from the

recorded sensor data:

Rotation: A gait pattern is created by the interaction

of several muscles. In case of deformed bones in the

lower limbs, gait pattern changes and therefore the

activity of the muscles. The change can be measured

externally with the help of EMG sensors. Since the

Concept for General Improvements in the Treatment of Femoral Shaft Fractures with an Intramedullary Nail

363

sensors are to be worn above the knee, the vastus

medialis and the vastus lateralis seem to be suitable

muscles for such measurements. Mohammad &

Elsais, 2020 found significant negative correlations

between hip internal rotation angle and EMG activity

for the gluteus maximus and vastus medialis

obliquus. Significant positive correlations were

observed between hip internal rotation angle and

EMG activity for the vastus lateralis obliquus

(Mohammad & Elsais, 2020). Those findings indicate

that the EMG measurement could be used to draw

conclusions about malrotation. A study to determine

this relationship is being planned.

Load and Muscle Strength: The load on the leg

influences the muscle force required for walking.

E.g., if the patient uses a walker, less load is placed

on one leg and less muscle force is required. Since

musculoskeletal electrical activity correlates with

muscle force, EMG sensors are useful for detecting

different loads. In fact, and Mokri et al., 2022 showed

that neuromuscular activation is a major contributor

to muscle strength (Mokri et al., 2022). However, the

research also showed that a direct model cannot be

created because muscle force also depends on muscle

volume, fiber length, and velocity (Roberts &

Gabaldon, 2008), which means that EMG

calculations can only be used as an indicator of the

healing process. For example, if the EMG detects an

increase in activity, improvement can be assumed.

Calculating absolute load values remains a challenge.

To gain more insight, a study will be conducted to

examine different loads and corresponding EMG

signals.

Inertial Measurement Units (IMUs) are available in

small sizes and for a low cost. They can be used to

obtain position and orientation. It usually consists of

an accelerometer, gyroscope and magnetometer. We

propose wearing at least two sensors. The following

information must be determined from the recorded

sensor data:

ROM: At least two sensors are needed to determine

a joint angle, quantifying the ROM. If the sensor axes

are perfectly aligned with the object axes the joint

angle can be computed by integrating the difference

of both angular rates (Seel et al., 2014). The

positioning of the sensors will be supported by

wearables, but it cannot be guaranteed, that the

positioning accuracy will repeatedly be sufficient. To

overcome this issue a joint is considered as a hinge

joint and therefore creating constraints allowing the

position and direction vector of the knee to be

determined. Concluding, only the individual

orientation of the sensors is required, directly

resulting in an accurate flexion/extension angle

(Favre et al., 2008). Seel et al., 2014 could achieve an

accuracy of 3° when measuring the knee joint (Seel et

al., 2014). This concept is suitable to be integrated in

the wearable.

Activity: Information on the patient’s activity can be

derived from the calculations of ROM, e.g., step

count. Another important aspect that should be

sensorially detected is the performance of

physiotherapeutic exercises in the home environment.

Komaris et al., 2022 have already presented a

working concept in which exercise sequences are

recorded and processed during supervised training

(Komaris et al., 2022). These recordings can now be

compared to home training, identifying exercises and

detecting changes in execution.

Gait: Insights into Gait irregularities are an indicator

for the healing process. To put as little additional

strain on the patient as possible, the aim is to use a

unilateral sensor fitting. This limits the ability to

detect gait differences based on lateral differences.

However, it is still possible to observe the change of

spatio-temporal gait parameters unilaterally (Shahar

& Agmon, 2021), allowing conclusions to be drawn

about gait irregularities. From this, e.g.,

Trendelenburg gait could be detected, a study is

planned to gain further insight.

Pressure sensors are one of the simplest methods to

measure the force under the foot while walking. In

example, Force Sensing Resistors (FSRs), are

suitable for this purpose. These consist of a

conductive polymer between two electrodes. If a

force is applied from outside, its conductive

properties change along with the resistance between

the electrodes. This change correlates with the

applied force (Abdul Razak et al., 2012). The

following objectives are to be measured:

Load: The load can be estimated, by real-time

pressure sensors worn inside the shoe sole. After a

calibration with the help of a scale, a threshold value

can be set, which is considered as a limit for the load

of the leg. This can be used to provide direct feedback

for the patient to assist in loading the leg accordingly.

In addition, the data shows the objective course of the

tolerable load allowing for exercises to be adapted

accordingly. Bril et al., 2016 showed the possible

usage of such threshold to directly support the patient

(Bril et al., 2016).

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Figure 3: Concept of digital patient pathway.

Mobility: Step frequency can be investigated to

derive information about the patient’s mobility. Since

steps are recognizable in recorded pressure data, a

Fast Fourier Transformation can provide information

about the step frequency. Also, classifying pressure

patterns while being active can help to differentiate

events such as stair climbing. Chakraborty & Dendou

were able to detect whether a patient was climbing up

or down stairs, with an accuracy of 100%

(Chakraborty & Dendou, 2014). Implemented in this

approach, it could provide additional information

about healing progress.

2.2.3 Overall Sensor Concept

A concept, to achieve the above-mentioned goals has

been created. It is based on a sensor set built into

wearables and a data collection unit. The wearable

will hold multiple sensors (FSR, IMU, EMG) while

keeping the additional burden on the patient to a

minimum. E.g., the sensors must be easy to place and

remain stable to ensure measurement reliability. To

meet these requirements, the sensors are divided into

two systems. System A is used on the thigh and holds

the EMG sensors and a single IMU sensor. It is

designed as a bandage, starting just below the knee,

and extending 15 cm above. A hole at the position of

the patella helps the patient to position it. System B is

built into the shoe and holds the pressure sensors and

a single IMU sensor. Because it is firmly installed in

the sole, it cannot be applied incorrectly or slip during

examination. To gather data from system A and B, a

gateway is needed that automatically connects to the

wearable and receives, encrypts, and forwards the

collected data to a server. The server stores, processes

and evaluates the data.

2.3 Digital Patient Pathway

The success of a treatment is influenced by many

factors, e.g., concomitant diseases, nail types, nail

techniques and interlocking methods. Thus, the

choice of the most suitable method for an individual

patient becomes a challenge. Additionally, there are

issues with data flow and accessibility, as not all

stakeholders, such as treating specialists, have access

to all the data generated during the treatment process.

Leading to two main problems, to be solved by

improved data handling. On the one hand, a concept

has to be developed, which allows to conduct studies

on the success of different treatment methods. On the

other hand, the availability of patient information as

a basis for individual treatment must be enhanced.

For an improved individual outcome patient

data is digitalised and stored in a centralized entity,

making the entire patient pathway traceable, see

Figure 4. A cloud (1) provides the ability to

automatically collect patient data and to process it

generating further information, cf., section 2.2.

This concept ensures security by providing a

REST API (2) and de- and encrypting data traffic.

Additionally, data will be standardized generating

comparability. Authentication and authorization

management is used to ensure that only the patient

can view, and share collected data.

Neither patient nor medical specialist is in need to

always be able to view all stored data. This creates the

need for an interface between the data cloud (1) and

the user (4). In Germany, the introduction of the

electronic patient record (ePA) has created a basis for

solving such issue (Bundesminesterium für

Gesundheit, 2021). For our proposed concept, the

principle is abstracted, which allows to build a

demonstrator on a known base while being

compatible with other concepts of electronic patient

Concept for General Improvements in the Treatment of Femoral Shaft Fractures with an Intramedullary Nail

365

data storage. The myoncare application, an approved

medical product, is used in this case (Oncare GmbH,

2022). It offers a communication platform for

healthcare providers and patients in a way that

information on health status, exercise videos,

questionnaires or educational sheets can be

exchanged directly between specialist and patient.

The platform can be connected to the central cloud (1)

via an interface. Thus, the patient’s healing process

can be monitored continuously, creating a basis for

improved individual outcome.

To enable further research, the data stored in the

cloud (1) can be utilized. With the patient’s consent,

the data is anonymized, standardized and made

accessible, providing the opportunity to evaluate the

success of different treatment methods in patient

cohorts.

3 CONCLUSION AND

DISCUSSION

LAR System

The LAR system is a good alternative to existing

techniques for intraoperatively measuring femoral

anteversion angle and length. Compared to existing

solutions the proposed system is designed to save

radiation, time, costs while increasing accuracy.

Initial experiments have had promising results and

have shown that the overall system design is

viable. Future work will concentrate on streamlining

the workflow and the handling of reference bodies to

make the system more usable. Additionally, the

algorithms for 3D reconstruction from 2D

fluoroscopic images will be made more accurate and

robust.

Wearable

Analysis of sensor data allows each of the objectives

described in section 2.2.1 to be addressed. The home

exercise will be monitored objectively, a continuous

picture of the healing process will be drawn, different

treatment methods will be comparable. This will be

an important improvement because, to our

knowledge, there is no universal standard for

rehabilitation after IM nailing. Further studies on the

concept in terms of feasibility and usability need to be

conducted.

Digital Patient Pathway

Limitations, identified in section 2.3, concerning the

data handling, can be improved with the proposed

idea. All information about the patient’s history will

be available for each treating specialist. In addition,

the data will be automatically processed so that

patient and specialist receive a comprehensive

overview of the treatment. In addition, treatment

methods can be compared and evaluated as data from

multiple patients is available. Big data analyses, for

example, can then be carried out. The addition of the

myoncare application enables to process all data in a

user-friendly way, while maintaining a certified

standard. Since the data handling concept is

abstracted from the established ePA, our proposed

concept is exchangeable and additionally transferable

into the ePA or other patient data management

concepts. Aspects of data privacy and security remain

to be discussed before the proposed concept can be

integrated into everyday clinical practice.

The proposed concept of a secure medical data

repository that facilitates both individual outcome

and further research is highly consistent with the

goals of the Secur-e-Health (ITEA) project.

ACKNOWLEDGEMENTS

This work was founded by the German Federal

Ministry of Education and Research (BMBF) (FKZ:

01IS21085).

We would like to thank Mrs. Rütten and Mr.

Schifflers for their consultative support.

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