MUSCLE ACTIVATION THRESHOLDS BEFORE

AND AFTER TOTAL KNEE ARTHROPLASTY

Protocol of a Randomized Comparison

of Minimally Invasive vs. Standard Approach

Carlos J. Marques

1, 2

, Hugo Gamboa

, Frank Lampe

, João Barreiros

and Jan Cabri

Faculty of Human Kinetics, Technical Universitty of Lisbon, Lisbon, Portugal

Physikal Therapy and Rehabilitation Department, ENDO-Klinik Hamburg, Hamburg, Germany

Joint Replacement Center, Schön Klinik Hamburg-Eilbek, Hamburg, Germany

Physics Department, Sciences and Technology Faculty, New University of Lisbon, Lisbon, Portugal

Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway

Keywords: Total knee replacement, Minimally invasive surgery, Brake response time, Reaction time, Automobile

driving, Muscle activation thresholds.

Abstract: After total knee arthroplasty (TKA) patients often ask when they can resume car driving. This question was

the aim of some studies in the past, however it is not clear whether minimally invasive surgery (MIS) for

total knee replacement has benefits in terms of faster recovering times. With the present study protocol the

effects of two surgery techniques for TKA (MIS vs. standard approach) on motor performance parameters

will be tested during the performance of an emergency brake in a car simulator. The brake response time

components and the muscle activation thresholds of four muscles involved in the task will be the outcomes

of the study.

1 INTRODUCTION

Minimal invasive surgery (MIS) for total knee

arthroplasty (TKA) has been used for several years

as an alternative to standard approaches. Different

MIS techniques have been described in the literature

(Laskin, 2003): mini-arthrotomy, mini-midvastus

(Floren et al., 2008, Haas et al., 2006), medial

squad-sparing and mini-subvastus (Schroer et al.,

2008). Supporters of MIS techniques go from the

assumption that a smaller soft tissue injury with a

reduction of the muscle quadriceps lesion leads to a

faster rehabilitation with better early functional

outcomes, less pain and shorter stay duration. Critics

fear a reduction of the intra-operative overview with

consecutive failure especially in relation to the

alignment of the prosthesis.

After TKA patients frequently ask when they can

resume car driving. Five studies on this topic were

published in the past years (Spalding et al., 1994,

Pierson et al., 2003, Marques et al., 2008b, Marques

et al., 2008a, Dalury et al., 2010). All studies

investigated the effects of TKA on brake response

time (BRT), an important human factor used in

traffic accident prevention and research. The results

of the studies document a BRT increase after right

TKA. The time frame needed for the BRT to return

to preoperative values varied among the studies and

ranged from 8 (Pierson et al., 2003) to 4 weeks

(Dalury et al., 2010). In a study by Dalury and

colleagues (2010), where the patients were

submitted to “contemporary TKA with less tissue

disruption”, the BRT of all patients returned to

preoperative values 4 weeks after surgery. A small

group of patients reached the preoperative values

already 2 weeks after surgery.

The aim of this randomized controlled trial is to

study the effects of two surgical technics used for

TKA (MIS vs. standard approch) on motor

performance parameters such as brake response time

(BRT), reaction time (RT), foot transfers time

(FTT), brake pedal traveling time (BPTT) and the

activation thresholds of four muscles of the right leg

during the performance of a emergency brake in a

car simulator.

544

Marques C., Gamboa H., Lampe F., Barreiros J. and Cabri J..

MUSCLE ACTIVATION THRESHOLDS BEFORE AND AFTER TOTAL KNEE ARTHROPLASTY - Protocol of a Randomized Comparison of Minimally

Invasive vs. Standard Approach .

DOI: 10.5220/0003318505440547

In Proceedings of the International Conference on Bio-inspired Systems and Signal Processing (BIOSIGNALS-2011), pages 544-547

ISBN: 978-989-8425-35-5

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

2 METHODS AND MATERIALS

2.1 Study Design

To study the effects of both surgical techniques on

the study variables a randomized controlled trial

with one between-subject factor (intervention group:

MIS and Standard) and one within-subject factor

(time: one day before and 8 days, 30 and 40 days

after surgery) was designed. After consent to

participate, the patients will be randomly assigned to

a group

(MIS or Standard approach).

The study protocol was approved by the Ethics-

Committee of the Federal State of Hamburg,

Germany (Project Nr.: PV3349). The trial

registration number at the German Clinical Trial

Database (DRKS) is: DRKS00000552.

2.2 Patient Selection

The patient selection will take place at the Schön

Klinik Hamburg-Eilbek in Hamburg, Germany. The

patients arriving at the clinic for elective right TKA

will be asked if they are car drivers. If the patient

drives regularly (at least once a week) he/she will be

informed about the study and asked to participate.

2.2.1 Inclusion Criteria

 Indication for TKA of the right knee;

 The patient is an active driver;

 Consent to participate in the study.

2.2.2 Exclusion Criteria

 Body Mass Index > 40 Kg/m

;

 Valgus or Varus deformity > 20°;

 Range of Motion < 75°;

 Neurological disorders such as Parkinson’s

disease;

 Rheumatoid arthritis.

2.2.3 Sample Size

A sample size of 2x25 Patients will be aimed.

2.3 The Car Simulator

The car simulator was made based on a European

middle class car. It was used during two previous

studies (Marques et al., 2008a, Marques et al.,

2008b) and was now equipped with new

instruments.

Figure 1: Car simulator with BioPlux Research system.

2.3.1 Instruments / Equipment

The data acquisition system consists of a BioPlux

Research system with wireless connectivity via

Bluetooth (PLUX –wireless biosignals). A trigger

will be used to command the stimulus light (red

LED) turn on/off. Two load cells are connected with

both pedals (break and accelerator). Four surface

electromyography (sEMG) signals will be acquired

from 4 muscles involved in the task. The following

acquisition channels will be used:

 Channel 1: Trigger

 Channel 2: Load cell of the accelerator

 Channel 3: Load cell of the brake pedal

 Channel 4: sEMG M. rectus femoris

 Channel 5: sEMG M. vastus medialis

 Channel 6: sEMG M. tibialis anterior

 Channel 7: sEMG M. gastrocnemius

The channel sample rate will be set at 1000Hz.

2.3.2 Electrode Type and Position

Surface EMG signals will be recorded using silver-

silver chloride (Ag/AgCl) pre-gelled electrodes

(MultiBiosensors). The electrode locations will be

found via palpation of the subjects anatomy over the

appropriate muscle belly, according to the

recommendations of the European SENIAM-Project

(Surface Electromyography for Non-Invasive

Assessment of Muscles). Electrode sites will be

shaved, abraded and cleaned with isopropyl alcohol

to reduce impedance.

MUSCLE ACTIVATION THRESHOLDS BEFORE AND AFTER TOTAL KNEE ARTHROPLASTY - Protocol of a

Randomized Comparison of Minimally Invasive vs. Standard Approach

545

Figure 2: Electrode position.

2.4 Study Outcomes

The brake response time (BRT) is a very important

human factor in accident prevention research. The

BRT can be fractionated in several components. The

primary outcomes of this research project are

components of the BRT and are defined below.

2.4.1 Primary Outcomes

 Brake Response Time (BRT): time frame

between the onset of the red LED and the achieving

of a brake force on the brake pedal of 100N (ms);

 Reaction Time (RT): time frame between the

onset of the red LED and the initiation of the

movement of the foot on the accelerator pedal (ms);

 Foot Transfer Time (FTT): time frame between

the initiation of the movement of the foot on the

accelerator pedal and the first contact with the brake

pedal (ms);

 Brake Pedal Travelling Time (BPTT): time

frame between the first contact with the brake pedal

and the achieving of a brake force of 100N on the

brake pedal (ms);

 Movement Time (MT): sum of the FTT and

BPTT.

Figure 3: Brake response time components

2.4.2 Secondary Outcomes

The secondary outcomes are the time frames

between the onset of the red LED and the muscle

activation thresholds of the above referred muscles.

3 DATA EXTRACTION

AND ANALYSIS

The patients will perform 10 emergency brake test

trials in a simple task, followed by 10 emergency

brake test trials in a more complex task in a car

simulator. The data of the 10 test trials on each task

(simple and complex) will be saved separately as

text files with the use of the software program

Monitor Plux.

3.1 Data Extraction

The signals collected are of three types: digital

signal (from the light trigger); force signals from the

accelerator and brake pedal load cells; and sEMG

signals from four muscles.

The digital signal is used to slice the signals in

the 10 breaks in each of the tasks. The force signals

are calibrated considering that in the initial instant

the foot is not pressing any of the pedals and the

acquired value in the initial 100ms is considered the

zero of the load cells. This signal is low pass filtered

with cut frequency at 10Hz with a 4

order

Butterworth IIR filter.

Figure 4: Graphic of one test trial in the simple task with

the 7 channels (1 Trigger; 2 Accelerator; 3 Brake pedal; 4-

7 sEMG signals of the 4 muscles) and the red lines

marking the detected thresholds for each signal.

BIOSIGNALS 2011 - International Conference on Bio-inspired Systems and Signal Processing

546

The sEMG signals are filtered with an envelope

detector that consists of a low pass filter of 5 Hz

(Butterworth IIR filter 4

order) after computing the

absolute value.

An adaptation of the Hodges onset detector

(Hodges and Bui, 1996) was created to be used on

force and sEMG signals on positive or negative

transitions.

3.2 Data Analysis

Mean values of the ten test trials for each task will

be calculated for each subject. A 2x4 ANOVA for

repeated measures will be performed to detect

differences within a surgery group along the time

and between the two groups (MIS vs. standard) at

each assessment day. Multiple comparisons will be

made with paired t tests using the Bonferroni

adjustment of alpha. All statistical tests will be

carried out using the SPSS software. For all

statistical tests, the .05 level of probability will be

accepted as the criterion for statistical significance.

4 DISCUSSION

The available evidence on which physicians and

doctors can relay when advising patients on when

they should resume car driving after TKA is few.

The components of BRT were investigated in 4

studies (Spalding et al., 1994, Marques et al., 2008b,

Marques et al., 2008a, Dalury et al., 2010). Ten days

after TKA central aspects related with stimulus

perception, response selection and response

initiation seem not to be affected, once RT was not

changed (Marques et al., 2008a, Marques et al.,

2008b). TKA seems to affect peripheral aspect

related to the execution of the movement. The soft

tissue lesion may be the cause of such performance

decreases after TKA.

In the past years minimally invasive approaches

for TKA have been used. The question whether a

smaller tissue lesion will improve the performance

of the patients will be investigated in this study.

The results of this study will increase the body of

evidence on this issue and will add a comparison of

two surgical techniques with a more detailed view

over the brake response time components and over

the effects of TKA on neuromuscular function of

four muscles involved in the task.

ACKNOWLEDGEMENTS

We thank the Technical Department at the Schön

Klinik Hamburg-Eilbek for the technical changes

and adaptations made in the car simulator.

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Randomized Comparison of Minimally Invasive vs. Standard Approach

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