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S T U D Y P R O T O C O L Open Access
Study protocol for the DEFENDD trial: an
RCT on the Dynamic Locking Blade Plate
(DLBP) versus the Dynamic Hip Screw
(DHS) for displaced femoral neck fractures
in patients 65 years and younger
J. H. Kalsbeek
1*
, W. H. Roerdink
1
, P. Krijnen
2
, M. E. van den Akker-van Marle
3
and I. B. Schipper
2
Abstract
Background: The Dynamic Locking Blade Plate (DLBP) was recently introduced for fixation of displaced femoral
neck fractures (FNF) and has been well received. Although the results of this implant in young patients are promising,
the DLBP has not yet been compared to a standard device such as the Dynamic Hip Screw (DHS). The aim of this
study is to compare the clinical outcome and costs of displaced FNF treated with internal fixation by means of either
the DLBP or the DHS in patients up to 65 years of age. We hypothesize that the DLBP is superior compared to the DHS
in terms of revision surgery rate, union rate, incidence of avascular necrosis and implant related failure.
Methods: The DEFENDD (DisplacEd Femoral Neck fractures Dlbp versus Dhs) trial is a multicentre randomized controlled
trial that will include 266 patients of 18–65 years with a displaced FNF. Patients will be randomized to receive either a DLBP
or a DHS with a 1:1 allocation using a random block size, stratified for centre. Clinical follow up will last 1 year
and questionnaires will be obtained up to 2 years. The main outcome parameter is the incidence of revision
surgery within 1 year, due to either non-union, avascular necrosis (AVN) or cut out of the implant. Secondary
study parameters are the incidence of avascular necrosis, non-union, (implant related) complications, functional
outcome, elective removal of the implant and health-related quality of life and costs.
Discussion: The outcome of the DEFENDD trial will provide high-level evidence of which implant is favourable
for the treatment of femoral neck fractures in young patients (≤65 years).
Trial registration: Netherlands Trial Register, NL7300 Registration date 25-09-2018.
Keywords: Hip fractures, Dynamic locking blade plate, Dynamic hip screw, Femoral neck fractures, Internal fixation,
Gannet, Displaced, DHS, DLBP
Background
In 1990 an estimated 1.66 million patients sustained a
hip fracture worldwide. This number has increased over
time and is estimated to be around 6 million in 2050
worldwide [1]. Despite these numbers the optimal treat-
ment of hip fractures is still under debate and subse-
quently evolving. This especially applies to the treatment
of displaced femoral neck fractures (FNFs), which differs
considerably worldwide. A general consensus is that
young patients (up to 65 years of age) should be treated
with fracture reduction and internal fixation [2,3]. Pa-
tients above 75 years of age are in majority treated with
arthroplasty. The treatment of FNFs in young elderly
(between 65 and 75 years old) is still under debate and is
therefore referred to as the ‘unsolved fracture’[4–6].
Nowadays, the most commonly used implants for fix-
ation of FNFs are multiple cannulated parallel screws
and the Dynamic Hip Screw (DHS) (Fig. 1). The DHS
© The Author(s). 2020 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
* Correspondence: jorn.kalsbeek@gmail.com
1
Department of Surgery, Deventer Hospital, Nico Bolkesteinlaan 75, 7416, SE,
Deventer, the Netherlands
Full list of author information is available at the end of the article
Kalsbeek et al. BMC Musculoskeletal Disorders (2020) 21:139
https://doi.org/10.1186/s12891-020-3131-x
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
has a small advantage over multiple parallel screws in
displaced FNFs, in that it is known to have a lower reop-
eration rate [8]. Despite the frequent use of both these
implants the failure rate of displaced FNFs is still high,
with a non-union rate of 30–33% and an incidence of
avascular necrosis (AVN) of 10–16% [3,9–11]. The re-
operation rate, as a result of non-union and AVN is be-
tween the 18–48% [3,11,12]. The Dynamic Locking
Blade Plate (DLBP) (Fig. 2), otherwise called ‘The Gan-
net’, is specifically designed for the surgical fixation of
intracapsular hip fractures though small metal ‘wings’.
The characteristics of the DLBP are its low implant vol-
ume, rotational stability, angular stability and its simple
instrumentation and surgical technique. In a prospective
multicenter cohort study in the Netherlands 172 patients
with an undisplaced FNF were treated with the DLBP.
The results of this study showed a failure rate of 4%
[13]. Another recent prospective cohort study of 106 pa-
tients of 60 years and younger with displaced FNF dem-
onstrated a DLBP related failure rate of 13.2% [14].
However, randomized controlled trials are needed to
provide high-level evidence to determine the value of
DLBP.
The aim of the current study is to test if the favorable
results with the DLBP persist in a multicenter random-
ized controlled trial for patients aged 65 years or youn-
ger with initially displaced FNFs. We hypothesize that
the DLBP is superior compared to the DHS in terms of
revision surgery rate, union rate, incidence of avascular
necrosis and implant related failure. Also, the cost-
effectiveness of the DLBP versus DHS will be assessed.
Method/design
Primary and secondary objectives
The primary objective is to test if the incidence of revi-
sion surgery (primary endpoint) is lower in patients ≤65
years with an initially displaced FNF treated with the
DLBP in comparison to treatment with DHS. Secondary
objectives are to determine the incidence of AVN, non-
union, implant related complications, non-implant re-
lated complications and elective removal after fixation
with the DLBP or DHS. Also, we compare operating
time, functional outcome and cost-effectiveness of DLBP
and the DHS.
Study design
The DEFENDD trial (DisplacEd Femoral Neck fractures
Dlbp versus Dhs) is a multicenter unblinded randomized
controlled trial with a superiority design comparing two
implants. One group will be treated with the DLBP. The
other group will be treated with DHS (control group).
The study will be performed in six trauma centers in the
Netherlands. Data will be registered in Castor EDC, an
online data capture program.
Eligibility criteria
All consecutive patients between 18 and 65 years with a
displaced FNF, Garden type III or IV according to the
Garden classification, admitted to the participating hos-
pitals are eligible for the study [15].
Exclusion criteria are:
Pathological fracture.
Ipsilateral or contralateral fracture(s) of the lower
extremity.
Injury Severity Score (ISS) of ≥16.
Local infection or inflammation at time of operation.
Symptomatic arthritis, diagnosed by a
rheumatologist.
Symptomatic osteoarthritis or radiographic
osteoarthritis grade III or IV [16].
Previous surgery of the ipsilateral hip.
Fig. 1 The Dynamic Hip Screw [7]. Copyright by AO
Foundation, Switzerland
Fig. 2 The Dynamic Locking Blade Plate with impaction anchors.
Permission was given bij Gannet B.V. Hengelo for using this figure
Kalsbeek et al. BMC Musculoskeletal Disorders (2020) 21:139 Page 2 of 6
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Open fracture.
Morbid obesity (BMI ≥35).
Patients who were wheelchair-bound in their pre-
injury situation.
Patients who were, at the time of trauma, admitted
to a nursing home.
Patients who are not mentally competent
Randomization
After obtaining written informed consent patients are
randomized with a 1:1 allocation using a random block
size, stratified for centre. Variable block sizes will be de-
termined by the estimated inclusion number of each
centre. An online randomization module is used for
treatment allocation.
Sample size calculation
The failure rate or revision rate of the DHS in patients
≤65 years with displaced FNFs described in today’s lit-
erature is 32–44% [8,17]. The failure rate of the DLBP
in patients of 60 years and younger with a displaced FNF
in a previous cohort study was 13.2% [14]. Analysis of
our data showed a failure rate of 15% for the DLBP in
patients of 65 years and younger (non-published data).
For the determination of the sample size we assumed a
30% failure rate for the DHS and 15% failure rate for the
DLBP. For a power of 80% we need 121 patients per
group to prove the superiority of the DLBP regarding
the primary outcome (need for revision surgery) with
alpha of 5% in a two-sided test. Taking into account that
up to 10% of the patients may be lost to follow up, 266
patients need to be included for adequate statistical
power, i.e. 133 patients per group.
Study interventions
This trial will be performed in six trauma centres in the
Netherlands. In three of the centres the DLBP will be in-
troduced before starting this trial. In the other three par-
ticipating centres the DLBP is already used. A learning
curve is taken into account. The first three DLBP’sin
each participating centre will be implanted under super-
vision of an instructor from the manufacturer or an ex-
perienced surgeon who has implanted three or more
DLBP’s. The first DLBP’s of a surgeon can be included,
provided that they are implanted under supervision.
Dynamic locking blade plate
The Dynamic Locking Blade Plate consists of a 2-hole
standard 135° side-plate combined with a low-volume
cannulated dynamic locking blade (Fig. 2). The side plate
provides angular stability combined with dynamic axial
compression of the fracture. Two side wings at the tip of
the blade provide rotational stable fixation of the locking
blade in the femoral head combined with a high weight-
bearing surface. The expandable impaction anchors lock
the blade in the femoral head and prevent perforation
and backing out of the implant and further augment the
rotational stability. The DLBP is now marketed as the
Gannet [13].
Dynamic hip screw
The control group will be treated with the Dynamic Hip
Screw, a stainless steel lag screw in the femoral neck and
head that is fixated to the femur shaft with a compres-
sion plate using two-four 4,5 mm cortical screws (Fig. 1).
The DHS is used globally and is provided by a wide
range of commercial producers in various sizes. It can
be implanted with or without an additional cannulated
antirotational screw. The type of DHS used in the con-
trol group is at the discretion of the surgeon. The
trauma and orthopaedic surgeons in participating
trauma centres have a wide experience with internal fix-
ation of FNF by means of DHS.
Direct post-operative care
Both groups receive standard care including direct
mobilization after surgery. Mobilization therapy will be
given by a physiotherapist according to the hospital
protocol for hip fracture after care. All patients receive
low-molecular-weight heparin anticoagulation therapy
during their stay in the hospital.
Study procedures
A time schedule of procedures and measurements is
presented in Table 1. The selection of eligible patients
will take place in the emergency department (ED). Ac-
cording to standard care, X-ray examinations of the pel-
vis and hip are made on admission and assessed by the
radiologist and trauma surgeon. Eligible patients will re-
ceive oral and written information about the study from
the physician in the ED. The patients have at least 6 h to
consider participation in the study and will be given the
opportunity to ask questions about the study. Written
informed consent will be obtained by the surgical resi-
dent or the surgeon after admission to the ward.
Randomization will be done by the treating surgeon.
After inclusion the patient will be allocated to one of the
two study groups (DLBP or DHS) using an online
randomization program. The baseline parameters will be
registered by a nurse upon arrival on the surgical ward
before surgery. The perioperative care will be the same
for all included patients.
Surgery will be performed by an (orthopaedic) trauma
surgeon or by an (orthopaedic) trauma resident under
the direct supervision of an (orthopaedic) trauma sur-
geon. The aim is to operate within 24–36 h based on the
Dutch guidelines for treatment of FNFs [18]. After sur-
gery, details about the surgery will be documented.
Kalsbeek et al. BMC Musculoskeletal Disorders (2020) 21:139 Page 3 of 6
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After discharge patients are scheduled for outpatient
visits after 6 weeks, 3 and 12 months. Conventional ra-
diographs will be taken and assessed during these visits
(Table 1). The patients need to fill out a questionnaire
before follow up visits and 6 months after discharge.
Also, the patient will be contacted by telephone 24
months after enrolment in the study for additional ques-
tionnaires about mobility and complication registration.
Study parameters
Primary outcome parameter
The primary outcome is the incidence of revision sur-
gery after fixation of an initially displaced FNF treated
with DLBP or DHS due to non-union, AVN or cut out
of the implant. This will be monitored during 1 year of
follow up after surgery.
Secondary outcome parameters
Incidence of avascular necrosis: AVN is defined as hip
pain in combination with radiographical signs for AVN
as described by Steinberg [19]. According to the Stein-
berg classification AVN is present from stage 2 and up-
ward. AVN will be assessed by the treating surgeon. As
is customary in the Netherlands, all radiographs are also
assessed by a radiologist.
Incidence of non-union: there is no consensus in the
literature regarding to the definition of (non-)union [20].
Our definition of non-union is based on the Radio-
graphic Union Score for Hip (RUSH) [21]. Non-union is
a visible fracture line on the radiograph, absence of cor-
tical bridging or bridging trabeculae over the fracture
site in combination with persisting pain in the hip and
the inability to bear weight at least 9 months post-
operative or sooner if revision surgery was performed
because it was no longer expected that fracture healing
would occur. Non-union will be assessed by the treating
surgeon.
Incidence of implant related complications: an implant
related complication is defined as breakage or cut-out of
the plate or screws, inadequate expansion/malfunction
of the anchors or any malfunction of the implant which
may or may not lead to revision surgery. Implant related
failure will be monitored during 1 year of follow up.
Post-operative complications: post-operative complica-
tion is defined as any unanticipated event other than the
above mentioned, for which operative treatment or med-
ical treatment is required, e.g. wound infection, bleeding
or pneumonia. Every complication occurring during the
hospital stay of the patient will be recorded.
Rate of elective implant removal after union: Elective
implant removal after union will be recorded during 1
year of follow up after surgery. Reasons for elective re-
moval will be described.
Functional outcome: patient-reported post-surgical
function will be scored using the validated Dutch version
of the International Hip Outcome Tool (iHOT-12NL)
[22]. The iHOT-12NL is a patient-reported question-
naire that measures health-related quality of life and
physical function in younger, active patients with hip
disorders. Scores on the iHOT-12NL range between 0
and 100 (worst - best possible function). This question-
naire will be filled out by the patient during admission
and at 6 weeks, 3, 6 and 12 months follow up.
Operation time: the operation time is recorded in the
surgical report.
Baseline parameters: Additional parameters that will
be recorded are: sex, date of birth, general health score
(using the ASA classification), fracture type and side,
trauma surgeon or orthopaedic trauma surgeon, type of
anaesthesia, Body Mass Index. These parameters will be
assessed during admission as a baseline measure.
Costs: Costs will be assessed from a societal perspec-
tive. Cost of (revision) surgery will be calculated using a
bottom-up approach. Using a questionnaire the patients
will report other health care use such as physiotherapy,
rehabilitation care or nursing home care, visits to the
general practitioners and medical specialists and medica-
tion, and non-medical care (domestic help and absentee-
ism). This questionnaire will be filled out by the patient
at 6 weeks, 3, 6 and 12 months follow up. Health care
use will be valued using Dutch reference prices [23].
Health related quality of life: the EuroQol (EQ-5D-5 L)
questionnaire measures five dimensions (mobility, self-
care, daily activities, pain/discomfort, anxiety/depres-
sion), on a five-point scale (no, some, moderate, much
or extreme problems). For each health state described by
Table 1 Time schedule for study procedures and measurements
Emergency
department
Admission Post-op visit
(≤5 days)
6 weeks
follow-up
3 months
follow-up
6 months
follow-up
12 months
follow-up
24
months
follow-up
a
Informed consent x
Baseline characteristics x
Radiography x x x x x
Questionnaires x xxxx x
Complications registration x x x x x x
a
Contact by telephone
Kalsbeek et al. BMC Musculoskeletal Disorders (2020) 21:139 Page 4 of 6
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
the patients, a utility score can be calculated that reflects
society’s valuation of that health state [24]. In addition,
patients rate their overall health-related quality of life on
a Visual Analogue scale (VAS). This questionnaire will
be filled out by the patient during admission and at 6
weeks, 3, 6 and 12 months follow up. The utility scores
obtained by the descriptive system and the VAS will be
used in the cost-effectiveness analysis.
Statistical analysis
Statistical analysis will be performed using SPSS (IBM
Corp., Armonk, NY, USA). Primary analysis will be done
according to the intention-to-treat principle. If patients
are not treated according their allocated treatment a
per-protocol analysis will be conducted to confirm the
intention-to-treat analysis. Baseline characteristics of the
treatment groups will be presented as mean with SD or
as median and range for continuous variables and as
number and percentage for categorical variables.
The primary outcome parameter, the incidence of re-
vision surgery after 1 year, will be compared between
the treatment groups using logistic regression analysis,
including study centre as a covariate, since some study
sites have used the DLBP for several years and whereas
in other medical centres the DLBP has only been intro-
duced recently. In literature there is no clear evidence of
other covariates that have a strong or moderate associ-
ation with the primary outcome. The secondary parame-
ters: the incidence of AVN, non-union, implant-related
complications, post-operative complications, and elective
implant removal after 1 year will be analysed in the same
manner as the primary outcome parameter. Operation
time will be compared between the treatment groups
using the independent samples t-test or the Mann-
Whitney test, as appropriate. Functional outcome at the
specified follow-up moments will be compared between
the treatment groups using an independent samples t-
test. In addition, the course of functional recovery over
time will be compared using a linear mixed model with
time, treatment and baseline characteristics as fixed ef-
fects, and patient as random effect. Missing data will be
imputed using multiple imputation before testing the
differences in the outcome parameters. P-values less
than 0.05 will be considered statistically significant.
The economic evaluation will compare differences in
societal costs, as described in the paragraph ‘Study pa-
rameters’, to differences in quality adjusted life years
(QALYs). Utilities obtained from the EQ-5D-5L will be
used to determine QALYs. The QALYs will be calcu-
lated from the area under the curve in a utility-time fig-
ure. The duration of the trial will be taken as the time-
horizon. Group averages will be statistically compared
using non-paired t-test and a net-benefit analysis will be
used to compare costs to patient outcome. Results will
be presented in a cost-effectiveness acceptability curve.
Monitoring
Patient data will be handled confidentially and in com-
pliance with the Dutch Personal Data Protection Act.
Collected data will be stored in Castor EDC, an elec-
tronic data capture program. Stored data will be coded,
using a unique combination for centre and successive
study number. The key to the code will be accessible by
the local investigators and the coordinating investigators.
Study data will be kept for 15 years and destroyed after-
wards. The local investigators will have access to the link
between code and personal data of the patients of only
his centre. The coordinating and the principal investiga-
tor have access to all the data. The co-investigators will
have access to the coded data of all patients.
The coordinating investigators will report all adverse
events to the accredited Medical Research Ethics Com-
mittee (MREC) that approved the protocol. No data
safety managing board is installed. The investigator will
submit a summary of the progress of the trial to the
accredited MREC once a year. Information will be pro-
vided on the date of inclusion of the first subject, num-
bers of subjects included and numbers of subjects that
have completed the trial, serious adverse events/ serious
adverse reactions, other problems, and amendments. No
planned interim analyses will be conducted.
Discussion
In this paper we present the rationale and design of a
randomized controlled trial that compares the clinical
outcomes of the DLBP and the DHS. The DHS is a glo-
bally accepted osteosynthesis and it has been for de-
cades. Yet the failure rate is high. The DLBP is a new
implant that is on the market since 2010. Today’s evi-
dence for this implant is not as widespread as for the
DHS, but the results from (non randomized) earlier
studies are promising [13,14]. The outcome of the
DEFENDD trial will provide high-level evidence of
which implant is favorable for the treatment of femoral
neck fractures in young patients (≤65 years). The results
of this trial will be published in peer-reviewed inter-
national journal.
Abbreviations
AVN: Avascular necrosis; BMI: Body mass index; DHS: Dynamic Hip Screw;
DLBP: Dynamic Locking Blade Plate; ED: Emergency department;
FNF: Femoral Neck Fractures; GCP: Good Clinical Practice; iHOT: International
Hip Outcome Tool; MREC: Medical Research Ethics Committee; QALY: Quality
Adjusted Life Years; RCT: Randomized Controlled Trial; WMO: Medical
Research Involving Human Subjects Act (in Dutch: Wet Medisch-
wetenschappelijk Onderzoek met Mensen)
Acknowledgements
We thank the local researchers (Dr. J.P.A.M. Verbruggen, Drs. M. Hogervorst,
Drs. C.A.S. Berende, Dr. A.H. van der Veen, Dr. A.K. Mostert) of the
Kalsbeek et al. BMC Musculoskeletal Disorders (2020) 21:139 Page 5 of 6
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
participating sites for their dedication to this project and the effort they put
on for this trial.
Sponsor: Deventer Hospital, Nico Bolkesteinlaan 75, 7416 SE Deventer, the
Netherlands.
Authors’contributions
JHK, WHR, PK, MEAM, IBS were responsible for designing the study and
writing the protocol. JHK wrote the primary protocol and manuscript. JHK
and WHR will act as the study coordinators. All authors have read and
approved the manuscript.
Funding
This trial is funded by the Research Committee of Deventer Hospital. Deventer
Hospital did not have any role in the design of the study and writing the
manuscript. Deventer Hospital is one of the participating study sites where
participants are included for the trial.
Availability of data and materials
The datasets generated and/or analysed during the current study are not
publicly available but are available from the corresponding author on
reasonable request.
Ethics approval and consent to participate
The DEFENDD trial has gained approval of the MREC Isala Zwolle, the
Netherlands (ref number: 180428) on 17 September 2018.
Consent for publication
Written patients’informed consent will be obtained by the surgical resident
or the surgeon after admission to the ward.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Surgery, Deventer Hospital, Nico Bolkesteinlaan 75, 7416, SE,
Deventer, the Netherlands.
2
Department of Trauma Surgery, Leiden
University Medical Center, Albinusdreef 2, 2333, ZA, Leiden, the Netherlands.
3
Department of Biomedical Data Sciences, Leiden University Medical Center,
Albinusdreef 2, 2333, ZA, Leiden, the Netherlands.
Received: 19 July 2019 Accepted: 11 February 2020
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