Low failure rate by means of DLBP fixation of undisplaced femoral neck fractures

Abstract

Background:
This study evaluated the clinical results of a new implant in the internal fixation of undisplaced femoral neck fractures.

Method:
Irrespective of their age, 149 patients with undisplaced (Garden I and II) femoral neck fractures were included in a prospective multicentre clinical cohort study and were treated by internal fixation by means of the Dynamic Locking Blade Plate (DLBP). The mean age was 69 years and the follow-up at least one year.

Results:
The DLBP fixation resulted in 6 out of 149 failures caused by AVN (2x), non-union (2x), loss of fixation (3x) or combination of these.

Conclusion:
The fixation of undisplaced femoral neck fractures by the DLBP resulted in a low failure rate of 4 %.

Full text

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DOI 10.1007/s00068-016-0659-4
Eur J Trauma Emerg Surg (2017) 43:475–480
ORIGINAL ARTICLE
Low failure rate by means of DLBP fixation of undisplaced
femoral neck fractures
A. D. P. van Walsum1 · J. Vroemen2 · H. M. J. Janzing3 · T. Winkelhorst4 ·
J. Kalsbeek1 · W. H. Roerdink5
Received: 25 September 2015 / Accepted: 7 March 2016 / Published online: 19 March 2016
© The Author(s) 2016. This article is published with open access at Springerlink.com
Introduction
The biology plays a leading role in the survival of the fem-
oral head and the bone healing of this intracapsular frac-
ture. Critical biological factors are the (re)-vascularisation
of the femoral head and the type of bone healing of the
femoral neck fractures. The viability of the femoral head
after a femoral neck fracture is dependent on preservation
of the remaining vascularity and on revascularisation and
repair of the necrotic areas before collapse of the necrotic
bone segment can occur. Although the vascularisation of
the femoral head in the undisplaced fracture is less dam-
aged than in the displaced fractures, the incidence of avas-
cular necrosis for undisplaced femoral neck fractures is 4.0
versus 9.5 % for the displaced fractures [1]. To preserve the
remaining vascularisation of the femoral head we must do
no further vascular harm during insertion of implants in the
head of femur. Therefore, any iatrogenic fracture displace-
ment should be avoided, especially rotation of the femo-
ral head on insertion of our implants. One of the sources
of revascularisation of the femoral head is the vascular
ingrowth across the uniting fracture line. It is of clinical
importance that these ingrowing tender vascular buds can
be torn repeatedly if there is persistent motion at the frac-
ture site as a result of inadequate fracture stabilisation [2].
Enlarging the volume of metal in the femoral head may fur-
ther compromise the revascularisation of the femoral head
and this may increase the incidence of avascular necrosis
[3, 4]. Unlike diaphyseal fractures, the femoral neck frac-
ture cannot heal by periosteal (external) callus formation.
Consequently, the bone healing is by primary osteonal
reconstruction that requires an anatomical reduction and
absolute stability [5–7]. Only when the undisplaced femo-
ral neck fracture is secured by stable fixation, revascularisa-
tion of the femoral head can take place and the fracture can
Abstract
Background This study evaluated the clinical results of a
new implant in the internal fixation of undisplaced femoral
neck fractures.
Method Irrespective of their age, 149 patients with
undisplaced (Garden I and II) femoral neck fractures
were included in a prospective multicentre clinical cohort
study and were treated by internal fixation by means of the
Dynamic Locking Blade Plate (DLBP). The mean age was
69 years and the follow-up at least one year.
Results The DLBP fixation resulted in 6 out of 149 fail-
ures caused by AVN (2x), non-union (2x), loss of fixation
(3x) or combination of these.
Conclusion The fixation of undisplaced femoral neck
fractures by the DLBP resulted in a low failure rate of 4 %.
Keywords Femoral neck fracture · Intracapsular hip
fracture · Hip fracture · Undisplaced · Non displaced ·
Internal fixation · Osteosynthesis · Avascular necrosis ·
Rotational stability
* A. D. P. van Walsum
vwalsum@gmail.com
1 Department of Trauma Surgery, Medisch Spectrum Twente,
Koningsplein 1, 7512 KZ Enschede, The Netherlands
2 Department of Trauma Surgery, Amphia Ziekenhuis,
Molengracht 21, 4818 CK Breda, The Netherlands
3 Department of Trauma Surgery, VieCuri Medical Centre,
Tegelseweg 210, 5912 BL Venlo, The Netherlands
4 Department of Trauma Surgery, Canisius Wilhelmina, Weg
door Jonkerbos 100, 6532 SZ Nijmegen, The Netherlands
5 Department of Trauma Surgery, Deventer Ziekenhuis, Nico
Bolkesteinlaan 75, 7416 SE Deventer, The Netherlands
Content courtesy of Springer Nature, terms of use apply. Rights reserved.

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A. D. P. van Walsum et al.
1 3
heal by primary osteonal reconstruction. The term “stable”,
in the context of fixation of femoral neck fractures, means
that transverse shear- and the rotational inter fragmentary
movements (IFM) are minimalized while allowing the con-
trolled axial compression IFM.
Approximately 20 % of the intracapsular hip frac-
tures are undisplaced [12]. Common treatment is internal
fixation of the fracture, but alternative treatments are con-
servative treatment or replacement arthroplasty. The con-
ventional implants used for the fixation of femoral neck
fractures are the sliding hip screw devices and multiple par-
allel screws or pins. The failure rate after internal fixation
of undisplaced femoral neck fractures is 8–14 % [8–13].
The potential disadvantages of the conventional implants
are rotational and/or angular instability combined with a
relative high implant volume in the femoral head [14]. The
aim of this study was to register the results in the internal
fixation of undisplaced femoral neck fractures by means of
the DLBP. This device is characterised by angular and rota-
tional stability, dynamic compression and a low implant
volume in the head of femur.
Patients and methods
Classification
According the conventional Garden classification an undis-
placed intracapsular fracture is defined as Garden grade I or
II fracture. This classification is based only on the AP radi-
ograph and includes all fractures impacted into any degree
of valgus (Garden I) and the undisplaced fractures (Garden
II). Consequently, also the fractures that show angulation
on the lateral radiograph are included and classified as
undisplaced.
Patients
Included were undisplaced femoral neck fractures in adult
patients irrespective the age of the patient. Excluded were
pathological fractures, concomitant fractures of the lower
extremity, symptomatic arthritis, local infection or inflam-
mation, inadequate local tissue coverage, morbid obesity
and any mental or neuromuscular disorder, which would
create an unacceptable risk of fixation failure or complica-
tions in postoperative care.
Implant
The DLBP consists of a 2-hole standard 135° side-plate
combined with a low-volume cannulated dynamic locking
blade. 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 fixa-
tion of the locking blade in the femoral head combined
with a high weight-bearing surface. The expandable impac-
tion anchors lock the blade in the femoral head and prevent
perforation and backing out of the implant and further aug-
ment the rotational stability. The DLBP is now marketed as
the Gannet (Fig. 1).
Technique
If there is any (anterior) angulation of the femoral neck
with dorsal displacement of the femoral head, anatomi-
cal reduction is performed by internal rotation and ante-
rior manual compression. To do no further vascular harm,
the reduction should be performed gently and accurately
as excessive longitudinal traction and rotation may result
in additional vascular damage by tearing the still surviv-
ing retinacular vessels. By a ±7 cm lateral approach
a 3.0-mm 135° guide wire is placed in the centre/centre
position in femoral head. After length measuring cannu-
lated reaming is performed up to 5 mm subchondrally in
the femoral head. Next the locking blade together with
a two-hole side plate is mounted on the introducer. The
Fig. 1 Design of the dynamic locking blade plate
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477
Low failure rate by means of DLBP fixation of undisplaced femoral neck fractures
1 3
complete implant is introduced over the guide wire and
gently tapped in while the mounted side plate functions
as a rotational guide. After the side plate is seated along
the lateral cortex, the introducer is released and the lock-
ing blade further tapped in the femoral head up to 5 mm
subchondrally. Next, the side plate is fixed to the proximal
femur by two self-tapping cortical screws. By turning the
setscrew, in the shaft of the locking blade in clockwise
direction, the impaction anchors are expanded by which
the blade is locked within the femoral head. On removal,
turning the setscrew anti clockwise retracts the impaction
anchors. After removal of the cortical screws, the locking
blade together with the side plate is tapped out by means
of an extractor mounted on the locking blade. The patients
were mobilised postoperatively by permissive weight bear-
ing as tolerated by the patient. The implant characteristics
and operative technique are further illustrated in YouTube
video (gannet implant) (Fig. 2).
Methods
The Garden classification is based on the pre-operative
AP radiograph of the hip. The (anterior) angulation of the
fracture is assessed on the lateral pre-operative radiograph
of the hip. Postoperative AP and lateral radiographs were
used to assess fracture healing. Union was defined by an
absence of visible margins of the fracture. Angular instabil-
ity was assessed radiologically by secondary interfragmen-
tary angulation and/or transverse shear. Interfragmentary
rotation was radiologically assessed by the observation of
a cortical step and diameter mismatch at the fracture site.
Non-union was identified by either displacement of the
fracture or clearly visible margins of the fracture 1 year
postoperatively. Avascular necrosis was defined accord-
ing to the Steinberg classification from stage 2 and upward
[15]. Failure of fixation is defined as the need for revision
surgery because of non-union, avascular necrosis or cut out
Fig. 2 a, b AP en lateral X-ray
of undisplaced femoral neck
fracture of the right hip, c, d AP
and lateral X-ray of undisplaced
femoral neck fracture of the
right hip after DLBP fixation
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478
A. D. P. van Walsum et al.
1 3
of the implant. The corrected Tip Apex Distance (TAD) on
the first postoperative X-rays assessed the position of the
locking blade in the femoral head [16]. A TAD greater then
25 mm is predictive of a higher extrusion rate. The impac-
tion at the fracture site was assessed by measuring the
degree of telescoping of the dynamic blade with correction
for magnification. Mobility was assessed by the need of
walking aids: no walking aids, one crutch, two crutches or
a walker.
Results
One Level-1 Community Trauma center (Medische
Spectrum Twente, Enschede) and four Level-2 Commu-
nity teaching hospitals (Deventer Ziekenhuis, Deventer;
Amphia Ziekenhuis, Breda; Canisius Wilhelmina Zieken-
huis, Nijmegen and VieCuri Medisch Centrum, Venlo)
participated. Between 01-08-2010 and 19-12-2013, and
384 consecutive patients with femoral neck fractures were
treated by means of the DLBP. Of these 384 patients, 172
a suffered undisplaced femoral neck fracture and 212 a dis-
placed femoral neck fracture. This manuscript addresses
the results of the patients who are treated for undisplaced
fractures. 172 patients with undisplaced (Garden I and II)
femoral neck fractures were included irrespective of the age
of the patient. Seven patients were lost for follow-up and
16 patients died during the follow-up period. This resulted
in 149 patients with a mean age of 69 years (35–101) with
a follow-up of at least 1 year from injury. Surgery was
undertaken by (orthopaedic) trauma surgeons (85 %), and
trainee surgeons (15 %). 79 % of operations took place
within 24 h. The average operating time was 39 min. There
were six general medical complications: one deep infec-
tion (healed without intervention surgery, two postoperative
bleedings and three pneumonia). Implant-related complica-
tions consisted of suboptimal expansion of the impaction
anchors in four cases. In two younger patients this was
caused by the high bone density, and in two elderly patients
by technical implant problems with the expansion mecha-
nism. Neither perforation, nor backing-out of the dynamic
blade was observed. No secondary rotational or angular
instability was observed. No breakage of the blade, plate
or screws occurred. The internal fixation of undisplaced
(Garden I and II) femoral neck fractures resulted in 6 out
of 149 failures (4.0 %) caused by AVN (2×), non-union
(2×), loss of fixation (3×) or combination of these. All of
the six failed fixations were revised by arthroplasty. Five
of the failures were classified as a Garden I fracture and
one Garden II. AVN was observed in two out of six failures
(one Garden I, one Garden II). In two out of the six failures
anterior angulation (posterior displacement) was more than
20°. The mean impaction of the healed fractures was 5 mm
with a mean age of 69 years. The mean age in the failure
group was 71 years. The average TAD in the healed frac-
ture group was 22 mm and 24 mm in the failure group.
Elective implant removal was performed in 9 % due to
suspected local complaints caused by the side plate or the
(dynamized) blade. In all patients the implant removal,
including the retraction of the anchors, went straight-
forward. Four per cent of the patients with healed femo-
ral neck fractures needed more walking aids than before
fracture.
Discussion
The most common treatment of undisplaced femoral neck
fractures is internal fixation by sliding hip screw devices or
multiple parallel screws or pins. However, alternative treat-
ments are conservative treatment or replacement arthro-
plasty. A review study by Conn and Parker confirmed a
non-union rate of 30–45 % for conservative treatment [11].
The recent review study concluded that the non-union rate
with secondary displacement was at least 30 % for the con-
servative treatment of undisplaced femoral neck fractures
[13]. To avoid the complications of avascular necrosis and
non-union, arthroplasty was advocated in the treatment of
undisplaced femoral neck fractures [17]. However, hemi-
arthroplasty is complicated by deep infection (3 %), super-
ficial infection (15 %), periprosthetic fracture (3 %), dislo-
cation (5 %), loosening (10 %), acetabular wear (20 %) and
a potentially higher mortality compared to internal fixation
[11].
The failure rate after internal fixation of undisplaced
femoral neck fractures remains relatively low [8]. Nev-
ertheless internal fixation is not without complications.
Parker described 6.4 % non-union, 4.0 % avascular necro-
sis and revision surgery in 7.7 % [11]. The review study
by Van Embden demonstrated a non-union rate of 4–8.5 %,
avascular necrosis in 2–4 % and revision surgery of 8–15 %
after osteosynthesis of undisplaced femoral neck fractures
[13]. The still considerable failure rate after internal fixa-
tion of undisplaced femoral neck fractures cannot be solely
attributed to the implants. Other factors such as a-traumatic
surgical technique and the positioning of the implant are as
important as the choice of implant.
In this study the DLBP fixation proved to provide sta-
ble fixation of the undisplaced femoral neck fractures with
a failure rate of 6 out of 149 (4 %). However, in two of
these failed fractures the lateral radiograph showed more
than 20° of anterior angulation (32° and 40°). Therefore,
it seems controversial if these so-called stable Garden 1
and 2 fractures, with significant anterior angulation (pos-
terior displacement), really behave as stable fractures or
should be classified as unstable. If only the Garden I and
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479
Low failure rate by means of DLBP fixation of undisplaced femoral neck fractures
1 3
II fractures with an angulation on lateral imaging of less
than 20° were classified as stable, the failure rate in this
study would drop from 4.0 to 2.9 %. The stability of the
DLBP fixation is further demonstrated by the fact that nei-
ther secondary, rotational or angular instability nor perfo-
ration or backing-out of the dynamic blade was observed.
Furthermore, a TAD greater then 25 mm did not prove to
be predictive of a higher extrusion rate as is the case with
the standard implants. The vascularity of the head of femur
after DLBP fixation is as such that AVN led to failure only
in 1.2 % of the included patients. The viability and stability
are also apparent from the low degree of fracture impaction
with a mean of 5 mm.
The DLBP was designed to follow the biology of the
femoral neck fracture. Therefore, the DLBP is a low-
volume, dynamic implant, providing angular and rota-
tional stability. The volume (of the proximal 25 mm of the
implant in the femoral head) of the DLPB is 1500 mm3
compared to 2600 mm3 for the DHS and 2800 mm3 for
DHS spiral blade. The volume of three Asnis screws is
2700 mm3. The square diameter of the DLBP is 31 mm2
compared to 133 mm2 for the DHS/DHS Spiral Blade and
99 mm2 for three Asnis screws. The weight-bearing sur-
face of the DLBP is 338 mm2 compared with 221 mm2 for
the DHS. Torsion test showed that the rotational stability
of the DLBP triples that of the DHS [14]. The resulting
failure rate of the DLBP fixation of the undisplaced femo-
ral neck fractures is low (4 %) and compares favourably
with the results of the common implants (8–14 %). The
most commonly used implants are the multiple parallel
screws or pins and the sliding hip screw devices (SHS)
with both comparable results. The potential implant-
related factors in the failure rate for the screw fixation
are the intrinsic lack of angular and rotational stability.
The stability reached is dependent of the exact position-
ing of the screws and is, therefore, surgeon dependent.
The SHS also lacks rotational stability with the added risk
of iatrogenic rotation of the head during insertion of the
implant [14, 18–20]. Another potential risk factor is the
relative high implant volume in the femoral head for the
screw fixation and the SHS devices [21]. In the operative
treatment of femoral neck fractures minimal invasiveness
seems to be more than the length of the skin incision.
Probably more important is the minimal invasiveness to
the femoral head characterised by a low volume and a
low cross section of he implant in the femoral head and
neck. The hypothesised advantageous characteristics of
the DLBP are the combination of angular and rotational
stability and low implant volume. Although the results of
the DLBP in this study are promising, we recognise that
this observational cohort study is not the strongest study
design to prove this. Also it is recognised that functional
evaluation was limited.
Conclusion
Based on the good clinical results, internal fixation seems
to be the optimum treatment for the undisplaced femoral
neck fracture. However, the failure rate of 8–14 % is still
disturbing. Although not all failures are implant-related,
the choice of implant plays a role in the final outcome. The
possible implant-related factors are the lack of angle and/or
rotational stability in combination of a high implant volume
in the head of femur. The DLBP (Gannet) was designed to
improve the stability of the femoral neck fracture paired to
minimal invasiveness to the femoral head. The low failure
rate of the DLBP fixation of undisplaced femoral neck frac-
tures of 4.0 % seems to be promising and further supports
the treatment algorithm that no effort should be spared to
preserve the femoral head after an undisplaced femoral
neck fracture by internal fixation irrespective of the age of
the patient.
Compliance with ethical standards
Financial support No financial support was received for this study.
Conflict of interest Ariaan van Walsum declares he shares the Intel-
lectual Property rights of the Dynamic Locking Blade Plate. Jos Vroe-
men, Heinrich Janzing, Tomas Winkelhorst, Jorn Kalsbeek and Willem
Roerdink declare that they have no conflict of interest.
Compliance with ethical requirements This study was approved
by the appropriate medical ethics committee.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea-
tivecommons.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.
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