Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review
Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review
Biomechatronics 0 1
Neurorehabilitation Laboratory 0 1
Department of Electrical Engineering 0 1
Chalmers University of Technology 0 1
Gothenburg 0 1
Sweden 0 1
Integrum AB 0 1
Mo¨ lndal 0 1
Sweden 0 1
0 and Neurorehabilitation Laboratory, Department of Electrical Engineering, Chalmers University of Technology , Gothenburg , Sweden. Electronic mail:
1 Education and Surgery (iCORES), Department of Orthopaedics, University of California , San Francisco, CA , USA
2 Department of Orthopaedics, Gothenburg University , Gothenburg , Sweden
-Bone-anchored limb prostheses allow for the direct transfer of external loads from the prosthesis to the skeleton, eliminating the need for a socket and the associated problems of poor fit, discomfort, and limited range of movement. A percutaneous implant system for direct skeletal attachment of an external limb must provide a long-term, mechanically stable interface to the bone, along with an infection barrier to the external environment. In addition, the mechanical integrity of the implant system and bone must be preserved despite constant stresses induced by the limb prosthesis. Three different percutaneous implant systems for direct skeletal attachment of external limb prostheses are currently clinically available and a few others are under investigation in human subjects. These systems employ different strategies and have undergone design changes with a view to fulfilling the aforementioned requirements. This review summarises such strategies and design changes, providing an overview of the biomechanical characteristics of current percutaneous implant systems for direct skeletal attachment of amputation limb prostheses.
Bone-anchored prostheses; Osseointegration; Di-
AEAHBM Alameda East Animal Hospital
ILP Integral leg prosthesis
ITAP Intraosseous transcutaneous amputation
OPL Osseointegrated prosthetic limb
OPRA Osseointegration prostheses for the
rehabilitation of amputees
POP Percutaneous osseointegrated prosthesis
Conventionally, a limb prosthesis is attached to the
stump of an amputee by the use of a socket, which
suspends the prosthesis to the stump by compressing
over soft tissues. However, the socket-stump interface
often causes such complications as poor fit,
discomfort, skin problems, sweating, and pressure
sores.19,29,52,58,70 An alternative way to attach limb
prostheses to the human body is to bypass the
softtissue in the stump for direct load transfer to the
skeletal system. In this concept, a percutaneous
implant system is surgically implanted with its proximal
end directly into bone tissue in the stump. The distal
end of the implant system extends percutaneously from
the residual limb and allows for the attachment of an
external prosthesis. This eliminates the need for a
compression socket and eliminates well-known
socketassociated problems. Additional benefits of direct
skeletal attachment of limb prostheses reported in the
literature include improved range of motion,31,74
walking ability,24,32 sitting comfort,31 reduced energy
expenditure,76 and improved awareness via
osseoperception.33,42 In the 1960s and 1970s, several attempts
were made on animals to achieve direct skeletal
attachment of limb prostheses. In most of these
experiments, intramedullary rods of stainless steel or
cobalt-chrome-molybdenum alloy were used,35,36
however, no long-term successful results were
2018 The Author(s). This article is an open access publication
reported. Sandblasted surface treatment, porous
ceramic coatings,35,36 composite materials of glass fibres or
carbon fibres in plastic matrices,36 and alternative
designs with supra-cortical-, or supra-periosteal
attachment,36–38 to the bone have also been tried, without
satisfactory outcomes. In 1977, Mooney reported on
unsuccessful attempts on three human transhumeral
amputees with intramedullary stainless steel implants
fixed with bone cement.59 Most of the failures have
been attributed to infection at the skin penetration site
and loosening at the bone-implant interface.
In the early 1960s, P.-I. Bra˚ nemark discovered the
ability of bone tissue to closely adhere and form a
strong mechanical bond to titanium. He introduced the
term osseointegration as direct anchorage to bone
tissue to describe this close contact.16 Bra˚ nemark
pioneered the use of titanium as implant material for
dental prostheses in the treatment of edentulous
patients, with positive clinical results.16 From these
findings, the concept was later extended to the
orthopaedic field when an implant system for direct skeletal
attachment of limb prostheses was developed and
implanted in a bilateral transfemoral amputee in Sweden
for the first time in 1990.21 The system was further
developed to accommodate other amputation levels.
Early implants were custom designed until 1999, when
the Swedish system was introduced to the market
under the name OPRA (Osseointegrated Prostheses for
the Rehabilitation of Amputees, Integrum AB, Mo¨
lndal, Sweden). The OPRA implant system is currently
available in 12 countries. Following the successful
results in Sweden, another implant system was
independently developed in Germany under the name of
ILP (Integral Leg Prosthesis, Orthodynamics GMbH,
Lu¨ beck, Germany). In 1999, the first patient was
treated with the ILP implant system,10 which is now in
clinical use in Germany, the Netherlands, and
Australia. Another system, based on the ILP design, was
recently developed in Australia under the name of OPL
(Osseointegrated Prosthetic Limb, Permedica s.p.a.,
Milan, Italy). This system is also clinically available in
The Netherlands. To date OPRA, ILP, and OPL are
the only commercially available systems for direct
skeletal attachment of external limb prostheses.
However, a number of newer systems are under
development, four of which have reached the stage of clinical
experiments in humans. These are the ITAP71
(Intraosseous Transcutaneous Amputation Prosthesis,
Stanmore Implants Worldwide, Watford, United
Kingdom) developed in the United Kingdom, the
Keep Walking Advanced27 (Tequir S.L., Valencia,
Spain) developed in Spain, and two systems developed
in the United States: POP20 (Percutaneous
Osseointegrated Prosthesis, DJO Global, Austin, USA) and
COMPRESS57 (Zimmer Biomet, Warsaw, USA). In
addition to these systems, implantation of a
custommade implant for attachment of an external prostheses
in a transfemoral amputee has been reported in a single
case study in the USA.39 A number of other systems
have been tested in animal studies, but only the
AEAHBM (Alameda East Animal Hospital
BioMedtrix, Boonton, USA) developed in the USA, has shown
successful outcome for a load-bearing prosthetic limb
for more than one year.18
Previous reviews have focused on clinical78 and
functional outcomes,54 as well as the design features of
the implant systems.67 The present review aims to
characterise the biomechanical interfaces between the
implant and biological tissue, and between individual
components within each implant system. In this article,
the term ‘implant system’ refers to implanted and
percutaneous components, including external safety
devices, to which an external prosthesis can be
A systematic literature review was performed using
the three databases: Scopus, Web of Science, and
PubMed. Article title, key words, and abstracts were
searched using the following search condition:
(osseointegrat* OR ‘‘skeletal attachment’’ OR
bone?anchored) AND (limb OR prosthes*) AND
(amput*) AND (implant*). The inclusion criteria for
the articles required them to contain a description of
an implant system that allows for direct skeletal
attachment of a load-bearing artificial limb.
Loadbearing limbs were defined as upper or lower legs and
arms. Journal articles published prior to 1 April 2017
were considered. Conference proceedings, book
chapters, editorial letters, non-English, and non-Spanish
articles were excluded. The screening procedure is
presented in detail in Fig. 1. The filtered search yielded
152 unique and relevant articles in total. The criteria
for inclusion was defined as implant systems that (
allow for direct skeletal attachment of a load-bearing
artificial limb and (
) have been evaluated in human or
animal models of a load-bearing artificial limb with
successful function for at least 1 year. We identified
eight relevant implant systems that fulfilled these
criteria. In addition, a patent search in Derwent
Innovations Index and Espacenet was performed to obtain
further information about these implant systems. Only
patents describing the components of the previously
identified implant systems were considered. The
peerreviewed research articles and patents were studied to
determine the characteristics of each of the implant
systems presented here.
The eight identified implant systems are shown in
Figs. 2, 3, 4, 5, and 6 and described briefly in this
section. Comparisons between the systems are
presented in Tables 1 and 2.
In 1998, the Swedish implant system, surgical
technique, and postoperative rehabilitation protocol was
standardized for transfemoral amputees by the
introduction of the OPRA treatment protocol. Similar
standardisation has also been done for transhumeral
and thumb/finger amputations. Apart from the
standardised implant versions, custom-made implants are
available for the aforementioned levels, as well as for
transtibial and transradial amputations. The OPRA
implant system mainly consists of three components:
) an externally threaded, cylinder-like, fully
implanted component known as a ‘‘fixture’’, where
osseointegration takes place; (
) a percutaneous
component called ‘‘abutment’’, which is press-fit into the
distal end of the fixture and to which the limb
prosthesis is attached; and (
) an ‘‘abutment screw’’, which
extends through the hollow centre of the abutment to
clamp the abutment and the fixture together by the
proximal thread engagement to the fixture and the
abutment screw head on the distal end of the abutment
(Fig. 2a). Loads are transferred from the limb
prosthesis to the abutment, then from the abutment to the
fixture, and finally from the fixture to the bone.
Implantation is normally done in two separate
surgeries, but it can also be done in a single surgery on
patients who have acceptable bone quality and
compliance.56 Since its introduction, the OPRA implant
system has undergone several design changes. The
material has been changed from commercially pure
titanium to the stronger medical grade titanium alloy
Ti6Al4 V. A surface treatment of the exterior of the
fixture called BioHelixTM (Fig. 2b) was added to
induce a nanoporous structure for improved
osseointegration.15 In addition to the design changes, the
surgical technique for lower limb amputations was
modified to implant the fixture 20 mm countersunk
into the bone to address the problem of distal bone
resorption, which was sometimes observed when the
fixture was placed flush with the distal bone end,60,72,75
and to reduce the risk of infection in the bone-fixture
interface.73 Because a fixture failure requires a major
surgical intervention, the system was designed to
ensure that the abutment and abutment screw fracture
before the fixture, or the bone, should the system be
exposed to excessive loads, as these components are
more easily replaced than the fixture. Additionally, the
lower limb systems and the transhumeral systems are
protected by a safety device that is attached between
the distal end of the abutment and the limb prosthesis.
The safety device automatically releases the connection
with the external prostheses if exposed to excessive
loads, thus protecting the implant system from
exposure to fracture inducing forces. In the studied
literature, fatigue failure of fixtures has been reported in a
transfemoral64 and a transradial patient,63 both using
an early design of the implant system. Mechanical
complications leading to revision of the abutment or
the abutment screw have also been reported,14,55 but
no measurement of the mechanical failure rate has
The OPRA implant system has been recently
enhanced at the transhumeral level to allow bidirectional
communication with implanted neuromuscular
interfaces for the closed-loop control of arm prosthesis.61 In
current clinical trials, this novel osseointegrated
interface has, for the first time, allowed the connection of
an arm prosthesis to the patient’s bone, nerves, and
muscles. This is currently the only neuroprosthetic
system that enables patients to operate a prosthetic
arm in daily life receiving sensory feedback via direct
The ILP implant system was designed for
transfemoral amputees, but tibial and humeral implantation
has also been reported.10,11,40 The implant has a cast
stem of cobalt-chrome-molybdenum alloy and the
implant stem is 140–180 mm long and slightly curved
to prevent rotation in the intramedullary cavity and to
fit to the normal curvature of the femur. Since its
introduction, the system has gone through several
design changes. Both the intramedullary part of the
implant and the subdermal part was initially covered with
a 1.5 mm thick macroporous surface known as
‘‘spongiosa metal’’, consisting of tripod-like structures
(Fig. 2d).1,23 The implant also had a bone-stabilising
bracket, which wrapped around the cortical bone
distally (Figs. 3a and 3b). As the bracket and the
macroporous surface towards the soft tissue were
found to cause complications, they were removed in
design versions 2 and 3, respectively (Figs. 3b and
3c).3,49 The latter design was introduced in Germany
200949 and subsequently in the Netherlands in
200953,77 and in Australia in 2010.3 Mechanical failures
of the intramedullary implant have been reported in all
The OPL was introduced in Australia in 20136 and
in the Netherlands in 2015.23 The system is used for
transfemoral or transtibial amputation levels.
Standardised implants are used for transfemoral amputees
with sufficient stump length (‡ 160 mm), while
custom-made implants are available for transtibial
amputees and transfemoral amputees with very short
stumps (Fig. 4).23 This implant system has two
standard designs: OPL type A, with an extramedullary
head (Fig. 4a), and OPL type B, with a flared
intramedullary head for distal transfemoral
amputations23 (Fig. 4b).
The changes from the ILP-3 to the OPL implant
design include material change to Ti6Al4 V, the
introduction of 1 mm high sharp longitudinal splines
proximally, and change from the macroporous
‘‘spongiosa metal’’ surface to a plasma-sprayed rough
titanium coating distally where osseointegration is
The POP system was developed in Salt Lake City,
USA. The system is currently being evaluated in an
early feasibility study in 10 transfemoral amputee
subjects.13,20,68 It is a modular system, implanted in
two separate surgeries. No further details have been
published regarding the design or the surgical protocol.
The human trial was preceded by animal studies of
load-bearing limb prostheses in sheep.41,43–46,69
However, the implant system used in the animal trials is
considerably different from the human system design.
The implant system in the animal trial consists of a
single component made of Ti6Al4 V (Fig. 5a). The
intramedullary part is divided into three regions: a
smooth region proximally, a ribbed region in the
middle, and a porous coated region distally. The
porous coating is combined with a collar shape to
interface against the distal end of the bone.
a12–18 months for transfemoral and transtibial amputations, 10–12 months for transhumeral amputations, 9 months for transradial
amputations, and 3 months for thumb amputations.
The ITAP implant system is under development in
the United Kingdom. A pre-CE mark clinical study for
transfemoral amputees71 has been started, but no
results have yet been published. The published results of
the ITAP system include a case study from a two-year
follow-up of a transhumeral amputee,50 and a clinical
and functional outcome report from implantation of
custom made implant systems in four dogs.22 The
ITAP is a single-component system implanted in a
single surgery. Similar to the other implant systems,
with the exception of the ILP, the implant is made of
the titanium alloy Ti6Al4 V. The proximal region of
the intramedullary part of the ITAP has longitudinal
Number Time between S1 and S2 Total recovery
of surgeries (months) time (months)
cutting flutes (Fig. 5c) aimed to improve rotational
stability. The subdermal and distal regions of the
intramedullary part of the implant have a
hydroxyapatite coating to promote soft tissue ingrowth and
boneanchorage. Since there are no publications available
from the clinical study, it is unclear whether the bone
anchorage is obtained with or without bone cement.
Another design characteristic of the ITAP system is a
subdermal porous flange towards the distal end of the
residual stump to serve as a platform for soft tissue
ingrowth and skin attachment to minimise the relative
movement at the percutaneous interface.22,50,66
The COMPRESS system (Figs. 6a and 6b) was first
developed as an endo-prosthetic system for oncologic
limb salvage reconstruction by Biomet Corporation
(now Zimmer Biomet, Warsaw, USA). The
intramedullary part of the implant is attached to the
bone by transverse pins in a bone-anchor plug. A
porous coated collar designed to promote
osseointegration is located at the distal interface of the
amputated bone. To enhance osseointegration and to
prevent stress-shielding of the bone, the concept of
compliant pre-stress is utilised, exposing the
bonecollar interface to a compressive force. Under a FDA
custom device exception, a percutaneous version of
this system enabling attachment of an external limb
prosthesis has been developed and implanted in 10
transfemoral amputees and one transhumeral
amputee. Both single-stage and two-stage surgeries have
been used for implantation of the system.57 Two cases
of periprosthetic fractures caused by falls have been
reported among the transfemoral subjects.57
Keep Walking Advanced
This system is under development in Valencia,
Spain. It is an extension of the Keep Walking system
for socket stabilization in transfemoral amputees. In
the Keep Walking system, an intramedullary titanium
rod is press-fit into the femur to allow for
osseointegration.28 The distal end of the rod is connected to a
large subdermal component, which serves to transfer
the load from the femur and distribute it evenly to the
socket of the prosthesis to avoid discomfort and soft
tissue damage. In the Keep Walking Advanced system
(Fig. 6c), a percutaneous extension is added to the
subdermal implant in a second surgery. The extension
allows for skeletal attachment of an external
prosthesis, eliminating the need for the compression socket.
The Keep Walking Advanced system is currently being
evaluated in a clinical trial. A single case study of a
38year-old female transfemoral amputee who received
the system in 2013 has been reported,27 but no
information about functional outcome has been presented.
The AEAHBM implant system developed in
Denver, Colorado was custom-made for a single surgery
implantation of a single-component system into both
pelvic limbs of a dog18 (Fig. 6d). One of the implants
had to be removed because of failed osseointegration
after 14 months, but a redesigned implant (Fig. 6e)
was implanted with successful results up to the time of
the report, 26 months after the initial surgery. The
original implant consisted of a threaded tapered
intramedullary stem consisting of Ti6Al4 V. The distal
end of the stem was covered by a porous tantalum
sleeve to allow for soft tissue integration while also
serving as a collar towards the distal end of the bone.
In the redesigned system, the tapered thread was
exchanged for an unthreaded stem with longitudinal
splines in order to provide more rotational stability.
Number of Treated Human Subjects
There is only limited information in peer-reviewed
publications regarding the number of patients who
have been recipients of implant systems for
bone-anchored limb prostheses. It has been reported that
approximately 150 patients were treated with the
OPRA system in Sweden between 1990 and 200934;
approximately 150 patients had been treated with the
ILP system in Germany, the Netherlands, and
Australia until 20163; and at least 22 patients were treated
with the OPL system in Australia between November
2013 and December 2014.6 Since those reports, more
patients have been treated with each of these systems.
Oral and unverified online reports indicate that the
current number of patients treated with each of the
clinically available systems is in the hundreds;
however, the actual numbers must be verified in formally
reported clinical studies. For the other systems, the
number of treated patients are lower. The
peer-reviewed literature has only reported a single subject
treated with the ITAP system,50 11 subjects treated
with the COMPRESS system,57 and a single subject
treated with the keep walking advanced27 system.
According to oral and unverified online reports, a
further 20 transfemoral patients have been treated with
the ITAP system in the clinical trial, and at least eight
people have been treated with the POP system in the
early feasibility study.
Of the systems implanted in human subjects, ITAP
is the only system that is always implanted in a single
surgery. The other systems have mostly followed
twostage surgical protocols, although single-stage
procedures have been reported for the OPRA, the OPL and
the COMPRESS systems.7,56,57 In the first stage, an
incision is made in the distal end of the stump, the
residual bone is reamed and prepared for insertion of
the implant, and the implant is then inserted and the
skin is closed. The bone and the skin are allowed to
heal for a period of time to enable osseointegration
between the bone and the implant. In the second stage,
the percutaneous part is inserted with its proximal end
into the implanted component and the distal end
extending through the skin.
Different healing and rehabilitation times are used
before the implant can be fully loaded. A schedule is
followed in which progressively higher loads are
applied to the external part of the implant system until
full loading with the external prosthesis is eventually
allowed.8,30,48,50 It is important to have a close
collaboration between the physiotherapist and prosthetist
to monitor the rehabilitation of the patient and to
ensure that the prosthetic components are carefully
selected and aligned. It is recommended that a
prosthetic knee component providing effortless flexion and
controlled extension is used before full weight-bearing
The recommended period between the first surgery
and the time when the patient is able/allowed to fully
load the system with an external prosthesis varies
among individuals, implant systems, and amputation
level. According to the standard OPRA protocol, this
period should be approximately 12 months for
transfemoral amputees,30,56 while for the ILP and the OPL,
full weight bearing on the prosthesis is recommended
after 2.5–3 and 4–5 months, respectively.8,10,49 For the
other systems, the number of cases reported in this
regard is too small.
In order to have a long-term successful outcome, it
is essential to obtain a stable connection between the
implant and the bone. It is believed that small relative
movements between the implant and the bone can
cause the formation of a fibrous layer around the
implant, leading to mechanical instability and the need
for implant revision. Different approaches have been
used to achieve a stable connection between the
implant and the bone. Osseointegration is often cited as
the underlying working mechanism, but limited
evidence has been provided in this regard. Verification of
achieved osseointegration would preferably include
Xray analysis and radiostereometric analysis (RSA),60 as
well as high-resolution interface analysis after implant
retrieval.64 The only system that has provided such
evidence in peer-reviewed literature is the OPRA
Three different anchoring strategies were found in
the studied systems: (
) a threaded connection, which is
utilised in the OPRA and the original AEAHBM
) a press-fit interface, which is present in the
ILP, OPL, ITAP, POP, Keep Walking Advanced, and
the redesigned AEAHBM system; and (
) a bone
anchor with transverse intraosseous pins in combination
with a compressive force and bone-ingrowth at the
bone-collar interface, as is used in the COMPRESS
system. A threaded connection inherently has good
mechanical stability in the longitudinal direction.
Initial rotational stability is achieved by friction and
longterm stability is achieved by a combination of friction
and mechanical interlocking, where the bone tissue
grows into macro, micro, and nano ‘‘irregularities’’ on
the implant surface. The press-fit interface has a lower
longitudinal axial stability, initially relying solely on
friction and in the long term relying on both friction
and bone ingrowth for longitudinal and rotational
stability. A bone anchor with transverse intraosseous
pins, in combination with a compressive bone collar
with bone ingrowth promoting surface properties,
naturally creates a high mechanical stability, both in
the longitudinal and the rotational directions. In order
to create a more stable interface between the implant
and the bone, additional features have been added to
some of these systems. These include longitudinal
splines or fluted regions for improved rotational
stability as in OPRA, OPL, ITAP, POP, Keep Walking
Advanced and the AEAHBM systems; a curvature
along the longitudinal axis, as is utilized in the ILP and
the OPL systems; and a flared, or collared interface at
the distal bone interface, as used in all systems except
OPRA. Geometrical fit between the implant and the
bone appears to be crucial for a successful outcome as
observed by loosening and failure of undersized
implants,5,8 or fracture at the insertion of oversized
implants.44 Bone ingrowth is dependent on the implant
material, the implant design, and the geometrical fit in
the bone.9 In all of the studied implant systems except
the ILP, the bulk material of the implant is the
titanium alloy Ti6Al4 V. In the ILP, a
cobalt-chromemolybdenum alloy is used instead. Porous exterior
surfaces are used locally in all implant systems to
enhance the bone ingrowth. The OPRA system has the
laser-induced nanoporous microstructure BioHelixTM
surface, the ILP system has a macroporous spongiosa
surface, and the OPL has a rough surface of plasma
sprayed titanium on the distal half of the implant.
Similarly, the distal region of the POP implant,
including a collar at the interface toward the distal end
of the bone, is covered by a porous layer of pure
titanium. The COMPRESS system utilises a
hydroxyapatite porous collar in combination with a
compressive force of 1.8-3.6 kN57,65 across the interface,
while the AEAHBM has a collar of porous tantalum
toward the distal bone end. In the Keep Walking
Advanced system, small holes are located on the
proximal end of the UHMWPE
(ultra-high-molecularweight polyethylene) spacer at the interface toward the
distal end of the bone.26 The ITAP has a coating of
hydroxyapatite on the distal part of the intramedullary
portion of the implant.
Implant-percutaneous Part Interface
In the OPRA system, the abutment is connected to
the fixture by a smooth surface press-fit. The abutment
is also clamped to the fixture by a preload from the
abutment screw with a thread engagement with the
fixture proximal to the abutment.
The ILP and OPL systems have a press-fit Morse
taper connection between the implant and the
percutaneous part, called the dual-cone adapter. A safety
screw inserted longitudinally from the dual-cone
adapter to the implant provides additional locking of
In the POP system used in the ongoing human trial,
the implant is connected to the exterior of the body by
a ceramic-coated percutaneous post, which is clamped
to the implant with a locking screw.12
The porous coated collar in the COMPRESS system
is connected to the bone anchor by a traction rod and a
compression nut, which, in combination with a
number of Belleville washers, apply a compressive force at
the distal bone end.
In the Keep Walking Advanced system, the implant
is attached to the percutaneous extension by a tapered
interface and a locking screw, which has a proximal
thread engagement with the implant.26
The percutaneous component of the OPRA system
is the abutment, which has a smooth polished surface
to minimise contact and friction at the skin interface.
In the ILP and the OPL systems, the percutaneous
interface consists of the dual-cone adapter and, in
some designs, also the distal end of the implant. The
percutaneous surfaces of the implant are
smooth-polished and have a niobium-oxide coating aimed to
minimise soft tissue adhesion at the percutaneous
In the ITAP system, the percutaneous interface is
stabilised by the subdermal porous flange, allowing for
soft tissue ingrowth and suture of the thinned skin flap
to minimise relative movement.50 Distal to the porous
flange, the peg for attachment of the external
prosthesis is coated with a low-friction DLC (diamond-like
carbon) surface coating to reduce bacterial
The COMPRESS and the AEAHBM systems both
have a porous subdermal surface distal to the bone to
promote soft tissue integration and to provide a soft
tissue seal to the implant. In the COMPRESS system,
the porous coating consists of titanium, while the
AEAHBM system uses tantalum.13,18,57 The
percutaneous interface of the POP and the COMPRESS
systems are characterised by smooth low-friction surfaces,
similar to the other implant systems for human
Safety precautions have been taken to protect the
bone and the implant from direct exposure to high
loads, especially in the event of a fall. The OPRA
implant system has different safety devices for different
amputation levels. They are separate components,
which are connected between the abutment and the
external prosthesis and automatically release the
connection between the implant and the prosthesis if they
are exposed to a load exceeding a pre-set limit. All
OPRA safety systems protect against excessive torque
around the longitudinal axis, while the transfemoral
system also protects from excessive bending moments
in the normal plane of the longitudinal axis. Release
limits for the systems are set to be high enough to
avoid release during normal use, but low enough to
ensure that the bone or the implant system is not
damaged. The limits are set to 15 Nm torque and
70 Nm bending moment. In case of release, the safety
system can be restored to normal operation by the
patient without the need to meet a prosthetist. The ILP
and OPL safety systems are protecting from high
torques being transferred to the implant by a connection
adapter25 or a click safety adapter23,77 attached
between the distal end of the dual-cone adapter and the
external prosthesis. The connection adapter is
equipped with a safety mechanism, consisting of one or
several shear pins, designed to break in case the
implant is exposed to high torsional loads.11 If this
happens, replacement of the broken part can be done in a
clinical setting.3 There is limited information about the
safety systems for the other implant systems. However,
the case report about the transhumeral ITAP patient
mentions that the ITAP is equipped with a safety
component, mounted between the implant and the
prosthesis, which is designed to break at loads
corresponding to 10 kg or more.50
Several systems have been developed for
bone-anchored limb prostheses and different approaches have
been employed to achieve a stable attachment between
the implant and the bone. Comparing the ILP and
OPL implant systems with the OPRA implant system
reveals that the latter follows a slower rehabilitation
protocol for lower limb amputations. This could
indicate that a longer time is needed to achieve a
mechanically stable interface for a threaded implant
than for a press-fit implant. However, the historical
development of the implants must also be considered.
The threaded implant design used in the OPRA system
was developed using experience gained from the dental
industry as the first and longest user of
osseointegration, whereas the press-fit implant design originates
from intramedullary hip implants, which have a
tradition of fixation to the bone by press-fit in
combination with bone cement.
The OPRA system follows a conservative approach,
with a healing period before any load is applied to the
implant. This is based on experimental results from
animal studies, which have shown that the mechanical
capacity of the bone-implant interface for threaded
implants is improved by healing under unloaded
conditions in both torsion and pull-out load.17,47 For the
pioneers in the field of bone-anchored limb prostheses,
the highest priority during the development has been to
achieve a successful end result, rather than
rehabilitation speed. The primary stability is determined by the
geometrical fit between the implant and the bone, the
bone quality and quantity, and thus varies between
individuals. If the primary stability of the implant after
the surgery is sufficient to withstand initial loading, the
rehabilitation could start earlier and significantly
reduce the total recovery time. On the other hand, if the
primary stability is insufficient, the reduced weakness
of the bone-implant interface during the initial healing
would potentially lead to a higher incidence of early
fixture loosening if such a reduced healing time
protocol was adopted.
Another difference between the clinically available
implant systems is the intramedullary length of the
implant (140–180 mm for ILP, 160 mm for OPL, and
80 mm for OPRA). This indicates that press-fit
implants require a longer intramedullary length to
achieve a stable connection in the longitudinal
direction than a threaded implant. A shorter implant length
is advantageous, as it imposes fewer eligibility
constraints on the residual stump length. Furthermore, in
the event of a catastrophic failure, with the worst-case
scenario requiring re-amputation above the implant, a
shorter intramedullary length leads to a longer residual
length of the stump after the re-amputation surgery.
To achieve bone ingrowth, the trend is to use the
titanium alloy Ti6Al4 V as the bulk material in
combination with porous surface on the implant. The
degree of porosity varies between systems, but inevitably
comes with a trade-off by having reduced mechanical
strength and fatigue properties in these regions. Most
of the systems used in humans are modular, which
limits the mechanical capacity but simplifies the
surgical intervention in case a revision surgery is needed.
To avoid irritation and superficial infections, which
could potentially lead to more severe deep infections,
two approaches are employed at the percutaneous
interface in the different implant systems. The first
approach is to try to prevent skin and soft tissue
adhesion by having a polished surface on the
percutaneous component as in the OPRA, OPL, POP, Keep
Walking Advanced and later designs of the ILP
system. In the OPRA system, this approach is combined
with suture of the skin directly to the distal end of the
bone at the percutaneous interface in order to
minimize relative movement and to create an infection
barrier. The other approach is to create an infection
barrier by promoting soft-tissue ingrowth to the
percutaneous component. This approach is used in the
ITAP, COMPRESS, AEAHBM, and earlier designs of
the ILP systems, by having a porous surface on the
The scientific literature contains limited information
about the mechanical features of bone-anchoring
implant systems. Reporting the performance of such
systems under mechanical stress in bench tests, or
activities of the daily living, has been given a low
priority by the development teams in favor of clinical
outcomes. The available literature refers to
osseointegration as the responsible mechanism that allows direct
skeletal attachment of limb prostheses; however,
insufficient evidence has been provided for most of the
implant systems on the degree of osseointegration
achieved with the different designs.
It is difficult to compare the available systems
because they have undergone several changes over time,
and clinical trials continue to be limited. The three
design principles known at present are fundamentally
different and pose particular advantages and
disadvantages, which might in the future serve as the basis
to determine which approach is most suitable for
Current systems for bone anchoring of limp
prostheses use intramedullary implants. Primary stability
between bone and implant is achieved by one of three
strategies: a threaded connection, a press-fit
connection, or axial compression. Secondary stability is
achieved by bone ingrowth into porous surfaces of the
implant. Although there are large differences between
current implant systems, the three clinically available
systems (OPRA, ILP, and OPL) have shown
functional improvements for patients with socket-related
issues. Recent developments of implant systems,
surgical protocols, and safety devices have reduced the
rate of mechanical failure and infectious
complications. Moreover, further improvements are likely to
continue based on field data and information from the
ongoing human trials. Future developments are likely
to address several factors, such as the perceived long
rehabilitation time before loading, the need for two
separate surgeries, the incidence of superficial infection
at the percutaneous interface, mechanical failures in
highly demanding activities, and the possibility of
additionally providing closed-loop, neuro-muscular
control of the limb prostheses.
This study was supported by research grants from
the Swedish Foundation for Strategic Research
(ID150089), the European Commission (H2020, DeTOP
project, GA 687905), and VINNOVA (2017-01471).
AT and MOC were funded by these grants. AT and
MOC are partially employed by, and RB is a board
member of Integrum AB. AT, MOC, and RB own
shares in Integrum AB. BH declares no conflict of
CONFLICT OF INTEREST
No benefits in any form have been or will be
received by author BH from a commercial party, related
directly or indirectly to the subject of this manuscript.
The authors AT, RB, and MOC have received or will
receive benefits for personal or professional use from a
commercial party, related directly or indirectly to the
subject of this manuscript.
This article is distributed under the terms of the
Creative Commons Attribution 4.0 International
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.
4Al Muderis, M., B. A. Bosley, A. V. Florschutz, P. A.
Lunseth, D. K. Tyler, J. M. Highsmith, and J. T. Kahle.
Radiographic assessment of extremity osseointegration for
the amputee. Technol. Innov. 18:211–216, 2016.
5Al Muderis, M., A. Khemka, S. J. Lord, H. Van de Meent,
and J. P. M. Fro¨ lke. Safety of osseointegrated implant for
transfemoral amputees, a two-center prospective cohort
study. J. Bone Jt. Surg. 98:900–909, 2016.
6Al Muderis, M., W. Lu, and J. J. Li. Osseointegrated
Prosthetic Limb for the treatment of lower limb
amputations : Experience and outcomes. Unfallchirurg 120:306–
7Al Muderis, M., W. Lu, K. Tetsworth, B. Bosley, and J. J.
Li. Single-stage osseointegrated reconstruction and
rehabilitation of lower limb amputees: The Osseointegration
Group of Australia Accelerated Protocol-2 (OGAAP-2)
for a prospective cohort study. BMJ Open 7:e013508, 2017.
8Al Muderis, M., K. Tetsworth, A. Khemka, S. Wilmot, B.
Bosley, S. J. Lord, and V. Glatt. The Osseointegration
Group of Australia Accelerated Protocol (OGAAP-1) for
two-stage osseointegrated reconstruction of amputated
limbs. Bone Joint J. 98:952–960, 2016.
9Albrektsson, T., P.-I. Bra˚ nemark, H.-A. Hansson, and J.
Lindstro¨ m. Osseointegrated titanium implants:
requirements for ensuring a long-lasting, direct bone-to-implant
anchorage in man. Acta Orthop. Scand. 52:155–170, 1981.
10Aschoff, H. H. Transcutaneous, distal femoral,
intramedullary attachment for above-the-knee prostheses: an
endo-exo device. J. Bone Jt. Surg. 92:180–186, 2010.
11Aschoff, H. TOPS—transkutane osseointegrierte
Prothesensysteme. Orthopa¨die und Unfallchirurgie up2date 12:87–
12Bachus, K., S. Jeyapalina, J. P. Beck, R. Bloebaum, J. P.
Agarwal, J. A. Longo, E. Kubiak, and B. Mueller Holt.
Percutaneous osseointegrated implant assembly for use in
supporting an exo-prosthesis. Patent: US 9,433,505, 2016.
13Beck, J., S. Sinclair, B. Gillespie, B. Darter, J. Agarwal, P.
Stevens, S. Turley, and E. Kubiak. Early observations of a
Federal Drug Administration feasibility study determining
the safety and efficacy of a percutaneous osseointegrated
prosthesis system. 7th international conference: advances in
orthopaedic osseointegration, San Diego, 2017.
14Bra˚ nemark, R., O¨ . Berlin, K. Hagberg, P. Bergh, B.
Gunterberg, and B. Rydevik. A novel osseointegrated
percutaneous prosthetic system for the treatment of patients with
transfemoral amputation: a prospective study of 51
patients. Bone Jt. J. 96:106–113, 2014.
15Bra˚ nemark, R., L. Emanuelsson, A. Palmquist, and P.
Thomsen. Bone response to laser-induced micro- and
nanosize titanium surface features. Nanomed. Nanotechnol. Biol.
Med. 7:220–227, 2011.
16Bra˚ nemark, P. I., B. O. Hansson, R. Adell, U. Breine, J.
Lindstro¨ m, O. Halle´ n, and A. O¨ hman. Osseointegrated
implants in the treatment of the edentulous jaw. Experience
from a 10-year period. Scand. J. Plast. Reconstr. Surg.
Suppl. 16:1–132, 1977.
17Bra˚ nemark, R., L. O. O¨ hrnell, P. Nilsson, and P. Thomsen.
Biomechanical characterization of osseointegration during
healing: An experimental in vivo study in the rat.
Biomaterials 18:969–978, 1997.
18Drygas, K. A., R. Taylor, C. G. Sidebotham, R. R.
Hugate, and H. McAlexander. Transcutaneous tibial implants:
A surgical procedure for restoring ambulation after
amputation of the distal aspect of the tibia in a dog. Vet.
Surg. 37:322–327, 2008.
19Dudek, N. L., M. B. Marks, S. C. Marshall, and J. P.
Chardon. Dermatologic conditions associated with use of a
lower-extremity prosthesis. Arch. Phys. Med. Rehabil.
20Encore Medical, L. P. Early Feasibility Study of the
Percutaneous Osseointegrated Prosthesis (POP)—Full Text
View—ClinicalTrials.gov, 2016, at http://clinicaltrials.
21Eriksson, E., and P.-I. Bra˚ nemark. Osseointegration from
the perspective of the plastic surgeon. Plast. Reconstr. Surg.
22Fitzpatrick, N., T. J. Smith, C. J. Pendegrass, R. Yeadon,
M. Ring, A. E. Goodship, and G. W. Blunn. Intraosseous
transcutaneous amputation prosthesis (ITAP) for limb
salvage in 4 dogs. Vet. Surg. 40:909–925, 2011.
23Fro¨ lke, J. P. M., R. A. Leijendekkers, and H. van de
Meent. Osseointegrated prosthesis for patients with an
amputation. Unfallchirurg 2017. https://doi.org/10.1007/
24Frossard, L., K. Hagberg, E. Ha¨ ggstro¨ m, D. L. Gow, R.
Bra˚ nemark, and M. Pearcy. Functional outcome of
transfemoral amputees fitted with an osseointegrated fixation:
Temporal gait characteristics. JPO J. Prosthetics Orthot.
25Grundei, H. Connection adapter. Patent: US 8,226,731,
26Guirao, L. Modular femoral endoprosthesis. Patent: EP
Patent application 2,138,133, 2009.
27Guirao, L., B. Samitier, J. Alos, R. Tibau, and E.
Pleguezuelos. Osteointegracio´ n con el sistema keep walking
advanced. Rehabilitacio´n 51:129–133, 2017.
28Guirao, L., C. B. Samitier, M. Costea, J. M. Camos, M.
Majo, and E. Pleguezuelos. Improvement in walking
abilities in transfemoral amputees with a distal weight bearing
implant. Prosthet. Orthot. Int. 2016. https://doi.org/
29Hagberg, K., and R. Bra˚ nemark. Consequences of
nonvascular trans-femoral amputation: A survey of quality of
life, prosthetic use and problems. Prosthet. Orthot. Int.
30Hagberg, K., and R. Bra˚ nemark. One hundred patients
treated with osseointegrated transfemoral amputation
prostheses -Rehabilitation perspective. J. Rehabil. Res.
Dev. 46:331–344, 2009.
31Hagberg, K., E. Ha¨ ggstro¨ m, M. Uden, and R. Bra˚ nemark.
Socket versus bone-anchored trans-femoral prostheses: Hip
range of motion and sitting comfort. Prosthet. Orthot. Int.
32Hagberg, K., E. Hansson, and R. Bra˚ nemark. Outcome of
percutaneous osseointegrated prostheses for patients with
unilateral transfemoral amputation at two-year follow-up.
Arch. Phys. Med. Rehabil. 95:2120–2127, 2014.
33Ha¨ ggstro¨ m, E., K. Hagberg, B. Rydevik, and R. Bra˚
nemark. Vibrotactile evaluation: osseointegrated versus
socket-suspended transfemoral prostheses. J. Rehabil. Res.
Dev. 50:1423–1434, 2013.
34Ha¨ ggstrom, E., E. Hansson, and K. Hagberg. Comparison
of prosthetic costs and service between osseointegrated and
conventional suspended transfemoral prostheses. Prosthet.
Orthot. Int. 37:152–160, 2013.
35Hall, C. W. Developing a permanently attached artificial
limb. Bull. Prosthet. Res. 22:144–157, 1974.
36Hall, C. Skeletal extension development: criteria for future
designs. Bull. Prosthet. Res. 10:69–94, 1976.
37Hall, C. W. A future prosthetic limb device. J. Rehabil. Res.
Dev. 22:99–102, 1985.
38Hall, C. W., A. Mallow, and P. A. Cox. Developing a
supraperiostial endoprosthesis. Trans. Am. Soc. Artif.
Intern. Organs 23:358–362, 1977.
39Hillock, R., J. Keggi, R. Kennon, E. McPherson, C. Terry,
D. Brasil, and T. McTighe. A global
collaboration—osteointegration implant (OI) for transfemoral amputation.
JISRF Reconstr. Rev. 3:50–54, 2013.
40Hoffmeister, T., F. Schwarze, and H. H. Aschoff. Das
Endo-Exo-Prothesen versorgungskonzept: verbesserung
der lebensqualita¨ t nach extremita¨ tenamputation.
Unfallchirurg 120:371–377, 2017.
41Holt, B. M., K. N. Bachus, J. P. Beck, R. D. Bloebaum,
and S. Jeyapalina. Immediate post-implantation skin
immobilization decreases skin regression around
percutaneous osseointegrated prosthetic implant systems. J.
Biomed. Mater. Res. Part A 101:2075–2082, 2013.
42Jacobs, R., R. Bra˚ nemark, K. Olmarker, B. Rydevik, D.
Van Steenberghe, and P. I. Bra˚ nemark. Evaluation of the
psychophysical detection threshold level for vibrotactile
and pressure stimulation of prosthetic limbs using bone
anchorage or soft tissue support. Prosthet. Orthot. Int.
43Jeyapalina, S., J. P. Beck, K. N. Bachus, and R. D.
Bloebaum. Cortical bone response to the presence of
loadbearing percutaneous osseointegrated prostheses. Anat.
Rec. 295:1437–1445, 2012.
44Jeyapalina, S., J. P. Beck, K. N. Bachus, O. Chalayon, and
R. D. Bloebaum. Radiographic evaluation of bone
adaptation adjacent to percutaneous osseointegrated prostheses
in a sheep model. Clin. Orthop. Relat. Res. 472:2966–2977,
45Jeyapalina, S., J. P. Beck, K. N. Bachus, D. L. Williams,
and R. D. Bloebaum. Efficacy of a porous-structured
titanium subdermal barrier for preventing infection in
percutaneous osseointegrated prostheses. J. Orthop. Res.
46Jeyapalina, S., J. P. Beck, R. D. Bloebaum, and K. N.
Bachus. Progression of bone ingrowth and attachment
strength for stability of percutaneous osseointegrated
prostheses. Clin. Orthop. Relat. Res. 472:2957–2965, 2014.
47Johansson, C. B., and T. Albrektsson. Integration of screw
implants in the rabbit: A 1-year follow-up of removal
torque of titanium implants. Int. J. Oral Maxillofac. Implant.
48Jo¨ nsson, S., K. Caine-Winterberger, and R. Bra˚ nemark.
Osseointegration amputation prostheses on the upper
limbs: methods, prosthetics and rehabilitation. Prosthet
Orthot Int 35:190–200, 2011.
49Juhnke, D.-L., J. P. Beck, S. Jeyapalina, and H. H.
Aschoff. Fifteen years of experience with integral-leg-prosthesis:
Cohort study of artificial limb attachment system. J.
Rehabil. Res. Dev. 52:407–420, 2015.
50Kang, N. V., C. Pendegrass, L. Marks, and G. Blunn.
Osseocutaneous integration of an intraosseous
transcutaneous amputation prosthesis implant used for
reconstruction of a transhumeral amputee: Case report. J. Hand Surg.
Am. 35:1130–1134, 2010.
51Kramer, M. J., B. J. Tanner, A. E. Horvai, and R. J.
O’Donnell. Compressive osseointegration promotes viable
bone at the endoprosthetic interface: Retrieval study of
Compress implants. Int. Orthop. 32:567–571, 2008.
52Legro, M. W., G. Reiber, M. del Aguila, M. J. Ajax, D. A.
Boone, J. A. Larsen, D. G. Smith, B. Sangeorzan, M.
Aguila, J. Megan, D. A. A Boone, J. A. Larsen, and D. G.
Smith. Issues of importance reported by persons with lower
limb amputations and prostheses. J. Rehabil. Res. Dev.
53Leijendekkers, R. A., J. B. Staal, G. van Hinte, J. P.
Fro¨ lke, H. van de Meent, F. Atsma, M. W. G. Nijhuis-van
der Sanden, and T. J. Hoogeboom. Long-term outcomes
following lower extremity press-fit bone-anchored
prosthesis surgery: a 5-year longitudinal study protocol. BMC
Musculoskelet. Disord. 17:484, 2016.
54Leijendekkers, R. A., G. van Hinte, J. P. Fro¨ lke, H. van de
Meent, M. W. G. Nijhuis-van der Sanden, and J. B. Staal.
Comparison of bone-anchored prostheses and socket
prostheses for patients with a lower extremity amputation:
A systematic review. Disabil. Rehabil. 39:1045–1058, 2017.
55Lennera˚ s, M., G. Tsikandylakis, M. Trobos, O. Omar, F.
Vazirisani, A. Palmquist, O¨ . Berlin, R. Bra˚ nemark, and P.
Thomsen. The clinical, radiological, microbiological, and
molecular profile of the skin-penetration site of
transfemoral amputees treated with bone-anchored prostheses.
J. Biomed. Mater. Res. Part A 2016. https://doi.org/
56Li, Y., and R. Bra˚ nemark. Osseointegrated prostheses for
rehabilitation following amputation: The pioneering
Swedish model. Unfallchirurg 2017. https://doi.org/
57McGough, R. L., M. A. Goodman, R. L. Randall, J. A.
Forsberg, B. K. Potter, and B. Lindsey. The Compress
transcutaneous implant for rehabilitation following limb
amputation. Unfallchirurg 2017. https://doi.org/10.1007/
58Meulenbelt, H. E., P. U. Dijkstra, M. F. Jonkman, and J.
H. Geertzen. Skin problems of the stump in lower limb
amputees. Disabil. Rehabil. 28:603–608, 2006.
59Mooney, V., S. A. Schwartz, A. M. Roth, and M. J.
Gorniowsky. Percutaneous implant devices. Ann. Biomed.
Eng. 5:34–46, 1977.
60Nebergall, A., C. Bragdon, A. Antonellis, J. Ka¨ rrholm, R.
Bra˚ nemark, and H. Malchau. Stable fixation of an
osseointegated implant system for above-the-knee
amputees: titel RSA and radiographic evaluation of migration
and bone remodeling in 55 cases. Acta Orthop. 83:121–128,
61Ortiz-Catalan, M., B. H a˚kansson, and R. Bra˚ nemark. An
osseointegrated human-machine gateway for long-term
sensory feedback and motor control of artificial limbs. Sci.
Transl. Med. 6:1–8, 2014.
62Ortiz-Catalan, M., E. Mastinu, R. Br a˚nemark, and B.
Ha˚ kansson. Direct neural sensory feedback and control via
osseointegration. XVI World Congress of the International
Society for Prosthetics and Orthotics (ISPO)., Cape Town,
South Africa., 2017.
63Palmquist, A., T. Jarmar, L. Emanuelsson, R. Br a˚nemark,
H. Engqvist, and P. Thomsen. Forearm bone-anchored
amputation prosthesis: a case study on the
osseointegration. Acta Orthop. 79:78–85, 2008.
64Palmquist, A., S. H. Windahl, B. Norlindh, R. Bra˚ nemark,
and P. Thomsen. Retrieved bone-anchored percutaneous
amputation prosthesis showing maintained
osseointegration after 11 years-a case report. Acta Orthop. 85:442–445,
65Pedtke, A. C., R. L. Wustrack, A. S. Fang, R. J. Grimer,
and R. J. O’Donnell. Aseptic failure: How does the
compress implant compare to cemented stems? Clin. Orthop.
Relat. Res. 470:735–742, 2012.
66Pendegrass, C. J., A. E. Goodship, J. S. Price, and G. W.
Blunn. Nature’s answer to breaching the skin barrier: an
innovative development for amputees. J. Anat. 209:59–67,
67Pitkin, M. Design features of implants for direct skeletal
attachment of limb prostheses. J. Biomed. Mater. Res. Part
A 101:3339–3348, 2013.
68Potter, B. K. From bench to bedside: A perfect fit?
Osseointegration can improve function for patients with
amputations. Clin. Orthop. Relat. Res. 474:35–37, 2016.
69Shelton, T. J., J. Peter Beck, R. D. Bloebaum, and K. N.
Bachus. Percutaneous osseointegrated prostheses for
amputees: Limb compensation in a 12-month ovine model. J.
Biomech. 44:2601–2606, 2011.
70Sherman, R. Utilization of prostheses among US veterans
with traumatic amputation: A pilot survey. J. Rehabil. Res.
Dev. 36:100–108, 1999.
71Stanmore Implants Ltd. Intraosseous transcutaneous
amputation prosthesis—ClinicalTrials.gov, 2016, at
72Stenlund, P., M. Trobos, J. Lausmaa, R. Bra˚ nemark, P.
Thomsen, and A. Palmquist. The effect of load on the
bone-anchored amputation prostheses. J. Orthop. Res.
1Ahlers , O. Verfahren zur herstellung eines implantates mit einer seine oberfla¨ che zumindest teilweise bedeckenden metallischen offenzelligen struktur . Patent: EP 0 , 502 , 349 , 1995 .
2Al Muderis, M. An osseointegrable device. Patent: US patent app . publ. 0 , 331 , 422 , 2016 , 2016 .
3Al Muderis, M. , H. H. Aschoff , B. Bosley , G. Raz , L.
Sport . Eng. 19 : 141 - 145 , 2016 .
73Tillander, J. , K. Hagberg , L. Hagberg , and R. Br a˚nemark. Osseointegrated titanium implants for limb prostheses attachments: Infectious complications . Clin. Orthop. Relat. Res . 468 : 2781 - 2788 , 2010 .
74Tranberg, R. , R. Zu ¨ gner, and J. Ka ¨ rrholm. Improvements in hip- and pelvic motion for patients with osseointegrated trans-femoral prostheses . Gait Posture 33 : 165 - 168 , 2011 .
75Tsikandylakis, G. , O ¨ . Berlin, and R. Bra ˚ nemark. Implant survival, adverse events, and bone remodeling of osseointegrated percutaneous implants for transhumeral amputees . Clin. Orthop. Relat. Res . 472 : 2947 - 2956 , 2014 .
76Van de Meent , H., M. T. Hopman , and J. P. Fro ¨ lke. Walking ability and quality of life in subjects with transfemoral amputation: a comparison of osseointegration with socket prostheses . Arch. Phys. Med . Rehabil. 94 : 2174 - 2178 , 2013 .
77Van de Meent , H., M. T. Hopman , and J. P. Fro ¨ lke. Walking ability and quality of life in subjects with transfemoral amputation: a comparison of osseointegration with socket prostheses . Arch. Phys. Med . Rehabil. 94 : 2174 - 2178 , 2013 .
78Van Eck, C. F. , and R. L. Mcgough . Clinical outcome of osseointegrated prostheses for lower extremity amputations: A systematic review of the literature . Curr. Orthop. Pract . 26 : 349 - 357 , 2015 .