Acrobot: Active Constraint Robots Improve Outcome in Arthritis Surgery
Submitting Institution
Imperial College LondonUnit of Assessment
Clinical MedicineSummary Impact Type
TechnologicalResearch Subject Area(s)
Information and Computing Sciences: Artificial Intelligence and Image Processing
Medical and Health Sciences: Clinical Sciences, Neurosciences
Summary of the impact
Collaboration between Imperial College Departments of Mechanical
Engineering and Surgery led to the development of active constraint robot
solutions which augment surgeon skills so that joint replacement
components are implanted accurately and successfully. This led to the
founding of Acrobot to develop innovative surgical technologies. Acrobot
was acquired by Stanmore Implants Worldwide in 2010. An orthopaedic
stereotaxic instrument, based on Imperial research, obtained US Food and
Drug Administration (FDA) clearance in 2013. This has led to Mako-Surgical
purchasing Stanmore Implants Acrobot technology in April 2013.
Underpinning research
Key Imperial College London researchers:
Professor Justin Cobb, Professor & Chair of Orthopaedics (2005 - present)
Professor Brian Davies, Professor of Medical Robotics (2000-2005,
currently Emeritus)
Dr Simon Harris, Postdoctoral researcher (1989-2003, 2008-present)
Dr Ferdinando Rodriguez y Baena, Reader (2000-2004; 2006-present)
Dr Matjaz Jakopec, Research Associate (1995-2002)
Since the mid-1990s, Imperial researchers have been working across
disciplines to design and trial an orthopaedic robot engineering solution
which has resulted in real translational clinical benefit. With Imperial
software and hardware engineers and surgeons working as a cohesive group,
an entire robotic system for surgical assistance was built. This system
comprised four fundamental technical advances: two software advances; in
robot 3D planning and registration and minimally invasive intra-operative
registration and two hardware developments in robot Active Constraint
boundary control and back-drivable surgical robots. All the work was
carried out in the Mechatronics in Medicine Laboratory under the technical
and academic supervision of Professor Davies and the clinical supervision
of Professor Cobb. In 1999, a spin out company `Acrobot' was formed. The
system was first trialled successfully on humans in 2002 (1). The study
demonstrated that the Acrobot system was successfully used to accurately
register and cut the knee bones in total knee replacement surgery and the
significant potential of a "hands-on" robot for improving accuracy and
increasing safety in surgery.
The first key software achievement seems simple now: to be able to make a
3D model of the bones that comprise the knee joint and to perform virtual
surgery on them, allowing the surgeon to plan and rehearse an operation
accurately (2). The second achievement was the development of an algorithm
by which allowed a low cost computer to co-register the bone model with
the cloud of points derived from touching the bone surfaces (3). This
recent paper discloses a method and algorithm which were shown to improve
by an order of magnitude the intra-operative localisation of the femur,
when performed through a single small incision in the knee. The method is
patented (WO2006048651). This paper forms part of a body of work on
robotic assisted orthopaedic surgery, with a "world-first" in
robotic-assisted unicompartmental knee arthroplasty and further two
licensed patents by the team (WO03043515, WO2007045810).
The key hardware development of a fully back-driveable robotic arm
allowed both enabling and resisting of a surgeons pressure on the
hand-piece, depending on whether the bone in that zone was planned for
removal or not. In addition to feeling this "active constraint" the
surgeon could also see onscreen the position of the tool in relation to
the plan (4).
In 2006, Professor Cobb and colleagues led randomised clinical trial. A
total of 27 patients had a unicompartmental knee arthroplasty operation
performed conventionally or with the assistance of the Acrobot. The
primary outcome measurement was the angle of tibio-femoral alignment in
the coronal plane, measured by CT. The entire Acrobot group had
tibio-femoral alignment in the coronal plane within 2° of the planned
position, while only 40% of the conventional group achieved this level of
accuracy (5). This proved that using robot assisted technology it was
possible for patients to have minimally invasive procedures with 100% of
cases within the 2mm/2° window that was considered desirable. In contrast
the control arm cases had examples of errors of translation and angulation
that were over three times those encountered in the robotic arm (6). The
clinical application of a robot for unicompartmental knee arthroplasty
represents a "world-first" in robotic assisted surgery.
References to the research
(1) Jakopec, M., Harris, S.J., Rodriguez y Baena, F., Gomes, P., Cobb,
J., Davies, B.L. (2001).The first clinical application of a "hands-on"
robotic knee surgery system. Comput Aided Surg., 6 (6), 329-339. DOI. Times cited:
132 (as at 11th November 2013). Journal Impact Factor: 0.78
(2) Harris, S.J., Jakopec, M., Cobb, J., Davies, B.L. (1999).
Intra-operative application of a robotic knee surgery system. Lect
Notes Comput Sc., 1679, 1116-1124. DOI.
Times cited: 6 (as at 11th November 2013 on ISI Web of
Science).
(3) Rodriguez y Baena, F., Hawke, T., Jakopec, M. (2013). A bounded
iterative closest point method for minimally invasive registration of the
femur. Proceedings of the Institution of Mechanical Engineers, Part H:
J. Engineering in Medicine, 227: 1135-1144. DOI.
Times cited: 0 (as at 11th November 2013 on ISI Web of
Science). Journal Impact Factor: 1.48
(4) Davies, B.L., Harris, S.J., Lin, W.J., Hibberd, R.D., Middleton, R.,
Cobb, J. (1997). Active compliance in robotic surgery--the use of force
control as a dynamic constraint. Proceedings of the Institution of
Mechanical Engineers, Part H: J. Engineering in Medicine, 211(4),
285-292. DOI.
Times cited: 32 (as at 11th November 2013 on ISI Web of
Science). Journal Impact Factor: 1.41
(5) Cobb, J., Henckel, J., Gomes, P., Harris, S., Jakopec, M., Rodriguez,
F., Barrett, A., Davies, B.L. (2006). Hands-on robotic unicompartmental
knee replacement: a prospective, randomised controlled study of the
acrobot system. J Bone Joint Surg Br., 88 (2), 188-197. DOI.
Times cited: 46 (as at 11th November 2013 on ISI Web of
Science). Journal Impact Factor: 2.73
Details of the impact
Impacts include: commercial, health and welfare, society
Main beneficiaries: industry, patients and the public
Knee replacement is now the largest surgical industry in the developed
world, with over 80,000 replacements performed last year in England and
Wales, and more than a million performed worldwide with continued growth
predicted for many years. However, it remains more expensive and less
successful than hip replacement. Surgical-error remains a significant
cause of poor outcomes across the field of conventional joint replacement.
The long `learning curve' associated with a less invasive technique such
as partial replacement is a powerful force delaying the adoption of newer,
cheaper yet more effective techniques, hence the drive for technological
assistance.
From the first 27 cases published in 2006 by Imperial surgeons, over
23,000 robot assisted CT-based partial knee replacements have now been
undertaken worldwide [1]. Despite the procedure having a lower
reimbursement than Total Knee Replacement, surgeons are now noticing that
patients want a more conservative approach, and armed with the technology
that enables reliable delivery of a high standard of care, they feel safe
to offer it. The prospects are good for this leading to a substantial
reduction in the cost of delivering appropriate care to patients with
osteoarthritis of the knee. It is estimated that about 50% of all patients
with osteoarthritis of the knee are suitable for this approach [2].
Our technology innovations have had considerable commercial impact. The
Imperial spin-out `Acrobot' was acquired by Stanmore Implants Worldwide in
2010 [3]. The method to improve by an order of magnitude the
intra-operative localisation of the femur, when performed through a single
small incision in the knee (patent: WO2006048651) is incorporated into the
Stanmore Sculptor Robotic Guidance Arm (RGA)[4]. The Stanmore Sculptor RGA
device obtained FDA clearance to be sold into the USA in January 2013 [5].
Following USA 510K acceptance [5], Acrobot technology and patents were
recently purchased by Mako Surgical [6]. Since their first clinical case
in 2006, shortly after our clinical trial was published, almost 25% of
partial joint replacements performed in the USA are now performed with
this approach. The value of the business is in the public domain as
indicated by the purchase of Mako by Stryker for $1.65 billion [7; 2013].
Methods developed by Imperial researchers have also generated a
knowledge-based economy. More than one company has used a method reported
by our group as reliable ways of orienting the tibia [8]. Informally, they
call it the `Cobb' method. Commercial competitors have used this method
for defining the accuracy of their own systems: in 2012 (and prior to the
acquisition of Stanmore Implants Worldwide), Mako surgeons reported their
accuracy, using our method, and then compared their clinical and
radiological outcome to the `gold standard' of robotic accuracy — the
method described by us in 2006 [9]. On the back of this proven clinical
demand for accuracy, planned accurate surgery is now performed in other
ways too: CT-based are now enabling more complex procedures such as the
world's first robot assisted combined replacement and ligament
reconstruction [10]
The programme to use robotic technologies to reconstruct injured soldiers
has now gained the support of the Military, and the DMRC, Headley Court
are discussing with the MSK lab the number of soldiers to be referred
[10]. This marriage of high tech planning, prosthesis manufacture and
robotic reconstruction (BBC1 2013) was another world first [10].
Sources to corroborate the impact
[1] Swank, M.L., Alkire, M., Conditt, M., Lonner, J.H. (2009). Technology
and cost-effectiveness in knee arthroplasty: computer navigation and
robotics. Am J Orthop., 38 (2), 32-36.
[2] Citak, M., Suero, E.M., Dunbar, N.J., Branch, S.H., Conditt, M.A.,
Banks, S.A., et al. (2012). Unicompartmental knee arthroplasty: Is robotic
technology more accurate than conventional technique? The Knee. DOI.
[3] Stanmore sale http://www.sciencebusiness.net/news/74387/Imperial-spin-out-Acrobot-acquired-for-computerised-surgery-system.
Archived on 11th
November 2013.
[4] Contact the Sr. Director of Clinical Research of Mako Surgical to
corroborate the claim
[5] FDA US. 510(k) Premarket Notification of Stanmore Sculptor Robotic
Guidance Arm (2013). http://bir-llc.com/wp-content/uploads/Stanmore-Sculptor-RGA-510k-Clearance.pdf.
Archived
on 11th November 2013.
[6] Mako-Surgical purchase Stanmore Implants Acrobot technology, April
2013
http://ir.makosurgical.com/releasedetail.cfm?ReleaseID=756741
(archived on
11th November 2013)
[7] Stryker buy Mako Surgical Sept. 2013
http://www.bloomberg.com/news/2013-09-25/stryker-to-buy-mako-for-1-65-billion-for-robotic-surgery-1-.html
(archived on
11th November 2013)
[8] Signature knee, Biomet 2010. www.biomet.co.uk/patient/signature
(archived on
11th November 2013)
[9] Mako Surgical Operating Results for 2012/2013
http://ir.makosurgical.com/releasedetail.cfm?ReleaseID=731773.
Archived on 11th
November 2013
[10] New complex surgeries: