Robotic-assisted total hip arthroplasty: a critical appraisal
Robotic Surgery: Research and Reviews
Robotic-assisted total hip arthroplasty: a critical appraisal
Jared M Newman Kaitlin M Carroll Michael B Cross 0
0 Department of Orthopaedic Surgery, Hospital for Special Surgery , New York, NY , USA
Improvements in implant design, surgical technique, and technology have decreased the incidence of complications following a total hip arthroplasty (THA). Robotic-assisted surgery is one technological advance that has improved the reproducibility and accuracy of component placement by customizing the procedure based on the patient's anatomy. However, the learning curve, additional imaging that is required, intraoperative and postoperative complications, and the cost have prevented the widespread use of robotics. The purpose of this systematic review is to analyze two US Food and Drug Administration approved robotic devices (MAKOplasty® and ROBODOC®) that are currently used in THA.
Total hip arthroplasty (THA) is one of the most successful operations in
orthopedic surgery.1 In the United States, it is projected that between the years 2005 and
2030 the number of primary THAs will increase by 174% to 572,000 per year and
the number of revision THAs will increase by 137% to 96,700 per year.2 Recent
research and product development in THA has been directed at improving clinical
outcomes and the survivorship of the prosthesis. A common cause of failure
leading to revision after THA is recurrent instability.1 Related to instability, another
major cause of poor outcomes after THA is impingement, which can lead to implant
dislocation, increased rate of material wear, implant loosening, and pain.3 In order
to reduce the incidence of impingement and instability, product development,
including the introduction of navigation and robotics, has focused on ways of
successfully implanting the femoral and acetabular components in the “safe” position
Robotic assistance in orthopedic surgery is not a new concept, as outcomes research
using robotic surgery has been published for over 20 years. From its inception, robotic
surgery was introduced to improve the accuracy of component positioning, with the
ultimate goal of increasing the surgeon’s reproducibility of performing a THA.6 While
some may argue that the increased imaging and cost associated with robotics is not
justified, proponents of robotics and navigation argue that due to variations in patient
anatomy, placing the acetabular and femoral components in a “standard” position
without robotic planning may lead to inaccurate component position in some patients
with altered anatomy.
Regardless of the robotic system used, studies have shown
that robotic-assisted THAs have better component positioning
and potentially better clinical outcomes than patients who
had a THA with standard instrumentation.6 However, other
studies have demonstrated an increased complication rate and
cost associated with robotic-assisted THA.7,8 Proponents of
robotic-assisted THA argue that despite the increased cost
and complication rate, better long-term results and more
accurate component positioning have been seen with
The purpose of this study was to analyze two different
US Food and Drug Administration (FDA) approved robotic
devices that are currently used in primary THA. We evaluated
1) accuracy of component placement, 2) reproducibility of the
procedure, 3) limb alignment 4) clinical outcomes of THA,
5) and complications associated with robotic-assisted THA.
The f irst active robotic-assisted system designed was
ROBODOC® (Curexo Technology Corporation, Fremont,
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CA, USA). Its development began in 1986 and the first human
study was conducted from 1992 to 1993.22 Prior to surgery,
patients undergo a computed tomography (CT) scan to identify
the patient’s normal anatomy. The CT images are transferred
to a computer system, ORTHODOC® (Curexo Technology
Corporation), which creates 3-dimensional (3-D) images to
allow the surgeon to view the femur concurrently in the axial,
sagittal, and coronal planes. The surgeon preoperatively uses
these computer generated 3-D plans to determine the size of
the prosthesis and its position on the femur.
Intraoperatively, position marking pins are inserted into
the patient’s lower extremity to help guide the robot and
anatomic information is transferred to the ROBODOC®. The
ROBODOC® has a robotic arm with a milling device that
prepares the femoral canal and is used during cementless
THA for preparation of the femoral component with the goal
of decreasing errors in version and sizing.22
The MAKOplasty® navigation system (MAKO Surgical
Corporation, Ft Lauderdale, FL, USA) is an advanced
surgical technique that uses a surgeon-controlled semiactive
robotic-assisted Robotic Arm Interactive Orthopaedic System
(RIO®, MAKO Surgical Corporation). Like the ROBODOC®,
MAKOplasty® requires that patients have a preoperative CT
scan for 3-D preoperative planning based on the patient’s
anatomy. The RIO® system utilizes haptic feedback, providing
proprioceptive information, along with auditory and visual
cues during the operation that guide the surgeon. The Femoral
Enhanced Workflow (Enhanced) requires a cortical array in
the greater trochanter and surface registration of the proximal
femur with a probe array. The Enhanced workflow allows for
a guided neck resection and broach and stem tracking.
During acetabulum reaming, the robot limits the reaming a
surgeon can perform using haptic feedback, preventing the
surgeon from reaming too much bone or improper reaming. During
component positioning, the robotic navigation system confirms
the appropriate acetabular cup version and inclination, femoral
stem version, combined offset, and leg length as compared to
the initial surgical plan. The MAKOplasty® provides an accurate
assessment of reduced hip length and combined offset.
Component positioning and alignment of the femoral and
acetabular components was statistically better with the
robotic-assisted THA with increased precision compared to
control groups (Table 2).9–17 Furthermore, robotic-assisted
THA had more reproducible clinical outcomes with
significantly less limb length variance.7,10,13,14
Overall, the robotic-assisted THA had significantly better
femoral component fit and fill compared to controls.9–12,14,17
Postoperatively the robotic-assisted THA had better lateral
and medial fit with significantly better stem fit and fill
compared to controls; however, Nogler et al20 found that there
was a large amount of motion around the implant in both the
robotic-assisted and control groups, therefore, they found no
statistical difference (Table 3).
Clinical outcomes were reported in nine studies
following robotic-assisted THA compared to control groups
Bargar et al9
Nakamura et al10
Nishihara et al11
Honl et al7
Nishihara et al17
Schulz et al8
Bach et al21
Clinical outcomes of THA
Modified Harris hip scores in robotics vs controls
at 12 months (89.4 vs 86.6) and at 24 months
(88.5 vs 91.1) were not significantly different.
There was no significant difference in the Short
Form 36 scores between the two groups
Robotic group had significantly better Japanese
Orthopaedic Association scores compared to
the control group (P=0.0003)
Robotic group had significantly higher Merle
D’Aubigne hip scores at 2 years postoperatively
compared with controls (P,0.05)
The robotics group had significantly higher Harris
hip scores compared to controls up to 12 months
At 3 months postoperatively no significant
differences were seen in Merle D’Aubigne scores
when compared to preoperative score
The Merle D’Aubigne score significantly
improved (P,0.001); 85% of patients reported
they were satisfied; positive Trendelenberg sign
was found in 17 patients
No statistical difference in gait between the
robotic and control groups at 6 months
postoperatively. Trendelenberg sign found in
five patients in robotic group
(Table 4).7–11,17,21 While some studies demonstrated that
patients who underwent a robotic-assisted THA had
significantly better outcome scores compared to controls, three
studies showed no significant differences.9,17,21
Complication rates following robotic assisted THA
ranged from 0% to 55.5% (Table 3), with seven studies
reporting no complications. While some complications were
directly associated to the robotic-THA such as pains near the
site of pin placement, other complications reported were not
directly associated with the robotic device.
The purpose of this systematic review was to analyze the
literature to determine the clinical outcomes, as well as
the complications associated with robotic-assisted primary
THAs. Overall, robotic-assisted surgery was found to have
more accurate component positioning and better alignment
compared to standard instrumentation; however, while some
studies reported no complications, others reported
complication rates up to 55%.
Several limitations to this study exist that are inherent
in all systematic reviews. The individual studies had varied
methodology, level of evidence, and duration of follow-up.
Most of the studies had small cohorts of patients, with only
a few studies reporting clinical outcomes in a large cohort
of patients. Further, the biases of the individual studies were
inherently transferred to this study.
Based on our review of the literature, our findings
confirm the conclusions reached by other recent studies that
robotic-assisted surgery is more accurate and has improved
reproducibility compared to standard instrumentation for
primary THA. Controversy still exists whether robotic assisted
surgery has improved clinical outcomes; Honl et al7 reported
statistically better Harris hip scores compared to controls;
however, Bargar et al9 found no significant difference in
Modified Harris hip scores or SF-36 (Short Form 36) scores
between the two groups. Further, Bach et al21 did not find any
difference in functional outcome in the robotic group.
Alignment of the femoral and acetabular components was
shown to be statistically superior in the robotic groups.9,11–14,16,17
Correct component positioning and sizing is important for the
success of THA. Lim et al14 reported better anteroposterior
femoral component alignment with the ROBODOC® group
compared to controls (P=0.046). Nishihara et al11 reported
similar results for the anteroposterior alignment (P,0.0001).
Nishihara et al17 compared pre- and postoperative CT images
and found a mean difference of less than 1° in both the
anteroposterior and mediolateral alignment. Domb et al13 reported
results of using the MAKOplasty® and found it was
significantly more likely to obtain correct acetabular cup alignment
(P=0.001), inclination (P=0.004), and anteversion (P=0.002)
compared to controls. The robotic-assisted devices allowed
for increased accuracy and precision for the acetabular cup
to have the correct orientation and center of rotation.13,16 Leg
length variations were significantly less in the robotic group
compared to controls.7,10 The robotic group also had
significantly better precision in alignment and vertical seating than
controls.14 Thus, the advantages of robotic-assisted surgery
include a patient specific preoperative plan based on each
patient’s anatomy, and improved reproducibility and accuracy
in component positioning. In other words, robotic-assisted
surgery may help to decrease human error.16
While robotic-assisted surgery certainly has its
advantages, it also has its disadvantages. In ROBODOC’s initial
design, two to three pins were placed in the greater
trochanter and femoral condyles to serve as position markers.
In one study, it was reported that 55.5% of patients had
severe and persistent medial femoral condyle pain at the
pin site; however, in other studies the incidence of thigh or
knee pin site pain was between 2.6% and 4%.10,15,17,19 As a
result, the system was upgraded to use a surface
identification technique, leading to significantly better clinical scores
and lower complications related to the pins.15 Furthermore,
the ROBODOC® is limited to only assisting with the femoral
component and it does not aid in preparation of the acetabular
portion of the THA. Similarly, other complications related to
robotic-assisted THA have been reported.7–10,15,18 A total of
22 dislocations,7–10,15 eight transient nerve injuries,7–9,15 and
eleven wound infections occurred in the combined cohorts.7,8
Honl et al7 reported a significantly higher dislocation rate,
revision surgery rate, and rate of nerve injury in patients
who had a THA with ROBODOC® compared to the control
group. The higher dislocation rate in this study is especially
concerning, as the purpose of robotics is to reduce the
dislocation rate. Additionally, Schulz et al8 reported similar
results with increased complications in patients who had
a THA using the ROBODOC® including femoral
perforation, damage to the trochanter, and damage to the rim of the
acetabulum. Further, patients must be exposed to an increased
amount of radiation because of the need for a preoperative
CT scan. Also, the operative time is increased (thought to
be due to the learning curve) subjecting the patient to more
anesthesia and theoretically increasing the risk of infection.9
Finally, although not often published in detail, the cost of
the robotic systems can be over a million dollars,23 thereby
preventing worldwide use of robotics in its current form.
The future of robotic-assisted orthopedic surgery is vast.
The concept of using a robot to improve the accuracy of the
position of the components is intriguing to most surgeons
worldwide; however, the cost, the learning curve involved,
and the complications described above may delay its
widespread use. Future robotics will likely use imageless
navigation, and the robotic consoles will be much smaller.
As robotic technology improves over time, it may
eventually lead to widespread use to reduce errors in component
position during THA.
The authors report no conflicts of interest.
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Robotic Surgery: Research and Reviews is an international, peer reviewed,
open access, online journal publishing original research, commentaries,
reports, and reviews on the theory, use and application of robotics in
surgical interventions. Articles on the use of supervisory-controlled
robotic systems, telesurgical devices, and shared-control systems are
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