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Embolic phenomena during computer-assisted and conventional total knee replacement

  • Ashford and St. Peter’s Hospitals NHS Foundation Trust

Abstract and Figures

Systemic emboli released during total knee replacement have been implicated as a cause of peri-operative morbidity and neurological dysfunction. We undertook a prospective, double-blind, randomised study to compare the cardiac embolic load sustained during computer-assisted and conventional, intramedullary-aligned, total knee replacement, as measured by transoesophageal echocardiography. There were 26 consecutive procedures performed by a single surgeon at a single hospital. The embolic load was scored using the modified Mayo grading system for echogenic emboli. Fourteen patients undergoing computer-assisted total knee replacement had a mean embolic score of 4.89 (3 to 7) and 12 undergoing conventional total knee replacement had a mean embolic score of 6.15 (4 to 8) on release of the tourniquet. Comparison of the groups using a two-tailed t-test confirmed a highly significant difference (p = 0.004). This study demonstrates that computer-assisted knee replacement results in the release of significantly fewer systemic emboli than the conventional procedure using intramedullary alignment.
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VOL. 89-B, No. 4, APRIL 2007 481
Embolic phenomena during computer-
assisted and conventional total knee
J. S. Church,
J. E. Scadden,
R. R. Gupta,
C. Cokis,
K. A. Williams,
G. C. Janes
From Perth
Orthopaedic and
Sports Medicine
Centre, Perth,
Western Australia
J. S. Church, BSc, FRCS(Orth),
Locum Consultant Orthopaedic
Department of Orthopaedics
Chelsea & Westminster Hospital,
369 Fulham Road, London SW10
9NH, UK.
J. E. Scadden, FRCS(Orth),
Consultant Orthopaedic Surgeon
St. Mary’s Hospital, Newport, Isle
of Wight PO30 5TG, UK.
R. R. Gupta, FRCS(Orth),
Consultant Orthopaedic Surgeon
St. Peter’s Hospital, Chertsey,
Surrey KT16 0PZ, UK.
C. Cokis, FANZCA, Consultant
Hollywood Hospital, Monash
Avenue, Perth 6009, Western
K. A. Williams, FANZCA,
Consultant Anaesthetist
Mount Hospital, 146 Mounts Bay
Road, Perth 6000, Western
G. C. Janes, FRACS(Orth),
Consultant Orthopaedic Surgeon
Perth Orthopaedic & Sports
Medicine Centre, 31 Outram
Street, West Perth 6005, Western
Correspondence should be sent
to Mr J. S. Church; e-mail:
©2007 British Editorial Society of
Bone and Joint Surgery
18470 $2.00
J Bone Joint Surg [Br]
Received 31 July 2006;
Accepted after revision
19 December 2006
Systemic emboli released during total knee replacement have been implicated as a cause of
peri-operative morbidity and neurological dysfunction. We undertook a prospective,
double-blind, randomised study to compare the cardiac embolic load sustained during
computer-assisted and conventional, intramedullary-aligned, total knee replacement, as
measured by transoesophageal echocardiography. There were 26 consecutive procedures
performed by a single surgeon at a single hospital. The embolic load was scored using the
modified Mayo grading system for echogenic emboli.
Fourteen patients undergoing computer-assisted total knee replacement had a mean
embolic score of 4.89 (3 to 7) and 12 undergoing conventional total knee replacement had a
mean embolic score of 6.15 (4 to 8) on release of the tourniquet. Comparison of the groups
using a two-tailed t-test confirmed a highly significant difference (p = 0.004).
This study demonstrates that computer-assisted knee replacement results in the release
of significantly fewer systemic emboli than the conventional procedure using
intramedullary alignment.
Systemic embolic phenomena are well recog-
nised during total knee replacement (TKR).1-6
They are widely believed to be the cause of
intra-operative hypotension and reduced car-
diac output, which may lead to circulatory col-
lapse and sudden death.7-9 Emboli have been
variously described as consisting of elements of
marrow,2,3 thrombus,1 fat2,10 and bone
particles11 released during preparation of the
femur and tibia.
The advent of transoesophageal echocardio-
graphy (ECG) has enabled the monitoring and
quantification of these emboli, and some stud-
ies have confirmed that techniques of
extramedullary alignment result in a reduced
cardiac embolic load compared with intra-
medullary methods.3,5 Other studies, however,
have found no difference4,6 and suggest that
the emboli are composed of venous thrombus
caused by tourniquet-induced venous stasis.
There have also been concerns about the accu-
racy of existing methods of extramedullary
alignment,12,13 as a result of which most sur-
geons continue to use intramedullary align-
ment rods when performing TKR.
Computer-assisted navigation in TKR is
becoming more popular and has several poten-
tial advantages over conventional procedures.
There is considerable evidence in the literature
that computer navigation results in greater
accuracy and reproducibility by way of
improved alignment and control of rotation.14-16
There is also evidence of a significant reduction
in peri-operative blood loss compared with
conventional techniques.16,17 Computer-
assisted TKR is performed without the use of
intramedullary alignment rods and potentially
may result in fewer embolic complications.
This prospective study was designed to com-
pare the cardiac embolic load during both
computer-assisted and conventional TKR.
Patients and Methods
After approval by the local ethics committee,
patients awaiting primary TKR for osteo-
arthritis were invited to take part in the study.
Exclusion criteria included a history of inflam-
matory arthritis, previous femoral instrumenta-
tion, thromboembolic disease and an
oesophageal disorder. Informed consent was
obtained from 26 consecutive patients who
met the criteria and who were subsequently
blinded as to the method of their knee replace-
Immediately before surgery the patients
were randomised to undergo either con-
ventional TKR using intramedullary alignment
or computer-assisted TKR. Randomisation
was achieved using a computerised random
number generator (Microsoft Excel, Red-
mond, Washington). All procedures were performed with
the use of a tourniquet, applied to the thigh to a pressure of
350 mmHg. The tourniquet was inflated prior to antiseptic
preparation of the skin and deflated after closure and dress-
ing of the incision in all cases. The patients did not receive
peri-operative thromboprophylaxis.
All patients were given a general anaesthetic and
underwent endotracheal intubation before the insertion
of a 5 mHz multiplane transoesophageal ECG probe
(Sequoia Echocardiography Platform C512, Siemens,
Munich, Germany). Continuous recordings from the right
atrium and ventricle began just prior to inflation of the
tourniquet and continued until five minutes after the tour-
niquet was deflated. The exact times of tourniquet inflation,
femoral breach, tibial breach, first cementation and tourni-
quet release were recorded to assist in identifying the cause
of any embolic ‘showers’ which were seen.
All operations were carried out by the senior author
(GCJ). All patients received the same cruciate-retaining
prosthesis (distal cut Genesis II, Smith & Nephew, Mem-
phis, Tennessee) and the patellae were not resurfaced.
Intramedullary femoral and extramedullary tibial align-
ment was used in the conventional TKR group. The fluted
intramedullary rod was inserted through an enlarged
(9.5 mm) femoral entry hole, in accordance with the man-
ufacturer’s instructions. In the computer-assisted group,
femoral and tibial alignment was achieved using the Vec-
torVision navigation system (BrainLAB, Heimstetten,
Germany). This required the percutaneous insertion of
two 3.2 mm threaded pins across the tibial and femoral
canals, on which to secure the reflective sphere arrays. No
further intramedullary instrumentation was necessary.
Two anaesthetists (CC, KAW), with over 20 years’ com-
bined experience in intra-operative transoesophageal ECG,
independently reviewed the videotapes of the ECG images
obtained during each operation. The observers were
blinded as to whether the patient had undergone conven-
tional or computer-assisted surgery. They were asked to
score each embolic event using the modified Mayo Clinic
grading system for echogenic emboli,1,18 which gives a total
score of three to nine points depending on the percentage of
the atrium filled, the duration of echogenesis and the diam-
eter of the largest particles (Table I). Each observer was
asked to review the videotapes a second time approxi-
mately six weeks later.
Before the study it was not known exactly when embolic
showers would be seen and what scores each shower would
achieve. It quickly became apparent that, although a few
small showers were seen intra-operatively, these were insig-
nificant compared with that seen upon release of the tour-
niquet. The small showers were not related to the type of
procedure performed and did not occur at any consistent
point during the operation. We did not observe an increase
in embolic phenomena in any patient at the time of inser-
tion of the intramedullary femoral rod. The decision was
therefore taken to focus our statistical analysis on the
scores obtained when the tourniquet was released.
The mean of the four ‘tourniquet’ scores obtained for
each operation was calculated and the data produced were
statistically analysed using the two-tailed t-test. Intra- and
inter-observer variabilities were assessed using two-way
ANOVA and the paired t-test, respectively.
Complete data were recorded for all 26 patients. There
were 14 patients (ten male, four female) in the computer-
assisted TKR group and 12 (four male, eight female) in the
conventional TKR group. There was no significant differ-
ence between the embolic scores of males or females in
either group. The groups did not differ significantly in age,
weight or body mass index (Table II) and there was no cor-
relation between any of these parameters and the embolic
score. Operation time was significantly longer in the
computer-assisted group by a mean of 17 minutes (mean
operative time: computer-assisted group 74.1 minutes
(60 to 98), conventional group 56.8 minutes (49 to 63))
(p = 0.0003).
Patients undergoing conventional TKR had a mean embo-
lic score of 6.15 (4 to 8) on release of the tourniquet. Those
undergoing computer-assisted TKR had a mean embolic
score of 4.89 (3 to 7). Comparison of the groups using a two-
tailed t-test shows a significant difference (p = 0.004; Fig. 1).
Intra-observer replication had a variance of 0.2, giving a
95% confidence limit of 0.9 units for a single observation.
Analysis of inter-observer variability revealed a significant
difference of 0.48 units between our two scores (p = 0.001).
In 24 (92%) of the cases, the mean scores produced by the
scorers were within one unit of each other.
No emboli larger than 0.5 cm were seen during any of the
operations. There were no significant intra- or post-operative
complications, including wound infection (superficial or
deep), chest infection, pulmonary embolism or deep venous
Embolic score
Fig. 1
Comparison of mean embolic scores in patients undergoing computer-
assisted total knee replacement (CA-TKR) against those undergoing
conventional total knee replacement (TKR).
VOL. 89-B, No. 4, APRIL 2007
This study demonstrates that significantly fewer echogenic
emboli are released into the cardiovascular system during
computer-assisted TKR than in conventional TKR. This
supports the recent study by Kalairajah et al,19 who
observed reduced cerebral emboli detected by transcranial
Doppler ultrasonography in computer-assisted TKR. Their
use of a non-invasive investigation only enabled the detec-
tion of emboli that had passed through the pulmonary
vasculature or bypassed it via a right-to-left shunt (e.g.
patent foramen ovale). The use of the more invasive trans-
oesophageal ECG probe in our study enabled us to confirm
that the true systemic embolic load is also significantly
The insertion of a femoral intramedullary guide was the
only invasive procedure performed during the conventional
TKR that was not undertaken during the computer-assisted
operations. It is therefore reasonable to assume that this
was the cause of the increased embolic load. This assump-
tion is supported by the findings of Morawa et al,5 who
observed significantly fewer emboli when using an
extramedullary femoral alignment guide. They found a
similar but less significant effect when comparing
extramedullary and intramedullary techniques of tibial
alignment. Markel et al3 similarly concluded that intramed-
ullary guides increase the generation of debris in dogs.
Takahashi, Kitagawa and Ishii20 observed moderate to
severe embolic events in 80% of patients undergoing instru-
mented spinal surgery but none in non-instrumented
patients, and Duwelius et al,10 when performing intra-
medullary nailing on sheep femora, found that the opera-
tive manoeuvre associated with the greatest embolic release
was opening the intramedullary canal with an awl. This evi-
dence would appear to support the theory that embolic
release is directly proportional to the degree of violation of
the femoral canal.
In 1995, however, Parmet et al6 found that there was no
significant difference in the number of large venous emboli
seen when performing intramedullary- and extramedullary-
aligned TKR. In a later study,4 they stated again that
marrow cavity invasion is not correlated to the release of
large emboli, but that use of a tourniquet increases the risk
fivefold. They were the first to suggest that there were dif-
ferent types of embolus.21 Small ‘miliary’ emboli, presum-
ably consisting of elements of marrow, are seen in all TKRs,
but may be more likely to occur with intramedullary
instrumentation. They suggest that large emboli occur
regardless of femoral instrumentation. These are responsi-
ble for producing the intense physiological response which
may lead to circulatory collapse, and appear to be related to
the use of a tourniquet. They suggested that these emboli
consist of venous thrombus caused by tourniquet-induced
stasis.6 A further study by Berman et al1 at the same insti-
tution found that the pulmonary vascular resistance index
increased after release of the tourniquet only in patients
who had echogenic material of at least 0.5 cm in diameter.
Blood aspirated from pulmonary artery catheters in these
patients was found to contain fresh venous thrombus. It is
worth noting that no emboli larger than 0.5 cm in diameter
were seen in our study, despite the use of a tourniquet.
The clinical relevance of our study is based on the premise
that there is a relationship between echogenic emboli and
peri-operative morbidity. In 1997, Lafont et al22 found no
correlation between frequency or size of embolic particles
and blood gas and haemodynamic variables (heart rate,
arterial blood pressure and central venous pressure) during
total hip replacement. The majority of published articles
disagree with this finding, however. Christie et al7 found
that pulmonary responses correlated with the severity of
embolic phenomena during invasive intramedullary pro-
cedures in humans, and Wheelwright et al8 observed that
hypotension and decreased cardiac output were directly
Table I. The modified Mayo Clinic grading system for echogenic emboli1
Score % filling of right atrium Duration of echogenesis (seconds) Diameter of largest particle (cm)
1< 50 < 25 < 0.5
250 to 75 25 to 35 0.5 to 1.0
3> 75 > 35 > 1.0
Table II. Mean (range) differences between the two groups and their significance
Age in yrs 62.3 (52 to 75) 67.1 (54 to 80) 0.18 (NS)
Weight in kg 91.8 (68 to 116) 82.2 (66 to 110) 0.10 (NS)
Body mass index in kg/m231.6 (23.5 to 40.2) 29.6 (23.4 to 43.0) 0.37 (NS)
Operation time in minutes 74.1 (60 to 98) 56.8 (49 to 63) 0.0003
Embolic score 4.89 (3 to 7) 6.15 (4 to 8) 0.004
* CA-TKR, computer-assisted total knee replacement
† TKR, total knee replacement
‡ NS, not significant
related to the magnitude of pulmonary embolism in dogs
undergoing bilateral cemented arthroplasty.
Kim2 took blood from the right atrium of patients under-
going TKR and found a significant increase in the number
of fat emboli 5 to 10 minutes after insertion of the femoral
alignment rod. In 12% of patients undergoing bilateral
TKR and 4% of those undergoing unilateral TKR there
were also bone marrow cells in the blood samples. These
patients had significantly lower arterial oxygen tension and
oxygen saturation on the first post-operative day than did
those without marrow cells in the samples. This not only
provides direct evidence of a measurable clinical response
resulting from embolism, but also suggests that embolic
content is as important as size.
Kim2 also showed that patients undergoing bilateral
TKR have a significantly increased risk of fat and marrow
embolism compared with those undergoing unilateral
TKR. This finding is supported by Dorr et al,23 who quote
a 12% incidence of fat embolism during bilateral TKR
which most often manifests as a change of mental status.
They suggest that a sustained fall in oxygen saturations
below 90% would be an indication to abort the second
knee arthroplasty. Bullock, Sporer and Shirreffs24 and
Oakes and Hanssen25 also found an increase in cardio-
vascular and neurological complications following bilateral
rather than unilateral TKR. Our finding of a significant
reduction in systemic embolic load with the use of
computer-assisted TKR would appear to support its use in
these potentially high-risk surgical procedures. Similar con-
clusions could be applied to patients with a patent foramen
ovale, which may be as many as 25% of the population
according to post-mortem studies.26
One potential weakness of this study is the quantification
of emboli with real-time ultrasound. We have used previ-
ously published techniques and methods of assessment, but
the true embolic load cannot be accurately quantified with
any currently known technique. However, scoring of embo-
lic showers using real-time ultrasound remains the best
means of comparative assessment of these phenomena. It is
our opinion that the scores obtained are at least propor-
tional to the embolic insult.
Another potential weakness of this study, and all studies
quantifying intra-operative cardiac embolic phenomena, is
that there are no data on what constitutes a ‘safe’ embolic
load. Although we are able to prove a statistically signific-
ant observed decrease in embolic phenomena when using
computer-assisted TKR, we cannot prove that this equates
to a clinically significant decrease. It is likely that there is
considerable inter-individual variation in the embolic
threshold, beyond which pathophysiological cardio-
pulmonary responses develop. It is also likely that this
threshold is reduced in the significant proportion of elderly
patients undergoing TKR who have reduced cardiopulmo-
nary reserve. Given that Kim2 has demonstrated that embo-
lic insult can result in measurable pathophysiological
responses, we feel that the responsible surgeon should pur-
sue all means to reduce this, provided the surgical outcome
is not compromised.
Analysis of the scoring system itself has revealed minimal
intra-observer variability. Although there was a statistically
significant inter-observer difference, this equated to fewer
than 0.5 units per patient. Our figure of 92% agreement or
disagreement within one unit between observers exactly
matches the figure of Ereth et al,18 who developed the scor-
ing system.
A further concern with this study is the relatively few
patients in each group. A visible difference in the quantity
of emboli and the duration of the showers was obvious
soon after commencement of the study, however, and statis-
tical significance was reached after ten patients. A further
16 patients were entered into the study to reduce the risk of
a type I error but, in view of the increasingly significant dif-
ference the study was abandoned and the senior author
(GCJ) reverted to performing solely computer-assisted
As one might expect, this study demonstrated a moderate
increase in the operative time when performing computer-
assisted TKR, as reported in previous studies.16,27 We did
not encounter any problems associated with this, however,
and it is our opinion that this increase is more than com-
pensated for by the improved accuracy, reproducibility and
margin of safety provided by this particular surgical tech-
This study demonstrates that computer-assisted TKR
results in significantly fewer systemic embolic events than
conventional TKR using intramedullary alignment. This is
likely to reduce the risk of peri-operative cardiovascular
complications and post-operative neurological dysfunction.
In the light of recent studies confirming improved accuracy
and reproducibility, as well as reduced blood loss, this
would appear to add to the growing list of compelling argu-
ments in favour of computer-assisted TKR.
We wish to thank Echo Services (Hollywood Specialist Centre, Nedlands, Perth,
Western Australia) for providing the transoesophageal echocardiographic
equipment and Mr Livio Mina for his assistance with the statistical analysis.
No benefits in any form have been received or will be received from a com-
mercial party related directly or indirectly to the subject of this article.
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Supplementary resource (1)

... 7 CATKAs have also been associated with a reduced risk of developing pulmonary emboli and lower rates of postoperative cardiac complications and hematomas. [8][9][10] Both image-based and imageless CATKAs were found to reduce in-hospital complications and reduce transfusion risk without markedly increasing hospital length of stay and costs. 11 However, most of these studies were conducted in small institutions where sample sizes were relatively small and, as a result, may not be generalizable to the broader cohort of patients having TKAs. ...
... Moreover, the few published cohort-based studies were conducted using International Classification of Diseases, Ninth Revision (ICD-9) data, which lack the clinical specificity of ICD-10 and are not reflective of utilization in recent years. [8][9][10][11][12][13] In a recently published study spanning 2010 to 2017, a modest increase in the adoption of CATKAs was observed, potentially driven by better patient outcomes. 14 To our knowledge, however, the relationship between CATKAs and patient outcomes in the ICD-10 era remains understudied. ...
... The primary variable of interest was the use of computerassisted navigation technology. [8][9][10][11][12][13][14] Covariates included age 21 and insurance type, 22 as well as the Charlson Comorbidity Index, which was applied to clinical comorbidity data to calculate a measure of disease burden. [23][24][25] Race/ethnicity was also included as a covariate because of its known effect on patient access and other outcomes. ...
Full-text available
Background: Population-based studies showing the advantage of computer-assisted total knee arthroplasty (CATKA) over conventional total knee arthroplasty (TKA) are outdated. More recent institution-based studies with relatively small sample sizes may hinder wider adoption. This cohort-based study aimed to compare postoperative CATKA and TKA in-hospital complications and 90-day all-cause readmissions using 2017-2018 data. Methods: Patients who underwent a primary unilateral CATKA or TKA were identified in the New York Statewide Planning and Research Cooperative System database. In-hospital complications were defined based on the 2020 Centers for Medicare & Medicaid Services total hip arthroplasty and TKA complications measure. Ninety-day readmissions were identified using unique patient identifiers. Logistic regression with a generalized estimating equation was used to assess associations of computer assistance with in-hospital complications and 90-day all-cause readmissions. Results: A total of 80,468 TKAs were identified during the study period, of which 7,395 (9.2%) were CATKAs. Significantly fewer complications occurred among patients who had CATKAs compared with conventional TKAs (0.4% of total CATKAs vs 2.6% of total conventional TKAs, P < 0.001); patients who had CATKAs had fewer 90-day all-cause readmissions compared with those who underwent TKAs (363 vs 4,169 revisits, P < 0.01). Computer assistance was associated with significantly lower odds of in-hospital complications (odds ratio, 0.15, 95% confidence interval, 0.09 to 0.24; P < 0.05) but not 90-day all-cause readmissions. Conclusion: Patients undergoing CATKAs had markedly lower odds of in-hospital complications, compared with patients having TKAs, which has implications for both patient outcomes and hospital reimbursement. These more recent cohort-based findings encourage wider CATKA adoption.
... The exclusion criteria included patients with diagnosed chronic or acute DVT preoperatively, patients with no postoperative computed tomographic venography (CTV) and patients with active bleeding, documented congenital or acquired bleeding disorders such as end-stage renal disease (ESRD), Von Willebrand disease, hemophilia, inflammatory diseases such as rheumatoid arthritis or secondary osteoarthritis. Computer-assisted surgeries such as navigation-or robot-assisted TKAs were also excluded since TKA without intramedullary instrumentation may affect the prevalence of postoperative DVT [13,14]. In addition, patients who had used anticoagulant before surgery for the treatment of various cardiovascular diseases such as myocardial infarction and ischemic stroke were excluded from this study. ...
... However, the study performed with some bias; small sample size with insufficient power, including computer-assisted TKA, which might affect the prevalence since it did not invade femoral intramedullary canal and including various preoperative diagnoses for TKA. Current study had sufficient sample size (more than 400 cases in each group) and included only conventional surgical technique [13,14]. ...
Introduction: Purpose of this study was to assess whether the intermittent pneumatic compression (IPC) device would be an effective prophylaxis for deep vein thrombosis (DVT) following total knee arthroplasty (TKA) in a low incidence population. Hypothesis: The mechanical thromboprophylaxis could reduce the incidence of DVT compared to non-prophylaxis group and would have similar efficacy as the chemoprophylaxis following TKA in a low DVT incidence population. Materials and methods: From January 2009 to June 2016, 1259 elective primary TKA with preoperative diagnosis of primary osteoarthritis in a single institute were enrolled. Patients were divided into three groups: those who were managed with chemoprophylaxis (CPX group, 414 cases), with mechanical prophylaxis (IPC group, 425 cases), or without pharmacological and mechanical prophylaxis (control group, 420 cases). All patients underwent preoperative ultrasonography and computed tomographic venography on postoperative day 6 to assess development of DVT. The incidence of overall, proximal, symptomatic DVT and symptomatic pulmonary embolism (PE) were compared among the groups. Major and minor bleeding complications were also evaluated. Results: The incidence of overall DVT was 14.8% in control group, 6.3% in CPX group and 11.3% in IPC group respectively and CPX group showed significantly lower incidence than other two groups (p<0.001). The incidence of proximal DVT was 1.9% in control group, 0.7% in CPX group and 0.9% in IPC group respectively (p>0.05). The incidence of symptomatic DVT was 0.7% in control group, 0% in CPX group and 0.7% in IPC group respectively (p>0.05). There was no case of symptomatic PE diagnosed during hospital stay in all patients. Discussion: Single use of IPC device could not reach significant level of DVT prophylaxis compared to control group and only chemoprophylaxis showed significantly reduce the incidence of overall DVT following TKA. Single use of IPC device does not show effective thromboprophylaxis in a low DVT incidence population. Level of evidence: III, case control study.
... Image-based systems use preoperative radiology, while image-free systems involve collecting and registering information intraoperatively [5]. CNTKA has been associated with lower blood loss [15][16][17][18], lower revision rates [19] and less systemic emboli [20][21][22] than mTKA. It is associated with a higher likelihood of satisfactory alignment in the postoperative period and at five- [5,23,24] and eight- [25] year follow-up. ...
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Background Robotic (RTKA) and computer-navigated total knee arthroplasty (CNTKA) are increasingly replacing manual techniques in orthopaedic surgery. This systematic review compared clinical outcomes associated with RTKA and CNTKA and investigated the utility of natural language processing (NLP) for the literature synthesis.MethodsA comprehensive search strategy was implemented. Results of included studies were combined and analysed. A transfer learning approach was applied to train deep NLP classifiers (BERT, RoBERTa and XLNet), with cross-validation, to partially automate the systematic review process.Results52 studies were included, comprising 5,067 RTKA and 2,108 CNTKA. Complication rates were 0–22% and 0–16% and surgical time was 70–116 and 77–102 min for RTKA and CNTKA, respectively. Technical failures were more commonly associated with RTKA (8%) than CNTKA (2–4%). Patient satisfaction was equivalent (94%). RTKA was associated with a higher likelihood of achieving target alignment, less femoral notching, shorter operative time and shorter length of stay. NLP models demonstrated moderate performance (AUC = 0.65–0.68).ConclusionsRTKA and CNTKA appear to be associated with similarly positive clinical outcomes. Further work is required to determine whether the two techniques differ significantly with regard to specific outcome measures. NLP shows promise for facilitating the systematic review process.
... Extramedullary devices are surgeon dependent while intramedullary jigs are unsuitable when there is abnormal bony anatomy. Furthermore, intramedullary jigs are invasive, breaching the femoral and tibial canals, increasing medullary pressure, which can lead to increased embolic events [5,6] . ...
... The role of robotic-and computer-assisted orthopedic (RCAOS) technologies in this new paradigm of episodic-based reimbursements and cost-efficiency has yet to be established. RCAOS technologies have the potential to improve outcomes through improved component positioning and soft tissue balance in TKA while reducing blood loss and systemic emboli release [5,6]. When integrated into a coordinated, evidence-based clinical care pathway, intraoperative robotic assistance may demonstrate increased value through the abovementioned benefits. ...
To gain widespread acceptance, robotic-assisted surgery must add value to total joint arthroplasty by demonstrating improved outcomes and reduced overall costs associated with the episode of care. We review the surgical technique as well as clinical and economic results associated with the introduction of a commercially available robotic-assisted total knee arthroplasty system (OMNIBotics®) in both an academic teaching and a community hospital setting. Clinical results demonstrate highly accurate and reproducible component placement and overall leg alignment, high patient satisfaction and knee functional outcomes as measured by the new Knee Society and KOOS scores, as well as a shortened length of stay and reduced 90-day readmission rates and overall episode of care costs when compared with manual intramedullary-based instrumentation.
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Objectives This study aims to compare early mortality after total knee arthroplasty (TKA) using conventional intramedullary instrumentation to TKA performed using technology-assisted (non-intramedullary) instrumentation. Design Comparative observational study. Using data from a large national registry, the 30-day mortality after unilateral TKA performed for osteoarthritis was compared between procedures using conventional instrumentation and those using technology-assisted instrumentation. Firth logistic regression was used to calculate ORs, adjusting for age, sex, use of cement and procedure year for the whole period, and additionally adjusting for American Society of Anesthesiologists physical status classification system class and body mass index (BMI) for the period 2015 to 2019. This analysis was repeated for 7-day and 90-day mortality. Setting National arthroplasty registry. Participants People undergoing unilateral, elective TKA for osteoarthritis from 2003 to 2019 inclusive. Interventions TKA performed using conventional intramedullary instrumentation or technology-assisted instrumentation. Main outcome measures 30-day mortality (primary), and 7-day and 90-day mortality. Results A total of 581 818 unilateral TKA procedures performed for osteoarthritis were included, of which 602 (0.10%) died within 30 days of surgery. The OR of death within 30 days following TKA performed with conventional instrumentation compared with technology-assisted instrumentation, adjusted for age, sex, cement use, procedure year, American Society of Anesthesiologists and BMI was 1.72 (95% CI, 1.23 to 2.41, p=0.001). The corresponding ORs for 7-day and 90-day mortality were 2.21 (96% CI, 1.34 to 3.66, p=0.002) and 1.35 (95% CI, 1.07 to 1.69, p=0.010), respectively. Conclusions The use of conventional instrumentation during TKA is associated with higher odds of early postoperative death than when technology-assisted instrumentation is used. This difference may be explained by complications related to fat embolism secondary to intramedullary rods used in conventional instrumentation. Given the high number of TKA performed annually worldwide, increasing the use of technology-assisted instrumentation may reduce early post-operative mortality.
The acronym for computer-assisted orthopaedic surgery is CAOS, CAS stands for computer-assisted surgery (CAS).
Fat embolism syndrome (FES) is a rare, but potentially devastating complication of cemented total knee arthroplasty. It is characterized by hypoxia, hypotension, cardiac arrhythmias, increased pulmonary vascular resistance, and occasionally cardiac arrest that occur when the marrow contents are manipulated during surgery. The pathophysiology is not well understood and both mechanical and biochemical theories have been proposed. The diagnosis is one of exclusion, and treatment remains supportive with oxygen and aggressive fluid resuscitation. Because of these gaps in our knowledge of pathophysiology, there is an enormous focus on prevention. In knee arthroplasty, this includes suctioning the femoral canal prior to inserting the guide rod, use of computer navigation to avoid instrumenting the medullary spaces, and even prophylactic use of corticosteroids preoperatively. There is significant room for further research into strategies to prevent this potentially debilitating syndrome.
Objective: To summarize the research progress of the causes and prevention methods of anterior femoral notching in total knee arthroplasty (TKA). Methods: The related literature at home and abroad about the causes and prevention methods of the anterior femoral notching in TKA was extensively reviewed and summarized. Results: The reasons for the occurrence of anterior femoral notching can be summarized as follows: the application of the posterior reference technique, the increase of the posterior condylar angle, the variant anatomical shape of anterior femoral cortex, the selective reduction of the femoral prosthesis size, backward movement of the entrance point, and the application of computer-assisted navigation technology or patient-specific instrumentation. To prevent the occurrence of anterior femoral notching, programs such as flex the femoral prosthesis, robot-assisted technology, and anterior and posterior reference techniques combination can be used. Conclusion: Anterior femoral notching is a common surgical complication of TKA. A complete preoperative plan, assessment of the patient's knee joint condition, and development of a reasonable surgical plan can effectively reduce the occurrence of anterior femoral notching.
Objective: To discuss the feasibility and accuracy of distal femoral patient-specific cutting guide in total knee arthroplasty (TKA) based on knee CT and full-length X-ray film of lower extremities. Methods: Between July 2016 and February 2017, 20 patients with severe knee joint osteoarthritis planned to undergo primary TKA were selected as the research object. There were 9 males and 11 females; aged 53-84 years, with an average of 69.4 years. The body mass index was 22.1-31.0 kg/m 2, with an average of 24.8 kg/m 2. The preoperative range of motion (ROM) of the knee joint was (103.0±19.4)°, the pain visual analogue scale (VAS) score was 5.4±1.3, and the American Hospital of Special Surgery (HSS) score was 58.1±11.3. Before operation, a three-dimensional model of the knee joint was constructed based on the full-length X-ray film of lower extremities and CT of the knee joint. The distal femoral patient-specific cutting guide was designed and fabricated, and the thickness of the distal femoral osteotomy was determined by digital simulation. The thickness of the internal and external condyle of the distal femur osteotomy before operation and the actual thickness of the intraoperative osteotomy were compared. The intraoperative blood loss, postoperative drainage loss, and hidden blood loss were recorded. The ROM of knee joint, VAS score, and HSS score at 3 months after operation were recorded to evaluate effectiveness. The position of the coronal and sagittal plane of the distal femoral prosthesis were assessed by comparing the femoral mechanical-anatomical angle (FMAA), anatomical lateral distal femoral angle (aLDFA), mechanical femoral tibial angle (mFTA), distal femoral flexion angle (DFFA), femoral prosthesis flexion angle (FPFA), anatomical lateral femoral component angle (aLFC), and the angle of the femoral component and femoral shaft (α angle) between pre- and post-operation. Results: TKA was successfully completed with the aid of the distal femoral patient-specific cutting guide. There was no significant difference between the thickness of the internal and lateral condyle of the distal femur osteotomy before operation and the actual thickness of the intraoperative osteotomy ( P>0.05). All patients were followed up 3 months. All incisions healed by first intention, and there was no complications such as periarticular infection and deep vein thrombosis. Except for 1 patient who was not treated with tranexamic acid, the intraoperative blood loss of the rest 19 patients ranged from 30 to 150 mL, with an average of 73.2 mL; the postoperative drainage loss ranged from 20 to 500 mL, with an average of 154.5 mL; and the hidden blood loss ranged from 169.2 to 1 400.0 mL, with an average of 643.8 mL. At 3 months after operation, the ROM of the knee was (111.5±11.5)°, and there was no significant difference when compared with the preoperative one ( t=-1.962, P=0.065). The VAS score was 2.4±0.9 and HSS score was 88.2±7.5, showing significant differences when compared with the preoperative ones ( t=7.248, P=0.000; t=-11.442, P=0.000). Compared with the preoperative measurements, there was a significant difference in mFTA ( P<0.05), and there was no significant difference in aLDFA, FMAA, or DFFA; compared with the preoperative plan, there was no significant difference in FPFA, aLFC, or α angle ( P>0.05). Conclusion: The use of distal femoral patient-specific cutting guide based on knee CT and full-length X-ray film of lower extremity can achieve precise osteotomy, improve coronal and sagittal limb alignment, reduce intraoperative blood loss, and obtain satisfactory short-term effectiveness.
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Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty (TKA). Recent developments in computer-assisted surgery have focused on systems for improving TKA. In a prospective study two groups of 80 patients undergoing TKA had operations using either a computer-assisted navigation system or a conventional technique. Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films. The mechanical axis of the leg was significantly better in the computer-assisted group (96%, within ±3° varus/valgus) compared with the conventional group (78%, within ±3° varus/valgus). The coronal alignment of the femoral component was also more accurate in the computer-assisted group. Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation.
We undertook a prospective, randomised study of 135 total knee arthroplasties to determine the most accurate and reliable technique for alignment of the tibial prosthesis. Tibial resection was guided by either intramedullary or extramedullary alignment jigs. Of the 135 knees, standardised postoperative radiographs suitable for assessment were available in 100. Correct tibial alignment was found in 85% of the intramedullary group compared with 65% of the extramedullary group (p = 0.019). We conclude that intramedullary guides are superior to extramedullary instruments for alignment of the tibial prosthesis.
Comment: It is well known that total hip and knee arthroplasty procedures are associated with increases in pulmonary vascular resistance (PVR). Previous studies have implicated the cement itself or, more likely, fat emboli associated with the increase in intramedullary pressure on inserting the prosthesis. This is an interesting study, which demonstrates that thrombus formation is also an etiology for increased PVR. The timing of the increase in PVR was associated with tourniquet deflation and the release of large echogenic masses. The increase in PVR was unrelated to metabolic changes. It would be interesting to know if such thrombi occur in other procedures in which a lower or upper extremity tourniquet is used. (C) Williams & Wilkins 1995. All Rights Reserved.
During total knee arthroplasty (TKA), instrumentation of the marrow cavity with an intramedullary guide appears responsible for fatal intraoperative pulmonary embolism.Transesophageal echocardiography demonstrates venous emboli (VE) after tourniquet deflation during intramedullary guided TKA. Extramedullary guides avoid manipulating the marrow cavity. We determined the incidence of VE in 20 patients undergoing extramedullary guided TKA. Recordings of hemodynamic variables, mixed venous oximetry, end-tidal CO2 and N2 tensions, and echocardiograph images occurred after induction of anesthesia, after tourniquet inflation, during cementing, and for 15 min after tourniquet deflation. Large VE appeared in 14 patients and small VE in the other 6 patients. Large VE occurred only after deflation of the tourniquet. Beginning 3 min after tourniquet deflation, mean pulmonary arterial pressures increased from the baseline of 21 +/- 1.0 to 30 +/- 1.3 mm Hg and remained increased for the duration of the procedure. The incidence of large VE with extramedullary guided TKA did not differ compared to the previously reported incidence with intramedullary guided TKA. These data suggest that VE might arise from a thrombogenic effect of the tourniquet rather than from manipulation of the marrow cavity. (Anesth Analg 1995;81:757-62)
We have compared a new technique of computer-assisted knee arthroplasty with the current conventional jig-based technique in 70 patients randomly allocated to receive either of the methods. Post-operative CT was performed according to the Perth CT Knee Arthroplasty protocol and pre- and post-operative Maquet views of the limb were taken. Intra-operative and peri-operative morbidity data were collected and blood loss measured. Post-operative CT showed a significant improvement in the alignment of the components using computer-assisted surgery in regard to femoral varus/valgus (p = 0.032), femoral rotation (p = 0.001), tibial varus/valgus (p = 0.047) tibial posterior slope (p = 0.0001), tibial rotation (p = 0.011) and femorotibial mismatch (p = 0.037). Standing alignment was also improved (p = 0.004) and blood loss was less (p = 0.0001). Computer-assisted surgery took longer with a mean increase of 13 minutes (p = 0.0001).
Intraoperative pulmonary fat and bone-marrow embolism is a serious complication of bone and joint surgery. We have investigated the occurrence and incidence of intraoperative embolism in patients undergoing elective lumbar spinal surgery with or without instrumentation. Sixty adult patients with lumbar degenerative disease were examined by intraoperative transoesophageal echocardiography while undergoing posterior lumbar surgery. Of these, 40 underwent surgery with instrumentation and 20 without. Moderate to severe (grade 2 or 3 according to the grading scale of Pitto et al) embolic events were seen in 80% of the instrumented patients but in none of the non-instrumented patients (p < 0.001). The insertion of pedicle screws was particularly associated with large numbers of pulmonary emboli, while the surgical approach, laminectomy, disc removal and bone harvesting were associated with small numbers of emboli. We consider that, as in arthroplasty and intramedullary fixation of fractures, these embolic events are relevant to the development of potentially fatal fat embolism during spinal surgery.
The right atrium and the right ventricle of fifty-five patients were imaged with transesophageal echocardiography during fifty-nine total knee arthroplasties performed with cement and the use of general anesthesia. The patients ranged in age from thirty-two to eighty-three years (mean, 65.5 years). Cardiopulmonary parameters were measured with use of hemodynamic monitoring systems, such as pulse oximeters, pulmonary artery catheters, and radial artery catheters. In addition, a femoral vein catheter was inserted on the side of the operation in ten of the fifty-five patients. Showers of echogenic material traversing the right atrium, the right ventricle, and the pulmonary artery after the tourniquet was deflated were observed to various degrees in all patients and lasted three to fifteen minutes. The mean peak intensity occurred within thirty seconds (range, twenty-four to forty-five seconds) after the tourniquet was released. The mean mixed venous oxygen saturation (and standard error of the mean) decreased (from 83+/-0.9 to 72+/-1.5 per cent) and the mean pulmonary arterial pressure increased (from 20+/-1.0 to 27+/-1.0 millimeters of mercury [2.67+/-0.13 to 3.60+/-0.13 kilopascals]), compared with the values before the tourniquet was released, in all patients. The pulmonary vascular resistance index increased after release of the tourniquet (to a maximum of 328+/-29; p = 0.00002) only in the patients who had echogenic material that was at least 0.5 centimeter in diameter. Clinical pulmonary embolism developed postoperatively in three patients; all three had had echogenic particles that were more than 0.5 centimeter in maximum diameter on imaging. Blood aspirated from one of the pulmonary artery catheters and from five of the ten femoral vein catheters demonstrated fresh venous thrombus. Histological evaluation of the aspirates failed to demonstrate fat, marrow, or particles of polymethylmethacrylate. Surgeons should consider acute pulmonary embolism as a diagnosis when evaluating a patient who has hemodynamic collapse during total knee arthroplasty performed with cement.
Bone cement implantation syndrome is characterized by hypotension, hypoxemia, cardiac arrhythmias, cardiac arrest, or any combination of these complications. It may result from venous embolization that occurs in conjunction with intramedullary hypertension in the femur during insertion of the prosthesis in patients undergoing cemented total hip arthroplasty (THA). Intramedullary hypertension does not occur in patients undergoing noncemented THA. In this study, we sought to compare embolization between patients undergoing cemented and noncemented THA and to determine whether this state resulted in cardiorespiratory deterioration. In this prospective investigation of 35 patients undergoing elective THA, we used transesophageal echocardiography and invasive hemodynamic monitoring, and in 12 of them, we monitored distribution of pulmonary ventilation and perfusion intraoperatively. Embolization was significantly greater after insertion of the prosthesis in patients undergoing cemented than in those undergoing noncemented THA. Cemented THA was also associated with decreased cardiac output and increased pulmonary artery pressure and pulmonary vascular resistance. Increases in ventilation-perfusion mismatching, however, could not be demonstrated 30 minutes after insertion of the femoral prosthesis. Intraoperative monitoring for embolism may help physicians assess patients in whom cardiorespiratory function deteriorates during THA.