Appendix 1: Summary of Visionscope Imaging System (VSI) versus MRI plus
clinical workup
Materials & Methodology:
A prospective multicenter study was performed of all patients who had a routine surgical
arthroscopy at one of the six participating clinical sites between July 2012 and May 2013.
Patients were consented by the physician investigator at each site. Study inclusion criteria
consisted of suspected meniscal tears or articular cartilage damage. Patients were
excluded from the study if they had (1) acute traumatic hemarthoses, (2) concomitant
ligament injury, (3) active systemic infection, (4) allergy to silicone or any medication
used during the procedure, (5) enrollment in another pharmacological or medical device
study, (6) institutionalized persons, prisoners and persons with decisional incapacity, or
(7) investigators own students and employees. All patients had a MRI and a
comprehensive physical exam prior to their surgical arthroscopy.
Patients were identified based on presentation of knee symptoms including effusion,
popping, locking and were prescribed a pre-operative diagnostic MRI for the purpose of
determining whether arthroscopic surgery may be necessary. Subjects were otherwise in
good health based on their medical history and physical examination. Prior to each
arthroscopy, physicians performed a VSI procedure. Surgeons were asked to record and
capture images during the VSI procedure on a standardized data collection form. After
the completion of the VSI procedure, a standard surgical arthroscopy was performed.
During the standard arthroscopy, Surgeon’s were asked to capture images and video.
Each was asked to provide a copy of the MR images, a completed arthroscopy case report
form [CRF], a completed VSI CRF, diagnostic arthroscopy images and VSI images.
1
The VSI and MRI images were reviewed by two blinded experts, an orthopedic surgeon
unaffiliated with the study sites and a musculoskeletal radiologist. These experts were
blinded to radiological readings and surgical notes. In addition, the images were reviewed
in a randomized order with separate readings. The diagnostic arthroscopy served as the
gold standard for comparison between the VSI and MRI images. Analyses were
performed separately for the Surgeon’s assessments, and the blinded reader’s
assessments. It was not considered appropriate to compare a blinded reader’s assessment
of an MRI, to the Surgeon’s assessment of arthroscopy, since the quality of the images
for the two could be quite different. Therefore, all analyses were done twice, once using
Surgeon’s assessments, and once using the Blinded Reader’s assessments. The primary
comparisons with MRI were with the Blinded Reader assessments. The primary
comparisons for VSI versus arthroscopy were done with the Surgeon’s assessments [i.e.
the Surgeon who had performed the actual VSI and surgical arthroscopy] (based on
CRFs).
Statistical analysis
All statistical analysis was completed by the author (JV). Comparisons were made using
the Cochrane Review statistical packages for diagnostic test1 and included: risk ratios
(probability of an incorrect event [a FP or FN] with VSI versus MRI; or the relative risk
reduction in an incorrect event with one diagnostic versus another) (Table 1); sensitivity,
specificity and accuracy analysis (Table 2); and receiver operating characteristic (ROC)
curves (Figures 1-6). ROC curves are a graph of the sensitivity versus the specificity. The
best possible diagnostic result (when compared to the gold standard of surgical
2
arthroscopy) would yield a point in the upper left corner or coordinate (1,1) of the ROC
space, representing 100% sensitivity (no false negatives) and 100% specificity (no false
positives).
Table 1: Risk ratios
Comparison
Medial meniscal tears
Risk ratio
RR =0.27; 95% CI
[0.11-0.68]
P value
P = 0.005
Lateral meniscus tears
RR = 0.41; 95% CI
[0.19-0.90]
P =0.03
Medial tibial articular
cartilage tears
RR = 0.18; 95% CI
[0.08-0.41]
P<0.0001
Lateral tibial articular
cartilage tears
RR = 0.25; 95% CI
[0.13-0.47]
P<0.0001
Medial femoral
articular cartilage
tears
RR = 0.21; 95% CI
[0.08-0.53]
P=0.001
Lateral femoral
articular cartilage
tears
RR = 0.31; 95% CI
[0.48-1.50]
P=0.002
3
Interpretation
Using VSI results in a
73% lower risk/chance
of obtaining an
incorrect result vs. MRI;
Using VSI results in a
59% lower risk/chance
of obtaining an
incorrect result;
Using VSI results in an
82% lower risk/chance
of obtaining an
incorrect result;
Using VSI results in a
75% lower risk/chance
of obtaining an
incorrect result;
Using VSI results in a
79% lower risk/chance
of obtaining an
incorrect result;
Using VSI results in a
69% lower risk/chance
of obtaining an
incorrect result
4
Table 2: Sensitivities, Specificities, Accuracy of VSI and MRI compared to standard
arthroscopy (gold standard)
Comparison
Medial
meniscal
tears
Lateral
meniscus
tears
Medial tibial
articular
cartilage tears
Lateral tibial
articular
cartilage tears
Medial
femoral
articular
cartilage tears
Lateral
femoral
articular
cartilage tears
VSI
Sensitivity
94%
MRI
Sensitivity
81%
VSI
Specificity
80%
MRI
Specificity
61%
Accuracy
VSI
93.5%
(n=78)
Accuracy
MRI
74%
(n=100)
90%
67%
93%
87%
92%
(n=100)
80.6%
(n=98)
88%
41%
96%
90%
94%
(n=94)
64.9%
(n=97)
83%
39%
96%
86%
89.2%
(n=93)
61.2%
(n=93)
96%
85%
94%
66%
95%
(n=102)
76.8%
(n=99)
82%
58%
95%
85%
92% (n=99)
73.6%
(n=95)
5
Figure 1: ROC curve Medial Meniscus Tears
6
Figure 2: ROC curve lateral meniscus tears
Figure 3: ROC curve medial tibia articular cartilage tears
7
Figure 3: ROC curve medial tibial cartilage tear:
8
Figure 4: ROC curve lateral tibia articular cartilage tears
9
Figure 5: ROC curve medial femoral articular cartilage tears
10
Figure 6: ROC curve lateral femoral articular cartilage tears
11
References:
12
1
Higgins JPT, Green S. (editors). Cochrane Handbook of Systematic Reviews and interventions. Version
5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochranehandbook.org.
13