a b s t r a c t

Background: Tendon ruptures are common musculoskeletal injuries all around the world. Correct and timely di- agnosis of tendon injuries is obviously important for improving the treatment and minimizing the community costs. Ultrasound is now being considered as one of useful modalities in this area.

Objective: The preset study is going to validate the Diagnostic ability of ultrasound in tendon injuries induced by penetrating extremity trauma.

Methods: In this prospective, observational study, patients with penetrating extremity trauma and suspicion of tendon injuries were enrolled in our study. A team of emergency medicine (EM) residents performed ultrasound examination in these cases after attending the specific workshop and acquiring necessary skills in normal and ab- normal tendon ultrasound examination. Then another team of either EM or orthopedic residents explored pa- tients’ wounds and determined intact or injured tendons under direct visual observation. The results were analyzed to validate sensitivity and specificity of ultrasound as an alternative diagnostic test.

Results: Seventy-one patients were enrolled in our study and 11 patients were excluded during one year in 2014. Sixty patients, 11 with lower extremity and 49 with upper limb injuries were evaluated, among them 32 patients had extensor zone and 28 patients had flexure zone injuries. The overall sensitivity and specificity were calculat- ed 94.4% (95% CI 72.7-99.8%) and 100% (95% 91.5-100.0%) respectively.

Conclusions: Our results were similar to previous findings. Ultrasound can effectively differentiate injured from intact tendons in penetrating extremity trauma.

(C) 2017

1. Introduction

Tendon injuries are one of the most common musculoskeletal com- plaints including 7% of referral to doctors in the united states [1-3]. These injuries constitute 50% of all sport injuries [1-3]. The most com- mon types of tendon injuries, imposing a great burden on the world health care system (HCS), are tendinopathy and tendon ruptures. Tendon ruptures are divided either into complete or partial injuries.

Tendons are unique structures with special radiographic view. In most imaging they appear as parallel bundles of Collagen fibers. The direction of these fibers are the same as tendon longitudinal alignment [3-6].

Diagnosing tendon injuries pose a great cost and the Medicare Payment Advisory Commission found that this cost has been increased in the recent years [7]. Proper and Timely diagnosis can lead to more ap- propriate treatment and less society expenses.

Magnetic resonance imaging (MRI) has been changed to the modality of choice in diagnosis of tendon injuries based on the American College of Radiology Appropriateness Criteria report [8]. Given the significant expense and limited access, MRI is uncommonly utilized in the acute setting [9].

* Corresponding author.

E-mail address: [email protected] (J. Seyedhosseini).

When trauma is concerned, most tendon injuries are identified based on physical examination. It is said that physical examination might be less sensitive than MRI, especially when the results of physical examination are equivocal [10].

Improvement in the ultrasound (US) technology has changed this modality to one good alternative and supplementary tool in diagnosing tendon injuries instead of MRI [11]. US is mobile, accessible in most emergency department (ED)s and affordable. It is predicted that by in- creasingly applying US, it will decrease 7 million dollars in HCS costs by 15 years later [9]. Advantages like high clarity and the feasibility of dynamic evaluation make US as a common diagnostic tool in Europe [12]. Performing musculoskeletal US has been recently increased in the united states among radiologists and non-radiologists [13].

Tendon rupture is typically diagnosed in the longitudinal (not trans- verse view) given the potential for misdiagnoses due to anisotropy. Ten- don bundles appear as echogenic parallel lines with the fibrillary appearance in the vertical US view. In the transverse US view tendon bundles appear as echogenic dots in tendon’s cross-section. The US high frequency probe should be put in the vertical direction comparing to the collagen fibers, if not, even the smallest misplacement can cause a different view mimicking pathologic views of tendons. This will cause false positive results, named anisotropy artifact [14,15].

http://dx.doi.org/10.1016/j.ajem.2017.01.059

0735-6757/(C) 2017

946 N. Mohammadrezaei et al. / American Journal of Emergency Medicine 35 (2017) 945-948

By the help of US, complete rupture of the tendon is diagnosed as an interruption of the tendon continuity by some hypoechoic or echo-free gaps within it, indicating hematoma formation. There may also be seen some echogenic structures with casting posterior shadow which resem- ble bone fragment within the tendon. The US criteria compatible with acute complete rupture of the tendon is the inability to find and follow tendon continuity thoroughly. The US criteria suggesting partial tendon rupture include break of some fibers with keeping the whole tendon continuity intact. In this situation there may be local tendon thickening with focal limited hypoechogenicity.

In this study, we aimed to evaluate the accuracy of point-of-care ul- trasound in the diagnosis of penetrating tendon injuries in an ED setting. It is said that US has a high resolution with the capability of dynamic evaluation comparing to MRI [10-12].

1. Materials and methods

We held a 6-hour-workshop about normal and abnormal tendon US under the supervision of the chief investigator. The sessions composed of lectures and hand-on practices on animal subjects. All emergency medicine (EM) faculties and residents attended the workshop and then in order to gain expertise they performed tendon US on real sub- jects as a 2-month-pilot study. The training workshop was designed in a way that each participant could perform 10 US exams of normal and abnormal cases (on real human subjects).

Finally, the chief investigator confirmed the attendants’ qualification in tendon US by a monitored exam. This was a prospective study, per- formed during 1 year involving two level 1 trauma centers; Shariati and Sina hospitals (with the admission rate of 30,000-40,000 annually). This study was approved by the Ethics Committee of Tehran University of Medical Sciences.

Patients older than 16 years old, who were suspicious of having tendon injuries induced by penetrating trauma of the upper or lower extremities, were enrolled in our study. The informed written consent was taken of all patients and the whole process was ex- plained to them. Our sampling method was convenient sampling. The exclusion criteria were patients with uncontrolled arterial bleeding, unstable vital signs, limb amputation, patients who re- quired emergent management for other coexisting conditions, not- specified results in US because of the poor view.

The EP responsible for the patient care, first anesthetized, then per-

formed the irrigation, prep and drape with povidone-iodine (only the borders of the wound). Before doing US, sterile Xylocaine gel was used to cover all the wound surface. The high frequency US probe (linear US probe with 7.5-12 MHz frequency-Medisson x8 model) was used in sterile cover with adequate US gel. Patients demographic data and the US appearance of their tendons (whether normal, partial thickness or full thickness tearing) were recorded.

Full thickness tear was determined when complete rupture of the tendon was noted. A partial thickness tear or tendinosis was diag- nosed when increased diameter of the tendon was seen with or without different degrees of detachment of tendon congruity. This was determined when there was evidence of at least some intact ten- don fibers. There might be some hypoechoic area around the tendon suggesting hematoma formation or there might be some echogenic materials suggesting bone fragment within the tendon. Intact, full thickness and partial thickness injures ultrasound images are shown in Fig. 1.

After doing US examination, wound exploration was done for all pa- tients by the orthopedic resident who was blinded to the study. By di- rect visualization, one could determine whether the tendon was intact or injured. Partial tearing was reported when less than 50% of the ten- don cross-section was involved.

All data were compared by the 2 techniques. The validity of ultra- sound in diagnosis of tendon injuries was then calculated.

Fig. 1. Ultrasound images of zone 6 Extensor tendon of hand in Penetrating injuries. Intact (A), full-thickness (B) and partial thickness (C) injuries are shown as hypoechoic area (white arrow) in tendon length.

Primary and secondary endpoints

Our primary endpoint was to determine the validity of US in detec- tion of tendon injuries (comparing to exploration), in penetrating trau- ma of the extremities. Our secondary outcomes were comparison of the 2 techniques based on the injured site (upper or lower extremity), the type of tendons involved (extensors or flexors) and the type of tendon injuries (complete or partial).

Sample size calculation, data collection and primary analysis

We calculated a sample size of 56 patients in this study by the for- mula used bellow:

n = (Z1-a/2)² * P(1-P)/d²

N. Mohammadrezaei et al. / American Journal of Emergency Medicine 35 (2017) 945-948 947

Table 1

General data of the patients in our study.

Variable		Number		Statistic	Value	95% CI
Age (year/old)		30.1 +- 12.1		Sensitivity	94.4%	72.7-99.8%
Gender (No (%))	Male	53 (88.3)		Specificity	100.0%	91.5-100.0%
	Female	7 (11.7)		Positive predictive value	100.0%	80.4-100.0%
Location of tendon injury determined	Upper extremity	13 (72.2)		Negative predictive value	97.6%	87.7-99.9%
by final exploration (No (%)) Lower extremity 5 (27.8) Positive likelihood ratio Negative likelihood ratio					-a 0.06	-a 0.01-0.37
Disease prevalence					30.0%

Table 3

Validity of ultrasound in the diagnosis of tendon injuries.

a = 0.05

P = 90%

d = 8%

All data were analyzed by SPSS version 21. Quantitative data are pre- sented as mean +- SD or median and analyzed by paired t-test. Qualita- tive data are presented by frequency (percent) and analyzed by chi- square test. The validity of US in comparison to exploration was deter- mined by crosstab 2 * 2 tables. The correlation of the 2 techniques was

estimated by kappa statistics.

1. Results

Seventy-one patients were enrolled in our study. Eleven patients were excluded: 1 had unstable vital signs, 1 had active bleeding due to arterial injury, 2 had limb amputation and 7 had not-specified results in US. Finally, 60 patients were assessed with laceration caused by pen- etrating trauma to the extremities. The average age of our patients was

30.1 +- 12.1, 53 (88.3%) patients were males and 7 (11.7%) patients were females. General data of the patients are shown in Table 1.

All cases were scanned by either PGY3 EM residents or EM attending physicians with 3-5 years in practice and they all passed our US training workshop successfully.

General comparison of the US with exploration in diagnosis of ten- don injuries is shown in Table 2. Based on what we previously men- tioned, the results not-specified by US, were excluded.

US reported a false negative result in one case with partial tearing.

US falsely reported complete tearing in 3 cases which has partial tearing in exploration.

Seven patients could not be evaluated by the US correctly because of the poor view on US examination. These cases were explored by the ortho- pedic resident and the result in all cases were positive (they had tendon in- juries on exploration). Based on our study design, we excluded all these cases from our evaluation thus their results are not shown in Table 2.

The validity of US in the diagnosis of tendon injuries is shown in Table 3.

Comparisons of the 2 techniques in relation to the site of injury and the type of tendons involved are shown in Tables 4 and 5.

1. Discussion

Most previous studies about tendon injuries, have evaluated the va- lidity of US in big tendons like Rotator cuff, Achilles, Patella tendons. US had an acceptable sensitivity and specificity (90-100%) in these studies

^a The value could not be calculated because of the small sample size.

[10-15]. Like other studies, we found that US had quite a good sensitivity and specificity.

There are only a few studies evaluated US in smaller tendons, but the usefulness of its performing was determined in them. In 2009, a case se- ries study was done and it was declared that US was an appropriate mo- dality in differentiating injured from intact finger tendons [16].

Our study showed that US had a sensitivity and specificity of 94.4%

and 100% respectively. The results about differentiating partial from complete tendon tearing are not attributable, because of the small sam- ple size.

In this study we anesthetized and debrided the wound before doing US, thus we tried to explore the wound in a brief period after performing US in order not to do the preparation process again and also avoid further complications. We tried to do the US exam in close proximity to the physical exam, because if the US or exam were delayed, it would be possible to convert an injury from partial to complete, resulting in less accurate data.

Nowadays, US gained a remarkable validity comparing to MRI and in different studies it showed a good sensitivity and specificity and pa- tients were satisfied with its performing [17-20].

Grant et al. recommended US as a first-line diagnostic tool for deter- mining the presence or absence of a peroneal tendon tear [21].

Physical examination, as an ultimate technique for detection of tendon injuries in penetrating trauma, face a great challenge nowa- days. Its accuracy needs physicians’ expertise and sufficient time to increase. In a study by Wu et al. in 2012, it was found that US was more sensitive and specific than physical examination in detecting tendon lacerations and it took less time to perform exploration or MRI [22].

1. Limitations of the study

One of our limitation in this study was the small number of patients with tendon injury, induced by penetrating trauma to the extremity. This lengthened the study period. Our sample size was not sufficient to detect the exact validity of US in the diagnosis of tendon injuries. In our study females compromised 14.1% of our sample size. The reason might be more susceptibility of males to penetrating injuries. The vari- ation in tendon types, the low number of partial tears, the limitation of physical exam as a gold standard method and patients’ enrollment at 2 only two centers were potential limitations on external applicability of our study. The other limitation was that we did not have any follow- ups after the patients’ discharge thus we could not assess missed tendon injuries.

Table 2

Comparison of the ultrasound versus exploration in all the patients suspicious of tendon injuries.

Number (percent) The sum of each column is 100%.		Exploration Injured Complete	Partial	Intact	Total
Ultrasound Injured	Complete	10 (55.5%)	3 (16.6%)	0 (0.0%)	17 (28.3%)
	Partial	0 (0.0%)	4 (22.3%)	0 (0.0%)
Intact		0 (0.0%)	1 (5.6%)	42 (100.0%)	43 (71.7%)
Total		18 (100.0%)		42 (100.0%)	60 (100%)

948 N. Mohammadrezaei et al. / American Journal of Emergency Medicine 35 (2017) 945-948

Table 4

Validity of ultrasound in tendon injuries based on the site involved (a in upper extremity and b in lower extremity).

1. Conclusion

We found that US had a good sensitivity and specificity in the

		Explore		Total	diagnosis of tendon injuries in the emergency setting and it could be
		+	-		performed as the modality of choice for this purpose in the ED.
a) Ultrasound	+	12	0	12	References

	-	1	36	37
Total		13	36	49
b)
Ultrasound	+	5	0	5

- 0 6 6

Total 5 6 11

Statistic Value 95% CI a)

Sensitivity 92.3% 63.9-99.8%

Specificity 100.0% 90.2-100.0%

Positive predictive value 100.0% 73.5-100.0%

Negative predictive value 97.3% 85.8-99.9% b)

Sensitivity 100.0% 47.8-100.0%

Specificity 100.0% 54.0-100.0%

Positive predictive value 100.0% 47.8-100.0%

Negative predictive value 100.0% 54.0-100.0%

Table 5

Validity of ultrasound in tendon injuries based on the type of tendon involved (a flexor and b extensor).

Explore Total

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Total		13	19	32
Statistic	Value	95% CI

Sensitivity 100.0% 47.8-100.0%

Specificity	100.0%	85.1-100.0%
Positive predictive value	100.0%	47.8-100.0%
Negative predictive value	100.0%	85.1-100.0%
b)
Sensitivity	100.0%	73.5-100.0%
Specificity	95.0%	75.1-99.8%
Positive predictive value	92.3%	63.9-99.8%
Negative predictive value	100.0%	82.3-100.0%

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