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Injury, Int. J. Care Injured 47 (2016) 2749–2754

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Injury

journal homepage: www.elsevier.com/locate/injury

Where is the true location of the femoral piriform fossa?

a,b, c

Pedro José Labronici, PhD, Professor *, Fernando Claudino dos Santos Filho, Physician ,

d e

Robinson Esteves Santos Pires, MSc , André Wajnsztejn, Staff Physician ,

f g

José Otávio Soares Hungria, Assistant , Vinicius Schott Gameiro, PhD, Professor ,

h

Luiz Henrique Penteado da Silva, Staff Physician

a

Universidade Federal Fluminense (UFF), Niterói, RJ, Brazil

b

Faculdade de Medicina de Petrópolis (FMP), Petrópolis, RJ, Brazil

c

Department of Orthopedics and Trauma, Hospital Santa Teresa, Petrópolis, RJ, Brazil

d

Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil

e

Trauma and Walk-in Clinic Team, Escola Paulista de Medicina (EPM), Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil

f

Trauma Team, Department of Orthopedics and Trauma, Irmandade de Misericórdia da Santa Casa de São Paulo, São Paulo, SP, Brazil

g

UFF, Niterói, RJ, Brazil

h

Department of Trauma, Member of Pelvic and Hip Surgery Team, Instituto de Ortopedia e Traumatologia (IOT), Hospital do Trauma, Hospital Escola São

Vicente Paula, Passo Fundo, RS, Brazil

A R T I C L E I N F O A B S T R A C T

Article history: Objective: To analyze knowledge of the anatomic location of the piriform fossa using a questionnaire with

Accepted 17 October 2016

anatomic ﬁgures.

Materials and methods: Participants taking AO Trauma Brasil courses were requested to complete a

Keywords: questionnaire containing a photograph of the superior surface and a photograph of the lateral surface of

Piriform fossa

the femur and answer a question asking which of four numbered points corresponded to the piriform

Trochanteric fossa fossa.

Point of entry

Results: Just 4.5% of respondents correctly chose point 2 (the piriform fossa) in both images, while 75.4%

Proximal femur

of respondents chose point 4 (the trochanteric fossa) as the correct anatomic structure. The subset of 4th-

year residents’ answers was signiﬁcantly different from those of the other subsets, with 7.5% of correct

answers.

Conclusions: The low rate of correct answers indicates a tendency for the respondents to be inﬂuenced by

illustrations in text books or examples in scientiﬁc publications that indicate the site of the piriform fossa

incorrectly. Interest in the specialty of traumatology is possibly the reason why the subset of 4th-year

residents had a better- than-average rate of correct answers.

ã 2016 Elsevier Ltd. All rights reserved.

Introduction including complications such as comminuted fractures, eccentric

reaming of the medial cortex and varus deformity [7–12].

Antegrade intramedullary nailing is currently the ﬁrst-choice Despite the importance of the correct insertion point to

procedure for treatment of fractures of the neck and shaft of the surgeons who perform anterograde intramedullary nailing pro-

femur [1–6]. Use of an intramedullary nail was originally cedures, the literature lacks clarity and consensus on terminology.

introduced by Küntscher, who proposed that the point of entry Anatomic references employed include “tip of the greater

for straight nails should be the greater trochanter. Later, Winquist trochanter,” “piriform fossa,” “trochanteric fossa,” “digital fossa”

recommended that the piriform fossa was a better point of entry in and “junction of femoral neck and trochanter”1, [13–16]. The

order to avoid problems attributed to insertion via the trochanter, majority of articles recommend the “piriform fossa” as the site for

insertion of the anterograde intramedullary nail. However, their

illustrations show the “trochanteric fossa” [1,7–9,17–26].

The objective of this study was to analyze anatomic knowledge

* Corresponding author at: Av. Roberto Silveira, 187/601 25685-040, Petrópolis, about the piriform fossa in a sample of participants taking trauma

RJ, Brazil. courses, using an illustrated questionnaire.

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

http://dx.doi.org/10.1016/j.injury.2016.10.016

0020-1383/ã 2016 Elsevier Ltd. All rights reserved.

2750 P.J. Labronici et al. / Injury, Int. J. Care Injured 47 (2016) 2749–2754

Materials and methods Results

Between January and December of 2014, during Basic Principles Analysis of the relationships between respondents’ answers for

and Advanced courses run by AO Trauma Brasil, course participants the image showing the superior view of the trochanter and the

were requested to complete a questionnaire with the following type of respondent (shown in Table 3) revealed that for all subsets

information, age; and year of residency, or, if not a resident, the the percentage of respondents who correctly answered point 2 (the

time since qualiﬁcation; and to indicate the location of the piriform piriform fossa) was small and that the majority chose point 4 (the

fossa on two illustrations. These ﬁgures consisted of one trochanteric fossa). There was a signiﬁcant difference between the

photograph of the superior surface and another of the lateral frequencies of answers between different subsets of respondents

surface of a femur on which four regions had been labeled. The (chi-square test p-value = 0.010). Exclusion of the subset of 4th-

labels corresponded to: 1- insertion of obturator and gemelli; 2- year residents resulted in the difference no longer achieving

piriform fossa; 3- tip of the greater trochanter and 4- trochanteric signiﬁcance (p-value = 0.312). It was therefore concluded that the

fossa (Fig. 1A and B). The question was as follows, “Which of the 4th-year residents’ answers are signiﬁcantly different from the

numbers in the ﬁgures below corresponds to the piriform fossa?” other subsets’ answers. It can be observed from the frequencies

(Fig. 2). shown in Table 3 that the subset of 4th-year residents had the

The questionnaire was administered to a total of 670 people highest frequency of correct answers (7.5%) and had the lowest

taking the courses, but 20 questionnaires were incomplete, so the frequency of respondents who chose point 4 (the trochanteric

sample used for analysis comprised 650 valid questionnaires. fossa, 77.6%).

Tables 1 and 2 list the data on experience and age, respectively, for For the lateral-view image, a greater percentage of respondents

those who responded to the questionnaire. in all subsets correctly chose point 2 (piriform fossa) as can be

observed from the results shown in Table 4. Notwithstanding, the

percentage of participants who chose correctly was less than 11% in

Statistical methods

all subsets and 80.5% of all of the respondents chose point 4 (the

trochanteric fossa). While the percentage of correct answers was

The data collected were used to construct a database containing

greater for the Post- residents subset (10.8%), the difference was

the variables age, classiﬁcation of respondent (2nd, 3rd, 4th-year

not signiﬁcant from a statistical point of view. The chi-square test

resident or post-resident), post- residency experience, answer for

did not detect signiﬁcant differences between the answers from

superior-view image and answer for lateral-view image. This

the different subsets; p-value = 0.436.

database was analyzed using SPSS (Statistical Package for the Social

Table 5 shows the distribution of the answers for both images

Science) version 22.0.

taken together. Just 4.5% of respondents chose point 2 (piriform

Data were synthesized using descriptive statistics, descriptive

fossa) as the correct anatomic structure in both images. For both

graphs, frequency distributions and contingency tables in order

images, 75.4% of respondents chose point 4 (the trochanteric fossa)

to characterize the sample and analyze the behavior of the

as the correct anatomic structure. As had been expected, the

variables. An inferential analysis of the signiﬁcance of differences

degree of agreement between images measured using the Kappa

between percentages for distinct groups was conducted using the

coefﬁcient is not high. There is moderate agreement (0.48),

chi-square test. Since distribution was not normal, independent

indicating that the angle from which the image is taken interferes

groups were compared using the Kruskal- Wallis nonparametric

with the choice made, since 15.7% of the respondents chose

test, with Tukey post-hoc analysis. Agreement between

different points for the two different views.

responses to the two images was assessed according to the

Figs. 3 and 4 illustrate the percentages by group, showing the

percentage of cases in which both answers were the same and

analysis of both images. In all subsets, there was a higher frequency

with the Kappa index, where possible. All analyses were

of correct answers for the lateral- view image. The subset of 4th-

conducted with a maximum cutoff for signiﬁcance of 5%, i.e.,

year residents had the highest percentage of correct answers for

the following decision rule was adopted for all tests: the null

both images combined (6.0%) and the highest percentage of correct

hypothesis was rejected whenever the p-value associated with a

answers for the image taken from above (7.5%). The subset of post-

test was less than 0.05.

residents had the highest percentage of correct answers for the

Fig. 1. A) lateral and B) superior views showing anatomic structures.

P.J. Labronici et al. / Injury, Int. J. Care Injured 47 (2016) 2749–2754 2751

Fig. 2. Study questionnaire.

image taken from the lateral (10.8%). For all groups, the most

frequent answer was point 4 (the trochanteric fossa), and the

Table 1

subset of

Distribution of respondents, by experience.

post-residents had the highest frequency of this choice (86.7%

Frequency Percentage

for the photograph taken from above, 83.1% for the lateral view and

2nd-year residents 134 20.6 80.7% for both images combined).

3rd-year residents 283 43.5

4th-year residents 67 10.3 Discussion

Post-residents 166 25.5

“ ” ﬁ

Total 650 100 The piriform fossa is an anatomic structure that is dif cult to

identify, particularly during orthopedic surgery to insert an

2752 P.J. Labronici et al. / Injury, Int. J. Care Injured 47 (2016) 2749–2754

Table 2

Distribution of respondents by age.

Subset Mean (years) Median (years) Minimum (years) Maximum (years) Standard deviation CV N % of total N

2nd-year residents 28.0 28 25 36 0.18 0.01 134 20.6

3rd-year residents 28.8 28 25 37 0.12 0.00 283 43.5

4th-year residents 30.6 30 27 59 0.50 0.02 67 10.3

Post-residents 35.1 34 26 59 0.45 0.01 166 25.5

Entire sample 30.4 29 25 59 0.18 0.01 650 100.0

CV, coefﬁcient of variation.

Table 3

The piriform fossa is an extracapsular area of the proximal

Relationship between respondent subsets and answer given in response to the

region of the femur. It is a small, shallow depression at the end of

superior-view image.

the greater trochanter where the piriformis tendon is inserted. In a

Subset Answers Total

study with cadavers, Georgiadis et al. [5] showed that the piriform

1 2 3 4 fossa is located approximately 2 cm posterior of the edge of the

greater trochanter. In contrast, the trochanteric fossa is a deep,

2nd-year residents% 15 7 0 112 134

11.2 5.2 0.0 83.6 100.0 extracapsular depression on the posterior and medial surface of

3rd-year residents% 31 11 0 241 283

the greater trochanter at the point of insertion of the external

11.0 3.9 0.0 85.2 100.0

obturator. It is an easily palpated site, and for this reason is also

4th-year residents% 8 5 2 52 67

11.9 7.5 3.0 77.6 100.0 called the digital fossa, and coincides with the exact position that

Post-residents% 12 10 0 144 166 the majority of surgeons recommend as the standard point of entry

7.2 6.0 0.0 86.7 100.0 [27].

Entire sample% 66 33 2 549 650

The majority of publications describing anterograde femoral

10.2 5.1 0.3 84.5 100.0

nailing, recommend that insertion should be via the piriform fossa,

but show the trochanteric fossa in their illustrations [1,7–9,17–26].

Recent publications on surgical technique that mention straight

Table 4

antegrade femoral nails often recommend the trochanteric fossa as

Relationship between respondent subsets and answer given in response to the

entry point. However, the illustrations indicate the piriform fossa

lateral-view image.

[26,28,29]. In some parts of the text, Whittle [30] mentions the

Subset Answers Total

trochanteric fossa in illustrations, but continues using

1 2 3 4 the term piriform fossa incorrectly in the same chapter,

probably referring to the same site. Nork22 recognizes this error

2nd-year residents% 11 13 0 110 134

8.2 9.7 0.0 82.1 100.0 of terminology in the latest edition and states that the term

3rd-year residents% 35 26 1 221 283

trochanteric fossa is the current term for describing the point of

12.4 9.2 0.4 78.1 100.0

entry, aligned with the medullary canal, but continues to use the

4th-year residents% 5 7 1 54 67

7.5 10.5 1.5 80.5 100.0 term piriform fossa for the point of entry. In a recent review, some

Post-residents% 9 18 1 138 166 authors chose to retain the term piriform fossa for the point of

5.4 10.8 0.6 83.1 100 entry, in line with the femoral medullary canal, rather than using

Entire sample% 60 64 3 523 650

the term trochanteric fossa to avoid confusion [22–26]. Ansari

9.2 9.8 0.5 80.5 100

Moein et al. [22,24–26] analyzed the terminology of utilization of

the terms piriform fossa and trochanteric fossa in an attempt to

review the incompatibility in denominations for the point of entry

Table 5

for femoral nails. Therefore, the terms piriform fossa and

Combined distribution of answers for both images.

trochanteric fossa are used in an inconsistent manner in the

Superior view Lateral view Total literature, even though the majority of authors stress the

importance of the correct positioning of point of entry for

1 2 3 4

placement of the anterograde nail and reduction of the fracture.

1 27 6 0 33 66

4.2 0.9 0.0 5.1 10.2 Therefore, this should be made clear in both texts and illustrations,

2 3 29 1 0 33 avoiding confusion with the terminology.

0.5 4.5 0.2 0.0 5.1

Other authors have observed that insertion of the intra-

3 0 1 1 0 2

medullary nail through the piriform fossa has the advantage of

0.0 0.2 0.2 0.0 0.3

being collinear with the anatomic femoral axis in the anteropos-

4 30 28 1 490 549

4.6 4.3 0.2 75.4 84.5 terior plane [12,13]. In contrast, Lakhwani et al. [31] demonstrated

in cadaveric femurs the point of entry for anterograde femoral nails

Total 60 64 3 523 650

with relation to the direction of the femoral shaft and the piriform

9.2 9.8 0.5 80.5 100.0

fossa, showing that in 12 out of 50 femurs (24%) the fossa was

located in the direction of the femoral shaft; in 34 (68%) the

femoral shaft was lateral of the fossa in the region of the greater

trochanter and in 4 (8%) cases the femoral canal was aligned medial

intramedullary nail into the femur. Analysis of our results shows to the fossa in the direction of the femoral neck. They stated that

ﬁ

that correct identi cation of the location of the piriform fossa was the correct point of entry for an anterograde femoral nail is variable

infrequent. This could be because of a lack of anatomic knowledge and cannot be deﬁned universally, because of differences in the

or because the respondents have been induced to error by alignment of the femoral canal. Stannard et al. [32] did not

literature containing incorrect terminology and/or illustrations. demonstrate signiﬁcant differences in the majority of measures of

P.J. Labronici et al. / Injury, Int. J. Care Injured 47 (2016) 2749–2754 2753

Fig. 3. Percentages of correct choices (point 2, piriform fossa) for each image, by subset of respondents.

Fig. 4. Percentages of incorrect choices (point 4, trochanteric fossa) for each image, by subset of respondents.

hip function in a randomized prospective study of piriform fossa The 4th-year residents’ results had the highest rate of correct

and trochanteric fossa entry for intramedullary nailing of femoral answers (6.0%) for both images, probably because they had a

fractures. greater interest in the specialty of traumatology. This may be due

Kale et al. [6] used a questionnaire to analyze the opinions of to greater concern with acquiring better knowledge of the anatomy

orthopedic surgeons on the correct point of entry for anterograde of this region in order to perform surgery. It also indicates a need to

femoral nailing. The majority of surgeons (96%) answered improve the traumatology specialty to improve results. However,

incorrectly, with respect to both selection and marking of the the 3rd-year residents’ results, which had a low rate of correct

point of entry. This result appears to conﬁrm the possibility that answers (superior view: 3.9%; lateral view: 3.2%; and both images:

illustrations and/or terminology on point of entry in the literature 3.2%), were unexpected. Another surprising factor was that

are incorrect. approximately 10% of respondents chose different sites in the

Our questionnaire was administered at a course speciﬁcally on superior and lateral views.

orthopedic trauma and showed that just 4.5% of respondents

indicated the correct location of the piriform fossa in two images Conclusions

taken from different directions (superior view and lateral view). In

the entire sample of respondents, 75.4% incorrectly identiﬁed the The low rate of correct answers indicates a tendency for the

trochanteric fossa as the piriform fossa. As shown above, there is respondents to be inﬂuenced by illustrations in text books or

still a great deal of confusion with respect to the terminology for examples in scientiﬁc publications that indicate the site of the

these anatomic structures. This low rate of correct answers piriform fossa incorrectly. Our ﬁndings strongly recommend a

indicates the possibility that respondents are being inﬂuenced by more consistent anatomy training in medical school and residency,

illustrations in text books or examples in scientiﬁc publications as well as revision of the ilustrations in text books and papers

that show an incorrect location for the piriform fossa. correctly indicating the true femoral piriform fossa.

2754 P.J. Labronici et al. / Injury, Int. J. Care Injured 47 (2016) 2749–2754

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