Transcript File - Temple University Hospital Foot and Ankle Surgical

The Effect of Patient Positioning on Radiographic Assessment of Fibular Length.
Corine L. Creech, DPMa, Laura E. Sansosti, DPMa, and Andrew J. Meyr, DPM FACFASb
aResident,
Temple University Hospital Podiatric Surgical Residency Program, Philadelphia, Pennsylvania
bAssociate Professor, Department of Podiatric Surgery, Temple University School of Podiatric Medicine, Philadelphia, Pennsylvania ([email protected])*
*Please don’t hesitate to contact AJM with any questions/concerns. He’s happy to provide you with a .pdf of this poster if you email him.
Introduction and Objective
Methods
Conclusion
The fibula contributes to the stability of the ankle joint as a
lateral buttress within the mortise. This stability is a product of
both its articular relationship to the talus and tibia, and its
ligamentous attachments. The fibula articulates with the lateral
aspect of the talus and lies relatively posterior and extends
relatively distal to the tibia. Muscular and ligamentous
attachments, such as the lateral collateral ligaments and
syndesmosis, help maintain this relationship. This combination of
osseous and ligamentous structures allow for the fibula to
translate medially and laterally, shift proximally and distally, and
allow for some rotation.
Acute injury or repetitive stress can disrupt this construct or
cause abnormal motion/positioning of the fibula. With rotational
ankle fractures, the proximal and lateral displacement of the distal
fibula is typically described as a “shortening”, and one of the
goals of surgical reconstruction is to “restore fibular length.”
The integrity and positional relationships of the ankle joint are
usually initially analyzed with plain film radiographs.
Anteroposterior, oblique, and lateral ankle radiographic
projections can be used to assess the position of the fibula within
the mortise, and how it changes in the setting of stress or injury.
Several objective radiographic measures specifically analyze
fibular length and position within the ankle mortise. Although
there is an abundance of literature reporting the abnormal change
in the position of the fibula related to injury, we are unaware of
evidence that describes changes that occur in these measurements
with weightbearing, patient positioning and radiographic
projection.
Radiographs were taken of a single, asymptomatic subject without
a history of foot/ankle pathology or surgery. Three different
radiographic projections were obtained (standard AP, internally rotated
10 degrees from AP, and externally rotated 10 degrees from AP) in
two different situations (full weightbearing and non-weightbearing).
Four radiographic measurements commonly utilized to evaluate
congruity of the ankle mortise (talar-crural angle, talar tilt angle,
medial clear space, and superior joint space) were performed using
computerized digital software (Opal-RAD PACS, Viztek, Garner, NC)
which measures to a precision of 0.1 degrees and 0.1mm.
As with any scientific investigation, readers are encouraged to review and critically assess the study design
and specific results in order to reach their own independent conclusions, while the following represents our
conclusions based on the preceding data. It is also important to note that as scientists we never consider data
to be definitive, but we do think there are some interesting findings here worthy of attention and future
investigation:
The objective of this study was to analyze normal
differences that may occur in the assessment of apparent
fibular length based on external human factors and
independent of actual patient anatomy.
Results
WB Internal
NWB Internal
WB External
Radiographic measurements of the talar-crural
angle varied along a range of -0.5 degrees to +3.9
degrees. Radiographic measurements of the talar
tilt angle varied along a range from 0.2 to 2.3
degrees. Measurement of the medial clear space
varied along a range of -0.16mm to +1.6mm. And
measurement of the superior joint space varied
along a range from -0.18mm to +0.78mm.
We think that the results of this preliminary data
demonstrate that relatively small differences in patient
positioning and radiographic projection can potentially
lead to clinically significant differences in the assessment
of fibular length. This finding has the potential to affect
intraoperative decision making when considering that
flouroscopic views taken during ankle ORIF procedures
are non-weightbearing, and can vary in terms of rotational
assessment based on surgeon positioning of the joint and
technical skill of the radiologic technologist.
These results have encouraged us to be cognizant of
both patient and radiographic positioning when making
intra-operative decisions of fibular length, and to attempt
to be as standardized as possible when making this
determination.
We hope that these results add to the body of
knowledge with respect to the normal and abnormal
radiographic anatomy of the ankle joint, as well as
surgeon assessment of correction during traumatic
reconstruction of the ankle mortise.
References
NWB AP
NWB External
How would your assessment
of fibular length change in
this same ankle with small
differences in radiographic
and patient positioning?
WB AP
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reliability in ankle radiographic measurements. Foot Ankle Int 18(6): 324329, 1997.
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[3] Rolfe B, Nordt W, Sallis JG, Distefano M. Assessing fibular length
using bimalleolar angular measurements. Foot Ankle Int 10(2): 104-109,
1989.