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, PennsylvaniabAssociate Professor, Department of Podiatric Surgery, Temple University School of Podiatric Medicine, Philadelphia, Pennsylvania (AJMeyr@gmail.com)*

*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.

Conclusion

Results

References

MethodsIntroduction and Objective 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. 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.

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:

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.

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.

[1] Brage ME, Bennett CR, Whitehurst JB, Getty PJ, Toledano A. Observer reliability in ankle radiographic measurements. Foot Ankle Int 18(6): 324-329, 1997.[2] Kragh JF Jr and Ward JA. Radiographic indicators of ankle instability: changes with plantarflexion. Foot Ankle Int 27(1): 23-28, 2006.[3] Rolfe B, Nordt W, Sallis JG, Distefano M. Assessing fibular length using bimalleolar angular measurements. Foot Ankle Int 10(2): 104-109, 1989.

How would your assessment of fibular length change in this same ankle with small differences in radiographic and patient positioning? WB AP

NWB AP NWB External

WB Internal NWB Internal WB External