Foot & Ankle International - July 2018 - 867
867
Kwon et al
While it has been recognized that normal measurements
may not ensure anatomic alignment (especially with syndesmotic malreduction) and that anatomic variation
exists,34,37 the effects of injury on these various parameters
have been commonly examined in the literature. In addition, the MCS continues to be the most utilized measurement to assess deltoid ligament incompetence and overall
mortise alignment.
The MCS is defined as the radiographic distance between
the medial wall of the talar body and the lateral most aspect
of the medial malleolus. Normal MCS has traditionally
been described to be less than 4 mm in width.4,18,36 Tornetta61
suggested that the MCS should be within 1 mm of the superior clear space (SCS) regardless of the absolute distance
measured. DeAngelis et al9 evaluated whether the SCS
could serve as an accurate point of comparison for the MCS.
In a retrospective study, they analyzed 94 asymptomatic
ankles and measured the MCS on a line parallel and 5 mm
below the talar dome. Their findings indicated that in the
large majority (98%) of normal adult ankles, the MCS
should be less than or equal to the SCS. Therefore, normalization to the SCS could be used to assess malalignment
regardless of absolute measurements.
The literature is replete with studies aimed at determining the threshold MCS that indicates instability. The most
widely accepted values associated with incompetence of
the deltoid ligament are an absolute MCS greater than or
equal to 4 to 5 mm.† Michelson et al40 noted that sectioning
of the deep deltoid ligament resulted in 2 mm or more of
lateral talar shift with gravity stress in cadaveric specimens
where a distal fibular osteotomy was created. Similarly, in
a retrospective review, Pankovich and Shivaram49 concluded that rupture of the deltoid should be considered if
initial or stress radiographs revealed a relative increase of
MCS >2 to 3 mm as those cases were reportedly confirmed
by intraoperative exploration. Both studies reported a
change or difference in MCS measurement from normal
baseline to indicate deltoid insufficiency. Park et al50
sequentially disrupted the osseous-ligamentous structures
in a cadaveric model to replicate the SER IV injury pattern
and demonstrated that an absolute MCS greater than or
equal to 5 mm on radiographs taken in dorsiflexion-external rotation was the most reliable criterion to predict deltoid incompetence with sensitivity, specificity, and positive
and negative predictive values of 100%.
Unfortunately, there is no established consensus as to
the proper technique for measuring the MCS. While
many studies have described the MCS as the distance
measured between the medial malleolus and talus at the
level of the talar dome on the mortise view,3,5,13,26,46,55,59
others have failed to describe in their reported methodology the level at which the measurement was obtained2,4,27
†
References 2, 5, 10, 13, 16, 21, 23, 28, 36, 42, 44, 46, 50, 55, 64.
or the measurement technique.16,21,23,42,49,52,64 Murphy
et al44 noted significant variability in MCS based on how
the measurement was obtained as well as differences
associated with gender/height in a retrospective radiographic study of paired uninjured ankles. They also
showed a mean difference in MCS between paired ankles
of 0.6 ± 0.6 mm and thereby recommended routine contralateral radiographic comparison of MCS to assess for
pathologic widening in the setting of known anatomic
variation and to avoid the potential for false-positives.45
Further support for the cautious use of an absolute measurement was provided by Metitiri et al.38 Using 3 normal ankle cadaver specimens, the authors transected the
deltoid/syndesmotic ligaments and artificially widened
the mortise using resin blocks to a defined distance of 4
and 6 mm (the third specimen was left intact). Radiographs
were obtained of each cadaver at varying degrees of rotation, and orthopedic providers were asked to measure the
MCS using a standardized technique. The authors demonstrated poor accuracy and precision of measurement of
the MCS with significant measurement error.38
Elucidating Instability: The Advent of
Stress Views
While early investigations emphasized the importance of
clinical examination to assess ankle instability, the advent
of stress fluoroscopy soon followed. Manual manipulation
was initially advocated by Lauge-Hansen and Cedell.4 In
his examination of SER injuries, Cedell noted that a small
minority of isolated fibular fractures without evidence of
mortise incongruence went on to displacement with nonoperative treatment. Accordingly, he advocated for a thorough clinical examination for potential deltoid ligament
injury.4 However, subsequent works challenged the
assumption that physical examination findings could predict deltoid ligament injury. Egol et al,13 McConnell
et al,36 and De Angelis et al10 all demonstrated relatively
poor sensitivity, specificity, and predictive value of physical examination findings such as tenderness, ecchymosis,
and swelling. Given that physical examination findings
were not found to reliably predict the stability of the mortise, other means of diagnosis such as radiographic stressing
were increasingly used.
While numerous studies have reported the use of stress
radiography in one form or another dating back to initial
publications in the 1950's and 60's, the origins of validating
the use of gravity stress fluoroscopy to predict mortise
instability can be most likely attributed to Michelson et al42
in 2001. Michelson et al noted that in 8 cadaveric samples
with an osteotomized distal fibula, deep deltoid ligament
transection resulted in lateral talar shift and valgus displacement when gravity stress was applied with the specimens
mounted horizontally, lateral side down.42
Table of Contents for the Digital Edition of Foot & Ankle International - July 2018
Contents
Foot & Ankle International - July 2018 - Intro
Foot & Ankle International - July 2018 - Cover1
Foot & Ankle International - July 2018 - Cover2
Foot & Ankle International - July 2018 - i
Foot & Ankle International - July 2018 - ii
Foot & Ankle International - July 2018 - Contents
Foot & Ankle International - July 2018 - iv
Foot & Ankle International - July 2018 - v
Foot & Ankle International - July 2018 - vi
Foot & Ankle International - July 2018 - vii
Foot & Ankle International - July 2018 - viii
Foot & Ankle International - July 2018 - 1A
Foot & Ankle International - July 2018 - 1B
Foot & Ankle International - July 2018 - ix
Foot & Ankle International - July 2018 - x
Foot & Ankle International - July 2018 - xi
Foot & Ankle International - July 2018 - xii
Foot & Ankle International - July 2018 - 2A
Foot & Ankle International - July 2018 - 2B
Foot & Ankle International - July 2018 - xiii
Foot & Ankle International - July 2018 - xiv
Foot & Ankle International - July 2018 - xv
Foot & Ankle International - July 2018 - xvi
Foot & Ankle International - July 2018 - xvii
Foot & Ankle International - July 2018 - xviii
Foot & Ankle International - July 2018 - xix
Foot & Ankle International - July 2018 - xx
Foot & Ankle International - July 2018 - xxi
Foot & Ankle International - July 2018 - xxii
Foot & Ankle International - July 2018 - xxiii
Foot & Ankle International - July 2018 - xxiv
Foot & Ankle International - July 2018 - xxv
Foot & Ankle International - July 2018 - xxvi
Foot & Ankle International - July 2018 - 3A
Foot & Ankle International - July 2018 - 3B
Foot & Ankle International - July 2018 - 763
Foot & Ankle International - July 2018 - 764
Foot & Ankle International - July 2018 - 765
Foot & Ankle International - July 2018 - 766
Foot & Ankle International - July 2018 - 767
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Foot & Ankle International - July 2018 - 809
Foot & Ankle International - July 2018 - 810
Foot & Ankle International - July 2018 - 811
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Foot & Ankle International - July 2018 - 813
Foot & Ankle International - July 2018 - 814
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Foot & Ankle International - July 2018 - 816
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Foot & Ankle International - July 2018 - 825
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Foot & Ankle International - July 2018 - 827
Foot & Ankle International - July 2018 - 828
Foot & Ankle International - July 2018 - 829
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Foot & Ankle International - July 2018 - 831
Foot & Ankle International - July 2018 - 832
Foot & Ankle International - July 2018 - 833
Foot & Ankle International - July 2018 - 834
Foot & Ankle International - July 2018 - 835
Foot & Ankle International - July 2018 - 836
Foot & Ankle International - July 2018 - 837
Foot & Ankle International - July 2018 - 838
Foot & Ankle International - July 2018 - 839
Foot & Ankle International - July 2018 - 840
Foot & Ankle International - July 2018 - 841
Foot & Ankle International - July 2018 - 842
Foot & Ankle International - July 2018 - 843
Foot & Ankle International - July 2018 - 844
Foot & Ankle International - July 2018 - 845
Foot & Ankle International - July 2018 - 846
Foot & Ankle International - July 2018 - 847
Foot & Ankle International - July 2018 - 848
Foot & Ankle International - July 2018 - 849
Foot & Ankle International - July 2018 - 850
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Foot & Ankle International - July 2018 - 852
Foot & Ankle International - July 2018 - 853
Foot & Ankle International - July 2018 - 854
Foot & Ankle International - July 2018 - 855
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Foot & Ankle International - July 2018 - 858
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Foot & Ankle International - July 2018 - 866
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Foot & Ankle International - July 2018 - 873
Foot & Ankle International - July 2018 - 874
Foot & Ankle International - July 2018 - 875
Foot & Ankle International - July 2018 - 876
Foot & Ankle International - July 2018 - 877
Foot & Ankle International - July 2018 - 878
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Foot & Ankle International - July 2018 - 881
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Foot & Ankle International - July 2018 - Cover3
Foot & Ankle International - July 2018 - Cover4
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