Alignment characteristics associated with a new … · a new generation ankle replacement:...
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Alignment characteristics associated with
a new generation ankle replacement:
evaluation of the first 15 cases
Garrett M. Wobst, DPM, AACFAS, Nicole M. Protzman, BS, MS,
Stephen A. Brigido, DPM, FACFAS
IFFAS • AOFAS
Chicago, 2014
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My disclosure is in the final AOFAS mobile app.
I have no potential conflicts with this presentation.
IFFAS • AOFAS
Chicago, 2014
Alignment characteristics associated with
a new generation ankle replacement:
evaluation of the first 15 cases
Garrett M. Wobst
![Page 3: Alignment characteristics associated with a new … · a new generation ankle replacement: evaluation of the ... To evaluate alignment characteristics associated with a ... o Appears](https://reader030.fdocuments.in/reader030/viewer/2022011800/5acfbbf37f8b9ac1478d2bdf/html5/thumbnails/3.jpg)
INTRODUCTION
• During ambulation
o Ankle joint is subjected to extreme
tensile forces
• Following total ankle replacement
(TAR)
o Off-center forces can result in
aseptic mechanical loosening,
implant migration, and premature
implant failure (1-3)
Image source:
http://www.active.com/running/articles/4-ways-walking-
can-improve-your-running
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INTRODUCTION
• To maximize prosthesis longevity and
patient outcomes, proper implant alignment
is required
o Minimize shear and angular forces
o Decrease stress on the underlying cancellous
bone
• Recently, a resurfacing TAR system,
utilizing a lateral transfibular approach for
implantation became available
Image source: http://www.zimmer.com/en-US/hcp.jspx
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HYPOTHESIS
PURPOSE
To evaluate alignment characteristics associated with a TAR
system implanted through a lateral approach
• Given the exceptional joint exposure that can be achieved through
a lateral approach, the authors hypothesized that proper alignment
would obtained with this new generation TAR system
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Inclusion Criteria
• ≥ 18 years of age
• Diagnosed with end-stage ankle arthritis
• Exhausted conservative treatments
• Elected to undergo surgical treatment with this new generation prosthetic
Medical Record Review
Materials & Methods
Procedure
• Via a lateral approach, a fibular osteotomy was performed, the TAR was implanted, and the
fibula was internally fixated
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Materials & Methods Outcomes
• Tibial component alignment • Neutral = 90° for the tibial component
• Anterior distal tibial angle (aDTA) (Figure 1A)
• Lateral distal tibial angle (lDTA) (Figure 1B)
• Misalignment = implant deviation > 5° from 90°
• Talar component alignment • Talar inclination = angle between a line draw from the
most superior posterior aspect of the subtalar joint to
the most superior aspect of the cartilaginous surface
of the talar head and a line drawn from the most
superior posterior aspect of the subtalar joint to the
most anterior aspect of the talar component (Figure
1B)
Figure 1. Alignment measurements.
A.
B.
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Patient Demographics
Results
Data presented as mean ± standard error or count (%).
Demographic Value
Patients 15 (100.0)
Age (yr) 55.6 ± 15.0
Body Mass Index (kg/m2) 32.3 ± 6.8
Gender
Female 12 (80.0)
Male 3 (20.0)
Injury Side
Left 8 (53.3)
Right 7 (46.7)
9 (60.0)
6 (40.0)
Etiology
Osteoarthritis Post-traumatic arthritis
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Measurement Misalignments
Tibial Component
aDTA (°) 89.3 ± 6.6 5 (33.3)
lDTA (°) 90.9 ± 1.8 0 (0.0)
Talar Component
Talar Inclination (°) 5.2 ± 5.1 N/A
Results Alignment Summary
Data presented as mean ± standard error or count (%).
Abbreviations: aDTA, anterior distal tibial angle; lDTA, lateral distal tibial angle; N/A, not applicable.
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Discussion
• Lateral Distal Tibial Angle
o Zero misalignments
o Appears as though the alignment jig effectively reduces varus / valgus
deformity
• Anterior Distal Tibial Angle
o Five misalignments
o Sagittal plane alignment may not be accurately defined using aDTA due
to the “resurfacing” nature of the curved tibial component
• Talar Inclination
o Average angle suggests a slightly posterior tilt of the talar component
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Discussion
• Collectively, data suggest that proper prosthetic alignment can
be achieved with TAR utilizing a lateral approach
• More studies are needed to determine proper sagittal plane
alignment for curved tibial components
• Long term follow up is necessary to determine what constitutes
proper alignment of the talar component using this measurement
methodology
• Additional outcome studies are warranted to further evaluate proper
alignment over time with this TAR system
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1. Gougoulias NE, Khanna A, Maffulli N. History and evolution in total ankle arthroplasty. Br Med Bull
89:111-151, 2009.
2. Gougoulias N, Khanna A, Maffulli N. How successful are current ankle replacements?: a
systematic review of the literature. Clin Orthop Relat Res 468:199–208, 2010.
3. Fong JW, Veljkovic A, Dunbar MJ, Wilson DA, Hennigar AW, Glazebrook MA. Validation and
precision of model-based radiostereometric analysis (MBRSA) for total ankle arthroplasty. Foot
Ankle Int 32:1155-1163, 2011.
REFERENCES