SLR - June 2023 - Michael A. Savisky, DPM
Title: A Novel Approach for Joint Line Restoration in Revision Total Ankle Arthroplasty Based on the Three-Dimensional Registration of the Contralateral Tibia and FibulaReference: Hodel S, Calek AK, Cavalcanti N, Fucentese SF, Vlachopoulos L, Viehöfer A, Wirth SH. A novel approach for joint line restoration in revision total ankle arthroplasty based on the three-dimensional registration of the contralateral tibia and fibula. J Exp Orthop. 2023 Feb 3;10(1):10.
Level of Evidence: IV
Scientific Literature Review
Reviewed By: Michael A. Savisky, DPM
Residency Program: West Penn Hospital, Pittsburgh, PA
Podiatric Relevance: Osteoarthritis of the tibiotalar joint is a common pathology frequently evaluated by foot and ankle providers. Although ankle arthrodesis has been the gold standard treatment for many years, impaired functional outcomes after fusion along with continued advancements in total ankle arthroplasty (TAA) technology have resulted in more TAA procedures over recent years. With the increasing number of primary TAA cases, inevitably the number of revisions will also see a rise. Restoration of the native joint line is an important component in arthroplasty procedures. This is often dependent upon consistent bony landmarks of the lower extremity, which may not be preserved in cases of severe post traumatic arthritis or revision surgery. The primary aim of this study was to evaluate the accuracy of a novel 3D registration algorithm using the contralateral extremity to restore the native joint line in revision TAA procedures. The authors hypothesized that the joint line could be accurately approximated based on contralateral 3D imaging incorporating anatomic landmarks of the tibia and fibula.
Methods: 96 paired lower leg specimens were assessed using CT to create 3D surface models. A surface registration algorithm was applied to superimpose the mirrored contralateral model onto the original and three (proximal, middle, distal) segments of the lower leg were defined. Distances of the distal fibular tip, anterior and posterior medial colliculus to the joint line were measured. The differences between the measured anatomic landmarks of paired limbs were analyzed. The mean absolute error of the approximated joint line compared to the original was calculated for each defined anatomic segment. Two independent observers defined the joint line in 10 randomly selected ankles to assess the validity of the novel described joint line definition.
Results: The novel joint line definition demonstrated a mean error of 0.3 ± 0.2 mm between observers. The average joint line approximation for each anatomically defined segment was 0.1 ± 1.4 mm for the distal, 0.1 ± 1.2 mm for the middle and -0.2 ± 1.6 for the proximal (p = 0.007). The joint line error was largest for the proximal segment 2.0 ± 1.7 mm and smallest for the middle 1.3 ± 1.0 mm as well as the distal segments 1.2 ± 1.0 (p = 0.003). No significant influence of gender, age, height, weight and side-to-side differences of the tibia length, fibula length, distal fibular tip, and medial colliculi on joint line error of each segment could be demonstrated. No significant side-to-side differences were found for the distances of the fibular tip, anterior and posterior medial colliculi to the joint line, ADTA and LDTA. All measurements demonstrated good to excellent inter-reader agreement.
Conclusions: Overall, the key finding of this study was that the contralateral tibia and fibula can reliably be used to restore the original ankle joint line. Inclusion of the distal segment of the tibia and fibula improved the accuracy of restoring the joint line compared to the proximal segment. In cases of severe post traumatic changes or in revision situations, the joint line becomes elevated. If not addressed, the joint line can remain elevated following TAA procedure which may result in decreased range of motion, stiffness, and poorer clinical outcomes. The advantage of this study’s method was that in scenarios where the distal anatomy is altered, the proximally defined segment and contralateral landmarks can still be used with accuracy to define the joint line. The accuracy with which the joint line can be restored remains unclear and further research is needed to analyze the impact that implant and mechanical alignment have on clinical outcomes.