Alessio Bernasconi1,2, Ali-Asgar Najefi3, Andrew J Goldberg4,5,6. 1. Foot and Ankle Unit, Royal National Orthopaedic Hospital, Stanmore, UK. 2. Trauma and Orthopaedics, University Federico II of Naples, Naples, Italy. 3. East & North Hertfordshire NHS Trust, Lister Hospital, Stevenage, Hertfordshire, UK. 4. UCL Institute of Orthopaedics & Musculoskeletal Science, Royal National Orthopaedic Hospital, Stanmore, UK. 5. MSK Lab, Faculty of Medicine, Department of Surgery & Cancer, Imperial College London, London, UK. 6. London Ankle & Arthritis Centre, Wellington Hospital, London, UK.
Abstract
BACKGROUND: Coronal plane ankle joint alignment is typically assessed using the tibiotalar angle (TTA), which relies on the anatomical axis of the tibia (AAT) and the articular surface of the talus as landmarks. Often, the AAT differs from the mechanical axis of the lower limb (MAL). We set out to test our hypothesis that the TTA using the MAL would differ from the TTA measured using the AAT in patients with ankle osteoarthritis. METHODS: Standardized standing long leg radiographs of 61 ankles with end-stage osteoarthritis were analyzed. We measured the MAL and the AAT. A line was drawn along the talar articular surface (TA) and the TTA was calculated using both the MAL (MAL-TA) and the AAT (AAT-TA). The mechanical axis of the tibia (MAT) was also recorded and the MAL-MAT angle calculated. The difference between MAL-TA and AAT-TA and its correlation with the MAL-MAT angle were assessed. Intra- and interobserver agreement were measured for MAL-TA and AAT-TA. RESULTS: The mean MAL-TA was 91.4 degrees (95% CI, 88.5-94.4) and the mean AAT-TA was 91.2 degrees (95% CI, 88.6-93.9). The difference ranged from -8.1 to 7.8 degrees, and was greater than 2 and 3 degrees in 42% and 18% of the patients, respectively. The difference, as an absolute value, also strongly correlated with the MAL-MAT angle (r = 0.91, P < .001). Intra- and interobserver reliability were excellent for both MAL-TA (intraclass correlation coefficient [ICC], 0.93 and 0.91, respectively) and AAT-TA (ICC, 0.91 and 0.89, respectively). CONCLUSION: We recommend that surgeons consider using the MAL-TA, which relies on long leg radiographs, especially with proximal deformity, to more accurately measure coronal plane ankle joint alignment. LEVEL OF EVIDENCE: Level III, retrospective comparative study.
BACKGROUND: Coronal plane ankle joint alignment is typically assessed using the tibiotalar angle (TTA), which relies on the anatomical axis of the tibia (AAT) and the articular surface of the talus as landmarks. Often, the AAT differs from the mechanical axis of the lower limb (MAL). We set out to test our hypothesis that the TTA using the MAL would differ from the TTA measured using the AAT in patients with ankle osteoarthritis. METHODS: Standardized standing long leg radiographs of 61 ankles with end-stage osteoarthritis were analyzed. We measured the MAL and the AAT. A line was drawn along the talar articular surface (TA) and the TTA was calculated using both the MAL (MAL-TA) and the AAT (AAT-TA). The mechanical axis of the tibia (MAT) was also recorded and the MAL-MAT angle calculated. The difference between MAL-TA and AAT-TA and its correlation with the MAL-MAT angle were assessed. Intra- and interobserver agreement were measured for MAL-TA and AAT-TA. RESULTS: The mean MAL-TA was 91.4 degrees (95% CI, 88.5-94.4) and the mean AAT-TA was 91.2 degrees (95% CI, 88.6-93.9). The difference ranged from -8.1 to 7.8 degrees, and was greater than 2 and 3 degrees in 42% and 18% of the patients, respectively. The difference, as an absolute value, also strongly correlated with the MAL-MAT angle (r = 0.91, P < .001). Intra- and interobserver reliability were excellent for both MAL-TA (intraclass correlation coefficient [ICC], 0.93 and 0.91, respectively) and AAT-TA (ICC, 0.91 and 0.89, respectively). CONCLUSION: We recommend that surgeons consider using the MAL-TA, which relies on long leg radiographs, especially with proximal deformity, to more accurately measure coronal plane ankle joint alignment. LEVEL OF EVIDENCE: Level III, retrospective comparative study.
Authors: M Pierce Ebaugh; Travis Alford; Kamen Kutzarov; Elizabeth Davis; Michael Greaser; William C McGarvey Journal: Foot Ankle Orthop Date: 2022-03-08