Anterior ankle arthroscopy, distraction or dorsiflexion?

Abstract

Anterior ankle arthroscopy can basically be performed by two different methods; the dorsiflexion- or distraction method. The objective of this study was to determine the size of the anterior working area for both the dorsiflexion and distraction method. The anterior working area is anteriorly limited by the overlying anatomy which includes the neurovascular bundle. We hypothesize that in ankle dorsiflexion the anterior neurovascular bundle will move away anteriorly from the ankle joint, whereas in ankle distraction the anterior neurovascular bundle is pulled tight towards the joint, thereby decreasing the safe anterior working area. Six fresh frozen ankle specimens, amputated above the knee, were scanned with computed tomography. Prior to scanning the anterior tibial artery was injected with contrast fluid and subsequently each ankle was scanned both in ankle dorsiflexion and in distraction. A special device was developed to reproducibly obtain ankle dorsiflexion and distraction in the computed tomography scanner. The distance between the anterior border of the inferior tibial articular facet and the posterior border of the anterior tibial artery was measured. The median distance from the anterior border of the inferior tibial articular facet to the posterior border of the anterior tibial artery in ankle dorsiflexion and distraction was 0.9 cm (range 0.7-1.5) and 0.7 cm (range 0.5-0.8), respectively. The distance in ankle dorsiflexion significantly exceeded the distance in ankle distraction (P = 0.03). The current study shows a significantly increased distance between the anterior distal tibia and the overlying anterior neurovascular bundle with the ankle in a slightly dorsiflexed position as compared to the distracted ankle position. We thereby conclude that the distracted ankle position puts the neurovascular structures more at risk for iatrogenic damage when performing anterior ankle arthroscopy.

Fig. 1

Anatomic view of the anterior ligaments of the ankle. 1 Tibia and medial malleolus. 2 Lateral malleolus. 3 Talus. 4 Head of the talus. 5 Anterior tibiofibular ligament. 6 Distal fascicle of the anterior tibiofibular ligament. 7 Anterior talofibular ligament. 8 Superficial and deep layers of the medial collateral ligament

Fig. 2

Invasive distractor for ankle arthroscopy [16]

Fig. 3

a Schematic view of the ankle joint in the neutral ankle position showing the anterior (1) and posterior working areas. b Interarticular work is possible when distraction (arrows) is used, but the capsular tension reduces the anterior and posterior working areas. c The anterior working area is opened in dorsiflexion of the foot; anterior ankle pathology can easily be treated

Fig. 4

Sagittal section of the ankle showing the most relevant anatomical structures. 1 Tibia. 2 Talus. 3 Neck of the talus. 4 Head of the talus. 5 Tibiotalar working area. 6 Posterior subtalar joint. 7 Talonavicular joint. 8 Capsule. 9 Intracapsular but extrasynovial fatty tissue. 10 Anterior tibial artery and vein painted with Adobe Photoshop (the deep peroneal nerve has not been identified). 11 Extensor hallucis longus. 12 Deep layer of inferior extensor retinaculum. 13 Superficial layer of inferior extensor retinaculum

Fig. 5

The device is formed by: a Aluminium sliding arm. b Methacrylate block. This block is used to fix the proximal part of the specimen to the device using a aluminium pin. c Aluminium pin. d Movable clamp used to adjust to lower leg length differences. e Fibreglass footplate. f Calibrated spring. g Movable methacrylate block. h Grip, used to vary the distance between the footplate (e) and the aluminium block (g)

Fig. 6

Example of specimen in the device, using ankle distraction

Fig. 7

The sagittal CT reconstructions in the distracted ankle position. A line parallel to the anterior and posterior most distal part of the tibia was drawn to determine the position of the anterior border of the inferior tibial articular facet. The shortest distance between the anterior border of the inferior tibial articular facet and artery was measured using E-film^®. This distance was regarded as the anterior working area

Fig. 8

The sagittal CT reconstructions in ankle dorsiflexion

Fig. 9

Median distance from the anterior border of the inferior articular tibial facet to the anterior tibial artery (cm) in ankle dorsiflexion and distraction (N = 6)

Fig. 10

Correlation between the degrees of ankle dorsiflexion in each specimen and the median distance from the anterior tibial artery to the anterior border of the inferior tibial articular facet (N = 6)