Ankle fusion percutaneous home run screw fixation: Technical aspects and soft tissue structures at risk.

INTRODUCTION: The objective of this cadaveric study was to identify the number of attempts necessary for a perfect positioning of the ankle fusion home run screw and the neurovascular and tendinous structures at risk. METHODS: Eleven cadaveric limbs were used. Guidewires were percutaneously placed into the distal posterolateral aspect of the leg, under fluoroscopic guidance, with the ankle held in neutral position. Malpositioned guidewires were not removed and served as guidance for the following wires. The number of guidewires needed to achieve an acceptable positioning of the implant was noted. Neurovascular and tendinous injuries were assessed, and the shortest distance between the closest guidewire and the soft tissue structures was measured using a precision digital caliper. RESULTS: Mean number of guidewires needed to achieve acceptable positioning of the implant was 2.34 (SD 0.81, range 2-4). The mean distances between the closest guide pin and the soft tissue structures of interest were: Achilles tendon 5.35 mm (SD 2.74 mm); peroneal tendons 9.65 mm (SD 5.19 mm); posteromedial neurovascular bundle 12.78 mm (SD 7.14 mm). The sural bundle was in contact with the guide pin in 5/11 specimens (45.5%) and impaled in 3/11 specimens (27.3%). The average distance from the sural nerve bundle was 3.58 mm (SD 2.16 mm). CONCLUSIONS: The placement of percutaneous ankle fusion home run screws is technically demanding requiring multiple attempts for acceptable placement. Important tendinous and neurovascular structures are in close proximity to the guidewires. The sural bundle was either injured or in direct contact with the guide wire in approximately 73% of the cases. When using a home run screw, a mini-open approach is recommended. LEVEL OF EVIDENCE: Level V, cadaveric study.

Tibiofibular syndesmosis in asymptomatic ankles: initial kinematic analysis using four-dimensional CT.

AIM: To evaluate the reliability of ankle syndesmotic measurements and their changes during active motion using four-dimensional computed tomography (4DCT) examination in asymptomatic ankles. MATERIALS AND METHODS: 4DCT was performed on both ankles of patients with signs and symptoms of unilateral ankle instability. Ankles from the asymptomatic side of 10 consecutive patients were included in this analysis. Five ankle syndesmotic measurements were adopted from the available literature and performed by two fellowship-trained foot and ankle surgeons: (1) syndesmotic anterior distance (SAD); (2) syndesmotic posterior distance (SPD); (3) syndesmotic translation (ST); (4) syndesmotic tibiofibular angle (STFA); and (5) ankle tibiofibular angle (ATFA). A Monte Carlo simulation was also performed to obtain exact p-values with 99% confidence intervals. RESULTS: Excellent interobserver reliability was observed among the two readers for four out of five measurements (intra-class correlation coefficients [ICC]: 0.767-0.995, p<0.001-0.020). The ICC values for SAD were not statistically significant (ICC=0.548 and 0.569 for dorsi and plantarflexion respectively, p=0.1). Among the five measurements, only ST measurements had significant changes during active motion (median [interquartile range] for change: -0.70 mm [-1.6-0.10]; p=0.012). Of the above measurements, only the ST measurements demonstrated a negative linear association with the tibiocalcaneal angle during active motion (beta=-2.5, p=0.04). CONCLUSIONS: Reliable quantitative kinematic assessment of ankle syndesmosis can be performed using 4DCT examination. Syndesmotic measurements remain unchanged during ankle motion except for the syndesmotic translation, which tends to decrease during plantar flexion.