Comparison of applied tension to the postero-medial structures in the traditional and modified postero-medial ankle approaches at different lengths of the posterior tibial plafond: Are there differences?

INTRODUCTION

Posterior malleolar fractures (PMF) occur in up to 46% of ankle fractures, with a higher incidence in women over 65 years old. The presence of a PMF worsens the prognosis of ankle fractures, making conservative treatment a poor option. PMFs represent a heterogeneous group of injury patterns, often associated with fibula fractures, medial malleolus extensions, and syndesmotic injuries, requiring surgeons to be well-versed in anatomy to select the appropriate surgical approach. An underexplored aspect of posterior ankle approaches is the applied tension required to displace the postero-medial structures - Posterior Tibialis tendon (PTT), Flexor Digitorum Longus tendon (FDL), Flexor Hallucis Longus tendon (FHL) and the neurovascular (N-V) bundle - for adequate visualization of the bone plane. This cadaveric anatomical study aimed to evaluate the displacement of these structures using the traditional postero-medial approach (TPM), as defined by our group, and the modified postero-medial approach (MPM), analyzing two tension measurements (in Newtons) at three distances from the distal border of the posterior tibial plafond.

METHODS

A randomized, analytical, and experimental cadaveric study was conducted. Eight lower limbs from freshly frozen cadavers were thawed at room temperature and subjected to below-knee amputation. The samples were randomly assigned to two groups (TPM or MPM). Tension measurements - "sufficient tension" (ST) and 5N - were recorded at 5, 7, and 10cm from the distal posterior tibial pilon to assess displacement of posteromedial structures. Each measurement was taken at 15s. Data were analyzed using univariate and bivariate methods; comparisons between groups were performed using the Wilcoxon-Mann-Whitney test.

RESULTS

Seventy-five percent of the TPM group were female donors, while 75% of the MPM group were male. The mean age was 65.5±14.01 years in the TPM group and 82.25±9.6 years in the MPM group. Statistically significant differences were found at "sufficient tension" in the 10cm measurement: the MPM approach required greater "sufficient tension" (ST) (13.1N vs. 8.5N; p=0.0433) to achieve medial displacement of the N-V bundle, while the TPM approach allowed for greater N-V bundle displacement with "sufficient tension" (23mm vs. 14mm; p=0.0433). However, no statistically significant differences were observed between the two approaches in medial displacement of the N-V bundle with 5N of tension at a distance of 10cm.

CONCLUSION

The TPM approach allows for greater medial displacement of the neurovascular bundle in ST with less tension at 10cm compared to the MPM approach, suggesting an advantage for fractures requiring wider surgical exposure.