Foot & Ankle

Simultaneous subtalar fusion and total ankle arthroplasty

It is now known that the nonunion rate of subtalar fusions is higher in feet with a pre-existing ankle fusion.¹⁰ This biomechanical study from The Hospital for Special Surgery, New York, New York (USA) demonstrates the relationship between this time by simulating subtalar fusion and measuring rotation and contact pressures in the ankle.¹¹ The conclusion of the basic science evidence appears to be that external rotation forces are increased across the ankle joint after simulated subtalar fusion. The addition of Chopart’s joint fusion segments are not thought to contribute to these changes. However, knowing this doesn’t really help the foot and ankle surgeon in deciding how to proceed for the patient with widespread hindfoot arthritis. This study from Milan (Italy) adds a lot to the application of current knowledge¹². The authors present the results of 24 subtalar fusions performed with a synchronous total ankle arthroplasty as a treatment alternative to a tibiotalocalcaneal nail for widespread hindfoot degeneration This type of hybrid reconstruction is becoming more common as surgeons seek to avoid a poorly-tolerated pantalar fusion as a solution to widespread hindfoot degeneration. Although ankle arthroplasty clearly has its shortcomings, in carefully selected patients arthroplasty and fusion offer the tantalising potential for preserving motion, avoiding nonunion and possibly avoiding the dreaded pantalar fusion. Although a small, elementary study, these authors report a 92% fusion rate of the subtalar joint at 12 months and significant improvements in visual analogue pain scale (VAS) of between 8.6 mm and 2.1 mm, and American Orthopedic Foot and Ankle scores of between 27.9 and 75.1 points as a result of their intervention. The Achilles and sural nerveThis article reports a retrospective review of MRI scans in patients both with and without Achilles tendon ruptures. The authors set out to establish simply what the anatomical relationship was between the Achilles tendon and the sural nerve, in addition to visualising the well-publicised ‘twist’ in the tendon with the eventual aim of establishing the safest and most effective form of percutaneous Achilles tendon release. Their observational study from the Hospital for Special Surgery, New York, New York (USA)¹³ established convincingly that the Achilles tendon was externally rotated in both rupture and non-rupture, with rotations of around 15° by the point at which the tendon reaches the ankle. However, there is no rotation at 10 cm proximal to the insertion. At the distal end, the sural nerve was close to the tendon anteriorly, lying laterally further in the ruptured tendons. Clearly there is an important message here for those undertaking a percutaneous Achilles tendon repair, as although the anatomy is relatively constant in the uninjured tendon, the relationships change during tendon rupture and the recommendations of external rotation of 11° at the proximal end of the rupture and 16° at the distal end when using percutaneous and limited-open Achilles tendon repair devices, are likely at the very least to reduce the rate of sural nerve injury, and may also increase the chances of tendon capture. Useful if you are going to undertake a percutaneous repair, but perhaps the bigger question remains, should one be undertaking a percutaneous repair at all?