ResearchPod Summary
Neglected Achilles tendon ruptures (ATR)—those where diagnosis or treatment is delayed by more than four weeks—present significant functional challenges. While surgical intervention is generally required, the optimal technique remains debated. This study evaluated the midterm clinical outcomes and return-to-sports activity levels of 28 patients who underwent flexor hallucis longus (FHL) tendon transfer to repair neglected ATR.
Researchers conducted a retrospective analysis of patients treated between 2010 and 2019. Clinical success was measured using the Achilles Tendon Total Rupture Score (ATRS) and the American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale. To assess physical activity, the study utilized the Tegner Activity Scale (TAS), comparing preinjury status to status at the final follow-up (mean of 57 months post-surgery).
The study found that FHL transfer provides favorable midterm results. The median TAS score for the entire cohort remained unchanged from the preinjury level (median score of 4). However, the results were not uniform: 32% of patients reported a decrease in their activity level (a drop of 1 point on the TAS). This subgroup also demonstrated significantly lower ATRS and AOFAS scores compared to those who maintained their activity levels, suggesting that the ability to return to preinjury sports is closely linked to overall functional recovery.
This research provides evidence that FHL transfer is a viable option for restoring function in patients with neglected ATR. By using validated scales, the study offers a more nuanced understanding of patient outcomes than previous literature, which often relied on binary measures of return-to-activity. It highlights that while most patients achieve good results, clinicians should manage expectations regarding the potential for a slight reduction in high-impact sports participation.
Alex: Nearly a third of patients who had a tendon transfer for a neglected Achilles rupture ended up with a measurable decline in sports participation, even though overall outcomes were favorable. That comes from a retrospective analysis of Flexor Hallucis Longus transfer by Jungtae Ahn and Bi O. Jeong at Kyung Hee University.
Sam: That's a significant caveat. We usually frame this surgery as restoring the pre-injury baseline. If thirty-two percent of patients end up below it, is the procedure failing to restore the power needed for high-demand activity?
Alex: The data suggests the functional cost is real. In their cohort of twenty-eight patients, those whose Tegner Activity Scale score declined also had lower Achilles Tendon Total Rupture Scores. So the activity decline travels with worse patient-reported function. It isn't just a change in lifestyle.
Sam: So the surgery isn't a binary success or failure. Even if the graft is stable, functional output falls short for a subset. How does the transfer compensate for an Achilles that has degenerated?
Alex: Think of it as re-routing a power line. The native tendon is beyond repair, so the surgeon harvests the Flexor Hallucis Longus tendon, which normally flexes the big toe. It's passed through a drill hole in the heel bone and sutured to the Achilles stumps.
Sam: So a secondary muscle becomes the primary actuator for the heel. Does harvesting it create a new deficit that limits return to jogging or court games?
Alex: That's the obvious question. The Flexor Hallucis Longus is a robust biological substitute, but it isn't a biomechanical equivalent of the triceps surae complex. The authors suspect this is where the functional ceiling sits. But that's a hypothesis, not something the study tested.
Sam: Can they predict who ends up in the declining group?
Alex: Not from what they measured. They found no significant differences between the maintained and decreased activity groups in age, body mass index, or the interval between injury and surgery.
Sam: I'd be cautious about reading that as independence. With twenty-eight patients and a decline group of perhaps a third of them, the comparison has very little power. A null on age or delay to surgery could just mean the study couldn't detect it.
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Alex: That's the right reading. Absence of a significant difference in a cohort this size isn't evidence of no effect. Combined with the retrospective design, it means the study can't tell us who is at risk. It can only say that those obvious candidates didn't separate the groups.
Sam: Then what's driving the decline? The lower scores might reflect a psychological barrier, such as fear of re-rupture, rather than a limit of the graft.
Alex: That's the main limitation. There's no kinetic data, no force-plate analysis, no measured ground reaction forces. So they can't separate a hardware problem, where the transferred tendon can't generate the power, from a software problem, where the patient avoids loading the leg out of fear. Both would produce the same Tegner and ATRS pattern.
Sam: That matters for counseling. Telling a middle-aged recreational athlete they have roughly a one-in-three chance of not returning to their previous level is a very different conversation from promising full restoration.
Alex: Yes, with the caveat that the estimate comes from a small, single-center retrospective series, so it's imprecise. The authors stress that overall results are favorable. But for the minority who decline, the activity ceiling appears to shift, and that group reports lower satisfaction.
Sam: So the next step isn't more activity scoring. It's measuring what the transferred muscle can actually produce.
Alex: Right. Objective kinetic testing alongside patient-reported outcomes, ideally in a prospective design, is what could show whether the gap between successful reconstruction and full return to sport is mechanical, psychological, or both.
Sam: If you want the figures and the method choices we skipped, you can generate a deep dive of this paper. The paper has the rest either way.
Alex: Thanks for listening.