High Uric Acid Linked to Slower Achilles Tendon Healing on MRI, But Experts Urge Caution

People undergoing surgery for a ruptured Achilles tendon may heal differently depending on the level of uric acid circulating in their blood before the operation, according to a recent study that has drawn both praise and pointed criticism from an international team of orthopaedic researchers. The original investigation, conducted by Ye and colleagues and published in Frontiers in Medicine, found that preoperative serum uric acid predicted the signal-to-noise quotient, or SNQ, a quantitative measure derived from T2-weighted magnetic resonance imaging performed three months after open repair of an acute Achilles tendon rupture. Patients with hyperuricaemia, an abnormally elevated concentration of uric acid in the blood, showed markedly higher SNQ values than patients with normal uric acid levels. Because higher signal on T2-weighted images is generally interpreted as indicating less mature repair tissue, the finding suggests that metabolic status could shape the early biological course of tendon healing after one of the most common and debilitating sports injuries.

A commentary on the study, authored by Filippo Spiezia, Francesco Oliva, Filippo Migliorini and Nicola Maffulli, acknowledges that the question is clinically important and that applying a quantitative imaging endpoint to metabolic status after Achilles repair is a genuine contribution to the field. The commentators, who work across institutions in Italy, Germany and the United Kingdom, nonetheless raise four substantive points that they argue qualify the strength of the conclusions, along with one additional observation drawn from earlier research. Their critique offers a window into how cautious scientists weigh an intriguing association against the many confounding factors that complicate studies of human healing.

The first concern involves rehabilitation, a variable the commentators describe not as a neutral background factor but as an active determinant of tendon healing. In the original study, patients followed a conservative protocol: a long-leg cast with the foot held in 20 to 30 degrees of plantarflexion and strict non-weight-bearing for four to six weeks, followed by an adjustable brace from six to twelve weeks, with resistance training introduced only after twelve weeks. Yet the authors of the study themselves cite randomised evidence that functional weight-bearing mobilisation enhances the early healing response after Achilles rupture. The commentators also draw on their own comparative work on a deliberately slowed rehabilitation timeline, in which wedge removal, discontinuation of the boot, and the introduction of resisted and eccentric loading were each deferred; that approach produced significantly better tendon resting angle and strength symmetry at one year. However, that cohort underwent percutaneous repair with early weight-bearing in both groups, making it not fully comparable with the open-repair patients in the uric acid study.

The problem, the commentators argue, is that the three-month assessment falls precisely where cumulative loading histories between patients diverge most. No data on weight-bearing progression or rehabilitation adherence were presented in the original paper. Because patients with hyperuricaemia commonly carry additional metabolic comorbidity, differential progression through an immobilisation-heavy protocol represents a plausible source of residual confounding for the observed difference in SNQ. In other words, the higher signal readings in hyperuricaemic patients might reflect differences in how much load their healing tendons experienced rather than a direct biochemical effect of uric acid on tendon tissue. The commentators encourage the original authors to report any available loading or adherence data, which they say would materially strengthen the causal argument.

The second concern concerns the imaging endpoint itself. SNQ has been validated principally in the assessment of ligament graft maturation, and its application to a repaired Achilles tendon rests on the assumption that higher T2 signal at three months indicates a less mature repair rather than a normal stage of the reparative process. That assumption, the commentators note, is not fully established for tendons. Elevated signal at this stage may equally reflect an active, well-vascularised reparative response rather than failed healing, and the direction of the association cannot be resolved without considering clinical outcomes. Achilles-specific data are beginning to address this question: in one longitudinal MRI study of repaired Achilles tendons, patients with poor tendon-stump coaptation had significantly higher SNQ at three months than those with good coaptation, but that difference had resolved by six and twelve months despite similar final AOFAS scores, Achilles tendon Total Rupture Scores and muscle strength between the groups. The authors of that study interpreted the early elevation as a relative delay in tissue maturation rather than a failure to heal.

This distinction matters because SNQ characterises the maturation status of local repair tissue, whereas the symptoms, activity capacity and macroscopic function of the muscle-tendon unit, which are also shaped by pain, muscle atrophy and rehabilitation progress, are better captured by measures such as the ATRS, the AOFAS score, the tendon resting angle and strength testing. The original study reported no functional scores, no tendon resting angle and no re-rupture data. Until SNQ is shown to track outcomes that matter to patients after Achilles repair, as distinct from the appearance of the local repair tissue alone, the commentators conclude that it remains an uncertain surrogate for a patient’s overall healing status.

The third point identifies an internal inconsistency between the study’s discussion and its conclusion. In the discussion, the original authors appropriately state that uric acid has limited predictive value, that it should serve only as an adjunctive risk predictor, and that treatment decisions should not rest on uric acid levels alone. The abstract and conclusion, however, recommend perioperative uric acid control in hyperuricaemic patients. The commentators are blunt about this gap: an association observed in 60 patients in a single-centre retrospective observational study cannot support a treatment recommendation, and the more measured language of the discussion should prevail. The randomised trial of urate-lowering intervention that the original authors propose is, in their view, the correct next step, and any recommendation to lower uric acid around surgery should await the results of such a trial.

The fourth point concerns the statistical analysis. The multivariable model carried nine parameters in only 60 patients and explained little variance, with an adjusted R-squared of 0.114, meaning the model accounted for roughly eleven percent of the variability in the imaging outcome. Lipid values were missing for a quarter of the cohort and had to be statistically imputed. Six markers were tested by rank correlation without adjustment for multiple comparisons, and the one marginal result, total bilirubin at a p-value of 0.042, disappeared in the regression analysis. Perhaps most strikingly, 58 of the 60 patients were male, and the hyperuricaemic group was male in its entirety. The findings therefore derive predominantly from male patients, and the commentators judge their generalisability to female patients to be very limited. The uric acid signal survives all of these weaknesses and is described as more credible than the other associations, but the commentators argue the model should be presented as hypothesis-generating rather than predictive.

Finally, the commentators take issue with the claim that the relationship between systemic metabolic function and postoperative tendon healing has been little explored. They point to a multicentre study of 340 patients treated surgically for Achilles tendon rupture across five Italian centres, in which the presence of a metabolic disorder independently and negatively predicted return to work and sporting activity. That earlier work used functional rather than imaging endpoints, which is precisely why, in the commentators’ view, the new contribution is worthwhile: it supplies a structural correlate, visible on MRI, for an association already documented clinically. Framed in that way, the finding gains rather than loses standing, even as its interpretation remains provisional.

None of these criticisms detracts from what the commentators describe as a carefully conducted study addressing an understudied issue. The mechanistic case that urate disrupts tendon stem and progenitor cell function is coherent, and the clinical question raised by the original research is considered worth pursuing. What the field needs next, according to the commentary, is a prospective design incorporating T2 mapping, documented loading progression, functional outcomes and a balanced sex distribution. Only such a study, the commentators conclude, could settle what the present data can only suggest: that the chemistry circulating in a patient’s blood before surgery may leave a measurable imprint on the tissue that heals afterwards, and that clinicians should treat the uric acid connection as a promising lead rather than a prescription.

Subject of Research: Metabolic predictors of postoperative tendon healing after Achilles tendon rupture repair

Article Title: Commentary: Correlation analysis of metabolic parameters influencing postoperative tendon healing after Achilles tendon rupture repair

Article References: Spiezia, F., Oliva, F., Migliorini, F., & Maffulli, N. (2026). Commentary: Correlation analysis of metabolic parameters influencing postoperative tendon healing after Achilles tendon rupture repair. Frontiers in Medicine, 13, Article 1970521. https://doi.org/10.3389/fmed.2026.1970521

Image Credits: AI Generated

DOI: 10.3389/fmed.2026.1970521

Keywords: Achilles tendon rupture, uric acid, hyperuricaemia, tendon healing, MRI, signal-to-noise quotient, rehabilitation, orthopaedic surgery, metabolic disorders, confounding, study commentary, Commentary