Current rehabilitation paradigms following Achilles tendon rupture emphasize early mobilization to mitigate muscle atrophy and functional impairment [19]. Traditional postoperative protocols recommended at least six weeks of immobilization. However, emerging clinical evidence suggests that reducing immobilization duration may facilitate earlier functional recovery. The biological basis for this approach lies in collagen composition dynamics: native Achilles tendon consists predominantly of mechanically robust type I collagen, whereas repaired tendon tissue initially contains weaker type III collagen. Prolonged immobilization may impede type I collagen synthesis and maturation, while controlled mechanical loading appears to promote its production, thereby enhancing tendon healing [20]. Our previous investigation [11] demonstrated that two weeks of postoperative immobilization following open AATR repair represents an optimal strategy for early rehabilitation, yielding satisfactory clinical outcomes with minimal discomfort. Building upon these findings, we attempted to develop and evaluate a more accelerated rehabilitation protocol while ensuring safety. Therefore this study was designed to extend our prior research by investigating the efficacy of an ultrasound-guided accelerated rehabilitation program.
One of the most crucial issues in AATR treatment is the incidence of re-rupture. Arner et al. [21] found that 53% of Achilles tendon ruptures occurred when the knee joint was hyperextended while pushing off the ground with the front foot during weight-bearing, such as athletes sprinting or jumping, and 27% occurred during sudden or rough ankle dorsiflexion movements, such as falling on stairs or falling from heights. Thus, it is necessary to strictly control the starting time of the ankle dorsiflexion movement while bearing weight, such as deep squatting, during the postoperative rehabilitation period. Without validated guidelines, the rehabilitation process after surgery largely rests on the clinical judgment and collaboration between the clinician and patient [22]. Patients typically demonstrate strong motivation for early rehabilitation initiation following brace removal, aiming to return to occupational and daily activities acceleratedly. However, premature or excessive mechanical loading may significantly increase the risk of postoperative complications, particularly re-rupture, due to compromised tendon integrity during the early healing phase [12]. Consequently, individualized rehabilitation protocols guided by evidential diagnostic assessment assume critical importance in optimizing recovery outcomes while minimizing adverse events.
Currently doctors in clinical practice utilize US or MRI for postoperative monitoring of Achilles tendon healing following AATR repair [13]– [14]. The US has emerged as the preferred imaging modality for routine follow-up examinations due to its distinct advantages of clinical accessibility, cost-effectiveness, and diagnostic reliability [23]. Notably, Ciszkowska-Łysoń et al. [14] developed an innovative dynamic US assessment protocol to quantitatively evaluate Achilles tendon tension during plantarflexion maneuvers. When there is tension in the Achilles tendon, a linear arrangement of tendon fibers and a main anechoic zone at the junction can be observed on the image. In our study, the ankle joint was dorsiflexed to increase tension, so as to observe whether there was any size change in the anechoic zone. When the range of the anechoic zone increased compared to that in the rest position, it was considered that there was a tendency of separation at the junction of ruptured Achilles tendon tissue. We also used this to distinguish whether the patient had further accelerated rehabilitation exercises. The patients could directly practice deep squat after removing the brace if there is no tendency of separation. A review investigating surgical interventions for acute ATR reported re-rupture rates of 3.6–8.3% [24]. Comparatively, our study reported a relatively low re-rupture rate of 3.8% (3/80). All three re-rupture cases in this study resulted from accidental falls or sudden traumatic events rather than protocol-guided rehabilitation exercises. These incidents occurred during unprotected dorsiflexion movements while not wearing the protective brace. Although no statistically significant difference in re-rupture rates was demonstrated between groups, the UR group exhibited a numerically lower incidence compared to the conventional rehabilitation group. Based on these, we initially believed that the accelerated recovery protocol might be could implemented with an acceptable safety profile. The studies with larger sample sizes are needed next to further prove that.
The other most important aspect of AATR treatment is Achilles tendon elongation. An effective way to evaluate Achilles tendon elongation is the heel-rise test [16]. Hoeffner et al. [25] conducted a randomized controlled trial about Achilles tendon elongation. 48 patients with a surgically repaired AATR were randomized to 2 groups: the standard group received the currently accepted rehabilitation, and the delayed group received the same rehabilitation except that initial loading was delayed by 6 weeks. Finally, they concluded that delayed loading was not superior to standard loading in reducing the heel-rise height difference at 1 year. The total excursion capacity of the musculotendinous unit is primarily determined by muscle fiber length, suggesting that deficits in heel-rise height may reflect alterations in tendon and fascicle length rather than muscular strength deficits [26,27,28]. This biomechanical principle implies that early rehabilitation exercises are unlikely to induce significant tendon elongation. In our cohort, all patients initiated weight-bearing rehabilitation following brace removal at 2 weeks postoperatively. During the rehabilitation period, we observed progressive improvement in the OHRH. Among patients with normal recovery, the OHRH index reached approximately 50% of preoperative values by 3 months post-surgery. Notably, the UR group demonstrated more rapid OHRH recovery compared to conventional rehabilitation. However, a limitation of our study was the lack of systematic assessment of long-term Achilles tendon elongation.
This study demonstrated considerable inter-individual variability in recovery trajectories. Comparative analysis revealed significantly shorter mean recovery times for both OHRH and LE measurements in the UR group compared to the CR group, suggesting more rapid functional recovery with the accelerated protocol. This was further supported by superior short-term clinical functional scores in the UR cohort. The VAS scores showed no significant intergroup differences, indicating that the accelerated protocol did not exacerbate postoperative discomfort. While the ATRS demonstrated statistically significant between-group differences from 10 to 14 weeks postoperatively, the AOFAS Ankle-Hindfoot scale failed to show similar discrimination. This discrepancy may be attributable to fundamental differences in scale composition: the ATRS relies exclusively on patient-reported subjective measures, whereas the AOFAS incorporates both subjective and objective clinical assessments [29]– [30].
Several important limitations should be acknowledged in this investigation. First, the study design was constrained by being a single-center retrospective cohort analysis with a relatively small sample size. These methodological characteristics necessitate validation through larger-scale, multicenter, prospective randomized controlled trials to substantiate our findings. Second, the demographic composition of our cohort exhibited a significant male predominance, potentially introducing sex-related bias that may limit the generalizability of our results to female populations. Third, the ultrasonographic assessment of tendon separation tendency relied principally on the subjective interpretation of the examining radiologist, representing a potential source of diagnostic variability. This highlights the need for developing more standardized, objective criteria for ultrasound evaluation of tendon healing. Additionally, the current study employed outcome measures that included subjective components. Future investigations would benefit from incorporating more objective, validated assessment tools. Finally, our follow-up period was insufficient to evaluate long-term outcomes, particularly regarding potential Achilles tendon elongation. Extended longitudinal studies are warranted to fully characterize the temporal progression of postoperative recovery.
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