Achilles Tendon Release in Clubfoot: Radiological Comparison of Needle and Scalpel Techniques

Introduction

Idiopathic congenital talipes equinovarus (CTEV) is one of the most common congenital foot deformities, and if not treated in the early stages, it can lead to permanent functional or cosmetic problems. Today, the Ponseti method is regarded as the most effective and reliable approach for correcting this deformity [1,2]. However, only a few decades ago, the treatment of CTEV commonly involved extensive soft-tissue releases and comprehensive surgical procedures. Such operations often resulted in long-term complications, such as stiffness, pain, and recurrence [3,4]. With the introduction of the Ponseti method, the treatment approach has changed substantially. Through serial casting and, when necessary, minimally invasive Achilles tenotomy, it has become possible to achieve better physiological and functional outcomes [5,6]. Nevertheless, even today, resistance to serial casting and relapse remain challenging issues in some cases [7]. One of the main reasons for this is thought to be insufficient relaxation of the Achilles tendon [8]. The Achilles tenotomy, which constitutes the final step of the Ponseti protocol, is therefore important for achieving complete correction of the equinus deformity and sufficient dorsiflexion [9].

The Achilles tenotomy, which is the final step of the Ponseti treatment protocol, is one of the most critical stages in the correction of equinus deformity. Today, this procedure is performed using 2 main techniques: percutaneous tenotomy with a scalpel and percutaneous tenotomy using a needle. The primary goal of both methods is to achieve adequate relaxation of the Achilles tendon, thereby restoring full dorsiflexion of the foot. Needle-assisted tenotomy has become increasingly preferred in recent years, as it allows for a smaller skin incision, can be performed under local anesthesia, involves minimal bleeding, and has been associated with lower complication rates [10,11]. In contrast, percutaneous Achilles tenotomy with a scalpel is still preferred by some clinicians, as it provides direct visualization and greater control for the surgeon [12]. In the literature, the number of studies directly comparing the clinical and radiological outcomes of these 2 techniques is limited. However, studies evaluating procedures with similar surgical principles have reported that open (limited-open) and percutaneous approaches yield largely comparable clinical results, with differences mainly observed in parameters such as operative time, healing rate, and the extent of soft-tissue trauma [13,14].

Lateral foot radiographs play an important role in the objective assessment of deformity correction after treatment in patients with CTEV. In particular, the tibiocalcaneal, talocalcaneal, and talo–first metatarsal angles measured on radiographs taken in dorsiflexion provide valuable information regarding foot biomechanics and the quality of correction. In general, a tibiocalcaneal angle below 85° is considered normal, while a talocalcaneal angle ranging between 25° and 40° is regarded as the ideal range for anatomical alignment [14,15]. Improvements in these angles reflect the adequacy of the performed Achilles tenotomy and indicate successful correction of the equinus deformity. Several studies have suggested that measurements obtained in dorsiflexion, particularly changes in the tibiocalcaneal angle, best demonstrate the functional relaxation of the Achilles tendon. Therefore, radiographic measurements are considered an objective and reliable criterion not only for assessing the degree of deformity correction but also for evaluating the effectiveness of the tenotomy technique applied [16,17].

The choice of Achilles tenotomy technique can vary depending on the surgeon’s experience, preferences, and patient characteristics. However, the current literature lacks sufficient data to determine whether Achilles tenotomies performed with a needle or a scalpel differ in terms of radiological or functional outcomes. This limitation has led to variations in the protocols adopted by different centers and has made it difficult to compare results across studies. Moreover, radiological parameters evaluating the effect of tenotomy on ankle dorsiflexion have been addressed only to a limited extent in previous research.

The primary aim of this study was to evaluate whether residual posterior soft-tissue tightness persists after percutaneous Achilles tenotomy in idiopathic CTEV by using the tibiocalcaneal angle as a dorsiflexion-sensitive radiographic parameter. Secondary aims were to compare other radiological measurements and maximum ankle dorsiflexion between needle and scalpel tenotomy techniques, and to assess differences between tenotomized feet and the unaffected contralateral feet.

Material and Methods

STATISTICAL ANALYSIS:

Continuous variables are summarized using median and interquartile range (IQR; 25^th–75^th percentile) due to non-normal distribution, which was assessed using the Shapiro-Wilk test. Group comparisons were conducted using the Kruskal-Wallis test for overall differences among the 3 groups. When a significant result was found, pairwise Dunn post hoc tests with Bonferroni correction were applied. Categorical variables were summarized as frequency and percentages and compared using the Pearson chi-square test. A P value <0.05 was considered statistically significant. All statistical analyses were performed using R (version 4.5.0). Statistical analyses were primarily focused on the predefined primary outcome (tibiocalcaneal angle), while analyses of secondary outcomes were considered supportive.

Results

A total of 130 feet from 90 patients were included in the study. Of these, 74 feet underwent percutaneous Achilles tenotomy with a needle (group 1), and 56 with a scalpel (group 2).

Table 1 presents the demographic and baseline clinical characteristics of patients who underwent percutaneous tenotomy with a needle or a scalpel. There were no statistically significant differences between the 2 groups in terms of sex distribution, laterality, or severity scores (Pirani and Dimeglio), as well as age at the beginning of casting or time elapsed since the last cast (P>0.05 for all comparisons).

The comparative analysis among the control, needle tenotomy, and scalpel tenotomy groups revealed significant differences in most angles, except for the talo–first metatarsal angle. The tibiocalcaneal angle was significantly smaller in the control group (median 65.4°, IQR: 58.2–72.0°) than in both the needle (median 77.8°, IQR: 73.4–78.8°) and scalpel (median 77.0°, IQR: 70.5–81.1°) groups (P<0.001).

Pairwise comparisons demonstrated that both the needle vs control (P<0.001) and scalpel vs control (p<0.001) differences were statistically significant, whereas there was no significant difference between the needle and scalpel groups (P=1.000). The talocalcaneal angle was significantly smaller in the needle (median 29.3°, IQR: 26.7–33.8°) and scalpel (median 28.1°, IQR: 25.6–33.7°) groups than in the control group (median 45.9°, IQR: 40.8–49.4°) (P<0.001). Post hoc analyses revealed significant differences between both operated groups and the control group (P<0.001 for each), whereas no significant difference was found between the needle and scalpel groups (P=0.824).

The dorsiflexion angle was also significantly smaller in both operated groups (needle group: median 15.0°, IQR: 15.0–20.0°; scalpel group: median 15.0°, IQR: 10.0–20.0°) than in the control group (median 20.0°, IQR: 20.0–30.0°) (P<0.001).

Pairwise comparisons showed that both the needle vs control and scalpel vs control differences were statistically significant (P<0.001 for both), whereas the needle vs scalpel comparison was not (P=1.000). In contrast, there was no significant difference among the groups in terms of the talo–first metatarsal angle (P=0.099). The results are summarized in Table 2 and illustrated in Figure 3.

Discussion

The main finding of this study is that percutaneous Achilles tenotomy performed with either a needle or a scalpel results in comparable functional and radiological outcomes. With respect to the predefined primary outcome, no significant difference was observed in the tibiocalcaneal angle between the 2 tenotomy techniques. However, when tenotomized feet were compared with the unaffected contralateral feet, significant differences in dorsiflexion-sensitive radiological parameters, particularly the tibiocalcaneal angle, were identified. Although clinical ankle dorsiflexion was similar between operated and unaffected feet, this finding did not consistently correspond to complete radiological normalization. This discrepancy suggests that clinical dorsiflexion alone may be an insensitive indicator of residual posterior soft-tissue tightness. Therefore, despite satisfactory clinical correction, subtle residual anatomical deviations can persist in treated CTEV feet, irrespective of the tenotomy technique used.

The Ponseti method is currently regarded as the gold standard casting protocol for the treatment of CTEV, and most cases require an Achilles tenotomy at the end of the casting phase. However, there is no clear consensus on whether the tenotomy should be performed through an open or percutaneous approach, and, if a percutaneous technique is preferred, whether it is more appropriate to use a scalpel or a needle. The available evidence on this topic remains limited [19]. From a historical perspective, although the Ponseti casting approach has largely replaced extensive surgical procedures, variations in tenotomy techniques persist. Previous long-term studies have reported that, despite achieving excellent clinical correction, radiographic parameters do not always return to normal values. For instance, Cooper and Dietz demonstrated that even after appropriate treatment, residual angular differences remained when compared with normal pediatric feet, while Church et al found persistent alterations in lateral talocalcaneal, tibiocalcaneal, and talo–first metatarsal angles in Ponseti-treated feet relative to normative data. These findings suggest that radiological normalization does not always parallel clinical recovery, and subtle anatomical differences can persist even after functionally successful outcomes [20,21].

More recently, studies aiming to objectify the indications for tenotomy have demonstrated radiographic improvement following tenotomy but emphasized that complete normalization compared with the unaffected foot is not always achieved. However, in all of these studies, the tenotomy was performed using the classical scalpel technique, and alternative approaches such as percutaneous needle-assisted tenotomy have not yet been systematically evaluated [22]. In this context, the present study provides a unique contribution to the literature by directly comparing 2 different tenotomy techniques within the same dataset. The findings demonstrate that both techniques yield comparable functional and radiological outcomes; however, in line with previous research, both groups continued to exhibit significant radiological differences when compared with the unaffected feet.

The final step of the Ponseti protocol, Achilles tenotomy, is critically important for achieving complete correction of the deformity and ensuring adequate dorsiflexion. In the literature, percutaneous tenotomies performed with a needle have been highlighted for their minimally invasive nature, feasibility under local anesthesia, and low complication rates. Studies by Richetta et al and Pigeolet et al reported that needle-assisted tenotomies achieved a high rate of complete correction, with very low risks of infection and bleeding, and demonstrated early functional recovery in patients [23,24]. In contrast, classical percutaneous tenotomies performed with a scalpel have been reported to offer greater procedural safety due to the surgeon’s direct control and visualization, allowing for a more predictable complete tendon release and achieving comparable clinical correction rates [25].

In line with these findings, our study also found no significant functional or radiological differences between the groups that underwent tenotomy using a scalpel and those treated with a needle. Although previous studies have suggested that achieving a complete cut during needle tenotomy can be technically challenging and could carry a risk of incomplete tendon release, the marked tightness of the Achilles tendon in patients with CTEV allows the surgeon to easily verify intraoperatively whether the tendon has been completely severed, ensuring adequate release in most cases [23]. Therefore, the achievement of adequate tendon release in the cases treated with needle tenotomy in our study is considered the most likely explanation for the comparable functional and radiological outcomes observed between the 2 techniques.

In our study, lateral foot radiographs were analyzed to objectively assess the degree of deformity correction, focusing on the tibiocalcaneal, talocalcaneal, and talo–first metatarsal angles. These parameters are among the most reliable radiological indicators, reflecting both the extent of Achilles tendon release and the degree of biomechanical restoration of the ankle and hindfoot [21,22]. However, in CTEV cases, these radiographic angles, although appearing clinically corrected after treatment, rarely reach the same values as those of normal, unaffected feet [20,21]. The main reason for this discrepancy is that the deformity in CTEV arises not only from soft-tissue contractures but also from abnormalities in the shape and alignment of the tarsal bones. In particular, the anterior and plantar rotation of the talus, although clinically corrected through treatment, often fails to fully realign with normal anatomical axes, which can cause the talocalcaneal and tibiocalcaneal angles to remain outside normal limits. Furthermore, during correction with the Ponseti protocol, soft-tissue adaptation tends to occur more rapidly than bony remodeling, resulting in a foot that appears functionally well-corrected but radiographically remains short of complete normalization. In the existing literature, it has been demonstrated that even when functional correction is fully achieved after treatment with the Ponseti method, residual radiographic deviations often persist [21,26]. This finding is largely consistent with the results of our study. Thus, the persistence of radiological differences despite full functional correction in treated CTEV cases can be interpreted as a consequence of the structural and morphological origin of the deformity.

This study has several limitations. Due to its retrospective design, observer bias could not be completely eliminated, despite blinded radiographic measurements. In addition, needle and scalpel tenotomies were performed by different surgeons and under different anesthesia modalities, which can be potential confounding factors. Adverse events were not systematically recorded; therefore, a comprehensive complication analysis could not be performed. Finally, as the study included only idiopathic CTEV cases, the findings may not be generalizable to non-idiopathic forms of clubfoot.

Conclusions

In patients with CTEV treated using the Ponseti method, percutaneous Achilles tenotomy performed with either a needle or a scalpel provides comparable radiological and functional outcomes. Although both techniques achieve satisfactory correction, radiological differences persist, compared with the unaffected feet, indicating that mild structural deviations can remain despite clinical normalization. Therefore, radiological recovery should not be interpreted as complete anatomical correction.