HyProCure for progressive collapsing foot deformity: is subtalar arthroereisis a good procedure?

Abstract

Purpose

To investigate the treatment outcomes of subtalar arthroereisis (SA) in progressive collapsing foot deformity (PCFD) patients, to assess the clinical efficacy in PCFD patients after HyProCure removal, and to evaluate safety and effectiveness of SA.

Methods

In this retrospective study, 202 cases (213 feet) of PCFD patients treated with SA from June 2015 to December 2022 were selected. General data and surgical information were recorded, and clinical efficacy was evaluated through imaging and clinical indicators. Furthermore, for 36 patients (36 feet) who underwent secondary surgery to remove HyProCure, imaging and clinical evaluation indicators at 1-year post-removal were recorded. Complications were also documented.

Results

The main complications were sinus tarsi pain (91.37%), with partial relief or disappearance of symptoms in some patients after conservative treatment. The imaging indicators improved significantly after SA (P < 0.01), and AOFAS score and VAS were significantly improved (P < 0.01), with a 100% excellent rate in patients one year after SA. For patients who removed HyProCure, the imaging indicators exhibited a significant improvement at preoperation and post-SA (P < 0.01), and no statistical difference was observed between post-SA and post-removal (P > 0.05). Regarding clinical indicators, AOFAS score at post-SA was difference compared with preoperation and post-removal separately (P < 0.01). However, the difference in VAS between preoperation and post-SA was not statistically significant (P > 0.05). Notably, there was a significant improvement at post-removal compared with post-SA (P < 0.01).

Conclusion

PCFD patients showed significant improvement in imaging and clinical evaluations after SA, with no significant flatfoot recurrence in patients who had HyProCure removed. Therefore, the application of HyProCure in SA can be considered a safe and effective surgical treatment for PCFD patients.

Introduction

Progressive collapsing foot deformity (PCFD) is a prevalent foot disease affecting the complex 3D progressive foot deformity of the forefoot, midfoot, and hindfoot [1]. The incidence rate is 3-25%, mostly found in middle-aged and elderly female patients. The disease may be related to factors such as obesity, female gender, and prolonged sitting posture [2,3,4,5]. Diagnosis is primarily based on a comprehensive medical history, thorough physical examination, and evaluation of the severity of the patient based on the changes in angles on weightbearing X-rays of the foot [6]. Using weightbearing CT scans, the foot anatomy of patients can be reconstructed to observe three-dimensional deformities, joint surface conditions, and identify specific presentations such as impingement, arthritis, or instability [7]. For patients with symptomatic flatfoot deformity, the initial treatment choice is conservative, including orthotic insoles, physical therapy, muscle strengthening exercises. However, when conservative treatment proves ineffective after a certain period, surgical intervention is recommended, with a preference to avoid joint fusion surgery whenever possible [8].

Subtalar arthroereisis (SA), as a minimally invasive surgery, has shown many advantages in the treatment of flatfoot. It can correct flatfoot without damaging the joints, and the most popular type II screw is HyProCure device (GraMedica, Macomb, MI, USA). SA using HyProCure involves implanting appropriately sized screws into the sinus tarsi through small incisions, stabilizing the subtalar joint, effectively controlling excessive eversion of the affected foot, correcting abnormal activity of the subtalar joint, and preserving hindfoot mobility. Compared with traditional surgery, SA is less invasive, preserves the joint with reversibility, and can remove HyProCure without negatively affecting the subtalar joint [9]. Current literature confirms its short and medium-term effectiveness in flatfoot patients, especially in children and adolescents [10,11,12,13].

However, as far as we know, there is little study regarding the treatment effectiveness of HyProCure removal in the treatment of PCFD of SA. Therefore, our study aims to assess the efficacy of SA in patients with PCFD and explore its effectiveness.

Methods

Study design and setting

A retrospective analysis of clinical data was conducted on 202 cases (213 feet) of patients with flatfoot who were admitted to Shanghai Sixth People’s Hospital from June 2015 to December 2022. All patients underwent SA. This included 36 patients (36 feet) who underwent a secondary surgery to remove HyProCure.

Participants/study subjects

The inclusion criteria were as follows: (1) all patients were flexible PCFD I A-B stage; (2) age between 19 and 75 years; (3) failed to respond to 6months of conservative treatment preoperatively, had poor plantar flexion strength on the affected side, continued to experience foot and ankle pain, and discomfort after walking; and (4) complete follow-up data available.

The exclusion criteria were as follows: (1) rigid or neurogenic flatfoot patients; (2) severe joint restriction; (3) severe peripheral vascular disease, autoimmune disease, or poorly controlled diabetes; (4) severe rheumatoid arthritis, gouty arthritis; (5) severe heart or lung function impairment; (6) inability to cooperate due to mental illness; and (7) history of trauma or surgery to the affected foot.

Postoperative management

All patients were treated with elevation of the affected limb, cold compress, routine deswelling, pain relief and other symptomatic treatments, along with short leg walking boots applied postoperatively. Patients were instructed to exercise early active function, flexion and extension of hips, knees, toes, lower limbs, and core muscles strength training. The swelling subsided, and the ankle joint dorsiflexion and plantarflexion training could be tolerated with pain after 1 week. Active ankle extension and plantarflexion activities were feasible 3 to 4 weeks postoperatively, and partial weightbearing walking, supported by crutches and walking boots, could be tolerated with pain. After 4 weeks of outpatient review, patients were able to walk with full weight and perform stability and balance training. Regular outpatient follow-up was conducted.

In addition, for patients with sinus tarsi pain after SA, a minimum of 6 months of rehabilitation exercise and symptomatic treatment is recommended. If the pain persists or does not relieve, a second surgery may be performed to remove HyProCure.

Data collection and evaluation indicators

General data such as patient gender, age, side, body mass index (BMI), adjunctive procedures, imaging indicators, and clinical indicators were recorded. Complications were also recorded. Furthermore, follow-up data were collected for the patients who underwent HyProCure removal, including imaging indicators, clinical indicators at 1-year post-removal and postoperative complications.

Imaging indicators included talar-first metatarsal angle (T1M), talar-second metatarsal angle (T2M), and talonavicular coverage angle (TNCA) in weightbearing anteroposterior X-ray, as well as Meary’s angle, pitch angle, kite angle in weightbearing lateral X-ray. Clinical evaluation indicators included the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and Visual Analogue Scale (VAS).

Statistical analysis

SPSS 26.0 statistical software (IBM, Armonk, NY, USA) was used for data analysis. The normality of the data was assessed using the Shapiro-Wilk test. Normally distributed data were presented as mean ± standard deviation (‾x ± s), and between-group comparisons are made using t-tests; non-normally distributed data were described using median (M (Q1, Q3)), and between-group comparisons are made using the Wilcoxon rank-sum test. Categorical data (e.g., gender) were presented as frequencies (%), and intergroup comparisons were performed using the chi-square test. Three groups of data with normally distributed data over different time points were compared using repeated measures analysis of variance, followed by pairwise comparisons with LSD-t test. For non-normally distributed data over different time points, Friedman test was used for comparison, followed by pairwise comparisons with Bonferroni test. In this study, P < 0.05 was considered statistically significant.

Ethical review committee statement

This study was approved by the Ethics Committee and conducted in compliance with the Helsinki Declaration.

Results

Follow-up and general results

This study included a total of 202 patients (213 feet), with 66 males (70 feet, 32.86%) and 136 females (143 feet, 67.14%). Among them, 123 feet were on the left side (57.75%) and 90 feet on the right side (42.25%). The age of the patients ranged from 19 to 75 years old, with a BMI of 23.24 ± 3.67 kg/m². Of these patients, 36 cases (36 feet) underwent secondary surgery to remove HyProCure, including 14 males (14 feet, 38.89%) and 22 females (22 feet, 61.11%), with 20 feet on the left side (55.56%) and 16 feet on the right side (44.44%). The age of these patients ranged from 19 to 69 years old, with a BMI of 24.25 ± 4.33 kg/m².

Surgery was performed in 13 feet (6.1%) with isolated SA and in 200 feet (93.9%) in combination with adjunctive procedures, including gastrocnemius lengthening in 76 feet (38%), achilles tendon lengthening in 17 feet (8.5%), calcaneus osteotomy in 3 feet (1.5%), Cotton osteotomy in 1 feet (0.5%), accessory navicular bone excision in 46 feet (23%), scarf osteotomy in 52 feet (26%), spring ligament repair in 1 feet (0.5%), and arthroscopic lateral ankle ligament repair in 4 feet (2%) (Fig. 1). No one underwent other bone and soft tissue balance surgery (0%). The surgery most often associated with SA were gastrocnemius lengthening, accessory navicular bone excision, and scarf osteotomy (Fig. 2).

Fig. 1

Number of adjunctive procedures performed

Fig. 2

A 46-year-old male patient with PCFD was treated with SA and scarf osteotomy. And further consultation was made: (A–E): The patient who had bilateral PCFD took a general photo before surgery. The left foot was more serious. The anterior foot abduction, arch collapse and posterior foot ectropion were shown. And weightbearing lateral and anteroposterior X-ray indicated that the angles of foot was abnormal; (F–J): The general view, weightbearing lateral and anteroposterior X-ray showed the deformity correction at 1 year postoperatively

Radiographic and clinical outcome after SA

Patients were followed up for 12–36 months, with an average follow-up period of (14.35 ± 6.11) months. Preoperative T1M was 12.73° (7.98, 16.88)°, T2M was 22.56° (15.34, 26.21)°, TNCA was 15.03° (7.67, 23.79)°, Meary’s angle was 10.08° (5.48, 17.91)°, pitch angle was 17.88° (12.14, 22.85)°, and kite angle was 47.00° (38.06, 52.06)°; T1M at the last follow-up after SA was 7.90° (5.04, 12.03)°, T2M was 13.48° (8.76, 20.12)°, TNCA was 5.41° (2.78, 8.75)°, Meary’s angle was 6.23° (3.23, 9.68)°, pitch angle was 20.13° (15.88, 23.75)°, and kite angle was 45.31° (39.55, 49.35)°. Compared with preoperation and the last follow-up after SA, all imaging indicators showed a significant improvement (P < 0.01) (Fig. 3) (Table 1).

Fig. 3

Violin plot of comparison of preoperative and postoperative imaging indicators

Table 1 Comparison of preoperative and postoperative imaging indicators

Compared with preoperation, the AOFAS score at 3 months and 1 year postoperatively showed significant improvement (P < 0.01). At 1 year postoperatively, there were 109 cases (51.17%) rated as excellent, 104 cases (48.83%) rated as good, 0 cases (0%) rated as fair, and 0 cases (0%) rated as poor, with an excellent-good rate of 100%. The VAS at 3 months and 1 year postoperatively were significantly lower than preoperatively (P < 0.01). There were statistically significant differences in AOFAS scores and VAS between 3 months and 1 year postoperatively (P < 0.05) (Fig. 4) (Table 2).

Fig. 4

Violin plot of comparison of preoperative and postoperative clinical evaluation

Table 2 Comparison of AOFAS score and VAS preoperatively, at 3 months postoperatively and at 1 year postoperatively

Radiographic and clinical outcome after HyProCure removal

For patients who removed HyProCure, a follow-up was conducted for 12–30 months, with an average follow-up period of (19.92 ± 5.87) months. Preoperative T1M was 14.90°(10.60, 17.80)°, T2M was 20.91°(9.55, 26.13)°, TNCA was 16.74°(5.87, 26.33)°, Meary’s angle was 12.55°(10.16, 19.08)°, pitch angle was 15.43°±7.37°, and kite angle was 47.94°(44.57, 51.87)°; T1M at post-SA was 6.79°(4.03, 9.14)°, T2M was 9.66°(7.06, 15.48)°, TNCA was 4.73°(2.48, 6.75)°, Meary’s angle was 6.72°(3.40, 10.30)°, pitch angle was 20.53°±5.58°, and kite angle was 41.19°(38.14, 45.57)°; T1M at post-removal was 6.86°(5.17, 8.09)°, T2M was 10.26°(6.23, 15.63)°, TNCA was 6.31°(3.80, 8.18)°, Meary’s angle was 7.55°(5.82, 9.33)°, pitch angle was 20.95°±3.17°, and kite angle was 43.60°(39.10, 46.22)°. There was no significant difference in all indicators between 6-month post-SA and 1-year post-removal (Fig. 5). Compared with preoperation, T1M, T2M, TNCA in weightbearing anteroposterior X-ray, as well as Meary’s angle and kite angle, showed a significant decrease in weightbearing lateral X-ray after 6-month post-SA and 1-year post-removal, whereas the pitch angle showed a noticeable increase before surgery (P < 0.05). Comparing with 6-month post-SA, the difference in angles at 1-year post-removal was not statistically significant (P > 0.05) (Fig. 6) (Table 3).

Fig. 5

A 28-year-old female patient with AAFD was treated with SA. And further consultation was made: (A) The patient who had PCFD on the right foot took a general photo before surgery. The anterior foot abduction, arch collapse and posterior foot ectropion were shown; (B–C) Before surgery, the weightbearing lateral and anteroposterior X-ray indicated that the angles of foot was abnormal; (D–E) The weightbearing lateral and anteroposterior X-ray showed the deformity correction at 6-month post-SA; (F) The general view showed the foot alignment was satisfactory after 1-year post-removal, and no flatfoot recurrence was found; (G–H) The weightbearing lateral and anteroposterior X-ray showed the angles was maintained well with no significant change at 1-year post-removal

Fig. 6

Violin plot of comparison of imaging indicators in HyProCure removal patients

Table 3 Comparison of angles, AOFAS score and VAS in HyProCure removal patients

Compared with preoperation, AOFAS score at 6-month post-SA and 1-year post-removal were significantly improved (P < 0.05). There were 0 excellent cases (0%), 19 good cases (52.78%), 17 acceptable cases (47.22%), and 0 poor cases (0%), resulting in an excellent and good rate of 52.78% preoperatively. At 6-month post-SA, there were 0 excellent cases (0%), 35 good cases (97.22%), 1 acceptable case (2.78%), 0 poor cases (0%), leading to an excellent and good rate of 97.22%. At 1-year post-removal, there were 13 excellent cases (36.11%), 23 good cases (63.89%), 0 acceptable cases (0%), and 0 poor cases (0%), resultinf in an improved excellent and good rate of 100%. Compared with preoperation, there was no statistically significant difference in VAS at 6-month post-SA (P > 0.05). However, when compared with preoperation and 6-month post-SA, VAS was significantly decreased at 1-year post-removal (P < 0.05) (Fig. 7) (Table 3).

Fig. 7

Violin plot of comparison of AOFAS score and VAS in HyProCure removal patients

Complications

In this study, there were 58 cases of complications after SA, with an incidence of 27.23%. 53 cases (24.88%) experienced sinus tarsi pain. Achilles tendon tension occurred in 2 cases (0.94%). Muscle strength decreased in 1 case (0.47%). 1 case (0.47%) had poor wound healing. Foreign body sensation occurred in 1 case (0.47%). The incidence of sinus tarsi pain was the highest among all complications, accounting for 91.37%.

For patients who removed HyProCure, there were 1 case of complication, resulting in an incidence of 2.78%. The patient had a poor wound healing, which resolved after dressing changes. There were no instances of vascular or nerve injury, and no patient reported recurrence of sinus tarsi pain following the removal of HyProCure.

Discussion

SA for PCFD patients

In this study, the imaging indicators of patients with PCFD showed a decrease in T1M, T2M, TNCA, Meary’s angle, and kite angle, while pitch angle increased, with statistical significance. This suggests that SA can have a more favorable orthopedic effect on patients with PCFD. Graham et al. [14] conducted a study on 70 patients with adult patients. After SA, T2M significantly decreased, and pitch angle increased, returning to the normal range. A systematic review indicated that postoperative T1M, TNCA, Meary’s angle, and kite angle were all improved in adult patients [15]. Zhu et al. [16] found that T1M and TNCA showed significant improvement during more than 1 year follow-up. These findings are consistent with the results of improved imaging indicators observed in this study.

In terms of clinical efficacy, in this study, AOFAS score and VAS continued to improve, the functional activities of the affected foot were good, and postoperative discomfort was relieved. Graham et al. [17] followed up and found that the patients’ clinical function improved after surgery and the patient satisfaction was high. Bresnahan et al. [18] reported that patients’ foot pain decreased and functional activities improved after SA, with the greatest improvement observed at the 4-week postoperative follow-up, and the enhancement gradually continued until the 1-year postoperative follow-up. This is consistent with the results of this study. Several previous studies have also shown that postoperative clinical evaluations are good and patient satisfaction has improved [10, 11, 14, 19]. Additionally, studies have reported that adult patients can regain their preoperative physical activity level, with good long-term effects, reduced pain, improved functional outcomes, and increased satisfaction with surgical treatment [9].

The results obtained in this study and the high level of patient satisfaction indicate that SA can effectively stabilize the subtalar joint and eliminate excessive abnormal pronation, thereby reducing foot pain and improving patients’ quality of life. Therefore, we believe that SA is an effective surgical method for PCFD patients, and if necessary, adjunctive procedures can be performed simultaneously, which can effectively improve the foot deformity of patients and achieve better therapeutic outcomes.

Complications of SA

The postoperative complications in the patients primarily consisted of sinus tarsi pain (57 cases, 26.76%). The symptoms of some patients could be relieved after symptomatic treatment, while the symptoms of others were also relieved after HyProCure removal. Although complications may occur after SA, they can be effectively controlled and treated after appropriate operation and postoperative management. Additionally, it can avoid the complications associated with traditional surgery, reduce the trauma to patients, and enhance the safety of the procedure. Therefore, this study suggests that SA has greater potential for foot correction outcomes in PCFD patients, providing a safer and more effective surgical option compared with traditional surgery. It is important to note that the incidence of complications is higher in PCFD patients than in children and adolescents with flatfeet. There was also a higher incidence of HyProCure removal due to sinus tarsi pain. In this study, 36 cases were removed, resulting in a removal rate of 16.9%. Previous reports indicate that the removal rate ranges from 5–40% [20, 21]. While Saxena et al. [20] suggested that removing implants is not necessarily a negative aspect to SA, and that the potential risks associated with implant removal should not be deemed a contraindication for its application, we still recommend that patients should be fully informed of possible complications and the possibility of secondary surgery before SA. Through effective doctor-patient communication, we can help patients better cooperate with treatment, thereby improving the success rate of surgery.

HyProCure removal

For the patients with HyProCure removal, there was no statistical significance in imaging indicators 6-month post-SA and 1-year post-removal, which can confirm the persistence and stability of SA on foot orthopedic effects in PCFD patients. Although there are changes in angles after HyProCure removal, it is basically maintained in the normal range. These changes have not affected the treatment outcomes of SA. In our study, the short-term follow-up results after HyProCure removal showed that the foot shape of patients was still significantly improved compared with preoperation, with no obvious arch collapse, and no significant flatfoot recurrence.

According to earlier studies, all types of implants are recommended to be retained in the patient for at least 2 years to ensure adequate bone and soft tissue adaptation in patients with flatfeet after undergoing orthopedic surgery [22, 23]. In recent studies, it has been reported that the effects of implants in adult patients may take 18 months or even longer to become apparent [21]. However, there is no precise data on the minimum time required to maintain long-term foot orthosis results [24] and there is insufficient literature reporting on the specific timing and removal of HyProCure for PCFD after SA. Therefore, although the treatment outcomes of PCFD have been maintained well after HyProCure removal, the timing and prognosis of HyProCure removal for patients still need further research and exploration.

In terms of clinical evaluation, it was considered that VAS at 6-month post-SA was higher, possibly due to postoperative foot discomfort such as sinus tarsi pain. However, there was a significant difference in VAS at 6-month post-SA versus 1-year post-removal, indicating that pain had basically disappeared or relieved after HyProCure removal. After HyProCure removal, our study observed that patients could rapidly resume daily activities without notable discomfort or serious complications.

Graham et al. [17] reported that there were no lasting adverse reaction after HyProCure removal. Previous studies have shown that sinus tarsi pain was relieved after HyProCure removal, while adverse reactions caused by HyProCure were not reported [10, 14, 18], which may be due to the fact that sinus tarsi pain is mainly related to implant stimulation and the surgery itself. This result further confirms the safety and effectiveness of SA. Our study concluded that although the patient may experience discomfort after SA, only symptomatic treatment or HyProCure removal can effectively alleviate the symptoms, without causing flatfoot recurrence.

Strengths and limitations

This study is one of the few analyses to investigate the efficacy of HyProCure removal after SA in PCFD patients, aiming to evaluate the clinical outcomes of SA and gain insight into the safety and efficacy of SA in PCFD patients. However, we acknowledge that this study had a number of limitations. First, this study is a retrospective study, and some patients are more likely to have retrospective bias, but it does not affect the quality of patient follow-up content. Second, this study only used AOFAS score to evaluate clinical outcomes. Due to the use of AOFAS score to assess patient functionality initially, while the application of PROMs has only commenced these years. Also, we found that adherence to PROMs was not ideal, leading to the omission of follow-up data. To maintain consistency in clinical evaluation, we still used AOFAS score in this study to evaluate treatment outcomes. Third, only 1 year of follow-up after HyProCure removal in this study, which is short-term follow-up. Longer follow-up can be conducted in the future to make the study more reliable.

Conclusion

In conclusion, PCFD patients showed significant improvement in imaging and clinical evaluations, with no significant flatfoot recurrence in patients who had HyProCure removed. Therefore, our study concludes that the application of HyProCure in SA can be regarded as a safe and effective surgical treatment for PCFD and suggests concurrent adjunctive procedures, if necessary, to improve patient symptoms. Future research should focus on conducting multi-center prospective studies and further explore the relationship between the underlying mechanisms of SA and PCFD.