Summary of Evidence

Subtalar arthroereisis (STA) has been suggested for treatment of flatfoot conditions and subtalar dislocation. The published clinical evidence evaluating STA for these conditions is minimal and of poor quality. In addition, professional societies have not endorsed STA for any purpose. Therefore, subtalar arthroereisis is considered experimental/investigative for all indications, including but not limited to, flatfoot conditions and talotarsal joint dislocation, due to the lack of clinical evidence demonstrating an impact on improved health outcomes.

Rationale

Arthroereisis is a surgical procedure that purposely limits movement across a joint. Subtalar arthroereisis (STA) is designed to correct excessive talar displacement and calcaneal eversion by reducing pronation across the subtalar joint. STA is also being evaluated as a treatment of talotarsal joint dislocation. It is performed by placing an implant in the sinus tarsi, which is a canal located between the talus and the calcaneus.

Numerous implants have been cleared for marketing by the U.S. Food and Drug Administration (FDA) via the 510(k) process for use in subtalar arthroereisis. Examples include Subtalar MBA®, HyProCure® Subtalar Implant System, MBAresorb Implant, Trilliant Surgical Subtalar Implant, IFS Subtalar Implant, and the Life Spine Subtalar Implant System.

The published clinical evidence evaluating the use of subtalar arthroereisis for treatment of flatfoot consists mainly of single-arm case series and a small nonrandomized controlled trial comparing subtalar arthroereisis with lateral column calcaneal lengthening. In 2015, Chong et al published results for a small prospective nonrandomized trial that compared subtalar arthroereisis (STA) with lateral column calcaneal lengthening for the treatment of 24 painful flatfeet in children. Seven children (13 feet) enrolled at a children’s medical center were treated with arthroereisis and 8 children (11 feet) enrolled at another children’s hospital were treated with lateral column lengthening. Children who underwent STA received a subdermal implant and were placed in below-knee walking casts for 3 weeks. Children treated with lateral column lengthening had an opening wedge osteotomy with the insertion of a wedge of cadaveric bone and were placed in non-weight-bearing casts for 1 month and “walker boots” for an additional month. Outcomes at a mean of 12.7 months after surgery included radiographs, foot pressure, kinematic analysis, and the Oxford Ankle-Foot Questionnaire for Children. The 2 groups showed similar improvements in the lateral talo-first metatarsal angle and talonavicular coverage and kinematics. Both groups showed statistically significant lateralization of the hindfoot and midfoot center of pressure (p<0.01). There were no between-group differences for any clinical or functional outcomes. On within-group comparison, only the STA group had a statistically significant reduction in time on the hindfoot (p=0.01). Both groups had improvements in the parental and child scores on the Oxford questionnaire, but only the STA group had a statistically significant improvement in this small sample. There were 2 complications in each group, with the removal of the hardware in 1 patient and removal of the implant in 2 patients. The improvement in pain and foot position was retained following implant removal. The researchers concluded that STA is a valid and potentially less-invasive alternative to lateral column lengthening that merits further investigation. This study is limited by its nonrandomized design and small sample size, as well as the lack of long-term outcomes.

In 2011, Metcalfe et al published a systematic review of the literature on STA for pediatric flexible flatfoot. Seventy-six case series (none controlled) or case reports were identified. Ten of the studies (756 feet) provided a clinician-based assessment of the surgical result graded from “excellent to poor” with follow-up between 36 and 240 months. Six studies (212 feet) included estimates of overall patient satisfaction using non-validated outcome measures, while 1 study (16 feet) found significant improvement using a validated foot-specific patient outcome measure. Data from 15 studies that reported radiographic values were combined for analysis. Although 8 of 9 radiographic parameters showed statistically significant improvements following arthroereisis procedures, the relation between radiographic and clinical outcomes is uncertain. The procedure was associated with several complications including sinus tarsi pain, device extrusion, and under correction. Complication rates ranged from 4.8-18.6%, with unplanned removal rates between 7.1% and 19.3% across all device types. The influence of adjunctive procedures on outcomes was not addressed in this review.

In 2012, Graham et al published a case series that was not confounded by adjunctive procedures and had a relatively long follow-up. This study reported mean 51-month follow-up of talotarsal stabilization in 117 feet using the HyProCure® device for the treatment of flexible talotarsal joint deformity. Patients who received adjunctive procedures affecting the talotarsal joint were excluded from analysis. Adults who met the inclusion and exclusion criteria were invited to participate in the study. 83 patients gave consent to participate, and 78 completed the Maryland Foot Score Questionnaire. Five patients did not complete the questionnaire because they had 7 (6%) implants removed. There were 16 revision surgeries with HyProCure®. Nine of the surgeries called for the repositioning of a partially displaced device, or a change in the size of the device altogether. Of the patients who retained the device, 52% reported complete alleviation of foot pain, 69% had no limitations in their foot functional abilities, and 80% reported complete satisfaction with the appearance of their feet. This case series is notable for its assessment of functional outcomes at medium-term follow-up in patients who did not have adjunct procedures.

Cicchinelli et al (2008) reported radiographic outcomes for a retrospective analysis of 20 pediatric patients with flatfoot (28 feet) treated with STA combined with gastrocnemius recession or with STA combined with gastrocnemius recession and medial column reconstruction. The authors reported that gastrocnemius recession had a measurable effect on correction of transverse plane deformity when used as an adjunct to STA; however, medial column reconstruction had a negative impact on the degree of correction in the transverse plane when used as an adjunct to STA and gastrocnemius recession.

Scher and et al (2007) described two cases of extensive implant reaction in two children two years after STA-peg procedures and tendo-Achilles lengthening were performed for painful flatfeet. The patients had minimal subtalar motion and pain at the sinus tarsi. Radiographs demonstrated surgical defects in the calcaneus. After failure of conservative management, implants were removed with good relief of pain in both patients. The authors stated that complications reported in the literature are common and wide ranging. The most seen complication is continued severe postoperative pain with failure to reconstitute the longitudinal arch on weight bearing and a residual flatfoot deformity. The authors concluded that they do not recommend arthroereisis in the treatment of painful flexible flatfoot in children.

Children with cerebral palsy and other neuromuscular disorders are another population of patients with flat feet. Vedantam et al (1998) reported on a case series of 78 children (140 feet) with neuromuscular disease who underwent STA with an STA-peg. The stem of this implant is placed into the calcaneous with the collar abutting the inferior surface of the lateral aspect of the talus, thus limiting motion. All but 5 of the children had additional procedures to balance the foot. Satisfactory results were reported in 96.4% of patients, although the contribution of the STA-peg cannot be isolated since the implantation was combined with other muscle-balancing procedures.

A case series conducted by Nelson et al (2004) evaluated use of the Maxwell-Brancheau Arthroereisis (MBA) implant in 34 patients with flexible flatfoot (67 feet). Patients in this study had failed an average of eight months of conservative therapy consisting of any combination of shoe-gear modifications, activity modifications, physical therapy, stretching exercises, oral anti-inflammatory medication, over-the-counter shoe inserts, and prescription orthotics. Average age of participants was 11.9 years (range, 6-17 years). While this study reported improvements in various radiographic anatomic measures (e.g., talo-first metatarsal and talar declination angles), no data were reported for improvement in symptoms. Two patients with pain due to sinus tarsi syndrome required implant removal and two patients required implant readjustment due to poor positioning.

Needleman (2006) reported significant improvements in pain and function in 78% of 23 patients (28 feet) with use of a subtalar implant as a component of reconstructive foot and ankle surgery. Average follow-up was 44 months. However, since results were not compared with controls receiving reconstructive surgery without STA, the contribution of the implants to these outcomes is unclear. In addition, Needleman reported an overall complication rate of 46% with surgical removal of 39% of the implants (11/28) due to sinus tarsi pain. In 9/11 feet, the implant was removed 8 months or more after the procedure. The author also commented that postoperative sinus tarsi pain was unpredictable.

The published clinical evidence evaluating the use of STA for treatment of talotarsal joint dislocation is very limited. In 2013, Bresnahan et al published a prospective single-arm study of talotarsal stabilization using HyProCure® in 35 patients (46 feet) diagnosed with recurrent and/or partial talotarsal joint dislocation. No procedures besides the insertion of the HyProCure® device were performed to address the dysfunctional joint. Subjective evaluation using the Maryland Foot Score assessment was obtained preoperatively and 1, 2, and 3 weeks, 1,2, 3, and 6 months, and 1 year postoperatively. The mean overall scores improved from a preoperative value of 69.53 + 19.56 to a postoperative value of 89.17 + 14.41 at the 1-year follow-up. Foot pain decreased by 37.0%, foot functional activities improved by 14.4%, and foot appearance improved by 29.5%. Implants were removed from 2 patients. No unresolved complications were observed. Limitations of this study include small sample size, lack of comparator group, single study site, and subjective evaluation of outcomes.

Hayes evaluates a wide range of medical technologies and provides evidence-based assessments to determine impacts on patient safety and health outcomes. The Hayes Rating has become the industry’s benchmark and reflects the strength and direction of the evidence regarding a medical technology. The Hayes Rating is D2 for subtalar arthroereisis (STA) for the treatment of adult-acquired flatfoot deformity associated with pain or impairment of function and not responsive to conservative treatment, indicating insufficient published evidence to assess the safety and/or impact on health outcomes. The Hayes Rating is also D2 for STA for the treatment of pediatric spastic flatfoot deformity associated with pain or impairment of function and not responsive to conservative treatment. The Hayes Rating is C for STA for the treatment of pediatric flexible flatfoot associated with pain or impairment of function and not responsive to conservative treatment, indicating unproven benefit and low quality of evidence.

In 2020, the American College of Foot and Ankle Surgeons (ACFAC) published a clinical consensus statement on management of adult-acquired flatfoot deformity. The following statement was made: “subtalar arthroereisis should not be considered as a single corrective procedure for stage IIB adult-acquired flatfoot.”

In 2004, the ACFAS also published a practice guideline on pediatric flatfoot stating that STA is controversial in the surgical community. Proponents argue that it is a minimally invasive technique that does not distort the normal anatomy of the foot, however other surgeons express concern about placing a permanent foreign body into a mobile segment of a child’s foot.

In 2012, clinical input was received through the Blue Cross Blue Shield Association clinical vetting process. Clinical input was received from two physician specialty societies and two academic medical centers. The clinical input was mixed, with most reviewers considering the STA procedure to be investigational.

Reference List

1. Blue Cross Blue Shield Association reference policy 7.01.104 - Subtalar Arthroereisis. Last accessed October 2024.
2. Bresnahan PJ, Chariton JT, Vedpathak A. Extraosseous talotarsal stabilization using HyProCure®: preliminary clinical outcomes of a prospective case series. J Foot Ankle Surg. 2013;52(2):195-202. DOI: 10.1053/j.jfas.2012.11.013.
3. Chong DY, Macwilliams BA, Hennessey TA, et al. Prospective comparison of subtalar arthroereisis with lateral column lengthening for painful flatfeet. J Pediatr Orthop B. 2015;24(4):345-353. DOI: 10.1097/BPB.0000000000000179.
4. Cicchinelli LD, Pascual Huerta J, García Carmona FJ, et al. Analysis of gastrocnemius recession and medial column procedures as adjuncts in arthroereisis for the correction of pediatric pes planovalgus: a radiographic retrospective study. J Foot Ankle Surg. 2008;47(5):385-391. DOI: 10.1053/j.jfas.2008.06.002.
5. Graham ME, Jawrani NT, Chikka A. Extraosseous talotarsal stabilization using HyProCure® in adults: a 5-year retrospective follow-up. J Foot Ankle Surg. 2012;51(1):23-29. DOI: 10.1053/j.jfas.2011.10.011.
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7. Hayes, Inc. Hayes Medical Technology Directory: Subtalar Arthroereisis for the Treatment of Adult-Acquired Flatfoot Deformity. 2023. Lansdale, PA. Last accessed October 2024.
8. Hayes, Inc. Hayes Medical Technology Directory: Subtalar Arthroereisis for the Treatment of Pediatric Flatfoot. 2023. Lansdale, PA. Last accessed October 2024.
9. Metcalfe SA, Bowling FL, Reeves ND. Subtalar joint arthroereisis in the management of pediatric flexible flatfoot: a critical review of the literature. Foot Ankle Int. 2011;32(12):1127-1139. DOI: 10.3113/FAI.2011.1127.
10. Needleman RL. A surgical approach for flexible flatfeet in adults including a subtalar arthroereisis with the MBA sinus tarsi implant. Foot Ankle Int. 2006;27(1):9-18. DOI: 10.1177/107110070602700103.
11. Nelson SC, Haycock DM, Little ER. Flexible flatfoot treatment with arthroereisis: radiographic improvement and child health survey analysis. J Foot Ankle Surg. 2004;43(3):144-155. DOI: 10.1053/j.jfas.2004.03.012.
12. Piraino JA, Theodoulou MH, Ortiz J, et al. American College of Foot and Ankle Surgeons clinical consensus statement: appropriate clinical management of adult-acquired flatfoot deformity. J Foot Ankle Surg. 2020;59(2):347-355. DOI: 10.1053/j.jfas.2019.09.001.
13. Scher DM, Bansal M, Handler-Matasar S, et al. Extensive implant reaction in failed subtalar joint arthroereisis: report of two cases. HSS J. 2007;3(2):177-181. DOI: 10.1007/s11420-007-9057-0.
14. Vedantam R, Capelli AM, Schoenecker PL. Subtalar arthroereisis for the correction of planovalgus foot in children with neuromuscular disorders. J Pediatr Orthop. 1998;18(3):294-298. Last accessed October 2024. Available at: https://journals.lww.com/pedorthopaedics/abstract/1998/05000/subtalar_arthroereisis_for_the_correction_of.4.aspx.