Surgery Section - Subtalar Arthroereisis

IMPORTANT REMINDER

Regence Medical Policies are developed to provide guidance for members and providers regarding coverage in accordance with contract terms. Benefit determinations are based in all cases on the applicable contract language. To the extent there may be any conflict between the Medical Policy and contract language, the contract language takes precedence.

PLEASE NOTE: Contracts exclude from coverage, among other things, services or procedures that are considered investigational or cosmetic. Providers may bill members for services or procedures that are considered investigational or cosmetic. Providers are encouraged to inform members before rendering such services that the members are likely to be financially responsible for the cost of these services.

Description

Pes planus deformity, also known as flatfoot, refers to loss of the normal medial longitudinal arch. Pes planus in children and adults is usually flexible and on non-weight-bearing a normal-appearing arch is present. Flexible flatfoot is a common disorder, anatomically described as excessive pronation during weight bearing due to anterior and medial displacement of the talus. It may be congenital in nature or may be acquired in adulthood due to posterior tibial tendon dysfunction which in turn may be caused by trauma, overuse, and inflammatory disorders. Symptoms include dull aching, throbbing and cramping pain which, in children, may be described as growing pains.

Conservative treatments include orthotics or shoe modifications. Operative intervention, particularly for juvenile flexible flatfoot, is considered only after a protracted course of orthotics and shoe modifications, and modifications in activity have failed to relieve associated symptoms.  Subtalar arthroereisis (also referred to as arthrorisis) has been performed for some 40 years with a variety of implant designs and compositions.  . This procedure is most often performed on young children and is designed to correct excessive talar displacement and calcaneal eversion by placing an implant in the sinus tarsi, a canal located between the talus and the calcaneus.  The subtalar implant acts as a spacer to block the anterior and inferior displacement of the talus, thus allowing normal subtalar joint motion but blocking excessive pronation and the resulting sequela. In young children, insertion of the implant is frequently offered as a stand alone procedure, while older children and adults often require adjunctive surgical procedures on bone and soft tissue to correct additional deformities. Possible complications include peroneal spastic flatfoot, pain, locking or stiffness of the subtalar joint and foreign body reaction. Although the procedure is reversible by removal of the implant, there is a risk of subtalar joint arthritis.  Poor tendon balancing with implant placement may occur, resulting in rearfoot pain due to overload of the implanted region. Inaccurate sizing may result in poor correction if the implant is too small, and painful locking of the rearfoot if the implant is too large.  Surgical alternatives to arthroereisis include tendon reconstruction or transfer, calcaneal osteotomy and arthrodesis, with the best results reported when a combination of these procedures is performed.

Note:  Subtalar arthroereisis and subtalar arthrodesis are significantly different procedures for which the description and coding are not interchangeable.  CPT code 28899 or HCPCS code S2117 are the only appropriate codes to be used when coding subtalar arthroereisis.

Policy/Criteria

Subtalar arthroereisis for the treatment of pes planus (flatfoot) in adults and children is considered investigational.

Scientific Background

Subtalar arthroereisis for the treatment of flexible flatfoot remains controversial within the surgical community. The current body of published literature consists primarily of unreliable single institution case series, retrospective reviews and individual case reports. The largest study was a case series in which Nelson and colleagues reported the results of retrospective follow-up of 37 patients (67 feet) at an average of 18.4 months post-MBA implantation. (3) While this study reported various improvements in certain anatomic angle measurements, there was no data on primary outcomes including improvement in symptoms, biomechanical control of excessive pronation and prevention of the progression of the deformity.

Vedantam and colleagues reported on a case series of 78 children (140 feet) with neuromuscular disease who underwent subtalar arthroereisis with a STA-peg. (4) Satisfactory results were reported in 96.4% of patients.  However, 73 of the children (94%) had additional procedures performed at the time of  the arthroereisis procedure to balance the foot; therefore, any contribution of the STA-peg cannot be isolated.  Needleman reported a nonrandomized, uncontrolled study of 28 feet in 23 patients with symptomatic flexible flatfoot deformities following reconstructive foot and ankle surgery that included subtalar arthroereisis with the MBA implant. (5) The American Orthopedic Foot and Ankle Society (AOFAS) Hindfoot Scale and a patient assessment questionnaire were obtained from all patients before surgery and at final follow-up.  Average follow-up was 44 months.  Significant improvement was reported for pain, activity level, ability to walk and footwear limitations, but not for walking distance. Radiographs showed significant correction of medial longitudinal arch, uncovering of the head of the talus and the difference in standing ankle height.  The authors reported an overall complication rate of 46% with surgical removal of 39% of the implants due to sinus tarsi pain. The authors also commented that postoperative sinus tarsi pain was unpredictable. The lack of randomized patient selection and a control group for comparison limits interpretation of these results. The results of this small trial support further study of this procedure with larger, well-designed randomized, controlled trials.

The American College of Foot and Ankle Surgeons published clinical practice guidelines which include subtalar arthroereisis in a list of surgical options. These guidelines note the controversial nature of this surgical technique:

Adult flatfoot (6)

Long-term results of arthroereisis in the adult flexible flatfoot patient have not been established.  Some surgeons advise against the subtalar arthroereisis procedure because of the risks associated with implantation of a foreign material, the potential need for further surgery to remove the implant, and the limited capacity of the implant to stabilize the medial column sag directly.

Pediatric flatfoot (7)

Proponents of this procedure argue that it is a minimally invasive technique that does not distort the normal anatomy of the foot.  Others have expressed concern about placing a permanent foreign body into a mobile segment of a child’s foot.  The indication for this procedure remains controversial in the surgical community.

In summary, data in the published literature is inadequate to permit scientific conclusions. One limitation of the published data is the lack of long term outcomes, particularly important since the procedure is often performed in growing children. Well-designed studies are needed to ascertain the effectiveness and durability of the subtalar arthroereisis implant for the treatment of pathologic flatfoot. An updated search of the MEDLINE database through March 19, 2009 failed to return any new clinical trials that alter these conclusions.

References

1. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.104
2. FDA 510(k) marketing clearance. Summary for Kinetikos Medical Incorporated (KMI) Subtalar MBA System™. Accessible at www.fda.gov/cdrh/pdf/k960692.pdf (Verified 2/4/09)
3. 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):144-55
4. 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):294-8
5. 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
6. Lee MS, Vanore JV, Thomas JL, et al.  Diagnosis and Treatment of Adult Flatfoot. Clinical Practice Guidelines; American College of Foot and Ankle Surgeons. J Foot Ankle Surg. 2005;44(2):78-113
7. Harris EJ, Vanore JV, Thomas JL, et al.  Diagnosis and treatment of pediatric flatfoot. Clinical Practice Guidelines; American College of Foot and Ankle Surgeons. J Foot Ankle Surg. 2004;43(6):341-73

Cross References

None

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