CAM 701104

Subtalar Arthroereisis and Subtalar Joint Implant

Category:Durable Medical Equipment   Last Reviewed:October 2019
Department(s):Medical Affairs   Next Review:October 2020
Original Date:October 2005    

Description:
Arthroereisis is a surgical procedure that purposely limits movement across a joint. Subtalar arthroereisis (STA) or extraosseous talotarsal stabilization is designed to correct excessive talar displacement and calcaneal eversion by reducing pronation across the subtalar joint. Extraosseous talotarsal stabilization 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.

For individuals who have flatfoot or talotarsal joint dislocation who receive STA, the evidence includes mainly single-arm case series and a small nonrandomized controlled trial comparing STA with lateral column calcaneal lengthening. Relevant outcomes are symptoms, functional outcomes, and quality of life. The small nonrandomized comparative trial (N=24 feet) is considered preliminary, and interpretation of the case series evidence is limited by the use of adjunctive procedures in addition to STA, creating difficulties in determining the extent to which each modality contributed to the outcomes. Another limitation of the published data is the lack of long-term outcomes, which is of particular importance because the procedure is often performed in growing children. In addition, some studies have reported high rates of complications and implant removal. The evidence is insufficient to determine the effects of the technology on health outcomes.   

Background
Subtalar arthroereisis has been performed for more than 50 years, with a variety of implant designs and compositions. The Maxwell-Brancheau Arthroereisis (MBA) implant is the most frequently reported, although other devices such as the HyProCure, subtalar arthroereisis peg, and Kalix are also described in the medical literature. The MBA implant is described as reversible and easy to insert, with the additional advantage that it does not require bone cement. In children, insertion of the MBA implant may be offered as a stand-alone procedure, although children and adults often require adjunctive surgical procedures on bone and soft tissue to correct additional deformities.

REGULATORY STATUS
A number of implants have been cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process, and are summarized in Table 1. In general, these devices are indicated for insertion into the sinus tarsi of the foot, allowing normal subtalar joint motion while blocking excessive pronation. 

Table 1. Representative Subtalar Implant Devices Cleared by FDA

Device

Manufacturer

Date Cleared

510(k) No.

Subtalar MBA®

Integra LifeSciences

07/96

K960692

OsteoMed Subtalar Implant System

OsteoMed

08/03

K031155

BioPro Subtalar Implant

BioPro

09/04

K041936

HyProCure Subtalar Implant System

Graham Medical Technologies

09/04

K042030

MBA resorb Implant

Kinetikos Medical

09/05

K051611

Metasurg Subtalar Implant

Metasurg

05/07

K070441

Subtalar Implant

Biomet Sports Medicine

07/07

K071498

Arthrex ProStop Plus Arthroereisis Subtalar Implant 

Arthrex 

01/08

K071456 

Trilliant Surgical Subtalar Implant

Trilliant Surgical 

02/11 

K103183 

Metasurg Subtalar Implant 

Metasurg 

08/11

K111265 

NuGait™ Subtalar Implant System

Ascension Orthopedic 

08/11

K111799 

Disco Subtalar Implant

Trilliant Surgical 

12/11 

K111834 

OsteoSpring FootJack Subtalar Implant System

OsteoSpring Medical 

12/11 

K112658 

IFS Subtalar Implant

Internal Fixation Systems 

12/11 

K113399 

The Life Spine Subtalar Implant System

Life Spring 

06/16 

K160169 

FDA: Food and Drug Administration.
a FDA 510(k) database search product code HWC (03/08/18). 

Policy:
Subtalar arthroereisis is investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY.

Extra-osseous subtalar joint implant is considered investigational and/or unproven and therefore considered NOT MEDICALLY NECESSARY.

Rationale
Evidence reviews assess the clinical evidence to determine whether the use of technology improves the net health outcome. Broadly defined, health outcomes are the length of life, quality of life, and ability to function---including benefits and harms. Every clinical condition has specific outcomes that are important to patients and managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of technology, two domains are examined: the relevance, and quality and credibility. To be relevant, studies must represent one or more intended clinical uses of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. Randomized controlled trials are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

Clinical Context and Therapy Purpose
The purpose of subtalar arthroereisis (STA) in patients who have flatfoot or who have talotarsal joint dislocation is to provide a treatment option that is an alternative to or an improvement on existing therapies.

The question addressed in this evidence review is: does STA improve the net health outcome in patients with flatfoot or talotarsal joint dislocation?

The following PICOTS were used to select literature to inform this review.

Patients
The relevant population(s) of interest are individuals with flatfoot and individuals with talotarsal joint dislocation.

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, or it may be acquired in adulthood due to posterior tibial tendon dysfunction, which in turn may be caused by trauma, overuse, inflammatory disorders, and other factors. Symptoms include dull, aching and throbbing, cramping pain, which in children may be described as growing pains. Additional symptoms include refusal to participate in athletics or walking long distances.

Talotarsal joint dislocation means that the joint surfaces of the talus are abnormally aligned on the heel and/or navicular bones.

Interventions
The therapy being considered is STA.

Arthroereisis is a surgical procedure that limits movement across a joint. STA (also called extraosseoustalotarsal stabilization) is designed to correct excessive talar displacement and calcaneal eversion by reducing pronation across the subtalar joint. The stabilization procedure is performed by placing an implant in the sinus tarsi, which is a canal located between the talus and the calcaneus.

Comparators
Surgical approaches for painful flatfoot deformities include tendon transfers, osteotomy, and arthrodesis. Conservative treatments include orthotics or shoe modifications.

Flatfoot
Literature searches on STA have identified few published studies, primarily consisting of single-institution case series and individual case reports, reporting on success rates following this procedure. There is a small controlled trial that has compared STA with alternative treatments.

Chong et al (2015) reported on a small prospective nonrandomized trial that compared STA with lateral column calcaneal lengthening for the treatment of 24 painful flatfeet in children.1 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 three 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 one month and “walker boots” for another 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 two 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 two complications in each group, with the removal of the hardware in one patient and removal of the implant in two patients. The improvement in pain and foot position was retained following implant removal.

Metcalfe et al (2011) published a systematic review of the literature on STA for pediatric flexible flatfoot.2 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 nonvalidated 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 eight of  nine radiographic parameters showed statistically significant improvements following arthroereisis procedures, the relation between radiographic and clinical outcomes is uncertain. The procedure was associated with a number of complications including sinus tarsi pain, device extrusion, and undercorrection. Complication rates ranged from 4.8% to 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.

Graham et al (2012) published a case series that was not confounded by adjunctive procedures and had a relatively long follow-up.3 This study reported mean 51-month follow-up of talotarsal stabilization in 117 feet using the HyProCure device. 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. Eighty-three patients gave consent to participate, and 78 completed the Maryland Foot Score Questionnaire; 5 patients did not complete questionnaire because they had 7 (6%) implants removed. There were 16 revision surgeries with HyProCure; 9 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.

Other case series have generally not excluded the use of other adjunctive treatments. For example, Vedantam et al (1998) reported on a series of 78 children (140 feet) with neuromuscular disease who underwent STA with an STA-peg.4 The stem of this implant is placed into the calcaneus with the collar abutting the inferior surface of the lateral aspect of the talus, thus limiting motion. All but five 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. Nelson et al (2004) reported on 37 patients (67 feet) who received a Maxwell-Brancheau Arthroereisis (MBA) implant and had an average of 18.4 months of follow-up.5 While this study reported various improvements in anatomic measurements, there were no data on improvement in symptoms. In another series, Needleman (2006) reported significant improvements in pain and function in 78% of patients (23 patients, 28 feet) with use of a subtalar implant as a component of reconstructive foot and ankle surgery.6 However, because results were not compared with controls receiving reconstructive surgery without STA, the contribution of the implants to these outcomes is unclear. Also, Needleman (2006) reported an overall complication rate of 46%, with surgical removal of 39% of the implants due to sinus tarsi pain; and that postoperative sinus tarsi pain was unpredictable.

Cicchinelli et al (2008) reported on radiographic outcomes in a retrospective analysis of 28 feet in 20 pediatric patients treated with STA combined with gastrocnemius recession or with STA combined with gastrocnemius recession and medial column reconstruction.7 Lucaccini et al (2008) analyzed clinical and radiographic results of 14 patients (16 feet) with hallux valgus in abnormal pronation syndrome treated with distal osteotomy of the first metatarsal bone and STA performed in 1 stage.8 Scharer et al (2010) conducted a retrospective radiographic evaluation of 39 patients (68 feet) who had received the MBA implant to treat painful pediatric flatfoot deformities.9 Patients’ average age at the time of surgery was 12 years (range, 6-16 years). Additional procedures included 12 (18%) gastrocnemius recessions, 6 (9%) Achilles tendon lengthening and 4 (6%) Kidner procedures. At an average 24-month follow-up (range, 6-61 months), there had been 10 (15%) complications requiring reoperation, including implant migration, undercorrection, overcorrection, and persistent pain. The implants were exchanged for a larger or a smaller implant. None of these case series permitted comparison with nonsurgical interventions or with other surgical interventions.

An example of a case series with longer follow-up is the retrospective study by Brancheau et al (2012), which reported on a mean 36-month follow-up (range, 18-48 months) in 35 patients (60 feet) after use of the MBA implant with adjunct procedures.8 Patients’ mean age was 14.3 years (range, 5-46 years). Significant changes were observed in radiographic measures (talocalcaneal angle, calcaneocuboid angle, first to second intermetatarsal angle, calcaneal inclination angle, talar declination angle). Seventeen percent of patients reported that 9 (15%) implants were removed after the initial surgery. Of the 24 (68.6%) patients who answered a subjective questionnaire (in person or by telephone at a mean of 33 months postoperatively), 95.8% reported resolution of the chief presenting complaint, and 79.2% said they were 100% satisfied with their surgical outcome. The contribution of the MBA implant to these results cannot be determined by this study design.

Section Summary: Flatfoot
The evidence evaluating the use of STA for treatment of flatfoot consists mainly of single-arm case series and a small nonrandomized controlled trial comparing STA with lateral column calcaneal lengthening. The small nonrandomized comparative trial (n=24 feet) is considered preliminary, and interpretation of the case series evidence is limited by the use of adjunctive procedures in addition to STA, creating difficulties in determining the extent to which each modality contributed to the outcomes. Another limitation of the published data is the lack of long-term outcomes, which is of particular importance because the procedure is often performed in growing children. Also, some studies have reported high rates of complications and implant removal.

Talotarsal Joint Dislocation
Bresnahan et al (2013) reported on a prospective study of talotarsal stabilization using HyProCure in 46 feet of 35 patients diagnosed with recurrent and/or partial talotarsal joint dislocation.9 No procedures besides insertion of the HyProCure device were performed to address the talotarsal joint dislocation. At 1 year postoperatively, scores on the Maryland Foot Score (/100) for 30 patients had improved from 69.53 preoperatively to 89.27 postoperatively. Foot pain decreased by 37.0%, foot functional activities improved by 14.4%, and foot appearance improved by 29.5%. Implants were removed from two feet with no unresolved complications.

Section Summary: Talotarsal Joint Dislocation
The current evidence on the use of STA for treatment of talotarsal joint dislocation is insufficient to draw conclusions about  treatment efficacy with certitude.

Adverse Events
Complications are frequently reported in the literature. Scher et al (2007) reported on 2 cases of extensive implant reaction in 2 children 2 years after a STA-peg procedure.10 Due to the commonly seen complication of severe postoperative pain with failure to reconstitute the longitudinal arch on weight-bearing and a residual flatfoot deformity, the authors do not recommend STA in the treatment of painful flatfoot in children. In a radiographic study, Saxena and Nguyen (2007) evaluated a bioabsorbable STA and found poor outcomes in 3 of 6 patients who met the inclusion criteria and consented to additional imaging.11 Two patients requested implant removal; a third patient had persistent pain but refused explantation. Radiographic measurement (magnetic resonance imaging or computed tomography) found that these three patients had smaller tarsal canal widths than the diameter of the inserted interference screw. The authors noted that the implant length also had to be reduced before implantation.

Cook et al (2011) conducted a retrospective case-control study to identify factors that might contribute to failure (explantation) of titanium arthroereisis implants.12 All patients who required removal of a self-locking wedge-type STA (n=22) were compared in a 1:2 ratio (n=44) with patients with nonexplantedarthroereisis who were treated during the same period. Subjects were matched for preoperative radiographic measurements, age, sex, presenting diagnosis, and length of follow-up. Multivariate logistic regression showed no significant effect of age, sex, implant size, shape, length of follow-up, implant position, surgeon experience, or concomitant procedures. Patients who required explantation had slightly greater odds of radiographic undercorrection (odds ratio, 1.175) or residual transverse plane-dominant deformities (odds ratio, 1.096). The percentage of explantations in this retrospective analysis was not described.

SUMMARY OF EVIDENCE
For individuals who have flatfoot or talotarsal joint dislocation who receive STA, the evidence includes mainly single-arm case series and a small nonrandomized controlled trial comparing STA with lateral column calcaneal lengthening. The relevant outcomes are symptoms, functional outcomes, and quality of life. The small nonrandomized comparative trial (n=24 feet) is considered preliminary, and interpretation of the case series evidence is limited by the use of adjunctive procedures in addition to STA, creating difficulties in determining the extent to which each modality contributed to the outcomes. Another limitation of the published data is the lack of long-term outcomes, which is of particular importance because the procedure is often performed in growing children. Also, some studies have reported high rates of complications and implant removal. The evidence is insufficient to determine the effects of the technology on health outcomes.

CLINICAL INPUT FROM PHYSICIAN SPECIALTY SOCIETIES AND ACADEMIC MEDICAL CENTERS
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process, through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.

2012 Input
In response to requests, input was received through 2 physician specialty societies and 2 academic medical centers while this policy was under review in 2012. Input was mixed, with most reviewers considering this procedure to be investigational.

2009 Input
In response to requests, input was received through 1 physician specialty society (3 reviews) and 5 academic medical centers while this policy was under review in 2009. Input was mixed regarding the medical necessity of arthroereisis. 

PRACTICE GUIDELINES AND POSITION STATEMENTS 
National Institute for Health and Care Excellence
Guidance from the National Institute for Health and Care Excellence (2009) concluded that current evidence on the safety and efficacy of sinus tarsi implant insertion for mobile flatfoot was inadequate in quality and quantity.13

American College of Foot and Ankle Surgeons
The ACFAS (2004,2005) published practice guidelines for the diagnosis and treatment of pediatric and adult flatfoot (neither is included in the ACFAS library of current clinical practice guidelines).14,15

ACFAS guidelines on adult flatfoot have stated:

“In the adult, arthroereisis is seldom implemented as an isolated procedure. Because of the long-term compensation and adaptation of the foot and adjunctive structures for flatfoot function, other ancillary procedures are usually used for appropriate stabilization. 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.”

The ACFAS guidelines on pediatric flatfoot have stated: “proponents of this procedure (arthroereisis) 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.”

U.S. PREVENTIVE SERVICES TASK FORCE RECOMMENDATIONS
Not applicable.  

ONGOING AND UNPUBLISHED CLINICAL TRIALS
A search of ClinicalTrials.gov in March 2019 did not identify any ongoing or unpublished trials that would likely influence this review. 

 References:  

  1. Chong DY, Macwilliams BA, Hennessey TA, et al. Prospective comparison of subtalar arthroereisis with lateral column lengthening for painful flatfeet. J Pediatr Orthop B. Jul 2015;24(4):345-353. PMID 25856275.
  2. 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. Dec 2011;32(12):1127-1139. PMID 22381197.
  3. Graham ME, Jawrani NT, Chikka A. Extraosseous talotarsal stabilization using HyProCure(R) in adults: a 5-year retrospective follow-up. J Foot Ankle Surg. Jan-Feb 2012;51(1):23-29. PMID 22196455.
  4. Vedantam R, Capelli AM, Schoenecker PL. Subtalar arthroereisis for the correction of planovalgus foot in children with neuromuscular disorders. J Pediatr Orthop. May-Jun 1998;18(3):294-298. PMID 9600551.
  5. Nelson SC, Haycock DM, Little ER. Flexible flatfoot treatment with arthroereisis: radiographic improvement and child health survey analysis. J Foot Ankle Surg. May-Jun 2004;43(3):144-155. PMID 15181430.
  6. Needleman RL. A surgical approach for flexible flatfeet in adults including a subtalar arthroereisis with the MBA sinus tarsi implant. Foot Ankle Int. Jan 2006;27(1):9-18. PMID 16442023.
  7. Cicchinelli LD, Pascual Huerta J, Garcia 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. Sep-Oct 2008;47(5):385-391. PMID 18725117.
  8. Brancheau SP, Walker KM, Northcutt DR. An analysis of outcomes after use of the Maxwell-Brancheau Arthroereisis implant. J Foot Ankle Surg. Jan-Feb 2012;51(1):3-8. PMID 22196453.
  9. Bresnahan PJ, Chariton JT, Vedpathak A. Extraosseous talotarsal stabilization using HyProCure(R): preliminary clinical outcomes of a prospective case series. J Foot Ankle Surg. Mar-Apr 2013;52(2):195-202. PMID 23313499.
  10. Scher DM, Bansal M, Handler-Matasar S, et al. Extensive implant reaction in failed subtalar joint arthroereisis: report of two cases. HSS J. Sep 2007;3(2):177-181. PMID 18751791.
  11. Saxena A, Nguyen A. Preliminary radiographic findings and sizing implications on patients undergoing bioabsorbable subtalar arthroereisis. J Foot Ankle Surg. May-Jun 2007;46(3):175-180. PMID 17466243.
  12. Cook EA, Cook JJ, Basile P. Identifying risk factors in subtalar arthroereisis explantation: a propensity-matched analysis. J Foot Ankle Surg. Jul-Aug 2011;50(4):395-401. PMID 21708340.
  13. National Institute for Health and Care Excellence (NICE). Sinus Tarsi Implant Insertion for Mobile Flatfoot [IPG305]. 2009; https://www.nice.org.uk/guidance/IPG305. Accessed March 13, 2019.
  14. Harris EJ, Vanore JV, Thomas JL, et al. Clinical Practice Guideline Pediatric Flatfoot Panel: American College of Foot and Ankle Surgeons (ACFAS). Diagnosis and treatment of pediatric flatfoot. J Foot Ankle Surg. Nov-Dec 2004;43(6):341-373. PMID 15605048.
  15. Lee MS, Vanore JV, Thomas JL, et al. Clinical Practice Guideline Adult Flatfoot Panel: American College of Foot and Ankle Surgeons (ACFAS). Diagnosis and treatment of adult flatfoot. J Foot Ankle Surg. Mar-Apr 2005;44(2):78-113. PMID 15768358.

Coding Section

Codes Number Description
CPT 0335T

Extra-osseous subtalar joint implant for talotarsal stabilization

  0510T (effective 01/01/2019)   Removal of sinus tarsi implant 
  0511T (effective 01/01/2019)  Removal and reinsertion of sinus tarsi implant 
ICD-9 Diagnosis 734 Flat foot, acquired
  754.61 Congenital pes planus
ICD-9 Procedure 81.18 Subtalar joint artroereisis
HCPCS S2117 Arthroereisis, subtalar
ICD-10-CM (effective 10/1/15)   Investigational for all diagnoses
  M21.40-M21.42 Flatfoot, acquired code range
ICD-10-PCS (effective 10/1/15) 0SUH0JZ, 0SUJ0JZ Surgical, lower joints, supplement, tarsal joint, open, synthetic substitute, right and left codes
  0SUH3JZ, 0SUJ3JZ Surgical, lower joints, supplement, tarsal joint, percutaneous, synthetic substitute, right and left codes.
  0SUH4JZ, 0SUJ4JZ Surgical, lower joints, supplement, tarsal joint, percutaneous endoscopic, synthetic substitute, right and left codes
Type of service    
Place of service    

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross and Blue Shield Association technology assessment program (TEC) and other non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies and accredited national guidelines.

"Current Procedural Terminology© American Medical Association.  All Rights Reserved" 

History From 2014 Forward     

10/01/2019 

Annual review, rewriting policy statement for clarity, updating rationale and references. Removing guidelines section as there are no criteria for medical necessity of subtalar arthroereisis or extra-osseous subtalar joint implants. 

12/20/2018 

Updating with 2019 codes.  

10/10/2018

Annual review, no change to policy intent. Updating background, regulatory status, rationale and references. 

10/03/2017 

Annual review, no change to policy intent. Updating background, description, rationale and references. 

10/03/2016

Annual review, no change to policy intent. 

10/08/2015 

Annual review, no change to policy intent. Updated background, description, regulatory status, rationale and references. Added guidelines.

10/08/2014

Annual review. No change to policy intent. Added coding section. Updated background, rationale and references. 


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