Current Insights On First MPJ Implants

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What About Emerging MPJ Implants?

There are also similar and modified designs that recently obtained FDA approval. The Metatarsal Decompression Implant (Solana Surgical) has a cantilever stem, which is angled between 45 and 75 degrees. This appears to facilitate a more anatomical design.

The Anatoemic Phalangeal Prosthesis (Arthrex) received FDA approval in 2007 but limited data has been published on this device. OsteoMed has two systems with the EnCompass Metatarsal Resurfacing device and a classic Hemi™ Great Toe Implant. Both systems are press-fit and appear similar to previous designs.

Author(s): 
Darryl J. Martins, DPM

   Carpenter and colleagues assessed the use of 32 implants in patients with hallux rigidus.10 Seventy-two percent of the study group had grade III hallux rigidus while the remaining 28 percent had grade II hallux rigidus. The average age of patients in the study was 63. The average follow-up was 27.3 months. The preoperative mean AOFAS-HMI score was 30.84 and the postoperative mean was 89.31. No implants were revised or removed, and no loosening occurred.

   In July 2009, Hopson and colleagues published a single case report involving a failed HemiCAP implant.11 The authors believe the HemiCAP system does not address the proximal phalanx of the hallux and is still too new to have substantial long-term studies describing its use. Unfortunately, if this implant fails and requires removal, as was the course of events in this case study, a large bone deficit remains in the first metatarsal head.

A Closer Look At EBM And Insurance Coverage For First MPJ Arthroplasty

The National Institute for Health and Clinical Excellence (NICE) published an Interventional Procedure Guidance in 2005 based on an analysis of seven case series.12 The NICE guidance concluded that current evidence on the safety and efficacy of first MPJ replacement of the hallux appears adequate to support the use of first MPJ arthroplasty. However, the guidance also states there is little evidence on the durability of newer implants and that complications may necessitate removal of the joint. These complications include persistent pain, infection, implant loosening, implant fracture, osteolysis, bone over-production, cyst formation, silastic granulomas and transfer metatarsalgia. With the lack of published data, insurance companies have not provided coverage for these devices as they deem them experimental and unproven.

   However, when reviewing Cigna’s policies, the company covers partial or total replacement of the first MPJ as a medically necessary alternative to arthrodesis.13 In order to receive coverage from Cigna, patients must have persistent severe disabling symptoms from hallux valgus or hallux rigidus due to degenerative joint disease of the first MPJ, and they must have previously failed conservative medical management. Aetna considers total prosthetic replacement arthroplasty with silastic implants and hemiarthroplasty medically necessary for people with disabling arthritis of the first MPJ and for hallux rigidus. However, Aetna considers other indications experimental and investigational.14

In Conclusion

Most surgeons consider first MPJ implants to be relatively contraindicated in young patients.15 In general, one should avoid joint replacement or resurfacing procedures in young patients as well as those who are required to participate in significant weightbearing activities.

   Contraindications to joint replacement include a history of joint or adjacent bone infection, poor bone stock, inadequate soft tissue coverage and a joint that can be preserved by means of osteotomy or other reconstructive options.15

   In 2008, Yee and Lau published a current concepts review and determined that most supporting evidence in regard to hemiarthroplasties for hallux rigidus is below Level 3 evidence and long-term consequences for hemiarthroplasties remain uncertain.16

   Although there is not consistent scientific evidence available that demonstrates the clinical effectiveness of partial implants, limited data from several studies suggest that MPJ replacement may be a reasonable option for a carefully selected subset of patients.15

   Dr. Martins is in private practice in Jackson, Mich., and Adrian, Mich.

References

1. Drago JJ Oloff L, et al. A comprehensive review of hallux limitus. J Foot Surg. 1984; 23(3):213-220.

2. Academy of Ambulatory Foot and Ankle Surgery. Academy of Ambulatory Foot and Ankle Surgery; Hallux limitus and hallux rigidus, 2003. Available at
http://guidelines.gov/content.aspx?id=4244&search=hallux+limitus

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