Expert Opinion on Published Articles

Abstract

Treatment of osteochondral defects of the talus with a metal resurfacing inlay implant after failed previous surgery

CJA van Bergen, ICM van Ekeren, ML Reilingh, IN Sierevelt, CN van Dijk Bone Joint J 2013;95-B:1650-55

This paper addresses a potential solution to a complex problem that sometimes occurs in a young active patient. Deep, large (>150 mm²) medial osteochondral lesions can be resistant to conventional arthroscopic treatment of marrow stimulation by microfracture, which then requires some form of revision procedure. Options include osteochondral allograft, osteochondral autograft transfer and autologous chondrocyte implantation. Each of these has its own limitations, expense, availability and donor site morbidity.

A metallic, modular implant has been developed (Hemi CAP; Arthrosurface Inc, Franklin Massachusetts) for the talus with 15 incremental offset sizes to resurface large defects and fill cystic lesions.

In this review, 20 patients underwent the procedure for medial talar osteochondral lesions (OCLs) following previous failed primary surgery. Four patients were not included because they had the procedure as their primary surgery, not revision.

All were symptomatic for at least a year. CT scans were obtained pre-operatively to size and grade the lesions according to the modified Berndt and Harty classification. The mean size of the lesion was 15 mm (11-20 mm) in the AP direction and 10 mm (8-14 mm) in the mediolateral direction.

Their technique required adequate exposure through a medial malleolar osteotomy. The lesion was debrided to a healthy cartilage rim and the implant placed after drilling with a guide pin perpendicular to the curvature of the talar dome. Trial implants allow precise positioning and seating depth of the implant on the screw to ensure counter sinking of 1-2 mm and a smooth interface with the shoulder and the dome. The malleolar osteotomy was fixed with two malleolar screws.

Outcome measures included the numeric rating scale (NRS) for pain at rest, walking, stair climbing and running, the AOFAS (American Orthopaedic Foot and Ankle hind foot score), SF36 and the Foot and Ankle Outcome score. Follow-up was for 2-5 years. There was no loss to follow-up. The patients were assessed and scored pre-operatively and then 3 months, 6 months, 1 year and 2 years, post-operatively.

The NRS scores improved significantly in all activities over the follow-up period and the AOFAS scores improved from a mean of 62 pre-op to 87 at final follow-up, which was significant. All patients who were working prior to the surgery returned to work and the majority were able to participate in some form of sport at final follow-up. One patient had a medialising calcaneal osteotomy for persistent ankle pain with varus hind foot mal-alignment, and in five patients the medial malleolar screws were removed because of irritation. There were no other re-operations in the follow-up period. Radiologically there were no cases of loosening and the osteotomy healed in all cases. In one patient there was persistent subchondral sclerosis of the plafond and one had progressive subchondral cysts on the plafond, which were pain-free.

Although this is only level IV evidence with relatively short-term follow-up, it does open the door for further research into the use of implantable solutions for a complex problem. The authors stress that recessing the device 1-2 mm is essential and proved this in a biomechanical cadaver study.¹ The recessed implant becomes covered in fibrocartilage and thus acts as more of a biological surface in the long term with the ability to load share.

Pain in these larger lesions originates from the subchondral bone and the associated high hydrostatic pressure under load. This implant may reduce this by filling the cystic lesion and covering the open communication of the subchondral bone with the joint. Other biological solutions aim for the same thing: filling the cyst and covering the subchondral bone with either hyaline or fibro-cartilage.

The NRS scores improved significantly in all activities over the follow-up period and the AOFAS scores also improved significantly

Some concerns do arise:

1. The difficulty in taking one of these out if one needed to. It would likely require another medial malleolar osteotomy through a scarred area and worsen the clinical result.

2. Erosion or wear of the corresponding tibial plafond. In this paper the authors identified changes in two patients at final follow-up. The clinical relevance is not clear, but is concerning. This may have a bearing on the longevity of the implant and the potential for OA.

3. The lack of long-term follow-up.

The authors stress that this implant is to be used in a salvage situation when other options include invasive, expensive restorative procedures. Further controlled prospective studies with longer follow-up are necessary to determine if this implant has a role in treating these lesions.

Reference

1. Van Bergen CJ, Zengerink M, Blanevoort L, et al. Novel metallic implantation technique for osteochondral defects of the medial talar dome: a cadaver study. Acta Orthop 2010;81:495-502.