This prospective case report is the first clinical report of a metal implant for OCDs of the talus and gives an insight into the surgical technique and clinical follow-up. Treatment of osteochondral lesions or osteonecrosis by means of metal resurfacing implants is relatively new. During the past 3 years, promising clinical results were reported for the treatment of the femoral [24
] and humeral head [18
], as well as the first metatarsal [10
] and patellar surface [7
]. Two biomechanical cadaveric studies provided foundations for use of the talus implant in the ankle joint [1
The ideal indications for treatment with this implant are not yet known. The authors consider its use in patients with a large OCD on the medial talar dome who have clinically significant pain more than 1 year after primary surgical treatment. The following are regarded as contraindications: age < 18 years, OCD size > 20 mm, ankle osteoarthritis grade II or III, concomitant ankle pathology, advanced osteoporosis, infection, diabetes, or a known allergy to implant material.
The surgical approach is an important part of the implantation technique because the accuracy of implantation of this device strongly depends on the approach and quality of vision. For adequate exposure, the authors make an oblique osteotomy of the medial malleolus. The osteotomy is ideally directed toward the intersection between the tibial plafond and medial malleolus at an angle of 30° relative to the long tibial axis [21
]. Although there are other osteotomy options, including anterior tibial, step-cut, and inverted V or U osteotomies, the oblique osteotomy is our preferred technique because it is relatively simple, exposure of the talus is excellent, and congruent reduction is well possible [12
The surface of the prosthetic device should be placed slightly recessed relative to the surrounding surface of the talar cartilage because talar cartilage deforms during weight bearing while the implant does not. Wan et al. [25
] measured a peak cartilage deformation of 34.5 ± 7.3% under full body weight in persons with a medial talar dome cartilage thickness of 1.42 ± 0.31 mm. We therefore aim at an implantation level of 0.5 mm below the adjacent cartilage. This implantation level was found appropriate in a previous cadaveric study [22
]. When the prosthetic device is correctly implanted, excessive contact pressures of the implant are avoided [22
While there are various offset sizes, each articular component has a diameter of 15 mm. This is based on the finding that primary arthroscopic treatment is generally successful for lesions up to 15 mm, while this treatment is less successful for larger lesions [6
]. The set diameter may be a disadvantage of the implant. In our patient, the largest defect diameter was 17 mm. The part of the OCD that was not covered by the implant is expected to be filled by fibrocartilaginous tissue.
Alternative current treatment methods for this patient are osteochondral autograft transfer system (OATS), cancellous bone grafting, an allograft, ankle arthrodesis or prosthesis. OATS and cancellous bone grafting carry the risk of donor-site pain and are available in limited amounts [19
]. Allografts can be used for massive defects but are not recommended for localized OCDs [20
]. Ankle arthrodesis or prosthesis is definite solutions for a recurrent OCD but are rather not used in young patients. Recently reported other treatment options are matrix-induced autologous chondrocyte implantation (MACI) and engineered osteochondral grafts [5