A prospective trial on the clinical efficacy of the Ankle Spacer for the surgical treatment of large, multiple, cystic and secondary or tertiary osteochondral defects of the talus.

Ankle sprains can result in talar osteochondral defects (OCDs) which have a
significant impact on the quality of life of patients. When these OCDs are of
large nature (anterior*posterior or medial*lateral diameter >1.5cm in
diameter), cystic, have failed prior surgical treatment, or when there are
multiple present on the talar articular surface, surgical care by means of
fixation or bone marrow stimulation is contra-indicated. An ankle arthrodesis
or fusion can be considered, but this results in functional limitation due to a
decreased range of motion (ROM). In order to serve for a bone sparing
prosthesis procedure, preserve range of motion, optimize physical functioning
and to resurface the talus, the Ankle Spacer has been developed. It is a
one-piece implant system that replaces the articulating upper talus surface of
the tibio-talar joint, and offers several implant sizes in order to fit to the
different talus sizes. It is anatomically designed to the native upper talus
surface to provide an optimal fit to the distal articular surface. It has a
rough titanium plasma spray (TPS) coated under surface with two posts and
spikes for implant fixation. The rough surface enables secondary fixation by
means of bone ingrowth and the spikes at the posterior part of the prosthesis
allowing for optimal adherence of the implant and for minimal iatrogenic damage
upon fixation. By these means, the anatomical situation and the natural
congruency of the ankle joint are mirrored to a optimal extent. Despite the
fact that no clinical trials have been published on this specific implant, it
is hypothesized that the 5-year postoperative clinical outcomes concerning pain
and prosthesis survival will be considered good.

* Primary Objective: determine the functional outcome and clinical efficacy
after open surgical implantation of the Ankle Spacer for patients with large,
cystic, previously surgically failed and/or multiple OCDs of the talus by means
of functional outcome questionnaires
* Secondary Objective(s): assess the implant survivorship (revision rate),
operation time, adverse events, and length of hospital stay

The present study concerns a non-randomized, non-blinded, non-comparative
prospective trial, with a five-year follow-up period at the outpatient clinic
aiming at assessing pain and implant survival, and thereby investigating the
clinical efficacy of the Ankle Spacer. Two interim analyses will be included in
the present study, one at 6 months postoperatively, and one at 2 years
postoperatively to assess short- and midterm results. The short-term follow-up
will assess surgical recovery, and the intermediate follow-up clinical efficacy
concerning pain levels and implant survival. All patients visiting the
outpatient department for large (anterior*posterior or medial*lateral >1.5 cm
in diameter), cystic defects, those that failed prior surgical intervention(s)
and multiple talar OCDs on the talar surface, eligible for surgical
implantation of the Ankle Spacer will be requested if they are willing to
participate in the present clinical trial. If they are interested, patients
will be informed about this study and are given two weeks to decide upon
participation. In case patients provide their consent, they are screened for
meeting the inclusion criteria, and are assessed pre-operatively by means of
standard (anteroposterior AP and lateral) standing weight-bearing conventional
radiographs, by documenting a questionnaire containing the Numeric Rating Scale
(NRS) of pain, the American Orthopaedic Foot and Ankle Hindfoot Score (AOFAS)
Foot and Ankle Outcome Score (FAOS) and the Short-Form 36 (SF-36) and
assessment of the range of motion (ROM) by means of a physical examination.
Additionally patients receive a preoperative CT-scan for surgical planning
according to the standard AMC protocol. Subsequently after surgery, patients
will be followed-up at two and six weeks, three and six months, one-year
post-operatively, and annually thereafter. At these follow-up moments the
patients will be requested to fill out a questionnaire, a physical examination
will be performed to test the ROM, and radiographs will be taken one day, 6
weeks, 1, 2 and 5-years post-operatively. Patients will also receive a
post-operative CT scan at one year post-operatively, as part of the normal
work-up/AMC protocol for osteochondral talar defects.

All included patients will be treated by means of surgical implantation of the
Ankle Spacer prosthesis in an open manner replacing the talar side of the
tibiotalar joint.

Preoperatively patients will be asked to fill out a questionnaire, and a
radiograph will be taken for appropriate sizing of the implant, and range of
motion (ROM) will be documented. Postoperatively patients will be asked to
visit the outpatient clinic 9 times and five times postoperatively a
radiographs will be taken.
Risks or complications associated with this specific surgical technique and all
prosthetic ankle surgery techniques are bleeding, infection, venous thrombosis,
pain, swelling, reduced ROM, delayed wound healing and damage to superficial
nerves. Less frequently occurring risks associated with the surgical procedure
are allergies and other reactions to device materials, loosening of the
implant, and bone fractures as a result of one-sided overload or weakened bone
substance.
Patients may find participation in the present study beneficial as this
treatment may provide a successful solution before deciding upon an
arthrodesis. In case of failed treatment, an arthrodesis is still an option.
Patient risk will be mainly caused by the implantation of a new bone-sparing
prosthesis with an unknown success rate, there will be no further burden with
regard to extra visits to the outpatient clinic, nor additional radiograph
taking. Our normal work up for a biological solution for secondary
osteochondral defects comprises the same number of outpatient clinic visits
with a radiograph and two additional CT scans.