Ankle Replacement-BOX total ankle replacement (MatOrtho)
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Learn the Ankle Replacement-BOX total ankle replacement (MatOrtho) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Ankle Replacement-BOX total ankle replacement (MatOrtho) surgical procedure.
Ankle replacement has been available as an intervention for ankle arthritis since the 1970s. The initial implants were engineered on the assumption that the human ankle joint functioned as a true hinge . They were therefore designed only to allow uniplanar movement (plantar and dorsiflexion) and comprised just 2 components which were mechanically linked. The ankle joints they were implanted into however also functioned with a degree of rotation which had to occur at the weakest point in the “mechanism”. Given the robustness of the implanted ankle hinges this transpired to be the implant/joint interface which therefore led invariably to early implant failure.
The next generation of ankle replacements used a 3 component design, in which the Tibial and Talar components were linked by a UHMW polyethylene meniscus which allowed rotation to occur within the joint itself. These ‘mobile-bearing’ prostheses used the congruity of the ‘articulating’ surfaces, to reduce the constrained forces and overcome the high contact stresses resulting in a reduction in polyethylene wear and mechanical loosening of the fixed components. These initial replacements whose results still define what longevity an ankle replacement should attain are the STAR , Beuchal-Pappas and Salto implants. Advancements have been made in the instrumentation and reproducibility of implantation. In general their 10 year survivorships are lower than reported for hip and knee replacements UK National Joint Registry survival rates are now in the region of 80 percent.
Total ankle replacement is generally not be recommended for younger or higher demand patients due to concerns of longevity due to accelerated wear of the implant, the exception being patients with severe poly-articular inflammatory arthropathy.
The BOX (Bologna-Oxford) ankle manufactured by MatOrth is a three component prosthesis. The Box ankle replacement prosthesis has been designed to maximise congruency throughout the arc of motion, aiming to mimic normal ankle biomechanics. The bearing surface of the tibial component has a subtle curve in the coronal plane to accommodate for varus/ valgus force through the talo-crural joint. Biomechanical modelling has demonstrated both rolling and sliding motions take place at the talocrural joint. In theory, full congruence should reduce wear by avoiding edge-loading. Similar to the STAR prosthesis, two anchorage bars on the tibial platform of the BOX ankle replacement provide stable primary fixation to the tibial bone. A precisely cut talar component allows a good press fit of the talar component, which is further stabilised with two vertical pegs.
Primary stability of the Box ankle replacement components reduces micromotion assisting the circumstances necessary to provide reliable bone ingrowth.
Readers will also find the following techniques of interest:
Author:Nick Cullen FRCS (Tr & Orth)
Institution: The Royal National Orthopaedic Hospital, Stanmore, London, UK.
- Each operation and the questions associated become a named course in the CPD section
- The operative technique itself is read as a lesson as is any company implant information if this is being assessed.
- You’ll need to tick the box to confirm this has been done and can do this immediately if you have already read the op tech.
- The vast majority of operations have a 10-15 MCQ quiz covering all aspects of the decision making and the technique
- There are four possible answers of which one is correct (or on occasion more correct) than the others.
- There are additional quiz modules on the surgical steps, the implants and problem cases being added continually
- The course is completed once all the lessons are read and quizzes submitted and passed.
- On successful completion of each quiz you will receive validated CPD points that add to the certificate in your CPD folder.
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- The timer suspends after 5 minutes though if there is no activity.
- When you restart you will resume at the same point in the module.
- Once you have completed each quiz you will need to feedback on the module first then click “submit” and your paper will be marked.
The pass mark is 75%.
- If you fall below this level you will be directed back to re-read the slides where you’ve tripped up.
- Once these have been read you can re-do just the questions you failed on.
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- Operation Quiz – 1 CPD point
- Surgical steps Quiz – 1/4 CPD point
- Implants Quiz – 1/4 CPD point
- Problem case Quiz – 1/2 CPD point
One CPD point equates to one hour of academic activity
Welcome to the Professional Development question section. The objective of taking these tests is to demonstrate that you have understood all aspects of the assessment and management of patients requiring surgical intevention. On successful completion you will receive a certificate accredited by both the Royal College of Surgeons of both England and Edinburgh as well as the British Orthopaedic Association.
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