T
he INBONE total ankle system is a third-generation system and was designed with the proven principles of the total joint arthroplasty in mind.
In contrast, to essentially all other total ankle systems, the INBONE total ankle system uses intramedullary rather than extramedullary referencing. To achieve reliable intramedullary alignment, the INBONE total ankle system uses a leg frame that requires pre-incision preparation. This technique allows the surgeon to correct deformities prior to making any bone cuts.
Initial total ankle arthroplasty procedures were performed in the early 1970s, as an alternative to arthrodesis of the ankle for patients who suffered from severe osteoarthritis or systemic inflammatory disease. The first implant designs were highly constraining and had high failure rates which were generally attributed to cement fixation causing an increase in loads across the implant-bone interface, increased bone resorption, and poor operative technique.
Second-generation ankle replacement implant designs more closely replicated anatomy, kinematics, stability and alignment and outcomes have been more favorable. The biomechanical superiority of these implants over the more classical arthrodesis procedures has been demonstrated in several recent studies showing an improvement in, or even return to, a normal gait pattern and an improvement in the mobility of adjacent joints.
Past ankle replacements have suffered from poor fixation because long tibial stems could not be placed into the ankle. In contrast to the knee, the ankle does not have the articulation range that would allow a long stem to be inserted. In contrast to the hip, the ankle cannot be dislocated to allow long stem access either. The only choice is to put a large anterior window in the tibia so that the long stem could be dropped in. Although this allows for a longer stem, it weakens the tibia at the same time.
Over the last 40 years, total joint replacements have been used successfully in three joints: the hip, the knee, and the shoulder. These successes came at the expense of many prosthetic failures. It was from the solving of those prosthetic failures, particularly those of the total knee, that the workable principles of the total joint replacement emerged.
Performing total ankle replacement requires a thorough knowledge of the ankle and foot biomechanics and frequent, practical experience operating in this anatomical area.
INBONE Meets an Unmet Need
Over the years, considerable research has gone into increasing the long-term survivorship of Total Joint Replacements. In the 1980s and 1990s, research focused on 3 attributes that increased survivorship:
- Increased implant fixation - metaphyseal-filling tibial stems and keels
- Polyethylene longevity and wear-reduction - minimal poly thickness and sterilization methods
- Accurate implant alignment - intramedullary alignment
INBONE Surgical Rationale
- Primary Osteoarthritis
- Characterized by loss of joint cartilage, osteophyte formation, subchondral bone cysts, and subchondral sclerosis
- Post-Traumatic Osteoarthritis
- The most common form of ankle arthritis (~78%)
- Joint incongruence, malalignment, and dislocation
- Rheumatoid Arthritis (inflammatory arthritis)
- Symmetric joint-space a narrowing, joint subluxation, juxta-articular erosions, and osteopenia
- Conservative (Non-Operative) Management
- Physical Therapy
- Bracing/Orthotics
- Medications
- Cortisone Injections
- Surgical Treatment
- Arthroscopic Debridement
- Distraction Arthroplasty (Ex-Fix)
- Ankle Allograft Transplant (very rare)
- Ankle Arthrodesis
- Total Ankle Arthroplasty
- Amputation
Compare and Contrast: INBONE vs. Ankle Joint Fusion
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Tibio-Talar Arthrodesis (Ankle Fusion)
Pros
- Considered “gold standard” for end-stage ankle arthritis
- Insurance coverage
- Can reduce pain and provide a stable, plantigrade foot
- Fewer complications compared to early TAR
Cons
- Can lead to Adjacent Joint Arthritis – costly additional surgery
- Less ROM compared to TAR
- Altered gait
- Decreased stride length
- Lower rates of patient satisfaction compared to ankle replacement patients
Total Ankle Arthroplasty
INBONE Ankle Arthroplasty
Pros
- ROM closer to the normal ankle
- Can reduce pain and provide a stable, plantigrade foot
- Decreased chance of adjacent joint arthritis
- Viable intermediate solution prior to fusion
- Higher patient satisfaction
Cons
- Polyethylene wear
- Component subsidence
- Failure rates of early designs
Known Complications
- Infection (superficial or deep)
- Neuralgia (superficial or deep peroneal nerve, rarely tibial nerve)
- Delayed wound healing
- Persistent pain despite optimal examination and radiographic appearance of implants
- Osteolysis, ballooning lysis, Aseptic loosening, and migration of the implant
- Subsidence of talar component
- Malleolar or distal tibial stress fracture
- Implant failure (including polyethylene), Implant fracture (very rare)
Are You Looking for a Foot Care Specialist in Austin, TX?
If you are looking for foot care, you should reach out to an experienced podiatrist. Austin Foot and Ankle Specialists can help. Our office provides a wide variety of advanced, effective treatment options for all kinds of painful conditions. Ready to schedule an appointment? Contact us online, or call our Austin office at 512-328-8900.
