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Ankle Arthroplasty / Ankle Replacement Surgery / INBONE Total Ankle Replacment

TIn Bonehe 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 which 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 have been demonstrated in several recent studies showing an improved 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 1980’s and 1990’s, research focused on 3 attributes that increased survivorship:

  1. Increased implant fixation - metaphyseal-filling tibial stems and keels
  2. Polyethylene longevity and wear-reduction - minimal poly thickness and sterilization methods
  3. 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
  • 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

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Compare and Contrast: INBONE vs. Ankle Joint Fusion

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
  • Less 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 Arthroplasy

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
  • Sudsidence of talar component
  • Malleolar or distal tibial stress fracture
  • Implant failure (including polyethylene), Implant fracture (very rare)