Arthroplasty is a revision of the total knee. Failure of primary knee arthroplasty is a time-dependent process and requires a Knee Revision Specialist consultation.
What is Knee Revision or Arthroplasty
Due to the increasing number of implanted primary prostheses and the greater life expectancy in developed countries, it is expected that in the next 20 years, knee replacements will multiply by six and hip replacements by two or three.
The costs and complexity of revision surgery are much greater than primary knee replacement. However, the appropriate selection of patients and indications and the correct application of revision techniques minimize complications improve results and implant survival.
The objective of the Knee Revision Specialist is to decorously remove the implant, minimizing bone loss and preserving soft tissues.
Surgical Technique: Arthroplasty
Important aspects include investigating risk factors for infection (therapy with immunosuppressants, corticosteroids, diabetes, psoriatic arthropathy, or inflammatory arthropathies), the pattern of pain, the degree of preoperative and postoperative mobility, or evolutionary aspects such as prolonged drainage of the surgical wound. The knee Revision Specialist will monitor the diagnosis.
- The patella is low, and there are posterior osteophytes. The components are replaced, distal wedges are added to restore the joint interline. The patella is fitted, and the posterior osteophytes are cleaned, improving pain and mobility.
- The clinical examination will look for the presence of effusion, selective pain, patellofemoral misalignment, or instability.
- The combination of a normal VDS and a CRP is almost exclusive for the diagnosis of infection.
- Arthrocentesis continues to be the "gold standard" in diagnosing infection. In so-called "low-grade infections," it may not be a definitive test either, although combined with molecular biology tests and cytology, it can increase the diagnostic yield.
- Cytology of fluid with a white blood cell count less than 1700 / microliter and a PMN percentage less than 50-60% has a negative predictive value of 98%.
- Nuclear medicine tests, CT, or MRI, will help us complete the study in some cases, but their indication must be selective.
Preoperative Planning of Knee Revision Surgery
When we use structural allografts to reconstruct acetabular defects, it is advisable to protect the reconstruction with antiprotrusion devices. This is so because the limit of contact with native bone to achieve biological fixation has to be 50%, with conventional coatings. Still, this limit and implications are not valid for reconstruction with new porous metals. In superior defects, the contact limit of the porous cup with the structural allograft must be 30%, unless we use cups with a porous metal coating, as in the case illustrated.
The success of revision total knee surgery is based on proper planning, which includes:
Differentiate a septic process from an aseptic process.
Do new histology if a septic process is suspected and pathological anatomy is available.
Identify the previous implant.
It is to identify the brand, degree of constriction, specific instruments for its extraction.
Possibility of an expanded approach
The section of the rectus femoris ("Quadriceps Snip") is the only approach that does not imply limitation in the immediate postoperative period.
Possibility of coverage for plastic surgery
Assess previous incisions, history of poor healing, circulatory problems.
Removal of components should be as traumatic as possible.
After removing the implant, the fibrous and granulation tissue and the remains of cement will be cleaned with gouges and high-speed drills to minimize bone loss.
Check the integrity of the ligaments
Have a reconstruction system with varying degrees of constriction, placing the implant with the least possible constriction.
Determine and classify bone loss.
Assess the need for offset or lateralized bone grafts, wedges, and stems.
Assess special needs, such as special antibiotic or dual antibiotic cement
Component extraction without bone loss is one of the goals of Knee Revision surgery.
