Total condylar knee arthroplasty. Prosthetic component positioning and radiolucent lines

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Radiology

Background:

• Total knee replacement (TKR) is a common procedure for knee osteoarthritis and rheumatoid arthritis.
• Prosthetic positioning and alignment are critical factors influencing TKR outcomes and longevity.
• Assessing radiolucency is important for monitoring implant fixation and potential loosening.

Purpose of the Study:

• To evaluate the relationship between prosthetic positioning, postoperative alignment, and tibial radiolucency after total knee replacement.
• To identify factors associated with increased radiolucency in TKR patients.

Main Methods:

• Retrospective analysis of 138 consecutive total knee replacements using the Insall/Burstein total condylar knee system.
• Assessment of overall limb alignment and tibial component positioning (tilt).
• Quantification of tibial radiolucency using a radiolucency index at 3 months and 2 years postoperatively.

Main Results:

• 63% of knees achieved overall alignment within 7±5 degrees of valgus.
• 53% of knees had tibial component positioning within 4 degrees of tilt.
• Tibial radiolucency increased from 3 months to 2 years postoperatively.
• Higher radiolucency index at 2 years was observed with varus alignment in rheumatoid arthritis patients.
• Tibial component tilt >4 degrees increased the radiolucency index in both groups.

Conclusions:

• Postoperative alignment and tibial component positioning significantly impact tibial radiolucency after total knee replacement.
• Varus alignment and excessive tibial tilt are risk factors for increased radiolucency, particularly in rheumatoid arthritis.
• Optimizing prosthetic positioning and alignment is essential for improving TKR implant survival.