Matthew G Teeter1,2,3,4, Douglas D Naudie5, Richard W McCalden5, Xunhua Yuan6, David W Holdsworth5,7,6, Steven J MacDonald5, Brent A Lanting5. 1. Division of Orthopaedic Surgery, Department of Surgery, Schulich School of Medicine and Dentistry, Western University and London Health Sciences Centre, 339 Windermere Road, London, ON, N6A 5A5, Canada. matthew.teeter@lhsc.on.ca. 2. Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. matthew.teeter@lhsc.on.ca. 3. Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. matthew.teeter@lhsc.on.ca. 4. Surgical Innovation Program, Lawson Health Research Institute, London, ON, Canada. matthew.teeter@lhsc.on.ca. 5. Division of Orthopaedic Surgery, Department of Surgery, Schulich School of Medicine and Dentistry, Western University and London Health Sciences Centre, 339 Windermere Road, London, ON, N6A 5A5, Canada. 6. Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada. 7. Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
Abstract
PURPOSE: To examine implant migration and articular behavior of primary total knee arthroplasty (TKA) at 10 years after index surgery and correlate to implant alignment. METHODS: Thirty-five patients underwent a cemented posterior stabilized total knee arthroplasty with a surgical objective of neutral alignment and were enrolled in a long-term radiostereometric analysis (RSA) study. At 10 years after surgery, patients were analyzed for implant migration using RSA as well as radiographic assessment of articular behavior at four positions of knee flexion. Implant position and alignment was measured on full-length radiographs. Patient demographics and reported outcomes were also collected. RESULTS: No difference between patient demographics or patient-reported outcomes were found. When categorized into neutral and varus groupings, no difference in migration was present. If alignment was considered as a continuous variable, there was no correlation between overall leg alignment and migration, however, migration increased with an increasing varus tibial alignment. Although contact location did not differ between neutral and varus groups through a range of motion, condylar liftoff was much more common in the varus group, of which all were lateral liftoff. CONCLUSIONS: Increased tibial varus results in increased implant migration. Overall varus limb alignment is correlated with isolated lateral compartment liftoff, and liftoff occurs more commonly than in neutral aligned knees. The increased migration and liftoff raise concerns about the longevity of malaligned total knee replacements. If a goal of overall varus limb alignment is desired for TKA, the tibia should remain neutral. LEVEL OF EVIDENCE: Level III.
PURPOSE: To examine implant migration and articular behavior of primary total knee arthroplasty (TKA) at 10 years after index surgery and correlate to implant alignment. METHODS: Thirty-five patients underwent a cemented posterior stabilized total knee arthroplasty with a surgical objective of neutral alignment and were enrolled in a long-term radiostereometric analysis (RSA) study. At 10 years after surgery, patients were analyzed for implant migration using RSA as well as radiographic assessment of articular behavior at four positions of knee flexion. Implant position and alignment was measured on full-length radiographs. Patient demographics and reported outcomes were also collected. RESULTS: No difference between patient demographics or patient-reported outcomes were found. When categorized into neutral and varus groupings, no difference in migration was present. If alignment was considered as a continuous variable, there was no correlation between overall leg alignment and migration, however, migration increased with an increasing varus tibial alignment. Although contact location did not differ between neutral and varus groups through a range of motion, condylar liftoff was much more common in the varus group, of which all were lateral liftoff. CONCLUSIONS: Increased tibial varus results in increased implant migration. Overall varus limb alignment is correlated with isolated lateral compartment liftoff, and liftoff occurs more commonly than in neutral aligned knees. The increased migration and liftoff raise concerns about the longevity of malaligned total knee replacements. If a goal of overall varus limb alignment is desired for TKA, the tibia should remain neutral. LEVEL OF EVIDENCE: Level III.
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