In the JournalsPerspectiveFrom OT Europe

Out-of-range alignment linked with tibial component migration after TKA

According to recently published results, mechanically out-of-range alignment was linked with higher tibial component migration after total knee arthroplasty.

Researchers measured coronal alignment parameters in full-leg radiographs from 85 cemented TKAs. Median follow-up was 11 years. Of the 85 TKAs, three underwent revision for aseptic loosening and four were considered loose. Investigators assessed the postoperative hip-knee angle relative to both the mechanical axis and constitutional alignment on tibial component migration. Linear mixed-effects model adjusted for sex, age, preoperative alignment, diagnosis and BMI was used for analysis.

In mechanically in-range knees, investigators did not see loose tibial components. However, they found all loose tibial components were out of range. After 5 years, the greatest mean migration in mechanically varus knees was 1.55 mm, was 1.07 mm for valgus knees and was 0.77 mm for in-range knees. Loose tibial components were seen in constitutionally in-range knees and in out-of-range knees. Comparable migration was seen among constitutionally in-range knees; however, more was seen in varus and in valgus knees, according to results from mixed model analyses. – by Monica Jaramillo

 

Disclosures: The authors report no relevant financial disclosures.

 

 

According to recently published results, mechanically out-of-range alignment was linked with higher tibial component migration after total knee arthroplasty.

Researchers measured coronal alignment parameters in full-leg radiographs from 85 cemented TKAs. Median follow-up was 11 years. Of the 85 TKAs, three underwent revision for aseptic loosening and four were considered loose. Investigators assessed the postoperative hip-knee angle relative to both the mechanical axis and constitutional alignment on tibial component migration. Linear mixed-effects model adjusted for sex, age, preoperative alignment, diagnosis and BMI was used for analysis.

In mechanically in-range knees, investigators did not see loose tibial components. However, they found all loose tibial components were out of range. After 5 years, the greatest mean migration in mechanically varus knees was 1.55 mm, was 1.07 mm for valgus knees and was 0.77 mm for in-range knees. Loose tibial components were seen in constitutionally in-range knees and in out-of-range knees. Comparable migration was seen among constitutionally in-range knees; however, more was seen in varus and in valgus knees, according to results from mixed model analyses. – by Monica Jaramillo

 

Disclosures: The authors report no relevant financial disclosures.

 

 

    Perspective
    David A. Crawford

    David A. Crawford

    There is growing debate on whether TKAs should be aligned to a neutral mechanical axis or more patient-specific kinematic alignment. This study by Koen T. van Hamersveld, MD, and colleagues aimed to shed some light on this topic by evaluating tibial component migration and long-term aseptic survivorship of 85 cemented primary TKAs based on alignment relative to these two targets. At 10-year minimum follow-up, seven tibial components (8.2%) were considered loose and/or revised. None of the knees that were within 3° of a neutral mechanical axis (47 knees) had tibial loosening, whereas two tibial components were loose in constitutionally “in-range” knees (36 knees). Varus aligned knees had significantly more tibial component migration based on radiostereometric analysis.

    While there are valid arguments for kinematic alignment, this study questions whether there may be a limit on alignment tolerances for long-term survival. One of the concerns with planning kinematic alignment with a varus tibial cut is overshooting that target by even a few degrees and placing the component in 6° or more of varus. The findings of this study may support the use of enabling technologies, such as robotics, to improve component and limb alignment, which ultimately may lead to better long-term survivorship, especially for those targeting kinematic alignment. It should be noted this study evaluated various implant manufacturers’ and component designs, which could confound the results.

    • David A. Crawford, MD
    • JIS Orthopedics
      New Albany, Ohio

    Disclosures: Crawford reports no relevant financial disclosures.

    Perspective
    David F. Scott

    David F. Scott

    Koen T. van Hamersveld, MD, and colleagues report a higher rate of tibial component migration in knees not aligned within ±3° of neutral TKA. Their analysis fails to account for native obliquity of the joint line as defined by the medial proximal tibial and lateral distal femoral angles, and the degree to which this unique individual anatomy was or was not replicated. They admit they did not follow kinematic alignment techniques. So, it is not logical to apply their results to the results produced/expected with kinematic alignment.

    • David F. Scott, MD
    • Spokane Joint Replacement Center
      Clinical instructor
      University of Washington Orthopedics and Sports Medicine
      Seattle

    Disclosures: Scott reports he receives IP royalties from Innomed; is a paid consultant and paid presenter or speaker for Medacta International; and receives research support from Medacta International, Microport, OMNI and Stryker.

    Perspective
    Ritesh R. Shah

    Ritesh R. Shah

    I read with great interest this study regarding the effect of coronal alignment on tibial component migration after TKA. 

    As orthopedic surgeons, we know that obtaining neutral coronal limb alignment during TKA has traditionally been considered optimal for implant longevity, outcomes and function. Among other studies, we previously published results showing only 70% of individuals had neutral alignment; the obvious question that arises is whether aiming for neutral limb alignment or constitutional limb alignment should be the goal. Some studies show no difference in survivorship between neutrally aligned TKA compared with knees aligned in greater than 3° varus and valgus. Innovatively, this study uses radiostereometric analysis from three studies to evaluate implant migration comparing neutral mechanical limb alignment vs. constitutional alignment after TKA.

    The authors conclude that out of range mechanical limb alignment leads to a higher rate of tibial component migration with the highest rate of migration occurring in mechanically varus TKA and no migration seen in mechanically neutral TKA. Although it is difficult to estimate premorbid constitutional alignment, when matching constitutional alignment, this study shows no difference in component migration if placed in mechanical neutral, varus or valgus. Further, although there are limitations to the study, including using only static coronal alignment measurements and lack of correlation between radiostereometric analysis (RSA)-evidenced tibial component migration and clinical symptomatology, previously published evidence has shown that RSA analysis demonstrating excessive tibial component migration is predictive of late aseptic loosening.  Thus importantly, when considering preventing late aseptic loosening, this study helps guide surgeons to aim for neutral when using mechanical limb alignment and specifically avoid varus.

     

     
    • Ritesh R. Shah , MD
    • Chief, Orthopedic Surgery
      Advocate Illinois Masonic Medical Center
      Illinois Bone and Joint Institute
      Des Plaines, Illinois

    Disclosures: Shah reports he receives research support from and is a speaker for Microport Orthopedics.