Patient‐Specific Instrumentation in Total Knee Arthroplasty


43 Patient‐Specific Instrumentation in Total Knee Arthroplasty


Seper Ekhtiari MD MSc, Luc Rubinger MD, Vickas Khanna MD, and Anthony Adili MD


Division of Orthopaedic Surgery, Department of Surgery, McMaster University, Hamilton, ON, Canada


Clinical scenario



  • You see a 65‐year‐old male patient in your office with tricompartmental knee osteoarthritis. He is quite symptomatic and is no longer responsive to nonoperative management.
  • He is interested in total knee arthroplasty (TKA), and has heard about “personalized” implants on social media. He would like to know if such implants are better than standard implants.
  • When you ask your company representative about patient‐specific instrumentation (PSI) options, she tells you that some systems use computed tomography (CT), while others use magnetic resonance imaging (MRI). You wonder if there is a difference between the two.

Top three questions



  1. In patients undergoing TKA, does PSI result in better radiographic outcomes compared to standard instrumentation?
  2. In patients undergoing TKA, does PSI result in better functional outcomes compared to standard instrumentation?
  3. In patients undergoing TKA with PSI, are CT‐based PSI systems more accurate than MRI‐ based PSI systems?

Rationale


PSI has increased in popularity in recent years as orthopedic surgery responds to the growing trend of personalized medicine. This technology utilizes the patient’s own anatomy, as visualized on advanced imaging, to create anatomically matched instruments, such as cutting jigs, to be used in that patient’s operation. The hypothesized advantages of PSI are preoperative planning to minimize bony resection thus resulting and more accurate component positioning compared to standard instrumentation.1


Clinical comment


Overall, TKA is quite successful. A recent systematic review of 208 studies found that the majority of studies reported a patient satisfaction rate of 81–90% as measured by a response of “satisfied” or “very satisfied” on a five‐point Likert scale. The median rate of satisfied patients was 88.9%.2 Nonetheless, this leaves 10–20% of patients who undergo a major elective operation that are not satisfied with their outcome. It has been hypothesized that this may be due, at least in part, to component malpositioning, which occurs in up to 40% of cases.3 PSI has the theoretical benefit of making accurate alignment technically easier, but it is important to understand whether this benefit is supported by evidence.


Available literature and quality of the evidence


Multiple randomized controlled trials (RCTs) have compared PSI to standard instrumentation in terms of radiographic outcomes. A recent meta‐analysis of RCTs (level I) analyzed 23 RCTs published before March 2018, involving a total of 2058 knees, with all patients randomized to either PSI or standard instrumentation.1 A number of radiographic measures were used to judge component position accuracy, and most commonly included: hip–knee–ankle axis (HKA), coronal, sagittal, and axial alignment of the femoral component, and coronal and sagittal alignment of the tibial component. No new RCTs have been published since the aforementioned meta‐analysis was performed and this publication was produced.


Findings


Based on the pooled estimate from trials assessing HKA as an outcome, there was no significant difference between PSI and standard instrumentation in terms of >3° deviation from target alignment (180°) or number of outliers. In fact, only 1 out of 14 trials found a significant difference in number of HKA outliers, favoring PSI.1


Coronal alignment of the femoral component was assessed in 13 RCTs. Meta‐analysis revealed no significant difference between PSI and standard instrumentation patients with regards to absolute deviation from target alignment (90°) or number of outliers. Similarly, the sagittal alignment of the femoral component, from eight RCTs, was not found to be significantly different between the two groups in terms of absolute deviation or outliers. When assessing axial alignment of the femoral component, there was no significant difference between the two groups in terms of number of outliers. There was, however, a significant difference in terms of absolute deviation from target alignment (mean difference: −0.46, p = 0.0004, I2 = 48%). In the context of moderate heterogeneity (I2 = 48%, p = 0.05), this finding should be interpreted with caution.1


Tibial component alignment was also assessed in the sagittal (nine RCTs) and coronal (14 RCTs) planes. There was no significant difference either in terms of absolute deviation from the desired target (90°) or in terms of outliers.1

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Nov 28, 2021 | Posted by in ORTHOPEDIC | Comments Off on Patient‐Specific Instrumentation in Total Knee Arthroplasty
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