The Knee, ISSN: 1873-5800, Vol: 21, Issue: 6, Page: 1244-9

Radiographic outcome of limb-based versus knee-based patient specific guides in total knee arthroplasty

Crane, Catherine; Marimuthu, Kanniraj; Chen, Darren B; Harris, Ian A; Wheatley, Emma; MacDessi, Samuel J
Knee

Background

Patient specific guides (PSG’s) were developed to improve overall component alignment in total knee arthroplasty (TKA). The aim of this study was to undertake a comparative radiographic study of two commonly used PSG and determine whether the radiographic technique used to construct the PSG had a significant effect on overall alignment.

Methods

This prospective cohort study examined the accuracy of limb-based (n = 112) versus knee-based (n = 105) MR PSG in restoring the mechanical axis in three planes according to post-operative Perth CT scan protocol.

Results

Limb-based MR and knee-based MR PSG systems both restored overall hip–knee–ankle angle (HKAA), femoral coronal alignment, tibial coronal alignment, femoral sagittal alignment, tibial sagittal alignment and femoral rotation alignment to within 3° of a neutral mechanical axis with similar precision (91.1% vs. 86.7% p = 0.30, 97.3% vs. 96.2% p = 0.63, 97.3% vs. 97.1% p = 0.94, 94.6% vs. 89.4% p = 0.16, 90.2% vs. 81.0% p = 0.05, 91.1% vs. 86.7% p = 0.30, respectively). However, when the secondary outcome measure of alignment within 2° was assessed, limb-based MR PSG restored HKAA, femoral coronal and tibial sagittal alignment with greater precision than knee-based MR PSG (73.2% vs. 64.8% p = 0.016, 93.8% vs. 80.8% p = 0.004 and 82.1% vs. 62.9% p = 0.001, respectively).

Conclusions

The findings of this study recommend the use of limb-based MR PSG for improved precision in the restoration of neutral mechanical alignment over knee-based MR PSG in TKA.

Level of Evidence

Therapeutic level III

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