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

- Comparative study of two patient-specific guide systems in total knee arthroplasty
- Accuracy and component alignment analyzed though post-op Perth CT scan protocol
- PSG systems restore neutral mechanical alignment in all 3 planes
- We recommend leg MR PSG over knee-only MR PSG for increased precision of alignment

BackgroundPatient 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.MethodsThis 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.ResultsLimb-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).ConclusionsThe 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 EvidenceTherapeutic level III