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

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.

A multi-planar CT-based comparative analysis of patient-specific cutting guides with conventional instrumentation in total knee arthroplasty.

Patient specific guides (PSGs) are postulated to improve the alignment of components in total knee arthroplasty. Three hundred consecutive total knee arthroplasties performed with either conventional (CON) (n = 185) or Visionaire PSG (n = 115) were evaluated with a CT protocol for coronal limb alignment, coronal and sagittal alignment of individual components and femoral component rotation. There was no statistically significant difference between the two groups in any of the above parameters. In addition, no difference was found in total operative time. PSGs do not offer any benefit over conventional guides in terms improving the coronal alignment of the limb or alignment of individual components.

A comparison of alignment using patient specific guides, computer navigation and conventional instrumentation in total knee arthroplasty.

BACKGROUND: Patient specific guides (PSG) have been introduced as a tool in total knee arthroplasty (TKA) in an attempt to improve limb alignment and reduce operative time compared to other established surgical techniques. The purpose of this study was to compare the post-operative radiographic alignment and operative time in patients who underwent TKA surgery with PSG, conventional instrumentation or computer-assisted navigation surgery using fully cemented components. METHODS: A cohort of 260 patients who underwent TKA surgery using PSG (PSG group, n=115) was compared to patients who underwent TKA using either conventional instrumentation (CON group, n=92) or computer-assisted navigation (CAS group, n=53). Post-operative CT imaging using the Perth CT protocol was used to compare alignment between the three groups. RESULTS: In the PSG and CAS groups, the post-operative hip-knee angle (HKA) was within 3° of neutral alignment in 91.3% and 90.7% of patients, respectively. This compared to 80.4% of patients in the CON group (p=0.02). There were no significant differences with respect to alignment when comparing individual component positioning between the PSG and CAS groups apart from tibial slope (Table 3). Total operative time was found to be significantly reduced in the PSG group (80.2 min) compared to both the CON group (86 min, p=0.002) and the CAS group (110.2 min, p<0.0001). CONCLUSIONS: The use of PSG resulted in similar alignment accuracy to CAS and superior alignment to CON with significantly shorter operative times.