Abstract
Background
An MRI scan of the patient's hip, knee and ankle is used to produce The Signature patient specific jig. The jig is used to aid the accuracy of implantation of a TKR. This study compared the accuracy of implantation of a TKR using The Signature patient specific jig or a standard jig.
Hypothesis
There is no difference in alignment between a patient specific and standard jig assisted TKR.
Method
30 patients were prospectively randomised using a random number generator. 16 patients had an MRI plus patient specific TKR. 14 patients had standard jig assisted TKR. All patients had a cemented Vanguard PS TKR. All patients had a post-op CT scan done according to the Perth protocol. An independent observer analysed the CT scans in 6 alignment parameters: femoral rotation, sagittal and coronal alignment, mechanical axis, tibial sagittal and coronal alignment.
Results
Greater than 3 degrees of variance from normal was considered an outlier in any alignment parameter. Mean operating time, PSI 75mins STD 70.5mins. Mechanical axis STD, 1 outlier, no significant difference in variance. Femoral coronal alignment PSI, 1 outlier, no significant difference in variance. Femoral sagittal alignment STD, 2 outliers, statistically significant difference in variance. Femoral rotation, no outliers, all between 0 - 3degrees external rotation. Tibial coronal alignment, no outliers. Tibial sagittal alignment, PSI 2 outliers, no significant difference in variance.
Conclusion
The Signature patient specific jig system can be used to insert a TKR with accurate alignment in multiple planes.
