Introduction Patient specific positioning guides (PSPGs) in TKA are based on MRI or CT data....
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Transcript of Introduction Patient specific positioning guides (PSPGs) in TKA are based on MRI or CT data....
IntroductionPatient specific positioning guides (PSPGs) in TKA are based on MRI or CT data. Preoperatively, knee component positions can be visualized in 3-dimensional reconstructed images. Software allows anticipation of component position. From software planning PSPGs are manufactured and those PSPGs represent intra-operative component alignment
AimTo investigate the correlation between pre-operative planning of component positioning and the post-operative achieved alignment with PSPG technique.
PatientsFirst 42 TKA (Vanguard® Complete Knee System, Biomet) withPSPG technique (Signature™, Materialise)
Methods- CT measurement of component position according Perth protocol- Compared CT measurements with softwareplan obtained from MRI- 2 independent observers
Femoral component angle: 3 planes
Tibial component angle: 2 planesMeasurements in the axial plane were not performed: intraoperative
tibial rotation was in most cases obtained by extra-medullary guide.
Results
Intra-class correlation (ICC) between observer 1 and observer 2
Target angle: pre-operative planned alignment from Signature software.Mean, SD and Range of post-operative CT measurements
ConclusionIn our study postoperative knee component positioning is not consistent with preoperative software planning.
Correlation between pre-operative planning and post-operative position of components in TKA with PSPG
Justin AMJ van leeuwen¹, Stephan M Röhrl², Bjarne Grøgaard², Finnur Snorrason³
¹Dep. of Orthopaedic Surgery, Betanien Hospital Skien, Norway ²Dep. of Orthopaedic Surgery, Oslo University Hospital, Norway ³Dep. of Orthopaedic Surgery, Vestre Viken Drammen, Norway
25 TKAs at Telemark Hospital, Skien Period: 2009-2010
17 TKAs at Oslo University Hospital Period: 2010-2011
CT Measurements: Component Angles
ICC
Femur Coronal 0.75
Femur Sagittal 0.93
Femur Axial 0.46
Tibia Coronal 0.89
Tibia Sagittal 0.91
Component Angle Target Mean SD Range
Femur
Coronal (valgus- / varus +) 0.0 1.2 1.6 -1.7 – 4.5
Sagittal (flexion- / extension+) -2.8 -4.4 3.9 -17.3 – 2.5
Axial (Internal rot- / external rot+) 0.0 0.5 0.1 -2.9 – 4.3
Tibia
Coronal (valgus- / varus +) 0.0 0.5 2.4 -3.6 – 7.3
Sagittal (flexion- / extension+) -3.0 -3.7 2.3 -8.8 – 2.4
DiscussionMean values of post-operative measurements are close to pre-operative software planning, but we found a considerable spread. Possible explanations might be error levels in pre-operative wrong identification of landmarks from MRI and/or different identification of bony landmarks on CT and intra-operative errors. There might be a learning curve in using PSPGs. Time gap between PSPG manufacturing and intra-operative use can theoretically provide a less proper fit due to slight change of anatomy in a progressive osteoarthritis. It is uncertain whether this inconsistency is of clinical relevance. More data is necessary to prove any benefit of PSPG compared to existing procedures for TKA.
- Victor J, Van Doninck D, Labey L, Innocenti B, Parizel PM, Bellemans J: How precise can bony landmarks be determined on a CT scan of the knee? The Knee 2009, 16(5):358-365.- Chareancholvanich K, Narkbunnam R, Pornrattanamaneewong C: A prospective randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement. The
bone & joint journal 2013, 95-B(3):354-359.- Boonen B, Schotanus MG, Kort NP: Preliminary experience with the patient-specific templating total knee arthroplasty. Acta orthopaedica 2012, 83(4):387-393.
Justin van Leeuwen E-mail: [email protected]