Mo Saffarini1, Jacobus H Müller2, Giuseppe La Barbera3, Gerjon Hannink4, Kyung Jin Cho2, Cécile Toanen3, David Dejour3. 1. ReSurg SA, 35 ch. de la Vuarpillière, 1260, Nyon, Switzerland. journals@resurg.eu. 2. Department of Mechanical and Mechatronic Engineering Stellenbosch University, Private Bag X1, Matieland, 7600, Stellenbosch, South Africa. 3. Lyon-Ortho-Clinic, Clinique de la Sauvegarde, 8 Avenue Ben Gourion, 69009, Lyon, France. 4. Orthopaedic Research Laboratory, Radboud University Medical Center, PO Box 9101, 6500HB, Nijmegen, The Netherlands.
Abstract
PURPOSE: To evaluate the accuracy of preoperative planning for patellofemoral arthroplasty (PFA) by comparing: (1) virtual implant positioning simulated on pre-operative images versus (2) real implant positioning from post-operative images. METHODS: The authors prospectively studied 15 patients that received a PFJ implant (Tornier, Montbonnot France). A pre-operative planning software was established to determine the size and position of the trochlear component. Pre-operative scans were used to perform virtual implantations by two different operators, which were then compared to the post-operative scans to calculate errors (ε) in implant positioning and intra-class correlation coefficients (ICC) for intra- and inter-observer repeatability. RESULTS: Analysis was performed for 13 patients, for whom agreement between virtual and real surgery was excellent for anteroposterior (AP) position (ICC = 0.84; ε max = 3.5 mm), fair for proximodistal (PD) position (ICC = 0.50; ε max = 9.5 mm), and poor for mediolateral (ML) position (ICC = 0.07; ε max = 9.0 mm). It was fair for flexum-recurvatum (FR) alignment (ICC = 0.53; ε max = 8.2°), poor for varus-valgus (VV) alignment (ICC = 0.34; ε max = 10.0°), and internal-external (IE) rotation (ICC = 0.34; ε max = 10.6°). CONCLUSIONS: Pre-operative planning was insufficiently accurate to follow intra-operatively, the greatest errors being angular alignment (VV and FR). The clinical relevance of these findings is that PFA is difficult to plan pre/operatively due to non-visibility of cartilage on CT scans and to trochlear dysplasia in most cases. LEVEL OF EVIDENCE: Prospective evaluation of operative tools on consecutive patients, Level III.
PURPOSE: To evaluate the accuracy of preoperative planning for patellofemoral arthroplasty (PFA) by comparing: (1) virtual implant positioning simulated on pre-operative images versus (2) real implant positioning from post-operative images. METHODS: The authors prospectively studied 15 patients that received a PFJ implant (Tornier, Montbonnot France). A pre-operative planning software was established to determine the size and position of the trochlear component. Pre-operative scans were used to perform virtual implantations by two different operators, which were then compared to the post-operative scans to calculate errors (ε) in implant positioning and intra-class correlation coefficients (ICC) for intra- and inter-observer repeatability. RESULTS: Analysis was performed for 13 patients, for whom agreement between virtual and real surgery was excellent for anteroposterior (AP) position (ICC = 0.84; ε max = 3.5 mm), fair for proximodistal (PD) position (ICC = 0.50; ε max = 9.5 mm), and poor for mediolateral (ML) position (ICC = 0.07; ε max = 9.0 mm). It was fair for flexum-recurvatum (FR) alignment (ICC = 0.53; ε max = 8.2°), poor for varus-valgus (VV) alignment (ICC = 0.34; ε max = 10.0°), and internal-external (IE) rotation (ICC = 0.34; ε max = 10.6°). CONCLUSIONS: Pre-operative planning was insufficiently accurate to follow intra-operatively, the greatest errors being angular alignment (VV and FR). The clinical relevance of these findings is that PFA is difficult to plan pre/operatively due to non-visibility of cartilage on CT scans and to trochlear dysplasia in most cases. LEVEL OF EVIDENCE: Prospective evaluation of operative tools on consecutive patients, Level III.