PSI loses accuracy as preoperative malalignment increases
ESSKA Academy. León-Muñoz V. Nov 8, 2019; 284394; epEKA-64 Topic: Joint Replacement
Dr. Vicente J León-Muñoz
Dr. Vicente J León-Muñoz
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PSI loses accuracy as preoperative malalignment increases

ePoster - epEKA-64

Topic: TKA

León-Muñoz V.J.1, López-López M.2, Martínez-Martínez F.1, Santonja-Medina F.1
1Hospital Clínico Universitario Virgen de la Arrixaca, Orthopaedic Surgery and Traumatology Department, Murcia, Spain, 2Servicio Murciano de Salud, Subdirección General de Tecnologías de la Información, Murcia, Spain

During the past decade patient-specific instrumentation (PSI) has been commercially introduced in order to simplify and make total knee arthroplasty (TKA) surgery more precise, effective and efficient.
Is the postoperative alignment related to preoperative deformity when using PSI for TKA surgery?
We have carried out a retrospective analysis of image studies of 97 cases operated with PSI after design of the surgery on 3D virtual models. Assessment of pre and post-operative full-leg standing radiographs (LLR) was performed by an observer in two occasions separated in time. Intra-observer correlation was high (> 0.9). For each case, the hip-knee-ankle (HKA) angle, the supplementary angle of the femoral lateral distal angle (sFLDA) and the proximal tibial angle (PTA) were determined.
Mean value (standard deviation) (minimum and maximum values): preoperative HKA 171.74º (7.35º) (158.5º - 194º), preoperative sFLDA 90.31º (3.2º) (82º - 99º), preoperative PTA 85.93º (3.34º) (76º - 96º). Postoperative HKA 179.05º (2.17º) (173º - 183º), postoperative sFLDA 89.98º (1.8º) (84º - 94º), postoperative PTA 89.08º (1.23º) (86º - 92º). Preoperative alignment: varus 80.4%, neutral (180º ± 3º) 10.3% and valgus 9.3%. Postoperative alignment: varus 10.3% and neutral 89.7%. 80% of the 180º ± 3º outliers presented a preoperative HKA ≤ 170º. 60% of the 180º ± 3º outliers presented a preoperative HKA ≤ 165º. There has been a weak correlation among the values of the pre- and post-operative HKA (r 0.266 with p 0.009) and among the values of the pre- and post-operative PTA (r 0.278 with p 0.006). There was no correlation between the pre- and post-operative sFLDA values (r 0.153 with p 0.135).
Outliers have occurred in varus. There is some significant correlation among tibial (PTA) and global limb (HKA) pre- and post-operative malalignment. PSI tends to lose accuracy with preoperative malalignment.
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