The indirect cost of Patient-Specific Instruments.

Purpose: To calculate the indirect costs of Patient Specific Instruments (PSI) based on an opportunity cost, cost of efforts and a supply chain cost model to compare PSI for value with conventional total knee arthroplasty (TKA).

Methods: In 81 patients the total (direct+indirect) cost of PSI-assisted TKA was compared with conventional TKA. Surgical times and coronal mechanical alignment were measured to evaluate the effectiveness of the PSI system.

Rotational alignment of the distal femur: anthropometric measurements with CT-based patient-specific instruments planning show high variability of the posterior condylar angle.

Purpose: Finding the anatomical landmarks used for correct femoral axial alignment can be difficult. The posterior condylar line (PCL) is probably the easiest to find during surgery. The aim of this study was to analyse whether a predetermined fixed angle referencing of the PCL could help find the surgical epicondylar axis (SEA) and this based on a large CT database with enough Caucasian diversity to be representable.

The use of patient-specific instruments does not reduce blood loss during minimally invasive total knee arthroplasty?

Purpose: Blood loss can be substantial and will influence morbidity and mortality after total knee arthroplasty. This study evaluated whether patient-specific instruments (PSI) can reduce blood loss because the intramedullary canal is not opened during the procedure and whether hidden blood loss can be reduced by its use.

Methods: Seventy-five patients operated with the Signature PSI technique were compared with a matched group operated with conventional instruments.

The combined Whiteside's and posterior condylar line as a reliable reference to describe axial distal femoral anatomy in patient-specific instrument planning.

Purpose: Aligning the femoral component in the axial plane parallel to the surgical epicondylar axis (SEA) has been generally recommended. In this retrospective study on the axial anatomy of the distal femur, as determined by the patient-specific instruments (PSI) planning tool based on MRI and 3D reconstructions, the different rotational axes were compared. The purpose of this study was to compare the impact of posterior axial anatomy on anterior anatomy and to compare the different angles of rotation obtained by a PSI-planning engineer.

The difference between weight-bearing and non-weight-bearing alignment in patient-specific instrumentation planning.

Purpose: Retrospective study to analyse the difference between weight-bearing and non-weight-bearing alignment in osteoarthritic knees planned for patient-specific instrumented (PSI) total knee arthroplasty (TKA). The aim of the study is to observe whether a difference in alignment can be linked to arthritis staging or zone mechanical axis.

Methods: Full-leg standing radiographs and non-weight-bearing MRI of the whole leg were compared for hip-knee-ankle (HKA) angle, measured according to Moreland criteria, in seventy osteoarthritic patients.

Total knee arthroplasty with patient-specific instruments improves function and restores limb alignment in patients with extra-articular deformity.

Background: Restoring function and alignment when treating knee arthritis with a total knee arthroplasty (TKA) in patients who have an extra-articular deformity (EAD) from a malunion or with retained femoral hardware is a challenge. The normal anatomical landmarks are hard to find and difficult to use to obtain correct alignment. The procedure will be further challenged by angular deformity of the femur or tibia.