Patient-specific instrumentation for total knee arthroplasty

Abstract

Purpose: To assess the accuracy of total knee replacements (TKRs) performed using CT-based patient-specific instrumentation by postoperative CT scan. Method: Approval from the Ethics Committee was granted prior to commencement of this study. Fifty prospective and consecutive patients who had undergone TKR (Evolis, Medacta International) using CT-based patient-specific instrumentation (MY KNEE, Medacta International) were assessed postoperatively using a CT scan and the validated Perth protocol measurement technique. The hip-knee-ankle (HKA) angle of the lower limb in the coronal plane; the coronal, sagittal, and rotational orientation of the femoral component; and the coronal and sagittal orientation of the tibial component were measured. These results were then compared to each patient's preoperative planning. The percentage of patients found to be less than or equal to 3 of planned alignment was calculated. One patient was excluded as the femoral cutting block did not fit the femur as predicted by planning and therefore underwent a conventional TKR. Results: Ninety-eight percent of patients were within 3 of planned alignment in the coronal plane reproducing the predicted HKA angle. Predicted coronal plane orientation of the tibial and femoral component was achieved in 100% and 96% of patients, respectively. The sagittal orientation of the femoral component was within 3 in 98% of patients. The planned sagittal positioning of the tibial component was achieved in 92% of patients. Furthermore, 90% of patients were found to have a femoral rotation within 3 of planning. Eighty-six percent of patients achieved goodto-excellent outcome at 12 months (Oxford Knee Score > 34). Conclusion: We have found that TKR using this patientspecific instrumentation accurately reproduces preoperative planning in all six of the parameters measured in this study.

Clinical Outcome of Total Knee Arthroplasty Performed Using Patient-Specific Cutting Guides

“…Since previous studies used many radiographic angles to evaluate the efficacy of patient-specific cutting guides on component alignment [ 1 ], it is difficult to compare our results with those of previous studies. Colombelli et al [ 2 ] and Nabavi et al [ 15 ] reported that patient-specific cutting guides provided the desired 180° of hip-knee-ankle angle in over 90% of patients. Seon et al [ 16 ] also reported accurate alignments provided by patient-specific guides without intraoperative complication in 38 knees, noting that severe varus deformity and osteophytes may interfere with seating of the guides.…”

Closed‐leg standing long leg radiographs can be a useful tool to assess whether the joint line is parallel to the ground in restricted kinematic alignment total knee arthroplasty

“…The following evaluations were performed after the mean values of each measurement were obtained: (1) Coronal Plane Alignment of the Knee (CPAK) classification to describe preoperative knee phenotypes, where arithmetic HKA and joint line obliquity are calculated by the sum and difference of MPTA and LDFA as reported previously [ 27 ]; (2) scatter plots of preoperative LDFA and MPTA to determine the number of patients who needed a modified PSI plan for rKA TKA [ 25 ]; (3) the outliers from the rKA target zone of postoperative HKA (more than ± 3º), LDFA (more than ± 5º), and MTPA (more than ± 5º); (4) the outliers from the alignment target, which are defined as deviations of postoperative HKA, LDFA, and MPTA from the planned alignment, to analyze the accuracy of bone resections (outliers from alignment target were defined as deviations from the planned alignment of more than ± 3º [ 28 ]); and (5) deviations of the postoperative JLOA from the target of the ground level to investigate if a joint line parallel to the floor was achieved (outliers were defined as deviations from the floor more than ± 3º). The definition of outliers from the JLOA target has not been established because there have been no reports of JLOA measurement using closed-leg standing long-leg radiographs.…”

Functional knee phenotypes: A helpful classification tool for visualizing potential femoral varus in restricted kinematic alignment total knee arthroplasty in Japan

“…The alignment target for JLOA was defined as the ground level, and outliers from the postoperative JLOA target were defined as deviations from the floor >±3° [22], assessing the achievement of a joint line parallel to the floor. Outliers from the HKA target were defined as deviations of postoperative HKA from the planned alignment of >±3° [ 23], analysing the reproducibility of targeted alignment.…”