CT-based patient-specific instrumentation for total knee arthroplasty in over 700 cases: single-use instruments are as accurate as standard instruments

Abstract

Purpose Efforts in total knee arthroplasty are made to improve accuracy for a correct leg axis and reduce component malpositioning using patient-specific instruments. It was hypothesized that use of patient-specific instruments (vs. computernavigated and conventional techniques) will reduce the number of outliers. Our second hypothesis was that single-use instrumentation will lead to the same accuracy compared to patient-specific instruments made of metal. Methods 708 primary total knee arthroplasties between 2014 and 2018 using computer tomography (CT)-based patientspecific cutting block technique and a preoperative planning protocol were retrospectively reviewed. Preoperative data [hip-knee-angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibial slope, femoral component flexion] was compared to postoperative performed standard radiological follow-up X-rays. Differences of > 3° between measurements were defined as outliers. Results Overall 500 prostheses using standard instrumentation and 208 prostheses using single-use instruments were implanted. Preoperative HKA axes (− 1.2°; p < 0.001), femoral component flexion (Δ 0.8°, p < 0.001), LDFA (Δ − 1.5°, p < 0.001), MPTA (Δ − 0.5°, p < 0.001) and tibial posterior slopes (Δ 0.5°, p < 0.001), respectively, were different from postoperative axes. More outliers occurred using standard (vs. single-use) instruments (p < 0.001) regarding postoperative HKA (ranges of standard-vs. single-use: instruments: HKA 178.0°-180.5° vs. 178.0°-180.5°, femoral component flexion 0.0°-6.0° vs. 0.0°-4.5°, LDFA 90.0°-91.0° vs. 90.0°-90.0°, MPTA 90.0°-90.0° vs. 90.0°-90.0°, tibial posterior slope − 10° to 10° vs. − 1° to 10°). No differences were seen for other angles measured. Comparing both systems, total number of outliers was higher using standard (8%) vs. single-use instruments (4.3%). Conclusion This study shows a high accuracy of CT-based patient-specific instrumentation concerning postoperative achieved knee angles and mechanical leg axes. Single-use instruments showed a similar accuracy. Level of evidence III.

Customized‐individually‐made origin® implants in total knee arthroplasty allow a reliable solution for accurate reproduction of planned implant positioning

“…Our results demonstrated a 19.6% and 7.8% rate of outliers outside the 2° and 3° target zones, respectively. Our results remain better than those found in the literature using conventional instruments [ 27 , 28 ], and are close to the best results found with custom cutting guides [ 29 ]. Levengood et al demonstrated a lower rate of 2° outliers, at 15.8% [ 30 ].…”

“…Our results align closely with their excellent findings for navigation. Studies investigating CIM cutting guide shows slightly lower rate of 3° outliers: with Gaukel et al reporting 2.3% [ 29 ] while Sariali et al reported a perfect rate of 0% [ 27 ].…”

The coronal alignment differs between two‐dimensional weight‐bearing and three‐dimensional nonweight bearing planning in total knee arthroplasty

“…Koch et al [26] reported a total of 12.4% of outliers in the frontal plane in 291 cases. Other studies of CT‐based PSI‐TKA showed comparable low outlier rates [27, 28]. This might be due to the surgeon dependent adjustment to the PSI cutting jigs of the 3D models and/or intraoperative corrections.…”

Ipsilateral Concurrent Knee Arthroplasty and Tibial Osteotomy with 3D-Printed Patient-Specific Instrumentation

“…Despite a number of studies 4 demonstrating no benefit associated with PSI in enhancing mechanical axes and implant survival, a review study in 2022 revealed the notable accuracy of CT-based PSI for mechanical leg axes and postoperative knee angles in over 700 cases 5 . Moreover, there is considerable research examining the efficacy of PSI in a variety of other contexts.…”