Ashkenazi I, et al. Clin Orthop Surg. 2024 Feb;16(1):41-48. https://doi.org/10.4055/cios23157

Introduction: The Coronal Plane Alignment of the Knee (CPAK) classification categorizes knee phenotypes based on constitutional limb alignment and joint line obliquity (JLO). Restricted Inverse Kinematic Alignment (RIKA) is a surgical philosophy that incorporates calculated perioperative parameters to achieve patient-specific alignment. This study investigated the reproducibility of restoring preoperative CPAK phenotypes via the tibia-first RIKA concept in total knee arthroplasty (TKA). Methods: This prospective study assessed 129 patients who underwent RIKA TKA using an imageless navigation robotic-assisted arm with a single implant design for primary osteoarthritis between January 2022 and December 2023. Preoperative and postoperative angles for the lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured from full-length standing anteroposterior X-ray imaging. Arithmetic HKA (aHKA) was defined as MPTA - LDFA, and JLO was outlined as MPTA + LDFA to classify each knee into one of nine CPAK phenotypes. CPAK boundaries for neutral aHKA and JLO were 0° ± 2° and 180° ± 3°, respectively. Results: The mean pre- and postoperative aHKA were − 2.73° (SD ± 4.9°) vs. -2.83° (SD ± 3.0°), respectively. The most common preoperative CPAK phenotypes were I ( n = 74, 42.5%) and II ( n = 40, 23.0%). Among patients with preoperative type I phenotype, 39.2% (29/74) preserved their composition postoperatively, while 48.6% (36/74) converted to type IV. Of 40 Type II knees, 65.0% (26/40) preserved alignment, with 25.0% (10/40) shifting to type V. In preoperative types IV and V, 75% (12/16) and 88.5% (23/26) preserved their phenotypes, respectively. Valgus categories (III, VI, IX) were neutralized into types II and V. CPAK types VII, VIII, and IV were rare throughout. Conclusion: The use of tibia-first RIKA achieved adequate preservation of the native coronal alignment postoperatively. These findings suggest that balancing a knee using tibia-first approach with the use of imageless navigation robotic-assisted systems is a valid tool for surgeons who seek contemplating RIKA TKA.

One of the main objectives of total hip arthroplasty (THA) is to recreate the center of rotation (COR). Accurate reconstruction of the COR is suggested to be within 5 mm of its anatomical location. The goal of our study was to assess whether accurate reconstruction of the COR, based on preoperative planning, is associated with improved clinical outcomes. The study population consisted of patients who underwent THA at our institution between August 2018 and May 2020. All patients underwent preoperative digital templating. The position of the predicted COR was compared to its actual postoperative position. Patients were subsequently stratified into two subgroups based on the difference between the distance of the predicted COR and the reconstructed COR, over or under 5 mm. A 12-Item Short Form Health Survey (SF-12) and visual analogue scale (VAS) were taken for each patient. 90 patients were included in this study. 60 patients (66%) had their COR reconstructed within 5 mm of preoperative planning, whereas for 30 patients (33%), reconstruction was outside of 5 mm of preoperative planning. Between the two cohorts, no significant difference existed in the physical component summary (PCS) (p = 0.33), the mental component summary (MCS = 0.16), or the visual analogue scale (VAS) (p = 0.12). The accurate restoration of COR based on preoperative planning is not associated with improved clinical outcomes. During postoperative evaluation, surgeons should feel confident if the COR is slightly greater than 5 mm of preoperative limitations.

Collared femoral stems in total hip arthroplasty (THA) offer reduced subsidence and periprosthetic fractures but raise concerns about fit accuracy and stem sizing. This study compares collared and non-collared stems to assess the stem–canal fill ratio (CFR) and fixation indicators, aiming to guide implant selection and enhance THA outcomes. This retrospective single-center study examined primary THA patients who received Corail cementless stems between August 2015 and October 2020, with a minimum of two years of radiological follow-up. The study compared preoperative bone quality assessments, including the Dorr classification, the canal flare index (CFI), the morphological cortical index (MCI), and the canal bone ratio (CBR), as well as postoperative radiographic evaluations, such as the CFR and component fixation, between patients who received a collared or a non-collared femoral stem. The study analyzed 202 THAs, with 103 in the collared cohort and 99 in the non-collared cohort. Patients’ demographics showed differences in age (p = 0.02) and ASA classification (p = 0.01) but similar preoperative bone quality between groups, as suggested by the Dorr classification (p = 0.15), CFI (p = 0.12), MCI (p = 0.26), and CBR (p = 0.50). At the two-year follow-up, femoral stem CFRs (p = 0.59 and p = 0.27) were comparable between collared and non-collared cohorts. Subsidence rates were almost doubled for non-collared patients (19.2 vs. 11.7%, p = 0.17), however, not to a level of clinical significance. The findings of this study show that both collared and non-collared Corail stems produce comparable outcomes in terms of the CFR and radiographic indicators for stem fixation. These findings reduce concerns about stem under-sizing and micro-motion in collared stems. While this study provides insights into the collar design debate in THA, further research remains necessary.