Yong Deok Kim

Cementless total knee arthroplasty (TKA) has regained attention in younger, active, and obese patients, supported by advances in implant design, porous coating, and 3D printing technologies. However, the success of cementless fixation depends on adequate initial mechanical stability and subsequent osseointegration, making the assessment of bone quality at the implant–bone interface essential. Although central dual-energy X-ray absorptiometry (DXA) is useful for evaluating systemic bone health, it has been reported to inadequately reflect the localized peripheral bone quality of the distal femur and proximal tibia. Therefore, cementless TKA candidate selection requires direct evaluation of the bone quality around the knee joint, particularly at the bone resection site. This narrative review summarizes the preoperative and intraoperative methods available for knee-specific bone quality assessment in the context of cementless TKA selection. Various X-ray-based methods are accessible but limited by two-dimensional projection and protocol variability. Peripheral DXA allows localized bone mineral density measurement but lacks standardization and remains two-dimensional. Magnetic resonance imaging (MRI) has potential for assessing marrow composition and trabecular microarchitecture, but evidence supporting its use in cementless TKA selection remains limited. By contrast, computed tomography (CT)-based assessment is considered the most practical modality, offering three-dimensional evaluation and region-specific analysis. Hounsfield unit analysis on conventional CT can be readily integrated into the routine preoperative workflow, while quantitative CT and dual-energy CT provide more quantitative evaluation through volumetric bone mineral density measurement. Intraoperative assessment has the advantage of directly evaluating the implant bed; however, conventional tactile assessment remains subjective, and visual grading systems and device-based assessments have been proposed to overcome this limitation. Nevertheless, no standardized method has yet been established, and further research is needed. CT-based assessment is the most practical current modality, and intraoperative assessment is gaining objectivity. The integration of these methods with artificial intelligence-driven multi-modal assessment is expected to enable more precise and patient-specific cementless TKA candidate selection.

Background/Objectives: Although unrestricted kinematic alignment (uKA) has gained increasing acceptance in total knee arthroplasty (TKA), its application in knees with lateral compartment osteoarthritis (OA) remains a subject of debate due to concerns over postoperative gap imbalance and alignment outliers. The purpose of this study was to evaluate the surgical, radiographic, and clinical outcomes of contralateral non-OA knee–referenced, caliper-verified uKA in lateral compartment OA. Methods: This retrospective study included 40 patients with isolated lateral compartment OA who underwent primary TKA using contralateral non-OA knee–referenced, caliper-verified uKA. Surgical outcomes were assessed by measuring bone resection thicknesses of the distal femur, posterior femur, and proximal tibia, as well as extension and 90° flexion gaps. Radiographic outcomes included mechanical hip–knee–ankle angle, medial proximal tibial angle, lateral distal femoral angle, and Coronal Plane Alignment of the Knee (CPAK) classification. Patient-reported outcomes (PROs), including Pain VAS, EQ-5D, satisfaction, and Forgotten Joint Score, were assessed at a minimum follow-up of 2 years. Results: The resected osteochondral thickness was consistently greater on the medial side than on the lateral side, and all gap balances were well maintained, with a gap difference ≤ 2 mm observed in 95% of knees in full extension. Postoperatively, restoration to the same CPAK category was achieved in approximately 90% of cases. All PROs improved and reached levels comparable to those of the contralateral knee. Conclusions: In patients with lateral compartment OA, caliper-verified uKA may be appropriately applied when guided by a reliable anatomic reference, such as the contralateral non-OA knee. This strategy achieves stable soft-tissue balance, reliable coronal alignment restoration, and favorable clinical outcomes in carefully selected valgus knees undergoing TKA.

Background/Objectives: Successful cementless total knee arthroplasty (TKA) requires adequate bone quality. However, reliable tools for intraoperative assessment remain limited. This study aimed to introduce a novel visual grading system for evaluating femoral bone during surgery and to assess its correlation with actual bone mechanical properties and suitability for cementless fixation. Methods: We prospectively recruited 193 patients receiving posterior-stabilized TKA. Intraoperatively, femoral cutting surfaces were classified into four visual grades (Excellent, Good, Fair, Poor) considering pore appearance and contour integrity. Femoral bone specimens were harvested during box preparation, and bone mechanical properties were measured through indentation testing. Spearman correlation was used to evaluate the relationship between visual grades and bone mechanical properties. Fisher’s exact test was used to evaluate the distribution pattern of cementless suitable and cemented mandatory classifications across visual grading. Receiver operating characteristic (ROC) analysis was used to evaluate diagnostic accuracy for each visual grade cutoff. Results: Visual grade strongly correlated with bone mechanical properties (Spearman’s ρ = 0.881, p < 0.01). Cementless suitable cases were predominantly distributed in Good/Excellent visual grades, while cemented mandatory cases were mostly found in Fair/Poor grades. However, 8% of Good visual grade specimens exhibited strength warranting cemented fixation, and 18% of Fair visual grade specimens demonstrated adequate mechanical properties for cementless fixation. Using the Good visual grade as a cutoff threshold, ROC analysis showed excellent diagnostic accuracy (AUC = 0.941) with high sensitivity (89%) and specificity (94%). Conclusions: The authors’ novel intraoperative visual assessment system demonstrated significant correspondence to measured bone mechanical properties in the distal femur and showed high accuracy in determining suitability for cementless TKA in Asian individuals. Given the ethnic homogeneity of this cohort, further validation in diverse populations is required to generalize these findings.

Background and Objectives: The use of cementless total knee arthroplasty (TKA) is increasing, but established methods for assessing bone quality to prevent early failure remain undefined. Current preoperative assessments using central bone mineral density (BMD) do not accurately reflect peripheral bone quality, and intraoperative evaluation is subjective. This study aimed to establish objective assessment methods by analyzing the correlations between a novel visual grading system, CT Hounsfield units (HU), and actual bone strength. Materials and Methods: This prospective study included 131 patients undergoing posterior-stabilized TKA. We developed a novel visual grading system (Excellent, Good, Fair, Poor) based on femoral cutting surface characteristics. CT HUs were measured preoperatively by an assisting surgeon in the box bone area. Femoral box specimens underwent indentation testing to determine their actual bone strength. Minimum Required Strength (MRS) was defined at 2.5-fold the patient’s body weight, and Estimated Withstanding Strength (EWS) was determined by scaling first failure load using area ratios. Patients were classified as “cementless suitable” (EWS > MRS) or “cemented mandatory” (EWS < MRS). Correlations were assessed using Spearman’s rank correlation for visual grade and Pearson correlation for Hounsfield units. ROC curve analysis determined diagnostic accuracy. Results: Visual grade exhibited an exceptionally robust relationship to bone strength (Spearman ρ = 0.903, p < 0.01), whereas HU showed substantial correlation (Pearson r = 0.660, p < 0.01, R² = 0.435). Visual grading achieved excellent diagnostic accuracy (AUC = 0.974, sensitivity 95.1%, specificity 95.9%) using “Good” grade as cutoff. HU demonstrated AUC of 0.938 with 92.7% sensitivity and 81.6% specificity at a cutoff value of 65.2. Conclusions: Our novel visual grading system and CT HU demonstrated excellent correlations with actual distal femoral bone strength and outstanding diagnostic performance for identifying cementless TKA candidates. Unlike traditional subjective intraoperative assessments such as the “thumb test”, this system provides objective visual criteria directly correlated with actual bone strength. Preoperative HU screening with intraoperative visual grading can help prevent early failure.

Background/Objectives: Central bone mineral density (cBMD) is widely utilized for assessing bone quality, but its reliability as a predictor of knee bone strength for cementless total knee arthroplasty (TKA) remains unclear. This study aimed to determine whether cBMD reliably estimates bone strength suitable for cementless fixation. Methods: 188 patients scheduled for TKA underwent preoperative cBMD assessment of the lumbar spine and femoral neck. During surgery, femoral bone specimens were collected for indentation tests. We compared distal femoral bone strength among osteoporosis classification groups (normal, osteopenia, osteoporosis) and examined the distribution of cementless suitable versus cemented mandatory cases with chi-square tests. ROC analysis evaluated cBMD’s diagnostic performance in predicting cementless TKA suitability, with AUC, sensitivity, and specificity calculated for both measurement sites. Results: No significant differences in distal femoral bone strength existed between osteopenia and osteoporosis groups (p = 0.845 for lumbar spine, p = 0.857 for femoral neck). Among patients with normal cBMD, 35.4% (lumbar spine) and 30.7% (femoral neck) were unsuitable for cementless TKA, whereas 30.8% and 45.0% of osteoporotic patients, respectively, had adequate bone strength for cementless fixation. The AUC values for predicting cementless suitability were 0.656 (lumbar spine) and 0.669 (femoral neck), with sensitivity and specificity below 0.75 for both measurements. Conclusions: Central BMD does not reliably represent distal femoral bone strength and demonstrates inadequate predictive capability for identifying appropriate candidates for cementless TKA in this predominantly Asian female cohort. Future multi-center, multi-ethnic studies are needed to enhance generalizability.

Background and Objectives: Adequate bone quality is essential for promoting initial bone ingrowth and preventing early migration during cementless total knee arthroplasty (TKA). However, gold-standard criteria for identifying suitable bone strength have yet to be established. Dual-energy computed tomography (DECT)-based volumetric bone mineral density (vBMD) is an emerging tool for assessing bone quality. This study aimed to determine whether DECT-derived vBMD can accurately predict suitable bone strength for cementless TKA. Materials and Methods: A total of 190 patients undergoing primary TKA with a standardized posterior-stabilized implant were prospectively enrolled. Prior to TKA, DECT-derived vBMD was measured in the femoral box region. Actual bone strength was evaluated using an indentation test on resected femoral box specimens. Correlation and linear regression analyses were performed to assess the relationship between DECT vBMD and actual bone strength. Receiver operating characteristic (ROC) curve analysis and area under the curve (AUC) calculations were used to determine the optimal cut-off value and diagnostic accuracy of DECT vBMD in identifying candidates suitable for cementless TKA. Results: DECT-derived vBMD exhibited a strong correlation with actual bone strength (correlation coefficient = 0.719, p < 0.01), while linear regression analysis revealed a moderate association (R² = 0.51, p < 0.01). In addition, it demonstrated excellent diagnostic performance in predicting adequate bone quality for cementless TKA, yielding an AUC of 0.984, with a sensitivity of 91.9% and a specificity of 92.0%. Conclusions: DECT-derived vBMD is a reliable and accurate tool for assessing bone strength around the knee and predicting the suitable bone quality for cementless TKA.

Introduction : With the advancement of porous surface processing technology, cementless total knee arthroplasty (TKA) has once again garnered attention. Cementless TKA lacks cement sealing, raising concerns regarding potential blood loss. Recently, patient blood management (PBM) protocols have been introduced to mitigate postoperative blood loss and transfusions. In this systematic review, we aimed to address whether cementless TKA leads to increased blood loss and transfusion rates as compared with cemented TKA. Additionally, we explored the impact of contemporary PBM protocols on post-TKA hemodynamics. Methods This systematic review included prospective randomized trials and retrospective studies that compared blood loss and PBM between cementless and cemented TKA. A comprehensive literature search for publications from 1980 onwards was conducted using databases such as PubMed, MEDLINE, and EMBASE. Furthermore, we conducted a thorough examination of the bibliographies of all relevant articles that were retrieved. Studies that met our inclusion criteria were assessed carefully for pertinent data. This systematic review followed the Preferred Reporting Items for Systematic Re-views and Meta-Analyses (PRISMA) statement and was registered in the PROSPERO register (CRD42024507236). Results A total of twelve studies were included in this study. Among these, six papers reported lower blood loss in cemented TKA, while the other six papers found no significant difference in perioperative blood loss between the two groups. From the perspective of PBM, seven studies applied PBM protocols including systematic and topical tranexamic acid, autogenous transfusion, strict transfusion threshold and drain clamping, while the remaining five studies did not. If PBM protocols were implemented, no significant difference in blood loss was observed based on the implant fixation method. Conclusion In the context of recent studies implementing PBM protocols, the choice of implant fixation method appears to have no relevant impact on post-TKA blood loss. Nevertheless, it is important to note that the reporting of outcomes and PBM protocols exhibit considerable variation and heterogeneity.

Purpose: The purpose of this study was to assess whether kinematic alignment (KA) outperforms mechanical alignment (MA) in restoring patellar tracking to native patterns by using a clustering algorithm.Methods: Twenty cadavers (40 knees) were evaluated. For each cadaver, one knee was randomly assigned to KA and the other to MA. KA total knee arthroplasty (TKA) procedures were performed using a caliper‐verified technique, while MA TKA procedures utilized a measured resection technique. Subsequently, all specimens were mounted on a customized knee‐testing system, and patellar tracking was measured using a motion analysis system. All patellar tracking data were clustered using the density‐based spatial clustering of applications with noise algorithm. Differences in patellar tracking patterns and the restoration of native patellar tracking were compared between the two alignment strategies.Results: Patellar tracking patterns following KA were considerably different from MA. Pre‐ and post‐TKA patellar tracking patterns following MA were grouped into separate clusters, whereas a substantial proportion of patellar tracking patterns following KA were grouped into the pre‐TKA dominant cluster. Compared to MA, a greater proportion of patellar tracking patterns following KA showed similar patterns to native knees (p < 0.05) and more patellar tracking patterns following KA paired with preoperative patterns (p < 0.01).Conclusion: KA restored native patellar tracking patterns more closely compared to MA.Level of Evidence: Level I, therapeutic study.

Suh D, et al. Clin Orthop Surg. 2024 Dec;16(6):917-924. https://doi.org/10.4055/cios24096

(1) Background: A cementless total knee arthroplasty (TKA) is a recent and an increasingly popular innovation that enhances porous fixation surfaces. However, the lack of cemented sealing of an exposed resected bone has raised concerns about the potential for greater blood loss. The goals of this study were to determine if a cementless approach impacts post-TKA hemodynamics and to identify risk factors for blood loss in instances of cementless (vs. cemented) TKAs under a contemporary patient blood management (PBM) protocol. (2) Methods: We recruited 153 consecutive patients undergoing unilateral TKAs between 2019 and 2023. All enrollees received cementless or cemented prostheses of the same design (cementless, 87; cemented, 66). After propensity score matching for demographics, there were 46 patients in each group. We then compared blood loss metrics (total [TBL] and estimated [EBL]), drainage volumes, hemoglobin (Hb) levels, and transfusion rates by group. (3) Results: Post-TKA hemodynamics (i.e., TBL, EBL, drainage, Hb level, and transfusion rate) of cementless (n = 46) and cemented (n = 46) TKA groups did not differ significantly. In addition, the proportions of patients with Hb drops > 3.0 g/dL were similar for the two groups. A logistic regression analysis revealed that only preoperative Hb and EBL during the early postoperative period were predictive of a substantial fall in Hb levels. The fixation method was not associated with Hb decline > 3.0 g/dL by postoperative Day 3. (4) Conclusion: The cementless TKA has no impact on customary post-TKA hemodynamics and is not associated with greater TKA-related blood loss when implementing a contemporary PBM protocol.