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Purpose: The goals of this study were (1) to assess whether the preoperative difference between modalities and extent of deformity are associated with a higher difference between planned and achieved surgical correction and (2) if they yield a higher probability of intraoperative adjustments., Methods: Retrospective single-centre analysis of patients undergoing patient-specific instrumented (PSI) total knee arthroplasty (TKA). Preoperative radiographic parameters were analysed on weightbearing (WB) long-leg radiographs (LLR) and nonweightbearing (NWB) computed tomography (CT). The 2D/3D difference was calculated as the difference between preoperative WB-LLR (2D) hip-knee-ankle angle (HKA), and NWB CT (3D) HKA. Surgical records were screened to retrieve intraoperative adjustments to the preoperative plan. Postoperative assessment was performed on WB LLR., Results: Two-hundred-eighty-two knees of 263 patients were analysed. The difference of postoperative achieved to planned HKA (HKA Difference ) was 2.2° ± 1.7°. The preoperative 2D HKA showed the highest correlation with HKA Difference ( r  = -0.37, 95% confidence interval [CI]: -0.48 to -0.26, p  < 0.001). Intraoperative adjustments were performed in 60% ( n  = 170) of all knees. Patients with a preoperative coronal deformity of >7.8° had 10.55 higher odds for an intraoperative coronal adjustment (95% CI: 4.60-24.20, p  < 0.001)., Conclusion: The extent of deformity is associated with residual coronal deformity following PSI-TKA. Patients with extensive coronal malalignment may benefit from an adaptation of the preoperative surgical plan to avoid unintended postoperative coronal malalignment. Despite the advancements with 3D preoperative planning, intraoperative adjustments in PSI-TKA are frequently performed, in particular in patients with a higher preoperative varus/valgus deformity., Level of Evidence: Level III., Competing Interests: Sandro F. Fucentese is a consultant for Medacta SA (Switzerland), Smith & Nephew (United Kingdom), Zimmer Biomet and Karl Storz SE & Co. KG (Germany). The remaining authors declare no conflict of interest., (© 2024 The Author(s). Journal of Experimental Orthopaedics published by John Wiley & Sons Ltd on behalf of European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Purpose: The goal of this study is (1) to assess differences between two-dimensional (2D) weight-bearing (WB) and three-dimensional (3D) nonweight-bearing (NWB) planning in total knee arthroplasty (TKA) and (2) to identify factors that influence intermodal differences., Methods: Retrospective single-centre analysis of patients planned for a TKA with patient-specific instruments (PSI). Preoperative WB long-leg radiographs and NWB computed tomography were analysed and following radiographic parameters included: hip-knee-ankle angle (HKA) (+varus/-valgus), joint line convergence angle (JLCA), femorotibial subluxation and bony defect classified according to Anderson. Preoperative range of motion was also considered as possible covariate. Demographic factors included age, sex, and body mass index., Results: A total of 352 knees of 323 patients (66% females) with a mean age of 66 ± 9.7 years were analysed. The HKA differed significantly between 2D and 3D planning modalities; varus knees ( n  = 231): 9.9° ± 5.1° vs. 6.7° ± 4°, p  < 0.001; valgus knees ( n  = 121): -8.2° ± 6° vs. -5.5° ± 4.4°, p  < 0.001. In varus knees, HKA ( β  = 0.38; p  < 0.0001) and JLCA ( β  = 0.14; p  = 0.03) were associated with increasing difference between 2D/3D HKA. For valgus knees, HKA ( β  = -0.6; p  < 0.0001), JLCA ( β  = -0.3; p  = 0.0001) and lateral distal femoral angle ( β  = -0.28; p  = 0.03) showed a significant influence on the mean absolute difference., Conclusion: The coronal alignment in preoperative 3D model for PSI-TKA significantly differed from 2D WB state and the difference between modalities correlated with the extent of varus/valgus deformity. In the vast majority of cases, the 3D NWB approach significantly underestimated the preoperative deformity, which needs to be considered to achieve the planned correction when using PSI in TKA., Level of Evidence: Level III., Competing Interests: Sandro F. Fucentese is a consultant for Medacta SA (Switzerland), Smith & Nephew (United Kingdom), Zimmer Biomet and Karl Storz SE & Co. KG (Germany). The other authors have no conflict of interest to declare., (© 2024 The Author(s). Journal of Experimental Orthopaedics published by John Wiley & Sons Ltd on behalf of European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Purpose: Posttraumatic fibular malunion alters ankle joint biomechanics and may lead to pain, stiffness, and premature osteoarthritis. The accurate restoration is key for success of reconstructive surgeries. The aim of this study was to analyze the accuracy of a novel three-dimensional (3D) registration algorithm using different segments of the contralateral anatomy to restore the distal fibula., Methods: Triangular 3D surface models were reconstructed from computed tomographic data of 96 paired lower legs. Four segments were defined: 25% tibia, 50% tibia, 75% fibula, and 75% fibula and tibia. A surface registration algorithm was used to superimpose the mirrored contralateral model on the original model. The accuracy of distal fibula restoration was measured., Results: The median rotation error, 3D distance (Euclidean distance), and 3D angle (Euler's angle) using the distal 25% tibia segment for the registration were 0.8° (- 1.7-4.8), 2.1 mm (1.4-2.9), and 2.9° (1.9-5.4), respectively. The restoration showed the highest errors using the 75% fibula segment (rotation error 3.2° (0.1-8.3); Euclidean distance 4.2 mm (3.1-5.8); Euler's angle 5.8° (3.4-9.2)). The translation error did not differ significantly between segments., Conclusion: 3D registration of the contralateral tibia and fibula reliably approximated the premorbid anatomy of the distal fibula. Registration of the 25% distal tibia, including distinct anatomical landmarks of the fibular notch and malleolar colliculi, restored the anatomy with increasing accuracy, minimizing both rotational and translational errors. This new method of evaluating malreductions could reduce morbidity in patients with ankle fractures., Level of Evidence: IV., (© 2022. The Author(s).)

Purpose: To assess a novel method of three-dimensional (3D) joint line (JL) restoration based on the contralateral tibia and fibula., Methods: 3D triangular surface models were generated from computed tomographic data of 96 paired lower legs (48 cadavers) without signs of pathology. Three segments of the tibia and fibula, excluding the tibia plateau, were defined (tibia, fibula, tibial tuberosity (TT) and fibular tip). A surface registration algorithm was used to superimpose the mirrored contralateral model onto the original model. JL approximation and absolute mean errors for each segment registration were measured and its relationship to gender, height, weight and tibia and fibula length side-to-side differences analyzed. Fibular tip to JL distance was measured and analyzed., Results: Mean JL approximation did not yield significant differences among the three segments. Mean absolute JL error was highest for the tibia 1.4 ± 1.4 mm (range: 0 to 6.0 mm) and decreased for the fibula 0.8 ± 1.0 mm (range: 0 to 3.7 mm) and for TT and fibular tip segment 0.7 ± 0.6 (range: 0 to 2.4 mm) (p = 0.03). Mean absolute JL error of the TT and fibular tip segment was independent of gender, height, weight and tibia and fibula length side-to-side differences. Mean fibular tip to JL distance was 11.9 ± 3.4 mm (range: 3.4 to 22.1 mm) with a mean absolute side-to-side difference of 1.6 ± 1.1 mm (range: 0 to 5.3 mm)., Conclusion: 3D registration of the contralateral tibia and fibula reliably approximated the original JL. The registration of, TT and fibular tip, as robust anatomical landmarks, improved the accuracy of JL restoration independent of tibia and fibula length side-to-side differences., Level of Evidence: IV., (© 2021. The Author(s).)

Purpose: To quantify the influence of the femoral tunnel exit (FTE) on the graft bending angle (GBA) and GBA-excursion throughout a full range of motion (ROM) in single-bundle anterior cruciate ligament (ACL) reconstruction., Methods: Three-dimensional (3D) surface models of five healthy knees were generated from a weight-bearing CT obtained throughout a full ROM (0, 30, 60, 90, 120°) and femoral and tibial ACL insertions were computed. The FTE was simulated for 16 predefined positions, referenced to the Blumensaat's line, for each patient throughout a full ROM (0, 30, 60, 90, 120°) resulting in a total of 400 simulations. 3D GBA was calculated between the 3D directional vector of the ACL and the femoral tunnel, while the intra-articular ACL insertions remained unchanged. For each simulation the 3D GBA, GBA-excursion, tunnel length and posterior tunnel blow-out were analysed., Results: Overall, mean GBA decreased with increasing knee flexion for each FTE (p < 0.001). A more distal location of the FTE along the Blumensaat's line resulted in an increase of GBA and GBA-excursion of 8.5 ± 0.6° and 17.6 ± 1.1° /cm respectively (p < 0.001), while a more anterior location resulted in a change of GBA and GBA-excursion of -2.3 ± 0.6° /cm (+ 0.6 ± 0.4°/ cm from 0-60° flexion) and 9.8 ± 1.1 /cm respectively (p < 0.001). Mean tunnel length was 38.5 ± 5.2 mm (range 29.6-50.5). Posterior tunnel blow-out did not occur for any FTE., Conclusion: Aiming for a more proximal and posterior FTE, with respect to Blumensaat's line, reliably reduces GBA and GBA-excursion, while preserving adequate tunnel length. This might aid to reduce excessive graft stress at the femoral tunnel aperture, decrease femoral tunnel widening and promote graft-healing., Level of Evidence: IV.