Nienke van Egmond

Purpose: Traditional lower limb deformity analysis in pediatrics and adults centers on the anatomical center of the knee. However, in high tibial osteotomy (HTO) for medial compartment knee osteoarthritis (KOA), the surgical goal is often valgus overcorrection toward a lateral weight-bearing point. This study quantified the effect of using a lateral weight-bearing point versus the center of the knee on lower-limb alignment parameters and assessed how these differences may influence surgical decision-making. Methods: A retrospective radiographic study was conducted in 20 patients with unicompartmental KOA who underwent HTO. Alignment was measured using 2 methods: the anatomical center of the knee and a 62.5% lateral weight-bearing point as the lateral weight-bearing reference point. Measured parameters included the mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal tibial angle (mLDTA), and mechanical hip-knee-ankle angle (mHKAA). Methods were compared using paired t tests. Results: Using a 62.5% lateral weight-bearing point altered all alignment parameters. Compared with knee-centered measurements, mLDFA increased by 1.52° (more varus), mMPTA decreased by 1.84° (more varus), and mLDTA decreased by 1.85° (more valgus) (all P < 0.001). These changes altered deformity classification, with femora classified as varus increasing from 4 to 10 and tibiae from 8 to 13. Conclusion: Using a lateral weight-bearing point for deformity analysis produces predictable changes in alignment measurements that frequently alter deformity classification. This approach may reveal occult femoral deformities underestimated by traditional methods and may provide a more biomechanically relevant framework for osteotomy planning.

Purpose: Medial open-wedge high tibial osteotomy (MOW-HTO) is effective for correcting varus knee deformity but may unintentionally affect ankle joint alignment. This study investigated radiographic factors associated with postoperative ankle alignment changes following valgus-producing MOW-HTO. Methods: A retrospective analysis was conducted on a prospective cohort of 50 knees in 49 patients (mean age 46.3 ± 8.2 years). Patients were included if they underwent MOW-HTO between 2016 and 2024, were enrolled in the hospital knee registry, and had both pre-and postoperative whole-leg radiographs available. These weight-bearing long-leg radiographs were used to assess tibial bone deformity and ankle joint alignment. Postoperative ankle alignment was classified as deviating closer to neutral or further from neutral. Correlation analyses and within- and between-group comparisons were performed, with significance set at p < 0.05. Results: After MOW-HTO in varus-shaped knees, all alignment parameters shifted toward valgus. Tibial deformity predominantly originated from the distal tibia, with a medial center of rotation of angulation (CORA), reflecting an overall valgus-shaped tibia. Distal tibial valgus showed a strong correlation with talar orientation relative to the ground (ρ = 0.81, p < 0.001). Patients deviating further from neutral had nearly 5° more distal tibial valgus than those deviating closer to neutral (p < 0.001), and more frequently showed an overall valgus-shaped tibia (p < 0.01). Additionally, larger correction angles were moderately associated with greater valgus shift of the ankle (ρ = −0.44, p < 0.001). Conclusion: MOW-HTO results in a valgus shift of the talar orientation, particularly in patients with preoperative distal tibial valgus, an overall valgus-shaped tibia, and larger correction angles. Thorough preoperative assessment of tibial morphology is essential to better anticipate postoperative ankle alignment changes.

Objective: A medial open-wedge high tibial osteotomy (MOWHTO) may increase the posterior tibial slope (PTS). The purpose of this study was to determine the effect of the osteotomy inclination angle (in the sagittal plane) in combination with different hinge positions (in the transverse plane) on the change in PTS due to a MOWHTO. Methods: We developed a mathematical approach to determine the effect of the osteotomy inclination angle combined with different hinge positions. The change in PTS was determined for different osteotomy inclination angles, hinge positions, and intended wedge angles. Anterior-inclined, parallel, and posterior-inclined osteotomy inclination angles were simulated. Hinge positions varied between 5° anterolateral and −45° posterolateral. The wedge angles were 5°, 10°, and 15°. Moreover, 2 in silico osteotomies were performed to verify the results of the mathematical model. Results: The PTS was maintained when the osteotomy cut was performed parallel to the tibial plateau with a lateral hinge position. The PTS changed when the osteotomy was not aligned in the sagittal plane, ranging between 0.0° and 0.6°. Different hinge positions, however, had a large effect on postoperative PTS change, ranging between 0.1° and 10.7°. Conclusions: Our mathematical approach showed that the hinge position has a strong effect on the PTS. The sagittal osteotomy inclination angle had little effect on the PTS. An inclination angle parallel to the medial tibial plateau combined with a lateral hinge position does not change the PTS.

Background: Osteotomies around the knee are a well-established treatment option for early and moderate unicompartmental osteoarthritis combined with a lower extremity malalignment. Moreover, osteotomies are often combined with cartilage treatment. Current image-based bone union assessments lack an accepted definition despite widespread use in research and clinical settings. The aim of this systematic review was to identify definitions and classification systems for bone union on radiographs after a proximal tibia or distal femur osteotomy. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we systematically searched MEDLINE and Embase database, applying specific inclusion and exclusion criteria. Two independent reviewers screened abstracts and full-texts. The modified Cochrane Risk of Bias Tool and Risk of Bias in Nonrandomized Studies of Interventions tool were used. Data extraction included study characteristics, imaging modality, bone union definition, classification systems, assessment of gap fillers, use of modifiers, and osteotomy type. Results: Of the 1,180 screened titles and abstracts, 105 studies were included, with the majority (69 studies [65.7%]) using a retrospective design. Fifty-five studies (52.4%) defined bone union based on one or more criteria, while 50 studies (47.6%) used a classification system. There were 13 different criteria for bone union and 9 different classification systems. Interestingly, none of the classification systems incorporated negative criteria, such as hardware failure. Notably, 137 studies (49.1%) described bone union as either a primary or secondary outcome but do not describe a system for assessing bone union. Conclusion: This systematic review highlights the lack of consensus in the literature in defining bone union after a proximal tibia or distal femur osteotomy, revealing many criteria and different classifications. None of the classification systems were applicable to osteotomies with and without gap filler. This systematic review shows the need for a straightforward, reproducible, and accurate method to assess bone union after a proximal tibia or distal femur osteotomy. Level of Evidence: Level III. See Instructions for Authors for a complete description of levels of evidence.

Purpose: Knee joint distraction (KJD) is a joint‐preserving treatment for younger osteoarthritis patients. KJD has shown positive results in regular care, but the external fixation frame often caused pin tract skin infections. Therefore, the use of cadexomer iodine was included in the wound care protocol. The goal of this cross‐sectional study was to evaluate whether use of this ointment reduced the number of patients with infections during KJD treatment.Methods: Patients treated with KJD in regular care were included if they gave consent for use of their data and completed treatment with the newest distraction device before 2020. All patients followed a wound care protocol, which since March 2019 included using cadexomer iodine ointment. The number of patients experiencing pin tract infections was compared between patients who did (March 2019–December 2019) and did not (November 2017–March 2019) use the ointment.Results: Sixty‐seven patients were included; 34 patients used cadexomer iodine and 33 patients did not. Patient who did not use cadexomer iodine experienced twice as many infections (64% vs 32%;p = 0.010). There was a significant difference in the number of patients with serious infections, requiring more antibiotics than the standard 7‐day oral antibiotics (30% without vs 6% with cadexomer iodine; p = 0.009).Conclusions: The use of cadexomer iodine ointment during KJD results in a significant reduction of the number of patients experiencing pin tract infections during treatment. Use of this ointment should be considered standard protocol during KJD treatment and could be of value in general external fixator usage as well.

The FlexitSystem implant is a novel implant used in open wedge high tibial osteotomy. A clinical safety study was performed. Retrospectively 50 patients were analyzed who were treated with an open wedge high tibial osteotomy and the new FlexitSystem implant, with a minimal follow-up of one year. Complication rate, radiographic outcomes and implant removal were investigated. One patient underwent a revision surgery because of loss of correction and non-union. The complication rate was 10.0%. No other radiographic complications (screw breakage, implant failure) were found. In 24 patients (48%) the FlexitSystem implant was removed at a mean follow-up of 12.6 months (range 2.6 till 24.0 months). The mean reason was irritation of the implant. The FlexitSystem implant is a clinical safe and stable implant for an open wedge high tibial osteotomy, with a low complication rate. The rate of implant irritation requiring removal remained high.