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[This corrects the article DOI: 10.1371/journal.pone.0327247.].

Purpose The purpose of this study was to investigate if one level of corrective femoral osteotomy (subtrochanteric or supracondylar) bears an increased risk of unintentional implications on frontal and sagittal plane alignment in a simulated clinical setting. Methods Out of 100 cadaveric femora, 23 three-dimensional (3-D) surface models with femoral antetorsion (femAT) deformities (> 22° or < 2°) were investigated, and femAT normalized to 12° with single plane rotational osteotomies, perpendicular to the mechanical axis of the femur. Change of the frontal and sagittal plane alignment was expressed by the mechanical lateral distal femoral angle (mLDFA) and the posterior distal femoral angle (PDFA), respectively. The influence of morphologic factors of the femur [centrum–collum–diaphyseal (CCD) angle and antecurvatum radius (ACR)] were assessed. Furthermore, position changes of the lesser (LT) and greater trochanters (GT) in the frontal and sagittal plane compared to the hip centre were investigated. Results Mean femoral derotation of the high-antetorsion group ( n  = 6) was 12.3° (range 10–17°). In the frontal plane, mLDFA changed a mean of 0.1° (− 0.06 to 0.3°) (n.s.) and − 0.3° (− 0.5 to − 0.1) ( p  = 0.03) after subtrochanteric and supracondylar osteotomy, respectively. In the sagittal plane, PDFA changed a mean of 1° (0.7 to 1.1) ( p  = 0.03) and 0.3° (0.1 to 0.7) ( p  = 0.03), respectively. The low-antetorsion group ( n  = 17) was rotated by a mean of 13.8° (10°–23°). mLDFA changed a mean of − 0.2° (− 0.5° to 0.2°) ( p  < 0.006) and 0.2° (0–0.5°) ( p  < 0.001) after subtrochanteric and supracondylar osteotomy, respectively. PDFA changed a mean of 1° (− 2.3 to 1.3) ( p  < 0.01) and 0.5° (− 1.9 to 0.3) ( p  < 0.01), respectively. The amount of femAT correction was associated with increased postoperative deviation of the mechanical leg axis ( p  < 0.01). Using multiple regression analysis, no other morphological factors were found to influence mLDFA or PDFA. Internal rotational osteotomies decreased the ischial-lesser trochanteric space by < 5 mm in both the frontal and sagittal plane ( p  < 0.001). Conclusions In case of femAT correction of ≤ 20°, neither subtrochanteric nor supracondylar femoral derotational or rotational osteotomies have a clinically relevant impact on frontal or sagittal leg alignment. A relevant deviation in the sagittal (but not frontal plane) might occur in case of a > 25° subtrochanteric femAT correction. Level of evidence IV.

Purpose Medial opening wedge high tibial osteotomy (MOW HTO) is now a successful operation with a range of indications, requiring an individualised approach to the choice of intended correction. This manuscript introduces the concept of surgical accuracy as the absolute deviation of the achieved correction from the intended correction, where small values represent greater accuracy. Surgical accuracy is compared in a randomised controlled trial (RCT) between gap measurement and computer navigation groups. Methods This was a prospective RCT conducted over 3 years of 120 consecutive patients with varus malalignment and medial compartment osteoarthritis, who underwent MOW HTO. All procedures were planned with digital software. Patients were randomly assigned into gap measurement or computer navigation groups. Coronal plane alignment was judged using the mechanical tibiofemoral angle (mTFA), before and after surgery. Absolute (positive) values were calculated for surgical accuracy in each individual case. Results There was no significant difference in the mean intended correction between groups. The achieved mTFA revealed a small under-correction in both groups. This was attributed to a failure to account for saw blade thickness (gap measurement) and over-compensation for weight bearing (computer navigation). Surgical accuracy was 1.7° ± 1.2° (gap measurement) compared to 2.1° ± 1.4° (computer navigation) without statistical significance. The difference in tibial slope increases of 2.7° ± 3.9° (gap measurement) and 2.1° ± 3.9° (computer navigation) had statistical significance ( P  < 0.001) but magnitude (0.6°) without clinical relevance. Conclusion Surgical accuracy as described here is a new way to judge achieved alignment following knee osteotomy for individual cases. This work is clinically relevant because coronal surgical accuracy was not superior in either group. Therefore, the increased expense and surgical time associated with navigated MOW HTO is not supported, because meticulously conducted gap measurement yields equivalent surgical accuracy. Level of evidence I.

Purpose To investigate the effect of proximal tibial tubercle osteotomy (PTO) and distal tibial tubercle osteotomy (DTO) in medial opening wedge high tibial osteotomy on patellofemoral alignment, patellofemoral osteoarthritis and clinical outcomes. Methods PTO ( n  = 41) and DTO ( n  = 43) for the same surgical indications were included. Radiographic measurements of the Caton-Deschamps index, patellar tilt and shift, and arthroscopic cartilage evaluation at the patellofemoral joint were performed at osteotomy and plate removal. The Knee Society Score (KSS) was evaluated preoperatively and at the latest follow-up. Results The follow-up period was longer in the PTO group (33.7 months; range 23–40 years) than in the DTO group (22.2 months; range 18–29 months) ( p  < 0.0001), whereas the period from osteotomy to plate removal was not different between the groups. The Caton-Deschamps index of the DTO group was unchanged from 0.9 (range 0.7–1.2) to 0.9 (range 0.6–1.4), whereas that of the PTO group changed from 0.9 (0.7–1.2) to 0.7 (0.5–1.0) ( p  < 0.0001). There were fewer deteriorated cases of cartilage status in the trochlear groove in the DTO group (20.9%) than in the PTO group (56.1%, p  < 0.05). There were more improved cases in the DTO group (23.3%) than in the PTO group (4.9%, p  < 0.05). Postoperative KSS was better in the DTO group than in the PTO group ( p  < 0.05). Conclusion DTO is associated not only with reduced deterioration but also with increased improvement of cartilage status in the trochlear groove and better KSS as compared with PTO. Level of evidence IV.

Purpose Aim of this systematic review was to evaluate the literature regarding the effect of tranexamic acid (TXA) on the outcome after knee osteotomy. Methods A systematic literature search was carried out in various databases on studies on the use of tranexamic acid in osteotomies around the knee. Primary outcome criterion was the hemoglobin (drop). Secondary outcome criteria were total blood loss, drainage volume, adverse effects such as thromboembolic events, blood transfusions, wound complications and clinical scores. A meta-analysis was performed for quantitative measures. The present study was registered prospectively ( www.crd.york.ac.uk/PROSPERO ; no.: CRD42021229624). Results Seven studies with 584 patients (TXA group: 282 patients, non TXA group: 302 patients) Hemoglobin decrease (1.54 g/dl vs. 2.28 g/dl), blood loss (394.49 ml vs. 595.54 ml) and drainage volume (266.5 ml vs. 359.05 ml) were significantly less in the TXA group compared to the non TXA group. No thromboembolic event was noted in any study. In the non TXA group four blood transfusions were given. Eleven wound complications occurred in the non TXA group in comparison to two wound complications in the TXA group. Conclusions The results of the present study show that the application of TXA reduces hemoglobin drop, blood loss and drainage volume. These effects could be responsible for the lesser rate of side effects after administration of TXA during knee osteotomy.

Background Double level osteotomy (DLO) has been introduced to prevent increased postoperative joint line obliquity. However, although DLO is planned, knees with postoperative medial proximal tibial angle (MPTA) > 95° in preoperative surgical planning are present. This retrospective study aimed to evaluate risk factors for an MPTA > 95° in preoperative surgical planning for DLO in patients with varus knee osteoarthritis (OA). Methods A total of 168 knees that underwent osteotomies around the knee for varus knee OA were enrolled. The hip-knee-ankle angle (HKA), weight-bearing line (WBL) ratio, mechanical lateral distal femoral angle (mLDFA), joint line convergence angle (JLCA) and mechanical medial proximal tibial angle (mMPTA) were measured on preoperative radiographs. The postoperative WBL ratio was planned to be 62.5%. When the postoperative mMPTA was more than 95° in isolated high tibial osteotomy (HTO), (DLO) was planned so that the postoperative mLDFA was 85°, and residual deformity was corrected by HTO. Knees with postoperative mMPTA ≤ 95° and > 95° were classified into the correctable group and uncorrectable group, respectively. Results DLO was required in 101 knees (60.1%). Among them, 41 knees (40.6%) were classified into the uncorrectable group. Binomial logistic regression analysis showed that preoperative JLCA and mMPTA were independent predictors in the uncorrectable group. Conclusions Even with DLO, postoperative mMPTA was more than 95° in approximately 40% of cases. Preoperative increased JLCA and decreased mMPTA were risk factors for a postoperative mMPTA of > 95° after DLO.

Purpose Both, knee joint distraction as a relatively new approach and valgus-producing opening-wedge high tibial osteotomy (HTO), are knee-preserving treatments for knee osteoarthritis (OA). The efficacy of knee joint distraction compared to HTO has not been reported. Methods Sixty-nine patients with medial knee joint OA with a varus axis deviation of <10° were randomized to either knee joint distraction ( n  = 23) or HTO ( n  = 46). Questionnaires were assessed at baseline and 3, 6, and 12 months. Joint space width (JSW) as a surrogate measure for cartilage thickness was determined on standardized semi-flexed radiographs at baseline and 1-year follow-up. Results All patient-reported outcome measures (PROMS) improved significantly over 1 year (at 1 year p  < 0.02) in both groups. At 1 year, the HTO group showed slightly greater improvement in 4 of the 16 PROMS ( p  < 0.05). The minimum medial compartment JSW increased 0.8 ± 1.0 mm in the knee joint distraction group ( p  = 0.001) and 0.4 ± 0.5 mm in the HTO group ( p  < 0.001), with minimum JSW improvement in favour of knee joint distraction ( p  = 0.05). The lateral compartment showed a small increase in the knee joint distraction group and a small decrease in the HTO group, leading to a significant increase in mean JSW for knee joint distraction only ( p  < 0.02). Conclusion Cartilaginous repair activity, as indicated by JSW, and clinical outcome improvement occurred with both, knee joint distraction and HTO. These findings suggest that knee joint distraction may be an alternative therapy for medial compartmental OA with a limited mechanical leg malalignment. Level of evidence Randomized controlled trial, Level I.

Purpose To systematically review and critically appraise the literature on double-level osteotomy (DLO) of the knee, and determine the indications, contraindications, targets and outcomes. Materials and methods A systematic literature search was performed on PubMed, Embase®, and Cochrane for studies that reported on DLO by any technique or approach, including indications, contraindications, and targets for DLO, as well as patient-reported outcome measures (pROMS) and radiographic angles. Results Twelve eligible studies were found: 9 case series and 3 studies that compared DLO to high-tibial osteotomy (HTO). In all studies, DLO was performed by medial opening-wedge tibial osteotomy and lateral closing-wedge femoral osteotomy. Seven specified that DLO was performed if simple HTO would exceed thresholds of postoperative medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and/or predicted wedge size. The targets were 88°–95° for MPTA, 84°–89° for LDFA, and 0°–4° for hip–knee–ankle (HKA) angle. The 3 comparative studies reported lower MPTA after DLO (89.6°–92.5°) than after HTO (91.5°–98.3°). All 3 reported similar postoperative HKA after DLO (0.2°–4.4°) as HTO (0.4°–4.8°); only 2 compared postoperative LDFA, which was lower after DLO (85.4° and 84.9°) than HTO (88.7° and 88.8°). Two comparative studies reported postoperative overall KOOS which was slightly lower after DLO (351–403) than HTO (368–410); only 1 study reported separate items of the KOOS. Conclusion There was relative consistency between studies on the indications, targets and techniques for DLO. Furthermore, while the comparative studies reported similar preoperative MPTA, LDFA and HKA, the postoperative MPTA and LDFA were lower after DLO than after HTO, though both treatments achieved equivalent postoperative HKA. Level of evidence IV, systematic review.

Purpose Open wedge high tibial osteotomy is a widespread treatment option in patients with varus malalignment and medial compartment osteoarthritis. There is no standardised protocol for post-operative rehabilitation available. The purpose of this study was to compare two post-operative rehabilitation protocols and to evaluate the clinical outcome of early full weight-bearing after open wedge HTO. Methods One hundred and twenty consecutive patients with varus malalignment and medial compartment osteoarthritis received an open wedge HTO using an angular locking plate fixation between December 2008 and December 2011. All patients were assigned randomly into one of two groups with different post-operative rehabilitation protocols (11-day vs. 6-week 20-kg partial weight-bearing). Clinical outcome was evaluated using established instruments (Lequesne, Lysholm, HSS and IKDC scores) preoperatively, 6, 12 and 18 months post-operatively. Deformity analysis was performed preoperatively and during follow-up. Results All clinical scores showed a significant pre- to post-operative improvement. After 6 months, there was a higher improvement in the group of early full weight-bearing. The difference between preoperative and 6-month follow-up for the group with early full weight-bearing and for the group with 20-kg PWB for 6 weeks was 28 ± 26 and 18 ± 22, respectively, for the Lysholm score and −5.0 ± 5.1 and −3.0 ± 3.6, respectively, for the Lequesne score. Conclusions Early full weight-bearing (11-day 20-kg partial weight-bearing) after open wedge HTO without bone graft leads to earlier improvement of the clinical results and can be recommended for post-operative rehabilitation after open wedge HTO and fixation with an angular locking plate. Level of evidence Therapeutic study, Level I.