
==== Front
Jt Dis Relat Surg
Jt Dis Relat Surg
Joint Diseases and Related Surgery
2687-4784
2687-4792
Bayçınar Medical Publishing

10.52312/jdrs.2024.1636
39189563
Original Article
Risk factors for delayed bone union in opening wedge high tibial osteotomy
Araya Naoko http://orcid.org/0009-0007-6306-9442
1
Koga Hideyuki http://orcid.org/0000-0003-4574-1796
1
Nakagawa Yusuke http://orcid.org/0000-0003-0170-9743
1
Shioda Mikio http://orcid.org/0000-0002-7020-0169
2
Ozeki Nobutake http://orcid.org/0000-0002-2927-7930
1
Kohno Yuji http://orcid.org/0000-0002-3879-6484
1
Nakamura Tomomasa http://orcid.org/0000-0001-5843-9575
1
Sekiya Ichiro http://orcid.org/0000-0002-6331-722X
1
Katagiri Hiroki http://orcid.org/0000-0002-8350-4962
1
1 Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital, Tokyo, Japan
2 Department of Orthopaedic Surgery, Dokkyo Medical University Saitama Medical Center, Saitama, Japan
Hiroki Katagiri, MD. Department of Joint Surgery and Sports Medicine, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. hirokik@dokkyomed.ac.jp.
9 2024
14 8 2024
35 3 546553
23 1 2024
24 6 2024
Copyright © 2024, Turkish Joint Diseases Foundation
2024
Turkish Joint Diseases Foundation
https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Objectives

The purpose of this study was to investigate the relationship between patient demographics and potential intraoperative factors and delayed bone union in opening wedge high tibial osteotomy (OWHTO).

Patients and methods

A retrospective review of 65 patients (37 females, 28 males; mean age: 60.1±10.1 years; range, 44 to 77 years) who underwent OWHTO using an angle-stable implant with beta-tricalcium phosphate gap filling between September 2016 and October 2019 was conducted. The osteotomy site was divided into five zones from the lateral hinge on anteroposterior radiographs, and we defined the zone in which bone healing was observed. The bone union area was assessed according to this definition at three, six, nine, and 12 months after surgery, and bone union was defined as union at the fourth zone or greater. A generalized estimating equations approach was employed to investigate longitudinal data pertaining to bone union area as a dependent variable. In addition, the association of bone union at six months postoperatively and predictors were evaluated using cross-sectional statistical methods. The categorical predictors included in the models were smoking, diabetes, hinge fracture, and autologous osteophyte grafting. The continuous variables included in the models were age, body mass index, opening gap width, and plate position.

Results

Smoking (odds ratio [OR]=0.478, p<0.01), large opening gap width (OR=0.941, p=0.014), and anterior plate placement (OR=0.971, p<0.01) were significantly associated with decreased bone union area. Union rate at six months in smokers was significantly lower compared to nonsmokers (16.6% and 67.8%, respectively; OR=0.10, p=0.023). Area under the curve in the receiver operating characteristic analysis for bone union at six months was 0.60 for gap width and 0.63 for plate placement.

Conclusion

Smoking, large opening gap width, and anterior plate placement are risk factors for delayed bone union after OWHTO. Surgeons should avoid anterior placement of the plate and carefully consider other options for smokers and those who require a large correction.

Bone union
opening wedge high tibial osteotomy
plate position
risk factors.
==== Body
pmcIntroduction

Opening wedge high tibial osteotomy (OWHTO) has been favored for patients with medial compartment osteoarthritis and a varus deformity leg. However, severe complications following OWHTO, including delayed union and nonunion, have been reported.[1-3] Delayed union was defined as the absence of radiographic evidence of bone healing or a combination of osteotomy site pain and radiographic findings at three to six months postoperatively in previous studies.[4,5] Delayed union relates to persistent osteotomy site pain with failure to achieve clinical recovery. Importantly, the rate of delayed union is reported to range from 0 to 12%.[1,6]

Smoking, obesity, large opening gaps, and unstable hinge fractures have been reported as risk factors for delayed union and nonunion after OWHTO.[4,5,7-10] To the best of our knowledge, few studies have focused on the effect of plate position on delayed union in OWHTO. Biomechanical tests and a numerical model based on the finite element method have demonstrated that plate location affects the resistance to applied mechanical loads, potentially leading to nonunion.[11-13] However, the relationship between plate position and delayed union remains to be elucidated in clinical settings. A factor hindering this elucidation has been that the number of events in delayed union subgroups in previous studies is too low to enable confident multivariate analysis.[1] For this and other reasons, ongoing debates persist regarding the factors leading to delayed union.

The purpose of this study was to use generalized estimating equations (GEEs), incorporating data from all time points, and examine a range of patient characteristics and intraoperative factors previously proposed as risk factors for delayed bone union in OWHTO. The underlying hypothesis for this study was that smoking, large opening gap width, and a more anterior plate placement would be detected as risk factors for delayed bone union after OWHTO.

Patients and Methods

Eighty-three patients who underwent primary OWHTO performed at the Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital between September 2016 and October 2019 were retrospectively reviewed. Study exclusion criteria were as follows: (i) patients with early plate removal prior to 12 months; (ii) patients who were lost to follow-up prior to one year; (iii) lack of radiographic data at measurement points (3, 6, 9, and 12 months). After excluding 18 knee joints from a total of 83 based on the exclusion criteria, 65 knee joints (37 females, 28 males; mean age: 60.1±10.1 years; range, 44 to 77 years) were eligible for inclusion (Figure 1). Demographic data, including age, sex, height, weight, and body mass index (BMI), were recorded preoperatively.

Figure 1 Flowchart of patients' selection.<br> OWHTO: Opening wedge high tibial osteotomy

All surgeries were performed by or under the supervision of two senior surgeons. A standard arthroscopic evaluation was performed before OWHTO. Any unstable meniscal tears were repaired using the “all-inside” or the “inside-out” suture techniques if possible[14,15] or were resected. The OWHTO procedure followed the method proposed by Staubli et al.[16] In brief, the preoperative plan involved shifting the mechanical axis to a point 57% lateral on the transverse diameter of the tibial plateau. The correction angle and opening width were then measured, and the osteotomy site was opened to the preoperatively planned width while limb alignment was simultaneously monitored using fluoroscopy to determine the position of the alignment rod at the knee. A beta-tricalcium phosphate wedge (Osferion 60; Olympus Terumo Biomaterials, Tokyo, Japan) was inserted into the opened osteotomy site. The osteotomy site was fixed with a tris medial high tibial osteotomy plate system (Olympus Terumo Biomaterials, Tokyo, Japan) placed on the medial side of the tibia under fluoroscopic control and fastened with locking screws.

Postoperative rehabilitation began with range of motion and quadriceps setting exercises one day after surgery. One-third, two-thirds, and full weight-bearing with crutches were initiated three, 10, and 14 days after surgery, respectively. Patients were allowed to commence running exercises at three months if bone union was considered sufficient. Patients progressed to full activity six months postoperatively.

The bone union area in the osteotomy site was assessed on postoperative anteroposterior radiographs at 3, 6, 9, and 12 months by a physician who had not performed any surgeries in this series. A triangle was drawn with the sides of the triangle converging from the opening at the medial tibial cortex along the borders of the osteotomy to form an apex at the lateral cortex. The triangular area was then divided into five numbered zones starting from the lateral cortex utilizing Brosset et al.’s[17] osteotomy filling index (Figure 2). The bone remodeling phase was determined using van Hemert et al.’s[18] criteria, the most medial zone showing the consolidation phase was recorded, and bone union was defined as consolidation at fourth zone or greater.[19]

Figure 2 Application of the Brosset's osteotomy filling index on a digitized radiograph. The osteotomy site of anteroposterior radiographs was divided into five zones using a radiological index.

The plate position was evaluated on postoperative radiographs as shown in Figure 3. From all postoperative lateral radiographs available for each patient, the truest possible lateral radiographs were chosen, based on alignment of the visible posterior outlines of the femoral condyles. The maximum anteroposterior diameter of the proximal tibial bone (referred to as value A) and the distance from the insertion site of the proximal posterior screw to the tibial posterior margin (referred to as value B) were measured along a line perpendicular to the tibial axis. The plate position was calculated as value B divided by value A such that values closer to one indicate more anterior placement. Intra- and interobserver reliability for plate position measurements were assessed using intraclass correlation coefficients. For intraobserver reliability, an interval of >4 weeks was maintained between the first and second assessments, and the observer was blinded to previous results. Once intraobserver reliability had been calculated, interobserver reliability was checked by having another observer additionally assess the plate position for randomly selected patients using the same lateral radiographs previously used to assess each patient.

Figure 3 Application of the plate anterior- posterior position calculation on a digitized radiograph. (Line A) Tibial axis. (Line B) The maximum anterior-posterior diameter of the proximal tibial bone on the perpendicular line to the reference line. (Line C) The distance from insertion site of proximal posterior screw to tibial posterior margin on the perpendicular line to the reference line.

Statistical analysis

Statistical analyses were performed using IBM SPSS version 25.0 software (IBM Corp., Armonk, NY, USA). Data were expressed as mean ± standard deviation or frequency and percentage. Generalized estimating equations with a ranking data logistic and type 3 Wald statistical tests were employed to investigate longitudinal data related to bone union area at 3, 6, 9, and 12 months after surgery as a dependent variable. The odds ratio (OR) in GEEs indicated the predicted change in odds for a unit increase in the predictor. When the OR was <1, increasing values of the variable correspond to decreasing odds of the progression of bone union area. The association of bone union (union area achieved in zones 4 or 5) at six months postoperatively and the risk factors identified by GEEs were evaluated using the chi-square test for categorical variables and a receiver operating characteristic (ROC) curve analysis for continuous variables. Categorical predictors that were included in the models were smoking, diabetes, hinge fracture, and autologous osteophyte grafting. The continuous variables included in the models were age, BMI, opening gap width, and plate position. Repeated measures ANOVA (analysis of variance) with Greenhouse-Geisser and Tukey’s post hoc correction were employed to analyze differences in bone union area between time points. A p-values <0.05 was considered statistically significant.

Results

Patient characteristics are shown in Table I. No patients suffered nonunion requiring reoperation. All cases of hinge fracture were type 1 according to the Takeuchi classification.[20] Repeated measures ANOVA determined that the bone union area significantly differed between time points (F (2.42, 155)=345, p<0.05). The radiological bone union area increased in a time-dependent manner (Figure 4). Representative radiographs of a moderate bone union case are presented in Figure 5. Bone union in the fourth zone was accomplished in 5%, 63%, 94%, and 100% of current cases at 3, 6, 9, and 12 months after OWHTO, respectively. Smoking (OR=0.478, p<0.01), large opening gap (OR=0.941, p=0.014), and anterior plate placement (OR=0.971, p<0.01) were statistically associated with decreased bone union area after surgery (Table II). Union rate at six months in smokers was significantly lower compared to nonsmokers (16.6% and 67.8%, respectively; OR=0.10, p=0.023). Area under the ROC curves for bone union at sine months were 0.60 for opening gap width (cut-off value=10.5 mm, sensitivity=61.0%, specificity=62.5%) and 0.63 for plate placement (cut-off value=0.74, sensitivity=50.0%, specificity=78.0%). The bone union progression for each risk factor is shown in Figure 6. The intra- and interobserver intraclass correlation coefficients for plate position assessment were 0.86 and 0.72, respectively. These reliability ratings were considered excellent.[21]

Table 1 Participant characteristics (n=65)

 	n	%	Mean±SD	Range	
Age (year)	 	 	60.1±10.1	 	
Sex	 	 	 	 	
Male	28	43	 	 	
Female	37	57	 	 	
Body mass index (kg/m2)	 	 	24.3±3.2	 	
Smoker	6	9	 	 	
Diabetes	 	5	 	 	
Autograft osteophyte grafting	27	42	 	 	
Opening gap width (mm)	 	 	10.2±2.6	5.5-15.5	
Plate position	 	 	0.68±0.11	0.41-0.94	
Hinge fracture	6	9	 	 	
SD: Standard deviation.	

Table 2 Logistic regression model of risk factor effects on bone union time with generalized estimating equation

 	OR	95% CI	p	
Age (year)	0.999	0.982-1.016	0.891	
Sex	 	 	 	
Female, (Male as reference)	0.883	0.681-1.145	0.347	
Body mass index (kg/m2)	0.978	0.931-1.027	0.368	
Smoking (nonsmoker as reference)	0.478	0.314-0.726	0.001	
Diabetes (no diabetes as reference)	0.688	0.413-1.146	0.151	
Autologous osteophyte grafting (no osteophyte grafting as reference)	0.875	0.633-1.208	0.417	
Opening gap width (mm)	0.941	0.896-0.988	0.014	
Plate position	0.970	0.959-0.981	<0.001	
Hinge fracture (no hinge fracture as reference)	1.508	0.896-2.583	0.122	
OR: Odds ratio; CI: Confidence interval.	

Figure 4 Line graph of Bone union progression.<br> * There was significant difference of Brosset's osteotomy filling index between two measurement points.

Figure 5 Representative radiographs of a moderate bone union case (A1-A5) and a delayed bone union case (B1-B5).

Figure 6 Line graph of bone union progression. The horizontal axis represents time after the surgery (months) and the vertical axis represents bone union rate (%).

Discussion

The most important findings of the present study were that smoking, a large opening gap width, and a more anterior plate placement emerged as risk factors for delayed bone union after OWHTO using beta-tricalcium phosphate bonesubstitute wedges.[22] Delayed bone union should be avoided since it leads to pain and requires extended nonoperative treatment, such as partial weight-bearing.[1,10]

Previous studies across a spectrum of techniques have found a large opening gap to be a risk factor for delayed bone union after OWHTO. In 2010, Jung et al.[23] reported that at three months, the degree of bone union was confirmed in 91.3% of patients with a 7-mm opening gap, while it was achieved in only 52.6% of those with a gap >13 mm. A systematic review by Slevin et al.[2] in 2016, designed primarily to compare bone void filler options, also provided substantial evidence regarding the impact of opening gap width on osteotomy healing. Another study by Goshima et al.[5] in 2019, using no graft material, reported that an opening gap >13.0 mm significantly delayed bone formation (OR=1.61) after OWHTO. Similarly, our current analysis using GEEs demonstrated that a large opening gap width was a risk factor for delayed bone union after OWHTO.

It is well-established that cigarette smoke inhalation impairs biological bone healing processes and delays fracture union in general.[24,25] However, specifically for OWHTO, the effect of smoking on delayed union has been subject to debate, with at least one study concluding that smoking has no significant impact on functional outcomes.[26] On the other hand, Meidinger et al.[7] noted in 2011 that 50% of nonunion OWHTO recipients were smokers, while only 23% of unproblematic patients were smokers. They concluded that for OWHTO, the risk of nonunion must be discussed with patients who smoke. Another study identified smoking as a risk factor for developing delayed union or nonunion in OWHTO with an OR of 4.[4] Furthermore, a tendency toward delayed gap filling over the entire follow-up period (12 weeks, 6 months, 12 months, and 18 months after surgery) was reported in a group of smokers.[27] Our study provides additional evidence that smoking is associated with delayed bone union after OWHTO.

Computational simulation studies and biomechanical tests indicate that plate location changes the resistance to applied mechanical loads.[11-13] A numerical model based on the finite element method previously demonstrated that an anteriorly placed plate results in increased stress at the tip of the osteotomy gap and increases micromotions in the osteotomy gap by up to 3.5-fold compared to a medially placed plate.[11] Biomechanical studies have indicated that anteromedial plate placement withstands lower loads with more displacement compared to medially placed plates and concluded that anterior placement is biomechanically inferior to posteromedial plate placement.[12,13] However, the relationship between plate position and delayed union has not been elucidated in clinical settings. In our patient population, a more anterior plate placement was associated with delayed bone union after surgery.

A biomechanical study of OWHTO demonstrated superior primary stability of the angle-stable implant (Tomofix plate; DePuy Synthes, Pennsylvania, USA) compared to other less rigid plates in the presence of lateral hinge fractures.[28] Furthermore, angle-stable implants with allograft or bone substitute gap filling have a higher loading capacity and reduced rate of nonunion and delayed union.[17,29] In this study, we used an angle-stable implant and bone substitute for these reasons. However, our findings may have been influenced by the use of angle-stable implants and bone substitute gap filling, potentially explaining why we did not observe a significant correlation between hinge fracture and delayed bone union.

Bone union progresses from the lateral hinge towards the medial side, with the bone union area increasing over time after surgery.[30] It is thought that although placing bone substitute into the site opening improves mechanical stability, the bone remodeling phase takes longer when using bone substitute. A previous study reported that bone union at the third zone was accomplished in only 25% of all patients six months after OWHTO using angle-stable implants with bone substitute.[31] In the current study, bone union in the third zone was accomplished in only 29% of current cases three months after OWHTO. In all cases, the current technique resulted in bone union in the fourth zone, which indicated thorough stability, before the end of the first year.

There were certain limitations to the present study. First, although three risk factors for delayed bone union after OWHTO were detected, the present study involved a relatively small number of participants. Additional studies with a larger number of participants are required to draw a robust conclusion. Second, this study was retrospective in nature, thus potentially introducing selection bias. In this patient population, the mean BMI was 24.3±3.2, and only six patients were >30. Our study involved only three patients with diabetes. The observed low mean BMI and small proportion of patients with diabetes potentially affected our results. Third, although two senior surgeons participated in each other’s surgeries to unify surgical methods, several other surgeons performed surgeries under their supervision, resulting in variations in surgical techniques based on the attending surgeon. Fourth, the bone union areas at all time points for any given patient were evaluated by one observer who was aware of the assessment results (i.e, nonblinded) from all previous time points, if any, for the patient being assessed. This could introduce a potential observer bias in assessments over the time course of bone union.

In conclusion, smoking, large opening gap width, and anterior placement of plates emerged as the main risk factors for delayed bone union after OWHTO. Surgeons should avoid anterior placement of plates and carefully consider other options for smokers and those who require major correction to mitigate the risk of delayed bone union. Further studies with greater numbers of participants are required to draw robust conclusions.

Financial Disclosure

The authors received no financial support for the research and/or authorship of this article.

Data Sharing Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Ethics Committee Approval: The study protocol was approved by the Tokyo Medical and Dental University Ethics Committee (date: April 03, 2015, no: M2000-2054-01). The study was conducted in accordance with the principles of the Declaration of Helsinki.

Patient Consent for Publication: A written informed consent was obtained from each patient.

Conflict of Interest: The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Author Contributions: Analyzed the data and drafted the manuscript: N.A.; Designed the initial plan, conducted the study and edited the manuscript: H.K.; Designed the initial plan: Y.N., M.S.; Collected the data: T.O., N.O., Y.K., T.N., I.S.; Designed the initial plan, conducted the study and completed the final manuscript: H.K. All authors read and approved the final manuscript.

Citation: Araya N, Koga H, Nakagawa Y, Shioda M, Ozeki N, Kohno Y, et al. Risk factors for delayed bone union in opening wedge high tibial osteotomy. Jt Dis Relat Surg 2024;35(3):546-553. doi: 10.52312/jdrs.2024.1636.
==== Refs
1 Martin R Birmingham TB Willits K Litchfield R Lebel ME Giffin JR Adverse event rates and classifications in medial opening wedge high tibial osteotomy Am J Sports Med 2014 42 1118 1126 10.1177/0363546514525929 24634450
2 Slevin O Ayeni OR Hinterwimmer S Tischer T Feucht MJ Hirschmann MT The role of bone void fillers in medial opening wedge high tibial osteotomy: A systematic review Knee Surg Sports Traumatol Arthrosc 2016 24 3584 3598 10.1007/s00167-016-4297-5 27557796
3 Woodacre T Ricketts M Evans JT Pavlou G Schranz P Hockings M Complications associated with opening wedge high tibial osteotomy--A review of the literature and of 15 years of experience Knee 2016 23 276 282 10.1016/j.knee.2015.09.018 26596554
4 van Houten AH Heesterbeek PJ van Heerwaarden RJ van Tienen TG Wymenga AB Medial open wedge high tibial osteotomy: Can delayed or nonunion be predicted Clin Orthop Relat Res 2014 472 1217 1223 10.1007/s11999-013-3383-y 24249537
5 Goshima K Sawaguchi T Shigemoto K Iwai S Nakanishi A Inoue D Large opening gaps, unstable hinge fractures, and osteotomy line below the safe zone cause delayed bone healing after open-wedge high tibial osteotomy Knee Surg Sports Traumatol Arthrosc 2019 27 1291 1298 10.1007/s00167-018-5334-3 30539305
6 Warden SJ Morris HG Crossley KM Brukner PD Bennell KL Delayed- and non-union following opening wedge high tibial osteotomy: Surgeons' results from 182 completed cases Knee Surg Sports Traumatol Arthrosc 2005 13 34 37 10.1007/s00167-003-0485-1 15103456
7 Meidinger G Imhoff AB Paul J Kirchhoff C Sauerschnig M Hinterwimmer S May smokers and overweight patients be treated with a medial open-wedge HTO. Risk factors for non-union Knee Surg Sports Traumatol Arthrosc 2011 19 333 339 10.1007/s00167-010-1335-6 21153542
8 Al-Musabi M Tahir M Seraj S Wasim A Khadabadi N Thakrar R The effect of smoking on union rates following corrective osteotomies around the knee: A systematic review and meta-analysis Knee 2023 44 11 20 10.1016/j.knee.2023.06.009 37480616
9 Dornacher D Leitz F Kappe T Reichel H Faschingbauer M The degree of correction in open-wedge high tibial osteotomy compromises bone healing: A consecutive review of 101 cases Knee 2021 29 478 485 10.1016/j.knee.2021.02.025 33743262
10 Kumagai K Yamada S Nejima S Muramatsu S Akamatsu Y Inaba Y Lateral hinge fracture delays healing of the osteotomy gap in opening wedge high tibial osteotomy with a beta-tricalcium phosphate block Knee 2020 27 192 197 10.1016/j.knee.2019.10.027 31883759
11 Luo CA Hwa SY Lin SC Chen CM Tseng CS Placementinduced effects on high tibial osteotomized construct - biomechanical tests and finite-element analyses BMC Musculoskelet Disord 2015 16 235 235 10.1186/s12891-015-0630-2 26337985
12 Takeuchi R Woon-Hwa J Ishikawa H Yamaguchi Y Osawa K Akamatsu Y Primary stability of different plate positions and the role of bone substitute in open wedge high tibial osteotomy Knee 2017 24 1299 1306 10.1016/j.knee.2017.07.015 29033262
13 Martinez de Albornoz P Leyes M Forriol F Del Buono A Maffulli N Opening wedge high tibial osteotomy: Plate position and biomechanics of the medial tibial plateau Knee Surg Sports Traumatol Arthrosc 2014 22 2641 2647 10.1007/s00167-013-2517-9 23624677
14 Katagiri H Nakagawa Y Miyatake K Ohara T Shioda M Sekiya I Short-term outcomes after high tibial osteotomy aimed at neutral alignment combined with arthroscopic centralization of medial meniscus in osteoarthritis patients J Knee Surg 2023 36 261 268 10.1055/s-0041-1731738 34261157
15 Koga H Watanabe T Horie M Katagiri H Otabe K Ohara T Augmentation of the pullout repair of a medial meniscus posterior root tear by arthroscopic centralization Arthrosc Tech 2017 6 e1335-9 10.1016/j.eats.2017.05.014
16 Staubli AE De Simoni C Babst R Lobenhoffer P TomoFix: A new LCP-concept for open wedge osteotomy of the medial proximal tibia--early results in 92 cases Injury 2003 34 Suppl 2 B55-62 10.1016/j.injury.2003.09.025
17 Brosset T Pasquier G Migaud H Gougeon F Opening wedge high tibial osteotomy performed without filling the defect but with locking plate fixation (TomoFix™) and early weight-bearing: Prospective evaluation of bone union, precision and maintenance of correction in 51 cases Orthop Traumatol Surg Res 2011 97 705 711 10.1016/j.otsr.2011.06.011 22001198
18 van Hemert WL Willems K Anderson PG van Heerwaarden RJ Wymenga AB Tricalcium phosphate granules or rigid wedge preforms in open wedge high tibial osteotomy: A radiological study with a new evaluation system Knee 2004 11 451 456 10.1016/j.knee.2004.08.004 15581763
19 Onodera J Kondo E Omizu N Ueda D Yagi T Yasuda K Beta-tricalcium phosphate shows superior absorption rate and osteoconductivity compared to hydroxyapatite in open-wedge high tibial osteotomy Knee Surg Sports Traumatol Arthrosc 2014 22 2763 2770 10.1007/s00167-013-2681-y 24045917
20 Takeuchi R Ishikawa H Kumagai K Yamaguchi Y Chiba N Akamatsu Y Fractures around the lateral cortical hinge after a medial opening-wedge high tibial osteotomy: A new classification of lateral hinge fracture Arthroscopy 2012 28 85 94 10.1016/j.arthro.2011.06.034 21982387
21 Landis JR Koch GG The measurement of observer agreement for categorical data Biometrics 1977 33 159 174 843571
22 Atik OŞ Writing for Joint Diseases and Related Surgery (JDRS): There is something new and interesting in this article! Jt Dis Relat Surg 2023 34 533 533 10.52312/jdrs.2023.57916 37750255
23 Jung KA Lee SC Ahn NK Hwang SH Nam CH Radiographic healing with hemispherical allogeneic femoral head bone grafting for opening-wedge high tibial osteotomy Arthroscopy 2010 26 1617 1624 10.1016/j.arthro.2010.05.025 20970947
24 Chang CJ Jou IM Wu TT Su FC Tai TW Cigarette smoke inhalation impairs angiogenesis in early bone healing processes and delays fracture union Bone Joint Res 2020 9 99 107 10.1302/2046-3758.93.BJR-2019-0089.R1 32435462
25 Pearson RG Clement RG Edwards KL Scammell BE Do smokers have greater risk of delayed and non-union after fracture, osteotomy and arthrodesis. A systematic review with meta-analysis BMJ Open 2016 6 e010303 10.1136/bmjopen-2015-010303
26 Floerkemeier S Staubli AE Schroeter S Goldhahn S Lobenhoffer P Does obesity and nicotine abuse influence the outcome and complication rate after open-wedge high tibial osteotomy. A retrospective evaluation of five hundred and thirty three patients Int Orthop 2014 38 55 60 10.1007/s00264-013-2082-3 24022738
27 Schröter S Freude T Kopp MM Konstantinidis L Döbele S Stöckle U Smoking and unstable hinge fractures cause delayed gap filling irrespective of early weight bearing after open wedge osteotomy Arthroscopy 2015 31 254 265 10.1016/j.arthro.2014.08.028 25442655
28 Agneskirchner JD Freiling D Hurschler C Lobenhoffer P Primary stability of four different implants for opening wedge high tibial osteotomy Knee Surg Sports Traumatol Arthrosc 2006 14 291 300 10.1007/s00167-005-0690-1 16284740
29 Fucentese SF Tscholl PM Sutter R Brucker PU Meyer DC Koch PP Bone autografting in medial open wedge high tibial osteotomy results in improved osseous gap healing on computed tomography, but no functional advantage: A prospective, randomised, controlled trial Knee Surg Sports Traumatol Arthrosc 2019 27 2951 2957 10.1007/s00167-018-5285-8 30456568
30 Staubli AE Jacob HA Evolution of open-wedge high-tibial osteotomy: Experience with a special angular stable device for internal fixation without interposition material Int Orthop 2010 34 167 172 10.1007/s00264-009-0902-2 19921189
31 Kobayashi H Akamatsu Y Kumagai K Kusayama Y Saito T Radiographic and computed tomographic evaluation of bone union after medial opening wedge high tibial osteotomy with filling gap Knee 2017 24 1108 1117 10.1016/j.knee.2017.06.002 28797873
