Coronal tibiofemoral subluxation is a risk factor for postoperative overcorrection in high tibial osteotomy

Postoperative patient-reported outcome measures after medial open-wedge high tibial osteotomy was improved by decreased joint line convergence angle

PURPOSE

To evaluate the relationship between pre- and postoperative joint line convergence angle (JLCA) changes and patient-reported outcome measures related to medial open-wedge high tibial osteotomy (MOWHTO).

METHODS

Sixty-one patients (71 knees) who underwent MOWHTO were examined. Preoperative and 2-year postoperative radiographic parameters (hip-knee-ankle angle, weight-bearing line ratio, medial proximal tibial angle and JLCA) were measured, and knee injury and osteoarthritis outcome scores (KOOS) were assessed. Patients were divided into two groups: group D (decreased JLCA compared with preoperative status) included 44 knees with a ΔJLCA < 0° and group I (increased JLCA and no-change JLCA compared with preoperative status) included 27 knees with a ΔJLCA ≥ 0°. KOOS sub-scores and the proportion of patients whose improvement exceeded the minimum clinically important difference (MCID) were compared between both groups using Student's t tests, Mann-Whitney U tests and chi-square tests. Multiple regression analysis was performed to determine the factor that had an influential effect on the postoperative KOOS total.

RESULTS

Significant differences in 2-year postoperative KOOS were observed between the two groups, including total, symptom, pain and activities of daily living scores. Group D had significantly more patients who achieved MCID for both KOOS symptoms and pain scores than group I did. Multivariate analysis indicated that JLCA change and body mass index were significantly associated with the postoperative KOOS total.

CONCLUSION

Patients with decreased JLCA had better 2-year post-MOWHTO KOOS and better symptom and pain improvements. Therefore, strategies that reduce JLCA are crucial to improving clinical outcomes, and efforts should be made to improve JLCA in surgical techniques.

LEVEL OF EVIDENCE

Level Ⅳ, Case series.

Preoperative medial meniscus extrusion on magnetic resonance imaging is associated with a tendency toward varus shifting of open-wedge high tibial osteotomy

PURPOSE

To investigate serial changes in postoperative alignment over 5 years after open-wedge high tibial osteotomy (OWHTO) and to identify risk factors associated with alterations in the postoperative weight-bearing line WBL ratio.

METHODS

Patients who underwent OWHTO during 2011-2017 were retrospectively reviewed. Inclusion criteria were (1) follow-up duration ≥5 years and (2) serial postoperative long-standing hip-to-ankle radiographs to evaluate alignment alterations. The WBL ratio was measured preoperatively and at 3 months, 6 months, 1 year, and 5 years postoperatively to evaluate serial changes. Alterations in the WBL ratio were analyzed using a linear mixed model, considering potential risk factors including International Cartilage Repair Society (ICRS) grades of each compartment, and medial meniscus extrusion (≥3 mm). Clinical outcomes were assessed using the Knee Society (KS) objective and functional scores, and the correlations between clinical outcomes and alignment alteration were examined.

RESULTS

A total of 78 knees were investigated. During the study period, the overall WBL ratio decreased by 5.5 ± 7.2%, signifying varus shifting, from 58.6 ± 11.5% at 3 months post-surgery to 51.5 ± 12.7% at 5 years post-surgery. Based on univariate regression analyses, ICRS grade of the medial compartment and medial meniscus extrusion were included in a linear mixed model regarding alignment alteration. The model identified medial meniscus extrusion as a significant risk factor after adjusting for time (p <0.001). Medial meniscus extrusion also had a significant interaction with time (p <0.001), indicating greater alignment alteration in cases of medial meniscus extrusion. The extrusion was noted in 68 out of 78 knees.

CONCLUSION

In the midterm following OWHTO, the overall alignment had a tendency toward varus shifting. A linear mixed model found that preoperative medial meniscus extrusion on magnetic resonance imaging is associated with the tendency.

The joint line convergence angle (JLCA) correlates with intra-articular arthritis

PURPOSE

Knees with unicompartmental varus osteoarthritis (OA) usually display a combination of tibiofemoral bony deformity and increased joint line convergence angle (JLCA). The JLCA is a product of intra-articular deformity and lateral soft tissue laxity. This study aims to define the correlation between the JLCA and progression of OA.

METHODS

A retrospective radiological analysis of 501 patients, who underwent either high tibial osteotomy (HTO) or unicompartmental knee arthroplasty (UKA), was performed. The preoperative OA grade was reported based on the Ahlbäck and the Kellgren-Lawrence (KL). The hip-knee-ankle angle (HKA), the medial proximal tibial angle (MPTA), the mechanical lateral distal femoral angle (mLDFA) and the joint line convergence angle (JLCA) were recorded. The primary outcome was the relationship between the JLCA values and the OA grade. The secondary outcomes were comparing the JLCA and other alignment parameter values between HTO and UKA groups.

RESULTS

A total of 501 (59.3% females n = 297) cases were included, comprising 293 cases of HTO and 208 cases of UKA. Patients had a mean age of 57.63 ± 8.97 years, a mean BMI of 28.37 ± 7.39 kg/m2. Patients with Ahlbäck grade 2 represented 49.3% of all patients (n = 247) and patients with KL grade 3 represented 54.7% of all patients (n = 274). A high JLCA was observed in both groups. The reported mean JLCA in the UKA group was 3.69 ± 2.1°, and in the HTO group was 2.93 ± 1.82. There was a significant association between the increase in the JLCA and the progression of OA based on both the Ahlbäck and KL grades (both p values < 0.001). The mean JLCA in patients with Ahlbäck grades 1 and 4 was 1.48 ± 1.32°, and 7 ± 0.93°, respectively. The mean JLCA in patients with KL grades 1 and 4 was 1.77 ± 1.42°, and 4.89 ± 1.73°, respectively. The mean recorded preoperative HKA angle in the UKA group was 175.06 ± 3.08°, and in the HTO group was 173.26 ± 3.02°, whereas the mean MPTA was 88.63 ± 1.72° for the UKA group and 89.31 ± 2.29° for the HTO group.

CONCLUSION

The JLCA progressively increases with osteoarthritis progression in patients with unicompartmental varus knee osteoarthritis. The JLCA can potentially be used as a grading parameter for osteoarthritis progression akin to Ahlbäck and Kellgren-Lawrence grading systems.

Anatomical Study of the Lateral Tibial Spine as a Landmark for Weight Bearing Line Assessment during High Tibial Osteotomy

Background: Accurate pre-operative planning is essential for successful high tibial osteotomy (HTO). The lateral tibial spine is a commonly used anatomical landmark for weight-bearing line assessment. However, studies on the mediolateral (M-L) position of the lateral tibial spine on the tibial plateau and its variability are limited. Purpose: This study aimed to (1) analyze the M-L position of the lateral tibial spine on the tibial plateau and its variability, (2) investigate radiologic parameters that affect the position of the lateral tibial spine, and (3) determine whether the lateral tibial spine can be a useful anatomical landmark for weight-bearing line assessment during HTO. Materials and Methods: Radiological evaluation was performed on 200 participants (64% female, mean age 42.3 ± 13.2 years) who had standing anterior-posterior plain knee radiographs with a patellar facing forward orientation. The distances from the medial border of the tibial plateau to the lateral spine peak (dLSP) and lateral spine inflection point (dLSI) were measured using a picture archiving and communication system. The medial-lateral inter-spine distance (dISP) was also measured. All parameters were presented as percentages of the entire tibial plateau width. The relationships between the parameters were also investigated. Results: The mean value of dLSP was 56.9 ± 2.5 (52.4-64.5)%, which was 5% lower than the Fujisawa point (62%). The mean value of dLSI was 67.9 ± 2.2 (63.4-75.8)%, which was approximately 5% higher than the Fujisawa point. The values of the dLSP and dLSI were variable among patients, and the upper and lower 10% groups showed significantly higher and lower dLSP and dLSI, respectively, than the middle 10% group. The mean value of dISP was 16.5 ± 2.4%, and it was positively correlated with dLSP and dLSI. Conclusions: On average, the dLSP and dLSI were located -5% and +5% laterally from the conventional Fujisawa point, and they may be useful landmarks for correction amount adjustment during HTO. However, it should be noted that correction based on the lateral tibial spine can be affected by anatomical variations, especially in patients with small or large inter-spine distances.

Coronal tibiofemoral subluxation under valgus stress force radiography is useful for evaluating postoperative coronal tibiofemoral subluxation in mobile-bearing UKA

PURPOSE

Coronal tibiofemoral subluxation (CTFS) is considered a controversial and potential contraindication to unicompartmental knee arthroplasty (UKA) but is less discussed. The study aims to observe the CTFS in a cohort of patients before and after mobile-bearing UKA and to investigate the relationship between preoperative variables (preoperative CTFS and preoperative CTFS under valgus stress) and postoperative CTFS after mobile-bearing UKA.

METHODS

The study retrospectively analyzed 181 patients (224 knees) undergoing mobile-bearing UKA from September 1 2019 to December 31 2021. By using hip-to-ankle anterior-posterior (AP) standing radiographs and valgus stress force radiographs, preoperative CTFS, preoperative CTFS under valgus stress, and postoperative CTFS were measured. CTFS was defined as the distance between the tangent line to the outermost joint edge of the lateral condyle of the femur and the tangent line of the lateral tibial plateau. All patients were divided into two groups based on postoperative CTFS, group A (postoperative CTFS ≤ 5 mm) and group B (postoperative CTFS > 5 mm). The Student's t-test, one-way ANOVA together with Tukey's post hoc test, the chi-square test, the Fisher's exact test, Pearson correlation analysis, simple and multiple linear regression, and univariate and multiple logistic regression were used in the analyses.

RESULTS

The means ± standard deviations (SD) of preoperative CTFS, preoperative CTFS under valgus stress, and postoperative CTFS were 4.96 ± 1.82 mm, 3.06 ± 1.37 mm, and 3.19 ± 1.27 mm. The difference between preoperative CTFS and postoperative CTFS was statistically significant (p < 0.001). The preoperative CTFS (6.35 ± 1.34 mm) in Group B (n = 22) was significantly higher than that (4.81 ± 1.82 mm) in Group A (n = 202) (p < 0.001), so was the variable-preoperative CTFS under valgus stress (5.41 ± 1.00 mm (Group B) > 2.80 ± 1.14 mm (Group A), p < 0.001). In Pearson correlation analysis, there was a correlation between preoperative CTFS and postoperative CTFS (r = 0.493, p < 0.001), while the correlation between preoperative CTFS under valgus stress and postoperative CTFS was stronger (r = 0.842, p < 0.001). In multiple linear regression analysis, preoperative CTFS under valgus stress (β = 0.798, 95% confidence interval (CI) = 0.714-0.883, p < 0.001) was significantly correlated with postoperative CTFS. In multiple logistic regression analysis, preoperative CTFS under valgus stress (OR = 12.412, 95% CI = 4.757-32.384, and p < 0.001) was expressed as the risk factor of postoperative CTFS (> 5 mm).

CONCLUSION

Preoperative CTFS can be improved significantly after mobile-bearing UKA. In addition, postoperative CTFS is correlated with preoperative CTFS under valgus stress and a higher preoperative CTFS under valgus stress will increase the risk of higher postoperative CTFS (> 5 mm).

LEVEL OF EVIDENCE

Level III.

Application of SolidWorks software in preoperative planning of high tibial osteotomy

Purpose

Open-wedge high tibial osteotomy (HTO) is a common surgical treatment for medial osteoarthritis in young and active patients. The accuracy of osteotomy is closely associated with postoperative efficacy. The accuracy of digital preoperative planning is higher than that of the preoperative manual measurement and several computer software with varying accuracy and convenience are used for digital preoperative planning. This study aimed to use the SolidWorks software for HTO preoperative planning and to determine its accuracy and reliability in HTO preoperative planning.

Methods

We reviewed the data of 28 patients with 54 with medial compartment knee arthritis who underwent open-wedge HTO preoperative planning using SolidWorks between June 2019 and March 2021. The standard anteroposterior standing whole-leg radiographs were assessed before and 6 weeks after the surgery. The correction angle, weight-bearing line (WBL) ratio, mechanical femorotibial angle (mFTA), and medial proximal tibial angle (MPTA) before and after the surgery were compared. The clinical results were evaluated using the Knee Society score.

Results

At 6 weeks after the surgery, the WBL ratio was corrected from 16.8% to 50.5%, mFTA was corrected from 6.4° varus to 1.2° valgus, and MPTA was corrected from 83.4° to 89.3°. No significant difference was observed between the predicted correction angle before the surgery and the correction angle measured 6 weeks after the surgery (t = -1.745, p = 0.087). The knee score and function score of Knee Society increased from 76.4 and 80.7 before surgery to 95.0 and 95.7, respectively.

Conclusions

The SolidWorks software showed high accuracy and reliability in preoperative planning of open-wedge HTO in patients with medial compartment knee arthritis.

Risk Factors for Increase in Posterior Slope After Medial Open-Wedge High Tibial Osteotomy

BACKGROUND

Whether lateral hinge fracture (LHF) after open-wedge high tibial osteotomy (OWHTO) is associated with the change in tibial posterior slope (PS) has not been determined. Risk factors for PS increase are still unknown.

HYPOTHESIS

There will be no difference in patient characteristics and radiographic factors when stratified by change in tibial PS (ΔPS).

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We reviewed the records of 148 patients who underwent OWHTO with locking-plate fixation from 2010 to 2016. Included were those with a minimum 2-year follow-up and true lateral radiographs before and at 1 year after surgery. ΔPS was defined as a difference between preoperative and 1-year postoperative PS, with positive values indicating PS increase. ΔPS was classified into <3°, 3° to <6°, and ≥6°. Any LHFs were grouped by Takeuchi classification as stable (type 1) or unstable (types 2 and 3). Risk factors for PS increase were evaluated using ordinal logistic regression analyses. Clinical outcomes according to ΔPS were evaluated using the Hospital for Special Surgery score.

RESULTS

There were 79 (53.4%) patients with ΔPS <3°, 44 (29.7%) with 3° ≤ ΔPS < 6°, and 25 (16.9%) with ΔPS ≥6°. LHFs were observed in 41 (27.7%) patients: 32 with type 1 and 7 and 2 with types 2 and 3, respectively. Results of the multivariate ordinal logistic regression analysis indicated that ΔPS was associated with unstable LHF (P = .005, exp[β] = 6.34), preoperative PS (P = .028, exp[β] = 0.90), and correction angle (P = .037, exp[β] = 1.09). ΔPS ≥6° was seen in 4 of 9 (44.4%) patients with unstable LHF, 9 of 32 (28.1%) with stable LHF, and 12 of 107 (11.2%) with no LHF (P = .017). The mean correction angle was 11.3° ± 3.6° in patients with ΔPS ≥6°, 9.4° ± 4.6° in cases of 3° ≤ ΔPS < 6°, and 8.8° ± 3.6° in cases of ΔPS <3° (P = .019). Hospital for Special Surgery scores did not differ according to ΔPS.

CONCLUSION

LHF type and correction angle were associated with ΔPS after OWHTO, and unstable LHF and large correction angle were risk factors for PS increase. There was no significant difference in clinical outcomes according to ΔPS.

Insufficient Correction and Preoperative Medial Tightness Increases the Risk of Varus Recurrence in Open-Wedge High Tibial Osteotomy

PURPOSE

To assess serial changes of limb alignment after open wedge high tibial osteotomy (HTO) using the weightbearing line (WBL) ratio in the midterm, with a focus on varus recurrence.

METHODS

Patients undergoing open wedge HTO from January 2010 to December 2016 were retrospectively reviewed. Those without serial postoperative weightbearing long-leg alignment films, those who showed remained varus alignment after osteotomy, and those who had <2 years of follow-up were excluded. In terms of immediate postoperative limb alignment (≤3 months) measured using WBL ratio, cases were categorized into 4 groups: <50%, undercorrection; 50% to 57%, insufficient correction; 57% to 67%, planned correction; and >67%, overcorrection. To determine risk factors for varus recurrence (WBL ratio <50%), immediate postoperative WBL ratio category and preoperative valgus and varus stress angles (which represent medial and lateral tightness of the joint, respectively) were investigated using logistic regression analysis, taking other related factors into account. Clinical outcomes according to varus recurrence were measured using Hospital for Special Surgery (HSS) scores.

RESULTS

A total of 148 cases were included. Varus recurrence was noted in 40 cases (27.0%), with a mean follow-up of 49.7 ± 21.8 months (range 24 to 102 months). The incidence of varus recurrence was different according to WBL ratio category: 10/10 (100.0%) in undercorrection; 16/33 (48.5%) in insufficient correction; 13/58 (22.4%) in planned correction; and 1/47 (2.1%) in overcorrection. Based on logistic regression analysis, insufficient correction and preoperative valgus stress angle were found to be significant risk factors (P = .038, and .008, respectively). With valgus stress angle <2°, 7 of 10 insufficient correction cases showed varus recurrence (P = .005). However, HSS scores did not differ according to varus recurrence (P = .363).

CONCLUSION

Insufficient correction and preoperative medial tightness increased the risk of varus recurrence. Especially in cases where preoperative valgus stress angle was <2°, insufficient correction was strongly associated with varus recurrence. However, no significant differences in clinical outcomes were observed according to varus recurrence in the midterm.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Influence of preoperative coronal and sagittal tibiofemoral subluxation in knee osteoarthritis on the outcome of primary total knee arthroplasty

BACKGROUND

The effect of osteoarthritis (OA) with tibiofemoral (TF) subluxation on patients undergoing total knee arthroplasty (TKA) has been less studied, and there have been no studies on sagittal knee subluxation which is a component of a three-dimensional problem. We aim to analyze the influence of preoperative coronal and sagittal knee subluxation with OA on other radiological parameters and the functional outcome in patients undergoing TKA.

METHODS

We retrospectively reviewed the 179-consecutive primary TKA in 151 patients from January 2017 to June 2017. The radiological parameters analyzed were the mechanical tibiofemoral angle (HKA), joint line congruence angle (JLCA) and coronal tibiofemoral (CTF) subluxation in long leg films. In the lateral view, posterior tibial slope, the settlement area of the femur over the tibia and the sagittal tibiofemoral (STF) subluxation were calculated. Preoperative and postoperative knee society and knee society functional scores were documented. Multivariate regression analysis was done to determine the association of preoperative radiological parameters with coronal and sagittal TF subluxation.

RESULTS

The average follow-up was 31 months (2.6 years). 102 knees (57%) had CTF subluxation (< 5 mm) within normal range, and 77 knees (43%) had CTF subluxation. There was a direct correlation between the magnitude of CTF subluxation and poor preoperative functional scores compared with the non-subluxation group (p < 0.05). CTF subluxation was not associated with the magnitude of varus deformity as it is correlated more with mild deformity (odds ratio [OR] 10.07, 95% confidence interval [CI] 3.47-29.25) than with moderate and severe varus deformity. The degree of the joint line convergence angle was positively correlated with the amount of CTF subluxation (p = 0.003). STF subluxation had a significant correlation with the posterior slope (p < 0.001), but not with the magnitude of varus deformity (p = 0.26).

CONCLUSION

Coronal and sagittal tibiofemoral subluxation had a significant association with poor preoperative clinical scores. The degree of CTF subluxation reduces with the increasing magnitude of varus deformity and JLCA. STF subluxation was associated with the posterior tibial slope. Patients who underwent posterior stabilized TKA had excellent clinical outcomes irrespective of preoperative knee subluxation.

Short-term outcomes of Oxford unicompartmental knee arthroplasty with coronal subluxation of the knee: a retrospective case–control study

Background

The goal of this study was to assess short-term outcomes in single compartment osteoarthritis patients associated with the coronal tibiofemoral subluxation (CTFS) of the knee joint after Oxford unicompartmental knee arthroplasty (OUKA), and to establish the potential impact of the degree of CTFS on operative outcomes.

Methods

Data pertaining to 183 patients with medial compartment osteoarthritis that underwent OUKA treatment between February 2016 and June 2019 were retrospectively analyzed. The presence and degree of severity of CTFS were assessed using preoperative weight-bearing anteroposterior X-ray images of the knee. Patients were stratified into three subgroups based upon the observed degree of subluxation: a normal group, a mild subluxation group (CTFS < 0.5 cm), and a severe subluxation group (CTFS ≥ 0.5 cm). Anterior and posterior X-ray examination of the knee was conducted at the time of most recent follow-up for each patient to assess the degree of CTFS correction following OUKA. Clinical function was assessed using Oxford knee score (OKS) and Hospital for Special Surgery score (HSS) values, while pain was rated using visual-analog scale (VAS) scores. The mechanical femoral tibial angle (mFTA), range of motion (ROM), and complication rates in these three groups were additionally compared.

Results

The average follow-up duration for patients in this study was 24.1 months (range: 17–32 months). There were no significant differences in patient age, sex, body mass index (BMI), follow-up duration, mFTA, ROM, OKS, HSS, or VAS scores among these three groups (P > 0.05). After surgery, OKS and HSS scores declined significantly, but no differences in these scores were observed among groups (P > 0.05). Of these patients, 135 (73.8%) were satisfied with the operation, of whom 80 (43.7%) were very satisfied. There were no significant differences in ROM or VAS scores among groups (P > 0.05). The degree of CTFS for patients in the mild and severe subluxation groups was significantly improved following OUKA relative to preoperative values such that the degree of postoperative CTFS did not differ significantly among these groups (P > 0.05). Postoperative mFTA was also significantly improved in these three patient subgroups (P < 0.05). No patients experienced operative complications over the follow-up period.

Conclusions

OUKA can successfully improve clinical symptoms in patients with single compartmental osteoarthritis. Moreover, OUKA can effectively correct CTFS of the knee in these patients, and the degree of preoperative CTFS has no impact on surgical efficacy.

Level of evidence

III.

Unstable Lateral Hinge Fracture or Occult Complete Osteotomy Adversely Affects Correction Accuracy in Open-Wedge High Tibial Osteotomy

PURPOSE

To verify whether lateral hinge fracture (LHF) affects correction accuracy in open-wedge high tibial osteotomy (OWHTO) and to identify the fracture characteristics responsible for inaccurate correction, including LHF type and hinge location.

METHODS

Patients undergoing OWHTO with locking plate fixation between 2010 and 2016 were retrospectively reviewed. Patients who did not have a minimum 2-year of follow-up or postoperative long-standing hip-to-ankle radiographs were excluded. Correction accuracy was assessed using the weight-bearing line ratio: 57% to 67%, planned correction; 50% to 70%, acceptable correction; otherwise, inappropriate correction. The association between LHF and correction accuracy was assessed using the χ² test. To identify the fracture characteristics responsible for inaccurate correction, LHF type (stable type 1 and unstable types 2 and 3) and hinge location (shallow osteotomy, deep osteotomy, and occult complete osteotomy) were analyzed using ordinal logistic regression analysis, taking other related demographic and radiologic factors into account. Clinical outcomes according to LHF type were evaluated using the Hospital for Special Surgery scores.

RESULTS

A total of 148 cases were included; 41 (27.7%) showed LHF: type 1, 32 cases; type 2, 7 cases; and type 3, 2 cases. Planned, acceptable, and inappropriate corrections were noted in 63 (42.6%), 36 (24.3%), and 48 (32.4%) cases, respectively. LHF had a significant association with correction accuracy (P = .010). Regarding fracture characteristics, unstable LHF and occult complete osteotomy were significant risk factors (P = .016 and P = .004, respectively). Specifically in cases of stable LHF, occult complete osteotomy adversely affected correction accuracy (P = .025). No difference was found in the final Hospital for Special Surgery scores according to LHF type (P = .816).

CONCLUSIONS

LHF affected the accuracy of coronal alignment correction in OWHTO. Unstable LHF or occult complete osteotomy were risk factors for inaccurate correction. Even among stable LHFs, those with occult complete osteotomy could lead to inaccurate correction.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Knee Joint Line Obliquity Causes Tibiofemoral Subluxation That Alters Contact Areas and Meniscal Loading

BACKGROUND

Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO) before and after coronal realignment osteotomy.

HYPOTHESES

Higher JLO would lead to abnormal relative position of the femur on the tibia, a shift of the joint contact areas, and elevated joint contact pressures.

STUDY DESIGN

Descriptive laboratory study.

METHODS

10 fresh-frozen human cadaveric knees (age, 59 ± 5 years) were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0°, 4°, 8°, and 12° varus ("downhill" medially) and valgus, at 0° and 20° of knee flexion. The mechanical compression axis was aligned to the center of the tibial plateau. Contact pressure and contact area were recorded by pressure sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system.

RESULTS

Both medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to subluxate medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes (P < .01), giving a 6-mm range of subluxation. The areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the downhill meniscus and the "uphill" tibial spine. Changes in JLO had only small effects on maximum contact pressures.

CONCLUSION

A 4° change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. This caused large movements of the tibiofemoral contact pressures across each compartment.

CLINICAL RELEVANCE

These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO. This information provides guidance regarding the choice of single- or double-level osteotomy. Excessive JLO alteration may cause abnormal tibiofemoral joint articulation and chondral or meniscal loading.

Difference of preoperative varus-valgus stress radiograph is effective for the correction accuracy in the preoperative planning during open-wedge high tibial osteotomy

PURPOSE

This study aimed to evaluate (1) the efficacy of varus-valgus stress radiographs to adjust the preoperative soft-tissue imbalance and (2) ascertain whether varus-valgus stress radiographs are effective for the correction accuracy in the preoperative planning of the opening wedge high tibial osteotomy (OWHTO).

METHODS

From February 2017 to December 2018, a total of 121 consecutive knees that underwent bi-planar OWHTO were enrolled in this retrospective analysis. Preoperative planning was performed using a weight-bearing line (WBL). Target WBL was determined according to the status of the medial compartments such as cartilage, meniscus, and preoperative arthritic grade. Preoperative varus-valgus stress radiographs were used to assess the preoperative mediolateral ligament imbalance. The final target correction length of the opening gap was determined by subtracting the difference between the varus-valgus stress radiographs (VVD). All patients were divided into two groups according to the preoperatively planned correction degree: (group A), smaller than average; (group B), larger than average. Patients were also divided into two other groups (VVD adjusted and neglected groups).

RESULTS

Groups A and B were 56 and 54 knees, respectively. The preoperatively planned correction lengths of the opening gap were 9.33 ± 1.5 and 14.16 ± 3.96 mm, respectively (p < 0.01). Mean values of the VVD were 0.85 ± 0.72, and 1.27 ± 1.78 mm, respectively (p < 0.01). Correction errors were 2.17 ± 2.06 and 3.52 ± 2.16%, respectively (p < 0.01). Planned and final correction degrees were also significantly larger (p < 0.01, and p < 0.01, respectively), because the preoperative WBL ratio was significantly smaller in the VVD adjusted group (p < 0.01).

CONCLUSION

The VVD values could reproduce the preoperative soft-tissue imbalance and it was more prominent as the correction degree increased. The strategy of subtracting the VVD as assumed soft-tissue imbalance in the preoperative planning worked well for the correction accuracy during OWHTO.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Current Measurement Strategies of Coronal Tibiofemoral Subluxation: A Systematic Review of Literature

OBJECTIVE. Coronal tibiofemoral (TF) subluxation has generated interest in the last several years due to newfound clinical implications of its presence. However, controversy within the literature concerning how to measure and calculate coronal TF subluxation on radiographic imaging remains. The purpose of this study was to describe how coronal TF subluxation is being measured and calculated in the literature with the goal of describing a reproducible and validated technique for clinical adoption. MATERIALS AND METHODS. A PubMed literature search was performed in March 2020 according to PRISMA guidelines. The terms "tibiofemoral subluxation" and "tibial femoral subluxation" were included in the search. Criteria of interest included radiographic view and evaluation, anatomic landmarks used, and measurement validity. RESULTS. Review of relevant literature resulted in 744 articles, 16 of which met our inclusion criteria. A wide range of measuring techniques, anatomic landmarks, and radiographic views were used with varying validity. Full-limb radiographic views were the most common. Six studies measured the translation of the mechanical axes of the tibia and femur. Eight studies measured the translation of either femoral condyle in reference to the tibial plateau. Coordinate-based software with the iterative closest point algorithm was used in two studies. Whether coronal TF subluxation should be divided by tibial plateau width to account for knee size was controversial. CONCLUSION. A variety of approaches exist for diagnosing and quantifying coronal TF subluxation because of the lack of clear anatomic landmarks within the TF joint that can be used to measure coronal TF subluxation in the horizontal plane. Even when using the same anatomic landmarks, studies varied on how to measure coronal TF subluxation radiographically and whether knee size should be accounted for. Further studies are necessary to standardize (via inter- and intraobserver validation with a control group) an easy, reproducible, and minimally biased approach to measuring coronal TF subluxation on radiographic imaging. We believe our systematic review succinctly provides the necessary information to either develop such a tool or encourage future studies to compare existing techniques to find the most reliable and clinically useful approach for evaluating coronal TF subluxation.

Tibiofemoral subluxation in the coronal plane does not affect WOMAC and KOOS after total knee arthroplasty

PURPOSE

To investigate the effect of preoperative coronal tibiofemoral subluxation (CTFS) on functional outcome, prosthesis type, insert thickness and revision rates in patients who underwent total knee arthroplasty (TKA).

METHODS

A total of 224 knees of 186 patients were included. Patients were divided into two groups as either with (Group 1, 114 knees of 86 patients) or without (Group 2, 124 knees of 100 patients) coronal lateral tibiofemoral subluxation. The mean follow-up period was 71.3 ± 7.3 (range 60-84) months in group 1 and 69.4 ± 6.6 (range 61-79) months in group 2 (n.s.). Coronal tibiofemoral subluxation degree was measured in degrees on standing anteroposterior knee radiographs. Group 1 was divided into three subgroups according to amount of subluxation (< 5 mm, 6-10 mm and > 10 mm). Functional outcome was evaluated using the Western Ontario and McMaster Osteoarthritis Index (WOMAC) score and Knee Injury and Osteoarthritis Outcome Score (KOOS) preoperatively and at the last follow-up visit. Prosthesis type, insert thickness and revision rates were compared between the two groups.

RESULTS

There were no significant differences between the two groups regarding patient demographics, prosthesis type, and revision rates (n.s.). The insert thickness was found significantly higher in group 1 (p < 0.001). The preoperative and postoperative WOMAC and KOOS scores were found no significantly different between the two groups (n.s.). Among subluxation (+) subgroups, there was no significant difference in functional outcome scores and revision rates (n.s.). However, prosthesis type and insert thickness were significantly associated with the amount of subluxation (p = 0.009 and p = 0.001, respectively). There was no significant correlation between the degree of lower extremity deformity and coronal tibiofemoral amount of subluxation (n.s.).

CONCLUSION

Preoperative CTFS does not adversely affect the WOMAC score, KOOS and revision rates after TKA. In the clinical practice, surgeons should be aware of the need for a posterior cruciate stabilizing prosthesis and a thicker insert in the presence of CTFS, especially with subluxation greater than 10 mm and to consider a spared bony resection on the tibia in patients suffering from CTFS.

LEVEL OF EVIDENCE

IV.

Increased preoperative medial and lateral laxity is a predictor of overcorrection in open wedge high tibial osteotomy

PURPOSE

This study aimed at determining whether overcorrection after open wedge high tibial osteotomy (OWHTO) would be predicted by the magnitude of preoperative medial and lateral coronal soft tissue laxity around the knee joint.

METHODS

Overall, 68 knees of 62 patients who underwent OWHTO for primary medial osteoarthritis were retrospectively reviewed. The mechanical hip-knee-ankle (HKA) axis, weight-bearing line (WBL) ratio, medial proximal tibial angle (MPTA), joint line obliquity, coronal subluxation, and joint line convergence angle (JLCA) were measured on full-weight-bearing long-standing HKA radiographs preoperatively and at 1 year postoperatively. The varus valgus stress angle was measured on preoperative radiographs. The correction amount due to soft tissue factors was calculated as the difference between the WBL ratio on postoperative 1-year radiographs and that on virtually corrected preoperative radiographs with the same amount of MPTA at 1 year postoperatively. The patients were grouped according to the presence or absence of a ≥ 10% overcorrection of WBL ratio (overcorrection or expected correction). Multiple logistic regression analysis was performed to identify the preoperative risk factors of overcorrection.

RESULTS

The average WBL ratio was corrected from 19.0 ± 13.5% preoperatively to 61.6 ± 9.1% postoperatively (P < 0.001). The average MPTA changed from 85.1 ± 1.7° preoperatively to 93.6 ± 2.6° postoperatively, resulting in an average tibia correction angle of 8.6 ± 3.1°. The average estimated correction from soft tissue factors was 5.8 ± 7.4% of the WBL ratio. Soft tissue correction of the WBL ratio > 10% was confirmed in 17 patients (28%). The preoperative JLCA and valgus stress angle were significantly greater in the overcorrection group than in the expected correction group: 5.0 ± 1.7° vs. 3.4 ± 1.9° (P = 0.003) and 2.4 ± 1.0° vs. 1.3 ± 1.2° (P = 0.002), respectively. Among the radiologic parameters, the presence of both ≥ 4° JLCA and ≥ 1.5° valgus stress angle was the only significant risk factor for overcorrection from soft tissue factors (P = 0.006; odds ratio, 30.2).

CONCLUSIONS

The magnitude of both medial and lateral coronal soft tissue laxity was a predictor of overcorrection from soft tissue factors after OWHTO. Overcorrection was more likely to occur in cases with both ≥ 4° JLCA and ≥ 1.5° valgus stress angle.

LEVEL OF EVIDENCE

III.

Managing intra-articular deformity in high Tibial osteotomy: a narrative review

The joint line convergence angle (JLCA) has a normal range between 0° to 2°, which increases in magnitude depending on the severity and stage of osteoarthritis in the knee.

The JLCA represents the interaction of the intra-articular deformity arising from the osteoarthritis and the surrounding soft tissue laxity. Therefore, the JLCA has become a vital parameter in analysing the long leg alignment views for corrective planning before osteotomy surgery. Recent studies have considered the influence on how the preoperative JLCA is measured and its influence on achieving accurate postoperative desired correction in high tibial osteotomy surgery.

The JLCA also reflects the influence of soft tissue laxity in a lower limb malalignment and many surgeons encourage it to be taken into account to avoid non physiological correction and/or overcorrection with negatively impacted postoperative patient outcome.

This present review addressed how to obtain an accurate preoperative measurement of the JLCA, its influence on postoperative deformity analysis and how to reduce errors arising from an elevated preoperative JLCA.

We have proposed a formula to help determine the value to subtract from the planned correction in order to avoid an overcorrection when performing a corrective osteotomy.

Level of clinical evidence IV, narrative review.

Is iliac autogenous graft augmentation in medial open wedge high tibial osteotomies superior to no augmentation in terms of bone healing?

OBJECTIVES

This study aims to investigate if iliac autogenous graft augmentation in medial open wedge high tibial osteotomies (OWHTOs) is superior to no augmentation in terms of bone healing.

PATIENTS AND METHODS

Twenty-five patients (14 males, 11 females; mean age 40.9±4.0 years; range, 33 to 48 years) with medial compartmental osteoarthritis of knee joint who underwent high tibial osteotomy with medial open wedge between January 2016 and December 2018 were included in this retrospective study. Twelve of the operated knees were the right knee. Graft was used in 13 patients (52%). Data including age, gender, body mass index (BMI), direction, follow-up period, union, Lysholm and International Knee Documentation Committee (IKDC) scores, pre- and postoperative femoral tibial angles (FTAs) and posterior tibial slopes were evaluated.

RESULTS

The mean BMI was 26.4±1.9 (range, 22.0 to 30.0). Only 48% of the patients were smoking. The mean follow-up period was 28.6±5.3 months (range, 24 to 38 months). No statistically significant difference was found between the grafted and non-grafted groups in terms of age, BMI, follow-up time, gender, side and smoking status (p>0.05) There was no statistically significant difference between two groups in terms of pre- and postoperative Lysholm scores, pre- and postoperative IKDC scores, or pre- and postoperative FTA values (p>0.050).

CONCLUSION

Iliac autogenous graft augmentation in medial OWHTO has no effect on union but shortens the union time. Preoperative high varus degree adversely affects union. Therefore, routine use of iliac crest autograft is not recommended.

Combined proximal tibial osteotomy for varus osteoarthritis of the knee: Biomechanical tests and finite-element analyses

BACKGROUND

A special combined proximal tibial osteotomy (CPTO) was designed to correct varus osteoarthritis of the knee with severe intra-articular pathologies, which could not be fully corrected by opening-wedge high tibial osteotomy (OWHTO). The biomechanical strength of the CPTO bone-implant construct was evaluated and compared with those of existing osteotomy methods.

METHODS

Three variations of osteotomy including OWHTO, tibial condylar valgus osteotomy (TCVO), and CPTO were performed on synthetic bones with locking plate and screws. Wedge stiffness, wedge displacement, and load failure were measured by biomechanical tests. Three types of numerical tibial models were also constructed by three-dimensional model reconstruction software. The stability parameters of the three variations including wedge stiffness, wedge displacement, and stress distribution were further measured by finite-element analyses.

RESULTS

The biomechanical testing results revealed that the wedge stiffness, wedge displacement, and failure load of the CPTO construct were very close to those of the OWHTO construct. The numerical results of wedge stiffness and displacement showed good conformity to the previous biomechanical results. The stress distribution at the lateral hinge, the plate corner, and the holes of the CPTO construct were close to those of the OWHTO counterpart, while the stress distribution at the inter-condylar eminence of the tibia and at the middle region of the screws was close to those of the TCVO counterpart.

CONCLUSIONS

The CPTO construct can provide comparable strength for early mobilization and rehabilitation to that of the OWHTO construct.