Intraoperatively accurate limb alignment after opening wedge high tibial osteotomy can be lost by large knee joint line convergence angle during surgery

The tipping point in medial opening wedge high tibial osteotomy relates to the shape of the proximal tibia more than to lower limb alignment correction

PURPOSE

The tipping point (TP) of the knee joint is the centre of rotation of the joint in the coronal plane. This study aimed to define the TP in medial opening wedge high tibial osteotomy (MOWHTO).

METHODS

Data from 154 consecutive patients with varus knee malalignment, who underwent MOWHTO between 2017 and 2021, was retrospectively reviewed. The degree of preoperative osteoarthritis (OA), using the Kellgren-Lawrence (KL) grading system, was recorded. Long-leg standing radiographs were used to record the alignment parameters, including the hip-knee-ankle angle (HKA), the mechanical lateral distal femoral angle (mLDFA), the medial proximal tibial angle (MPTA), the joint line convergence angle (JLCA) and the joint line obliquity (JLO) angle. Postoperative Tegner activity scores, Western Ontario and McMaster University Scores and patients' satisfaction were recorded. To define the TP, the relationship of all variables to Δ JLCA (absolute difference between preoperative to postoperative JLCA values) was analysed. Linear regression was employed for Δ JLCA to preoperative JLCA and postoperative and Δ MPTA (absolute difference between preoperative and postoperative values). K-means clustering was used to partition observations into clusters, in which each observation belongs to the cluster with the nearest mean serving as a prototype of the cluster, and analysed if there was any specific threshold influencing Δ JLCA. After defining the TP, further subanalysis of the TP based on the preoperative KL OA grade and analysis of variance of this TP to the KL OA grade was performed.

RESULTS

A total of 154 patients (77.9% males and 22.1% females) were included. The mean age was 48.2 ± 11 years, and the mean body mass index was 27.1 ± 4 kg/m2. Preoperatively, 26 (16.9%) patients had KL grade IV OA. The mean preoperative and postoperative JLCA and the significance of their relation to Δ JLCA were 2.6° ± 1.8° (p < 0.0001) and 1.9° ± 1.8° (p = 0.6), respectively. The mean Δ JLCA was 1.4° ± 1.5°. The mean pre- and postoperative MPTA and the significance of their relation to Δ JLCA were 84.6 ± 2.2 (p = 0.005) and 91.8 ± 2.5 (p < 0.0007), respectively. The mean Δ MPTA was 7.2 ± 2.3 (p = 0.3). The mean preoperative and postoperative HKA and the significance of their relation to Δ JLCA were 174.6 ± 2.5 (p = 0.2) and 181.9 ± 2.4 (p = 0.7), respectively. The overall linear regression for Δ JLCA was statistically significant for preoperative JLCA (R2 = 0.3, p < 0.0001) and postoperative MPTA (R2 = 0.09, p = 0.0001) and statistically insignificant for Δ MPTA (R2 = 0.01, p = 0.2) and postoperative HKA (R2 = 0.04, p = 0.7). MPTA > 91.5° was the optimal threshold dividing this series data set between substantial and nonsignificant Δ JLCA.

CONCLUSION

In this study, the main predictive factors for intra-articular correction (Δ JLCA) after MOWHTO were the preoperative value of JLCA and the postoperative value of MPTA. A value of 92° for postoperative MPTA is potentially the optimal threshold to predict intra-articular correction.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

High survivorship and low complication rate in a single-centre series of 651 medial opening wedge high tibial osteotomy cases with a mean follow-up of 13 years

PURPOSE

This study aimed to report the early to midterm results of medial opening wedge high tibial osteotomy (MOWHTO) from the largest single-centre osteotomy database. The primary outcomes were reporting the radiological corrections and the functional outcomes represented by multiple patient-reported outcome measures (PROMs). The secondary outcomes were to report the complications, revisions and survivorship up to 10 years postoperatively.

METHODS

A prospectively maintained single-centre database of 1138 knee osteotomies was retrospectively reviewed. Patients who underwent MOWHTO and met the inclusion criteria were included. Those inclusion criteria were moderate to severe knee pain that failed conservative management; varus knee malalignment; and isolated medial osteoarthritis of the knee. A total of 651 cases, with a mean age of 46.7 ± 9 years and a mean body mass index of 29.6 ± 5.2 kg/m2 , were included. This comprised 71% males (n = 462) and 29% females (n = 189). The mean follow-up was 158.1 ± 45.4 months. Multiple PROMs were recorded preoperatively and serially postoperatively. This included the Knee injury and Osteoarthritis Outcome Scores, the Oxford Knee Score, the Oxford Knee Score-Activity and Participation Questionnaire, the Western Ontario and McMaster University Scores, the Visual Analogue Scale for health and pain, and the EQ-5D, which is a standardised measure of health-related quality of life. All lower limb alignment measurements were recorded pre- and postoperatively. The rates of osteotomy revision, conversion to arthroplasty, complications, and 5- and 10-year survivorship were recorded.

RESULTS

A total of 651 cases were followed up to a mean of 158.1 ± 45.4 months. The mean planned correction angle was 7.6° ± 2.9°. The mean planned opening wedge distance was 8.1 ± 3.1 mm. The mean intraoperative anterior and posterior osteotomy gaps opening were 7.7 ± 3.4 and 8.9 ± 3.8 mm, respectively. Postoperatively, the mean mechanical tibiofemoral angle improved from -5.7° ± 2.9° varus to 1.3° ± 2.5° valgus, the mean medial proximal tibial angle improved from preoperative 85.5° ± 2.3° to postoperative 91.6° ± 2.7° and the mean Mikulicz point improved from 21.7 ± 12.6% to 54.8 ± 11% (all p values < 0.001). All PROMs significantly improved at 24 months follow-up (all p values < 0.001). The rate of osteotomy revision was 1.1% at a mean of 2 ± 2.5 years postoperatively. The overall rate of arthroplasty conversion was 9.1%. This comprised 5.8% total knee arthroplasty conversion at a mean of 6.9 ± 3.5 years postoperatively and 3.2% unicompartmental knee arthroplasty conversion at a mean of 5.7 ± 2.5 years postoperatively. An overall 10.3% complication rate was recorded. The 5 and 10-year survivorship was 97.2% and 91.9%, respectively.

CONCLUSION

MOWHTO is a radiologically and clinically rewarding procedure with a high survival rate at 5 and 10 years and a low complication rate in experienced hands. MOWHTO should be considered in patients presenting with medial unicompartmental knee pain with an evidence of overload and a varus mechanical coronal plane axis.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Preoperative joint line obliquity, a newly identified factor for overcorrection, can be incorporated into a novel preoperative planning method to optimise alignment in high tibial osteotomy

PURPOSE

The aim of this study was to analyse the factors associated with additional postoperative alignment changes after accurate bony correction by selecting only patients with well-performed bony correction as planned and develop a method of incorporating significant factors into preoperative planning.

METHODS

Among 104 consecutive patients who underwent medial open wedge high tibial osteotomy (MOWHTO) between October 2019 and July 2022, 61 with well-performed bony corrections were retrospectively reviewed. The major criterion for well-performed bony correction was a difference of <1° between the simulated medial proximal tibial angle (MPTA) and the actual postoperative MPTA as measured in three dimensions. Radiographic parameters, such as the joint line convergence angle (JLCA) and joint line obliquity (JLO), were measured preoperatively and postoperatively, utilising standing and supine whole lower extremity anteroposterior, valgus and varus stress radiographs. Multiple linear regression analysis identified the factors affecting alignment changes, and a prediction model was developed. A method for applying this prediction model to preoperative planning was proposed.

RESULTS

Preoperative JLCA on standing (preJLCAstd ), preoperative JLCA on 0° valgus stress radiograph (vgJLCA0 ), and preoperative JLO (preJLO) were significantly correlated with JLCA change (∆JLCA) (p < 0.001, p < 0.001, p = 0.006). The prediction model was estimated as ∆JLCA = 0.493 × (vgJLCA0 ) - 0.727 × (preJLCAstd ) + 0.189 × (preJLO) - 1.587 in. (R = 0.815, modified R2  = 0.646, p < 0.001). The proposed method resulted in a reduced overcorrection rate (p = 0.003) and an improved proportion of acceptable alignments (p = 0.013).

CONCLUSION

PreJLCAstd , vgJLCA0  and preJLO can be used to estimate ∆JLCA. PreJLO was recently identified as a significant factor associated with additional alignment changes. Utilising the proposed preoperative planning and a prediction model with these factors shows promise in calibrating postoperative alignment after MOWHTO.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Constitutional and postoperative joint line obliquity can predict serial alignment change after opening-wedge high tibial osteotomy: analysis using coronal plane alignment of the knee classification

PURPOSE

The purposes of this study were (1) to clarify the distribution of the Coronal Plane Alignment of the Knee (CPAK) phenotype in patients who underwent medial opening-wedge high tibial osteotomy (OWHTO) and (2) to identify the predictive factors for postoperative serial alignment changes after OWHTO by analyzing constitutional phenotypes.

METHODS

Patients who underwent OWHTO between March 2014 and December 2019 were retrospectively evaluated. Those who completed a minimum follow-up of 3 years were divided into three groups based on the direction of alignment changes from postoperative 3 months to the final follow-up: Group 1 (varus direction) when the weight-bearing line ratio (WBLR) change was less than - 4%, Group 2 (maintained) when the WBLR change was between - 4% and 4%, and Group 3 (valgus direction) when the WBLR change was greater than 4%. The following parameters were assessed serially and compared between the groups: (1) radiologic parameters of coronal limb alignment such as joint line obliquity (JLO), (2) CPAK phenotypes, and (3) clinical outcomes.

RESULTS

In total, 163 knees were included, and the average duration of follow-up was 4.8 ± 1.6 years. More apex distal JLO was observed in the order of Group 1, 2, and 3 at all times (all p < 0.05). The most common CPAK type was type (I + II) (constitutional: apex distal JLO) + type (V + VI) (postoperative 3 months: neutral JLO) in Group 1 (29.4%; p = 0.000); otherwise, the most common CPAK type was type (IV + V) (constitutional: neutral JLO) + type (VIII + IX) (postoperative 3 months: apex proximal JLO) in Group 3 (11.7%; p = 0.000). Clinical outcomes did not differ between the groups.

CONCLUSION

Constitutional and postoperative JLO were predictive factors of postoperative alignment changes after OWHTO. Constitutional apex distal and postoperative neutral JLO had a tendency for varus alignment progression, whereas constitutional neutral and postoperative apex proximal JLO had a tendency for valgus alignment progression.

LEVEL OF EVIDENCE

Retrospective cohort study; Level III.

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.

Hip abduction angle after open-wedge high tibial osteotomy is associated with the timed up & go test and recurrence of varus alignment

The aim of this study is to investigate the association between the hip abduction angle (HAA) and lower limb alignment as well as the clinical assessments in open-wedge high tibial osteotomy (OWHTO) patients. A total of 90 patients who underwent OWHTO were included. The demographic characteristics and clinical assessments (the Visual Analogue Scale for activities of daily living, the Japanese knee osteoarthritis measure, the Knee injury and Osteoarthritis Outcome Score, the Knee Society score, the Timed Up & Go (TUG) test, the single standing (SLS) test and muscle strength) were recorded. The patients were divided into two groups according to the HAA at 1 month after operation: the HAA (-) group (HAA < 0°) and the HAA (+) group (HAA ≥ 0°). Clinical scores except for the SLS test and radiographic parameters except for the posterior tibia slope (PTS), lateral distal femoral angle (LDFA) and lateral distal tibial angle (LDTA) were significantly improved at 2 years postoperatively. Regarding the two groups, scores on the TUG test in the HAA (-) group were significantly lower than those in the HAA (+) group (p = 0.011). The hip-knee-ankle angle (HKA), weight bearing line (WBLR) and knee joint line obliquity (KJLO) in the HAA (-) group were significantly higher than those in the HAA (+) group (p < 0.001, 0.001 and p = 0.025). In contrast, the LDFA in the HAA (-) group were significantly lower than those in the HAA (+) group (p < 0.001). The TUG test and the LDFA were weakly positively correlated with the HAA (r = 0.34, 0.42, p < 0.001 and 0.001). In contrast, the HKA, WBLR and KJLO had a weak negative correlation with the HAA (r = - 0.43, - 0.38 and - 0.37, p < 0.001, 0.001 and 0.001). This study showed the postoperative HAA was significantly associated with the TUG test and the HKA, WBLR, LDFA, and KJLO. A higher postoperative HAA might induce varus recurrence and poor outcomes of the gait parameter.

Influence of hindfoot alignment on postoperative lower limb alignment in medial opening wedge high tibial osteotomy

INTRODUCTION

We have experienced unexpected under-correction after medial opening wedge high tibial osteotomy (MOWHTO). Although the tibia was corrected accurately, the postoperative mechanical axis (MA) was less than 57%. The purpose of this study was to evaluate the relationship between hindfoot alignment and postoperative lower limb alignment, and to reveal whether hindfoot alignment affects lower limb alignment after MOWHTO. Our hypothesis was that hindfoot alignment influences the postoperative MA in MOWHTO.

MATERIALS AND METHODS

This study was a retrospective comparative study. The study cohort comprised 43 knees in 43 patients who underwent MOWHTO and had standing long-leg anteroposterior view and hindfoot alignment view radiographs taken preoperatively and at 3 months postoperatively. To evaluate the hindfoot alignment, the absolute value of the ankle joint line orientation relative to the ground was added to the absolute value of the hindfoot angle. We defined a postoperative MA of 57-67% as acceptable correction (A group) and a MA of < 56% as under-correction (U group). The two groups were analyzed to identify factors that affected postoperative limb alignment.

RESULTS

The preoperative hindfoot alignment angle was significantly larger in the U group than the A group. The preoperative hindfoot alignment angle was a significant predictive factor of the postoperative MA, and the cut-off value that distinguished under-correction from acceptable correction was 15.9 degrees.

CONCLUSION

Abnormal hindfoot alignment is one of the causes of under-correction after MOWHTO. Attention should be paid to the preoperative ankle joint line orientation relative to the ground and hindfoot angle. If the preoperative hindfoot alignment angle is ≥ 15.9 degrees, surgeons should reconsider the operative procedure and correction angle.

LEVEL OF EVIDENCE

Therapeutic level III, retrospective study.

Influence of Medial Osteotomy Height and Hinge Position in Open Wedge High Tibial Osteotomy: A Simulation Study

(1) Background: In treating medial unicompartmental gonarthrosis, medial open wedge high tibial osteotomy (mOWHTO) reduces pain and is intended to delay a possible indication for joint replacement by relieving the affected compartment. This study aimed to investigate the influence of the osteotomy height with different hinge points in HTO in genu varum on the leg axis. (2) Methods: Fifty-five patients with varus lower leg alignment obtained full-weight bearing long-leg radiographs were analyzed. Different simulations were performed: Osteotomy height was selected at 3 and 4 cm distal to the tibial articular surface, and the hinge points were selected at 0.5 cm, 1 cm, and 1.5 cm medial to the fibular head, respectively. The target of each correction was 55% of the tibial plateau measured from the medial. Then, the width of the opening wedge was measured. Intraobserver and interobserver reliability were calculated. (3) Results: Statistically significant differences in wedge width were seen at an osteotomy height of 3 cm below the tibial plateau when the distance of the hinge from the fibular head was 0.5 cm to 1.5 cm (3 cm and 0.5 cm: 8.9 +/− 3.88 vs. 3 cm and 1.5 cm: 11.6 +/− 4.39 p = 0.012). Statistically significant differences were also found concerning the wedge width between the distances 0.5 to 1.5 cm from the fibular head at the osteotomy height of 4 cm below the tibial plateau. (4 cm and 0.5 cm: 9.0 +/− 3.76 vs. 4 cm and 1.5 cm: 11.4 +/− 4.27 p = 0.026). (4) Conclusion: A change of the lateral hinge position of 1 cm results in a change in wedge width of approximately 2 mm. If hinge positions are chosen differently in preoperative planning and intraoperatively, the result can lead to over- or under-correction.

Changes in joint space width over time and risk factors for deterioration of joint space width after medial opening-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to evaluate the changes in joint space width (JSW) over time after medial opening-wedge high tibial osteotomy (MOWHTO) and identify risk factors for deterioration of JSW using anteroposterior (AP) and Rosenberg views.

METHODS

We retrospectively analyzed changes in JSW of 104 MOWHTO patients whose preoperative osteoarthritis (OA) grade was K-L grade 3 or less on AP and Rosenberg views. Serial changes in JSW were assessed from preoperatively to at least 3 years postoperatively. Patients were divided into two groups according to JSW change patterns on each of AP and Rosenberg views: non-deterioration group had either unchanged or increased JSW, and deterioration group had decreased JSW. Clinical outcomes were compared using Western Ontario and McMaster Universities OA Index (WOMAC) score between groups. Multivariate logistic regression analysis was performed to identify risk factors for deterioration of JSW.

RESULTS

JSW on average for all patients increased 0.5 mm and 0.8 mm on AP and Rosenberg views, respectively (p < 0.05). Non-deterioration group showed significant improvement based on patient-reported outcomes (WOMAC) than deterioration group (all p < 0.05). Undercorrection was an independent risk factor for failure to achieve maintained or increased JSW on both AP (OR 6.885, 95% CI 1.976-23.986, p = 0.002) and Rosenberg (OR 12.756, 95% CI 2.952-55.129, p = 0.001) views.

CONCLUSION

JSW increased gradually and continuously on standing AP and Rosenberg views until postoperative 3 years after MOWHTO. Deterioration of JSW following MOWHTO was closely related to the undercorrection and affected clinical outcomes.

LEVEL OF EVIDENCE

Level III, case control study.

Risk factors and preventive strategy for excessive coronal inclination of tibial plateau following medial opening-wedge high tibial osteotomy

PURPOSE

To investigate risk factors and suggest preventive strategy for excessive coronal inclination of tibial plateau following medial opening-wedge high tibial osteotomy (MOWHTO).

METHODS

A total of 133 consecutive patients who underwent MOWHTO were retrospectively enrolled. Patients were divided into two groups based on postoperative medial proximal tibial angle (post-MPTA) of 95°: control group (n = 111, 83.5%) with post-MPTA less than 95° and excessive MPTA group (n = 22, 16.5%) with post-MPTA 95° or more. Demographics, radiographic parameters [mechanical lateral distal femoral angle (mLDFA), MPTA, posterior tibial slope, joint line obliquity (JLO), hip-knee-ankle angle, joint line convergence angle (JLCA), weight bearing line ratio, and correction angle], and clinical outcomes of patients were compared. Multiple logistic regression analysis was performed to determine risk factors for post-MPTA 95° or more.

RESULTS

Multiple logistic regression analysis showed that preoperative JLO ≥ 3° [odds ratio (OR) 6.940, 95% confidence interval (CI) 2.373-20.296, p < 0.001] and preoperative JLCA ≥ 5° (OR 5.723, 95% CI 1.833-17.865, p = 0.008) were statistically significant risk factors for post-MPTA ≥ 95°. Incidences of excessive MPTA following MOWHTO in patients with none, one, and two risk factors preoperatively were 3.7%, 26.7%, and 77.8%, respectively.

CONCLUSION

Preoperative JLO ≥ 3° and JLCA ≥ 5° were two significant risk factors for excessive MPTA following MOWHTO. Thus, surgeon should consider other types of osteotomy if these two risk factors are present together preoperatively in MOWHTO candidates.

LEVEL OF EVIDENCE

Level III.

Global varus malalignment increase from double-leg to single-leg stance due to intra-articular changes

PURPOSE

Preoperatively planned correction for tibial osteotomy surgery is usually based on weightbearing long-leg Xrays, while the surgery is performed in a supine non-weightbearing position. The purpose of this study was to assess the differences in lower limb alignment in three different weightbearing conditions: supine position, double-leg (DL) stance and single-sleg (SL) stance prior to performing a medial opening wedge high tibial osteotomy (MOWHTO) for varus malalignment. The hypothesis of this study was that progressive limb-loading would lead to an increased preoperative varus deformity.

MATERIAL AND METHODS

This retrospective study included 89 patients (96 knees) with isolated medial knee osteoarthritis (Ahlbäck grade I or II) and significant metaphyseal tibial vara (> 6°). The differences between supine position, DL stance and SL stance were analysed for the hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), weight-bearing line ratio (WBL) and joint line convergence angle (JLCA).

RESULTS

From a supine position to DL stance, the HKA angle slightly increased from 175.5° ± 1.1° to 176.3° ± 1.1° and JLCA changed from 2.0° ± 0.3° to 1.8° ± 0.3° without a statistically significant difference. From DL to SL stances, the HKA angle decreased from 176.3° ± 1.1° to 174.4° ± 1.1° (p < 0.05) and the JLCA increased from 1.8° ± 0.3° to 2.6° ± 0.3° (p < 0.05). A significant correlation was found between ΔHKA and ΔJLCA between the DL and the SL stances (R² = 0.46; p = 0.01).

CONCLUSION

Varus malalignment increases with weight-bearing loading from double-leg to single-leg stances with an associated JLCA increase. Thus, single-leg stance radiographs may be useful to correct preoperative planning considering patient-specific changes in JLCA.

LEVEL OF CLINICAL EVIDENCE

III, retrospective comparative study.

Distance from the magnification device contributes to differences in lower leg length measured in patients with TSF correction

INTRODUCTION

In absence of deformity or injury of the contralateral leg, the contralateral leg length is used to plan limb lengthening. Length variability on long-leg weight-bearing radiographs (LLR) can lead to inaccurate deformity correction. The aim of the study was to (1) examine the variability of the measured limb length on LLR and (2) to examine the influence of the position of the magnification device.

MATERIALS AND METHODS

The limb lengths of 38 patients during deformity correction with a taylor-spatial-frame were measured retrospectively on 7.3 ± 2.6 (4-13) LLR per patient. The measured length of the untreated limb between LLR were used to determine length variability between LLR in each patient. To answer the secondary aim, we took LLR from a 90 cm validation distance. A magnification device was placed in different positions: at the middle of the 90 cm distance (z-position), 5 cm anterior and 5 cm posterior from the z-position, at the bottom and top of the validation distance as well as 5 cm medial and 15 cm lateral from the z-position.

RESULTS

The measured length variability ranged within a patient from 10 to 50 mm. 76% of patients had a measured limb length difference of ≥ 2 cm between taken LLR. Compared to length measurement of the 90 cm test object with the magnification device in the z-position (90.1 cm), positioning the device 5 cm anterior led to smaller (88.6 cm) and 5 cm posterior led to larger measurements (91.7 cm). The measured length with the magnification device at the bottom, top, medial or lateral (90.4; 89.9; 90.2; 89.8 cm) to the object differed not relevantly.

CONCLUSIONS

High variability of limb length between different LLR within one patient was observed. This can result from different positions of the magnification device in the sagittal plane. These small changes in positioning the device should be avoided to achieve accurate deformity correction and bone lengthening. This should be considered for all length and size measurements on radiographs.

Editorial Commentary: Early Postoperative Knee Joint Space Width Change Is Attributable to Change in the Joint Line Convergence Angle After High Tibial Osteotomy and May Not Reflect Cartilage Regeneration

Realignment of the weightbearing axis by high tibial osteotomy (HTO) can alter the forces acting on the articular cartilage within the knee, reducing the load on the medial compartment. This unloading effect is thought to allow the repair of the articular cartilage of the affected compartment. It is important to evaluate the serial changes of joint space width (JSW) after HTO for assessing the state of the cartilage and the unloading effect by HTO. However, early postoperative knee JSW change is attributable to change in the joint line convergence angle after HTO and may not reflect cartilage regeneration. In addition, the soft tissue laxity of the knee and changes in joint line convergence angle after HTO should be considered for assessing these early postoperative JSW changes.

Open-wedge high tibial osteotomy using intraoperative control of joint line convergence angle with reference to preoperative supine radiograph

INTRODUCTION

Preoperative supine joint line convergence angle (JLCA) correlates with postoperative standing JLCA. Here, we compared the radiographic and clinical outcomes of knees with preoperative JLCAs of ≥ 4° and < 4° in open-wedge high tibial osteotomy (OWHTO). We hypothesized that the postoperative coronal alignment in both groups would not be affected by a change in JLCA if this change could predict before surgery.

MATERIALS AND METHODS

Eighty-four patients with medial knee osteoarthritis who underwent OWHTO were enrolled retrospectively. A weight-bearing line (WBL) ratio of 62% and a JCLA equivalent to the preoperative supine JLCA were anticipated in preoperative planning. These were intraoperatively set using an alignment rod and a radiolucent protractor under fluoroscopy. Soft tissue correction was defined as correction angle minus bone correction. The participants with preoperative JLCAs of < 4° (low-JLCA group) and ≥ 4° (high-JLCA group) were compared.

RESULTS

No significant difference in the coronal alignment was found between the groups after OWHTO. No significant differences in correction angle or bone correction were found between the groups, but the soft tissue correction in the high-JLCA group was higher than that in the low-JLCA group after OWHTO (p = 0.013).

CONCLUSIONS

When we controlled intraoperative JLCA, the postoperative coronal alignment was not affected by the change in JLCA and the differences in soft tissue correction between the low-JLCA and high-JLCA groups. However, overcorrection compared with the target coronal alignment remained in both groups.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Difference in the early postoperative change of the joint line convergence angle between opening wedge and closed wedge high tibial osteotomies

Background

The purpose of this study was to investigate the correction error associated with soft tissue balance in high tibial osteotomy (HTO) and the difference between opening wedge HTO (OWHTO) and closed wedge HTO (CWHTO).

Methods

A total of 170 knees of 130 patients (85 knees of 68 patients in OWHTO and 85 knees of 62 patients in CWHTO) were evaluated. Anteroposterior radiographs of the knee and full-length leg were taken preoperatively, immediately under general anesthesia postoperatively, 2 days, and 1 and 12 months postoperatively. The femorotibial angle (FTA), joint line convergence angle (JLCA), and medial proximal tibial angle (MPTA) were measured.

Results

The postoperative FTA was decreased from 170.5 ± 2.1° at 0 day to 168.6 ± 2.2° at 2 days in OWHTO (P < 0.05), whereas it was not changed from 168.7 ± 2.4° at 0 day to 168.1 ± 2.8° at 2 days in CWHTO. The JLCA was 4.8 ± 1.8° preoperatively, 4.2 ± 1.9° at 0 day, 2.2 ± 1.8° at 2 days (P < 0.05 vs 0 day), 2.6 ± 1.7° at 1 month, and 2.7 ± 1.6° at 12 months in OWHTO, and 7.1 ± 3.2° preoperatively, 4.1 ± 2.4° at 0 day (P < 0.05 vs preoperative), 3.4 ± 2.5° at 2 days, 3.9 ± 2.3° at 1 month, and 4.2 ± 2.6° at 12 months in CWHTO. Multiple regression analysis showed that preoperative factors affecting change of the JLCA from preoperative to postoperative 1 month were the correction angle in OWHTO (P = 0.001) and the preoperative standing JLCA in OWHTO (P < 0.001) and CWHTO (P < 0.001).

Conclusions

A significant decrease of the JLCA occurred immediately after osteotomy under anesthesia in CWHTO, whereas in OWHTO there was no decrease under anesthesia, but it decreased several days postoperatively.

Preoperative planning by osteotomy master software helps to improve the accuracy of target limb alignment in high tibial osteotomy

Background

The accuracy of targeted lower limb alignment correction following HTO is closely related to patients’ pain relief and knee joint survival time. How to accurately perform osteotomy and how to obtain the ideal target limb alignment to maximize the curative effect are the difficulty in HTO practice. The purpose of this study is to evaluate the predictive and application value of osteotomy master software (OsteoMaster) in coronal plane preoperative planning of high tibial osteotomy.

Method

Sixty-seven patients with medial compartment osteoarthritis and varus deformity treated by medial open-weight high tibial osteotomy were enrolled and divided into observation group (31 cases) and control group (36 cases). The observation group was planned by OsteoMaster, while the control group was planned by Miniaci. The preoperative predicted values of osteotomy depth, open height, correction angle, WBL ratio, and FTA of the observation group were compared with the actual intraoperative values to study their accuracy. The operative time, blood loss, number of fluoroscopy, and WBL ratio were compared between the observation group and the control group to study its application value.

Result

There was no significant difference between two groups in preoperative prediction and intraoperative reality of osteotomy depth, open height, correction angle, FTA, and WBL ratio (P > 0.05). The operation time and number of fluoroscopy in the observation group were significantly less than those in the control group (P < 0.05), while the difference in blood loss was not statistically significant (P > 0.05). The good rate of WBL ratio was 87.1% in the observation group and 75% in the control group.

Conclusion

OsteoMaster has predictive value in osteotomy depth, open height, correction angle, FTA, and WBL ratio of HTO, which is also helpful to reduce the number of fluoroscopy, shorten the operation time, and improve the accuracy of target limb alignment. The drawback of this approach is 2-dimensional approach in contrast to 3-dimensional preoperative planning that is including the more real study.

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.