Three-dimensional relationships between secondary changes and selective osteotomy parameters for biplane medial open-wedge high tibial osteotomy

Factors Causing Unintended Sagittal and Axial Alignment Changes in High Tibial Osteotomy: Comparative 3-Dimensional Analysis of Simulation and Actual Surgery

BACKGROUND

Unintended secondary changes in the posterior tibial slope (PTS) and tibial torsion angle (TTA) may occur after medial open-wedge high tibial osteotomy (MOWHTO). In surgical procedures using patient-specific instruments (PSIs), it is essential to reproduce the PTS and TTA that were planned in simulations.

PURPOSE

To analyze the factors causing unintended sagittal and axial alignment changes after MOWHTO.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Overall, 63 patients (70 knees) who underwent MOWHTO using a PSI between June 2020 and June 2023 were retrospectively reviewed. Preoperative and postoperative computed tomography scans were 3-dimensionally reconstructed. Simulated osteotomy was performed so that the weightbearing line could pass through the target point. A PSI gapper was 3-dimensionally printed to fit the posteromedial corner of the osteotomy gap in the simulated HTO model. After MOWHTO using the PSI gapper, the actual postoperative model was compared with the preoperative or simulation model. This assessment included PTS, TTA, hinge axis, and osteotomy-related parameters. Cortical breakage around the lateral hinge was evaluated to assess stability.

RESULTS

The mean PTS and TTA did not change in the simulation. However, significant changes were observed in the actual postoperative PTS and TTA (change, -2.4°± 2.2° and -3.9°± 4.7°, respectively). The PTS was reduced, while the TTA decreased with internal rotation of the distal fragment. The difference in the axial hinge axis angle (AHA) between the simulation and actual surgery was the factor most correlated with the difference in the PTS (r = 0.625; P < .001). In regression analysis, the difference in the AHA was the only factor associated with the difference in the PTS (β = 0.558; P = .001), and there were no factors that showed any significant associations with the difference in the TTA. In subgroup analyses for the change in the TTA, the correction angle and anterior osteotomy angle were significantly higher in the more internal rotation group (P = .023 and P = .010, respectively). The TTA change was significantly higher in the unstable group with lateral cortical breakage (P = .018). The unstable group was more likely to show an internal rotation of ≥5° (odds ratio, 5.0; P = .007).

CONCLUSION

The AHA was associated with a difference in the PTS between the simulation and actual surgery. The change in the TTA was caused by a combination of multiple factors, such as a large correction angle and anterior osteotomy angle, but mainly by instability of the lateral cortical hinge.

Osseous factors influencing distal tibial rotation in biplane medial opening wedge high tibial osteotomy

PURPOSE

There is a lack of studies investigating the distal tibial rotation (DTR) during medial opening wedge high tibial osteotomy (MOWHTO). This study was designed to evaluate osseous factors influencing DTR in patients who underwent biplane MOWHTO.

METHODS

A total of 106 knee joints in 69 patients who underwent surgery for varus malalignment of knee were reviewed. Based on several software, standard and actual hinge positions were defined in pre-operative and post-operative CT data. Pearson's correlation and Spearman's correlation analysis were performed with DTR change as the dependent variable. Independent variables included angles between standard and actual hinge in the sagittal (ASAHS) and axial (ASAHA) planes, pre-operative and post-operative medial proximal tibial angle, opening width (OW), tuberosity osteotomy angle, flange angle (FA), gap ratio, and hinge fracture.

RESULTS

The distal tibia rotated approximately 0.35° internally. Pearson's and Spearman's correlation analysis showed that DTR change was associated with ASAHS, OW, and FA. Larger OW and FA resulted in higher external rotation angles.

CONCLUSIONS

DTR change was significantly associated with ASAHS, followed by OW and FA rather than ASAHA if only considering osseous factors in biplane MOWHTO. The distal tibia tended to rotate externally when the actual hinge was inclined posteriorly to the standard hinge in the sagittal planes, but rotate externally or internally when the actual hinge was inclined anteriorly.

A preoperative simulation of medial open-wedge high tibial osteotomy for predicting postoperative realignment

Three-dimensional preoperative surgical simulation of the medial open-wedge high tibial osteotomy (OWHTO), simplified as the rigid rotation around the hinge axis, has been performed to predict postoperative realignment. However, the practicality of this highly simplified simulation method has not been verified. This study aimed to investigate the validity of realignment simulation simplified as a rotation around a hinge axis compared with a postoperative CT model. A three-dimensional surface model of the tibia and femur was created from preoperative computed tomography (CT) images (preoperative model) of three patients. The simulation of medial OWHTO created sixty computer simulation models in each patient simplified as the rigid rotation of the proximal part of the tibia relative to the distal part from 1° to 20° around three types of hinge axes. The simulation models were compared with the actual postoperative model created from postoperative CT images to assess the reality of the simulation model. The average surface distance between the two models was calculated as an index representing the similarity of the simulation model to the postoperative model. The minimum value of average surface distances between the simulation and postoperative CT models was almost 1 mm in each patient. The rotation angles at which the minimum value of average surface distances was represented were almost identical to the actual correction angles. We found that the posterior tibial tilt and the axial rotation of the proximal tibia of the simulation model well represented those of the postoperative CT model, as well as the valgus correction. Therefore, the realignment simulation of medial OWHTO can generate realistic candidates for postoperative realignment that includes the actual postoperative realignment, suggesting the efficacy of the preoperative simulation method.

The influence of different hinge position on PTS during HTO: comparison between open-wedge and closed-wedge HTO

PURPOSE

The purpose of this study was to determine the significance of hinge position through comparison between open-wedge and closed-wedge high tibial osteotomy (HTO) and to determine the ideal hinge position to minimize the effect of HTO on the posterior tibial slope (PTS) and medial proximal tibial angle (MPTA).

METHODS

Procedures were performed on 32 cadaveric knees using open-wedge HTO with the standard hinge position or a low hinge position or closed-wedge HTO with the standard hinge position or a low hinge position. To define the standard hinge position in open wedge HTO, we drew a line 3-cm inferior to the medial tibial plateau toward the fibular head and located the intersection of this line with a longitudinal line 1-cm medial to fibular shaft. The low hinge position was then defined as the point 1-cm inferior to the standard position. For the standard hinge position for closed-wedge HTO, we drew a line parallel with joint line from 2-cm inferior to the lateral tibial plateau. The low hinge position was then defined as the point 1-cm inferior to the standard position.

RESULTS

For the open-wedge procedure, osteotomy through the low hinge position resulted in a significantly greater PTS compared to osteotomy through the standard hinge position. MPTA was also significantly greater for the low hinge position compared to standard hinge position. In the closed-wedge HTO, neither the PTS nor MPTA was significantly different for the low and standard hinge positions.

CONCLUSIONS

Hinge position significantly affects changes in the PTS and MPTA following open-wedge but not closed-wedge HTO. Understanding how to hinge position affects the PTS and MPTA is critical for surgeons performing open-wedge HTO procedures. Adopting an accurate hinge position is crucial for preventing complications, especially in open-wedge osteotomy, due to postoperative changes in the PTS and MPTA.

Extreme Hinge Axis Positions Are Necessary to Achieve Posterior Tibial Slope Reduction With Small Coronal-Plane Corrections in Medial Opening Wedge High Tibial Osteotomy

Background:

Both coronal- and sagittal-plane knee malalignment can increase the risk of ligamentous injuries and the progression of degenerative joint disease. High tibial osteotomy can achieve multiplanar correction, but determining the precise hinge axis position for osteotomy is technically challenging.

Purpose:

To create computed tomography (CT)–based patient-specific models to identify the ideal hinge axis position angle and the amount of maximum opening in medial opening wedge high tibial osteotomy (MOWHTO) required to achieve the desired multiplanar correction.

Study Design:

Descriptive laboratory study.

Methods:

A total of 10 patients with lower extremity CT scans were included. Baseline measurements including the mechanical tibiofemoral angle (mTFA) and the posterior tibial slope (PTS) were calculated. Virtual osteotomy was performed to achieve (1) a specified degree of PTS correction and (2) a planned degree of mTFA correction. The mean hinge axis position angle for MOWHTO to maintain an anatomic PTS (no slope correction) was 102.6° ± 8.3° relative to the posterior condylar axis (PCA). Using this as the baseline correction, the resultant hinge axis position and maximum opening were then calculated for each subsequent osteotomy procedure.

Results:

For 5.0° of mTFA correction, the hinge axis position was decreased by 6.8°, and the maximum opening was increased by 0.49 mm for every 1° of PTS correction. For 10.0° of mTFA correction, the hinge axis position was decreased by 5.2°, and the maximum opening was increased by 0.37 mm for every 1° of PTS correction. There was a significant difference in the trend-line slopes for hinge axis position versus PTS correction (P = .013) and a significant difference in the trend-line intercepts for maximum opening versus PTS correction (P < .0001).

Conclusion:

The mean hinge axis position for slope-neutral osteotomy was 102.6° ± 8.3° relative to the PCA. For smaller corrections in the coronal plane, more extreme hinge axis positions were necessary to achieve higher magnitudes of PTS reduction.

Clinical Relevance:

Extreme hinge axis positions are technically challenging and can lead to unstable osteotomy. Patient-specific instrumentation may allow for precise correction to be more readily achieved.

The validity and accuracy of 3D-printed patient-specific instruments for high tibial osteotomy: a cadaveric study

Objective

High tibial osteotomy (HTO) has been used for the treatment of patients with knee osteoarthritis. However, the successful implementation of HTO requires precise intraoperative positioning, which places greater requirements on the surgeon. In this study, we aimed to design a new kind of 3D-printed patient-specific instrument (PSI) for HTO, including a positioning device and an angle bracing spacer, and verify its effectiveness using cadaveric specimens.

Methods

This study included ten fresh human lower-limb cadaveric specimens. Computed tomography (CT) and X-ray examinations were performed to make preoperative plans. PSI was designed and 3D-printed according to the preoperative plan. Then, the PSI was used to guide HTO. Finally, we performed X-ray and CT after the operation to verify its validity and accuracy.

Results

The PSI using process was adjusted according to the pre-experimental procedure in 1 case. Hinge fracture occurred in 1 case. According to X-rays of the remaining eight cadaveric specimens, no statistically significant difference was noted between the preoperative planning medial proximal tibial angle (MPTA) and postoperative MPTA (P > 0.05) or the preoperative and postoperative posterior slope angle (PSA) (P > 0.05). According to the CT of 10 cadaveric specimens, no statistically significant difference was noted between the design angle and actual angle, which was measured according to the angle between the osteotomized line and the cross section (P > 0.05). The gap between the designed osteotomy line and the actual osteotomy line was 2.09 (0.8 ~ 3.44) mm in the coronal plane and 1.58 (0.7 ~ 2.85) mm in the sagittal plane.

Conclusion

This 3D-printed PSI of HTO accurately achieves the angle and position of the preoperative plan without increasing the stripping area. However, its use still requires a certain degree of proficiency to avoid complications, such as hinge fracture.

Effect of the Osteotomy Inclination Angle in the Sagittal Plane on the Posterior Tibial Slope of the Tibiofemoral Joint in Medial Open-Wedge High Tibial Osteotomy: Three-Dimensional Computed Tomography Analysis

The posterior tibial slope of the tibiofemoral joint changes after medial open wedge high tibial osteotomy (MOWHTO), but little is known about the effect of the sagittal osteotomy inclination angle on the change in the posterior tibial slope of the tibiofemoral joint. The purpose of this study was to investigate the effect of the osteotomy inclination angle in the sagittal plane on changes in the posterior tibial slope after MOWHTO by comparing how anterior and posterior inclination affect the posterior tibial slope of the tibiofemoral joint. The correlation between the osteotomy inclination angle and the postoperative posterior tibial slope angle was also assessed. Between May 2011 and November 2017, 80 patients with medial compartment osteoarthritis who underwent MOWHTO were included. The patients were divided into two groups according to the sagittal osteotomy inclination angle on the 3D reconstructed model. Patients with an osteotomy line inclined anteriorly to the medial tibial plateau line were classified into group A (58 patients). Patients with posteriorly inclined osteotomy line were classified as group P (22 patients). In the 3D reconstructed model, the preoperative and postoperative posterior tibial slope, osteotomy inclination angle relative to medial tibial plateau line in sagittal plane, and gap distance and ratio of the anterior and posterior osteotomy openings were measured. The preoperative and postoperative hip-knee-ankle angle, weight-bearing line ratio, and posterior tibial slope were also measured using plain radiographs. In the 3D reconstructed model, the postoperative posterior tibial slope significantly increased in group A (preoperative value = 9.7 ± 2.9°, postoperative value = 10.7 ± 3.0°, p < 0.001) and decreased in group P (preoperative value = 8.7 ± 2.7°, postoperative value = 7.7 ± 2.7°, p < 0.001). The postoperative posterior tibial slope (group A = 10.7 ± 3.0°, group P = 7.7 ± 2.7°, p < 0.001) and posterior tibial slope change before and after surgery (group A = 1.0 ± 0.8°, group P = −0.9 ± 0.8°, p < 0.001) also differed significantly between the groups. The Pearson correlation coefficient was 0.875 (p < 0.001) for the osteotomy inclination angle, and multivariate regression analysis showed that the only significant factor among the variables was the sagittal osteotomy inclination angle (β coefficient = 0.216, p < 0.001). The posterior tibial slope changed according to the osteotomy inclination angle in the sagittal plane after MOWHTO. The postoperative posterior tibial slope tended to increase when the osteotomy line was inclined anteriorly with respect to the medial tibial plateau line but decreased when the osteotomy line was inclined posteriorly. To avoid inadvertent change of posterior tibial slope, close attention needs to be paid to maintaining the sagittal osteotomy line parallel to the medial joint line during MOWHTO.

Radiographic Evaluation of Medial Opening-Wedge High Tibial Osteotomy Using a New Internal Fixator with a Wedge-Shaped Spacer Block

We developed a new internal fixator: a rigid T: -shaped plate with locking screws and wedge-shaped spacer block for high tibial osteotomy. The purpose of the present study was to evaluate the radiographic outcome of opening-wedge high tibial osteotomy (OWHTO) using this new internal fixator. Sixty OWHTOs were performed in patients with medial compartment osteoarthritis and varus deformity (28 males and 23 females). Patients' mean age was 60.4 years. Preoperative and postoperative radiographs were obtained. The paired t-test was used to evaluate the differences over time with respect to radiographic variables. Union of the osteotomy gap was obtained in all patients, and no implant breakage was found. On anterior-posterior radiographs, a significant difference was observed (p < 0.01) between the preoperative and postoperative mean values of femorotibial angles (179.6 ± 3.2 vs. 170.6 ± 2.5 degrees), weight-bearing line ratios (23.8 ± 13.5 vs. 60.5 ± 11.5%), anatomical medial proximal tibial angles (84.8 ± 2.5 vs. 91.0 ± 2.6 degrees), and joint line coverage angles (3.6 ± 2.0 vs. 2.4 ± 1.7 degrees). On lateral radiographs, posterior tibial slopes were 11.5 ± 3.9 degrees preoperatively and 12.2 ± 4.0 degrees postoperatively (p < 0.01), and Insall-Salvati ratios were 1.04 ± 0.12 preoperatively and 1.06 ± 0.13 postoperatively (p = 0.24). Performing OWHTO using a new internal fixator with a wedge-shaped spacer achieves adequate correction of lower limb alignment without implant-related complications. This is a Level IV, case series study.

Axial But Not Sagittal Hinge Axis Affects Posterior Tibial Slope in Medial Open-Wedge High Tibial Osteotomy: A 3-Dimensional Surgical Simulation Study

PURPOSE

The purpose of this 3-dimensional (3D) surgical simulation study was to investigate the effects of axial and sagittal hinge axes (hinge axes in the axial and sagittal planes) on medial and lateral posterior tibial slope (PTS) in medial open-wedge high tibial osteotomy (OWHTO), and evaluate the quantitative relationship between hinge axis and PTS change.

METHODS

Preoperative computed tomography data from patients with varus knee deformity were collected. A standard hinge axis (0°) and 12 different hinge axes (6 axial hinge axes and 6 sagittal hinge axes: ±10°, ±20°, and ±30°) were defined in a 3D surgical simulation of OWHTO using a bone model. The differences between before and after simulation surgery in medial and lateral PTS, medial proximal tibial angle, opening gap, and opening wedge angle were measured.

RESULTS

In total, 93 varus knees in 93 patients were included for study. Compared with the standard hinge axis, axial hinge axis significantly affected medial and lateral PTS (P < .001). In contrast, sagittal hinge axis had no significant effect on medial and lateral PTS (P > .05). Every 10° change in axial hinge axis with a mean coronal valgus correction of 10° might result in approximately 1.6° of alteration in PTS. Stepwise regression analysis showed that axial hinge axis is the most significant factors affecting PTS (β coefficient = 0.78, P < .001), followed by opening wedge angle (β coefficient = 0.36, P < .001) and gap ratio (β coefficient = 0.12, P < 0.001).

CONCLUSION

Based on our findings of 3D OWHTO simulation, axial hinge axis significantly influences medial and lateral PTS in OWHTO, but sagittal hinge axis has no effect on change in PTS. Every 10° change of axial hinge axis with a 10° coronal valgus correction caused approximately 1.6° change of PTS.

CLINICAL RELEVANCE

Hinge axis in the axial plane significantly affects PTS, but hinge axis in the sagittal plane has no effect on PTS. To maintain PTS, surgeons should make hinge axis at the true lateral position of the tibia in the axial plane. To intentionally alter PTS, an anterolateral axial hinge axis could be used to decrease PTS or a posterolateral axial hinge axis could be used to increase PTS. Opening wedge angle or gap ratio is also useful for intentional modification of PTS.

How the orientation of osteotomy in biplanar lateral closed-wedge distal femoral osteotomy influences the rotational alignment of the knee in all dimensional planes

BACKGROUND

Correction of coronal plane deformity by osteotomies around the knee is theoretically three-dimensional (3D) and can be associated with changes in other planes. It has been shown that 3D rotational changes are induced by biplanar high tibial osteotomy; however, relevant information in biplanar lateral closed-wedge distal femoral osteotomy (LCW-DFO) has not been reported in literatures. This study aimed to investigate rotational changes in axial and sagittal planes in LCW-DFO using computer-aided design (CAD) simulations.

METHODS

LCW-DFO is composed of three cuts: one ascending cut and two transverse cuts. In the simulations, the following geometrical parameters were adopted as factors potentially influencing 3D changes occurring in the osteotomy. The ascending cut angle measured as the angle between the edge of the ascending cut and the edge of the transverse cut in the lateral view, and the ascending cut obliquity measured as the angle corresponding to anterior/posterior inclination of the ascending cut with reference to the posterior condylar tangent line in the axial view. In the analysis, the effects of these bony cut angles on associated rotational changes in the axial and sagittal planes (internal/external rotation and flexion/extension) were calculated. Variation of wedge size ranged from 2 to 8 mm.

RESULTS

The degree of the ascending cut obliquity substantially correlated with associated change in the sagittal plane (extension/flexion) while inducing only minimal change in rotation in the axial plane (internal/external rotation). When the osteotomy was made without ascending cut obliquity, the change in knee extension/flexion was minimal for the conditions analyzed while coupled internal rotation of the distal bony segment was induced.

CONCLUSIONS

In biplanar LCW-DFO, the ascending cut angle substantially influenced the amount of internal rotation of the distal bony segment with little effect on flexion/extension angles. By contrast, ascending cut obliquity in the axial plane yields an effect on flexion/extension angles and little effect on internal rotation of the distal bony segment.

Rotational Changes in the Distal Tibial Fragment Relative to the Proximal Tibial Fragment at the Osteotomy Site after Open-Wedge High-Tibial Osteotomy

The present study is aimed at assessing the changes in tibial rotation at the osteotomy site after an open-wedge, high-tibial osteotomy (OWHTO) and analysing the factors that affect rotational changes in the distal tibial fragment relative to the proximal tibial fragment at the same site. This study involved 53 patients (60 knees; 16 males and 37 females) with medial osteoarthritis (OA) who underwent OWHTO and preoperative and 3-month postoperative computed tomography (CT) scans. Rotational angles of the distal tibia were measured using Stryker OrthoMap 3D by comparing preoperative and postoperative CTs. The mean rotational angle yielded an external rotation of 2.9° ± 4.8°. There were 17 knees with internal rotations, 37 knees with external rotations, and one knee with no rotation. The rotational angle significantly correlated with the resultant change in the femorotibial angle (correction angle) and the angle between the ascending and transverse osteotomy lines on the anterior osteotomised surface on which a flange was formed with the distal tibial osteotomised surface (flange angle). The flange angle affected the rotation, but it may have been affected by our surgical technique. The rotational angle did not significantly correlate with the change in the angle of the posterior tibial slope or body mass index. There were significant correlations between the rotational angle and correction angle (r = 0.42, p < 0.05). Additionally, the rotational angle correlated with the flange angle (r = -0.41, p < 0.05).

Rotational Changes in the Tibia After High Tibial Valgus Osteotomy: A Comparative Study of Lateral Closing Versus Medial Opening Wedge Osteotomy

BACKGROUND

After high tibial valgus osteotomy (HTO), rotational changes in the tibia may occur, which can affect the biomechanics of the patellofemoral joint and may lead to anterior knee pain.

PURPOSE

To compare the rotational changes in the tibia between closing wedge HTO (CWHTO) and opening wedge HTO (OWHTO).

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Among the patients who underwent HTO between May 2012 and August 2015, 53 (28 CWHTO and 25 OWHTO) who had computed tomography scans before and at 1 year after the HTO were included. The following parameters were compared between CWHTO and OWHTO: (1) tibial torsion angle, (2) knee rotation angle, and (3) tibial tuberosity-trochlear groove (TT-TG) distance. During the last follow-up, patients were asked to rate their anterior knee pain when climbing the stairs, using the visual analog scale.

RESULTS

The tibial torsion angle significantly decreased (internal rotation of the distal fragment) after CWHTO (mean ± SD, -2.1°± 4.1°; P = .019) and OWHTO (-1.8°± 3.3°; P = .029). The knee rotation angle significantly decreased (external rotation of the proximal fragment) after OWHTO (-1.8°± 3.4°; P = .039) but was not changed after CWHTO (0.1°± 3.1°; P = .859). The mean TT-TG distance significantly decreased after CWHTO (-3.1 ± 3.0 mm; P < .001) but increased after OWHTO (2.0 ± 4.3 mm; P = .012). At the final follow-up (minimum, 4 years), the visual analog scale pain score during stair climbing was significantly higher after OWHTO than after CWHTO (3.1 ± 1.4 vs 2.2 ± 1.3, P = .024).

CONCLUSION

Internal rotation of the distal fragment occurred after both CWHTO and OWHTO. However, external rotation of the proximal fragment and increased TT-TG distance occurred after OWHTO. Because such rotational changes could affect anterior knee pain, further studies are warranted to investigate the definite relationship between tibial rotational changes and anterior knee pain after HTO.

Opening gap width influences distal tibial rotation below the osteotomy site following open wedge high tibial osteotomy

Purpose

Although rotation of the distal portion of the tibia below the osteotomy site is considered an inevitable change in the axial plane in open wedge high tibial osteotomy (HTO), several studies on this issue have shown contradictory results. The purpose of this study was, therefore, to determine the direction and amount of distal tibial rotation following open wedge HTO using a three-dimensional reconstructed model.

Methods

This study involved 41 patients (42 knees) undergoing open wedge HTO for primary medial osteoarthritis. Distal tibial rotation was measured on the overlaid tibial plateau of a preoperative and postoperative 3-dimensional reconstructed model based on computed tomography.

Results

The mean distal tibial external rotation was 2.7° ± 2.3° (range, -0.9° to 9.9°), and the opening gap was larger in the group with > 3° distal tibial rotation than in the group with ≤ 3° distal tibial rotation (11.4 mm vs. 9.6 mm, P = 0.027). Multiple regression analysis showed that the opening gap was the only predictor of distal tibial rotation. On receiver operating characteristics analysis, an opening gap of 10 mm was found to be the optimal cutoff value for achieving greater than 3° of distal tibial rotation.

Conclusions

Following medial opening wedge HTO, the distal tibial portion below the osteotomy site rotated approximately 3° externally. The magnitude of the external rotation of the distal tibia was affected by the opening gap width.

Tibial rotational alignment after opening-wedge and closing-wedge high tibial osteotomy

A lot of good outcomes have been reported after opening-wedge high tibial osteotomy (OWHTO) and closing-wedge high tibial osteotomy (CWHTO).The purpose of this study was to examine the rotational alignment after OWHTO and CWHTO performed by the same surgeon in one hospital.

The sample included 30 knees from 24 patients. In all cases, the same orthopaedic surgeon performed the osteotomy surgeries using the same method. The tibial external rotation angle (TERA) was measured using the CT images of proximal tibial plateau and distal tibial malleolus from the consecutive axial CT slices of tibia. In this study, two considerations were examined. The first was the change in rotation angle, which was defined by TERA noted before and after the operation. The second was the relationship between the correction angle of the osteotomy and the rotation angle change of the distal tibia. The first was evaluated using the paired-Student’s t-test, while the second was analyzed with Pearson’s correlation coefficient. In the OWHTO group, the mean TERA was 21.4± 7.0° preoperatively and 20.2 ± 8.0° postoperatively, but no significant difference was seen between pre- and post-operation measurements (p = 0.21). Significant TERA increasing (that is, external rotation of the distal tibia) was seen postoperatively in only three knees. In the CWHTO group, the mean TERA was 19.9 ± 10.5° preoperatively and 16.5 ± 9.5° postoperatively, and significant difference was seen between pre- and post-operative TERA (p < 0.05). No significant correlation was seen between the correction angle and the change of the rotation angle in either group (r = 0.40, r = 0.12) .

In the OWHTO group, both internal and external rotation of the distal tibia can occur after surgery. In the CWHTO group, the distal tibia rotated internally postoperatively. No significant correlation was seen between the correction angle and the change in the rotation angle in either group

Retro-tubercular gap widening can be caused by inappropriate anterior osteotomy and large opening gap in the medial biplanar open-wedge HTO

PURPOSE

The purpose of this study was to investigate the causes of retro-tubercular gap widening and to confirm whether this widened gap causes instability of the osteotomy configuration during open-wedge high tibial osteotomy (OWHTO).

METHODS

Operative records and radiologic findings of patients who underwent biplanar medial OWHTO between 2014 and 2016 were retrospectively evaluated. To identify the osteotomy configuration including lateral hinge fracture, postoperative simple radiographs and CT images were analyzed. Postoperative CT scan was used to evaluate the widening of the retro-tubercular gap, thickness, and axial angle of retro-tubercular osteotomy, as well as the ratios of anterior and posterior osteotomy, and hinge length. The correlation of each factor was evaluated and analyzed in accordance with the lateral hinge fracture (LHF).

RESULTS

Widening of the retro-tubercular gap showed a significant correlation with the axial angle of retro-tubercular osteotomy, anterior osteotomy ratio, and opening gap distance, but not with the thickness of retro-tubercular osteotomy, posterior osteotomy ratio, and hinge length ratio. The LHF group showed significantly larger value than the non-LHF group with respect to the thickness of retro-tubercular osteotomy (P = 0.003), axial angle of retro-tubercular osteotomy (P = 0.033), retro-planar gap distance (P = 0.001), anterior osteotomy ratio (P = 0.000), and opening gap distance (P = 0.003). The hinge length ratio was smaller in the LHF group than in the non-LHF group (P = 0.001). However, the posterior osteotomy ratio was not different between the two groups (n.s.).

CONCLUSION

Retro-tubercular gap widening can be caused by inappropriate anterior osteotomy and large opening gap distance, which can be related to LHF. Therefore, anterior cortical osteotomy may also be an important factor for preventing instability of the proximal fragment in biplanar OWHTO.

LEVEL OF EVIDENCE

Case-control study, Level III.

Comparison of torsional changes in the tibia following a lateral closed or medial open wedge high tibial osteotomy

OBJECTIVE

The aim of this study is to evaluate, by computed tomography (CT), whether different torsional changes occur in the tibia following a lateral closed wedge high tibial osteotomy (CWHTO) versus a medial open wedge high tibial osteotomy (OWHTO) procedure. It was hypothesized that the distal fragment of the tibia would show greater internal rotation after CWHTO.

METHODS

Thirty knees from 25 patients who underwent HTO were enrolled. Fifteen knees of 14 patients who underwent CWHTO and 15 knees of 11 patients who received OWHTO were match-paired. CT scans were taken before and three weeks after surgery. Rotational changes in the distal fragment of the tibia were assessed by measuring the tibial torsion angle (TTA).

RESULTS

The mean TTA in the CWHTO group pre-operatively and postoperatively was +23.9° ± 7.8° and + 18.2° ± 7.0°, respectively. Internal rotation of the distal fragment of the tibia after CWHTO was -5.7 ± 3.3° (P < 0.001). In the OWHTO group, the mean TTA pre-operatively and postoperatively was +27.9° ± 6.9° and + 26.8 ± 7.7°, respectively, with no significant change in torsion observed (P > 0.05).

CONCLUSIONS

The distal fragment of the tibia rotated internally after CWHTO but not after OWHTO.

LEVEL OF EVIDENCE

Level III: case-control study.

[Effectiveness of medial open wedge high tibial osteotomy combined with posterior slope angle of tibial plateau correction in treatment of osteoarthritis of limited flexion knee with varus deformity]

Objective

To explore the short-term effectiveness of medial open wedge high tibial osteotomy (OWHTO) combined with posterior slope angle of tibial plateau correction to treat the osteoarthritis of limited flexion knee with varus deformity.

Methods

The data of 18 cases (18 knee) with osteoarthritis of limited flexion knee with varus deformity between January 2014 and July 2016 were analyzed retrospectively. There were 6 males and 12 females with an average age of 54.9 years (range, 48-64 years). There were 8 cases of left knee and 10 cases of right knee. The varus of knee ranged from 7.45 to 15.52° (mean, 10.63°). According to Kellgren-Lawrence grading standard, there were 4 cases of grade Ⅱ and 14 of grade Ⅲ. OWHTO was used to adjust the varus deformity, and the posterior slope angle of tibial plateau was adjusted to solve the limited flexion.

Results

The thickness of osteotomy was 10-19 mm (mean, 14.91 mm). The operation time was 1.2-2.0 hours (mean, 1.4 hours). All incisions healed by first intension. All patients were followed up 1.0-2.5 years, with an average of 1.5 years. At last follow-up, the range of knee flexion and Lysholm score, Hospital for Special Surgery (HSS) score, and International Knee Documentation Committee (IKDC) score were significantly higher than preoperative ones, showing significant differences ( P<0.05). X-ray films showed that the osteotomy healed at 3- 7 months (mean, 3.6 months) after operation. At last follow-up, the limb alignment by the relative position of tibial plateau and the posterior slope angle of tibial plateau were significantly improved, showing significant differences when compared with preoperative ones ( P<0.05).

Conclusion

The OWHTO combined with posterior slope angle of tibial plateau correction can significantly improve the range of flexion and functional score in short-term.