'Fine-tuned' correction of tibial slope with a temporary external fixator in opening wedge high-tibial osteotomy

Effect of posteriorly inclined sagittal osteotomy on posterior tibial slope in biplanar medial opening wedge high tibial osteotomy: a case series study

BACKGROUND

Medial opening wedge high tibial osteotomy aims to correct coronal plane deformities and redistribute the load in varus-aligned knees. However, changes in the sagittal plane during medial opening wedge high tibial osteotomy can influence the posterior tibial slope, potentially affecting knee biomechanics. The sagittal inclination angle of the osteotomy, which is the angle between the medial joint line and the osteotomy line on lateral view, is a relatively new parameter that has been discussed in the literature, as a factor influencing the posterior tibial slope. The aim of this study is to investigate success rates in achieving the targeted postoperative slope, which is to avoid increasing the slope, with posteriorly inclined sagittal osteotomy.

METHODS

This research was designed as a retrospective single-center case-series study. In order to avoid increasing the posterior tibial slope, our modified surgical technique involves adjusting the sagittal inclination angle to be 10o posteriorly inclined. This angle was considered to be posteriorly inclined if the anterior portion of the osteotomy was inclined proximally. Pre- and postoperative posterior tibial slope measurements were recorded. Changes in postoperative tibial slope compared to preoperative tibial slope were statistically evaluated using the paired t-test. Changes were categorized as decreases, no change, or increases, and these three groups were compared using the one-sample binomial test.

RESULTS

Ninety-five patients (77 women and 18 men) with a mean age of 52.8 ± 7.0 were included in this study. The preoperative mean posterior tibial slope was measured as 12.5 ± 3.9° and the postoperative mean PTS was 10.6 ± 4.3°. A paired t-test revealed a statistically significant difference of 1.9 ± 3.8° (95% confidence interval: 1.13-2.71; p < .01). In four cases (4.2%), the PTS remained the same, while for 67 patients (70.5%) the PTS decreased and for 24 patients (25.3%) the posterior tibial slope increased. Therefore, a decrease or no change in the posterior tibial slope was achieved in 74.7% of all cases (p < .01).

CONCLUSIONS

Modifying the sagittal inclination angle to achieve a posteriorly inclined osteotomy during medial opening wedge high tibial osteotomy may prevent increasing the posterior tibial slope in the majority of cases.

Effect of the amount of correction on posterior tibial slope and patellar height in open-wedge high tibial osteotomy

Objectives: To evaluate the effect of amount of correction on postoperative changes in PTS (posterior tibial slope), PH (patellar height), and clinical outcomes following biplanar OWHTO (open-wedge high tibial osteotomy). Method: This study included 79 knees (32 left and 47 right) of 79 patients (mean age 60.28 ± 4.2 years, 24 males, 55 females) with varus malalignment and symptomatic isolated medial joint osteoarthritis who underwent OWHTO. According to the amount of correction angles, all patients were divided into three groups: LCA (large correction angle) group (>14°), MCA (medium correction angle) group (10°-14°), and SCA (small correction angle) group (<10°). All patients were clinically assessed according to the Lysholm score, HSS (hospital for special surgery knee score), and KSS (knee society score) prior to and after surgery. For radiographic analysis, we measured the PTS, PH [ISI (Insall-Salvati index), and BPI (Blackburne-Peel index)]. The pre-post difference of PTS, ISI, and BPI was calculated by subtracting the post-OWHTO value to the pre-OWHTO value in three groups, respectively. The preoperative, postoperative, and difference of PTS, ISI, and BPI values were analyzed according to the correction angle. The mean follow-up period was 28.5 months (SD, 4.9; range 18-52 months). Results: Radiologically, PTS increased and PH decreased after surgery on the whole (p < .05). The relationship between amount of correction and slope increase is significant (p < .001). Furthermore, the pairwise difference between the LCA group and SCA group and MCA group is significant respectively (p < .05). In terms of PH, the LCA group yielded ISI and BPI that were significantly different from baseline for the SCA group and MCA group. In addition, the pairwise difference between the SCA group and LCA group in ISI and BPI is significant (p = .031). Clinically, significant improvements were observed in postoperative clinical scores of the Lysholm score, HSS, and KSS (p < .05). Seventy-four patients (93.67%) reported satisfaction with surgery. However, no correlation was found between changes in PTS and PH with postoperative knee score. No severe adverse complications were observed. Conclusions: The amount of correction angle is a significant factor affecting the PTS and PH in OWHTO. With increased correction angle, the likelihood of increasing the PTS and decreasing the PH increases. Special attention should be paid to keep PTS and PH unchanged in cases where large corrections are required. Otherwise, closing wedge osteotomy or other intraoperative effective measures are supposed to be adopted.

Posteromedial Open-Wedge High Tibial Osteotomy to Avoid Posterior Tibial Slope Increase

PURPOSE

The primary aim was to evaluate the influence of the surgical modification on posterior tibial slope (PTS) and patellar height in open-wedge high tibial osteotomy (OWHTO). The secondary aim was to evaluate the influence of preoperative mechanical axis deviations (MA) on PTS METHODS: Between January 2014 and February 2016, patients with a diagnosis of medial-compartment osteoarthritis who had undergone OWHTO with posteromedial osteotomy technique with a minimum follow-up of 3 months were included in this retrospective study. Preoperative and postoperative PTS angles with 3 different methods and patellar heights with respect to the Insall-Salvati and Caton-Deschamps indices were measured on lateral radiographs by 2 observers. Patients were grouped according to preoperative MA (either <10° or ≥10°). PTS changes were compared between groups RESULTS: Thirty consecutive knees of 28 patients were evaluated. Preoperative mean PTS angles were 9.50° ± 4.47° (posterior tibial cortex referenced), 11.51° ± 4.50° (tibial anatomical axis referenced), and 10.80° ± 4.58° (posterior fibular cortex referenced); postoperative angles were 6.10° ± 4.23°, 8.78° ± 4.57°, and 8.11° ± 4.55°, respectively. PTS was significantly decreased postoperatively with respect to all 3 methods (P < .0001). Mean preoperative and postoperative Insall-Salvati indices were 1.04 ± 0.16 and 1.07 ± 0.17, respectively (P = .088). Mean preoperative and postoperative Caton-Deschamps indices were 0.87 ± 0.18 and 0.78 ± 0.18, respectively (P = .017). PTS changes were not statistically significant between groups with respect to MA (P values .861, .723, and .727, respectively) CONCLUSIONS: It is possible to preserve and even decrease PTS with an OWHTO performed posterior to MCL in a posteromedial to anterolateral direction.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Clinical efficacy of preoperative 3D planning for reducing surgical errors during open-wedge high tibial osteotomy

Increases in posterior tibial slope (PTS) with open-wedge high tibial osteotomy (OWHTO) are often related to two surgical errors: Symmetric opening of the osteotomy gap and a tendency to open the gap from the anteromedial direction. The study objective was to define trends in these two errors using computer simulation and clinical effects of their countermeasures. First, 60 knees with varus deformity were assessed with three-dimensional (3D) planning using computed tomography to allow for the mechanical axis to pass through a point at 62.5% of the width of the tibial plateau, defined as the weight-bearing line percentage (WBL%). Anterior and posterior widths of the opening gap to maintain PTS were measured. The effect on PTS when osteotomy gaps were opened from the anteromedial direction up to 30° was evaluated. Mean anterior width (y) was 6.6 mm (range, 2.2-10.9) and mean posterior width (x) was 9.1 mm (range, 3.9-15.7), which can be expressed as y = 0.75x - 0.24. Opening gaps from the anteromedial direction at 10°, 20°, and 30° led to a mean PTS increase of 1.9°, 3.9°, and 5.6°, respectively. In most cases, WBL% with anteromedial opening at 30° passed through a point at less than 60%. In 47 knees that underwent OWHTO using 3D planning, postoperative coronal and sagittal bone corrections were mostly accurate. However, postoperative WBL% was negatively correlated with correction angle because of difficulties in predicting medial joint tightness. Preoperative 3D planning for OWHTO can reduce surgical errors, but postoperative WBL% remains variable. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Short-term functional outcomes of computer assisted navigated high tibial osteotomy

Purpose

High tibial osteotomy (HTO) is a surgical procedure performed on patients with knee osteoarthritis (OA). Computer assisted navigated high tibial osteotomy (CAN-HTO) may result in improved outcomes for patients undergoing this procedure.

Methods

Retrospective study involving patients undergoing CAN-HTO.

Results

Surveyed thirty-three patients. Average follow-up: 2.3 years. 97% patients reported they would have this procedure performed again, if indicated. Re-operation rate: 6.1% and complication rate: 12.1%. Patients had decreased KOOS for symptoms when compared to non-navigation based HTO (p = 0.000).

Conclusion

There may be merit with the use of CAN-HTO, with demonstrated patient-reported benefits at 2-year follow-up.

Sagittal osteotomy inclination in medial open-wedge high tibial osteotomy

PURPOSE

Unlike postoperative changes in posterior tibial slope after medial open-wedge high tibial osteotomy, sagittal osteotomy inclination has not been examined. It has been recommended that the osteotomy line in the sagittal plane be parallel to the medial posterior tibial slope. The purpose of this study was to determine the frequency of parallel osteotomy in medial open-wedge high tibial osteotomy.

METHODS

To determine the sagittal osteotomy inclination, the angle between the medial joint line and the osteotomy line was measured in the lateral radiograph. A positive angle value indicates that the osteotomy is anteriorly inclined relative to the medial posterior tibial slope. Correlation between the sagittal osteotomy inclination and posterior tibial slope was also evaluated.

RESULTS

The mean sagittal osteotomy inclination was 15.1 ± 7.5°. The majority 87.1 % of knees showed an anterior-inclined osteotomy. There was a significantly positive correlation between the postoperative posterior tibial slope and the sagittal osteotomy inclination (r, 0.33; 95 % confidence interval (CI) 0.19-0.46; P < 0.001). The postoperative change in posterior tibial slope also showed a significantly positive correlation with the sagittal osteotomy inclination (r, 0.35; 95 % CI 0.21-0.47; P < 0.001).

CONCLUSION

Although parallel osteotomy in the sagittal plane relative to the medial joint line was planned, only 12.9 % of cases achieved osteotomy parallel to the medial posterior tibial slope in the sagittal plane. Because of high rate of the anterior-inclined osteotomy and their correlations with posterior tibial slope, surgeons should make all efforts to perform parallel osteotomy relative to medial posterior tibial slope.

LEVEL OF EVIDENCE

IV.

Changes in posterior tibial slope angle in patients undergoing open-wedge high tibial osteotomy for varus gonarthrosis

PURPOSE

In this study, postoperative changes in the posterior tibial slope angle and clinical outcomes following open-wedge high tibial osteotomy were evaluated.

METHODS

This study included 39 knees (18 left, 21 right) of 35 patients (three male, 32 female; median age, 53 years; age range 37-64 years) with symptomatic isolated medial joint osteoarthritis who underwent open-wedge high tibial osteotomy and fixation with a Puddu plate. The patients were clinically assessed according to the Lysholm knee score, a visual analogue pain scale, and a patient satisfaction questionnaire. Radiological assessment was made according to the changes in the posterior tibial slope angle and the correlation between these changes and clinical signs. The median follow-up period was 11 years (range 7-14 years).

RESULTS

Significant improvements were observed in the preoperative and postoperative clinical scores of the Lysholm knee scale, visual analogue pain scale, and patient satisfaction questionnaire (p < 0.05). Radiological assessment showed that the posterior tibial slope angle was significantly higher during the postoperative and follow-up periods (p  0.05). There was no correlation between the postoperative Lysholm scores and the increase in the posterior tibial slope angle (p = n.s.).

CONCLUSIONS

We conclude that both the conventional Puddu plate design and its anteromedial plate placement are what increase the tibial slope after an opening-wedge proximal tibial osteotomy. Therefore, current new plate design may help preserve the posterior tibial slope angle.

LEVEL OF EVIDENCE

IV.

Comparative Study of Opening-Wedge High Tibial Osteotomy With and Without a Combined Computed Tomography-Based and Image-Free Navigation System

PURPOSE

To assess whether a combined computed tomography (CT)-based and image-free navigation system results in better coronal and sagittal alignment than the conventional method for performing opening-wedge high tibial osteotomy (OWHTO) and whether CT-based navigation results in acquisition of an accurate osteotomy plane.

METHODS

Sixty-two consecutive knees were randomly divided into navigated and conventional groups. The intraoperative correction angle was determined by the change in hip-knee-ankle angle in the navigated group and by the predicted medial opening width in the conventional group. Outliers of femorotibial angle (FTA) and tibial posterior slope (TPS) were defined as angles of >175° or <165° and angles of >2.5° or <-2.5°, respectively. Radiographic and clinical data were compared between the 2 groups at 2 years postoperatively.

RESULTS

Mean postoperative FTAs were 168.5° in the navigated group and 168.1° in the conventional group. Mean change in TPS of -0.2° in the navigated group was significantly lower than that of 1.6° in the conventional group (P = .005). On postoperative CT, mean angle between the tibial plateau and osteotomy planes in the sagittal plane showed a significantly higher anterior opening of 12° in the conventional than in the navigated group (P < .001). There was a significantly greater proportion of TPS outliers in the conventional (51.6%) than in the navigated group (12.9%) (P = .001), and a significantly greater proportion within the normal range in both planes in the navigated (74.2%) than in the conventional group (48.4%) (P = .037).

CONCLUSIONS

Combined CT-based and image-free navigation in OWHTO better preserves the original TPS and more frequently restores normal coronal and sagittal plane knee joint alignment. CT-based navigation also enabled acquisition of our target osteotomy plane in the sagittal plan. The navigation system in OWHTO was helpful for simultaneous control of the alignment in 2 planes.

LEVEL OF EVIDENCE

Level II, lesser-quality prospective randomized trial.

The effect of biplane medial opening wedge high tibial osteotomy on patellofemoral joint indices

PURPOSE

This study was designed to examine the effect of biplane medial opening wedge high tibial osteotomy (MOWHTO) on patellofemoral indices and posterior tibial slope.

MATERIALS AND METHODS

Sixty-two knees (61 patients) underwent biplane MOWHTO for unicompartmental osteoarthritis of the knee. Patellar indices were measured by radiographic assessment postoperatively. The Merchant's views were used for patellar tilt and shift while standing lateral view radiographs were used for the patellar height analysis using the modified Blackburne-peel ratio (mBP). The patients were divided into two groups according to the change between the pre- and postoperative mechanical axis. Group A constituted the correction angle of equal more than 10°, and group B of less than 10°.

RESULTS

Group A demonstrated a significant change of mechanical axis and the tibial slope. Patellar indices including the patellar tilt, shift, and mBP did not show significant difference. Group B demonstrated the statistical significant difference in only the mechanical axis deviation. Patellar indices including the patellar tilt, shift, and mBP as well as the tibia slope did not show significant difference. When evaluated as a whole group, the mean shift in weight bearing line, patellar height (mBP), and tibial slope from preoperative to postoperative value was statistically significant. However, the patellar tilt and shift were not changed significantly.

CONCLUSIONS

After biplane MOWHTO, patellar tilt and shift do not significantly change when measured on static mode supine X-ray. However, patella was lowered and tibia slope increased after MOWHTO.

LEVEL OF EVIDENCE

II.

Open-wedge high tibial osteotomy: comparison between manual and computer-assisted techniques

PURPOSE

The purpose of our study was to compare clinical and radiological results of two groups of patients treated for medial compartment osteoarthritis of the knee with either conventional or computer-assisted open-wedge high tibial osteotomy (HTO). Goals of surgical treatment were a correction of the mechanical axis between 2° and 6° of valgus and a modification of posterior tibial slope between -2° and +2°.

METHODS

Twenty-four patients (27 knees) affected by varus knee deformity and operated with HTO were prospectively followed-up. They were randomly divided in two groups, A (11 patients, conventional treatment) and B (13 patients, navigated treatment). The American Knee Society Score and the Modified Cincinnati Rating System Questionnaire were used for clinical assessment. All patients were radiologically evaluated with a comparative lower limb weight-bearing digital radiograph, a standard digital anteroposterior, a latero-lateral radiograph of the knee, and a Rosenberg view.

RESULTS

Patients were followed-up at a mean of 39 months. Clinical evaluation showed no statistical difference (n.s.) between the two groups. Radiological results showed an 86% reproducibility in achieving a mechanical axis of 182°-186° in group B compared to a 23% in group A (p = 0.0392); furthermore, in group B, we achieved a modification of posterior tibial slope between -2° and +2° in 100% of patients, while in group A, this goal was achieved only in 24% of cases (p = 0.0021).

CONCLUSION

High tibial osteotomy with navigator is more accurate and reproducible in the correction of the deformity compared to standard technique.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Different changes in slope between the medial and lateral tibial plateau after open-wedge high tibial osteotomy

PURPOSE

In contrast to radiographic measurements, MRI provides multiple slices of the knee joint in the sagittal plane, making it possible to assess the medial and lateral tibial slope separately. The purpose of this study is to investigate the effect of medial open-wedge high tibial osteotomy (MOWHTO) on bony and meniscal slope in the medial and lateral tibiofemoral compartments. It was hypothesised that greater changes on the medial tibial plateau would be observed compared with the lateral one.

METHODS

A retrospective analysis of prospectively collected data was performed on pre- and post-operative MRIs from 21 patients (17 men and 4 women; age 52 ± 9 years). Inclusion criteria were varus alignment, medial compartment osteoarthritis and election for a primary MOWHTO. Each patient had a preoperative and a post-operative high-resolution MRI (3Tesla, Magnetom Trio, Siemens AG) at an average follow-up of 2.1 years. A previously published method was used to measure bony and meniscal slope for each compartment. The difference between pre- and post-operative tibial slope for both compartments was calculated and associated with the amount of frontal correction.

RESULTS

There was a significant increase in bony tibial slope in both compartments following MOWHTO. When a change in bony tibial slope was detected in an individual patient, the change was larger in the medial compartment, with the average change also significantly greater (p < 0.01) in the medial compartment (2.4° ± 1.3°) compared with the lateral compartment (0.9° ± 1.1°). There was also a significant increase (p < 0.01) in the lateral tibial meniscal slope of 0.9° ± 1.4°, which was equivalent to the change in the bony lateral slope. The amount of frontal correction was not significantly associated with the amount of change in slope.

CONCLUSIONS

The results suggest that the modification of the bony slope is larger in the medial compartment after MOWHTO, which is likely related to the location of the hinge on the lateral tibial cortex. These findings suggest that consideration of the medial and lateral tibial slope intra-operatively could be important to identify the optimal location of the hinge. However, further studies are required before recommending any modification to the surgical technique, as the potential clinical consequences of tibial slope alterations remain unknown.

LEVEL OF EVIDENCE

IV.

Posterior tibial slope changes after opening- and closing-wedge high tibial osteotomy: a comparative prospective multicenter study

INTRODUCTION

Valgus high tibial osteotomy is considered to be an effective treatment for unicompartmental medial osteoarthritis. It is generally admitted that tibial slope increases after open-wedge high tibial osteotomy and decreases after closing-wedge high tibial osteotomy. However, the effects on posterior tibial slope of closing- or opening-wedge osteotomies remain controversial.

HYPOTHESIS

We analyzed the modifications of tibial slope after opening- and closing-wedge high tibial osteotomies and compared the results of these two procedures. We hypothesized that there was no difference in postoperative tibial slope between opening and closing-wedge osteotomies.

PATIENTS AND METHODS

This prospective consecutive nonrandomized multicenter study was conducted between January 2008 and March 2009 and included 321 patients: 205 men and 116 women. A total of 224 patients underwent an opening-wedge high tibial osteotomy and 97 a closing-wedge osteotomy. The mean age was 52 years ± 9 and the mean body mass index was 28kg/m(2) ± 5. The main etiology was primary arthritis. Posterior tibial slope was measured preoperatively and at the last follow-up on a lateral radiograph in relation to the posterior tibial cortex.

RESULTS

In the opening-wedge group, a definite 0.6° increase in tibial slope (P=0.016) was observed. In the closing-wedge group, a definite 0.7° decrease in tibial slope (P=0.02) was found. Fourteen percent of the opening-wedge osteotomies increased tibial slope by 5° or more versus only 2% of the closed-wedge osteotomies (P<0.001). Twelve percent of the closing-wedge high tibial osteotomies led to a decrease of 5° or more of the tibial slope versus 7% of the opening-wedge osteotomies (P<0.02).

DISCUSSION AND CONCLUSION

These results confirm what is generally reported in the literature, i.e., an increase in tibial slope in opening-wedge high tibial osteotomy and a decrease in the slope in closing-wedge osteotomies. These tibial slope changes appear to be very limited in this series, less than 1° on average. However, there was a bias since the open-wedge technique was preferred in cases with substantial varus deformity. We emphasize the importance of surgical technique to avoid alteration of the tibial slope, particularly in opening-wedge high tibial osteotomy for which we recommend a release of posterior soft tissue and a complete osteotomy of the posterior cortex of the tibia.

LEVEL OF EVIDENCE

III. Prospective consecutive nonrandomized multicenter study.

Development and validation of a new method for the radiologic measurement of the tibial slope

PURPOSE

The posterior tibial slope has a huge influence on the kinematics of the knee. In several orthopedic interventions such as high tibial osteotomy and unicondylar or bicondylar knee replacement changing, the tibial slope can result in altered knee mechanics. Therefore, an exact preoperative measurement of the posterior tibial slope is mandatory. Several methods are used on conventional radiographs and CT scans, but until now there is no standard validated method. The aim of this study was to compare several methods and imaging techniques to measure the posterior tibial slope and to establish a standard and reliable measurement method by radiography.

METHODS

Fourteen knees (seven cadavers) were scanned by a 64-slice CT, a 3T-MRI, and true lateral radiographs were performed. The anatomical references (TPAA = tibial proximal anatomical axis; ATC = anterior tibial cortex; PTC = posterior tibial cortex) and the new computed reference (MPA = mean of PTA and ATC) were compared by short as well as long radiographs, CT scan and MRI. The influence of a malrotation in radiographs of the knees was also analyzed.

RESULTS

CT scan and MRI are suitable for the measurement of the medial and lateral posterior tibial slopes, the results of the radiographs varied depending on the method used. The new method (MPA) showed the best correlation to the CT scan (r = 0.997), even on short radiographs (10 cm distal the joint line).

CONCLUSION

The measurement of the posterior tibial slope on a short lateral radiograph using the MPA is a reliable method and should be established as a standard.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

Radiographic healing with hemispherical allogeneic femoral head bone grafting for opening-wedge high tibial osteotomy

PURPOSE

The aim of this study was to investigate the remodeling process after hemispherical femoral head allograft grafting in opening-wedge high tibial osteotomy with a plate and screw.

METHODS

The study group included 105 knees in 92 women and 7 knees in 7 men from January 2007 through December 2007. The radiographic bone remodeling process was determined by use of a modification of the radiologic rating system described previously by van Hemert et al. in 4 groups: group A, 7-mm plate correction; group B, 9-mm plate correction; group C, 11-mm plate correction; and group D, 13-mm plate correction.

RESULTS

The postoperative femorotibial angle and tibial slope were not significantly changed at latest follow-up in comparison to immediate postoperative status. The mean follow-up period was 25.4 months (range, 18 to 30 months). In all groups radiologic bone healing higher than phase 3 was successfully achieved between 3 and 6 months. The healing process slowed with increasing correction angle.

CONCLUSIONS

A hemispherical femoral head allograft is a good alternative osseous graft material when patients are selected appropriately with the following criteria: body mass index lower than 40, no symptomatic osteoarthritis of the patellofemoral joint and lateral compartment, no systemic inflammatory arthritis, no history of fracture or previous open surgery to the lower limb, and no flexion contracture.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Avoiding intraoperative complications in open-wedge high tibial valgus osteotomy: technical advancement

Open-wedge high tibial osteotomy for varus osteoarthritis of the knee is a successful treatment option, but is associated with potential intraoperative complications, jeopardizing outcome. We describe four technical hints avoiding complications as tibia plateau fracture, lateral hinge dislocation, over- and undercorrection, and unwanted increase of the posterior tibial slope and axial malrotation. The technique, which is primarily based on placing five Kirschner-wires (one for the osteotomy direction, two for the external fixator, and two for rotational and slope control) is simple, reproducible, inexpensive, and readily available.

Modification of tibial slope after medial opening wedge high tibial osteotomy: clinical study and mathematical modelling

A prospective non-randomized non-comparative study involved 30 patients who underwent a medial opening wedge high tibial osteotomy for medial knee osteoarthritis using a specific surgical procedure. The tibial slope was calculated pre-operatively and at a mean follow-up of 14 months. A mathematical model of the surgical procedure was developed in order to plan the height of the medial opening wedge and to predict tibial slope changes. Tibial-slope measurements accuracy was good (0.04 degrees +/- 0.92 degrees ). There was no significant difference for the mean tibial slope before and after surgery (9.2 degrees +/- 5.6 degrees vs. 9.1 degrees +/- 5.6 degrees , P = 0.47). There was a perfect agreement between the model and the real values for the HKA angle (0.85) and the tibial slope (0.98). The surgical technique used did not modify the tibial slope. Our mathematical model for pre-operative planning was validated with very good accuracy.

ACL injury while jumping rope in a patient with an unintended increase in the tibial slope after an opening wedge high tibial osteotomy

High tibial osteotomy (HTO) is an accepted surgical technique for the treatment of medial compartmental arthrosis of the knee in younger patients. Compared to total knee arthroplasty, HTO may be a good choice in patients who wish to continue with heavy labor and/or impact sports. Based on the rehabilitation protocol after HTO, impact sports, such as running, jumping rope, and full sports activities, are generally permitted 6 months postoperatively. Jumping rope is an excellent form of aerobic exercise, and when done properly, jumping rope can lead to a dramatic improvement in rehabilitation and full sports activities. However, an adequate evaluation should be performed prior to initiating impact sports. We present the case of a ruptured anterior cruciate ligament that occurred in a patient with an unintended increase in the tibial slope after an opening wedge HTO who was jumping rope.