Navigated opening wedge high tibial osteotomy improves intraoperative correction angle compared with conventional method

Surgical accuracy of coronal and sagittal alignment in conventional closed-wedge high tibial osteotomy after computer-assisted surgery experience

BACKGROUND

Although intraoperative navigation can improve the surgeon's proficiency, no studies have analyzed postoperative outcomes of high tibial osteotomy (HTO) after computer-assisted surgery (CAS) experience. The present study compared the clinical and radiographic results between conventional and CAS closed-wedge (CW) HTOs after CAS experience.

METHODS

Each of the 50 conventional and CAS CW HTOs performed by single surgeon between 2015 and 2017 were included. The surgeon had experience of 140 cases of CAS CW HTOs before the study period. The groups were not different in terms of demographics. Clinically, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM) were investigated. Radiographically, the mechanical axis (MA), change in posterior tibial slope angle (PTS), and parallel angle were evaluated. The proportions of inlier groups for the postoperative MA (within valgus 2° ± 3°), change in the PTS (within ± 3°), and parallel angle (< 3°) were compared.

RESULTS

There were no significant differences in postoperative clinical results between the conventional and CAS groups. The MA was appropriately corrected in both groups (2.4° versus 2.9°, p = 0.317). The amount of change in PTS was significantly greater in the conventional group (-2.2° versus -0.8°, p = 0.018). The parallel angle was 5.3° in the conventional groups and 3.1° in the CAS group (p = 0.003). The proportion of inlier group was not significantly different in the postoperative MA (72% versus 78%) and change in the PTS (52% versus 66%). The proportion of inlier for the parallel angle was significantly lower in the conventional group (36% versus 60%, p = 0.027).

CONCLUSIONS

The surgical proficiency after CAS experience could cover the advantages of an intraoperative navigation in coronal adjustment, not in the sagittal adjustments in CW HTOs. A larger cohort with multiple surgeons in multiple centers would be required to identify the general trend.

STUDY DESIGN

Level of evidence 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.

Postoperative change in the joint-line convergence angle is associated with inaccurate correction in open-wedge high tibial osteotomy

OBJECTIVE

Accurate correction is a prerequisite for the favorable outcomes of open-wedge high tibial osteotomy (OWHTO). However, previous studies have reported disappointing results regarding correction accuracy despite the use of intra-operative navigation, which implies that a certain factor other than bony components is involved in the inaccurate correction (mainly overcorrection). The joint-line convergence angle (JLCA) can represent soft tissue effects in OWHTO. This study tried to determine whether the postoperative change in the JLCA (∆JLCA) led to inaccurate correction.

METHODS

Medical records of 78 OWHTO patients from 2005 to 2021 were retrospectively reviewed. The hip-knee-ankle angle (HKA) was measured with a positive value indicating varus alignment. Inaccurate correction was defined as postoperative HKA < - 3°. The JLCA was measured before and 6 months after surgery on long-standing hip-to-ankle radiographs, and ∆JLCA was defined as the difference between the preoperative and 6-month postoperative JLCAs. ∆JLCA was compared between the accurate correction group and the inaccurate correction group, and a receiver operating characteristic (ROC) curve was used to obtain the cutoff ∆JLCA at which the sensitivity and the specificity for inaccurate correction were maximized. Clinical outcomes were also compared between the groups using the knee injury and osteoarthritis outcome score (KOOS) at final follow-up (60.9 ± 53.3 months postoperatively).

RESULTS

Of the 78 patients, inaccurate correction was noted in 10 patients. The overall preoperative and postoperative HKAs were 7.0 ± 3.1° and - 0.4 ± 1.5°, respectively. The accurate correction group and the inaccurate correction group had a difference in ∆JLCA (p = 0.010). However, no significant difference was found in the preoperative HKA (p = 0.529). An ROC curve showed that the cutoff ∆JLCA was 1.9°. In the patients having ∆JLCA ≥ 1.9°, the mean JLCA was 4.9 ± 1.6° preoperatively and 1.7 ± 1.2° postoperatively. In the other patients having ∆JLCA < 1.9°, the mean preoperative and postoperative JLCA were 2.5 ± 1.8° and 2.3 ± 1.8°, respectively. The difference in the preoperative JLCA was significant (p < 0.001). The postoperative KOOS subscales did not differ according to correction accuracy.

CONCLUSION

Inaccurate correction in OWHTO, specifically valgus overcorrection, is associated with large ∆JLCA which represents the postoperative change of soft tissue effects. Overcorrection should be checked in cases of large preoperative JLCAs.

Comparison of the Miniaci and Dugdale techniques on functional outcomes in medial open wedge high tibial osteotomy

PURPOSE

To compare the correction angles determined by the Miniaci and Dugdale techniques in patients treated with medial open wedge high tibial osteotomy (MOWHTO) and show their impact on clinical outcomes.

METHODS

Seventy-four patients constituted the study group. The correction angles in Group 1 were measured using the Miniaci technique, and those in Group 2 were measured using the Dugdale technique. The clinical evaluations included the Tinetti Gait and Balance Assessment (TGBA), the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores, and the Visual Analogue Scale (VAS). The effect of the correction angle on the patient's clinical outcomes was evaluated. Measurement techniques were also changed between groups for comparison.

RESULTS

Seventy-four patients (62 females, 12 males) with a mean age of 53.7 ± 4.9 years were followed up for a mean of 67.4 ± 5.5 months. The TGBA, WOMAC, and VAS scores were improved at the last follow-up compared to the preoperative scores (p < 0.05). The preoperative TGBA and WOMAC scores were not significantly different between the two groups, but the last follow-up TGBA and WOMAC scores in Group 2 were worse than those in Group 1 (p < 0.05). When measuring techniques were changed, the preoperative correction angle (PCA) value and the last follow-up correction angle (LFCA) value were lower in Group 1 measured with the Dugdale technique but higher in Group 2 measured with the Miniaci technique (p < 0.05).

CONCLUSION

Since the correction angle values measured with the Miniaci technique in MOWHTO are higher than those measured with the Dugdale technique; the functional results are better.

LEVEL OF EVIDENCE

Retrospective cohort study, III.

Editorial Commentary: Alignment for Open-Wedge High Tibial Osteotomy Can Be Planned Using the Hip-Knee-Ankle Angle and the Weightbearing Line

Correct alignment of the limb mechanical axis is a principal goal of open-wedge high tibial osteotomy and determines successful postoperative outcomes. Excessive postoperative joint line obliquity must be avoided. A mechanical medial proximal tibial angle (mMPTA) less than 95° results in poor outcomes. Preoperative planning is commonly performed using a picture archiving and communication system; however, this is time-consuming and sometimes inaccurate because many landmarks and parameters need to be confirmed manually. Hip-knee-ankle (HKA) angle and weightbearing line (WBL) percentage are perfectly correlated to the Miniaci angle when planning open-wedge high tibial osteotomy, and ΔmMPTA and ΔWBL percentage are nearly perfectly correlated with the ΔHKA angle. Surgeons can easily measure the Miniaci angle according to the preoperative HKA and preoperative WBL percentage without digital software, and mMPTA greater than 95° can be avoided. Finally, bony and soft tissue components must be considered during preoperative planning. Medial soft tissue laxity must be specifically avoided.

Large Versus Small Opening Wedge High Tibial Osteotomies Performed With a Protective Wire Over the Lateral Hinge: Incidence of Lateral Hinge Fracture and Early Clinical Outcomes

BACKGROUND

The incidence of lateral hinge fractures (LHFs) during medial opening wedge high tibial osteotomy (MOW-HTO) is unacceptably high, especially with distractions >10 mm. LHFs result in malunion, loss of correction, and recurrence of symptoms adversely affecting clinical outcomes.

PURPOSE

(1) To investigate the incidence of LHF when a protective guide wire is utilized during MOW-HTO in small and large corrections and (2) to study the effect of correction size on early clinical outcomes.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective analysis was performed of 96 knees that underwent MOW-HTO between 2019 and 2020. A protective wire applied intraoperatively across the lateral hinge point before opening wedge distraction was performed for all patients. Patients were divided into 2 groups based on opening wedge sizes: group A (opening distraction <10 mm) and group B (opening distraction ≥10 mm). LHF and wound complications were recorded. Prospective Knee Score and Function Score (Knee Society), Oxford Knee Score, and Physical and Mental Component Summaries of the 36-Item Short Form Health Survey questionnaire were recorded preoperatively and at 6 months and 2 years after surgery.

RESULTS

Incidence of LHF was low in group A (n = 2; 6.1%) and group B (n = 3; 9.1%). A single case of intraoperative LHF was noted in each group, with each case resulting in a type 1 fracture. The incidence of postoperative fractures was comparable between groups (groups A vs B, n = 1 vs 2). At 6 months, clinical outcomes in group A were superior to those of group B (Knee Score, 85.7 ± 14.7 vs 73.1 ± 20.3, P = 0.028; Function Score, 73.5 ± 16.5 vs 63.1 ± 19.5, P = 0.047; Oxford Knee Score, 20.2 ± 4.7 vs 25.6 ± 8.5, P = 0.008; Physical Component Summary, 46.8 ± 8.1 vs 40.2 ± 10.9, P = 0.018). However, clinical outcomes were comparable at 2 years (P > .05).

CONCLUSION

A protective wire was associated with a low incidence of LHF, even in larger MOW-HTO corrections. Large corrections had poorer clinical outcomes as compared with small corrections at 6 months. However, clinical outcomes between groups were comparable at 2 years.

Opening-Wedge High Tibial Osteotomy With High Hinge Position Risks Lateral Hinge Fracture in Men With Posterolateral Tibial Condyle Protrusion

PURPOSE

The primary aim of this study was to evaluate the 3-dimensional morphology of the proximal tibia around the osteotomy plane in open-wedge high tibial osteotomy, focusing on the posterolateral (PL) and posteromedial (PM) tibial condyles, and to clarify the changes in morphologic parameters due to differences in patient characteristics and hinge position. The secondary aim was to examine whether morphologic features were associated with insufficient osteotomy, which increases the risk of lateral hinge fracture (LHF).

METHODS

The PL and PM anteroposterior distance, asymmetry ratio, and discrepancy between PL and PM distances along the tibial osteotomy plane were measured. We investigated changes in the parameters due to differences in patient characteristics and hinge position. Osteotomy configurations and LHFs were evaluated using postoperative computed tomography scans.

RESULTS

The 3-dimensional preoperative plans of 117 knees (male, 41 knees; female, 76 knees) were evaluated. PL distances were larger than PM distances in almost all cases. The average asymmetry ratio was 1.35, and the standard deviation was 0.22. Higher hinge position was associated with a larger asymmetry ratio and discrepancy (P < .001). The asymmetry ratio and discrepancy were independently positively correlated with male sex (P = .002 and P = .001, respectively) and gentle posterior tibial slope (P < .001 and P < .001, respectively). Osteotomies with type III LHFs showed lower osteotomy sufficiency than osteotomies without LHFs (P < .001).

CONCLUSIONS

PL tibial condyle protrusion was more pronounced in male patients and those with a high hinge position, and may result in insufficient PL osteotomy, which is a risk factor for type III LHF during open-wedge high tibial osteotomy. The optimal hinge position was located approximately 15 mm and 20 mm distal to the lateral tibial plateau in female and male patients, respectively.

LEVEL OF EVIDENCE

IV: retrospective case series.

Comparison of computer-assisted navigated technology and conventional technology in high tibial osteotomy (HTO): a meta-analysis

BACKGROUND

Though some studies have reported navigated high tibial osteotomy (HTO) is a useful procedure to correct knee deformity. There is still great controversy whether navigated HTO can achieve better accuracy of limb alignment and greater clinical outcomes. Current meta-analysis was conducted to investigate whether better radiographic outcomes and clinical outcomes could be acquired in navigated HTO compared with the conventional procedure.

METHOD

We conducted a literature search in the electronic databases, including Medline, Embase, the Cochrane Library, and Web of Science. We identified studies published before August 2020. We also checked the references of the related articles for any relevant studies. We strictly followed the Preferred Reporting Items for Systematics reviews and Meta-Analysis (PRISMA) guidelines in this review. This research was performed using Review Manager 5.4 software.

RESULTS

Fourteen articles were included, involving 1399 knees. Our meta-analysis indicated that patients undergoing navigated HTO had significantly better outcomes in outliers of aimed limb alignment (RD=-0.24, 95% CI: =-0.34 to -0.13, p < 0.01), outliers of aimed tibial posterior slope (TPS) (RD=-0.41, 95% CI: -0.51 to -0.30, p < 0.01), Range of Motion (ROM) (MD = 6.37, 95%CI: 0.83-11.91, p = 0.02), and American knee society knee score (AKS knee score) (MD = 3.88, 95%CI: 1.37-6.39, p = 0.002). No significant differences were found in Lysholm score (MD = 1.30, 95%CI: -0.31 to 2.90, p = 0.11), American knee society function score (AKS function score) (RD = 1.42, 95%CI: -0.15 to 2.99, p = 0.08), complications (RD=-0.01, 95% CI: = -0.05 to 0.04, p = 0.77), delayed union (RD=-0.01, 95% CI: = -0.02 to 0.03, p = 0.59), and reoperation (RD = 0, 95% CI: -0.09 to 0.10, p = 0.98) between the two groups. The operation time in the navigated group was 15.46 min longer than in the conventional group.

CONCLUSION

Navigated HTO provided more accurate and reproducible radiographic outcomes in the correction of the malalignment than conventional techniques, and there is no difference in the risk of complications compared with conventional HTO. However, it is unclear whether navigation HTO can achieve better clinical results. More randomized controlled trials (RCTs) with high quality, large sample size, and sufficient follow-up period are required.

Clinical efficacy and feasibility of laser correction technology with an ordinary laser pen and surgical instrument box in open-wedge high tibial osteotomy

Background

The clinical outcomes of open-wedge high tibial osteotomy (OWHTO) for medial knee osteoarthritis primarily depend on the corrective precision. The present study aimed to determine the efficacy and feasibility of laser correction technology with an ordinary laser pen and surgical instrument box.

Methods

This prospective and randomized trial included 71 patients randomly divided into laser (n = 36) and traditional groups (n = 35). In the laser group, the hip centre, knee (Fujisawa point), and ankle centre were located preoperatively using the surgical instrument box lid. The leg was aligned with an ordinary laser pen. In the traditional group, the lower limb alignment was corrected by a metal cable. Radiation exposure, operative time, and rate of outliers (lower limb force line does not pass through 62–66% of the lateral tibial plateau) were evaluated. The visual analogue scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were recorded. After 24 months, the femoral tibial angle (FTA), medial proximal tibial angle (MPTA), and posterior slope angle (PSA), were recorded. The Kaplan-Meier method was used to evaluate the survival time of affected knees, and postoperative complications were recorded.

Results

The radiation exposure, operative time and rate of outliers were lower in the laser correction group (P < 0.05). Six months postoperatively, the VAS and WOMAC scores were significantly improved in both groups (P < 0.001). At 24 months, the FTA, MPTA, and PSA were corrected in both groups (P < 0.001). There were no differences in the postoperative knee survival time from OWHTO to knee arthroplasty between the groups or postoperative complications (P = 0.53; P = 0.61).

Conclusions

Laser correction technology can effectively reduce radiation exposure, the operative time, and the rate of outliers (trial identification number (retrospectively registered): ChiCTR2200060480; date of register: 03/06/2022).

The relationship between the ''Fujisawa point'' and anatomical femorotibial angle following simulated open wedge high tibial osteotomy

Background

We evaluated the relationship between the weight-bearing line (WBL) ratio and anatomical femorotibial angle (FTA) by simulated open wedge high tibial osteotomy (OWHTO). This study evaluated the correlation between the ‘‘Fujisawa point’’ and FTA, and identified factors which caused deviations between the two measurement methods. We hypothesized that the Fujisawa point corresponded with 170° of the FTA.

Methods

Preoperative antero-posterior full-length lower limb radiographs of 82 patients were obtained for the OWHTO to place the WBL ratio at a target of 62.5% of the width of the tibial plateau (Fujisawa point). The coronal alignment was measured pre- and post-planning. The patients were divided into two groups by the post-planning FTA: a correspondence group (168.5°≦FTA≦171.5°) and a non-correspondence group (FTA < 168.5°, 171.5° < FTA). The relationship between the Fujisawa point and the FTA was analyzed with multivariate regression analysis.

Results

The post-planning FTA was 169.8 ± 1.1° and within 170 ± 1.5° in 69 cases (84.1%) when the WBL ratio was 62.5%. The neck shaft angle was 128.1 ± 5.2° in the correspondence group, and 122.3 ± 6.3° in the non-correspondence group. The multivariate linear regression analysis revealed that the neck shaft angle was the only factor that predicted the correspondence of the Fujisawa point with the FTA at 170° (p = 0.006, odd 1.28).

Conclusions

The post-planning FTA converged at 170° when the WBL ratio passed through the Fujisawa point and the neck shaft angle was the only predictor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05734-7.

Undercorrection: the undesired effect of compression on the osteotomy gap of the medial opening wedge high tibial osteotomy and its clinical significance

INTRODUCTION

Undercorrection is a common problem in opening wedge high tibial osteotomy (OWHTO). We investigated the compression effect of cortex screw on the osteotomy gap and its clinical significance.

MATERIALS AND METHODS

A standard OWHTO using the TomoFix plate was conducted on 20 bone models in two groups to get a 10-mm medial osteotomy gap. A cortex screw was used temporarily in a neutral (at the center) and an eccentric position (near the inclined plane) of the dynamic hole in group 1 and group 2, respectively. The mean of undercorrection observed in the two groups was compared using an independent t test. Also, the effect of compression on the gap between the plate and medial tibial cortex, and the osteotomy gap was evaluated using a Sine rule. Besides, the mean undercorrection observed was assessed for clinical significance based on the effect on the weight-bearing axis (WBA) using a Cosine Rule.

RESULTS

The mean undercorrection was 1.3 ± 0.6 mm and 2.6 ± 0.6 mm in group 1 and group 2, respectively. A significantly greater undercorrection was observed in group 2 (p < 0.001). The correction loss in group 2 has resulted from combinations of the sliding effect of the dynamic hole and oblique compression effect over the gap between the plate and medial tibial cortex whereas in group 1 it has only resulted from the oblique compression effect. The observed undercorrection in group 2 has resulted in clinically significant WBA shift (10%) over the width of the tibial plateau.

CONCLUSIONS

In OWHTO, compression is important for the stability and healing of osteotomy, but it can also cause loss of correction. In patients requiring large correction, the surgeon should control the amount of compression required and consider making extra osteotomy gap to avoid undercorrection. Furthermore, the placement of cortex screws in neutral is essential to lower the risk of undercorrection.

"One millimetre equals one degree": a simple way to achieve in 92% of cases the desired correction after opening proximal tibial osteotomy for genu varum

INTRODUCTION

When performing a high tibial osteotomy (HTO) for genu varum deformity, it is not always easy to obtain the correct amount of overcorrection. The aims of this study were to review the results of a simple and reproducible method of correction that we have called "1 mm equals 1°". We have applied this technique to the medial opening wedge osteotomy. Our hypothesis was that one degree of correction corresponded with one degree of opening.

METHODS

97 proximal medial opening wedge osteotomies were measured intraoperatively with a navigation system and at 3 months with long-leg X-rays. The hip-knee-ankle (HKA) angle preoperatively was on average 173.8 ± 2.3° (170°-177°). In most cases, an opening of 4° greater than the initial varus was performed using our formula that one degree varus was equal to 1 mm of opening. In other words, when the varus was 6°, an opening of 10 mm was performed. The void left by the opening wedge was filled with a calcium triphosphate wedge and the construct fixed and held with a locking plate.

RESULTS

Aiming for a knee axis of 184 ± 2°, which corresponds to 2°-6° of overcorrection, we obtained the following results: HKA intraoperatively measured angle with navigation was on average 183.5 ± 0.9° (182°-184°) and HKA radiologically postoperatively angle was 182.5° ± 1.6° (179°-189°). We therefore achieved the desired overcorrection of 2°-6° in 92% of cases based on our postoperative radiographs and in 100% cases based on intraoperative measurements with computer navigation.

CONCLUSION

The method of "1 mm equals 1°" is a simple, reliable, and reproducible method to achieve in 92% of cases the desired overcorrection (i.e., 184 ± 2°) with valgising proximal medial opening wedge osteotomy in genu varum.

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.

Joint line obliquity was maintained after double-level osteotomy, but was increased after open-wedge high tibial osteotomy

PURPOSE

To compare the radiographic, clinical, and arthroscopic outcomes of varus osteoarthritic knees treated with an open-wedge high tibial osteotomy (OWHTO) alone or with a double-level osteotomy (DLO). It was hypothesized that treatment with DLO would maintain the joint line obliquity (JLO) and acquire better arthroscopic and clinical outcomes after surgery than OWHTO alone.

METHODS

Knees with predicted medial proximal tibial angle (MPTA) > 95° were treated with OWHTO alone or with DLO. Preoperatively, age, body mass index, and hip-knee-ankle angle (HKA) differed between the two groups. Therefore, after adjustment for those factors, 34 knees with OWHTO alone and 34 knees with DLO were compared. On whole-leg radiographs for a single leg, HKA, weightbearing line (WBL) ratio, lateral distal femoral angle (LDFA), MPTA, and JLO were measured before and 2 years after surgery. Clinical outcomes were evaluated by the Knee Society Score (KSS) knee, KSS function, Lysholm, and Knee injury and Osteoarthritis Outcome Score (KOOS) scores before and 2 years after surgery. Arthroscopic findings were obtained before and 1 year after surgery. Various factors were compared between the two groups.

RESULTS

JLO increased significantly from 1.4° to 6.3° in the OWHTO group (p < 0.001) and changed from 1.0° to 1.3° in the DLO group (n.s.). Postoperative MPTA and JLO in the OWHTO group were significantly higher than those in the DLO group (both p < 0.001). There were no significant differences in the KSS knee, KSS function, and KOOS scores between the two groups. Postoperative Lysholm score in the DLO group was higher than that in the OWHTO group (p < 0.025). Femoral and tibial cartilage regeneration in the medial condyles and deterioration in the lateral condyles did not differ between the two groups on second-look arthroscopy.

CONCLUSIONS

JLO was not significantly changed after surgery in the DLO group. DLO enabled the acquisition of physiological JLO compared with OWHTO alone.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Long Term Outcomes of Computer-Navigated Lateral Opening Wedge Distal Femoral Osteotomy for Lateral Compartment Knee Arthrosis

Objective  The primary aim of the present study was to evaluate the long-term outcomes including survivorship of computer navigated distal femoral lateral opening wedge osteotomy (DFLOWO). The secondary aim was to identify the potential factors that may influence its survivorship. Methods  A retrospective analysis of prospectively collected data for patients with lateral compartment arthritis who underwent navigated DFLOWO from December 2006 to November 2012 was performed. The International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores were analyzed for outcome measures. Conversion to arthroplasty during the follow-up was the end point. Results  A total of 19 DFLOWOs were performed in 17 patients with a mean age of 46.6 ± 6.5 years formed the study cohort. The coronal alignment was corrected from a mean of 7.1° (2-11°) valgus to a mean of 2.1° (0.5°-3°) varus. The IKDC scores improved from mean of 39 preoperatively to 53 at the mean long-term follow-up of 9.1 years. The mean KOOS scores at the long-term follow-up were pain 71, symptoms 56, activities of daily living 82, sports and recreation 59, quality of life 43. Survivorship of the DFLOWO was 78.9% at a follow-up of 9.1 years. Presence of ≥ grade 2 according to the International Cartilage Repair Society (ICRS) cartilage degeneration in the medial compartment of the knee and >7° preoperative valgus deformity were strongly correlated with conversion to total knee arthroplasty (TKA) at the long-term follow-up ( r  = 0.66). Conclusions  Computer navigated DFLOWO has satisfactory clinical outcomes and 79% survivorship in long-term follow-up. Presence of more than ICRS ≥ grade 2 degenerative changes in the medial compartment of knee with > 7° preoperative valgus deformity negatively affects the survivorship of DFLOWO in the long-term follow-up.

CAS and PSI increase coronal alignment accuracy and reduce outliers when compared to traditional technique of medial open wedge high tibial osteotomy: a meta-analysis

PURPOSE

Medial open-wedge high tibial osteotomy (MOWHTO) is an accepted option in the treatment of medial compartment osteoarthritis of the knee in young and active patients. Functional results are closely correlated to the correction of the mechanical axis of the lower limb. Although several angular and geometrical methods and values have been proposed in the past, the ideal target is still debated. In addition, it is important to have a deep correlation between the planned correction and the achieved correction after surgery. The aim of the present systematic review was to identify the ideal coronal correction after MOWHTO and the most accurate method to achieve it.

METHODS

A systematic review of the literature was completed on July 3rd 2020 in the Pubmed, Medline, Cochrane Reviews, and Google Scholar databases using the Medical Subject Headings (MeSH) terms: "high tibial osteotomy" AND "accuracy" OR "planning".

RESULTS

28 studies were included; 18 were focused on computer-assisted surgery (CAS) and 10 on patient-specific instrumentation (PSI). There were 598 patients in the CAS group and 501 in the control group; the rate of outliers was 16% and 38.2% respectively (P = 0.04), while there was no significant difference between the two groups (SMD = - 0.10; 95% CI 1.31 to 1.12; P = n.s.) in terms of coronal accuracy. Likewise, there were 318 patients in the PSI group and 40 in the control group; the rate of outliers was 15% and 40% respectively (P = 0.98), while there was no significant difference between the two groups (SMD = 0.01; 95% CI 0.58 to 0.59; P = 0.98).

CONCLUSIONS

A statistically significant reduced outlier rate and a non-significant increased accuracy emerged with the use of CAS when compared to the traditional surgical technique, whereas the results of PSI were still inconclusive. In addition, it emerged clearly that no consensus still exists on the ideal correction target to be achieved after surgery.

LEVEL OF EVIDENCE

III.

Reliability of Preoperative Planning Method That Considers Latent Medial Joint Laxity in Medial Open-Wedge Proximal Tibial Osteotomy

Background:

Soft tissue laxity around the knee joint has been recognized as a crucial factor affecting correction error during medial open-wedge proximal tibial osteotomy (MOWPTO). Medial laxity in particular, which represents the changes in joint-line convergence angle (JLCA), affects soft tissue correction.

Purpose:

The purpose of this study was to quantify medial laxity and develop a preoperative planning method that considers medial laxity.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

This study retrospectively reviewed 139 knees in 117 patients who underwent navigation-assisted MOWPTO from January 2014 to July 2019 for symptomatic medial compartment osteoarthritis with varus alignment >5°. We compared the results of 2 preoperative planning methods: conventional Miniaci (n = 47) and latent medial laxity reduction (LMLR) (n = 92). We evaluated the incidence of undercorrection, acceptable correction, and overcorrection. The radiologic parameters were analyzed using multiple linear regression with a stepwise selection model to establish an equation for the optimal preoperative planning method. The intraclass correlation coefficients (ICCs) of intraobserver, interobserver, and intermethod reliability were calculated.

Results:

The Miniaci method showed a higher incidence of overcorrection (55.3%) than the LMLR method (22.8%) at postoperative 6 months (P = .0006). Multiple linear regression with a stepwise selection model revealed a high correlation coefficient (R² = 0.888) for the following equation: Adjusted planned correction angle = 0.596 + 0.891 × Target correction angle – 0.255 × ΔJLCA_valgus. Upon simplification, the following equation showed the highest intermethod ICC value (0.991): Target correction angle – ⅓ΔJLCA_valgus, while the Miniaci method showed a relatively low ICC value of 0.875.

Conclusion:

There was a risk of overcorrection after MOWPTO using the conventional Miniaci method. An equation that considers medial laxity may help during preoperative planning for optimal correction during MOWPTO.

Open-wedge high tibial osteotomy in patients with discoid lateral meniscus

BACKGROUND

There are concerns about the progression of the lateral osteoarthritis (OA) should be taken into account when high tibial osteotomy (HTO) is performed in patients with discoid lateral meniscus (LM). This study evaluated the clinical results of HTO in patients with discoid LM and elucidated factors affecting the results.

METHODS

This study evaluated 32 female patients with varus deformity and medial OA. Patients with discoid LM (8 patients) or without discoid LM (24 patients) underwent open-wedge HTO. The mean age was 53.5 years and the mean follow-up period was 35 months. Clinical results, including the Hospital for Special Surgery (HSS) score, Knee Society knee score (KS) and function score (FS), were evaluated. The progression of OA in the lateral compartment was also evaluated. Finally, we evaluated the factors affecting the clinical results and OA progression in the lateral compartment.

RESULTS

Between two groups, all clinical scores were not different (p = 0.964, 0.963, and 0.559, respectively). Three of eight patients (37.5%) in the discoid group developed OA in the lateral compartment, whereas 2 of 24 patients (8.3%) in the control group developed such; however, this was not significantly different (p = 0.085). In discoid group, patients with undercorrection has higher KS relative to patients with acceptable correction (p = 0.044). Other clinical results and OA change in the lateral compartment were not affected by evaluated factors.

CONCLUSIONS

Patients who underwent open-wedge HTO showed the satisfactory clinical results and lateral OA progression regardless of the presence or absence discoid LM. However, when discoid LM was present, patients with undercorrection showed higher KS in comparison with patients with acceptable correction.

Salvage of severe knee osteoarthritis: efficacy of tibial condylar valgus osteotomy versus open wedge high tibial osteotomy

INTRODUCTION

To compare the clinical outcomes and the radiographic features between tibial condylar valgus osteotomy (TCVO) and open wedge high tibial osteotomy (OWHTO). New insight into the indication criteria for TCVO was also clarified for achieving satisfactory results.

MATERIALS AND METHODS

Sixty-three knees with medial-compartment osteoarthritis were retrospectively studied. Thirty-four knees with subluxated lateral joint and depression of the medial tibial plateau underwent TCVO and the rest underwent OWHTO. Among the 63 knees included, 27 knees with a pre-operative femorotibial angle (FTA) ≥ 185° were defined as severe varus (subgroup S, 15 in S_TCVO group and 12 in S_HTO group). Lower limb alignment, intra-, and extra-articular congruency were evaluated according to the radiograph obtained before and 24 months after surgery. The visual analog scale (VAS) score and Hospital for Special Surgery (HSS) score were obtained to assess the clinical results. Opening angle and distance of the opening gap in each group were measured by intra-operative fluoroscopy.

RESULTS

During the 2-year follow-up period, the mean HSS score increased from 70.3 to 81.4 in HTO group and 65.9 to 87.3 in TCVO group (p < 0.05). The mean VAS score decreased from 5.9 to 2.6 and 6.0 to 2.1, respectively (p < 0.01). Pre-operative FTA was restored to 172.9° in HTO group and 171.3° in TCVO group, and percentage of mechanical axis (%MA) was improved to 59.7% and 61.2%, respectively. Joint line convergence angle (JLCA) was slightly restored and medial tibial plateau depression (MTPD) was relatively the same before and after OWHTO, while these parameters improved greatly (from 6.4° to 1.2° and - 8.0° to 5.9°, p < 0.01) in TCVO group. More undercorrected knees were observed in S_HTO group than S_TCVO group (58.3% and 13.3%, p < 0.05). Opening angle and distance of the opening gap were larger in TCVO group (19.1° and 14.0 mm) than those in OWHTO group (9.3° and 10.1 mm, p < 0.05).

CONCLUSION

Compared to OWHTO, TCVO had priority in treating advanced knee OA with intra-articular deformity. However, TCVO had a limited capacity to correct the varus angle. Besides, TCVO might be suitable for medial-compartment OA with a pre-operative FTA ≥ 185°.

Patient-specific high tibial osteotomy for varus malalignment: 3D-printed plating technique and review of the literature

PURPOSE

We report our experience with a 3D patient-specific instrument (PSI) in an opening-wedge tibial osteotomy for the correction of varus malalignment in a patient with prior anterior cruciate ligament reconstruction. Previous studies have not reported the use of 3D PSI in patients with prior knee surgeries.

METHODS

A pre-operative CT was used to create a 3D model of the lower extremity using Bodycad Imager. The pre-operative medial proximal tibial angle (MPTA), lateral distal femoral ankle, hip-knee-ankle (HKA), and tibial slope were calculated. The Bodycad Osteotomy software package was used to create a simulated osteotomy and correction. The resulting 3D patient-specific surgical guide and plate were used to conduct the high tibial osteotomy. Radiographic measurements and range of motion were evaluated at 6-week follow-up.

RESULTS

The arthroscopy and open portions of the procedure were performed in 65 min, with only three fluoroscopy shots taken intraoperatively. At 6-week follow-up, the patient had 125° of flexion and minimal pain. The angular correction of the bone was achieved within 1.9° (planned MPTA 91.9° vs. actual 90°); the HKA angle was achieved with an error of 0.7° (planned 2.4° vs. actual 1.7°); and there was no change in the posterior tibial slope (planned 13.5° vs 13.8° actual).

CONCLUSION

Three-dimensional PSI can be successfully used for the accurate and efficient correction of varus malalignment while accommodating pre-existing hardware, with good short-term clinical outcomes.

Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?

INTRODUCTION

Preoperative planning in high tibial osteotomy (HTO) is a critical step for achieving the desired correction and a clinically satisfactory outcome. Conventional radiography, navigation assistance and patient-specific instrumentation (PSI) are the 3 means of planning, but no prospective studies have compared precision between the 3. The aims of the present study were: (1) to analyze and compare correction precision between the 3 planning approaches at 1 year's follow-up; (2) to compare results to those reported in the literature; and (3) to analyze factors influencing the achievement of planned correction.

HYPOTHESIS

The study hypothesis was that PSI provides more precise and reproducible planned correction than conventional methods or navigation.

MATERIAL AND METHOD

Between June 2017 and June 2018, a multicenter non-randomized prospective observational study was conducted in 11 centers. One hundred and twenty-six patients with Ahlbäck grade I, II or III idiopathic medial tibiofemoral osteoarthritis with stable knee were included and allocated to 3 preoperative planning groups: conventional (group 1), navigation (group 2) and PSI (group 3). Mean age at surgery was 51.2 years (range, 19-69 years; median, 53.2 years); 100 male, 26 female. Complete weight-bearing radiographic work-up was performed preoperatively and at 1 year's follow-up. The PSI group also underwent CT as part of guide production. Target angular correction and mechanical Hip-Knee-Ankle (HKA) axis were set preoperatively. The main endpoint was the difference between planned HKA and HKA at a minimum 12 months.

RESULTS

Mean HKA difference was 1.1±3 in group 1, 2.1±2.6 in group 2 and 0.3±3.1 in group 3. Precision was better with PSI, but not significantly when comparing all 3 groups together. On pairwise intergroup comparison, there was a significant difference only between groups 2 and 3, in favor of PSI (P=0.011).

DISCUSSION

None of the 3 techniques demonstrated superiority in achieving target correction at 1 year. The study hypothesis was thus not confirmed. All 3 techniques proved reliable and precise in HTO planning.

LEVEL OF EVIDENCE

III, prospective non-randomized comparative study.

The relationship between the posterior tibial slope and the sagittal femoral condylar shape: Two circles and ellipses

BACKGROUND

Whether the posterior tibial slope (PTS) is associated with the femoral condylar shape has remained unclear. Classical anatomical studies considered the sagittal profiles of femoral condyles to consist of two circles. Recently, an elliptical method was described to simplify the "two circles" model. Our purpose was to analyze the relationship between the PTS and the shape of the sagittal femoral condyle, that is, two circles and two ellipses, using magnetic resonance imaging (MRI) scans.

METHODS

Eighty right knees of healthy subjects were scanned by MRI at full extension. The medial and lateral PTS were measured (mPTS and lPTS). On the distal-most medial and lateral slices, the femoral condylar articular surfaces were best fitted by circles or ellipses, respectively. The radii of the medial and lateral posterior circles and inferior circles (r_m and r_l , R_m and R_l , respectively), the semi-major axes and the semi-minor axes of the medial and lateral ellipses (a_m and a_l , b_m and b_l , respectively), and the r_m /R_m , b_m /a_m , r_l /R_l , b_l /a_l ratios were measured and calculated.

RESULTS

mPTS correlated significantly with the parameters of the medial condyle (all p < .05) and the ratios b_m /a_m and r_m /R_m (p = .017 and p = .027, respectively). However, the lPTS did not correlate with the parameters of the lateral condyle (all p > .05) or the ratios b_l /a_l and r_l /R_l (p = .461 and p = .241, respectively).

CONCLUSION

The mPTS is associated with the sagittal shape of the medial femoral condyle but the lPTS is not. Both two circles and two ellipses are feasible ways to represent the sagittal femoral condylar shape.

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.

Joint line convergence angle predicts outliers of coronal alignment in navigated open-wedge high tibial osteotomy

INTRODUCTION

Using a navigation system in open-wedge high tibial osteotomy (OWHTO) has higher accuracy than using the conventional method. However, unintentional over- and under-correction still exist. This study aimed to compare various factors related to over- and under-correction and to assess their predictive factors in the preoperative radiographs.

MATERIALS AND METHODS

This study involved 96 knees. The difference in the hip-knee-ankle angle (HKA) between the intraoperative navigation system and postoperative radiograph was termed navigation correction loss (NCL). Knees with absolute values of NCL (|NCL|) ≦ 1.5° and |NCL| > 1.5° were categorised into acceptable (n = 46) and outlier (n = 50) groups, respectively. The differences in joint line convergence angle (JLCA) between varus and valgus radiographs, varus JLCA, valgus JLCA, standing JLCA and standing HKA were compared between the two groups. Clinical results were evaluated using the American Knee Society (AKS) scores.

RESULTS

The mean intraoperative HKA in the navigation system was - 3.8 ± 1.8°, and that in the postoperative standing radiograph was - 4.2 ± 2.5° (p = 0.033). Preoperative varus, valgus and standing JLCA were higher in the outlier group (p = 0.018, p = 0.020 and p = 0.001, respectively). Logistic regression analyses for preoperative factors of |NCL| ≦ 1.5° showed that standing JLCA was a determining factor, with an odds ratio of 1.334 (confidence interval was 1.087-1.637, p = 0.006). AKS score was higher in the acceptable group (p = 0.040) postoperatively.

CONCLUSIONS

Higher preoperative standing JLCA was the predictive factor of |NCL| > 1.5°. This factor reduced the rates of under- and over-correction and resulted in better AKS score in OWHTO.

Classical target coronal alignment in high tibial osteotomy demonstrates validity in terms of knee kinematics and kinetics in a computer model

PURPOSE

The purpose of this study was to determine the ideal coronal alignment under dynamic conditions after open-wedge high tibial osteotomy (OWHTO). It was hypothesised that, although the classical target alignment was based on experimental evidence, it would demonstrate biomechanical validity.

METHODS

Musculoskeletal computer models were analysed with various degrees of coronal correction in OWHTO during gait and squat, specifically with the mechanical axis passing through points at 40%, 50%, 60%, 62.5%, 70%, and 80% of the tibial plateau from the medial edge, defined as the weight-bearing line percentage (WBL%). The peak load on the lateral tibiofemoral (TF) joint, the medial collateral ligament (MCL), and anterior cruciate ligament (ACL) tensions, and knee kinematics with or without increased posterior tibial slope (PTS) were evaluated.

RESULTS

The classical alignment with WBL62.5% achieved sufficient load on the lateral TF joint and maintained normal knee kinematics after OWHTO. However, over-correction with WBL80% caused an excessive lateral load and non-physiological kinematics. Increased WBL% resulted in increased MCL tension due to lateral femoral movement against the tibia. With WBL80%, abnormal contact between the medial femoral condyle and the medial intercondylar eminence of the tibia occurred at knee extension. The screw-home movement around knee extension and the TF rotational angle during flexion were reduced as WBL% increased. Increased PTS was associated with increased ACL tension and decreased TF rotation angle because of ligamentous imbalance.

CONCLUSIONS

The classical target alignment demonstrated validity in OWHTO, and over-correction should be avoided as it negatively impacts clinical outcome.

LEVEL OF EVIDENCE

IV.

Preoperative latent medial laxity and correction angle are crucial factors for overcorrection in medial open-wedge high tibial osteotomy

PURPOSE

This study aimed to determine which preoperative factors affect the postoperative change in the joint line convergence angle (JLCA) by preoperatively quantifying soft tissue laxity.

METHODS

Thirty-four patients who underwent medial open-wedge high tibial osteotomy (HTO) with a navigation were analysed. The JLCA change after HTO was calculated using standing long-bone anteroposterior radiographs taken preoperatively and 6 months postoperatively. Latent soft tissue laxity was defined as the amount of soft tissue that can be extended to valgus or varus from the weight-bearing position, and calculated by subtracting the JLCA on weight-bearing standing radiographs from that on stress radiographs. Multiple linear regression was performed to determine the preoperative factors that statistically correlated with the postoperative JLCA change.

RESULTS

In multiple linear regression, JLCA change had a statistically significant correlation with latent medial laxity (R = 0.6) and a statistically borderline significant correlation with correction angle (R = 0.2). These imply that the postoperative JLCA change increased by 0.6° per 1° increase in latent medial laxity, and increased by 0.2° per 1° increase in correction angle. Latent medial laxity was the most crucial factor associated with postoperative JLCA changes.

CONCLUSION

The JLCA change could be larger in patients with large latent medial laxity or severe varus deformity requiring a large correction, which could lead to unexpected overcorrection in HTO. Postoperative JLCA change should be considered in preoperative surgical planning. Target point shifting within the hypomochlion point could be a strategy to prevent overcorrection, especially in patients with large latent medial laxity.

LEVEL OF EVIDENCE

Level IV.

Severe varus knees result in a high rate of undercorrection of lower limb alignment after opening wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clarify the indication for opening wedge high tibial osteotomy (OWHTO) in terms of lower limb alignment to achieve satisfactory clinical results.

METHODS

Ninety-two patients (98 knees) with medial compartment knee osteoarthritis were investigated in this study. The average follow-up period was 34 months (range, 24-68 months). The average age of the patients at the time of surgery was 63 years (range, 41-77 years).

RESULTS

The patients were divided into the following two groups according to the preoperative femorotibial angle (FTA) on anteroposterior full-length radiographs of the lower limbs while weight bearing: 29 knees with a preoperative FTA of ≥185° were defined as those with severe varus (S group), and the remaining 69 knees with a preoperative FTA of <185° were defined as those with mild varus (M group). Knees with a postoperative FTA of >175° were defined as undercorrected. The Lysholm score was used to assess the clinical results. The average postoperative FTA was 175.7° ± 4.1° in the S group and 174.6° ± 3.1° in the M group ( p = 0.013). Significantly, more undercorrected knees were observed in the S than M group ( p = 0.00035). The postoperative Lysholm score was 85.6 ± 8.5 in the S group and 88.5 ± 5.7 in the M group at the last follow-up ( p = 0.0033).

CONCLUSION

Based on these results, we recommend that a preoperative FTA of <185° should be included as a criterion for OWHTO alone.

Preoperative planning of medial opening wedge high tibial osteotomy using 3D computer-aided design weight-bearing simulated guidance: Technique and preliminary result

BACKGROUND

High tibial osteotomy (HTO) is an established treatment for uni-compartmental osteoarthritis with varus deformity in relatively active young patients with good knee mobility. The most important factor for success and low complications of HTO is the precise correction of osteotomy. The objective of this study was to evaluate the accuracy of pre-operative planning of open-wedge HTO using t3D computer-aided design (CAD) weight-bearing simulated guidance technique for the succession of surgery.

MATERIALS AND METHODS

Nineteen patients who met the inclusion criteria were recruited between July 2013 and June 2014. 3D CAD weight-bearing simulated guidance technique was obtained from standard anterior-posterior, lateral of hip-to-ankle full leg standing radiographs, and computed tomography (CT) scan provided the weight-bearing corrective axis of preoperative planning and predictive corrective mechanical axis value. Post-operative mechanical axis value was obtained after surgery.

RESULTS

This comparative study between the predictive corrective, using 3D CAD weight-bearing simulated guidance technique, and post-operative mechanical axis value, analysed with t-test statistical analysis, showed the insignificant difference ( p > 0.05).

CONCLUSION

We conclude that the 3D CAD weight-bearing simulated guidance technique has good accuracy as preoperative planning of open-wedge HTO for succession surgery.

The Use of Navigation in Osteotomies Around the Knee

Osteotomies around the knee for treating osteoarthritis or knee instability are currently well-established procedures. Success of these realignment procedures is based on the accuracy and the reliability of correction angles in the coronal and sagittal alignment. In this context of improving precision and adapting the correction to each patient, navigation is currently being widely used. The rationale for its use is based on understanding the advantages and limitations, technical principles, and potential pitfalls. This article describes these areas and the overall clinical outcomes of this system for knee osteotomies.

[Complication analysis after angle-stable CW and OW high tibial osteotomy]

BACKGROUND

High tibial osteotomy (HTO) is a good joint-preserving alternative to joint replacement in the treatment of isolated medial varus gonarthrosis. It is, however, accompanied by a number of complications, which can compromise the outcome of the treatment.

OBJECTIVES

Analysis and comparison of the complication structure after angle-stable navigated closed wedge (CW) HTO and conventional angle-stable open wedge (OW) HTO, as well as determination of influence factors.

MATERIAL AND METHODS

281 HTO (187 CW- and 94 OWHTO) were analyzed retrospectively. Age, sex, BMI, time of surgery and radiological parameters were included as possible influence factors. A statistical analysis was performed with binary logistic regression.

RESULTS

An overall complication rate of 21.4% was revealed (25.1% after CW- and 13.8% after OWHTO, p = 0.02); the major complications occurred after 13.9% CW- and 10.6% OWHTO (p = 0.27); minor complications were observed after 11.2% CW- and 3.2% OWHTO (p = 0.03). This difference results from complications specific to CWHTO (peroneal lesions and pseudarthrosis fibulae). The incidence of pseudarthrosis tibiae was equal in both procedures (7.5%). Age ≥ 52 years and body mass index (BMI) ≥ 30 kg/m² were the relevant predictors for mechanical complications after CWHTO; these were not relevant for OWHTO.

CONCLUSION

The correct patient selection is essential to avoid postoperative complications after HTO. The overall complication rates are lower after OWHTO, mainly through the avoidance of complications typical for CWHTO. OWHTO offers a wider choice with respect to the selection of patients.

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.

Navigation for lower limb alignment during internal fixation of complex tibial-plateau fractures

In complex fractures of the proximal tibial metaphysis and epiphysis, possible adverse outcomes after internal fixation include not only joint surface incongruity, but also lower limb malalignment requiring revision surgery. Navigation has been proven effective for the intraoperative control of lower limb alignment during osteotomy and knee arthroplasty. In complex traumatic fractures, temporary fixation by a locking screw plate allows sensor positioning followed by navigation maneuvers to adjust lower limb alignment. If malalignment is found, the construct can be modified economically by altering the diaphyseal fixation without modifying the metaphyseal screws. The objective of this study was to describe the use of navigation in three patients who required internal fixation of tibial-plateau fractures.

Clinical Experience Using a 3D-Printed Patient-Specific Instrument for Medial Opening Wedge High Tibial Osteotomy

Purpose

High tibial osteotomy (HTO) has been adopted as an effective surgery for medial degeneration of the osteoarthritis (OA) knee. However, satisfactory outcomes necessitate the precise creation and distraction of osteotomized wedges and the use of intraoperative X-ray images to continually monitor the wedge-related manipulation. Thus HTO is highly technique-demanding and has a high radiation exposure. We report a patient-specific instrument (PSI) guide for the precise creation and distraction of HTO wedge.

Methods

This study first parameterized five HTO procedures to serve as a design rationale for an innovative PSI guide. Preoperative X-ray and computed tomography- (CT-) scanning images were used to design and fabricate PSI guides for clinical use. The weight-bearing line (WBL) of the ten patients was shifted to the Fujisawa's point and instrumented using the TomoFix system. The radiological results of the PSI-guided HTO surgery were evaluated by the WBL percentage and tibial slope.

Results

All patients consistently showed an increased range of motion and a decrease in pain and discomfort at about three-month follow-up. This study demonstrates the satisfactory accuracy of the WBL adjustment and tibial slope maintenance after HTO with PSI guide. For all patients, the average pre- and postoperative WBL are, respectively, 14.2% and 60.2%, while the tibial slopes are 9.9 and 10.1 degrees. The standard deviations are 2.78 and 0.36, respectively, in postoperative WBL and tibial slope. The relative errors of the pre- and postoperative WBL percentage and tibial slope averaged 4.9% and 4.1%, respectively.

Conclusion

Instead of using navigator systems, this study integrated 2D and 3D preoperative planning to create a PSI guide that could most likely render the outcomes close to the planning. The PSI guide is a precise procedure that is time-saving, radiation-reducing, and relatively easy to use. Precise osteotomy and good short-term results were achieved with the PSI guide.

Comparison of navigated and conventional high tibial osteotomy for the treatment of osteoarthritic knees with varus deformity: A meta-analysis

BACKGROUND

High tibial osteotomy (HTO) is a usefully surgical procedure to correct the malalignment and delay the progression of osteoarthritis. It is still controversy whether navigation system can offer more accuracy of targeted alignment and achieve better clinical outcomes than conventional method. The purpose of present meta-analysis was to investigate whether navigation system was superior to conventional method with regard to clinical and radiographic outcomes.

METHOD

The included studies compared the clinical and radiographic outcomes between navigated HTO group and conventional group. The clinical assessments were Lysholm Score, AKS Function Score and Arc of motion, and the radiographic outcomes were Mechanical axis (MA), Weight bearing line ratio (WBL), Outliers of alignment and Change in TPS used to evaluate alignment correction. The meta-analysis was performed using Review Manager 5.3 software. Downs and Black and the Newcastle-Ottawa Scale (NOS) were used to evaluate the study quality.

RESULT

Sixteen studies were eligible in present meta-analysis, including thirteen studies concerning opening wedge HTO and three studies involving closing wedge HTO. Clinical outcomes were only reported in studies which used opening wedge HTO. No significant differences were observed in all clinical outcomes between navigated and conventional HTO. Regarding radiographic outcomes, no significant difference in WBL ratio was observed between navigated and conventional HTO. Patients undergoing navigated HTO were associated with significantly greater in MA and lower in Outliers of alignment compared with those undergoing conventional HTO. Compared with conventional HTO, increase in TPS was significantly lower in navigated HTO group using opening wedge HTO, but decrease in TPS was significantly greater in navigated HTO group using closing wedge HTO.

CONCLUSION

Our meta-analysis demonstrated that navigated HTO offered more accuracy and precision of alignment correction, except WBL ratio. However, better clinical outcomes were not observed in navigation group.

Effect of Computer Navigation on Accuracy and Reliability of Limb Alignment Correction following Open-Wedge High Tibial Osteotomy: A Meta-Analysis

Background

It is unclear whether computer navigation can improve the accuracy and reliability of targeted lower limb alignment correction following open-wedge high tibial osteotomy (HTO). This meta-analysis was designed to compare the accuracy and reliability of limb alignment correction between computer navigated and conventional open-wedge HTOs.

Methods

Studies that compared postoperative coronal alignment, including mechanical axis (MA) and weight bearing line (WBL) ratio, outliers of alignment correction, and change in tibial posterior slope, following open-wedge HTO performed using computer navigated and conventional methods were included.

Results

Ten studies were included in the meta-analysis. The MA (0.93°; 95% confidence interval [CI]: 0.45–1.41°; P < 0.001) and WBL ratio (1.5%; 95% CI: 0.03–2.98%; P = 0.048) were significantly greater for computer navigated HTO than for conventional HTO. Outliers of alignment correction after surgery were significantly lower in patients who underwent computer navigated HTO than in those who underwent conventional HTO (odds ratio: 0.25; 95% CI: 0.08–0.79; P = 0.02). Changes in posterior tibial slope from before to after surgery, however, were similar for the two approaches.

Conclusion

Computer navigated HTO resulted in slightly more valgus postoperative alignment and effectively reduced outliers of alignment correction but had no effect on change in posterior tibial slope when compared with conventional HTO.

Assessing accuracy requirements in high tibial osteotomy: a theoretical, computer-based model using AP radiographs

PURPOSE

High tibial osteotomy (HTO) is a recognised treatment for medial compartment knee arthritis and in recent years has regained popularity. Preoperative planning of wedge opening is based on standing AP radiographs, aiming to deliver the WBL to a desired point. Clinical results can be unpredictable, and this may be due to an inability to deliver the preoperative plan. This study explores the theoretical wedge opening accuracy required to deliver preoperative plans, based on clinical AP radiographs.

METHODS

A theoretical 2-D model of osteotomy was developed to determine the degree of radiological wedge opening accuracy required to deliver the weight-bearing line to a preoperative target of 62-66 % of the width of the tibial plateau.

RESULTS

This model suggests that, to deliver the weight-bearing line to the preoperative target on plane radiographs, the theoretical medial wedge must be opened to an accuracy of ±0.9 mm.

CONCLUSION

Although this study only explores a model of wedge opening based on AP radiographs, with current surgical systems, it is unlikely that the surgeon can achieve this level of accuracy within a real-life surgical setting. Surgical accuracy in HTO is known to be important for both short- and long-term clinical outcomes. This study highlights the need for improved surgical accuracy aids and/or patient stratification to mitigate the effects of surgical errors.

LEVEL OF EVIDENCE

II.

Intraoperative adjustment of alignment under valgus stress reduces outliers in patients undergoing medial opening-wedge high tibial osteotomy

INTRODUCTION

A considerable percentage of outliers with under- or over-correction continue to be reported despite precise preoperative planning and cautious intraoperative correction of lower limb alignment in medial opening-wedge high tibial osteotomy (MOWHTO). The purpose of this study was to determine whether our novel technique for the intraoperative adjustment of alignment under valgus stress reduces the number of outliers in patients undergoing MOWHTO compared to the conventional technique, which corrects alignment according to the cable method only.

MATERIALS AND METHODS

One hundred seventeen consecutive knees were enrolled in this case-control study. The first 52 knees (51 patients) were corrected in accordance with preoperative plans using the Dugdale method with modification with an intraoperative cable (group 1). In the other 65 knees (60 patients), the angle was corrected using the Dugdale method and limb alignment was adjusted using the intraoperative cable technique by applying valgus stress to the knee joint (group 2). The postoperative weight bearing line ratios and mechanical axis of the lower limb were compared at postoperative one year. Each knee was evaluated according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score preoperatively and at postoperative one year.

RESULTS

A significant reduction in the number of outliers was seen in group 2 compared to group 1 (group 1 = 48.1%, group 2 = 9.2%, p < 0.001). Nineteen of 52 knees (36.5%) were under-corrected in group 1, whereas 6 of 65 knees (9.2%) were under-corrected in group 2 (p < 0.001). Six of 52 knees (11.6%) were over-corrected in group 1, whereas 0 of 65 knees (0.0%) were over-corrected in group 2 (p = 0.005). At one -year after operation, group 2 showed significantly lower WOMAC score than group 1 (p = 0.014).

CONCLUSIONS

Intraoperative adjustment of alignment under valgus stress significantly reduced the number of outliers compared to a technique that corrected alignment using the cable method in patients undergoing MOWHTO.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Sports and Physical Activities of Elderly Patients with Medial Compartment Knee Osteoarthritis after High Tibial Osteotomy

Objective

We retrospectively investigated the preoperative and postoperative sports and physical activities (SPA) of elderly patients with medial compartment knee osteoarthritis who underwent opening-wedge high tibial osteotomy (OWHTO).

Methods

Fifty-six patients (62 knees) with medial compartment knee osteoarthritis were included in the study. The patients comprised 45 women and 11 men with a mean age at surgery of 71.6 years (range, 65-81 years). The mean follow-up period was 51±7 months. Patients who performed SPA to maintain their health for at least 30 min per session more than once a week were defined as SPA cases. The preoperative and postoperative ratios of SPA cases, the time to resuming or starting postoperative SPA, and the frequency of performing postoperative SPA were investigated. Clinical results were assessed using the Lysholm score.

Results

Fifteen patients (26.7%) performed SPA before OWHTO and 14 (25.0%) performed SPA after OWHTO (P=0.21). The mean time to resuming or starting SPA after surgery was 14.1±10.0 months, and the frequency of postoperative SPA sessions was 4.2±2.1 per week. The mean Lysholm score significantly improved from 60.8±8.9 preoperatively to 92.5±2.5 postoperatively (P<0.0001).

Conclusion

The ratio of patients who performed SPA after OWHTO was still <30% , and it took a comparatively long time for patients to resume or start SPA after surgery.

Is overcorrection preferable for repair of degenerated articular cartilage after open-wedge high tibial osteotomy?

PURPOSE

This study was performed to determine whether the overcorrected knee could obtain a higher ratio of articular cartilage repair in the medial compartment of the femorotibial joint after open-wedge high tibial osteotomy (HTO). The hypothesis of the study was that overcorrected knees had a higher ratio of articular cartilage repair than moderately corrected knees.

METHODS

A total of 71 knees that underwent arthroscopy to evaluate the articular cartilage during open-wedge HTO and second-look arthroscopy were reviewed. The articular cartilage was classified as no repair or repair according to Koshino et al. Overcorrection was defined as knees with femorotibial angle ≤166°.

RESULTS

Second-look arthroscopy was performed 410 ± 64 days after HTO. Based on arthroscopic observations, 45 knees (63.4 %) showed no repair and 26 knees (36.6 %) showed repair. In terms of the ratio of cartilage repair, there was no difference between overcorrected knees with mean femorotibial angle of 165° ± 1° and moderately corrected knees with mean femorotibial angle of 170° ± 2° (n.s.).

CONCLUSIONS

No significant differences were found in the ratio of cartilage repair between overcorrected and moderately corrected knees.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Comparing the accuracy of high tibial osteotomies between computer navigation and conventional methods

BACKGROUND

The accuracy of correction has been shown to be an important determinant in long-term outcomes of patients who were treated with a medial open-wedge high tibial osteotomy (HTO) who suffer from unicompartmental osteoarthritis (OA). Computer navigation systems have the potential to improve surgical precision. The purpose of this study was to compare radiographic outcomes between patients treated with a navigation system and those treated through conventional methods of assessing alignment intra-operatively. The null hypothesis was that the method of assessing the alignment intra-operatively would make no difference in the accuracy of correction.

METHODS

In this retrospective study, 107 patients with medial varus OA who were managed by open-wedge HTO were included. Of the 107 patients, 41 were treated using an intraoperative navigation system and 66 were treated using conventional methods. Pre-operative and post-operative single-leg, long-leg standing alignment films were used to determine the extent of pre-operative varus deformity and the post-surgical correction achieved compared to the predetermined target range.

RESULTS

The navigational system had eight instances of software malfunction (19.5%) intra-operatively and correction was determined using the cable method. These results were analyzed as part of the conventional group. Post-operative radiographic differences were significant between the two groups. In the navigation group, 75.8% of the patients were corrected within the target range compared to 66.2% in the conventional group. More patients were also under corrected (to the point of remaining in varus) using conventional methods compared to a navigation system. There was no statistically significant difference in the degree of correction in the sagittal plane between the two groups. Regardless of the method used for checking alignment intra-operatively, there was a statistically significant difference in post-operative weight-bearing measurements when the surgeon had intra-operative axial loading versus when they did not.

CONCLUSION

For coronal plane corrections, the navigation system was shown to have greater success in achieving the desired correction value and in having fewer patients who were under corrected. Despite the measurement technique a surgeon chooses to assess the accuracy of correction, axial loading the extremity in order to simulate the weight-bearing film alignment post-operatively is important to maximize the accuracy of correction needed.

The effect of distal tibial rotation during high tibial osteotomy on the contact pressures in the knee and ankle joints

PURPOSE

Intraoperative fracture of the lateral cortex fractures of the tibia is a potential complication of high tibial osteotomy (HTO), which may result in inadequate rotational alignment of the distal tibia. Our aim was to determine how rotational malalignment of the distal tibial segment distal would affect intraarticular contact pressure distribution in the knee and ankle joints.

METHODS

A medial, L-shaped opening-wedge HTO was performed on seven human lower body specimens. A stainless steel device with integrated load cell was used to axially load the leg. Pressure-sensitive sensors were used to measure intraarticular contact pressures. Intraoperative changes in alignment were monitored in real time using computer navigation. Measurements were performed in the native knee alignment, after 10° and 15° of alignment correction and with the distal tibia fixed at 15° of external rotation.

RESULTS

Moderate-to-large alignment changes after medial opening-wedge HTO resulted in a shift in intraarticular contact pressures from the medial compartment of the knee towards the lateral compartment. However, fixation of the distal tibial segment at 15° of external rotation neutralized this intended beneficial effect. In the ankle, external rotation of the distal tibia also caused a reduction in contact pressures and tibiotalar contact area.

CONCLUSION

Malrotation of the distal tibial fragment negates the intended effect of offloading the diseased compartment of the knee, with the contact pressures remaining similar to those of the native knee. Furthermore, malrotation leads to abnormal ankle contact pressures. Care should be taken to ensure appropriate rotational alignment of the distal tibial segment during intraoperative fixation of HTO procedures.

Differences in Medial and Lateral Posterior Tibial Slope: An Osteological Review of 1090 Tibiae Comparing Age, Sex, and Race

BACKGROUND

Injuries to the anterior cruciate ligament (ACL) are common, and a number of knee morphological variables have been identified as risk factors for an ACL injury, including the posterior tibial slope (TS). However, limited data exist regarding innate population differences in the TS.

PURPOSE

To (1) establish normative values for the medial and lateral posterior TS; (2) determine what differences exist between ages, sexes, and races; and (3) determine how internal or external tibial rotation (as occurs during sagittal knee motion) influences the stereotactic perception of the TS.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 545 cadaveric specimens (1090 tibiae) were obtained from the Hamann-Todd osteological collection. Specimens were leveled in the coronal, sagittal, and axial planes using a digital laser. Virtual representations of each bone were created with a 3-dimensional digitizer apparatus. The TS of the medial and lateral tibial plateaus were measured using techniques adapted from previous radiographic protocols. Medial and lateral TS were then again measured on 200 tibiae that were internally and externally rotated by 10° (axially).

RESULTS

The mean (±SD) medial TS was 6.9° ± 3.7° posterior, which was greater than the mean lateral TS of 4.7° ± 3.6° posterior ( P < .001). Neither the medial nor lateral TS changed with age. Women had a greater mean TS compared with men on both the medial (7.5° ± 3.8° vs 6.8° ± 3.7°, respectively; P = .03) and lateral (5.2° ± 3.5° vs 4.6° ± 3.5°, respectively; P = .04) sides. Black specimens had a greater mean medial TS (8.7° ± 3.6° vs 5.8° ± 3.3°, respectively; P < .001) and lateral TS (5.9° ± 3.3° vs 3.8° ± 3.5°, respectively; P < .001) compared with white specimens. Axial rotation was shown to increase the perception of the medial and lateral TS ( P < .001).

CONCLUSION

The medial TS was shown to be greater than the lateral TS. Important sex- and race-based differences exist in the TS. This study also highlights the role of axial rotation in measuring the TS.

Coronal subluxation of the proximal tibia relative to the distal femur after opening wedge high tibial osteotomy

BACKGROUND

The coronal subluxation of the proximal tibia relative to the distal femur is a common radiological finding in patients with knee osteoarthritis. The purpose was to evaluate whether the coronal subluxation was corrected after opening wedge high tibial osteotomy (OWHTO), and whether this subluxation was one cause of inconsistency between the actual and predicted alignments (correction loss).

METHODS

Fifty-one patients (55 knees) were treated with OWHTO. The change of location between the intersection points of the femoral and tibial axes on the tibial plateau (subluxation-C), the change of location between the lines through the most lateral points of the lateral femoral and tibial condyles (subluxation-L), and joint space angle (JSA) were compared in standing knee radiographs before and one year after OWHTO. The subluxation-C and subluxation-L were converted to a percentage of the tibial plateau width.

RESULTS

The mean subluxation-C of 6.5% before OWHTO significantly increased to a mean subluxation-C of 7.3% one year after OWHTO. The mean subluxation-L of 6.3% and JSA of 4.5° before OWHTO significantly decreased to a subluxation-L of 1.8% and JSA of 3.3° one year after OWHTO. The change in subluxation-L correlated with the change in femorotibial angle and correction loss (r=0.634, P<0.001 and r=0.463, P<0.001, respectively).

CONCLUSION

The proximal tibia shifted medially relative to the distal femur after OWHTO. This medial shift correlated with the correction loss. The coronal subluxation might be one cause of correction loss.

Computer-Assisted Navigation in High Tibial Osteotomy

Computer-assisted navigation is used to improve the accuracy and precision of correction angles during high tibial osteotomy. Most studies have reported that this technique reduces the outliers of coronal alignment and unintended changes in the tibial posterior slope angle. However, more sophisticated studies are necessary to determine whether the technique will improve the clinical results and long-term survival rates. Knowledge of the navigation technology, surgical techniques and potential pitfalls, the clinical results of previous studies, and understanding of the advantages and limitations of the computer-assisted navigation are crucial to successful application of this new technique in high tibial osteotomy. Herein, we review the evidence concerning this technique from previous studies.

Outcome reporting following navigated high tibial osteotomy of the knee: a systematic review

PURPOSE

This systematic review evaluates radiographic and clinical outcome reporting following navigated high tibial osteotomy (HTO). Conventional HTO was used as a control to compare outcomes and furthermore investigate the quality of evidence in studies reporting outcomes for navigated HTO. It was hypothesized that navigated HTO will show superior clinical and radiographic outcomes compared to conventional HTO.

METHODS

Two independent reviewers searched PubMed, Ovid (MEDLINE), EMBASE, and Cochrane databases for studies reporting outcomes following navigated HTO. Titles, abstracts, and full-text were screened in duplicate using an a priori inclusion and exclusion criteria. Descriptive statistics were calculated using Minitab ^® statistical software. Methodological Index for Nonrandomized Studies (MINORS) and Cochrane Risk of Bias Scores were used to evaluate methodological quality.

RESULTS

Thirty-four studies which involved 2216 HTOs were analysed in this review, 1608 (72.6 %) navigated HTOs and 608 (27.4 %) conventional HTOs. The majority of studies were of level IV evidence (16). Clinical outcomes were reported in knee and function scores or range of motion comparisons. Postoperative clinical and functional scores were improved by navigated HTO although it is not demonstrated if there is significant improvement compared to conventional HTO. Most common clinical outcome score reported was Lysholm scores (6) which report postoperative scores of 87.8 (standard deviation 5.9) and 88.8 (standard deviation 5.9) for conventional and navigation-assisted HTO, respectively. Radiographic outcomes reported commonly were weight-bearing mechanical axis, coronal plane angle, and posterior tibial slope angle in the sagittal plane. Studies have shown HTO gives significant correction of mechanical alignment and navigated HTO produces significantly less change in posterior tibial slope postoperatively compared to conventional. The mean MINORS for the 17 non-comparative studies was 9/16, and 15/24 for the 14 non-randomized comparative studies.

CONCLUSION

Navigation HTO results in improved mechanical axis alignment and demonstrates significantly better control over the tibial slope angle change postoperatively compared to conventional methods; however, these improvements have not yet been reflected in clinical outcome scores. Overall the studies report HTO does create significantly improved knee scores and functions compared to patients' preoperative ratings regardless of technique. Future studies on HTO outcomes need to focus on consistency of outcome reporting.

LEVEL OF EVIDENCE

IV.

Surgical accuracy in high tibial osteotomy: coronal equivalence of computer navigation and gap measurement

PURPOSE

Medial opening wedge high tibial osteotomy (MOW HTO) is now a successful operation with a range of indications, requiring an individualised approach to the choice of intended correction. This manuscript introduces the concept of surgical accuracy as the absolute deviation of the achieved correction from the intended correction, where small values represent greater accuracy. Surgical accuracy is compared in a randomised controlled trial (RCT) between gap measurement and computer navigation groups.

METHODS

This was a prospective RCT conducted over 3 years of 120 consecutive patients with varus malalignment and medial compartment osteoarthritis, who underwent MOW HTO. All procedures were planned with digital software. Patients were randomly assigned into gap measurement or computer navigation groups. Coronal plane alignment was judged using the mechanical tibiofemoral angle (mTFA), before and after surgery. Absolute (positive) values were calculated for surgical accuracy in each individual case.

RESULTS

There was no significant difference in the mean intended correction between groups. The achieved mTFA revealed a small under-correction in both groups. This was attributed to a failure to account for saw blade thickness (gap measurement) and over-compensation for weight bearing (computer navigation). Surgical accuracy was 1.7° ± 1.2° (gap measurement) compared to 2.1° ± 1.4° (computer navigation) without statistical significance. The difference in tibial slope increases of 2.7° ± 3.9° (gap measurement) and 2.1° ± 3.9° (computer navigation) had statistical significance (P < 0.001) but magnitude (0.6°) without clinical relevance.

CONCLUSION

Surgical accuracy as described here is a new way to judge achieved alignment following knee osteotomy for individual cases. This work is clinically relevant because coronal surgical accuracy was not superior in either group. Therefore, the increased expense and surgical time associated with navigated MOW HTO is not supported, because meticulously conducted gap measurement yields equivalent surgical accuracy.

LEVEL OF EVIDENCE

I.