Reliability of navigated lower limb alignment in high tibial osteotomies

What Is the Correlation between Coronal Plane Alignment Measured on Pre- and Postoperative Weight-bearing Radiographs and Intraoperative Navigation When Stress Is Applied to the Knee?

This study examines the correlation between the weight-bearing (WB) long leg radiograph (LLR)-derived hip-knee-ankle angle (HKAA) and intraoperative supine computer-assisted surgery (CAS)-derived HKAA measurements at the beginning and end of total knee arthroplasty (TKA). The primary aim of the study was to determine if WB alignment could be mimicked or inferred based on intraoperative alignment findings. We conducted a prospective analysis from a cohort of 129 TKAs undergoing a CAS TKA at a single center by a single surgeon. The HKAA was recorded using the CAS navigation system immediately postregistration of navigation data and after implantation of the prosthesis. The intraoperative HKAA was recorded in both the supine "resting" position of the knee and also while the knee was manipulated in an effort to replicate the patient's WB alignment. These measurements were compared with the HKAA recorded on pre- and postoperative WB LLRs. There was a strong correlation between the preoperative WB LLR HKAA and the intraoperative preimplant CAS-derived stressed HKAA (R = 0.946). However, there was no correlation between the postoperative WB LLR HKAA and the postimplant insertion HKAA as measured intraoperatively via CAS for either a "resting" or "stressed" position of the operated knee (R = 0.165 and R = 0.041, respectively). Thus, the interpretation of intraoperative alignment data is potentially problematic. Despite technological advances in the development and utilization of computer navigation and robotics in arthroplasty to help obtain the optimal alignment, it would seem apparent from our study that this alignment does not correlate to upright stance postoperatively. Surgeons should apply caution to the strength of assumptions they place on intraoperative coronal plane alignment findings.

3D osteotomies-improved accuracy with patient-specific instruments (PSI)

PURPOSE

Three-dimensional (3D) printed patient-specific instruments (PSI) have been introduced to increase precision and simplify surgical procedures. Initial results in femoral and tibial osteotomies are promising, but validation studies on 3D planning, manufacturing of patient-specific cutting blocks and 3D evaluation of the attained results are lacking.

METHODS

In this study, patient-specific cutting blocks and spacers were designed, fabricated, and used to perform a high tibial osteotomy (HTO). After segmentation of CT data sets from 13 human tibiae, 3D digital planning of the HTO was performed with a medial opening of 8 mm. These 3D models were used to fabricate patient-specific cutting blocks and spacers. After the surgical procedure, accuracy was evaluated measuring 3D joint angles and surface deviations.

RESULTS

The lowest mean deviation was found to be 0.57° (SD ± 0.27) for the MPTA. Medial and lateral tibial slope deviated from the 3D planning by an average of 0.98° (SD ± 0.53) and 1.26° (SD ± 0.79), respectively, while tibial torsion deviated by an average of 5.74° (SD ± 3.24). Color analysis of surface deviations showed excellent and good agreement in 7 tibiae.

CONCLUSION

With 3D cutting blocks and spacers, the 3D planning of the HTO can be translated into reality with small deviations of the resulting joint angles. Within this study, the results of the individual steps are examined for errors and thus a critical evaluation of this new and promising method for performing patient-specific HTOs is presented.

Superior survivorship and plate-related results of TomoFix compared to Puddu plate fixation for opening-wedge high tibial osteotomy: A systematic review of the literature

PURPOSE

This systematic review aimed to compare survivorship and plate-related results of Puddu and TomoFix plates in opening-wedge high tibial osteotomy (OWHTO).

METHODS

PubMed, Scopus, EMBASE, and CENTRAL databases were searched from January 2000 until September 2021 for clinical studies involving patients with medial compartment knee disease and varus deformity undergoing OWHTO using the Puddu or TomoFix plating systems. We extracted survival data, plate-related complications, and functional and radiological outcomes. The risk of bias assessment had been carried out using Cochrane Collaboration's quality assessment tool for randomised controlled trials (RCTs) and Methodological Index for Non-Randomised Studies (MINORS).

RESULTS

Twenty-eight studies were included. The total number of knees was 2568 in 2372 patients. The Puddu plate was used in 677 knees, while the TomoFix plate was used in 1891. The follow-up ranged from 5.8 to 147.6 months. Both plating systems were able to delay conversion to arthroplasty at different follow-up intervals. However, osteotomies fixed by the TomoFix plate achieved higher survival rates, especially at mid-term and long-term follow-ups. In addition, fewer complications were reported with the TomoFix plating system. Although both implants achieved satisfactory functional outcomes, high scores could not be maintained throughout long-term intervals. Regarding radiological results, TomoFix plate was able to achieve and maintain larger degrees of varus deformity, while preserving the posterior tibial slope.

CONCLUSIONS

This systematic review demonstrated the superiority of the TomoFix over the Puddu system as a safer and more effective fixation device in OWHTO. Nevertheless, these results should be interpreted with caution due to the lack of comparative evidence through high-quality RCTs.

Limb alignment changes with knee flexion: A study based on CAS data

BACKGROUND

Recent evidence has questioned the value of standing limb alignment for predicting the adduction moment and forces exerted on healthy and prosthetic knees. The purpose of this study was to assess the lower limb alignment of OA knee patients at various knee flexion angles. The main hypothesis was that lower limb alignment measured throughout knee flexion does not significantly differ between patients displaying different extension alignment (neutral, varus or valgus).

METHODS

206 arthritic knee patients undergoing computer-assisted total (CAS) knee prosthesis were included. Frontal limb alignment was assessed in a systematic manner by CAS at three knee positions: extension, 90 degrees of flexion and maximal flexion. The HKA angle at each knee position and the change in HKA angle between two knee positions (delta value) were reported and compared.

RESULTS

A large proportion of OA patients had significant variation in their lower limb alignment (32% with Δ HKA > 5°). The extended limb deformity tended to reduce with knee flexion: mean of 5° and 6° deformity reduction for varus and valgus patients, 40% and 66% of varus and valgus patients progressed to neutral alignment with 90° knee flexion. Forty percent of neutral extended lower limb did not maintain their neutral alignment but rather progressed to either varus or valgus at 90° knee flexion.

CONCLUSIONS

Limb alignment in extension is a poor predictor of limb alignment in flexion in OA patients. Only considering the traditional frontal alignment of an extended lower limb for planning knee arthroplasty or osteotomy is likely insufficient.

Optimal definitions for computing HKA angle in caos: an in-vitro comparison study

The goal of this study was to assess and compare the precision and accuracy of nine and seven methods usually used in Computer Assisted Orthopedic Surgery (CAOS) to estimate respectively the Knee Center (KC) and the Frontal Plane (FP) for the determination of the HKA angle (HKAA). An in-vitro experiment has been realized on thirteen cadaveric lower limbs. A CAOS software application was developed and allowed the computation of the HKAA according to these nine KC and seven FP methods. The precision and the accuracy of the HKAA measurements were measured. The HKAA precision was highest when the FP is determined using the helical method. The HKAA accuracy was highest using the helical approach to determine the FP and either the notch or the tibial spines to determine the KC. This study shows that the helical approach to determine the FP and either the notch or the middle of tibia spines are the combinations that provide both a good enough accuracy and precision to estimate the HKA.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

Level IV, retrospective study.

Patient-specific prediction of joint line convergence angle after high tibial osteotomy using a whole-leg radiograph standing on lateral-wedge insole

PURPOSE

To assess the usefulness of a whole-leg radiograph standing on lateral-wedge insole (LWI) for predicting the change in joint line convergence angle (JLCA) before vs. after high tibial osteotomy (HTO).

METHODS

Forty knees with medial osteoarthritis underwent open-wedge HTO. Pre-operatively, all patients had whole-leg radiographs taken in three different conditions: supine, standing, and standing on LWI inclined at 20°. A standing whole-leg radiograph was also obtained post-operatively. Radiological measurements including JLCA and percentage of mechanical axis (%MA) were compared. Using pre-operative radiographs, correction angles were calculated with the target %MA at 62.5%. Correlations between the difference in calculated correction angle among the three pre-operative conditions and the change in JLCA before vs. after HTO were assessed.

RESULTS

In the pre-operative standing conditions, the mean JLCA of 3.8° was significantly decreased to 3.2° using LWI, which did not differ from post-operative JLCA of 3.1°. Mean %MA significantly shifted laterally from 20.6 to 24.8% using LWI, and was strongly correlated with the change in JLCA (coefficient, 0.83). Calculated correction angles differed significantly among the three pre-operative conditions. The difference in calculated correction angle between standing with and without LWI was strongly correlated to the change in standing JLCA before vs. after HTO (coefficient, 0.73).

CONCLUSION

Larger differences in calculated correction angles between pre-operative radiographs standing with and without LWI predicted larger changes in JLCA after HTO. Whole-leg radiograph standing on LWI is a promising modality for correct pre-operative planning considering patient-specific changes in JLCA before vs. after HTO.

LEVEL OF EVIDENCE

IV.

The influence of computer-assisted surgery experience on the accuracy and precision of the postoperative mechanical axis during computer-assisted lateral closing-wedge high tibial osteotomy

Background

There is debate regarding the influence of a surgeon’s experience with computer-assisted surgery (CAS) on the postoperative mechanical axis (MA) in CAS-high tibial osteotomy. The purpose of the present study was to compare radiographic results between early and late cohorts of a consecutive series of patients to assess the influence of CAS experience on accuracy and precision of the postoperative MA during CAS lateral closing-wedge high tibial osteotomy (LCWHTO).

Materials and methods

Results from 140 CAS-LCWHTO operations were retrospectively reviewed. The first 70 cases, performed during the learning curve period for CAS between 2005 and 2009, were considered to be the “early cohort.” The subsequent 70 cases, performed with greater CAS experience after the completion of the learning curve between 2009 and 2014, were considered to be the “late cohort.” The target postoperative MA angle was valgus 3°. Pre- and postoperative MA angles were evaluated by navigation and radiographs. The proportion of postoperative MA inliers (≤ target angle ±3°) was investigated radiographically. The correlation between the navigation and radiographic measurements was analyzed.

Results

The average postosteotomy MA angle on navigation was 3.4° in both cohorts. The average postoperative MA angle on radiographs was 1.0° in the early cohort and 2.2° in the late cohort (P = 0.003). Radiographically, the proportion of postoperative MA inliers was greater in the late cohort than in the early cohort (early versus late, 71.4% versus 90%; P = 0.011). The pre- and postoperative correlation between navigation and radiographic measurements was also stronger in the late cohort (early versus late; preoperative r = 0.558 versus 0.663; postoperative r = 0.310 versus 0.376).

Conclusions

Greater experience with CAS increased the accuracy and precision of postoperative MA alignment as well as the correlation between navigation and radiographic measurements. Caution should be taken during registration procedures to achieve accurate alignment correction in CAS-LCWHTO.

Radiographic changes and clinical outcomes after open and closed wedge high tibial osteotomy: a systematic review and meta-analysis

BACKGROUND

The purpose of this meta-analysis is to examine changes in radiological variables and clinical outcomes between open and closed wedge high tibial osteotomy (OWHTO and CWHTO, respectively), which have ongoing controversial issues in numerous quantitative clinical studies.

METHODS

PubMed, Embase, and the Cochrane Library were systematically searched for suitable controlled trials between Jan 1, 1999, and Feb 2, 2018. The inclusion criteria included studies written in English, studies with a level of evidence of I-IV, and studies presenting comparisons between OWHTO and CWHTO. The main clinical and radiographic results were extracted and pooled using Stata 12.0.

RESULTS

After searching for and screening trials, 28 trials involving 2840 knees were eligible for the meta-analysis. After OWHTO or CWHTO, clinical scores, including the American Knee Society Score, Hospital for Special Surgery Knee Score, Lysholm score, and Visual Analog Scale pain score, improved (p < 0.05), but the range of motion was unchanged (p > 0.05). The anatomical femorotibial angle (SMD 0.04, 95% CI - 0.66 to 0.74) and hip-knee-ankle angle (SMD 0.11, 95% CI - 0.11 to 0.33) data suggested that the OWHTO and CWHTO groups were similar in function of correction. Posterior tibial slope increased (SMD - 0.71, 95% CI - 1.04 to - 0.37) after OWHTO but decreased (SMD 0.72, 95% CI 0.35 to 1.08) after CWHTO. OWHTO decreased patellar height (p < 0.05), while patellar height did not change significantly after CWHTO (p > 0.05).

CONCLUSION

This meta-analysis indicates that compared with CWHTO, OWHTO increases the posterior slope, decreases the patellar height, and provides a similar accuracy of correction; however, CWHTO leads to a decreased posterior slope and an unchanged patellar height. Therefore, programs should be personalized and customized for the specific situation of each patient.

A Comparison Between Chinese and Caucasian 3-Dimensional Bony Morphometry in Presimulated and Postsimulated Osteotomy for Total Knee Arthroplasty

BACKGROUND

The bone morphologies of intact knees were measured and compared between Chinese and Caucasian populations. However, to assess if distinct designs of implants are necessary for the Chinese population owing to different morphologies and sizes, the knee measurements after osteotomy performed in total knee arthroplasty were evaluated.

METHODS

Thirty-seven Caucasian and 50 Chinese patients' knees were examined using computed tomography scans. Mimics were applied to reconstruct 3-dimensional bone models. Dimensions of the 3-dimensional knee models and simulated bone resections during total knee arthroplasty were measured using Geomagic Studio and Pro/ENGINEER. The morphologic measurements of the native and resected femur and tibia included the anteroposterior (AP) depth, mediolateral (ML) width, notch width, knee physical valgus angle, tibial slope angle, and the ML-to-AP ratio of the femur, tibia, and resected femur. Statistical analysis was performed using the independent samples t test and the Pearson correlation coefficient in SPSS for Windows. Values of P < .05 were considered significant.

RESULTS

No measurements were significantly different between the Chinese and Caucasian knees. However, the Chinese female showed significant differences compared with the Chinese male on distal femoral measurements both presimulated and postsimulated osteotomy such as a smaller mean ML-to-AP ratio in presimulated (1.3 ± 0.1) and postsimulated (1.3 ± 0.1) osteotomy.

CONCLUSION

The necessity of designing a full set of total knee components specifically for the Chinese population is still undetermined. However, we suggest designing femoral components specific for the Chinese females because of different postosteotomy distal femoral ML-to-AP ratio between the Chinese males and the Chinese females.

Preoperative planning using the picture archiving and communication system technique in high tibial osteotomy

PURPOSE

This study aimed to evaluate the accuracy of the picture archiving and communication system (PACS) method in order to select the correction angle and gap in open-wedge high tibial osteotomy (HTO) and clinical results of the patients.

MATERIAL AND METHODS

This retrospective study analyzed 27 consecutive patients (30 knees) underwent open-wedge HTO using the PACS method between April 2013 and March 2015. Full-length lower limb radiographs obtained preoperatively and at the final follow-up were used to the percentages of crossing points of the weight-bearing line and tibial plateau with respect to the medial border and mechanical femur-tibia angle. Preoperatively predicted and postoperatively measured wedge angles and gaps were compared. The clinical results were evaluated using the Hospital for Special Surgery (HSS) knee score and the Knee Society score.

RESULTS

At the 20.5 months (12-26.5) follow-up, the weight-bearing line on the tibial plateau was corrected from 17.3% to 61.3%, and the mechanical femur-tibia angle was corrected from 7.3° varus to 3.1° valgus. No significant difference in preoperative and postoperative measured values was observed ( p = 0.440 and p = 0.505). The mean HSS score increased from 66.7 to 88.8 ( p < 0.001). The knee score and function score of Knee Society increased from 62.0 to 88.7 ( p < 0.001) and from 60.2 to 91.7 ( p < 0.001), respectively.

CONCLUSION

In open-wedge HTO, correction of angular deformity based on the PACS method could be an accurate correction method and the good clinical results could be obtained.

Comparison of Cable Method and Miniaci Method Using Picture Archiving and Communication System in Preoperative Planning for Open Wedge High Tibial Osteotomy

Purpose

The purpose was to compare the accuracy of Miniaci method using picture archiving and communication system (PACS) with a cable method in high tibial osteotomy (HTO).

Materials and Methods

This study analyzed 47 patients (52 knees) with varus deformity and medial osteoarthritis. From 2007 to 2013, patients underwent HTO using either a cable method (20 knees) or Miniaci method based on a PACS image (32 knees). In the cable method, the 62.5% point of the mediolateral tibial plateau width was located using an electrocautery cord under fluoroscopy (cable group). The Miniaci method used preoperative radiographs to shift the weight bearing axis (PACS group). Full-length lower limb radiographs obtained preoperatively and at the sixth postoperative week were used to compare the percentage of crossing point of the weight bearing line on the tibial plateau with respect to the medial border.

Results

The weight bearing line on the tibial plateau was corrected from a preoperative 11.0±7.0% to a postoperative 47.2±7.4% in the cable group and from 12.7±4.9% to 59.5±5.3% in the PACS group. The mechanical femorotibial angle was corrected from varus 8.9±3.7° to valgus 0.3±4.0° in the cable group and from varus 9.0±3.3° to valgus 2.9±2.6° in the PACS group.

Conclusions

In HTO, correction based on the Miniaci method using a PACS was more accurate than correction using the cable method.

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.

Computer-assisted navigation decreases the change in the tibial posterior slope angle after closed-wedge high tibial osteotomy

PURPOSE

The purpose of the present study was to compare the change in tibial posterior slope angle (PSA) between patients treated via computer-assisted and conventional closed-wedge high tibial osteotomy (CWHTO). It was hypothesized that a decrease in the PSA would be less in the computer-assisted group than in the conventional group.

METHODS

Data on a total of 75 computer-assisted CWHTOs (60 patients) and 75 conventional CWHTOs (49 patients) were retrospectively compared using matched pair analysis. The pre- and postoperative mechanical axis (MA) and the PSA were radiographically evaluated. The parallel angle was defined as the angle between the joint line and the osteotomy surface. The data were compared between the two groups.

RESULTS

The postoperative radiographic MA averaged 1.3° ± 2.6° valgus in the computer-assisted group and 0.3° ± 3.1° varus in the conventional group. The change in PSA averaged -0.8° ± 0.9° in the computer-assisted group and -4.0° ± 2.2° in the conventional group. The parallel angle averaged 0.2° ± 3.0° in the computer-assisted group and 6.2° ± 5.3° in the conventional group.

CONCLUSION

Computer-assisted CWHTO using four guide pins could avoid inadvertent change in the PSA. The navigation can be used in anticipation of decreasing the risk of change in the PSA in CWHTO, especially in patients whose preoperative PSA is small. The special attention should be paid to locate the hinge axis acutely and to make the parallel proximal and distal osteotomy surfaces during CWHTO.

LEVEL OF EVIDENCE

III.

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.

Opening wedge high tibial osteotomy: navigation system compared to the conventional technique in a controlled clinical study

PURPOSE

This study aimed to verify if the navigation system used in high tibial osteotomy (HTO) adds precision to the procedure regarding mechanical axis correction and prevention of tibial slope increases.

METHODS

In this historically controlled study, patients with medial osteoarthrosis and genuvarum underwent HTO between 2004 and 2012; the first 20 were operated with the conventional technique, using pre-planning correction by the Dugdale method and 18 further patients were operated with the navigation system introduced in our hospital.

RESULTS

The two groups were similar for pre-operative mechanical axis (mean 8.10 ± 3.14 for the control and 6.60 ± 2.50 for the navigated group), pre-operative tibial slope (mean 8.95 ± 3.47 versus 8.17 ± 3.11, respectively) and Lyshom score (40.85 ± 15.46 and 44.83 ± 16.86). After surgery, the control group presented mean mechanical axis of 3.35 ± 3.27, tibial slope of 13.75 ± 3.75 and Lyshom score of 87.60 ± 11.12. The navigated group showed a postoperative mechanical axis mean of 3.06 ± 1.70, tibial slope of 10.11 ± 0.18 and Lyshom score of 91.94 ± 11.61.

CONCLUSIONS

The navigation system allowed a significantly better control of tibial slope. Patients operated with the navigation system had significantly better Lysholm scores.

Virtual 3D planning and patient specific surgical guides for osteotomies around the knee: a feasibility and proof-of-concept study

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, sd 0.71) in the coronal plane and 0.3° (-0.9 to 3, sd 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, sd 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome.

Are navigation systems accurate enough to predict the correction angle during high tibial osteotomy? Comparison of navigation systems with 3-dimensional computed tomography and standing radiographs

BACKGROUND

Unpredicted overcorrection of the mechanical axis can occur during navigation-assisted high tibial osteotomy (HTO). It is not clear whether the erroneous overcorrection stems from the navigation system itself or from other causes.

PURPOSE

To evaluate the accuracy of the navigation system in HTO by comparing the change in the femorotibial angle provided by the navigation system with the bony correction angle of the proximal tibia on 3-dimensional computed tomography (3D CT) and with the change in mechanical femorotibial alignment on standing whole-leg radiographs.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

A total of 16 knees underwent navigation-assisted HTO, and their alignment data were obtained before and after correction. For comparison, preoperative and follow-up standing whole-leg anteroposterior radiographs, lateral knee radiographs, and preoperative and postoperative 3D CT scans were taken. The medial proximal tibial angle (MPTA), posterior tibial slope, and mechanical femorotibial angle (mFTA) were measured in these images, and the 3 coronal and 3 sagittal correction angles were compared with each other.

RESULTS

In the coronal plane, the mean correction angle of the navigation system was 9.3° ± 2.0° valgus (range, 6°-13°), and the mean MPTA on 3D CT increased 9.7° ± 2.0° (range, 6.7°-13.8°) after correction. The mean correction angle of the mFTA on standing radiographs was 11.9° ± 3.2° valgus (range, 6.9°-16.5°). There was no statistical significance between the navigation system and 3D CT (P = .187), but there was a statistically significant difference between the navigation system and standing radiographs (P = .001). The results of the correction angle in the sagittal plane were similar to those in the coronal plane.

CONCLUSION

The correction of the femorotibial angle by the navigation system was not different from the bony correction angle on 3D CT. There was a discrepancy between the correction angle of the navigation system and that of the standing radiograph.

CLINICAL SIGNIFICANCE

Surgeons must be cautious about the tension of soft tissue, even when using the navigation system during HTO.

The long leg radiograph is a reliable method of assessing alignment when compared to computer-assisted navigation and computer tomography

BACKGROUND

The mechanical alignment of the knee is an important factor in planning for, and subsequently assessing the success of a knee replacement. It is most commonly measured using a long-leg anteroposterior radiograph (LLR) encompassing the hip, knee and ankle. Other modalities of measuring alignment include computer tomography (CT) and intra-operative computer navigation (Cas). Recent studies comparing LLRs to Cas in measuring alignment have shown significant differences between the two and have hypothesized that Cas is a more accurate modality. This study aims to investigate the accuracy of the above mentioned modalities.

METHODOLOGY

A prospective study was undertaken comparing alignment as measured by long-leg radiographs and computer tomography to intra-operative navigation measurements in 40 patients undergoing a primary total knee replacement to test this hypothesis. Alignment was measured three times by three observers. Intra- and inter-observer correlation was sought between modalities.

RESULTS

Intra-observer correlation was excellent in all cases (>0.98) with a coefficient of repeatability <1.1°. Inter-observer correlation was also excellent measuring >0.960 using LLRs and >0.970 using CT with coefficient of repeatability <2.8°. Inter-modality correlation proved to be higher when comparing LLRs and CT (>0.893), than when comparing either of these modalities with Cas (>0.643 and >0.671 respectively). Pre-operative values had the greatest variability.

CONCLUSION

Given its availability and reduced radiation dose when compared to CT, LLRs should remain the mainstay of measuring the mechanical alignment of the lower limb, especially post-operatively.

LEVEL OF EVIDENCE

II.

Preoperative surgical planning versus navigation system in valgus tibial osteotomy: a cross-sectional study

PURPOSE

The objective of this study was to verify whether the correction obtained using a navigation system (NS) corresponds to the wedge calculated by the Dugdale method (DM) in high tibial osteotomy (HTO).

METHODS

We included 17 patients with primary varus and HTO indication, consecutively admitted to a public university hospital. All patients underwent panoramic radiography with bipedal load for the wedge calculation by DM. They underwent HTO with an opening wedge, fixed with an HTO plate and monitored by the OrthoPilot NS. Bone grafts were used in every case. The wedge opening obtained by the NS was compared to that calculated in the radiographs.

RESULTS

The mean opening by DM was 9.53° and by the NS 11.8° (p < 0.045).

CONCLUSIONS

There was a significant difference in the calculation of the wedge opening between the DM and NS. HTO without the aid of the NS could theoretically lead to undercorrection of the deformity.

Preoperative and postoperative comparisons of navigation and radiologic limb alignment measurements after high tibial osteotomy

PURPOSE

To determine whether navigation-assisted intraoperative lower limb alignment in open wedge high tibial osteotomy (HTO) correlates with preoperative and postoperative radiographic alignment.

METHODS

This prospective study involved 35 patients (39 knees) who underwent navigation HTO for primary medial osteoarthritis. The mechanical axis (MA) and weight-bearing line (WBL) ratio were calculated from preoperative radiographs, intraoperative navigation, and postoperative (6 months) radiographs. Reliability between navigation and radiographic alignment was analyzed by use of intraclass correlation coefficients (ICCs) with thresholds as follows: good, greater than 0.75; fair, 0.4 to 0.75; and poor, less than 0.4. The surgical target for the MA was a final valgus overcorrection of 2° to 8°, and the WBL ratio target was between 50% and 70%. Outliers for differences between intraoperative navigation and postoperative radiographic results were defined as greater than ±3° for the MA and greater than ±10% for the WBL ratio.

RESULTS

The MA target was achieved in 33 of 39 knees (84.6%), and the WBL ratio target was achieved in 30 of 39 knees (74.4%). ICCs for navigational reliability were good for preoperative MA and WBL ratio and fair for postoperative MA and WBL ratio. The ICCs for the MA were better than those for the WBL ratio for both preoperative and postoperative measurements. The differences between the number of outliers between the navigation and radiographic MA and WBL were greater postoperatively than preoperatively. In addition, the postoperative differences in the extent of the outliers between navigation and radiographic measurements were greater for WBL ratios than the MA (P = .023).

CONCLUSIONS

This study found that use of a navigation system achieved the target value for MA lower limb correction in over 80% of open wedge HTO cases, using radiographic data as the gold standard for alignment. Because the navigational measurements of lower limbs during open wedge HTO did not correlate with postoperative radiographic alignment, corrections should not be based solely on navigational results. In assessing the reliability of navigational open wedge HTO for correction of lower limb alignment, the MA is a better radiologic parameter than the WBL ratio.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Computer-assisted navigation in high tibial osteotomy: a systematic review of the literature

High tibial osteotomy (HTO) is a procedure which aims to change the mechanical axis of the lower limb, transferring the body weight across healthy articular cartilage. Several studies have shown that accurate correction is the leading predictor for success.

In this article, we systematically review the computer-assisted techniques that have been used in attempts to increase the accuracy of the surgery and improve postoperative outcomes. The results of the cadaveric and clinical studies to date are presented and the benefits and pitfalls of navigation are discussed.

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

PURPOSE

The correction angle after high tibial osteotomy (HTO) depends on an accurate preoperative planning and an accurate intraoperative technique. We hypothesized that the use of a navigation system in opening wedge HTO would improve the intraoperative target angles in the coronal and sagittal planes.

METHODS

Postoperative femoro-tibial angle (FTA) and tibial posterior slope (TPS) in 28 knees with navigated opening wedge HTO were compared to those in 31 knees with the conventional method. Intraoperative correction angle was determined by the predicted medial opening width in the conventional group, and by the change of hip-knee-ankle angle in the navigated group. We defined lateral unstable knee as the knees with lateral cortex breakage or lateral tibial plateau fracture.

RESULTS

Mean postoperative FTA was higher in the conventional group than in the navigated group (P < 0.037). In the conventional group, 4 lateral unstable knees were corrected to 174.6°. In the navigated group, 5 lateral unstable knees were corrected to 170.3° and no knees showed FTA > 173°. Mean change in TPS was greater in the conventional group than in the navigated group (P = 0.001).

CONCLUSION

The navigation system in opening wedge HTO might reduce undercorrection in the knees with lateral cortex breakage or lateral tibial plateau fracture, and provide the better intraoperative FTA and TPS.

LEVEL OF EVIDENCE

III.

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.

Simultaneous anterior cruciate ligament reconstruction and computer-assisted open-wedge high tibial osteotomy: a report of eight cases

Eight patients, aged 37-50 years, with chronic anterior cruciate ligament (ACL) deficiency, medial compartment osteoarthritis and varus deformity underwent simultaneous arthroscopic ACL reconstruction and open-wedge high tibial osteotomy controlled by a computer navigation system. Despite preoperative planning, the surgeon may need to choose a different osteotomy site during the procedure, invalidating the previous plans. The intraoperative wire control for osteotomies is not precise. The navigation system can help obtain precise alignment during high tibial osteotomy. The average preoperative mechanical axis was 7.5 of varum (sd±1.17°), the average postoperative axis was 1.2° of valgus (sd±1.04°) (p<0.01), and the average correction of the mechanical axis was 8.7° (sd±0.76°). The site of the osteotomy was 3.9 cm (3.5-4.8 cm, sd±0.35 mm) from the articular line, with an inclination of 27.9° (24-35, sd±4.8). The simultaneous use of these procedures allowed proper correction of the knee axis during the surgery. The surgery can be performed concomitantly with ACL reconstruction.

Assessment of the accuracy of infrared and electromagnetic navigation using an industrial robot: Which factors are influencing the accuracy of navigation?

Our objectives were to detect factors that influence the accuracy of surgical navigation (magnitude of deformity, plane of deformity, position of the navigation bases) and compare the accuracy of infrared with electromagnetic navigation. Human cadaveric femora were used. A robot connected with a computer moved one of the bony fragments in a desired direction. The bases of the infrared navigation (BrainLab) and the receivers of the electromagnetic device (Fastrak-Pohlemus) were attached to the proximal and distal parts of the bone. For the first part of the study, deformities were classified in eight groups (e.g., 0 to 5(°)). For the second part, the bases were initially placed near the osteotomy and then far away. The mean absolute differences between both navigation system measurements and the robotic angles were significantly affected by the magnitude of angulation with better accuracy for smaller angulations (p < 0.001). The accuracy of infrared navigation was significantly better in the frontal and sagittal plane. Changing the position of the navigation bases near and far away from the deformity apex had no significant effect on the accuracy of infrared navigation; however, it influenced the accuracy of electromagnetic navigation in the frontal plane (p < 0.001). In conclusion, the use of infrared navigation systems for corrections of small angulation-deformities in the frontal or sagittal plane provides the most accurate results, irrespectively from the positioning of the navigation bases.

Update in surgery for osteoarthritis of the knee

Osteoarthritis is a leading cause of disability with incidence and prevalence rising in most nations. Management to address the degenerative joint is stratified according to degree of severity of involvement and always begins with non-surgical modalities before progressing through a range of surgeries, including arthroscopy, osteotomy, unicompartmental and total knee replacement. Predictability of results depends on the type of procedure with total joint replacement giving the most sustainable relief from symptoms, improvement of function and longevity of construct. Obesity is a health priority in developed countries where it is overrepresented in patients presenting for joint replacement. Complications, poor patient satisfaction and joint function can be directly attributable to obesity. Efforts to address obesity should be considered as part of the approach to managing osteoarthritis.

High tibial osteotomy with a dynamic axial fixator

We report the outcome of 32 patients (37 knees) who underwent hemicallostasis with a dynamic external fixator for osteoarthritis of the medial compartment of the knee. There were 16 men (19 knees) and 16 women (18 knees) with a mean age at operation of 54.6 years (27 to 72). The aim was to achieve a valgus overcorrection of 2° to 8° or mechanical axis at 62.5% (± 12.5%). At a mean follow-up of 62.8 months (51 to 81) there was no change in the mean range of movement, and no statistically significant difference in the Insall-Salvati index or tibial slope (p = 0.11 and p = 0.15, respectively). The mean hip-knee-ankle angle changed from 190.6 (183° to 197°) to 176.0° (171° to 181°), with a mean final position of the mechanical axis of 58.5% (35.1% to 71.2%).

The desired alignment was attained in 31 of 37 (84%) knees. There were 21 excellent, 13 good, two fair and one poor result according to the Oxford knee score with no correlation between age and final score. This score was at its best at one year with a statistically significant deterioration at two years (p = 0.001) followed by a small but not statistically significant deterioration until the final follow-up (p = 0.17). All the knees with Ahlback grade 1 osteoarthritis had excellent or good results. Complications included pin tract infections involving 16.4% of all pins used, delayed union in two, knee stiffness in four, fracture of the lateral cortex in one and ring sequestrum in one.

In conclusion, hemicallostasis provides precision in attaining the desired alignment without interfering with tibial slope or patellar height, and is relatively free of serious complications.

Precision of navigated and conventional open-wedge high tibial osteotomy in a cadaver study

High tibial osteotomy (HTO) is an established treatment option for isolated medial osteoarthritis in young and active patients. One important factor for success of this procedure is the degree of correction of the weight-bearing line. Computer-assisted navigation systems are believed to improve the precision of axis correction through intraoperative real-time monitoring. This study investigates the precision of correction of the weight-bearing line in open-wedge HTO with and without a navigation system.

Nineteen legs of well-preserved human cadaver were randomly assigned to navigated (n = 10) or conventional (n = 9) HTO. In order to achieve a sufficient amount of correction in all legs the weight-bearing line was aimed at 80 percent of the width of the tibial plateau.

The mean deviation of the weight-bearing line from the desired 80 percent was 1 percent in the navigated and 8.6 percent in the conventional operated legs (p = 0.002). The weight-bearing line of all navigated but only 5 of the 9 conventional operated legs was within a ± 5 percent tolerance level (p = 0.33).

Navigated open-wedge HTO achieved better correction of the weight-bearing line than the conventional method in human cadaver legs. Future studies have to prove this advantage in a clinical setting and it's effect on patient outcome.

Osteotomies about the knee for tibiofemoral malalignment in the athletic patient

Osteotomies have a role in the active patient with degenerative joint disease of the medial or lateral knee who, for reasons of age or activity level, is not yet a good candidate for prosthetic arthroplasty. Recognition and treatment of malalignment associated with ligamentous instability is essential if long-term good outcomes are to be expected from ligamentous reconstruction. Also, treatment of concomitant malalignment and the unloading of the operative site is now recognized as an important adjunct to any cartilage-preserving surgery. This review examines the use of osteotomies about the knee in the athletic patient. Indications, contraindications, preoperative planning, surgical techniques, and complications are reviewed.

Reliability of limb alignment measurement for high tibial osteotomy with a navigation system

Objective

High tibial osteotomy (HTO) is one treatment option for young and active patients with unicompartmental osteoarthritis. The success of this procedure substantially depends on the degree of correction of the mechanical axis. Computer-assisted navigation systems are believed to improve the precision of axis correction through intraoperative real-time monitoring. This study investigates the accuracy of limb alignment measurements with a navigation system on a cadaver specimen.

Materials and methods

The measurements were performed on a well-preserved cadaver specimen with a mechanical leg axis of 4° varus. Data was collected during the HTO workflow. Repeated serial measurements were undertaken by four different surgeons. After these measurements, different landmarks were deliberately set at the wrong place to examine the influence of mistakes during registration.

Results

There was a high intra-and interobserver reliability with a mean mechanical leg axis of 3.9° ± 0.7° and a mean error of 0.6°. The grossly incorrect placement of landmarks for knee and ankle center resulted in an incorrect mechanical leg axis of 1° valgus up to 10° varus.

Conclusion

The computer-assisted navigation system provided precise information about the mechanical leg axis, irrespective of the observer's experience.

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.

Reliability of leg alignment using the OrthoPilot system depends on knee position: a cadaveric study

Despite the increase in clinical use of navigation systems in total knee arthroplasty, few studies have focused on the reproducibility of these systems. The aim of the present study was to assess the influence of knee position and observer experience on intra- and inter-observer agreement in limb alignment assessment with the OrthoPilot system. Limb alignment in the coronal plane and extension range of the knee were assessed in four embalmed cadaveric specimens by five independent observers and measurements were repeated four times to determine intra- and inter-observer agreement, expressed as intraclass correlation coefficients (ICCs). Additionally, navigation results were compared against figures from conventional measurement of leg alignment (ground truth). Intra- and inter-observer agreements were excellent for assessing the extension range (ICC, 0.97 and 0.95) and the coronal femuro-tibial axis in knee extension (ICC, 0.92 and 0.88) but were generally worse in knee flexion (ICC, 0.62 and 0.55). There was an increased tendency of intraobserver errors in observers with less clinical experience. Mean correlation with conventional measurements was fair (Spearman's rho 0.61). The OrthoPilot system showed excellent reproducibility for assessment of extension range and coronal limb alignment. However, assessments of coronal limb alignment in flexion were prone to error and caution should be taken when relying on these measurements.

Surgical options for patients with osteoarthritis of the knee

Osteoarthritis (OA) of the knee is a progressive disease that ultimately damages the entire joint. Knee OA should initially be treated conservatively, but surgery should be considered if symptoms persist. Surgical treatments for knee OA include arthroscopy, osteotomy and knee arthroplasty; determining which of these procedures is most appropriate will depend on several factors, including the location and severity of OA damage, patient characteristics and risk factors. Arthroscopic lavage and debridement do not alter disease progression, and should not be used as a routine treatment for the osteoarthritic knee. Bone marrow stimulation techniques such as microfracture are primarily used to treat focal chondral defects; the evidence for the use of these techniques for knee OA remains unclear. The goal of osteotomy for unicompartmental knee OA is to transfer the weight load from the damaged compartment to undamaged areas, delaying the need for joint replacement. This procedure should be considered in young and active patients who are not suitable candidates for knee arthroplasty. For patients with severe OA, total knee arthroplasty can be a safe, rewarding and cost-effective treatment. In selected patients with isolated medial or patellofemoral OA, unicompartmental knee arthroplasty and patellofemoral replacement, respectively, can be successful.