Reliability of image-free navigation to monitor lower-limb alignment

Intraoperative femurofibular angle combined with tibiofibular angle measurement has fewer correction errors in open-wedge high tibial osteotomy

AIM

This study aimed to verify the accuracy of intraoperative femurofibular angle combined with tibiofibular angle (FFA-TFA) measurement and compare it with traditional alignment line methods in open-wedge high tibial osteotomy (OWHTO).

METHODS

A total of 174 knees of 122 patients undergoing OWHTO and using an alignment line or FFA-TFA measurement as an index of optimal correction were included in this retrospective study. The intraoperative alignment line passed through the targeted weight-bearing line (WBL) of the tibial plateau in the alignment line group. The intraoperative FFA-TFA aligned to the preplanned FFA-TFA angle in the FFA-TFA group. WBL, FFA, TFA, and knee joint-line convergence angle of the femur and tibia were assessed as radiological results preoperatively and one year after surgery. The Knee Society Score and the Western Ontario and McMaster Universities were assessed as objective clinical results.

RESULTS

Postoperative WBL in the FFA-TFA group was closer to the target WBL than in the alignment line group (FFA-TFA vs alignment line group: 1.43 ± 1.20% vs 3.82 ± 3.29%; P < 0.001). The FFA-TFA group had fewer over-correction and under-correction rates than the alignment line group (28.7% and 12.6% vs 11.5% and 3.40%; P < 0.001). No significant differences were observed in the clinical results between the two groups one year after surgery (P > 0.05).

CONCLUSIONS

The intraoperative measurement of FFA-TFA had fewer complications in terms of under-correction and over-correction compared with the alignment line measurement. No significant differences between the two methods were observed in clinical results one year after surgery.

An automated optimization pipeline for clinical-grade computer-assisted planning of high tibial osteotomies under consideration of weight-bearing

3D preoperative planning for high tibial osteotomies (HTO) has increasingly replaced 2D planning but is complex, time-consuming and therefore expensive. Several interdependent clinical objectives and constraints have to be considered, which often requires multiple rounds of revisions between surgeons and biomedical engineers. We therefore developed an automated preoperative planning pipeline, which takes imaging data as an input to generate a ready-to-use, patient-specific planning solution. Deep-learning based segmentation and landmark localization was used to enable the fully automated 3D lower limb deformity assessment. A 2D-3D registration algorithm allowed the transformation of the 3D bone models into the weight-bearing state. Finally, an optimization framework was implemented to generate ready-to use preoperative plannings in a fully automated fashion, using a genetic algorithm to solve the multi-objective optimization (MOO) problem based on several clinical requirements and constraints. The entire pipeline was evaluated on a large clinical dataset of 53 patient cases who previously underwent a medial opening-wedge HTO. The pipeline was used to automatically generate preoperative solutions for these patients. Five experts blindly compared the automatically generated solutions to the previously generated manual plannings. The overall mean rating for the algorithm-generated solutions was better than for the manual solutions. In 90% of all comparisons, they were considered to be equally good or better than the manual solution. The combined use of deep learning approaches, registration methods and MOO can reliably produce ready-to-use preoperative solutions that significantly reduce human workload and related health costs.

Poor Accuracy of Intraoperation Medial Proximal Tibial Angle Measurement Compared to Alignment Rod Methods in Open-Wedge High Tibial Osteotomy for Medial Knee Osteoarthritis

The alignment rod is widely used as an index for intraoperative alignment but alignment error is inevitable. The purpose of this study was to verify the accuracy of lower limb alignment correction by measurement of mechanical medial proximal tibial angle (MPTA) as an index in open-wedge high tibial osteotomy (OWHTO). This study was retrospective case series. This study involved 152 patients undergoing OWHTO for primary medial osteoarthritis. Alignment rod or MPTA measurement board was used as an index of optimal correction in OWHTO. Alignment rod was used from October 2013 to May 2017, and MPTA measurement board was used from June 2017 to April 2020. The correction using an alignment rod was that the weight-bearing line ratio (WBLR) passed through 62.5% of the tibial plateau which was defined as Fujisawa's point under intraoperative fluoroscopy (A rod group). The correction using MPTA measurement board was aligning the intraoperative MPTA to the preplanned angle (MPTA group). Preplanned optimal alignment was defined as Fujisawa's point in all patients. Knee injury and osteoarthritis outcome measure (KOOS), Knee Society scoring system objective knee score (KSS), 3-m timed up-and-go test (TUG), single-limb standing test (SLS), and isometric muscle strength of quadriceps and hamstrings were assessed as clinical results. WBLR, MPTA, joint-line convergence angle (JLCA), and joint-line obliquity (JLO) were assessed as radiological results preoperatively and at 1 year after surgery. The clinical and radiological results after OWHTO were compared with both groups. Postoperative WBLR in A rod group was closer to the target alignment (Fujisawa's point: 62.5) than in the MPTA group at all stage (A rod group vs. MPTA group: 63.1 vs. 54.6 at 6 months; 62.0 vs. 53.4 at 1 year; p < 0.001). There were no significant differences in the clinical results between both groups. The intraoperative measurement of medial proximal tibial angle has a risk of undercorrection after OWHTO. His study is a retrospective case series and reflects level of evidence IV.

The medial proximal tibial angle accurately corrects the limb alignment in open-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to detect the pre- and intra-operative influential factors for lower limb alignment correction error in open-wedge high tibial osteotomy (OWHTO).

METHODS

This study involved 69 patients (71 knees) undergoing OWHTO for primary medial osteoarthritis. The weight-bearing line (WBL) ratio, medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) were measured on radiographs preoperatively and at 1 month after surgery, and the differences between the pre- and postoperative values were calculated. The correction angle during surgery was also investigated. The radiological correction angle was defined as the difference between the pre- and postoperative MPTA. The correction error was defined as the difference between the correction angle during surgery and the radiological correction angle. The ideal correction angle was defined as when the postoperative WBL passed through Fujisawa's point (WBL = 62.5%), and the alignment error was defined as the difference between the postoperative WBL ratio and 62.5. The correlations among the alignment error, the correction error, correction angle during surgery, pre- and postoperative WBL ratio, MPTA, and JLCA and the differences between the pre and postoperative WBL ratio, MPTA, and JLCA were investigated. In addition, the factor most influential on the alignment error was determined.

RESULTS

The preoperative MPTA was the only predictor of the alignment error after OWHTO. The alignment error was positively correlated with the correction error and correction angle during surgery, and negatively correlated with pre- and postoperative WBL ratio, MPTA, and differences between the pre- and postoperative WBL ratio and JLCA.

CONCLUSION

The preoperative MPTA was the only pre- and intra-operative predictor of the alignment error after OWHTO. The larger the correction angle, the greater the alignment error. The MPTA was recommended as an indicator for improving the correction accuracy. Accurate correction based on the MPTA provides good lower limb alignment and better clinical results.

LEVEL OF EVIDENCE

III Case-control study/Retrospective comparative study.

Reliability of two techniques and training level of the observer in measuring the correction angle when planning a high tibial osteotomy

BACKGROUND

In high tibial osteotomy, planning is critical for achieving successful realignment. Any method selected needs to be reliable, with inter-observer and intra-observer correlation. A literature review demonstrated two distinct methods of planning for high tibial osteotomy.

HYPOTHESIS

Both methods are precise and show excellent inter and intra-observer correlation.

METHOD

Fifty consecutive weight-bearing long leg alignment antero-posterior (AP) radiographs were identified and planning undertaken on suitable radiographs using the methods of Puddu (method 1) and Miniaci (method 2). Two observers, one junior trainee and one Specialist Knee Fellow, recorded measurements to calculate inter and intra-observer correlation.

RESULTS

Thirty-two radiographs were included. Inter-observer and intra-observer correlation, and correlation between the two methods were all greater than 0.97 (p<0.0001).

CONCLUSION

Our results show excellent correlation between both methods and both observers. Both methods are reliable for planning and can be performed by both junior trainees and subspecialists. Further work should consider how planning can ensure adequate intraoperative correction.

Effect of soft tissue laxity of the knee joint on limb alignment correction in open-wedge high tibial osteotomy

PURPOSE

Open-wedge high tibial osteotomy (HTO) cannot always accurately correct limb alignment, resulting in under- or over-correction. This study assessed the relationship between soft tissue laxity of the knee joint and alignment correction in open-wedge HTO.

METHODS

This prospective study involved 85 patients (86 knees) undergoing open-wedge HTO for primary medial osteoarthritis. The mechanical axis (MA), weight-bearing line (WBL) ratio, and joint line convergence angle (JLCA) were measured on radiographs preoperatively and after 6 months, and the differences between the pre- and post-surgery values were calculated. Post-operative WBL ratios of 57-67 % were classified as acceptable correction. WBL ratios <57 and >67 % were classified as under- and over-corrections, respectively.

RESULTS

Preoperative JLCA correlated positively with differences in MA (r = 0.358, P = 0.001) and WBL ratio (P = 0.003). Difference in JLCA showed a stronger correlation than preoperative JLCA with differences in MA (P < 0.001) and WBL ratio (P < 0.001). Difference in JLCA was the only predictor of both difference in MA (P < 0.001) and difference in WBL ratio (P < 0.001). The difference between pre- and post-operative JLCA differed significantly between the under-correction, acceptable-correction, and over-correction groups (P = 0.033). Preoperative JLCA, however, did not differ significantly between the three groups. Neither preoperative JLCA nor difference in JLCA correlated with change in posterior slope.

CONCLUSIONS

Preoperative degree of soft tissue laxity in the knee joint was related to the degree of alignment correction, but not to alignment correction error, in open-wedge HTO. Change in soft tissue laxity around the knee from before to after open-wedge HTO correlated with both correction amount and correction error. Therefore, a too large change in JLCA from before to after open-wedge osteotomy may be due to an overly large reduction in JLCA following osteotomy, suggesting alignment over-correction during surgery.

LEVEL OF EVIDENCE

II.

Computer assisted alignment of opening wedge high tibial osteotomy provides limited improvement of radiographic outcomes compared to flouroscopic alignment

INTRODUCTION

There are numerous methods available to assist surgeons in the accurate correction of varus alignment during medial opening wedge high tibial osteotomy (MOWHTO). Preoperative planning performed with radiographs or more recently intraoperative computer navigation software has been used. The aim of the study was to compare the accuracy of computer navigated versus non-navigated techniques to correct varus alignment of the knee.

METHOD

The preoperative and postoperative radiographs of 117 knees that underwent MOWHTO were investigated to assess radiographic limb alignment 12-months postoperatively. The desired correction was defined as a weight bearing line (Mikulicz point {MP}) 58% of the width of the tibial plateau from the medial tibial margin. Sixty-five knees were corrected using a conventional technique and 52 knees were corrected using computer navigation.

RESULTS

The mean MP percentage was 59% in the navigated group, compared with 56% in the fluoroscopic group (p=0.183). 51.9% of the navigation knees were corrected to within five percent of the desired correction, in contrast to 38.5% of the fluoroscopically corrected knees (p=0.15). 71.2% of the navigated knees were corrected to within 10% of the desired correction, compared with 63.1% of the fluoroscopically corrected knees (p=0.36). Large preoperative deformities were more accurately corrected with navigation assistance (57% vs 49%, p=0.049).

CONCLUSION

No statistically significant difference was found in the radiographic correction of varus alignment twelve months postoperatively between navigated and fluoroscopic techniques of MOWHTO. However, a subgroup analysis demonstrated that larger preoperative varus deformities may be more accurately corrected using computer navigation.

The weight-bearing scanogram technique provides better coronal limb alignment than the navigation technique in open high tibial osteotomy

BACKGROUND

Successful outcomes following high tibial osteotomy (HTO) require precise realignment of the mechanical axis of the lower extremity. The present study investigated whether the weight-bearing limb scanogram (WBS) technique provided a more accurate mechanical axis realignment than the navigation technique in open high tibial osteotomy (OHTO).

METHODS

This prospective study involved 80 knees (78 patients) undergoing OHTO. The WBS technique was used in 40 knees and the navigation technique in 40 knees. Each technique was performed by a different surgeon in a different hospital. Postoperative coronal limb alignment was assessed using the weight-bearing line (WBL) ratio on full-length standing hip-to-ankle radiographs.

RESULTS

We found that the mean postoperative WBL ratio was greater in the WBS compared to the navigation group (p=0.001), and hence the ratio for the WBS group was closer to the ratio target of 62%. There was a greater proportion of WBL ratio outliers in the navigation group than the WBS group (25% vs. 10%, p=0.034).

CONCLUSION

We conclude that the WBS technique was more accurate than the navigation technique for restoration of coronal leg alignment in OHTO.

LEVEL OF EVIDENCE

Level II.

Computer-assisted navigation in orthopedic surgery

Computer-assisted navigation has a role in some orthopedic procedures. It allows the surgeons to obtain real-time feedback and offers the potential to decrease intra-operative errors and optimize the surgical result. Computer-assisted navigation systems can be active or passive. Active navigation systems can either perform surgical tasks or prohibit the surgeon from moving past a predefined zone. Passive navigation systems provide intraoperative information, which is displayed on a monitor, but the surgeon is free to make any decisions he or she deems necessary. This article reviews the available types of computer-assisted navigation, summarizes the clinical applications and reviews the results of related series using navigation, and informs surgeons of the disadvantages and pitfalls of computer-assisted navigation in orthopedic surgery.

Applications of computer navigation in sports medicine knee surgery: an evidence-based review

Computer-assisted surgery (CAS) has been investigated in a number of sports medicine procedures in the knee. Current barriers to its widespread introduction include increased costs, duration, and invasiveness of surgery. Randomized trials on the use of CAS in anterior cruciate ligament reconstruction have failed to demonstrate a clinical benefit. Data on CAS use in high tibial osteotomy are more promising; however, long-term studies are lacking. CAS has a number of research applications in knee ligament surgery, and studies continue to explore its use in the treatment of osteochondral lesions. This article reviews the applications of CAS in sports medicine knee surgery and summarizes current literature on clinical outcomes.

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.

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.

Angle estimation of human femora in a three-dimensional virtual environment

The estimation of human femur morphology and angulation provide useful information for assisted surgery, follow-up evaluation and prosthesis design, cerebral palsy management, congenital dislocation of the hip and fractures of the femur. Conventional methods that estimate femoral neck anteversion employ planar projections because accurate 3D estimations require complex reconstruction routines. In a recent work, we proposed a cylinder fitting method to estimate bifurcation angles in coronary arteries and we thought to test it in the estimation of femoral neck anteversion, valgus and shaft-neck angles. Femora from 10 patients were scanned using multisliced computed tomography. Virtual cylinders were fitted to 3 regions of the bone painted by the user to automatically estimate the femoral angles. Comparisons were made with a conventional manual method. Inter- and intra-reading measurements were evaluated for each method. We found femoral angles from both methods strongly correlated. Average anteversion, neck-shaft and valgus angles were 17.5°, 139.5°, 99.1°, respectively. The repeatability and reproducibility of the automated method showed a 5-fold reduction in inter- and intra-reading variability. Accordingly, the coefficients of variation for the manual method were below 25% whereas for the automated method were below 6%. The valgus angle assessment was globally the most accurate with differences below 1°. Maximum distances from true surface bone points and fitting cylinders attained 6 mm. The employment of virtual cylinders fitted to different regions of human femora consistently helped to assess true 3D angulations.

Complications of closing wedge high tibial osteotomy

Closing wedge high tibial osteotomy is a common, effective and well-established procedure to treat unicompartment osteoarthrosis of the knee. It is, however, not without its complications. This article will discuss some of these complications and present an overview of the current literature. It will examine current thoughts on aetiology, techniques to try to avoid, and methods of treatment of these complications.