Reproducibility of digital measurements of lower-limb deformity on plain radiographs and agreement with CT measurements

Measurement of tibial slope using biplanar stereoradiography (EOS®)

OBJECTIVES

Posterior tibial slope (PTS) is an important anatomic parameter of the knee related to anteroposterior instability. Biplanar stereoradiography allows for simultaneous low-dose acquisition of anteroposterior and lateral views with 3D capability, enabling separate lateral and medial plateau analyses. We aimed to evaluate the possibility and compare the reproducibility of measuring medial and lateral PTS on EOS® images with two different patient positionings and compare it with CT of the knees as the gold standard.

METHODS

This is a retrospective study including volunteers who underwent lower limb stereoradiography and knee CT from 01/08/2016 to 07/31/2019. Sixty legs from 30 patients were studied. PTS were measured using stereoradiography and CT by two radiologists. Intraclass correlation was used to calculate intrarater and interrater reproducibilities. Pearson's correlation coefficients were used to calculate the correlation between stereoradiography and CT. We also compared the reproducibility of the stereoradiography of volunteers with 2 different positionings.

RESULTS

The mean stereoradiography PTS values for right and left knees were as follows: lateral, 12.2° (SD: 4.1) and 10.1° (SD: 3.5); medial,12.2° (SD: 4.4) and 11.6° (SD: 3.9). CT PTS mean values for right and left knee are as follows: lateral, 10.3° (SD:2.5) and 10.6° (SD: 2.8); medial: 8.7° (SD: 3.7) and 10.4° (SD: 3.5). Agreement between CT and EOS for angles between lateral and medial PTS was good (right, 0.874; left, 0.871). Regarding patient positioning on stereoradiography, interrater and intrarater reproducibilities were greater for patients with nonparallel feet (0.738-0.883 and 0.870-0.975).

CONCLUSIONS

Stereoradiography allows for appropriate delineation of tibial plateaus, especially in patients with nonparallel feet, for the purpose of measuring PTS. The main advantage is lower radiation doses compared to radiography and CT.

'One millimetre equals one degree' is a major source of inaccuracy in planning osteotomies around the knee for metaphyseal deformities compared to the digital planning

PURPOSE

The objective of this study was to compare the accuracy of virtually performed osteotomies around the knee. The comparison was made between the Miniaci method (method 1), considered the gold standard planning, with the widely held dogma that one degree of correction required equates to one millimetre of opening/closing (method 2).

METHODS

This retrospective cross-sectional study was conducted between December 2018 and September 2022 in patients aged at least 15 years with metaphyseal knee deformity. Osteotomy planning was performed in methods 1 and 2 utilising calibrated long-leg alignment X-rays in the frontal plane. In both methods, the desired correction was defined by the Fujisawa point. The error % in measurement (ratio method 1/method 2) and the difference in millimetres (method 1 - method 2) between the two methods were analysed.

RESULTS

A total of 107 osteotomies with 27 (25.2%) distal femoral osteotomies, 54 (50.5%) proximal tibial osteotomies and 26 (24.3%) double-level osteotomies were performed virtually with a mean hip-knee-ankle angle of 176.4 ± 6.6. In distal femur osteotomy, the mean error % between methods 1 and 2 was 38.9 ± 16.7% and 22.4 ± 16.8% for the opening and closing groups, respectively. In proximal tibial osteotomies, the mean error % was 22.7 ± 15.6% and 9 ± 10.8% for the opening and closing groups, respectively. In double-level osteotomy, the mean error % of femur-based corrections was 34.9 ± 19% and 19.5 ± 21% for the opening and closing groups, respectively, and the mean error of the tibial-based corrections was 26.4 ± 12.1% for the opening group and 10.8 ± 10% for the closing group, respectively.

CONCLUSION

Planning one millimeter per degree of desired correction for osteotomies around the knee in metaphyseal deformities is a major source of error when compared with digital planning using the Miniaci method. This was seen most frequently with osteotomies of the distal femur and all opening wedge osteotomies.

LEVEL OF EVIDENCE

Level Ⅲ, retrospective cross-sectional study.

3D-printed patient-specific instrumentation decreases the variability of patellar height in total knee arthroplasty

Objective

Three-dimensionally (3D) printed patient-specific instrumentation (PSI) might help in this regard with individual design and more accurate osteotomy, but whether the utility of such instrumentations minimizes the variability of patellar height in total knee arthroplasty (TKA) and the reasons for this effect are unknown. Our aim is to compare and analyze the variability of patellar height with PSI and conventional instrumentation (CI) in TKA.

Methods

Between March 2018 and November 2021, 215 patients with severe knee osteoarthritis who were treated with primary unilateral TKA were identified for this observational study. The patients were divided into the CI-TKA group and PSI-TKA group according to the osteotomy tools used in TKA. Preoperative and postoperative radiographic parameters including hip-knee-ankle angle (HKA), posterior tibial slope (PTS), Insall-Salvati ratio, modified Caton-Deschamps (mCD) ratio, anterior condylar offset (ACO), and posterior condylar offset (PCO) were evaluated.

Results

The groups were similar in patients' demographic data, clinical scores, and radiographic parameters preoperatively. Overall, according to the results of the Insall-Salvati ratio, postoperative patellar height reduction was noted in 140 patients (65.1%). Interestingly, the variability of patellar height was smaller in the PSI-TKA group. Radiographic evaluation revealed that the Insall-Salvati ratio after TKA had a minor change in the PSI-TKA group (p = 0.005). Similarly, the mCD ratio after TKA also had a minor change in the PSI-TKA group (p < 0.001). Compared to those in the CI-TKA group, the ACO (p < 0.001) and PCO (p = 0.011) after TKA had a minor change in the PSI-TKA group, but no minor PTS change (p = 0.951) was achieved in the PSI-TKA group after TKA. However, even with 3D-printed patient-specific instrumentation, there were still significant reductions in patellar height, ACO, PCO, and PTS after TKA (p < 0.001).

Conclusion

The variability of patellar height was sufficiently minimized with more accurate anterior and posterior femoral condyle osteotomy when 3D printed PSI was used. Furthermore, there was a trend in over-resection of the femoral anterior and posterior condyle and a marked reduction in PTS during TKA, which could lead to a change in patellar height and might result in more patellofemoral complications following TKA.

Level of evidence

Level II.

Tibiofemoral lift-off and resulting laxity following total knee arthroplasty: Frequency in a series of 906 continuous cases and functional consequences at 4 years' follow-up in a case-control study

BACKGROUND

Tibiofemoral instability is one reason for early revision of total knee arthroplasty. It can be the consequence of tibiofemoral laxity, especially in the coronal plane with tibiofemoral lift-off. But does femoral condyle lift-off on conventional postoperative radiographs suggest the presence of laxity or potential instability? To our knowledge, this question has not yet been answered. This led us to conduct a retrospective study to evaluate (1) the frequency of lift-off on postoperative radiographs, (2) the relationship between lift-off and laxity in the short term and (3) the functional consequences of lift-off.

HYPOTHESIS

Postoperative lift-off is a rare event that is predictive of laxity.

METHODS

We carried out a single-center retrospective study using postoperative radiographs from patients who underwent primary total knee arthroplasty between 2014 and 2016. The sample consisted of 906 patients. Lift-off was defined as a tibiofemoral angle of 3° or more on immediate postoperative radiographs (day 0) that were non-weightbearing and had no stress applied. The functional outcomes were determined in the 17 patients identified as having lift-off who had been operated in the first year (2014) to ensure the follow-up was long enough. These patients were compared to 34 matched control patients who were operated the same year and chosen randomly among patients not having lift-off. The matching ratio was 2 controls to 1 case. Preoperative and surgical data were compiled from each patient's electronic medical record. Patients were evaluated at 4 years postoperatively using the subjective Oxford-48, objective HSS score, IKS score, overall patient satisfaction and stress radiographs of the knee. The cases of lift-off observed in 2014 (n=17) were paired with a control group of patients selected randomly during 2014.

RESULTS

The frequency of the lift-off event was 63/906 or 7%. The frequency was consistent over the three years studied: 7.1% in 2014 (19/269), 6.2% in 2015 (22/354) and 7.8% in 2016 (22/283). There was no significant difference between the two groups (17 with lift-off and 34 without) in the sex, age, body mass index and coronal plane deformity (preoperative HKA angle). At a mean follow-up of 4 years (range 12-49 months), the knees with postoperative lift-off had more laxity (p=0.002), particularly laxity when varus stress was applied (p=0.009). There were no other significant differences in the outcomes.

DISCUSSION

Immediate postoperative lift-off after total knee arthroplasty is not a rare event, with a 7% frequency in our study. While it reveals that laxity is present in the particular compartment, there is no evidence of functional consequences at 4 years' follow-up; however, a long-term assessment is required to verify this finding.

LEVEL OF EVIDENCE

III - case-control study.

Visual Inspection for Lower Limb Malalignment Diagnosis Is Unreliable

OBJECTIVE

Visual inspection of the lower limb is often part of standard clinical practice during a physical examination at the outpatient clinic. This study aims to investigate how reliable visual inspections are in terms of detecting lower limb malalignments without additional tools and physical examinations.

DESIGN

This study enrolled 50 patients. Each patient underwent a whole leg radiograph (WLR); in addition, a standardized digital photograph was taken of the lower limbs. Four persons (different experience levels) visually rated the digital photograph twice (unaware of the hip knee angle [HKA] on the WLR) and placed them in the category: severe valgus (>5°); moderate valgus (2°-5°); neutral, moderate varus (2°-5°); and severe varus (>5°). Visual ratings were compared with the measured HKA on WLRs for correlation using Spearman's rho. Linear ordinal regression models with significance when P < 0.05 were used to test whether body mass index (BMI), age, gender, and HKA were possible risk factors for incorrect visual HKA assessment.

RESULTS

Spearman's rho between the visual assessment and measured HKA on the WLR was moderate with 0.478 (P < 0.01). Women had an increased odds ratio of 3.7 (P = 0.001) for incorrect visual assessment. Higher HKA also increased the odds ratio for erroneous visual assessment with 1.4 (P = 0.003). BMI and age did not significantly increase the odds of erroneous visual leg axis assessments in this study.

CONCLUSIONS

Visual assessment of the lower limb alignment does not provide clinically relevant information. Lower limb malalignment diagnoses cannot be performed using only a visual inspection. Physical examination tests and radiographical assessments are advised.

LEVEL OF EVIDENCE

Diagnostic level II.

Slope-decreasing anterior closing wedge proximal tibial osteotomies using the freehand technique are accurate to within 2̊

INTRODUCTION

Anterior cruciate ligament (ACL) reconstruction requires a detailed analysis of the posterior tibial slope (PTS) as excessive values may cause the reconstruction to fail and require a slope-decreasing anterior closing wedge tibial osteotomy combined with revision of the failed ACL reconstruction. The main purpose of this study was to assess the accuracy of correction after slope-decreasing anterior closing wedge tibial osteotomy in cases of chronic anterior instability caused by ACL rerupture.

MATERIALS AND METHODS

This single-center retrospective study included 19 patients (20 knees) operated on by slope-decreasing anterior closing wedge tibial osteotomy combined with a second revision ACL reconstruction. The mean age was 22.4±3.3 years and the mean follow-up was 12.7±4.4 months. The preoperative planning was based on lateral calibrated X-rays of the entire tibia. The height of the closing wedge, which corresponded to the base of the osteotomy, was measured in millimeters. The procedure was performed using the freehand technique. The accuracy of the correction was defined as the difference between the desired preoperative PTS and the postoperative PTS achieved. An inter- and intraobserver analysis was performed.

RESULTS

The mean preoperative PTS was 13.9±2̊ and the mean postoperative PTS was 4.0±1.7̊. The mean PTS correction was 10.1±2.1̊ with a planned target of 5.4±1.8̊. The accuracy obtained between the planned target and the postoperative corrections was 1.7±1.1̊. The regression analysis showed that the accuracy of the PTS correction was not influenced by the patient's age, BMI, excessive preoperative PTS, or degree of correction achieved (p>0.05).

CONCLUSION

Slope-decreasing anterior closing wedge tibial osteotomies performed using the freehand technique for ACL graft rerupture can correct an excessive PTS within 2̊ of the planned slope correction. This accuracy is not determined by demographic factors, excessive preoperative PTS or degree of correction achieved.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Kinematic alignment matches functional alignment for the extension gap: a consecutive analysis of 749 primary varus osteoarthritic knees with stress radiographs

PURPOSE

The alignment goal in total knee arthroplasty (TKA) remains debated. Two major strategies have emerged based on recreating the native knee: kinematic and functional alignment (KA and FA). Recently a new Coronal Plane Alignment of the Knee (CPAK) classification for KA, based on bony landmarks, was described considering joint line obliquity and the arithmetic HipKneeAnkle angle (aHKA). Valgus corrected HKA medial angle (vcHKA) was measured on distractive valgus preoperative radiographs compensating for cartilage wear and ligament balance in varus osteoarthritis. The purpose of this study was to determine if aHKA accounts for differences in medial laxity for the extension gap by comparing vcHKA to aHKA. The hypothesis was that no significant difference would be observed between the two measurements.

METHODS

This is a retrospective analysis of 749 knees in consecutive patients presenting to a single-centre with primary medial osteoarthritis. Patients underwent standardized weight bearing long-leg and valgus stress radiographs. Tibial mechanical angle (TMA), femoral mechanical angle (FMA) and vcHKA were measured using digital software. aHKA and vcHKA were compared to determine differences due to soft tissue balancing.

RESULTS

The mean FMA was 91.3 ± 2.2° (range 82°-97°), the mean TMA was 85.7 ± 2.5° (range 75°-98°), the mean aHKA was 177.0 ± 3.0° (range 164°-185°) and the mean vcHKA was 176.6 ± 3.1° (range 165°-192°). No significant difference was observed between aHKA and vcHKA (p = 0.06). A significant correlation was found between vcHKA and TMA (ρ = 0.3; p < 0.001) and between vcHKA and FMA (ρ = 0.41; p < 0.001).

CONCLUSION

This study showed that vcHKA was similar to aHKA confirming that aHKA accounts for ligamentous medial laxity. Therefore, kinematic alignment based on the CPAK classification matches the pre-arthritic coronal alignment of the knee for the extension gap.

LEVEL OF EVIDENCE

IV.

Coronal knee alignment measurements differ on long-standing radiographs vs. by navigation

BACKGROUND

The long-standing radiograph (LSR) is the reference tool for assessing knee alignment after total knee arthroplasty (TKA). However, its value is debatable, as many factors can influence measurement accuracy. Computer-assisted surgery (CAS) provides accurate measurements. Few studies have compared LSR and computer-assisted measurements of knee alignment. The objective of this study was to compare hip-knee-ankle (HKA) angle values obtained before and after TKA on LSRs to those obtained during CAS.

HYPOTHESIS

The HKA angle values measured on LSRs before and after surgery are identical to those measured during CAS.

MATERIAL AND METHODS

The HKA angles of 126 knees were measured on bipedal full-weight-bearing LSRs obtained before and 3 months after TKA. The results were compared to the values obtained during CAS.

RESULTS

Before surgery, the standard deviation was 2.672, with limits of agreement of {-5.391; + 5.082}. The intra-class coefficients were good for the overall measurements (0.9), good for detecting>10° varus (0.89), fair for<10° varus and valgus (0.66 and 0.71, respectively), poor for>10° valgus (0.43) and poor for normal alignment (0). Post-operatively, the standard deviation was 3.113, with limits of agreement of {-6.426; +5.776}. The intra-class coefficient was poor for the overall measurements (0.20), negative for normal alignment (-0.05) and<10° valgus (-0.05), and positive for<10° varus (0.017) and for>10° varus and valgus (0.33).

CONCLUSION

Before TKA, the LSR overestimates the deformity compared to CAS. After surgery, the two methods are not comparable. These findings underline the relevance of routinely obtaining LSRs and for using LSR results to estimate costs for healthcare insurance reimbursement purposes.

LEVEL OF EVIDENCE

IV, retrospective observational cohort study.

Mechanical alignment for primary TKA may change both knee phenotype and joint line obliquity without influencing clinical outcomes: a study comparing restored and unrestored joint line obliquity

PURPOSE

In total knee arthroplasty (TKA), knee phenotypes including joint line obliquity are of interest regarding surgical realignment strategies. The hypothesis of this study is that better clinical results, including decreased postoperative knee pain, will be observed for patients with a restored knee phenotype.

METHODS

A retrospective analysis was performed on prospective data, including 1078 primary osteoarthritic knees in 936 patients. The male:female ratio was 780:298, mean age at surgery was 71.3 years ± 8.0. International Knee Society Scores and standardized long-leg radiographs (LLR) were collected preoperatively and at 2 years follow-up after TKA. Patients were categorized using the Coronal Plane Alignment of the Knee (CPAK) classification including the lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) measured on LLR by a single observer, allowing knee phenotypes to be categorized considering the arithmetic hip-knee-ankle (aHKA) angle (MPTA-LDFA) as measure of constitutional alignment, and joint line obliquity (JLO) (MPTA + LDFA). Clinical results were compared between patients with surgically restored preoperative constitutional knee phenotype to patients without restored constitutional knee phenotypes. Descriptive data analysis such as means, standard deviations and ranges were performed. T tests for independent samples were performed to compare group differences. Comparisons of categorical data were performed using the χ² test. Significance was set at p < 0.05.

RESULTS

A third of patients (33.4%) had constitutional knee varus with apex distal JLO. 63.5% of patients had preoperative apex distal JLO. Postoperatively, 57.8% of patients had a neutral HKA (- 2° to 2°) and a neutral JLO (- 3° and 3°), with only 18% of patients with restored constitutional knee phenotype. Of these patients, statistically less postoperative pain was observed in patients where apex distal JLO was restored compared to non-restored apex distal JLO (pain score 46.7 vs. 44.6; p = 0.02) without clinical relevance. Other categories of restored JLO or arithmetic HKA angle were not associated with improved outcomes.

CONCLUSION

This study showed that performing mechanical alignment for primary TKA resulted in most cases in a change of the preoperative knee phenotype. These results emphasize the relevance of considering joint line obliquity to better understand preoperative knee deformity and better restore knee phenotypes with a more personalized realignment strategy to potentially improve TKA postoperative results.

LEVEL OF EVIDENCE

III.

Accuracy of the correction achieved after a valgus high tibial osteotomy: Comparison of the Hernigou table and navigation

INTRODUCTION

The outcome of a medial opening wedge valgus high tibial osteotomy indicated for the treatment of isolated medial tibiofemoral osteoarthritis depends mainly on the accuracy of the correction of the hip-knee-ankle angle (HKAA) and the mechanical medial proximal tibial angle (mMPTA). Most authors aim for a desired correction target between 2° and 4° of valgus. Several planning and surgical techniques have been described to achieve this target value that is specific to each surgeon.

OBJECTIVE

The purpose of this study was to compare the accuracy of the correction achieved using either the Hernigou table (HT) planning method or a computer-assisted navigation system (CAS). It was hypothesized that no difference would be found between these 2 techniques.

MATERIALS AND METHODS

This retrospective single-center study involved 43 knees: 21 in the HT group and 22 in the CAS group. Two surgeons (ME, JYJ), who were experts in 1 of the 2 planning methods performed these procedures, with a single surgeon assigned to each group. The correction was noted in the operative report and was considered to be the desired correction target. The surgical correction was calculated by comparing preoperative and immediate postoperative mMPTA measurements. The surgical accuracy, where a value close to 0 represented optimal accuracy, was defined as the absolute value of the difference between the correction target set by the surgeon and the surgical correction achieved. The median accuracy between the 2 groups was compared by a Mann-Whitney U test (significance level at 5%). The number of patients deviating from the target by>3° was analyzed with a Fisher exact test (significance level at 5%). Pre- and postoperative comparisons of the HKAA measurements could not be used because the measurement was not performed postoperatively for the CAS group.

RESULTS

The median surgical accuracy on the mMPTA was 1.4° (0-4.1) for the HT group versus 1.9° (0.2-6.7) for the CAS group (p=0.85). Sixteen procedures (76%) were performed with an accuracy of<3° in the HT group versus 15 in the CAS group (68%) (p=0.73).

DISCUSSION-CONCLUSION

The working hypothesis was confirmed: no differences were found between the HT and CAS groups regarding the surgical accuracy in achieving the corrections set in this series. We therefore demonstrated that HT was a highly accessible, simple and reliable technique for achieving the planned target. It can be used widely.

LEVEL OF EVIDENCE

III; comparative retrospective series.

Primary osteoarthritic knees have more varus coronal alignment of the femur compared to young non-arthritic knees in a large cohort study

PURPOSE

Many surgeons are performing total knee arthroplasty (TKA) with an aim to reproducing native anatomical coronal alignment. Yet, it remains unclear if primary osteoarthritic and non-osteoarthritic populations have similar knee coronal alignment. This study aims to describe and compare the distribution of femoral and tibial coronal alignment in a large primary osteoarthritic cohort and a young non-osteoarthritic cohort.

METHODS

This is a retrospective analysis of a monocentric prospectively gathered data, from 1990 to 2019, of 2859 consecutive primary osteoarthritic knees in 2279 patients. Patients underwent standardized long-leg radiographs. Femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were digitally measured using software. Femoral, tibial and knee phenotypes were analyzed, and descriptive data were reported. Data were compared to a young non-osteoarthritic population previously described.

RESULTS

In osteoarthritic knees, the mean FMA was 91° ± 2.9° (range 86°-100°) and the mean TMA was 87° ± 3.1° (range 80°-94°). No significant difference was observed for FMA and TMA between genders. The most common femoral and tibial phenotypes were varus (38.7%) and neutral (37.1%). The most frequent knee phenotype was a varus femoral phenotype with a neutral tibial phenotype (15.5%), which is different to the non-osteoarthritic population.

CONCLUSION

This study showed the wide distribution of knee phenotypes in a large osteoarthritic cohort. There was more varus distribution of the femoral coronal alignment compared to a non-osteoarthritic population, suggesting consideration and potential adaptation of the realignment strategy of the femoral component during TKA.

LEVEL OF EVIDENCE

III.

Reliability of Plain Radiographs Versus Magnetic Resonance Imaging to Measure Tibial Slope in Sports Medicine Patients: Can They Be Used Interchangeably?

Background:

The slope of the tibial plateau has been proposed as a reason for failure of anterior cruciate ligament reconstruction.

Purpose:

To evaluate the interobserver reliability of measurements of tibial slope on radiographs versus magnetic resonance imaging (MRI) scans and to assess whether the modalities can be used interchangeably for this purpose.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

This retrospective study included 81 patients aged 18 to 30 years who were evaluated in a sports medicine setting for knee pain and who had lateral knee radiographs as well as knee MRI scans on file. Medial and lateral tibial plateau slope measurements were made by 3 blinded reviewers from the radiographs and MRI scans using graphic overlay software. The paired t test was used to compare measurements of the medial tibial plateau slope (MTPS) and lateral tibial plateau slope (LTPS) from radiographs and MRI scans. Intraclass correlation coefficients (ICCs) were calculated to determine intra- and interobserver reliability of measurements within each imaging modality, and Pearson correlation coefficients were calculated to determine the relationship between measurements on radiographs versus MRI scans.

Results:

Imaging from 81 patients were included. The average MTPS was significantly larger on radiographs compared with MRI scans (8.7° ± 3.6° vs 3.7° ± 3.4°; P < .001), and the average LTPS was also significantly larger on radiographs compared with MRI scans (7.9° ± 3.4° vs 5.7° ± 3.7°; P < .001). ICC values indicated good to excellent intraobserver agreement for all imaging modalities (ICC, 0.81-0.97; P ≤ .009). The ICCs for interobserver reliability of MTPS and LTPS measurements were 0.92 and 0.85 for radiographs, 0.87 and 0.83 for MRI based off the subchondral bone, and 0.86 and 0.71 for MRI based off the cartilage, respectively (P < .001). Medium correlation was noted between radiographic and MRI measurements; Pearson correlation coefficients for radiographic versus subchondral MRI measurements were 0.30 and 0.37 for MTPS and LTPS, respectively.

Conclusion:

The average MTPS and LTPS were significantly larger on radiographs compared with MRI scans. Although tibial slope measurements using radiography and those using MRI are reliable between individuals, the measurements from radiographs and MRI scans cannot be used interchangeably, and caution should be used when interpreting and comparing studies using measurements of the tibial slope.

A New Accurate, Simple and Less Radiation Exposure Device for Distal Locking of Femoral Intramedullary Nails

Background

Due to the metal elasticity of intramedullary nails (IMs) and irregularities of the long bone marrow cavity and other reasons, one of the greatest challenges for surgeons is to position the distal locking screw. Therefore, a novel laser guiding navigation device was designed for the distal locking of femoral IMs. The purpose of this study was to compare the effectiveness of the novel device and freehand technique for distal locking of IMs in the femoral model.

Methods

The laser guiding navigation device (laser group) and freehand technique (freehand group) were used in the distal locking of the IMs in the femoral model. All operations were performed by surgeons of the same level. The differences between the two groups were compared in terms of operative time, radiation exposure time, first success rate, deviation angle between ideal trajectory and actual trajectory, and learning curve.

Results

The distal locking of the IMs in the femoral model was performed 40 times in each group. The results showed that the laser group was better than the freehand group in terms of operative time (345±165 VS 212±105 seconds, t=4.27, P<0.001), radiation exposure time (164±57 VS 41±15 seconds, t=13.15, P<0.001) and first successrate (χ ²=21.36, P<0.001). Compared with the freehand group, the actual trajectory of the laser group was closer to the ideal trajectory in coronal and horizontal planes. Furthermore, the learning curve time of the laser group was shorter.

Conclusion

Compared with traditional freehand technique, the novel laser guiding navigation device can shorten the operative time and reduce radiation exposure invitro. In addition, it is easy to master with more accuracy and a higher first success rate in vitro.

Advantages of patient-specific cutting guides with disposable instrumentation in total knee arthroplasty: a case control study

Background

Total knee arthroplasty (TKA) is most frequently planned using conventional two-dimensional weight-bearing lower limb radiographs and is performed with conventional femoral and tibial cutting guides. Questions have been raised about the accuracy of conventional TKA instrumentation and planning for an anatomically standard or complex joint. Use of computed tomography (CT)-based three-dimensional (3D) templating and patient-specific cutting guides printed in 3D has shown improved postoperative lower limb alignment parameters. This case-control study compared costs and operative times of using CT-based, patient-specific, single-use instruments versus conventional metal instruments for TKA.

Methods

In this case-control, retrospective chart review, all TKAs were performed by one senior surgeon, using the F.I.R.S.T. posterior-stabilised knee prosthesis (Symbios, CH), with a similar protocol and identical operating room setup. Group A included 51 TKAs performed with patient-specific cutting guides and conventional metal instruments. Group B included 49 TKAs performed with patient-specific cutting guides and patient-specific, single-use instrumentation. Operation duration, number of instrumentation trays and sterilisation costs were evaluated.

Results

The groups were similar for age, body mass index, hip-knee-ankle angle and operation duration. The mean number of instrumentation trays was 8.0 ± 0.8 for group A (controls) and 5.1 ± 0.9 for group B (p<0.001). The mean sterilisation costs were 380 ± 47 Swiss Francs (CHF) for group A and 243 ± 55 CHF for group B (p<0.001), for a mean cost reduction of 130.50 CHF per intervention in group B. The time interval between two consecutive surgeries was 24 min for group A and 18 min for group B. There were no adverse events or complications, instrument-related or otherwise.

Conclusion

Compared to conventional instrumentation, use of patient-specific, single-use instruments for TKA reduced the number of instrumentation trays by more than one-third and saved 36% in sterilisation costs. If fabrication costs of single-use instruments are included by the company, the total cost is significantly diminished. There was no operative time advantage for single-use instrumentation.

Long-term radiological changes and functional outcomes after proximal row carpectomy: Retrospective study with 3 years' minimum follow-up

INTRODUCTION

The aim of this study was to analyze the radiological changes and determine the clinical and functional outcomes of proximal row carpectomy (PRC) over the long term.

HYPOTHESIS

Radiological changes after PRC occur in every patient while the clinical and functional outcomes remain stable over time.

METHODS

This was a retrospective single-center study of patients who underwent PRC between January 2004 and December 2014. A clinical assessment (range of motion, grip strength), functional assessment (Mayo Wrist score and QuickDASH) and radiographic assessment (radiocapitate osteoarthritis, radiocapitate congruency) was done in every patient at the longest follow-up.

RESULTS

Thirty-one patients were reviewed with a mean follow-up of 97.9 months. The indications for PRC were SLAC (n=10), SNAC (n=5), Kienböck disease (n=9) and other conditions (n=7). The radiocapitate index, which is the radius of curvature of the tip of the capitate divided by the mean radius of curvature of the lunate fossa, went from 0.68 immediately postoperative to 0.74 at the final assessment (p=0.035). The mean flexion/extension arc was 93°. The mean grip strength was 25 kg. The mean QuickDASH was 29 and the mean Mayo Wrist score was 69. Fifteen patients had radiocapitate osteoarthritis. Seven patients (22%) required revision surgery for wrist fusion after a mean of 18.6 months.

CONCLUSION

Radiological adaptation in the radiocapitate joint after PRC was found in this study. PRC is a reliable solution and yields stable outcomes over time for treating radiocarpal osteoarthritis, except in young adults and manual laborers who had a notable early revision rate.

LEVEL OF EVIDENCE

IV - retrospective study.

Accuracy of the correction obtained after tibial valgus osteotomy. Comparison of the use of the Hernigou table and the so-called classical method

INTRODUCTION

Medial valgus-producing tibial osteotomy (MVTO) is classically used to treat early medial femorotibial osteoarthritis. Long-term results depend on the mechanical femorotibial angle (HKA) obtained at the end of the procedure. A correction goal between 3 and 6° valgus is commonly accepted. Several planning methods are described to achieve this goal, but none is superior to the other.

OBJECTIVE

The main objective was to compare the accuracy of the correction obtained using either the Hernigou table (HT) or a so-called conventional method (CM) for which 1° of correction corresponds to 1° of osteotomy opening. The secondary objective was to analyze the variations observed in the sagittal plane on the tibial slope and on the patellar height. The working hypothesis was that the HT allowed a more accurate correction and that the tibial slope and patellar height were modified in both groups.

MATERIAL AND METHOD

In this monocentric and retrospective study, two senior surgeons operated on 39 knees (18 in the CM group, 21 in the HT group) between January 1, 2009 and December 31, 2014. The operator was unique for each group and expert in the technique used. The correction objective chosen for each patient, and written in the operative report, was considered as the one to be achieved. The surgical correction was the difference between the pre-operative and immediate post-operative data (< 5 J) for the mechanical tibial angle (MTA) and the hip-knee-ankle (HKA) angle. Surgical accuracy, where a value close to 0 is optimal, was the absolute value of the difference between the surgical correction performed and the goal set by the surgeon.

RESULTS

The median surgical accuracy on the MTA was 3.5° [0.2-7.4] versus 1.4° [0-4.1] in the CM and HT groups, respectively (p = 0.006). In multivariate analysis, with the same objective, the CM had a significantly lower accuracy of 1.9° ± 0.8 (p = 0.02). For HKA, the median accuracy was 3.1° [0.3-7.3] versus 0.8° [0-5] in the CM and HT groups, respectively (p = 0.006). Five (5/18, 28%) and 16 (16/21, 76%) knees were within 3° of the target in the CM and HT groups, respectively (p = 0.004). The median tibial slope increased in both groups. This increase was significantly greater in the CM group compared with the HT group, with 5.5° [- 0.3-13] versus 0.5 [- 5.2-5.6], respectively (p < 0.001). The median Caton-Deschamps index decreased (patella lowered) in both groups after surgery, by - 0.21 [- 1.03; - 0.05] and - 0.14 [- 0.4-0.16], but without significant difference (p = 0.19). In univariate analysis, changes in tibial slope and patellar height were not significantly related to frontal surgical correction performed according to ΔMTA (R² = 0.07; p = 0.055) and (R² = - 0.02; p = 0.54) respectively.

DISCUSSION

The correction set by the surgeons was achieved with greater accuracy and more frequently in the HT group, confirming the working hypothesis. The HT is therefore recommended as a simple way of achieving the set objective; the tibial slope and patellar height were modified unaffected by the frontal correction performed.

Morphometric study of gender difference in osteoarthritis posterior tibial slope using three-dimensional magnetic resonance imaging

Posterior tibial slope (PTS) is an important parameter of sagittal alignment associated with postoperative stability and kinematics after total knee arthroplasty (TKA). However, data are limited regarding the innate gender differences in PTS in Koreans. The current study separately measured the PTS of the medial and lateral tibial plateau on magnetic resonance images of 511 patients with knee joint osteoarthritis who had Kellgren and Lawrence grade 3 and 4 (430 women, 81 men) and compared the measurements between and within the genders. The tibia was then rotated to the tibial plateau with the tibial centroid axis and the PTS was evaluated from best-fit planes on the surface of the proximal tibia and individually for the medial, lateral, and overall plateaus. The average overall PTS was 10.0° ± 3.5°. The average overall PTS of the female and male patients was 10.2° ± 3.4° and 8.8° ± 4.0°, respectively. The average medial PTS was 10.4° ± 4.0°, significantly greater than the mean lateral PTS of 8.7° ± 3.9° (P < 0.05). The average medial and lateral tibial slopes for female patients were 10.7° ± 3.8° and 8.8° ± 3.8°, respectively, while the average medial and lateral tibial slopes for male patients were 8.9° ± 4.8° and 7.9° ± 4.7°, respectively. The medial and overall PTS were significantly greater in female patients than in male patients (P < 0.05). The results showed a gender difference in PTS and that medial PTS was greater than lateral PTS. These findings have clinical relevance in knee reconstructive surgery for determining ideal placement of the posterior slope tibial component. Surgeons should be aware of variability and gender differences in the tibial slope of patients undergoing TKA.

Over-voluming predicted by pre-operative planning in 24% of total knee arthroplasty

PURPOSE

Numerous studies demonstrated that prosthetic overhang and over-sizing cause pain and stiffness following total knee arthroplasty (TKA), but none considered volume changes within the joint capsule. This study was designed to investigate differences in volumes of resected bone compared to implanted components in TKA, and to determine the incidence and factors related to 'over-voluming'.

METHODS

Three-dimensional reconstructions were created from 100 magnetic resonance imaging scans taken to design patient-specific instruments for TKA. The preoperative simulations were used to calculate the volume ratio (VR) by dividing volume of planned components by that of planned bone resections. Uni- and multi-variable linear regressions were performed to determine associations between 'over-voluming' (VR > 1.0) and gender, implant size and version (standard versus narrow), osteophytes, resection levels, external rotation of the femoral component, hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA).

RESULTS

The overall implant/bone volume ratio was 0.91 ± 0.11 (range 0.63-1.16) with 'over-voluming' observed in 24 knees. Multi-variable regression confirmed over-voluming to be associated with lower mLDFA (OR 0.66; CI 0.45-0.93; p = 0.026) and extensive osteophytes (OR 0.14; CI 0.03-0.61; p = 0.014), but not HKA angle (OR 0.98; CI 0.76-1.26; p = n.s.).

CONCLUSIONS

Over-voluming was observed in 24% of knees, in which the implant volume exceeded the resected volume by up to 16%. Over-voluming was associated with intra-articular femoral valgus (low mLDFA), but not directly associated with tibial deformity (mMPTA) or HKA angle. Over-voluming could be associated with prosthetic overhang or excessive tensions within the joint capsule, and, therefore, contribute to unexplained pain and stiffness following TKA.

LEVEL OF EVIDENCE

IV, Retrospective cohort study.

Noninvasive navigated assessment of the lower limb axis prior to knee arthroplasty: a feasibility study

The purpose of the study was to assess accuracy and repeatability of a noninvasive navigated (NIN) measurement of the lower limb axes by comparison with the conventional, invasive navigated (IN) technique. The tested hypothesis was that NIN measure will significantly differ from IN measure when performed on a supine patient under general anesthesia just prior to knee arthroplasty. The accuracy study involved 20 cases. The following measures were performed with both systems: maximal extension angle, coronal mechanical femoro-tibial angle at the previously assessed maximal extension angle, coronal mechanical femoro-tibial angle at 30° of knee flexion. NIN and IN measures were compared with the appropriate statistical tests. The repeatability study involved 14 cases. The same measures were performed with the NIN system twice by two independent observers. The intra- and inter-observer variability was assessed by the calculation of the intra-class correlation coefficient. After correction for the systematic biases, the differences between the two systems were not significant. A good correlation, a good coherence and an excellent agreement between NIN and IN measures of maximal extension angle and coronal femoro-tibial mechanical angle at maximal extension. But measures at 30° of flexion were inconsistent. The NIN system can be considered as an accurate and precise tool for the assessment of the knee extension angle and the coronal deformation at maximal extension prior to knee arthroplasty. But this system is less accurate and less repeatable when measuring coronal femoro-tibial mechanical angle at 30° of flexion and should not be used for this purpose.

Three-Dimensional Computed Tomography Analysis of the Posterior Tibial Slope in 100 Knees

BACKGROUND

The posterior tibial slope (PTS) is an important consideration in knee arthroplasty. However, there is still no consensus for the optimal slope. The objectives of this study were (1) to reliably determine the native PTS in this population using 3-dimensional computed tomography scans and (2) to determine the normal reference range for PTS in this population.

METHODS

One hundred computed tomography scans of disease-free knees were analyzed. A 3-dimensional reconstructed image of the tibia was generated and aligned to its anatomic axis in the coronal and sagittal planes. The tibia was then rotationally aligned to the tibial plateau (tibial centroid axis) and PTS was measured from best-fit planes on the surface of the proximal tibia and individually for the medial and lateral plateaus. This was then repeated with the tibia rotationally aligned to the ankle (transmalleolar axis).

RESULTS

When rotationally aligned to the tibial plateau, the mean PTS, medial PTS, and lateral PTS were 11.2° ± 3.0 (range, 4.7°-17.7°), 11.3° ± 3.2 (range, 2.7°-19.7°), and 10.9° ± 3.7 (range, 3.5°-19.4°), respectively. When rotationally aligned to the ankle, the mean PTS, medial PTS, and lateral PTS were 11.4° ± 3.0 (range, 5.3°-19.3°), 13.9° ± 3.7 (range, 3.1°-24.4°), and 9.7° ± 3.6 (range, 0.8°-17.7°), respectively.

CONCLUSION

The PTS in the normal Asian knee is on average 11° (mean) with a reference range of 5°-17° (mean ± 2 standard deviation). This has implications to surgery and implant design.