Patellofemoral Indices Research Articles

Minimal impact of beam projection angle deviations in skyline (Laurin) view and the efficacy of the anterior border of proximal tibia as a guiding landmark.

Obtaining an optimal knee skyline view is challenging due to inaccuracies in beam projection angles (BPAs) and soft tissue obscuring bony landmarks. This study aimed to assess the impact of BPA deviations on patellofemoral index measurements and assessed the anterior border of the proximal tibia as an anatomic landmark for guiding BPAs. This retrospective study consisted of three parts. The first was a simulation study using 52 CT scans of knees with a 20° flexion contracture to replicate the skyline (Laurin) view. Digitally reconstructed radiographs simulated neutral, 5° downward, and 5° upward tilt BPAs. Five patellofemoral indices (sulcus angle, congruence angle, patellar tilt angle, lateral facet angle, and bisect ratio) were measured and compared. The second part was a proof of concept study on 162 knees to examine patellar indices differences across these BPAs. Lastly, the alignment of the anterior border of the proximal tibia with the BPA tangential to the patellar articular surface was tested from the CT scans. No significant differences in patellofemoral indices were found across various BPAs in both the simulation and proof of concept studies (all p > 0.05). The angle between the anterior border of the proximal tibia and the patellar articular surface was 1.5 ± 5.3°, a statistically significant (p = 0.037) yet clinically acceptable deviation. Patellofemoral indices in skyline view remained consistent regardless of BPA deviations. The anterior border of the proximal tibia proved to be an effective landmark for accurate beam projection.

Osteotomy Correction Angle Cut-off Points Can Guide the Operation to Prevent a Significant Decrease in Patella Height.

Patients who undergo a biplanar ascending medial open-wedge high tibial osteotomy with an excessive correction angle might experience patella infera and even knee pain after surgery. The purpose of this study was to identify the cut-off points for the degree of knee varus correction of open-wedge high tibial osteotomy, which is related to the symptomatic patellar position change. This retrospective study included 124 patients (mean age 61.69 ± 6.28 years; 78 women, 46 men) with varying degrees of varus knee osteoarthritis. All patients had undergone standard biplanar medial open-wedge high tibial osteotomy. They were divided into nine groups according to the change in hip-knee-ankle angle. Plain radiographs and three-dimensional CT images were obtained preoperatively and 18 months postoperatively. Patellar height was assessed using the Caton-Deschamps index, the Insall-Salvati index, and the Blackburne-Peel index. The patellofemoral index and patellar tilt were used to evaluate the degree of horizontal displacement of the patella. The varus correction, medial-proximal tibial angles, joint line convergence angles, and hip-knee-ankle angles were also measured. The subjective score was evaluated using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC). There were significant changes in patella indexes in each group after surgery, among which there was no significant difference in patellar height changes for Groups A to F (p > 0.05), which were significantly lower than those in Group G, H, and I (p < 0.001). The patellar tilt and patellofemoral index also followed the same trend. The improvement in WOMAC scores for Groups G, H, and I was also significantly less for Groups A to F (p < 0.001). The patellar height, patellar tilt, and patellofemoral index all changed significantly in parallel with increasing degrees of osteotomy correction. The cut-off points for correction angle are 12.5° to 13.4°. When the correction angle is larger than this range, the patellar position can be significantly affected. Postoperative patellofemoral joint pain may be related to the changes in patella position.

Poster 241: Outcomes of Trochleoplasty for Recurrent Patellar Dislocation in Adolescents with Open Physes

Objectives: Patellofemoral dislocation, the most severe presentation on the spectrum of patellar instability, is most common in adolescent populations. Trochlear dysplasia is an integral component of the disorder, and procedures aimed at correcting instability by addressing this dysplasia are often necessary. A theoretical risk of injury to the distal femoral physis exists in these surgeries. At our institution, a thick-flap sulcus deepening technique is used to re-shape the trochlear groove. The risk of injury to the physis in this procedure is not clearly delineated in the current literature. We investigated the outcomes in adolescent patients undergoing this procedure, hypothesizing that patients with open distal femoral physes and less than 2 years of remaining growth can safely and successfully undergo thick-flap sulcus deepening trochleoplasty. Methods: Seventeen adolescents (21 knees) with open physes underwent thick-flap trochleoplasty at our institution. Preoperative radiographs were used to evaluate leg axis and patella alta. Preoperative MRI was used to determine trochlear dysplasia (sulcus depth, spur height, patellofemoral index) and tibial tuberosity to trochlear groove distance (TTTG) distance. Preoperative and postoperative AP and lateral radiographs were used to evaluate and compare the lateral distal femoral angle (LDFA) and Blumensaat’s angle (BA). Preoperative and postoperative IKDC and Kujala outcome scores were measured to evaluate clinical improvement. Results: Median age at time of operation was 14.9 years for girls and 15.5 for boys. Mean follow up was 5.4 years from surgery. At two-year follow up, growth plates were closed in all but one knee. No clinical differences to the leg length or alignment were appreciated. There was no statistically significant change in lateral distal femoral angle (mean change 0.74 degrees, p = 0.1074). There was a statistically significant change in Blumensaat’s angle (mean change 0.89 degrees, p = 0.0477). Mean Kujala score improved significantly from 60.19 preoperatively to 90.36 postoperatively, p= 0.0008. Mean IKDC score improved significantly from 59.37 preoperatively to 87.21 postoperatively, p = 0.00064. There was recurrent instability in one knee, requiring revision surgery with distal femur and Fulkerson osteotomies. Conclusions: Adolescent patients nearing skeletal maturity can safely and successfully undergo thick- flap sulcus deepening trochleoplasty for patellar instability resulting from trochlear dysplasia. At follow- up, there was no clinical evidence of growth disturbances, and postoperative imaging demonstrated less than 1 degree difference in LDFA and BA at skeletal maturity, which are unlikely to be of clinical significance. These findings should be interpreted very carefully, as specific patient selection, trochleoplasty expertise, and extreme caution are still necessary to prevent iatrogenic injury to the distal femoral physis.

Comparative study on imaging and clinical results of patellofemoral joint with kinematic alignment and mechanical alignment in total knee arthroplasty

Objective: To investigate the changes of imaging parameters of patellofemoral joint after kinematic alignment total knee arthroplasty (KA-TKA) and mechanical alignment total knee arthroplasty (MA-TKA) and the effects on clinical outcomes. Methods: A retrospective analysis was performed on 227 patients diagnosed with knee osteoarthritis, 105 males and 122 females, with the age of (68.6±7.2) years (range: 52 to 86 years). The patients underwent unilateral TKA at the Department of Orthopaedic Surgery, Beijing Chaoyang Hospital, Capital Medical University, from January 2020 to July 2021. The patients were divided into the KA-TKA group (n=102) and the MA-TKA group (n=125) according to the alignment method. The Blackburne-Peel index, lateral patellofemoral angle, patellofemoral tilt angle and patellofemoral index of the two groups were recorded before and 6 months after operation. The frequency of lateral patellar retinaculum release, preoperative and postoperative knee range of motion (ROM), and Oxford knee score(OKS) were also recorded. The differences between preoperative and postoperative measurement data of each group were calculated. If the difference was in line with normal distribution, the independent sample t-test or t'-test was used for comparison between the two groups. If it did not conform to normal distribution, Mann-Whitney U test was used. Paired sample t-test was used for comparison before and after treatment. Chi-square test was used for comparation of categorical data between the two groups. Results: After 6 months of operation, the patellar tilt angles of the KA-TKA group and the MA-TKA group were (14.22±3.26)° and (13.35±2.27)°, and the lateral patellar angles were (9.73±4.86)° and (11.91±3.89)°, respectively. The change of lateral patellofemoral angle in the KA-TKA group was significantly less than that in the MA-TKA group ((1.68±4.86)° vs. (4.15±4.88)°, t=3.805, P<0.01). OKS and ROM were improved in the both groups at 6 months after operation (all P<0.05), but there were no statistic significance in preoperative and postoperative difference between the two groups (all P>0.05). The intraoperative lateral patellar retinacular release rate was 14.4% (18/125) in the MA-TKA group and 6.9% (7/102) in the KA-TKA group, with no statistical difference (χ2=3.256,P=0.071). Conclusions: There are greater patella lateral tilt at 6 months postoperatively in the KA-TKA group compared with the MA-TKA group, but this radiographic difference could not show differences of clinical outcomes and postoperative ROM, the frequency of intraoperative lateral patellar retinacular release wouldn't increase. Therefore, KA-TKA does not increase the difficulty of postoperative patellofemoral joint complications and intraoperative lateral patellar release.

Anatomic Risk Factors for Osteochondral Fracture of Acute First-Time Patellar Dislocation in Adolescents: A Retrospective Magnetic Resonance Imaging Study.

Objective To analyze the risk factors for osteochondral fracture (OCF) of first-time acute patellar dislocation (APD) through measurements of patellofemoral anatomy in adolescents. Methods In this prospective study, all patients were divided into two groups according to whether OCF was detected on magnetic resonance imaging (MRI): Group A (associated with OCF) and Group B (without OCF). Patellofemoral anatomy was evaluated with four aspects including trochlear/patellar dysplasia, patella location, patellofemoral matching, and morphologic classification. On MRI scans, trochlear facet asymmetry ratio (TFAR), lateral trochlear inclination (LTI), sulcus angle (SA), trochlear depth (TD), and patellar depth (PD) were measured to assess trochlear/patellar dysplasia. Insall–Salvati index (ISI), Caton–Deschamps index (CDI), Blackburne–Peel index (BPI), lateral patellofemoral angle (LPFA), patellar tilt angle (PTA), and lateral patellar displacement (LPD) were measured to show the location of patella. Patellofemoral matching was analyzed through the measurements of patellofemoral congruence angle (PFCA), patellofemoral index (PFI), and patellotrochlear index (PTI). Results A total of ninety-four adolescents from 49 boys and 45 girls (mean age, 15 years; range, 10–18 years) with first-time APD were recruited and included in Group A (65) and Group B (29). The PFI (2.62 ± 0.51 vs. 2.10 ± 0.44) and PTI (0.28 ± 0.05 vs. 0.22 ± 0.07) were significantly higher in Group B than Group A (P < 0.05). There were no significant differences in other quantitative outcomes of the two groups (P > 0.05). The distribution of Dejour/Wiberg classification was statistically similar between the two groups (P > 0.05). Conclusions Adolescent patients with first-time APD complicating OCF have closer morphologic features of patellofemoral dysplasia and patella location when compared to adolescents without OCF. Abnormal patellofemoral matching increases the risk of OCF after first-time APD in adolescents.

Many Radiographic and Magnetic Resonance Imaging Assessments for Surgical Decision Making in Pediatric Patellofemoral Instability Patients Demonstrate Poor Interrater Reliability

To evaluate the interrater reliability of several common radiologic parameters used for patellofemoral instability and to attempt to improve reliability for measurements demonstrating unacceptable interrater reliability through consensus training. Fifty patients with patellar instability between the ages of 10 and 19 years were selected from a prospectively enrolled cohort. For measurements demonstrating unacceptable interrater reliability (intraclass correlation coefficient [ICC]: <0.6), raters discussed consensus methods to improve reliability and re-examined a subset of 20 images from the previous set of images. If reliability was still low after the second round of assessment, the measure was considered unreliable. Of the 50 included subjects, 22 (44%) were male and the mean age at the time of imaging was 14 ± 2 years. With 1 or fewer consensus training sessions, the interrater reliability of the following radiograph indices were found to be reliable: trochlea crossing sign (ICC: 0.625), congruence angle (ICC: 0.768), Caton-Deshamps index (ICC: 0.644), lateral patellofemoral angle (ICC: 0.768), and mechanical axis deviation on hip-to-ankle alignment radiographs (ICC: 0.665-0.777). Reliable magnetic resonance imaging (MRI) indices were trochlear depth (ICC: 0.743), trochlear bump (ICC: 0.861), sulcus angle (ICC: 0.684), patellar tilt (ICC: 0.841), tibial tubercle to trochlear groove distance (ICC: 0.706), effusion (ICC: 0.866), and bone marrow edema (ICC: 0.961). With 1 or fewer consensus training sessions, the interrater reliability of the following patellofemoral indices were found to be reliable for trochlear morphology: trochlea crossing sign and congruence angle on radiograph and trochlear depth, trochlear bump, and sulcus angle on MRI. Reliable patellar position measurements included: Caton-Deshamps index and lateral patellofemoral angle on radiograph and patellar tilt and tibial tubercle to trochlear groove distance on MRI. Additional global measurements (e.g., mechanical axis deviation on standing radiographs) and MRI assessments demonstrated acceptable reliability. II, prospective diagnostic study.

Weight-bearing MRI with a knee flexion angle of 20\xb0: a study on additional MRI investigation modalities to support a more accurate understanding of patellofemoral instability

BackgroundDiagnosing patellofemoral instability disorders correctly, weight-bearing MRI (WB-MRI) has become an option. Aiming for a best possible accuracy in displaying potentially underlying causes, the named MRI modalities were sporadically even investigated in different knee flexion angles. However, despite confirmed MRI-outcome-differences between WB-MRI and non-WB-MRI, none of the described MRI modalities have so far established themselves. Mainly this is due to an unfeasibility in daily clinical routine in regard to time and economic aspects. Thus, we intended to evaluate an additional but reduced patellofemoral MR-imaging solely in a relevant 20° of knee flexion under WB- and non-WB-MRI conditions.MethodsSeventy-three subjects with and without patellofemoral instability were investigated under supine as well as under WB-MRI conditions in a 20° of knee flexion angle. Patellofemoral risk indices in the sagittal plane (Insall-Salvati-Index, Caton-Deschamps-Index, Patellotrochlear Index) and the axial plane (Patella tilt of Fulkerson and Sasaki) were detected and compared between the different MRI conditions. Significance, reliability and Cohen’s effect size was calculated.ResultsNearly all assessed indices showed significant differences between patients and controls in the different MRI positions. Comparing pairwise, all measured indices failed to show significant differences between the two MRI positions. However, patella tilt angles of the patient group showed an elevation from supine to WB-MRI (14.00 ± 7.54° to 15.97 ± 9.10° and 16.34 ± 7.84° to 18.54 ± 9.43°). Here, Cohen’s d showed small to medium effects between supine and WB-MRI.ConclusionIn comparison to standard MRI in supine position, axial risk indices seem to be accentuated under WB-MRI and a knee flexion angle of 20°. In particular, symptomatic cases with inconspicuous conventional MRI imaging, additional MRI imaging only in the axial plane in a 20° of knee flexion could be beneficious and useful in clinical daily routine.

Three-dimensional assessment of patellofemoral anatomy: Reliability and reference ranges

BackgroundThree-dimensional (3D) imaging and analysis offer new possibilities in preoperative diagnostics and surgical planning. Simultaneous 3D analysis of the joint angles and the patellofemoral anatomy allow for a realistic assessment of bony pathologies in patients with patellofemoral complaints. This study aims to develop a standardized and validated assessment of the 3D patellofemoral morphology and to establish reference ranges. MethodsThirteen patellofemoral anatomic landmarks were defined on 3D bone models of the lower limbs based on computer tomography data and evaluated regarding inter- and intra-observer variability. Further, 60 3D models of the lower limbs of young subjects without any previous knee operation/injury were assessed and rescaled reference values for relevant patellofemoral indices were obtained. ResultsThe mean inter- and intra-observer deviation of all landmarks was below 2.3 mm. The interobserver intraclass correlation coefficient (ICC) was between 0.8 and 1.0 and the intra-observer ICC between 0.68 and 0.99 for all patellofemoral parameters. The calculated reference ranges are: Insall–Salvati index 1.0–1.4; patella tilt 6–18°; patella shift −4 to 3 mm; patella facet angle 118–131°; sulcus angle 141–156°; trochlear depth 3–6 mm; tibial-tuberosity to trochlear groove distance(TT-TG) 2D 14–21 mm; TT-TG 3D 11–18 mm; lateral trochlear inclination 13–23°; trochlear facet angle 43–65°. ConclusionThe demonstrated 3D analysis of the patellofemoral anatomy can be performed with high inter- and intra-observer correlation. Applying the obtained reference ranges and using existing 3D assessment tools for lower limb alignment, a preoperative 3D analysis and planning for complex knee procedures now is possible.

Association between increased signal intensity at the proximal patellar tendon and patellofemoral geometry in community-based asymptomatic middle-aged adults: a cross-sectional study

BackgroundHistological and epidemiological data suggest that increased signal intensity at the proximal patellar tendon on magnetic resonance imaging is a response to tendon loading. As patellofemoral geometry is a mediator of loading, we examined the association between patellofemoral geometry and the prevalence of increased signal intensity at the patellar tendon in community-based middle-aged adults.MethodsTwo hundred-one adults aged 25–60 years in a study of obesity and musculoskeletal health had the patellar tendon assessed from magnetic resonance imaging. Increased signal intensity at the proximal patellar tendon was defined as hyper-intense regions of characteristic pattern, size and distribution on both T1- and T2-weighted sequences. Indices of patellofemoral geometry, including Insall-Salvati ratio, patellofemoral congruence angle, sulcus angle, and lateral condyle-patella angle, were measured from magnetic resonance imaging using validated methods. Binary logistic regression was used to examine the association between patellofemoral geometrical indices and the prevalence of increased signal intensity at the patellar tendon.ResultsThe prevalence of increased signal intensity at the patellar tendon was 37.3%. A greater Insall-Salvati ratio (odds ratio 0.80, 95% confidence interval 0.66–0.97 per 0.1 change in the ratio, p = 0.02), indicative of a higher-riding patella, and a larger patellofemoral congruence angle (odds ratio 0.91, 95% confidence interval 0.85–0.98 per 5 degree change in the angle, p = 0.01), indicating a more laterally placed patella, were associated with reduced odds of increased signal intensity at the patellar tendon. Sulcus angle and lateral condyle-patella angle were not significantly associated with the odds of increased signal intensity at the patellar tendon.ConclusionsIn community-based asymptomatic middle-aged adults, increased signal intensity at the patellar tendon was common and associated with Insall-Salvati ratio and patellofemoral congruence angle, suggesting a biomechanical mechanism. Such work is likely to inform tissue engineering and cell regeneration approaches to improving outcomes in those with tendon pathology.

Associations of trochlea morphology and patellofemoral alignment with prevalent radiographic patellofemoral osteoarthritis

To investigate the relation of trochlea morphology and patellofemoral alignment to prevalent radiographic patellofemoral osteoarthritis (PFOA). A within-person knee-matched case-control study was performed. Participants with unilateral radiographic PFOA were selected from the Multicenter Population-based Osteoarthritis Study (MPOA) in three towns in northern China that was approved by Peking University Health Science Center Ethics Committee (2018PHB166-01). Radiographic PFOA, radiographic tibiofemoral OA, sulcus angle, patellofemoral index and patella displacement were assessed using posterio-anterior and skyline views of the knee. We classified sulcus angle, patellofemoral index and patella displacement into quarters and investigated the relation of each of these measures to prevalent radiographic PFOA. Among 451 participants (mean age: 65.2 years, women: 66.8%) with unilateral radiographic PFOA, a reverse J-shaped relationship was observed between sulcus angle and prevalent radiographic PFOA (P=0.039 for quadratic term). Both higher patellofemoral index and patella displacement were associated with higher prevalent radiographic PFOA. Adjusted odds ratios (ORs) of prevalent radiographic PFOA in the highest quarter of patellofemoral index and patella displacement were 4.69 and 3.60 (Pfor trend <0.001), respectively, compared with the lowest quarter of each measurement. A similar relationship was observed between sulcus angle with either prevalent radiographic lateral or medial PFOA. Higher values of patellofemoral index and patella displacement were statistically significantly associated with higher prevalent radiographic lateral (ORs=5.07 and 4.59, respectively), but not medial PFOA (ORs=0.58 and 0.76, respectively). Extreme sulcus angles as well as higher values of patellofemoral index and patella displacement were associated with higher prevalent radiographic PFOA.

The role of arthroscopic release of gluteal muscle contracture in improving patellofemoral instability

BackgroundGluteal muscle contracture (GMC) is a notable problem in some developing countries and includes features such as a snapping sound of the hip, abnormal gait, and unusual posture when patients squat with the knees together. Arthroscopic release can not only resolve symptoms, as previously reported, but can also greatly improve accompanying patellofemoral instability. This study was conducted to evaluate the effect of arthroscopic release of GMC on patellofemoral instability and its underlying mechanism.MethodsA total of nearly 500 patients who underwent arthroscopic release of GMC over 2.5 years were filtered, and 54 patients were enrolled in the study. The selected research subjects all had combined patellofemoral instability preoperatively. The Lysholm scores and CT scans of the knee were evaluated pre- and postoperatively.ResultsThe mean follow-up time was 12.2 months. All of the surveyed patients had satisfactory clinical outcomes for hip snapping sounds and abnormal gait. In addition, a significant difference (p < 0.05) was observed between pre- and postoperative Lysholm scores, along with significant knee pain relief. Furthermore, the changes in CT scan parameters were significant as well. The average patellar tilt angle (PTA), patellofemoral index (PFI), and lateral patellar displacement (LPD) were obviously decreased (p < 0.05) after the release. Conversely, the mean lateral patellofemoral angle (LPFA) showed a clear difference (p < 0.05) between preoperative and postoperative CT examinations.ConclusionsArthroscopic release of GMC can reduce the tilt and lateral shift of the patella and enhance its stability due to the release of the iliotibial band.

Development and evaluation of a minimally aggressive method of patellofemoral osteoarthritis surgical treatment.

The purpose of this study was to assess the impact of developed minimally invasive operation such as the partial lateral facetectomy (PLFE) with patella thickness resection in patients with lateral patellofemoral (PF) osteoarthritis on short-term clinical and radiographic outcomes. This is a prospective study of 27 knees in 27 patients (18 females and 9 males, mean aged at surgery 59.1-year old) whom a PLFE with patella thickness resection using developed minimally invasive method was performed. Data of preoperative and postoperative questionnaires, physical examinations, and radiographs were analyzed. The minimum follow-up was 12 months (mean, 24.1 months; range, 12-36 months). The subjective outcomes included the anterior pain relief assessed by scores using the Western Ontario and McMaster Universities Arthritis Index score (scores improved considerably by 2.34 points with respect to pain and by 1.63 points with respect to function), visual analog scale, and Knee Society Score (that improved in 78% of the knees). The majority of these patients experienced improvement in their PF symptoms. The PF index decreased considerably after surgery. The mean patellar width and thickness were decreased after surgery, maintaining a width/thickness ratio of 1.8:1.0 after surgery. PLFE with patella thickness resection aiming to decrease the high pressure in the lateral facet and improving congruence of the patella confirmed frequent pain relief. This surgical procedure is minimally invasive, relatively simple, and effective in selected patients and can be a valid early alternative to more complex operations. Level of Evidence: Level IV Therapeutic study.

Clinical application of three-dimensional printing in the treatment of knee varus with high tibial os-teotomy

Objective To evaluate the clinical application of a three-dimensional (3D) printing personalized guide for medial open wedge high tibial osteotomy(MOWHTO) in the treatment of knee varus osteoarthritis. Methods A retrospective study was conducted of the 16 patients with knee varus os-teoarthritis who had been treated at Department of Orthopaedics, Zhengzhou Central Hospital of Zhengzhou University from January 2016 to January 2017. They were 6 men and 10 women, aged from 49 to 65 years (mean, 55.8 years). Bilateral knees were involved in 2 cases and a unilateral knee was involved in 14 cases. Their disease duration ranged from one to 12 years (mean, 5.3 years). A personalized guide for MOWHTO was designed and manufactured by 3D printing for every patient preoperatively. All the patients underwent knee arthroscopy before osteotomy which was assisted by the personalized guide. The femorotibial angle (FTA), medial proximal tibial angle (MPTA), weight bearing line (WBL), posterior tibial slope (PTSA) and the patellofemoral height Insall-Salvati index (IS index) were measured on their X-ray radiographs preoperatively and 6 months postoperatively. The Hospital for Special Surgery (HSS) score and visual analogue scale (VAS) were used to evaluate the outcomes at the final follow-ups. Results All surgeries were successful. The 16 patients were followed up for 6 to 12 months (mean, 9.1 months). The FTA, MPTA, WBL and IS index at postoperative 6 months were significantly improved than the preoperative values (P<0.05). There was no significant difference between postoperative PTSA and preoperative PTSA (P=0.990). The mean VAS scores for the 16 patients at the final follow-ups were 0.8±0.7 points, significantly better than the preoperative ones (4.2±0.9 points) (P<0.05); their mean postoperative HSS scores (89.3±6.7 points) were also significantly improved than the preoperative ones (61.9±10.5 points) (P<0.05). According to the HSS scores at the final follow-ups, the surgical outcomes were excellent in 14 knees, good in 3 and fair in one. Conclusion A 3D printed osteotomy guide can be used to perform precise osteotomy in MOWHTO for knee varus osteoarthritis, leading to effective correction of the alignment of the lower limb and good short-term surgical outcomes. Key words: Knee joint; Osteoarthritis; Abnormalities; Osteotomy; 3D printing technology

The adaptive change of patellofemoral joint after arthroscopic discoid lateral meniscus plasty: An observational study.

The purpose of this study was to investigate the patellofemoral joint adaptive changes after discoid lateral meniscus (DLM) plasty.Forty-one patients with unilateral complete type DLM tears were included in this study. Demographic variables, including gender, age, body mass index (BMI), injury to operation interval, type of injury, and follow-up time, were recorded. The evolution of physical examination, imaging index, and functional score were analyzed by Chi-squared test, Wilcoxon signed ranks test, and Friedman test. Mann–Whitney test was used to analyze the difference at different time points between group PFI > 1.6 and PFI < 1.6.After the patients received arthroscopic DLM plasty, the positive rate of Patella grinding test increased from 19.5% to 29.3%, and it showed significant increased at last follow-up time point (48.8%) (P = .005). Mechanical axis deviation (MAD) significant decreased from −0.7 ± 2.1 mm to −9.4 ± 3.2 mm (P < .001). Lateral patellofemoral angle (LPFA) and lateral shift distance (LSD), respectively, decreased from 11.9 ± 5.8° and 1.0 ± 4.0 mm to 7.2 ± 4.5° and −0.5 ± 3.3 mm (P < .001). Patellofemoral index (PFI) increased from 1.7 ± 0.3 to 1.9 ± 0.4 (P < .001). Kujala score and Lysholm score, respectively, increased from 65.9 ± 10.0 and 85.2 ± 6.4 mm to 61.8 ± 10.2 and 89.5 ± 5.0 (P < .001). Only LSD in group > 1.6 were significant lower than those in group < 1.6 (>1.6: −1.5 ± 2.8, −1.6 ± 2.7, −1.5 ± 2.6; <1.6: 0.8 ± 3.4, 0.4 ± 3.6, 0.6 ± 2.8. P = .010,.038,.011) at the 3 postoperative follow-up time points.After arthroscopic plasty for complete type DLM which decreased the thickness and width of the residual meniscus, in turn causing the varus deformity significantly decreased or a valgus inclination developed. Moreover, the consequent changes of patellofemoral joint caused a certain amount of patellar tilt and patellar dislocation, might aggravated the symptomatic anterolateral knee pain or the lateral patellar compression syndrome.

Variability of Measurement of Patellofemoral Indices with Knee Flexion and Quadriceps Contraction: An MRI-Based Anatomical Study.

PurposeThe purpose of this study was to investigate the impact of varying knee flexion and quadriceps activity on patellofemoral indices measured on magnetic resonance imaging (MRI).Materials and MethodsMRI of the knee was performed in 20 patients for indications other than patellar or patellofemoral pathology. Axial and sagittal sequences were performed in full extension of the knee with the quadriceps relaxed, full extension of the knee with the quadriceps contracted, 30° flexion of the knee with the quadriceps relaxed, and 30° flexion with the quadriceps contracted. Bisect offset, patella tilt angle, Insall-Salvati ratio and Caton-Deschamps index were measured.ResultsWith the knee flexed to 30° and quadriceps relaxed, the mean values of patellar tilt angle, bisect offset, Insall-Salvati ratio and Caton-Deschamps index were all within normal limits. With the knee extended and quadriceps contracted, the mean patellar tilt angle (normal value, <15°) was 14.6° and the bisect offset (normal value, <65%) was 65%, while the Caton-Deschamps index was 1.34 (normal range, 0.6 to 1.3). With the knee extended and quadriceps relaxed, the mean Caton-Deschamps index was 1.31.ConclusionsMRI scanning of the knee in extension with the quadriceps contracted leads to elevated patellofemoral indices. MRI taken with the knee in 30° of flexion allows more reliable assessment of the patellofemoral joint and minimises the confounding effect of quadriceps contraction.

Effects of upright weight bearing and the knee flexion angle on patellofemoral indices using magnetic resonance imaging in patients with patellofemoral instability.

This study analysed the effects of upright weight bearing and the knee flexion angle on patellofemoral indices, determined using magnetic resonance imaging (MRI), in patients with patellofemoral instability (PI). Healthy volunteers (control group, n=9) and PI patients (PI group, n=16) were scanned in an open-configuration MRI scanner during upright weight bearing and supine non-weight bearing positions at full extension (0° flexion) and at 15°, 30°, and 45° flexion. Patellofemoral indices included the Insall-Salvati Index, Caton-Deschamp Index, and Patellotrochlear Index (PTI) to determine patellar height and the patellar tilt angle (PTA), bisect offset (BO), and the tibial tubercle-trochlear groove (TT-TG) distance to assess patellar rotation and translation with respect to the femur and alignment of the extensor mechanism. A significant interaction effect of weight bearing by flexion angle was observed for the PTI, PTA, and BO for subjects with PI. At full extension, post hoc pairwise comparisons revealed a significant effect of weight bearing on the indices, with increased patellar height and increased PTA and BO in the PI group. Except for the BO, no such changes were seen in the control group. Independent of weight bearing, flexing the knee caused the PTA, BO, and TT-TG distance to be significantly reduced. Upright weight bearing and the knee flexion angle affected patellofemoral MRI indices in PI patients, with significantly increased values at full extension. The observations of this study provide a caution to be considered by professionals when treating PI patients. These patients should be evaluated clinically and radiographically at full extension and various flexion angles in context with quadriceps engagement. Explorative case-control study, Level III.

The effects of a dynamic patellar realignment brace on disease determinants for patellofemoral instability in the upright weight-bearing condition.

BackgroundPatellar stabilizing braces are used to alleviate pain and prevent subluxation/dislocation by having biomechanical effects in terms of improved patellar tracking. The purpose of this study is to analyze the effects of the dynamic patellar realignment brace, Patella Pro (Otto Bock GmbH, Duderstadt, Germany), on disease determinants in subjects with patellofemoral instability using upright weight-bearing magnetic resonance imaging (MRI).MethodsTwenty subjects (8 males and 12 females) with lateral patellofemoral instability were studied in an open-configuration magnetic resonance imaging scanner in an upright weight-bearing position at full extension (0° flexion) and 15° and 30° flexion with and without the realignment brace. Disease determinants were defined by common patellofemoral indices that included the Insall–Salvati Index, Caton–Deschamps Index, and the Patellotrochlear Index to determine patella height and patella tilt angle, bisect offset, and tuberositas tibiae–trochlear groove (TT–TG) distance to determine patellar rotation and translation with respect to the femur and the alignment of the extensor mechanism.ResultsAnalyses of variance revealed a significant effect of the brace with reduction of the three patellar height ratios, patella tilt angle, and bisect offset as well as TT–TG distance. Post hoc pairwise comparisons of the corresponding conditions with and without the realignment brace revealed significantly reduced patella height ratios, patella tilt angles, and bisect offsets at full extension and 15° and 30° flexion. No significant differences between the TT–TG distances at full extension but significant reductions at 15° and 30° flexion were observed when using the realignment brace compared to no brace.ConclusionsThis study suggests that the dynamic patellar realignment brace is capable of improving disease determinants in the upright weight-bearing condition in the range of 0° to 30° flexion in patients with patellofemoral instability.

Discrepancies of Patellofemoral Indices between Supine and Standing Merchant Views

PurposeThis research was conducted to compare supine and standing Merchant views, to observe radiographic changes of the patellofemoral joint according to weight-bearing conditions, and to evaluate correlation factors affecting patellofemoral joint indices.Materials and MethodsForty-four patients without skeletal problems were selected for this study. Patellar tilt angle, lateral patellofemoral angle, congruence angle, lateral subluxation distance and lateral patellar displacement were measured on each radiograph and evaluated for statistical significance. Possible correlation factors that can affect the radiographic discrepancy were analyzed using the univariate and multivariate regression analysis.ResultsIn the standing Merchant view, the patellar tilt angle, congruence angle and lateral patellar displacement were significantly decreased (p<0.001), whereas the lateral patellofemoral angle was significantly increased (p<0.001) compared to that in the supine Merchant view. Thigh width (p<0.001, r2=0.22) and radiographic Q-angle (p<0.001, r2=0.34) were found correlated with the radiographic discrepancy of congruence angle. Discrepancy of the lateral patella displacement increased as radiographic Q-angle increased (p=0.027, r2=0.112).ConclusionsCompared with the supine Merchant view, standing (weight-bearing) Merchant view showed decreased patella tilt angle, congruence angle, and lateral patella displacement. The results indicate that both supine and standing Merchant views should be considered in the radiographic evaluation of the patellofemoral joint.

The effects of weight-bearing conditions on patellofemoral indices in individuals without and with patellofemoral pain syndrome

The purpose of this study is to evaluate differences between the patellofemoral joint indices after supine, non-weight-bearing and standing position, and weight-bearing Merchant view radiographs in individuals without and with patellofemoral pain syndrome (PFPS). Radiographs of 44 knees without PFPS and 51 knees with PFPS were retrospectively evaluated. In both positions, the non-weight-bearing and weight-bearing Merchant views, patellar indices such as patellar tilt angle, lateral patellofemoral angle, lateral subluxation distance, lateral patellar displacement, and congruence angle were measured, respectively. The differences between the patellofemoral joint indices in knees with and without PFPS were analyzed using univariate and multivariate regression analysis, in regards to correlation factors. The patellar tilt angle (p = 0.0002), lateral subluxation distance (p = 0.038), lateral patellar displacement (p = 0.0004), and congruence angle (p < 0.0001) on the weight-bearing Merchant view was significantly decreased in normal knees without PFPS. In pathologic knees with PFPS, the patellar tilt angle (p < 0.0001), lateral subluxation distance (p < 0.0001), lateral patella displacement (p < 0.0001), and congruence angle (p < 0.0001) on weight-bearing Merchant view was also significantly decreased. The difference between the patellofemoral indices was significantly more in knees specifically with PFPS (p < 0.05). These results suggest that patellofemoral indices measured during non-weight-bearing supine position do not sufficiently represent the patellofemoral kinematics during normal weight-bearing activities. We conclude that this study establishes the clinical significance and relevance of assessing the patellofemoral kinematics by weight-bearing, standing Merchant view radiographs, when evaluating patients with patellofemoral problems.

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

PurposeThis study was designed to examine the effect of biplane medial opening wedge high tibial osteotomy (MOWHTO) on patellofemoral indices and posterior tibial slope. Materials and methodsSixty-two knees (61 patients) underwent biplane MOWHTO for unicompartmental osteoarthritis of the knee. Patellar indices were measured by radiographic assessment postoperatively. The Merchant's views were used for patellar tilt and shift while standing lateral view radiographs were used for the patellar height analysis using the modified Blackburne-peel ratio (mBP). The patients were divided into two groups according to the change between the pre- and postoperative mechanical axis. Group A constituted the correction angle of equal more than 10°, and group B of less than 10°. ResultsGroup A demonstrated a significant change of mechanical axis and the tibial slope. Patellar indices including the patellar tilt, shift, and mBP did not show significant difference. Group B demonstrated the statistical significant difference in only the mechanical axis deviation. Patellar indices including the patellar tilt, shift, and mBP as well as the tibia slope did not show significant difference. When evaluated as a whole group, the mean shift in weight bearing line, patellar height (mBP), and tibial slope from preoperative to postoperative value was statistically significant. However, the patellar tilt and shift were not changed significantly. ConclusionsAfter biplane MOWHTO, patellar tilt and shift do not significantly change when measured on static mode supine X-ray. However, patella was lowered and tibia slope increased after MOWHTO. Level of evidenceII.