Insall-Salvati Research Articles

Different Patellar Indices and Their Role in Decision-Making: An MRI-Based Study.

Magnetic resonance imaging (MRI) of knee has become the integral part of knee evaluation, hence any MRI based study adds more value if it helps in the decision-making process, especially for surgery in treating patellofemoral pain. We tried to determine normal patellar indices using knee MR images and the correlation between them and also compared the results with different ethnic population. We analyzed the prospectively collected MR images of 117 knees/patients, and Insall-Salvati (IS) index, modified IS index, patellotrochlear (PT) index, and patellophyseal (PP) index were calculated. Two standard deviations from the mean were used to define the normal and abnormal patellar position. Cohen's kappa values were used to assess the agreement between the indices and the correlation between them was analyzed using Pearson's correlation. The mean values for IS index, modified IS index, PT index, and PP index were 1.00, 1.53, 0.40, and 0.58, respectively. There was very good agreement between PT index and PP index. There was weak correlation between all the indices except the one between PT and PP indices which had a strong negative correlation. Based on commonly used methodology, there were 4% of asymptomatic patients who were outside the standardized cut-off values and different indices classified different knees as abnormal. This indicates patellar position should be one among the many other factors, not as a sole factor when making a surgical decision in patellofemoral pain. We also noted that the indices compared fairly with other populations. Further research is needed to determine the clinical applicability of these indices.

Comparison of five patellar height measurement methods in a Turkish adult cohort

Aim: The aim of this study was to investigate the correlation between the methods traditionally used for patellar height measurements [Insall-Salvati (IS), Modified Insall-Salvati (MIS), Blackburne-Peel (BP), Caton-Deschamps (CD)] and the plateau-patellar angle (PPA) in Turkish adult population.Material and Methods: A cross-sectional retrospective study was conducted. A total of 100 lateral knee radiographs in 30° flexion were analyzed by two blinded orthopedist independently to each other’s measurements. The average IS ratio, MIS ratio, BP ratio, CD ratio and PPA measurement were calculated by taking the average of the measurement values of both observers. The inter-observer reliability for two observers was determined using intraclass correlation coefficients (ICC). Spearman rank correlation analysis was performed to analyze correlations between mean ratios/angle measurements. Results: The mean age at the time of the radiographs was 30.18 ± 5.78 (range:20-40) years, 60% were female, and 58 radiographs were of the right knee. The mean and standard deviations of the patella height measurements were found 1.05 ± 0.12 according to the IS ratio; 1.66 ± 0.29 according to the MIS ratio; 0.91 ± 0.15 according to the CD ratio; 0.84 ± 0.14 according to the BP ratio; 24.74° ± 2.87° according to PPA measurement. There was highest inter-observer agreement between the two observers with an ICC of 0.926 (95% confidence interval: 0.89-0.950), excellent reliability, for the PPA measurement. Inter-observer agreement between two observers was good reliability for other measurements (IS, MIS, CD, BP). The highest correlation was between CD ratio and BP ratio, strong correlation, with a Pearson's correlation coefficient of 0.790.Conclusion: The PPA appears to be a feasible tool that can assess patellar height with higher reliability compared to the four most commonly used methods, in a Turkish adult population.

Comparison of Insall-Salvati Index and Its Modification in Normal Dogs from Four Different Body Weight Groups.

The objectives of this study were to record the values of Insall-Salvati (IS) index and its modification in dogs classified into four different body weight groups and to determine whether these index values were influenced by sex. Bilateral mediolateral radiographs of 86 dogs were obtained. The dogs were classified into four different body weight groups: small, medium, large and giant. The patellar length (PL), caudal and cranial patellar ligament lengths (LLca and LLcr), stifle angle and superimposition of the femoral condyles were measured on the radiographs. The IS index and its modification (LLcr:PL) were calculated by dividing LLca or LLcr by the PL respectively. Spearman's correlation test and analysis of variance were used for statistical analyses. The sex of the dog and the presence of enthesophytes at the apex of the patella were two influential factors for the IS and LLcr:PL values. The mean IS values were 1.60 ± 0.28 in small dogs, 1.73 ± 0.27 in medium dogs, 1.82 ± 0.21 in large dogs and 1.97 ± 0.13 in giant dogs. The mean LLcr:PL for the same groups were 2.05 ± 0.23, 2.13 ± 0.19, 2.23 ± 0.21 and 2.27 ± 0.16 respectively. The reference intervals for the IS index were 1.04 to 2.16 in the small dogs, 1.19 to 2.27 in the medium dogs, 1.40 to 2.24 in the large dogs and 1.71 to 2.23 in the giant dogs. The reference intervals for the LLcr:PL index were 1.59 to 2.51 in the small dogs, 1.75 to 2.51 in the medium dogs, 1.81 to 2.65 in the large dogs and 1.95 to 2.59 in the giant dogs. Dogs with values exceeding these reference intervals have patella alta and those with values below these intervals have patella baja.

Survival of total knee arthroplasty after high tibial osteotomy versus primary total knee arthroplasty: A meta-analysis.

Background:Theoretical considerations suggest that total knee arthroplasty (TKA) is technically more challenging after high tibial osteotomy (HTO), resulting in inferior results compared to primary TKA. However, several studies on this issue have shown contradictory results. The purpose of this meta-analysis to compare survivorship and clinical outcomes between TKA with and without previous HTO.Methods:We reviewed studies that evaluated pain and function scores, range of motion (ROM), operation time, Insall-Salvati (IS) ratio, complications, and survival rates in patients treated with TKA with previous HTO or with primary TKA with short- to midterm (<10 years) or long-term (>10 years) follow-up.Results:Fifteen studies were included in the meta-analysis. There were no significant differences between TKA with and without previous HTO in pain score (95% CI: −0.27 to 0.29; P = .94), function score (95% CI: −0.08 to 0.24; P = .32), operation time (95% CI: −5.43 to 26.85; P = .19), IS ratio (95% CI: −0.03 to 0.08; P = .40), complication rates (TKA with previous HTO, 62/1717; primary TKA, 610/31386; OR 1.31, 95% CI: 0.97–1.77; P = .08), and short- to midterm survival rates (TKA with previous HTO, 1860/2009; primary TKA, 37848/38765; OR 0.55, 95% CI: 0.28–1.10; P = .09). Conversely, ROM (95% CI: −7.40 to −1.26; P = .006) and long-term survival rates (TKA with previous HTO, 1426/1523; primary TKA, 29810/31201; OR 0.71, 95% CI: 0.57–0.89; P = .003) were significantly different between the two groups. In addition, both groups had substantial proportions of knees exhibiting short- to midterm survivorship (92.6% by TKA with previous HTO and 97.6% by primary TKA) and long-term survivorship (93.6% by TKA with previous HTO and 95.5% by primary TKA).Conclusions:This meta-analysis suggests that a previous HTO affected ROM or survival of TKA in the long-term even though both groups have equivalent clinical outcomes and complications. Thus, orthopedic surgeons should offer useful information regarding the advantages and disadvantages of both procedures to patients, and should provide advice on the generally higher risk of revision after TKA with previous HTO at long-term follow-up when counseling patients.

Patella Height in Different Ethnic Populations: An Observational Multicenter Study.

Patella height appears to have a crucial role in knee biomechanics. Patellar malalignment and maltracking are therefore believed to be associated with development and progression of patellofemoral pain and disease. Published data are scant regarding the effect of everyday tasks on patella height and patellofemoral disease. We included 150 subjects in a retrospective observational study. Group A had 75 subjects (24 male and 51 female, with a mean age of 58.5 yr), whose daily activities included squatting (the traditional Muslim praying position called Sujud). Group B had 75 subjects (42 male and 33 female, with a mean age of 47.6 yr), who were non-Muslim. Patella height was measured using Insall-Salvati (IS) and Blackburne-Peel (BP) ratios. The mean IS ratio was 0.86 (confidence interval [CI]: 0.7-1.02) for group A and 1.1 (CI: 0.96-1.23) for group B. The mean BP ratio was 0.66 (CI: 0.49-0.83) for group A and 0.89 (CI: 0.73-1.04) for group B. We found 26 subjects (34.7%) in group B to have patella alta, when measured by either ratio, compared to one subject (1.3%) in group A (p < 0.01) with patella alta. We found 61 subjects (81.3%) in group A to have patella baja, when measured by either ratio, compared to 21 subjects (28%) in group A (p < 0.01) with patella baja. In group A, the IS ratio was reduced in 29 subjects (38.7%), the BP ratio was reduced in 59 subjects (78.7%), and both were reduced in 27 subjects (36%). A similar pattern was noted for group B. Our results show that a significant increase in patella baja was associated with repeated squatting/kneeling, compared to the predominance of patella alta in the control group. On the basis of these findings, we hypothesize that biomechanical stresses associated with repeated hyperflexion of the knee asymmetrically affect the more flexible quadriceps muscle fibers greater than patella tendon fibers. Thus, repeated hyperflexion in everyday tasks leads to elongation of quadriceps fibers and patella baja.

Is There a Relationship between Patellofemoral Alignment and Osgood-Schlatter Disease? A Case-Control Study.

This study was aimed to investigate the role of anatomic variations in patellofemoral alignment in patients with or without Osgood-Schlatter disease (OSD) and to determine the potential anatomic risk factors that may play role in the etiology. This prospective observational case-control study was conducted on two groups of adolescent patients. Group 1 comprised patients who were diagnosed as having OSD and group 2 consisted of an equal number of age-matched patients who presented to the outpatient clinic with traumatic knee injury and underwent knee radiographic examination but without a diagnosis of OSD. Age, height, weight, body mass index (BMI), dominant side, and level of sporting activity were recorded. Quadriceps (Q) angles were measured using a long-arm goniometer with patients lying in the supine position with their knees in full extension and contracting the Q muscles. On anteroposterior, lateral knee, and tangential patella (Merchant and Laurin views) radiographs, the following measurements were performed: Insall-Salvati (IS), Caton-Deschamps (CD), and Blackburne-Peel (BP) indexes, congruence angles, lateral patellofemoral angles, sulcus angles, and patella type according to Grelsamer's morphology classification. Both groups were similar in respect of age (p = 0.160), sex (p = 0.311), height (p = 0.326), weight (p = 0.596), BMI (p = 0.153), and dominancy (p = 0.500). The rate of patients engaged in sports activities was significantly greater in the OSD group (p = 0.003). No significant difference was determined between the groups in respect to IS index, CD index, BP index, sulcus angle, lateral patellofemoral angle, and congruence angle (p-values: 0.358, 0.995, 0.912, 0.802, 1.000, and 0.907, respectively). The mean Q angle was measured as 15.6 ± 2.2 degrees in the OSD group and 14.3 ± 2.5 degrees in the control group (p = 0.014). Despite the difference being statistically significant, it was clinically insignificant because the difference was only 1.3 degrees. The principle etiologic factor seems to be increased physical activity rather than subtle variations is patellofemoral anatomy and alignment of extensor mechanism.

Comparison of Patellofemoral Geometry Between Opening Wedge and Hybrid High Tibial Osteotomy

Hybrid High Tibial Osteotomy is better than Opening Wedge in patellofemoral geometry. Opening wedge high tibial osteotomy (OWHTO) is a successful treatment option for uni-compartmental OA. However, changes of patellar height and tracking may be affected and HTO causes significant unfavorable changes in the patellofemoral mechanics. Hybrid HTO is a novel surgical procedure combining OWHTO and closed wedge HTO. The purpose of this study was to compare the patellofemoral geometry after OWHTO and hybrid HTO and determine the indication for varus knee with patellofemoral malalignment. Thirty-three OWHTO and 12 hybrid HTO were enrolled in this study. The average age was 66.9 ± 8.4 in hybrid HTO and 63.0 ± 7.9 in OWHTO, which were no significant difference. Correction angle and percent mechanical axis (%MA) with HTO were measured pre- and post operatively. To clarify the alternation of PF geometry, patella height was evaluated with Insall-Salvati (IS) ratio and Caton-Deschamps (CD) index. Patellofemoral malalignment was analyzed by patellar tilt Trochlar groove-tibial tuberosity distance (TT-TG). Joint space narrowing at lateral facet was measured for patellofemoral compression. All these were elucidated at pre- and post operative at 6 months. Correction angle in hybrid HTO was 12.5°, which was significant higher than in OWHTO (8.9°, p < 0.01), while no significant difference was shown in postoperative %MA. Patellar tilt, IS and CD were no significant difference between two groups, however ?CD, which was the difference between pre and postoperative CD, were significantly decreased in OWHTO (p < 0.01) whereas it was no difference in hybrid HTO. Postoperative TT-TG in hybrid HTO was significantly decreased rather than OWHTO (p < 0.01). Delta joint space narrowing in hybrid was increased rather than OWHTO (p = 0.03). It is considered an advantage of hybrid HTO over OWHTO regarding PF geometry. Hybrid HTO might have better indication for varus knee with PF malalignment.

The quadriceps active ratio: A dynamic MRI based assessment of patellar height

Objective:Precise and accurate surgical correction of Patella Alta (PA) requires both a diagnosis of the condition and a target for correction. The radiographic ratios widely used for assessing patella height are flawed for a number of reasons. The Patellotrochlear Index (PTI) addresses some of these deficiencies but is done under passive conditions and in Bierdet’s paper was not related to the diagnosis of PFI. We describe a quadriceps active modification of the PTI, the quads active ratio (Q+R) and assess its reliability and accuracy as a test for the diagnosis of PFI due to PA.Methods:One hundred patients undergoing a clinically indicated knee MRI scan were recruited into the study. Participants had an additional sagittal T1 sequence acquired with maximal static quadriceps contraction. Six scans were technically inadequate. The remaining 94 scans were screened for trochlear dysplasia and 16 scans were subsequently discarded so PFI could be assessed solely in terms of PA. There were 9 cases of PFI in the remaining 78 scans. In 56 of these scans a lateral radiograph was also available. The PTI and Q+R were calculated from MRI scans and the Insall Salvati (IS), Modified Insall-Salvati (MIS), Blackburn Peel (BP) and Caton-Deschamp (CD) ratios from lateral radiographs by 3 surgeons at 3 times points. The inter- and intra-rater reliability of the measures were calculated using intra-class correlation coefficient. Receiver operator curves were constructed to determine the ideal cut-off for each MRI based test for the diagnosis of PFI. Sensitivity and specificity of the MRI based tests for PFI was compared to the IS, MIS, BP and CD ratios using their previously published cut-offs.Results:A main effect of time was found for the PTI (P < 0.01) but not for the Q+R (P = 0.052). A time x surgeon interaction effect was shown for both the PTI and the Q+R (P < 0.01, respectively). However, one-way ANOVA at time point 3 showed no main effect of surgeons for either the PTI (p=0.05) or Q+R (p = 0.09). The Intra-class Correlation Coefficient between surgeons for the PTI and the Q+R ranged from 0.65-0.75 and 0.69-0.83 respectively. The coefficient of variation between surgeons for the PTI and the Q+R ranged from 0.88-9.88% and 2.24-4.85% respectively. According to the area under the receiver operator characteristics curve, the Q+R (AUC, 0.76; SE, 0.06; 95%CI, 0.87-0.64; P < 0.01) was more accurate to detect PFI than the PTI (AUC, 0.74; SE, 0.06; 95%CI, 0.86-0.62; P < 0.05). The Q+R and PTI cut-off scores of 0.12 and 0.36 gave sensitivities of 79.2% and specificities of 55.0% and 50.0% respectively. Of the widely used radiographic indices the Insall-Salvati ratio was the most accurate.Conclusion:The Q+R is more accurate than the PTI for the diagnosis of patella alta causing PFI and addresses many of the deficiencies in other assessment methods. In the absence of trochlear dysplasia a Q+R cut-off of 0.12 may be a reasonable target for correction of Patella Alta.

Patellar Height After Total Knee Arthroplasty: Comparison of 3 Methods

BackgroundTotal knee arthroplasty (TKA) is the gold standard procedure for knee osteoarthritis. However, there have been conflicting reports concerning whether TKA is associated with modifications in patellar height. This controversy might be partially explained by the diversity of methods used to measure patellar height. Therefore, we aimed at assessing the reproducibility of 3 radiological indices commonly used to evaluate patellar height—Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) ratios. Additionally, we aimed at evaluating the short-term differences between preoperative and postoperative patellar heights as measured by those 3 methods. MethodsPatellar heights were blindly measured by 2 researchers using IS, BP, and CD ratios in 203 knees. Interobserver agreement was evaluated by determination of intraclass correlation coefficients (ICC) and Bland-Altman plots. Preoperative and postoperative patellar heights were compared with Wilcoxon test. The association between postoperative pain and modifications in patellar height was assessed using Mann-Whitney U test. ResultsHigh interobserver agreement was found for IS (preoperative and postoperative ICC = 0.93), BP (preoperative ICC = 0.89; postoperative ICC = 0.91), and CD (preoperative ICC = 0.89; postoperative ICC = 0.90) ratios. Preoperative and postoperative patellar heights were not significantly different whatever the method used. Postoperative pain was reported after 23% procedures and was significantly associated with wider patellar height variations as measured by the BP ratio (P = .018). ConclusionThe methods evaluated appear to be reproducible. Although patellar height tended to be lower when measured postoperatively, this difference was not significant for any of the methods studied.

Impact of the patella height on the strain pattern of the medial patellofemoral ligament after reconstruction: a computer model-based study.

Medial patellofemoral ligament (MPFL) reconstruction is a key procedure for treating patellofemoral instability. However, controversy exists regarding the correct graft placement in different patellar heights. Therefore, our study aimed to investigate the influence of patellar height on MPFL insertion points. Strain patterns of the reconstructed MPFL were calculated using a dynamic musculoskeletal multibody simulation. Numerous patellar (proximal, central, distal) and femoral attachment sites (around the radiological point according to Schöttle) were analysed in the presence of different patella heights [Insall-Salvati (IS) indices 0.74, 1.0, 1.5] during dynamic knee flexion from 0° to 120°. The reconstructed MPFL showed an almost isometric behaviour at the anatomic insertion (IS 1.0). Slight variation (<5mm) around the ideal femoral insertion point resulted in only small changes in MPFL tension. However, a displacement of 10mm led to a significant increase in MPFL tension, especially in the more anteriorly/proximally located femoral attachment points. Depending on the patella height, there exists an area of absolute isometry of the MPFL (length change <3%) on the femoral condyle, which did not necessarily coincide exactly with the radiological point, but was located within a radius of 5mm around it. When reconstructed in the radiological femoral insertion point, MPFL strain patterns were only slightly affected by different patella heights (IS 0.74-1.5) suggesting that MPFL reconstruction could be safely performed using the radiological insertion. However, in case of a patella alta (IS 1.5), a slightly more proximal femoral insertion is beneficial for the biomechanical behaviour of the reconstructed MPFL.

Joint line and patellar height restoration after revision total knee arthroplasty.

Background:Restoration of proper joint line (JL) position and patellar height in revision total knee arthroplasty (TKA) is essential in the recovery of knee function and kinematics. We determined whether the JL position and patellar height could be restored in patients undergoing septic and aseptic revision TKA.Materials and Methods:We retrospectively reviewed 70 patients (74 knees) who had revision TKA between September 2004 and December 2010. Forty seven knees had a two stage revision for infected TKA and 27 knees for aseptic failure. The JL position, patellar height and patellar tendon (PT) length were measured and compared between primary TKA and post revision. The clinical scores including a hospital for special surgery (HSS), Knee Society Score (KSS), Western Ontario and McMaster Universities (WOMAC) and range of motion (ROM) were compared.Results:The overall JL increased from 17.51 mm to 18.37 mm post revision, the Insall-Salvati (IS) ratio declined from 0.98 to 0.92, and the PT length declined from 42.92 mm to 39.45 mm. 9 of the 21 patellar baja knees improved to normal patellar height. After revision, the JL in the septic group (17.02 mm) was significantly lower than the aseptic group (20.74 mm). The changes of the JL position and IS ratio in the septic group were significantly larger than the aseptic groups (P < 0.05). JL position had a positive correlation to the IS ratio and PT length post revision. The knee function scores including HSS, KSS, WOMAC scores, and ROM all improved post revision compared to pre revision (P < 0.05), and the septic group had a lower knee function compared to the aseptic group. JL position and IS ratio post revision had no correlation to the HSS, KSS, WOMAC scores, and ROM.Conclusions:JL position can be sufficiently restored with appropriate distal femoral augment reconstruction after revision TKA, but the patellar height cannot be well improved, especially in the septic revision with obvious PT contracture. No correlation was found between the JL position and patellar height to the knee function post revision TKA.

Focal intratendinous radiolucency: A new radiographic method for diagnosing patellar tendon ruptures

BackgroundDiagnosis of patellar tendon rupture is usually based on clinical history and examination. In equivocal cases, imaging may be required. Lateral radiograph is a simple and cost-effective method for prompt diagnosis. However, no specific radiological sign has been described. Rather than utilising patella alta as an indirect measure of patellar tendon rupture, we hypothesise that a focal intratendinous radiolucency is another reliable and accurate radiological sign for diagnosis. Sensitivity and specificity analysis was undertaken to evaluate the diagnostic value of this radiographic sign. MethodsLateral radiographs of mid-substance patellar tendon ruptures from 19 patients were analysed. These were then randomised with another 19 normal knee radiographs from age-matched patients to create a pool of 38 radiographs for interpretation. Six independent interpreters who were blinded to the diagnosis were requested to indicate whether rupture was present or absent based on the visualisation of a focal intratendinous radiolucency in the patellar tendon. The Insall–Salvati (IS), Caton–Deschamps (CD) and Blackburne–Peel (BP) ratios were measured in the same radiographs. Sensitivity and specificity for each of the radiographic measurements were calculated. Inter- and intraobserver correlations were reported in kappa statistics. ResultsThe average sensitivity and specificity for focal radiolucency in the patellar tendon substance were 82.5% and 95.2%, respectively. Sensitivity and specificity for the IS ratio were 84.2% and 78.9%, for CD was 68.4% and 84.2% and for BP was 68.4% and 89.4% respectively. ConclusionThe presence of a focal intratendinous radiolucency in the patellar tendon is both accurate and reliable in diagnosing patellar tendon ruptures.

Comparative evaluation of patellar height methods in the Brazilian population

ObjectiveThe methods most used for patellar height measurement were compared with the plateau–patella angle method. MethodsA cross-sectional study was conducted, in which lateral-view radiographs of the knee were evaluated using the three methods already established in the literature: Insall–Salvati (IS), Blackburne–Peel (BP) and Caton–Deschamps (CD). These were compared with the plateau–patella angle method. One hundred and ninety-six randomly selected patients were included in the sample. ResultsThe data were initially evaluated using the chi-square test. This analysis was deemed to be positive with p<0.0001. We compared the traditional methods with the plateau–patella angle measurement, using Fisher's exact test. In comparing the IS index with the plateau–patella angle, we did not find any statistically significant differences in relation to the proportion of altered cases between the two groups. The traditional methods were compared with the plateau–patella angle with regard to the proportions of cases of high and low patella, by means of Fisher's exact test. This analysis showed that the plateau–patella angle identified fewer cases of high patella than did the IS, BP and CD methods, but more cases of low patella. In comparing pairs, we found that the IS and CD indices were capable of identifying more cases of high patella than was the plateau–patella angle. In relation to the cases of low patella, the plateau–patella angle was capable of identifying more cases than were the other three methods. ConclusionsThe plateau–patella angle found more patients with low patella than did the classical methods and showed results that diverged from those of the other indices studied.

Avaliação comparativa de métodos da altura patelar na população brasileira

ObjectiveThe methods most used for patellar height measurement were compared with the plateau‐patella angle method. MethodsA cross‐sectional study was conducted, in which lateral‐view radiographs of the knee were evaluated using the three methods already established in the literature: Insall‐Salvati (IS), Blackburne‐Peel (BP) and Caton‐Deschamps (CD). These were compared with the plateau‐patella angle method. One hundred and ninety‐six randomly selected patients were included in the sample. ResultsThe data were initially evaluated using the chi‐square test. This analysis was deemed to be positive with p<0.0001. We compared the traditional methods with the plateau‐patella angle measurement, using Fisher's exact test. In comparing the IS index with the plateau‐patella angle, we did not find any statistically significant differences in relation to the proportion of altered cases between the two groups. The traditional methods were compared with the plateau‐patella angle with regard to the proportions of cases of high and low patella, by means of Fisher's exact test. This analysis showed that the plateau‐patella angle identified fewer cases of high patella than did the IS, BP and CD methods, but more cases of low patella. In comparing pairs, we found that the IS and CD indices were capable of identifying more cases of high patella than was the plateau‐patella angle. In relation to the cases of low patella, the plateau‐patella angle was capable of identifying more cases than were the other three methods. ConclusionsThe plateau‐patella angle found more patients with low patella than did the classical methods and showed results that diverged from those of the other indices studied.

The reliability of four widely used patellar height ratios.

The objective of this study was to evaluate the inter-observer reliability and the intra-observer reliability of four patellar height ratios: Insall-Salvati (IS), modified Insall-Salvati (MIS), Blackburne-Peel (BP) and Caton-Deschamps (CD). The patellar height ratios were assessed by four independent examiners using weight-bearing lateral knee radiographs in 30° flexion. Intra-class correlation coefficients and Fleiss' kappa's were determined. The inter-observer reliability was excellent for the IS and moderate for the other ratios. When the ratio values were categorized, the inter-observer reliability was strong for the IS, moderate for the MIS and BP, and poor for the CD. The intra-observer reliability was excellent for the IS, MIS and CD, and strong for the BP. When the ratio values were categorized, the intra-observer reliability was strong for the IS and MIS, and moderate for the other ratios. Although the IS showed best reliability, we advise to use the MIS as it showed the second best reliability but is, according to the literature, associated with better validity.

Assessing the validity of the modified Blumensaat method for radiographic evaluation of patellar height.

Although several indexes have been used for patellar height evaluation, the literature on patellar height evaluation using a femoral reference point is scant. We have previously reported on a new index, the modified Blumensaat (MB) method, which evaluates the patellar height using a femoral reference point. The purpose of this study was to evaluate the validity of the MB method. In addition to 10 volunteers (group C), 10 men (group M) and 10 women (group F) who underwent knee surgery were selected for the study. The Insall-Salvati (IS), modified IS (MIS), Blackburne-Peel (BP), MB, and modified intercondylar-shelf-angle-corrected Blumensaat (MIB) ratios were measured on lateral knee radiographs with the knee in 30°, 40°, and 50° flexion. In group C, the MB and MIB ratios were similar; the IS ratio was not dependent on the knee flexion angle, and there was no significant difference in the MIS and BP ratios between 40° and 50° of knee flexion and in the MB and the MIB ratios between 30° and 40° of knee flexion. There were no differences between group M and group F with respect to any of the indexes. Furthermore, the differences in all indexes among the different knee flexion angles, in groups M and F, were similar to those in group C. The MB method is applicable for patellar height evaluation and is recommended with a knee flexion angle of 30°-40°.

Comparison of the change in patellar height between opening and closed wedge high tibial osteotomy: measurement with a new method

The purposes of this study were to examine patellar height at preoperation and postoperation, and compare the change of patellar height between opening wedge high tibial osteotomy (HTO) and closed wedge HTO by using Insall-Salvati (IS) ratio and our original method. Twenty patients (26 knees) were included. There were 6 males (6 knees) and 14 females (20 knees). Sixteen knees underwent closed method and 10 knees underwent opening method. Patellar height was measured at preoperation, immediately after the operation (postoperation) and 1 year after the operation according to IS ratio and modified Blumensaat (MB) ratio. We defined MB ratio as the ratio of distance from Blumensaat line to the midpoint of patellofemoral joint of patella against the length of Blumensaat line. In opening wedge HTO, though IS ratio significantly increased postoperatively compared with preoperative IS ratio, IS ratio at 1 year after operation was not significantly different from preoperative values. MB ratio at postoperation and that at 1 year after the operation significantly decreased compared with preoperative MB ratio. In closed wedge HTO, there was no difference between preoperative and postoperative values of both IS ratio and MB ratio. In the postoperative period after opening wedge HTO, IS ratio was significantly increased, whereas MB ratio was decreased. We recommend that patients with low preoperative MB ratio must be treated with closed wedge HTO.

Does MPFL Reconstruction Alter Patellar Height? (SS-78)

Does MPFL Reconstruction Alter Patellar Height? (SS-78)

Avaliação dos métodos de mensuração da altura patelar na radiografia digital

OBJETIVO: Analisar os métodos mais comuns de medida da altura patelar e o impacto da experiência do observador na correlação com os outros avaliadores utilizando a radiografia digital. MÉTODOS: Sessenta radiografias digitais do joelho na incidência em perfil foram analisadas por quatro observadores, sendo um médico residente do segundo ano de ortopedia (R2), um médico residente do terceiro ano de ortopedia (R3), um ortopedista especialista em joelho (EJ) e um radiologista especialista na área musculoesquelética (ER). Os índices estudados foram: Insall-Salvati (IS), Blackburne-Peel (BP), Caton-Deschamps (CD) e Insall-Salvati modificado (ISM). Foi calculada a concordância interobservadores por meio do coeficiente de concordância Kappa (κ). RESULTADOS: Os maiores coeficientes de correlação foram obtidos com o método de IS seguido pelo método de CD. A pior correlação foi observada no método de ISM. A maior concordância interobservadores foi obtida entre o ortopedista especialista em joelho e o radiologista especializado na área musculoesquelética nos quatro métodos de aferição utilizados. CONCLUSÃO: Utilizando a radiografia digital, os índices de Insall-Salvati e Caton-Deschamps apresentaram maior concordância interobservadores, sendo esta também influenciada positivamente pela experiência do observador.

Multimodality correlations of patellar height measurement on X-ray, CT, and MRI

To investigate whether the universally accepted range of normal patellar height ratios derived from radiography for the Insall-Salvati (IS) and Blackburne-Peel (BP) methods could be similarly applied to both CT and MRI. Institutional review board approval was obtained with waiver of informed consent for this HIPPA-compliant study. A total of 45 knees in 42 patients (15 men, 27 women; age range 11 to 75 years, mean age 39 ± 20 years) who underwent tri-modality (radiograph, CT, and MRI) examinations were selected. All patients had knee imaging obtained for a variety of reasons and measurements were performed by two independent readers who were blinded to each other's measurements or the respective measurements derived from each of the methods. Paired t test was used to compare the mean values among the modalities. Inter-observer and inter-method agreements were assessed using intra-class correlation coefficients. Statistically significant, but small quantitative differences are noted between tri-modality patellar height ratios. For comparable results, the small addition of 0.13 and 0.10 are needed for the Insall-Salvati measurements on MRI and CT respectively, compared with radiographs. For the Blackburne-Peel ratio, an additional adjustment of 0.09 is needed between radiographs and MRI, but not between radiographs and CT. These adjustments are independent of gender. The interobserver reproducibility was excellent (ICC ≥ 0.94) for both the Insall-Salvati and Blackburne-Peel methods for all modalities. The results indicate that cut-off values for patella alta and baja derived from radiographs should not be directly transposed to CT and MRI; however, the adjustments are relatively minor. These measurements show excellent reproducibility for all modalities currently used for patellar height measurements.