Blackburne-Peel Research Articles

Conventional plate and screws in medial opening-wedge high tibial osteotomy: are they sufficiently stable? A retrospective study

ObjectiveOpening-wedge osteotomy of the proximal tibia is a widely performed procedure for treating medial gonarthrosis in active patients and in the presence of varus malalignment of the lower limb. The fixation method is controversial, and the use of conventional implants has been abandoned in favor of implants with more modern locking screws. The aim of the present clinical study was to assess the maintenance of the correction achieved in cases wherein fixation was performed using conventional implants. MethodsThis retrospective study included 51 patients who underwent opening-wedge high tibial osteotomy wherein fixation was performed using conventional implants (4.5-mm DCP plate and non-locking screws). Radiological findings regarding patellar height, tibial slope, and varus correction postoperatively and after consolidation were analyzed to assess the maintenance of the correction achieved by osteotomy. ResultsThe mean loss of correction angle, calculated by the difference between the correction angle in the immediate postoperative period and that after consolidation, was 0.92°±0.9°. In addition, changes in patellar height determined by the Blackburne–Peel method and in the sagittal slope of the tibial plateau were not significant or clinically relevant. ConclusionsThe use of conventional plates and screws is viable in the fixation of opening-wedge high tibial osteotomy because they provide enough stability to maintain the achieved correction until consolidation, without significant changes.

The SPECT/CT Evaluation of Compartmental Changes after Open Wedge High Tibial Osteotomy

PurposeThe purpose of this study was to evaluate compartmental changes using combined single-photon emission computerized tomography and conventional computerized tomography (SPECT/CT) after open wedge high tibial osteotomy (OWHTO) for providing clinical guidance for proper correction.Materials and MethodsAnalysis was performed using SPECT/CT from around 1 year after surgery on 22 patients who underwent OWHTO. Postoperative mechanical axis was measured and classified into 3 groups: group I (varus), group II (0°–3° valgus), and group III (>3° valgus). Patella location was evaluated using Blackburne-Peel (BP) ratio. On SPECT/CT, the knee joint was divided into medial, lateral, and patellofemoral compartments and the brighter signal was marked as a positive signal.ResultsIncreased signal activity in the medial compartment was observed in 12 cases. No correlation was observed between postoperative mechanical axis and medial signal increase. Lateral increased signal activity was observed in 3 cases, and as valgus degree increased, lateral compartment’s signal activity increased. Increased signal activity of the patellofemoral joint was observed in 7 cases, and significant correlation was observed between changes in BP ratio and increased signal activity.ConclusionsFor the treatment of medial osteoarthritis, OWHTO requires overcorrection that does not exceed 3 valgus. In addition, the possibility of a patellofemoral joint problem after OWHTO should be kept in mind.

Inter-rater reliability of common quantitative knee X-ray parameters in the Indian scenario

PurposeThe reliability of knee radiograph measurements is an important factor to consider for these measurements to be a useful tool in patient evaluation. Inter-rater reliability of the common knee radiograph measurements like patellar height and sulcus angle has never been established among observers of varied expertise in the Indian setting. Research has established that ethnic differences exist in knee morphology among different races and deep squatters like Indians have different knee anatomy. Globally, there is very limited published literature evaluating reliability of sulcus angle measurement on X-rays. AimWe performed a study to evaluate the inter-rater reliability of 3 patellar height indices and sulcus angle in the Indian scenario among observers of varied expertise. MethodThe participants were males and females between 18 and 54 years, both, with anterior knee pain and without any knee complaints. Three independent observers from Sports Medicine, Orthopaedic Surgery and Radiology assessed 148 radiographs including 74 lateral and 74 axial views from 74 participants. All the measurements were analysed for Intraclass Correlation Coefficient (2,1). ResultsAll patellar height indices had moderate to good reliability. Insall Salvati index (ICC 0.74) and Caton Deschamp index (ICC 0.74) had better reliability among our observers than Blackburne Peel index (ICC 0.67). Sulcus angle had an excellent reliability (ICC 0.92) in our study. ConclusionIn the Indian scenario, there is an excellent inter-rater reliability for sulcus angle and moderate to good reliability for Insall-Salvati index, Caton-Deschamp index and Blackburne-Peel index, in that order, among 3 independent raters of varied expertise.

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.

Medial opening wedge high tibial osteotomy: A technique to avoid patella infera

Background High tibial osteotomy (HTO) is an established treatment for medial compartment osteoarthritis of the knee with varus malalignment. Medial opening wedge osteotomy eliminates most of the disadvantages of the lateral closing wedge osteotomy. Nevertheless, the changes in tibial slope and patellar height after opening wedge HTO with frequent occurrence of patella baja make subsequent knee arthroplasty more difficult. Purpose The purpose of this study was to evaluate the results of a simple technique for medial opening wedge HTO with internal fixation and early mobilization in patients with combined medial compartment osteoarthritis and varus alignment of the knee. Patients and methods Opening-wedge HTO and internal fixation with a standard AO large-fragment T plate with posterior tricortical iliac bone autograft was assessed. Forty-five patients with 61 knees with combined medial femorotibial osteoarthritis and varus deformity of the knee were treated with opening wedge HTO. There were 21 women with 29 knees, with a mean age 45.5 years (30–58 years), and 24 men with 32 knees, with a mean age 41.63 years (30–55 years). Mean follow-up was 35.9 months (13–62 months). Radiographic measurements [femorotibial angle, tibial slope, Insall–Salvati, and Blackburne–Peel (BP) ratios] were taken preoperatively and postoperatively and on follow-up. Preoperative and postoperative (last follow up) values of these parameters were compared. Results Fifty of the 61 (82%) knees had an excellent or good result, whereas in 11 knees there was recurrent pain. There were no implant failures, loss or correction, delayed union, or nonunion. Femorotibial angle was changed from a mean of −7.2° of varus into a mean of 8.3° of valgus (P=0.000). Tibial slope was significantly decreased from a mean of 11.4° to a mean of 9.2° (P=0.002). Insall–Salvati ratio was significantly increased from a mean of 1.1 to a mean of 1.2 (P=0.000). There was a significant decrease in the BP ratio from a mean of 0.9 to a mean of 0.7 (P=0.005). Twenty-five percent of postoperative BP values satisfied the criteria for patella infera (BP Conclusion Opening wedge HTO using a simple technique with rigid fixation and early mobilization decreased the posterior inclination of the tibial slope, straightened the patellar tendon, and elevated the tibiofemoral joint line. The decrease in the inclination of the posterior slope of the tibia and the stretching of the patellar ligament compensate for the elevation of the joint line. This together with the early mobilization protocol resulted in the low incidence of patella infera.

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.

Effect of patient position on measurement of patellar height ratio.

Patient position is an important factor which can affect the accuracy of patellar height ratio measurement. Varying degree of knee flexion angles and action of quadriceps muscle while supine or standing positions are the most concerning factors. Forty healthy subjects had radiographs taken of their knees at 0°, 30°, and 60° of flexion in the supine (non-weight-bearing) and standing (weight-bearing) positions. Patellar height was assessed by five different measurement methods including Insall-Salvati (IS), Modified Insall-Salvati (MIS), Caton-Deschamps (CD), Blackburne-Peel (BP), and Knee triangular ratio (KT). The mean and standard deviation (SD) in the supine/standing position of each method were IS 1.0 (0.1)/1.05 (0.1), MIS 1.6 (0.2)/1.8 (0.3), CD 1.0 (0.2)/1.2 (0.2), BP 0.9 (0.2)/1.0(0.2), and KT 1(0.1)/1(0.1). Significant differences were found between supine and standing positions using all of the methods except for KT ratio. Comparisons between the various knee flexion angles were found to be statistically significant by most of the measurement methods, although the differences between the means were less than their SD. Quadriceps action had a significant influence on the mean values obtained by the MIS, CD, and BP methods. In clinical practice, interpretation for patella alta or patella baja of these measurement methods should be normalized according to the patient position. Varying the degree of knee flexion did not produce clinically important effects in any of the five patellar height measurement methods.

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°.

Changes in patellofemoral alignment do not cause clinical impact after open-wedge high tibial osteotomy.

The objectives of this study were (1) to evaluate the clinical and radiologic outcomes of open-wedge high tibial osteotomy focusing on patellofemoral alignment and (2) to search for correlation between variables and patellofemoral malalignment. A total of 46 knees (46 patients) from 32 females and 14 males who underwent open-wedge high tibial osteotomy were included in this retrospective case series. Outcomes were evaluated using clinical scales and radiologic parameters at the last follow-up. Pre-operative and final follow-up values were compared for the outcome analysis. For the focused analysis of the patellofemoral joint, correlation analyses between patellofemoral variables and pre- and post-operative weight-bearing line (WBL), clinical score, posterior slope, Blackburn Peel ratio, lateral patellar tilt, lateral patellar shift, and congruence angle were performed. The minimum follow-up period was 2 years and median follow-up period was 44 months (range 24-88 months). The percentage of weight-bearing line was shifted from 17.2 ± 11.1 to 56.7 ± 12.7%, and it was statistically significant (p < 0.01). Regarding the clinical results, statistical significance was observed using all scores (p < 0.01). In the radiologic evaluation, patellar descent was observed with statistical significance (p < 0.01). Last follow-up lateral patellar tilt was decreased with statistical significance (p < 0.01). In correlation analysis between variables of patellofemoral malalignment, the pre-operative weight-bearing line showed an association with the change in lateral patellar tilt and lateral patellar shift (correlation coefficient: 0.3). After open-wedge high tibial osteotomy, clinical results showed improvement, compared to pre-operative values. The patellar tilt and lateral patellar shift were not changed; however, descent of the patella was observed. Therefore, mild patellofemoral problems should not be a contraindication of the open-wedge high tibial osteotomy. Case series, Level IV.

Plateau-patella angle in evaluation of patellar height in osteoarthritis

BackgroundThe plateau-patella angle (PPA), recently introduced as a new and simpler method of measuring patellar height from the lateral radiograph, has the advantage of simplicity over previously described methods as it involves a single angular measurement without the need for calculations. The purpose of this study was to validate the use of the PPA as a measurement for patellar height in knees with moderate to severe osteoarthritis. MethodsA total of 331 patients who underwent total knee arthroplasty at our institution with radiographs prior to surgery were evaluated. Of those, 297 (89.2%) were felt to be adequate for review. Three observers with different levels of orthopedic training measured PPA, Insall–Salvati, Caton–Deschamps, and Blackburne–Peel indices on a subset of 50 consecutive patients. Interobserver agreement for each of the four measurements was calculated and correlation between each of the measurements within each observer was calculated. The measurement of the PPA was repeated. Intraobserver agreement for the PPA was determined and a normal range and distribution was defined for this population. ResultsFor the three observers, the mean PPA for the entire cohort was 25.55, 25.31, and 24.42. The intraclass correlation coefficient (ICC) was 0.81, The ICC and intraobserver assessment were the highest for the PPA compared with the other ratios. The PPA was found to correlate most strongly with the Blackburne–Peel method. ConclusionsThe plateau-patella angle is a reliable way to evaluate patellar height in the osteoarthritic population. The measurement demonstrated a higher interobserver reliability compared with previously described methods. Level of evidenceRetrospective Level IV.

Assessment of the Patellar Height Ratios in Normal Adult Nigerians

Background: Patella bone is the largest sesamoid bone in the human body, it lies in the quadriceps tendon. The height of the Patella has been found to vary in some disease conditions. Ratios are therefore formulated to determine the normal values using various parameters related to the Patella bone. The aim of this study was therefore to determine the normal Patella height ratios in Nigerians from the different methods. Method:A total of 500 normal radiographs of the knee joint from different regions of Nigeria were utilized for this study. The ratios calculated were from:- (a) The Blumensaat’s line method (LP / WCBL) (b) The Install and Salvati method (LT / LP) (c) The Blackburn Peel method (A / B) Results: The mean Male Patella height ratios for the three different methods were as follows: LP / WCBL (0.97± 0.01), LT / LP (1.04 ± 0.07), A / B (0.87 ± 0.01) while that of the females were as follows: LP / WCBL (0.97± 0.01), LT / LP (1.04 ± 0.08), and A / B (0.87 ± 0.02). There was no significant differences in all the ratios (P>0.05). Conclusion: The study has re-evaluated the different methods at arriving at Patella height ratios in Nigerians. The findings are in keeping with earlier authors that irrespective of sex and race, the normal Patella height ratios do not vary and can be used for restoring knee function and kinematics in diseased states.

Patellar maltracking is prevalent among patellofemoral pain subjects with patella alta: An upright, weightbearing MRI study

The purpose of this study is to determine if patellar maltracking is more prevalent among patellofemoral (PF) pain subjects with patella alta compared to subjects with normal patella height. We imaged 37 PF pain and 15 pain free subjects in an open-configuration magnetic resonance imaging scanner while they stood in a weightbearing posture. We measured patella height using the Caton-Deschamps, Blackburne-Peel, Insall-Salvati, Modified Insall-Salvati, and Patellotrochlear indices, and classified the subjects into patella alta and normal patella height groups. We measured patella tilt and bisect offset from oblique-axial plane images, and classified the subjects into maltracking and normal tracking groups. Patellar maltracking was more prevalent among PF pain subjects with patella alta compared to PF pain subjects with normal patella height (two-tailed Fisher's exact test, p<0.050). Using the Caton-Deschamps index, 67% (8/12) of PF pain subjects with patella alta were maltrackers, whereas only 16% (4/25) of PF pain subjects with normal patella height were maltrackers. Patellofemoral pain subjects classified as maltrackers displayed a greater patella height compared to the pain free and PF pain subjects classified as normal trackers (two-tailed unpaired t-tests with Bonferroni correction, p<0.017). This study adds to our understanding of PF pain in two ways-(1) we demonstrate that patellar maltracking is more prevalent in PF pain subjects with patella alta compared to subjects with normal patella height; and (2) we show greater patella height in PF pain subjects compared to pain free subjects using four indices commonly used in clinics.

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.

ASSESSMENT OF PATELLAR HEIGHT MEASUREMENT METHODS FROM DIGITAL RADIOGRAPHY

Objective: To analyze the most common methods for measuring patellar height and the impact of observer experience in correlations with the other observers using digital radiography. Methods: Sixty digital radiographs of the knee in lateral view were analyzed by four observers: a physician in the second year of medical residence in orthopedics (R2); a physician in the third year of medical residence in orthopedics (R3); an orthopedic surgeon who was a specialist in knee surgery (SK); and a radiologist who was a specialist in musculoskeletal radiology (SR). The indices used were: Insall-Salvati (IS), Blackburne-Peel (BP), Caton-Deschamps (CD) and modified Insall-Salvati (ISM). The interobserver agreement was calculated using the kappa coefficient (κ). Results: The highest correlation coefficients were found when using the IS method followed by the CD method. The worst correlation was observed in the ISM method. The highest interobserver agreement was found between the orthopedic surgeon specializing in knee surgery and the radiologist specializing in musculoskeletal radiology, for the four measurement methods used. Conclusion: Using digital radiography, the Insall-Salvati and Caton-Deschamps indexes presented the highest interobserver agreement, and this was also positively influenced by the observer's level of experience.

Five patellar proximodistal positioning indices compared in clinically normal Greenland sled dogs

Patellar luxation in large-breed dogs is associated with abnormal proximodistal patellar positioning. Using a clinically normal population of Greenland sled dogs, measurement reliability and the effect of limb position were compared for five patellar proximodistal positioning indices based on the Insall-Salvati (IS), modified Insall-Salvati (mIS), de Carvalho (dC), patellotrochlear (PT) and Blackburne-Peel (BP) indices. Indices were measured at one knee angle in 44 dogs and two knee angles in 10 dogs. Index susceptibility to error was modelled for different errors in knee angle estimation. Two reported techniques for determining knee angle were compared in a fox hind limb model. Indices dC and PT were significantly affected by knee angle (P<0.001). Error susceptibility was the lowest for IS and the greatest for PT. Intra- and inter-observer agreements were moderate to substantial for all indices. Measurement precision was good for all indices except BP. Patellar ligament laxity significantly affected IS, mIS, dC and BP (P<0.05). Knee angle measurements were technique dependent, with a bias of 9° to 13° and limits of agreement of ±5°. All five indices were reliable, but precision varied. For pre- and post-operative comparison, dC showed less error susceptibility than PT and better precision than BP. An ideal index for clinical use remains to be defined; the best option is dC, although with limitations. The method of knee angle measurement must be defined prior to index measurement and comparison of index values. Index values may vary with species and/or body size.