Lateral Patellar Displacement Research Articles

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.

Does Degree of Trochlear Dysplasia and Position of Femoral Tunnel Influence Outcome After Medial Patellofemoral Ligament Reconstruction?

Background: The medial patellofemoral ligament (MPFL) is the main restraining force against lateral patellar displacement. It is disrupted after patellar subluxation or dislocation. Reconstruction of the MPFL is frequently performed when nonoperative management fails and the patient experiences recurrent patellar dislocation. Purpose: To determine the relationship between the degree of trochlear dysplasia and femoral tunnel position and outcome after MPFL reconstruction. Study Design: Case series; Level of evidence, 4. Methods: A total of 68 patients (72 knees) with recurrent dislocation of the patella underwent MPFL reconstruction. The mean follow-up was 31.3 months (range, 13-72 months). Clinical and functional outcomes were recorded using the Kujala, Lysholm, and Tegner scores. Postoperative complications, participation in sporting activity, and overall patient satisfaction were determined. Radiographs were analyzed to evaluate congruence angle, lateral patellofemoral angle, patellar height, trochlear dysplasia, trochlear boss height, and position of the femoral tunnel. Results: The mean Kujala, Lysholm, and Tegner scores postoperatively were 76.2, 73.8, and 3.6, respectively (n = 61). The mean congruence angle (n = 30) improved from 22.5° to 1.0° postoperatively (P = .000038), the lateral patellofemoral angle (n = 30) improved from 7.4° to 7.8° postoperatively (P = .048), and the patellar height (n = 46) using the Caton-Deschamps method improved from 1.1 to 1.0 postoperatively (P = .000016). Mild trochlear dysplasia grade A/B was found in 89% of patients (n = 54), and 11% of patients (n = 7) had severe grade C/D dysplasia. The mean distance from the anatomic insertion of the MPFL to the center of the tunnel was 9.3 mm (range, 0.5-28.2 mm), with 71.7% thought to be within 10 mm of the anatomic position defined by Schottle (n = 46). When patients with high-grade trochlear dysplasia were excluded, anatomically placed femoral tunnels demonstrated significantly better clinical scores than did tunnels not placed anatomically (Kujala score, P = .028; Lysholm score, P = .012). A multivariate logistic regression analysis also demonstrated that the distance of the femoral tunnel from the anatomic position predicted clinical outcome (Kujala score, P = .043; Lysholm score, P = .028). All of the patients with severe trochlear dysplasia (n = 7) suffered from recurrent dislocations postoperatively, compared with only 9.3% of patients (n = 5) with mild trochlear dysplasia (P = .0001). Four patients had patellar fractures postoperatively. Of patients with mild dysplasia, 83% were either very satisfied or satisfied with the outcome of their surgery compared with only 57% with severe dysplasia (P = .05). Of patients with mild trochlear dysplasia, 56% returned to sport postoperatively compared with only 43% of patients with severe trochlear dysplasia (P = .526). Conclusion: This study demonstrates the importance of restoration of the anatomic insertion point of the MPFL when performing MPFL reconstruction and proposes that this procedure should not be performed in isolation in patients with high-grade trochlear dysplasia.

Restorative effects of exercise rehabilitation and bracing on females with lateral displacement of patella.

Background:This investigation compared the effects of exercise rehabilitation and bracing on muscle flexibility and strength as well as knee proprioception and pain in female sufferers of lateral displacement of patella (LDP).Materials and Methods:Twenty-two females with unilateral LDP were randomly divided into two groups to receive exercises (n = 12) or patellar brace (n = 10). Both groups were evaluated before and after 8 weeks with isokinetic dynamometer (Biodex System 3 Pro) for muscle strength and proprioception, with SLR, Active Knee Flexion, and Sit and Reach tests for flexibility assessment and with a visual analog scale for pain.Results:Muscle flexibility in both exercise and bracing groups improved (F(1,20)≥5.99 and P ≤ 0.024), whereas improvement in bracing group was not significant. Significant interaction was observed in favor of exercise group in 2 strength tests of knee flexion and knee extension (F(1,20)≥6.564 and P ≤ 0.019). For proprioception, a significant interaction was observed in favor of bracing group (F(1,20) =7.944 and P = 0.011). Also the results showed both exercise rehab and brace decreased significantly pain severity during stair ascending and descending.Conclusion:These results suggest that better flexibility and more strength in exercise group somehow reduced the stress on patellofemoral joint and it, in turn, alleviated the symptoms and pain. It is also likely that relieving effects of brace and improvement of proprioception by it allows patients to be more physically active and it could have, more or less, effects similar to exercise. Therefore both exercise and brace could be prescribed for patients with LDP. It seems application of the patellar brace combined with exercise might be a better treatment for these patients, because they could improve strength, flexibility and proprioception.

Axial MRI index of patellar engagement: A new method to assess patellar instability

The aim of this study was to define a new index to measure lateral patellar displacement (LPD) using nuclear magnetic resonance imaging (MRI), an axial index of engagement of the patella (AEI) obtained from two different axial MRI views then to validate its use in a prospective series of patients presenting an objective patellar instability (OPI). One hundred and thirty-five patients with OPI and no history of surgery of the patella were included in a prospective study organized by the French Society of Arthroscopy performed between June 2010 and August 2012. All patients underwent axial and sagittal MRI. The AEI was obtained by projecting predefined patellar and trochlear landmarks (cartilaginous landmarks) on 2 different axial MRI views (one trochlear and one patellar). The results were compared with a series of controls (n=45). The preoperative AEI of the patella was 0.94 ± 0.09 for the control group and 0.84 ± 0.16 for OPI group (P=0.000016). The AEI could be obtained in 100% of the cases if it was measured on 2 MRI views while it could not be measured in 38.5% of the cases if the measurement was only obtained from one MRI view or whenever the widest part of the patella was not across from the femoral trochlea. The AEI did not significantly depend on dysplasia or the presence of a supratrochlear spur. The lowest AIE values were associated with trochlear dysplasia with a supratrochlear spur (P=0.0023) and a more prominent trochlea (P=0.0016). The AEI was correlated with patellar tilt (P<0.000001) and TT-TG on MRI (P<0.000001). AEI is a new index to measure LPD. It can be obtained in all cases because it is obtained from two different MRI views. The normal value is close to 1. It can be used to measure patellar instability on the axial plane in patients with OPI, especially in the most severe cases.

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.

Patellofemoral anatomy and biomechanics: current concepts.

The patellofemoral joint, due to its particular bone anatomy and the numerous capsuloligamentous structures and muscles that act dynamically on the patella, is considered one of the most complex joints in the human body from the biomechanical point of view. The medial patellofemoral ligament (MPFL) has been demonstrated to contribute 60% of the force that opposes lateral displacement of the patella, and MPFL injury results in an approximately 50% reduction in the force needed to dislocate the patella laterally with the knee extended. For this reason, recent years have seen a growing interest in the study of this important anatomical structure, whose aponeurotic nature has thus been demonstrated. The MPFL acts as a restraint during motion, playing an active role under conditions of laterally applied stress, but an only marginal role during natural knee flexion. However, it remains extremely difficult to clearly define the anatomy of the MPFL and its relationships with other anatomical structures.

The patellar shift index: a reliable and valid measure for patellofemoral congruence following total knee arthroplasty with unresurfaced patella

The aim of this study was to develop a new radiographic measure, the patellar shift index (PSI), for the precise estimation of patellar position relative to the trochlea after a total knee replacement with an unresurfaced patella. This study included radiographs of 51 patients suffering from anterior knee pain following total knee arthroplasty. Patellofemoral axial radiographs were analyzed to compare the reliability of the PSI to the classical measures of patellofemoral congruence, the lateral patellar tilt (LPT) and patellar displacement (PD). Intra-rater reliability of the PSI, LPT and PD was estimated using the intraclass correlation coefficient (ICC) and the inter-rater reliability using Krippendorff's alpha (Kα). Agreement proportion of was calculated for the PD. Face validity of the PSI was also tested. The PSI had excellent intra (mean ICC=0.91) and inter-rater (Kα=0.92) reliability, as did LPT (mean ICC=0.96; Kα=0.89). The calculation of PD caused a low level of agreement (47.1%) between evaluators in terms of which images could be measured. The exclusion of these radiographs resulted in a high PD intra (ICC=0.96) and inter-rater (Kα=0.97) reliability. The PSI appears to be a reliable and valid measure for patellofemoral congruence in a replaced knee joint with an unresurfaced patella. The superiority of the PSI is the result of its consideration of the geometry and size of the replaced knee joint and independence from radiographic magnification.

Dynamic KINE-MRI in patellofemoral instability in adolescents

The impact of kinematic MRI (KINE-MRI) in the patellofemoral instability and anterior knee pain of the adolescents is rarely reported. Our special interest was to evaluate the patellofemoral joint biomechanics with KINE-MRI in adolescents with affected and unaffected knees in a case-control study. KINE-MRI was performed in 29 adolescents (affected knee group, n = 29 and unaffected knee group, n = 26) aged 11-16 years with unilateral patellofemoral instability. For the control group, we enrolled ten healthy age- and sex-matched volunteers (healthy knee group, n = 19). The study parameters, bisect offset, lateral patellar displacement, patellar tilt angle, sulcus angle and Insall-Salvati ratio at 0, 10, 20 and 30° of flexion-extension, were measured for the affected knee patients (n = 29), unaffected knee patients (n = 26) and the healthy knee subjects (n = 19). The affected knee and the healthy knee subjects had a significant difference in the bisect offset ratio, lateral patellar displacement test and patellar tilt angle test. In these parameters, the difference between the affected knee patients and the healthy knee subjects progressively increased towards the full extension of the knee. In the affected knee and unaffected knee patients, bisect offset ratio at 0° ranged between 0.50 and 1.20 in both groups, whereas the bisect offset ratio in the healthy knee subjects ranged between 0.33 and 0.75 (p < 0.001). At the 0°, the lateral patellar displacement test ranged between 0 and 10 mm in the affected knee patients and between 0 and 35 mm in the unaffected knee patients, whereas the lateral displacement test ranged between 0 and 5 mm in the healthy knee subjects (p = 0.003). Patellar tilt angle test ranged between -30 and 20° in the affected knee patients and between -30 and 24° in the unaffected knee patients, and in the healthy knee subjects, the patellar tilt angle test ranged between 10 and 24° (p < 0.001). The KINE-MRI was able to detect significant differences in patellofemoral joint kinematics between the patients and the healthy subjects. A new finding with clinical relevance in our work is that the unaffected knee is very similar to the dislocated knee in adolescents and this should be taken in account in rehabilitation of patients. II.

Predictors of patellar alignment during weight bearing: An examination of patellar height and trochlear geometry

BackgroundPatellar malalignment is thought to be an etiological factor with respect to the development of patellofemoral pain. Although previous studies have suggested that the geometry of the femoral trochlea and the height of the patella play an important role in determining patellar alignment, no investigation has systematically examined these relationships during weight bearing. The aim of this study was to determine whether patellar height and/or trochlear geometry predicts patellar alignment (lateral patellar displacement and lateral patellar tilt) during weight bearing. MethodsMR images of the patellofemoral joint were acquired from 36 participants during weight bearing (25% of body weight) at 4 knee flexion angles (0°, 20°, 40° and 60°). Using the axial images, patellar alignment (lateral displacement and tilt) and femoral trochlear geometry (sulcus angle and inclination of the lateral femoral trochlea) were measured. Patellar height (Insall–Salvati ratio) was measured on reconstructed sagittal plane images. ResultsStepwise regression analysis revealed that at 0° of knee flexion, the height of the patella was the best predictor of lateral patellar tilt while the lateral trochlea inclination angle was the best predictor of lateral patellar displacement. Lateral trochlear inclination was the best predictor of patellar lateral displacement and tilt at 20°, 40° and 60° of knee flexion. ConclusionSimilar to a previous study performed under non-weight bearing condition, our findings suggest that lateral trochlear inclination is an important determinant of patellar alignment in weight bearing. Level of EvidenceLevel III

No difference in patellar tracking between symmetrical and asymmetrical femoral component designs in TKA

Poor knee extension function after total knee arthroplasty (TKA) is associated with factors including articular geometry and alignment. Femoral trochlear geometry has evolved from symmetrical to become more prominent proximal-laterally, with the groove aligned proximal-lateral to distal-medial. This study in vitro tested the hypothesis that a modern asymmetrical prosthesis would restore patellar tracking and stability to more natural behaviour than an older symmetrical prosthesis. Six knees had their patellar tracking measured optically during active knee extension. Medial-lateral force versus displacement stability was measured at fixed angles of knee flexion. The measurements were repeated after inserting each of the symmetrical and asymmetrical TKAs. Significant differences of patellar lateral displacement stability, compared to normal, were not found at any angle of knee flexion. The patella tracked medial-laterally within 2.5mm of the natural path with both TKAs. However, for both TKAs near knee extension, the patella was tilted laterally by approximately 6° and was also flexed approximately 8° more than in the natural knee. The hypothesis was not supported: The more anatomical component design did not provide more anatomical patellar kinematics and stability.

Association Between Measures of Patella Height, Morphologic Features of the Trochlea, and Patellofemoral Joint Alignment: The MOST Study

Patellofemoral joint (PFJ) malalignment (lateral patella displacement and tilt) has been proposed as a cause of patellofemoral pain. Patella height and/or the morphologic features of the femoral trochlea may predispose one to patella malalignment. The purposes of our study were to assess the associations among patella height, morphologic features of the trochlea, and measures of PFJ alignment and to determine which measures of patella height and morphologic features of the trochlea were the best predictors of PFJ alignment. Measures of patella height (Insall-Salvati ratio and modified Insall-Salvati ratio), morphologic features of the trochlea (sulcus angle, trochlear angle, lateral trochlear inclination, medial trochlear inclination), and PFJ alignment (bisect offset and patella tilt angle) were assessed in 566 knees from the Multicenter Osteoarthritis Study. Bisect offset was correlated with the Insall-Salvati ratio (r = 0.25) and lateral trochlear inclination (r = -0.38). Patella tilt angle correlated with the trochlear angle (-0.27) and lateral trochlear inclination (-0.32). Linear regression models including the Insall-Salvati ratio and lateral trochlear inclination explained 20% and 11% of the variance in bisect offset and patella tilt angle, respectively. Of the variables measured in the current study, the Insall-Salvati ratio and lateral trochlear inclination were the best predictors of lateral patella displacement and lateral tilt. This knowledge will aid clinicians in the identification of anatomic risk factors for PFJ malalignment and/or PFJ dysfunction.

Response of therapeutic exercise and patellar taping on patella position and pain control in the Patellofemoral pain syndrome

Objective: To evaluate the effect of multiple applications of patellar taping over a longer period of time, alone and along with the application of therapeutic exercise on patella position and pain control in Patellofemoral Pain Syndrome (PFPS). Study Design: A different subject pretest-post test, experimental group design. Materials and Methods: Twenty-one subjects participated in the study. The subjects were randomly assigned to one of the three groups: Patellar taping combined with Close Kinetic Chain (CKC) exercise, Patellar taping only, and CKC exercise only (n = 7 in each group). Taping was applied and exercise was performed on a daily basis for three weeks. The measures were obtained on the Visual Analog Scale (VAS) for pain and lateral patellar displacement for patella position. Results: The paired t-test was used for within-group comparison of pre-test and post test measurement and Analysis of Variance (ANOVA) was used for between-group comparisons of the three groups. The result of the study showed that the group receiving patellar taping and CKC exercise had better pain relief ( p p > .05). Conclusion: The combination of daily patella taping along with CKC exercise program for three weeks has been seen to be more effective than only patella taping and only the CKC exercise program, in reducing pain in patients with PFPS. Patella taping alone or in conjunction with CKC exercises is not able to bring any significant change in the patella position in patients with PFPS.

Acute patellar dislocation. What to do?

Acute patellar dislocation is a common knee injury that occurs most often in adolescents, frequently associated with sporting and physical activities. Patellar re-dislocation after the first episode appears to depend primarily on the medial patellofemoral ligament injury which represents the primary ligamentous restraint, providing about 50-60% of the restraining force against lateral patellar displacement. Clinically, up to 94-100% of patients suffer from medial patellofemoral ligament rupture after first-time patellar dislocation. Controversy regarding how patients with first patellar dislocation should be managed still exists. Though most authors have reported good results with the conservative treatment after a first-time dislocation, several circumstances may warrant surgical intervention. A surgical approach would be necessary in the presence of severe cartilage damage or a relevant disruption of the medial stabilizers with subluxation of the patella. In these cases, the repair/reconstruction of medial stabilizers should follow the treatment of the chondral injury. Medial patellofemoral ligament reconstruction may be a more reliable method of stabilizing the patella than its repair, which has limitations related to the medial patellofemoral ligament injury location. Nowadays, there is no evidence available where osseous abnormalities should be addressed in addition to restoring the medial patellofemoral ligament.

Minimally invasive surgical technique In treating recurrent patellar dislocation

Introduction: Recurrent patellar dislocation is one of the most common pathologies affecting the knee joint in young people. The underlying pathology is either soft tissue, bony or combination of both. The literature describes more than 100 different surgical approaches to address recurrent patellar dislocation. The medial patello-femoral ligament (MPFL) has been identified as the primary medial restraint to prevent lateral patellar displacement. The MPFL accounts for 80% of the medial restraining force on the patellar.

Paper 105: Changes in Patellar Alignment After Total Knee Arthroplasty

Although the results of total knee arthroplasty continue to improve, problems related to the patellofemoral joint remain significant. This study examined the factors affecting patellar alignment after total knee arthroplasty and subsequent changes during a postoperative period of 5.3 years. Fifty-five knees in 39 patients were retrospectively evaluated by radiography for postoperative patellar alignment. This study included four men and 35 women with a mean follow-up time of 5.3 years (range: 2.5 to 8.4). All procedures utilized identical surgical technique; through a midline skin incision and medial parapatellar arthrotomy, the patella was fully everted. We adjusted the rotation of the femoral component until it was parallel to the surgical epicondylar axis. Using the posterior femoral condyles as references, we inserted the femoral components with 3° to 5° of external rotation to the posterior condylar axis according to preoperative CT scans. Tibial components were set using the medial third of the tibial tuberosity as a reference. All patellae were resurfaced with three-peg offset-dome all-polyethylene patellar component. Patellar alignment was assessed by measuring the lateral tilt and lateral displacement in skyline views taken with the knees at approximately 60° of flexion. Patellar alignment was evaluated one month after surgery, and at final follow-up. Changes in patellar lateral tilt angle and lateral displacement in the postoperative period were calculated using data obtained one month after surgery and at final follow-up. We did not observe severe malalignment of the femorotibial joint, patellar bone fracture, prosthesis failure, or any other clinical complications after TKA in any cases. The mean patellar lateral tilt angle was -0.7° (range: −13.7 to 7.0°) one month after surgery and −0.4° (range: −11.4 to 11.6°) at final follow-up. The mean patellar lateral displacement was 1.1mm (−2.7 to 6.6mm) one month after surgery and 0.9mm (−3.7 to 5.8mm) at final follow-up. We observed a negative correlation between the patellar resection angle and lateral tilt one month after surgery (p<0.0001) and between the patellar resection angle and patellar lateral displacement one month after surgery (p=0.0003). Lateral retinacular release was required for thirteen knees. In these cases, the resection angle was significantly smaller than that seen in knees without lateral retinacular release (p=0.0012). These results demonstrate that a smaller resection angle correlated with an increased frequency of lateral retinacular release. The change in patellar lateral tilt angle after 5.3 years was 0.3° (range: −7.2 to 7.0°), while the change in patellar lateral displacement was −0.3 mm (range: −5.2 to 3.7 mm). These changes did not significantly correlate with patellar alignment at any time point, resection angle, resection thickness, lateral retinacular release, or clinical results. The postoperative femorotibial alignment, however, exhibited a statistically significant correlation with the changes in lateral tilt angle (p=0.020). A more varus postoperative alignment correlated with increased lateral tilt of the patella in the postoperative period. We observed a satisfactory patellar alignment after a postoperative period of 5.3 years. The patellar resection angle had a significant effect on postoperative patellar alignment. Our findings suggest that leaving a thicker patellar remnant on the medial side can decrease postoperative lateral tilt and the resulting need for lateral retinacular release. Postoperative changes in patellar alignment were very small; none of the knees demonstrated complications of the patellofemoral joints. In this study, we observed the tendency that a postoperative varus alignment leads to patellar lateral tilt. Surgeons should pay scrupulous attention to femorotibial alignment during total knee arthroplasty to decrease patellofemoral complications and femorotibial problems.

Reconstruction of medial patellofemoral ligament for chronic patellar instability

Background:Disruption of the capsule, medial patellar retinaculum, and/or vastus medialis obliqus has been associated with recurrent patellar instability. Biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement and reconstruction of the MPFL has become an accepted surgical technique to restore patellofemoral stability in patients having recurrent patellar dislocation. We report a prospective series of patients of chronic patellar instability treated by reconstruction of medial patellofemoral ligament.Materials and Methods:Twelve patients (15 knees) with recurrent dislocation of patella, were operated between January 2006 and December 2008. All patients had generalised ligament laxity with none had severe grade of patella alta or trochlear dysplasia. The MPFL was reconstructed with doubled semitendinosus tendon. Patients were followed up with subjective criteria, patellar inclination angle, and Kujala score.Results:The mean duration of followup after the operative procedures was an average of 42 months (range 24–60 months) 10 knees showed excellent results, 3 knees gave good results, and 2 knees had a fair result. The average patellar inclination angle decreased from 34.3° to 18.6°. The average preoperative Kujala functional score was 44.8 and the average postoperative score was 91.9.Conclusion:MPFL reconstruction using the semitendinosus tendon gives good results in patients with chronic patellar instability without predisposing factors like severe patella alta and high-grade trochlear dysplasia, and for revision cases.

Correlation Between Trochlear Groove Depth and Patellar Position During Open and Closed Kinetic Chain Exercises in Subjects With Anterior Knee Pain

The purpose of this study was to correlate the trochlear shape and patellar tilt angle and lateral patellar displacement at rest and maximal voluntary isometric contraction (MVIC) exercises during open (OKC) and closed kinetic chain (CKC) in subjects with and without anterior knee pain. Subjects were all women, 20 who were clinically healthy and 19 diagnosed with anterior knee pain. All subjects were evaluated and subjected to magnetic resonance exams during OKC and CKC exercise with the knee placed at 15, 30, and 45 degrees of flexion. The parameters evaluated were sulcus angle, patellar tilt angle and patellar displacement using bisect offset. Pearson's r coefficient was used, with p < .05. Our results revealed in knee pain group during CKC and OKC at 15 degrees that the increase in the sulcus angle is associated with a tilt increase and patellar lateral displacement. Comparing sulcus angle, patellar tilt angle and bisect offset values between MVIC in OKC and CKC in the knee pain group, it was observed that patellar tilt angle increased in OKC only with the knee flexed at 30 degrees. Based on our results, we conclude that reduced trochlear depth is correlated with increased lateral patellar tilt and displacement during OKC and CKC at 15 degrees of flexion in people with anterior knee pain. By contrast, 30 degrees of knee flexion in CKC is more recommended in rehabilitation protocols because the patella was more stable than in other positions.

The intra- and inter-rater reliability of X-ray radiological measurements for patellar instability

AimPatellar instability is a complex, multi-factorial disorder. Radiological assessment is regarded as an important part of the management of this population. The purpose of this study was to determine the intra- and inter-rater reliability of common radiological measurements used to evaluate patellar instability. Methods and materialsOne hundred and fifty X-rays from 51 individuals were reviewed by five reviewers, two orthopaedic trainees, a radiological trainee, a consultant radiologist and an orthopaedic physiotherapist. Radiological measurements assessed included patellar shape, sulcus angle, congruence angle, lateral patellofemoral angle, lateral patellar displacement (LPD), lateral displacement measurement (LDM), boss height, and patellar height ratios. All assessors were provided with a summary document outlining the method of assessing each measurement. No further formal teaching was provided. Bland–Altman analyses were adopted to assess intra- and inter-rater reliability. ResultsThe results indicated generally low measurement error on intra-rater reliability assessment, particularly for LPD, LDM and boss height measurements. Whilst the inter-rater reliability between assessors indicated a low mean difference for assessments of patellar height measurements, patellar angle, lateral patellar dislocation and lateral displacement, wide 95% limits of agreement for all measurements indicated poor precision. ConclusionMany of the standard measurements used to assess the patellofemoral joint on plain radiographs have poor precision. Intra-rater reliability may be related to experience but it seems likely that to achieve good inter-rater reliability, specific training may be required to calibrate observers. More formal training in the technique of radiological measurement for those who were inexperienced might have improved the inter-rater reliability.

Patellofemoral Alignment and Anterior Knee Pain After Closing- and Opening-Wedge Valgus High Tibial Osteotomy

The purpose of this study was to compare the clinical and radiographic outcomes of opening- and closing-wedge valgus high tibial osteotomy (HTO) for the treatment of medial unicompartmental knee osteoarthritis with a minimum follow-up of 3 years, with a focus on patellofemoral alignment and anterior knee pain. We performed a retrospective comparison of 50 patients who underwent closing-wedge HTO and 50 patients who underwent opening-wedge HTO for isolated medial joint arthritis of the knee with varus deformity. All patients were evaluated and the 2 study groups were compared after a minimum follow-up of 3 years with a focus on patellofemoral alignment, patellofemoral osteoarthritis, and anterior knee pain while climbing stairs. Patellar alignment (patellar tilt and lateral patellar displacement) was not significantly different in the 2 groups either preoperatively or at follow-up. Furthermore, there were no significant differences in the extent of patellofemoral arthritis and incidence of anterior knee pain at follow-up between the 2 groups. In addition, no significant intergroup difference was found in terms of the incidence of anterior knee pain (28% in closing-wedge group and 32% in opening-wedge group at follow-up). The results of closing- and opening-wedge valgus HTO were not found to be significantly different with respect to patellar alignment, osteoarthritis of the patellofemoral joint, or anterior knee pain. Level III, retrospective comparative study.

Incidence and radiologic predictor of postoperative patellar instability after Fulkerson procedure of the tibial tuberosity for recurrent patellar dislocation

Excellent results of anteromedialization of the tibial tuberosity for recurrent patellar dislocation have been reported; however, the contribution of the preoperative anatomic factors to postoperative patellar instability has not been well established. The purpose of this study was to investigate the mid-term results and the incidence of postoperative patellar instability after Fulkerson procedure for recurrent patella dislocation, and to determine the radiologic predictor of the postoperative patellar instability. Sixty-two knees of 41 patients underwent Fulkerson procedure with or without lateral retinacular release for recurrent patellar dislocation and were followed-up for 85-155 months. Predisposing anatomic factors for recurrent patellar dislocation were evaluated preoperatively, including valgus knee alignment (femorotibial angle), patella alta (Insall-Salvati ratio), trochlear dysplasia (trochlear depth), lateral patellar displacement (congruence angle) and lateral malposition of the tibial tuberosity (tibial tuberosity-trochlear groove distance). The relationship between the measurements of anatomic factors and postoperative patellar instability, which was defined by the patellar re-dislocation or residual apprehension after surgery, was analyzed. The Fulkerson score and the Kujala score were significantly improved from the median of 65 (35-80) points and 68 (36-82) points preoperatively to 95 (60-100) points and 92 (57-100) points at the final follow-up, respectively. Three knees (4.8%) experienced postoperative patellar re-dislocation and 4 knees (6.5%) showed the positive apprehension sign at the final follow-up. The statistical analysis showed that the postoperative patellar instability correlated with only patella alta. Patella alta was the only predictor of postoperative patellar instability after Fulkerson procedure. These results indicated that isolated Fulkerson procedure should not be indicated for recurrent patellar dislocation with severe patella alta. Case-control study, Level III.