Lateral Patellofemoral Angle Research Articles

Preoperative Patello-femoral Alignment Affects Anterior Knee Pain After Primary Total Knee Arthroplasty Without Patellar Resurfacing

Anterior knee pain (AKP) after total knee arthroplasty (TKA) results in dissatisfaction with the surgical outcomes. This study aimed to investigate risk factors for AKP after TKA using radiographic assessments. This retrospective matched-pair, case-control study included 284 patients who underwent primary fixed-bearing, posterior-stabilized TKA from 2016 to 2020, with a minimum follow-up of two years. The inclusion criterion was varus osteoarthritis in the knees without patellar resurfacing. The exclusion criteria were the use of bone graft or metal block, valgus knees, and patellar resurfacing. The patellar tilt angle, lateral patello-femoral angle, length of the tibial tuberosity to the trochlear groove (TT-TG), hip-knee-ankle (HKA) angle, patellar height, and trochlear dysplasia index were measured. Patients were divided into two groups according to the presence of AKP based on the Feller score (≤ 20 points) at a 2-year follow-up, then a 1:2 propensity matching was performed. Risk factors for AKP were identified through a logistic regression analysis. A total of 135 patients were enrolled in this study after matching. The preoperative patellar tilt angle, lateral patello-femoral angle, TT-TG, and trochlear dysplasia index significantly differed between the groups (P < 0.05), but not the postoperative parameters (P > 0.05). The Western Ontario and McMaster Universities total score and Feller score were significantly different postoperatively. (P < 0.05) Logistic regression analysis revealed that the preoperative patellar tilt angle, preoperative trochlear dysplasia index, and preoperative lateral patello-femoral angle were significant risk factors. Care should be exercised when performing TKA in patients who have a large patellar tilt angle, a small lateral patello-femoral angle, and a small trochlear dysplasia index preoperatively, as there can be an increased risk of postoperative anterior knee pain in TKA with unresurfaced patellae. Surgeons may consider counseling patients about their increased risk of AKP if these factors are present preoperatively.

Analysis of Risk Factors on Patellofemoral Osteoarthritis: Distribution Characteristics and Radiographic Parameters of Patellofemoral Joint.

The risk factors for the degeneration of the patellofemoral joint (PFJ) have not been adequately and thoroughly studied. This study aimed to analyze the population distribution characteristics of patients with patellofemoral osteoarthritis (PFOA) and assess the correlation between PFOA and radiological parameters, including patella morphology, PFJ congruity, and patellar alignment. Moreover, the risk factors across various demographic groups were further analyzed. A retrospective analysis was conducted to examine the population distribution characteristics of PFOA patients from September 2020 to September 2023. Radiological parameters of the PFJ were measured from the anteroposterior and lateral views of knee joint as well as axial view of patella using X-ray imaging and the PACS imaging system at the First Affiliated Hospital of Kunming Medical University. These parameters included patella morphology (patella type, width, thickness, and Wiberg index), PFJ congruity (patella height, Wiberg angle, sulcus angle, and lateral patella angle), and patellofemoral alignment (patella tilt angle, displacement, and lateral patellofemoral angle). PFOA severity was classified according to the Iwano PFJ radiological classification, and its correlation with the aforementioned parameters was examined. Additionally, risk factors for PFOA across different populations were further evaluated. The study included 1080 patients according to the inclusion and exclusion criteria. Age, female gender, overweight or obesity, and manual workers were significantly associated with PFOA. Moreover, type III patella (OR = 3.03, p < 0.05), greater patella width (OR = 1.12, p = 0.01), sulcus angle (OR = 1.04, p < 0.01), patella tilt angle (OR = 1.13, p < 0.01), and patella displacement (OR = 1.22, p < 0.01) as well as smaller patella thickness (OR = 0.87, p < 0.01), Insall-Salvati index (OR = 0.24, p = 0.04), and lateral patellofemoral angle (OR = 0.93, p = 0.02) were identified as risk factors for PFOA. Furthermore, greater patella thickness (OR = 1.17, p < 0.05) and smaller patella displacement (OR = 0.79, p < 0.01) correlated with higher Kujala patellofemoral scores. Discrepancies in risk factors across different populations were also observed. Older age, female gender, obesity, manual workers, and specific aberrations in patellofemoral parameters are predictive factors for PFOA. Additionally, greater patella thickness and smaller patella displacement were associated with increased severity of clinical symptoms. Thus, more attention should be paid to the discrepancies that exist in different populations.

Clinical and Radiological Outcomes After Isolated Double-Bundle Medial Patellofemoral Ligament Reconstruction: A 5-Year Analysis.

There are few studies that have examined clinical and radiological outcomes at 5 years after isolated medial patellofemoral ligament (MPFL) reconstruction. To date, midterm outcomes after isolated double-bundle (DB) MPFL reconstruction are not well known. Isolated DB MPFL reconstruction using a patellar suture anchor technique would lead to improved functional scores and radiological findings, and these improvements would remain stable over the 5-year postoperative period. Case series; Level of evidence, 4. Isolated MPFL reconstruction was performed in patients with recurrent patellar instability between March 2013 and February 2017. Clinical and functional evaluations were performed via an interview using the Kujala, Lysholm, and Tegner scores preoperatively and at 6, 12, 24, and 60 months postoperatively. Radiographs were taken preoperatively, immediately postoperatively, and at 24 and 60 months after surgery. Radiographic assessments included measuring the modified Insall-Salvati ratio, congruence angle, and lateral patellofemoral angle. A total of 31 patients (31 knees) underwent isolated MPFL reconstruction; 4 patients did not complete 5-year follow-up, and thus, 27 patients (27 knees) were enrolled in the study. The mean age at the time of surgery was 22.0 ± 6.4 years (range, 14-32 years). All clinical and functional scores significantly improved in the first 2 years (P < .001), with the mean Kujala, Lysholm, and Tegner scores improving from 52.7 to 90.7, 49.6 to 92.7, and 2.9 to 5.1, respectively. There was no significant difference in scores between 2- and 5-year follow-up. All radiographic parameters significantly improved between preoperatively and immediately postoperatively (P < .001), with mean values for the modified Insall-Salvati ratio, congruence angle, and lateral patellofemoral angle improving from 1.7° to 1.6°, 5.7° to -6.6°, and 3.0° to 5.9°, respectively. No significant differences were observed in radiographic measurements between the postoperative time points. No patients experienced a patellar redislocation or fracture. The prospective analysis of isolated DB MPFL reconstruction at 5-year follow-up showed that clinical and radiological outcomes significantly improved postoperatively and were maintained to 5 years. These midterm results suggest that isolated DB MPFL reconstruction is an effective treatment option for patients with patellar instability.

Comparison of Clinical and Radiological Outcomes With Body Mass Index After Medial Patellofemoral Ligament Reconstruction.

Medial patellofemoral ligament (MPFL) reconstruction is a commonly employed surgical approach for recurrent patellar dislocation. However, the impact of elevated body mass index (BMI) on postoperative complication rates remains controversial. To compare the clinical, radiographic, and functional outcomes of patients with normal BMI (18.5-24.9 kg/m2) and those with elevated BMI (≥25 kg/m2) who underwent MPFL reconstruction for recurrent acquired lateral traumatic patellar dislocation. Cohort Study; Level of evidence, 3. A total of 70 patients who underwent MPFL reconstruction for recurrent patellar dislocation were included in this study. Patients with recurrent patellar dislocation were categorized into 2 groups based on their BMI: the normal BMI group and the elevated BMI group. Functional scores (Lysholm, International Knee Documentation Committee [IKDC], Tegner, and Kujala scores) and radiological measurements (patellar tilt angle, patellofemoral trochlear congruence, lateral patellofemoral angle, and lateral patellar displacement) were evaluated both preoperatively and at the last follow-up. The occurrence of postoperative complications at the last follow-up was also recorded. Differences in functional scores and radiological parameters before and after surgery were analyzed with paired-samples t tests or Wilcoxon signed-rank tests. Comparisons between groups were conducted using independent-samples t tests or the Kolmogorov-Smirnov test. In the normal BMI group, there were 13 male patients and 27 female patients, with a mean follow-up duration of 26.15 ± 13.16 months. The mean age in this group was 21.93 ± 7.94 years. The elevated BMI group consisted of 12 male patients and 18 female patients, with a mean follow-up duration of 27.50 ± 15.79 months and a mean age of 23.30 ± 8.43 years. At the final follow-up, the incidence of surgical failure (patellar redislocation or subluxation and necessitating secondary surgery) was significantly higher in the elevated BMI group (6 out of 30 patients; 20.0%) compared with the normal BMI group (1 out of 40 patients; 2.5%) (P < .05). Both groups demonstrated significant improvement in postoperative Lysholm, IKDC, Tegner, and Kujala scores compared with the preoperative period (P < .05). Notably, the normal BMI group had significantly higher preoperative Lysholm and Tegner scores compared with the elevated BMI group (P < .05). Furthermore, the elevated BMI group exhibited less improvement in Tegner and Kujala scores compared with the normal BMI group (P < .05). Postoperative radiological parameters in both groups returned to the normal range (P < .05). There were no statistically significant differences between the 2 groups in terms of radiological parameters and their corresponding differences. Our study demonstrated statistically significant increases in postoperative clinical scores for both groups, although the intergroup differences varied. Specifically, patients with elevated BMI demonstrated poorer preoperative Lysholm and Tegner scores. The postoperative improvement in radiological parameters was equally good between the 2 groups.

The effect of high tibial osteotomy and unicompartmental knee arthroplasty on patellofemoral joint in young patients with medial knee arthrosis.

Osteoarthritis of the knee is a debilitating disease. In most cases, only the medial compartments are affected. High tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are the two main procedures commonly used in the surgical treatment of unicompartmental knee osteoarthritis patients not responding to conservative treatment. The aim of our study was to compare UKA and biplanar medial open-wedge HTO in terms of patellofemoral changes and functional score in patients under 60 years of age with medial compartment arthrosis. A retrospective study. A total of 79 patients (37 HTO, 42 UKA) who received one of the two treatments in a single center were examined preoperatively and at a single postoperative follow-up. Posterior tibial slope, lateral patellofemoral angle (LPFA), Q-angle, patellar height, Cincinnati Rating System and Knee Injury and Osteoarthritis Outcome Score (KOOS) functional scores were evaluated in all patients preoperatively and at the 6-month follow-up examination. Insall-Salvati ratio remained stable in the HTO group, while there was a minor decrease in the UKA group and the changes between the groups were not statistically significant. Caton-Deschamps ratio increased in the UKA group and decreased in the HTO group, and this change was statistically significant (p < 0.001). LPFA did not change in the UKA group in the postoperative period, while it increased in the HTO group (p < 0.001). Changes in Q angle and Cincinnati Rating System scores were statistically similar between the UKA and HTO groups (p = 0.827 and p = 0.340). In our study, biplanar medial open-wedge HTO and UKA performed with appropriate surgical technique had no negative effect on patellofemoral joint. In patients under 60 years of age with medial compartment osteoarthritis of the knee, both surgical treatments can be performed with appropriate patient selection.

Ellipsoidal patellar bone tunnel fixation with Toggleloc suspension system for medial patellofemoral ligament reconstruction: A 5 years follow-up.

This study aimed to evaluate the clinical and radiological features of the patella fixation technique using Toggleloc suspension system in a single ellipsoidal blind patellar tunnel during medial patellofemoral ligament (MPFL) reconstruction. This study included 52 patients (25 men, 27 women) who underwent MPFL reconstruction using a semitendinosus tendon graft. The graft was fixed to the ellipsoidal single blind tunnel opened on the medial side of the patella with an endobutton and was fixed to the femoral tunnel by using bioabsorbable screw. Clinical scores (Kujala score, Lysholm score, Tegner activity score and the visual analog scale [VAS] score) were evaluated preoperatively and at the end-follow up. Preoperative and postoperative radiological measurements (trochlea depth, sulcus angle, patellar height, patellar congruence angle, patellar tilt angle and lateral patellofemoral angle) were evaluated with X-ray (Merchant X-ray, anteroposterior and lateral radiography) and computed tomography (CT) of the knee. Postoperative patellar redislocation or subluxation was not observed in any patient. Patellar congruence angle, patellar tilt angle and lateral patellofemoral angle mean values were found to return to normal values in the postoperative period and the results were statistically significant. Also statistically significant improvement in all clinical scores postoperatively. According to the Insall-Salvati index (ISI) and Caton-Deschamps index (CDI) on lateral radiography of the knee at 30° flexion, patellar height decreased in the postoperative period statistically significant. The CDI was above 1.3 in 17 (%32) of our patients. Thirteen of these values decreased to normal values. No radiological progression of patellofemoral osteoarthritis was observed in all patients at the final follow-up evaluation. In cases of patellofemoral instability, fixation of the tendon graft in blind ellipsoid tunnel using the Toggleloc suspension system provides satisfactory patellar graft fixation strength, significant functional improvement and a low failure rate.

Initial investigation into patellofemoral morphology in hemophilic arthritis patients.

Hemophilic arthritis (HA) is associated with significant changes in the morphology of mature knee joints due to abnormal growth plate development. Previous studies have established marked distinctions between the femur and tibia of subjects with Haemophilia and those with osteoarthritis (OA). This study explored the morphological characteristics of the patella and patellofemoral joint in subjects with Haemophilia. These findings can inform the design of knee joint prostheses tailored to this condition, improve the precision of total knee replacement surgery, and reduce postoperative knee pain and patellar dislocation. Before surgery, we conducted preoperative measurements of patellar length, patellar diagonal length, patellar ligament length, patellar width, patellar thickness, the INSALL index, the lateral patellofemoral angle, the trochlear groove angle,the patellar lateral displacement rate, and the patellofemoral index using lateral and axial x-ray images in 40 subjects with Haemophilia, 40 OA patients, and 40 normal individuals. Significant statistical differences in certain morphological parameters were observed among the three groups of patients (P < 0.05). Compared with the OA and normal control groups, the HA group presented significant disparities in patellar thickness, patellar ligament length, the Insall ratio, the patellar lateral shift rate, the lateral patellar angle, and the patellofemoral index. Compared with OA and normal individuals, Subjects with Haemophilia presented with smaller and thinner patellae, more significant patellar ligament contracture, reduced patellar height, and more pronounced patellar dislocation. Consequently, during total knee arthroplasty, we lean toward patellar reshaping in subjects with Haemophilia, exercise caution when considering patellar replacement, and, for those with severe preoperative patellar dislocation, perform intraoperative lateral retinacular release.

Application of functional magnetic resonance imaging for evaluation of cartilage injury effect on knee joint function by recurrent patellar dislocation.

Explore the therapeutic effect of vastus medialis oblique plasty and the reliability and applicability of functional magnetic resonance imaging as a diagnostic method for early cartilage degeneration and injury diagnosis. From July 2020 to July 2022, there were 53 patients with recurrent patellar dislocation who met the inclusion criteria for surgery, including 34 women and 19 men, aged 11 to 53 years, with an average age of 24.4 years. After patient selection, functional magnetic resonance imaging was performed before surgery. According to the presence or absence of cartilage injury, they were divided into cartilage injury group (n = 28) and non-cartilage injury group (n = 25), and underwent vastus medialis oblique plasty. Preoperative patellar axial radiographs were performed in both groups of patients to measure the patellar tilt angle and lateral patellofemoral angle. The Lysholm, Kujala, and VAS (visual analogue scale) scores were applied to assess changes in knee joint function and anterior knee pain. All patients were postoperatively followed up. The patellar tilt angle and lateral patellofemoral angle of the 2 groups were significantly improved postoperatively (P < .05), with no statistical difference between the 2 groups (P > .05). Significant differences were observed in the VAS changes between the cartilage injury group and the non-cartilage injury group before and after operation (P < .05). There was a statistical difference in VAS score between the groups (P < .05). The changes in the Lysholm and Kujala scores before and after the operation in the cartilage injury and the non-cartilage injury groups were statistically different (P < .05). There was statistical difference between the 2 groups in Lysholm score and Kujala score after operation (P < .05). Vastus medialis oblique plasty significantly improved knee joint function and pain. Patients with cartilage injury had worse preoperative and postoperative knee function than patients without cartilage injury. Functional magnetic resonance imaging can reflect the early-stage changes in the biochemical cartilage components caused by recurrent patellar dislocation.

Reconstruction of medial patellofemoral ligament with adductor magnus tendon for recurrent patellar dislocation in children: a retrospective comparative cohort study

BackgroundThe purpose of current retrospective study was to explore the outcomes of using the adductor magnus tendon to reconstruct the medial patellofemoral ligament in the treatment of recurrent patellar dislocation in children.MethodThirty-two children with recurrent patellar dislocation were selected. Sixteen cases in the conservative group, seven males and nine females, with an average age of 11.81 ± 1.28 years; sixteen cases in the surgical group, eight males and eight females, with an average age of 11.56 ± 1.15 years. All patients had no surgery history. The IS index (> 1.2), Q angle (> 20°) and tibial tubercle–femoral trochlear groove (TT–TG) distance (> 20 mm) were measured by X-ray and MRI. The conservative group was treated with closed reduction and a brace, and the surgical group received surgical treatment. Two years after surgery, congruence angle (CA) (− 6° to 6°) and lateral patellofemoral angle (LPFA) (7.7°–18.7°) were measured by X-ray image and all children were evaluated based on Kujala and Lysholm scores. The re-dislocation rate was recorded. Analysis was performed by t test and chi-square with the statistical SPSS software. P < 0.05 was considered a statistically significant difference. Furthermore, we measured the length (mm) of the adductor tendon and MPFL in three knee cadaveric specimens, and also observed the positional relationship between the two structures.ResultThere were no significant differences in sex, age, injury site between groups (P > 0.05). Patients in the two groups were followed up for 2 years in average. Among the 16 cases in the conservative group, 7 cases (43.75%) had recurrence of patellar dislocation, while none of recurrence in the surgical group (P < 0.05). The Lysholm score of the surgical group (94.63 ± 8.99) was significantly better than that of the conservative group (79.31 ± 18.90), and the Kujala score of the surgery group (95.25 ± 10.32) was also significantly better than that of the conservative group (77.06° ± 14.34°) (P < 0.05). The CA and LPFA of the two groups of patients after treatment were significantly recovered. The CA (− 5.81° ± 7.90°) in the surgical group was significantly better than that in the conservative group (20.94° ± 8.21°), and the LPFA (6.44° ± 3.22°) was also significantly better than that in the conservative group (− 9.18 ± 11.08), and the difference is statistically significant (P < 0.05). We found it through autopsy that adductor magnus tendon was 124.33 ± 1.53 mm long, MPFL was 48.67 ± 2.08 mm, and the femoral insertion of the adductor magnus tendon was adjacent to the MPFL femoral insertion.ConclusionReconstruction of Medial patellofemoral ligament with the adductor magnus tendon, fixing with PEEK suture anchors on the patellar side, can achieve satisfactory results in the treatment of children with recurrent patellar dislocation. Compared with conservative treatment, the rate of recurrence is lower and the stability of the patella is better.

Original surgical technique for the treatment of patellofemoral instability after failure of conservative treatment

IntroductionAcute patellar dislocation is a common but serious injury that can significantly impact a patient's functional prognosis. The objective of this retrospective study is to evaluate the clinical outcomes of arthroscopic medial patellofemoral ligament (MPFL) reconstruction and plication of the medial patellar retinaculum using suture anchors in adolescent patients with first-time acute patellar dislocation (APD) and MPFL insertion injury. HypothesisTightening repair of the medial retinaculum complex can result in favorable clinical and functional outcomes in this patient population. Materials and methodsA total of 84 adolescent patients with first-time APD and with an average age of 15.5 years (10-22) were included in the study. Of these patients, 61 (7 male and 54 female) underwent arthroscopic suture anchor plication for medial patellar retinaculum, while the other 23 were successfully treated non-operatively. Radiographic outcomes, including the congruence angle (CA), lateral patellofemoral angle (LPA), and patellar tilt angle (PTA), were evaluated preoperatively and at the last follow-up visit in the surgical group. Functional outcomes were assessed using the Lille Patello-Femoral Score, Lysholm Score, and Kujala Score at the same time points. In addition, the surgical and non-operative treatment success groups were compared in terms of both radiographic and functional outcomes. ResultsMean follow-up was 40.9 months (24–60). Fifty-nine knees showed excellent or good results postoperatively, 2 patients had a recurrent patellar subluxation. The Lille Patello-Femoral Score was 96.9±4.7 at the last follow-up. The subjective Lysholm Score and Kujala Score improved significantly, from 58.6 to 91.9 and from 60.4 to 88.9, respectively. The radiographic CA, LPA and PTA improved significantly, from 19.8±2.1° to –6.7±1.7°, from –7.4±2.2° to 5.7±1.8° and from 23.8±2.9° to 12.3±2.3°, respectively. There was no statistically significant difference in functional and radiographic assessments between the success with non-operative treatment group and the surgery group. ConclusionThe results of this study suggest that arthroscopic MPFL insertion reconstruction and plication using suture anchors, which is less invasive and improves patella stability, can lead to favorable clinical and functional outcomes in adolescent patients with first-time acute patellar dislocation and insertion injury. This treatment approach should be considered as a viable option for this patient population. Level of evidenceIV; monocentric retrospective descriptive study.

Analysis of the relationship between meniscal tears and medial patellofemoral rupture according to the treatment method and gender

Objective: The aim of this study was to make a detailed anatomical analysis of the parameters of patellar height, the congruence angle, the lateral patellofemoral angle in patients with medial patellofemoral rupture, according to the treatment method (surgical or conventional), gender and whether or not there is a lateral and medial meniscus tears.&#x0D; Methods: This study was planned as retrospective study between January 2010 and January 2021. Magnetic resonance images (MRI) of 61 knees (61 individuals) were obtained for analysis. Of those, 38 knees were left, and 23 were right. One orthopaedic surgeons and two anatomist independently measured patellar morphology, patellar height and patellar alignment and evaluation lateral and medial meniscus tears. Knee MRI protocol including axial T2-weighted turbo spin echo (TR:3600, TE:87 ms; slice thickness 5 mm; gap 1.5 mm) was used.&#x0D; Results: There was a significant difference patellar height (surgery; 1.21±0.27 and conventional; 0.99±0.16), the congruence angle (surgery; -4.94±4.72 and conventional; 4.93±5.72), the lateral patellofemoral angle (surgery; -35.61±16.62 and conventional; 10.93±15.00), except for age parameter (surgery; 27.06±6.20 and conventional; 27.47±5.33) between the conventional and surgical treatment groups (p

Lateral Retinacular Release During Medial Unicompartmental Knee Arthroplasty in the Presence of Patello-Femoral Joint Arthritis Relieves Patello-Femoral Joint Pressure and Improves Associated Symptoms

BackgroundThis study evaluated the effects of concomitant lateral patellar retinacular release (LPRR) during medial unicompartmental knee arthroplasty (UKA). MethodsWe retrospectively analyzed 100 patients who had patello-femoral joint (PFJ) arthritis who underwent medial UKA with (n = 50) and without (n = 50) LPRR who had ≥2 years follow-up. Radiological parameters associated with lateral retinacular tightness, including patellar tilt angle (PTA), lateral patello-femoral angle (LPFA), and congruence angle, were measured. Functional evaluation was performed using the Knee Society Pain Score, Knee Society Function Score (KSFS), Kujala Score, and the Western Ontario McMaster Universities Osteoarthritis Index score. Intraoperative patello-femoral pressure evaluation was performed on 10 knees to evaluate the pressure changes before and after LPRR. Mann–Whitney U-tests were used for statistical analyses. ResultsDemographic data did not differ between the LPRR(+) and LPRR(−) groups. A decrease in PTA and an increase in LPFA were observed in the LPRR(+) group compared to those in the LPRR(−) group (PTA; −0.54 versus −1.74, P = .002, LPFA; 0.51 versus 2.01, P = .010). The LPRR(+) group showed significantly better KSFS and Kujala scores than the LPRR(−) group (KSFS: 90 versus 80, P = .017; Kujala score: 86 versus 79, P = .009). Intraoperative patello-femoral pressure analysis showed a 22.6% reduction in the PFJ contact pressure and an 18.7% reduction in PFJ peak pressure after LPRR. (P = .0015, P < .0001, respectively) ConclusionA LPRR during UKA may be a simple and useful adjunct procedure to relieve PFJ symptoms with concomitant PFJOA.

Radiological Measures of Patellofemoral Alignment in Healthy Small-Breed Dogs: Reference Values and Sex Variability

Background: The evaluation of vertical kneecap position within the trochlear groove is essential for understanding the anatomical changes that may lead to canine patellar luxation. Unlike other important diagnostic imaging measurements (e.g. measures of pelvic limb alignment), no data on patellofemoral congruence parameters of canine stifles (congruence angle, linear axial patellar displacement, lateral patellofemoral angle, patellar tilt angle) are reported. The aim of this study was to present metric values of these parameters in healthy dogs from small breeds from both sexes in order to use them for identification of animals with increased risk for MPL. Materials, Methods &amp; Results: The study was performed on 44 stifle joints from 22 healthy dogs of both sexes from 4 small breeds (Pinscher, Pomeranian, Chihuahua and Yorkshire terrier). Inclusion criteria were negative patellar displacement and dancing patella tests after orthopaedic examination, lack of femoral and gluteal muscles asymmetry after palpation, lack of signs of long-term proprioceptive dysfunction, normal patellar and withdrawal reflexes after neurological examination. The translation of the patella in the axial plane was evaluated by means of congruence angle and axial linear patellar displacement. The rotation of the patella in the axial plane was evaluated through measurement of lateral patellofemoral angle and patellar tilt angle. Reference ranges of parameters were analysed in agreement with the guidelines of the American College of Veterinary Pathologists for the determination of reference intervals in ve­terinary species for sample sizes of 40-120 with non-Gaussian distribution - robust me­thod, 95% confidence interval (CI) with 90 percent CI for upper and lower reference limits. All measured patellofemoral congruence angles were negative. Their reference range was from -8.06 o to -0.58o (median value -3o). The axial patellar displacement was negligible, with values ranging from 0.1 to 0.8 mm. Lateral patellofemoral angles in all dogs were open to the lateral side (positive); the computed reference interval was from 21.61o to 41.80o (median 31.5o). Patellar tilt angles ranged from 2o to 8o (median 5o). A statistically significant difference between sexes was demonstrated for angles describing the rotation of the patella in the axial plane: the lateral patellofemoral angle (P = 0.0248) and the patellar tilt angle (P = 0.0004) were greater in stifles of male dogs. Discussion: This is the first study presenting reference values of parameters describing patellofemoral alignment in healthy dogs from small breeds on tangential radiographs. The values of one of most commonly measured parameters on tangential radiographs (the lateral patellofemoral angle) in stifles of small breed dogs were higher than values in humans, supposedly due to the specific joint anatomy. The patellar tilt angle is considered as more objective and not influenced by limb rotation. For the detection of patellar misalignment, the tilt angle was reported to be almost as specific as the congruence angle but more sensitive and more accurate. It is the most specific and sensitive parameter determining the direction of patellar luxation. In male dogs, the median lateral patellofemoral angle was greater than in females (P = 0.0248). Similar tendency was shown for patellar tilt angle that was also greater in male stifles (P = 0.0004). The reported statistically significant between-sex differences in lateral patellofemoral angle and patellar tilt angle with higher values of both angles in stifles of male dogs could be attributed to the better developed femoral muscles, in particular m. vastus medialis and m. sartorius, and to differences in trochlear groove and kneecap morphology. The presented reference intervals may be useful for early detection of subjects with increased risk to medial patellar luxation. Keywords: patellofemoral congruence, small-breed dogs, reference values, sex dimorphism.

A study on the correlation between patellofemoral joint morphology and early patella malacia in young adults: quantitative analysis based on magnetic resonance.

The aim of this study was to quantitatively measure the morphology of the patellofemoral joint by magnetic resonance imaging (MRI) in young adults, to investigate the relationship between the morphology of the patellofemoral joint and chondromalacia patellae (CP), and to provide an imaging reference for early clinical diagnosis of CP. A total of 57 cases of CP and 138 cases of normal knees were retrospectively collected and assigned to the CP group and control group, respectively. The morphological parameters of the patellofemoral joint were measured systematically. The statistical software SPSS 22.0 was used in correlation analysis. Logistic regression was used for univariate analysis. A P value <0.05 was defined as statistically significant. Wiberg index, patellar depth, and the lateral angle of the patella in the CP group were significantly lower than those in the control group (P=0.043, 0.001, 0.040, respectively). The width of the medial side of the trochlea, the ratio of the internal and external articular surfaces of the trochlea, the depth of the trochlea, and the inclination angle of the lateral trochlea in the CP group were significantly lower than those in the control group (P=0.003, 0.020, 0.000, 0.040, respectively), whereas the angle of the trochlea in the CP group was significantly higher than that in the control group (P=0.010). The lateral patellofemoral angle (LPA) and lateral patellofemoral contact width in the CP group were significantly lower than those in the control group (P=0.010, 0.010, respectively). In the CP group, with gender as a covariate, there were significant statistical differences between male and female in patellar depth, lateral patellar inclination angle, lateral trochlear inclination (LTI) angle, and lateral patellar contact surface width (P<0.05), whereas in the control group, there were significant differences in Wiberg index, patellar depth, medial trochlear width, and lateral patellofemoral contact surface width between male and female gender (P<0.05). The prevalence of CP in women was significantly higher than that in men and the reduction of trochlea width and the patella depth is an important factor for the incidence of female CP. Morphological characteristics of the patellofemoral joint are significantly correlated with the occurrence of CP in young adults.

Active exercise therapy improves the recovery of knee joint function and reduction of muscle atrophy after medial patellofemoral ligament reconstruction for recurrent patellar dislocation.

Medial patellofemoral ligament (MPFL) reconstruction is an important surgical therapy for recurrent patellar dislocation. However, few studies have focused on exercise therapy after MPFL reconstruction. Therefore, the first purpose was to compare the active and traditional postoperative exercise therapies on the recovery of knee joint function and reduction of muscle atrophy after MPFL reconstruction, and the second purpose was to compare the active and traditional postoperative exercise therapies on the patellar stability after MPFL reconstruction. The cases of 31 patients with recurrent patellar dislocation treated with patella double semi-tunnel anatomical MPFL reconstruction from February 2016 and February 2019 were retrospectively reviewed. The clinical outcomes, including the patellar tilt angle (PTA), lateral patellofemoral angle (LPFA), thigh circumference reduction, Kujala score, and Lysholm score, were compared between two groups (i.e., active exercise and traditional exercise groups) preoperatively, 3 months postoperatively, 6 months postoperatively, 12 months postoperatively, and 24 months postoperatively. The Kujala score was significantly higher in the active exercise group than traditional exercise group 3 months postoperatively (80.06 vs. 74.80, P < 0.01), 6 months postoperatively (89.19 vs. 82.07, P < 0.01), 12 months postoperatively (91.43 vs. 86.60, P < 0.01), and 24 months postoperatively (92.50 vs. 90.27, P = 0.02). Similarly, there was a higher Lysholm score in the active exercise group compared with traditional exercise group 3 months postoperatively (81.25 vs. 76.53, P < 0.01), 6 months postoperatively (89.81 vs. 84.80, P < 0.01), 12 months postoperatively (93.25 vs. 88.40, P < 0.01), and 24 months postoperatively (93.69 vs. 90.67, P < 0.01). Significantly lower thigh circumference reduction was reported in the active exercise group compared with that in the traditional exercise group 3 months postoperatively (1.90 ± 0.57 vs. 2.45 ± 0.45, P < 0.01) and 6 months postoperatively (1.50 ± 0.31 vs. 1.83 ± 0.32, P < 0.01). No statistical difference was observed between the two groups in terms of PTA (P > 0.05) or LPFA postoperatively (P > 0.05). Our results suggested that active exercise therapy might benefit the early recovery of knee joint function and reduction of muscle atrophy in patients with recurrent patellar dislocation after MPFL reconstruction.

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

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

Comparison of Clinical and Radiological Results of Lateral Retinacular Release or Lateral Retinacular Lengthening Methods Combined With Medial Retinaculum Plication in Patellofemoral Instability.

Introduction In this study, we aimed to compare the clinical and radiological results of patients who underwent medial retinaculum plication (MRP) combined with lateral retinacular release (LRR) or lateral retinacular lengthening (LRL) with the diagnosis of patellofemoral (PF) instability. Methods In our study, we retrospectively analyzed 75 knees of 75 adult patients (43 females and 32 males) who underwent MRP+LRR or MRP+LRL due to PF instability without osseous pathologies. Patients were divided into two groups (MRP+LRR and MRP+LRL) according to the surgical method. The clinical and radiological results of the two groups were compared. Results MRP+LRL surgery was performed on 45 knees and MRP+LRR surgery on 30 knees. The mean age was 26.5 (18-43) years. There was no significant difference between the two groups in the change in patellar lateral shift (PLS) (p=0.429) and congruence angle (CA) (p=0.218) values. However, there was a significant difference between the two groups in the change in patellar tilt angle (PTA) (p=0.009) and lateral patellofemoral angle (LPFA) (p<0.001) values. The change in PTA and LPFA values was higher in the MRP+LRL group. There was no significant difference between the two groups in terms of pre-operative and post-operative Lysholm knee scoring scale (p=0.205, p=0.228), Kujala pain scale (p=0.393, p=0.596), and Tegner activity level scale values (p=0.121, p=0.899). Conclusions MRP+LRR or MRP+LRL provided successful results for correcting the instability in PF instability without osseous pathologies such as patella alta, tibial tubercle-trochlear groove (TT-TG) dysplasia, trochlea dysplasia, genu valgus, and tibial-femoral torsion. While PTA and LPFA values improved more with the MRP-LRL method, clinical results were similar in both methods.

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

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

The association between patellofemoral alignment and osteoarthritis in magnetic resonance imaging.

ObjectivesOsteoarthritis (OA) is the most common joint disease in the world, becoming more prevalent with increasing age, and causes a significant burden on individuals and society. So far, several factors have been identified in association with OA of the knee joint. Age is the most crucial uncontrollable risk factor for OA. There are conflicting results regarding the relationship between patellofemoral joint orientation and OA. This study aims to elucidate the relationship between patellofemoral joint alignment and OA evidence.Material and methodsA total of 277 MRIs performed at Imam Reza Hospital during the first half of 2017 were included. Patients were divided into two groups, under 50 years old and over 50 years old. Femoral sulcus angle (SA) and depth (SD), lateral patellar displacement (LPD), tibial tubercle-trochlear groove (TTTG), lateral patellofemoral angle (LPFA), and Insall-Salvati index were measured in axial and sagittal images. The morphology of the patellofemoral articular cartilage was evaluated and the grade of joint damage was determined. P-value < 0.05 was considered as significant.ResultsSignificant correlations between SA (p-value = 0.01), SD (p-value < 0.001), Insall-Salvati index (p-value < 0.001), LPD (p-value = 0.02) values and OA in patients less than 50 years old were observed. A weak correlation was observed between SD and Insall-Salvati index values with increasing grade of articular cartilage damage (r = 0.21 and r = 0.21, respectively).ConclusionsPatellofemoral joint asymmetry in the younger people was significantly associated with joint cartilage damage and premature patellofemoral joint OA. Joint misalignment by stressing the articular cartilage causes joint cartilage changes that may be congenital or due to bone injuries such as trauma and surgery.

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

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