Lateral Patellar Inclination Angle Measured via a Two-Image Technique on Axial Magnetic Resonance Imaging

Lateral patellar inclination (LPI) measures patellar tilt and is historically described on axial X-ray or a single magnetic resonance image (MRI). Given the variability in patellar height, LPI may be better represented by performing this measurement on two separate axial MRI images. We hypothesized that a two-image LPI measurement would be different from the current single-image LPI and have similar, if not superior reliability. Sixty-five patients treated for patellar instability (PI) between 2014 and 2017 were identified. Single image and two-image LPI were measured on axial MRI images. All measurements were performed by two independent observers. Reliability analysis was based on three observers' measurements of 30 randomly selected patients. Both the one image and two image LPI showed good inter-rater reliability (intraclass correlation coefficient [ICC] = 0.71 and 0.89, respectively), although the two image LPI had less variability. Both single image and two image LPI had near perfect intra-rater reliability (ICC = 0.98 and 0.98, respectively). Average single image LPI (14.6 ± 9.9 degrees) was 6.1 ± 3.4 degrees less than the average two image LPI (19.6 ± 9.4 degrees) (p = 0.037). Referencing a previously described 13.5 degrees maximum threshold, 54% of the patients had excessive patellar tilt based on single image LPI, while 73% had pathologic patellar tilt based on two image LPI. Two image LPI has similar reliability with less inter-rater variability compared with the historical single image LPI measurement. Significantly greater patellar tilt was identified with two image LPI that was found with single image LPI. A larger percentage of patients were classified as having pathologic patellar tilt based on two image LPI than single image LPI. The two image LPI provides more consistent and representative measurements of patellar tilt. Previously described threshold values for patellar tilt should be re-examined using this new measurement technique to appropriately risk stratify patients with PI and patellofemoral pain.

The Influence of Mathematical Definitions on Patellar Kinematics Representations

A correlation between patellar kinematics and anterior knee pain is widely accepted. However, there is no consensus on how they are connected or what profile of patellar kinematics would minimize anterior knee pain. Nevertheless, answering this question by merging existing studies is further complicated by the variety of ways to describe patellar kinematics. Therefore, this study describes the most frequently used conventions for defining patellar kinematics, focusing on the rotations. The similarities and differences between the Cardan sequences and angles calculated by projecting axes are analyzed. Additionally, a tool is provided to enable the conversion of kinematic data between definitions in different studies. The choice of convention has a considerable impact on the absolute values and the clinical characteristics of the patello-femoral angles. In fact, the angles that result from using different mathematical conventions to describe a given patello-femoral rotation from our analyses differ up to a Root Mean Squared Error of 111.49° for patellar flexion, 55.72° for patellar spin and 35.39° for patellar tilt. To compare clinical kinematic patello-femoral results, every dataset must follow the same convention. Furthermore, researchers should be aware of the used convention’s implications to ensure reproducibility when interpreting and comparing such data.

MPFL reconstruction and tibial tuberosity transposition in patients with patellar instability: May it troubleshots also trochlear dysplasia?

Purpose This study aimed to highlight short- and medium-term outcomes of combined medial patello-femoral ligament (MPFL) reconstruction and anterior tibial tuberosity (ATT) transposition surgery in patients with recurrent patellar instability and different degrees of trochlear dysplasia. Methods Between January 2014 and May 2019, 25 patients with patellar instability underwent a surgical procedure combining the lowering/transposition of the ATT and the MPFL reconstruction. Each patient were preoperative assessed by Kujala score, International Knee Documentation Committee (IKDC), Tegner activity level scale. The assessment of instability predisposing factors was carried out with patellar height, tibial tuberosity-trochlear groove (TT-TG) distance, trochlear dysplasia, sulcus angle, patellar tilt and MPFL injuries. Functional outcomes were evaluated with Kujala, IKDC and Tegner scores at 3, 6 and 12 months after surgery. Results The average age of the patients was 20 years (range 13–43 years). Pre- operative Caton–Deschamps index was pathological in 10 (40%). Sulcus angle was elevated in 13 patients (52%) and TT-TG distance was irregular in 17 patients (68%). Trochlear dysplasia was present in 13 patients (9 type A, 3 type B, 1 type C according to Dejour’s Classification). No re-dislocation occurred during the follow-up. There was a significant increase in the Kujala, IKDC and Lysholm scores after 3, 6 and 12 months, and the results were compared for the different follow-up times and patient’s trochlear dysplasia degree. Conclusion This prospective observational longitudinal study identified good clinical outcomes in patients who underwent MPFL reconstruction and ATT transposition for patellar instability. Finally, the different risk factors for patellar instability examined, particularly the presence of trochlear dysplasia, did not significantly influence the final functional results, which range from good to excellent without re-dislocation episodes.

Arthroscopic Medial Patellofemoral Ligament Insertion Reconstruction and Plication for Medial Patellar Retinaculum Using Suture Anchor in First Acute Patellar Dislocation

Background: The objective of this study was to evaluate the clinical results of arthroscopic medial patellofemoral ligament (MPFL) insertion reconstruction and plication for medial patellar retinaculum using suture anchor combined with lateral retinacular release in first acute patellar dislocation (APD) with MPFL insertion injury in adolescents.Methods: A prospective study was performed between January 2016 and July 2019. The series included 61 cases of adolescent patients with first APD. There were 7 males and 54 females with an average age of 15.5 years (10 to 22). All cases were treated with arthroscopic suture anchor plication for medial patellar retinaculum combined with lateral retinacular release. Congruence angle (CA), lateral patellar angle (LPA), and patellar tilt angle (PTA) are measured by CT scan between last follow-up and preoperative. In addition, the patients were evaluated with the Lysholm and Kujala scores.Results: The average follow-up time was 40.9 months (24-60 months). All 61 knees showed excellent or good results postoperatively. The Lysholm score increased significantly from 58.6±8.1 to 91.9±5.0 at the last follow-up postoperatively (P<0.001 ). The Kujala scores increased significantly from 60.4±7.3 to 88.9±4.8 at the last follow-up postoperatively (P < 0.001). CA in 0° extension position was improved significantly from 19.8±2.1° preoperatively to -6.7±1.7° at the last follow-up (P<0.001), LPA was increased from -7.4±2.2° to 5.7±1.8° (P<0.001), and PTA was increased from 23.8±2.9° to 12.3 ±2.3° (P<0.001). The postoperative mean Lysholm and Kujala scores were 91.9 (81–100) and 88.9 (79–100), respectively.Conclusions: When the first APD occurs associated with the MPFL avulsed from the patella, the presented technique could not only reattach MPFL at the patellar border but also strengthen the medial patellar retinaculum. This anatomical repair technique can significantly improve the stability of the patella and has the advantage of being less invasive by the full-arthroscopic approach.

Association of patellofemoral morphology and alignment with the radiographic severity of patellofemoral osteoarthritis

Background Risk factors for the severity of patellofemoral osteoarthritis (PFOA) are poorly understood. This research aims to evaluate the association between patellofemoral joint (PFJ) morphology and alignment with the radiographic severity of PFOA. Methods A retrospective analysis of CT scan and lateral radiograph data were acquired in patients with PFOA. The radiographic grade of PFOA and tibiofemoral osteoarthritis (TFOA), lateral and medial trochlear inclination angle, sulcus angle, and the Wiberg classification of patella morphology, the congruence angle, patellar tilt angle, and lateral patellar angles, and tibial tubercle trochlear groove distance (TT-TG) and patella height (i.e., Caton-Deschamps index) were assessed using CT scans and sagittal radiographs of the knee. All the PFJ morphology and alignment data were divided into quarters, and the relationships between each of these measures and the severity of PFOA were investigated. Results By studying 150 patients with PFOA, we found a U-shaped relationship between the Caton-Deschamps index and the severity of PFOA (P < 0.001). A lower value of sulcus angle and lateral patellar angle, a higher value of congruence angle, and type III patella were associated with more severity of lateral PFOA. Compared with the highest quarter of each measure, the adjusted odds ratios (OR) of the severity of PFOA in the lowest quarter of sulcus angle, lateral patellar angle, and congruence angle; and type I patella was 8.80 (p = 0.043), 16.51 (P < 0.001), 0.04 (P < 0.001), and 0.18 (p = 0.048) respectively. Conclusions Extreme value of patella height, a higher value of lateral patellar displacement and lateral patellar tilt, lower value of sulcus angle, and type III patella were associated with more severity of PFOA.

1053 Comparing MRI Parameters in Quantifying Patellofemoral Instability

Aim Patellofemoral instability is where various stabilising factors of the patellofemoral joint undergo pathomorphological changes. It has an incidence rate of 5.8 per 100,000 in UK and has been associated with osteoarthritis[1]. Variations in the factors that stabilise the patellofemoral joint can be observed on MRI including measurements of the trochlea in relation to the patella, the femur and soft tissue changes. This study aims to compare different measures used to detect and quantify patellofemoral instability on MRIs and to look for any significant difference in their use both in isolation and together. Method 109 MRI reports of 78 patients diagnosed with patellofemoral instability were reviewed and all quantitative and qualitative parameters reported were inputted in a data table. Quantitative elements known as the Dejour protocol included the trochlear sulcus angle, patellar tilt angle, tibial tuberosity-trochlear groove distance and the Insall-Salvati ratio. Qualitative factors involved facet changes, patellar position, and any damage to soft tissue. Results It was found that the Insall-Salvati ratio greater than 1.2 and the patellar tilt angle of greater than 11 degrees irregular ranges had the greatest incidence in the MRI reports found 77.1% and 87.6% respectively in MRIs that reported them. Conclusions There is a discrepancy between quantitative parameters in their correlation with patellofemoral instability for the MRI reports observed. [1]: Ye Q, Yu T, Wu Y, Ding X, Gong X. Patellar instability: the reliability of magnetic resonance imaging measurement parameters. BMC Musculoskeletal Disorders. 2019;20(1).

Patellar instability MRI measurements are associated with knee joint degeneration after reconstruction of the medial patellofemoral ligament

Objective To qualitatively and quantitatively evaluate the 2-year magnetic resonance imaging (MRI) outcome after MPFL reconstruction at the knee and to assess MRI-based risk factors that predispose for inferior clinical and imaging outcomes. Materials and methods A total of 31 patients with MPFL reconstruction were included (22 ± 6 years, 10 female). MRI was performed preoperatively in 21/31 patients. Two-year follow-up MRI included quantitative cartilage T2 and T1rho relaxation time measurements at the ipsilateral and contralateral knee. T2relative was calculated as T2patellofemoral/T2femorotibial. Morphological evaluation was conducted via WORMS scores. Patellar instability parameters and clinical scores were obtained. Statistical analyses included descriptive statistics, t-tests, multivariate regression models, and correlation analyses. Results Two years after MPFL reconstruction, all patellae were clinically stable. Mean total WORMS scores improved significantly from baseline to follow-up (mean difference ± SEM, − 4.0 ± 1.3; P = 0.005). As compared to patients with no worsening of WORMS subscores over time (n = 5), patients with worsening of any WORMS subscore (n = 16) had lower trochlear depth, lower facetal ratio, higher tibial-tuberosity to trochlear groove (TTTG) distance, and higher postoperative lateral patellar tilt (P < 0.05). T2relative was higher at the ipsilateral knee (P = 0.010). T2relative was associated with preoperatively higher patellar tilt (P = 0.021) and higher TTTG distance (P = 0.034). TTTG distance, global T2 values, and WORMS progression correlated with clinical outcomes (P < 0.05). Conclusion MPFL reconstruction is an optimal treatment strategy to restore patellar stability. Still, progressive knee joint degeneration and patellofemoral cartilage matrix degeneration may be observed, with patellar instability MRI parameters representing particular risk factors.

Association of Patellofemoral Morphology and Alignment With the Radiographic Severity of Patellofemoral Osteoarthritis

Background: Risk factors for the progression of patellofemoral osteoarthritis (PFOA) are poorly understood. This research aims to evaluate the association between patellofemoral joint (PFJ) morphology and alignment with the radiographic severity of PFOA.Methods: A retrospective analysis of CT scan and lateral radiograph data were acquired in patients with PFOA. The radiographic severity of PFOA and tibiofemoral OA (TFOA), lateral and medial trochlear inclination angle, sulcus angle and the Wiberg classification of patella morphology, the congruence angle, patellar tilt angle, and lateral patellar angles, and tibial tubercle trochlear groove distance (TT-TG), patella height (i.e., Caton-Deschamps index) were assessed using CT scans and sagittal radiographs of the knee. All the PFJ morphology and alignment data were divided into quarters and the relationship between each measure and the severity of PFOA was investigated.Results: By studying 150 patients with PFOA, we found a U-shaped relationship between the Caton-Deschamps index and the severity of PFOA (P <0.001). A lower value of sulcus angle and lateral patellar angle, a higher value of congruence angle, and type III patella were associated with more severity of lateral PFOA. Compared with the highest quarter of each measure, the adjusted odds ratios (OR) of the severity of PFOA in the lowest quarter of sulcus angle, lateral patellar angle, and congruence angle, and type I patella was 8.80 (p=0.043), 16.51 (P <0.001), 0.04(P <0.001), and 0.18 (p=0.048) respectively.Conclusions: Extreme value of patella height, a higher value of lateral patellar displacement and lateral patellar tilt, lower value of sulcus angle, and type III patella were associated with more severity of PFOA.

Does patellar tilt affect the outcome of total knee arthroplasty? a retrospective study

<p><strong>Background</strong>: Patellofemoral joint management during total knee replacement remains a controversial topic among knee surgeons. The purpose of this study is to evaluate the influence of resurfaced patellar component tilt on the functional outcome of total knee arthroplasty.</p><p><strong>Methods</strong>: This is a retrospective study reviewing all the patients who underwent total knee arthroplasty in our institution, operated by a single surgeon using a single implant design.</p><p><strong>Results:</strong> A total of 48 patients and 82 knees were enrolled into this study. Patients were evaluated by Oxford knee score, knee society score, Melbourne patellar score, anteroposterior, lateral, and Merchant’s view radiographs. The patellar tilt was divided into three grades according the measurement obtained from knee radiographs.</p><p><strong>Conclusions: </strong>A higher degree of patella tilt (more than 10 degree) is associated with poor outcome following total knee arthroplasty. Melbourne patella score is more sensitive than knee society score and Oxford score in assessing the effect of patella tilt on the outcome of total knee arthroplasty.</p>