The Impact of Adding a Tibial Tubercle Osteotomy to Medial Patellofemoral Ligament Reconstruction in the Treatment of Patellar Instability.

BACKGROUND: An isolated medial patellofemoral ligament (MPFL) reconstruction (MPFLR) has been demonstrated to be an effective treatment option in the prevention of patellar instability, but there is growing support for performing a tibial tubercle osteotomy (TTO) in patients with an elevated tibial tubercle-trochlear groove distance. The purpose of this study was to evaluate the impact of adding a TTO to MPFLR on patient reported outcomes. METHODS: A retrospective review of patients who underwent MPFLR with or without TTO with a minimum of 12-month follow-up was performed. Patients in both groups were matched based on age, sex, and follow-up time. Recurrent instability (including re-dislocation and subluxation), visual analog scale (VAS) for pain score, Kujala score, and satisfaction were evaluated. RESULTS: There were 59 patients who underwent MPFLR with concomitant TTO performed at our institution and met our inclusion and exclusion criteria. These patients were then matched to patients undergoing isolated MPFLR based on demographics and follow-up time. The mean age was 25.0, 76.3% were female, and the mean follow-up time was 49 months. There was a significant difference in mean tibial tubercle-trochlear groove distance (19.8 ± 3.9 vs. 14.1 ± 2.8) between groups. There was no significant difference in VAS (1.48 ± 2.0 vs. 1.49 ± 2.1, p = 0.972), satisfaction (86.1% ± 24.2% vs. 81.2% ± 27.9, p = 0.311), or revision surgeries (10.2% vs. 10.2%) between groups. CONCLUSION: There was a low complication rate, excellent patient reported outcomes, and a low rate of recurrent patellar instability following TTO and MPFLR with allograft.

Patellar articular overlap is better associated with patellar alignment during weight-bearing than traditional measures of patellar height.

BACKGROUND: A consequence of a high riding patella is reduced osseous stability and malalignment of the patella (i.e., lateral patellar tilt and displacement). Although quantification of patellar height is a routine part of the radiographic examination of the patellofemoral joint, it is not clear which measure of patellar height is best associated with patella alignment. HYPOTHESIS/PURPOSE: To determine if patellar articular overlap (PAO) is better associated with lateral patellar tilt and lateral patellar displacement compared to traditional measures of patellar height. STUDY DESIGN: Cross-sectional. METHODS: Magnetic resonance images were obtained from 50 female participants (21 with patellofemoral pain and 29 healthy controls) under loaded conditions (25-35% bodyweight) at 15-20 degrees of knee flexion. Measurements of lateral patellar tilt and displacement as well as the PAO, Insall-Salvati ratio (ISV), Caton Deschamps-index (CD-index), or the Blacburn Peel-index (BP-index) were obtained from sagittal and axial plane images. RESULTS: The PAO was found to significantly correlated with lateral patellar tilt (r = -0.77, p < 0.001). In contrast, the ISV, CD-index, or the BP-index were not found to be associated with lateral patellar tilt (r = 0.13, p = 0.34; r = -0.14, p = 0.33; r = -0.08, p = 0.56, respectively). Both the PAO and ISV were found to be significantly correlated with lateral patellar displacement (r = -0.52, p < 0.001; r = 0.43, p = 0.002, respectively). Conversely, the CD-index and BP-index were not found to be associated with lateral patellar displacement (r = 0.03 p = 0.83; r = 0.05 p = 0.74, respectively). CONCLUSION: Of the measures of patellar height evaluated, the PAO was found to provide the greatest association with lateral patellar tilt and displacement.

Trochlea Dysplasia as the Major Anatomic Risk Factors for Patellofemoral Joint Instability: An Infographic as a Visual Learning Tool.

Patellofemoral instability (PFI) is a common condition in children and adolescents, ranging from mild discomfort and mal-tracking to lateral patellar dislocation [1]. A number of anatomical risk factors have been described in the literature, such as trochlear dysplasia, patella alta, excessive tibial tuberosity to trochlear groove (TT-TG) distance, patellar tilt and soft tissue alterations [2]. Among them, TD has been identified as the main anatomical risk factor with the strongest association with PFI [1, 2]. In the study by Dejour et al. [2] radiographically observed TD was identified in 96% of patients with a history of patellofemoral dislocation [1, 2]. Patients with Dejour Type D dysplasia are characterized by a prominent and convex lateral facet with a vertical connection to a hypoplastic medial facet (Figure 1), which provides inadequate tracking of the patella in the trochlea during flexion leading to patella subluxation [2]. Non-operative treatment of lateral patellar dislocation presents a rate of re-dislocation up to 70% within 24 months of the first episode [3]. Sulcus deepening trochleoplasty is indicated for Type B and D dysplasia, in order to improve patella tracking, reduce the rate of re-dislocation and achieve good functional outcomes [2, 4]. Trochlea dysplasia is defined as a shallow or flattened groove with decreased resistance to lateral patellar translation. TD can be assessed on computed tomography (CT) and magnetic resonance imaging (MRI) with the use of overlapping axial images and are able to show perfectly the global shape of the femoral trochlea [2]. The thresholds for identifying trochlear dysplasia are established based on the sulcus angle ≥ 145°, medial/lateral trochlea facet asymmetry < 40%, trochlear depth < 3 mm and lateral trochlear inclination ≤ 11° and therefore it can be used in young adolescents [4, 5]. A deep knowledge of anatomic variations and abnormalities of the patellofemoral joint, which may predispose to PFI, is crucial in order to choose the appropriate treatment for each patient.

Initial graft tension affects patellofemoral alignment during anatomical anterior cruciate ligament reconstruction.

BACKGROUND: This study aimed to evaluate the effects of the differences in initial graft tension (IGT) on patellofemoral alignment in the axial plane after anatomical anterior cruciate ligament reconstruction (ACLR). METHODS: A total of 102 patients who underwent primary anatomical ACLR using a bone-patellar-tendon-bone autograft were enrolled. The grafts were fixed with maximum manual force at full knee extension (higher graft tension; H group) and with 5-20 N at 20° knee flexion which corresponded to 80 N at full knee extension (lower graft tension; L group) pulls in 39 and 63 patients, respectively. All patients underwent computed tomography of the bilateral knee joints with knee extension 1 week postoperatively. The patellofemoral alignment (sulcus angle, lateral trochlear inclination angle, lateral patellofemoral angle (LPFA), condylar-patellar angle (CPA) (lateral facet, patellar tilt), congruence angle, and bisect offset index) on the axial computed tomography images were evaluated, and the side-to-side differences (SSDs) between the injured knee and the contralateral knee were calculated. RESULTS: Congruence angle SSD was remarkably higher in the H group than in the L group (3.8 ± 4.7 vs. 0.4 ± 5.7, P < 0.01). Furthermore, the LPFA SSD and CPA (patellar tilt) SSD were significantly higher in the H group (-1.8 ± 3.1 vs. -0.4 ± 2.7, P = 0.04 and -1.6 ± 2.8 vs. -0.3 ± 2.7, P = 0.04, respectively). CONCLUSIONS: A higher IGT during anatomical ACLR induces a lateral shift and tilt of the patella against the femur immediately after surgery compared with the lower IGT.

Physiopathology of patello-femoral osteoarthritis: current concepts.

Patellofemoral osteoarthritis (PFOA) is the result of degeneration and loss of articular cartilage of the patella and trochlea, and is a common cause of anterior knee pain. PFOA is triggered by insufficient adaptation to overload of the articular cartilage of the PF joint created by abnormal biomechanics. It is important to understand the pathophysiology and natural history to make the diagnosis and to plan treatment. Innate factors including malalignment, patellar instability, kinematic disorders, and acquired factors like trauma, obesity, and endocrine diseases have been found to be causes of PFOA. Genetic predisposition is also described as a contributing cause but without much scientific evidence. The diagnosis will be based on clinical manifestations, such as anterior knee pain aggravated by overloading activities, identification of risk factors, and exclusion of referred pain from other pathologies, followed by a systematic and structured physical examination. Imaging will be useful for assessing the presence of early osteoarthritis in the other compartments, for classification of the PFOA, and to identify features to establish an adequate treatment. This paper discusses varying management options for different causes of patellofemoral disease and explains the complexity of the PF joint and its often poorly understood biomechanics.

Is kinesiophobia associated with functional outcome measures in patients following medial patellofemoral ligament reconstruction?

BACKGROUND: This study aimed to investigate the potential relationship between kinesiophobia and functional outcomes in patients following medial patellofemoral ligament reconstruction (MPFLr). METHODS: Twenty-one patients (six males, 15 females) who underwent MPFLr between 2016 and 2020, (23.57 ± 9.49 years old) with a mean follow up period of 52.33 ± 24.82 months were included in the study. Following an assessment of patellar stability and alignment, kinesiophobia levels, function and balance were measured. The kinesiophobia was measured using the Tampa Scale of Kinesiophobia, while functional outcomes were assessed with the single-leg hop test, Y-Balance test and single-leg sway index. The self-reported function was measured by Kujala patellofemoral score and Lysholm knee score. RESULTS: The patients exhibited kinesiophobia scores of 43.10 ± 6.90. A negative correlation existed between kinesiophobia and both the Kujala scores (r = -0.75, P < 0.001) and the Lysholm scores (r = -0.79, P < 0.001). Moderate negative correlations were observed between kinesiophobia and the single-leg hop distance (r = -0.64, P < 0.01), as well as in Y-Balance test anterior reach distance (r = -0.51, P < 0.01) and posterolateral reach distance (r = -0.55, P < 0.01). Additionally, a low negative correlation was noted between kinesiophobia and Y-Balance test posteromedial reach distances (r = -0.43, P = 0.05), as well as the total sway index (r = -0.46, P = 0.04). CONCLUSIONS: A high level of kinesiophobia was strongly correlated with self-reported functional scores and moderately correlated with measured functional outcomes. The findings underscore a notable prevalence of kinesiophobia following biomechanically successful MPFLr. Investigating the impact of kinesiophobia on outcomes after MPFLr may provide a better understanding of patient recovery.

No significant change of tibiofemoral rotation after femoral rotational osteotomy in patients with patellofemoral instability.

PURPOSE: An increased value of tibiofemoral rotation is frequently observed in patients with patellofemoral instability or maltracking. Nevertheless, the appropriate approach for addressing this parameter remains unclear so far. One potential approach for correcting tibiofemoral rotation is femoral rotational osteotomy. We hypothesized that femoral rotational osteotomy affects tibiofemoral rotation. METHODS: All patients who underwent femoral rotational osteotomy between January 2018 and May 2022 were included in this study. Pre- and postoperative tibiofemoral rotation and the degree of femoral rotation were measured using two-dimensional (2D) and three-dimensional (3D) measurements. The effect of femoral rotation on tibiofemoral rotation was assessed. RESULTS: Forty knees (18 right and 22 left) of 36 patients (28 females and 8 males) were included. Mean preoperative femoral torsion was 32.1 ± 10.1° in 2D and 30.8 ± 10.1° in 3D. Femoral rotation was performed by -14.1 ± 8.3° using 2D measurements and -15.0 ± 8.0° using 3D measurements. Tibiofemoral rotation changed from 9.9 ± 6.2° to 9.7 ± 6.0° (p = n.s.) in 2D, and from 10.2 ± 5.5° to 9.4 ± 5.4° (p = n.s.) in 3D. CONCLUSION: Tibiofemoral rotation showed no significant changes after femoral rotational osteotomy. Hence, femoral rotational osteotomy cannot be used to correct tibiofemoral rotation in addition to correcting the femoral version. Other surgical techniques need to be evaluated if correction of tibiofemoral rotation is required. LEVEL OF EVIDENCE: Level III.

Superior Pain Reduction with Anteromedialization Tibial Tubercle Osteotomy Versus Non-Operative Management for Patellofemoral Osteoarthritis.

PURPOSE: The purpose of this study was to compare the clinical outcomes of patients with patellofemoral osteoar-thritis (PFOA) treated non-operatively with those treated operatively with an unloading anteromedialization tibial tubercle osteotomy (TTO). METHODS: A retrospective chart review was performed to identify patients with isolated PFOA who were either managed non-operatively or surgically with a TTO and who had a minimum follow-up of 2 years. Patients were surveyed with the visual analog scale (VAS) for pain, Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR), Anterior Knee Pain scale (Kujala), and Tegner Activity scale. Statistical analysis included two-sample t-testing, one-way ANOVA, and bivariate analysis. RESULTS: The clinical outcomes of 49 non-operatively managed patients (mean age: 52.7 ± 11.3 years; mean follow-up: 1.7 ± 1.0 years) and 35 operatively managed patients (mean age: 31.8 ± 9.4 years; mean follow-up: 3.5 ± 1.7 years) were assessed. The mean VAS improved sig-nificantly in both groups [6.12 to 4.22 (non-operative), p < 0.0001; 6.94 to 2.45 (TTO); p < 0.0001], with operatively treated patients having significantly lower postoperative pain than non-operatively managed patients at the time of final follow-up [2.45 (TTO) vs. 4.22 (non-operative), p < 0.001]. The mean KOOS-JR score was significantly greater in the operative group at time of final follow-up [78.7 ± 11.6 (TTO) vs. 71.7 ± 17.8 (non-operative), p = 0.035]. There was no significant difference in Kujala or Tegner scores between the treatment groups. Additionally, there was no sig-nificant relationship between the number of intra-articular injections, duration of NSAID use, and number of physical therapy sessions on clinical outcomes in the non-operatively treated group (p > 0.05). CONCLUSIONS: An unloading anteromedialization TTO provides significantly better pain relief and restoration of function compared to non-operative management in the treatment of symptomatic PFOA.

Prediction of specific structural damage to the knee joint using qualitative isokinetic analysis.

BACKGROUND: An isokinetic moment curve (IMC) pattern-damaged structure prediction model may be of considerable value in assisting the diagnosis of knee injuries in clinical scenarios. This study aimed to explore the association between irregular IMC patterns and specific structural damages in the knee, including anterior cruciate ligament (ACL) rupture, meniscus (MS) injury, and patellofemoral joint (PFJ) lesions, and to develop an IMC pattern-damaged structure prediction model. METHODS: A total of 94 subjects were enrolled in this study and underwent isokinetic testing of the knee joint (5 consecutive flexion-extension movements within the range of motion of 90°-10°, 60°/s). Qualitative analysis of the IMCs for all subjects was completed by two blinded examiners. A multinomial logistic regression analysis was used to investigate whether a specific abnormal curve pattern was associated with specific knee structural injuries and to test the predictive effectiveness of IMC patterns for specific structural damage in the knee. RESULTS: The results of the multinomial logistic regression revealed a significant association between the irregular IMC patterns of the knee extensors and specific structural damages ("Valley" - ACL, PFJ, and ACL + MS, "Drop" - ACL, and ACL + MS, "Shaking" - ACL, MS, PFJ, and ACL + MS). The accuracy and Macro-averaged F1 score of the predicting model were 56.1% and 0.426, respectively. CONCLUSION: The associations between irregular IMC patterns and specific knee structural injuries were identified. However, the accuracy and Macro-averaged F1 score of the established predictive model indicated its relatively low predictive efficacy. For the development of a more accurate predictive model, it may be essential to incorporate angle-specific and/or speed-specific analyses of qualitative and quantitative data in isokinetic testing. Furthermore, the utilization of artificial intelligence image recognition technology may prove beneficial for analyzing large datasets in the future.

Relationship between exacerbating patellofemoral pain and dynamic knee valgus in females with patellofemoral pain after a patellofemoral joint loading protocol: A cross-sectional.

OBJECTIVE: The aim of the present study is to 1) the effect of exacerbating patellofemoral pain (PFP) on dynamic knee valgus (DKV) 2) the relationship between exacerbating PFP and DKV in females with patellofemoral pain. DESIGN: Cross-sectional study. METHODS: Sixty women with PFP were recruited from the orthopedic clinics. We evaluated pain intensity and DKV in two conditions without (condition 1) and with (condition 2) PFJ loading during the single-leg squat (SLS) task. The MANOVA test was used to compare pain intensity and DKV angle between the two conditions. Furthermore, the Pearson correlation was used to examine the correlation between pain intensity with DKV angle. RESULTS: The MANOVA analysis showed that pain intensity (P < 0.000, η2 = 0.623) and DKV angle (P < 0.000, η2 = 0.544) with a medium effect size significantly increased after PFJ loading. Furthermore, an excellent positive correlation was observed between an increase in pain intensity and DKV angle (P < 0.000, r = 0.840). CONCLUSION: It seems that after the PFJ loading protocol and the subsequent pain exacerbation, the neuromuscular biomechanics of the lower limb are deficits. As a result, the stabilizing muscles activation decreases and increases the lower limb movement in the frontal plane.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats.

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Different gait pattern in adolescence with patellofemoral instability.

BACKGROUND: Patellofemoral instability influences the gait pattern and activity level in adolescents. However, gait biomechanics to cope with recurrent patella instability and its relation to radiological findings has hardly been studied. METHODS: We retrospectively analyzed kinematic and kinetic gait analysis data, magnetic resonance images and X-ray of 32 adolescents with unilateral recurrent patellofemoral instability aged 12 to 18 years. Subjects were assigned to 3 groups based on their sagittal knee moment in the loading response and mid stance phase. Kinematic and kinetic differences among the groups were analyzed using a one-way ANOVA. A multinomial logistic regression model provided a further analysis of the relationship between gait biomechanics and MRI as well as X-ray parameters. FINDINGS: All three groups showed different characteristics of the knee kinematics during loading response and single stance: while the patella-norm-loading group showed a slightly reduced knee flexion (p ã€ˆ0,01), the patella-unloading group kept the knee nearly extended (p < 0,01) and patella-overloading group showed an increased knee flexion (p = 0,01) compared to the other groups. In single stance the patella-overloading group maintained increased knee flexion (p < 0,01) compared to patella-unloading group and patella-norm-loading group. None of the radiological parameters proved to be related to gait patterns. INTERPRETATION: The paper describes different gait coping strategies and their clinical relevance in subjects with patellofemoral instability. However, we did not find any relation of gait biomechanics to skeletal morphology.

The ability to kneel before and after total knee arthroplasty : the role of the pattern of osteoarthritis and the position of the femoral component.

AIMS: The aims of this study were to investigate the ability to kneel after total knee arthroplasty (TKA) without patellar resurfacing, and its effect on patient-reported outcome measures (PROMs). Secondary aims included identifying which kneeling positions were most important to patients, and the influence of radiological parameters on the ability to kneel before and after TKA. METHODS: This prospective longitudinal study involved 209 patients who underwent single radius cruciate-retaining TKA without patellar resurfacing. Preoperative EuroQol five-dimension questionnaire (EQ-5D), Oxford Knee Score (OKS), and the ability to achieve four kneeling positions were assessed including a single leg kneel, a double leg kneel, a high-flexion kneel, and a praying position. The severity of radiological osteoarthritis (OA) was graded and the pattern of OA was recorded intraoperatively. The flexion of the femoral component, posterior condylar offset, and anterior femoral offset were measured radiologically. At two to four years postoperatively, 151 patients with a mean age of 70.0 years (SD 9.44) were included. Their mean BMI was 30.4 kg/m2 (SD 5.36) and 60 were male (40%). They completed EQ-5D, OKS, and Kujala scores, assessments of the ability to kneel, and a visual analogue scale for anterior knee pain and satisfaction. RESULTS: The ability to kneel in the four positions improved in between 29 (19%) and 53 patients (35%) after TKA, but declined in between 35 (23%) and 46 patients (30%). Single-leg kneeling was most important to patients. After TKA, 62 patients (41%) were unable to achieve a single-leg kneel, 76 (50%) were unable to achieve a double-leg kneel, 102 (68%) were unable to achieve a high-flexion kneel and 61 (40%) were unable to achieve a praying position. Posterolateral cartilage loss significantly affected preoperative deep flexion kneeling (p = 0.019). A postoperative inability to kneel was significantly associated with worse OKS, Kujala scores, and satisfaction (p < 0.05). Multivariable regression analysis identified significant independent associations with the ability to kneel after TKA (p < 0.05): better preoperative EQ-5D and flexion of the femoral component for single-leg kneeling; the ability to achieve it preoperatively and flexion of the femoral component for double-leg kneeling; male sex for high-flexion kneeling; and the ability to achieve it preoperatively, anterior femoral offset, and patellar cartilage loss for the praying position. CONCLUSION: The ability to kneel was important to patients and significantly influenced knee-specific PROMs, but was poorly restored by TKA with equal chances of improvement or decline. Cite this article: Bone Joint J 2021;103-B(9):1514-1525.

Automated detection of patellofemoral osteoarthritis from knee lateral view radiographs using deep learning: data from the Multicenter Osteoarthritis Study (MOST).

OBJECTIVE: To assess the ability of imaging-based deep learning to detect radiographic patellofemoral osteoarthritis (PFOA) from knee lateral view radiographs. DESIGN: Knee lateral view radiographs were extracted from The Multicenter Osteoarthritis Study (MOST) public use datasets (n = 18,436 knees). Patellar region-of-interest (ROI) was first automatically detected, and subsequently, end-to-end deep convolutional neural networks (CNNs) were trained and validated to detect the status of patellofemoral OA. Patellar ROI was detected using deep-learning-based object detection method. Atlas-guided visual assessment of PFOA status by expert readers provided in the MOST public use datasets was used as a classification outcome for the models. Performance of classification models was assessed using the area under the receiver operating characteristic curve (ROC AUC) and the average precision (AP) obtained from the Precision-Recall (PR) curve in the stratified 5-fold cross validation setting. RESULTS: Of the 18,436 knees, 3,425 (19%) had PFOA. AUC and AP for the reference model including age, sex, body mass index (BMI), the total Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and tibiofemoral Kellgren-Lawrence (KL) grade to detect PFOA were 0.806 and 0.478, respectively. The CNN model that used only image data significantly improved the classifier performance (ROC AUC = 0.958, AP = 0.862). CONCLUSION: We present the first machine learning based automatic PFOA detection method. Furthermore, our deep learning based model trained on patella region from knee lateral view radiographs performs better at detecting PFOA than models based on patient characteristics and clinical assessments.

Isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability: analysis of outcomes and risk factors.

BACKGROUND: The medial patellofemoral ligament (MPFL) is always damaged after patellar dislocation. In selected patients, MPFL reconstruction is necessary to restore a correct patellar tracking. Despite the large number of different techniques reported to reconstruct the MPFL, there is no consensus concerning the optimal procedure, and debates is still ongoing. The present study analysed the results after isolated MPFL reconstruction in patients with patellofemoral instability. Furthermore, a subgroup analysis of patients presenting pathoanatomical risk factors was made. METHODS: In November 2020, the main electronic databases were accessed. All articles reporting the results of primary isolated MPFL reconstruction for recurrent patellofemoral instability were considered for inclusion. Only articles reporting a minimum 12-month follow-up were eligible. RESULTS: Data from a total of 1777 knees were collected. The mean age of the patients involved was 22.8 ± 3.4 years. The mean follow-up was 40.7 ± 25.8 months. Overall, the range of motion (+ 27.74; P < 0.0001) and all the other scores of interests improved at last follow-up: Kujala (+ 12.76; P = 0.0003), Lysholm (+ 15.69; P < 0.0001), Tegner score (+ 2.86; P = 0.006). Seventy-three of 1780 patients (4.1%) showed a positive apprehension test. Thirty of 1765 patients (1.7%) experienced re-dislocations, while 56 of 1778 patients (3.2%) showed persisting joint instability. Twenty-five of 1786 patients (1.4%) underwent revision surgeries. CONCLUSION: Isolated MPFL reconstruction for recurrent patellofemoral instability provides reliable surgical outcomes. Patients with pathoanatomical predisposing factors reported worse surgical outcomes.

Development of a Multivariable Model Based on Individual Risk Factors for Recurrent Lateral Patellar Dislocation.

BACKGROUND: Nonoperative treatment after first-time patellar dislocation is the standard of care. There is evidence that certain patients may be at high risk for recurrent instability. The aim of this study was to develop a multivariable model to guide management of patients based on their individual risk of recurrent dislocation. METHODS: A multivariable model was developed using 291 patients from 4 institutions to identify which patients were at higher risk for recurrent patellar dislocation within 2 years. This model was informed by a univariable logistic regression model developed to test factors based on the patient's history, physical examination, and imaging. The discriminatory ability of the model to classify who will or will not have a recurrent dislocation was measured using the area under the receiver operating characteristic curve (AUC). RESULTS: Age, a history of a contralateral patellar dislocation, skeletal immaturity, lateral patellar tilt, tibial tubercle-trochlear groove (TT-TG) distance, Insall-Salvati ratio, and trochlear dysplasia were the most important factors for recurrent patellar dislocation. Sex, mechanism of injury, Caton-Deschamps ratio, sulcus angle, inclination angle, and facet ratio were not factors for recurrent dislocation. The overall AUC for the multivariable model was 71% (95% confidence interval [CI]: 64.7% to 76.6%). CONCLUSIONS: Optimizing the management of lateral patellar dislocation will improve short-term disability from the dislocation and reduce the long-term risk of patellofemoral arthritis from repeated chondral injury. This multivariable model can identify patients who are at high risk for recurrent dislocation and would be good candidates for early operative treatment. Further validation of this model in a prospective cohort of patients will inform whether it can be used to determine the optimal treatment plan for patients presenting with an initial patellar dislocation. Until validation of the model is done with new patients, it should not be used in clinical practice. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Weight bearing versus conventional CT for the measurement of patellar alignment and stability in patients after surgical treatment for patellar recurrent dislocation.

PURPOSE: To compare weight-bearing cone-beam computer tomography (CBCT) and conventional computer tomography (CT)-based measurements of patellofemoral alignment and stability in patients surgically treated for recurrent patellar dislocation. These scans implied respectively single-leg up-right posture, the knee flexed, and lower limb muscles activation, versus supine position with the knee extended. METHODS: A total of 17 patients (11 males/6 females) after surgical reconstruction with fascia lata allograft for recurrent patellofemoral dislocation were analyzed at 60-month follow-up. Tilt and congruence angles and tibial tuberosity-trochlear groove (TT-TG) offset were measured on images obtained from CBCT and conventional CT scans by three independent and expert radiologists. Paired t tests were performed to compare measurements obtained from the two scans. Inter-rater reliability was assessed using a two-way mixed-effects model intra-class correlation coefficient (ICC). RESULTS: Only TT-TG offset was found significantly smaller (p < 0.001) in CBCT (mean 9.9 ± 5.3 mm) than in conventional CT (mean 15.9 ± 4.9 mm) scans. ICC for tilt and congruence angles and for TT-TG offset ranged between 0.80-0.94 with measurements in CBCT scans, between 0.52 and0.78 in conventional CT. CONCLUSION: In patients surgically treated for recurrent patellar dislocation, TT-TG offset was found overestimated with conventional CT. All measurements of patellofemoral stability and alignment were found more consistent when obtained with weight-bearing CBCT compared to conventional CT.

Relationship between patellofemoral finite helical axis and femoral trans-epicondylar axis using a static magnetic resonance-based methodology.

BACKGROUND: To manage patellofemoral joint disorders, a complete understanding of the in vivo patellofemoral kinematics is critical. However, as one of the parameters of joint kinematics, the location and orientation of the patellofemoral finite helical axis (FHA) remains unclear. The purpose of this study is to quantify the location and orientation of the patellar FHA, both in vivo and non-invasively at various flexion angles, and evaluate the relationship of the FHA and the trans-epicondylar axis (TEA). METHODS: The magnetic resonance (MR) images of 18 unilateral knees were collected at full extension, 30°, 60°, 90°, and maximum angle of knee flexion. Three-dimensional models of the knee joint at different flexion angles were created using the MR images, and then used to calculate the patellar tracking and FHA with a spline interpolation algorithm. By using a coordinate system based on the TEA, the FHA tracking was quantified. Six parameters concerning the location and orientation of the patellar FHA were analysed. RESULTS: The average patellar FHA drew an L-shaped tracking on the midsagittal plane moving from the posteroinferior to the anterosuperior side of the TEA with knee flexion. Before 90° flexion, the patellar rotational radius decreased slightly, with an average value of 5.65 ± 1.09 cm. During 20° to 90° knee flexion, the average angle between the patellar FHA and the TEA was approximately 10° and that between the FHA and the coronal plane was maintained at about 0°, while that between the FHA and the level plane fluctuated between - 10° and 10°. CONCLUSIONS: This study quantitatively reported the continuous location and direction of the patellar FHA during knee flexion. The patellar FHA was close to but not coincident with the femoral TEA both in location and orientation, and the patellar rotational radius decreased slightly with knee flexion. These findings could provide a clear direction for further studies on the difference in patellofemoral FHA among various types of patellofemoral disorders, and provide a foundation for the application of FHA in surgical evaluation, preoperative planning and prosthesis design, thereby assisting in the diagnosis and treatment of patellofemoral disorders.

Single-tunnel and double-tunnel medial patellofemoral ligament reconstructions have similar clinical, radiological and functional results.

PURPOSE: The aim of the present study was to evaluate the clinical, radiological and functional results of patients underwent single-tunnel (ST) and double-tunnel (DT) medial patellofemoral ligament(MPFL) reconstructions with hamstring autograft following recurrent patella dislocation prospectively in a single institution. METHODS: From 2013 to 2017, 80 patients with symptomatic recurrent patellar dislocation or instability were randomly divided into 2 groups for MPFL reconstruction with ST technique or DT technique and evaluated prospectively. In the ST group, there were 20 male and 20 female with a median follow-up of 46.5 months (range 24-74). The median age was 15 years (range 10-28). In the DT group, there were 18 male and 22 female with a median follow-up of 40 months (range 24-74). The median age was 19 years (range 14-29). Clinical scores (Kujala score, Lysholm score, Tegner score and IKDC score) and radiological measurements (congruence angle and patellar tilt angle) of the patients were evaluated preoperatively and at postoperative 24th month. Isokinetic dynamometric tests were performed at postoperative 24th month and the difference between the operated leg and the non-operated leg was found as a percentage deficit. RESULTS: There were no postoperative complications, redislocation or subluxation in any patient. Kujala, Lysholm, Tegner and IKDC scores were better and statistically significant postoperatively in both groups (p < 0.05). However, there was no statistically significant difference between the groups (n.s.). The congruence angle and patellar tilt angle were found to be returned to normal values postoperatively, but there was no statistically significant difference between the groups (n.s.). There was no statistically significant difference between the two groups in isokinetic dynamometric tests performed as 60° flexion, 60° extension, 180° flexion and 180° extension (n.s.). CONCLUSION: The present study is the first that compared the clinical, radiological and functional results of the ST and DT techniques to date. Regardless of the number of the tunnels, similar results were obtained in ST and DT reconstruction using transpatellar tunnel technique. LEVEL OF EVIDENCE: Level I.

A Word of Caution for Future Studies in Patellofemoral Pain: A Systematic Review With Meta-analysis.

BACKGROUND: Patellar maltracking is widely accepted as an underlying mechanism of patellofemoral pain. However, methodological differences in the literature hinder our ability to generate a universal quantitative definition of pathological patellofemoral kinematics (patellar maltracking) in patellofemoral pain, leaving us unable to determine the cause of patellofemoral pain. PURPOSE: To systematically review the literature to provide evidence regarding the influence of confounding variables on patellofemoral kinematics. STUDY DESIGN: Systematic review and random effects meta-analysis of control-case studies. METHODS: A literature search of case-control studies that evaluated patellofemoral kinematics at or near full extension and were written in English was conducted using Embase, PubMed, Scopus, and Web of Science up to September 2019. Cases were defined as patients with patellofemoral pain. Studies were eliminated if they lacked quantitative findings; had a primary aim to assess therapy efficacy; or included participants with osteoarthritis and/or previous trauma, pathology, or surgery. A quality assessment checklist was employed to evaluate each study. Meta-analyses were conducted to determine the influence of confounding variables on measures of patellofemoral kinematics. RESULTS: Forty studies met the selection criteria, with quality scores ranging from 13% to 81%. Patient characteristics, data acquisition, and measurement methods were the primary sources of methodological variability. Active quadriceps significantly increased lateral shift (standardized mean difference [SMD]shift = 0.33; P = .0102) and lateral tilt (SMDtilt = 0.43; P = .006) maltracking. Individuals with pain secondary to dislocation had greater effect sizes for lateral maltracking than had those with isolated patellofemoral pain (ΔSMDshift = 0.71, P = .0071; ΔSMDtilt = 1.38, P = .0055). CONCLUSION: This review exposed large methodological variability across the literature, which not only hinders the generalization of results, but ultimately mitigates our understanding of the underlying mechanism of patellofemoral pain. Although our meta-analyses support the diagnostic value of maltracking in patellofemoral pain, the numerous distinct methods for measuring maltracking and the limited control for cofounding variables across the literature prohibit defining a single quantitative profile. Compliance with specific standards for anatomic and outcome measures must be addressed by the scientific and clinical community to establish methodological uniformity in this field.