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Background: In most cases, lateral patellar dislocation (LPD) is accompanied by chondral injury and may initiate gradual degeneration of patellar cartilage, which might be detected with a T 2 mapping, a well-established method for cartilage lesions assessment., Purpose: To examine short-term consequences of single first-time LPD in teenagers by T 2 mapping of the patellar-cartilage state., Study Type: Prospective., Population: 95 patients (mean age: 15.1 ± 2.3; male/female: 46/49) with first-time, complete, traumatic LPD and 51 healthy controls (mean age: 14.7 ± 2.2, male/female: 29/22)., Field Strength/sequence: 3.0 T; axial T 2 mapping acquired using a 2D turbo spin-echo sequence., Assessment: MRI examination was conducted 2-4 months after first LPD. T 2 values were calculated in manually segmented cartilage area via averaging over three middle level slices in six cartilage regions: deep, intermediate, superficial layers, and medial lateral parts., Statistical Tests: ANOVA analysis with Tukey's multiple comparison test, one-vs.-rest logistic regression analysis. The threshold of significance was set at P < 0.05., Results: In lateral patellar cartilage, a significant increase in T 2 values was found in deep and intermediate layers in both patient groups with mild (deep: 34.7 vs. 31.3 msec, intermediate: 38.7 vs. 34.6 msec, effect size = 0.55) and severe (34.8 vs. 31.3 msec, 39.1 vs. 34.6 msec, 0.55) LPD consequences as compared to controls. In the medial facet, only severe cartilage damage showed significant prolongation of T 2 times in the deep layer (34.3 vs. 30.7 msec, 0.55). No significant changes in T 2 values were found in the lateral superficial layer (P = 0.99), whereas mild chondromalacia resulted in a significant decrease of T 2 in the medial superficial layer (41.0 vs. 43.8 msec, 0.55)., Data Conclusion: The study revealed substantial difference in T 2 changes after LPD between medial and lateral areas of patellar cartilage., Evidence Level: 2 TECHNICAL EFFICACY STAGE: 2., (© 2023 International Society for Magnetic Resonance in Medicine.)

Background: Nail-patella syndrome (NPS) is a rare autosomal dominant disorder that is characterized by dysplasia of the nails, hypoplasia and/or dislocation of the patella and the presence of iliac horns. Using the CARE guidelines, we present the first reported case of NPS that was newly diagnosed at the onset of rheumatoid arthritis (RA)., Case Presentation: A 74-year-old man was admitted to our hospital due to an 8-month history of arthralgia in bilateral wrists, elbows and fingers. He had a past history of glaucoma and left patella dislocation that had been operatively recentered at the age of 15 years. Laboratory data showed elevated levels of serum C-reactive protein and rheumatoid factor and an elevated titer of anti-SS-A antibodies, while estimated glomerular filtration rate (eGFR), titers of other antibodies and the results of a urinary test were normal. An X-ray showed deformity of bilateral radial heads and the right elbow, and magnetic resonance imaging (MRI) of his hands showed synovitis and erosion in the multiple swollen joints of the wrists and fingers. In addition to these typical features of RA, he had bilateral thumb nail dysplasia with mild hypoplasia of bilateral patellae and iliac horns as shown by the X-ray. He was diagnosed as having autosomal dominant disorder NPS co-existing with RA and he was treated with methotrexate in combination with an oral Janus kinase (JAK) inhibitor, leading to induction of remission., Conclusions: We have presented a rare case of NPS that was newly diagnosed at the onset of RA. Clinical and radiographic findings of NPS are highlighted in this case report for diagnosing NPS on the basis of typical manifestations., (© 2024. The Author(s).)

Purpose: To describe the characteristics of femoral torsion in patients with different segmental torsion types and to evaluate the correlations between segmental torsion and the morphology of the femoral condyles and trochlea in patients with patellar dislocation and increased femoral torsion., Methods: Between January 2021 and March 2023, 69 patients were included and classified into two groups according to the femoral segment contributing the most to total torsion: 32 patients in Group A (femoral neck and shaft torsion) and 37 patients in Group B (distal torsion). Trochlear dysplasia was evaluated using Dejour's classification and sulcus angle. The morphology of the femoral condyles was evaluated using the lengths and ratios of the medial and lateral condyles. Correlations between femoral torsion and morphology were evaluated., Results: Total torsion was significantly correlated with femoral neck and shaft torsion (r = 0.882, P < 0.001) and distal torsion (r  = 0.262, P = 0.030). Femoral neck and shaft torsion was significantly increased with increasing total torsion. The trochlear sulcus was flatter and more dysplastic, and the anterior condyles were shorter in Group B. Distal torsion was significantly correlated with the lengths of the medial and lateral anterior condyles (r  = - 0.567, P < 0.001; r = -0.701, P < 0.001), sulcus angle (r  = 0.611, P < 0.001) and Dejour trochlea type (r  = 0.512, P = 0.001), while femoral neck and shaft torsion showed no correlations., Conclusion: Femoral torsion is a complex of femoral neck and shaft torsion and distal torsion, especially femoral neck and shaft torsion. Distal torsion was significantly correlated with a flatter trochlear sulcus, higher-grade trochlear dysplasia, and shorter anterior condyles. The new findings highlighted the importance of the segmental evaluation of femoral torsion, which would facilitate understanding of the anatomical characteristics of femoral torsion in patients with patellar dislocation and increased femoral torsion and may lead to improvement in the surgical options regarding femoral torsion., Level of Evidence: Level III., (© 2023. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Purpose: Bilateral involvement is common in patients with patellar instability. The management of bilateral patellar instability is associated with increased complication rate. The higher complication rate in this cohort may be related to the presence of underlying anatomic risk factors. The purpose of the study was to evaluate the presence and side-to-side differences in risk factors between knees in bilateral patellar instability., Methods: In a retrospective study (2008-2017), demographic information, characteristics of patellar dislocation and anatomic risk factors on MRI (trochlear dysplasia, patellar height, tibial tubercle lateralization, patellar tilt, sulcus angle, bump height) were evaluated in both knees of all patients (n = 32, 15 males and 17 females) with bilateral patellar instability. The risk factors were analyzed based on established cut off values and were compared between gender, laterality and more symptomatic (index) knee. Knee symmetry and absolute differences between risk factors for both knees were analyzed., Results: The mean age of 32 patients was 14.6 ± 2.3 years. Of the 4 major anatomic risk factors, the most common were trochlear dysplasia in 59/64 (92.1%) knees and patella alta in 51/64 (79.7%) knees. Tibial tubercle lateralization was the least common risk factor being present in 8/64 (12.5%) knees. Of 64 knees, 55 (85.9%) had 2 or more risk factors and 30 (46.8%) had 3 or all 4 risk factors present. There were no significant differences in risk factors based on gender, laterality or index knee. There was symmetry between paired knees for 31/32 (96.8%) patients for trochlear depth, 29/32 (90.6%) for patellar tilt, 27/32 (84.3%) for TT-TG distance and 25/32 (78.1%) for patellar height. There were no significant differences in absolute measurements between knees for any of the risk factors., Conclusion: Patients with bilateral instability had multiple risk factors, with trochlear dysplasia being the most common and increased TT-TG distance being the least common. Majority of patients had 2 or more risk factors and about half had 3 or 4 risk factors in each knee. There was symmetry between paired knees for each risk factor without any significant differences between the index knee compared to the contralateral knee., Level of Evidence: Level III., (© 2023. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Objectives: To assess the inter- and intra-rater reliability of the classification of the J-sign as "large" versus "small or none" as compared to another two-level system ("present" versus "absent") and a three-level system ("large," "small," or "none") and to identify anatomical and patient factors associated with the presence of a large J-sign., Methods: Forty patients (40 knees) with recurrent patellar instability were prospectively enrolled and recorded on video actively extending their knee while seating. Four raters classified patellar tracking on two separate occasions using three systems: 1) two groups: J-sign versus no J-sign; 2) three groups: large J-sign, small J-sign, or no J-sign; and 3) two groups: large J-sign versus small or no J-sign. The intra- and inter-rater reliability of each system was assessed using kappa statistics. Anatomical (trochlear dysplasia, tibial tubercle-trochlear groove (TT-TG) distance, patellar height) and patient (Beighton score) factors as well as Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales were compared between patients with a large J-sign and patients with a small or no J-sign., Results: Inter- and intra-rater reliability were found to be highest with the two-level classification system of a large J-sign versus a small or no J-sign (inter-rater kappa ​= ​0.76, intra-rater kappa ​= ​0.75). Patients with a large J-sign had more severe trochlear dysplasia as assessed with the sulcus angle (p ​= ​0.042) and were more likely to have a tight lateral retinaculum (p ​= ​0.032) and an elevated Beighton score (p ​= ​0.009). No significant differences in KOOS subscales were noted based on the presence of a large J-sign versus a small J-sign or no J-sign., Conclusion: Qualitative visual assessment of patellar tracking with the J-sign demonstrates substantial inter- and intra-rater reliability, particularly when utilizing a two-group classification system to identify knees with a large J-sign. Patients with a large J-sign demonstrate an increased incidence of a tight lateral retinaculum, generalized ligamentous laxity, and trochlear dysplasia., Level of Evidence: Level III - cross-sectional study., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to systematically review the evidence in the literature in order to evaluate the outcomes following medial patellofemoral ligament (MPFL) reconstruction with allograft compared to autograft reconstruction., Methods: A systematic literature search was performed based on PRISMA guidelines using the EMBASE, MEDLINE, and The Cochrane Library databases. Inclusion criteria for the study was clinical studies reporting on MPFL reconstruction with allograft. Recurrence rate, complications, rate of return-to-play, and functional outcomes including the Kujala, Tegner, and visual analog scale (VAS) scores were evaluated. Statistical analysis was performed using GraphPad Prism 8.3., Results: Our review identified 12 studies with a total of 336 patient knees meeting the inclusion criteria. The majority of patients were female (61.6%), with a mean age of 22.3 years and a mean follow-up of 43.4 months. The overall rate of recurrence of lateral patellar instability was 2.7% in the allograft cohort as compared to 7.8% in the autograft cohort (p = 0.01). The mean Kujala score was 91.8%, and the mean VAS score was 1.3 at final follow-up. Additionally, 81.5% of patients were able to return to play in the studies reporting this outcome measure. The overall complication rate was 1.4%., Conclusion: The overall rate of recurrence was lower following MPFL reconstruction with allograft as compared to autograft in the treatment of lateral patellar instability. Additionally, there were excellent patient reported outcomes and a low complication rate following the use of allograft for MPFL reconstructionPurpose: The purpose of this study was to systematically review the evidence in the literature in order to evaluate the outcomes following medial patellofemoral ligament (MPFL) reconstruction with allograft compared to autograft reconstruction., Methods: A systematic literature search was performed based on PRISMA guidelines using the EMBASE, MEDLINE, and The Cochrane Library databases. Inclusion criteria for the study was clinical studies reporting on MPFL reconstruction with allograft. Recurrence rate, complications, rate of return-to-play, and functional outcomes including the Kujala, Tegner, and visual analog scale (VAS) scores were evaluated. Statistical analysis was performed using GraphPad Prism 8.3., Results: Our review identified 12 studies with a total of 336 patient knees meeting the inclusion criteria. The majority of patients were female (61.6%), with a mean age of 22.3 years and a mean follow-up of 43.4 months. The overall rate of recurrence of lateral patellar instability was 2.7% in the allograft cohort as compared to 7.8% in the autograft cohort (p = 0.01). The mean Kujala score was 91.8%, and the mean VAS score was 1.3 at final follow-up. Additionally, 81.5% of patients were able to return to play in the studies reporting this outcome measure. The overall complication rate was 1.4%., Conclusion: The overall rate of recurrence was lower following MPFL reconstruction with allograft as compared to autograft in the treatment of lateral patellar instability. Additionally, there were excellent patient reported outcomes and a low complication rate following the use of allograft for MPFL reconstruction.

Background: The aim of this study was to investigate the risk factors of neglected osteochondral fractures in primary acute traumatic patellar dislocation in the pediatric population., Methods: A total of 113 patients with primary acute traumatic patellar dislocation for whom coincident osteochondral fractures could not be confirmed by X-ray examination at initial diagnosis between January 2010 and February 2022 were retrospectively analyzed. Medical history, physical examination, and radiographic images were recorded in detail. The greatest dimension of the suprapatellar pouch (SP) effusion on radiograph was measured. Computed tomography and magnetic resonance imaging were used to confirm the presence of neglected osteochondral fractures and measure the fragment size. Potential risk factors were calculated and correlated with reference to the neglected osteochondral fractures and fragment size using multivariate linear regression analysis., Results: Weight, walking ability, effusion grade, and SP measurement had a significant correlation with neglected osteochondral fractures in primary acute traumatic patellar dislocation (p = 0.046; p < 0.001; p = 0.048; p < 0.001). The cutoff point was 53.5 kg for weight and 18.45 mm for SP measurement. In the neglected fractures group, SP measurement was statistically significant with larger fragment size (beta value = 0.457; p < 0.001), and the cutoff point was 26.2 mm., Conclusions: SP effusion is not only associated with an increased risk of neglected osteochondral fractures in primary acute traumatic patellar dislocation but also with larger fragment size. Knee radiograph, medical history, and physical examination can predict the need for further imaging examination and even surgery in primary acute traumatic patellar dislocation., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Purpose: Medial patellofemoral ligament reconstruction (MPFL-R) is a recognised surgical procedure for the treatment of recurrent patellofemoral instability with excellent outcomes reported. The aim of this study is to determine if body mass index can influence these outcomes., Methods: This is a single-centre retrospective analysis of a longitudinal patellofemoral database. Patients with recurrent patellar instability, without patellar alta or severe trochlear dysplasia were treated using a MPFL-R between 2015 and 2019 at The Robert Jones & Agnes Hunt Orthopaedic Hospital. The clinical efficacy following surgery was assessed by Kujula, International Knee Documentation Committee Score (IKDC), and EuroQol-5 score (EQ-5D) at baseline and up to 26 months post-operatively; their safety assessed by complication rate and requirement for further surgery. The effect of Body Mass Index (BMI) on clinical outcome was analysed using linear, curvilinear, and segmented models following propensity score weighting., Results: A total of 97 patients (97 Knees, mean age 25y) were analysed. Of these, 61 patients had a BMI < 30 kg/m 2 (mean age 23y, mean BMI 24) of which 7 patients (12.3%) required additional surgery. A further 36 patients had a BMI > 30 kg/m 2 (mean age 27y, mean BMI 36) of which 2 patients (5.6%) required additional surgery. The re-dislocation rate was 0% in each BMI group. Both groups had a significantly improved mean outcome following surgery, with improvements in mean IKDC above the minimum clinical important differences (MCID) of 20.5. BMI had an inverted J-shaped association with functional outcome, showing peak outcomes at BMI of 20.5 (95% CI 18.5 to 22.4; IKDC and Kujala) or BMI of 28 (EQ-5D index). No evidence for an association between BMI and complication risk was found., Conclusion: BMI influences the functional outcomes in MPFL-R with an inverted J-shaped relation, without evidence it affected the complication or re-dislocation rate. In the absence of patella alta and severe trochlear dysplasia, an isolated MPFL reconstruction is a safe and effective procedure to treat patellar instability, with the best functional outcome in patients with a BMI around 20 to 21., Level of Evidence: Level III., (© 2023. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

While traumatic popliteal artery injury historically has a low incidence, failure to acutely recognize the vascular insult poses a significant risk of limb loss and functional impairment. A 71-year-old male presented with left lower extremity pain in setting of a crush injury working underneath a vehicle resulting in an isolated lateral dislocation of his patella and complete occlusion of the distal popliteal artery. He was taken to the operating room for an in-situ bypass and four-compartment fasciotomy. His hospital stay included three staged washouts/debridements with eventual closure. He was discharged after 38 days to a rehabilitation facility with ability to self-ambulate with assistance within one month. This patient's presentation is unique for his isolated patellar dislocation without associated injuries characteristically associated with a traumatic vascular injury of the popliteal artery and serves to remind the importance of complete examination in the setting of blunt trauma.

Purpose: Understanding how surgical procedures influence anatomic factors associated with patellofemoral instability can help guide surgeons when planning treatments for individual patients. This study sought to understand how patellar tilt is affected in adolescent patients with elevated pre-operative tibial tuberosity to trochlear groove (TT-TG) values undergoing medial patellofemoral ligament reconstruction (MPFLR) with or without an anterior medializing osteotomy (AMZ)., Methods: Utilizing a prospective database of 274 patellofemoral instability patients who underwent MPFLR ± AMZ by one of two orthopedic surgeons at a single institution, those who underwent MPFLR + AMZ were identified. Pre-operative and post-operative magnetic resonance imaging (MRI) were used to measure TT-TG distance, while radiographs were used to measure patellar tilt (tilt). Patients were matched based on age at surgery (within 2 years) and pre-operative TT-TG distance (within 2 mm) to a comparison cohort of patients who underwent isolated MPFLR (iMPFLR) without osseous procedures., Results: A total of 56 patients were analyzed (28 per group). The mean age of the cohort was 15.5 ± 2.0 years and was similar between both groups (15.9 ± 1.9 versus 15.1 ± 2.0 years [n.s]). When comparing the two cohorts, significant pre- to post-operative decreases in patellar tilt for both MPFLR + AMZ (6.6 degrees, p < 0.001) and iMPFLR (3.9 degrees, p = 0.013) were noted. While there were no differences in pre-operative patellar tilt (21.2 ± 3.5 versus 21.1 ± 3.4 [n.s]), post-operatively, MPFLR + AMZ had significantly less patellar tilt than iMPFLR (13.2 ± 5.5 versus 16.5 ± 4.4, p = 0.017)., Conclusions: This study found that patellar tilt significantly improved in participants undergoing either MPFLR + AMZ or iMPFLR. In addition, those undergoing MPFLR + AMZ were found to have significantly lower post-operative tilt than those undergoing iMPFLR. If patellar tilt is found pre-operatively to be significantly elevated and a risk for future dislocations, these findings suggest that surgeons might strongly consider MPFLR with AMZ to further address the increased tilt., Level of Evidence: III., (© 2023. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Background: Patella alta is an anatomic risk factor for patellar instability in adolescents that is also linked to the risk factor of trochlear dysplasia. This study aims to determine the age of onset and age-related incidence of patella alta in a pediatric population of patients with patellar instability. We hypothesized that patellar height ratios would not increase with age, suggesting a congenital rather than the developmental origin of patella alta., Methods: A retrospective cross-sectional cohort of patients was collected with the following inclusion criteria: patients aged 5 to 18 who had a knee magnetic resonance imaging performed from 2000 to 2022 and the International Classification of Diseases code for patellar dislocation. Demographic information and details of the patellar instability episode(s) were collected with a chart review. Sagittal magnetic resonance imaging was used to measure Caton-Deschamps Index (CDI) and the Insall-Salvati Ratio (ISR) by 2 observers. Data were analyzed to assess for associations between patellar height ratios and age of the first dislocation and to assess if the proportion of patients categorized as having patella alta changed with age., Results: The 140 knees included in the cohort had an average age of 13.9 years (SD=2.40; range: 8-18) and were 55% female. Patella alta was present in 78 knees (55.7%) using CDI>=1.2 and in 59 knees (42.1%) using ISR>=1.3. The earliest age patella alta was observed was at age 8 using CDI>=1.2 and age 10 using ISR>=1.3. There were no statistically significant associations between CDI and age without adjustment ( P =0.14) nor after adjustment for sex and body mass index ( P =0.17). The proportion of knees above the CDI threshold for patella alta to the knees below the cutoff did not show a significant change with age ( P =0.09)., Conclusions: Patella alta, as defined by CDI, is seen in patients as young as 8 years old. Patellar height ratios do not change with age in patients with patellar dislocation, suggesting that patella alta is established at a young age rather than developing during the adolescent years., Level of Evidence: Level III-diagnostic, cross-sectional., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: To determine the effect of isolated medial patellofemoral ligament reconstruction (MPFLR) versus concomitant MPFLR and tibial-tubercle osteotomy (TTO) on patient-reported functional outcomes, rate of patellar redislocation, and rate of return to sport in skeletally mature patients with recurrent patellar instability and lateralization as defined by elevated tibial-tubercle trochlear groove (TT-TG) distance., Methods: Three databases MEDLINE, PubMed and EMBASE were searched from inception to July 10th, 2022 for literature outlining the management of patients with TT-TG indices greater than 15 mm with either isolated MPFLR or concomitant MPFLR and TTO procedures. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on functional outcomes via the Kujala anterior knee pain score, redislocation rates, return to sport rates, and complications were recorded. The MINORS score was used for all studies to perform a quality assessment of included studies., Results: A total of 31 studies comprising 1405 patients (1452 knees) were included in this review. The mean Kujala score in 13 studies comprising 848 total patients in the isolated MPFLR group was 85.0 (range 80.9-97.5) compared to a score of 83.7 (range 77.2-94.0) in 14 studies comprising 459 patients in the concomitant group. The mean pooled redislocation rate in 19 studies examining isolated MPFLR procedures comprising 948 patients was 3.1% (95% CI 2.1-4.4%, I 2  = 7%) as opposed to 3.2% (95% CI 1.9-5.0%, I 2  = 0%) in 15 studies comprising 486 patients in the concomitant group. The mean pooled return to sport rate in seven studies with 472 total patients in the isolated MPFLR group was 82% (95% CI 78-86%, I 2  = 16%) compared to a score of 92% (95% CI 78-99%, I 2  = 58%) in four studies comprising 54 patients in the concomitant group. There were similar complication rates between both treatment groups, including range of motion deficits, fractures, infections, and graft failures., Conclusion: Isolated MPFLR leads to similar anterior knee pain, similar redislocation rates and lower return to sport rates than concomitant MPFLR and TTO procedures in patients with TT-TG distances greater than 15 mm. Information from this review can aid surgeons in their decision to choose MPFLR versus concomitant procedures for this patient population, and can also guide future studies on this topic., Level of Evidence: Level IV., (© 2022. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Patellofemoral pain and instability are common indications for imaging that are encountered in everyday practice. The authors comprehensively review key aspects of patellofemoral instability pertinent to radiologists that can be seen before the onset of osteoarthritis, highlighting the anatomy, clinical evaluation, diagnostic imaging, and treatment. Regarding the anatomy, the medial patellofemoral ligament (MPFL) is the primary static soft-tissue restraint to lateral patellar displacement and is commonly reconstructed surgically in patients with MPFL dysfunction and patellar instability. Osteoarticular abnormalities that predispose individuals to patellar instability include patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Clinically, patients with patellar instability may be divided into two broad groups with imaging findings that sometimes overlap: patients with a history of overt patellar instability after a traumatic event (eg, dislocation, subluxation) and patients without such a history. In terms of imaging, radiography is generally the initial examination of choice, and MRI is the most common cross-sectional examination performed preoperatively. For all imaging techniques, there has been a proliferation of published radiologic measurement methods. The authors summarize the most common validated measurements for patellar malalignment, trochlear dysplasia, and tibial tubercle lateralization. Given that static imaging is inherently limited in the evaluation of patellar motion, dynamic imaging with US, CT, or MRI may be requested by some surgeons. The primary treatment strategy for patellofemoral pain is conservative. Surgical treatment options include MPFL reconstruction with or without osseous corrections such as trochleoplasty and tibial tubercle osteotomy. Postoperative complications evaluated at imaging include patellar fracture, graft failure, graft malposition, and medial patellar subluxation. © RSNA, 2023 Quiz questions for this article are available in the supplemental material.

➤: Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology. Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient., ➤: Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity., ➤: Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment., ➤: Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability., ➤: Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation., ➤: Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta., ➤: The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding., ➤: Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30° to improve patient outcomes and reduce recurrence rates., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article ( http://links.lww.com/JBJS/H402 )., (Copyright © 2023 by The Journal of Bone and Joint Surgery, Incorporated.)

PURPOSE OF THE STUDY Patellofemoral stability and congruency are influenced by different parameters. Their contribution to anterior knee pain and instability is not fully understood. We investigated, if isolated femoral antetorsion of more than 25° leads to patellofemoral instability. MATERIAL AND METHODS We analyzed 90 knees in patients with patellofemoral complaints and correlated clinical and radiological characteristics. Patients presenting at our center between January 2018 and December 2020 because of patellofemoral pain or instability were included, provided that there was no previous surgical intervention done. RESULTS The severity of trochlea dysplasia classified using the Oswestry-Bristol classification significantly correlated with events of patellofemoral dislocations. (χ=8.152, p=0.043, φ=0.288). All males with a history of patella dislocation had at least a mild trochlea dysplasia. The majority of females complaining about patellofemoral symptoms in general had a dysplastic trochlea. Patella alta is more frequently found in patients with trochlea dysplasia than in patients with a normal femoral trochlea anatomy. DISCUSSION The majority of unstable patellofemoral joints showed a dysplastic trochlea. A high femoral antetorsion was found to be an additional minor factor contributing to instability. Isolated high femoral antetorsion without trochlea dysplasia rather leads to anterior knee pain without patella dislocation. Furthermore, no direct significant correlation between patella alta and patellofemoral instability was found. Patella alta can therefore rather be seen as a result of a dysplastic trochlea than a primary major risk factor for patellofemoral instability. CONCLUSIONS Trochlea dysplasia is the major risk factor for patellofemoral instability. Patella alta can rather be seen as a result of a dysplastic trochlea than as a primary risk factor for patella instability or pain. Isolated high femoral antetorsion often leads to patellofemoral pain syndrome but not to patella dislocations. Key words: MPFL, patella instability, patellofemoral instability.

Purpose: Patella alta is an established risk factor for recurrent lateral patella dislocations. Medial patellofemoral ligament (MPFL) reconstruction has been shown to reduce patella height. Our hypothesis is that isolated MPFL reconstruction corrects patella alta, thereby reducing the risk of recurrent patella dislocation., Methods: A prospective cohort study of 33 knees which underwent MPFL reconstruction for recurrent patella dislocation. The pre-operative and post-operative patella height and Kujala knee outcome scores, as well as tibial tuberosity-trochlear groove (TT-TG) distance, and the grade of trochlear dysplasia were recorded., Results: The mean age was 21.5 years (16-34 years). There was significant reduction in patella height in all patients (p < 0.001), a 67% normalisation of patella alta (CD ≥ 1.2) (p < 0.004), and improvement in the Kujala scores 57.1 (pre-operatively) to 94.8 (post-operatively, p < 0.0001). The recurrent dislocation rate was 3%., Conclusion: MPFL reconstruction alone results in correction in patella alta and improvement in clinical outcomes., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Rationale: Evaluation of clinical and radiologic abnormalities in patients with postaxial hypoplasia of the lower extremity (PHLE) for treatment decisions represents a major challenge, which is more complicated when PHLE is associated with congenital dislocation of the patella., Patient Concerns: : Herein, we present the case of an 8-year-old female patient with evident length inequality in her left lower extremity and inability to walk., Diagnoses: Radiological evaluation revealed PHLE with fibular hemimelia, proximal femoral focal deficiency, tarsal coalition, and congenital patellar dislocation of the patella. The right lower extremity was also affected by fibular hemimelia., Interventions and Outcomes: Surgical management included the Roux-Goldthwait technique for patellofemoral joint realignment, a medial knee stapled with Blount technique, and femur enlargement using the Wagner technique. The results from surgical intervention included a left femoral elongation of 6.7 cm featuring callus with angulation, displacement, and a discrepancy of 5 cm between femurs with a flexor contraction in the knee of -15° and a centralized knee., Lesson: PHLE accompanied by congenital dislocation of the patella has not been extensively described in the literature; therefore, there is no established management. Starting reconstruction at an early age, together with an adequate classification of the deformity, are essential factors when opting for limb reconstruction., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Case: A 55-year-old man with Down syndrome (DS) suffered from chronic irreducible right patellar dislocation. Imaging studies showed an attenuated appearance of the medial patellar retinaculum, and the tibial tubercle to trochlear groove distance measured 1.6 cm. Right medial patellofemoral ligament reconstruction (MPFLR) and lateral lengthening (LL) with proximalization of the tibial tubercle (PTT) were performed with good surgical outcomes., Conclusion: The combination of MPFLR, LL, and PTT is a viable option for treating a skeletally mature DS patient with patellofemoral instability causing recurrent patellar dislocation., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/B842)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Purpose: To determine which risk factors for patellar instability contribute most relevantly to patients' subjective disease-specific quality of life, aiming to provide implications on the overall treatment decision-making process., Methods: A total of 182 consecutive patients (male/female 70/112; mean age 23.6 ± 7.3 years) with a history of patellar instability were prospectively enrolled in this study. Patient age, body mass index (BMI), number of dislocations, reversed dynamic patellar apprehension test (ReDPAT), J-sign severity, and pathoanatomic risk factors of patellar instability were assessed. The statistical analysis evaluated the relationships among those variables and determined their ability to predict the Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) as a disease-specific quality of life measure. Using Spearman correlation, ANOVA and Fisher's exact test, all variables with ANOVA p ≤ 0.1 or Spearman's abs (rho) > 0.1 were entered into a multivariate linear model using backward-stepwise selection., Results: Analysis of the individual variables' ability to predict BPII 2.0 score values revealed 'age', 'BMI', 'ReDPAT', 'high grade of trochlear dysplasia', and 'high-grade J-Sign' as possible relevant factors. Backward-stepwise multivariate regression analysis yielded a final parsimonious model that included the factors 'BMI' and 'J-Sign (Grade II and III)' as the most relevant parameters influencing BPII 2.0 score values (adjusted R 2  = 0.418; p < 0.001), with a cutoff value for BMI found at 28 kg/m 2 (p = 0.01)., Conclusion: The results of this study indicate that in patients with lateral patellar instability, a high-grade J-sign and an increased BMI significantly impact subjective disease-specific quality of life., Level of Evidence: Level IV., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Background: Previous research supports that distal translation of the tibial tubercle osteotomy (dTTO) for patients with recurrent lateral patellar dislocation (R-LPD) and patella alta is effective for surgical patellar stabilization., Hypothesis/purpose: The main purpose of this article is to evaluate (1) the results of modifying the surgical threshold and postoperative goal of patellar height measurements for surgical stabilization originated in the "menu à la carte" approach to patellar surgical stabilization and (2) the relationship between the distance distalized in millimeters and postoperative complications. Our hypothesis was that dTTO with medial patellofemoral ligament reconstruction (MPFL-R) will successfully stabilize the patella with improvement in outcome scores and few complications, using a modification of the original menu à la carte as our surgical algorithm., Study Design: Case series; Level of evidence, 4., Methods: A total of 68 consecutive patients with R-LPD underwent dTTO and MPFL-R for surgical patellar stabilization by a single surgeon between May 2009 and September 2015. Surgical indications were R-LPD combined with patella alta. The surgical threshold for dTTO was Caton-Deschamps index (CDI) or Insall-Salvati ratio ≥1.4 and/or a patellar trochlear index <0.15. The postoperative surgical goal for patellar height was a CDI of 1.1 to 1.2. Length of the distalization was computed by using the CDI measurement as the primary intraoperative guide and measured intraoperatively with a ruler. Clinical, radiographic, and patient outcome measures were reviewed., Results: The mean CDI preoperatively was 1.40 and postoperatively it was 1.09. The mean distalization was 9.9 mm (range, 4-15 mm). Three patients (4.4%) had frank R-LPD postoperatively. Ten patients had residual patella alta (CDI >1.2), with 1 redislocation. Mean postoperative CDI in the recurrent dislocation group was 1.13 (range, 1.06-1.25) as compared with 1.09 (range, 0.92-1.35) in the nonrecurrent group ( P = 0.65). Complications included 3 tibial fractures (4.4%) and postoperative knee arthrofibrosis in 6 patients (8.8%), with mean distalization greater in the arthrofibrosis group ( P = .04). Knee injury and Osteoarthritis Outcome Score (KOOS) values improved in all domains, including a 31-point increase in Quality of Life., Conclusion: dTTO with MPFL-R for patients with patella alta leads to a high rate of normalization of patellar height measurements (87%) and patellar stabilization (95.6%). Residual patella alta is not associated with an increased risk of recurrence. The length of dTTO up to 15 mm is not associated with an increase in postoperative complications, except for an increased prevalence of arthrofibrosis (8.8%).

Background: Medial patellofemoral ligament (MPFL) reconstruction is a common surgical treatment for patients with recurrent patellar instability. A variety of risk factors, such as age, trochlear dysplasia, patella alta, and increased tibial tubercle-trochlear groove (TT-TG) distance, have been identified and may lead to postoperative failure or poor outcomes., Purpose: While a large number of risk factors have been identified, significant heterogeneity exists in evaluating and reporting these risk factors in the literature. The goal of this study was to perform a systematic review to determine risk factors associated with worse outcomes after MPFL reconstruction and their consistency of being controlled for or analyzed among studies., Study Design: Systematic review; Level of evidence, 4., Methods: A systematic review of the literature was performed using the MEDLINE database to identify relevant clinical outcome studies after MPFL reconstruction for recurrent patellar instability. Eligible studies were evaluated for risk factors that were associated with MPFL failure, defined as recurrent instability or lack of improvement on patient-reported outcome (PRO) scores. Each study was then evaluated for inclusion of these risk factors., Results: Ten studies were included in the final analysis, comprising 1287 knees from 1275 patients who underwent isolated MPFL reconstruction. Of these 10 studies, 8 defined outcomes based on PROs and 3 defined outcomes based on postoperative recurrent instability (1 study included both outcomes). In the PRO failure group, 12 risk factors were found across all studies: trochlear dysplasia, trochlear bump height, elevated TT-TG, patellar tilt, hyperlaxity, age at first dislocation, age at surgery, body mass index, bilateral symptoms, WARPS/STAID score (weak atraumatic, risky anatomy, pain, and subluxation/strong, traumatic, anatomy normal, instability, and dislocation), femoral tunnel malposition, and femoral tunnel widening. In the recurrent instability failure group, 7 risk factors were found across all studies: trochlear dysplasia, bump height, patella alta, higher sulcus angle, higher congruence angle, preoperative J sign, and femoral tunnel malposition. Trochlear dysplasia and femoral tunnel malposition were consistently cited in several studies as risk factors for worse PROs and higher rates of recurrent instability. Patella alta was indicated as a significant risk factor for recurrent instability in 1 of 2 studies analyzing postoperative instability failures and was not associated with worse PROs in any of the studies analyzed. Similarly, elevated TT-TG distance was not a significant risk factor in any of the studies that analyzed recurrent instability as the failure endpoint., Conclusion: While various risk factors are postulated to affect outcomes after MPFL reconstruction, there remains inconsistency within the literature regarding the inclusion of all risk factors in a given analysis. Furthermore, the significance of these risk factors varies among studies in terms of whether they affect postoperative outcomes. We found that more severe trochlear dysplasia (types C and D) and femoral tunnel malposition (>10 mm from Schöttle's point) appear to have the most consistent effect on producing higher rates of recurrent dislocation as well as worse PROs. Despite this, the role of concomitant bony procedures to adjust certain pathoanatomic risk factors in addition to MPFL reconstruction remains unknown. Future high-level studies must be conducted that respect the multifactorial nature of patellar instability and should analyze all risk factors (demographic, anatomic, and radiographic) reported to affect outcomes.

Purpose: The present study aimed to systematically review and compare 2 femoral autograft fixation techniques, namely, interference screws and suture anchors, for isolated medial patellofemoral ligament reconstruction in patients with recurrent patellofemoral instability at mid- to long-term follow-up., Methods: A literature search was performed in September 2020. All studies reporting the outcomes of primary isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability were considered for inclusion. Only studies reporting the type of femoral autograft fixation under examination were considered. Studies reporting data from patients with elevated tibial tuberosity-tibial groove, patella alta, and/or Dejour's trochlear dysplasia types C and D, were not included. Only articles reporting data with a minimum follow-up period of 18 months were considered., Results: Data from 19 studies (615 patients) were retrieved. The overall age was 24.4 ± 6.7 years (mean ± SD). The mean follow-up was 46.5 ± 20.9 months. There were 76 patients in the anchor group and 539 in the screw group. Comparability was found with regard to age and follow-up duration between the 2 study groups. There was comparability between the Kujala, Lysholm, and Tegner scores at baseline. At the last follow-up, no worthy differences were found in terms of mean Kujala (+2.1%; p = 0.04), Lysholm (+1.7%; p = 0.05), and Tegner (+15.8%; p = 0.05) scores. Although complications occurred almost exclusively in the screw cohort, no statistically significant difference was found., Conclusion: Femoral autograft fixation through interference screws or suture anchors report similar clinical scores and rate of apprehension test, persistent joint instability, re-dislocations, and revisions. These results must be interpreted within the limitations of the present study., Competing Interests: Competing interests The authors declare that they have no conflicts of interest., (Copyright © 2021. Production and hosting by Elsevier B.V.)

The dogma that (every) primary patellar dislocation should be treated non-operatively is considered outdated. Therefore, every first-time dislocation, as well as every recurrent dislocation, should be fully diagnosed with regard to the injury pattern and anatomically predisposing risk factors. This enables the use of risk stratification models to assess the risk of recurrent episodes of instability, thereby supporting the clinical decision-making process. The reconstruction of the MPFL can be considered an established and successful treatment strategy for patellar instability. However, the additional correction of bony risk factors is often useful. In this context, the preoperative grading of the J sign and dynamic assessment of patellar instability (dynamic apprehension test) are of utmost importance. These findings, combined with the radiographic imaging findings, can be used as a clinical decision aid for a bony correction procedure., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

Objective: The purpose of this study was (1) to determine which risk factors for patellar instability were associated with the presence of patellofemoral cartilage lesions and (2) to determine how cartilage lesion presence, size, and grade affect postoperative disease-specific quality of life., Design: Preoperative, intraoperative, and postoperative demographic, anthropometric (body mass index, Beighton score, hip rotation), radiographic (crossover sign, trochlear bump), cartilage lesion morphology (presence, size, location, grade), and outcomes data (Banff Patella Instability Instrument 2.0 [BPII 2.0]) were prospectively collected from patients undergoing isolated medial patellofemoral ligament reconstruction. For all knees ( n = 264), single and multivariable logistic regression was used to determine if any patellar instability risk factors affected the odds of having a cartilage lesion. In patients with unilateral symptoms ( n = 121), single variable linear regression was used to determine if the presence, size, or ICRS (International Cartilage Regeneration & Joint Preservation Society) grade of cartilage lesions could predict the 12 or 24+ month postoperative BPII 2.0 score., Results: A total of 84.5% of knees had patellofemoral cartilage lesions (88.3% involved the distal-medial patella). Trochlear dysplasia (high grade: odds ratio = 15.7, P < 0.001; low grade: odds ratio = 2.9, P = 0.015) was associated with the presence of a cartilage lesion. The presence, size, and grade of cartilage lesions were not associated with 12 or 24+ month postoperative BPII 2.0 scores., Conclusions: Trochlear dysplasia was a risk factor for the development of patellofemoral cartilage lesions in this patient population. Cartilage lesions most commonly involve the distal-medial patella. There was no significant relationship between patellofemoral cartilage lesion presence, size, or grade and postoperative BPII 2.0 scores in short-term follow-up.

Case: Combined medial and lateral patellar instability is exceptionally rare with only 3 reported cases to date. Here, we present the case of a 37-year-old White woman with multiple recurrent medial and lateral patellar instability. After failure of conservative care with bracing and therapy, she underwent surgical stabilization with medial and lateral allograft reconstruction., Conclusion: This case provides an example of the condition and successful surgical follow-up., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/B634)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Purpose: In this study, the functional mid-term outcomes of the modified Grammont and Langenskiöld technique was assessed in skeletally immature patients with habitual patellar dislocation, with emphasis on knee function, pain, and other possible post-surgical complications. This is the first study concerning the application of the modified Grammont and Langenskiöld technique in habitual patellar dislocations., Methods: This retrospective cohort study considered 10 patients (15 knees), ranging from 7 to 11 years old, who underwent the modified Grammont and Langenskiold procedure between 2015 and 2018. History of dislocation, patellar stability and range of motion (ROM) were analysed. To assess functional improvement and knee pain, the Kujala Anterior Knee Pain Scale and KOOS-Child Knee Survey were used before and after surgical treatment., Results: No history of dislocation was noted after surgical treatment. All 15 knees showed full ROM. There were no signs of genu recurvatum and no length discrepancies were found. The subjective assessment revealed significant improvement in the scores of the KOOS-Child questionnaire in all five sections (p < 0.001), as well as in The Kujala Anterior Knee Pain Scale (p = 0.001)., Conclusion: The modified Grammont and Langenskiöld technique yields remarkable results in terms of knee stability and knee function, while decreasing recurrence risk and intensity of pain in patients with challenging cases of patellofemoral joint dislocation. This surgical technique is most effective in cases where the patella remains dislocated continuously; however, it may also be used in immature patients with recurrent instability., Level of Evidence: IV.

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., Competing Interests: Disclosure: The authors indicated that no external funding was received for any aspect of this work. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJS/G334)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Patellar instability and associated patellar dislocation can result in significant pain, disability, and associated injuries in young athletes. The patellofemoral joint is a complex articulation with stabilizing restraints, both medially and laterally, that help guide the patella into the corresponding trochlear groove as the knee cycles through an extension-to-flexion arc. In addition to soft tissue injuries, many osseous aberrancies can contribute to patellar instability in young athletes, including trochlear dysplasia, patella alta, and axial and coronal plane abnormalities. There is a role for nonoperative treatment in these young athletes; however, if recurrent or associated injuries are identified surgical intervention is warranted. Correct diagnosis of the underlying cause of the patellar instability is paramount to developing a surgical plan that will yield the most favorable outcome for these young athletes., Competing Interests: Disclosure Dr J. Lee Pace is a paid consultant for Arthrex, Inc. receiving both consulting fees and research funding. All other authors have nothing to disclose., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Introduction: The first approach for acute patellar dislocation is still a debated topic. The purpose of the present study was to perform a meta-analysis evaluating the outcomes of the surgical approach compared to the conservative treatments for primary acute patellar dislocation. We hypothesize that a prompt surgical treatment may lead to better outcomes in terms of re-dislocations and quality of life., Methods: This meta-analysis was performed according to the PRISMA guidelines. All the prospective clinical trials comparing surgical and conservative treatment for first acute patellofemoral dislocation were included in this study. For the methodological quality assessment, the PEDro appraisal score was adopted. For the risk of publication bias, the funnel plot was performed. The statistical analysis was performed using the Review Manager Software 5.3 (The Nordic Cochrane Collaboration, Copenhagen)., Results: The funnel plot detected a low risk of publication bias. According to the PEDro score, the methodological quality assessment was good. Data from 654 patients were collected, undergoing a mean of 53.8 ± 48.4 month follow-up. A total of 311 patients (17.66 ± 4.1 years old) were analyzed in the surgery group and 291 patients (19.25 ± 4.5 years old) in the conservative ones. The mean Kujala score resulted in greater favor of the surgery group (MD: 9.99%; P = 0.006). The analysis of the comparison of re-dislocations resulted in favor of the surgery group (OR: 0.41; P < 0.0001). The analysis of the comparison of persistent joint instability resulted in favor of the surgery group (OR: 0.41; P < 0.0001)., Conclusions: Data from the present study encourage a prompt surgical approach for the first patellofemoral dislocation.

Background: Tibial tuberosity transposition (TTT) causes caudalization of the patellar ligament insertion in canine medial patellar luxation, which can lead to increases in patellofemoral contact pressure., Objectives: The purpose of this study is to confirm the effect of patellofemoral contact mechanics after craniolateral and caudolateral transposition of tibial tuberosity in normal canine hindlimbs., Methods: Craniolateral and caudolateral transposition of tibial tuberosity was performed in 5 specimens, respectively. The pressure was measured in the specimen before TTT, and then in the same specimen after TTT. In this process, data was obtained in 10 specimens. The measurement results were output as visualization data through the manufacturer's software and numerical data through spreadsheet. Based on these 2 data and the anatomical structure of the patellofemoral joint (PFJ) surface, whole measurement area was analysed by dividing into medial, lateral and central area., Results: In craniolateralization of tibial tuberosity, total, medial, central contact pressure was decreased and lateral contact pressure was not statistically changed lateral contact pressure than normal PFJ. In caudolateralization of tibial tuberosity, total, lateral contact pressure was increased and medial contact pressure was not statistically changed than normal PFJ. Although not statistically significant changed, central contact pressure in caudolateralization of tibial tuberosity was increased in all 5 specimens., Conclusions: These results imply that traditional TTT, prone to caudal shift of patellar tendon, can increase retropatellar pressure may lead to various complications and diseases of the stifle joint., Competing Interests: The authors declare no conflicts of interest., (© 2020 The Korean Society of Veterinary Science.)

Acute patellar dislocation affects approximately 1:1000 healthy children 9-15 years of age, and up to 50% are at risk for recurrent dislocations. In adults the condition is associated with long-term complications, such as osteoarthritis and impairment of knee function. However, literature describing the outcome in a pediatric population is sparse. The present review article evaluates the long-term effects on knee function and cartilage quality after traumatic patellar dislocation in childhood, and also to evaluate the reliability of two clinical tests of medio-lateral knee position, in healthy children.

Purpose: The purpose of the study was to investigate the association between preoperative opioid use and persistent postoperative use, and determine the impact of preoperative opioid use on patient-reported outcomes (PROs) in patients undergoing patellofemoral stabilization surgery., Methods: A retrospective analysis of 60 patients after patellofemoral stabilization surgery with a minimum of 2-year follow-up was performed using a prospectively collected patellar instability registry. Patients were categorized as opioid naïve (n = 48) or preoperative opioid users (n = 12). Postoperative opioid use was assessed for all patients at 2 and 6 weeks. Knee Injury and Osteoarthritis Outcome Score (KOOS) and Kujala questionnaires were administered at baseline, and 6 months and 2 years postoperatively., Results: Preoperative opioid use was identified as an independent risk factor for postoperative opioid use at 2- and 6-weeks following surgery (p = 0.0023 and p < 0.0001, respectively). Preoperative opioid use was associated with significantly lower KOOS and Kujala scores at baseline, 6 months and 2 years postoperatively. Both groups significantly improved from baseline KOOS and Kujala scores at 6 months and 2 years postoperatively. Regardless of preoperative opioid use, opioid use at 6 weeks after surgery was associated with worse KOOS scores at 6 months and 2 years postoperatively., Conclusion: In patients undergoing patellofemoral stabilization surgery, preoperative opioid use was predictive of postoperative use. Additionally, preoperative opioid use was associated with worse PROs at 6 months and 2 years following surgery., Level of Evidence: III.

Case: A healthy 15-year-old girl presented with osteochondral fracture at the posterior aspect of the lateral femoral condyle (LFC) associated with a right patellar dislocation after a noncontact injury. The patient remained asymptomatic 18 months after the arthroscopically assisted reduction and internal fixation of the osteochondral fracture using bioabsorbable pins and was able to eventually resume her usual activities of daily living., Conclusions: This is the first report of an osteochondral fracture at the posterior aspect of the LFC after an acute patellar dislocation, successfully treated with arthroscopically assisted reduction and internal fixation using bioabsorbable pins. This rare injury and unique mechanism of injury have been discussed.

Background: Developmental factors were assumed to be the key factors that influenced the morphology of femoral trochlea. This study investigated the effects of insufficient patellar stress after birth on the morphological development of the femoral trochlea. Effects of insufficient patellar stress on femoral trochlea were investigated using surgical induced patellectomy and patellar dislocation in growing rat model., Methods: In this study, two experimental groups and one sham group (SG) were established. Thirty-six Wistar rats (female, 28 days of age) were randomly assigned to three groups. The patellectomy group (PG), rats underwent the patellectomy in this group. The dislocation group (DG), rats underwent the surgery-induced patellar dislocation. Histological staining (Safranin-O and fast green), Micro-computed tomographic (Micro-CT) analysis in two experimental endpoints (3, 12 weeks postoperatively) were selected to evaluate morphological changes of the femoral trochlea., Results: Articular cartilage on the trochlear sulcus was remodeled at 3 weeks after the surgery, and degenerated at 12 weeks through the histological staining. The femoral trochlear angle (FTA) did not show a significant difference at 3 week between the experimental groups and the sham group (PG vs SG P = 0.38, DG vs SG p = 0.05), but the FTA was significantly increased in experimental groups at 12 weeks(PG vs SG P = 0.001, DG vs SG p = 0.005). The Bone volume density (BV/TV), Trabecular number (Tb.N) under the trochlea groove were significantly reduced at 3 weeks postoperatively in the experimental groups (PG vs SG p = 0.001, DG vs SG p = 0.002). No significant difference was found in BV/TV and Tb. N among the three groups at 12 weeks postoperatively., Conclusion: Surgical induced patellectomy and patellar dislocation leads to the dysplastic trochlear sulcus in growing rats. Besides the bone morphology of trochlear sulcus, the articular cartilage and subchondral trabecula under the trochlear sulcus were remodeled early stage after the surgery.

Context: Anatomic differences of the knee in first-time patellar dislocators have not been clearly elucidated., Objective: To compare structural differences of the knee in those who have sustained an acute first-time patellar dislocation resulting in a medial patellofemoral ligament (MPFL) tear by sex and age (≤17 years old, ≥18 years old)., Design: Case series., Setting: Retrospective magnetic resonance imaging analysis., Patients or Other Participants: Thirty-five acute first-time patellar dislocators with an associated MPFL tear., Main Outcome Measure(s): Patellar height using 3 methods, patellar alignment using congruency angles, and trochlear morphology using the sulcus angle. We compared the means of these variables by sex and age. The intraclass correlation coefficient was then calculated to assess the agreement of the independent reviewers., Results: A total of 21 left and 14 right knees were analyzed. The MPFL tear location did not differ by sex ( P = .34) or age ( P = .43). Patellar height did not differ as measured by the Caton-Deschamps ratio ( P = .29 for sex, P = .49 for age), Insall-Salvati index ( P = .15 for sex, P = .33 for age), or patellotrochlear index ( P = .67 for sex, P = .49 for age). The congruence angle ( P = .81 for sex, P = .06 for age) and trochlear morphology as measured by the sulcus angle ( P = .64 for sex, P = .45 for age) were similar between groups., Conclusions: Patellar height and trochlear morphology did not differ by sex or age among patients whose first-time patellar dislocations resulted in an MPFL tear. In addition, the location of the tear did not appear to vary by sex or age.

Background: Surgical treatment of young patients with recurrent lateral patella dislocation (RLDP) is often recommended because of loss of knee function that compromises their level of activity or even their daily life functioning. This situation is comparable to young patients with an anterior cruciate ligament (ACL) rupture. The purpose of this study was therefore to explore the time from injury to surgery and the pre-operative symptoms and knee function of young RLPD patients scheduled for stabilizing surgery and compare this group to age and sex-matched ACL-deficient patients., Method: Forty-seven patients with unilateral RLPD listed for isolated medial patellofemoral ligament reconstruction were included in the study (RLPD-group). This group was compared to an age, sex and BMI matched ACL patient group obtained from the Norwegian knee ligament registry (ACL-group) for the following outcome measures: the knee injury and osteoarthritis outcome score (KOOS) assessed on the day of surgery and time from injury to surgery., Results: The RLPD-group scored significantly lower than the ACL-group for the three KOOS subscales "Pain" (73.6 vs. 79.8, p < 0.05), "Symptoms" (71.7 vs. 79.3, p < 0.05) and "ADL" (84.7 vs 89.5, p < 0.05). The lowest KOOS values were found for Sports/Recreation (53.5 vs. 51.3, p = 0.65) and Quality of life (37.6 vs. 36.7, p = 0.81). The average time from primary injury to surgery was 6 months for the ACL group and 31 months for the RLPD group., Conclusion: RLPD affected knee function as much as ACL deficiency, and was associated with more pain. Still the RLDP patients waited on average 5 times longer for surgery., Trial Registration: The patients with RLPD consisted of patients who were examined for possible recruitment for a concurrent prospective randomized controlled trial comparing conservative treatment and isolated surgical medial patellofemoral ligament (MPFL) reconstruction (Clinical trials no: NCT02263807 , October 2014).

Rationale: Upper pole sleeve fractures of the patella are rare in adolescents; however, they are serious injuries that require early diagnosis and treatment., Patient Concerns: We present a rare case of a 15-year-old girl who suffered a sleeve fracture at the superior pole of the right patella. The patient had a history of dislocation of the patella 2 weeks ago. Physical examination showed tenderness on palpation over the upper pole of the patella and absence of active movement of the knee accompanied by swelling and joint effusion. A plain radiograph showed an avulsed fragment of the superior pole of the patella., Diagnoses: Magnetic resonance imaging showed a superior pole patellar avulsion fracture and dysfunction of the knee extensor mechanism., Interventions: Under general anesthesia, the patient underwent open surgery for reduction of the patellar fracture and reconstruction of the knee extension apparatus through an anterior approach., Outcomes: Six months after the operation, the knee function was fully restored, there was absence of pain and swelling, and the patient was able to return to sports., Lessons: Upper pole sleeve fracture of the patella is usually serious and it needs to be diagnosed and treated as soon as possible, the sports medicine practitioner must be aware of this type of injury.

Femoral nerve palsy with concomitant patellar dislocation is a rare clinical entity that has not previously been well documented. The authors present the case of a 16-year-old female ballet dancer who sustained a patellar dislocation with concomitant femoral nerve palsy. She experienced muscle weakness after the initial injury and developed neuropathic symptoms through the anterior left thigh. The patient exhibited muscle atrophy in her left lower extremity verified by circumferential thigh measurements as well as magnetic resonance imaging showing clear atrophy of the anterior compartment. Electromyography of the left lower extremity verified femoral neuropathy. Gross improvements in muscle strength were noted during the year following initial injury, but circumferential thigh differences persisted. Two years after initial injury, repeat electrodiagnostic studies had normal findings, but subjective left quadriceps weakness persisted and the patient was unable to return to competitive dance. [Orthopedics. 2019; 42(2):e273-e275.]., (Copyright 2018, SLACK Incorporated.)

Introduction: Medial patellofemoral ligament reconstruction (MPFLR) is regularly combined with a tibial tuberosity transfer (TTT) in cases of recurrent patellar instability with underlying structural deformity. However, these indications for a TTT have recently come into question. This study aimed to assess the traditional indications by comparing the outcomes of isolated and combined MPFLR for the treatment of recurrent lateral patellar dislocation., Methods: A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included studies were those which reported the outcomes of either isolated or combined or both MPFLR. Studies were required to report at least one of the following: redislocation rate, revision due to instability, or the Kujala score., Results: We found no difference between isolated and combined MPFLR in terms of redislocation ( p = 0.48), revisions due to instability ( p = 0.36), positive apprehension tests ( p = 0.25), or the Kujala score ( p = 0.58). Combined reconstruction presented more complications compared to isolated procedures ( p = 0.05). Subgroup analysis revealed no significant difference between studies investigating isolated medial patellofemoral ligament reconstruction MPFLR performed in patients with normal tibial tuberosity-trochlear groove (TT-TG) distances only or in patients with both normal and elevated TT-TG distances., Conclusions: According to the published data, there is no difference in outcomes between isolated and combined MPFLR. Underlying structural deformity did not demonstrate any significant effect on the success of the isolated MPFLR. Although there are definite indications for combined reconstruction, the current evidence suggests that our inclusion criteria may not be entirely correct. Further study is required to clarify and refine the true indications for combined MPFLR., Level of Evidence: III, meta-analysis of nonrandomized studies.

Purpose: To investigate the effects of early patellar dislocation on the tibial tubercle location., Methods: Sixty knees from 30 healthy 1-month-old New Zealand white rabbits were randomly divided into two groups of 30 knees each. Group A (control group) comprised the left knees, which underwent no surgical procedures. Group B comprised the right knees, which underwent patellar dislocation surgery. Computed tomography (flexion 0°) was performed preoperatively and 6 months post-operatively. Measurements included the tibial tuberosity-trochlear groove distance (TT-TG) and tibial tubercle lateralization., Results: No significant difference in the TT-TG or tibial tubercle lateralization was found between the two groups preoperatively. Six months post-operatively, however, the mean TT-TG in Group A (no patellar dislocation) and Group B (patellar dislocation) was 1.0 ± 0.4 and 3.0 ± 0.7 mm, respectively (p < 0.05). The mean tibial tubercle lateralization also showed a significant difference between Groups A and B at 6 months post-operatively (0.5 ± 0.1 and 0.6 ± 0.0, respectively; p < 0.05)., Conclusions: Early patellar dislocation can lead to tibial tubercle lateralization and an increased TT-TG. Clinically, early intervention for adolescent patients with patellar dislocation will be important., Level of Evidence: Prospective comparative study, Level II.

Congenital dislocation of the patella is a rare and difficult pathology to treat. We present a case of bilateral congenital dislocation of the patella with synostosis of proximal tibiofibular and proximal radioulnar joints without genu valgum deformity of both knees in a 30-year-old man. To our knowledge, congenital dislocation of the patella associated with synostosis of proximal tibiofibular and proximal radioulnar joints has not been reported in the literature yet.

Osteochondral injuries in pediatric patients may occur as a result of a traumatic injury or secondary to an osteochondritis dissecans (OCD) lesion. Lateral patella dislocation is a common traumatic cause of osteochondral injury that typically occurs at the medial facet of the patella or at the lateral aspect of the distal femur. Multiple theories have been proposed for the cause of an OCD lesion in the knee, including trauma or repetitive microtrauma, local vascular insufficiency, and family history. The most "classic" location for OCD lesions of the knee is the lateral aspect of the medial femoral condyle of the distal femur. Multiple treatment options are available for both traumatic osteochondral injuries and OCD lesions, with important determining factors of treatment being skeletal maturity of the patient, instability of the fragment, lesion location, and size of the lesion. Nonsurgical management is appropriate in some situations. Surgical options range from simple fragment excision to internal fixation of the fracture fragment to more complex cartilage restoration or replacement procedures. This special focus section will discuss the diagnosis and treatment options for traumatic osteochondral knee injuries, including the subset secondary to juvenile OCD lesions., Competing Interests: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Introduction: Although several surgical treatments for patellar instability with patella alta have been reported, the clinical outcomes and optimal surgical procedures for patellar instability with patella alta in middle-aged patients are still controversial. We hypothesized that optimal surgical procedures for patellar instability with patella alta in middle-aged patients may induce good clinical outcomes with better patellofemoral geometry., Materials and Methods: Twelve middle-aged patients with a mean age of 44 years (range: 40-55 years), who presented with patellar instability and patella alta, were treated with a combination of several surgeries, such as medial patellofemoral ligament (MPFL) reconstruction, trochleoplasty, lateral release, and three-dimensional transfer of the tibial tuberosity, based on a surgical algorithm. Patellar position and clinical outcomes were evaluated postoperatively. The mean follow-up time was 41.5 months (range: 24-72 months)., Results: Patellar position altered from 1.31 (1.21-1.53) preoperatively to 0.88 (0.69-1.06) postoperatively on the Caton-Deschamps Index (p<0.01). The tibial tuberosity-trochlear groove (TT-TG) distance altered from 21.8mm (20.1-25.8mm) to 10.3mm (5.1-14.7mm), and patellar tilt ranged from 28.1° (21-40°) to 14.6° (5-28°), respectively (p<0.01). Clinical outcomes on the Lysholm and Kujala scales improved from 43.1 and 38.4 to 86.7 and 78.3, respectively, at final follow-up (p<0.01). Surgical treatment that included trochleoplasty resulted in better outcomes than other surgical combinations without trochleoplasty (p<0.05). Sulcus angle and postoperative patellar tilt improved more in those who underwent trochleoplasty than in those who did not (p<0.05)., Discussion: Surgical treatment for patellar instability with patella alta in middle-aged patients resulted in improved clinical outcomes. In particular, a combination surgery including trochleoplasty resulted in the greatest improvement in case of severe trochlear dysplasia., Level of Evidence: IV. Retrospective case series study., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Purpose: The primary goal was to describe the injury patterns in a population of primary (first time) lateral patellar dislocators (LPD) to lend clarity to commonly held notions about injury patterns in this population., Methods: A prospective study identifying patients presenting with LPD between 2008 and 2012. Inclusion criteria were a history and physical exam consistent with primary LPD, and an MRI consistent with the diagnosis without other significant ligamentous injury. On MRI, location of cartilage, medial patellofemoral ligament (MPFL) injury, and bone bruising were noted. Severity was categorized as partial or complete for MPFL and cartilage lesions. Anatomic patellar instability risk factors (patella alta, trochlear dysplasia, increased TT-TG, and lateral patella tilt) were recorded and compared to the injury patterns., Results: This study involved 157 patients; 107 patients were skeletally mature. Of the 157 patients, 26 had surgery for this injury due to clinician-perceived need for cartilage debridement. MPFL injury severity was complete rupture (N = 69, 44%), partial (N = 67, 43%), and none (N = 19, 13%). MPFL injury location was isolated femoral (N = 16, 10%), isolated patella (N = 26, 17%), isolated mid-substance (0%), multiple locations (N = 95, 61%), and none (N = 20, 13%). Chondral injury location was patella (N = 67, 43%), lateral femoral condyle (N = 11, 7%), multiple locations (N = 53, 34%), and none (N = 26, 17%). A majority (61%) of patellar chondral lesions were at its inferomedial aspect; all medial patellar retinacular partial injuries involved the inferomedial aspect of the patella, consistent with the insertion of the medial patellotibial ligament (MPTL). Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. No clear relationship was found between/across the location and/or severity of bone bruising, MPFL, or chondral injury., Clinical Relevance: Underlying anatomic patellar instability risk factors defined by MRI, do not predict injury patterns. MPFL and chondral injury, as well as bone bruising, are common following LPD. The medial patellotibial ligament is torn in patellar-based medial retinacular injuries, based on MRI injury location. Skeletal immaturity plays a role in the location of the injury pattern with isolated patellar-based MPFL/chondral injury being more common in the skeletally immature patient. Sex does not appear to be a factor in injury patterns after primary LPD. Knowledge of these injury trends will help focus the clinician in injury evaluation when managing primary patellar dislocations., Level of Evidence: Case series, Level IV.

Objective: To study clinical effects of multi-point fixation with bioabsorbable cartilage screws for the treatment of osteochondral fracture caused by patellar instability., Methods: During the period from August 2014 to Steptember 2016, there were 21 patients with osteochondral fracture caused by patellar dislocation, including 7 males and 14 females, ranging in age from 12 to 42 years old, with an average of 27 years old. During the operation, free fractures fragments of cartilage were found with a open surgery, and the patients were treated with fixation by absorbable cartilage screws combined with lateral retinaculum release and medial retinaculum shrinkage. The Lysholm scoring scale was used to evaluate the knee joint functions before and after operation. The retrospective study analyzing the data was carried out., Results: All the patients underwent successful surgeries and were followed up with a mean period of 12 months(ranged, 8 to 22 months). The CT and X-ray examinations were performed after the operation which showed the fracture fragments were on good positon. The exercise level in all the patients basically returned to the pre-injury level. The postoperative Lysholm score was 86.11±4.97., Conclusions: The absorbable cartilage nail can effectively fix the free cartilage fragments of the osteochondral fracture due to the patellar instability, which is a simple operation, and worthy of clinical promotion., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose.

Isolated chondral defects have a limited capacity to heal and predispose to the development of osteoarthritis. Current surgical management can be unpredictable in outcome. Improved understanding of the action of mesenchymal stem cells (MSCs) has seen renewed interest in their role in cartilage repair. A 26-year-old athlete presented with a post-traumatic, isolated patella chondral defect. The patient underwent an arthroscopy with removal of a chondral loose body. After failure to symptomatically improve 12 months following surgery, the patient received intra-articular autologous adipose-derived mesenchymal stem cell (ADMSC) therapy., Competing Interests: Competing interests: JF is affiliated with Magellan Stem Cells and is a member of Magellan Stem Cells Clinical and Scientific Advisory Board. KS is affiliated with Magellan Stem Cells and is the Chief Scientific Officer of Magellan Stem Cells. AT is affiliated with Magellan Stem Cells., (© BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)