Explore the vast range of titles available.

Background: Particulated juvenile articular cartilage (PJAC) implantation has demonstrated promising early results in the treatment of symptomatic articular cartilage defects of the patella. However, some uncertainty exists regarding the stability of this cell-based technique in lesions that are not well contained or shouldered. Purpose: To compare clinical and magnetic resonance imaging (MRI) outcomes of PJAC treatment in shouldered versus unshouldered full-thickness cartilage defects of the patella. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective review of prospectively collected data from an institutional knee registry was conducted to identify patients treated with PJAC for full-thickness symptomatic patellar cartilage lesion between January 2009 and August 2017. Cartilage defects were graded arthroscopically according to the Outerbridge classification and characterized as shouldered or unshouldered. For the primary outcome, postoperative MRI studies were read by a musculoskeletal fellowship-trained radiologist who characterized the percentage of fill based on both coronal and sagittal images. Patient-reported outcome measures (PROMs) were obtained at baseline and 2-year follow-up. MRI and PROM results were compared between the shouldered and unshouldered cohorts. Results: A total of 64 knees in 60 patients (mean age, 26.3 ± 7.6 years) were identified, of which 62 (97%) knees underwent a concomitant patellar stabilization or offloading procedure. There were 32 (50%) shouldered and 32 (50%) unshouldered defects. On postoperative MRI, 68.8% of shouldered lesions demonstrated 67% to 100% fill, compared with 59.4% of unshouldered lesions; 12.5% of shouldered lesions and 15.6% of unshouldered lesions demonstrated 34% to 66% fill; and 18.8% of shouldered lesions and 25.0% of unshouldered lesions demonstrated 0% to 33% fill (P = .604). At 2 years, significant improvements were observed in Knee Injury and Osteoarthritis Outcome Score (KOOS) Quality of Life (QOL) (23.1 to 65.3; P < .001), International Knee Documentation Committee (IKDC) (41.2 to 76.0; P < .001), KOOS Physical Function Shortform (PS) (34.8 to 13.9; P < .001), Kujala (52.0 to 87.5; P < .001), 12-Item Short Form Survey (SF-12) Physical Health (39.5 to 51.5; P < .001), Veterans Rand 12 Item Health Survey (VR-12) Physical Health (40.7 to 52.8; P < .001), Veterans Rand 6D (0.66 to 0.79; P < .001), SF-12 Mental Health (48.9 to 53.4; P = .015), and VR-12 Mental Health (49.4 to 54.0; P = .019) values. No significant change was observed in Pediatric Functional Activity Brief Scale score (9.1 to 10.3; P = .384). All PROMs were equivalent between shouldered and unshouldered defects at the 2-year follow-up (P = .318-.980). There was a greater improvement in both KOOS PS (27.2 vs 10.7; P = .015) and Kujala (44.3 vs 26.9; P = .039) values from baseline to the 2-year follow-up in the shouldered group. Conclusion: PJAC implantation with concomitant patellar stabilization led to significantly improved PROMs for both shouldered and unshouldered patellar cartilage lesions over time. Additionally, minimal differences were observed between shouldered and unshouldered defects treated with PJAC at the 2-year follow-up.

Background: Cartilage restoration procedures for patellar cartilage defects have produced inconsistent results, and optimal management remains controversial. Particulated juvenile articular cartilage (PJAC) allograft tissue is an increasingly utilized treatment option for chondral defects, with previous studies demonstrating favorable short-term outcomes for patellar chondral defects. Purpose: To identify whether there is an association between defect fill on magnetic resonance imaging (MRI) with functional outcomes in patients with full-thickness patellar cartilage lesions treated with PJAC. Study Design: Case series; Level of evidence, 4. Methods: A retrospective review of prospectively collected data was conducted on patients treated with PJAC for a full-thickness symptomatic patellar cartilage lesion between March 2014 and August 2019. MRI was performed for all patients at 6, 12, and 24 months postoperatively. Patient-reported outcome measures (PROMs) were obtained preoperatively and at 1, 2, and >2 years postoperatively. Clinical outcome scores—including the International Knee Documentation Committee (IKDC) score, the Kujala, the Knee injury and Osteoarthritis Outcome Score–Physical Function Short Form (KOOS-PS), the Knee Injury and Osteoarthritis Outcome Score–Quality of Life (KOOS-QoL), and the Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS)—were analyzed and evaluated for a relationship with tissue fill on MRI. Results: A total of 70 knees in 65 patients (mean age, 26.6 ± 8.1 years) were identified, of which 68 knees (97%) underwent a concomitant patellar stabilization or offloading procedure. Significant improvements were observed on all postoperative PROM scores at the 1-, 2-, and >2-year follow-up except for the Pedi-FABS, which showed no significant difference from baseline. From baseline to the 2-year follow-up, the KOOS-QoL improved from 24.7 to 62.1, the IKDC improved from 41.1 to 73.5, the KOOS-PS improved from 35.6 to 15, and the Kujala improved from 52 to 86.3. Imaging demonstrated no difference in the rate of cartilage defect fill between the 3-month (66%), 6-month (72%), 1-year (74%), and ≥2-year (69%) follow-ups. No association was observed between PROM scores and the percent fill of cartilage defect on MRI at the 1- and 2-year follow-up. Conclusion: PROM scores were significantly improved at the 2-year follow-up in patients who underwent PJAC for full-thickness patellar cartilage defects. On MRI, a cartilage defect fill of >66% was achieved by 3 months in most patients. In our sample, PROM scores were not significantly associated with the defect fill percentage at the short-term follow-up.

Objectives: Unique challenges exist in treating patellar cartilage defects such as the contour of the articular surface and the high dynamic shear and compressive forces at the trochlear articulation. When considering restoration techniques osteochondral autograft or allograft can be used when the underlying bone is also involved but for isolated chondral defects, cell-based restoration is the standard of care. Previous literature has demonstrated that success of these cell-based therapies depends on a fully shouldered, stable rim of healthy cartilage to achieve repair stability. More recently, particulated juvenile articular cartilage (PJAC), minced hyaline cartilage from young donors, has demonstrated promising and practical results in the treatment of symptomatic articular defects of the patella and other surfaces. The newer cell-based techniques are more stable than previous options such as autologous chondrocyte implantation (ACI). The purpose of this study is to compare clinical outcomes of PJAC in patients with shouldered versus unshouldered full-thickness cartilage defects of the patella. We hypothesized that there will be no significant difference in short-term clinical outcomes and radiographic cartilage fill between shouldered and unshouldered lesions. Methods: A retrospective review of prospectively collected data was conducted on patients treated with PJAC for a full-thickness symptomatic patellar cartilage lesion between March 2014 and August 2019. Magnetic resonance imaging (MRI) was performed for all patients at 6, 12, and 24 months postoperatively and analyzed for percent fill, categorized by 0% to 33%, 34% to 66%, and 67% to 100% fill. Patient-reported outcome measures (PROMs) were obtained preoperatively and at 1, 2 and >2 years postoperatively. Arthroscopic images were independently assessed, and cartilage defect characteristics were documented as shouldered or unshouldered by an orthopaedic surgery resident and an orthopaedic surgery sports fellow. Percent fill on MRI and clinical outcome scores (International Knee Documentation Committee, Kujala, Knee injury and Osteoarthritis Outcome Score – Physical Function Short-Form [KOOS-PS], Knee injury and Osteoarthritis Outcome Score – Quality of Life, The Hospital for Special Surgery Pediatric Functional Activity Brief Scale) were analyzed and correlated with the shouldered or unshouldered classification of the lesions. Results: Between March 2014 and August 2019, a total of 70 lesions in 65 patients were treated with PJAC for patellar cartilage lesions. The mean patient age was 26.6 years old (range, 14 – 51) and 76% (n = 53) were female. Twenty-five (36%) knees had undergone prior surgery and average symptom duration was 7.5 years. The average patellar lesion size was 277 mm2 (range, 77 – 800 mm2), the average number of allografts packets used was 2.4 (range, 1 – 5), and the average donor age was 46.1 months (range, 1 – 120). Arthroscopic pictures were available for 64 out of 70 lesions. There was perfect inter-rater reliability of whether the lesions were considered to have a continuous, stable rim (shouldered) or not (unshouldered). Thirty-two lesions were shouldered and the remaining 32 lesions were unshouldered according to their intraoperative pictures. Patients with shouldered lesions reported a significantly lower duration of symptoms than those with unshouldered lesions (5.29 ± 7.12 years vs.10.11 ± 9.85 years, p < 0.05). Patients with shouldered lesions were also significantly more likely to have a prior knee surgery (p < 0.05). Patients did not differ significantly by MRI percent fill in the shouldered versus unshouldered groups (Figure 1). There were no significant differences in baseline, 1-, or 2-year patient-reported outcomes based between patients with shouldered and unshouldered lesions (Table 1). The only statistically significant difference in outcomes was a lower score for KOOS-PS in the unshouldered group at >2 years compared to the shouldered group (p < 0.05), and in the change in KOOS-PS from baseline to 2-years between the 2 groups (p <0.05). Conclusions: Patellofemoral joint cartilage defects are difficult to treat due to their unique thickness and topography. Historically, emphasis has been placed on having a stable, fully shouldered defect in order to achieve success of repair with microfracture or ACI. However, with the increased stability of newer cell-based treatments, these unshouldered cartilage lesions do well both clinically and radiographically. Our study found no significant differences between the shouldered and unshouldered groups with regard to both clinical outcomes as well as radiographic cartilage fill. This suggests that, with newer cartilage restoration techniques, whether a lesion is shouldered does not affect the outcomes achieved by these procedures. Figure 1

Abstract The aim of this observational study was to examine differences in milk fatty acid (FA) concentrations for different metabolic health statuses and for associated factors—specifically to examine with which FA concentrations an increased risk for developing a poor metabolic adaptation syndrome (PMAS) was associated. During weekly visits over 51 wk, blood samples were collected from cows between 5 and 50 days in milk. The farmer collected corresponding milk samples from all voluntary milkings. The analysis was performed on n = 2,432 samples from n = 553 Simmental cows. The observations were assigned to five different cow types (healthy, clever, athletic, hyperketonemic, and PMAS, representing five metabolic health statuses), based on the thresholds of 0.7 mmol/L, 1.2 mmol/L, and 1.4 for the concentrations of β-hydroxybutyrate and nonesterified fatty acids and for the milk fat-to-protein ratio, respectively. Linear regression models using the predictor variables cow type, parity, week of lactation, and milk yield as fixed effects were developed using a stepwise forward selection to test for significant associations of predictor variables regarding FA concentrations in milk. There was a significant interaction term found between PMAS cows and parity compared to healthy cows for C18:1 (P < 0.001) and for C18:0 (P < 0.01). It revealed higher concentrations for PMAS in primiparous and multiparous cows compared to healthy cows, the slope being steeper for primiparous cows. Further, an interaction term was found between PMAS cows and milk yield compared to healthy cows and milk yield for C16:0 (P < 0.05), revealing a steeper slope for the decrease of C16:0 concentrations with increasing milk yield for PMAS compared to healthy cows. The significant associations and interaction terms between cow type, parity, week of lactation, and milk yield as predictor variables and C16:0, C18:0, and C18:1 concentrations suggest excellent opportunities for cow herd health screening during the early postpartum period. The significant associations and interaction terms between cow type (healthy, clever, athletic, hyperketonemic, and poor metabolic adaptation syndrome, representing five metabolic health statuses), parity, week of lactation, and milk yield as predictor variables and C16:0, C18:0, and C18:1 concentration suggest excellent opportunities to improve cow herd health screening during the early postpartum period regarding metabolic health. Lay Summary The focus of this observational study was to examine with which milk fatty acid (FA) concentrations an increased risk for developing a poor metabolic adaptation syndrome (PMAS) was associated. Poor metabolic adaptation syndrome is a condition to which high-yielding dairy cows are most susceptible during the first weeks after calving. Further, relevant associated factors (parity, week of lactation, and milk yield) were examined. The collected milk and corresponding blood samples were assigned to five different cow types (healthy, clever, athletic, hyperketonemic, and PMAS, representing five metabolic health statuses), based on the concentrations of β-hydroxybutyrate and nonesterified FA and on the milk fat-to-protein ratio. There was a significant interaction term found between PMAS cows and parity compared to healthy cows. The analyses revealed higher FA concentrations for PMAS primiparous and multiparous cows compared to healthy cows, with the slope being steeper for primiparous cows. Further, an interaction term was found between PMAS cows and milk yield compared to healthy cows and milk yield, revealing a steeper slope for the decrease of the FA C16:0 concentrations with increasing milk yield for PMAS compared to healthy cows. The significant associations and interaction terms between cow type, parity, week of lactation, and milk yield suggest excellent opportunities for cow herd health screening during the early postpartum period.

Objectives: It is not currently understood which subset of patients with recurrent patellofemoral instability require concomitant bony realignment procedures in addition to a soft tissue stabilization. Additionally, the optimal timing of surgical intervention is not well defined by current literature and can be dictated by the skeletal maturity of a patient. If the patient’s complete pathology is not addressed at their primary procedure, there can be a high risk of recurrent instability necessitating revision surgery. It is not known if the outcomes of medial patellofemoral reconstruction with concomitant tibial tubercle osteotomy (MPFL+TTO) performed as a revision procedure equate the outcomes of MPFL+TTO performed in the primary setting. This study compares patients who underwent primary MPFL+TTO versus those who underwent the same procedure in the revision setting. Methods: Patients who underwent a MPFL+TTO from March 2014 to December 2018 were identified from an institutional patellofemoral registry. Patients were separated into two groups, those undergoing a primary MPFL+TTO and those undergoing a MPFL+TTO after a previously failed surgical attempt for patellar stabilization. Baseline demographic, radiographic, and knee-specific patient reported outcome measures (PROMs) including KOOS QOL, Pedi-Fabs, IKDC, KOOS-PS, and Kujala were collected prior to surgery and at 1- and 2-years following surgical intervention. Return to sport (RTS) rates and recurrent instability events were also collected. Results: 92 knees (84 patients) were included; 59 in the primary group and 33 in the revision group. No differences were identified between the groups with respect to sex (85% vs. 82%, p=0.715), age (23.7 vs. 22.5, p=0.468), BMI (26.3 vs 24.5, p=0.144), TT-TG (20.3 vs 19.3, p=0.238), or patella alta (33% vs 19%, p=0.354). Previous procedures in the revision cohort included 12 MPFL reconstructions, 3 tibial tubercle transfers, 16 lateral releases, 9 imbrications/reefings/plications, 7 loose body removals and 9 chondroplasties. 53 (90%) patients in the primary group and 29 (88%) patients in the revision group had a minimum of 2-year follow-up. There was no difference between the groups for recurrent dislocation (4% vs 0%, p=0.547), recurrent subluxation (9% vs 0%, p=0.162) and RTS (88% vs 83%, p=0.713). In regard to RTS, 79% of the primary surgery group and 71% of the revision group returned at an equal or higher level (p=0.461). At baseline, the primary group had a higher IKDC (42.0 vs 34.7, p=0.049). At 2-year follow-up both groups had significant improvements from baseline in all PROMs, except Pedi-FABS which had no change. There was no difference between groups at 2-year follow-up in KOOS-QoL (60.8 vs 51.1, p=0.186), Pedi-FABS (8.0 vs 7.3, p=0.796), IKDC (75.2 vs 67.7, p=0.206), KOOS-PS (15.8 vs 20.9, p=0.379), and Kujala (86.5 vs 77.9, p=0.143). Conclusions: Management of patellofemoral instability is complex. The optimal timing of surgical intervention and whether a concomitant bony realignment procedure is indicated has yet to be elucidated. This study demonstrates that primary MPFL+TTO versus revision MPFL+TTO have comparable objective and subjective outcomes at short term follow-up. Ongoing data collection for this patient cohort will determine whether these results are sustained at long term follow-up.

Objectives: Treatment options for articular cartilage lesions of the patella have evolved over the past several years due to the development of novel cell-based cartilage restoration techniques, including particulated juvenile allograft cartilage (PJAC) and matrix-induced autologous chondrocyte implantation (MACI). The objective of this study was to evaluate the cost -effectiveness of these modalities in the management of patellar cartilage defects. Methods: A Markov state-transition model was utilized to evaluate the cost-effectiveness of three strategies for patients with patellar chondral lesions: (1) nonoperative management, (2) PJAC, and (3) MACI. Probabilities, health utilities, and costs of surgical procedures and rehabilitation protocols were derived from institutional data and literature review. Effectiveness was assessed using quality-adjusted life-year (QALY). Cost-effectiveness was evaluated from societal and payer perspectives over a 15-year time horizon. The principal outcome measure was the incremental cost-effectiveness ratio (ICER). Sensitivity analyses were performed on pertinent model parameters to assess their effect on base case conclusions. Results: From a societal perspective, nonoperative management, PJAC, and MACI cost $4,140, $52,683, and $83,073 respectively. Nonoperative management, PJAC, and MACI were associated with 4.91, 7.07, and 7.79 QALYs gained, respectively. Therefore, PJAC and MACI were cost-effective relative to nonoperative management (ICERs $22,527/QALY and $27,456/QALY, respectively; Figure 1). Although MACI was more cost-effective than PJAC in the base case, this was strongly sensitive to the estimated probabilities of full versus intermediate benefit following PJAC and MACI (Table 1). If the probabilities of full and intermediate benefit following PJAC were assumed to be the same as those following MACI (i.e., PJAC and MACI were equally effective), then PJAC dominated MACI by being cheaper and more effective. At a $100,000/QALY willingness-to-pay threshold, MACI, PJAC, and nonoperative management were the preferred strategies in 63%, 33%, and 4% of the Monte Carlo probabilistic sensitivity analyses, respectively (Figures 2 and 3). Similar results were seen from a payer perspective. Conclusions: In the management of symptomatic patellar cartilage defects, PJAC and MACI were both cost-effective compared to nonoperative treatment in the management of symptomatic patellar cartilage defects; however, MACI was the preferred strategy in our base-case analysis. The cost-effectiveness of PJAC compared to MACI depended heavily on the probability of achieving full versus intermediate benefit after PJAC and MACI.

Objectives: Medial patellofemoral ligament (MPFL) reconstruction is the standard of care surgical treatment for recurrent patellar instability. Recurrent patellar instability is common after a first-time dislocation in the skeletally immature population. Adult-type reconstruction techniques are often avoided in skeletally immature patients due to the proximity of the femoral insertion of the MFPL to the distal femoral physis. It is currently unclear how outcomes of MPFL reconstruction in skeletally immature patients compare to those for skeletally mature patients. The objective of this study is to present the outcomes of isolated MPFL reconstruction in skeletally immature patients and compare their findings to a skeletally mature population. Methods: Patients were identified from an institutional patellofemoral registry who underwent isolated MPFL reconstruction from March 2014 to July 2018. Demographic, radiographic, and knee-specific patient-reported outcome measures (PROMs) were collected prior to surgery. Follow-up data collection included knee surveys collected at 1 and 2-years following MPFL reconstruction. Additionally, return to sport rates and episodes of re-dislocations were also collected. Comparisons of demographic and clinical data were made between skeletally immature and mature patients. Sub-analysis was performed on outcomes in skeletally immature patients who underwent MPFL reconstruction where the graft was placed distal to the physis to avoid the growth plate versus those who had standard placement of the graft. Baseline factors were analyzed using independent samples t-tests or chi-square analysis. Longitudinal analysis of knee PROMs was conducted using generalized estimating equation (GEE) modeling. Statistical significance was defined as p-values of 0.05 or less. Results: The study cohort included 107 patients (25 skeletally immature, 82 skeletally mature). Mean age of the study groups was 13.8 years in the immature group (range 11-15) and 21.3 in the mature group (range 14-34). No differences in sex (72% female in both groups) or obesity (0% vs. 8%) was observed between immature and mature patients. Radiographic measures of Caton-Deschamps Index (1.18 in both groups), TT-TG (14.9 vs. 14.8), and Dejour classification (P=0.328) also saw no differences between groups. Longitudinal outcomes in KOOS QoL, IKDC, KOOS PS, and Kujala surveys found no differences between immature versus mature patients over time. However, higher PediFABS was observed in the immature group versus mature at baseline (21.6 vs. 11.9, P<0.001), 1-year (18.1 vs. 11.5, P=0.006), and 2-years (22.4 vs. 11.5, P=0.003). Low incidence of post-operative dislocation and a high return to sport rate was observed in both skeletally immature and mature patients. No statistical differences were observed in all outcomes between immature patients who had standard graft placement and those where the graft was placed distal to the physis. Conclusion: Controversy exists in how best to treat the skeletally immature patient with recurrent lateral patellar instability. Due to the risk of injury to the growth plate, many believe it is best to wait to stabilize these patients until they have stopped growing. However, given the high risk of cartilage injury with each dislocation and the long term sequelae of such injuries in these young knees, the risk of waiting may be high. This study demonstrates similar outcomes and recurrence rates in skeletally immature patients with those seen in the mature population without disturbance or injury to the growth plates. Figure 1. Figure 2.

Objectives: It remains unclear which subset of patients with recurrent patellofemoral instability would benefit from a concomitant bony realignment procedure in addition to a medial patellofemoral ligament (MPFL) reconstruction. The purpose of this study is to provide midterm results on previously reported patient reported outcomes (PRO), return to sport (RTS) and imaging measurements collected for patients who underwent an isolated MPFL reconstruction as part of an ongoing prospective trial. This includes minimum 5-year outcomes data on a cohort of 55 patients as well as 2-year outcomes data on an expanded cohort of 121 patients. Methods: Patients with recurrent patellar instability who did not meet exclusion criteria were prospectively enrolled in an institutional registry beginning in March 2014. Exclusion criteria included patients with a prior history of a patellar stabilization procedure, an off-loadable (inferior/lateral) Outerbridge Grade IV chondral defect, obligatory dislocators (patients who require patellar dislocation in order to achieve full knee extension) or patients with a “Jumping J” sign and patients who reported anterior knee pain as more than 50% of their chief complaint. All patients who were not excluded by the above criteria underwent primary, unilateral, isolated MPFL reconstruction regardless of their bony anatomy (tibial tubercle - trochlear groove (TT-TG), trochlear morphology, trochlear depth, or patellar height) for treatment of recurrent patellar instability. Patient data including PROs, episodes of recurrent instability or dislocation, and ability to return to sport (RTS) was obtained annually. Radiographic MRI measurements including TT-TG, Caton-Deschamps Index (CDI), Patellar Trochlear Index (PTI), Trochlear Depth Index (TDI), Patellar Tendon to Lateral Trochlear Ridge (PT-LTR) and Tibial Tubercle to Lateral Trochlear Ridge (TT-LTR) were obtained at baseline. Results: 138 patients (72% female; mean age 20.1 ± 6.1 years) underwent isolated MPFL reconstruction between March 2014 and December 2019. 55 patients reached the ≥5-year postoperative time point, of which 40 (72%) completed follow-up PROs. 121 patients reached the ≥2-year postoperative time point, of which 89 (74%) completed follow-up PROs. 99% (n=136) of patients at 2 years and 96% (n=132) of patients at ≥ 5 years had no self-reported post-operative patellofemoral instability: 6 patients (4%) reported recurrent instability at a mean of 3.0 ± 0.7 years postoperatively. Activities during which failure occurred included jumping on a trampoline, dancing, and playing lacrosse. Preoperatively, 100 (72%) patients participated in sports or physical activity, of which 87 reported return to sport (87%). All patients that returned to sport did so within 24 months postoperatively with a mean RTS of 9.3 months. KOOS-Qol, Pedi-Fabs, IKDC, KOOS-PS and Kujala PROS are reported in Table 1. The mean TT-TG was 15.1 ± 4.9 mm (1.90 to 27.2 mm), mean CDI was 1.14 ± 0.16 (0.72 to 1.65), mean PTI was 46.9 ± 15.1% (13 to 100%) and mean trochlear depth was 2.5 ± 1.2 mm (-1.55 to 5.15 mm). Trochlear dysplasia, defined as a TDI < 3 mm, was present in 77 (56%) of patients. The mean measure of extensor mechanism containment, TT-LTR, was -8.4 ± 5.7 mm (-24.0 to 3.20 mm) and the rate of TT-LTR within 1 mm, found to be predictive of recurrent instability, was 8% (n=11). The mean PT-LTR, a measurement of lateral patellar tracking, was 5.7 ± 6.2 mm (-5.70 to 21.1 mm). The six patients who experienced recurrent instability after an isolated MPFL reconstruction had a mean CDI of 1.19 and a mean TT-TG of 18.75. Individual imaging data for these six patients can be seen in Table 2. Conclusions: Midterm outcomes for patients who underwent isolated MPFL reconstruction (within strict exclusion criteria parameters) are shown to be favorable and maintained at 5 years. Additionally, the outcomes for the expanded cohort of patients with a minimum of 2-year follow up supports the previously published results. Most athletes were able to return to sport. Completion of this study enrollment with long term follow up will allow for more robust assessment of long-term outcomes and incidence of recurrent instability after isolated MPFL reconstruction. The ultimate goal of this work is the creation of a predictive model utilizing the bony and clinical characteristics of those patients who sustain recurrent instability in order to better predict who might benefit from additional bony realignment procedures at the time of their index procedure. Table 1. Patient Reported Outcomes at Baseline, 2 years and ≥ 5 years Table 2. Radiographic Measurements for Patients with Recurrent Patellar Instability after Isolated MPFL Reconstruction

Objectives: The purpose of this study is to provide an objective analysis of patient demographics and clinical features for the young patients with patellar instability. JUPITER (Justifying Patellar Instability Treatment by Early Results) is a hypothesis-driven, multi-center, multi-armed, prospective cohort study developed to better describe demographic and clinical characteristics and predictors of clinical outcomes in the young patellar instability population. Methods: 21 surgeons from 12 institutions enrolled patients between 10-30 years of age who presented with at least one documented patellar dislocation episode. Radiographs and MRI were evaluated for all patients at baseline to confirm patellar dislocation and skeletal maturity status. Patient demographics, dislocation history, physical exam characteristics and baseline validated patient reported outcome (PRO) scores were collected and analyzed. Conservative versus operative treatment was based on treating physician’s preference following standard of care guidelines. The cohort was divided between first-time vs recurrent dislocators and between conservative vs operative treatment. Results: At the end of enrollment in December 2020, a total of 1722 knees with patellar instability were enrolled. The mean age of the cohort was 17.7 years, 62.4% were female. 306 were skeletally immature. 59% of knees reported that they had more than 1 dislocation. ). 71% knees were enrolled in the operative group and 29% in the conservative group. For patients with recurrent dislocation, 89.7% were treated operatively and 10.2% were treated conservative (p<0.001). Operative treatment was indicated in 42.9% of first-time dislocators; 50% were due to presence of an osteochondral fracture. The recurrent and operative group patients were noted to have a higher percent of positive physical exam findings than first-time and conservative group patients on the affected knee (J-sign [p<0.001], apprehension [p<0.001], crepitus [p=0.041]) and the contralateral knee (except for the crepitus test [p=0.648]). The recurrent group was nearly twice as likely to be ligamentously lax (Beighton score of 5 or greater) compared to first-time dislocators (p<0.001). Baseline PROs varied with the recurrent group having lower Pedi-FABS (p=0.001) and KOOS-QoL (0.008) scores and higher Kujala (0.009), KOOS ADL (0.008), KOOS Sports (<0.001), and Pedi-IKDC (0.014) scores than the first-time dislocator group. Conclusions: Based on large prospective cohort of JUPITER group, operative management was indicated in 42.9% of first-time dislocators and 89.7% of recurrent dislocators. Besides osteochondral fracture, recognition of risk factors (young age, contralateral dislocation, anatomic risk factors) may account for higher rates of operative treatment after first-time dislocation. Recurrent dislocators were more likely to have positive physical exam findings on both knees and lower activity scores. However, the knee specific outcome scores were higher in patients with recurrent dislocations which may reflect adaptive mechanisms to improve function. This prospective study provides insights related to demographic information, clinical presentation and baselines PROs of patients with patellar instability. These baseline characteristics would help to identify the at-risk population and compare outcomes in a longitudinal fashion.

Background: Patellar instability is a common injury in young patients and can lead to significant morbidity and arthritis. Its management is controversial. JUPITER (Justifying Patellar Instability Treatment by Early Results) is a hypothesis-driven, multi-center, multi-armed, prospective cohort study developed to describe clinical characteristics and predictors of clinical outcomes in the young patellar instability population. Purpose: To describe the formation of JUPITER and provide a descriptive, epidemiologic analysis of patient demographics and clinical features of the patients in this prospective cohort. Methods: After training and institutional review board approval, surgeons began enrolling patients between 10-30 years of age who sustained a patellar dislocation. Patient demographics, dislocation history, physical exam characteristics, and PROMs were collected. Results: By January 1, 2019, 28 surgeons from 12 sites had prospectively enrolled 661 patients (677 knees) with patellar instability. 62% were female and mean age was 15.8 years. 447 knees (66%) were in the operative group and 230 (34%) in the non-operative group. 55% of knees reported that they had more than 1 dislocation (operative group 73%; non-operative group 27%, p<0.001). Operative treatment was indicated in 39% of first-time dislocators and 85% of recurrent dislocators (p<0.001). Recurrent and operative group patients had more positive physical exam findings than first-time and non-operative group patients on the affected knee (p<0.05 for J-sign, apprehension, crepitus) and the contralateral knee (p<0.05 J-sign, apprehension). The recurrent group was nearly twice as likely to be ligamentously lax (Beighton score 5 or greater) compared to first-time patients (p<0.001). Baseline PROMs varied with the recurrent group having lower Pedi-FABS (p=0.001) and KOOS-QoL (0.008) scores and higher Kujala (0.009), KOOS ADL (0.008), KOOS Sports (<0.001), and Pedi-IKDC (0.014) scores than the first-time dislocator group. Conclusions: The JUPITER Group has been able to accumulate the largest prospectively collected patellar instability database to date. Over half of patients in this group reported they sustained more than one dislocation. Operative management was indicated in 39% of first-time dislocators, 50% of which had sustained an osteochondral fracture, and 85% of recurrent dislocators. Recurrent dislocators were more likely to have positive physical exam findings on both the affected and contralateral knee.