Recurrent Patellar Instability Research Articles

Predictive Scoring for Recurrent Patellar Instability After a First-time Patellar Dislocation.

Patellofemoral instability is a common acute knee injury seen in the pediatric population. First-time patellar dislocations usually undergo conservative management, but ~15% to 80% of patients experience recurrent instability. This study aims to develop a prediction model using radiographic parameters of the patellofemoral joint seen on computed tomography scans in different degrees of knee flexion, to determine the risk of recurrence after the first episode of patellofemoral instability. A 12-year retrospective case-control study was performed. All patients in a single institution aged 18 years or younger who had a computed tomography patellar tracking scan performed for patellar instability were included. Predictors included in the score were determined through backward logistic regression and compared using receiver operating characteristic curve analysis. This study revealed that recurrent dislocation in first-time patellofemoral dislocation could be accurately predicted using the prediction score that consisted of age, tibial tubercle-trochlear groove distance and congruence angle at 10- and 20-degree flexion. The sensitivity of the score was 100% and specificity was 73.3%. Three diagnostic zones were identified and used to categorize patients into low-, intermediate-, and high-probability groups. This study presented a scoring system that incorporated radiographic knee kinematics in the risk assessment for recurrent patellofemoral instability for patient stratification. The scoring system could guide the decision for early surgical intervention after the first-episode patellofemoral dislocation for patients at high risk of recurrent patellofemoral dislocation.

Paper 50: Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle - Trochlear Groove Distance and Patellar Height: Minimum 5-Year Outcomes

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 yearsTable 2.Radiographic Measurements for Patients with Recurrent Patellar Instability after Isolated MPFL Reconstruction

Medial Patellofemoral Reconstruction With a Hamstring Allograft

Background: Lateral patellar instability is common in young, active patients. Patients who fail conservative treatment may benefit from medial patellofemoral ligament (MPFL) reconstruction. Indications: Recurrent lateral patellar instability. Technique Description: Examination assesses patellar translation, eversion and range of instability. Diagnostic arthroscopy is performed for loose bodies, cartilage damage, trochlear dysplasia, and tracking. A longitudinal incision is made from superomedial to mid-body of the patella. The plane between the capsule and retinaculum is developed for palpation of the medial epicondyle and adductor tubercle. Electrocautery and rongeur are used to create a trough on the patella from centromedially to superomedially. Two suture anchors are placed at the proximal and distal trough. Fluoroscopy is utilized to identify Schöttle point with a perfect lateral radiograph. A 3-centimeter incision is made, and blunt dissection connects the 2 incisions in the developed plane. A guidepin is advanced at Schöttle point, and suture anchor sutures are shuttled through the plane, posterior to the guidepin. There should be loosening of tension with knee flexion. A semitendinosus allograft is whipstitched with terminal tapering. The whipstitched end is tunneled around the guidepin and brought back to the patella, so that both ends have an excess of 20 to 25 millimeters, and excess graft is trimmed from the free end prior to whipstitching. The doubled graft is sized. The midportion of the tendon is tagged and passed through both anchors. The graft is tensioned to the patellar trough and the graft ends are advanced through the developed plane. The femoral tunnel is reamed, and the graft is tensioned into the tunnel after nitinol wire placement with the knee in full extension. Isometry and lateral patellar translation are assessed, aiming for 1 quadrant with firm endpoint. The patella is proximalized and the tensioned graft is secured with an interference screw. Results: MPFL reconstruction is successful for the majority of patients, with 1.2% reporting instability, 3.6% apprehension, and 3.1% reoperation. Possible complications include patellar fracture, patellofemoral pain, and knee stiffness (loss of range of motion). Discussion/Conclusion: Lateral patellar instability is common, and MPFL reconstruction is typically successful for the majority of patients.

Poster 221: Application of Machine Learning to Diagnose Patellar Instability on MRI Using a Data-Driven Model

Objectives:Patellar instability has multiple anatomic risk factors including trochlear dysplasia, patella alta and tuberosity lateralization. However, the exact contribution of each factor on patellar stability has not been clearly delineated due to the fact that 1) each abnormality exists along a spectrum that varies between individuals, 2) multiple measurements exist to describe each risk factor, and 3) the additive effects of these morphological abnormalities are not yet understood. The advent of modern machine learning techniques allows us the opportunity to extract predictive insights by detecting complex patterns underlying health data. We aimed to apply machine learning to differentiate between knee MRI measurements of patients with and without patellar instability to determine the complex relationships across variables that contribute to patellar instability.Methods:Utilizing an institutional database, knee MRIs of patients between the ages 18 to 40 at the time of imaging with a diagnosis of recurrent patellar instability were identified. Age and sex matched controls were selected from a database of MRIs with a diagnosis of meniscal tear for comparison. 26 standard measurements that have been used to describe trochlear dysplasia, patella alta, and tuberosity lateralization were performed on each knee, including bony and cartilaginous landmarks for each measurement when applicable. Using these measurements, 3 categories of machine learning methods were performed, including interpretable model-based methods (linear model, decision tree, random forest, and gradient boosted tree), non-interpretable model-based methods (neural network, and support vector machine [SVM]), and instance-based method (k-nearest neighbor [KNN]). A split validation method was used to divide the entire dataset into train, validation, and test subsets with an 80:10:10 split-ratio.Results:130 knees with patellar instability (47M, 83F) were included in this study and compared with 130 age- and sex-matched control knees. Table 1 summarizes the performance of each method on the test subset. The decision tree achieved the highest overall accuracy among the interpretable model-based methods, followed by SVM, and KNN among non-interpretable model-based and instance-based methods, respectively. Figure 1 depicts the decision tree model, demonstrating that bisect offsect measurement >72.1%, followed by length of patello-trochlear overlap <= 1.35mm, and cartilaginous trochlear depth <= 3.18mm predicted the presence of patellar instability with an accuracy of 84.62%.Conclusions:We present a novel approach to identify patellar instability from MRI measurements, in which an interpretable model-based machine learning method (decision tree) achieved the highest overall performance. Furthermore, patellar lateralization as reflected by bisect offset, patella alta as reflected by patellotrochlear overlap, and cartilaginous trochlear depth indicating dysplasia were found to identify knees with patellar instability. Application of this model and the utilization of uniform measurements can potentially improve the diagnostic accuracy of patellar instability from MRI images. Prospective clinical studies are recommended to further validate this model for its utility in the prediction of patellar instability.Table 1.Diagnostic Performance of machine learning methods on the test subgroupFigure 1.Decision tree model

Paper 54: MPFL Repair has a Higher Failure Rate at Long-term Follow-up compared to MPFL Reconstruction for Recurrent Patellar Instability

Objectives:The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint to lateral patellar translation and is often disrupted with a lateral patellar dislocation. Surgical management for recurrent patellar instability focuses on restoring MPFL function with repair or reconstruction techniques. Recent studies have favored reconstruction over repair, but no long-term, comparative studies are available in the literature.Methods:A total of 55 patients (58 knees) with recurrent lateral instability were treated between 2005 and 2012 with either MPFL repair or MPFL reconstruction. Exclusion criteria included prior or concomitant tibial tubercle osteotomy or trochleoplasty, and follow-up less than 8 years. Pre- and post-operative demographic, surgical, imaging and clinical data were recorded for each patient.Results:MPFL repair was performed on 26 patients (29 knees; 14 females, 15 males) at a mean age of 19.1 years. MPFL reconstruction was performed on 29 patients (29 knees; 18 females, 11 males) at a mean age of 18.2 years. Mean follow-up was 12.0 years (range 8.3-18.9). The reconstruction group had a significantly lower rate of recurrent dislocation compared to the repair group (14% vs 41%, p=0.019) at final follow up. There were no differences in the number of pre-operative dislocations (greater than or less than 3), degree of patellar facet chondromalacia, TT-TG distance, or Tegner scores. The reconstruction group had significantly more time from injury to surgery compared to the repair group (median, 1,460 days vs 627 days, p =0.007). There were no differences in post-operative Tegner, Lysholm or Kujala scores at final follow-up. Additionally, there were no differences in return to play rates (repair 80.8% vs reconstruction 75.0%, p=0.610) or reoperation rates (repair 20.7% vs reconstruction 13.8%, p=0.487).Conclusions:Repair of the MPFL leads to nearly 3-fold higher rate of recurrent patellar dislocation (41% vs. 14%) at long term follow-up compared to MPFL reconstruction. However, MPFL repair and reconstruction provide similar clinical results, return to play rates and reoperation rates.

Paper 51: Multiple Prior Dislocations Lead to Poorer Outcomes of Isolated Medial Patellofemoral Ligament Reconstruction: A Retrospective Chart Review

Objectives:Patellar dislocation is a common knee injury and up to 35% who dislocate can develop recurrent patellar instability. In the setting of recurrent instability, medial patellofemoral ligament reconstruction (MPFLR) often restores knee stability. There has been recent interest in the evaluation of patient and surgical factors that may influence the outcomes of isolated MPFLR. Much of the previous work has focused on influences of anatomical measures; however, patient and injury characteristics may also impact surgical outcomes. We hypothesize that patients who suffer > 2 patellar dislocations prior to MPFLR will demonstrate poorer patient-reported outcomes (PROs) than those who experience ≤ 2 prior dislocations.Methods:Records were reviewed to identify patients who underwent MPFLR at a single academic institution in the United States between 2008 and 2016. Patients were excluded if they underwent concomitant tibial tubercle osteotomy or fixation of an osteochondral fracture. Patient demographics (age, sex, BMI), number of prior patellar dislocations, and patient anatomical measures (Caton-Deschamps index, tibial tubercle-trochlear groove distance, and trochlear sulcus angle) were collected. PROs were assessed with Norwich Patellar Instability (NPI) score, Knee injury and Osteoarthritis Outcome Score (KOOS), and Marx activity score. Outcomes of those with > 2 or ≤ 2 patellar dislocations were compared using linear regression analysis.Results:A total of 160 patients were identified who underwent isolated MPFLR. Ninety-five patients (60%) were available to complete PROs at a mean follow-up of 4.8 years post-operation. Patients with < 2 dislocations were younger (≤ 2 dislocations: 20.7 ± 9.4yrs, > 2 dislocations: 27.4 ± 9.4yrs; p < 0.001), though there were no other differences between groups in terms of demographics or radiographic anatomical measures (Table 1). Controlling for age, sex, BMI, and anatomical factors linear regression analysis found that patients with > 2 dislocations had lower KOOS pain (p = 0.003), ADLs (p = 0.025), Sports/rec (p = 0.009), and knee related QOL (p = 0.008) subscales (Table 2).Conclusions:Patients who suffer > 2 patellar dislocations prior to MPFLR demonstrate poorer PROs at 4.8 years post-operation than those who suffer < 2 dislocations prior to surgery. To our knowledge, no other study has investigated the relationship between the number of pior patellar dislocations and outcomes following MPFLR. Our findings emphasize the role patient and injury factors may play in determining outcomes following MPFLR.Table 1.Comparison of patients based on number of prior dislocations controlling for age, sex, BMI, CDI, TT-TG distance, and sulcus angleTable 2.PROs for patients with ≤ 2 or > 2 patellar dislocations prior to MPFLR, controlling for age, sex, BMI, CDI, TT-TG distance, and sulcus angle

Poster 226: Autograft versus Allograft for Medial Patellofemoral Ligament Reconstruction: A Systematic Review

Objectives:Patients with recurrent lateral patellar dislocations are often treated with reconstruction of the medial patellofemoral ligament (MPFL). The purpose of this study was to perform a systematic review to evaluate clinical outcomes and the risk of recurrent patellar dislocation following medial patellofemoral ligament reconstruction (MPFLR) with autograft versus allograft.Methods:A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to identify studies comparing outcomes of MPFLR with autograft versus allograft. The search phrase used was: medial patellofemoral ligament reconstruction autograft allograft. The inclusion criteria were full-text studies that directly compared clinical outcomes and/or risk of recurrent patellar instability events between patients undergoing MPFLR with autograft versus allograft. A quality assessment was performed using the Modified Coleman Methodology Score (MCMS). Risk of bias was performed using the ROBINS-I and the Cochrane Collaboration’s risk of bias tools.Results:Seven studies (one level II, three level III, three level IV) were identified that met inclusion criteria, including a total of 150 patients who underwent MPFLR with autograft and 193 with allograft (Figure 1, Table 1). All studies showed a moderate risk of bias due to confounding, and five studies showed a moderate risk of bias for using non-blinded but identical postoperative protocols. All six studies showed serious risk of bias for using physicians not blinded to the treatment group (Figure 2). One study found a significantly higher failure rate among autograft patients, and another study found a trend toward a significantly higher failure rate among autograft patients (Table 2). One study demonstrated no significant difference between tibial tubercle-trochlear groove distance (measured on magnetic resonance imaging) in failed versus successful grafts. One study found that patellar tilt angle improved significantly from preoperatively to postoperatively (p<0.001), but there was no difference between the groups. Kujala scores significantly improved for both autograft and allograft patients across studies. Two studies found significant differences in postoperative Kujala scores between the two groups, one of which found better scores in allograft patients (p=0.0032) and another in which scores were better in autograft patients (p=0.02).Conclusions:This is the first systematic review limited to comparative studies comparing autograft versus allograft for MPFL reconstruction. Patients undergoing MPFLR with either autograft or allograft can expect to experience improvement in clinical outcomes. Graft failure was more frequently observed in autograft patients. Subjective outcomes improved to a similar degree in both groups. Allograft may be a better option for MPFLR due to lower failure rate.Figure 1.Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram.Figure 2.ROBINS-I risk of biasTable 1.Study characteristicsTable 2.Failure rates.

Trochleoplasty for severe trochlear dysplasia significantly improves the quality of life of patients with symptomatic patellar instability

BackgroundTrochleoplasty is a recognized surgical technique to address severe trochlear dysplasia. The clinical and radiological outcomes of trochleoplasty surgery in trochlear dysplasia have been well reported. There is a paucity in literature regarding the correlation between trochleoplasty and quality of life (QoL). The aim of this study is to measure the improvement in QoL, in patients with severe trochlear dysplasia and recurrent patellar instability following trochleoplasty. MethodsBetween 2013 and 2019, 51 trochleoplasty cases were performed in 48 patients. They were identified from our prospectively kept database. All operations were performed by a fellowship trained consultant sports knee surgeon. Functional outcomes and QoL scores were assessed using Kujala, IKDC and EQ-5D index. Objective outcomes were obtained following each patient’s latest follow-up assessment. ResultsThe mean age at operation was 22y (SD ± 4.7, range 14–37y) and the mean follow-up period was 21.6 months (SD ± 15.2, range 12–60 months). The mean Kujala score improved from 58.1 (SD 14.9) to 77.9 (SD 17.3) at latest follow-up (p < 0.001). The mean IKDC score improved from 40.5 (SD 14.2) to 69.5 (SD 22.8) at latest follow up (p < 0.001). The mean EQ-5D index also improved from 0.593 (SD 0.257) to 0.824 (SD 0.189) at latest follow-up (p = 0.003). A higher Body Mass Index (BMI; >30 kg/m2) was associated with inferior outcomes. ConclusionTrochleoplasty is an effective surgical technique which improves the QoL in patients suffering from patellar instability secondary to severe trochlear dysplasia. BMI can be used to predict post-operative outcomes.

Double-Tunnel Technique Was Similar to Single-Tunnel Technique in Clinical, Imaging and Functional Outcomes for Medial Patellofemoral Ligament Reconstruction: A Randomized Clinical Trial

This study aimed to compare the clinical, functional, and imaging outcomes of single-tunnel (ST) and double-tunnel (DT) techniques for medial patellofemoral ligament (MPFL) reconstruction. Ninety-four patients with recurrent patellar instability were randomly divided into 2 groups, receiving either ST or DT MPFL reconstruction. Lateral reticulum release (LRR) and tibial tuberosity (TT) transfer were performed as combined procedures when necessary. Preoperative and postoperative clinical characteristics (symptoms and episodes of redislocation), functional outcomes (Kujala, Lysholm, Tegner, IKDC, and KOOS score), and radiological measurements (congruence angle, patellar tilt angle, lateral patellar angle, and lateral patellar translation) were analyzed. The analysis included data from 90 patients with 48 patients in the ST group and 42 patients in the DT group. Patients were followed up for a mean period of 37.8 (range: 27-50) months in the ST group and 38.6 (range: 25-53) months in the DT group. Forty-three patients in the ST group and 40 patients in the DT group received combined TT transfer, and all patients underwent LRR. At thelatestfollow-up, 1 patient in ST group experienced redislocation, while no patient in the DT group sustained clinical failure (P= .347). Imaging measurements decreased significantly to the normal range postoperatively. No significant difference was noted between the postoperative radiological results of the 2 groups. All clinical scores significantly improvedpostoperatively,and no significant difference was observed between the 2 groups except for the higher Lysholm score (P= .031), KOOS symptoms score (P= .021) and KOOS knee-related quality of life score (P= .043) in the DT group. Both techniques could equally mitigate the patellar lateral translation or redislocation. Our results demonstrate several significant differences in functional outcomes that favored DT MPFL reconstruction but no difference in clinical failure rates and radiological results between ST and DT MPFL reconstruction. Level I, randomized clinical trial.

Influence of Patellofemoral Anatomy on Outcomes of Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability.

Background:Patella alta and elevated tibial tubercle–trochlear groove (TT-TG) distance can predispose patients to lateral patellar dislocations and recurrent instability. Their influence on patient-reported outcomes (PROs) after medial patellofemoral ligament (MPFL) reconstruction is less clear.Hypothesis:We hypothesized that neither moderately increased TT-TG distance nor patella alta would negatively affect PROs after isolated MPFL reconstruction in patients with relatively normal patellar tracking (no large J-sign).Study Design:Cohort study; Level of evidence, 3.Methods:We identified patients who underwent isolated MPFL reconstruction at a single institution between 2008 and 2016. The decision to perform an isolated MPFL reconstruction was at the discretion of the operating surgeon but was not performed in the setting of a large J-sign. Patient characteristics and surgical details were collected, and patients completed the Norwich Patellar Instability Score, Knee injury and Osteoarthritis Outcome Score, and Marx activity score. Patellar height (Caton-Deschamps Index [CDI]) was assessed on preoperative lateral radiographs, and TT-TG distance was measured on preoperative axial magnetic resonance imaging (MRI) scans. Patients were grouped based on CDI and TT-TG distance, and outcomes were compared. Linear regression modeling was performed to determine whether patella alta or elevated TT-TG distance was associated with poorer PRO scores.Results:Of 165 knees in 152 patients who underwent isolated MPFL reconstruction, 115 patients (125 knees; 76%) with minimum 1-year follow-up were contacted at a mean of 5.2 years after surgery. Recurrent dislocation occurred in 5 of 125 knees (4%). Preoperative radiographs were available in 111 knees (89%), and preoperative MRI scans were available in 89 knees (71%). Mean CDI was 1.13, and 35% had a CDI ≥1.20. Mean TT-TG distance was 17.5 mm, and 26% had a TT-TG distance >20 mm. After adjusting for patient age, sex, body mass index, and graft choice, we observed that neither patella alta nor elevated TT-TG distance were associated with poorer PROs.Conclusion:Isolated MPFL reconstruction in the setting of moderately elevated TT-TG distance or patella alta was not associated with worse PROs in this cohort with relatively normal patellar tracking (no large J-sign).

Is Caton–Deschamps Index Reliable and Reproducible in Preoperative Assessment of Patellar Height for Patellar Instability Surgery?

The patellar height measurement is fundamental for surgical planning in patellar instability. The Caton–Deschamps index (CDI) is a widely employed method, but a gold standard is still lacking. The aim of this study was to evaluate the reliability and reproducibility of the CDI in a patellar height assessment and to hypothesize its employment in the preoperative planning of patellar stabilization surgery. A total of 29 cases of recurrent patellar instability undergoing surgical treatment were analyzed. The preoperative and postoperative CDI were measured by six different raters (three seniors and three juniors). The interclass correlation coefficient (ICC) of the six raters was calculated to evaluate the interobserver agreement. The seniors’ and juniors’ measurements were compared to assess the CDI reproducibility. The Fleiss kappa was calculated among the six raters to estimate the agreement in favor of an anterior tibial apophysis (ATA) transposition surgery. This study shows excellent absolute agreement in terms of the ICC for the raters’ average and for single raters as units, both preoperatively (p &lt; 0.001) and postoperatively (p &lt; 0.001). The agreement of the surgical choice between the six observers corresponds to “substantial agreement”. This study demonstrates that the CDI is reliable and reproducible, and it could represent a valuable tool in the clinical assessment, treatment choice and pre-surgical planning of patellar instability surgery.

Medial Patellofemoral Ligament Repair with Suture Tape Augmentation: A Case Series With Five-Year Follow Up.

The medial patellofemoral ligament (MPFL) is the main restraining force against lateral patellar displacement in the first 20 degrees of knee flexion and is often disrupted following patellar subluxation or dislocation. MPFL reconstruction is commonly performed to restore patellar stability but requires autograft harvest with associated donor site morbidity. The aim of this study was to assess the five-year outcomes of MPFL repair performed with suture tape augmentation. All patients who underwent isolated MPFL repair for recurrent patellar instability between 2011 and 2017 were included. Patients requiring any additional surgery, such as osteotomy, were excluded. Patient-reported outcomes were measured at two-year follow up using the Knee Injury and Osteoarthritis Outcome (KOOS) Score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Visual Analogue Pain Scale (VAS-pain), Veterans RAND 12-Item Health Survey (VR-12), Marx Activity Scale, and an overall satisfaction questionnaire. At the end of the study period, any complications or secondary surgeries were determined. Eighteen patients underwent MPFL repair with one lost to follow up. There was a significant improvement in all subscales of the KOOS scoring systems, the WOMAC functional score, and the VR-12 physical score. A significant decrease was seen in the VAS-pain score. A non-significant decrease was seen in the Marx activity scale from pre-injury. The majority of patients reported satisfaction with reduction in pain and return to sporting activities. There were no complications with no further instability episodes. This is the first study that describes the five-year follow-up results of patients treated with MPFL repair and suture tape augmentation. Our results show that this technique is an alternative treatment to traditional MPFL reconstruction with comparable outcomes and avoidance of autograft harvest.

Higher pathologic threshold of increased tibial tuberosity-trochlear groove distance should be considered for taller patients.

The aim of this study was to evaluate the correlation between tibial tuberosity-trochlear groove distance (TT-TG) and body height or knee size, and to find height-related pathologic thresholds of increased TT-TG. One-hundred and fifty-three patients with recurrent patellar instability and 151 controls were included. The TT-TG was measured on axial computed tomography (CT) images. Femora width and tibial width were selected to represent knee size. The correlation of TT-TG and gender, body height, femora width, and tibial width was evaluated. The height-related pathologic threshold of increased TT-TG was produced according to Dejour's method. To combine TT-TG with body height and knee size, three new indexes were introduced, ratio of TT-TG to body height (RTH), ratio of TT-TG to femoral width (RTF), and ratio of TT-TG to tibial width (RTT). The ability to predict patellar instability was assessed by the receiver-operating characteristic (ROC) curve, odds ratios (ORs), sensitivity, and specificity. In patients with patellar instability, TT-TG showed significantly correlation with patient height, femoral width, and tibial width respectively (range r = 0.266-0.283). This correlation was not found in the control group. The pathologic threshold of TT-TG was 18mm in patients < 169cm (53%), and the mean TT-TG was 21mm in patients ≥ 169cm (54%). There was significant difference in RTH, RTF, and RTT between the two groups. RTH, RTF and RTT have similar large area under the curve (AUC) with TT-TG. TT-TG showed significant correlation with body height and knee size, respectively. The pathologic threshold of increased TT-TG was suggested to be 21mm for patients [Formula: see text] 169cm and 18mm for patients [Formula: see text] 169cm. Body height-related pathologic threshold provided a supplement for indications of tibial tuberosity medialization. IV.

Quantifying the Relationship Between the Medial Patellofemoral Complex and Patellar Borders: A Pediatric Cadaveric Study

Background:The medial patellofemoral complex (MPFC) is comprised of the medial quadriceps tendon-femoral ligament (MQTFL) superiorly and the medial patellofemoral ligament (MPFL) inferiorly. The anatomy of the pediatric MPFL has been well-described, however, the MPFC in skeletally immature patients and its relationship to the quadriceps tendon and superior patellar border has yet to be described.Purpose:To evaluate the relationship between the MPFC attachment and quadriceps tendon and patella in skeletally immature patients.Methods:16 pediatric knees were dissected to analyze the MPFC insertion on the quadriceps tendon. Dissection was performed using a lateral parapatellar arthrotomy followed by eversion of the extensor mechanism to evaluate the MPFC fibers from its undersurface. The patellar articular length (PL), patellar width, and quadriceps tendon attachment (QTA) of the MPFC above the superior pole of the patella were measured using the ImageJ program. Additionally, the ratio of quadriceps tendon attachment to patellar length was calculated as a percent (QTA/PL%). Two sample t-tests were used to identify significant differences.Results:The average age of the specimens included in this study was 9.6 years. Specimens were divided into two cohorts: a younger cohort (4-8 years), and an older cohort (9-12 years). The QTA above the patella averaged 10.6 mm in the younger cohort and 13.4 mm in the older cohort with no significant difference between the two groups (Figure 1). There was no significant difference in average QTA/PL% which was found to be 47.8% and 48% for the younger and older cohorts respectively (Figure 1). PL was significantly longer in the older cohort (Figure 1). As shown in Figure 2, the insertion of the proximal MPFC into the quadriceps tendon can be variable across specimens.Conclusion:This study clarifies the anatomy of the pediatric MPFC in exceptionally rare pediatric specimens. The MQTFL relationship to the quadriceps tendon is important to guide surgical reconstructions of the medial stabilizers of the patellofemoral joint. Primary and recurrent patella instability remains a significant problem in those under 20 years. A better understanding of the MPFC (both the MQTFL and MPFL components) will support anatomic reconstructions to stabilize the joint.Figure 1:QTA, PL, and QTA/PL% for individual specimens.Figure 2:MPFC Insertion into the Quadriceps Tendon.

Isolated Lateral Release is Inferior to Medial Patellofemoral Ligament Reconstruction for Surgical Management of Patella Instability in Pediatric Patients

Background:The optimal treatment for chronic patella instability remains controversial. Medial patellofemoral ligament reconstruction (MPFLR) has emerged as the “gold standard” for soft tissue stabilization. However, isolated lateral release (ILR) is still commonly performed to treat chronic patella instability despite growing evidence against this approach.Hypothesis/Purpose:Our purpose is to evaluate long-term revision rates and short-term post-operative complications in pediatric patients undergoing either MPFLR or ILR for recurrent patellar instability. The hypothesis is that MPFLR is a superior treatment option with reduced long term revision rates and comparable short-term complications.Methods:The MarketScan database was queried from 2007-2015 to identify patients who underwent MPFLR or ILR as their primary surgical treatment of their chronic patellar instability. Patients were excluded if they had incomplete records up to 5 years or if they underwent concomitant osteotomy or cartilage restoration during their index stabilization procedure. Baseline demographic data and patient co-morbidities were documented. Two and five year revision surgical stabilization rate and post-operative complications were reported. Results were analyzed statistically.Results:This study identified 471 patients (mean age 15.6 years, female 56.9%) who underwent MPFLR and 528 patients (mean age 15.5 years, female 70.5%) who underwent ILR for chronic patellar instability. Patients were stratified into two mutually exclusive groups: 1) MPFLR only or 2) ILR only. Patients who underwent MPFLR experienced higher rates of overall complications within 90 days of surgery (8.7% vs 4.9%, p = 0.0171). MPFLR had a higher rate of early wound complications (0.8% vs. 0%, p <.033) There was no difference in revision stabilization rate between MPFLR and ILR at 2 year follow-up. However, at 5 years of follow-up, 8.9% of patients who underwent ILR underwent revision surgery compared to 3.0% of patients who underwent MPFLR as their index surgery (p < 0.0001).Conclusions:Isolated lateral release is an inferior treatment option for surgical stabilization of chronic patella instability as compared to medial patellofemoral ligament reconstruction in pediatric patients. Despite slightly higher rate of short term complications in the MPFLR group and similar revision rates at 2 years, MPFLR has significantly decreased risk of revision stabilization at 5 year follow-up.Table 1.Postoperative Complications - within 90 daysTable 2.Quality Outcomes

Outcomes of Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability in Ehlers-Danlos Syndrome

Background:Ehlers-Danlos syndrome (EDS) -hypermobility type is characterized by generalized hyperlaxity which is considered to be a risk factor for patellar instability. Surgery is discouraged in this subset of patients due to high rates of failure. The outcomes following isolated Medial Patellofemoral Ligament Reconstruction (MPFLR) for patellar instability in EDS population has not been reported.Purpose:To analyze re-dislocation rates and patient-reported outcomes of isolated MPFLR for recurrent patellar instability in adolescents with EDS. The second purpose of the study was to compare allograft vs autograft for MPFL reconstruction in this specific population.Methods:Between 2010 and 2016, 21 knees in 16 consecutive patients underwent isolated MPFLR reconstruction for recurrent patellar instability. The diagnosis of EDS-hypermobility type, was confirmed by genetics for all patients, with Beighton score as the chief determinants. All patients underwent isolated MPFL reconstruction with hamstring tendon graft. Recurrent dislocation rate and patient-reported outcomes, including Pedi-IKDC, Kujala Score, HSS Pedi-FABS, Banff Instability Instrument 2.0, and KOOS Knee Survey were collected at minimum 2 year follow-up.Results:The mean age of the cohort was 15.4 years (range 13-18 years). All patients were females. 16 knees had atraumatic mechanism of patellar dislocation. 2 patients had an osteochondral fracture. 5 patients underwent bilateral MPFLR. 9 patients had prior surgeries on their knee; 6 were failed patellar stabilization procedures but only 1 was failed MPFLR. 14 knees had hamstring autograft and 7 had hamstring allograft. At minimum 2 years follow-up, 3 of 21 knees (14.2%) had recurrent dislocation. There were no other complications. The mean pedi IKDC, Kujala, Pedi-FABS, and BANFF scores were 66.62 (95% CI 8.52), 73.5 (95% CI 8.68), 6.73 (95% CI 2.86) and 57.15 (95% CI 10.24) respectively. The overall mean KOOS pain subscale was 73.85 (95% CI 9.95) and KOOS symptoms subscale score was 48.54 (95% CI 5.56). There were no significant differences in outcome scores and re-dislocation rates between autograft and allograft (p>0.5). There was no significant correlation between functional score and Beighton score.Conclusion:EDS-related patellar instability are primarily atraumatic in origin without an osteochondral fracture. Patients had significant improvements in function following isolated MPFLR at minimum 2 years follow-up. However, these functional improvements were less than historical controls. Re-dislocation rate of 14% is higher than normal population. EDS and joint hypermobility is not a contraindication to MPFLR but caution is recommended in managing patient expectations.

The winking sign is an indicator for increased femorotibial rotation in patients with recurrent patellar instability

PurposeRotation of the tibia relative to the femur was recently identified as a contributing risk factor for patellar instability, and correlated with its severity. The hypothesis was that in patellofemoral dysplastic knees, an increase in femorotibial rotation can be reliably detected on anteroposterior (AP) radiographs by an overlap of the lateral femoral condyle over the lateral tibial eminence.MethodsSixty patients (77 knees) received low-dose computed tomography (CT) of the lower extremity for assessment of torsional malalignment due to recurrent patellofemoral instability. Three-dimensional (3D) surface models were created to assess femorotibial rotation and its relationship to other morphologic risk factors of patellofemoral instability. On weight-bearing AP knee radiographs, a femoral condyle/lateral tibial eminence superimposition was defined as a positive winking sign. Using digitally reconstructed radiographs of the 3D models, susceptibility of the winking sign to vertical/horizontal AP knee radiograph malrotation was investigated.ResultsA positive winking sign was present in 30/77 knees (39.0%) and indicated a 6.3 ± 1.4° increase in femorotibial rotation (p < 0.001). Femoral condyle/tibial eminence superimposition of 1.9 mm detected an increased femorotibial rotation (> 15°) with 43% sensitivity and 90% specificity (AUC = 0.72; p = 0.002). A positive winking sign (with 2 mm overlap) disappeared in case of a 10° horizontally or 15° vertically malrotated radiograph, whereas a 4 mm overlap did not disappear at all, regardless of the quality of the radiograph. In absence of a winking sign, on the other hand, no superimposition resulted within 20° of vertical/horizontal image malrotation. Femorotibial rotation was positively correlated to TT–TG (R2 = 0.40, p = 0.001) and patellar tilt (R2 = 0.30, p = 0.001).ConclusionsThe winking sign reliably indicates an increased femorotibial rotation on a weight-bearing AP knee radiograph and could prove useful for day-by-day clinical work. Future research needs to investigate whether femorotibial rotation is not only a prognostic factor but a potential surgical target in patients with patellofemoral disorders.Level of evidenceIII.

The tibial tubercle-posterior cruciate ligament (TT-PCL) distance does not truly reflect the lateralization of the tibial tubercle.

The role of the tibial tubercle-posterior cruciate ligament (TT-PCL) and tibial tubercle-trochlear groove (TT-TG) in recurrent patellar instability (RPI) remains unclear. This study aims to confirm the validity of the TT-TG and TT-PCL in predicting RPI and to verify whether the TT-PCL can truly reflect the lateralization of the tibial tubercle. A total of 50 patients with RPI and 50 controls were recruited and underwent magnetic resonance imaging examinations. The TT-TG, TT-PCL, and tibial tubercle lateralization (TTL) were measured independently by two authors in a blinded and randomized fashion. T-test was used for parametric variances and the Mann-Whitney U and Chi-square tests were used for non-parametric variances. Pearson's product moment correlation coefficients were calculated to determine correlations between the defined measurements. The intraclass correlation coefficient was used to assess the reliability of the measurements. All defined measurements showed excellent intra- and inter-observer reliability. The TT-TG distance, TT-PCL distance, and TTL were significantly greater in the PI group than in the control group. The AUC was highest for the TT-TG distance compared with that for the TT-PCL distance, and TTL were 0.798, 0.764, and 0.769, with the calculated cut-off value of 12.5mm, 16.5mm, and 66.1 percentages. There was a moderate correlation (r = 0.595) between the TT-TG distance and TTL, and a weak correlation (r = 0.430) between the TT-PCL distance and TTL. Both the TT-TG distance and TT-PCL distance can be measured with excellent reliability on magnetic resonance imaging. The TT-TG distance, rather than the TT-PCL distance, has a better performance in predicting RPI. Most interestingly, the TT-PCL distance cannot reflect the real lateralization of TT. This study provides new information to evaluate TTL in patients with RPI. III.

Outcomes of Patellar Stabilization Utilizing a Combined Arthroscopic and Open Technique: A Retrospective Review With 5-Year Follow-up

Background:Few studies have reported the long-term outcomes of patellar stabilization surgery in an active duty military cohort.Purpose:To evaluate the long-term results of a combined open and arthroscopic patellar stabilization technique for the treatment of recurrent lateral patellar instability in members of a military population.Study Design:Case series; Level of evidence, 4.Methods:We performed a retrospective review of a consecutive series of 63 patients who underwent operative management for patellar instability at a tertiary military medical center between 2003 and 2017. All cases were performed by a single sports medicine fellowship–trained orthopaedic surgeon. Patients with recurrent lateral patellar instability whose nonoperative management failed were included. All patients underwent arthroscopic imbrication of the medial patellar retinaculum, an open lateral retinacular release, and an Elmslie-Trillat tibial tubercle osteotomy. Outcome measures at final follow-up included recurrent instability, need for surgical revision, subjective assessments, and military-specific metrics. We also analyzed anatomic risk factors for failure: patella alta, coronal plane alignment, trochlear dysplasia, and tibial tubercle–trochlear groove distance.Results:A total of 51 patients were included (34 men, 17 women; mean ± SD age at surgery, 27.2 ± 5.8 years; mean follow-up, 5.3 years). The mean postoperative SANE score (Single Assessment Numeric Evaluation) was 75.0 ± 17.7, and the mean visual analog scale pain score was 2.5 ± 2.1. Four patients (7.8%) reported redislocation events, and 4 underwent revision surgery. Twenty-five patients (49.0%) reported a decrease in activity level as compared with preinjury, while 10 (19.6%) cited restrictions in activities of daily living. Of the 21 patients remaining on active duty, 6 (28.6%) required an activity-limiting medical profile. Of the 48 active duty patients, 12 (25.0%) underwent evaluation by a medical board for separation from the military. Differences in the Caton-Deschamps Index and tibial tubercle–trochlear groove distance between surgical success and failure were not statistically significant.Conclusion:Surgical management of patellar instability utilizing a multifaceted technique resulted in low recurrence rates and may be independent of predisposing anatomic risk factors for instability. At 5-year follow-up, most patients retained their active duty status, although nearly half experienced a decrease in activity level.

Modified Recession Wedge Trochleoplasty

Background: Trochlear dysplasia represents one of the main anatomic risk factors for patellar instability, with risk of failure and unfavorable clinical outcomes in patients with unaddressed dysplasia undergoing patellar stabilization. Indications: Patients with trochlear dysplasia characterized by supratrochlear prominence (DeJour B or D) and recurrent patellar instability, especially following failed soft tissue or bony stabilization. This technique addresses an anterior trochlea without pathologic convexity, as convexity may require conversion to other techniques for groove deepening (eg, DeJour “thick flap” or Schottle “thin flap”). Technique Description: A 6-cm lateral parapatellar arthrotomy is created. A marking pen is used to identify the native center of the trochlea, as well as the location of the planned resection and bony hinge point laterally. An osteotome is used to remove a wedge of bone proximally, such that the posterior aspect of the osteotomy is in line with the anterior femoral cortex. A resection guide is then used to perforate the lateral cortex, with care to avoid damaging the cartilage, and carried laterally and distally to ensure the bony cuts are connected, creating the bony flap. To ensure that all bony bridges are eliminated, the arthroscope is placed into the osteotomy to visualize reduction of the trochlea with manual pressure. A knotless PEEK anchor loaded with 8 loaded sutures is then placed on the roof of the trochlear notch. Sutures are then secured using anchors placed at the center of the trochlea, at the superolateral corner and far lateral edge of the trochlea to reduce the osteotomy, with 2 to 3 sutures placed in each anchor depending on surgeon preference. Results: Trochleoplasty has been reported to decrease the rate of recurrent patellar dislocation while improving mean Kujala score and knee function. Benefits of trochleoplasty must be balanced against the high rate of potential complications, primarily pain and decreased knee range of motion, secondary to the technical challenges and steep learning curve inherent to effectively performing the procedure. Discussion/Conclusion: Patients with recurrent patellar instability with trochlear dysplasia and failed prior stabilization may experience improved stability and outcomes following trochleoplasty.