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

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

Clinical and Radiological Outcomes at ≥10-Year Follow-up After Matrix-induced Autologous Chondrocyte Implantation in the Patellofemoral Joint.

BACKGROUND: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in the treatment of knee cartilage defects, although limited research is available on its longer term (≥10 years) sustainability in the patellofemoral joint. PURPOSE: To report the clinical and radiological outcomes at ≥10 years in a prospectively recruited cohort of patients undergoing MACI in the patellofemoral joint and compare outcomes in patients undergoing MACI on the patella versus the trochlea. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: The current study prospectively enrolled 95 patients who underwent patellofemoral MACI, of whom 29 (13 patella, 16 trochlea) underwent concomitant tibial tubercle osteotomy. Patients were assessed preoperatively and at 2, 5, and ≥10 years using a range of patient-reported outcome measures (PROMs) including the Knee injury and Osteoarthritis Outcome Score, the 36-item Short Form Health Survey, and the frequency and severity of knee pain as well as patient satisfaction, full active knee flexion and extension, and peak isokinetic knee extensor and flexor torques. High-resolution magnetic resonance imaging (MRI) was performed to assess pertinent graft parameters, as well as determine an overall MRI composite score, per the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system. Results were analyzed according to the graft location (patella or trochlea). RESULTS: Of the 95 patients recruited, 82 patients (41 patella, 41 trochlea) were available for a clinical review at ≥10 years after surgery (mean follow-up, 11.9 years [range, 10-15 years]). For the whole patellofemoral MACI cohort, all PROMs significantly improved over time (P < .05), with no significant changes (P > .05) observed in any MRI-based score from 2 to ≥10 years after surgery. At ≥10 years, 90.2% (n = 74) were satisfied with MACI in relieving their knee pain, and 85.4% (n = 70) were satisfied with the improvement in their ability to participate in sports. No differences (P > .05) were observed in PROMs between those undergoing patellar MACI and those undergoing trochlear MACI, although a significant group effect was observed for limb symmetry indices of knee extensor (P = .009) and flexor (P = .041) strength, which were greater in those undergoing patellar (vs trochlear) MACI. No statistically significant differences (P > .05) were observed between patellar and trochlear grafts on any MRI-based measure. In the cohort assessed at ≥10 years after surgery, 4 patients (2 patella, 2 trochlea) demonstrated graft failure on MRI scans, although a further 3 patients (all trochlea) were omitted from the ≥10-year review for having already progressed to total knee arthroplasty. CONCLUSION: Good clinical scores, high levels of patient satisfaction, and adequate graft survivorship were observed at ≥10 years after MACI on the patella and trochlea.

Anatomical medial patellofemoral ligament reconstruction improves sport participation and activity levels in adolescents with recurrent patellar dislocation.

OBJECTIVES: This study aims to evaluate the clinical outcomes of an anatomical medial patellofemoral ligament (MPFL) reconstruction and the effects of concomitant patellofemoral joint injuries and radiological findings on outcomes in adolescents with recurrent patellar dislocation (RPD). PATIENTS AND METHODS: Between January 2011 and January 2020, a total of 34 patients (19 males, 15 females; median age: 15.6 years; range, 13 to 17 years) with RPD who underwent anatomic MPFL reconstruction were retrospectively analyzed. Lateral release was performed as indicated. Clinical outcomes were evaluated preoperatively and at the final follow-up using the Visual Analog Scale (VAS), Lysholm, Kujala, and Tegner activity rating scales. Magnetic resonance imaging was performed to detect concomitant injuries such as bone, cartilage, and soft tissue injuries. RESULTS: The mean follow-up was 5±2 years. All postoperative knee functions and activity levels were statistically significantly improved without re-dislocation (p<0.001). There was no statistically significant relationship between the presence and location of cartilage lesions and clinical outcomes (p>0.05). Patients with cartilage lesions had a significantly higher CatonDeschamps index and a higher incidence of bone edema in both the patella and femur than patients without. CONCLUSION: Anatomic MPFL reconstruction with meticulous physical therapy has successful clinical outcomes, prevents re-dislocation, and increases participation in sports and activity levels in adolescent patients with RPD. Although cartilage injuries are common after RPD, it has no adverse effect on clinical outcomes in the mid-term.

Less risk of patellofemoral degeneration without significant clinical and survivorship difference for distal tibial tuberosity high tibial osteotomy compared to biplanar high tibial osteotomy over a mid-term follow-up.

PURPOSE: This study aims to compare the mid-term radiographic, clinical results and survivorship between distal tibial tuberosity high tibial osteotomy (DTT-HTO) and conventional biplanar medial open-wedge high tibial osteotomy (cOW-HTO). METHODS: The weight-bearing line ratio (WBL%) and medial proximal tibial angle (MPTA) were evaluated using a standing anteroposterior view of lower extremity. The posterior tibial slope (PTS), Caton-Deschamps index (CDI), tilting angle (TT) and lateral shift ratio (LSR) were evaluated using the lateral views and Merchant views. The Knee Society (KS) knee and function score, Lysholm score, and Anterior Knee Pain Scale (Kujala score) were were used to evaluate the functional outcomes. All parameters were evaluated preoperatively and at the final follow-up. The postoperative complications and survivorship for both groups were also evaluated during the follow-up period. RESULTS: The WBL% and MPTA exhibited no significant differences between the two groups preoperatively and at the final follow-up. The postoperative CDI and TT in the cOW group decreased significantly compared with the DTT group (p = .037 and .041, respectively). The PF grade showed a significant increase after DTT-HTO and cOW-HTO (p = .036 and <0.001, respectively). Furthermore, the postoperative PF grade of cOW group was significantly higher than that of DTT group (p = .039). The KS knee and function score, Lysholm score, and Kujala score for both groups improved similarly at the final follow-up. The survivorship free of revision was 92.7 % in the DTT group and 94.2% in the OW group. CONCLUSIONS: Despite observing a lower risk of PF joint progression in DTT-HTO compared to cOW-HTO, the clinical outcomes and survivorship after DTT-HTO and cOWHTO were comparable over a mid-term follow-up.

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

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

[Patellofemoral instability in children and adolescents]. / Patellofemorale Instabilität bei Kindern und Jugendlichen.

Patellofemoral instability is a common and clinically relevant disorder of multifactorial causes. Several concomitant problems such as genua valga, hyperlaxity, injuries or sports-related overuse may contribute to the development of instability and recurrent patellar dislocations. A thorough diagnosis is of paramount importance to delineate every contributing factor. This includes radiographic modalities and advanced imaging such as magnetic resonance imaging or torsional analyses. The authors recommend non-operative management (including physiotherapy, gait and proprioceptive training, orthoses) and, whenever non-operative measures fail, surgical patellar stabilization using, e.g. MPFL reconstruction.

Effect of patellofemoral joint overstuffing following total knee arthroplasty without patella resurfacing on clinical efficacy and related factors analysis.

OBJECTIVE: To analyze the influencing factors for patellofemoral joint (PFJ) overstuffing following total knee arthroplasty (TKA) without patella resurfacing, and explore the effect of PFJ overstuffing on clinical efficacy. METHODS: A retrospective analysis was conducted on 168 patients with end-stage knee osteoarthritis who underwent TKA without patella resurfacing at our hospital between Match 2019 and September 2021. The clinical data of these patients were retrospectively analyzed. In this study, PFJ overstuffing was defined as a postoperative PFJ distance greater than 1 mm compared to the preoperative measurement. The occurrence of postoperative PFJ overstuffing was counted. The patients were divided into the overstuffing group (n = 109) and the non-overstuffing group (n = 59) to count the patellar thickness and thickness of femoral anterior condyle in all patients before and after surgery, and analyze the influencing factors for postoperative PFJ overstuffing in such patients. Patients were followed up for 2 years to compare the recovery time of postoperative pain, score of visual analogue scale (VAS) and flexion activity between the two groups. RESULTS: There was no significant difference in patellar thickness between preoperative and postoperative measurements of the patients (P > 0.05). However, the thickness of the femoral anterior condyle and the PFJ distance after surgery increased significantly compared with those before surgery (P < 0.05). Among the 168 patients, 109 cases (64.88%) experienced PFJ overstuffing. The risk of PFJ overstuffing was higher in female patients than in male (P < 0.05). The preoperative thickness of the femoral anterior condyle in the overstuffing group was significantly smaller compared to the non-overstuffing group (P < 0.001). Compared with the non-overstuffing group, the overstuffing group had longer recovery time of postoperative pain (P < 0.05), and had lower flexion activity at 2 years after surgery (P < 0.001). However, no significant difference was found in VAS score between the overstuffing group and the non-overstuffing group at 2 years after surgery (P > 0.05). Spearman rank correlation analysis indicated females tend to have a lower preoperative thickness of the femoral anterior condyle (r=-0.424, P < 0.001), as well as a positive postoperative PFJ overstuffing (r = 0.237, P < 0.05). Furthermore, there was a negative correlation between preoperative thickness of the femoral anterior condyle and postoperative PFJ overstuffing (r=-0.540, P < 0.001). CONCLUSION: Following TKA without patella resurfacing, there is a high risk of PFJ overstuffing, particularly among female patients and those with a small thickness of the femoral anterior condyle. Therefore, special attention should be given to these high-risk groups during clinical treatment.

Arthroscopic medial patellofemoral ligament reconstruction with polyethylene suture combined with medial retinaculum plication for the treatment of acute patellar dislocation in young and middle-aged patients with a follow-up of at least 2 years.

PURPOSE: The purpose of this study was to propose a surgical technique for arthroscopic medial patellofemoral ligament (MPFL) reconstruction with polyethylene suture combined with medial retinaculum plication and to evaluate the efficacy of this surgical technique in the treatment of acute patellar dislocation. METHODS: Clinical data of patients with acute patellar dislocations treated with arthroscopic MPFL reconstruction with polyethylene tape (FiberTape) combined with medial support band compression were analyzed retrospectively from January 2018 to January 2021. The mean age of the patients was 25.15 ± 4.66 years; the mean follow-up time was 27.5 (24-36) months. Clinical evaluation consisted of apprehension test results, patellar extrapolation test results, Lysholm score, Kujala score, and IKDC score, the Patellar lateral shift distance and patellar tilt angle (PTA) measured by CT scan. RESULTS: All patients had no recurrent patellar dislocation or subluxation after surgery, and the apprehension test was negative. In all patients, the Kujala score (36.0 ± 9.9 vs. 98.2 ± 3.1), the IKDC score (48.6 ± 7.0 vs. 90.6 ± 4.4) and the Lysholm score (32.8 ± 10.4 vs. 96.7 ± 3.1) had improved at the 24-month follow up (P < 0.05). In addition, PTA was significantly lower at the 12-month follow-up and 24-giving-month follow-up compared to the preoperative period (P < 0.05, Table 2). The patellar lateral shift distance decreased from 14.94 ± 6.11 mm preoperatively to 3.00 ± 1.40 mm (12-month follow up) and 3.26 ± 1.37 mm (24-month follow up), respectively. CONCLUSION: Arthroscopic MPFL reconstruction with polyethylene suture combined with medial retinaculum plication is a safe and reliable surgical technique for the treatment of acute patellar dislocation in young and middle-aged patients. LEVEL OF EVIDENCE: Level III, Therapeutic Study.

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

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

The thickness change ratio and preservation ratio of the infrapatellar fat pad are related to anterior knee pain in patients following medial patellofemoral ligament reconstruction.

BACKGROUND: The infrapatellar fat pad (IPFP) lies extrasynovial and intracapsular, preserving the joint cavity and serving as a biochemical regulator of inflammatory reactions. However, there is a lack of research on the relationship between anterior knee pain (AKP) and the IPFP after medial patellofemoral ligament reconstruction (MPFLR). Pinpointing the source of pain enables clinicians to promptly manage and intervene, facilitating personalized rehabilitation and improving patient prognosis. METHODS: A total of 181 patients were included in the study. These patients were divided into the AKP group (n = 37) and the control group (n = 144). Clinical outcomes included three pain-related scores, Tegner activity score, patient satisfaction, etc. Imaging outcomes included the IPFP thickness, IPFP fibrosis, and the IPFP thickness change and preservation ratio. Multivariate analysis was used to determine the independent factors associated with AKP. Finally, the correlation between independent factors and three pain-related scores was analyzed to verify the results. RESULTS: The control group had better postoperative pain-related scores and Tegner activity score than the AKP group (P < 0.01). The AKP group had lower IPFP thickness change ratio and preservation ratio (P < 0.001), and smaller IPFP thickness (P < 0.05). The multivariate analysis revealed that the IPFP thickness change ratio [OR = 0.895, P < 0.001] and the IPFP preservation ratio [OR = 0.389, P < 0.001] were independent factors related to AKP, with a significant correlation between these factors and pain-related scores [|r| > 0.50, P < 0.01]. CONCLUSIONS: This study showed the lower IPFP change ratio and preservation ratio may be independent factors associated with AKP after MPFLR. Early detection and targeted intervention of the underlying pain sources can pave the way for tailored rehabilitation programs and improved surgical outcomes. LEVEL OF EVIDENCE LEVEL III.

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

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

Tibial Tubercle Osteotomy With and Without Medial Patellofemoral Ligament Reconstruction in Adolescent Patients Leads to Decrease in Patellar Height and Patella Tendon Length.

OBJECTIVE: Patellar height changes after tibial tubercle osteotomy (TTO) have not yet been described. We aimed to evaluate whether TTO ± medial patellofemoral ligament reconstruction (MPFL-R) influences patellar height and tendon length, hypothesizing that TTO would decrease patellar height and tendon length. METHODS: A retrospective review was performed of skeletally mature adolescents (<18 y) receiving primary anteromedialization or medialization TTO ± MPFL-R. Patients with at least 6 months of radiographic follow-up were included in the study. Pre and postoperative patellar heights were assessed on lateral, weight-bearing, and flexion (30 to 70 degrees) radiographs using the Blackburne-Peel Index (BPI), Caton-Deschamps Index (CDI), and Insall-Salvati Ratio (ISR). Subgroup analyses were performed to compare patellar height changes in patients with preoperative patella alta, norma, and baja, as well as between patients undergoing medialization and anteromedialization TTO. Data were analyzed for normality using a Shapiro-Wilk test, and paired-sample t tests were performed. RESULTS: Forty-nine knees were included (mean age: 15 y; range: 12 to 17). A significant decrease in mean patellar height after TTO ± MPFL-R was observed across all measures: BPI (0.12, P = 0.000783), CDI (0.08, P = 0.01062), and ISR (0.15, P = 0.00000075). Patellar tendon length decreased by 2.26 mm ( P = 0.001272). Subgroup analyses demonstrated a decrease in mean patellar height across all 3 measurements ( P < 0.001; BPI, CDI, and ISR) for patients with preoperative patella alta but not patella norma or baja. Additional subgroup analysis showed a patellar height decrease using BPI (0.15, P = 0.004583) and ISR (0.14, P = 0.0002806) for patients receiving medialization TTO but not anteromedialization. The anteromedialization cohort did not demonstrate patellar height change using BPI and CDI; ISR demonstrated a decrease (0.10, P = 0.00917). CONCLUSIONS: Mean patellar height and tendon length decreases after TTO ± MPFL-R in skeletally mature, adolescent patients. Subgroup analyses suggest these changes occur in patients with preoperative patella alta and/or patients who undergo medialization TTO. These data suggest that some distalization in patellar positioning may be achieved without formal distalization osteotomy.

Ellipsoidal patellar bone tunnel fixation with Toggleloc suspension system for medial patellofemoral ligament reconstruction: A 5 years follow-up.

BACKGROUND: This study aimed to evaluate the clinical and radiological features of the patella fixation technique using Toggleloc suspension system in a single ellipsoidal blind patellar tunnel during medial patellofemoral ligament (MPFL) reconstruction. METHODS: This study included 52 patients (25 men, 27 women) who underwent MPFL reconstruction using a semitendinosus tendon graft. The graft was fixed to the ellipsoidal single blind tunnel opened on the medial side of the patella with an endobutton and was fixed to the femoral tunnel by using bioabsorbable screw. Clinical scores (Kujala score, Lysholm score, Tegner activity score and the visual analog scale [VAS] score) were evaluated preoperatively and at the end-follow up. Preoperative and postoperative radiological measurements (trochlea depth, sulcus angle, patellar height, patellar congruence angle, patellar tilt angle and lateral patellofemoral angle) were evaluated with X-ray (Merchant X-ray, anteroposterior and lateral radiography) and computed tomography (CT) of the knee. RESULTS: Postoperative patellar redislocation or subluxation was not observed in any patient. Patellar congruence angle, patellar tilt angle and lateral patellofemoral angle mean values were found to return to normal values in the postoperative period and the results were statistically significant. Also statistically significant improvement in all clinical scores postoperatively. According to the Insall-Salvati index (ISI) and Caton-Deschamps index (CDI) on lateral radiography of the knee at 30° flexion, patellar height decreased in the postoperative period statistically significant. The CDI was above 1.3 in 17 (%32) of our patients. Thirteen of these values decreased to normal values. No radiological progression of patellofemoral osteoarthritis was observed in all patients at the final follow-up evaluation. CONCLUSION: In cases of patellofemoral instability, fixation of the tendon graft in blind ellipsoid tunnel using the Toggleloc suspension system provides satisfactory patellar graft fixation strength, significant functional improvement and a low failure rate.

Quantitative MRI Analysis of Patellofemoral Joint Cartilage Health 2 Years After Anterior Cruciate Ligament Reconstruction and Lateral Extra-Articular Tenodesis.

BACKGROUND: The addition of an iliotibial band-based lateral extra-articular tenodesis (LET) to anterior cruciate ligament (ACL) reconstruction (ACLR) has been shown to reduce failure rates. However, there are concerns as to the potential overconstraint of tibiofemoral kinematics that may increase the risk of cartilage degradation. To date, no clinical study has investigated the effect of LET on patellofemoral joint articular cartilage health. HYPOTHESIS: It was hypothesized that at 2 years postoperatively, (1) the addition of LET at the time of ACLR would have no effect on cartilage health on magnetic resonance imaging (MRI), and (2) higher cartilage relaxation values would be associated with worse patient-reported and functional outcomes. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A subset of patients from the STABILITY 1 randomized controlled trial were included. All patients underwent primary ACLR with a hamstring autograft. Patients were randomized to either LET augmentation or not. Cartilage status in the patellofemoral joint between the ACLR group and ACLR+LET group was compared using 2-year postoperative quantitative MRI and the ACL osteoarthritis scores of both the surgical and the contralateral nonsurgical knees. Objective functional outcomes and patient-reported outcome measures (PROMs) were attained. RESULTS: A total of 92 patients (43 patients in the ACLR group; mean age, 18.9 ± 3.2 years; 60.5% female; and 49 patients in the ACLR+LET group; mean age, 18.7 ± 3.2 years, 63.3% female) were included. No significant differences were seen in the mean values (ms) for adjusted T1ρ/T2 relaxation times in the medial patella (47.8/42.2 vs 47.3/43.2), central patella (45.5/42.5 vs 44.1/42.7), lateral patella (48.2/43.5 vs 47.3/43.0), medial trochlea (54.7/50.9 vs 56.4/50.9), central trochlea (53.3/51.1 vs 53.1/52.0), and lateral trochlea (54.9/52.1 vs 53.9/52.6) between the ACLR and ACLR+LET groups. No difference in overall ACL osteoarthritis scores was observed (P = .99). An increase in medial patellar T2 relaxation times was associated with a decreasing International Knee Documentation Committee score (P = .046), Knee injury and Osteoarthritis Outcome Score (KOOS) Symptoms subscale score (P = .01), and total KOOS (P = .01). CONCLUSION: There was no statistical difference in patellofemoral cartilage health between knees 2 years after primary ACLR with hamstring tendon autograft with or without LET. Statistically significant correlations were found between quantitative MRI relaxation times, functional outcome scores, and PROMs; however, the correlations were weak and the clinical significance is unknown. REGISTRATION: NCT02018354 (ClinicalTrials.gov identifier).

Three-dimensional magnetic resonance imaging-based statistical shape analysis and machine learning-based prediction of patellofemoral instability.

This study performed three-dimensional (3D) magnetic resonance imaging (MRI)-based statistical shape analysis (SSA) by comparing patellofemoral instability (PFI) and normal femur models, and developed a machine learning (ML)-based prediction model. Twenty (19 patients) and 31 MRI scans (30 patients) of femurs with PFI and normal femurs, respectively, were used. Bone and cartilage segmentation of the distal femurs was performed and subsequently converted into 3D reconstructed models. The pointwise distance map showed anterior elevation of the trochlea, particularly at the central floor of the proximal trochlea, in the PFI models compared with the normal models. Principal component analysis examined shape variations in the PFI group, and several principal components exhibited shape variations in the trochlear floor and intercondylar width. Multivariate analysis showed that these shape components were significantly correlated with the PFI/non-PFI distinction after adjusting for age and sex. Our ML-based prediction model for PFI achieved a strong predictive performance with an accuracy of 0.909 ± 0.015, and an area under the curve of 0.939 ± 0.009 when using a support vector machine with a linear kernel. This study demonstrated that 3D MRI-based SSA can realistically visualize statistical results on surface models and may facilitate the understanding of complex shape features.

Common radiographic indices used to measure patellar height do not consistently identify patella alta and lack interchangeability between measurements.

PURPOSE: Abnormal patellar height has been identified as a source of aberrant mechanical functioning within the patellofemoral joint. The purpose of this study is to examine the statistical agreement among three commonly used classification methods: Blackburne-Peel (BPI), Caton-Deschamps (CDI) and Insall-Salvati (ISR), by evaluating (1) the rates of patella alta identification and (2) the ability for one index to predict another. METHODS: One hundred lateral knee radiographs were evaluated using BPI, CDI and ISR to classify each knee as patella normal, patella alta or patella baja. Linear regression analysis was performed to evaluate the relationship between each index. Conversion equations were then derived using the reported linear regression best-fit line, comparing each pair of indices. RESULTS: Patella alta was identified in 15 knees using BPI, 15 using CDI and 25 using ISR. A total of seven knees were classified as patella alta by all BPI, CDI and ISR. Statistical analysis revealed significant correlation (p ≤ 0.001) among BPI and CDI (R2 = 0.706), BPI and ISR (R2 = 0.328) and CDI and ISR (R2 = 0.288). Wilcoxon Signed-Rank test between the three indices revealed no significant difference between the means of converted and original indices. CONCLUSION: Despite their significant correlations and adequate reproducibility, variability between common patellar height indices render predictions and conversions between BPI, CDI and ISR inequivalent. Users of these indices must be aware of their incongruent properties when considering application to patients in the clinical setting. Furthermore, it remains unclear which patellar height measurement technique is the correct index to use in a given knee. This study highlights the need for further investigation to create a reliable and standardised method for identifying patella height. LEVEL OF EVIDENCE: Level IV.

Patellar Instability: Imaging Findings.

Patellofemoral instability results from impaired engagement of the patella in the trochlear groove at the start of flexion and may lead to pain and lateral patellar dislocation. It occurs most frequently in adolescents and young adults during sporting activities. Trochlear dysplasia, patella alta, and excessive lateralization of the tibial tuberosity are the most common risk factors for patellar instability. The main role of imaging is to depict and assess these anatomical factors and highlight features indicating previous lateral dislocation of the patella.

The Importance of Medial Patellar Shape as a Risk Factor for Recurrent Patellar Dislocation in Adults.

BACKGROUND: Research on the cause of lateral patellar dislocation (LPD) has focused on trochlear morphologic parameters, joint alignment, and patellofemoral soft tissue forces. A paucity of information is available regarding how patellar morphologic parameters influence the risk for LPD. PURPOSE/HYPOTHESIS: The purpose was to assess whether patellar morphology is a risk factor for recurrent LPD. It was hypothesized that (1) patients with recurrent LPD would have decreased patellar width and volume and (2) patellar morphologic parameters would accurately discriminate patients with recurrent LPD from controls. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: A total of 21 adults with recurrent LPD (age, 29.7 ± 11.1 years; height, 170.8 ± 9.9 cm; weight, 76.1 ± 17.5 kg; 57% female) were compared with 21 sex- and height-matched controls (age, 27.2 ± 6.7 years; height, 172.0 ± 10.6 cm; weight, 71.1 ± 12.8 kg; 57% female). Three-dimensional axial fat-saturated magnetic resonance imaging scans were used to measure patellar medial, lateral, and total width; patellar volume; patellar medial and lateral facet length; the Wiberg index; and previously validated knee joint alignment and femoral shape measurements (eg, tibial tuberosity to trochlear groove distance, trochlear dysplasia). RESULTS: The LPD group demonstrated reduced medial patellar width (Δ = -3.6 mm; P < .001) and medial facet length (Δ = -3.7 mm; P < .001) but no change in lateral width or facet length. This resulted in decreased total patellar width (Δ = -3.2 mm; P = .009), decreased patellar volume (Δ = -0.3 cm3; P = .025), and an increased Wiberg index (Δ = 0.05; P < .001). No significant differences were found for all other patellar shape measures between cohorts. Medial patellar width was the strongest single discriminator (83.3% accuracy) for recurrent LPD. Combining medial patellar width, patellofemoral tilt, and trochlear groove length increased the discrimination to 92.9%. CONCLUSION: The medial patellar width was significantly smaller in patients with recurrent LPD and was the single most accurate discriminator for recurrent LPD, even compared with traditional trochlear shape and joint alignment measures (eg, trochlear dysplasia, patella alta). Therefore, medial patellar morphology should be assessed in patients with LPD as a risk factor for recurrence and a potential means to improve treatment.

Patellar osteochondritis dissecans: maturation-dependent patellofemoral joint characteristics.

BACKGROUND: The likelihood of healing of osteochondritis dissecans decreases with skeletal maturity and there are theories that abnormal biomechanical forces contribute to the development and progression of these lesions. OBJECTIVE: To characterize, according to regional skeletal maturity, the morphology and alignment indices of the patellofemoral joint on MRI in patients with patellar osteochondritis dissecans. MATERIALS AND METHODS: MRI examinations of patients with patellar osteochondritis dissecans obtained between January 2008 and May 2023 were retrospectively reviewed to determine regional skeletal maturity, osteochondritis dissecans lesion size and location, patellar and trochlear morphology (Wiberg/Dejour classifications), and to calculate trochlear sulcus angles, trochlear depth index, lateral trochlear inclination, Insall-Salvati index, Caton-Deschamps index, patellar tendon-lateral trochlear ridge, and tibial tubercle-trochlear groove distances. Values were compared between skeletally immature and mature groups. RESULTS: Sixty-eight children (22 girls, 46 boys, age: 14.0 ± 1.7 years) yielded 74 knees with patellar osteochondritis dissecans lesions, 14 (19%) of which were skeletally mature. The most common anatomic location was over the central patella [median ridge (34/74 - 46%) on the axial images and over the middle third (45/74 - 61%) on the sagittal images]. Overall, mean trochlear sulcus angle (high, 151 ± 11°), trochlear depth index (low, 2.8 ± 1.4 mm), and Insall-Salvati index (borderline, 1.3 ± 0.1) were abnormal for the entire sample. Skeletally mature knees were significantly more likely to have higher (more dysplastic) Dejour types when compared to skeletally immature knees (p < 0.01). Knees in the mature group, compared to immature, had significantly more abnormal mean lateral trochlear inclination (15 ± 8° vs. 19 ± 6°, p = 0.03) and patellar tendon-lateral trochlear ridge distance (5.55 ± 4.31 mm vs. 2.89 ± 4.69 mm, p = 0.04). Half of the knees had ≥ 4 abnormal features that predispose to patellofemoral maltracking; mature knees were significantly (p = 0.02) more likely to have a higher number of abnormal features (> 6 features, 7/14, 50.0%) versus immature knees (0-3 features, 33/60, 55.0%). CONCLUSION: In children with patellar osteochondritis dissecans, abnormal patellofemoral morphology and alignment indices were common in all patients and more severe in mature knees.

Outcomes of surgical treatment of patellar instability in children with Down syndrome.

BACKGROUND: patellar instability is a relatively frequent musculoskeletal disorder in children with Down syndrome (DS). However, such a condition has seldom been studied in the literature, even less its surgical treatment. Different techniques have been offered for this condition; the evidence for surgical options is scarce and primarily based on case reports or case series with few patients and heterogeneous techniques. Given this background, we aimed to evaluate the outcomes of a uniform kind of surgical procedure for such a condition that combined lateral soft tissue release, medial patellofemoral ligament (MPFL) reconstruction (using a partial-thickness quadriceps tendon autograft), the Roux-Goldthwait procedure, and V-Y quadricepsplasty (if needed). MATERIALS AND METHODS: This retrospective study involved 11 skeletally immature patients (12 knees; 9 males and 2 females), 5.5 to 14.1 years of age, with DS who had patellofemoral instability (PFI) and were managed by this technique between October 2018 and March 2020. Preoperative radiography, CT scan, and MRI were performed to evaluate the physis status, lower limb alignment, patellar height, trochlear morphology, and any associated knee pathology. A functional knee assessment was done by using the Kujala score and the modified Lysholm score. RESULTS: The mean time of follow-up (± SD) was 47.7 ± 5.8 months (range: 39-56). Pre-operatively, the Kujala score (± SD) was 52.6 ± 14.3 (range: (31-74), and at final follow-up, it was 92.2 ± 4.4 (range: (88-98), showing a significant improvement (P < 0.001). The preoperative modified Lysholm score (± SD) was 54.3 ± 8.1 (range: 39-62), and at final follow-up it was 92.4 ± 5.3 (range: 82-96), showing a significant improvement (P < 0.001). All patients had a stable patella without a recurrence of instability and regained full ROM. There was no incidence of a patellar fracture or femoral physis injury. CONCLUSIONS: Our proposed technique of combined soft tissue procedures, including lateral soft tissue release, MPFL reconstruction (using a partial-thickness quadriceps tendon autograft), the Roux-Goldthwait procedure, and V-Y quadricepsplasty, was an effective method for treating patellar instability in children with DS while avoiding physeal injury and patellar fracture. Functional scores and radiological outcomes were improved. LEVEL OF EVIDENCE: IV; retrospective case series.