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Background Evidence concerning the influence gender, age, and the time elapsed from the first dislocation to surgery in the outcomes of Medial Patella Femoral Ligament (MPFL) reconstruction are lacking. This systematic review was conducted to investigate whether patient characteristics have an influence in the clinical outcomes of MPFL reconstruction for patients with patellofemoral instability. Material and methods This study followed the PRISMA guidelines. The main databases were accessed in February 2021. All the studies reporting outcomes of primary MPFL reconstruction in patients with recurrent patellofemoral instability were considered for inclusion. A multivariate analysis diagnostic tool was used to analyse the association between age, gender and time from injury to surgery and the surgical outcomes at last follow-up. Results A total of 50 articles (2037 procedures) were included. The mean follow-up was 40.90 ± 24.8 months. The mean age was 23.6 ± 3.9 years. 64.3% (1309 of 2037 patients) were female. The mean time from injury to surgery was 64.5 ± 48.9 months. Women showed no statistically significant association with the Kujala score or complications. Older patients had a reduced risk to incur re-dislocations (P = 0.01) and revisions (P = 0.01). Longer time from injury to surgery was associated with greater risk to incur re-dislocations (P = 0.01), and with lower Kujala score (P Conclusion The time span from the first patellar dislocation to the surgical reconstruction was a negative prognostic factor, while sex had no influence on surgical outcomes. The role of patients age on surgical outcomes remains unclear.

Osteochondral defect or osteochondritis dissecans (OCD) of the knee usually affects young, active populations. It is a challenging diagnosis as patients typically present with poorly localised activity-related pain, which is non-specific and covers many differentials. We present an active 11-year-old girl with bilateral osteochondral defects of the patellae: a rare clinical disorder which was affecting her sporting activities. She had a 12-month history of bilateral anterior knee pain before the diagnosis was achieved with appropriate imaging. Her pain significantly improved with activity modification and physiotherapy. Follow-up will require outpatient clinic assessment and imaging to determine if non-operative management continues to be successful or surgery may be required. This case report emphasises the importance of appropriate high index of suspicion when managing patients with non-specific knee pain. It also demonstrates the importance of judicious use of imaging to avoid a missed or delayed diagnosis.

article i nfo Article history: Received 6 February 2013 Accepted 15 April 2013 A biomechanical computer-based model was developed to simulate the influence of patellar thickness on passive knee flexion after arthroplasty. Using the computer model of a single-radius, PCL-sacrificing knee prosthesis, a range of patella-implant composite thicknesses was simulated. The biomechanical model was then replicated using two cadaveric knees. A patellar-thickness range of 15 mm was applied to each of the knees. Knee flexion was found to decrease exponentially with increased patellar thickness in both the biomechanical and experimental studies. Importantly, this flexion loss followed an exponential pattern with higher patellar thicknesses in both studies. In order to avoid adverse biomechanical and functional consequences, it is recommended to restore patellar thickness to that of the native knee during total knee arthroplasty.

We describe here an interesting case of a 7-day-old male infant brought with parental concerns of inability to extend both knees. Clinical evaluation revealed dysplastic fingernails, bilateral abnormal patellae, triangular lunules in conjunction with pathognomic iliac horns on pelvic radiographs suggesting the possibility of nail-patella syndrome (NPS). Other competing diagnoses with similar phenotypic features were considered and sequentially excluded. A definitive diagnosis was established by the identification of the principal mutation at the LMX1B gene locus of chromosome 9. NPS is seldom diagnosed in neonates due to the heterogeneity of clinical presentations as well as the subtlety of clinical clues in this population. NPS is a dominantly inherited disorder that is predominantly familial in origin and thus carries important implications for the prenatal diagnosis of future pregnancies as well as pre-emptive surveillance of nephropathy in the index child.

Introduction The current technique of angulating for a skyline knee projection relies heavily on the radiographer's estimation of the patella tilt, rendering it subjective and prone to errors. This study therefore aims to (i) examine the correlation between angle ABC measured on the lateral X-ray image and skyline angulation (measured in degrees) and (ii) determine the inter-rater reliability of angle ABC measurements. Methods 145 sets of lateral and skyline X-ray images from patients aged 40–70 years old were retrospectively analysed. Angle ABC was measured using prominent landmarks such as the trochlear sulcus, tibial tuberosity and the anterior border of the patella on the lateral knee radiograph. It was then retrospectively compared with the skyline tube angulations to identify any correlation between the two. An inter-rater reliability test was also conducted using the intraclass correlation coefficient (ICC) to determine the reproducibility of the measurement method. Results A weak correlation was found between angle ABC and skyline angulation (r = 0.1, p = 0.25). The proposed method of measurement shows good inter-rater reliability (ICC = 0.81, 95% CI: 0.77 to 0.84). Conclusion There is insufficient evidence to indicate a correlation between angle ABC and skyline angulation. However, angle ABC can be reliably measured, implying the replicability of the measurement method for other purposes. Implications for practice The proposed measurement method of angle ABC on the lateral view could have future applications in other areas such as in the measurement of patellofemoral alignment and trochlear morphology.

To compare T1ρ relaxation times of the medial and lateral regions of the patella and femoral trochlea at 6 and 12 months following anterior cruciate ligament reconstruction (ACLR) on the ACLR and contralateral extremity. Greater T1ρ relaxation times are associated with a lower proteoglycan density of articular cartilage.This study involved 20 individuals (11 males, 9 females; mean ± SD age 22 ± 3.9 years, weight 76.11 ± 13.48 kg, and height 178.32 ± 12.32 cm) who underwent a previous unilateral ACLR using a patellar tendon autograft. Magnetic resonance images from both extremities were acquired at 6 and 12 months post-ACLR. Voxel by voxel T1ρ relaxation times were calculated using a 5-image sequence. The medial and lateral regions of the femoral trochlea and patellar articular cartilage were manually segmented on both extremities. Separate extremity (ACLR and contralateral extremity) by time (6 months and 12 months) analysis of variance tests were performed for each region (P 0.05).For the medial patella and lateral trochlea, T1ρ relaxation times increased in both extremities between 6 and 12 months post-ACLR (medial patella P = 0.012; lateral trochlea P = 0.043). For the lateral patella, T1ρ relaxation times were significantly greater on the contralateral extremity compared to the ACLR extremity (P = 0.001). The T1ρ relaxation times of the medial trochlea on the ACLR extremity were significantly greater at 6 (P = 0.005) and 12 months (P 0.001) compared to the contralateral extremity. T1ρ relaxation times of the medial trochlea significantly increased from 6 to 12 months on the ACLR extremity (P = 0.003).Changes in T1ρ relaxation times occur within the first 12 months following ACLR in specific regions of the patellofemoral joint on the ACLR and contralateral extremity.

Purpose To analyze the clinical outcomes and survival curve of arthroscopic lateral patellar facetectomy and lateral release for isolated patellofemoral osteoarthritis (PFOA). Methods All patients undergoing arthroscopic lateral patellar facetectomy and lateral release between January 2008 and January 2018 were evaluated retrospectively. The inclusion criteria were 1) diagnosis of isolated symptomatic lateral PFOA, 2) PFOA with kissing lesions (defined as a lesion on both the patella and trochlea, which were in direct contact, 3) arthroscopic lateral patellar facetectomy and lateral release, and 4) two-year minimum follow-up. Evaluation included preoperative and postoperative subjective International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS) scores, and visual analogue pain scale (VAS). The primary end point determining the survival curve was revision of lateral facetectomy. Results A retrospective analysis was conducted of 61 consecutive arthroscopic lateral patellar facetectomy and lateral release procedures, performed in 55 patients for a diagnosis of isolated PFOA. Five patients were lost to follow-up, leaving 56 knees (50 patients) available at a mean follow up of 7.5 years (range: 2-10). The cohort included 37 women and 13 men with a mean age of 59 years (range: 34-87). Nine patients (18%) underwent revision surgery: six total knee replacements (TKR), two high tibial osteotomies, and one revision arthroscopic lateral patellar facetectomy. The mean time from arthroscopic facetectomy to TKR was 51 months (range: 10-114). The survival curve rate was 86% at 7.5 years. Both KOOS and IKDC scores improved significantly. These results are confirmed by an analysis of MCID. The mean VAS decreased from 6.98 ± 1.2 preoperatively to 2.06 ± 1.6 at the last follow-up (ΔCI95% = [−5.6; −4.4]; P = .0001). Conclusion Arthroscopic lateral patellar facetectomy and lateral release for isolated PFOA demonstrates sustained significant improvement in knee clinical outcome scores and pain with a low rate of complications and revision surgery at mid-term follow-up. This operation can be recommended in cases of symptomatic isolated PFOA. Level of Evidence IV, case series

Background While periprosthetic fractures following total hip arthroplasty (THA) are a well-known phenomenon for orthopedic surgeons, fragility fractures following THA are also a significant, though less studied, concern. Furthermore, patients who have undergone THA have several additional risk factors for fragility fractures, including motor weakness, bone atrophy, and limping. The aims of this study were to evaluate the incidence of fragility fractures following THA and to clarify the characteristics of these fractures. Methods This study included 5678 primary THA procedures in 4589 female patients. This study evaluated body morphology data, disease type leading to THA, Japanese Orthopaedic Association hip score, range of motion of the hip joint, and medical history. Distal radius and patella fractures were defined as fragility fractures. Risk factors for fragility fractures after THA were calculated by comparing the fragility fracture group with the non-fracture group. Results Fifty-three fragility fractures were confirmed in 53 patients (distal radius fracture: 32 fractures in 32 patients, patella fracture: 21 fractures in 21 patients). In the univariate analysis, the following eight risk factors for fragility fractures were significantly different between the groups: height, weight, follow-up period, developmental dysplasia of the hip, primary osteoarthritis, abduction before THA, internal rotation before THA, and external rotation before THA. Medical histories were not significantly different between the groups. There was no difference in any study factor and in the time of occurrence between the radius fractures and patella fractures analyzed as fragility fractures. Conclusions This study revealed that there are significant preoperative factors of fragility fractures following THA. These factors will serve as useful data for THA treatment strategies, preoperative explanations, and future studies.

Medial dislocation of patella has been commonly reported as a complication of the surgical release of the lateral patella-femoral ligament. A traumatic medial eversion-dislocation of the patella has not been earlier reported. We report an unusual case of traumatic medial patellar eversion-dislocation in a young adult patient whose MRI showed a discontinuity in medial and lateral patellar retinacula. However, intraoperatively the retinacula were found intact and relocation of the patella was achieved by flipping the patella through a small hole in the patellar tendon. No reconstruction of the ligaments was needed. At 1-year follow-up, the patient achieved full range of movements of the knee and there were no subjective complaints of instability. In our case, although the patella was medially everted and dislocated, both the retinacula were still intact. Clinicians should be aware that acute traumatic patella medial dislocation and eversion can occur without disruption of the medial or lateral retinaculum. Furthermore, knee MRI may suggest patellar retinacula disruption due to the retinaculum's obscure and tortuous course in patients with these injuries.

Introduction: Patellar fractures constitute almost 1% of total skeletal injuries. Existing common operative methods include the use of different types of Tension band wiring techniques like cannulated screws and K-wires. The Patellar plating construct is a relatively newer operative method for patellar fracture fixation with promising outcomes with fewer complications. Method: We conducted a pilot prospective study at our Apex Trauma Centre in twenty patients aged 18- 65years with displaced patellar fractures, AO type A2, A3, B2, B3, C1, C2, C3. Fractures were fixed with low profile patellar plates (1.8mm). Radiological and functional follow-up was done using X-rays, CT scans and BKS scoring (Bostman-Knee-Scale), Knee Society Score(KSS), and Tegner Lysholm knee scores respectively for two years. Result: Mean functional outcome scores at 6 weeks, 3 months, 6 months and 2 years was 25.5, 28.3, 29.05 and 29.9 for BKS; 64.62, 84.12, 90.6, and 97.5 for KSS; 73.75, 89.7,94.8, and 99.3 for Tegner Lysholm knee score respectively. Radiological union, confirmed by CT scan, was observed in all patients at 3 months. Two patients had superficial surgical site infection (SSI) at 2 weeks. Implant impingement was also found in 2 patients at 3 months. None of the patients had a failure of fixation at the end of the study. Conclusion: Patients with low profile patellar plate constructs have favorable clinical and radiological outcomes with minimal non-specific complications.

A triangular configuration with three parallel cannulated screws is an established treatment for fixing transverse patellar fractures; however, the stability achieved with this approach is slightly lower than that attained with cannulated screws combined with anterior wiring. In the present study, triangular configurations were modified by partially or totally replacing the cannulated screws with headless compression screws (HCSs). Through finite element simulation involving a model of distal femoral, patellar, and proximal tibial fractures, the mechanical stability levels of the modified triangular configurations were compared with that of two cannulated screws combined with anterior wiring. Four triangular screw configurations were developed: three HCSs in a forward and backward triangular configuration, two deep cannulated screws along with one superficial HCS, and two superficial cannulated screws with one deep HCS. Also considered were two parallel cannulated screws (inserted superficially or deeply) combined with anterior wiring. The six approaches were all examined in full knee extension and 45° flexion under physiological loading. The highest stability was obtained with the three HCSs in a backward triangular configuration, as indicated by the least fragment displacement and the smallest fracture gap size. In extension and flexion, this size was smaller than that observed under the use of two deeply placed parallel cannulated screws with anterior wiring by 50.3% (1.53 vs. 0.76 mm) and 43.2% (1.48 vs. 0.84 mm), respectively. Thus, the use of three HCSs in a backward triangular configuration is recommended for the fixation of transverse patellar fractures, especially without the use of anterior wiring.

Patella alta is described as abnormally high-riding patella in relation to the femur, the trochlear groove, or the tibia with decreased bony stability. Patella alta represents an important predisposing factor for patellofemoral instability. Different measurement methods are used to define patella alta. Despite the clinical importance of patella alta, there is only limited consensus on cutoff values, indications for treatment, and ideal correction. In addition, the impact of patella alta on other risk factors for lateral patellar instability is significant. This must be considered when assessing clinical complaints and choosing the best individual treatment. Combined surgical interventions may be necessary.

Congenital dislocation of the patella is a rare condition characterized by lateral dislocation of the patella that is irreducible without surgical correction. Although there is no clear inheritance pattern, it is associated with several congenital syndromes. Patients often demonstrate flexion contracture, loss of active knee extension, increased tibial external rotation, and absent patella in the trochlea. Treatment requires surgical management and is comprised of lateral release, medial stabilization, quadriceps lengthening, and distal realignment. Results are generally favorable after treatment; persistent flexion contracture and redislocation are the most common complications. Further study is needed to define the optimal timing and treatment strategy for this uncommon condition.

Objective To confirm whether a novel sagittal patellar angle linear equation used for evaluating patellar height by calculating expected sagittal patellar angle (SPA) at any degree of knee flexion angle is suitable for patients older than 17 years and its reliability compared with other commonly used methods. Methods From September 2016 to September 2019, a total number of 202 consecutive outpatients' knee lateral X‐ray radiographs were retrospectively measured and evaluated using a recently proposed linear equation Y = 1.94 + 0.74 × knee flexion (KF) angle. Patients were divided by ages into ayounger group, whose ages were between 17–49 years, and an older group, whose ages were older than 49 years, which has not been validated in the original study. Parameters such as KF, SPA, patella and patella tendon length and so on were measured on computer with picture archiving and communication system by two independent observers at an interval of 1 month. Insall‐Salvati (IS) index, Caton‐Deschamps (CD) index and Y value, correlation coefficients were calculated and compared using SPSS 22.0 software. Results In the younger group, 143 patients (165 knees) were included, ages were 17–49 (31.62 ± 11.38) years, males/females were 70 (48.95%)/73 (51.05%), left knees/right knees were 83 (50.30%)/82 (49.70%), mean value of Y was 31.50° ± 10.07°, and SPA was 34.38° ± 12.38°, mean value of IS was 1.06 ± 0.17, mean value of CD was 1.04 ± 0.18. While in older group, 59 patients (78 knees) were included, ages were 50–60 (mean 54.61 ± 2.99) years, there were 32 males (54.24%) and 27 females (45.76%), 42 knees were left (53.85%) and 36 knees were right (46.15%), mean values of Y and SPA were 25.90° ± 11.55° and 29.36° ± 14.22°, mean IS index in older group was 1.06 ± 0.18, mean CD index was 1.00 ± 0.16. Intra‐ and inter‐observer reliabilities of Y in younger and older groups were 0.999, 0.999, 1.000 and 0.999, meaning high reliability and reproducibility, but low Pearson's correlation coefficients with IS and CD index were showed as −0.213 and − 0.216 in younger group and − 0.113 and − 0.316 in older group. Conclusions In patients older than 17 years, the linear equation Y = 1.94 + 0.74 × KF is a reliable and practical method to evaluate SPA regardless of age and knee flexion angle, but has weak correlation coefficients with the IS and CD index., To confirm the effectiveness of a novel sagittal patellar angle equation used for evaluating patellar height by calculating expected sagittal patellar angle(SPA) with knee flexion angle.

The lateral patellofemoral complex is an important stabilizer to medial and lateral displacement of the patella. Soft tissue abnormalities can range from pathologic tightness to laxity, presenting with symptoms related to patellar instability, anterior knee pain, or arthritis. Clinical evaluation should be performed to confirm patellar dislocation, assess the integrity of the lateral and medial soft tissues, and explore other pathoanatomic factors that may need to be addressed. Lateral retinacular lengthening is recommended over lateral release owing to the potential of iatrogenic medial instability with release, and a lateral patellofemoral ligament reconstruction can be performed to effectively treat medial instability.

Comminuted fractures of the patella mostly occur at the inferior pole and require appropriate reduction and fixation to restore the extensor mechanism. Conventional methods such as tension-band wiring are not enough to gain proper fixation strength. Numerous methods have been reported, including circumferential cerclage wiring, osteosynthesis, and suture anchors depending on the fracture pattern. Herein, the author reports a relatively rare case of a comminuted fracture of the upper pole of the patella, for which we used augmented Krackow sutures in the quadriceps and fixation with tying of the suture limbs through patellar bone tunnels. Satisfactory results were obtained in terms of reduction and extensor mechanism recovery.

PURPOSE Patellar dislocation is associated with a range of anatomical abnormalities affecting the trochlea, extensor mechanism and the tibia. The relationship between patellofemoral instability and rotational abnormalities of the posterior condyles, trochlear groove and proximal tibia has not been adequately determined. This study aimed to identify the frequency and severity of anatomical risk factors to determine their relative contribution to patellofemoral instability. METHODS A retrospective morphological study was undertaken comparing multiple anatomical measurements with magnetic resonance imaging of 50 patients with patellofemoral instability to an age- and gender-matched Control group (n = 50). Several techniques were assessed measuring both femoral and tibial axial asymmetry. A new measurement, tibial rotational asymmetry, comparing a line between the midpoints of the collateral ligaments to the axis between the patellar tendon and posterior cruciate ligament, was assessed for its association with patellofemoral instability. RESULTS Compared to the controls, the patellofemoral instability group demonstrated a significant difference in tibial rotational asymmetry, with a mean of 2.9° (SD 3.2°) externally rotated vs - 1.6° (SD 2.2°) in the control group. Significant differences were also demonstrated regarding the sulcus angle, tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, patellar size and the Insall-Salvati ratio. There were no differences between groups regarding the lengths of the posterior condyles, the heights of the trochlear ridges or lateralisation of the trochlear groove. Further analysis of the patellofemoral instability group revealed a subgroup of males with normal anatomy (7/50) and a subgroup of females with isolated patella alta (7/50). CONCLUSION Patellofemoral instability is associated with tibial rotational asymmetry due to lateralisation of the tibial tubercle. It is also associated with patella alta and reduced trochlear groove depth. The femoral axial shape is otherwise unchanged. LEVEL OF EVIDENCE III.

Background The International Classification of Diseases-10 (ICD-10) came into effect in October 2015. The new procedural codes (ICD-10-PCS) were designed to specify granular aspects of the procedure, including laterality and revised components. This specificity could improve data collection in institutional databases, large registries, and administrative claims data. Given these possible applications, this study’s purpose was to assess the accuracy of ICD-10-PCS coding for revision total knee arthroplasty (rTKA). Methods This multicenter retrospective analysis utilized the rTKA databases at four academic medical centers for all aseptic rTKAs between October 1, 2015 and July 3, 2019. Operative reports were reviewed to determine laterality and revised components (tibial, femoral, liner, and patellar component), which were then compared with the ICD-10-PCS codes associated with the billing records. Proper coding required both component removal and replacement codes. The correct series of removal and replacement codes was determined using the American Joint Replacement Registry’s guidelines. Results In total, 1906 rTKAs were examined, and 98.0% had at least one proper ICD-10-PCS code, indicating an rTKA had occurred. Coding for components replaced was correct in 76.3% of cases. When examining both removal and replacement codes, accuracy dropped to 57.0%. Conclusion Nearly 25% of rTKA procedures were incorrectly coded for replaced components, and over 40% were incorrectly coded for removed and replaced components. ICD-10-PCS codes can accurately identify that an rTKA has occurred; however, the inaccuracy in identifying which specific components were revised should prompt further evaluation of the coding process before utilizing ICD-10-PCS codes to report granular rTKA data. Level of Evidence III, retrospective observational analysis.

Anterior knee pain is an important complication after total knee arthroplasty (TKA). One possible contributor is the elevation of the joint line, known as pseudo-patella baja (PPB). Limited research has been conducted regarding this condition impacting TKA management. This study aims to evaluate the incidence, identify possible related factors and assess PPB clinical repercussions.A total of 813 consecutive TKAs were retrospectively reviewed. Patients were submitted to the same surgical procedure and information regarding TKA characteristics was collected. Lateral postoperative knee radiographs were analyzed using the modified Insall-Salvati Ratio and the Blackburne-Peel Index. A clinical evaluation was conducted on 112 knees where the Oxford Knee and Kujala Scores were applied. Range of motion was evaluated, and knee pain was assessed using the numeric pain rating scale, in addition to analgesic consumption.A cohort of 612 knees was analyzed, of which 64 knees developed PPB (10.5% incidence). Statistically significant differences were found for advance components sizes (femoral P = 0.026 and tibial P 0.001), polyethylene thickness (P 0.001) and patients' height (P = 0.022) with smaller implant sizes, greater insert thicknesses and lower height showing an association with PPB. The PPB group had a significantly lower median Kujala score (P = 0.011), higher frequency of flexion contracture and of anterior knee pain (P = 0.039).PPB has a clinical relevance that should not be overlooked. Its prevention through the recreation of the natural position of the joint line and correct choice of implant sizes and polyethylene thickness is of major importance and should always be considered.

Background The medial patellofemoral ligament (MPFL) is considered the primary soft tissue restrain to lateral translation of the patella during the first 15–30 degrees of knee flexion. The primary restraint thereafter is the slope of the lateral wall of the trochlea. A plenty of procedures are described in literature for MPFL reconstruction with different types of graft, angle of knee flexion for fixation and rehabilitation protocols. In this study we used MPFL reconstruction with doubled autologous gracilis tendon with the Schottle’s technique. The aim of our study is to evaluate outcomes at medium-long term follow up of MPFL reconstruction. Methods Patients who underwent arthroscopic MPFL reconstruction for recurrent patellar dislocation were followed up for a minimum of 2 to 10 years. Patient-reported outcomes including the Kujala, Visual Analogue Scale (VAS) score were collected preoperatively and postoperatively. Clinical complications such as loss of ROM, recurrent sub-luxation or dislocation were recorded. Results A total of 38 patients with recurrent patellar dislocation were treated with MPFL reconstruction and data were available for final follow up (mean 72.3 months, SD 33.6). Mean age at time of surgery was 23.4 (SD 7.8). Mean number of dislocations before surgery was 7.1 (SD 10.5). Recurrent dislocations were not observed in any of the patients treated at last follow-up. Significant clinical improvements were also noted with Kujala and VAS score. Patellar tilt angle decreased significantly from pre to post-operative. Conclusion Our study demonstrated that MPFL reconstruction with patellar suture anchors fixation using autologous gracilis tendon is an effective, safe and reliable method for treating recurrent patellar dislocation.

In skeletally immature patients with recurrent patella dislocation that needs operation, how to increase the medial stability of the patella effectively without disturbance of the epiphysial plate is of concern. Through evaluation of multiple techniques that designed to avoid injury to the epiphysial plate, we found that medial patellofemoral ligament augmentation with high-strength nonabsorbable sutures is feasible and effective. Thus, we would like to describe this technique, whose critical point is the correct location and creation of the 2 femoral tunnels. We consider the introduction of the current technique will provide reasonable choices when operation is needed in this special group of patients., Technique Video Video 1 Polyethylene suture augmentation of the medial patellofemoral ligament in skeletally immature patients with recurrent patella dislocation. This procedure is performed in the right knee. One incision is made over the medial edge of the patella, at a level of the junction of the proximal and middle one-third of the patella. A K wire is first drilled at a level approximately 5 mm proximal to the junction point, from the medial edge of the patella to its anterior surface. The K wire is overdrilled with a 4.5-mm drill to create a patellar tunnel. Another K wire is drilled at a level approximately 5 mm distal to the junction point, from the medial edge of the patella to its anterior surface. The K wire is overdrilled with a 4.5-mm drill to create the second patellar tunnel. One guide suture is passed through each patellar tunnel from the medial to the lateral side. Three No 2 ultra-high molecular weight polyethylene sutures are passed through the proximal patellar tunnel from the medial to the lateral side and then passed through the distal patellar tunnel from the lateral to the medial side. One incision is made over the medial femoral epicondyle and the adductor tubercle. The proximal femoral tunnel is located and created sequentially with a K wire and a 4.5-mm cannulated drill. A polydioxanone suture is placed in the proximal femoral tunnel. The distal femoral tunnel is located and created in the same way. The augmentation sutures are pulled subcutaneously out of the medial incision. The proximal and distal sutures limbs are pulled into the proximal and distal femoral tunnels, respectively, out of the lateral thigh. A 2-mm lateral incision is made at the anterior edge of the iliotibial band at a level at the proximal pole of the patella. With the knee at full extension, the suture limbs are pulled tight and exposed. The sutures are retrieved out of the lateral incision through the space resulted from lateral retinaculum release. The knee is flexed at 90°. The sutures are tied over the bone bridge between the lateral orifices of the femoral tunnels.

Background The purpose of this study was to evaluate the ultimate failure load and stiffness of two patellar fixation techniques for medial patellofemoral ligament (MPFL) reconstruction: (1) quadriceps tendon fixation (QT), (2) single tunnel (STG) patella fixation with gracilis autograft. Methods A total of 16 fresh-frozen cadaveric knees (eight matched pairs) were randomized into two groups (QT vs. STG). The MPFL reconstructions were subjected to cyclic loading for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). Failure mode, ultimate failure load and stiffness were recorded for each cadaveric specimen. Results There was no significant difference in mean ultimate failure load among groups (P = 0.35). The STG group failed at a mean ultimate load of 190.04 N [standard deviation (SD) 23.18] and the QT group failed at 206.24 N (SD 37.99). The STG group had a mean stiffness of 21.38 N/mm (SD 1.44). This was not significantly higher than the mean stiffness value achieved for the QT group at 20.36 N/mm (SD 1.3) (P = 0.19). In the QT group all reconstructions failed due to tendon rupture at the patella attachment. The reason for failure in the STG group was the graft–suture connection. Conclusions This cadaver study showed no statistically significant difference in biomechanical performance of the evaluated patella fixation techniques, in terms of maximum load to failure and stiffness. Both techniques are reliable in terms of biomechanical properties and could offer additional surgical solutions.

Patellofemoral instability is one of the knee problems that can be found in up to 3% of knee injuries, especially in younger aged females. Recent biomechanical studies showed that the main soft tissue stabilizer for patellofemoral stability is the medial patellofemoral ligament (MPFL). More than 200 articles on MPFL reconstruction have been published. Some surgical techniques create multiple holes in the patellar area that may increase the risk of patellar fractures. This technique that we present here attempts to reduce the chance of patella-related complications, while maintaining stability of the reconstructed construct, reducing the use of a lengthy tendon graft within the patella and covering the footprint at the border of the patella closed to the native anatomy of the MPFL., Technique Video Video 1 The surgical technique performing the single patellar tunnel technique for anatomical double-bundle.

BACKGROUND The quadriceps femoris may be a reliable reference to proper alignment in total knee arthroplasty (TKA). We previously showed the quadriceps vector (QV) to be the most parallel to the spherical axis (SA-center hip to center medial condyle) for healthy knees. The purpose of this study was to determine whether the QV is the most parallel to the SA in knees with varus osteoarthritis (OA). METHODS CT imaging for 35 varus OA and 40 healthy Japanese knees was used to construct 3D models of the femur, patella and each quadriceps component for each subject. The QV was calculated using principal component analysis for direction and was compared with the relationship of the QV to the measurement axes of the lower extremity, including the anatomical, mechanical and spherical axes. RESULTS The direction of the QV for the OA knee group was different from that for the healthy knee group in 3D space (medio-lateral direction: women, p = 0.532, men, p = 0.540; antero-posterior direction: women, p = 0.141, men, p

An 8-day-old female Shetland pony was referred to the Jeonbuk animal medical center for evaluation of bilateral hindlimb lameness. The foal had been severely lame in the both hind leg since birth. The luxation of the patella was confirmed on physical examinations. During the operation, extensive soft tissue damage and hemorrhage were observed around the medial patellar ligament. Lateral patellar luxation was surgically repaired using lateral release of the patella and medial imbrication of the joint capsule. Follow up revealed that lameness improved during postoperative period. It was concluded that patella luxation as a traumatic cause of lameness in foals can be corrected by surgical techniques successfully. Key words: Lateral patellar luxation, surgery, shetland pony, foal, stifle.

PURPOSE Automatic muscle segmentation is critical for advancing our understanding of human physiology, biomechanics, and musculoskeletal pathologies, as it allows for timely exploration of large multi-dimensional image sets. Segmentation models are rarely developed/validated for the pediatric model. As such, autosegmentation is not available to explore how muscle architectural changes during development and how disease/pathology affects the developing musculoskeletal system. Thus, we aimed to develop and validate an end-to-end, fully automated, deep learning model for accurate segmentation of the rectus femoris and vastus lateral, medialis, and intermedialis using a pediatric database. METHODS We developed a two-stage cascaded deep learning model in a coarse-to-fine manner. In the first stage, the U2 -Net roughly detects the muscle subcompartment region. Then, in the second stage, the shape-aware 3D semantic segmentation method SASSNet refines the cropped target regions to generate the more finer and accurate segmentation masks. We utilized multifeature image maps in both stages to stabilize performance and validated their use with an ablation study. The second-stage SASSNet was independently run and evaluated with three different cropped region resolutions: the original image resolution, and images downsampled 2× and 4× (high, mid, and low). The relationship between image resolution and segmentation accuracy was explored. In addition, the patella was included as a comparator to past work. We evaluated segmentation accuracy using leave-one-out testing on a database of 3D MR images (0.43 × 0.43 × 2 mm) from 40 pediatric participants (age 15.3 ± 1.9 years, 55.8 ± 11.8 kg, 164.2 ± 7.9 cm, 38F/2 M). RESULTS The mid-resolution second stage produced the best results for the vastus medialis, rectus femoris, and patella (Dice similarity coefficient = 95.0%, 95.1%, 93.7%), whereas the low-resolution second stage produced the best results for the vastus lateralis and vastus intermedialis (DSC = 94.5% and 93.7%). In comparing the low- to mid-resolution cases, the vasti intermedialis, vastus medialis, rectus femoris, and patella produced significant differences (p = 0.0015, p = 0.0101, p

BACKGROUND: Increased surgical time in TKA may impact economic costs and clinical outcomes. Prior work has found that TKAs in patients with high BMI take longer, and these patients may be at greater risk for postoperative complications like infection. However, these studies included small numbers of patients and surgeons from single institutions and they did not consider surgeon volume. QUESTIONS/PURPOSES: Using the New Zealand Joint Registry (NZJR), we asked: (1) Is there a relationship between increasing patient BMI and TKA operative time? (2) Is the effect of BMI on surgical time less pronounced among surgeons who perform more TKAs per year than those who perform fewer? METHODS: Data were collected from the NZJR between January 2010 and December 2018 as it is the only national registry that records both BMI and surgical time. Primary TKA performed for osteoarthritis by surgeons with more than 50 TKAs over the period of the study were identified. BMI and operative time (skin incision to closure in minutes) were recorded. Patients with the following were excluded: lateral parapatellar or minimally invasive approaches; navigated, patient-specific instrumentation, or robot-assisted TKA; uncemented or hybrid fixation; those with procedures performed by a trainee (all or part); or a nonosteoarthritic indication. Of 64,108 TKAs performed during the study period, a total of 42% (27,057) met our inclusion criteria. The primary outcome was the effect of BMI on operative time. Operative time is expressed in minutes as a mean for each single-unit BMI increase across all surgeons, controlled for other variables that might influence operative time such as patella resurfacing and cruciate-retaining versus posterior-stabilized designs. Overall, the mean operative time (skin incision to closure) was 79 ± 22 minutes. Surgical experience was assessed by subdividing surgeons into six groups according to the number of TKAs performed annually (< 10, 10 to 24, 25 to 49, 50 to 74, 75 to 99, and > 100). Statistical analyses were performed including a general linear model to assess the independent association between BMI and operative time, allowing for the effects of other patient and surgical features. In addition, linear regression analyses explored the associations between BMI and operative time in the whole group and within surgical volume groups. RESULTS: There was an association between increasing BMI and increasing surgical duration. The mean operative time increased from 75 ± 22 minutes in patients with a normal BMI of 25 kg/m(2) to 87 ± 24 minutes in patients with a BMI of 40 kg/m(2) to 94 ± 28 minutes in patients with a BMI > 50 kg/m(2) (p < 0.001). Surgeons performing fewer than 25 TKAs per year took 14% longer to perform a TKA on a patient with a BMI of 40 kg/m(2) than on a patient with a normal BMI of 25 kg/m(2). However, surgeons performing greater than 25 TKAs per year took 10% longer. CONCLUSION: In this study, an increase BMI was associated with increased surgical time in TKA. Surgical duration for high-volume surgeons appears less influenced by increases in BMI than lower volume surgeons. Although the absolute increase in duration was small, prolonged surgical time may reduce theater productivity. Even though the issues around managing patients with high BMI are multifactorial and complex, considerations from these findings include ensuring appropriate theater scheduling and possibly referring patients with high BMI to specialist centers. Further studies should focus on assessing the effectiveness of such measures in reducing complications and improving outcomes in patients with elevated BMI. LEVEL OF EVIDENCE: Level III, therapeutic study.

To determine the reoperation rate, risk factors for reoperation, and patient-reported outcomes after isolated or combined tibial tubercle transfer and medial patellofemoral ligament reconstruction, for patellofemoral instability surgery. Patient’s records who underwent medial patellofemoral ligament reconstruction and/or tibial tubercle transfer for patellar instability by 35 surgeons from 2002 to 2018 at a single academic institution were retrospectively reviewed using CPT codes. Four-hundred-and-eighty-six patients were identified. Radiographic measurements, demographic parameters, and subsequent revision procedures and their indications were identified. A modified anterior knee pain survey was conducted by mail and with follow-up phone survey. The overall rate of reoperation was 120/486 (24.7%). The most common cause for reoperation was removal of hardware 42/486 (8.6%). The rate of reoperation for isolated medial patellofemoral ligament reconstruction 43/226 (19%) was lower than that of isolated tibial tubercle transfer 45/133 (33.8%) or a combined procedure 32/127 (25.2%) (P = 0.007). Woman had a higher rate of reoperation (29.4%) compared to men (15.9%) (P = 0.002). Patients at risk for a revision stabilization procedure included those with severe trochlear morphology (C or D) (6.1%) and those with Caton–Deschamps index > 1.3 (7.3%). Patients who underwent reoperation of any kind had poorer patient-reported outcomes. The overall reoperation rate after patellofemoral instability surgery remains high, and any reoperation portends worse patient-reported outcomes. Re-operations for instability are more likely in patients with trochlear dysplasia and patella alta and may benefit from more aggressive initial treatment, such as medial patellofemoral ligament reconstruction and tibial tubercle transfer in combination. Using the results of this study, surgeons will be able to engage in meaningful discussion with patients to counsel patients on expectations postoperatively. IV.

Background It has been hypothesized that the patella, working in conjunction with both medial and lateral femoral condyles, can influence kinematic parameters such as posterior femoral rollback and axial rotation. The objective of this study is to determine the in vivo kinematics of subjects implanted with a fixed-bearing (FB) or mobile-bearing (MB) posterior-stabilized (PS) total knee arthroplasty (TKA), with a specific focus on evaluating the impact that Anatomic and Medialized Dome patellar components have on tibiofemoral kinematic patterns. Methods Tibiofemoral kinematics were assessed for 40 subjects; 20 with an anatomic patella and 20 with a dome patella. Within these groups, 10 subjects received an FB PS TKA and 10 subjects received an MB PS TKA. All subjects were analyzed using fluoroscopy while performing a deep knee bend activity. Kinematics were collected during specific intervals to determine similarities and differences in regard to patella and bearing type. Results The greatest variation in kinematics was detected between the 2 Anatomic patellar groups. Specifically, the MB-Anatomic subjects experienced greater translation of the lateral condyle, the highest magnitude of axial rotation, and the highest range of motion compared to the FB-Anatomic subjects. Subjects with a Dome Patella displayed much variability among the average kinematics, with all parameters between FB and MB cohorts being similar. Conclusion The findings in this study suggest that subjects with an Anatomic patellar component could have more normal kinematic patterns with an MB PS TKA as opposed to an FB PS TKA, while subjects with a Dome patella could achieve similar kinematics regardless of TKA type.

In most cases, a standard access via a medial parapatellar arthrotomy with a carefully performed release technique is sufficient for a good exposure of the knee joint in the revision situation. Crucial steps are targeted scar removal, sufficient soft tissue release and recreation of the shifting layers. Tuberosity osteotomy is an effective option for extended exposure at the distal joint region, facilitating a patella replacement to correct abnormalities in the patellofemoral joint. Extended exposure to the proximal joint is possible with the rectus snip and the VY plasty technique. Due to the rather poor results, a quadriceps turndown should be seen more historically and should no longer be used. In extreme cases, a femoral peel or an osteotomy of the medial epicondyle can help achieve the reconstruction of a joint. The latter techniques are reserved for selected cases and always require a linked implant.

Purpose of the review The incidence of patellar instability in pediatric patients ranges is 50-100 in 100,000 patients per year. Risk of recurrent dislocations however has been cited from 8.6% to 88% depending on individual patient factors. This manuscript highlights the demographical, historical, and anatomic factors associated with recurrent patellar instability following a first-time patella dislocation in the pediatric population. Recent findings In recent years, various studies have focused on identifying risk factors for recurrent patellar instability following a primary patellar dislocation. A mix of patient factors, including age of first dislocation, patella alta, elevated tibial tubercle to trochlear groove and trochlear dysplasia have all been noted in the literature, which have helped to develop various scoring tools to predict recurrent dislocation following nonoperative treatment. Summary Risk of recurrent patellar instability in patients who have previously suffered a patellar dislocation can be due to many factors. These risk factors should be used and applied to a variety of risk scores in order to provide physicians and healthcare providers with a tool to counsel patients and families on their patellar redislocation risk and help guide further management.

Patellar instability is a common pathology of the knee in pediatric patients. The management of this condition can be a challenge for the orthopedic surgeon, and a comprehensive understanding of the anatomy and biomechanics of the structures around the knee is of utmost importance in formulating a treatment plan. Predisposing factors can be related to: trochlear and patellar morphological abnormalities, ligamentous stabilizers, limb geometries in the axial plane, and patellar height abnormalities. Traditionally, first-time dislocators have been treated non-operatively; however, recent evidence suggests that certain factors are related to recurrent instability, and surgical treatment may be considered even after the first dislocation. It is important to keep in mind that younger children with open physes are not suitable candidates for certain surgical techniques. In this comprehensive review, we aimed to focus on the most up-to-date information on this topic and emphasize the importance of individualizing the treatment of pediatric patients.

Introduction To perform a systematic review and assess the indications, outcomes, complications, and union rates associated with plate osteosynthesis in patellar fractures compared to tension band wiring. Methods The systematic search was conducted for articles in PubMed, Embase Biomedical, Cochrane central, and LILACS databases (date of inception to July 30, 2020). Articles were included if they were randomized control trials, cohort studies, case-control studies, and case series (with more than five cases), which focused on the clinical outcomes of patients with plate osteosynthesis as a treatment for fracture of the patella and had a minimum follow-up of 3 months. All studies were assessed according to their level of evidence, the number of patients, age of patients, fracture patterns described, complications of treatment, and results summarized. Meta-analysis could only be done for two parameters (complications and reoperations) due to the paucity of data and heterogeneity of studies' limited statistical analysis. The data are presented as a review table with the key points summarized. Results Twenty studies (seven prospective and 13 retrospective articles) identified 533 patients with 534 fractures who had undergone plate osteosynthesis for fracture of the patella. The most common fracture treated with plate osteosynthesis was 34C. Conclusion Basket plate was most commonly used for inferior pole fractures, while mesh plates were for intra-articular patella fractures. Overall plating was associated with better clinical outcomes, fewer complication rates, and high union rates compared to tension band wiring for patella fractures.

Purpose Reconstruction of the medial patellofemoral ligament (MPFL) is an established procedure to restore patellar stability. Aim of this study is to evaluate the results of a dynamic MPFL reconstruction technique in a large university hospital setting. Methods Two hundred and thirteen consecutive patients with 221 knees were surgically treated for recurrent lateral patellar dislocation. All patients obtained dynamic reconstruction of the MPFL with detachment of the gracilis tendon at the pes anserinus while maintaining the proximal origin at the gracilis muscle. Patellar fixation was performed by oblique transpatellar tunnel transfer. Follow-up data including Kujala and BANFF score, pain level as well as recurrent patella instability were collected at a minimum follow-up of 2 years. Results Follow-up could be obtained from 158 patients (71%). The mean follow-up time was 5.4 years. Mean pain level was 1.9 ± 2.0 on the VAS. Mean Kujala score was 78.4 ± 15.5. Mean BANFF score was 62.4 ± 22.3. MPFL-reconstructions that were performed by surgeons with a routine of more than ten procedures had a significantly shorter surgical time 52.3 ± 17.6 min. Male patients yielded higher satisfaction rates and better clinical scores compared to females. Complications occurred in 27.2% of procedures, 20.9% requiring revision surgery of which were 9.5% related to recurrent patellar instability. 78% of all patients indicated they would undergo the procedure again. Conclusion Dynamic MPFL reconstruction presents a reproducible procedure with increased complication rates, inferior to the results of static reconstruction described in the literature. Despite, it appears to be an efficient procedure to restore patellar stability in a large university hospital setting, without the necessity for intraoperative fluoroscopy. Trial registration The study was registered in ClinicalTrials.gov with the registration number NCT04438109 on June 18th 2020.

Background The Insall-Salvati ratio is a technique for determining patellar height that relies on bony landmarks. Magnetic resonance imaging (MRI) and plain radiography are used interchangeably to assess the Insall-Salvati ratio in the pediatric population despite the lack of validity in the literature. Objective The purpose of this study was to investigate if the Insall-Salvati ratio and patella alta as determined on MRI are comparable to those determined on radiography in pediatric patients. Materials and methods We conducted a retrospective review of 49 pediatric patients (age range: 7.5-17.0 years) with unfused growth plates who underwent both knee MRI and lateral knee radiography. Measurements for calculating the Insall-Salvati ratio (the ratio of patella tendon length to patella length) were obtained by three observers. Data were analyzed using paired t-tests and Pearson's correlation. A reliability assessment and inter-method agreements were performed. Patella alta was defined as an Insall-Salvati ratio > 1.2. Additional cutoffs of Insall-Salvati ratios > 1.3 and > 1.4 were also analyzed. Results There was no statistically significant difference between Insall-Salvati ratio as determined on MRI (mean: 1.20) and radiographs (mean: 1.25; P > 0.05). There was a strong correlation between Insall-Salvati ratio as determined on MRI and radiographs (Pearson's r = 0.6) with moderate consistency (Cronbach's alpha = 0.78). There was a good level of agreement between the diagnosis of patella alta on MRI and radiographs when defined as an Insall-Salvati ratio greater than 1.2 and 1.3 (Cohen's kappa = 0.61). Conclusion The results demonstrate a strong association between Insall-Salvati ratio and patella alta derived from MRI and radiographs in children ages 7.5 years and older.

The quadriceps tendon often ruptures spontaneously without trauma, frequently following an eccentric load on the tendon (walking down stairs) in the case of a previous degenerative injury. Rupture after endoprosthetic knee replacement is a special etiological case. Predominantly men between 50 and 65 years of age are affected. Clinical signs are suprapatellar hematoma and the inability to actively straighten the knee. A typical examination finding is the "suprapatellar gap sign". Ultrasonography is the diagnostic imaging modality of first choice as it can be reliably visualize the rupture and the resulting hematoma. Magnetic resonance imaging has a high sensitivity and specificity for detecting quadriceps tendon ruptures. However, its limited availability should not delay therapy. The treatment of choice is surgical transosseous refixation of the tendon at the upper patellar pole. Following surgery, a straight splint, partial weight bearing and limited mobility are required for 6-8 weeks.

Introduction: Patellar injuries are usually caused while a person slips or falls on a flexed knee and when the forces from the extensors surpass the inherent strength of patella. As the bony failure advances, it concurs or follows injury to medial and lateral extensions of quadriceps mechanism. This happens by pulling mechanism of the muscles. The patient is unable to extend the affected knee actively. This is indicative of disruption of the extensor mechanism and a torn retinaculum. This requires repair or reconstruction through operative means. Case Presentation: To find out complications of comminuted fracture of patella and open reduction after 15 years of surgery. Case Report: A 32-year-old man had a history of fall on ground due to slipping of the wheelchair over wet floor while taking a patient on wheelchair which led to comminuted fracture of left patella with shift knee and had undergone Open reduction and Tension band Osteosynthesis. After this surgical intervention, the patient presented with knee stiffness and pain (rated 6 on numerical pain rating scale) and was referred to physiotherapy. Conclusion: This case study concluded that there is evident stiffness and muscle wasting observed after 15 years of post-fracture surgery of patella, which was managed with the physiotherapeutic rehabilitations.

Patellar instability is a broad term that encompasses patellar dislocation, patellar subluxation, and patellar instability. Although both functional and anatomic considerations contribute to symptoms of patellar instability, the most important are thought to be patella alta, trochlear dysplasia, and lateralization of the tibial tubercle. In patients with a history suspicious for prior patellar dislocation, careful evaluation of MRI and radiographic studies can reveal characteristic findings. The most common methods to address patellofemoral instability are medial patellofemoral ligament reconstruction and tibial tubercle osteotomy with either anteromedialization or medialization. Less commonly trochleoplasty is indicated as well. Patients may be treated with one of or a combination of these techniques, each of which has specific indications and complications.

Background: High tibial osteotomy is an established and helpful treatment for unicompartmental osteoarthritis associated with varus deformity. However, asupratubercle high tibial osteotomy leads to a decrease in patellar height making the technique not suitable in the case of concomitant patella Baja. Moreover, this kind of osteotomy can change in situ forces at the patellofemoral joint and the lateral patellar tilt. To widen the indication of high tibial osteotomy was proposed a biplane opening wedge high tibial osteotomy with a distal tuberosity osteotomy (B-OWHTO). Objective: To assess the clinical and radiological outcome of biplane open wedge high tibial osteotomy in the treatment of medially arthritic varus knees. Patient and Methods: Twenty varus knees (20) patients, with MCOA, were operated upon from 2019 to 2020 at Al-Azhar University Hospital (Assiut). They all had Medially Opening Wedge High Tibial (MOWHTO) using the biplanar technique and fixed by locking plates. We compared the data fetched preoperatively (at day 0 = D0) with data one year or more after surgery with a mean of 14.5 months (at year 1=Y1). The mean age was 49.39 ± 8.15 years old, 13 were females, while others were males. Eleven were right knees, and 7 were left. Types of occupation were; 9 employed, 7 unemployed. Sixteen were no sportive, and 2 were recreational athletes. Seven patients were normal weight, while 11 were overweight. Two patients were diabetic, and 2 were perceived as treated HCV infection. According to the MCOA K-L scale; 5 were grade 3, 9 were grade 2 and 4 were grade 1. Results: The mean western Ontario and Macmaster universities osteoarthritis index (WOMAC), value was 51.44 ± 26.8 and then dropped to 24. 39 ± 17.41. The difference was statistically significant (p-value was

Background: Patellar height is a valuable measure to evaluate the effect of patellar tendon advancement (PTA) on knee function. In the literature, there is no validated procedure to measure the patellar height. In this study we aimed to (1) determine the patella position through musculoskeletal modeling, (2) investigate the effects of two surgical procedures applied for PTA, and (3) assess the effect of PTA in combination with single-event multilevel surgery (SEMLS) on the knee kinematics of patients with cerebral palsy (CP) and crouch gait. Method: Three-dimensional gait and X-ray data of children with CP and crouch gait were retrospectively analyzed if they had received a SEMLS in combination with PTA (PTA group, n = 18) or without PTA (NoPTA group, n = 18). A computational musculoskeletal model was used to quantify patella position, knee extension moment arm, and knee kinematics pre and postoperatively. Results: Patellar height significantly decreased in the PTA group (P = 0.004), while there was no difference in the NoPTA group (P > 0.05). The bony procedure for PTA provided a better Insall-Salvati ratio than the soft tissue procedure. The peak knee extension moment arm significantly increased in the PTA group (P = 0.008). In terms of postoperative knee joint kinematics, the PTA group was closer to typically developed children than the NoPTA group. Conclusion: Musculoskeletal modeling was found to be an effective tool for the determination of the patellar height. PTA improved the patella position, knee extension moment arm, and knee kinematics and was an effective procedure for the surgical management of crouch gait in patients with CP. (c) 2021 Elsevier B.V. All rights reserved.

The measurements of lower extremity rotational deformities in patients with recurrent patellar dislocation (RPD) in the standing position are available with the application of the EOS imaging system. The aim of our case-control study was to identify the differences on the femur rotation between the supine and standing positions, and to investigate the differences of anatomical and functional femur rotation between RPD patients and controls.Thirty-five lower extremities affected by RPD from 30 patients and 27 intact lower extremities from 27 controls with acute meniscus tear or anterior cruciate ligament injury were recruited. Anatomical femoral anteversion (AFA), functional femoral anteversion (FFA), femorotibial rotation (FTR) and distal femoral torsion (DFT) of all subjects were measured with the EOS imaging system. Computed tomography scans were carried out to analyze the AFA and FFA in the supine position in PRD patients. The differences in FFA between supine and standing position and in AFA, FTR and DFT between RPD and controls were analyzed. The predictor importance of each variable on RPD was observed after cluster analysis.The EOS images were available in all subjects. The FFA was significantly smaller in the standing position than in the supine position (P 0.05) in RPD patients. When comparing with the controls, RPD patients showed higher AFA, FTR and DFT (P 0.05) but comparable FFA (P 0.05). The cluster model prompted that FTR and DFT had higher predictor importance than AFA.Larger AFA but comparable FFA in patients with RPD than the controls in an upright standing position suggested more internally rotated distal femur in the RPD patients. AFA may be inadequate and FFA should also be considered while planning the treatment for RPD. DFT and FTR should be taken into consideration when evaluating the abnormalities in femur rotation in RPD patients.