The role of the medial ligamentous structures on patellar tracking during knee flexion

Partial LRR over complete LRR: a preferable option - an FEA study of A - B trochlear dysplasia with critical abnormalities of patella alta and TT - TG value

Objective

This study analyzed the effects of medial patellofemoral ligament (MPFL) injury and varying degrees of lateral retinacular release (LRR) on patellofemoral joint (PFJ) contact pressure using finite element analysis (FEA).

Methods

A PFJ FE model was developed and validated at four knee flexion angles (0°, 30°, 60°, and 90°) using imaging data from a patient with A-B trochlear dysplasia and critical abnormalities of patella alta and tubercle-trochlear groove (TT-TG) value. MPFL injury was simulated by inhibiting its function, while LRR was modeled by adjusting the stiffness of the lateral retinaculum. Changes in PFJ contact pressure were systematically analyzed.

Results

At 0° flexion, LRR led to increased PFJ pressure with an intact MPFL, whereas it resulted in a reduction with a ruptured MPFL. At 30° flexion, partial LRR didn't elevate PFJ pressure when MPFL was intact, while complete LRR did with both intact and ruptured MPFL. At 60° flexion, partial LRR effectively reduced PFJ pressure, but complete release reversed this effect. At 90° flexion, PFJ pressure increased with the extent of LRR, irrespective of MPFL integrity. Specifically, complete LRR led to an increase in medial pressure, resulting in a shift of the pressure center from lateral to medial at 30° and 60° flexion.

Clinical Implications

This study provides new theoretical basis for the expected outcomes of varying degrees of LRR, which helps clinicians better conduct preoperative planning, especially in avoiding over - aggressive LRR procedures which may not yield improved outcomes.

Conclusion

In patients with A- B trochlear dysplasia and critical abnormalities, excessive LRR does not consistently lower PFJ pressure but rather increases medial compartment pressure, suggesting that partial release may be a more effective and precise surgical approach in these patients.

Medial patellofemoral ligament fixation with suture tape augmentation decreases lateral patellar motion without changing contact pressure

Purpose

Medial patellofemoral ligament (MPFL) reconstruction has been the standard of care for recurrent patellar dislocations and chronic patellar instability. MPFL repair has been used as an alternative surgical option. The purpose of this study was to assess patellar stability and patellofemoral contact mechanics following MPFL fixation with suture tape augmentation. We hypothesized that lateral patellar motion would be reduced.

Methods

In twelve cadaver knees, a hole was drilled near the midpoint of the medial patella. Three locations were drilled on the femur Schöttle's point, 1 cm anterior to Schöttle's point and 1 cm proximal to Schöttle's point. Each knee was then held at 30° of knee flexion, and the patella was subjected to a physiologic lateral force. The resulting motion was measured, and patellofemoral contact forces were recorded. This process was performed with the MPFL torn and then bolstered with suture tape augmentation anchored centrally in the medial patella and each of the three femur hole locations.

Results

All MPFL augmentations provided significantly less lateral patellar motion compared to the torn condition. Contact area was significantly greater in the augmented condition than in the torn condition, but no statistical differences were observed in patellofemoral contact pressure. No significant differences in lateral patellar motion, contact pressure or contact area were found between femoral anchor positions.

Conclusions

MPFL fixation with suture tape augmentation significantly decreased lateral patellar motion compared to the torn condition without causing significant changes in contact pressures within the patellofemoral joint.

Level of Evidence

N/A.

Recurrent patellar dislocation: treatments and challenges

Recurrent Patellar Dislocation (RPD) is a common knee sports injury, mainly affecting pediatric and adolescent populations, posing a significant challenge in orthopedic clinical practice. Although a variety of treatments have been reported, and many of them have shown good initial results, there is a lack of long-term follow-up results. Each treatment method has its own unique characteristics and limitations, and there is no standardized and unified treatment plan. This article provides a comprehensive review of current treatments for RPD. We believe that regardless of the surgical method used, patellar dislocation should not occur at 0°-90° of postoperative knee flexion and extension, and the range of motion should not be limited. Our ultimate goal is to restore patellar stability and improve lower limb alignment, thereby restoring knee function as much as possible. In addition, future treatment options for RPD are also discussed. In the future, there should be more in-depth research on the risk factors and pathogenesis that lead to recurrent patellar dislocation, as well as more randomized controlled trials focusing on different treatment methods. A comprehensive understanding of these is crucial for implementing preventive measures and developing targeted treatment strategies. The goal of this narrative review is to offer clinicians a deeper understanding of RPD treatment, enhance clinical decision-making skills, and encourage personalized and efficient management of RPD treatment.

Preoperative Positioning and Socket-Anchor Technique for Arthroscopic Medial Patellofemoral Ligament Reconstruction Using Allograft Tendon

Accurate positioning of the femoral insertion of the medial patellofemoral ligament (MPFL) is the main difficulty in MPFL reconstruction. This article describes an all-arthroscopic MPFL reconstruction procedure. Preoperative 3-dimensional computed tomography assists in MPFL patellar and femoral insertion positioning, with arthroscopic reconfirmation of femoral insertion positioning through a subcutaneous tunnel during surgery. In the socket-anchor technique for patellar insertion fixation, a 10-mm-deep bone tunnel (socket) is created along a previously located guide pin at the MPFL patellar insertion; then, an absorbable suture anchor is inserted into the end of the socket to fix the tendon graft. This technique provides the advantages of being minimally invasive, yielding accurate positioning, ensuring a sufficient tendon-bone interface healing area of the graft, and having no need for intraoperative fluoroscopy.

Patellofemoral instability part 1 (When to operate and soft tissue procedures): State of the art

Patellofemoral instability is usually initially treated non-operatively. Surgery is considered in patients with recurrent patellar dislocation and after a first-time patellar dislocation in the presence of either an associated osteochondral fracture or high risk of recurrence. Stratifying the risk of recurrence includes evaluating risk factors such as age, trochlear dysplasia, contralateral dislocation, and patellar height. Surgery with soft tissue procedures includes restoring the medial patellar restraints and balancing the lateral side of the joint. Reconstruction of the medial patellofemoral ligament is the most frequent way of addressing the medial soft tissues in patients with patellofemoral instability. Meanwhile, lateral tightness can be achieved by lateral retinaculum lengthening or release. Approaching patellofemoral instability in a patient-specific approach, combined with a shared decision-making process with the patient/family, will guide surgeons to the deliver optimal care for the patellar instability patient.

Techniques for surgical stabilization of the patella in children

Patellar instability can be defined as dislocation or subluxation of the patella relative to the femoral trochlea. It is a common reason for consulting a pediatric orthopedic surgeon. Its etiology is multifactorial. Because of the work of Hughston, Merchant, Ficat, Insall and Dejour, the overall care of this pathology has changed greatly. Surgical stabilization of the patella in children is being performed more often due to better understanding of the pathology and widespread adoption of reconstruction techniques for the medial patellofemoral ligament. However, some surgical techniques should not be used in children. Determining the type of instability is the first step to selecting the appropriate technique and to avoiding the biggest pitfall - recurrence. LEVEL OF EVIDENCE: Expert opinion.

Patellofemoral Instability: Preoperative Considerations and Postoperative Imaging

Patellofemoral instability is common, often affecting young female patients. It contributes to significant morbidity, such as pain and premature osteoarthritis. Patient presentation varies, from acute instability events to chronic/recurrent instability. This article provides a detailed description of the anatomy and biomechanics of the patellofemoral joint and relates it to the pathology of patellofemoral instability. There are well-recognized predisposing anatomical factors, such as trochlear morphology, patella height, excessive lateralization of the tibial tubercle, excessive valgus alignment, and femoral or tibial torsion.Diagnosis of patellofemoral instability requires a thorough clinical history and physical examination, combined with a multimodality imaging approach. Imaging is useful in surgical planning to define the severity of predisposing anatomical factors and to detect postoperative complications. The operative management of patellofemoral instability targets predisposing anatomical factors, such as medial stabilizing ligament reconstruction or repair, tibial tubercle osteotomy, femoral trochleoplasty, coronal plane realignment osteotomy, and torsional osteotomy.

Patterns of Avulsion and Osteochondral Fractures Associated with Patellar Dislocations: A Descriptive Study Using 3-Dimensional Computed Tomography

Background

This retrospective study aimed to analyze avulsion and osteochondral fractures associated with patellar dislocation using 3-dimensional (3D) computed tomography (CT).

Methods

A retrospective analysis was conducted on patients admitted between 2015 and 2023 with acute or recurrent patellar dislocations. A musculoskeletal radiologist and 2 orthopedic surgeons evaluated CT scans of 148 patients (160 knees) to identify and categorize all avulsion and osteochondral fractures. The included fracture patterns were as follows: pattern I: medial patellofemoral ligament (MPFL) avulsion from the upper two-thirds of the patella, pattern II: medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML) avulsion from the lower one-third, pattern III: inferomedial patellar facet osteochondral fracture, pattern IV: lateral femoral condyle osteochondral fracture, and pattern V: MPFL avulsion from the femoral footprint. The dimensions of patellar articular surface osteochondral fractures were measured, and patient age, sex, and side were recorded. Descriptive statistics and chi-squared tests were performed.

Results

A total of 148 patients (93 female and 55 male patients) with a mean age of 18.7 ± 6.8 years were included. Of these, 116 patients (72.5%) had 1 or more fractures, with 71 (44.4%) having isolated lesions and 45 (28.1%) having combined lesions. Pattern II was the most prevalent, observed in 66 knees (41.2%), followed by pattern I in 52 knees (32.5%), and pattern III in 45 knees (28.1%). Patterns IV and V were seen in 4 (2.5%) and 1 (0.6%) knee, respectively. The mean articular fragment size in pattern III was 128.4 ± 95.6 mm2 (range, 12-412.5 mm2), all involving the inferomedial facet of the patella. Osteochondral fragments were found in the lateral gutter (35.5%), anterior joint space (51.1%), posterior joint space (8.9%), and suprapatellar space (4.5%). No significant sex differences were observed in isolated versus combined lesions (p = 0.542) or fracture patterns (p = 0.274).

Conclusions

This study, the first to evaluate fractures after patellar dislocation using 3D CT, identified 5 distinct fracture patterns. The results show that MPTL/MPML injuries are more common than previously thought, challenging traditional views on patellar dislocation injuries and emphasizing the need for a comprehensive diagnostic approach.

Digging into the Cause of Abnormal Patellar Kinematics After Open-Wedge High Tibial Osteotomy via a Quantitative Study on In Vivo Soft Tissue Functional Changes

The biomechanical mechanism of postoperative patellofemoral joint (PFJ) complications after open-wedge high tibial osteotomy (OWHTO) has not been investigated. This study was to determine the length changes in the patellar tendon (PT), medial patellotibial ligament (MPTL), medial patellofemoral ligament (MPFL), and quadriceps moment arm (QMA) during staircase motion before and after OWHTO. Computed tomography (CT) scans of 15 patients' lower extremities were used to reconstruct three-dimensional models, and magnetic resonance imaging (MRI) of the knee and hip joints was used to mark the soft tissue footprints. Then, such soft tissue lengths were quantified by a dual fluoroscopic imaging system (DFIS). Additionally, function scores were used to assess patient outcome changes. The results showed that there was a contraction of the PT after OWHTO due to its adhesion to the osteotomy site, causing PT length to be negatively correlated to the open-wedge angle. In addition, the shortening of the MPTL and QMA caused patellar instability and an imbalance in the strength of the lower extremities. Additionally, most knee function scores improved after OWHTO, except the Feller scores. Multiple methods should be considered to optimize surgical procedures, postoperative rehabilitation, and physical therapy.

Navigating medial patellotibial ligament reconstruction: Clinical perspectives and surgical strategies

The surgical approach for patellar instability usually refers to reconstruction of the medial patellofemoral ligament associated with an osteotomy of the tibial tuberosity or a trochleoplasty when required. The medial patellotibial ligament and the medial patellomeniscal ligament are secondary stabilizers of the patella. Despite this, both the medial patellotibial and patellofemoral ligaments aid in patellar rotation and tilt when the knee is flexed beyond 45°. The medial patellotibial ligament plays a particularly important role in the final stages of stretching in extension and between 40 degrees to 90 degrees of flexion. The clinical relevance and surgical indications for medial patellotibial ligament reconstruction associated with medial patellofemoral ligament reconstruction are still controversial. This editorial explores the surgical indications and clinical results for medial patellotibial ligament reconstruction to improve readers’ understanding of this technique, especially because reported clinical outcomes have remained sparse.

Femoral tunnel enlargement after medial patellofemoral ligament reconstruction is common and can be monitored using plain radiographs

Introduction

medial patellofemoral ligament reconstruction (MPFLr) is a common surgical procedure for treating patellar instability. Grafts can be fixed to the femur using a bone-tunnel technique with an interference screw. However, this may lead to femoral tunnel enlargement (FTE) post-operatively. The aim of this study was to assess the correlation between time after MPFLr and FTE, to evaluate factors that might influence FTE and to determine if FTE can be reliably evaluated with plain radiographs.

Methods

we conducted a single-surgeon series, retrospective review of 70 MPFLr (52 female; 18 male) between 2014 and 2022. We assessed change in femoral tunnel area compared with original tunnel area (TP0), on lateral radiographs at two time points. Time point one (TP1): mean 34 days (standard deviation (SD): 25); and Time Point 2 (TP2): mean 490 days (SD: 333). We analysed the relationship between surgical characteristics to FTE, and assessed inter- and intra-rater reliability of FTE.

Results

tunnel area significantly increased from TP0 to TP1 and TP2 (p < 0.001). Mean percentage increase in cross-sectional tunnel area (CTA) between TP0 and TP1 was 113 % (SD: 49 %). Mean percentage increase in CTA between TP0 and TP2 was 139 % (SD: 64 %). There were 25 cases (36 %) of tunnel malposition. There was no significant correlation between distance from the isometric point and FTE at TP1 (r = 0.05; 95 % confidence intervals (CI): -0.19 to 0.29) or TP2 (r = 0.17: 95 % CI: -0.068 to 0.39). There were no other significant correlations with FTE. Inter-rater reliability for FTE at TP1 was moderate (Inter-Class Coefficient (ICC): 0.67; 95 % CI: 0.47 to 0.80; p < 0.001), with intra-rater reliability being excellent (ICC: 0.94; 95 % CI: 0.90 to 0.96; p < 0.001).

Conclusion

FTE after MPFLr is common. Plain radiographs can be used reliably to monitor tunnel enlargement in clinical practice.

Evaluating the Association Between Vastus Medialis Oblique Characteristics and Patellar Instability: A Comprehensive Case-Control Study

BACKGROUND

The contribution of vastus medialis oblique muscle (VMO) weakness or dysfunction to patellofemoral pain syndrome is well recognized, yet its role in lateral patellar instability and recurrent patellar dislocations remains unclear. This study investigates the association between VMO characteristics and patellar instability.

HYPOTHESIS

Altered VMO structure, characterized by differences in muscle elevation and cross-sectional area (CSA), is associated with patellar instability.

STUDY DESIGN

A case-control study.

LEVEL OF EVIDENCE

Level 3.

METHODS

The study included 204 participants, matched on a 1:1 ratio by age and sex, from a local hospital registry from 2005 to 2020. VMO measurements were taken via magnetic resonance imaging, and included muscle elevation, CSA, fiber angulation, and CSA-to-thigh circumference ratio. Univariate analysis, and multivariable regression model with adjustment for potential confounders were constructed. In addition, a secondary analysis was performed to evaluate the variations in VMO characteristics and mass across primary and recurrent patellar instability groups.

RESULTS

Patients with patellar instability demonstrated significant differences in VMO characteristics compared with controls, including increased muscle elevation (13 mm vs 5.9 mm; P < 0.01), increased muscle fiber angulation (42.5° vs 35.3°; P < 0.01), reduced CSA (716 mm2 vs 902 mm2; P < 0.01), and a lower CSA-to-thigh circumference ratio (0.05 vs 0.07; P < 0.01). These findings remained significant in the multivariable adjusted model. Moreover, the secondary analysis revealed that both primary and recurrent instability patients had similar VMO characteristics alterations compared with controls, with slightly more pronounced reductions in VMO CSA in those sustaining recurrent instability episodes.

CONCLUSION

This study confirms a statistically significant association between altered VMO characteristics and patellar instability, emphasizing the importance of considering VMO characteristics in the evaluation and management of patients with patellar instability.

Is fascia lata a viable graft for MPFL reconstruction? An overview of surgical technique and scoping literature review

Lateral patellar dislocation is irrefutably one of the most common knee injuries, while subsequent medial patellofemoral ligament (MPFL) damage requires proper orthopedic care. Treatment of these injuries is regularly associated with the need for MPFL reconstruction surgery. This operation, often in combination with other procedures, can result very fruitful in restoring knee kinematics. There is a considerable variety of options for the orthopedic surgeon to choose from regarding graft selection when performing MPFL reconstruction surgery, including the semitendinosus tendon, the gracilis, and others. Notwithstanding, utilizing the fascia lata as an autograft or allograft for MPFL reconstruction has emerged as a promising alternative. Perusing the existing literature, not any review paper could be found examining the efficacy of fascia lata as a MPFL reconstruction graft. As a result, a thorough search was conducted in various databases to investigate and explore the studies analyzing this type of MPFL reconstruction surgery. The number of papers scrutinizing this operation was exceedingly narrow. However, out of these studies, it can be concluded that opting for fascia lata grafts when executing MPFL reconstruction surgery features some considerable advantages, involving similar biomechanics to the native MPFL, no hamstrings damage and quicker rehabilitation among others. This paper accentuates the requirement for considering fascia lata as a viable graft option in MPFL reconstruction surgery and the necessity for more pertinent research in order to attain more reliable inferences.

Biomechanical Evaluation of Medial Patellofemoral Ligament Reconstruction Grafts Fixed at Nonanatomic Femoral Insertion Points: MPFL Reconstruction And Femoral Tunnel Location

Background

Improved patient outcomes and decreased patellar instability have been reported after medial patellofemoral ligament (MPFL) reconstruction for recurrent lateral patellar dislocation; however, there is a lack of comparative evidence on functional outcomes associated with different femoral attachment sites for the MPFL graft.

Purpose

To identify differences in MPFL reconstruction graft isometry with femoral tunnel malpositioning, specifically evaluating isometric differences as the femoral position is moved anterior, posterior, proximal, and distal relative to the Schöttle point, the femoral radiographic landmark of the MPFL.

Study Design

Descriptive laboratory study.

Methods

A biomechanical study evaluating 11 fresh-frozen cadaveric knees was conducted. Nonelastic suture, used as an analog to the MPFL graft, was anchored with the knee at 30° flexion at the Schöttle point and at 5 and 10 mm anterior, posterior, superior, and distal to the Schöttle point. A draw wire displacement sensor was used to evaluate length changes of the MPFL graft analog through 0° to 120° knee flexion. Knee flexion position was continuously measured using a motion tracking system. Pairwise t tests with Bonferroni correction were used to compare isometry between the Schöttle point and the nonanatomic femoral insertion points.

Results

Grafts placed at the Schöttle point proved mildly anisometric, with tightening in extension and loosening in flexion. Similarly, grafts placed distally and posteriorly also demonstrated tightening in extension and loosening in flexion. Grafts placed anteriorly and proximally demonstrated tightening in flexion. Pairwise comparisons relative to the Schöttle point found that grafts placed proximally or distally demonstrated significant differences in total MPFL excursion magnitude (10 mm proximal: 0.36 [P = .03], 5 mm distal: 0.14 [P = .01], 10 mm distal: 0.22 [P < .001]).

Conclusion

When deviating from the Schöttle point, posterior and distal femoral tunnel positionings minimized the risk of MPFL graft tightening during knee flexion. Errant anterior and proximal positioning were concerning for MPFL overconstraint, and proximal tunnel placement was most at-risk.

Clinical Relevance

An understanding of the effects that femoral tunnel malpositioning has on graft isometry is crucial to minimizing instability or overconstraint, which leads to anterior knee pain, increased patellofemoral contact pressures, or graft failure.

Original surgical technique for the treatment of patellofemoral instability after failure of conservative treatment

INTRODUCTION

Acute patellar dislocation is a common but serious injury that can significantly impact a patient's functional prognosis. The objective of this retrospective study is to evaluate the clinical outcomes of arthroscopic medial patellofemoral ligament (MPFL) reconstruction and plication of the medial patellar retinaculum using suture anchors in adolescent patients with first-time acute patellar dislocation (APD) and MPFL insertion injury.

HYPOTHESIS

Tightening repair of the medial retinaculum complex can result in favorable clinical and functional outcomes in this patient population.

MATERIALS AND METHODS

A total of 84 adolescent patients with first-time APD and with an average age of 15.5 years (10-22) were included in the study. Of these patients, 61 (7 male and 54 female) underwent arthroscopic suture anchor plication for medial patellar retinaculum, while the other 23 were successfully treated non-operatively. Radiographic outcomes, including the congruence angle (CA), lateral patellofemoral angle (LPA), and patellar tilt angle (PTA), were evaluated preoperatively and at the last follow-up visit in the surgical group. Functional outcomes were assessed using the Lille Patello-Femoral Score, Lysholm Score, and Kujala Score at the same time points. In addition, the surgical and non-operative treatment success groups were compared in terms of both radiographic and functional outcomes.

RESULTS

Mean follow-up was 40.9 months (24-60). Fifty-nine knees showed excellent or good results postoperatively, 2 patients had a recurrent patellar subluxation. The Lille Patello-Femoral Score was 96.9±4.7 at the last follow-up. The subjective Lysholm Score and Kujala Score improved significantly, from 58.6 to 91.9 and from 60.4 to 88.9, respectively. The radiographic CA, LPA and PTA improved significantly, from 19.8±2.1° to -6.7±1.7°, from -7.4±2.2° to 5.7±1.8° and from 23.8±2.9° to 12.3±2.3°, respectively. There was no statistically significant difference in functional and radiographic assessments between the success with non-operative treatment group and the surgery group.

CONCLUSION

The results of this study suggest that arthroscopic MPFL insertion reconstruction and plication using suture anchors, which is less invasive and improves patella stability, can lead to favorable clinical and functional outcomes in adolescent patients with first-time acute patellar dislocation and insertion injury. This treatment approach should be considered as a viable option for this patient population.

LEVEL OF EVIDENCE

IV; monocentric retrospective descriptive study.

Evaluation of an Active Rehabilitation Program With Early Weightbearing and No Immobilization After Tibial Tubercle Distalization

Background

Abnormal patellar height (patella alta) has been reported to be one of the main predisposing factors for recurrent patellar dislocation, and it can be surgically corrected by distalizing tibial tubercle osteotomy (DTTO). Rehabilitation after DTTO often includes limitations on weightbearing and restrictions on knee range of motion by means of bracing, increasing the risk of slow progression of the rehabilitation.

Hypothesis

An active rehabilitation program with no restrictions on weightbearing and range of movement would yield a low risk of postoperative complications and a fast recovery period.

Study Design

Case series; Level of evidence, 4.

Methods

Included were 102 consecutive knees in 80 patients who underwent DTTO between January 2010 and December 2017. In the majority of knees (89.2%), the patient underwent simultaneous medial patellofemoral ligament reconstruction. The mean age of the patients at the time of surgery was 19.39 ± 8.02 years, and 80.4% of the knees (82/102) were of female patients. The patients underwent an active rehabilitation program with immediate weightbearing as tolerated and active quadriceps and hip muscle exercises with no immobilization or bracing. The protocol was active (patient unsupervised), including daily exercises, as instructed by a physical therapist. Crutches were recommended for the first 3 to 4 weeks.

Results

There were 3 acute failures of fixation (2.9% of knees) requiring revision surgery. In these cases, the patients had a fall, slip, or knee-twisting accident during the first 6 weeks after surgery. Two late failures characterized by tibial stress fracture at the distal part of the osteotomy level occurred at 2 and 3 months postoperatively and were considered unrelated to the early rehabilitation process. The stress fracture rate was 2%, and the overall DTTO failure rate was 6.9%. With the active rehabilitation program, adverse effects such as knee stiffness, arthrofibrosis, or delayed ability to perform daily activities were rare.

Conclusion

An active rehabilitation program after DTTO was found to be safe and effective. Furthermore, the risk of failure related to surgical fixation strength and of later stress fracture was low.

Distally Based Patella Tendon Shortening With Medial Patellotibial Ligament Reconstruction

Patella alta is a common pathoanatomic contributor to various knee pathologies, including patella instability, fat pad impingement, and patellar tendinopathy. The 2 most common surgical techniques used to treat patella alta include a distalizing tibial tubercle osteotomy and patella tendon imbrication. Although these 2 surgical techniques are effective, they are associated with significant surgical morbidity and a limiting postoperative course with prolonged rehabilitation. In this Technical Note, we propose a simple means of distalizing the patella and improving patella maltracking via the addition of a medial patellotibial ligament reconstruction. The described technique is easy to perform, has little postoperative morbidity, and is familiar to most knee surgeons who perform anterior cruciate ligament reconstruction.

Patellofemoral Disorders in Soccer Players

Patellofemoral disorders are common in the world of soccer and impact players across all levels and ages of the sport. Patellofemoral disorders encompass a spectrum of conditions, from anterior knee pain to patellar instability, and are often influenced by complex biomechanical factors and anatomic variations that can predispose to these conditions. In recent years, there has been a growing emphasis on injury prevention strategies and data-driven approaches, championed by organizations like the Union of European Football Associations and individual professional clubs. Conservative management remains the initial approach for many players, including physical therapy and supportive devices. However, surgical intervention, particularly in cases of recurrent patellar dislocations, is often necessary. The understanding of patellofemoral biomechanics in soccer continues to evolve and offers opportunities for more effective injury prevention and tailored treatment strategies. Despite the challenges, a comprehensive approach to patellofemoral disorders in soccer is essential to preserve player health, enhance performance, and sustain the sport's vitality.

Long-term results after medial patellotibial ligament reconstruction for the treatment of patellofemoral instability

PURPOSE

To evaluate long-term clinical outcomes and redislocation rate after medial patellotibial ligament reconstruction.

MATERIALS AND METHODS

A total of 26 knees with mean age 26.3 ± 10.6 years (25 patients, 7 males and 18 females) treated for patellar instability (at least two objective dislocations) with medialization of the patellar tendon medial third were evaluated with an intermediate clinical follow-up (FU) at a mean of 6.5 ± 2.1 years and with a final telephone interview follow-up at mean of 15.6 ± 2.5 years (11.4-20.1). Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC), Kujala, Visual Analog Scale (VAS) for pain and Tegner activity scores were used. Information about further redislocation and knee surgery was also collected.

RESULTS

All the clinical scores had a significant improvement compared to preoperative status (WOMAC pre-op 55.9 ± 27.2 vs. WOMAC final FU 80.8 ± 22.2; KUJALA pre-op 41.0 ± 24.0 vs. KUJALA final FU 77.2 ± 24.1; VAS pre-op 6.0 ± 3.1 vs. VAS final FU 3.44 ± 2.35; TEGNER pre-op 2.1 ± 2.0 vs. TEGNER final FU 3.6 ± 1.8; p < 0.001), and the outcomes remained stable at the final follow-up compared to the intermediate follow-up (p > 0.05). A total of 4 knees had at least one redislocation at the final follow-up, while 3 knees underwent total knee replacement surgery. The redislocation-survival rate at 5 years is 92%, meanwhile is 84% at 10 and 15 years.

CONCLUSIONS

MPTL reconstruction produced good clinical results and a survival rate of 84% at a mean of 16 years follow-up and could be considered as associated procedure in case of patellofemoral instability.

LEVEL OF EVIDENCE

Level IV.

Is kinesiophobia associated with functional outcome measures in patients following medial patellofemoral ligament reconstruction?

BACKGROUND

This study aimed to investigate the potential relationship between kinesiophobia and functional outcomes in patients following medial patellofemoral ligament reconstruction (MPFLr).

METHODS

Twenty-one patients (six males, 15 females) who underwent MPFLr between 2016 and 2020, (23.57 ± 9.49 years old) with a mean follow up period of 52.33 ± 24.82 months were included in the study. Following an assessment of patellar stability and alignment, kinesiophobia levels, function and balance were measured. The kinesiophobia was measured using the Tampa Scale of Kinesiophobia, while functional outcomes were assessed with the single-leg hop test, Y-Balance test and single-leg sway index. The self-reported function was measured by Kujala patellofemoral score and Lysholm knee score.

RESULTS

The patients exhibited kinesiophobia scores of 43.10 ± 6.90. A negative correlation existed between kinesiophobia and both the Kujala scores (r = -0.75, P < 0.001) and the Lysholm scores (r = -0.79, P < 0.001). Moderate negative correlations were observed between kinesiophobia and the single-leg hop distance (r = -0.64, P < 0.01), as well as in Y-Balance test anterior reach distance (r = -0.51, P < 0.01) and posterolateral reach distance (r = -0.55, P < 0.01). Additionally, a low negative correlation was noted between kinesiophobia and Y-Balance test posteromedial reach distances (r = -0.43, P = 0.05), as well as the total sway index (r = -0.46, P = 0.04).

CONCLUSIONS

A high level of kinesiophobia was strongly correlated with self-reported functional scores and moderately correlated with measured functional outcomes. The findings underscore a notable prevalence of kinesiophobia following biomechanically successful MPFLr. Investigating the impact of kinesiophobia on outcomes after MPFLr may provide a better understanding of patient recovery.

Radiographic Landmark Measurements for the Femoral Footprint of the Medial Patellofemoral Complex May Be Affected by Visible Femoral Shaft Length on Lateral Knee Radiographs

PURPOSE

To assess the effect of visible femoral shaft length on the accuracy of radiographic landmarks of the medial patellofemoral complex (MPFC).

METHODS

In 9 cadaveric knees, the MPFC footprint was exposed on the medial femur, and its proximal and distal boundaries were marked. Lateral fluoroscopic images of the knee were assessed in 1-cm length increments, beginning 1 cm proximal to the medial condyle and continuing proximally to 8 cm. The MPFC midpoint was described on each image relative to the posterior cortical line of the femur and a line perpendicular to this line through the proximal margin of the medial condyle. In addition, the MPFC midpoint was assessed relative to a line from the proximal posterior cortex to the midpoint of Blumensaat line.

RESULTS

Using the posterior cortical line as a reference, the MPFC radiographic landmark moved anteriorly with decreasing visible femoral shaft on radiographs, particularly at 4 cm and less. However, no proximal-distal change was noted. Linear regression analysis demonstrated a relationship between visible femoral shaft and MPFC position on radiographs (R = 0.461, R2 = 0.212, B = -0.636, P < .001). For every centimeter decrease in the visible femoral shaft, the radiographic MPFC footprint moved anteriorly by 0.636 mm. Receiver operating characteristic curve analysis revealed that a minimum of 4 cm of femoral shaft on lateral radiographs is required for accurate MPFC footprint localization (area under the curve = 0.80; sensitivity = 76.7%; specificity = 69.0%; P < .001). In contrast, no anterior-posterior change was seen when referencing a line from the proximal posterior cortex to the midpoint of Blumensaat line.

CONCLUSIONS

When using the posterior cortical line to identify the midpoint of the MPFC, at least 4 cm of femoral shaft should be visible for accurate assessment. If less than 4 cm of shaft is visible, a line through the midpoint of Blumensaat line and the proximal posterior cortex can be used as an alternative method to estimate the position of the femoral footprint.

CLINICAL RELEVANCE

As fluoroscopy is frequently used intraoperatively for MPFC reconstruction, our findings may serve as a guide when assessing femoral tunnel placement on fluoroscopy.

Patellar Lateralization, Absence of Joint Hypermobility, and the Mechanism of Injury Are Associated With Osteochondral Fracture After First-time Acute Lateral Patellar Dislocation in Adolescents: An MRI-based Evaluation

BACKGROUND

Although the risk factors for patellofemoral dislocation are clearly defined, risk factors for osteochondral fracture (OCF) after patellar dislocation are not as well defined. The aim of this study was to investigate the risk factors for OCF by evaluating patients with and without OCF after first-time acute patellar dislocation.

METHODS

This multicenter study was conducted as a retrospective examination of the radiologic measurements on the magnetic resonance imaging of 306 patients. The patients were divided into the OCF group and non-OCF group, and OCFs were grouped according to whether the fracture was in the patella or femur. Patellar height, patellar lateralization, trochlear morphology, patellofemoral matching, and patella types were evaluated on patient magnetic resonance imaging. The presence of joint hypermobility in the patients was determined according to the Beighton scale score. The injury mechanisms of the patients were grouped as sports-related injuries, injuries resulting from simple falls, and injuries during daily activities.

RESULTS

A total of 120 OCFs were detected in 108 (35.2%) patients, of which 96 (80%) were in the patella and 24 (20%) in the femur. The rate of OCF after sports-related injuries was found to be significantly higher than in other injury mechanisms ( P =0.001). More joint hypermobility was detected in patients without OCF ( P =0.041). The measurements of tibial tubercle-trochlear groove, tibial tubercle-posterior cruciate ligament distance and lateral patellar displacement were statistically higher in cases with OCF ( P =0.001). In patients with normal joint mobility, the rate of OCF localization in the patella was significantly higher ( P =0.035). No correlation was found between any other parameters and OCF ( P >0.05). The absence of joint hypermobility and the measurements of tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, and lateral patellar displacement were independent risk factors for the incidence of OCF according to the logistic regression analysis.

CONCLUSIONS

The absence of joint hypermobility and patellar lateralization are independent risk factors for the occurrence of OCF after first-time patellar dislocation. Sports-related injury is a nonindependent risk factor for the presence of OCF. In patients with normal joint mobility, the incidence of OCF in the patella is higher than in the femur. These important factors should be considered when evaluating patients and starting their treatment.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Minimally Invasive Medial Patellofemoral Ligament Reconstruction With Patellar-Sided Tensioning Using All-Suture Anchors

Medial patellofemoral ligament (MPFL) reconstruction is a commonly performed procedure to reestablish the checkrein to the lateral patellar translation in patients with recurrent patellofemoral instability. Graft tensioning is one of the most critical aspects of the procedure. Most surgical methods for MPFL reconstruction involve tensioning and securing the graft on the femoral side. In this article, we describe a technique for patellar-sided tensioning of the graft using all-suture anchors, which provides the surgeon with the ability to finely control graft tension with two independent graft limbs, while preserving patellar bone stock.

Patients who undergo tibial tubercle anteromedialization with medial patellofemoral ligament reconstruction demonstrate similar rates of return to sport compared to isolated MPFL reconstruction

PURPOSE

To investigate the rate of return to sports and sport psychological readiness between patients who underwent isolated MPFLR (iMPFLR) compared to a matched cohort of patients who underwent MPFLR with anteromedializing tibial tubercle osteotomy (MPFLR/TTO).

METHODS

Patients who underwent primary MPFLR with or without TTO for recurrent patellar instability were retrospectively reviewed from 2012 to 2020 at a single institution. Preinjury sport and work information, Kujala, Tegner, Visual Analogue Score for pain, satisfaction and MPFL-Return to Sport after Injury (MPFL-RSI) score were collected. Two readers independently measured the tibial tuberosity-trochlear groove distance, Caton-Deschamps index and Dejour classification for trochlear dysplasia. Patients in iMPFLR and MPFLR/TTO groups were matched 1:1 on age, sex, body mass index and follow-up length. Multivariate regression analysis was performed to determine whether the MPFL-RSI was associated with a return to sport.

RESULTS

This study included 74 patients at mean follow-up of 52.5 months (range: 24-117). These groups returned to sport at similar rates (iMPFLR: 67.6%, MPFLR/TTO: 73.0%, not significant [ns]), though iMPFLR patients returned more quickly (8.4 vs. 12.8 months, p = 0.019). Rates of return to preinjury sport level were also similar (45.9% vs. 40.5%, ns). Patients with Dejour B/C took more time to return to sport compared to patients with mild/no trochlear pathology (13.8 vs. 7.9 months, p = 0.003). Increasing MPFL-RSI score was significantly predictive of the overall return to sport (odds ratio [OR]: 1.08, 95% confidence interval [CI] [1.03, 1.13], p < 0.001) and return to preinjury level (OR: 1.07, 95% CI [1.04, 1.13], p < 0.001). Most patients in iMPFLR and MPFLR/TTO groups resumed work (95.7% vs. 88.5%, ns), though iMPFLR patients who returned to preinjury work levels did so more quickly (1.7 vs. 4.6 months, p = 0.005).

CONCLUSION

Patients who underwent MPFLR with anteromedializing TTO demonstrated similar rates of return to sport and psychological readiness compared to an isolated MPFLR matched comparison group, though iMPFLRs returned more quickly. Patients with more severe trochlear pathology required more time to return to sports.

LEVEL OF EVIDENCE

Level III.

The 100 Top-Cited Articles on Medial Patellofemoral Ligament: A Bibliometric Analysis and Review

Background

The medial patellofemoral ligament (MPFL) has been investigated widely in the past 30 years, resulting in many research achievements in this field.

Purpose

To perform a comprehensive bibliometric analysis to evaluate the 100 top-cited articles on the MPFL.

Study Design

Cross-sectional study.

Methods

We searched the Scopus database in December 2022 using the terms "medial patellofemoral ligament" OR "MPFL." The search was confined to English-language articles, including technical notes, systematic reviews on clinical outcomes and/or complications, clinical studies, studies regarding complications, and basic science articles (either cadaveric or biomechanical); we excluded letters, case reports, personal opinions, guidelines, editorials, and narrative or other types of reviews. Analysis of the 100 top-cited articles was performed according to total number of citations, average citations per year (ACY), study type, country of origin, journal of publication, affiliated institution, and most published authors.

Results

The total number of citations was 16,358 (range of citations per article, 72-692). The majority of articles were published as clinical studies (54%), with cadaveric studies being the second most common (21%). Most studies originated in the United States (32%), with Japan (15%) and Germany (13%) following. The American Journal of Sports Medicine published the majority of the 100 top-cited articles (37/100; 6304 citations) as well as the 10 top-cited articles according to ACY (7/10; mean, 285.14 citations). The most prolific authors were Nomura (8 articles); Burks (6 articles); and Inoue, Sillanpää, and Dreyhaupt (5 articles each).

Conclusion

By analyzing the characteristics of the 100 top-cited articles, this study demonstrated that the MPFL is a growing and popular area of research, with the focus varying through timeline trends. Questions regarding MPFL anatomy, isometry, and biomechanics might have been answered adequately, but research regarding optimal fixation technique under various circumstances is still ongoing.

A modified Delphi consensus statement on patellar instability: part II

Aims

The aim of this study was to establish consensus statements on medial patellofemoral ligament (MPFL) reconstruction, anteromedialization tibial tubercle osteotomy, trochleoplasty, and rehabilitation and return to sporting activity in patients with patellar instability, using the modified Delphi process.

Methods

This was the second part of a study dealing with these aspects of management in these patients. As in part I, a total of 60 surgeons from 11 countries contributed to the development of consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered unanimous.

Results

Of 41 questions and statements on patellar instability, none achieved unanimous consensus, 19 achieved strong consensus, 15 achieved consensus, and seven did not achieve consensus.

Conclusion

Most statements reached some degree of consensus, without any achieving unanimous consensus. There was no consensus on the use of anchors in MPFL reconstruction, and the order of fixation of the graft (patella first versus femur first). There was also no consensus on the indications for trochleoplasty or its effect on the viability of the cartilage after elevation of the osteochondral flap. There was also no consensus on postoperative immobilization or weightbearing, or whether paediatric patients should avoid an early return to sport.

Soft Tissue Lengthening for Flexion Dislocation of Patella

PURPOSE OF REVIEW

Obligatory dislocation of the patella (also known as habitual dislocation) is a rare subset of patellofemoral instability in which the patella dislocates every time the knee is flexed. The problem arises due to contracture of the quadriceps muscles. Soft tissue lengthening procedures such as quadriceps tendon lengthening are the mainstay of treatment, in contrast to medial patellofemoral reconstruction (MPFL-R) for the more common recurrent lateral patellar dislocation. The current review explores the existing literature surrounding the pathophysiology and treatment strategies for this unique cause of knee instability.

RECENT FINDINGS

Flexion dislocation of the knee often presents in children when they begin to walk. It is also termed obligatory or habitual because the patella dislocates laterally with each flexion and extension cycle of the knee. In contrast to other forms of patellar dislocation, the displacement is painless in obligatory dislocation. Likewise, the underlying biomechanical cause of this issue is related to contracture of tissues lateral to the patella rather than disruption of medial soft tissues as seen in recurrent/traumatic dislocation or subluxation of the patella. A number of procedures have been described for management of obligatory dislocation of the patella, with the general consensus that a combination of procedures including release/lengthening of the proximal lateral soft tissues as a critical component for a successful outcome. Soft tissue release/lengthening has been performed for over 50 years to treat obligatory dislocation of the patella. This procedure must be used in combination with other proximal and distal reconstructive with careful intraoperative assessment of knee flexion and patellar tracking for satisfactory outcomes. Further research using standardized outcome measures is needed to identify the optimal step-wise approach in treatment of obligatory patellar dislocation.

Patient-Individualized Identification of Medial Patellofemoral Ligament Attachment Site to Femur Using "CLASS" MRI Sequences

Background

Malposition of the femoral tunnel during medial patellofemoral ligament (MPFL) reconstruction may increase the risk of recurrence of patellar dislocation due to isometric changes during flexion and extension. Different methods have been described to identify the MPFL isometric point using fluoroscopy. However, femoral tunnel malposition was found to be the cause of 38.1% of revisions due to patellar redislocation. This high rate of malposition has raised the question of individual anatomical variability.

Methods

Magnetic resonance imaging (MRI) was performed on 80 native knees using the CLASS (MRI-generated Compressed Lateral and anteroposterior Anatomical Systematic Sequence) algorithm to identify the femoral MPFL insertion. The insertions were identified on the MRI views by 2 senior orthopaedic surgeons in order to assess the reliability and reproducibility of the method. The distribution of the MPFL insertion locations was then described in a 2-plane coordinate system and compared with MPFL insertion locations identified with other methods in previously published studies.

Results

The CLASS MPFL footprint was located 0.83 mm anterior to the posterior cortex (line 1) and 3.66 mm proximal to the Blumensaat line (line 2). Analysis demonstrated 0.90 and 0.89 reproducibility and 0.89 and 0.80 reliability of the CLASS method to identify the anatomical femoral MPFL insertion point. The distribution did not correlate with previously published data obtained with other methods. The definitions of the MPFL insertion point in the studies by Schöttle et al. and Fujino et al. most closely approximated the CLASS location in relation to the posterior femoral cortex, but there were significant differences between the CLASS method and all 4 previously published methods in relation to the proximal-distal location. When we averaged the distances from line 1 and line 2, the method that came closest to the CLASS method was that of Stephen et al., followed by the method of Schöttle et al.

Conclusions

The CLASS algorithm is a reliable and reproducible method to identify the MPFL femoral insertion from MRI views. Measurement using the CLASS algorithm shows substantial individual anatomical variation that may not be adequately captured with existing measurement methods. While further research must target translation of this method to clinical use, we believe that this method has the potential to create a safe template for sagittal fluoroscopic identification of the femoral tunnel during MPFL surgical reconstruction.

Level of Evidence

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Patellar Dislocation: Workup and Decision-Making

Acute patellar dislocation (PD) is usually a problem of adolescents and young adults. In most cases, it is a sports-related injury. It is the result of an indirect force on the knee joint, which leads to valgus and external rotation of the tibia relative to the femur. PD is unlikely to occur on a knee with normal patellofemoral joint (PFJ) anatomy. Acute PD consists of an acute injury of the ligamentous medial patellar stabilizers in the background of factors predisposing to patellar instability. These factors are classified into three groups. The first group refers to the integrity of the ligamentous medial patellar restraints, particularly, the medial patellofemoral ligament (MPFL). The second group refers to an abnormal PFJ anatomy, which renders the patella inherently unstable inside the trochlea. The third group refers to the overall axial and torsional profile of the lower limb and to systemic factors, such as ligament laxity and neuromuscular coordination of movement. PD at a younger age is associated with an increased number and severity of patellar instability predisposing factors and lower stress to dislocate the patella. Acute primary PD is usually treated conservatively, while surgical treatment is reserved for recurrent PD. The aim of treatment is to restore the stability and function of the PFJ and to reduce the risk of patellar redislocation. Surgical procedures to treat patellar instability are classified into non-anatomic and anatomic procedures. Non-anatomic procedures are extensor mechanism realignment techniques that aim to center the patella into the trochlear groove. Anatomic procedures aim to restore the PFJ anatomy (ruptured ligaments, osteochondral fractures), which has been severed after the first incident of PD. Anatomic procedures, especially MPFL reconstruction, are more effective in preventing recurrent PD, compared with non-anatomic techniques. Theoretically, all factors that affect PFJ stability should be evaluated and, if possible, addressed. This is practically impossible. Considering that the MPFL ruptures in almost all PDs, MPFL reconstruction is the primary procedure, which is currently selected by most surgeons as a first-line treatment for patients with recurrent PD. Restoration of the axial and torsional alignment of the lower limbs is also increasingly implemented by surgeons. Non-anatomic surgical techniques, such as tibial-tuberosity osteotomy, are used as an adjunct to anatomic procedures. In the presence of multiple PFJ instability factors, acute MPFL reconstruction may be the treatment of choice for acute primary PD as well. Skeletal immaturity of the patient precludes osseous procedures to avoid premature physis closure and subsequent limb deformity. Unfortunately, restoration of the patient's previous activity level or participation in more strenuous sports is questionable and not easy to predict. In the case of competitive athletes, PD may prevent participation in elite levels of sports.

Male sex is an independent risk factor for patellar osteochondral fractures following acute patellar dislocation in pediatric patients

PURPOSE

Although most patellar dislocations are associated with medial patellofemoral ligament (MPFL) injury, many patients also sustain concomitant patellar osteochondral fractures following a patellar dislocation. Few prior studies have described or evaluated risk factors for patellar osteochondral fractures in pediatric patients. The purpose of the present study was to describe the incidenceand location of patellar osteochondral fractures following acute patellar dislocation in pediatric patients. In addition, we described risk factors for patellar osteochondral fractures in this population. We hypothesized that most fractures would occur at the inferomedial quadrant of the patella following a traumatic injury mechanism.

METHODS

Following Institutional Review Board approval, the electronic medical record was queried to identify pediatric patients ≤ 18 years old who underwent MPFL reconstruction (MPFLR) or non-operative treatment for patellar instability between July 2016 and February 2020. Osteochondral fractures were defined as full-thickness chondral injuries with attached subchondral bone or purely osseous injuries measuring ≥ 3 mm (mm) in at least two magnetic resonance imaging (MRI) planes. Patients were included in the study if they had complete preoperative x-ray and MRI studies with minimum 6-month follow-up. Patients were excluded if they had incomplete imaging, isolated chondral fractures, or less than 6 months follow-up. Univariate analysis was used to identify patient factors associated with osteochondral fractures. Multivariate regression analysis was used to identify risk factors for osteochondral fractures.

RESULTS

Sixty patients (63 knees) were included in the study, 15 (23.8%) of whom had a patellar osteochondral fracture. The majority of osteochondral fractures (87%) involved the inferomedial quadrant of the patella. Univariate analysis showed an association between male sex (p = 0.041), skeletal immaturity (p = 0.028), and decreased patellar tilt (p = 0.021) and patellar osteochondral fractures. Multivariate regression analysis identified male sex as an independent risk factor for osteochondral fractures (relative risk: 4.8, 95% confidence interval [CI]: 1.08-20.9, p = 0.039). No patients had recurrent dislocation at minimum 6-month follow-up. All patients with osteochondral fractures returned to sports at most recent follow up.

CONCLUSION

In this study, 23% of pediatric patients with acute patellar dislocations have a concomitant patellar osteochondral fracture. The majority of patellar osteochondral fractures involve the inferomedial quadrant of the patella. Male sex is an independent risk factor for patellar osteochondral fractures, and skeletal immaturity is associated with patellar osteochondral fractures in this population.

LEVEL OF EVIDENCE

Level III.

Combined medial patellofemoral ligament and medial patellotibial ligament reconstruction in recurrent patellar instability: A systematic review and meta-analysis

BACKGROUND

The medial patellofemoral ligament (MPFL), along with the medial patellotibial ligament (MPTL) and medial patellomeniscal ligament, aid in the stabilization of the patellofemoral joint. Although the MPFL is the primary stabilizer and the MPTL is a secondary limiter, this ligament is critical in maintaining joint stability. There have been few studies on the combined MPFL and MPTL reconstruction and its benefits.

AIM

To look into the outcomes of combined MPFL and MPTL reconstruction in frequent patellar instability.

METHODS

By May 8, 2022, four electronic databases were searched: Medline (PubMed), Scopus, Web of Science, and Google Scholar. General keywords such as "patellar instability," "patellar dislocation," "MPFL," "medial patellofemoral ligament," "MPTL," and "medial patellotibial ligament" were co-searched to increase the sensitivity of the search.

RESULTS

The pooled effects of combined MPFL and MPTL reconstruction for Kujala score (12-mo follow-up) and Kujala score (24-mo follow-up) were positive and incremental, according to the findings of this meta-analysis. The mean difference between the Cincinnati scores was also positive, but not statistically significant. The combination of the two surgeries reduces pain. According to cumulative meta-analysis, the trend of pain reduction in various studies is declining over time.

CONCLUSION

The combined MPFL and MPTL reconstruction has good clinical results in knee function and, in addition to providing good control to maintain patellofemoral joint balance, the patient's pain level decreases over time, making it a valid surgical method for patella stabilization.

Medial patellofemoral ligament reconstruction in skeletally immature patients without correction of bony risk factors leads to acceptable outcomes but higher failure rates

OBJECTIVES

To report outcomes and re-dislocation rates of medial patellar stabilizers reconstruction without bone procedures for correction of anatomical risk factors for patellar instability in skeletally immature patients; to compare isolated medial patellofemoral ligament (MPFL) reconstruction to combined MPFL and medial patellotibial ligament (MPTL) reconstruction in this population.

METHODS

Patients with open physis and bone abnormalities including patella alta and/or increased tibial tubercle-trochlear groove (TT-TG) distance and/or trochlear dysplasia underwent MPFL reconstruction, either isolated or associated with MPTL reconstruction. Preoperative, 1-year follow-up and the latest follow-up (5 years minimum) data were collected. Radiological and clinical evaluations were conducted, with special attention to failure rate. Comparison of results from isolated MPFL and combined MPFL/MPTL reconstructions was performed.

RESULTS

Twenty-nine patients were included, 19 in the isolated MPFL group (median 14 years old; follow-up 5.8 ​± ​1.7 years) and 10 in the combined MPFL/MPTL group (median 13.5 years old; follow-up 5.2 ​± ​1.4 years). Kujala and Tegner scores increased over time, although without statistically significant differences between the two groups at the latest follow-up (p ​= ​0.840 and p ​> ​0.999, respectively). During follow-up, 5 of 19 (26.3%) isolated MPFL and 2 of 10 (20%) MPFL/MPTL reconstructions experienced recurrence of patellar dislocation (p ​> ​0.999). Trochlear dysplasia type D (p ​= ​0.028), knee rotation (p ​= ​0.009) and lateral patellar tilt angle (p ​= ​0.003) were associated with patellar instability recurrence. The isolated MPFL group showed increased laxity on physical exam at the latest follow-up compared to the 1-year follow-up (patellar glide test (p ​= ​0.002), patellar tilt test (p ​= ​0.042) and subluxation in extension (p ​= ​0.019). This increased laxity was not observed in the MPFL/MPTL group (p ​> ​0.999). Comparing both groups, the glide test was significantly better in the combined MPFL/MPTL group in comparison to the isolated MPFL reconstruction group at the latest follow-up (p ​= ​0.021).

CONCLUSION

MPFL reconstruction in isolation or combined with MPTL reconstruction in skeletally immature patients with additional uncorrected anatomical patellofemoral abnormalities leads to acceptable clinical outcomes within a minimum of 5 years follow-up, although has a high failure rate of 24.1%. Addition of a MPTL reconstruction to the MPFL may result in decreased patellar laxity on physical exams, as demonstrated by better patellar glide test, patellar tilt test and subluxation in extension.

LEVEL OF EVIDENCE

Level III; retrospective cohort study.

Patellar Tracking: An Old Problem with New Insights

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

Combined Medial Patellofemoral Ligament, Medial Quadriceps Tendon-Femoral Ligament, and Medial Patellotibial Ligament Reconstruction for Patellar Instability: A Technical Note

Lateral patellar dislocations often occur in a young, athletic population of recurrent dislocators with generalized laxity and an interest in returning to an active lifestyle. A recent appreciation for the distal patellotibial complex has directed surgeons toward attempting to re-create the native anatomy and knee biomechanics during medial patellar reconstructive procedures. By reconstructing the medial patellotibial ligament (MPTL) in addition to the medial patella-femoral ligament (MPFL) and medial quadriceps tendon-femoral ligament (MQTFL), the current article describes a potentially more stable construct that can be utilized in patients with subluxation with the knee in full extension, patellar instability with the knee in deep flexion, genu recurvatum, and generalized hyperlaxity. Additionally, the current technique utilizes a tibialis anterior allograft. The purpose of this Technical Note is to describe, in detail, the current authors' technique for a combined MPFL, MQTFL, and MPTL reconstruction.

Lateral Patellar Instability

➤

Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology. Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient.

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Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity.

➤

Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment.

➤

Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability.

➤

Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation.

➤

Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta.

➤

The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding.

➤

Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30° to improve patient outcomes and reduce recurrence rates.

Cross-sectional Analysis Study Between SIGMA Knee System and ATTUNE in a Cruciate-Retaining Fixed-Bearing Total Knee Replacement, with no Patellar Resurfacing

Background

The purpose of our study was to compare the knee implant SIGMA to the ATTUNE knee implant in a cruciate-retaining (CR) fixed-bearing (FB) total knee replacement (TKR) surgery, with no patellar resurfacing.

Methods

We examined 40 patients (19 SIGMA; 21 ATTUNE) who underwent a TKR FB CR surgery, without patellar resurfacing, due to osteoarthritis, between August 2013 and July 2017. All surgeries were performed by a single surgeon. We performed a cross-sectional analytical study based on preoperative patient data and data collected in follow-up sessions. All patients were asked to fill a quality-of-life (QOL) questionnaire, SF-36 translated to the Hebrew language. All patients were clinically evaluated using the Knee Society Score (KSS) and the Knee Function Score (KFS).

Results

Patients from the SIGMA cohort reported fewer postoperative physical function limitations in the SF-36 (p = 0.01) and the KFS (p = 0.04). Patients who underwent surgery using the SIGMA implant reported increased vitality when compared to the ATTUNE (p = 0.02). No significant differences were found between the groups in other measures of quality of life, ranges of motion, valgus, and postoperative knee stability. The average follow-up period was significantly longer for the SIGMA (p < 0.00001).

Conclusion

Significant differences were found in postoperative physical function and vitality scores between SIGMA and ATTUNE knee implants. SIGMA cohort presented superior results. Presumably, these findings are due to the differences in follow-up times.

Patellar Instability

➢

Certain anatomic factors, such as patella alta, increased tibial tubercle-trochlear groove distance, rotational deformity, and trochlear dysplasia, are associated with an increased risk of recurrent patellar instability.

➢

The presence of a preoperative J-sign is predictive of recurrent instability after operative management.

➢

Isolated medial patellofemoral ligament reconstruction may be considered on an individualized basis, considering whether the patient has anatomic abnormalities such as valgus malalignment, trochlear dysplasia, or patella alta in addition to the patient activity level.

➢

More complex operative management (bony or cartilaginous procedures) should be considered in patients with recurrent instability, malalignment, and certain anatomic factors.

Quadriceps Tendon Lengthening for Obligatory (Habitual) Patellar Dislocation in Flexion

Obligatory patella dislocation in flexion is an uncommon form of patellar instability, where the patella is located in extension and dislocates with every episode of knee flexion. This results in dramatically altered patellofemoral kinematics and can be extremely debilitating due to extensor strength deficits and lack of knee confidence in flexion. Concomitant pathology, which is often seen, includes a tight lateral retinaculum and a shortened extensor mechanism. Lengthening the extensor mechanism is a critical part of successful patellar stabilization, and has not been well-reported. Herein, we present a technique of quadriceps lengthening for the treatment of obligatory patellar dislocation.

Lateral Patellar Dislocation: A Critical Review and Update of Evidence-Based Rehabilitation Practice Guidelines and Expected Outcomes

»

Nonoperative treatment of a lateral patellar dislocation produces favorable functional results, but as high as 35% of individuals experience recurrent dislocations.

»

Medial patellofemoral ligament reconstruction is an effective treatment to prevent recurrent dislocations and yield excellent outcomes with a high rate of return to sport.

»

Both nonoperative and postoperative rehabilitation should center on resolving pain and edema, restoring motion, and incorporating isolated and multijoint progressive strengthening exercises targeting the hip and knee.

»

Prior to return to sports, both functional and isolated knee strength measurements should be used to determine leg symmetry strength and to utilize patient-reported outcome measures to assess the patient's perceived physical abilities and patellofemoral joint stability.

Medial patellofemoral ligament is a part of the vastus medialis obliquus and vastus intermedius aponeuroses attaching to the medial epicondyle

PURPOSE

This study aimed to investigate the bony surface characteristic of the femoral attachment of the medial patellofemoral ligament (MPFL) and the correlation between the relevant layered structures, including muscular aponeurosis and the joint capsule, which contribute to patellofemoral joint (PFJ) stability.

METHODS

The morphology of the medial aspect of the medial condyle using micro-computed tomography and analysed cortical bone thickening in 24 knees was observed. For the macroscopic and histological analyses, 21 and 3 knees were allocated, respectively. The Kruskal-Wallis one-way analysis of variance test with Dunn post hoc testing was performed for statistical analysis.

RESULTS

At the level of the adductor tubercle, there were no significant differences in cortical bone thickness. At the level of the medial epicondyle (MEC), cortical bone thickness was considerably greater than that in other areas of the medial condyle (mean ± standard deviation, 0.60 ± 0.20 mm; p < 0.0001). Macroscopic analysis revealed that the deep aponeurosis of the vastus medialis obliquus and the tendinous arch of the vastus intermedius distally formed the composite membrane and adjoined to the joint capsule to firmly attach to MEC, which was located at 41.3 ± 5.7 mm posterior and 14.2 ± 3.1 mm superior to the joint cartilage. Histological analysis showed a composite membrane and adjoining capsule attached to MEC via fibrocartilage.

CONCLUSION

MPFL could be interpreted as part of the deep aponeurosis of the vastus medialis obliquus (VMO) and the tendinous arch of the vastus intermedius, which combined with the joint capsule to attach to MEC. The cortical bone thickening indicated that the tensile stresses were loaded on MEC in aged cadavers. Involvement of VMO and vastus intermedius aponeuroses in restored graft of MPFL could utilise the dynamic stability of surrounding muscles to mimic a native structure.

Arthroscopic lateral retinacular release improves patello-femoral and femoro-tibial kinematics in patients with isolated lateral retinacular tightness

PURPOSE

Arthroscopic lateral retinacular release (LRR) has long been considered the gold standard for the treatment for anterior knee pain caused by lateral retinacular tightness (LRT). However, one-third of patients experience continuous pain postoperatively, which is thought to be related to persistent maltracking of the patella and altered femoro-tibial kinematics. Therefore, the aim of the present study was to simultaneously assess femoro-tibial and patello-femoral kinematics and identify the influence of arthroscopic LRR.

METHODS

Sixteen healthy volunteers and 12 patients with unilateral, isolated LRT were prospectively included. Open MRI scans with and without isometric quadriceps contraction were performed in 0°, 30° and 90° of knee flexion preoperatively and at 12 months after surgery. Patellar shift, tilt angle, patello-femoral contact area and magnitude of femoro-tibial rotation were calculated by digital image processing.

RESULTS

Postoperatively, patellar shift was significantly reduced at 90° of knee flexion compared to preoperative values. The postoperative patellar tilt angle was found to be significantly smaller at 30° of knee flexion compared to that preoperatively. Isometric muscle contractions did not considerably influence patellar shift or tilt in either group. The patello-femoral contact area increased after LRR over the full range of motion (ROM), with significant changes at 0° and 90°. Regarding femoro-tibial kinematics, significantly increased femoral internal rotation at 0° was observed in the patient group preoperatively, whereas the magnitude of rotation at 90° of knee flexion was comparable to that of healthy individuals. The pathologically increased femoral internal rotation at 30° without muscular activity could be significantly decreased by LRR. With isometric quadriceps contraction no considerable improvement of femoral internal rotation could be achieved by LRR at 30° of knee flexion.

CONCLUSIONS

Patello-femoral and femoro-tibial joint kinematics could be improved, making LRR a viable surgical option in carefully selected patients with isolated LRT. However, pathologically increased femoral internal rotation during early knee flexion remained unaffected by LRR and thus potentially accounts for persistent pain.

LEVEL OF EVIDENCE

II.

A 10-Year Follow-up on Arthroscopic Medial Plica Syndrome Treatments with Special Reference to Related Cartilage Injuries

OBJECTIVE

The aim of this study was to evaluate the factors that can affect long-term results of arthroscopic resection of medial synovial plica of the knee.

DESIGN

A total of 52 knees in 50 consecutive patients with medial plica syndrome (MPS) were enrolled to prospective study. Preoperatively the age, gender, level of activity, symptoms' duration, Lysholm knee scoring scale (LKSS), Q angle, range of motion (ROM), and quadriceps output torque (QOT) were recorded. The plica was then arthroscopically excised while plica morphological type and cartilage lesions (International Cartilage Repair Society [ICRS] classification) were registered. The postoperative evaluation was done after 1 month, 3 months, 6 months, 3 years, and 10 years. The final assessment after 10 years covered LKSS, ROM, QOT, and was enriched with functional tests: the single leg squat test (SLS), the modified Ober test (MO), and the manual palpation of the vastus medialis obliquus (VMO).

RESULTS

The mean LKSS increased from 52 (15-85, SD 16.479) preoperative to 80 (48-100, SD 15.711) at final follow-up examination. A significant negative correlation was found between LKSS and the patients' age. Cartilage lesions higher than ICRS 1 significantly decreased the final LKSS. Results were significantly better in the subgroups with normal outcome of functional tests.

CONCLUSIONS

Clinical results of arthroscopic plica resection are better in patients without coexisting cartilage lesions. Poor neuromuscular control may contribute to abnormal patella tracking, leading to both medial plica irritation and further cartilage deterioration.

Surgical and Radiological Anatomy of the Medial Patellofemoral Ligament: A Magnetic Resonance Imaging and Cadaveric Study

The purpose of this study was to compare the measurement of several anatomical features of the medial patellofemoral ligament (MPFL) between magnetic resonance imaging (MRI) and by direct fashion during dissection. We hypothesized that the measurements between these two techniques would agree. MRI of 30 fresh-frozen cadaveric knees was followed by dissection. MPFL patella and femoral attachment were evaluated; their shape, length, and width were measured; and measurements were compared. MRI was deemed unreliable for the determination of several of the aforementioned anatomical features. Important findings include: (a) observations on MPFL attachment at medial patella side and attachment to quadriceps were identical between dissection and MRI; (b) average width at patella insertion was significantly different between the two methods (p = 0.002); and (c) an attachment to the quadriceps tendon was present in 20/30 specimens and d. detailed measurements of a thin, non-linear, and three-dimensional structure, such as the MPFL, cannot be performed on MRI, due to technical difficulties. This anatomical radiological study highlights the shape, anatomical measurements (length and width), and attachment of the MPFL using a relatively large cadaveric sample and suggests that MRI is not reliable for detailed imaging of its three-dimensional anatomy.

The Superficial "Swing-Down" Quadriceps Tendon Autograft Is a Viable Option for Medial Patellofemoral Ligament Reconstruction: A Systematic Review

PURPOSE

The purpose of this systematic review is to ascertain the reported clinical outcomes and complication profiles of medial patellofemoral ligament (MPFL) reconstruction performed using a superficial "swing-down" quadriceps tendon autograft.

METHODS

Three databases (PubMed, EMBASE, and MEDLINE) were searched from January 1, 2000, to April 06, 2020. Keywords used in the search included: "medial patellofemoral ligament" and "reconstruction". After screening based on inclusion and exclusion criteria, patient demographics, graft type, outcomes, and complications were extracted. Methodological Index for Non-Randomized Studies criteria were used to assess the quality of each included study.

RESULTS

Eleven studies were included, comprising data from 226 patients with mean follow up ranging from 12 to 38 months. All reconstructions used a superficial "swing-down" quadriceps tendon autograft fixed at 20-30 degrees of knee flexion where reported. Eight of eleven studies reported significant improvement in patient reported outcomes such as Kujala score, Lysholm score, and Tegner score. The mean preoperative Kujala score ranged from 35.8 to 82.1 (167 patients), while the mean postoperative Kujala score ranged from 88.4 to 94.8 (197 patients). The mean of the preoperative Lysholm score ranged from 43.3 to 79.3 (77 patients), while the mean of the postoperative Lysholm score ranged from 81.9 to 90.9 (99 patients). The I² statistic for Lysholm and Kujala scores was 94% and 97%, respectively. Across data reported on 194 patients, there was no incidence of patellar redislocation, patellar fracture, or graft site morbidity.

CONCLUSION

The quadriceps tendon produced improved clinical outcomes with low rates of recurrent postoperative patellar dislocation. These data suggest that the quadriceps tendon remains a suitable alternative for MPFL reconstruction and should remain part of the arsenal of knee ligament surgeons.

LEVEL OF EVIDENCE

Systematic review of Level III and IV studies.

Elongation and orientation pattern of the medial patellofemoral ligament during lunging

Unfavorable clinical outcomes after medial patellofemoral ligament (MPFL) reconstruction, such as early osteoarthritis of the patellofemoral joint, were considered to be associate with tunnel malpositioning. Length change studies have found that small changes in the femoral position can cause great changes in elongation trends. Further studying the MPFL kinematics may help us to understand the consequences of tunnel malpositioning and optimize the reconstruction techniques. Fifteen healthy subjects were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion. Five femoral and three patellar attachments were used to simulate different MPFL bundles. Kinematics of MPFL was defined as elongation and orientation changes (i.e., deviation angle and elevation angle). The mean deviation angle was 28.7° (95% confidence interval, 28.0°-29.4°) at full extension and remained nearly unchanged up to 60° of flexion, and increased to 56.5° (54.1°-58.9°) at 110°. The elevation angle decreased linearly from 12.6° (9.3°-15.9°) at full extension to -86.2° (-92.7-79.7°) at 110° of flexion. The MPFL was most stretched anteriorly and laterally relative to femur from full extension to 30° of flexion and remained near isometric beyond 30°. The current study found that proximal and anterior femoral attachments caused excessive lateral stretching of the MPFL at deeper flexion angles. Such abnormal MPFL kinematics may subsequently cause overconstraint and increased cartilage pressures of the medial patellofemoral joint.

Quadriceps activation during maximal isometric and isokinetic contractions: The minimal real difference and its implications

BACKGROUND: A method of measurement of voluntary activation (VA, percent of full muscle recruitment) during isometric and isokinetic concentric contractions of the quadriceps femoris (QF) at 60∘/s and 120∘/s was previously validated. OBJECTIVE: This study aimed to quantify the test-retest minimal real difference (MRD) of VA during isometric (ISOM) and isokinetic concentric contractions of QF (100∘/s, ISOK) in a sample of healthy individuals. METHODS: VA was measured through the interpolated twitch technique. Pairs of electrical stimuli were delivered to the QF at 40∘ of knee flexion during maximal voluntary contractions. Twenty-five healthy participants (20–38 years, 12 women, 13 men) completed two testing sessions with a 14-day interval. VA values were linearized through logit transformation (VAl). The MRD was estimated from intraclass correlation coefficients (model 2.1). RESULTS: The VA (median, range) was 84.20% (38.2–99.9%) in ISOM and 94.22% (33.8–100%) in ISOK. MRD was 0.78 and 1.12 logit for ISOM and ISOK, respectively. As an example, in terms of percent VA these values correspond to a change from 76% to 95% and from 79% to 98% in ISOM and in ISOK, respectively. CONCLUSIONS: The provided MRD values allow to detect significant individual changes in VA, as expected after training and rehabilitation programs.

Gender-related differences in concomitant articular injuries after acute lateral patellar dislocation

OBJECTIVES

To explore the gender differences in the concomitant articular injuries after acute lateral patellar dislocation (LPD).

METHODS

Magnetic resonance images were prospectively analyzed in 166 patients after an acute LPD. Concomitant articular injuries included bone contusion, medial patellofemoral ligament (MPFL) injury, articular cartilage lesion, and vastus medialis obliquus (VMO) lesion. Statistical analyses were performed between the patient's gender and the incidence of concomitant articular injuries in adolescent and adult subgroups.

RESULTS

The incidence of partial and complete MPFL tear in adolescent males and females were (45%, 50%) and (63.2%, 29.8%), respectively. Compared with adolescent females, adolescent males showed higher incidence of complete MPFL tear (P = 0.049). The incidence of articular cartilage lesion of patella in adolescent males and females were 40% and 21.1%, respectively. Compared with adolescent females, adolescent males showed higher incidence of articular cartilage lesion of the patella (P = 0.043). No correlations were identified in other injuries in the adolescent group. The incidence of partial and complete MPFL tear in adult males and females were (34.4%, 65.6%) and (56.8%, 37.8%), respectively. Compared with adult females, adult males showed higher incidence of complete MPFL tear (P = 0.036). The incidence of articular cartilage lesion of patella in adult males and females were 56.3% and 32.4%, respectively. Compared with adult females, adult males showed higher incidence of articular cartilage lesion of patella (P = 0.047). The incidence of VMO injury in adult males and females were 59.4% and 35.1%, respectively. Compared with adult females, adult males showed higher incidence of VMO injury (P = 0.044). No correlations were identified in other injuries in the adult group.

CONCLUSIONS

Compared with females, males predispose to complete MPFL tear and articular cartilage lesion of patella after acute LPD. Compared with female adults, male adults predispose to VMO injury.

Isolated MPTL reconstruction fails to restore lateral patellar stability when compared to MPFL reconstruction

PURPOSE

To biomechanically evaluate MPTL reconstruction and compare it with two techniques for MPFL reconstruction in regard to changes in patellofemoral contact pressures and restoration of patellar stability.

METHODS

This is an experimental laboratory study in eight human cadaveric knees. None had patellofemoral cartilage lesions or trochlear dysplasia as evaluated by conventional radiographs and MRI examinations. The specimens were secured in a testing apparatus, and the quadriceps was tensioned in line with the femoral shaft. Contact pressures were measured using the TekScan sensor at 30°, 60° and 90°. The sensor was placed in the patellofemoral joint through a proximal approach between femoral shaft and quadriceps tendon to not violate the medial and lateral patellofemoral complex. TekScan data were analysed to determine mean contact pressures on the medial and lateral patellar facets. Patellar lateral displacement was evaluated with the knee positioned at 30° of flexion and 9 N of quadriceps load, then a lateral force of 22 N was applied. The same protocol was used for each condition: native, medial patellofemoral complex lesion, medial patellofemoral ligament reconstruction (MPFL-R) using gracilis tendon, MPFL-R using quadriceps tendon transfer, and medial patellotibial ligament reconstruction (MPTL-R) using patellar tendon transfer.

RESULTS

No statistical differences were found for mean and peak contact pressures, medial or lateral, among all three techniques. However, while both techniques of MPFL-R were able to restore the medial restraint, MPTL-R failed to restore resistance to lateral patellar translation to the native state (mean lateralization of the patella [mm]: native: 9.4; lesion: 22; gracilis MPFL-R: 8.1; quadriceps MPFL-R: 11.3; MPTL-R: 23.4 (p < 0.001).

CONCLUSION

MPTL-R and both techniques for MPFL-R did not increase patellofemoral contact pressures; however, MPTL-R failed to provide a sufficient restraint against lateral patellar translation lateral translation in 30° of flexion. It, therefore, cannot be recommended as an isolated procedure for the treatment of patellar instability.

The quadriceps insertion of the medial patellofemoral complex demonstrates the greatest anisometry through flexion

PURPOSE

A comprehensive understanding of the biomechanical properties of the medial patellofemoral complex (MPFC) is necessary when performing an MPFC reconstruction. How components of the MPFC change over the course of flexion can influence the surgeon's choice of location for graft fixation along the extensor mechanism. The purpose of this study was to (1) determine native MPFC length changes throughout a 90° arc using an anatomically based attachment and using Schöttle's point, and (2) compare native MPFC length changes with different MPFC attachment sites along the extensor mechanism.

METHODS

Eight fresh-frozen (n = 8), cadaveric knees were dissected of all soft tissue structures except the MPFC. The distance between the femoral footprint (identified through anatomical landmarks and Schottle's point) and the MPFC was calculated at four attachment sites along the extensor mechanism [midpoint of the patella [MP], the center of the osseous footprint of the MPFC (FC), the superomedial corner of the patella at the quadriceps insertion (SM), and the proximal extent of the MPFC along the quadriceps tendon (QT)] at 0°, 20°, 40°, 60°, and 90° of flexion.

RESULTS

Length changes were investigated between the MPFL femoral attachment site and the radiographic surrogate of the MPFL attachment site, Schottle's Point (SP). Paired t tests at each of the four components showed no differences in length change from 0° to 90° when comparing SP to the anatomic MPFC insertion. MPFL length changes from 0° to 90° were greatest at the QT point (13.9 ± 3.0 mm) and smallest at the MP point (2.7 ± 4.4 mm). The FC and SM points had a length change of 6.6 ± 4.2 and 9.0 ± 3.8, respectively. Finally, when examining how the length of the MPFC components changed through flexion, the greatest differences were seen at QT where all comparisons were significant (p < 0.01) except when comparing 0° vs 20° (n.s.).

CONCLUSION

The MPFC demonstrates the most significant length changes between 0° and 20° of flexion, while more isometric behavior was seen during 20°-90°. The attachment points along the extensor mechanism demonstrate different length behaviors, where the more proximal components of the MPFC display greater anisometry through the arc of motion. When performing a proximal MPFC reconstruction, surgeons should expect increased length changes compared to reconstructions utilizing distal attachment sites.

Combined Medial Patellofemoral Ligament and Medial Patellotibial Ligament Reconstruction for Recurrent Lateral Patellar Dislocation in Flexion

Recurrent lateral patellar dislocation can be a challenging entity to manage. It results from an imbalance between the restraints to lateralization of the patella and the forces applied to the patella within the biomechanical environment of the knee. The medial patellofemoral ligament has been recognized as the most important static soft-tissue restraint. However, the medial patellotibial ligament and medial patellomeniscal ligament are important for patellar stability at higher degrees of knee flexion. Lateral patellar dislocation in flexion poses a particularly challenging clinical entity with a combination of unique characteristics that need to be addressed to achieve optimal patellar tracking and stability. In this technical note, we describe a combined medial patellofemoral ligament and medial patellotibial ligament reconstruction technique to address lateral patellar dislocation in flexion.