Trochleoplasty: Indications and Technique

Generating 3D pseudo-healthy knee MR images to support trochleoplasty planning

PURPOSE

Trochlear dysplasia (TD) is a common malformation in adolescents, leading to anterior knee pain and instability. Surgical interventions such as trochleoplasty require precise planning to correct the trochlear groove. However, no standardized preoperative plan exists to guide surgeons in reshaping the femur. This study aims to generate patient-specific, pseudo-healthy MR images of the trochlear region that should theoretically align with the respective patient's patella, potentially supporting the preoperative planning of trochleoplasty.

METHODS

We employ a wavelet diffusion model (WDM) to generate personalized pseudo-healthy, anatomically plausible MR scans of the trochlear region. We train our model using knee MR scans of healthy subjects. During inference, we mask out pathological regions around the patella in scans of patients affected by TD and replace them with their pseudo-healthy counterpart. An orthopedic surgeon measured the sulcus angle (SA), trochlear groove depth (TGD) and Déjour classification in MR scans before and after inpainting. The code is available at https://github.com/wehrlimi/Generate-Pseudo-Healthy-Knee-MRI .

RESULTS

The inpainting by our model significantly improves the SA, TGD and Déjour classification in a study with 49 knee MR scans.

CONCLUSION

This study demonstrates the potential of WDMs in providing surgeons with patient-specific guidance. By offering anatomically plausible MR scans, the method could potentially enhance the precision and preoperative planning of trochleoplasty and pave the way to more minimally invasive surgeries.

The Morphologic Patella Entry Point Into the Proximal Trochlea Is More Lateral in Recurrent Dislocators Than Controls as Measured by Entry Point-Trochlear Groove Angle

PURPOSE

To create a metric for evaluating the degree of laterality of the patella's entry into the trochlea, the entry point-trochlear groove (EP-TG) angle, and to evaluate if this laterality is associated with recurrent patella instability.

METHODS

The time frame of the study was January 2020 to February 2023. The inclusion criteria were patients treated by the senior author (J.P.F.) (with the exception of 2 patients who were treated by another provider at the institution who was aware of the study) who have been diagnosed with recurrent atraumatic patellar dislocations. Controls without knee pathology were selected from the New Mexico Decedent Imaging Database (NMDID). Simpleware ScanIP was used to create 3-dimensional (3D) models of the distal femurs from computed tomography scans. Anteroposterior images of these 3D models were uploaded to a custom EP-TG angle measuring tool. Three measurers used the tool to measure the EP-TG angle of the distal femurs.

RESULTS

Twenty-eight patients were included for the recurrent dislocator group. Twenty-four decedents from the NMDID were selected for the control group, each with a left or right knee chosen randomly for measurement. A 1-sided Mann-Whitney U test, used to evaluate whether the recurrent dislocators had higher EP-TG angle values, yielded a P value <.001, demonstrating a high level of significance. A Bayesian mixed-effect model, used to determine how different the EP-TG angles are between the 2 groups, gave a posterior predictive interval of [11.93°, 19.12°] for the EP-TG angle shift of dislocators. The intraclass correlation coefficient was 0.648.

CONCLUSIONS

The morphologic entry point of the patella into the proximal trochlea is more lateral in recurrent patella dislocators than in controls. This increased laterality can be measured by the EP-TG angle, which may be useful information for optimizing treatment of recurrent patella instability.

LEVEL OF EVIDENCE

Level III, case control study.

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.

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.

Trochleoplasty Utilization in the Management of Patellofemoral Instability: Results From an International Survey of Surgeons

Background

Considerable variability exists in the described clinical and radiographic indications for use, surgical techniques, postoperative management, and risk profile after trochleoplasty for the management of patellofemoral instability (PFI). In areas of clinical uncertainty, a cohesive summary of expert opinion and identification of areas of variation in current practice can be useful in guiding current practice and future research efforts.

Purpose

To assess the current indications for use, surgical techniques, postoperative rehabilitation practices, and observed complication profile for trochleoplasty in the management of PFI among surgeons who perform this procedure.

Study Design

Cross-sectional study.

Methods

A 21-item cross-sectional survey was developed to evaluate trochleoplasty in its current practice among surgeons around the world. The survey was distributed between December 2021 and April 2022 to the orthopaedic surgeon membership of multiple national and international knee, arthroscopy, and sports medicine societies to identify any surgeon with experience performing the trochleoplasty procedure in practice for the management of PFI. Descriptive statistics of survey responses were performed to address study aims, and univariate analyses were performed to compare differences between high- and low-volume trochleoplasty surgeons.

Results

Survey distribution identified 32 orthopaedic surgeons with experience performing the trochleoplasty procedure. Procedural indications were most commonly felt to be met with Dejour classification of B or D on magnetic resonance imaging. Trochleoplasty was felt by most to be appropriate as a primary surgical intervention for PFI. A majority of surgeons utilized a Bereiter (thin-flap) trochleoplasty technique with suture-based fixation and performed concurrent medial patellofemoral ligament reconstruction, but other concomitant procedures varied. Range-of-motion precautions and bracing practices varied among respondents, and arthrofibrosis was the most frequently cited observed complication. High- and low-volume trochleoplasty surgeons differed in their radiographic and age-based indications for the procedure.

Conclusion

Study findings indicated that variation exists in the surgical indicators, technique, and postoperative rehabilitation practices of trochleoplasty surgeons, with specific differences noted between high- and low-volume trochleoplasty surgeons. The results of this survey identified areas of equipoise and treatment variation that should direct future research efforts in the study of the trochleoplasty procedure.

No secondary osteoarthritis after recession wedge trochleoplasty associated with tibial tubercle osteotomy for treating recurrent patellar dislocation in high-grade dysplasia

PURPOSE

To determine in the long-term the rate of osteoarthritis of recession wedge trochleoplasty performed in patients with high-grade trochlear dysplasia and recurrent patellar dislocations. The hypothesis was that the rate of secondary osteoarthritis was low.

METHODS

Fifteen consecutive patients (17 knees) undergoing a recession wedge trochleoplasty surgery for recurrent patellar dislocation were retrospectively included. Recurrence of dislocation and functional scores of Lille and Kujala were collected. A complete radiological assessment was carried out to assess secondary patella-femoral and femoro-tibial osteoarthritis.

RESULTS

No recurrence of dislocation was observed. Mean Lille and Kujala scores were respectively 84 ± 9/100 and 78 ± 12/100 at an average follow-up of 11.2 ± 1.8 years (132 ± 22 months, range 96-165). No significant radiological changes in osteoarthritis were observed. Of the 15 knees without any radiological signs of patellofemoral osteoarthritis at time of surgery, 7 presented a bone remodeling (Iwano1) and 8 had no signs of osteoarthritis at the latest follow-up. Among the 2 knees with a preoperative Iwano stage 1, one evolved to Iwano stage 2.

CONCLUSION

Recession wedge trochleoplasty is an effective treatment for recurrent patellar instability in patients with a high-grade trochlear dysplasia. In the long term, the patellofemoral joint is stable, the functional scores are good, and there is no significant arthritic degeneration.

LEVEL OF EVIDENCE

IV, retrospective series.

Patellofemoral Instability Part II: Surgical Treatment

Treatment of patellofemoral instability in skeletally mature patients remains an important area of clinical and research interest. Both nonsurgical and surgical interventions are used to treat the underlying causes. Surgical management is the mainstay of treatment of recurrent PFI that fails nonsurgical treatment, and it is broadly classified into bony and soft-tissue procedures. Proximal bony procedures include femoral trochleoplasty, derotational osteotomies, and coronal alignment correction of the femur. Distal bony procedures include tibial tubercle transfer and derotational (supratubercle and infratubercle) osteotomies. Soft-tissue procedures consist of medial patellofemoral ligament repair or reconstruction and lateral lengthening procedures. This article is the second part of our two-article review on PFI, which focuses on surgical treatment options, their indications, outcomes, and potential complications.

No significant difference in thick versus thin osteochondral flap trochleoplasty in the treatment of trochlear dysplasia: A systematic review

PURPOSE

Trochleoplasty has become increasingly utilised to address patellar instability in the setting of severe trochlear dysplasia. There remains a paucity of literature on the outcomes of 'thick'- versus 'thin'-osteochondral flap trochleoplasty. The purpose of this study is to compare clinical and radiographic outcomes between patients with patellar instability with symptomatic trochlear dysplasia treated using a 'thick' versus 'thin' osteochondral flap trochleoplasty.

METHODS

A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using a PRISMA checklist. Quality assessment of final articles was conducted by two blinded reviewers. Articles were separated based on the use of a 'thick' versus 'thin' flap trochleoplasty. Data collection consisted of recording the following variables: patient demographics, indications for trochleoplasty, mean follow-up time, additional procedures performed during trochleoplasty, patient-reported outcome measures (PROMs), radiographic outcomes (tibial tubercle-trochlear groove [TT-TG] distance, Caton-Deschamps Index [CDI] and sulcus angle [SA]) and the incidence of any postoperative complications and patellar redislocation rates.

RESULTS

A total of 24 studies, consisting of 927 patients, were identified as meeting inclusion criteria. A total of five papers described a 'thick' flap technique, while 19 papers described the use of a 'thin' flap technique. No significant difference in the mean improvement of Kujala scores was appreciated when comparing 'thick' versus 'thin' techniques (p > 0.05). Improvements in mean radiographic outcomes based on TT-TG, CDI and SA were observed in both 'thick' and 'thin' flap trochleoplasty groups. The overall redislocation rate was 0.35%.

CONCLUSION

No significant difference in Kujala scores was observed in patients undergoing trochleoplasty utilising 'thick' versus 'thin' technique, while improvements in mean TT-TG, CDI and SA were noted in both technique groups, with an overall redislocation rate of 0.35%.

LEVEL OF EVIDENCE

Level IV.

Evaluation of Patella Anatomy for Total Knee Arthroplasty Approaches

BACKGROUND

The patella, or kneecap, is a sesamoid bone situated deep to the fascia latae and the tendinous fibers of the rectus femoris. The medial and lateral facets of the patella articulate with the medial and lateral condyles of the femur, respectively, to form the patellofemoral component of the knee joint. When joint cartilage is destroyed due to osteoarthritis, inflammatory arthritis, post-traumatic degenerative joint disease, or osteonecrosis/joint collapse with cartilage loss, a surgical treatment called knee arthroplasty, or total knee arthroplasty (TKA), is used to rebuild the knee joint.

OBJECTIVES

The purpose of our study is to provide a detailed morphometric analysis of the human patella.

METHODS

A total of 168 patellae (86 left, 82 right) were examined. Eleven parameters were determined to evaluate patella morphometry, and the bones were also evaluated with the Wiberg classification.

RESULT

Type I patella was observed in 13 samples (7.74%); 109 (64.88%) and 46 (27.38%) were Type II and Type III, respectively. In the statistical analysis, significant differences were found between the right and left patellae in terms of patellar thickness, vertical ridge length, and Wiberg angle (p<0.05). There were also significant differences between the Wiberg types and the medial articular width and lateral articular width (p<0.05).

CONCLUSION

In order to avoid potential difficulties during knee surgery, it is crucial to understand the typical morphological and morphometric properties of the patella. We believe that this study will be useful to surgeons who perform surgical approaches to the knee and to clinicians who evaluate the diseases of the region.

Use of patellofemoral digital twins for patellar tracking and treatment prediction: comparison of 3D models and contact detection algorithms

Introduction: Poor patellar tracking can result in painful contact pressures, patella subluxation, or dislocation. The use of musculoskeletal models and simulations in orthopedic surgeries allows for objective predictions of post-treatment function, empowering clinicians to explore diverse treatment options for patients. Although a promising approach for managing knee surgeries, the high computational cost of the Finite Element Method hampers its clinical usability. In anticipation of minimal elastic deformations in the involved bodies, the exploration of the Multibody Dynamics approach emerged as a viable solution, providing a computationally efficient methodology to address clinical concerns related to the knee joint. Methods: This work, with a focus on high-performance computing, achieved the simulation of the patellofemoral joint through rigid-body multibody dynamics formulations. A comparison was made between two collision detection algorithms employed in the simulation of contact between the patellar and femoral implants: a generic mesh-to-mesh collision detection algorithm, which identifies potential collisions between bodies by checking for proximity or overlap between their discretized mesh surface elements, and an analytical contact algorithm, which uses a mathematical model to provide closed-form solutions for specific contact problems, but cannot handle arbitrary geometries. In addition, different digital twins (3D model geometries) of the femoral implant were compared. Results: Computational efficiency was considered, and histories of position, orientation, and contact force of the patella during the motion were compared with experimental measurements obtained from a sensorized 3D-printed test bench under pathological and treatment scenarios. The best results were achieved through a purely analytical contact detection algorithm, allowing for clinical usability and optimization of clinical outcomes.

C-Arm Guidance During Thin Flap Arthroscopic Trochleoplasty for Chronic Patellar Instability

The purpose of this paper is to provide a complete Technical Note for our treatment of choice for recurrent patellar dislocation in cases of trochlear dysplasia, especially in patients with types B and D trochlear dysplasia according to the Dejour classification. Different surgical procedures have been reported for the treatment of recurrent patellar instability. One of the most important anatomic factors to address when treating a recurrent patella dislocation is trochlear dysplasia. Few types of open trochleoplasty have been classically described to treat a dysplastic trochlea. However, in recent years, arthroscopic techniques have been reported to reduce invasiveness and complications as well as to improve accuracy and clinical outcomes. In this technique is described an arthroscopic thin-flap tracheoplasty with the use of C-arm guidance in order to precisely control the bone resection and to verify intraoperatively the disappearance of the radiologic landmarks used for diagnosis and classification of the dysplasia. The advantage of this technique is the precision in removal of the supratrochlear spur and bump, the accurate and delicate reshaping of the sulcus with preservation of cartilage vitality, combined with increased reproducibility and safety.

Interdisciplinary Orthopedic Management of Pediatric Patella Dislocation and Instability: An Educational Case Series

Pediatric patellar instability and/or dislocation is a challenging diagnosis category that requires an interdisciplinary team consisting of orthopedic surgeons and physical therapists for optimized patient outcomes. This educational case series outlines core concepts for three patients with unique patellar dislocation presentations. Case 1 is a 16-year-old male who presented with a history of five knee traumatic patellar dislocations with self-reduction and underwent knee arthroscopic surgery with debridement and microfracture of the patella chondral defect, arthroscopic lateral release to improve the patellar tilt, and medial patellofemoral ligament (MPFL) reconstruction. Case 2 is a 15-year-old female who presented with chronic knee pain and patella instability who underwent knee arthroscopic surgery with abrasion arthroplasty, microfracture of the patella, lateral release, tibial tubercle osteotomy medializing osteotomy, and MPFL reconstruction. Case 3 is a 14-year-old male who presented after a single episode of lateral patella dislocation and underwent open reduction and fixation of the lateral femoral condyle osteochondral fracture, a Grammont patellar medialization procedure, and MPFL reconstruction. All three patients received postoperative physical therapy (PT) to improve function and outcomes. These cases represent important concepts of patellar containment, risk factors for recurrent instability, associated pathology, and appropriate surgical care and postoperative rehabilitation. Furthermore, this case series highlights management decisions and pathways for three patients with different symptoms related to patellar instability, subsequent surgical correction, and postoperative physical therapy. Overall, interdisciplinary care of common pediatric orthopedic conditions can help improve patient outcomes and satisfaction. By understanding the biomechanics and decision-making surgical parameters regarding patellofemoral instability, clinicians can provide patients with better care.

Association of Trochlear Length on Sagittal MRI to Trochlear Dysplasia in Knees With Patellar Instability

Background

Trochlear dysplasia is a primary risk factor for patellar instability and leads to loss of the osteochondral constraint of the patella. Trochleoplasty techniques include the Peterson grooveplasty, which alters the length of the trochlea; however, a radiographic measurement of trochlear length to support this has not been described.

Purpose

To describe measurements to quantify trochlear length on sagittal magnetic resonance imaging in patients with and without patellar instability and to correlate trochlear length with measurements of trochlear dysplasia.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 66 age- and sex-matched knees (36 female and 30 male; mean age, 20.8 ± 4.8 years) were included in this study, of which 33 had patellar instability. Trochlear extension length (TEL) and trochlear alpha angle (TAA) were measured on 3 sagittal magnetic resonance imaging scans (center of the knee, center of the medial condyle, and center of the lateral condyle), and measurements were compared between symptomatic and control knees. Receiver operating characteristic curve analysis was performed, and the area under the curve (AUC) was calculated to describe the accuracy of each measurement to distinguish between knees with and without patellar instability. Linear and multivariate regression analyses were performed to assess the relationship between sagittal measurements and axial measurements of trochlear dysplasia, including lateral trochlear inclination, sulcus angle, and trochlear depth, as well as patient size reflected by the epicondylar distance.

Results

In symptomatic knees, the central trochlea extended more proximally than in control knees, as determined by the TEL (14.0 ± 3.0 vs 11.5 ± 2.3 mm, respectively; P < .001) and TAA (68.4° ± 3.8° vs 70.5° ± 3.4°, respectively; P = .017). AUC calculations showed that a TEL ≥11 mm at the central trochlea was predictive of patellar instability in both male and female knees (AUC = 0.83 and 0.77, respectively), as was a TAA ≤67° in female knees (AUC = 0.72). An independent association between the central TEL and sulcus angle was found. The central TEL showed a weak correlation with patient size, as measured by the epicondylar distance, while the TAA did not.

Conclusion

In knees with symptomatic patellar instability, the central trochlea was found to extend 2.5 mm more proximally than in control knees, and this increase in length correlated with severity of trochlear dysplasia. As radiographic examinations of the trochlea and grooveplasty procedures are often based on the proximal extent of the cartilaginous trochlea, further studies are needed to identify the role of trochlear length in the assessment and treatment of trochlear dysplasia in the setting of patellar instability.

Deep learning-assisted diagnosis of femoral trochlear dysplasia based on magnetic resonance imaging measurements

BACKGROUND

Femoral trochlear dysplasia (FTD) is an important risk factor for patellar instability. Dejour classification is widely used at present and relies on standard lateral X-rays, which are not common in clinical work. Therefore, magnetic resonance imaging (MRI) has become the first choice for the diagnosis of FTD. However, manually measuring is tedious, time-consuming, and easily produces great variability.

AIM

To use artificial intelligence (AI) to assist diagnosing FTD on MRI images and to evaluate its reliability.

METHODS

We searched 464 knee MRI cases between January 2019 and December 2020, including FTD (n = 202) and normal trochlea (n = 252). This paper adopts the heatmap regression method to detect the key points network. For the final evaluation, several metrics (accuracy, sensitivity, specificity, etc.) were calculated.

RESULTS

The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of the AI model ranged from 0.74-0.96. All values were superior to junior doctors and intermediate doctors, similar to senior doctors. However, diagnostic time was much lower than that of junior doctors and intermediate doctors.

CONCLUSION

The diagnosis of FTD on knee MRI can be aided by AI and can be achieved with a high level of accuracy.

Lateral Patellar Instability

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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.

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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.

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

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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.

Good patient satisfaction with low complications rate after trochleoplasty in patellofemoral instability

PURPOSE

Trochlear dysplasia has been recognized as the most common factor in patients with patellofemoral dislocation. Trochleoplasty is a surgical procedure whose primary goal is to modify the femoral trochlea's abnormal shape in patients suffering from patellar instability, requiring good surgical skills, correct indication, and accurate patient information.

METHODS

The review aims to describe preoperative planning, patient selection, most common surgical techniques, and clinical results of trochleoplasty in patellar instability in a reproducible manner.

RESULTS

Trochleoplasty can be considered a general term to describe a group of different procedures that reduce trochlear dysplasia's impact on patellar instability, aiming to restore patella-trochlear congruency, remove the supratrochlear bump, allowed a new groove positioning and are generally associated with other procedures. Recent studies showed satisfactory long-term results with the restoration of patellar stability, improving radiological findings of patellofemoral instability.

CONCLUSION

Trochleoplasty is a technically demanding technique, requiring careful patient selection, detailed knowledge, and surgical skills to avoid severe complications. Good patient satisfaction with a low risk of significant complications such as patellofemoral arthritis has been revealed. In conclusion, trochleoplasty should be systematically included in the treatment of patellar dislocation, if indicated.

LEVEL OF EVIDENCE

V.

Can Traditional Straight-leg Swaddling Influence Developmental Dysplasia of the Femoral Trochlea? An In Vivo Study in Rats

BACKGROUND

It has been reported that trochlear dysplasia occurs very early in development, and environmental factors like swaddling may cause developmental dysplasia of the hip, which is associated with a shallower trochlear groove. However, to our knowledge, there are no definitive studies about the relationship between trochlear dysplasia and traditional straight-leg swaddling.

QUESTIONS/PURPOSES

Using a rat model of femoral trochlear dysplasia, we asked: Does straight-leg swaddling for 1 and 2 weeks in newborn Wistar rats alter the femoral trochlea with respect to (1) gross morphology, (2) histologic appearance, as well as (3) trochlear sulcus angle, width, and depth?

METHODS

Eighty-four newborn Wistar rats (44 females and 40 males) were divided into two equal groups: 42 in the unswaddled group and 42 in the swaddled group; each group was comprised of 22 females and 20 males. In the swaddled group, the rats were wrapped in surgical tape to maintain hip and knee extension to simulate traditional human straight-leg swaddling. To determine whether longer periods of swaddling were associated with more severe trochlear dysplasia, 21 rats in each group were euthanized at 1 and 2 weeks, respectively, and the gross morphology of the femoral trochlea was observed by one observer blinded to condition. Then hematoxylin and eosin staining of the femoral trochlea was performed and the distribution and number of the chondrocytes of the trochlear groove were viewed through a microscope. The trochlear sulcus angles, depth, and width were measured by an experienced technician blinded to condition.

RESULTS

By observing the gross morphology, we found that the trochlear groove in the swaddled group became qualitatively flatter compared with the unswaddled group at 1 week, and at 2 weeks, the trochlear groove became much shallower. At 1 and 2 weeks, histologic examinations showed obvious qualitative changes in the distribution and number of chondrocytes of the trochlear groove in the swaddled than in the unswaddled groups. In the swaddled group, trochlear dysplasia was more common at 2 weeks, occurring in 62% (26 of 42 [16 of 22 females and 10 of 22 males]) versus 33% (14 of 42 [8 of 22 females and 6 of 20 males]) at 1 week. At 1 week, the swaddled group showed more trochlear dysplasia compared with the unswaddled group as measured by angle of the trochlear groove (137° ± 6° versus 132°± 3.6°, mean difference 5° [95% confidence interval 2.9° to 7.2°]; p < 0.001), depth of the trochlear grove (0.28 ± 0.04 mm versus 0.31 ± 0.02 mm, mean difference 0.03 mm [95% CI 0.01 to 0.04]; p < 0.001). At 2 weeks, the swaddled group showed more severe trochlear dysplasia than at 1 week compared with the unswaddled group as measured by the angle of the trochlear groove (135° ± 6.0° versus 128° ± 4.8°, mean difference 7° [95% CI 5.7° to 10.4°]; p < 0.001), depth of the trochlear grove (0.32 ± 0.04 mm versus 0.36 ± 0.02 mm, mean difference 0.04 mm [95% CI 0.03 to 0.06]; p < 0.001). There was no difference in the width of the trochlear sulcus between the swaddled and the unswaddled groups at 1 week (1.29 ± 0.14 mm versus 1.30 ± 0.12 mm, mean difference 0.01 mm [95% CI -0.05 to 0.07]; p = 0.73) and 2 weeks (1.55 ± 0.12 mm versus 1.56 ± 0.12 mm, mean difference 0.01 mm [95% CI -0.05 to 0.07]; p = 0.70).

CONCLUSION

Our results indicate that traditional straight-leg swaddling could induce trochlear dysplasia in this model of newborn rats. With an increased swaddling time of 2 weeks, more severe trochlear dysplasia appeared in the swaddled group.

CLINICAL RELEVANCE

Our findings suggest that traditional straight-leg swaddling may impair trochlear development in the human neonate and lead to trochlear dysplasia in infants. We believe our animal model will be useful in future work to observe and study the change of cartilage and subchondral bone in each stage of the development of trochlear dysplasia and the change of mechanotransduction-associated proteins (such as, TRPV4/ Piezo1 and CollagenⅡ) in cartilage and subchondral osteocytes. It will also be helpful to further investigate the mechanism of developmental femoral trochlea dysplasia caused by biomechanical changes.

Radiographic Evaluation of Pediatric Patients with Patellofemoral Instability

PURPOSE OF REVIEW

The purpose of this review is to highlight the radiographic assessments of utility in the evaluation of a pediatric patient with patellofemoral instability to facilitate a thorough work-up. Understanding of these measures is useful in understanding evolving research in this field, providing accurate patient risk assessment, and appropriately directing surgical decision-making.

RECENT FINDINGS

Recent literature has broadened the radiographic characterization of the pediatric patellar instability and its anatomic risk factors. Knee MRI can inform the assessment of skeletal maturity and novel axial alignment measurements may enhance our identification of patients at increased risk of recurrent instability. Additional improvements have been made in the objective measurement and classification of trochlear dysplasia. Knee MRI-based skeletal age assessments may obviate the need for hand bone age assessments in growing children with patellofemoral instability. Novel objective measures exist in the evaluation of pediatric patellar instability both in the assessment of axial alignment and trochlear dysplasia. Future work should focus on how these measures can aid in guiding surgical decision-making.

Groove-deepening trochleoplasty reduces lateral patellar maltracking and increases patellofemoral contact pressures: Dynamic simulation

Groove-deepening trochleoplasty is performed to restore patellar stability by increasing the lateral constraint applied to the patella by the trochlear groove. Multibody dynamic simulation of knee function was used to characterize the influence of groove-deepening trochleoplasty on patellar tracking and patellofemoral contact pressures. Computational models were created to represent seven knees with trochlear dysplasia, indicated by a flat trochlear groove and supratrochlear spur. The models were manipulated to remove the spur and deepen the trochlear groove to represent the average shape following a trochleoplasty. Knee squatting was simulated for the preoperative and postoperative conditions. Statistically significant (p < 0.05) differences in output parameters were identified with repeated measures comparisons at every 5° of knee flexion. Trochleoplasty significantly decreased lateral patellar tracking, particularly at low knee flexion angles. Trochleoplasty decreased the peak lateral shift of the patella (bisect offset index) with the knee extended from 0.87 ± 0.14 to 0.75 ± 0.12. Trochleoplasty also significantly decreased the contact area and increased the maximum contact pressure at multiple flexion angles. Trochleoplasty decreased the average contact area by approximately 10% in mid-flexion, with a corresponding increase in the average maximum contact pressure of 13%-23%. Decreased contact area and increased contact pressures are related to altered patellofemoral congruity due to reshaping the femur without a corresponding change to the patella. Clinical significance: The results indicate groove-deepening trochleoplasty decreases lateral patellar maltracking, reducing the risk of patellar dislocations, but can elevate patellofemoral contact pressures, which could contribute to long-term degradation of cartilage.

Outcomes and reoperation rates after tibial tubercle transfer and medial patellofemoral ligament reconstruction: higher revision stabilization in patients with trochlear dysplasia and patella alta

PURPOSE

To determine the reoperation rate, risk factors for reoperation, and patient-reported outcomes after isolated or combined tibial tubercle transfer and medial patellofemoral ligament reconstruction, for patellofemoral instability surgery.

METHODS

Patient's records who underwent medial patellofemoral ligament reconstruction and/or tibial tubercle transfer for patellar instability by 35 surgeons from 2002 to 2018 at a single academic institution were retrospectively reviewed using CPT codes. Four-hundred-and-eighty-six patients were identified. Radiographic measurements, demographic parameters, and subsequent revision procedures and their indications were identified. A modified anterior knee pain survey was conducted by mail and with follow-up phone survey.

RESULTS

The overall rate of reoperation was 120/486 (24.7%). The most common cause for reoperation was removal of hardware 42/486 (8.6%). The rate of reoperation for isolated medial patellofemoral ligament reconstruction 43/226 (19%) was lower than that of isolated tibial tubercle transfer 45/133 (33.8%) or a combined procedure 32/127 (25.2%) (P = 0.007). Woman had a higher rate of reoperation (29.4%) compared to men (15.9%) (P = 0.002). Patients at risk for a revision stabilization procedure included those with severe trochlear morphology (C or D) (6.1%) and those with Caton-Deschamps index > 1.3 (7.3%). Patients who underwent reoperation of any kind had poorer patient-reported outcomes.

CONCLUSION

The overall reoperation rate after patellofemoral instability surgery remains high, and any reoperation portends worse patient-reported outcomes. Re-operations for instability are more likely in patients with trochlear dysplasia and patella alta and may benefit from more aggressive initial treatment, such as medial patellofemoral ligament reconstruction and tibial tubercle transfer in combination. Using the results of this study, surgeons will be able to engage in meaningful discussion with patients to counsel patients on expectations postoperatively.

LEVEL OF EVIDENCE

IV.

Trochlear Osteochondral Shell Allograft Technique to Treat Trochlear Dysplasia in the Setting of Chondral Damage and Chronic Patellar Instability

Chronic patellar instability is characterized by recurrent dislocation events due to anatomical distortions as well as insufficiency of surrounding stabilizing structures, ultimately impacting patients' quality of life. In the setting of recurrent instability, patella alta, and trochlear dysplasia, there is also increased likelihood of symptomatic chondral damage in these patients. In this Technical Note, we describe the management of a patient with chronic lateral patellar instability, pain outside of dislocation events, and extensive surgical history to the knee. The surgical management included a combined approach, using a shell osteochondral allograft transplant to the trochlea, cylindrical osteochondral allograft transplantation to the patella, and revision tibial tubercle osteotomy with medial patellofemoral ligament reconstruction.

Interference screws vs. suture anchors for isolated medial patellofemoral ligament femoral fixation: A systematic review

PURPOSE

The present study aimed to systematically review and compare 2 femoral autograft fixation techniques, namely, interference screws and suture anchors, for isolated medial patellofemoral ligament reconstruction in patients with recurrent patellofemoral instability at mid- to long-term follow-up.

METHODS

A literature search was performed in September 2020. All studies reporting the outcomes of primary isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability were considered for inclusion. Only studies reporting the type of femoral autograft fixation under examination were considered. Studies reporting data from patients with elevated tibial tuberosity-tibial groove, patella alta, and/or Dejour's trochlear dysplasia types C and D, were not included. Only articles reporting data with a minimum follow-up period of 18 months were considered.

RESULTS

Data from 19 studies (615 patients) were retrieved. The overall age was 24.4 ± 6.7 years (mean ± SD). The mean follow-up was 46.5 ± 20.9 months. There were 76 patients in the anchor group and 539 in the screw group. Comparability was found with regard to age and follow-up duration between the 2 study groups. There was comparability between the Kujala, Lysholm, and Tegner scores at baseline. At the last follow-up, no worthy differences were found in terms of mean Kujala (+2.1%; p = 0.04), Lysholm (+1.7%; p = 0.05), and Tegner (+15.8%; p = 0.05) scores. Although complications occurred almost exclusively in the screw cohort, no statistically significant difference was found.

CONCLUSION

Femoral autograft fixation through interference screws or suture anchors report similar clinical scores and rate of apprehension test, persistent joint instability, re-dislocations, and revisions. These results must be interpreted within the limitations of the present study.

Using a 3D handheld scanner to capture trochlear groove shape: proof of concept study

INTRODUCTION

Trochleoplasty is a surgical procedure used to treat patellar instability by modifying the trochlear groove. Analysis of the groove with a handheld scanner would enable accurate real-time planning and facilitate tailormade correction. We aimed to measure trochlear depth, sulcus angle, trochlear facet ratio, trochlear angle and lateral trochlear inclination angle and to establish inter- and intra-rater reliability for knee models to determine reliability and repeatability.

METHODS

The trochlear grooves of three knee models were scanned by two investigators. Three-dimensional reference models were created and surface-matched. Custom software was used to determine the desired parameters. The intraclass correlation coefficient (ICC) was used to determine test-retest reliability and the parameter results for each model that showed best reproducibility.

RESULTS

There was good interobserver reliability (trochlear depth, 1.0mm; sulcus angle, 2.7°; trochlear angle, 4.0°; lateral trochlear inclination angle, 4.0°), except in the trochlear facet ratio (32.0%) of one knee model. With outliers removed, the ICC was moderate to excellent in 73.34% of measurements, with trochlear depth showing the best reproducibility.

DISCUSSION

This feasibility study showed a handheld scanner in conjunction with supporting software can measure trochlear parameters with good to excellent inter- and intra-observer reliability.

Current Concepts Regarding Patellofemoral Trochlear Dysplasia

Optimal treatment of patients with patellofemoral trochlear dysplasia and recurrent patellar instability requires in-depth understanding of this complex structural anomaly. An extensive review of the literature suggests that dysplasia occurs as a result of aberrant forces applied to the patellofemoral joint in the majority of cases. Evidence supports surgical stabilization that reconstructs the medial patellofemoral and/or medial quadriceps tendon-femoral ligament without added trochleoplasty in the majority of patients with trochlear dysplasia and recurrent patellar instability. Adding tibial tubercle transfer distally, medially, or anteromedially in those who need it to treat specific deficits in alignment or articular cartilage can be beneficial in selected patients with trochlear dysplasia and recurrent patellar instability. Trochleoplasty may be appropriate in those few cases in which permanent stable patellofemoral tracking cannot be restored otherwise, but the indications are not yet clear, particularly as trochleoplasty adds risk to the articular cartilage. Improved understanding of imaging techniques and 3-dimensional reproductions of dysplastic patellofemoral joints are useful in surgical planning for patients with recurrent patellar instability and trochlear dysplasia.

Return-to-Play Guidelines After Patellar Instability Surgery Requiring Bony Realignment: A Systematic Review

Background

Recurrent patellar instability can be treated nonoperatively or surgically, and surgical management may vary based on the causative pathology in the structures surrounding the patella. Although isolated soft tissue reconstruction is among the most common operative treatments, certain patient populations require bony realignment for adequate stabilization.

Purpose

To evaluate postoperative guidelines, including return to play and rehabilitation, after bony procedures involving the tibial tubercle for patellar instability.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review on return-to-play guidelines was conducted with studies published from 1997 to 2019 that detailed procedures involving bony realignment by tibial tubercle osteotomies and tibial tubercle transfers with or without soft tissue reconstruction. Exclusion criteria included animal or cadaveric studies, basic science articles, nonsurgical rehabilitation protocols, and patients with mean age <18 years. Studies were assessed for return-to-play criteria, rehabilitation protocols, and bias.

Results

Included in the review were 39 studies with a total of 1477 patients and 1598 knees. Mean patient age ranged from 17.5 to 34.0 years, and mean follow-up ranged from 23 to 161 months. All 39 studies described postoperative rehabilitation; however, only 16 studies specifically outlined return-to-play criteria. The most commonly cited return-to-play criterion was quadriceps strength (62.5%). Range of motion (50.0%), physical therapy protocols (18.8%), and radiographic evidence of healing (18.8%) were other cited objective criteria for return-to-play. Four of 16 (25.0%) studies described subjective criteria for return to play, including pain, swelling, and patient comfort and confidence. Of the 11 studies that described a timeline for return to play, the range was between 2 and 6 months.

Conclusion

The results revealed that 100% of papers evaluated lacked adequate return-to-play guidelines. Moreover, timelines significantly varied among studies. More clearly defined return-to-play guidelines after tibial tubercle transfer for patellar instability are required.

Sulcus-Deepening Trochleoplasty as an Isolated or Combined Treatment Strategy for Patellar Instability and Trochlear Dysplasia: A Systematic Review

Purpose

To highlight the indications and outcomes for sulcus-deepening trochleoplasty, when used as an isolated procedure as well as in combination with other stabilization techniques for patellar instability.

Methods

We performed a systematic review focused on outcomes and complications following trochleoplasty performed either as an isolated procedure or in combination with other procedures to address patellar instability. Inclusion criteria included studies in English that reported on outcomes following primary open trochleoplasty, including Kujala scores and recurrent instability or dislocation events.

Results

Twelve papers including 702 patients who underwent sulcus-deepening trochleoplasty were included. A total of 504 patients underwent isolated sulcus-deepening trochleoplasty, whereas 198 patients underwent trochleoplasty in combination with 1 or more additional stabilization procedures. In total, 67% of patients were female compared with 33% male. The procedure was done was a primary surgical intervention 74% of the time. Postoperative Kujala scores for isolated trochleoplasty ranged from 80 to 92, whereas those for combined stabilization procedures ranged from 76 to 95. The dislocation rate among the studies ranged from 0 to 8%. There was a persistent J-sign in 0 to 12% of treated knees among all studies, and a persistent apprehension test in 0 to 29% of treated knees. Return to play ranged from 65% to 83% in studies in which this was reported as an outcome.

Conclusions

Sulcus-deepening trochleoplasty performed for recurrent patellar instability in the setting of trochlear dysplasia results in improved Kujala scores and a low redislocation rate, when performed as an isolated procedure or in combination with other stabilization procedures. Greater-level evidence is needed to better evaluate the overall efficacy of this procedure in addressing patellar instability.

Level of Evidence

Level of Evidence, IV; Systematic review of level III and IV studies.

Update on Patellar Instability

Patellar instability is a multifactorial clinical condition that affects a significant number of patients and occurs due to morphological variations of the joint and patellofemoral alignment. The present literature review study aimed to identify and summarize current concepts on patellar instability, in relation to associated risk factors, diagnostic criteria, and the benefits and risks of conservative and surgical treatments. For this purpose, a search was conducted in the following electronic databases: MEDLINE (via Pubmed), LILACS and Cochrane Library. It is concluded that the accurate diagnosis depends on the detailed clinical evaluation, including the history and possible individual risk factors, as well as imaging exams. The initial treatment of patellar instability is still controversial, and requires the combination of conservative and surgical interventions, taking into consideration both soft tissues and bone structures, the latter being the most common reason for choosing surgical treatment, especially lateral patellar instability.

Precise Arthroscopic Mini-trochleoplasty and Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability With Severe Trochlear Dysplasia

More than 100 surgical procedures have been reported to address recurrent patellar instability. Trochlear dysplasia is the most common finding among the anatomic risk factors for recurrent patellar instability. Various studies have shown that trochleoplasty combined with medial patellofemoral ligament reconstruction is an effective technique to treat recurrent patellar instability. Nevertheless, trochleoplasty is still a daunting procedure for surgeons because of its multiple and gloomy complications. This article introduces a technique to treat recurrent patellar instability with severe trochlear dysplasia: precise arthroscopic mini-trochleoplasty (PAM trochleoplasty) combined with medial patellofemoral ligament reconstruction. This technique precisely removes the supratrochlear spur and trochlear bump, accurately reshapes the trochlear sulcus with minimal invasion and less osteotomy volume, and keeps the sulcus cartilage intact. The purpose of this technique is to develop trochleoplasty into a common and safe technique, which has good outcomes and low complications.

[Trochleoplasty: Surgical technique : Video article]

A 29-year-old physically active patient presented with recurrent right-sided patellar dislocation. Clinical and radiological investigation showed patellar instability with stable cruciate and collateral ligaments, excess internal rotation of the right femur, as well as trochlear dysplasia. Treatment consisted of trochleoplasty in combination with medial patellofemoral ligament reconstruction.

Assessing Femoral Trochlear Morphologic Features on Cross-Sectional Imaging Before Trochleoplasty: Dejour Classification Versus Quantitative Measurement

OBJECTIVE. The purpose of this study is to assess the use of cross-sectional imaging to qualitatively and quantitatively categorize trochlear dysplasia as low grade (type A) or high grade (types B-D) according to the Dejour classification. MATERIALS AND METHODS. A retrospective review of CT and MRI knee examinations performed before patients underwent deepening trochleoplasty was independently conducted by two musculoskeletal radiologists. Each case of trochlear dysplasia was qualitatively assigned a Dejour type. Subsequently, quantitative measurements of the sulcus angle, distance from the tibial tubercle to the trochlear groove, trochlear depth, lateral trochlear inclination, trochlear facet asymmetry, and degree of patellar lateralization were performed. RESULTS. A total of 35 patients (29 female patients and six male patients; mean age, 21.1 years) with 39 affected knees (17 right knees and 22 left knees) were included. Readers had exact qualitative agreement using Dejour classification for 30 of 39 knees (77% [κ = 0.77; 95% CI, 0.62-0.91]) and agreement on classification of low-grade versus high-grade dysplasia for 36 of 39 knees (92%). For these 36 knees, the mean differences in measurements of low- versus high-grade dysplasia, respectively, were as follows: for sulcus angle, 153° versus 168° (p < 0.001); for trochlear depth, 4 versus 1 mm (p < 0.001); for lateral trochlear inclination, 12 versus 7 mm (p < 0.02); and for decreased trochlear facet asymmetry, 13% versus 92% (p < 0.001). Trochlear depth, lateral trochlear inclination, and trochlear facet asymmetry were also different in comparisons of knees with Dejour type B and C trochlear dysplasia versus those with Dejour types B and D (all p < 0.05). No quantitative measurement differentiated between trochlear dysplasia of Dejour types C and D. The distance from the tibial tubercle to the trochlear groove and the degree of patellar lateralization were not statistically different between low- and high-grade dysplasia. CONCLUSION. Qualitative use of the Dejour classification accurately categorizes trochlear dysplasia as low grade or high grade in 92% of cases, with exact agreement reached in 77% of cases. Furthermore, the trochlear depth, lateral trochlear inclination, trochlear facet asymmetry, and sulcus angle can differentiate between low-grade and high-grade dysplasia, with trochlear depth, lateral trochlear inclination, and trochlear facet asymmetry useful for differentiating between Dejour types B and C and Dejour types B and D.

Surgical management of patellofemoral instability part 2: post-operative imaging

The patellofemoral joint is a complex joint requiring contributions from both bone and soft tissue for its stability. Pathology of the patellofemoral joint manifests as instability or anterior knee pain. Careful clinical and imaging assessment is important for managing these patients with cross-sectional imaging being a vital component in pre-surgical planning. Operative treatment can involve soft tissue procedures, bony procedures or both. The purpose of part 2 of this two-part article is to review the post-operative imaging findings of the knee extensor mechanism. In doing so, we will provide an overview of some of the bony and soft tissue procedures performed with details of their indications and possible complications. An appreciation of the post-operative surgical appearances will ensure a more comprehensive report and can prevent misinterpretation by the radiologist.

Surgical management of patellofemoral instability. I. Imaging considerations

The patellofemoral joint is a complex joint that relies on both bone and soft tissues for its stability. Dysfunction of the patellofemoral joint, whether pain or instability, is a common cause of medial consultation. Thorough clinical and imaging assessment is important for managing these patients, who may require a combination of a bony and soft tissue surgical procedure. Trochlear dysplasia, a cause of anterior knee pain and patellar instability, has been classified using conventional radiography. Radiographic signs on a lateral projection, such as the "double contour" sign and the "crossing sign", can alert the radiologist to the grade of trochlear dysplasia. Magnetic resonance imaging (MRI) is the gold standard for accurately assessing the soft tissue around the patellofemoral joint, such as the medial patellofemoral ligament and the medial and lateral patella retinacula, especially in the context of a transient patella dislocation. Risk factors for patellofemoral instability, such as patella alta, an increased tibial tubercle to trochlear groove distance and trochlear dysplasia, can all be assessed on MRI. Advanced imaging techniques such as dynamic MRI and CT are able to demonstrate patellar maltracking. These techniques can also be employed to reliably assess the outcomes of treatment. In this article, we review the normal and abnormal pre-operative imaging findings of the knee extensor mechanism in relation to patellofemoral joint instability. This review provides a useful tool for the reporting radiologist and highlights the imaging findings that are of relevance to the orthopaedic surgeon.