Trochlear dysplasia and the role of trochleoplasty

Isolated Medial Patellofemoral Ligament Reconstruction Results in Lower Failure and Complication Rates Than Isolated Trochleoplasty and Tibial Tubercle Osteotomy: A Systematic Review

PURPOSE

To evaluate outcomes and complications of isolated medial patellofemoral ligament reconstruction (MPFLR), tibial tubercle osteotomy (TTO), and trochleoplasty for management of patellar instability.

METHODS

A query of Scopus, PubMed, Google Scholar, Cochrane CENTRAL Register of Controlled Trials, and the Cochrane Database of Systematic Reviews was performed in accordance with 2020 Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included studies reported clinical outcome data after isolated MPFLR, TTO, or trochleoplasty for patellar instability with a minimum 12-month follow-up. Meta-analysis and data aggregation was not performed.

RESULTS

Thirty-six studies (5 trochleoplasty, 14 TTO, and 18 MPFLR) consisting of 1,389 patients (114 trochleoplasty, 374 TTO, and 1,001 MPFLR) were included. Risk of bias was assessed with the Methodological Index for Non-Randomized Studies score, which ranged from 11 to 12 in trochleoplasty, 10 to 18 in TTO, and 8 to 18 in MPFLR studies. Patient-reported outcome measures, including Lysholm score (trochleoplasty: 51.1-71 to 71-95; TTO: 57-63.3 to 84-98; MPFLR: 37.4-59.1 to 74-92.5), Kujala score (trochleoplasty: 56-71 to 78-92; TTO: 48.6-68 to 78-92; MPFLR: 53.3-60 to 81.5-92), visual analog scale for pain (trochleoplasty: 52-25; TTO: 54-76 to 14-27; MPFLR: 29 to 17, out of 100), and Tegner score (TTO: 3-4 to 3-4; MPFLR: 2.5-6 to 4.9-5), improved after all surgeries. Failure rates ranged from 0% to 33.3% after MPFLR, 0% to 30.8% after TTO, and 5.3% to 40% after trochleoplasty. Complication rates ranged from 0% to 14.7% after MPFLR, 1.6% to 58.3% after TTO, and 8% to 26.3% after trochleoplasty.

CONCLUSIONS

Isolated MPFLR, TTO, or trochleoplasty may be effective treatment options for patellar stabilization. Although failure rates were highest after isolated trochleoplasty and complication rates were highest after TTO, these procedures are not interchangeable as each addresses a specific pathology.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II to IV studies.

Outcomes of Surgical Interventions for Patellofemoral Instability in the Presence of Trochlear Dysplasia: A Systematic Review and Meta-analysis

BACKGROUND

Patellar instability is frequently encountered by orthopaedic surgeons. One of the major risk factors of this condition is underlying trochlear dysplasia (TD). Recent trends have indicated the use of multiple procedures to correct patellar instability under these conditions. Medial patellofemoral ligament reconstruction (MPFLR) and trochleoplasty (TP) are surgical strategies that have demonstrated successful outcomes. However, it is unclear whether isolated MPFLR suffices for patellar instability in the presence of severe TD. Furthermore, the need for TP or a combined approach, considering its invasiveness and technical demands, to achieve better clinical outcomes and patellofemoral stability remains uncertain.

PURPOSE

To compare the outcomes of 3 surgical interventions for addressing patellar instability due to TD: MPFLR, TP, and combined MPFLR and TP.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

Studies reporting the clinical outcomes of MPFLR, TP, and both in combination, regardless of additional procedures, were identified using the MEDLINE, PubMed, Embase, Scopus, Cochrane Library, Cochrane Central Register of Controlled Trials, and Cumulative Index to Nursing and Allied Health Literature databases. An important inclusion criterion was that studies should include the mean preoperative and postoperative Kujala scores and any complications. A random-effects model was used for the meta-analysis.

RESULTS

Overall, 30 studies were included: 10 describing the outcomes of TP, 13 describing the outcomes of MPFLR, and 7 describing the outcomes of combined TP and MPFLR. Furthermore, 1457 patients (1571 knees) were evaluated with a mean follow-up of 42.4 ± 32.8 months. No statistically significant differences were found between the 3 methods regarding the mean difference using the Kujala score. However, combined MPFLR and TP had the highest weighted mean difference compared with the other 2 procedures (28.5 points; P < .001). Evidential analysis revealed a robust log-likelihood ratio (S = 3.2) supporting the superiority of the combined procedure when comparing this mean and the weighted grand mean of 23.7. The redislocation rate after patellar stabilization remained minimal, irrespective of the surgical procedure (mean, 0.7%). However, the rate of residual patellar instability was the highest in the TP group (mean, 13.5%).

CONCLUSION

This study found no statistically significant difference between the outcomes of the 3 procedures. However, the combined approach of MPFLR and TP was associated with the most promising clinical outcomes and a low redislocation rate in patients with varying severities of TD.

Lateral Opening Distal Femoral Osteotomy with Concomitant MPFL Reconstruction is Efficacious in Addressing Patellar Instability

PURPOSE

To describe the clinical and radiographic outcomes of patients undergoing a lateral opening distal femur osteotomy (DFO) to address valgus alignment and restore patellar stability.

METHODS

A retrospective review of patients who underwent lateral opening DFO for recurrent patellar instability in the setting of valgus leg alignment at a single academic institution between January 2016 to December 2021 was performed. Patients without a minimum 24-month postoperative follow-up were excluded. Rates of recurrent patellar instability, patient-reported outcomes, and complications were assessed. Pre- and post-operative radiographic anatomic lateral distal femoral angle (aLDFA) was evaluated to assess alignment correction.

RESULTS

20 lateral opening DFO cases were included from 15 patients [mean age 19.6 years, mean follow-up 42.4 months (range 24-63 months)]. 19 of 20 (95.0%) knees experienced no recurrent patellar dislocation. 13 of 20 (65.0%) knees underwent re-operation [hardware removal (n = 10); revision stabilization procedure (n = 1); lysis of adhesions and manipulation under anesthesia (LOA/MUA) (n = 1); nonunion revision with bone grafting (n = 1). mLDFA significantly changed from 86.3 degrees preoperatively to 91.4 degrees postoperatively (p < 0.001). Mean aLDFA changed significantly from 77.4 preoperatively to 84.4 degrees postoperatively (p < 0.001). The final Kujala score had a median value of 92 (IQR 85.5 - 98), Lysholm score was 90 (IQR 76 - 95), and Tegner score was 5 (IQR 4 - 7).

CONCLUSION

Lateral opening DFO is an efficacious procedure to address recurrent patellar instability in patients with valgus leg alignment. The present retrospective case series demonstrates good functional outcomes and low rates of recurrent instability and major complications after a lateral opening DFO, despite a large proportion of patients having undergone previous surgery. There were relatively high rates of reoperation and hardware irritation.

LEVEL OF EVIDENCE

Retrospective case series; Level of evidence, 4.

Combination of the medial patellofemoral ligament reconstruction with the quasi-anatomic technique, tibial tuberosity osteotomy, lateral retinaculum release and mosaicplasty produces satisfactory results for patients with patello-femoral instability. 2-Year follow-up

INTRODUCTION

This study aimed to evaluate the effectiveness and safety of a combined surgical approach for treating complex patellofemoral instability. This approach combines four procedures: medial patellofemoral ligament (MPFL) reconstruction with the quasi-anatomic technique, lateral retinaculum release, anteromedialization and distalization of tibial tuberosity and patellar/femoral mosaicplasty.

MATERIAL AND METHODS

Between August and November 2021, we enrolled 27 patients in the study (21 females, 6 males, average age 28.6 years). All with patella alta, recurrent patellar instability, severe cartilage focal damage, and increased tibial tubercle-trochlear groove distance. All underwent the combined procedure during this period. We assessed their pain and functional scores before surgery and at 6, 12, and 24 months after surgery using standardized scoring systems.

RESULTS

Patients initially reported significant pain and functional limitations. However, at 24 months, their pain scores significantly reduced, averaging 1.5 compared to 8.2 pre-surgery. Similarly, their functional scores substantially improved, with Lysholm, Tegner, Kujala, BPII scores reaching 87.44, 8.44, 90.03, 86.07 compared to 56.4, 3.7, 42.48, 23 pre-surgery, respectively. Importantly, no cases of recurrent instability occurred, and 96.3% of patients reported complete satisfaction.

CONCLUSIONS

This combined surgical approach has a high rate of success for patients with patella alta, recurrent lateral patellar instability, severe focal chondral lesions, and increased TT-TG distance. Moreover, 26 out of 27 patients (96.3%) reported total satisfaction. Therefore, we conclude that although this procedure combination is not simple, it is a safe, reproducible, and alleviates pain at 24 months postoperatively, and significantly improves functional scores.

Prevalence of trochlear dysplasia in an 1162 retrospective cohort study using CT scans

HYPOTHESIS/PURPOSE

The prevalence of trochlear dysplasia is common in different populations.

BACKGROUND

The prevalence of trochlear dysplasia in the general population, categorised by sex, race, age, and body mass index, has been sparse. This study aimed to define the prevalence of trochlear dysplasia based on the latter categories.

STUDY DESIGN

Cohort retrospective study.

METHODS

1162 skeletal mature healthy femora were obtained from a CT-scan-based modelling system (SOMA). Thin slice CT scans were acquired exclusively for medical indications such as polytrauma (20%), CT angiography (70%) and other reasons (i.e. Total Joint Replacement) (10%). Trochlear dysplasia was measured using Pfirmann's method. Patient demographics such as age, race and sex were recorded.

RESULTS

The overall prevalence of trochlear dysplasia is 4.5% and is far more common in Asian female patients compared to Caucasian, African and Middle Eastern knees.

CONCLUSION

Overall, the prevalence of dysplasia in the general population was determined to be 4.5%, with female patients being more likely to suffer from the condition. Patients of Asian and Caucasian race were more likely to have trochlear dysplasia, while Middle Eastern male patients displayed more dysplastic values than their female counterparts.

Evaluation of femoral condyle volumes in patients with trochlear dysplasia: a pilot study

AIM

To examine the volumes of the medial and lateral femoral condyles and the trochlear groove, and to determine their relationship with trochlear dysplasia.

MATERIALS AND METHODS

Computed tomography images of the knees of 21 patients with trochlear dysplasia and 18 healthy individuals were analysed retrospectively. According to the modified Dejour classification, the degree of trochlear dysplasia was recorded, such as type A trochlea being low-grade dysplasia and types B, C, and D trochlea being high-grade dysplasia. Volume of the trochlear groove and medial and lateral femoral condyles were calculated using the three-dimensional (3D) volume-rendering method.

RESULTS

The volumes of lateral condyle, medial condyle, and trochlear groove were statistically significantly lower in patients with trochlear dysplasia when compared to healthy participants. When compared according to Dejour types, all parameters were statistically significantly lower in both high- and low-grade dysplasia patients (p<0.05). The correlation between femoral condyle volumes and trochlear groove volume was low in the control group, but there was a moderate positive correlation in the patient group (r=0.50-0.75, p<0.05).

CONCLUSION

In trochlear dysplasia, the volume of the trochlear groove decreases and hypoplasia may occur in both lateral femoral and medial femoral condyles. Therefore, hypoplasia of only one condyle should not be interpreted as trochlear dysplasia. A holistic approach to patients is required.

Reconstruction of High-Grade Trochlea Dysplasia in a Young Female with Recurrent Patella Dislocation: A Case Report

The patellofemoral joint involves a combination of bony structures and soft tissues to maintain stability. Patella instability is a disabling condition, and the cause is multifactorial. The main risk factors include patella alta, trochlea dysplasia, excessive tibial tuberosity to trochlea grove (TT-TG) distance, and excessive lateral patella tilt. In this case report, we highlight the thinking process of diagnosis and method for selecting the optimal treatment in accordance with the guidelines by Dejour et al. when we are presented with a patient with patella instability. A 20-year-old Asian woman without underlying medical conditions, presented with recurrent (>3 episodes) right patella dislocation for 7 years. Investigations revealed a type D trochlea dysplasia, increased TT-TG distance, and excessive lateral tilt angle. She underwent trochlea sulcus deepening, sulcus lateralization and lateral facet elevation, lateral retinacular release, and medial quadriceps tendon-femoral ligament (MQTFL) reconstruction. Due to the complexity behind the anatomy and biomechanics of patella instability, an easy-to-follow treatment algorithm is essential for the treating surgeon to provide effective and efficient treatment. MQTFL reconstruction is recommended for recurrent patella dislocation due to satisfactory clinical and patient reported outcomes and a reduced risk of iatrogenic patella fracture. Controversies for surgical indication in lateral retinacular release, and whether the sulcus angle is an accurate parameter for diagnosis of trochlea dysplasia, remain, and further research is required.

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.

Patellofemoral Instability Part I: Evaluation and Nonsurgical Treatment

Patellofemoral instability (PFI) is a prevalent cause of knee pain and disability. It affects mostly young females with an incidence reported as high as 1 in 1,000. Risk factors for instability include trochlear dysplasia, patella alta, increased tibial tubercle-to-trochlear groove distance, abnormal patella lateral tilt, and coronal and torsional malalignment. Nonsurgical and surgical options for PFI can treat the underlying causes with varied success rates. The goal of this review series was to synthesize the current best practices into a concise, algorithmic approach. This article is the first in a two-part review on PFI, which focuses on the clinical and radiological evaluation, followed by nonsurgical management. The orthopaedic surgeon should be aware of the latest diagnostic protocol for PFI and its nonsurgical treatment options, their indications, and outcomes.

Radiological evaluation of patellofemoral instability and possible causes of assessment errors

Patellofemoral instability (PI) is the disruption of the patella’s relationship with the trochlear groove as a result of abnormal movement of the patella. To identify the presence of PI, conventional radiographs (anteroposterior, lateral, and axial or skyline views), magnetic resonance imaging, and computed tomography are used. In this study, we examined four main instability factors: Trochlear dysplasia, patella alta, tibial tuberosity–trochlear groove distance, and patellar tilt. We also briefly review some of the other assessment methods used in the quantitative and qualitative assessment of the patellofemoral joint, such as patellar size and shape, lateral trochlear inclination, trochlear depth, trochlear angle, and sulcus angle, in cases of PI. In addition, we reviewed the evaluation of coronal alignment, femoral anteversion, and tibial torsion. Possible causes of error that can be made when evaluating these factors are examined. PI is a multi-factorial problem. Many problems affecting bone structure and muscles morphologically and functionally can cause this condition. It is necessary to understand normal anatomy and biomechanics to make more accurate radiological measurements and to identify causes. Knowing the possible causes of measurement errors that may occur during radiological measurements and avoiding these pitfalls can provide a more reliable road map for treatment. This determines whether the disease will be treated medically and with rehabilitation or surgery without causing further complications.

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.

Complex Patellofemoral Reconstruction for Recurrent Instability

Background

Patellofemoral instability is due to a combination of bony and soft tissue factors. While recurrent patellar dislocations are rare, evaluation and treatment of these conditions require addressing patellar height and lateralization of the tibial tubercle (TT), restraint to lateral patellar subluxation, and trochlear dysplasia. Other factors to consider are coronal limb-length alignment outside of the physiologic 5 to 8° of valgus, which may significantly alter the Q angle and contribute to lateral instability. Other ligaments around the patella contribute to soft-tissue restraint, including the medial and lateral patellotibial ligaments, patellomeniscal ligaments, and the medial quadriceps tendon femoral ligament. Patellar tilt is assessed with and without quadriceps contraction to further evaluate the patella's relationship to the trochlear groove. The Caton-Deschamps Index, as well as patellar trochlear index (PTI), are used to measure patellar height for patella alta or baja.

Technique Description

The technique is to surgically manage a patient in neutral mechanical alignment on standing limb radiographs, with moderate-to-severe DeJour type B trochlear dysplasia and a trochlear sulcus angle of around 145°, patella alta with a Caton-Deschamps Index of 1.6 and PTI of 0.22, a TT to trochlear groove (TT-TG) distance of 8 mm, and a deficient medial patellofemoral ligament (MPFL). The MPFL reconstruction is done first, with harvesting of the ipsilateral quadriceps tendon and maintenance of its distal attachment on the superior patellar pole. The quadriceps tendon graft is folded medially upon its distal attachment and fixed in this position with suture anchors. Tibial tubercle osteotomy is accomplished by spacing drill holes 2 mm apart, medially and laterally, on the TT and connecting the drill holes with an osteotome and reciprocating saw. A distalized location to secure the TT is selected and superficial bone is excised. A medial parapatellar arthrotomy is performed, and bur attachments are used to drill into the subchondral bone beneath the femoral articular surface to create a V-shaped flap of trochlear cartilage. An arthroscope is inserted under the trochlear flap during this process to visualize the appropriate depth. The trochlear flap is then secured with screws passed over guide pins to secure the flap to the desired location. Cannulated screws and washers are then used to secure the TT to its distalized and/or medialized position, with fluoroscopic verification of screw depth and location. The arthrotomy is then closed with the knee at 45°. The quadriceps graft is passed through a subretinacular channel and secured with suture anchors, adjacent to the adductor tubercle, to complete the MPFL reconstruction. Before closure, appropriate tracking and translation of the patella is verified.

Results

Sulcus-deepening trochleoplasty, with or without MPFL reconstruction, has been reported to obtain satisfactory outcomes at 2 years, with close to 85% return to sport and 100% return to work, with improvements in International Knee Documentation Committee (IKDC) scores from 50.8 to 79.1 in some studies. MPFL reconstruction with tibial tubercle osteotomy (TTO) has yielded a 94.5% patient satisfaction rate in the literature.

Discussion/Conclusion

In patients with recurrent patellar instability and DeJour types B-D trochlear dysplasia, MPFL reconstruction with TTO and sulcus-deepening trochleoplasty provides excellent subjective outcomes and restores patellar tracking with elimination of recurrent subluxation.

Patient-Reported Outcomes After a Modified Albee Procedure

Background:

Trochlear dysplasia (TD) is a recognized condition that can become a risk factor for patellofemoral instability. A modified Albee osteotomy procedure using a trapezoidal-shaped wedge to elevate the lateral wall of the trochlea can be used with the goal of preventing further dislocation. However, outcomes studies are lacking, and scores on patient-reported outcome measures (PROMs) are largely unknown.

Purpose/Hypothesis:

The purpose of this study was to identify PROM scores for the Kujala Anterior Knee Pain Scale (AKPS), International Knee Documentation Committee (IKDC), Activity Rating System (ARS), and 100-point pain visual analog scale (VAS) for patients having undergone the modified Albee osteotomy. The hypothesis was that patients will have acceptable pain and function at mid- to long-term follow-up.

Study Design:

Case series; Level of evidence, 4.

Methods:

From 1999 to 2017, a total of 46 consecutive patients (49 knees) underwent a modified Albee procedure by a single surgeon at a single health care system. These 46 patients were contacted and asked to complete the AKPS, IKDC, ARS, and pain VAS. Additional demographic information was obtained via chart review. Frequencies and rates for categorical variables and means and standard deviations for continuous variables of the demographics and PROM scores were calculated.

Results:

PROM scores were obtained in 28 (30 knees; 61%) of the 46 patients. At minimum follow-up of 82 months, the mean scores were 78.5 ± 18.2 for AKPS, 61.2 ± 11.4 for IKDC, 5.2 ± 5.3 for ARS, and 24.4 ± 28.7 for VAS pain. Notably, only 1 of the 28 patients reported a patellofemoral dislocation since surgery, and this was an isolated incident without further instability.

Conclusion:

A modified Albee trochlear osteotomy can be a successful adjunctive procedure to prevent recurrent patellar dislocations in patients with mild TD. However, owing to the loss of one-third of patient follow-up scores and the absence of baseline function scores in this study, the procedure deserves further investigation as a way to address a particularly difficult dilemma for a select subset of patients with patellofemoral instability.

Clinical outcomes and predictive factors for failure with MPFL reconstruction combined with tibial tubercle osteotomy and lateral retinacular release for recurrent patellar instability

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction combined with tibial tubercle osteotomy (TTO) and lateral retinacular release (LRR) is one of the main treatment methods for patellar instability. So far, few studies have evaluated the clinical effectiveness and assessed potential risk factors for recurrent patellar instability.

PURPOSE

To report the clinical outcomes of MPFL reconstruction combined with TTO and LRR at least three years after operation and to identify potential risk factors for recurrent patellar instability.

METHODS

A retrospective analysis of medical records for patients treated with MPFL, TTO and LRR from 2013 to 2017 was performed. Preoperative assessment for imaging examination included trochlear dysplasia according to Dejour classification, patella alta with the Caton-Deschamps index (CDI), tibial tubercle-trochlear groove distance. Postoperative assessment for knee function included Kujala, IKDC and Tegner scores. Failure rate which was defined by a postoperative dislocation was also reported.

RESULTS

A total of 108 knees in 98 patients were included in the study. The mean age at operation was 19.2 ± 6.1 years (range, 13-40 years), and the mean follow-up was 61.3 ± 15.4 months (range, 36-92 months). All patients included had trochlear dysplasia (A, 24%; B, 17%; C, 35%; D, 24%), and 67% had patellar alta. The mean postoperative scores of Tegner, Kujala and IKDC were 5.3 ± 1.3 (2-8), 90.5 ± 15.5 (24-100) and 72.7 ± 12.1 (26-86). Postoperative dislocation happened in 6 patients (5.6%). Female gender was a risk factor for lower IKDC (70.7 vs 78.1, P = 0.006), Tegner (5.1 vs 6.0, P = 0.006) and Kujala (88.2 vs 96.6, P = 0.008). Age (p = 0.011) and trochlear dysplasia (p = 0.016) were considered to be two failure factors for MPFL combined with TTO and LRR.

CONCLUSION

As a surgical method, MPFL combined with TTO and LRR would be a reliable choice with a low failure rate (5.6%). Female gender was a risk factor for worse postoperative outcomes. Preoperative failure risk factors in this study were age and trochlear dysplasia.

LEVEL OF EVIDENCE

Level IV; Case series.

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.

Medial Patellofemoral Reconstruction Using Quadriceps Tendon Autograft, Tibial Tubercle Osteotomy, and Sulcus-Deepening Trochleoplasty for Patellar Instability

Recurrent patellar dislocations have been correlated with an elevated risk of further patellar dislocations, often requiring surgical treatment. Risk factors include medial patellofemoral ligament (MPFL) tears, patella alta, trochlear dysplasia, and an increased tibial tubercle-trochlear groove distance. Surgical management must be based on a patient's unique joint pathoanatomy and may require MPFL reconstruction with tibial tubercle osteotomy or trochleoplasty either alone or in combination. This article discusses our preferred technique for surgical treatment of recurrent patellar instability with MPFL reconstruction using a quadriceps tendon autograft, an open trochleoplasty, and a tibial tubercle osteotomy for patients with patella alta, trochlear dysplasia, and an increased tibial tubercle-trochlear groove distance.

Medial Patellofemoral Ligament Reconstruction Using a Quadriceps Tendon Autograft in a Patient with Open Physes

Recurrent patellar dislocations are correlated with an elevated risk for further patellar dislocations. Chronic patellar instability is a disabling issue for some patients and may require surgical intervention for proper treatment. Risk factors for recurrent dislocations include medial patellofemoral ligament (MPFL) tears, patella alta, trochlear dysplasia, and increased tibial tubercle to trochlear groove distance. Surgical management must be based on a patient's unique joint pathoanatomy and typically requires medial patellofemoral ligament reconstruction, with or without accompanying procedures such as tibial tubercle osteotomy or sulcus-deepening trochleoplasty. Chronic patellar instability in minors with open growth plates, requires alternative MPFL reconstruction techniques to prevent physeal injury, because of the close proximity of the femoral physis to the MPFL insertion. This article discusses the authors' preferred technique for surgical treatment of recurrent patellar instability with a medial patellofemoral ligament reconstruction using a quadriceps tendon autograft.

Predicting Risk of Recurrent Patellofemoral Instability With Measurements of Extensor Mechanism Containment

BACKGROUND

Identifying risk factors for recurrent patellar dislocation after a primary dislocation may help guide initial treatment. Magnetic resonance imaging (MRI) measurements relating the alignment of the extensor mechanism to trochlear morphology have been shown to distinguish patients with dislocations from controls, but their usefulness in predicting the risk of a second dislocation is not known.

PURPOSE

To identify the association of novel MRI measures of patellar containment with recurrent instability in pediatric patients presenting with a first-time patellar dislocation.

STUDY DESIGN

Cohort study (Prognosis); Level of evidence, 3.

METHODS

The study was conducted at a tertiary care children's hospital (2005-2014) on patients (age, 8-19 years) with a first-time patellar dislocation. MRI measurements were made by 2 independent raters. Interobserver reliability was assessed for all measurements via an intraclass correlation coefficient (ICC). Only measurements with an ICC >0.8 were included. Univariable and multivariable logistic regression analyses were used to evaluate variables associated with recurrence.

RESULTS

A total of 165 patients with a median age of 14 years and a slight (57.6%) female predominance was identified. The median follow-up length of the whole cohort was 12.2 months (interquartile range, 1.6-37.1 months). Subsequent instability was documented in 98 patients (59.4%). MRI measurements with excellent correlation (ICC > 0.8) were the tibial tubercle to trochlear groove distance (TT-TG), the tangential axial width of the patella, the tangential axial trochlear width, the axial width of the patellar tendon beyond the lateral trochlear ridge (LTR), and the tibial tubercle to LTR distance. In univariate analysis, all mentioned MRI measurements had significant association with recurrent instability. However, after both backward and forward stepwise regression analyses, the tibial tubercle to LTR distance was the only independent predictor of recurrent instability (P = .003 in both). Patients with a tibial tubercle to LTR distance value greater than -1 mm had a significantly higher rate of recurrent patellar dislocation (72%).

CONCLUSION

Of numerous axial view MRI parameters, only the tibial tubercle to LTR distance demonstrated a statistically significant association with recurrent patellar instability upon multivariable logistic regression analysis during short-term follow-up of a pediatric population presenting with initial lateral patellar dislocation. Interobserver correlation of the tibial tubercle to LTR distance was good (ICC > 0.8) and similar to that of TT-TG.

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.

Traumatic Patellar Dislocations in Childhood and Adolescents

Patellar instability and associated patellar dislocation can result in significant pain, disability, and associated injuries in young athletes. The patellofemoral joint is a complex articulation with stabilizing restraints, both medially and laterally, that help guide the patella into the corresponding trochlear groove as the knee cycles through an extension-to-flexion arc. In addition to soft tissue injuries, many osseous aberrancies can contribute to patellar instability in young athletes, including trochlear dysplasia, patella alta, and axial and coronal plane abnormalities. There is a role for nonoperative treatment in these young athletes; however, if recurrent or associated injuries are identified surgical intervention is warranted. Correct diagnosis of the underlying cause of the patellar instability is paramount to developing a surgical plan that will yield the most favorable outcome for these young athletes.

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.

Mid inter-epicondyle trochlea intersection (MIELTI): Proposal of a new index for identifying the deepest part of the trochlea

BACKGROUND

Tibial tuberosity trochlear groove distance (TT-TG) is an important radiological measurement in patellofemoral instability (PFI). Where instability is recurrent, a value ≥20 mm is considered an indication for tubercle medialisation. Trochlear dysplasia commonly accompanies PFI. It can make identification of the deepest part of the trochlea difficult, which makes the TT-TG difficult or impossible to assess. To address this, we propose a new method of identifying the deepest part of trochlea based on the femoral epicondyles. It is named the tibial tuberosity mid inter-epicondyle trochlea intersection distance (TT-MIELTI).

METHODS

The TT-TG and TT-MIELTI of 30 consecutive non-dysplastic knee MRIs were compared, excluding 96 knees with dysplasia, sulcus angles ≥135°, a tibial tuberosity anterior cortex which was not fully demonstrated, artefact, fracture, or Osgood Schlatter's disease. To assess inter-observer reliability three blinded researchers measured the TT-TG and the TT-MIELTI of all 30 knees. To assess intra-observer repeatability one researcher repeated the measurements after six weeks.

RESULTS

The intraclass correlation coefficient (ICC) test demonstrated good to excellent values for all measurements (TT-TG and TT-MIELTI correlation ICC 0.94-0.97; TT-TG inter-observer reliability ICC = 0.85, intra-observer repeatability ICC = 0.90; TT-MIELTI inter-observer reliability ICC = 0.86, intra-observer repeatability ICC = 0.89. All p values < .001.) CONCLUSIONS: In non-dysplastic knees the mid inter-epicondyle trochlea intersection (MIELTI) accurately identifies the deepest part of the trochlea, and TT-MIELTI is a reliable alternative to the TT-TG. Re-assessment in dysplastic knees would be of benefit to establish its usefulness in the clinical setting.

When is Trochleoplasty a Rational Addition?

Trochlear dysplasia has been recognized as a dominant anatomic risk factor in patients with recurrent patellar instability. Sulcus-deepening trochleoplasty is a very effective and powerful procedure for correcting trochlear dysplasia and, specifically, eliminating the supratrochlear spur. However, it must be emphasized that trochleoplasty is not appropriate for patients with mild trochlear dysplasia or those without a large supratrochlear spur or bump. We discuss the characteristics and classification of trochlear dysplasia and discuss specific indications for sulcusdeepening trochleoplasty.

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.

Stacked sparse autoencoder networks and statistical shape models for automatic staging of distal femur trochlear dysplasia

BACKGROUND

The quantitative morphological analysis of the trochlear region in the distal femur and the precise staging of the potential dysplastic condition constitute a key point for the use of personalized treatment options for the patella-femoral joint. In this paper, we integrated statistical shape models (SSM), able to represent the individual morphology of the trochlea by means of a set of parameters and stacked sparse autoencoder (SSPA) networks, which exploit the parameters to discriminate among different levels of abnormalities.

METHODS

Two datasets of distal femur reconstructions were obtained from CT scans, including pathologic and physiologic shapes. Both of them were processed to compute SSM of healthy and dysplastic trochlear regions. The parameters obtained by the 3D-3D reconstruction of a femur shape were fed into a trained SSPA classifier to automatically establish the membership to one of three clinical conditions, namely, healthy, mild dysplasia, and severe dysplasia of the trochlea. The validation was performed on a subset of the shapes not used in the construction of the SSM, by verifying the occurrence of a correct classification.

RESULTS

A major finding of the work is that SSM are able to represent anomalies of the trochlear geometry by means of specific eigenmodes of variation and to model the interplay between morphologic features related to dysplasia. Exploiting the patient-specific morphing parameters of SSM, computed by means of a 3D-3D reconstruction, SSPA is demonstrated to outperform traditional discriminant analysis in classifying healthy, mild, and severe trochlear dysplasia providing 99%, 97%, and 98% accuracy for each of the three classes, respectively (discriminant analysis accuracy: 85%, 89%, and 77%).

CONCLUSIONS

From a clinical point of view, this paper contributes to support the increasing role of SSM, integrated with deep learning techniques, in diagnostics and therapy definition as quantitative and advanced visualization tools.

Osteoarticular Allograft Transplantation of the Trochlear Groove for Trochlear Dysplasia: A Case Report

CASE

A 21-year-old woman with recurrent lateral patellar instability caused by severe trochlear dysplasia and concomitant grade-IV trochlear chondromalacia was treated successfully with osteoarticular allograft transplantation of the entire trochlear groove.

CONCLUSION

The treatment of chronic lateral patellar instability caused by trochlear dysplasia can be challenging. When nonoperative treatment is unsuccessful, a sulcus-deepening trochleoplasty may be indicated. However, contraindications for a trochleoplasty include grade-IV chondromalacia of the patellofemoral joint. Even with this contraindication, an osteoarticular allograft transplant of the trochlear groove can serve as a salvage procedure to improve knee function.

Patellofemoral reconstruction for patellar instability with patella alta in middle-aged patients: Clinical outcomes

INTRODUCTION

Although several surgical treatments for patellar instability with patella alta have been reported, the clinical outcomes and optimal surgical procedures for patellar instability with patella alta in middle-aged patients are still controversial. We hypothesized that optimal surgical procedures for patellar instability with patella alta in middle-aged patients may induce good clinical outcomes with better patellofemoral geometry.

MATERIALS AND METHODS

Twelve middle-aged patients with a mean age of 44 years (range: 40-55 years), who presented with patellar instability and patella alta, were treated with a combination of several surgeries, such as medial patellofemoral ligament (MPFL) reconstruction, trochleoplasty, lateral release, and three-dimensional transfer of the tibial tuberosity, based on a surgical algorithm. Patellar position and clinical outcomes were evaluated postoperatively. The mean follow-up time was 41.5 months (range: 24-72 months).

RESULTS

Patellar position altered from 1.31 (1.21-1.53) preoperatively to 0.88 (0.69-1.06) postoperatively on the Caton-Deschamps Index (p<0.01). The tibial tuberosity-trochlear groove (TT-TG) distance altered from 21.8mm (20.1-25.8mm) to 10.3mm (5.1-14.7mm), and patellar tilt ranged from 28.1° (21-40°) to 14.6° (5-28°), respectively (p<0.01). Clinical outcomes on the Lysholm and Kujala scales improved from 43.1 and 38.4 to 86.7 and 78.3, respectively, at final follow-up (p<0.01). Surgical treatment that included trochleoplasty resulted in better outcomes than other surgical combinations without trochleoplasty (p<0.05). Sulcus angle and postoperative patellar tilt improved more in those who underwent trochleoplasty than in those who did not (p<0.05).

DISCUSSION

Surgical treatment for patellar instability with patella alta in middle-aged patients resulted in improved clinical outcomes. In particular, a combination surgery including trochleoplasty resulted in the greatest improvement in case of severe trochlear dysplasia.

LEVEL OF EVIDENCE

IV. Retrospective case series study.

A stand-alone lateral condyle-elevating trochlear osteotomy leads to high residual instability but no excessive increase in patellofemoral osteoarthritis at 12-year follow-up

PURPOSE AND HYPOTHESIS

Trochlear osteotomy is a rarely performed procedure, only indicated in selected cases. Due to its nature, it can potentially lead to cartilage damage and subsequent early osteoarthritis. Satisfactory short-term results from lateral condyle-elevating osteotomy have previously been reported. The long-term effects of this procedure on clinical outcomes, patellar stability and radiological osteoarthritis are reported here.

METHODS

Sixteen patients (19 knees) with patellar instability due to trochlear dysplasia were included. An isolated lateral condyle-elevating trochlear osteotomy was performed between 1995 and 2002. All patients were re-examined at a minimum of 12-year follow-up. Three patients were lost to follow-up, and one patient underwent a patellofemoral arthroplasty 3 years post-operatively due to progressive osteoarthritis. Complete follow-up was therefore available in 12 patients (15 knees). Recurrent instability, VAS pain, WOMAC, Lysholm and Kujala scores were used as outcome measures. Radiological osteoarthritis was recorded using the Iwano and the Kellgren-Lawrence classifications. A repeated-measures ANOVA was used to test for repeated measures (pre-operative, 2-year and final follow-up), and Spearman's correlation coefficient for relationships between osteoarthritis and functional scores.

RESULTS

At final follow-up, VAS pain showed a non-significant improvement from 52 to 25, and the median Kujala score was 78. Median Lysholm (54-71, p = 0.021) and WOMAC (78-96, p = 0.021) scores improved from the pre-operative assessment to final follow-up. There was no significant difference observed between clinical scores at the 2-year and final follow-up. Residual patellar instability was reported in four out of 15 knees. Three knees showed no patellofemoral osteoarthritis, eight knees had grade 1 and four knees grade 2. No correlation between VAS pain, Lysholm, WOMAC or Kujala scores and osteoarthritis could be identified (n.s.).

CONCLUSION

A stand-alone lateral condyle-elevating trochleoplasty results in the significant improvement of most clinical scores; however, when performed as a stand-alone procedure, it leads to a high percentage of residual instability. In contrast to general belief, the development of patellofemoral osteoarthritis at 12-year follow-up did not exceed the findings from other trochleoplasty case series.

LEVEL OF EVIDENCE

Case series with no comparison group, Level IV.

The inferomedial patellar protuberance and medial patellar ossicle in patellar instability

PURPOSE

The purpose of the study was to define the frequency of an inferomedial patellar protuberance in patients presenting to a specialist Patella Clinic and to characterise the clinical and radiological features as well the association between the inferomedial patellar protuberance and the medial patellar ossicle.

METHODS

A cohort of 163 patients (166 knees) was reviewed from a prospectively collected clinical database and radiological imaging. This included a record of patellar tracking.

RESULTS

An inferomedial patellar protuberance was found in 62 (37 %) knees. A medial patellar ossicle was noted in 56 (34 %) knees. In all, an inferomedial patellar protuberance or medial patellar ossicle or both was found in 90 (54 %) knees. The association between inferomedial patellar protuberance and significant trochlear dysplasia was highly significant (p = 0.01), but not for the medial patellar ossicle (n.s.). The presence of an inferomedial patellar protuberance was significantly less likely in patients with hypermobility syndrome (p = 0.001); however, there was no significant association between hypermobility syndrome and medial patellar ossicle (n.s.), or the presence of either or both an inferomedial patellar protuberance and medial patellar ossicle (n.s.). All patients with a clunk at 20°-30° flexion had significant trochlear dysplasia and an inferomedial patellar protuberance.

CONCLUSION

Radiological changes consistent with an inferomedial patellar protuberance were found in about one-third of patients presenting to a specialist Patella Clinic. Patellar maltracking and a clunk at 20°-30° flexion are associated with significant trochlear dysplasia plus an inferomedial patellar protuberance. If undertaking an operative correction, both deformities should be considered in order to avoid joint incongruity.

LEVEL OF EVIDENCE

III.

Why Do Patellofemoral Stabilization Procedures Fail? Keys to Success

In recent years, surgical interventions for patellofemoral joint instability have gained popularity, possibly revitalized by the recent advances in our understanding of patellofemoral joint instability and the introduction of a number of new surgical procedures. This rise in surgical intervention has brought about various complications. In this review article, we present the complications that are associated with 5 main surgical procedures to stabilize the patella-medial patellofemoral ligament reconstruction, tibial tubercle osteotomy, trochleoplasty, lateral release/lateral retinacular lengthening, and derotation osteotomies. The key to success and potential problems with these surgical techniques are highlighted in the form of "expert takeaways."

Conventional Radiographs and Magnetic Resonance Imaging for the Analysis of Trochlear Dysplasia: The Influence of Selected Levels on Magnetic Resonance Imaging

BACKGROUND

Trochlear dysplasia is one of the most important risk factors for recurrent patellar instability. It is defined on true lateral conventional radiographs (CR) and axial magnetic resonance imaging (MRI). The type of trochlear dysplasia is decisive for surgical treatment; however, low agreement between CR and MRI has been reported.

PURPOSE

To compare the Dejour classification of trochlear dysplasia on CR and axial MRI using differing levels defined in the literature.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

The 4-type classification of trochlear dysplasia by Dejour was used to analyze 228 knees with recurrent patellar dislocations on true lateral CR and axial MRI. The 2-type modification of the Dejour classification was also similarly analyzed. Measurements on axial MRI were performed at 3 different levels: MR1, the most proximal level where the intercondylar notch forms a "Roman arch"; MR2, 3 cm above the joint line; and MR3, the midpatellar height.

RESULTS

MR1 was measured at a mean distance of 29 ± 3.5 mm and MR3 at a mean of 38 ± 5.8 mm above the joint line. MR1 and MR2 were always measured on the cartilaginous trochlea, whereas 52% of MR3 was found more proximally. Overall agreement was fair between CR and MR1/MR2 (31.1%/25.4%, respectively) and highest for MR3 (45.2%; P < .01). The highest agreement (81.8%) was found for MR3 with the 2-type trochlear dysplasia classification (low-grade trochlear dysplasia: type A vs high-grade trochlear dysplasia: types B, C, and D) and lower for MR1 (67.5%) and MR2 (62.0%).

CONCLUSION

Trochlear dysplasia measured on CR and MRI shows only fair agreement, especially when the supratrochlear region of the distal femur is not analyzed on axial MRI. MRI analysis that considers the cartilaginous trochlea only tends to underestimate the severity of dysplasia according to Dejour. For a more precise evaluation of trochlear dysplasia, the entire distal femur should be analyzed on axial MRI.

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids

Diagnostic and therapeutic purposes are issuing pressing demands to improve the evaluation of the dysplasia condition of the femoral trochlea. The traditional clinical assessment of the dysplasia, based on Dejour classification, recognized 4 increasing (A, B, C, D) levels of severity. It has been extensively questioned in the literature that this classification methodology can be defective suggesting that quantitative measures can ensure more reliable criteria for the dysplasia severity assessment. This study reports on a novel technique to model the trochlear surface (TS), digitally reconstructed by 3D volumetric imaging, using three hyperbolic paraboloids (HP), one to describe the global trochlear aspect, two to represent the local aspects of the medial and lateral compartments, respectively. Results on a cohort of 43 patients, affected by aspecific anterior knee pain, demonstrate the consistency of the estimated model parameters with the morphologic aspect of the TS. The obtained small fitting error (on average lower than 0.80 mm) demonstrated that the ventral aspect of the trochlear morphology can be modeled with high accuracy by HPs. We also showed that HP modeling provides a continuous representation of morphologic variations in shape parameter space while we found that similar morphologic anomalies of the trochlear aspect are actually attributed to different severity grades in the Dejour classification. This finding is in agreement with recent works in the literature reporting that morphometric parameters can only optimistically be used to discriminate between the Grade A and the remaining three grades. In conclusion, we can assert that the proposed methodology is a further step toward modeling of anatomical surfaces that can be used to quantify deviations to normality on a patient-specific basis.

Patellar malalignment: a new method on knee MRI

Purpose

The medial patellofemoral ligament (MPFLL)/lateral patellar retinaculum (LPR) ratio were assessed in knees as a means to detect patellar malalignment. We also aimed to evaluate the prevalence of the various types of trochlear dysplasia in patients with patellar malalignment.

Materials and methods

After approval of our institutional ethics committee, we conducted a retrospective study that included 450 consecutive patients to evaluate them for the presence of patellar malalignment. Parameters investigated were the trochlear type, sulcus angle, presence of a supratrochlear spur, MPFLL, LPR, patella alta, and patella baja by means of 1.5T magnetic resonance imaging (MRI). Overall, 133 patients were excluded because of the presence of major trauma, multiple ligament injuries, bipartite patella, and/or previous knee surgery. The Dejour classification was used to assess trochlear dysplasia. Two experienced radiologists (HKY, EEE) evaluated the images. Their concordance was assessed using the kappa (κ) test.

Results

The frequencies of patellar malalignment and trochlear dysplasia were 34.7 and 63.7 %, respectively. The frequency of trochlear dysplasia associated with patellar malalignment was 97.2 %. An MPFLL/LPR ratio of 1.033–1.041 had high sensitivity and specificity for malalignment. The researchers’ concordance was good (κ = 0.89, SE = 0.034, P < 0.001).

Conclusion

Trochlear dysplasia is frequently associated with patellar malalignment. An increased MPFLL/LPR ratio is useful for detecting patellar malalignment on knee MRI, which is a novel quantitative method based on ligament length.

An Algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation

High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations. Recurrent instability is often multifactorial and can be the result of a combination of coronal limb malalignment, patella alta, malrotation secondary to internal femoral or external tibial torsion, a dysplastic trochlea, or disrupted and weakened medial soft tissue, including the medial patellofemoral ligament (MPFL) and the vastus medialis obliquus. MPFL reconstruction requires precise graft placement for restoration of anatomy and minimal graft tension. MPFL reconstruction is safe to perform in skeletally immature patients and in revision surgical settings. Distal realignment procedures should be implemented in recurrent instability associated with patella alta, increased tibial tubercle-trochlear groove distances, and lateral and distal patellar chondrosis. Groove-deepening trochleoplasty for Dejour type-B and type-D dysplasia or a lateral elevation or proximal recession trochleoplasty for Dejour type-C dysplasia may be a component of the treatment algorithm; however, clinical outcome data are lacking. In addition, trochleoplasty is technically challenging and has a risk of substantial complications.

Patellofemoral Joint Reconstruction for Patellar Instability: Medial Patellofemoral Ligament Reconstruction, Trochleoplasty, and Tibial Tubercle Osteotomy

Recurrent patellar instability can be very debilitating and may require surgical intervention. A thorough workup must be completed in this subset of patients. Risk factors for recurrent instability include patella alta, trochlear dysplasia, an increased tibial tubercle-trochlear groove distance, and insufficiencies in the medial retinacular structures. Necessary treatment of these risk factors, once identified, should be addressed surgically. Patellofemoral reconstruction must be individually tailored to each patient's anatomy and may necessitate medial patellofemoral ligament reconstruction, tibial tubercle osteotomy, or trochleoplasty in any combination or as a standalone procedure. This article details our technique for surgical treatment of recurrent patellar instability with a medial patellofemoral ligament reconstruction, an open trochleoplasty, and a tibial tubercle osteotomy for patients with severe trochlear dysplasia, an increased tibial tubercle-trochlear groove distance, or patella alta.

Deepening Trochleoplasty With a Thick Osteochondral Flap for Patellar Instability: Clinical and Functional Outcomes at a Mean 6-Year Follow-up

BACKGROUND

In patients with patellar instability and severe trochlear dysplasia, trochleoplasty has become increasingly used as part of its surgical management.

HYPOTHESIS

Deepening trochleoplasty for severe dysplasia in patellofemoral instability improves function and increases sports participation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between 1995 and 2010, deepening trochleoplasty with a thick flap was performed in 90 patients (107 knees) with severe trochlear dysplasia. Data were collected prospectively preoperatively, at 6 weeks, and at 1-year follow-up. The patients were surveyed retrospectively to determine the clinical and functional outcomes including sports and exercise participation at a minimum of 2 years, with complete data available in 92%.

RESULTS

The average follow-up was 6 years (range, 2-19 years). The median Kujala score was 63 (interquartile range [IQR], 47-75) preoperatively, rising to 79 (IQR, 68-91) at 1-year follow-up and 84 (IQR, 73-92) at final follow-up (P < .05). Seventy-two percent were satisfied with their knee function at 1-year follow-up, rising to 83% at final follow-up (P < .0001). Sports and exercise participation increased from 36 patients (40%) preoperatively to 60 (67%) at final follow-up. The number of patients involved in competitions increased slightly from 10 (11%) to 11 (12%). Of those sports that involved twisting (e.g., soccer, cricket, badminton), the number of patients participating increased from 16 (18%) to 22 (24%), whereas in nontwisting sports (e.g., running, swimming, cycling), it increased from 24 (27%) to 47 (52%), of whom 12 (16%) used walking as exercise. Two patients who had undergone medial patellofemoral ligament (MPFL) reconstruction as the index operation needed the MPFL revised, and a further 8 patients needed MPFL reconstruction subsequently for instability symptoms and a mediolateral glide in extension of more than 2 quadrants' displacement. At final follow-up, no patient had mechanical patellofemoral instability.

CONCLUSION

Deepening trochleoplasty with a thick flap improves clinical and functional outcomes for patients with symptomatic patellar instability with severe trochlear dysplasia. These results improve over time and beyond 1-year clinical follow-up. However, trochleoplasty does not lead to a significant improvement in sports participation at a competitive level. It does improve patient participation in sports and exercise, principally in nontwisting sports activities.

Systematic technique-dependent differences in CT versus MRI measurement of the tibial tubercle-trochlear groove distance

BACKGROUND

The tibial tubercle-trochlear groove (TTTG) distance is used to quantify the degree of lateralization of the patellar tendon insertion on the tibial tubercle relative to the deepest part of the trochlear groove. Disagreement exists as to whether the TTTG distance measured on computed tomography (CT) and magnetic resonance imaging (MRI) can be considered equivalent.

PURPOSE

To compare TTTG distance as measured on axial CT and MRI and to investigate the potential effect of patient positioning between modalities.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

Patients who received both CT and MRI of the same knee for any indication from August 2010 to April 2014 were included in this study. The TTTG distances were measured twice by 2 raters in a randomized order, with at least 30 days between ratings to minimize recall bias. Inter- and intrarater reliability of CT and MRI measurements and intermethod reliability were assessed with intraclass correlation coefficients (ICCs). Bland-Altman plots were also created to assess agreement. Differences in patient positioning were investigated to determine its effect on the TTTG distance.

RESULTS

Fifty-nine patients (age, 32.8 ± 12.9 years) were included. Interrater ICCs were excellent for both CT and MRI measurements. Intrarater ICCs were excellent for both raters. Absolute agreement ICCs for intermethod reliability were fair to good, but consistency type agreement was excellent. A systematic bias of lower MRI distances (bias = -2.8 mm) compared with CT was observed. The investigation of CT versus MRI imaging techniques demonstrated that the standard MRI examination places the knee in approximately 4.6° of relative varus alignment compared with CT.

CONCLUSION

A systematic bias toward lower TTTG distances on MRI compared with CT was found. This finding is likely dependent on imaging technique, including patient positioning. Patient knees were positioned in varus on the MRI compared with the CT examination, with resulting lower TTTG distances on MRI compared with CT. The TTTG distances on CT and MRI vary with imaging technique, which may be attributable to patient positioning and result in differences among imaging centers.