Quality-of-Life Outcomes of Patients following Patellofemoral Stabilization Surgery: The Influence of Trochlear Dysplasia

Sulcus-Deepening Trochleoplasty for High-Grade Trochlear Dysplasia: Demystifying the Procedure-a Review of the Current Literature

PURPOSE OF REVIEW

The most common and biomechanically influential pathoanatomic risk factor for recurrent patellofemoral instability is trochlear dysplasia. Sulcus-deepening trochleoplasty is a procedure developed to address high-grade trochlear dysplasia in the setting of patellofemoral instability. The purpose of this paper is to outline the current classification and surgical management of trochlear dysplasia as well as to review the current literature on the clinical outcomes and complications of sulcus-deepening trochleoplasty.

RECENT FINDINGS

This review outlines the most recent literature reporting evidence behind the decision-making to perform a trochleoplasty in the setting of patellofemoral instability and high-grade trochlear dysplasia. Critical parameters include grade of trochlear dysplasia, severity of symptoms, pertinent physical examination findings, surgical techniques, modifications for skeletally immature patients, and considerations for the revision setting. Historic studies have elicited concerns regarding high reported complication rates for trochleoplasty; however, recent studies consistently report good clinical outcomes and acceptable complication rates, similar to those of other patellar stabilizing procedures. The addition of a trochleoplasty in patients with high-grade dysplasia results in a lower re-dislocation rate, significant improvements in patient-reported outcome measures (PROMs) as well as high levels of patient satisfaction and return to sport. The use of sulcus-deepening trochleoplasty for the treatment of high-grade dysplasia and recurrent patellofemoral instability is a well-established technique with good outcomes and an acceptable complication profile. In patients with high-grade dysplasia, trochleoplasty results in lower re-dislocation rates, high patient satisfaction scores, and good clinical and functional outcomes. An understanding of trochleoplasty and its indications should be in the armamentarium of surgeons treating patellofemoral instability.

Trochleoplasty for severe trochlear dysplasia significantly improves the quality of life of patients with symptomatic patellar instability

BACKGROUND

Trochleoplasty is a recognized surgical technique to address severe trochlear dysplasia. The clinical and radiological outcomes of trochleoplasty surgery in trochlear dysplasia have been well reported. There is a paucity in literature regarding the correlation between trochleoplasty and quality of life (QoL). The aim of this study is to measure the improvement in QoL, in patients with severe trochlear dysplasia and recurrent patellar instability following trochleoplasty.

METHODS

Between 2013 and 2019, 51 trochleoplasty cases were performed in 48 patients. They were identified from our prospectively kept database. All operations were performed by a fellowship trained consultant sports knee surgeon. Functional outcomes and QoL scores were assessed using Kujala, IKDC and EQ-5D index. Objective outcomes were obtained following each patient's latest follow-up assessment.

RESULTS

The mean age at operation was 22y (SD ± 4.7, range 14-37y) and the mean follow-up period was 21.6 months (SD ± 15.2, range 12-60 months). The mean Kujala score improved from 58.1 (SD 14.9) to 77.9 (SD 17.3) at latest follow-up (p < 0.001). The mean IKDC score improved from 40.5 (SD 14.2) to 69.5 (SD 22.8) at latest follow up (p < 0.001). The mean EQ-5D index also improved from 0.593 (SD 0.257) to 0.824 (SD 0.189) at latest follow-up (p = 0.003). A higher Body Mass Index (BMI; >30 kg/m²) was associated with inferior outcomes.

CONCLUSION

Trochleoplasty is an effective surgical technique which improves the QoL in patients suffering from patellar instability secondary to severe trochlear dysplasia. BMI can be used to predict post-operative outcomes.

Mental and physical health-related quality of life in patients with recurrent patellar dislocations-a generic and disease-specific quality of life questionnaire assessment

Purpose

There is a paucity of quality of life (QoL) assessments in studies evaluating patients treated for recurrent lateral patellar dislocation (LPD). The primary aim of this study was to investigate whether mental well-being is impaired in patients with chronic (recurrent) LPD and, if so, to assess whether the mental health-related QoL dimension improves equivalently to the physical-related QoL dimension after successful surgical treatment.

Methods

Thirty-eight patients with recurrent LPD over a mean course of the disease of 4.7 ± 3.9 years (1—18 years) prior to surgery were included. Generic health-related QoL (HRQoL) (Short Form 36; SF-36) and disease-specific QoL (Banff Patella Instability Instrument 2.0; BPII 2.0) were assessed preoperatively and after a mean follow-up of 3.5 ± 0.8 years (2 – 5 years) postoperatively.

Results

Untreated LPD significantly impacted the physical dimension of patients’ generic HRQoL and their disease-specific QoL. When compared to age-equivalent normative data sets, the mental HRQoL dimension was not reduced prior to operative treatment but increased during the follow-up period. Surgical treatment normalized the physical dimension of patients’ generic HRQoL and significantly improved their disease-specific QoL. However, BPII 2.0 values remained reduced, albeit patellae were successfully stabilized.

Conclusion

The results of this study indicate that patients with recurrent LPD are generally in good mental health, although physical impairment is striking. Notwithstanding that surgery prevented further dislocations and normalized the generic HRQoL, the disease-specific QoL remained reduced as far as this can be interpreted without population-based data.

Level of evidence

Level IV; Retrospective case series.

Medial patellofemoral ligament reconstruction with and without trochleoplasty for patients with patella instability-correlation of trochlear dysplasia and patient outcome, classification and outcome measure in the past decade-a systematic review

PURPOSE

The primary aim of the study is to compare the patient outcome in medial patellofemoral ligament reconstruction (MPFLR) or MPFLR concurrent with trochleoplasty (MPFLR + TP) and correlate it with the degree of trochlear dysplasia (TD). The secondary aim is to review TD classification, outcome measure, chronological and geographical trend of such studies in the past decade.

METHODS

A systemic review of the literature in the past decade on studies of patients with patella instability and underwent either a MPFLR or MPFLR + TP. The degree of TD with the patient outcome was correlated and compared between the 2 groups. The TD classification, outcome measures, chronological and geographical trends of these studies were documented.

RESULTS

There is no statistical difference in the overall improvement in the compared outcome scores between the 2 groups. However, the MPFLR studies reported a total of 16 re-dislocation in contrast to none in the MPFLR + TP studies. The 24 selected studies in the current review utilized different TD classification as well as outcome measures. A more homogeneous subgroup of 12 studies utilized Dejour classification as well as Kujala score that enabled comparison and showed no significant difference in outcome. The highest number of MPFLR publications was in 2019 and was from North and South Americas, Asia and Europe. The MPFLR + TP studies were from Europe during 2013 to 2017.

CONCLUSION

Though there is an overall improvement in post-operative outcomes scores with no statistical significance between MPFLR and MPFLR + TP, the documented re-dislocations in the MPFLR studies suggested an undetermined zone where the choice of procedure could result in a different outcome. The current review did not show correlation between the degree of TD with the patient outcome to provide a clear indication for either procedure according to the degree of TD. The diverse TD classifications and varied outcome measures indicated the need for standardization and consistency in documentation to guide the treating clinician in the choice of procedure. MPFLR was more commonly performed and studied than MPFLR + TP in the past decade.

Complications and Recurrence of Patellar Instability after Medial Patellofemoral Ligament Reconstruction in Children and Adolescents: A Systematic Review

Background: This study aimed to review the data available in the current literature concerning the complications and recurrence of instability following medial patellofemoral ligament (MPFL) reconstruction for patellar instability in young and adolescent patients (those <20 years old). Methods: A systematic review was performed based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Two independent reviewers searched the PubMed, Scopus, EMBASE, and Cochrane databases. The terms “medial patellofemoral ligament” or “MPFL” and “reconstruction” and “young” or “adolescents” or “children” were used. The inclusion criteria for the literature review comprised studies that reported the complications and recurrences of instability in patients who had undergone MPFL reconstruction for patellar instability. Results: In all, 332 patients were included in the review, of which 195 were females (63.5%) and 112 were males (36.5%), and they totaled 352 treated knees. The mean age at the time of the surgery was 14.28 years, and the mean follow-up duration was 30.17 months. A total of 16 (4.5%) complications were reported: one (0.3%) patella fracture, one (0.3%) screw removal due to intolerance, one (0.3%) infection, five (1.4%) wound complications, six (1.7%) subluxations and two (0.6%) instances of post-operative stiffness. A total of 18 (5.1%) recurrences of patellar instability were recorded. Conclusions: MPFL reconstruction in young patients can be considered an effective and safe treatment leading to clinical improvement in terms of recurrence of dislocation. No major complications related to the technique were reported, but a high level of research evidence is required to better evaluate the clinical results in a long-term follow-up.

Complex patellofemoral reconstruction leads to improved physical and sexual activity in female patients suffering from chronic patellofemoral instability

PURPOSE

To analyze postoperative physical and sexual activity as well as Quality of Life (QoL) after complex patellofemoral reconstructions in female patients suffering from chronic patellofemoral instability (PFI).

METHODS

Female patients aged > 18 years undergoing complex patellofemoral reconstruction for chronic PFI were included. Complex patellofemoral reconstruction was defined as medial patellofemoral ligament reconstruction (MPFL-R) combined with at least one major bony procedure (distal femoral osteotomy, high tibial osteotomy, and trochleoplasty). Outcome was evaluated retrospectively after a minimum follow-up of 12 months using Tegner activity scale, Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0), EuroQol-5D-3L (EQ-5D-3L), EuroQol Visual analog scale (EQ-VAS), and a questionnaire about sexual activity.

RESULTS

A total of 34 females (mean age, 26 ± 5 years) with a mean follow-up of 45 ± 16 months were included. Seventy-seven percent had one major bony correction + MPFL-R and 24% had at least two major bony corrections + MPFL-R. The re-dislocation rate was 6%. Median Tegner activity scale improved from 3 (range 0-10) to 4 (range 2-6) (n.s.) and an improved activity level was observed in 49% of subjects. QoL scores showed an EQ-5D-3L Index Value of 0.89 ± 0.15, EQ-VAS of 80.3 ± 11.4, and BPII of 68.3 ± 19.1. Thirty-four percent of patients reported restrictions of sexual activities due to PFI preoperatively with an improved sexual function observed in 60% postoperatively due to less pain, improved mobility, and less apprehension. Postoperative return to sexual activity was 91%, whereof 19% reported current restrictions of sexual function because of pain and/or limited range of motion.

CONCLUSION

Despite the complexity and invasiveness of complex patellofemoral reconstruction, combined bony procedures and MPFL-R resulted in a low redislocation rate, improved physical activity and QoL comparable to values reported after isolated MPFL-R. Furthermore, sexual activity was improved in 60% of females with preoperative restrictions.

LEVEL OF EVIDENCE

IV.

Failure Analysis in Patients With Patellar Redislocation After Primary Isolated Medial Patellofemoral Ligament Reconstruction

Background:

Reconstruction of the medial patellofemoral ligament (MPFL) has become a popular surgical procedure to address patellofemoral instability. As a consequence of the growing number of MPFL reconstructions performed, a higher rate of failures and revision procedures has been seen.

Purpose:

To perform a failure analysis in patients with patellar redislocation after primary isolated MPFL reconstruction.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patients undergoing revision surgery for reinstability after primary isolated MPFL reconstruction were included. Clinical notes were reviewed to collect demographic data, information on the primary surgery, and the mechanism of patellar redislocation (traumatic vs nontraumatic). Preoperative imaging was analyzed regarding femoral tunnel position and the prevalence of anatomic risk factors (ARFs) associated with patellofemoral instability: trochlear dysplasia (types B through D), patella alta (Caton-Deschamps index >1.2, patellotrochlear index <0.28), lateralization of the tibial tuberosity (tibial tuberosity–trochlear groove distance >20 mm, tibial tuberosity–posterior cruciate ligament [TT-PCL] distance >24 mm), valgus malalignment (mechanical valgus axis >5°), and torsional deformity (internal femoral torsion >25°, external tibial torsion >35°). The prevalence of ARF was compared between patients with traumatic and nontraumatic redislocations and between patients with anatomic and nonanatomic femoral tunnel position.

Results:

A total of 26 patients (69% female) with a mean age of 25 ± 7 years were included. The cause of redislocation was traumatic in 31% and nontraumatic in 69%. Position of the femoral tunnel was considered nonanatomic in 50% of patients. Trochlear dysplasia was the most common ARF with a prevalence of 50%, followed by elevated TT-PCL distance (36%) and valgus malalignment (35%). The median number of ARFs per patient was 3 (range, 0-6), and 65% of patients had 2 or more ARFs. Patients with nontraumatic redislocations showed significantly more ARFs per patient, and the presence of 2 or more ARFs was significantly more common in this group. No significant difference was observed between patients with anatomic versus nonanatomic femoral tunnel position.

Conclusion:

Multiple anatomic risk factors and femoral tunnel malposition are commonly observed in patients with reinstability after primary MPFL reconstruction. Before revision surgery, a focused clinical examination and adequate imaging including radiographs, magnetic resonance imaging (MRI), standing full-leg radiographs, and torsional measurement with computed tomography or MRI are recommended to assess all relevant anatomic parameters to understand an individual patient’s risk profile. During revision surgery, care must be taken to ensure anatomic placement of the femoral tunnel through use of anatomic and/or radiographic landmarks.

Relationship Between Lateral Patellar Stability Following Tibial Tubercle Osteotomy for Varying Patellofemoral Geometries

The geometry of the patellofemoral joint affects function and pathology. However, the impact of trochlear groove depth on treatments for patellar instability and pain is not clear. Tibial tubercle osteotomy is a common surgical intervention for patellar instability where the tibial insertion of the patellar tendon is translated to align the extensor mechanism and stabilize the joint. The aim of this work was to investigate the interaction between trochlear groove depth and patellar tendon insertion and their effect on patellar stability. Patellofemoral geometry was modified based on a statistical shape model to create knees with a range of trochlear groove depths. A Monte Carlo approach was used and 750 instances of a musculoskeletal model were generated with varying geometry and anterior and medial transfer of the patellar tendon. Stability was assessed by applying a lateral perturbation force to the patella during simulation of overground walking. In knees with deep trochlear grooves, a medialized patellar tendon increased stability. However, in knees with shallow trochlear grooves, stability was maximized for tendon insertion ~1 mm medial to its neutral location. This patellar tendon insertion also corresponded to the best alignment of the patella in the trochlear groove in these knees, indicating that good alignment may be important to maximizing stability. Anterior patellar tendon transfer had minimal effect on stability for all geometries. A better understanding of the effects of articular geometry and tubercle location on stability may aid clinicians in patient-specific surgical planning.

Influence of Risky Pathoanatomy and Demographic Factors on Clinical Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction: A Regression Analysis

BACKGROUND

Multiple studies have demonstrated that a number of demographic and pathoanatomic characteristics are associated with patellofemoral instability, recurrence of instability, and less satisfactory results following medial patellofemoral ligament reconstruction (MPFL-R). Despite the growing volume of research, the relationship of risk factors to patient-reported outcome after MPFL-R is unclear.

PURPOSE

To determine if certain pathoanatomic and demographic factors predict disease-specific quality-of-life outcome after isolated MPFL-R for symptomatic patellofemoral instability.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The study analyzed 224 isolated MPFL-Rs. Demographic data were collected, including age at first dislocation, sex, and presence of bilateral instability. Pathoanatomic risk factors included the presence of high-grade trochlear dysplasia, tibial tubercle-trochlear groove (TT-TG) distance, patella alta ratio, Beighton score, and patellar tilt. Other factors included femoral tunnel position accuracy and WARPS/STAID score. Descriptive analyses were conducted, followed by calculation of individual Spearman rank correlation coefficients for the predictor variables versus the Banff Patellofemoral Instability Instrument (BPII) scores. A multivariable regression with stepwise selection was employed to establish the final model predicting BPII score, with all significant variables for alpha ≤ .05 included in the final model.

RESULTS

The cohort of 224 patients included 66 (29.5%) males and 158 (70.5%) females, with a mean age of 24.1 years and a mean body mass index of 23.9 kg/m². The mean age of first patellar dislocation was 15.7 years, and 41.4% of patients had bilateral instability. Pathoanatomic variables within the cohort included the following: high-grade trochlear dysplasia = 41%; mean TT-TG = 14.6 mm, with 16.8% of patients demonstrating a TT-TG ≥18 mm; mean Caton-Deschamps ratio = 1.09, with 22% of patients demonstrating a ratio ≥1.2; and positive Beighton score = 37.5%. The mean BPII score at postoperative 2 years was 67.1 out of 100. A stepwise elimination in the regression model demonstrated no statistically significant 3- or 2-way relationships. Assessment of individual variables indicated that bilateral symptoms (P = .004), higher age at first dislocation (P = .024), and femoral tunnel position >10 mm from the Schöttle point (P = .042) were statistically significant predictors of lower quality-of-life scores. The R² value for the regression analysis model was 0.07.

CONCLUSION

In this large cohort of patients undergoing isolated MPFL-R for symptomatic lateral patellofemoral instability, a multivariable forward stepwise regression demonstrated that bilateral symptoms, femoral tunnel position, and age at first dislocation were statistically significant predictors of lower postoperative BPII scores. No anatomic risk factors were predictive of quality-of-life outcome score 2 years after MPFL-R surgery. The R² value indicated that there were many other important contributing factors affecting BPII outcome scores than those explored in this study.

Trochleoplasty provides good clinical outcomes and an acceptable complication profile in both short and long-term follow-up

PURPOSE

The purpose of this study is to report on the global distribution and clinical outcomes of published articles related to trochleoplasty.

METHODS

The online databases OVID Medline, OVID EMBASE, and the Cochrane Library were searched for the literature assessing trochleoplasty performed for lateral patellofemoral instability (LPI). Study data were abstracted looking at global trends in the literature, as well as clinical and patient-reported outcomes following this technique.

RESULTS

For the assessment of global distribution, 29 studies including 998 patients met the inclusion criteria. The majority of the studies were conducted in Europe (93%) and most used an open thin flap technique (52%). For the secondary analysis of clinical outcomes, 21 studies were included with significant heterogeneity in patient selection, reporting on the degree of trochlear dysplasia, and patient-reported outcomes. All trochleoplasty techniques showed statistically significant improvement in clinical outcomes at average 50 months (range 3-228 months) post-operative, with most patients being satisfied with their procedure. Re-dislocation and complication rates were low.

CONCLUSIONS

European centers have published majority of data on trochleoplasty surgery, which has been shown to be an acceptable procedure for patients with high-grade trochlear dysplasia and LPI. Trochleoplasty has demonstrated good clinical outcomes, a low re-dislocation rate, and an acceptable complication profile in both short and long-term follow-up. This study highlights the difficulty in reporting outcomes in this group of patients due to heterogeneity in patient selection, grading of trochlear dysplasia, and the lack of disease-specific outcome measures.

LEVEL OF EVIDENCE

IV.

Clinical and Radiological Predictors of Functional Outcome After Isolated Medial Patellofemoral Ligament Reconstruction at Midterm Follow-up

BACKGROUND

Isolated medial patellofemoral ligament reconstruction (iMPFLR) is increasingly used for the surgical treatment of recurrent patellofemoral instability.

PURPOSE

The purpose of this study was to identify the clinical and radiological predictors that can significantly influence the functional outcomes after an iMPFLR.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 107 patients (112 ligament reconstructions) who underwent iMPFLR were evaluated with a mean ± SD follow-up of 59 ± 33 months (range, 12-123 months). Functional International Knee Documentation Committee (IKDC) and Kujala scores were assessed preoperatively and every 12 months. Radiological assessment of patellar height and tilt (Laurin angle, Merchant angle, Maldague classification) and computed tomography (CT) scan measurement of patellar tilt (contracted and relaxed quadriceps) and tibial tubercle-trochlear groove distance were performed preoperatively and at 6 months. Femoral tunnel position was assessed following the criteria formulated by Schöttle. The amount of femoral tunnel widening was measured by means of 3-dimensional CT scan at 6 months. Predictors were determined from univariate and multivariate regression analyses integrating clinical and radiological criteria pre- and postoperatively. The dependent variable was defined as the difference between pre- and postoperative scores.

RESULTS

Between pre- and postoperative measurement at last follow-up, a significant improvement for IKDC and Kujala functional scores was observed (Kujala: 57 ± 11.3 to 87 ± 12.9, P < .001; IKDC: 47.8 ± 13.1 to 79 ± 15.8, P < .001). Demographics (age, body mass index, sex), dislocation characteristics (number of dislocations, time between first dislocation and surgery, age at first dislocation, mechanism of first dislocation, knee side), clinical data (frontal limb alignment, hyperlaxity, recurvatum, pre- and postoperative range of motion), and complications (quadriceps atrophy, complex regional pain syndrome) did not influence functional scores. The predictors of lower improvement in functional scores included small correction of the patellar tilt reported on the CT scan measurement, malpositioning of the femoral tunnel, and a widening of this tunnel near the medial cortex. Malpositioning of the femoral tunnel was correlated with tunnel widening, and patients with anterior and proximal malpositioning experienced stiffness in flexion.

CONCLUSION

Overall, iMPFLR demonstrated good outcomes. Predictors influencing the functional results were identified. Less improvement in clinical outcome was reported for patients with a high preoperative patellar tilt and only a small correction in tilt and for those who had femoral tunnel malpositioning, which was correlated with tunnel widening.

Geometry of Torsional Malalignment Syndrome: Trochlear Dysplasia but Not Torsion Predicts Lateral Patellar Instability

Background

The clinical impact of increased torsion on patellar instability and patellofemoral pain syndrome (PFPS) has been suggested by several studies.

Hypothesis

The hypotheses of this study were that (1) torsional malalignment (TM) is characterized by a positive correlation between different malalignment parameters that represent an overall picture of the malalignment syndrome and (2) an increase in overall torsion is the underlying difference between patellar instability and isolated patellofemoral pain.

Study Design

Cohort study; Level of evidence, 3.

Methods

Between April 2015 and July 2017, a total of 428 patients were treated for lateral patellar dislocation (LPD), and 333 patients were treated for PFPS. Sixty-two patients (14.5%) with patellar instability (LPD group) and 29 patients (8.7%) with patellofemoral pain (PFPS group) had additional TM and were included in this study. All patients underwent magnetic resonance imaging for torsional alignment and patellar tracking, including femoral antetorsion, tibial torsion, knee rotation, tibial tuberosity-trochlear groove (TT-TG) distance, tibial tuberosity-posterior cruciate ligament (TT-PCL) distance, Dejour classification of trochlear dysplasia, lateral trochlear inclination (LTI) angle, and patellar height.

Results

The LPD and PFPS groups differed significantly in terms of trochlear dysplasia (P < .001), LTI angle (P < .001), and TT-TG distance (P = .0167) but did not differ in terms of femoral antetorsion (20.02° ± 8.80° vs 20.03° ± 7.91°, respectively; P = .8545), tibial torsion (39.53° ± 9.23° vs 41.24° ± 7.28°, respectively; P = .3616), or knee rotation (10.42° ± 5.16° vs 8.48° ± 7.81°, respectively; P = .0163). Only measures of TT-TG distance and TT-PCL distance and measures of TT-TG distance and knee rotation were positively correlated. Trochlear dysplasia (type B-D) was identified as the only significant predictor of patellar instability.

Conclusion

TM in patients with either PFPS or LPD does not appear to be characterized by a fixed constellation of different malalignment parameters. Between groups, the parameters differed significantly only in terms of trochlear dysplasia and the TT-TG distance, and trochlear dysplasia (type B-D) (but not torsion) was identified as a predictor of lateral patellar instability.

Femoral trochlea does not remodel after patellar stabilization in children older than 10 years of age

Trochlear dysplasia is a major risk factor for patellar instability. It has been sparsely reported that the trochlea can remodel when patellar stabilization is performed in skeletally immature patients before the age of 10 years. It is not known whether trochlea can remodel significantly after the age of 10 years. The purpose of the study was to evaluate trochlear remodeling in skeletally immature patients after patellar stabilization surgery, with a focus on children older than 10 years of age. In a retrospective study, knee MRI of 21 patients who had undergone patellar stabilization surgery, were evaluated. Twenty of these 21 patients were older than 10 years of age at time of surgery. The measurements of cartilaginous and bony sulcus angles, trochlear depth, and cartilaginous trochlear bump were compared between preoperative and postoperative MRI, using paired t-tests. In 20 patients older than 10 years of age, the mean cartilaginous sulcus angle change between preoperative and postoperative axial MRI was not significant (2.2°±7.9°, P=0.6). The mean change in the bony sulcus angle value was not significant (3.6°±6.8°, P=0.07). Similarly, there was no significant change in trochlear depth (P=0.8), or size of the trochlear bump (P=0.1). For one patient under 10 years of age at the time of surgery, there was a 21° and a 15° improvement in cartilaginous and bony sulcus angle, respectively. There were no significant changes in the trochlear parameters and trochlear remodeling in patients older than 10 years of age. Patellar stabilization at a younger age (<10 years), may allow for trochlear remodeling. Level of Evidence: Level IV, case series.

Recent developments in evaluation and treatment of lateral patellar instability

Recent years have been characterized by an ongoing increase in knowledge about the different conditions associated with lateral patellar instability. This increase in knowledge provides differentiated approaches to the various pathologies of the patellofemoral joint. Though current guidelines consider medial patellofemoral ligament (MPFL) reconstruction the basic treatment for the unstable patella, medial soft tissue-stabilizing procedures should not be interpreted as stand-alone procedures in every case. The influence of different anatomical factors leading to patellar instability, as well as their impact on clinical outcome measures, is becoming increasingly apparent and deserves further attention. Therefore, the purpose of this review was to summarize recent developments in lateral patellar instability beyond MPFL reconstruction techniques. For this goal, the literature published within the last 3 years considering all aspects of lateral patellar instability was analysed. Six main topics evolved according to the number of publications and in terms of novel aspects and recent developments in the evaluation and treatment of lateral patellar instability. Those topics formed the basis of this article: (1) treatment of first-time patellar dislocation, (2) the impact of trochlear dysplasia and trochleoplasty procedures, (3) the relevance of torsional deformities, (4) patellar instability in open physis, (5) the implementation of new outcome measures, and (6) rehabilitation after patellar stabilizing procedures.