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

Trochlear Morphological Changes in Skeletally Immature Patients Across Consecutive MRI Studies

BACKGROUND

Trochlear dysplasia is a consistent risk factor for recurrent patellofemoral instability (PFI), but there is limited understanding of how the trochlea develops during growth. The aim of this study was to evaluate serial magnetic resonance imaging (MRI) studies performed in skeletally immature patients with and without PFI to characterize changes in trochlear anatomy over time.

HYPOTHESIS

PFI leads to progressive worsening of trochlear dysplasia over time.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective case-control study was conducted on pediatric patients (<18 years of age) with and without a diagnosis of PFI who had multiple ipsilateral MRI studies of the knee at least 6 months apart. Inclusion criteria were patients with open distal femoral physes at the initial MRI study and no intervening surgery between MRI studies. All patients with PFI were included, and 30 patients without PFI were identified for comparison. MRI scans were retrospectively reviewed to evaluate trochlear morphology using the Dejour and Oswestry-Bristol classifications and to measure the sulcus angle, trochlear depth index, medial condylar trochlear offset, and lateral trochlear inclination (LTI). Univariate and bivariate statistics were performed to evaluate differences in morphology between MRI studies and between groups.

RESULTS

A total of 128 patients were identified (98 in the PFI group, 30 in the non-PFI group) with a mean age of 12.3 ± 2.4 years and mean time between MRI studies of 2.3 ± 1.5 years (range, 0.5-6.5 years). Among patients with PFI, rates of moderate to severe (Dejour grades B-D and Oswestry-Bristol classification flat or convex) trochlear dysplasia increased from the initial to most recent imaging study (67% vs 89%; P < .001), and statistically significantly more dysplastic LTI and sulcus angle were observed on follow-up (P < .05). Among the non-PFI group, the percentage of patients with normal trochlear morphology increased from 53% to 87% (P < .001), and less dysplastic measures of trochlear depth index, LTI, and sulcus angle were seen on follow-up imaging (P < .05). When comparing rates of change, trochlear metrics changed toward a more shallow and dysplastic direction in the PFI cohort and toward a deeper and less dysplastic direction in the non-PFI group.

CONCLUSION

Skeletally immature patients with untreated PFI have trochlear dysplasia that progressively worsens over time. Conversely, those without PFI have trochlear characteristics that appear to normalize with growth.

Techniques for surgical stabilization of the patella in children

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

Ultrasound evaluation of the femoral trochlea in newborns: incidence of trochlear dysplasia and associated risk factors

This study aimed to describe the femoral groove morphology using ultrasound in children under 6 months, estimate the incidence of trochlear dysplasia, and evaluate associated risk factors. A prospective study included 298 patients who underwent universal ultrasound screening for hip dysplasia [developmental dysplasia of the hip (DDH)] and knee ultrasound. Measurements of sulcus angle (SA), trochlear depth (TD), and trochlear facet asymmetry (TFA) were analyzed. Trochlear dysplasia was considered present if the ASO was ≥159°. Reproducibility was assessed using the intraclass correlation coefficient (ICC) in 60 knees. Logistic regression adjusted for confounders, presenting odds ratios (OR) and 95% confidence intervals (CI). Significance was set at P  < 0.05. Analysis included 596 knees (298 patients). Females accounted for 51% of patients, with 7% having breech presentation, 4.4% DDH, 6.4% family history of DDH, and 5% family history of patellofemoral instability. ICC showed excellent agreement for SA and TD, but poor for TFA. Trochlear dysplasia incidence was 3% (9/298; 67% bilateral). Median (IQR) values were 147.5 (144.0-150.5) for SA, 2.4 (2.2-2.8) for TD, and 1.1 (1.0, 1.1) for TFA. Breech presentation (OR, 9.68; 95% CI 1.92-48.71, P  = 0.006) and concomitant DDH (OR 6.29, 95% CI 1.04-37.78, P  = 0.044) were associated with trochlear dysplasia. Ultrasound effectively evaluates femoral groove morphology and diagnoses trochlear dysplasia in newborns. Trochlear dysplasia incidence was 3%, with a 10-fold higher risk in breech presentation and 6-fold higher risk in concomitant DDH. Standardized screening and timely treatment protocols should be further investigated. Level of evidence: Diagnostic Level II.

Patellar Dislocation: Workup and Decision-Making

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

Association of Hip Dysplasia With Trochlear Dysplasia in Skeletally Mature Patients

Background

Developmental dysplasia of the hip (DDH) and trochlear dysplasia (TD) are distinct pathologies with several important features in common. In addition to shared risk factors, both forms of dysplasia cause abnormal joint kinematics and force transmission, predisposing patients to pain, injuries to cartilage and soft tissue stabilizers, and ultimately arthritis.

Purpose

To evaluate for an association between hip dysplasia and TD in skeletally mature patients with symptomatic hip dysplasia.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 48 patients with DDH who underwent periacetabular osteotomy were compared with 48 sex-matched patients who underwent hip arthroscopy for femoroacetabular impingement (FAI) between July 2014 and February 2021. All patients were skeletally mature. The Tönnis angle and lateral center-edge angle were measured on preoperative pelvis radiographs. Femoral version, trochlear depth, lateral trochlear inclination (LTI), tibial tubercle-trochlear groove distance (TTTG-d), and posterior lateral condylar angle (PLCA) were measured on preoperative magnetic resonance imaging scans of the symptomatic hip and ipsilateral knee. Continuous variables were compared between the patient groups using 2-sample t tests. Interobserver reliability was measured using the intraclass correlation coefficient.

Results

Patients with DDH demonstrated a reduced trochlear depth compared with patients with FAI (3.6 vs 4.6 mm; P < .001). There were no differences between groups in femoral anteversion, LTI, TTTG-d, or PLCA. Two (4.2%) patients with FAI and 17 (35.4%) patients with DDH had a trochlear depth <3 mm (P < .001). One (2.1%) patient with FAI and 7 (14.6%) patients with DDH had an LTI <11° (P = .027). There was no difference between groups in frequency of a convex proximal trochlea, patient-reported ipsilateral knee pain, or ipsilateral knee procedures.

Conclusion

Patients with DDH had reduced trochlear depth compared with patients with FAI, demonstrating a higher incidence of dysplastic trochlear features that may predispose patients to patellofemoral joint disease. Further research is needed to determine whether screening at-risk patients and treating TD will help to prevent symptomatic patellofemoral disease.

Early Identification and Treatment of Trochlear Knee Dysplasia

A shallow sulcus characterizes trochlear dysplasia (TD) of the femoral trochlea, which can lead to chronic pain or instability of the patellofemoral joint. Breech presentation at birth has been identified as a risk factor for developing this condition, which an ultrasound can identify early. Early treatment could be considered at this stage, given the potential for remodelling in these skeletally immature patients. Newborns with breech presentation at birth who meet the inclusion criteria will be enrolled and randomised in equal proportions between treatment with the Pavlik harness and observation. The primary objective is to determine the difference in the means of the sulcus angle between the two treatment arms at two months. Ours is the first study protocol to evaluate an early non-invasive treatment for TD in the newborn with breech presentation at birth using a Pavlik harness. We hypothesised that trochlear dysplasia could be reverted when identified and treated early in life with a simple harness, as it is done with developmental dysplasia of the hip.

The Onset and Development of Patella Alta in Children With Patellar Instability

BACKGROUND

Patella alta is an anatomic risk factor for patellar instability in adolescents that is also linked to the risk factor of trochlear dysplasia. This study aims to determine the age of onset and age-related incidence of patella alta in a pediatric population of patients with patellar instability. We hypothesized that patellar height ratios would not increase with age, suggesting a congenital rather than the developmental origin of patella alta.

METHODS

A retrospective cross-sectional cohort of patients was collected with the following inclusion criteria: patients aged 5 to 18 who had a knee magnetic resonance imaging performed from 2000 to 2022 and the International Classification of Diseases code for patellar dislocation. Demographic information and details of the patellar instability episode(s) were collected with a chart review. Sagittal magnetic resonance imaging was used to measure Caton-Deschamps Index (CDI) and the Insall-Salvati Ratio (ISR) by 2 observers. Data were analyzed to assess for associations between patellar height ratios and age of the first dislocation and to assess if the proportion of patients categorized as having patella alta changed with age.

RESULTS

The 140 knees included in the cohort had an average age of 13.9 years (SD=2.40; range: 8-18) and were 55% female. Patella alta was present in 78 knees (55.7%) using CDI>=1.2 and in 59 knees (42.1%) using ISR>=1.3. The earliest age patella alta was observed was at age 8 using CDI>=1.2 and age 10 using ISR>=1.3. There were no statistically significant associations between CDI and age without adjustment (P=0.14) nor after adjustment for sex and body mass index (P=0.17). The proportion of knees above the CDI threshold for patella alta to the knees below the cutoff did not show a significant change with age (P=0.09).

CONCLUSIONS

Patella alta, as defined by CDI, is seen in patients as young as 8 years old. Patellar height ratios do not change with age in patients with patellar dislocation, suggesting that patella alta is established at a young age rather than developing during the adolescent years.

LEVEL OF EVIDENCE

Level III-diagnostic, cross-sectional.

4-in-1 Quadricepsplasty for Habitual and Fixed Lateral Patellar Dislocation in Children

BACKGROUND

Habitual and fixed patellar dislocations represent extreme forms of patellar instability and can lead to significant functional loss. The underlying complex pathoanatomy of a laterally positioned and shortened extensor mechanism poses challenges in its management. The purpose of our study was to evaluate the anatomic risk factors and outcomes of a 4-in-1 quadricepsplasty (wide lateral releases, Insall proximal tube realignment, Roux-Goldthwait patellar tendon hemi-transfer, and step-wise quadriceps lengthening) for stabilization of habitual and fixed patellar dislocation.

METHODS

In a retrospective study, all patients with habitual and fixed patellar dislocation who underwent 4-in-1 quadricepsplasty and had a minimum 2-year follow-up were identified. Preoperative magnetic resonance imagings were evaluated for the presence of anatomic risk factors. As a prospective part of the study, patient-reported outcomes were collected using validated instruments including Pedi-IKDC, HSS-Pedi FABS activity score, BPII 2.0 score, Kujala score, and KOOS score.

RESULTS

Seventeen knees (12 patients) formed the study cohort. Twelve knees had habitual dislocation (9 in extension and 4 in flexion) and 5 had fixed dislocation. Mean age was 9 years. 6/17 (35.3%) knees were associated with syndromes. On magnetic resonance imaging, trochlear dysplasia was the most common anatomic risk factor present in 15/17 (88.2%) knees. 13/17 (76%) knees had presence of 2 or more risk factors. At the mean follow-up of 43.3 months, the mean Pedi-IKDC score was 88.1, the HSS-Pedi FABS activity score was 15.6, the BPII 2.0 score was 78.2, the Kujala score was 90, KOOS score was 93.9, and overall patient satisfaction score was 83.3. For complications, 3/17 knees (17.6%) had recurrent patellar instability, 1 knee had postoperative stiffness that required manipulation under anesthesia and 1 knee had a superficial wound infection.

CONCLUSIONS

Most patients with habitual and fixed patellar dislocation present during the first decade of life. There are several underlying anatomic risk factors, the most common being trochlear dysplasia and patellar tilt. The 4-in-1 quadricepsplasty technique provides reliable patellar stabilization, satisfactory clinical results, and acceptable patient-reported outcomes at a minimum 2-year follow-up, with a 17.6% redislocation rate.

LEVEL OF EVIDENCE

Level IV.

Abnormal patellar loading may lead to femoral trochlear dysplasia: an experimental study of patellar hypermobility and patellar dislocation in growing rats

BACKGROUND

This animal study aimed to explore the effects of patellar hypermobility and patellar dislocation on the developing femoral trochlea.

METHODS

Seventy-two 3-week-old Wistar rats were randomly divided into three groups. The sham group (SG) underwent simple incision and suture of the skin and subcutaneous tissue; the patellar hypermobility group (PHG) underwent medial and lateral retinacular release and pie-crusting technique for the patellar ligament; the patellar dislocation group (PDG) underwent plication of the medial patellofemoral retinaculum. Twelve rats in each group were euthanized at 3 and 6 weeks postoperatively, respectively, and specimens were collected. The bony sulcus angle (BSA), cartilaginous sulcus angle (CSA), trochlear sulcus depth (TSD), and thickness of the cartilage on the lateral facet (CTL), medial facet (CTM), and center (CTC) of the trochlea were measured on hematoxylin and eosin-stained sections.

RESULTS

In the PHG and PDG, the femoral condyles became blunt, the trochlear groove became shallower, and cartilage became thicker compared with the SG. Compared with the SG, the PHG and PDG had significantly larger BSA and CSA values at 3 (p < 0.05) and 6 weeks (p < 0.005), and a significantly shallower TSD (p < 0.05). At 3 weeks, all cartilage thicknesses in the PHG and the CTC and CTM in the PDG were significantly thinner than in the SG (PHG vs. SG: p = 0.009 for CTL, p < 0.001 for CTM, p = 0.003 for CTC; PDG vs. SG: p = 0.028 for CTC, p = 0.048 for CTM). At 6 weeks, the CTC was thicker in the PHG and PDG than the SG (PHG vs. SG: p = 0.044; PDG vs. SG: p = 0.027), and the CTL was thinner in the PDG than the SG (p = 0.044).

CONCLUSION

Patellar hypermobility and patellar dislocation may result in trochlear dysplasia that worsens with age. Excessive or insufficient loading leads to trochlear dysplasia.

Patellar shape is associated with femoral trochlear morphology in individuals with mature skeletal development

Background

As several studies have detected correlations between patellar and femoral trochlear development, this raises the question of whether patellar shape is associated with trochlear developmental outcomes.

Methods

Patellar shape and femoral trochlear morphology were retrospectively analyzed in 183 subjects, of whom 61 each were classified as having Wiberg type I, II, and III patellae (groups A, B, and C, respectively). The sulcus angle (SA), lateral trochlea inclination angle (LTA), medial trochlear inclination angle (MTA), lateral facet length (LFL), medial facet length (MFL), lateral trochlear height (LTH), medial trochlear height (MTH), trochlea sulcus height (TH), and lateral-medial trochlear facet distance (TD) were analyzed as a means of evaluating trochlear morphology. Trochlear depth, trochlear condyle asymmetry, and trochlear facet asymmetry were additionally calculated, and differences in trochlear morphology and correlations between trochlear morphology and patellar shape were evaluated.

Results

The femoral trochlear parameters of patients in group A differed significantly from those of patients in groups B and C. No significant differences between groups B and C were evident. Patellar shape was positively correlated with LTA, MTA, MFL, trochlear condyle asymmetry, and trochlear facet asymmetry, and was negatively correlated with SA.

Conclusions

These data indicated that patellar shape and trochlear morphology are related to one another,which suggest normalized patella morphology surgery and trochlear surgery are better choices for patients with patella instability.

Trial registration

Retrospectively registered.

Changes in patellar morphology following surgical correction of recurrent patellar dislocation in children

Background

The aim of this study was to evaluate patellar morphological changes following surgical correction of recurrent patellar dislocation in children.

Methods

A total of 35 immature children aged 5 to 10 years who suffered from bilateral recurrent patellar dislocation associated with abnormal patella morphology were enrolled in this study. The knees with the most frequent dislocations (treated with medial patellar retinacular plasty) were selected as the study group (SG), and those undergoing conservative treatment for the contralateral knee were selected as the control group (CG). Computed tomography (CT) scans were performed on all children preoperatively and at the last follow-up to evaluate morphological characteristics of the patella.

Results

All the radiological parameters of the patella showed no significant difference between the two groups preoperatively. At the last follow-up for CT scans, no significant differences were found for the relative patellar width (SG, 54.61%; CG, 52.87%; P = 0.086) and the relative patellar thickness (SG, 26.07%; CG, 25.02%; P = 0.243). The radiological parameters including Wiberg angle (SG, 136.25°; CG, 122.65°; P < 0.001), modified Wiberg index (SG, 1.23; CG, 2.65; P < 0.001), and lateral patellar facet angle (SG, 23.35°; CG, 15.26°; P < 0.001) showed statistical differences between the two groups.

Conclusions

The patellar morphology can be improved by early surgical correction in children with recurrent patellar dislocation. Therefore, early intervention is of great importance for children diagnosed with recurrent patellar dislocation.

Distal femoral morphological dysplasia is correlated with increased femoral torsion in patients with trochlear dysplasia and patellar instability

AIMS

The purpose of this study was to explore the correlation between femoral torsion and morphology of the distal femoral condyle in patients with trochlear dysplasia and lateral patellar instability.

METHODS

A total of 90 patients (64 female, 26 male; mean age 22.1 years (SD 7.2)) with lateral patellar dislocation and trochlear dysplasia who were awaiting surgical treatment between January 2015 and June 2019 were retrospectively analyzed. All patients underwent CT scans of the lower limb to assess the femoral torsion and morphology of the distal femur. The femoral torsion at various levels was assessed using the a) femoral anteversion angle (FAA), b) proximal and distal anteversion angle, c) angle of the proximal femoral axis-anatomical epicondylar axis (PFA-AEA), and d) angle of the AEA-posterior condylar line (AEA-PCL). Representative measurements of distal condylar length were taken and parameters using the ratios of the bianterior condyle, biposterior condyle, bicondyle, anterolateral condyle, and anteromedial condyle were calculated and correlated with reference to the AEA, using the Pearson Correlation coefficient.

RESULTS

The femoral torsion had a strong correlation with distal condylar morphology. The FAA was significantly correlated with the ratio of the bianterior condyle (r = 0.355; p = 0.009), the AEA-PCL angle (r = 0.340; p = 0.001) and the ratio of the anterolateral condyle and lateral condyle (ALC-LC) (r = 0.309; p = 0.014). The PFA-AEA angle was also significantly correlated with the ratio of the bianterior condyle (r = 0.319; p = 0.008), the AEA-PCL angle (r = 0.231; p = 0.031), and the ratio of ALC-LC (r = 0.261; p = 0.034). In addition, the bianterior condyle ratio showed a significant correlation with the biposterior condyle ratio (r = -0.324; p = 0.027) and the AEA-PCL angle (r = 0.342; p = 0.021).

CONCLUSION

Increased femoral torsion correlated with a prominent anterolateral condyle and a shorter posterolateral condyle compared with the medial condyle. The deformities of the anterior and posterior condyles are combined deformities rather than being isolated and individual deformities in patients with trochlear dysplasia and patella instability. Cite this article: Bone Joint J 2020;102-B(7):868-873.

Recurrent patellofemoral instability rates after MPFL reconstruction techniques are in the range of instability rates after other soft tissue realignment techniques

PURPOSE

Recurrent patellofemoral instability is a common knee injury in skeletally immature patients. Many surgical techniques have been described in the literature, all with different success rates. Purpose of this study was to perform a systematic review and meta-analysis of the available literature to assess recurrent patellofemoral instability rates after surgical treatment using MPFL reconstruction techniques and other soft tissue realignment techniques in skeletally immature patients.

METHODS

PubMed, Embase, Web of Science, and The Cochrane Library were searched to identify all original articles concerning the surgical treatment for patellofemoral instability in skeletally immature patients and that reported post-operative recurrent patellofemoral instability rates. Subsequently a risk of bias assessment was conducted and a meta-analysis was performed on reported post-operative recurrent patellofemoral instability rates after MPFL reconstruction techniques and other soft tissue realignment techniques.

RESULTS

Of the 21 eligible studies (448 knees in 389 patients), 10 studies reported on MPFL reconstruction techniques using different grafts and fixation techniques and 11 reported on other soft tissue realignment procedures. In total, 62 of the 448 (13.8%) treated knees showed recurrent patellofemoral instability during follow-up. The overall pooled recurrent patellofemoral instability rate was estimated to be 0.08 (95% CI 0.02-0.16). For MPFL reconstruction techniques, the pooled recurrent patellofemoral instability rate was estimated to be 0.02 (95% CI 0.00-0.09). For the other soft tissue realignment techniques, the pooled rate was estimated to be 0.15 (95% CI 0.04-0.31). No statistically significant difference in recurrent patellofemoral instability rates between MPFL reconstruction techniques and other soft tissue realignment techniques were found (n.s.). There was a large variation in treatment effects over different settings, including what effect is to be expected in future patients.

CONCLUSION

This systematic review and meta-analysis found that recurrent patellofemoral instability rates after MPFL reconstruction techniques are in the range of instability rates after other soft tissue realignment techniques. The clinical relevance of this study is that it provides clinicians with the best currently available evidence on recurrent patellofemoral instability rates after surgical treatment for patellofemoral instability in skeletally immature patients.

LEVEL OF EVIDENCE

IV.

The dysplastic trochlear sulcus due to the insufficient patellar stress in growing rats

BACKGROUND

Developmental factors were assumed to be the key factors that influenced the morphology of femoral trochlea. This study investigated the effects of insufficient patellar stress after birth on the morphological development of the femoral trochlea. Effects of insufficient patellar stress on femoral trochlea were investigated using surgical induced patellectomy and patellar dislocation in growing rat model.

METHODS

In this study, two experimental groups and one sham group (SG) were established. Thirty-six Wistar rats (female, 28 days of age) were randomly assigned to three groups. The patellectomy group (PG), rats underwent the patellectomy in this group. The dislocation group (DG), rats underwent the surgery-induced patellar dislocation. Histological staining (Safranin-O and fast green), Micro-computed tomographic (Micro-CT) analysis in two experimental endpoints (3, 12 weeks postoperatively) were selected to evaluate morphological changes of the femoral trochlea.

RESULTS

Articular cartilage on the trochlear sulcus was remodeled at 3 weeks after the surgery, and degenerated at 12 weeks through the histological staining. The femoral trochlear angle (FTA) did not show a significant difference at 3 week between the experimental groups and the sham group (PG vs SG P = 0.38, DG vs SG p = 0.05), but the FTA was significantly increased in experimental groups at 12 weeks(PG vs SG P = 0.001, DG vs SG p = 0.005). The Bone volume density (BV/TV), Trabecular number (Tb.N) under the trochlea groove were significantly reduced at 3 weeks postoperatively in the experimental groups (PG vs SG p = 0.001, DG vs SG p = 0.002). No significant difference was found in BV/TV and Tb. N among the three groups at 12 weeks postoperatively.

CONCLUSION

Surgical induced patellectomy and patellar dislocation leads to the dysplastic trochlear sulcus in growing rats. Besides the bone morphology of trochlear sulcus, the articular cartilage and subchondral trabecula under the trochlear sulcus were remodeled early stage after the surgery.