Grooveplasty Compared With Trochleoplasty for the Treatment of Trochlear Dysplasia in the Setting of Patellar Instability

The Effect of a Supratrochlear Spur on Patellofemoral Cartilage in Patients With Trochlear Dysplasia

BACKGROUND

The presence of a supratrochlear spur has been shown to influence outcomes in patients with trochlear dysplasia and is thought to accelerate cartilage wear. However, the current literature does not provide an evidence-based threshold for a relevant supratrochlear spur height.

PURPOSE/HYPOTHESIS

The purpose of this study was to establish a clinically significant supratrochlear spur height associated with patellofemoral chondral damage to guide surgeons in surgical decision-making. It was hypothesized that a supratrochlear spur negatively affects patellofemoral articular cartilage, with large spurs having the greatest effect.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study evaluated 363 knees with trochlear dysplasia that were scheduled to undergo surgery for the treatment of patellar instability at a single institution. All patients underwent preoperative true lateral radiography and magnetic resonance imaging (MRI). There were 2 independent reviewers who analyzed the supratrochlear spur height by measuring the distance between a tangent at the anterior femoral cortex and the most prominent point of the trochlea on sagittal MRI as well as other common patellofemoral parameters. All MRI scans were assessed for full-thickness cartilage lesions.

RESULTS

Of the included 363 knees, 91 (25.1%) showed full-thickness cartilage defects on the patella, while 21 (5.8%) had full-thickness trochlear cartilage damage. Patellar defects were significantly correlated with patient's age (r = 0.237; P < .001), body mass index (r = 0.148; P = .005), and supratrochlear spur height (r = 0.196; P < .001). Trochlear defects were significantly associated with patient's age (r = 0.160; P = .002), patellar tilt (r = 0.202; P < .001), tibial tubercle-trochlear groove distance (r = 0.128; P = .014), and supratrochlear spur height (r = 0.151; P < .004). Trochlear dysplasia types B and D showed a trend toward a higher prevalence in patellar defects (P = .082), while they were significantly associated with a higher prevalance of trochlear defects (P = .003) compared with types A and C. Knees with patellar (5.1 ± 2.0 vs 4.3 ± 1.7 mm, respectively; P = .001) and trochlear (5.3 ± 2.1 vs 4.4 ± 1.8 mm, respectively; P = .015) cartilage defects had a significantly larger supratrochlear spur height than knees without patellar and trochlear defects. A supratrochlear spur height ≥6 mm had adjusted odds ratios of 2.7 (95% CI, 1.6-4.5; P < .001) and 3.4 (95% CI, 1.3-8.8; P = .014) for developing patellar and trochlear cartilage damage, respectively.

CONCLUSION

A supratrochlear spur was significantly associated with patellofemoral cartilage damage. Large supratrochlear spurs demonstrated a substantially increased risk of developing patellofemoral cartilage damage.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Level III, case control study.

Supratrochlear Rim is Correlated with Isolated Patellar Chondromalacia on Magnetic Resonance Imaging of the Knee

Purpose

To investigate the relationship between the supratrochlear rim and isolated patellar chondromalacia (PC) using magnetic resonance imaging (MRI) scans of the knee.

Methods

Patients without patellofemoral pain (control group) and patients with patellofemoral pain and diagnosed with stage III or IV PC based on MRI (defect group) were retrospectively identified. Patients with a history of patellar subluxation were excluded. We used patient MRI scans to perform 20 anatomical measurements of the patellofemoral joint. We also performed 2 measurements of the anterior femoral curvature. A total of 30 patients (29 ± 8.7 years) were in the control group, and 20 patients were in the defect group (29.4 ± 9.7 years).

Results

The maximum curvature (P < .001) and mean curvature (P < .001) of the anterior femoral condyle were found statistically significantly different between the groups. Patellotrochlear index (P = .03) and Insall-Salvati index (P < .001) were also found statistically significantly different between the 2 groups. Patella type III and trochlear dysplasia grade B were found more common in the defect group.

Conclusions

In this Level III prognostic, case-control study, we have shown through MRI knee measurements that the isolated patellar chondromalacia in patients without a history of patellar subluxation and dislocation is correlated with the increased anterior femoral curvature in combination with patella alta.

3D Printed Models of Trochlear Dysplasia and Trochleoplasty Simulation for Trainee Education

Trochlear dysplasia is a major contributor to patellofemoral instability and subsequent failure of isolated soft tissue reconstruction procedures in the treatment of recurrent patellar dislocation and/or subluxation. Trochleoplasty procedures aim to address abnormal osseous trochlear morphologic factors that contribute to patellar maltracking. However, teaching these techniques is limited by the lack of reliable training models for trochlear dysplasia and trochleoplasty simulation. Although a cadaveric knee model of trochlear dysplasia for trochleoplasty simulation has been recently described, cadaveric knees are less amenable for use in trochleoplasty planning and surgeon training because of the absence of reliable, natural dysplastic anatomic relationships, such as suprapatellar spurs due to the rarity of dysplastic cadavers and the high cost of cadaveric specimens. Furthermore, readily available sawbone models represent "normal" osseous trochlear morphology and are difficult to modify and bend due to their material composition. Given this, we have developed a cost-effective, reliable, and anatomically accurate three-dimensional (3D) knee model of trochlear dysplasia for trochleoplasty simulation and trainee education.