Evaluation of Patellar Contact Pressure Changes after Static versus Dynamic Medial Patellofemoral Ligament Reconstructions Using a Finite Element Model

MR imaging after patellar MACI and MPFL reconstruction: a comparison of isolated versus combined procedures

OBJECTIVE

To qualitatively and quantitatively evaluate the 2.5-year MRI outcome after Matrix-associated autologous chondrocyte implantation (MACI) at the patella, reconstruction of the medial patellofemoral ligament (MPFL), and combined procedures.

METHODS

In 66 consecutive patients (age 22.8 ± 6.4years) with MACI at the patella (n = 16), MPFL reconstruction (MPFL; n = 31), or combined procedures (n = 19) 3T MRI was performed 2.5 years after surgery. For morphological MRI evaluation WORMS and MOCART scores were obtained. In addition quantitative cartilage T2 and T1rho relaxation times were acquired. Several clinical scores were obtained. Statistical analyses included descriptive statistics, Mann-Whitney-U-tests and Pearson correlations.

RESULTS

WORMS scores at follow-up (FU) were significantly worse after combined procedures (8.7 ± 4.9) than after isolated MACI (4.3 ± 3.6, P = 0.005) and after isolated MPFL reconstruction (5.3 ± 5.7, P = 0.004). Bone marrow edema at the patella in the combined group was the only (non-significantly) worsening WORMS parameter from pre- to postoperatively. MOCART scores were significantly worse in the combined group than in the isolated MACI group (57 ± 3 vs 88 ± 9, P < 0.001). Perfect defect filling was achieved in 26% and 69% of cases in the combined and MACI group, respectively (P = 0.031). Global and patellar T2 values were higher in the combined group (Global T2: 34.0 ± 2.8ms) and MACI group (35.5 ± 3.1ms) as compared to the MPFL group (31.1 ± 3.2ms, P < 0.05). T2 values correlated significantly with clinical scores (P < 0.005). Clinical Cincinnati scores were significantly worse in the combined group (P < 0.05).

CONCLUSION

After combined surgery with patellar MACI and MPFL reconstruction inferior MRI outcomes were observed than after isolated procedures. Therefore, patients with need for combined surgery may be at particular risk for osteoarthritis.

Outcomes of an All-Soft Tissue Fixation Technique for Reconstruction of the Medial Patellofemoral Complex Using Double-Bundle Quadriceps Tendon Autograft for Recurrent Patellar Dislocation in Skeletally Immature Patients

Background

Patellar fracture, femoral physis injury, and recurrent instability are concerning complications in medial patellofemoral ligament (MPFL) reconstruction (MPFLR) techniques for recurrent patellar dislocation in children and adolescents.

Purpose

To evaluate the outcomes of an anatomic all-soft tissue fixation technique for reconstruction of the medial patellofemoral complex (MPFC) using a double-bundle quadriceps tendon (QT) autograft for recurrent patellar dislocation in skeletally immature patients.

Study Design

Case series; Level of evidence, 4.

Methods

This retrospective study involved 24 skeletally immature patients (24 knees; 16 women and 8 men; age range, 9.5-15 years) with recurrent patellar dislocation who underwent MPFC reconstruction using a double-bundle QT autograft between September 2018 and January 2021. Only soft tissue suture fixation was used on the femoral and patellar sides of the 2 bundles of the QT. Radiographs, computed tomography, and magnetic resonance imaging were used to evaluate physeal status, lower limb alignment, patellar height and tilt, trochlear morphology, tibial tubercle-trochlear groove distance, and any associated knee pathology. Functional outcomes were assessed with the Kujala score, the visual analog scale (VAS) for pain, and the grading system of Insall et al.22.

Results

The mean follow-up time was 40 ± 9.6 months (range, 28-56 months). At the final follow-up, the Kujala and VAS pain scores showed a significant improvement versus preoperative scores (P < .001), and the passive lateral patellar glide showed a significant reduction (P < .001). All patients had negative apprehension and J signs. Of the 24 patients, 23 regained full range of motion, while 1 patient had a knee flexion deficit. The patellar tilt angle improved significantly at the final follow-up (P < .001). There was no patellar fracture, femoral physis injury, or recurrence of patellar dislocation. According to the grading system of Insall et al, the results were excellent in 15 knees (62.5%), good in 8 knees (33.3%), fair in 1 knee (4.2%), and no knees showed poor results.

Conclusion

Reconstruction of the MPFC using a double-bundle QT autograft with an all-soft tissue fixation technique was an effective method for treating patellar instability in skeletally immature patients.

Medial quadriceps tendon femoral ligament reconstruction and medial patellofemoral ligament reconstruction have no significant differences in clinical outcomes for treatment of lateral patellar instability: a matched-cohort study

OBJECTIVES

The purpose of this study was to compare clinical outcomes of medial quadriceps tendon-femoral ligament reconstruction (MQTFLR) and medial patellofemoral ligament reconstruction (MPFLR) among patients with recurrent lateral patellar instability.

METHODS

A retrospective matched-cohort study was conducted involving patients who underwent MQTFLR or MPFLR with or without tibial tubercle osteotomy (TTO) from 2019 to 2021. Subjects were matched 1:1 on age, concomitant osteochondral allograft (OCA), concomitant TTO, and follow-up time. Measured outcomes included 90-day complications, Visual Analog Scale (VAS) knee pain, return to sport/work, Kujala score, Tegner score, and MPFL-Return to Sport after Injury (MPFL-RSI) score. Outcomes were compared between groups using Mann-Whitney U-test for continuous variables and Fisher's exact test for categorical variables. P-values <0.05 were considered significant.

RESULTS

Ten MQTFLR patients (mean age 28.7 years, 80% female, mean follow-up 19.7 months) and ten MPFLR patients (mean age 29.1 years, 90% female, mean follow-up 28.3 months) were included in the study. One MQTFLR patient (10%) and three MPFLR patients (30%) underwent reoperation for postoperative arthrofibrosis. Postoperative VAS resting pain was not significantly different between the groups (MQTFLR mean 1.1, MPFLR mean 0.6, p ​= ​0.31). There were no significant differences in rates of recurrent subluxations (MQTFLR 20%, MPFLR 0%, p ​= ​0.47), return to sport (MQTFLR 50%, MPFLR 75%, p ​= ​0.61), return to work (MQTFLR 100%, MPFLR 88%, p ​= ​1.00), or MPFL-RSI pass rate (MQTFLR 75% vs. MPFLR 38%, p ​= ​0.31).

CONCLUSION

There were no significant differences in knee pain and function, return to work, and rates of recurrent patellar instability between patients who underwent MQTFLR versus MPFLR, though these results should be interpreted with caution given the small sample size and potential selection bias.

LEVEL OF EVIDENCE

III.

Model Properties and Clinical Application in the Finite Element Analysis of Knee Joint: A Review

The knee is the most complex joint in the human body, including bony structures like the femur, tibia, fibula, and patella, and soft tissues like menisci, ligaments, muscles, and tendons. Complex anatomical structures of the knee joint make it difficult to conduct precise biomechanical research and explore the mechanism of movement and injury. The finite element model (FEM), as an important engineering analysis technique, has been widely used in many fields of bioengineering research. The FEM has advantages in the biomechanical analysis of objects with complex structures. Researchers can use this technology to construct a human knee joint model and perform biomechanical analysis on it. At the same time, finite element analysis can effectively evaluate variables such as stress, strain, displacement, and rotation, helping to predict injury mechanisms and optimize surgical techniques, which make up for the shortcomings of traditional biomechanics experimental research. However, few papers introduce what material properties should be selected for each anatomic structure of knee FEM to meet different research purposes. Based on previous finite element studies of the knee joint, this paper summarizes various modeling strategies and applications, serving as a reference for constructing knee joint models and research design.

After MPFL reconstruction, femoral tunnel widening and migration increase with poor tunnel positioning and are related to poor clinical outcomes

PURPOSE

Isolated MPFL reconstruction (iMPFLR) is increasingly used for the surgical treatment of treatment for recurrent patella dislocation. The purpose of this study was to evaluate the influence of tunnel widening and migration on clinical outcomes after iMPFL using a CT-scannographic analysis at 6 months postoperatively.

METHODS

One hundred and sixty patients (91 females for 69 males) with an average age of 23 years [14-54] who underwent iMPFLR and had an evaluation scan at 6 months postoperatively were evaluated with a mean follow-up of 97 ± 89 months [12 to 166]. Functional International Knee Documentation Committee (IKDC) Score, Kujala score, and joint mobility were assessed preoperatively, at 6 months and at the latest follow-up. The IKDC and Kujala scores were expressed as the difference between pre- and postoperative scores (dIKDC and dKujala). The position of the femoral tunnel was assessed according to the Schöttle criteria on post-operative radiographic profiles. Tunnel widening (at three levels of measurement) and the migration of the center of the tunnel were studied on a CT-scan analysis at 6 months. Any correlation and regression between the evolution of the clinical scores and the measured scannographic parameters were investigated. The relationships between tunnel position and tunnel changes were also studied.

RESULTS

Between pre- and post-op, the IKDC (45 ± 13 to 80 ± 15, p < 0.001) and Kujala (55 ± 11 to 87 ± 12, p < 0.001) scores were significantly improved. Patients with tunnel changes had decreased clinical and functional results at 6 months post-op of an iMPFLR (p < 0.001). These changes in the femoral tunnel, evidenced by a tunnel entrance widening and migration of the tunnel center, were related to an initial malposition of the tunnel (p < 0.001).

CONCLUSION

In iMPFLR, changes in the femoral tunnel, corresponding to dilatation and migration of the tunnel center, may occur. These changes are increased by the initial malpositioning of the femoral tunnel and are correlated with less good clinical and functional outcomes.

LEVEL OF EVIDENCE

Level IV.

Patellar instability MRI measurements are associated with knee joint degeneration after reconstruction of the medial patellofemoral ligament

OBJECTIVE

To qualitatively and quantitatively evaluate the 2-year magnetic resonance imaging (MRI) outcome after MPFL reconstruction at the knee and to assess MRI-based risk factors that predispose for inferior clinical and imaging outcomes.

MATERIALS AND METHODS

A total of 31 patients with MPFL reconstruction were included (22 ± 6 years, 10 female). MRI was performed preoperatively in 21/31 patients. Two-year follow-up MRI included quantitative cartilage T2 and T1rho relaxation time measurements at the ipsilateral and contralateral knee. T2_relative was calculated as T2_{patellofemoral}/T2_femorotibial. Morphological evaluation was conducted via WORMS scores. Patellar instability parameters and clinical scores were obtained. Statistical analyses included descriptive statistics, t-tests, multivariate regression models, and correlation analyses.

RESULTS

Two years after MPFL reconstruction, all patellae were clinically stable. Mean total WORMS scores improved significantly from baseline to follow-up (mean difference ± SEM, - 4.0 ± 1.3; P = 0.005). As compared to patients with no worsening of WORMS subscores over time (n = 5), patients with worsening of any WORMS subscore (n = 16) had lower trochlear depth, lower facetal ratio, higher tibial-tuberosity to trochlear groove (TTTG) distance, and higher postoperative lateral patellar tilt (P < 0.05). T2_relative was higher at the ipsilateral knee (P = 0.010). T2_relative was associated with preoperatively higher patellar tilt (P = 0.021) and higher TTTG distance (P = 0.034). TTTG distance, global T2 values, and WORMS progression correlated with clinical outcomes (P < 0.05).

CONCLUSION

MPFL reconstruction is an optimal treatment strategy to restore patellar stability. Still, progressive knee joint degeneration and patellofemoral cartilage matrix degeneration may be observed, with patellar instability MRI parameters representing particular risk factors.

The quantitative influence of current treatment options on patellofemoral stability in patients with trochlear dysplasia and symptomatic patellofemoral instability - a finite element simulation

BACKGROUND

Trochlear dysplasia is highly associated with patellofemoral instability. The goal of conservative and surgical treatment is to stabilize the patella while minimizing adverse effects. However, there is no literature investigating the quantitative influence of different treatment options on patellofemoral stability in knees with trochlear dysplasia. We created and exploited a range of finite element models to address this gap in knowledge.

METHODS

MRI data of 5 knees with trochlear dysplasia and symptomatic patellofemoral instability were adapted into this previously established model. Vastus medialis obliquus strengthening as well as double-bundle medial patellofemoral ligament reconstruction and the combination of medial patellofemoral ligament reconstruction and trochleoplasty were simulated. The force necessary to dislocate the patella by 10 mm and fully dislocate the patella was calculated in different flexion angles.

FINDINGS

Our model predicts a significant increase of patellofemoral stability at the investigated flexion angles (0°-45°) for a dislocation of 10 mm and a full dislocation after medial patellofemoral ligament reconstruction and the combination of medial patellofemoral ligament reconstruction and trochleoplasty compared to trochleodysplastic (P = 0.01) and healthy knees (P = 0.01-0.02). Vastus medialis obliquus strengthening has a negligible effect on patellofemoral stability.

INTERPRETATIONS

This is the first objective quantitative biomechanical evidence supporting the place of medial patellofemoral ligament reconstruction and medial patellofemoral ligament reconstruction combined with trochleoplasty in patients with symptomatic patellofemoral instability and trochlear dysplasia type B. Vastus medialis obliquus strengthening has a negligible effect on patellar stability at a low total quadriceps load of 175 N.

Isolated reconstruction of medial patellofemoral ligament with an elastic femoral fixation leads to excellent clinical results

PURPOSE

The primary objective was to compare the functional outcomes after an isolated MPFL reconstruction using either a quasi-anatomical technique (group A) or an anatomical MPFL reconstruction (group B). The secondary objectives were to compare the rates of redislocation, range-of-motion and subjective patellar instability (Smillie test).

METHODS

A multicenter longitudinal prospective comparative study was performed. Group A had 29 patients and 28 were included in Group B. Patients with trochlear dysplasia types C and D and patients who had undergone a trochleoplasty, a distal realignment or patella distalization concurrently with MPFL reconstruction were excluded. The main evaluation criterion was the Kujala functional score.

RESULTS

The mean postoperative Kujala was 90.4 (89.4 in group A and 92.1 in group B). Upon comparing the mean difference between pre- and post-operative values, no differences were detected between the two groups (n.s).

CONCLUSIONS

Isolated quasi-anatomical MPFL reconstruction using a gracilis tendon autograft for recurrent patellar dislocation provides outcomes as good as the isolated anatomical MPFL reconstruction in patients with no trochlear dysplasia up to those with trochlear dysplasia type A and B at the 2-5 years follow-up.

LEVEL OF EVIDENCE

Level IV.

Dynamic-Anatomical Reconstruction of Medial Patellofemoral Ligament in Open Physis

Patellar dislocation is a common knee problem, 10 times more frequent in childhood and adolescence. Medial patellofemoral ligament is injured up to 94% of the time, and its reconstruction is effective in terms of stabilization of the patella. However, distal femoral physis can be damaged with different techniques of reconstruction, due to the location of the femoral footprint. The purpose of this Technical Note is to describe a quasi-anatomical and dynamic reconstruction of the medial patellofemoral ligament, using no tunnel in the femur, passing the graft behind the adductor tendon, and fixing it with one tunnel in the patella and one passage through the quadriceps tendon.