MR IMAGING OF THE PATELLOFEMORAL COMPARTMENT

Medial patellar retinaculum plasty versus medial capsule reefing for patellar dislocation in children and adolescents

INTRODUCTION

The purpose of this study was to evaluate the clinical effect of medial patellar retinaculum plasty for children and adolescent patients with patellar dislocation.

MATERIALS AND METHODS

A prospective study was performed between October 2005 and December 2009. Sixty-one cases of children and adolescent patients with patellar dislocation were admitted to our study. Twenty-nine patients received medial capsule reefing, of which 13 patients also received lateral retinacular release (LRR) (Group I). Thirty-two patients received medial patellar retinaculum plasty, of which 12 patients also received LRR (Group II). Preoperatively, all patients received magnetic resonance imaging (MRI) to evaluate the injury of medial patellofemoral ligament. And all patients received computed tomography (CT) scans on which the congruence angle (CA) and patellar lateral shift (PLS) could be evaluated with 30° knee flexion. Physical apprehension tests were examined and the redislocation was recorded. In addition, knee function was evaluated using the Kujala score and subjective questionnaires.

RESULTS

Patients were followed up for a mean period of 50 months (25-75 months). For the comparison between the preoperative and postoperative results, the Kujala score improved significantly from 52.3 ± 2.9 to 78.1 ± 3.6 in Group I and from 53.5 ± 3.4 to 82.2 ± 3.4 in Group II (P < 0.05). There was significant difference of CA on CT scans and PLS with a statistical difference between the two groups (P < 0.05). Results of the apprehension test showed that nine patients had patellar lateral shift exceeding 1.5 cm with a soft end point in Group I and two patients had patellar lateral shift exceeding 1.5 cm with a hard end point in Group II (P < 0.05). Moreover, the subjective questionnaire revealed a significant difference of subjective effects between two groups (P < 0.05), including 7 excellent, 10 good and 12 fair in Group I and 18 excellent, 9 good, and 5 fair in Group II.

CONCLUSION

The medial retinaculum plasty was better than medial capsule reefing in improving the subjective effects and decreasing the rate of patellar instability postoperatively in children and adolescent patients.

Magnetic resonance imaging characteristics of the medial patellofemoral ligament lesion in acute lateral patellar dislocations considering trochlear dysplasia, patella alta, and tibial tuberosity-trochlear groove distance

PURPOSE

The objective of this study was to analyze the injury patterns of the medial patellofemoral ligament (MPFL) in acute lateral patellar dislocations (LPDs) considering the anatomically relevant factors of patellar instability.

METHODS

Knee magnetic resonance images were collected from 73 patients within 7 weeks after LPD, and the injury patterns of the MPFL were evaluated for trochlear dysplasia, for patellar height, and for the tibial tuberosity-trochlear groove (TT-TG) distance.

RESULTS

Injury to the MPFL was found in 98.6% of the patients (72 of 73) after the acute LPD, with a complete tear in 51.4% (37 of 72), most frequently localized at the femoral attachment site, and a partial tear in 48.6% (35 of 72). Injury to the femoral origin (Fem), to the midsubstance (Mid), and to the patellar insertion (Pat) of the MPFL was found in 50.0% (36 of 72), 13.9% (10 of 72), and 13.9% (10 of 72), respectively. More than 1 site of injury was found in 22.2% (16 of 72), most frequently as a combined injury at the femoral origin and at the patellar insertion sites (Pat+Fem) (13 of 16). The study population, as well as the Pat, Fem, and Pat+Fem subgroups, showed significantly different values of trochlear dysplasia and patellar height when compared with the control group, whereas the data of the Mid group were not significantly different. In addition, injury at the patellar insertion (Pat) was accompanied by a significantly increased TT-TG distance when compared not only with the control group but also with the Fem, Mid, and Pat+Fem groups.

CONCLUSIONS

The data from our study indicate that patterns of MPFL injury depend on trochlear dysplasia, patellar height, and TT-TG distance. They show a new aspect in the complex interplay between active, passive, and static stabilizers of the patellofemoral joint.

LEVEL OF EVIDENCE

Level IV, diagnostic case-control study.

Grading articular cartilage of the knee using fast spin-echo proton density-weighted MR imaging without fat suppression

OBJECTIVE

The objective of this work was to determine the accuracy of fast spin-echo proton density-weighted MR imaging in the evaluation of the articular cartilage of the knee using arthroscopy as a gold standard.

MATERIALS AND METHODS

We retrospectively reviewed MR images of the knee in 54 patients for whom arthroscopic results were available. All MR imaging studies included fast spin-echo proton density-weighted coronal and axial sequences as part of our routine protocol. Evaluation of the articular surfaces was performed by three independent observers who were unaware of the arthroscopic results. The cartilage surfaces were graded using a 3-point system, and results were compared with arthroscopic findings.

RESULTS

Of 324 cartilage surfaces evaluated, arthroscopy showed 241 surfaces as normal, 56 as containing partial-thickness defects, and 27 as containing full-thickness defects. Compared with arthroscopic data, sensitivity of MR imaging for the three reviewers was 59-73.5%; specificity, 86.7-90.5%; positive predictive value, 60.5-72.6%; negative predictive value, 86.0-90.8%; and accuracy, 79.6-86.1%. Interobserver variability for the presence of disease, which was measured using the kappa statistic, was 0.63.

CONCLUSION

Fast spin-echo proton density-weighted MR imaging sequences can be used to evaluate the cartilage of the knee with accuracy comparable to that of previously reported cartilage-specific sequences.

Comprometimento ósseo do joelho pós-trauma: avaliação pela ressonância magnética

Neste trabalho são apresentados 50 casos de trauma do joelho submetidos a ressonância magnética, no período de janeiro de 1996 a dezembro de 1997. Foram avaliados o aspecto e a incidência das principais alterações ósseas, correlacionando-as com os mecanismos de agressão e com os dados clínicos, e demonstrando as principais lesões associadas. As contusões ósseas foram os achados mais comuns, sendo encontradas em 38 indivíduos (76%). As fraturas osteocondrais ocorreram em cinco pacientes (10%). As fraturas ósseas foram detectadas em cinco casos (10%), sendo três deles associados a contusão de outros compartimentos ósseos adjacentes. A condromalácia da patela mostrou-se presente em apenas dois indivíduos (4%). Concluímos que a ressonância magnética é o método de escolha no estudo por imagem para o diagnóstico das lesões ósseas no trauma do joelho.

Nondestructive imaging of human cartilage glycosaminoglycan concentration by MRI

Despite the compelling need mandated by the prevalence and morbidity of degenerative cartilage diseases, it is extremely difficult to study disease progression and therapeutic efficacy, either in vitro or in vivo (clinically). This is partly because no techniques have been available for nondestructively visualizing the distribution of functionally important macromolecules in living cartilage. Here we describe and validate a technique to image the glycosaminoglycan concentration ([GAG]) of human cartilage nondestructively by magnetic resonance imaging (MRI). The technique is based on the premise that the negatively charged contrast agent gadolinium diethylene triamine pentaacetic acid (Gd(DTPA)2-) will distribute in cartilage in inverse relation to the negatively charged GAG concentration. Nuclear magnetic resonance spectroscopy studies of cartilage explants demonstrated that there was an approximately linear relationship between T1 (in the presence of Gd(DTPA)2-) and [GAG] over a large range of [GAG]. Furthermore, there was a strong agreement between the [GAG] calculated from [Gd(DTPA)2-] and the actual [GAG] determined from the validated methods of calculations from [Na+] and the biochemical DMMB assay. Spatial distributions of GAG were easily observed in T1-weighted and T1-calculated MRI studies of intact human joints, with good histological correlation. Furthermore, in vivo clinical images of T1 in the presence of Gd(DTPA)2- (i.e., GAG distribution) correlated well with the validated ex vivo results after total knee replacement surgery, showing that it is feasible to monitor GAG distribution in vivo. This approach gives us the opportunity to image directly the concentration of GAG, a major and critically important macromolecule in human cartilage.