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

Analysis of failed surgery for patellar instability in children with open growth plates

PURPOSE

Many surgical procedures have been proposed to treat recurrent patellar dislocation in children. In recent years, a more tailored approach considering the underlying pathology has been advocated. The aim of the study was to analyze a group of patients with recurrent patellofemoral instability after unsuccessful operative stabilization (Roux-Goldthwait procedure, lateral release, medial reefing or in combination) in childhood and adolescence.

METHODS

A total of 37 children and adolescents with recurrent patellofemoral instability despite previous surgery were analyzed retrospectively. Radiographic examination included AP and lateral views to assess patella alta and limb alignment. MRI was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TTTG) distance. As a control group, 23 age- and sex-matched adolescents that were treated with a favorable outcome after medial reefing alone or combined with a Roux-Goldthwait procedure were analyzed.

RESULTS

Severe trochlear dysplasia (type B-D according to Dejour) as detected on MRI scans was found significantly more often in the study group (89%) than in the control group (21%). No statistical difference of patellar height ratio (Insall-Salvati index) and TTTG distance between the two groups could be found.

CONCLUSION

Of the measured parameters, only the incidence of trochlear dysplasia was increased. Trochlear dysplasia therefore seems to be a major risk factor for failure of operative stabilization of recurrent patellofemoral instability in children and adolescents. The results in children are in consensus with the literature in adults that a more tailored operative therapy including reconstruction of the MPFL and trochleaplasty has to be considered.

LEVEL OF EVIDENCE

Retrospective study, Level III.

Reconstruction of the medial patello-femoral and patello-tibial ligaments for treatment of patellar instability

PURPOSE

The importance of the medial patello-femoral (MPFL) and medial patello-tibial ligaments (MPTL) to the stability of the patella is undoubted. The purpose of this work was to present a technique for the reconstruction of both ligaments and prospectively record its outcome.

METHODS

Cadaveric part: the MPFL and MPTL were identified in five knee specimens. Sequential cutting and reattaching of these ligaments were performed to study their effect on patellar stability. CLINICAL PART: In the years between 2005 and 2008, twenty-five knees in twenty-one patients had reconstruction of their MPFL and MPTL using the semitendinosus tendon. In eight of these knees, ligament reconstruction was combined with tibial tubercle osteotomy. The IKDC and Insall's classification of outcome were used for the evaluation of all knees.

RESULTS

Cadaveric study revealed that resecting the MPTL increased the lateral translation of the patella up to subluxation at full extension. Intact MPFL avoids full dislocation. Regarding the clinical study, at a minimum 24-months follow-up, all patients reported to have stable patello-femoral joints. There was a significant improvement of the IKDC score 54 ± 2 pre-operatively to 81 ± 2 (Mean ± SD) at 24 months post-operative (P < 0.0003). Nineteen knees scored excellent, five were good and one had fair result.

CONCLUSION

A technique for the reconstruction of the MPFL and MPTL that can be performed through minimally invasive approach has been presented and shown to be successful in restoring knee function in cases of traumatic and recurrent patellar dislocation.

LEVEL OF EVIDENCE

III.

Effects of medial patellofemoral ligament reconstruction on patellar tracking

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction has been performed to treat recurrent patellar dislocation. However, the effects on patellar tracking have not been well documented, particularly in patients. The purpose of this study is to compare patellar tracking pattern and chondral status at MPFL reconstruction with those at second-look arthroscopy.

METHODS

Between 1999 and 2008, 71 patients with recurrent patellar dislocation underwent MPFL reconstruction using a double-looped semitendinosus tendon. Of these, 25 knees in 24 patients underwent second-look arthroscopy (at 6-26 months after initial surgery), forming the subject for the present study. No other surgical procedures such as tibial tuberosity transfer, lateral release, or osteotomy were performed in any patients. To assess the patellar tracking pattern, the position of the patella on femoral groove was evaluated arthroscopically during passive knee motion through lateral suprapatellar portal.

RESULTS

Before MPFL reconstruction, the patella in all patients was shifted laterally throughout the entire range of knee motion. Immediately after MPFL reconstruction, patellar malalignment was corrected in all cases. On second-look arthroscopy, two different patellar tracking patterns were observed. In 9 knees, the patella was located on the center of the femoral groove throughout the range of motion. Meanwhile, in the remaining 16 knees, the patella was shifted laterally at knee extension and migrated to the center of femoral groove with increased knee flexion. No significant deteriorations in chondral status were seen on second-look arthroscopy.

CONCLUSION

The present study revealed that not all improved patellar trackings after MPFL reconstruction remained intact at follow-up. Chondral status in patellofemoral joint was not aggravated by MPFL reconstruction.

LEVEL OF EVIDENCE

Therapeutic studies, Level IV.

Medial patella retinaculum plasty for treatment of habitual patellar dislocation in adolescents

PURPOSE

The surgical technique, medial patellar retinaculum plasty, can almost restore both static and dynamic stability and verge on anatomical repair for the treatment of habitual patellar dislocation in adolescents.

METHODS

In accordance with the injury patterns of the medial patellar retinaculum through knee MRI, we repaired different injury sites with this surgical procedure. We reviewed this technique in 16 patients with an average age of 15 years. Retrospective review of charts and radiographs immediately after the surgery up to the latest follow-up (range 12-36 months) was undertaken.

RESULTS

All patients were evaluated clinically and radiologically over an average of 20.7 months. The recovery of knee mobility results were good. No recurrence of patellar instability has been found.

CONCLUSION

We think this could be a valid technique to treat habitual patellar dislocation in adolescents.

Observer agreement on the Dejour trochlear dysplasia classification: a comparison of true lateral radiographs and axial magnetic resonance images

BACKGROUND

Trochlear dysplasia is known to be an important cause of patellofemoral instability. D. Dejour's radiographic and magnetic resonance imaging (MRI) classifications are widely used in clinical practice and in the orthopaedic literature to assess the severity of trochlear dysplasia. The indication for deepening trochleoplasty to treat trochlear dysplasia is also mainly based on the severity of trochlear dysplasia according to Dejour's criteria.

PURPOSE

To our knowledge, there is no study evaluating the efficacy of the Dejour classification. The aim of this study was to assess the intraobserver and interobserver agreements of the radiographic and MRI-based classification as described by Dejour.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

From 50 patients, 50 lateral radiographs as well as 50 MRI scans were read twice independently within 4 weeks by 4 surgeons (2 senior and 2 junior examiners). Analysis was made according to Dejour's 4 grades of radiological criteria of trochlear dysplasia as well as differentiating between 2 grades: low-grade (type A) and high-grade trochlear dysplasia (types B-D).

RESULTS

The 4-grade analysis showed fair intraobserver and interobserver agreements (24%-78%), while the 2-grade analysis showed good to excellent agreement (56%-96%). The best overall agreement was found for the 2-grade analysis on MRI scans (62%-96%). The lateral radiographs tended to underestimate the severity of trochlear dysplasia compared with axial MRI.

CONCLUSION

D. Dejour's classification is valid for typing trochlear dysplasia and is particularly useful in separating low-grade from high-grade dysplasia.

Non-anatomic proximal realignment for recurrent patellar dislocation does not sufficiently prevent redislocation

Several operative techniques have been described for recurrent patellar dislocation. Clinical results vary depending on the procedure and indication. The present study aimed to evaluate the clinical outcome of Insall's proximal realignment for recurrent patellar dislocation at mid-term follow-up. Forty-five patients were reviewed with a mean follow-up period of 49 months after having undergone Insall's procedure. Outcome measures included reports of redislocations, complications, patient-reported outcome scores (Kujala, Tegner activity scale) and subjective assessment. No statistically significant improvements (p < 0.05) in patient-reported outcome measures were noted. Sixteen patients (35%) had poor to fair results using the Kujala score. Subjective assessment revealed that 12 patients (27%) were dissatisfied with the outcome of their surgery and would not undergo the same procedure. Ten patients (22%) had suffered from redislocation at the latest follow-up. In 4 cases (9%), intra-articular knee hematoma occurred which required arthroscopic intervention. The overall mid-term outcome of the present study shows low patient satisfaction. Non-anatomic realignment for recurrent patellar dislocation does not adequately prevent redislocation.

Magnetic resonance imaging of acute patellar dislocation in children: patterns of injury and risk factors for recurrence

BACKGROUND

Acute patellar dislocation is a common traumatic condition of the knee seen in the active adolescent. The patterns of injury to the ligamentous and chondral surfaces following dislocation have not been well defined in the pediatric population. The purpose of this study was to characterize the patterns of medial patellofemoral ligament (MPFL), vastus medialis obliqus (VMO), and osteochondral injury on magnetic resonance imaging (MRI) following first-time acute lateral patellar dislocation in pediatric patients.

METHODS

Following approval by the Institutional Review Board, a radiology query was performed to identify all patients between the ages of 11 and 18 years who underwent MRI following an acute first-time patellar dislocation over a 10-year period. The presence and location of injury to the MPFL, VMO, and chondral surfaces were evaluated on MRI images. A retrospective review of the patient's chart was conducted to confirm that clinical history was consistent with an acute patellar dislocation. Demographic data, including age at the time of injury, sex, knee affected, mechanism of injury, and recurrence of dislocation, were retrieved from the chart. The data were analyzed as a single cohort.

RESULTS

One hundred and eleven patients, including 56 males and 46 females with a mean age of 14.9 years (range, 11 to 18 y), were included. MRI demonstrated MPFL injury in 87 patients (78.4%). MPFL injury was present at an isolated patellar insertion in 34 patients (31%) and an isolated femoral insertion in 16 patients (14%). MPFL injury at more than one location was present in 37 patients (33%). VMO edema was present in 62 patients (56%), consistent with sprain or tear. Osteochondral fracture was identified in 38 knees (34%), with 25 from the medial patellar facet, 5 from the lateral femoral condyle, and 8 from both locations.

CONCLUSIONS

Acute patellar dislocations remain a common injury in pediatric patients. The pattern of injury to the MPFL and VMO on MRI has not been described in a pediatric population. The triad of injury to the MPFL, VMO, and chondral surfaces should be recognized and understood, particularly when surgical reconstruction is necessary.

LEVEL OF EVIDENCE

Level III.

Development of femoral trochlear groove in growing rabbit after patellar instability

PURPOSE

The geometry of an articular surface is an important determinant of joint function. Although the geometry of the trochlear groove is considered to be important in the pathogenesis of patellofemoral joint disorders, the effects of the patella during the development of the femoral trochlear groove are unclear. This animal study aimed to investigate the relationship between the position of the patella and development of femoral trochlear groove in growing rabbits.

METHODS

Twenty-four knees of 12 rabbits were included in this study and were divided into two groups. First group consisted of the left knees and was used as the control group to which no surgical procedures were applied. Second group involved the right knees to which medial soft tissue restraints release was applied before 1 month of age. Computed tomographic (CT) evaluation of both knees of each rabbit was made in their first month of age before medial retinacular release and also during post-op 1-year follow-up. CT measurements included both the angle and depth of the femoral trochlear groove from 3 different parts (proximal, middle and distal) of the distal femur, and then these measurements were averaged.

RESULTS

Measurements revealed that while in the control group the groove angle decreased 27.4 degrees and the depth increased 0.11 mm, in the operated counterparts groove angle decreased 16.8 degrees and groove depth increased 0.03 mm, which indicated the flattening of the femoral groove in the operated group. These differences were found to be statistically significant (P < 0.05).

CONCLUSION

The results indicated that distal femoral groove with inadequate patellar position becomes more flattened and causes predisposition for patellar instability. Consequently, the clinical relevance of this study was that early reconstruction of the patellofemoral joint should be performed in the childhood to prevent the patellofemoral problems that are likely to be encountered in the following years.

MRI but not arthroscopy accurately diagnoses femoral MPFL injury in first-time patellar dislocations

PURPOSE

The purpose of this study was to investigate whether the femoral part of the medial patellofemoral ligament (MPFL) and its injury can be accurately assessed by standard knee arthroscopy in first-time patellar dislocations or whether preoperative MRI is required to determine injury location in patients where primary MPFL repair is attempted.

METHODS

Twelve patients with acute first-time dislocations and MRI-based injury of the femoral MPFL and ten patients with recurrent patellar dislocations underwent knee arthroscopy with the use of a 30-degree optic and standard antero-medial and antero-lateral portals. The femoral origin was marked with a cannula under lateral fluoroscopy. Arthroscopic findings of the location of the native femoral MPFL and its injury were compared to the results of MRI and mini-open exploration.

RESULTS

In acute cases, the average time from primary patellar dislocation to MRI evaluation was 3 days (1-9 days), and the average time from MRI to surgery was 8 days (3-20 days). The native femoral origin of the MPFL was not visible in any of the chronic cases during arthroscopy. In addition, in all acute cases, arthroscopy failed to directly visualize injury of the femoral MPFL (0 of 12), but mini-open exploration confirmed injury in 11 of 12 patients. This means that arthroscopy was less accurate than MRI for the diagnosis of femoral MPFL injury (P < 0.05).

CONCLUSION

The results of this study indicate the limitations of knee arthroscopy in identifying the femoral disruption of the MPFL, a crucial injury that occurs in patellar dislocations. Thus, if a primary MPFL repair is planned, determination of the site of repair should be based on the preoperative MRI.

LEVEL OF EVIDENCE

Diagnostic study of non-consecutive patients, Level III.

Arthroscopic patellar reinsertion of the MPFL in acute patellar dislocations

PURPOSE

The objective of this study was to evaluate the mid-term results of a new technique for the arthroscopic repair of MPFL after an acute patellar dislocation (APD).

MATERIALS

The series included 17 patients (11 men and 6 women) with a first episode of acute patellar dislocation; treated over a period of 6 years. Re-dislocation, subjective symptoms and functional limitations were evaluated at an average follow-up of 2.2 years (1-5.5). The patients were evaluated with the Lysholm and the Kujala scoring systems.

RESULTS

At follow-up, no re-dislocation was reported. Only one patient referred an episode of patellar instability, without a distinct dislocation. The postoperative median Lysholm score was 90 (72-100). The median Kujala score was 92 (75-100). Fourteen out of 17 patients were able to return to sports at the same level as before.

CONCLUSION

When the MPFL is avulsed from the patella, the proposed technique has the advantage of restoring tension of the ligament through reattachment at the patellar border with two trans-patellar sutures. The full-arthroscopic approach has the advantage of being less invasive and having a shorter recovery time.

The role of trochlear dysplasia in patellofemoral instability

Trochlear dysplasia is characterized by abnormal trochlear morphology and a shallow groove. It is associated with recurrent patellar dislocation, but it is unclear whether the dysplasia is congenital, the result of lateral tracking and chronic instability, or caused by a combination of factors. Lateral radiographs elucidate the crossing sign and characteristic trochlear prominence. Recurrent patellofemoral instability is multifactorial, and each component must be considered in determining treatment. Managing other factors associated with recurrent instability may compensate for a deficient trochlea and provide stability. Medial patellofemoral ligament reconstruction is recommended for patellofemoral instability in the presence of trochlear dysplasia in patients without patella alta or increased tibial tubercle-trochlear groove distance. Trochleoplasty should be reserved for severe dysplasia in which patellofemoral stability cannot otherwise be obtained.

Patellar dislocations in children, adolescents and adults: a comparative MRI study of medial patellofemoral ligament injury patterns and trochlear groove anatomy

PURPOSE

The first aim was to compare medial patellofemoral ligament injury patterns in children and adolescents after first-time lateral patellar dislocations with the injury patterns in adults. The second aim was to evaluate the trochlear groove anatomy at different developmental stages of the growing knee joint.

MATERIALS AND METHODS

Knee magnetic resonance (MR) images were collected from 22 patients after first-time patellar dislocations. The patients were aged 14.2 years (a range of 11-15 years). The injury pattern of the medial patellofemoral ligament was analysed, and trochlear dysplasia was evaluated with regard to sulcus angle, trochlear depth and trochlear asymmetry. The control data consisted of MR images from 21 adult patients who were treated for first-time lateral patellar dislocation.

RESULTS

After patellar dislocation, injury to the medial patellofemoral ligament was found in 90.2% of the children and in 100% of the adult patients. Injury patterns of the medial patellofemoral ligament were similar between the study group and the control group with regard to injury at the patellar attachment site (Type I), to the midsubstance (Type II) and to injury at the femoral origin (Type III) (all p>0.05). Combined lesions (Type IV) were significantly less frequently observed in adults when compared to the study group (p=0.02). The magnitude of trochlear dysplasia was similar in children, adolescents and adults with regard to all three of the measured parameter-values (all p>0.05). In addition, the articular cartilage had a significant effect on the distal femur geometry in both paediatrics and adults.

CONCLUSION

First, the data from our study indicated that the paediatric medial patellofemoral ligament injury patterns, as seen on MR images, were similar to those in adults. Second, the trochlear groove anatomy and the magnitude of trochlear dysplasia, respectively, did not differ between adults and paediatrics with patellar instability. Thus, physicians are confronted with similar anatomical risk factors and similar injuries to the medial soft-tissue restraints in children when compared to adults with patellar instability.