Anatomy of patellar dislocation

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.

Cross-cultural adaptation and validation of the Italian versions of the Kujala, Larsen, Lysholm and Fulkerson scores in patients with patellofemoral disorders

BACKGROUND

The Kujala, Fulkerson, Larsen and Lysholm questionnaires have been demonstrated to be reliable and sensitive in assessing patients with patellofemoral pathology. The purpose of this study is to translate and cross-culturally adapt into Italian the English versions of the Kujala, Fulkerson, Larsen and Lysholm questionnaires, and undertake reliability and validity evaluations of the Italian versions of these scores in patients with patellofemoral pathology.

MATERIALS AND METHODS

The cross-cultural adaptation process was carried out following the simplified Guillemin criteria. The questionnaires were administered to 63 patients with either patellar instability or painful patella syndrome. To assess the validity of the questionnaires, they were compared with the Oxford knee score. The questionnaires were administered to a subsample of 33 patients 5 days later to assess test-retest reliability.

RESULTS

The interclass coefficient correlation was 0.96 for the Kujala score, 0.92 for the Larsen score, 0.96 for the Lysholm score, 0.94 for the Fulkerson score (P < 0.01), and 0.83 for the Oxford score. Pearson's correlation was0.96 between the Kujala and Oxford scores, 0.90 between the Larsen and Oxford scores, 0.94 between the Lysholm and Oxford score, and 0.93 between the Fulkerson and Oxford scores. Responsiveness, calculated by standardized response mean, was 1.2, and effect size was 1.4.

CONCLUSIONS

The Italian versions of the Kujala, Larsen, Lysholm and Fulkerson scoring systems were shown to be equivalent to their English versions and demonstrated good validity, reliability and responsiveness to surgical treatment of patellofemoral pathology. To the best of the authors' knowledge, this is the first attempt to adapt four of the most common patellofemoral-specific scoring scales to the Italian language.

LEVEL OF EVIDENCE

Level II.

Patellar position in patients with patellofemoral syndrome as characterized by anatomo-radiographic study

Objectives

To determine the prevalence of high patella in adult patients with knee pain, and to correlate patellar height with symptoms of patellar instability, episode of patellofemoral dislocation and anterior pain in the knee; and also verify the concordance correlation between the Insall-Salvati and Caton-Deschamps indices.

Method

Cross-sectional study analyzing the medical records of patients with knee pain, using lateral view knee radiographs with 30° degrees of flexion and computed tomography. The values of the Insall-Salvati index and the Caton-Deschamps index were used to determine the patellar height.

Results

A total of 756 records were analyzed, resulting in 140 knees studied, 39% men and 61% women. Both indices produced statistically significant associations for the occurrence of high patella and signs of instability and episodes of dislocation, but there was no significant association for anterior knee pain. The Kappa index obtained when analyzing the concordance correlation between the Insall-Salvati index and Caton-Deschamps index points to a regular association between them.

Conclusion

Patients with high patella present a higher prevalence of instability. Having a high patella has no significant relationship with the presence of anterior knee pain. The Insall-Salvati and Caton-Deschamps indices demonstrate a regular agreement on the presentation of patellar heights results.

When and How Far to Move the Tibial Tuberosity in Patients With Patellar Instability

The many factors contributing to patellar instability have led to various surgical techniques that are used commonly today. When surgery is deemed necessary, the operation should be tailored to the patient's specific pathoanatomy. Patients with malalignment can often be stabilized by moving the tibial tuberosity to a more medial, anteromedial, or distal position. Subsequent changes in the forces acting on the patellofemoral joint will depend on the direction and distance of the tuberosity repositioning. When planning tuberosity osteotomies, it is crucial to understand how to use clinical and imaging modalities to measure and quantify tuberosity position accurately to achieve the desired degree of realignment.

[Reconstruction of the medial patellofemoral ligament after lower-leg amputation]

The reconstruction of the medial patellofemoral ligament has been an increasingly popular approach for patellar instability over the last ten years. It is a conglomeration of symptoms with varying degree of severity. For pinpointed surgery planning, magnetic resonance imaging is now the obligate diagnosic tool. Therefore, in the preoperative stage, collateral pathology can be observed.

An anatomic study of the lateral patellofemoral ligament

Objective

The lateral patellofemoral ligament (LPFL) is part of the lateral retinaculum cut during arthroscopic or open release. We investigated its anatomic and morphometric characteristics.

Materials and methods

We identified the LPFL insertion point on the condyle in vertical and sagittal planes in 32 adult cadaveric knees. We measured its length and width at the insertion point. We located the midpoint of this point and measured from it to the distal and posterior condylar ends. We measured anterior-posterior and proximal-distal lateral condylar lengths. We evaluated the insertion point shape on the lateral femoral condyle. Degree of relationship between variables was assessed using Pearson's correlation coefficient. p < 0.05 was considered statistically significant.

Results

The LPFL mean length was 23.2 mm, and mean width at the insertion point was 15.6 mm. Regarding its insertion into the lateral condyle, central insertions were more frequent (vertical plane: 53.1% central and sagittal plane: 75% central). A significant positive correlation was evident between the LPFL length and width at the insertion point (p = 0.05). Thus, the LPFL length was proportional to its width at the insertion point. A significant positive correlation was found between the anterior-posterior condylar length and width of the LPFL at the insertion point (p = 0.017). Therefore, greater anterior-posterior condylar length equates to a larger area of insertion on the condyle.

Conclusion

Greater width of the LPFL at the insertion point corresponds to greater LPFL and anterior-posterior lateral condylar lengths.

Medial patellofemoral ligament reconstruction in patellar instability

BACKGROUND

Medial patellofemoral ligament (MPFL) is one of the major static medial stabilising structures of the patella. MPFL is most often damaged in patients with patellar instability. Reconstruction of MPFL is becoming a common surgical procedure in treating patellar instability. We hypothesised that MPFL reconstruction was adequate to treat patients with patellar instability if the tibial tubercle and the centre of the trochlear groove (TT-TG) value was less than 20 mm and without a dysplastic trochlea.

MATERIALS AND METHODS

30 patients matching our inclusion criteria and operated between April 2009 and May 2011 were included in the study. MPFL reconstruction was performed using gracilis tendon fixed with endobutton on the patellar side and bio absorbable interference screw or staple on the femoral side. Patients were followed up with subjective criteria, Kujala score and Lysholm score.

RESULTS

The mean duration of followup was 25 months (range 14-38 months). The mean preoperative Kujala score was 47.5 and Lysholm score was 44.7. The mean postoperative Kujala score was 87 and Lysholm score was 88.06. None of the patients had redislocation.

CONCLUSION

MPFL reconstruction using gracilis tendon gives excellent results in patients with patellar instability with no redislocations. Some patients may have persistence of apprehension.

Technical failure of medial patellofemoral ligament reconstruction

In patients with chronic patellofemoral instability who have normal alignment and deficient proximal medial restraints, medial patellofemoral ligament (MPFL) reconstruction is a good option to treat patellar instability. However, medial subluxation, medial patellofemoral articular overload, and recurrent lateral instability are possible when the graft is positioned non-anatomically. The clinical presentation of MPFL femoral tunnel malpositioning has not been highlighted in the literature. We have had 5 patients referred to us after a malpositioned femoral MPFL graft led to disabling symptoms and a need for revision surgery. This report highlights the effects of a malpositioned graft and describes strategies to identify the anatomic MPFL insertion during surgery.

The relationship between trochlear dysplasia and medial patellofemoral ligament rupture location after patellar dislocation: an MRI evaluation

The medial patellofemoral ligament (MPFL) and the native trochlear geometry represent two of the most critical components of patellofemoral stability. We sought to define the relationship between trochlear dysplasia and MPFL rupture location in patients with documented patellar dislocations. We hypothesized that patients with lower grades of trochlear dysplasia would have patellar based MPFL ruptures, while patients with higher grade dysplasia would have femoral-sided ruptures. We reviewed post-injury MRIs of 59 patients with documented patella dislocation. Information gathered included: type of trochlear dysplasia in the axial plane MRI, location of MPFL rupture, patellar height ratio, tibial tuberosity to trochlear groove distance (TTTG), number of dislocations prior to MRI, and time between the latest patella dislocation and the MRI. Statistical calculations utilized the Chi-Square-Test. We classified 11 cases as a dysplasia type A, 35 as a type B, 11 as a type C, and 2 cases as a trochlear dysplasia type D. In 7 patients (12%) the MPFL rupture was patella based, in 18 patients (31%) intra-ligamentous, in 33 cases (56%) femoral sided and in one case no MPFL could be identified. In contrast to our original hypothesis, the type of trochlear dysplasia does not appear to be related to the rupture location of the MPFL after patellar dislocation. According to our results, it is not possible to presume the location of the MPFL rupture based on assessment of the trochlear morphology. Therefore, a MRI is mandatory for final indication of any surgery.

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.

[The medial patellofemoral ligament: function, injury, and treatment]

The medial patellofemoral ligament or MPFL is the prime soft tissue stabilizer of the patella. The MPFL is a non-isometric ligament lying in the second fascial layer of the knee; it is tight in extension and lax in flexion. The ligament is always torn in acute patellar dislocations. As "form follows function" we believe that the MPFL should be reconstructed in such a way that it stabilizes the patella without changing its movement pattern.

The management of recurrent patellar dislocation

Acute and chronic trauma, chronic abnormal joint loading conditions, and hemarthroses have been implicated in the development of degenerative joint disease. Patellar instability with acute and recurrent patellar dislocation provides all of these ingredients. This article describes an approach to the treatment of recurrent patellar instability that considers the unique features and expectations of the patient rather than using a generic algorithm.

Long-term follow-up and knee osteoarthritis change after medial patellofemoral ligament reconstruction for recurrent patellar dislocation

BACKGROUND

Proximal or distal realignment procedures have long been selected as treatment for recurrent patellar dislocation, but associated knee osteoarthritis has been a substantial problem that leads to poor results. A new approach, medial patellofemoral ligament reconstruction, has recently started, but there have been no reports on the long-term follow-up.

HYPOTHESIS

Anatomical medial patellofemoral ligament reconstruction can lead to satisfactory long-term outcome and a low association rate of knee osteoarthritis.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-four knees from 22 patients who underwent medial patellofemoral ligament reconstruction for recurrent patellar dislocation were reviewed at a mean follow-up of 11.9 years (range, 8.5-17.2 years). A lateral release was done on 14 of 24 knees. The clinical/physical outcome and the association of knee osteoarthritis were investigated. Patellofemoral and femorotibial osteoarthritis on the radiographs was evaluated using the Crosby/Insall and the Kellgren/Lawrence grading systems.

RESULTS

According to the Crosby/Insall criteria, 11 knees (46%) were classified as excellent, 10 (42%) as good, 3 (12%) as fair/poor, and none as worse at follow-up. Further lateral subluxation or dislocation occurred in only 2 knees. The mean Kujala score improved significantly from 63.2 points preoperatively to 94.2 points at follow-up (P < .0001). According to the Crosby/Insall grading system, patellofemoral osteoarthritis was none to mild in 23 of the 24 knees and moderate in 1 knee, pre-operatively. At the final follow-up, 21 knees were none to mild, and 3 knees were moderate. There were only 2 knees that had definite progression from none to mild to a moderate grade.

CONCLUSION

The association of definite knee osteoarthritis in medial patellofemoral ligament reconstruction with or without lateral release was small in the long-term follow-up. The conclusion is that medial patellofemoral ligament reconstruction not only prevents further patellar dislocation but also shows no or only slight progression of knee osteoarthritis.

Generalized joint laxity and contralateral patellar hypermobility in unilateral recurrent patellar dislocators

PURPOSE

The purpose of this study was to assess the relation between generalized joint laxity and patellar hypermobility in unilateral recurrent patellar dislocators.

TYPE OF STUDY

Case series.

METHODS

A total of 82 patients (23 male and 59 female patients) with unilateral recurrent patellar dislocation were studied compared with an age- and sex-matched control group. The modified Carter and Wilkinson criteria for generalized joint laxity and lateral patellar hypermobility test were examined.

RESULTS

Generalized joint laxity (score of 4 or 5) was present in 20 patients (24%) with recurrent patellar dislocation in 8 subjects (10%) of the control group. The mean total score was 2.5 (SD, 1.4) in the recurrent patellar dislocators and 1.7 (SD, 1.3) in the control group. The incidence of generalized joint laxity (P = .013) and the mean total score (P = .00004) were statistically significant between the two groups. A hypermobile patella was present in 42 patients (51%) and in 5 subjects (6%) of the control group. There was a large statistically significant difference between the two groups (P < .00001).

CONCLUSIONS

Although a hypermobile patella and generalized joint laxity were significant between the recurrent patellar dislocators and the control group, a hypermobile patella was more significant than generalized joint laxity as the predisposing factors of patellar dislocation.

LEVEL OF EVIDENCE

Level IV, prognostic case series.

Hybrid medial patellofemoral ligament reconstruction using the semitendinous tendon for recurrent patellar dislocation: minimum 3 years' follow-up

PURPOSE

The purpose of this study was to evaluate the results of a new hybrid medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar dislocation.

METHODS

Hybrid MPFL reconstruction by use of the semitendinous tendon was performed in 12 knees with recurrent patellar dislocation. The results were evaluated at a minimum follow-up of 3 years (mean, 4.2 years).

RESULTS

According to the grading system of Insall et al., the results were classified as excellent in 8 knees (66%), good in 2 (17%), and fair in 2 (17%), with none being classified as poor. The mean Kujala score was 56.3 points (range, 29 to 82) preoperatively and 96.0 points (range, 84 to 100) at follow-up. There were no patients with recurrent dislocation and subluxation. No knees had a positive apprehension sign, and there were no postoperative complications.

CONCLUSIONS

At a midterm follow-up, hybrid MPFL reconstruction by use of the semitendinous tendon for recurrent patellar dislocation should be considered as an effective operation for cases without severe predisposing factors.

LEVEL OF EVIDENCE

Level IV, therapeutic case series, no or historical control group.

Anatomical analysis of the medial patellofemoral ligament of the knee, especially the femoral attachment

The purpose of this study was to investigate the anatomical morphology and measurement of the medial patellofemoral ligament (MPFL), especially the femoral attachment. A total of 20 knee specimens were dissected and the total length, width, thickness, inclination, as well as the attachment points of the MPFL were measured. The MPFL was well-developed in seven knees, moderate in ten knees and wispy in three knees. Total length of the MPFL was 58.8 +/- 4.7 mm. The width and thickness was 12.0 +/- 3.1 mm and 0.44 +/- 0.19 mm at the middle point. The long axis of the MPFL inclined at 15.9 +/- 5.6 degrees proximally. The center of the patellar attachment was located at 27 +/- 10% from the upper end of the patella in the longitudinal patellar height. The femoral attachment was superoposterior to the medial femoral epicondyle and just distal to the adductor tubercle. The center of the anterior edge of the femoral attachment was 9.5 +/- 1.8 mm proximally and 5.0 +/- 1.7 mm posteriorly from the center of the medial femoral epicondyle. The femoral attachment was located at 61 +/- 4% of anteroposterior length of the medial femoral condyle from the anterior edge.

Augmented repair of avulsion-tear type medial patellofemoral ligament injury in acute patellar dislocation

This study investigated the results of augmented repair for avulsion-tear type medial patellofemoral ligament (MPFL) injury performed on a total of five knees with initial acute lateral patellar dislocation. Augmented repair was performed using a medial retinaculum slip on all five knees. The average follow-up was 5.9 years. The results were evaluated with the Insall, Aglietti, and Tria grading system. Three knees were classified as excellent, one knee as good, and one knee as fair. The mean Kujala score at follow-up was 97.6 points. Augmented repair of the injured MPFL for avulsion-type MPFL injury may be considered as one good option to prevent subsequent dislocation and subluxation.

Surgical technique and rationale for medial patellofemoral ligament reconstruction for recurrent patellar dislocation

This article describes a medial patellofemoral ligament (MPFL) reconstruction procedure using an artificial ligament for recurrent patellar dislocation. The MPFL has been shown biomechanically to be the primary restraint among the medial patellar stabilizers. Although various predisposing factors are involved in lateral patellar dislocation, we believe that the MPFL, as a primary restraint, should undergo primary reconstruction for patellar dislocation. The results of MPFL reconstruction using a mesh-type artificial ligament and medial retinaculum slip coverage for recurrent patellar dislocation were as good as we had expected. In this article, we describe the detailed surgical technique and its rationale. We believe technique has also wide applications in MPFL reconstruction using autogenous tendons.

Correlation of MR imaging findings and open exploration of medial patellofemoral ligament injuries in acute patellar dislocations

The purpose of this investigation was to correlate magnetic resonance (MR) images of medial patellofemoral ligament (MPFL) injuries with gross macroscopic findings. Twenty-seven knees with MPFL injury following an initial patellar dislocation were examined using axial proton-density and T2-weighted fast spin-echo MR imaging. MR findings were subsequently correlated with open exploration. MPFL injury was observed in 26 (96%) of the 27 knees. From the MR images, discontinuity, irregularity and/or high-signal intensity changes anterior to the femoral attachment were seen in 13 (82%) of the 16 knees with substantial-tear type injuries of the MPFL. In 8 (80%) of the 10 knees with avulsion-tear type injuries, detachment of the MPFL from the femoral attachment, accompanied with or without high-signal intensity changes, was confirmed. MPFL injury types could be accurately diagnosed on 21 (81%) out of 26 knees using MR imaging. MR imaging was an acceptable method in diagnosing MPFL injury types.