The Anatomy of the Medial Patellofemoral Complex

Double-Limb Graft Versus Single-Limb Graft Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocation: A Meta-analysis of Randomized Controlled Trials and Cohort Studies

BACKGROUND

The medial patellofemoral ligament (MPFL) is the most important stabilizer of lateral dislocation of the patella. Single-limb (SL) and double-limb (DL) graft MPFL reconstructions have been increasingly used to treat recurrent patellar dislocations, but the clinical efficacy of SL versus DL graft MPFL reconstructions remains controversial owing to the inconsistent conclusions of previous studies.

PURPOSE

This study aimed to compare the clinical outcomes of SL and DL graft MPFL reconstructions for patients with recurrent patellar dislocation by conducting a meta-analysis of randomized controlled trials and cohort studies.

STUDY DESIGN

Meta-analysis; Level of evidence, 3.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were searched for relevant studies. The retrieval time was up to July 25, 2022. Two evaluators independently screened the literature, extracted data, and assessed the methodological quality of the enrolled studies. Meta-analysis was conducted using RevMan 5.4 software.

RESULTS

A total of 4 randomized controlled trials and 3 cohort studies with 451 patients were included. The joint stability and functional scores in both groups improved significantly from baseline. When compared with SL graft reconstruction, DL graft reconstruction provided reduced recurrent instability (P = .01), anterior patella-related pain (P = .02), and patellar lateral shift rate (P = .02). Regarding functional recovery, patients undergoing DL graft reconstruction presented better scores on the Kujala (P < .001), Tegner (P = .009), and International Knee Documentation Committee (IKDC) (P < .001) but similar Lysholm scores as compared with SL graft reconstruction. No statistically significant difference was found between the techniques in the reduction of the patellar tilt angle, complications other than anterior patella-related pain, or postoperative pain.

CONCLUSION

When compared with SL graft MPFL reconstruction, DL graft MPFL reconstruction yielded better outcomes in terms of postoperative recurrent instability, anterior patella-related pain, patellar lateral shift rate, Kujala score, Tegner score, and IKDC score. The amount of high-quality evidence is insufficient, so this conclusion should be interpreted with caution.

The Top 50 Most Cited Articles on the Medial Patellofemoral Ligament (MPFL): A Bibliometric Analysis

Objectives

To determine which original articles on the topic of the medial patellofemoral ligament (MPFL) have been cited the most in the literature utilizing a bibliometric approach. Secondarily, to determine temporal trends between article types.

Methods

Articles on the topic of the MPFL were identified by utilizing the Web of Science Database. The search yielded 1596 results and the top 50 cited original articles were collected for further analysis. The following information was gathered for all included articles: title, first author's name, journal name, year of publication, impact factor of the journal in 2021, total number of citations of the article, average citations per year (ACY), geographic origin, institutions, research theme, and keywords. Articles were then grouped into one of three categories: cadaveric/anatomic, clinical, and radiologic.

Results

The total number of citations was 10,393. Most were published between the years 2000-2009 (66%) and in the journal, American Journal of Sports Medicine (34%). The mean ACY was 11.73 ± standard deviation 5.86 and the Kawasaki Municipal Hospital was the institution with the most articles included in the top 50 (n = 6, 12%). The top-cited articles focused on 3 themes: cadaveric/anatomic (n = 18, 36%), clinical (n = 25, 50%), and radiologic (n = 7, 14%). Cadaveric/anatomic articles had the highest average number of citations at 271.4 ± 153.9, followed by radiologic (173.3 ± 53.0) and clinical articles (171.8 ± 102.4). Over time, clinical articles were more likely to be included in the top 50 list, compared to cadaveric/anatomic/radiologic articles.

Conclusion

The most impactful MPFL articles relate to cadaveric/anatomic articles; however, over time, clinical articles became more prevalent.

A Novel Technique of Arthroscopic Femoral Tunnel Placement during Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocation

Recurrent patellar dislocation is a commonly encountered patellofemoral disease. Prompt surgical intervention is indicated for recurrent dislocation to restore patellofemoral stability. As one of the most preferred procedures, medial patellofemoral ligament (MPFL) reconstruction has been implemented on a large scale. Femoral tunnel placement remains a crucial technical issue during MPFL reconstruction and is critical to ensure the isometry and proper tension of the graft. Currently, visual-palpatory anatomic landmarks and fluoroscopy-guided radiographic landmarks comprise the main approaches to intraoperative femoral tunnel positioning. However, the accuracy of both methods has been questioned. This article introduces an arthroscopic femoral tunnel placement technique. Apart from traditional anteromedial and anterolateral portals, two auxiliary arthroscopic portals are specially designed. The adductor tubercle, the medial epicondyle and the posterior edge are selected as main anatomic landmarks and are directly visualized in sequence under arthroscope. The relative position between the femoral attachment of the MPFL and the three landmarks is measured on preoperative three-dimensional computed tomography, providing semi-quantified reference for intraoperative localization. This technique achieves minimally invasive tunnel placement without X-ray exposure, and especially suits obese patients for whom palpatory methods are difficult to perform.

Arthroscopic Anatomical Double-Bundle Medial Patellofemoral Complex Reconstruction Improves Clinical Outcomes in Treating Recurrent Patellar Dislocation Despite Trochlear Dysplasia, Elevated Tibial Tubercle-Trochlear Groove Distance, and Patellar Alta

PURPOSE

To evaluate the clinical outcomes of arthroscopically assisted double-bundle medial patellofemoral complex reconstruction (MPFC-R).

METHODS

A retrospective review was carried out among adult patients who experienced at least 2 patellar dislocations and underwent primary arthroscopically assisted MPFC-R between January 2014 and November 2019. Dejour classification, tibial tubercle-trochlear groove (TT-TG) distance, and patellar height (with Insall-Salvati index) were measured. Pre- and postoperative patellar tilt were compared. Information on outcome scores, ability to return to sports, postoperative recurrent dislocations, and complications was recorded.

RESULTS

A total of 42 MPFC-Rs in 39 patients were included. Mean age at surgery was 22.2 ± 7.6 years; 69.2% of patients were female. Mean follow-up was 47.3 ± 20.2 months. Seventy-four percent of cases had Dejour B (19.0%), C (33.3%), and D (21.4%) trochlear dysplasia; mean TT-TG distance was 19.6 ± 3.5 mm, and mean Insall-Salvati index was 1.21 ± 0.17. Mean patellar tilt decreased from 27.6 ± 11.6° to 9.4 ± 6.5° (P < .001). All patients had statistically significant (P < .001) improvement in mean International Knee Documentation Committee (IKDC) (44.9 ± 18.2 to 87.5 ± 6.9), Lysholm (61.4 ± 16.6 to 94.1 ± 6.4), Kujala (56.0 ± 16.8 to 92.9 ± 5.3), and Tegner score (2.7 ± 1.3 to 4.6 ± 1.4). The majority of patients (96.9%) returned to sports, with 90.3% returning to the same or greater level of activity. No postoperative dislocations or subluxations were reported.

CONCLUSIONS

Arthroscopically assisted double-bundle MPFC-R is a promising procedure to treat recurrent patellar instability at 2- to 7-year mid-term follow-up, despite the presence of trochlear dysplasia, elevated TT-TG distance and patellar alta. The improvement of IKDC score exceeded the minimal clinically important difference in 95.2% patients, and 66.7% surpassed the patient acceptable symptomatic state based on postoperative IKDC score with no redislocations being reported at latest follow-up.

LEVEL OF EVIDENCE

Level IV, case series, retrospective.

Medial Patellofemoral Complex Reconstruction Techniques Are Not Equivalent at Lower Flexion in the Setting of Patella Alta: A Biomechanical Comparison

PURPOSE

To (1) determine the effect of severe patella alta on lateral patellar displacement after medial patellofemoral ligament (MPFL) reconstruction and medial quadriceps tendon-femoral ligament (MQTFL) reconstruction and (2) determine whether lateral displacement significantly differs between MPFL and MQTFL reconstructions in the setting of severe patella alta (Caton-Deschamps Index [CDI] of 1.6).

METHODS

Eight cadaveric specimens were included. High-tensile strength suture was used to create a model of adjustable patellar height. Patellar height was set using fluoroscopy to CDI ratios of 1.0 (normal) and 1.6 (alta). Specimens underwent testing (1) with MPFL reconstruction, (2) with MQTFL reconstruction, and (3) in a medial patellofemoral complex (MPFC)-deficient control state, in randomized order, at both CDI settings: 1.0 and 1.6. Lateral patellar translation was measured at 0°, 10°, 20°, 30°, 45°, 60°, and 90° of knee flexion with 10 N of laterally directed load.

RESULTS

At a CDI of 1.6, MPFL reconstruction showed significantly lower lateral displacement than MQTFL reconstruction at 0° and 20°. When compared with MPFC-deficient controls at a CDI of 1.6, MPFL reconstruction showed significantly lower displacement at 0° and 20° whereas MQTFL reconstruction was not significantly different at any degree of flexion.

CONCLUSIONS

In the setting of severe patella alta (CDI of 1.6), MPFL reconstruction results in less lateral patellar displacement than MQTFL reconstruction at 0° and 20° of knee flexion. At higher flexion angles (≥30°), there is no difference between the 2 reconstruction techniques and the CDI no longer has an effect. At a CDI of 1.0, MPFL reconstruction shows lower displacement than MQTFL reconstruction in full extension only. Surgeons performing MPFC reconstruction should evaluate patients for patella alta and consider patellar height when deciding on the reconstruction technique.

CLINICAL RELEVANCE

This study suggests that MQTFL reconstruction may be less stable than MPFL reconstruction in the setting of patella alta, without other known pathoanatomic factors, at early knee flexion angles. Patellar height should be considered when choosing the appropriate reconstruction technique in the absence of a distalization procedure.

Quantifying the Relationship Between the Medial Quadriceps Tendon-Femoral Ligament and Patellar Borders: A Pediatric Cadaveric Study

BACKGROUND

The medial patellofemoral complex (MPFC) is a structure composed of the medial quadriceps tendon-femoral ligament (MQTFL) superiorly and the medial patellofemoral ligament (MPFL) inferiorly. The pediatric MPFL anatomy has been well described, but the precise anatomy of the MQTFL has only recently been described and studied in skeletally immature patients.

PURPOSE

To describe the anatomic relationship between the MQTFL and its insertion on the quadriceps tendon and patella in pediatric specimens.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 22 pediatric cadaveric knee specimens were dissected to analyze attachment of the MQTFL to the quadriceps tendon and patella. Dissection was facilitated using lateral parapatellar arthrotomy followed by eversion of the extensor mechanism to evaluate MQTFL fibers from its undersurface.

RESULTS

The mean specimen age was 7.4 years. Specimens were divided based on age into a younger cohort (1-2 years), middle cohort (4-8 years), and older cohort (9-12 years). The quadriceps tendon attachment (QTA) of the MQTFL proximal to the patella extended a median of 5.0 mm in the younger cohort, 11.4 mm in the middle cohort, and 12.0 mm in the older cohort, with significant differences found between the younger and middle cohorts (P < .047) and the younger and older cohorts (P < .001). The QTA as a percentage of patellar articular height averaged 44.4% across all specimens. The vertical height of the patella measured a median of 14.0 mm, 22.3 mm, and 27.3 mm in the younger, middle, and older cohorts, respectively.

CONCLUSION

This study expands on the recently described anatomy of the pediatric MPFC to quantify the anatomic relationship between the MQTFL attachment to the quadriceps tendon and patella in a more clinically relevant cohort of donor specimens.

CLINICAL RELEVANCE

As access to pediatric cadaveric tissue is extremely limited, a better understanding of MPFC and MQTFL anatomy will support surgeons in preoperative planning and intraoperative considerations for their approach to MQTFL and MPFL reconstruction. This may facilitate improved anatomic surgical stabilization of the patellofemoral joint in pediatric patients.

A Comprehensive Description of the Lateral Patellofemoral Complex: Anatomy and Anisometry

BACKGROUND

The lateral patellofemoral complex (LPFC) is an important stabilizer of the patella composed of the lateral retinacular structures including the lateral patellofemoral ligament (LPFL), the lateral patellomeniscal ligament (LPML), and the lateral patellotibial ligament (LPTL). While the isolated anatomy of the LPFL has been previously described, no previous study has investigated the entirety of the LPFC structure, length changes, and radiographic landmarks. An understanding of LPFC anatomy is important in the setting of LPFL injury or previous lateral release resulting in iatrogenic medial instability requiring LPFC reconstruction.

PURPOSE

To both qualitatively and quantitatively describe the anatomy and length changes of the LPFC on gross anatomic dissections and standard radiographic views.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ten nonpaired cadaveric specimens were utilized in this study. Specimens were dissected to identify distinct attachments of the LPFL, LPML, and LPTL. Ligament lengths, footprints, and centers of each attachment were described with respect to osseous landmarks using a 3-dimensional coordinate measuring device. Ligament length changes were also assessed from 0° to 90° of flexion. Radiopaque markers were subsequently utilized to describe attachments on standard anteroposterior and lateral radiographic views.

RESULTS

The individual elements of the LPFC were identified in all specimens. The LPFL patellar attachment had an average total length of 22.5 mm (range, 18.3-27.5 mm), involving a mean of 59% (range, 50%-75%) of the sagittal patella. Based on the average patellar size, a mean of 63% of the LPFL attached to the patella, and the remainder (11.1 ± 1.4 mm) inserted into the patellar tendon. The femoral attachment of the LPFL had a mean maximum length of 24.4 ± 4.3 mm. The center of the LPFL femoral attachment was a mean distance of 13.5 ± 3.2 mm anterior and distal to the lateral epicondyle. The LPFL demonstrated significant shortening, especially in the first 45° of flexion (7.5 ± 5.1 mm). In contrast, the LPTL (5.5 ± 3.0 mm) and LPML (10.0 ± 3.3 mm) demonstrated significant shortening from 45° to 90°. On lateral radiographs, the center of the femoral attachment of the LPFL was a mean total distance of 19.2 ± 7.2 mm from the lateral epicondyle.

CONCLUSION

The most important findings of this study were the correlative anatomy of 3 distinct lateral patellar ligaments (LPFL, LPML, and LPTL) and their anisometry through flexion. All 3 components demonstrated significant shortening during flexion. The quantitative and radiographic measurements detailed the LPFL osseous attachment on the patella; soft tissue attachment on the patellar tendon; and finally, the osseous insertion on the femur distal and anterior to the lateral epicondyle. Similarly, the authors documented the meniscal insertion of the LPML and defined a patellar insertion of the LPTL and LPML as a single attachment. These data allow for reproducible landmarks to aid in the understanding and reconstruction of the lateral patellar restraints.

CLINICAL RELEVANCE

The data produced from this investigation provide a comprehensive description of these 3 lateral patellar stabilizers (LPFL, LPML, LPTL). These data can be used intraoperatively to facilitate anatomic reconstructions of the lateral patellar stabilizers.

Medial Patellofemoral Ligament Reconstruction in Skeletally Immature Patients

Patellofemoral instability is a common problem affecting children and adolescents, with recurrent instability often requiring surgical intervention. Medial patellofemoral ligament (MPFL) reconstruction has become a mainstay for the treatment of patellofemoral instability because of the biomechanical importance of the MPFL against lateral dislocation as well as the high frequency of MPFL injury following traumatic patellar dislocation. The concern in managing skeletally immature patients is the potential for injury to the distal femoral physis. Here, we highlight 2 techniques for MPFL reconstruction. The first technique utilizes a hamstring autograft. The steps include: Step 1: Harvest the semitendinosus graft from a 2-cm posteromedial incision with use of an open tendon harvester proximally and a closed tendon harvester distally. Step 2: Prepare the graft for double-bundle reconstruction, allowing for approximately 50 to 60 mm for the reconstructed MPFL and 15 to 20 mm for graft placement within the patella and femoral sockets. Step 3: Use a guidewire and reamer to create 2 patellar sockets approximately 15 mm long each. Step 4: Use a guidewire under fluoroscopy to position and create a femoral socket distal to the distal femoral physis approximately 15 mm long. Step 5: Fix the graft on the femur with use of a tenodesis screw, pass the graft through the soft-tissue space between the fascia and synovium to the superior half of the patella, then dock the free ends of the graft onto the 2 patellar sockets with "PEEK (polyetheretherketone) SwiveLocks (Arthrex)" while the knee is in 30° of flexion. We also review a second technique of docking the hamstring graft onto the adductor tubercle and suturing it proximally to the deep distal medial aspect of the quadriceps tendon. Although only a limited number of studies have reported the outcomes of MPFL reconstruction in skeletally immature patients, such studies have demonstrated a high return to preoperative level of sports activity and a reduced prevalence of recurrent patellar instability.

Pediatric Management of Recurrent Patellar Instability

Patellofemoral instability is a common orthopedic condition in children and adolescents, with recurrent instability often requiring surgical intervention. Age, bilateral instability, and various anatomic features such as trochlear dysplasia, patella alta, increased tibial tubercle to trochlear groove distance, and patellar tilt have all been described as risk factors for recurrent patellar instability. Medial patellofemoral ligament reconstruction has become the mainstay of treatment for addressing recurrent patellar instability in skeletally immature patients. For some patients, additional interventions such as distal realignment and guided growth procedures may be required to address anatomic pathology. This article discusses various risk factors associated with patellofemoral instability, reconstruction techniques, and a case example.

Medial Quadriceps Tendon Femoral Ligament Reconstruction Technique and Surgical Anatomy

Medial patellofemoral ligament reconstruction risks patellar fracture with the osseous violation necessary for patellar attachment. Anatomic studies identify an entire medial patellofemoral complex of structures responsible for medial restraint to patellar lateral instability. One specific component of this complex is the medial quadriceps tendon femoral ligament (MQTFL). This note presents the technique, pearls and pitfalls, and critical surgical anatomy necessary for successful MQTFL reconstruction-a treatment strategy for patellar instability with no increased risk for patellar fracture. An autograft hamstring tendon or allograft tendon is fixed to the anatomically identified femoral origin and passed deep to the vastus medialis obliquus to then weave around the distal medial quadriceps tendon. This simulates the native anatomic interdigitation of the MQTFL with the quadriceps tendon and provides a stable restraint to prevent lateral patellar subluxation or dislocation.

Editorial Commentary: What Is the Optimal Management of First and Recurrent Patellar Instability? Patellofemoral Instability Management Continues to Evolve

Patellar instability patients may present for evaluation after their first instability episode or after recurrent episodes. Current management differs for these 2 groups. The accepted "common denominator" of patellar instability is the medial patellofemoral ligament, or medial patellar restraints, to be more all-encompassing. These patients often have multiple contributing comorbidities (e.g., trochlear dysplasia, patellar alta, excessive lateral position of tibial tubercle). Historically, the recommended treatment for a first-time patellar dislocation was nonoperative because medial soft tissue repairs had not been proven more effective. Indications for primary repair of the medial patellar restraints are a single discrete tear identified on magnetic resonance imaging. In the case of recurrent patellar instability, medial patellofemoral ligament reconstruction, rather than repair/reef, has been the recommended approach. The keys to reconstruction remain: honor the anatomy and avoid overconstraint of the patella. For first time dislocation patients with trochlear dysplasia, patellar alta, and age <25 years, recurrent instability is common.

The medial patellofemoral complex

PURPOSE OF REVIEW

The purpose of this review is to describe the current understanding of the medial patellofemoral complex, including recent anatomic advances, evaluation of indications for reconstruction with concomitant pathology, and surgical reconstruction techniques.

RECENT FINDINGS

Recent advances in our understanding of MPFC anatomy have found that there are fibers that insert onto the deep quadriceps tendon as well as the patella, thus earning the name "medial patellofemoral complex" to allow for the variability in its anatomy. In MPFC reconstruction, anatomic origin and insertion points and appropriate graft length are critical to prevent overconstraint of the patellofemoral joint. The MPFC is a crucial soft tissue checkrein to lateral patellar translation, and its repair or reconstruction results in good restoration of patellofemoral stability. As our understanding of MPFC anatomy evolves, further studies are needed to apply its relevance in kinematics and surgical applications to its role in maintaining patellar stability.