Quantitative and Qualitative Analysis of the Medial Patellar Ligaments: An Anatomic and Radiographic Study

Editorial Commentary: Proper Femoral Tunnel Placement for Medial Patellofemoral Ligament Reconstruction Requires Optimal Radiographic Technique

Femoral tunnel malposition has been shown to be a risk factor for medial patellofemoral ligament reconstruction failure. Palpation of the "saddle point" between the adductor tubercle and medial epicondyle can be an effective strategy; however, compared to using fluoroscopy, tunnel placement using palpation alone may result in significantly more frequent malposition. Accordingly, use of radiographic landmarks has gained in popularity. However, the technique is not without its pitfalls. The first issue lies with obtaining an adequate x-ray. Deviation from a true lateral x-ray by as little as 5° can result in significant tunnel malposition. Including sufficient visible femoral shaft is also required; a minimum requirement is 4 cm. The literature widely varies as to the anatomic, fluoroscopic position. Schottle's point (1.3 mm anterior to the posterior cortical extension line) is the most well studied.

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.

Radiographic Landmark Measurements for the Femoral Footprint of the Medial Patellofemoral Complex May Be Affected by Visible Femoral Shaft Length on Lateral Knee Radiographs

PURPOSE

To assess the effect of visible femoral shaft length on the accuracy of radiographic landmarks of the medial patellofemoral complex (MPFC).

METHODS

In 9 cadaveric knees, the MPFC footprint was exposed on the medial femur, and its proximal and distal boundaries were marked. Lateral fluoroscopic images of the knee were assessed in 1-cm length increments, beginning 1 cm proximal to the medial condyle and continuing proximally to 8 cm. The MPFC midpoint was described on each image relative to the posterior cortical line of the femur and a line perpendicular to this line through the proximal margin of the medial condyle. In addition, the MPFC midpoint was assessed relative to a line from the proximal posterior cortex to the midpoint of Blumensaat line.

RESULTS

Using the posterior cortical line as a reference, the MPFC radiographic landmark moved anteriorly with decreasing visible femoral shaft on radiographs, particularly at 4 cm and less. However, no proximal-distal change was noted. Linear regression analysis demonstrated a relationship between visible femoral shaft and MPFC position on radiographs (R = 0.461, R2 = 0.212, B = -0.636, P < .001). For every centimeter decrease in the visible femoral shaft, the radiographic MPFC footprint moved anteriorly by 0.636 mm. Receiver operating characteristic curve analysis revealed that a minimum of 4 cm of femoral shaft on lateral radiographs is required for accurate MPFC footprint localization (area under the curve = 0.80; sensitivity = 76.7%; specificity = 69.0%; P < .001). In contrast, no anterior-posterior change was seen when referencing a line from the proximal posterior cortex to the midpoint of Blumensaat line.

CONCLUSIONS

When using the posterior cortical line to identify the midpoint of the MPFC, at least 4 cm of femoral shaft should be visible for accurate assessment. If less than 4 cm of shaft is visible, a line through the midpoint of Blumensaat line and the proximal posterior cortex can be used as an alternative method to estimate the position of the femoral footprint.

CLINICAL RELEVANCE

As fluoroscopy is frequently used intraoperatively for MPFC reconstruction, our findings may serve as a guide when assessing femoral tunnel placement on fluoroscopy.

Patellofemoral instability part 1 (When to operate and soft tissue procedures): State of the art

Patellofemoral instability is usually initially treated non-operatively. Surgery is considered in patients with recurrent patellar dislocation and after a first-time patellar dislocation in the presence of either an associated osteochondral fracture or high risk of recurrence. Stratifying the risk of recurrence includes evaluating risk factors such as age, trochlear dysplasia, contralateral dislocation, and patellar height. Surgery with soft tissue procedures includes restoring the medial patellar restraints and balancing the lateral side of the joint. Reconstruction of the medial patellofemoral ligament is the most frequent way of addressing the medial soft tissues in patients with patellofemoral instability. Meanwhile, lateral tightness can be achieved by lateral retinaculum lengthening or release. Approaching patellofemoral instability in a patient-specific approach, combined with a shared decision-making process with the patient/family, will guide surgeons to the deliver optimal care for the patellar instability patient.

Medial Patellofemoral Complex Reconstruction (Combined Reconstruction of Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament) With Semitendinosus Autograft Resulted in Similar Clinical and Radiographic Outcomes to Medial Patellofemoral Ligament Reconstruction in Treating Recurrent Patellar Dislocation

PURPOSE

To compare clinical and radiographic outcomes of medial patellofemoral ligament reconstruction (MPFL-R) and medial patellofemoral complex reconstruction (MPFC-R) for recurrent patellar dislocation. Outcome measures were compared based on the Insall-Salvati index.

METHODS

Patients who were diagnosed with recurrent patellar dislocation and underwent either MPFL-R or MPFC-R (combined reconstruction of MPFL and medial quadriceps tendon-femoral ligament) were retrospectively analyzed. Group allocation was based on surgical procedure and patient characteristics were collected. Clinical assessments included patient-reported outcome measures (PROMs) and return-to-sports rates. Minimal clinically important difference analysis was performed. A subgroup analysis of PROMs was carried out between patients with an Insall-Salvati index ≤1.2 versus >1.2. The patellar tilt angle, lateral patellar displacement, and bisect offset ratio were measured pre- and postsurgery. Functional failures and complications were assessed.

RESULTS

Overall, 70 patients (72 knees) in the MPFL-R group and 58 patients (61 knees) in the MPFC-R group were included. Patient characteristics were comparable between the groups. At a minimum follow-up of 24 (mean, 50.6 ± 22.1) months, all PROMs were substantially improved (P < .001), without significant intergroup differences. The percentages of patients reaching the minimal clinically important difference were similar after MPFL-R and MPFC-R: 98.6% versus 93.4% (International Knee Documentation Committee), 97.2% versus 98.4% (Lysholm), 98.6% versus 100% (Kujala), and 77.8% versus 72.1% (Tegner). The subgroup analysis based on patellar height and the return-to-sport rates also suggested comparable results. Radiographic evaluation demonstrated significantly smaller lateral patellar displacements (P = .004) and bisect offset ratios (P < .001) but similar patellar tilt angles after MPFC-R. Four (5.6%) patients receiving MPFL-R and 2 (3.3%) patients receiving MPFC-R reported recurrence of functional instability, without statistically significant difference.

CONCLUSIONS

MPFC-R resulted in similar overall clinical and radiographic outcomes to MPFL-R in treating recurrent patellar dislocation. MPFC-R might not provide additional benefits for patients with an Insall-Salvati index >1.2.

LEVEL OF EVIDENCE

Level IV, therapeutic, retrospective cohort study.

Anterior meniscus extrusion is associated with anterior tibial osteophyte width in knee osteoarthritis - The Bunkyo Health Study

Background

In knee osteoarthritis (OA), medial meniscus extrudes both medially and anteriorly. We reported that full-length width of medial tibial osteophyte, which comprises cartilage and bone parts, is directly associated with medial meniscus extrusion in early-stage knee OA and hypothesized that anterior tibial osteophyte (ATO) is also associated with anterior meniscus extrusion (AME). Thus, we aimed to examine their prevalence and relationship.

Methods

Elderly subjects (638 females and 507 males; average 72.9 years old) in the Bunkyo Health Study cohort were enrolled. MRI-detected OA changes were evaluated according to the Whole Organ Magnetic Resonance Imaging Score. ATO was evaluated using the method which can assess both cartilage and bone parts of osteophyte by pseudo-coloring images of proton density-weighted fat-suppressed MRI.

Results

Most subjects showed the Kellgren-Lawrence grade 1/2 of the medial knee OA (88.1%), AME (94.3%, 3.7 ​± ​2.2 ​mm), and ATO (99.6%, 4.2 ​± ​1.5 ​mm). Among the OA changes, AME was most closely associated with full-length width of ATO (multivariable β ​= ​0.877, p ​< ​0.001). The area under the receiver operating characteristic curve for determining the presence of AME as evaluated by ATO width was 0.75 (95% confidence interval 0.60-0.84, p ​< ​0.001). The odds ratio for the presence of AME as evaluated by ATO width at 2.9 ​mm was 7.16 (4.23-12.15, p ​< ​0.001, age, gender, BMI, and K-L adjusted).

Conclusions

AME and ATO were inevitably observed in the elderly subjects and AME was closely associated with full-length width of ATO. Our study provides the first evidence on the close relationship between AME and ATO in knee OA.

Double-Bundle Quadriceps Tendon Autograft for Reconstruction of the Medial Patellofemoral Complex to Manage Recurrent Patellar Dislocation in Patients With Open Physes

Management of chronic patellar instability in patients with open physis requires special reconstruction techniques to minimize the risks of femoral growth plate injury due to the close proximity of the open physis to the native femoral origin of the medial patellofemoral ligament (MPFL). Children and adolescents have a relatively smaller patella than the adult group, so, there is a higher risk of patellar fracture when tunnels are performed in the patella. It is wise to mimic the normal anatomy of the medial patellofemoral complex (MPFC) by reconstruction of both of the medial quadriceps tendon femoral ligament (MQTFL) and MPFL, so as to restore the normal fan-shaped MPFC, with its wide anterior attachment to both of the patella and quadriceps tendon (QT). This article describes a simple, safe, reproducible, and cost effective technique for surgical management of chronic patellar instability in patients with open physis by reconstruction of the MPFC using a double-bundle QT autograft.

Lateral Patellar Instability

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Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology. Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient.

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Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity.

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Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment.

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Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability.

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Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation.

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Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta.

➤

The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding.

➤

Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30° to improve patient outcomes and reduce recurrence rates.

Biomechanical Comparison of 3 Medial Patellofemoral Complex Reconstruction Techniques Shows Medial Overconstraint but No Significant Difference in Patella Lateralization and Contact Pressure

PURPOSE

The purpose of this study was to investigate biomechanical differences of medial patellofemoral ligament (MPFL) reconstruction, medial quadriceps tendon femoral ligament (MQTFL) reconstruction, and a combination of these techniques to restore lateral patellar constraint and contact pressures.

METHODS

Eight fresh frozen cadaver knees were mounted to a custom jig with physiological quadriceps tendon loading. Flexion angles and contact pressure (CP) were dynamically measured using Tekscan® pressure sensors and Polhemus® Liberty 6 degree of freedom (6DOF) positioning sensors in the following conditions: 1) intact 2) MPFL and MQTFL deficient, 3) MPFL reconstructed, 4) Combined MPFL + MQTFL reconstructed, and 5) MQTFL reconstructed. Lateral patellar translation was tested using horizontally directed 30 N force applied at 30° of knee flexion. The knees were flexed in dynamic fashion, and CP values were recorded for 10°, 20°, 30°, 50°, 70°, and 90° degrees of flexion. Group differences were assessed with ANOVA's followed by pairwise comparisons with Bonferroni correction.

RESULTS

MPFL (P = .002) and combined MPFL/MQTFL (P = .034) reconstruction significantly reduced patellar lateralization from +19.28% (9.78%, 28.78%) in the deficient condition to -17.57% (-27.84%, -7.29%) and -15.56% (-33.61%, 2.30%), respectively. MPFL reconstruction was most restrictive and MQTFL reconstruction the least -7.29% (-22.01%, 7.45%). No significant differences were found between the three reconstruction techniques. Differences in CP between the three reconstruction techniques were not significant (<.02 MPa) at all flexion angles.

CONCLUSION

The present study found no significant difference for patellar lateralization and patellofemoral CP between MPFL, combined MPFL/MQTFL, and MQTFL reconstruction. All 3 techniques resulted in stronger lateral patellar constraint compared to the native state, while the MQTFL reconstruction emulated the intact state the closest.

CLINICAL RELEVANCE

Various surgical techniques for medial patellofemoral complex reconstruction can restore patellar stability with similar patellofemoral articular pressures.

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.

Patellar Tendon-Trochlear Groove Angle Measured on a Single Computed Tomography Slice of the Distal Femoral Trochlear Groove Is a Reliable Measurement for the Evaluation of Patellar Instability

PURPOSE

To verify the reliability of patellar tendon-trochlear groove angle (PTTG-A) measured by computed tomography (CT) and the clinical significance in evaluation of patellar instability.

METHODS

A retrospective study of hospitalized patients with knee pain or injury and had knee CT from January 2017 to June 2021 was performed. PTTG-A and tibial tuberosity-trochlear groove (TT-TG) distance were measured on CT. Spearman correlation analysis was analyzed between the 2 measurements. The intraclass correlation coefficient was determined for inter- and intraobserver reproducibility. The capacity of PTTG-A and TT-TG to predict patellar instability was evaluated by the receiver operating characteristic curve. Data from the control group were used to determine the pathologic thresholds and logistic regression analysis.

RESULTS

Included were 113 patients. There were 60 patients with the history of at least 2 episodes of patellar dislocation (study group) and 53 patients without a history of patellar dislocation (control group). The respective PTTG-A and TT-TG distances in the study group (35.2 ± 8.4° and 19.6 ± 4.6 mm) were significantly greater than those of the controls (20.8 ± 5.8° and 13.3 ± 4.5 mm) (P < .001). The correlation between the 2 measurements was strong (r = 0.730, P < .001). The inter- and intraobserver reliability of the PTTG-A were better than TT-TG distance in both groups. The AUC of PTTG-A was greater than that of the TT-TG distance (0.895 vs 0.769, respectively). With the cutoff value of PTTG-A and TT-TG being 26.3° and 16.3 mm, the value of the pathologic threshold of PTTG-A was 30.0°, with a dominance ratio of 16.88 (95% confidence interval 2.88-98.89, P = .002).

CONCLUSIONS

The PTTG-A measured on a single CT slice of the distal femoral trochlear groove is a more reliable measurement than TT-TG distance for the prediction of patellar instability.

LEVEL OF EVIDENCE

III; A retrospective cohort study.

Qualitative and Quantitative Assessment of the Medial Patellar Retinaculum Anatomy: the Anteromedial Side of the Knee Revisited

BACKGROUND

In the current literature, studies on the anatomy of the anteromedial region of the knee are scarce. However, the anteromedial structures, especially the longitudinal medial patellar retinaculum (MPR), may play an important role in restraining external tibial rotation.

PURPOSE

To conduct a layer-by-layer dissection of the anteromedial side of the knee and describe qualitatively and quantitatively the MPR anatomy pertaining to surgically relevant landmarks.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 10 fresh-frozen human cadaveric knees (mean age 81 ± 16.3 years) without history of previous ligament injury were used in this study. A layer-by-layer dissection was performed, and measurements were obtained using a tactile 3-dimensional (3-D) measuring arm to define the anatomy of the MPR in relation to surgically relevant landmarks, such as the superficial medial collateral ligament (sMCL) and medial patellofemoral ligament (MPFL). The 3-D datasets were used for multiplanar reconstruction.

RESULTS

The tibial and femoral attachment of the MPR were identified in 100% of cases. Layer-by-layer dissection confirmed its close topography to the sMCL. The mean length of the MPR was 84.9 ± 9.1 mm. The average width of the tibial and femoral attachment was 23.8 ± 3.1 mm and 69.2 ± 8.2 mm, respectively. The distance from the midpoint of the MPR tibial attachment to the midpoint of the distal tibial attachment of the sMCL was 27.2 ± 5.8 mm. Femorally, the MPR attached at the anterior border of the MPFL over a mean distance of 52.3 ± 9.4 mm.

CONCLUSION

The MPR is a distinct tibiofemoral structure with well-defined tibial and femoral attachments, which could be consistently identified. Layer-by-layer dissection confirmed its close topography to the sMCL and MPFL.

CLINICAL RELEVANCE

As injuries to the anteromedial side of the knee may contribute to anteromedial rotational rotatory instability (AMRI), precise knowledge of the underlying anatomy of the MPR may be necessary to perform an anatomic reconstruction of the anteromedial side of the knee.

Landmarks Used in Medial Patellofemoral Ligament Reconstruction Have Variable Topography

Purpose

To describe the morphology of the adductor tubercle (AT), medial epicondyle (ME), and gastrocnemius tubercle (GT); to quantify their relationships to the medial patellofemoral ligament (MPFL) footprint location; and to classify the reliability of each landmark based on measurement variability.

Methods

Eight cadaveric specimens were dissected to expose the following landmarks on the femur: MPFL footprint, AT, ME, and GT. Using the MicroScribe 3D digitizer, each landmark was projected into a 3-dimensional coordinate system and reconstructed into a complex, closed polygon. For each specimen tubercle, the base surface area, volume, height, base:height ratio, sulcus point, and distance from the MPFL footprint center were calculated. Levene's test was performed to evaluate differences in variance of the morphologic parameters between the three osseous structures.

Results

The ME had significantly greater variance in volume than the GT (P = .032), and the AT (17.5 ± 3.9) and GT (19.5 ± 3.6) were significantly less variable in base:height ratio than the ME (95.3 ± 19.2; P < .001). The GT was the closest to the MPFL footprint center (7.1 ± 3.1 mm) compared with the AT (13.4 ± 3.6 mm, P = .002) and ME (13.2 ± 2.7 mm, P = .003). However, the tubercles were equally variable in terms of distance to the MPFL footprint center (P = .86). Lastly, the sulcus point was estimated to be on average 1.9 ± 2.9 mm distal and 2.0 ± 2.0 mm posterior to the MPFL center point.

Conclusions

The 3 major osseous landmarks of the medial femur have significantly different variances in volume and base:height ratio. Specifically, the variability and elongated morphology of the ME differentiated this landmark from the AT and GT, which demonstrated the most consistent morphology.

Clinical Relevance

The results of this study may be useful to accurately locate landmarks for femoral tunnel placement and determine the isometric MPFL point during reconstruction.

Radiographic Landmarks for the Femoral Attachment of the Medial Patellofemoral Complex: A Cadaveric Study

PURPOSE

To report the radiographic landmarks for the medial patellofemoral complex (MPFC) footprint on the medial femur and describe the difference between the radiographic positions corresponding to the medial quadriceps tendon femoral ligament (MQTFL) and medial patellofemoral ligament (MPFL) fibers.

METHODS

In 8 unpaired cadaveric knees, the MPFC footprint was exposed on the medial femur, and the proximal and distal boundaries of the footprint were marked. Lateral fluoroscopic images of the knee were obtained and analyzed using Image J. The proximal boundary corresponding to the MQTFL, the MPFC midpoint, and distal boundary corresponding to the MPFL were described radiographically and compared for differences in position.

RESULTS

The proximal MQTFL footprint was 0.8 ± 0.6 mm anterior (P = .013) and 5.2 ± 1.8 mm proximal to the MPFC midpoint (P <.001), whereas the distal MPFL footprint was 0.8 ± 0.7 mm posterior (P = .012) and 5.9 ± 1.1 mm distal to the radiographic MPFC midpoint (P <.001). The radiographic point corresponding to the distal MPFL footprint was 0.8 ± 0.9 mm posterior (P = .011) and 11.1 ± 2.3 mm distal to the radiographic point of the proximal MQTFL footprint (P <.001). When using the point of intersection of the posterior cortical line and the proximal posterior condyle as a reference, 91.6% of all points correlating to the MQTFL, MPFC midpoint and MPFL, were within 10 mm in any direction from this radiographic landmark.

CONCLUSIONS

On fluoroscopic imaging, the proximal MQTFL and distal MPFL fibers had significantly different radiographic positions from the MPFC midpoint on the femur. These findings should be considered when reconstructing specific components of the MPFC.

CLINICAL RELEVANCE

As fluoroscopy is often used intraoperatively to guide graft placement, our findings may serve as a reference when differentiating the locations of the MPFL vs MQTFL on the femur for anatomic reconstruction.

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.

Simultaneous Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament Reconstructions Using an Artificial Ligament for Lateral Patella Instability

Recent studies on the detailed anatomy of the medial patellar stabilizer have revealed that the medial patellofemoral ligament (MPFL) not only attaches to the patella but also has fibers that attach to the quadriceps muscle, known as the medial quadriceps tendon femoral ligament (MQTFL). Reconstruction of the medial stabilizer for patellar dislocation that includes both the MPFL and MQTFL may achieve better anatomical and physiological correction. In this Technical Note, we will describe a simultaneous reconstruction technique of the MPFL and MQTFL for patellar dislocation using an artificial ligament.

Utility of Diagnostic Ultrasound in the Assessment of Patellar Instability

Background

The use of imaging to diagnose patellofemoral instability is often limited by the inability to dynamically load the joint during assessment. Therefore, the diagnosis is typically based on physical examination using the glide test to assess and quantify lateral patellar translation. However, precise quantification with this technique remains difficult.

Purpose

To quantify patellar position using ultrasound imaging under dynamic loading conditions to distinguish between knees with and without medial patellofemoral complex (MPFC) injury.

Study Design

Controlled laboratory study.

Methods

In 10 cadaveric knees, the medial patellofemoral distance was measured to quantify patellar position from 0° to 40° of knee flexion at 10° increments. Knees were evaluated at each flexion angle under unloaded conditions and with 20 N of laterally directed force on the patella to mimic the glide test. Patellar position measurements were made on ultrasound images obtained before and after MPFC transection and compared for significant differences. To determine the ability of medial patellofemoral measurements to differentiate between MPFC-intact and MPFC-deficient states, area under the receiver operating characteristic (ROC) curve analysis and the Delong test were used. The optimal cutoff value to distinguish between the deficient and intact states was determined using the Youden J statistic.

Results

A significant increase in medial patellofemoral distance was observed in the MPFC-deficient state as compared with the intact state at all flexion angles (P = .005 to P < .001). When compared with the intact state, MPFC deficiency increased medial patellofemoral distance by 32.8% (6 mm) at 20° of knee flexion under 20-N load. Based on ROC analysis and the J statistic, the optimal threshold for identifying MPFC injury was 19.2 mm of medial patellofemoral distance at 20° of flexion under dynamic loading conditions (area under the ROC curve = 0.93, sensitivity = 77.8%, specificity = 100%, accuracy = 88.9%).

Conclusion

Using dynamic ultrasound assessment, we found that medial patellofemoral distance significantly increases with disruption of the MPFC.

Clinical Relevance

Dynamic ultrasound measurements can be used to accurately detect the presence of complete MPFC injury.

Computed Tomography Imaging Analysis of the MPFL Femoral Footprint Morphology and the Saddle Sulcus: Evaluation of 1094 Knees

Background:

The medial patellofemoral ligament (MPFL) has been reported to be anatomically attached from an osseous saddle region (saddle sulcus) between neighboring landmarks on the femur, including the adductor tubercle (AT), medial epicondyle (ME), and medial gastrocnemius tubercle (MGT). However, the position and prevalence of the saddle sulcus remain unknown.

Purpose:

To study the femoral footprint of MPFL and the prevalence of the saddle sulcus with computed tomography (CT) imaging; quantify the position of the saddle sulcus; and determine the relevant factors of the identified position and measuring distances.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 1094 knees in 753 patients were studied. Knees were organized into an anterior cruciate ligament reconstruction (ACLR) group (controls) and a recurrent patellar dislocation (RPD) group. Using 3-dimensionally reconstructed CT images, the authors determined the prevalence of the saddle sulcus and its position relative to the AT, the ME, the Schöttle point (1.3 mm anterior to the distal posterior cortex and 2.5 mm distal to the posterior origin of the medial femoral condyle), and the Fujino point (approximately 10 mm distal to the AT). Analysis of covariance was used to adjust for age, sex, side, and body mass index on the measurements.

Results:

There were 555 knees in the control group and 539 knees in the RPD group. The MPFL femoral footprint presented as an oblique, oblong, osseous region (saddle sulcus) in 75.7% of knees (75.0%, ACLR group vs 76.4%, RPD group; P < .001). The saddle sulcus was located a mean of 12.2 mm (95% CI, 12.0-12.4 mm) from a line connecting the apex of the AT to the ME (AT-ME) and a mean of 7.6 mm (95% CI, 7.5-7.8 mm) posteriorly perpendicular to that line. The location as a proportion of the AT-ME distance was 63.1% (95% CI, 62.6%-63.7%) in the X direction and 39.8% (95% CI, 39.1%-40.5%) in the Y direction. The Schöttle and Fujino points lay anterior and proximal to the saddle sulcus more than 5 mm away from the center of the saddle sulcus. Women had a higher prevalence of saddle sulcus (odds ratio [OR], 1.33 [95% CI, 1.00-1.75]; P = .046) compared with men.

Conclusion:

The saddle sulcus was identified in 75.7% of knees from the medial femoral aspect, with its center located consistently between the AT and ME.

Alteration of patellar tendon morphology in patellofemoral instability (trochlear dysplasia)

INTRODUCTION

Trochlear Dysplasia (TD) is a condition that is characterized by the presence of an abnormally shaped trochlear groove, which hinders the patellofemoral joint (PFJ) stability. PFJ stability is determined by static and dynamic structures around the knee joint. We analysed whether the patellar tendon morphology is altered in patients with patellofemoral instability in Trochlear Dysplasia (TD).

MATERIAL AND METHODS

Magnetic Resonance Imaging (MRI) studies for 50 consecutive knees with TD and 50 consecutive knees with normal PFJ morphology were obtained for evaluation. For each MRI study, the cross-sectional area (CSA) of the medial and lateral components of the patellar tendon was measured and used to calculate the cross-sectional area ratio (CSAR) by two readers.

RESULTS

There was a statistically significant difference in the CSAR of the lateral-to-medial components of the patellar tendon between knees with normal PFJ morphology and knees with TD (one way ANOVA, F (4,95) = 7.743, p < 0.001). Pairwise comparisons amongst the Dejour subtypes of TD, revealed a statistically significance difference (p < 0.05) in the CSAR ratio between patients with normal PFJ morphology, and patients with type A (p = 0.007) and type C, TD. There was moderate correlation between the readers on Intraclass Correlation Coefficient (ICC) analysis (ICC- 0.7).

CONCLUSION

Our findings reveals hypertrophy of the medial part of the patellar tendon in patients with PFJ instability and TD. These differences could reflect the dynamic compensatory changes occurring at the PFJ to counteract the laterally directed instability vectors found in this condition.

A Balanced Arthroscopic Debridement of the Inner Layer of the Knee Retinaculum Increases the Tibiofemoral Joint Space Width

Introduction

Traditional techniques can enlarge the medial tibiofemoral joint space width (JSW) for meniscal repairs, but a remnant ligament laxity may be developed. Alternatively, the debridement of the inner retinaculum layer may result in a balanced JSW without causing extra-ligament damage (retinaculum layers II and collateral ligament).

Purpose

The purpose of this study was to determine whether a concentric arthroscopic debridement of the inner retinaculum layer increases the tibiofemoral JSW in patients with meniscal injuries. Secondarily, we determine whether the increase in JSW is symmetrical between compartments and describe the rate of complications and patient satisfaction.

Method

Twenty middle-aged (15 male and five female) patients diagnosed with acute meniscal injury aged 36 ± 12 years were enrolled. The patients were submitted to an arthroscopic debridement of the inner layer of the knee retinaculum for both the medial and lateral compartments. The tibiofemoral JSW was measured intra-articularly using a custom instrument. A two-way ANOVA for repeated measures was used to compare the JSW. A Bland–Altman analysis and test-retest analysis were performed.

Results

The JSW increased following the debridement of the inner retinaculum layer, for both the medial and lateral compartments (p < 0.001). No complications were identified, and the patients were satisfied with the intervention. The minimal detectable change and bias of the custom instrument were 0.06 mm and 0.02 mm, respectively.

Conclusion

The debridement allows a clinically important (>1 mm) symmetric tibiofemoral JSW enlargement. The technique suggests favoring the diagnosis of meniscus injuries and manipulating arthroscopic instruments without secondary complications after one year.

Medial patellofemoral ligament is a part of the vastus medialis obliquus and vastus intermedius aponeuroses attaching to the medial epicondyle

PURPOSE

This study aimed to investigate the bony surface characteristic of the femoral attachment of the medial patellofemoral ligament (MPFL) and the correlation between the relevant layered structures, including muscular aponeurosis and the joint capsule, which contribute to patellofemoral joint (PFJ) stability.

METHODS

The morphology of the medial aspect of the medial condyle using micro-computed tomography and analysed cortical bone thickening in 24 knees was observed. For the macroscopic and histological analyses, 21 and 3 knees were allocated, respectively. The Kruskal-Wallis one-way analysis of variance test with Dunn post hoc testing was performed for statistical analysis.

RESULTS

At the level of the adductor tubercle, there were no significant differences in cortical bone thickness. At the level of the medial epicondyle (MEC), cortical bone thickness was considerably greater than that in other areas of the medial condyle (mean ± standard deviation, 0.60 ± 0.20 mm; p < 0.0001). Macroscopic analysis revealed that the deep aponeurosis of the vastus medialis obliquus and the tendinous arch of the vastus intermedius distally formed the composite membrane and adjoined to the joint capsule to firmly attach to MEC, which was located at 41.3 ± 5.7 mm posterior and 14.2 ± 3.1 mm superior to the joint cartilage. Histological analysis showed a composite membrane and adjoining capsule attached to MEC via fibrocartilage.

CONCLUSION

MPFL could be interpreted as part of the deep aponeurosis of the vastus medialis obliquus (VMO) and the tendinous arch of the vastus intermedius, which combined with the joint capsule to attach to MEC. The cortical bone thickening indicated that the tensile stresses were loaded on MEC in aged cadavers. Involvement of VMO and vastus intermedius aponeuroses in restored graft of MPFL could utilise the dynamic stability of surrounding muscles to mimic a native structure.

Biomechanical comparison of two medial patellofemoral ligament reconstruction techniques: Quadriceps tendon fixation versus single-tunnel patella fixation with gracilis autograft did not differ in load to failure and stiffness

BACKGROUND

The purpose of this study was to evaluate the ultimate failure load and stiffness of two patellar fixation techniques for medial patellofemoral ligament (MPFL) reconstruction: (1) quadriceps tendon fixation (QT), (2) single tunnel (STG) patella fixation with gracilis autograft.

METHODS

A total of 16 fresh-frozen cadaveric knees (eight matched pairs) were randomized into two groups (QT vs. STG). The MPFL reconstructions were subjected to cyclic loading for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). Failure mode, ultimate failure load and stiffness were recorded for each cadaveric specimen.

RESULTS

There was no significant difference in mean ultimate failure load among groups (P = 0.35). The STG group failed at a mean ultimate load of 190.04 N [standard deviation (SD) 23.18] and the QT group failed at 206.24 N (SD 37.99). The STG group had a mean stiffness of 21.38 N/mm (SD 1.44). This was not significantly higher than the mean stiffness value achieved for the QT group at 20.36 N/mm (SD 1.3) (P = 0.19). In the QT group all reconstructions failed due to tendon rupture at the patella attachment. The reason for failure in the STG group was the graft-suture connection.

CONCLUSIONS

This cadaver study showed no statistically significant difference in biomechanical performance of the evaluated patella fixation techniques, in terms of maximum load to failure and stiffness. Both techniques are reliable in terms of biomechanical properties and could offer additional surgical solutions.

Surgical and Radiological Anatomy of the Medial Patellofemoral Ligament: A Magnetic Resonance Imaging and Cadaveric Study

The purpose of this study was to compare the measurement of several anatomical features of the medial patellofemoral ligament (MPFL) between magnetic resonance imaging (MRI) and by direct fashion during dissection. We hypothesized that the measurements between these two techniques would agree. MRI of 30 fresh-frozen cadaveric knees was followed by dissection. MPFL patella and femoral attachment were evaluated; their shape, length, and width were measured; and measurements were compared. MRI was deemed unreliable for the determination of several of the aforementioned anatomical features. Important findings include: (a) observations on MPFL attachment at medial patella side and attachment to quadriceps were identical between dissection and MRI; (b) average width at patella insertion was significantly different between the two methods (p = 0.002); and (c) an attachment to the quadriceps tendon was present in 20/30 specimens and d. detailed measurements of a thin, non-linear, and three-dimensional structure, such as the MPFL, cannot be performed on MRI, due to technical difficulties. This anatomical radiological study highlights the shape, anatomical measurements (length and width), and attachment of the MPFL using a relatively large cadaveric sample and suggests that MRI is not reliable for detailed imaging of its three-dimensional anatomy.

Biomechanical evaluation of three patellar fixation techniques for MPFL reconstruction: Load to failure did not differ but interference screw stabilization was stiffer than suture anchor and suture-knot fixation

PURPOSE

The purpose of this study was to compare the maximum load to failure and stiffness of three medial patella-femoral ligament (MPFL) reconstruction techniques: (i) suture anchor fixation (SA), (ii) interference screw fixation (SF), and (iii) suture knot (SK) patellar fixation. The null hypothesis was that the comparison between these three different patella fixation techniques would show no difference in the ultimate failure load and stiffness.

METHODS

Reconstruction of the MPFL with gracilis tendon autograft was performed in 12 pairs of fresh-frozen cadaveric knees (24 knees total; mean age, 63.6 [Formula: see text] 8.0 years). The specimens were randomly distributed into 3 groups of 8 specimens; SA reconstruction was completed with two 3.0-mm metal suture anchors; (SF) fixation was accomplished by two 6-mm bio-composite interference screws; SK fixation at the lateral side of the patella was accomplished after drilling two semi-patellar tunnels with a diameter of 4.5 mm. The reconstructions were subjected to cyclic loading for 10 cycles to 30 N and tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). The final load of failure (N), stiffness (N / mm) and failure mode was recorded in each specimen and followed by statistical analysis.

RESULTS

There was no significant difference in mean ultimate failure load among the three groups. The SK group failed at a mean ([Formula: see text] SD) ultimate load of 253.5 [Formula: see text] 38.2 N, the SA group failed at 243 [Formula: see text] 41.9 N and the SF group at 263.2 [Formula: see text] 9.06 N. The SF group had a mean stiffness of 37.8 [Formula: see text] 5.7 N/mm. This was significantly higher (p < 0.05) than the mean stiffness value achieved for the SK group 21.4 [Formula: see text] 9.5 N/mm and the SA group 18.7 [Formula: see text] 3.4 N/mm. The most common mode of failure in the SA group was anchor pullout, and in the SK group was failure at the graft-suture interface. All the reconstructions in the SF group failed due to tendon graft slippage from the tunnel.

CONCLUSION

Load to failure was not significantly different between the 3 techniques. However, screw fixation was found to be significantly stronger than the anchor and the suture knot fixation in terms of rigidity of the reconstruction. From a clinical point of view, all methods of fixation can be used reliably for MPFL reconstruction, since they were found to be stronger than the native MPFL.

Elongation and orientation pattern of the medial patellofemoral ligament during lunging

Unfavorable clinical outcomes after medial patellofemoral ligament (MPFL) reconstruction, such as early osteoarthritis of the patellofemoral joint, were considered to be associate with tunnel malpositioning. Length change studies have found that small changes in the femoral position can cause great changes in elongation trends. Further studying the MPFL kinematics may help us to understand the consequences of tunnel malpositioning and optimize the reconstruction techniques. Fifteen healthy subjects were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion. Five femoral and three patellar attachments were used to simulate different MPFL bundles. Kinematics of MPFL was defined as elongation and orientation changes (i.e., deviation angle and elevation angle). The mean deviation angle was 28.7° (95% confidence interval, 28.0°-29.4°) at full extension and remained nearly unchanged up to 60° of flexion, and increased to 56.5° (54.1°-58.9°) at 110°. The elevation angle decreased linearly from 12.6° (9.3°-15.9°) at full extension to -86.2° (-92.7-79.7°) at 110° of flexion. The MPFL was most stretched anteriorly and laterally relative to femur from full extension to 30° of flexion and remained near isometric beyond 30°. The current study found that proximal and anterior femoral attachments caused excessive lateral stretching of the MPFL at deeper flexion angles. Such abnormal MPFL kinematics may subsequently cause overconstraint and increased cartilage pressures of the medial patellofemoral joint.

A computed tomography cadaveric study of the radiological anatomy of the patella: the size of the patella correlates with bone bridge between tunnels and R angles are introduced for safe tunnel drilling during MPFL reconstruction

PURPOSE

To measure the safe range of angles during tunnel drilling and map ideal patella tunnel placement with the use of preoperative computed tomography (CT) scan and compare results after medial patellofemoral ligament (MPFL) reconstruction using a hardware-free patellar fixation technique with two semi-patellar tunnels between a) a free-hand technique, and b) its modification with the use of an anterior cruciate ligament (ACL) tibia aiming device.

METHODS

CT scan was performed on 30 fresh-frozen cadaveric knees a) prior to any intervention and b) after MPFL reconstruction. For MPFL reconstruction, specimens were randomly allocated to 1) Group A, which consisted of knees operated with free-hand, hardware-free patellar fixation technique with two semi-patellar tunnels and 2) Group B, which consisted of knees operated on with a technique modification with the ACL tibia device.

PATELLAR MEASUREMENTS

L1 was the maximal patellar length. L2 was the minimum possible distance of placement for the upper tunnel from the proximal pole of the patella. The maximum bone bridge between tunnels was calculated as half of L1 minus the L2 distance (L1/2-L2). We also measured R1 and R2 angles at the proximal and distal tunnel that represent safe angles at the entry point during tunnel drilling (without breaching the anterior cortex or articular cartilage).

RESULTS

Preoperatively, mean L1 was 3.45 cm (range 3.05-4.52). Mean L2 was 0.62 cm (range 0.49-0.89). The mean maximum possible bone bridge between tunnels (L1/2-L2) was 1.1 cm (range 0.77-1.58). R1 was 6.05⁰ (range 4.78-7.44), R2 was 6.64⁰ (range 4.57-9.03), and their difference reached statistical significance (p = 0.03). Postoperatively, in group A, in 4 out of 15 patellas, multiple attempts were made during tunnel drilling in order to avoid anterior cortex or cartilage breaching. In group B, all tunnels were correctly drilled with the first attempt. Bone bridge between tunnels was significantly shorter postoperatively (0.93 cm, p < 0.01).

CONCLUSION

Small-size patellae correlate with short maximum bone bridge between tunnels, which makes anatomic, double-bundle, hardware-free patella fixation, with two semi-patellar tunnels MPFL reconstruction challenging. Furthermore, R angles create a narrow window to avoid intraoperative breaching, rendering the use of the ACL tibia device an extremely useful instrument.

LEVEL OF EVIDENCE

II.

Medial Patellofemoral Reconstruction Using Quadriceps Tendon Autograft, Tibial Tubercle Osteotomy, and Sulcus-Deepening Trochleoplasty for Patellar Instability

Recurrent patellar dislocations have been correlated with an elevated risk of further patellar dislocations, often requiring surgical treatment. Risk factors include medial patellofemoral ligament (MPFL) tears, patella alta, trochlear dysplasia, and an increased tibial tubercle-trochlear groove distance. Surgical management must be based on a patient's unique joint pathoanatomy and may require MPFL reconstruction with tibial tubercle osteotomy or trochleoplasty either alone or in combination. This article discusses our preferred technique for surgical treatment of recurrent patellar instability with MPFL reconstruction using a quadriceps tendon autograft, an open trochleoplasty, and a tibial tubercle osteotomy for patients with patella alta, trochlear dysplasia, and an increased tibial tubercle-trochlear groove distance.

Predicting Risk of Recurrent Patellofemoral Instability With Measurements of Extensor Mechanism Containment

BACKGROUND

Identifying risk factors for recurrent patellar dislocation after a primary dislocation may help guide initial treatment. Magnetic resonance imaging (MRI) measurements relating the alignment of the extensor mechanism to trochlear morphology have been shown to distinguish patients with dislocations from controls, but their usefulness in predicting the risk of a second dislocation is not known.

PURPOSE

To identify the association of novel MRI measures of patellar containment with recurrent instability in pediatric patients presenting with a first-time patellar dislocation.

STUDY DESIGN

Cohort study (Prognosis); Level of evidence, 3.

METHODS

The study was conducted at a tertiary care children's hospital (2005-2014) on patients (age, 8-19 years) with a first-time patellar dislocation. MRI measurements were made by 2 independent raters. Interobserver reliability was assessed for all measurements via an intraclass correlation coefficient (ICC). Only measurements with an ICC >0.8 were included. Univariable and multivariable logistic regression analyses were used to evaluate variables associated with recurrence.

RESULTS

A total of 165 patients with a median age of 14 years and a slight (57.6%) female predominance was identified. The median follow-up length of the whole cohort was 12.2 months (interquartile range, 1.6-37.1 months). Subsequent instability was documented in 98 patients (59.4%). MRI measurements with excellent correlation (ICC > 0.8) were the tibial tubercle to trochlear groove distance (TT-TG), the tangential axial width of the patella, the tangential axial trochlear width, the axial width of the patellar tendon beyond the lateral trochlear ridge (LTR), and the tibial tubercle to LTR distance. In univariate analysis, all mentioned MRI measurements had significant association with recurrent instability. However, after both backward and forward stepwise regression analyses, the tibial tubercle to LTR distance was the only independent predictor of recurrent instability (P = .003 in both). Patients with a tibial tubercle to LTR distance value greater than -1 mm had a significantly higher rate of recurrent patellar dislocation (72%).

CONCLUSION

Of numerous axial view MRI parameters, only the tibial tubercle to LTR distance demonstrated a statistically significant association with recurrent patellar instability upon multivariable logistic regression analysis during short-term follow-up of a pediatric population presenting with initial lateral patellar dislocation. Interobserver correlation of the tibial tubercle to LTR distance was good (ICC > 0.8) and similar to that of TT-TG.

The quadriceps insertion of the medial patellofemoral complex demonstrates the greatest anisometry through flexion

PURPOSE

A comprehensive understanding of the biomechanical properties of the medial patellofemoral complex (MPFC) is necessary when performing an MPFC reconstruction. How components of the MPFC change over the course of flexion can influence the surgeon's choice of location for graft fixation along the extensor mechanism. The purpose of this study was to (1) determine native MPFC length changes throughout a 90° arc using an anatomically based attachment and using Schöttle's point, and (2) compare native MPFC length changes with different MPFC attachment sites along the extensor mechanism.

METHODS

Eight fresh-frozen (n = 8), cadaveric knees were dissected of all soft tissue structures except the MPFC. The distance between the femoral footprint (identified through anatomical landmarks and Schottle's point) and the MPFC was calculated at four attachment sites along the extensor mechanism [midpoint of the patella [MP], the center of the osseous footprint of the MPFC (FC), the superomedial corner of the patella at the quadriceps insertion (SM), and the proximal extent of the MPFC along the quadriceps tendon (QT)] at 0°, 20°, 40°, 60°, and 90° of flexion.

RESULTS

Length changes were investigated between the MPFL femoral attachment site and the radiographic surrogate of the MPFL attachment site, Schottle's Point (SP). Paired t tests at each of the four components showed no differences in length change from 0° to 90° when comparing SP to the anatomic MPFC insertion. MPFL length changes from 0° to 90° were greatest at the QT point (13.9 ± 3.0 mm) and smallest at the MP point (2.7 ± 4.4 mm). The FC and SM points had a length change of 6.6 ± 4.2 and 9.0 ± 3.8, respectively. Finally, when examining how the length of the MPFC components changed through flexion, the greatest differences were seen at QT where all comparisons were significant (p < 0.01) except when comparing 0° vs 20° (n.s.).

CONCLUSION

The MPFC demonstrates the most significant length changes between 0° and 20° of flexion, while more isometric behavior was seen during 20°-90°. The attachment points along the extensor mechanism demonstrate different length behaviors, where the more proximal components of the MPFC display greater anisometry through the arc of motion. When performing a proximal MPFC reconstruction, surgeons should expect increased length changes compared to reconstructions utilizing distal attachment sites.

[Research progress in femoral tunnel positioning points of medial patellofemoral ligament reconstruction]

Objective

To review the research progress of location methods and the best femoral insertion position of medial patellofemoral ligament (MPFL) reconstruction of femoral tunnel, and provide reference for surgical treatment.

Methods

The literature about femoral insertion position of the MPFL reconstruction in recent years was extensively reviewed, and the anatomical and biomechanical characteristics of MPFL, as well as the advantages and disadvantages of femoral tunnel positioning methods were summarized.

Results

The accurate establishment of the femoral anatomical tunnel is crucial to the success of MPFL reconstruction. At present, there are mainly two kinds of methods for femoral insertion: radiographic landmark positioning method and anatomical landmark positioning method. Radiographic landmark positioning method has such advantages as small incision and simple operation, but it can not be accurately positioned for patients with severe femoral trochlear dysplasia. It is suggested to combine with the anatomical landmark positioning method. These methods have their own advantages and disadvantages, and there is no unified positioning standard. In recent years, the use of three-dimensional design software can accurately assist in the MPFL reconstruction, which has become a new trend.

Conclusion

Femoral tunnel positioning of the MPFL reconstruction is very important. The current positioning methods have their own advantages and disadvantages. Personalized positioning is a new trend and has not been widely used in clinic, its effectiveness needs further research and clinical practice and verification.

Combined Medial Patellofemoral Ligament and Medial Patellotibial Ligament Reconstruction for Recurrent Lateral Patellar Dislocation in Flexion

Recurrent lateral patellar dislocation can be a challenging entity to manage. It results from an imbalance between the restraints to lateralization of the patella and the forces applied to the patella within the biomechanical environment of the knee. The medial patellofemoral ligament has been recognized as the most important static soft-tissue restraint. However, the medial patellotibial ligament and medial patellomeniscal ligament are important for patellar stability at higher degrees of knee flexion. Lateral patellar dislocation in flexion poses a particularly challenging clinical entity with a combination of unique characteristics that need to be addressed to achieve optimal patellar tracking and stability. In this technical note, we describe a combined medial patellofemoral ligament and medial patellotibial ligament reconstruction technique to address lateral patellar dislocation in flexion.

The majority of patellar avulsion fractures in first-time acute patellar dislocations included the inferomedial patellar border that was different from the medial patellofemoral ligament attachment

PURPOSE

Accurate assessment of the locations of patellar avulsion fractures in acute patellar dislocations is clinically relevant for decision making for treatment. The study aim was to classify the locations of patellar avulsion fractures with a focus on the ligament attachments of medial stabilizing structures.

METHODS

Out of 131 first-time acute traumatic patellar dislocations, 61 patients had patellar fractures. Subsequently, 10 patients with isolated osteochondral fractures of the articular surface in the patella were excluded. Finally, 51 patients (34 females and 17 males, average age: 18.5 years, 95% CI 16.1-20.9) were included in the study cohort. Based on the locations of the patellar attachment, the patients were divided into three groups: the superior group [medial patellofemoral ligament (MPFL) attachment], inferior group [medial patellotibial ligament (MPTL)/medial patellomeniscal ligament (MPML) attachment], and mixed group.

RESULTS

In the patellar avulsion group (51 patients), the superior group, mixed group, and inferior group contained 8/51 (16%), 12/51 (24%), and 31/51 (61%) patients, respectively.

CONCLUSIONS

This study showed that 84% of the patellar avulsion fractures were located in the inferomedial patellar border, which consisted of MPTL/MPML attachments that were clearly different from the true "MPFL" attachment at the superomedial patellar border. In terms of the clinical relevance, the acute surgical repair of MPTL/MPML attachments in the inferomedial patellar border may not sufficiently control the patella if optimal management of the MPFL is not performed.

LEVEL OF EVIDENCE

IV.

Femoral Origin Anatomy of the Medial Patellofemoral Complex: Implications for Reconstruction

PURPOSE

To report the shape and orientation of the medial patellofemoral complex (MPFC) footprint on the medial femur and describe the difference between the proximal (medial quadriceps tendon femoral ligament, MQTFL) and distal (medial patellofemoral ligament, MPFL) fibers.

METHODS

In 20 cadaveric knees, the MPFC footprint on the medial femur was exposed. Images of the medial femur were analyzed using ImageJ software. The length and width of the MPFC footprint were described to the nearest 0.1 mm; the angle of its long axis was described relative to the axis of the femoral shaft (0.1°). The footprint's most proximal and distal margins were described in relation to the adductor tubercle and medial epicondyle. The differences between each were compared using paired t tests.

RESULTS

17 knees from 10 cadavers were included in this study. The MPFC footprint had a length of 11.7 ± 1.8 mm and a width of 1.7 ± 0.4 mm. The long axis of the footprint was at an angle 14.6° ± 16.6° anterior to the axis of the femoral shaft. The most proximal (MQTFL) fibers originated 7.4 ± 3.8 mm anterior and 1.8 ± 4.7 mm distal to the adductor tubercle and 4.1 ± 2.9 mm posterior and 8.4 ± 5.6 mm proximal to the medial epicondyle. The most distal (MPFL) fibers originated 4.9 ± 4.2 mm anterior and 12.7 ± 4.3 mm distal to the adductor tubercle, as well as 7.1 ± 2.4 mm posterior and 0.5 ± 5.6 mm distal to the medial epicondyle. The distal margin of the femoral MPFC footprint was 10.9 ± 1.7 mm distal (p < .001) and 2.6 ± 3.2 mm more posterior (p = .005) than the proximal margin.

CONCLUSIONS

The femoral footprint of the MPFC has a length almost 7 times greater than its width, with the distal margin being 10.9 mm distal and 2.6 mm posterior to the proximal margin.

CLINICAL RELEVANCE

This differential anatomy within the femoral origin suggests that MPFL and MQTFL reconstruction may require separate positions of femoral fixation to recreate the anatomy of these fibers.

Anatomy and biomechanics of the medial patellotibial ligament: A systematic review

BACKGROUND

The knowledge of the anatomy and biomechanics of patellar stabilizers is mandatory to achieve good clinical results with surgical reconstructive procedures. Few articles provide clear anatomical and biomechanical picture of medial patello-tibial ligament (MPTL).

METHODS

After a systematic review of the literature we selected in vivo or ex vivo studies providing anatomical or biomechanical measurements. We included 7 studies about MPTL anatomy for a total of 96 knees and 4 biomechanical studies.

RESULTS

The MPTL is a true ligament and important component of the medial patellar stabilizers, together with the medial patello-femoral ligament (MPFL) and medial patello-meniscal ligament. The contribution of MPTL on restriction forces of the patello-femoral joint is still unclear. Quadriceps, patellar, semitendinous and gracilis tendons are adequate grafts for surgical MPTL reconstruction.

CONCLUSIONS

MPTL is a well defined anathomical structure and histologically can be considered a ligament. It plays an important role in patellar stability especially it has a main role on patellar rotation and tilt instead on shift.

Medial Patellotibial Ligament Reconstruction Improves Patella Tracking When Combined With Medial Patellofemoral Reconstruction: An In Vitro Kinematic Study

PURPOSE

To investigate the isolated and combined effects of medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) deficiency and reconstruction on patellofemoral kinematics.

METHODS

Sixteen matched-paired female cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were tested in 5 conditions: (1) intact, (2) MPFL or MPTL cut, (3) MPFL and MPTL combined cut, (4) MPFL or MPTL reconstruction, and (5) MPFL and MPTL combined reconstruction. Dynamic testing allowed continuous analysis of kinematics from 0° to 90° of knee flexion. Knees were also tested statically using a lateral load of 45 N at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Random-intercepts linear mixed-effects models were used to compare patellar kinematics.

RESULTS

The MPFL is the primary restraint to lateral translation of the patella at all knee flexion angles. MPTL deficiency alone did not create significant patella instability, but further increased instability when the MPFL was deficient. Isolated MPFL and combined reconstruction provided improved stability. Through full range of motion native patella tracking was best recreated with combined ligament reconstruction.

CONCLUSIONS

The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have an influence on patella tracking. This study provides further understanding to the impact of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

CLINICAL RELEVANCE

This study provides further understanding of the role of the MPFL and MPTL on patellofemoral motion with implications for reconstruction to improve stability and optimize patellofemoral tracking.

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.

Differential Contributions of the Quadriceps and Patellar Attachments of the Proximal Medial Patellar Restraints to Resisting Lateral Patellar Translation

PURPOSE

To define the contributions of the of the medial patellofemoral ligament (MPFL) and medial quadriceps tendon femoral ligament (MQTFL) to lateral patellar translation as the knee moves through a 90° arc of motion.

METHODS

Six pairs of bilateral cadaveric knee specimens (12 knees) were dissected and potted in perfect lateral position using fluoroscopy. An eye screw was placed in the midpoint on the lateral aspect of the patella. Each knee underwent testing in 4 conditions after sequential sectioning: intact, lateral retinacular release, randomized MQTFL or MPFL sectioning, and complete proximal medial patellar restraint (PMPR) sectioning. With a custom machined jig, all knees were tested at 0, 10, 20, 30, 45, 60, and 90° of flexion on an MTS machine with 20N of lateral patellar force applied and displacement recorded.

RESULTS

PMPR extensor mechanism insertion on all specimens was identified 50% on the quadriceps tendon and 50% on the proximal aspect of the medial patella. Isolated MPFL sectioning resulted in significantly increased lateral displacement compared to the lateral release state at all flexion angles tested except 0°. There was significantly increased lateral patellar displacement with complete sectioning compared with isolated proximal sectioning at all degrees of knee flexion except 0°. However, complete sectioning following isolated MPFL sectioning did not demonstrate significance at any angle.

CONCLUSIONS

Compared with the MQTFL, the MPFL is primarily responsible for resistance to lateral patellar translation throughout a 0° to 90° arc of motion. The MPFL provides a similar resistance to lateral patellar displacement as the fully intact PMPR; however, the MQTFL may contribute to resistance in full extension.

CLINICAL SIGNIFICANCE

Proximal medial patellar restraint reconstruction techniques involving both the patellar and quadriceps insertion have been described; however, the unique contributions of the native anatomy to lateral patellar restraint have not been investigated.

Patellofemoral Contact Pressure for Medial Patellofemoral Ligament Reconstruction Using Suture Tape Varies With the Knee Flexion Angle: A Biomechanical Evaluation

PURPOSE

The purpose of this study was to evaluate the effect of the knee flexion angle during graft fixation on patellofemoral (PF) contact pressure in medial patellofemoral ligament (MPFL) reconstruction using polyester suture tape and knotless anchors.

METHODS

Nine human knees (mean age 74.9 ± 14.1 years) were used in this study. Polyester suture tape was fixed at the medial edge of the patella with two 3.5-mm knotless anchors, and then to the femur with a 4.75-mm knotless anchor at 4 different knee flexion angles (0°, 30°, 60°, and 90°). A pressure sensor was used to measure the maximum contact pressure (MCP) of the medial and lateral PF joints in the intact knee and in postreconstruction knees at each knee flexion angle (0°, 30°, 60°, and 90°). Each MCP was normalized to that of the intact knee. A statistical comparison was made between MCP in the intact and reconstructed knees.

RESULTS

The normalized MCP of the medial PF joint fixed at either 0° or 30° significantly increased at 60° of knee flexion (P = .036 and .042, respectively) and at 90° of knee flexion (P = .002 and .001, respectively). Conversely, the normalized MCP fixed at 60° and 90° remained at the same level as the intact knees at all angles of knee flexion. The normalized MCP of the lateral PF joint showed no significant difference at any fixation angle compared with intact knees.

CONCLUSION

To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be best to fix polyester suture tape between 60° and 90° of knee flexion.

CLINICAL RELEVANCE

Fixation of the polyester suture tape with a knotless anchor for MPFL reconstruction should be at 60° to 90° of knee flexion to most closely restore PF joint contact pressures to that of the intact knee.

Effect of Patella Alta on the Native Anatomometricity of the Medial Patellofemoral Complex: A Cadaveric Study

BACKGROUND

Patella alta has been identified as an important risk factor for lateral patellar instability and medial patellofemoral complex (MPFC) reconstruction failure.

PURPOSE

To evaluate the length changes of the MPFC at multiple possible reconstruction locations along the extensor mechanism in varying degrees of patella alta throughout knee motion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric knees were used in this study. The MPFC was identified and dissected with the patellar tendon and quadriceps tendon. A custom-made jig was utilized to evaluate lengths from 0° to 90° of flexion with physiological quadriceps loading. Length was measured with a 3-dimensional robotic arm at 4 possible reconstruction locations along the extensor mechanism: the midpoint patella (MP), the MPFC osseous center (FC), the superior medial pole of the patella (SM) at the level of the quadriceps insertion, and 1 cm proximal to the SM point along the quadriceps tendon (QT). These measurements were repeated at 0°, 20°, 40°, 60° and 90° of flexion. Degrees of increasing severity of patella alta at Caton-Deschamps index (CDI) ratios of 1.0, 1.2, 1.4, and 1.6 were then investigated.

RESULTS

Patella alta and MPFC attachment site location significantly affected changes in MPFC length from 0° to 90° of flexion (P< .0005). Length changes at attachment MP showed no difference when CDI 1.0 was compared with all patella alta values (CDI 1.2, 1.4, 1.6; P > .05). Similarly, FC showed no difference in length change from 0° to 90° until CDI 1.6, in contrast to proximal attachments (SM, QT), which demonstrated significant changes at CDI 1.4 and 1.6. When length changes were analyzed at each degree of flexion (0°, 20°, 40°, 60°, 90°), Spearman correlation analysis showed a moderate negative linear correlation for QT at CDI 1.0 (r= -0.484; P = .002) and 1.6 (r = -0.692; P < .0005), demonstrating constant loosening at the QT point at normal and elevated patellar height. In contrast, no differences in length were observed for MP at CDI 1.0 throughout flexion, and at CDI 1.6, there was a difference only at 0° (P < .05). Points FC and MP at CDI 1.6 had similar length change properties to points SM and QT at CDI 1.0 (P > .05), suggesting that distal attachments in the setting of patella alta may provide similar length changes to proximal attachmentswith normal height.

CONCLUSION

Anisometry of the MPFC varies not only with attachment location on the extensor mechanism but also with patellar height. Increased patellar height leads to more significant changes in anisometry in the proximal MPFC attachment point as compared with the distal component. In the setting of patella alta, including a CD ratio of 1.6, the osseous attachments of the MPFC remain nearly isometric wheras the proximal half length changes increase significantly.

CLINICAL SIGNIFICANCE

The results of this study support the idea that the MPFC should be considered as 2 separate entities (proximal medial quadriceps tendon femoral ligament and distal medial patellofemoral ligament) owing to their unique length change properties.

Why and Where to Move the Tibial Tubercle: Indications and Techniques for Tibial Tubercle Osteotomy

Patellofemoral disorders including pain and instability are common orthopedic problems, particularly in the adolescent population. Patellofemoral pain is usually anterior, poorly localized, and diffuse. Because of its multifactorial etiology, patellofemoral pain can be clinically challenging to diagnose and manage. With regards to instability, predisposing factors include trochlear dysplasia, patella alta, patellar tilt, and an elevated tibial tuberosity and trochlea groove distance. Initially, nonoperative management is recommended to treat patellofemoral maladies such as overload, maltracking, and acute first-time dislocations. However, tibial tubercle transfer (TTT) is commonly used to address cases of symptomatic malalignment and overload and recurrent patellar instability. The tubercle can be translated in multiplanar directions to correct patellar height, maltracking associated with instability, and to offload chondral defects. A thorough understanding of the anatomy and biomechanics of the patellofemoral joint is essential for optimizing results after TTT. Individualizing the direction and degree of tubercle transfer on the basis of patient parameters is critical to producing successful long-term results after surgery. This article will review the indications for performing a TTT and highlight the various techniques.

An Updated Overview of the Anatomy and Function of the Proximal Medial Patellar Restraints (Medial Patellofemoral Ligament and the Medial Quadriceps Tendon Femoral Ligament)

The medial patellofemoral ligament (MPFL) has been widely accepted to function as "the primary static restraint to lateral patellar displacement." However, current growing evidence suggests that there is a complex of medial patellofemoral/tibial ligaments, both proximal [MPFL, and medial quadriceps tendon femoral ligament (MQTFL)], and distal (medial patellotibial ligament and the medial patellomeniscal ligament) which restrain lateral patellar translation at different degrees of knee flexion. Specifically, the MQTFL has gained popularity over the last decade because of pure soft tissue attachments into the extensor mechanism that allow for avoidance of drilling tunnels into the patella during reconstruction. The purpose of this article was to report on the current knowledge (anatomy, biomechanics, diagnosis, indications for surgery, and techniques) on the proximal medial patellar restraints, namely the MPFL and the MQTFL, collectively referred to as the proximal medial patellar restraints.

Concepts of the Distal Medial Patellar Restraints: Medial Patellotibial Ligament and Medial Patellomeniscal Ligament

The important medial patellar ligamentous restraints to lateral dislocation are the proximal group (the medial quadriceps tendon femoral ligament and the medial patellofemoral ligament) and the distal group [medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML)]. The MPTL patellar insertion is at inferomedial border of patella and tibial insertion is in the anteromedial tibia. The MPML originates in the inferomedial patella, right proximal to the MPTL, inserting in the medial meniscus. On the basis of anatomy and biomechanical studies, the MPTL and MPML are more important in 2 moments during knee range of motion: terminal extension, when it directly counteracts quadriceps contraction. In a systematic review on MPTL reconstructions 19 articles were included detailing the clinical outcomes of 403 knees. All were case series. Overall, good and excellent outcomes were achieved in >75% of cohorts in most studies and redislocations were <10%, with or without the association of the medial patellofemoral ligament. The MPTL is a relevant additional tool to proximal restraint reconstruction in select patient profiles; however, more definitive clinical studies are necessary to better define surgical indications.

Isolated medial patellofemoral ligament reconstruction significantly improved quality of life in patients with recurrent patella dislocation

PURPOSE

The purpose of this study was to measure the improvement in quality of life (QoL) following isolated anatomical double-bundle medial patellofemoral ligament reconstruction.

METHODS

This is a single-centre, prospective study of 56 consecutive patients (57 knees) who underwent isolated MPFL reconstruction between 2014 and 2017. Functional outcome and QoL were assessed with the Kujala score and the EQ-5D-3L questionnaire, respectively. Objective outcomes were obtained through clinical examination at the latest follow-up assessing redislocation rate, patella apprehension test, patellar tilt, pain and range of motion.

RESULTS

The median Kujala score increased from 60 (range 31-96) to 92 (range 34-100) at latest follow-up (p < 0.001). The median EQ-5D index also increased, from 0.69 (range 0.10-1) at baseline to 1 (range 0.16-1) at latest follow-up (p < 0.001), as well as the median EQ-5D VAS from 75 (range 20-95) to 92 (range 40-100) (p < 0.001). Four dimensions of the EQ-5D were significantly improved except for the anxiety/depression scores. Female patients reported lower scores at baseline and at latest follow-up, for all three outcomes (Kujala, EQ-5D index, EQ-5D VAS), however there was no evidence that gender negatively impacted on the benefit of surgery. The re-dislocation rate was 0%. Apprehension and patellar tilt test were negative in all patients and no flexion deficit was identified at latest follow-up. Two patients had tenderness along the reconstruction requiring femoral screw removal in one of them.

CONCLUSIONS

Isolated anatomical double-bundle aperture MPFL reconstruction, offered significantly improved short-term QoL along with excellent functional outcome. Female patients scored lower, but this did not affect the overall outcome. Including QoL tools in the assessment of ligament reconstruction operations, such as the MPFL, can provide more accurate understanding of the overall patient benefit.

LEVEL OF EVIDENCE

II.

Recognition of evolving medial patellofemoral anatomy provides insight for reconstruction

PURPOSE

The scientific literature concerning the anatomy of medial soft-tissue stabilizers of the patella is growing exponentially. Much of the surgical literature has focused on the role of the medial patellofemoral ligament (MPFL) and techniques to reconstruct it, yet our understanding of its anatomy has evolved during the past several years. Given this, we report on the current understanding of medial patellofemoral anatomy and implications for reconstruction.

METHODS

Current and historical studies of medial patellar anatomy were reviewed, which include the MPFL and medial quadriceps tendon femoral ligament (MQTFL), as well as that of the distal medial patellar restraints, the medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML). In addition to the reported findings, the authors' anatomic descriptions of each ligament during their dissections were identified and recorded.

RESULTS

Despite the name of the MPFL, which implies that the ligament courses between the femur and patella, recent studies have highlighted the proximal MPFL fibers that attach to the quadriceps tendon, known as the MQTFL. The MPFL and MQTFL have also been referred to as the medial patellofemoral complex, reflecting the variability in anatomical attachment sites. The MPFL accounts for only half of the total restraint to lateral patellar displacement, and the remaining contributions to patellar stability are derived from the combination of the MPTL and MPML, which function primarily in greater degrees of knee flexion.

CONCLUSION

The understanding of the complexity of the medial patellar stabilizers continues to evolve. Although MPFL reconstruction is gaining wide acceptance as a procedure to treat patellar instability, it is important to recognize the complex and changing understanding of the anatomy of the medial soft-tissue stabilizers and the implications for reconstruction.

LEVEL OF EVIDENCE

V.

Medial patellofemoral ligament (MPFL) reconstruction using quadriceps tendon autograft provides good clinical, functional and patient-reported outcome measurements (PROM): a 2-year prospective study

PURPOSE

The medial patellofemoral ligament (MPFL) is the most important ligamentous stabilizer preventing lateral patella dislocation. Numerous surgical procedures for MPFL reconstruction have been described in the literature. The aim of this study was to investigate the clinical, functional and patient-reported (PROM) outcomes 2 years after minimally invasive MPFL reconstruction performed using an autologous strip of the quadriceps tendon.

METHODS

Thirty-six patients (38 knees) were included in the study. For MPFL reconstruction, a partial thickness autologous quadriceps tendon graft was used. All patients were evaluated clinically and with patient-reported outcome questionnaires including the Tegner, Lysholm and Kujala scores as well as a visual analogue scale (VAS) for pain preoperatively and at 6, 12 and 24 months postoperatively. A functional Back-in-Action (BIA) test battery, including a total of seven stability, agility and jumping tests, was performed on 19 (50%) patients at the final follow-up. One patient was lost to follow-up at 24 months.

RESULTS

The mean age at the time of operation was 25.2 ± 6.1 years. No redislocations occurred during the period of investigation. The mean Lysholm score improved significantly from 79.3 ± 16.1 preoperatively to 83.2 ± 14.4 at 6 months, 88.1 ± 11.3 at 12 months and to 90.0 ± 9.6 at 24 months follow-up. No change throughout the study period was observed for the median Tegner Activity Score (median 6). The mean Kujala score increased from a preoperative value of 82.0 ± 12.4, to 84.5 ± 8.4 at 6 months, and 88.2 ± 5.8 at 12 months up to 88.7 ± 4.5 at 24 months follow-up. A total of 77.8% of the performed functional BIA tests were equal to or above the norm for patients of the corresponding ages and activity levels.

CONCLUSIONS

Minimally invasive MPFL reconstruction with a partial thickness strip of quadriceps tendon is a safe and effective treatment for patellofemoral instability. Good clinical, functional and subjective results were observed at the 2-year follow-up.

LEVEL OF EVIDENCE

Prospective cohort study, non-randomized, Level IV.

The Medial Patellofemoral Ligament Is a Dynamic and Anisometric Structure: An In Vivo Study on Length Changes and Isometry

BACKGROUND

Medial patellofemoral ligament (MPFL) reconstruction is associated with a high rate of complications, including recurrent instability and persistent knee pain. Technical errors are among the primary causes of these complications. Understanding the effect of adjusting patellofemoral attachments on length change patterns may help surgeons to optimize graft placement during MPFL reconstruction and to reduce graft failure rates.

PURPOSE

To determine the in vivo length changes of the MPFL during dynamic, weightbearing motion and to map the isometry of the 3-dimensional wrapping paths from various attachments on the medial femoral epicondyle to the patella.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Fifteen healthy participants were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion (full extension to ~110° of flexion). On the medial femoral epicondyle, 185 attachments were projected, including the anatomic MPFL footprint, which was divided into 5 attachments (central, proximal, distal, posterior, and anterior). The patellar MPFL area was divided into 3 possible attachments (proximal, central, and distal). The length changes of the shortest 3-dimensional wrapping paths of the various patellofemoral combinations were subsequently measured and mapped.

RESULTS

For the 3 patellar attachments, the most isometric attachment, with an approximate 4% length change, was located posterior and proximal to the anatomic femoral MPFL attachment, close to the adductor tubercle. Attachments proximal and anterior to the isometric area resulted in increasing lengths with increasing knee flexion, whereas distal and posterior attachments caused decreasing lengths with increasing knee flexion. The anatomic MPFL was tightest in extension, decreased in length until approximately 30° of flexion, and then stayed near isometric for the remainder of the motion. Changing both the femoral and patellar attachments significantly affected the length changes of the anatomic MPFL ( P < .001 for both).

CONCLUSION

The most isometric location for MPFL reconstruction was posterior and proximal to the anatomic femoral MPFL attachment. The anatomic MPFL is a dynamic, anisometric structure that was tight in extension and early flexion and near isometric beyond 30° of flexion.

CLINICAL RELEVANCE

Proximal and anterior MPFL tunnel positioning should be avoided, and the importance of anatomic MPFL reconstruction is underscored with the results found in this study.