Femoral insertion site in medial patellofemoral ligament reconstruction

MPFL reconstruction with proximal rather than distal femoral tunnel position leads to less favorable short-term results

BACKGROUND

This study aimed to compare the clinical and radiological outcomes of medial patellofemoral ligament (MPFL) reconstruction (MPFLR) between anatomic femoral tunnel positions: proximal (near adductor tubercle [AT]) and distal (near medial epicondyle [ME]).

HYPOTHESIS

MPFLR with the proximal femoral tunnel position has worse clinical and radiological outcomes than those with the distal femoral tunnel position.

PATIENTS AND METHODS

Fifty-five patients who underwent isolated MPFLR with proximal or distal femoral tunnels with at least 2 years of follow-up were retrospectively analyzed. Based on postoperative CT images, 28 patients were classified as group AT and the remaining 27 patients were classified as group ME. The International Knee Documentation Committee, Lysholm, Tegner, Kujala scores, and complications were evaluated. Radiologically, the Caton-Deschamps Index (CDI), patellar tilt angle, patellofemoral osteoarthritis (PFOA), patellofemoral cartilage status by the International Cartilage Repair Society (ICRS) grade, bone contusion, and MPFL graft signal intensity were evaluated.

RESULTS

All clinical scores significantly improved in both groups (p<0.01). No statistically significant difference was noted between the two groups in regards to their preoperative demographic data, postoperative clinical scores, complications, or radiological findings (CDI, patellar tilt angle, PFOA, bone contusion, and graft signal intensity). The group AT had worse cartilage status on the medial facet of the patella (p=0.02). The ICRS grade for the medial facet of the patella statistically progressed in group AT compared to group ME (p=0.04) as well.

DISCUSSION

Both groups showed significantly improved clinical outcomes. However, for the medial facet of the patella, MPFLR with the proximal femoral tunnel position had worse cartilage status and ICRS grade progression than those with the distal femoral tunnel position.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Anatomic femoral tunnel position in medial patellofemoral ligament reconstruction: anterior versus posterior

BACKGROUND

This study aimed to compare the clinical and radiological outcomes of medial patellofemoral ligament reconstruction (MPFLR) between anatomic femoral tunnel positions at anterior and posterior footprints.

METHODS

Fifty-seven patients who underwent MPFLR for patellofemoral instability with anterior or posterior femoral tunnels between 2014 and 2021 with at least 2 years of follow-up were retrospectively analyzed. Based on postoperative images, the femoral tunnel positions anterior to the line connecting the adductor tubercle and medial epicondyle were assigned to the anterior group, group A, and those posterior to the line to the posterior group, group P. Thirty-two patients were included in group A (mean age, 22.4 ± 8.8 years), and another 25 patients were included in group P (mean age, 21.1 ± 6.1 years). The International Knee Documentation Committee (IKDC) subjective score, Lysholm score, Tegner activity score, Kujala score, and complications were evaluated. Radiologically, the Caton-Deschamps index (CDI), patellar tilt angle, and patellofemoral osteoarthritis (PFOA) using the Kellgren-Lawrence (KL) scale were evaluated. The patellofemoral cartilage status according to the International Cartilage Repair Society (ICRS) grade, bone contusion, femoral tunnel enlargement, and MPFL graft signal intensity were also evaluated.

RESULTS

All clinical scores significantly improved in both groups (p < 0.01). No differences were noted between the two groups in terms of their preoperative demographic data, postoperative clinical scores (IKDC, Lysholm, Tegner, and Kujala), complications, or radiological findings (CDI, patellar tilt angle, PFOA, bone contusion, femoral tunnel enlargement, and graft signal intensity). The ICRS grade for the medial facet of the patella progressed in group A (30%, p = 0.02) but not in group P (18%, p = n.s.). Additionally, no significant differences were observed in the other compartments of the patellofemoral joint.

CONCLUSIONS

The clinical outcomes were significantly improved in both groups; however, MPFLR with anterior femoral tunnel position had worse cartilage status on the medial facet of the patella than the posterior femoral tunnel position.

LEVEL OF EVIDENCE

Level III.

Elongation Patterns of the Superficial Medial Collateral Ligament and the Posterior Oblique Ligament: A 3-Dimensional, Weightbearing Computed Tomography Simulation

Background:

Although length change patterns of the medial knee structures have been reported, either the weightbearing state was not considered or quantitative radiographic landmarks that allow the identification of the insertion sites were not reported.

Purpose:

To (1) analyze the length changes of the superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL) under weightbearing conditions and (2) to identify the femoral sMCL insertion site that demonstrates the smallest length changes during knee flexion and report quantitative radiographic landmarks.

Study Design:

Descriptive laboratory study.

Methods:

The authors performed a 3-dimensional (3D) analysis of 10 healthy knees from 0° to 120° of knee flexion using weightbearing computed tomography (CT) scans. Ligament length changes of the sMCL and POL during knee flexion were analyzed using an automatic string generation algorithm. The most isometric femoral insertion of the sMCL that demonstrated the smallest length changes throughout the full range of motion (ROM) was identified. Radiographic landmarks were reported on an isometric grid defined by a true lateral view of the 3D CT model and transferred to a digitally reconstructed radiograph.

Results:

The sMCL demonstrated small ligament length changes, and the POL demonstrated substantial shortening during knee flexion ( P = .005). Shortening of the POL started from 30° of flexion. The most isometric femoral sMCL insertion was located 0.6 ± 1.7 mm posterior and 0.8 ± 1.2 mm inferior to the center of the sMCL insertion and prevented ligament length changes >5% during knee flexion in all participants. The insertion was located 47.8% ± 2.7% from the anterior femoral cortex and 46.3% ± 1.9% from the joint line on a true lateral 3D CT view.

Conclusion:

The POL demonstrated substantial shortening starting from 30° of knee flexion and requires tightening near full extension to avoid overconstraint. Femoral sMCL graft placement directly posteroinferior to the center of the anatomical insertion of the sMCL demonstrated the most isometric behavior during knee flexion.

Clinical Relevance:

The described elongation patterns of the sMCL and POL aid in guiding surgical medial knee reconstruction and preventing graft lengthening and overconstraint of the medial compartment. Repetitive graft lengthening is associated with graft failure, and overconstraint leads to increased compartment pressure, cartilage degeneration, and restricted ROM.

Elongation Patterns of Posterolateral Corner Reconstruction Techniques: Results Using 3-Dimensional Weightbearing Computed Tomography Simulation

Background:

The isometric characteristics of nonanatomic and anatomic posterolateral corner (PLC) reconstruction techniques under weightbearing conditions remain unclear.

Purpose:

To (1) simulate graft elongation patterns during knee flexion for 3 different PLC reconstruction techniques (Larson, Arciero, and LaPrade) and (2) compute the most isometric insertion points of the fibular collateral ligament (FCL) graft strands for each technique and report quantitative radiographic landmarks.

Study Design:

Descriptive laboratory study.

Methods:

The authors performed a 3-dimensional simulation of 10 healthy knees from 0° to 120° of flexion using weightbearing computed tomography (CT) scans. The simulation was used to calculate ligament length changes during knee flexion for the PLC reconstruction techniques of Larson (nonanatomic single-bundle fibular sling reconstruction), Arciero (anatomic reconstruction with additional popliteofibular ligament graft strand), and LaPrade (anatomic reconstruction with popliteofibular ligament graft strand and popliteus tendon graft strand). The most isometric femoral insertion points for the FCL graft strands were computed within a 10-mm radius around the lateral epicondyle (LE), using an automatic string generation algorithm (0 indicating perfect isometry). Radiographic landmarks for the most isometric points were reported.

Results:

Median graft lengthening during knee flexion was similar for the anterior graft strands of all 3 techniques. The posterior graft strands demonstrated significant differences, from lengthening for the Arciero (9.9 mm [range, 6.7 to 15.9 mm]) and LaPrade (10.2 mm [range, 4.1 to 19.7 mm]) techniques to shortening for the Larson technique (−17.1 mm [range, −9.3 to −22.3 mm]; P < .0010). The most isometric point for the FCL graft strands of all techniques was located at a median of 2.2 mm (range, −2.2 to 4.5 mm) posterior and 0.3 mm (range, −1.8 to 3.7 mm) distal to the LE.

Conclusion:

Overconstraint can be avoided by tensioning the posterior graft strands in the Larson technique in extension, and in the Arciero and LaPrade techniques at a minimum of 60° of knee flexion. The most isometric point was located posterodistal to the LE.

Clinical Relevance:

The described isometric behavior of nonanatomic and anatomic PLC reconstruction techniques can guide optimal surgical reconstruction and prevent graft lengthening and overconstraint of the lateral compartment in knee flexion. Repetitive graft lengthening has been found to be associated with graft failure, and overconstraint favors lateral compartment pressure and cartilage degeneration.

Influence of femoral tunnel exit on the 3D graft bending angle in anterior cruciate ligament reconstruction

Purpose

To quantify the influence of the femoral tunnel exit (FTE) on the graft bending angle (GBA) and GBA-excursion throughout a full range of motion (ROM) in single-bundle anterior cruciate ligament (ACL) reconstruction.

Methods

Three-dimensional (3D) surface models of five healthy knees were generated from a weight-bearing CT obtained throughout a full ROM (0, 30, 60, 90, 120°) and femoral and tibial ACL insertions were computed. The FTE was simulated for 16 predefined positions, referenced to the Blumensaat's line, for each patient throughout a full ROM (0, 30, 60, 90, 120°) resulting in a total of 400 simulations. 3D GBA was calculated between the 3D directional vector of the ACL and the femoral tunnel, while the intra-articular ACL insertions remained unchanged. For each simulation the 3D GBA, GBA-excursion, tunnel length and posterior tunnel blow-out were analysed.

Results

Overall, mean GBA decreased with increasing knee flexion for each FTE (p < 0.001). A more distal location of the FTE along the Blumensaat's line resulted in an increase of GBA and GBA-excursion of 8.5 ± 0.6° and 17.6 ± 1.1° /cm respectively (p < 0.001), while a more anterior location resulted in a change of GBA and GBA-excursion of -2.3 ± 0.6° /cm (+ 0.6 ± 0.4°/ cm from 0–60° flexion) and 9.8 ± 1.1 /cm respectively (p < 0.001).

Mean tunnel length was 38.5 ± 5.2 mm (range 29.6–50.5). Posterior tunnel blow-out did not occur for any FTE.

Conclusion

Aiming for a more proximal and posterior FTE, with respect to Blumensaat’s line, reliably reduces GBA and GBA-excursion, while preserving adequate tunnel length. This might aid to reduce excessive graft stress at the femoral tunnel aperture, decrease femoral tunnel widening and promote graft-healing.

Level of Evidence

IV

[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.

Studies of the criteria for determining optimal location of medial patellofemoral ligament attachment sites

Identifying appropriate attachment sites is important in the planning of medial patellofemoral ligament (MPFL) reconstruction. Two criteria are advanced to describe normal MPFL function, namely isometric criterion and desired pattern criterion. Subsequently, computational methods have applied these criteria to determine optimal attachment sites. So far, there is no study that compares the outcomes of these two criteria. For five subjects' 3D models of the patella and femur, three patellar sites and many femoral sites were identified as pairs of candidate attachment sites. For each patellar site, the criteria were applied to identify the matching femoral sites that satisfy them. The matching femoral site with the smallest length change was identified as the optimal femoral site. The desired pattern criterion finds fewer matching sites compared to the isometric criterion. In contrast, the isometric criterion can always find matching sites. The optimal femoral sites obtained vary significantly across different subjects. For most subjects, the optimal sites obtained using the isometric criterion are closer to known anatomical sites than those obtained using the desired pattern criterion. This study reaffirms that MPFL reconstruction is subject specific. The isometric criterion may be more reliable than the desired pattern criterion for determining optimal attachment sites. Graphical Abstract. Highlight of the paper. The location of the patella site significantly affects the location of the optimal femoral site. The isometric criterion option 1, with length at 0° regarded as MPFL's natural length, may be more reliable than other criteria or options for the planning of MPFL surgery because the optimal sites that it finds are closest to known anatomical sites.ᅟ.

Editorial Commentary: Medial Patellofemoral Complex: Driving a Better Understanding of Medial Knee Anatomy

Although its importance as the prime restraint to lateral patellar instability is undoubted, the anatomy of the medial patellofemoral ligament has never been agreed on. Since it was first described by Warren and Marshall in 1979, most of the anatomic studies confirmed its presence in 90% of the cases, but they usually provide inconsistent descriptions of its femoral and patellar attachments. It is proven that length changes in the reconstructed medial patellofemoral ligament depend principally on the femoral attachment site. Moreover, the femoral attachment site affects the patellar tilt, translation, and joint reaction force. Because of the early inconsistent descriptions of the medial patellofemoral ligament attachment sites, some authors have suggested that its anatomy is not fixed or may be patient specific.

The Relationship of Femoral Tunnel Positioning in Medial Patellofemoral Ligament Reconstruction on Clinical Outcome and Postoperative Complications

PURPOSE

To analyze the relation of the femoral tunnel (FT) positioning on clinical outcome.

METHODS

Patients with recurrent patellar dislocation who underwent medial patellofemoral ligament (MPFL) reconstruction with or without tibial tubercle osteotomy between 1998 and 2012 were included in this retrospective study. Strict postoperative lateral radiographs were mandatory. Knees with previous osseous stabilization surgery, fixed lateral patellar dislocation, valgus knee (>5°), or open growth plates were excluded. The distance between the FT and the validated radiographic landmark (the "Schoettle point") was measured. An FT with a distance greater than 10 mm was considered as malpositioned. The distance was correlated to subjective outcome measurements (patient satisfaction and Kujala score) and postoperative complications (a loss of range of motion and revision surgery).

RESULTS

Sixty-three knees in 60 patients (aged 23.7 ± 7.5 years at the time of surgery, 79.4% female) were included with a mean follow-up of 5.7 ± 3.3 years. The FT showed an average distance of 13.3 mm (±6.0 mm; 95% confidence interval [CI]: 11.7-14.8) to the Schoettle point, and 45 of 63 knees (71.4%) were deemed malpositioned. The postoperative Kujala score of malpositioned FT (75.9 points; 95% CI: 71.2-80.7) was not significantly inferior to knees with an FT within 10 mm (80.5; 95% CI: 73.7-87.3, P = .315). However, all 5 knees that underwent revision surgery showed an FT outside the 10-mm area.

CONCLUSIONS

Malpositioning of the FT in MPFL reconstruction is associated with postoperative complications. However, a malpositioned FT in MPFL reconstruction will not necessarily lead to an unsatisfactory subjective or objective clinical outcome. Other factors, such as surgical indication or graft tensioning, might also significantly influence postoperative outcome.

LEVEL OF EVIDENCE

Level IV, case-control study.

The trochlear isometric point is different in patients with recurrent patellar instability compared to controls: a radiographical study

PURPOSE

The purpose of the study was to investigate the theoretical isometric point based of the curve of the femoral groove and relating it to the origin of the MPFL femoral tunnel on lateral radiograph by comparing a patellar instability cohort with a control cohort.

METHODS

From a Patellar Instability database the radiographs of 40 consecutive patients were analysed to define Schöttle's point, and the arc of the circle of the trochlear groove. A comparison population of 20 radiographs from comparable patients with tibiofemoral joint disorders was used as a control. The distance from Schöttle's point to the most anterior part of the groove (extension) was also compared to the distance to the distal end of the roof of the notch (flexion).

RESULTS

The trochlea was circular in the controls but not the Patellofemoral Instability cohort where trochlear dysplasia is usually present. The difference between the extension and flexion length was a mean of - 2.0 ± 0.5 mm in the controls and + 6.0 ± 0.5 mm in the patellofemoral cohort. In neither cohort did the centre of the circle correspond to Schöttle's point. The extension distance correlated with the boss height.

CONCLUSIONS

The dysplastic trochlea is not circular and the centre of the best matched circle was different to the control trochleae which were circular. The circle centres did not correlate with Schöttle's point for either cohort, and was more proximal in the Patellofemoral Instability cohort.

CLINICAL RELEVANCE

For the MPFL to have equal tension throughout flexion within the groove, the length should not change. In normal knees the MPFL does not behave isometrically. The change in length, as measured from Schöttle's point to the trochlea, was greater for patellofemoral instability patients explaining why an isolated MPFL reconstruction in the presence of severe trochlear dysplasia risks poor outcomes. Level of evidence III.

Assessment of the Isometry of the Anterolateral Ligament in a 3-Dimensional Weight-Bearing Computed Tomography Simulation

PURPOSE

To simulate the most isometric insertion points of the anterolateral ligament (ALL) in a weight-bearing 3-dimensional computed tomography (CT) model using previously published anatomic landmarks and to define radiographic landmarks, which make for an easier identification of the optimal insertion points.

METHODS

The most isometric femoral insertion points were analyzed for 10 individuals, using data of weight-bearing CT scans in increasing knee flexion positions. An automatic string generation algorithm helped identify isometrically optimal points using an isometric score (0 indicating optimal isometry). Subsequently, a general femoral insertion point was determined, which preserved the isometry in all tested individuals. Based on the femoral insertion point, we assessed the influence of varying tibial insertion points on the isometric behavior of the ALL.

RESULTS

The defined femoral insertion point, which preserved the isometry in all analyzed individuals, had a median isometric score between 0.167 × 10^-3 and 0.559 × 10^-3. The average distance from the most prominent point of the lateral epicondyle was 9.7 mm (standard deviation [SD], 1.6) in a straight superior direction. In a straight lateral radiographic view, this point is located exactly at the intersection of a tangent set between the posterior cortex of the femur and a second perpendicular line intersecting at the level of the most (superior-) posterior point of the Blumensaat line. The best isometric behavior was found on the anatomically defined mean tibial insertion point, located at 37% of the width of the tibial plateau, which worsened gradually if corrected to anterior or posterior.

CONCLUSIONS

We determined femoral and tibial insertion points as well as radiographic landmarks for the reconstruction of the ALL that are based on published anatomic descriptions and preserve isometry in all analyzed individuals in this study.

CLINICAL RELEVANCE

This study provides new information, which might be helpful to define isometrically optimal insertion points for ALL reconstruction.