Medial Patellofemoral Ligament Reconstruction Using Adductor-Transfer and Adductor-Sling at Nonanatomic Femoral Attachment Sites Leads to Unfavorable Graft-Length Change Patterns: A Descriptive Biomechanical Study

Biomechanical Properties and Kinematics of Medial Patellofemoral Ligament Reconstruction: A Systematic Review

Background

While the biomechanical properties of the native medial patellofemoral ligament (MPFL) have been well studied, there is no comprehensive summary of the biomechanics of MPFL reconstruction (MPFLR). An accurate understanding of the kinematic properties and functional behavior of current techniques used in MPFLR is imperative to restoring native biomechanics and improving outcomes.

Purpose

To provide a comprehensive review of the biomechanical effects of variations in MPFLR, specifically to determine the effect of graft choice and reconstruction technique.

Study Design

Systematic review.

Methods

A systematic review was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A total of 32 studies met inclusion criteria: (1) using ≥8 human cadaveric specimens, (2) reporting on a component of MPFLR, and (3) having multiple comparison groups.

Results

Gracilis, semitendinosus, and quadriceps grafts demonstrated an ultimate load to failure (N) of 206.2, 102.8, and 190.0 to 205.0 and stiffness (N/mm) of 20.4, 8.5, and 21.4 to 33.6, respectively. Single-bundle and double-bundle techniques produced an ultimate load to failure (N) of 171 and 213 and stiffness (N/mm) of 13.9 and 17.1, respectively. Anchors placed centrally and superomedially in the patella produced the smallest degree of length changes throughout range of motion in contrast to anchors placed more proximally. Sutures, suture anchors, and transosseous tunnels all produced similar ultimate load to failure, stiffness, and elongation data. Femoral tunnel malpositioning resulted in significant increases in contact pressures, patellar translation, tilt, and graft tightening or loosening. Low tension grafts (2 N) most closely restored the patellofemoral contact pressures, translation, and tilt. Graft fixation angles variably and inconsistently altered contact pressures, and patellar translation and tilt.

Conclusion

Data demonstrated that placement of the MPFLR femoral tunnel at the Schöttle point is critical to success. Femoral tunnel diameter should be ≥2 mm greater than graft diameter to limit graft advancement and overtensioning. Graft fixation, regardless of graft choice or fixation angle, is optimally performed under minimal tension with patellar fixation at the medial and superomedial patella. However, lower fixation angles may reduce graft strain, and higher fixation angles may exacerbate anisometry and length changes if femoral tunnel placement is nonanatomic.

Arthroscopically Assisted Double-Bundle Medial Patellofemoral Ligament Augmentation With Physeal-Sparing Suture Fixation for Recurrent Patellar Dislocation in Skeletally Immature Patients

Recurrent patellar dislocation is a common patellofemoral disease that affects active adolescents. The optimal surgical treatment of recurrent patellar dislocation in skeletally immature patients remains controversial. This Technical Note describes an arthroscopically assisted double-bundle medial patellofemoral ligament (MPFL) augmentation. Orthocord suture, with ideal strength and partial bioabsorbable characteristics, is used as the stabilizer to augment and protect the native MPFL during its biological healing. Under an arthroscope, patellar tunnels are created with Kirshner wire at the upper third point of the medial articular margin and the midpoint of the proximal articular margin. A physeal-sparing transosseous suture fixation technique is applied at the femoral attachment. Two femoral tunnels are made with half-circle cutting needle, which is pierced into the femoral origin of the MPFL and exits the posterior femoral cortex. After dynamic assessments of knee range of motion and patellofemoral congruence, free ends of the Orthocord suture bundle are tied together at the external opening of the femoral tunnel. Transosseous suture fixation balances the requirements of anatomic restoration, reliable fixation, and physeal preservation, and thus may provide a promising alternative to current algorithm of addressing recurrent patellar dislocation in pediatric population.

Surgical techniques for medial Patellofemoral ligament reconstruction: a systematic review and meta-analysis of level I and II studies

PURPOSE

To determine the most optimal surgical technique for medial patellofemoral ligament reconstruction (MPFLR).

METHODS

Three databases MEDLINE, PubMed, and EMBASE were searched from inception to December 13th, 2022, for level I or II studies comparing MPFLR techniques. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on patient-reported outcome measures were recorded. Quality assessment was carried out using the MINORS and Cochrane Risk of Bias assessment tools. Certainty of evidence was carried out with the GRADE assessment tool.

RESULTS

Ten studies comprising 723 patients (723 knees) were included in this review. The weighted mean difference in Kujala, Lysholm, and IKDC scores comparing single- and double-tunnel patellar drilling techniques was 2.66 (95% CI -1.05-6.37, p = 0.16, I2 = 0%) with moderate certainty, 0.78 (95% CI -9.02-10.58, p = 0.88, I2 = 87%) with low certainty, and 1.71 (95% CI -2.43-5.86, p = 0.42, I2 = 0%) with low certainty, respectively. Double-suture anchor patellar fixation demonstrated greater Kujala scores than transpatellar fixation (87.1 ± 2.8 vs 84.0 ± 3.8, p < 0.001) with moderate certainty. Y-shaped graft patellar fixation demonstrated superior Kujala scores to C-shaped graft patellar fixation (95.9 ± 4.7 vs 91.3 ± 9.7, p = 0.001) with moderate certainty. Augmentation of femoral fixation with polyester sutures demonstrated superior Kujala scores (97.8 ± 6.4. vs 88.0 ± 6.3, p < 0.005) with low certainty. Four-stranded grafts demonstrated greater Kujala scores than two-stranded grafts (93.5 ± 2.6 vs 91.6 ± 3.5, p = 0.01) with low certainty.

CONCLUSION

The optimal MPFLR surgical technique is likely to utilize a four-stranded graft using either endobutton, double-suture anchor, or transosseous suture patellar fixation with polyester suture augmented interference screw femoral fixation. Orthopedic surgeons can consider employing such a technique to improve patient outcomes by conferring greater graft stability, strength, and function. Level of evidence Level II.

The adductor magnus tendon is a viable option for medial patellofemoral ligament reconstruction, but with a busy surrounding neurovascular topography

PURPOSE

To describe the proximity of the neurovascular structures surrounding the adductor magnus (ADM), to delineate a safe boundary focusing on the techniques used during graft harvest and to evaluate whether the length of the ADM tendon is sufficient for safe medial patellofemoral ligament (MPFL) reconstruction.

METHODS

Sixteen formalin-fixed cadavers were dissected. The area surrounding the ADM, the adductor tubercle (AT) and the adductor hiatus was exposed. The following measurements were performed: the (1) total length of MPFL, (2) distance between the AT and the saphenous nerve, (3) the point where the saphenous nerve pierces the vasto-adductor membrane, (4) the point where the saphenous nerve crosses the ADM tendon, (5) the musculotendinous junction of the ADM tendon, and (6) the point where the vascular structures exit the adductor hiatus. Additionally, (7) the distance between the ADM musculotendinous junction and the nearest vessel (popliteal artery), (8) the distance between the ADM (at the level where the saphenous nerve crosses) and the nearest vessel, (9) the length between the AT and the superior medial genicular artery, and finally (10) the depth between the AT and the superior medial genicular artery were analyzed.

RESULTS

The in situ length of the native MPFL was 47.6 ± 42.2 mm. The saphenous nerve pierces the vasto-adductor membrane at a mean distance of 100 mm, although it crosses the ADM itself at an average of 67.6 mm. The vascular structures, on the other hand, become vulnerable at a distance of 89.1 ± 114.0 mm from the AT. After harvesting the ADM tendon, the mean length was found to be 46.9 mm, which was insufficient for fixation. Partial release from the AT resulted in a more adequate length for fixation (65.4 ± 88.7 mm).

CONCLUSION

The adductor magnus tendon is a viable option for the dynamic reconstruction of the MPFL. Knowledge of the surrounding busy neurovascular topography is paramount for a procedure typically performed in a minimally invasive way. The study results are clinically relevant, as they suggest that tendons should be shorter than the minimum distance from the nerve. If in some cases the length of the MPFL is longer than the distance of the ADM from the nerve, the results suggest that a partial dissection of the anatomical structures might be needed. Direct visualization of the harvesting region might be considered in such cases.

Combined Autologous Adductor Magnus and Partial Quadriceps Tendon Technique for Medial Patellofemoral Ligament Reconstruction and Cellularized Scaffold Implantation of the Patella

There are many studies in the literature on the use of adductor magnus and quadriceps tendons in primary or revision surgery of patellofemoral instability in skeletally immature patients. In this Technical Note, the combination of both tendons is presented with cellularized scaffold implantation cartilage surgery in the patella.

Modified Lemaire Lateral Extra-articular Tenodesis With the Iliotibial Band Strip Fixed on the Femoral Cortical Surface Reduces Laxity and Causes Less Overconstraint in the Anterolateral Lesioned Knee: A Biomechanical Study

PURPOSE

To compare the biomechanical effects of femoral cortical surface fixation and intra-tunnel fixation in modified Lemaire tenodesis on the restoration of native kinematics in anterolateral structure-deficient knees.

METHODS

Eight fresh-frozen cadaveric knees were mounted in a knee-customized jig to evaluate anterior translation in anterior load and internal rotation degree in internal rotation torque at 0°, 30°, 60°, and 90°, as well as anterolateral translation (ALT) in a simulated pivot-shift test at 0°, 15°, 30°, and 45°. Kinematic tests were performed in the following states: intact; anterolateral knee lesion (AL-Les); modified Lemaire lateral extra-articular tenodesis (LET) with the femoral iliotibial band (ITB) strip fixed on the cortical surface (cortical fixation), deep to the lateral collateral ligament (LCL) (deep LET-C); and LET with the femoral ITB strip fixed into a tunnel (intra-tunnel fixation), deep to the LCL (deep LET-IT) or superficial to the LCL (superficial LET-IT). The knee kinematic changes in the AL-Les state and the 3 LET states were compared with each other, with the intact state as the baseline.

RESULTS

In the AL-Les state, the increased anterior translation instabilities were significantly mitigated by the 3 LETs at 30°, 60°, and 90° (all P < .001), with overconstraint observed in both the deep LET-IT and superficial LET-IT states at 60° (P = .047 and P < .001, respectively) and 90° (both P < .001). Similarly, the 3 LETs significantly reduced the internal rotation instabilities in the AL-Les state at all flexion angles. The superficial LET-IT state overconstrained the knee at 60° (P = .009) and 90° (P < .001) during internal rotation torque, and the deep LET-IT state did so at 60° (P = .012). Furthermore, the ALT instabilities found in the AL-Les state were significantly reduced by the 3 LETs during the simulated pivot-shift test. At 30° and 45°, these LET states resulted in overconstraint when compared with the intact state, but the superficial LET-IT state (P < .001) or deep LET-IT state (P = .016) presented a larger overconstraint than that in the deep LET-C at 45°, respectively.

CONCLUSIONS

The 3 Lemaire LET procedures evaluated reduced the anterior, internal rotational, and ALT laxities in AL-Les knees and restored these parameters to the native baseline of the intact state at most flexion angles. However, in deep flexion, some overconstraint occurred in all LETs when compared with the intact state, of which the deep LET-C state resulted in less overconstraint in anterior translation and internal rotation than the deep LET-IT and superficial LET-IT states.

CLINICAL RELEVANCE

This biomechanical study supports using the femoral cortical fixation technique to fix the ITB strip in the modified Lemaire LET, which similarly improves knee kinematic stability and causes less overconstraint compared with conventional intra-tunnel fixation. These findings need more verification in clinical scenarios.

Anterolateral Structure Reconstructions With Different Tibial Attachment Sites Similarly Improve Tibiofemoral Kinematics and Result in Different Graft Force in Treating Knee Anterolateral Instability

PURPOSE

To compare the biomechanical effects of anterolateral structure reconstructions (ALSRs) with different tibial attachments on tibiofemoral kinematics and anterolateral structure (ALS) graft forces.

METHODS

Eight cadaveric knees were tested in a customized knee testing system, using a novel pulley system to simulate more muscle tensions by loading the iliotibial band at 30 N and quadriceps at 10 N in all testing states. Anterior stability during anterior load and anterolateral rotatory stability during 2 simulated pivot-shift tests (PST1 and PST2) were evaluated in 5 states: intact, ALS-deficient (Def), ALSR-Ta (anterior tibial site), ALSR-Tm (middle tibial site), and ALSR-Tp (posterior tibial site). Tibiofemoral kinematics and resulting ALS graft forces against the applied loads were measured and compared in the corresponding states.

RESULTS

In anterior load, 3 ALSRs mitigated the anterior laxities of the ALS Def state at all degrees, which were close to intact state at 0° and 30° but showed significantly overconstraints at 60° and 90°. In both PSTs, all ALSRs significantly reduced the anterolateral rotatory instability of ALS Def, whereas the significant overconstraints were detected in ALSR-Ta and ALSR-Tm at greater knee flexion angles. All ALS grafts carried forces in resisting anterior and pivot-shift loads. Only ALS graft force in ALSR-Ta increased continuously with knee flexion angles. The ALS graft forces carried by ALSR-Ta were significantly larger than those by ALSR-Tp and ALSR-Tm when resisting anterior load and PSTs at greater knee flexion angles.

CONCLUSIONS

ALSRs with different tibial attachment sites similarly restored knee laxities close to the native tibiofemoral kinematics in an ALS-deficient knee, whereas the ALSR-Tp showed less propensity for overconstraining the knee at greater flexion angles. The ALS graft in ALSR-Ta carried more forces than those in ALSR-Tp and ALSR-Tm against simulated loads.

CLINICAL RELEVANCE

Altering the tibial attachment sites of ALSRs may not significantly affect tibiofemoral kinematics at most degrees whereas the posterior may have less overconstraints at greater flexion angles. However, ALS graft positioning at a more anterior tibial attachment site may carry more forces in resisting anterior and pivot-shift loads.

Editorial Commentary: The Medial Patellofemoral Ligament Is Not Isometric and Anatomic Reconstruction Is Important, But Just a Small Piece of the Patellar Instability Puzzle

Medial patellofemoral ligament (MPFL) reconstruction has proven to be a reliable procedure to reduce patellar instability events in patients with recurrent patellar instability. As our reconstruction techniques have evolved to address pathology in a diverse patient population, there continues to be an obsessive focus on the precise anatomy of the MPFL origin on the medial knee, due in large part to concerns that improper femoral tunnel position may result in excessive graft anisometry and failure. However, recurrent patellar instability involves many complexities and should not be simply reduced to a single point on the medial knee.