Patellar Translation Research Articles

Open wedge high tibial osteotomy alters patellofemoral joint kinematics: A multibody simulation study.

Changes in lower limb alignment after open-wedge high tibial osteotomy (owHTO) influence joint kinematics. The aim of this study was to investigate the morphological and kinematic changes of the knee joint, in particular the patellofemoral joint, using a multibody simulation model. OwHTO with an open tibial wedge of 6-12 mm (1 mm intervals) was virtually performed on each of 13 three-dimensional (3D) computer-aideddesign models (CAD models) derived from computer tomography scans of full-leg cadaver specimens. For each owHTO, an individual biomechanical simulation model was built and knee flexion from 5° to 100° was simulated using a multibody simulation model of the native knee. Morphologic and alignment parameters as well as tibiofemoral and patellofemoral kinematic parameters were evaluated. Almost linear changes in tibial tuberosity trochlea groove(TT-TG) (0.42 mm/1 mm wedge height) were observed which led to pathological values (TT-TG > 20 mm) in 3 out of 13 knees. Furthermore, a 6 mm increase in osteotomy wedge height increased lateral patellofemoral rotation by 0.8° (range: 0.39° to 1.11°) and led to a lateral patellar translation of 0.8 mm (range: 0.37-3.11 mm) on average. Additionally, valgisation led to a medial translation of the tibia and a decrease in the degree of tibial internal rotation during knee flexion of approximately 0.3°/1 mm increase in osteotomy wedge height. The increase in TT-TG and the biomechanical effects observed influence patellofemoral tracking, which may increase retropatellar pressure and are potential risk factors for the development of anterior knee pain.

Three different patellar fixation techniques yield similar clinical and radiological outcomes in recurrent patellar dislocation undergoing medial patellofemoral ligament reconstruction.

The purpose of this study was to evaluate and compare the clinical and radiological outcomes of three different patellar fixation techniques on medial patellofemoral ligament reconstruction (MPFLR) in the treatment of patellar dislocation (PD). Between 2015 and 2020, 130 patients with recurrent PD who underwent surgical reconstruction were eligible for this retrospective study: 48 patients were treated with the semi-tunnel bone bridge fixation technique (Group A), 42 patients were treated with the suture anchor fixation technique (Group B) and 40 patients were treated with the transpatellar tunnel fixation technique (Group C). Clinical outcomes included functional outcomes (Kujala, Lysholm and International Knee Documentation Committee scores), activity levels (Tegner activity score and return to sports), physical examinations, patellar re-dislocation rate and complications. Radiological outcomes included patellar congruence angle, patellar tilt angle, lateral patellar translation and lateral patellar angle. All clinical and radiological outcomes improved significantly in all groups, without any significant difference among these three groups. At the final follow-up, no re-dislocation occurred, and all groups achieved a successful return to sports. However, the semi-tunnel bone bridge and suture anchor fixation techniques showed statistically higher Tegner activity scores (p = 0.004) and shorter time from surgery to return to sports (p = 0.007) than the transpatellar tunnel fixation technique. The three MPFLR patellar fixation techniques achieved favourable and comparable clinical and radiological outcomes in the treatment of PD. Compared with the transpatellar tunnel fixation technique, the semi-tunnel bone bridge and suture anchor fixation techniques may be more effective with higher activity levels. Level III.

Effect of Medial Patellofemoral Complex Reconstruction Technique on Patellofemoral Contact Pressure, Contact Area, and Kinematics.

Medial patellofemoral ligament (MPFL) reconstruction is considered by many to be the gold standard to treat lateral patellar instability; however, some investigators have reported good clinical results after isolated medial quadriceps tendon-femoral ligament (MQTFL) reconstruction or a combined MPFL/MQTFL reconstruction. A handful of studies have preliminarily investigated the biomechanical consequences of these various medial patellar stabilizing procedures. Despite this, no existing study has included multiple medial patellofemoral complex (MPFC) reconstructions and assessment of lateral patellar translation at distinct flexion angles. Combined MPFL/MQTFL reconstruction would restore patellofemoral contact areas, forces, and kinematics closest to the native state compared with isolated reconstruction of the MPFL or MQTFL alone. Controlled laboratory study. Ten adult cadaveric knee specimens were prepared and analyzed under 5 different conditions: (1) intact state, (2) transected MPFC, (3) isolated MPFL reconstruction, (4) isolated MQTFL reconstruction, and (5) combined MPFL/MQTFL reconstruction. Patellar tilt, lateral patellar translation, patellofemoral contact forces, and patellofemoral contact areas were measured in each condition from 0° to 80° through simulated knee flexion using a custom servohydraulic load frame with pressure sensor technology and a motion capture system for kinematic data acquisition. The isolated MPFL, isolated MQTFL, and combined MPFL/MQTFL reconstruction conditions produced significantly less lateral patellar tilt compared with the transected MPFC state (P < .05). No statistically significant differences were found when each reconstruction technique was compared with the intact state in patellar tilt, lateral patellar translation, contact forces, and contact areas. All 3 reconstruction techniques (isolated MPFL reconstruction, isolated MQTFL reconstruction, and combined MPFL/MQTFL reconstruction) restored native knee kinematics, contact forces, and contact areas without overconstraint. Isolated MPFL reconstruction, isolated MQTFL reconstruction, and combined MPFL/MQTFL reconstruction all restore patellofemoral stability comparable with the intact MPFC state without the overconstraint that could be concerning for increasing risk of patellofemoral arthritis.

Trochlea Dysplasia as the Major Anatomic Risk Factors for Patellofemoral Joint Instability: An Infographic as a Visual Learning Tool.

Patellofemoral instability (PFI) is a common condition in children and adolescents, ranging from mild discomfort and mal-tracking to lateral patellar dislocation [1]. A number of anatomical risk factors have been described in the literature, such as trochlear dysplasia, patella alta, excessive tibial tuberosity to trochlear groove (TT-TG) distance, patellar tilt and soft tissue alterations [2]. Among them, TD has been identified as the main anatomical risk factor with the strongest association with PFI [1, 2]. In the study by Dejour et al. [2] radiographically observed TD was identified in 96% of patients with a history of patellofemoral dislocation [1, 2]. Patients with Dejour Type D dysplasia are characterized by a prominent and convex lateral facet with a vertical connection to a hypoplastic medial facet (Figure 1), which provides inadequate tracking of the patella in the trochlea during flexion leading to patella subluxation [2]. Non-operative treatment of lateral patellar dislocation presents a rate of re-dislocation up to 70% within 24 months of the first episode [3]. Sulcus deepening trochleoplasty is indicated for Type B and D dysplasia, in order to improve patella tracking, reduce the rate of re-dislocation and achieve good functional outcomes [2, 4]. Trochlea dysplasia is defined as a shallow or flattened groove with decreased resistance to lateral patellar translation. TD can be assessed on computed tomography (CT) and magnetic resonance imaging (MRI) with the use of overlapping axial images and are able to show perfectly the global shape of the femoral trochlea [2]. The thresholds for identifying trochlear dysplasia are established based on the sulcus angle ≥ 145°, medial/lateral trochlea facet asymmetry < 40%, trochlear depth < 3 mm and lateral trochlear inclination ≤ 11° and therefore it can be used in young adolescents [4, 5]. A deep knowledge of anatomic variations and abnormalities of the patellofemoral joint, which may predispose to PFI, is crucial in order to choose the appropriate treatment for each patient.

Medial Quadriceps Tendon Femoral Ligament Reconstruction for Anatomic Reconstruction of the Medial Patellofemoral Complex

The medial patellofemoral complex (MPFC) refers to the primary static restraint to lateral patellar translation. Originally thought of as the medial patellofemoral ligament, anatomic studies over the past 10 years have identified the additional fibers that attach to the quadriceps tendon, which some have termed the medial quadriceps tendon femoral ligament. Anatomic studies have demonstrated that the MPFC midpoint is at the junction of the medial border of the quadriceps tendon and the articular surface of the patella, indicating that fixation can be on either structure. This technique describes a single-bundle reconstruction technique with anatomic fixation on the quadriceps tendon at the MPFC midpoint that involves fixation on the extensor mechanism first.

Double-Level Knee Derotational Osteotomy Yields Better Postoperative Outcomes Than Tibial Tubercle Transfer Combined With Medial Patellofemoral Ligament Reconstruction in Patients With Recurrent Patellar Instability and Severe Malrotation

PurposeTo assess the postoperative outcomes of double level knee derotational osteotomy (KDRO) combined with medial patellofemoral ligament reconstruction (MPFLR), and to compare it with tibial tuber transfer (TTT) and MPFLR without derotational osteotomy in patients with recurrent patellar instability (RPI) and a marked torsional deformity. MethodsFrom March 2020 to December 2021, patients with torsion deformity (combined femoral torsion and tibial torsion ≥ 30°) were retrospectively included. The minimum follow-up time was 18 months. Patients received KDRO and MPFLR were categorized into KDRO group and patients received a combined TTT and MPFLR were categorized into control group. Preoperative and postoperative clinical symptoms, patient-reported outcomes (PROs) (Kujala, visual analogue scale [VAS], Lysholm, International Knee Documentation Committee [IKDC], Tegner, and Knee Injury and Osteoarthritis Outcome [KOOS] scores) and imaging parameters (femoral torsion, tibial torsion, patellar height, femoral trochlear dysplasia, congruence angle, patellar tilt angle, lateral patellar angle, lateral patellar translation, and tibial tubercle–trochlear groove distance) were analyzed. ResultsIn all, 36 patients were included with 18 in KDRO group and 18 in control group. The mean follow-up time was 30 (range 21-39) months. At the latest follow-up, no patient experienced re-dislocation in either group. Except for the femoral torsion and tibial torsion in the control group, postoperative imaging parameters were significantly reduced to the normal range. KDRO group has a lower patellar tilt angle (P=.043, effect size 0.64). All clinical scores in both groups significantly improved postoperatively. KDRO group has better functional scores than control group except the KOOS daily living activities subscore and the KOOS sports and recreation subscore. More proportions of patients in KDRO group met the minimal clinically important difference (MCID) for most PROs than control group. Eight patients (44%) in the control group complained of postoperative anterior knee pain, compared with 1 patient (6%) in KDRO group (P=.018). ConclusionKDRO combined with MPFLR was associated with better postoperative outcomes than TTT combined with MPFLR in patients with RPI and a torsion deformity.

Evaluation of the Results of Reconstruction of Medial Patellofemoral Ligament in the Treatment of Recurrent Patellar Instability Using Hamstring Autograft by Dual Patella Docking Technique

Abstract Background: Recurrent patellar instability can significantly affect a patient’s life quality. This study evaluated the results of medial patellofemoral ligament (MPFL) reconstruction in the recurrent patellar instability treatment using hamstring autograft by dual patellar docking technique. Materials and Methods: This prospective study was performed on 20 recurrent patellar instability patients. Magnetic resonance imaging and computed tomography scans were performed to confirm MPFL tear and assess the tibial tubercle-trochlear groove distance. Various clinical and radiographic evaluations were performed preoperatively. The surgical technique involved diagnostic arthroscopy, graft preparation, patellar preparation, graft passage, femoral tunnel preparation, and graft fixation. Results: Postoperatively, a substantial progression was observed in the International Knee Documentation Committee score, Kujala score, Cincinnati score, and Lysholm score compared to preoperative values (P &lt; 0.001). In addition, the postoperative measurements of patellar tilt angle and patellar congruence angle were significantly lower than their respective preoperative values (P &lt; 0.001). All 20 (100%) patients had negative findings in the postapprehension test, indicating improved stability. In the postcompression test, 3 (15%) patients showed positive results, whereas 17 (85%) patients had negative results. In terms of complications, 2 (10%) patients experienced patellofemoral pain, 1 (5%) patient had residual patellar translation without dislocation, 1 (5%) patient had limited flexion, and the majority of patients (16, 80%) had no complications. Conclusions: MPFL reconstruction with patellar docking yielded good results with Kujala and Lysholm, as well as adequate, satisfactory congruence angles for most patients. This procedure has exhibited a high success rate in addressing patellofemoral instability.

Minimally Invasive Medial Patellofemoral Ligament Reconstruction With Patellar-Sided Tensioning Using All-Suture Anchors

Medial patellofemoral ligament (MPFL) reconstruction is a commonly performed procedure to reestablish the checkrein to the lateral patellar translation in patients with recurrent patellofemoral instability. Graft tensioning is one of the most critical aspects of the procedure. Most surgical methods for MPFL reconstruction involve tensioning and securing the graft on the femoral side. In this article, we describe a technique for patellar-sided tensioning of the graft using all-suture anchors, which provides the surgeon with the ability to finely control graft tension with two independent graft limbs, while preserving patellar bone stock.

Comparison of Failure Rates at Long-term Follow-up Between MPFL Repair and Reconstruction for Recurrent Lateral Patellar Instability.

The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint to lateral patellar translation and is often disrupted by lateral patellar dislocation. Surgical management for recurrent patellar instability focuses on restoring the MPFL function with repair or reconstruction techniques. Recent studies have favored reconstruction over repair; however, long-term comparative studies are limited. To compare long-term clinical outcomes, complications, and recurrence rates of isolated MPFL reconstruction and MPFL repair for recurrent lateral patellar instability. Cohort study; Level of evidence, 3. A total of 55 patients (n = 58 knees) with recurrent lateral patellar instability were treated between 2005 and 2012 with either MPFL repair or MPFL reconstruction. The exclusion criteria were previous or concomitant tibial tubercle osteotomy or trochleoplasty and follow-up of <8 years. Pre- and postoperative descriptive, surgical, imaging, and clinical data were recorded for each patient. MPFL repair was performed on 26 patients (n = 29 knees; 14 women, 15 men), with a mean age of 18.4 years. MPFL reconstruction was performed on 29 patients (n = 29 knees; 18 women, 11 men), with a mean age of 18.2 years. At a mean follow-up of 12 years (range, 8.3-18.9 years), the reconstruction group had a significantly lower rate of recurrent dislocation compared with the repair group (14% vs 41%; P = .019). There were no differences in the number of preoperative dislocations or tibial tubercle-trochlear groove distance. The reconstruction group had significantly more time from initial injury to surgery compared with the repair group (median, 1460 days vs 627 days; P = .007). There were no differences in postoperative Tegner, Lysholm, or Kujala scores at the final follow-up. In addition, no statistically significant differences were detected in return to sport (RTS) rates (repair [81%] vs reconstruction [75%]; P = .610) or reoperation rates for recurrent instability (repair [21%] vs reconstruction [7%]; P = .13). MPFL repair resulted in a nearly 3-fold higher rate of recurrent patellar dislocation (41% vs 14%) at the long-term follow-up compared with MPFL reconstruction. Given this disparate rate, the authors recommend MPFL reconstruction over repair because of the lower failure rate and similar, if not superior, clinical outcomes and RTS.

Poster 291: Ultrasound-based patellar glide test: A new dynamic assessment of patellar instability

Objectives: Patellar instability can be difficult to assess due to the dynamic nature of this condition. While MRI and CT can demonstrate the morphology of the patellofemoral joint, the assessment of instability relies on dynamic testing. The patellar glide test is commonly utilized as a method of dynamic assessment on physical examination, yet precise quantification with this method remains difficult. Recently, cadaveric studies have demonstrated the utility of ultrasound in quantifying patellar translation. Therefore, our study aimed to apply the ultrasound-based patellar glide test to determine its utility in differentiating between knees with and without patellar instability in a clinical population. Methods: Patients with recurrent patellar instability were included in this study. Using a portable device, the ultrasound-based patellar glide test was performed with the knee in extension, and patellar position was visualized with and without a manual lateralizing force. The ultrasound probe was placed at the medial patellofemoral joint to visualize the relation of the medial patellar facet to the medial trochlea. Descriptive statistics were used to describe patellar position in the unloaded and loaded states, and patellar translation was calculated as the difference between the loaded and unloaded positions. Values were compared between symptomatic and asymptomatic knees. For each measurement of translation, receiver operating characteristic (ROC) curve analysis was performed. Youden’s J statistic was calculated to determine the optimal cutoff values to distinguish between asymptomatic vs symptomatic knees. Results: 50 knees from 25 patients (17F, 8M, mean age 26.9+/-9.4) were included in this study, of which 29 knees were unstable and 21 were stable and asymptomatic. When comparing symptomatic and asymptomatic knees, patellar position in the unloaded (4.6+/-2.8mm vs 3.8+/-2.3mm, p=0.277) and loaded states (1.1+/-3.24mm, 2.1+/-2.5mm, p=0.252) were not significantly different. Patellar translation was found to be significantly different between the symptomatic and asymptomatic states (3.5+/-2.2mm vs 1.7+/-1.5mm, p=0.002). ROC curve analysis demonstrated that patellar translation &gt;3mm detected the presence of patellar instability with AUC 0.88 (95% CI 0.77, 0.98). 3mm translation was found to identify patellar instability with sensitivity 43.4%, specificity 95.2%, PPV 90.9%, and NPV 60.6%. Conclusions: The ultrasound-based patellar glide test was found to differentiate between symptomatic and asymptomatic knees in patients with patellar instability with high accuracy. Given the increasing availability of portable ultrasound devices and the need for quantification of patellar laxity, further studies are recommended to evaluate the role of this method of assessment in the diagnosis and management of patellar instability.

Internal Rotation, Varus, and Anterior Femoral Component Malalignments Adversely Affect Patellofemoral Joint Kinematics in Patellofemoral Arthroplasty.

Patellofemoral arthroplasty (PFA) is reported to provide nearly normal PF joint kinematics but only with adequate surgical techniques. This study evaluated the effects of various femoral component settings on patellar component biomechanics. A dynamic musculoskeletal computer simulation analyzed normal knee and standard PFA models, as well as 8 femoral component malposition models: 5° internal or external rotation, 5° valgus or varus, 5° extension or flexion, and 3-mm or 5-mm anterior positioning. Mediolateral patellar translation, lateral patellar tilt, and contact force and stress at the PF joint were measured in each model during gait. The patella in the standard PFA model was shifted up to 5.0 mm laterally near heel off and was tilted up to 3.0° laterally at heel strike compared to the normal knee model. The patella in the external rotation model translated more laterally in the direction of the femoral component setting than in the standard model. However, in the internal rotation and varus alignment models, the patellar lateral shift occurred largely in the opposite direction of the femoral component setting. The patella in most models was tilted in the same direction as the femoral component setting. The PF contact force was increased, especially in the anterior femoral position models, by up to 30 MPa compared with 20 MPa in the standard model. Internal rotation, varus, and anterior femoral component settings during PFA should be avoided to reduce postoperative complications, whereas external rotation might be appropriate only for cases with lateral patellar instability.

The Effectiveness of Anterior Cruciate Ligament Reconstruction on the Patellofemoral Stability and Patellar Height

Background: Considering the critical role the anterior cruciate ligament (ACL) plays in knee biomechanics, it is a logical hypothesis that ACL reconstruction (ACLR) will have positive effects on knee kinematics, and stability. Our objective was to investigate the effect of single-bundle ACLR on patellar height, and patellofemoral balance radiologically and clinically.&#x0D; Methods: In this prospective study, 87 patients operated with hamstring autograft-used single-bundle ACLR were analyzed. History of dislocation, stability-related physical examination findings, Tegner-Lysholm Knee Scoring Scale, and Kujala Anterior Knee Pain Scale were used for functional assessment. All patients underwent pre-and post-operative magnetic resonance imaging and Insall-Salvati (IS) Index, Caton Deschamps Index, Blackburne-Peel Index, and Patella-patellar tendon (P-PT) angles were measured on T1-weighted sagittal section images. &#x0D; Results: A total of 79 patients (90.8%) achieved excellent or good result, according to Tegner-Lysholm Knee Scoring Scale, and the patients' postoperative 1st year mean Kujala Anterior Knee Pain Score was calculated as 90.4 (Range: 79.1 – 96.4). On physical examination, increased passive patellar translation was observed in 2 patients (2.3%), but the J sign was appeared to be negative in all the patients. While all patellar height indices decreased after reconstruction, only the decrease in IS index was statistically significant (p=0.007). Moreover, the P-PT angle was found to be significantly lower after ACLR (p

Lateral Patellofemoral Ligament Reconstruction: A Biomechanical Comparison of 2 Techniques

Background: The importance of maintaining lateral patellar stabilizing structures has been demonstrated by the presence of iatrogenic medial patellar instability after lateral retinacular release (LRR) procedures. In patients with medial patellar instability, lateral patellofemoral ligament (LPFL) reconstruction has been clinically shown to restore patellar stability while improving patient-reported outcomes. However, the biomechanics associated with different LPFL reconstruction techniques remain largely unknown. Purpose: To (1) investigate whether LPFL reconstruction restores medial patellar translation compared with the intact state after LRR and (2) evaluate for any biomechanical differences between soft tissue and osseous LPFL reconstruction techniques. Study Design: Controlled laboratory study. Methods: A total of 7 knees were included in the final analysis. The knees were dissected, and the tibia and femur were potted. An eye screw was then placed at the midpoint of the patella perpendicular to the medial surface. A custom jig was constructed to allow for a 1-kg load to be applied to the quadriceps muscle. Medial patellar displacement was investigated at 0°, 10°, 20°, 30°, 45°, 60°, and 90° of knee flexion using a tensile testing machine with a 20-N medial force applied to the patella. Medial patellar displacement was assessed in 4 states: intact, LRR, soft tissue LPFL reconstruction (inserted through incisions in the iliotibial band, quadriceps tendon, and patellar tendon), and osseous LPFL reconstruction. Results: The LRR group had significantly greater medial patellar translation compared with the intact group throughout flexion (P < .01 to P = .029). The soft tissue LPFL reconstruction group demonstrated significantly greater medial patellar translation at 30° (P = .020) and 45° (P = .025) compared with the intact group, with less translation compared with the LRR group at all degrees of knee flexion except for 45° (P = .065). The osseous LPFL reconstruction group demonstrated significantly greater medial patellar translation compared with the intact group at 30° of flexion (P = .036), with significantly less translation compared with the LRR group from 0° to 30° (P < .01 to P = .013). The soft tissue LPFL reconstruction group (15.94 ± 2.55 mm) demonstrated significantly greater medial patellar translation at 10° of flexion compared with the osseous LPFL reconstruction group (14.16 ± 2.34 mm) (P = .033). Conclusion: Soft tissue LPFL reconstruction led to significantly greater medial patellar translation at 30° and 45° compared with the intact state, while osseous LPFL reconstruction produced significantly greater translation only at 30°. Both the soft tissue and the osseous reconstruction techniques resulted in comparable medial patellar translation at all degrees of knee flexion except for 10°, in which osseous reconstruction was more similar to the intact state. Clinical Relevance: Compared with LRR, soft tissue LPFL reconstruction was able to restore stability against medial patellar translation at most degrees of knee flexion, while osseous LPFL reconstruction did not provide adequate stabilization beyond 30° of flexion. While the LPFL does appear to have osseous insertions, soft tissue reconstruction functioned more similarly to the intact state after LRR.

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

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

All-arthroscopic Knee Patellofemoral Ligament Repair

Patellar dislocations are common injuries in the pediatric and adolescent population, with an estimated mean incidence of 42/100,000 person-years. The medial patellofemoral ligament is the most important structure preventing lateral patellar translation, whereas its patellar attachment is frequently damaged after patellar dislocations. This technical note presents an all-arthroscopic medial patellofemoral ligament repair technique suggested after a first episode of patellar dislocation.

Medial Patellofemoral Reconstruction With a Hamstring Allograft

Background: Lateral patellar instability is common in young, active patients. Patients who fail conservative treatment may benefit from medial patellofemoral ligament (MPFL) reconstruction. Indications: Recurrent lateral patellar instability. Technique Description: Examination assesses patellar translation, eversion and range of instability. Diagnostic arthroscopy is performed for loose bodies, cartilage damage, trochlear dysplasia, and tracking. A longitudinal incision is made from superomedial to mid-body of the patella. The plane between the capsule and retinaculum is developed for palpation of the medial epicondyle and adductor tubercle. Electrocautery and rongeur are used to create a trough on the patella from centromedially to superomedially. Two suture anchors are placed at the proximal and distal trough. Fluoroscopy is utilized to identify Schöttle point with a perfect lateral radiograph. A 3-centimeter incision is made, and blunt dissection connects the 2 incisions in the developed plane. A guidepin is advanced at Schöttle point, and suture anchor sutures are shuttled through the plane, posterior to the guidepin. There should be loosening of tension with knee flexion. A semitendinosus allograft is whipstitched with terminal tapering. The whipstitched end is tunneled around the guidepin and brought back to the patella, so that both ends have an excess of 20 to 25 millimeters, and excess graft is trimmed from the free end prior to whipstitching. The doubled graft is sized. The midportion of the tendon is tagged and passed through both anchors. The graft is tensioned to the patellar trough and the graft ends are advanced through the developed plane. The femoral tunnel is reamed, and the graft is tensioned into the tunnel after nitinol wire placement with the knee in full extension. Isometry and lateral patellar translation are assessed, aiming for 1 quadrant with firm endpoint. The patella is proximalized and the tensioned graft is secured with an interference screw. Results: MPFL reconstruction is successful for the majority of patients, with 1.2% reporting instability, 3.6% apprehension, and 3.1% reoperation. Possible complications include patellar fracture, patellofemoral pain, and knee stiffness (loss of range of motion). Discussion/Conclusion: Lateral patellar instability is common, and MPFL reconstruction is typically successful for the majority of patients.

Paper 54: MPFL Repair has a Higher Failure Rate at Long-term Follow-up compared to MPFL Reconstruction for Recurrent Patellar Instability

Objectives:The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint to lateral patellar translation and is often disrupted with a lateral patellar dislocation. Surgical management for recurrent patellar instability focuses on restoring MPFL function with repair or reconstruction techniques. Recent studies have favored reconstruction over repair, but no long-term, comparative studies are available in the literature.Methods:A total of 55 patients (58 knees) with recurrent lateral instability were treated between 2005 and 2012 with either MPFL repair or MPFL reconstruction. Exclusion criteria included prior or concomitant tibial tubercle osteotomy or trochleoplasty, and follow-up less than 8 years. Pre- and post-operative demographic, surgical, imaging and clinical data were recorded for each patient.Results:MPFL repair was performed on 26 patients (29 knees; 14 females, 15 males) at a mean age of 19.1 years. MPFL reconstruction was performed on 29 patients (29 knees; 18 females, 11 males) at a mean age of 18.2 years. Mean follow-up was 12.0 years (range 8.3-18.9). The reconstruction group had a significantly lower rate of recurrent dislocation compared to the repair group (14% vs 41%, p=0.019) at final follow up. There were no differences in the number of pre-operative dislocations (greater than or less than 3), degree of patellar facet chondromalacia, TT-TG distance, or Tegner scores. The reconstruction group had significantly more time from injury to surgery compared to the repair group (median, 1,460 days vs 627 days, p =0.007). There were no differences in post-operative Tegner, Lysholm or Kujala scores at final follow-up. Additionally, there were no differences in return to play rates (repair 80.8% vs reconstruction 75.0%, p=0.610) or reoperation rates (repair 20.7% vs reconstruction 13.8%, p=0.487).Conclusions:Repair of the MPFL leads to nearly 3-fold higher rate of recurrent patellar dislocation (41% vs. 14%) at long term follow-up compared to MPFL reconstruction. However, MPFL repair and reconstruction provide similar clinical results, return to play rates and reoperation rates.

Double-Tunnel Technique Was Similar to Single-Tunnel Technique in Clinical, Imaging and Functional Outcomes for Medial Patellofemoral Ligament Reconstruction: A Randomized Clinical Trial

This study aimed to compare the clinical, functional, and imaging outcomes of single-tunnel (ST) and double-tunnel (DT) techniques for medial patellofemoral ligament (MPFL) reconstruction. Ninety-four patients with recurrent patellar instability were randomly divided into 2 groups, receiving either ST or DT MPFL reconstruction. Lateral reticulum release (LRR) and tibial tuberosity (TT) transfer were performed as combined procedures when necessary. Preoperative and postoperative clinical characteristics (symptoms and episodes of redislocation), functional outcomes (Kujala, Lysholm, Tegner, IKDC, and KOOS score), and radiological measurements (congruence angle, patellar tilt angle, lateral patellar angle, and lateral patellar translation) were analyzed. The analysis included data from 90 patients with 48 patients in the ST group and 42 patients in the DT group. Patients were followed up for a mean period of 37.8 (range: 27-50) months in the ST group and 38.6 (range: 25-53) months in the DT group. Forty-three patients in the ST group and 40 patients in the DT group received combined TT transfer, and all patients underwent LRR. At thelatestfollow-up, 1 patient in ST group experienced redislocation, while no patient in the DT group sustained clinical failure (P= .347). Imaging measurements decreased significantly to the normal range postoperatively. No significant difference was noted between the postoperative radiological results of the 2 groups. All clinical scores significantly improvedpostoperatively,and no significant difference was observed between the 2 groups except for the higher Lysholm score (P= .031), KOOS symptoms score (P= .021) and KOOS knee-related quality of life score (P= .043) in the DT group. Both techniques could equally mitigate the patellar lateral translation or redislocation. Our results demonstrate several significant differences in functional outcomes that favored DT MPFL reconstruction but no difference in clinical failure rates and radiological results between ST and DT MPFL reconstruction. Level I, randomized clinical trial.

An anatomo-functional implant positioning technique with robotic assistance for primary TKA allows the restoration of the native knee alignment and a natural functional ligament pattern, with a faster recovery at 6months compared to an adjusted mechanical technique.

An anatomo-functional implant positioning (AFIP) technique in total knee arthroplasty (TKA) could restore physiological ligament balance (symmetric gap in extension, asymmetric gap in flexion). The purposes were to compare (1) ligament balancing in extension and flexion after TKA in the AFIP group, (2) TKA alignment, implant positioning and patellar tracking between AFIP and adjusted mechanical alignment (aMA) techniques, (3) clinical outcomes between both groups at 12months. All robotic-assisted TKA with an AFIP technique were included (n = 40). Exclusion criteria were genu valgum (HKA angle > 183°), extra-articular deformity more than 10°, and patellar maltracking (high-grade J-sign). One control patient with a TKA implanted by an aMA technique was matched for each case, based on age, body mass index, sex, and knee alignment. Ligament balancing (medial and lateral gaps in millimeters) in full extension and at 90° of flexion after TKA in the AFIP group was assessed with the robotic system. TKA alignment (HKA angle), implants positioning (femoral and tibial coronal axis, tibial slope, joint-line orientation), patellar tracking (patellar tilt and translation) and the Knee Society Score (KSS) at 6 and 12months were compared between both groups. The ligament balancing was compared using a t test for paired samples in the AFIP group. The radiographic measurements and KSS scores were compared between groups using a t test for independent samples. In the AFIP group, there was no significant difference between the medial and lateral gap laxity in extension (NS). A significant opening of the lateral gap was observed in flexion compared to extension (mean: + 2.9mm; p < 0.0001). The mean postoperative HKA angle was comparable between both groups (177.3° ± 2.1 in the AFIP group vs 176.8° ± 3.2; NS). In the AFIP group, the femoral anatomy was restored (90.9° ± 1.6) and the tibial varus was partially corrected (87.4° ± 1.8). The improvement of Knee and Function KSS at 6months was better in the AFIP group (59.3 ± 11.9 and 51.7 ± 20, respectively, versus 49.3 ± 9.7 and 20.8 ± 13; p < 0.001). The AFIP concept allowed the restoration of the native knee alignment and a natural functional ligament pattern. With a more physiological target for ligament balancing, the AFIP technique had equivalent clinical outcomes at 12months compared to aMA, with a faster recovery. III retrospective therapeutic case control series.

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.