Dysplastic Patellofemoral Joints Lead to a Shift in Contact Forces: A 3D-Printed Cadaveric Model.

BACKGROUND: The distribution of contact forces across the dysplastic patellofemoral joint has not been adequately quantified because models cannot easily mimic the dysplasia of both the trochlea and the patella. Thus, the mechanical consequences of surgical treatments to correct dysplasia cannot be established. PURPOSE/HYPOTHESIS: The objective of this study was to quantify the contact mechanics and kinematics of normal, mild, and severely dysplastic patellofemoral joints using synthetic mimics of the articulating surfaces on cadavers. We tested the hypothesis that severely dysplastic joints would result in significantly increased patellofemoral contact forces and abnormal kinematics. STUDY DESIGN: Controlled laboratory study. METHOD: Patellofemoral dysplasia was simulated in 9 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic patellar and trochlear implants. For each knee, 3 synthetic surface geometries (normal, showing no signs of dysplasia; mild, exemplifying Dejour type A; and severe, exemplifying Dejour type B) were randomized for implantation and testing. Patellar kinematics and the sum of forces acting on the medial and lateral patellar facets were computed for each knee and for each condition at 10° increments from 0° to 70° of flexion. RESULTS: A pronounced lateral shift in the weighted center of contact of the lateral facet occurred for severely dysplastic knees from 20° to 70° of flexion. Compared with normal geometries, lateral patellar facet forces exhibited a significant increase only with mild dysplasia from 50° to 70° of flexion and with severe dysplasia at 70° of flexion. No measurable differences in medial patellar facet mechanics or joint kinematics occurred. CONCLUSION: Our hypothesis was rejected: Severely dysplastic joints did not result in significantly increased patellofemoral contact forces and abnormal kinematics in our cadaveric simulation. Rather, severe dysplasia resulted in a pronounced lateral shift in contact forces across the lateral patellar facet, while changes in kinematics and the magnitude of contact forces were not significant. CLINICAL RELEVANCE: Including dysplasia of both the patella and trochlea is required to fully capture the mechanics of this complex joint. The pronounced lateralization of contact force in severely dysplastic patellofemoral joints should be considered to avoid cartilage overload with surgical manipulation.

Optimizing Anterior Cruciate Ligament (ACL) Outcomes: What Else Needs Fixing Besides the ACL?

This review focuses on the management of anterior cruciate ligament (ACL) reconstruction patients when other concomitant pathology may need to be addressed at the time of surgery. Given the role of the posterior horn of the medial meniscus in preventing osteoarthritis progression and contributing to knee stability, medial meniscus repair should always be considered when performing ACL reconstruction. Meniscal transplant may also be appropriate in select patients with normal knee alignment and absent of cartilage abnormalities in the compartment. Varus alignment with a varus thrust or increased posterior tibial slope will increase stress on the ACL graft and may predispose to early failure. Alignment should be assessed with appropriate radiographs and corrective osteotomy in isolation or in conjunction with ACL reconstruction should be considered for certain patients. Low-grade medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries can be treated nonsurgically prior to ACL reconstruction. These are frequently missed with either physical examination or radiographic imaging. High-grade LCL injuries are often treated with repair versus reconstruction in conjunction with ACL reconstruction depending on the timing of the injury. When chronic MCL injuries show opening in extension, MCL reconstruction may be needed in addition to the ACL reconstruction to improve outcome. The role of extra-articular reconstruction or anterolateral ligament (ALL) reconstruction remains controversial but may have a role in protecting rotatory stability in primary ACL reconstruction for high-risk patients, and in the revision setting. Cartilage lesions noted in the setting of ACL injury should be considered. Small, asymptomatic lesions in locations unrelated to the ACL injury may not necessitate additional intervention. Large symptomatic lesions may require additional cartilage restoration procedures at the time of ACL reconstruction or in a staged fashion. In this ICL, we will address the diagnosis, management, and surgical indications of other concomitant pathology associated with ACL ruptures.

Combined Reconstruction of the Medial Patellofemoral Ligament (MPFL) and Medial Quadriceps Tendon-Femoral Ligament (MQTFL) for Patellar Instability in Children and Adolescents: Surgical Technique and Outcomes.

OBJECTIVES: A variety of surgical options exist to treat the challenging problem of recurrent patellar instability in children and adolescents. The goal of the current study is to describe a novel combined reconstruction technique of both the medial patellofemoral ligament (MPFL) and the medial quadriceps tendon-femoral ligament (MQTFL) and report patient outcomes of a single-surgeon series. METHODS: All patients studied underwent simultaneous MPFL and MQTFL reconstruction for patellar instability using gracilis allograft. Demographic, clinical, and radiographic data were collected. Subjective outcomes were assessed for a minimum of 1 year postoperatively. RESULTS: Twenty-five patients (27 knees), including 15 female and 10 male individuals with an average age of 15.0±2.2 years (range, 10.3 to 18.9), were included. Prior ipsilateral patellofemoral surgery had been performed in 6 of 25 (24%) patients. Simultaneous hemiepiphysiodesis for valgus deformity at the time of combined reconstruction was performed in 5 of 25 (20%) patients. Preoperative imaging showed a mean tibial tubercle-trochlear groove of 17.2±3.8, Caton-Deschamps Index (CDI) of 1.13±0.16, and trochlear dysplasia Dejour A/B [22/26 (85%)] or Dejour C/D [4/26 (15%)]. A total of 18 patients (19 knees, 72%) returned outcomes questionnaires at a mean 2.0±0.5 years after surgery. Mean Kujala, Pedi-IKDC, and Lysholm scores were 85.9±13.9, 81.5±15.2, and 84.3±13.5, respectively. Later revision procedure (tibial tubercle osteotomy) for recurrent patellar instability was required in 2 of 25 patients (8%) patients, and another patient reported persistent instability not requiring revision. Return to sports was possible in 10 of 13 self-reported athletes (77%) at a mean of 5.8±3.9 months (range, 2 to 15). CONCLUSIONS: The present study describes a combined MPFL-MQTFL reconstruction technique with favorable short-term results. Although particularly useful in the skeletally immature patient where tibial tubercle osteotomy should be avoided and patellar fixation minimized, combined reconstruction may potentially be appropriate for older patients with patellofemoral instability as well. This technique more closely recreates the native anatomy of both the MPFL and MQTFL, may decrease the risk of patellar fracture, and can be useful in the revision setting. LEVEL OF EVIDENCE: Level IV.