Meniscal Root Attachment Research Articles

Consequences of Tibial Tunnel Reaming on the Meniscal Roots During Cruciate Ligament Reconstruction in a Cadaveric Model, Part 2

Background: Recent emphasis has turned to reconstructing the posterior cruciate ligament (PCL) after injury. However, single-bundle PCL reconstruction of the anterolateral bundle may potentially injure the posterior meniscal roots. Purpose/Hypothesis: The purpose of this study was to determine if posterior meniscal root injuries occurred because of tunnel reaming for single-bundle PCL reconstruction. It was hypothesized that tibial tunnel reaming within the anterolateral bundle footprint during PCL reconstruction would result in clinically significant decreases in posteromedial (PM) root attachment areas and in ultimate failure strength for the PM root. Study Design: Controlled laboratory study. Methods: Testing was performed on 12 matched pairs of human cadaveric knees. For each pair of knees, one knee was left intact, while the contralateral knee was prepared with a tibial tunnel placed 5 mm anterior to the center of the tibial PCL attachment and within the previously described footprint of the anterolateral bundle of the PCL for single-bundle PCL reconstruction. The attachment areas of the posterior meniscal roots were measured with a coordinate measuring device before and after PCL tunnel reaming. The posterior meniscal roots were then pulled to failure with a dynamic tensile testing machine. Results: There was a significant mean decrease in the attachment area of the PM root (%Δ, 28%; 95% CI, 16-40) after PCL tunnel reaming compared with the intact state (P = .005). The mean ultimate failure strength of the native PM root (mean, 440 N; 95% CI, 347-534) was also significantly stronger (mean, 40%; 95% CI, 18-61; P = .005) than that of the PM root after PCL tunnel reaming (mean, 243 N; 95% CI, 176-309). No changes were found for the posterolateral (PL) root after PCL tunnel reaming. Conclusion: Tibial tunnel reaming for single-bundle PCL reconstruction in the anterolateral bundle footprint significantly reduced the ultimate failure strength and attachment area of the PM meniscal root. The attachment area and ultimate failure strength of the PL root were unaffected by tunnel reaming. Clinical Relevance: Tibial tunnels reamed in the footprint of the anterolateral bundle during single-bundle PCL reconstruction can cause iatrogenic damage to the PM meniscal root attachment. Thus, tibial tunnels should strive to be reamed in the center of the entire tibial PCL attachment site during PCL reconstruction.

Radiographic Identification of the Anterior and Posterior Root Attachments of the Medial and Lateral Menisci

Background: Anatomic root placement is necessary to restore native meniscal function during meniscal root repair. Radiographic guidelines for anatomic root placement are essential to improve the accuracy and consistency of anatomic root repair and to optimize outcomes after surgery. Purpose: To define quantitative radiographic guidelines for identification of the anterior and posterior root attachments of the medial and lateral menisci on anteroposterior (AP) and lateral radiographic views. Study Design: Descriptive laboratory study. Methods: The anterior and posterior roots of the medial and lateral menisci were identified in 12 human cadaveric specimens (average age, 51.3 years; age range, 39-65 years) and labeled using 2-mm radiopaque spheres. True AP and lateral radiographs were obtained, and 2 raters independently measured blinded radiographs in relation to pertinent landmarks and radiographic reference lines. Results: On AP radiographs, the anteromedial and posteromedial roots were, on average, 31.9 ± 5.0 mm and 36.3 ± 3.5 mm lateral to the edge of the medial tibial plateau, respectively. The anterolateral and posterolateral roots were, on average, 37.9 ± 5.2 mm and 39.3 ± 3.8 mm medial to the edge of the lateral tibial plateau, respectively. On lateral radiographs, the anteromedial and anterolateral roots were, on average, 4.8 ± 3.7 mm and 20.5 ± 4.3 mm posterior to the anterior margin of the tibial plateau, respectively. The posteromedial and posterolateral roots were, on average, 18.0 ± 2.8 mm and 19.8 ± 3.5 mm anterior to the posterior margin of the tibial plateau, respectively. The intrarater and interrater intraclass correlation coefficients (ICCs) were >0.958, demonstrating excellent reliability. Conclusion: The meniscal root attachment sites were quantitatively and reproducibly defined with respect to anatomic landmarks and superimposed radiographic reference lines. The high ICCs indicate that the measured radiographic relationships are a consistent means for evaluating meniscal root positions. Clinical Relevance: This study demonstrated consistent and reproducible radiographic guidelines for the location of the meniscal roots. These measurements may be used to assess root positions on intraoperative fluoroscopy and postoperative radiographs.

Anatomy of the Anterior Root Attachments of the Medial and Lateral Menisci

Background: While the biomechanical importance of the meniscal roots has been demonstrated, the anatomy of the anterior meniscal roots remains largely unknown. Defining the quantitative anatomy of the anterior meniscal root attachments is essential for developing improved diagnostic and surgical techniques. Hypothesis: The anterior medial (AM) and anterior lateral (AL) meniscal roots could be quantitatively defined relative to open and arthroscopic surgical landmarks. Study Design: Descriptive laboratory study. Methods: Twelve nonpaired human cadaveric knees were used (average age, 51.3 years). A coordinate measuring device quantified the anatomic relationships of the AM and AL root attachments to open and arthroscopic surgical landmarks. The tibial attachments of both anterior roots were defined and quantified by categorizing the fibers of the root as either central, dense attachments or peripheral, supplemental attachments. Results: The center of the tibial tuberosity and the medial tibial eminence apex were 27.0 mm lateral and distal and 27.5 mm posterior to the center of the AM root, respectively. The center of the anterior cruciate ligament (ACL) and the lateral tibial eminence apex were 5.0 mm posteromedial and 14.4 mm posterolateral to the center of the AL root, respectively. The AM root attachment had a mean area of 110.4 mm2 (95% CI, 92.2-128.5) with a central attachment of 56.3 mm2 (95% CI, 46.9-65.8). The AL root attachment had a mean area of 140.7 mm2 (95% CI, 121.6-159.8) and inserted deeply beneath the ACL in all specimens. The overlap of the ACL on the AL root averaged 88.9 mm2 (95% CI, 63.3-114.6), comprising 63.2% of the AL root attachment. Conclusion: The anterior meniscal roots were identified in relation to pertinent open and arthroscopic landmarks. The extended overlap between the AL root and ACL attachment revealed a more intimate tibial attachment relationship than previously recognized. Clinical Relevance: Quantitative descriptions of the anterior meniscal roots elucidate the relationship between the root attachments and pertinent surgical landmarks. In addition, the supplemental attachments of both menisci may contribute to native meniscal function, and further investigation is recommended.

Structural Properties of the Meniscal Roots

Background: Current surgical techniques for meniscal root repair reattach the most prominent, dense portion of the meniscal root and fail to incorporate recently identified peripheral, supplemental attachment fibers. The contribution of supplemental fibers to the biomechanical properties of native meniscal roots is unknown. Hypothesis/Purpose: The purpose was to quantify the ultimate failure strengths, stiffness, and attachment areas of the native posterior medial (PM), posterior lateral (PL), anterior medial (AM), and anterior lateral (AL) meniscal roots compared with the most prominent, dense meniscal root attachment after sectioning of supplemental fibers. It was hypothesized that the ultimate failure strength, stiffness, and attachment area of each native root would be significantly higher than those of the respective sectioned root. Study Design: Controlled laboratory study. Methods: Twelve matched pairs of male human cadaveric knees were used. The 4 native meniscal roots were left intact in the native group, whereas the roots in the contralateral knee (sectioned group) were dissected free of all supplemental fibers. A coordinate measuring device quantified the amount of tissue resected in the sectioned group compared with the native group. A dynamic tensile testing machine pulled each root in line with its circumferential fibers. All root attachments were preconditioned from 10 to 50 N at a rate of 0.1 Hz for 10 cycles and subsequently pulled to failure at a rate of 0.5 mm/s. Results: Supplemental fibers composed a significant percentage of the native PM, PL, and AM meniscal root attachment areas. Mean ultimate failure strengths (in newtons) of the native PM, PL, and AM roots were significantly higher than those of the sectioned state, while the ultimate failure strength of the native AL root was indistinguishable from that of the sectioned state. Conclusion: Three of the 4 meniscal root attachments (PM, PL, AM) contained supplemental fibers that accounted for a significant percentage of the native root attachment areas, and these fibers significantly contributed to the failure strengths of the native roots. Clinical Relevance: These supplemental fibers are not routinely reattached during root repair surgery, suggesting that current techniques fail to reattach the biomechanically relevant attachments of native meniscal roots.

Anterior meniscus root avulsion following intramedullary nailing for a tibial shaft fracture

This paper presents the first reported case of iatrogenic injury to the anterior medial meniscal root attachment following intramedullary nailing for a tibial shaft fracture. The patient experienced a closed right tibia-fibula fracture 7years prior to presentation, which was treated with a reamed intramedullary nail. The nail was removed 3years after the index surgery due to chronic anterior knee pain, which persisted following hardware removal. At presentation, the patient was diagnosed with an anterior horn medial meniscal root tear likely secondary to insertion of the intramedullary nail through the anatomic footprint of the anterior medial root. After undergoing a medial meniscus anterior horn root repair, the patient was asymptomatic and resumed normal activities. Case report, Level IV.

Internal pressure of human meniscal root attachments during loading

This study investigated the internal fluid pressure of human cadaver meniscal root attachments. A pressure micro-sensor was implanted inside each attachment site. Tibiofemoral joints were compressed to 2× body weight at various flexion angles and pressure recorded for 20 min. The anterior cruciate ligament (ACL) was then transected and joints retested. Lastly, a longitudinal incision of the lateral posterior (LP) horn was made and the joint retested. Ramp pressure was defined as the pressure when 2× body weight was reached, and equilibrium pressure was recorded at the end of the hold period. The medial posterior (MP) attachment was subjected to greater ramp pressure than the medial anterior (p = 0.002) and greater equilibrium pressure than all other root attachment sites (p < 0.001). Flexion angle had a significant effect on pressure as full extension was greatest at ramp (p = 0.040). Transection of the ACL decreased ramp pressure in the LP attachment (p = 0.025) and increased equilibrium pressure (p = 0.031) in the MP attachment. The results suggest that repair strategies should be developed which reconstruct the MP attachments to be sufficient to withstand large pressures. Furthermore, since meniscal pressure is highest at full extension, this fact should be considered when prescribing rehabilitation following repair of an attachment.

Qualitative and Quantitative Anatomic Analysis of the Posterior Root Attachments of the Medial and Lateral Menisci

Background: The clinical importance of the meniscal posterior root attachments has been recently reported by both biomechanical and clinical studies. Although several studies have been performed to evaluate surgical techniques, there have been few studies on the quantitative arthroscopically pertinent anatomy of the posterior meniscal root attachments. Hypothesis: The posterior root attachments of the medial and lateral menisci are consistent among specimens, and repeatable quantitative measurements using arthroscopically pertinent landmarks are achievable. Study Design: Descriptive laboratory study. Methods: Twelve nonpaired, fresh-frozen cadaveric knees were used. The positions of the posterior root attachments of the medial and lateral menisci were identified, and 3-dimensional measurements to arthroscopically pertinent landmarks were performed using a coordinate measuring system. Results: The direct distance (±standard error of the mean) between the medial tibial eminence apex and the medial meniscus posterior root attachment center was 11.5 (±0.9) mm. When split into directional components along the knee’s main axes, the medial meniscus posterior root attachment center was 9.6 (±0.8) mm posterior and 0.7 (±0.4) mm lateral along the bony surface from the medial tibial eminence apex. It was located 3.5 (±0.4) mm lateral from the medial articular cartilage inflection point and directly 8.2 (±0.7) mm from the nearest tibial attachment margin of the posterior cruciate ligament. The direct distance between the lateral tibial eminence apex and the lateral meniscus posterior root attachment center was 5.3 (±0.3) mm. When it was split into directional components using the knee’s main axes, the lateral meniscus posterior root attachment center was 4.2 (±0.4) mm medial and 1.5 (±0.7) mm posterior from the lateral tibial eminence apex. The lateral meniscus posterior root attachment center was located 4.3 (±0.5) mm medial from the nearest articular cartilage margin and directly 12.7 (±1.1) mm from the nearest margin of the tibial attachment of the posterior cruciate ligament. Conclusion: This quantitative study reproducibly identified the posterior root attachment centers of the medial and lateral menisci in relation to arthroscopically pertinent landmarks and guidelines. Clinical Relevance: These data can be directly applied to assist in anatomic meniscal root repairs.