Christopher M. LaPrade

Meniscal Root Tears: Significance, Diagnosis, and Treatment

Meniscal root tears, less common than meniscal body tears and frequently unrecognized, are a subset of meniscal injuries that often result in significant knee joint disorders. The meniscus root attachment aids meniscal function by securing the meniscus in place and allowing for optimal shock-absorbing function in the knee. With root tears, meniscal extrusion often occurs, and the transmission of circumferential hoop stresses is impaired. This alters knee biomechanics and kinematics and significantly increases tibiofemoral contact pressure. In recent years, meniscal root tears, which by definition include direct avulsions off the tibial plateau or radial tears adjacent to the root itself, have attracted attention because of concerns that significant meniscal extrusion dramatically inhibits normal meniscal function, leading to a condition biomechanically similar to a total meniscectomy. Recent literature has highlighted the importance of early diagnosis and treatment; fortunately, these processes have been vastly improved by advances in magnetic resonance imaging and arthroscopy. This article presents a review of the clinically relevant anatomic, biomechanical, and functional descriptions of the meniscus root attachments, as well as current strategies for accurate diagnosis and treatment of common injuries to these meniscus root attachments.

Altered Tibiofemoral Contact Mechanics Due to Lateral Meniscus Posterior Horn Root Avulsions and Radial Tears Can Be Restored with in Situ Pull-Out Suture Repairs

BACKGROUND An avulsion of the posterior root attachment of the lateral meniscus or a radial tear close to the root attachment can lead to degenerative knee arthritis. Although the biomechanical effects of comparable injuries involving the medial meniscus have been studied, we are aware of no such study involving the lateral meniscus. We hypothesized that in situ pull-out suture repair of lateral meniscus root avulsions and of complete radial tears 3 and 6 mm from the root attachment would increase the contact area and decrease mean and peak tibiofemoral contact pressures, at all knee flexion angles, relative to the corresponding avulsion or tear condition. METHODS Eight human cadaveric knees underwent biomechanical testing. Eight lateral meniscus conditions (intact, footprint tear, root avulsion, root avulsion repair, radial tears at 3 and 6 mm from the posterior root, and repairs of the 3 and 6-mm tears) were tested at five different flexion angles (0°, 30°, 45°, 60°, and 90°) under a compressive 1000-N load. RESULTS Avulsion of the posterior root of the lateral meniscus or an adjacent radial tear resulted in significantly decreased contact area and increased mean and peak contact pressures in the lateral compartment, relative to the intact condition, in all cases except the root avulsion condition at 0° of flexion. In situ pull-out suture repair of the root avulsion or radial tear significantly reduced mean contact pressures, relative to the corresponding avulsion or tear condition, when the results for each condition were pooled across all flexion angles. CONCLUSIONS Posterior horn root avulsions and radial tears adjacent to the root attachment of the lateral meniscus significantly increased contact pressures in the lateral compartment. In situ pull-out suture repairs of these tears significantly improved lateral compartment joint contact pressures. CLINICAL RELEVANCE In situ repair may be an effective treatment to improve tibiofemoral contact profiles after an avulsion of the posterior root of the lateral meniscus or a complete radial tear adjacent to the root. In situ repairs should be further investigated clinically as an alternative to partial lateral meniscectomy.

Emerging Updates on the Posterior Cruciate Ligament A Review of the Current Literature

The posterior cruciate ligament (PCL) is recognized as an essential stabilizer of the knee. However, the complexity of the ligament has generated controversy about its definitive role and the recommended treatment after injury. A proper understanding of the functional role of the PCL is necessary to minimize residual instability, osteoarthritic progression, and failure of additional concomitant ligament graft reconstructions or meniscal repairs after treatment. Recent anatomic and biomechanical studies have elucidated the surgically relevant quantitative anatomy and confirmed the codominant role of the anterolateral and posteromedial bundles of the PCL. Although nonoperative treatment has historically been the initial treatment of choice for isolated PCL injury, possibly biased by the historically poorer objective outcomes postoperatively compared with anterior cruciate ligament reconstructions, surgical intervention has been increasingly used for isolated and combined PCL injuries. Recent studies have more clearly elucidated the biomechanical and clinical effects after PCL tears and resultant treatments. This article presents a thorough review of updates on the clinically relevant anatomy, epidemiology, biomechanical function, diagnosis, and current treatments for the PCL, with an emphasis on the emerging clinical and biomechanical evidence regarding each of the treatment choices for PCL reconstruction surgery. It is recommended that future outcomes studies use PCL stress radiographs to determine objective outcomes and that evidence level 1 and 2 studies be performed to assess outcomes between transtibial and tibial inlay reconstructions and also between single- and double-bundle PCL reconstructions.

Meniscal Root Tears A Classification System Based on Tear Morphology

Background: Meniscal root tears present in many forms and can have profound consequences on the health of knee articular cartilage. While the biomechanics, natural history, and treatment of root tears have been increasingly investigated, the spectrum of meniscal root tear patterns observed during arthroscopic examination has yet to be defined and categorized. Purpose: To establish a classification system for meniscal root tears by reporting the morphology of meniscal root tears from a consecutive series of arthroscopic surgeries. It was hypothesized that meniscal root tears could be grouped into types by distinct tear patterns and that recognition of tear pattern would affect treatment choice. Study Design: Case series; Level of evidence, 4. Methods: All patients who underwent arthroscopic surgery from April 2010 to May 2014 by a single orthopaedic surgeon were included. After arthroscopic examination, data regarding the integrity of the meniscal roots were prospectively recorded in a data registry. Tear morphology and treatment received were subsequently extracted by 2 independent reviewers from operative notes and arthroscopic surgical photos. Results: A total of 71 meniscal root tears in 67 patients were grouped into tear types with similar tear morphologies. Meniscal root tear patterns were categorized into partial stable root tears (type 1; n = 5); complete radial tears within 9 mm of the bony root attachment (type 2; n = 48), further subclassified into types 2A, 2B, and 2C, located 0 to <3 mm, 3 to <6 mm, and 6 to 9 mm from the root attachment, respectively; bucket-handle tears with a complete root detachment (type 3; n = 4); complex oblique tears with complete root detachments extending into the root attachment (type 4; n = 7); and bony avulsion fractures of the root attachments (type 5; n = 7). Conclusion: This study demonstrated that it was possible to establish a concise classification system to group patients with meniscal root tears by tear morphology. Treatments received varied across tear types.

A Biomechanical Comparison of Femoral Cortical Suspension Devices for Soft Tissue Anterior Cruciate Ligament Reconstruction Under High Loads

Background: Graft healing after soft tissue anterior cruciate ligament (ACL) reconstruction requires rigid fixation to allow for soft tissue healing. Cortical suspension devices for femoral fixation should be biomechanically tested under high loads representative of early rehabilitation to evaluate whether they provide sufficient fixation. Purpose/Hypothesis: To biomechanically compare current fixed-loop and adjustable-loop cortical suspension devices for soft tissue femoral fixation under high loads. The hypotheses were that there would be significant differences in cyclic displacement between devices, independent of loop type, and that retensioning of the adjustable-loop devices would not significantly alter the biomechanical properties of these devices. Study Design: Controlled laboratory study. Methods: Five different femoral ACL graft cortical suspension devices (3 fixed and 2 adjustable) were compared under high cyclic forces (100-400 N for 1000 cycles) and then pulled to failure at 50 mm/min. In addition, the effect of retensioning after simulated preconditioning was evaluated for the 2 adjustable-loop devices. Results: On average, the least amount of cumulative peak cyclic displacement (mean ± SD) was observed for the ENDOBUTTON (1.05 ± 0.05 mm), followed by the RIGIDLOOP (1.09 ± 0.16 mm), XO Button (1.65 ± 0.43 mm), TightRope with retensioning (1.81 ± 0.51 mm), TightRope without retensioning (2.20 ± 0.62 mm), ToggleLoc with retensioning (3.22 ± 1.41 mm), and ToggleLoc without retensioning (3.69 ± 2.39 mm). The ENDOBUTTON displaced significantly less after cyclic loading than all adjustable-loop devices (TightRope and ToggleLoc, both with and without retensioning) and the XO Button. The RIGIDLOOP displaced significantly less than the TightRope without retensioning and ToggleLoc with and without retensioning. There was no significant difference in biomechanical properties after retensioning for both adjustable-loop devices. Conclusion: Significant differences were observed between current fixed-loop and adjustable-loop cortical suspension devices for soft tissue femoral fixation when subjected to high loads experienced during rehabilitation. Retensioning did not significantly alter the biomechanical properties of adjustable-loop devices. Clinical Relevance: Early rehabilitation protocols subject the graft construct to higher forces than what has been previously tested biomechanically. Biomechanical testing of cortical suspension devices under simulated high rehabilitation loads demonstrated significant differences between devices. Future studies should investigate the clinical implications of these time zero results.

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.

Biomechanical Consequences of a Nonanatomic Posterior Medial Meniscal Root Repair

Background: Posterior medial meniscal root tears have been reported to extrude with the meniscus becoming adhered posteromedially along the posterior capsule. While anatomic repair has been reported to restore tibiofemoral contact mechanics, it is unknown whether nonanatomic positioning of a meniscal root repair to a posteromedial location would restore the loading profile of the knee joint. Purpose/Hypothesis: The purpose of this study was to compare the tibiofemoral contact mechanics of a nonanatomic posterior medial meniscal tear with that of the intact knee or anatomic repair. It was hypothesized that a nonanatomic root repair would not restore the tibiofemoral contact pressures and areas to that of the intact or anatomic repair state. Study Design: Controlled laboratory study. Methods: Tibiofemoral contact mechanics were recorded in 6 male human cadaveric knee specimens (average age, 45.8 years) using pressure sensors. Each knee underwent 5 testing conditions for the posterior medial meniscal root: (1) intact knee; (2) root tear; (3) anatomic transtibial pull-out repair; (4) nonanatomic transtibial pull-out repair, placed 5 mm posteromedially along the edge of the articular cartilage; and (5) root tear concomitant with an ACL tear. Knees were loaded with a 1000-N axial compressive force at 4 flexion angles (0°, 30°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated. Results: Contact area was significantly lower after nonanatomic repair than for the intact knee at all flexion angles (mean = 44% reduction) and significantly higher for anatomic versus nonanatomic repair at all flexion angles (mean = 27% increase). At 0° and 90°, and when averaged across flexion angles, the nonanatomic repair significantly increased mean contact pressures in comparison to the intact knee or anatomic repair. When averaged across flexion angles, the peak contact pressures after nonanatomic repair were significantly higher than the intact knee but not the anatomic repair. In contrast, when averaged across all flexion angles, the anatomic repair resulted in a 17% reduction in contact area and corresponding increases in mean and peak contact pressures of 13% and 26%, respectively, compared with the intact knee. Conclusion: For most testing conditions, the nonanatomic repair did not restore the contact area or mean contact pressures to that of the intact knee or anatomic repair. However, the anatomic repair produced near-intact contact area and resulted in relatively minimal increases in mean and peak contact pressures compared with the intact knee. Clinical Relevance: Results emphasize the importance of ensuring an anatomic posterior medial meniscal root repair by releasing the extruded menisci from adhesions and the posteromedial capsule. Similar caution toward preventing displacement of the meniscal root repair construct should be emphasized.

Anatomy of the Anterior Root Attachments of the Medial and Lateral Menisci: A Quantitative Analysis

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.

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

Background: The current standard for treating complete tears of the anterior cruciate ligament (ACL) is reconstruction, which requires reaming a tibial tunnel. Based on recent anatomic and biomechanical studies, this reconstruction tunnel may cause injuries to the anterior meniscal root attachments. Purpose/Hypothesis: The purpose was to determine if injuries occurred to the anteromedial (AM) and anterolateral (AL) meniscal root attachments because of reaming a tibial reconstruction tunnel in the anatomic center of the ACL footprint. It was hypothesized that tibial tunnel reaming for ACL reconstruction would result in significant decreases in the attachment area and in ultimate failure strength for the AL root. Study Design: Controlled laboratory study. Methods: Twelve matched pairs of human cadaveric knees were tested. One knee from each pair remained intact, while the contralateral knee was reamed with a tibial tunnel for an anatomic ACL reconstruction. The attachment areas of the anterior meniscal roots were measured with a coordinate measuring device before and after tunnel reaming. The anterior meniscal roots were then pulled to failure with a dynamic tensile testing machine. Results: There was a significant mean decrease in the attachment area for the AL root (%Δ, 38%; 95% CI, 25-51) after ACL tunnel reaming compared with the intact state (P = .003). The mean ultimate failure strength of the native AL root (mean, 610 N; 95% CI, 470-751) was significantly stronger (P = .015) than that of the AL root with a reamed ACL reconstruction tunnel (mean, 506 N; 95% CI, 353-659). Tunnel reaming did not significantly affect the AM root attachment area or ultimate failure strength. Conclusion: Tibial tunnel reaming during anatomic single-bundle ACL reconstruction significantly decreased the AL meniscal root attachment area and ultimate failure strength. The AM root was not significantly affected by reaming of the ACL reconstruction tunnel. Future studies should investigate the clinical importance of these iatrogenic injuries to the AL root. Clinical Relevance: The ACL reconstruction tunnels reamed in the center of the ACL tibial footprint caused a significant decrease in the attachment area and ultimate strength of the AL meniscal root attachment. Clinically, repositioning guide pins placed in the lateral aspect of the ACL attachment before tibial tunnel reaming may minimize iatrogenic injuries to the AL meniscal root attachment.

Biomechanical evaluation of a transtibial pull-out meniscal root repair: challenging the bungee effect.

Background: A common treatment for posterior meniscal root tears is transtibial pull-out repair, which has been biomechanically reported to restore tibiofemoral contact mechanics to those of the intact knee. Biomechanical data suggest that there is significant displacement of the repaired meniscal root with cyclic loading, which may be responsible for the poor healing and meniscal extrusion demonstrated in some clinical studies. Hypothesis/Purpose: The purpose of this study was to quantify the time-zero displacement of the posterior meniscal root in response to cyclic loading after transtibial pull-out repair and to quantify the individual contributions to displacement of the following: (1) suture elongation, (2) button-bone interface, and (3) meniscus-suture interface. The meniscus-suture interface was hypothesized to result in significantly more displacement than the button-bone interface or suture elongation. Study Design: Descriptive laboratory study. Methods: Transtibial pull-out repair of the posterior medial meniscal root was performed in 6 porcine knees, and cyclic displacement was measured using a loading protocol representative of postoperative rehabilitation. Displacement from (1) suture elongation, (2) the button-bone interface, and (3) the meniscus-suture interface was determined by cyclically loading 6 specimens for each construct using the same loading protocol to determine the contribution of each component to the overall displacement of the repair construct. Results: After 1000 cycles, the repair construct displaced by a mean of 3.28 mm (95% CI, 2.07-4.49). The meniscus-suture component (mean, 2.52 mm; 95% CI, 2.21-2.83) displaced significantly more than the button-bone component (mean, 0.90 mm; 95% CI, 0.64-1.15; P = .006) and suture elongation component (mean, 0.71 mm; 95% CI, 0.36-1.06; P = .006) after 1000 cycles. Displacement of the button-bone and suture elongation components was not significantly different after 1000 cycles (P = .720). Conclusion: There was substantial displacement of the posterior medial meniscal root repaired with the transtibial pull-out technique under a cyclic loading protocol simulating postoperative rehabilitation. The meniscus-suture interface contributed to significantly more displacement than the button-bone interface and suture elongation in the transtibial pull-out repair construct. Clinical Relevance: The results provide a framework for optimizing the transtibial pull-out repair technique. Future studies should focus on improving suture fixation strength within the meniscus-suture interface.