Quantifying the differential functional behavior between the medial and lateral meniscus after posterior meniscus root tears

Meniscus tears of the knee are among the most common orthopedic knee injury. Specifically, tears of the posterior root can result in abnormal meniscal extrusion leading to decreased function and progressive osteoarthritis. Despite contemporary surgical treatments of posterior meniscus root tears, there is a low rate of healing and an incidence of residual meniscus extrusion approaching 30%, illustrating an inability to recapitulate native meniscus function. Here, we characterized the differential functional behavior of the medial and lateral meniscus during axial compression load and dynamic knee motion using a cadaveric model. We hypothesized essential differences in extrusion between the medial and lateral meniscus in response to axial compression and knee range of motion. We found no differences in the amount of meniscus extrusion between the medial and lateral meniscus with a competent posterior root (0.338mm vs. 0.235mm; p-value = 0.181). However, posterior root detachment resulted in a consistently increased meniscus extrusion for the medial meniscus compared to the lateral meniscus (2.233mm vs. 0.4705mm; p-value < 0.0001). Moreover, detachment of the posterior root of the medial meniscus resulted in an increase in extrusion at all angles of knee flexion and was most pronounced (4.00mm ± 1.26mm) at 30-degrees of knee flexion. In contrast, the maximum mean extrusion of the lateral meniscus was 1.65mm ± 0.97mm, occurring in full extension. Furthermore, only the medial meniscus extruded during dynamic knee flexion after posterior root detachment. Given the differential functional behaviors between the medial and lateral meniscus, these findings suggest that posterior root repair requires reducing overall meniscus extrusion and recapitulating the native functional responses specific to each meniscus.

Kinematic Analysis of Lateral Meniscal Oblique Radial Tears in the Anterior Cruciate Ligament–Deficient Knee

Background: Lateral meniscal oblique radial tears (LMORT) occur frequently in conjunction with anterior cruciate ligament (ACL) disruption and are anatomically distinct from meniscus root tears. Hypothesis/Purpose: The purpose of this study was to characterize the effects of LMORT types 3 (LMORT3) and 4 (LMORT4) lesions on joint stability and meniscal extrusion in ACL-deficient knees. Our hypothesis was that both lesions would promote significant increases in anterior translation and meniscal extrusion, with the LMORT4 lesion having a greater effect. Study Design: Controlled laboratory study. Methods: Two matched pairs of cadaveric knees (n = 4) were used to optimize the testing sequence. Additional cadaveric knees with LMORT3 (n = 8) and LMORT4 (n = 8) lesions created after ACL transection underwent robotic kinematic testing for anterior drawer and pivot-shift simulations with associated ultrasound-measured meniscal extrusion at clinically relevant knee flexion angles. Results: Optimization testing showed no differences on the effect of LMORT4 lesions for anterior translation and lateral meniscal extrusion with ACL-intact versus ACL-deficient knees. ACL deficiency and LMORT3 and LMORT4 lesions with ACL deficiency were associated with significantly greater anterior translation compared with ACL-intact state for both anterior drawer and pivot-shift testing at all flexion angles ( P < .001). ACL deficiency with either LMORT3 or LMORT4 lesion was associated with significantly greater anterior translation than was ACL deficiency only ( P < .005) for anterior drawer testing at 90° of flexion. Meniscal extrusion was greater with LMORT3 and LMORT4 lesions compared with ACL deficiency only ( P < .05) for anterior drawer at 60° of flexion and for pivot shift at 15° of flexion. The LMORT4 lesion demonstrated increased anterior translation for anterior drawer ( P = .003) at 60° of flexion (12%) as well as for pivot shift at 15° of flexion (7%) and 30° of flexion (13%) ( P < .005) compared with ACL deficiency only. Conclusion: In this cadaveric model, the addition of an LMORT3 or LMORT4 lesion increased anterior laxity for both the anterior drawer and the pivot shift when compared with an isolated ACL tear. Lateral meniscal extrusion was also exacerbated by these LMORT lesions. Clinical Relevance: LMORT lesions, distinct from meniscus root tears, occur frequently in conjunction with ACL tears. This study characterized the biomechanical consequences of LMORT3 and LMORT4 lesions on joint stability and meniscal function, highlighting the importance of diagnosing and treating LMORT lesions at the time of ACL reconstruction.

Are Outcomes of Acute Meniscus Root Tear Repair Better Than Debridement or Nonoperative Management? A Systematic Review

Background: Meniscus root tears (MRTs) are defined as radial tears within 1 cm of the meniscus root insertion or an avulsion of the meniscus root itself. They lead to altered joint loading because of the failure to convert axial (compressive) loads into hoop stresses. Untreated MRTs can result in altered joint biomechanics and accelerated articular cartilage degeneration and the development of osteoarthritis (OA), yet optimal management remains unclear. Purpose: To review treatment outcomes after acute MRTs by surgical repair, debridement, meniscectomy, or nonoperative treatment. Design: Systematic review; Level of evidence, 4. Methods: A systematic review of the evidence from human clinical studies was conducted with electronic searches of the PUBMED, Medline, EMBASE, and the Cochrane Library databases. One reviewer extracted the data and 2 reviewers assessed the risk of bias and performed synthesis of the evidence. Results: Eleven studies of low to moderate methodological quality were identified. All treatment options improved functional scores after >12 months. Arthroscopic repair may be associated with better functional outcomes when compared with partial meniscectomy and nonoperative management at 12-month follow-up. Radiographic progression of OA occurred in all treatment groups; there was some evidence that this was delayed after repair when compared with other treatments. Baseline severity of meniscal extrusion, varus malalignment, and pretreatment degeneration were predictors of poor functional outcomes. Age was not found to be an independent predictor of functional outcome. Conclusion: The current level 3 and 4 evidence suggests that arthroscopic repair may result in slower progression of radiological deterioration compared with meniscectomy and nonoperative management. The current literature does not support the exclusion of patients from MRT repair on the basis of age. Patients undergoing acute MRT treatments (repair, debridement, or nonoperative) can be expected to experience improvement in functional outcomes after >12 months. The strength of conclusions are limited because of the paucity of high-quality studies on this subject. Further studies, preferably randomized sham controlled trials with function-oriented rehabilitation programs, are needed to compare treatment strategies and stratification of care based on the risk of meniscal extrusion. Registration: CRD42018085092 (PROSPERO).

Heterotopic Ossification after Open Anchor Fixation of the Posterior Cruciate Ligament Avulsion in a Multiligament Injury of the Knee: A Case Report

Introduction: Heterotopic ossifications (HO) are a well-recognized but infrequently encountered condition. In the lower limb, the literature commonly reports the formation of HO around the hip after surgeries. However, HO is uncommon around the knee and a rare complication after open fixation of posterior cruciate ligament (PCL) avulsion fracture. Case Report:Here, we describe a case of HO in a 42-year-old patient with multiligament injury, including PCL and arcuate ligament avulsion, partial ACL tear, and medial meniscus root tear with suspected vascular compromise. He underwent open reduction and internal fixation of PCL avulsion fracture and medial meniscus root repair after the injury. At a 6-week follow-up, a plain radiograph revealed posterior capsule HO which kept increasing over successive follow-ups compromising his knee function. The patient was not willing for any mode of intervention for the same at any given time. Conclusion:HO after open PCL avulsion fixation is an uncommon entity. This article sheds light on how open fixation of PCL bony avulsion in a multiligament injured knee could result in a HO. Keywords: Posterior cruciate ligament avulsion, multiligament injury, open fixation, suture anchor, heterotopic ossification, posterior capsule.

Meniscal Root Repair in Pediatric Patients: Minimum 2-Year Outcomes (196)

Objectives: The medial and lateral menisci function to optimize force transmission across the knee by increasing contact area between the femur and tibia, absorbing shock, and transmitting loads. The anterior and posterior meniscus roots anchor the meniscus to bone. Injuries to the meniscus root attachments result in extrusion of the meniscus, impaired distribution of hoop stresses, and progressive degenerative articular wear. As a result of these deleterious effects, there has been increasing emphasis on repair of meniscus root injuries to restore structure and function. The purpose of this study is to describe meniscus root tears, associated injuries, and minimum 2-year treatment outcomes in a series of pediatric patients. Methods: A single-institution, IRB approved, retrospective review was performed of consecutive pediatric patients less than 19 years of age with a meniscus root tear treated with transosseous root repair over a 4-year period. All patients had minimum 24-month clinical follow-up. Partial root tears treated with partial meniscectomy or irreparable root tears were excluded. All meniscus root tears were classified arthroscopically based on the tear types described by LaPradeADDIN EN.CITE 9. The primary outcomes were revision meniscus surgery and patient reported outcome scores (PROs) (Lysholm, Patient Satisfaction, and Tegner activity). Results: Twenty-one patients, 11 males and 10 females with a mean age of 15 years (range 7 – 18 years), met inclusion criteria. There were 15 lateral meniscus root tears and 6 medial meniscus root tears. The tears occurred in the posterior root in 20 patients (95%). The most common injury pattern was a lateral meniscus posterior root tear (14 patients, 67%). 18 patients (86%) had an associated ligament tear: 13 ACL tears and 5 PCL tears. Two root tears occurred in isolation, and both were the posterior root of the medial meniscus. The majority of meniscus root tears (15 patients, 71%) were root avulsions (type 5). Mean follow-up was 42 months (range 25 – 71 months). Three patients had a second surgery on the affected knee. In two patients, one with revision ACL reconstruction and one treated with chondroplasty of the patella, the meniscus root repair was noted to be well healed. A third patient sustained a new injury to the knee 4 years following medial meniscus posterior root repair and underwent partial medial meniscectomy. At final follow-up, PROs were obtained for 17 patients (81%). Mean Lysholm score was 91 (range 51 – 100). Mean patient satisfaction score was 8.7 (range 5 – 10). Fourteen of 16 patients (88%) reported returning to the same or higher level of activity following surgery. Conclusions: Meniscus root tears occur in pediatric patients, most commonly as root avulsions of the posterior root of the lateral meniscus and in association with ACL tears. This is unique as compared to the adult population, in which the medial meniscus posterior root is often injured in isolation and radial tears adjacent the root are the most commonly described injury pattern. In our case series, transosseous root repair resulted in successful outcomes in the majority of patients with durable results at midterm follow-up.

The Natural History of Medial Meniscal Root Tears: A Biomechanical and Clinical Case Perspective

Posterior medial meniscus root tears (PMMRTs) make up a relatively notable proportion of all meniscus pathology and have been definitively linked to the progression of osteoarthritis (OA). While known risk factors for development of OA in the knee include abnormal tibial coronal alignment, obesity and female gender, PMMRTs have emerged in recent years as another significant driver of degenerative disease. These injuries lead to an increase in average contact pressure in the medial compartment, along with increases in peak contact pressure and a decrease in contact area relative to the intact state. Loss of the root attachment impairs the function of the entire meniscus and leads to meniscal extrusion, thus impairing the force-dissipating role of the meniscus. Anatomic meniscus root repairs with a transtibial pullout technique have been shown biomechanically to restore mean and peak contact pressures in the medial compartment. However, nonanatomic root repairs have been reported to be ineffective at restoring joint pressures back to normal. Meniscal extrusion is often a consequence of nonanatomic repair and is correlated with progression of OA. In this study, the authors will describe the biomechanical basis of the natural history of medial meniscal root tears and will support the biomechanical studies with a case series including patients that either underwent non-operative treatment (5 patients) or non-anatomic repair of their medial meniscal root tears (6 patients). Using measurements derived from axial MRI, the authors will detail the distance from native root attachment center of the non-anatomic tunnels and discuss the ongoing symptoms of those patients. Imaging and OA progression among patients who were treated nonoperatively before presentation to the authors will be discussed as well. The case series thus presented will illustrate the natural history of meniscal root tears, the consequences of non-anatomic repair, and the findings of symptomatic meniscal extrusion associated with a non-anatomic repair position of the meniscus.

Association Between Transtibial Meniscus Root Repair and Rate of Meniscal Healing and Extrusion on Postoperative Magnetic Resonance Imaging: A Prospective Multicenter Study

Background: Prospective studies evaluating second-look imaging of meniscus root repair using a transtibial pull-out technique are limited; therefore, optimal surgical indications and the technique for meniscus root repair remain uncertain. Hypothesis: It was hypothesized that there would be a high rate of healing, improvement in meniscal extrusion, and prevention of articular cartilage degeneration and subchondral bone abnormalities after meniscus root repair. Study Design: Case series; Level of evidence, 4. Methods: Consecutive patients undergoing transtibial root repair were prospectively enrolled at 2 orthopaedic centers between March 2017 and January 2019. Pre- and postoperative magnetic resonance imaging (MRI) scans were reviewed by a musculoskeletal radiologist in a blinded fashion for meniscal healing, quantification of extrusion, articular cartilage grade, subchondral bone changes, and coronary/meniscotibial ligament abnormalities. Given persistent extrusion observed on postoperative MRI scans, an additional 10 patients gave consent and were enrolled for immediate (before weightbearing) postoperative MRI scans. Results: A total of 45 patients (16 male, 29 female; mean ± standard deviation age, 42.3 ± 12.9 years; body mass index, 31.6) were prospectively enrolled in the study; there were 47 meniscus root repairs: 29 medial and 18 lateral (2 with both). Postoperative MRI was obtained at an average of 6.3 months (range, 5.1-8 months); 98% of meniscal repairs had evidence of healing. Mean extrusion increased significantly, from 1.9 ± 1.5 mm preoperatively to 2.6 ± 1.4 mm postoperatively ( P = .03). There was no significant progression of chondromalacia grade, subchondral edema, insufficiency fracture, subchondral cysts, or subchondral collapse. In the additional 10-patient cohort, the mean preoperative extrusion (1.6 ± 1.2 mm) was not significantly different from that immediately postoperatively (2.0 ± 1.0 mm; P = .23). Conclusion: Prospective MRI analysis of transtibial meniscus root repair confirmed a high rate of meniscal healing and no observable progression of cartilage degeneration or subchondral bone abnormalities at the short-term follow-up. However, meniscal extrusion worsened in the first 6 months after surgery. Registration: NCT03037242 ( ClinicalTrials.gov identifier).

Increased MRI Signal Intensity of Allografts in the Midterm Period After Meniscal Allograft Transplant: An Evaluation of Clinical Significance According to Location and Morphology

Background: Magnetic resonance imaging (MRI) is an effective tool for objective evaluation after meniscal allograft transplant (MAT). Little is known about the association between MRI features of allograft and clinical outcomes. Purpose/Hypothesis: To assess the degree and location of signal intensity (SI) as well as the morphology of allografts on MRI after MAT and evaluate the association between clinical outcomes and MRI features in the midterm period. It was hypothesized that a high SI accompanied by a deformed allograft in specific locations on MRI would be associated with inferior clinical outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: Included were patients who underwent MAT with fresh-frozen allografts and had >3 years of follow-up with 3.0-T MRI scans. Allograft status was assessed by SI on MRI as grade 0 (normal), grade 1 (globular increased SI not adjacent to the articular surface), grade 2 (linear SI within the meniscus), or grade 3 (increased SI extended to the articular surface). Allograft morphology was assessed by the presence of distorted contours. Clinical outcomes were evaluated using the Lysholm score. The association between clinical outcomes and MRI findings was assessed by multiple linear regression analysis. Results: A total of 138 patients (156 MAT procedures: 132 lateral, 24 medial) with a mean follow-up period of 55.4 ± 19.9 months (range, 36-110 months) were enrolled in this study. Grade 3 SI was observed in the posterior meniscus root and posterior third of the allograft in 39 (25%) and 62 (39.7%) MATs, respectively. Among the 62 MATs with grade 3 SI in the posterior third of the allograft, 34 (54.8%) were accompanied by distorted allograft contour. The presence of grade 3 SI with distorted contour in the posterior third of the allograft was significantly associated with inferior outcomes (β = –6.5 [95% CI, –12.5 to –0.5]; P < .035), as was the presence of grade 3 SI in the posterior meniscus root (β = –5.5 [95% CI, –10.5 to –0.4]; P < .034). Conclusion: On MRI evaluation in the midterm period after MAT, grade 3 SIs of the meniscal allograft were observed in about a third of the cases, and the association with clinical outcomes was dependent on the specific location and morphology of the allograft on MRI.