Importance of the medial meniscus in the anterior cruciate ligament-deficient knee

Dynamically tensioned ACL functional knee braces reduce ACL and meniscal strain

PURPOSE

The effectiveness of ACL functional knee braces to reduce meniscal and ACL strain after ACL injury or reconstruction is not well understood. A new dynamic knee tensioning brace system has been designed to apply an active stabilizing force to the knee. The ability of this system to reduce tissue strains is unknown. The purpose of this study was to test the ability of the dynamically tensioned brace to reduce strain in both the ACL and meniscus during rehabilitation activities.

METHODS

A combined in vivo/in silico/in vitro method was used to study three activities: gait, double leg squat, and single leg squat. Muscle forces and kinematics for each activity were derived through in vivo motion capture and applied to seven cadaveric knee specimens fitted with custom braces. Medial meniscal strain and ACL strain were measured in ACL intact, deficient and reconstructed conditions.

RESULTS

The brace lowered peak and average meniscal strain in ACL deficient knees (P < 0.05) by an average of 1.7%. The brace was also found to lower meniscal strain in reconstructed knees (1.1%) and lower ACL strain in ACL intact (1.3%) and reconstructed knees (1.4%) (P < 0.05).

CONCLUSIONS

This study supports the use of a brace equipped with a dynamic tensioning system to lower meniscal strain in ACL-deficient knees. Its use may help decrease the risk of subsequent meniscal tears in chronic ACL deficiency or delayed reconstruction. In ACL-intact and reconstructed knees, the brace may be beneficial in injury prophylaxis or in protecting the ACL graft following reconstruction. These results will aid clinicians make informed recommendations for functional brace use in patients with unstable knees.

LEVEL OF EVIDENCE

II.

Improvement in the medial meniscus posterior shift following anterior cruciate ligament reconstruction

PURPOSE

Anterior cruciate ligament (ACL) reconstruction can reduce the risk of developing osteoarthritic knees. The goals of ACL reconstruction are to restore knee stability and reduce post-traumatic meniscal tears and cartilage degradation. A chronic ACL insufficiency frequently results in medial meniscus (MM) injury at the posterior segment. How ACL reconstruction can reduce the deformation of the MM posterior segment remains unclear. In this study, we evaluated the form of the MM posterior segment and anterior tibial translation before and after ACL reconstruction using open magnetic resonance imaging (MRI).

METHODS

Seventeen patients who underwent ACL reconstructions without MM injuries were included in this study. MM deformation was evaluated using open MRI before surgery and 3 months after surgery. We measured medial meniscal length (MML), medial meniscal height (MMH), medial meniscal posterior body width (MPBW), MM-femoral condyle contact width (M-FCW) and posterior tibiofemoral distance (PTFD) at knee flexion angles of 10° and 90°.

RESULTS

There were no significant pre- and postoperative differences during a flexion angle of 10°. At a flexion angle of 90°, MML decreased from 43.7 ± 4.5 to 41.4 ± 4.5 mm (P < 0.001), MMH from 7.5 ± 1.4 to 6.9 ± 1.4 mm (P = 0.006), MPBW from 13.1 ± 2.0 to 12.2 ± 1.9 mm (P < 0.001) and M-FCW from 10.0 ± 1.5 to 8.5 ± 1.5 mm (P < 0.001) after ACL reconstruction. The PTFD increased from 2.1 ± 2.8 to 2.7 ± 2.4 mm after ACL reconstruction (P = 0.015).

CONCLUSIONS

ACL reconstruction affects the contact pattern between the MM posterior segment and medial femoral condyle and can reduce the deformation of the MM posterior segment in the knee-flexed position by reducing abnormal anterior tibial translation. It possibly prevents secondary injury to the MM posterior segment and cartilage that progresses to knee osteoarthritis.

LEVEL OF EVIDENCE

IV.

The Anterolateral Ligament is Not the Whole Story: Reconsidering the Form and Function of the Anterolateral Knee and its Contribution to Rotatory Knee Instability

The heterogeneity of available cadaveric, histologic, and radiographic results related to the anterolateral ligament (ALL) does not support its existence as a discrete anatomic structure. Moreover, focusing narrowly on the ALL in isolation, what has previously been referred to as “ALL myopia,” obscures a thorough appreciation for the stability contributions of both capsular and extracapsular structures. We consider injury to the soft tissues of the anterolateral knee–the anterolateral complex—just one component of what is frequently found to be a spectrum of pathology observed in the rotationally unstable, anterior cruciate ligament (ACL)-deficient knee. Increased lateral tibial slope, meniscal root tears, and “ramp” lesions of the medial meniscocapsular junction have all been implicated in persistent rotatory knee instability, and the restoration of rotational stability requires a stepwise approach to the assessment of each of these entities. Through an appreciation for the multifactorial nature of rotatory knee instability, surgeons will be better equipped to perform durable ACL reconstructions that maximize the likelihood of optimal clinical outcomes for patients. The purposes of this review are to provide an update on the relevant anatomy of the anterolateral knee soft tissues and to explain the multifactorial nature of rotatory knee instability in the setting of ACL deficiency.

In Vivo Tibial Cartilage Strains in Regions of Cartilage-to-Cartilage Contact and Cartilage-to-Meniscus Contact in Response to Walking

BACKGROUND

There are currently limited human in vivo data characterizing the role of the meniscus in load distribution within the tibiofemoral joint. Purpose/Hypothesis: The purpose was to compare the strains experienced in regions of articular cartilage covered by the meniscus to regions of cartilage not covered by the meniscus. It was hypothesized that in response to walking, tibial cartilage covered by the meniscus would experience lower strains than uncovered tibial cartilage.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Magnetic resonance imaging (MRI) of the knees of 8 healthy volunteers was performed before and after walking on a treadmill. Using MRI-generated 3-dimensional models of the tibia, cartilage, and menisci, cartilage thickness was measured in 4 different regions based on meniscal coverage and compartment: covered medial, uncovered medial, covered lateral, and uncovered lateral. Strain was defined as the normalized change in cartilage thickness before and after activity.

RESULTS

Within each compartment, covered cartilage before activity was significantly thinner than uncovered cartilage before activity ( P < .001). After 20 minutes of walking, all 4 regions experienced significant cartilage thickness decreases ( P < .01). The covered medial region experienced significantly less strain than the uncovered medial region ( P = .04). No difference in strain was detected between the covered and uncovered regions in the lateral compartment ( P = .40).

CONCLUSION

In response to walking, cartilage that is covered by the meniscus experiences lower strains than uncovered cartilage in the medial compartment. These findings provide important baseline information on the relationship between in vivo tibial compressive strain responses and meniscal coverage, which is critical to understanding normal meniscal function.

Factors That Predict Failure in Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction

BACKGROUND

Anatomic graft placement in anterior cruciate ligament (ACL) reconstruction has become the preferred technique for many surgeons. The predictive factors for graft failure in anatomic single-bundle ACL reconstruction are relatively unknown.

PURPOSE

To determine the risk factors for graft failure and the relative importance of those factors in anatomic single-bundle ACL reconstruction.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

All primary anatomic ACL reconstructions undertaken at a single institution over a 2-year period were evaluated for subjective and objective measures of graft failure. Risk factors evaluated included time since ACL rupture, age, sex, body mass index, intact or deficient medial and lateral meniscus, meniscal repair, hamstring graft size, and femoral and tibial tunnel position as assessed by 3D computed tomography (CT) scan. The significant factors predicting failure and the relative importance of those factors were determined.

RESULTS

At a median follow-up of 26 months, 123 patients were available for analysis. Ninety-seven patients underwent postoperative 3D CT for tunnel positions, including all 20 cases with graft failure. The significant predictors of graft failure were medial meniscal deficiency (hazard ratio [HR] 15.1; 95% CI, 4.7-48.5; P < .001), lateral meniscal deficiency (HR 9.9; 95% CI, 3-33; P < .001), shallow nonanatomic femoral tunnel positioning (HR 4.3; 95% CI, 1.6-11.6; P = .004), and younger patient age (HR 0.9; 95% CI, 0.9-1; P = .008).

CONCLUSION

Meniscal deficiency is the most significant factor to predict graft failure in single-bundle anatomic ACL reconstruction. Shallow nonanatomic femoral tunnel positioning and younger patient age are additional risk factors for failure, but their relative importance is less.

Meniscal Allograft Transplantation With Soft Tissue in Bone Socket Fixation: Arthroscopic Technique With Technical Pearls

Meniscal allograft transplantation may slow the progression of degenerative changes in the meniscus-deficient knee. The current literature suggests patients can experience good early to mid-term satisfaction and patient-reported outcomes with reasonable expectations of return to work. More ambitious applications in athletes have also shown good results although long-term data are lacking. Traditionally, meniscal allograft transplantation has been considered an open procedure with incorporation of bone blocks from the allograft source. However, as arthroscopic techniques have advanced, it has become possible to perform this procedure through a predominantly arthroscopic approach while securing the soft tissue graft in bone tunnels. The current demonstration provides this background and technical pearls for success in arthroscopic meniscal allograft transplantation.

Combined measurement and modeling of specimen-specific knee mechanics for healthy and ACL-deficient conditions

Quantifying the mechanical environment at the knee is crucial for developing successful rehabilitation and surgical protocols. Computational models have been developed to complement in vitro studies, but are typically created to represent healthy conditions, and may not be useful in modeling pathology and repair. Thus, the objective of this study was to create finite element (FE) models of the natural knee, including specimen-specific tibiofemoral (TF) and patellofemoral (PF) soft tissue structures, and to evaluate joint mechanics in intact and ACL-deficient conditions. Simulated gait in a whole joint knee simulator was performed on two cadaveric specimens in an intact state and subsequently repeated following ACL resection. Simulated gait was performed using motor-actuated quadriceps, and loads at the hip and ankle. Specimen-specific FE models of these experiments were developed in both intact and ACL-deficient states. Model simulations compared kinematics and loading of the experimental TF and PF joints, with average RMS differences [max] of 3.0° [8.2°] and 2.1° [8.4°] in rotations, and 1.7 [3.0] and 2.5 [5.1] mm in translations, for intact and ACL-deficient states, respectively. The timing of peak quadriceps force during stance and swing phase of gait was accurately replicated within 2° of knee flexion and with an average error of 16.7% across specimens and pathology. Ligament recruitment patterns were unique in each specimen; recruitment variability was likely influenced by variations in ligament attachment locations. ACL resections demonstrated contrasting joint mechanics in the two specimens with altered knee motion shown in one specimen (up to 5mm anterior tibial translation) while increased TF joint loading was shown in the other (up to 400N).

Does the Chronicity of Anterior Cruciate Ligament Ruptures Influence Patient-Reported Outcomes Before Surgery?

BACKGROUND

The time between an anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) may influence baseline knee-related and general health-related patient-reported outcome measures (PROMs). Despite the common use of PROMs as main outcomes in clinical studies, this variable has never been evaluated.

PURPOSE

To compare baseline health-related quality of life measures and the prevalence/pattern of meniscal and articular cartilage lesions between patients who underwent acute and chronic ACLR so as to provide clinicians with benchmark PROMs in 2 different patient populations with ACL injuries.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 1192 patients from the MOON (Multicenter Orthopaedic Outcomes Network) cohort who underwent primary ACLR were eligible. "Acute" ACLR was defined as <3 months (n = 853; 71.6%) and "chronic" ACLR as >6 months (n = 339; 28.4%) from injury. Patient demographics, surgical characteristics (articular cartilage injury, medial meniscal [MM] and lateral meniscal [LM] tears), and baseline PROM scores (Marx activity rating scale, International Knee Documentation Committee [IKDC] subjective form, Knee injury and Osteoarthritis Outcome Score [KOOS], and Short Form-36 Health Survey [SF-36]) were collected to determine whether the time from injury to ACLR influences (1) baseline PROMs and (2) the pattern and prevalence of concurrent articular cartilage and meniscal injuries. Analysis of covariance models were used to adjust for confounders on baseline outcome scores (age, sex, body mass index [BMI], smoking status, competition level, education).

RESULTS

The median patient age was 23 years (interquartile range [IQR], 17-35 years), 530 (44.5%) were female, and the median BMI was 25.0 kg/m² (IQR, 22.3-27.9 kg/m²); however, the chronic group was older, had a higher BMI, and consisted of fewer collegiate athletes. A significantly greater number of partial LM tears were seen in the acute group versus the chronic group (14.2% vs 6.5%, respectively; P < .001), but there were more meniscal tears overall (73.5% vs 63.2%, respectively; P = .001), complete MM tears (49.0% vs 22.5%, respectively; P < .001), and articular cartilage injuries (54.0% vs 32.8%, respectively; P < .001) in the chronic group versus the acute group. After controlling for confounders, patients in the chronic ACLR group reported a significantly lower baseline Marx score (7.75 vs 12.10, respectively; P < .001) but higher baseline IKDC, SF-36 physical functioning, and all KOOS subscale scores except the KOOS-quality of life subscale score compared to those in the acute ACLR group; however, only the KOOS-sports and recreation subscale exceeded the minimum clinically importance difference of 8 points (62.30 vs 48.26, respectively; P < .001).

CONCLUSION

After controlling for age, sex, competition level, smoking, and BMI, patients in the chronic ACLR group participated in less pivoting and cutting sports but reported better pain/function. Whether decreased activity is deliberate after an ACL injury or patients who undergo chronic ACLR are simply less active and may be treated successfully without surgery warrants further investigation. Nonrandomized studies that utilize PROMs should consider time from injury in study design and data interpretation.

Prospective Clinical and Radiographic Outcomes After Concomitant Anterior Cruciate Ligament Reconstruction and Meniscal Allograft Transplantation at a Mean 5-Year Follow-up

BACKGROUND

Concomitant anterior cruciate ligament reconstruction and meniscal allograft transplantation (ACLR/MAT) has demonstrated short-term success in small, retrospective cohort studies. Patient- and disease-specific predictors of success after ACLR/MAT are largely unknown.

PURPOSE

To (1) prospectively evaluate the subjective and objective clinical and radiographic outcomes after ACLR/MAT and (2) conduct a subgroup analysis to identify patient- or disease-related factors that correlate with failure.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patient-reported outcomes (PROs) were prospectively collected on 40 patients undergoing concomitant ACLR/MAT. Nineteen athletes responded to return-to-sport data. Clinical data (physical examination including Lachman and pivot-shift testing and KT-1000 arthrometer testing) were obtained on 28 patients who returned for an evaluation, while 24 of those patients additionally had radiographic data (progression of Kellgren-Lawrence [KL] grade and joint-space narrowing) evaluated. Reoperations and failures were documented for all patients at their final follow-up.

RESULTS

The overall cohort of 40 patients had a mean age of 30.3 ± 9.6 years (range, 16.0-54.0 years) and a mean body mass index of 27.7 ± 4.2 kg/m². The mean follow-up time was 5.7 ± 3.2 years (range, 1.7-16.5 years). There were 33 (83%) medial meniscal transplants performed compared with 7 (17%) lateral meniscal transplants. Patients underwent a mean of 2.9 ± 1.9 prior surgical procedures. Nineteen patients underwent concomitant procedures, including, most commonly, 9 hardware removals and 9 osteochondral allografts. There were significant improvements in 11 of 14 PRO measures as well as a 50% return-to-sport rate. Knee stability significantly improved in 28 patients who returned for a physical examination, and KT-1000 arthrometer testing indicated no differences between the affected and unaffected sides at final follow-up (mean, 0.9 ± 1.5 mm [range, -2 to 4 mm] in comparison to contralateral knee at 30 lb of testing; mean, 0.9 ± 1.9 mm [range, -4 to 4 mm] in comparison to contralateral knee at maximum manual strength). Significant improvements were seen in patients with Lachman grade ≥2A at final follow-up (18% vs 97%, respectively; P < .01) and with pivot shift ≥1+ at final follow-up (36% vs 94%, respectively; P < .01) compared with preoperatively. For the 24 patients with radiographic data, no significant joint-space decrease was recorded in the medial compartment for medial MAT-treated patients or the lateral compartment for lateral MAT-treated patients. The mean KL grade increased from 0.7 ± 0.8 to 1.6 ± 0.9 at final follow-up ( P < .01). There were no major (0%) and 2 minor (5%) complications, which constituted early postoperative drainage treated successfully with oral antibiotics. While 35% of patients underwent reoperations, the majority of these were simple arthroscopic debridements and occurred after nearly 4 years from the index surgery. The overall survival rate at final follow-up was 80%. Failures occurred at a mean of 7.3 years, and those who converted to arthroplasty did so at a mean of 8.3 years from the time of index ACLR/MAT. Patients with failed grafts were more frequently associated with workers' compensation claims (38% vs 13%, respectively) and less frequently self-identified as athletes (13% vs 56%, respectively) compared with patients with intact grafts.

CONCLUSION

Concomitant ACLR/MAT can provide significant improvements in clinical outcomes and enhancement in objective knee stability and was associated with an insignificant degree of radiographic joint-space narrowing changes with a 5-year survivorship of more than 80% for those with data available. Athlete status may be a preoperative predictor of midterm survival.

Effect of radial meniscal tear on in situ forces of meniscus and tibiofemoral relationship

PURPOSE

To clarify the effect of the radial tear of the lateral meniscus on the in situ meniscus force and the tibiofemoral relationship under axial loads and valgus torques.

METHODS

Ten intact porcine knees were settled to a 6-degree of freedom robotic system, while the force and 3-dimensional path of the knees were recorded via Universal Force Sensor (UFS) during 3 cycles of 250-N axial load and 5-Nm valgus torque at 15°, 30°, 45°, and 60° of knee flexion. The same examination was performed on the following 3 meniscal states sequentially; 33, 66, and 100% width of radial tears at the middle segment of the lateral meniscus, while recording the force and path of the knees via UFS. Finally, all paths were reproduced after total lateral meniscectomy and the in situ force of the lateral meniscus were calculated with the principle of superposition.

RESULTS

The radial tear of 100% width significantly decreased the in situ force of the lateral meniscus and caused tibial medial shift and valgus rotation at 30°-60° of knee flexion in both testing protocols. Under a 250-N axial load at 60° of knee flexion, the in situ force decreased to 36 ± 29 N with 100% width of radial tear, which was 122 ± 38 N in the intact state. Additionally, the tibia shifted medially by 2.1 ± 0.9 mm and valgusrotated by 2.5 ± 1.9° with the complete radial tear. However, the radial tear of 33 or 66% width had little effect on either the in situ force or the tibial position.

CONCLUSION

A radial tear of 100% width involving the rim significantly decreased the in situ force of the lateral meniscus and caused medial shift and valgus rotation of the tibia, whereas a radial tear of up to 66% width produced only little change. The clinical relevance is that loss of meniscal functions due to complete radial tear can lead to abnormal stress concentration in a focal area of cartilage and can increase the risk of osteoarthritis in the future.

Factors associated with the status of meniscal tears following meniscal repair concomitant with anterior cruciate ligament reconstruction

PURPOSE

Anterior cruciate ligament (ACL) injuries are often accompanied by meniscal tears. Meniscal repair is typically performed during ACL reconstruction. However, retear of the meniscus after repair is frequent. The purpose of this study was to analyze the factors associated with meniscal healing after meniscal repair concomitant with ACL reconstruction.

MATERIALS AND METHODS

Eighty-seven meniscal repairs in 87 patients who received meniscal repair combined with ACL reconstruction and received second-look arthroscopy at a mean of postoperatively 15.7 months were examined retrospectively. The menisci were divided into three groups (complete heal, incomplete heal, and retear), and factors thought to affect the healing status of repaired menisci were analyzed using multivariate logistic regression analysis.

RESULTS

Meniscal healing was judged to be complete in 49 knees (56%), incomplete in 19 knees, (22%), and retear in 19 knees (22%). There were no significant differences among the three groups in age, sex, time from injury to operation, mean Tegner activity scale, tear location, or mean postoperative anteroposterior tibial translation on KT-1000. The mean length of the tear was significantly higher in the retear group. Additionally, the proportion patients with complete tear and the proportion with postoperative positive pivot shift test were significantly higher in the retear group than in the other groups. Multivariate logistic regression analysis showed that complete tear and positive pivot shift test were associated with retear.

CONCLUSIONS

These findings suggest that complete tears and residual instability are associated with retears after meniscal repair concomitant with ACL reconstruction.

Matrix metalloproteinase activity and prostaglandin E2 are elevated in the synovial fluid of meniscus tear patients

PURPOSE

Meniscus tears are a common knee injury and are associated with the development of post-traumatic osteoarthritis (OA). The purpose of this study is to evaluate potential OA mediators in the synovial fluid and serum of meniscus tear subjects compared to those in the synovial fluid of radiographic non-OA control knees.

MATERIALS AND METHODS

Sixteen subjects with an isolated unilateral meniscus injury and six subjects who served as reference controls (knee Kellgren-Lawrence grade 0-1) were recruited. Twenty-one biomarkers were measured in serum from meniscus tear subjects and in synovial fluid from both groups. Meniscus tear subjects were further stratified by tear type to assess differences in biomarker levels.

RESULTS

Synovial fluid total matrix metalloproteinase (MMP) activity and prostaglandin E2 (PGE2) were increased 25-fold and 290-fold, respectively, in meniscus tear subjects as compared to reference controls (p < 0.05). Synovial fluid MMP activity and PGE2 concentrations were positively correlated in meniscus tear subjects (R = 0.83, p < 0.0001). In meniscus tear subjects, synovial fluid levels of MMP activity, MMP-2, MMP-3, sGAG, COMP, IL-6, and PGE2 were higher than serum levels (p < 0.05). Subjects with complex meniscus tears had higher synovial fluid MMP-10 (p < 0.05) and reduced serum TNFα and IL-8 (p < 0.05) compared to other tear types.

CONCLUSIONS

Given the degradative and pro-inflammatory roles of MMP activity and PGE2, these molecules may alter the biochemical environment of the joint. Our findings suggest that modulation of PGE2 signaling, MMP activity, or both following a meniscus injury may be targets to promote meniscus repair and prevent OA development.

Clinical and radiographic outcomes of meniscus surgery and future targets for biologic intervention: A review of data from the MOON Group

Meniscus injury and treatment occurred with the majority of anterior cruciate ligament reconstructions (ACLR) in the multicenter orthopedic outcomes (MOON) cohort. We describe the patient-reported outcomes, radiographic outcomes, and predictors of pain from meniscus injuries and treatment in the setting of ACLR. Patient-reported outcomes improve significantly following meniscus repair with ACLR, but differences exist based on the meniscus injury laterally (medial or lateral). Patients undergoing medial meniscus repair have worse patient-reported outcomes and more pain compared to those with uninjured menisci. However, lateral meniscal tears can be repaired with similar outcomes as uninjured menisci. Medial meniscal treatment (meniscectomy or repair) results in a significant loss of joint space at 2 years compared to uninjured menisci. Menisci treated with excision had a greater degree of joint space loss compared to those treated with repair. Clinically significant knee pain is more common following injuries to the medial meniscus and increased in patients who undergo early re-operation after initial ACLR. Future research efforts aimed at improving outcomes after combined ACLR and meniscus treatment should focus on optimizing biologic and mechanical environments that promote healing of medial meniscal tears sustained during ACL injury.

Anterior Cruciate Ligament Injuries Alter the Kinematics of Knees With or Without Meniscal Deficiency

BACKGROUND

Numerous studies have investigated kinematic alterations in patients with an isolated anterior cruciate ligament (ACL) injury. However, a substantial proportion of patients with injured ACLs also have concomitant meniscal tears.

PURPOSE

To evaluate the in vivo alteration of knee kinematics after an ACL tear, with or without a combined medial or lateral meniscal tear, during level walking activity.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifty-six patients with unilateral ACL-deficient (ACLD) knees were studied. Among these patients, 15 had isolated ACL injuries (group 1), 15 had combined ACL and medial meniscal injuries (group 2), 15 had combined ACL and lateral meniscal injuries (group 3), and 11 had combined ACL and medial/lateral meniscal injuries (group 4). The kinematics of each knee was determined using an optical tracking system during treadmill gait. Range of motion (ROM) and kinematic alterations were compared between the contralateral ACL-intact (ACLI) and ACLD knees.

RESULTS

All ACLD knees, with or without meniscal deficiency, had significantly less flexion than the ACLI knees (~3°-8°; P < .05). In groups 1, 3, and 4, the injured knees exhibited more femoral external rotation by approximately 1° to 2° (P < .05). Group 4 showed posterior femoral translation (anterior tibial translation) in the swing phase (~13 mm), while groups 2 and 3 showed increased anterior femoral translation (~2-3 mm). During medial-lateral translation, patients in group 2 had a more medial femoral shift (~4 mm) relative to the tibia initially, while those in group 4 exhibited a lateral femoral shift.

CONCLUSION

The results indicate that meniscal injuries alter the kinematics of the ACLD knee when compared with knees with an isolated ACL injury. The location of the meniscal tear also affects knee kinematics.

CLINICAL RELEVANCE

Considering the varying effects of meniscal injuries on knee joint kinematics, these data provide insight into the pathological function of the ACL-injured knee joint during walking.

Complications in posteromedial arthroscopic suture of the medial meniscus

INTRODUCTION

All-inside posteromedial suture for lesions of the posterior horn of the medial meniscus in anterior cruciate ligament (ACL) repair provides effective freshening and good healing.

HYPOTHESIS

The posteromedial portal provides satisfactory healing rates without increasing morbidity or complications rates.

MATERIAL AND METHODS

Intra- and postoperative complications were collected for a consecutive single-center series of 132 patients undergoing posteromedial hook suture of the medial meniscus in ACL repair. Meniscal healing was assessed as the rate of recurrence of symptomatic medial meniscus lesions (Barret criteria) and on revision surgery, if any, in terms of the aspect and extent of the iterative lesion. The severity of any sensory disorder was assessed by questionnaire.

RESULTS

The intraoperative complications rate was 1.5% (2 saphenous vein punctures). At a mean 31months (range, 28-35months), there was no loss to follow-up. Twelve patients (9%) showed symptomatic recurrence of the medial meniscus lesion, requiring 10 repeat surgeries. In 6 cases (4.5%), the iterative lesion involved a smaller, more central part of the meniscus anterior to the sutures, of "postage-stamp" effect, possibly implicating the suture hook and/or non-absorbable sutures. There were no cases of infection or fistula. Postoperative hematoma occurred in 7% of patients. In total, 1.8% reported dysesthesia areas equal to or greater than the size of a credit card (45cm²).

DISCUSSION

Some retears, or "partial failures", may implicate a new lesion caused by the suture hook and possibly prolonged by non-resorbable sutures. Hematoma and sensory disorder rates were comparable to those reported in isolated ACL repair without posteromedial portal.

CONCLUSION

The present results show that posteromedial arthroscopic hook suture in posterior medial meniscus tear provides good healing rates without increased morbidity due to the supplementary portal.

LEVEL OF EVIDENCE

IV.

Magnesium ring device to restore function of a transected anterior cruciate ligament in the goat stifle joint

A bioresorbable, mono-crystalline magnesium (Mg) ring device and suture implantation technique were designed to connect the ends of a transected anterior cruciate ligament (ACL) to restabilize the knee and load the ACL to prevent disuse atrophy of its insertion sites and facilitate its healing. To test its application, cadaveric goat stifle joints were evaluated using a robotic/universal force-moment sensor testing system in three states: Intact, ACL-deficient, and after Mg ring repair, at 30°, 60°, and 90° of joint flexion. Under a 67-N anterior tibial load simulating that used in clinical examinations, the corresponding anterior tibial translation (ATT) and in-situ forces in the ACL and medial meniscus for 0 and 100 N of axial compression were obtained and compared with a control group treated with suture repair. In all cases, Mg ring repair reduced the ATT by over 50% compared to the ACL-deficient joint, and in-situ forces in the ACL and medial meniscus were restored to near normal levels, showing significant improvement over suture repair. These findings suggest that Mg ring repair could successfully stabilize the joint and load the ACL immediately after surgery, laying the framework for future in vivo studies to assess its utility for ACL healing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2001-2008, 2016.

Does meniscus removal affect ACL-deficient knee laxity? An in vivo study

PURPOSE

The purpose of the present study was to determine, in vivo, the effect of different types of meniscectomy on an ACL-deficient knee.

METHODS

Using a computer-assisted navigation system, 56 consecutive patients (45 men and 11 women) were subjected to a biomechanical testing with Lachman test (AP30), drawer test (AP90), internal/external rotation test, varus/valgus rotation test and pivot-shift test. The patients were divided into three groups according to the status of the medial meniscus. Group BH, 8 patients with bucket-handle tear of medial meniscus underwent a subtotal meniscectomy; Group PHB, 19 patients with posterior horn body of medial meniscus tear underwent a partial meniscectomy; and Group CG with isolated ACL rupture, as a control group, with 29 patients.

RESULTS

A significant difference in anterior tibial translation was seen at 30 grades and in 90 grades between BH and PHB groups compared to the CG. In response to pivot-shift test, no significant differences in terms of AREA and POSTERIOR ACC were found among the three groups (n.s). Concerning the anterior displacement of the pivot shift a statistically significant differences among the three tested groups was found.

CONCLUSION

The present study shows that meniscal defects significantly affect the kinematics of an ACL-deficient knee in terms of anterior tibial translation under static and dynamic testing.

Association Between Meniscal and Chondral Lesions and Timing of Anterior Cruciate Ligament Reconstruction

Background:

Rupture of the anterior cruciate ligament (ACL) is a common sports injury and is known to be associated with an increased risk of knee osteoarthritis. Several studies have indicated that the risk of additional injuries to the menisci and articular cartilage increases with delays in the treatment of ACL tears. However, no consensus has been reached regarding the ideal timing for ACL reconstruction in terms of preventing secondary lesions.

Purpose:

To determine how the time elapsed between an ACL lesion and its reconstruction affects the incidence of meniscal and chondral lesions.

Study Design:

Case series; Level of evidence, 4.

Methods:

Medical records of 764 patients who underwent primary ACL reconstruction were reviewed. Data from arthroscopic findings that included information about meniscal lesions and full-thickness articular cartilage lesions at the time of surgery were collected. The association between time elapsed between ACL lesion and reconstruction surgery and incidence of articular cartilage and meniscal lesions was analyzed by chi-square or Fisher exact test. The risk of secondary lesion was calculated by odds ratios (ORs) obtained from simple logistic regression analysis.

Results:

A positive correlation was observed between time after injury and the presence of any articular lesions (P = .003), cartilage lesions (P = .01), and medial meniscus lesions (P < .001). When analyzing the risk of secondary lesion relative to the reference period (<2 months), it was observed that the odds of finding any articular injury at the time of ACL reconstruction increased when the time from ACL injury to surgery was between 12 and 24 months (OR = 2.62) and >24 months (OR = 5.88). Furthermore, the odds of lesions on the medial meniscus increased when the timing between injury and surgery was 6 to 12 months (OR = 2.71) and continued to increase when the timing was 12 to 24 months (OR = 3.78) and >24 months (OR = 9.07).

Conclusion:

Associated articular lesions are more common if ACL reconstruction is delayed by ≥6 months (medial meniscus lesion) and ≥1 year (chondral or any meniscal lesion).

ACL Deficiency Increases Forces on the Medial Femoral Condyle and the Lateral Meniscus with Applied Rotatory Loads

BACKGROUND

The articular surfaces and menisci act with the anterior cruciate ligament (ACL) to stabilize the knee joint. Their role in resisting applied rotatory loads characteristic of instability events is unclear despite commonly observed damage to these intra-articular structures in the acute and chronic ACL injury settings.

METHODS

Ten fresh-frozen human cadaveric knees were mounted to a robotic manipulator. Combined valgus and internal rotation torques were applied in the presence and absence of a 300-N compressive load. Forces carried by the individual menisci and via cartilage-to-cartilage contact on each femoral condyle in ACL-intact and ACL-sectioned states were measured using the principle of superposition.

RESULTS

In response to applied valgus and internal rotation torques in the absence of compression, sectioning of the ACL increased the net force carried by the lateral meniscus by at most 65.8 N (p < 0.001). Moreover, the anterior shear force carried by the lateral meniscus increased by 25.7 N (p < 0.001) and 36.5 N (p = 0.042) in the absence and presence of compression, respectively. In response to applied valgus and internal rotation torques, sectioning of the ACL increased the net force carried by cartilage-to-cartilage contact on the medial femoral condyle by at most 38.9 N (p = 0.006) and 46.7 N (p = 0.040) in the absence and presence of compression, respectively. Additionally, the lateral shear force carried by cartilage-to-cartilage contact on the medial femoral condyle increased by at most 21.0 N (p = 0.005) and by 28.0 N (p = 0.025) in the absence and presence of compression, respectively. Forces carried by the medial meniscus and by cartilage-to-cartilage contact on the lateral femoral condyle changed by <5 N as a result of ACL sectioning.

CONCLUSIONS

ACL sectioning increased the net forces carried by the lateral meniscus and medial femoral condyle-and the anterior shear and lateral shear forces, respectively-in response to multiplanar valgus and internal rotation torque.

CLINICAL RELEVANCE

These loading patterns provide a biomechanical rationale for clinical patterns of intra-articular derangement such as lateral meniscal injury and osseous remodeling of the medial compartment seen with ACL insufficiency.

Kinematic outcomes following ACL reconstruction

Anterior cruciate ligament (ACL) reconstruction aims to restore the translational and rotational motion to the knee joint that is lost after injury. However, despite technical advancements, clinical outcomes are less than ideal, particularly in return to previous activity level. A major issue is the inability to standardize treatment protocols due to variations in materials and approaches used to accomplish ACL reconstruction. These include surgical techniques such as the transtibial and anteromedial portal methods that are currently under use and the wide availability of graft types that will be used to reconstruct the ACL. In addition, concomitant soft tissue injuries to the menisci and capsule are frequently present after ACL injury and, if left unaddressed, can lead to persistent instability even after the ACL has been reconstructed. Advances in the field of biomechanics that help to objectively measure motion of the knee joint may provide more precise data than current subjective clinical measurements. These technologies include extra-articular motion capture systems that measure the movement of the tibia in relation to the femur. With data gathered from these devices, a threshold for satisfactory knee stability may be established in order to correctly identify a successful reconstruction following ACL injury.

Accuracy of MRI evaluation of meniscus tears in the setting of ACL injuries

BACKGROUND

Our purpose was to evaluate the diagnostic performance of magnetic resonance imaging (MRI) for the pre-operative detection of meniscus tears requiring operative intervention, and identify factors that determined accuracy of diagnosing meniscus tears, in the setting of anterior cruciate ligament (ACL) reconstruction.

METHODS

Patients who underwent primary ACL reconstruction were retrospectively reviewed. A meniscus tear was classified as requiring treatment if it was debrided or repaired at the time of ACL reconstruction. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of pre-operative MRIs were determined for medial and lateral meniscus tears.

RESULTS

Sensitivity, specificity, PPV, and NPV of MRI were 0.90, 0.75, 0.58, and 0.95 for medial meniscus tears, respectively, and 0.67, 0.81, 0.65, and 0.82 for lateral meniscus tears. MRI-diagnosed medial meniscus tears were associated with a longer time interval between initial injury and imaging compared to ACL tears without concomitant meniscus injury on MRI (p=0.038). Vertical medial meniscus tears were less likely than other tear patterns to require treatment at the time of ACL reconstruction (p=0.03). MRI showed a higher diagnostic performance for lateral meniscus tears when surgery was performed within 30days of imaging.

CONCLUSIONS

This study demonstrates only moderate sensitivity and specificity of pre-operative MRI in the detection of meniscus tears requiring operative treatment in the setting of ACL injury. High rates of false diagnoses were observed, suggesting MRI may not be as accurate in predicting positive or negative meniscus findings at the time of ACL reconstruction as previously reported.

LEVEL OF EVIDENCE

Level III.

The role of meniscal tissue in joint protection in early osteoarthritis

It is widely accepted that partial meniscectomy leads to early onset of osteoarthritis (OA). A strong correlation exists between the amount and location of the resected meniscus and the development of degenerative changes in the knee. On the other hand, osteoarthritic changes of the joint alter the structural and functional integrity of meniscal tissue. These alterations might additionally compromise the limited healing capacity of the meniscus. In young, active patients without cartilage damage, meniscus therapy including partial meniscectomy, meniscus suture, and meniscus replacement has proven beneficial effects in long-term studies. Even in an early osteoarthritic milieu, there is a relevant regenerative potential of the meniscus and the surrounding cartilage. This potential should be taken into account, and meniscal surgery can be performed with the correct timing and the proper indication even in the presence of early OA.

Revision Meniscal Surgery in Children and Adolescents: Risk Factors and Mechanisms for Failure and Subsequent Management

BACKGROUND

The mechanisms of failure and risk factors for failed meniscal surgery in children and adolescents have not been well described.

PURPOSE

To investigate the risk factors, mechanisms of failure, and subsequent operative management for revision meniscal surgery in a pediatric population, as well as to identify the local incidence of failed meniscal surgery.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

All patients younger than 20 years who had arthroscopic management for meniscal injuries at a single institution between 2008 and 2012 underwent retrospective review. Demographic data and intraoperative findings at the time of the initial surgery were documented. All patients undergoing a second procedure on the same meniscus were further analyzed. Multivariate logistic regression with purposeful selection was performed to identify independent risk factors for revision meniscal surgery.

RESULTS

Arthroscopic knee surgery was performed on 293 patients and 324 menisci, including 129 primary repairs, 149 primary partial meniscectomies, and 46 discoid saucerizations ± stabilization. At a mean of 40 months (range, 19-62 months) after surgery, 13% of all menisci required a revision procedure. The primary repair cohort had the highest failure rate (18%), followed by the primary discoid saucerization cohort (15%) and the partial meniscectomy cohort (7%). Multivariate analysis indicated that meniscal repair was predictive of retear (odds ratio, 2.04 [95% CI, 1.01-4.1]; P = .046), and children with an open physis and a bucket-handle tear had the highest retear rate of 46% (P = .039). Independent variables shown to have no significant relationship to revision meniscal surgery included age, sex, body mass index, extremity side, laterality (medial-lateral), time to repair, tear location, and associated ligament reconstruction. The most common indication for revision surgery was an acute reinjury during intense physical activity. Revision procedures were performed at a mean of 14 months after the index procedure, and the majority of failures (83%) were identified within 1 year. Of patients undergoing a revision surgery, 44% underwent a further debridement, whereas 56% underwent a repair.

CONCLUSION

The success rate of meniscal surgery is 87% in children and adolescents. The revision rate was higher when repair was attempted in the index procedure, particularly in those children with open physes and bucket-handle tears. Most failures are the result of an acute reinjury within 1 year, and nearly half will require debridement of the retorn meniscus.

Biomechanics of the anterior cruciate ligament: Physiology, rupture and reconstruction techniques

The influences and mechanisms of the physiology, rupture and reconstruction of the anterior cruciate ligament (ACL) on kinematics and clinical outcomes have been investigated in many biomechanical and clinical studies over the last several decades. The knee is a complex joint with shifting contact points, pressures and axes that are affected when a ligament is injured. The ACL, as one of the intra-articular ligaments, has a strong influence on the resulting kinematics. Often, other meniscal or ligamentous injuries accompany ACL ruptures and further deteriorate the resulting kinematics and clinical outcomes. Knowing the surgical options, anatomic relations and current evidence to restore ACL function and considering the influence of concomitant injuries on resulting kinematics to restore full function can together help to achieve an optimal outcome.

Posteromedial Meniscocapsular Lesions Increase Tibiofemoral Joint Laxity With Anterior Cruciate Ligament Deficiency, and Their Repair Reduces Laxity

BACKGROUND

Injury to the posteromedial meniscocapsular junction has been identified after anterior cruciate ligament (ACL) rupture; however, there is a lack of objective evidence investigating how this affects knee kinematics or whether increased laxity can be restored by repair. Such injury is often overlooked at surgery, with possible compromise to results.

HYPOTHESES

(1) Sectioning the posteromedial meniscocapsular junction in an ACL-deficient knee will result in increased anterior tibial translation and rotation. (2) Isolated ACL reconstruction in the presence of a posteromedial meniscocapsular junction lesion will not restore intact knee laxity. (3) Repair of the posteromedial capsule at the time of ACL reconstruction will reduce tibial translation and rotation to normal. (4) These changes will be clinically detectable.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine cadaveric knees were mounted in a test rig where knee kinematics were recorded from 0° to 100° of flexion by use of an optical tracking system. Measurements were recorded with the following loads: 90-N anterior-posterior tibial forces, 5-N·m internal-external tibial rotation torques, and combined 90-N anterior force and 5-N·m external rotation torque. Manual Rolimeter readings of anterior translation were taken at 30° and 90°. The knees were tested in the following conditions: intact, ACL deficient, ACL deficient and posteromedial meniscocapsular junction sectioned, ACL deficient and posteromedial meniscocapsular junction repaired, ACL patellar tendon reconstruction with posteromedial meniscocapsular junction repair, and ACL reconstructed and capsular lesion re-created. Statistical analysis used repeated-measures analysis of variance and post hoc paired t tests with Bonferroni correction.

RESULTS

Tibial anterior translation and external rotation were both significantly increased compared with the ACL-deficient knee after posterior meniscocapsular sectioning (P < .05). These parameters were restored after ACL reconstruction and meniscocapsular lesion repair (P > .05).

CONCLUSION

Anterior and external rotational laxities were significantly increased after sectioning of the posteromedial meniscocapsular junction in an ACL-deficient knee. These were not restored after ACL reconstruction alone but were restored with ACL reconstruction combined with posterior meniscocapsular repair. Tibial anterior translation changes were clinically detectable by use of the Rolimeter.

CLINICAL RELEVANCE

This study suggests that unrepaired posteromedial meniscocapsular lesions will allow abnormal meniscal and tibiofemoral laxity to persist postoperatively, predisposing the knee to meniscal and articular damage.

Optical spectroscopic determination of human meniscus composition

This study investigates the correlation between the composition of human meniscus and its absorption spectrum in the visible (VIS) and near infrared (NIR) spectral range. Meniscus samples (n = 24) were obtained from nonarthritic knees of human cadavers with no history of joint diseases. Specimens (n = 72) were obtained from three distinct sections of the meniscus, namely; anterior, center, posterior. Absorption spectra were acquired from each specimen in the VIS and NIR spectral range (400-1,100 nm). Following spectroscopic probing, the specimens were subjected to biochemical analyses to determine the matrix composition, that is water, hydroxyproline, and uronic acid contents. Multivariate analytical techniques, including principal component analysis (PCA) and partial least squares (PLS) regression, were then used to investigate the correlation between the matrix composition and it spectral response. Our results indicate that the optical absorption of meniscus matrix is related to its composition, and this relationship is optimal in the NIR spectral range (750-1,100 nm). High correlations (R(2) (uronic)  = 86.9%, R(2) (water)  = 83.8%, R(2) (hydroxyproline)  = 81.7%, p < 0.0001) were obtained between the spectral predicted and measured meniscus composition, thus suggesting that spectral data in the NIR range can be utilized for estimating the matrix composition of human meniscus. In conclusion, optical spectroscopy, particularly in the NIR spectral range, is a potential method for evaluating the composition of human meniscus. This presents a promising technique for rapid and nondestructive evaluation of meniscus integrity in real-time during arthroscopic surgery.

Results of meniscectomy and meniscal repair in anterior cruciate ligament reconstruction

Meniscal tears are commonly associated with anterior cruciate ligament (ACL) injuries. A deficient medial meniscus results in knee instability and could lead to higher stress forces on the ACL reconstruction. Comparison of results in meniscectomy and meniscal repairs revealed worse clinical outcomes in meniscectomy, but higher re-operation rates in meniscal repairs. Our aim was to review the results of ACL reconstruction associated with meniscectomy or meniscal repair.

The relationship between medial meniscal subluxation and stress distribution pattern of the knee joint: Finite element analysis

BACKGROUND

Degenerative changes of the knee joint and clinical follow-up after meniscal subluxation are well documented. In the current study three-dimensional (3D) finite element analysis (FEA) of human lower limb was used to investigate the effect medial meniscal subluxation on the loadings of the knee structures.

METHODS

Apart from the reference model, a total of ten 3D models were created, according to amount of medial meniscal subluxation. ANSYS® 14 was used to analyze the stress/load distribution, that is to say the maximum equivalent stress (MES) (von Mises stress) on bones, cartilages, ligaments and menisci. MES was expressed as Newton/mm(2) = Megapascal (MPa).

RESULTS

In a static and standing upright position the MES on all knee structures were evaluated in the reference model. Although MES increased in all structures with the increase of medial meniscal subluxation degree, tibia cartilage was found to be the most affected structure with an increase of 22.73-fold in the 10 mm subluxation model when compared with references values.

CONCLUSION

This study showed that medial meniscus subluxation is associated with increased loadings on all knee structures especially the tibia cartilage. Also the degree of the medial meniscal subluxation correlates with distribution and the amount of loadings on tibia cartilage which may be a prominent feature of knee osteoarthritis.

Long-term outcomes of medial CMI implant versus partial medial meniscectomy in patients with concomitant ACL reconstruction

PURPOSE

To compare the clinical, objective and radiographic long-term results of patients with anterior cruciate ligament (ACL) lesion and partial medial meniscus defects, treated with ACL reconstruction and partial medial meniscectomy or medial CMI implant.

METHODS

Seventeen patients treated with combined ACL reconstruction and medial CMI and 17 patients treated with ACL reconstruction and partial medial meniscectomy were evaluated with mean follow-up 9.6 years with Lysholm, Tegner, objective and subjective International Knee Documentation Committee scores, and VAS for pain. Arthrometric evaluation was performed with KT 2000. Weigh-bearing radiographs, antero-posterior and Rosenberg view, were also performed and evaluated with Kellgren-Lawrence score, Ahlback score and joint space narrowing.

RESULTS

Pre-operative demographic parameters and clinical scores between patients treated with CMI and partial medial meniscectomy revealed no significant differences. A significant improvement of all the clinical scores was detected in both groups from pre-operative status to final follow-up. No significant difference between groups were found for clinical and radiographic scores; however, the chronic subgroup of patients treated with CMI showed a significantly lower level of post-operative knee pain compared to patients treated with partial medial meniscectomy and the acute subgroup of medial CMI showed better arthrometric scores.

CONCLUSION

Good long-term clinical results in terms of stability, subjective outcomes and objective evaluation were reported both for medial CMI implant and partial medial meniscectomy, combined with ACL reconstruction for the treatment of partial medial meniscus tears combined with ACL lesions. Chronic meniscal tears treated with medial CMI reported lower levels of post-operative pain compared to meniscectomy, while acute lesions treated with medial CMI showed less knee laxity. Therefore, the use of the collagen meniscus implant in the case of anterior knee instability with a meniscal defect appears justified and able to improve clinical outcomes in the long term.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Kinematic change of the meniscus and the tibiofemoral joint space in asymptomatic volunteers using a wide bore 3T closed MRI system

OBJECTIVES

To evaluate kinematic changes in menisci and tibiofemoral joint spaces in extension and flexion using asymptomatic volunteers using a wide-bore 3-T closed MRI system.

METHODS

Twenty-two knees from asymptomatic volunteers were examined in knee extension and flexion using a 3-T MRI (sagittal 2D FSE T2-weighted sequence and sagittal 3D isotropic FSE proton density-weighted cube sequence). The meniscal positions, meniscal floating and flounce were evaluated. The widths of the medial and lateral tibiofemoral joint spaces and coronal tibiofemoral angles were measured.

RESULTS

In the anteroposterior direction, meniscal extrusion was most frequently seen in the anterior horn of the medial menisci (100%) in extensions (maximum 6.04 mm). Most of the menisci moved significantly to the posterior side from extension to flexion. The anteroposterior meniscal movement was the greatest for the anterior horn of the medial meniscus and least for the posterior horn of the medial meniscus. In the mediolateral direction, meniscal extrusion was seen in 52% of the medial menisci in extensions (maximum 1.91 mm) and 29% of lateral menisci in flexions (maximum 2.36 mm). From the extension to flexion, all medial and lateral menisci moved significantly to the lateral side. Meniscal floating was frequently observed in the posterior horn of medial menisci in extension. Meniscal flounce was frequently seen in lateral menisci in flexion with a widened lateral tibiofemoral joint space gap. The coronal tibiofemoral angle showed medial wedging in flexion, but not in extension.

CONCLUSIONS

Wide-bore 3-T closed MRI revealed significant kinematic changes in the menisci and tibiofemoral joint spaces in asymptomatic volunteers.

Effect of unstable meniscal injury on three-dimensional knee kinematics during gait in anterior cruciate ligament-deficient patients

BACKGROUND

Our purpose was to clarify the differences of three-dimensional knee kinematics in anterior cruciate ligament (ACL)-deficient patients between with and without meniscal injury using gait analysis.

METHODS

A total of 72 knees in 36 young athletes with primary and unilateral ACL injury, with a mean age of 22 years, participated. Gait analysis was done before surgery. According to the arthroscopic findings, patients were divided into two groups. The patients with an unstable meniscal tear were allocated to the meniscal injury group (ACL+M group), and the patients without a meniscal tear were allocated to the no meniscal injury group (ACL group). In the gait analysis, three-dimensional knee kinematics was evaluated and compared.

RESULTS

The patients in both groups exhibited lower sagittal plane knee excursions and peak knee extension angles on the affected limb than on the unaffected limb during the mid-stance. In terms of the axial plane, a rotation angle was significantly smaller in the affected knees than in the unaffected knees in the ACL group. On the other hand, an opposite phenomenon was observed in the ACL+M group. Moreover, a significantly larger rotation angle in the affected knees during the stance phase and the whole gait cycle was observed in the ACL+M group than in the ACL group.

CONCLUSION

Increased rotational motion during the gait was observed in the ACL-deficient knees combined with unstable meniscal injuries. Meniscal condition may be a key factor for compensatory gait mechanics to prevent rotatory instability in ACL-deficient patients patients.

LEVEL OF EVIDENCE

III.

The role of the meniscotibial ligament in posteromedial rotational knee stability

PURPOSE

Tears of the posterior horn of the medial meniscus (PHMM) are very common in the ACL-deficient knee. Specific lesions of the PHMM have been described in the setting of ACL rupture: ramp lesions and injuries to the meniscotibial ligament. There are little data available regarding the role these lesions play in knee instability. The aim of this study is to analyse the biomechanical consequences of ramp and meniscotibial ligament lesions on knee stability. Our hypothesis was that these lesions would cause increased instability in the setting of ACL rupture.

METHODS

A cadaveric study was undertaken: ten knees were included for analysis. The biomechanical repercussions of different meniscoligamentous injuries were studied in four stages: stage 1 involved testing the intact knee, stage 2 after transection of the ACL, stage 3 following creation of a ramp lesion, and stage 4 after detachment of the meniscotibial ligament. Four parameters were measured during the experiment: anterior tibial translation under a force of 134 N, internal and external tibial rotation under a torque of 5 Nm, and valgus angulation under a torque of 10 Nm. Measurements were taken in four knee flexion positions: 0° or full extension, 30°, 70°, and 90° of flexion.

RESULTS

There was a statistically significant increase in anterior tibial translation for stage 2 (6.8 ± 1.3 mm, p ≤ 0.001), stage 3 (9.4 ± 1.3 mm, p ≤ 0.001), and stage 4 (9.3 ± 1.3 mm, p ≤ 0.001) compared to stage 1. There was no significant difference between stage 2 and stage 3 (2.6 mm, n.s.) or stage 4 (2.5 mm, n.s.). We did, however, demonstrate an increase in anterior tibial translation of 2.6 mm after the creation on a lesion of the PHMM compared to isolated division of the ACL, for all flexion angles combined. There was an increase in internal tibial rotation between stage 1 and stage 4 (3.2° ± 0.7°, p ≤ 0.001) and between stage 2 and stage 4 (2.0° ± 0.7°, p = 0.023). A significant difference was demonstrated for external rotation under 5 Nm torque between stages 4 and 1 (2.2° ± 0.5°, p ≤ 0.001) and between stages 4 and 2 (1.7° ± 0.5°, p = 0.007) for all knee flexion angles combined. No created lesion had a significant effect on medial laxity under a 10-Nm valgus torque at any degree of knee flexion.

CONCLUSION

Lesions of the posterior horn of the medial meniscus are frequent in cases of anterior cruciate ligament rupture. These lesions appear to play a significant role in knee stability. Ramp lesions increase the forces in the ACL, and the PHMM is a secondary restraint to anterior tibial translation. Lesions of the meniscotibial ligament may increase rotatory instability of the knee.

Tibiofemoral contact pressures in radial tears of the meniscus treated with all-inside repair, inside-out repair and partial meniscectomy

BACKGROUND

To test contact pressures in the knee after treatment of a radial meniscus tear with an all-inside meniscal repair technique and compare the results with inside-out repair and partial meniscectomy.

METHODS

Six non-paired cadaveric knees were analyzed with intra-compartment pressures measured at loads of 250 N, 500 N and 1000 N at 0°, eight degrees, 15°, and 30° of knee flexion. Compartmental contact pressures were measured for the intact medial meniscus, radial tear in the posterior horn, all-inside repair using the NovoStitch suture passer device (Ceterix Orthopaedics Inc., Menlo Park, CA), inside-out repair method, and partial meniscectomy. One-way ANOVA was used for statistical analysis.

RESULTS

The greatest differences in peak pressures between treatments were observed under 1000 N load at 30° flexion (0.8± (SD) 0.1 MPa (intact meniscus), 0.8± (SD) 0.1 MPa (all-inside), 0.9± (SD) 0.1 MPa (inside-out) and 1.6± (SD) 0.2 MPa (partial meniscectomy)). Treatment with partial meniscectomy resulted in the highest peak pressures compared to all other states (p<0.0001 at each angle). Repair of the radial tear using the all-inside technique as well as the inside-out technique resulted in significantly decreased compartment pressures compared to partial meniscectomies (p<0.0001 at each angle). There were no significant differences between peak pressures in the intact state and after repair with the all-inside or inside-out techniques.

CONCLUSION

An all-inside repair technique using the NovoStitch suture passer can decrease contact pressures for a radial meniscus tear similarly to the inside-out repair technique when compared to partial meniscectomy.

CLINICAL RELEVANCE

This novel arthroscopic suture passer warrants further analysis in the clinical setting as it may be a reliable method for repair of radial meniscal tears through an arthroscopic all-inside technique.

Biomechanical evaluation of knee kinematics after anatomic single- and anatomic double-bundle ACL reconstructions with medial meniscal repair

PURPOSE

To evaluate knee laxity after anatomic ACL reconstruction with additional suture repair of a medial meniscus tear.

METHODS

Kinematics of the intact knee were determined in 12 human cadaver specimens in response to a 134-N anterior tibial load (aTT) and a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation (aTTPS) using a robotic/universal force moment sensor testing system. Subsequently, the ACL was resected following the creation of a standardized tear of the medial meniscus, a standard meniscus repair and an ACL reconstruction using an anatomic single-bundle (6) or an anatomic double-bundle technique (6). Knee kinematics were determined following every sub-step.

RESULTS

Significant increase of aTT in the ACL-deficient knee was found (p ≤ 0.001) with a further increase in the ACL-deficient knee with additional medial meniscal rupture (p ≤ 0.001). ACL reconstructions significantly decreased aTT compared with the ACL and meniscus-ruptured knee. No significant differences were seen between the intact knee and the ACL-reconstructed knee with additional meniscal repair (p < 0.05). In response to a simulated pivot shift, aTTPS in the intact knee significantly increased in the ACL-deficient knee and meniscus-ruptured knee (p = 0.005). No significant differences in knee kinematics were found between SB as well as DB ACL reconstruction with additional medial meniscal repair compared with the intact knee. Comparison of SB versus DB ACL reconstruction did not reveal any significant differences in a simulated Lachman test or simulated pivot shift test (n.s.).

CONCLUSIONS

aTT as well as aTTPS significantly increased with ACL deficiency compared with the intact knee; additional medial meniscal rupture further increased aTT. Anatomic ACL reconstruction with medial meniscal repair did not reveal significant differences in knee kinematics compared with the intact knee. Comparison of anatomic SB versus DB ACL reconstruction with additional repair of the medial meniscus did not show significant differences neither in a simulated Lachman nor in a simulated pivot shift test.

The effect of tibial slope in acute ACL-insufficient patients on concurrent meniscal tears

INTRODUCTION

The aim of this study is to evaluate the effect of the medial and lateral posterior tibial slope (MPTS, LPTS) in patients with acutely ruptured ACL on the menisci. It was hypothesized that medial and lateral meniscus lesions are seen more often with high PTS (posterior tibial slope). We hypothesized that in case of a high tibial slope a possible meniscus lesion is more often located in the posterior horn of the meniscus than in knees with a low tibial slope.

MATERIALS AND METHODS

We identified 537 patients with ACL insufficiency between 2012 and 2013. Of these, 71 patients were eligible for the study according to the study's criteria. PTS was measured via MRI and classified into two groups: >10° for high tibial slope and ≤10° for low tibial slope. Any meniscal lesion was documented during arthroscopic ACL reconstruction and evaluated regarding meniscal lesion patterns with high and low PTS, taking into account the type and the location of the tear (anterior horn, intermediate part and posterior horn). Statistical analysis for differences in meniscal lesion was performed using Chi-square tests and McNemar tests for dependent variables. The level of significance was set at p ≤ 0.05.

RESULTS

High PTS (MPTS and LPTS) was associated with a higher incidence of meniscal lesions with an odds ratio of 2.11, respectively, 3.44; however, no statistical significance was found. Among the total number of ACL-insufficient knees studied, the meniscal lesion spread more often to the posterior part in the group with a low PTS. In contrast, less damage of the posterior horn of the meniscus could be found in the group with a high PTS.

CONCLUSION

High PTS seems to predetermine for meniscal lesion in an acute ACL-insufficient knee. More damage to the posterior part of the menisci could generally be seen but was not associated with a high PTS. There was no statistical significance to support the initial hypothesis. Further research is needed to find out if factors other than tibial slope are risk factors for meniscal lesion in acute ACL injury.

LEVEL OF EVIDENCE

IV.

Characteristic arthroscopic signs of cartilage injuries indicating concomitant occult medial meniscal peripheral tears of posterior horn

BACKGROUND

Medial posterior horn meniscal tear is difficult to visualise during arthroscopy and is occasionally undetected by preoperative magnetic resonance imaging (MRI). Consequently, attention should be paid to performing a thorough examination and to some characteristic signs that indicate occult meniscal tear. The purpose of this study was to assess an indicative correlation between arthroscopic features of cartilage injury and a concomitant occult meniscal tear.

METHODS

We performed a retrospective clinical and radiographic study of a consecutive series of patients between January 2013 and December 2014. Of 1,596 patients, all 78 with wave-like chondral injury of the medial femoral condyle diagnosed at arthroscopy were included in the study. The occurrence, pattern, location and concomitant pathology of medial meniscal injury were analysed.

RESULTS

The characteristic wave sign associated with chondral injury in the medial femoral condyle was detected by MRI preoperatively in two cases only; all others were discovered intraoperatively at arthroscopy. Cartilage injury was rated as Outerbridge type II in 53 patients, type III in 24, and type IV in one. Wave sign defects were all characterised by their transverse orientation in the load-bearing femoral condyle. The occult longitudinal peripheral meniscus tear of the posterior horn was seen in all patients with a positive wave sign visualised under arthroscopy. The wave sign was positively correlated with medial peripheral meniscal injury of the posterior horn (P < 0.01).

CONCLUSION

Wave sign chondral injury in the medial femoral condyle seen at arthroscopy is a characteristic indicator for concomitant occult medial longitudinal peripheral meniscus tears of the posterior horn.

LEVEL OF EVIDENCE

Case series, Level IV.

Effect of lateral meniscal root tear on the stability of the anterior cruciate ligament-deficient knee

BACKGROUND

Meniscal root tears are an increasingly recognized subset of meniscal injury. The menisci are critical secondary stabilizers of the anterior cruciate ligament (ACL). The kinematic effect of lateral meniscus posterior root tear in the setting of ACL injury is not known.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine the effect of tear of the lateral meniscal root on stability of the ACL-deficient knee. The hypothesis was that disruption of the lateral meniscal root will further destabilize the ACL-deficient knee during a simulated pivot shift.

STUDY DESIGN

Controlled laboratory study.

METHODS

Pivot-shift testing of 8 fresh-frozen cadaveric knees was performed after attachment of photoreflective flags and preparation of CT scans. Each knee was mounted in a custom activity simulator and dynamically loaded from 15° to 90° of flexion with all the permutations of the following: iliotibial band force (50, 75, 100, 125, 150, and 175 N), internal rotation moments (1, 2, and 3 N·m), and valgus moments (5 and 7 N·m). In addition, anterior stability tests were performed by applying a 90-N anterior force to the tibia at flexion angles of 15°, 30°, 45°, 60°, and 90°. During each test, the anterior tibial translation and rotation of the tibia were measured with a high-resolution multiple infrared camera motion analysis system for the following 3 conditions: ACL-intact (ACL-I), ACL-deficient (ACL-D), and ACL-deficient/lateral meniscal posterior root avulsion (ACL-D/LMR-A).

RESULTS

A pivot-shift phenomenon was observed in the ACL-D and ACL-D/LMR-A conditions. The mean tibial translation of the lateral tibial condyle during the pivot-shift maneuver was 2.62 ± 0.53 mm for the ACL-I knees, 6.01 ± 0.51 mm for the ACL-D knees (P value vs. intact: .0005), and 8.13 ± 0.75 mm for the ACL-D/LMR-A knees (P value vs intact: <.0001). During the pivot-shift maneuver, translation was significantly increased in the ACL-D/LMR-A condition compared with the ACL-D condition (P = .0146). Compared with the intact group, anterior tibial translation during the Lachman maneuver also increased at 30° and 90° of flexion in the ACL-D group (P < .0001) and the ACL-D/LM group (P < .0001). No statistically significant difference was found between the ACL-D and ACL-D/LMR-A groups during the Lachman maneuver at 30° and 90° (P = .16 and .72, respectively).

CONCLUSION

A tear of the lateral meniscal posterior root further reduces the stability of the ACL-deficient knee during rotational loading.

CLINICAL RELEVANCE

This study shows that lateral meniscal root injury further destabilizes the ACL-deficient knee and thus advances the concept that the lateral meniscus is a secondary stabilizer of the knee under pivot-shift loading. In the absence of stronger evidence, the study data suggest a rationale for surgical repair of lateral meniscal root tears encountered in the setting of ACL tears.

The prevalence of meniscal tears in young athletes undergoing revision anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to determine the incidence of meniscal injury, specifically medial meniscal injury, in US Army soldiers undergoing revision anterior cruciate ligament (ACL) reconstruction.

METHODS

A retrospective review was performed of all patients who underwent revision ACL reconstruction from 2002 to 2011 at our institution. A complete chart review was performed to identify the prevalence of meniscal pathology identified at the time of revision ACL surgery. Patient demographic data and meniscal injury patterns were analyzed.

RESULTS

Sixty-seven patients were identified, with a mean age of 28 years. The mean time to revision reconstruction was 67 months. Most patients (64.1%) reported a distinct reinjury. Reinjury was reported as the cause for revision ACL reconstruction in 43 patients. In this subgroup the mean time from reinjury to revision surgery was 13.9 months. Meniscal pathology was identified in 50 patients (74.6%). Medial meniscal tears were noted in 38 patients (56.7%), a rate significantly greater than that previously described (P = .008). Lateral meniscal tears were noted in 26 patients (38.8%), which was similar to previously published data (P = .52).

CONCLUSIONS

The prevalence of meniscal injury at the time of revision ACL reconstruction in active-duty US Army soldiers is nearly identical to that of previously published data looking at a civilian population (74.6% v 74%) in the Multicenter ACL Revision Study (MARS) cohort. However, the incidence of medial meniscal injury was greater in the active-duty population than in the civilian population (56.7% v 40%). The observed increase in the prevalence of medial meniscal pathology is likely multifactorial, relating to the unique demands on young military athletes in both combat and training environments, rate of reinjury, and various delays to treatment after reinjury.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Comparison of the biomechanical tensile and compressive properties of decellularised and natural porcine meniscus

Meniscal repair is widely used as a treatment for meniscus injury. However, where meniscal damage has progressed such that repair is not possible, approaches for partial meniscus replacement are now being developed which have the potential to restore the functional role of the meniscus, in stabilising the knee joint, absorbing and distributing stress during loading, and prevent early degenerative joint disease. One attractive potential solution to the current lack of meniscal replacements is the use of decellularised natural biological scaffolds, derived from xenogeneic tissues, which are produced by treating the native tissue to remove the immunogenic cells. The current study investigated the effect of decellularisation on the biomechanical tensile and compressive (indentation and unconfined) properties of the porcine medial meniscus through an experimental-computational approach. The results showed that decellularised medial porcine meniscus maintained the tensile biomechanical properties of the native meniscus, but had lower tensile initial elastic modulus. In compression, decellularised medial porcine meniscus generally showed lower elastic modulus and higher permeability compared to that of the native meniscus. These changes in the biomechanical properties, which ranged from less than 1% to 40%, may be due to the reduction of glycosaminoglycans (GAG) content during the decellularisation process. The predicted biomechanical properties for the decellularised medial porcine meniscus were within the reported range for the human meniscus, making it an appropriate biological scaffold for consideration as a partial meniscus replacement.

Postoperative change in the length and extrusion of the medial meniscus after anterior cruciate ligament reconstruction

PURPOSE

The medial meniscus is a secondary stabilizer of anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. ACL reconstruction effectively restores an increased anterior tibial translation in the ACL-deficient knee. However, knee osteoarthritis sometimes develops in ACL-reconstructed patients during a long-term follow-up period. We hypothesized that the medial meniscal position would be different between the ACL-deficient and reconstructed knees. The aim of this study was to investigate pre-operative and postoperative location of the medial meniscus in patients who underwent ACL reconstruction.

METHODS

ACL-reconstructed knees (28 knees) and normal knees (27 knees) were investigated. Medial tibial plateau length (MTPL) and medial tibial plateau width (MTPW) were determined using radiographic images. Magnetic resonance imaging (MRI)-based medial meniscal length (MML), medial meniscal width (MMW), and medial meniscal extrusion (MME) were measured. Postoperative change in the MML, MMW, and MME were evaluated and compared with those in normal knees.

RESULTS

No significant differences between the ACL-deficient (pre-operative) and normal groups were noted. The ACL-reconstructed (postoperative) group showed an increase in the MML, in the percentage of the MML (%MML = 100 MML/MTPL), and in the MME. Significant differences between postoperative and normal groups were observed in the MML, %MML, and MME. MMW and MMW percentage (100 MMW/MTPW) were similar in all groups.

CONCLUSIONS

The anteroposterior length and radial extrusion of the medial meniscus increased after ACL reconstruction. Transposition of the medial meniscus may be a possible cause of developing further degenerative knee joint disorders after ACL reconstruction.

Meta-analysis on biomechanical properties of meniscus repairs: are devices better than sutures?

PURPOSE

Meniscal repair devices have been extensively tested during the past decades as reported in the literature. Reviewing the different meniscal repair devices and sutures with their respective biomechanical properties.

METHODS

For this meta-analysis, we conducted a systematic online search using PubMed, EMBASE, CCTR, and CINAHL using the search terms Meniscus OR Meniscal AND Biomechanics AND Repair). Load-to-failure (LtF), stiffness, and cyclic outcome measures were extracted independently and in duplicate. The systematic search revealed 841 manuscripts in total. After exclusion of duplicates and irrelevant publications, 41 studies remained for final analysis. The studies were published in English and German from 1995 to 2013. Due to differing cyclic force protocols, cyclic outcomes had to be excluded.

RESULTS

Overall, sutures had a higher LtF [suture: 87.7 ± 0.3 N (weighted mean ± standard error), device: 56.3 ± 0.1 N] and stiffness (suture: 8.9 ± 0.04 N/mm, device: 8.6 ± 0.04 N/mm) than devices, both p < 0.05. In LfT testing, PDS 0 Vertical (145.0 ± 8.1 N), OrthoCord 2-0 (143.6 ± 11.3 N), and Ethibond No 0 Vertical (133.4 ± 7.7 N) were the strongest sutures and Meniscal Viper (140.9 ± 5.1 N), MaxFire Vertical (136.2 ± 11.3 N), and FasT-Fix Vertical (115.2 ± 1.6 N) were the strongest devices. Second-generation devices were significantly stronger and stiffer than first-generation devices (p < 0.001).

CLINICAL RELEVANCE

Suture repair remains the gold standard with a vertically oriented suture configuration showing superior LtF values compared to a horizontal configuration. Nevertheless, some meniscal repair devices have similar biomechanical properties to suture repairs. Both suture repairs and devices have a place in meniscal restoration.

LEVEL OF EVIDENCE

None, meta-analysis of controlled laboratory studies.

Cartilage MRI relaxation times after arthroscopic partial medial meniscectomy reveal localized degeneration

PURPOSE

Little is known about the early changes in cartilage composition and tibiofemoral kinematics following partial meniscectomy. The purpose of this study was to determine the effects of partial meniscectomy on cartilage compositional properties using T1ρ and T2 relaxation time mapping and to assess changes in tibiofemoral kinematics. It is hypothesize that abnormal tibiofemoral kinematics and relaxation time elevation (a reflection of changes in cartilage biochemical composition) in the weight-bearing regions of the knees following meniscectomy will be observed.

METHODS

Nine patients (7 males and 2 females; mean age, 48.6 ± 10.8 years; BMI = 27.3 ± 3.8 kg/m(2)) with tears of the posterior horn of the medial meniscus underwent arthroscopic partial meniscectomy. Pre-surgical and 6 months post-surgical MRIs were obtained in all subjects to evaluate cartilage relaxation times and tibiofemoral kinematics. Paired t tests were performed to determine significant changes in cartilage relaxation times from baseline.

RESULTS

T1ρ relaxation time in the region of the medial femoral condyle directly adjacent to the resection showed an increase of 7.4% at 6 months (p = 0.02). T2 relaxation times in both the medial and lateral tibial plateaus showed significant elevation at 6 months. Consistent kinematic trends were not found in post-meniscectomized knees.

CONCLUSIONS

These results suggest that arthroscopic partial meniscectomy affects the biochemical composition of articular cartilage in the knee in as early as 6 months. The largest responses were observed in the weight-bearing regions and the cartilage immediately adjacent to the resection. This suggests that the loading environment has been altered enough to result in cartilage compositional changes in a very brief period of time following meniscectomy.

LEVEL OF EVIDENCE

IV.

Why menisci show higher healing rate when repaired during ACL reconstruction? Growth factors release can be the explanation

PURPOSE

Healing rate of meniscus repair is higher when the suture is associated with anterior cruciate ligament reconstruction. A possible explanation can be a different pattern of release of growth factors between anterior cruciate ligament reconstruction and isolated meniscus surgery. Hypothesis of this study is that the concentrations of bFGF, TGF-β and platelet-derived growth factor (PDGF) in joint fluid, immediately after single-bundle anterior cruciate ligament reconstruction and arthroscopic partial meniscectomy, can be different.

METHODS

Twenty consecutive patients underwent partial medial meniscectomy and twenty consecutive patients underwent single-bundle anterior cruciate ligament reconstruction with hamstring grafts were enrolled in the study. Thirty minutes after the end of the surgical procedure, a sample of joint fluid, as well of venous blood, was collected from all the patients. Concentrations of growth factors were determined by enzyme-linked immunosorbent assay.

RESULTS

The peripheral blood concentration of TGF-β, bFGF and PDGF was comparable between partial meniscectomy and anterior cruciate ligament reconstruction groups. No differences between the two surgical techniques were also found in term of TGF-β and bFGF joint fluid concentration, whereas joint PDGF concentration of anterior cruciate ligament reconstruction patients was significantly higher than the one found in partial meniscectomy patients.

CONCLUSIONS

A significant growth factors release was detected in the knee joint during arthroscopic surgery. PDGF concentration was significantly higher in anterior cruciate ligament reconstructed knee than in the meniscectomy group. PDGF can play an important role enhancing the healing response of meniscus suture and can be one of the biological reasons of the higher meniscal healing rate in anterior cruciate ligament reconstructed knee.

Evaluation of meniscal mechanics and proteoglycan content in a modified anterior cruciate ligament transection model

Post-traumatic osteoarthritis (PTOA) develops as a result of traumatic loading that causes tears of the soft tissues in the knee. A modified transection model, where the anterior cruciate ligament (ACL) and both menisci were transected, was used on skeletally mature Flemish Giant rabbits. Gross morphological assessments, elastic moduli, and glycosaminoglycan (GAG) coverage of the menisci were determined to quantify the amount of tissue damage 12 weeks post injury. This study is one of the first to monitor meniscal changes after inducing combined meniscal and ACL transections. A decrease in elastic moduli as well as a decrease in GAG coverage was seen.