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

Function of the anterior cruciate ligament after unicompartmental knee arthroplasty: an in vitro robotic study

The objective of this study was to investigate the role of the anterior cruciate ligament (ACL) in the anterior-posterior (AP) stability of the knee after unicompartmental knee arthroplasty (UKA). AP tibial loads were applied to human cadaveric knee specimens using a robotic testing system. After UKA, the knee exhibited tibial translations similar to that of the native knee, and the forces in the ACL were also similar to those seen in the native knee. The ACL-deficient knee after UKA exhibited significantly greater anterior tibial translations than the native knee and the knee after UKA with an intact ACL. These data suggest that medial UKA does not alter the anterior stability of the knee, but a functional ACL is necessary to ensure normal stability after UKA.

Long-term results after combined medial meniscal allograft transplantation and anterior cruciate ligament reconstruction: minimum 8.5-year follow-up study

PURPOSE

The purpose of this study was to evaluate the long-term results after medial meniscal allograft transplantation combined with anterior cruciate ligament (ACL) reconstruction.

TYPE OF STUDY

Retrospective clinical outcome study.

METHODS

Between 1990 and 1992, 9 medial meniscal allograft transplantations were performed in symptomatic knees with a previous total or near-total medial meniscectomy. One of the 9 patients required transplant removal postoperatively because of a presumed low-grade infection versus immune reaction. The remaining 8 patients were evaluated, with an average follow-up time of 9.7 years. All 8 patients underwent an ACL reconstruction. One patient also had a staged high tibial osteotomy.

RESULTS

All 8 patients were evaluated with the standard International Knee Documentation Committee (IKDC) form with no normal scores: 1 had a nearly normal score, 4 had abnormal scores, and 3 severely abnormal scores. The IKDC symptoms evaluation produced 2 normal scores, 5 nearly normal scores, and 1 abnormal score. The IKDC function test showed 5 normal scores, 1 nearly normal score, and 2 abnormal scores. Six of the 8 patients were extremely pleased with the function of the knee and were active in recreational sports. All 8 patients would recommend the procedure to a friend and would undergo the procedure again given similar circumstances.

CONCLUSIONS

The findings of this study agree with several other studies with shorter follow-up times that medial meniscal allograft transplantation can significantly improve knee function in symptomatic medial meniscus-deficient knees. The addition of a ligament-stabilizing procedure probably improved the results in this patient population.

LEVEL OF EVIDENCE

Level IV, Case Series.

Clinical outcomes after combined meniscal allograft transplantation and anterior cruciate ligament reconstruction

BACKGROUND

Concomitant meniscal transplantation performed at the time of ligament surgery may help to protect the anterior cruciate ligament graft.

PURPOSE

To determine the objective and subjective clinical outcomes after combined anterior cruciate ligament reconstruction and meniscal allograft transplantation.

STUDY DESIGN

Uncontrolled retrospective review.

METHODS

Twenty-eight patients who underwent anterior cruciate ligament reconstruction along with meniscal transplantation were retrospectively evaluated postoperatively at an average of 2.8 years (range, 1.8 to 5.6).

RESULTS

On the International Knee Documentation Committee overall subjective assessment, 86% had normal or nearly normal scores. The SF-36 physical and mental component summary scores were at higher levels than those of the patients' age- and sex-matched populations. Objectively, nearly 90% had normal or nearly normal Lachman and pivot shift test scores. The KT-1000 arthrometer testing at 30 pounds and maximum manual both demonstrated an average increased anterior translation of 1.5 mm compared with the contralateral knee. Joint space narrowing of the transplanted compartments was not significantly different from that of the contralateral knee.

CONCLUSIONS

Meniscal transplantation with anterior cruciate ligament reconstruction can be a beneficial procedure in properly selected patients with either chronic anterior cruciate ligament insufficiency or failed anterior cruciate ligament surgery. Restoration of meniscal function may provide protection for the articular cartilage and improve joint stability.

Biomechanics of passive knee joint in drawer: load transmission in intact and ACL-deficient joints

A non-linear 3D finite element model of the passive human tibiofemoral knee joint consisting of two bony structures and their articular cartilage layers, menisci, and four principal ligaments was used to investigate the detailed response of the unconstrained joint under up to 100 N posterior femoral force at different flexion angles from 0 to 90 degrees. The analysis was repeated after the transection of the anterior cruciate ligament (ACL). The boundary conditions were selected to assure a stable and unconstrained response of the joint throughout the range of motion. The results indicated the ACL as the primary structure to resist the drawer load throughout the range of flexion considered and that the joint primary and coupled laxities substantially increased in its absence. At full extension under drawer, forces in collateral ligaments increased significantly resulting in larger overall contact forces as the ACL was transected. In the ACL-deficient joint, such large forces in collateral ligaments, however, diminished as flexion angle varied from 0 to 90 degrees. At full extension or flexion angles up to approximately 30 degrees, the medial meniscus and adjacent medial tibial and femoral cartilage layers were subjected to substantially larger loads and stresses following the transection of the ACL. Adequate consideration of such couplings is important in avoiding further damage to joint structures subsequent to an injury and restoring adequate function following injuries to primary components.

Meniscal tears sustained awaiting anterior cruciate ligament reconstruction

We reviewed 68 patients who underwent anterior cruciate ligament (ACL) reconstruction after initial EUA & arthroscopy in the knee unit of a United Kingdom district general hospital. Mean time between injury and ACL reconstruction surgery was 23.3 months with the incidence of meniscal tear at reconstruction being 67.6%. In this series 10.3% of patients sustained a meniscal tear in the delay period between arthroscopy and reconstruction surgery. Meniscal tear is strongly associated with ACL rupture and also a poorer outcome following reconstruction surgery. The delay in diagnosis and wait for reconstruction surgery that patients experience are potentially worsening surgical outcomes in the anterior cruciate deficient knee.

The use of sequential MR image sets for determining tibiofemoral motion: reliability of coordinate systems and accuracy of motion tracking algorithm

The use of magnetic resonance imaging has been proposed by many investigators for establishment of joint reference systems and kinematic tracking of musculoskeletal joints. In this study, the intraobserver and interobserver reliability of a strategy to establish anatomic reference systems using manually selected fiducial points were quantified for seven sets of MR images of the human knee joint. The standard error of the measurement of the intraobserver and interobserver errors were less than 2.6 degrees, and 1.2 mm for relative tibiofemoral orientation and displacement, respectively. An automated motion tracking algorithm was also validated with a controlled motion experiment in a cadaveric knee joint. The controlled displacements and rotations prescribed in our motion tracking validation were highly correlated to those predicted (Pearson's correlation = 0.99, RMS errors = 0.39 mm, 0.38 degree). Finally, the system for anatomic reference system definition and motion tracking was demonstrated with a set of MR images of in vivo passive flexion in the human knee.

Current status of meniscal transplantation

The current status of meniscal transplantation is reviewed. Results of 36 meniscal transplants carried out by the authors are also presented.

Meniscal and Chondral Loss in the Anterior Cruciate Ligament Injured Knee

Rupture of the anterior cruciate ligament (ACL) of the knee is a commonly occurring injury in the athletic population. Associated meniscal and chondral injury is well recognised. This occurs both at the time of index injury and also secondarily over time in the ACL-deficient knee as a result of several related pathways culminating in osteoarthritis. ACL reconstruction is a well established surgical technique for treatment of symptomatic instability in ACL-deficient knees but the role of ACL reconstruction in the prevention of osteoarthritis remains unclear. This article reviews the contemporary literature on the pathophysiology of chondral and meniscal loss in ACL-injured knees and the role of current treatment techniques, including surgical reconstruction of ligamentous, meniscal and chondral pathology, in altering the natural history of the ACL-deficient knee.

Topographical analysis of the structural, biochemical and dynamic biomechanical properties of cartilage in an ovine model of osteoarthritis

OBJECTIVE

The relationship between the topographical variations in the structural, biochemical and dynamic biomechanical properties of articular cartilage (AC) before and 6 months after meniscectomy has not been previously reported but is clearly relevant to our understanding of the role of mechanical factors on the pathogenesis of osteoarthritis (OA). The objective of this study was to address this deficiency using an ovine model of OA induced by bilateral lateral meniscectomy.

DESIGN

The dynamic effective shear modulus (G*) and phase lag were determined ex vivo at 26 individual locations over the medial and lateral tibial plateaux of non-operated and meniscectomized ovine joints 6 months after surgery using a novel hand-held dynamic indentation probe. AC thickness was measured with a needle penetration probe. The AC from the same topographical locations as indented was then analysed for sulfated glycosaminoglycans (S-GAG) as a measure of proteoglycan (PG) levels, collagen and water content. Histological evaluation of the collagen organization using quantitative analysis of birefringence intensity was performed on stained tissue sections from the same topographical locations of each animal.

RESULTS

It was demonstrated that the AC of the entire lateral tibial compartment of the meniscectomized joints underwent significant local degenerative and compensatory changes as indicated by a decreased G* and an increase in phase lag and water content. This was accompanied by a decrease in PG content of the AC of the middle and inner regions. While the AC of the outer region of the lateral meniscectomized compartment showed a marked increase in PG content and a more than two-fold increase in thickness, these tissues were also found to be structurally inferior, as indicated by a decreased G* and abnormal collagen birefringence intensity. The AC thickness was elevated at all locations of the lateral and medial tibial plateau of the meniscectomized joints. Strong and significant correlations between the biomechanical and biochemical data were established for a number of the parameters examined, especially between collagen content and G*, collagen content and AC thickness, and G* and AC thickness. An inverse correlation between S-GAG content and G* was only apparent in non-operated control tissues, whereas correlations between collagen and water content, water content and G*, and water content and thickness were evident for AC of the meniscectomized tibial plateaux. Less striking changes were noted in the medial compartment where the intact meniscus remained in place. However, elevated PG content, thicker AC together with slight changes in G* suggested an early hypertrophic response in these tissues.

CONCLUSION

This study has highlighted the variable response of AC in different topographical regions of meniscectomized joints to the altered mechanical stresses introduced by this surgical procedure. The AC at the joint margins, while thicker and richer in PG, was found to be biomechanically softer (lower shear modulus) than normal AC, and because of this, would be expected to undergo degenerative changes with time leading to the onset of OA.

Approach to meniscal tears in anterior cruciate ligament reconstruction

It is generally accepted that meniscus repair in a knee with persistent anterior cruciate ligament (ACL) insufficiency leads to a higher retear rate, and that meniscal repair in conjunction with ACL reconstruction is associated with a higher rate of meniscal healing compared with patients who do not undergo ACL reconstruction. In this article, we will review the background of thses concepts and present treatment strtegies for meniscal tears in ACL-insufficient knees, with particular attention to meniscal repair and meniscal allograft transplanatation.

Revision anterior cruciate ligament reconstruction

Revision ACL surgery is indicated in patients who present with pathologic anterior laxity on clinical examination that reproduces their symptoms of instability during activities of daily living or athletic activities. The goals of the revision ACL surgery are to stabilize the knee, prevent further injury to the articular cartilage and menisci, and maximize the patient's function. Successful revision ACL surgery requires a thorough preoperative evaluation, including a detailed history, physical examination, and radiographic evaluation. Preoperative planning begins with a determination of the mechanisms of failure for the initial ACL reconstruction. Often a primary, as well as secondary cause, for failure can be identified. The determination of the cause of failure is the first step in a carefully-constructed treatment plan, which includes consideration of skin incisions to be used, method of graft removal, hardware removal, the need for a staged procedure or concomitant surgery, graft material selection, tunnel placement, graft fixation, and postoperative rehabilitation protocol. Despite the most meticulous planning, unanticipated findings may be encountered in the operating room, and the preoperative plan should have enough flexibility to accommodate these developments. Finally, it is crucial to counsel the patient preoperatively to limit his or her expectations regarding their surgical outcome. Given the complexity of revision ACL reconstruction, patient expectations must be adjusted to realistically match the potential for success. With proper planning, attention to detail, and appropriate patient expectations, revision ACL surgery can result in a beneficial and satisfying patient outcome.

Effects of meniscal and articular surface status on knee stability, function, and symptoms after anterior cruciate ligament reconstruction: a long-term prospective study

BACKGROUND

Concomitant injuries to secondary structures have been proposed as a major cause of failure of anterior cruciate ligament reconstruction.

PURPOSE

Our purpose was to determine the relationship between meniscal status at the time of anterior cruciate ligament reconstruction and ultimate long-term function and stability.

STUDY DESIGN

Prospective cohort study.

METHODS

We prospectively studied 63 patients for an average of 10.4 years after arthroscopically assisted bone-patellar tendon-bone anterior cruciate reconstruction. All surgeries were performed between 1988 and 1991; concomitant meniscal surgery was performed if necessary. Subjects were divided into subgroups relative to the integrity of their menisci at the end of the reconstruction procedure (intact meniscus, partial meniscectomy, complete meniscectomy).

RESULTS

Patients who had undergone any degree of meniscal resection reported significantly more subjective complaints and activity limitations than those with intact menisci. Subjective International Knee Documentation Committee and Lysholm scores were lower in the meniscectomy subgroups than in the meniscus-intact group. Objective testing revealed a significantly lower ability to perform the single-legged hop in the meniscectomy subgroups. Ligament stability based on instrumented laxity measurements was not significantly different between the subgroups. Radiographic abnormalities were also more common in the subgroups that had undergone meniscectomy.

CONCLUSIONS

The menisci should be repaired if at all possible, especially in the setting of anterior cruciate ligament reconstruction, for optimal functional outcome and patient satisfaction.

Associated injuries in pediatric and adolescent anterior cruciate ligament tears: does a delay in treatment increase the risk of meniscal tear?

PURPOSE

To evaluate the incidence of associated injuries and meniscal tears in children and adolescents with anterior cruciate ligament (ACL) tears, we performed a retrospective review of patients, age 14 and younger, who were treated surgically at our institution.

TYPE OF STUDY

Retrospective review.

METHODS

We reviewed 39 patients (30 girls, 9 boys) with an average age of 13.6 years (range, 10 to 14 years) who underwent surgical treatment of the ACL; 24 right knees and 15 left knees were treated. Of the injuries treated, 24 occurred by a twisting mechanism, 10 were the result of contact, and 5 occurred from hyperextension. Thirty-five injuries occurred during sports activities, and 2 were sustained in motor vehicle accidents. The mean duration from injury to operative treatment was 101 days (range, 7 to 696 days). Injuries were classified as acute (n = 17) if surgery was performed within 6 weeks of injury and chronic (n = 22) if surgery was performed after 6 weeks from injury. Relationships between medial and lateral meniscal injuries and the time from injury to surgery were analyzed, and the 2 groups, acute and chronic, were compared. Finally, the patterns of meniscal injury were compared.

RESULTS

Twenty-six patients had associated injuries (10 medial meniscal tears, 15 lateral meniscal tears, 3 medial collateral ligament tears, and 1 fractured femur). The association between medial meniscal tears and time from injury to surgery was highly statistically significant (P =.0223). There was no statistical significance between the incidence of lateral meniscal tears and time. Medial meniscal tears were more common in the chronic group (36%) than in the acute group (11%), whereas lateral meniscal tears were found with equal frequency. Medial meniscal tears that required surgical treatment (either partial excision or repair) were more common in the chronic group, and lateral meniscal tear patterns were equally distributed.

CONCLUSIONS

Evidence from this study supports the contention that associated injuries are common in young individuals with ACL tears. Furthermore, the data also show that a delay in surgical treatment was associated with a higher incidence of medial meniscal tears.

Soft tissue allografts for knee reconstruction in sports medicine

Soft tissue allografts are an important substitute tissue for the reconstruction of deficient ligaments, torn menisci, and osteochondral defects during knee surgery. Interest in allografts for soft tissue reconstruction has arisen from the demand to obtain a stable knee with restoration of function and protection against additional injury. Use of allografts for soft tissue reconstruction is associated with less donor tissue site morbidity and reduced surgical time. Nevertheless, use of allografts has a potential for disease transmission, delayed graft incorporation, and host versus donor immunologic response to the graft. Experimental studies and animal models have provided information about the biologic aspects of graft incorporation and remodeling and have contributed to the development of methods of graft preparation and transplantation. Clinical studies of allograft transplantation in humans have helped to define surgical indications and techniques and have allowed for the assessment of clinical outcome. The current authors review the current literature concerning the basic and clinical principles of soft tissue allografts for knee reconstruction, and underscore the scientific basis for the clinical application of allograft tissue during knee surgery.

Biomechanical properties under cyclic loading of seven meniscus repair techniques

The purpose of the current study was to obtain additional information about the biomechanical behavior of different fixation techniques for meniscus repair using recently developed biodegradable implants and suture repair techniques. The posterior horns of human menisci were used to investigate the meniscus repair construct of the Arrow, Screw, Stinger, Fastener, T-fix, and horizontal and vertical mattress suture. A 20 mm-longitudinal incision was made in the meniscus, similar to a bucket handle lesion, 3 mm from the meniscosynovial rim and was repaired. One hundred cycles between 5 N and 15 N were done using a tension load machine with a loading rate of 10 N/second. The stiffness, displacement, and pullout strength were examined. The significantly highest stiffness was found for the vertical mattress suture (17.1 N/mm) and Stinger (15 N/mm) followed by the Arrow (13.7 N/mm), T-fix (10.5 N/mm), and horizontal mattress suture (10 N/mm). Superior load to failure was obtained for the suture repair in comparison with the biodegradable implants. Despite the lower pullout strength of biodegradable implants, similar stiffnesses were found for the Stinger and Arrow in comparison with the mattress suture technique. These techniques provide the most rigid fixation that is essential for tissue healing.

Meniscal injury: I. Basic science and evaluation

The patient with meniscal injury may present with pain, swelling, or mechanical symptoms and often requires surgical intervention for symptom resolution. Treatment of such injuries relies on understanding the gross and microanatomic features of the meniscus that are important in maintaining meniscal function. The ability of the meniscus to participate in load bearing, shock absorption, joint lubrication, and joint stability depends on the maintenance of its structural integrity. The diagnosis of meniscal injury often can be made by clinical evaluation utilizing the history, physical examination, and plain radiographs. Magnetic resonance imaging can be useful in confirming the diagnosis when clinical findings are inconclusive. Treatment depends on tear pattern, vascularity, and an assessment of tissue quality. Surgical decision making for the treatment of meniscal injury is based on patient factors and understanding of the meniscal structure, function, and pathology.

The future of anterior cruciate ligament surgery

Future anterior cruciate ligament surgery techniques will evolve from emphasizing the technical factors involved in successful ligament reconstruction to emphasizing the biomechanical, neuromuscular, and biologic factors, which will enhance healing. Advances in computer and robotic technology will help the surgeon perform anterior cruciate ligament reconstruction. The importance of the anterior cruciate ligament and its relationship with other anatomic and neuromuscular structures of the knee has been well researched over the past decade; the next decade will combine this knowledge with technological and biological advancements.

Dynamic knee stability: current theory and implications for clinicians and scientists

We will discuss the mechanisms by which dynamic knee stability may be achieved and relate this to issues that interest clinicians and scientists concerned with dynamic knee stability. Emphasis is placed on the neurophysiologic evidence and theory related to neuromuscular control. Specific topics discussed include the ensemble firing of peripheral mechanoreceptors, the potential for muscle stiffness modulation via force and length feedback, postural control synergies, motor programs, and the neural control of gait. Factors related to answering the difficult question of whether or not knee ligament injuries can be prevented during athletic activities are discussed. Prevention programs that train athletes to perform their sport skills in a safe fashion are put forth as the most promising prospect for injury prevention. Methods of assessing neuromuscular function are reviewed critically and the need for future research in this area is emphasized. We conclude with a brief review of the literature regarding neuromuscular training programs.

Medial and lateral meniscal tear patterns in anterior cruciate ligament-deficient knees. A prospective analysis of 575 tears

We used our database to evaluate the locations of meniscal tears associated with anterior cruciate ligament injuries. Five hundred seventy-five meniscal tears were seen in 476 patients. Each tear was categorized prospectively according to the side (medial/lateral), the radial zone of the tear, and the circumferential zone of the tear. The different tear locations were then compared for the medial and lateral menisci and evaluated for statistical significance. We found a nearly equal number of tears on the medial (305) and lateral (270) sides. A significantly greater number of tears on the medial side as compared with the lateral side were posterior (99.4% versus 87.8%) and peripheral (75.4% versus 44.1%). Peripheral posterior horn tears of the medial meniscus were the most common type of tear (230 of 575, 40%) by a statistically significant amount.

In-situ force in the medial and lateral structures of intact and ACL-deficient knees

The anterior cruciate ligament (ACL) is the major contributor to limit excessive anterior tibial translation (ATT) when the knee is subjected to an anterior tibial load. However, the importance of the medial and lateral structures of the knee can also play a significant role in resisting anterior tibial loads, especially in the event of an ACL injury. Therefore, the objective of this study was to determine quantitatively the increase in the in-situ forces in the medial collateral ligament (MCL) and posterolateral structures (PLS) of the knee associated with ACL deficiency. Eight fresh-frozen cadaveric human knees were subjected to a 134-N anterior tibial load at full extension and at 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. The resulting 5 degrees of freedom kinematics were measured for the intact and the ACL-deficient knees. A robotic/universal force-moment sensor testing system was used for this purpose, as well as to determine the in-situ force in the MCL and PLS in the intact and ACL-deficient knees. For the intact knee, the in-situ forces in both the MCL and PLS were less than 20 N for all five flexion angles tested. But in the ACL-deficient knee, the in-situ forces in the MCL and PLS, respectively, were approximately two and five times as large as those in the intact knee (P < 0.05). The results of this study demonstrate that, although both the MCL and PLS play only a minor role in resisting anterior tibial loads in the intact knee, they become significant after ACL injury.

The biomechanical interdependence between the anterior cruciate ligament replacement graft and the medial meniscus

To establish a quantitative biomechanical relationship between the anterior cruciate ligament graft and the medial meniscus, 10 human cadaveric knees were examined using the robotic/universal force-moment sensor testing system. In response to a combined 134-N anterior and 200-N axial compressive tibial load, the resulting kinematics of the knee and the in situ forces in the anterior cruciate ligament, the anterior cruciate ligament graft, and the medial meniscus were measured. Anterior tibial translation significantly increased after anterior cruciate ligament transection, between 6.8 +/- 2.3 mm at full extension and 12.6 +/- 3.3 mm at 30 degrees of flexion. Consequently, the resultant forces on the medial meniscus, ranging from 52 +/- 30 N to 63 +/- 51 N between full extension and 90 degrees of knee flexion in the intact knee, were doubled as a result of anterior cruciate ligament deficiency. However, after anterior cruciate ligament reconstruction, anterior tibial translations were restored to the levels of the intact knee, and thus the forces on the medial meniscus were restored as well. Likewise, the in situ forces in the anterior cruciate ligament replacement graft increased between 33% and 50% after medial meniscectomy.

Meniscal allografts--where do we stand?

Meniscal transplantation has been recommended for selected meniscus-deficient patients in an effort to forestall progressive joint degeneration. Meniscal allograft transplantation may be considered for patients with symptoms (pain and swelling) due to meniscal deficiency in an effort to prevent progressive articular cartilage degeneration. Medial meniscal transplantation may also be considered during concomitant anterior cruciate ligament reconstruction, since absence of the medial meniscus results in increased forces in the anterior cruciate ligament graft. Contraindications for meniscal transplantation include advanced articular cartilage degeneration (especially on the flexion weightbearing zone of the condyle), axial malalignment, and flattening of the femoral condyle. Patient evaluation should include standing, long-leg radiographs for assessment of the mechanical axis and magnetic resonance imaging with appropriate pulse sequences for evaluation of hyaline cartilage thickness. Fresh-frozen and cryopreserved allografts are currently the most commonly used transplantation materials. Appropriate graft sizing is critical; most tissue banks size the meniscus based on radiographic tibial plateau measurements. Early results of meniscal transplantation indicate predictable improvements in pain, swelling, and knee function; however, no long-term results are available. Poor results have been reported in patients with advanced cartilage degeneration. Objective evaluations often demonstrate some degree of degeneration of the posterior horn of the transplant. Earlier transplantation should be considered for patients with known meniscal deficiency.