Treatment of the medial collateral ligament injury. I: The importance of anterior cruciate ligament on the varus-valgus knee laxity

Comparison of side-cutting maneuvers versus low impact baseball swing on knee ligament loading in adolescent populations

BACKGROUND

High impact sports are associated with an increased incidence rate for knee ligament injuries, specifically pertaining to the anterior cruciate ligament and medial collateral ligament. What is less clear is (i) the extent to which high impact activities preferentially load the anterior cruciate ligament versus the medial collateral ligament, and (ii) whether both ligaments experience similar stretch ratios during high loading scenarios. Therefore, the goal of this project was to assess how different loading conditions experienced through more at-risk sporting maneuvers influence the relative displacements of the anterior cruciate ligament and medial collateral ligament. The focus of the study was on adolescent patients - a group that has largely been overlooked when studying knee ligament biomechanics.

METHODS

Through kinetic knee data obtained through motion capture experimentation, two different loading conditions (high vs low impact) were applied to 22 specimen-specific adolescent finite element knee models to investigate the biomechanical impact various sporting maneuvers place on the knee ligaments.

FINDINGS

The high impact side cutting maneuver resulted in 102% and 47% increases in ligament displacement compared to the low impact baseball swing (p < 0.05) for both the anterior cruciate ligament and medial collateral ligament.

INTERPRETATION

Quantifying biomechanical risks that sporting activities place on adolescent subjects provides physicians with insight into knee ligament vulnerability. More specifically, knowing the risks that various sports place on ligaments helps guide the selection of sports for at-risk patients (especially those who have undergone knee ligament surgery).

Treating Combined Anterior Cruciate Ligament and Medial Collateral Ligament Injuries Operatively in the Acute Setting Is Potentially Advantageous

Combined injury of the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) remains among the most common knee injury patterns in orthopaedics. Optimal treatment of grade III MCL injuries is still debated, especially when combined with ACL injury. Most patients with these severe injuries are treated conservatively for at least 6 weeks to allow for MCL healing, followed by delayed ACL reconstruction. Although acute treatment of the MCL was common in the 1970s, postoperative stiffness was frequently reported. Moreover, studies of such treatment failed to show clinical benefits of surgical over conservative treatment, and the MCL exhibited intrinsic healing capacity, leading to the consensus that all MCL injuries are treated conservatively. The current delayed treatment algorithm for ACL-MCL injuries has several disadvantages. First, MCL healing may be incomplete, resulting in residual valgus laxity that places the ACL graft at greater risk of failure. Second, delayed treatment lengthens the overall rehabilitation period, thereby prolonging the presence of atrophy and delaying return to preinjury activity levels. Third, the initial healing period leaves the knee unstable for longer and risks further intra-articular damage. Acute simultaneous surgical treatment of both ligaments has the potential to avoid these shortcomings. This article will review the evolution of treatment of ACL-MCL injuries and explain how it shifted toward the current treatment algorithm. We will (1) discuss why the consensus shifted, (2) discuss the shortcomings of the current treatment plan, (3) discuss the potential advantages of acute simultaneous treatment, and (4) present an overview of the available literature.

The management of combined ACL and MCL injuries: A systematic review

Background

The management of combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injuries remains contentious. Clinical outcomes of surgical, conservative, and combined approaches have been described in a range of prospective and retrospective studies. The aim of the current systematic review was to evaluate these outcomes and assess the study methodologies.

Methods

A comprehensive literature search of the following databases was performed: PubMed, OVID, Cochrane Database of Systematic Reviews and Google Scholar. Studies were assessed using the Coleman Methodology Score.

Results

52 articles were included (3 randomised controlled trials, 8 prospective comparative studies, 17 retrospective comparative studies and 24 case series). Outcome measures were heterogeneous amongst articles. The most common outcomes assessed were AP laxity, Lysholm score and medial/valgus laxity. Complications at varying follow-up times with differing grades of MCL injury were reported in 25 (48%) studies. Evidence was conflicting, with no consensus from the available published literature regarding the best method of treatment for a combined ACL and MCL injury.

Conclusions

Heterogeneous outcome measures and limited randomised controlled trials prevent advocacy of a single treatment option. Good outcomes have been reported from repair, reconstruction and conservative management of the MCL together with ACL reconstruction. Further prospective comparative data is required to evaluate MCL management choice and prognostic signs for successful nonsurgical MCL treatment.

Effect of Sectioning of the Anterior Cruciate Ligament and Posterolateral Structures on Lateral Compartment Gapping: A Randomized Biomechanical Study

Background:

The contribution of anterior cruciate ligament (ACL) injury to lateral instability under varus stress, particularly compared with posterolateral structures, is not well known.

Purpose:

To investigate the effect of sectioning the ACL and posterolateral knee structures on lateral compartment gapping under varus stress.

Study Design:

Controlled laboratory study.

Methods:

Fourteen nonpaired cadaveric knees were randomized to 1 of 2 groups: sequential sectioning of the ACL, fibular collateral ligament (FCL), popliteus tendon (PLT), and popliteofibular ligament (PFL) (ACL-first group) or sequential sectioning of the FCL, PLT, PFL, and ACL (FCL-first group). Knees were loaded onto a custom jig at a 20° flexion angle. A standardized 12-N·m varus moment was applied to each specimen in the intact state and after each randomized sequential-sectioning state. Lateral compartment opening was measured on radiographs to assess the contribution to the increase in the lateral gap caused by resecting the respective structure. The distance was measured by 3 observers on 15 images (5 testing states each imaged 3 times) per specimen, for a total of 210 radiographs. The articular cartilage surfaces were not included in the measurements.

Results:

The mean increase in lateral opening after sectioning all structures (ACL and posterolateral corner) was 4.6 ± 1.8 mm (range, 1.9-7.7 mm). The ACL and FCL sectioning contributed the most to lateral knee opening (1.3 ± 0.6 and 2.2 ± 1.3 mm, respectively). In both groups, lateral gapping >3 mm was achieved only after both the ACL and FCL were sectioned. All comparisons of increased mean gapping distances demonstrated a significant difference with subsequent sequential sectioning of structures, except comparisons between the FCL and PLT and the PLT and PFL. When considering the effect of the ACL on lateral opening, no significant difference was found between sectioning the ACL first or FCL first (P = .387).

Conclusion:

ACL deficiency significantly increased lateral opening under varus stress, regardless of the sequence of injury. The effect of injury to the ACL in addition to the lateral structures should be considered when using varus stress radiographs to evaluate knee injuries.

Clinical Relevance:

With the current findings, understanding the effect of ACL and posterolateral corner injuries on lateral gapping under varus stress can aid in correctly diagnosing knee injuries and determining appropriate treatment plans.

Meniscus repair with simultaneous anterior cruciate ligament reconstruction: Clinical outcomes, failure rates and subsequent processing

PURPOSE

To retrospectively analyze the clinical outcomes of meniscus repair with simultaneous anterior cruciate ligament (ACL) reconstruction and explore the causes of failure of meniscus repair.

METHODS

From May 2013 to July 2018, the clinical data of 165 patients who were treated with meniscus surgery and simultaneous ACL reconstruction, including 69 cases of meniscus repair (repair group) and 96 cases of partial meniscectomy (partial meniscectomy group) were retrospectively analyzed. The exclusion criteria were as follows: (1) ACL rupture associated with fracture, collateral ligament injury, or complex ligament injury; (2) a history of knee surgery; or (3) a significant degree of osteoarthritis. The 69 patients in the repair group were divided into the non-failure group (62 cases) and the failure group (7 cases) depending on the repair effect. Postoperative outcomes of the repair group and the partial meniscectomy group were compared. General conditions and postoperative outcomes of the failure group and the non-failure group were compared. During the median follow-up period of 28 months (range, 4 - 65 months) after the second arthroscopy, postoperative outcomes of seven patients in the failure group were summarized. SPSS 25.0 statistical software was used for statistical analysis. A p value less than 0.05 was considered statistically significant.

RESULTS

Seven patients in the failure group who underwent the second arthroscopy were followed up for (30 ± 17.4) months and their postoperative outcomes were summarized. Compared with the partial meniscectomy group, the International Knee Documentation Committee scores of patients in the repair group improved significantly (p = 0.031). Compared with the non-failure group, more patients in the failure group were younger than 24 years (p = 0.030). The median follow-up period was 39.5 months. All patients recovered well after subsequent partial meniscectomy and relieved clinical symptoms. Visual analog scale scores decreased significantly (p = 0.026), and the International Knee Documentation Committee and Lysholm scores improved significantly (p = 0.046 for both).

CONCLUSION

The failure rate of meniscus repair in this study was 10.1% (7/69), all of which were medial meniscus tears. However, the surgical outcomes of ACL reconstruction were not affected, and there might be a role for graft protection. Therefore, meniscus retears can be successful treated by performing subsequent partial meniscectomy in patients with repair failure.

Effects of and Response to Mechanical Loading on the Knee

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Bioinspired Scaffold Designs for Regenerating Musculoskeletal Tissue Interfaces

The musculoskeletal system works at a very advanced level of synchrony, where all the physiological movements of the body are systematically performed through well-organized actions of bone in conjunction with all the other musculoskeletal soft tissues, such as ligaments, tendons, muscles, and cartilage through tissue-tissue interfaces. Interfaces are structurally and compositionally complex, consisting of gradients of extracellular matrix components, cell phenotypes as well as biochemical compositions and are important in mediating load transfer between the distinct orthopedic tissues during body movement. When an injury occurs at interface, it must be re-established to restore its function and stability. Due to the structural and compositional complexity found in interfaces, it is anticipated that they presuppose a concomitant increase in the complexity of the associated regenerative engineering approaches and scaffold designs to achieve successful interface regeneration and seamless integration of the engineered orthopedic tissues. Herein, we discuss the various bioinspired scaffold designs utilized to regenerate orthopedic tissue interfaces. First, we start with discussing the structure-function relationship at the interface. We then discuss the current understanding of the mechanism underlying interface regeneration, followed by discussing the current treatment available in the clinic to treat interface injuries. Lastly, we comprehensively discuss the state-of-the-art scaffold designs utilized to regenerate orthopedic tissue interfaces.

Graft Choice for Anterior Cruciate Ligament Reconstruction With a Concomitant Non-surgically Treated Medial Collateral Ligament Injury Does Not Influence the Risk of Revision

PURPOSE

To compare the risk of anterior cruciate ligament (ACL) revision and the patient-reported outcome after ACL reconstruction with a concomitant non-surgically treated medial collateral ligament (MCL) injury with regard to 3 ACL graft choices; the use of semitendinosus (ST), the use of semitendinosus-gracilis (ST-G), and the use of patellar tendon (PT) autograft. It was hypothesized that the use of ST-G would be associated with a greater risk of ACL revision and poorer patient-reported knee function.

METHODS

Patients older than 15 years of age registered for a primary ACL reconstruction with a concomitant non-surgically treated MCL injury in the Swedish National Knee Ligament Registry were assessed for eligibility. Three groups were created according to ACL autograft choice; the ST, the ST-G, and the PT group. The primary outcomes were ACL revision and the 1- and 2-year Knee injury and Osteoarthritis Outcome Score (KOOS), including the KOOS patient acceptable symptom state (PASS). Cox regression analysis was applied to determine the proportional hazard ratio (HR) of primary ACL reconstruction survival. The KOOS was compared using the Mann-Whitney U test and Fisher exact test.

RESULTS

A total of 622 patients (mean age 29.7 years, 42.4% women) were included. There was no difference in the risk of ACL revision for either the ST group (HR 1.354; 95% confidence interval [CI] 0.678-2.702 or the PT group (HR 0.837; 95% CI 0.334-2.100), compared with the ST-G group. The ST group reported a greater mean 2-year KOOS sports and recreation (68.5, standard deviation [SD] 28.5) than the ST-G group (57.4 [SD 27.6], P = .010) and the PT group (54.1 [SD 30.3], P = .006). The ST group was superior in terms of achieving PASS in sports and recreation (55.3%; 95% CI 44.1-66.1%) compared with both the ST-G (37.4%; 95% CI 29.8-45.5%; P = .014) and the PT group (33.9%; 95% CI 22.1-47.4%; P = .009).

CONCLUSIONS

The risk of ACL revision did not differ between HT and PT autografts in patients undergoing ACL reconstruction with a non-surgically treated MCL injury. However, the use of ST-G was associated with poorer 2-year patient-reported knee function compared with the ST.

LEVEL OF EVIDENCE

Retrospective comparative trial, Level III.

Non-uniform strain distribution in anterolateral capsule of knee: Implications for surgical repair

The existence of a ligamentous structure within the anterolateral capsule, which can be injured in combination with the anterior cruciate ligament, has been debated. Therefore, the purpose of this study was to determine the magnitude and direction of the strain in the anterolateral capsule in response to external loads applied to the knee. The anterolateral capsule was hypothesized to not function like a traditional ligament. A 6-degree-of-freedom robotic testing system was used to apply ten external loads to human cadaveric knees (n = 7) in the intact and anterior cruciate ligament (ACL) deficient states. The position of strain markers was recorded on the midsubstance of the anterolateral capsule during the resulting joint kinematics to determine the magnitude and direction of the maximum principal strain. The peak maximum principal strain ranged from 22% to 52% depending on the loading condition. When histograms of strain magnitude values were analyzed to determine strain uniformity, the mean kurtosis was 1.296 ± 0.955, lower than a typical ligament, and the mean variance was 0.015 ± 0.008, higher than a typical ligament. The mean angles of the strain direction vectors compared to the proposed ligament ranged between 38° and 130° (p < 0.05). The magnitude of the maximum principal strain in the anterolateral capsule is much larger than a typical ligament and does not demonstrate a uniform strain distribution. The direction of strain is also not aligned with the proposed ligament. Clinical Significance: Reconstruction methods using tendons will not produce normal joint function due to replacement of a multi-axial structure with a uni-axial structure. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Combined Anterior Cruciate Ligament and Medial Collateral Ligament Knee Injuries: Anatomy, Diagnosis, Management Recommendations, and Return to Sport

PURPOSE OF REVIEW

The diagnosis and management of combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injuries have been a controversial topic for several decades. No single approach has proven optimal for treatment and there is no consensus between most specialists. This review seeks to describe and clarify the current state and the future of management.

RECENT FINDINGS

Most authors agree on reconstructing of the ACL with non-operative management of the MCL in grade I and II injuries, respectively. However, controversy still exists about the optimal method of treating a combined ACL with higher grade MCL injuries. Management should be customized based on acuity, injury grade, and specific goals for each patient. Future research with clinical outcomes may facilitate creating guidelines to optimize recovery.

Increased risk of ACL revision with non-surgical treatment of a concomitant medial collateral ligament injury: a study on 19,457 patients from the Swedish National Knee Ligament Registry

PURPOSE

To determine how concomitant medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries affect outcome after anterior cruciate ligament (ACL) reconstruction.

METHODS

Patients aged > 15 years who were registered in the Swedish National Knee Ligament Registry for primary ACL reconstruction between 2005 and 2016 were eligible for inclusion. Patients with a concomitant MCL or LCL injury were stratified according to collateral ligament treatment (non-surgical, repair or reconstruction), and one isolated ACL reconstruction group was created. The outcomes were ACL revision and the 2-year Knee Injury and Osteoarthritis Outcome Score (KOOS), which were analyzed using univariable and multivariable Cox regression and an analysis of covariance, respectively.

RESULTS

A total of 19,457 patients (mean age 27.9 years, 59.4% males) met the inclusion criteria. An isolated ACL reconstruction implied a lower risk of ACL revision compared with presence of a non-surgically treated MCL injury (HR = 0.61 [95% CI 0.41-0.89], p = 0.0097) but not compared with MCL repair or reconstruction. A concomitant LCL injury did not impact the risk of ACL revision. Patients with a concomitant MCL or LCL injury reported inferior 2-year KOOS compared with isolated ACL reconstruction. The largest difference was found in the sports and recreation subscale across all groups, with MCL reconstruction resulting in the maximum difference (14.1 points [95% CI 4.3-23.9], p = 0.005).

CONCLUSION

Non-surgical treatment of a concomitant MCL injury in the setting of an ACL reconstruction may increase the risk of ACL revision. However, surgical treatment of the MCL injury was associated with a worse two-year patient-reported knee function. A concomitant LCL injury does not impact the risk of ACL revision compared with an isolated ACL reconstruction.

LEVEL OF EVIDENCE

Cohort study, Level III.

Medial collateral ligament reconstruction is necessary to restore anterior stability with anterior cruciate and medial collateral ligament injury

PURPOSE

The purpose of this study was to compare knee kinematics and graft forces in anterior cruciate ligament (ACL) reconstruction combined with one of two superficial medial collateral ligament (sMCL) reconstruction techniques (parallel or triangular vector sMCL reconstruction).

METHODS

Twenty porcine knees were divided into two groups (n = 20), parallel or triangular vector sMCL reconstruction, with both groups having anatomic single-bundle ACL reconstruction. The knees were tested under (1) an 89-N anterior tibial load, (2) 4 Nm internal and external rotational tibial torques, and (3) a 7 Nm valgus torque.

RESULTS

With ACL/sMCL co-injuries, single-bundle ACL reconstruction alone does not restore anterior, valgus, and internal stability. Triangular vector sMCL reconstruction better restored anterior stability, and parallel sMCL reconstruction better restored valgus stability.

CONCLUSION

This study showed that single-bundle ACL reconstruction alone was not able to restore anterior tibial translation, valgus rotation, and external rotation of the intact knee with combined ACL and sMCL injuries and sMCL reconstruction was also required. The combined ACL and parallel sMCL reconstruction better restored valgus and external rotation stability, while the combined ACL and triangular vector method better restored anterior tibial translation. With combined ACL and severe sMCL injury, both ligaments should be reconstructed. The two sMCL reconstruction techniques exhibited slightly different kinematics and graft force; however, there was not enough difference to recommend one over the other.

Varus-valgus instability in the anterior cruciate ligament-deficient knee: effect of posterior tibial load

Background

Anterior cruciate ligament (ACL) injury is often accompanied with medial collateral ligament (MCL) injury. Assessment of varus-valgus (V-V) instability in the ACL-deficient knee is crucial for the management of the concomitant ACL-collateral ligaments injury. We evaluated the V-V laxity and investigated the effect of additional posterior tibial load on the laxity in the ACL-deficient knee. Our hypothesis was that the V-V laxity in the ACL-deficient knee was greater than that in the intact knee and attenuated by additional posterior tibial load.

Methods

Eight fresh-frozen porcine knees were used, and a 6°-of-freedom (DOF) robotic system was utilized. A 5 Nm of V-V torque was applied to the intact knee, the ACL-deficient knee, and the ACL-deficient knee with 30 N of constant posterior tibial load, at 30° and 60° of flexion. Then, the 3D path in the intact knee was reproduced on the ACL-deficient knee. The total V-V angle under 5 Nm of V-V torque was assessed and compared among the three statuses. The in situ forces of the ACL under 5 Nm of varus and valgus torques, respectively, were also calculated.

Results

The total V-V angle in the ACL-deficient knee under 5 Nm of V-V torque was significantly greater than that in the intact knee, whereas the angle in the ACL-deficient knee with 30 N of posterior tibial load was significantly smaller than that in the ACL-deficient knee and approached that in the intact knee, at both 30° and 60° of flexion. The in situ force of the ACL was approximately 30 N at 30° and 16 N at 60° of flexion under 5 Nm of both varus and valgus torques.

Conclusions

The V-V laxity in the isolated ACL-deficient knee was greater than that in the intact knee. The increased laxity was attenuated and approached that in the intact knee by adding posterior tibial load. Application of posterior tibial load is necessary for accurate assessment of V-V instability in the ACL-deficient knee. Clinically, the V-V laxity in the combined ACL-MCL or ACL-LCL injured knee may be overestimated without posterior tibial load.

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.

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.

Deconstructing the Anterior Cruciate Ligament: What We Know and Do Not Know About Function, Material Properties, and Injury Mechanics

Anterior cruciate ligament (ACL) injury is a common and potentially catastrophic knee joint injury, afflicting a large number of males and particularly females annually. Apart from the obvious acute injury events, it also presents with significant long-term morbidities, in which osteoarthritis (OA) is a frequent and debilitative outcome. With these facts in mind, a vast amount of research has been undertaken over the past five decades geared toward characterizing the structural and mechanical behaviors of the native ACL tissue under various external load applications. While these efforts have afforded important insights, both in terms of understanding treating and rehabilitating ACL injuries; injury rates, their well-established sex-based disparity, and long-term sequelae have endured. In reviewing the expanse of literature conducted to date in this area, this paper identifies important knowledge gaps that contribute directly to this long-standing clinical dilemma. In particular, the following limitations remain. First, minimal data exist that accurately describe native ACL mechanics under the extreme loading rates synonymous with actual injury. Second, current ACL mechanical data are typically derived from isolated and oversimplified strain estimates that fail to adequately capture the true 3D mechanical response of this anatomically complex structure. Third, graft tissues commonly chosen to reconstruct the ruptured ACL are mechanically suboptimal, being overdesigned for stiffness compared to the native tissue. The net result is an increased risk of rerupture and a modified and potentially hazardous habitual joint contact profile. These major limitations appear to warrant explicit research attention moving forward in order to successfully maintain/restore optimal knee joint function and long-term life quality in a large number of otherwise healthy individuals.

Operative and nonoperative treatment options for ACL tears in the adult patient: a conceptual review

Injury to the anterior cruciate ligament (ACL) is common among athletic individuals. Both nonoperative and operative treatment options exist. The optimal treatment of an adult with an ACL tear depends on several patient-specific factors, including age, occupation, and desired activity level. In less active patients with sedentary jobs, nonoperative management, consisting of physical therapy, bracing, and activity modification can yield successful results. In active patients who want to resume participation in jumping, cutting, or pivoting sports, patients who have physically demanding occupations, or patients who fail a trial of nonoperative management, ACL reconstruction is recommended. Reconstruction utilizing autograft tissue is preferred over allograft, especially in the younger athlete, but allograft tissue is a reasonable option in the older (aged > 40 years) and less active adult, as well. Successful results have been achieved with both patellar tendon and hamstring grafts. The optimal treatment in adult patients with ACL tears should be based on careful consideration of the patient's goals for return to activity, knee-specific comorbidities, such as coexistent meniscal pathology or osteoarthritis, and his or her willingness to follow a detailed rehabilitation regimen. Our article provides an overview of current nonoperative and operative treatment options for adults with ACL tears, considers the outcomes of both nonoperative and operative strategies, and provides general recommendations as to the ideal management for a given patient.

Preventing ACL injuries in team-sport athletes: a systematic review of training interventions

The purpose of this systematic review was to assess the efficacy of training interventions aimed to prevent and to reduce anterior cruciate ligament injury (ACLI) rates in team sport players. We searched MEDLINE from January 1991 to July 2011 using the terms knee, ACL, anterior cruciate ligament, injury, prevention, training, exercise, and intervention. Nine out of 708 articles met the inclusion criteria and were independently rated by two reviewers using the McMaster Occupational Therapy Evidence-Based Practice Research Group scale. Consensus scores ranged from 3 to 8 out of 10. Seven out of nine studies demonstrated that training interventions have a preventive effect on ACLI. Collectively, the studies indicate there is moderate evidence to support the use of multifaceted training interventions, which consisted of stretching, proprioception, strength, plyometric and agility drills with additional verbal and/or visual feedback on proper landing technique to decrease the rate of ACLIs in team sport female athletes, while the paucity of data preclude any conclusions for male athletes.

Consideration of growth factors and bio-scaffolds for treatment of combined grade II MCL and ACL injury

The literature suggests that a Grade II medial collateral ligament (MCL) injury in combination with anterior cruciate ligament (ACL) injury will heal naturally and not compromise patient outcome following ACL reconstruction. Evidence based on bone-patella tendon-bone autograft use is stronger than evidence supporting anatomically placed soft tissue graft use. Current ACL reconstruction practices make greater use of soft tissue grafts, differing fixation methods, and anatomically lower placement on the inner wall of the lateral femoral condyle. Anatomical graft placement aligns the femoral bone tunnel more directly with valgus knee loading forces. Differences in the soft tissue graft-bone tunnel integration and ligamentization timetable following ACL reconstruction also increase concerns regarding residual Grade II MCL laxity and functional deficiency during accelerated functional rehabilitation. MCL dysfunction may increase susceptibility to early ACL graft slippage, elongation, outright failure, and medial femoral condyle lift-off with valgus knee loading. This concept paper discusses the potential role of growth factors and bio-scaffolds for improving Grade II MCL injury healing and mechanical integrity when the injury occurs in combination with an ACL injury that is reconstructed with a soft tissue graft and an anatomical surgical approach.

Surgical technique: does mini-invasive medial collateral ligament and posterior oblique ligament repair restore knee stability in combined chronic medial and ACL injuries?

BACKGROUND

Residual laxity remains after ACL reconstruction in patients with combined chronic ACL and medial instability. The question arises whether to correct medial capsular and ligament injuries when Grade II and III medial laxity is present.

DESCRIPTION OF TECHNIQUE

We developed a mini-invasive medial ligament plasty to repair the medial collateral ligament to correct residual medial valgus and rotatory laxity after ACL reconstruction.

PATIENTS AND METHODS

We prospectively followed 36 patients with an ACL deficiency combined with chronic Grade II or III valgus and rotatory medial instability. The mean age was 37 years (range, 15-70 years). For all patients, we obtained preoperative and postoperative Knee Injury and Osteoarthritis Outcome, International Knee Documentation Committee, Lysholm, and Tegner Activity Level Scores. The minimum followup was 2 years (median, 3 years; range, 2-7 years).

RESULTS

The mean subjective International Knee Documentation Committee score improved from 36 preoperatively to 94 at the last followup. While all patients had an International Knee Documentation Committee score of Grade C or D preoperatively, no patient did postoperatively. The mean Knee Injury and Osteoarthritis Outcome Score improved from 45 preoperatively to 93 postoperatively. Valgus and external rotatory tests were negative in all patients. The mean Tegner activity level decreased from 7 preinjury to 6 postoperatively, and the mean Lysholm score improved from 40 preoperatively to 93 at last followup.

CONCLUSIONS

This simple technique restored medial stability and knee function to normal or nearly normal in all patients.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Surgical management of grade 3 medial knee injuries combined with cruciate ligament injuries

PURPOSE

Although various surgical procedures have attempted to restore valgus stability in medial knee injuries, so far none has achieved satisfactory results. The purpose of this study was to assess clinical outcome for patients with grade 3 valgus instability who were treated according to our surgical management strategy.

METHODS

Eighteen patients with both acute and chronic grade 3 medial knee injuries, all of which had combined cruciate ligament injuries, were treated with a proximal advancement of both the superficial medial collateral ligament (MCL) and posterior oblique ligament together with underlying deep MCL and joint capsule, in conjunction with cruciate ligament reconstructions in chronic phase. Augmentation with doubled semitendinosus tendon was added in 7 patients whose medial knee stability had been considered to be insufficient with only the proximal advancement procedure. They were evaluated preoperatively and at final follow-up.

RESULTS

Manual valgus laxities at 0° and 30°, as well as side-to-side difference in medial joint opening in stress radiograph, were significantly improved at final follow-up. The Lysholm knee scale was also significantly improved. Median values of the subjective evaluations of the patients' satisfaction, stability and sports performance level measured with visual analogue scale at final follow-up were 82 (60-100), 94 (71-100) and 88 (60-100), respectively.

CONCLUSIONS

Clinical outcomes of our surgical management strategy were reasonable in terms of restoring medial knee stability. This treatment protocol can help determine the surgical management of grade 3 medial knee injuries combined with cruciate ligament injuries.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Suture augmentation following ACL injury to restore the function of the ACL, MCL, and medial meniscus in the goat stifle joint

Functional tissue engineering (FTE) approaches have shown promise in healing an injured anterior cruciate ligament (ACL) of the knee. Nevertheless, additional mechanical augmentation is needed to maintain joint stability and appropriate loading of the joint while the ACL heals. The objective of this study was to quantitatively evaluate how mechanical augmentation using sutures restores the joint kinematics as well as the distribution of loading among the ACL, medial collateral ligament, and medial meniscus (MM) in response to externally applied loads. Eight goat stifle joints were tested on a robotic/universal force-moment sensor testing system under two loading conditions: (1) a 67N anterior tibial load (ATL) and (2) a 67N ATL with 100N axial compression. For each joint, four experimental conditions were tested at 30°, 60°, and 90° of flexion: the (1) intact and (2) ACL-deficient joint, as well as following (3) suture repair of the transected ACL, and (4) augmentation using sutures passed from the femur to the tibia. Under the 67N ATL, suture augmentation could restore the anterior tibial translation (ATT) to within 3mm of the intact joint (p>0.05), representing a 54-76% improvement over suture repair (p<0.05). With the additional axial compression, the ATT and in-situ forces of the sutures following suture augmentation remained 2-3 times closer to normal (p<0.05). Also, the in-situ forces in the MM were 58-73% lower (p<0.05). Thus, suture augmentation may be helpful in combination with FTE approaches for ACL healing by providing the needed initial joint stability while lowering the loads on the MM.

Application of robotic technology in biomechanics to study joint laxity

PRIMARY OBJECTIVE

To evaluate whether in vitro joint testing using a robot with six degrees of freedom is useful for evaluating changes in joint laxity as a result of chronic osteoarthritis (OA).

RESEARCH DESIGN

Repeated measures.

METHODS

Broyden's method of solving nonlinear systems of equations drove a hybrid method of load and position robotic control. Sheep stifles (knee joints) were loaded between 3 Nm of internal load through to 3 Nm of external load in 1 Nm increments. Kinematic and morphologic data from five healthy ovine stifles were compared to the chronic OA effects in four surgically destabilized stifles.

RESULTS

Stifles with chronic OA showed increases in stiffness while range of motion decreased. Gross morphologic changes included osteophytes and cartilage fibrillation.

DISCUSSION

Robotic testing proved useful for evaluating changes in joint mechanics as a result of chronic OA. We observed morphological changes and associated increases in joint stiffness and decreased laxity.

Osteochondral microdamage from valgus bending of the human knee

BACKGROUND

Valgus bending of the knee is promoted as an anterior cruciate ligament injury mechanism and is associated with a characteristic "footprint" of bone bruising. The hypothesis of this study was that during ligamentous failure caused by valgus bending of the knee, high tibiofemoral contact pressures induce acute osteochondral microdamage.

METHODS

Four knee pairs were loaded in valgus bending until gross injury with or without a tibiofemoral compression pre-load. The peak valgus moment and resultant motions of the knee joint were recorded. Pressure sensitive film documented the magnitude and location of tibiofemoral contact. Cartilage fissures were documented on the tibial plateau, and microcracks in subchondral bone were documented from micro-computed tomography scans.

FINDINGS

Injuries were to the anterior cruciate ligament in three knees and the medial collateral ligament in seven knees. The mean (standard deviation) peak bending moment at failure was 107 (64)Nm. Valgus bending produced regions of contact on the lateral tibial plateau with average maximum pressures of approximately 30 (8)MPa. Cartilage fissures and subchondral bone microcracks were observed in these regions of high contact pressure.

INTERPRETATION

Combined valgus bending and tibiofemoral compression produce slightly higher contact pressures, but do not alter the gross injury pattern from isolated valgus bending experiments. Athletes who sustain a severe valgus knee bending moment, may be at risk of acute osteochondral damage especially if the loading mechanism occurs with a significant tibiofemoral compression component.

Operative management of the medial collateral ligament in the multi-ligament injured knee: an evidence-based systematic review

While it is generally accepted that most partial and isolated medial collateral ligament (MCL) injuries can be treated non-operatively, ideal treatment of the MCL in multi-ligament knee injuries remains controversial. High failure rates with repair of the posterolateral corner in the multi-ligament injured knee have been recently reported, favoring reconstruction instead. The same maybe true for MCL injuries, however evidence-based treatment recommendations are lacking in the current orthopedic literature. The purpose of this study was to perform an evidence-based systematic review of the operative management (repair and/or reconstruction) of the MCL in the setting of multi-ligament knee injuries. A comprehensive search of MEDLINE and the Cochrane databases for all relevant articles published in English from 1978 to 2008 on the outcomes of surgical management (repair and/or reconstruction) of the MCL in the setting of combined ligament injuries was performed. Inclusion criteria included articles published in (1) English, (2) on human subjects, (3) between the years of 1978 and 2008, (4) had minimum 12-month follow-up, with a mean of at least 24 months, (5) on surgical management of MCL injuries, (6) associated with multi-ligament injuries (three or more ligaments) and/or knee dislocation, and (7) reported objective outcome data on the respective patient cohorts. Exclusion criteria consisted of technique papers, case reports, studies that included fractures associated with MCL injury and those that included pediatric patients. The review identified eight relevant studies. Five articles focused on MCL repair, while three articles focused on MCL reconstruction. No prospective studies compared MCL repair or reconstruction with non-operative treatment or directly compared MCL reconstruction with MCL repair. Currently there is a paucity of objective data on the outcomes regarding surgical management of MCL tears in the combined ligament injured knee. This systematic review demonstrated satisfactory results in both repair and reconstruction groups. Future objective outcome-based studies as well as comparative studies are needed to further evaluate the optimal treatment modality before evidence-based recommendations can be made. Therefore, individual treatment decisions for each patient should be based on the characteristics and nature of the injury.

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis.

The healing of ligament and tendon injuries varies from tissue to tissue. Tendinopathies are ubiquitous and can take up to 12 months for the pain to subside before one could return to normal activity. A ruptured medial collateral ligament (MCL) can generally heal spontaneously; however, its remodeling process takes years and its biomechanical properties remain inferior when compared to the normal MCL. It is also known that a midsubstance anterior cruciate ligament (ACL) tear has limited healing capability, and reconstruction by soft tissue grafts has been regularly performed to regain knee function. However, long term follow-up studies have revealed that 20–25% of patients experience unsatisfactory results. Thus, a better understanding of the function of ligaments and tendons, together with knowledge on their healing potential, may help investigators to develop novel strategies to accelerate and improve the healing process of ligaments and tendons.

With thousands of new papers published in the last ten years that involve biomechanics of ligaments and tendons, there is an increasing appreciation of this subject area. Such attention has positively impacted clinical practice. On the other hand, biomechanical data are complex in nature, and there is a danger of misinterpreting them. Thus, in these review, we will provide the readers with a brief overview of ligaments and tendons and refer them to appropriate methodologies used to obtain their biomechanical properties. Specifically, we hope the reader will pay attention to how the properties of these tissues can be altered due to various experimental and biologic factors. Following this background material, we will present how biomechanics can be applied to gain an understanding of the mechanisms as well as clinical management of various ligament and tendon ailments. To conclude, new technology, including imaging and robotics as well as functional tissue engineering, that could form novel treatment strategies to enhance healing of ligament and tendon are presented.

Medial collateral ligament injuries and subsequent load on the anterior cruciate ligament: a biomechanical evaluation in a cadaveric model

BACKGROUND

Numerous studies have documented the effect of complete medial collateral ligament injury on anterior cruciate ligament loads; few have addressed how partial medial collateral ligament disruption affects knee kinematics.

PURPOSE

To determine knee kinematics and subsequent change in anterior cruciate ligament load in a partial and complete medial collateral ligament injury model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten human cadaveric knees were sequentially tested by a robot with the medial collateral ligament intact, in a partial injury model, and in a complete injury model with a universal force-moment sensor measuring system. Tibial translation, rotation, and anterior cruciate ligament load were measured under 3 conditions: anterior load (125 N), valgus load (10 N x m), and internal-external rotation torque (4 N x m; all at 0 degrees and 30 degrees of flexion).

RESULTS

Anterior and posterior translation did not statistically increase with a partial or complete medial collateral ligament injury at 0 degrees and 30 degrees of flexion. In response to a 125 N anterior load, at 0 degrees , the anterior cruciate ligament load increased 8.7% (from 99.5 to 108.2 N; P = .006) in the partial injury and 18.3% (117.7 N; P < .001) in the complete injury; at 30 degrees , anterior cruciate ligament load was increased 12.3% (from 101.7 to 114.2 N; P = .001) in the partial injury and 20.6% (122.7 N; P < .001) in the complete injury. In response to valgus torque (10 N x m) at 30 degrees , anterior cruciate ligament load was increased 55.3% (30.4 to 47.2 N; P = .044) in the partial injury model and 185% (86.8 N; P = .001) in the complete injury model. In response to internal rotation torque (4 N.m) at 30 degrees , anterior cruciate ligament load was increased 29.3% (27.6 to 35.7 N; P = .001) in the partial injury model and 65.2% (45.6 N; P < .001) in the complete injury model. The amount of internal rotation at 30 degrees of flexion was significantly increased in the complete injury model (22.8 degrees ) versus the intact state (19.5 degrees ; P < .001).

CONCLUSION

Partial and complete medial collateral ligament tears significantly increased the load on the anterior cruciate ligament. In a partial tear, the resultant load on the anterior cruciate ligament was increased at 30 degrees of flexion and with valgus load and internal rotation torque.

CLINICAL RELEVANCE

Patients may need to be protected from valgus and internal rotation forces after anterior cruciate ligament reconstruction in the setting of a concomitant partial medial collateral ligament tear. This information may help clinicians understand the importance of partial injuries of the medial collateral ligament with a combined anterior cruciate ligament injury complex.

Regeneration of anterior cruciate ligament by biodegradable scaffold combined with local controlled release of basic fibroblast growth factor and collagen wrapping

The objective of this study was to increase the therapeutic efficacy of anterior cruciate ligament (ACL) surgery using an artificial ligament material developed through a combination of tissue engineering technologies. A poly-L-lactic acid (PLLA) scaffold of plain-woven braid was incorporated with a gelatin hydrogel for controlled release of basic fibroblast growth factor (bFGF) and wrapped with a collagen membrane to allow space for ligament regeneration. For the ACL reconstruction surgery, the PLLA braid scaffold combined with the gelatin hydrogel incorporating bFGF and the collagen wrapping was applied to a tunnel prepared in the femur and tibia of rabbits. The hydrogel was placed in the bone, whereas the portion of the braid inside the joint cavity was wrapped with the membrane. As controls, the PLLA scaffold was applied with the hydrogel or the membrane, or without either material. Bone regeneration in the tunnel and ACL tissue regeneration in the joint cavity were histologically evaluated, and the mechanical strength and collagen content of the regenerated ACL were assessed. When the PLLA scaffold was integrated with both the hydrogel and the membrane, bone and ACL tissues were regenerated in the corresponding sites, in marked contrast to the control groups. Combination of bFGF-controlled release resulted in enhanced mechanical strength of the regenerated ACL tissue. In the joint cavity, it is possible that the local bFGF release inside the membrane enhanced the cell migration and collagen production, and that the surrounding PLLA scaffold results in the biological regeneration of ligament-like tissue. Additionally, significant bone regeneration around the scaffold was observed in the bone tunnel. It is therefore possible that the local controlled release of bFGF near the PLLA braid induced both osseointegration and intrascaffold cell migration in the bone tunnel and joint cavity, respectively, resulting in an overall increase in the mechanical strength of the regenerated ACL.

Current concepts review: comprehensive physical examination for instability of the knee

A careful history and physical examination are the cornerstones of orthopaedic sports medicine. When evaluating a patient for ligamentous instability of the knee joint, an understanding of the contribution of anatomic structures to stability enhances a practitioner's ability to achieve an accurate clinical diagnosis. This article reviews the various types of knee instability and the associated anatomic structures. Ultimately, information must be obtained from multiple tests to reach the final diagnosis. We describe in detail the pathologic and biomechanical basis of the tests for both tibiofemoral and patellofemoral instability of the knee joint and provide recommendations for performance and interpretation of these physical examinations.

Isolated anterior cruciate ligament reconstruction in patients with chronic anterior cruciate ligament insufficiency combined with grade II valgus laxity

BACKGROUND

There is no consensus about whether isolated anterior cruciate ligament reconstruction using multistrand hamstring tendon with nonoperative treatment for chronic medial collateral ligament injury is sufficient.

PURPOSE

To assess clinical outcome for patients with chronic anterior cruciate ligament injury and accompanying grade II valgus laxity who received medial hamstring anterior cruciate ligament reconstruction alone. Results were compared with those of patients with isolated chronic anterior cruciate ligament injury without valgus laxity.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Two hundred eighty-nine patients with isolated anterior cruciate ligament injury were compared with 53 patients with accompanying valgus laxity (minimum follow-up, 24 months). The following parameters were compared between the 2 groups at the last follow-up: range of motion, KT-1000 arthrometer value, pivot-shift test result, Lysholm knee scale, knee extensor muscle strength, return to sporting activities, subjective recovery, and International Knee Documentation Committee grade. Differences in clinical outcome were evaluated between those with preoperative International Knee Documentation Committee grade B and grade C and between those with grade A and grade B or C at final evaluation.

RESULTS

Postoperative KT-1000 arthrometer value averaged 1.2 mm for those with isolated anterior cruciate ligament injury and 1.6 mm for those with accompanying valgus laxity (not significant, P = .281). There was no significant difference between these 2 groups regarding the other items. In patients with preoperative valgus laxity, KT-1000 arthrometer values at final evaluation between patients with preoperative grade B and C were not significantly different. The value for subjects with grade A at final evaluation was 1.3 mm and for those with grade B or C at final evaluation was 2.7 mm (P = .065).

CONCLUSION

There was no clinically significant difference regarding outcome of anterior cruciate ligament multistrand hamstring reconstruction alone for 90% of patients with grade II valgus laxity who regained medial stability with nonoperative management compared with those who underwent the same anterior cruciate ligament reconstruction for an isolated anterior cruciate ligament tear.

Does ACL reconstruction restore knee stability in combined lesions?: An in vivo study

Treating anterior cruciate ligament (ACL) lesions combined with a torn medial collateral ligament (MCL) is controversial because residual laxity may lead to stretching of the ACL graft and eventual failure of the reconstruction. Few studies describe the in vivo translations of combined ACL and MCL injuries. We compared the preoperative and postoperative laxity between patients with combined ACL+MCL Grade II injuries and isolated ACL ruptures and tested whether an ACL reconstruction could restore all laxities in both groups. We evaluated knee kinematics during ACL reconstruction in 57 patients (37 ACL lesions and 20 ACL+MCL injury). Laxity tests were performed before and after graft fixation. Postoperatively, there was greater anteroposterior laxity and greater varus-valgus laxity in the group with MCL injury compared to the group with an ACL lesion only. This finding suggests residual laxities remain when ACL reconstruction is performed in patients with combined ACL+MCL lesion, and raises the question of addressing the MCL ligament when Grade II laxity is found.

The role of the medial collateral ligament and posteromedial capsule in controlling knee laxity

BACKGROUND

The medial aspect of the knee has a complex capsular structure; the biomechanical roles of specific structures are not well understood.

HYPOTHESIS

The 3 strong stabilizing structures, the superficial and deep medial collateral ligaments and the posteromedial capsule, make distinct contributions to controlling tibiofemoral laxity.

STUDY DESIGN

Controlled laboratory study.

METHODS

Changes in knee laxity under anterior-posterior drawer, valgus, and internal-external rotation loads were found by sequential cutting in 18 cadaveric knees. Three cutting sequences allowed the roles of the 3 structures to be seen in isolation and in combination. Some force contributions were also calculated.

RESULTS

The posteromedial capsule controlled valgus, internal rotation, and posterior drawer in extension, resisting 42% of a 150-N drawer force when the tibia was in internal rotation. The superficial collateral ligament controlled valgus at all angles and was dominant from 30 degrees to 90 degrees of flexion, plus internal rotation in flexion. The deep collateral ligament controlled tibial anterior drawer of the flexed and externally rotated knee and was a secondary restraint to valgus.

CONCLUSION

Distinct roles in controlling tibiofemoral laxity have been found for these structures that vary according to knee flexion and tibial rotation.

CLINICAL RELEVANCE

The restraining functions demonstrated provide new information about knee stabilization, which may allow better evaluation of structural damage at the medial aspect of the knee.

Operative and nonoperative treatments of medial collateral ligament rupture with early anterior cruciate ligament reconstruction: a prospective randomized study

BACKGROUND

The apparent consensus is that solitary medial collateral ligament rupture can be treated nonoperatively, but treatment of severe combined ruptures of the medial collateral ligament and anterior cruciate ligament remains controversial.

HYPOTHESES

Nonoperative and early operative treatments of grade III medial collateral ligament rupture lead to similar results when the anterior cruciate ligament is reconstructed in the early phase.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Forty-seven consecutive patients with combined anterior cruciate ligament and grade III medial collateral ligament injuries were randomized into 2 groups. The medial collateral ligament injury was treated operatively in group 1 (n = 23) and non-operatively in group 2 (n = 24). In both groups, the anterior cruciate ligament injury was treated with early reconstruction, using bone-patellar tendon-bone graft and interference screw. Two years postoperatively, knee stability was measured with a KT-1000 arthrometer and Telos valgus radiography and knee extension strength with a Biodex dynamometer and a 1-legged hop test. An International Knee Documentation Committee evaluation form and Lysholm score were completed.

RESULTS

All 47 patients were available for clinical evaluation for a mean of 27 months (range, 20-37 months) after surgery. There were no statistically significant differences between the 2 groups with respect to subjective function of the knee, postoperative stability, range of motion, muscle power, return to activities, Lysholm score, and overall International Knee Documentation Committee evaluation. The subjective outcome and Lysholm score were good and anteroposterior knee stability excellent in both groups.

CONCLUSION

Nonoperative and operative treatments of medial collateral ligament injuries lead to equally good results. Medial collateral ligament ruptures need not be treated operatively when the anterior cruciate ligament is reconstructed in the early phase.

Medial collateral ligament insertion site and contact forces in the ACL-deficient knee

The objectives of this research were to determine the effects of anterior cruciate ligament (ACL) deficiency on medial collateral ligament (MCL) insertion site and contact forces during anterior tibial loading and valgus loading using a combined experimental-finite element (FE) approach. Our hypothesis was that ACL deficiency would increase MCL insertion site forces at the attachments to the tibia and femur and increase contact forces between the MCL and these bones. Six male knees were subjected to varus-valgus and anterior-posterior loading at flexion angles of 0 degrees and 30 degrees. Three-dimensional joint kinematics and MCL strains were recorded during kinematic testing. Following testing, the MCL of each knee was removed to establish a stress-free reference configuration. An FE model of the femur-MCL-tibia complex was constructed for each knee to simulate valgus rotation and anterior translation at 0 degrees and 30 degrees, using subject-specific bone and ligament geometry and joint kinematics. A transversely isotropic hyperelastic material model with average material coefficients taken from a previous study was used to represent the MCL. Subject-specific MCL in situ strain distributions were used in each model. Insertion site and contact forces were determined from the FE analyses. FE predictions were validated by comparing MCL fiber strains to experimental measurements. The subject-specific FE predictions of MCL fiber stretch correlated well with the experimentally measured values (R2 = 0.95). ACL deficiency caused a significant increase in MCL insertion site and contact forces in response to anterior tibial loading. In contrast, ACL deficiency did not significantly increase MCL insertion site and contact forces in response to valgus loading, demonstrating that the ACL is not a restraint to valgus rotation in knees that have an intact MCL. When evaluating valgus laxity in the ACL-deficient knee, increased valgus laxity indicates a compromised MCL.

Tissue engineering for anterior cruciate ligament reconstruction: a review of current strategies

The anterior cruciate ligament (ACL) is one the most commonly injured ligaments of the knee. Chronic ACL insufficiency can result in episodic instability, chondral and meniscal injury, and early osteoarthritis. The intra-articular environment of the ligament precludes normal healing and surgical replacement of the injured ligament is often mandated to restore stability. Current surgical strategies include the use of local autograft or allograft tissues for ligament reconstruction. These procedures have yielded superior long-term clinical results yet have the potential for serious associated morbidities. Existing limitations have prompted ongoing research designed to engineer a replacement ligament that will parallel the native ACL in both its biologic properties and mechanical durability. Ligament engineering necessitates the use of appropriate source cells and a growth matrix to support cell proliferation and collagen synthesis. The identification of appropriate growth modulators including both biochemical factors and mechanical stimuli are requisites for successful tissue growth. The characterization of the elements essential for successful graft development represents a significant challenge for investigators. This review examines the current literature regarding the potential and limitations of ligament engineering and describes the development of a novel 3-dimensional scaffold and bioreactor system at our institution.

Medial collateral ligament reconstruction using autogenous hamstring tendons: technique and results in initial cases

BACKGROUND

Although various surgical procedures that attempt to restore the function of the medial collateral ligament have been reported, none have achieved consistently satisfactory results.

HYPOTHESIS

Our reconstructive procedure using autogenous semitendinosus and gracilis tendons yields improved results compared with conventional procedures.

STUDY DESIGN

Case series. Level of evidence, 4.

METHOD

In our surgical procedure, autogenous semitendinosus and gracilis tendons were used to anatomically reconstruct the anterior longitudinal component of the superficial medial collateral ligament. From April 1995 through December 2000, 27 patients with symptomatic medial instability underwent this surgical procedure. The majority of the subjects were diagnosed with combined cruciate ligament injuries, necessitating concomitant cruciate ligament reconstructions. Of these 27 patients, 24 were evaluated after a minimum period of 2 years, with a mean follow-up period of 27 months (range, 24-48 months).

RESULTS

At follow-up, medial stability, as well as postoperative range of motion in all patients, was graded as normal or nearly normal according to the International Knee Documentation Committee evaluation system. No significant postoperative complications were encountered.

CONCLUSION

Although this is a short-term follow-up study involving a small number of cases, we considered our procedure to be an effective method of surgically restoring the function of the medial collateral ligament.

Contribution of biomechanics, orthopaedics and rehabilitation: the past present and future

Biomechanics is a field that has a very long history. From its beginnings in ancient Chinese and Greek literature, the field of orthopaedic biomechanics has grown in the areas of biomechanics of bone, articular cartilage, soft tissues, upper extremities, spine and so on. Bioengineers in collaboration with orthopaedic surgeons have applied biomechanical principles to study clinically relevant problems, improving patient treatment and outcome. In the past 30 years, my colleagues and I have focused our research on the biomechanics of musculoskeletal soft tissues, ligaments and tendons in particular. Therefore, in this review article, the function of the knee ligaments and the associated homeostatic responses secondary to immobilisation and exercise will be described. Research on healing of the medial collateral ligament (MCL) of the knee and possible future approaches in improving the healing of the knee ligaments will be presented. Finally, improvement of the understanding of ligament reconstruction, specifically of the anterior cruciate ligament (ACL), through the use of robotics technology will be included. Throughout the manuscript, specific scientific findings that have guided or changed the clinical management of injury to these soft tissues will be emphasised.

The healing medial collateral ligament following a combined anterior cruciate and medial collateral ligament injury--a biomechanical study in a goat model

The ideal treatment of a combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injury to the knee is still debated. In particular, the question of whether reconstruction of the ACL can provide the knee with sufficient multidirectional stability to allow for effective MCL healing needs to be better elucidated. Therefore, the first objective of this study was to quantify the changes in the function of goat knees between time-zero and 6 weeks following a combined ACL/MCL injury treated with ACL reconstruction. Using a robotic/universal force-moment sensor testing system, the kinematics of the knee and in situ forces in the ACL/ACL graft as well as in the sham-operated and healing MCL were evaluated in response to (1) a 67 N anterior-posterior (A-P) tibial load and (2) a 5 Nm varus-valgus (V-V) moment. The second objective was to evaluate the structural properties of the healing femur-MCL-tibia complex (FMTC) and the mechanical properties of the healing MCL at 6 weeks under uniaxial tension. In response to the 67 N A-P tibial load, the A-P translations for the experimental knee increased by as much as 4.5 times from time-zero to 6 weeks (p<0.05). Correspondingly, the in situ forces in the ACL graft decreased by as much as 45% (p<0.05). There was no measurable changes of the in situ force in the healing MCL. In response to a 5 Nm V-V moment, V-V rotations were twice as much as controls, but similar for both time periods. From time-zero to 6 weeks, the in situ forces in the ACL graft dropped by over 71% (p<0.05), while the in situ force in the healing MCL was as much as 35+/-19 N. In terms of the structural properties of the healing FMTC, the stiffness and ultimate load values at 6 weeks reached 53% and 29% of sham-operated contralateral controls, respectively (p<0.05). For the mechanical properties of the healing MCL substance, the values for tangent modulus and tensile strength were only 13% and 10% of sham-operated controls, respectively (p<0.05). These results suggest that the ACL graft stabilized the knee initially, but became loose over time. As a result, the healing MCL may have been required to take on excessive loads and was unable to heal sufficiently as compared to an isolated MCL injury.

The effect of medial collateral ligament insufficiency on the reconstructed anterior cruciate ligament: a study in the rabbit

The treatment for severe combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) ruptures is disputed. Using a rabbit model, we examined the effect of insufficiency of medial structures on the reconstructed ACL in combined ACL and MCL injury. 40 rabbits were divided into 2 groups. In both groups, ACL was subjected to in situ freeze-thaw treatment. In group F, only freeze-thaw treatment of ACL was given. In group FM, partial resection of MCL was also done. We killed 5 rabbits on each of 4 occasions: immediately after the operation (time 0), at 6, 12 and 24 weeks postoperatively. At each time, we measured valgus instability and mechanical properties of the ACL. Valgus instability in group FM persisted from time 0 to 24 weeks, and was significantly greater than that in group F. The tensile strength and tangent modulus of the ACL in group FM were lower than those in group F. We found that continuous valgus instability reduces the mechanical properties of the in situ frozen ACL.

A review of ski injuries resulting in combined injury to the anterior cruciate ligament and medial collateral ligaments

Alpine skiing is a global winter recreational sport with 15 million participants in the United States alone, and an overall injury rate of 2.5 per 1,000 ski person-days. Isolated injury to the anterior cruciate ligament (ACL) or the medial collateral ligament (MCL) is common among ski injuries; however, combined injury to these structures is rare. Controversy in the management of ACL instability following alpine ski injury is diminishing with improvements in the techniques of intra-articular cruciate reconstruction. However, the management of the combined ACL-MCL injury remains something of an enigma. Evidence exists to support both surgical and nonsurgical management strategies for the medial structures, but little consensus exists for the timing of the repair. This paper highlights the mechanisms of ski injuries that can result in combined injury to the ACL and MCL. The anatomy and biomechanics of the medial complex as it relates both to stability and operative repair are reviewed, and literature on the techniques and indications used for MCL repair in the setting of a combined injury is presented. On the basis of this review, we believe that an injury to the MCL does not need to be repaired if the ACL is reconstructed after a combined injury.

The effect of axial tibial torque on the function of the anterior cruciate ligament: a biomechanical study of a simulated pivot shift test

PURPOSE

Various techniques are used to produce the pivot shift phenomenon after anterior cruciate ligament (ACL) injury. In particular, the amount of applied axial tibial torque varies among examiners. Thus, the objective of this study was to determine the effect of the magnitude and direction of axial tibial torque in combination with valgus torque on the resulting knee kinematics during such a simulated pivot shift test.

TYPE OF STUDY

This was a biomechanical study that used cadaveric knees with the intact knee of the same specimen serving as a control.

METHODS

On 19 human cadaveric knees (age, 26 to 69 years), a constant 10-Nm valgus torque was applied at 15 degrees of knee flexion. Then, internal and external tibial torque was applied incrementally from 0 to 10 Nm and the resulting kinematics of the ACL-intact and ACL-deficient knee, as well as the in situ force in the ACL, were measured using a robotic/universal force-moment sensor testing system.

RESULTS

In response to isolated valgus torque, the coupled anterior tibial translation for the ACL-intact and ACL-deficient knee was 1.6 +/- 2.4 mm and 8.5 +/- 4.7 mm, respectively; therefore the difference between the ACL-intact and ACL-deficient knee was 6.9 +/- 3.4 mm. With an external tibial torque greater than 5 Nm, the tibia translated up to 4 mm posteriorly for both the ACL-intact and ACL-deficient knee. Whereas, internal tibial torque greater than 1.6 Nm caused a rapid increase in coupled anterior tibial translation up to 10.2 mm in the ACL-deficient knee, while causing only a gradual increase for the ACL-intact knee. With excessive internal torque of 10 Nm, the difference in coupled anterior tibial translation was only 4.4 +/- 2.2 mm, suggesting a decrease in the sensitivity of the test. Correspondingly, the in situ force in the ACL under 10 Nm valgus tibial torque was 43 +/- 17 N, and increased up to 87 +/- 32 N as a 10-Nm internal torque was added. By applying a 3.3-Nm external tibial torque in addition to the 10-Nm valgus torque, the in situ force decreased to 21 +/- 14 N.

CONCLUSIONS

This study showed that a minimal amount of internal torque in combination with valgus torque may be a suitable way to elicit a pivot shift from an ACL-deficient knee.

Biology and biomechanics

Increased participation by the general population in athletic activities leads to increased trauma to bones, joint surfaces, and soft tissues. Management and treatment of these injuries has significantly improved over the past few decades. The application of knowledge gained from basic science research in biology and biomechanics has continuously contributed to that. Biological advances have been made in the field of gene therapy, cell therapy, and tissue engineering. Certainly, the greatest focus is bone and cartilage research that will lead to improved fracture repair in the traumatic injured population, as well as prevention of early osteoarthritic changes in the injured athletic population. In biomechanical research, contributions have been made to further understand kinematic behavior of joints that will lead to improved ligament reconstruction techniques and rehabilitation regimens. Various fixation techniques and several different ligament reconstruction techniques have been studied and validated. In the future, improved understanding of ligament healing, graft incorporation, and revascularization will lead to improved outcome of surgical reconstruction techniques in orthopaedic sports medicine. Exciting research has been performed over the past years and will be reviewed in this article.

Stability after medial collateral ligament release in total knee arthroplasty

Six knees from cadavers were tested for change in stability after release of the medial collateral ligament with posterior cruciate-retaining and substituting total knee replacements. Load deformation curves of the joint were recorded in full extension and 30 degrees, 60 degrees, and 90 degrees flexion under a 10 N-m varus and valgus torque, 1.5 N-m internal and external rotational torque, and a 35 N anterior and posterior force to test stability in each knee. The intact specimen and posterior cruciate ligament-retaining total joint replacement were tested for baseline comparisons. The superficial medial collateral ligament was released, followed by release of the posterior cruciate ligament. The knee then was converted to a posterior-stabilized implant. After medial collateral ligament release, valgus laxity was statistically significantly greater at 30 degrees, 60 degrees, and 90 degrees flexion after posterior cruciate ligament sacrifice than it was when the posterior cruciate ligament was retained. The posterior-stabilizing post added little to varus and valgus stability. Small, but significant, differences were seen in internal and external rotation before and after posterior cruciate ligament sacrifice. The posterior-stabilized total knee arthroplasty was even more rotationally constrained in full extension than the knee with intact medial collateral ligament and posterior cruciate ligament.

Strain in the human medial collateral ligament during valgus loading of the knee

The medial collateral ligament is one of the most frequently injured ligaments in the knee. Although the medial collateral ligament is known to provide a primary restraint to valgus and external rotations, details regarding its precise mechanical function are unknown. In this study, strain in the medial collateral ligament of eight knees from male cadavers was measured during valgus loading. A material testing machine was used to apply 10 cycles of varus and valgus rotation to limits of +/- 10.0 N-m at flexion angles of 0 degrees, 30 degrees, 60 degrees, and 90 degrees. A three-dimensional motion analysis system measured local tissue strain on the medial collateral ligament surface within 12 regions encompassing nearly the entire medial collateral ligament surface. Results indicated that strain is significantly different in different regions over the surface of the medial collateral ligament and that this distribution of strain changes with flexion angle and with the application of a valgus torque. Strain in the posterior and central portions of the medial collateral ligament generally decreased with increasing flexion angle, whereas strain in the anterior fibers remained relatively constant with changes in flexion angle. The highest strains in the medial collateral ligament were found at full extension on the posterior side of the medial collateral ligament near the femoral insertion. These data support clinical findings that suggest the femoral insertion is the most common location for medial collateral ligament injuries.