Effect of meniscal loss on knee stability after single-bundle anterior cruciate ligament reconstruction

A High Grade of Postoperative Knee Laxity Is Associated With an Increased Hazard of Revision Surgery: A Cohort Study of 4697 Patients With Primary ACL Reconstruction

BACKGROUND

There is still debate regarding the association between arthrometric knee laxity measurements and subjective knee outcome and revision surgery after primary anterior cruciate ligament reconstruction (ACLR).

PURPOSE

To assess whether arthrometric knee laxity (measured with the KT-1000 arthrometer) 6 months after primary ACLR was associated with the 1-, 2-, and 5-year subjective knee outcomes or revision ACLR at a 5-year follow-up.

STUDY DESIGN

Cohort study, Level of evidence 3.

METHODS

Patients who underwent primary ACLR with a hamstring tendon autograft at the authors' institution between January 1, 2005, and December 31, 2017, with no concomitant ligamentous injuries, were identified. Anterior knee laxity (KT-1000 arthrometer, 134 N) was assessed 6 months postoperatively. The Knee injury and Osteoarthritis Outcome Score (KOOS) was collected preoperatively and 1, 2, and 5 years postoperatively. Patients who underwent revision ACLR at any institution in the country within 5 years of primary surgery were identified through the Swedish National Knee Ligament Registry.

RESULTS

A total of 4697 patients (54.3% male) with available KT-1000 arthrometer measurements were included (normal: side-to-side [STS] ≤2 mm, 3015 [64.2%]; nearly normal: STS 3-5 mm, 1446 [30.8%]; abnormal: STS >5 mm, 236 [5.0%]). The only significant difference in subjective knee outcome between the groups was for the KOOS Symptoms subscale at the 1-year follow-up (STS ≤2 mm, 79.9 ± 16.2; STS 3-5 mm, 82.5 ± 14.8; STS >5 mm, 85.1 ± 14.2; P < .001). No other significant differences between the groups were found preoperatively or at 1, 2, or 5 years postoperatively for any of the KOOS subscales. The hazard for revision ACLR within 5 years of the primary surgery was significantly higher for the groups with an STS of 3 to 5 mm (6.6%; 95/1446) (hazard ratio [HR], 1.42; 95% CI, 1.07-1.87; P = .01) and an STS >5 mm (11.4%; 27/236) (HR, 2.61; 95% CI, 1.69-4.03; P < .001) compared with the group with an STS ≤2 mm (3.8%; 116/3015).

CONCLUSION

A high grade of postoperative knee laxity (STS 3-5 mm and STS >5 mm) 6 months after primary ACLR was associated with an increased hazard of revision ACLR within 5 years, but it was not associated with an inferior subjective knee outcome.

Navigation in anterior cruciate ligament reconstruction: State of the art

Computer navigation (CN) for anterior cruciate ligament (ACL) surgery has been used mainly for two purposes: to enhance the accuracy of tunnel position and to evaluate the kinematics of the ACL reconstruction (ACLR) and the stability achieved by different surgical techniques. Many studies have shown that navigation may improve the accuracy of anatomical tunnel orientation and position during ACL reconstructive surgery compared with normal arthroscopic tunnel placement, especially regarding the femoral side. At the same time, it has become the gold-standard method for intraoperative knee kinematic assessment, as it permits a quantitative multidirectional knee joint laxity evaluation. CN in ACL surgery has been associated with diverse problems. First, in most optic systems additional skin incisions and drill holes in the femoral bone are required for fixation of a reference frame to the femur. Second, additional radiation exposure and extra medical cost to the patient for preoperative planning are usually needed. Third, CN, due to additional steps, has more opportunities for error during preoperative planning, intraoperative registration, and operation. Fourth, soft tissues, including the skin and subcutaneous tissues, are usually not considered during the preoperative planning, which can be a problem for kinematic and stability assessment. Many studies have concluded that ACLR using a CN system is more expensive than conventional surgery, it adds extra time to the surgery and it is not mitigated by better clinical outcomes. This, combined with costs and invasiveness, has limited the use of CN to research-related cases. Future technology should prioritize less invasive intra-operative surgical navigation.

The Effects of Lateral Meniscus Posterior Root Tear and its Repair on Knee Stability of Internal Rotation and Forward Shift: A Biomechanical Kinematics Cadaver Study

Objective: Lateral meniscal posterior root (LMPR) is an important stabilizer for knee joint, providing the stability during tibia forward shifting and internal rotating. It is still controversial that whether the LMPR tear (LMPRT) should be repaired together with ACL reconstruction. This study aims to investigate the effects of LMPR on knee stability with intact ACL.

Methods: Eight cadaver knees were used and performed the biomechanical kinematics tests in orders of: Group A: the LMPR was intact; Group B: the LMPR was cut off from its tibial end; Group C: the LMPRT has been repaired. 1) An internal rotation moment (5 Nm) was given to the tibia, then the internal rotation angle of the tibia was measured; 2) An forward shifting force (134 N) was given to the tibia, then the anterior displacement of the tibia was measured; 3) An internal rotation moment (5 Nm) and a valgus moment (10 Nm) were given to the tibia, then the internal rotation angle and the anterior displacement was measured. The stability was inferred from smaller rotation angle and displacement, and all of the angles and displacements were measured at knee flexion of 0°, 30°, 60° and 90°, respectively.

Results: Comparing to Group A, the internal rotation angle in Group B was increased significantly at knee flexion of 30° (p = 0.025), 60° (p = 0.041), 90° (p = 0.002); the anterior tibia displacement in Group B was increased significantly at knee flexion of 30° (p = 0.015), 60° (p = 0.024); at knee valgus, the internal rotation angle was also increased significantly at knee flexion of 60° (p = 0.011), 90° (p = 0.037). Comparing to Group B, the internal rotation angle in Group C was decreased significantly at knee flexion of 30° (p = 0.030), 60° (p = 0.019), 90° (p = 0.021); the anterior displacement in Group C was decreased significantly at knee flexion of 30° (p = 0.042), 60° (p = 0.037); at valgus, the internal rotation angle was also decreased significantly at knee flexion of 60° (p = 0.013), 90° (p = 0.045). Comparing to Group A, only the internal rotation angle (p = 0.047) and anterior displacement (p = 0.033) in Group C were increased at knee flexion of 30°.

Conclusion: In simulated knee with intact ACL, LMPRT can still lead to the notable internal rotational instability at knee flexion from 30° to 90°, as well as the anterior shift instability at knee flexion from 30° to 60°. LMPRT repair help to improve the internal rotation stability at 30° and restore it at 60° to 90°, and improve the anterior shift stability at 30° and restore it at 60°.

Double-Bundle Anterior Cruciate Ligament Reconstruction With Lateral Extra-Articular Tenodesis Is Effective in Restoring Knee Stability in a Chronic, Complex Anterior Cruciate Ligament-Injured Knee Model: A Cadaveric Biomechanical Study

PURPOSE

To compare knee stability after intra-articular isolated double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) and single-bundle (SB) and DB ACLR combined with lateral extra-articular tenodesis (LET) in a chronic, complex anterior cruciate ligament (ACL)-injured knee model.

METHODS

In 10 fresh-frozen cadaveric knees, we measured knee laxity in the following order: (1) intact knee; (2) ACL-sectioned knee; (3) complex ACL-injured knee model with additional sectioning of the anterolateral complex and the posterior horns of the medial and lateral menisci; (4) SB ACLR plus LET; (5) DB ACLR; and (6) DB ACLR plus LET.

RESULTS

In comparison with the intact knee, significantly increased internal rotation (IR) laxity persisted at 60° and 90° after DB ACLR (P = .002 and P = .003, respectively). SB ACLR plus LET and DB ACLR plus LET resulted in significant reductions in IR laxity at 90° (P = .003 and P = .037, respectively), representing overconstraint in IR. SB ACLR plus LET resulted in persistently increased external rotation (ER) laxity at 30°, 60°, and 90° (P = .001, P < .001, and P < .001, respectively). The DB ACLR condition persistently showed significant increases in anterior tibial translation laxity at 60° and 90° (P = .037 and P = .024, respectively). A greater increase in ER laxity was seen after SB ACLR plus LET versus DB ACLR plus LET at 30°, 60°, and 90° (P < .001, P < .001, and P < .001, respectively).

CONCLUSIONS

DB ACLR plus LET restored intact knee stability in IR, ER, and anterior tibial translation laxity at 0°, 30°, 60°, and 90° of knee flexion except for overconstraint in IR at 90° in a chronic, complex ACL-injured knee model.

CLINICAL RELEVANCE

This cadaveric study provides some biomechanical evidence to support performing DB ACLR combined with LET to restore knee stability after a complex, chronic knee injury involving an ACL tear combined with anterolateral complex injury and irreparable tears of the posterior horns of the medial and lateral menisci.

Editorial Commentary: The Pivot Shift and Lachman Examinations: Teammates With Distinct Roles

The pivot shift and Lachman examinations are "teammates" with complementary but distinct roles in the successful diagnosis and treatment of anterior cruciate ligament rupture and injury to the surrounding soft-tissue envelope of the knee. The Lachman test measures anterior tibial translation in response to an applied anterior tibial load. This test assesses the integrity of the native or reconstructed anterior cruciate ligament and the secondary medial restraints including the medial meniscus and medial collateral ligament. In contrast, the pivot shift exam creates coupled tibiofemoral motions in response to a complex combination of multiplanar loads. This test assesses the stabilizing role of the native or reconstructed anterior cruciate ligament and the secondary lateral restraints including the lateral meniscus and anterolateral complex. The pivot shift grade depends not only on the soft the tissue stabilizers of the knee but also on the shape of the proximal tibia and the distal femur including lateral tibial slope and femoral condylar offset. Both examinations have unique strengths and weaknesses, but when combined as diagnostic tools, they achieve far more collectively than what each can achieve alone.

Lateral Meniscal Allograft Transplantation With Bone Block and Suture-Only Techniques Partially Restores Knee Kinematics and Forces

BACKGROUND

The ability of lateral meniscal allograft transplantation (MAT) to improve knee stability and the meniscal load-bearing function in patients after meniscectomy is critical for surgical success.

PURPOSE

To compare the effects of 2 lateral MAT fixation techniques-bone block and suture only-on knee kinematics and forces.

STUDY DESIGN

Controlled laboratory study.

METHODS

With a robotic testing system, loads were applied during flexion on 10 fresh-frozen cadaveric knees: 134-N anterior tibial load + 200-N axial compression, 5-N·m internal tibial + 5-N·m valgus torques, and 5-N·m external tibial + 5-N·m valgus torques. Kinematic data were recorded for 4 knee states: intact, total lateral meniscectomy, lateral MAT bone block, and lateral MAT suture-only fixation. In situ force in the anterior cruciate ligament and resultant forces in the lateral meniscus and in the meniscal allograft were quantified via the principle of superposition. A repeated measures analysis of variance was used to analyze variations in kinematics and forces at 0°, 30°, 60°, and 90° of knee flexion. Significance was set at P < .05.

RESULTS

When anterior loads were applied, a decrease in medial translation of the tibia that was increased after total lateral meniscectomy was observed at 30°, 60°, and 90° of knee flexion for both the lateral MAT bone block (54.2%, 48.0%, and 50.0%) and the MAT suture-only (50.0%, 40.0%, and 34.6%) fixation techniques (P < .05). Yet, most of the increases in knee kinematics after lateral meniscectomy were not significantly reduced by either lateral MAT technique (P > .05 for each MAT technique vs the total lateral meniscectomy state). Resultant forces in the meniscal allograft were 50% to 60% of the resultant forces in the intact lateral meniscus in response to all loading conditions at all flexion angles (P < .05). Overall, no significant differences between lateral MAT techniques were observed regarding kinematics and forces (P > .05).

CONCLUSION

Lateral MAT partially restored medial translation of the tibia, and the resultant forces in the meniscal allograft were only 50% to 60% of the intact lateral meniscus forces in the cadaver model. In the majority of testing conditions, no significant changes of the in situ force in the anterior cruciate ligament were observed. Surgeons should consider the potential benefits of lateral MAT when deciding the appropriate treatment for symptomatic patients after lateral meniscectomies. Both lateral MAT techniques functioned similarly.

CLINICAL RELEVANCE

The load-bearing function of the meniscal allograft observed in this study may be beneficial in ameliorating the short- and long-term disability associated with lateral meniscal deficiency.

The biomechanical role of meniscal allograft transplantation and preliminary in-vivo kinematic evaluation

Background

Meniscus allograft transplantation (MAT) is a surgical procedure performed in patients complaining post-meniscectomy syndrome. Although the effectiveness of MAT on knee stability has been already demonstrated in cadaveric studies, its biomechanical role has been poorly evaluated in-vivo.

Methods

A narrative review of the biomechanical effect of meniscectomy and MAT was performed. Furthermore, two cases were presented, of one patient who underwent Medial MAT and Anterior Cruciate Ligament (ACL) reconstruction, and one who underwent Lateral MAT. During the surgery, knee laxity was evaluated using a surgical navigation system.

Results

AP laxity and IE rotation were reduced of 25% to 50% at both 30° and 90° of knee flexion after MAT transplantation.

Discussion

In both cases, almost all the tests performed showed a reduction of knee laxity after meniscus transplant, when compared with pre-operative knee laxity. This assessment confirms the insights of previous in-vitro studies and underline a crucial role of MAT in knee biomechanics.

The ACL-deficient knee and the prevalence of meniscus and cartilage lesions: a systematic review and meta-analysis (CRD42017076897)

INTRODUCTION

The purpose of this systematic review and meta-analysis was to analyze and compare the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction.

MATERIALS AND METHODS

A systematic search for articles comparing the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction was performed. PubMed central was the database used for the literature review.

RESULTS

Forty articles out of 1836 were included. In 35 trials (88%), there was evidence of a positive correlation between the rate of meniscus and/or cartilage lesions and the time since ACL injury. This correlation was more evident for the medial meniscus in comparison with the lateral meniscus. In particular, a delay of more than 6 months was critical for secondary medial meniscus injuries [risk ratio 0.58 (95% CI 0.44-0.79)] and a delay of more than 12 months was critical for cartilage injuries [risk ratio 0.42 (95% CI 0.29-0.59)]. Additionally, there is evidence that the chance for meniscal repair decreases as the time since ACL rupture increases.

CONCLUSION

Chronic instability in the ACL-deficient knee is associated with a significant increase of medial meniscus injuries after 6 months followed by a significant increase of cartilage lesions after 12 months.

Predictive Factors and Duration to Return to Sport After Isolated Meniscectomy

Background:

Return to sport (RTS) after meniscectomy is an important metric for young, active patients. However, the impact of the duration from surgery to RTS on clinical outcomes is not fully understood and is not reflected in outcome scores.

Purpose:

To establish when patients RTS after meniscectomy and to determine predictive measures for the ability to return to their preinjury activity.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

All patients undergoing meniscectomy between 2016 and 2017 from a single institution were assessed for inclusion. RTS, type of activity, and level of function upon returning were obtained. The minimal clinically important difference (MCID), substantial clinical benefit, and patient acceptable symptom state (PASS) were calculated for the Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) questionnaire using anchor-based and distribution-based approaches. Preoperative knee-specific and generic quality-of-life scores were analyzed to determine their predictive power of RTS. A multivariate logistical analysis was also performed to determine which demographic variables corresponded to RTS.

Results:

Overall, 94 patients (mean age, 51.0 ± 11.1 years) who underwent meniscectomy participated in sports within 6 months of surgery. Of these patients, 76.6% returned to sport without permanent restrictions at a mean of 8.6 ± 6.9 weeks postoperatively. RTS rates for low-, medium-, and high-intensity activities were 75.0%, 70.0%, and 82.5%, respectively. RTS was associated with achieving the PASS for the KOOS–Physical Function short form (PS), KOOS-Pain, and KOOS-Sports (P = .004, P = .007, and P = .006, respectively) but not for the IKDC questionnaire (P = .3). Achieving the MCID was associated with RTS for the KOOS-Sports, KOOS-Pain, and IKDC questionnaire (P < .001, P = .03, and P = .001, respectively). There was no preoperative or intraoperative variable that was predictive of RTS. Preoperative KOOS-PS scores ≥37.8 (area under the curve = 76.3%) and KOOS-Pain scores ≥51.4 (area under the curve = 72.5%) were predictive of RTS.

Conclusion:

Approximately 77% of patients returned to sport after meniscectomy at a mean of 2 months postoperatively. The level of activity intensity did not significantly alter the rate of RTS. Higher preoperative scores on the KOOS-PS and KOOS-Pain were predictive of RTS. Identifying these factors allows physicians to counsel patients on expected outcomes after meniscectomy.

Partial meniscectomy adversely affects return-to-sport outcome after anatomical double-bundle anterior cruciate ligament reconstruction

PURPOSE

The purposes of this study were to determine whether the partial meniscectomy combined with ACL reconstruction affect the postoperative return-to-sport and to identify if partial meniscectomy has an influence on the graft failure following an anatomical double-bundle ACL reconstruction case.

METHODS

A retrospective cohort study including 426 primary double bundle ACL reconstruction cases. There were 206 males and 220 females, median age of 28.4 years, median BMI of 23.0, median preinjury Tegner score of 7.0 and median follow-up period after surgery of 24.0 months. Patients with less than 12 months of follow-up, revision surgery, multi-ligaments injury, previous contralateral knee ligaments injury and postoperative infection cases were excluded. Furthermore, patients who had meniscal repair were excluded in order to compare the outcomes between patients who had intact menisci and those who underwent partial meniscectomy. There were 227 patients with intact menisci (group A) and 199 patients with partial meniscectomy (group B). The median age was younger and the preoperative Tegner score was higher in group A. The patients in group B were subcategorized as the site of partial meniscectomy, including medial (group C), lateral (group D) and bicompartmental (group E) meniscectomy. There were 74, 94, and 31 patients in group C, D, and E, respectively. Return-to-sport (running and sport phase) and graft failure were included in our primary outcomes, and functional outcome as Lysholm knee scores was included in secondary outcome.

RESULTS

The rate of return to running phase and sport phase were 91% (387/426) and 76% (303/399), the mean time taken to return to running and sport phase were 5.7 months and 11.1 months, respectively. There was significant difference in the returning to sport phase between group A and B (p = 0.01), and between group A and D/E subgroups (p = 0.007). There were fourteen graft failures (3.5%) in total. In addition, 9 and 5 graft failures in group A and B, respectively. Of the 5 graft failures in group B, 2 and 3 graft failures in group C and D, respectively. There was no significant difference of the graft failure ratio among the groups.

CONCLUSION

Our study demonstrates that partial meniscectomy has an adverse effect on the return to sport phase following the anatomical double-bundle ACL reconstruction. Therefore, greater postoperative care would be needed to return to sport with partial meniscectomy in ACL reconstruction cases. On the contrary, partial meniscectomy is not considered to be the risk factor for graft failure at short-term follow-up.

LEVEL OF EVIDENCE

Case-control study, Level III.

Lateral Meniscal Posterior Root Repair With Anterior Cruciate Ligament Reconstruction Better Restores Knee Stability

BACKGROUND

The effect of lateral meniscal posterior root tear and repair-commonly seen in clinical practice in the setting of anterior cruciate ligament (ACL) reconstruction-is not known.

PURPOSE/HYPOTHESIS

This study evaluated the effect of tear and repair of the lateral meniscal posterior root on the biomechanics of the ACL-reconstructed knee. It was hypothesized that anterior tibial translation would increase under anterior loading and simulated pivot-shift loading with the root tear of the posterior lateral meniscus, while repair of the root tear would reduce it close to the noninjured state.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirteen fresh-frozen adult human knees were tested with a robotic testing system under 2 loading conditions: (1) an 89.0-N anterior tibial load applied at full extension and 15°, 30°, 60°, and 90° of knee flexion and (2) a combined 7.0-N·m valgus and 5.0-N·m internal tibial torque (simulated pivot-shift test) applied at full extension and 15° and 30° of knee flexion. The following knee states were tested: intact knee, ACL reconstruction and intact lateral meniscus, ACL reconstruction and lateral meniscal posterior root tear, and ACL reconstruction and lateral meniscal posterior root repair.

RESULTS

In the ACL-reconstructed knee, a tear of the lateral meniscal posterior root significantly increased knee laxity under anterior loading by as much as 1 mm. The transosseous pullout suture root repair improved knee stability under anterior tibial and simulated pivot-shift loading. Root repair improved the ACL graft force closer to that of the native ACL under anterior tibial loading.

CONCLUSION

Lateral meniscal posterior root injury further destabilizes the ACL-reconstructed knee, and root repair improves knee stability.

CLINICAL RELEVANCE

This study suggests a rationale for surgical repair of the lateral meniscus, which can restore stability close to that of the premeniscal injury state.

Alteration of Knee Kinematics After Anatomic Anterior Cruciate Ligament Reconstruction Is Dependent on Associated Meniscal Injury

BACKGROUND

Limited in vivo kinematic information exists on managing meniscal injury during anterior cruciate ligament reconstruction (ACLR).

HYPOTHESIS

Isolated anatomic ACLR restores knee kinematics, whereas ACLR in the presence of medial meniscal injury is associated with altered long-term knee kinematics.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From March 2011 to December 2012, 49 of 57 participants in a clinical trial underwent anatomic ACLR with successful kinematic testing at 24 months after ACLR. Twenty-five patients had associated meniscal tears: medial (n = 11), lateral (n = 9), or bilateral (n = 5). With a dynamic stereo radiography system with superimposed high-resolution computed tomography scans of patient knees, kinematics were measured during downhill running. The initial single-support phase of the gait cycle (0%-10%) was analyzed.

RESULTS

Anterior tibial translation (ATT) was the only kinematic outcome between patients' ACLR and contralateral knees that had significant interactions among meniscal groups ( P = .007). There was significant difference in ATT between patients with intact menisci and medial tears ( P = .036) and with medial tears and lateral tears ( P = .025). Patients with intact menisci had no difference in ATT, with a negligible effect size between the ACLR and contralateral knees (mean ± SEM: 13.1 ± 0.7 mm vs 12.6 ± 0.5 mm, P = .24, Cohen d = 0.15, n = 24), while patients with medial meniscal tears had an increase in ATT, with a medium effect size between the ACLR and contralateral knees (15.4 ± 1.0 mm vs 13.2 ± 1.0 mm, P = .024, Cohen d = 0.66, n = 11).

CONCLUSION

Associated medial meniscal injury in the setting of ACLR leads to increased ATT at 24-month follow-up. Furthermore, isolated anatomic ACLR in the absence of meniscal injury demonstrated no significant difference from native knee kinematics at 24-month follow-up during rigorous "high demand" knee activity with the current sample size. Patients undergoing anatomic ACLR in the presence of medial meniscal injury remained at a higher likelihood of sustaining altered long-term knee kinematics.

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

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

[Meniscal root lesions: clinical relevance and treatment]

Meniscal roots play an important role in load distribution of the tibiofemoral knee joint. Thus, meniscal root tears are severe injuries of the knee, which significantly expose cartilage to increased stress. Two entities are distinguished: (i) acute root tears that mainly affect the posterolateral root and often occur with ruptures of the anterior cruciate ligament; and (ii) chronic, degenerative root tears that mainly affect the posteromedial root. For diagnosis of both entities, the patient's medical history, a knee examination and especially MRI play key roles. The treatment of choice is in general transtibial fixation of the torn root, which leads to an increased clinical improvement and a decrease of the progression of arthritis.

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

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

Current use of navigation system in ACL surgery: a historical review

PURPOSE

The present review aims to analyse the available literature regarding the use of navigation systems in ACL reconstructive surgery underling the evolution during the years.

METHODS

A research of indexed scientific papers was performed on PubMed and Cochrane Library database. The research was performed in December 2015 with no publication year restriction. Only English-written papers and related to the terms ACL, NAVIGATION, CAOS and CAS were considered. Two reviewers independently selected only those manuscripts that presented at least the application of navigation system for ACL reconstructive surgery.

RESULTS

One hundred and forty-six of 394 articles were finally selected. In this analysis, it was possible to review the main uses of navigation system in ACL surgery including tunnel positioning for primary and revision surgery and kinematic assessment of knee laxity before and after different surgical procedures. In the early years, until 2006, navigation system was mainly used to improve tunnel positioning, but since the last decade, this tool has been principally used for kinematics evaluation. Increased accuracy of tunnel placement was observed using navigation surgery, especially, regarding femoral, 42 of 146 articles used navigation to guide tunnel positioning. During the following years, 82 of 146 articles have used navigation system to evaluate intraoperative knee kinematic. In particular, the importance of controlling rotatory laxity to achieve better surgical outcomes has been underlined.

CONLUSIONS

Several applications have been described and despite the contribution of navigation systems, its potential uses and theoretical advantages, there are still controversies about its clinical benefit. The present papers summarize the most relevant studies that have used navigation system in ACL reconstruction. In particular, the analysis identified four main applications of the navigation systems during ACL reconstructive surgery have been identified: (1) technical assistance for tunnel placement; (2) improvement in knowledge of the kinematic behaviour of ACL and other structures; (3) comparison of effectiveness of different surgical techniques in controlling laxities; (4) navigation system performance to improve the outcomes of ACL reconstruction and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

Experimental Execution of the Simulated Pivot-Shift Test: A Systematic Review of Techniques

PURPOSE

To conduct a systematic review to identify and summarize the various techniques that have been used to simulate the pivot-shift test in vitro.

METHODS

Medline, Embase, and the Cochrane Library were screened for studies involving the simulated pivot-shift test in human cadaveric knees published between 1946 and May 2014. Study parameters including sample size, study location, simulated pivot-shift technique, loads applied, knee flexion angles at which simulated pivot shift was tested, and kinematic evaluation tools were extracted and analyzed.

RESULTS

Forty-eight studies reporting simulated pivot-shift testing on 627 cadaveric knees fulfilled the criteria. Reviewer inter-rater agreement for study selection showed a κ score of 0.960 (full-text review). Twenty-seven studies described the use of internal rotation torque, with a mean of 5.3 Nm (range, 1 to 18 Nm). Forty-seven studies described the use of valgus torque, with a mean of 8.8 Nm (range, 1 to 25 Nm). Four studies described the use of iliotibial tract tension, ranging from 10 to 88 N. Regarding static simulated pivot-shift test techniques, 100% of the studies performed testing at 30° of knee flexion, and the most tested range of motion in the continuous tests was 0° to 90°. Anterior tibial translation was the most analyzed parameter during the simulated pivot-shift test, being used in 45 studies. In 22% of the studies, a robotic system was used to simulate the pivot-shift test. Robotic systems were shown to have better control of the loading system and higher tracking system accuracy.

CONCLUSIONS

This study provides a reference for investigators who desire to apply simulated pivot shift in their in vitro studies. It is recommended to simulate the pivot-shift test using a 10-Nm valgus torque and 5-Nm internal rotation torque. Knee flexion of 30° is mandatory for testing.

LEVEL OF EVIDENCE

Level IV, systematic review of basic science studies.

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

BACKGROUND

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

PURPOSE/HYPOTHESIS

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

STUDY DESIGN

Controlled laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Use of inertial sensors to predict pivot-shift grade and diagnose an ACL injury during preoperative testing

BACKGROUND

The pivot-shift (PS) examination is used to demonstrate knee instability and detect anterior cruciate ligament (ACL) injury. Prior studies using inertial sensors identified the ACL-deficient knee with reasonable accuracy, but none addressed the more difficult problem of using these sensors to determine whether a subject has an ACL deficiency and to correctly assign a PS grade to a patient's knee.

HYPOTHESIS

Inertial sensor data recorded during a PS examination can accurately predict ACL deficiency and the PS score assigned by the examining physician.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

A total of 32 patients with unilateral ACL deficiency and 29 with intact ACLs in both knees had inertial sensor modules strapped to the tibia and femur of each limb for preoperative PS testing under anesthesia. Support vector machine (SVM) methods assessed PS grades on the basis of these data, with the examiner's clinical grading shift used as ground truth. A fusion of regression and SVM classification techniques diagnosed ACL deficiency.

RESULTS

The clinically determined PS grades of all 122 knees were as follows: 0 (n = 69), +1 (n = 23), +2 (n = 27), and +3 (n = 3). The SVM classification analysis was 77% accurate in correctly classifying these grades, with 98% of computed PS grades falling within ±1 grade of the clinically determined value. The system fusion algorithm diagnosed ACL deficiency in an individual with an overall accuracy of 97%. This method yielded 6% false negatives and 0% false positives.

CONCLUSION

This study used inertial sensor technology with SVM algorithms to accurately determine clinically assigned PS grades in ACL-intact and ACL-deficient knees. By extending the assessment to a separate group of patients without ACL injury, the inertial sensor data demonstrated highly accurate diagnosis of ACL deficiency.

Different patterns of lateral meniscus root tears in ACL injuries: application of a differentiated classification system

PURPOSE

Posterior lateral meniscus root tears (PLMRTs) affect the intra-articular pressure distribution in the lateral compartment of the knee. The biomechanical consequences of these injuries are significantly influenced by the integrity of the meniscofemoral ligaments (MFLs). A newly introduced arthroscopic classification system for PLMRTs that takes MFL integrity into account has not yet been clinically applied but may be useful in selecting the optimal method of PLMRT repair.

METHODS

Prospective ACL reconstruction data were collected. Concomitant injuries of the lateral meniscus posterior horn were classified according to their shape and MFL status. The classifications were: type 1, avulsion of the root; type 2, radial tear of the lateral meniscus posterior horn close to the root with an intact MFL; and type 3, complete detachment of the posterior meniscus horn.

RESULTS

Between January 2011 and May 2012, 228 consecutive ACL reconstructions were included. Lateral and medial meniscus tears were identified in 38.2% (n = 87) and 44.7% (n = 102), respectively. Of the 87 lateral meniscus tears, 32 cases had PLMRTs; the overall prevalence of PLMRTs was 14% (n = 32). Two medial meniscus root tears were detected. All PLMRTs were classified according to the classification system described above, and the fixation procedure was adapted to the type of meniscus tear.

CONCLUSION

The PLMRT tear is a common injury among patients undergoing ACL repair and can be arthroscopically classified into three different types. Medial meniscus root tears are rare in association with ACL tears. The PLMRT classification presented here may help to estimate the injury's impact on the lateral compartment and to identify the optimal treatment. These tears should not be overlooked, and the treatment strategy should be chosen with respect to the type of root tear.

LEVEL OF EVIDENCE

IV.

Short-term effects of partial meniscectomy on the clinical results of anterior cruciate ligament reconstruction

PURPOSE

This study aims to analyse the short-term effects of partial meniscectomy on the clinical results of anterior cruciate ligament reconstruction surgery.

METHODS

Clinical outcomes of 19 patients who had partial medial meniscectomy and anterior cruciate ligament reconstruction during the same surgery (Group 1) were compared with the outcomes of 25 patients who had also reconstruction but did not have any meniscal lesion (Group 2). Median follow-up time was 29 months (range 12-67 months) in Group 1 and 27 months (range 12-70 months) in Group 2. Feeling of apprehension in sports activities, International Knee Documentation Committee (IKDC) score, KT-2000 Arthrometer(®) measurements and post-operative time to return to sports activity were the criteria for data analysis.

RESULTS

Eight patients (42%) in Group 1 and 5 patients (20%) in Group 2 stated feeling of apprehension in sports activities. IKDC score improved to A in 11 patients (58%) from Group 1, and 18 patients (72%) from Group 2. Mean anterior translation according to KT-2000 arthrometer measurements was 5.2 ± 1.3 mm in Group 1, and 4.6 ± 1.3 mm in Group 2. Post-operative time to return to sports activity was 8.5 ± 3.0 months in Group 1, and 6.5 ± 2.2 months in Group 2.

CONCLUSION

Partial meniscectomy for irreparable medial meniscal tears, applied during the same surgery with anterior cruciate ligament reconstruction, negatively affects the clinical outcomes in the short-term follow-up. This study may be a reference for long-term clinical trials and also future investigations of new methods in the treatment of similar cases.

LEVEL OF EVIDENCE

IV.

Anatomy and Histology of the Knee Anterolateral Ligament

BACKGROUND

Reconstruction of the anterior cruciate ligament (ACL) is one of the most common procedures in orthopaedic surgery. However, even with advances in surgical techniques and implants, some patients still have residual anterolateral rotatory laxity after reconstruction. A thorough study of the anatomy of the anterolateral region of the knee is needed.

PURPOSE

To study the anterolateral region and determine the measurements and points of attachments of the anterolateral ligament (ALL).

STUDY DESIGN

Descriptive laboratory study.

METHODS

Dissections of the anterolateral structures of the knee were performed in 20 human cadavers. After isolating the ALL, its length, thickness, width, and points of attachments were determined. The femoral attachment of the ALL was based on the anterior-posterior and proximal-distal distances from the attachment of the lateral collateral ligament (LCL). The tibial attachment point was based on the distance from the Gerdy tubercle to the fibular head and the distance from the lateral tibial plateau. The ligaments from the first 10 dissections were sent for histological analysis.

RESULTS

The ALL was found in all 20 knees. The femoral attachment of the ALL at the lateral epicondyle averaged 3.5 mm distal and 2.2 mm anterior to the attachment of the LCL. Two distal attachments were observed: one inserts into the lateral meniscus, the other between the Gerdy tubercle and the fibular head, approximately 4.4 mm distal to the tibial articular cartilage. The mean measurements for the ligament were 37.3 mm (length), 7.4 mm (width), and 2.7 mm (thickness). The histological analysis of the ligaments revealed dense connective tissue.

CONCLUSION

The ALL is consistently present in the anterolateral region of the knee. Its attachment to the femur is anterior and distal to the attachment of the LCL. Moving distally, it bifurcates at close to half of its length. The ALL features 2 distal attachments, one at the lateral meniscus and the other between the Gerdy tubercle and the fibular head.

CLINICAL RELEVANCE

The ALL may be important in maintaining normal rotatory limits of knee motion; ALL rupture could be responsible for rotatory laxity after isolated intra-articular reconstruction of the ACL.

Return to sport after arthroscopic meniscectomy on stable knees

Background

Athletes suffering from any injuries want to know when they will be able to return sports activity. The period of return-to-sport after the arthroscopic meniscectomy is still unknown. The aim of this study is to investigate the period of the return-to-sport from surgery and the clinical symptoms after the meniscectomy on stable knees.

Methods

Fifty-six athletes who underwent the arthroscopic meniscectomy were evaluated. The patients with an average age of 26.7 years (range, 13–67) comprised 45 men and 11 women, 16 medial meniscus and 40 lateral meniscus injuries. The average of the follow-up period was 9.2 months. The parameter examined were age, the injured side of meniscus (medial or lateral), articular cartilage status, amount of resection, and sports activity level.

Results

The mean period was 54 days in young group, and was 89 days in old group (p = 0.0013). The period was 79 days in medial meniscus (MM) injured group, and was 61 days in lateral meniscus (LM) group (p = 0.017). There was a significant difference among the groups in activity levels and in amount of resection. Pain and/or effusion in the knee after the return-to-sport were found 22% of the MM group and 53% in the LM group.

Conclusions

The period of the return-to-sport was shorter in young age, high activity and large amount of resection group. Although athletes in LM group can return to sports earlier than those in MM group, more than half of athletes have pain or effusion at the time of return-to sport.

Double-bundle versus single-bundle anterior cruciate ligament reconstructions: a prospective, randomized study with 2-year follow-up

This prospective, randomized study was conducted to compare the short-term results of arthroscopic double-bundle with single-bundle anterior cruciate ligament (ACL) reconstruction. One hundred and eight patients with a symptomatic ACL rupture were randomized to either double-bundle (Group DB) or single-bundle (Group SB) ACL reconstruction. Follow-up was conducted at 6, 12, 18 and 24 months postoperatively. At the 24-month follow-up, 94 of the 108 patients (87%) were available for evaluation. The rotational stability, as evaluated by pivot shift test, was significantly superior in the Group DB to that in the Group SB. No significant difference with regard to ACL revisions, total flexion work, mean peak flexion torque and extension work between the groups was detected. There was no significant difference between the groups in terms of the Tegner activity score, the knee injury and osteoarthritis outcome score, the Lysholm functional score, anterior knee pain or mobility, subjective knee function. In addition, no significant difference in laxity on the Lachman test or the KT-1000 maximum manual force test was investigated. All the results were significantly more satisfactory at each follow-up period than preoperatively, in both groups. Both SB- and DB-ACL reconstruction resulted in satisfactory subjective outcome and objective stability. Both these techniques can therefore be considered as suitable alternatives for ACL reconstruction. Moreover, as it seems to be according to the pivot shift test, the risk for the development of degenerative changes of the knee joint in a long run could be smaller in the Group DB.

Quantifying the pivot shift test: a systematic review

PURPOSE

This study aims to identify and summarize the evidence on the biomechanical parameters and the corresponding technologies which have been used to quantify the pivot shift test during the clinical and functional assessment of anterior cruciate ligament (ACL) injury and surgical reconstruction.

METHODS

Search strategy Internet search of indexed scientific articles on the PubMed database, Web of Science and references on published manuscripts. No year restriction was used. Selection criteria Articles included were written only in English and related to search terms: "pivot shift" AND (OR "ACL"). The reviewers independently selected only those studies that included at least one quantitative parameter for the analysis of the pivot shift test, including both in vitro and in vivo analyses performed on human joint. Those studies that analysed only clinical grading were excluded from the analysis. Analysis After evaluating the methodological quality of the articles, the parameters found were summarized.

RESULTS

Six hundred and eight studies met the inclusion criteria, and finally, 68 unique studies were available for the systematic review. Quantitative results were heterogeneous. The pivot shift test has been quantified by means of 25 parameters, but most of the studies focused on anterior-posterior translations, internal-external rotation and acceleration in anterior-posterior direction.

CONCLUSION

Several methodologies have been identified and developed to quantify pivot shift test. However, clinical professionals are still lacking a 'gold standard' method for the quantification of knee joint dynamic laxity. A widespread adoption of a standardized pivot shift manoeuvre and measurement method to allow objective comparison of the results of ACL reconstructions is therefore desirable. Further development of measurement methods is indeed required to achieve this goal in a routine clinical scenario.

Do pre-operative knee laxity values influence post-operative ones after anterior cruciate ligament reconstruction?

The objective of this study was to verify whether pre-reconstruction laxity condition effects post-reconstruction outcome. A total of 100 patients who underwent navigated Anterior Cruciate Ligament (ACL) reconstruction were included in the study and knee laxity analysed retrospectively. The knee was assessed in six different laxity tests before and after ACL reconstruction, namely antero-posterior (AP) and internal-external (IE) at 30° and 90°, and varus-valgus (VV) rotations at 0° and 30° of flexion. For each test, the least square (LS) fitting line based on pre-operative-to-post-operative laxity value was calculated. To what degree the post-operative laxity value is explainable by the corresponding pre-operative condition was evaluated by the LS line slope. Post-operatively, for each single patient, the grade of laxity decreased at any evaluated test. The strongest influence of pre-operative-to-post-operative laxity values was found during IE30 and IE90 tests. While AP30 and VV0 tests seem to be those in which the post-reconstruction laxity was barely affected by the pre-surgery condition. The analysis of the global laxity reduction confirms the previous results. Following this hypothesis, our study remarks on the importance of combined lesions to secondary restraints and the importance of fully understanding the residual laxity to optimize the surgical technique.