The Effect of Mechanical Varus on Anterior Cruciate Ligament and Lateral Collateral Ligament Stress: Finite Element Analyses

The use of four K-wires does not lead to a reduction of the MPTA in the context of a one-dimensional tibial deflection correction of patients with ACL re-rupture and pathologically increased tibial slope

Purpose

Anterior tibial closing wedge osteotomy (ATCWO) has been shown to significantly reduce failure rates of revision anterior cruciate ligament (ACL) reconstructions in patients with a posterior tibial slope (PTS) ≥12°. Recent findings suggest a slight but significant reduction of the medial proximal tibial angle (MPTA) resulting in a varus knee where the sagittal osteotomy plane is based on a total of two guide wires defining the osteotomy wedge without respecting the frontal plane. We hypothesize that the placement of a total of four guide wires intraoperatively can reduce the influence on the MPTA.

Methods

This study retrospectively reports on a two-centre series of 42 ATCWOs for PTS correction between January 2022 and December 2023 at two clinical centres. A total of four guide wires were placed based on a true lateral intraoperative view of the tibia, with two positioned each at the cranial and at the caudal pole of the osteotomy wedge, serving as guides for the saw to create the osteotomy, with careful attention to ensuring that the proximal and distal K-Wires were placed parallel to each other. A retrospective analysis was conducted by examining true lateral and anteroposterior radiographs to identify changes in sagittal and coronal plane alignment.

Results

The study included 19 women and 23 men, with a mean age of 29.7 ± 8.6 years with first-time ACL revision surgery and a minimum PTS of ≥12°. PTS decreased significantly from 14.5 ± 2.8° preoperatively to 8.2 ± 1.9° post-operatively (p < 0.001). The aMPTA demonstrated no significant difference between preoperative (mean aMPTA: 86.9 ± 2.1°) and post-operative (mean aMPTA: 86.6 ± 1.9°) measurements (p > 0.05).

Conclusion

With our technique of placing four guide wires to achieve precise guidance during the insertion of the osteotomy wedge, there is no substantial impact on the aMPTA during slope correction.

Level of Evidence

Level IV.

Patient-specific cutting guides allow 1° precision in asymmetric anterior closing-wedge osteotomy

Purpose

Asymmetric anterior closing-wedge high tibial osteotomy (ACWHTO) allows correction of both excessive posterior tibial slope (PTS) and varus deformity. However, the complexity of this surgery requires a high degree of accuracy, which is less likely to be achieved with standard instrumentations. This study aimed to determine the accuracy of 3D patient-specific cutting guides (PSCGs) to provide the accurate planned correction in the frontal and sagittal planes.

Methods

Eight sawbones tibiae were identically printed from the same patient data. An ACWHTO with a PSCG was performed on each sawbone. Postoperative measurements of PTS, mechanical medial proximal tibial angle (mMPTA), hinge area and hinge-posterior cruciate ligament (hinge-PCL) distance were compared with the preoperative planned measurements. The precision was defined as the absolute difference (∆) between the target planned values and postoperative values.

Results

The mean accuracy was 0.6° ± 0.74° for PTS, 0.8° ± 0.71° for mMPTA, 0.3 ± 0.2 cm2 for hinge area and 0.1 ± 0.06 mm for hinge-PCL distance.

Conclusion

In the setting of sawbones, the use of PSCGs was a reliable and accurate method of achieving simultaneous correction in the frontal and sagittal planes during asymmetric ACWHTO.

Level of Evidence

Level V, basic science biomechanical laboratory study.

Around-the-knee osteotomies part 1: definitions, rationale and planning-state of the art

Knee osteotomies are essential orthopedic procedures with the ability to preserve the joint and correct ligament instabilities. Literature supports the correlation between lower limb malalignment and outcomes after knee ligament reconstruction and cartilage procedures. Concepts such as joint line obliquity, posterior tibial slope angle, and intra-articular deformity correction are integral components of both preoperative planning and postoperative evaluations. The concept of preserving and/or restoring joint line congruence during simultaneous correction of varus or valgus deformity can be achieved through several different approaches. With advancements in osteotomy research and surgical planning technology, the surgical decision-making has increased in complexity. Based upon a patient's specific deformity, decisions need to be made whether to perform a single-level (proximal tibia or distal femur) versus double-level (both proximal tibia and distal femur) osteotomy, and whether to correct deformity in a single plane (coronal or sagittal) or perform a biplanar osteotomy, correcting two of the malalignments in either coronal, sagittal, or axial planes. Osteotomy procedures prioritize safety, reproducibility, precision, and meticulous planning. Equally important is the proactive management of possible complications and the implementation of preventive strategies for complications such as hinge fractures and unintentional changes to alignment in other planes. This review navigates the intricate landscape of lower limb alignment, commencing with foundational definitions and rationale for performing osteotomies, progressing through the planning phase, and addressing the critical aspect of complication prevention, all while looking ahead to anticipate future advancements in this field. However, rotational osteotomies and tibial tubercle osteotomies in isolation or as an adjunct procedure are beyond the scope of this review.

[Influence of the bony alignment on the ligaments of the knee joint]

In recent years biomechanical and clinical studies have shown that the three-dimensional bony alignment of the lower extremities has a relevant influence on the ligamentous structures of the knee and consequently on the stability of the knee joint. Therefore, in the case of pathological ligamentous damage of the knee joint, a possible malalignment must always be thoroughly evaluated and if necessary, included in the treatment planning. Varus malalignment plays an important role especially with respect to the cruciate ligaments as well as the posterolateral ligamentous structures and has been identified as a significant risk factor for failure after surgical reconstruction of these ligamentous structures. Similar data have also been published for valgus malalignment particularly with respect to its negative influence on the anterior cruciate ligament and the medial capsuloligamentous complex. Alignment deviations in the sagittal plane, especially the inclination of the tibial articular surface (slope), have been extensively investigated in several recent studies. It has been demonstrated that the tibial slope has a relevant influence on the anteroposterior stability of the knee joint and hence on the cruciate ligaments. First clinical studies on the surgical correction of the axis in selected patients showed very promising results with the potential of protecting ligament reconstructions against repeated failure; however, further data especially regarding the importance and the exact indications for an additional alignment correction are necessary.

Effect of Tibiofemoral Rotation Angle on Graft Failure After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Coronal and sagittal malalignment of the knee are well-recognized risk factors for failure after anterior cruciate ligament (ACL) reconstruction (ACLR). However, the effect of axial malalignment on graft survival after ACLR is yet to be determined.

PURPOSE

To evaluate whether increased tibiofemoral rotational malalignment, namely, tibiofemoral rotation angle (TFA) and tibial tubercle-trochlear groove (TT-TG) distance, is associated with graft failure after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

In this retrospective matched control study of a single center's database, 151 patients who underwent revision ACLR because of graft failure (ACLR failure group, defined as symptomatic patients with anterior knee instability and an ACL graft tear appreciated on magnetic resonance imaging [MRI] and confirmed during arthroscopic surgery) were compared with a matched control group of 151 patients who underwent primary ACLR with no evidence of failure after ≥2-year follow-up (intact ACLR group). Patients were matched by sex, age, and meniscal injury during primary ACLR. Axial malalignment was assessed on preoperative MRI through the TFA and the TT-TG distance. Sagittal alignment was measured through the posterior tibial slope on MRI. The optimal TFA cutoff associated with graft failure was identified by a receiver operating characteristic curve. The Kaplan-Meier curve with log-rank analysis was performed to evaluate the influence of the TFA on ACLR longevity.

RESULTS

The mean age was 25.7 ± 10.4 years for the ACLR failure group and 25.9 ± 10.0 years for the intact ACLR group. Among all the included patients, 174 (57.6%) were male. In the ACLR failure group, the mean TFA was 5.8°± 4.5° (range, -5° to 16°), while it was 3.0°± 3.3° (range, -3° to 15°) in the intact ACLR group (P < .001). Neither the TT-TG distance nor the posterior tibial slope presented statistical differences between the groups. The receiver operating characteristic curve suggested an optimal TFA cutoff of 4.5° for graft failure (area under the curve = 0.71; P < .001; sensitivity, 68.2%; specificity, 75.5%). Considering this a threshold, patients who had a TFA ≥4.5° had 6.6 times higher odds of graft failure compared with patients with a TFA <4.5° (P < .001). Survival analysis demonstrated a 5-year survival rate of 81% in patients with a TFA <4.5°, while it was 44% in those with a TFA ≥4.5° (P < .001).

CONCLUSION

An increased TFA was associated with increased odds of ACLR failure when the TFA was ≥4.5°. Measuring the TFA in patients with ACL tears undergoing reconstruction may inform the surgeon about additional factors that may require consideration before ACLR for a successful outcome.

Simultaneous anterior cruciate ligament reconstruction and implant-mediated guided growth to correct genu valgum in skeletally immature patients

OBJECTIVES

Adolescents with anterior cruciate ligament (ACL) tears can present with concomitant lower extremity coronal plane angular deformity (CPAD) that both predispose to injury as well as may increase the risk of graft rupture following ACL reconstruction (ACLR). The goal of this study was to examine the safety and efficacy of concomitant ACLR with implant-mediated guided growth (IMGG) compared to isolated IMGG procedures in paediatric and adolescent patients.

METHODS

Operative records of all paediatric and adolescent patients (age ≤ 18 years) that underwent simultaneous ACLR and IMGG by one of two paediatric orthopaedic surgeons between 2015 and 2021 were retrospectively reviewed. A comparison cohort of isolated IMGG patients was identified and matched based on bone age within one year, sex, laterality, and fixation type (i.e. transphyseal screw vs. tension band plate and screw construct). Pre- and post-operative mechanical axis deviation (MAD), angular axis deviation (AAD), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) were recorded.

RESULTS

A total of 9 participants who underwent concomitant ACLR and IMGG (ACLR ​+ ​IMGG) were identified, with 7 of these participants meeting the final inclusion criteria. The participants had a median age of 12.7 (IQR ​= ​12.1 - 14.2) years and median bone age of 13.0 (IQR ​= ​12.0 - 14.0) years. Of the 7 participants that underwent ACLR and IMGG, 3 underwent a modified MacIntosh procedure with ITB autograft, 2 received quadriceps tendon autograft, and 1 underwent hamstring autograft reconstruction. There were no significant differences in the amount of correction obtained between ACLR ​+ ​IMGG and matched IMGG subjects with respect to any measurement variable (MAD difference: p ​= ​0.47, AAD difference: p ​= ​0.58, LDFA difference: p ​= ​0.27, MPTA difference: p ​= ​0.20). There were also no significant differences in alignment variables per unit time between cohorts (MAD/month: p ​= ​0.62, AAD/month ​= ​0.80, LDFA/month ​= ​0.27, MPTA/month ​= ​0.20).

CONCLUSION

The results of the current study indicate that concomitant ACLR and lower extremity CPAD correction is a safe approach to treat CPAD concomitantly with ACLR in young patients who present with an acute ACL tear. Furthermore, one can expect reliable correction of CPAD after combined ACLR and IMGG, no different than the correction obtained in the setting of IMGG alone.

LEVEL OF EVIDENCE

III.

The stress and strain pattern in the ligaments of the acromioclavicular joint using a quasi-static model

BACKGROUND

The precise role of the acromioclavicular and coracoclavicular ligaments during shoulder motion is unclear. We evaluate changes in the stress-strain distribution of the acromioclavicular joint's ligaments during different shoulder passive motion positions.

METHODS

A 3D acromioclavicular joint model was reconstructed. A constitutive hyperelastic model was used for the ligaments. The kinematics of the shoulder girdle was taken to simulate shoulder abduction (Motion 1) and horizontal adduction (Motion 2). A computer-generated quasi-static and non-linear finite element model was used to predict the 3D stress-strain distribution pattern of the acromioclavicular ligament and the coracoclavicular ligament complex.

FINDINGS

In motion 1, from 20 to 90° the peak von Mises stress was found in the conoid (4.14 MPa) and the anteroinferior bundle (2.46 MPa), while from 90 to 120° it was found in the conoid and the trapezoid. However, there were no significant differences between the mean stress values between anteroinferior bundle and trapezoid throughout the motion (p = 0.98). In Motion 2, from 20 to 80° the maximum equivalent elastic strain was found in the anteroinferior bundle (0.68 mm/mm) and the conoid (0.57 mm/mm), while from 80 to 100° it was higher in the conoid (0.88 mm/mm) than in the anteroinferior bundle (0.77 mm/mm).

INTERPRETATION

The coracoclavicular ligament complex demonstrated a high stress-strain concentration during simulated passive shoulder abduction. Additionally, it was shown that the acromioclavicular ligament plays an important role in joint restraint during passive horizontal adduction, changing the primary role with the trapezoid and conoid at different motion intervals.

Role of the proximal tibiofibular joint on the biomechanics of the knee joint: A three-dimensional finite element analysis

PURPOSE

The proximal tibiofibular joint (PTFJ) is easily ignored, although many diseases of the knee are caused by PTFJ injuries. Therefore, studying PTFJ biomechanics is very important. The effects of PTFJ injury on ankle function have been reported. However, few studies have assessed the effects of PTFJ injury on the knee joint. This study was performed to describe the biomechanical effects of PTFJ on the knee joint according to a three-dimensional finite element model.

METHODS

The knee joint of a healthy volunteer was scanned by CT and MRI. CT and MRI scanning data in DICOM format were imported into Mimics software. Subsequently, 3D models of the normal and PTFJ injured knee, including the bone, cartilage, meniscus and ligament structures were established, and their validity was verified on the basis of available studies in literature. The biomechanical changes in the two knee models under different conditions were compared.

RESULTS

The validity of the intact model was verified. No significant difference was observed in tibial mobility in the two models under the conditions of 134 N forward, 10 N·m internal rotation and 10 N·m valgus load. After application of 134 N backward, 10 N·m varus and external rotation load with respect to the tibia, the posterior movement of the tibia and the varus and external rotation angles of the tibia were 3.583±0.892 mm, 4.799±0.092° and 18.963±0.027° in the normal knee model, and 5.127±1.224 mm, 5.277±0.104° and 21.399±0.031° in the PTFJ injury model, respectively, and a significant statistical difference was observed.

CONCLUSIONS

PTFJ played an important role in maintaining the posterolateral stability of the knee joint and thus deserves more attention in clinical operations.

Anteroinferior bundle of the acromioclavicular ligament plays a substantial role in the joint function during shoulder elevation and horizontal adduction: a finite element model

Background

Postoperative acromioclavicular (AC) ligament deficiency has been identified as a common cause of failure after isolated coracoclavicular reconstruction. The two-bundle arrangement of the acromioclavicular ligament has recently been reported in histological and anatomical research. In addition, a clear structural advantage of the superoposterior bundle (SPB) over the less consistent anteroinferior bundle (AIB) was also found. However, the current understanding of the function of the acromioclavicular ligament in joint stability is based on uniaxial bone loading experiments and sequential ligament sectioning. Consequently, these rigid biomechanics models do not reproduce the coupled physiological kinematics, neither in the normal joint nor in the postoperative condition. Therefore, our goal was to build a quasi-static finite element model to study the function of the acromioclavicular ligament based on its biomechanical performance patterns using the benefits of computational models.

Methods

A three-dimensional bone model is reconstructed using images from a healthy shoulder. The ligament structures were modeled according to the architecture and dimensions of the bone. The kinematics conditions for the shoulder girdle were determined after the osseous axes aligned to simulate the shoulder elevation in the coronal plane and horizontal adduction. Three patterns evaluated ligament function. The peak von Mises stress values were recorded using a clock model that identified the stress distribution. In addition, the variation in length and displacement of the ligament during shoulder motion were compared using a two-tailed hypotheses test. P values < 0.01 were considered statistically significant.

Results

The peak von Mises stress was consistently observed in the AIB at 2:30 in coronal elevation (4.06 MPa) and horizontal adduction (2.32 MPa). Except in the position 2:00, statistically significant higher deformations were identified in the two bundles during shoulder elevation. The highest ligament displacement was observed on the Y- and Z-axes.

Conclusions

The AIB has the primary role in restricting the acromioclavicular joint during shoulder motion, even though the two bundles of the AC ligament have a complementary mode of action. During horizontal adduction, the SPB appears to prevent anterior and superior translation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-02966-0.

DETERMINATION OF THE STRESS OF ANTERIOR CRUCIATE LIGAMENT IN VARIOUS DEGREES OF KNEE FLEXION, COMPARISON OF NORMAL AND RECONSTRUCTED LIGAMENT

Background: Knee joint stability is enhanced by ligamentus structures such as anterior cruciate (ACL), posterior cruciate (PCL), medial collateral (MCL) and lateral collateral ligaments (LCL). Rupture of ACL is the most common knee injuries, especially in sport related activities. The aim of this study is to evaluate the stress developed in knee joint structures in various degrees of knee flexion in ACL ruptured compared to normal condition.

Method: CT scan images of knee joint were used to create 3d model of knee joint by use of Mimics software. Abaqus software was used to evaluate the stress developed in knee joint in normal and in ACL reconstructed conditions in various degrees of knee flexion.

Results: The stress developed in ACL and other knee joint structures increased significantly by increase in knee joint flexion. The stress of knee joint structures (especially in ACL) in ACL reconstructed condition was more than that of normal condition.

Conclusion: It is recommended to immobilize the knee joint in extension up to [Formula: see text] of knee flexion in those with ACL injuries. The stress of ACL increased due to an increase in tibia translation associated with knee flexion.

The Effect of Knee Flexion on Length Changes and Stress Distribution of Ligaments: A Displacement Controlled Finite Element Analysis

The use of dynamic finite element analysis to investigate the biomechanical behavior of the knee joint is mainly based on movement of the joint. Challenges are associated with simulation of knee joint flexion-extension activity. This study investigated changes in the length and stress state of ligaments during lunge with a displacement controlled finite element analysis of the knee joint based on in vivo fluoroscopic kinematic data. The geometric center axis (GCA) was used to represent knee kinematics to quantify femoral motion relative to the tibia. Because the GCA was considered as a functional flexion axis, 2 degrees of freedom could be reduced. Published data on the in vivo fluoroscopic kinematic features of the GCA were used to establish the equations for degrees of freedom. Data for 4 degrees of freedom were obtained simultaneously at every 5° of knee flexion. Displacement and rotation were applied to the femur and tibia to produce relative displacement, and the elongation and stress state of the knee ligaments were computed. The predictions confirmed that lunge affected the biomechanical behavior of ligaments. Displacement controlled finite element analysis of knee flexion can be simulated on the basis of fluoroscopic kinematic data to achieve physiologic movement. [Orthopedics. 2021;44(1):e61-e67.].

Osseous valgus alignment and posteromedial ligament complex deficiency lead to increased ACL graft forces

PURPOSE

To biomechanically investigate the influence of osseous valgus alignment, with and without deficiency of the posteromedial ligament complex (PMC), on ACL-graft forces under axial load.

METHODS

ACL reconstruction was performed on ten cadaveric knee joints. A lateral distal femur osteotomy was then done to adjust for three different alignment conditions according to the position, where the axial weight bearing line (WBL) dissected the tibial plateau (% from medial to lateral): 50%, 85% and 115%. Each alignment was tested with the PMC intact, deficient and reconstructed. Axial loads of 400 N were applied in 15° of knee flexion and changes of ACL-graft forces and dynamic valgus angle (DVA) were recorded.

RESULTS

In the PMC intact state, lateralization of the WBL to 85% and to 115% led to significantly increased ACL graft forces (85%: p = 0.010; 115%: p < 0.001) and DVAs (85%: p = 0.027; 115%: p = 0.027). Dissection of the PMC led to a significant increase of ACL graft forces and DVAs at 85% and 115% valgus alignment (p < 0.001) only. In comparison to valgus aligned knees with additional PMC deficiency, ligament reconstruction alone was able to significantly decrease ACL graft forces (p < 0.001) and DVAs (p < 0.001). However, alignment correction alone was significantly more effective in reducing ACL graft forces (p < 0.001) and DVAs (p = 0.010).

CONCLUSION

Osseous valgus alignment led to significantly increased forces on ACL grafts under axial joint compression, which was even further enhanced, when the PMC was deficient. In the valgus aligned and PMC deficient knee, correction to a straight leg axis was significantly more effective in decreasing forces on the ACL graft than reconstruction of the PMC. In patients with valgus alignment and combined injuries of the ACL and PMC, a correction osteotomy to a straight leg axis as well as reconstruction of the PMC should be considered to protect the reconstructed ACL.

The Role of High Tibial Osteotomy in ACL Reconstruction in Knees with Coronal and Sagittal Plane Deformity

PURPOSE OF REVIEW

Coronal and sagittal malalignment in the setting of anterior cruciate ligament (ACL) deficiency alters knee biomechanics and is shown to increase stress and strain on the native ACL and on the ACL graft during reconstruction. The purpose of this review was to determine the role and indications of high tibial osteotomy to correct coronal and/or sagittal plane malalignment with ACL reconstruction.

RECENT FINDINGS

Recent literature illustrates that an increase in varus malalignment and increased posterior tibial slope increases the biomechanical stress that is seen in a native or reconstructed ACL graft. It has been proposed to correct the sagittal and coronal malalignment by employing a high tibial osteotomy either prior to or at the time of ACL reconstruction to correct these deformities and to decrease the stress placed on the reconstructed ACL graft. The use of high tibial osteotomy for deformity correction creates a more stable knee for ACL reconstruction and has been shown to have good outcomes with regard to post-operative pain, stability, satisfaction scores, and function.

Revision Multiligament Knee Reconstruction: Clinical Outcomes and Proposed Treatment Algorithm

PURPOSE

To (1) assess clinical outcomes of revision multiligament knee injury (MLKI) reconstruction at a minimum of 2 years' follow-up and (2) present a standardized treatment algorithm used in treating revision MLKI patients.

METHODS

A retrospective review of our institution's MLKI database was performed to identify all patients who underwent revision MLKI reconstructions (≥2 ligaments reconstructed) after implementation of a standardized treatment algorithm in 2000 and had a minimum of 2 years' follow-up. Patient demographic information, injury description (mechanism of injury, neurovascular status, knee dislocation grade, associated chondral or meniscal injury), surgical technique (repair vs reconstruction, staged vs nonstaged, concomitant procedures), mechanism of failure, knee stability, and range of motion, as well as International Knee Documentation Committee and Lysholm scores, were obtained.

RESULTS

We assessed 23 patients (8 female and 15 male patients), with an average age of 26.7 ± 11.5 years at primary surgery and 30.8 ± 11.0 years at revision surgery. The mean follow-up period was 7.5 ± 5.3 years. Of the 23 patients, 10 (43.4%) underwent staged revision procedures: isolated bone grafting in 3, osteotomy in 4, hardware removal with osteochondral allograft in 1, hardware removal with bone grafting in 1, and meniscus repair for a locked knee in 1. The average International Knee Documentation Committee and Lysholm scores were 74.5 ± 22.3 and 79.4 ± 20.2, respectively. High-energy injury and increasing age at revision surgery were the only risk factors found to be associated with significantly worse outcomes (P < .05).

CONCLUSIONS

Patients with recurrent instability after MLKI reconstruction present with many concomitant pathologies, including limb malalignment, bone tunnel widening, retained hardware, meniscal incompetence, and cartilage defects. Revision MLKI reconstruction can provide these patients with modest functional outcomes when a standardized treatment algorithm is used focusing on identification and treatment of the concomitant pathology, often in a staged manner.

LEVEL OF EVIDENCE

Level IV, case series.

Effect of femoral tunnel positions on graft stress in outside-in ACL reconstruction surgery during continuous knee motion: A simulation study

BACKGROUND

Previous studies regarding the optimal femoral tunnel location for an anterior cruciate ligament (ACL) reconstruction were based on static experiments at specific angles, and did not consider continuous motion of the knee.

METHODS

Twenty-four surgical sites were set and continuous kinematic data, obtained from motion analysis, was used to describe knee movement. The bending angle and stress of the ACL graft as well as the length of the femoral tunnel was calculated through multi-flexible body dynamics analysis.

RESULTS

The lowest stress was found at both 5 mm and 10 mm radius at a proximal posterior of 45°, and the highest stress was also found at a distal 15 mm radius. Relatively high stresses were also identified between the distal and anterior regions as well as the distal and posterior regions at 15 mm radius.

CONCLUSION

Considering the availability of surgery, it was identified that the optimum femoral tunnel location is at 10 mm radius locations at a proximal posterior of 45°.

The Impact of Osseous Malalignment and Realignment Procedures in Knee Ligament Surgery: A Systematic Review of the Clinical Evidence

Background:

Failure rates of knee ligament surgery may be high, and the impact of osseous alignment on surgical outcome remains controversial. Basic science studies have demonstrated that osseous malalignment can negatively affect ligament strain and that realignment procedures may improve knee joint stability.

Hypothesis/Purpose:

The purpose of this review was to summarize the clinical evidence concerning the impact of osseous malalignment and realignment procedures in knee ligament surgery. The hypotheses were that lower extremity malalignment would be an important contributor to knee ligament surgery failure and that realignment surgery would contribute to increased knee stability and improved outcome in select cases.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

According to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic electronic search of the PubMed database was performed in November 2015 to identify clinical studies investigating (A) the influence of osseous alignment on postoperative stability and/or failure rates after knee ligament surgery and (B) the impact of osseous realignment procedures in unstable knees with or without additional knee ligament surgery on postoperative knee function and stability. Methodological quality of the studies was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence and the Coleman Methodological Score (CMS).

Results:

Of the 1466 potentially relevant articles, 28 studies fulfilled the inclusion and exclusion criteria. Average study quality was poor (CMS, 40). For part A, studies showed increased rerupture rate after anterior cruciate ligament (ACL) replacement in patients with increased tibial slope. Concerning the posterior cruciate ligament (PCL)/posterolateral corner (PLC)/lateral collateral ligament (LCL), varus malalignment was considered a significant risk factor for failure. For part B, studies showed decreased anterior tibial translation after slope-decreasing high tibial osteotomy in ACL-deficient knees. Correcting varus malalignment in PCL/PLC/LCL instability also showed increased stability and better outcomes.

Conclusion:

In cases of complex knee instability, the 3-dimensional osseous alignment of the knee should be considered (eg, mechanical weightbearing line and tibial slope). In cases of failed ACL reconstruction, the tibial slope should be considered, and slope-reducing osteotomies are often helpful in the patient revised multiple times. In cases of chronic PCL and/or PLC instability, osseous correction of the varus alignment may reduce the failure rate and is often the first step in treatment. Changes in the mechanical axis should be considered in all cases of instability accompanied by early unicompartmental osteoarthritis.

Technical Considerations in Revision Anterior Cruciate Ligament (ACL) Reconstruction for Operative Techniques in Orthopaedics

As the incidence of anterior cruciate ligament (ACL) reconstruction continues to increase, the rate of revision surgery continues to climb. Revision surgery has inherent challenges that must be addressed in order to achieve successful results. The cause of the primary ACL reconstruction failure should be determined, and careful preoperative planning should be performed to address the cause(s) of failure. Each patient undergoing revision surgery should undergo a thorough history and physical examination, receive full length alignment radiographs, lateral radiographs, 45-degree flexion weight-bearing postero-anterior radiographs, and patellofemoral radiographs. 3-dimensional computed topography (CT) scan should be performed to assess tunnel position and widening. Magnetic resonance imaging (MRI) should be used to assess for intra-articular soft tissue pathology. Meniscal tears, meniscal deficiency, anterolateral capsule injuries, bony morphology, age, activity level, connective tissue diseases, infection, graft choice, and tunnel position can all impact the success of ACL reconstruction surgery. Meniscal lesions should be repaired, and in cases of persistent rotatory instability, extra-articular procedures may be indicated. Furthermore, osteotomies may be needed to correct malalignment or excess posterior tibial slope. Depending on the placement and condition of the original femoral and tibial tunnels, revision surgery may be performed in a single procedure or in a staged manner. In most cases, the surgery can be performed in one procedure. Regardless, the surgeon must communicate with the patient openly regarding the implications of revision ACL surgery and the treatment plan should be developed in a shared fashion between the surgeon and the patient.