Anterior Cruciate Ligament Graft Research Articles

Anterior Closing Wedge Osteotomy for Failed Anterior Cruciate Ligament Reconstruction: State of the Art

The sagittal anatomy of the proximal tibia has a bearing on the forces exerted on the cruciate ligaments. A high posterior tibial slope is now a well-known risk factor causing failure of anterior cruciate ligament (ACL) reconstructions. The posterior slope can be calculated on short or full-length radiographs, MRI scans, or three-dimensional CT scans. Reducing the slope surgically by a sagittal tibial osteotomy is biomechanically protective for the ACL graft. An anterior closing wedge osteotomy may be contemplated when the lateral tibial slope is greater than 12°, in the setting of ACL reconstruction failure(s). Careful surgical planning to calculate the correction, taking into account knee hyperextension and patella height, is critical to avoid complications. It can be done above, at, or below the tibial tuberosity level. A transtuberosity correction can be done with or without a tibial tubercle osteotomy. This complex surgery can be conducted safely by meticulous execution to protect the posterior hinge and neurovascular structures and achieving stable fixation with staples. The limited literature available justifies the usage of anterior closing wedge osteotomy in appropriately selected patients.

Graft choices for anterolateral ligament knee reconstruction surgery: Current concepts

The anterolateral ligament (ALL) is a primary structure of the anterolateral complex of the knee that contributes to internal rotational stability of the joint. Injury of the ALL is commonly associated with rupture of the anterior cruciate ligament. If left untreated, ALL lesions may lead to residual anterolateral rotational instability of the knee after anterior cruciate ligament reconstruction, which is a common cause of anterior cruciate ligament graft failure. The function of the ALL can be restored by lateral extraarticular tenodesis or anterolateral ligament reconstruction (ALLR). In the lateral extraarticular tenodesis procedure, a strip of the iliotibial band is placed in a non-anatomical position to restrain the internal rotation of the tibia, while in ALLR, a free graft is fixed at the insertion points of the native ALL. Gracilis and semitendinosus grafts have mainly been utilized for ALLR, but other autografts have also been suggested. Furthermore, allografts and synthetic grafts have been applied to minimize donor-site morbidity and maximize the size and strength of the graft. Nevertheless, there has been no strong evidence to fully support one method over another thus far. The present review presents a detailed description of the graft choices for ALLR and the current literature available in regard to the effectiveness and outcomes of published surgical techniques.

Effects of modified trans-tibial versus trans-portal technique on stress patterns around the femoral tunnel in anatomical single-bundle ACL reconstruction with different knee flexion angles using finite element analysis

BackgroundIt is unclear whether different anterior cruciate ligament (ACL) graft trajectories in the distal femur would have different effects on stress generated within the distal femur around the femoral tunnel during knee motion. Thus, the purpose of this study was to determine differences in stress patterns around the femoral tunnel created by trans-portal (TP) vs. modified trans-tibial (TT) technique in anatomical ACL reconstruction at different knee flexion angles.MethodsTwelve male subjects’ right knees were scanned with a high-resolution computed tomography (CT) scanner (slice thickness: 1 mm) at four different knee flexion angles (0°, 45°, 90°, and 135°). Three-dimensional (3D) models of these four different flexion angles were created and manipulated with several modelling programs. For the TP group, the virtual femoral tunnelling procedure was performed in a 135° flexion model from the low far anteromedial (AM) portal. For the modified TT group, the same knee models were drilled through the modified TT technique at 90° of flexion separately. Virtual grafts under tension of 40 N were put into corresponding bone tunnel and fixed at the outer aperture of femoral tunnels to simulate the suspensory fixation, followed by fixation of the grafts at the middle of tibial tunnels in the 0° knee flexion models. Finally, the models were exported to a finite element analysis package and analysed using ABAQUS/Explicit code (ABAQUS, USA) to monitor the stress occurring at the node where stress distribution occurred most significantly in the femoral bone around the bone tunnel.ResultsIn general, both groups showed a high stress distribution in bony structures around inner and outer orifices of the femoral tunnel. Mean maximal stresses occurring at the lateral femoral condyle around the inner orifice of the femoral tunnel in the TP group were found to be significantly greater than those in the modified TT group at all flexion angles except 90° of flexion. Mean maximal stresses monitored around the outer orifice of the femoral tunnel in the TP group were also significantly greater than those in the modified TT group at all flexion angles.ConclusionsDifferent tunnelling technologies could yield different stress patterns in the lateral femoral condyle around the femoral tunnel. During knee motion, higher stresses were noticed in the TP group than in the modified TT group, especially around inner and outer orifices of the tunnel. Position of the tunnel after reconstruction with the TP technique can have a greater effect on the stress increase in the femur compared to that with the modified TT technique.

ACL Graft Matching: Cadaveric Comparison of Microscopic Anatomy of Quadriceps and Patellar Tendon Grafts and the Femoral ACL Insertion Site

Background: The optimal graft choice between the bone–patellar tendon–bone (BPTB) and the quadriceps tendon remains controversial. Studies evaluating the microscopic anatomy of the quadriceps tendon–patellar bone (QTB) and BPTB grafts for anterior cruciate ligament (ACL) reconstruction are currently lacking. Hypothesis: The relationship between post–ACL reconstruction graft bending angle (GBA) and the angle corresponding to the GBA (cGBA) would indicate that the BPTB can bend more than the QTB at the femoral tunnel aperture. Study Design: Controlled laboratory study. Methods: Twenty paired human cadaveric knees fixed at <10° of knee joint flexion (mean age, 82.5 years) underwent histological sectioning and staining with Masson trichrome and toluidine blue. The femoral ACL insertion, QTB graft, and BPTB graft were microscopically analyzed. The width of the direct insertion, thickness of the uncalcified fibrocartilage and calcified fibrocartilage, ligament attachment angle, and cGBA for each group were measured. Eighteen patients who underwent ACL reconstruction with QTB or BPTB autograft were included for the evaluation of GBA using computed tomography images at 1 week postoperatively. Results: The mean insertion widths of the femoral ACL, QTB, and BPTB were 7.81, 9.07, and 6.54 mm, respectively. The QTB was 16% wider than the ACL, while the BPTB was 16% narrower than the ACL. The mean insertion thicknesses of the femoral ACL, QTB, and BPTB were 0.53, 0.94, and 0.38 mm, respectively. The QTB was 77% thicker than the ACL (P < .001), while the BPTB was 28% thinner than the ACL (P = .017). The mean ligament attachment angles of the femoral ACL, QTB, and BPTB were 20.3°, 30.2°, and 33.3°, respectively, and the QTB and the BPTB were 49% and 64% larger, respectively, than the ACL. The mean cGBAs of the femoral ACL, QTB, and BPTB were 33.9°, 35.1°, and 12.3°, respectively. The BPTB was 64% smaller than the ACL, while there was no significant difference between the QTB and the ACL. The mean GBA was 57.7°. Conclusion: The insertion width and thickness were significantly greater and smaller in the QTB and BPTB grafts, respectively, than in the ACL. The relationship between GBA after ACL reconstruction and cGBA in knee extension indicates that at the femoral tunnel aperture, the BPTB can bend more than the QTB. Clinical Relevance: QTB graft may allow more anatomic ACL reconstruction to be performed.

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.

Rates of Anterior Cruciate Ligament Rerupture in Adolescent Patients with and without Patella Alta.

The objective of this study was to compare rates of anterior cruciate ligament (ACL) failure among adolescent patients to evaluate patella alta as a high-risk variable. Demographic and surgical data were retrospectively queried for patients ≤18 years of age with primary ACL reconstruction performed at a single academic center between 2011 and 2016 and minimum of 2-year clinical surveillance. Patellar height indices, including Caton-Deschamps index (CDI) and Insall-Salvati index (ISI), were retrospectively calculated from preoperative imaging to assess the presence of patella alta. Failure was defined as (1) ACL graft rerupture, (2) Lachman's grade 2 + , (3) presence of pivot shift, and (4) side-to-side difference of 3 mm on KT-1000 arthrometer. A total of 184 patients (84 females and 100 males) and 192 knees were identified, with an average age of 16.2 ± 1.8 years. Of these, 30 (15.63%) experienced ACL failure. Male sex was the only significant risk factor for rerupture (p = 0.026). The mean CDI was 1.06 ± 0.17 and mean ISI was 1.04 ± 0.15. Of the 49 knees that met criteria for patella alta on radiographic evaluation, rerupture occurred in seven (14.29%). Patella alta was not a significant risk factor for ACL failure among adolescent patients (p = 0.359 and 0.277). Only male sex was associated with increased rates of ACL failure. Age, graft selection technique, fixation construct, and presence of patella alta were not risk factors for reinjury. This study is a therapeutic case series and reflects level of evidence IV.

Poster 261: Increased TT-TG and Tibial Slope are Independent Predictors of ACLR Failure

Objectives:Tibial tubercle-trochlear groove (TT-TG) distance is a surrogate measure of valgus and rotational stress on the anterior cruciate ligament (ACL) and may predict ACL injury. Increased posterior tibial slope has been associated with risk of ACL re-tear but no studies have evaluated TT-TG as a predictor of ACL re-tear. We hypothesized TT-TG distance and posterior tibial slope would be independent predictors of ACL graft re-tear.Methods:All patients who underwent ACL revision surgery between 2010-2018 at a single institution were identified. A control cohort underwent primary ACL reconstruction (ACLR) between 2006-2015, with no evidence of graft failure at 8.1 ± 2.5 yrs post-op. Record review included anthropometrics, graft type, and estimated highest Tegner activity score at ≥ 6 months post primary ACLR. Magnetic resonance images (MRI) following native ACL tear (controls) or graft failure (revision cohort) were assessed for the following: 1) medial, lateral, and coronal tibial slope, 2) depth of tibial plateau concavity, 3) TT-TG distance, and 4) tunnel position. Logistic regression analyses were used to associate ACL graft failure with radiographic parameters, surgical variables, and demographics. Sensitivity analyses, excluding patients in the revision group with tunnel malposition, were performed to confirm multivariable results.Results:Participants included 153 revisions and 146 controls. Controls were older than revisions (26.6 ± 8.8 yrs vs. 20.6 ± 7.3 yrs). Mean TT-TG distance and lateral tibial slope values were smaller for the control vs. revision group (TT-TG = 9.4 ± 3.9 mm vs. 11.2 ± 4.2 mm; lateral tibial slope = 6.2o ± 3.4° vs. 7.2o ± 3.6°). TT-TG distance and lateral tibial slope were associated with increased risk of ACL graft failure by multivariable analysis (OR: 1.14, CI: 1.07, 1.22, p < 0.001 and OR: 1.11, CI: 1.02, 1.20, p = 0.007, respectively). With sensitivity analyses, age at index surgery, TT-TG distance, and lateral tibial slope remained significant predictors of ACL revision.Conclusions:Increased TT-TG distance, increased lateral tibial slope, and younger age are associated with increased odds of ACL graft failure. These patients may require a more comprehensive strategy to reduce the risk of ACL re-tear.Table 1.Demographic and Clinical Characteristics of Study Population by Revision Status

Paper 23: The Impact of Graft Choice on Return to Sport Testing After Adolescent ACL Reconstruction

Objectives:The number of anterior cruciate ligament (ACL) injuries and reconstructions observed in the adolescent population continues to rise. While the use of quadriceps tendon autograft has increased in popularity in this population, there remains no consensus on the ideal graft for pediatric ACL reconstruction. The objective of this study was to compare three commonly used ACL graft types with respect to i) performance on return to sport assessments and ii) timing to clearance for return to sports in an adolescent population.Methods:All patients, less than or equal to 19 years of age, who underwent reconstruction for ACL tears between 2016 and 2020 at a large, urban, academic institution were identified. Graft choice was made in a shared decision-making model with patient, parents, and surgeon. Patient demographics, laterality, graft type, time from surgery to clearance, number of physical therapy (PT) visits, and presence of concomitant meniscus injuries were collected from the electronic medical record. At a minimum of 6 months postoperatively, patients completed a formal return to sport test (RTS) including isometric strength assessments, Y- balance testing, and hop testing. Treatment cohorts based on graft type were compared with respect to RTS performance and timing to clearance. Associations between patient demographics and return to sport timing and performance were also assessed. Clearance for return to sport was determined by the treating surgeon with limb symmetry index of 90% on RTS as the goal for clearance.Results:A total of 110 adolescents, 44 female (40%), with a mean age of 16.3 years (SD, 1.7; range, 10-19) met our inclusion criteria (Table 1). Average time to first RTS assessment was 280 days (9.3 months) and average time to clearance was 371 days (12.2 months) after surgery. ACL grafts included 58 (52.7%) hamstring autografts, 26 (23.6%) bone-patellar tendon-bone (BPTB) autografts, 21 (19.1%) bone quadriceps (BQT) autografts, and 5 (4.6%) iliotibial band (ITB) autografts. ITB patients were younger on average (12.5 years old) than those receiving hamstring, BPTB or BQT grafts. There were no significant differences between groups with respect to laterality, number of physical therapy visits, or rate of concurrent meniscus surgery.Patients receiving BQT grafts were more likely to be cleared within 1 year of surgery compared to hamstring graft patients (82.4% vs. 39.6%, p=0.002) and had similar rates of clearance within 1 year compared to BPTB patients (82.4% vs. 65.2%, p=0.230). Patients with BQT and BPTB grafts both demonstrated significantly better hamstring strength symmetry compared to hamstring graft patients (5.8% strength deficit compared to healthy side vs. 1.3% vs. 29.3%, p<0.001) (Table 2). There were no differences in quadriceps strength or hop test asymmetry between graft types. Multivariate regression with age, gender, and number of PT sessions included as covariates demonstrated that hamstring graft choice was associated with decreased odds of clearance at 1 year.Conclusions:In this study of 110 adolescent ACL reconstruction patients who underwent return to sport evaluations, we found no significant difference between BPTB and BQT autografts with respect to RTS performance and time to clearance. Hamstring autograft was associated with significantly worse hamstring strength asymmetry and significantly lower rates of clearance within 1 year. Concurrent meniscus surgery, age, gender, and number of PT sessions completed prior to RTS evaluation were not significantly associated with timing of clearance or performance on the RTS assessment.Table 1.Patient Demographics and Surgical CharacteristicsTable 2.Patient Demographics and Performance by 3 Common Graft Types

Poster 203: Mechanical Loading Effects on OA Progression Following ACL Injury and Reconstruction in a Murine Model: Radiographic Assessment of Synovial Fibroblast Activity

Poster 203: Mechanical Loading Effects on OA Progression Following ACL Injury and Reconstruction in a Murine Model: Radiographic Assessment of Synovial Fibroblast Activity

Poster 213: Increased Vascularity might Peak at 3 to 6 Months Postoperatively on the Reconstructed Anterior Cruciate Ligament Assessed with Superb Microvascular Imaging (SMI)

Poster 213: Increased Vascularity might Peak at 3 to 6 Months Postoperatively on the Reconstructed Anterior Cruciate Ligament Assessed with Superb Microvascular Imaging (SMI)

Bone Grafting Technique in Revision ACL Reconstruction: Coring Reamer and Dowel Trick

One- or two-staged bone grafting is sometimes required for tunnel malposition and/or tunnel widening in revision anterior cruciate ligament (ACL) reconstruction. The aim of this procedure is to restore the correct position of the ACL graft in the revision setting to provide a stable and functional ACL, thereby reproducing normal knee kinematics. We present a technique that allows for a cost-effective, convenient tunnel grafting of a femoral head allograft bone dowel into both femoral and tibial defects in revision ACL reconstruction.

Notchplasty is associated with decreased risk of anterior cruciate ligament graft revision.

Despite influencing knee biomechanics and outcomes, the use of notchplasty at time of anterior cruciate ligament reconstruction (ACLR) has not been evaluated with regards to risk of secondary injury and revision. This study evaluates this association. 42 patients (21.7-years, IQR = 19.0-27.5) that underwent primary then revision ACLR at a single institution were contrasted with a case matched control group of patients with grafts that did not fail. Patients were propensity score matched in a 1:2 ratio by age, gender, and date of index procedure. Post-hoc statistical correction was made for post-index procedure sports participation level. Notchplasty was performed in 2 of 42 cases that went on to revision, and in 31 of 84 cases in the control group (p < 0.001). This was associated with reduced rates of revision ACLR (OR = 0.085, 95%CI = 0.019-0.378). A significant difference was seen in the post-ACLR activity level between groups (p = 0.028), with post-hoc testing highlighting those returning to competitive sport to be more likely to require subsequent revision (OR = 9.647, 95%CI = 1.947-47.795). Notchplasty remained significantly associated with (reduced) risk of revision surgery, despite the observed variation in post-ACLR activity (p = 0.001). Individuals whose graft failed following ACLR were significantly less likely to have had notchplasty performed as part of their surgery than a control group who did not suffer graft reinjury. We propose that this may be due to decreased tensioning of the graft as the knee enters dynamic valgus, which may be of great relevance to athletes undergoing ACLR to enable return to sport.

Considerations of the Posterior Tibial Slope in Anterior Cruciate Ligament Reconstruction: a Scoping Review

The significance of posterior tibial slope (PTS) in the setting of anterior cruciate ligament (ACL) injury and reconstruction has been increasingly recognized in recent years. The purpose of this article is to review the biomechanical and clinical studies of PTS in conjunction with ACL injuries, providing an evidence-based approach for the evaluation and management of this patient population. Several biomechanical and clinical studies suggest that PTS > 12° may be considered with increased strain on the native ACL fibers (or reconstructed graft) and greater anterior tibial translation, predisposing patients to a recurrent ACL injury. The increased rates of ACL injury and graft failure seen in those with increased PTS have garnered attention to diagnose and surgically address increased PTS in the revision ACL setting; however, the role of a slope-reducing high tibial osteotomy (HTO) in primary ACL reconstruction (ACL-R) has yet to be defined. Various HTO techniques to decrease PTS during revision ACL-R have demonstrated promising outcomes, though conclusions are limited by the multifactorial nature of revision surgery and concomitant procedures performed. Recent evidence suggests that increased PTS is a risk factor for failure following ACL-R, which may be mitigated by a slope-reducing HTO. Further investigation is needed to elucidate abnormal PTS values and to determine appropriate indications for a slope-reducing HTO in primary ACL-R.

Is There an Association in Young Patients Between Quadriceps or Hamstring Strength After ACL Reconstruction and Graft Rupture?

Background:Younger patients who sustain anterior cruciate ligament (ACL) ruptures are at high risk for reinjury after ACL reconstruction. Restoring muscle strength before return to sports (RTS) is regarded as an important factor in reducing the reinjury risk, and quadriceps and hamstring strength assessment is commonly included in RTS testing. However, it is not clear whether reduced strength is a risk factor for subsequent graft rupture in this patient population.Purpose:To investigate the association between quadriceps and hamstring strength at 12 months after primary ACL reconstruction and ACL graft rupture in young patients.Study Design:Case-control study; Level of evidence, 3.Methods:The cohort consisted of 210 patients (100 men and 110 women) who were younger than 20 years at the time of primary ACL reconstruction with a hamstring tendon autograft and who had no previous contralateral ACL injury. Isokinetic strength testing (60 and 180 deg/s) of knee flexors and extensors was performed at 12 months postoperatively, and the limb symmetry index (LSI) for each strength outcome was calculated. RTS rates and the incidence of further ACL graft ruptures were recorded.Results:Measures of central tendency (mean and median) of LSI values ranged from 88 to 98. The percentage of patients with LSI ≥90 was 57% to 69% for quadriceps strength and 45% to 47% for hamstring strength. Overall, 19 patients (9%) sustained an ACL graft rupture. No significant differences were found between the patients who sustained an ACL graft rupture and those who did not in terms of quadriceps and hamstring strength at 12 months. No significant associations were found between achieving LSI ≥90 for quadriceps peak torque and subsequent ACL graft rupture.Conclusion:In young patients who underwent an ACL reconstruction, no association was noted between quadriceps and hamstring strength at 12 months postoperatively and subsequent graft ruptures. The role of strength testing as part of the RTS criteria after ACL reconstruction, and specifically the use of limb symmetry thresholds, warrants further investigation and clarification.

Females have Lower Knee Strength and Vertical Ground Reaction Forces During Landing than Males Following Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport

Purpose There is a high rate of second anterior cruciate ligament (ACL) injury (ipsilateral graft or contralateral ACL) upon return-to-sport (RTS) following ACL reconstruction (ACLR). While a significant amount of epidemiological data exists demonstrating sex differences as risk factors for primary ACL injury, less is known about sex differences as potential risk factors for second ACL injury. The purpose of this study is to determine if there are sex-specific differences in potential risk factors for second ACL injury at the time of clearance for RTS. Methods Ten male and eight female athletes (age: 20.8 years ±6.3, height: 173.2 cm ±10.1, mass: 76.6 kg ±18.3) participated in the study following ACLR at time of RTS (mean 10.2 months). Performance in lower extremity isokinetic and isometric strength testing, static and dynamic postural stability testing, and a single leg stop-jump task was compared between the sexes. Results Normalized for body weight, males had significantly greater isokinetic knee flexion (141±14.1 Nm/kg vs. 78±27.4 Nm/kg, p=0.001) and extension strength (216±45.5 Nm/kg vs. 159±53.9 Nm/kg, p=0.013) as well as isometric flexion (21.1±6.87% body weight vs. 12.5±5.57% body weight, p=0.013) and extension (41.1±7.34% body weight vs. 27.3±11.0% body weight, p=0.016) strength compared to females. In the single-leg stop jump task, males had a greater maximum vertical ground reaction force during landing (332±85.5% vs. 259±27.4% body weight, p=0.027) compared to females. Conclusions Based on these results, there are significant differences between sexes following ACLR at the time of RTS. Lower knee flexion and extension strength may be a potential risk factor for second ACL injury among females. Alternatively, the increased maximum vertical force observed in males may be a potential risk factor of second ACL injury in males. Although these results should be interpreted with some caution, they support that rehabilitation programs in the post-ACLR population should be individualized based on the sex of the individual. Level of Evidence Level 3

Functional Ultra-High Molecular Weight Polyethylene Composites for Ligament Reconstructions and Their Targeted Applications in the Restoration of the Anterior Cruciate Ligament.

The selection of biomaterials as biomedical implants is a significant challenge. Ultra-high molecular weight polyethylene (UHMWPE) and composites of such kind have been extensively used in medical implants, notably in the bearings of the hip, knee, and other joint prostheses, owing to its biocompatibility and high wear resistance. For the Anterior Cruciate Ligament (ACL) graft, synthetic UHMWPE is an ideal candidate due to its biocompatibility and extremely high tensile strength. However, significant problems are observed in UHMWPE based implants, such as wear debris and oxidative degradation. To resolve the issue of wear and to enhance the life of UHMWPE as an implant, in recent years, this field has witnessed numerous innovative methodologies such as biofunctionalization or high temperature melting of UHMWPE to enhance its toughness and strength. The surface functionalization/modification/treatment of UHMWPE is very challenging as it requires optimizing many variables, such as surface tension and wettability, active functional groups on the surface, irradiation, and protein immobilization to successfully improve the mechanical properties of UHMWPE and reduce or eliminate the wear or osteolysis of the UHMWPE implant. Despite these difficulties, several surface roughening, functionalization, and irradiation processing technologies have been developed and applied in the recent past. The basic research and direct industrial applications of such material improvement technology are very significant, as evidenced by the significant number of published papers and patents. However, the available literature on research methodology and techniques related to material property enhancement and protection from wear of UHMWPE is disseminated, and there is a lack of a comprehensive source for the research community to access information on the subject matter. Here we provide an overview of recent developments and core challenges in the surface modification/functionalization/irradiation of UHMWPE and apply these findings to the case study of UHMWPE for ACL repair.

Arthroscopic Revision of Attenuated Anterior Cruciate Ligament Graft With Enlarged Bone Tunnels Using Injectable Bone Graft Substitute

Revision anterior cruciate ligament (ACL) reconstruction is a technically demanding procedure, and the surgeon should be prepared to address bone tunnel osteolysis, concurrent meniscal, ligamentous, or cartilage lesions, and limb malalignment. ACL revision can typically be done in one procedure, but it may need to be staged if there is poor previous tunnel positioning or excessive tunnel osteolysis. Bone grafting of the tunnels can be accomplished in several ways, including autograft, allograft, or bone substitutes. Currently, no consensus is available regarding the optimal choice of bone graft material for bone tunnel augmentation in revision ACL reconstruction. Bone graft substitute for tunnel augmentation has been showed to have good histologic, radiographic, and intraoperative integration, comparable to that of autologous bone. In this Technical Note, the technical details of arthroscopic treatment of attenuated anterior cruciate ligament graft with enlarged bone tunnels are described. The tunnels are debrided arthroscopically and filled up with PRO-DENSE injectable regenerative graft.

Modern solutions in reconstruction of the anterior cruciate ligament

The rapid development of medical technologies makes the attitude to anterior cruciate ligament (ACL) reconstruction constantly reconsidered. In our work, we evaluated the results of surgical treatment of patients after ACL reconstruction using different options of graft fixation. We retrospectively analyzed the treatment of 125 patients with anterior instability of the knee joint. No great difference in the results of choosing the method of ACL graft fixation was revealed. The «all-inside» technology seems more promising. Correct positioning of the bone canals is very important. In the case of simultaneous meniscus injury it is necessary to perform a suture in order to preserve an important passive stabilizer of the knee joint.

Biomechanical Analysis of Tibial Motion and ACL Graft Forces After ACLR with and without let at Varying Tibial Slopes

Background:Lateral extra-articular tenodesis (LET) is being performed with increasing frequency in the setting of anterior cruciate ligament reconstruction (ACLR) as a way to decrease rotational instability and graft failure rates, especially in young, active patients. The degree of posterior tibial slope has been shown to affect ACL graft failure rates.1 The effect of LET plus ACLRs on tibial motion and graft forces in the setting of varying tibial slopes has not been elucidated.Hypothesis/Purpose:LET will decrease tibial translation, tibial rotation, and ACL graft forces compared to ACLR alone with increasing tibial slope throughout knee range of motion.Methods:Twelve cadaveric knees (40.5 mean age, all female) were tested in 4 conditions (1: intact; 2: ACLR; 3: ACLR + LET; and 4: ACL cut) with varying posterior tibial slopes (5°, 10°, 15°, and 20°) at three flexion angles (0°, 30, ° and 60°). Specimens were mounted to a load frame which applied a 500-N axial load with 1 N-M of internal rotation torque (Figure 1). The amount of tibial translation was measured using a laser sensor and rotation was measured along the axis of the load frame. ACL graft forces were measured via a force transducer.Results:No clinically relevant difference was found in graft force (all differences <6.8 N, except the 5° posterior tibial slope at 30° of flexion showing a 12.1 N reduction with LET), anterior tibial translation (all differences <2.4 mm), or internal rotation (all differences < 1.59°). Compared to the intact state, the cut ACL state had higher anterior tibial translation (maximum increase +9.1 mm at slope 20°, Flexion 60°) and internal rotation (maximum increase +4.3° at slope 5°, flexion 30°). Higher ACL graft forces were observed with increasing posterior tibial slope (ACLR graft force at 0° of flexion was 81.6 N at 5°, 97.8 N at 10°, 107.0 N at 15°, 113.9 N at 20° of slope). Figure 2 shows ACL graft forces in N, Figure 3 shows anterior tibial translation in mm and Figure 4 shows internal rotation in degrees. All figures present data at 30°of flexion.Conclusion:No clinically relevant difference was shown with the addition of LET in the setting of ACLR for patients with posterior tibial slopes from 5° to 20° at flexion angles of 0°, 30°, and 60° in regards to graft force, anterior tibial translation, and internal tibial rotation under a 500 N compressive load.Figure 1.AP and Posteromedial views of the testing specimen mounted on load frameFigure 2.ACL Graft Force at 500N compression at Flexion 30° for ACLR (Red) vs ACLR+LET (Blue) states at varying posterior tibial slopes (5°, 10°, 15°, and 20°)Figure 3.Anterior Tibial Translation at Flexion 30° for all states (Intact (blue), ACLR+LET (red), ACLR (green), ACL cut (orange)) at varying posterior tibial slopes (5°, 10°, 15°, and 20°)Figure 4.Internal Tibial Rotation at Flexion 30° for all states (Intact (blue), ACLR+LET (red), ACLR (green), ACL cut (orange)) at varying posterior tibial slopes (5°, 10°, 15°, and 20°)Reference:1. Bernhardson AS, Aman ZS, Dornan GJ, et al. Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases. Am J Sports Med. 2019;47(2):296-302. doi:10.1177/0363546518820302

ACL Graft Growth in Pediatric Patients After ACL Reconstruction

Background:The native anterior cruciate ligament (ACL) changes in diameter and cross-sectional area throughout growth and up until age 18. The size and morphology of the native ACL continues to change throughout skeletal maturation. While ACL autografts have been shown to increase in size following ACL reconstruction in adults, there have been no similar studies to evaluate the change in ACL autografts in skeletally immature patients.Purpose:The primary aim of this study was to measure changes in ACL graft diameter in pediatric patients based on subsequent magnetic resonance imaging (MRI) after ACL reconstruction surgery. The second aim was to determine if there is evidence of ACL autograft growth after ACL reconstruction in skeletally immature patients.Methods:This was a retrospective review of 21 skeletally immature patients (mean age 14 years, range 12-16 years, 76% female) who underwent ACL reconstruction from January 2009 to July 2020 and had a subsequent MRI following surgery. We excluded patients who were treated with an allograft or underwent subsequent MRI for ACL re-injury. We measured the mid-substance ACL cross-sectional area and the post-operative graft diameter on subjects’ subsequent MRI. The recorded intra-operative graft diameter was compared to the post-operative graft diameter to determine the change in graft size.Results:76% (n=16) of subjects were treated with a quadriceps autograft. Follow-up MRIs were performed at a mean of 1.7 years (range 0.3 – 3.8 years) post-operative. Post-operative grafts increased 2.2mm (p<0.001, 95% CI = 1.8-2.7) in diameter compared to the intra-operative graft diameter (Figure 1).Conclusions:In our study population, there was a significant increase of 2.2mm in ACL graft diameter an average of 1.7 years after ACL reconstruction in skeletally immature patients. Our results are similar to previous studies demonstrating an increase in graft size post-operatively in adults. These results suggest that it may be useful for surgeons to take the likely changes in graft size into account when determining appropriate autograft size in skeletally immature patients.Figure 1.Comparison between initial mid graft diameter measurement size and follow-up MRI graft diameter size. The line within the box defines the median value. The range of the box defines the 25th and 75th percentile, and whiskers extending from the box plots define the range of measurements obtained.