INTRODUCTION. In native knees the anterior cruciate ligament (ACL) plays a major role in joint stability and kinematics. Sacrificing the ACL in contemporary total knee arthroplasty (TKA) is known to cause abnormal knee motion, and reduced function. Hence, there is growing interest in the development of ACL retaining TKA implants. Accommodation of ACL insertion around the tibial eminence is a challenge with these designs. Therefore, a reproducible and practical test setup is necessary to characterize the strength of the ACL/bone construct in ACL retaining implants. Seminal work showed importance of loading the ACL along its anatomical orientation. However, prior setups designed for this purpose are complex and difficult to incorporate into a standardized test for wide adoption. The goal of this study was to develop a standardized and anatomically relevant test setup for repeatable strength assessment of ACL construct using basic force-displacement testing equipment. METHODS. Cadaver knees were positioned with the ACL oriented along the loading axis and being the only connection between femur and tibia. 15° knee flexion was selected based on highest ACL tensions reported in literature. Therefore, the fixtures were adjusted accordingly to retain 15° knee flexion when the ACL was tensioned. The test protocol included 10 cycles of preconditioning between 6N and 60N at 1mm/s, followed by continuous distraction at 1mm/s until failure (Fig. 1). Eleven cadaveric knees (4 male, 7 female; 70.9 yrs +/−13.9 yrs) were tested using this setup to characterize a baseline ACL pullout strength (peak load to failure) in native knees. RESULTS. The average ACL pullout strength was 935.6N +/−327.5N with the extremes ranging from a minimum of 346N to a maximum of 1425N. There were five failure modes observed: [1] ACL avulsion from the femur with bony attachment (one knee), [2] ACL pull-off from the femur w/o bony attachment (two knees), [3] ACL tear (three knees), [4] ACL pull-off from the tibia w/o bony attachment (one knee), [5] ACL avulsion from the tibia with bony attachment (three knees). One knee showed a combined failure mode of 2 & 4, meaning part of the ACL was pulled off the femur and part pulled off the tibia. CONCLUSION. There was a large variation in failure load between specimens. The knee with the minimum failure load had severe arthritis, osteophytes and signs of ACL deficiency. The average failure load (935.6N +/−327.5N) is in line with those published in literature for a comparable age group. This indicates that failure loads and modes obtained with more complex setups could be reproduced by using standard uniaxial load frames and simple fixtures. The failure modes in our experiment were evenly spread between mid-substance, and insertions (either femur or tibia). This test could be used as a standardized method to investigate the strength of the ACL complex following procedures such as ACL reconstruction, partial- and total knee arthroplasty. In particular, this setup provides a reliable mechanism for evaluation of the ACL-bone construct in bi-cruciate retaining (BCR) TKA, which is likely required for regulatory pathways

Knee joint infection after an ACL reconstruction procedure is infrequently but might be a devastating clinical problem, if not diagnosed promptly and treated wisely. The results of functional outcomes in these patients are not well known because there aren't large patient series in the literature. The objective of this study was to evaluate the prevalence and determine the adequate management of septic arthritis following ACL reconstruction and to assess the patient functional outcomes. The authors conducted a retrospective multicentric analysis of septic arthritis cases occurring after arthroscopically assisted ACL reconstructions (hamstrings and BTB), in patients submitted to surgery between 2010 to 2014. The study reviewed patients submitted do ACL reconstruction, that presented objective clinical suspicion of joint infection, in post-operative acute and sub-acute phases, associated with high inflammatory seric parameters (CRP >=10,0, ESR>=30,0) and synovial effusion laboratory parameters highly suggestive (PMN >=80, leucocytes >=3000). All this patients were treated with antibiotic empiric suppressive therapy and then directed antibiotherapy according to antibiotic sensitivity profile, then the patients were submitted to arthroscopic lavage procedure, without arthropump, but with debris and fibrotic tissue removal preserving always the ACL plasty. The functional outcomes analyzed were the Lysholm and the IKDC score. Eleven (2.2 %) out of 490 patients analyzed in the sudy were diagnosed with a post-operative septic arthritis. The microbiologic exams showed coagulase-negative Staphylococcus was present in 5 patients (S. lugdunensis in 4 cases and S. capitis in 1 case), Staphylococcus Aureus in 2 patients (1 MSSA and 1 MRSA). In four patients, the micro-organism was not identified. The studied patients had a mean follow-up of 28 ± 16 months, the Lysholm score was 74.8 ± 12.2, the IKDC score was 66.4 ± 20.5. Functional outcomes in the control group were better than those obtained in the infected group. (Lysholm score 88.2 ± 9.4 (NS); IKDC score 86.6 ± 6.8 (NS). All patients retained their reconstructed ACL. None of the patients relapsed or need other intervention because of ACL failure and chronic instability. The prevalence of septic arthritis after an ACL reconstruction in this series was 2.2 %, slightly higher than other international series (0.14 to 1.7 %). Arthroscopic lavages along with antibiotic treatment showed to be a secure procedure and allowed the preservation of the ACL plasties, without infection relapse. But the functional outcomes after active intra-articular infection were largely inferior to those obtained in patients without infection, probably to uncontrolled and intense inflammatory local response

Introduction and purpose: To assess the diagnostic usefulness of MRI to diagnose ACL lesions using quantitative instead of qualitative parameters. Materials and methods: A retrospective study was made of the MRIs of a group of 50 patients with an athroscopically confirmed ACL tear and a control group of 50 patients with meniscal lesions and with an arthroscopic confirmation that they had a normal ACL. Multiple MRI findings were studied in order to evaluate their sensitivity and Specificity to detect an ACL lesion. Special emphasis was placed on 3 quantitative parameters, including a simplified method to measure the angle between the ACL and the tibial plateau. Results: Using 45° as a cutoff value, the ACL/tibial plateau angle yielded a sensitivity and Specificity of 100%. With a 0° cutoff value, the angle together with Blumensaat’s line showed a sensitivity of 90% and a Specificity of 98%. With a cutoff value of 115°, the PCL angle showed a sensitivity of 70% and a Specificity of 82%. Conclusions: The quantitative parameters studied are valuable to predict ACL lesions and can increase both the sensitivity and Specificity of MRI images. The ACL/ tibial plateau angle can be measured easily using a single MRI image and can be regarded as the best clue to diagnose ACL lesions

Anterior cruciate ligament reconstruction has become a standard procedure with a documented good and excellent outcome of 70–90%. It has been demonstrated by previous research that all patients following surgery demonstrate a strength deficit of almost 20%. However it is not known whether these strength deficits have an influence on postoperative functionality. 52 consecutive patients (38 males and 14 females) were selected (mean age 27.9 years). All subjects were tested prior and 12 month following anterior cruciate ligament reconstruction. Muscle strength was assessed using a Biodex dynamometer. Isometric strength was examined at 30 and 60 degrees of flexion. Isokinetic testing was performed at 180 degrees/sec and peak torque and symmetry indices were analysed. No correlations were found between the Cinncinnati Score and isokinetic peak torque for extension. A moderate significant (p=0.001–0.007) correlation (r=0.200.45) was found for peak flexion torque in ACL reconstructed patients. In ACL deficient patients symmetry indices (r=0.36–0.43, p=0.001–0.004) were moderately related to functionality for both flexion and extension. Quadriceps muscle strength does not seem to be an important predictor of knee function after ACL reconstruction. Flexors seem to be important to protect the graft from overload. In ACLD knees functionality is related to high symmetry indices suggesting similar strength is necessary to perceive knee function as near normal. This is possibly a normal neuromuscular adaptation caused by contralateral quadriceps avoidance

Introduction. Understanding knee joint biomechanics is crucial, but studying Anterior cruciate ligament (ACL) biomechanics in human adolescents is challenging due to limited availability cadaveric specimens. This study aims to validate the adolescent porcine stifle joint as a model for ACL studies by examining the ACL's behavior under axial and torsion loads and assessing its deformation rate, stiffness, and load-to-failure. Methods. Human knee load during high-intensity sports can reach 5-6 times body weight. Based on these benchmarks, the study applied a force equivalent to 5-times body weight of juvenile porcine samples (90 pounds), estimating a force of 520N. Experiments involved 30 fresh porcine stifle joints (Yorkshire breed, Avg 90 lbs, 2-4 months old) stored at -22°C, then thawed and prepared. Joints were divided into three groups: control (load-to-failure test), axially loaded, and 30-degree torsion loaded. Using a servo-hydraulic material testing machine, the tibia's longitudinal axis was aligned with the load sensor, and specimens underwent unidirectional tensile loading at 1 mm/sec until rupture. Data on load and displacement were captured at 100 Hz. Results. One-way ANOVA showed statistically significant differences in maximum failure force among loading conditions (p = 0.0039). Post hoc analysis indicated significant differences between the control and 500N (non-twisted) groups (p = 0.014) and between the control and 500N (twisted) groups (p = 0.003). However, no significant difference was found between 500N (non-twisted) and 500N (twisted) groups (p = 0.2645). Two samples broke from the distal femur growth plates, indicating potential growth plate vulnerability in adolescent porcines. Conclusions. The study validates the adolescent porcine stifle joint as a suitable model for ACL biomechanical research, demonstrating that torsional loads are as damaging to the ACL's integrity as equivalent axial loads. It also highlights the potential vulnerability of growth plates in younger populations, reflected in the porcine model

The level of hamstring antagonist activation is thought to be related to knee functionality following anterior cruciate ligament (ACL) injury/surgery as pronounced co-activation can control anterior tibial translation (ATT). The purpose of this study was to examine relationships between knee functionality and hamstring antagonist activation during isokinetic knee extension in ACL deficient (ACLD) and ACL reconstructed (ACLR) patients. Knee functionality was rated using the Cincinnati Knee Rating System for the involved limb of 10 chronic, functional ACLD patients and 27 ACLR patients (14 using a patella tendon (PT) graft and 13 using a semitendinosus/gracilis tendon (STGT) graft). Each subject also performed maximal effort isokinetic knee extension and flexion at 180°. s. -1. for the involved limb with electromyographic (EMG) electrodes attached to the semitendinosus (ST) and biceps femoris (BF) muscles. Antagonist activity of the ST and BF muscles was calculated in 10° intervals between 80-10° knee flexion. For the ACLD group, Pearson product moment correlations revealed significant (p<0.05) moderate, positive relationships between knee functionality and ST and BF antagonist activity across the majority of the knee flexion intervals. For both ACLR groups, several significant (p<0.05) moderate, negative associations were found between ST and BF antagonist activity and knee functionality. Amplified hamstring antagonist activity in ACLD patients at flexion angles representative of those at footstrike and deceleration improves knee functionality as increased crossbridge formation increases hamstring stiffness and decreases ATT. Lower-level hamstring activation is sufficient to unload the ACL graft and improve knee functionality in ACLR patients

The purpose of this study was initially to examine the effect of tibial slope on anterior tibial translation in the ACL deficient knee measured objectively using the KT 1000 arthrometer. Patients were then evaluated one year post ACL reconstruction to determine the effect of tibial slope on the outcome of ACL reconstruction. One-hundred patients (male = 70, female 30) aged between 14 and 49 years (Mean = 28.70, SD 8.80) with a diagnosis of isolated anterior cruciate ligament rupture were prospectively recruited. All participants had intact ACLs of the contralateral limb. The following information was recorded for all patients preoperatively and one year post surgery; time from injury to surgery, IKDC objective and subjective assessment and KT 1000 arthrometer readings. Tibial slope was assessed from long tibial lateral x-rays as described by Dejour and Bonnin. Finally, assessment of the menisci occurred intra-operatively. Tibial slope was correlated with KT 1000, meniscal integrity and IKDC assessments. Patients underwent an arthroscopic hamstring ACL reconstruction using Endobutton and Intrafix fixation. All procedures were performed by one surgeon. Pre Reconstruction – Bivariate correlations showed a significant correlation between tibial slope and KT 1000 (r= .29, p < .001). This relation was strengthened when the integrity of the menisci were controlled for (r = .32, p < . 001). When time to surgery was controlled for, correlations between tibial slope and KT 1000 were unaffected. There was also a negative correlation between medial meniscal integrity and time to surgery (r = −.41, p < . 001). No relationships between time to surgery and KT 1000 were evident. Post Reconstruction – Eighty patients were evaluated at a one year post surgery. One patient had a rerupture. The mean KT 1000 difference was 1mm. KT 1000 was > 2mm in 9% and > 5mm in the re rupture only. The mean subjective IKDC score was 89. Using objective IKDC 89% were classified as normal, 10% as nearly normal and 1% as severely abnormal (the rerupture). Bivariate correlations showed no significant correlation between tibial slope and post operative KT 1000 (r= .178, p = .0.115). This study demonstrates a significant relationship between increasing tibial slope and anterior tibial translation of the ACL deficient knee. The relationship did not exist in the post ACL reconstructed knee. However this needs to be investigated further with greater numbers and in the ACL revision group

One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). Therefore, retaining the ACL is often considered to be the “holy grail” of TKA. However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or non-functional ACL. Therefore, the goal of this research was to investigate whether substitution of ACL function through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining (CR) implants. This was done using KneeSIM, a previously established dynamic simulation tool based on an Oxford-rig setup. Deep knee bend, chair-sit, stair-ascent and walking were simulated for a contemporary ACL sacrificing (CR) implant, two ACL retaining implants, and an ACL substituting and PCL retaining implant. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons. Our results revealed that, like ACL retaining implants, the ACL substituting implant could also provide kinematic improvements over contemporary ACL sacrificing implants by reducing early posterior femoral shift and preventing paradoxical anterior sliding. Such ACL substituting implants may be a valuable addition to the armament of joint surgeons, allowing them to provide improved knee function even when ACL retention is not feasible. Further research is required to investigate this mechanism in vitro and in vivo to verify the results of the simulations, and to determine whether kinematic improvements translate into improved clinical outcomes

Combined anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) disruptions are uncommon orthopaedic injuries. They are usually caused by high- or low-velocity knee dislocations. Because knee dislocations might spontaneously reduce before initial evaluation, the true incidence is unknown. Dislocation involves injury to multiple ligaments of the knee. Both of the cruciate ligaments are usually disrupted, and they are often combined with a third ligamentous disruption (medial collateral ligament or lateral collateral ligament and/or posterior lateral complex). Associated neurovascular, meniscal, and osteochondral injuries are often present and complicate treatment. Classification Knee dislocations are classified by relating the position of the displaced tibia on the femur; anterior, posterior, medial, lateral, or rotational. Both cruciate ligaments might be disrupted in all these injuries. A rotatory knee dislocation occurs around one of the collateral ligaments (LCL) leading to a combined ACL and PCL injury and a tear of the remaining collateral ligament. Knee dislocations that spontaneously reduce are classified according to the direction of instability. Knee dislocations are classified as acute (< 3 weeks) or chronic (> 3 weeks). Initial management The vascular status of the limb must be determined quickly. The knee should be reduced immediately through gentle traction-countertraction with the patient under anesthesia. After reduction, repeat vascular examination. If the limb remains ischemic, emergent surgical exploration and revascularisation is required. If the initial vascular examination is normal, postreduction a formal angiogram should be done especially if the patient has a high velocity injury, is polytraumatized or have altered mental status. Compartment syndrome, open injury, and irreducible dislocation are other indications for emergent surgery. Definitive management Many authors have noted superior results of surgical treatment of bicruciate injuries when compared to nonsurgical treatment. In most cases early ligament surgery (at the second or third week) seems to produce better results compared to late reconstructions. Still the management of knee dislocations remains controversial. Controversies persist regarding surgical timing, technique, graft selection, and rehabilitation. The goal of operative treatment is to retain knee stability, motion, and function. The most common injury patterns include both cruciate ligaments and either medial collateral ligament (MCL) or lateral collateral ligament (LCL) and/or posterolateral structures. Less commonly both collateral ligaments are disrupted. Our policy has been early (from 7 to 21 days) simultaneous reconstruction of both cruciate ligaments and repairing of grade III LCL and posterolateral structures. Most acute grade III MCL tears are successfully treated with brace treatment when ACL and PCL are reconstructed early. Most cruciate ligament injuries are midsubstance tears that need to be reconstructed with autografts or allografts. Repairs can be done in cases of bony avulsion of cruciate ligaments or grade III collateral ligament or capsular injuries. Bone-patellar tendon-bone (BPTB) autograft has mainly used in our clinics to reconstruct the ACL. In some cases BTPB allograft or hamstring tendon autografts has been used. For PCL reconstruction, BPTB allograft (11 mm in diameter) or Achilles tendon allograft has been used. Intrasubstance grade III tears of the LCL can be repaired (in early state) but may need to be augmented with tendon allograft. The LCL and/or the popliteofibular ligament are reconstructed either with an Achilles tendon allograft, hamstring tendon autograft/allograft, tibialis anterior tendon allograft, or the BPTB allograft. Both cruciate ligaments are reconstructed arthroscopically. The ACL tunnels are placed in the center of its anatomic insertion in tibia and in its isometric or anatomic insertion in femur. A transtibial tunnel technique for PCL reconstruction is used. The PCL tibial tunnel is drilled first under arthroscopic guidance using the PCL guide. The ACL tibial guide is drilled at least 2 cm proximal to the PCL tunnel to ensure that wide enough bone bridge remains between these tunnels. Fluoroscopy is used to ensure the right guidewire placement. Sequence of bicruciate ligament reconstruction with BPTB grafts. Drill PCL tibial tunnel first, then ACL tibial tunnel. Drill ACL femoral tunnel, then PCL femoral tunnel. Pass PCL graft through tibial tunnel and fix in femoral tunnel. Pass ACL graft through tibial tunnel and fix in femoral tunnel. Fix PCL graft on tibia at 90° of flexion with anteromedial step off. Fix ACL graft on tibia at extension. Rehabilitation Our protocol after bicruciate ligament reconstruction with MPTB grafts has been very active. Progressive range of motion is started early after the operation with an unlocked functional brace. If simultaneous suturation of a meniscus tear has been performed, motion is limited to 60° of flexion during the first 4 weeks. Progression from partial to full weight bearing is done over the first 6 weeks. Quadriceps exercises are progressed to open-chain knee extension exercises early as well as closed-chain hamstring exercises. Brace is discontinued after 12 weeks

Summary. This study describes the use of a quasi-static, 6DOF knee loading simulator using cadaveric specimens. Muscle force profiles yield repeatable results. Intra-articular pressure and contact area are dependent on loading condition and ACL integrity. Introduction. Abnormal contact mechanics of the tibiofemoral joint is believed to influence the development and progression of joint derangements. As such, understanding the factors that regulate joint stability may provide insight into the underlying injury mechanisms. Muscle action is believed to be the most important factor since it is the only dynamic regulator of joint stability. Furthermore, abnormal muscle control has been experimentally linked to the development of OA [Herzog, 2007] and in vivo ACL strain [Fleming, 2001]. However, the individual contributions to knee joint contact mechanics remain unclear. Thus, the purpose of this study was to examine the effects of individual muscle contributions on the tibiofemoral contact mechanics using an in-vitro experimental protocol. Methodology. Contact mechanics of 6 fresh frozen cadaver knee specimens were evaluated using the UofO Oxford knee loading device. Various combinations of quadriceps-hamstring co-contraction ratios were applied to the knee while it was “suspended” between the hip and foot components of the device. Loads of six muscle groups were computed using a hill-type musculoskeletal model [Buchanan, 2004]. Simulated ground reaction forces were also applied to the knee to represent force profiles of weight acceptance during gait as it has been shown to produce peak knee joint force in the gait cycle [Shelburne et al., 2006]. For respective medial and lateral joint compartments, the mean contact area (MC-CA and LC-CA), mean contact pressure (MC-CP and LC-CP), peak pressure (MC-PP and LC-PP), and centre of force displacement (MC-COFD and LC-COFD) were determined using a 4011 piezoelectric sensor form Tekscan (Tekscan Inc. Boston, MA). Additionally, the ACL was resected and measurements were repeated. Pearson correlations (r) examined the reliability of measurements as well as the effect an ACL transection on articular loads. Results. Positive correlations were computed for the following: COFD with intact ACL (r=0.99), COFD with resected ACL (r=0.82), MC-COFD pre vs. post ACL- resection (0.91). Furthermore, preliminary results indicated a positive correlation between MC-CA and ACL integrity (r=0.97). Discussion. The repeatability of the measured dependant variables validates the use of the knee-loading device. Interestingly, contact mechanics are more variable post ACL resection for a given muscle loading condition, indicating a decrease in knee joint stability. Also, the COFD is dependent on the different ratios of muscle loads applied to the knee, which demonstrates the importance of muscle action to the modulation of contact forces

ACL injured patients show variability in the ability to perform functional activities (Button et al., 2006). It is unknown whether this is due to differences in physical capability or whether fear of re-injury plays a role. Fear of re-injury is not commonly addressed in rehabilitation. This study aimed to investigate whether fear of re-injury impacts rehabilitation of ACL injured patients. An initial group of five ACL reconstructed participants (ACLR, age: 30±11 years, weight: 815±115 N, height: 1.74±0.07 m, all male), five ACL deficient participants (ACLD, age: 31±12 years, weight: 833±227 N, height: 1.80±0.11 m, four male and one female), and five healthy controls (age: 30±3 years, weight: 704±126 N, height: 1.70±0.09 m, three male and two female) were compared. Fear of re-injury was assessed using the Tampa Scale for Kinesiophobia (Kvist, 2004). Quadriceps strength was measured on a Biodex dynamometer. Functional activity was assessed by a single legged maximum distance hop (on the injured leg for ACL patients). Motion analysis was performed with a VICON system, and a Kistler force plate. Hop distance was calculated using the ankle position. The peak knee extension moment during landing, and the knee angle at this peak moment were calculated in VICON Nexus. The ACLD group scored worse on the Tampa scale for Kinesiophobia than the ACLR group (32±4 and 26±4). The ACLD patients did not hop as far as the ACLR and control groups (1.0±0.3, 1.3±0.1 and 1.4±0.3 m). The peak knee extension moments during landing were lowest in the ACLD group (263±159 Nm), slightly higher in the control group (354±122 Nm) and highest in the ACLR group (490±222 Nm), while knee flexion angles at these moments were similar (ACLD: 28±11, ACLR: 33±7 and control: 36±13 degrees). The ACLD group had weaker quadriceps than the control group, while the ACLR group was stronger (143±44 Nm, 152±42, and 167±50 Nm respectively). Fear of re-injury and decreased quadriceps strength potentially both impact on the functional performance of ACL injured patients. Rehabilitation of ACL injured patients could therefore be improved by addressing strength and fear of re-injury. Future research with more participants will further clarify this

Background. Anterior cruciate ligament (ACL) reconstruction with concomitant meniscal injury occurs frequently. Meniscal repair is associated with improved long-term outcomes compared to resection but is also associated with a higher reoperation rate. Knowledge of the risk factors for repair failure may be important in optimizing patient outcomes. Purpose. This study aimed to identify the patient and surgical risk factors for meniscal repair failure, defined as a subsequent meniscectomy, following concurrent primary ACL reconstruction. Methods. Data recorded by the New Zealand ACL Registry and the Accident Compensation Corporation, the New Zealand Government's sole funder of ACL reconstructions and any subsequent surgery, was reviewed. Meniscal repairs performed with concurrent primary ACL reconstruction was included. Root repairs were excluded. Univariate and multivariate survival analysis was performed to identify the patient and surgical risk factors for meniscal repair failure. Results. Between 2014 and 2020, a total of 3,024 meniscal repairs were performed during concurrent primary ACL reconstruction (medial repair = 1,814 and lateral repair = 1,210). The overall failure rate was 6.6% (n = 201) at a mean follow-up of 2.9 years, with a failure occurring in 7.8% of medial meniscal repairs (142 out of 1,814) and 4.9% of lateral meniscal repairs (59 out of 1,210). The risk of medial failure was higher in patients with a hamstring tendon autograft (adjusted HR = 2.20, p = 0.001), patients aged 21–30 years (adjusted HR = 1.60, p = 0.037) and in those with cartilage injury in the medial compartment (adjusted HR = 1.75, p = 0.002). The risk of lateral failure was higher in patients aged ≤ 20 years (adjusted HR = 2.79, p = 0.021) and when the procedure was performed by a surgeon with an annual ACL reconstruction case volume of less than 30 (adjusted HR = 1.84, p = 0.026). Conclusion. When performing meniscal repair during a primary ACL reconstruction, the use of a hamstring tendon autograft, younger age and the presence of concomitant cartilage injury in the medial compartment increases the risk of medial meniscal repair failure, whereas younger age and low surgeon volume increases the risk of lateral meniscal repair failure

The aim of this study was to assess the value of plain AP and lateral radiographs in determining ACL condition in medial unicompartmental osteoarthritis. Background: A functioning ACL has been shown to be important in the success of certain unicompartmental knee replacements. White (2001) has shown MRI to be too sensitive in this age group of patients. Keyes (1992) suggested that stress radiographs were necessary to accurately assess ACL integrity. Method: One hundred and twenty-six patients undergoing knee arthroplasty for medial osteoarthritis, had their ACL’s graded as Normal, Frayed or Absent intra-operatively. Standard pre-operative AP and lateral standing radiographs were graded by the Ahlback system. On the lateral view, the plateau was divided into 5 zones from anterior to posterior. The zone, in which the point of deepest wear occurred, was recorded. Results: There was a significant difference between the occurrence of deepest wear in the anterior three zones versus the posterior two zones for ACL normal and absent knees (. 2. = 46.85, P< 0.001). There was a significant difference between the occurrence of normal and absent ACL’s in Ahlback grades ≤3 versus ≥4 (. 2. = 53.8, P< 0.001). There was a moderately strong correlation between both zone of deepest wear on lateral radiograph and Ahlback grade with ACL condition (Spearman’s rho = 0.62 and 0.69 respectively). The Positive Predictive Values for the ACL being normal are 64% for Ahlback grades 3 or less and 67% for Zone of deepest wear in the anterior 3 zones. The Positive Predictive Values for the ACL being intact (but not necessarily normal) are 95% for Ahlback grade 3 or less; 91% for Zone of deepest wear in the anterior 3 zones; and 97% if these criteria are combined. Combining Ahlback grade ≤3 with wear in the anterior 3 zones also gave a Negative Predictive Value of 92% for the ACL not being normal. Conclusion: There is a “watershed” in ACL condition between Ahlback grade 3 and 4. Prostheses requiring Normal or Intact ACL’s should only be performed if Ahlback grade is ≤3. Standard radiographs can reliably predict ACL condition with high Positive and Negative predictive values

Purpose. Patients with anterior cruciate ligament (ACL) deficiency and symptomatic medial compartment osteoarthritis (OA) present a challenge in management. These are often younger than typical primary OA patients and aspire to remain athletically active beyond simple ADLs. Combined ACL reconstruction and valgus tibial osteotomy (ACLHTO) is a well documented surgical option for patients deemed wither too young or too active for total knee arthroplasty. Unicompartmental knee arthroplasty (UKA) is an established surgical treatment for symptomatic medial osteoarthritis of the knee refractory to conservative management. A commonly cited contraindications is symptomatic ACL deficiency because of previous reports detailing premature failure through loosening of the tibial component. Improved results and endoscopic ACL reconstructive procedures have led to an enticing concept of combining ACL reconstruction with medial unicompartmental knee arthroplasty (ACLUKR) for those ACL-deficient medial osteoarthritic (OA) knees. We sought to compare the outcomes in 2 cohorts of patients who underwent either ACLHTO or ACLUKR for this clinical problem. Method. Patients presenting with symptomatic bone on bone medial compartment OA and concomitant ACL deficiency (clinical or asymptomatic) were evaluated for surgery after exhausting non operative management. Patients who were under 40 or had plans to return to high impact loading sports and/or who had more moderate OA were offered combined ACL – medial opening wedge tibia osteotomy as a surgical procedure of choice. Patients were considered for combined ACL Oxford replacement if they were primarily seeking pain relief and were not engaged or aspiring to return to high impact or pivoting sports. All cases but one were concurrent ACL with either HTO or UKR with autogenous hamstring grafts used in all but 2 cases. Results. Thirty of 34 consecutive cases were available for follow-up for a rate of 88%. The median ages for 14 cases of ACLUKR was 51 (range 43 60) whereas 16 patients with ACLHTO had median age 43.4 (range 32 −59). Median FU was 4.65 yrs with minimum 2 year follow up (range 2–8.3). Three of the cases were revision ACL cases all from previous Gore-Tex reconstructions. All but the first patient had concomitant ACL and Oxford unicompartmental knee replacement at 1 surgical sitting and are the subject of this report. The first patient had an autogenous patella bone tendon bone graft performed 6 months prior to the UKA. There were similar change scores for patients in both groups. For ACLUKR, WOMAC pain improvements from 48.1 10.2 SD preoperatively to 79.0 17 SD postop. For ACLHTO, WOMAC improvements from 55.1 13.2 SD preoperatively to 85.0 17 SD postop. To date there have been no cases of infection or bearing dislocation in the ACLUKR group. One patient in the ACLHTO group was revised to TKR for ongoing pain and postoperative flexion contracture. Patient activities ranged from ambulation to vigorous hiking, tennis, and downhill skiing in the UKR group whereas a few in the ACLHTO group were also running mid distances. Overall satisfaction was similar in both groups. Conclusion. ACL reconstruction can safely be combined with medial UKR. The procedure has been used in younger patients with a view toward bone preservation while anticipating need for future revision. Both cohorts showed similar improvements and can be considered. The choice should be geared toward patient athletic demand. While short term results are encouraging though longer term data are necessary to thoroughly evaluate the role of this procedure in patients with medial compartment osteoarthritis and ACL deficiency

Introduction: Anthropometric anatomical factors may influence mechanical and functional stability of joints. An increased posterior tibial slope places the anterior cruciate ligament at a theroretical biomechanical disadvantage. An increased posterior tibial slope can potentially alter forces during landing tasks by either increasing anterior tibial translation and/or ACL loading. The purpose of this study is to investigate the relationship between posterior tibial slope and anterior cruciate ligament injuries. It is hypothesized that subjects with an ACL injury have an increased posterior tibial slope compared to a normal population. Methods: Posterior tibial slope in 211 patients (154 male, 57 female) aged 15–49 who underwent anterior cruciate ligament reconstruction was measured using the posterior tibial cortex as reference. A matched control group was used for comparison. Results: The average posterior tibial slope in the ACLR population was 6.1 degrees while the control group had average values of 5.4 degrees. This finding nearly reached statistical significance (p=0.057). In the male population average values were 5.5 degrees in the ACLR group and 5.9 in the control group. This was not significant (p=0.21). However there was a significant difference (p=0.04) in the female group. ACLR females had higher values 6.5 degrees whereas the control group had average values of 5.2 degrees. Discussion: Increased posterior tibial slope decreases the inclination of the ACL and potentially decreases vector force during dynamic tasks. It may further result in suboptimal length-tension relationships of agonistic muscles, increases in electromechanical delays and result in lower force development further leading to increased vector forces on the ACL. Posterior tibial slope angles were slightly smaller than with other published studies. However by using the posterior tibial cortex as reference an average of 3 degrees must be added to the measured values. We could not confirm the results of previous studies demonstrating an increased degree of posterior tibial slope in ACL injured patients. However we demonstrated a significant difference in tibial slope in females. Based on our results an increased posterior tibial slope is not a risk factor in males but possibly contributes to ACL injuries in females. Increased posterior tibial slope may be one of the reasons why females have a higher incidence of ACL injuries

INTRODUCTION. In native knees anterior cruciate ligament (ACL) and asymmetric shape of the tibial articular surface with a convex lateral plateau are responsible for differential medial and lateral femoral rollback. Contemporary ACL retaining total knee arthroplasty (TKA) improves knee function over ACL sacrificing (CR) TKA; however, these implants do not restore the asymmetric tibial articular geometry. This may explain why ACL retention addresses paradoxical anterior sliding seen in CR TKA, but does not fully restore medial pivot motion. To address this, an ACL retaining biomimetic implant, was designed by moving the femoral component through healthy in vivo kinematics obtained from bi-planar fluoroscopy and sequentially removing material from a tibial template. We hypothesized that the biomimetic articular surface together with ACL preservation would better restore activity dependent kinematics of normal knees, than ACL retention alone. METHODS. Kinematic performance of the biomimetic BCR design (asymmetric tibia with convex lateral surface), a contemporary BCR implant (symmetric shallow dished tibia) and a contemporary CR implant (symmetric dished tibia) was analyzed using KneeSIM software. Chair-sit, deep knee bend, and walking were analyzed. Components were mounted on an average bone model created from magnetic resonance imaging (MRI) data of 40 normal knees. Soft-tissue insertions were defined on the average knee model based on MRI data, and mechanical properties were obtained from literature. Femoral condyle center motions relative to the tibia were tracked to compare different implant designs. RESULTS. During simulated chair-sit, the biomimetic BCR implant showed knee motion similar to that reported for healthy knees in vivo including medial pivot rotation with greater rollback of the lateral femoral condyle (5 mm medial vs. 11 mm lateral). The CR implant showed posterior femoral subluxation in extension, paradoxical anterior sliding until 60° flexion followed by limited rollback until 105° with no medial pivot rotation. The conventional BCR implant reduced initial posterior shift of the femur in extension, however, medial pivot rotation and steady posterior rollback was not achieved. Similar trends were also found for deep knee bend activity. During walking the CR implant showed posterior subluxation in extension followed by anterior motion similar to the chair-sit activity. Both BCR implants showed less femoral excursion without posterior subluxation similar to published in vivo kinematics data for bi-uni patients. CONCLUSION. By simulating a variety of daily activities with different ranges of knee motion we were able to show that the ACL preserving biomimetic TKA implant could restore activity dependent normal knee kinematics unlike contemporary ACL retaining and ACL sacrificing implants. For chair-sit activity there was a clear medial pivot pattern for the biomimetic BCR design (unlike any other implant), while for lower flexion activities there was no medial pivot apparent in our simulations. These activity dependent knee motions are consistent with published in vivo kinematics and confirmed our hypothesis that biomimetic articular surface together with ACL preservation may be required to restore normal knee function. The biomimetic BCR design with its anatomical articular surface together with ACL preservation may provide patients with a more normal feeling knee following TKA surgery

Introduction: The use of the LARS (Ligament Augmentation and Reconstruction System. ®. , Corin) ligament for the surgical treatment of ACL deficiency has increased exponentially in Australia, particularly over the past 12 months. Given the well documented failure of synthetic ACL implants used during the 1980s, a review of the current literature regarding the LARS is required. Methods and Results: There is a paucity of current literature regarding the use of the LARS in the surgical management of ACL deficiency. 1 laboratory based, and 3 clinical publications were available for review. The transcriptions of 4 podium presentations were also available for review. Therefore, a total of 8 papers were analysed. The maximum duration of patient follow-up in any of the papers was 10 years. All papers presented results of at least 2 years follow up. In all papers, standardized outcome measures produced results equivalent to those obtained using traditional ACL reconstruction techniques. Complications were detailed in all papers, with each reporting the absence of synovitis in patients for whom the LARS had been used. Conclusion: Whilst there is insufficient long-term evidence to support the use of the LARS, the early results are promising. In particular, the problem of postoperative synovitis and synthetic ligament abrasion that led to the spectacular failure of early synthetic ACL designs appears to be absent in patients treated with the LARS. The LARS should be used in accordance with the strict patient selection criteria and technical guidelines recommended by the designing surgeon

Anthropometric anatomical factors may influence mechanical and functional stability of joints. An increased posterior tibial slope places the anterior cruciate ligament at a theroretical biomechanical disadvantage. An increased posterior tibial slope can potentially alter forces during landing tasks by either increasing anterior tibial translation and/or ACL loading. The purpose of this study is to investigate the relationship between posterior tibial slope and anterior cruciate ligament injuries. It is hypothesised that subjects with an ACL injury have an increased posterior tibial slope compared to a normal population. Posterior tibial slope in 211 patients (154 male, 57 female), aged 15–49, who underwent anterior cruciate ligament reconstruction was measured using the posterior tibial cortex as reference. A matched control group was used for comparison. The average posterior tibial slope in the ACLR population was 6.1 degrees, whilst the control group had average values of 5.4 degrees. This finding nearly reached statistical significance (p=0.057). In the male population, average values were 5.5 degrees in the ACLR group and 5.9 in the control group. This was not significant (p=0.21). However, there was a significant difference (p=0.04) in the female group. ACLR females had higher values 6.5 degrees whereas the control group had average values of 5.2 degrees. Increased posterior tibial slope decreases the inclination of the ACL and potentially decreases vector force during dynamic tasks. We could not confirm the results of previous studies demonstrating an increased degree of posterior tibial slope in ACL injured patients. However, we demonstrated a significant difference in tibial slope in females. Based on our results, an increased posterior tibial slope is not a risk factor in males but possibly contributes to ACL injuries in females. Increased posterior tibial slope may be one of the reasons why females have a higher incidence of ACL injuries

Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. The arthritic lesion on the tibia is localised to the anteromedial quadrant with an intact ACL. Deficiency of the ACL leads to a progression to tricompartmental disease. Within the spectrum of intact ACL a varying degree of ligament damage is seen. Our aim was to correlate the progression of ACL damage to the geographical extent of disease and the degree of cartilage loss on the tibial plateau. We systematically digitally mapped 50 tibial plateau resection specimens from clinical photographs of patients undergoing unicompartmental arthroplasty, additionally the damage to their ACL was graded (0: normal, 1:synovium loss, 2:longitudinal splits). These images were imported into image analysis software. Accurate measurements were made of the dimensions of the specimen. Measurements included the AP distance to the anterior and posterior aspect of the lesion, and the distance to the start of the macroscopically non damaged cartilage. The areas of cartilage damage and full thickness loss were also recorded. The results were represented as a % of total area to account for variation in size of the resection specimens. We compared % of full thickness loss in patients with normal to those with damaged, but functionally intact ligaments. All specimens had a similar macroscopic appearance. A significant difference was seen with the progression of ACL damage and area of eburnation of bone. Using an unpaired t test, a significant difference in area of % full thickness cartilage loss (P=0.047) was seen between patients with a normal and longitudinal splits within their ACL. No correlation between the clinical status of the ACL and start or finish point of cartilage loss on the tibial plateau. We surmise that the progression from anteromedial to tricompartmental osteoarthritis of the knee may be related to the graduated damage of the ACL

Purpose: Previous research has reported that increasing the posterior tibial slope through an opening wedge osteotomy results in an anterior shift in the position of the tibia relative to the femur. However, the effect of this on anterior cruciate ligament (ACL) strain remains insufficiently understood. The purpose of this study was to examine the relationship between tibial slope and tibial translation, as well as between tibial slope and ACL strain. It was hypothesized that increasing the posterior tibial slope would result in an increase in anterior tibial translation thereby increasing strain in the ACL. Methods: Five cadaveric knees were subjected to a randomized experimental design study. One knee was excluded due to failure of a strain gauge during experimentation, resulting in data for four knees. The femoral and tibial portions of the knee were potted with PMMA and fixed using fixation pins. An anterior-based osteotomy was performed with no osteotomy plate present. A strain gauge was then placed in the anteromedial bundle of the ACL. Each knee was mounted at a flexion angle of 15° and loaded with various combinations of A-P loads (18N, 108N, 209N) and axial loads (216N, 418N), according to the study design. Osteotomies of 5mm and 10mm were then performed and measurements of strain and tibial translation were taken after each according to the study design. Tibial slopes were determined through lateral fluoroscopic imaging. Results: As posterior tibial slope increased, anterior tibial translation increased as anticipated. However, contrary to expectations, as posterior slope increased, ACL strain decreased. One explanation for this result could be that by performing the osteotomy, the insertions sites of the ACL were being moved closer together resulting in increased ACL laxity. At higher slope angles, translation levels off, suggesting constraint of some tissue besides the ACL. Conclusions: Although increasing the tibial slope through opening wedge osteotomy leads to an anterior tibial translation, there is no increase in strain on the ACL. Further studies are needed to examine the effect of opening wedge osteotomy on other soft tissue restraints of the knee