External validation of machine learning predictive models is achieved through evaluation of model performance on different groups of patients than were used for algorithm development. This important step is uncommonly performed, inhibiting clinical translation of newly developed models. Recently, machine learning was used to develop a tool that can quantify revision risk for a patient undergoing primary anterior cruciate ligament (ACL) reconstruction (https://swastvedt.shinyapps.io/calculator_rev/). The source of data included nearly 25,000 patients with primary ACL reconstruction recorded in the Norwegian Knee Ligament Register (NKLR). The result was a well-calibrated tool capable of predicting revision risk one, two, and five years after primary ACL reconstruction with moderate accuracy. The purpose of this study was to determine the external validity of the NKLR model by assessing algorithm performance when applied to patients from the Danish Knee Ligament Registry (DKLR). The primary outcome measure of the NKLR model was probability of revision ACL reconstruction within 1, 2, and/or 5 years. For the index study, 24 total predictor variables in the NKLR were included and the models eliminated variables which did not significantly improve prediction ability - without sacrificing accuracy. The result was a well calibrated algorithm developed using the Cox Lasso model that only required five variables (out of the original 24) for outcome prediction. For this external validation study, all DKLR patients with complete data for the five variables required for NKLR prediction were included. The five variables were: graft choice, femur fixation device, Knee Injury and Osteoarthritis Outcome Score (KOOS) Quality of Life subscale score at surgery, years from injury to surgery, and age at surgery. Predicted revision probabilities were calculated for all DKLR patients. The model performance was assessed using the same metrics as the NKLR study: concordance and calibration. In total, 10,922 DKLR patients were included for analysis. Average follow-up time or time-to-revision was 8.4 (±4.3) years and overall revision rate was 6.9%. Surgical technique trends (i.e., graft choice and fixation devices) and injury characteristics (i.e., concomitant meniscus and cartilage pathology) were dissimilar between registries. The model produced similar concordance when applied to the DKLR population compared to the original NKLR test data (DKLR: 0.68; NKLR: 0.68-0.69). Calibration was poorer for the DKLR population at one and five years post primary surgery but similar to the NKLR at two years. The NKLR machine learning algorithm demonstrated similar performance when applied to patients from the DKLR, suggesting that it is valid for application outside of the initial patient population. This represents the first machine learning model for predicting revision ACL reconstruction that has been externally validated. Clinicians can use this in-clinic calculator to estimate revision risk at a patient specific level when discussing outcome expectations pre-operatively. While encouraging, it should be noted that the performance of the model on patients undergoing ACL reconstruction outside of Scandinavia remains unknown

Aim. Quadrupled hamstring anterior cruciate ligament plasties (4xHp) have been described as having a higher risk of infection than bone patellar tendon bone plasties (BPTBp). There are 2 theories that might explain this phenomenon. One is the presence of sutures in a 4xHp that could act as a foreign body, The other is the more complex preparation of a 4xHp that might lead to higher contamination rates during the process. The objective of the present study was to evaluate the formation of biofilm in these plasties and to compare it between a 4xHp and a BPTBp. The hypothesis was that the presence of sutures in 4xHp would increase the amount of biofilm present in them in comparison to BPTBp. Method. A descriptive in vitro study was conducted. One 4xHp and one BPTBp were prepared. They were subsequently divided into 8 fragments. Three of them were reserved for negative control, and the rest were contaminated with a strain of S. Epidermidis (ATCC 35984) 10–5. Finally, a quantitative analysis was carried out by means of microcalorimetry and sonication with plating. Additionally, a qualitative analysis was carried out by means of electron microscopy. Results. In isothermal microcalorimetry, both contaminated plasties showed the same growth dynamics with a population peak (200uW) at 8h. No significant differences were found between the bacterial growth profiles of 4xHp and BPTBp. The product of sonication was plated and the number of colony forming units per milliliter (CFU/ml) was counted at 24 hours. No significant differences were detected between the 4×Hp (mean +/− sem = 3,5×107 +/− 3450000) and the BPTBp (4,6 ×107 +/− 1,455e+7). With a p value of 0.6667, there were no differences of significance (Mann-Whitney test). In the samples analyzed with electron microscopy, no specific biofilm growth pattern was identified upon comparing BPTBp with 4xHp. Conclusions. There were no significant differences at either the quantitative or qualitative level when comparing bacterial growth in BPTBp and 4xHp. Therefore, the presence of sutures in 4xHp cannot be established as a predisposing factor to higher infection rates. These findings may be justified in the sense that the plasties themselves already behave like foreign bodies. Therefore, the presence of sutures does not increase the possibility of biofilm forming on their surface

Increasing expectations from arthroscopic anterior cruciate ligament (ACL) reconstructions require precise knowledge of technical details such as minimum intra-femoral tunnel graft lengths. A common belief of having ≥20mm of grafts within the femoral tunnel is backed mostly by hearsay rather than scientific proof. We examined clinico-radiological outcomes in patients with intra-femoral tunnel graft lengths <20 and ≥20mm. Primary outcomes were knee scores at 1-year. Secondarily, graft revascularization was compared using magnetic resonance imaging (MRI). We hypothesized that outcomes would be independent of intra-femoral tunnel graft lengths. This prospective, single-surgeon, cohort study was conducted at a tertiary care teaching centre between 2015–2018 after obtaining ethical clearances and consents. Eligible arthroscopic ACL reconstruction patients were sequentially divided into 2 groups based on the intra-femoral tunnel graft lengths (A: < 20 mm, n = 27; and B: ≥ 20 mm, n = 25). Exclusions were made for those > 45 years of age, with chondral and/or multi-ligamentous injuries and with systemic pathologies. All patients were postoperatively examined and scored (Lysholm and modified Cincinnati scores) at 3, 6 and 12 months. Graft vascularity was assessed by signal-to-noise quotient ratio (SNQR) using MRI. Statistical significance was set at p<0.05. Age and sex-matched patients of both groups were followed to 1 year (1 dropout in each). Mean femoral and tibial tunnel diameters (P =0.225 and 0.595) were comparable. Groups A (<20mm) and B (≥20mm) had 27 and 25 patients respectively. At 3 months, 2 group A patients and 1 group B patient had grade 1 Lachman (increased at 12 months to 4 and 3 patients respectively). Pivot shift was negative in all patients. Lysholm scores at 3 and 6 months were comparable (P3= 0.195 and P6= 0.133). At 1 year both groups showed comparable Cincinnati scores. Mean ROM was satisfactory (≥130 degrees) in all but 2 patients of each group (125–130 degrees). MRI scans at 3 months and 1 year observed anatomical tunnels in all without any complications. Femoral tunnel signals in both groups showed a fall from 3–12 months indicating onset of maturation of graft at femoral tunnel. Our hypothesis, clinical and radiological outcomes would be independent of intra-tunnel graft lengths on the femoral aspect, did therefore prove correct. Intra-femoral tunnel graft lengths of <20 mm did not compromise early clinical and functional outcomes of ACL reconstructions. There seems to be no minimum length of graft within the tunnel below which suboptimal results should be expected

Reconstruction of the anterior cruciate ligament (ACL) allows to restore stability of the knee, in order to facilitate the return to activity (RTA). Although it is understood that the tendon autograft undergoes a ligamentous transformation postoperatively, knowledge about longitudinal microstructural differences in tissue integrity between types of tendon autografts (ie, hamstring vs. patella) remains limited. Diffusion tensor imaging (DTI) has emerged as an objective biomarker to characterize the ligamentization process of the tendon autograft following surgical reconstruction. One major limitation to its use is the need for a pre-injury baseline MRI to compare recovery of the graft, and inform RTA. Here, we explore the relationship for DTI biomarkers (fractional anisotropy, FA) between knees bilaterally, in healthy participants, with the hypothesis that agreement within a patient's knees may support the use of the contralateral knee as a reference to monitor recovery of the tendon autograft, and inform RTA. Fifteen participants with no previous history of knee injuries were enrolled in this study (age, 26.7 +/− 4.4 years; M/F, 7/8). All images were acquired on a 3T Prisma Siemens scanner using a secured flexible 18-channel coil wrapped around the knee. Both knees were scanned. A 3D anatomical Double Echo Steady State (DESS) sequence was acquired on which regions of interest (ROI) were placed consistent with the footprints of the ACL (femur, posteromedial corner on medial aspect of lateral condyle; tibia, anteromedial to intercondylar eminence). Diffusion images were acquired using fat saturation based on optimized parameters in-house. All diffusion images were pre-processed using the FMRIB FSL toolbox. The footprint ROIs of the ACL were then used to reconstruct the ligament in each patient with fiber-based probabilistic tractography (FBPT), providing a semi-automated approach for segmentation. Average FA was computed for each subject, in both knees, and then correlated against one another using a Pearson correlation to assess the degree of similarity between the ACLs. A total of 30 datasets were collected for this study (1/knee/participant; N=15). The group averaged FA (+/− standard deviation) for the FBPT segmented ACLs were found to equal 0.1683 +/− 0.0235 (dominant leg) and 0.1666 +/− 0.0225 (non-dominant leg). When comparing both knees within subjects, reliable agreement was found for the FBPT-derived ACL with a linear correlation coefficient (rho) equal to 0.87 (P < 0 .001). We sought to assess the degree of concordance in FA between the knees of healthy participants with hopes to provide a method for using the contralateral “healthy” knee in the comparison of autograft-dependent longitudinal changes in microstructural integrity, following ACL reconstruction. Our results suggest that good agreement in anisotropy can be achieved between the non-dominant and dominant knees using DTI and the FBPT segmentation method. Contralateral anisotropy of the ACL, assuming no previous injuries, may be used as a quantitative reference biomarker for monitoring the recovery of the tendon autograft following surgical reconstruction, and gather further insight as to potential differences between chosen autografts. Clinically, this may also serve as an index to supplement decision-making with respect to RTA, and reduce rates of re-injuries

Due to unsatisfactory results and reported drawbacks of anterior cruciate ligament (ACL) reconstruction new regenerative approaches based on tissue-engineering strategies are currently under investigation. It was the purpose of this study to determine if a novel silk fiber-based ACL scaffold is able to initiate osteointegration in the femoral and tibial bone tunnels under in vivo conditions. Furthermore we tested if the osteointegration process will be improved by intraoperatively seeding the scaffolds with the autologous stromal vascular fraction, an adipose-derived, stem cell-rich isolate from knee fat pads. In this controlled laboratory study, 33 sheep underwent ACL resection and were then randomly assigned to 2 experimental groups: ACL reconstruction with a scaffold alone and ACL reconstruction with a cell-seeded scaffold. Half of the sheep in each group were randomly chosen and euthanized 6 months after surgery and the other half at 12 months. To analyze the integration of the silk-based scaffold in the femoral and tibial bone tunnels, hard tissue histology and micro-computed tomography measurements were performed. The histological workup showed that in all treatment groups, with or without the application of the autologous stromal vascular fraction, an interzone of collagen fibers had formed between bone and silk-based graft. This collagen-fiber continuity partly consisted of Sharpey fibers, comparable with tendon-bone healing known for autografts and allografts. Insertion sites were more broad based at 6 months and more concentrated on the slightly protruding, bony knoblike structures at 12 months. Histologically, no differences between the treatment groups were detectable. Analysis of micro-computed tomography measurements revealed a significantly higher tissue density for the cell-seeded scaffold group as compared with the scaffold-alone group in the tibial but not femoral bone tunnel after 12 months of implantation. The novel silk fiber-based scaffold for ACL regeneration demonstrated integration into the bone tunnels via the formation of a fibrous interzone similar to allografts and autografts. Histologically, additional cell seeding did not enhance osteointegration. No significant differences between 6 and 12 months could be detected. After 12 months, there was still a considerable amount of silk present, and a longer observation period is necessary to see if a true ligament-bone enthesis will be formed

The aim of the this study was to determine the effect of the knee flexion angle (KFA) during tibial anterior cruciate ligament (ACL) graft fixation on patient reported outcomes, graft stability, extension loss and re-operation following anatomic single-bundle ACL reconstruction. All 169 included patients (mean age 28.5 years, 65% male) were treated with anatomic single bundle ACL reconstruction using patellar tendon autograft and randomized to tibial fixation of the ACL graft at either 0o (n=85) or 30o (n=84). The primary outcome was the Knee Injury and Osteoarthritis Outcome Score (KOOS) two years following surgery. Secondary outcomes were the Marx Activity Scale (MAS), the rate of re-operation, and physical exam findings at one year including KT-1000 and side to side differences in knee extension. The follow-up rate was 82% (n=139) for the primary outcome. Graft failure rate at two years was 1% (n=2, 1 per group). ACL tibial graft fixation at 0o or 30o did not have a significant effect on KOOS scores at two years following ACLR. Patients whose graft was fixed at a knee flexion angle of 0o had greater scores on the Marx Activity Scale (mean 9.6 [95%CI 8.5-10.6] versus 8.0 [95%CI 6.9-9.1, p=0.04) and a greater proportion of patients who achieved the minimal clinical important difference (MCID) for the KOOS pain subscale (94% vs 81%, p=0.04). There was no significant difference in knee extension loss, KT-1000 measurements or re-operation between the two groups. In the setting of anatomic single-bundle ACLR using patellar tendon autograft and anteromedial portal femoral drilling, there was no difference in KOOS scores among patients fixed at 0o and 30o. Patient fixed in full extension did demonstrate higher activity scores at 2 years following surgery and a greater likelihood of achieving the MCID for KOOS pain

Anterior cruciate ligament (ACL)-retaining total knee arthroplasty (TKA) has been associated with more physiologic motion patterns, more normal knee kinematics, and higher patient preference than ACL-sacrificing implant designs. However, it remains unclear how many osteoarthritic patients can be expected to have an intact ACL at the time of surgery in order to undergo ACL-retaining TKA. A systematic literature review was performed in November 2018 using the PubMed and EMBASE databases. Papers written in English, with more than 10 adult patients relevant to the research question were included, whereas cadaveric, revision, animal and simulation studies and conference abstracts were excluded. Data on ACL retention during intraoperative assessment or MRI scans were extracted and analysed using proportional meta-analyses. Twenty-six eligible publications (4167 knees) were included: 20 using intraoperative assessment, 4 using MRI, and 2 using both. Intraoperative assessment of the ACL during TKA showed that the ligament was present in 78% (95% confidence interval [CI]: 72–84%) and intact in 55% (95% CI: 45–65%) of the patients examined. MRI scans revealed higher percentages of ACL presence and intactness than intraoperative assessment, with 91% (95% CI: 79–96%) of the ACL being present and 68% (95% CI: 28–92%) intact. Fewer studies reported on MRI results compared to studies reporting on the intraoperative status of the ACL. In conclusion, intraoperative assessment suggests that over half of the osteoarthritic patients have an intact ACL at the time of TKA surgery, some of whom may qualify for bicruciate-retaining arthroplasty. For any figures or tables, please contact authors directly

Introduction. A common problem for patients receiving total knee arthroplasty (TKA) is postoperative functional impairment of the joint. This is minimized in bicruciate-retaining (ACL preserving) knee replacements, due to the important role of the anterior cruciate ligament (ACL) in normal kinematic patterns of the knee. We explore ACL sparing TKA by estimating the fraction of osteoarthritic TKA patients with a compatible ACL (assessed intraoperatively), while also examining potential preoperative indicators of ACL status. Method. We retrospectively examined 498 patients with a primary diagnosis of osteoarthritis who underwent a TKA by one surgeon between September 2013 and March 2015. Exclusion criteria included a prior TKA, a unicompartmental knee replacement, or inflammatory arthritis. Extensive preoperative data (within four months of surgery) for each patient was collected (anatomical alignment, extension, flexion, range of motion (ROM), Lachman test, and BMI) in addition to de-identified demographic data. The intraoperative assessment of ACL status (normal/functionally intact, compromised/deficient, or absent) was then obtained from our local database and compared with the preoperative data. IRB exemption was obtained to retrospectively collect data. Results. Intraoperative assessment of ACL status found 73.5% normal ACL, 12.9% compromised ACL, and 13.6% absent ACL. A significant demographic predictor of ACL status was gender (female - more likely intact, male - more likely absent; χ2 = 12.43, P<0.002). Patients with an intact ACL were also shown to have significantly better preoperative extension (χ2=14.83, P<0.022), flexion (F. 2, 469. = 9.93, P < 0.001), and ROM (F. 2, 469. = 9.38, P < 0.001) than those with a compromised ACL. We had a very small number of positive Lachman test results, and therefore could not draw any valid conclusion for preoperative predictive ability of the test. There was no significant difference in age, ethnicity, BMI or preoperative alignment between ACL status groups. Conclusion. Our study found 73.5% of 498 osteoarthritic TKA patients have an intact ACL. The strongest preoperative indicators of ACL status were gender, flexion, and ROM. Taken together, our results highlight a significant percentage of patients who are potential candidates for a bicruciate-retaining TKA

Introduction. Cruciate retaining knee replacements are only implanted into patients with “healthy” ligaments. However, partial anterior cruciate ligament (ACL) tears are difficult to diagnose with conventional MRI. Variations of signal intensity within the ligament are suggestive of injury but it is not possible to confirm damage or assess the collagen alignment within the ligaments. The potential use of Magic Angle Directional Imaging (MADI) as a collagen contrast mechanism is not new, but has remained a challenge. In theory, ligament tearing or joint degeneration would decrease tissue anisotropy and reduce the magic angle effect. Spontaneous cruciate ligament rupture is relatively common in dogs. This study presents results from ten canine knees. Methods. Ethical approval was obtained to collect knees from euthanized dogs requiring a postmortem (PM). A Siemens Verio 3T MRI scanner was used to scan a sphere containing the canine knees in 9 directions to the main magnetic field (B. 0. ) with an isotropic 3D-T1-FLASH sequence. After imaging, the knees were dissected and photographed. The images were registered and aligned to compare signal intensity variations. Segmentation using a thresholding technique identified voxels containing collagen. For each collagen-rich voxel the orientation vector was computed using Szeverenyi and Bydder's method. Each orientation vector reflects the net effect of all fibers comprised within a voxel. The assembly of all unit vectors represents the fiber orientation map and was visualised in ParaView using streamlines. The Alignment Index (AI) is defined as a ratio of the fraction of orientations within 20° (solid angle) centred in that direction to the same fraction in a random (flat) case. By computing AI for a regular gridded orientation space we can visualise differences in AI on a hemisphere. AI was normalised so that AI=0 indicates isotropic collagen alignment. Increasing AI values indicate increasingly aligned structures: AI=1 indicates that all collagen fibers are orientated within the cone of 20° centred at the selected direction. Results. Dogs cranial cruciate ligament (CCL) is similar to human ACL. It's composed of an anteromedial (AM) bundle and a posterolateral (PL) bundle. Two knees were damaged with partial CCL tears, the PL bundle was intact but the AM bundle was torn. Paraview streamlines of the CCL for healthy and damaged knees differ. The healthy knee has continuous fiber tracts with no ligament disruption. In the AM bundle fibers are discontinuous and the PL bundle fibers are continuous as expected in a partially torn CCL. The AI for healthy (mean AI=0.25) and damaged CCL (mean AI= 0.075) is significantly different (p<0.01). The damaged AM bundle has a more diffuse spread of less aligned fibers compared to the more concentrated and aligned PL fiber bundle. Conclusion. This study demonstrates the first visualisation of a CCL partial tear using MADI. Combined with AI, our scanning technique offers a tool to visualise and quantify changes in collagen fiber orientation. Thus, MRI can be used to improve the diagnosis and quantification of partial ligament tears in the knee

Introduction/aims. Anterior cruciate ligament (ACL) reconstruction is now routinely performed arthroscopically. However, there are only a few centres in the UK which offer this procedure as a day case. We aimed to assess the clinical outcomes of day case ACL reconstruction using a tourniquet-less pump regulated procedure. Material/methods. A retrospective analysis of day case ACL reconstructions by a single surgeon between January 2003 and December 2010 was undertaken. All reconstructions were performed without a tourniquet, instead, haemostasis was achieved using saline – epinephrine irrigation. Outcomes were measured using Lysholm knee scores, Mohtadi index and pain scores. Results. 374 ACL reconstructions were performed on 331 patients (288 unilateral, 43 bilateral) during the study period. The average age was 31 years (range 15–58 years). All patients were followed up at regular intervals for 12 months. Lysholm knee scores improved from an average of 25 to 90. Mohtadi index scores also showed significant improvement; from an average of 22 to 90 post-operatively. All patients were pain free by 6 weeks post ACL reconstruction based on the VAP score. Complications occurred in 3% (n=11) of patients, these included DVT, wound infection and haemoarthorosis. Metal work failure occurred in 2 patients, both of whom had the EZLoc™ fixation system. Conclusions. Our experience shows that day case ACL reconstructions without the use of a tourniquet are cost effective, safe and the patients' preferred choice. Perhaps, therefore, it is time to include ACL reconstructions in the British Association of Day Case Surgery “basket” of day case procedures?

Abstract

Introduction. Anterior cruciate ligament (ACL) rupture is a common sporting injury, often managed surgically with patella-tendon or hamstrings autograft. Surgeons are under increasing pressure for open transparent assessment of their performance. Scoring systems can be used to assess outcome. More than 50 different scoring systems have been identified to assess the ACL deficient knee. Aims. The survey is investigating the use of ACL scoring systems between knee surgeons in the United Kingdom as a method of assessing performance. Method. 134 knee surgeons in the United Kingdom, performing ACL reconstruction, were asked to complete a written questionnaire regarding their use of scoring systems & outcome measures. Written questionnaires were sent and responses were received by post. Results. 81 (60%) surgeons responded to the questionnaire by stating their preferred scoring system. 40 (49%) surgeons routinely use ACL scoring systems versus 41 (51%) surgeons who do not. The Lysholm (I and II) knee scoring scale (80%) and Tegner activity score (67.5%) were most commonly used (57.5% both of them) followed by the Knee injury and osteoarthritis outcome score (KOOS) (30%), International Knee Documentation Committee (IKDC) subjective knee score (22.5%), Medical Outcome Study 12 Item Short Form (SF12) (20%), the Medical Outcome Study 36 Item Short Form (SF 36) (12.5%), Cincinnati Knee Scoring System (10%), and ACL Quality of Life scoring system (7.5%). Recommendations. The routine use of ACL scoring systems by 49% of surgeons raises the question - should all surgeons be using scoring systems in their ACL practice? This would be relatively easy to do as most patients are followed up post operatively for 6 months. This will help to adopt a transparent assessment of the performance of every consultant to the procedure they perform

Biomechanical stimuli have fundamental roles in the maintenance and remodeling of ligaments including collagen gene expressions. Mechanical stretching signals are mainly transduced by cell adhesion molecules such as integrins. However, the relationships between stress-induced collagen expressions and integrin-mediated cellular behaviors are still unclear in anterior cruciate ligament cells. Human ACL cells were harvested from ligament samples donated by patients who underwent total knee arthroplasties with informed consents. Interface cells were isolated from the 5-mm-end of ACL. Midsubstance cells were cultured from the middle part of ACL. The cells were seeded onto stretch chambers (2Ä−2 cm, 50,000 cells/chamber) and uni-axial cyclic mechanical stretch (0.5 Hz, 7%) was applied for 2 h using a ST140. RNA samples were reverse-transcripted and quantitative real-time RT-PCR analysis were performed. To inhibit the function of integrin alphaVbeta3 subunit or alpha5 in stretching experiments, anti-human integrin alphaVbeta3 and alpha5 functional blocking antibodies (alphaVbeta3: 20 mg/ml, alpha5: 4 mg/ml) were used. To investigate the cellular attachments responding to mechanical stretch, we observed the distribution of integrins and stress fibers in both ACL cells. The shape of midsubstance cells showed spindle and fibroblastic cellular morphologies. On the other hand, the interface cells displayed chondroblastic appearances such as small and triangular morphologies. The expressions of COL1A1, COL2A1, and COL3A1 genes were detected in the tissue RNAs of interface zones. However, these expressions were decreased in cultured interface cells. In midsubstance cells, the expression of COL1A1 gene was equally detected in both tissues and cultured cells. COL3A1 gene expression was maintained in cultured midsubstance cells. These results indicated that the phenotypes of both ACL cells were changed by cultured conditions, especially in the interface cells. After mechanical stretch, the COL1A1 expression of midsubstance and interface cells were stimulated up to 6 and 14-fold levels of each non-stretched control, respectively. The COL3A1 expressions were also enhanced up to 1.8-fold level of controls by stretching treatment in both cells. Integrin alphaVbeta3 was shifted to the peripheral edge of cells by stretching treatment. In addition, mechanical stretch changed the integrin alphaVbeta3-dependent stress fiber formation in both ACL cells. The functional blocking of integrin alphaVbeta3 inhibited stretch-activated COL1A1 and COL3A1 expressions. However, the functional blocking of integrin alpha5 did not suppress the stretch-induced COL1A1 and COL3A1 expressions in both ACL cells. Cultured interface cells loose their phenotypes in collagen gene expressions. However, mechanical stretch reproduces the expression of COL1A1 and COL3A1 genes in cultured ACL cells. The present study demonstrated that stretch-activated collagen gene expressions depend on the integrin alphaVbeta3-mediated cellular adhesions

The purpose of this study was to evaluate the results of selective anatomic augmentation of partial anterior cruciate (ACL) ligament tears in 36 consecutive patients with mean 3years follow-up. Our hypothesis is that this selective augmentation of partial ACL tears could restore knee stability and function. In a consecutive series of 314 ACL reconstructions, 40 patients in which intact ACL fibers remained in the location corresponding to the anteromedial or posterolateral bundle were diagnosed perioperatively. All patients underwent selective augmentation of the torn bundle, while keeping the remaining fibers intact using autogenous hamstring graft. 38 patients (28 males, 10 females) were available with minimum 3 year follow- up. 26 cases had AM bundle tears and 12 cases had PL bundle tears respectively. Patients were assessed with International Knee Documentation Committee (IKDC) 2000 Knee Evaluation Form, Lysholm score; instrumented knee testing was performed with the arthrometer (KT 2000).

Statistical analysis was performed to compare the preoperative and postoperative objective evaluation. At 3 year follow-up, 12 (31.6%) patients were graded A, 25 (65.8%) graded B and 1 C (2.6%) at IKDC objective evaluation. Lysholm's score and mean side to side instrumental laxity improved significantly. The results of anatomic single bundle augmentation in partial ACL tears are encouraging with excellent side to side laxity.

INTRODUCTION

ACL retaining (BCR) Total Knee Arthroplasty (TKA) provides more normal kinematics than ACL sacrificing (CR) TKA. However, in the native knee the ACL and the asymmetric shape of the tibial articular surface with a convex lateral plateau are responsible for the differential medial/lateral femoral rollback (medial pivot). Therefore, the hypothesis of this study was that an asymmetric biomimetic articular surface together with ACL preservation would better restore native knee kinematics than retention of the ACL alone. Normal knee kinematics from bi-planar fluoroscopy was used to reverse engineer the tibial articular surface of the biomimetic implant. This was achieved by moving the femoral component through the healthy knee kinematics and removing material from a tibial template.

The purpose of the study was to compare prospectively and randomly two ACL reconstruction single bundle techniques, one referred to as traditional and the other referred to as anatomical, where the coronal angulation of the femoral tunnel aimed a more horizontal position at 2 and 10 o'clock. Orthopilot® System (Aesculap, Tuttlingen, Germany) was used to assist tunnel positioning in order to obtain and register translational and rotational stability.

Eighteen patients (14 men and 4 women), average age 33.8 years (range 18 to 49), with isolated ACL lesion were randomized in two groups, A (Conventional) and B (Anatomical). All patients were submitted to ACL navigated arthroscopic reconstruction with quadruple hamstrings grafts. Anteromedial portal access for femoral tunnel drilling was used in all patients. The tibial and femoral tunnels drillings were monitored by the Aesculap® Orthopilot Navigation System. In Group A, the femoral tunnel positioning aimed isometricity. In Group B, femoral tunnel was drilled at 25% of Blumensaat's line length from the posterior cortex, and 30° orientation in coronal plane. Initial and final Maximum Anterior tibial Displacement (MATD), Internal Tibial Rotation (ITR) and External Tibial Rotation (ETR) at 30° knee flexion data were recorded intra operatively by the navigation system.

No horizontal or rotational stability differences were found for MATD (p = 0.68), ITR (p = 014) and ETR (0.13). This study did not support the hypothesis that a more anatomical positioning leads to better rotational or anterior stability.

There are a few papers in the literature to indicate the likely functional outcome of conservatively managed sportsmen in whom primary outcome cruciate ligament [ACL] healing occurs.

We reviewed 298 sportsmen presenting with isolated ACL rupture that were conservatively managed with a rehabilitation programme, based on regaining proprioceptive and hamstring control, and aimed at achieving primary ACL healing. All were protected in a hinged brace. In 50 patients, the ACL was determined as having healed clinically; these patients underwent instrumented laximetry testing with KT 1000 arthrometry and were determined: IKDC A [Normal] or IKDC B [nearly normal]. An MRI was also performed which confirmed healing in 39 patients with ACL fibres parallel to Blumenstat's line. In 11 patients the ACL stump had healed to the PCL. The 50 patients were followed up for an average 16 months [range, 14 to 17 months].

56% of patients suffered recurrent instability when they returned to their preinjury level of contact or pivoting sport. For competitive athletes, 76.5% suffered further instability on return to sport despite the four-month rehabilitation and independent arthrometry score or MRI findings. However, for occasional, recreational athletes only 7% suffered recurrent instability.

This study suggests that a rehabilitation programme aimed at primary ACL healing affords satisfactory results for the occasional, recreational athlete but does not achieve the quality of restraint sufficient for contact or pivoting sports in competitive athletes. These patients suffer high levels of recurrent instability and are exposed to the risk of secondary chondral and meniscal injury.

Anterior Cruciate Ligament injuries are a common cause of downgrade in Service personnel. The Multidisciplinary Injury Assessment Clinic (MIAC) is a service which patients can be referred to for expert musculoskeletal injury management. MIAC has a Fast Track (FT) referral system in place for imaging, and can subsequently refer isolated ACL injuries to a private provider for reconstruction. We examined this pathway in the South West region which has an overall population at risk of 19775. Over 4 years 173 knee injuries were referred to MIAC, of which 32 were ACL injuries. Of the 29 patients referred for MRI, the median time to imaging was 8 days with FT (n=13, range 2–14) and

15 days via the NHS (n=16, range 5–64). The majority of injuries were found to involve multiple pathologies (n=19), excluding them from FT surgery. Time to NHS clinic from point of referral took a median time of 54 days, and onward delay to surgery was 47 days. None of the referrals to the private provider for reconstruction were accepted (n=3). We have identified aspects of current referral and treatment pathways that are inefficient and discuss a current solution utilising Military surgeons.

Objectives

We hypothesise that a long-term bioresorbable hydrophilic silkworm silk device, the SeriACL(tm) scaffold, can support the development and remodelling of native functional ligament tissue if designed to anticipate the remodelling curve of an ACL graft. This study evaluated the SeriACL scaffold for ACL replacement in a goat model at 3, 6 and 12 months.

Anterior cruciate ligament (ACL) injuries have been increasing, especially amongst adolescents. These injuries can increase the risk for early-onset knee osteoarthritis (OA). The consequences of late-stage knee OA include structural joint change, functional limitations and persistent pain. Interleukin-6 (IL-6) is a pro-inflammatory biomarker reflecting knee joint healing, and increasing evidence suggests that IL-6 may play a critical role in the development of pathological pain. The purpose of this study was to determine the relationship between subjective knee joint pain and function, and synovial fluid concentrations of the pro-inflammatory cytokine IL-6, in adolescents undergoing anterior cruciate ligament reconstruction surgery. Seven youth (12-17 yrs.) undergoing anterior cruciate ligament (ACL) reconstruction surgery participated in this study. They completed the Pedi International Knee Documentation Committee (Pedi-IKDC) questionnaire on knee joint pain and function. At the time of their ACL reconstruction surgery, synovial fluid samples were collected through aspiration to dryness with a syringe without saline flushing. IL-6 levels in synovial fluid (sf) were measured using enzyme linked immunosorbent assay. Spearman's rho correlation coefficient was used to determine the correlation between IL-6 levels and scores from the Pedi-IKDC questionnaire. There was a statistically significant correlation between sfIL-6 levels and the Pedi-IKDC Symptoms score (-.929, p=0.003). The correlations between sfIL-6 and Pedi-IKDC activity score (.546, p = .234) and between sfIL-6 and total Pedi-IKDC score (-.536, p = .215) were not statistically significant. This is the first study to evaluate IL-6 as a biomarker of knee joint healing in an adolescent population, reported a very strong correlation (-.929, p=0.003) between IL-6 in knee joint synovial fluid and a subjective questionnaire on knee joint pain. These findings provide preliminary scientific evidence regarding the relationship between knee joint pain, as determined by a validated questionnaire and the inflammatory and healing status of the patient's knee. This study provides a basis and justification for future longitudinal research on biomarkers of knee joint healing in patients throughout their recovery and rehabilitation process. Incorporating physiological and psychosocial variables to current return-to-activity (RTA) criteria has the potential to improve decision making for adolescents following ACL reconstruction to reduce premature RTA thereby reducing the risk of re-injury and risk of early-onset knee OA in adolescents