Introduction:Complex proximal ulna fractures that are associated with radial head dislocation or fracture-dislocation, often referred to as "Monteggia-like" or trans-ulnar fracture-dislocations, constitute a heterogeneous group that poses challenges for classification and treatment. Management often relies on surgeon expertise rather than systematic approaches, leading to poor outcomes, high complication rates, and frequent surgical revisions. We hypothesize that a systematic, coronoid-centric, step-by-step surgical technique could improve outcomes in trans-ulnar fracture-dislocations. Methods:A retrospective study was conducted on patients with trans-ulnar fracture-dislocations treated between 2017 and 2023. Exclusion criteria included patients younger than 18 years, open fractures beyond Gustilo grade 1, and follow-up shorter than 12 months. Fractures were classified using the coronoid-centric Mayo classification based on preoperative radiographs and CT scans. Two additional fracture patterns, characterized by distinct coronoid detachment features, were identified. Outcomes were evaluated through subjective elbow scores Subjective Elbow Value, Mayo Elbow Performance Score (MEPS), Oxford Elbow Score, QuickDASH, and range of motion (ROM) evaluations. Results:Among the 39 patients included, the most common fracture pattern was the trans-ulnar basal coronoid fracture-dislocation (49%). At a mean follow-up of 3.9 years (range 1-7), 90% (35/39) of the patients achieved a functional ROM. The mean MEPS was 85 (range 60-100), and the mean QuickDASH was 18 (range 0-45). The revision rate was 13% (5/39), due to coronoid nonunion (n = 1), olecranon fixation failure after a new trauma (n = 1), and elbow stiffness (n = 3). Ulnar nerve neuropathy was recorded in 2 of 39 patients. Discussion:A systematic, coronoid-centric surgical approach led to satisfactory outcomes in trans-ulnar fracture-dislocation with an acceptable rate of complication and revision rate. Recognizing the prognostic value of the coronoid may reduce complication rates. Level of Evidence:Level III. See Instructions for Authors for a complete description of levels of evidence.

Knee stiffness is a widely known and worrying condition in several postoperative knees. Less is known about native stiff knee. The aim of this manuscript is to summarize the available literature on native stiff knee epidemiology, classification and treatment. In 1989 stiff knee was defined as a knee with less than 50° of total range of motion. If range of motion is <30°, it is defined as an ankylosed knee. Knee stiffness can be divided into three main types: flexion contractures, extension contractures, and combined contractures. Different risk factors have been associated to native stiff knee and grouped into modifiable or not modifiable. Furthermore, risk factors can be divided into patients' related no patients'-related. Different treatment modalities can be indicated to treat knee stiffness, including manipulation under anesthesia (MUA), arthroscopic and open surgical release. When stiffness is associated with articular disruption TKA represent an option. TKA in native stiff knee can be challenging for the surgeon. Implant's choice and knee exposure are the first steps. In some cases, additional release and extensive can be considered. A stepwise approach and careful preoperative planning are mandatory to obtain long-term satisfactory outcomes. Native stiff knee is a rare but invalidating condition. Different treatment modalities have been proposed as treatment. However, considering that it is frequently associated to sever arthritis, TKA can be an option in painful stiff knees. Nature of knee stiffness necessitates a customized approach to ensure successful management and achieve satisfying outcomes.

In pediatric anterior cruciate ligament reconstruction, many factors should be considered: (1) risk of growth disturbance; (2) high risk of re-tear; (3) determination of the skeletal age, which is sometimes challenging; and (4) no single technique indicated for all patients. The choice of the technique mostly depends on the patients' age and growth potential. Whereas prepubescent patients can be safely treated with physeal sparing techniques (i.e., the Kocher-Micheli technique or its modifications), in postpubescent patients physeal respecting or adult-type reconstructions are generally indicated. In pubescent patients, both all-inside all-epiphyseal and partial transphyseal techniques can be safely performed, but these are not without shortcomings. With the goal of overcoming some of the drawbacks of the existing techniques, the authors describe this technical note. The technique entails an over-the-top femoral position of a 6-strand hamstring graft and an all-epiphyseal tibial tunnel. The femoral physis is completely preserved, and only a 4.5 mm transphyseal tunnel is drilled in the tibia with an all-epiphyseal tibial half socket. With this technique, the graft diameter is adequate, there is no need for fluoroscopy, no risk of graft/tunnel mismatch, and a modified Arnold-Coker lateral tenodesis can be associated via the same lateral incision.

BACKGROUND:The lateral extra-articular tenodesis (LET) procedure associated with anterior cruciate ligament (ACL) reconstruction can be considered in selected patients to diminish the risk of persistent rotatory instability and achieve a protective effect on the graft. Several techniques have been described in the literature to treat rotatory instability. Usually, a strip of the iliotibial band (ITB) is harvested from its middle while leaving the distal insertion, then passed underneath the lateral collateral ligament and fixed on the lateral aspect of the distal femur with various fixation methods such as staples, screws, anchors or extracortical suspensory devices. Despite their effectiveness, these fixation methods may be associated with complications such as lateral pain, over-constraint and tunnel convergence. METHODS:This study presents a detailed surgical description of a new technique to perform an LET during ACL reconstruction with any type of graft fixing the ITB strip with the sutures of the ACL femoral button, comparing its pros and cons in relation to similar techniques found in the literature. CONCLUSIONS:This technique represents a reproducible, easy to learn and inexpensive solution to perform a lateral extra-articular tenodesis associated with an ACL reconstruction using the high-resistance sutures of the femoral button.

INTRODUCTION:Knee osteotomies are effective procedures to treat different deformities and to redistribute the load at the joint level, reducing the risk of wear and, consequently, the need for invasive procedures. Particularly, knee osteotomies are effective in treating early arthritis related to knee deformities in young and active patients with high functional demands, with excellent long-term results. Precise mathematical calculations are imperative during the preoperative phase to achieve tailored and accurate corrections for each patient and avoid complications, but sometimes those formulas are challenging to comprehend and apply. METHODS:Four specific questions regarding controversial topics (planning methods, patellar height, tibial slope, and limb length variation) were formulated. An electronic search was performed on PubMed and Cochrane Library to find articles containing detailed mathematical or trigonometrical explanations. A team of orthopedic surgeons and an engineer summarized the available Literature and mathematical rules, with a final clear mathematical explanation given by the engineer. Wherever the explanation was not available in Literature, it was postulated by the same engineer. RESULTS:After the exclusion process, five studies were analyzed. For three questions, no studies were found that provided mathematical analyses or explanations. Through independent calculations, it was demonstrated why Dugdale's method underestimates the correction angle compared to Miniaci's method, and it was shown that the variation in patellar height after osteotomy can be predicted using simple formulas. The five included studies examine postoperative variations in limb length and tibial slope, providing formulas applicable in preoperative planning. New formulas were independently computed, using the planned correction angle and preoperatively obtained measurements to predict the studied variations. CONCLUSIONS:There is a strict connection among surgery, planning, and mathematics formulas in knee osteotomies. The aim of this study was to analyze the current literature and provide mathematical and trigonometric explanations to important controversial topics in knee osteotomies. Simple and easy applicable formulas are provided to enhance the accuracy and outcomes of this surgical procedure.

PurposeDifferent methods for quantifying joint-line obliquity (JLO) have been described, including joint-line obliquity angle (JLOA), Mikulicz joint-line angle (MJLA) and medial proximal tibial angle (MPTA). The goal of the present study was to quantify the variation of JLOA based on the position of the hip. The hypothesis of our study is that JLO is significantly influenced by the abduction/adduction of the limb, unlike MJLA.MethodsOne hundred long-leg-weightbearing X-rays were used. At time 0 and after 30 days, two observers performed different measurements, including (1) distance between pubic symphysis and center of the femoral head, (2) distance between center of the femoral head and center of the ankle joint, (3) distance between center of the ankle and medial malleolus, (4) hip-knee-ankle angle, (5) MPTA, (6) lateral distal femoral angle, (7) joint-line congruency angle, (8) JLOA, (9) MJL and (10) angle between Mikulicz line and line perpendicular to the ground. The changes of the JLOA based on the position of the hip (abducted, neutral, bipedal stance adduction and monopodal stance adduction) were calculated with trigonometric formulas and with simulation on an orthopaedic planning digital software.ResultsThe JLOA change between adducted and abducted positions was on average 12.8 degrees (SD 0.9 mm). The MJL did not vary significantly based on hip position.ConclusionsThe adduction/abduction of the lower limb has a considerable impact on JLOA. Methods like MJLA which are not affected by hip position should be preferred for JLO evaluation.Level of EvidenceDiagnostic study, level III.

Total knee arthroplasty (TKA) is a successful and highly effective procedure in most patients with tricompartmental knee arthritis. Despite the innovations in surgical techniques due to planning software and technological innovations, patients’ dissatisfaction after TKA is still high, at up to 20%. Robotic-assisted surgery (RAS) could be considered as a future option for improving outcomes due to its higher accuracy, precision, and reliability. Robotic systems can be classified as fully active, semi-active, or passive depending on the surgeon’s involvement during the procedure, and as imageless or image-based according to the necessity of radiological exams for the pre-operative planning. Three of the most well-known robotic systems for knee surgery are MAKO® (Stryker Ltd., Kalamazoo, MI, USA), NAVIO® (Smith & Nephew, Andover, TX, USA), and ROSA® (Zimmer Inc., Warsaw, IN, USA). These systems show differences in terms of surgeon involvement, the use of CT scans or X-rays for pre-operative planning, the possibility to perform both unicompartmental knee arthroplasty (UKA) and TKA (or even total hip arthroplasty THA), and in the different kinds of knee prosthesis that can be implanted. This article aims to describe the features of the most used robotic systems for knee arthroplasty, to examine their outcomes and analyze their cost-effectiveness, and to evaluate future perspectives.

The aim of this study was to evaluate the accuracy of a patient-specific cutting guide on both coronal and sagittal alignment compared to the pre-operative planning in OWHTO. Twelve OWHTO on 6 cadaveric specimens were performed by 3 experienced knee surgeons using patient-specific cutting guides based on 3D pre-operative planning. Since the specimens had no major deformities, a fixed correction of 6° on the left and 10° on the right legs were carried out to simulate different scenarios. A pre-operative and post-OWHTO 3D CT scans were performed, and images were superimposed using the dedicated 3D planning software to align their reference axes. A pre-operative planning was performed considering both Medial Proximal Tibial Angle (MPTA) and Posterior Tibial Slope (PTS), and a patient-specific cutting guide was produced. Planned and post-OWHTO MPTA and PTS were evaluated (mean and standard deviation), and Pearson’s correlation coefficient was calculated to assess precision and accuracy of the whole treatment. A mean correction of 6,1° (SD 1,9°) and 1,2° (SD 1°) was obtained respectively in the coronal plane (MPTA) and in the sagittal plane (PTS). The average difference between planned and post-OWHTO MPTA and PTS was respectively 1,2° (SD 0,6°) and 1,2° (SD 1°) in the sagittal plane (PTS). Pearson’s correlation coefficient demonstrated a good accuracy of the treatment in both coronal and sagittal plane (respectively r=0,95 and r=0,86). No lateral hinge fractures were detected at the post-operative CT scan. OWTHO performed with the help of 3D patient specific cutting guide on cadaveric specimens demonstrated good accuracy and reliability in obtaining the planned correction. In vivo studies are necessary to confirm these results and evaluate cost-effectiveness of this system. Level IV cadaveric study.

Three-dimensional (3D) printing was introduced firstly for industrial use, but it gained popularity in different medical fields, including orthopedic surgeries. Particularly, 3D-printed models have been used in the pre-operative planning for spine surgery, oncology, acetabular fracture treatment and complex primary total hip arthroplasty (THA) or revision THA. In knee surgery, some authors described good accuracy with 3D-printed wedge for Opening Wedge High Tibial Osteotomy (OWHTO), but there are no studies describing its application in Total Knee Arthroplasty (TKA). In both primary and revision TKA, a 3D-printed model may be useful to better evaluate knee morphology and deformity, implants, bone losses and the compatibility between different components used. Furthermore, some companies provide a bone thickness evaluation, which may be useful to identify zones at risk of intra-operative fracture, especially in those cases in which a cone or sleeve must be used. The first aim of this manuscript was to evaluate possible application of 3D-printed model in pre-operative planning of both complex primary and revision TKA, compared to standard planning. Two clinical cases will also be described to show how these models can be used for planning purposes.

Background The aim of this study is to find a correlation between linear measurements and the graft length required for different anterior cruciate ligament (ACL) revision techniques, to extract formulas to predict required graft length during the preoperative planning. Methods At time 0 and 30 days later, two observers measured eight linear distances on standard 2D knee magnetic resonance imaging (MRI), and nine curved distances on 3D MRI sequences, corresponding to different techniques for ACL revision, anatomic anterolateral ligament (ALL) reconstruction, and lateral extrarticular tenodesis (LET). Intra- and interobserver reliability was tested for 2D and 3D measurements. The correlation between 2D and 3D measurements was tested. The 2D measurements with highest repeatability and reproducibility, and with strongest correlation with 3D measurements were used to extract formulas to calculate the graft length from 2D values. Results Fifty MRIs acquired with both 2D and 3D sequences were used. The intra- and interobserver reliability of linear 2D measurement was high, with the transepicondylar distance (TD) showing the highest reproducibility and repeatability. The intra- and interobserver reliability of 3D measurements was lower than 2D, but acceptable for all measurements except for ALL reconstruction. The TD showed the strongest correlation with 3D measurements. The formulas extracted to calculate the graft length from the TD proved to be accurate. Conclusion Accurate formulas were created to calculate the graft length needed for different ACL revision techniques and ALL reconstruction/LET techniques from TD. These formulas can be used during preoperative planning of ACL revision cases.

Importance: Tibial tubercle osteotomy (TTO) is indicated to treat patellofemoral (PF) malalignment and chondral disease refractory to conservative treatment. However, there are no systematic reviews describing TTO outcomes in chondral damages without instability. Aim: The aims of this study were to (1) assess the quality of the published studies, (2) identify indication for TTO to treat PFP with chondral disease without instability, (3) evaluate the most common TTO techniques, (4) evaluate the clinical outcomes, and (5) evaluate TTO's complication and failure rates. Evidence review: In December 2020, a literature search was performed applying the following criteria: (1) peer reviewed Level 1-4 studies; (2) English language; (3) human subjects with clinical and/or radiological outcomes; (4) TTO alone or associated with minor cartilage procedure (only drilling, no instability); (5) minimum follow-up 12 months, minimum 10 patients; and (6) no more than 20% of drop-out rate. Data from studies were collected and described with weighted averages and standard deviations. Findings: A total of 18 Level 4 studies were included. The average Coleman Methodology Score was 61.5 points (range 48-81). A total of 851 patients (892 knees) were included, with 64.8% of female patients. The weighted average follow-up was 49.1 months (range 12-128.5). Indication for TTOs was poorly described. The main technique used was anteromedialisation (60.4%). In 27.7% of the cases, TTO was associated with lateral release. Different scoring systems were used to evaluate outcomes, with significant improvements. The average rate of good/excellent results was 78.7% (range 57%-100%). Fifteen studies described the complication rate (9.9%), whereas only four reported the failure rate (6.2%). Conclusion and relevance: TTOs performed to treat PF malalignment associated with chondral disease without instability provided good clinical outcomes, with acceptable complication/failure rates. However, high-level studies are necessary because of studies' heterogeneity regarding patellofemoral malalignment and chondral disease treatment. Study design and level of evidence: Systematic review. Level IV. Level of the study: Level IV, systematic review of Level IV studies.

Background: A significant number of high tibial osteotomies (HTOs) result in an overcorrected tibia and subsequent excessive lateral joint line obliquity (JLO). The correlation between excessive JLO and poor outcomes is controversial. Purpose: To evaluate the prognostic factors (including a pathological postoperative JLO) related with the outcomes of opening wedge HTO at 10 years of follow-up. Study Design: Case series; Level of evidence, 4. Methods: All patients undergoing HTO between 2004 and 2017 for medial osteoarthritis and with a postoperative hip-knee-ankle angle between 176° and 185° were included. Clinical evaluation included Knee Society Score (KSS; knee score and function score), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and visual analog scale for pain. Several mechanical and anatomic angles were measured pre- and postoperatively on long-leg weightbearing radiographs. Abnormal JLO was defined as a Mikulicz–joint line angle (MJL) ≥94° or a mechanical medial proximal tibial angle (mMPTA) ≥95°. Regression analysis was performed to evaluate the association between independent variables and each outcome. A Kaplan-Meier cumulative survival analysis was performed. Results: A total of 92 knees in 76 patients were included. The mean age of the patients was 53.5 years (SD, 9.7 years), and the mean follow-up was 129.4 months (SD, 44.4 months). Increased JLO was associated with a significant preoperative varus deformity (small preoperative hip-knee-ankle angle), increased mechanical lateral distal femoral angle, increased joint line congruency angle, and increased knee-ankle joint angle. Male sex was associated with better WOMAC scores (P = .0277), and increased body mass index (BMI) was associated with inferior WOMAC scores (P = .0024). A good preoperative range of motion was associated with better knee score (P = .0399) and function score (P = .0366) on the KSS. An increased BMI was associated with inferior KSS function scores (P = .0317). MJL ≥94° and mMPTA ≥95° were not associated with inferior WOMAC or KSS outcomes. With indication to total knee arthroplasty as an endpoint, Kaplan-Meier analysis showed a survival rate of 98.7% at 5 years, 95.5% at 10 years, and 92.7% at 12 years. Conclusion: Increased lateral JLO (MJL ≥94° or mMPTA ≥95°) was not correlated with the clinical outcomes of opening wedge HTO at 10 years of follow-up.

Total knee arthroplasty (TKA) in major deformities with ligament insufficiency may require a higher constraint, with bone sacrifice and concerns about long-term survivorship. Mid-level constraint liners have been recently introduced, but few studies described their outcomes. The aim of this study is to evaluate the short to mid-term outcomes of a constrained postero-stabilized (CPS) insert for primary TKA in moderate to severe deformities. All patients who underwent TKA using a CPS liner in two centers between 2015 and 2017 were included in the study. The indications were: (1) valgus deformity type 2–3 partially correctable; (2) severe varus deformity with varus thrust; (3) post-traumatic deformity with major ligamentous insufficiency and any case of intra-operative ligament insufficiency. Patients were evaluated according to the Knee Society Scoring System (KSS), the Hospital for Special Surgery score (HSS), the Western Ontario and Mc Master University (WOMAC) and the Oxford Knee score (OKS). X-rays were evaluated according to the Knee Society Roentgenographic Evaluation System. Forty-seven TKA were included, with an average age of 66.1 ± 10.3 years and an average follow-up of 68.4 ± 6 months. All patients demonstrated a moderate to severe pre-operative mediolateral instability. All the scores significantly improved (p < 0.0001). In 71.4% of cases, the outcomes were excellent or very good. There were no failures due to aseptic loosening but one failure due to a traumatic ligament rupture. The cumulative survivorship was 97.9% ± 2.1% at 84 months. This mid-range constraint total knee replacement demonstrated promising outcomes and survival at mid-term follow-up. IV (case series).

PURPOSE:To find a correlation and mathematical formulas between a linear 2-dimensional (2D) magnetic resonance imaging (MRI) measurement around the knee and the length of the grafts and tunnels required for both all-inside-all-epiphyseal and Kocher-Micheli pediatric anterior cruciate ligament (ACL) reconstruction techniques. METHODS:At time 0 and 30 days after, 2 observers measured: (1) on standard 2D knee MRI, 7 linear distances, representing morphologic measurements, such as transepicondylar distance (TD), and (2) on 3-dimensional (3D) MRI, 5 curved distances, corresponding to Kocher-Micheli and all-epiphyseal ACL reconstruction techniques. Intra- and interobserver reliability was tested for all measurements. The correlation between 2D and 3D measurements was tested. The 2D measurement with highest repeatability and reproducibility and with strongest correlation with 3D measurements was used to extract formulas to calculate the tunnel and graft length for the 2 techniques. RESULTS:Seventy-six MRIs were used. The intra- and interobserver reliability of 2D measurement was high, with TD showing the highest reproducibility and repeatability. 3D measurements also showed good intra and inter-observer reliability. A linear correlation was found between 2D and 3D measurements, with TD showing the strongest correlation. TD was used to extract formulas to calculate graft or tunnel length for Kocher-Micheli and all-epiphyseal ACL reconstruction. All formulas were proven to be accurate. A reference chart was also created to be used in the surgical setting. CONCLUSIONS:With specific formulas, TD can be used to calculate the length of the tunnels, intra-articular portion and graft length for an all-inside all-epiphyseal pediatric ACL reconstruction and the length of the iliotibial band required for the Kocher-Micheli technique. CLINICAL RELEVANCE:The surgeon can use these formulas in pediatric ACL reconstruction preoperative planning, graft harvesting and tunnel drilling.

An increasing number of anterior cruciate ligament (ACL) injuries are seen in children now than in the past due to increased sports participation. The natural history of ACL deficient knees in active individuals, particularly in children is poor. Surgical management of ACL deficiency in children is complex due to the potential risk of injury to the physis and growth disturbance. Delaying ACL reconstruction until maturity is possible but risks instability episodes and intra-articular damage. Surgical options include physeal-sparing, partial transphyseal and complete transphyseal procedures. This article reviews the management of ACL injured skeletally immature patients including the functional outcome and complications of contemporary surgical techniques.

Postoperative rehabilitation after simultaneous anterior cruciate ligament reconstruction and opening wedge high tibial osteotomy is a complex concept. Different osteotomy techniques, extremely selected patients, high expectations in returning to previous sport activities, and the different individual physical profile and performances make traditional chronological criteria impractical and unfeasible. This study presents a novel rehabilitation in which functional objective criteria are considered the key factors for standardizing a 4-step protocol. Each step is "individualized", based on the patient's response to the healing processes and to the different training phases, allowing for a safe return to sports competitions. This definitively implies a strict collaboration between patient, surgeon, physician and physiotherapists, as well as thorough and detailed patient education. Due to the high versatility of these new rehabilitation concepts, the application of the "individualized" steps described in this study may be broadened to include different sports medicine knee injuries that may benefit from a specific, detailed and carefully patient-centered rehabilitation project.

An original scientific manuscript is the target for any researchers whose aim is to show the innovative results arising from the original intuitions that drove all their experiments. Time and patience are essential to decide how to present the data, how to conceive the tables and figures representing the main outcomes of the research, and how to read and mention the necessary references. Few basic rules may help in this difficult task. The first basic rule is: "do not follow the sequence of the paper". On the opposite, i) start writing the "Materials and Methods (or Patients and Methods when dealing with a clinical study)", ii) then write the "Results" section, iii) then, write the "Discussion" paragraph, in which the principal investigator explains the results and the innovations proposed, iv) then, write the "Introduction", which should be clear and concise. The last element to be written should be the "Abstract", which is the "interface" between the authors and the readers. The second basic rule is that any of the central chapters of the manuscript, i.e. "Materials and Methods" (MM), "Results" (R) and "Discussion" (D), should follow a methodical and sequential description of the topics in a "corresponding sequence of paragraphs". In other words, in the R and the D chapter sequence of the paragraphs should be linked to the sequence of the concepts described and discussed in the paragraphs of the MM chapter. Thus, a sequential description of concepts will be easily followed by the writers, facilitating both the authors in the organization of the data and the reader in finding a reasonable "answer" to all the aspects of the study mentioned in the MM chapter. In this article, these two rules are extensively described and several tips and tricks for each chapter are suggested to ease the composition of a scientific paper. Indeed, it may be possible to solve the complex problem of "writing a scientific paper" by means of separating it in main sections (chapters) and subsections (paragraphs) and dealing with them one by one. Naturally, this takes time and passion, but, as affirmed by Steve Jobs, "the only way to do great work is to love what you do".

Objectives: High Tibial Osteotomy (HTO) is widely performed to treat early arthiritis in the varus knee. The aim of this prospective study is to evaluate different prognostic factors affecting the outcomes of HTO and, with special attention to the role of the site of deformity. Methods: 231 Opening Wedge HTO (OWHTO) were performed in 202 patients and included in the study. Inclusion criteria were: 1) age > 18 years, 2) no major associated procedures (i.e. ACL reconstruction, major cartilage procedure, 3) only OWHTO, 4) pre-operative complete clinical and radiological evaluation available. Patients were evaluated with (1) the Knee Society score (KSS), (2) the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, (3) another self-evaluation scale, (4) long-leg radiographs, and (5) plain radiographs. On the x-ray different angles were evaluated, including Join Line Congruence Angle. Furthermore, the location of deformity was established. Three main outcomes were identified: Indication to Total Knee Arthroplasty (TKA), KSS poor or fair and WOMAC < 76 points), and different prognostic factors were identified (Fig. 1). All the variables were firstly tested in a single regression model to evaluate the association with each outcome. All the variables with p<0.1 were re-tested in a multiple regression model. Results: 32 patients were lost to follow-up and 31 patients did not meet the inclusion criteria, leaving 139 patients (156 OWHTOs) for the study. The average age was 52.9 ± 9.6 years, and the average follow-up was 97.7 ± 42.8 months. Post-operatively there was a significant improvement in both the KSS and WOMAC score compared to the pre-operative period (p<0.0001). The only variable related to TKA indication was a pre-operative JLCA ≥5° (OR=24.3, p=0.0483). Conversely, different variables were related to a worse KSS, including pre-operative BMI >30 Kg/m2 (OR=78.9, p=0.0028), pre-operative ROM <120° of flexion (OR=40.8, p=0.0421), pre-operative mLDFA ≥91° (OR=36,6,p=0.0401) and femoral pre-operative CORA ≥3° of varus (OR=39,9 p=0.0269). Furthermore, a pre-operative BMI >30 Kg/m2 (OR=29,5, p=0.0314) was associated to a worse WOMAC score. Conversely, patients with a pre-operative mMPTA ≤84° had lower risk to obtain a worse KSS oe WOMAC score (respectively OR= 0,2 p=0.0364 and OR=0,3 p=0.0071). The cumulative survivorship was calculated with the Kaplan-Meier method, and it resulted equal to 98.6% at 5 years and decreased to 85.5% at 10 years. Conclusion: OWHTO is a good treatment for early arthritis in the varus knee if the correct indications are applied. The outcomes can be considered good, with 85% of 10-year survivorship. It is mandatory to correctly address the location of the deformity, because the presence of a femoral varus deformity is related to worse outcomes. Similarly, presence of a pre-operative JLCA ≥5° is the only factor associated to TKA indication. Table 1. Pre-Operative Intra-Operative BMI Associated procedures Age (≥56 years) Cartilage damage Gender Educational status Post-Operative Amount of deformity Weight bearing line (%) ROMI (Range of motion) JLCA Knee Society score mLDTA (mechanical lateral distal tibial angle) Function score WOMAC scale Amount of medial arthritis Presence of lateral arthritis mLDFA (mechanical lateral distal femoral angle) mMPTA (mechanical medial proximal tibial angle) JLCA (Joint Line Congruence Angle) Femoral CORA (center of rotation and angulation)

Hamstring tendons represent one of the commonest autologous graft used during ACL reconstruction. The harvest of the tendon and the time of tendon processing on the operating table, together with the pretensioning maneuvers and the permanence out of the joint during the time of surgery, might impair tendon derived cells (TCs) viability. The aim of the study was: i) to assess the effective viability of the TCs at the end of the surgical procedure; ii) to investigate if TCs viability and the expression of tendon specific markers may be improved through exposure to prolonged pulsed electromagnetic fields (PEMF) similar to that of clinical practice. Remnants of semitendinosus and gracilis tendons (discarded at the end of the ACL reconstruction) were collected from 13 healthy donors. To isolate TCs, the tendon tissue was minced and digested enzymatically with 0.3% type I collagenase in DMEM with continuous agitation for 15 h at 37°C. The isolated nucleated cells were then plated at 5x103 cells/cm2 in a complete medium composed of DMEM, 10% fetal bovine serum, 50 U/ml Penicillin, 50 mg/ml Streptomycin, 2 mM L-glutamine, and supplemented with 5 ng/ml basic fibroblast growth factor (b-FGF). They were maintained at 37 °C in a humidified atmosphere with 5% CO2, changing culture medium every 3 days. When they reached 80-90% of confluence, the cells were detached by incubation with trypsin/EDTA and then cultured at a density of 5x103 cells/cm2. TCs were cultured in complete medium for 7, 14, 21 days (in chamber slides, to optimize the final immunofluorescence analysis). The following cell cultures were set up: i) TCs cultured with differentiation medium + exposure to PEMF 8 h/day; ii) TCs cultured with differentiation medium without exposure to PEMF. The stimulation with PEMF was generated by a pair of electrical coils, connected with the generator of pulsed electromagnetic fields (PEMF generator system IGEA, Carpi, Italy, intensity of magnetic field = 1.5 mT, frequency = 75 Hz). At day 0, day 7, day 14 and day 21 immunofluorescence analysis was performed to evaluate the expression of tendon specific markers (collagen type I, collagen type VI, scleraxis) and proliferative markers (PCNA, beta-catenin). The TCs from the hamstring tendon fragments at the end of the ACL reconstruction were alive and they expressed markers of proliferation and tendon phenotype at the end of the culture period. The TCs in the presence of PEMF 8h/day showed a greater production of collagen type I, collagen type VI and scleraxis than TCs cultured without PEMF (p<0.05). The expression of these markers increased from 7 to 21 days of culture. The expression of proliferative markers in the presence of PEMF stimulus was significantly lower (p<0.05) than that of TCs cultured without PEMF. Hamstring tendons are not simple "tenoconductive" scaffolds but biologic alive tenogenic constructs rich in cells that can sustain tenogenic behavior and tendon matrix synthesis. Prolonged exposure to PEMF improves their phenotype. Thus, from a clinical perspective, the use of PEMF may represent a possible future strategy to positively influence the early phase of graft remodeling and, ultimately, improve the ligamentization process. Following these concepts, further studies might also exploit the anabolic role of PEMF as an adjunctive postoperative strategy in different tendon pathologies.