Preoperative ultrasound predicts the intraoperative diameter of the quadriceps tendon autograft more accurately than preoperative magnetic resonance imaging for anterior cruciate ligament reconstruction.

PURPOSE: Sizing of potential autografts is essential to match the native anterior cruciate ligament (ACL) dimensions when performing ACL reconstruction (ACLR). We aimed to investigate the accuracy and reliability of the thickness and cross-sectional area (CSA) assessments for the prediction of the intraoperative diameter of the QT autograft using preoperative ultrasound and MRI. METHODS: Thirty patients (mean age ± standard deviation, 19.9 ± 5.0 years), who underwent ACLR using QT autograft, were included. The maximum thickness of the QT was assessed at 15 and 30 mm proximal using ultrasound with a long axis image, and at 15 mm proximal to the superior pole of the patella using MRI with a sagittal image. The CSA was assessed at the central 10 mm of the medial-lateral QT width at 30 mm proximal using ultrasound with a short axis image, and at 15 mm proximal to the superior pole of the patella using MRI with an axial image. Intraoperatively, QT autograft was harvested with a 10 mm width and the diameter was measured using a graft sizing device. RESULTS: Intra- and inter-observer reliabilities of all measurements using ultrasound and MRI were good (Intra-class correlation coefficient, 0.720-0.941). Correlation coefficient with the intraoperative diameter of the QT autograft was higher in ultrasound (R = 0.738-0.791, P < 0.001) than MRI (R = 0.449-0.543, P = 0.002-0.013). CONCLUSIONS: Preoperative ultrasound predicted the intraoperative diameter of the QT autograft more accurately than MRI. Ultrasound may be used clinically to assure a sufficiently large QT autograft diameter to match the diameter of the patient's native ACL. LEVEL OF EVIDENCE: Level III.

Two-fragment Segond fracture validates historical descriptions of independent soft tissue attachments.

This is a case report of a 26-year-old male who sustained a Segond fracture in the context of an acute anterior cruciate ligament (ACL) rupture incurred while downhill skiing. Further work-up revealed that the Segond fracture consisted of two distinct fragments with separate soft tissue attachments, including the capsule-osseous layer of the iliotibial band and the short arm of the biceps femoris. Imaging showed interval healing of the Segond fracture between initial presentation and the performance of arthroscopic ACL reconstruction approximately 4 months later. As intraoperative evaluation demonstrated that anatomic ACL reconstruction restored translational and rotatory knee stability, surgical repair of the Segond fracture, or the anterolateral complex of the knee more broadly, was not required. Maintenance of translational and rotatory knee stability was confirmed at serial post-operative appointments up through final follow-up.Level of evidence Level V.

Superb microvascular imaging (SMI) detects increased vascularity of the torn anterior cruciate ligament.

PURPOSE: Ultrasound with superb microvascular imaging (SMI) is a novel microvascular imaging technology which may be useful to assess the vascularity of the torn anterior cruciate ligament (ACL) as a potential measure of healing potential following surgery. This study aimed to quantify the vascularity of the torn and intact ACL using ultrasound with SMI. METHODS: 23 patients (mean age ± standard deviation, 27.1 ± 12.8 years), who were diagnosed with an ACL tear with an intact contralateral ACL were enrolled (ACL injury group). Ten healthy volunteers (36.1 ± 4.9 years) who had intact ACLs in both knees were also recruited (ACL healthy controls). The vascularity of the ACL was assessed using SMI within 15 mm from the tibial insertion in both knees. The amount of the vascular signal was assessed using a semi-quantitative grading scale (vascularity grade: grade 0-3) and a quantified ratio of vascularized area with respect to total area of the region of interest (vascularity ratio). RESULTS: In the ACL injury group, a significantly higher vascularity grade and ratio were observed in the torn ACL (vascularity grade 0-3: 1, 8, 7, and 7 patients, respectively; vascularity ratio: 1.3 ± 1.4%) than the contralateral intact ACL (vascularity grade 0-3: 21, 1, 1, and 0 patients, respectively; vascularity ratio: 0.1 ± 0.5%) (P < 0.001), whereas no significant difference was observed between both ACLs in the ACL healthy control group. CONCLUSIONS: SMI was useful to assess the increased vascularity in torn ACL, which may reflect the potential for, or state of, ACL maturation following reconstruction or repair. LEVEL OF EVIDENCE: Level III.

Freddie Fu: A Leader of Leaders.

Freddie Fu had a profound and undeniable impact on the field of orthopaedic surgery. He was a leader both personally and professionally and dedicated his career to ensuring that those around him had the opportunity to thrive. His life and career were distinguished by his exceptional leadership, boundless collaboration, and dedication to diversity. Freddie Fu's ability to train future leaders represents one of his greatest professional legacies, which will continue to permeate the field of orthopaedic surgery for decades to come. He was a giant, and those fortunate enough to train under him are better because of it.

Tendon-derived extracellular matrix induces mesenchymal stem cell tenogenesis via an integrin/transforming growth factor-ß crosstalk-mediated mechanism.

Treatment of tendon injuries is challenging. To develop means to augment tendon regeneration, we have previously prepared a soluble, low immunogenic (DNA-free), tendon extracellular matrix fraction (tECM) by urea extraction of juvenile bovine tendons, which is capable of enhancing transforming growth factor-ß (TGF-ß) mediated tenogenesis in human adipose-derived stem cells (hASCs). Here, we aimed to elucidate the mechanism of tECM-driven hASC tenogenic differentiation in vitro, focusing on the integrin and TGF-ß/SMAD pathways. Our results showed that tECM promoted hASC proliferation and tenogenic differentiation in vitro based on tenogenesis-associated markers. tECM also induced higher expression of several integrin subunits and TGF-ß receptors, and nuclear translocation of p-SMAD2 in hASCs. Pharmacological inhibition of integrin-ECM binding, focal adhesion kinase (FAK) signaling, or TGF-ß signaling independently led to compromised pro-tenogenic effects of tECM and actin fiber polymerization. Additionally, integrin blockade inhibited tECM-driven TGFBR2 expression, while inhibiting TGF-ß signaling decreased tECM-mediated expression of integrin α1, α2, and ß1 in hASCs. Together, these findings suggest that the strong pro-tenogenic bioactivity of tECM is regulated via integrin/TGF-ß signaling crosstalk. Understanding how integrins interact with signaling by TGF-ß and/or other growth factors (GFs) within the tendon ECM microenvironment will provide a rational basis for an ECM-based approach for tendon repair.

In situ cross-sectional area of the quadriceps tendon using preoperative magnetic resonance imaging significantly correlates with the intraoperative diameter of the quadriceps tendon autograft.

PURPOSE: Preoperative assessment to determine the sizes of potential autografts is necessary for individualized anterior cruciate ligament reconstruction (ACLR). However, no study has investigated the prediction of the intraoperative diameter of the quadriceps tendon (QT) autograft based upon preoperative imaging. This study investigated the correlation between the intraoperative diameter of a QT autograft and in situ thickness or cross-sectional area (CSA) measured using preoperative MRI. METHODS: Thirty-one knees of 31 patients (mean age 20.9 ± 5.0 years) who underwent individualized anatomic ACLR using all soft tissue QT autograft were included retrospectively. At 15 mm proximal to the superior pole of the patella, the maximum QT thickness was assessed in the sagittal plane and the CSA was assessed at the central 10 mm of the QT in the axial plane. The angle between the axial plane and a line perpendicular to the QT longitudinal axis was used to calculate an adjusted CSA using a cosine function. Intraoperatively, each QT autograft was harvested with 10 mm width and the diameter was measured using a graft sizing device. RESULTS: Intra- and inter-observer reliabilities of all measurements using preoperative MRI were excellent (intra-class correlation coefficient, 0.833-0.970). Significant correlations were observed between the thickness, CSA, or adjusted CSA, and the intraoperative diameter (R = 0.434, 0.607, and 0.540, respectively; P < 0.05). CONCLUSIONS: The CSA correlated most strongly with the QT autograft diameter. For individualized anatomic ACLR, measuring in situ CSA can be useful for preoperative planning of appropriate graft choices prior to surgery. LEVEL OF EVIDENCE: III.

Clinical studies of single-stage combined ACL and PCL reconstruction variably report graft tensioning, fixation sequence, and knee flexion angle at time of fixation.

PURPOSE: In single-stage ACL-PCL reconstruction, there is uncertainty regarding the order of graft tensioning and fixation, as well as the optimal knee flexion angle(s) for graft fixation. A systematic review of clinical studies of single-stage combined ACL-PCL reconstruction was performed to determine whether a particular fixation sequence and/or knee flexion angle is associated with superior outcomes. METHODS: A systematic review was performed according to PRISMA guidelines. All levels of evidence were included. All outcome measures were extracted, including physical examination values, radiographic measurements, and objective and subjective outcomes. RESULTS: Of the 19 included studies, 17 tensioned and fixed the PCL before the ACL. Only four studies reported the methods/forces used for graft tensioning. Across studies, the ACL was fixed at variable knee flexion angles, from full extension to 70°. Conversely, 3 studies fixed the PCL at a knee flexion angle < 45°, while the remaining 16 studies fixed the PCL at a flexion angle > 70°. Patient-reported outcomes were qualitatively similar between groups. CONCLUSIONS: This systematic review found considerable variability in graft tension, fixation sequence, and knee flexion angle at the time of fixation, with insufficient evidence to support specific surgical practices. Most commonly, the PCL is fixed before the ACL graft, with fixation occurring at a knee flexion angle between 70° and 90° and near full extension, respectively. The methodology for quantifying the forces applied for graft tensioning is rarely described. Given this clinical equipoise, future studies should consistently report these surgical details. Furthermore, prospective, randomized studies on the treatment of multiligament knee injuries are needed to improve outcomes in patients. LEVEL OF EVIDENCE: IV.

Decellularized bone extracellular matrix in skeletal tissue engineering.

Bone possesses an intrinsic regenerative capacity, which can be compromised by aging, disease, trauma, and iatrogenesis (e.g. tumor resection, pharmacological). At present, autografts and allografts are the principal biological treatments available to replace large bone segments, but both entail several limitations that reduce wider use and consistent success. The use of decellularized extracellular matrices (ECM), often derived from xenogeneic sources, has been shown to favorably influence the immune response to injury and promote site-appropriate tissue regeneration. Decellularized bone ECM (dbECM), utilized in several forms - whole organ, particles, hydrogels - has shown promise in both in vitro and in vivo animal studies to promote osteogenic differentiation of stem/progenitor cells and enhance bone regeneration. However, dbECM has yet to be investigated in clinical studies, which are needed to determine the relative efficacy of this emerging biomaterial as compared with established treatments. This mini-review highlights the recent exploration of dbECM as a biomaterial for skeletal tissue engineering and considers modifications on its future use to more consistently promote bone regeneration.

Editorial Commentary: The Segond Fracture Has Multiple Attachments: Yet Another Demonstration of the Anatomical Complexity of the Anterolateral Complex of the Knee.

The anterolateral complex (ALC) of the knee comprises multiple layers, with continued debate on the identity and function of the structures of the ALC. The Segond fracture, long considered pathognomonic of an anterior cruciate ligament injury, has now been shown to have several attachments to soft tissues of the ALC. To the extent that a Segond fracture, or injury to the ALC more broadly, increases knee rotatory instability in vivo is a question of ongoing investigation. By extension, it remains uncertain whether an untreated Segond fracture adversely affects outcomes and therefore warrants consideration for operative intervention. Prospective randomized studies of anatomic anterior cruciate ligament reconstruction with or without concomitant treatment of Segond fractures are needed to more definitively answer these questions.

Over-the-top ACL reconstruction restores anterior and rotatory knee laxity in skeletally immature individuals and revision settings.

PURPOSE: To investigate the objective outcomes following anterior cruciate ligament reconstruction (ACLR) with the over-the-top (OTT) technique. METHODS: Thirty-five ACL-deficient patients with mean follow-up of 2.2 years were retrospectively reviewed. This included 14 skeletally immature individuals (age: 14 ± 1 years) who underwent primary OTT ACLR (adolescent group) and 21 skeletally mature individuals (age: 25 ± 8 years) who underwent OTT revision ACLR (revision group). The tibial tunnel was created at the anatomic position for all cases. No lateral extra-articular tenodesis was performed. Before and after surgery, the side-to-side difference (SSD) in anterior laxity was measured using KT-1000 arthrometer. Lachman and pivot-shift tests were assessed according to IKDC grade. The graft failure rate was assessed. RESULTS: The post-operative SSD in anterior laxity was significantly reduced in the adolescent (pre-op, 3.9 ± 1.8 mm; post-op, 1.2 ± 0.8 mm; p = 0.040) and revision groups (pre-op, 4.2 ± 1.7 mm; post-op, 1.2 ± 1.4 mm; p < 0.001). Postoperative knee laxity measured by Lachman and pivot-shift tests were also significantly improved in both groups. Graft rupture occurred in two patients in the adolescent group (14.3%), and one patient in the revision group (4.8%). CONCLUSION: ACLR with the OTT technique restored anterior and rotatory knee laxity in skeletally immature individuals and in revision settings. This one-step procedure may be a good option for skeletally immature individuals and revision settings. LEVEL OF EVIDENCE: IV.

Anatomic ACL reconstruction reduces risk of post-traumatic osteoarthritis: a systematic review with minimum 10-year follow-up.

PURPOSE: To systematically review the literature for radiographic prevalence of osteoarthritis (OA) at a minimum of 10 years following anterior cruciate ligament (ACL) reconstruction (ACLR) with anatomic vs. non-anatomic techniques. It was hypothesized that the incidence of OA at long-term follow-up would be lower following anatomic compared to non-anatomic ACLR. METHODS: A systematic review was performed by searching PubMed, MEDLINE, EMBASE, and the Cochrane Library, for studies reporting OA prevalence by radiographic classification scales at a minimum of 10 years following ACLR with autograft. Studies were categorized as anatomic if they met or exceeded a score of 8 according the Anatomic ACL Reconstruction Scoring Checklist (AARSC), while those with a score less than 8 were categorized as non-anatomic/non-specified. Secondary outcomes included graft failure and measures of knee stability (KT-1000, Pivot Shift) and functional outcomes [Lysholm, Tegner, subjective and objective International Knee Documentation Committee (IKDC) scores]. OA prevalence on all radiographic scales was recorded and adapted to a normalized scale. RESULTS: Twenty-six studies were included, of which 5 achieved a score of 8 on the AARSC. Using a normalized OA classification scale, 87 of 375 patients (23.2%) had diagnosed OA at a mean follow-up of 15.3 years after anatomic ACLR and 744 of 1696 patients (43.9%) had OA at mean follow-up of 15.9 years after non-anatomic/non-specified ACLR. The AARSC scores were 9.2 ± 1.3 for anatomic ACLR and 5.1 ± 1.1 for non-anatomic/non-specified ACLR. Secondary outcomes were relatively similar between techniques but inconsistently reported. CONCLUSIONS: This study showed that anatomic ACLR, defined as an AARSC score ≥ 8, was associated with lower OA prevalence at long-term follow-up. Additional studies reporting long-term outcomes following anatomic ACLR are needed, as high-level studies of anatomic ACLR are lacking. The AARSC is a valuable resource in performing and evaluating anatomic ACLR. Anatomic ACLR, as defined by the AARSC, may reduce the long-term risk of post-traumatic OA following ACL injury to a greater extent than non-anatomic ACLR. LEVEL OF EVIDENCE: IV.

Clinical outcomes after anterior cruciate ligament injury: panther symposium ACL injury clinical outcomes consensus group.

PURPOSE: A stringent outcome assessment is a key aspect for establishing evidence-based clinical guidelines for anterior cruciate ligament (ACL) injury treatment. The aim of this consensus statement was to establish what data should be reported when conducting an ACL outcome study, what specific outcome measurements should be used and at what follow-up time those outcomes should be assessed. METHODS: To establish a standardized approach to assessment of clinical outcome after ACL treatment, a consensus meeting including a multidisciplinary group of ACL experts was held at the ACL Consensus Meeting Panther Symposium, Pittsburgh, PA; USA, in June 2019. The group reached consensus on nine statements by using a modified Delphi method. RESULTS: In general, outcomes after ACL treatment can be divided into four robust categories-early adverse events, patient-reported outcomes, ACL graft failure/recurrent ligament disruption and clinical measures of knee function and structure. A comprehensive assessment following ACL treatment should aim to provide a complete overview of the treatment result, optimally including the various aspects of outcome categories. For most research questions, a minimum follow-up of 2 years with an optimal follow-up rate of 80% is necessary to achieve a comprehensive assessment. This should include clinical examination, any sustained re-injuries, validated knee-specific PROs and Health-Related Quality of Life questionnaires. In the mid- to long-term follow-up, the presence of osteoarthritis should be evaluated. CONCLUSION: This consensus paper provides practical guidelines for how the aforementioned entities of outcomes should be reported and suggests the preferred tools for a reliable and valid assessment of outcome after ACL treatment. LEVEL OF EVIDENCE: V.

Return to sport after anterior cruciate ligament injury: Panther Symposium ACL Injury Return to Sport Consensus Group.

PURPOSE: A precise and consistent definition of return to sport (RTS) after anterior cruciate ligament (ACL) injury is lacking, and there is controversy surrounding the process of returning patients to sports and their previous activity level. The aim of the Panther Symposium ACL Injury RTS Consensus Group was to provide a clear definition of RTS and description of the RTS continuum, as well as to provide clinical guidance on RTS testing and decision-making. METHODS: An international, multidisciplinary group of ACL experts convened as part of a consensus meeting. Consensus statements were developed using a modified Delphi method. Literature review was performed to report the supporting evidence. RESULTS: Key points include that RTS is characterized by achievement of the pre-injury level of sport and involves a criteria-based progression from return to participation to return to sport, and ultimately return to performance. Purely time-based RTS decision-making should be abandoned. Progression occurs along a RTS continuum with decision-making by a multidisciplinary group that incorporates objective physical examination data and validated and peer-reviewed RTS tests, which should involve functional assessment as well as psychological readiness. Consideration should be given to biological healing, contextual factors and concomitant injuries. CONCLUSION: The resultant consensus statements and scientific rationale aim to inform the reader of the complex process of RTS after ACL injury that occurs along a dynamic continuum. Research is needed to determine the ideal RTS test battery, the best implementation of psychological readiness testing and methods for the biologic assessment of healing and recovery. LEVEL OF EVIDENCE: IV.

Treatment after anterior cruciate ligament injury: Panther Symposium ACL Treatment Consensus Group.

Treatment strategies for anterior cruciate ligament (ACL) injuries continue to evolve. Evidence supporting best practice guidelines for the management of ACL injury is to a large extent based on studies with low-level evidence. An international consensus group of experts was convened to collaboratively advance toward consensus opinions regarding the best available evidence on operative vs. non-operative treatment for ACL injury. The purpose of this study is to report the consensus statements on operative vs. non-operative treatment of ACL injuries developed at the ACL Consensus Meeting Panther Symposium 2019. Sixty-six international experts on the management of ACL injuries, representing 18 countries, were convened and participated in a process based on the Delphi method of achieving consensus. Proposed consensus statements were drafted by the Scientific Organizing Committee and Session Chairs for the three working groups. Panel participants reviewed preliminary statements prior to the meeting and provided the initial agreement and comments on the statement via an online survey. During the meeting, discussion and debate occurred for each statement, after which a final vote was then held. Eighty percent agreement was defined a-priori as consensus. A total of 11 of 13 statements on operative v. non-operative treatment of ACL injury reached the consensus during the Symposium. Nine statements achieved unanimous support, two reached strong consensus, one did not achieve consensus, and one was removed due to redundancy in the information provided. In highly active patients engaged in jumping, cutting, and pivoting sports, early anatomic ACL reconstruction is recommended due to the high risk of secondary meniscus and cartilage injuries with delayed surgery, although a period of progressive rehabilitation to resolve impairments and improve neuromuscular function is recommended. For patients who seek to return to straight plane activities, non-operative treatment with structured, progressive rehabilitation is an acceptable treatment option. However, with persistent functional instability, or when episodes of giving way occur, anatomic ACL reconstruction is indicated. The consensus statements derived from international leaders in the field will assist clinicians in deciding between operative and non-operative treatments with patients after an ACL injury.Level of evidence V.

The effect of adipose-derived stem cells on enthesis healing after repair of acute and chronic massive rotator cuff tears in rats.

BACKGROUND: Chronic massive rotator cuff tears heal poorly and often retear. This study investigated the effect of adipose-derived stem cells (ADSCs) and transforming growth factor-ß3 (TGF-ß3) delivered in 1 of 2 hydrogels (fibrin or gelatin methacrylate [GelMA]) on enthesis healing after repair of acute or chronic massive rotator cuff tears in rats. METHODS: Adult male Lewis rats underwent bilateral transection of the supraspinatus and infraspinatus tendons with intramuscular injection of botulinum toxin A (n = 48 rats). After 8 weeks, animals received 1 of 8 interventions (n = 12 shoulders/group): (1) no repair, (2) repair only, or repair augmented with (3) fibrin, (4) GelMA, (5) fibrin + ADSCs, (6) GelMA + ADSCs, (7) fibrin + ADSCs + TGF-ß3, or (8) GelMA + ADSCs + TGF-ß3. An equal number of animals underwent acute tendon transection and immediate application of 1 of 8 interventions. Enthesis healing was evaluated 4 weeks after the repair by microcomputed tomography, histology, and mechanical testing. RESULTS: Increased bone loss and reduced structural properties were seen in chronic compared with acute tears. Bone mineral density of the proximal humerus was higher in repairs of chronic tears augmented with fibrin + ADSCs and GelMA + ADSCs than in unrepaired chronic tears. Similar improvement was not seen in acute tears. No intervention enhanced histologic appearance or structural properties in acute or chronic tears. CONCLUSIONS: Surgical repair augmented with ADSCs may provide more benefit in chronic tears compared with acute tears, although there was no added benefit to supplementing ADSCs with TGF-ß3.

Rapidly dissociated autologous meniscus tissue enhances meniscus healing: An in vitro study.

PURPOSE: Treatment of meniscus tears is a persistent challenge in orthopedics. Although cell therapies have shown promise in promoting fibrocartilage formation in in vitro and preclinical studies, clinical application has been limited by the paucity of autologous tissue and the need for ex vivo cell expansion. Rapid dissociation of the free edges of the anterior and posterior meniscus with subsequent implantation in a meniscus lesion may overcome these limitations. The purpose of this study was to explore the effect of rapidly dissociated meniscus tissue in enhancing neotissue formation in a radial meniscus tear, as simulated in an in vitro explant model. MATERIALS AND METHODS: All experiments in this study, performed at minimum with biological triplicates, utilized meniscal tissues from hind limbs of young cows. The effect of varying collagenase concentration (0.1%, 0.2% and 0.5% w/v) and treatment duration (overnight and 30 minutes) on meniscus cell viability, organization of the extracellular matrix (ECM), and gene expression was assessed through a cell metabolism assay, microscopic examination, and quantitative real-time reverse transcription polymerase chain reaction analysis, respectively. Thereafter, an explant model of a radial meniscus tear was used to evaluate the effect of a fibrin gel seeded with one of the following: (1) fibrin alone, (2) isolated and passaged (P2) meniscus cells, (3) overnight digested tissue, and (4) rapidly dissociated tissue. The quality of in vitro healing was determined through histological analysis and derivation of an adhesion index. RESULTS: Rapid dissociation in 0.2% collagenase yielded cells with higher levels of metabolism than either 0.1% or 0.5% collagenase. When seeded in a three-dimensional fibrin hydrogel, both overnight digested and rapidly dissociated cells expressed greater levels of collagens type I and II than P2 meniscal cells at 1 week. At 4 and 8 weeks, collagen type II expression remained elevated only in the rapid dissociation group. Histological examination revealed enhanced healing in all cell-seeded treatment groups over cell-free fibrin controls at weeks 1, 4, and 8, but there were no significant differences across the treatment groups. CONCLUSIONS: Rapid dissociation of meniscus tissue may provide a single-step approach to augment regenerative healing of meniscus repairs.

Arthroscopic image distortion-part I: the effect of lens and viewing angles in a 2-dimensional in vitro model.

PURPOSE: Arthroscopic images are subject to distortion, which may increase when using arthroscope lenses with greater reflecting angles and/or viewing structures at oblique angles. The purpose of this study was to determine the magnitude of image distortion experienced when using arthroscopes with different lens angles and when the line-of-sight (i.e., viewing angle) is not directly perpendicular to the target. METHODS: A dot calibration target was captured through 0°, 30°, and 70° arthroscopes from straight (i.e., directly perpendicular) and 30° oblique viewing angles. Distortions in horizontal and vertical distances in deep (located at 87.5 % length of arthroscopic image diameter) or shallow (12.5 % diameter length) regions were calculated, from which a deformity ratio (horizontal/vertical distance) was determined. RESULTS: From the straight viewing angle (0°), both horizontal and vertical distances were artificially reduced (i.e., <100 % magnification) in the shallow and deep regions. The deformity ratio was ~100 % in the central region, declining to ~80 % peripherally. From the oblique viewing angle (30°), magnification was below 100 % in the deep area but exceeded 100 % in the shallow area, with increasing distortion associated with increasing lens angle (0° < 30° < 70°). For all lens angles, the deformity ratio was ~50 % in the deep area but neared 100 % in the shallow region. CONCLUSIONS: Arthroscopic image distortion in peripheral regions should be considered when using angled-lens arthroscopes, especially when the viewing angle is not straight. As viewing the femoral ACL footprint through the anterolateral portal involves using an oblique viewing angle, visualization through the anteromedial portal is recommended.

Arthroscopic image distortion-part II: the effect of lens angle and portal location in a 3D knee model.

PURPOSE: Distortion in arthroscopic views can interfere with accurate graft placement in ACL reconstruction, yet the effect of arthroscopic lens angle and portal location on image distortion is unknown. The purpose of this study was to quantify the image distortion resulting from the use of angulated arthroscope lenses through multiple portals, thereby identifying the optimal parameters to minimize distortion. METHODS: A uniform grid of dots was attached to the lateral wall of the intercondylar notch of a Sawbones(®) knee model. The inferior half of the lateral wall was divided equally along the distoproximal axis into three regions-shallow, central, and deep. Each region was imaged using five different arthroscopic configurations [0° arthroscope through anteromedial (AM) portal, 30° arthroscope through AM and anterolateral (AL) portals, 70° arthroscope through AM and AL portals]. For each configuration, the differences in magnification and deformity ratios between the three regions were calculated. RESULTS: Less than 100 % of central region magnification was observed in the deep region, while more than 100 % was found in the shallow region. The AL approach produced larger magnification errors in the shallow region, as compared to the AM approach. Deformity ratios less than 100 % were found with both 0° and 30° arthroscopes, whereas deformity ratios exceeding 100 % were found with 70° arthroscopes. CONCLUSIONS: The least distorted and the most consistent image of the femoral ACL insertion is provided through the AM portal using either a 30° or 70° arthroscope lens. Surgeons should carefully select the arthroscope and portal to minimize image distortion and ensure accurate surgical procedure.