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Computer navigation increases accuracy and precision of component alignment in total knee arthroplasty (TKA) compared to the manual technique, but is often associated with increases in surgical time. In a previous cadaver study, we demonstrated a significant improvement in guide positioning precision, final bone cut precision, and procedure length when using adjustable cutting blocks (ACB) compared to conventional cutting blocks (CCB) in computer-navigated TKA. The aim of this study was to evaluate the use of ACB in vivo. We radiographically compared component alignment and mechanical leg alignment, as well as tourniquet time, in 94 patients who underwent TKA using either ACB (N = 30) or CCB (N = 64). Postoperative mechanical alignment variability was significantly less in the ACB group (SD = 1.7°) than in the CCB group (SD = 2.7°). Tourniquet time was significantly reduced by 14.8 min in the ACB group compared to the CCB. Differences in component alignment were not significant. ACB for TKA significantly reduced postoperative mechanical alignment variability and tourniquet time compared to conventional navigated instrumentation, while providing equal or better component alignment. III.

The purpose of this study was to compare a freehand arthroscopic approach versus mosaicplasty for treatment of osteochondral lesions of the knee with a navigated arthroscopic technique.Four whole cadaveric lower limbs were used. A conventional navigation system was used in combination with an autologous osteochondral graft transplantation system (Osteochondral Autograft Transfer System [OATS]; Arthrex, Naples, FL). The congruity of the articular surface was measured with the navigation probe to detect any difference between the surface created by the grafts and the surface of the femoral condyle surrounding them. The angle relates to a line perpendicular to the articular surface. This line is made by the cutting instrument for graft harvesting and insertion and the articular surface.The mean angle of graft harvest was 3.4° (range, 0° to 10°) in the navigated group versus 14.8° (range, 6° to 26°) in the freehand group (P.0003). The mean angle for recipient-site coring was 1.5° (range, 0° to 5°) in the navigated group versus 12.6° (range, 4° to 17°) in the freehand group (P.0003). The mean angle of graft placement was 2° (range, 1° to 5°) in the navigated group versus 10.8° (range, 5° to 15°) in the freehand group (P = .0002). The mean protrusion height of the plug was 0.23 mm (range, 0.1 to 0.5 mm; SD, 0.16) in the navigated group versus 0.34 mm (range, 0.0 to 0.7 mm; SD, 0.25) in the freehand group (P = .336).Computer-assisted arthroscopic mosaicplasty for treatment of osteochondral lesions in the cadaveric model presented in this study allows permanent visualization of the angle of recipient-site preparation, the depth of the donor plug and the recipient plug, and the angle of insertion of the graft at the recipient site.This study shows evidence of potentially greater precision and reproducibility of navigated arthroscopic mosaicplasty when compared with an arthroscopic freehand technique in a cadaveric model. However, true clinical outcome benefit will only be elucidated upon performance of appropriate clinical studies.

Patients with anterior cruciate ligament (ACL) deficiency may have increased failure rates with UKA as a result of abnormal contact stresses and altered knee kinematics. Variations in the slope of the tibial component in UKA may alter tibiofemoral translation, and affect outcomes. This cadaveric study evaluated tibiofemoral translation during the Lachman and pivot shift tests after changing the slope of a fixed bearing unicondylar tibial component. Sectioning the ACL increased tibiofemoral translation in both the Lachman and pivot shift tests (P0.05). Tibial slope leveling (decreasing the posterior slope) of the polyethylene insert in a UKA decreases anteroposterior tibiofemoral translation in the sagittal plane to a magnitude similar to that of the intact knee. With 8° of tibial slope leveling, anterior tibial translation during the Lachman test decreased by approximately 5mm. However, no variation in slope altered the pivot shift kinematics in the ACL deficient knees.

Background: Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint. Purpose: To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction. Study Design: Controlled laboratory study. Methods: Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions—over the top (OTT), anterior footprint (AT), and posterior footprint (PT)—with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition. Results: A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension. Clinical Relevance: The OTT and anterior tibial tunnel positions better control the Lachman and the pivot shift compared with an ACL graft placed in the posterior aspect of the tibial footprint. However, an anterior tibial tunnel position must be balanced against an increased risk and magnitude of graft impingement in extension.

Background: Recent laboratory and clinical studies report no difference between single-bundle (SB) and double-bundle (DB) anterior cruciate ligament (ACL) reconstruction.Hypothesis: Anatomical DB ACL reconstruction would restore knee kinematics in a complex injury model of ACL–meniscus injury closer to the intact state when compared with 2 common SB ACL reconstructions.Study Design: Controlled laboratory study.Methods: Five fresh-frozen cadaveric hip-to-toe lower extremity specimens were used for this study (10 knees). A surgical navigation system recorded the 3-dimensional motion path of a tracked point at the center of the medial and lateral compartments during a 68-N Lachman test and a mechanized pivot-shift test. Testing was performed on the intact knee, after ACL, medial meniscus, and lateral meniscus resection and after 3 ACL reconstructions: anatomical anteromedial SB, nonanatomical SB (posterolateral tibia to anteromedial femur), and anatomical DB. Same-sized hamstring grafts were used for all reconstructions. Repeated-measures analysis of variance with a post hoc Tukey multiple-comparison test was used to compare the anterior tibial translations of the 3 grafts during laxity testing.Results: Regarding the Lachman test, there was no difference between the anatomical anteromedial SB and DB reconstructions. For the mechanized pivot shift, anatomical DB reconstruction restored anterior tibial translation to the intact state; however, significantly greater anterior tibial translation was detected after anatomical anteromedial SB and nonanatomical SB reconstruction, compared with the intact knee. In addition, there was no difference in medial compartment translations during the pivot shift between the intact and reconstructed states.Conclusion: Anatomical DB ACL reconstruction was able to restore intact knee kinematics during the pivot shift even in the severe injury model.Clinical Relevance: Double-bundle ACL reconstruction procedures may be preferred in cases of high-grade instability or meniscus deficiency.

The goals of computer-assisted surgery (CAS) are to be patient-specific, minimally invasive, and quantitative. CAS can involve preoperative imaging and planning, intraoperative execution, and postoperative evaluation. Ideally, these components are integrated such that sophisticated diagnostic technologies are used to inform a patient-specific surgical plan. A recently developed CAS/robotic system has the potential to improve alignment in and results of unicompartmental knee arthroplasty. This new robot is "semiactive"; that is, the surgeon retains ultimate control of the procedure while benefiting from robotic guidance within target zones and boundaries. Surgeons who use the robotic arm-assisted technique described in this article can prepare and then precisely execute a patient-specific computed-tomography-based operative plan. The surgical field is predefined, and the active constraints used by the robotic arm eliminate inadvertent deviation outside this field, thus minimizing iatrogenic morbidity and maximizing bone preservation. In this article, we detail the preoperative planning and intraoperative technique for robotic arm-assisted unicompartmental knee arthroplasty.

Unicompartmental knee arthroplasty (UKA) is a popular treatment for unicompartmental knee arthritis. Indications for UKA include mechanical axis of less than 10 degrees varus and less than 5 degrees valgus, intact anterior cruciate ligament (ACL), and absence of femorotibial subluxation. Appropriately selected patients can expect UKA to last at least 10 years. UKA failures are not common and involve technical errors that are thought to be corrected with use of newly developed robotic technology. The surgeon using this technology may be able to arrive at a set target, enhance surgical precision, and avoid outliers. Whether improved precision will result in improved long-term clinical outcome remains a subject of research. In this article, we describe the perioperative management of patients who undergo UKA whether with conventional techniques or robotic arm assistance. We also describe the distinct aspects of preoperative, intraoperative, and postoperative pain management and of intraoperative anesthesia and blood management.

The objective of this study was to design a navigated mechanized pivot shift test setup and evaluate its repeatability in the ACL-deficient knee. It was hypothesized that translations and rotations measured with the mechanized pivot shift would be more repeatable when compared to those obtained with a manual pivot shift. Twelve fresh frozen cadaveric hip-to-toe whole lower extremities were used for this study. A manual pivot shift test was performed in the intact knee and in the ACL-deficient knee and was repeated three times. A navigation system simultaneously recorded tibial translation and rotation. The mechanized pivot shift test consists of a modified continuous passive motion (CPM) machine and a custom-made foot holder to allow for the application of internal rotation moments at the knee. Valgus moments were achieved by a 45 degrees tilt of the CPM machine with respect to the supine position and a Velcro strap secured across the proximal tibia. The mechanized pivot shift was repeated three times. Repeated measures ANOVA was used to compare manual and mechanized pivot shift testing. An intra-class correlation coefficient (ICC) was used to determine variability within each knee at each testing condition. In the ACL-deficient knee, translation with manual pivot shift testing (11.7 +/- 2.6 mm) was significantly higher than with mechanized pivot shift testing (7.4 +/- 2.5 mm; p0.05). Rotation with the manual pivot shift testing (18.6 +/- 5.4 degrees) was also significantly higher than with mechanized pivot shift testing (11.0 +/- 2.3 degrees; p0.05). The intra-class ICC for translations was 0.76 for manual pivot shift and 0.92 for the mechanized pivot shift test. The intra-class ICC for rotations was 0.89 for manual pivot shift and 0.82 for the mechanized pivot shift test. This study introduced a modified CPM for mechanized pivot shift testing. Although recorded translations and rotations with the mechanized pivot shift test were lower than with manual testing, the clinical advantage of mechanized pivot shift testing is a more repeatable measurement of ATT when compared to manual pivot shift testing. This setup may increase consistency of clinical grading of the pivot shift test.

Background The medial collateral ligament is a broad ligament that functions as the primary stabilizer against valgus knee stress, particularly at 30° of flexion. Hypothesis A double-bundle reconstruction technique that better restores the native medial collateral ligament anatomy will restore valgus and external rotation stability to a medial collateral ligament–deficient knee. Study Design Controlled laboratory study. Methods Seven fresh-frozen cadaveric knees were studied. A surgical navigation system was used to determine valgus opening and external rotation at 0° and 30° with a 9.8-N·m valgus stress applied to the tibia graft isometry at multiple points on the tibia and femur. Intact and disrupted medial collateral ligament knees were used as controls. Four repair techniques were tested: Bosworth, modified Bosworth, anatomical single bundle, and anatomical double bundle. Results Complete sectioning of the medial collateral ligament resulted in an increase in valgus opening of 5° at 0° and 7.7° at 30°. External rotation increased 4.6° at 0° and 9.7° at 30°. Single-bundle techniques (Bosworth, anatomical single bundle) did not restore valgus laxity at 0° or 30°; the anatomical single bundle did not restore external rotation at 0°. Double-bundle techniques (modified Bosworth, anatomical double bundle) restored valgus laxity and external rotation to the native knee conditions at 0° and 30°. At 30°, the modified Bosworth was 0.3° tighter and the anatomical double bundle 0.2° tighter than was the intact knee. The center of the medial collateral ligament origin on the femur to the proximal insertion of the superficial medial collateral ligament resulted in the most isometric graft position. Conclusion Medial collateral ligament reconstruction configurations that use a double-bundle reconstruction better resist valgus and external rotations in response to valgus stress than do single-bundle techniques. Clinical Relevance Although the medial collateral ligament often heals without surgical intervention, surgical reconstruction is occasionally necessary in grade III medial collateral ligament and combined ligamentous injuries to the knee. Double-bundle reconstruction of the medial collateral ligament better resists valgus forces across the knee and may allow for better surgical outcome after medial collateral ligament reconstruction.

Anterior cruciate ligament reconstruction was one of the first procedures in which computer-assisted techniques were used in orthopaedic surgery. However, the use of navigation for tunnel placement in anterior cruciate ligament surgery remains problematic, as the optimal position for placement of the tunnels is debatable. The technical specification of tunnel position is clinically relevant, but the targets and tolerances for this technical specification are poorly understood. The inability to reliably quantify knee kinematics and stability before, during, or after anterior cruciate ligament reconstruction remains a problem. A navigated examination to assess knee stability could potentially close the computer-assisted surgery treatment loop by providing quantitative feedback about various reconstruction techniques. Recent iterations of navigated examinations for the assessment of stability include even complex pathologic movements, such as those detected with the pivot-shift examination. In this paper, we review conventional stability measurements of the knee and compare them with navigated techniques, with a focus on the navigated pivot-shift examination. In summary, direct intraoperative measurements and quantifications of knee stability, including the pivot-shift phenomenon, are now possible with the use of navigation. Consequently, more reproducible and clinically meaningful quantification of the pivot-shift phenomenon may allow for more accurate evaluation of various anterior cruciate ligament reconstruction techniques in the future.

The 2008 AAOS/ORS Advanced Imaging and Computer-Assisted Surgery of the Knee and Hip (AICKH) Research Symposium explored avenues for technology integration between advanced imaging and computer-assisted surgery, and it assessed the value of imaging in evaluating the progression of joint disease and the efficacy of therapeutic interventions. The four overarching themes that were explored during the symposium and the consensus statements for future research are detailed below. The concept of technical specifications and standards for computer-assisted surgery procedures and imaging protocols was highlighted. For example, most computer-assisted surgery procedures rely on the use of quantitative data rather than surgeon feel and intuition to inform clinical decision-making. As this quantitative feedback becomes more important in surgical decision-making, we must establish appropriate specifications for various operations. These specifications must be clinically relevant and must have known target values and tolerances. In addition, we must understand the reliability of our computer-assisted tools in achieving the desired specifications. Navigated total knee replacement is an excellent example of the use of quantitative data to affect surgical technique. The first-generation navigated total knee replacement protocols focused on achieving neutral alignment in the coronal plane. The relevant specification for the navigation system is therefore coronal plane alignment. The target is well established as 0°; the tolerance has also been established as ±3°. Many authors have demonstrated the reliability of navigation in achieving neutral alignment of the lower limb within this specification. However, while navigated total knee replacement has been shown to reduce the number of outliers in terms of alignment, it has not been shown to improve short-term results. This is likely because the chosen specification (knee alignment) for this procedure …

Purpose The objective of this study was to analyze 2 different single-bundle anterior cruciate ligament (ACL) reconstruction procedures and compare their ability to reduce the pivot-shift phenomenon with an anatomic double-bundle (DB) technique. Methods Twelve fresh-frozen cadaveric hip-to-toe lower extremity specimens were used. ACL reconstructions were performed by conventional single-bundle, anteromedial (AM) single-bundle, and DB techniques. Anterior tibial translation was measured in the intact knee, ACL-deficient knee, and the 3 ACL reconstructions in response to a Lachman test and a mechanized pivot-shift test. A surgical navigation system (Praxim Medivision, Grenoble, France) simultaneously tracked kinematics. Results Intact knees were clinically graded as grade 0 (n = 12). ACL-deficient knees were graded as grade 1 (n = 10) and grade 2 (n = 2). With a mechanized pivot-shift test, anterior tibial translation was 1.7 ± 3.0 mm, 9.7 ± 3.8 mm, 4.4 ± 1.0 mm, 1.8 ± 1.5 mm, and −1.7 ± 3.3 mm for intact knees, ACL-deficient knees, conventional technique, AM technique, and DB technique, respectively. There was a significant difference between the DB technique and both single-bundle techniques tested ( P Conclusions The model used represents an isolated ACL injury without concomitant injury to the capsuloligamentous restraints or menisci. However, during the pivot shift, neither type of single-bundle ACL reconstruction stabilized the knee to the same degree as the DB ACL reconstruction. Clinical Relevance: In this cadaveric model a DB repair offers great anterior and rotational stability. Although this study suggests that the DB technique is biomechanically superior to a single-bundle technique using traditional transtibial tunnel positions, there appear to be minimal differences in knee kinematics during stability testing with the DB technique versus an AM graft position. Indeed, compared with the AM position alone, the DB technique "overconstrained" the kinematics of the knee during a pivoting maneuver at time zero in a cadaveric model with an isolated ACL injury.

The purpose of this study was to determine the femoral and tibial fixation sites that would result in the most isometric MCL reconstruction technique. Seven cadaveric knees were used in this study. A navigation system was utilized to determine graft isometry continuously from 0 masculine to 90 masculine. Five points on the medial side of the femur and four on the tibia were tested. A graft positioned in the center of the MCL femoral attachment (F(C)) and attached in the center of the superficial MCL attachment on the tibia led to the best isometry (2.7 +/- 1.1 mm). Movement of the origin superiorly only 4 mm (F(S)) led to graft excursion of greater than 10 mm (P < 0.01). MCL reconstruction performed with the origin of the MCL within the femoral footprint and the insertion in tibial footprint of the superficial MCL results in the least graft excursion when the knee is cycled between 0 masculine and 90 masculine. Although the MCL often heals without surgical intervention, surgical reconstruction is occasionally in Grade III MCL and combined ligamentous injuries to the knee. This study demonstrates the optimal position of the MCL reconstruction to reproduce the kinematics of the native knee.

Computer-navigation in total knee arthroplasty has been reported to increase accuracy but also procedure duration. We compared surgical time and precision using a novel adjustable cutting block vs freehand navigation with conventional blocks on 12 bilateral cadaver tibiae. The mean time required was significantly less to position the adjustable block than the conventional block (2 minutes 10 seconds vs 6 minutes 35 seconds, P = .006). Guide positioning precision (standard deviation) for the adjustable block vs conventional block was as follows: varus/valgus, 0.24 degrees vs 1.16 degrees (P = .015); posterior slope, 0.35 degrees vs 0.74 degrees (P = .13); and cut height, 0.37 vs 1.41 mm (P = .010). There were no significant differences in the final bone cut accuracy between the 2 groups. The use of adjustable cutting blocks simplifies navigated procedures and may reduce the time required to perform a navigated total knee arthroplasty.

Valgus alignment affects the biomechanical behavior of the ACL, resulting in an increase of the in situ forces in the posterolateral (PL) bundle of the graft. The amount of valgus alignment creating such effects on the force remains unclear. Furthermore, the mechanistic rational for the increase in situ forces on the PL bundle when compared with the AM during the valgus osteotomy remained unclear. We hypothesized that increasing valgisation of the knee results in significantly increased obliquity and a resulting increasing elongation pattern and apparent strain of the PL bundle compared to the AM bundle. Six cadaver legs were used utilizing two commercial navigation systems including navigated high tibial osteotomy (HTO) and ACL measurements simultaneously. ACL footprints were registered for the central and identified AM and PL bundle. A stepwise oblique open wedge osteotomy was performed for 7.5° and 15° valgisation. Length changes and coronal plane obliquity were determined at 0° and 30° flexion. The apparent strain for each fiber was calculated. Valgisation significantly affects the length and obliquity of the PL portion of ACL. Valgisation of 7.5° appears to be a threshold for affecting PL length and obliquity without significant changes compared to 15°. The mean apparent strain for the PL bundle increases up to 14% with a 15° osteotomy in full extension, compared to 4% for the central and 2% for the AM bundle. HTO should be done prior to fixation the ACL graft in combined procedures as valgisation does affect graft length. Relative alignment influence on obliquity and length of the PL bundle should be considered in valgus knees.

The use of computer navigation in ACL reconstruction was first established in the mid- 1990s. Initial applications of this new technology focused on improving the accuracy and repeatability of tunnel placement. More recent indications focus on intraoperative assessment of knee ligament dynamic laxity measurements. Computer navigation has been used increasingly as a quantitative measurement tool to assess ACL graft obliquity or visualization of the pivot-shift phenomenon. Applications for PCL and MCL reconstruction have not been extensively studied thus far, although specific isometric or laxity measurements could be performed. Future applications include noninvasive registration techniques to use navigation as a combined preoperative, intraoperative and postoperative measurement tool. The purpose of this review is to provide an overview of the current applications and limitations of navigation in knee ligament reconstruction by reviewing the currently available literature.

The authors present a case of heterotopic ossification (HO) following a navigated high tibial osteotomy which necessitated a second surgical procedure. There is no evidence in the literature of HO following the use of invasive navigation reference markers. Although osseous reference marker fixation is the current standard technique, this case underscores the need for non-invasive reference markers.

BackgroundConventional tunnel positions for single-bundle (SB) transtibial anterior cruciate ligament (ACL) reconstruction are located in the posterolateral (PL) tibial footprint and the anteromedial (AM) femoral footprint, resulting in an anatomic mismatch graft that is more vertical than native fibers. This vertical mismatch position may significantly influence the ability of an ACL graft to stabilize the knee.HypothesisAnatomic ACL fibers undergo a greater change in length during anterior translation and internal rotation than a conventional SB reconstruction from the PL tibial footprint to the AM femoral footprint.Study DesignControlled laboratory study.MethodsThe Praxim ACL Surgetics navigation system was used to acquire kinematic data during a flexion/extension cycle and to register all points within the ACL footprint from 5 fresh-frozen cadaveric knees. Virtual fibers were placed in the center of the AM and PL bundles as well as central and conventional SB positions. After transection of the ACL, the absolute length change and apparent strain of the fibers were computed for each knee during the Lachman and anterior drawer tests and internal rotation at 0° and 30° of flexion.ResultsEach of the anatomic fibers (AM, PL, and central) had more elongation and apparent strain than the conventional SB fiber during the Lachman maneuver. During the anterior drawer test, the AM and central (but not the PL) fibers lengthened significantly more and the AM had more apparent strain than the conventional SB fiber. During internal rotation at 0° and 30° of flexion, anatomic fibers elongated significantly more than the conventional fiber. Except for the AM fiber with the knee at full extension, apparent strain was greater in all anatomic fibers than in the conventional SB fiber during internal rotation maneuvers.ConclusionIn ACL-deficient cadaveric knees, anatomic fibers undergo greater elongation and apparent strain in response to anterior translation and internal rotation maneuvers than a conventional SB graft. Because of their optimal orientation, anatomic fibers may resist pathologic anterior translation and internal rotation more than the conventional SB position.Clinical RelevanceConventional placement of a single-bundle graft results in suboptimal changes in fiber length and strain, suggesting that alternatives such as anatomic placement of an SB graft or double-bundle reconstruction may result in greater control of translation and rotation.

Obtaining symmetric and balanced gaps under equilateral loads is a common goal in posterior cruciate ligament (PCL)-retaining and -sacrificing TKAs. Owing to limitations in existing surgical tensors, however, tensing knee ligaments with standardized and symmetric loads has been possible only with the patella subluxated or everted. We therefore determined the influences of (1) patellar eversion versus complete reduction, (2) PCL resection, and (3) load magnitude on gap symmetry and balance in the anterior cruciate ligament (ACL)-deficient knee. We used a novel computer-controlled tensioner to measure gaps in 10 cadavers with an applied force of 50 N, 75 N, and 100 N per side. Gap data were acquired at 0 masculine, 30 masculine, 60 masculine, 90 masculine, and 120 masculine flexion with the patella reduced and everted and with the PCL intact and resected. Everting the patella tightened the medial and lateral flexion gaps between 90 masculine and 120 masculine by 0.7 mm to 2.7 mm. PCL resection increased gaps from 30 degrees to 120 degrees by 1 mm to 3 mm. Increasing the force from 50 N to 100 N increased the mean gap by 0.5 mm. Everting the patella and resecting the PCL influenced gap balance and symmetry. Surgeons should be aware of how these conditions affect gaps during assessment and balancing.

BackgroundSurgical navigation allows continuous intraoperative monitoring of ACL graft anisometry and 3-dimensional obliquity. However, normative anisometry and obliquity measurements for different single-bundle anterior cruciate ligament graft positions are not well described.HypothesisACL Grafts placed in anteromedial and posterolateral bundle positions will have distinct anisometric profiles and 3-dimensional obliquities. A graft placed centrally in anterior cruciate ligament insertion sites will have different obliquity and anisometry than a conventional (single-bundle) graft extending from the tibia's posterolateral aspect to the femur's anteromedial aspect.Study DesignControlled laboratory study.MethodsFive cadaveric knees were tested. A surgical navigation system was used to create 4 virtual graft positions in the anterior cruciate ligament footprint: (1) anteromedial, (2) posterolateral, (3) central, and (4) posterolateral tibia to anteromedial femur (conventional). Obliquity at various flexion angles and anisometry of each virtual graft's central fiber were determined.ResultsAnteromedial and posterolateral fibers are relatively parallel up to 30° of flexion. At higher degrees of flexion, the anteromedial position is more oblique in the sagittal plane, while the posterolateral position is more oblique in the axial plane. The conventional single-bundle position is significantly more vertical than the central position in multiple planes throughout the range of motion. The anteromedial fiber is most isometric, while the posterolateral fiber is the least isometric at all flexion angles. There is no significant difference in the anisometry between the central or conventional positions at any flexion angle. The posterolateral, central, and conventional fibers were longest at full extension and slackened with progressive flexion.ConclusionAnteromedial and posterolateral graft positions can be distinguished by sagittal and axial plane obliquity at flexion angles >30° and by anisometry measurements. Conventional positioning produces a relatively vertical graft placement compared with the central position but has similar anisometry characteristics. Our data suggest that posterolateral, central, and conventional grafts should be fixed at or near full extension to avoid excessive tightening during motion.Clinical RelevanceThis study provides anisometry and 3-dimensional obliquity data for various graft positions using surgical navigation. The failure of single-bundle anterior cruciate ligament reconstruction to restore intact knee kinematics may be partly due to the relative vertical placement of conventional grafts compared with the central anterior cruciate ligament footprint position.

Inaccurate coronal plane and inadvertent sagittal plane realignment is a common problem after high tibial osteotomies (HTO). While the effects of an HTO on the coronal have been studied extensively, the influence on axial rotation has not been described in detail. The current study examines the effect of HTO on tibial rotation in the axial plane as determined by computed tomography. We hypothesized that high tibial osteotomies have an effect on tibial rotation in the axial plane and that depending on the predefined osteosynthetic implant used, a corresponding change in the tibial slope would occur. HTOs with a tapered 12.5 mm Puddu plate were performed on 13 limbs under computer-navigated control. All limbs were CT scanned before and after the HTO. Using specific software, the CT data was converted into 3D computer models and the following parameters compared: (a) varus-valgus leg alignment; (b) tibial axial rotation; (c) tibial slope (including determination of lateral and medial tibial slope, (d) leg length including determination of the tibial length. Results revealed: (a) a varus-valgus alignment increase of 11 +/- 4.7 degrees (P0.005); (b) an axial tibial rotation of 2.7 +/- 6.3 degrees (P0.075) occurred with external rotation in 10 out of 13 limbs (12 degrees max external; 9.5 degrees max internal); (c) tibial slope revealed differences of 4.2 +/- 5.9 degrees (P0.025); (d) the tibial length increased after HTO by 7.1 +/- 3.7 mm (P0.005), while there was no significant change in overall leg length. In summary, tibial rotation does occur in high tibial osteotomies with though the degree of external rotation in this study tended not to be statiscally significant. Tapered implants do not guarantee maintenance of a steady tibial slope, while tibial length changes significantly when HTOs are performed. The combined use of CT and 3D software measurement techniques is reproducible and can be used without any further invasive fixation devices.

Long bone fracture reduction during intramedullary nailing can result in a small but significant rate of angular and rotational malalignment, which can in turn lead to long-term morbidity. Current techniques for intraoperative reduction rely heavily on fluoroscopy, and their reproducibility can be limited. We suggest that fluoroscopy-based navigation may improve the precision of long bone fracture reduction and reduce radiation exposure.A cadaveric tibia was stripped of soft tissues and fractured at its midline. The ends were then cemented to two mobile brackets within a fracture/deformity simulator. Optical trackers were drilled into each fragment. Radiographs were obtained including AP and lateral views of the proximal and distal ends of the bone as well as the fracture site. These radiographs were stored in the computer navigation system. Fracture reduction was performed using a fluoroscopy-based navigation system with virtual intraoperative planning software. The system used 4 sets of lines drawn by the surgeon on the fluoroscopic AP and lateral images. While navigating the reduction of the fracture these lines aligned together, providing graphic and numerical descriptions of the reduction. The lines included the anatomic axis of the bone, the matching of the fracture lines, the short segment anatomic axis (near the fracture site), and the AP mid-sagittal joint line (MSJL) of both the plateau and the plafond. Anatomic reduction was then performed and the computer assessment of the angulation and translation of the fragments was recorded. Each stage was repeated 25 times for each set of lines. For the control group the surface of the bone was tracked using an optical probe.The accuracy of the system varied according to the planning method. The most accurate technique was matching of the fracture lines, which yielded 2.68 +/- 1.18 mm of translation and 2.5 +/- 1.27 degrees of angulation. The next most accurate method was using the short segment anatomic axis, followed by using the anatomic axis method. The control group was the most accurate (1.78 +/- 0.67 mm translation, 1.58 +/- 0.97 degrees angulation). The AP MSJL yielded errors greater than 10 degrees.Fluoroscopy-based navigation is sufficiently accurate for long bone fracture reduction, potentially increasing angular and translational accuracy while reducing the amount of intraoperative fluoroscopy. Navigation may improve the outcome of treatment of a long bone fracture by better restoring the normal mechanical axis of the limb in a less-invasive closed manner.

BACKGROUND: Combined latissimus dorsi and teres major musculotendinous transfer has been described for the treatment of massive rotator cuff deficits. The procedure is technically complex because of the proximity of the radial nerve, the axillary nerve and its posterior branches, and the neurovascular bundles to the muscles. The purpose of the present cadaveric study was to examine surgically relevant relationships for latissimus dorsi and teres major tendon transfers. METHODS: Twelve cadaveric shoulder girdles were dissected, and the latissimus dorsi, the teres major, and the posterior cord of the brachial plexus and its branches were identified. The relationships between the tendons and local neurologic structures were measured during various steps of the latissimus dorsi/teres major transfer procedure. The effect of humeral rotation on the exposure of the latissimus dorsi and teres major tendons through the posterior approach was quantified, and relevant surgical landmarks were described. RESULTS: The radial nerve passed directly anterior to the tendons at an average of 2.9 cm medial to the superior aspect and 2.3 cm medial to the inferior aspect of the humeral insertions. From the posterior axillary approach, maximal internal rotation facilitated exposure for tenotomy by delivering the tendon insertions on the humerus into the surgical field. During axial mobilization of the musculotendinous units, the neurovascular pedicles to the latissimus dorsi and teres major were identified at an average of 13.1 and 7.4 cm axial to the humeral insertions, respectively. The posterior branch of the axillary nerve was noted to cross superficially over the transferred tendons as they were tunneled under the posterior deltoid. CONCLUSIONS: Multiple steps of the combined latissimus dorsi and teres major musculotendinous transfer place local neurologic structures at risk. These steps include tendon release, musculotendinous axial mobilization, and tendon tunneling in the plane between the infraspinatus-teres minor and the posterior deltoid. We have quantified and described the relationship of the axillary and radial nerves to the tendons during tenotomy, the distance from the tendons9 insertions to their neurovascular bundle that must be identified during axial mobilization, and the course of the posterior branch of the axillary nerve in relation to the tunneled path of the tendons. CLINICAL RELEVANCE: The present study provides important anatomic findings for the safe mobilization and transfer of the latissimus dorsi and teres major tendons during the surgical treatment of irreparable rotator cuff tears. ORIGINAL ABSTRACT CITATION: “Surgical Technique and Anatomic Study of Latissimus Dorsi and Teres Major Transfers” (2006;88:1524-31).

Anatomic reduction and appropriate implant placement is essential for optimal treatment of intraarticular tibial plateau fractures. Standard intraoperative fluoroscopy provides limited visualization of the reduction and hardware placement compared with pre- or postoperative three-dimensional (3-D) imaging modalities. As such, postoperative computed tomography has become a common procedure to evaluate the quality of the reduction and fixation. The Iso-C3D provides 3-D intraoperative imaging to dynamically assess the surgical reduction and fixation at different anatomic regions. We report on our first 19 clinical tibial plateau fractures scanned intraoperatively with the Iso-C3D. When compared with conventional c-arm images, the Iso-C3D scans demonstrated improved ability to identify articular malreduction and implant malposition.

Restoration of rotational and translational stability is a goal of ACL reconstruction. Intraoperative instability measurements of AP translation and rotation are not well established clinically. We compared navigated measurements of tibial AP translation and rotation with mechanical measuring devices: the KT 1000 and a modified goniometer tool. Tests were repeated with intact and dissected ACLs, and measures of translation and rotation statistically compared. There was no significant difference in AP translation between navigation, 3.2 mm (range 1-6 mm) and the KT 1000, 4.8 mm (range, 4-7 mm) in our experimental set up (p0.05). Tibial rotation revealed no significant difference, 0.12 degrees (range, 0 degrees -1 degrees ) between navigation and goniometer (p0.05). Total range of rotation was 4.2 degrees (range, 2 degrees -6 degrees ) in intact and 7.05 degrees (range, 4 degrees -9 degrees ) in dissected ACLs (p0.05). Stability parameters in ACL navigation can be measured precisely under laboratory conditions and results are not significantly different from mechanical testing devices.

Background Clinical examination remains empirical and may be confusing in the setting of rotatory knee instabilities. Computerized navigation systems provide the ability to visualize and quantify coupled knee motions during knee stability examination. Hypothesis An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination. Study Design Controlled laboratory study. Methods Coupled knee motions were determined by a robotic/UFS testing system and by an image-free navigation system in 6 cadaveric knees that were subjected to (1) isolated varus stress and (2) combined varus and external rotation force at 0°, 30°, and 60°. This protocol was performed in intact knees and after complete sectioning of the posterolateral corner (lateral collateral ligament, popliteus tendon, and popliteofibular ligament). The correlation between data from the surgical navigation system and the robotic positional sensor was assessed using the intraclass correlation coefficient. The 3-dimensional motion paths of the intact and sectioned knees were assessed qualitatively using the navigation display system. Results Intraclass correlation coefficients between the robotic sensor and the navigation system for varus and external rotation at 0°, 30°, and 60° were all statistically significant at P < .01. The overall intraclass correlation coefficient for all tests was 0.9976 (P < .0001). Real-time visualization of the coupled motions was possible with the navigation system. Post hoc analysis of the knee motion paths during loading distinguished distinct rotatory patterns. Conclusion Surgical navigation is a precise intraoperative tool to quantify knee stability examination and may help delineate pathologic multiplanar or coupled knee motions, particularly in the setting of complex rotatory instability patterns. Repeatability of load application during clinical stability testing remains problematic. Clinical Relevance Surgical navigation may refine the diagnostic evaluation of knee instability.

The natural history of the blood supply to the rotator cuff and its role in the etiology of rotator cuff disease has not been definitively established. To date, there has not been an in-vivo dynamic assessment of the baseline vascularity of the asymptomatic rotator cuff. This study was designed to test the hypothesis that regional variations in supraspinatus tendon vascularity exist with an age-dependent decrease in asymptomatic individuals with intact rotator cuffs. Lipid microsphere, contrast-enhanced ultrasound shoulder examinations were done in 31 patients with a mean age of 41.5 years (range, 22-65 years). Images were obtained at baseline, after contrast administration at rest, and after contrast administration following exercise to visualize the intratendinous blood flow to the supraspinatus tendon. Qualitative and quantitative analysis was performed by determining 4 regions of interest (bursal medial, articular medial, bursal lateral, and articular lateral) with quantification and analysis software (QLAB Philips, Andover, MA) to examine each region of interest and normalize data for interpretation of the mean intensity per pixel. A statistically significant decrease in blood flow to the supraspinatus tendon with age was observed in a comparative analysis of patients aged younger than 40 and older than 40, (P < .05 for all 4 zones after exercise and for the bursal medial, articular medial, and bursal lateral zones after exercise; P = .07 for the articular lateral zone after exercise). A statistically significant increase in blood flow with exercise was observed in an analysis of all patients (P < .001). The age-related decrease in the vascular supply of the tendon observed in this study is consistent with published reports demonstrating an increasing prevalence of rotator cuff pathology with age and may predispose to the development of rotator cuff tendinopathy and, ultimately, attritional tears.

The ability of noninvasive magnetic resonance imaging (MRI) to obtain reproducible, accurate images of cartilage has enabled early detection of cartilage lesions and provides clinically relevant information when planning cartilage repair. With appropriate pulse sequencing, MRI depicts not only the integrity of the surface cartilage, which would be seen at arthroscopy, but also that of the subchondral bone, which would not be visualized at arthroscopic inspection. This information is vital when planning for complex, sometimes multistage, techniques that require careful size delineation of the cartilage lesion and evaluation of the surrounding subchondral bone. In addition to aiding in preoperative planning, these techniques offer an important objective evaluation of cartilage repair to be correlated with the more subjective clinical outcome instruments and provide insight into the biology of the repair process. Finally, newer matrix assessment techniques will disclose information about the ultrastructure of these individual cartilage repair procedures.

Among failures due to surgical techniques, the most common technical error is poor tunnel placement [6, 13]. Anisometric graft positioning can cause graft stretch and poor control of knee rotational or translational stability. For example, anterior femoral tunnel placement produces strain in flexion and laxity in extension while posterior femoral tunnel placement produces strain in extension and laxity in flexion and risks back wall »blow out«. Anterior tibial tunnel placement results in strain in flexion and possible impingement in extension. Posterior tibial tunnel placement places strain on the graft in extension and possible PCL impingement. Medial or lateral tibial tunnel positioning can cause impingement conflicts with the PCL and femoral condyles. Current surgical techniques rely on anatomic criteria, intra-operative fluoroscopy, and alignment jigs to create an isometric, non-impinging, and appropriately positioned graft. However, arthroscopic landmarks may be variable and inaccurate, fluoroscopic monitoring is cumbersome, and conventional transtibial approaches jigs such as the over-the-top guide can affect the femoral and tibial positioning (femoral tunnel tends to be anterior and vertical and tibial tunnel tends to be posterior) [5]. Surgical navigation offers an additional means of supervising tunnel positioning. In addition to anatomic criteria, quantitative isometric and impingement criteria can be used to plan tunnel positioning. This provides the surgeon with increased control in choosing tunnel position to optimize graft placement for the individual knee anatomy. This chapter represents a summary of some recent research and clinical experience carried out at our institutes with the PRAXIM ACL navigation system. Below, a brief history and detailed description of the system is provided. Three recent studies related to the technical and clinical evaluation of the system, as well as to its use in revision procedures, are then presented, followed by a brief discussion.

BackgroundEarly protection of articular cartilage, before degenerative changes appear on radiographs, should result in better long-term results, but scientific evidence regarding the effectiveness of meniscal transplantation is lacking.PurposeTo assess the chondroprotective effects of a new meniscal allograft transplantation animal model and evaluate a magnetic resonance imaging parameter, T2 mapping, in articular cartilage after meniscectomy and meniscal transplantation.Study DesignControlled laboratory study.MethodsForty-five skeletally mature sheep were placed into 3 surgical groups lateral meniscectomy (n = 24), meniscal allograft transplant (n = 17), and sham (n = 4). Animals were sacrificed at 2, 4, or 12 months. Cartilage was assessed by gross inspection, magnetic resonance imaging, T2 mapping, biomechanical testing, and semiquantitative histologic analysis.ResultsThere were no differences between the sham operation and nonoperated control limbs. Compared with control limbs, meniscectomy resulted in significant increases in cartilage degeneration by all objective criteria (P < .01). Compared with meniscectomy, meniscal allograft transplantation resulted in significant decreases in cartilage degeneration (P < .02). There were significant correlations between T2-mapping data and all other traditional outcomes measures (P < .05, r2 = 0.37-0.67). Compared with the nonoperated control limbs, allograft transplants demonstrated no significant differences at 2 months in any category, except magnetic resonance imaging data. By 4 months, nonoperated control limbs demonstrated significantly less wear compared to allograft limbs in all categories except modified Mankin scores.ConclusionThis model demonstrated significant chondroprotection compared with meniscectomy but demonstrated more cartilage wear at 4 months compared to control limbs. A high degree of allograft cell viability and vascular ingrowth was seen in allograft explants. T2 mapping may provide an accurate noninvasive measure of early cartilage degeneration after meniscectomy, as well as cartilage protection after meniscal allograft transplantation.Clinical RelevanceThis study establishes a reliable animal model for meniscal allograft transplantation and provides evidence for the utility of T2 mapping at clinically relevant magnetic resonance imaging field strengths for evaluation of early cartilage degeneration.

An unusual case of Clostridium perfringens infection after an allograft reconstruction of an extensor mechanism in a multiply revised total knee arthroplasty is reported. The case occurred in an elderly patient with an underlying bleeding dyscrasia who had previously undergone two revision total knee arthroplasties. The patient was treated by open irrigation, debridement, removal of allograft and prosthesis, intravenous antibiotics, and implantation of an antibiotic impregnated cement spacer utilizing an intramedullary rod.

In North America, staged reimplantation is the preferred treatment for infected total hip arthroplasty. A simple technique for implantation of an antibiotic-loaded cement spacer molded in the shape of a hemiarthroplasty prosthesis is described. A Teflon mold was cast in the shape of an Austin Moore hip hemiarthroplasty prosthesis. This mold allows for fabrication of a solid antibiotic-loaded cement spacer that accurately reproduces the shape of a hemiarthroplasty prosthesis. This technique allows for easy insertion, patient comfort, between-stage mobility, and local concentric delivery of antibiotic.

Objectives: Histological studies have shown that the ACL has a direct and indirect insertion on the femur [1]. The direct insertion is located along the lateral intercondylar ridge and the indirect insertion is located ‘lower’ on the lateral wall of the notch. The trend towards anatomic ACL reconstruction using the anteromedial (AM) portal technique has resulted in ‘lower’ non-isometric femoral tunnel positions and increased graft failures [2]. To our knowledge, the load transfer properties of the direct and indirect ACL insertions have not been studied. This information may help in understanding the increased failures reported with AM portal drilling. The purpose of this study was, 1) to compare the load transferred across the native ACL at the direct and indirect femoral insertions and, 2) to determine the strain behavior of ACL grafts placed at different tunnel locations within the direct and indirect insertions. Methods: Ten fresh-frozen cadaveric knees (mean age, 52.5 years; range, 29-65) were mounted to a six degree of freedom robot. A 134N anterior load at 30 and 90° flexion and a combined valgus (8Nm) and internal (4Nm) rotational moment at 15° flexion were applied. The ACL was subsequently sectioned at the femoral footprint by detaching either the direct or indirect insertion (partially sectioned state), followed by the remainder of the ACL (completely sectioned state) (Figure 1). The kinematics of the intact knee were replayed after each stage of sectioning to determine the loads transferred across the direct and indirect ACL fibers. Loads were expressed as a percentage of the total load borne by the ACL. Strain behaviour was tested by generating 3D models of the femur and tibia from CT scans of each knee. Three tunnel locations (anteromedial bundle [AM], center [C], posterolateral bundle [PL]) each were selected for the direct and indirect insertions and a virtual ACL graft was inserted. The isometry of the virtual graft was calculated through a flexion path of 0 to 90°. Results: Under an anterior tibial load at 30° flexion, the direct insertion carried 83.9% of the total ACL load compared to 16.1% in the indirect insertion (pConclusion: Fibers in the direct insertion of the ACL carry more load than fibers in the indirect insertion. Virtual ACL grafts placed in the ‘higher’ direct location are more isometric than in the ‘lower’ indirect location during range of motion testing. Clinical Relevance: ‘Low’ ACL grafts in the indirect ACL insertion, resulting from AM portal drilling techniques, may experience higher loads in-vivo due to unfavorable biomechanics. With the current shift towards anatomic ACL reconstruction, it may be beneficial to create a ‘higher’ femoral tunnel within the direct insertion at the lateral intercondylar ridge. This position remains anatomical but may also be biomechanically favorable.

Objectives: Recent histological studies have shown that the ACL consists of two different structures: the direct and indirect insertions. The direct insertion is located along the lateral intercondylar ridge and the indirect insertion is ‘lower’ in the notch, adjacent to the posterior articular cartilage. The ‘lower’ position has become more popular for locating the femoral tunnel, as surgeons switch to the anteromedial (AM) portal drilling technique in order to place the graft in the region of the native footprint. However, a recent registry-based outcomes study has reported a 1.5 times higher graft failure rate for AM portal versus traditional transtibial techniques. The objective of this study was to investigate the load characteristics of the native ACL in the regions of the direct and indirect insertions. We hypothesized that the direct insertion would carry more load than the indirect insertion. Methods: Twelve cadaveric knees were mounted to a six degree of freedom robot equipped with a universal force-moment sensor. We simulated the Lachman and anterior drawer tests at 30oand 90o of flexion by applying a 134N anterior load, and the pivot shift test at 15o flexion by applying combined valgus (8Nm) and internal (4Nm) rotational moments. The kinematic pathway required to achieve these loading conditions was recorded for each intact knee. Using position control to repeat the loading paths, the robot recorded the loads for the ACL intact, ACL partially sectioned, and ACL completely sectioned states. Sectioning Protocol: The lateral intercondylar ridge and posterior articular margin was identified in each case. The 50% mark between this two areas was used to delineate the regions of the direct and indirect insertions (Fig. 1). Sectioning order was alternated between each cadaver. Footprint Digitization: The borders of the sectioned areas were digitized post-sectioning and mapped onto a computed tomography (CT) scan of each knee. The sectioning method was assessed under a blinded validation by experienced observers (TW, AP) who excluded two specimens that did not conform to the objective definitions of the sectioning method. Statistics: Loads were compared between direct and indirect locations at different flexion angles by conducting two-way repeated measures ANOVA models. Results: Under an anterior tibial load at 30o flexion, the direct insertion carried 83.9% (±7.2%) of the total ACL load compared to 16.1% (±7.2%) in the indirect insertion (po flexion (95.2% vs 4.8%; po flexion, the direct insertion carried 84.2% (±4.2%)of the total ACL load compared to 15.8% (±4.2%) in the indirect insertion (pConclusion: The fibres in the direct insertion of the ACL carry more load than fibres in the indirect insertion. Previous studies have suggested that the direct insertion plays a major role in the mechanical link between the ACL and bone. With the current shift in emphasis towards anatomic ACL reconstruction, it may be beneficial to create the femoral tunnel within the direct insertion rather than ‘lower’ in the notch. Although further work is required in determining graft behaviour at the new insertions sites described in this study, our findings suggest that placing a graft in the region of the direct insertion may be an important consideration when adhering to the principles of anatomic ACL reconstruction.

National Institute of Arthritis and Musculoskeletal and Skin Diseases (Grant Number R13 AR054313-01)

Unrestricted physiologic joint motion results in multidirectional displacement of the anatomic structures. When performing real-time magnetic resonance (MR) imaging of such a joint motion, continuous adjustment of the scan plane position may be required. The purpose of this study was to evaluate the clinical feasibility of a method to guide the scan plane position during dynamic-motion MR imaging of freely moving joints.The location of a small tracker device (dedicated hardware) placed on the patient's skin overlying a joint was determined by an ultrashort MR sequence and used to automatically adjust the scan plane position prior to each dynamic-motion MR image. Using a vertically open MR unit, this MR tracking system was applied in ten dynamic-motion MR examinations to evaluate flexion/extension manoeuvres in the weight-bearing knee joint, and in ten dynamic-motion MR examinations of the shoulder joint to evaluate manoeuvres such as internal/external rotation of the humerus, stress testing of the glenohumeral joint and abduction/adduction manoeuvres. Average number of manoeuvre repetitions, total number of images and percentage of useful images per manoeuvre were calculated. Imaging time per scan plane for each manoeuvre was recorded.Average repetition of manoeuvres varied between 1.6 and 5.8, with an average number of 7 to 18 images per manoeuvre. Average percentage of useful images varied between 61% and 89%. Total imaging time per scan plane ranged between 1 min 10 s and 4 min 51 s.The MR tracking system to guide the slice position for each consecutive dynamic-motion MR image of the freely but slowly moving shoulder or knee joint was feasible for clinical use, providing a high percentage of useful images for each manoeuvre within a clinically acceptable time frame.

Periprosthetic femoral fracture post-total knee arthroplasty can lead to malunion. This may lead to abnormal force transmission and accelerated wear of the prosthesis. Accurate femoral deformity correction depends on the combined correction of the mechanical axis alignment and the lateral distal femoral angle. Modern external fixation correction devices allow for simultaneous gradual corrections in multiple planes through one osteotomy site. Despite the accuracy of the devices, technical failures occur and are typically due to difficulty in assessing the exact intraoperative correction. Furthermore, conventional intraoperative measurements display high interobserver and intraobserver variations. Computer navigation has demonstrated great accuracy. Combining a mechanical corrective device and navigation should allow for increased precision and dynamic control intraoperatively. The current authors report on a clinical application of a novel minimally invasive fixator-assisted correction of a posttraumatic distal femoral varus deformity after total knee arthroplasty with combined navigated measurements. Keywords: limb correction, femoral osteotomy, navigation, alignment, deformity, external fixator corrections.

Improved understanding and management of the risk factors associated with osteoarthritis of the knee are clearly desirable, especially considering the shifts in the age distribution of the US population toward older ages. Among the various genetic, constitutional, and biomechanical insults that are believed to cause metabolic and structural changes in the synovial joint, two of the recognized local adverse biomechanical factors are rupture of the anterior cruciate ligament and malalignment of the lower limb. Over the past three decades, both in vitro and in vivo biomechanical studies have documented the complex anatomy of the anterior cruciate ligament and its function …

The research symposia of the American Academy of Orthopaedic Surgeons (AAOS) have a history of successfully fostering interdisciplinary collaboration, defining challenging medical problems, and encouraging future solutions. The 2008 AAOS/Orthopaedic Research Society Advanced Imaging and Computer-Assisted Surgery of the Knee and Hip (AICKH) Research Symposium sought to build consensus in the emerging areas of imaging and surgical navigation in the treatment of knee and hip disease. Specifically, in aging Western …

Summary Objective C-reactive protein (CRP) has been associated with disease progression in patients with osteoarthritis (OA), but the reasons for this remain unclear. We hypothesized that higher CRP would be related to local inflammatory findings in the joints of patients with OA. Methods Plasma and synovial membrane specimens from 54 OA patients undergoing total hip or knee arthroplasty or arthroscopy were obtained. Synovial fluid was obtained from 25 of these patients. Hematoxylin and eosin stained synovial membrane sections were scored for degree of inflammatory cell infiltration. Plasma high-sensitivity CRP (hsCRP) levels, and serum and synovial fluid interleukin (IL)-6 and IL-1β levels were measured by enzyme-linked immunosorbent assay. Results Fifty-seven percent of patients with idiopathic OA had inflammatory infiltrates within the synovial membrane. The mean hsCRP level in patients with inflammatory infiltrates was significantly higher than those without inflammation (4.7±5.0mg/L vs 1.7±3.6mg/L, P =0.003). There were significant correlations between hsCRP levels and synovial fluid IL-6 ( r =0.64, P =0.0006), degree of synovial inflammatory infiltration ( r =0.43, P =0.002), and body mass index ( r =0.31, P =0.02). Multivariate analysis indicated that only degree of inflammatory infiltrate was significantly associated with hsCRP level ( P =0.026). Conclusion These results suggest that systemic hsCRP levels reflect synovial inflammation in OA patients, perhaps by means of synovial IL-6 production. Future studies are needed to clarify how these infiltrates and their products may contribute to disease pathogenesis.