Posterior Tibial Plateau Research Articles

Spectrum of T2* values in knee joint cartilage at 3 T: a cross-sectional analysis in asymptomatic young adult volunteers

To establish baseline T2* values in healthy knee joint cartilage at 3 T. Thirty-four volunteers (mean age: 24.6 ± 2.7 years) with no history or clinical findings indicative of any knee joint disease were enrolled. The protocol included a double-echo steady-state (DESS) sequence for morphological cartilage evaluation and a gradient-echo multi-echo sequence for T2* assessment. Bulk and zonal T2* values were assessed in eight regions: posterior lateral femoral condyle; central lateral femoral condyle; trochlea; patella; lateral tibial plateau; posterior medial femoral condyle; central medial femoral condyle; and medial tibial plateau. Statistical evaluation comprised a two-tailed t test and a one-way analysis of variance to identify zonal and regional differences. T2* mapping revealed higher T2* values in the superficial zone in all regions (P values ≤ 0.001) except for the posterior medial femur condyle (P = 0.087), and substantial regional differences demonstrating superior values in trochlear cartilage, intermediate values in patellar and central femoral condylar cartilage, and low T2* values in posterior femoral condylar cartilage and tibial plateau cartilage. Substantial regional differences in T2* measures should be taken into consideration when conducting T2* mapping of knee joint cartilage.

Posterolateral fragment characteristics in tibial plateau fractures

Dear Editor, We read the article “Morphological characteristics of split-depression fractures of the lateral tibial plateau (Schatzker type II): a computer-tomography-based study” by Zhai et al. [1] with great interest. To the best of our knowledge, this report presents the largest number of case series concerning posterolateral tibial plateau fractures. Posterolateral quadrant tibial plateau fractures are a hot topic in recent years in orthopaedic traumatology. This unique fracture pattern is relatively common in China because of the wide use of electric bicycles in daily life [2]. This kind of bicycle is a lower speed (<20 km/h) personal vehicle driven by storage battery. When riding an electric bicycle, the person is sitting with his/her knees relaxed in a 90° position. When the bicycle falls onto one side, an axial compression load with valgus force is applied to the posterior tibial plateau with the knee in flexed position, which is prone to result in posterolateral quadrant fracture of the lateral plateau. This is the reason why most clinical reports on this fracture pattern come from China [1–4]. Posterolateral quadrant fracture can occur in isolation (only involving the posterolateral quadrant) or in combination (involving more than one quadrant). Several factors, such as the force direction, magnitude, and contact location, as well as the position of the knee at impact, may determine the fracture pattern, location, and degree of displacement. A thorough understanding of fracture morphology can help surgeons better understand the mechanism of injury and select an appropriate treatment plan. In recent years some authors [1–5], most from mainland China, investigated the fracture features and found the fracture patterns in posterolateral quadrants are usually depression or split-depression, the fragments are usually in conical shape with a relatively small articular surface area, short cortical split length and limited articular depression depth (Table 1). Isolated posterolateral quadrant fractures are usually low-energy trauma, while combined posterolateral fractures are high-energy trauma. The concomitant fibular head fracture is also an indicator of high-energy trauma and is significantly associated with greater displacement of the posterolateral fracture fragments. Table 1 Posterolateral fragment characteristics in tibial plateau fractures With the large number of cases, in our opinion, Dr. Zhai et al. [1] can provide more detailed data in subgroups, for example, stratified by differentiation of fracture area involving only the posterolateral one quadrant (isolated pattern) from posterolateral and anterolateral two quadrants (combined patterns), and by fracture patterns with or without concomitant fibular head fractures. As such, the posterolateral fragment morphology may be more specific and useful for treatment strategy selections, such as operative or nonoperative, and different surgical approaches and fragment fixation modes. Yours faithfully, Qing Li, MD Ying-Qi Zhang, MD Shi-Min Chang, MD, PhD

The slope of anterior cruciate ligament bundles for accurate transtibial anatomic reconstruction: a cadaveric study

Objectives Several studies have shown that femoral tunnel placement during double bundle anterior cruciate ligament reconstruction through the anteromedial (AM) portal is more accurate compared with the transtibial technique. Our hypothesis is that, for proper transtibial placement of the femoral tunnels, not only the anatomical sites of the tibial tunnels are important but also the slope of the tibial tunnels should match the native slope of the corresponding bundle. The anatomic insertions of the anterior cruciate ligament bundles in the femur and the tibia are well reported in the literature, but to our knowledge no study has reported the degrees of slope of the bundles. Materials and methods We examined eight cadaveric knees of middle-aged adults. The angle between each bundle and the tibial plateau was measured in both planes. The sagittal plane was measured between the bundle and the posterior tibial plateau with the knee flexed at 90°. The coronal plane was measured between the bundle and the lateral tibial plateau with the knee flexed at 90°. Results In the sagittal plane, the mean slope angle was 55.5° for the AM bundles and 90.6° for the posterolateral (PL) bundles. In the coronal plane, the mean slope angle was 80.6° for the AM and 81.3° for the PL bundles. Conclusion Focusing on the slope angles of the PL bundle in the sagittal plane (90.6°), we found that this bundle is oriented almost perpendicular to the tibial plateau. This means that for proper transtibial drilling the starting point should be from the posteromedial surface of the tibia behind the medial collateral ligament. Clinical relevance We confirm that transtibial drilling of the PL bundle is not applicable with the classic starting points on the AM surface of the tibia, and thus transportal techniques are better.

Prevalence and Location of Bone Bruises Associated with Anterior Cruciate Ligament Injury and Implications for Mechanism of Injury: A Systematic Review

Bone bruising is commonly observed on magnetic resonance imaging (MRI) after non-contact anterior cruciate ligament (ACL) injury. The primary objective of this study was to determine if the location and prevalence of tibial and femoral bone bruises after ACL injury can be explained by specific injury mechanism(s). The secondary objective was to determine whether the bone-bruise literature supports sex-specific injury mechanism(s). We hypothesized that most studies would report bone bruising in the lateral femoral condyle (LFC) and on the posterior lateral tibial plateau (LTP). MEDLINE, PubMed, and SCOPUS were searched for studies that reported bone bruise prevalence and location in ACL-injured subjects. Sex differences in bone-bruise patterns were assessed. Time from injury to imaging was assessed to account for confounding effects on bone-bruise size and location. Thirty-eight studies met the inclusion/exclusion criteria. Anterior-posterior location of bone bruises within the tibiofemoral compartment was assessed in 11 studies. Only five of these studies reported bone-bruise locations on both the tibia and the femur. The most common bone-bruise combination in all five studies was on the LFC and the posterior LTP. Sex differences were only assessed in three studies, and only one reported significantly greater prevalence of LTP bruising in females. Bone-bruise patterns in the current literature support a valgus-driven ACL injury mechanism; however, more studies should report the specific locations of tibialandfemoral bone bruises. There is insufficient evidence in the literature to determine whether there are sex-specific bone-bruise patterns in ACL-injured subjects.

THU0029 Anatomical variation in the morphology of the posterior cruciate ligament synovio-entheseal complex and correlation with degenerative change

BackgroundThe concept of the synovio-entheseal complex (SEC) anatomical functional unit has been developed in the context of arthritic disease (1). Previous studies have demonstrated the involvement of SECs in the...

In Vivo Cyclic Compression Causes Cartilage Degeneration and Subchondral Bone Changes in Mouse Tibiae

Alterations in the mechanical loading environment in joints may have both beneficial and detrimental effects on articular cartilage and subchondral bone, and may subsequently influence the development of osteoarthritis (OA). Using an in vivo tibial loading model, the aim of this study was to investigate the adaptive responses of cartilage and bone to mechanical loading and to assess the influence of load level and duration. Cyclic compression at peak loads of 4.5N and 9.0N was applied to the left tibial knee joint of adult (26-week-old) C57BL/6 male mice for 1, 2, and 6 weeks. Only 9.0N loading was utilized in young (10-week-old) mice. Changes in articular cartilage and subchondral bone were analyzed by histology and micro-computed tomography. Mechanical loading promoted cartilage damage in both age groups of mice, and the severity of joint damage increased with longer duration of loading. Metaphyseal bone mass increased with loading in young mice, but not in adult mice, whereas epiphyseal cancellous bone mass decreased with loading in both young and adult mice. In both age groups, articular cartilage thickness decreased, and subchondral cortical bone thickness increased in the posterior tibial plateau. Mice in both age groups developed periarticular osteophytes at the tibial plateau in response to the 9.0N load, but no osteophyte formation occurred in adult mice subjected to 4.5N peak loading. This noninvasive loading model permits dissection of temporal and topographic changes in cartilage and bone and will enable investigation of the efficacy of treatment interventions targeting joint biomechanics or biologic events that promote OA onset and progression.

The incidence of posterior tibial plateau fracture: an investigation of 525 fractures by using a CT-based classification system

Fractures of the tibial plateau are seen frequently in orthopedic trauma units and traditionally classified based on two-dimension plain radiographs with the Schatzker Classification system, the most popular. This system focuses on fractures involving the medial and lateral plateau but does not comment on fractures that involve the posterior aspect of the tibial plateau. The purpose of this study was to investigate the incidence of posterior tibial plateau fracture and propose a new computed tomography (CT)-based three-column classification system to guide fracture treatment. Between January 2008 and December 2009, 525 tibial plateau fractures admitted to a level 1 trauma center were retrospectively analyzed by four orthopedic trauma surgeons. Antero-posterior plain radiographs were used for Schatzker classification. CT imaging was used to further classify the fracture types with axial views dividing the plateau into three columns: a lateral, medial, and posterior. Posterior tibial plateau fracture (PTPF) was defined as a fracture with an independent fragment of the posterior column PTPFs were found in 151 cases and had an incidence of 28.8 % in this studied population. Except for type III, PTPFs were observed in each type of the Schatzker classification system. The Schatzker type VI, V, and IV fractures had the three highest percentages of PTPFs, with 76.1, 51.2, and 22.4 %, respectively. Fractures of the posterior tibial plateau are not uncommon, especially in high-energy trauma. CT imaging is required to appreciate these fracture patterns, and a three-column classification allows for a better understanding of the fracture morphology and the injury mechanism, which guides surgical management.

Three-Dimensional Reconstruction Computed Tomography Evaluation of Tunnel Location during Single-Bundle Anterior Cruciate Ligament Reconstruction: A Comparison of Transtibial and 2-Incision Tibial Tunnel-Independent Techniques

BackgroundAnatomic tunnel positioning is important in anterior cruciate ligament (ACL) reconstructive surgery. Recent studies have suggested the limitations of a traditional transtibial technique to place the ACL graft within the anatomic tunnel position of the ACL on the femur. The purpose of this study is to determine if the 2-incision tibial tunnel-independent technique can place femoral tunnel to native ACL center when compared with the transtibial technique, as the placement with the tibial tunnel-independent technique is unconstrained by tibial tunnel.MethodsIn sixty-nine patients, single-bundle ACL reconstruction with preservation of remnant bundle using hamstring tendon autograft was performed. Femoral tunnel locations were measured with quadrant methods on the medial to lateral view of the lateral femoral condyle. Tibial tunnel locations were measured in the anatomical coordinates axis on the top view of the proximal tibia. These measurements were compared with reference data on anatomical tunnel position.ResultsWith the quadrant method, the femoral tunnel centers of the transtibial technique and tibial tunnel-independent technique were located. The mean (± standard deviation) was 36.49% ± 7.65% and 24.71% ± 4.90%, respectively, from the over-the-top, along the notch roof (parallel to the Blumensaat line); and at 7.71% ± 7.25% and 27.08% ± 7.05%, from the notch roof (perpendicular to the Blumensaat line). The tibial tunnel centers of the transtibial technique and tibial tunnel-independent technique were located at 39.83% ± 8.20% and 36.32% ± 8.10%, respectively, of the anterior to posterior tibial plateau depth; and at 49.13% ± 4.02% and 47.75% ± 4.04%, of the medial to lateral tibial plateau width. There was no statistical difference between the two techniques in tibial tunnel position. The tibial tunnel-independent technique used in this study placed femoral tunnel closer to the anatomical ACL anteromedial bundle center. In contrast, the transtibial technique placed the femoral tunnel more shallow and higher from the anatomical position, resulting in more vertical grafts.ConclusionsAfter single-bundle ACL reconstruction, three-dimensional computed tomography showed that the tibial tunnel-independent technique allows for the placement of the graft closer to the anatomical femoral tunnel position when compared with the traditional transtibial technique.

Mid-term Results of Total Knee Arthroplasty Using PFC Sigma RP-F

PurposeWe compared the mid-term results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model.Materials and MethodsWe analyzed 45 knees that underwent TKA with PFC Sigma RP-Fn (study group) and 45 knees with PFC Sigma PS (control group). The mean follow-up period was 65 months (range, 60-69 months). The evaluation system of the American knee society was used for clinical and radiological assessment. Also, the maximal knee flexion angle was assessed.ResultsThe mean maximum flexion angle in the study group (135°) was greater than that in the control group (125°) at the early post-operation & final follow-up period (p=0.033). The range of motion (ROM) in the study group was recovered earlier at the postoperative 6 months, and ROM gain was improved to a greater extent at the final follow-up period (p=0.039). The knee score and function score and radiographic evaluation were no difference between the two groups (p>0.05) at the final follow-up. The two cases of radiolucency in posterior condyle and medial tibial plateau and one case of patellar elongation were seen in the study group.ConclusionsThe PFC Sigma RP-F mobile system appears to facilitate greater maximum flexion angle and ROM gain with two cases of radiolucent line.

Modified posteromedial and posterolateral approaches for the treatment of posterior tibial plateau fractures

Objective To observe the clinical outcomes of modified posteromedial and posterolateral approaches for the treatment of posterior tibial plateau fractures.Methods Between January 2006 and October 2011,25 patients with posterior tibial plateau fracture were identified.They were 17 men and 8 women,aged from 22 to 76 years (average,46.4 years).According to the AO/OTA classification,there were 4 cases of type 41-B1,6 cases of type 41-B2 and 15 cases of type 41-B3.According to Luo's three-column classification,they were all posterior column fractures.Ten patients with posterolateral tibial plateau fracture were treated by the modified posterolateral approach and the other 15 patients with posteromedial tibial plateau fracture by the modified posteromedial approach.The posterior fractures were fixated with a buttress plate.The knee function was evaluated at the last follow-up by the The Hospital for Special Surgery (HSS) Score.Results All the 25 cases were followed up for a mean time of 13.2 months (from 10 to 24 months).By the radiological Rasmussen criteria for fracture reduction,the mean score immediately after surgery was 16.5 points (from 13 to 18 points),with 20 excellent cases,4 good cases and one fair case.All patients were pain-free with full range of motion.Radiologically,bone union was achieved in all cases after a mean time of 13.9 weeks (from 12 to 18 weeks).No surgery-related complications were found.The mean HSS score was 91 points(range,74 to 97 points) and the good to excellent rate was 100％ (17 excellent and 8 good cases) at the last follow-up.The average range of knee motion ranged from 0° to 125°.Conclusion In the treatment of posterior tibial plateau fractures,because the modified posteromedial and posterolateral approaches can result in excellent fracture reduction under direct visualization and allow for posterior buttress plating,soft tissues can be well preserved and good functional results can be expected. Key words: Tibial fractures; Fracture fixation, internal; Bone plates; Procedures approach

A posterior inverted L-shaped approach for the treatment of posterior bicondylar tibial plateau fractures

To present a case series of patients with posterior bicondylar tibial plateau fractures treated by direct exposure and buttress plate fixation through posterior inverted L-shaped approach. Between August 2007 and July 2010, eight middle aged patients were identified to have posterior bicondylar tibial plateau fractures. All the eight patients underwent direct fracture exposure, reduction under visualization, and buttress plate fixation through posterior inverted L-shaped approach. All the cases were followed for an average of 28.1 months (24-36 months). All the cases had satisfactory reduction except one case, which had a 3-mm stepoff postoperatively. None of the complications such as infection, necrosis of the skin incision or the loosening and breakage of the internal fixator occurred. The average radiographic bony union time and full weightbearing time were 11.5 weeks (10-14 weeks), and 13.8 weeks (11-17 weeks) respectively. The average range of motion of the affected knee was from 3.6° to 127.8° at 1 year after the operation. The posterior inverted L-shaped approach would not involve osteotomy, tendotomy or division of muscles, while allowing satisfied visualization of the entire posterior aspect of tibial plateau and appropriate placement of hardware. This approach is a safe and effective way for the treatment of posterior bicondylar tibial plateau fractures.

Tibial Plateau Geometry Influences Lower Extremity Biomechanics During Landing

Background: Intersubject differences in lateral and medial posterior tibial plateau slope, coronal tibial slope (CTS), and medial tibial plateau depth (MTD) may influence one’s susceptibility for anterior cruciate ligament (ACL) injury. Understanding how these structural characteristics influence hip and knee joint biomechanics during weightbearing activity may advance our understanding of how tibial plateau geometry influences one’s injury risk potential. Purpose/Hypotheses: To determine the extent to which tibial plateau geometry is associated with frontal and transverse plane hip and knee joint biomechanics during the initial landing phase of a double-legged drop landing. Greater lateral tibial slope combined with lower medial/lateral tibial slope ratio would predict greater tibial internal rotation motion and moments. Lower CTS would predict greater hip adduction and knee valgus motion and reduced internal peak varus moments. These associations would be stronger when combined with a shallower MTD. Study Design: Descriptive laboratory study. Methods: Magnetic resonance scans of the knee were obtained on 23 female participants who were also assessed for hip and knee joint biomechanics during the initial landing phase of double-legged drop jumps. Results: Once controlling for the respective initial hip flexion or initial knee flexion angle at ground contact, lower CTS consistently predicted greater initial and peak hip adduction and knee valgus angles (R2 range, .212-.427, P < .027). Greater coronal and lateral tibial slope predicted greater hip internal rotation (femur relative to pelvis) at initial contact (R2 = .504) and greater CTS and lower medial/lateral tibial slope ratio predicted greater knee internal rotation (tibia relative to femur) excursions (R2 = .594, P = .001). Joint geometry was not associated with hip or knee peak joint moments. Conclusion: These data confirm substantial intersubject differences in tibial condylar geometry that are associated with intersubject differences in hip and knee motion patterns when landing from a jump. Clinical Relevance: The current findings may partially explain a female’s greater likelihood of demonstrating combined motion patterns of knee valgus and external rotation during landing. Although tibial geometry cannot be modified through training, these associations suggest that tibial geometry may have a substantial influence on tibiofemoral joint biomechanics when the knee is subjected to external loads and deserves further study in our understanding of ACL injury.

Paper # 277: Biomechanical Consequence of Posterior Medial Meniscal Root Tears with Subsequent Repair Using a Physiologic Loading Model

A physiologic load, simulating a knee squat and a pressure sensitive, capacitive, electronic sensor were used to investigate the biomechanical consequence of a meniscal root tear, subsequent repair and total meniscectomy. Posterior root tears of the medial meniscus cause a detachment of the meniscus at its insertion onto the posterior tibial plateau. Recent literature has identified these tears as common and clinically significant entities associated with meniscal extrusion and the development of degenerative arthritis. Recent studies demonstrated that meniscal root tears are biomechanically equivalent to total meniscectomy in axial load models, while these same studies also report that repair of the meniscal root corrects compartment loading (Marzo, 2008; Allaire et. al. 2008). The current study investigates the effect of posterior medial meniscal root tears on medial compartment loading using a physiologic model that recreates a knee squat. An all arthroscopic meniscal root repair technique which uses a retrograde reaming device (FlipCutterTM, Arthrex, Naples, FL, USA) to create a blind socket at the tibial insertion into which the meniscal root is advanced, recreating the tibial attachment, was then performed to repair the posterior root tear(Nicholas et al 2009). The knees were then similarly loaded after root repair and subsequent total meniscectomy, examining their effect on medial compartment loading. Nine fresh-frozen cadaver knees were dissected of soft tissue to the joint capsule while preserving the insertion and entire length of the quadriceps and hamstring tendons. Knee moments during squatting were simulated in a custom testing jig by application of angle specific loads to the quadriceps and hamstring tendons (based on body mass) with an axial compressive load at the tibia used to flex the knee to the desired angle (simulating the ground reaction force). Anterior and posterior, submeniscal arthrotomies were made allowing for passage of a pressure sensitive, capacitive, electronic sensor, custom made to approximate the medial tibial plateau shape and surface area. This sensor measures both contact area and peak pressures. Each specimen was then tested in four conditions: medial meniscus intact, after creation of posterior root tear, after repair of the meniscal root, and after total medial meniscectomy. Each condition was tested at 15, 45 and 90 degrees of knee flexion. Transection of the meniscal root significantly decreased the contact area of the medial compartment by 13% (p=0.002). After meniscal root repair, contact area was not significantly different from the intact meniscal state (decreased 6%, p=0.302). Additionally, total meniscectomy reduced contact area by 53% (p=0.025). Root transection also resulted in an overall increase in peak contact pressure of 21% (p=0.167) in the medial compartment. Meniscal root repair showed no difference when compared to the intact meniscal state (increased 10% p=0.425) and total meniscectomy increased peak contact pressure by 97% at 15 degrees (p=0.015) with no significant effect at 45 or 90 degrees of knee flexion. Our study differs from previous studies in the use of a physiologic load model that recreates the loads seen in the knee during the performance of a squat rather than an axial load model using supraphysiological loads and/or non-angle specific loading. In contrast to previous reports, our results show that meniscal root tears are not equivalent to total meniscectomies. The reduction in tibiofemoral contact area with meniscal root transection was approximately 25% of that seen with total meniscectomy. The previously described meniscal root repair technique (Nicholas et al 2009) recreated normal compartment loading.

Surgical approach for high-energy posterior tibial plateau fractures

Background:High-energy fractures of posterior tibial plateau always need surgical treatment. Generally, posterior fragments of these fractures could not be exposed and reduced well in conventional anterior approaches. Although a posterolateral/posteromedial approach to manage posterior tibial plateau fractures can achieve satisfactory results, there are few presentations concerning the treatment of these high-energy injuries based on posterior approaches combined with anterior approach if necessary.Materials and Methods:Ten cases of posterior tibial plateau fractures from high-energy injuries were retrospectively reviewed and followed up for mean 26.5 months (range 14–45 months). A posterolateral/posteromedial approach was adopted primarily to fix main fragment in posterior tibial plateau, and intraoperative assessment of the stability of knee was done. An anterior approach was added if required.Results:Posterolateral approach was employed in seven cases, posteromedial in three, and additional anteromedial in three, and anterolateral in two cases. The average time to union of all 10 fractures was 3.7 months (range 3–5.5 months). Nine patients had satisfactory articular reduction. The range of motion of the knee averaged 2° of extension to 110.5° of flexion. No patient complained of knee instability. The average postoperative HSS score at the final followup was 92.70.Conclusions:High-energy fractures of posterior tibial plateau could be well treated based on posterior approaches combined with necessary anterior approach if required.

Operative treatment of complex posterior tibial plateau fractures via posterior approach

Objective To evaluate the clinical results of operative treatments for the complex posterior tibial plateau fractures via posterior approach. Methods Eleven cases with complex posterior tibial plateau fracture from June 2008 through June 2010 were reviewed retrospectively. There were 7 males and 4females, with age from 33 years to 60 years (average, 47.8 years). According to AO classification, there were 41-B2.2.4 type in 2 cases, 41-B3.1.2 type in 3, 41-B3.3.2 type in 3, 41-B3.1.2 type combined 41-B3.3.2 type in 2, 41-C3.3 type in 1. Carlson posterior lateral approach were used in 5 cases, posterior medial approach were used in 3 cases, and posterior medial and/or lateral approach combined with anterior approach were used in 3 cases. All fractures were fixed with plates. Autogenous ilium grafts were used if necessary.Results All cases were followed up. The average follow-up time was 1.6 years (range, 3-24 months). At the final follow-up visit, bone union was obtained in all cases. The mean Rasmussen score was 16.7 (range, 15-18), and the mean HSS was 86.2 (range, 75-96). The postoperative knee range of motion were 0°-135°, 0°-130° and -10°-125° in 5 cases with posterior lateral plateau fractures, 3 cases with posterior medial plateau fractures and 3 cases with anterior and posterior plateau and intercondylar fractures respectively. There was no vascular and nerve injuries. Loosing or breaking of hardware's was not found. Conclusion The Carlson posterior lateral and/or medial approach is preferred for the complex posterior plateau fractures, with the advantages of direct reduction and stabilization. Key words: Tibial fractures; Fracture fixation, internal; Treatment outcome

Anterior Cruciate Ligament Reconstruction

Background: Recent reports have suggested that a traditional transtibial technique cannot practically accomplish an anatomic anterior cruciate ligament (ACL) reconstruction. Hypothesis: The degree to which a transtibial technique can anatomically position both tibial and femoral tunnels is highly dependent on tibial tunnel starting position. Study Design: Descriptive laboratory study. Methods: Eight fresh-frozen adult knee specimens were fixed at 90° of flexion and then dissected to expose the femoral and tibial ACL footprints. After the central third patellar tendon length was measured for each specimen, computer-assisted navigation was used to identify 2 idealized tibial tunnel starting points, optimizing alignment with the native ligament in the coronal plane but distal enough on the tibia to provide manageable bone-tendon-bone autograft–tibial tunnel mismatch (point A = 10-mm mismatch; point B = 0-mm mismatch). Tibial tunnels were then reamed to the center of the tibial insertion using point A in half of the knees and point B in the other half. Guide pin positioning on the femoral side was then assessed before and after tibial tunnel reaming, after beveling the posterolateral tibial tunnel rim, and after performing a standard notchplasty. After the femoral tunnel was reamed, the digitized contours of the native insertions were compared with those of both tibial and femoral tunnels to calculate percentage overlap. Results: Starting points A and B occurred 15.9 ± 4.5 mm and 33.0 ± 3.3 mm distal to the joint line, respectively, and 9.8 ± 2.4 mm and 8.3 ± 4.0 mm from the medial edge of the tibial tubercle, respectively. The anterior and posterior aspects of both tibial tunnels’ intra-articular exits were within a few millimeters of the native insertion’s respective boundaries. After the tibial tunnel was reamed from the more proximal point A, a transtibial guide pin was positioned within 2.1 ± 1.6 mm of the femoral insertion’s center (vs 9.3 ± 1.9 mm for point B; P = .02). After beveling a mean 2.6 mm from the back of the point A tibial tunnels, positioning improved to within 0.3 ± 0.7 mm from the center of the femoral insertion (vs 4.2 ± 1.1 mm for the point B tibial tunnels; P = .008). Compared with the more distal starting point, use of point A provided significantly greater insertional overlap (tibial: 97.9% ± 1.4% vs 71.1% ± 15.1%, P = .03; femoral: 87.9% ± 9.2% overlap vs 59.6% ± 8.5%, P = .008). No significant posterior femoral or tibial plateau breakthrough occurred in any specimen. Conclusion: Tibial and femoral tunnels can be positioned in a highly anatomic manner using a transtibial technique but require careful choice of a proximal tibial starting position and a resulting tibial tunnel that is at the limits of practical. Traditional tibial tunnel starting points will likely result in less anatomic femoral tunnels. Clinical Relevance: A transtibial single-bundle technique can accomplish a highly anatomic reconstruction but does require meticulous positioning of the tibial tunnel with little margin for error and some degree of graft-tunnel mismatch.

Computed tomographic classification of posterior condylar tibial plateau fractures

To study the new computed tomographic (CT) classification, surgical approaches and clinical efficacy of posterior condylar tibial plateau fractures. From January 2006 to July 2009, a total of 39 patients of posterior condylar tibial plateau fractures were treated by posteromedial and posterolateral knee approaches. There were 23 males and 16 females. The mean age was 41.6 years old (range: 28 - 68). Among all patients, the causes were traffic accidents (n = 26), falls (n = 9) and other injuries (n = 4). By CT classification, there were type I with posteromedial condylar tibial plateau split fracture (n = 7), type II with posterolateral condylar tibial plateau split fracture (n = 5), type III with posterolateral condylar tibial plateau depression fracture (n = 11), type IV with posterolateral condylar tibial plateau split depression fracture (n = 2) and type V with posteromedial split and posterolateral condylar tibial plateau depression fracture (n = 14). The mean follow-up period was 18.1 months (range: 12 - 30). The radiographic bony union time was 11 - 16 weeks (mean: 15.2) and the full weight-bearing time 12 - 20 weeks (mean: 15.6). No infection, knee varus/valgus, nerve injury or screw loosening/breakage was found. Bony union was achieved in all cases. According to the Rasmussen functional scoring, the results were excellent in 20, good in 14 and fair in 5. And the excellent and good rate was 87.2%. The radiological results were graded with the Rasmussen score to evaluate the reduction of fracture. The outcome was excellent in 28, good in 8 and fair in 3. And the excellent and good rate was 92.3%. This new CT classification scheme of posterior condylar tibial plateau fractures can significantly improve the reliability, guide the clinicians to select appropriate treatment plans and design an ideal regimen of operative approach and internal fixation.

Biomechanic study of posterior tibial anatomic plate in the treatment of posterior tibial plateau fracture

Objective To investigate the biomechanical properties of the posterior tibial anatomic plate. Methods A total of 25 fresh frozen adult tibial top and matching femur specimens were randomly divided into four groups. One specimen was used as normal control （ N group）, and the remaining 24specimens were with Schatzker Ⅵ tibial plateau fracture and accompanied by rear split and backward fracture displacement. The lateral margin of the tibia was fixed with a L-type plate, and the medial margin was fixed with the same plate after remodeling. The 24 specimens were divided into three groups, eight specimens per group. The posterior margin of the tibia was fixed by posterior tibial anatomic plate （ Group A）, T-type plate （ Group B） or straight reconstruction plate （ Group C）. The strength, stiffness, torsional biomechanics and failure load performance of the plates in each group were evaluated. Results The strength and stiffness of test groups was superior to that of Group N （ P 〉 0.05 ）, and the torsional biomechanics of test groups was close to that of Group N （ P 〉 0.05 ）. The posterior tibial anatomic plate was superior to T-type plate and straight reconstruction plate in aspects of strength, stiffness, torsional biomechanics and failure load performance （ P 〈 0.05 ）. Conclusions Posterior tibial anatomic plate has excellent biomechanical properties, and it is superior to other materials in treating posterior tibial plateau fracture and restoring the stability of the knee. Key words: Tibial fractures; Biomechanics; Posterior tibial anatomic plate

The Direct Posterior Approach to the Knee –Surgical and Anatomic Approach

The direct posterior surgical approach to the knee provides broad exposure of posterior neurovascular structures, the posterior aspect of the femoral condyles and tibial plateau, the posterior joint capsule, and a variety of additional soft-tissue structures including the popliteus, hamstring insertions, and origins of the gastrocnemius. Reported indications for this approach include tumor resection, posterior synovectomy, open reduction and internal fixation of posterior tibial plateau shear fractures, fixation of bone avulsions associated with a posterior cruciate ligament (PCL) injury, repair of posterior vascular injuries, and more recently, posterior inlay PCL reconstructions. However, use of this approach is uncommon and as a result, orthopedic residents and practicing orthopedic surgeons may not be familiar with the appropriate surgical anatomy. This report demonstrates in stepwise fashion the surgical approach and relevant anatomy through a detailed series of fresh cadaveric dissections.

Direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact

Anterior tibial loading is a major factor involved in the anterior cruciate ligament (ACL) injury mechanism during ski impact landing. We sought to investigate the direct contribution of axial impact compressive load to anterior tibial load during simulated ski landing impact of intact knee joints without quadriceps activation. Twelve porcine knee specimens were procured. Four specimens were used as non-impact control while the remaining eight were mounted onto a material-testing system at 70° flexion and subjected to simulated landing impact, which was successively repeated with incremental actuator displacement. Four specimens from the impacted group underwent pre-impact MRI for tibial plateau angle measurements while the other four were subjected to histology and microCT for cartilage morphology and volume assessment. The tibial plateau angles ranged from 29.4 to 38.8°. There was a moderate linear relationship ( Y=0.16X; R 2=0.64; p<0.001) between peak axial impact compressive load ( Y) and peak anterior tibial load ( X). The anterior and posterior regions in the impacted group sustained surface cartilage fraying, superficial clefts and tidemark disruption, compared to the control group. MicroCT scans displayed visible cartilage deformation for both anterior and posterior regions in the impacted group. Due to the tibial plateau angle, increased axial impact compressive load can directly elevate anterior tibial load and hence contribute to ACL failure during simulated landing impact. Axial impact compressive load resulted in shear cartilage damage along anterior–posterior tibial plateau regions, due to its contribution to anterior tibial loading. This mechanism plays an important role in elevating ACL stress and cartilage deformation during impact landing.