Posteromedial Bundle Research Articles

Specific fibre areas in the femoral footprint of the posterior cruciate ligament act as a major contributor in resisting posterior tibial displacement: A biomechanical robotic investigation.

Similar to the anterior cruciate ligament, the femoral footprint of the posterior cruciate ligament (PCL) is composed of different fibre areas, possibly having distinct biomechanical functions. The aim of this study was to determine the role of different fibre areas of the femoral footprint of the PCL in restraining posterior tibial translation (PTT). A sequential cutting study was performed on eight fresh-frozen human knee specimens, utilizing a six-degrees-of-freedom robotic test setup. The femoral attachment of the PCL was divided into 15 areas, which were sequentially cut from the bone in a randomized sequence. After determining the native knee kinematics, a displacement-controlled protocol was performed replaying the native motion, while constantly measuring the force. The reduction of the restraining force presented the percentage contribution of each cut, according to the principle of superposition. The PCL was found to contribute 29 ± 16% in 0°, 51 ± 24% in 30°, 60 ± 22% in 60° and 55 ± 18% in 90°, to restricting a PTT. The fibre areas contributing the most were located at the proximal border of the PCL footprint, away from the cartilage, and directly adjacent to the medial intercondylar ridge (p < 0.05). Of these, one fibre area showed the highest contribution at all flexion angles. This area was located at the posterior half of the medial intercondylar ridge. No clear assignment of the areas to either the anterolateral or posteromedial bundle was possible. An area towards the proximal and posterior part of the femoral PCL footprint was found to significantly restrain a posterior tibial force. Based on the data of this testing setup, a PCL graft positioned at the identified area may best mimic the part of the native PCL, which bears the most load in resisting a PTT force. No evidence level (laboratory study).

Nonanatomic Posteromedial Bundle Augmentation of the Posterior Cruciate Ligament after Hyperextension Trauma

The surgical management of posterior cruciate ligament (PCL) injuries can be challenging. As most PCL injuries occur in a flexed knee position, the anterolateral bundle is thought to be more commonly injured than the posteromedial bundle (PMB); however, in hyperextension, the PMB plays a more significant role. The smaller size of the PMB compared with the anterolateral bundle and its lower strength may explain why isolated hyperextension PMB injuries can be easily overlooked. In this Technical Note, a surgical technique to perform a nonanatomic PMB augmentation of the PCL using a gracilis tendon autograft or allograft is reported. These technical features aim to overcome current limitations in existing techniques to address the symptoms after partial PCL hyperextension injuries.

Risk factors of failure results after double-bundle reconstruction with autogenous hamstring grafts for isolated posterior cruciate ligament rupture cases

Posterior tibial translation (PTT) after double-bundle posterior cruciate ligament (PCL) reconstruction has sometimes occurred. Purpose of this study is to identify the risk factors for postoperative PTT after double-bundle PCL reconstruction with a hamstring autograft. Comparing the results of bilateral gravity sag view (GSV) at 12 months after surgery, over 5-mm PTT was defined as ‘failure’ in this study. Of 26 isolated PCL reconstruction cases, over 5-mm PTT was seen in 7 cases (group F: 9.57 ± 1.28 mm), and 19 cases had less than 5 mm (group G: 2.84 ± 1.29 mm). Age, sex, body mass index (BMI), preoperative GSV, posterior slope angle of the tibia, anterolateral bundle (ALB) and posteromedial bundle (PMB) graft diameters, and tibial tunnel diameter were evaluated. The two groups were compared with the 2 × 2 chi-squared test, the Mann Whitney U-test, and Spearman’s rank correlation coefficient. Multivariate logistic regression analysis was also performed to determine the risk factor. Statistical significance was indicated as p < 0.01 for correlation with postoperative PTT, and as p < 0.05 for all other comparisons. Mean age (group G 31.8 ± 12.5 vs group F 34.9 ± 15.9 years), sex (male/female: 15/4 vs 3/4), BMI (25.6 ± 4.6 vs 24.9 ± 3.9 kg/m2), preoperative GSV (11.3 ± 2.2 vs 11.6 ± 2.9 mm), PMB diameter (5.37 ± 0.33 vs 5.36 ± 0.48 mm), and tibial tunnel diameter (9.32 ± 0.58 vs 9.29 ± 0.49 mm) showed no significant differences. ALB diameter was significantly greater in group G (7.0 ± 0.5 mm) than in group F (6.5 ± 0.29 mm; p = 0.022). There was also a significant difference in posterior tibial slope angle (group G 9.19 ± 1.94 vs group F 6.54 ± 1.45, p = 0.004). On Spearman rank correlation coefficient analysis, ALB diameter GSV (correlation coefficient: − 0.561, p = 0.003) and posterior tibial slope angle (correlation coefficient: − 0.533, p = 0.005) showed a significant correlation with postoperative PTT. Multivariate logistic regression analysis showed that ALB diameter (OR 19.028; 95% CI 1.082–334.6; p = 0.044) and posterior slope angle of tibia (OR 3.081; 95% CI 1.109–8.556; p = 0.031) were independently associated with postoperative PTT, respectively. In double-bundle PCL reconstruction with hamstring, smaller ALB graft diameter and lower (flatted) tibial slope angle were considered risk factors for postoperative PTT.

Concomitant Anatomic PCL and FCL Reconstructions With Partial Lateral Meniscectomy

Background: Fibular collateral ligament (FCL) injuries commonly present in a multiligament knee injury pattern. These injuries are associated with significant instability leading to altered tibiofemoral biomechanics and therefore require surgical intervention. Similarly, grade 3 posterior cruciate ligament (PCL) injuries may disrupt normal tibiofemoral and patellofemoral biomechanics and increase the risk of secondary osteoarthritis. Therefore, concomitant reconstruction of the FCL and PCL should be performed to decrease knee laxity and optimize functional outcomes. Indications: Early operative treatment is indicated for patients with combined grade 3 FCL injuries and complete PCL tears. Contraindications to this procedure include patients who have significant osteoarthritis, open knee dislocations, or medical comorbidities making them unfit for surgery. Technique Description: The fundamental idea behind this technique is a stepwise treatment starting with open aspects of the procedure and followed by arthroscopic work. The technique is initiated with a lateral approach, common peroneal neurolysis, fibular and femoral FCL reconstruction tunnel preparation, and a gracilis or semitendinosus tendon autograft harvest. After that, focus shifts to intra-articular work such as associated meniscal assessment and treatment, PCL femoral and tibial tunnel preparation, graft passage, and PCL femoral tunnel fixation. Final graft fixation order is as follows: anterolateral bundle of PCL, posteromedial bundle of PCL, and finally FCL. Results: Multiple studies have reported that an anatomic FCL reconstruction in the setting of multiligament injury results in improved patient outcomes. In a prospective study of 20 patients, LaPrade et al reported −0.4 mm difference in side-to-side lateral compartment gapping and significant postoperative improvement of symptom and functional scores at a minimum 2 year postoperative follow-up after anatomic reconstruction of the FCL. Similarly, Moulton et al reported significant improvement in the average Western Ontario and Lysholm scores at 2.7 years follow-up. LaPrade et al also reported significant improvement in function and objective outcome scores at 3 years’ follow-up from anatomic double-bundle PCL reconstruction. Discussion: Anatomic FCL and PCL reconstructions successfully restore near native knee objective stability and provide superior clinical outcomes when compared to nonanatomic-based FCL reconstructions that continue to be performed. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

In Vivo Kinematics and Cruciate Ligament Tension Are Not Restored to Normal After Bicruciate-Preserving Arthroplasty

BackgroundWhether cruciate ligament forces in cruciate-preserving designs, such as unicompartmental knee arthroplasty (UKA) or bi-cruciate-retaining total knee arthroplasty (BCR-TKA), differ from those in normal knees remains unknown. The purpose of this study was to compare the in vivo kinematics and cruciate ligament force in knees before and after UKA or BCR-TKA to those in normal knees during high-flexion activity. MethodsOverall, twenty normal knees, 17 knees with medial UKA, and 15 knees with BCR-TKA were fluoroscopically examined while performing a squatting activity. A 2-dimensional or 3-dimensional registration technique was employed to measure tibio-femoral kinematics. Ligament strains and tensions in the anteromedial bundle of the anterior cruciate ligament and posterolateral bundle of the anterior cruciate ligament and the anterolateral bundle of the posterior cruciate ligament (aPCL) and posteromedial bundle of the posterior cruciate ligament (pPCL) during knee flexion were analyzed. ResultsTension in both bundles of the anterior cruciate ligament decreased with flexion. At 60° of flexion, anteromedial bundle of the anterior cruciate ligament tension in postoperative UKA knees was greater than that in normal knees. At 30° of flexion, posterolateral bundle of the anterior cruciate ligament tension in postoperative UKA knees was greater than that in normal knees. On the other hand, aPCL and pPCL tensions increased with flexion. From 40 to 110° of flexion, the postoperative aPCL tension in UKA knees was greater than that in normal knees. At 110° of flexion, the preoperative pPCL tension in UKA knees was greater than that in normal knees. In addition, the postoperative pPCL tension in UKA knees was larger than that in normal knees beyond 20° of flexion. Furthermore, the pPCL tension of postoperative BCR-TKA knees was larger than that in normal knees from 20 to 50° and beyond 90° of flexion. ConclusionsThe cruciate ligament tensions, especially posterior cruciate ligament tension in knees after UKA, were greater than those in the normal knees. Surgeons performing bi-cruciat-preserving knee arthroplasties should therefore balance cruciate ligament tension more carefully in flexion and extension.

Double-Bundle PCL Reconstruction in the Multiple-Ligament Injured Knee

Background: Multi-ligament knee injuries and knee dislocations are potentially devastating injuries that typically result in injury to both cruciate ligaments and variable injury to collateral ligament complexes. Indications: Surgical intervention typically leads to better patient outcomes than nonoperative management. We describe our preferred technique for bicruciate ligament reconstruction with a focus on double-bundle posterior cruciate ligament (PCL) reconstruction. Technique Description: A transtibial approach is used to drill the PCL tibial tunnel. A safety incision on the proximal medial tibia, which may incorporate the distal aspect of a medial-sided incision for medial collateral ligament (MCL) reconstruction, allows palpation of the PCL fovea for anatomic tunnel placement, protection of the posterior neurovascular structures, and egress of arthroscopic fluid during the case. This technique uses an inside-out approach for creation of the 2 femoral sockets to recreate the 2 PCL bundles. The grafts are passed in antegrade fashion, with passage and femoral fixation of the posteromedial (PM) bundle followed by the anterolateral (AL) bundle. After passage of the anterior cruciate ligament (ACL) graft and fixation on the femur in standard fashion, attention is turned to PCL tibia-sided fixation. We use a screw and spiked washer to fix the AL bundle at 90° of flexion with an anterior drawer maneuver. The PM bundle is then fixed with a polyetheretherketone (PEEK) interference screw in near full extension. Fixation of the ACL on the tibia in standard fashion completes the bicruciate ligament reconstruction. Results: In biomechanical cadaveric studies, double-bundle PCL reconstruction has been shown to more closely approximate native knee kinematics, with more restraint to posterior translation at all knee flexion angles and less internal rotation laxity at higher knee flexion angles. In clinical results, both single-bundle and double-bundle reconstructions improve knee stability and patient-reported outcomes. Double-bundle PCL reconstruction may provide improved objective posterior tibial stability and objective International Knee Documentation Committee (IKDC) scores. Discussion: Double-bundle PCL reconstruction can be performed efficiently with good outcomes and potentially less residual posterior translation or internal rotation laxity than single-bundle PCL reconstruction. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Modern Total Knee Arthroplasty Bearing Designs and the Role of the Posterior Cruciate Ligament.

The role of the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA) surgery continues to be a source of debate among the adult reconstruction community. In native knee flexion, the PCL is comprised of an anterolateral and posteromedial bundle that work together to limit posterior tibial translation and allow adequate femoral rollback for deep flexion. In the arthritic knee, the PCL can often become dysfunctional and attenuated, which led to the development of posterior stabilized (PS) TKA bearing options. PS TKAs implement a cam-post construct to functionally replace a resected PCL. While PS designs may facilitate balancing knees with significant deformity, they are associated with complications such as postfracture, increased wear, and patellar clunk/crepitus. In recent years, newer designs have been popularized with greater degrees of congruency and incorporation of medial and lateral pivoting to better recreate native knee kinematics. The American Joint Registry has confirmed the recent predilection for ultra-congruent and cruciate-retaining TKA inserts over PS TKAs during the last decade. Studies have failed to identify an overall clinical superiority between the cruciate substituting and sacrificing designs. The literature has also failed to identify clinical consequences from PCL resection with modern, more conforming TKA designs. In this article, we review modern PCL sacrificing designs and discuss the impact of each on the kinematics after TKA. We also will delineate the role of the PCL in modern TKA in the hopes to better understand the recent surge in sacrificing but not substituting knee implants.

PCL Reconstruction Surgery in Third Grade PCL Rupture: A Case Series

Objective: The PCL is the largest and strongest intraarticular ligament of the knee joint, comprising of 2 functional bundles: the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB). Posterior cruciate ligament (PCL) tears comprise 3% of outpatient knee injuries. The treatment of complete, isolated PCL tears remains controversial. Some studies have reported good outcomes after conservative treatment of partial PCL tears, while others have reported poor results at long-term follow-up with disabling symptoms and functional limitations. This case series reported the first experience of PCL reconstruction in our institution and its associated outcome. Methods: This prospective case series was conducted from January to December 2021. Two patients were included in this case series. All the patients were diagnosed with PCL tear by an Orthopaedic surgeon. clinical examination, knee radiograph, and MRI were obtained in both patients. All patients underwent arthroscopic PCL reconstruction by a single senior Orthopaedic surgeon. Physical therapy was performed after the surgery. Clinical evaluation was followed up for 9 months. The outcome in this case series was the posterior drawer test and range of motion. Result: Two patients were included in this case series. A favorable outcomes were noted following PCL reconstruction surgery. There were negative posterior drawer test, posterior sag sign, and full range of motion in both patients. Conclusion: A PCL reconstruction surgery provided a satisfactory clinical outcome in terms of posterior drawer test, posterior sag sign, and range of motion. PCL reconstruction surgery is recommended in patients who present with grade 3 PCL injury.

A Comprehensive Meta-analysis of Clinical and Biomechanical Outcomes Comparing Double-Bundle and Single-Bundle Posterior Cruciate Ligament Reconstruction Techniques

Background: Posterior cruciate ligament (PCL) reconstruction techniques have historically focused on single-bundle (SB) reconstruction of the larger anterolateral bundle without addressing the codominant posteromedial bundle. The SB technique has been associated with residual laxity and instability, leading to the development of double-bundle (DB) reconstruction techniques. Purpose: To perform a meta-analysis of comparative clinical and biomechanical studies to differentiate the pooled outcomes of SB and DB PCL reconstruction cohorts. Study Design: Meta-analysis and systematic review: Level of evidence, 3. Methods: Six databases were queried in February 2022 for literature directly comparing clinical and biomechanical outcomes for patients or cadaveric specimens undergoing DB PCL reconstruction against SB PCL reconstruction. Biomechanical outcomes included posterior tibial translational laxity, external rotational laxity, and varus laxity at 30° and 90° of knee flexion. Clinical outcomes included the side-to-side difference in posterior tibial translation during postoperative stress radiographs, risk of a major complication, and the following postoperative patient-reported outcome measures: Lysholm, Tegner, and International Knee Documentation Committee (IKDC) subjective and objective scores. A random-effects model was used to compare pooled clinical and biomechanical outcomes between the cohorts. Results: Fifteen biomechanical studies and 13 clinical studies were included in this meta-analysis. The DB group demonstrated significantly less posterior tibial translation at 30° and 90° of knee flexion (P < .00001). Additionally, the DB group demonstrated significantly less external rotation laxity at 90° of knee flexion (P = .0002) but not at 30° of knee flexion (P = .33). There was no difference in varus laxity between the groups at 30° (P = .56) or 90° (P = .24) of knee flexion. There was significantly less translation on stress radiographs in the DB group (P = .02). Clinically, there was no significant difference between the groups for the Lysholm score (P = .95), Tegner score (P = .14), or risk of a major complication (P = .93). DB PCL reconstruction led to significantly higher odds of achieving “normal” or “near normal” objective IKDC outcomes for the included prospective studies (P = .04) and higher subjective IKDC scores (P = .01). Conclusion: DB PCL reconstruction leads to superior biomechanical outcomes and clinical outcomes relative to SB PCL reconstruction. Re-creating native anatomy during PCL reconstruction maximizes biomechanical stability and clinical outcomes.

Stability of the knee after posterior cruciate ligament reconstruction using peroneus longus tendon graft with three femoral insertion sites. A cadaveric study

IntroductionMany kinds of grafts were used for single-bundle reconstruction of the posterior cruciate ligament (PCL). Recently, the peroneus longus tendon (PLT) was used in some clinical reports. This study aimed to test the best position of the femoral insertion in the case of using PLT for PCL reconstruction. MethodsSeventeen fresh frozen cadaveric knees were randomized into three groups. Group AL (6 knees): the femoral insertion in PCL reconstruction was at the footprint center of the anterolateral bundle (ALB). Group PM (5 knees): at the footprint center of the posteromedial bundle (PMB). And group MC (6 knees) was at the midpoint of the center of the anterolateral bundle and posteromedial bundle. The PCL of all knees was cut and a PCL reconstruction procedure was performed with autologous peroneus longus tendon (PLT). The stability of each knee was tested in three conditions: PCL was intact, PCL was resected, and PCL was reconstructed. The KT-1000 machine was used to measure the maximum posterior displacement of the tibia under force with the knees at 0, 30, 60, 90, and 120 degrees of flexion. ResultsAverage posterior displacement of the tibia under force for intact PCL of group AL was 1.6 mm, group MC was 1.2 mm, and group PM was 1.3 mm. After PCL was resected, the knee laxity was increased remarkably: posterior displacement of the tibia of group AL was 8.9 mm, group MC was 9.4 mm, and group PM was 13.6 mm. After PCL was reconstructed, group AL was 1.5 mm, group MC was 2.0 mm, and group PM was 5.6 mm. The results showed that after PCL reconstruction the group AL and group MC give better stability to the knee (p < 0.05, except knee at 120 degrees of flexion). Group AL got more stability than group MC, but the difference was not significant (p ≥ 0.164) ConclusionIn a single-bundle reconstruction of the PCL with the graft PLT, the femoral insertion at the footprint center of the ALB and the midpoint of the center of the ALB and PMB showed better stability than that at PMB.

Cruciate ligament force of knees following mobile-bearing unicompartmental knee arthroplasty is larger than the preoperative value

We analyzed the implantation effects on cruciate ligament force in unicompartmental knee arthroplasty (UKA) and determined whether kinematics is associated with the cruciate ligament force. We examined 16 patients (17 knees) undergoing medial UKA. Under fluoroscopy, each participant performed a deep knee bend before and after UKA. A two-dimensional/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Forces in the anteromedial and posterolateral bundles of both the anterior cruciate ligament (aACL and pACL) and the anterolateral and posteromedial bundles of the posterior cruciate ligament (aPCL and pPCL) during knee flexion were analyzed pre- and post-UKA. Correlations between changes in kinematics and ligament forces post-UKA were also analyzed. Preoperatively, the aACL forces were highly correlated with anteroposterior (AP) translation of the lateral condyles (Correlation coefficient [r] = 0.59). The pPCL forces were highly correlated with the varus–valgus angulation (r = − 0.57). However, postoperatively, the PCL forces in both bundles were highly correlated with the AP translation of the medial femoral condyle (aPCL: r = 0.62, pPCL: r = 0.60). The ACL and PCL forces of the knees post-UKA were larger than those of the knees pre-UKA. Kinematic changes were significantly correlated with the cruciate ligament force changes.

Multiple Ligament Knee Reconstructions

Patients with multiligament knee injuries require a thorough examination (Lachman, posterior-drawer, varus, valgus, and rotational testing). Diagnoses are confirmed with magnetic resonance imaging as well as stress radiographs (posterior, varus, and valgus) when indicated. Multiple systematic reviews have reported that early (<3 weeks after injury) single-stage surgery and early knee motion improves patient-reported outcomes. Anatomic-based reconstructions of the torn primary static stabilizers and repair of the capsular structures and any tendinous avulsions are performed in a single-stage. Open anteromedial or posterolateral incisions are preferentially performed first to identify the torn structures and to prepare the posterolateral corner (PLC) and medial knee reconstruction tunnels. Next, arthroscopy allows preparation of the anterior cruciate ligament (ACL) and double-bundle (DB) posterior cruciate ligament (PCL) tunnels. Careful attention to tunnel trajectory minimizes the risk for convergence. Meniscal tears are preferentially repaired (root and ramp tears are commonly seen in this patient group). Graft passage is performed after all tunnels are reamed. The graft tensioning and fixation sequence is as follows: anterolateral bundle of the PCL to restore the central pivot, posteromedial bundle of the PCL, ACL, PLC (including fibular [lateral] collateral ligament), and posteromedial corner (including medial collateral ligament). Graft integrity and full knee range of motion should be verified before closure. Physical therapy commences on postoperative day 1 with immediate knee motion (flexion from 0°-90°; prone for DB-PCL reconstruction) and quadriceps activation. Patients are nonweightbearing for 6 weeks. Patients with ACL-based reconstructions wear an immobilizer for 6 weeks then transition to a hinged ACL brace. Patients with PCL-based reconstructions transition into a dynamic PCL brace once swelling subsides and wear it routinely for 6 months. Functional testing and stress radiography are performed to validate return to sports.

The Posterior Cruciate Ligament: Anatomy, Biomechanics, and Double-Bundle Reconstruction

The posterior cruciate ligament (PCL) is the largest intra-articular ligament in the knee and is the primary stabilizer to posterior tibial translation. Historically, the PCL’s functional dynamics and appropriate management after injury have been controversial. However, recent biomechanical and anatomic studies have elucidated a better understanding of PCL function, which has led to development of more anatomic reconstruction techniques. The larger anterolateral bundle and the smaller posteromedial bundle of the PCL exhibit a codominant relationship and have a wide femoral attachment footprint. For these reasons, the native kinematics of the knee is better restored with a double-bundle PCL reconstruction (DB-PCLR) technique than with a single-bundle PCL reconstruction (SB-PCLR). Likewise, clinical studies have demonstrated excellent outcomes for DB-PCLR compared to SB-PCLR, with decreased posterior knee laxity on stress radiography and improved International Knee Documentation Committee scores. This review will provide a detailed overview of the clinically relevant anatomy, biomechanics, injury evaluation, and treatment options, with an emphasis on arthroscopic DB-PCLR.

Anatomy and Biomechanics of the Posterior Cruciate Ligament.

Posterior cruciate ligament (PCL) injuries are often encountered in the setting of other knee pathology and sometimes in isolation. A thorough understanding of the native PCL anatomy is crucial in the successful treatment of these injuries. The PCL consists of two independent bundles that function in a codominant relationship to perform the primary role of resisting posterior tibial translation relative to the femur. A secondary role of the PCL is to provide rotatory stability. The anterolateral (AL) bundle has a more vertical orientation when compared with the posteromedial (PM) bundle. The AL bundle has a more anterior origin than the PM bundle on the lateral wall of the medial femoral condyle. The tibial insertion of AL bundle on the PCL facet is medial and anterior to the PM bundle. The AL and PM bundles are 12-mm apart at the center of the femoral origins, while the tibial insertions are more tightly grouped. The different spatial orientation of the two bundles and large distance between the femoral centers is responsible for the codominance of the PCL bundles. The AL bundle is the dominant restraint to posterior tibial translation throughout midrange flexion, while the PM bundle is the primary restraint in extension and deep flexion. Biomechanical testing has shown independent reconstruction of the two bundles that better reproduces native knee biomechanics, while significant differences in clinical outcomes remain to be seen. Stress X-rays may play an important role in clinical decision-making process for operative versus nonoperative management of isolated PCL injuries. Strong understanding of PCL anatomy and biomechanics can aid surgical management.

Elongation Patterns of the Posterior Cruciate Ligament after Total Knee Arthroplasty.

This study aimed to understand the ability of fixed-bearing posterior cruciate ligament (PCL)-retaining implants to maintain functionality of the PCL in vivo. To achieve this, elongation of the PCL was examined in six subjects with good clinical and functional outcomes using 3D kinematics reconstructed from video-fluoroscopy, together with multibody modelling of the knee. Here, length-change patterns of the ligament bundles were tracked throughout complete cycles of level walking and stair descent. Throughout both activities, elongation of the anterolateral bundle exhibited a flexion-dependent pattern with more stretching during swing than stance phase (e.g., at 40° flexion, anterolateral bundle experienced 3.9% strain during stance and 9.1% during swing phase of stair descent). The posteromedial bundle remained shorter than its reference length (defined at heel strike of the level gait cycle) during both activities. Compared with loading patterns of the healthy ligament, postoperative elongation patterns indicate a slackening of the ligament at early flexion followed by peak ligament lengths at considerably smaller flexion angles. The reported data provide a novel insight into in vivo PCL function during activities of daily living that has not been captured previously. The findings support previous investigations reporting difficulties in achieving a balanced tension in the retained PCL.

Dynamic Three-Dimensional Computed Tomography Mapping of Isometric Posterior Cruciate Ligament Attachment Sites on the Tibia and Femur: Single- Versus Double-Bundle Analysis

(1) To determine the area of posterior cruciate ligament (PCL) insertion sites on the lateral wall of the medial femoral condyle (LWMFC) that demonstrates the least amount of length change through full range of motion (ROM) and(2) to identify a range of flexion that would be favorable for graft tensioning for single-bundle (SB) and double-bundle (DB) PCL reconstruction. Six fresh-frozen cadaveric knees were obtained. Three-dimensional computed tomography point-cloud models were obtained from 0° to 135°. A point grid was placed on the LWMFC and the tibial PCL facet. Intra-articular length was calculated for each point on the femur to the tibia at all flexion angles and grouped to represent areas for bone tunnels of SB and DB PCLR. Normalized length changes were evaluated. Femoral tunnel location and angle of graft fixation were significant contributors to mean, minimum, and maximum normalized length of the PCL (all p < .001). Tibial tunnel location was not significant in any case (all p < .22). A femoral tunnel in the location of the posteromedial bundle of the PCL resulted in the least length change at all tibial positions (maximum change 13%). Fixation of the anterolateral bundle in extension or at 30° flexion resulted in significant overconstraint of the PCL graft. The femoral tunnel location for a SB PCLR resulted in significant laxity at lower ranges of flexion. PCL length was significantly dependent on femoral tunnel position and angle of fixation, whereas tibial tunnel position did not significantly contribute to observed differences. All PCL grafts demonstrated anisometry, with the anterolateral bundle being more anisometric than the posteromedial bundle. For DB PCLR, the posteromedial bundle demonstrated the highest degree of isometry throughout ROM, although no area of the LWMFC was truly isometric. The anterolateral bundle should be fixed at 90° to avoid overconstraint, and SB PCLR demonstrated significant laxity at lower ranges of flexion. Surgeons can apply the results of this investigation to surgical planning in PCLR to optimize isometry, which may ultimately reduce graft strain and the risk of graft failure. Additionally, DB PCLR demonstrated superiority compared with SB PCLR regarding graft isometry, as significant laxity was encountered at lower ranges of flexion in SB PCLRs. Fixation of the ALB at 90° flexion should be performed to avoid overconstraint in knee extension.

Posterior Cruciate Ligament

Improved understanding of the anatomy and biomechanics of the posterior cruciate ligament (PCL) has led to the evolution and improvement of anatomic-based reconstructions. The PCL is composed of the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB). On the femoral side, the ALB spans from the trochlear point to the medial arch point on the roof of the notch, while the PMB occupies the medial wall from the medial arch point to the most posterior aspect of the articular cartilage. Because of these broad and distinct attachments, the bundles have a load-sharing, synergistic and codominant relationship. Both restrict posterior translation; however, the ALB has a proportionally larger role in restricting translation throughout flexion, whereas the PMB has a role comparable to that of the ALB in full extension. In addition, the PMB resists internal rotational at greater flexion angles (> 90°). Consequently, it is difficult to restore native kinematics with a single graft. Biomechanical analysis of single- versus double-bundle PCL reconstructions (SB PCLR vs DB PCLR) demonstrates improved restoration of native kinematics with a DB PCLR, including resistance to posterior translation throughout flexion (15°-120°) and internal rotation in deeper flexion (90°-120°). Similarly, clinical research demonstrates excellent outcomes following DB PCLR, including functional outcomes comparable to those of anterior cruciate ligament reconstructions, with no significant differences between isolated and multiligament PCL injuries. Compared to SB PCLR, systematic review has demonstrated the superiority of DB PCLR based on objective postoperative stress radiography and International Knee Documentation Committee scores in randomized trials. In addition to reconstruction techniques, recent research has identified other factors that impact kinematics and PCL forces, including decreased tibial slope, which leads to increased graft stresses, and incidence of native PCL injuries. As the understanding of these other contributing factors evolves, so will surgical and treatment algorithms that will further improve patients’ outcomes.

The Anatomical Numerical Measurement of Posterior Cruciate Ligament: A Vietnamese Cadaveric Study.

BACKGROUND:The posterior cruciate ligament (PCL) is crucial to restrain the posterior translation of the tibia. Its anatomical structure is complex. A proper understanding of PCL anatomy may assist surgeon in reconstructing anatomically native PCL.AIM:To describe the anatomical numerical measurement of the PCL in Vietnamese adults.METHODS:Twenty-one fresh cadaveric knees were examined. The macroscopic details of the intra-articular PCL, the attachment of the anterolateral bundle (ALB), posteromedial bundles (PMB) to the femur and tibia were analysed. We used a digital camera to photograph the cadaveric specimens and used the ImageJ software to analyse the collected images.RESULTS:The ALB and PMB length were 35.5 ± 2.78 and 32.6 ± 2.28 mm, respectively. The smallest and the biggest diameter of middle third of the PCL were 5.9 ± 0.71 and 10.0 ± 1.39 mm, respectively. The area of cross section of middle third of the PCL was 53.6 ± 12.37 mm2. The femoral insertion area of ALB and PMB were 88.4 ± 16.89 and 43.5 ± 8.83 mm2, respectively. The distance from the central point of femoral ALB, PMB, and total PCL insertion to the Blumensaat line were 5.5 ± 0.91, 11.5 ± 1.98, and 7.6 ± 1.42 mm, respectively. The shortest distance from medial femoral cartilage rim to the central point of femoral ALB, PMB, and total PCL insertion were 7.0 ± 0.79, 7.3 ± 0.95, and 7.8 ± 1.73 mm, respectively. The tibial insertion area of ALB and PMB were 84.5 ± 12.52 and 47.8 ± 6.20 mm2 respectively. The shortest distance from the posterior cartilage corner of the medial tibial plateau to the central point of ALB, PMB, and total PCL insertion to tibia were 8.5 ± 1.02, 9.4 ± 1.11, and 8.3 ± 1.1 mm, respectively. The central point of tibial PCL insertion was 9.7±1.08 mm below cartilage plane of the medial tibial plateau.CONCLUSION:This study describes the detailed anatomical measurement of the PCL and its bundles in adults.

TL 18104 - Ankle fusion percutaneous home run screw fixation

Introduction: During internal fixation of ankle fusions, in addition to the standard crossed screw fixation pattern, the use of a percutaneously placed augmenting screw, directed from the posterolateral tibial metaphysis proximally across the ankle into the talar neck (“home run screw”), is a widely used technique. The placement of this screw is technically demanding, and for the majority of surgeons, multiple attempts under fluoroscopy guidance are frequently needed to achieve perfect positioning of the implant. There is a risk of injury to local neurovascular and tendinous structures. Objective: To identify the number of attempts necessary for perfect positioning of the ankle fusion home run screw and the neurovascular and tendinous structures at risk. Methods: Eleven fresh-frozen cadaver limbs were used. Guide wires for cannulated screw placement were percutaneously placed into the distal posterolateral aspect of the leg under fluoroscopic guidance, with the ankle held in the neutral position. Malpositioned guidewires were not removed and served as guidance for the following pins. The number of guide wires needed to achieve acceptable positioning of the implant was noted. After a layered dissection from the skin to the tibia, we evaluated neurovascular and tendinous injuries and measured the shortest distance between the closest guidewire and the soft tissue structures using a precision digital caliper. Results: The mean number of guide wires needed to achieve an acceptable positioning of the implant was 2.34 (SD 0.81, range 2 – 4). The mean distances between the closest guide pin and soft tissue structures of interest were as follows: Achilles tendon 5.35 mm (SD 2.74 mm); peroneal tendons 9.65 mm (SD 5.19 mm); posteromedial neurovascular bundle 12.78 mm (SD 7.14 mm). The sural bundle was in contact with the guide pin in 5/11 specimens (45.5%) and impaled in 3/11 specimens (27.3%). In the remaining 3 specimens, the average distance from the sural nerve bundle was 3.58 mm (SD 2.16 mm). Conclusion: The placement of percutaneous ankle fusion home run screws is technically demanding, requiring multiple attempts to achieve acceptable placement. We have shown that important tendinous and neurovascular structures are in close proximity to the guidewires and that the sural bundle is injured in approximately 73% of cases.

Tibial Slope and Its Effect on Graft Force in Posterior Cruciate Ligament Reconstructions

Background: A flattened posterior tibial slope may cause excessive unwanted stress on the posterior cruciate ligament (PCL) reconstruction graft and place patients at risk for PCL reconstruction graft failure. To date, there is a paucity of biomechanical studies evaluating the effect of posterior tibial slope on the loading properties of single-bundle (SB) and double-bundle (DB) PCL grafts. Purpose/Hypothesis: The purpose of this study was to quantify the effect of sagittal plane tibial slope on PCL reconstruction graft force at varying slopes and knee flexion angles for SB and DB PCL reconstructions. The null hypothesis was that there would be no differences in SB or DB PCL graft forces with changes in posterior tibial slope or knee flexion angle. Study Design: Controlled laboratory study. Methods: Ten male fresh-frozen cadaveric knees had a proximal posterior tibial osteotomy performed and an external fixator placed for tibial slope adjustment. SB (anterolateral bundle [ALB] only) and DB PCL reconstruction procedures were performed and tested consecutively for each specimen. The ALB and posteromedial bundle graft forces were recorded before (unloaded force) and after (loaded force) compression with a 300-N axial load. Unloaded and loaded graft forces were tested at flexion angles of 45°, 60°, 75°, and 90°. Tibial slope was varied between −2° and 16° of posterior slope at 2° increments under these test conditions. Results: Modeling for unloaded testing revealed that tibial slope had an independently significant and linear decreasing effect on the force of all PCL grafts regardless of flexion angle (coefficient = −1.0, SE = 0.08, P < .001). Higher knee flexion angles were significantly associated with higher unloaded graft force for all PCL grafts (P < .001). After the graft was subjected to loading, tibial slope also had an independently significant and linear decreasing effect on the loaded force of all PCL grafts regardless of flexion angle (coefficient = −0.70, SE = 0.11, P < .001). The ALB graft of DB reconstructions had a significantly lower loaded graft force than the ALB graft of the SB PCL reconstruction (coefficient = 14.8, SE = 1.62, P < .001). The posteromedial bundle graft had a significantly lower loaded graft force than the ALB graft in both reconstruction states across all flexion angles (both P < .001). Higher knee flexion angles were also significantly associated with higher loaded graft force for all graft constructs (P < .001). Conclusion: PCL graft forces increased as tibial slope decreased (flattened) in the loaded and unloaded states. An increased posterior tibial slope was protective of PCL reconstruction grafts. The findings of this study support the effect of tibial slope on PCL grafts that has been noted clinically, and a flat tibial slope should be considered a factor when evaluating the cause of failed PCL reconstructions. Clinical Relevance: The authors validated that decreased tibial slope increased the loads on PCL reconstruction grafts. Patients with flat tibial slopes in chronic tears or revision PCL reconstruction cases should be evaluated closely for the possible need of a first-stage or concurrent slope-increasing tibial osteotomy.