Impact of sex and age on the lateralisation of the tibial tubercle in normal paediatric and adolescent populations

PURPOSE

Numerous methods have been proposed to characterise tubercle lateralisation. However, their normal values and related changes remain unclear. Accordingly, it was aimed to determine the potential sex and age effects and determined the optimal individualised method of diagnosing lateralisation of the tibial tubercle in patients with recurrent patellar dislocation (RPD).

METHODS

Measurements included the tibial tubercle-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance and tibial tubercle lateralisation (TTL); and the proximal tibial width (PTW), trochlear width (TW) and trochlear dysplasia index (TDI), for adjustment. A two-way analysis of variance was used to determine the effect of age, sex and their interaction within the normal group. When the age effect was statistically significant, a nonlinear regression was created. Areas under the receiver-operating characteristic curve (AUCs) were calculated to assess diagnostic accuracy.

RESULTS

A total of 277 normal participants (mean [SD] age, 13.5 [2.6] years; 125 [45.1%] female) and 227 patients with RPD (mean [SD] age, 13.5 [2.6] years; 161 [58.1%] female) were analysed. It was found that in the normal group, in patients aged 7-10, TT-PCL distance (p = 0.006), TTL (p = 0.007) and TT-PCL/PTW (p < 0.001) were significantly larger in females than in males. A significant sex effect was also detected on TT-TG/TW (p = 0.014). TT-TG distance, TT-PCL distance, TTL and TT-PCL/PTW (in male patients) approached an established normal adult value of 12.3 mm, 20.9 mm, 0.64 and 0.28, respectively, with increasing age (p < 0.001). The AUC was greater for TT-TG/TDI and TT-TG/TW (p ≤ 0.01) and TT-TG/TDI outperformed TT-TG/TW in patients aged 15-18 (p = 0.004).

CONCLUSIONS

Tubercle lateralisation increased with age and was affected by sex, with the exception of TT-TG distance and TT-TG/TDI. TT-TG/TDI is the optimal method of diagnosing a lateralized tibial tubercle in patients with RPD. These findings assist with the evaluation of tubercle lateralisation in that they provide a proper protocol for paediatric and adolescent populations with RPD; and thus, will help determine whether medial tubercle transfer should be included among the tailored surgical procedures considered for the treatment of patients with RPD.

LEVEL OF EVIDENCE

Level III.

Preoperative patellofemoral anatomy affects failure rate after isolated patellofemoral inlay arthroplasty

PURPOSE

To analyze whether preoperative patellofemoral anatomy is associated with clinical improvement and failure rate after isolated patellofemoral arthroplasty (PFA) using a modern inlay-type trochlear implant.

METHODS

Prospectively collected 24 months data of patients treated with isolated inlay PFA (HemiCAP^® Wave, Arthrosurface, Franklin, MA, USA) between 2009 and 2016, and available digitalized preoperative imaging (plain radiographs in three planes and MRI) were retrospectively analyzed. All patients were evaluated using the WOMAC score, Lysholm score, and VAS pain. Patients revised to TKA or not achieving the minimal clinically important difference (MCID) for the total WOMAC score or VAS pain were considered failures. Preoperative imaging was analyzed regarding the following aspects: Tibiofemoral OA, patellofemoral OA, trochlear dysplasia (Dejour classification), patellar height (Insall-Salvati index [ISI]; Patellotrochlear index [PTI]), and position of the tibial tuberosity (TT-TG and TT-PCL distance).

RESULTS

A total of 41 patients (61% female) with a mean age of 48 ± 13 years could be included. Fifteen patients (37%) were considered failures, with 5 patients (12%) revised to TKA and 10 patients (24%) not achieving MCID for WOMAC total or VAS pain. Failures had a significantly higher ISI, and a significantly lower PTI. Furthermore, the proportion of patients with a pathologic ISI (> 1.2), a pathologic PTI (< 0.28), and without trochlear dysplasia were significantly higher in failures. Significantly greater improvements in clinical outcome scores were observed in patients with a higher preoperative grade of patellofemoral OA, ISI ≤ 1.2, PTI ≥ 0.28, TT-PCL distance ≤ 21 mm, and a dysplastic trochlea.

CONCLUSION

Preoperative patellofemoral anatomy is significantly associated with clinical improvement and failure rate after isolated inlay PFA. Less improvement and a higher failure rate must be expected in patients with patella alta (ISI > 1.2 and PTI < 0.28), absence of trochlear dysplasia, and a lateralized position of the tibial tuberosity (TT-PCL distance > 21 mm). Concomitant procedures such as tibial tuberosity transfer may, therefore, be considered in such patients.

LEVEL OF EVIDENCE

Level III, retrospective analysis of prospectively collected data.

Evaluation of age-dependent morphometrics of the meniscofemoral ligaments in reference to the posterior cruciate ligament in routine MRI

OBJECTIVES

To quantify the morphological correlation between the posterior cruciate ligament (PCL) and the meniscofemoral ligaments (MFLs), to propose normal ranges for different age populations, and to define guidelines for correct identification and differentiation of MFLs in routine MRI.

METHODS

Three hundred forty-two subjects were included retrospectively and subdivided into five age groups. Morphometrics of the PCL and the MFLs were measured on standard MRI in the sagittal, coronal, and axial planes. Student's t test, Mann-Whitney U test, and ANOVA and Kruskal-Wallis tests with Bonferroni correction were used for comparison.

RESULTS

The MFLs did not vary significantly between sexes (p > 0.05) or in those older than 10 years (p > 0.05). Longitudinal MFL growth is completed before age 11 years, with cross-sectional area (CSA) increasing until age 20. The CSA of the PCL was significantly (p = 0.028) larger in knees without a pMFL (Mdn = 39.7 mm2) than with a pMFL (Mdn = 35.4 mm2). MFLs were more often detected on sagittal than coronal images.

CONCLUSIONS

This study describes the morphometric relation between the PCL and the MFLs on routine MRI. When reporting imaging findings in preparation for arthroscopic knee surgery, evaluation of MFLs, first in the sagittal and then the coronal plane, will achieve the best results.

KEY POINTS

• The MFLs and the PCL have distinct morphological patterns throughout life. • These patterns show intimate anatomical relationships and a potential biomechanical impact. • Those patterns and relationships can be quantified with MRI. • A correlation exists between age and morphometrics of the MFLs. • Recommendations for correct identification of the MFLs are provided.

Posterolateral portal tibial tunnel drilling for posterior cruciate ligament reconstruction: technique and evaluation of safety and tunnel position

PURPOSE

To evaluate the safety for neurovascular structures and accuracy for tunnel placement of the posterolateral portal tibial tunnel drilling technique in posterior cruciate ligament (PCL) reconstruction.

METHODS

Fifteen fresh-frozen human cadaveric knees were used. The tibial tunnel for the PCL was created using a flexible reamer from the posterolateral portal. Then, the flexible pin was left in place, and the distance from the posterolateral portal, the flexible pin, and the tibial tunnel to the peroneal nerve and popliteal artery was measured. Additionally, the distance between the tibial tunnel and several landmarks related to the PCL footprint was measured, along with the distance from the exit point of the flexible pin to the superficial medial collateral ligament and gracilis tendon.

RESULTS

The peroneal nerve and the popliteal neurovascular bundle were not damaged in any of the specimens. The median (range) distance in mm from the peroneal nerve and popliteal artery to the posterolateral portal and flexible pin was: 52 (40-80) and 50 (40-61), and 35 (26-51) and 22 (16-32), respectively. The median (range) distance from the tibial tunnel to the popliteal artery was 21 mm (15-38). The tibial tunnel was located at a median (range) distance in mm of 3 (2-6), 6 (3-12), 5 (2-7), 4 (1-8), 9 (3-10), 10 (4-19), and 19 (6-24) to the champagne-glass drop-off, lateral cartilage point, shiny white fibre point, medial groove, medial meniscus posterior root, lateral meniscus posterior root, and posterior aspect of the anterior cruciate ligament, respectively.

CONCLUSIONS

The posterolateral portal tibial tunnel technique is safe relative to neurovascular structures and creates an anatomically appropriate tibial tunnel location. The clinical relevance of study is that this technique may be safely and accurately used in PCL reconstruction to decrease the risk of neurovascular damage (avoid use of a posteriorly directed pin), avoid the use of intraoperative fluoroscopy, and avoid the sharp turn during graft passage.

Location of the Neurovascular Bundle of the Knee during Flexed and Extended Position: An MRI Study

BACKGROUND

The popliteal vessels and nerve are the structures most at risk during surgery of the posterior knee compartment. Common procedures that could interfere with or otherwise affect these structures include synovectomy, meniscal repair, proximal tibial osteotomy, knee replacement and fixation around the knee joint. Magnetic resonance imaging (MRI) can be used to locate the neurovascular structures from the posterior bony landmark. MRI imaging is routinely studied in the extended knee, but surgery of the posterior knee compartment is most often performed with the knee in a flexed position.

OBJECTIVE

The aim of this study was to investigate the location of the posterior neurovascular bundle relative to the posterior aspect of the femur, tibia, and posterior cruciate ligament during fully extended knee position and 90-degree flexed knee position using MRI.

MATERIAL AND METHOD

MRI images of 26 knees were obtained from 25 patients. Ten left knees, 14 right knees, and 1 bilateral knees were obtained from 18 males and 7 females. Axial plane and sagittal plane studies were used to measure the shortest distance of the popliteal artery, popliteal vein, and tibial nerve to the posterior bony aspect of the knee and the posterior cruciate ligament using a digital ruler tool from the PACS X-ray system. Measurement was performed at joint line level, 1 cm above joint line level, and 1 cm below joint line level in the fully extended knee position and in the 90-degree flexed knee position. At the joint line level, the mediolateral distance of the popliteal artery, popliteal vein, and tibial nerve to the posterior cruciate ligament were also measured.

RESULTS

At 1 cm above joint line level, mean anteroposterior (AP) distance from the distal femoral condyle to the popliteal artery, popliteal vein, and tibial nerve was 1.83+3.35 mm, 6.44+4.55 mm and 10.29+4.41 mm for full knee extension, and 15.60+5.01 mm, 20.63+4.62 mm and 26.24+7.70 mm for 90-degree knee flexion, respectively (p<0.001). At joint line level, mean AP distance from the posterior tibial cortex to the popliteal artery, popliteal vein, and tibial nerve was 5.43+3.22 mm, 8.75+3.72 mm and 13.10+4.15 mm for full knee extension, and 11.64+5.48 mm, 17.59+6.53 mm and 21.52+10.67 mm for 90-degree knee flexion, respectively (p<0.001). At 1 cm below joint line level, mean AP distance from the posterior tibial cortex to the popliteal artery, popliteal vein, and tibial nerve was 1.98+1.95 mm, 4.26+2.74 mm and 8.66+3.85 mm for full knee extension, and 6.91+2.86 mm, 12.34+5.23 mm and 16.58+9.22 mm for 90-degree knee flexion, respectively (p<0.001). At joint line level, mean distance from the posterolateral border of the PCL to the popliteal artery, popliteal vein, and tibial nerve was 11.12+2.62 mm, 11.30+4.05 mm and 15.14+5.05 mm for full knee extension, and 19.89+5.67 mm, 23.87+6.96 mm and 29.41+10.72 mm for 90-degree knee flexion, respectively (p<0.001).

CONCLUSION

During 90-degree knee flexion, the neurovascular structures move posterolaterally, as compared to fully extended knee position at joint line level and 1 cm above and below joint line level. To prevent neurovascular injury during surgery, surgeons should avoid or be cautious during blind penetration of the midline joint capsule and 90 degree flexed knee position increases the distance of the neurovascular bundle away from the posterior bony aspect.

Functional evaluation in cruciate-retaining-type TKA: anatomical relationship between tibial osteotomy level and PCL attachment

INTRODUCTION

The level and morphology of posterior cruciate ligament (PCL) attachment vary greatly among individuals, and the function of the PCL after tibial osteotomy performed during total knee arthroplasty (TKA) surgery remains unclear. Therefore, we evaluated the resection amount of PCL attachment and the function of the residual PCL in cruciate-retaining (CR)-type TKA.

METHODS

We examined 76 patients with knee osteoarthritis who had undergone CR-type TKA. The level of the tibial PCL attachment was measured by preoperative MRI and the amount resected into the tibial PCL attachment from the osteotomy level as well as the longitudinal diameter of the residual PCL by postoperative radiography. The relationships between these and joint gap tension value at flexion or amount of tibial posterior transfer by postoperative stress radiography were examined.

RESULTS

The longitudinal diameter of the PCL attachment and the attachment level varied widely among patients. There were 39 patients (51%) with tibial osteotomy level caudal to the PCL attachment. Flexion gap tension in patients with residual PCL (residual PCL group) was slightly higher than those without residual PCL (fully-resected group). There was no correlation between amount of PCL residual and joint gap tension at the flexion position. Even in those without residual PCL, no correlation was observed between the resected amount and flexion joint gap tension value. Comparison of amount of posterior transfer by postoperative stress radiography between those with and without residual PCL revealed no significant difference.

CONCLUSIONS

It was confirmed that the level and morphology of the PCL attachment vary greatly among individuals and the amount of PCL resected at tibial osteotomy during TKA surgery varies depending on the patient. The tension due to flexion position tended to decrease if the tibial osteotomy line was caudal to the PCL attachment; however, the amount of tibial posterior transfer due to stress was not changed.

The posterior cruciate ligament: a study on its bony and soft tissue anatomy using novel 3D CT technology

PURPOSE

The bony insertion sites of the PCL have been studied and described extensively using 2D technology such as macroscopic images, plain radiograph, computerized tomography (CT) and MRI. The purpose of this study is to visualize both the tibial and the femoral bony insertion sites but also the soft tissue anatomy of the native PCL using novel 3D CT imaging. In addition, new concepts of best-fit cylinder and central axis are introduced and evaluated.

METHODS

Nine unpaired knees of embalmed cadavers were used in this study. Following the dissection process, the PCL was injected with a contrast medium for computed tomography (CT) imaging. The obtained CT images were segmented and rendered in 3D allowing morphological and morphometric analysis of PCL. Femoral and tibial footprint surface area, best-fit PCL-cylinder intersection area, best-fit PCL-cylinder/footprint coverage ratio, best-fit PCL-cylinder central axis projections at the tibial and femoral footprint were used to describe the anatomy of the PCL.

RESULTS

Mean footprint surface area of the tibial and femoral footprint were 189.1 and 293.3 mm², respectively. The mean diameter of the best-fit cylinder was 10.5 mm. The mean coverage of the best-fit cylinder on the tibial and femoral footprint was 76.5 and 46.5, respectively. The best-fit cylinder central axis was located in the anterolateral AL bundle footprint on the femur and more centrally in the PCL footprint on the tibia.

CONCLUSION

This study is the first to describe the detailed anatomy of the human PCL with respect to its course and footprints using a 3D approach. It confirms the large difference between the tibial and the femoral footprint area with the former being significantly smaller. In addition, a large inter-patient variability is observed. The best-fit cylinder and central axis concept offer additional insights into the optimal tunnel placement at the tibia and femoral footprint in order to cover the largest portion of the native PCL soft tissue.

ACL-PCL and intercondylar notch impingement: magnetic resonance imaging of native and double-bundle ACL-reconstructed knees

PURPOSE

The purpose of this study was to: (1) define the relationship between the ACL and PCL in normal knees; (2) determine whether ACL-PCL impingement occurs in native knees; and (3) determine whether there is a difference in impingement between double-bundle reconstructed and native knees.

METHODS

Eight subjects were identified (age 20-50; 6 females, 2 males). All were at least 1-year status postanatomic double-bundle ACL reconstruction (allograft; AM = 8 mm; PL = 7 mm) and had no history of injury or surgery to the contralateral knee. MRIs of both knees were performed with the knee at 0 and 30° of flexion. The images were evaluated by a non-treating surgeon and two musculoskeletal radiologists. Coronal and sagittal angles of AM and PL bundles, Liu's PCL index and the distance between ACL and PCL on modified axial oblique images were recorded. Impingement was graded (1) no contact; (2) contact without deformation; or (3) contact and distortion of PCL contour.

RESULTS

Seventy-five percent (6) of the native ACL's showed no contact with the roof of the intercondylar notch or PCL, compared to 25 % (2) of the double-bundle reconstructed ACLs. One double-bundle reconstructed ACL showed intercondylar notch roof and ACL-PCL impingement (12.5 %). Significant differences were found between the native ACL and the double-bundle reconstructed ACL for the coronal angle of the AM (79° vs. 72°, p = 0.002) and PL bundle (75° vs. 58°, p = 0.001). No differences in ROM or stability were noted at any follow-up interval between groups based on MRI impingement grade.

CONCLUSION

ACL-PCL contact occurred in 25 % of native knees. Contact between the ACL graft and PCL occurred in 75 % of double-bundle reconstructed knees. ACL-PCL impingement, both contact and distortion of the PCL, occurred in one knee after double-bundle reconstruction. This study offers perspective on what can be considered normal contact between the ACL and PCL and how impingement after ACL reconstruction can be detected on MRI.

LEVEL OF EVIDENCE

Cohort Study, Level III.

[Anatomic features of posterior septum of knee joint and its application in posterior trans-septal portal for arthroscopic surgery]

OBJECTIVE

To summarize the anatomic features of the posterior septum of the knee joint and its application in posterior trans-septal portal for arthroscopic surgery.

METHODS

The literature related to posterior septum of the knee joint and arthroscopic surgery was extensively reviewed and analyzed.

RESULTS

The posterior septum of the knee joint has more mechanoreceptors and blood vessels in the upper part, which are close to arteria popliteal at the tibial plateau level; the posterior compartment is divided into wider posteromedial and narrower posterolateral compartments. A safe arthroscopic trans-septal portal is established, in the knee flexion of 90 degrees, in a lateral-to-medial direction, and with an inserting location below the middle of posterior septum.

CONCLUSION

The establishment method of posterior trans-septal portal is not uniform and all the features of posterior septum should be considered to decrease the complications.

Radiographic assessment of the safe zone for medial oblique opening wedge high tibial osteotomy

PURPOSE

To compare different cephalocaudal angles of the X-ray beam in measuring internal rotation of the proximal tibia that best demonstrates the safe zone.

METHODS

10 pairs of embalmed, disarticulated knee joints from 10 cadavers were used. Soft tissues around the proximal tibia and the proximal tibiofibular joint (PTFJ) were dissected to reveal the articular cartilage. A narrow area between the end of the articular cartilage of the posterolateral proximal tibia and of the PTFJ was identified as the safe zone with a U-shape metal used as a radiographic marker. Translation of the proximal tibia was controlled during internal rotation of the proximal tibia. Internal rotation of the proximal tibia that best demonstrated the safe zone (the U-shape metal at its most outermost point) was measured at 0º, 5º, 10º, 15º, 20º, and 25º cephalocaudal angles of the X-ray beam.

RESULTS

The mean internal rotation of the proximal tibia that best demonstrated the safe zone at 0º, 5º, 10º, 15º, 20º, and 25º cephalocaudal angle of the X-ray beam were 50º, 45º, 37º, 32º, 23º, and 19º, respectively.

CONCLUSION

The safe zone was best demonstrated with 50º and 45º internal rotation of the proximal tibia at 0º and 5º cephalocaudal angles of the X-ray beam, respectively.

In vivo open-bore MRI reveals region- and sub-arc-specific lengthening of the unloaded human posterior cruciate ligament

Open-bore MRI scanners allow joint soft tissue to be imaged over a large, uninterrupted range of flexion. Using an open-bore scanner, 3D para-sagittal images of the posterior cruciate ligament (PCL) were collected from seven healthy subjects in unloaded, recumbent knee extension and flexion. PCL length was measured from one 2D MRI slice partition per flexion angle, per subject. The anterior surface of the PCL lengthened significantly between extension and flexion (p<0.001). Conversely, the posterior surface did not. Changes were not due to the PCL moving relative to the 2D slice partition; measurements made from 3D reconstructions, which compensated for PCL movement, did not differ significantly from measurements made from 2D slice partitions. In a second experiment, videos of knee flexion were made by imaging two subjects at several flexion angles. Videos allowed soft tissue tracking; examples are included. In a third experiment, unloaded knees of seven healthy, recumbent subjects were imaged at extension and at 40°, 70°, 90°, 100°, 110° and 120° flexion. The distance between PCL attachments increased between extension and 100°, and then decreased (p<0.001). The anterior surface of the PCL lengthened over the flexion angles measured (p<0.01). The posterior surface of the PCL lengthened between extension and 40° and then shortened (p<0.001). Both attachment separation and anterior surface length increased dramatically between extension and 40°, but varied less afterwards. Results indicate that PCL dynamics differ between terminal extension and active function sub-arcs. Also, attachment separation cannot predict the lengthening of all parts of the PCL, nor can lengthening of one part of the PCL predict the lengthening of another part. A potential connection between lengthening and loading is discussed. We conclude that low-field MRI can assess ligament lengthening during flexion, and that the dynamics of the PCL for any given region and sub-arc should be measured directly.

Anatomical study of the anterolateral and posteromedial bundles of the posterior cruciate ligament for double-bundle reconstruction using the quadruple bone-tunnel technique

BACKGROUND

Several techniques have been described for posterior cruciate ligament (PCL) reconstruction. However, double-bundle PCL reconstruction using the quadruple bone-tunnel technique has been seldom reported. The current study investigated this technique, focusing on the anatomy of the femoral and tibial insertions of the anterolateral (AL) and posteromedial (PM) bundles of the PCL.

METHODS

Twenty-two fresh, healthy adult cadaveric knees were dissected and measured. The PCL was divided into the AL bundle and PM bundle at the insertion footprint. The insertion footprints of the AL and PM bundles, their location, size, and the clock positions were measured and described.

RESULTS

On the femur, the clock position of the footprint of the AL bundle was 11:21 ± 0:23 (left) or 0:39 ± 0:23 (right), and the PM bundle was 9:50 ± 0:18 (left) or 2:10 ± 0:18 (right), with the knee flexed at 90 degrees. The distances from the center of the femoral insertions of the AL and PM bundles to the anterior cartilage margins of the medial femoral condyle were (7.79 ± 1.22) mm and (8.36 ± 1.63) mm, respectively. On the tibia, the vertical distances from the center of the tibial insertions of the AL and PM bundles to the tibial articular surface were (3.25 ± 1.20) mm and (6.91 ± 1.57) mm, respectively.

CONCLUSIONS

These results have led to a better definition of the anatomy of the AL and PM bundle footprint of the PCL. The technique of double-bundle PCL reconstruction using quadruple bone-tunnel is feasible. Application of these data during PCL reconstruction using the quadruple bone-tunnel technique may help optimize knee stability.

How much of the PCL is really preserved during the tibial cut?

PURPOSE

There are two different techniques for retaining the posterior cruciate ligament (PCL) in total knee arthroplasty. The attachment of the PCL can be spared during resection of the tibial plateau, so that a small posterior bone block remains. In contrast to this, many surgeons resect the tibial plateau completely and detach a part of the tibial PCL attachment from the resected material. The objective of this study was to determine how big this part is in an anatomical resection of the tibial plateau with 0° and 7° slope and whether it is gender-dependent.

METHODS

Two hundred consecutive patients who had undergone MRI of a knee joint were included. Patients were excluded if they were younger than 18 years or had dysplasia of the knee joint or injuries of the posterior cruciate ligament. The MRIs of 182 knees that fulfilled the inclusion criteria were analysed. For each knee, an anatomical tibial resection with 0° and 7° posterior slope was simulated, and the parts of the tibial PCL attachment that were resected and retained were determined.

RESULTS

Given a measured tibial resection with 0° slope, 45 ± 28% of the tibial PCL attachment was removed in the men, compared with 46 ± 30% in the women (n.s.). Given a resection with 7° slope, 69 ± 24% of the tibial PCL attachment was removed in the men and 67 ± 25% in the women. This corresponded to a complete resection in 19 men (20%) and 16 women (24%).

CONCLUSIONS

Independently of gender, the anatomical resection of the tibia leads to the removal of a considerable part of the tibial PCL attachment, if this is not spared in the form of a bone block during resection. This becomes increasingly relevant with higher posterior slope of the resection plane. In the case of a cruciate-retaining surgical technique, the retention of the posterior tibial cortical bone in the area of attachment of the PCL is therefore strongly recommended.

LEVEL OF EVIDENCE

II.

Posterior cruciate ligament: anatomy, biomechanics, and outcomes

The optimal treatment of posterior cruciate ligament ruptures remains controversial despite numerous recent basic science advances on the topic. The current literature on the anatomy, biomechanics, and clinical outcomes of posterior cruciate ligament reconstruction is reviewed. Recent studies have quantified the anatomic location and biomechanical contribution of each of the 2 posterior cruciate ligament bundles on tunnel placement and knee kinematics during reconstruction. Additional laboratory and cadaveric studies have suggested double-bundle reconstructions of the posterior cruciate ligament may better restore normal knee kinematics than single-bundle reconstructions although clinical outcomes have not revealed such a difference. Tibial inlay posterior cruciate ligament reconstructions (either open or arthroscopic) are preferred by many authors to avoid the "killer turn" and graft laxity with cyclic loading. Posterior cruciate ligament reconstruction improves subjective patient outcomes and return to sport although stability and knee kinematics may not return to normal.

[Applied anatomical research of location of bone tunnel for posterolateral corner reconstruction of knee]

OBJECTIVE

To obtain the anatomical data of the insertions of the lateral collateral ligament (LCL), popliteus tendon (PT), and popliteofibular ligament (PFL) for the posterolateral corner of the knee (PLC) reconstruction.

METHODS

Thirty human cadaveric knees were chosen to observe the structure of PLC, including 14 males and 16 females with an average age of 55 years (range, 45-71 years ). The insertions of LCL, PT, and PFL were identified, then the distances from the centers of the insertions to specific bony landmarks were measured, which were lateral epicondyle, the most proximal point on the styloid process and the most anterior point on the anterior surface of the fibular head. Normalization processing of the actual numerical values from each knee was performed.

RESULTS

The center of the LCL insertion was at the site of (1.27 +/- 3.10) mm proximal and (2.99 +/- 1.29) mm posterior to the lateral epicondyle of the femur respectively, and the center of the PT insertion was at the site of (8.85 +/- 3.38) mm distal and (3.83 +/- 1.95) mm posterior to the lateral epicondyle of the femur respectively. The center of the LCL insertion was at the site of (10.56 +/- 2.17) mm distal and (7.51 +/- 1.81) mm anterior to the nearest point of the fibular styloid respectively, and the center of the PFL insertion was at the sites of (1.31 +/- 0.55) mm distal and (0.49 +/- 1.36) mm anterior to the nearest point of the fibular styloid respectively. The cross-sectional area of the insertions of femur was (44.96 +/- 13.29) mm2 for the LCL and (52.52 +/- 11.93) mm2 for the PT, respectively; the cross-sectional area of the insertions of fibula was (35.93 +/- 11.21) mm2 for the LCL and (14.71 +/- 6.91) mm2 for the PFL, respectively.

CONCLUSION

The LCL, PT, and PFL have a consistent pattern of insertion.

An analysis of the posterior cruciate ligament isometric position using an in vivo 3-dimensional computed tomography-based knee joint model

PURPOSE

This study aimed to review the isometric point of the posterior cruciate ligament (PCL) based on insertional locations identified in recent anatomic studies by use of a 3-dimensional knee model.

METHODS

Ten living subjects with healthy knees were evaluated. High-resolution computed tomography scans were performed at 3 positions of 0°, 90°, and 135°, and 3-dimensional knee images were constructed. Customized software was used to define tibial and femoral insertion points of the PCL, based on recently described anatomy. The femoral attachment site of the PCL was divided into 4 sectors (labeled A through D), and the tibial attachment site was divided into 6 sectors (labeled 1 through 6). Twenty-four virtual PCL bundles were created between these sectors, and their length was measured in the 3 knee flexion positions.

RESULTS

In 0° and 90° of knee flexion, the virtual bundle showing the least amount of length change (1.10 ± 0.66 mm) was at sector D-6, that is, a posteromedial bundle inserting into the most posterior femoral sector (sector D) and the most distal tibial sector (sector 6). This change was not significantly different compared with all other virtual bundles with tibial points connected to femoral sector D (P > .05). An isometric position for the PCL (length change <2 mm) could not be found in 135° of knee flexion because of lengthening of all virtual bundles.

CONCLUSIONS

Our data suggest that the femoral attachment point is more important than the tibial attachment point: any of the 6 tibial bundles attached to the most posterior femoral sector had similar isometric properties.

CLINICAL RELEVANCE

Reproducing normal tibial and femoral anatomy underpins PCL surgical reconstruction. These findings suggest that to perform an isometrically accurate PCL reconstruction, particular attention should be paid to the location of the femoral attachment site, once the tibial footprint has been established. There were no isometric points in any virtual PCL bundle in the fully flexed knee because of excessive lengthening. Therefore, to avoid lengthening of the reconstructed graft, we recommend that fixation is performed at knee flexion angles between 0° and 90° and that patients avoid high flexion during postoperative rehabilitation.

Anatomic single- and double-bundle anterior cruciate ligament reconstruction flowchart

Anatomy is the foundation of orthopaedic surgery, and the advancing knowledge of the anterior cruciate ligament (ACL) anatomy has led to the development of improved modern reconstruction techniques that approach the anatomy of the native ACL. Current literature on the anatomy of the ACL and its reconstruction techniques, as well as our surgical experience, was used to develop a flowchart that can aid the surgeon in performing anatomic ACL reconstruction. We define anatomic ACL reconstruction as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. A guideline was written to accompany this flowchart with more detailed information on anatomic ACL reconstruction and its pitfalls, all accompanied by relevant literature and helpful figures. Although there is still much to learn about anatomic ACL reconstruction methods, we believe this is a helpful document for surgeons. We continue to modify the flowchart as more information about the anatomy of the ACL, and how to more closely reproduce it, becomes available.

Anatomy of the posterior cruciate ligament

The purpose of the study was to explain the architecture of the posterior cruciate ligament because the views on its structure presented in the literature are inconsistent - from those considering it as indivisible to those presenting it as a multifascicular structure. Twenty formalin-fixed ligaments from human knee joints were tested using the preparation technique. All posterior cruciate ligaments clearly divided into the anterolateral bundle and the posteromedial bundle (20/20). In all ligaments, 2 fascicles were identified in the posteromedial bundle (20/20). In most cases, 2 fascicles were also seen in the anterolateral bundle (14/20). Less commonly, it consisted of multiple fascicles (6/20).

A novel approach to the dissection of the human knee

The knee is one of the most frequently injured joints of the human body with injuries affecting the general population and the athletic population of many age groups. Dissection procedures for the knee joint typically do not allow unobstructed visualization of the anterior cruciate or posterior cruciate ligaments without sacrificing the collateral ligaments. In many cases, the relationships of the intraarticular structures are lost as dissection systematically removes superficial structures to gain access to deeper structures. The authors present an alternative technique for dissection of the human knee joint that allows maximal visualization of intraarticular structures such as the cruciate ligaments and menisci with minimal disturbance to the tibial and fibular collateral ligaments, thus preserving the relationships of the ligamentous and intraarticular structures.

Anatomic relation between the posterior cruciate ligament and the joint capsule

PURPOSE

The aim of this anatomic study on cadavers was to determine the anatomic relation between the posterior cruciate ligament (PCL) and the posterior joint capsule attachment.

METHODS

Thirty knees were dissected by means of a posterior approach to the knee. The presence of the posterior popliteal ligament and Wrisberg meniscofemoral ligament was observed and a U-shaped capsulotomy was performed while preserving the distal insertion of the ligament. After detaching the PCL and determining its area on the tibia, we determined its geometric center and posterior margin and measured the distances between the tibial insertion of the capsule and these points.

RESULTS

The distance between the center of the PCL and the posterior capsule was 10.3 mm, and the distance between the posterior margin of the PCL and the capsule was 1.7 mm. The posterior popliteal ligament was easy to see in all the specimens, measuring around 42 mm in length. The Wrisberg meniscofemoral ligament was seen in 12 specimens.

CONCLUSIONS

We can conclude that the distances from the center of the tibial insertion and the margin of the PCL to the joint capsule were 10.3 mm and 1.7 mm, respectively, thus enabling greater knowledge of the anatomy of the posterior compartment of the knee.

CLINICAL RELEVANCE

Our findings provide anatomic data that increase the safety and knowledge regarding the surgical procedures related to the PCL, because we have supplied information that can contribute to obtaining the best arthroscopic view of this area, thus decreasing the risk of vascular and nerve damage.

[The clinical anatomical research of the tibial attachment of the posterior cruciate ligament and the tibial tunnel position in double-bundle posterior cruciate ligament reconstruction]

OBJECTIVES

To provide the data on the shape, sizes, and locations of the attachments of the anterolateral bundle (ALB) and posteromedial bundle (PMB) of the posterior cruciate ligament (PCL) to the tibia, and to determine the reference landmarks and the methods for tibial tunnel positioning in double-bundle PCL reconstruction using double-double tunnel.

METHODS

Thirty cadaveric knees were used as specimens. PCLs were separated into bundles according to the PCL tension pattern during knee flexion-extension, and the functional bundle in each bundle was determined. Data were obtained to describe the size, shape, position, and center of the attachments of PCL bundles. The reference landmarks and methods for tibial tunnels positioning in double-bundle PCL reconstruction using double-double tunnel were determined.

RESULTS

The PCL insertion site was situated in the posterior intercondylar fossa. The longitudinal axis of the tibial attachment of PCL proceeded from proximal medial to distal lateral, and the mean angle between them and the tibial shaft was (16.5 +/- 1.4) degrees . The tibial insertion site of ALB and PMB were arranged in the proximal and distal on the whole, the tibial attachment of ALB could generally be described as rhomb in shape, and the mean area of it was (90 +/- 20) mm(2); the tibial attachment of PMB was rectangle in shape, the mean area of it was (96 +/- 32) mm(2), there was no statistic difference between the area of them (P > 0.05). There were functional bundles in both ALB and PMB persistently, which attached to the distal-lateral portion of the tibial attachment of ALB and the distal-medial portion of the tibial attachment of PMB respectively, they were both oval in shape, the mean area of them were (35 +/- 12) mm(2) and (36 +/- 6) mm(2) respectively, the difference between them was no statistic significant (P > 0.05). The mean distance between the centres of the tibial attachments of the functional bundles of ALB and that of PMB was (12.7 +/- 1.9) mm. The medial tibial spine, lateral tibial spine and the bony ridge on the posterior-proximal tibia were the key anatomic landmarks that could be used to aid in placement of independent tibial tunnels for a 2-bundle PCL reconstruction.

CONCLUSIONS

The tibial attachment of the PCL is sufficiently large to allow for placement of 2 independent tunnels. There are functional bundles in both ALB and PMB persistently and the optimum position for the tibial tunnel in double-bundle PCL reconstruction using double-double tunnel should be located in the attachment sites of the functional bundles of ALB and PMB.

Anatomy of the posterior cruciate ligament

The views on the structure of the posterior cruciate ligament presented in the literature are not uniform. They can be ranged from those that refer to the ligament as an indivisible structure to those that regard it as an increasingly complex structure consisting of a number of bundles. The divisions are based on criteria related to the attachments, arrangement and functions of the components of the posterior cruciate ligament. Some researchers also specify the role of the receptors of the ligament.

Experimental evaluation of 3-dimensional kinematic behavior of the cruciate ligaments

PURPOSE

The purpose of this study was to evaluate a low-cost and easily reproducible technique for biomechanical studies in cadavers. In this kind of study, the natural effect of loading of the joint and shear forces are not taken into account. The objective is to describe the plastic deformation of the ligaments into 3-dimensional space.

METHOD

For 18 intact human cadaver knees, the cruciate ligaments were divided into 3 fiber bundles, the tibial or femoral fixation points were marked, and 2 perpendicular different x-ray exposures were performed, thus obtaining radiographs of spatial projections of the bundle in 3 anatomic planes (frontal, sagittal, and transversal). From the measurements made on the x-ray films, we obtained the average distance between the 2 fixation points of the cruciate ligaments on the tibia and the femur at 4 different flexion angles.

RESULTS

The distance between the fixation points of the medial and lateral fiber bundles of the cruciate ligaments did not change significantly during movement. There were, however, significant variations (P < .05) in the distance between the fixation points of the posterior fiber bundles of the anterior cruciate ligament and the anterior fiber bundles of the posterior cruciate ligament.

CONCLUSIONS

This technique was efficient for demonstrating the plastic deformability of the cruciate ligaments. The results proceeding from this type of study can assist in the planning of physical rehabilitation programs.

Diagnosis and treatment of posterior cruciate ligament injuries

Posterior cruciate ligament (PCL) injuries are less common than other knee injuries and may result in a spectrum of symptoms and disability. The predictive factors that may determine which patients with isolated PCL lesions will develop knee pain and degenerative arthritis have yet to be identified. As such, the optimal treatment algorithm for these patients remains a matter of debate. This article provides a concise review of the anatomy and function of the PCL, as well as an overview of diagnostic methods and treatment options for patients with PCL injuries.

Correlation of intercondylar notch cross sections to the ACL size: a high resolution MR tomographic in vivo analysis

INTRODUCTION

To correlate cross sections of the intercondylar notch to cross sections of the anterior cruciate ligament (ACL) and to analyze gender-related differences in notch and ACL morphometry with an attempt to explain the observation that a small intercondylar notch and the female gender predispose to a rupture of the ACL.

MATERIAL AND METHODS

High resolution MR imaging was performed on a 1.5 T magnet using a dedicated extremity-coil in ten left and ten right knee joints of 20 volunteers (10 male, 10 female, mean age 25 years) with no history of knee abnormalities. Continuous axial T2-weighted MR images perpendicular to the longitudinal axis of the ACL were acquired. Cross-sectional areas of the ACL midsubstance at the contact area to the posterior cruciate ligament were measured. For imaging and evaluation of the osseous limits of the intercondylar notch a 3D-dataset of the knee was acquired. Anterior, middle and posterior planes of the intercondylar notch were calculated and analyzed for measurement of the notch area AN and notch width index NWI. The ratio of the ACL cross-sectional area of the ACL and the cross-sectional area of the notch was defined as the ACL notch index (ANI) and used as a standardized tool for evaluation. For statistical evaluation, linear regression analysis was performed. Mean values between male and female were compared using a t test. In addition, five matched pairs of male and female volunteers of same height were analyzed.

RESULTS

Mean cross-sectional size of the ACL at the crossing with the PCL was 54.4 +/- 20.4 mm2. Regression analysis showed a significant correlation (P < 0.05) of the ACL cross-sectional area to the notch areas on all three planes and NWI, respectively. Comparison between the sexes revealed that female participants had significantly smaller cross-sectional areas of the ACL, the notch areas, the NWI and ANI. This difference was found for both the complete study group and the matched pairs of same height.

CONCLUSIONS

The smaller the intercondylar notch the smaller the cross-sectional area of the ACL midsubstance. In addition to the impingement of the ACL at the anterior and posterior roof of the notch, a biomechanically weaker ACL may be the reason for disposition to an ACL rupture in patients with a small intercondylar notch. Women have a thinner ACL midsubstance than men of the same height which may be one of the critical etiologic factors that predispose women to an ACL rupture.

The attachments of the fiber bundles of the posterior cruciate ligament: an anatomic study

PURPOSE

This study aimed to provide data on the sizes and locations of the attachments of the posterior cruciate ligament (PCL) to the tibia and the femur.

METHODS

We studied 39 cadaveric knees. The PCL consistently separated into anterolateral (AL) and posteromedial (PM) fiber bundles. Data were obtained to describe the size, position, and center of the PCL bundles related to clock positions and referenced to the center of the circular posterior medial condyle on the femur, as well as to the mediolateral and anteroposterior dimensions of the tibia. The coordinates for the femoral attachment of the PCL bundles were measured parallel to the femoral shaft and to the femoral intercondylar notch roof.

RESULTS

A wide variation in shape and size of the PCL attachment was found on the femur, but the pattern of attachment to the tibia was consistent. The tibial attachment of the PCL occupied the posterior intercondylar fossa. The AL bundle's anterior limit was the root of the posterior horn of the medial meniscus, and the PM bundle extended below the joint line by 7 +/- 2 mm (mean +/- SD). On the femur, the AL bundle was centered at 7 +/- 2 mm from the articular cartilage at 10:20 +/- 00:30 o'clock, and the PM bundle was centered at 10 +/- 3 mm from the cartilage at 08:30 +/- 00:30 o'clock. The PCL extended from beyond the 12-o'clock position in all specimens.

CONCLUSIONS

Accurate knowledge of the anatomic positions of the bundles of the PCL on both femur and tibia is essential to developing more successful reconstruction techniques.

CLINICAL RELEVANCE

The results of this study may be applied to the design of guidance systems for double-bundle PCL reconstruction techniques and as a reference for graft tunnel placement in in vitro or clinical follow-up studies.

Advanced MR Imaging of the Cruciate Ligaments

The anterior and posterior cruciate ligaments are crucial stabilizers of the knee. These ligaments are named by the location of their tibial attachments. Each ligament is composed of separate functional bundles that differ in size but are equally important in function. MR imaging is accurate and sensitive, making it the imaging technique of choice for evaluating these ligaments. Acute and chronic injuries involving the cruciate ligaments have typical appearances and associated findings. MR imaging interpretation must take into account atypical injuries and imaging pitfalls. Knowledge of normal ligament reconstruction techniques allows differentiation of the normal postoperative appearance from reconstruction failure and complications. Ligament reconstruction techniques, complications, and appearances are reviewed in this article.

Anatomical study of the femoral and tibial insertions of the anterolateral and posteromedial bundles of human posterior cruciate ligament

For posterior cruciate ligament (PCL) reconstruction, two root, anterolateral and posteromedial bundles restruction are performed. However, little has been mentioned of anatomical measurements of the insertions to the bone of these bundles in previous publications. The aim of this study is to determine the precise anatomical measurements of the femoral and tibial insertions for anterolateral and posteromedial bundles of PCL. A total of 32 femur and 33 tibiae were selected from 50 cadavers after exclusion of knees that displayed macroscopically degenerative changes or evidence of trauma. PCL were divided into anterolateral bundles and posteromedial bundles to the insertion footprint, and those locations were measured and described. The distance from the center of the femoral insertions of the anterolateral and posteromedial bundles, and the Wrisberg ligament to the anterior margin of the medial femoral condyle averaged 9.6, 10.6, and 17.1 mm, respectively. The distance from the center of the femoral insertions of the anterolateral, posteromedial bundles, and Wrisberg ligament to the intercondylar roof averaged 4.8, 11.4, and 10.4 mm, respectively. The distance from the medial margin of the articular cartilage of the tibial plateau to the center of the tibial insertions of the anterolateral and posteromedial bundles averaged 51.0 and 50.0% of the total widest width of the tibial plateau, respectively. The vertical distance from the tibial insertion of the center of the posteromedial bundle to the plane of the tibial articular surface averaged 4.6 mm. This study leads to a better definition of the anatomy of the anterolateral and posteromedial bundles of PCL. It is very important to know the precise anatomy of PCL bundles when performing PCL reconstruction, and to evaluate PCL reconstruction surgery on an anatomical basis.

An analysis of the causes of failure in 57 consecutive posterolateral operative procedures

PURPOSE

To investigate 57 failed posterolateral procedures in 30 consecutive knees to determine factors that may have contributed to the failure.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty patient records were reviewed by an independent surgeon. The index posterolateral operations were done for 13 acute and 17 chronic knee injuries. The anterior cruciate ligament was ruptured in 17 knees, the posterior cruciate ligament was torn in 5 knees, and both cruciates were ruptured in 8 knees. In 25 knees, 46 revision posterolateral procedures had been performed, of which 27 had also failed (in 21 knees). Five knees did not undergo revision of the posterolateral structures.

RESULTS

In 22 knees, multiple factors were identified that most likely contributed to the failure of the posterolateral procedures. The most common factors were nonanatomical graft reconstruction (23 knees), untreated varus malalignment (10 knees), and failure to successfully reconstruct all ruptured knee ligaments, including cruciates (27 knees). Thirty-nine anterior cruciate ligament procedures were done in 24 knees, including 24 primary and 15 revision operations. Seventeen posterior cruciate ligament procedures were done in 13 knees, including 13 primary and 4 revision operations. At the time of writing, 16 of 24 knees had a functional anterior cruciate ligament graft and 5 of 13 had a functional posterior cruciate ligament graft.

CONCLUSION

The results suggest greater emphasis during the index operation for anatomical graft reconstruction of one or more of the posterolateral structures as necessary, restoration of all ruptured cruciate ligaments, and correction of varus malalignment.

The incidence and cross-sectional area of the meniscofemoral ligament

BACKGROUND

The incidence, morphologic characteristics, and cross-sectional area of meniscofemoral ligaments of the knee are still not clarified.

HYPOTHESIS

The incidence of meniscofemoral ligaments is very high, and they contribute significantly to the cross-sectional area of the posterior cruciate ligament complex.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Clinical study: During arthroscopic anterior cruciate ligament reconstruction, the presence of a meniscofemoral ligament was confirmed in 38 patients (16 men, 22 women; mean age, 23.6 years) by observation and probing. Laboratory study: Posterior cruciate ligaments with the lateral meniscus attached were obtained as specimens from 30 patients (3 men, 27 women; mean age, 71.9 years) during total knee arthroplasty. The posterior cruciate ligament and meniscofemoral ligaments were observed, and the cross-sectional area was measured using an area micrometer.

RESULTS

Clinical study: The anterior meniscofemoral ligament was found in 36.8% of patients, the posterior meniscofemoral ligament was found in 71.1%, and both ligaments were found in 26.7%. The overall incidence of at least 1 meniscofemoral ligament was 84.2%. Laboratory study: The anterior meniscofemoral ligament was present in 5 (16.7%) cases, and the posterior meniscofemoral ligament was present in all cases (100.0%). The cross-sectional area of the posterior cruciate ligament proper was 50.1 +/- 16.9 mm(2), that of the anterior meniscofemoral ligament was 2.3 +/- 1.2 mm(2), and that of the posterior meniscofemoral ligament was 7.5 +/- 2.5 mm(2). The mean ratio of the cross-sectional area of meniscofemoral ligaments to the posterior cruciate ligament proper was 17.2% (4.0%-38.9%). The origin of the posterior meniscofemoral ligament from the posterior horn of the lateral meniscus could be classified into 5 types.

CONCLUSION

The meniscofemoral ligaments contributed significantly to the cross-sectional area of the posterior cruciate ligament complex.

Proximity of the popliteal artery to the PCL during simulated knee arthroscopy: implications for establishing the posterior trans-septal portal

This study defines the sagittal distance from the posterior cruciate ligament (PCL) to the popliteal artery under simulated arthroscopic conditions. This information is relevant for posterior knee arthroscopy, particularly for the safe establishment of the posterior trans-septal portal. Measurements from the PCL to the popliteal artery were made on sagittal magnetic resonance images obtained in a previous study of 10 fresh-frozen cadaveric knees. The mean sagittal distance from the mid-PCL to the popliteal artery was 29.1 +/- 11 mm (range: 18-55 mm). The mean sagittal distance from the proximal PCL fovea to the popliteal artery was 9.7 +/- 5 mm (range: 3-16 mm). The results of this study provide the arthroscopist working in the posterior compartments of the knee with a more detailed knowledge of the anatomic relationship between the PCL and popliteal artery. This knowledge will help minimize the risk of iatrogenic vascular injury during arthroscopic knee surgery.

Morphometric side-to-side differences in human cruciate ligament insertions

Graft placement in cruciate ligament reconstruction is known to significantly influence postoperative knee stability and range of motion. Improvement of bone tunnel positioning has been advocated by computer-assisted surgical procedures that require reliable input and reference data. This study validates the hypothesis that morphometric reference data can be obtained from the uninjured controlateral knee for accurate bone tunnel and graft positioning. Thirty pairs of human cadaver knees were dissected and the femoral and tibial footprints of the anterior and posterior cruciate ligaments (PCL) were radiopaquely marked. Radiographs were taken of the corresponding left- and right-sided femora and tibiae, and digitally processed. Controlateral specimens were mirrored and overlapped precisely, the areas and intersections of ligament insertion were digitally determined. There were no significant differences in the total area of cruciate ligament insertion between left and right knee specimens or between female and male specimens. Intersection areas (IAs) in femoral and tibial anterior cruciate ligament (ACL) insertions averaged 31.3 and 33.4% of the total insertion area, respectively. The center of gravity for the femoral and tibial ACL footprint differed by 4.7 and 4.5 mm between left and right knees, respectively. IAs in femoral and tibial PCL insertions averaged 46.1 and 61.3% of the total insertion area, respectively. The center of gravity for the femoral and tibial PCL footprint differed by 4.5 and 2.4 mm between left and right knees, respectively. Our study does not support the concept of obtaining morphologic reference data from the uninjured controlateral knee for individual bone tunnel placement.

Analysis of meniscofemoral ligament tension during knee motion

PURPOSE

The goal of this study was to show a functional role for the meniscofemoral ligaments (MFL) by analyzing MFL tension change through the full range of flexion and extension found at the human knee joint.

METHODS

Ten fresh-frozen human knees containing both the anterior and posterior MFLs (aMFL and pMFL) were studied. An analysis of ligament tension during passive motion was undertaken using an isometric transducer.

RESULTS

The MFLs functioned in a nonisometric and reciprocal manner. The aMFL developed tension with flexion and the pMFL tension with extension. The aMFL tension increased with tibial external rotation compared with internal rotation. Combined MFL tension was greater in flexion (P < .001) and increased as the tibia was externally rotated (P = .008).

CONCLUSIONS

The MFL tension changes identified through knee flexion and extension support the theory that the MFLs have a functional role in knee stability and protection. This warrants their consideration in the clinical management of meniscal and PCL injuries.

CLINICAL RELEVANCE

This cadaver study of the lateral MFLs indicates that the anterior and posterior portions work in a reciprocal manner with flexion and extension and supports the fact that these ligaments have a functional role in the human knee joint.

Anatomy of the posterior cruciate ligament and the meniscofemoral ligaments

This paper describes the anatomy of the posterior cruciate ligament (PCL) and the meniscofemoral ligaments (MFLs). The fibres of the PCL may be split into two functional bundles; the anterolateral bundle (ALB) and the posteromedial bundle (PMB), relating to their femoral attachments. The tibial attachment is relatively compact, with the ALB anterior to the PLB. These bundles are not isometric: the ALB is tightest in the mid-arc of knee flexion, the PMB is tight at both extension and deep flexion. At least one MFL is present in 93% of knees. On the femur, the anterior MFL attaches distal to the PCL, close to the articular cartilage; the posterior MFL attaches proximal to the PCL. They both attach distally to the posterior horn of the lateral meniscus. Their slanting orientation allows the MFLs to resist tibial posterior drawer.

Posterior Cruciate Ligament Recess and Normal Posterior Capsular Insertional Anatomy: MR Imaging of Cadaveric Knees

PURPOSE

To analyze the normal pattern of fluid accumulation adjacent to the posterior cruciate ligament and anatomic variations of joint capsule insertion sites in the posterosuperior corner of the human knee by using magnetic resonance (MR) imaging in cadaveric specimens.

MATERIALS AND METHODS

Fourteen fresh cadaveric knees (obtained and used according to institutional guidelines, with informed consent from relatives of the deceased) from 11 men and three women (six left knees, eight right knees; age range, 70-82 years at time of death; mean age, 76 years +/- 4.4 [standard deviation]) were studied with high-spatial-resolution MR imaging performed before and after intraarticular injection of 35-45 mL gadopentetate dimeglumine. MR images were evaluated by two readers in consensus, with emphasis on location of fluid posterior to the posterior cruciate ligament, communication of that fluid with the medial or lateral compartment of the knee, and the relation of fluid to surrounding structures. Readers also were asked to measure, in the sagittal plane, the distance between the posterior capsular insertion sites and the femoral physeal scar. For anatomic analysis, cadaveric specimens were sectioned in 3-mm-thick slices in the sagittal plane that approximated the sections acquired at MR imaging.

RESULTS

In all 14 cadaveric specimens, MR arthrographic images showed a fluid collection behind the posterior cruciate ligament (in the posterior cruciate ligament recess), a finding not evident on images obtained prior to contrast material injection. The recess was distended during flexion, and it communicated only with the medial femorotibial compartment in all cases. Posterior to the posterior cruciate ligament recess, a fat pad was observed in all specimens. Incomplete joint capsule was seen behind the fat pad in seven specimens. Joint capsule insertion was at the level of the femoral physeal scar or between it and a point 15 mm above it.

CONCLUSION

The posterior cruciate ligament recess has specific characteristics that allow its identification: communication with the medial compartment of the knee and absence of the adjacent joint capsule.

Elastic properties of an intact and ACL-ruptured knee joint: measurement, mathematical modelling, and haptic rendering

An analytical, dynamic model of the human knee joint has been developed to simulate the unloaded knee joint behaviour in 6 degrees of freedom. It is based on extensive robot-based measurements of the elastic properties of a human cadaver knee joint. The measured data are compared with data from the literature to ensure that a proper database for modelling is used. The analytical modelling of the passive elastic joint properties is done with Local Linear Model Trees. The deduced knee joint model incorporates passive elastic properties of the internal knee joint structures, passive elastic muscle forces, damping forces, gravitational forces, and external forces. There are two sets of parameters, one simulating the movement of the intact knee joint, and a second simulating the knee joint with ruptured anterior cruciate ligament. The dynamic model can be easily processed in real-time. It is implemented in the haptic display of the Munich Knee Joint Simulator (MKS), which enables a person to move a plastic leg driven by a robot manipulator and feel the simulated knee joint force. Orthopaedic physicians judged the performance of the dynamic knee joint model by executing physical knee joint tests at the MKS.

The anatomic characteristics of the tibial insertion of the posterior cruciate ligament

PURPOSE

The purpose of the study was to better define the tibial insertion of the posterior cruciate ligament (PCL) and to identify landmarks that could be used to aid in placement of independent tibial tunnels for a 2-bundle PCL reconstruction.

TYPE OF STUDY

Descriptive anatomic study.

METHODS

Ten knees from 8 cadavers were dissected and the PCL was identified. The ligament was peeled away from its insertion and the sides of the insertion site were measured and recorded. The 4 corners of the insertion site were identified and marked. Observations were made of the morphology of the insertion site and the presence of any reproducible anatomic landmarks. A note was made of landmarks that could be easily identified on all of the specimens by direct vision and by palpation with a probe.

RESULTS

The ligament consisted of 2 regions, 1 anterolateral, and 1 posteromedial, with a gradual change in the laxity of the ligament as the knee was passed through flexion and extension. The insertion site was situated in a depression between the plateaus of the tibia and extended below the articular surface. The average length +/- standard deviation of the 4 sides was 128 +/- 21.2 mm (medial side), 107 +/- 26.5 mm (superior side), 160 +/- 30.0 mm (lateral side), and 169 +/- 34.5 mm (inferior side). The shape and sides of the insertion site were visually similar among the 10 specimens. The superolateral and superomedial corners were both represented by depressions and a reproducible ridge represented the inferior border. These structures could be visualized as well as palpated on all specimens.

CONCLUSIONS

Based on the findings of this study, we describe the anatomic characteristics of the tibial footprint of the PCL. Anatomic reference points that represent the corners of the tibial insertion of the PCL were identified by direct vision or palpation consistently on all specimens included in the study. These reference points could potentially aid in the placement of an anterolateral and posteromedial tibial tunnel for a 2 tibial tunnel PCL reconstruction.

CLINICAL RELEVANCE

Reproducible anatomic reference points exist at the tibial insertion of the PCL that can be identified by direct vision and palpation. These reference points may potentially aid in the placement of separate tibial tunnels for a 2-bundle PCL reconstruction.

Variability of extraarticular tibial rotation references for total knee arthroplasty

Anatomic reference axes that determine rotational alignment of the tibial component have not been established. To assess variability of three anatomic reference axes (a new tibial anteroposterior axis that we proposed, the transmalleolar axis of the ankle, and the second metatarsus bone axis of the foot), we measured the angles between a defined anteroposterior axis of the tibia (a line perpendicular to the transepicondylar axis) and each of the three axes in 57 knees of healthy subjects using computed tomography scans. The angle between the defined anteroposterior axis and our proposed anteroposterior axis (a line connecting the middle of the posterior cruciate ligament and the medial edge of the patellar tendon attachment) averaged -0.2 degrees +/- 2.8 degrees (range, -5.5 degrees -6.3 degrees). The angle between the defined anteroposterior axis and the transmalleolar axis averaged 25.9 degrees +/- 9 degrees (range, 8 degrees -49.4 degrees), and the angle between the defined anteroposterior axis and the second metatarsus bone axis averaged 5.2 degrees +/- 10 degrees (range, -21.9 degrees -24 degrees). The variability of the anteroposterior axis was less than than the other reference axes. These data indicate that our proposed tibial anteroposterior axis is more reliable for determining rotational alignment of the tibial component in total knee arthroplasty.

Ultrasonographic examination of the normal and injured posterior cruciate ligament

PURPOSE

The purpose of the study was to determine the echogenicity and thickness of both the normal and injured posterior cruciate ligament (PCL).

METHODS

Eight patients with anterior cruciate ligament injury received ultrasonographic evaluation during arthroscopic examination. With the aid of the comet-tail artifact produced by the metal hook during arthroscopic examination, the normal PCL was located on sonograms. Thereafter, 11 patients with PCL injury were examined. In all subjects, the PCL thickness was measured at 2.0 cm proximal from posterior end of the distal PCL inserting onto the tibia.

RESULTS

The normal PCL was located just posterior to the posterior tibial intercondylar area. It was hypo-echoic and was thickened proximally and tapered distally. The mean thickness of the injured PCL was 0.71 +/- 0.12 cm, which was significantly (p < 0.05) greater than that of the normal ligament (0.52 +/- 0.08 cm). Different appearances could be observed, including ligamental rupture and avulsion fracture of the tibial insertion of the PCL.

CONCLUSIONS

The normal PCL appears on longitudinal sonograms as a hypoechoic fan-shape structure. Sonographic examination can identify different types of PCL lesions.

Imaging evaluation of the postoperative knee ligaments

Until the advent of magnetic resonance imaging (MRI), evaluation of ligament reconstruction of the knee was largely based on clinical examination and radiographs. MRI is the modality of choice for noninvasive evaluation of reconstructed ligaments, menisco-capsular structures and soft tissues. This article reviews the surgical techniques, normal and abnormal appearances of the ACL and PCL grafts and common complications following ligament reconstruction.

In vivo function of the posterior cruciate ligament during weightbearing knee flexion

BACKGROUND

Current knowledge of posterior cruciate ligament function is mainly based on in vitro cadaveric studies. There are few studies on the in vivo function of the posterior cruciate ligament. The objective of the study was to quantify the multidimensional deformation of the posterior cruciate ligament.

HYPOTHESIS

During in vivo weightbearing flexion, the posterior cruciate ligament undergoes complex 3-dimensional deformations, including elongation, twist, and changes in orientation.

STUDY DESIGN

In vivo biomechanical study.

METHODS

Magnetic resonance images of 5 human knees were used to create 3-dimensional computer models of each subject's knee, including the insertion areas of the posterior cruciate ligament. Orthogonal fluoroscopic images of each subject's knee were acquired as a quasi-static lunge was performed. The images and computer models were used to reproduce the in vivo motion of the knee. The relative motion of the femoral and tibial insertions was described in terms of elongation, twist, elevation (the angle between the tibial plateau and posterior cruciate ligament, measured in the sagittal plane), and deviation (mediolateral orientation, measured in plane of tibial plateau).

RESULTS

The length of the posterior cruciate ligament increased significantly with increasing flexion. It twisted almost 80 degrees as the knee flexed from 0 degrees to 90 degrees . The elevation angle remained relatively constant at 50 degrees . The deviation angle was medially oriented by 20 degrees at full extension, then decreased to approximately 10 degrees at 30 degrees through 90 degrees of flexion.

CONCLUSION

The posterior cruciate ligament undergoes a complex twisting motion as it elongates with flexion.

CLINICAL RELEVANCE

During reconstruction, the tunnels and graft may need to be placed such that the multidimensional deformation of the intact posterior cruciate ligament is reproduced.

Evaluation and treatment of posterior cruciate ligament injuries: revisited

Current knowledge and treatment of posterior cruciate ligament injuries continue to lag behind that of anterior cruciate ligament injuries. This is the result of the relative infrequency of posterior cruciate ligament injuries and the lack of consensus with respect to its natural history, surgical indications, technique, and postoperative rehabilitation. Recent anatomical and biomechanical studies have improved our understanding of the posterior cruciate ligament in an attempt to reproduce its anatomy and function during reconstruction. The following is a comprehensive review on the evaluation and treatment of posterior cruciate ligament injuries with special focus on the current surgical techniques.

In vivo elongation of the anterior cruciate ligament and posterior cruciate ligament during knee flexion

BACKGROUND

Most knowledge regarding cruciate ligament function is based on in vitro experiments.

PURPOSE

To investigate the in vivo elongation of the functional bundles of the anterior cruciate ligament and posterior cruciate ligament during weightbearing flexion.

HYPOTHESIS

The biomechanical role of functional bundles of the anterior cruciate ligament and posterior cruciate ligament under in vivo loading is different from that measured in cadavers.

STUDY DESIGN

In vivo biomechanical study.

METHODS

Elongation of the anterior cruciate ligament and posterior cruciate ligament was measured during a quasi-static lunge using imaging and 3-dimensional computer-modeling techniques.

RESULTS

The anterior-medial bundle of the anterior cruciate ligament had a relatively constant length from full extension to 90 degrees of flexion. The posterior-lateral bundle of the anterior cruciate ligament decreased in length with flexion. Both bundles of the posterior cruciate ligament had increased lengths with flexion.

CONCLUSION

The data did not demonstrate the reciprocal function of the 2 bundles of the anterior cruciate ligament or the posterior cruciate ligament with flexion observed in previous studies. Instead, the data suggest that there is a reciprocal function between the anterior cruciate ligament and posterior cruciate ligament with flexion. The anterior cruciate ligament plays a more important role in low-flexion angles, whereas the posterior cruciate ligament plays a more important role in high flexion.

CLINICAL RELEVANCE

Understanding the biomechanical role of the knee ligaments in vivo is essential to reproduce the structural behavior of the ligament after injury (especially for 2-bundle reconstructions) and thus improve surgical outcomes.

The posterior cruciate ligament during flexion of the normal knee

The posterior cruciate ligament (PCL) was imaged by MRI throughout flexion in neutral tibial rotation in six cadaver knees, which were also dissected, and in 20 unloaded and 13 loaded living (squatting) knees. The appearance of the ligament was the same in all three groups. In extension the ligament is curved concave-forwards. It is straight, fully out-to-length and approaching vertical from 60° to 120°, and curves convex-forwards over the roof of the intercondylar notch in full flexion. Throughout flexion the length of the ligament does not change, but the separations of its attachments do.

We conclude that the PCL is not loaded in the unloaded cadaver knee and therefore, since its appearance in all three groups is the same, that it is also unloaded in the living knee during flexion. The posterior fibres may be an exception in hyperextension, probably being loaded either because of posterior femoral lift-off or because of the forward curvature of the PCL. These conclusions relate only to everyday life: none may be drawn with regard to more strenuous activities such as sport or in trauma.

An anteroposterior axis of the tibia for total knee arthroplasty

The objective of the current study was to identify a new extraarticular anatomic landmark indicating the anteroposterior orientation of the tibia using computed tomography. In 39 volunteers (20 males, 19 females), computed tomography scans for healthy right knees in extension were done perpendicular to the tibial shaft axis. The anteroposterior axis of the tibia was defined as a line perpendicular to the transepicondylar axis and passing through the middle of the posterior cruciate ligament. At the level of the tibial plateau and the patellar tendon attachment, the mean medial percentage width of intersecting point of the patellar tendon and the anteroposterior axis was 10.8% +/- 9.8% (range, -9.3% - +30.0%) and -0.2% +/- 10.4% (range, -23.6% -+23.0%), respectively. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment was 0.0 degrees +/- 2.8 degrees (range, -6.3 degrees -+5.2 degrees). The medial border of this attachment therefore can serve as a reliable anterior anatomic landmark to determine the anteroposterior axis of the tibia, and the line connecting the middle of the posterior cruciate ligament and the medial border of the attachment may be useful as a reference axis indicating the anteroposterior orientation of the tibia.

Biomechanics of the PCL and related structures: posterolateral, posteromedial and meniscofemoral ligaments

This paper reviews and updates our knowledge of the anatomy and biomechanics of the posterior cruciate ligament, and of the posterolateral, posteromedial and meniscofemoral ligaments of the knee. The posterior cruciate ligament is shown to have two functional fibre bundles that are tight at different angles of knee flexion. It is the primary restraint to tibial posterior draw at all angles of knee flexion apart from near full extension. In contrast, the posterolateral and posteromedial structures are shown to tighten as the knee extends, and to be well-aligned to resist tibial posterior draw. These structures also act as primary restraints against other tibial displacements. Tibial internal rotation is restrained by the medial and posteromedial structures, while tibial external rotation is restrained by the lateral and posterolateral structures. They are also the primary restraints against tibial abduction-adduction rotations. The meniscofemoral ligaments are shown, for the first time, to contribute significantly to resisting tibial posterior draw, and to have a strength of approximately 300 N. Taken together, this evidence shows how the posterolateral and posteromedial structures are responsible for posterior knee stability near extension, and this, along with the action of the meniscofemoral ligaments, may explain why an isolated rupture of the posterior cruciate ligament does not often lead to knee instability

An anatomic study of the popliteofibular ligament

Our study was prompted by the varied reports in literature about the existence of the popliteofibular ligament as an integral part of the posterolateral corner of the knee. We performed 25 formalinised cadaveric knee dissections and identified the popliteofibular ligament. It was on an average 11.06 (5-16) mm in width and 11.8 (6-16) mm in length. Our study did not include a functional evaluation. We found the ligament to be a constant structure of the posterolateral knee complex, and recommend its repair in acute injuries as well as reconstruction in chronic injuries of the posterolateral corner of the knee.

Vascular risk associated with a posterior approach for posterior cruciate ligament reconstruction using the tibial inlay technique

This study evaluated the risk to the popliteal artery associated with the tibial inlay technique in posterior cruciate ligament (PCL) reconstruction. Barium was injected into the femoral arteries of eight fresh-frozen cadaveric knees and anteroposterior (AP) radiographs were obtained. Dissection of the fascia overlying the gastrocnemius muscle, identification of the interval between the medial head of the gastrocnemius and the semimembranosus, and lateral retraction of the medial head of the gastrocnemius (the Burks and Schaffer approach) was performed. Subsequently, a bicortical screw was placed from posterior to anterior through the tibia as is performed in the tibial inlay technique. A second AP radiograph was obtained. The distance from the center of the screw to the edge of the popliteal artery was measured using digital calipers. The closest any screw came to the popliteal artery was 18.1 mm, and the average distance was 21.1 mm (21.1 +/- 4.6 mm, range: 18.1-31.7 mm). When this distance was calculated as a percentage of the tibial plateau width, the smallest value was 19.2% (24% +/- 4.9%, range: 19.2%-35.1%). A posterior approach for a tibial inlay PCL reconstruction procedure appears safe with respect to the popliteal artery.