Comparative study of the size and shape of human anterior and posterior cruciate ligaments

As an important step toward determination of the function of cruciate ligaments, the cross-sectional shapes and areas of the anterior cruciate, posterior cruciate, and meniscofemoral ligaments were evaluated in situ within the same knee with use of a laser micrometer system. Measurements were made in eight human cadaveric knees at five levels along the midsubstance of each ligament, with the knee at 0°, 30°, 60°, and 90° of flexion. The posterior cruciate ligament was found to be widest in the medial-lateral direction, whereas the anterior cruciate ligament usually was larger in the anterior-posterior direction. The cross-sectional shapes of the anterior cruciate ligament generally were noted to be more circular along the entire midsubstance than were those of the posterior cruciate ligament. In contrast, the cross-sectional shapes of the posterior cruciate ligament were more circular near the tibia, becoming progressively more elongated toward the femur. The meniscofemoral ligaments were more circular than the cruciate ligaments, with an occasional medial-lateral widening similar to that of the posterior cruciate ligament. The cross-sectional area of both the cruciate ligaments changed along the length of the midsubstance, with the anterior cruciate ligament becoming slightly larger distally and the posterior cruciate ligament enlarging proximally. The angle of flexion of the knee was not found to have a significant effect on the cross-sectional areas of the ligaments but was noted to alter the cross-sectional shapes. Using within-specimen comparisons, the cross-sectional area of the posterior cruciate ligament was found to be approximately 1.5 times larger than that of the anterior cruciate ligament at the proximal and midsubstance levels but was only 1.2 times larger at the most distal level. The total cross-sectional area of the meniscofemoral ligaments was approximately 22% that of the posterior cruciate ligament.     

Healing of the medial collateral ligament after a combined medial collateral and anterior cruciate ligament injury and reconstruction of the anterior cruciate ligament: Comparison of repair and nonrepair of medial collateral ligament tears in rabbits

The optimal treatment for a combined injury of the medial collateral and anterior cruciate ligaments is controversial, and the question remains as to whether repair of the medial collateral ligament and reconstruction of the anterior cruciate ligament improves healing of the medial collateral ligament. We compared reconstruction of the anterior cruciate ligament with and without repair of the medial collateral ligament in a rabbit model of a combined injury of these two ligaments. The anterior-posterior translation and varus-valgus rotation of the knee, the structural properties of the femur-medial collateral ligament-tibia complex, and the mechanical properties of the midsubstance of the medial collateral ligament were evaluated immediately after surgery and at 6 and 12 weeks postoperatively. Repair of the medial collateral ligament led to significantly less varus-valgus rotation of the knee than did no repair, but the anterior-posterior translation of the knees in the repair and nonrepair groups were not significantly different at any study time. At 12 weeks, the cross-sectional area and ultimate load in the repair group were 60 and 53% greater, respectively, than in the nonrepair group. Among 12 specimens that were repaired (six specimens at 6 weeks and six specimens at 12 weeks), failure occurred within the midsubstance in four (two at each time period); in all of the specimens that were not repaired, failure occurred at the tibial insertion site. There was no significant difference between the modulus of the midsubstance in the repaired and the nonrepaired medial collateral ligaments. Thus, the improved structural properties of the femur-medial collateral ligament-tibia complexes that were repaired resulted from an increase in cross-sectional area of the repaired medial collateral ligament and healing of the tibial insertion site. Postoperative healing time had little effect on the tensile properties. In this rabbit model, repair of the medial collateral ligament with reconstruction of the anterior cruciate ligament may lead to better healing of the medial collateral ligament in the early phase than does reconstruction of the anterior cruciate ligament alone.     

Macroscopic and histological assessments of the cruciate ligaments in arthrosis of the knee

We examined the macroscopic appearance of both cruciate ligaments in 52 knees during knee replacement. It was classsified as normal, abnormal or ruptured. The ligaments were also evaluated histologically: stage 0 (normal), stage I (degeneration of < 1/3 of the collagen fibers), stage 2 (degeneration of 1/3-2/3) and stage 3 (> 2/3). 17 anterior cruciate ligaments (ACL) were normal, 14 were abnormal and 21 ruptured. All the posterior cruciate ligaments (PCL) were normal. 14 ACL were stage 0, 6 stage 1, 8 stage 2 and 24 were stage 3. 22 PCL were stage 0, 14 stage 1, 13 stage 2 and 3 were stage 3. When the ACL was abnormal or ruptured, the PCL was stage 0 only in one fourth of the cases. The long-term results of TKR retaining the PCL should be better if the ligament is strong. The intraoperative assessment of the macroscopic appearance of the ACL reflects the histological state of the PCL.     

Macroscopic and histological assessments of the cruciate ligaments in arthrosis of the knee

We examined the macroscopic appearance of both cruciate ligaments in 52 knees during knee replacement. It was classsified as normal, abnormal or ruptured. The ligaments were also evaluated histologically: stage 0 (normal), stage 1 (degeneration of < 1/3 of the collagen fibers), stage 2 (degeneration of 1/3-2/3) and stage 3 (> 2/3). 17 anterior cruciate ligaments (ACL) were normal, 14 were abnormal and 21 ruptured. All the posterior cruciate ligaments (PCL) were normal. 14 ACL were stage 0, 6 stage 1, 8 stage 2 and 24 were stage 3. 22 PCL were stage 0, 14 stage 1, 13 stage 2 and 3 were stage 3. When the ACL was abnormal or ruptured, the PCL was stage 0 only in one fourth of the cases. The long-term results of TKR retaining the PCL should be better if the ligament is strong. The intraoperative assessment of the macroscopic appearance of the ACL reflects the histological state of the PCL.     

Primary repair of the cruciate and collateral ligaments after traumatic dislocation of the knee

The management of traumatic dislocation of the knee in 40 patients (41 knees) with a mean age of 26.3 years is described. They were treated by primary repair and reconstruction with autologous grafting of the anterior (ACL) and posterior cruciate ligaments (PCL) and repair injuries to the collateral ligament and soft-tissue. The ACL and PCL were reconstructed using the patellar tendon and the gracilis and semitendinosus tendons, respectively. Early mobilisation using a continuous-passive-movement machine and active exercises was started on the second day after operation. At a mean follow-up of 39 months no patient reported 'giving way' and all except one had good range of movement. Of the 41 knees, 21 were rated as excellent, 15 good, four fair and one poor. Early reconstruction of the cruciate ligaments and primary repair of the collateral ligaments followed by an aggressive rehabilitation programme are recommended for these young, active patients.     

Nonuniform distribution of collagen density in human knee ligaments

It is generally recognized that the mechanical properties of soft connective tissues are affected by their structural components. We documented collagen density distributions in human knee ligaments to quantify differences in density within and between these ligaments. In order to explain the variations in mechanical properties within and between different knee ligaments as described in the literature, the distributions of collagen density were correlated with these biomechanical findings. Human knee ligaments were shown to be nonhomogeneous structures with regard to collagen density. The anterior bundles of all ligaments contained significantly more collagen mass per unit of volume than the posterior bundles did. The percentage differences between the anterior and posterior bundles, in relation to the posterior bundles, were about 25% for the anterior cruciate ligament (ACL) and the collateral ligaments and about 10% for the posterior cruciate ligament (PCL). Along the cruciate ligaments, the central segments had higher collagen densities than did segments adjacent to the ligament insertions (ACL 9%, PCL 24%). The collagen density in the ACL was significantly lower than that in the other ligaments. These variations within and between the ligaments correlate well with the variations in mechanical properties described in the literature; however, other structural differences have to be taken into account to fully explain the variations in mechanical properties from the structural components.     

The gross morphology of torn human anterior cruciate ligaments in unstable knees.

To evaluate the presence and incidence of reattachments of torn human anterior cruciate ligaments (ACL), we prospectively investigated 101 patients undergoing arthroscopic ACL reconstruction to study the intra-articular morphology of ACLs under circumstances in which functional healing had failed. Results showed that roughly 72% of these unstable knees had reattachment of the torn ACL to the posterior cruciate ligament (PCL). Eighteen percent had no signs of ACL reattachment but only 2% of previously torn ACLs were absent. These results suggest that even in chronic situations in which the knee remains functionally unstable, human ACLs rarely resorb. It also suggests that torn human ACLs commonly reattach in the knee, mainly to the PCL via a process that is consistent with scarring. While the function of these reattachments is clearly inadequate in people with unstable knees because of a combination of reattachment location, scar quantity, or quality, these results nonetheless show that the intra-articular environment in humans often maintains ACL stumps and it is not totally inhibitory to ACL reattachment via some biological process.     

Anterior cruciate ligament and intercondylar notch in the coronal oblique plane: anatomy complemented by magnetic resonance imaging in cruciate ligament-intact knees.

We assessed the anatomy of the anterior cruciate ligament (ACL) and femoral intercondylar notch on cryosections from one cadaveric knee specimen in the coronal oblique plane oriented parallel to the intercondylar roof. We determined the course of the ACL, the widths of the cruciate ligaments at intersection, and the intercondylar notch configuration on coronal oblique plane magnetic resonance images in 51 adult cruciate ligament-intact knees (25 women, 26 men; age range, 16 to 47 years). The intercondylar notch widths were measured at the notch entrance, at the intersection of the ACL and posterior cruciate ligament (PCL), and at the notch outlet. In the coronal oblique plane, the ACL exhibited a diagonal course from the central and medial part of the anterior intercondylar area of the tibia distally, across the lateral third of the intercondylar notch, to the intercondylar surface of the lateral femoral condyle proximally. At the cruciate ligament intersection, the absolute widths of the ACLs measured on average 6.1+/-1.1 mm in men and 5.2+/-1.0 mm in women representing 31.9% and 31.1% of the ACL/central intercondylar notch width ratios. The absolute widths of the PCLs measured on average 9.6+/-1.3 mm in men and 8.5+/-1.3 mm in women representing 50.4% and 51.4% of PCL/central intercondylar notch width ratios. On average for both groups, men and women, the absolute widths of the PCLs were significantly larger than the absolute widths of the ACLs. However, the relative widths of the cruciate ligaments with respect to corresponding intercondylar notch widths were not significantly different. In the coronal oblique plane, the intercondylar notch widths showed on average a significant decrease from posterior to intersection and from intersection to anterior. At notch outlet, the mean notch width measured 21.4 mm in men and 18.5 mm in women. At intersection, the mean notch width measured 19.1 mm in men and 16.6 mm in women. At notch entrance, the notch width measured 14.6+/-1.8 mm in men and 12.7+/-2.1 mm in women. We recommend magnetic resonance tomography of the knee in the coronal oblique plane oriented parallel to the intercondylar roof as the imaging modality of choice to visualize accurately the anatomic diagonal course of the ACL and its relation to the intercondylar notch and posterior cruciate ligament complex.     

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 A_N 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.     

Tensions in the anterior and posterior cruciate ligaments of the knee during passive loading: predicting ligament loads from in situ measurements

Cruciate ligament tensions were predicted for anteroposterior (AP) tibial translation at 20 degrees, 30 degrees, 80 degrees, and 90 degrees of knee flexion based on in vitro measurements from six cadaver knees. A three-dimensional trigonometric equation was derived to calculate cruciate ligament tension as functions of AP force applied to the tibia and knee flexion angle (KFA). AP forces less than or equal to 150 N were applied. Ligament tension increased with applied AP force. The relationship between ligament tension and applied AP force appeared linear, but a Hotteling's T2 test failed to demonstrate a linear relationship. Tensions in the anterior cruciate ligament (ACL) attained magnitudes of approximately equal to 140 N. Tensions in the posterior cruciate ligament (PCL) attained magnitudes of approximately equal to 220 N. An analysis was performed to determine the sensitivity of ligament tension to hypothetical errors in the experimentally measured parameters used to compute ligament tension. The new method we report can be used to determine tensions in the ligaments of the knee or other joints for various loading conditions.     

Proprioception of the cruciate ligaments: receptor mapping in an animal model

Ten anterior and posterior cruciate ligaments (ACL and PCL) harvested from adult sheep were investigated under light microscopy for data on the frequency and localisation of neural structures. Serial sections of 25 μm thickness were stained with a modified gold chloride technique. Receptors were classified according to their histological structure. Topographic distribution and frequency within the ligament texture were determined with the help of computerized image analysis. Three distinct neural structures could be identified: Ruffini endings, Ruffini corpuscles of the Golgi tendon organ-like type and Pacinian corpuscles. Golgi tendon organs were not found. In total, 274 and 238 neural structures were present in the 10 ACL and 10 PCL, respectively. Pacinian receptors were the most common structures, with a mean frequency of 13.6 ± 5.3 (ACL) and 12.4 ± 5.1 (PCL), followed by Ruffini endings with 8.9 ± 3.2 (ACL) and 7.8 ± 2.9 (PCL), whereas Ruffini corpuscles had the lowest frequency with a mean value of 4.9 ± 2.1 (ACL) and 3.4 ± 1.1 (PCL). The majority of the neural structures were located in the subsynovial sheath or closely associated with endotenon structures. The tibial and femoral insertion areas had a significantly increased receptor density compared with the midpart of the ACL and PCL (P < 0.001), where only 19.3% and 23.7% of the receptors were located. These results emphasise the complex sensory structure of the cruciate ligaments and provide a valid morphological basis for further neurophysiological investigations. Received: 3 June 1997     

Lateral thrust of anterior cruciate ligament-insufficient knees and posterior cruciate ligament-insufficient knees

Leaving anterior cruciate ligament (ACL) insufficiency and posterior cruciate ligament (PCL) insufficiency untreated frequently leads to osteoarthritis (OA). The purpose of this study was to evaluate dynamically the lateral thrust of ACL-insufficient knees and PCL-insufficient knees, and from the findings investigate the relationship between cruciate ligament insufficiency and OA occurrence. An acceleration sensor was attached to the affected and control anterior tibial tubercles, acting in medial-lateral and perpendicular directions. The lateral thrust immediately after heel strike was measured continuously by a telemeter under stabilised walking conditions. When compared to the contralateral healthy knee, the peak value of lateral acceleration immediately after heel strike was significantly larger in the ACL-insufficient knee; and lateral thrust was increased, but not significantly, in the PCL-insufficient knee. Given that lateral thrust of the knee during walking increases due to ACL or PCL injury, it may be a principal contributor to OA progression.     

The free synovial graft as a shield for collagen ingrowth in cruciate ligament repair

The anterior cruciate ligament (ACL) was excised bilaterally in the knee joint of three dogs and was replaced in a conventional manner with a composite polyglycolic acid (PGA) and Dacron braided ligament prosthesis. In one knee of each dog, the ligaments were wrapped with a free synovial graft taken from the suprapatellar pouch in an attempt to keep the prosthesis extrasynovial, while the ligaments in the opposite three knees were left uncovered and thus directly exposed to synovial fluid. The dogs were killed at approximately one year postoperation, and microscopic sections of all ligaments were taken. The three knees with the synovial sheath showed a significantly greater bulk of fibrous tissue along the ligament scaffold grossly and a greater abundance of collagen producing cells microscopically, compared to the unwrapped ligaments. The gross and microscopic findings were identical in each of the three knees with the covered ligaments and were equally consistent in the three that had been left unprotected from the synovial fluid. These findings suggest that a free synovial graft may simulate the normal protective role of the synovial membrane and allow and/or induce collagen ingrowth in synthetic or autogeneic tissue stints for the repair of acute cruciate ligament tears.     

Management of the dislocated/multipleligament injured knee

The multiple ligament injured knee is a complex problem in orthopaedic surgery. Most dislocated knees involve tears of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and at least one collateral ligament complex. Careful assessment of the vascular status of the extremity is essential because of the possibility of arterial and/or venous compromise. These complex injuries require a systematic approach to evaluation and treatment. Physical examination and imaging studies enable the surgeon to make a correct diagnosis and to formulate a treatment plan. Arthroscopically assisted combined ACL/PCL reconstruction is a reproducible procedure. Knee stability is improved postoperatively when evaluated using knee ligament rating scales, arthrometer testing, and stress radiographic analysis. Acute medial cruciate ligament tears, when combined with ACL/PCL tears, may, in certain cases, be treated with bracing. Posterolateral corner injuries combined with ACL/PCL tears are best treated with primary repair as indicated combined with reconstruction using a post of strong autograft (split biceps tendon, biceps tendon, semitendinosus) or allograft (Achilles tendon, bone patellar tendon bone) tissue. Surgical timing depends on the ligaments injured, the vascular status of the extremity, reduction stability, and the overall health of the patient. We prefer the use of allograft tissue for reconstruction in these cases because of the strength of these large grafts and the absence of donor site morbidity.     

Sensorimotor potential of the intact and injured anterior and posterior cruciate ligaments--a neurophysiological study in an animal model

AIM: This neurophysiological study is intended to investigate the sensomotor potential of the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) which may provide joint stabilization via a ligamentomuscular reflex arch. In addition, the role of ligamentous injury on the sensomotor potential has been investigated. METHOD: The sensomotor potential was investigated using 24 knee joints in a sheep model under in-vivo conditions. The cruciate ligaments were mechanically loaded and the muscular activities of the hamstrings and the quadriceps were recorded simultaneously via electromyography. Injury to the ligaments was simulated by defined mechanical elongation of the ACL and PCL to failure. RESULTS: The results confirm the hypothesis of the existence of a ligamentomuscular reflex loop between ligamentary mechanoreceptors and the joint-stabilizing muscles. Mechanical loading of the ACL triggered mainly the activity of the hamstrings, whereas loading of the PCL led to the activation of the quadriceps. The rate of elongation which caused disturbances to the sensomotor potential was significantly smaller as compared to the elongation to failure. CONCLUSION: The cruciate ligaments provide dynamic joint stabilization via a ligamentomuscular reflex arch. It was demonstrated that the sensomotor potential of both structures is significantly more susceptible to ligament injury than the biomechanical potential.     

The adverse effects of sectioning the posterior cruciate ligament in rabbits

This study examined the changes in the structural properties of the femur-anterior cruciate ligament —tibia complex (FATC) and the histologic changes of the anterior cruciate ligament (ACL) following sectioning of the posterior cruciate ligament (PCL) of 20 rabbits. The PCL in the right knee was sectioned through an arthrotomy. The left knee underwent arthrotomy only and was used as a control. The animals were killed 3 and 6 months postoperatively. The tensile properties of the FATCs were tested, and the ACLs were histologically examined using polarized light microscopy and transmission electron microscopy. There were significant decreases in the ultimate load following sectioning of the PCL, although there were no significant changes in the stiffness. There were no significant differences in either the crimp period or the crimp amplitude of the ACL following sectioning of the PCL. There were significant increases in the number of collagen fibrils per square micrometer, and significant decreases in the collagen fibril diameter and proportion of total collagen fibril area per square micrometer following sectioning of the PCL. These findings suggest that isolated PCL injury may cause pathological changes in the ACL and its insertion sites.     

Double-contrast CT arthrography of the cruciate ligaments

The value of computed tomography (CT) in evaluating the cruciate ligaments was assessed by studying an amputated knee in order to find the most suitable position for detecting minimal defects of the ligaments. The ACL or PCL, or both, of 60 patients (61 knees) were then examined by CT and the findings were compared with those of arthroscopy. Defects 3mm in length were shown by CT. A sufficient quantity of air and an adequate amount of positive contrast medium were required to obtain an accurate picture of the ligaments. For the ACL, the sensitivity of CT was 96.6%, specificity was 95.5%, and accuracy was 96.1%. For the PCL, sensitivity was 78.6%, specificity was 91.7%, and accuracy was 84.6%. Ruptures of the cruciate ligaments shown by CT were classified into four types. Their CT images coincided significantly with their arthroscopic findings. This study shows double-contrast CT arthrography to be a valuable method for evaluating the cruciate ligaments, and especially the ACL.     

前交叉韧带股骨等距重建位置的比较

目的 :比较模拟生理负荷条件下前交叉韧带股骨重建位置的等距特性。方法 :7具新鲜冷冻尸体膝关节标本 ,在前交叉韧带胫骨附着区取 3点以及胫骨附着区取 5点分别钻骨隧道 ,通过钢丝和等距测量器施加初负荷 ,检测膝关节屈曲过程中胫骨和股骨隧道间的距离变化。结果 :膝关节从 0～ 90°屈曲过程中 ,股骨韧带附着区中点、上点和后点与胫骨附着区 5点间呈等距变化 ,但股骨韧带附着区中点、上点与胫骨附着区 5点间距离变化具有组内显著性差异。结论 :股骨韧带附着区后点是理想的等距重建点。     

关节镜下同种异体跟腱骨一期重建膝关节前后交叉韧带

目的 评价关节镜下利用同种异体跟腱骨一期重建膝关节前后交叉韧带的疗效.方法 2000年7月至2005年2月收治15例患膝前后交叉韧带断裂但对侧膝关节完好者,在关节镜下先对合并存在的半月板损伤进行修复,然后使用2条同种异体跟腱骨一期重建前后交叉韧带.亚急性期或慢性期(>3周)重建12例,急性期(<3周)重建3例.手术前后采用IKDC和Lysholm评分系统对患膝关节功能进行评估,随访结果与对侧健康膝火节进行比较.结果 所有患者均获得36～40个月(平均38个月)随访.根据IKDC评分,术前所有患膝关节功能都严重异常,术后9例患膝功能改善为止常,5例接近正常,1例异常.Lysholm评分由术前平均(56±5)分改善为术后(90±4)分,差异有统汁学意义(t=15.660,P<0.05.结论同种异体跟腱骨可用于关节镜下重建膝关节前后交叉韧带,疗效满意.