股骨单隧道内分叉双束纤维重建后交叉韧带的实验研究

目的在人膝关节标本上行股骨单隧道分叉双束纤维重建后交叉韧带(posterior cruciate ligament,PCL),探讨其术式的优缺点。方法应用力学试验机对14侧捐赠新鲜冷冻人膝关节标本进行生物力学测试,男12侧,女2侧;年龄20～31岁。标本股骨段长20cm,胫骨段长20cm。首先测量PCL完整时胫骨后移距离和交叉韧带的应变(完整组,n=14);然后切断PCL(切断组,n=14),测量胫骨受力时的后移距离后,再将标本随机分为两组:单束重建组(n=7)和分叉双束重建组(n=7),分别测量屈膝0、30、60、90和120°5个角度时胫骨后移距离和移植韧带的应变。结果胫骨受到100N后向力量,完整组在不同屈膝角度下,胫骨向后移位1.97±0.29～2.60±0.23mm,前外束和后内束纤维交替紧张松弛。切断组膝关节明显松弛,胫骨向后移位达11.27±1.06～14.94±0.67mm,与完整组比较差异有统计学意义(P<0.05);单束纤维重建组,在不同屈膝角度下胫骨向后移位1.99±0.19～2.72±0.38mm,移植韧带持续紧张。双束纤维重建组在不同屈膝角度下胫骨向后移位2.27±0.32～3.05±0.44mm,移植的双束纤维交替紧张,协同作用。组内比较:双束重建组在不同屈膝角度时胫骨向后位移差异无统计学意义(P>0.05),而单束重建组在屈膝90°时与屈膝30、60和120°时相比,胫骨后移增大,差异有统计学意义(P<0.05)。结论股骨单隧道内分叉双束纤维重建PCL术在各屈膝角度均能有效防止胫骨后移,股骨单隧道单束重建术屈膝90°时后移较其他角度时增大。分叉双束重建PCL的两束纤维束交替紧张,生物力学特征更接近于正常PCL。     

In situ forces of the anterior and posterior cruciate ligaments in high knee flexion: an in vitro investigation.

The function of the anterior and posterior cruciate ligaments (ACL and PCL) in the first 120 degrees of flexion has been reported extensively, but little is known of their behavior at higher flexion angles. The aim of this investigation was to study the effects of muscle loads on the in situ forces in both ligaments at high knee flexion (>120 degrees). Eighteen fresh-frozen human knee specimens were tested on a robotic testing system from full extension to 150 degrees of flexion in response to quadriceps (400 N), hamstrings (200 N), and combined quadriceps and hamstrings (400 N/200 N) loads. The in situ forces in the ACL and PCL were measured using the principle of superposition. The force in the ACL peaked at 30 degrees of flexion (71.7 +/- 27.9 N in response to the quadriceps load, 52.3 +/- 24.4 N in response to the combined muscle load, 32.3 +/- 20.9 N in response to the hamstrings load). At 150 degrees, the ACL force was approximately 30 N in response to the quadriceps load and 20 N in response to the combined muscle load and isolated hamstring load. The PCL force peaked at 90 degrees (34.0 +/- 15.3 N in response to the quadriceps load, 88.6 +/- 23.7 N in response to the combined muscle load, 99.8 +/- 24.0 N in response to the hamstrings load) and decreased to around 35 N at 150 degrees in response to each of the loads. These results demonstrate that the ACL and PCL carried significantly less load at high flexion in response to the simulated muscle loads compared to the peak loads they carried in response to the same muscle loads at other flexion angles. The data could provide a reference point for the investigation of non-weight bearing flexion and extension knee exercises in high flexion. Furthermore, these data could be useful in designing total knee implants to achieve high flexion.     

膝关节后内侧结构损伤合并单一交叉韧带断裂的早期治疗

目的 探讨膝关节后内侧结构损伤合并单一交叉韧带断裂进行早期手术的疗效.方法 2002年1月至2005年12月共治疗12例后内侧结构损伤合并单一交叉韧带断裂患者,其中10例合并前交叉韧带(ACL)断裂,2例合并后交叉韧带(PCL)断裂.交叉韧带损伤术前Lysholm评分为50～60分(平均56.7分).关节镜下重建交叉韧带,开放修复后内侧结构.8例采用自体半腱肌、股薄重建ACL(transfix术式),2例采用骨.髌腱.骨重建ACL.2例采用一端带骨块的异体跟腱蓖建PCL.后内侧结构损伤修复:8例采用星状钢板螺钉同定,2例采用GⅡ锚钉固定.1例采用自体半肌腱、股薄肌移植重建,1 例采用端对端缝合.结果 12例中除2例随访4个月后失访外,其余10例患者术后获平均12个月(6～18个月)随访.交叉韧带损伤重建后Lysholm评分为74～94分(平均81.2分).后内侧结构修复后10例膝伸屈范围正常,2例伸直受限5.外翻应力试验于O啦时,9例正常,2例弱阳性(+),1例阳性(++).结论 膝后内侧结构损伤合并单一交叉韧带断裂时,早期重建交叉韧带同时一期修复膝后内侧结构可以较好地恢复膝关节稳定性.     

In vitro study of knee stability after two-band two-tunnel posterior cruciate ligament reconstruction

Objective: To compare the ability of three different reconstruction procedures in restoring the posterior displacement of tibia and the posterior stability of the knee joint from 0°to 120°flexion. Methods: Three posterior cruciate ligaments (PCL) reconstruction procedures were performed, namely two-band two-tunnel reconstruction, one-band anterior tunnel reconstruction and one-band posterior tunnel reconstruction. The posterior displacement of the tibia in relation to the femur was measured when a 200 N posterior force was applied. Results: Within the flexion range of 0°to 30°, the displacement in the one-band posterior tunnel reconstruction showed little difference from that of an intact knee (P>0.05). But when the flexion exceeded 30°, especially when it exceeded 60°, the displacement in one band posterior tunnel reconstruction was much greater than that of an intact knee (P<0.01). In two-band two-tunnel reconstruction and one-band anterior tunnel reconstruction, the displacement was approximately the same as that of an intact knee ranging from 0°to 120°(P>0.05), while a slight over-restriction might be found at some angles. Conclusions: Two-band reconstruction could effectively restrict the posterior displacement of the tibia and restore anterior, posterior stability of the knee joint within its full range of flexion. One-band anterior tunnel reconstruction also could maintain the posterior stability of the knee, while the result of one-band posterior tunnel reconstruction is the most unsatisfactory.     

A follow-up study of arthroscopic combined reconstruction of anterior and posterior cruciate ligaments with allograft patellar tendon

Objective： To evaluate the therapeutic effect of combined reconstruction of anterior cruciate ligament （ ACL ） and posterior cruciate ligament （ PCL ） simultaneously by using allograft patellar tendon under arthroscopy. Methods： From May 2003 to November 2005, 10 cases of ruptured ACL and PCL were fixated with compressed screws and reconstructed under arthroscopy with allograft patellar tendon simultaneously. The clinical results were evaluated according to IKDC, Lysholm, and Tegner clinical rating scales. Results. All patients were followed up for 12-30 months （mean： 18 months ）. At the last follow-up, there was no knee extension limitation and knee flexion was between 120° and 135°, with an average of 128.38°. The Lysholm score of the 10 cases was 66. 5 ± 5. 6 before operation and 89.8 ± 3.4 at last follow up. The difference was statistically significant （ P 〈 0.01 ）. The average Tegner activity score decreased from 6.9 ± 1.7 （ range ： 4-9 ） before injury to 5.5 ± 1. 6 （rang： 2-9） at the follow-up （P=0.53）. At the end of follow-up, IKDC score was graded as A in 4 cases （40.0 % ）, B in 5 （50.0 % ）, and C in 1 （10.0%）. Of the 10 patients, 8 returned to the same sports level as before injury and 2 were under the level. Conclusion. Arthroscopic combined reconstruction of ACL and PCL with allograft patellar tendon has the advantages of minimal trauma in surgery and reliable satisfactory outcome.     

关节镜下韧带末端缝扎固定治疗后十字韧带胫骨止点骨折

 目的探讨关节镜下韧带末端缝扎固定治疗后十字韧带（posterior cruciate ligament,PCL）胫骨止点撕脱骨折的手术方法、疗效及适应证。方法2007年6月至2009年6月,采用关节镜下韧带末端缝扎固定治疗PCL胫骨止点骨折21例,男14例,女7例;年龄13~52岁,平均31.5岁;其中青少年患者5例。骨折块横径> 10mm 8例,5~10mm 11例,＜5mm 2例。在关节镜下使用两股5号爱惜邦缝线在韧带末端缝扎,从胫骨前内侧向胫骨骨床的4∶30和7∶30钻两个2.5mm骨隧道,经骨隧道将缝线拉出,固定于门型钉上。术后观察骨折复位情况、愈合时间、膝关节的松弛度及活动度、对青少年患者骨骺的影响,测量K T-2000值,采用L ysholm评价系统对膝关节功能进行评价。结果骨折复位均满意;骨折均愈合,平均愈合时间2.5个月。21例患者均获得随访,随访时间10～24个月,平均13.5个月。1例患者后抽屉试验（+）,但其终点为硬性;所有患者伸膝均不受限,2例患者有10°~ 15°屈膝受限,平均屈膝角度为140.5°±3.8°;KT-2000为平均（1.2±0.4）mm,Lysholm评分为平均（95.2±2.7）分。结论关节镜下采用韧带末端缝合固定的方法治疗PCL胫骨止点撕脱骨折,固定可靠,可较好恢复患膝的功能;适用于合并关节内其他结构损伤的患者、粉碎性骨折或骨折块较小的患者、骨骺未闭的青少年患者。     

Posterior instability of the knee joint. An experimental study

We investigated the importance of the posterior cruciate ligament (PCL) and the medial and lateral compartmental structures for translatory and simultaneous axial rotatory instability in 25 osteoligamentous knee preparations. Instability was registered continuously from 0 degree to 90 degrees of flexion with application of a constant force to the tibia. Isolated transection of the PCL increased the posterior tibial displacement with flexion to a maximum of 10 mm at 90 degrees of flexion; when combined lesions to the lateral structures were included, the popliteal tendon (PT) in particular turned out to have a major secondary stabilizing function. The posterior tibial displacement in flexion was doubled when all lateral structures were included in the lesions. Transection of the PCL and all the medial structures led to a notable increment in posterior displacement increasing with flexion. Major increments in simultaneous tibial rotation were recorded only after combined lesions to either medial or lateral structures. A reverse pivot shift was provoked after combined lateral lesions when the PT was included. Even an anteromedial subluxation was released after lesions to the medial structures. Regardless of the type of lesion, the specimens remained stable concerning anterior-posterior displacement in extension. No changes in the anterior tibial displacement were observed.     

Functional anatomy of the anterior cruciate ligament and a rationale for reconstruction

In thirty-three normal cadaver knees from adults (mean age, twenty-nine years), the average length of the anterior cruciate ligament was 31 +/- 3 millimeters and the angle between the ligament and the long axis of the femur was 28 +/- 4 degrees with the knee at 90 degrees of flexion. We could find no macroscopic or microscopic evidence of discrete subdivisions of the anterior cruciate ligament. We studied the functional importance of the positions of the attachments of the anterior cruciate ligament. The distance between the central points of the normal attachment areas on the tibia and on the femur was found to be isometric during flexion and extension. The so-called over-the-top position on the femur was the least favorable of the positions that we tested, since it resulted in an average elongation of the ligament of ten millimeters with the knee in full extension as compared with full flexion. On the basis of the results in the present study, we suggest some basic principles for a standardized replacement operation for a deficient anterior cruciate ligament.     

MRI analysis of in vivo meniscal and tibiofemoral kinematics in ACL-deficient and normal knees.

The objectives of this study were to analyze simultaneously meniscal and tibiofemoral kinematics in healthy volunteers and anterior cruciate ligament (ACL)-deficient patients under axial load-bearing conditions using magnetic resonance imaging (MRI). Ten healthy volunteers and eight ACL-deficient patients were examined with a high-field, closed MRI system. For each group, both knees were imaged at full extension and partial flexion ( approximately 45 degrees ) with a 125N compressive load applied to the foot. Anteroposterior and medial/lateral femoral and meniscal translations were analyzed following three-dimensional, landmark-matching registration. Interobserver and intraobserver reproducibilities were less than 0.8 mm for femoral translation for image processing and data analysis. The position of the femur relative to the tibia in the ACL-deficient knee was 2.6 mm posterior to that of the contralateral, normal knee at extension. During flexion from 0 degrees to 45 degrees , the femur in ACL-deficient knees translated 4.3 mm anteriorly, whereas no significant translation occurred in uninjured knees. The contact area centroid on the tibia in ACL-deficient knees at extension was posterior to that of uninjured knees. Consequently, significantly less posterior translation of the contact centroid occurred in the medial tibial condyle in ACL-deficient knees during flexion. Meniscal translation, however, was nearly the same in both groups. Axial load-bearing MRI is a noninvasive and reproducible method for evaluating tibiofemoral and meniscal kinematics. The results demonstrated that ACL deficiency led to significant changes in bone kinematics, but negligible changes in the movement of the menisci. These results help explain the increased risk of meniscal tears and osteoarthritis in chronic ACL deficient knees.     

关节镜下缝线“8”字打结空心钉固定治疗前交叉韧带胫骨止点撕脱性骨折

目的探讨关节镜下缝线“8”字打结、空心钉固定治疗前交叉韧带（ACL）胫骨止点撕脱性骨折的可行性及近期疗效。方法对15例ACL胫骨止点撕脱性骨折行关节镜下ACL胫骨止点缝合及空心钉固定术,采用在关节镜下结合常规关节镜人路和经髌腱人路进行骨折复位固定,术中使用双根5号Ethibond聚乙烯缝线,在韧带下方、骨块上方经前内侧人路从后往前拢住韧带,并打结呈“8”字形,经韧带两侧胫骨骨隧道拉到胫骨内下方。在骨隧道下方2cm处打入带垫圈的直径4．5mm空心钉,做后抽屉试验,同时拉紧固定线,复位骨块,将固定线固定于空心钉垫圈下,拧紧空心钉。结果手术时间40～60min,平均50min。15例随访6～18个月,平均12个月。术后6周,所有骨折均获愈合,未出现移位。术后3个月,1例有I度前抽屉试验阳性,其余患者均为阴性。所有患者屈伸膝活动度正常。术后半年Lysholm膝关节功能评分90～96分。结论关节镜下缝线“8”字打结空心钉固定治疗ACL胫骨止点撕脱性骨折,术中关节镜监控可靠,操作简便,效果满意,值得推广。     

Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads.

The anterior cruciate ligament (ACL) can be anatomically divided into anteromedial (AM) and posterolateral (PL) bundles. Current ACL reconstruction techniques focus primarily on reproducing the AM bundle, but are insufficient in response to rotatory loads. The objective of this study was to determine the distribution of in situ force between the two bundles when the knee is subjected to anterior tibial and rotatory loads. Ten cadaveric knees (50+/-10 years) were tested using a robotic/universal force-moment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion and a combined rotatory load of 10 Nm valgus and 5 Nm internal tibial torque at 15 degrees and 30 degrees of flexion. The resulting 6 degrees of freedom kinematics of the knee and the in situ forces in the ACL and its two bundles were determined. Under an anterior tibial load, the in situ force in the PL bundle was the highest at full extension (67+/-30 N) and decreased with increasing flexion. The in situ force in the AM bundle was lower than in the PL bundle at full extension, but increased with increasing flexion, reaching a maximum (90+/-17 N) at 60 degrees of flexion and then decreasing at 90 degrees. Under a combined rotatory load, the in situ force of the PL bundle was higher at 15 degrees (21+/-11 N) and lower at 30 degrees of flexion (14+/-6 N). The in situ force in the AM bundle was similar at 15 degrees and 30 degrees of knee flexion (30+/-15 vs. 35+/-16 N, respectively). Comparing these two external loading conditions demonstrated the importance of the PL bundle, especially when the knee is near full extension. These findings provide a better understanding of the function of the two bundles of the ACL and could serve as a basis for future considerations of surgical reconstruction in the replacement of the ACL.     

Knee Kinematics in Anterior Cruciate Ligament-Substituting Arthroplasty With or Without the Posterior Cruciate Ligament

Few studies have compared functional kinematics in knees using identical prostheses with or without the posterior cruciate ligament (PCL). This study contrasted in vivo knee kinematics with an anterior cruciate ligament-substituting arthroplasty with and without PCL retention. We hypothesized that knees without PCLs would exhibit less femoral posterior translation, and consequently less maximum knee flexion. Fifty-six knees were studied using dynamic radiography at least one year post-surgery, with twenty-seven knees retaining the PCL and twenty-nine knees having the PCL sacrificed. Consistent with our hypothesis, PCL-sacrificing knees showed more anterior femoral condylar positions. Contrary to our hypothesis, PCL-sacrificing knees demonstrated greater knee flexion during kneeling (122° versus 115°). Contracted PCLs in severely deformed knees likely were the cause of limited flexion in some retaining knees.     

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.     

胫骨后倾角的测量及与后交叉韧带生物力学关系的研究进展

胫骨后倾角(tibial posterior slope,TPS)最可靠最便捷的测量方式及与后交叉韧带(posterior cruciate ligament,PCL)的生物力学关系存在较大争议。使用X线测量时,推荐使用下肢全长侧位X线片4等份法,其具有高度的可重复性及在日常诊疗过程的普遍性,但仅仅适用于胫骨旋转在15°以内的患者,当旋转超过30°时,平台内侧轮廓不好辨认,不再适用;若仅仅用于日常诊疗评估,当胫骨旋转角在15°以内时,膝关节侧位X线片也具有一定的参考意义,但精准度不能满足要求较高的临床研究。CT测量方法虽能纠正胫骨旋转,但利用在三维CT重建上放置拟合点来测量的方法只适用于无关节退变的膝关节,较多的骨赘会影响利用拟合点的方式来确定的胫骨平面与真实胫骨平台的符合度,具有一定的局限性。MRI不仅可以纠正胫骨旋转,而且使用胫骨解剖轴作为参考轴可以最大程度减少骨赘的影响从而测量出TPS,是一种较好的测量方式。TPS与PCL的生物力学关系,在胫骨截骨术中增大的TPS通过胫骨前移位间接减轻PCL的张力或直接减轻对PCL的负荷都提示可对其产生保护机制;在保留交叉韧带的全膝关节置换术中,...     

In situ forces in the human posterior cruciate ligament in response to muscle loads: a cadaveric study.

The objectives of this study were to determine the effects of hamstrings and quadriceps muscle loads on knee kinematics and in situ forces in the posterior cruciate ligament of the knee and to evaluate how the effects of these muscle loads change with knee flexion. Nine human cadaveric knees were studied with a robotic manipulator/universal force-moment sensor testing system. The knees were subjected to an isolated hamstrings load (40 N to both the biceps and the semimembranosus), a combined hamstrings and quadriceps load (the hamstrings load and a 200-N quadriceps load), and an isolated quadriceps load of 200 N. Each load was applied with the knee at full extension and at 30, 60, 90, and 120 degrees of flexion. Without muscle loads, in situ forces in the posterior cruciate ligament were small, ranging from 6+/-5 N at 30 degrees of flexion to 15+/-3 N at 90 degrees. Under an isolated hamstrings load, the in situ force in the posterior cruciate ligament increased significantly throughout all angles of knee flexion, from 13+/-6 N at full extension to 86+/-19 N at 90 degrees. A posterior tibial translation ranging from 1.3+/-0.6 to 2.5+/-0.5 mm was also observed from full extension to 30 degrees of flexion under the hamstrings load. With a combined hamstrings and quadriceps load, tibial translation was 2.2+/-0.7 mm posteriorly at 120 degrees of flexion ut was as high as 4.6+/-1.7 mm anteriorly at 30 degrees. The in situ force in the posterior cruciate ligament decreased significantly under this loading condition compared with under an isolated hamstrings load, ranging from 6+/-7 to 58+/-13 N from 30 to 120 degrees of flexion. With an isolated quadriceps load of 200 N, the in situ forces in the posterior cruciate ligament ranged from 4+/-3 N at 60 degrees of flexion to 34+/-12 N at 120 degrees. Our findings support the notion that, compared with an isolated hamstrings load, combined hamstrings and quadriceps loads significantly reduce the in situ force in the posterior cruciate ligament. These data are in direct contrast to those for the anterior cruciate ligament. Furthermore, we have demonstrated that the effects of muscle loads depend significantly on the angle of knee flexion.     

Effects of posterior cruciate ligament resection on the tibiofemoral joint gap

The effect of posterior cruciate ligament resection on the tibiofemoral joint gap was analyzed in 30 patients with varus osteoarthritis of thee knee who underwent total knee replacement. The medial soft tissue was released and the bone cut was made without preserving the bone segment of the tibia to which the posterior cruciate ligament was attached. Then the medial and lateral joint gaps in full extension and 90 degrees flexion were measured before and after the posterior cruciate ligament was resected using a tensioning device. After the resection, the flexion gap significantly increased in the medial and the lateral sides (4.8 +/- 0.4 and 4.5 +/- 0.4 mm, respectively, mean +/- standard error) compared with those seen in the extension gap (0.9 +/- 0.2 and 0.8 +/- 0.2 mm). There was no significant difference between the changes in the medial and lateral gaps. The mean value of the flexion gap was 2 mm smaller than the extension gap before the resection and 1.7 mm larger after the sacrifice. Overall, posterior cruciate ligament resection resulted in an increase in the flexion gap and made space for approximately 3-mm thicker polyethylene. The flexion gap can be controlled selectively with posterior cruciate ligament release.     

胫骨骨道定位对前交叉韧带单束重建的影响

[目的]探讨胫骨骨隧道定位对前交叉韧带单束重建术后临床疗效的影响.[方法]将60例前交叉韧带断裂患者随机分为对照组和观察组.对照组胫骨骨隧道内口采用外侧半月板游离缘的切线与前后髁间突连线的交点定位;观察组选择原前内侧束和后外侧束中间位置定位.术后矢状位MRI测量胫骨骨道位置、胫骨纵向位移、后交叉韧带指数、膝关节功能评分进行分析评价.[结果]对照组和观察组胫骨骨道分别位于胫骨平台全长的前(38.67±4.23)％和(34.21±2.46)％.胫骨纵向位移为(11.14±2.64)mm和(14.34±2.23)mm,上倾角为(56.2±4.3)°和(44.6±5.2)°,后交叉韧带指数为(3.97±0.45)和(4.78±0.78);两组比较差异均有统计学意义(t检验,P＜0.05).术后1年,对照组与观察组IKDC膝关节主观评分分别为(79.63±4.67)分和(89.76±5.21)分;Lysholm评分分别为(85.61±4.92)分和(92.54±3.22)分,两组比较差异有统计学意义(t检验,P＜0.05).[结论]前交叉韧带单束重建能使患者的关节稳定性与功能均得到显著改善.膝关节MRI测量可较客观、准确地反映胫骨的骨道定位情况.理想的胫骨骨道在矢状位MRI上位于胫骨平台的前(34.21±2.46)％.     

Isolated posterior cruciate ligament injuries associated with closed tibial shaft fractures: a report of two cases

Introduction  Knee ligament injuries associated with tibia shaft fractures are usually neglected and treatment is delayed. To our knowledge, no case presentation discusses the clinical result of closed tibial shaft fracture with concomitant ipsilateral isolated PCL injury. In this literature, we report the clinical result of two cases that sustained closed tibial shaft fracture with concomitant PCL injury and discuss the treatment options. Materials and methods  We report the clinical result of two cases that sustained closed tibial shaft fracture with concomitant posterior cruciate ligament (PCL) injury. Case 1 received open reduction with plate fixation for the tibial shaft fracture, and he also received arthroscopic reconstruction of PCL with bone-patellar tendon-bone graft due to neglecting PCL injury 5 months later after fracture fixation. Case 2 sustained left tibial-fibular shaft fracture with isolated PCL injury confirmed by magnetic resonance image on the first day of injury. She received tibia fixation with intramedullary nail and conservative treatment with bracing and rehabilitation for PCL injury. Results  In case 1, the male patient only focused on fracture healing without any knee rehabilitation. His knee flexed deeply for protected weight bearing in the injured leg which may have exacerbated the posterior instability and reduced the possibility of PCL healing. The end result of knee function was poor even though PCL reconstruction was done later. In case 2, the female patient with diagnosed posterior cruciate ligament injury on the day of injury, her knee was immobilized in brace with full extension, which improved PCL healing. In addition, she received rehabilitation of quadriceps strengthening, and hamstring muscle contraction was avoided in her daily activity. After rehabilitation, the female patient did not complain of severe subjective instability even with an obvious posterior translation on posterior drawer test. Conclusions  We need to perform a careful physical examination of ipsilateral knee in cases of leg fractures, and MRI of knee before surgery if any doubt exists. However, a further research is needed to conclude on the best operation and rehabilitation program in patients with combined tibial shaft fracture and PCL injury. No support from any institution was gained for this study.     

Anterior cruciate ligament replacements: a mechanical study of femoral attachment location, flexion angle at tensioning, and initial tension

We examined three surgical variables that affect the ability of an anterior cruciate ligament replacement to restore the limit of anterior tibial translation. These were the placement site of the substitute on the femur, the initial tension applied to the replacement, and the flexion angle of the knee at the time of tensioning. An anterior load of 100 N was applied to the tibia. As the knee was flexed, we measured the tensile force in the substitute and the anteroposterior position of the femur relative to the tibia. Placement largely determined whether the force in the replacement increased or decreased with flexion. Placement also largely determined whether the tibia moved anteriorly or posteriorly with flexion compared to its position in the intact knee. The initial tension and the flexion angle at tensioning affected the magnitude of force in the substitute and the magnitude of the change in AP position. They did not affect how force and AP position changed with flexion. Greater increases in force and greater posterior shifts in tibial position were produced by changing the flexion angle at tensioning from 0 degrees to 30 degrees than by increasing the initial tension from 22 to 44 N.     

Reconstruction of knees with combined cruciate deficiencies: a biomechanical study

BACKGROUND: Clinical results of dual cruciate-ligament reconstructions are often poor, with a failure to restore normal anterior-posterior laxity. This could be the result of improper graft tensioning at the time of surgery and stretch-out of one or both grafts from excessive tissue forces. The purpose of this study was to measure anterior-posterior laxities and graft forces in knees before and after reconstructions of both cruciate ligaments performed with a specific graft-tensioning protocol. METHODS: Eleven fresh-frozen cadaveric knee specimens underwent anterior-posterior laxity testing and installation of load cells to record forces in the native cruciate ligaments as the knees were passively extended from 120 degrees to -5 degrees with no applied tibial force, with 100 N of applied anterior and posterior tibial force, and with 5 N-m of applied internal and external tibial torque. Both cruciate ligaments were reconstructed with a bone-patellar tendon-bone allograft. Only isolated cruciate deficiencies were studied. We determined the nominal levels of anterior and posterior cruciate graft tension that restored anterior-posterior laxities to within 2 mm of those of the intact knee and restored anterior cruciate graft forces to within 20 N of those of the native anterior cruciate ligament during passive knee extension. Both grafts were tensioned at 30 degrees of knee flexion, with the posterior cruciate ligament tensioned first. Measurements of anterior-posterior knee laxity and graft forces were repeated with both grafts at their nominal tension levels and with one graft fixed at its nominal tension level and the opposing graft tensioned to 40 N above its nominal level. RESULTS: The anterior and posterior cruciate graft tensions were found to be interrelated; applying tension to one graft changed the tension of the other (fixed) graft and displaced the tibia relative to the femur. The posterior cruciate graft had to be tensioned first to consistently achieve the nominal combination of mean graft forces at 30 degrees of flexion. At these levels, mean forces in the anterior cruciate graft were restored to those of the intact anterior cruciate ligament under nearly all test conditions. However, the mean posterior cruciate graft forces were significantly higher than the intact posterior cruciate ligament forces at full extension under all test conditions. Anterior-posterior laxity was restored between 0 degrees and 90 degrees of flexion with both grafts at their nominal force levels. Overtensioning of the anterior cruciate graft by 40 N significantly increased its mean force levels during passive knee extension between 110 degrees and -5 degrees of flexion, but it did not significantly change anterior-posterior laxity between 0 degrees and 90 degrees of flexion. In contrast, overtensioning of the posterior cruciate graft by 40 N significantly increased posterior cruciate graft forces during passive knee extension at flexion angles of <5 degrees and >95 degrees and significantly decreased anterior-posterior laxities at all flexion angles except full extension. CONCLUSIONS: It was not possible to find levels of graft tension that restored anterior-posterior laxities at all flexion positions and restored forces in both grafts to those of their native cruciate counterparts during passive motion. Our graft-tensioning protocol represented a compromise between these competing objectives. This protocol aimed to restore anterior-posterior laxities and anterior cruciate graft forces to normal levels. The major shortcoming of this tensioning protocol was the dramatically higher posterior cruciate graft forces produced near full extension under all test conditions.