Arthroscopic Reconstruction of the Posterior Cruciate Ligament Using Tibial-Inlay and Double-Bundle Technique

Biomechanical research has suggested that the double-bundle and tibial inlay technique is superior to the single-bundle and the transtibial tunnel method for posterior cruciate ligament (PCL) reconstruction. A combination the posterior tibial inlay and femoral double-bundle technique is thought to be an ideal method for PCL reconstruction. Recently, we successfully performed arthroscopic PCL reconstruction using the tibial-inlay and double-bundle technique. Achilles tendon–bone allograft is used and the bone plug for the arthroscopic tibial inlay fixation is designed in a cylindrical shape and perpendicular to the fiber texture of the Achilles tendon. Achilles tendon is manually split into deep and superficial layers to reconstruct anterolateral and posteromedial bundles as the natural insertion of PCL. The intra-articular lengths of each bundle between tibial tunnel and 2 femoral tunnels are measured to achieve fixation of the graft to the original PCL attachment. After tibial bone plug fixation with an absorbable interference screw and additional suture anchoring, the anterolateral bundle is fixed in a reduction position with the knee in 90° of flexion and the posteromedial bundle is fixed nearly in extension. This procedure makes it possible not only to reproduce the original concept of PCL tibial inlay graft arthroscopically without posterior arthrotomy, but also to achieve a more anatomic PCL reconstruction of the 2 bundles.     

Soft-tissue graft fixation in posterior cruciate ligament reconstruction: evaluation of the effect of tibial insertion site on joint kinematics and in situ forces using a robotic/UFS testing system

Introduction Surgical reconstruction of the posterior cruciate ligament (PCL) is recommended in acute injuries that result in severe tibial subluxation and instability. The surgical outcome level may be affected by the tibial fixation site. In response to a 110-N posterior tibial load, kinematics and in situ forces of anatomical soft-tissue graft fixation in single-bundle PCL reconstruction using an interference screw fixation are significantly closer to those in the intact knee than with extracortical fixation with two staples.Materials and methods Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of porcine knees following single-bundle PCL reconstruction fixed at two different tibial fixation sites: anatomical interference screw and extracortical fixation.Results The site of the tibial graft fixation had significant effect on the resulting posterior displacement and in situ forces of the graft. Both PCL reconstruction techniques reduced the posterior tibial translation significantly. Proximal fixation techniques provided significantly less posterior tibial translation than extracortical fixation. Single-bundle PCL reconstruction with an interference screw showed higher in situ forces of the graft than the extracortical fixation.Conclusions The kinematics and in situ forces of a single-bundle PCL reconstruction using an interference screw fixation technique are superior to the primary stability of an extracortical fixation with staples.     

Biomechanical comparison of different fixation methods on the tibial side in anterior cruciate ligament reconstruction: a biomechanical study in porcine tibial bone

Background The fixation strength of the hamstring tendon graft on the tibial side is considered the weak point in anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the biomechanical characteristics of four types of ACL reconstruction methods on the tibial side. Methods Extensor digitorum tendons harvested from fresh bovine forelimbs were used as the graft materials in this study. Twenty-eight porcine tibias were divided into four groups based on different fixation methods. Group D was fixed using a double spike plate (DSP), group I was fixed using an interference screw, group DI-80 was fixed using both an interference screw and DSP (80 N tension was applied to DSP), and group DI-150 was fixed using both an interference screw and DSP (150 N tension was applied to DSP). Results The displacement of the grafts in response to 500 cycles of 0–150 N loading was significantly greater in groups D (10.3 ± 15 mm) and I (5.5 ± 1.7 mm) than that in groups DI-80 (2.1 ± 0.3 mm) and DI-150 (1.2 ± 0.4 mm), with no significant differences between groups DI-80 and DI-150. The ultimate failure load and stiffness were significantly higher in groups DI-80 (745 ± 156 N, 103 ± 17 N/mm) and DI-150 (801 ± 129 N, 151 ± 35 N/mm) than those in groups D (374 ± 53 N, 70 ± 13 N/mm), and I (520 ± 76 N, 78 ± 18 N/mm). The stiffness of group DI-150 was significantly greater than that of group DI-80. Conclusions Our results indicate that the initial fixation strength of the hamstring tendon can be increased by using an interference screw combined with DSP on the tibial side.     

Cyclic loading of posterior cruciate ligament replacements fixed with tibial tunnel and tibial inlay methods

BACKGROUND: The optimal method of replacement of the posterior cruciate ligament with a bone-patellar tendon-bone graft is not known. The purpose of this study was to compare the mechanical responses to cyclic loading tests of bone-patellar tendon-bone allograft replacements fixed to the tibia with one of two methods: a tibial tunnel or a tibial inlay technique. METHODS: The proximal ends of sixty-two posterior cruciate graft replacements, thirty-one fixed with the tibial tunnel technique and thirty-one fixed with the tibial inlay technique in cadaver knees, were subjected to 2000 cycles of tensile force of 50 to 300 N with the angle of pull at 45 to the tibial plateau. The central 10 mm of the medial and lateral halves of previously fresh-frozen bone-patellar tendon-bone preparations from cadaver knees were used as the grafts. Two pairs of tibiae were used for testing; the two types of fixation and the medial and lateral halves of the patellar tendons were distributed between the tibial pairs. Graft thickness was measured at the point of highest anticipated tissue deformation and at two additional locations at distances from these points. The total change in graft length after cyclic loading at an applied force level of 200 N was recorded. Elongation of the graft during loading cycles between 20 and 200 N of applied tensile force was also measured. A repeated-measures analysis of variance was used to compare all measurements between the inlay and tunnel techniques, and between the medial and lateral halves of the graft used for the inlay method. RESULTS: Ten of the thirty-one grafts that had been passed through a tibial tunnel failed at the acute angle before 2000 cycles of testing could be completed; all thirty-one grafts that had been fixed to the tibia with use of the inlay method survived the testing intact. Evaluation of the twenty-one graft pairs that survived testing after both fixation techniques revealed that the grafts that had been fixed with the inlay method had significantly less thinning at all three measurement sites at the completion of testing; the mean reduction of thickness was 40.6% (at the acute angle) in the grafts fixed with the tunnel method and 12.5% (adjacent to the bone block) in those fixed with the inlay method. After 2000 cycles, the mean lengths of the grafts fixed with the inlay and tunnel methods increased 5.9 and 9.8 mm, respectively; 38% of this increase occurred during the first six loading cycles. After both methods of fixation, the mean graft elongation during a loading cycle decreased approximately 50% from cycle 1 to cycle 2000, resulting in an effectively stiffer graft construct. There was no significant difference in any measured parameter between medial and lateral graft halves. CONCLUSIONS: These tests showed that the inlay technique of posterior cruciate ligament replacement was superior to the tunnel technique with respect to graft failure, graft thinning, and permanent increase in graft length.     

关节镜下股骨双束双隧道胫骨Inlay技术同种异体跟腱移植重建后交叉韧带

目的：探讨关节镜下同种异体跟腱重建后交叉韧带（PCL）的方法，验证股骨双柬双隧道、胫骨Inlay技术重建PCL的临床疗效。方法：2005年9月至2007年8月，采用经深低温冷冻及γ射线照射处理后的异体跟腱对10例PCL损伤的患者行关节镜下PCL重建术，手术方式股骨端为双束双隧道重建，可吸收挤压螺钉固定，胫骨端为Inlay固定。通过物理检查、Lysholm及IKDC评分来评价手术疗效。结果：术后8d内患者体温恢复正常，免疫排斥轻，无感染发生。所有患者术后获6～23个月（平均17个月）随访，终末随访时10例患者术膝胫骨下陷征（Sagsign）阴性，后抽屉试验（PDT）及Lachman征均为阴性或I度。疗效评定采用Lysholm评分和IKDC评分。Lysholm评分中交锁、不稳、疼痛、肿胀、爬楼、下蹲和总分术前术后比较差异有统计学意义，术后优7例，良2例，中1例；IKDC评分中疼痛频率、疼痛程度、规律活动量、活动影响程度、功能自评和总分等术前术后比较差异有统计学意义，术后IKDC评分A级7例，B级3例。结论：同种异体跟腱是重建PCL的可靠替代物，双束双隧道和Inlay技术固定可靠，可减少移植物损伤，是PCL重建的理想技术。     

Pullout strength of tibial graft fixation in ACL-replacement with a patellar tendon graft: Interference screw versus staple fixation in human knees

Summary The endoscopic single incision technique for ACL reconstruction with a femoral half-tunnel may lead to a graft/tunnel mismatch and subsequent protrusion of the block from the tibial tunnel. The typical tibial fixation with an interference screw is not possible in these cases. Fixation with staples in a bony groove inferior to the tunnel outlet can be used as an alternative technique. Current literature does not provide biomechanical data of both fixation techniques in a human model. This study was performed to evaluate primary biomechanical parameters of this technique compared to a standard interference screw fixation of the block. 55 fresh-frozen human cadaver knee joints of a younger age (mean age: 44 years) were used. Grafts were harvested from the patellar tendon midportion with bone blocks of 25 mm length and 9 mm width. A 10 mm tibial tunnel was drilled from the anteromedial cortex to the center of the tibial insertion of the ACL. 3 different sizes of interference screws (7 × 30, 9 × 20 and 9 × 30 mm) were chosen as a standard control procedure (n = 40). For tibial bone-block fixation the graft was placed through the tunnel, the screw was then inserted on the cancellous or the cortical surface respectively. 15 knees were used for staple fixation. A groove was created inferior to the tunnel outlet with a chisel. The bone block was fixed in this groove with 2 barbed stainless steel staples. Tensile testing in both of the groups was carried out under axial load parallel to the tibial tunnel in a Zwick-testing-machine with a velocity of 1 mm/sec. Dislocation of the graft and stiffness were calculated at 175 N load. Maximum load to failure using interference screws varied between 506 and 758 N. Load to failure using staples was 588 N. Dislocation of the graft ranged between 3.6 and 4.7 mm for interference screw fixation and was 4.2 mm for staples. With both fixation techniques, the recorded failure loads were sufficient to withstand the graft loads which are to be expected during the rehabilitation period. Staple fixation of the bone block outside of the tunnel resulted in fixation strength comparable to interference screw fixation.      

Posterior cruciate ligament reconstruction: current trends

A survey was conducted of the Herodicus Society membership to assess the current status of treating posterior cruciate ligament (PCL) injuries and compared to a similar survey conducted in 1991. The survey addressed indications, graft choice, surgical technique, graft tensioning, and graft fixation. Seventy-eight active surgeons were sent a 34-question survey pertaining to isolated PCL injuries. The majority of respondents (78%) performed < or = 10 PCL reconstructions per year. The arthroscopic assisted with posteromedial portal technique was the most commonly used (49%). The tibial inlay/onlay technique was used by 15%, and 68% used the single femoral tunnel technique. The remainder used a double femoral tunnel technique. Allograft Achilles tendon was the most commonly selected graft for acute (43%) and chronic (50%) PCL reconstructions. An interference screw for femoral fixation was used 67% of the time. The majority of respondents (55%) tensioned their single bundle or anterolateral band of a double bundle in 71 degrees-90 degrees of flexion. A significant difference in technique was noted when comparing those who performed < or = 10 PCL reconstructions per year (group 1) versus > 10 PCL reconstructions per year (group 2). In group 1, 25% of surgeons used a double tunnel technique versus 59% of surgeons in group 2. The most common operative treatment for PCL injuries consisted of a single femoral tunnel with an Achilles tendon allograft. When compared to a similar survey conducted in 1991, the notable differences were a trend toward Achilles tendon allograft and the popularization of the double femoral tunnel and tibial inlay/onlay technique.     

One-incision endoscopic technique for posterior cruciate ligament reconstruction with quadriceps tendon–patellar bone autograft

Quadriceps tendon–patellar bone autograft is an alternative graft choice for posterior cruciate ligament (PCL) reconstruction. A 2-incision technique with outside-in fixation at the femoral condyle is generally used. In this article, we describe a 1-incision endoscopic technique for PCL reconstruction with quadriceps tendon–patellar bone autograft. The graft consists of a proximal patellar bone plug and central quadriceps tendon. The bone plug is trapezoidal, 20 mm long, 10 mm wide, and 8 mm thick. The tendon portion is 80 mm long, 10 mm wide, and 6 mm thick, including the full-thickness of the rectus femoris and partial thickness of the vastus intermedius. Three arthroscopic portals, including anteromedial, anterolateral, and posteromedial, are used. All procedures are performed in an endoscopic manner with only 1 incision at the proximal tibia. At the femoral side, the bone plug is fixed by an interference screw. At the tibial side, the tendon portion is fixed by a suture to a screw on the anterior cortex and an interference bioscrew in the posterior tibial tunnel opening. Quadriceps tendon autograft has the advantages of being self-available, allowing for easier arthroscopic technique, and providing comparable graft size. The 1-incision technique provides a simple reconstruction method for PCL insufficiency without a second incision at the medial femoral condyle.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 3 (March), 2001: pp 329–332     

A modified technique for tibial interference screw fixation of hamstring anterior cruciate ligament grafts.

This article describes a modified technique for tibial fixation of quadrupled hamstring grafts in anterior cruciate ligament reconstruction. Using this technique common problems with tibial interference screw fixation of hamstring grafts-such as loss of tension of the graft during screw introduction or twisting of the graft in the tunnel around the screw-are avoided.     

Endopearl augmentation of bioabsorbable interference screw fixation of a soft tissue tendon graft in a tibial tunnel

In this technical note, we introduce a new technique for tibial side soft tissue graft fixation using a bioabsorbable interference screw augmented with an EndoPearl (Linvatec, Largo, FL) for ACL reconstruction. This technique will enable the knee surgeon to use shorter grafts while minimizing slippage without reducing fixation strength.     

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.     

Biomechanical comparison of tibial inlay and tibial tunnel techniques for reconstruction of the posterior cruciate ligament. Analysis of graft forces

BACKGROUND: The tibial inlay technique of reconstruction of the posterior cruciate ligament offers potential advantages over the conventional transtibial tunnel technique, particularly with regard to the graft force levels that develop over a functional range of knee flexion. Abnormally high graft forces generated during rehabilitation activities could lead to stretch-out of the graft during the critical early healing period. The purpose of this study was to compare graft forces between these two techniques and with forces in the native posterior cruciate ligament. METHODS: A load cell was installed at the femoral origin of the posterior cruciate ligament in twelve fresh-frozen cadaveric knees to measure resultant forces in the ligament during a series of knee loading tests. The posterior cruciate ligament was then excised, and the femoral ends of 10-mm-wide bone-patellar tendon-bone grafts were attached to the load cell to measure resultant forces in the grafts. For the tunnel reconstruction, the distal bone block of the graft was placed into a tibial tunnel and thin stainless-steel cables interwoven into the bone block were gripped in a split clamp attached to the anterior tibial cortex. With the inlay technique, the distal bone block was fixed in a tibial trough with use of a cortical bone screw with a washer and nut. The proximal ends of all grafts were pretensioned to a level of force that restored intact knee laxity at 90 degrees of flexion, and loading tests were repeated. RESULTS: There were no significant differences in mean graft forces between the two techniques under tibial loads consisting of 100 N of posterior tibial force, 5 N-m of varus and valgus moment, and 5 N-m of internal and external tibial torque. Mean graft forces with the tibial tunnel technique were approximately 10 to 20 N higher than those with the inlay technique with passive knee flexion beyond 95 degrees. Mean graft forces with both reconstruction techniques were significantly higher than forces in the native posterior cruciate ligament with the knee flexed beyond approximately 90 degrees for all but one mode of loading. CONCLUSIONS: In this cadaveric testing model, neither technique for reconstruction of the posterior cruciate ligament had a substantial advantage over the other with respect to generation of graft forces.     

Arthroscopic anterior cruciate ligament reconstruction using autogenous hamstring tendon graft without detachment of the tibial insertion

This article describes a modified arthroscopic technique of anterior cruciate ligament reconstruction using quadrupled hamstring tendon graft. The autogenous semitendinosus and gracilis grafts are harvested without detachment of the tibial insertion. To obtain longer grafts, the accessory tibial insertions of the hamstring tendons are dissected. The EndoButton (Acufex Microsurgical, Andover, MA) is used for femoral fixation and two spiked staples are used for tibial fixation in a belt buckle fashion. Then the residual anterior laxity is restored by additional absorbable interference screw fixations. In this technique, more viable graft is obtained and more firm distal fixation is achieved by preservation of the tibial insertion of hamstring tendons.     

Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone

It has recently been shown that graft fixation close to the ACL insertion site is optimal in order to increase anterior knee stability. Hamstring tendon fixation using interference screws offers this possibility and a round threaded titanium interference screw has been previously developed. The use of a round threaded biodegradable interference screw may be equivalent. In addition, to increase initial fixation strength, graft harvest with a distally attached bone plug may be advantageous, but biomechanical data do not exist. This study compares the initial pullout force, stiffness of fixation, and failure modes of three strand semitendinosus grafts in 36 proximal calf tibiae using either biodegradable poly-(D,L-lactide) (Sysorb; Sulzer Orthopaedics Ltd, Munsingen, Switzerland) or round threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA) interference screws, harvested either without (biodegradable: group I, titanium III) or with (biodegradable: group II, titanium: group IV) attached tibial bone plugs. Maximum pullout force in group I (507 ± 93 N) was significantly higher than in group III (419 ± 77 N). Pullout force of bone plug fixation was significantly higher than that of direct tendon fixation (717 ± 90 N in group II and 602 ± 117 N in group IV). Pullout force of biodegradable fixation was significantly higher in both settings. These results indicate that initial pullout force of hamstring-tendon graft interference screw fixation can be increased by using a biodegradable interference screw. In addition, initial pullout force of hamstring-tendon graft fixation with an interference screw can be greatly increased by harvesting the graft with its distally attached tibial bone plug.Arthroscopy 1998 Jan-Feb;14(1):29-37     

Tibial tunnel bone grafting: a new technique for dealing with graft- tunnel mismatch in endoscopic anterior cruciate ligament reconstruction

A problem that is frequently encountered during endoscopic anterior cruciate ligament reconstruction bone-patellar tendon-bone autograft is that the graft is often too long and protrudes from the tibial tunnel. If less than 20 mm of the bone plug remains in the tibial tunnel, interference screw fixation cannot safely be used, and an alternate form of fixation may have to be employed. A simple technique has been developed to deal with this problem. The technique involves bone-grafting the tibial tunnel with a cancellous core of bone that is removed while creating the tibial tunnel. This not only makes it possible to safely use interference screw fixation in all cases, but it also makes it possible to place the point of graft fixation very near the anatomic anterior cruciate ligament insertion site.Arthroscopy 1998 Mar;14(2):224-8     

Initial fixation strength of modified patellar tendon grafts for anatomic fixation in anterior cruciate ligament reconstruction.

Recently it has been shown that anatomic tibial graft fixation in anterior cruciate ligament (ACL) reconstruction is preferable in order to increase isometry and knee stability. To facilitate anatomic patellar tendon graft fixation, customized graft length shortening is necessary. The purpose of this study was to compare the initial fixation strength of four different shortened patellar tendon grafts including three bone plug flip techniques and direct patellar tendon-to-bone interference fit fixation in a model with standardized bone density. Ninety calf tibial plateaus (22 to 24 weeks old) with adjacent patella and extensor ligaments were used. Tendon grafts were shortened by flipping the bone plug over the tendon leaving a tendon-tendon-bone (TTB) construct and, as the first modification in the opposite direction resulting in a tendon-bone-tendon (TBT) construct. The second modification consisted of the TBT construct with interference screw position at the lateral aspect of the bone plug (TBTlat). As the fourth modification the tendon graft was directly fixed (Tdirect) with an interference screw. In addition, a round-threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA), a round-threaded biodegradable screw (Sysorb; Sulzer Orthopedics, Münsingen, Switzerland), and a conventional titanium interference screw (Arthrex Inc, Naples, FL) were compared. We found that TTB (mean 441 N for biodegradable screw, 357 N for RCI screw, 384 N for conventional screw) and TBT (mean 407 N for biodegradable screw, 204 N for RCI screw, 392 N for conventional screw) construct fixation achieves comparable fixation strength, although failure in the TTB was due to tendon strip off at its ligamentous insertion. The highest failure load was found in TBTlat fixation (mean 610 N for biodegradable screw, 479 N for RCI screw). Therefore, this technique should be recommended when using a tendon flip technique. The failure load for Tdirect fixation (mean 437 N for biodegradable screw, 364 N for RCI screw) was similar to that of TTB and TBT fixation, which may indicate that a patellar-tendon graft harvested without its patellar bone plug and directly fixed with an interference screw is equivalent to a flipped graft. This may additionally reduce harvest site morbidity and eliminates the risk of patellar fracture. The fixation strength of round-threaded biodegradable and conventional titanium interference screws was similar, whereas that of round-threaded titanium screws was significantly lower in the patellar tendon flip-techniques. However, it should be taken into consideration that round-threaded titanium screws are proposed for direct tendon-to-bone fixation.     

Surgical Technique: Aperture Fixation in PCL Reconstruction: Applying Biomechanics to Surgery

Background  

Biomechanical studies suggest reducing the effective graft length during transtibial posterior cruciate ligament (PCL) reconstruction by augmenting the distal tibial fixation with a proximal screw near the tibial tunnel aperture could increase graft stiffness and provide a more stable reconstruction. However, it remains unknown to what extent this mechanical theory influences in vivo graft performance over time.     

前交叉韧带重建术胫骨端两种固定方法的比较

[目的]比较单独应用带鞘界面螺钉或联合运用带鞘界面螺钉与门型钉固定前交叉韧带胫骨骨道远端的临床效果。[方法]回顾性分析2014年1月~2016年8月71例接受前交叉韧带重建的患者。按胫骨固定方式分为两组,单螺钉组37例,采用单一带鞘界面螺钉固定胫骨侧;联合组34例,采用带鞘界面螺钉联合门型钉固定胫骨侧。比较两组围手术期、随访与影像资料。[结果]71例患者均成功接受手术,术中未出现神经和血管损伤。两组手术时间、住院时间的差异无统计学意义(P>0.05);单螺钉组的住院费用稍低于联合组,但差异无统计学意义(P>0.05)。术后两组患者的Lachman试验、轴移试验均转为阴性。所有患者随访12~24个月,平均(14.13±2.54)个月。末次随访时,两组共71例患者中,除带联合组3例患者仍有跪地疼痛外,其他患者均无明显交锁、疼痛打软腿等症状,所有患者生活均可自理。末次随访时两组患者的Lachman试验、轴移试验结果、伸屈ROM、IKDC2000评分和Lysholm评分差异均无统计学意义(P>0.05)。术后影像学检查示两组患者膝关节骨道位置良好。[结论]单纯使用界面螺钉固定与联合使用界面螺钉与门型钉在术后膝关节功能、膝关节稳定性方面效果相当,然而,联合使用界面螺钉与门型钉可能与术后跪地疼痛有关。     

Hybrid hamstring graft tibial fixation in anterior cruciate ligament reconstruction

Tibial fixation of the anterior cruciate ligament hamstring tendon graft is commonly considered more problematic than femoral fixation. When interference screws are used for tibial hamstring tendon graft fixation, graft sometimes looses its tension, so a hybrid fixation (more than one method of fixation) must be applied. Biomechanical studies show that an implementation of interference screws combined with different indirect distal hamstring tendon fixation techniques can withstand much higher tearing forces when compared with one type of fixation. We made a technique of hybrid tibial fixation of the hamstring graft using round interference screws and an additional bi-cortical 4.5-mm diameter screw with a modified head that allows control over the initial tension of the graft.     

Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: The impact of fixation level and fixation method under cyclic loading

Purpose: To mechanically test different reconstruction techniques of the anterior cruciate ligament (ACL) under incremental cyclic loading and to evaluate the impact of the level and method of graft fixation on tensile properties of each technique. Type of Study: In vitro biomechanical study. Methods: Four hamstring and 1 patellar tendon reconstruction techniques were performed on 40 young to middle-aged human cadaveric knees (average age, 39 years). An anterior drawer with increasing loads of 20 N increments was applied at 30° of knee flexion. Anatomic, direct interference screw fixation was tested in 2 hamstring and in the patellar tendon groups. Nonanatomic (extracortical) graft anchorage was tested in the remaining 2 hamstring groups with indirect graft fixations on both sides and the combination of indirect tibial and direct femoral fixation. Structural properties were determined throughout the cyclic loading test. Results: The more anatomic reconstruction techniques provided significantly higher structural properties and smaller loss of fixation compared with nonanatomic, extracortical fixation, with indirect repair on both fixation sites resulting in the lowest structural properties. The tibial fixation site was the weakest link in all of the anatomic reconstructions. Patellar tendon fixation with attached bone blocks in both bone tunnels significantly improved construct stiffness and decreased graft slippage. Conclusions: The results of this study suggest that anatomic fixation should be preferred for anchorage of hamstring tendons and linkage materials should be avoided. Direct soft-tissue fixation with interference screws still allows considerable graft slippage, which can be limited by using a bone block or application of a backup or hybrid fixation, especially on the tibial fixation site.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 3 (March), 2002: pp 304–315