Impact of tendon suturing on the interference fixation strength of quadrupled hamstring tendon grafts

Introduction

Interference screw fixation of soft tissue grafts has been a widely used fixation technique for cruciate ligament reconstruction. Suturing of the graft construct prior to graft fixation has been proposed to increase fixation strength; however, the effect on mechanical properties has not been well characterized. The goal of this study was to determine whether uniform suturing of the tendon graft affects (1) ultimate fixation strength of the hamstring tendon graft and (2) motion of the tendon in the bone tunnel during cyclic loading when comparing sutured grafts vs. unsutured grafts.

Method

Eight pairs of matched mature porcine tibias (age <2 years) and eight paired fresh-frozen human quadrupled hamstring tendon grafts were used. One quadrupled graft from each pair was placed into one of two groups. In the group A a single cerclage suture 3 cm from the doubled end of the graft was placed to join the four tendon strands. In group B a heavy suture was used to tightly unite the four strands of tendon graft to provide a better grip for the interference screw during fixation. The grafts were placed in tibial bone tunnels that matched the graft’s diameter and fixed with an interference screw. The looped end of the graft and the attached tibia were rigidly fixed in a material testing machine. The graft constructs were subjected to 100 cycles of 20–250 N load, followed by a load-to-failure test. In addition, a motion analysis system was used during cyclic testing to better determine the amount of elongation at the graft–tunnel interface. Statistical analysis of the failure load and stiffness and the overall elongation following cyclical loading was performed using the Wilcoxon rank sum test. Level of significance was set at p < 0.05.

Results

Elongation at the tendon–bone interface during sub-maximal cyclic loading was 2.4 ± 1.4 mm (unsutured) vs. 2.0 ± 0.7 mm (sutured) (p > 0.05). Failure load of the grafts without sutures (634 ± 86 N) was significantly lower than with the sutures (837 ± 183 N). Ultimate stiffness of group A (283 ± 34 N/mm) was lower than that of group B (331 ± 51 N/mm); however, this was not statistically significant (p = 0.051).

Conclusion

This study confirms that suturing of the graft construct before interference screw fixation may increase ultimate failure load. However, an improvement of structural properties in response to cyclic loading with sub-maximal loads could not be confirmed. Clinicians using interference screw fixation may suture the graft to improve fixation strength; however, suturing does not appear to allow a more aggressive rehabilitation after surgery.     

Viscoelasticity and temperature variations decrease tension and stiffness of hamstring tendon grafts following anterior cruciate ligament reconstruction

BACKGROUND: Hamstring tendon grafts used for anterior cruciate ligament reconstruction are typically harvested early in the surgical procedure and are preconditioned prior to reimplantation. Postoperatively, the grafts undergo stress relaxation and warm from the temperature of the operating room to body temperature. The hypothesis of this study was that the tension within semitendinosus and gracilis tendon grafts and the stiffness of the grafts significantly decrease postoperatively because of both stress relaxation and an increase in temperature. METHODS: Double-strand grafts were created from six semitendinosus tendons and six gracilis tendons harvested from cadaver specimens. The grafts were loaded to 65 N while at operating-room temperature (20 degrees C). After fifteen minutes of stress relaxation, graft tension was measured and the grafts were stretched by 0.1 mm to determine stiffness. The tension and stiffness measurements represented graft properties immediately following reconstruction. Additional tension and stiffness measurements were made following three hours of stress relaxation and after increasing the temperature to the body temperature at the knee (34 degrees C). Both types of graft were examined for differences in stiffness and tension due to stress relaxation and the temperature increase. RESULTS: For both types of graft, the tension and stiffness decreased following stress relaxation to approximately 50% and 80%, respectively, of the value immediately after reconstruction. Increasing the temperature decreased the tension and stiffness further to approximately 40% and 70%, respectively, of the value after reconstruction for both types of graft. All changes in tension and stiffness were significant (p < 0.01). CONCLUSIONS: Graft tension and stiffness achieved immediately following reconstruction are not maintained postoperatively because of stress relaxation and a temperature increase. This could lead to increased knee laxity.     

腘绳肌腱移植包埋法重建内侧髌股韧带治疗复发性髌骨脱位

目的 :探讨腘绳肌腱移植包埋法重建内侧髌股韧带治疗复发性髌骨脱位的疗效。方法 :2008年3月至2013年6月间收治复发性髌骨脱位67例,其中男28例,女39例;年龄10~42岁,平均22岁。临床表现为膝关节不稳感,"打软腿",髌骨错位感,膝前疼痛等。67例均行腘绳肌腱移植包埋法重建内侧髌股韧带。术前后采用Lysholm评分及Q角变化对疗效进行评估。结果:术后67例均获随访,随访时间4~60个月,平均(27.5±13.4)个月。术后切口均愈合良好,无髌骨脱位或半脱位发生。Lysholm评分由术前76.35±2.86提高到术后82.71±2.29;Q角从术前(18.75±2.33)°降至术后(13.28±1.75)°。结论:腘绳肌腱移植包埋方法重建内侧髌股韧带可以提供足够的张力,恢复髌骨稳定性,改善膝关节功能。     

Response of hamstring and patellar tendon grafts for anterior cruciate ligament reconstruction during cyclic tensile loading

The efficacy of anterior cruciate ligament (ACL) reconstruction in the knee using hamstring tendon or patellar tendon grafts is thought to depend on the relative amounts of graft elongation, or creep, following postoperative rehabilitation. In this study, the creep responses of the tendinous portions of these two graft types were compared during 1 hour of cyclic loading to 200 N at 1 Hz. In the hamstring tendon grafts, strains were measured in both the tissue and in the length-augmentation tape to identify the relative contribution of this particular graft fixation to overall creep. Differences in tissue strain between graft types during cyclic loading were not statistically significant. For both types of grafts, overall graft length significantly increased after 3600 cycles while tissue creep was not significant. The greatest creep in the hamstring tendon grafts occurred at the tissue-tape interface, indicating a potential disadvantage of this composite graft construct.     

The EndoPearl device increases fixation strength and eliminates construct slippage of hamstring tendon grafts with interference screw fixation

Purpose: The EndoPearl (Linvatec, Largo, FL), a biodegradable device to augment the femoral interference screw fixation of hamstring tendon grafts has been developed. The first objective of this study was to compare the initial fixation strength of quadrupled hamstring tendons and biodegradable interference screw fixation with and without the application of the EndoPearl device. The second objective was to determine the influence of the EndoPearl device on the fatigue behavior under incremental cyclic loading conditions in a simulation of critical fixation conditions. Type of Study: Biomechanical study. Methods: Fresh human hamstring tendons were harvested and grafts were fixed with biodegradable poly-L-lactide interference screws. Twenty proximal calf tibias were used to compare the initial fixation strength of the study and the control group. In the study group, the EndoPearl device was secured to the graft using two No. 5 Ethibond sutures (Ethicon, Somerville, NJ). Specimens were loaded until failure in a materials testing machine. For cyclic testing, human hamstring tendons and 20 distal porcine femurs were used. Critical graft fixation conditions were simulated by increasing tunnel diameter 2 mm over the graft diameter. Grafts were loaded progressively in increments of 100 N until failure; 100 cycles were applied per load increment. Results: Graft fixation with the additional EndoPearl device had a significantly higher maximum load to failure (658.9 ± 118.1 N v 385.9 ± 185.6 N, P =.003) and stiffness (41.7 ± 11 N/mm v 25.7 ± 8.5 N/mm). Graft fixation with the EndoPearl device sustained a significant higher total number of cycles (388.5 ± 125.6) compared with the control group (152.8 ± 144.9, P =.002). Conclusions: We demonstrated that the augmentation of a hamstring tendon graft with the EndoPearl device increases interference screw fixation strength significantly. Under dynamic loading conditions, specimens of the study group sustained substantially higher loads and a larger number of cycles, which indicates a greater resistance to graft slippage. The application of the EndoPearl device may also allow for a secure soft-tissue graft fixation with interference screws in cases of critical fixation conditions.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 4 (April), 2001: pp 353–359     

Biomechanical study of ACL reconstruction grafts

There are no published studies describing the strength quadrupled gracilis tendon alone and quadrupled semitendinosus tendon alone in the configuration used for anterior cruciate ligament (ACL) reconstruction. The primary objective was to compare the mechanical properties of grafts used for ACL reconstruction during a tensile failure test. The secondary objective was to evaluate the effect of uniform suturing on graft strength. Fifteen pairs of knees were used. The mechanical properties of five types of ACL grafts were evaluated: patellar tendon (PT), sutured patellar tendon (sPT), both hamstring tendons (GST4), quadrupled semitendinosus (ST4), and quadrupled gracilis (G4). Validated methods were used to perform the tensile tests to failure and to record the results. Student's t‐test was used to compare the various samples. The maximum load to failure was 630.8N (± 239.1) for the ST4, 473.5N (± 176.9) for the GST4, 413.3N (± 120.4) for the sPT, and 416.4N (± 187.7) for the G4 construct. Only the ST4 had a significantly higher failure load than the other grafts. The sPT had a higher failure load than the PT. The ST4 construct had the highest maximum load to failure of all the ACL graft types in the testing performed here. Uniform suturing of the grafts improved their ability to withstand tensile loading. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1188–1196, 2015.     

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.     

Fremdmaterialfreier Kreuzbandersatz mit Diamanthohlschleifen

Hamstring and patella tendons are usually used for anterior cruciate ligament (ACL) reconstruction and fixed with foreign material, partially executed far from the original point of insertion. Besides the biomechanical questions bone defects are a severe problem in cases of revision. We developed a biological method with diamond cutting instruments for graft fixation with bone dowels near the native insertion. The graft is tensioned and fixed in 120° knee flexion and is self-adapting in extension. The technique has been used in a large number of cases during a prospective study with a follow-up of 10 years for patella tendon and 4 years for hamstring tendon grafts. In this investigation 124 patients with bone-patellar tendon-bone (BPTB) grafts showed an International Knee Documentation Committee (IKDC) score A/B in 87% after a mean follow-up of 9.6 years, a Lachman test (maximum side-to-side difference) of 1.38±0.93 mm and a negative pivot shift test in 91% of the cases. Of the 147 patients with hamstring tendon grafts 89% had an IKDC score A/B after a mean follow-up of 4.3 years, a Lachman test of 1.14±0.76 mm and no pivot shift in 90% of the cases. The Tegner activity score decreased by ?1.8 in both groups. Conclusion: This method allows a reliable biological press-fit fixation for every kind of graft near the original point of insertion, preventing bone defects, allowing early intensive rehabilitation and low costs.     

Effects of initial graft tension on knee stability after anterior cruciate ligament reconstruction using hamstring tendons: a cadaver study

Purpose: Tension degradation within hamstring grafts and anterior knee laxity were analyzed in a cadaveric anterior cruciate ligament (ACL) reconstruction model undergoing cyclic motion. It was hypothesized that suture fixation of a hamstring graft would lose tension during cycling initially and then stabilize, and that anterior knee laxity would increase as tension was lost. Hamstring grafts fixed under 3 different loads were evaluated to determine how initial graft tension affected knee laxity after cyclic motion. Type of Study: Cadaveric biomechanical analysis. Methods: Eighteen pairs of fresh-frozen hamstring tendons were tested on 2 cadaveric knees undergoing ACL reconstruction. The hamstring pairs were separated equally and randomly into one of 3 tension groups: 68 N (15 lb), 45 N (10 lb), and 23 N (5 lb). The loads were applied to the graft at 30° of flexion, and the grafts were secured to the tibia with a suture and post technique. The knee was then cycled 1,000 times using an Instron machine (Instron, Canton, MA) through a range of motion between 0° to 90°. Constant monitoring and recording of graft tension was performed. A KT-1000 (Medmetrics, San Diego, CA) was performed (1) on the intact knee, (2) after ACL excision, (3) after ACL reconstruction and initial graft fixation, and (4) at the completion of the 1,000 cycles. An analysis of variance test was used to evaluate data. Results: The tension within the grafts after 1,000 cycles decreased to 34.5 N (7.6 lb), 16.8 N (3.7 lb), and 15.4 N (3.4 lb) from the preloads of 68, 45, and 23 N, respectively (P < .05 in all cases). This represented an average decrease of 50.2% of the initial tension after 1,000 cycles. Manual-maximum KT testing of the intact knees was 5.8 ± 0.3 mm, and after ACL excision was 13.2 ± 0.9 mm. KT testing revealed 6.0 ± 0.9 mm, 8.1 ± 1.9 mm, and 8.9 ± 1.1 mm of anterior translation after fixation in the tension groups of 68, 45, and 23 N, respectively. After 1,000 cycles, the translation increased to 7.8 ± 1.0 mm, 10.5 ± 1.9 mm, and 10.3 ± 1.5 mm, respectively. Conclusions: This study showed that initial graft tension decreases with cyclic loading, resulting in increased knee laxity. To restore anterior translation to within 3 mm of the native ACL condition after cyclic loading, approximately 68 N of initial tension is required using this fixation technique.     

How four and twelve weeks of implantation affect the strength and stiffness of a tendon graft securely fixed in a bone tunnel: a study of Evolgate fixation in an extra-articular model ovine model

Healing of a tendon graft to a bone tunnel is slower than the healing of a bone plug. Therefore, the device chosen for hamstring fixation may need to maintain its strength and stiffness longer than the device chosen for bone-tendon-bone fixation. We evaluated, in an extraarticular ovine model, how 4 and 12 weeks of implantation affect the strength of a tendon graft fixed to bone with the Evolgate. The long digital extensor tendon was transplanted and fixed with the Evolgate into a 30-mm long, 8 mm diameter bone tunnel drilled in the tibial metaphysis of both posterior limbs of 15 skeletally mature Suffolk sheep. Immediately after implantation, and 4 and 12 weeks later, biomechanical cyclic load tests in 50 N increments were performed until failure to evaluate the ultimate failure load (UFL). Histological analysis was also performed at 4 and 12 weeks. Biomechanical tests revealed a UFL of 339±120 N at time 0, and increases to 635±19 N (4 weeks) and to 867±80 N (12 weeks). The differences between all 3 groups were significant (p<0.001, paired t test). The histological evaluation showed a layer of cellular, fibrous tissue between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey’s fibers. The strength of the interface significantly and progressively increased between weeks 4 and 12 after transplantation, and was associated with a degree of bone ingrowth noted histologically. The use of the Evolgate seems not to interfere with the bone ingrowth after implantation, allowing an improvement in strength of the bonetendon- device complex.     

Effect of acute tensile loading on gender‐specific tendon structural and mechanical properties

Stretching is commonly used prior to exercise, as it is thought to reduce the risk of injury, and it is also used in the preconditioning of tendon grafts. As tendon properties have been shown to be different between genders, it is proposed that stretching will differentially affect the structure. Here we examine the effect of acute stretch on the mechanical properties of both male and female medial gastrocnemius tendon. Female [20 years ± 1 (SEM), n = 17] and male (22 years ± 1, n = 18) subjects underwent a 5‐min passive dorsiflexion stretch. Prior to and post stretch medial gastrocnemius tendon stiffness (K), length (l) and cross‐sectional area (csa) were measured using ultrasonography and dynamometry. Stiffness and Young's modulus (ε) were significantly reduced with stretch for both genders (p < 0.05). Females showed significantly (p < 0.05) greater pre‐ to poststretch decreases in K (22.4 vs. 8.8%) and ε (20.5 vs. 8.4%) in comparison to males. The present results show that stretching acutely reduces stiffness of the medial gastrocnemius tendon in females and males, with females showing significantly greater change. The observed disparity between genders may be due in part to variations in tendon moment arm and intrinsic differences in tendon composition. These differential changes in tendon mechanical properties have functional, motor control, and injury risk implications, as well as possible implications for preconditioning of tendon grafts. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 510–516, 2009     

Tension in a double loop tendon anterior cruciate graft during a simulated open chain knee extension exercise.

Concerns exist regarding the tension developed in a reconstructed anterior cruciate ligament (ACL) during open chain knee extension exercises used to rehabilitate the knee. Therefore, the primary objective was to measure tension in an ACL graft during a simulated open chain knee extension exercise as a function of ankle weight. A secondary objective was to determine whether the graft tension was reduced with relatively high stiffness fixation. The open chain exercise was simulated in seven cadaveric specimens in which the ACL had been reconstructed with double loop tendon grafts. Graft tension was measured at 15 degrees of flexion as the effective ankle weight was increased from 22.5 to 67.5 and then to 112.5 N for three different fixation stiffnesses (25, 125, and 225 N/mm). The initial tension was set to restore the 225 N anterior limit of motion to that of the intact knee at 30 degrees of flexion. Increasing the ankle weight caused the graft tension to increase significantly (p<0.0001), but the increase with the highest ankle weight was only 62 N on average. Increasing the fixation stiffness caused the graft tension to decrease significantly (p<0.0001) because the initial tension decreased by 107 N as the fixation stiffness increased. Because the graft tension with the highest ankle weight was limited to 112 N on average, high stiffness fixation methods, which are also resistant to lengthening in the region of the fixation, may reduce the risk of graft construct lengthening during open chain knee extension exercises.     

An artificial tendon to connect the quadriceps muscle to the Tibia

No permanent, reliable artificial tendon exists clinically. Our group developed the OrthoCoupler? device as a versatile connector, fixed at one end to a muscle, and adaptable at the other end to inert implants such as prosthetic bones or to bone anchors. The objective of this study was to evaluate four configurations of the device to replace the extensor mechanism of the knee in goats. Within muscle, the four groups had: (A) needle‐drawn uncoated bundles, (B) needle‐drawn coated bundles, (C) barbed uncoated bundles, and (D) barbed coated bundles. The quadriceps tendon, patella, and patellar tendon were removed from the right hind limb in 24 goats. The four groups (n = 6 for each) were randomly assigned to connect the quadriceps muscle to the tibia (with a bone plate). Specimens were collected from each operated leg and contralateral unoperated controls both for mechanical testing and histology at 90 days post‐surgery. In strength testing, maximum forces in the operated leg (vs. unoperated control) were 1,288 ± 123 N (vs. 1,387 ± 118 N) for group A, 1,323 ± 144 N (vs. 1,396 ± 779 N) for group B, 930 ± 125 N (vs. 1,337 ± 126 N) for group C, and 968 ± 109 N (vs. 1,528 ± 146 N) for group D (mean ± SEM). The strengths of the OrthoCoupler? legs in the needled device groups were equivalent to unoperated controls (p = 0.6), while both barbed device groups had maximum forces significantly lower than their controls (p = 0.001). We believe this technology will yield improved procedures for clinical challenges in orthopaedic oncology, revision arthroplasty, tendon transfer, and tendon injury reconstruction. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1775–1782, 2011     

术前MRI测量腘绳肌腱横截面积与前交叉韧带重建中移植物的相关性研究

目的:探讨测量MRI腘绳肌腱横截面积在行前交叉韧带重建术前与前交叉韧带重建中移植物的相关性。方法:收集2021年11月至2022年3月在骨关节科拟行前交叉韧带重建术的50例患者的MRI资料,男32例,女18例,年龄19～48(31.1±8.7)岁。术前对半腱肌和股薄肌腱进行MRI测量并记录,然后在关节镜下行前交叉韧带重建术,术中取股薄肌腱与半腱肌腱来制备最终所需移植的肌腱,并且在术中测量已制备好的最终移植物的直径。最后使用统计学软件分析得到数据。结果:MRI测量半腱肌肌腱横截面积、股薄肌肌腱横截面积、半腱肌肌腱与股薄肌肌腱横截面积之和与前交叉韧带术中所需移植物的直径大小呈显著正相关,r值分别为0.858、0.728、0.842(P<0.001),半腱肌肌腱与股薄肌肌腱横截面积之和的曲线下面积(area uder curve,AUC)、灵敏度、和特异性分别为0.925、90.48%、85.71%。结论:在进行前交叉韧带重建术的患者中,术前MRI测量与术中腘绳肌移植直径大小有具有较强的统计学相关性,半腱肌肌腱与股薄肌肌腱横截面积之和对于前交叉韧带重建术中移植物的直径大小有较高的预测价...     

Biomechanical properties of interference screw implantation in replacement of the anterior cruciate ligament with patellar and hamstring transplants. An experimental study using roentgen stereometry analysis (RSA)

This experimental roentgen stereometric analysis (RSA) study was performed to measure micromotions between the graft and tunnel under submaximal load in anterior cruciate ligament (ACL) reconstruction. The aim was to evaluate the maximum load at failure, linear stiffness, and slippage of bone-patellar-tendon-bone (BPTB) grafts fixed with interference screws compared to quadrupled hamstring grafts fixed with interference screws. We used 15 porcine tibia specimens for the study. In the BPTB group, the 10 x 25-mm bone plugs were fixed in a tunnel with 10 mm in diameter using a 7 x 25-mm titanium interference screw (n = 5) or a biodegradable screw (n = 5). The five hamstring transplants were folded to a four-stranded graft and armed with a baseball stitch suture. The sutured side was fixed with a 7 x 25-mm biodegradable polylactide screw in an 8-mm tunnel. The tibial bones, tendon grafts, and interference screws were marked with tantalum beads. The grafts were mounted to a custom made load frame and loaded parallel to the axis under RSA control increasing the force in steps of 50 N. Micromotions between bone plug, screw, and tibia were measured with RSA. Accuracy of RSA for the in vitro study was evaluated as 0.05 mm. Hamstring grafts failed at significantly lower maximum loads (492 +/- 30 N) than BPTB grafts (658 +/- 98 N). Linear stiffness of the hamstring graft fixations was eight times lower compared to the BPTB grafts (403 +/- 141 N/mm vs 3500 +/- 1300 N/mm). There was no significant difference between the biodegradable and titanium screws in the BPTB group. Slippage of the graft started at 82 +/- 35 N load in the hamstring group and at 428 +/- 135 N in the BPTB group. Slippage of the graft at 75% of the maximum pull-out strength was measured as 0.36 +/- 0.25 mm in the BPTB and 2.58 +/- 1.08 mm in the hamstring group. The interference screw fixation of a quadrupled hamstring graft showed a lower linear stiffness and an earlier slippage compared to a patellar tendon bone plug. Slippage of the hamstring grafts at submaximal loads may result in fixation failure during rehabilitation.     

Can the gracilis replace the anterior cruciate ligament in the knee? A biomechanical study

Purpose

The purpose of this study was to determine whether a four-strand gracilis-only construct possesses the biomechanical properties needed to act as an anterior cruciate ligament (ACL) reconstruction graft.

Methods

This was a pilot study with 32 cadaver specimens. The biomechanical properties of three types of grafts were determined using validated tensile testing methods: patellar tendon (BTB), both hamstring tendons together (GST4) and gracilis alone (G4).

Results

The maximum load at failure of the G4 was 416.4 N (±187.7). The GST4 and BTB had a maximum load at failure of 473.5 N (±176.9) and 413.3 N (±120.4), respectively. The three groups had similar mean maximum load and stiffness values. The patellar tendon had significantly less elongation at failure than the other two graft types.

Conclusions

The biomechanical properties of a four-strand gracilis construct are comparable to the ones of standard grafts. This type of graft would be useful in the reconstruction of the anteromedial bundle in patients with partial ACL ruptures.

     

Implantatfreie tibiale Fixierung des hinteren Kreuzbandes

Background

A secure tibial press fit technique in posterior cruciate ligament reconstructions may be a relevant alternative to common techniques because no hardware is necessary. Up to the present point in time no biomechanical data exist for a tibial press fit posterior cruciate ligament (PCL) reconstruction. This study compares the biomechanical properties of hamstring and quadriceps tendon grafts using a press fit technique with those of an interference screw fixation.

Methods

Quadriceps and hamstring tendons of 20 human cadavers (age 49.2±18.5 years) were used. A press fit fixation with a knot in the semitendinosus tendon (K) and a quadriceps tendon bone block graft (Q) were compared to an interference screw fixation (I) in 27 porcine tibiae. In each group, nine constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclical loading were investigated.

Results

The maximum load to failure was 518±157 N (387–650 N) for the K group, 558±119 N (466–650 N) for the I group and 620±102 N (541–699 N) for the Q group. The stiffness was 55±27 N/mm (18–89 N/mm) for the K group, 117±62 N/mm (69–165 N/mm) for the I group and 65±21 N/mm (49–82 N/mm) for the Q group. The stiffness of the I group was significantly larger (ANOVA on ranks, P=0.01). The elongation during cyclical loading was significantly larger for all groups from the 1st to the 5th cycle compared to the elongation in between the 5th and the 20th cycle (P<0.03).

Conclusion

All techniques exhibited larger elongation during initial loading. Load to failure and stiffness were significantly different between the fixations. The Q fixation showed equal biomechanical properties compared to a pure tendon fixation (I) with an interference screw. The results of group K were inferior. All three investigated fixation techniques exhibit comparable biomechanical properties. Preconditioning of the constructs is critical. Future randomized, clinical trials have to investigate the biological effectiveness of these fixation techniques.     

Arthroscopic transtibial single-bundle posterior cruciate ligament reconstruction using patellar tendon graft compared with hamstring tendon graft

Purpose

The purpose of this study was to compare the outcomes of arthroscopic transtibial single-bundle posterior cruciate ligament reconstruction using autologous patellar tendon and hamstring tendon grafts.

Methods

From 1998 to 2007, 59 patients with symptomatic isolated posterior cruciate ligament injury were included in this retrospective study. Twenty-five knees were reconstructed using bone-patellar tendon-bone graft, and 34 knees were reconstructed using hamstring graft. In both groups, surgical techniques were similar, except material of fixation screws. Patients were evaluated pre-operatively and post-operatively at the latest follow-up with several parameters, including symptoms, physical examination, outcome satisfaction, functional scores, radiography and complications.

Results

Average follow-up period was 51.6 months in patellar tendon group and 51.1 months in hamstring tendon group. Significantly more kneeling pain (32 vs. 3 %), squatting pain (24 vs. 3 %), anterior knee pain (36 vs. 3 %), posterior drawer laxity and osteoarthritic change were shown in patellar tendon group than in hamstring tendon group post-operatively. No significant differences were found in other parameters between both groups.

Conclusions

Several shortcomings, including anterior knee pain, squatting pain, kneeling pain and osteoarthritic change, have to be concerned when using patellar tendon autograft. In conclusion, hamstring tendon autograft may be a better choice for transtibial tunnel PCL reconstruction.     

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