Intraarticular migration of a broken biodegradable interference screw after anterior cruciate ligament reconstruction

Poly-l-lactic acid biodegradable screws have been used effectively for graft fixation in anterior cruciate ligament (ACL) reconstruction. The overall complication rate associated with the use of this implant is low, although some authors reported complications, such as osteolysis and aseptic effusion of the knee joint. We report a case of a 29-year-old female patient with a failure of a biodegradable interference screw at 22 months after ACL reconstruction using bone–patellar tendon–bone graft. In this illustrated case, the screw broke and migrated into the knee joint. In addition, we performed a detailed review of the medical literature from 1990–2005 to identify possible causes of biodegradable screw failures. We identified six published cases of bioabsorbable interference screw failure with migration into the knee joint. Several authors have reported small diameter of the screw, poor bone quality, bone resorption, and screw divergence as potential causes for intraarticular migration of metallic interference screws. With regard to bioscrews, no specific risk factors for screw breakage and intraarticular migration have been reported. ACL reconstruction with the use of bioabsorbable interference screws for fixation is considered to be reliable. However, we need to be aware of potential problems associated with the use of this implant. Early recognition of bioscrew failure may prevent associated morbidities, such as subsequent cartilage damage.     

Intra-articular pull out of an interference screw after anterior cruciate ligament reconstruction

We report a rare case of late femoral interference screw migration in the posterior compartment of the knee after anterior cruciate ligament reconstruction. The graft was intact with no signs of damage. The screw was successfully removed through the posteromedial portal site and the patient regained full function of the knee     

Intra-articular pull out of an interference screw after anterior cruciate ligament reconstruction

We report a rare case of late femoral interference screw migration in the posterior compartment of the knee after anterior cruciate ligament reconstruction. The graft was intact with no signs of damage. The screw was successfully removed through the posteromedial portal site and the patient regained full function of the knee.     

Graft choice and graft fixation in PCL reconstruction

Several grafts and several fixation techniques have been introduced for PCL reconstruction over the past years. To date, autograft and allograft tissues are recommended for PCL reconstruction, whilst synthetic grafts should be avoided. Autograft tissues include the bone-patellar tendon-bone graft, the hamstrings and the quadriceps tendon. Allograft tissues are increasingly being used for primary PCL reconstruction. The use of allograft tissues requires a number of formal prerequisites to be fulfilled. Besides the previous mentioned graft types allograft tissues include Achilles and tibialis anterior/posterior tendons. To date no superior graft type has been identified. Several techniques and devices have been used for fixation of a PCL replacement graft. Most of these were originally developed for ACL reconstruction and then adapted to PCL reconstruction. However, biomechanical requirements of the PCL differ substantially from those of the ACL. To date, requirements for PCL graft fixations are not known. From a systematic approach femoral graft fixation can either be achieved within the bone tunnel (nearly anatomic) with an interference screw or outside the bone tunnel on the medial femoral condyle using a staple, an endobutton or a screw. Tibial graft fixation can be achieved either with an interference screw in the bone tunnel or with a staple, screw/washer or sutures tied over a bone bridge outside the bone tunnel (extra-anatomic). An alternative fixation on the tibial side is the inlay technique that reduces the acute angulation of the graft at the posterior aspect of the tibia. Further research is necessary to identify the differences between the various fixation techniques.     

Arthroscopic and endoscopicallograft reconstruction

Advantages for the choice of an allograft anterior cruciate ligament (ACL) reconstruction include the following:rapid and uncomplicated rehabilitation; avoidance of the need to harvest a graft from the affected individual, thus avoiding possible complications; prolonged rehabilitation; a readily available source of graft material in the case of revision ACL surgery; adequate tissue availability when the need exists for multiple ligament replacement within the knee; a shortened anesthesia in surgical time to perform the procedure and tissue alternatives for individuals with a congenital tissue laxity. Disadvantages for allograft use include expense, the possibility of disease transmission, and variables in the harvest procurement in preparation of the graft. The surgical technique for installation of an allograft, bone-patellar-bone preparation, is described. This technique is designed for endoscopic tandem tunnel, minimally invasive surgery. The described use of a right-angle set screw for a femoral fixation permits ease in installation and also ease of removal of the implant device if revision or other reasons for removal of hardware is ever necessary. Right-angle set screw femoral fixation and interference screw tibial fixation permit aggressive rehabilitation in an effort to return the athlete to sport in a minimal amount of time. Pull strengths of fixation approach the tensile strength of the ligament itself.     

自体腘绳肌腱重建前交叉韧带股骨端两种固定方式的比较

目的:比较自体腘绳肌腱重建前交叉韧带(ACL)过程中,采用Endobutton和Rigidfix两种股骨端韧带固定方式的疗效。方法:回顾性研究了48例陈旧性ACL病例,其中A组24例,B组24例;分别应用自体半腱肌、股薄肌腱重建ACL,其中A组股骨端固定采用Rigidfix交锁钉,B组采用Endobutton纽扣钢板,两组胫骨端固定均为Intrafix界面螺钉+Spiked Washer栓桩固定。平均随访27个月,采用MRI测量两组骨隧道扩大情况,并用Lysholm、TegnerI、KDC、KT1000对患膝进行术前、术后测试和评分。结果:MRI测量发现,B组股骨端和胫骨端骨隧道扩大均较A组明显(P<0.05)。两组病人术后Lysholm、TegnerI、KDC评分均较术前明显提高,KT1000测试结果较术前明显改善(P<0.05);但两组间术后评分无显著性差异(P>0.05)。结论:在自体腘绳肌腱重建前交叉韧带中,与采用Rigidfix固定相比,股骨端采用Endobutton固定自体腘绳肌腱更容易引起术后骨隧道扩大,但在临床疗效上两种固定方式并无明显差别。     

Recurrent locking of knee joint caused by intraarticular migration of bioabsorbable tibial interference screw after arthroscopic ACL reconstruction

Two cases are reported in which, after ACL reconstruction with autologous hamstring grafts, tibial polylactide interference screws migrated into the knee joint. Clinically, both patients presented with recurrent locking of the joint. In one case, a broken 15 mm-long tip of the screw was found intra-articularly. In the other case, the whole screw had migrated into the joint cavity. The degradation process of polylactic acid, operative technique and bone quality are discussed as possible reasons for these complications.     

Anterior cruciate ligament reconstruction using autografts and double biodegradable femoral cross-pin fixation: functional,radiographic and MRI outcome after 2-year minimum follow-up

Double biodegradable cross-pins are increasingly used for femoral fixation in arthroscopically assisted reconstruction of the anterior cruciate ligament (ACL). There are no studies combining functional outcome analysis, radiographs and magnetic resonance images (MRI) to evaluate this technique. The authors examined 45 patients after ACL reconstruction using double biodegradable femoral cross-pin fixation and biodegradable tibial interference screw fixation with a minimum follow-up of 24 months. Clinical evaluation included International Knee Documentation Committee (IKDC) and modified Lysholm score. Radiographic analysis included standard X-rays in anterior–posterior and lateral views and Telos stress device measurements. MRI was analyzed to obtain information about hardware, intra-articular graft, osseous graft-integration and cartilage. IKDC score revealed 28 (62.2%) patients with normal knee function (group A), 15 (33.3%) patients with nearly normal (group B) knee function and 2 (4.4%) patients with abnormal knee function (group C). The Lysholm score was 94.6 (±7.2) in the operated knee and 98.8 (±7.4) in the non-operated knee. Mean Telos stress device values were +4.6 (±2.6) in the operated and +3.9 (±2.4) in the non-operated knee. MRI showed an intact intra-articular graft in all but one patient. Complete femoral graft integration was seen in 88.9% and complete tibial graft integration in 86.7%. Biodegradable cross-pins were partially or fully visible in all patients. The biodegradable tibial interference screw was fully visible in 16 (35.6%) and partially visible in 20 (44.4%) patients. Thirty-one (68.9%) patients showed signs of cartilage degeneration on MRI at follow-up. The graft fixation with double biodegradable pin fixation appears to be a reliable technique for ACL reconstruction providing a stable close-to-joint graft fixation.     

Comparison of eccentric and concentric screw placement for hamstring graft fixation in the tibial tunnel

Interference screw fixation of four-strand hamstring grafts for ACL reconstruction has recently been introduced. By this method, the interference screw is placed in the tibial and femoral tunnels eccentric (adjacent) to the bundled limbs of the graft. In order to maximize the graft to tunnel contact to promote ¶biological fixation, it is proposed to place the screw concentrically in ¶the tunnel, in the middle of the four limbs of the graft, pressing each limb of the graft into the tunnel wall. This would be difficult to do in the proximal, folded end of the four limb graft situated in the femoral tunnel but can be done easily in the tibial tunnel. The purpose of this study was to evaluate the effect of screw placement on the stiffness, yield load, and ultimate load of hamstring graft fixation in the tibial tunnel. Five pairs of human knees were ¶used for the study. Pull out tests ¶were performed using an MTS system, pulling along the axis of the ¶tibial tunnel. Tibial fixation stiffness was greater using concentric screw placement (P < 0.05) although there was no statistical difference in yield load, slippage, or ultimate load.     

Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length

Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated.     

MRI in ACL reconstructive surgery with PDLLA bioabsorbable interference screws: evaluation of degradation and osteointegration processes of bioabsorbable screws

PURPOSE: Anterior cruciate ligament (ACL) reconstructive surgery has seen significant progress since bioabsorbable interference screws have replaced synthetic metallic screws for ligament graft fixation within the femoral and tibial osseous tunnel. Our study compared the MR images of patients who underwent ACL reconstruction using bioabsorbable interference screws with those of patients who underwent ACL reconstruction using metallic screws to evaluate the MR aspects of degradation and osteointegration processes of bioabsorbable interference screws post-operatively. MATERIALS AND METHODS: Between September 1999 and December 2002 we performed MRI on 40 patients who underwent arthroscopic ACL reconstruction with patellar tendon auto-graft using PDLLA bioabsorbable screws in 35 cases and metallic screws in 5 cases. After surgery, all patients underwent an intensive rehabilitation programme along with clinical evaluation using the standard knee ligament evaluation form of the International Knee Documentation Committee (IKDC) and radiological examinations. MR studies were performed 1, 2 and 3 years post-operatively using a 0.5-Tesla MR scanner with T1- and T2*-weighted and STIR sequences. RESULTS: Thirty-three patients were clinically classified as group A IKDC (full return to sports activity) and 7 patients as group B IKDC. No foreign-body reaction was found in patients treated with bioabsorbable interference screws, both from a clinical point of view and from laboratory exams. Ferromagnetic artefacts were found in all patients treated with metallic interference screws. In patients with bioabsorbable interference screws, degradation of the screws and absence of significant artefacts allowed correct evaluation of the signal of the reconstructed ligament throughout its length, the osseous tunnels and the joint cavity. In 34 of 35 patients with bioabsorbable interference screws, the screw could not be detected due to complete degradation. In 8, 12 and 4 cases, a small cyst-like formation due to screw hydrolysis was present at the screw site within 1, 2 and 3 years from surgery respectively. Only in 4 cases was the process of osteointegration of the screw and bone plug complete 3 years after the operation, with consequent restoration of bone morphology. DISCUSSION AND CONCLUSIONS: The use of bioabsorbable interference screws is a valuable alternative to synthetic metallic fixation implants as the absence of artefacts allows correct post-operative MR follow-up. MRI is the only technique able to visualize all the portions of the transplant and to evaluate the healing process. Bioabsorbable interference screws usually degrade within one year. However, full osteointegration requires a long time and may not be complete 3 years after surgery. The presence of cyst-like formations at the screw site has to be regarded as a normal feature of the screw degradation process. Therefore, the use of bioabsorbable interference screws is recommended as it enables MR follow-up of the knee after ACL reconstruction.     

Femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction: biomechanical evaluation of different fixation techniques: is there an acute angle effect?

BACKGROUND: The literature provides little biomechanical data about femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction. HYPOTHESIS: A hybrid fixation technique with use of an undersized screw has sufficient strength to provide secure fixation of posterior cruciate ligament grafts. Additional aperture fixation with a biodegradable interference screw can prevent graft damage that might be caused by an acute angle on the edge of the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: In part 1, extracortical fixation of posterior cruciate ligament reconstructions with quadrupled porcine flexor digitorum grafts to simulate human hamstring grafts was compared with hybrid fixation methods using 6-, 7-, and 8-mm screws. Groups were tested in cycling loading with the load applied in line with the bone tunnel. In part 2, extracortical fixation was compared with hybrid fixation using a 1-mm undersized screw anterior and posterior to the graft. Structural properties and graft abrasion were evaluated after cyclic loading with the load applied at 90 degrees to the tunnel. In each group, 8 porcine knees were tested. RESULTS: In part 1, stiffness, maximum load, and yield load were significantly higher for hybrid fixation than for extracortical fixation. Hybrid fixation with an 8-mm screw resulted in higher yield load than with a 7-mm screw. In part 2, graft laceration was more pronounced in specimens with extracortical fixation than with hybrid fixation. Posterior screw placement was superior to the anterior position. CONCLUSION: For all parameters, hybrid fixation with an interference screw provided superior structural results. No relevant disadvantages of undersized screws could be found. Graft damage due to abrasion at the edge of the femoral bone tunnel was reduced by use of an interference screw. The posterior screw placement seems favorable. CLINICAL RELEVANCE: Hybrid fixation of hamstring grafts in posterior cruciate ligament reconstruction is superior to extracortical fixation alone with no relevant disadvantages of undersized screws. The results raise the suspicion of an acute angle effect of the femoral bone tunnel.     

Bioabsorbable interference screw versus bioabsorbable cross pins: influence of femoral graft fixation on the clinical outcome after ACL reconstruction

Purpose

The aim of this study was to evaluate the clinical outcome and differences in anterior–posterior laxity of ACL reconstruction using a bioabsorbable interference screw for femoral graft fixation when compared to femoral bioabsorbable cross pin fixation.

Methods

Clinical outcome was evaluated among 59 patients 1?year after arthroscopic ACL reconstruction with hamstrings graft in a prospective, non-randomised study. In 31 cases, femoral fixation of the graft was performed using a bioabsorbable interference screw. In 28 cases, two bioabsorbable cross pins were used for femoral fixation. Patients were evaluated using Tegner, Lysholm and Marshall scores, the visual analogue scale for pain and KT-1000 arthrometer measurement.

Results

No significant difference (P?≥?0.05) was observed at follow-up for the knee scores. The average Tegner score was 5.83 points (±2.00) for the interference screw fixation and 5.83 points (±1.24) for the cross pin fixation; the average Lysholm score was 93.58 (±5.79) to 92.72 (±6.34) points; and the average Marshall score 46.72 (±2.4) to 47.30 (±2.35) points. No significant difference was found for the visual analogue scale for pain. KT-1000 arthrometer measurement revealed a significant (P?<?0.05) difference in the mean side-to-side anterior translation at all applied forces. At 67?N, the mean difference was 1.53?mm (±1.24) in the interference screw group and 0.47?mm (±1.18) in the cross pin group (P?<?0.05). At 89?N, the mean differences were 1.85?mm (±1.29) versus 0.59?mm (±1.59), respectively, (P?<?0.05), and maximum manual displacements were 2.02?mm (±1.26) versus 1.22?mm (1.18; P?<?0.05).

Conclusions

In ACL reconstruction with hamstrings graft, similar clinical results are obtained for the use of bioabsorbable cross pins when compared to bioabsorbable interference screws for femoral fixation. Cross pin fixation was superior with regard to the anteroposterior laxity as measured with KT-1000.     

Interference screw fixation of hamstring vs patellar tendon grafts for anterior cruciate ligament reconstruction

The present study was designed to investigate the fixation strength of a quadruple semitendinosus-gracilis graft compared with a middle-third bone-patellar tendon-bone graft using a new interference screw developed to fix hamstrings grafts for ACL reconstructions (RCI, Smith & Nephew Donjoy). Five pairs of human cadaveric knees from donors with a mean age of 43 (range 33–52) years were used. One knee of each pair was randomly allocated to be reconstructed on the femoral side with a semitendinosus-gracilis graft from the same donor using RCI screw fixation. As the control, the contralateral knee was correspondingly reconstructed with a bone-patellar tendon-bone graft using the same interference screw. The grafts were pulled out at a velocity of 30 mm/s by an axially applied load using a MTS machine. The mean (SD) failure load for the bone-patellar tendon-bone graft fixations was 505 (25) N, 110% stronger than the mean failure load for the semitendinosus-gracilis graft fixations, which was 240 (47) N (P = 0.003). The stiffness for the patellar tendon-bone graft fixations was 46 (11) N/mm, 120% stiffer than the semitendinosus-gracilis graft fixations, which was 22 (11) N/mm (P = 0.01). This study shows that the interference screw principle used for ACL reconstructions with hamstrings tendons is inferior to that for bone-patellar tendon-bone reconstructions although the screw was developed especially for soft-tissue fixation in bone tunnels. Received: 14 August 1996 Accepted: 25 September 1997     

Hamstring anterior cruciate ligament reconstruction using femoral cross pin fixation

Surgical reconstruction of the anterior cruciate ligament (ACL) with bone-patella tendon-bone (BPTB) graft hasbecome the most commonly performed procedure for the unstable cruciate-deficient knee. The use of BPTB has been complicated by chronic anterior knee pain, loss of extension, patella tendon rupture, and patella fractures. The TransFix technique uses a double-looped semitendinosis and gracilis (DLSG) graft that is stronger than BPTB, and has less graft site and operative morbidity. This technique uses cross-pin femoral fixation and tibial interference screw fixation in the tibia that allows immediate weight bearing and an aggressive rehabilitation program. Results are equal to those previously reported for BPTB.     

The effect of graft placement on the clinical outcome of the anterior cruciate ligament reconstruction: a prospective study

The effect of the graft placement on the clinical outcome of patients after anterior cruciate ligament (ACL) reconstruction has been studied sparsely. We conducted a prospective follow-up of 140 patients who underwent an arthroscopic ACL reconstruction with a hamstring graft. One hundred and four of them (74%) could be examined at the 2-year follow-up. Clinical examination included Lysholm, Tegner, and International Knee Documentation Committee rating scores, arthrometric anterior–posterior knee laxity assessment, and muscle strength assessments. The graft placement was measured from lateral radiographs using a system recommended for measuring the attachment positions of the cruciate ligaments as well as a method called ‘the sumscore of the graft placement’, which takes into account both the femoral and the tibial graft placements simultaneously. The sumscore was smaller in knees with normal anterior–posterior knee laxity in the Lachman test (P = 0.002) and normal rotational knee laxity in the pivot shift test (P = 0.01) than in those with abnormal laxity. The tibial graft placement was more anterior when the Lachman test was normal (P = 0.04). The Lysholm score was better when the femoral graft placement was more posterior (r = −0.20, P = 0.04). The optimal femoral graft placement was between 25 and 29% of length of the femoral condyle along the Blumensaat’s line from posterior to anterior. The optimal tibial graft placement was between 32 and 37% of the length of the tibial plateau from the anterior corner, and the optimal sumscore was between 61 and 66. The sumscore and its components (the femoral and tibial graft placements) showed a clear association with the clinical outcome of the patients. The best outcome was achieved when the sumscore was small; that is the graft placement showed posterior enough in the femur, and anterior enough in the tibia.     

Arthroscopic loose-body removal in posterior compartment of the knee joint: a technical note

The arthroscopic removal of loose bodies in the knee joints is a relatively common procedure. Quite often intra-articular loose bodies tend to localize at the posterior compartment due to gravity effect. However, it is often technically demanding to find and remove loose bodies located at the posterior compartment of the knee joint arthroscopically. We present the technical aspects of arthroscopic removal of the loose bodies located in the posterior compartment of the knee joint. Loose bodies at posterior compartment were subdivided into six regions in posterior knee compartment with preoperative MRI and arthroscopic findings. Each section needs slight different application of arthroscopic techniques for removal. We retrospectively studied 52 knees in 50 patients who underwent arthroscopic loose-body removal in posterior compartment, in 28 knees, additional posterior trans-septal portal was needed for removal of loose bodies. With the help of trans-septal portal, we have successfully removed the loose bodies even from the most difficult locations in posterior compartment.     

Comparison of femoral fixation methods for anterior cruciate ligament reconstruction with patellar tendon graft: a mechanical analysis in porcine knees

The aim of the present study was to evaluate the structural properties of femur–patellar tendon graft complex in anterior cruciate ligament (ACL) reconstruction using different femoral fixation devices. Type of study is biomechanical testing. An ACL reconstruction was performed on 40 cadaver porcine knees, using patellar tendon (PT) graft. Specimens were divided into four groups according to the femoral fixation: interference absorbable screw (Group A), metallic setscrew (Group B), absorbable pins (Group C), and a combination of metallic setscrew and pin (Group D). Other ten knees were used as controls. On each sample, a cyclic loading test, then a load-to-failure test were performed. Elongation after 1,000 loading cycles, ultimate failure load, yield load, stiffness, deformation at the yield point, and mode of failure were recorded. Kruskal–Wallis test and Tukey test were used to compare the differences between groups. The lowest mean elongation after 1,000 load cycles was observed for Group B (1.7 ± 1.4 mm) and D (1.2 ± 0.3 mm). Ultimate failure load of Group D (1,021.8 ± 199.4 N) was comparable with that of normal ACL (1,091.2 ± 193.3 N) and PT graft (1,140.6 ± 285.7 N). All other groups were lower than the controls. For mean stiffness, all the groups, excepting for Group D (172.8 ± 40.4 N/mm), were significantly lower than PT control group (216 ± 78.4 N/mm). Mode of failure was graft pullout for Groups A and B, distal pin breakage for Group C, and midsubstance graft rupture in 80% of the cases for Group D. Only combined compression and suspension fixation did not show significantly different structural properties in comparison with normal ACL and PT graft. Furthermore, it showed no risk of graft pullout or hardware breakdown in comparison with other fixation devices.     

Magnetic resonance imaging appearance of anterior cruciate ligament reconstruction using Calaxo screws

Bioabsorbable interference screws are commonly used to secure the graft during anterior cruciate ligament (ACL) reconstruction, in part because they result in less image degradation on subsequent magnetic resonance imaging (MRI). However, some bioabsorbable screws are associated with abnormalities on MRI examination not reported with metallic interference screws. We describe a finding on knee MRI examination after ACL reconstruction using a polylactide carbonate (PLC) bioabsorbable screw that we believe to be previously unreported with any other bioabsorbable screws. The finding raised suspicion of hemorrhage or infection, neither of which were present clinically. Analysis of tissue from the tibial tunnel suggested an explanation for the MRI finding: calcite crystals. An additional five patients with knee MRI examinations after ACL reconstruction using a PLC screw were reviewed and correlated with clinical findings with four having similar imaging abnormalities present. The PLC (Calaxo screw, Smith and Nephew, Andover, MA) screw used in these patients has been recalled in the United States and Europe by the manufacturer after a greater than expected incidence of adverse reactions, and legal action may be pending.     

A biomechanical comparison of different surgical techniques of graft fixation in anterior cruciate ligament reconstruction

Different surgical methods of graft fixation in ACL reconstruction were examined to determine the effects on mechanical properties of the reconstructed ACL. Ten human cadavers were used in this study. Six different types of grafts were studied. The tendon grafts were removed from each cadaver and fixed to femurs and tibias as ACL substitutes with different surgical fixation methods, leaving femur-reconstructed graft-tibia preparations. The surgical techniques used were staple fixation, tying sutures over buttons, and screw fixation. In the latter, the screws were introduced through femoral and tibial drill holes from the outside in order to achieve interference fit as described by Lambert. Tensile testing demonstrated that the original ACL is significantly stronger than the graft used for reconstruction in linear load, stiffness, and maximum tensile strength. All of the failures of the reconstructed ACL grafts occurred at the fixation site, indicating that the mechanically weak link of the reconstructed graft is located at the fixation site. Among the different methods of fixation, one-third of the patellar tendon secured with a cancellous screw, especially with a custom designed large diameter screw, showed significantly higher values. Although many other factors affect the success of ACL reconstruction, our study indicates that the method of surgical fixation is the major factor influencing the graft's mechanical properties in the immediate postoperative period.