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.     

Endoscopic anterior cruciate ligamentreconstruction using doubled gracilis and semitendinosus tendons and endobutton femoral fixation

Donor site complications associated with the use of patellar tendon autografts have resulted in increased interest in the use of multiple-stranded hamstring tendon grafts (semitendinosus and gracilis tendons) for anterior cruciate ligament (ACL) reconstruction. Two major advantages of hamstring tendon grafts are their high initial strength and stiffness, and their harvest results in minimal donor site morbidity. The EndoButton (Smith and Nephew, Andover, MA) provides a quick, simple, strong, and reproducible endoscopic method of securing the femoral end of hamstring tendon grafts. This article describes our technique of endoscopic ACL reconstruction using a doubled semitendinosus and gracilis autograft with EndoButton femoral fixation.     

Comparison of the bioabsorbable and metal screw fixation after ACL reconstruction with a hamstring autograft in MRI and clinical outcome: a prospective randomized study

There has never been an MRI study of tunnel widening comparing bioabsorbable to metal screw fixation in autologous hamstring anterior cruciate ligament (ACL) reconstruction. We randomized 62 patients to hamstring ACL reconstruction with either a bioabsorbable (n = 31) or metal screw (n = 31) fixation. The evaluation methods were clinical examination, KT-1000 arthrometric measurement, the International Knee Documentation Committee and Lysholm scores, and MRI. There were no differences between the groups preoperatively. Fifty-five patients (89%) were available at a minimum of 2-year follow-up (range 24–36 months). There was tunnel widening in both groups, but the increase was significantly greater in the AP dimension of the femoral tunnel in the bioabsorbable screw group compared to metal group (P = 0.01). The tibial tunnels showed no intergroup difference. Ninety-four percent of the knees were normal or nearly normal according to the IKDC scores and the average Lysholm score was 91 with no intergroup difference. The follow-up AP tibial tunnel diameter was smaller with normal knee laxity compared to abnormal knee laxity. The graft failure rate in the bioabsorbable screw group was 23% (7/31 patients) and 6% (2/31 patients) in the metal screw group. The use of bioabsorbable screws resulted in more femoral tunnel widening, and more graft failures compared to metal screws. The tunnel widening in the tibia was associated with the knee laxity (P = 0.02).     

Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws

The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction.     

Pullout strength of tibial graft fixation in anterior cruciate ligament replacement with a patellar tendon graft: interference screw versus staple fixation in human knees

The endoscopic single incision technique for anterior cruciate ligament (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 either fixation technique in a human model. This study was performed to evaluate the primary biomechanical parameters of this technique compared with a standard interference screw fixation of the block. Fifty-five fresh-frozen relatively young (mean age 44 years) human cadaver knee joints 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. Three different sizes of interference screws (7 × 30, 9 × 20, 9 × 30 mm) were chosen as a standard control procedure (n = 40). For tibial bone-block fixation the graft was placed through the tunnel, and the screw was then inserted on the cancellous or the cortical surface, respectively. Fifteen knees were treated by staple fixation. A groove was created inferior to the tunnel outlet with a chisel. The bone block was fixed in this groove with two barbed stainless steel staples. Tensile testing in both groups was carried out under an axial load parallel to the tibial tunnel in a Zwick testing machine with a velocity of 1 mm/s. 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 3.8 and 4.7 mm for interference screw fixation and was 4.7 mm for staples. Stiffness calculated at 175 N load was significantly higher in staple fixation. With either fixation technique, 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 a fixation strength comparable to interference screw fixation. Received: 2 September 1996 Accepted: 30 January 1997     

Poly-L-lactic acid — hydroxyapatite (PLLA-HA) bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament (ACL) reconstruction surgery: MR evaluation of osteointegration and degradation features

Purpose

We evaluated with magnetic resonance imaging (MRI) the degradation and osteointegration features of a new type of bioabsorbable interference (BioRCI) screw composed of poly-L-lactic acid and hydroxyapatite (PLLA-HA) used for tibial graft fixation in anterior cruciate ligament (ACL) reconstruction.

Materials and methods

Thirty-one patients underwent arthroscopic surgery for ACL reconstruction using doubled gracilis and semitendinosus tendons fixed to the tibial tunnel with PLLA-HA (BioRCI-HA) screws. Two groups of patients were evaluated, one group 10–13 months after surgery and the other after 30–40 months. The standard knee ligament evaluation form of the International Knee Documentation Committee (IKDC) was used for clinical assessment and MRI for the radiological assessment.

Results

MRI after 10–13 months revealed findings referable to healing and integration of the bone-graft-screw system, findings that disappeared at later follow-up examinations. The BioRCI-HA screw remained constantly visible in all patients, although with changes in signal intensity over time.

Conclusions

BioRCI-HA screws allow adequate primary stability and superior osteoconduction and biocompatibility in comparison with plain PLLA screws. The absence of ferromagnetic artefacts allows accurate MRI follow-up and adequate evaluation of ligament synovialisation, screw degradation and graft osteointegration.     

Anterior cruciate ligament reconstruction using hamstrings for a two-incision technique

Anterior cruciate ligament (ACL) reconstructions are most commonly performed through a single incision, using either a patellar tendon or a hamstring graft. This technique, however, may be problematic in circumstances such as revision ACL reconstructions or reconstructions in patients with open growth plates. In these cases, a second incision may be needed to avoid existing tunnels or an open physis. The two-incision ACL reconstruction technique described in this article incorporates a four-stranded, gracilis-semitendinosus graft. The four free tendon ends are fixed proximally in a figure-of eight fashion with two bicortical screws and soft tissue washers. The distal looped end is secured with three No. 5 sutures tied to a screw and post. This construct provides graft (2800–4500 N) and fixation (821 N) strengths exceeding that of a 10 mm patellar tendon graft with interference screw fixation. This technique allows for an accelerated rehabilitation program, has low graft harvest morbidity, and provides the freedom necessary for tunnel placement and orientation in complicated reconstructions. For these reasons, this technique should be familiar to surgeons specializing in knee ligament reconstruction.     

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     

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.     

Tibial tunnel widening after bioresorbable poly-lactide calcium carbonate interference screw usage in ACL reconstruction

Developing bio-absorbable interference screws for anterior cruciate ligament (ACL) reconstruction has proven to be a challenging task. The aim of this study was to investigate the osteogenetic response of poly-lactide carbonate (PLC) interference screws in ACL reconstruction in humans. Ten patients (median age, 28 years) underwent arthroscopic ACL reconstruction with semitendinosus/gracilis tendon graft and a PLC interference screw. The patients were scanned with a multi-slice CT scanner 2 weeks and 1 year postoperatively. Fourteen days postoperatively a mean tunnel widening of 78% [52%; 110%] was observed. At 1-year follow-up, the mean tunnel widening was 128% [84%; 180%]. No sign of bone replacement or bone ingrowth was observed. Factors such as accelerated rehabilitation, micro-motions, and early screw degradation might be responsible for this large tunnel widening. Our results demonstrate the difficulty in translation of preclinical data. This study illustrates the need for extensive preclinical investigation of new materials for clinical purposes.     

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.     

Principles for placing the tibial tunnel and avoiding roof impingement during reconstruction of a torn anterior cruciate ligament

Reconstruction of a torn anterior cruciate ligament (ACL) cannot be successful without a properly placed tibial tunnel. Preventable complications such as anterior knee pain, effusions, extension loss, and recurrent instability can occur when the tibial tunnel is improperly placed and the roof and notchplasty are insufficient. This article reviews the principles for anatomic placement of the tibial tunnel so that complications associated with impingement of the ACL graft on the intercondylar roof can be prevented. Five factors that contribute to roof impingement are discussed, including differences in the size and shape of the ACL and the graft, variability in knee extension and roof angle between patients, inability to view the contact between the intercondylar roof and the graft, accentuation of roof impingement from anterior tibial translation caused by quadriceps contraction, and the use of tibial guides that rely on soft-tissue landmarks. A surgical technique is presented which consistently places the tibial tunnel in the pathway of the normal ACL (i.e., anatomic placement) and avoids roof impingement. The indications and need for roof- and wallplasty are discussed.     

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.     

Anatomic double-bundle ACL reconstruction using a bone–patellar tendon–bone autograft: a technical note

This article describes an original arthroscopic double-bundle anterior cruciate ligament (ACL) reconstruction technique using a bone–patellar tendon–bone autograft. A rectangular patellar bone block, with a double strand patellar tendon, and a double tibial bone block is harvested. The femoral anteromedial tunnel is made using an all-inside technique by the anteromedial portal. The femoral posterolateral (PL) tunnel is created with an outside-in technique, with a 30° divergence between both tunnels. A single tibial tunnel is drilled, the graft is then passed through the tibial tunnel, and the bundles are separately tensioned and fixed with three bioabsorbable interference screws. The femoral AM bone block is fixed by the anteromedial portal, the tibial bone block is then fixed in an oblique manner in order to mimic the ACL orientation with the knee at 30° of flexion. The femoral PL bone block is fixed at the end with the knee in full extension.     

Anterior cruciate ligament reconstruction with double-looped semitendinosus and gracilis tendon graft directly fixed to cortical bone: 5-year results

Forty-three patients who had undergone an anterior cruciate ligament (ACL) reconstruction using a doubled semitendinosus and gracilis graft were prospectively reviewed at 5-year follow-up. All had suffered subacute or chronic tears of the ligament. At surgery, the femoral tunnel was drilled first through the antero-medial portal. The correct position of the femoral and tibial guide wire was checked fluoroscopically. A cortical fixation to the bone was achieved in the femur with a Mitek anchor, directly passing the two tendons in the slot of the anchor, and in the tibia with an RCI screw, supplemented with a spiked washer and bicortical screw. Rehabilitation was aggressive, controlled and without braces. The International Knee Documentation Committee (IKDC) form, KT-1000 arthrometer, and Cybex dynamometer were employed for clinical evaluation. A radiographic study was also performed. At the 5-year follow-up all the patients had recovered full range of motion and 2% of them complained of pain during light sports activities. Four patients (9.5%) reported giving-way symptoms. The KT-1000 side-to-side difference was on average 2.1 mm at 30 lb, and 68% of the knees were within 2 mm. The final IKDC score showed 90% satisfactory results. There was no difference between the 2-year and 5-year evaluations in terms of stability. Extensor and flexor muscle strength recovery was almost complete (maximum deficit 5%). Radiographic study showed a tunnel widening in 32% of the femurs and 40% of the tibias. A correlation was found between the incidence of tibial tunnel widening and the distance of the RCI screw from the joint (the closer the screw to the joint, the lower the incidence of widening). In conclusion, we can state that, using a four-strand hamstring graft and a cortical fixation at both ends, we were able to achieve satisfactory 5-year results in 90% of the patients.     

Measurement of the graft angles for the anterior cruciate ligament reconstruction with transtibial technique using postoperative magnetic resonance imaging in comparative study

The aims of this study were to quantify the angle and placement of an anterior cruciate ligament (ACL) grafted with a single incision ACL reconstruction technique using postoperative magnetic resonance imaging (MRI), and to compare the results with those with a native ACL. Between February 1996 and May 2004, 96 consecutive patients, who had undergone postoperative MRI of the knee followed by an arthroscopically assisted ACL reconstruction with either a hamstring tendon or bone-patellar tendon-bone (BTB) autograft, were enrolled in this study. The femoral tunnel was drilled using the transtibial technique. The patients were divided into two groups; the hamstring tendon graft group (group H; 50 patients) and the BTB graft group (group B; 46 patients). All the patients including both groups in this study underwent postoperative MRI and were followed up for a minimum of 2 years. The control group (group C) consisted of 50 patients whose meniscus tear had been operated on by arthroscopy and whose ACL was intact. The orientation of the ACL ligament or graft was measured using three different methods: the sagittal ACL angle, the ACL-Blumensaat line angle, and the coronal ACL angle. The mean sagittal ACL angle in group C (58.7 ± 3.8°) was significantly lower than in groups H (64.6 ± 4.2°) and B (71.3 ± 6.0°). The mean ACL-Blumensaat line angle in group C (8.6 ± 3.6°) was also significantly lower than in groups H (12.8 ± 5.2°) and B (18.0 ± 5.3°). The mean coronal ACL angle in group C (65.9 ± 4.4°) was lower than that in groups H (73.5 ± 2.4°) and B (75.2 ± 2.9°). The grafted ACL of the hamstring tendon and BTB grafts on the postoperative MRI showed a significant vertical angle in the coronal and sagittal plane compared with the native ACL. In the sagittal plane, the hamstring tendon graft was positioned more obliquely than the BTB graft, which had a larger angle of the tibial tunnel, in an attempt to prevent a graft-tunnel mismatch. The postoperative MRI study showed that the more horizontally the angle of the tibial tunnel can be placed in a single incision ACL reconstruction, the more efficiently it can produce a graft closer to the native ACL.     

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.     

Differences in graft orientation using the transtibial and anteromedial portal technique in anterior cruciate ligament reconstruction: a magnetic resonance imaging study

The purpose of this study was to evaluate differences in graft orientation between transtibial (TT) and anteromedial (AM) portal technique using magnetic resonance imaging (MRI) in anterior cruciate ligament (ACL) reconstruction. Fifty-six patients who were undergoing ACL reconstruction underwent MRI of their healthy and reconstructed knee. Thirty patients had ACL reconstruction using the TT (group A), while in the remaining 26 the AM (group B) was used. In the femoral part graft orientation was evaluated in the coronal plane using the femoral graft angle (FGA). The FGA was defined as the angle between the axis of the femoral tunnel and the joint line. In the tibial part graft orientation was evaluated in the sagittal plane using the tibial graft angle (TGA). The TGA was defined as the angle between the axis of the tibial tunnel and a line perpendicular to the long axis of the tibia. The ACL angle of the normal knee in the sagittal view was also calculated. The mean FGA for group A was 72°, while for the group B was 53° and this was statistically significant (P < 0.001). The mean TGA for group A was 64°, while for the group B was 63° (P = 0.256). The mean intact ACL angle for group A was 52°, while for the group B was 51°. The difference between TGA and intact ACL angle was statistically significant (P < 0.001) for both groups. Using the AM portal technique, the ACL graft is placed in a more oblique direction in comparison with the TT technique in the femoral part. However, there are no differences between the two techniques in graft orientation in the tibial part. Normal sagittal obliquity is not restored with both techniques. Paper presented at the 6th Biennial ISAKOS Congress, Florence, ITALY, 2007 and 12th ESSKA 2000 Congress, Innsbruck, Austria 2006.     

Mechanical stability of the femoral fixation for single‐ and double‐bundle ACL reconstruction in an in vitro experimental model

Anterior cruciate ligament ACL reconstruction using the double‐bundle (DB) technique is gaining popularity. A possible weak link in the DB technique could be that two tendon grafts of smaller diameters are used. The purpose of this study was to test different femoral fixation methods and graft diameters representing single‐bundle (SB) and DB ACL reconstructions and compare their biomechanical properties. We hypothesized that SB 6‐mm graft constructs had inferior biomechanical properties than SB 9‐mm grafts or DB 2 × 6‐mm grafts. Furthermore, we hypothesized that interference (IF) screw fixation would demonstrate less elongation and a higher stiffness than Endobutton (Smith & Nephew®, Inc., Andover, Massachusetts, USA) fixation (EBF). We performed an in vitro study using porcine knees and extensor tendons. The mechanical test consisted of a cyclic test followed by a load‐to‐failure test. We found that 6‐mm graft constructs had an ultimate failure load that was up to 40% less than both the 9‐mm and 2 × 6‐mm graft constructs, despite the fixation method (P‐values ≥ 0.004). Comparing fixation methods, EBF was superior to IF concerning maximum load to failure (P < 0.001); IF resulted in a higher stiffness of the femur/graft complex than the EBF (P < 0.001) but no significant difference in elongation between fixation methods. Since the two graft strands are subjected to different loads in different knee flexion angles, the reduced strength of the individual graft strands in DB ACL reconstruction could be a concern.     

Graft-tunnel mismatch in endoscopic anterior cruciate ligament reconstruction Intraoperative and cadaver measurement of the intra-articular graft length and the length of the patellar tendon

The results of a study conducted on 50 knees endoscopically reconstructed for an anterior cruciate ligament (ACL) lesion with a free bone-patellar tendon-bone graft and 9 cadaver knees are reported. The mean lengths of the patellar tendon (45.48 ± 4.71 mm) and intra-articular ACL graft (20.44 ± 1.98 mm) were measured in the operated knees. The mean length of the tibial bone tunnel (51.62 ± 2.60 mm) was also measured with a tibial guide at 55°. No statistically significant correlation was found between these three measurements. The length of the patellar tendon was weakly correlated with body height. Measurement of the tibial tunnel on the cadaver knees with increasing degrees of inclination revealed a mean length increase of 0.68 mm per degree (confidence limits: 0.49–0.86). Comparison between the tunnel lengths obtained with the guide and those measured with a Kirschner wire showed a mean difference of 2.3 mm. It is thus desirable to make the tunnel about 53 mm long to ensure excellent fixation of a 28 mm bone block with a 25 mm interference screw. Correct measurement of the anatomical structures involved is in any event an essential requirement for proper execution of the surgical technique. Received: 26 June 1997 Accepted: 12 November 1997