A rationale for predicting anterior cruciate graft impingement by the intercondylar roof. A magnetic resonance imaging study

This study was designed to analyze how anterior tibial tunnel placement can result in graft impingement by the intercondylar roof. The relationship of the ACL to the intercondylar roof was studied using magnetic resonance scans. An attempt was made to predict the amount of bone that may need to be removed from the intercondylar roof to prevent impingement on a 10 mm thick ACL graft. Magnetic resonance scans of 19 normal ACLs were analyzed. The amount of bone removal required to correct roof impingement was determined for a graft placed either eccentrically or centrally within the ACL insertion, and within the bulk of the normal ACL fibers. An eccentric tibial tunnel placement required approximately 5 to 6 mm and a central placement required 2 to 3 mm of bone removal from the intercondylar roof to prevent impingement. Placing the graft within the bulk of the ACL fibers, just 3 mm posterior to the center of the ACL insertion, required little bone resection to prevent impingement. To prevent ACL graft impingement, roofplasties need to be performed in both acute and chronic ACL reconstructions if the presently accepted locations for positioning the tibial tunnel are used. A more anteriorly placed tibial tunnel requires more bone removal to prevent roof impingement than a more posteriorly positioned tibial tunnel.     

Posterior cruciate ligament (PCL) reconstruction-an in vitro study of isometry

Isometric positioning of the posterior cruciate ligament (PCL) graft is important for successful reconstruction of the PCL-deficient knee. This study documents the relationship between graft placement and changes in intra-articular graft length during a passive range of motion of the knee. In eight cadaveric knees the PCL was identified and cut. The specimens were mounted in a stabilising rig. PCL reconstruction was performed using a 9-mm-thick synthetic cord passed through tunnels 10 mm in diameter. Three different femoral graft placement sites were evaluated: (1) in four specimens the tunnel was located around the femoral isometric point, (2) in two specimens the tunnel was positioned over the guide wire 5 mm anterior to the femoral isometric point, (3) in two specimens the tunnel was positioned over the guide wire 5 mm posterior to the isometric femoral point. In all knees only one tibial tunnel was created around the isometric tibial point. The location of the isometric points is described in part I of this study. The proximal end of the cord was fixed to the lateral aspect of the femur. Distally, the cord was attached to a measuring unit. The knees were flexed from 0° to 110°, and the changes in the graft distance between the femoral attachment sites were measured in 10° steps. Over the entire range of motion measured, the femoral tunnels positioned around the isometric point produced femorotibial distance changes of within 2 mm. The anteriorly and posteriorly placed tunnels produced considerable changes in femorotibial distance with knee flexion, e.g. about 8 mm at 110° of flexion.     

A biomechanical comparison of posterior cruciate ligament reconstruction techniques

Most posterior cruciate ligament reconstruction techniques use both tibial and femoral bone tunnels for graft placement. Because of the acute angle the graft must make to gain entrance into the tibial tunnel, abnormal stresses are placed on the graft that could lead to graft failure. An alternative technique for posterior cruciate ligament reconstruction involves placement of the bone plug from the graft anatomically on the back of the tibia (inlay), preventing formation of an acute angle at the tibial attachment site. We used six pairs of human cadaver knees to compare the biomechanical properties of these two techniques. One knee from each pair underwent tunnel reconstruction while the other knee underwent inlay reconstruction. There was significantly less anterior-posterior laxity in the inlay group when compared with the tunnel group from 30 degrees to 90 degrees of knee flexion and after repetitive loading at 90 degrees of knee flexion. Evaluation of the grafts revealed evidence of mechanical degradation in the tunnel group but not in the inlay group. The inlay technique resulted in less posterior translation with less graft degradation than did the tunnel technique for posterior cruciate ligament reconstruction.     

前交叉韧带重建术后三维MRI表现

目的 探讨前交叉韧带(ACL)重建术后ACL移植物和骨隧道的3D MRI表现和演变规律.方法 回顾性分析26例双束ACL重建和16例单束ACL重建患者行3D MRI术后随访56例次的资料,用多平面重组法显示和评价移植物、骨隧道、固定器及并发症,计算术后不同时期低信号及高信号移植物的比例和骨隧道周围骨髓水肿的出现率.结果 发现低信号移植物24例次,高信号移植物32例次.移植物固定2例股骨端采用横杆,1例股骨端使用纽扣,其余部位使用可吸收螺钉.术后3个月、6～9个月和12个月及以上低信号移植物比例分别为20/25、0/14和4/10,高信号移植物比例分别为5/25、14/14和6/10,骨隧道周围骨髓水肿出现比例分别为54/54、10/32和4/26.发现1例移植物撕裂,4例胫骨隧道偏前伴ACL移植物髁间窝顶撞击,3例股骨隧道偏前,2例可吸收螺钉与骨隧道不匹配.结论 3D MRI可准确显示ACL重建术后移植物、骨隧道和固定器的状态及并发症信息,移植物信号在术后呈先增高再恢复低信号的过程.     

Evaluation of the vascular status of autogenous hamstring tendon grafts after anterior cruciate ligament reconstruction in humans using magnetic resonance angiography

The purpose of this study is to evaluate the vascular status of autogenous semitendinosus grafts after anterior cruciate ligament reconstruction in humans using magnetic resonance angiography. Twelve patients (mean age, 24.3 years) who underwent anterior cruciate ligament reconstruction with the 4-strand semitendinosus tendon were studied. All patients underwent contrast-enhanced magnetic resonance angiography and second-look arthroscopy in their reconstructed knees on an average of 15.8 months (range 9–22 months) after surgery. Blood vessels to the graft were visualised and contrast medium enhancement for visualising the femoral tunnel, graft, and tibial tunnel was evaluated. Magnetic resonance angiography showed that a branch of the middle genicular artery extended to the upper side of the graft through the posterior capsule and that branches of the inferior genicular artery ended at the lower side of the graft in all patients. These were consistent with the actual findings of the second-look arthroscopy. We found contrast medium enhancement in the femoral and tibial tunnels in all patients. The effect of enhancement at 9 months after ACL reconstruction was higher than that at 22 months. The graft showed enhancement patterns in the posterior portion of the femoral side and the anterior portion of the tibial side. This study demonstrated that the branches of the middle and inferior genicular arteries provide blood supply to the graft, which may influence the maturation of the graft. The revascularisation of the bone tunnels could play an important role in the healing of the ligament–bone tunnel junction.     

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     

Tibial bone bridge and bone block fixation in double-bundle anterior cruciate ligament reconstruction without hardware: a technical note

Current techniques for tibial graft fixation in four tunnels double bundle (DB) anterior cruciate ligament (ACL) reconstruction are by means of two interference screws or by extracortical fixation with a variety of different implants. We introduce a new alternative tibial graft fixation technique for four tunnels DB ACL reconstruction without hardware. About 3.5 to 5.5 cm bone cylinder with a diameter of 7 mm is harvested from the anteromedial (and posterolateral) tibial bone tunnel (s) with a core reamer. The anteromedial (AM) and posterolateral (PL) hamstring tendon grafts (or alternatively tendon allografts) are looped over an extracortical femoral fixation device and cut in length according to the total femorotibial bone tunnel length. The distal 3 cm of each, the AM- and PL bundle graft are armed with two strong No. 2 nonresorbable sutures and the four suture ends of each graft are tied to each other over the 2 cm wide cortical bone bridge between the tibial AM and PL bone tunnel. In addition the AM- and/or PL bone block which was harvested at the beginning of the procedure is re-impacted into the two tibial bone tunnels. A dorsal splint is used for the first two postoperative weeks and physiotherapy is started the second postoperative day. The technique is applicable for four tunnels DB ACL reconstruction in patients with good tibial bone quality. The strong fixation technique preserves important tibial bone stock and avoids the use of tibial hardware which knows disadvantages. It does increase tendon to bone contact and tendon-to-bone healing and does reduce implant costs to those of a single bundle (SB) ACL reconstruction. Revision surgery may be facilitated significantly but the technique should not be used when bony defects are present. In case of insufficient bone bridge fixation or bone blocks hardware fixation can be applied as usual. Not supported by outside funding or grant(s): No benefits in any form have been received, or will be received, from a commercial party related directly or indirectly to the subject of this article. The study complies with the current laws of the country, in which it was performed.     

Importance of femoral tunnel placement in double-bundle posterior cruciate ligament reconstruction: biomechanical analysis using a robotic/universal force-moment sensor testing system

BACKGROUND: Previous studies have identified the femoral attachment of the posterior cruciate ligament fibers as one of the primary determinants of fiber tension behavior. In addition, a double-bundle posterior cruciate ligament reconstruction has been shown to restore the intact knee kinematics more closely than does a single-bundle reconstruction. HYPOTHESIS: An anterior tunnel position in double-bundle posterior cruciate ligament reconstruction restores the biomechanics of the normal knee more closely than does a posterior tunnel position. STUDY DESIGN: Controlled laboratory study. METHODS: Kinematics and in situ forces of human knees after double-bundle posterior cruciate ligament reconstruction with 2 different femoral tunnel positions (anterior vs posterior) were evaluated using a robotic/universal force-moment sensor testing system. Within the same specimen, the resulting knee kinematics and in situ forces were compared. For statistical analysis, 2-way analysis of variance repeated measures were performed. RESULTS: The femoral tunnel position of the double-bundle hamstring graft had significant effect on the resulting posterior tibial displacement and in situ forces of the hamstring grafts. The anterior femoral tunnel position provided significantly less posterior tibial translation than did the posterior tunnel position. There was a tendency toward higher in situ forces of grafts fixed in the anterior tunnel when compared to the posterior position, but this difference was statistically not significant. CONCLUSION: An anterior position of the bone tunnels in double-bundle posterior cruciate ligament reconstruction restores the normal knee kinematics more closely than does a posterior position of the tunnels. CLINICAL RELEVANCE: In double-bundle posterior cruciate ligament reconstruction, posterior placement of the tunnel should be avoided.     

Tibial inlay procedure for PCL reconstruction: One tunnel and two tunnel

Many operative techniques have been described for reconstructing the posterior cruciate ligament (PCL). Nocurrent surgical procedure has been able to consistently correct abnormal posterior laxity or provide consistent functional results. This may be because of the nonanatomic placement of the tibial portion of the PCL graft with the tibial tunnel technique. With this method, the graft must make a greater than 90° turn toward the medial femoral condyle. It is believed that this “killer turn” may degrade the graft with time. The tibial inlay technique avoids this by securing the graft with a bone block anatomically within the PCL footprint on the posterior tibia. By using this technique, both a decrease in posterior translation and less graft degradation can be found when compared with the standard tunnel technique of PCL reconstruction. A double-bundle reconstruction may also be performed with the inlay technique. In this article, we present the operative indications, surgical technique, and postoperative rehabilitation protocol for the tibial inlay technique of PCL 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.     

Behavior of the graft within the bone tunnels following anterior cruciate ligament reconstruction, studied by cinematic magnetic resonance imaging

The behavior of a ligament graft following cruciate ligament reconstruction is still an area of limited knowledge. Cinematic magnetic resonance imaging (MRI) offers the possibility of visualizing the graft, including the graft tunnels and fixation during knee motion. Twenty-three patients underwent cinematic MRI (0.2 T; Artoscan) mean ¶23.4 months (range 14–39 months) after autologous anterior cruciate ligament reconstruction (eight bone-tendon-bone, seven semitendinosus-gracilis, and eight iliotibial band). The images were read without knowledge of the clinical condition or the type of surgery performed. Signal intensity and continuity of the anterior cruciate ligament reconstruction and movement of the graft in the tibial or femoral tunnel anteriorly and posteriorly were noted. In two of the 23 patients the graft (semitendinosus-gracilis) moved in the tibial canal. The initial 9-mm tunnel had expanded by 2 mm in the anteroposterior direction at the entrance to the joint space. Only these two had a slight knee laxity, with a side-to-side difference in anterior translation measured by the KT-2000 of 4 and ¶5 mm. No movement was observed in any of the femoral tunnels. Cinematic MRI thus makes it possible to study graft behavior within the bone tunnels.     

Effect of ACL reconstruction tunnels on stress in the distal femur

Purpose

This study examined the change in femoral stress caused by graft tunnels drilled for anterior cruciate ligament (ACL) reconstruction. Using a computational model, the number, geometry and position of the graft tunnels exits were varied to determine the effect on bone stress.

Methods

A finite element model of the distal femur was developed from a CT scan of a cadaveric knee. To assess the model, the strain calculated computationally was compared to experimentally measured strains in eleven unpaired human cadaver femurs. Using the computational model, the number, geometry and position of the graft tunnel exits were varied to determine the effect on bone stress based on the stress concentration factor: the ratio of bone stress with tunnels to intact bone stress.

Results

The results indicated that the second tunnel in double-bundle ACL reconstruction results in approximately a 20 % increase in the maximum femoral stress as compared to single-bundle reconstruction. The highest stresses occur at the tunnel exits. The position of the tunnel exits effects femoral stress with the stress increasing slightly (AM SCR from 0.7 to 1 and PL SCR from 1.2 to 1.3) when the AM tunnel exit is moved anteriorly and having greater increases as the posterior lateral (PL) tunnel exit is moved laterally (PL SCR from 1.2 to 1.7) or posteriorly (PL SCR from 1.2 to 2).

Conclusion

In anatomical ACL reconstruction, the tunnel entrances are dictated by anatomy; however, there can be variations in tunnel exit positions. Consideration should be given when positioning tunnel exits on the effect on stress in the femur. Moving the PL tunnel exit laterally or posteriorly increases in the stress at the PL tunnel exit.     

A biomechanical comparison of tibial inlay and tibial tunnel posterior cruciate ligament reconstruction techniques: graft pretension and knee laxity

BACKGROUND: Most posterior cruciate ligament reconstruction techniques use a tibial bone tunnel, which results in an acute bend in the graft as it passes over the posterior portion of the tibial plateau. HYPOTHESIS: The tibial inlay technique will result in lower graft pretensions, less laxity, and less stretch-out after cyclic loading. STUDY DESIGN: Controlled laboratory study. METHODS: Graft pretensions necessary to restore normal laxity at 90 degrees of knee flexion (laxity match pretension) and anteroposterior laxities at five knee flexion angles were recorded in 12 fresh-frozen knee specimens with bone-patellar tendon-bone posterior cruciate ligament graft reconstructions using both techniques and two femoral tunnel positions. RESULTS: When the graft was placed in a central femoral tunnel, the tibial tunnel reconstruction required an average 15.6 N greater laxity match pretension than the tibial inlay reconstruction. There were no significant differences in mean knee laxities between the tibial tunnel and tibial inlay techniques at any knee flexion angle; both reconstruction techniques restored mean knee laxity to within 1.6 mm of intact knee values over the entire flexion range. CONCLUSIONS: There was no important advantage of one technique over the other with respect to the biomechanical parameters measured.     

Arthroscopic posterior cruciate ligament reconstruction using bioabsorbable cross-pin femoral fixation: a technical note

There are many methods for fixation of the posterior cruciate ligament grafts. We introduce a new surgical technique that provides more secure femoral and tibial fixation of a tibialis posterior allograft. The tendon was prepared as a four-stranded graft. The tibial tunnel was made using a standard trans-tibial technique. A femoral tunnel was prepared through a low anterolateral portal. The graft was inserted into the femoral tunnel through the anterolateral portal and TransFix (Arthrex, Naples, FL) was fixed at the femur. Four stands of the graft were passed through the tibial tunnel and IntraFix (DePuy Mitek, Raynham, MA) was fixed at the tibia.     

Insertion of autologous tendon grafts to the bone: a histological and immunohistochemical study of hamstring and patellar tendon grafts

This study examined the structure of the insertion of autologous tendon grafts used for anterior cruciate ligament reconstruction. Biopsy specimens of the femoral ¶and tibial bone graft interface were obtained at revision surgery in 14 patients (6 with hamstring grafts, 8 with a patella tendon graft). The specimens were analyzed by light microscopy and immunohistochemistry (confirming type I, type II, and type III collagen). The insertions of hamstring autografts to the bone tunnel have three characteristic histological zones. Zone 1 is composed of the dense connective tissue of the graft. The collagen fibers of the graft enter the bone under oblique angles. Zone 2 is composed of woven bone with ¶a sharp transition to the lamellar bone of the tibia (zone 3). Immunohistochemistry revealed the presence of type I and type III collagen within the dense connective tissue of the graft. The woven and lamellar bone showed positive immunostaining for antibodies against type I collagen only. This structure resembled a fibrous ligament or tendon insertion. In the majority of patients with a patella tendon graft the structure of the insertion resembled a chondral enthesis. The chondral insertion of the graft to the bone is composed of four characteristic zones. Between the dense connective tissue of the graft (zone 1) and bone (zone 4) there is a zone of fibrocartilage (zone 2). Close to the bone the fibrocartilage is mineralized (zone 3). Within the fibrocartilage the immunohistochemical analysis confirmed type II collagen. This structure resembled the chondral enthesis of the normal anterior cruciate ligament. However, in cases in which the distal bone bloc has been fixated outside the tibial tunnel, the tibial insertion of the patellar tendon graft resembled a fibrous insertion. While both types of tendon grafts heal to the bone of femur and tibia, the insertion of patella tendon grafts healing by bone plug incorporation resembles the chondral insertion of the normal anterior cruciate ligament and may have a more physiological connection to the bone than hamstring grafts.     

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.     

Bone tunnel enlargement after anterior cruciate ligament reconstruction using hamstring tendons

We retrospectively reviewed 87 anterior cruciate ligament reconstructions using autogenous hamstring tendons with the Endobutton technique to investigate the relationship between bone tunnel enlargement and clinical outcome and to identify factors that contribute to the enlargement. The clinical outcome was evaluated using the Lysholm score and KT-1000 arthrometer. The location of the femoral tunnel with respect to Blumensaat's line, the tibial tunnel with respect to the tibial plateau, and the angle between the femoral tunnel and Blumensaat's line (femoral tunnel angle) were measured. Bone tunnel enlargement was observed in 32 patients (37%). Enlargement occurred in 22 of the femoral tunnels and 26 of the tibial tunnels. Enlargement of both tunnels occurred in 16 knees. There was no statistical difference in Lysholm scores or KT-1000 arthrometer measurements between the enlarged group and the unenlarged group. The femoral tunnel was placed more anteriorly in the enlarged femoral tunnel group than in the unenlarged femoral tunnel group. The tibial tunnel was placed more anteriorly in the enlarged tibial tunnel group than in the unenlarged tibial tunnel group. The femoral tunnel angle was significantly smaller in the enlarged femoral tunnel group than in the femoral unenlarged group. Gender, patient age, intraoperative isometricity, and graft size were not significant factors. Bone tunnel enlargement was not correlated with the clinical outcome measures. We conclude that the main factor associated with tunnel enlargement are the locations and angles of the tunnels. The windshield-wiper motion of the graft may be enhanced by changing tension in the graft due to tunnel malposition. An acute femoral tunnel angle may increase the mechanical stress on the anterior margin of the femoral tunnel.     

Biomechanical properties of patellar and hamstring graft tibial fixation techniques in anterior cruciate ligament reconstruction: experimental study with roentgen stereometric analysis

BACKGROUND: Reliable fixation of the soft hamstring grafts in ACL reconstruction has been reported as problematic. HYPOTHESIS: The biomechanical properties of patellar tendon (PT) grafts fixed with biodegradable screws (PTBS) are superior compared to quadrupled hamstring grafts fixed with BioScrew (HBS) or Suture-Disc fixation (HSD). STUDY DESIGN: Controlled laboratory study with roentgen stereometric analysis (RSA). METHODS: Ten porcine specimens were prepared for each group. In the PT group, the bone plugs were fixed with a 7 x 25 mm BioScrew. In the hamstring group, four-stranded tendon grafts were anchored within a tibial tunnel of 8 mm diameter either with a 7 x 25 mm BioScrew or eight polyester sutures knotted over a Suture-Disc. The grafts were loaded stepwise, and micromotion of the graft inside the tibial tunnel was measured with RSA. RESULTS: Hamstring grafts failed at lower loads (HBS: 536 N, HSD 445 N) than the PTBS grafts (658 N). Stiffness in the PTBS group was much greater compared to the hamstring groups (3500 N/mm versus HBS = 517 N/mm and HSD = 111 N/mm). Irreversible graft motion after graft loading with 200 N was measured at 0.03 mm (PTBS), 0.38mm (HBS), and 1.85mm (HSD). Elasticity for the HSD fixation was measured at 0.67 mm at 100 N and 1.32 mm at 200 N load. CONCLUSION: Hamstring graft fixation with BioScrew and Suture-Disc displayed less stiffness and early graft motion compared to PTBS fixation. Screw fixation of tendon grafts is superior to Suture-Disc fixation with linkage material since it offers greater stiffness and less graft motion inside the tibial tunnel. Clinical Relevance: Our results revealed graft motion for hamstring fixation with screw or linkage material at loads that occur during rehabilitation. This, in turn, may lead to graft laxity.     

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.     

Bone tunnel enlargement following anterior cruciate ligament reconstruction: a randomised comparison of hamstring and patellar tendon grafts with 2-year follow-up

Radiographic tibial and femoral bone tunnel enlargement has been demonstrated following anterior cruciate ligament (ACL) reconstruction. This study investigated whether bone tunnel enlargement differs between four-strand hamstring (HS) and patellar tendon (PT) ACL reconstructions over the course of a 2-year follow-up. Patients undergoing primary ACL reconstruction (n = 65) were randomised to receive either a PT or HS autograft. Femoral fixation in both groups was by means of an Endobutton. On the tibial side the PT grafts were fixed using a metallic interference screw, and the HS tendons by sutures tied to a fixation post. The PT grafts were inserted such that the proximal end of the distal bone block was within 10 mm of the tibial articular surface, resulting in a portion of free patellar tendon in the femoral tunnel immediately proximal to the articular surface. Patients were reviewed after 4 months and 1 and 2 years. Tunnel enlargement was determined by measuring the widths of the femoral and tibial tunnels with a digital caliper in both lateral and anteroposterior radiographs. Because of the presence of the interference screw and the proximity of the bone block to the tibial articular surface, the tibial tunnel could not be reliably measured in the PT group. Measurements were corrected for magnification, and changes in tunnel width were recorded relative to the diameters drilled at surgery. Standard clinical measures were also noted. In 32% of patients in the PT group there was femoral tunnel obliteration from 4 months onwards. For the other patients there was a significantly greater increase in femoral tunnel width in the HS group than in the PT group at each follow-up, but no significant change with time. There was also a marked increase in tibial tunnel width in the HS group at 4 months but not thereafter. There was no relationship between tunnel enlargement and clinical measurements. Although tunnel enlargement is more common and greater with HS grafts, it does not appear to affect the clinical outcome in the first 2 postoperative years. Femoral suspensory fixation does not in itself appear to be the principal cause of femoral tunnel enlargement, at least for PT grafts.