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Thore Zantop

Publications and source records attributed to Thore Zantop.

At least 19 recordsLinked to original sources
PubMed2007

Initial and 6 weeks postoperative structural properties of soft tissue anterior cruciate ligament reconstructions with cross-pin or interference screw fixation: an in vivo study in sheep.

PURPOSE: The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique. METHODS: In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur-graft-tibia complex were evaluated immediately after surgery and 6 weeks postoperatively. RESULTS: For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance. CONCLUSIONS: After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation. CLINICAL RELEVANCE: Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.

Achilles Tendon↗
PubMed2007

Anatomy of the anterior cruciate ligament with regard to its two bundles.

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

Anterior Cruciate Ligament↗
PubMed2007

Intraarticular rupture pattern of the ACL.

To date, the intraarticular rupture pattern of the anterior cruciate ligament (ACL) has not been reported. The ACL is a complex structure consisting of two functionally synergistic structures: the anteromedial (AM) and posterolateral (PL) bundle. The purpose of our study was to evaluate the intraarticular rupture pattern of the ACL with regard to its two functional bundles. We examined ACL rupture patterns with regard to the integrity of AM and PL bundle in 121 consecutive patients undergoing anterior cruciate ligament reconstruction surgery within 120 days after injury. The intraarticular pattern was observed by one experienced surgeon. In 25% of the patients a partial rupture of the ACL was found, whereas in the remaining 75% a complete rupture of AM and PL bundles was seen. A partial rupture could only be detected by careful dissection of the ligament. In 44% of all patients the AM and PL bundles did not rupture at the same location. In 12% of the patients the PL bundle showed no signs of rupture. When performing ACL reconstruction, care should be taken when dissecting down the ACL remnants to evaluate intact fiber bundles of the ACL.

Adult↗
PubMed2006

Biomechanical evaluation of different fixation methods for tibial eminence fractures.

BACKGROUND: Tibial eminence fractures have become more common, but the best method of fixing these fractures arthroscopically has not been elucidated. OBJECTIVE: The objective of this study is to assess the stability of different fixation methods for tibial eminence fractures. STUDY DESIGN: Controlled laboratory study. METHODS: The authors evaluated the initial fixation strength of 4 different fixation techniques for tibial eminence fractures (2 screws, 1 screw, suture fixation with 1 mm Ethibond, and suture fixation with No. 5 FiberWire) using single cycle and cyclic loading tests. The tests were performed by loading the knee with an anterior tibial shear force. RESULTS: Suture cerclage with the FiberWire showed significantly higher maximum load (599.6 N) and stiffness (36.99 N/mm) than all other fixation methods tested. The lowest maximum load in the single cycle loading test was observed in the group with 2 screws (1 screw, 371.2 N; 2 screws, 249.8 N). The lowest stiffness was found in the Ethibond group (14.5 N/mm). After 1000 cycles of loading, the maximum load of the FiberWire fixation was significantly higher than the maximum load of the Ethibond fixation (399.4 N), the fixation with 1 screw (354.2 N), and the fixation with 2 screws (301.5 N). CONCLUSION: These biomechanical data suggest that under cyclic loading conditions, suture fixation of tibial eminence fractures provides more fixation strength than screw fixation. CLINICAL RELEVANCE: A second screw has no positive effect on the biomechanical characteristics of screw fixation.

Animals↗
PubMed2006

The role of the anteromedial and posterolateral bundles of the anterior cruciate ligament in anterior tibial translation and internal rotation.

BACKGROUND: A rupture of the entire fibers of the anterior cruciate ligament leads to knee instability due to increased anterior tibial translation and increased internal tibial rotation. The influence of isolated deficiency of the anteromedial or posterolateral bundle of the anterior cruciate ligament on the resulting knee kinematics have not yet been reported. HYPOTHESIS: Transection of the anteromedial bundle will lead to increased anterior tibial translation at 90 degrees. Transection of the posterolateral bundle will show an increased anterior tibial translation as well as a combined rotatory instability at 30 degrees. STUDY DESIGN: Controlled laboratory study. METHODS: Kinematics of the intact knee were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 N.m valgus and 4 N.m internal tibial rotation using a robotic/universal force moment sensor testing system. Subsequently, the fibers of the anteromedial and posterolateral bundle were resected in an alternating order and the new translation in response to the same external loading conditions measured. Statistical analysis was performed using a 2-way ANOVA test. RESULTS: Transection of the anteromedial bundle increased anterior tibial translation at 60 degrees and 90 degrees of knee flexion significantly. Isolated transsection of the posterolateral bundle increased anterior tibial translation in response to 134-N anterior load at 30 degrees of knee flexion significantly and resulted in a significant increase in combined rotation at 0 degrees and 30 degrees in response to a combined rotatory load compared with the intact knee and isolated resection of the anteromedial bundle. CONCLUSION: The anteromedial and posterolateral bundles stabilize the knee joint in response to anterior tibial loads and combined rotatory loads in a synergistic way. CLINICAL RELEVANCE: The results of the current study suggest that, from a biomechanical point of view, it may be beneficial to reconstruct both bundles of the anterior cruciate ligament to better restore normal anterior tibial translation and combined rotation.

Aged↗
PubMed2006

Biomechanical evaluation of two techniques for double-bundle anterior cruciate ligament reconstruction: one tibial tunnel versus two tibial tunnels.

BACKGROUND: This research was undertaken to determine whether there is a need for a second tibial tunnel in anatomic anterior cruciate ligament reconstruction. HYPOTHESIS: Anatomic two-bundle reconstruction with two tibial tunnels restores knee anterior tibial translation in response to 134 N and to 5-N.m internal tibial torque combined with 10-N.m valgus torque more closely to normal than does double-bundle reconstruction with one tibial tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were subjected to a 134-N anterior tibial load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees and to 5-N.m internal tibial torque and 10-N.m valgus torque at 15 degrees and 30 degrees. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) double-bundle/one tibial tunnel, and (4) double-bundle/two tibial tunnels. RESULTS: Anterior tibial translation for the reconstruction with two tibial tunnels was significantly closer to that of the intact knee than was the reconstruction with one tibial tunnel at 0 degrees and 30 degrees of flexion (0 degrees = 3.82 vs 6.0 mm, P < .05; 30 degrees = 7.99 vs 11 mm, P < .05). The in situ force normalized to the intact anterior cruciate ligament for the reconstruction with two tibial tunnels was significantly higher than the in situ force of the reconstruction with one tibial tunnel (30 degrees = 89 vs 82 N, P < .05). With a combined rotatory load, the anterior tibial translation of specimens with a tibial two-tunnel technique was significantly lower than that of specimens with one tunnel (0 degrees = 5.7 vs 8.4 mm, P < .05; 30 degrees = 7.5 vs 9.5 mm, P < .05). CONCLUSIONS: Anatomic reconstruction with two tibial tunnels may produce a better biomechanical outcome, especially close to extension. CLINICAL RELEVANCE: At the time of initial fixation, there appears to be a small biomechanical advantage to the second tibial tunnel in the setting of two-bundle anterior cruciate ligament reconstruction.

Aged↗
PubMed2006

Anterolateral rotational knee instability: role of posterolateral structures. Winner of the AGA-DonJoy Award 2006.

INTRODUCTION: The aim of this study was to determine the anterolateral rotational instability (ALRI) of the human knee after rupture of the anterior cruciate ligament (ACL) and after additional injury of the different components of the posterolateral structures (PLS). It was hypothesized that a transsection of the ACL will significantly increase the ALRI of the knee and furthermore that sectioning the PLS [lateral collateral ligament (LCL), popliteus complex (PC)] will additionally significantly increase the ALRI. MATERIALS AND METHODS: Five human cadaveric knees were used for dissection to study the appearance and behaviour of the structures of the posterolateral corner under anterior tibial load. Ten fresh-frozen human cadaver knees were subjected to anterior tibial load of 134 N and combined rotatory load of 10 Nm valgus and 4 Nm internal tibial torque using a robotic/universal force moment sensor (UFS) testing system and the resulting knee kinematics were determined for intact, ACL-, LCL- and PC-deficient (popliteus tendon and popliteofibular ligament) knee. Statistical analyses were performed using a two-way ANOVA test with the level of significance set at P < 0.05. RESULTS: Sectioning the ACL significantly increased the anterior tibial translation (ATT) and internal tibial rotation under a combined rotatory load at 0 and 30 degrees flexion (P < 0.05). Sectioning the LCL further increased the ALRI significantly at 0 degrees , 30 degrees and 60 degrees of flexion (P < 0.05). Subsequent cutting of the PC increased the ATT under anterior tibial load (P < 0.05), but did not increase the ALRI (P > 0.05). CONCLUSION: The results of the current study confirm the concept that the rupture of the ACL is associated with ALRI. Current reconstruction techniques should focus on restoring the anterolateral rotational knee instability to the intact knee. Additional injury to the LCL further increases the anterior rotational instability significantly, while the PC is less important. Cautions should be taken when examining a patient with ACL rupture to diagnose injuries to the primary restraints of tibial rotation such as the LCL. If an additional extraarticular stabilisation technique is needed for severe ALRI, the technique should be able to restore the function of the LCL and not the PC.

Aged↗
PubMed2006

Initial fixation strength of a new hybrid technique for femoral ACL graft fixation: the bone wedge technique.

BACKGROUND: Aperture fixation with interference screws matching the diameter of the tunnel is associated with the risk of graft laceration and graft rotation. HYPOTHESIS: A hybrid fixation technique (extracortical and aperture fixation) with undersized interference screw placed behind a bone wedge provides a higher fixation strength as aperture fixation with a screw alone matching the size of the tunnel. STUDY DESIGN: Experimental laboratory study. METHODS: We evaluated the initial fixation strength (single cycle and cyclic loading tests) of hybrid and interference screw aperture fixation using different sized interference screws in porcine knees. RESULTS: Analysis of yield load, maximum load and stiffness in the single cycle loading test showed no statistically significant differences for hybrid fixation with a 1 mm undersized screw and aperture fixation with a screw matching the size of the tunnel. The use of an undersized screw alone resulted in low fixation strength. CONCLUSION: The initial fixation strength of the hybrid technique with undersized screws is comparable to that of interference screw fixation matching the size. CLINICAL RELEVANCE: The new "bone wedge fixation" is an alternative for ACL graft fixation without the risk of graft laceration and graft rotation.

Analysis of Variance↗
PubMed2006

Initial fixation strength of a hybrid technique for femoral ACL graft fixation.

Aperture fixation with interference screws matching the diameter of the tunnel is associated with the risk of graft laceration and graft rotation. A hybrid fixation technique (extracortical and aperture fixation) with undersized interference screws provides a higher fixation strength when compared to an aperture fixation using only a screw matching the size of the tunnel and also reduces the risk of graft laceration. This research is an experimental laboratory study. We evaluated the initial fixation strength at time-zero of an extracortical-, a hybrid- and an aperture fixation in ACL reconstruction using extracortical buttons and different sized interference screws in porcine knees. The tests were performed using a single cycle and cyclic loading protocol. Analysis of yield load, maximum load and stiffness in the single cycle loading test showed no statistically significant differences for hybrid fixation with a 1 mm undersized screw and aperture fixation with a screw matching the size of the tunnel. Cyclic loading tests showed a statistically significant difference between hybrid and aperture fixation. The use of an undersized screw alone in aperture fixation resulted in insufficient fixation strength. The initial fixation strength of the hybrid technique with undersized screws is higher compared to an interference screw fixation alone. The hybrid fixation technique is an alternative for ACL graft fixation.

Absorbable Implants↗
PubMed2006

Anterior cruciate ligament anatomy and function relating to anatomical reconstruction.

Recently, the interest in surgical techniques that reconstruct the anteromedial (AM) and the posterolateral (PL) bundles of the anterior cruciate ligament (ACL) has risen. This review focuses on the structural as well as the mechanical properties of the ACL and the anatomical details of the femoral origin, midsubstance, and tibial insertion of AM and PL bundles of the ACL. The terminology of AM and PL bundles is chosen according to the tibial insertion and determined by their functional tensioning pattern throughout knee flexion. Close to extension the AM is moderately loose and the PL is tight. As the knee is flexed, the femoral attachment of the ACL becomes more horizontally oriented, causing the AM bundle to tighten and the PM bundle to loosen up. The ACL has been described to be restraint to anterior tibial displacement and internal tibial rotation. The rotational component might be represented by the PL bundle. The femoral origin has an oval shape with the center of the AM close to over-the-top position and the center of the PL close to the anterior and inferior cartilage margin. Tibial and femoral insertions of the ACL are over 3.5 times larger when compared to the midsubstance and tunnel placement is more challenging because of the limited size of potential grafts selection of tunnel site placement. For reconstruction, both bone-patellar tendon-bone (BPTB) and quadrupled hamstring grafts are used. Structural properties of a 10 mm wide BPTB or quadrupled hamstring graft have been reported to be comparable with those of the native ACL.

Anterior Cruciate Ligament↗
PubMed2006

The effect of locally applied vascular endothelial growth factor on meniscus healing: gross and histological findings.

INTRODUCTION: Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. We hypothesized that healing of meniscus tears in the avascular zone can be promoted by the local application of the angiogenic factor vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: A tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). RESULTS: After 6 weeks, we observed increased immunostaining for factor VIII in the VEGF-treated group 3. However, in this treatment group no meniscus healed completely. In the uncoated suture group and in the PDLLA-coated-suture group, partial healing was observed in three animals and complete healing in three animals, respectively. CONCLUSION: In this experiment the local application of VEGF via PDLLA-coated sutures did not promote meniscus healing. Growth factors might not always be a promising tool for tissue repair.

Animals↗
PubMed2006

Elongation and structural properties of meniscal repair using suture techniques in distraction and shear force scenarios: biomechanical evaluation using a cyclic loading protocol.

BACKGROUND: Most biomechanical studies on meniscal repairs have focused on testing distraction scenarios to evaluate structural properties of the repaired meniscus. An application of shear forces might replicate the in vivo situation more closely. HYPOTHESIS: In the shear force scenario, meniscal repair using a vertical suture technique will result in significantly less elongation when subjected to a cyclic loading protocol than that resulting from a horizontal suture technique. STUDY DESIGN: Controlled laboratory study. METHODS: In fresh-frozen porcine menisci (n = 10 in each group), horizontal and vertical 2.0 Ethibond suturing techniques were tested in distraction and shear force scenarios. Elongation after 1000 cycles between 5 and 20 N and the structural properties such as stiffness, yield load, maximum load to failure, and failure mode were evaluated using a testing machine at a rate of 12.5 mm/s. RESULTS: In the distraction force scenario, no statistically significant difference in elongation after cyclic loading was found between specimens repaired with vertical or horizontal suture techniques. After 1000 cycles of cyclic loading in the shear force scenario, the horizontal suturing revealed significantly less elongation (2.8 +/- 1.1 mm) than did the vertical suture technique (4.6 +/- 2.0 mm). No statistically significant difference in yield and maximum load was found (P > .05). CONCLUSION: The results of the present study do not support the authors' hypothesis. In the shear force test, horizontal sutures were superior to vertical suture techniques. CLINICAL RELEVANCE: Meniscal repair with horizontal suture techniques can withstand elongation due to shear forces more effectively than can vertical mattress sutures.

Animals↗
PubMed2006

Extracellular matrix scaffolds are repopulated by bone marrow-derived cells in a mouse model of achilles tendon reconstruction.

The extracellular matrix derived from porcine small intestinal submucosa (SIS-ECM), an FDA-approved material currently used clinically for rotator cuff repair, has been shown to attract bone marrow-derived cells during in vivo remodeling of a subcutaneous implant and produce chemoattractant peptides following chemical degradation in vitro. The purpose of the present study was to determine if bone marrow-derived cells participate in the long-term remodeling of the Achilles tendon in a mouse model when repaired with SIS-ECM. A 2-mm gap was produced in the Achilles tendon of 40 chimeric mice produced to express green fluorescent protein (GFP) in all of their bone marrow-derived cells. Tendons were repaired by replacing the resected section with autologous tendon tissue or with a single layer sheet of lyophilized SIS-ECM. Four animals from each treatment group were sacrificed at 1, 2, 4, 8, and 16 weeks, and sections were harvested for histologic and fluorescence microscopy. Both groups showed accumulation of GFP-expressing marrow-derived cells at the site of tendon remodeling at 1 and 2 weeks that were associated with areas of angiogenesis and inflammation. By 16 weeks, the SIS-ECM-treated group showed GFP expressing cells throughout the remodeled tendon in the absence of any inflammatory response, while the autologous tendon repair group showed no GFP expressing cells within the tendon except for occasional cells in the lumen of blood vessels. An SIS-ECM scaffold used for tendon repair recruits a population of bone marrow-derived cells that participates in the long-term remodeling process. The ability of SIS-ECM to recruit a population of marrow-derived cells to the remodeling site may alter the default mechanism of tendon healing. The involvement of these cells in the remodeling process may explain in part the process of site specific constructive remodeling as opposed to scar tissue formation when the ECM is used as a biologic scaffold for tendon reconstruction.

Achilles Tendon↗
PubMed2006

[Arthroscopic meniscal suture].

OBJECTIVE: Restoration of the function of the meniscus by suturing a tear to prevent long-term degeneration. INDICATIONS: Unstable longitudinal meniscal tear in the red and red-white zones with an intact central fragment. Dislocated bucket-handle tear near the base in the presence of good-quality tissue. CONTRAINDICATIONS: Lesion of the central meniscal fragment. Meniscal tears in the white, avascular zone. Degenerative meniscal lesions. Complex meniscal lesions. Untreated knee ligament instability. Uncooperative patient. SURGICAL TECHNIQUE: Standard anterior arthroscopy approach. Revitalization of the tear margins and the perimeniscal synovial membrane, trephination of the base of the meniscus to promote healing. Fixation of the tear with a resorbable or nonresorbable suture size 2-0 to 0 USP by means of different suture techniques. "Outside-in technique": the suture is introduced from outside the joint through the base of the meniscus using a cannulated needle and is then pulled back out using a suture loop inserted with another cannulated needle. The U-suture is knotted over the joint capsule through a stab incision. "Inside-out technique": the suture is introduced using a needle through a guide cannula from outside the joint through the meniscus and joint capsule and then brought out of the joint. The U-suture is knotted over the capsule through a short skin incision. "All-inside technique": the suture loop is passed through the meniscal tear and knotted within the joint using a posterior arthroscopy approach. POSTOPERATIVE MANAGEMENT: Full weight bearing without a brace for short tears with one suture. For tears with two sutures, partial weight bearing for 4 weeks without a brace. For large tears with three to four sutures, partial weight bearing up to 20 kp for 6 weeks and restricted knee motion in a brace up to 0/0/60 degrees . RESULTS: The healing rate for knee joints with stable ligaments and an isolated meniscal tear is between 50% and 75%. In cases with simultaneous ACL (anterior cruciate ligament) plasty, the healing rate is > 75%; for unstable knee joints it is < 50%.

Adolescent↗
PubMed2006

Graft laceration and pullout strength of soft-tissue anterior cruciate ligament reconstruction: in vitro study comparing titanium, poly-d,l-lactide, and poly-d,l-lactide-tricalcium phosphate screws.

PURPOSE: The aim of part 1 of this study was to compare the structural properties of tibia-graft-interference screw constructs of soft-tissue graft fixation via the anterior cruciate ligament (ACL) by use of different interference screws. In part 2 the influence of graft laceration as a result of 1 single interference screw insertion on the mechanical properties of the graft was evaluated. METHODS: In part 1 of the study, in a bovine knee model, soft-tissue graft fixation with titanium, biodegradable poly-D,L-lactide (PLDLA), and PLDLA-tricalcium phosphate (TCP) interference screws was performed, and the structural properties were determined by use of a materials testing machine at a rate of 12.5 mm/s. In part 2 the bone was cut after 1 single insertion of titanium, PLDLA, or PLDLA-TCP interference screws, and the mechanical properties of the graft were determined. RESULTS: Soft-tissue graft fixation with a biodegradable PLDLA interference screw showed a statistically significantly higher maximum load when compared with PLDLA-TCP and titanium interference screws. PLDLA-TCP screw fixation revealed a significantly higher ultimate load than titanium screw fixation. The mechanical properties of the grafts after 1 single insertion of PLDLA-TCP interference screws showed a statistically significantly higher stiffness, yield load, and maximum load when compared with the PLDLA and titanium interference screw groups. CONCLUSIONS: The results of this study suggest that the use of a titanium screw to fix a soft-tissue graft in cruciate ligament reconstruction surgery may cause damage to the graft. Soft-tissue ACL reconstruction fixed with a PLDLA interference screw resulted in a significantly higher pullout strength than ACL reconstructions fixed with a PLDLA-TCP or titanium interference screw. CLINICAL RELEVANCE: In contrast to fixation with a biodegradable interference screw, fixation with a titanium interference screw may damage the integrity of a soft-tissue graft in cruciate ligament reconstruction and should therefore be avoided.

Absorbable Implants↗
PubMed2006

Partial rupture of the anterior cruciate ligament.

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial (AM) and posterolateral (PL) bundles. Although disagreement exists among arthroscopic surgeons about the occurrence of isolated ruptures of the AM or PL bundle, there are reports of partial ruptures of the ACL in the literature. A potential reason for controversy could be that with conventional magnetic resonance imaging, isolated PL ruptures are difficult to diagnose because of the oblique course of this bundle. Another reason could be that isolated ruptures of the AM or PL bundle are difficult to diagnose during arthroscopy. During arthroscopy, an isolated PL bundle rupture can easily be missed when viewing from the standard anterolateral portal. The AM bundle overlies the PL bundle, and the PL bundle can only be seen by retraction of the AM bundle with a probe. When the knee is extended, the PL bundle is tight and the AM bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes horizontally oriented, causing the AM bundle to tighten and the PL bundle to relax. Whereas the AM bundle is the primary restraint against anterior tibial translation in flexion, the PL bundle tends to stabilize the knee near full extension, particularly against rotatory loads. The different bundle contributions to knee stability in the flexed or extended positions can aid in the diagnosis of partial ACL ruptures. Isolated rupture of the AM bundle has more effect on the anterior drawer sign than on the Lachman test, whereas the converse is true for isolated rupture of the PL bundle. Rotational instability as a result of PL bundle rupture can be tested with the pivot-shift test. Pivot shift can be negative in cases with isolated AM bundle rupture. If only one bundle of the ACL is torn, isolated AM or PL bundle reconstruction should be considered. Although potentially difficult, a careful diagnostic evaluation is necessary before ACL surgery.

Anterior Cruciate Ligament↗
PubMed2005

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.

Aged↗