Mechanoreceptors in Remnant Posterior Cruciate Ligament and Achilles Tendon Allografts After Remnant-Preserving Posterior Cruciate Ligament Reconstruction: Hematoxylin-Eosin and Immunohistochemical Assessments.

BACKGROUND: Mechanoreceptor is a subtype of somatosensory receptor. It conveys extracellular stimuli through intracellular signal conduction via mechanically gated ion channel. It conveys not only kinetic stimuli but also pressure, stretching, touch, and even sound wave. Few studies have determined whether mechanoreceptors are present in Achilles tendon allografts used during remnant-preserving posterior cruciate ligament (PCL) reconstruction (PCLR). PURPOSE/HYPOTHESIS: The purpose was to investigate whether mechanoreceptors are present in remnant tissues of the PCL and allograft tissues after PCLR. It was hypothesized that mechanoreceptors may be present in the remnant PCL tissue of the patients who underwent remnant PCLR technique. STUDY DESIGN: Controlled laboratory study. METHODS: Tissue samples were obtained from 14 participants who had undergone PCLR by means of Achilles tendon allografts (PCLR group) and from 4 healthy controls (control group). Among the PCLR group, 12 patients had undergone a remnant PCLR technique and the remaining 2 patients had undergone a nonremnant PCLR technique. In the PCLR group, we obtained samples during second-look arthroscopy or total knee arthroplasty after PCLR. In the control group, 4 biopsy specimens of normal PCL tissues were obtained from patients who had undergone other arthroscopic procedures. To check the presence of mechanoreceptors, immunohistochemical studies were performed on all biopsy specimens to identify neuronal and neurocytic markers by using monoclonal antibodies against glial fibrillary acidic protein, neuron-specific enolase, neurofilament, and S-100 protein. Only 1 of these markers needed to be positive to prove the presence of mechanoreceptors. RESULTS: Neural tissue analogs, confirmed to be mechanoreceptors with monoclonal antibodies by the Ultraview DAB detection kit, were found in all specimens obtained from the control group. Mechanoreceptors were not found in the allograft specimens. However, remnant PCL tissues were found to have mechanoreceptors in 11 of 12 samples (91.7%). CONCLUSION: The results demonstrate that Achilles tendon allografts lack mechanoreceptors. This study can be used as histological evidence to support the advantage of remnant-preserving techniques for PCLR because they preserve proprioception. CLINICAL RELEVANCE: To preserve proprioception, which leads to better functional outcome, using the remnant technique is a better procedure for PCL reconstruction.

Modified tibial tunnel placement for single-bundle posterior cruciate ligament reconstruction reduces the "Killer Turn" in a biomechanical model.

BACKGROUND: Our previous three-dimensional finite element analysis found that posterior cruciate ligament (PCL) reconstruction in the modified tibial tunneling placement (MTT, 10 mm inferior and 5 mm lateral to the PCL anatomical insertion) could reduce the peak stress of the graft and may reduce the killer turn. The purpose of the current study was to compare the biomechanical results between MTT and traditional tibial tunneling technique (TTT, PCL anatomical insertion) during transtibial PCL reconstruction. METHODS: Fifty-six 3D-printed tibia models and fresh mature porcine flexor digitorum tendons were studied. The PCL reconstruction specimens were randomly divided into TTT group and MTT group based on tibial tunnel placement. A 50 to 300 N cyclic loading was applied using a material testing system. Each specimen completed 2000 cycles at a rate of 200 mm/min and a loading frequency of 80 cycles/min. Load-displacement curves, failure mode, and graft displacement were recorded. Mean maximum contact pressure was measured using a pressure-sensitive film. After cyclic loading test, the surviving grafts were randomly assigned to load-to-failure group or Scanning Electron Microscopy (SEM) group. Ultimate failure load and the appearance of graft abrasion were recorded and analyzed. RESULT: During the cyclic loading test, 3 samples in the TTT group, and 2 in the MTT group were excluded because of the graft pullout during the test. Mean maximum contact pressure of killer turn was 9.30 ±â€Š0.29 MPa in the TTT group and 7.27 ±â€Š0.25 MPa in MTT group (P < .05). Mean graft displacement was 4.54 ±â€Š0.23 mm in the TTT group and 3.37 ±â€Š3.56 mm in the MTT group (P < .05). Maximum failure load was 1886.0 ±â€Š41.83 N in the TTT group and 2019.30 ±â€Š20.10 N in the MTT group (P < .05). The SEM analysis showed heavy abrasion and fiber discontinuity in graft in the TTT group, while it showed slight abrasion and fiber arrangement disorders in the MTT group. CONCLUSIONS: The MTT PCL reconstruction significantly reduced stress concentration and graft abrasion as compared with the TTT PCL reconstruction, and it may be a better choice for the reduction of "killer Turn" effect during transtibial PCL construction.

The use of the ligament augmentation and reconstruction system (LARS) for posterior cruciate reconstruction.

PURPOSE: To systematically review and assess the use of the Ligament Advanced Reinforcement System (LARS; Surgical Implants and Devices, Arc-sur-Tille, France) for posterior cruciate ligament (PCL) reconstruction. METHODS: A search of multiple databases was conducted using the following terms: (LARS[All Fields] AND posterior[All Fields]) OR (LARS[All Fields] AND PCL[All Fields]). The methodologic quality of each article was assessed by use of abridged Downs and Black criteria. RESULTS: Fifty-four studies were found from the database search, of which 5 were included in the final review (4 case series and 1 case-control study). One hundred twenty-nine PCL reconstructions with LARS were performed. The mean patient age was 32.2 years, with 89 male and 40 female patients included. The mean follow-up time ranged from 10.5 to 44 months. Lysholm scores improved from a mean of 64.8 preoperatively to 89.8 postoperatively. No patients had International Knee Documentation Committee grade 1 or 2 preoperatively, with 93.0% achieving this postoperatively. Only 1 case of synovitis and 1 case of graft rupture were reported. CONCLUSIONS: There is little evidence on the effectiveness of PCL reconstructions using LARS ligaments. What data there are show great promise, with short- and medium-term outcome data appearing favorable to autograft reconstruction. Complication rates are encouragingly low. CLINICAL RELEVANCE: LARS has great potential for PCL reconstruction. Further studies are needed regarding the use of LARS ligaments during PCL reconstruction, including longer follow-up periods and investigation into the optimal timing for reconstruction. This may be best achieved by way of a multicenter study.

Remnant posterior cruciate ligament-augmenting stent procedure for injuries in the acute or subacute stage.

PURPOSE: To evaluate the results of a remnant posterior cruciate ligament (PCL)-augmenting stent procedure for acute- or subacute-stage PCL injuries in terms of stability and clinical results. METHODS: Between September 2003 and March 2006, 32 patients with a PCL tear underwent a reconstructive stent procedure with an autogenous hamstring tendon graft to augment the remains of the injured PCL. Of these patients, 20 who satisfied our inclusion criteria and could be followed up for a minimum duration of 24 months were enrolled in our study. The remnant PCL and synovium were preserved, and augmentation was performed by use of the transtibial technique. A femoral tunnel was created near the footprint of the anterolateral bundle. Stability was measured on posterior stress radiographs and by use of a maximum manual displacement test performed with a KT-1000 arthrometer (MEDmetric, San Diego, CA). The International Knee Documentation Committee (IKDC) and Orthopädische Arbeitsgruppe Knie scoring systems were used for clinical evaluation. RESULTS: Stress radiographs showed that the mean side-to-side differences in displacement were reduced from 9.9 +/- 4.0 mm preoperatively to 3.0 +/- 2.6 mm at the last follow-up, whereas KT-1000 tests showed that these differences were reduced from 6.9 +/- 2.1 mm preoperatively to 2.7 +/- 1.5 mm. The final IKDC score was A in 7 patients (35%), B in 10 (50%), C in 2 (10%), and D in 1 (5%). The mean Orthopädische Arbeitsgruppe Knie score improved from 61.6 +/- 13.1 to 88.2 +/- 9.5. CONCLUSIONS: Of the patients, 90% showed satisfactory posterior stability and 85% had a normal or nearly normal rating based on the IKDC score at a mean of 3 years after the remnant PCL-augmenting stent procedure in the acute or subacute stage of PCL injuries.

The graft/femoral tunnel angles in posterior cruciate ligament reconstruction: a comparison of 3 techniques for femoral tunnel placement.

This study compared the graft/femoral tunnel angle produced with the outside-in technique with the inside-out technique at 90 degrees and 120 degrees of flexion. Three femoral tunnels were marked with guidewires and measured radiographically in 8 fresh-frozen cadaveric knees using both techniques. Results were analyzed. The mean graft/femoral tunnel angle was 34.4 degrees +/- 14.4 degrees for the outside-in technique, 52.3 degrees +/- 14.1 degrees for the inside-out technique at 120 degrees of flexion, and 74.4 degrees +/- 11 degrees for the inside-out technique at 90 degrees of flexion. The angle was smaller for the outside-in technique versus the inside-out technique at both 120 degrees (P = .019) and 90 degrees of knee flexion (P < .001). The outside-in technique for femoral tunnel placement produces the lowest graft/femoral tunnel angle in cadavers. With the inside-out technique, 120 degrees of flexion produces smaller angles than does 90 degrees of flexion. The outside-in technique results in lower angles and perhaps lower graft failure rates. However, additional clinical studies are needed.

Checkpoints for judging tunnel and anterior cruciate ligament graft placement.

This article examines how the relationship between sagittal and coronal anatomy, anterior cruciate ligament (ACL) graft dimensions, and tibial and femoral tunnel placement affects the posterior cruciate ligament (PCL) and roof impingement, and their undesirable clinical consequences of motion loss and instability. Based on these interrelationships, a variety of checkpoints are defined that can be used intraoperatively to determine whether placement of the tibial tunnel guidewire avoids PCL and roof impingement, and whether placement of the femoral tunnel guidewire avoids PCL impingement with either transtibial or transportal techniques. A simple, 3-dimensional tibial drill guide that consistently places the tibial tunnel correctly without PCL and roof impingement so the femoral tunnel, when drilled through the tibial tunnel, restores the normal tension pattern in the ACL graft also is described. Arthroscopic and radiographic checkpoints that assess the final placement of the ACL graft and tibial and femoral tunnels are discussed.

The biomechanical performance of bone block and soft-tissue posterior cruciate ligament graft fixation with interference screw and cross-pin techniques.

PURPOSE: The purpose of this study was to evaluate the biomechanical properties of 4 different graft fixation constructs on the tibial side of the posterior cruciate ligament with reconstruction by use of an Achilles tendon graft. METHODS: Biomechanical testing of 4 different fixation techniques was performed on 20 human cadaveric tibias and Achilles tendons. Cross-pin fixation with bone blocks (group A), interference screw fixation with bone blocks (group B), cross-pin fixation of soft tissue with backup fixation (group C), and interference screw fixation of soft tissue with backup fixation (group D) were tested. The tibia-graft fixation complex was cyclically loaded between 50 N and 250 N at 1 Hz for 1,000 cycles. After cycling, the amount of graft displacement was determined by measuring the change in grip-to-grip distance. The complex was then loaded to failure at 1 mm/s, and maximum failure load, stiffness, and mode of failure were determined. RESULTS: Group C had a higher maximum failure load and stiffness than groups A and B (P < .05 and P < .001, respectively) but poor results for displacement (P < .05 and P < .05, respectively). The failure modes were bone block fracture, graft laceration, or cross-pin fracture in the cross-pin groups and graft pullout in the interference screw groups. CONCLUSIONS: Our study suggests that maximum failure load and stiffness of hybrid fixation for Achilles tendon graft are comparable to those of both single calcaneal bone plug fixation methods that we studied. However, tendon graft displacement was significantly greater regardless of fixation method when compared with bone plug fixation. CLINICAL RELEVANCE: Hybrid fixation for soft-tissue graft on the tibial fixation site provides comparable biomechanical properties of bone-to-bone fixation.

Evaluation of posterolateral rotatory knee instability using the dial test according to tibial positioning.

PURPOSE: This study examined the effect of the anteroposterior (AP) direction force on the tibial external rotation of a posterior cruciate ligament (PCL)/posterolateral corner (PLC)-deficient knee in a clinical setting. METHODS: Between December 2006 and December 2007, 21 patients with a PCL-PLC injury were assessed using a dial test. The thigh-foot angle (TFA) and patella-tubercle angle (PTA) were measured with an external rotation stress applied to the tibia at both 30 degrees and 90 degrees of knee flexion in 2 different positions (reduced and posterior subluxed). The test was performed with the patient in the supine position and with an AP force applied to the tibia by an assistant. To reduce intra- and interobserver bias, the measurements were taken twice by 2 orthopaedic surgeons for all patients. RESULTS: In the subluxed position, the mean side-to-side differences in the TFA at 30 degrees and 90 degrees knee flexion were 12.6 degrees +/- 2.0 degrees and 12.3 degrees +/- 1.4 degrees , respectively. In the reduced position, the mean side-to-side differences in the TFA at 30 degrees and 90 degrees knee flexion were 18.4 degrees +/- 1.4 degrees and 18.5 degrees +/- 1.5 degrees , respectively. In the subluxed position, the mean side-to-side differences in the PTA at 30 degrees and 90 degrees knee flexion were 9.1 degrees +/- 0.8 degrees and 9.0 degrees +/- 0.7 degrees , respectively. In the reduced position, the mean side-to-side differences in the PTA at 30 degrees and 90 degrees knee flexion were 13.3 degrees +/- 0.6 degrees and 13.2 degrees +/- 0.6 degrees , respectively. CONCLUSIONS: The reduction of a posteriorly subluxed knee increased the tibial external rotation (TFA and PTA) during the dial test of combined PCL-PLC injuries in a clinical setting. The accuracy of the dial test may help present surgeons from missing a combined PLC injury that should be corrected in a PCL deficient knee. LEVEL OF EVIDENCE: Level I, testing of previously developed diagnostic criteria in series of consecutive patients.

Preoperative magnetic resonance imaging cross-sectional area for the measurement of hamstring autograft diameter for reconstruction of the adolescent anterior cruciate ligament.

PURPOSE: We conducted this study to determine if preoperative magnetic resonance imaging (MRI) cross-sectional area measurements would correlate with intraoperative graft size in hamstring anterior cruciate ligament (ACL) reconstructions. METHODS: We retrospectively reviewed ACL reconstructions performed by a single surgeon using a quadruple-looped hamstring allograft. Preoperative MRI axial images were used to determine the combined cross-sectional area of the semitendinosis and gracilis tendons. These cross-sectional areas were correlated to the intraoperative graft size. RESULTS: We found a strong correlation between the MRI cross-sectional areas and graft size. If the combined cross-sectional areas were >or=18 mm(2), there was an 88% probability of obtaining a graft of sufficient size at the time of surgery. CONCLUSIONS: We conclude that our technique is a reliable option to assist the surgeon with preoperative determination of graft size. This is valuable to the orthopaedist to more accurately discuss graft options with the patient and improve preoperative preparation with respect to graft choice. LEVEL OF EVIDENCE: Level II, development of diagnostic criteria on the basis of consecutive patients with universally applied gold standard.

Simultaneous double-bundle anterior cruciate ligament and posterior cruciate ligament reconstruction with autogenous hamstring tendons.

PURPOSE: The purpose of this study was to evaluate the clinical results of simultaneous double-bundle anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction. METHODS: We performed arthroscopic reconstruction in 21 cases of combined ACL/PCL rupture, 14 chronic and 7 acute, with autogenous hamstring tendons in 1 stage, both in a double-bundle and 4-tunnel manner. The semitendinosus tendon and gracilis tendon from the uninjured leg were used to make two 4-stranded grafts to reconstruct the PCL, and those from the injured leg were used to make two 4-stranded grafts to reconstruct the ACL. The grafts were suspended with a mini-plate and buttons. The patients were followed up for a minimum of 2 years and evaluated according to the International Knee Documentation Committee (IKDC) and Lysholm rating scale. The anterior-posterior knee laxity was assessed by KT-1000 examination (MEDmetric, San Diego, CA). RESULTS: At the last follow-up, all patients showed normal knee extension. One patient had a 10 degrees flexion limitation, and four had a 5 degrees flexion limitation. KT-1000 examination showed that the side-to-side difference in overall anterior-posterior laxity at 70 degrees flexion was 0 to 2 mm in 16 patients, 3 to 5 mm in 4 patients, and 6 to 10 mm in 1 patient; the side-to-side difference in overall anterior-posterior laxity at 25 degrees flexion was 0 to 2 mm in 14 patients, 3 to 5 mm in 6 patients, and 6 to 10 mm in 1 patient. The IKDC subjective, Lysholm, and Tegner scores were 85.5 +/- 5.8, 91.9 +/- 4.2, and 5.0 +/- 1.9, respectively. According to the last IKDC evaluation, the results were graded as normal in 13 patients (61.9%), nearly normal in 7 patients (33.3%), and abnormal in 1 patient (4.8%). CONCLUSIONS: Simultaneous double-bundle ACL and PCL reconstruction with autogenous hamstring tendons can yield normal results in 61.9% of patients and nearly normal results in 33.3% at a minimum of 2 years. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Antegrade tibial tunnel technique for posterior cruciate ligament reconstruction.

Posterior cruciate ligament (PCL) reconstruction remains a difficult procedure even in experienced hands because there is a lack of consensus regarding the most reliable and least technically challenging technique. The commonly used retrograde anteromedial tibial tunnel leads to excessive angulation at the posterior tibia and risks catastrophic neurovascular complications. We present a technique of drilling the transtibial PCL tunnel in an antegrade fashion through a posteromedial portal. This technique offers the advantage of an anterolateral route to reduce graft angulation, as well as drilling away from the important posterior neurovascular structures.

[Allografts for cruciate ligament reconstruction]. / Allogene Kreuzbandtransplantation.

Allografts have an essential significance in the surgical reconstruction of ligamentous injuries around the knee joint. While in primary anterior cruciate ligament reconstruction allografts are less important than autografts, at least in the European countries, the usage of allografts in anterior cruciate ligament revision surgery is increasing. In addition, allografts represent a good alternative for the reconstruction of the posterior cruciate ligament and the posterolateral structures. Especially in multiligament reconstructions of the knee joint, the usage of allografts may prevent iatrogenic damage of the already traumatized periarticular soft tissue. The present article focuses on the application and clinical results of allografts for ligament reconstruction around the knee joint. Furthermore, the immunological and biological principles of tendon allografts, their availability, processing, and security are discussed.

Effects of posterolateral reconstructions on external tibial rotation and forces in a posterior cruciate ligament graft.

BACKGROUND: In patients with a Grade-3 injury, reconstructions of the lateral collateral ligament, popliteus tendon, and popliteofibular ligament are commonly performed in conjunction with a reconstruction of the posterior cruciate ligament. The objectives of this study were (1) to compare the abilities of three types of posterolateral graft reconstruction to restrain external tibial rotation and alter forces in a posterior cruciate graft and (2) to compare tibial rotations and posterior cruciate graft forces associated with two levels of initial posterolateral graft tension. METHODS: Forces in the posterior cruciate ligament were recorded as the knee was extended from 120 degrees to 0 degrees and a 5-N-m external tibial torque was applied. The posterior cruciate ligament was reconstructed, and external tibial rotation and the forces in the posterior cruciate graft were recorded. These measurements were again recorded after sectioning of the posterolateral structures and after reconstruction of the lateral collateral ligament, alone as well as in combination with reconstruction of the popliteus tendon and in combination with reconstruction of the popliteofibular ligament. RESULTS: With the lateral collateral ligament intact, removal of the popliteus tendon from its femoral origin significantly increased external tibial rotation. Applying tension to a popliteus or popliteofibular graft internally rotated the tibia, with no significant difference between the rotations caused by the tensioning of the two grafts. Tibial rotation was significantly greater when graft tensioning had been performed with the tibia free to rotate than it was when the tensioning had been done with the tibia locked in neutral rotation. With an applied external tibial torque, a reconstruction of the lateral collateral ligament alone was not sufficient to reduce posterior cruciate graft forces to normal. The addition of a popliteus or popliteofibular reconstruction to the lateral collateral ligament reconstruction significantly reduced posterior cruciate graft forces to normal (or below normal) levels. The external rotations associated with these two combined reconstructions were equivalent and significantly less than that in the intact knee. Increasing tension in either the popliteus or the popliteofibular graft from 10 to 30 N significantly decreased external rotation. CONCLUSIONS: The posterolateral grafts acted to resist applied external torque, thereby off-loading the posterior cruciate graft. Popliteus and popliteofibular grafts were more favorably aligned than a lateral collateral ligament graft to resist external rotation, and they had similar effects.

MR imaging of stable posterior cruciate ligament grafts in 21 arthroscopically proven cases.

OBJECTIVE: To describe the magnetic resonance (MR) appearance of intact posterior cruciate ligament (PCL) grafts. MATERIALS AND METHODS: Thirty-one postoperative MR examinations were performed in 21 grafts of 20 patients after PCL reconstruction. All 21 grafts were proven to be intact on second-look arthroscopic examination. Two musculoskeletal radiologists retrospectively analyzed the MR findings and reached decisions by consensus. The signal intensity (SI) of the graft on proton density-weighted and T2-weighted images, as well as the shapes, locations, and segments of increased SI were recorded. The graft thickness was also recorded and correlated to elapsed time since reconstructive surgery. RESULTS: The SI of the graft was high (15/31, 48%), intermediate (10/31, 32%), or low (6/31, 19%) on proton density-weighted images, and high (9/31, 29%), intermediate (6/31, 19%), or low (16/31, 52%) on T2-weighted images. The graft SI decreased significantly as postoperative time elapsed. The shape of the increased SI within the grafts was band-like (14/25, 56%) or focal (11/25, 44%). The increased SI was located in the proximal (18/25, 72%), middle (21/25, 82%), and distal (12/25, 48%) segments. In the axial plane, the location of increased SI was intrasubstance (19/25, 76%) or peripheral (10/25, 40%). A 'focal' shape of increased SI was found significantly more in Achilles tendon allografts, while a band-like shape was more frequent in autogenous double-loop hamstring tendon grafts. Graft thickness ranged from 5-15 mm. The difference in graft thickness relative to postoperative time was not statistically significant (p = 0.79). CONCLUSION: Stable PCL grafts commonly showed an increased SI at any segment or location, even though they were stable. The shape of increased SI differed according to allograft donor sites. However, SI tended to decrease as time elapsed.

How well do anatomical reconstructions of the posterolateral corner restore varus stability to the posterior cruciate ligament-reconstructed knee?

BACKGROUND: With grade 3 posterolateral injuries of the knee, reconstructions of the lateral collateral ligament, popliteus tendon, and popliteofibular ligament are commonly performed in conjunction with a posterior cruciate ligament reconstruction to restore knee stability. HYPOTHESIS: A lateral collateral ligament reconstruction, alone or with a popliteus tendon or popliteofibular ligament reconstruction, will produce normal varus rotation patterns and restore posterior cruciate ligament graft forces to normal levels in response to an applied varus moment. STUDY DESIGN: Controlled laboratory study. METHODS: Forces in the native posterior cruciate ligament were recorded for 15 intact knees during passive extension from 120 degrees to 0 degrees with an applied 5 N .m varus moment. The posterior cruciate ligament was removed and reconstructed with a single bundle inlay graft tensioned to restore intact knee laxity at 90 degrees . Posterior cruciate ligament graft force, varus rotation, and tibial rotation were recorded before and after a grade 3 posterolateral corner injury. Testing was repeated with lateral collateral ligament, lateral collateral ligament plus popliteus tendon, and lateral collateral ligament plus popliteofibular ligament graft reconstructions; all grafts were tensioned to 30 N at 30 degrees with the tibia locked in neutral rotation. RESULTS: All 3 posterolateral graft combinations rotated the tibia into slight valgus as the knee was taken through a passive range of motion. During the varus test, popliteus tendon and popliteofibular ligament reconstructions internally rotated the tibia from 1.5 degrees (0 degrees flexion) to approximately 12 degrees (45 degrees flexion). With an applied varus moment, mean varus rotations with a lateral collateral ligament graft were significantly less than those with the intact lateral collateral ligament beyond 0 degrees flexion; mean decreases ranged from 0.8 degrees (at 5 degrees flexion) to 5.6 degrees (at 120 degrees flexion). Addition of a popliteus tendon or popliteofibular ligament graft further reduced varus rotation (compared with a lateral collateral ligament graft) beyond 25 degrees of flexion; both grafts had equal effects. A lateral collateral ligament reconstruction alone restored posterior cruciate ligament graft forces to normal levels between 0 degrees and 100 degrees of flexion; lateral collateral ligament plus popliteus tendon and lateral collateral ligament plus popliteofibular ligament reconstructions reduced posterior cruciate ligament graft forces to below-normal levels-beyond 95 degrees and 85 degrees of flexion, respectively. CONCLUSIONS: With a grade 3 posterolateral corner injury, popliteus tendon or popliteofibular ligament reconstructions are commonly performed to limit external tibial rotation; we found that they also limited varus rotation. With the graft tensioning protocols used in this study, all posterolateral graft combinations tested overconstrained varus rotation. Further studies with posterolateral reconstructions are required to better restore normal kinematics and provide more optimum load sharing between the PCL graft and posterolateral grafts. CLINICAL RELEVANCE: A lower level of posterolateral graft tension, perhaps applied at a different flexion angle, may be indicated to better restore normal varus stability. The clinical implications of overconstraining varus rotation are unknown.

Biomechanical studies of double-bundle posterior cruciate ligament reconstructions.

BACKGROUND: Double-bundle reconstruction of the posterior cruciate ligament has been advocated to better replicate the anatomy of the native ligament and restore normal knee biomechanics. The goal of this study was to measure knee laxities and graft forces following single and double-bundle reconstructions and to compare these values with those for the intact knee in a cadaver model. METHODS: Forces in the posterior cruciate ligament were measured as the knee was passively extended from 120 degrees to 0 degrees with applied tibial loading. Anterior-posterior laxities were measured as well. An anterolateral tunnel was located at the anterolateral margin of the native ligament footprint, and a posteromedial tunnel was placed at one of two locations within the footprint; one location resulted in a wide bridge separating the tunnels and the other, a narrow bridge. Testing was repeated with a single anterolateral graft tensioned to match, within +/-1 mm, the laxity in the intact knee at 90 degrees of flexion. Double-bundle reconstructions were tested with the addition of a posteromedial graft tensioned at 30 degrees of flexion. Two levels of posteromedial graft tension (10 and 30 N) were studied in both the narrow and the wide-bridge posteromedial tunnels. RESULTS: Mean laxities with a single anterolateral graft were 1.1 to 2.0 mm greater than normal between 0 degrees and 30 degrees of flexion. With the posteromedial graft tensioned to 10 N in the wide-bridge tunnel, the mean laxity of the double grafts was not significantly different from that in the intact knee at any flexion angle. With the posteromedial graft tensioned to 10 N in the narrow-bridge tunnel, the mean laxity at 0 degrees was 0.9 mm greater than that in the intact knee. With the posteromedial graft tensioned to 30 N, the mean laxity at 10 degrees was 1.7 mm less than the intact-knee value in the wide-bridge tunnel and 1.3 mm less than the intact-knee value in the narrow bridge-tunnel. Increasing posteromedial graft tension from 10 to 30 N decreased the mean laxities by 0.5 to 1.1 mm between 0 degrees and 30 degrees . Mean graft forces following a single anterolateral reconstruction were not significantly different from the native posterior cruciate ligament forces under any mode of loading except valgus moment. With the wide-bridge tunnel, the mean forces with the posteromedial graft tensioned to 10 N were somewhat higher than the native posterior cruciate ligament forces at full extension; when the graft was tensioned to 30 N, the mean forces were substantially higher. CONCLUSIONS: A single anterolateral graft best reproduced the normal posterior cruciate ligament force profiles, but laxities were greater than normal between 0 degrees and 30 degrees of knee flexion. The addition of a second, posteromedial graft reduced laxity in this flexion range but did so at the expense of higher-than-normal forces in the posteromedial graft.

Joint kinematics and in situ forces after single bundle PCL reconstruction: a graft placed at the center of the femoral attachment does not restore normal posterior laxity.

INTRODUCTION: Femoral tunnel placement has a great influence on the clinical outcome after PCL reconstruction. MATERIALS AND METHODS: Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of human knees following soft-tissue single bundle PCL reconstruction fixed at the center of the femoral attachment. RESULTS: Posterior tibial translation significantly increased at all flexion angles after transsection of the posterior cruciate ligament (p<0.05). PCL reconstruction resulted in significantly less posterior tibial translation at all flexion angles when compared to the PCL deficient knee (p<0.05). The differences in the in situ force between the intact ligament and the reconstructed graft were statistical significant (p<0.05). CONCLUSION: Single bundle PCL reconstruction with a soft-tissue graft fixed at the center of the femoral attachment is able to reduce the posterior tibial translation significantly. However, it cannot restore kinematics of the intact knee and in situ forces of the intact PCL.

Determination of optimal graft lengths for posterior cruciate ligament reconstruction--a theoretical analysis.

Various graft materials have been used in posterior cruciate ligament (PCL) reconstruction. However, it is unclear if these grafts can reproduce the structural behavior of the PCL. This paper analyzed the effect of graft length on the structural behavior of the graft using a minimal deformation energy method. An analytical solution was obtained to determine the optimal effective graft length that can best reproduce the structural behavior of the PCL. This optimal graft length was determined as a function of the axial rigidity of the graft. Two typical grafts, bone-patella tendon-bone (BPTB) and Achilles tendon, were analyzed. The data demonstrated that in order to reproduce the PCL behavior, the effective length of a BPTB graft (10 mm width) should be 34 mm, while the Achilles tendon graft (with a cross sectional area of 55 mn2) needs to be 48 mm in length. Longer grafts result in less resistance and shorter graft increased the graft resistance. An initial graft tension cannot help recreate the overall structural behavior of the PCL. These results suggest that graft length is an important surgical variable in PCL reconstruction. An optimal reconstruction of the PCL should reproduce the structural properties of the PCL by using a graft with an optimal length.

Effects of knee position, graft tension, and mode of fixation in posterior cruciate ligament reconstruction: a cadaveric knee study.

PURPOSE: Many knees exhibit residual ligament laxity after posterior cruciate ligament (PCL) reconstruction, which is believed to be technique related. The purpose of this study was to investigate the optimal graft tension, the best angle of knee flexion, and the mode of fixation in PCL reconstruction. TYPE OF STUDY: Anatomic biomechanical study. METHODS: A testing apparatus with frictionless bearing that allows other degrees of freedom except for flexion and extension of the knee joint was designed. The normal PCL tension at different angles of knee flexion was measured with a force transducer, and the optimal tension of the PCL graft that allows full range of knee motion was studied with a tensiometer in 12 cadaver knees. The modes of fixation failure between interference screw fixation and post fixation were studied with an Instron (Canton, MA) machine in 8 cadaver knees. RESULTS: The lowest PCL tension in normal knees was noted at 20 degrees to 30 degrees of knee flexion and the highest at 90 degrees. The optimal tension of PCL graft, which allows full range of knee motion, was 15 lb (68 N). The average load of graft failure was 417 (179-730) N with interference screw fixation and 367 (149-701) N with post fixation when the patellar bone-tendon-bone graft was tested. There was no statistical difference in the failure load between interference screw fixation and post fixation (P =.753); however, the modes of failure differ. The sites of failure for interference screw fixation were 25% caused by rupture of ligament substance and 75% bone plug pullout; those of post fixation were 25% caused by rupture of ligament substance, 37.5% caused by fracture, and 37.5% as a result of suture breakage. CONCLUSIONS: The results of this study suggested that a 15-lb tension to the graft at 20 degrees to 30 degrees of knee flexion is optimal in PCL reconstruction. There was no statistical difference in the failure load between interference fixation and post fixation despite different modes of fixation failure.