Comparison of 2 surgical techniques of posterolateral corner reconstruction of the knee

BACKGROUND: Various surgical techniques to treat posterolateral knee instability have been described. To date, the recommended treatment is an anatomical form of reconstruction, in which the 3 key structures of the posterolateral corner are addressed: the lateral collateral ligament, the popliteofibular ligament, and the popliteus tendon. HYPOTHESIS: Two methods of surgical reconstruction will restore posterolateral knee instability, in terms of static laxity as well as dynamic 6 degrees of freedom kinematics, to statistically significant levels compared with the intact state. STUDY DESIGN: Controlled laboratory study. METHODS: Two surgical techniques (A and B) were used to reconstruct the posterolateral structures in 10 cadaveric knees. Static tests were performed on the intact, sectioned, and reconstructed knees at 30 degrees and 90 degrees of flexion for anterior-posterior laxity and external rotational laxity, as well as at 0 degrees and 30 degrees of flexion for varus laxity; dynamic 6 degrees of freedom kinematic testing, through a path of motion from 90 degrees of flexion to full extension, was also performed. RESULTS: For the static varus tests, external rotation and varus laxity were significantly increased after the posterolateral structures were cut. Both reconstruction techniques restored external rotation and varus laxity to levels not significantly different from the intact state. For technique B, dynamic testing did not show any significant difference for all degrees of freedom kinematics compared with the intact state. However, for technique A, a significant internal tibial rotation was observed throughout the entire path of motion from 0 degrees to 90 degrees of knee flexion. CONCLUSIONS: Both surgical techniques for anatomical posterolateral corner reconstruction showed good results in the static laxity tests. The anatomical reconstruction of all structures, including the popliteus tendon, resulted in an abnormal internal tibial rotation during dynamic testing.     

An in vivo injury model of posterolateral knee instability

BACKGROUND: Posterolateral knee instability is a difficult clinical problem to diagnose and treat. To best evaluate its natural history and the effects of interventional treatments, it is important to develop an in vivo model in an attempt to validate human cadaveric and clinical observational studies. PURPOSE: To develop an in vivo model of posterolateral knee instability in the rabbit and to determine the natural history of untreated posterolateral knee injuries at 6 months postoperatively. STUDY DESIGN: Controlled laboratory study. METHODS: The fibular collateral ligament and popliteus tendon were surgically transected in 1 knee in each of 10 skeletally mature New Zealand White rabbits, with the contralateral knee serving as a control knee. At 6 months postoperatively, the rabbits were euthanized, the knees were removed, and biomechanical testing of knee joint stability was performed. After biomechanical testing, histological sections of each proximal tibia and distal femur were evaluated, and each proximal tibia was graded using an osteoarthritis grading scheme. RESULTS: Biomechanical testing revealed a statistically significant difference in amount of rotation in the operated knees compared with the unoperated control knees to varus moments at 30 degrees , 60 degrees , and 90 degrees and to external rotation torques at 30 degrees and 60 degrees . Morphological analysis revealed no significant difference in lesions of osteoarthritis in the medial compartment of the operated knees compared with the unoperated knees. CONCLUSIONS: Although the presence of posterolateral knee instability was validated 6 months after surgery in this model, the authors did not identify significant differences in lesions of osteoarthritis in the operated knees compared with the unoperated control knees. Clinical Significance: This study confirms that posterolateral knee instability can be created in an animal model. It also recapitulates the clinical observation in humans that untreated posterolateral knee injuries do not heal. Similar to animal models of medial collateral ligament sectioning, further studies to validate a posterolateral instability knee model may lead to interventional studies to determine the best way to treat this complex knee instability pattern.     

Intraarticular anterior cruciate ligament graft placement on the average most isometric line on the femur. Does it reproducibly restore knee kinematics?

In the past, there has been a plausible hypothesis that anterior cruciate ligament graft placement at isometric sites, such that the tibial and femoral attachment sites remain equidistant from each other throughout knee range of motion, would increase the likelihood of a satisfactory outcome. For a given tibial placement we wanted to determine whether placing the graft on the average of the most isometric femoral line, a fixed distance from the outlet of the intercondylar notch, would return normal laxity to all knees. The three-dimensional kinematics of seven cadaveric knees were measured for angles from full extension to 90 degrees of flexion at 15 degrees increments. Physiologic levels of quadriceps muscle forces were applied to the intact knee, after transection of the anterior cruciate ligament, and after ligament reconstruction with a patellar tendon graft. On average, the reconstruction was found to return anterior-posterior translation, internal-external rotation, and varus-valgus rotation to levels not significantly different from those of the intact knee. However, the ranges of the translation and rotations were large. Placing the graft on the average most isometric femoral line did not restore knee laxity to normal in all knees. This supports the need to customize graft placement in each knee at the time of surgery.     

Three-dimensional tibiofemoral kinematics of the anterior cruciate ligament-deficient and reconstructed knee during walking

BACKGROUND: It is possible that gait abnormalities may play a role in the pathogenesis of meniscal or chondral injury as well as osteoarthritis of the knee in patients with anterior cruciate ligament deficiency. HYPOTHESIS: The three-dimensional kinematics of anterior cruciate ligament-deficient knees are changed even during low-stress activities, such as walking, but can be restored by reconstruction. STUDY DESIGN: Case control study. METHODS: Using a three-dimensional optoelectronic gait analysis system, we examined 13 patients with anterior cruciate ligament-deficient knees, 21 patients with anterior cruciate ligament-reconstructed knees, and 10 control subjects with uninjured knees during walking. RESULTS: Normal patterns of knee flexion-extension, abduction-adduction, and internal-external rotation during the gait cycle were maintained by all subjects. A significant difference in tibial rotation angle during the initial swing phase was found in anterior cruciate ligament-deficient knees compared with reconstructed and control knees. The patients with anterior cruciate ligament-deficient knees rotated the tibia internally during the initial swing phase, whereas the others rotated externally. CONCLUSIONS: Patients with anterior cruciate ligament-deficient knees experienced repeated episodes of rotational instability during walking, whereas patients with reconstruction experienced tibial rotation that is closer to normal. CLINICAL RELEVANCE: Repeated episodes of knee rotational instability may play a role in the development of pathologic knee conditions.     

Posterolateral knee reconstruction with an anatomical bone-patellar tendon-bone reconstruction of the fibular collateral ligament

BACKGROUND: The authors have long advocated a graft reconstruction of the fibular collateral ligament, believing that direct suture repair or augmentation procedures do not provide a stable construct. PURPOSE: To describe an operative technique and determine the clinical outcome of a bone-patellar tendon-bone graft anatomical replacement of the fibular collateral ligament in a consecutive series of knees. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A consecutive group of knees undergoing anatomical posterolateral reconstruction that included a fibular collateral ligament reconstruction with a bone-patellar tendon-bone graft was prospectively followed to determine the functional outcome and failure rate. Thirteen patients (14 posterolateral reconstructions) were observed 2 to 13.7 years postoperatively. All major posterolateral structures were surgically restored. The procedure represented a primary reconstruction in 7 patients and a revision in 6 patients. Anterior cruciate ligament ruptures were found in 7 patients and bicruciate ruptures in 5 patients, all of which were reconstructed. The rehabilitation protocol allowed immediate knee motion from 0 degrees to 90 degrees but included protection against lateral joint loads to prevent graft stretching and failure. The results were determined by a knee examination, stress radiography, KT-2000 arthrometer, the Cincinnati Knee Rating System, and the International Knee Documentation Committee Rating System. RESULTS: Significant improvements were found at follow-up for pain (P = .0001), swelling (P = .02), patient rating of the overall knee condition (P < .001), walking (P < .05), and stair climbing (P < .05). Thirteen of the 14 (93%) reconstructions restored normal or nearly normal lateral joint opening and external tibial rotation and 1 failed. The anterior cruciate ligament reconstructions were normal or nearly normal in 11 knees and abnormal in 1 knee. CONCLUSIONS: The anatomical posterolateral procedure was effective in restoring normal limits to lateral joint opening and external tibial rotation, allowed immediate knee motion, and appeared to protect other soft tissue repairs.     

Weight-bearing knee kinematics in subjects with two types of anterior cruciate ligament reconstructions

Weight-bearing knee kinematics in patients who received two types of anterior cruciate ligament reconstruction were studied using a fluoroscopy-based three-dimensional measurement technique. Eleven patients with more than 1-year follow-up and good or excellent results participated in this study. Six subjects received anterior cruciate ligament reconstruction using a multiply folded semitendinosus and gracilis tendon graft, and five received combined intra- and extra-articular anterior cruciate ligament reconstruction using the iliotibial tract. The step up/down activity of normal and operated knees was recorded using lateral fluoroscopy. A customized three-dimensional contour model was created from two orthogonal views of each knee and all six degrees of freedom of knee movement were determined using a model matching technique. Both the normal and the reconstructed knees exhibited posterior condylar translation and internal tibial rotation with knee flexion, consistent with previous reports of normal kinematics. There were no statistically significant differences in the axial rotations or lateral or medial condylar anterior/posterior translations between operated and normal knees or between the two groups of operated knees.     

Posterior instability near extension is related to clinical disability in isolated posterior cruciate ligament deficient patients

The purpose of this study is to evaluate the relationship between the magnitude of knee laxity and posterior instability at different knee flexion angles and clinical disability in isolated posterior cruciate ligament (PCL) deficient patients. Knee laxity at 20° and 70° of knee flexion were evaluated using KT-2000 arthrometer, and the posterior instability at 20°, 45° and 90° of flexion were evaluated using stress radiography. We assessed the differences in the knee laxity and the tibial translation between isolated PCL deficient knees and normal knees, and between the patients with giving-way during activities of daily living (ADL) and without giving-way. There were statistical differences in the knee laxity and the tibial translation at all knee flexion angles between the PCL deficient knees and normal knees. The magnitude of the knee laxity at 20° of flexion measured with KT-2000 arthrometer was significantly larger in the patients with giving-way than those in the patients without giving-way although there was no significant difference in the tibial translation at 70° between the two groups. The tibial translation in both medial and lateral compartments at 20° and 45° measured with stress radiography were significantly larger in the patients with giving-way than those in the patients without giving-way although there was not significant difference at 90° between the two groups. These results suggested that the magnitude of the knee laxity and the posterior tibial translation at shallow knee flexion angles would be related to giving-way during ADL in isolated PCL deficient patients.     

The effect of anterior cruciate ligament reconstruction on knee joint kinematics under simulated muscle loads

BACKGROUND: Numerous studies have investigated anterior stability of the knee during the anterior drawer test after anterior cruciate ligament reconstruction. Few studies have evaluated anterior cruciate ligament reconstruction under physiological loads. PURPOSE: To determine whether anterior cruciate ligament reconstruction reproduced knee motion under simulated muscle loads. STUDY DESIGN: Controlled laboratory study. METHODS: Eight human cadaveric knees were tested with the anterior cruciate ligament intact, transected, and reconstructed (using a bone-patellar tendon-bone graft) on a robotic testing system. Tibial translation and rotation were measured at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion under anterior drawer loading (130 N), quadriceps muscle loading (400 N), and combined quadriceps and hamstring muscle loading (400 N and 200 N, respectively). Repeated-measures analysis of variance and the Student-Newman-Keuls test were used to detect statistically significant differences between knee states. RESULTS: Anterior cruciate ligament reconstruction resulted in a clinically satisfactory anterior tibial translation. The anterior tibial translation of the reconstructed knee was 1.93 mm larger than the intact knee at 30 degrees of flexion under anterior load. Anterior cruciate ligament reconstruction overconstrained tibial rotation, causing significantly less internal tibial rotation in the reconstructed knee at low flexion angles (0 degrees-30 degrees) under muscle loads (P < .05). At 30 degrees of flexion, under muscle loads, the tibia of the reconstructed knee was 1.9 degrees externally rotated compared to the intact knee. CONCLUSIONS: Anterior cruciate ligament reconstruction may not restore the rotational kinematics of the intact knee under muscle loads, even though anterior tibial translation was restored to a clinically satisfactory level under anterior drawer loads. These data suggest that reproducing anterior stability under anterior tibial loads may not ensure that knee joint kinematics is restored under physiological loading conditions. CLINICAL RELEVANCE: Decreased internal rotation of the knee after anterior cruciate ligament reconstruction may lead to increased patellofemoral joint contact pressures. Future anterior cruciate ligament reconstruction techniques should aim at restoring 3-dimensional knee kinematics under physiological loads.     

Symptomatic ring-shaped lateral meniscus: magnetic resonance imaging and arthroscopy

In addition to minimizing graft site morbidity, providing stable fixation, and enabling early progressive rehabilitation, the ideal PCL reconstruction would closely simulate natural ligament function. This study retrospectively examined the 2-year postoperative outcomes of 19 athletically active patients referred with clinically symptomatic PCL-deficient knees. Preoperatively 18 patients had severely abnormal knee ligament examination scores, and one had an abnormal score (IKDC). All but one patient was confirmed negative for observable posterolateral corner injury via MRI. Eighteen patients had clinical evidence of posterolateral instability. All patients underwent double-bundle PCL reconstruction (using allograft tissue) without concomitant posterolateral corner reconstruction. Two years after surgery 100% of patients had normal ( n=18) or near normal ( n=1) passive knee joint motion. The results were: one-leg hop test, 58% normal, 37% nearly normal, 5% abnormal; knee ligament examination, 47% normal, 42% nearly normal, 5% abnormal, 5% severely abnormal; knee arthrometry, 2.4+/-2 mm posterior tibial displacement; IKDC subjective assessment section, 47% normal, 42% nearly normal, 5% abnormal, 5% severely abnormal; IKDC symptom-activity level section, 47% normal, 42% nearly normal, 5% abnormal, 5% severely abnormal; final knee ligament evaluation, 47% normal, 42% nearly normal, 5% abnormal, 5% severely abnormal; Lysholm knee scoring scale, 63% excellent, 27% good, 5% fair and 5% poor. Improved stability with clinical ligamentous laxity tests and good IKDC subjective and symptom-activity results 2 years after surgery suggest that for patients with PCL rupture and grade I or II posterolateral instability the double-bundle procedure alone sufficiently restores PCL function through a greater range of knee motion than traditional single-bundle techniques.     

The anterior cruciate ligament does play a role in controlling axial rotation in the knee

This study deals with the influence of peroperative ligament tension on total tibial rotation at different knee flexion angles. Fourteen human cadaver knees with a mean age of 56 years (range 42–84 years) were examined. The cadaver knees were subjected to internal/external (i/e) rotational torque of 6 Nm, at 10, 30, 50, 70 and 90 deg of knee flexion. The mean total i/e rotation with the anterior cruciate ligament (ACL) intact at 10 deg of knee flexion was 30.4 deg and after removing the ACL, 33.1 deg. At 10 and 30 deg of knee flexion, the increase in i/e rotation was significant, while there was no significant difference in mean values at greater knee flexion. Ligament reconstruction with a tension of 5 N at 30 deg of knee flexion using either the over the top or through the femoral condyle reconstructive procedure restored normal tibial rotation. With increased graft tension the knee motion was increasingly restricted at low angles of knee flexion. Our results indicate that the ACL does play a role in limiting axial rotation, and even minor tensioning forces introduced in any of the two ACL reconstructions used produced restricted knee motion.     

What really happens during the Lachman test? A dynamic MRI analysis of tibiofemoral motion

BACKGROUND: The Lachman test is the most reliable clinical test for diagnosing rupture of the anterior cruciate ligament (ACL). It is generally believed that the lateral side contributes more than the medial side to anterior tibial translation, but this has never been convincingly proven. The MRI study presented in this article addresses this issue. HYPOTHESIS: The lateral side of the ACL-deficient knee contributes more than the medial side to anterior tibial translation. STUDY DESIGN: Prospective cohort study. METHODS: The Lachman test and the radiologic Lachman test were performed on 10 patients with isolated rupture of the ACL while the knee was scanned dynamically using open-access magnetic resonance imaging. The amount of movement in the midmedial and midlateral compartments of both the contralateral normal knee and the ACL-deficient knee was measured. RESULTS: In both normal and ACL-deficient knees, the lateral compartment contributes more than the medial to anterior translation of the tibia. Rupture of the ACL leads to increased laxity in both medial and lateral compartments with a statistically significant greater contribution from the lateral side. CONCLUSION: Rupture of the ACL leads to increased anterior tibial translation coupled with tibial internal rotation.     

Anatomical double-bundle anterior cruciate ligament reconstruction after valgus high tibial osteotomy: a biomechanical study

BACKGROUND: Although anatomical double-bundle anterior cruciate ligament reconstruction can successfully restore normal knee biomechanics for knees with typical varus-valgus alignment, the efficacy of the same reconstruction method for knees after a valgus high tibial osteotomy is unclear. HYPOTHESIS: Anatomical double-bundle anterior cruciate ligament reconstruction for valgus knees after a high tibial osteotomy cannot restore normal knee kinematics and can result in abnormally high in situ forces in the ligament graft. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were subjected to valgus high tibial osteotomy followed by an anatomical double-bundle anterior cruciate ligament reconstruction. The valgus knees were tested using a robotic/universal force-moment sensor system before and after the ligament reconstruction. The knee kinematics in response to anterior tibial load and combined rotatory loads, as well as the corresponding in situ forces of the anterior cruciate ligament bundles and grafts, were compared between the ligament-intact and ligament-reconstructed valgus knees. RESULTS: After reconstruction, the anterior tibial translation and internal tibial rotation for the valgus knee decreased approximately 2 mm and 2 degrees , respectively, at low flexion angles compared with those of the anterior cruciate ligament-intact knee (P < .05). The in situ forces in the posterolateral graft became 56% to 200% higher than those in the posterolateral bundle of the intact anterior cruciate ligament (P < .05). CONCLUSION: Performing an anatomical double-bundle anterior cruciate ligament reconstruction on knees after valgus high tibial osteotomy may overconstrain the knee and result in high forces in the posterolateral graft, which could predispose it to failure. CLINICAL RELEVANCE: Modifications of anterior cruciate ligament reconstruction procedures to reduce posterolateral graft force may be needed for valgus knees after a high tibial osteotomy.     

Global rotation has high sensitivity in ACL lesions within stress MRI

Purpose

This study aims to objectively compare side-to-side differences of P-A laxity alone and coupled with rotatory laxity within magnetic resonance imaging, in patients with total anterior cruciate ligament (ACL) rupture.

Methods

This prospective study enrolled sixty-one patients with signs and symptoms of unilateral total anterior cruciate ligament rupture, which were referred to magnetic resonance evaluation with simultaneous instrumented laxity measurements. Sixteen of those patients were randomly selected to also have the contralateral healthy knee laxity profile tested. Images were acquired for the medial and lateral tibial plateaus without pressure, with postero-anterior translation, and postero-anterior translation coupled with maximum internal and external rotation, respectively.

Results

All parameters measured were significantly different between healthy and injured knees (P < 0.05), with exception of lateral plateau without stress. The difference between injured and healthy knees for medial and lateral tibial plateaus anterior displacement (P < 0.05) and rotation (P < 0.001) was statistically significant. It was found a significant correlation between the global rotation of the lateral tibial plateau (lateral plateau with internal + external rotation) with pivot-shift, and between the anterior global translation of both tibial plateaus (medial + lateral tibial plateau) with Lachman. The anterior global translation of both tibial plateaus was the most specific test with a cut-off point of 11.1 mm (93.8 %), and the global rotation of the lateral tibial plateau was the most sensitive test with a correspondent cut-off point of 15.1 mm (92.9 %).

Conclusion

Objective laxity quantification of ACL-injured knees showed increased sagittal laxity, and simultaneously in sagittal and transversal planes, when compared to their healthy contralateral knee. Moreover, when measuring instability from anterior cruciate ligament ruptures, the anterior global translation of both tibial plateaus and global rotation of the lateral tibial plateau add diagnostic specificity and sensitivity. This work strengthens the evidence that the anterior cruciate ligament plays an important biomechanical role in controlling the anterior translation, but also both internal and external rotation. The high sensitivity and specificity of this device in objectively identifying and measuring the multiplanar instability clearly guides stability restoration clinical procedures. Level of evidence Cross-sectional study, Level III.

     

Reliability of navigated knee stability examination: a cadaveric evaluation

BACKGROUND: Clinical examination remains empirical and may be confusing in the setting of rotatory knee instabilities. Computerized navigation systems provide the ability to visualize and quantify coupled knee motions during knee stability examination. HYPOTHESIS: An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination. STUDY DESIGN: Controlled laboratory study. METHODS: Coupled knee motions were determined by a robotic/UFS testing system and by an image-free navigation system in 6 cadaveric knees that were subjected to (1) isolated varus stress and (2) combined varus and external rotation force at 0 degrees, 30 degrees, and 60 degrees. This protocol was performed in intact knees and after complete sectioning of the posterolateral corner (lateral collateral ligament, popliteus tendon, and popliteofibular ligament). The correlation between data from the surgical navigation system and the robotic positional sensor was assessed using the intraclass correlation coefficient. The 3-dimensional motion paths of the intact and sectioned knees were assessed qualitatively using the navigation display system. RESULTS: Intraclass correlation coefficients between the robotic sensor and the navigation system for varus and external rotation at 0 degrees, 30 degrees, and 60 degrees were all statistically significant at P < .01. The overall intraclass correlation coefficient for all tests was 0.9976 (P < .0001). Real-time visualization of the coupled motions was possible with the navigation system. Post hoc analysis of the knee motion paths during loading distinguished distinct rotatory patterns. CONCLUSION: Surgical navigation is a precise intraoperative tool to quantify knee stability examination and may help delineate pathologic multiplanar or coupled knee motions, particularly in the setting of complex rotatory instability patterns. Repeatability of load application during clinical stability testing remains problematic. CLINICAL RELEVANCE: Surgical navigation may refine the diagnostic evaluation of knee instability.     

The effect of posterior cruciate ligament deficiency on knee kinematics

BACKGROUND: Alteration of the kinematics of the PCL-deficient knee might be a factor in producing the articular damage. Very little is known about the in vivo weightbearing kinematics of the PCL-deficient knee. HYPOTHESIS: Isolated rupture of the posterior cruciate ligament alters knee kinematics, predisposing the patient to development of early osteoarthritis. STUDY DESIGN: Case series. METHODS: Tibiofemoral motion was assessed using open-access magnetic resonance imaging, weightbearing in a squat, through the arc of flexion from 0 degrees to 90 degrees in 6 patients with isolated rupture of the posterior cruciate ligament in one knee and a normal contralateral knee. Passive sagittal laxity was assessed by performing the posterior and anterior drawer tests while the knees were scanned, again using the same magnetic resonance imaging scanner. The tibiofemoral positions during this stress magnetic resonance imaging examination were measured from midmedial and midlateral sagittal images of the knees. RESULTS: Rupture of the posterior cruciate ligament leads to an increase in passive sagittal laxity in the medial compartment of the knee (P < .006). In the weightbearing scans, posterior cruciate ligament rupture alters the kinematics of the knee with persistent posterior subluxation of the medial tibia so that the femoral condyle rides up the anterior upslope of the medial tibial plateau. This fixed subluxation was observed throughout the extension-flexion arc and was statistically significant at all flexion angles (P < .018 at 0 degrees , P < .013 at 20 degrees , P < .014 at 45 degrees , P < .004 at 90 degrees ). The kinematics of the lateral compartment were not altered by posterior cruciate ligament rupture. The posterior drawer test showed increased laxity in the medial compartment. CONCLUSION: Posterior cruciate ligament rupture alters the kinematics of the medial compartment of the knee, resulting in "fixed" anterior subluxation of the medial femoral condyle (posterior subluxation of the medial tibial plateau). This study helps to explain the observation of increased incidence of osteoarthritis in the medial compartment, and specifically the femoral condyle, in posterior cruciate ligament-deficient knees.     

Follow-up evaluation 2 years after ACL reconstruction with bone-patellar tendon-bone graft shows that excessive tibial rotation persists.

OBJECTIVE: To investigate in vivo if the increased tibial rotation found in anterior cruciate ligament (ACL)-deficient patients before surgery is restored 2 years after the reconstruction, during 2 high-demanding activities. DESIGN: Prospective follow-up study. SETTING: A gait analysis laboratory. PARTICIPANTS: Nine subjects with unilateral ACL rupture, reconstructed with a bone-patellar tendon-bone (BPTB) graft, and 10 healthy control subjects. INTERVENTIONS: All the ACL-deficient patients underwent a unilateral ACL reconstruction after prereconstruction data acquisition. MAIN OUTCOME MEASUREMENTS: Using a 6-camera motion analysis system, kinematics were collected as subjects (1) descended from a stair and, after foot contact, pivoted on the landing leg at 90 degrees; and (2) jumped from a platform, landed with both feet on the ground and, after foot contact, pivoted on the right or left leg at 90 degrees in a similar fashion. The dependent variable examined was the maximum range of motion of tibial rotation during the pivoting period. RESULTS: For both activities, no significant differences were found between the control healthy knee and the intact knee of the patient group before and 2 years after the ACL reconstruction. Significant differences were found between the control healthy knee and the affected knee of the patients group for both activities, both before and 2 years after the ACL reconstruction. CONCLUSION: The increased tibial rotation found in the ACL-deficient knees was not restored with reconstruction using a BPTB graft, even 2 years postoperatively. The authors propose that this excessive tibial rotation over time may lead to further deterioration of the knee resulting from abnormal loading at areas of the cartilage that are not commonly loaded in a healthy knee.     

Dynamic instability during stair descent in isolated PCL-deficient knees: what affects abnormal posterior translation of the tibia in PCL-deficient knees?

Posterior cruciate ligament (PCL)-deficient patients usually display few functional disabilities during activities of daily living (ADL), even in the presence of significant objective knee laxity. This suggests that the magnitude of posterior instability occurring in ADL (dynamic instability) does not parallel the knee laxity detected in clinical examinations. The present study analyzed kinematics of the knee joint during stair descent in 14 isolated PCL-deficient patients and ten healthy volunteers using fluoroscopy. Factors influencing dynamic instability were investigated. In addition, magnitude of posterior tibial translation occurring during stair descent was measured and compared with static knee laxity measured on posterior stress radiography. Increased posterior tibial translation was observed in early swing phase (52.5 ± 5.6%) in PCL-deficient knees compared with normal knees (48.2 ± 8.6%). Almost the same magnitude of posterior instability was observed at early swing phase during stair descent using fluoroscopy and on posterior stress radiography. These results indicate that in PCL-deficient patients, posterior instability does not occur when weight is loaded onto the knee, but occurs when weight-bearing is released during stair descent.     

Medial opening wedge tibial osteotomy and the sagittal plane: the effect of increasing tibial slope on tibiofemoral contact pressure

BACKGROUND: Altering the tibial slope in an anterior cruciate ligament-deficient knee has been shown to affect anterior-posterior tibial translation. The effects on articular contact pressure of altering tibial slope during a high tibial osteotomy are unknown. HYPOTHESES: Performing an opening wedge osteotomy anterior to the midaxial line will increase tibial slope. Increasing tibial slope with a high tibial osteotomy in an anterior cruciate ligament-deficient knee redistributes tibiofemoral joint contact pressures onto the posterior tibial plateau. STUDY DESIGN: Controlled laboratory study. METHODS: Medial opening wedge high tibial osteotomies were performed, and a plate fixation with a known diameter inset was placed along the medial tibia in an anterior position and a posterior position on 9 cadaveric knees. Medial and lateral tibiofemoral contact pressures were measured at the resulting 2 different tibial slopes in both ligament-intact and ligament-deficient states using thin electronic sensors. RESULTS: Anterior plate application resulted in an increase in posterior tibial slope by an average of 6.6 degrees (P < .001) compared with posterior plate placement. After medial opening wedge high tibial osteotomy, the mean peak lateral tibiofemoral contact pressure (3.4 MPa) was significantly greater (P = .002) than was the mean peak medial pressure (2.6 MPa). In ligament-intact specimens, altering the tibial slope did not significantly shift peak contact pressures. However, in ligament-deficient knees, increasing tibial slope by an average of 5.5 degrees significantly redistributed the location of peak intra-articular pressure, shifting it posteriorly by 24% (P = .003). CONCLUSION: Increasing tibial slope in anterior cruciate ligament-deficient knees with a high tibial osteotomy redistributes pressure into the posterior tibial plateau. CLINICAL RELEVANCE: In knees with chronic anterior cruciate ligament deficiency, posteromedial compartment degeneration is observed. Inadvertent redistribution of contact pressure into this area may be a cause of pain and premature clinical failure after medial opening wedge tibial osteotomy.     

In vivo measurement of the pivot-shift test in the anterior cruciate ligament-deficient knee using an electromagnetic device

BACKGROUND: The pivot-shift test is commonly used for assessing dynamic instability in anterior cruciate ligament-insufficient knees, which is related to subjective knee function, unlike static load-displacement measurement. Conventional measurements of 3-dimensional position displacement cannot assess such dynamic instability in vivo and produce comparable parameters. Not only 3-dimensional position displacement but also its 3-dimensional acceleration should be measured for quantitative evaluation of the pivot-shift test. HYPOTHESIS: Knees with a positive pivot-shift test result have increased tibial anterior translation and acceleration of its subsequent posterior translation, and they are correlated with clinical grading. STUDY DESIGN: Controlled laboratory study. Materials and METHODS: Thirty patients with isolated anterior cruciate ligament injury were included. Pivot-shift tests were evaluated under anesthesia manually and experimentally using an electromagnetic knee 6 degrees of freedom measurement system. From 60 Hz of 6 degrees of freedom data, coupled tibial anterior translation was calculated, and acceleration of posterior translation was computed by secondary derivative. RESULTS: All anterior cruciate ligament-deficient knees demonstrated a positive pivot-shift test result. The coupled tibial anterior translation was 7.7 and 15.6 mm in anterior cruciate ligament-intact and -deficient knees, respectively. The acceleration of posterior translation was -797 and -2001 mm/s(2), respectively. These differences were significant (P < .01). The coupled tibial anterior translation and acceleration of posterior translation in the anterior cruciate ligament-deficient knee were larger in correlation with clinical grading (P = .03 and P < .01, respectively). CONCLUSION: The increase of tibial anterior translation and acceleration of subsequent posterior translation could be detected in knees with a positive pivot-shift result, and this increase was correlated to clinical grading. CLINICAL RELEVANCE: These measurements can be used for quantified evaluation of dynamic instability demonstrated by the pivot-shift test.