Rotational Stability Of Knee Research Articles

Anatomic Single-Graft Anterior Cruciate Ligament Reconstruction Restores Rotational Stability: A Robotic Study in Cadaveric Knees

First, we aimed to investigate the ability of a single bone-patellar tendon-bone graft placed in the anatomic center of the femoral and tibial attachment sites to restore normal tibiofemoral compartment translations and tibial rotation. Second, we aimed to investigate what combination of anterior load and internal rotation torque applied during a pivot-shift test produces maximal anterior tibiofemoral subluxations. We used a 6-df robotic simulator to test 10 fresh-frozen cadaveric specimens under anterior cruciate ligament (ACL)-intact, ACL-sectioned, and ACL-reconstructed conditions measuring anterior translations of the medial, central, and lateral tibiofemoral compartments and degrees of tibial rotation. Specimens were loaded under Lachman, anterior limit, and internal rotation conditions, as well as 3 different pivot-shift conditions. On ACL sectioning, compartment translations in the Lachman and 3 pivot-shift tests increased significantly and were restored to ACL-intact values after single-graft ACL reconstruction. In the pivot-shift tests, the single graft restored lateral and medial compartment translations (e.g., group 3, within 1.3 ± 0.6 mm and 0.8 ± 0.6 mm, respectively, of the ACL-intact state and internal rotation within 0.7° ± 1.2°). Anterior subluxation of the medial compartment during pivot-shift loading was reduced when internal rotation torque was increased from 1 to 5 Nm (P < .0001). A single-graft ACL reconstruction performed at the central femoral and tibial ACL attachment sites restored anterior-posterior translation and tibial rotation motion limits. In addition, rotational knee stability as defined by tibiofemoral compartment translations was restored under all simulated pivot-shift testing conditions. This study provides invitro evidence to support the clinical use of single-graft ACL reconstructions in restoring tibiofemoral compartment translations. It also shows the advantage of describing ACL insufficiency in terms of medial and lateral compartment subluxations as compared with the common approach of describing changes in central tibial translations and rotations.

Anterior Cruciate Ligament Function in Providing Rotational Stability Assessed by Medial and Lateral Tibiofemoral Compartment Translations and Subluxations

Background: Rotational knee stability provided by the anterior cruciate ligament (ACL) in the pivot-shift phenomena involves analysis of more complex robotic testing profiles and resulting tibiofemoral compartment kinematics and subluxations. Hypotheses: Using anterior-posterior tibial forces along with internal and valgus tibial moments will produce a major anterior subluxation of both tibiofemoral compartments not obtained with internal and valgus moments alone. Increasing the internal torque in pivot-shift testing will constrain the anterior subluxations of the medial and central tibial compartments. Study Design: Controlled laboratory study. Methods: A 6 degrees of freedom robotic knee testing system applied anterior translation and rotational loading profiles in 10 cadaveric knees before and after ACL sectioning. Changes in knee motion limits were measured, and medial and lateral tibiofemoral compartment translations were determined by digitization of tibial plateau anatomic landmarks. Loading profiles simulated Lachman and tibial rotation tests as well as typical pivot-shift loading profiles from prior in vitro and in vivo studies. Results: After ACL sectioning, anterior tibial translation increased by 10.3 ± 3.7 mm at 25° of flexion (P < .001). Internal tibial rotation increased by 1.6° ± 1.1° (5 N·m; P > .05). In pivot-shift tests (anterior translation, 100 N; internal rotation, 1 N·m; valgus, 7 N·m), the tibial rotation center shifted outside the medial tibial margin, with abnormal anterior translation of both compartments (medial, 12.9 ± 3.9 mm; lateral, 7.5 ± 3.7 mm; P < .001), with internal rotation decreasing by 4.1° ± 3.5° (P < .05). A greater internal rotation torque (5 vs 1 N·m) in the pivot-shift test constrained and limited anterior tibial translation and prevented anterior subluxation of the medial compartment (P < .001). Conclusion: Sectioning of the ACL produces major increases in tibiofemoral compartment translations and only small increases in internal tibial rotation. The simulation of the pivot shift requires a combined loading profile of anterior translation, internal rotation, and valgus, which produces the greatest anterior subluxation of the medial and lateral tibiofemoral compartments. This testing profile is recommended to be included along with other loading profiles for future ACL studies. The application of a high internal rotation torque in cadaveric pivot-shift tests constrains anterior tibial subluxation of the medial and center compartments and appears less ideal for analysis of ACL function and graft reconstructions. Clinical Relevance: Surgeons should be cautious in interpreting conclusions on ACL function and graft reconstructions without knowing the resulting tibiofemoral subluxations or loading conditions that may limit maximum anterior tibial femoral subluxations.

Rotational laxity after anatomical ACL reconstruction measured by 3-D motion analysis: a prospective randomized clinical trial comparing anatomic and nonanatomic ACL reconstruction techniques.

To compare the ability of three different anterior cruciate ligament (ACL) reconstruction techniques to normalize rotational knee stability 1 year after ACL reconstruction. Two of these techniques are so-called anatomic techniques. Three different ACL reconstruction techniques were tested for their ability to normalize rotational knee stability in a prospective randomized study. Forty-seven ACL-deficient (ACLD) patients were randomized to transtibial single-bundle (SB), anatomic SB, and double-bundle ACL reconstruction. Three-dimensional motion analysis was performed preoperatively and at 1-year follow-up to evaluate tibial rotation and rotational stiffness. Motion data were captured using an eight-camera motion analysis system. Tibial rotation was determined during walking, running, and a pivoting task. Other outcome parameters were KT-1000 knee laxity measurements and the subjective outcome scores KOOS and IKDC. Three-dimensional motion analysis demonstrated that the tibial internal rotation and the rotational stiffness did not differ between the ACL reconstruction techniques during walking, running, and pivoting at 1-year follow-up. Objective knee stability and subjective outcome scores did not differ between the reconstruction groups. No significant difference in rotational stability walking, running, and pivoting was seen between anatomic and nonanatomic ACL reconstruction techniques at 1-year follow-up. Therapeutic study, Level I.

Extraaarticular Reconstruction In ACL Deficient Knee: 25 Years Later

Objectives:Extraarticular Reconstructions (ERs), isolated or in association with Intraarticular ACL Reconstructions (IRs) were popular in the eighties. However they were almost completely given up as a result of a consensus conference organized by AOSSM in 1989 in Snowmass (Co) where the experts concluded that ERs, even if biomechanically justified, were unable to provide any improvement in clinical results with greater morbidity, higher risk of complications and increased rate of degenerative osteoarthritis (DOA). However, as since then the surgical techniques and postoperative rehabilitation have radically changed, it could be helpful to reconsider ERs and their long term effect on knee stability and on DOA.Methods:One hundred consecutive patients who underwent an anatomic single bundle ACL reconstruction with hamstrings were re-evaluated at a minimum follow up of eleven years. In 23 cases (group B), due to the presence of a Pivot Shift test graded as +++ or in cases of athletes involved in high risk sports, a lateral tenodesis (Coker/Arnold) was associated. The other 77 patients, where an isolated IR was performed with the same technique (group A), served as control. All patients followed the same, standard postoperative rehabilitation program. At follow up Lysholm, IKDC and Tegner activity scores were used. A side to side maximum manual (S/S MM) KT1000 measurement was done. Comparative weight bearing antero-posterior and lateral radiograms were performed and analyzed according to Fairbank, Kellgren and IKDC classification. Tibio-femoral and patella-femoral joints were analyzed separately. Statistical analysis was performed using Student t-test, Pearson chi-square test with SPPS 9.0 software.Results:Group A and B were homogeneous for sex and age. At final follow up seven patients were lost. Subjectively Lysholm score, IKDC and Tegner Activity score improved significantly in both groups with no significant difference. Objectively the number of patient categorized as A and B according to the IKDC was significantly higher in group B than in group A ( P=0.05). Considering as a failure a S/S M/M difference > 5mm or a Pivot Shift test graded as ++ or +++ or a recurrence of any giving way episode, we found 7 cases in group A and no cases in group B (P=0.006). Radiogical evaluation showed no statistically significant difference between the two groups in all scales in both femoro-tibial and patello-femoral joints.Conclusion:The main limitation of the study is that the two groups were not homogeneous in term of preoperative conditions. However as highest grades of activity level and Pivot Shift correlate with an increased risk of DOA, this limitation appears to strengthen the value of the study. Adding a lateral tenodesis to an ACL IR with hamstrings, followed by a standard rehabilitative protocol, seems not to increase the risk of development of DOA, improving rotatory knee stability and reducing risk of recurrence. The meeting in Snowmass has been a milestone event in the evaluation of role of ERs in ACL deficent knee, giving an outstanding contribution to their definition, their biomechanical effect and their role in rotatory instability. However, on the basis of the results of this study, we could speculate that the conclusions of the meeting were somewhat misleading or at least misinterpreted, as they were based on surgical techniques and rehabilitation procedures no more in use in the modern ACL surgery.

The role of the deep medial collateral ligament in controlling rotational stability of the knee.

The tibial insertion of the deep medial collateral ligament (dMCL) is frequently sacrificed when the proximal tibial cut is performed during total knee arthroplasty. The role of the dMCL in controlling the knee's rotational stability is still controversial. The aim of this study was to quantify the rotational laxity induced by an isolated lesion of the dMCL as it occurs during tibial preparation for knee arthroplasty. An isolated resection of the deep MCL was performed in 10 fresh-frozen cadaver knees. Rotational laxity was measured during application of a standard 5.0N.m rotational torque. Maximal tibial rotation was measured at different knee flexion angles using an image-guided navigation system (Medivision Surgetics system, Praxim, Grenoble, France) before and after dMCL resection. In all cases, internal and external tibial rotation increased after dMCL resection. Total rotational laxity increased significantly for all knee flexion angles, with an average difference of +7.8° (SD 5.7) with the knee in extension, +8.9° (SD 1.9) in 30° flexion, +7° (SD 2.9) in 60° flexion and +5.3° (SD 2.8) in 90° flexion. Sacrificing the tibial insertion of the deep MCL increases rotational laxity of the knee by 5°-9°, depending on the knee flexion angle. Based on our findings, new surgical techniques and implants that preserve the dMCL insertion such as tibial inlay components should be developed. Further clinical evaluations are necessary.

A two- and five-year follow-up of clinical outcome after ACL reconstruction using BPTB or hamstring tendon grafts: a prospective intervention outcome study

The aim of the present study was to evaluate and compare objective and subjective outcome in patients 2 and 5 years after anterior cruciate ligament (ACL) reconstruction with either bone-patellar tendon-bone (BPTB) or hamstring grafts. The second aim was to report the prevalence of re- and contralateral ACL ruptures. Sixty-eight patients (BPTB, n = 34 and hamstring graft, n = 34) were evaluated preoperatively, 2 and 5 years after ACL reconstruction. Anterior knee laxity and rotational knee joint stability, muscle torque, hop length, anterior knee pain, activity level and self-reported knee function and quality of life were evaluated within and between groups. The prevalence of re- and contralateral ACL ruptures was also recorded. No significant difference in anterior knee laxity, rotational knee joint stability, hop length anterior knee pain or knee function and quality of life were noted at the 5-year follow-up. No significant differences in concentric or eccentric quadriceps torque at 90°/s and 230°/s were found at any of the follow-ups between and within grafts. A significant group difference in hamstring torque 1.05 (0.02) for BPTB and 0.89 (0.02) for hamstring grafts, and in hop length (leg symmetry index) follow-up 0.94 (0.07) for BPTB compared to 0.99 (0.07) for hamstring grafts (P = 0.002) was found at the 2 year follow-up in favour of the BPTB graft, but not at the 5 year follow-up. A significant improvement over time, irrespective of graft, was found in the KOOS's subscales Sport/Rec and quality of life (P < 0.001). None of the patients, irrespective of group, returned to their pre-injury level of sport (P < 0.05). Over the five postoperative years, one man and eight women (13 %) (hamstring graft, n = 5 and BPTB graft, n = 4), sustained a total of 11 (16.2 %) new ACL ruptures: seven (10.2 %) re-ruptures and four (5.9 %) ruptures of the contralateral ACL. At the 5-year follow-up, there were no significant differences in terms of anterior knee laxity, rotational knee joint stability, muscle torque, anterior knee pain, hop performance, quality of life or activity level between patients who had undergone reconstruction with BPTB or hamstring grafts. None of the patients, irrespective of group, had returned to their pre-injury level of activity. Eight out of the nine patients who had sustained a second ACL rupture were women.

Kinematic Analysis of the Posterior Cruciate Ligament, Part 2

Background: A more thorough understanding of the posterior cruciate ligament (PCL) has led to an increase in awareness and treatment of complex PCL injuries. Controversy exists about whether PCL reconstruction (PCLR) using an anatomic single-bundle (aSB) or anatomic double-bundle (aDB) technique is the most effective. Hypothesis: An aDB PCLR provides significantly better anterior-posterior and rotatory knee stability compared with an aSB PCLR and more closely recreates normal knee kinematics. Study Design: Controlled laboratory study. Methods: A total of 18 match-paired, cadaveric knees (mean age, 54.8 years; range, 51-59 years; 5 male and 4 female pairs) were used to evaluate the kinematics of an intact PCL, an aSB and aDB PCLR, and a complete sectioned PCL. A 6 degrees of freedom robotic system was used to assess knee stability with a 134-N applied posterior tibial load, 5-N·m external and internal rotation torques, 10-N·m valgus and varus rotation torques, and a coupled 100-N posterior tibial load and 5-N·m external rotation torque at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120°. Results: The aDB PCLR had significantly less posterior translation than the aSB PCLR at all flexion angles of 15° and greater. The largest difference in posterior translation was seen at 105° of flexion, where the aSB PCLR had 5.3 mm (P = .017) more posterior translation than the aDB PCLR. The aDB PCLR also had significantly less internal rotation than the aSB PCLR at all tested angles of 90° and greater. Neither reconstruction was able to fully restore native knee kinematics. Conclusion: An aDB PCLR more closely approximated native knee kinematics when compared with an aSB PCLR. Specifically, the aDB PCLR demonstrated significantly more restraint to posterior translation at flexion angles between 15° and 120° and less internal rotational laxity at high flexion angles 90° to 120°. Clinical Relevance: Comparison of the 2 reconstruction techniques illustrates the time-zero kinematic advantage imparted by the addition of the posteromedial bundle reconstruction. The benefit is most pertinent for resistance to posterior translation across a full range of flexion and rotational stability beyond 90° of knee flexion.

The Effect of Knee Braces on Tibial Rotation in Anterior Cruciate Ligament – Deficient Knees During High Demand Athletic Activities

OBJECTIVE To examine if bracing can restrict tibial rotation in anterior cruciate ligament (ACL)-deficient patients during high loading activities. DESIGN Repeated measures. Kinematic data were collected with an 8-camera Vicon system while each patient performed 2 tasks that are known to cause increased rotational and translational loads on the knee: (1) descending from a stair and subsequent pivoting, and (2) landing from a platform and subsequent pivoting. The tasks were repeated under 3 brace conditions for the ACL-deficient knee: (1) wearing a prophylactic brace (braced condition), (2) wearing a patellofemoral brace (sleeved condition), and (3) without brace (unbraced condition). SETTING Biomechanical laboratory study. PATIENTS Twenty-one male subjects with a confirmed unilateral ACL rupture were assessed in vivo. MAIN OUTCOME MEASURES Tibial internal rotation. Two repeated measures ANOVAs tested for differences in tibial internal rotation among the 3 conditions of the ACL-deficient knee and the unbraced condition of the intact knee. RESULTS In both tasks, tibial rotation was significantly lower in the intact knee compared with all 3 conditions of the ACL-deficient knee (P ≤ 0.031). Bracing the ACL-deficient knee resulted in lower rotation than the unbraced (P ≤ 0.001) and sleeved (P ≤ 0.033) conditions. The sleeved condition resulted in lower tibial rotation in the drop landing and pivoting task compared with the unbraced condition (P = 0.019) but not in the stair descending and pivoting task (P = 0.256). CONCLUSIONS Bracing decreased the excessive tibial rotation in ACL-deficient patients during high-demand activities but failed to fully restore normative values. If knee braces can enhance rotational knee stability in ACL-deficient patients, then they could possibly play an important role in preventing further knee pathology in such patients.

The Effect of Knee Braces on Tibial Rotation in Anterior Cruciate Ligament–Deficient Knees During High-Demand Athletic Activities

To examine if bracing can restrict tibial rotation in anterior cruciate ligament (ACL)-deficient patients during high loading activities. Repeated measures. Kinematic data were collected with an 8-camera Vicon system while each patient performed 2 tasks that are known to cause increased rotational and translational loads on the knee: (1) descending from a stair and subsequent pivoting, and (2) landing from a platform and subsequent pivoting. The tasks were repeated under 3 brace conditions for the ACL-deficient knee: (1) wearing a prophylactic brace (braced condition), (2) wearing a patellofemoral brace (sleeved condition), and (3) without brace (unbraced condition). Biomechanical laboratory study. Twenty-one male subjects with a confirmed unilateral ACL rupture were assessed in vivo. Tibial internal rotation. Two repeated measures ANOVAs tested for differences in tibial internal rotation among the 3 conditions of the ACL-deficient knee and the unbraced condition of the intact knee. In both tasks, tibial rotation was significantly lower in the intact knee compared with all 3 conditions of the ACL-deficient knee (P ≤ 0.031). Bracing the ACL-deficient knee resulted in lower rotation than the unbraced (P ≤ 0.001) and sleeved (P ≤ 0.033) conditions. The sleeved condition resulted in lower tibial rotation in the drop landing and pivoting task compared with the unbraced condition (P = 0.019) but not in the stair descending and pivoting task (P = 0.256). Bracing decreased the excessive tibial rotation in ACL-deficient patients during high-demand activities but failed to fully restore normative values. If knee braces can enhance rotational knee stability in ACL-deficient patients, then they could possibly play an important role in preventing further knee pathology in such patients.

A review of anterior cruciate ligament injuries and reconstructive techniques. Part 1: Basic science

Anterior cruciate ligament rupture is a common soft tissue knee injury, often affecting young athletic individuals keen to return to pre-injury levels of function. Increasing sporting activity is reflected by an increasing incidence of anterior cruciate ligament rupture. Although treatment has advanced considerably over the years, there are still a number of contentious issues that are considered in this review. The anterior cruciate ligament is a dense band of connective tissue, comprising an anteromedial and posterolateral bundle based on tibial insertion sites. It is important to appreciate the position and orientation of these bundles at the time of reconstructive surgery. The bundles, with their load sharing behaviour through knee flexion, affect antero-posterior and rotational stability of the knee. In the first part of this review, we consider the clinical presentation of anterior cruciate ligament injury and relevant anatomy, knee kinematics, mechanism of injury and incidence of anterior cruciate ligament ruptures.

Reconstruction of the Anterior Cruciate Ligament in the Skeletally Immature Athlete: A Review of Current Concepts

Intrasubstance tears of the anterior cruciate ligament (ACL) were once considered a rare injury in skeletally immature athletes but are now observed with increasing frequency. Treatment strategies have evolved as recent studies have identified unique considerations specific to the skeletally immature patient. The current literature now supports the trend toward early operative treatment to restore knee stability and prevent progressive meniscal and/or articular cartilage damage, but the optimal approach to ACL reconstruction in this age group remains controversial. Despite the reported clinical success of transphyseal reconstruction, iatrogenic growth disturbance secondary to physeal damage remains a genuine concern. The reluctance to place drill-holes across open physes has led to the development of numerous "physeal-sparing" reconstruction techniques using anatomic femoral and tibial footprints that have adequately restored anteroposterior and rotational knee stability in biomechanical studies but have demonstrated mixed results in the clinical setting. The intent of this review is to (1) highlight the unique anatomic considerations pertaining to ACL reconstruction in the skeletally immature athlete, (2) discuss preoperative clinical and radiographic assessment of the pediatric patient with a suspected ACL injury, (3) review transphyseal and physeal-sparing reconstruction techniques and highlight surgical technical considerations, (4) present clinical outcomes according to patient and technique-specific factors, and (5) review age-specific injury prevention treatment strategies and a novel treatment algorithm based on skeletal maturity. ACL reconstruction in the skeletally immature athlete typically results in a successful clinical outcome, yet the optimal surgical technique is still controversial. This review will help guide the management of ACL injuries in the pediatric athlete.

Double-bundle versus single-bundle reconstruction for anterior cruciate ligament rupture in adults.

Arthroscopic reconstruction for anterior cruciate ligament rupture is a common orthopaedic procedure. One area of controversy is whether the method of double-bundle reconstruction, which represents the 'more anatomical' approach, gives improved outcomes compared with the more traditional single-bundle reconstruction. To assess the effects of double-bundle versus single-bundle for anterior cruciate ligament reconstruction in adults with anterior cruciate ligament deficiency. We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to February 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 2), MEDLINE (1966 to February week 3 2012) and EMBASE (1980 to 2012 Week 8). We also searched trial registers, conference proceedings, and contacted authors where necessary. Randomised and quasi-randomised controlled clinical trials comparing double-bundle versus single-bundle reconstruction for anterior cruciate ligament (ACL) rupture in adults. Two review authors independently selected articles, assessed risk of bias and extracted data. We contacted investigators to obtain missing information. Where appropriate, results of comparable studies were pooled. Seventeen trials were included. These involved 1433 people, mostly young physically active adults. All included trials had methodological weaknesses and were at risk of bias, notably selection bias from inadequate or lack of allocation concealment. Data for pooling individual outcomes were available for a maximum of nine trials and 54% of participants.There were no statistically or clinically significant differences between double-bundle and single-bundle reconstruction in the subjective functional knee scores (subjective IKDC score, Tegner activity score, Lysholm score) in the intermediate (six months up to two years since surgery) or long term (two to five years from surgery). For example, the long term results for the Lysholm score (0 to 100: best score) were: mean difference (MD) 0.12, 95% confidence interval (CI) -1.50 to 1.75; 5 trials, 263 participants). The only trial reporting on long term knee pain found no statistically significant differences between the two groups. There were no significant differences between the two groups in adverse effects and complications (e.g. infection reported by nine trials (7/285 versus 7/393; risk ratio (RR) 1.14, 95% CI 0.46 to 2.81); graft failure reported by six trials (1/169 versus 4/185; RR 0.45; 95% CI 0.07 to 2.90).Limited data from five trials found a better return to pre-injury level of activity after double-bundle reconstruction (147/162 versus 208/255; RR 1.15, 95% CI 1.07 to 1.25). At long term follow-up, there were statistically significant differences in favour of double-bundle reconstruction for IKDC knee examination (normal or nearly normal categories: 325/344 versus 386/429; RR 1.05, 95% CI 1.01 to 1.08; 9 trials), knee stability measured with KT-1000 arthrometer (MD -0.74 mm, 95% CI -1.10 to -0.37; 5 trials, 363 participants) and rotational knee stability tested by the pivot-shift test (normal or nearly normal categories: 293/298 versus 382/415; RR 1.06, 95% CI 1.02 to 1.09; 9 trials). There were also statistically significant differences in favour of double-bundle reconstruction for newly occurring meniscal injury (9/240 versus 24/358; RR 0.46, 95% CI 0.23 to 0.92; 6 trials) and traumatic ACL rupture (1/120 versus 8/149; RR 0.17, 95% CI 0.03 to 0.96; 3 trials). There were no statistically significant differences found between the two groups in range of motion (flexion and extension) deficits. There is insufficient evidence to determine the relative effectiveness of double-bundle and single-bundle reconstruction for anterior cruciate ligament rupture in adults, although there is limited evidence that double-bundle ACL reconstruction has some superior results in objective measurements of knee stability and protection against repeat ACL rupture or a new meniscal injury. High quality, large and appropriately reported randomised controlled trials of double-bundle versus single-bundle reconstruction for anterior cruciate ligament rupture in adults appear justified.

Anatomic double-bundle ACL reconstruction restricts knee extension in knees with hyperextension

Double-bundle ACL reconstruction has been demonstrated to be at least as effective as single-bundle reconstruction in terms of restoring knee rotational and translational stability. Until now, the influence on knees with hyperextension has not been evaluated. It was the purpose of this study to evaluate whether double-bundle ACL reconstruction restricts extension in hyperextendable knees. Hamstring tendon reconstructions of 10 human cadaveric knees with the ability of hyperextension (age: 48±14years) were performed as single bundle (SB) on one side and double bundle (DB) on the other side. A surgical navigation system (BrainLab, Germany) was used to assess the kinematics of each knee at the intact and reconstructed state. A difference with regard to the anterior-to-posterior translation (AP) and rotational stability at 30° of knee flexion, 90° of flexion and the hyperextension capability of each specimen was analysed. The difference in AP translation before and after the reconstruction was not significantly different in 30° and 90° of flexion (n.s). Both single- and double-bundle reconstructions restored the preoperative kinematics at 30° and 90° of knee flexion (n.s). The knee extension was 4°±1.8° with the intact ACL and 4°±1.7° after reconstruction in the SB group (n.s). The knee extension was 5° of hyperextension±1.1° with the intact ACL and 0°±0.4° after reconstruction in the DB group; the limitation of the extension was significantly larger in this group (p=0.013). Both single- and double-bundle ACL reconstruction techniques are capable of restoring knee anteroposterior and rotational stability. Double-bundle reconstructions significantly reduce knee extension in knees with hyperextension capability. Care must be taken when using double-bundle techniques in patients with knee hyperextension as this procedure may limit the knee extension after double-bundle ACL reconstruction.

Paper 155: Measurement of Anteroposterior and Rotational Stability of Knee using Navigation System

Paper 155: Measurement of Anteroposterior and Rotational Stability of Knee using Navigation System

Anteroposterior and rotational stability in fixed and mobile bearing unicondylar knee arthroplasty: a cadaveric study using the robotic force sensor system

Different bearing designs in unicondylar knee arthroplasty (UKA) have been developed in order to influence the rate of polyethylene wear. Increased anteroposterior translation and rotation after UKA has been hypothesized due to changes in joint surface geometry. The mobile bearing design was expected to show increased anteroposterior translation compared to the fixed bearing and biconcave bearing design. Six human cadaver knees were used for the tests. Anteroposterior and rotational knee stability was analysed in 0°, 30°, 60°, 90° and 120° of knee flexion using a robotic testing system (KR 125, KUKA Robots Augsburg, Germany). Three forces and moments were measured in a Cartesian coordinate system with a resolution of 1.0 N and 0.1 Nm. There was no difference between the native knees and the knees after UKA in AP translation and rotation in all knee flexion angles. The factor knee flexion angle had a significant impact on the anterior translation when the type of bearing was neglected (p ≤ 0.015). This study shows that the natural knee stability in AP translation and rotation can be preserved in UKA. The preserved knee stability in different planes after UKA underlines the advantage of UKA when surgery is required in osteoarthritic changes of the medial compartment.

Comparison of 2 Femoral Tunnel Locations in Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

To evaluate knee stability after anterior cruciate ligament (ACL) reconstruction using 2 modern clinically relevant single-bundle constructs. Two arthroscopic ACL reconstructions were performed on 6 fresh-frozen human cadaveric knees using bone-patellar tendon-bone autografts. The tibial tunnel was centered in the anatomic tibial footprint. The femoral tunnel was reamed through the anteromedial (AM) portal and centered alternately in either the AM portion of the femoral footprint (center-AM) or the center of the femoral footprint (center-center). Two external loading conditions were applied: (1) a 134-N anterior tibial load and (2) a 10-Nm valgus load combined with a 5-Nm internal tibial torque. Resulting kinematics were determined under 4 conditions: (1) ACL intact, (2) ACL deficient, (3) center-AM reconstruction, and (4) center-center reconstruction. In response to anterior tibial loading, anterior translation was similar in the ACL-intact knee and the 2 reconstructions at 0° to 60° of flexion but was greater in the reconstructed specimens at 90°. In response to the complex rotatory load, internal tibial rotation (ITR) at 30° of flexion was slightly greater in center-AM knees compared with ACL-intact knees (11.0° ± 0.6° v 10.5° ± 0.6°, P = .03). At other angles tested, ITR in both reconstructions was similar to the ACL-intact knee (P > .05). When we compared the 2 reconstruction alternatives, however, center-center knees exhibited greater resistance to ITR at all angles (P < .05). Anatomic single-bundle ACL reconstruction performed with the femoral tunnel placed through the AM portal restores translational and rotational knee stability to an extent that closely approximates the ACL-intact condition. When compared with the AM femoral tunnel position, a femoral tunnel positioned in the anatomic center of the femoral origin of the ACL may further improve rotatory stability without sacrificing anterior stability. This study provides additional biomechanical evidence in support of anatomic single-bundle ACL reconstruction with tunnels positioned in the center of the femoral and tibial footprints.

Oblique femoral tunnel or oblique graft? A modified anteromedial portal technique to obtain vertical femoral tunnel and oblique graft in anatomic anterior cruciate ligament reconstruction

In anterior cruciate ligament (ACL) reconstruction, transtibial drilling of the femoral tunnel has been criticized for its vertical and less anatomical tunnel, which accompanied rotational instability of knee. Many authors recommend anteromedial (AM) portal drilling technique, which creates more oblique and anatomic femoral tunnel. However, recent researches show that oblique tunnel is related to risks of too short femoral tunnel, blowout of back wall, and posterolateral structures injury. Is oblique femoral tunnel really essential for anatomic reconstruction? We introduce a modified AM technique, which abandons the oblique tunnel and provides vertical femoral tunnel and oblique graft with anatomic starting point. The fundamental of the new technique is that oblique graft but not oblique tunnel is essential for rotational stability of knee. Thus, it avoids the risks and preserves anatomic reproduction of ACL.

The effect of tunnel placement on rotational stability after ACL reconstruction: evaluation with use of triaxial accelerometry in a porcine model

Conventional transtibial technique fails to restore the rotational knee stability in spite of successful anterior laxity, while anatomic anterior cruciate ligament reconstruction using the anteromedial portal technique has been developed expecting better rotational kinematics because of closer reproduction of the native anterior cruciate ligament anatomy. However, the rotational instability after those two procedures has not been fully examined especially in terms of dynamic component of the rotational stability. The purpose was to assess the effect of anatomic versus non-anatomic tunnel placement on rotational knee stability after anterior cruciate ligament reconstruction using triaxial accelerometry. Sixteen porcine knees underwent a manual pivot-shift test at four different conditions: (1) anterior cruciate ligament intact, (2) anterior cruciate ligament deficient, (3) non-anatomic transtibial reconstruction, and (4) anatomic anteromedial portal reconstruction. The three-dimensional acceleration of knee motion during the pivot-shift test was recorded using a triaxial accelerometer. Both anterior cruciate ligament reconstructions decreased significantly the acceleration of the pivot-shift test from the increased level in the anterior cruciate ligament-deficient condition. However, the transtibial technique fails to reach the intact level of acceleration, while the anteromedial portal technique reduced the acceleration to even less than the intact level. The transtibial anterior cruciate ligament reconstruction could not restore the dynamic rotational stability of the intact knee, whereas the anteromedial portal technique restored the dynamic rotational stability closer to the intact level. III.

Sagittal and rotational knee stability following single- and double-bundle reconstruction of the anterior cruciate ligament: a randomized clinical trial

Propose The aim of this study was to compare the sagittal and rotational stability of anterior cruciate ligament (ACL) reconstructions with anatomic double-bundle and single-bundle techniques.

Biomechanical techniques to evaluate tibial rotation. A systematic review

This article systematically reviewed the biomechanical techniques to quantify tibial rotation, for an overview of how to choose a suitable technique for specific clinical application. A systematic search was conducted and finally 110 articles were included in this study. The articles were categorized by the conditions of how the knee was examined: external load application, physical examination and dynamic task. The results showed that two-thirds of the included studies measured tibial rotation under external load application, of which over 80% of the experiments employed a cadaveric model. The common techniques used included direct displacement measurement, motion sensor, optical tracking system and universal force moment sensor. Intra-operative navigation system was used to document tibial rotation when the knee was examined by clinical tests. For dynamic assessment of knee rotational stability, motion analysis with skin reflective markers was frequently used although this technique is less accurate due to the skin movement when compared with radiographic measurement. This study reports various biomechanical measurement techniques to quantify tibial rotation in the literatures. To choose a suitable measurement technique for a specific clinical application, it is suggested to quantify the effectiveness of a new designed surgical technique by using a cadaveric model before applying to living human subjects for intra-operative evaluation or long-time functional stability assessment. Attention should also be paid on the study's purpose, whether to employ a cadaveric model and the way of stress applied to the knee. IV.