Dynamic function of the ACL-reconstructed knee during running

In vivo measurement of ACL length and relative strain during walking

Although numerous studies have addressed the effects of ACL injury and reconstruction on knee joint motion, there is currently little data available describing in vivo ACL strain during activities of daily living. Data describing in vivo ACL strain during activities such as gait is critical to understanding the biomechanical function of the ligament, and ultimately, to improving the surgical treatment of patients with ACL rupture. Thus, our objective was to characterize the relative strain in the ACL during both the stance and swing phases of normal level walking. Eight normal subjects were recruited for this study. Through a combination of magnetic resonance imaging, biplanar fluoroscopy, and motion capture, we created in vivo models of each subject's normal walking movements to measure knee flexion, ACL length, and relative ACL strain during gait. Regression analysis demonstrated an inverse relationship between knee flexion and ACL length (R(2)=0.61, p<0.001). Furthermore, relative strain in the ACL peaked at 13±2% (mean±95%CI) during mid-stance when the knee was near full extension. Additionally, there was a second local maximum of 10±7% near the end of swing phase, just prior to heel strike. These data are a vital step in further comprehending the normal in vivo biomechanics experienced by the ACL. In the future, this information could prove critical to improving ACL reconstruction and provide useful validation to future computational models investigating ACL function.

Tibiofemoral cartilage contact biomechanics in patients after reconstruction of a ruptured anterior cruciate ligament

We investigated the in vivo cartilage contact biomechanics of the tibiofemoral joint in patients after reconstruction of a ruptured anterior cruciate ligament (ACL). A dual fluoroscopic and MR imaging technique was used to investigate the cartilage contact biomechanics of the tibiofemoral joint during in vivo weight-bearing flexion of the knee in eight patients 6 months following clinically successful reconstruction of an acute isolated ACL rupture. The location of tibiofemoral cartilage contact, size of the contact area, cartilage thickness at the contact area, and magnitude of the cartilage contact deformation of the ACL-reconstructed knees were compared with those previously measured in intact (contralateral) knees and ACL-deficient knees of the same subjects. Contact biomechanics of the tibiofemoral cartilage after ACL reconstruction were similar to those measured in intact knees. However, at lower flexion, the abnormal posterior and lateral shift of cartilage contact location to smaller regions of thinner tibial cartilage that has been described in ACL-deficient knees persisted in ACL-reconstructed knees, resulting in an increase of the magnitude of cartilage contact deformation at those flexion angles. Reconstruction of the ACL restored some of the in vivo cartilage contact biomechanics of the tibiofemoral joint to normal. Clinically, recovering anterior knee stability might be insufficient to prevent post-operative cartilage degeneration due to lack of restoration of in vivo cartilage contact biomechanics.

Revision anterior cruciate ligament reconstruction: an update

With the rising number of anterior cruciate ligament (ACL) reconstructions performed, revision ACL reconstruction is increasingly common nowadays. A broad variety of primary and revision ACL reconstruction techniques have been described in the literature. Recurrent instability after primary ACL surgery is often due to non-anatomical ACL graft reconstruction and altered biomechanics. Anatomical reconstruction must be the primary goal of this challenging revision procedure. Recently, revision ACL reconstruction has been described using double bundle hamstring graft. Successful revision ACL reconstruction requires an exact understanding of the causes of failure and technical or diagnostic errors. The purpose of this article is to review the causes of failure, preoperative evaluation, graft selection and types of fixation, tunnel placement, various types of surgical techniques and clinical outcome of revision ACL reconstruction.

The effect of modified Broström-Gould repair for lateral ankle instability on in vivo tibiotalar kinematics

BACKGROUND

Lateral ankle instability leads to an increased risk of tibiotalar joint osteoarthritis. Previous studies have found abnormal tibiotalar joint motions with lateral ankle instability that may contribute to this increased incidence of osteoarthritis, including increased anterior translation and internal rotation of the talus under weightbearing loading. Surgical repairs for lateral ankle instability have shown good clinical results, but the effects of repair on in vivo ankle motion are not well understood.

HYPOTHESIS

The modified Broström-Gould lateral ligament reconstruction decreases anterior translation and internal rotation of the talus under in vivo weightbearing loading conditions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven patients underwent modified Broström-Gould repair for unilateral lateral ankle instability. Ankle joint kinematics as a function of increasing body weight was studied with magnetic resonance imaging and biplanar fluoroscopy. Tibiotalar kinematics was measured in unstable ankles preoperatively and postoperatively at a mean follow-up of 12 months as well as in the uninjured contralateral ankles of the same patients.

RESULTS

Surgical repair resulted in statistically significant decreases (expressed as mean ± standard error of the mean) in anterior translation of the talus (0.9 ± 0.3 mm; P = .018) at 100% body weight and internal rotation of the talus at 75% (2.6° ± 0.8°; P = .019) and 100% (2.7° ± 0.8°; P = .013) body weight compared with ankle kinematics measured before repair. No statistically significant differences were detected between repaired ankles and contralateral normal ankles.

CONCLUSION

The modified Broström-Gould repair improved the abnormal joint motion observed in patients with lateral ankle instability, decreasing anterior translation and internal rotation of the talus.

CLINICAL RELEVANCE

Altered kinematics may contribute to the tibiotalar joint degeneration that occurs with chronic lateral ankle instability. The findings of the current study support the efficacy of this repair in improving the abnormal ankle motion observed in these patients.

Biomechanical techniques to evaluate tibial rotation. A systematic review

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

LEVEL OF EVIDENCE

IV.

TransLateral ACL reconstruction: a technique for anatomic anterior cruciate ligament reconstruction

Anatomic placement of the femoral tunnel in anterior cruciate ligament (ACL) reconstruction confers biomechanical advantages over the traditional tunnel position. The anteromedial portal technique for anatomic ACL reconstruction has many well-described technical challenges. This paper describes the TransLateral technique. The technique produces anatomic femoral tunnel placement using direct measurement of the medial wall of the lateral femoral condyle and out to in drilling. All work is carried out through the lateral portal with all viewing via the medial portal. There is no need for an accessory medial portal or hyperflexion of the knee. Level of evidence Expert opinion, Level V.

The effect of distal femur bony morphology on in vivo knee translational and rotational kinematics

PURPOSE

Tibio-femoral kinematics are clearly influenced by the bony morphology of the femur. Previous morphological studies have not directly evaluated relationships between morphology and knee kinematics. Therefore, the purpose of this study was to examine the relationship between distal femur bony morphology and in vivo knee kinematics during running. It was hypothesized that the posterior offset of the transcondylar axis would be related to the magnitude of anterior/posterior tibio-femoral translation and that the rotational angle of the transcondylar axis would be related to the magnitude of internal/external knee rotation.

METHODS

Seventeen contralateral (uninjured) knees of ACL-reconstructed patients were used. Distal femoral geometry was analyzed from 3D-CT data by determining the anteroposterior location (condyle offset ratio--COR) and rotational angle (condylar twist angle--CTA) of the femoral transcondylar axis. Six degree-of-freedom knee kinematics were obtained during running using a dynamic stereo radiograph system. Knee kinematics were correlated with the femoral morphologic measures (COR and CTA) to investigate the influence of femoral geometry on dynamic knee function.

RESULTS

Significant correlations were identified between distal femur morphology and knee kinematics. Anterior tibial translation was positively correlated with the condyle offset ratio (R(2) = 0.41, P < 0.01). Internal tibial rotation was positively correlated with the condylar twist angle (R(2) = 0.48, P < 0.01).

CONCLUSIONS

Correlations between knee kinematics and morphologic measures describing the position and orientation of the femoral transcondylar axis suggest that these specific measures are valuable for characterizing the influence of femur shape on dynamic knee function.

LEVEL OF EVIDENCE

III.

Internal tibial rotation during in vivo, dynamic activity induces greater sliding of tibio-femoral joint contact on the medial compartment

PURPOSE

Although extensive research has been conducted on rotational kinematics, the internal/external rotation of the tibio-femoral joint is perhaps less important for protecting joint health than its effect on joint contact mechanics. The purpose of this study was to evaluate tibio-femoral joint contact paths during a functional activity (running) and investigate the relationship between these arthrokinematic measures and traditional kinematics (internal/external rotation).

METHODS

Tibio-femoral motion was assessed for the contralateral (uninjured) knees of 29 ACL-reconstructed individuals during downhill running, using dynamic stereo X-ray combined with three-dimensional CT bone models to produce knee kinematics and dynamic joint contact paths. The joint contact sliding length was estimated by comparing femoral and tibial contact paths. The difference in sliding length between compartments was compared to knee rotation.

RESULTS

Sliding length was significantly larger on the medial side (10.2 ± 3.8 mm) than the lateral side (2.3 ± 4.0 mm). The difference in sliding length between compartments (mean 7.8 ± 3.0 mm) was significantly correlated with internal tibial rotation (P < 0.01, R (2) = 0.74).

CONCLUSION

The relationship between rotational knee kinematics and joint contact paths was specifically revealed as greater tibial internal rotation was associated with larger magnitude of sliding motion in the medial compartment. This could suggest that lateral pivot movement occurs during running.

CLINICAL RELEVANCE

Rotational kinematics abnormality should be treated for restoring normal balance of joint sliding between medial and lateral compartments and preventing future osteoarthritis.

LEVEL OF EVIDENCE

Prognostic studies, Level II.

Gender difference of the femoral kinematics axis location and its relation to anterior cruciate ligament injury: a 3D-CT study

PURPOSE

The variation of distal femur morphology has been often reported, especially in relation to ACL injury. However, it remains unknown how morphological differences affect knee kinematics and ACL function. The location of the transcondylar axis, a common anatomical reference line, may be a significant aspect of morphological variation. It was hypothesized that the location of this axis would be different between genders, and between ACL-injured and non-injured subjects.

METHODS

3D CT scans of contralateral healthy femurs in 38 unilateral soft tissue injured patients (20 men/18 women, 26 ACL injury/12 non-ACL injury (7 with PCL injuries and 5 with medial meniscus root tears)) were analyzed three-dimensionally. Condyle offset was calculated as the distance between the transcondylar axis and the anatomical axis of the femur. Condyle offset ratio (COR) was then calculated by dividing the condyle offset by the condyle radius. Gender and ACL-injured and non-injured group differences were assessed.

RESULTS

Larger COR was found in women, 1.10 ± 0.14, than men, 0.96 ± 0.08. In women, the ACL-injured group had significantly larger COR than the non-ACL injury group, but no difference was found in men.

CONCLUSION

COR is a unique morphological feature which is measureable from 3D CT. COR is larger in women, and could be a possible risk indicator for ACL injury in the female population.

LEVEL OF EVIDENCE

III.

Measurement of tibiofemoral kinematics using highly accelerated 3D radial sampling

This study investigated the use of dynamic, volumetric MRI to measure 3D skeletal motion. Ten healthy subjects were positioned on a MR-compatible knee loading device and instructed to harmonically flex and extend their knee at 0.5 Hz. The device induced active quadriceps loading with knee flexion, similar to the load acceptance phase of gait. Volumetric images were continuously acquired for 5 min using a 3D cine spoiled gradient-echo sequence in conjunction with vastly under-sampled isotropic projection reconstruction. Knee angle was simultaneously monitored and used retrospectively to sort images into 60 frames over the motion cycle. High-resolution static knee images were acquired and segmented to create subject-specific models of the femur and tibia. At each time frame, bone positions and orientations were determined by automatically registering the skeletal models to the dynamic images. Three-dimensional tibiofemoral translations and rotations were consistent across healthy subjects. Internal tibia rotations of 7.8±3.5° were present with 35.8±3.8° of knee flexion, a pattern consistent with knee kinematic measures during walking. We conclude that vastly under-sampled isotropic projection reconstruction imaging is a promising approach for noninvasively measuring 3D joint kinematics, which may be useful for assessing cartilage contact and investigating the causes and treatment of joint abnormalities.

Tibial rotation during pivoting in anterior cruciate ligament reconstructed knees using a single bundle technique

BACKGROUND

Anterior cruciate ligament reconstruction does not necessarily restore normal knee movement. Increased tibial rotation has previously been noted during pivoting activities and may be due to the orientation of the anterior cruciate ligament graft associated with traditional single bundle reconstruction techniques. Recent research has shown that it is possible to limit rotation during level walking using a single bundle anterior cruciate ligament reconstruction. This study evaluated rotational knee kinematics during a pivot task in a group of patients who had undergone anterior cruciate ligament reconstruction using a single bundle technique and compared the findings to a normal control group.

METHODS

In 27 anterior cruciate ligament reconstruction and 25 control participants, internal-external rotation was measured during a descend stairs and pivot task in a gait laboratory.

FINDINGS

Results showed that the anterior cruciate ligament reconstruction patients had less internal tibial rotation (for both range of rotation and maximum rotation) than the control participants (effect size=0.7).

INTERPRETATION

These results suggest that it is possible to limit rotation after anterior cruciate ligament reconstruction using a single bundle technique, even during a pivoting movement that places a high rotational load at the knee joint. The positioning of the femoral tunnel in a more anatomical position may be responsible for the reduced tibial rotation.

Variations in the three-dimensional location and orientation of the ACL in healthy subjects relative to patients after transtibial ACL reconstruction

Recent reports have indicated that anatomical placement of the anterior cruciate ligament (ACL) graft is an important factor for restoration of joint function following ACL reconstruction. The objective of this study was to address a need for a better understanding of anatomical variations in ACL position and orientation within the joint. Specifically, variations in the ACL anatomy were assessed by testing for side-to-side ACL footprint location symmetry in a healthy population relative to the operative and contralateral knee in a patient population after traditional transtibial single-bundle ACL reconstruction. MRI and three-dimensional modeling techniques were used to determine the in vivo tibiofemoral ACL footprint centers and the resulting ACL orientations in both knees of 30 healthy subjects and 30 subjects after transtibial ACL reconstruction. While there were substantial inter-subject variations in ACL anatomy, the side-to-side RMS differences in the ACL footprint center were 1.20 and 1.34 mm for the femur and tibia, respectively, for the healthy subjects and no clinically meaningful intra-subject differences were measured. However, there were large intra-subject side-to-side differences after transtibial ACL reconstruction, with ACL grafts placed 5.63 and 7.64 mm from the center of the contralateral femoral and tibial ACL footprint centers, respectively. Grafts were placed more medial, anterior, and superior on the femur and more posterior on the tibia; producing grafts that were more vertical in the sagittal and coronal planes. Given the large variation among subjects, these findings advocate the use of the contralateral ACL morphology for retrospectively evaluating patient-specific anatomic graft placement.

Tibial rotation in anterior cruciate ligament reconstructed knees during single limb hop and drop landings

BACKGROUND

Alterations in knee joint kinematics have been suggested as a potential mechanism that influences the development of osteoarthritis of the knee after anterior cruciate ligament reconstruction. Whilst previous work has shown changes in internal-external tibial rotation during level walking, many patients aim to return to high impact activities following surgery. This study examined tibial rotation during single limb hop and drop landings in anterior cruciate ligament reconstructed knees compared to a control group, and also evaluated the influence of graft type (hamstring or patellar tendon).

METHODS

In 48 participants (17 patellar tendon graft, 18 hamstring graft and 13 controls) internal-external rotation was measured during single limb hop and drop landings in a gait laboratory at mean of 10 months after surgery.

FINDINGS

There was no difference between the two graft types and both patient groups had less internal rotation when compared to the control group. For 60% of patients, internal rotation values were at least 5° less than the control group mean.

INTERPRETATION

Anterior cruciate ligament reconstructed knees with both hamstring tendon and patellar tendon grafts show altered rotational kinematic patterns during high impact dynamic load activities.

Static and dynamic error of a biplanar videoradiography system using marker-based and markerless tracking techniques

The use of biplanar videoradiography technology has become increasingly popular for evaluating joint function in vivo. Two fundamentally different methods are currently employed to reconstruct 3D bone motions captured using this technology. Marker-based tracking requires at least three radio-opaque markers to be implanted in the bone of interest. Markerless tracking makes use of algorithms designed to match 3D bone shapes to biplanar videoradiography data. In order to reliably quantify in vivo bone motion, the systematic error of these tracking techniques should be evaluated. Herein, we present new markerless tracking software that makes use of modern GPU technology, describe a versatile method for quantifying the systematic error of a biplanar videoradiography motion capture system using independent gold standard instrumentation, and evaluate the systematic error of the W.M. Keck XROMM Facility's biplanar videoradiography system using both marker-based and markerless tracking algorithms under static and dynamic motion conditions. A polycarbonate flag embedded with 12 radio-opaque markers was used to evaluate the systematic error of the marker-based tracking algorithm. Three human cadaveric bones (distal femur, distal radius, and distal ulna) were used to evaluate the systematic error of the markerless tracking algorithm. The systematic error was evaluated by comparing motions to independent gold standard instrumentation. Static motions were compared to high accuracy linear and rotary stages while dynamic motions were compared to a high accuracy angular displacement transducer. Marker-based tracking was shown to effectively track motion to within 0.1 mm and 0.1 deg under static and dynamic conditions. Furthermore, the presented results indicate that markerless tracking can be used to effectively track rapid bone motions to within 0.15 deg for the distal aspects of the femur, radius, and ulna. Both marker-based and markerless tracking techniques were in excellent agreement with the gold standard instrumentation for both static and dynamic testing protocols. Future research will employ these techniques to quantify in vivo joint motion for high-speed upper and lower extremity impacts such as jumping, landing, and hammering.

Are the kinematics of the knee joint altered during the loading response phase of gait in individuals with concurrent knee osteoarthritis and complaints of joint instability? A dynamic stereo X-ray study

BACKGROUND

Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional decline in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear.

METHODS

Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait.

FINDINGS

Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P<0.01), while the total abduction/adduction range of motion was increased (P<0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P<0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait.

INTERPRETATIONS

The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics.

The role of static and dynamic rotatory laxity testing in evaluating ACL injury

In this article, we discuss current topics for rotatory knee laxity. All tests for knee laxity have a value. Static knee laxity tests reveal information for each individual patient's laxity status, especially compared to the contralateral side. Static knee laxity tests are simple to do, and some of them are instrumented, therefore quantifiable. Dynamic knee laxity tests are more complex. Dynamic stereo radiography (DSX) is considered the gold standard. Utilizing DSX, information can be gained on 3-D kinematics, functional joint space, and joint contact patterns. The disadvantage is that DSX is expensive and can only be performed in a laboratory environment. The pivot shift test is a unique test, because it is dynamic and easily performed in the office. However, it is subjective and only recently quantifiable. Future endeavors will attempt to improve the value of the pivot shift test by standardizing the test and improving measurement technologies, while keeping the pivot shift test simple and non-invasive.

Dynamic knee laxity measurement devices

PURPOSE

Studies have reported that knee kinematics and rotational laxity are not restored to native levels following traditional anterior cruciate ligament (ACL) reconstruction. This has led to the development of anatomic ACL reconstruction, which aims to restore native knee kinematics and long-term knee health by replicating normal anatomy as much as possible. The purpose of this review is to give an overview of current dynamic knee laxity measurement devices with the purpose of investigating the significance of dynamic laxity measurement of the knee. Gait analysis is not included.

METHODS

The subject was discussed with experts in the field in order to perform a level V review. MEDLINE was searched according to the discussions for relevant articles using multiple different search terms. All found abstracts were read and scanned for relevance to the subject. The reference lists of the relevant articles were searched for additional articles related to the subject.

RESULTS

There are a variety of techniques reported to measure dynamic laxity of the knee. Technical development of methods is one important part toward better understanding of knee kinematics. Validation of devices has shown to be difficult due to the lack of gold standard. Different studies use various methods to examine different components of dynamic laxity, which makes comparisons between studies challenging.

CONCLUSION

Several devices can be used to evaluate dynamic laxity of the knee. At the present time, the devices are continuously under development. Future implementation should include primary basic research, including validation and reliability testing, as well as part of individualized surgery and clinical follow-up.

LEVEL OF EVIDENCE

Diagnostic study, Level V.

Radial displacement of the lateral meniscus before and after anterior cruciate ligament reconstruction

INTRODUCTION

The purpose of this study was to investigate radial displacement (RD) of the lateral meniscus in patients with anterior cruciate ligament (ACL) injury by using magnetic resonance imaging both pre- and post-operatively.

MATERIALS AND METHODS

This study included 59 knees that had undergone ACL reconstruction. The length that extruded from the lateral tibial plateau was measured in the coronal plane.

RESULTS

Mean pre-operative RD was 1.8 mm, and mean post-operative RD was 2.4 mm (P < 0.001). Mean pre-operative RD was 1.6 mm in the group with lateral meniscus tears <1 cm, and 2.8 mm in the group with tears ≥1 cm (P = 0.033); the corresponding post-operative values were 2.1 and 3.2 mm (P = 0.038), respectively. Mean pre-operative RD was 1.9 mm in the longitudinal tear group and 2.4 mm in the radial tear, flap tear, or complex tear group (P = 0.21); the corresponding post-operative values were 2.2 and 4.1 mm (P = 0.036), respectively.

CONCLUSION

We found that RD of the lateral meniscus was not a rare finding, and that RD was related to the meniscus status. Moreover, RD did not improve after ACL reconstruction. Thus, the treatment for meniscus tear should be carefully assessed. Level of evidence Level 4, case series, therapeutic studies.

Surgical technique: aperture fixation in PCL reconstruction: applying biomechanics to surgery

BACKGROUND

Biomechanical studies suggest reducing the effective graft length during transtibial posterior cruciate ligament (PCL) reconstruction by augmenting the distal tibial fixation with a proximal screw near the tibial tunnel aperture could increase graft stiffness and provide a more stable reconstruction. However, it remains unknown to what extent this mechanical theory influences in vivo graft performance over time.

SURGICAL TECHNIQUE

We developed a technique to augment tibial distal fixation with a proximal screw near the tibial tunnel aperture to shorten the effective graft length and increase graft stiffness.

PATIENTS AND METHODS

We retrospectively reviewed all 10 patients who had isolated PCL reconstructions with combined distal and proximal tibial fixation from 2003 to 2007. Mean age of the patients was 36.5 years. We measured ROM and obtained Tegner, International Knee Documentation Committee (IKDC), and Lysholm scores. Anteroposterior stability was evaluated with a KT-2000 arthrometer. Minimum followup was 1 year (mean, 2.5 years; range, 1-4.8 years).

RESULTS

Mean Tegner scores before injury and at last followup were 7.3 and 6.5, respectively. Mean postoperative IKDC score was 87 versus a preoperative IKDC score of 43. Mean Lysholm score was 89 at last followup. All patients achieved full terminal extension. No patient had greater than a 5-mm difference in anterior or posterior displacement from the contralateral knee as measured by a KT-2000 arthrometer postoperatively (0.93 ± 0.79 mm).

CONCLUSIONS

In this small series, augmentation of tibial distal fixation with a proximal screw near the tibial tunnel aperture during reconstruction of the isolated PCL rupture restored function, motion, and stability.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Effect of lower limb dominance on knee joint kinematics after anterior cruciate ligament reconstruction

BACKGROUND

Normal ambulatory kinematics of the knee joint is often not fully restored after anterior cruciate ligament reconstruction, which may increase the risk for cartilage degeneration and premature osteoarthritis in the involved knees. Lower limb dominance may have impacts on knee joint kinematics after anterior cruciate ligament reconstruction, which may lead to a different prevalence of cartilage degeneration. This study aimed to evaluate the knee joint kinematics among patients with reconstruction on the dominant and non-dominant side.

METHODS

Forty-one subjects with unilateral anterior cruciate ligament reconstruction (19 dominant, 22 non-dominant) were recruited after being discharged from rehabilitation programs. Twenty healthy subjects were recruited as the control group. Six degrees-of-freedom tibiofemoral motion during level walking was determined using a redundant point cluster-based marker set. Tibiofemoral joint motion and its bilateral differences were compared within each group and between groups.

FINDINGS

The non-dominant reconstructed knees had less extension compared to their contralateral knees at heel strike and during middle stance phase (P=0.02); whereas, the dominant reconstructed knees exhibited significantly reduced varus rotation (-2.1° on mean, P=0.027) and internal tibial rotation (P=0.034) compared to their contralateral knees during both stance and swing phases.

INTERPRETATION

The results show that different kinematics has been developed between the involved dominant and non-dominant knees after anterior cruciate ligament reconstruction, especially the secondary rotations. The differences are consistent with the unequal prevalence of cartilage degeneration in the knee joint. The findings demonstrated that the lower limb dominance had a significant effect on post-surgery knee kinematics.

Transtibial ACL reconstruction technique fails to position drill tunnels anatomically in vivo 3D CT study

PURPOSE

The purpose of this study was to visualize and quantify the positions of femoral and tibial tunnels in patients who underwent traditional transtibial single-bundle ACL reconstruction, as performed by multiple surgeons, utilizing 3D CT models, and to compare these positions to our previously reported anatomical tunnel positions.

METHODS

Fifty-eight knee computed tomography (CT) scans were performed on patients who underwent primary or revision transtibial single-bundle ACL reconstruction, and three-dimensional reconstructions of the CT scans were aligned within an anatomical coordinate system. The position of femoral tunnel aperture centers was measured with (1) the quadrant method and (2) in the anatomic posterior-to-anterior and proximal-to-distal directions. The position of tibia tunnel aperture centers were measured similarly, in the anterior-to-posterior and medial-to-lateral dimensions on the tibial plateau. Comparisons were made to previously established anatomical tunnel positions, and data were presented as "mean value ± standard deviation (range)."

RESULTS

The location of tibial tunnels was at 48.0 ± 5.4% (35.6-59.5%) of the anterior-to-posterior plateau depth and at 47.9 ± 2.9% (42.2-57.4%) of the medial-to-lateral plateau width. The location of femoral tunnels was at 55.8 ± 8.0% (41.5-79.5%) in the anatomic posterior-to-anterior direction and at 41.2 ± 10.4% (15.1-67.4%) in the proximal-to-distal directions. Utilizing a quadrant method, femoral tunnels were positioned at 37.4 ± 5.1% (24.9-50.6%) from the proximal condylar surface, parallel to Blumensaat line, and at 11.0 ± 7.3% (-6.0-28.7%) from the notch roof, perpendicular to Blumensaat line. In summary, tibial tunnels were positioned medial to the anatomic PL position (p < 0.001), and femoral tunnels were positioned anterior to both AM and PL anatomic tunnel locations (p < 0.001 and p < 0.001).

CONCLUSION

ACL reconstruction via traditional transtibial technique fails to accurately position femoral and tibial tunnels within the native ACL insertion site. To achieve anatomical graft placement, other surgical techniques should be considered.

LEVEL OF EVIDENCE

IV.

Accelerated versus nonaccelerated rehabilitation after anterior cruciate ligament reconstruction: a prospective, randomized, double-blind investigation evaluating knee joint laxity using roentgen stereophotogrammetric analysis

BACKGROUND

The relationship between the biomechanical dose of rehabilitation exercises administered after anterior cruciate ligament (ACL) reconstruction and the healing response of the graft and knee is not well understood.

HYPOTHESIS

After ACL reconstruction, rehabilitation administered with either accelerated or nonaccelerated programs produces the same change in the knees' 6 degrees of freedom, or envelope, laxity values.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Patients who underwent ACL reconstruction with a bone-patellar tendon-bone autograft were randomized to rehabilitation with either accelerated (19 week) or nonaccelerated (32 week) programs. At the time of surgery, and then 3, 6, 12, and 24 months later, the 6 degrees of freedom knee laxity values were measured using roentgen stereophotogrammetric analysis and clinical, functional, and patient-oriented outcome measures.

RESULTS

Eighty-five percent of those enrolled were followed through 2 years. Laxity of the reconstructed knee was restored to within the limits of the contralateral, normal side at the time of surgery (baseline) in all participants. Patients in both programs underwent a similar increase in the envelope of knee laxity over the 2-year follow-up interval (anterior-posterior translation 3.2 vs 4.5 mm, and coupled internal-external rotations 2.6° vs 1.9° for participants in the accelerated and nonaccelerated programs, respectively). Those who underwent accelerated rehabilitation experienced a significant improvement in thigh muscle strength at the 3-month follow-up (P < .05) compared with those who participated in nonaccelerated rehabilitation, but no differences between the programs were seen after this time interval. At the 2-year follow-up, the groups were similar in terms of clinical assessment, patient satisfaction, function, proprioception, and isokinetic thigh muscle strength.

CONCLUSION

Rehabilitation with the accelerated and nonaccelerated programs administered in this study produced the same increase in the envelope of knee laxity. A majority of the increase in the envelope of knee laxity occurred during healing when exercises were advanced and activity level increased. Patients in both programs had the same clinical assessment, functional performance, proprioception, and thigh muscle strength, which returned to normal levels after healing was complete. For participants in both treatment programs, the Knee Injury and Osteoarthritis Outcome Score (KOOS) assessment of quality of life did not return to preinjury levels.

Image-matching technique can detect rotational and AP instabilities in chronic ACL-deficient knees

PURPOSE

The purpose of this study was to quantify rotational and antero-posterior instabilities using biplanar image-matching technique.

METHODS

Biplanar radiographs of both chronic ACL-deficient knees and contralateral uninjured knees were taken in the pivot shift test and in the "giving way position" and lateral radiographs in stress arthrometer at 30° and 90°. Three-dimensional knee models were constructed using computed tomography. Using biplanar image-matching technique, the external rotational angle and the translation of the center of the both condyles of the femur were analyzed.

RESULTS

The external rotation angle of geometric center axis in the pivot shift test was 16.9° ± 5.6° and 10.9° ± 7.3° (P = 0.004), and in the "giving way position" was 16.1° ± 5.7° and 10.7° ± 6.6° (P = 0.004) in ACL-deficient knees and intact knees, respectively. In the pivot shift test, the medial and the lateral femoral condylar centers of ACL-deficient knees were translated 1.2 ± 5.1 mm anteriorly and 3.9 ± 3.4 mm posteriorly, respectively, and in the "giving way position," 2.0 ± 3.7 mm anteriorly and 2.9 ± 2.6 mm posteriorly, respectively. In stress arthrometer at 30°, the medial and the lateral femoral condylar center translated 7.1 ± 6.0 and 6.6 ± 4.8 mm posteriorly (n.s.), respectively, and at 90° translated 2.7 ± 3.4 and 2.6 ± 3.5 mm posteriorly (n.s.), respectively.

CONCLUSION

Rotational instability was evaluable in the pivot shift test and in the "giving way position." Translation of both condylar centers was similar in stress arthrometry. The image-matching technique is able to quantify dynamic rotational and antero-posterior instabilities with static parameters in ACL-deficient knees.

Factors used to determine return to unrestricted sports activities after anterior cruciate ligament reconstruction

PURPOSE

Anterior cruciate ligament (ACL) reconstruction is commonly performed in athletes, with the goal of return to sports activities. Unfortunately, this operation may fail, and the rates of either reinjuring an ACL-reconstructed knee or sustaining an ACL rupture to the contralateral knee range from 3% to 49%. One problem that exists is a lack of information and consensus regarding the appropriate criteria for releasing patients to unrestricted sports activities postoperatively. The purpose of this study was to determine the published criteria used to allow athletes to return to unrestricted sports activities after ACL reconstruction.

METHODS

A systematic search was performed to identify the factors investigators used to determine when return to athletics was allowed after primary ACL reconstruction. Inclusion criteria were English language, publication within the last 10 years, clinical trial, all adult patients, primary ACL reconstruction, original research investigation, and minimum 12 months' follow-up.

RESULTS

Of 716 studies identified, 264 met the inclusion criteria. Of these, 105 (40%) failed to provide any criteria for return to sports after ACL reconstruction. In 84 studies (32%) the amount of time postoperatively was the only criterion provided. In 40 studies (15%) the amount of time along with subjective criteria were given. Only 35 studies (13%) noted objective criteria required for return to athletics. These criteria included muscle strength or thigh circumference (28 studies), general knee examination (15 studies), single-leg hop tests (10 studies), Lachman rating (1 study), and validated questionnaires (1 study).

CONCLUSIONS

The results of this systematic review show noteworthy problems and a lack of objective assessment before release to unrestricted sports activities. General recommendations are made for quantification of muscle strength, stability, neuromuscular control, and function in patients who desire to return to athletics after ACL reconstruction, with acknowledgment of the need for continued research in this area.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I to IV studies.

Anatomic single- and double-bundle anterior cruciate ligament reconstruction, part 2: clinical application of surgical technique

The anterior cruciate ligament has been and is of great interest to scientists and orthopaedic surgeons worldwide. Anterior cruciate ligament reconstruction was initially performed using an open approach. When the approach changed from open to arthroscopic reconstruction, a 2- and, later, 1-incision technique was applied. With time, researchers found that traditional arthroscopic single-bundle reconstruction did not fully restore rotational stability of the knee joint and a more anatomic approach to reconstruct the anterior cruciate ligament has been proposed. Anatomic anterior cruciate ligament reconstruction intends to replicate normal anatomy, restore normal kinematics, and protect long-term knee health. Although double-bundle anterior cruciate ligament reconstruction has been shown to result in better rotational stability in both biomechanical and clinical studies, it is vital to differentiate between anatomic and double-bundle anterior cruciate ligament reconstruction. The latter is merely a step closer to reproducing the native anatomy of the anterior cruciate ligament; however, it can still be done nonanatomically. To evaluate the potential benefits of reconstructing the anterior cruciate ligament in an anatomic fashion, accurate, precise, and reliable outcome measures are needed. These include, for example, T2 magnetic resonance imaging mapping of cartilage and quantification of graft healing on magnetic resonance imaging. Furthermore, there is a need for a consensus on which patient-reported outcome measures should be used to facilitate homogeneous reporting of outcomes.

Anatomic single- and double-bundle anterior cruciate ligament reconstruction, part 1: Basic science

Anterior cruciate ligament reconstruction is a frequently performed orthopaedic procedure. Although short-term results are generally good, long-term outcomes are less favorable. Thus, there is renewed interest in improving surgical techniques. Recent studies of anterior cruciate ligament anatomy and function have characterized the 2-bundle structure of the native ligament. During non-weightbearing conditions, the anteromedial (AM) and posterolateral (PL) bundles display reciprocal tension patterns. However, during weightbearing, both the AM and PL bundles are maximally elongated at low flexion angles and shorten significantly with increasing knee flexion. Conventional single-bundle reconstruction techniques often result in nonanatomic tunnel placement, with a tibial PL to a femoral "high AM" tunnel position. In vitro studies have demonstrated that these nonanatomic single-bundle reconstructions cannot completely restore normal anterior-posterior or rotatory laxity. Cadaveric studies suggest that anatomic single-bundle and anatomic double-bundle reconstruction may better restore knee stability. Although many cadaver studies suggest that double-bundle reconstruction techniques result in superior stability when compared with single-bundle techniques, others failed to demonstrate a clear benefit of this more complex procedure. Cadaver studies generally do not apply physiologically relevant loads and provide only a "time-zero" assessment that ignores effects of healing and remodeling after anterior cruciate ligament reconstruction. In vivo, dynamic studies offer the most comprehensive assessment of knee function after injury or reconstruction, as they can evaluate dynamic stability during functional joint loading. Studies of knee kinematics during activities such as gait and running suggest that nonanatomic single-bundle anterior cruciate ligament reconstruction fails to restore preinjury knee function under functional loading conditions. Similar studies of more anatomic single- and double-bundle surgical approaches are in progress, and preliminary results suggest that these anatomic techniques may be more effective for restoring preinjury knee function. However, more extensive, well-designed studies of both kinematics and long-term outcomes are warranted to characterize the potential benefits of more anatomic reconstruction techniques for improving long-term outcomes after anterior cruciate ligament reconstruction.

Three-dimensional joint kinematics of ACL-deficient and ACL-reconstructed knees during stair ascent and descent

Mechanical environmental changes in the knee are induced by altered joint kinematics under cyclic loading during activities of daily living after anterior cruciate ligament (ACL) injury. This is considered a risk factor in progressive cartilage degeneration and the early onset of osteoarthritis following ACL injury and even after reconstructive surgery. The purpose of this study was to examine 3D joint kinematics of ACL-deficient and ACL-reconstructed knees to health controls during stair ascent and descent. A 3D optical video motion capture system was used to record coordinate data from reflective markers positioned on subjects as they ascended and descended a custom-built staircase. Spatiotemporal gait and knee joint kinematic variables were calculated and further analyzed. The ACL-deficient knees exhibited a significant extension deficit compared to the ACL-intact controls. A more varus and internally rotated tibial position was also identified in the ACL-deficient knees during both stair ascent and descent. The ACL-reconstructed knees exhibited less abnormality in both spatiotemporal gait parameters and joint kinematics, but these variables were not fully restored to a normal level. The kinematic profiles of the ACL-reconstructed knees were more similar to those of the ACL-deficient knees when compared to the ACL-intact knees. This suggests that the ACL-reconstructed knees had been "under-corrected" rather than "over-corrected" by the reconstructive surgery procedure. Findings from this study may provide more insight with respect to improving ACL reconstruction surgical techniques, which may aid the early progression of cartilage degeneration in ACL-reconstructed knees.

Comparison of rotatory stability after anterior cruciate ligament reconstruction between single-bundle and double-bundle techniques

BACKGROUND

Controversy persists as to whether double-bundle reconstruction of the anterior cruciate ligament (ACL) has any clinical advantage over single-bundle reconstruction. Several studies have used subjective and nonquantitative manual tests to evaluate the rotatory stability of the knee. The authors have developed a method to quantitate the rotatory stability of the ACL-deficient knee using open magnetic resonance imaging (MRI).

HYPOTHESIS

Anatomic double-bundle reconstruction restores rotatory stability significantly better than does single-bundle reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Twenty-three consecutive patients treated with the single-bundle reconstruction (group S) and 25 consecutive patients treated with the anatomic double-bundle reconstruction (group D) were evaluated. Both reconstruction procedures were performed using hamstring tendon autografts. The Slocum anterolateral rotatory instability (ALRI) test was performed 1 year after surgery using open MRI. To assess rotatory stability, we measured the difference in anterior tibial translation between medial and lateral compartments in the sagittal plane and defined this difference as the ALRI value. In addition, clinical examinations consisting of the Lysholm knee score, Tegner activity score, KT-2000 arthrometer anterior translation examination, and the pivot-shift test were carried out.

RESULTS

The mean side-to-side difference in ALRI values was significantly less (P < .001) in double-bundle reconstruction (mean, 1.2 mm) than in single-bundle reconstruction (mean, 4.1 mm). The mean side-to-side difference in KT-2000 arthrometer measurements was significantly less (P = .014) in double-bundle reconstruction (mean, 1.2 mm) than in single-bundle reconstruction (mean, 2.6 mm). The difference in the incidence of positive pivot-shift tests between group S (43%) and group D (16%) did not reach the level of statistical significance (P = .058). No significant differences in Lysholm score or Tegner score between the groups were observed.

CONCLUSION

The rotatory stability of anatomic double-bundle reconstruction was significantly better than the rotatory stability of single-bundle reconstruction.

Closing the gap between bench and bedside research for early arthritis therapies (EARTH): report from the AOSSM/NIH U-13 Post-Joint Injury Osteoarthritis Conference II

This report summarizes the 2010 AOSSM/NIH (American Orthopaedic Society for Sports Medicine/National Institutes of Health) U13 Post-Joint Injury Osteoarthritis II Conference to include the discussion concerning potential study cohorts, assessment considerations, and research priorities. There was strong consensus and enthusiasm for approaching the development of disease-modifying treatments for osteoarthritis through study of "pre-osteoarthritic" cohorts, particularly human subjects under 30 years of age following acute anterior cruciate ligament injuries. Clinical study of acute treatment strategies initiated within a few days after injury will need development of recruitment pathways and short-term proof-of-concept outcome measures that are specific to the intervention being studied. For example, measures of joint inflammation can be used in short-term prospective randomized controlled trials to determine whether an anti-inflammatory intervention was effective in decreasing early inflammation. These short-term clinical trials will need to be followed by longer-term evaluation of the clinical cohorts for joint and cartilage degeneration to determine if the acute intervention affected later development of osteoarthritis. Research priorities were identified in several disciplines, particularly regarding development and validation of quantitative imaging, biomechanics, and biomarker measures of joint structure, composition, and function that predict the accelerated development of osteoarthritis. Systematic study of posttraumatic osteoarthritis is anticipated to advance understanding and treatment of all forms of osteoarthritis.

Relation of tunnel enlargement and tunnel placement after single-bundle anterior cruciate ligament reconstruction

PURPOSE

To determine the relation between tunnel placement and tunnel enlargement after single-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

Seventy-two subjects (mean age, 30.1 years; 17.5 months' follow-up) who underwent single-bundle ACL reconstruction with hamstring autograft were studied. EndoButton fixation (Ethicon, Somerville, NJ) was used on the femoral side, whereas staples were used on the tibial side. A transtibial femoral tunnel position technique was used in 53 subjects, whereas positioning through the medial portal was used in the other 19 cases. Tunnel enlargement was determined by comparing the diameter of the tunnel on the radiograph obtained after 12 months and the radiograph obtained instantly after the operation. The centers of the femoral and tibial tunnels and the angles between the graft and tibial plateau were also measured on standard radiographs. Clinical outcomes including KT-1000 assessment (MEDmetric, San Diego, CA) and International Knee Documentation Committee (IKDC) score were also collected in all patients. The relations between tunnel enlargement/tunnel position and knee joint laxity and IKDC score were analyzed.

RESULTS

The mean KT-1000 side-to-side difference significantly decreased, from 6.07 ± 2.75 mm to 1.57 ± 2.14 mm, after ACL reconstruction; the IKDC subjective score increased from 52.8 to 87.5. On lateral radiographs, the tunnel enlargement rates were 41% on the femoral side and 35% on the tibial side; on plain anteroposterior radiographs, the tunnel enlargement rates were 39% on the femoral side and 32% on the tibial side. Subjects with a higher femoral tunnel had a greater enlargement rate (P < .001). Subjects with a more vertical graft also had a larger femoral enlargement (P < .05). More anterior placement of the femoral tunnel was associated with larger tibial tunnel enlargement on anteroposterior plain radiographs (P < .05). A more vertical graft was also associated with larger tibial tunnel enlargement. Subjects in whom the transtibial femoral position technique was used had more femoral tunnel enlargements (P < .01).

CONCLUSIONS

Drilling the femoral tunnel through the medial portal created a lower, more posterior, and less vertical tunnel than drilling through the tibial tunnel. Femoral and tibial tunnel enlargements were greater with more anterior, more proximal, and more vertical femoral tunnels. Whereas no clinical differences were seen in the 2 groups, drilling the femoral tunnel from the medial portal will result in smaller postoperative tunnel enlargements.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The effect of femoral tunnel placement on ACL graft orientation and length during in vivo knee flexion

Anatomically placed grafts are believed to more closely restore the function of the ACL. This study measured the effect of femoral tunnel placement on graft orientation and length during weight-bearing flexion. Both knees of twelve patients where the graft was placed near the anteroproximal border of the ACL and ten where the graft was placed near the center of the ACL were imaged using MR. These images were used to create 3D models of the reconstructed and intact contralateral knees, including the attachment sites of the native ACL and graft. Next, patients were imaged using biplanar fluoroscopy while performing a quasi-static lunge. The models were registered to the fluoroscopic images to reproduce in vivo knee motion. From the relative motion of the attachment sites on the models, the length and orientation of the graft and native ACL were measured. Grafts placed anteroproximally on the femur were longer and more vertical than the native ACL in both the sagittal and coronal planes, while anatomically placed grafts more closely mimicked ACL motion. In full extension, the grafts placed anteroproximally were 12.3±5.2° (mean and 95%CI) more vertical than the native ACL in the sagittal plane, whereas the grafts placed anatomically were 2.9±3.7° less vertical. Grafts placed anteroproximally were up to 6±2 mm longer than the native ACL, while the anatomically placed grafts were a maximum of 2±2 mm longer. In conclusion, grafts placed anatomically more closely restored native ACL length and orientation. As a result, anatomic grafts are more likely to restore intact knee kinematics.

Current concepts in anatomic single- and double-bundle anterior cruciate ligament reconstruction

An anterior cruciate ligament (ACL) tear is one of the most common orthopedic sport injuries. The ACL consists of 2 functional bundles-the anteromedial and posterolateral-which are named for the position of their insertion sites on the tibia. Anatomic ACL reconstruction can be defined as the restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. Some biomechanical studies have demonstrated that anatomic ACL reconstruction can restore knee motion significantly similar to that of the normal knee, as compared with traditional, nonanatomic single-bundle procedures. In vivo kinematic studies have also shown that nonanatomic single-bundle reconstruction fails to restore normal dynamic knee stability in all cases. Accurate restoration of knee kinematics with anatomic ACL reconstruction is critical to protect against the possibility that nonatomic surgical technique could result in early osteoarthritis, which is common in patients who sustain ACL tears. Surgical techniques for ACL reconstruction vary, and if different aspects of the surgery are compared for superiority (eg, single- vs double-bundle techniques), it is necessary that both procedures meet criteria to be designated as "anatomic." By emphasizing the importance of restoring the native anatomy of the knee, surgeons can give their patients the best chance at restoration of joint function and preservation of long-term knee health.

Investigating the effects of anterior tibial translation on anterior knee force in the porcine model: is the porcine knee ACL dependent?

This study sought to determine anterior force in the porcine knee during simulated 6-degree-of-freedom (DOF) motion to establish the role of the anterior cruciate ligament (ACL). Using a 6-DOF robot, a simulated ovine motion was applied to porcine hind limbs while recording the corresponding forces. Since the porcine knee is more lax than the ovine knee, anterior tibial translations were superimposed on the simulated motion in 2 mm increments from 0 mm to 10 mm to find a condition that would load the ACL. Increments through 8 mm increased anterior knee force, while the 10 mm increment decreased the force. Beyond 4 mm, anterior force increases were non-linear and less than the increases at 2 and 4 mm, which may indicate early structural damage. At 4 mm, the average anterior force was 76.9 ± 10.6 N (mean ± SEM; p < 0.025). The ACL was the primary restraint, accounting for 80-125% of anterior force throughout the range of motion. These results demonstrate the ACL dependence of the porcine knee for the simulated motion, suggesting this model as a candidate for studying ACL function. With reproducible testing conditions that challenge the ACL, this model could be used in developing and screening possible reconstruction strategies.

Biomechanical comparison of anatomic double-bundle, anatomic single-bundle, and nonanatomic single-bundle anterior cruciate ligament reconstructions

BACKGROUND

Although both anatomic double-bundle and single-bundle anterior cruciate ligament reconstruction procedures are in use, it remains controversial whether the anatomic double-bundle procedure is biomechanically superior.

HYPOTHESIS

The anatomic double-bundle procedure would be better than both laterally placed anatomic and nonanatomic transtibial single-bundle procedures at restoring to normal the tibial anterior translation, internal rotation, and pivot-shift instability. It was also hypothesized that tibial internal rotation would be closer to normal after laterally placed anatomic single-bundle reconstruction than after the nonanatomic reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight cadaveric knees were mounted in a 6 degrees of freedom rig and tested using the following loading conditions: 90-N anterior and posterior tibial forces, 5-N·m internal and external tibial rotation torques, and a simulated pivot-shift test. Tibiofemoral kinematics during the flexion-extension cycle were recorded with an optical tracking system for (1) intact, (2) anterior cruciate ligament-deficient knee, (3) anatomic double-bundle reconstruction, (4) nonanatomic single-bundle reconstruction, and (5) laterally placed single-bundle reconstruction.

RESULTS

Rotational laxity with internal tibial torque and anterior laxity in the simulated pivot shift were significantly less in the double-bundle reconstruction and laterally placed single-bundle reconstruction compared with the nonanatomic single-bundle reconstruction. There were no significant differences between the 3 procedures when anterior and posterior tibial translation forces and external rotation torques were applied. In addition, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.

CONCLUSION

The postoperative rotational and pivot-shift laxity after anatomic double-bundle anterior cruciate ligament reconstruction was significantly better than that after nonanatomic single-bundle reconstruction. However, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.

CLINICAL RELEVANCE

This work suggests that a single-bundle reconstruction may be better able to control both knee laxity and pivot-shift instability if the femoral tunnel is moved to a more lateral position and that then the double-bundle reconstruction may not offer significant further advantages.

The ability of 3 different approaches to restore the anatomic anteromedial bundle femoral insertion site during anatomic anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to determine whether drilling the femoral tunnel when performing anterior cruciate ligament (ACL) reconstruction through the accessory medial portal, as opposed to drilling the tunnel transtibially, will lead to more frequent location of the anteromedial femoral tunnel within the anatomic anteromedial bundle insertion site.

METHODS

Primary anatomic double-bundle reconstruction was performed on 113 patients. Intraoperatively, we placed a guide pin through the anteromedial and posterolateral tibial tunnels and accessory medial portal, attempting to reach the center of the native femoral anteromedial bundle insertion. For each approach, the position of the guide pin was classified as (1) within the center of, (2) off-center within, or (3) outside of the femoral anteromedial insertion.

RESULTS

There were significant differences in the ability of each approach to reach the center of the femoral anteromedial bundle insertion. Through the tibial anteromedial tunnel, the femoral anteromedial insertion center was reached in 4.4% of cases, whereas it was off-center within and outside of the femoral anteromedial insertion in 23.0% and 72.6%, respectively. Through the tibial posterolateral tunnel, the femoral anteromedial insertion center was reached in 60.2% of cases, whereas it was off-center within and outside of the femoral anteromedial insertion in 23.9% and 15.9% of cases, respectively. When approached from the accessory medial portal, the center of the femoral anteromedial insertion was reached in 100% of the cases. Ultimately, the femoral anteromedial tunnel was drilled through the tibial anteromedial tunnel in 0.9%, through the posterolateral tunnel in 62.8%, and through the accessory medial portal in 36.3% of cases.

CONCLUSIONS

Drilling the femoral tunnel for the anteromedial graft through the accessory medial portal, as opposed to drilling the tunnel transtibially, leads to more frequent location of the anteromedial femoral tunnel within the anterior cruciate ligament anteromedial bundle anatomic footprint.

The effects of femoral graft placement on in vivo knee kinematics after anterior cruciate ligament reconstruction

Achieving anatomical graft placement remains a concern in Anterior Cruciate Ligament (ACL) reconstruction. The purpose of this study was to quantify the effect of femoral graft placement on the ability of ACL reconstruction to restore normal knee kinematics under in vivo loading conditions. Two different groups of patients were studied: one in which the femoral tunnel was placed near the anterior and proximal border of the ACL (anteroproximal group, n=12) and another where the femoral tunnel was placed near the center of the ACL (anatomic group, n=10) MR imaging and biplanar fluoroscopy were used to measure in vivo kinematics in these patients during a quasi-static lunge. Patients with anteroproximal graft placement had up to 3.4mm more anterior tibial translation, 1.1mm more medial tibial translation and 3.7° more internal tibial rotation compared to the contralateral side. Patients with anatomic graft placement had motion that more closely replicated that of the intact knee, with anterior tibial translation within 0.8mm, medial tibial translation within 0.5mm, and internal tibial rotation within 1°. Grafts placed anteroproximally on the femur likely provide insufficient restraint to these motions due to a more vertical orientation. Anatomical femoral placement of the graft is more likely to reproduce normal ACL orientation, resulting in a more stable knee. Therefore, achieving anatomical graft placement on the femur is crucial to restoring normal knee function and may decrease the rates of joint degeneration after ACL reconstruction.

Model-based tracking of the hip: implications for novel analyses of hip pathology

This study investigated the efficacy of a combined high-speed, biplane radiography and model-based tracking technique to study hip joint kinematics and arthrokinematics. Comparing model-based tracking to the gold standard of radiostereometric analysis using implanted metal beads, joint translation was measured with a bias of 0.2 mm and a precision of 0.3 mm, whereas joint rotation was measured with a bias of 0.2° and a precision of 0.8°. A novel measure of hip arthrokinematics characterizing the region of closest contact in the anterosuperior acetabulum was measured with a bias of 0.9% and a precision of 2.5%. Model-based tracking of the hip thus provides the opportunity to noninvasively study hip pathologic conditions such as osteoarthritis and femoroacetabular impingement with great accuracy.

Delay of 2 or 6 weeks adversely affects the functional outcome of augmented primary repair of the porcine anterior cruciate ligament

BACKGROUND

Enhanced primary anterior cruciate ligament repair, in which suture repair is performed in conjunction with a collagen-platelet composite to stimulate healing, is a potential new treatment option for anterior cruciate ligament injuries. Previous studies have evaluated this approach at the time of anterior cruciate ligament disruption.

HYPOTHESIS

Delaying surgery by 2 or 6 weeks would have a significant effect on the functional outcome of the repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen female Yorkshire pigs underwent staged, bilateral surgical anterior cruciate ligament transections. Anterior cruciate ligament transection was initially performed on 1 knee and the knee closed. Two or 6 weeks later, enhanced primary repair was performed in that knee while the contralateral knee had an anterior cruciate ligament transection and immediate repair. Biomechanical parameters were measured after 15 weeks in vivo to determine the effect of delay time relative to immediate repair on the healing response.

RESULTS

Yield load of the repairs at 15 weeks was decreased by 40% and 60% in the groups where repair was delayed for 2 and 6 weeks, respectively (P = .01). Maximum load showed similar results (55% and 60% decrease in the 2- and 6-week delay groups, respectively; P = .011). Linear stiffness also was adversely affected by delay (50% decrease compared with immediate repair after either a 2- or 6-week delay, P = .011). Anterior-posterior laxity after 15 weeks of healing was 40% higher in knees repaired after a 2-week delay and 10% higher in those repaired after a 6-week delay (P = .012) when tested at 30° of flexion, but was not significantly affected by delay when tested at 60° or 90° (P = .21).

CONCLUSION

A delay between anterior cruciate ligament injury and enhanced primary repair has a significant negative effect on the functional performance of the repair.

CLINICAL RELEVANCE

As future investigations assess new techniques of anterior cruciate ligament repair, the timing of the repair should be considered in the design and the interpretation of experimental studies.

Knee joint anatomy predicts high-risk in vivo dynamic landing knee biomechanics

BACKGROUND

With knee morphology being a non-modifiable anterior cruciate ligament injury risk factor, its consideration within injury prevention models is limited. Knee anatomy, however, directly influences joint mechanics and the potential for injurious loads. With this in mind, we explored associations between key knee anatomical and three-dimensional biomechanical parameters exhibited during landings. We hypothesized that lateral and medial posterior tibial slopes and their ratio, and tibial plateau width, intercondylar distance and their ratio, were proportional to peak stance anterior knee joint reaction force, knee abduction and internal rotation angles.

METHODS

Twenty recreationally active females (21.2 (1.7) years) had stance phase three-dimensional dominant limb knee biomechanics recorded during ten single leg land-and-cut tasks. Six anatomical indices were quantified for the same limb via a series of two dimensional (sagittal, transverse and coronal) magnetic resonance images. Linear stepwise regression analyses examined which of these anatomical factors were independently associated with each of the three mean subject-based peak knee biomechanical measures.

FINDINGS

Lateral tibial slope was significantly (P<0.0001) correlated with peak anterior knee joint reaction force, explaining 60.9% of the variance. Both tibial plateau width:intercondylar distance (P<0.0001) and medial tibial slope:lateral tibial slope (P<0.001) ratios were significantly correlated with peak knee abduction angle, explaining 75.4% of the variance. The medial tibial slope:lateral tibial slope ratio was also significantly (P<0.001) correlated with peak knee internal rotation angle, explaining 49.2% of the variance.

INTERPRETATION

Knee anatomy is directly associated with high-risk knee biomechanics exhibited during dynamic landings. Continued understanding of multifactorial contributions to the anterior cruciate ligament injury mechanism should dictate future injury screening and prevention efforts in order to successfully cater to individual joint vulnerabilities.

Evaluation of bone tunnel placement for suture augmentation of an injured anterior cruciate ligament: effects on joint stability in a goat model

Use of novel tissue engineering approaches to heal an injured anterior cruciate ligament (ACL) requires suture repair and/or augmentation to provide joint stability. We evaluated the effects of the location of suture augmentation at the femur and tibia in terms of joint stability using a goat model. Eight goat stifle joints were tested with augmentation sutures placed in two femoral tunnel locations: (1) anterior to, or (2) through the ACL footprint, and two tibial tunnel locations: (1) medial to, or (2) medial and lateral to the footprint. Using a robotic/universal force-moment sensor testing system, the anterior tibial translation (ATT) and the corresponding in situ force carried by the sutures were obtained at 30°, 60°, and 90° of flexion in response to external loads. No significant differences were found between augmentation groups due to tunnel location in terms of ATT or the in situ forces carried by the sutures at all flexion angles tested. Similar results were found under 5 N m of varus-valgus torque. Under a 67 N anterior tibial load, the ATT was restored to within 3 mm of the intact joint following suture augmentation (p > 0.05). Suture augmentation, when placed close to the ACL insertion, could be helpful in providing initial joint stability to aid ACL healing in the goat model.

Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee during a single-legged hop landing

BACKGROUND

Abnormal 3-dimensional tibiofemoral joint kinematics have been identified in anterior cruciate ligament-reconstructed knees during functional gait tasks, which is suggested to directly affect risk of knee osteoarthritis. However, the extent to which similar high-risk abnormalities are present during more demanding maneuvers, such as single-legged hopping, is largely unknown.

HYPOTHESIS

When performing a single-legged forward hop landing, the reconstructed knee will demonstrate altered sagittal, frontal, and transverse plane kinematics compared with the contralateral limb.

STUDY DESIGN

Controlled laboratory study.

METHODS

High-speed biplane radiography was used to quantify bilateral 3-dimensional tibiofemoral joint kinematics in 9 subjects with unilaterally reconstructed anterior cruciate ligaments (mean time after surgery, 4 months) during 3 single-legged, forward hop landing trials. Mean subject-based initial foot contact and maximum stance (0-250 ms) values were calculated for each kinematic variable. Two-tailed paired t tests were subsequently applied to examine for the main effect of limb (reconstructed vs contralateral).

RESULTS

The reconstructed knees exhibited significantly greater extension (P = .04), external tibial rotation (P = .006), and medial tibial translation (P = .02) than the contralateral knees at initial contact. Reconstructed knees underwent significantly greater maximum flexion (P = .05), maximum external tibial rotation (P = .01), and maximum anterior tibial translation (P = .02). No significant differences existed between limbs for initial contact (P = .65) or maximum adduction-abduction (P = .55).

CONCLUSION

Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee are significantly different from those of the uninjured contralateral limb during a single-legged hop landing. This altered kinematic profile, in conjunction with the large impact loads associated with hopping, may further contribute to the risk of posttraumatic knee osteoarthritis.

CLINICAL RELEVANCE

Returning to sports involving dynamic single-legged landings at 4 months after anterior cruciate ligament reconstruction surgery may contribute to accelerated knee joint degeneration.

Tunnel location in transparent 3-dimensional CT in anatomic double-bundle anterior cruciate ligament reconstruction with the trans-tibial tunnel technique

It is difficult to precisely identify the locations of tunnels after double-bundle anterior cruciate ligament (ACL) reconstruction postoperatively. Using our novel transparent 3-dimensional computed tomography (T-3DCT), we evaluated intra-articular outlet locations and the angles of the anteromedial (AM) and posterolateral (PL) tunnels after anatomic double-bundle ACL reconstruction using the trans-tibial technique. A prospective study was performed with 123 consecutive patients. Tunnel outlet locations were identified on T-3DCT images showing the true lateral view of the femur and indicated by our originally defined X, Y coordinates. We also determined the angles between the tunnel axis and a joint surface line in the coronal plane, the long axis of the femur in the sagittal plane, and the posterior condyle line in the axial plane of both the femur and the tibia. The mean X, Y coordinates of the AM and PL tunnel outlets were 21, 43% and 0, 33%, respectively. In the coronal, sagittal, and axial planes, the mean AM femoral tunnel angles were 63 degrees, 48 degrees, and 55 degrees, respectively; the mean AM tibial tunnel angles in the tibia were 63 degrees, 49 degrees, and 71 degrees, respectively; the mean PL femoral tunnel angles were 38 degrees, 58 degrees, and 43 degrees, respectively; and the mean PL tibial tunnel angles were 46 degrees, 53 degrees, and 45 degrees, respectively. The AM and PL tunnel outlets and angles could be detailed precisely in three dimensions by using T-3DCT. This imaging technique may be useful to confirm surgical techniques and to improve clinical outcomes.

Osseous deficits after anterior cruciate ligament injury and reconstruction: a systematic literature review with suggestions to improve osseous homeostasis

PURPOSE

This systematic review was performed to improve our understanding of the current evidence regarding the influence of anterior cruciate ligament (ACL) injury and reconstruction on involved lower extremity apparent bone mineral density, bone content, or bone area mass (bone integrity).

METHODS

Two independent reviewers performed a Medline search from 1966 to January 2010 using the terms "anterior cruciate ligament" or "ACL" combined with "wound" or "injury" and "bone density" or "osteoporosis." Study inclusion criteria were English-language human studies. Reference sections of selected studies were also reviewed.

RESULTS

Ten studies were identified that met our inclusion criteria. Eight studies performed ACL reconstruction with bone-patellar tendon-bone autografts and interference screw fixation. One study performed ACL reconstruction by use of Achilles tendon allografts with interference screw and staple fixation. Two ACL injury studies either did not involve ACL reconstruction or attempted primary repair with sutures. All studies reported varying levels of decreased bone mineral density, bone content, or bone area mass (bone integrity) at the involved lower extremity after ACL injury that did not return to premorbid levels even with ACL reconstruction and rehabilitation. Sites of reduced bone integrity included the proximal and distal femur, proximal tibia, patella, and calcaneus. Bone loss was increased with limited weight bearing and prolonged disuse or immobilization; however, significant improvements were not observed with accelerated rehabilitation. Some studies reported relations between Lysholm, Tegner, International Knee Documentation Committee survey, or function scores and bone integrity, whereas others reported no or poor relations.

CONCLUSIONS

Involved lower extremity bone integrity is decreased after ACL injury. Current evidence suggests that premorbid bone integrity is not re-established after ACL reconstruction even when accelerated rehabilitation is performed. Recommendations to improve osseous homeostasis and bone health after ACL injury and reconstruction are provided.

Anatomic double-bundle anterior cruciate ligament reconstruction

Several double-bundle anterior cruciate ligament (ACL) reconstruction procedures were reported in the 1980s and 1990s. However, no significant differences were found in the clinical results between these double-bundle procedures and single-bundle procedures because the double-bundle procedures appeared to reconstruct only the anteromedial bundle with 2 bundles. In the early 2000s, we proposed a new concept of anatomic reconstruction of the anteromedial and posterolateral bundles, in which 4 independent tunnels were created through the center of each anatomic attachment of the 2 bundles. We called it "anatomic" double-bundle ACL reconstruction. Biomechanical studies have shown that the anatomic double-bundle ACL reconstruction can restore knee stability significantly more closely to the normal level than the conventional single-bundle reconstruction. Recent intraoperative measurement studies have shown that the clinically available anatomic double-bundle procedures can reconstruct knee stability significantly better and improve knee function close to the normal level at the time immediately after surgery compared with the conventional single-bundle procedures. However, the greatest criticism of the anatomic double-bundle reconstruction is whether its clinical results are better than the results of single-bundle reconstruction. To date (January 2010), 10 prospective comparative clinical trials (Level I or II) and 1 meta-analysis have been reported comparing single-bundle and anatomic double-bundle reconstructions using hamstring tendons. In 8 of the 10 studies, the anterior and/or rotatory stability of the knee was significantly better with the anatomic double-bundle ACL reconstruction than with the conventional single-bundle reconstruction. However, 1 original trial and the meta-analysis found that there were no differences in the results between the 2 types of reconstructions. Thus the utility of the anatomic double-bundle reconstruction has not yet been established. Our review does show how much evidence exists as to the benefits of double-bundle ACL reconstruction at present.