The pivot-shift phenomenon during computer-assisted anterior cruciate ligament reconstruction

Navigation in anterior cruciate ligament reconstruction: State of the art

Computer navigation (CN) for anterior cruciate ligament (ACL) surgery has been used mainly for two purposes: to enhance the accuracy of tunnel position and to evaluate the kinematics of the ACL reconstruction (ACLR) and the stability achieved by different surgical techniques. Many studies have shown that navigation may improve the accuracy of anatomical tunnel orientation and position during ACL reconstructive surgery compared with normal arthroscopic tunnel placement, especially regarding the femoral side. At the same time, it has become the gold-standard method for intraoperative knee kinematic assessment, as it permits a quantitative multidirectional knee joint laxity evaluation. CN in ACL surgery has been associated with diverse problems. First, in most optic systems additional skin incisions and drill holes in the femoral bone are required for fixation of a reference frame to the femur. Second, additional radiation exposure and extra medical cost to the patient for preoperative planning are usually needed. Third, CN, due to additional steps, has more opportunities for error during preoperative planning, intraoperative registration, and operation. Fourth, soft tissues, including the skin and subcutaneous tissues, are usually not considered during the preoperative planning, which can be a problem for kinematic and stability assessment. Many studies have concluded that ACLR using a CN system is more expensive than conventional surgery, it adds extra time to the surgery and it is not mitigated by better clinical outcomes. This, combined with costs and invasiveness, has limited the use of CN to research-related cases. Future technology should prioritize less invasive intra-operative surgical navigation.

Computer-Assisted Orthopedic and Trauma Surgery

BACKGROUND

There are many ways in which computer-assisted orthopedic and trauma surgery (CAOS) procedures can help surgeons to plan and execute an intervention.

METHODS

This study is based on data derived from a selective search of the literature in the PubMed database, supported by a Google Scholar search.

RESULTS

For most applications the evidence is weak. In no sector did the use of computer-assisted surgery yield any relevant clinical or functional improvement. In trauma surgery, 3D-navigated sacroiliac screw fixation has become clinically established for the treatment of pelvic fractures. One randomized controlled trial showed a reduction in the rate of screw misplacement: 0% with 3D navigation versus 20.4% with the conventional procedure und 16.6% with 2D navigation. Moreover, navigation-assisted pedicle screw stabilization lowers the misplacement rate. In joint replacements, the long-term results showed no difference in respect of clinical/functional scores, the time for which the implant remained in place, or aseptic loosening.

CONCLUSION

Computer-assisted procedures can improve the precision of certain surgical interventions. Particularly in joint replacement and spinal surgery, the research is moving away from navigation in the direction of robotic procedures. Future studies should place greater emphasis on clinical and functional results.

Triaxial accelerometer evaluation is correlated with IKDC grade of pivot shift

PURPOSE

The purpose of this study was to evaluate the correlation between tibial acceleration parameters measured by the KiRA device and the clinical grade of pivot shift. The secondary objective was to report the risk factors for pre-operative high-grade pivot shift.

METHODS

Two-hundred and ninety-five ACL deficient patients were examined under anesthesia. The pivot shift tests were performed twice by an expert surgeon. Clinical grading was performed using the International Knee Documentation Committee (IKDC) scale and tibial acceleration data was recorded using a triaxial accelerometer system (KiRA). The difference in the tibial acceleration range between injured and contralateral limbs was used in the analysis. Correlation coefficients were calculated using linear regression. Multivariate logistic regression was used to identify risk factors for high grade pivot shift.

RESULTS

The clinical grade of pivot shift and the side-to-side difference in delta tibial acceleration determined by KiRA were significantly correlated (r = 0.57; 95% CI 0.513-0.658, p < 0.0001). The only risk factor identified to have a significant association with high grade pivot shift was an antero-posterior side to side laxity difference > 6 mm (OR = 2.070; 95% CI (1.259-3.405), p = 0.0042).

CONCLUSION

Side-to-side difference in tibial acceleration range, as measured by KiRA, is correlated with the IKDC pivot shift grade in anaesthetized patients. Side-to-side A-P laxity difference greater than 6 mm is reported as a newly defined risk factor for high grade pivot shift in the ACL injured knee.

DIAGNOSTIC STUDY

Level II.

Diagnosis and treatment of rotatory knee instability

BACKGROUND

Rotatory knee instability is an abnormal, complex three-dimensional motion that can involve pathology of the anteromedial, anterolateral, posteromedial, and posterolateral ligaments, bony alignment, and menisci. To understand the abnormal joint kinematics in rotatory knee instability, a review of the anatomical structures and their graded role in maintaining rotational stability, the importance of concomitant pathologies, as well as the different components of the knee rotation motion will be presented.

MAIN BODY

The most common instability pattern, anterolateral rotatory knee instability in an anterior cruciate ligament (ACL)-deficient patient, will be discussed in detail. Although intra-articular ACL reconstruction is the gold standard treatment for ACL injury in physically active patients, in some cases current techniques may fail to restore native knee rotatory stability. The wide range of diagnostic options for rotatory knee instability including manual testing, different imaging modalities, static and dynamic measurement, and navigation is outlined. As numerous techniques of extra-articular tenodesis procedures have been described, performed in conjunction with ACL reconstruction, to restore anterolateral knee rotatory stability, a few of these techniques will be described in detail, and discuss the literature concerning their outcome.

CONCLUSION

In summary, the essence of reducing anterolateral rotatory knee instability begins and ends with a well-done, anatomic ACL reconstruction, which may be performed with consideration of extra-articular tenodesis in a select group of patients.

Medial and lateral meniscus have a different role in kinematics of the ACL-deficient knee: a systematic review

Importance

Meniscal tears are frequently associated with anterior cruciate ligament (ACL) injury and the correct management of this kind of lesion during ACL-reconstruction procedure is critical for the restoration of knee kinematics. Although the importance of meniscus in knee biomechanics is generally accepted, the influence of medial and lateral meniscus in stability of ACL-deficient knee is still unclear.

Objective

The aim of this study was to review literature, which analysed effects in cadaveric specimens of meniscal tear and meniscectomy of medial and lateral meniscus on laxity in the ACL-deficient knee.

Evidence review

Authors performed a systematic search for cadaveric studies analysing the effect of medial and lateral meniscus tears or resection on kinematics of ACL-deficient knee. Extracted data included year of publications, number of human cadaver knee specimens, description of apparatus testing and instrumented kinematic evaluation, testing protocol and results.

Findings

Authors identified 18 studies that met inclusion and exclusion criteria of current review. The major finding of the review was that the works included reported a difference role of medial and lateral meniscus in restraining ACL-deficient knee laxity. Medial meniscus tear or resection resulted in a significant increase of anterior tibial displacement. Lateral meniscus lesions or meniscectomy on the other hand significantly increased rotation and translation under a coupled valgus stress and internal-rotation torque/pivot shift test.

Conclusions

Medial and lateral meniscus have a different role in stabilising the ACL-deficient knee: while the medial meniscus functions as a critical secondary stabilisers of anterior tibial translation under an anterior/posterior load, lateral meniscus appears to be a more important restraint of rotational and dynamic laxity.

Level of evidence

Level IV, systematic review of level I–IV studies.

Tibial tunnel placement in anatomic anterior cruciate ligament reconstruction: a comparison study of outcomes between patient-specific drill template versus conventional arthroscopic techniques

INTRODUCTION

Accurate anatomic graft tunnel positioning is essential for the successful application of anatomic anterior cruciate ligament (ACL) reconstruction. The accurate insertion of the tibial tunnel (TT) remains challenging. Here, we explored a novel strategy of patient-specific drill template (PDT) for the placement of TT in ACL reconstruction and assessed its efficacy and accuracy.

MATERIALS AND METHODS

TT placement was randomized and performed by use of the PDT technique in 40 patients (PDT group) and the conventional arthroscopic technique in 38 patients (Arthroscopic group). After surgery, the deviations at the center point of the ACL tibial attachment area and radiological TT positioning were assessed in both groups. The preoperative and follow-up examinations included pivot-shift testing, KT-1000 arthrometer testing, the Lysholm and International Knee Documentation Committee scales were used to compare the knee stability and the functional state.

RESULTS

The ideal center points achieved in the PDT group were more precise than that in the arthroscopic group (p < 0.001). Radiological TT positioning performed by use of the PDT technique was more accurate than that by the arthroscopic technique (p = 0.027). Statistical differences could not be found between the groups in terms of the pivot-shift test, KT-1000 arthrometer laxity measurements, the Lysholm or International Knee Documentation Committee scales. Both groups improved at follow-up compared with the preoperative assessment in terms of the pivot-shift test, the laxity tests, and scoring scales.

CONCLUSIONS

The novel PDT strategy could provide more accurate TT positioning than the traditional arthroscopic technique in ACL reconstruction. However, functional scales and stability tests gave similar results in the PDT and the standard techniques.

LEVEL OF EVIDENCE

I.

Correlation between a 2D simple image analysis method and 3D bony motion during the pivot shift test

BACKGROUND

The pivot shift test is the most specific clinical test to detect anterior cruciate ligament injury. The purpose of this study was to determine the correlation between the 2D simple image analysis method and the 3D bony motion of the knee during the pivot shift test and assess the intra- and inter-examiner agreements.

METHODS

Three orthopedic surgeons performed three trials of the standardized pivot shift test in seven knees. Two devices were used to measure motion of the lateral knee compartment simultaneously: 1) 2D simple image analysis method: translation was determined using a tablet computer with custom motion tracking software that quantified movement of three markers attached to skin over bony landmarks; 2) 3D bony motion: electromagnetic tracking system was used to measure movement of the same bony landmarks.

RESULTS

The 2D simple image analysis method demonstrated a good correlation with the 3D bony motion (Pearson correlation: 0.75, 0.76 and 0.79). The 3D bony translation increased by 2.7 to 3.5 times for every unit increase measured by the 2D simple image analysis method. The mean intra-class correlation coefficients for the three examiners were 0.6 and 0.75, respectively for 3D bony motion and 2D image analyses, while the inter-examiner agreement was 0.65 and 0.73, respectively.

CONCLUSIONS

The 2D simple image analysis method results are related to 3D bony motion of the lateral knee compartment, even with skin artifact present. This technique is a non-invasive and repeatable tool to quantify the motion of the lateral knee compartment during the pivot shift test.

Current use of navigation system in ACL surgery: a historical review

PURPOSE

The present review aims to analyse the available literature regarding the use of navigation systems in ACL reconstructive surgery underling the evolution during the years.

METHODS

A research of indexed scientific papers was performed on PubMed and Cochrane Library database. The research was performed in December 2015 with no publication year restriction. Only English-written papers and related to the terms ACL, NAVIGATION, CAOS and CAS were considered. Two reviewers independently selected only those manuscripts that presented at least the application of navigation system for ACL reconstructive surgery.

RESULTS

One hundred and forty-six of 394 articles were finally selected. In this analysis, it was possible to review the main uses of navigation system in ACL surgery including tunnel positioning for primary and revision surgery and kinematic assessment of knee laxity before and after different surgical procedures. In the early years, until 2006, navigation system was mainly used to improve tunnel positioning, but since the last decade, this tool has been principally used for kinematics evaluation. Increased accuracy of tunnel placement was observed using navigation surgery, especially, regarding femoral, 42 of 146 articles used navigation to guide tunnel positioning. During the following years, 82 of 146 articles have used navigation system to evaluate intraoperative knee kinematic. In particular, the importance of controlling rotatory laxity to achieve better surgical outcomes has been underlined.

CONLUSIONS

Several applications have been described and despite the contribution of navigation systems, its potential uses and theoretical advantages, there are still controversies about its clinical benefit. The present papers summarize the most relevant studies that have used navigation system in ACL reconstruction. In particular, the analysis identified four main applications of the navigation systems during ACL reconstructive surgery have been identified: (1) technical assistance for tunnel placement; (2) improvement in knowledge of the kinematic behaviour of ACL and other structures; (3) comparison of effectiveness of different surgical techniques in controlling laxities; (4) navigation system performance to improve the outcomes of ACL reconstruction and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

Clinical advantages of image-free navigation system using surface-based registration in anatomical anterior cruciate ligament reconstruction

PURPOSE

To evaluate the clinical advantages of a navigation system developed with an emphasis on attaining an appropriate femoral tunnel length and posterior wall margin with no posterior wall blowout, as well as having accurate tunnel positioning, in anatomical anterior cruciate ligament reconstruction (ACLR).

METHODS

Ten freshly frozen human knees were transected at mid-femur and mid-tibia. Each knee specimen underwent arthroscopic single-bundle anterior cruciate ligament reconstruction using the outside-in technique, with two knees by manual ACLR (control group) and another eight knees by only the navigational ACLR without arthroscopic assistance (experimental group). The position/orientation information of tunnel entry point, tunnel length, and posterior wall distance of pre-, intra-, and postoperative tunnel were recorded, and the reliability and errors among them were evaluated.

RESULTS

From comparison of the 3D models for preoperative planning and postoperative reconstruction, the mean differences for navigational femoral tunnelling and arthroscopic-assisted femoral tunnelling were recorded, respectively: (1) tunnel entry position, 1.4 mm (SD 0.3) versus 4.9 mm; (2) tunnel length, 0.7 mm (SD 0.2), similar to 0.6 mm in arthroscopic-assisted femoral tunnelling, and (3) posterior wall distance, 0.5 mm (SD 0.2), much smaller than 4.7 mm for arthroscopic-assisted femoral tunnelling. The intraclass correlation coefficients, calculated to determine the accuracy and reliability of navigational femoral tunnelling, showed excellent internal consistency that ranged from 0.965 to 0.989 for tunnel length and from 0.810 to 0.953 for posterior wall distance.

CONCLUSION

Navigation systems with enhancement of the registration accuracy by the developed system are feasible in anatomical ACLR, in reducing surgical failures such as short tunnel length or posterior wall breakage of distal femur. The present study revealed that computer navigation could aid in avoiding major mistakes in exact positioning and posterior wall blowout and help in attaining appropriate length for femoral tunnelling in anatomical ACLR.

Biomechanics of the anterior cruciate ligament: Physiology, rupture and reconstruction techniques

The influences and mechanisms of the physiology, rupture and reconstruction of the anterior cruciate ligament (ACL) on kinematics and clinical outcomes have been investigated in many biomechanical and clinical studies over the last several decades. The knee is a complex joint with shifting contact points, pressures and axes that are affected when a ligament is injured. The ACL, as one of the intra-articular ligaments, has a strong influence on the resulting kinematics. Often, other meniscal or ligamentous injuries accompany ACL ruptures and further deteriorate the resulting kinematics and clinical outcomes. Knowing the surgical options, anatomic relations and current evidence to restore ACL function and considering the influence of concomitant injuries on resulting kinematics to restore full function can together help to achieve an optimal outcome.

Quantitative comparison of the pivot shift test results before and after anterior cruciate ligament reconstruction by using the three-dimensional electromagnetic measurement system

PURPOSE

Tibial acceleration during the pivot shift test is a potential quantitative parameter to evaluate rotational laxity of anterior cruciate ligament (ACL) insufficiency. However, clinical application of this measurement has not been fully examined. This study aimed to measure and compare tibial acceleration before and after ACL reconstruction (ACLR) in ACL-injured patients. We hypothesized tibial acceleration would be reduced by ACLR and tibial acceleration would be consistent in the same knee at different time points.

METHODS

Seventy ACL-injured patients who underwent ACLR were enrolled. Tibial acceleration during the pivot shift test was measured using an electromagnetic measurement system before ALCR and at the second-look arthroscopy 1 year post-operatively. Tibial acceleration was compared to clinical grading and between ACL-injured/ACL-reconstructed and contralateral knees.

RESULTS

Pre-operative tibial acceleration was increased stepwise with the increase in clinical grading (P < 0.01). Tibial acceleration in ACL-injured knee (1.9 ± 1.2 m/s(2)) was larger than that in the contralateral knee (0.8 ± 0.3 m/s(2), P < 0.01), and reduced to 0.9 ± 0.3 m/s(2) post-operatively (P < 0.01). There was no difference between ACL-reconstructed and contralateral knee (n.s.). Tibial acceleration in contralateral knees was consistent pre- and post-operatively (n.s.).

CONCLUSION

Tibial acceleration measurement demonstrated increased rotational laxity in ACL-injured knees and its reduction by ALCR. Additionally, consistent measurements were obtained in ACL-intact knees at different time points. Therefore, tibial acceleration during the pivot shift test could provide quantitative evaluation of rotational stability before and after ACL reconstruction.

LEVEL OF EVIDENCE

III.

Individualized ACL reconstruction

The pivot shift test is the only physical examination test capable of predicting knee function and osteoarthritis development after an ACL injury. However, because interpretation and performance of the pivot shift are subjective in nature, the validity of the pivot shift is criticized for not providing objective information for a complete surgical planning for the treatment of rotatory knee laxity. The aim of ACL reconstruction was eliminating the pivot shift sign. Many structures and anatomical characteristics can influence the grading of the pivot shift test and are involved in the genesis and magnitude of rotatory instability after an ACL injury. The objective quantification of the pivot shift may be able to categorize knee laxity and provide adequate information on which structures are affected besides the ACL. A new algorithm for rotational instability treatment is presented, accounting for patients' unique anatomical characteristics and objective measurement of the pivot shift sign allowing for an individualized surgical treatment.

LEVEL OF EVIDENCE

V.

Extra-articular ACL Reconstruction and Pivot Shift: In Vivo Dynamic Evaluation With Navigation

BACKGROUND

The pivot-shift test is considered a reliable examination to evaluate the results of anterior cruciate ligament (ACL) reconstruction, as it strongly correlates with patient satisfaction, giving-way episodes, and activity level. The addition of lateral tenodesis (LT) to current techniques of intra-articular reconstruction with a hamstring graft could potentially improve knee laxity in cases of severe rotational instability.

PURPOSE

To biomechanically investigate the effect of intra- and extra-articular ACL reconstructions on knee laxity and the pivot-shift phenomenon.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty patients underwent anatomic single-bundle ACL reconstruction with doubled semitendinosus and gracilis tendons with the addition of extra-articular reconstruction. In patients in group A, intra-articular reconstruction was performed first and LT thereafter; in patients in group B, LT was performed first and intra-articular reconstruction thereafter. A navigator equipped with software designed for both static and dynamic evaluations was used to measure maximum anterior tibial translation (ATT) and axial tibial rotation (ATR) at 30° of flexion (static evaluation) and during the pivot-shift test (dynamic evaluation). Measurements were performed before reconstruction, after the first procedure, and after the second procedure.

RESULTS

For the static evaluation, in group A, the mean ATT significantly decreased from 14.1 ± 3.7 mm in the preoperative (ACL-deficient) condition to 6.0 ± 1.9 mm after ACL reconstruction and to 5.3 ± 1.6 mm after LT. The mean ATR at 30° of knee flexion significantly decreased from 35.7° ± 4.8° to 28.9° ± 4.1° and to 20.9° ± 4.8°, respectively. In group B, the mean ATT significantly decreased from 13.5 ± 6.5 mm in the preoperative (ACL-deficient) condition to 10.2 ± 3.2 mm after LT and to 4.0 ± 1.6 mm after ACL reconstruction. The mean ATR at 30° of knee flexion significantly decreased from 36.7° ± 4.8° to 26.2° ± 6.2° and to 23.5° ± 4.9°, respectively. For the dynamic evaluation (pivot-shift test), in group A, the mean ATT significantly decreased from 15.0 ± 6.8 mm in the preoperative (ACL-deficient) condition to 9.4 ± 6.4 mm after ACL reconstruction and to 8.5 ± 5.4 mm after LT. The mean ATR significantly decreased from 16.9° ± 4.7° to 11.6° ± 4.1° and to 6.1° ± 2.2°, respectively. In group B, the mean ATT significantly decreased from 12.5 ± 3.3 mm in the preoperative (ACL-deficient) condition to 9.1 ± 5.9 mm after LT and to 8.1 ± 5.4 mm after ACL reconstruction. The mean ATR significantly decreased from 16.0° ± 4.5° to 9.2° ± 4.3° and to 7.5° ± 4.0°, respectively.

CONCLUSION/CLINICAL RELEVANCE

Extra-articular reconstruction had little effect in reducing the anterior displacement of the tibia at 30° of flexion, but it was more effective than intra-articular reconstruction in reducing ATR. Anatomic ACL reconstruction and LT were synergic in controlling the pivot-shift phenomenon.

Non-invasive, non-radiological quantificationof anteroposterior knee joint ligamentous laxity: A study in cadavers

OBJECTIVES

We performed in vitro validation of a non-invasive skin-mounted system that could allow quantification of anteroposterior (AP) laxity in the outpatient setting.

METHODS

A total of 12 cadaveric lower limbs were tested with a commercial image-free navigation system using trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° of knee flexion and 100 N of force was applied perpendicular to the tibia. Acceptable coefficient of repeatability (CR) and limits of agreement (LOA) of 3 mm were set based on diagnostic criteria for anterior cruciate ligament (ACL) insufficiency.

RESULTS

Reliability and precision within the individual invasive and non-invasive systems was acceptable throughout the range of flexion tested (intra-class correlation coefficient 0.88, CR 1.6 mm). Agreement between the two systems was acceptable measuring AP laxity between full extension and 40° knee flexion (LOA 2.9 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (LOA > 3 mm).

CONCLUSIONS

These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard validated commercial system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative evaluation of ACL pathology. Cite this article: Bone Joint Res 2013;2:233-7.

Rotatory instability of the knee after ACL tear and reconstruction

Although ACL reconstructions provide satisfactory clinical results nowadays, regardless of the type of graft or the surgical technique used (out-in vs in-out or single- vs double-bundle), the residual rotatory instability which is often detected at clinical follow-ups is still a matter of concern among surgeons. In this paper we try to analyze all the aspects which might contribute to this phenomenon by summarizing the biomechanical functions of the two bundles of the ACL, and by evaluating all the other factors strictly related to the rotatory instability of a reconstructed knee, such as the anatomical positioning of the single- or double-bundle new ACL, or the importance of a valid lateral compartment (LCL, ALTFL). Clinical, biomechanical and cadaver studies are discussed in order to contribute to better understanding of the origin of post-operative residual rotatory instability.

[Evaluation of intraoperative anterior cruciate ligament laxity using a navigation system in the anatomical single bundle reconstruction]

PURPOSE

The anatomical anterior cruciate ligament (ACL) reconstruction attempts to, by reproducing the natural orientation of its fibres, achieve a better rotational stability of the knee. The aim of this paper is to quantify the anteroposterior and rotational laxity of the knee before and after an anatomic ligamentoplasty using the Orthopilot(®) navigation system as a supporting tool. MATHERIAL AND METHOD: We describe the distinctive steps of Orthopilot(®) navigation as well as conducting a retrospective cross-sectional study on a cohort of 20 patients operated in our hospital for chronic primary ACL rupture from january 2010 to may 2011. The precise location of the tunnels was defined with the help of the navigator and the intra-articular landmarks and stability tests were performed in both the sagittal and axial planes.

RESULTS

In our technique for anatomical ACL reconstruction placed the tibial tunnel at a mean distance of 16.8±4.92 mm from the posterior cruciate ligament in a position that represented 44.1%±4.35 of the total width of the tibial plateau. The average distance from the centre of the femoral tunnel to the posterior cortex of the lateral condyle was 7.89±2.78 mm. Intra-operatively and before ACL reconstruction, the mean (±SD) anteroposterior movement, internal rotation and external rotation of the tibia at 30° position were 15.5 mm (±5.11), 19° (±3.62) and 19.65° (±3.26), respectively. After reconstruction these values decreased to 5.6 mm (±1.72°), 12.17° (±3.76) and 16.9° (±4.42), respectively.

CONCLUSIONS

The use of navigation systems supporting the surgery allows the systematic positioning of bone tunnels and standardises the procedures for the desired reconstruction. ACL reconstruction using the technique described, improves the anteroposterior and rotational stability compared to preoperative status, to a stability state that could be considered physiological according to current scientific knowledge.

Quantitative evaluation of the pivot shift by image analysis using the iPad

PURPOSE

To enable comparison of test results, a widely available measurement system for the pivot shift test is needed. Simple image analysis of lateral knee joint translation is one such system that can be installed on a prevalent computer tablet (e.g. iPad). The purpose of this study was to test a novel iPad application to detect the pivot shift. It was hypothesized that the abnormal lateral translation in ACL deficient knees would be detected by the iPad application.

METHODS

Thirty-four consecutive ACL deficient patients were tested. Three skin markers were attached on the following bony landmarks: (1) Gerdy's tubercle, (2) fibular head and (3) lateral epicondyle. A standardized pivot shift test was performed under anaesthesia, while the lateral side of the knee joint was monitored. The recorded movie was processed by the iPad application to measure the lateral translation of the knee joint. Lateral translation was compared between knees with different pivot shift grades.

RESULTS

Valid data sets were obtained in 20 (59 %) ACL deficient knees. The remaining 14 data sets were invalid because of failure to detect translation or detection of excessive translation. ACL deficient knees had larger lateral translation than the contra-lateral knees (p < 0.01). In the 20 valid data sets, which were graded as either grade 1 (n = 10) or grade 2 (n = 10), lateral translation was significantly larger in the grade 2 pivot shift (3.6 ± 1.2 mm) than the grade 1 pivot shift (2.7 ± 0.6 mm, p < 0.05).

CONCLUSION

Although some technical corrections, such as testing manoeuvre and recording procedure, are needed to improve the image data sampling using the iPad application, the potential of the iPad application to classify the pivot shift was demonstrated.

Dynamic evaluation of pivot-shift kinematics in physeal-sparing pediatric anterior cruciate ligament reconstruction techniques

BACKGROUND

Conventional transphyseal anterior cruciate ligament (ACL) reconstruction techniques in skeletally immature patients have been questioned because of potential physeal injuries. Consequently, multiple alternative reconstruction options have been described to restore stability while sparing the physes in the skeletally immature patient.

HYPOTHESIS

All pediatric reconstruction techniques will restore knee stability to intact levels, and the knee stability index (KSI) will discriminate stability patterns between reconstruction techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

A novel mechanical pivot-shift device (MPSD) that consistently applies dynamic loads to cadaveric knees was used to study the effect of different physeal-sparing ACL reconstruction techniques on knee stability. Six adult cadaveric fresh-frozen knees were used. All knees were tested with 3 physeal-sparing reconstruction techniques: all epiphyseal (AE), transtibial over the top (TT), and iliotibial band (ITB). The MPSD was used to consistently perform a simulated pivot-shift maneuver. Tibial anterior displacement (AD), internal rotation (IR), posterior translational velocity (PTV), and external rotational velocity (ERV) were recorded using an Optotrak navigation system. The KSI (score range, 0-100; 0 = intact knee) was quantified using a regression analysis of AD, IR, PTV, and ERV. Repeated-measures analysis of variance and logistic regression were used for comparison of kinematics and derivation of KSI coefficients, respectively.

RESULTS

ACL deficiency resulted in an increase of 20% to 115% in all primary stability measures tested compared with the ACL-intact state. All reconstructions resulted in a decrease in ADmax and IRmax as well as PTVmax and ERVmax to within intact ranges, indicating that all reconstructions do improve stability compared with the ACL-deficient state. The ITB reconstruction overconstrained AD and IR by 38% and 52%, respectively. The mean (±SD) KSI for the ACL-deficient state was 61.7 ± 22.2 (range, 47-100), while the ITB reconstruction had a mean KSI of 0.82 ± 24.0 (range, -24 to 35), the TT reconstruction had a mean KSI of 13.3 ± 8.9 (range, 0.3-23), and the AE reconstruction had a mean KSI of -4.0 ± 15.2 (range, -24 to 14). The KSI was not significantly different between reconstructions, and all were significantly lower than the ACL-deficient state (P < .0001).

CONCLUSION

Although all reconstruction techniques tested were able to partially stabilize an ACL-deficient knee, the AE reconstruction was most effective in restoring native knee kinematics under dynamic loading conditions that mimic the pivot-shift test.

CLINICAL RELEVANCE

This study provides orthopaedic surgeons with objective dynamic rotational data on the ability of physeal-sparing ACL reconstructions to better determine the ideal technique for ACL construction in skeletally immature patients.

Innovative technology for knee laxity evaluation: clinical applicability and reliability of inertial sensors for quantitative analysis of the pivot-shift test

There has been an increased interest in the quantification of the knee laxity secondary to anterior cruciate ligament (ACL) injury. In clinical practice, the diagnosis is performed by clinical examination and magnetic resonance imaging analysis and confirmed arthroscopically. The pivot shift phenomenon has been identified as one of the essential signs of functional ACL insufficiency. A reliable system to adequately assess patients with ACL injury, quantifying the pivot shift test outcome, is needed. Several studies have been conducted in this regard but the proposed methods remain confined to a research area. The goal of this article is to summarize the actual knowledge and current concepts.

Influence of the valgus force during knee flexion in neutral rotation

PURPOSE

The pivot shift test is generally accepted to be a clinically useful tool. In the current study, the authors aimed to determine the minimum amount of valgus force required to elicit a positive pivot shift test utilizing a mechanized pivot shifter device in ACL-deficient knees. The authors proposed that increasing the applied force from a minimum critical value would lead to greater magnitudes of femoro-tibial translation.

MATERIALS AND METHODS

Six fresh-frozen pelvis-to-toes specimens were used in this cadaveric study. Tracking and recording of tibiofemoral kinematics during throughout testing was achieved by an image-free surgical navigation system with dedicated ACL software. A load cell was attached to the mechanized pivot shifter through a three-degree-of-freedom arm. Valgus force magnitudes of 0-5 kg were then sequentially applied, and knee flexion in neutral rotation was performed on the ACL-deficient knees. A total of two trials were performed for each force.

RESULTS

The greatest difference in lateral and medial compartment translation, during the pivot shift test, utilizing a mechanized pivot shifter in an ACL-deficient knee, was measured between an applied valgus force of 0 and 1 kg. The mean difference between 4 and 5 kg was 0.2 mm (CI = -11.29 to 10.89) for the lateral compartment, and there was no difference in translation for the medial compartment (CI = -17.43 to 17.43).

CONCLUSIONS

The principal finding of the current study was that a greater force does not produce a greater magnitude of femoro-tibial translation during knee flexion in neutral rotation, contrary to the initial hypothesis.

Effect of tibial slope on the stability of the anterior cruciate ligament-deficient knee

PURPOSE

We aimed to quantify the effect of changes in tibial slope on the magnitude of anterior tibial translation (ATT) in the anterior cruciate ligament (ACL)-deficient knee during the Lachman and mechanized pivot shift tests. We hypothesized that increased posterior tibial slope would increase the amount of ATT of an ACL-deficient knee, while leveling the slope of the tibial plateau would decrease the amount of ATT.

METHODS

Lachman and mechanized pivot shift tests were performed on hip-to-toe cadaveric specimens, and ATT of the lateral and the medial compartments was measured using navigation (n = 11). The ACL was then sectioned. Stability testing was repeated, and ATT was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5 or -5° of tibial slope variation after which stability testing was repeated (n = 10).

RESULTS

Sectioning the ACL resulted in a significant increase in ATT in both the Lachman and mechanized pivot shift tests (P < 0.05). Increasing or decreasing the slope of the tibial plateau had no effect on ATT during the Lachman test (n.s.). During the mechanized pivot shift tests, a 5° increase in posterior slope resulted in a significant increase in ATT compared to the native knee (P < 0.05), while a 5° decrease in slope reduced ATT to a level similar to that of the intact knee.

CONCLUSIONS

Tibial slope changes did not affect the magnitude of translation during a Lachman test. However, large changes in tibial slope variation affected the magnitude of the pivot shift.

The effect of proximal tibial slope on dynamic stability testing of the posterior cruciate ligament- and posterolateral corner-deficient knee

BACKGROUND

Proximal tibial slope has been shown to influence anteroposterior translation and tibial resting point in the posterior cruciate ligament (PCL)-deficient knee. The effect of proximal tibial slope on rotational stability of the knee is unknown.

HYPOTHESIS

Change in proximal tibial slope produced via osteotomy can influence both static translation and dynamic rotational kinematics in the PCL/posterolateral corner (PLC)-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Posterior drawer, dial, and mechanized reverse pivot-shift (RPS) tests were performed on hip-to-toe specimens and translation of the lateral and medial compartments measured utilizing navigation (n = 10). The PCL and structures of the PLC were then sectioned. Stability testing was repeated, and compartmental translation was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5° or -5° of tibial slope variation, after which stability testing was repeated (n = 10). Analysis was performed using 1-way analysis of variance (ANOVA; α = .05).

RESULTS

Combined sectioning of the PCL and PLC structures resulted in a 10.5-mm increase in the posterior drawer, 15.5-mm increase in the dial test at 30°, 14.5-mm increase in the dial test at 90°, and 17.9-mm increase in the RPS (vs intact; P < .05). Increasing the posterior slope (high tibial osteotomy [HTO] +5°) in the PCL/PLC-deficient knee reduced medial compartment translation by 3.3 mm during posterior drawer (vs deficient; P < .05) but had no significant effect on the dial test at 30°, dial test at 90°, or RPS. Conversely, reversing the slope (HTO -5°) caused a 4.8-mm increase in medial compartment translation (vs deficient state; P < .05) during posterior drawer and an 8.6-mm increase in lateral compartment translation and 9.0-mm increase in medial compartment translation during RPS (vs deficient state; P < .05).

CONCLUSION

Increasing posterior tibial slope diminished static posterior instability of the PCL/PLC-deficient knee as measured by the posterior drawer test but had little effect on rotational or dynamic multiplanar stability as assessed by the dial and RPS tests, respectively. Conversely, decreasing posterior slope resulted in increased posterior instability and a significant increase in the magnitude of the RPS.

CLINICAL RELEVANCE

These results suggest that increasing posterior tibial slope may improve sagittal stability in the PCL/PLC-deficient knee. Moreover, a knee with diminished posterior tibial slope may demonstrate greater multiplanar instability in this setting. Consequently, proximal tibial slope should be considered when treating combined PCL/PLC injuries of the knee.

Navigated knee kinematics after cutting of the ACL and its secondary restraint

PURPOSE

The purpose of this study is to evaluate the kinematics changes of the knee after cutting of the ACL with or without injury of the anterolateral structures.

METHODS

In this study, the role of the ACL and one of the secondary restraints in controlling knee stability using a navigation system was evaluated. The kinematics of the knee was evaluated in different conditions of instability: ACL intact, after dissection of the posterolateral (PL) bundle, after dissection of the anteromedial (AM) bundle, and after lesion of the lateral capsular ligament (LCL). Anterior tibial translation and rotation were measured with a computer navigation system in 10 fresh-frozen cadaveric knees by use of a manual maximum load. Anterior translation was evaluated at 30°, 60°, and 90° of flexion; rotation at 0°, 15°, 30°, 45°, 60°, and 90°.

RESULTS

Cutting the PL bundle does not increase anterior translation and rotation of the knee. Cutting the AM bundle significantly increased the anteroposterior (AP) translation at 30° and 60° (P = 0.01), but does not increase rotation of the knee. Cutting the LCL increased anterior translation at 60° (P = 0.04) and rotation at 30°, 45°, and 60° (P = 0.03).

CONCLUSIONS

Within the testing conditions of this study, the PL bundle does not affect anterior translation and rotation of the knee; the AM bundle is the primary restraint of the anterior translation but does not affect rotation of the knee while the lesion of the LCL increases tibial rotation and could be related to the pivot shift phenomenon, so it is more correct and biomechanical valid to assess and repair the associated lesion of the antero-lateral structure of the knee at the time of ACL surgery.

Standardized pivot shift test improves measurement accuracy

PURPOSE

The variability of the pivot shift test techniques greatly interferes with achieving a quantitative and generally comparable measurement. The purpose of this study was to compare the variation of the quantitative pivot shift measurements with different surgeons' preferred techniques to a standardized technique. The hypothesis was that standardizing the pivot shift test would improve consistency in the quantitative evaluation when compared with surgeon-specific techniques.

METHODS

A whole lower body cadaveric specimen was prepared to have a low-grade pivot shift on one side and high-grade pivot shift on the other side. Twelve expert surgeons performed the pivot shift test using (1) their preferred technique and (2) a standardized technique. Electromagnetic tracking was utilized to measure anterior tibial translation and acceleration of the reduction during the pivot shift test. The variation of the measurement was compared between the surgeons' preferred technique and the standardized technique.

RESULTS

The anterior tibial translation during pivot shift test was similar between using surgeons' preferred technique (left 24.0 ± 4.3 mm; right 15.5 ± 3.8 mm) and using standardized technique (left 25.1 ± 3.2 mm; right 15.6 ± 4.0 mm; n.s.). However, the variation in acceleration was significantly smaller with the standardized technique (left 3.0 ± 1.3 mm/s(2); right 2.5 ± 0.7 mm/s(2)) compared with the surgeons' preferred technique (left 4.3 ± 3.3 mm/s(2); right 3.4 ± 2.3 mm/s(2); both P < 0.01).

CONCLUSION

Standardizing the pivot shift test maneuver provides a more consistent quantitative evaluation and may be helpful in designing future multicenter clinical outcome trials.

LEVEL OF EVIDENCE

Diagnostic study, Level I.

Kinematic predictors of subjective outcome after anterior cruciate ligament reconstruction: an in vivo motion analysis study

PURPOSE

The purpose of this study was to test whether rotational knee kinematics during dynamic pivoting activities are predictive of subjective functional outcome (IKDC, Lysholm), objective laxity scores (KT max), and activity levels (Tegner) in patients after anterior cruciate ligament reconstruction (ACLR).

METHODS

Thirty-one patients with single-bundle ACLR were evaluated prospectively with 3D-motion analysis during (1) descending a stairway and pivoting and (2) landing from a jump and pivoting. The side-to-side difference of tibial rotation range of motion (SSDTR) between the ACLR and the contralateral intact knee was calculated for the pivoting phase of each task. Linear regression models were applied with SSDTR, for each task predictors of the subjective IKDC score, Lysholm score, anterior tibial translation, and Tegner activity level.

RESULTS

SSDTR for descending and landing were predictive of the IKDC subjective score (R(2) = 0.46, p < 0.001 and R(2) = 0.40, p < 0.001, respectively) with "medium" effect sizes and of the Lysholm score (R(2) = 0.13, p < 0.05 and R(2) = 0.09, n.s.) with "small" to "none" effect sizes. SSDTR was not predictive of anterior translation or Tegner activity level (n.s.).

CONCLUSIONS

Restoring rotational kinematics during dynamic pivoting activities after ACLR is predictive of functional outcome. The ability of the athlete after ACLR to control tibial rotation during pivoting activities may be predictive of functional outcome.

LEVEL OF EVIDENCE

Case series study. Level IV.

Quantitative assessment of pivot-shift using inertial sensors

PURPOSE

The pivot-shift phenomenon has been identified to be one of the essential signs of functional anterior cruciate ligament (ACL) insufficiency. However, the pivot-shift test remains a surgeon-subjective examination, lacking a general recognized quantitative measurement. The goal of the present study was to validate the use of an inertial sensor for quantifying the pivot-shift test, using a commercial navigation system.

METHODS

An expert surgeon intra-operatively performed the pivot-shift test on 15 consecutive patients before ACL reconstruction. A single accelerometer and a commercial navigation system simultaneously acquired limb kinematics. An additional optical tracker mounted on the accelerometer allowed following sensor movements. Anteroposterior (a-p) tibial acceleration obtained with the navigation system was compared with three-dimensional (3D) acceleration acquired by the accelerometer. The effect of skin artifacts and test-retest positioning were estimated. Repeatability of the acceleration parameter and waveform was analyzed. Correlation between the two measurements was also assessed.

RESULTS

Average root mean square (RMS) error in test-retest positioning reported a good value of 5.5 ± 2.9 mm. Mean RMS displacement due to soft tissue artifacts was 4.9 ± 2.6 mm. The analysis of acceleration range repetitions reported a good intra-tester repeatability (Cronbach's alpha = 0.86). Inter-patients similarity analysis showed a mean acceleration waveform correlation of 0.88 ± 0.14. The acceleration ranges demonstrated a good positive correlation between the two measurements (rs = 0.72, P < 0.05).

CONCLUSION

This study showed good reliability of the new device and good correlation with the navigation system results. Therefore, the accelerometer is a valid method to assess dynamic joint laxity.

LEVEL OF EVIDENCE

II.

Comparison of three non-invasive quantitative measurement systems for the pivot shift test

PURPOSE

The purpose of this study was to evaluate three different non-invasive measuring devices for the pivot shift phenomenon with reference to direct bony movement measured by an electromagnetic device rigidly attached to the tibia and femur.

METHODS

A lower body cadaveric specimen was prepared to create a positive pivot shift in both knees. Twelve expert knee surgeons from worldwide performed their preferred pivot shift technique three times in each knee. After watching an instructional video, the examiners used a standardized technique to perform three additional pivot shift maneuvers in each knee. An electromagnetic tracking system, rigidly attached to femur and tibia, was used to provide reference measurements during the pivot shift test. Three different devices were correlated to the reference method and evaluated in this study: (1) Electromagnetic tracking system with skin sensors; (2) Triaxial accelerometer system; (3) Simple image analysis.

RESULTS

When results from both pivot shift techniques (preferred and standardized) were combined, the electromagnetic tracking system with skin sensors showed positive correlation with the reference measurement for acceleration and translation parameters (r = 0.88 and r = 0.67, respectively; both P < 0.01); The triaxial accelerometer system demonstrated good correlation with the reference measurement for acceleration (r = 0.75; P < 0.001). The image analysis system was poorly correlated to the translation of the reference measurement (r = 0.24; P < 0.01).

CONCLUSION

The electromagnetic tracking system with skin sensors provided the best correlation with the reference method. The triaxial accelerometer showed also a good correlation and the image analysis system showed a positive, but poor correlation with the reference method. More research is needed in order to validate simple and non-invasive devices for clinical application.

Does computer navigation system really improve early clinical outcomes after anterior cruciate ligament reconstruction? A meta-analysis and systematic review of randomized controlled trials

Inaccurate tunnel placement is an important cause of failure in conventional anterior cruciate ligament (ACL) reconstruction. Controversy currently exists over the usefulness of computer-assisted navigation systems in addressing this problem. Five randomized or quasi-randomized, controlled trials comparing computer-navigated versus conventional technique in ACL reconstructions until December 1, 2009 were identified through a systematical database search. The clinical outcomes of the trials were analyzed by Lachman test, pivot-shift test, International Knee Documentation Committee knee score, Lysholm score, and Tegner score. Mean difference or risk ratio with 95% confidence interval was calculated using a fixed-effects or random-effects model. Heterogeneity across the studies was also assessed. We found that the use of computer-assisted navigation systems led to additional operative time (8-17min). No significant differences between computer-navigated and conventional groups were found in terms of knee stability and functional assessment during short-term follow-up. The role of computer-assisted navigation systems on clinical performance and longevity needs further investigation in large sample, long-term randomized trials.

Posterior cruciate ligament and posterolateral corner deficiency results in a reverse pivot shift

BACKGROUND

As measured via static stability tests, the PCL is the dominant restraint to posterior tibial translation while the posterolateral corner is the dominant restraint to external tibial rotation. However, these uniplanar static tests may not predict multiplanar instability. The reverse pivot shift is a dynamic examination maneuver that may identify complex knee instability.

QUESTIONS/PURPOSES

In this cadaver study, we asked whether (1) isolated sectioning or (2) combined sectioning of the PCL and posterolateral corner increased the magnitude of the reverse pivot shift and (3) the magnitude of the reverse pivot shift correlated with static external rotation or posterior drawer testing.

METHODS

In Group I, we sectioned the PCL followed by structures of the posterolateral corner. In Group II, we sectioned the posterolateral corner structures before sectioning the PCL. We performed posterior drawer, external rotation tests, and mechanized reverse pivot shift for each specimen under each condition and measured translations via navigation.

RESULTS

Isolated sectioning of the PCL or posterolateral corner had no effect on the reverse pivot shift. Conversely, combined sectioning of the PCL and posterolateral corner structures increased the magnitude of the reverse pivot shift. The magnitude of the reverse pivot shift correlated with the posterior drawer and external rotation tests.

CONCLUSIONS

Combined sectioning of the PCL and posterolateral corner was required to cause an increase in the magnitude of the mechanized reverse pivot shift. The reverse pivot shift correlated with both static measures of stability.

CLINICAL RELEVANCE

Combined injury to the PCL and posterolateral corner should be considered in the presence of a positive reverse pivot shift.

Software for compartmental translation analysis and virtual three-dimensional visualization of the pivot shift phenomenon

Anterior cruciate ligament (ACL) injury may cause knee instability and may result in damage to the menisci and the articular cartilage. The pivot shift test is commonly used to identify rotational instability of the knee following injury to the ACL. The magnitude of lateral compartment translation correlates well with the grade of the pivot shift. However, commonly used navigation systems do not readily provide individualized compartmental translation. We aimed to develop software to (a) quantify individual medial and lateral compartmental translation in the knee during the pivot shift test, and (b) generate animated three-dimensional renderings of recorded pivot shift examinations. Twelve paired cadaveric knees were used to test the software. Three mechanized pivot shift tests were performed on each knee with the ACL intact and again after sectioning the ACL. Using the Pivot Shift Processor, we successfully analyzed the data recorded using the navigation system. After sectioning the ACL, there was a greater increase in tibiofemoral translation in the lateral compartment compared to the medial compartment. The Pivot Shift Visualizer successfully produced a 3D rendering of the knee joint and the recorded pivot shift maneuvers. This virtual representation of the pivot shift phenomenon from multiple points of view allows for efficient side-by-side comparison of tibiofemoral motion tracking across conditions, which is not possible in the in vivo / in vitro settings. This, in turn, could lead to a better understanding of the kinematics in play during the pivot shift phenomenon.

An image analysis method to quantify the lateral pivot shift test

PURPOSE

Although various kinematic measurements with advanced technology have been used for quantitative evaluation of the pivot shift test, there is no clinically available quantification method of the pivot shift test. The purpose was to describe a novel image analysis technique for quantitative assessment of the pivot shift test using universally available and affordable devices.

METHODS

Five ACL deficient knees were tested during examination under anesthesia. Three skin markers were attached to bony landmarks on the lateral side of the knee joint, (1) Gerdy's tubercle, (2) fibular head, and (3) lateral epicondyle. A standard digital video camera captured motion of the lateral aspect of the knee during the pivot shift test. The image was processed into a 2-dimensional (2-D) coordinate system with Image J software (National Institute of Health, USA) to trace the three landmarks. The anteroposterior (AP) position of the femur was calculated on consecutive still images extracted from the video recording. AP translation over time was reported.

RESULTS

The reduction phase of the pivot shift could be tracked consistently by a sudden anterior translation of the distal femur. The sudden anterior translation of the lateral epicondyle was on average 3.7 ± 2.1 mm and occurred within 0.2 ± 0.1 s from the start of this anterior translation till the end.

CONCLUSION

The sudden shift of the lateral compartment of the knee joint was successfully detected by this newly developed image analysis measurement method. This image analysis technique facilitates a simple and affordable method to evaluate the lateral pivot shift test.

LEVEL OF EVIDENCE

Diagnostic studies, Level IV.

Similarities and differences of diagnostic manual tests for anterior cruciate ligament insufficiency: a global survey and kinematics assessment

BACKGROUND

The Lachman and pivot-shift tests are 2 standard manual tests to diagnose anterior cruciate ligament (ACL) insufficiency. However, the global variation of these testing procedures is not known.

PURPOSE

To survey currently used testing techniques and to measure the knee movement during manual tests among various expert surgeons from across the globe.

STUDY DESIGN

Controlled laboratory study.

METHODS

Part 1: descriptive survey. A questionnaire asking about testing procedures of Lachman and pivot-shift tests was conducted among 33 ACL surgeons. Part 2: knee kinematics comparison. Lachman and pivot-shift tests were performed on a unilateral ACL-injured patient by 5 surgeons, while knee kinematics was recorded by an electromagnetic system. Tibial translation was measured during the Lachman test, while tibial translation, rotation, and pivot-shift acceleration were calculated during the pivot-shift test.

RESULTS

Part 1: Tibial anterior drawer by a medially placed hand was widely advocated for the Lachman test. Flexion type of the pivot-shift test maneuver was supported by two thirds, while extension type was supported by one third. However, the "feeling" of subluxation or reduction during the pivot shift was the primary evaluation method used by the vast majority of surgeons. Part 2: Increased tibial translation during the Lachman test was observed in the ACL-injured knee with significant variation between examiners (P < .01). Tibial translation and pivot-shift acceleration during the pivot-shift test increased in the ACL-injured side (P < .01), but tibial rotation was too diverse to find any trend (P = .31). Tibial translation and acceleration of the pivot shift in the ACL-injured knee showed no significant difference between examiners (P > .05).

CONCLUSION

The Lachman test can display a wide variation of actual movement despite maneuver similarity, while the pivot-shift test could possibly be measurable by tibial translation and/or acceleration beyond their procedural variation.

CLINICAL RELEVANCE

We should recognize the limitations of these manual tests and the possibilities of their objective measurement.

Anterior cruciate ligament reconstruction after unicompartmental knee arthroplasty

PURPOSE

ACL deficiency may cause abnormal knee kinematics and is associated with a tenfold increase in surgical failures after unicompartmental knee arthroplasty, such as aseptic loosening of the tibial compartment and medial bearing instability. The current investigators hypothesized that in a knee with UKA, single-bundle ACL reconstruction would restore tibiofemoral translation to levels similar to those of the intact ACL.

METHODS

Two fresh frozen pelvis-to-toes specimens (four paired knees) were used. On each knee, medial unicompartmental knee arthroplasty was performed by a single surgeon. ACL reconstructions were performed by conventional single-bundle technique. Three trials of Lachman and pivot shift tests were performed and recorded for each knee with the ACL-intact, after sectioning the ACL and after single-bundle ACL reconstruction. A mechanized pivot shifter was used to perform the pivot shift maneuvers. A surgical navigation system (Praxim Grenoble, France) simultaneously tracked tibiofemoral kinematics.

RESULTS

There was a significant difference in lateral compartment translation during the Lachman and pivot shift tests between the ACL-intact/UKA knee and the ACL-deficient/UKA knee (P < 0.05). There was no significant difference in lateral compartment translation during the Lachman and pivot shift tests between the intact/UKA knee and the ACL-reconstructed/UKA knee (n.s.).

CONCLUSIONS

For both the Lachman test and the pivot shift test, single-bundle ACL reconstruction restored kinematics in the UKA knee to magnitudes similar to those in the ACL-intact knee.

Morphometric analysis and functional correlation of tibial and femoral footprints in anatomical and single bundle reconstructions of the anterior cruciate ligament of the knee

INTRODUCTION

The anterior cruciate ligament (ACL) is composed of an infinite number of fibers whose individual anatomical and biomechanical features have been well defined. Although numerous biomechanical studies have shown that reconstruction that is as anatomical as possible results in better control of rotational laxity, very few studies have investigated the surface area of tibial and femoral insertion sites in these reconstructions. The aim of this study was to compare the surface areas of tibial and femoral insertion sites in single and double bundle reconstructions and correlate these findings with the isometry profile obtained. Our hypothesis was that double bundle (DB) reconstruction results in better filling of the native ACL footprint thus increasing the biomechanical value of available graft tissue.

PATIENTS AND METHODS

Forty-six patients underwent computer navigated ACL using hamstring tendons: 23 underwent single bundle (SB) and 23 DB reconstruction. The Praxim navigation station equipped with ACL logics software made it possible to digitize insertion site footprints, register perioperative data for graft position as well as anteroposterior and rotational laxities and pivot shift.

RESULTS

There was a statistically significant difference between the two groups for tibial and femoral insertion site surface areas: 71 mm(2) ± 17 (SB) versus 99.9 mm(2) ± 30 (DB) for the tibia, 67 ± 11 mm(2) (SB) versus 96.9 mm(2) ± 28 (DB) for the femur. Isometry profiles showed that anisometry was favorable in all cases: 2.5 mm ± 2 for SB; 2.9 mm ± 2 for the anteromedial bundle (AMB) with DB and 9.6 mm ± 3.7 for the posterolateral bundle. When both groups were combined, there was a statistically significant correlation between the size of tibial insertion surface area and anteroposterior and rotational laxity.

DISCUSSION

This study confirms that better filling of native ACL footprint surface areas results in better control of anteroposterior laxity.

LEVEL OF EVIDENCE

Level IV.

Analysis of anatomic positioning in computer-assisted and conventional anterior cruciate ligament reconstruction

INTRODUCTION

Anterior cruciate ligament (ACL) reconstruction should be anatomic while achieving favorable anisometric behavior to avoid impingement with the femoral notch. Computerization enables these biomechanical conditions to be optimally fulfilled; but what of anatomic positioning? The present study compared the positioning of tibial and femoral tunnels, drilled using either a conventional ACL guide or a navigation system, using the anatomic foot-print areas of the native ACL.

MATERIAL AND METHODS

This cadaver study used computerized recording to compare tibial and femoral ACL attachment areas to the positioning of tunnels created either conventionally or under computer-guided navigation.

RESULTS

Computer guidance enabled the tibial and femoral tunnels to be systematically positioned within the anatomic area and, as regards the tibial area, within the anterior third near to the medial tibial spine, without femoral notch impingement. Anisometry was in all cases favorable, at a mean 3.3 ± 0.7 mm; using a conventional guide, anisometry was favorable in only 50% of cases, at a mean 5.4 ± 1.2 mm.

CONCLUSION

Computer-guided navigation ensured implant positioning within the so-called anatomometric area of the native ACL attachment, avoiding impingement with the femoral notch.

LEVEL OF EVIDENCE

Level 2.

Intraoperative comparisons of knee kinematics of double-bundle versus single-bundle anterior cruciate ligament reconstruction

PURPOSE

Based on biomechanical anatomical studies, double-bundle reconstruction of the anterior cruciate ligament (ACL) was introduced to achieve better stability in the knee, particularly in respect of rotatory loads. An in vivo, computer-assisted, double-bundle (DB) ACL reconstruction is superior to a single-bundle (SB) ACL reconstruction at reducing rotatory, and AP laxities of the tibia at 20 degrees of knee flexion and also during the pivot shift test.

METHODS

The data of 63 patients who had ACL reconstruction were prospectively collected. Thirty-two patients had single-bundle reconstruction (SB group), and 31 received double-bundle reconstruction (DB group). The per-operative navigation system (Praxim ACL surgetics System) helped to search for a minimal anisometry profile of the grafts, which was favorable (graft loosened with flexion) in the anatomic area of ACL insertion and preventing any conflict between the graft and the femoral notch. The system also evaluated anteroposterior (AP) rotational stabilities and pivot shift. The value of the pivot shift was calculated from the values of the maximum rotation and AP translation obtained when performing the manoeuver before and after ACL reconstruction, comparing SB and DB reconstruction.

RESULTS

The post-operative AP displacement of the lateral compartment during the Lachman test was statistically reduced in DB group in comparison with SB group (5.1 ± 4.4 mm vs. 7.1 ± 3.2 mm, P = 0.04), whereas the AP displacements of the medial compartment were also reduced (3.4 ± 3.7 mm vs. 4.5 ± 2.6 mm, P = 0.15) but with no statistical significance. Internal and external rotations at 20° of knee flexion were lower in the DB group than in SB group with statistical significance (respectively, 13.2 ± 4.9° vs. 17.5 ± 4.0°, P < 0.001 and 9.1 ± 3.6° vs. 11.5 ± 3.5°, P = 0.01). During the pivot shift test, the post-operative AP maximal translation was statistically different in both groups: 4.5 ± 2.1 mm in DB group and 6.3 ± 2.7 mm in SB group (P = 0.01)), whereas the maximal rotation was not statistically different: 3.8 ± 2.5° in DB group and 3.4 ± 1.2° in SB group (n.s.). Therefore, Colombet's index was similar in DB group and SB group (respectively, 0.21 ± 0.16 and 0.17 ± 0.06, (n.s.)).

CONCLUSIONS

This study shows a significant intraoperative advantage in anterior and rotational stability for four-tunnel DB ACL reconstruction compared with SB ACL reconstruction.

LEVEL OF EVIDENCE

II.

Double-bundle and double-tunnel ACL reconstruction with looped proximal tibial fixation

Double-bundle anterior cruciate ligament (ACL) reconstruction can be demanding and time consuming and requires twice as many implants, increasing both costs and possible complications. In this article, we present a new approach to double bundle ACL reconstruction: a biological fixation of the tibial side by means of a double tunnel and a U-shape passage of an anterior tibialis allograft, fixed into a double tunnel on the femoral condyle with 2 interference bioabsorbable screws. The technique is designed to combine 2 known procedures for the regular knee surgeon: the mono-tunnel technique and the medial-portal approach.

A mechanized and standardized pivot shifter: technical description and first evaluation

PURPOSE

The pivot shift test (PST) is a complex, multiplanar maneuver used to assess rotatory instability of the knee. The grading is subjective due to the broad range of examination techniques and lack of tibiofemoral motion quantification. The goal of this study was to develop and evaluate a mechanized device for quantitative assessment of the PST.

METHODS

We constructed a mechanized pivot shifter (MPS). In five cadaveric hip-to-toes specimens, the anterior cruciate ligament was resected. We used a surgical navigation system for acquisition of the tibiofemoral motion path during the PST. Two sets of measurements were obtained for the MPS and for two examiners performing the manual technique.

RESULTS

Mean lateral compartment translation magnitudes for each MPS measurement were 13.5 mm (σ = 6.7) and 13.6 mm (σ = 6.7). For examiner 1, 14.9 mm (σ = 6.5) and 15.7 mm (σ = 6.3). For examiner 2, 16.9 mm (σ = 6.3) and 16.1 mm (σ = 5.2). Differences were not significant (n.s.). The MPS had narrower limits of agreement than both examiner 1 and examiner 2.

CONCLUSION

The MPS demonstrated no significant differences in the tibiofemoral translation magnitudes compared to the manual technique. It resulted in better test-retest reliability and more consistent measurements of tibiofemoral translation when compared to manual PST. The high repeatability factor conferred by the MPS is a clinical advantage.

Effect of tibial tunnel position on stability of the knee after anterior cruciate ligament reconstruction: is the tibial tunnel position most important?

BACKGROUND

Minimal attention has been directed toward tibial tunnel position and the native tibial anterior cruciate ligament (ACL) footprint.

PURPOSE

To evaluate the effect of tibial tunnel position on restoration of knee kinematics and stability after ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten paired cadaveric knees were subjected to biomechanical testing (standardized Lachman and mechanized pivot-shift examination). With each maneuver, a computer-assisted navigation system recorded the 3-dimensional motion path of a tracked point at the center of the tibia, medial tibial plateau, and lateral tibial plateau. The testing protocol consisted of evaluation in the intact state and after complete ACL transection, after ACL transection with bilateral meniscectomy, and after ACL reconstruction using 3 tibial tunnel positions--over the top (OTT), anterior footprint (AT), and posterior footprint (PT)--with a standard femoral socket placed in the center of the femoral footprint. Repeated-measures analysis of variance with a post hoc Tukey test compared measured translations with each condition.

RESULTS

A significant difference in anterior translation was seen with Lachman examination between the ACL-deficient condition and both the OTT and AT reconstructions, but no significant difference was observed between the ACL-deficient and PT reconstruction. The OTT and AT constructs were significantly better in limiting anterior translation of the lateral compartment compared with the PT ACL reconstruction during a pivot-shift maneuver in the ACL- and meniscal-deficient knee. However, anteriorizing the tibial position was accompanied by a correspondingly greater risk and magnitude of graft impingement in extension.

CLINICAL RELEVANCE

The OTT and anterior tibial tunnel positions better control the Lachman and the pivot shift compared with an ACL graft placed in the posterior aspect of the tibial footprint. However, an anterior tibial tunnel position must be balanced against an increased risk and magnitude of graft impingement in extension.

Navigated knee kinematics after tear of the ACL and its secondary restraints: preliminary results

In this study we evaluated the role of the anterior cruciate ligament (ACL) and its secondary restraint in controlling knee stability using a navigation system. The purpose of this study was to evaluate the kinematics of the knee in different conditions of instability: ACL intact, after transection of the posterolateral (PL) bundle, after transection of the anteromedial (AM) bundle, and after lesion of the anterolateral femorotibial ligament (ALFTL). Anterior tibial translation and rotation were measured with a computer navigation system in 6 knees in whole fresh-frozen human cadavers by use of a manual maximum load. Anterior translation was evaluated at 30°, 60°, and 90° of flexion; rotation at 0°, 15°, 30°, 45°, 60°, and 90° of flexion. Cutting the PL bundle does not increase anterior translation and rotation of the knee. Cutting the AM bundle significantly increased the anteroposterior (AP) translation at 30° and 60° of flexion (P=.01), but does not increase rotation of the knee. Cutting the ALFTL increased anterior translation at 60° of flexion (P=.04) and rotation at 30°, 45°, and 60° of flexion (P=.03). The PL bundle does not affect anterior translation and rotation of the knee. The AM bundle is the primary restraint of the anterior translation but does not affect rotation of the knee. The lateral compartment becomes the primary restraint of rotation after ACL cut. The primary kinematic effect of an ACL injury is an increase in anterior tibial translation, but there is no significant change in maximum internal or external rotation. The lesion of the ALFTL increases tibial rotation and could be correlated to the pivot shift phenomenon.

A comparison of the effect of central anatomical single-bundle anterior cruciate ligament reconstruction and double-bundle anterior cruciate ligament reconstruction on pivot-shift kinematics

BACKGROUND

Biomechanical differences between anatomical double-bundle and central single-bundle anterior cruciate ligament reconstruction using the same graft tissue have not been defined.

PURPOSE

The purpose of this study was to compare these reconstructions in their ability to restore native knee kinematics during a reproducible Lachman and pivot-shift examination.

STUDY DESIGN

Controlled laboratory study.

METHODS

Using a computer-assisted navigation system, 10 paired knees were subjected to biomechanical testing with a standardized Lachman and mechanized pivot-shift examination. The navigation system recorded the 3D motion path of a tracked point at the center of the tibia, center of the medial tibial plateau, and center of the lateral tibial plateau with each maneuver. The testing protocol consisted of evaluation in the intact state, after complete anterior cruciate ligament transection, after medial and lateral meniscectomy, and after anterior cruciate ligament reconstruction with (1) a single-bundle center-center or (2) anatomical double-bundle technique. Repeated-measures analysis of variance with a post hoc Tukey test was used to compare the measured translations with each test condition.

RESULTS

A significant difference in anterior translation was seen with Lachman examination between the anterior cruciate ligament- and medial and lateral meniscus-deficient condition compared with both the double-bundle and single-bundle center-center anterior cruciate ligament reconstruction (P < .001); no significant difference was observed between reconstructions. The double-bundle construct was significantly better in limiting anterior translation of the lateral compartment compared with the single-bundle reconstruction during a pivot-shift maneuver (2.0 +/- 5.7 mm vs 7.8 +/- 1.8 mm, P < .001) and was not significantly different than the intact anterior cruciate ligament condition (2.7 mm +/- 4.7 mm, P > .05).

DISCUSSION

Although double-bundle and single-bundle, center-center anterior cruciate ligament reconstructions appear equally effective in controlling anterior translation during a Lachman examination, analysis of pivot-shift kinematics reveals significant differences between these surgical reconstructions. An altered rotational axis resulted in significantly greater translation of the lateral compartment in the single-bundle compared with double-bundle reconstruction.

CLINICAL RELEVANCE

A double-bundle anterior cruciate ligament reconstruction may be a favorable construct for restoration of knee kinematics in the at-risk knee with associated meniscal injuries and/or significant pivot shift on preoperative examination.

The effect of medial versus lateral meniscectomy on the stability of the anterior cruciate ligament-deficient knee

BACKGROUND

The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position.

PURPOSE

To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination.

STUDY DESIGN

Controlled laboratory study.

METHODS

A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05.

RESULTS

The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 +/- 6.0 vs 10.5 +/- 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001).

CONCLUSION

Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver.

CLINICAL RELEVANCE

This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.

Instrumented examination of anterior cruciate ligament injuries: minimizing flaws of the manual clinical examination

The clinical examination is a basic language of orthopaedics; it is how orthopaedic surgeons communicate with one another. However, each surgeon speaks a different dialect that has been influenced by where and with whom that surgeon trained, as well as that person's own experiences. Because of the inherent variability in the magnitude, direction, and rate of force application during the clinical examination, manual arthrometers were developed in an attempt to more consistently quantify the clinical examination. Instrumented manual devices, such as the KT-1000 (MEDmetric, San Diego, CA), were the first to provide objective numbers to surgeons and researchers evaluating anteroposterior (AP) knee joint laxity. Although these devices provide surgeons with feedback related to the amount of force applied, the rate at which the force is applied is uncontrolled, resulting in a lack of reliability similar to that of the clinical examination itself. In addition to potential errors in measuring AP laxity, rotational laxity has proven to be very difficult to quantify. Robotic systems that make use of computer-driven motors to perform laxity testing have recently been developed to control the magnitude, direction, and rate of force application and thus improve the accuracy and reliability of both AP and rotational laxity evaluation. This review discusses the evolution of instrumented clinical knee examination over the past 3 decades and highlights the advantages and disadvantages of the various testing systems, as well as how current and future developments in this area may improve the field of orthopaedics by minimizing the flaws of the manual clinical examination.

Computer-assisted anterior cruciate ligament reconstruction: an evidence-based approach of the first 15 years

In the last 15 years, computer-assisted surgery (CAS) has been used for many purposes during anterior cruciate ligament (ACL) reconstruction, such as tunnel positioning, joint laxity evaluation, and biomechanical studies. This article is an evidence-based literature review of the contribution of such technology to ACL surgery. A search of the PubMed and Medline databases was performed. Articles were classified according to the study design and to the research topic: anatomy, laxity, kinematics, and comparison of surgical techniques. An evidence-based approach was used to verify the clinical usefulness of CAS to ACL surgery. The use of CAS for research purposes was also evaluated. CAS was shown to improve femoral tunnel positioning, even if clinical outcomes showed no differences compared with manual techniques. CAS technology was found to be useful for research purposes in terms of providing a better comprehension of the effect of different ACL reconstructions and of the different bundles on joint laxity, as well as describing tunnel positioning in relation to native ACL insertion. CAS in ACL surgery can improve results at time 0 and can improve knowledge about ACL anatomy and kinematics. Its application remains limited mostly to research purposes because of the invasiveness of the system and the absence of improved clinical results at follow-up.

Anatomic single- and double-bundle anterior cruciate ligament reconstruction flowchart

Anatomy is the foundation of orthopaedic surgery, and the advancing knowledge of the anterior cruciate ligament (ACL) anatomy has led to the development of improved modern reconstruction techniques that approach the anatomy of the native ACL. Current literature on the anatomy of the ACL and its reconstruction techniques, as well as our surgical experience, was used to develop a flowchart that can aid the surgeon in performing anatomic ACL reconstruction. We define anatomic ACL reconstruction as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. A guideline was written to accompany this flowchart with more detailed information on anatomic ACL reconstruction and its pitfalls, all accompanied by relevant literature and helpful figures. Although there is still much to learn about anatomic ACL reconstruction methods, we believe this is a helpful document for surgeons. We continue to modify the flowchart as more information about the anatomy of the ACL, and how to more closely reproduce it, becomes available.