Paulo Araujo

Dynamic knee laxity measurement devices

PurposeStudies 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.MethodsThe 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.ResultsThere 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.ConclusionSeveral 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 evidenceDiagnostic study, Level V.

How to optimize the use of MRI in anatomic ACL reconstruction.

PurposeMagnetic resonance imaging (MRI) is the most current diagnostic imaging procedure for suspected ACL injuries. It is an accurate, highly sensitive and specific tool for the diagnosis of ACL tears, graft tears and associated injuries. However, it can also be used for various other aspects of anatomic ACL reconstruction.MethodsSpecial sequences as the oblique sagittal plane should be obtained from a parallel line to the lateral epicondyle, ensuring a proper visualization of both bundles of the ACL. Another special set of images, the oblique-coronal sequence, allows for the ACL long-axis evaluation. The coronal-oblique sequence increases the sensitivity and specificity of diagnosing isolated AM or PL bundle injuries and also helps to visualize the proximal insertion of the bundles for haemorrhage and rupture.ResultsQuantitative measurements can be taken from a proper MRI protocol, so as to determine the rupture pattern; measure insertion site size, inclination angle and autograft size; and evaluate for post-operative complications. These parameters help surgeons to objectively decide for a better graft and technique for an individualized approach and to evaluate the anatomic placement of the graft.ConclusionsMRI can be used in different ways, serving as a very valuable tool in anatomic ACL reconstruction. Special protocols can provide accurate visualization of the double-bundle anatomy. Objective parameters to aid in pre-operative decisions and graft’s anatomic placement evaluation can be also extracted from the MR images.

Development of computer tablet software for clinical quantification of lateral knee compartment translation during the pivot shift test

The pivot shift test is a commonly used clinical examination by orthopedic surgeons to evaluate knee function following injury. However, the test can only be graded subjectively by the examiner. Therefore, the purpose of this study is to develop software for a computer tablet to quantify anterior translation of the lateral knee compartment during the pivot shift test. Based on the simple image analysis method, software for a computer tablet was developed with the following primary design constraint – the software should be easy to use in a clinical setting and it should not slow down an outpatient visit. Translation of the lateral compartment of the intact knee was 2.0 ± 0.2 mm and for the anterior cruciate ligament-deficient knee was 8.9 ± 0.9 mm (p < 0.001). Intra-tester (ICC range = 0.913 to 0.999) and inter-tester (ICC = 0.949) reliability were excellent for the repeatability assessments. Overall, the average percent error of measuring simulated translation of the lateral knee compartment with the tablet parallel to the monitor increased from 2.8% at 50 cm distance to 7.7% at 200 cm. Deviation from the parallel position of the tablet did not have a significant effect until a tablet angle of 45°. Average percent error during anterior translation of the lateral knee compartment of 6mm was 2.2% compared to 6.2% for 2 mm of translation. The software provides reliable, objective, and quantitative data on translation of the lateral knee compartment during the pivot shift test and meets the design constraints posed by the clinical setting.

Individualized ACL reconstruction

AbstractThe 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.

Individualized anatomic anterior cruciate ligament reconstruction.

Arthroscopic anterior cruciate ligament reconstruction (ACL-R) is a technique that continues to evolve. Good results have been established with respect to reducing anteroposterior laxity. However, these results have come into question because nonanatomic techniques have been ineffective at restoring knee kinematics and raised concerns that abnormal kinematics may impact long-term knee health. Anatomic ACL-R attempts to closely reproduce the patients individual anatomic characteristics. Measurements of the patients anatomy help determine graft choice and whether anatomic reconstruction should be performed with a single- or double-bundle technique. The bony landmarks and insertions of the anterior cruciate ligament (ACL) are preserved to assist with anatomic placement of both tibial and femoral tunnels. An anatomic single- or double-bundle reconstruction is performed with a goal of reproducing the characteristics of the native ACL. Long-term outcomes for anatomic ACL reconstruction are unknown. By individualizing ACL-R, we strive to reproduce the patients native anatomy and restore knee kinematics to improve patient outcomes.

Validation of Quantitative Measures of Rotatory Knee Laxity.

Background: Prior attempts to quantify the pivot-shift examination have been too invasive or impractical for clinical use. A noninvasive method for quantifying rotatory knee laxity is needed. Hypothesis: Greater quantitative measurements of rotatory knee laxity (both of the involved knee as well as compared with the contralateral healthy knee) are associated with an increasing clinical pivot-shift grade. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 103 patients undergoing anatomic single-bundle anterior cruciate ligament (ACL) reconstruction at 4 international centers underwent a standardized pivot-shift test preoperatively on both knees while anesthetized. Clinical grading of the pivot shift was performed according to the International Knee Documentation Committee (IKDC) knee ligament rating system. Two different quantitative technologies were used to measure rotatory knee laxity: an inertial sensor and an image analysis were independently used to measure tibial acceleration and lateral compartment translation, respectively, during the pivot-shift test. Patients were dichotomized to “high-grade” (abnormal and severely abnormal) or “low-grade” (normal and nearly normal) rotatory knee laxity groups based on the clinical pivot-shift test result of the involved side. Tibial acceleration and lateral compartment translation of the involved knee and the side-to-side difference between the involved and contralateral knees were separately compared between the high- and low-grade rotatory knee laxity groups utilizing t tests; significance was set at P < .05. Results: Forty-three patients were in the low-grade rotatory knee laxity group, and 60 patients were in the high-grade rotatory knee laxity group. Patients in the high-grade knee laxity group had significantly higher lateral compartment translation as measured with the image analysis (involved knee: 3.8 ± 2.3 mm; side-to-side difference: 2.5 ± 2.4 mm) compared with patients in the low-grade group (involved knee: 2.0 ± 1.4 mm; side-to-side difference: 1.4 ± 1.5 mm) (both P < .01). As measured with the inertial sensor, tibial acceleration for patients in the high-grade group was significantly higher (involved knee: 7.2 ± 5.3 m/s2; side-to-side difference: 4.2 ± 5.4 m/s2) compared with patients in the low-grade group (involved knee: 4.2 ± 1.6 m/s2; side-to-side difference: 1.2 ± 1.2 m/s2) (both P < .01). Conclusion: The inertial sensor and image analysis techniques were able to detect differences between low- and high-grade pivot-shift test results. A quantitative assessment of the pivot-shift test could augment the diagnosis of an ACL injury and improve the ability to detect changes in rotatory knee laxity over time.

Use of a Fluoroscopic Overlay to Assist Arthroscopic Anterior Cruciate Ligament Reconstruction

Background: A growing body of evidence supports the importance of anatomic tunnel positioning in the success of anterior cruciate ligament (ACL) reconstruction, which stimulates the need for technologies to aid surgeons in achieving accurate anatomic tunnel placement. Intraoperative fluoroscopy is potentially one such technology, while its efficacy and usability have yet to be established. Purpose: To investigate the performance of an intraoperative fluoroscopic overlay in guiding tunnel placement during ACL reconstruction. Study Design: Controlled laboratory study. Methods: Twenty cadaveric knees underwent computed tomography (CT) scans and arthroscopic digitization of ACL insertion sites. The outlines of the digitized insertion sites were mapped to the corresponding CT-acquired bone models through a co-registration procedure. Twenty orthopaedic surgeons performed simulated ACL reconstructions, each on a randomly assigned cadaveric knee, first without and then with the aid of a fluoroscopic overlay system. The overlay system displayed on a lateral fluoroscopic image targets points representing the locations of the ACL insertion sites estimated from the literature data. Surgeons were allowed to adjust their tunnel positions under the guidance of the fluoroscopic image. Their initial, intermediate, and final positions were documented and compared with the target points as well as the native insertion sites. Results: Surgeons demonstrated significant (P < .01) improvements in femoral and tibial tunnel placements relative to the target points from an average distance of 3.9 mm to 1.6 mm on the femur and 2.1 mm to 0.9 mm on the tibia. The improvements toward the knee-specific actual insertion sites were significant on the tibial side but not on the femoral side. Conclusion: Surgeons can be successfully guided with fluoroscopy to create more consistent femoral and tibial tunnels during ACL reconstruction. More research is warranted to develop better population representations of the locations of natural insertion sites. Clinical Relevance: Intraoperative fluoroscopy can be an effective, easy, and safe method for improving tunnel positioning during ACL reconstruction.

Acl Graft Position Affects in Situ Graft Force Following Acl Reconstruction

BACKGROUND The purpose of our study was to evaluate the relationship between graft placement and in situ graft force after anterior cruciate ligament (ACL) reconstruction. METHODS Magnetic resonance imaging (MRI) was obtained for twelve human cadaveric knees. The knees, in intact and deficient-ACL states, were subjected to external loading conditions as follows: an anterior tibial load of 89 N at 0°, 15°, 30°, 45°, 60°, and 90° of flexion and a combined rotatory (simulated pivot-shift) load of 5 Nm of internal tibial torque and 7 Nm of valgus torque at 0°, 15°, and 30° of flexion. Three ACL reconstructions were performed in a randomized order: from the center of the tibial insertion site to the center of the femoral insertion site (Mid), the center of the tibial insertion site to a more vertical femoral position (S1), and the center of the tibial insertion site to an even more vertical femoral position (S2). The reconstructions were tested following the same protocol used for the intact state, and graft in situ force was calculated for the two loadings at each flexion angle. MRI was used to measure the graft inclination angle after each ACL reconstruction. RESULTS The mean inclination angle (and standard deviation) was 51.7° ± 5.0° for the native ACL, 51.6° ± 4.1° for the Mid reconstruction (p = 0.85), 58.7° ± 5.4° for S1 (p < 0.001), and 64.7° ± 6.5° for S2 (p < 0.001). At 0°, 15°, and 30° of knee flexion, the Mid reconstruction showed in situ graft force that was closer to that of the native ACL during both anterior tibial loading and simulated pivot-shift loading than was the case for S1 and S2 reconstructions. At greater flexion angles, S1 and S2 had in situ graft force that was closer to that of the native ACL than was the case for the Mid reconstruction. CONCLUSIONS Anatomic ACL reconstruction exposes grafts to higher loads at lower angles of knee flexion. CLINICAL RELEVANCE Rehabilitation and return to sports progression may need to be modified to protect an anatomically placed graft after ACL reconstruction.

Double-bundle ACL reconstruction with use of a single tibial tunnel: a technique or an anatomic concept?

Despite good outcomes reported after traditional anterior cruciate ligament (ACL) reconstruction techniques, a substantial number of patients have been found to develop osteoarthritis in mid-to-long-term follow-up studies1,2 as the dynamic function of the knee was not reestablished after surgery3. As a consequence, in the past decade, the debate regarding the importance of restoring native anatomy in ACL reconstructions has led to a school of thought that suggests the solution to avoid degenerative changes following an ACL rupture could rest on reestablishing the anatomic characteristics of the ligament. As part of this recent debate, Ahn et al. presented a well-designed, retrospective study with the purpose of reporting the clinical outcomes of double-bundle ACL reconstruction with use of a single tibial tunnel and its correlation with graft appearance in a second-look arthroscopy. The assessment parameters included outcome scores such as the Lysholm knee score, International Knee Documentation Committee (IKDC) evaluation, side-to-side anterior laxity measured with use of a KT-2000 arthrometer, rotational stability graded by the pivot-shift test, and degenerative changes graded on anteroposterior and lateral weight-bearing radiographs. The overall results showed a substantial improvement after surgery in the outcome scores, …

Are We Allowing Patients to Return to Participation Too Soon? Letter to the Editor

Dear Editor: We were very interested by the information presented in the articles ‘‘When Do Rotator Cuff Repairs Fail? Serial Ultrasound Examination After Arthroscopic Repair of Large and Massive Rotator Cuff Tears’’ by Miller et al and ‘‘Longterm Survivorship of Rotator Cuff Repairs Using Ultrasound and Magnetic Resonance Imaging Analysis’’ by Kluger et al. Both studies report failure rates as high as 33% and 41% after rotator cuff repair. In the majority of cases in these studies, the recurrent tears happened in the early rehabilitation phase, within 3 months postoperatively. The presented numbers clearly parallel what is currently happening in the field of anterior cruciate ligament (ACL) reconstruction and certainly to other sports medicine pathologies. Failure rates in ACL surgery show impressive numbers as well. Barrett et al reported failure rates of up to 29.2% in allograft ACL reconstruction and 25% when semitendinosus-gracilis autograft is used. In a similar study, van Eck et al showed failure rates of up to 13% in young patients with allograft. In this study, most failures happened between 3 and 9 months after surgery. This time period when failures are most likely to happen represents the period that patients are often released to return to sports. Pressure from the media, coaches, family members, and patients for an early return to sports has resulted in surgeons prematurely releasing their patients to activities while the graft is still undergoing the tissue healing process. Moreover, rehabilitation protocols base the decision for return to sports or previous activities exclusively on functional parameters that do not always correlate with the condition of the graft or secondary stabilizers for this return. Objective assessment of tissue healing is often neglected. For example, surgeons rarely obtain a postoperative magnetic resonance image (MRI) to assess graft or tissue maturation. Tissue healing takes time, and surgeons must learn to be patient. In order to best take care of our patients we must allow for adequate healing before authorizing certain activities. Further studies to define imaging properties of tissues and grafts are needed to aid in rehabilitation protocols after surgery. Hopefully, in the near future we will be able to develop objective assessment tools of tissue and graft healing so that we may decrease the presented data regarding failures after tendon and ligament repairs and reconstructions.