Yuichi Hoshino

In Vivo Measurement of the Pivot-Shift Test in the Anterior Cruciate Ligament–Deficient Knee Using an Electromagnetic Device

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

A prospective randomised study of anatomical single-bundle versus double-bundle anterior cruciate ligament reconstruction: quantitative evaluation using an electromagnetic measurement system

We conducted a prospective randomised study of anatomical single-bundle (A-SB group) versus double-bundle (A-DB group) anterior cruciate ligament (ACL) reconstruction using the hamstrings tendons. Twenty patients with unilateral ACL deficiency were randomised into two groups. We created the bone tunnels at the position of the original insertion of the anteromedial bundle footprint and posterolateral bundle footprint in the A-DB group and at the central position between these two bundles in the A-SB group. All of the patients were tested before ACL reconstruction and one year after surgery. The KT-1000 measurements, isokinetic muscle peak torque and heel-height difference were evaluated and the general knee condition was assessed by Lysholm score. For pre- and postoperative stability assessment, we used the six-degrees-of-freedom of knee kinematic measurement system using an electromagnetic device (the EMS) for quantitative assessment during the Lachman test and the pivot shift test. There were no significant differences in the KT-1000 measurements, isokinetic muscle peak torque, heel-height difference, and Lysholm score at one-year follow-up between these two groups. The EMS data showed there were significant differences in the acceleration of the pivot shift test between the operated knee and the contralateral normal knees in the A-SB group. In conclusion, clinical outcomes were equally good in both groups. However, the EMS data showed the anatomical double-bundle ACL reconstruction tended to be biomechanically superior to the single-bundle reconstruction.

Analysis of the graft bending angle at the femoral tunnel aperture in anatomic double bundle anterior cruciate ligament reconstruction: a comparison of the transtibial and the far anteromedial portal technique

The aim of this study is to investigate and compare the three dimensional bending angle of the graft at the femoral tunnel aperture in the transtibial and the far anteromedial portal technique. Seven fresh-frozen human cadaveric knees were used. Six degrees-of-freedom of knee kinematics and knee position data were measured using an electromagnetic device and the three dimensional bending angles of the each graft at the femoral tunnel aperture were calculated by computer simulation. Additionally, in order to assess the stress on the graft, the length change between the femoral and tibial attachment sites of the AM and PL bundle were calculated. The maximum length of each bundle was detected at full extension of the knee. The relative change of the length of the PL bundle in the range of 70°–0° of knee flexion was significantly larger than that of the AM bundle. (Pxa0<xa00.05) Maximum graft bending angles in both techniques were obtained at full extension where the graft was fully stretched. The AM and PL graft bending angles in the transtibial technique were significantly larger than in the far anteromedial portal technique at low flexion angle (AM: 0°–10°, PL: 0°–50°) (Pxa0<xa00.01). This suggests use of the far anteromedial portal technique might result in lower stress on the graft at the femoral tunnel aperture and therefore might reduce graft damage.

The pivot shift: a global user guide

PurposeThe use of several different maneuvers for the pivot shift test has resulted in inconsistent quantitative measurements. The purpose of this study was to describe, analyze, and group several surgeon-specific techniques for the pivot shift test and to propose a standardized pivot shift test.MethodsTwelve expert surgeons examined a whole lower cadaveric extremity with their preferred technique and assigned a clinical grade, I–III. Anterior tibial translation and acceleration were measured using an electromagnetic system. The test was repeated after watching an instructional video focused on a standardized pivot shift technique. Measurements were repeated and compared with the preferred technique.ResultsThe expert surgeons utilized valgus stress unanimously in addition to fixed internal rotation (nxa0=xa05), fixed external rotation (nxa0=xa01), a motion-allowing technique (nxa0=xa03), a dislocation-type maneuver (nxa0=xa02), and a fixed anterior drawer type of maneuver in extension (nxa0=xa01). Anterior tibial translation measured was on average 15.9xa0±xa03.7xa0mm. Average tibial acceleration was 3.3xa0±xa02.1xa0mm/s2. Average clinical grading was 2.3xa0±xa00.5. There were no differences in average clinical grading when using high stress (2.5xa0±xa00.6) versus low stress (2.3xa0±xa00.5, n.s.), or using fixed rotation (2.2xa0±xa00.5) versus a motion-allowing technique (2.3xa0±xa00.6; n.s.).ConclusionsClinical grading, tibial translation, and acceleration vary between examiners performing the pivot shift test. High forces and extremes of rotation are not necessary to produce a clinical detectable pivot shift. In the future, a standardized pivot shift test—which can be performed universally and utilizes only gentle forces allowing motion to occur—may be beneficial when assessing differences in outcome following ACL reconstruction.

Standardized pivot shift test improves measurement accuracy

PurposeThe 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.MethodsA 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.ResultsThe anterior tibial translation during pivot shift test was similar between using surgeons’ preferred technique (left 24.0xa0±xa04.3xa0mm; right 15.5xa0±xa03.8xa0mm) and using standardized technique (left 25.1xa0±xa03.2xa0mm; right 15.6xa0±xa04.0xa0mm; n.s.). However, the variation in acceleration was significantly smaller with the standardized technique (left 3.0xa0±xa01.3xa0mm/s2; right 2.5xa0±xa00.7xa0mm/s2) compared with the surgeons’ preferred technique (left 4.3xa0±xa03.3xa0mm/s2; right 3.4xa0±xa02.3xa0mm/s2; both Pxa0<xa00.01).ConclusionStandardizing the pivot shift test maneuver provides a more consistent quantitative evaluation and may be helpful in designing future multicenter clinical outcome trials.Level of evidenceDiagnostic study, Level I.

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.

Evaluation of rotational instability in the anterior cruciate ligament deficient knee using triaxial accelerometer: a biomechanical model in porcine knees

PurposeTo measure the acceleration in multiple directions of the rotational instability in ACL deficient models using porcine knees.MethodsTen porcine knees were tested with ACL intact and tear models. The pivot shift test was performed manually, and the acceleration of the pivot shift phenomenon was recorded by the use of a triaxial accelerometer. Tests were repeated in four different ACL states: (1) intact; (2) partial AM deficient; (3) complete AM deficient, and (4) complete ACL (AMxa0andxa0PL) deficient. The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between different ACL conditions.ResultsSignificantly increased accelerations were observed in the complete deficient ACL model, while the partial ACL tear models demonstrated a slight increase without statistical significance. The accelerometer detected stepwise increases in the acceleration with the extent of ACL tear. Additionally, the PL bundle exhibited the largest contribution for rotational instability (80.4%) when compared with the AM (19.5%) bundles.ConclusionTriaxial accelerometer could serve as a quantitative evaluation of rotational instability. The present study demonstrated that PL bundle has the most important contribution for rotational instability (80.4%) when compared to IM bundle (0.01%) and AM bundle (19.5%) in porcine knee model.

Comparison of the Clinical Outcome of Double-Bundle, Anteromedial Single-Bundle, and Posterolateral Single-Bundle Anterior Cruciate Ligament Reconstruction Using Hamstring Tendon Graft With Minimum 2-Year Follow-up

PURPOSEnThe purpose of this study was to obtain more than 2 years follow-up after surgery to investigate the effect of the difference in rotatory stability based on our previous data on the clinical outcome among 3 groups: double-bundle (DB) reconstruction group, anteromedial (AM) single-bundle reconstruction group, and posterolateral (PL) single-bundle reconstruction group.nnnMETHODSnWe randomly separated 55 patients with anterior cruciate ligament rupture into 3 groups: 18 in DB group, 18 in AM group, and 19 in PL group. The mean follow-up period is 33.7 months for the DB group, 31.9 months for the AM group, and 33.2 months for the PL group. We evaluated the Lysholm score, Tegner score, anterior laxity with the KT-1000 arthrometer (MEDmetric, San Diego, CA), rotator instability with the pivot-shift test, and muscle strength with knee extensor and flexor isokinetic peak torques at 60°/s.nnnRESULTSnThere were no significant differences in postoperative Lysholm score and Tegner score. Anterior stability of the knee, as measured by the KT-1000 arthrometer, was significantly better in the DB group than the PL group (P < .05). The negative rate of the manual pivot-shift test in the DB group was significantly superior to the PL group (P < .05). Muscle strength of the extensor in the DB group was significantly superior to that in the AM group (P < .05), and muscle strength of the flexor in the PL group was significantly inferior to that in both the DB and AM groups (P < .05). Two patients in the PL group had rerupture; however, there was no graft failure in the other groups.nnnCONCLUSIONSnAt 2 years follow-up, patients undergoing DB anterior cruciate ligament reconstruction had greater extension strength than patients receiving an AM single-bundle reconstruction. The DB and AM groups had greater flexion strength than the PL group. The DB and AM groups had a similar rate of negative pivot-shift test results, whereas the PL group had fewer negative pivot-shift test results than the DB group. There were no KT-1000 side-to-side differences between the DB and AM groups, whereas the DB group had better results than the PL group. Overall, the clinical outcome as measured by Lysholm and Tegner scores was not different between groups.nnnLEVEL OF EVIDENCEnLevel II, prospective comparative study.

Therapeutic Advantage in Selective Ligament Augmentation for Partial Tears of the Anterior Cruciate Ligament Results in an Animal Model

Background: As a result of recent studies describing the double-bundle anterior cruciate ligament (ACL), selected ACL augmentation procedures, either anteromedial (AM) or posterolateral (PL), have been introduced as the treatment of choice for partial ACL ruptures. The preserved mechanoreceptor and vascularity of the remnant ACL are considered to provide additional biological benefits. Although enhanced knee joint proprioception in ACL augmented patients has been previously reported, there is no study assessing biological healing advantages of the graft after the ACL augmentation procedure. Hypothesis: Selected ACL augmentation for partial tears can accelerate the healing process of the grafted tendon, which promotes better biomechanical recovery of the tendon, compared with conventional ACL reconstruction of complete tears. Study Design: Controlled laboratory study. Methods: Two rat models were established in this study: an ACL augmentation partial tear model and conventional ACL reconstruction for a complete tear. Biological assessments of cellularity and angiogenesis were measured by hematoxylin and eosin staining and immunostaining, respectively. Additionally, rat-specific type III collagen and α-smooth muscle actin were evaluated by immunohistochemical staining to analyze the healing process, whereas anti-rat neurofilament antigen was assessed to examine proprioceptive recovery. Biological assessments of the augmented and reconstructed grafts were conducted postoperatively at week 2, whereas biomechanical testing was performed postoperatively at week 8. Results: An increase in cellularity and angiogenesis was observed in the augmented grafts compared with the conventionally reconstructed grafts. Also, increased amounts of rat-specific type III collagen, α-smooth muscle actin, and anti-rat neurofilament antigen were expressed in the augmented grafts. Biomechanical testing showed that failure to load was significantly higher in the augmentation group compared with the conventional reconstruction group (augmentation, 15.9 ± 1.0; reconstruction, 7.0 ± 1.3; P < .01). Clinical Relevance: Selected ACL augmentation could be a good choice for the repair of partial ACL injury by preserving the uninjured portion of the ACL, which in turn could maintain the anatomic position of the ligament and its biomechanical function.

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

PurposeThe 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.MethodsA 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.ResultsWhen 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 (rxa0=xa00.88 and rxa0=xa00.67, respectively; both Pxa0<xa00.01); The triaxial accelerometer system demonstrated good correlation with the reference measurement for acceleration (rxa0=xa00.75; Pxa0<xa00.001). The image analysis system was poorly correlated to the translation of the reference measurement (rxa0=xa00.24; Pxa0<xa00.01).ConclusionThe 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.