Effect of scapular external rotation on the axillary nerve during the arthroscopic Latarjet procedure: an anatomical investigation.

PURPOSE: The first purpose of this study is to measure the distance between the axillary nerve and the exit point of K-wires placed retrograde through the glenoid in the setting of an arthroscopic Latarjet procedure. The second objective is to evaluate whether manual external rotation of the scapula alters that distance. METHODS: In seven fresh-frozen specimens, two 2.0-mm K-wires were drilled through the glenoid using an arthroscopic Latarjet retrograde glenoid guide. These were drilled into the glenoid at the 7- and 8-o'clock positions (right shoulders) and at the 4- and 5-o'clock positions (left). K-wires were oriented parallel to the glenoid articular surface and perpendicular to the long superoinferior axis of the glenoid, 7 mm medial to the joint surface. Two independent evaluators measured the distances between the axillary nerve and the exit point of the K-wires in the horizontal plane (AKHS for the superior K-wire and AKHI for the inferior K-wire) and in the vertical plane (AKV). Measurements were taken with the scapula left free and were repeated with the scapula placed at 15° and 30° of external rotation. RESULTS: With the scapula left free, scapular external rotation was 34° ± 2.3°. In this position, the AKHS was 2.5 ± 1.6, 6.3 ± 1.2 mm at 15° of external rotation (ER) and 11.4 ± 1.4 mm at 30° ER. The AKHI distance was 0.37 ± 1.6, 3.4 ± 1.4 and 10.6 ± 2.1 mm, respectively, for the scapula left free, at 15° ER and 30° of ER. The AKV distances were, respectively, 0.12 ± 0.2, 4.9 ± 1.6 and 9.9 ± 1.7 mm. The increase in all distances was statistically significant (p < 0.001). CONCLUSION: Increasing scapular external rotation significantly increases the distance between the axillary nerve and the exit point of the K-wires, increasing the margin of safety during this procedure. Therefore, increased external rotation of the scapula could be an effective tool to decrease the risk of iatrogenic axillary nerve injury. LEVEL OF EVIDENCE: Cadaveric study, Level V.

Peroneal electromechanical delay and fatigue in patients with chronic ankle instability.

PURPOSE: The purpose of this study was to investigate the effect of chronic ankle instability (CAI) on electromechanical delay times (EMD) before and after fatigue. Understanding the mechanisms that contribute to CAI is essential for the development of effective rehabilitation programmes. It was hypothesized that patients with CAI will demonstrate prolonged EMD times compared to healthy subjects and that fatigue will cause greater increases in EMD times in the CAI group. METHODS: Twenty-one male volunteers participated in the study providing data on 16 ankles with CAI and 26 with no history of ankle injury. EMD was measured on an isokinetic dynamometer. Measurements were taken with the ankle in neutral (0°) and at 30° of inversion. All subjects followed an isokinetic fatigue protocol until eversion torque fell below 50 % of initial torque for three consecutive repetitions. A 2 × 2 × 2 ANOVA was used to calculate the effect of ankle status (CAI vs. healthy), fatigue, angle (0° vs. 30°) and their interactions on EMD. RESULTS: Fatigue caused a significant increase on EMD [non-fatigued: 122(29)ms vs. fatigue 155(54)ms; p < 0.001]. EMD times were shorter at 30° of inversion compared to neutral [neutral: 145(39)ms vs. 30° of inversion: 132(40)ms, p = 0.015]. An interaction effect for ankle status and angle was found (p = 0.026) with CAI ankles demonstrating longer EMD [CAI: 156(45)ms vs. healthy: 133(40)ms] in neutral but not at 30° of inversion [CAI: 133(46)ms vs. 132(33)ms]. CONCLUSIONS: Patients with CAI had longer EMD times in neutral, but not when the ankle was placed in inversion. This suggests that rehabilitation programmes may be more effective when retraining occurs with the ankle in neutral position. It is likely that low EMD times prevent ankle acceleration at the beginning of the mechanism of injury, but they are less important when the ankle has already inverted at 30°. Both CAI and healthy subjects demonstrated longer EMD after fatigue, emphasizing the importance of proper conditioning in the prevention of delayed peroneal response and subsequent ankle injury. Improving resistance to fatigue of the peroneals may prove to be an effective prevention tool of ankle sprain recurrence in patients with CAI. LEVEL OF EVIDENCE: III.

Description and reproducibility assessment of a new computerised tomography scan index to measure the glenoid orientation in relation to the anterior glenoid surface.

PURPOSE: To propose and to assess the reproducibility of a new method (GO [glenoid orientation] index) for the estimation of the glenoid orientation in relation to the anterior surface of the glenoid. METHODS: This is a retrospective study on computed tomography (CT) scan. The GO index was defined as the angle formed by a line perpendicular to the tangent to the anterior surface of the scapula and the glenoid line (which is defined as the line connecting the anterior and the posterior rim of the glenoid). The measurements were performed at the level of the glenoid where its diameter is the greatest. Two independent observers performed each measurement twice. The intra- and inter-observer reproducibility was evaluated by the Pearson coefficient (r) and the intra-class correlation coefficient (ρ, ICC). The correlation between GO index and glenoid version as described by Friedman was also studied. RESULTS: Seventy-eight CT scans were analysed, 38 shoulders with glenohumeral arthritis and 40 healthy shoulders, 32 females/46 males, mean age 53.9 ± 22.7 years. The measures were all highly correlated (r > 0.50, p = 0.00001). The intra- and inter-observer reproducibility was good to excellent (0.71 < ρ < 0.84, p = 0.00001). GO index was 26.9 ± 6.3°, 28.4 ± 6° in the group with glenohumeral osteoarthritis and 25.5 ± 6.4° in the healthy group, p = 0.04. The glenoid version was -0.8 ± 7.9° in the group with glenohumeral osteoarthritis and -3.9 ± 6° in the healthy group, p = 0.05. No agreement was found between the glenoid version and GO index. CONCLUSIONS: GO index is simple and reproducible. It could be very useful for the pre-operative planning and intra-operative positioning of the implants in total shoulder arthroplasty.

Comparison of functional gains after arthroscopic rotator cuff repair in patients over 70 years of age versus patients under 50 years of age: a prospective multicenter study.

PURPOSE: To assess rotator cuff rupture characteristics and evaluate healing and the functional outcome after arthroscopic repair in patients older than 70 years versus patients younger than 50 years. METHODS: We conducted a multicenter, prospective, comparative study of 40 patients younger than 50 years (group A) and 40 patients older than 70 years (group B) treated with arthroscopic rotator cuff repair. Patients older than 70 years were operated on only if symptoms persisted after 6 months of conservative treatment, whereas patients younger than 50 years were operated on regardless of any persistent symptoms. Imaging consisted of preoperative magnetic resonance imaging and postoperative ultrasound. Preoperative and postoperative function was evaluated with Constant and modified Constant scores. Patient satisfaction was also assessed. The evaluations were performed at least 1 year postoperatively. RESULTS: No patient was lost to follow-up. The incidence of both supraspinatus and infraspinatus tears was greater in group B. Greater retraction in the frontal plane and greater fatty infiltration were observed in group B. The Constant score was significantly improved in both groups (51 ± 12.32 preoperatively v 77.18 ± 11.02 postoperatively in group A and 48.8 ± 10.97 preoperatively v 74.6 ± 12.02 postoperatively in group B, P < .05). The improvement was similar in both groups. The modified Constant score was also significantly improved in both groups (57.48 ± 18.23 preoperatively v 81.35 ± 19.75 postoperatively in group A and 63.09 ± 14.96 preoperatively v 95.62 ± 17.61 postoperatively in group B, P < .05). The improvement was greater for group B (P < .05). Partial rerupture of the rotator cuff occurred in 2 cases in group A and 5 cases in group B. Complete rerupture was observed in 2 patients in group B. In group A, 29 patients (72.5%) were very satisfied, 8 (20%) were satisfied, and 3 (7.5%) were less satisfied. In group B, 33 patients (82.5%) were very satisfied, 6 (15%) were satisfied, and only 1 (2.5%) was less satisfied. CONCLUSIONS: Rotator cuff tears are characterized by greater retraction in the frontal plane and greater fatty infiltration in patients older than 70 years compared with patients younger than 50 years. After arthroscopic repair, healing is greater for patients younger than 50 years. Functional gain is at least equal between the 2 groups. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Reliability of a new radiological method for assessment of the postoperative immobilization of the first metatarsophalangeal joint.

BACKGROUND: The success of the operative treatment of mild to moderate hallux valgus (HV) relies greatly on the osseous union of the osteotomies at the desired position. Full weight-bearing is often allowed immediately postoperatively with special forefoot off-loading shoes. No precise methodology exists for the estimation of foot immobilization inside those shoes. The aim of this study was to assess the reliability of a new radiological measurement method to assess the immobilization of the first metatarsophalangeal (M1P1) joint inside a postoperative forefoot off-loading rocker shoe. METHODS: A prospective single-center study was conducted during 2012. Patients operated on for mild or moderate HV deformity with a percutaneous technique by the same surgeon were included. Twenty-four patients (33 feet) fulfilled the inclusion criteria, all women and mean age of 56.6 ± 12.7 years. Standard lateral foot X-rays were obtained 1 week postoperatively with the patient standing in 2 positions, wearing the same forefoot off-loading rocker shoe: the foot flat on the ground (imitating midstance) and on the toes (imitating propulsion). The main evaluation criterion was the immobilization of the M1P1 joint estimated through the difference between the values of the M1P1 angle in the sagittal plane in these positions. Validity and reliability of this new measurement were assessed with Pearson's correlation coefficients (r) and intraclass correlation (ICC, ρ) coefficients. RESULTS: The inter- and intraobserver reliability of the measurement was excellent to good. The mean M1P1 angle was 17.5 ± 7 degrees in the position imitating the midstance and 20.7 ± 7.5 degrees in the position imitating propulsion (P < 10(-5)). CONCLUSION: This new radiological measurement for assessing immobilization of the M1P1 joint was a valid and reliable method.

Transfer of the clavicular or sternocostal portion of the pectoralis major muscle for irreparable tears of the subscapularis. Technique and clinical results.

PURPOSE: The transfer of the pectoralis major in cases of irreparable rupture of the subscapularis has been described through different techniques. The aim of this prospective study was to compare the clinical results of transferring the clavicular or the sternal head of the pectoralis major tendon underneath the conjoint tendon. METHODS: Fifteen patients underwent the procedure, including eight clavicular head of the pectoralis major tendon transfers and seven sternal head transfers. The mean age at the time of surgery was 57 years (range, 37-66). Each patient had pre-operative MRI and CT scan. The criteria for an irreparable subscapularis tear were retraction at the level of the glenoid and fatty infiltration of the muscle graded III or IV. Pre-operative and postoperative functions were assessed by the Constant score. Patients were finally asked if they were very satisfied, satisfied or unhappy with the functional outcome. RESULTS: The average follow-up was 24 months (range, 12-50). The mean absolute Constant score of the entire series increased significantly from 36 preoperatively to 69 at the latest follow up (p < 0.01); it improved significantly and similarly in both types of tendon harvested. Nine patients were very satisfied, three were satisfied and three were dissatisfied with the clinical outcome. CONCLUSION: A clavicular or a sternocostal head transfer of the pectoralis major under the coracoid process reduced pain, and improved the strength and function of the shoulder.

Results of 45 arthroscopic Bankart procedures: Does the ISIS remain a reliable prognostic assessment after 5 years?

PURPOSE: The Instability Severity Index Score (ISIS) includes preoperative clinical and radiological risk factors to select patients who can benefit from an arthroscopic Bankart procedure with a low rate of recurrence. Patients who underwent an arthroscopic Bankart for anterior shoulder instability with an ISIS lower than or equal to four were assessed after a minimum of 5-year follow-up. METHODS: Forty-five shoulders were assessed at a mean of 79 months (range 60-118 months). Average age was 29.4 years (range 17-58 years) at the time of surgery. Postoperative functions were assessed by the Walch and Duplay and the Rowe scores for 26 patients; an adapted telephonic interview was performed for the 19 remaining patients who could not be reassessed clinically. A failure was defined by the recurrence of an anterior dislocation or subluxation. Patients were asked whether they were finally very satisfied, satisfied or unhappy. RESULTS: The mean Walch and Duplay score at last follow-up was 84.3 (range 35-100). The final result for these patients was excellent in 14 patients (53.8 %), good in seven cases (26.9 %), poor in three patients (11.5 %) and bad in two patients (7.7 %). The mean Rowe score was 82.6 (range 35-100). Thirty-nine patients (86.7 %) were subjectively very satisfied or satisfied, and six (13.3 %) were unhappy. Four patients (8.9 %) had a recurrence of frank dislocation with a mean delay of 34 months (range 12-72 months). Three of them had a Hill-Sachs lesion preoperatively. Two patients had a preoperative ISIS at 4 points and two patients at 3 points. CONCLUSION: The selection based on the ISIS allows a low rate of failure after an average term of 5 years. Lowering the limit for indication to 3 points allows to avoid the association between two major risk factors for recurrence, which are valued at 2 points. The existence of a Hill-Sachs lesion is a stronger indicator for the outcome of instability repair. LEVEL OF EVIDENCE: Level IV, Retrospective Case Series, Treatment Study.

"Relaxed" biceps proximal tenodesis: an arthroscopic technique with decreased residual tendon tension.

Tenodesis of the long head of the biceps tendon (LHB) at the upper part of the bicipital groove has been related to persistent postoperative bicipital pain. This is possibly due to the inflammation of the remaining tendon within the groove. This, in turn, could be attributed to the continual mechanical stress placed on the tendon in the narrow bicipital groove. Theoretically, should the LHB be more "relaxed," the mechanical stress applied on it would be diminished. On the basis of this rationale, we present an arthroscopic biceps tenodesis technique, according to which the tendon is fixed at the entrance of the bicipital groove, using a bioabsorbable screw, relaxed by 5 mm. In this lax position, the residual LHB tension is expected to be decreased compared with the initial tension, whereas no cosmetic deformity (Popeye sign) or impaired muscular performance is anticipated.

New insights into anterior cruciate ligament deficiency and reconstruction through the assessment of knee kinematic variability in terms of nonlinear dynamics.

PURPOSE: Injuries to the anterior cruciate ligament (ACL) occur frequently, particularly in young adult athletes, and represent the majority of the lesions of knee ligaments. Recent investigations suggest that the assessment of kinematic variability using measures of nonlinear dynamics can provide with important insights with respect to physiological and pathological states. The purpose of the present article was to critically review and synthesize the literature addressing ACL deficiency and reconstruction from a nonlinear dynamics standpoint. METHODS: A literature search was carried out in the main medical databases for studies published between 1990 and 2010. RESULTS: Seven studies investigated knee kinematic variability in ACL patients. Results provided support for the theory of "optimal movement variability". Practically, loss below optimal variability is associated with a more rigid and very repeatable movement pattern, as observed in the ACL-deficient knee. This is a state of low complexity and high predictability. On the other hand, increase beyond optimal variability is associated with a noisy and irregular movement pattern, as found in the ACL-reconstructed knee, regardless of which type of graft is used. This is a state of low complexity and low predictability. In both cases, the loss of optimal variability and the associated high complexity lead to an incapacity to respond appropriately to the environmental demands, thus providing an explanation for vulnerability to pathological changes following injury. CONCLUSION: Subtle fluctuations that appear in knee kinematic patterns provide invaluable insight into the health of the neuromuscular function after ACL rupture and reconstruction. It is thus critical to explore them in longitudinal studies and utilize nonlinear measures as an important component of post-reconstruction medical assessment. LEVEL OF EVIDENCE: II.

Stride-to-stride variability is altered during backward walking in anterior cruciate ligament deficient patients.

BACKGROUND: Recently backward walking is used by physical therapists to strengthen the hamstring muscles and thus improve the function of the knee joint of anterior cruciate ligament deficient patients. The aim of this study was to examine the stride-to-stride variability of anterior cruciate ligament deficient patients during backward walking. The variation of how a motor behavior emerges in time is best captured by tools derived from nonlinear dynamics, for which the temporal sequence in a series of values is the facet of interest. METHODS: Fifteen patients with unilateral anterior cruciate ligament deficiency and eleven healthy controls walked backwards at their self-selected speed on a treadmill while three-dimensional knee kinematics were collected (100 Hz). A nonlinear measure, the largest Lyapunov Exponent was calculated from the resulted knee joint flexion-extension data of both groups to assess the stride-to-stride variability. FINDINGS: Both knees of the deficient patients exhibited significantly lower Lyapunov Exponent values as compared to the healthy control group revealing more rigid movement pattern. The intact knee of the deficient patients showed significantly lower Lyapunov Exponent values as compared to the deficient knee. INTERPRETATION: Anterior cruciate ligament (ACL) deficiency leads to loss of optimal variability regardless of the walking direction (forwards in previous studies or backwards here) as compared to healthy individuals. This could imply diminished functional responsiveness to the environmental demands for both knees of ACL deficient patients which could result in the knees being more susceptible to injury.

Cadaveric study of anterior cruciate ligament failure patterns under uniaxial tension along the ligament.

PURPOSE: The purpose of our study was to clarify the events that take place during anterior cruciate ligament (ACL) failure, focusing on the behavior of the ACL as a composition of multiple fibers, during uniaxial tension along the ligament. METHODS: Ten fresh-frozen human cadaveric knee specimens were fixed in an Instron machine (Instron, Norwood, MA), and load was applied parallel to the ACL axis. Two cameras were used to detect the failure mode of the ACL and its different groups of fibers. The distinct bundles of fibers were marked in each specimen before testing. The macroscopic findings during the experiment were used for comparison with the biomechanical results. RESULTS: The ACL showed a non-monotonic response during testing. The load-elongation curve showed a plateau or a second peak after the initial drop in load. Macroscopically, some fibers were failing initially, whereas the intact fibers had a remaining load potential. In our setting, 3 different failure patterns were recognized, specifically, a midsubstance tear of the anteromedial or the posterolateral bundle with a subsequent failure of the intact bundle or an initial avulsion of the anteromedial attachment. Analysis of the video frames showed a direct connection between the failure patterns in the load-elongation curves and the macroscopic sequence of events during ACL failure. CONCLUSIONS: The ACL ligament acts as a multifiber construction. In our setting, rupture follows 3 specific patterns where a complete or partial tear of the fiber bundles occurs first and the remaining intact fiber bundles have a potential load resistance. CLINICAL RELEVANCE: Our study allows a better understanding of the mechanical properties of the ACL. An update on the biomechanics of ACL failure during uniaxial tension after the "double-bundle revolution" could provide data helpful for ACL reconstruction.

Anterior cruciate ligament reconstruction results in alterations in gait variability.

INTRODUCTION: The temporal structure of gait variability has shown that healthy human gait exhibits long-range correlations and deterministic properties which allow the neuromuscular system to be flexible and adaptable to stresses. Pathology results in deterioration of these properties. We examined structure of gait variability after ACL reconstruction with either BPTB or quadrupled ST/G tendon autografts. METHODS: Six patients with BPTB reconstruction, six with ST/G reconstruction and six healthy controls walked on a treadmill at their self-selected pace. Two minutes of continuous kinematic data were recorded with a 6-camera optoelectronic system. The nonlinear measure of the largest Lyapunov Exponent (LyE) was estimated from the knee flexion-extension time series from 100 continuous walking strides to assess the structure of gait variability. RESULTS: The reconstructed limbs in both reconstructed groups exhibited significantly larger LyE values than the control limbs (p<0.05), even though clinical outcomes indicated complete restoration. No significant differences were found between the two autografts. In addition, the intact contralateral leg produced significant higher LyE values as compared with the ACL-reconstructed leg in both groups. No interaction was found. DISCUSSION: The larger LyE values indicate that the reconstructed knees of both reconstructed groups exhibit more divergence in the movement trajectories during gait. The larger Lye values found in the intact leg in both reconstructed groups could be interpreted as a compensatory mechanism. However, the increased divergence found in both limbs may present an alternative explanation for the impaired neuromuscular performance and increased susceptibility to future pathology, which is supported by the increased amount of osteoarthritis found in ACL-reconstructed patients.

The effect of anterior cruciate ligament reconstruction on stride-to-stride variability.

PURPOSE: The purpose of our study was to investigate the functional outcome after anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon-bone (BPTB) and quadrupled semitendinosus and gracilis tendon (ST/G) autografts by evaluating stride-to-stride variability. METHODS: Six patients with BPTB and 6 patients with STG ACL reconstruction, 2 years postoperatively, and 6 healthy control subjects walked on a treadmill at a self-selected pace while 2 minutes of continuous kinematic data were recorded with a 6-camera optoelectronic system. Stride-to-stride variability was calculated from the knee flexion/extension data using the nonlinear measure of approximate entropy, which estimates the regularity of movement patterns over time. RESULTS: ACL reconstruction affects stride-to-stride variability. Both the BPTB and the ST/G groups had significantly larger approximate entropy values than the healthy controls. No differences were found between the BPTB and the ST/G approximate entropy values. CONCLUSIONS: After ACL reconstruction using either BPTB or quadrupled ST/G, there is increased gait variability as compared to healthy individuals. This could be caused by the altered neuromuscular activity found in ACL-reconstructed limbs. LEVEL OF EVIDENCE: Level III, case control study.

ACL deficiency affects stride-to-stride variability as measured using nonlinear methodology.

Previous studies suggested that the small fluctuations present in movement patterns from one stride to the next during walking can be useful in the investigation of various pathological conditions. Previous studies using nonlinear measures have resulted in the development of the "loss of complexity hypothesis" which states that disease can affect the variability and decrease the complexity of a system, rendering it less able to adjust to the ever changing environmental demands. The nonlinear measure of the Lyapunov Exponent (LyE) has already been used for the assessment of stride-to-stride variability in the anterior cruciate ligament (ACL) deficient knee in comparison to the contralateral intact knee. However, there is biomechanical evidence that after ACL rupture, adaptations are also present in the contralateral intact knee. Thus, our goal was to investigate stride-to-stride variability in the ACL deficient knee as compared to a healthy control knee. Seven subjects with unilateral ACL deficiency and seven healthy controls walked at their self-selected speed on a treadmill, while three-dimensional knee kinematics was collected for 80 consecutive strides. A nonlinear measure, the largest LyE was calculated from the resulted knee joint flexion-extension data of both groups. Larger LyE values signify increased variability and increased sensitivity to initial conditions. Our results showed that the ACL deficient group exhibited significantly less variable walking patterns than the healthy control. These changes are not desirable because they reflect decreases in system's complexity, which indicates narrowed functional responsiveness, according to the "loss of complexity hypothesis." This may be related with the increased future pathology found in ACL deficient patients. The methods used in the present paper showed great promise to assess the gait handicap in knee injured patients.

Tibial rotation in anterior cruciate ligament (ACL)-deficient and ACL-reconstructed knees: a theoretical proposition for the development of osteoarthritis.

Excessive tibial rotation has been documented in anterior cruciate ligament (ACL) deficiency during walking. ACL reconstruction has been unable to correct this abnormality in activities that are more demanding than walking and involve both anterior and rotational loading of the knee. These findings persist regardless of graft selection for the ACL reconstruction (bone-patellar tendon-bone or semitendinosus gracilis). Based on this research work, we propose a theoretical perspective for the development of osteoarthritis in both the ACL-deficient and the ACL-reconstructed knee. We propose that excessive tibial rotation will lead to abnormal loading of the cartilage areas that are not commonly loaded in the healthy knee. Over time, this abnormal loading will lead to osteoarthritis. We hypothesise that the development of new surgical procedures and grafts, such as a more horizontally oriented femoral tunnel or a double-bundle ACL reconstruction, could possibly restore tibial rotation to normal levels and prevent future knee pathology. However, in vivo gait analysis studies are needed to examine the effects of these surgical procedures on tibial rotation. Prospective in vivo and in vitro studies are also necessary to verify or refute our theoretical proposition for the development of osteoarthritis.

Effectiveness of reconstruction of the anterior cruciate ligament with quadrupled hamstrings and bone-patellar tendon-bone autografts: an in vivo study comparing tibial internal-external rotation.

BACKGROUND: The 2 most frequently used autografts for anterior cruciate ligament reconstruction are the bone-patellar tendon-bone and the quadrupled hamstrings tendon. HYPOTHESIS: Hamstring tendon graft is superior to patellar tendon graft in restoring tibial rotation during highly demanding activities because of its superiority in strength and linear stiffness and because it is closer morphologically to the anatomy of the natural anterior cruciate ligament. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Eleven patients with patellar tendon graft anterior cruciate ligament reconstruction, 11 patients with hamstring tendon graft anterior cruciate ligament reconstruction, and 11 controls were assessed. Kinematic data were collected (50 Hz) with a 6-camera optoelectronic system while the subjects descended stairs and, immediately after, pivoted on their landing leg. The dependent variable examined was the tibial internal-external rotation during pivoting. All patients in both groups were also assessed clinically and with the use of a KT-1000 arthrometer to evaluate anterior tibial translation. RESULTS: The results demonstrated that reconstructions with either graft successfully restored anterior tibial translation. However, both anterior cruciate ligament reconstruction groups had significantly increased tibial rotation when compared with the controls, whereas no differences were found between the 2 reconstructed groups. CONCLUSION: The 2 most frequently used autografts for anterior cruciate ligament reconstruction cannot restore tibial rotation to normal levels. CLINICAL RELEVANCE: New surgical techniques are needed that can better approximate the actual anatomy and function of the anterior cruciate ligament.

Tibial rotation is not restored after ACL reconstruction with a hamstring graft.

Recent research suggests ACL reconstruction does not restore tibial rotation to normal levels during high demand activities when a bone-patellar tendon-bone graft is used. We asked if an alternative graft, the semitendinosus-gracilis (ST/G) tendon graft, could restore tibial rotation during a high demand activity. Owing to its anatomic similarity with the normal ACL we hypothesized the ST/G graft could restore excessive tibial rotation to normal healthy levels along with a successful reinstatement of the clinical stability of the knee. We assessed tibial rotation in vivo, using gait analysis. We compared the knees of ACL reconstructed patients with an ST/G graft to their intact contralateral and healthy controls during a pivoting task that followed a stair descent. We also evaluated knee stability after ACL reconstruction with standard clinical tests. ACL reconstruction with the ST/G graft and with current techniques did not restore tibial rotation to previous physiological levels during an activity with increased rotational loading at the knee, although abnormal anteroposterior (AP) tibial translation was restored.

Follow-up evaluation 2 years after ACL reconstruction with bone-patellar tendon-bone graft shows that excessive tibial rotation persists.

OBJECTIVE: To investigate in vivo if the increased tibial rotation found in anterior cruciate ligament (ACL)-deficient patients before surgery is restored 2 years after the reconstruction, during 2 high-demanding activities. DESIGN: Prospective follow-up study. SETTING: A gait analysis laboratory. PARTICIPANTS: Nine subjects with unilateral ACL rupture, reconstructed with a bone-patellar tendon-bone (BPTB) graft, and 10 healthy control subjects. INTERVENTIONS: All the ACL-deficient patients underwent a unilateral ACL reconstruction after prereconstruction data acquisition. MAIN OUTCOME MEASUREMENTS: Using a 6-camera motion analysis system, kinematics were collected as subjects (1) descended from a stair and, after foot contact, pivoted on the landing leg at 90 degrees; and (2) jumped from a platform, landed with both feet on the ground and, after foot contact, pivoted on the right or left leg at 90 degrees in a similar fashion. The dependent variable examined was the maximum range of motion of tibial rotation during the pivoting period. RESULTS: For both activities, no significant differences were found between the control healthy knee and the intact knee of the patient group before and 2 years after the ACL reconstruction. Significant differences were found between the control healthy knee and the affected knee of the patients group for both activities, both before and 2 years after the ACL reconstruction. CONCLUSION: The increased tibial rotation found in the ACL-deficient knees was not restored with reconstruction using a BPTB graft, even 2 years postoperatively. The authors propose that this excessive tibial rotation over time may lead to further deterioration of the knee resulting from abnormal loading at areas of the cartilage that are not commonly loaded in a healthy knee.

A novel approach to measure variability in the anterior cruciate ligament deficient knee during walking: the use of the approximate entropy in orthopaedics.

OBJECTIVE: The evaluation of variability of biological rhythmic activities through measures such as Approximate Entropy (ApEn) has provided important information regarding pathology in disciplines such as cardiology and neurology. This research lead to the "loss of complexity hypothesis" where decreased variability is associated with loss of healthy flexibility rendering the system more rigid and unable to adapt to stresses. ApEn as a measure of variability and complexity, correlates well with pathology while, in some cases, it is predictive of subsequent clinical changes. The study of human gait could benefit from the application of ApEn since it is also a rhythmical oscillation. Our aim was to assess the variability of the ACL deficient knee, since ACL rupture is a common musculoskeletal injury and is accompanied by altered gait patterns and future pathology in the joint. We hypothesized that the ACL deficient knee will exhibit more regular and less variable walking patterns than the contralateral intact knee. METHODS: Ten subjects with unilateral deficiency walked on a treadmill at their self-selected speed, 20% faster, and 20% slower, while kinematics were collected (50 Hz) from 80 consecutive strides for each condition. The ApEn of the resulted knee joint flexion-extension time series was calculated. RESULTS: Significantly smaller ApEn values were found in the ACL deficient knee when compared with the contralateral intact (F = 5.57, p = 0.022), for all speeds. ApEn values significantly increased (F = 5.79, p = 0.005) with increases in walking speed. CONCLUSIONS: The altered properties of the ACL deficient knee, which exhibits more regular and less variable patterns than the contralateral intact knee, may decrease the adaptability of the system rendering it less able to adjust to perturbations. This could explain the increased future pathology found in the deficient knee. ApEn can be an important tool in assessing pathology and therapeutic interventions in orthopaedics.

The effect of the walking speed on the stability of the anterior cruciate ligament deficient knee.

BACKGROUND: The reasons behind the development of future pathology in individuals with anterior cruciate ligament deficiency are unknown. This is due to the lack of appropriate methods to assess functional dynamic knee stability. In this study, we investigated the effect of walking speed on the functional dynamic stability of the anterior cruciate ligament deficient knee. We defined functional dynamic stability as local stability or the sensitivity of the knee to small perturbations. The natural stride-to-stride variations that exist during locomotion reflect exactly the presence of these perturbations. We hypothesized that speed will affect local stability in the deficient knee, especially when compared with the contralateral intact. METHODS: Ten subjects with unilateral deficiency walked on a treadmill at their self-selected speed, 20% faster, and 20% slower, while kinematic data were collected (50 Hz) for 100 consecutive footfalls for each condition. The largest Lyapunov Exponent of the resulted knee joint flexion-extension time series was calculated to quantify local stability. FINDINGS: The deficient knee was significantly more locally unstable than the contralateral knee. Furthermore, increases in walking speed did not affect local stability for our subject population. INTERPRETATIONS: The altered local stability may render the deficient knee less adaptable to the ever-changing environmental demands. This may explain the increased future pathology found in these knees. However, future efforts should attempt to evaluate this speculation using longitudinal studies. We also propose that the tools utilized in this study can be used eventually to assess functional dynamic knee stability in clinical gait analysis.