Two Different Knee Rotational Instabilities Occur With Anterior Cruciate Ligament and Anterolateral Ligament Injuries: A Robotic Study on Anterior Cruciate Ligament and Extra-articular Reconstructions in Restoring Rotational Stability.

PURPOSE: To determine the effect of 2 extra-articular reconstructions on pivot-shift rotational stability and tibial internal rotation as a basis for clinical recommendations. METHODS: A robotic simulator tested 15 cadaver knees. Group 1 (anterior cruciate ligament [ACL] cut) underwent ACL bone-patellar tendon-bone reconstruction followed by sectioning the anterolateral structures and an extra-articular, manual-tension iliotibial band (ITB) tenodesis. Group 2 (ACL intact) tested the rotational stabilizing effect of a low-tension ITB tenodesis before and after sectioning the anterolateral ligament/ITB structures. Lateral and medial tibiofemoral compartment translations and internal-external tibial rotations were measured under Lachman, 5N·m tibial rotation, and 2 pivot-shift simulations using 4-degree-of-freedom loading. Statistical equivalence was defined within 2 mm tibiofemoral compartment translation and 2° tibial rotation at P < .05. RESULTS: The bone-patellar tendon-bone ACL reconstruction (group 1) restored pivot-shift lateral compartment translation within 0.7 mm (95% confidence interval [CI], -0.6 to 1.9; P = .70) of normal. The internal rotation limit was not affected by ACL sectioning or reconstruction. After anterolateral ligament/ITB sectioning there was no change in pivot-shift lateral compartment translation, however internal rotation increased 2.9° (95% CI, 0.6-5.2; P = .99) at 90° flexion. The manual-tension ITB tenodesis (fixated 13-22 N tension) decreased pivot-shift lateral compartment translation 4.8 mm (95% CI, 1.4-8.1; P = .99) and internal rotation by 21.9° (95% CI, 13.2-30.6; P = .99) at 90° flexion. The ACL forces decreased 45.8% in the pivot-shift test. In group 2 knees, with the ACL intact, the anterolateral ligament/ITB sectioning had no effect on pivot-shift translations; however, the internal rotation limit increased by 4.3° (95% CI, 1.9-6.8; P = .99) at 60° flexion. The low-tension ITB tenodesis (fixated 8.9 N tension) had no effect on pivot-shift translations and corrected internal tibial rotation with a mild overconstraint of 4.2° (95% CI, 1.9-6.8; P = .99) at 60° flexion. CONCLUSIONS: A low-tension ITB tenodesis, fixated at neutral tibial rotation to avoid constraining internal tibial rotation, has no effect in limiting abnormal pivot-shift subluxations. CLINICAL RELEVANCE: A low-tension ITB tenodesis has limited clinical utilization as the pivot-shift subluxations are not affected, assuming appropriate tensioning to not overconstrain internal tibial rotation.

The Effect of an ACL Reconstruction in Controlling Rotational Knee Stability in Knees with Intact and Physiologic Laxity of Secondary Restraints as Defined by Tibiofemoral Compartment Translations and Graft Forces.

BACKGROUND: The effect of an anterior cruciate ligament (ACL) reconstruction on restoring normal knee kinematics in unstable knees with physiologic laxity of secondary ligamentous restraints remains unknown. The purpose of this study was to determine the stabilizing function of an ACL reconstruction and the resulting ACL graft forces in knees with severely abnormal anterior subluxation due to associated laxity of secondary restraints. METHODS: A 6-degree-of-freedom robotic simulator was used to test 21 cadaveric knees studied as a whole and in subgroups of lax secondary restraints (Lax-SR) and intact secondary restraints (Intact-SR), based on abnormal translations and tibial rotations. Native, ACL-sectioned, and ACL-reconstructed conditions were tested. An instrumented bone-patellar tendon-bone (BPTB) graft measured ACL graft forces. The loading profile involved the Lachman test (25° of flexion and 100-N anterior load), anterior tibial loading (100-N anterior load across 10° to 90° of flexion), internal rotation (25° of flexion and 5-Nm torque), and 2 pivot-shift simulations (100-N anterior load, 7-Nm valgus, and either 5 Nm of internal rotation [Pivot Shift 1] or 1 Nm of internal rotation [Pivot Shift 2]). Equivalence between conditions was defined as being within 2 mm for compartment translation and within 2° for internal tibial rotation, with p < 0.05. RESULTS: ACL sectioning increased center translation in the Lachman test by a mean of 10.9 mm (95% confidence interval [CI], 9.3 to 12.5 mm; p = 0.99), which was equivalent to native values after ACL reconstruction in all knees (mean difference, 0.0 mm [95% CI, -0.4 to 0.4 mm]; p = 0.0013), and in subgroups of Lax-SR (mean difference, 0.2 mm [95% CI, -0.5 to 0.8 mm]; p = 0.03) and Intact-SR (mean difference, -0.2 mm [95% CI, -0.8 to 0.4 mm]; p = 0.002). ACL sectioning in the pivot-shift (5-Nm) test increased lateral compartment translation to non-native-equivalent levels, which were restored to native-equivalent values after ACL reconstruction in all knees (mean difference, 0.9 mm [95% CI, 0.4 to 1.4 mm]; p = 0.055), in the Intact-SR subgroup (mean difference, 1.1 mm [95% CI, 0.5 to 1.8 mm]; p = 0.03), and to nearly native-equivalence in the Lax-SR subgroup (mean difference, 0.6 mm [95% CI, -0.3 to 1.6 mm; p = 0.06). The highest ACL graft force reached a mean of 190.9 N in the pivot-shift (5-Nm) test. CONCLUSIONS: The ACL reconstruction restored native kinematics and native rotational stability in all knees, including knees having laxity of secondary ligamentous restraints and clinically equivalent Grade-3 pivot-shift subluxation, and did so at ACL graft forces that were not excessive. CLINICAL RELEVANCE: An ACL reconstruction with a BPTB graft restored normal stability parameters regardless of the integrity of secondary ligamentous restraints.

Rotational Knee Instability in ACL-Deficient Knees: Role of the Anterolateral Ligament and Iliotibial Band as Defined by Tibiofemoral Compartment Translations and Rotations.

BACKGROUND: The anterolateral ligament (ALL) has been proposed as a primary restraint for knee rotational stability. However, the data remain inconclusive. The purpose of this study was to determine the effect of the ALL and the iliotibial band (ITB) on knee rotational stability. METHODS: A 6-degrees-of-freedom robotic simulator was used to test 14 fresh-frozen cadaveric knee specimens. There were 4 testing conditions: intact, anterior cruciate ligament (ACL)-sectioned, ACL and ALL or ITB-sectioned (determined at random), and ACL and both ALL and ITB-sectioned. Lateral, central, and medial tibiofemoral compartment translations and internal tibial rotations were measured under 100-N anterior drawer (Lachman), 5-Nm internal rotation torque, and 2 pivot-shift simulations (Pivot Shift 1 was 5 Nm of internal rotation torque, and Pivot Shift 2 was 1 Nm of internal rotation torque). Statistical equivalence within 2 mm and 2° was defined as p < 0.05. RESULTS: Sectioning the ACL alone produced increased pivot shift and Lachman compartment translations (p > 0.05). Further sectioning of either the ALL or the ITB separately produced minor added increases in pivot-shift compartment translations and tibial internal rotations (<2 mm or <3°) in the ACL-deficient knee. Sectioning both the ALL and ITB produced increases not equivalent to the ACL-deficient knee in pivot-shift lateral compartment translations (4.4 mm; 95% confidence interval [CI], 2.7 to 6.1 mm [p = 0.99] for Pivot Shift 1 and 4.3 mm; 95% CI, 2.6 to 6.0 mm [p = 0.99] for Pivot Shift 2), with 10 of 14 knees being converted to a corresponding Grade-3 pivot-shift (>20 mm of lateral translation). Increases in internal rotation after ALL and ITB sectioning occurred at 25°, 60°, and 90° (p = 0.99 for all) and ranged from 1° to 12°, with 21% of the knees having 8° to 12° increases. CONCLUSIONS: With ACL sectioning, a positive pivot-shift anterior subluxation occurred even with intact ALL and ITB structures, which indicates that the latter are not primary restraints but function together as anterolateral secondary restraints. With ACL deficiency, concurrent loss of the ALL and ITB resulted in conversion in a majority of knees (71%) to a Grade-3 pivot-shift subluxation, along with major increases of internal rotation in select knees. CLINICAL RELEVANCE: With ACL rupture, major increases in rotational instability are not adequately resisted by native ALL or ITB structures. Therefore, anatomic ALL or ITB surgical reconstruction would not block a positive pivot shift. The potential protective effects of ACL graft-unloading from these structures require further study.

Is an Anterolateral Ligament Reconstruction Required in ACL-Reconstructed Knees With Associated Injury to the Anterolateral Structures? A Robotic Analysis of Rotational Knee Stability.

BACKGROUND: The effect of an anterolateral ligament (ALL) reconstruction on rotational knee stability and corresponding anterior cruciate ligament (ACL) graft forces using multiple knee loading conditions including the pivot-shift phenomenon has not been determined. PURPOSE: First, to determine the rotational stability and ACL graft forces provided by an anatomic bone-patellar tendon-bone ACL reconstruction in the ACL-deficient knee alone and with an associated ALL/iliotibial band (ITB) injury. Second, to determine the added rotational stabilizing effect and reduction in ACL graft forces provided by an ALL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: A 6 degrees of freedom robotic simulator was used to test 7 fresh-frozen cadaveric specimens during 5 testing conditions: intact, ACL-sectioned, ACL-reconstructed, ALL/ITB-sectioned, and ALL-reconstructed. Lateral and medial tibiofemoral compartment translations and internal tibial rotations were measured under Lachman test conditions, 5-N·m internal rotation, and 2 pivot-shift simulations. Statistical equivalence within 2 mm and 2° was defined as P < .05. RESULTS: Single-graft ACL reconstruction restored central tibial translation under Lachman testing and internal rotation under 5-N·m internal rotation torque ( P < .05). A modest increase in internal rotation under 5-N·m internal rotation torque occurred after ALL/ITB sectioning of 5.1° (95% CI, 3.6° to 6.7°) and 6.7° (95% CI, 4.3° to 9.1°) at 60° and 90° of flexion, respectively ( P = .99). Lateral compartment translation increases in the pivot-shift tests were <2 mm. ALL reconstruction restored internal rotation within 0.5° (95% CI, -1.9° to 2.9°) and 0.7° (95% CI, -2.0° to 3.4°) of the ACL-reconstructed state at 60° and 90° of flexion, respectively ( P < .05). The ALL procedure reduced ACL graft forces, at most, 75 N in the pivot-shift tests and 81 N in the internal rotation tests. CONCLUSION: Although the ALL reconstruction corrected the small abnormal changes in the internal rotation limit at high flexion angles, the procedure had no effect in limiting tibiofemoral compartment translations in the pivot-shift test and produced only modest decreases in ACL graft forces. Accordingly, the recommendation to perform an ALL reconstruction to correct pivot-shift abnormalities is questioned. CLINICAL RELEVANCE: The small changes in rotational stability after ALL/ITB sectioning would not seem to warrant the routine addition of an ALL reconstruction in primary ACL injuries. Clinical exceptions may exist, as in grossly unstable grade 3 pivot-shift knees and revision knees. However, the concern exists of overconstraining normal tibial rotations.

Anterolateral Ligament and Iliotibial Band Control of Rotational Stability in the Anterior Cruciate Ligament-Intact Knee: Defined by Tibiofemoral Compartment Translations and Rotations.

PURPOSE: To determine the stabilizing effect of the anterolateral ligament (ALL) and iliotibial band (ITB) in resisting internal tibial rotation limits and anterior subluxations of the tibiofemoral compartments in anterior cruciate ligament (ACL)-intact knees during anterior drawer, internal rotation, and under 2 different 4-degree-of-freedom pivot-shift conditions. METHODS: A 6-degree-of-freedom robotic simulator tested 19 fresh-frozen cadaver specimens with 3 testing conditions: intact, ALL- or ITB-sectioned (random), and both ALL and ITB sectioned. Anterior translation of the medial and lateral compartments and internal tibial rotation were measured under 100 N anterior drawer, 5 Nm internal rotation, and 2 pivot-shift conditions. Statistical equivalence was defined as P < .05. RESULTS: Sectioning the ALL alone had no effect on lateral compartment translation or internal rotation under any loading condition (equivalent P < .05). After ITB sectioning alone, small increases in internal rotation were found under 5 Nm internal rotation at 60° (3.0° [90% confidence interval 1.9-4.1]; P = .99) and 90° (2.2° [90% confidence interval 1.5-2.9]; P = .84) flexion. After both ALL and ITB were sectioned, increases in internal rotation of 1.7°, 4.5°, and 3.9° occurred at 25°, 60°, and 90° flexion, respectively (P > .05). Small increases in pivot-shift internal rotation (Group 1: 2.0° [90% confidence interval 1.4-2.6]; P = .52) and lateral compartment translation occurred (Group 1: 0.9 mm [90% confidence interval 0.7-1.1]; P < .001). CONCLUSIONS: Sectioning the ALL does not lead to an increase in tibiofemoral compartment subluxations in the pivot-shift test with an intact ACL. Accordingly the ALL would not represent a primary restraint to pivot-shift subluxations. ALL sectioning alone does not lead to an increase in internal rotation motion limits, however sectioning both the ALL and ITB did produce small increases in rotation limits at higher flexion angles which would likely not be clinically detectable. CLINICAL RELEVANCE: A deficiency to both the ALL and ITB during in vitro-simulated pivot-shift tests and internal rotation tests results in small, clinically undetectable changes in knee kinematics in the majority of knees assuming intact ACL function.

Reliability of a New Clinical Instrument for Measuring Internal and External Glenohumeral Rotation.

BACKGROUND: The shoulder plays a critical role in many overhead athletic activities. Several studies have shown alterations in shoulder range of motion (ROM) in the dominant shoulder of overhead athletes and correlation with significantly increased risk of injury to the shoulder and elbow. The purpose of this study was to measure isolated glenohumeral joint internal/external rotation (IR/ER) to determine inter- and intraobserver reliability of a new clinical device. HYPOTHESIS: (1) Inter- and intraobserver reliability would exceed 90% for measures of glenohumeral joint IR, ER, and total arc of motion; (2) the dominant arm would exhibit significantly increased ER, significantly decreased IR, and no difference in total arc of motion compared with the nondominant shoulder; and (3) a significant difference exists in total arc between male and female patients. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: Thirty-seven subjects (mean age, 23 years; range, 13-54 years) were tested by 2 orthopaedic surgeons. A single test consisted of 1 arc of motion from neutral to external rotation to internal rotation and back to neutral within preset torque limits. Each examiner performed 3 tests on the dominant and nondominant shoulders. Each examiner completed 2 installations. RESULTS: Testing reliability demonstrated that neither trial, installation, nor observer were significant sources of variation. The maximum standard deviation was 1.3° for total arc of motion and less than 2° for most other measurements. Dominant arm ER was significantly greater than nondominant arm ER (P = 0.02), and dominant arm IR was significantly less than nondominant arm IR (P = 0.00). Mean total rotation was 162°, with no significant differences in total rotation between dominant and nondominant arms (P = 0.34). Mean total arc of motion was 45° greater in female subjects. Differences in total arc of motion between male and female subjects was statistically significant (P < 0.00). CONCLUSION: This simple, clinical device allows for both inter- and intraobserver reliability measurements of glenohumeral internal and external rotation.

Anatomic Single-Graft Anterior Cruciate Ligament Reconstruction Restores Rotational Stability: A Robotic Study in Cadaveric Knees.

PURPOSE: First, we aimed to investigate the ability of a single bone-patellar tendon-bone graft placed in the anatomic center of the femoral and tibial attachment sites to restore normal tibiofemoral compartment translations and tibial rotation. Second, we aimed to investigate what combination of anterior load and internal rotation torque applied during a pivot-shift test produces maximal anterior tibiofemoral subluxations. METHODS: We used a 6-df robotic simulator to test 10 fresh-frozen cadaveric specimens under anterior cruciate ligament (ACL)-intact, ACL-sectioned, and ACL-reconstructed conditions measuring anterior translations of the medial, central, and lateral tibiofemoral compartments and degrees of tibial rotation. Specimens were loaded under Lachman, anterior limit, and internal rotation conditions, as well as 3 different pivot-shift conditions. RESULTS: On ACL sectioning, compartment translations in the Lachman and 3 pivot-shift tests increased significantly and were restored to ACL-intact values after single-graft ACL reconstruction. In the pivot-shift tests, the single graft restored lateral and medial compartment translations (e.g., group 3, within 1.3 ± 0.6 mm and 0.8 ± 0.6 mm, respectively, of the ACL-intact state and internal rotation within 0.7° ± 1.2°). Anterior subluxation of the medial compartment during pivot-shift loading was reduced when internal rotation torque was increased from 1 to 5 Nm (P < .0001). CONCLUSIONS: A single-graft ACL reconstruction performed at the central femoral and tibial ACL attachment sites restored anterior-posterior translation and tibial rotation motion limits. In addition, rotational knee stability as defined by tibiofemoral compartment translations was restored under all simulated pivot-shift testing conditions. CLINICAL RELEVANCE: This study provides in vitro evidence to support the clinical use of single-graft ACL reconstructions in restoring tibiofemoral compartment translations. It also shows the advantage of describing ACL insufficiency in terms of medial and lateral compartment subluxations as compared with the common approach of describing changes in central tibial translations and rotations.

Effect of anteromedial and posterolateral anterior cruciate ligament bundles on resisting medial and lateral tibiofemoral compartment subluxations.

PURPOSE: This study analyzed the interaction of the anteromedial and posterolateral portions of the anterior cruciate ligament (ACL) in resisting medial and lateral tibiofemoral compartment subluxations under multiple loading conditions. METHODS: By use of a 6-df robotic simulator, 10 human cadaveric knees were tested in 3 states: intact ACL, partial ACL (loss of either the anteromedial bundle [AMB] or posterolateral bundle [PLB]), and deficient ACL. The testing profile involved anterior-posterior translation and internal-external rotation, as well as 3 pivot-shift loading conditions with varying internal rotation torque (1- or 5-Nm) and coupled anterior force (35- or 100-N). Digitization of anatomic landmarks provided tibiofemoral compartment translations and centers of tibial rotation. RESULTS: During pivot-shift testing (100-N anterior force, 1-Nm internal rotation torque, and 7-Nm valgus), the lateral and medial compartment anterior translation increased by a mean of 2.5 ± 0.8 mm (P = .016) and 3.4 ± 2.0 mm (P = .001), respectively, on AMB sectioning and 1.3 ± 0.9 mm (P = .329) and 0.6 ± 0.7 mm (P = .544), respectively, on PLB sectioning. Higher internal rotation torque (5 Nm v 1 Nm) on pivot-shift testing reduced central and medial anterior translation after ACL sectioning. There was no change in internal rotation on AMB or PLB sectioning. During the Lachman test (100-N), AMB and PLB sectioning increased central translation by 3.6 ± 1.6 mm (P = .001) and 0.7 ± 0.6 mm (P = .498), respectively. CONCLUSIONS: Both ACL bundles function synergistically in resisting medial and lateral compartment subluxations on the Lachman and pivot-shift tests. The AMB provided more restraint to anterior tibial translation during both tests as compared with the PLB. PLB sectioning produced no statistically significant change in anterior translation on the Lachman or pivot-shift test. Neither bundle contributed to resisting internal rotation. CLINICAL RELEVANCE: An ACL graft designed to duplicate the AMB would theoretically resist medial and lateral compartment anterior subluxations under multiple loading conditions. The PLB provides a secondary restraint at low flexion angles. Neither ACL bundle resists internal tibial rotation or allows a positive pivot-shift subluxation.

Severe obesity effect on low back biomechanical stress of manual load lifting.

BACKGROUND: Little research is available on low back biomechanical stresses that obese and overweight workers experience from manual load lifting. OBJECTIVE: The study objective was to quantitatively evaluate low back biomechanical stresses of severely obese (BMI≥35 kg/m2) workers during manual lifts of moderate load weights. METHOD: Twenty severely obese and 20 normal weight participants performed infrequent lifting in 16 task conditions. In each task condition, NIOSH recommended load weights were computed for the origin and destination of lift and were employed as the load weights. Optical motion capture was performed to collect lifting posture data. For each participant and each lifting condition, L5/S1 disc compression forces were computed at the origin and destination of lift using a static low back biomechanical model. RESULTS: The L5/S1 disc compression forces estimated for the severely obese participants ranged from 3000N to 8500N and many exceeded the 3400N NIOSH action limit by large margins. Group mean disc compression force was significantly larger for the severely obese than the normal weight group. CONCLUSION: In light of previous research on spine, bone and obesity, the study results seem to suggest that severely obese individuals are likely at an increased risk of lifting-related low back pain compared with normal weight individuals.

Anterior cruciate ligament function in providing rotational stability assessed by medial and lateral tibiofemoral compartment translations and subluxations.

BACKGROUND: Rotational knee stability provided by the anterior cruciate ligament (ACL) in the pivot-shift phenomena involves analysis of more complex robotic testing profiles and resulting tibiofemoral compartment kinematics and subluxations. HYPOTHESES: Using anterior-posterior tibial forces along with internal and valgus tibial moments will produce a major anterior subluxation of both tibiofemoral compartments not obtained with internal and valgus moments alone. Increasing the internal torque in pivot-shift testing will constrain the anterior subluxations of the medial and central tibial compartments. STUDY DESIGN: Controlled laboratory study. METHODS: A 6 degrees of freedom robotic knee testing system applied anterior translation and rotational loading profiles in 10 cadaveric knees before and after ACL sectioning. Changes in knee motion limits were measured, and medial and lateral tibiofemoral compartment translations were determined by digitization of tibial plateau anatomic landmarks. Loading profiles simulated Lachman and tibial rotation tests as well as typical pivot-shift loading profiles from prior in vitro and in vivo studies. RESULTS: After ACL sectioning, anterior tibial translation increased by 10.3 ± 3.7 mm at 25° of flexion (P < .001). Internal tibial rotation increased by 1.6° ± 1.1° (5 N·m; P > .05). In pivot-shift tests (anterior translation, 100 N; internal rotation, 1 N·m; valgus, 7 N·m), the tibial rotation center shifted outside the medial tibial margin, with abnormal anterior translation of both compartments (medial, 12.9 ± 3.9 mm; lateral, 7.5 ± 3.7 mm; P < .001), with internal rotation decreasing by 4.1° ± 3.5° (P < .05). A greater internal rotation torque (5 vs 1 N·m) in the pivot-shift test constrained and limited anterior tibial translation and prevented anterior subluxation of the medial compartment (P < .001). CONCLUSION: Sectioning of the ACL produces major increases in tibiofemoral compartment translations and only small increases in internal tibial rotation. The simulation of the pivot shift requires a combined loading profile of anterior translation, internal rotation, and valgus, which produces the greatest anterior subluxation of the medial and lateral tibiofemoral compartments. This testing profile is recommended to be included along with other loading profiles for future ACL studies. The application of a high internal rotation torque in cadaveric pivot-shift tests constrains anterior tibial subluxation of the medial and center compartments and appears less ideal for analysis of ACL function and graft reconstructions. CLINICAL RELEVANCE: Surgeons should be cautious in interpreting conclusions on ACL function and graft reconstructions without knowing the resulting tibiofemoral subluxations or loading conditions that may limit maximum anterior tibial femoral subluxations.

Reverse shoulder arthroplasty using an implant with a lateral center of rotation: outcomes, complications, and the influence of experience.

Reverse shoulder arthroplasty (RSA) has revolutionized treatment of arthritis and rotator cuff insufficiency and is performed using implants with either a medial or a lateral center of rotation. We conducted a study of the outcomes and the effect of surgeon learning after the first 60 consecutive lateral-center-of-rotation RSAs implanted by a single surgeon unaffiliated with the design team for this particular reverse shoulder prosthesis. At minimum 2-year followup, mean improvements in active forward elevation, abduction, and external rotation were 69°, 55°, and 23°, respectively; mean active internal rotation improved significantly as well (P < .001 for all). Mean Simple Shoulder Test (SST) scores improved from 1.8 (range, 0-6) to 6.9 (range, 0-12) (P < .0001), and mean final American Shoulder and Elbow Surgeons score was 72 (range, 27-100). Final radiographs showed scapular notching in 5 shoulders (11%). Gains in SST scores, active forward elevation, and active abduction were lower for the first 15 cases than for the next 45 cases, and 5 of the 8 reoperations were performed after the first 15 cases. Overall improvements in active motion and self-assessed shoulder function in this series are comparable to those previously reported by the design team. Experience with RSA appears to influence efficacy, but the learning curve may not be as steep as previously reported.

Using time-series intervention analysis to understand U.S. Medicaid expenditures on antidepressant agents.

BACKGROUND: Medicaid programs' spending on antidepressants increased from $159 million in 1991 to $2 billion in 2005. The National Institute for Health Care Management attributed this expenditure growth to increases in drug utilization, entry of newer higher-priced antidepressants, and greater prescription drug insurance coverage. Rising enrollment in Medicaid has also contributed to this expenditure growth. OBJECTIVES: This research examines the impact of specific events, including branded-drug and generic entry, a black box warning, direct-to-consumer advertising (DTCA), and new indication approval, on Medicaid spending on antidepressants. METHODS: Using quarterly expenditure data for 1991-2005 from the national Medicaid pharmacy claims database maintained by the Centers for Medicare and Medicaid Services, a time-series autoregressive integrated moving average (ARIMA) intervention analysis was performed on 6 specific antidepressant drugs and on overall antidepressant spending. Twenty-nine potentially relevant interventions and their dates of occurrence were identified from the literature. Each was tested for an impact on the time series. Forecasts from the models were compared with a holdout sample of actual expenditure data. RESULTS: Interventions with significant impacts on Medicaid expenditures included the patent expiration of Prozac® (P<0.01) and the entry of generic paroxetine producers (P=0.04), which reduced expenditures on Prozac® and Paxil®, respectively, and the 1997 increase in DTCA (P=0.05), which increased spending on Wellbutrin®. Except for Paxil®, the ARIMA models had low prediction errors. CONCLUSIONS: Generic entry at the aggregate level did not lead to a reduction in overall expenditures (P>0.05), implying that the expanding market for antidepressants overwhelmed the effect of generic competition.

Knee injuries and the use of prophylactic knee bracing in off-road motorcycling: results of a large-scale epidemiological study.

BACKGROUND: The effectiveness of prophylactic knee bracing in preventing knee injuries during sports has been evaluated; however, because of the variability in study conclusions, the topic remains controversial. Despite a paucity of data, the authors believe that prophylactic knee bracing is frequently used in off-road motorcycling. HYPOTHESIS: No statistically significant difference exists in the frequency and types of knee injuries incurred between braced and nonbraced riders using commercially available knee braces in off-road motorcycling. STUDY DESIGN: Descriptive epidemiology study. METHODS: Data from 2115 off-road motorcycle riders was obtained using an Internet-based survey over a 1-year period. Participants were grouped by use or nonuse of prophylactic knee bracing, and an incidence rate ratio was used for injury rate comparison. RESULTS: Participants recorded 39 611 riding hours over the study period. A total of 57 riders (2.7%) sustained at least 1 knee injury, for a total of 89 injuries. The most common injuries involved the anterior cruciate ligament, menisci, and medial collateral ligament. There was a significantly higher rate of overall injuries in the nonbraced group versus the braced group (3.675 vs 1.587 per 1000 rider hours, P < .001). Significantly higher incidence rates of anterior cruciate ligament rupture (1.518 vs 0.701 per 1000 rider hours, P = .0274) and medial collateral ligament injury (0.799 vs 0.111 per 1000 rider hours, P = .002) were found among nonbraced riders compared with braced riders. CONCLUSION: The most common knee injuries in off-road motorcycling involve the anterior cruciate ligament, menisci, and medial collateral ligament. The use of prophylactic knee bracing appears to have a beneficial effect in preventing medial collateral ligament and anterior cruciate ligament injuries as well as overall knee injury occurrence. These findings may be applicable to other sports that involve similar forces and mechanics.

Predictors of outcome after nonoperative and operative treatment of adhesive capsulitis.

BACKGROUND: Few studies regarding adhesive capsulitis have concurrently evaluated nonoperative and operative treatment. PURPOSE: The objectives were to evaluate the efficacy of operative and nonoperative treatment of adhesive capsulitis and to determine predictors of clinical outcome. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: At minimum 24 months' follow-up, 85 patients underwent self-assessment using the Simple Shoulder Test (SST) and American Shoulder and Elbow Surgeons (ASES) score, including 24 patients treated operatively. RESULTS: Mean number of yes responses on the SST improved from 4.0 ± 2.7 at initial presentation to 9.9 ± 2.8 at final follow-up (P < .0001). Patients who received nonoperative treatment and patients who underwent surgery demonstrated similar improvements on the SST. For the entire cohort, forward elevation and external rotation at the side improved from 119° ± 20° to 152° ± 15° and from 29° ± 18° to 46° ± 11° (P < .0001), respectively, between initial presentation and discharge from treatment. Internal rotation to the back improved from the gluteal area to the thoracolumbar junction (P < .0001). Improvements in forward elevation and external rotation were greater for patients undergoing surgery. After nonoperative treatment, patients with diabetes had a lower final SST than patients without diabetes (P < .05). For the entire cohort, initial SST predicted final SST (P < .05), and a shorter duration of symptoms predicted a higher final ASES score (P < .05). Younger patients (P < .001) and those with a lower initial SST (P < .05) were more likely to undergo surgery. CONCLUSIONS: A multimodal nonoperative treatment program is effective for most patients with adhesive capsulitis. Patients who do not improve, including those with diabetes, respond well to manipulation and arthroscopic release. Residual motion deficits at discharge from treatment do not appear to affect longer-term clinical outcome.

Obesity effect on perceived postural stress during static posture maintenance tasks.

Postural stresses related to manual work tasks may be significantly affected by the bodily condition of workers. One such condition is obesity, which is characterised by excess fat mass in the body. This study empirically examined the obesity effect on postural stress during static posture maintenance tasks. In total, 20 obese and 20 non-obese participants performed static box-holding for a set of 84 working postures defined based on the Ovako Working Posture Analysing System. The participants reported postural stresses using the rated perceived exertion scale. Obesity was found to significantly increase postural stress across the 84 working postures and, also, amplify the effects of postural changes on postural stress. The study findings suggest that ergonomic workplace/job design for obese workers would be a challenge requiring a proactive approach and creativity in problem solving. In addition, the use of ergonomic knowledge in design would be more critical when targeting obese than non-obese workers. The study findings are relevant to ergonomic workplace/job design for obese workers.

Obesity does not reduce maximum acceptable weights of lift.

The maximum acceptable weights of lift (MAWL) of obese and non-obese participants were empirically investigated. Three obesity levels were considered: non-obese (18.5 kg/m(2)< or= body mass index (BMI)or= 40 kg/m(2)). Ten male and 10 female participants were recruited for each obesity level. The participants determined their MAWL for 18 different lifting task conditions (six lifting frequencies x three lifting heights). An analysis of variance (ANOVA) was conducted to determine the effects of obesity level, gender, lifting height, lifting frequency and their interactions on MAWL. Overall, the ANOVA results indicated that obesity does not reduce MAWL, and thus, suggested that the existing MAWL data can be used to accommodate both general and obese workers. However, further studies based on the biomechanical and physiological approaches are required to provide more complete understanding of obesity effects on lifting tolerance limits.

Effects of cell seeding density and collagen concentration on contraction kinetics of mesenchymal stem cell-seeded collagen constructs.

Our group has been engineering cell-scaffold constructs to improve tendon repair by contracting mesenchymal stem cells (MSCs) in collagen gels and then evaluating their repair potential in wound sites in rabbits. Because the construct's initial conditions may influence the ultimate repair outcome, this two-part study sought to distinguish which factors most influence contraction kinetics in culture. (1)We optically determined if varying cell-to-collagen ratio significantly affected construct contraction. Temporal changes in construct area were monitored up to 168 h for 4 cell-to-collagen ratios (HK = 0.04, LK = 0.08, HM = 0.4, and LM = 0.8, where H, L = 2.6, 1.3 mg/mL collagen and K,M = 0.1, 1 million cells/mL, respectively).A mathematical model was created with terms that represent the different combinations of cell densities and collagen concentrations in order to predict the contraction kinetics as a function of time. Highly significant differences in construct areas were found among all 4 ratios after 8 h of contraction with the exception of the LK (0.08) vs. HM(0.4) conditions. This similar pattern raised the question of whether cell density or collagen concentration more influenced these events. (2) To isolate these effects, the contraction kinetics of the HM construct were compared to those of a new construct (L5K) with equivalent cell-to-collagen ratio (0.4) but half the cell density (500 K MSCs/mL) and half the collagen concentration (1.3 mg/mL). The L5K construct contracted significantly faster and more completely than the HM construct but no differently than the LM construct. These results indicate that above a threshold value of cell density, percentage reductions in collagen concentration influence contraction kinetics more than equivalent percentage increases in cell seeding density. The fact that our model successfully predicted intermediate time points of contraction suggests its utility for examining other cell and collagen densities. Controlling scaffold as well as cellular initial conditions will be critical in achieving our goal of functional tissue engineering (FTE) a successful tendon repair.

Effect of age on collagen fibril diameter in rabbit patellar tendon repair.

The effect of aging on soft tissue repair is poorly understood. We examined collagen fibril diameter in repairing patellar tendons from young adult and aging rabbits. We hypothesized that repairing tendons from older (geriatric) rabbits would have similar diameter fibrils compared with the younger (young adult) rabbits. Full-length, full-thickness, central-third (2.5 to 3 mm) patellar tendon injuries were made by cutting out the center of the tendon in twelve 1-y-old and thirteen 4- to 5.5 (average, 4.25)-y-old female New Zealand White rabbits. The contralateral tendon served as an unoperated control. The rabbits were euthanized at 6, 12, and 26 wk after surgery. The collagen fibril diameter was examined by electron microscopy at the patellar end, middle, and tibial end of the patellar tendon. There was no significant decline in collagen fibril diameter at any location in the aging rabbit healing patellar tendons compared with those of the 1-y-old rabbits. This study found that collagen fibril diameter was not altered with increasing age in the healing rabbit patellar tendon.

One- and two-strand posterior cruciate ligament reconstructions: cyclic fatigue testing.

This study examined how one- and two-strand posterior cruciate ligament (PCL) reconstructions resist the return of posterior translation during repetitive knee cycling. The femoral attachment of the one-strand graft and the anterior strand of the two-strand (AD2) grafts were located within the anterior one-third of the femoral PCL footprint. The second strand was placed within the middle third of the femoral footprint in one of three locations: middle-distal (MD), middle-middle (MM), or middle-proximal (MP). During repetitive knee cycling from 5 degrees to 120 degrees flexion with a 100 N posterior force, the intact knee had less than 1mm of residual posterior translation after 2048 flexion-extension cycles. Under similar cyclic conditions, the AD2-MM reconstruction achieved the most cycles before failure; however, this two-strand configuration failed in less than 700 cycles. The other reconstructions, either one strand or two strand, failed in less than 350 cycles. The surface failure location for 19 of 25 graft strands was within the femoral one-third of the strand. We concluded that one- and two-strand reconstructions under moderate loading and a range of motion from 5 degrees to 120 degrees flexion have an unacceptably high cyclic failure rate suggesting modifications of the allowable postoperative knee flexion and loading.