Augmented Ulnar Collateral Ligament Repair With Structural Bioinductive Scaffold: A Biomechanical Study.

BACKGROUND: Elbow ulnar collateral ligament (UCL) repair with suture brace augmentation shows good time-zero biomechanical strength and a more rapid return to play compared with UCL reconstruction. However, there are concerns about overconstraint or stress shielding with nonabsorbable suture tape. Recently, a collagen-based bioinductive absorbable structural scaffold has been approved by the Food and Drug Administration for augmentation of soft tissue repair. PURPOSE/HYPOTHESIS: This study aimed to assess the initial biomechanical performance of UCL repair augmented with this scaffold. We hypothesized that adding the bioinductive absorbable structural scaffold to primary UCL repair would impart additional time-zero restraint to the valgus opening. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric elbow specimens-from midforearm to midhumerus-were utilized. In the native state, elbows underwent valgus stress testing at 30o, 60o, and 90o of flexion, with a cyclical valgus rotational torque. Changes in valgus rotation from 2- to 5-N·m torque were recorded as valgus gapping. Testing was then performed in 4 states: (1) native intact UCL-with dissection through skin, fascia, and muscle down to an intact UCL complex; (2) UCL-transected-distal transection of the ligament off the sublime tubercle; (3) augmented repair with bioinductive absorbable scaffold; and (4) repair alone without scaffold. The order of testing of repair states was alternated to account for possible plastic deformation during testing. RESULTS: The UCL-transected state showed the greatest increase in valgus gapping of all states at all flexion angles. Repair alone showed similar valgus gapping to that of the UCL-transected state at 30° (P = .62) and 60° of flexion (P = .11). Bioinductive absorbable scaffold-augmented repair showed less valgus gapping compared with repair alone at all flexion angles (P = .021, P = .024, and P = .024 at 30°, 60°, and 90°, respectively). Scaffold-augmented repair showed greater gapping compared with the native state at 30° (P = .021) and 90° (P = .039) but not at 60° of flexion (P = .059). There was no difference when testing augmented repair or repair alone first. CONCLUSION: UCL repair augmented with a bioinductive, biocomposite absorbable structural scaffold imparts additional biomechanical strength to UCL repair alone, without overconstraint beyond the native state. Further comparative studies are warranted. CLINICAL RELEVANCE: As augmented primary UCL repair becomes more commonly performed, use of an absorbable bioinductive scaffold may allow for improved time-zero mechanical strength, and thus more rapid rehabilitation, while avoiding long-term overconstraint or stress shielding.

Optimal assessment for anterior talofibular ligament injury utilizing stress ultrasound entails internal rotation during plantarflexion.

OBJECTIVES: An optimal load and ankle position for stress ultrasound of the injured anterior talofibular ligament (ATFL) are unknown. The objectives of this study were to compare stress ultrasound and ankle kinematics from a 6 degree-of-freedom (6-DOF) robotic testing system as a reference standard for the evaluation of injured ATFL and suggest cut-off values for ultrasound diagnosis. METHODS: Ten fresh-frozen human cadaveric ankles were used. Loads and ankle positions examined by the 6-DOF robotic testing system were: 40 N anterior load, 1.7 Nm inversion, and 1.7 Nm internal rotation torques at 30° plantarflexion, 15° plantarflexion, and 0° plantarflexion. Bony translations were measured by ultrasound and a robotic testing system under the above conditions. After measuring the intact ankle, ATFL was transected at its fibular attachment under arthroscopy. Correlations between ultrasound and robotic testing systems were calculated with Pearson correlation coefficients. Paired t-tests were performed for comparison of ultrasound measurements of translation between intact and transected ATFL and unloaded and loaded conditions in transected ATFL. RESULTS: Good agreement between ultrasound measurement and that of the robotic testing system was found only in internal rotation at 30° plantarflexion (ICC â€‹= â€‹0.77; 95% confidence interval 0.27-0.94). At 30° plantarflexion, significant differences in ultrasound measurements of translation between intact and transected ATFL (p â€‹< â€‹0.01) were found in response to 1.7 Nm internal rotation torque and nonstress and stress with internal rotation (p â€‹< â€‹0.01) with mean differences of 2.4 â€‹mm and 1.9 â€‹mm, respectively. CONCLUSION: Based on the data of this study, moderate internal rotation and plantarflexion are optimal to evaluate the effects of ATFL injury when clinicians utilize stress ultrasound in patients. LEVEL OF EVIDENCE: III.

A Dynamic Elbow Testing Apparatus for Simulating Elbow Joint Motion in Varying Shoulder Positions.

Purpose: To develop and evaluate the capabilities of a dynamic elbow testing apparatus that simulates unconstrained elbow motion throughout the range of humerothoracic (HTA) abduction. Methods: Elbow flexion was generated by six computer-controlled electromechanical actuators that simulated muscle action, while six degree-of-freedom joint motion was measured using an optical tracking device. Repeatability of joint kinematics was assessed at four HTA angles (0°, 45°, 90°, 135°) and with two muscle force combinations (A1-biceps brachialis, brachioradialis and A2-biceps, brachioradialis). Repeatability was determined by comparing kinematics at every 10° of flexion over five flexion-extension cycles (0° to 100°). Results: Multiple muscle force combinations can be used at each HTA angle to generate elbow flexion. Trials showed that the testing apparatus produced highly repeatable joint motion at each HTA angle and with varying muscle force combinations. The intraclass correlation coefficient was greater than 0.95 for all conditions. Conclusions: Repeatable smooth cadaveric elbow motion was created that mimicked the in vivo situation. Clinical relevance: These results suggest that the dynamic elbow testing apparatus can be used to characterize elbow biomechanics in cadaver upper extremities.

The Effect of Elbow Flexion On Valgus Carrying Angle.

PURPOSE: This study aimed to examine the effect of flexion on valgus carrying angle in the human elbow using a dynamic elbow testing apparatus. METHODS: Active elbow motion was simulated in seven cadaveric upper extremities. Six electromechanical actuators simulated muscle action, while 6 degrees-of-freedom joint motion was measured with an optical tracking system to quantify the kinematics of the ulna with respect to the humerus as the elbow was flexed at the side position. Repeatability of the testing apparatus was assessed in a single elbow over five flexion-extension cycles. The varus angle change of each elbow was compared at different flexion angles with the arm at 0° of humerothoracic abduction or dependent arm position. RESULTS: The testing apparatus achieved excellent kinematic repeatability (intraclass correlation coefficient, >0.95) throughout flexion and extension. All elbows decreased their valgus carrying angle during flexion from 0° to 90° when the arm was maintained at 0° of humerothoracic abduction. Elbows underwent significant total varus angle change from full extension of 3.9° ± 3.4° (P = .007), 7.3° ± 5.2° (P = .01), and 8.9° ± 7.1° (P = .02) at 60°, 90°, and 120° of flexion, respectively. No significant varus angle change was observed between 0° and 30° of flexion (P = .66), 60° and 120° of flexion (P = .06), and 90° and 120° of flexion (P = .19). CONCLUSIONS: The dynamic elbow testing apparatus characterized a decrease of valgus carrying angle during elbow flexion and found that most varus angle changes occurred between 30° and 90° of flexion. All specimens underwent varus angle change until at least 90° of flexion. CLINICAL RELEVANCE: Our model establishes the anatomic decrease in valgus angle by flexion angle in vitro and can serve as a baseline for testing motion profiles of arthroplasty designs and ligamentous reconstruction in the dependent arm position. Future investigations should focus on characterizing motion profile change as the arm is abducted away from the body.

Screws or Sutures? A Pediatric Cadaveric Study of Tibial Spine Fracture Repairs.

BACKGROUND: Tibial spine fractures are common in the pediatric population because of the biomechanical properties of children's subchondral epiphyseal bone. Most studies in porcine or adult human bone suggest that suture fixation performs better than screw fixation, but these tissues may be poor surrogates for pediatric bone. No previous study has evaluated fixation methods in human pediatric knees. PURPOSE: To quantify the biomechanical properties of 2-screw and 2-suture repair of tibial spine fracture in human pediatric knees. STUDY DESIGN: Controlled laboratory study. METHODS: Cadaveric specimens were randomly assigned to either 2-screw or 2-suture fixation. A standardized Meyers-Mckeever type 3 tibial spine fracture was induced. Screw-fixation fractures were reduced with two 4.0-mm cannulated screws and washers. Suture-fixation fractures were reduced by passing 2 No. 2 FiberWire sutures through the fracture fragment and the base of the anterior cruciate ligament. Sutures were secured through bony tunnels over a 1-cm tibial cortical bridge. Each specimen was mounted at 30° of flexion. A cyclic loading protocol was applied to each specimen, followed by a load-to-failure test. Outcome measures were ultimate failure load, stiffness, and fixation elongation. RESULTS: Twelve matched pediatric cadaveric knees were tested. Repair groups had identical mean (8.3 years) and median (8.5 years) ages and an identical number of samples of each laterality. Ultimate failure load did not significantly differ between screw (mean ± SD, 143.52 ± 41.9 7 N) and suture (135.35 ± 47.94 N) fixations (P = .760). Screws demonstrated increased stiffness and decreased elongation, although neither result was statistically significant at the .05 level (21.79 vs 13.83 N/mm and 5.02 vs 8.46 mm; P = .076 and P = .069, respectively). CONCLUSION: Screw fixation and suture fixation of tibial spine fractures in human pediatric tissue were biomechanically comparable. CLINICAL RELEVANCE: Suture fixations are not biomechanically superior to screw fixations in pediatric bone. Pediatric bone fails at lower loads, and in different modes, compared with adult cadaveric bone and porcine bone. Further investigation into optimal repair is warranted, including techniques that may reduce suture pullout and "cheese-wiring" through softer pediatric bone. This study provides new biomechanical data regarding the properties of different fixation types in pediatric tibial spine fractures to inform clinical management of these injuries.

Introduction of a Novel Sequential Approach to the Ponte Osteotomy to Minimize Spinal Canal Exposure.

Ponte osteotomy is an increasingly popular technique for multiplanar correction of adolescent idiopathic scoliosis. Prior cadaveric studies have suggested that sequential posterior spinal releases increase spinal flexibility. Here we introduce a novel technique involving a sequential approach to the Ponte osteotomy that minimizes spinal canal exposure. One fresh-frozen adult human cadaveric thoracic spine specimen with 4 cm of ribs was divided into three sections (T1-T5, T6-T9, T10-L1) and mounted for biomechanical testing. Each segment was loaded with five Newton meters under four conditions: baseline inferior facetectomy with supra/interspinous ligament release, superior articular process (SAP) osteotomy in situ, spinous process (SP) osteotomy in situ, and complete posterior column osteotomy with SP/SAP excision and ligamentum flavum release (PCO). Compared to baseline, in situ SAP osteotomy alone provided 3.5%, 7.6%, and 7.2% increase in flexion/extension, lateral bending, and axial rotation, respectively. In situ SP osteotomy increased flexion/extension, lateral bending, and axial rotation by 15%, 18%, and 10.3%, respectively. PCO increased flexion/extension, lateral bending, and axial rotation by 19.6%, 28.3%, and 12.2%, respectively. Our report introduces a novel approach where incremental increases in range of motion can be achieved with minimal spinal canal exposure and demonstrates feasibility in a cadaveric model.

Reliability, Concurrent Validity, and Minimal Detectable Change of Timed Up and Go Obstacle Test in People With Stroke.

OBJECTIVE: The aims of this study were to investigate the psychometric property of the timed Up and Go Obstacle (TUGO) test in people with stroke. DESIGN: Cross-sectional design. SETTING: University based neurorehabilitation laboratory. PARTICIPANTS: Twenty-eight people with stroke and 30 healthy older adults. INTERVENTION: Not Applicable. OUTCOME MEASURES: The TUGO (obstacle heights: 0, 5, 17 cm) test completion times, Fugl-Meyer Assessment (FMA) score, ankle dorsiflexor and plantarflexor muscle strength, Berg Balance Scale (BBS) score, Narrow Corridor Walking Test (NCWT) completion time, timed Up and Go (TUG) test completion time, and Community Integrated Measure. RESULTS: Excellent inter-rater (intraclass correlation coefficient [ICC]=0.999-1.000) and test-retest reliabilities (ICC=0.917-0.975) were found for TUGO test completion times for all obstacle heights. The TUGO test completion times for all obstacle heights were significantly correlated with NCWT and TUG test completion times (r=0.817-0.912). Only TUGO test completion times for 0 and 5 cm obstacle heights showed significant correlations with BBS scores (r=-0.518 to -0.534), while the TUGO test completion time for the 17 cm obstacle height correlated significantly with FMA scores. The minimal detectable change and optimal cut-off values for TUGO test completion times for the 0, 5, and 17 cm obstacle heights were 2.54, 3.60, and 3.07 s, and 14.69, 14.76, and 16.10 s, respectively. CONCLUSION: The TUGO test is a reliable, valid, and easy-to-administer clinical measure to discriminate between people with stroke and healthy older adults.

Distal Metaphyseal Ulnar Shortening Osteotomy Fixation: A Biomechanical Analysis.

PURPOSE: Ulnar shortening osteotomy can be used to treat ulnar impaction syndrome and other causes of ulnar wrist pain. Distal metaphyseal ulnar shortening osteotomy (DMUSO) is one technique that has been proposed to reduce the complications seen with a diaphyseal USO or a wafer resection. However, to our knowledge, the optimal fixation construct for DMUSO has not been studied. We sought to characterize the biomechanical stiffness and rotational stability of different DMUSO constructs. METHODS: A DMUSO was performed on 40 human cadaveric ulnas using 4 different fixation constructs (10 specimens per group): one 3.0 mm antegrade screw; two 2.2 mm antegrade screws; one 3.0 mm retrograde screw; and two 2.2 mm retrograde screws. Biaxial testing using axial load and cyclical axial torque was performed until failure, defined as 10° of rotation or 2 mm displacement. Specimens were assessed for stiffness at failure. Bone density was assessed using the second metacarpal cortical percentage. RESULTS: Bone density was similar between all 4 testing groups. Of the 4 groups, the 2 antegrade screw group exhibited the highest rotational stiffness of 232 ± 102 Nm/deg. In paired analysis, this was significantly greater than 1 retrograde screw constructs. In multivariable analysis, 2-screw constructs were significantly stiffer than 1 screw and antegrade constructs were significantly stiffer than retrograde. Maximum failure torque did not differ with orientation, but 2 screws failed at significantly higher torques. CONCLUSION: Using 2 screws for DMUSO fixation constructs may provide higher stiffness and maximum failure torque, and antegrade screw constructs may provide more stiffness than retrograde constructs. CLINICAL RELEVANCE: Antegrade screw fixation using 2 screws may provide the strongest construct for DMUSO. Antegrade fixation may be preferred because it avoids violating the distal radioulnar joint capsule and articular surface of the ulna.

Increasing the posterior tibial slope lowers in situ forces in the native ACL primarily at deep flexion angles.

High tibial osteotomy is becoming increasingly popular but can be associated with unintentional posterior tibial slope (PTS) increase and subsequent anterior cruciate ligament (ACL) degeneration. This study quantified the effect of increasing PTS on knee kinematics and in situ forces in the native ACL. A robotic testing system was used to apply external loads from full extension to 90° flexion to seven human cadaveric knees: (1) 200 N axial compressive load, (2) 5 Nm internal tibial + 10 Nm valgus torque, and (3) 5 Nm external tibial + 10 Nm varus torque. Kinematics and in situ forces in the ACL were acquired for the native and increased PTS state. Increasing PTS resulted in increased anterior tibial translation at 30° (1.8 mm), 60° (1.7 mm), and 90° (0.9 mm) flexion and reduced in situ force in the ACL at 30° (57.6%), 60° (69.8%), and 90° (75.0%) flexion in response to 200 N axial compressive load. In response to 5 Nm internal tibial + 10 Nm valgus torque, there was significantly less (39.0%) in situ force in the ACL at 90° flexion in the increased compared with the native PTS state. Significantly less in situ force in the ACL at 60° (62.8%) and 90° (67.0%) flexion was observed in the increased compared with the native PTS state in response to 5 Nm external tibial + 10 Nm varus torque. Increasing PTS affects knee kinematics and results in a reduction of in situ forces in the native ACL during compressive and rotatory loads at flexion angles exceeding 30°. In a controlled laboratory setting PTS increase unloads the ACL, affecting its natural function.

Increased superior translation following multiple simulated anterior dislocations of the shoulder.

PURPOSE: Recurrent shoulder dislocations can result in kinematic changes of the glenohumeral joint. The number of prior shoulder dislocations may contribute to increased severity of capsulolabral lesions. The kinematics of the glenohumeral joint following multiple dislocations remain poorly understood. The purpose of this study was to assess the kinematics of the glenohumeral joint during anterior dislocations of the shoulder, and more specifically, altered translational motion following multiple dislocations. The kinematics of the glenohumeral joint were hypothesized to change and correlate with the number of dislocations. METHODS: Eight fresh-frozen cadaveric shoulders were dissected free of all soft tissues except the glenohumeral capsule. Each joint was mounted in a robotic testing system. At 60 degrees of glenohumeral abduction, an internal and external rotational torque (1.1 Nm) were applied to the humerus, and the resulting joint kinematics were recorded. Anterior forces were applied to the humerus to anteriorly dislocate the shoulder and the resulting kinematics were recorded during each dislocation. Following each dislocation, the same rotational torque was applied to the humerus, and the resulting joint kinematics were also recorded. A repeated-measures analysis of variance (ANOVA) was used to compare the kinematics following each dislocation. RESULTS: During the 7th, 8th, 9th, and 10th dislocations, the humerus significantly translated superiorly compared with the shoulder during the 1st dislocation (p < 0.05). Following the 3rd, 4th, 5th, and 10th dislocations, the humeral head significantly translated superiorly compared with the shoulder following the 1st dislocation in the position of 60 degrees of abduction in response to external rotation torque (p < 0.05). CONCLUSION: Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus. This may contribute to pathologic superior extension of capsulolabral injuries. Superior translation of the humerus with overhead motion in the setting of recurrent instability may also place the shoulder at risk for extension of the capsulolabral injuries.

Direction of non-recoverable strain in the glenohumeral capsule following multiple anterior dislocations: Implications for anatomic Bankart repair.

The study aimed to analyze the direction of non-recoverable strain and determine the optimal direction for anatomic capsular plication within four sub-regions of the inferior glenohumeral capsule following multiple dislocations. Seven fresh-frozen cadaveric shoulders were dissected. A grid of strain markers was affixed to the inferior glenohumeral capsule. Each joint was mounted in a 6-degree-of-freedom robotic testing system and repeatedly dislocated in the anterior direction 10 times at 60° of abduction and 60° of external rotation of the glenohumeral joint. The 3D positions of the strain markers were compared before and after dislocations to define the non-recoverable strain. The strain map was divided into four sub-regions. The angles of deviation between each maximum principle strain vector and the anterior band of the inferior glenohumeral ligament (AB-IGHL) or posterior band of the IGHL (PB-IGHL) for the anterior and posterior regions of the capsule were determined. The mean direction of all strain vectors in each sub-region was categorized. The direction of the non-recoverable strain in the anterior-band and anterior-axillary-pouch sub-regions was categorized as parallel to the AB-IGHL, whereas the posterior-axillary-pouch and posterior-band sub-regions were mostly perpendicular to the PB-IGHL. Clinical Significance: Plication of the anteroinferior capsule parallel to the AB-IGHL may be preferred during arthroscopic Bankart repair to restore anatomy; posteroinferior capsular plication may also be necessary and best performed perpendicular to the PB-IGHL. The direction of the capsular injury remains the same irrespective of the number of dislocations. This study provides the scientific and quantitative rationale for an anatomic approach to capsular plication.

The lateral meniscus extrudes with and without root tear evaluated using ultrasound.

PURPOSE: The purpose of the current study was to measure extrusion of the intact lateral meniscus as a function of knee flexion angle and loading condition and to compare the changes in extrusion with a posterior root tear using a robotic testing system and ultrasound. STUDY DESIGN: Controlled laboratory study. METHODS: Eight fresh-frozen cadaveric knees were subjected to external loading conditions (passive path position (no external load), 200 axial compression, 5-N-m internal tibial torque, 5-N-m valgus torque) at full extension, 30°, 60° and 90° of flexion using a robotic testing system. A linear array transducer was placed in the longitudinal orientation. Extrusion and kinematics data were recorded for two meniscus states: intact and posterior lateral root deficiency. Therefore, a complete radial root tear in the lateral meniscus at 10 mm from the tibial insertion was made in all 8 cadaveric knees using arthroscopy. The resultant forces in the lateral meniscus were also quantified by reproducing recorded paths after the removal of the lateral meniscus. RESULTS: A lateral meniscus root tear resulted in a statistically significant increase (up to 250%) of extrusion for the lateral meniscus (p < 0.05) in comparison to the intact lateral meniscus for all externally applied loads. Without external load (passive path position), significant differences were also found between the intact and posterior lateral root deficient meniscus except at full extension (1.0 ± 0.7 mm vs. 1.9 ± 0.4 mm) and 30° of flexion (1.4 ± 0.5 mm vs. 1.8 ± 0.5 mm). Overall, with increasing flexion angle, lateral meniscus extrusion decreased for the intact as well as for the posterior lateral root deficient meniscus, with the lowest measurements in response to internal tibial torque at 90° of flexion (-3.3 ± 1.1 mm). Knee kinematics were similar whether intact or posterior lateral root tear (n.s.). Ultrasound measurement of lateral meniscus extrusion showed good inter-rater (0.65 [0.30-0.97]-0.71 [0.34-0.94]) and excellent intra-rater reliability (0.81 [0.43-0.99]). CONCLUSION: Dynamic Ultrasound is a reliable diagnostic modality to measure the lateral meniscus extrusion which can be helpful in the diagnosis and quantification of lateral meniscal root tears. LEVEL OF EVIDENCE: III.

Ultrasound-Guided Anterior Talofibular Ligament Repair With Augmentation Can Restore Ankle Kinematics: A Cadaveric Biomechanical Study.

Background: Anterior talofibular ligament (ATFL) repair of the ankle is a common surgical procedure. Ultrasound (US)-guided anchor placement for ATFL repair can be performed anatomically and accurately. However, to our knowledge, no study has investigated ankle kinematics after US-guided ATFL repair. Hypothesis: US-guided ATFL repair with and without inferior extensor retinaculum (IER) augmentation will restore ankle kinematics. Study Design: Controlled laboratory study; Level of evidence, 4. Methods: A 6 degrees of freedom robotic testing system was used to apply multidirectional loads to fresh-frozen cadaveric ankles (N = 9). The following ankle states were evaluated: ATFL intact, ATFL deficient, combined ATFL repair and IER augmentation, and isolated US-guided ATFL repair. Three loading conditions (internal-external rotation torque, anterior-posterior load, and inversion-eversion torque) were applied at 4 ankle positions: 30° of plantarflexion, 15° of plantarflexion, 0° of plantarflexion, and 15° of dorsiflexion. The resulting kinematics were recorded and compared using a 1-way repeated-measures analysis of variance with the Benjamini-Hochberg test. Results: Anterior translation in response to an internal rotation torque significantly increased in the ATFL-deficient state compared with the ATFL-intact state at 30° and 15° of plantarflexion (P = .022 and .03, respectively). After the combined US-guided ATFL repair and augmentation, anterior translation was reduced significantly compared with the ATFL-deficient state at 30° and 15° of plantarflexion (P = .0012 and .005, respectively). Anterior translation was not significantly different for the isolated ATFL-repair state compared with the ATFL-deficient or ATFL-intact states at 30° and 15° of plantarflexion. Conclusion: Combined US-guided ATFL repair with augmentation of the IER reduced lateral ankle laxity due to ATFL deficiency. Isolated US-guided ATFL repair did not reduce laxity due to ATFL deficiency, nor did it increase instability compared with the intact ankle. Clinical Relevance: US-guided ATFL repair with IER augmentation is a minimally-invasive technique to reduce lateral ankle laxity due to ATFL deficiency. Isolated US-guided ATFL repair may be a viable option if accompanied by a period of immobilization.

Continuous-Loop Tape Technique Has Greater Stiffness and Less Elongation Compared With Tied-Suture Fixation of Full-Thickness All-Soft Tissue Quadriceps Tendon Autografts.

BACKGROUND: Many graft fixation techniques are utilized for full-thickness soft tissue quadriceps tendon autografts during anterior cruciate ligament reconstruction (ACLR). PURPOSE: To determine the tensile properties of all-soft tissue quadriceps tendon graft fixation using a tied-suture versus continuous-loop tape technique. It was hypothesized that the continuous-loop tape technique would have less cyclic elongation and greater ultimate load to failure and stiffness compared with a commonly used tied-suture technique. STUDY DESIGN: Controlled laboratory study. METHODS: Sixteen fresh-frozen human knee specimens were used to harvest a full-thickness all-soft tissue quadriceps tendon graft; half were secured using a Krackow suture technique with 2 braided sutures, and half were secured using a continuous-loop tape suspensory fixation button with a rip-stop stitch. Cyclic and permanent elongation, toe- and linear-region stiffness, and ultimate load were determined. Statistical analysis was performed at P <.05. RESULTS: The tied-suture fixation group demonstrated significantly higher permanent elongation (11.7 ± 3.6 vs 4.2 ± 1.0 mm, P < .001) and cyclic elongation (5.9 ± 1.3 vs 2.0 ± 0.4 mm, P < .001) compared with the continuous-loop tape fixation group. There was a significantly higher linear-region stiffness with continuous-loop tape fixation compared with tied-suture fixation (98.8 ± 12.7 vs 85.5 ± 7.5 N/mm, P = .022). No significant difference in ultimate load between groups (517.1 ± 149.2 vs 465.6 ± 64.6 N) was found. The mode of failure was tendon pull-through for the continuous-loop tape group and suture breakage in the tied-suture group (P < .001). CONCLUSION: Continuous-loop tape fixation is superior to tied-suture fixation in regard to elongation and stiffness for all-soft tissue quadriceps tendon grafts, but there was no significant difference in ultimate load. CLINICAL RELEVANCE: Continuous-loop tape fixation of all-soft tissue quadriceps tendon grafts for ACLR is a valid technique with superior tensile properties.

An improved quantitative ultrasonographic technique could assess anterior translation of the glenohumeral joint accurately and reliably.

PURPOSE: Since poor repeatability of the load and shift test using a grading scale has been reported, an objective and quantitative method to assess anterior translation should be established to assess glenohumeral joint function. The purpose of this study was to assess the accuracy and repeatability of the ultrasonographic techniques to quantify anterior translation of the glenohumeral joint. METHODS: Eight fresh-frozen cadaveric shoulders were used. For the standard technique, the ultrasound transducer was positioned on the anterolateral aspect of the shoulder viewing the coracoid process, glenoid, and humeral head. For the revised technique, the transducer was positioned on the anterior aspect of the shoulder, perpendicular to the scapular plane, viewing the conjoint tendon, glenoid, and humeral head. During the load and shift test, the distance between anterior edges of the glenoid and the humeral head was measured. The difference between distances before and after applying an anterior load was calculated as an anterior translation and compared with the anterior translation assessed using a motion tracking system. The repeatability and accuracy of both techniques were analyzed statistically. RESULTS: Intra- and inter-observer repeatability was good-excellent for both ultrasonographic techniques (ICC, 0.889-0.998). The revised technique achieved a stronger correlation to the anterior translations obtained using the motion tracking system (R = 0.810-0.913, p < 0.001) than the standard technique (R = 0.619-0.806, p < 0.001). CONCLUSION: Better accuracy and repeatability was found in the revised technique than the standard technique. The revised technique will be useful to determine the individual laxity and modify the treatment plan and return-to-sports protocol. LEVEL OF EVIDENCE: III.

Location and magnitude of capsular injuries varies following multiple anterior dislocations of the shoulder: Implications for surgical repair.

Capsular injuries can occur during multiple shoulder dislocations. The purpose of this study is to evaluate the location and magnitude of glenohumeral capsular injury following multiple dislocations. We hypothesized that the magnitude of capsular injury would increase and the location of peak injury would vary depending on the number of dislocations. Seven fresh-frozen cadaveric shoulders were used. A 7 × 11 grid of strain markers was affixed to the anteroinferior capsule. Each joint was then mounted to a six degree-freedom robotic testing system. Marker tracking was performed following 1, 2, 3, 4, 5, and 10 dislocations to determine the nonrecoverable strain as capsular injury. Following each dislocation, the magnitude of the maximum principal strain representing the nonrecoverable strain in the inferior glenohumeral capsule was quantified by comparing the strain marker positions following each dislocation. The peak value of nonrecoverable strain statistically increased with the number of dislocations in five of seven specimens (p = .0007). The capsular location that had the peak value of nonrecoverable strain varied according to the number of dislocations, and from specimen to specimen. The nonrecoverable strain was identified in the posterior capsule and anterior axillary pouch, which increased with the number of dislocations compared to the other regions of the capsule (p = .001-.012) by up to 16%. Clinical significance: While plication of the anterior axillary pouch is important following multiple dislocations, a more extensive anterior capsular shift may be necessary with an increased number of dislocations in addition to a posterior capsular shift when appropriate.

Small lateral meniscus tears propagate over time in ACL intact and deficient knees.

PURPOSE: To quantify propagation of small longitudinal tears in the lateral meniscus in ACL intact and deficient knees. METHODS: Using a robotic testing system, 5-Nm of external tibial torque + 5-Nm of valgus torque + 250-N of axial compression was applied to 14 fresh-frozen cadaveric knees while the knees were flexed from 30° to 90°. Knees were divided into two groups: intact (N = 8) and ACL deficient (N = 6). Kinematic data was recorded for four knee states: intact or ACL deficient knee, after posterior arthrotomy, meniscus tear at baseline, and after 500 cycles of the applied loading condition. RESULTS: Lateral meniscus tear length increased throughout the 500 cycles regardless of the ACL integrity (p < 0.001). Overall, an increase of 28.7% and 26.1% was observed in intact and ACL deficient knees, respectively. In intact knees, external tibial rotation increased with meniscus tear propagation at all flexion angles by up to 45.5% (p = 0.019). In contrast, knee kinematics in ACL deficient knees were not affected by meniscus tear propagation (n.s.). In ACL deficient knees, resultant forces in the lateral meniscus increased at all flexion angles by up to 116.5% (p = 0.012). No differences in forces were observed in the intact knees (n.s.). CONCLUSION: The data of this study show that small longitudinal tears in the lateral meniscus propagate significantly regardless of the integrity of the ACL and even after only 100 cycles of knee loading. The propagation of such tears altered kinematics and forces in the knee. Therefore, small, longitudinal lateral meniscus tears that are untreated in current clinical practices may propagate when loaded.

Does Lateral Extra-articular Tenodesis of the Knee Affect Anterior Cruciate Ligament Graft In Situ Forces and Tibiofemoral Contact Pressures?

PURPOSE: To quantify the effects of lateral extra-articular tenodesis (LET) on tibiofemoral compartment contact area and pressures, knee kinematics, and forces. METHODS: Nine cadaveric knees were tested using a robotic testing system. Two loading conditions, (1) anterior tibial translational load coupled with axial compression and (2) internal tibial torque coupled with axial compression, were applied for each knee state at full extension and 30°, 60°, and 90° of knee flexion. Kinematic data was recorded for 3 knee states: anterolateral capsule (ALC) competent, ALC deficient, and post-LET using a 6-mm semitendinosus graft. In situ force in the anterior cruciate ligament (ACL) was quantified using the principle of superposition by comparing the change in force measured before and after the removal of the ALC. Contact area and pressures in each tibiofemoral compartment were measured by replaying kinematics after soft tissues were removed and pressure sensors were inserted. RESULTS: In response to an anterior tibial translational load, mean contact area in the medial compartment decreased by 33.1% from the ALC-competent to post-LET knee states at 90° of knee flexion (P = .042). No significant differences in lateral compartment contact pressure were found between knee states. In situ force in the ACL in response to an anterior tibial translational load decreased by 43.4% and 50% from the ALC-deficient to post-LET knee states at 60° (P = .02) and 90° (P = .006). No significant difference in kinematics was observed between the ALC-competent and post-LET knee states in each of the loading conditions at all knee flexion angles (P > .05). CONCLUSIONS: In this in vitro model, LET with a semitendinosus graft did not significantly overconstrain the knee or increase pressure in the lateral compartment. Additionally, LET reduced the in situ force in the ACL in the setting of ALC injury. CLINICAL RELEVANCE: The lack of knee overconstraint without significant increases in lateral compartment pressures indicates that if an LET with semitendinosus graft is not overtensioned, accelerated degenerative changes in the lateral compartment may not be expected after this procedure.

Partial Lateral Meniscectomy Affects Knee Stability Even in Anterior Cruciate Ligament-Intact Knees.

BACKGROUND: The effects of a partial lateral meniscectomy on knee kinematics and forces in the lateral meniscus are critical to understand. The purpose of this study was to quantify the effects of varying sizes of partial lateral meniscectomies of the posterior horn and a total lateral meniscectomy on knee kinematics and resultant forces in the lateral meniscus. METHODS: Using a robotic testing system, loads (134-N anterior tibial load + 200-N axial compression, 5-Nm internal tibial torque + 5-Nm valgus torque, and 5-Nm external tibial torque + 5-Nm valgus torque) were applied to 10 fresh-frozen cadaveric knees. The resulting joint motion and resultant forces in the lateral meniscus were determined for 4 knee states: intact, one-third and two-thirds partial lateral meniscectomies of the posterior horn, and total lateral meniscectomy. RESULTS: A decrease in lateral translation of the tibia (up to 166.7%) was observed after one-third partial lateral meniscectomies of the posterior horn compared with the intact knee, in response to an anterior load at all knee flexion angles tested (p < 0.05). One-third partial lateral meniscectomies of the posterior horn decreased the resultant forces in the lateral meniscus compared with the intact knee at all knee flexion angles tested in response to an anterior load (p < 0.05) and to an internal tibial torque (p < 0.05). The results of two-thirds partial lateral meniscectomies of the posterior horn were similar to those of one-third partial meniscectomies (p > 0.05). Total lateral meniscectomies further decreased the lateral translation of the tibia (up to 316.6%) compared with the intact knee in response to an anterior load (p < 0.05). CONCLUSIONS: The changes in joint motion and meniscal forces observed in this study after even small partial lateral meniscectomies may predispose knees to further injury. CLINICAL RELEVANCE: Surgeons should always consider repairing and minimizing the resection of even small lateral meniscal tears to prevent the potential deleterious effects of partial meniscectomy reported in this cadaveric study.