Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Greater Tuberosities.

PURPOSE: The purpose of this study was to evaluate the cyclic displacement, stiffness, and ultimate load to failure of 3 all-suture anchors in human cadaveric greater tuberosities. METHODS: Three all-suture anchors indicated for rotator cuff repair were tested in 14 matched pairs of human cadaver fresh-frozen humeri. Anchors were inserted at 3 locations from anterior to posterior along the greater tuberosity and placed 5 mm from the articular margin. The constructs were cycled from 10 to 60 N at 1 Hz for 200 cycles. The anchors that survived cycling were then subjected to a single pull to failure test. A Kruskal-Wallis 1-way analysis of variance on ranks was performed to compare the displacement, stiffness, and ultimate load to failure of the different anchors tested. RESULTS: One matched pair was excluded because of poor bone quality; therefore, 13 matched pairs were included in the study. After 20, 100, and 200 cycles, there was no difference in median displacement between the anchors tested (P = .23, P = .21, P = .18, respectively). The median ultimate load-to-failure between the Iconix (295.2 N, 95% confidence interval [CI], 125-762.2), JuggerKnot (287.6 N, 95% CI, 152.9-584.4), and Q-fix (333.3 N, 95% CI, 165.0-671.9) showed no statistically significant difference (P = .58). After 20, 100, and 200 cycles, there was no difference in median stiffness between the anchors tested (P = .41, P = .19, P = .26 respectively). Displacement greater than 5 mm occurred in 0 Iconix anchors (0%), 1 JuggerKnot anchor (3.64%), and 2 Q-fix anchors (7.69%). One JuggerKnot anchor failed by anchor pullout during cyclic loading. CONCLUSIONS: When tested in human cadaveric humeral greater tuberosities 3 all-suture anchors, the 2.9-mm JuggerKnot, the 2.8-mm Q-fix, and the 2.3-mm Iconix, showed no significant differences in median displacement or stiffness after 20, 100, or 200 cycles or in median ultimate load to failure. Although not statistically significant, the Iconix was the only anchor tested to have no failures, whereas the JuggerKnot had both a clinical and catastrophic failure and the Q-fix had 2 clinical failures. LEVEL OF EVIDENCE: Level V, Controlled Laboratory Study.

Use of an instrumented dual-task timed up and go test in children with traumatic brain injury.

BACKGROUND: Wearable sensors have allowed researchers to instrument tests of gait-related mobility, including the widely used timed 'up-and-go' test (TUG). Currently, there is a lack of instrumented test data on whether children with moderate to severe traumatic brain injury (TBI) perform differently on the TUG compared to typically developed (TD) controls during a cognitive-motor task. RESEARCH QUESTION: The aim was to explore the effects of a cognitive-motor task on TUG subcomponents among children with TBI compared to TD children. METHODS: This observational cross-sectional study included 12 children with moderate to severe TBI (6 males and 6 females, age 10.5 ±â€¯1.5 years of age) and 10 age and sex-matched TD controls (5 males and 5 females, 10.4 ±â€¯1.3 years of age). Each participant completed 6 trials of the TUG wearing a single inertial measurement unit sensor at a self-selected walking pace while listening to an array of 10 randomly presented single digits during each TUG trial. RESULTS: Total time to complete the TUG was not significantly different between groups. The cognitive-motor task led to significantly lower mean turn and peak turn angular velocity values during the turn-around-the-cone and turn-before-sitting TUG subcomponents in children with TBI compared to the TD controls (p ≤ 0.05). Additionally, the cognitive-motor task led to significantly lower values for maximum torso flexion to extension angle, peak flexion and extension angular velocity and peak vertical acceleration for the sit-to-stand subcomponent (p < 0.05). Peak flexion angular velocity during the stand-to-sit subcomponent was lower for the TBI group compared to the children with TD (p < 0.05). SIGNIFICANCE: The study provides new insights into the performance of complex gait-related mobility tasks in the context of an instrumented TUG among children with moderate to severe TBI. Our results highlight the potential benefits of outfitting pediatric inpatients with an IMU while completing the TUG.

Evaluation of the Clavicle Hook Plate for Treatment of Acromioclavicular Joint Dislocation: A Cadaveric Study.

OBJECTIVES: To describe surgical technique for proper placement of the clavicle hook plate, determine whether there is subacromial impingement caused by hook plate fixation, and evaluate the mechanical strength of the clavicle hook plate construct. METHODS: Eight fresh-frozen cadaveric shoulders with a mean age of 48 years (range, 37-69) were used. Open reduction and internal fixation of simulated Rockwood type V AC joint dislocation was performed with the clavicle hook plate. Three-dimensional computed tomography studies and arthroscopic evaluation were performed with the glenohumeral joint in different orientations to assess the position of the hook plate relative to relevant joint structures. The clavicle was then superiorly loaded to mechanical failure. RESULTS: Computed tomography evaluations showed no contact between the humerus and the hook plate. Distance between the greater tuberosity and hook plate ranged from 14 to 31 mm with maximal shoulder forward flexion and 8.1-25.4 mm with maximal shoulder abduction. Arthroscopic evaluation of the subacromial space demonstrated that with maximal abduction/forward flexion, there was abutment of the rotator cuff with the hook plate in 6 of 8 specimens. In mechanical testing, mean failure load was determined to be 1011 N (range, 380-1563 N). Failure mechanisms included acromion fracture (4), slippage of the hook under acromion (3), and distal clavicle fracture (1). CONCLUSIONS: This study demonstrates that the clavicle hook plate reduces AC joint dislocation or distal clavicle fractures anatomically, has supra-physiologic mechanical strength, does not cause bony impingement, and exhibits rotator cuff impingement only with maximal abduction/forward flexion of the shoulder.

Cyclic and Load-to-Failure Properties of All-Suture Anchors in Human Cadaveric Shoulder Glenoid Bone.

PURPOSE: To evaluate the cyclic displacement and ultimate load to failure of 4 all-suture anchors in human cadaveric shoulder glenoid bone. METHODS: Four all-suture anchors indicated for glenoid labral repair were tested in 14 matched pairs of human cadaveric fresh-frozen glenoids. Anchors were inserted at 4 different locations for a total of 112 tests (12-, 3-, 6-, and 9-o'clock positions for right glenoids). Cyclic loading (10 to 60 N at 1 Hz for 200 cycles) and single pull-to-failure testing (33 mm/s) were performed. A Kruskal-Wallis 1-way analysis of variance with the Dunn multiple-comparison post hoc test was used for statistical analysis. RESULTS: One matched pair was excluded because of poor bone quality. Thus, 13 matched pairs were included in the study, and a total of 104 tests were performed. The Q-Fix anchors showed significantly less displacement after 100 cycles (mean ± standard deviation, 1.40 ± 0.97 mm; P < .001) and 200 cycles (1.53 ± 1.00 mm, P < .001) than all other anchors tested. The Q-Fix (191.3 ± 65.8 N), Suturefix (188.3 ± 61.4 N), and JuggerKnot (183.6 ± 63.5 N) anchors had significantly greater ultimate loads to failure than the Iconix anchors (143.5 ± 54.1 N) (P = .01, P = .012, and P = .021, respectively). Displacement greater than 5 mm occurred in 6 Iconix anchors (22.1%), 5 Suturefix anchors (19.2%), 4 JuggerKnot anchors (15.4%), and 0 Q-Fix anchors (0%). CONCLUSIONS: The Q-Fix anchors showed less displacement with cyclic loading than the Iconix, JuggerKnot, and Suturefix anchors. The Iconix anchors had a lower ultimate load to failure than the Q-Fix, Suturefix, and JuggerKnot anchors. Only the Q-Fix group had no anchors displace greater than 5 mm with cyclic loading. CLINICAL RELEVANCE: All-suture anchors vary in their deployment mechanism, which may alter their strength and performance. Operators must be aware of these anchors' propensity to displace while deploying them.

Electronically augmented gait abnormality assessment following lower extremity trauma.

BACKGROUND: Objective evaluation of patient outcomes has become an essential component of patient management. Along with patient-reported outcomes, performance-based measures (PBMs) such as gait analysis are an important part of this evaluation. The purpose of this study was to evaluate the validity of utilizing a wearable inertial measurement unit (IMU) in an outpatient clinic setting to assess its ability to provide clinically relevant data in patients with altered gait resulting from lower extremity trauma. METHODS: Five orthopaedic trauma patients with varying degrees of gait pathologies were compared to 5 healthy control subjects. Kinematic data were simultaneously recorded by the IMU and a gold standard Vicon video motion analysis system (Vicon Motion Systems Ltd, Oxford, UK) during a modified 10-m walk test. Raw data captured by the IMU were directly compared to Vicon data. Additionally, 5 objective gait parameters were compared for controls and the 5 trauma patients. RESULTS: The IMU data streams strongly correlated with Vicon data for measured variables used in the subsequent gait analysis: vertical acceleration, vertical displacement, pitch angular velocity, and roll angular velocity (Pearson r-value > 0.9 for all correlations). Quantitative kinematic data in post-trauma patients significantly differed from control data and correlated with observed gait pathology. CONCLUSIONS: When compared to the gold standard motion capture reference system (Vicon), an IMU can reliably and accurately measure clinically relevant gait parameters and differentiate between normal and pathologic gait patterns. This technology is easily integrated into clinical settings, requires minimal time, and represents a performance-based method for quantifiably assessing gait outcomes. LEVEL OF EVIDENCE: Diagnostic Level 1.

Far Cortical Locking Fixation of Distal Femur Fractures is Dominated by Shear at Clinically Relevant Bridge Spans.

OBJECTIVES: Far cortical locking (FCL) constructs have been shown to increase axial interfragmentary displacement while limiting shear and have been specifically recommended in the treatment of distal femur fractures. However, there is no available data regarding their mechanical behavior within the range of bridge spans typically used for comminuted distal femur fractures. This biomechanical study of distal femur locked plate fixation assessed 4 methods of diaphyseal fixation for associated axial and shear displacement at bridge spans typically used in clinical practice. METHODS: Distal femur locking plates were used to bridge simulated fractures in femur surrogates with 4 different methods of diaphyseal fixation (bicortical locking, bicortical nonlocking, near cortical locking, and FCL). Axial and shear displacement were assessed at 5 different bridge spans for each fixation method. RESULTS: Diaphyseal fixation type was associated with the amount of shear (P = 0.04), but not the amount of axial displacement (P = 0.39). Specifically, FCL constructs demonstrated greater shear than bicortical locking (median 4.57 vs. 2.94 mm, P = 0.02) and bicortical nonlocking (median 4.57 vs. 3.41 mm, P = 0.02) constructs. CONCLUSIONS: Unexpectedly, FCL constructs demonstrated greater shear than bicortical locking and nonlocking constructs and similar axial displacement for all fixation methods. Bridge span had a dominant effect on displacement that interacted negatively with more flexible FCL diaphyseal fixation. Potentially interactive construct features are best studied in concert. Given the complexity of these relationships, computational modeling will likely play an integral role in future mechanotransduction research.

Greater Tuberosity Decortication Decreases Load to Failure of All-Suture Anchor Constructs in Rotator Cuff Repair.

PURPOSE: To evaluate the effect of greater tuberosity decortication on ultimate load to failure and displacement after cyclic loading with an all-suture anchor. METHODS: A 2.9-mm all-suture anchor was evaluated in decorticated and nondecorticated greater tuberosities of 10 matched pairs of human cadaveric shoulders. Greater tuberosity decortication was performed to a mean depth of 1.7 mm. Anchors were placed in the anterior, middle, and posterior tuberosity. Anchors were tested under cyclic loads followed by load-to-failure testing. Displacement after 20, 100, and 200 cycles and ultimate failure strength were determined. Clinical failure was defined as displacement greater than 5 mm during cyclic loading. RESULTS: After 20 and 100 cycles, there was no difference in mean displacement between the decorticated and nondecorticated cohorts (P = .139 and P = .127, respectively). The mean displacement after 200 cycles was greater in the decorticated cohort, although not significantly (3.4 vs 2.7 mm; P = .05). The mean ultimate load to failure was significantly lower in the decorticated cohort (314 vs 386 N, P = .049). There were 2 clinical failures in the decorticated specimens and 1 in the nondecorticated specimens. CONCLUSIONS: A minimal greater tuberosity decortication significantly decreases the ultimate load to failure of an all-suture anchor. However, decreased biomechanical strength may not necessitate actual clinical failure. CLINICAL RELEVANCE: A decrease in ultimate load to failure could increase the risk of catastrophic postoperative anchor failure. However, while this decrease in strength is statistically significant, the overall decrease in strength may not be sufficient in magnitude to translate to clinical failure.

Reliability of the sub-components of the instrumented timed up and go test in ambulatory children with traumatic brain injury and typically developed controls.

BACKGROUND: Studies have evaluated the test-re-test reliability of subcomponents of the timed up and-go test in adults by using body-worn inertial sensors. However, studies in children have not been reported in the literature. RESEARCH QUESTION: To evaluate the within-session reliability of subcomponents of a newly developed electronically augmented timed 'upand-go' test (EATUG) in ambulatory children with traumatic brain injury (TBI) and children with typical development (TD). METHOD: The timed up and go test was administered to twelve consecutive ambulatory children with moderate to severe TBI (6 males and 6 females, age 10.5 ±â€¯1.5 years, range 8-13 years, during inpatient rehabilitation at 27.0 ±â€¯11.8 days following injury) and 10 TD age and sex-matched children (5 males and 5 females, 10.4 ±â€¯1.3 years, range 8-11 years). Participants wore a single chest-mounted inertial measurement sensor package with custom software that measured angular and acceleration velocity and torso flexion and extension angles, while they performed 6 trials of the EATUG test. Measures were derived from the overall time to complete the TUG test, angular velocity and angular displacement data for torso flexion and extension during sit-to-stand and stand-to-sit segments and both mean and peak angular velocities for two turning segments (i.e. turning around a cone and turning-before-sitting). RESULTS: Within-session reliability of the subcomponents of the TUG test for children with TBI assessed by the intra-class correlation coefficient was ICC (1,1) = 0.84, (range 0.82-0.96), and for TD children ICC (1,1) = 0.73, (range 0.53-0.89). Scores on Total Time, maximum torso flexion/extension angle and peak flexion angular velocity during sit-tostand, and peak turn angular velocity for both turns around the cone and turns before sitting were lower for children with TBI than for TD children (p ≤ 0.05). SIGNIFICANCE: The EATUG test is a reliable measure of physical function in children with TBI who are being discharged from inpatient rehabilitation.

Slight Reduction in the Insertion Depth for an All-Suture Anchor Decreases Cyclic Displacement in the Shoulder Glenoid.

PURPOSE: To determine if the depth of anchor insertion affects the biomechanical performance of a 1.5-mm all-suture anchor in glenoid bone. METHODS: A 1.5-mm all-suture anchor was tested in 8 matched pairs of human cadaver fresh-frozen glenoids. Anchors were inserted at 6 different locations and tested at 3 different depths: 21 mm (preset drilling depth), 17 mm, and 13 mm. Cyclic loading and destructive testing was performed. Displacement after 100 and 200 cycles, along with ultimate failure strength, was determined. RESULTS: After 100 and 200 cycles, anchors placed at 13 and 17 mm had undergone significantly less displacement than those at 21 mm (P < .05). No difference was observed in ultimate load to failure between anchors placed at 21 and 17 mm. However, the ultimate load to failure was significantly lower in anchors placed at 13 mm (P < .05). There were 5 clinical failures in anchors placed at 21 mm, one at 17 mm, and none at 13 mm. CONCLUSIONS: The 1.5-mm all-suture anchor tested in this study has an optimal insertion depth of 17 mm, 4 mm shallower than the preset drill depth. At the optimal insertion depth of 17 mm, it underwent significantly less displacement after cyclic loading without a reduction in the ultimate load to failure. CLINICAL RELEVANCE: Given the results of this study, the optimal insertion depth for this 1.5-mm all-suture anchor is 17 mm, 4 mm shallower than the preset drill depth.

Transtibial Versus Anteromedial Portal ACL Reconstruction: Is a Hybrid Approach the Best?

BACKGROUND: Improved biomechanical and clinical outcomes are seen when the femoral tunnels of the anterior cruciate ligament (ACL) are placed in the center of the femoral insertion. The transtibial (TT) technique has been shown to be less capable of this than an anteromedial (AM) portal approach but is more familiar to surgeons and less technically challenging. A hybrid transtibial (HTT) technique using medial portal guidance of a transtibial guide wire without knee hyperflexion may offer anatomic tunnel placement while maintaining the relative ease of a TT technique. PURPOSE: To evaluate the anatomic and biomechanical performance of the HTT technique compared with TT and AM approaches. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-six paired, fresh-frozen human knees were used. Twenty-four knees (12 pairs) underwent all 3 techniques (TT, AM, HTT) for femoral tunnel placement, with direct measurement of femoral insertional overlap and femoral tunnel length. The remaining 12 knees (6 pairs) underwent completed reconstructions to evaluate graft anisometry and tunnel orientation, with each technique performed in 4 specimens and tested using motion sensors with a quad-load induced model. Graft length changes and graft/femoral tunnel angle were measured at varying degrees of flexion. RESULTS: Percentage overlap of the femoral insertion averaged 37.0% ± 28.6% for TT, 93.9% ± 5.6% for HTT, and 79.7% ± 7.7% for AM, with HTT significantly greater than both TT (P = .007) and AM (P = .001) approaches. Graft length change during knee flexion (anisometry) was 30.1% for HTT, 12.8% for AM, and 8.5% for TT. When compared with the TT approach, HTT constructs exhibited comparable graft-femoral tunnel angulation (TT, 150° ± 3° vs HTT, 142° ± 2.3°; P < .001) and length (TT, 42.6 ± 2.8 mm vs HTT, 38.5 ± 2.0 mm; P = .12), while AM portal tunnels were significantly shorter (31.6 ± 1.6 mm; P = .001) and more angulated (121° ± 6.5°; P < .001). CONCLUSION: The HTT technique avoids hyperflexion and maintains femoral tunnel orientation and length, similar to the TT technique, but simultaneously achieves anatomic graft positioning. CLINICAL RELEVANCE: The HTT technique offers an anatomic alternative to an AM portal approach while maintaining the technical advantages of a traditional TT reconstruction.

Effect of Polyether Ether Ketone on Therapeutic Radiation to the Spine: A Pilot Study.

STUDY DESIGN: Cadaveric model. OBJECTIVES: To compare the effect of PEEK versus conventional implants on scatter radiation to a simulated tumor bed in the spine SUMMARY OF BACKGROUND DATA.: Given the highly vasculature nature of the spine, it is the most common place for bony metastases. After surgical treatment of a spinal metastasis, adjuvant radiation therapy is typically administered. Radiation dosing is primarily limited by toxicity to the spinal cord. The scatter effect caused by metallic implants decreases the accuracy of dosing and can unintentionally increase the effective dose seen by the spinal cord. This represents a dose-limiting factor for therapeutic radiation postoperatively. METHODS: A cadaveric thorax specimen was utilized as a metastatic tumor model with two separate three-level spine constructs (one upper thoracic and one lower thoracic). Each construct was examined independently. All four groups compared included identical posterior instrumentation. The anterior constructs consisted of either: an anterior polyether ether ketone (PEEK) cage, an anterior titanium cage, an anterior bone cement cage (polymethyl methacrylate), or a control group with posterior instrumentation alone. Each construct had six thermoluminescent detectors to measure the radiation dose. RESULTS: The mean dose was similar across all constructs and locations. There was more variability in the upper thoracic spine irrespective of the construct type. The PEEK construct had a more uniform dose distribution with a standard deviation of 9.76. The standard deviation of the others constructs was 14.26 for the control group, 19.31 for the titanium cage, and 21.57 for the cement (polymethyl methacrylate) construct. CONCLUSION: The PEEK inter-body cage resulted in a significantly more uniform distribution of therapeutic radiation in the spine when compared with the other constructs. This may allow for the application of higher effective dosing to the tumor bed for spinal metastases without increasing spinal cord toxicity with either fractionated or hypofractionated radiotherapy. LEVEL OF EVIDENCE: N/A.

Proximity of the Triangular Fibrocartilage Complex to Key Surrounding Structures and Safety Assessment of an Arthroscopic Repair Technique: A Cadaveric Study.

PURPOSE: To quantify the distance of the dorsal ulnar sensory branch, floor of the extensor carpi ulnaris (ECU) subsheath, and ulnar neurovascular bundles from the triangular fibrocartilage complex (TFCC), and secondarily to assess the safety of an all-inside arthroscopic repair of the TFCC with a commonly used meniscal repair device with respect to the aforementioned structures. METHODS: A custom K-wire with 1-mm gradation was used to determine the distance of at-risk structures from the periphery of the TFCC in 13 above-elbow human cadaver specimens. An all-inside repair of the TFCC at the location of a Palmer 1B tear was then performed using a commonly employed meniscal repair device. The distance from the deployed devices to the structure in closest proximity was then measured using digital calipers. RESULTS: The mean distance from the deployed device to the nearest structure of concern for iatrogenic injury was 9.4 mm (range, 5-15 mm). The closest structure to iatrogenic injury was usually, but not always, the dorsal ulnar sensory nerve in 9 of 13 wrists (69.2%) at 9.3 mm (range, 5-15 mm); on 3 occasions it was instead the ulnar nerve (23.1%) at 9.5 mm (range, 9-10 mm), and on 1 occasion 6 mm from the flexor digitorum profundus to the little finger (7.7%). Forearm rotation had no significant effect on measured distances (ulnar nerve: P = .98; dorsal sensory: P = .89; ECU: P = .90). The largest influence of forearm rotation was a 0.4-mm difference between pronation and supination with respect to the distance of the TFCC periphery on the ECU subsheath. CONCLUSIONS: An all-inside arthroscopic TFCC repair using a commonly used meniscal repair device appears safe with respect to nearby neurovascular structures and tendons under typical arthroscopic conditions. CLINICAL RELEVANCE: An all-inside arthroscopic TFCC repair using a commonly employed meniscal repair device appears safe in terms of proximity to important structures although further clinical investigation is warranted.

The Relationship Between Early-Stage Knee Osteoarthritis and Lower-Extremity Alignment, Joint Laxity, and Subjective Scores of Pain, Stiffness, and Function.

CONTEXT: Knee osteoarthritis (OA) is a debilitating disease that affects an estimated 27 million Americans. Changes in lower-extremity alignment and joint laxity have been found to redistribute the medial and/or lateral loads at the joint. However, the effect that changes in anteroposterior knee-joint laxity have on lower-extremity alignment and function in individuals with knee OA remains unclear. OBJECTIVE: To examine anteroposterior knee-joint laxity, lower-extremity alignment, and subjective pain, stiffness, and function scores in individuals with early-stage knee OA and matched controls and to determine if a relationship exists among these measures. DESIGN: Case control. SETTING: Sports-medicine research laboratory. PARTICIPANTS: 18 participants with knee OA and 18 healthy matched controls. INTERVENTION: Participants completed the Western Ontario McMaster (WOMAC) osteoarthritis questionnaire and were tested for total anteroposterior knee-joint laxity (A-P) and knee-joint alignment (ALIGN). MAIN OUTCOME MEASURES: WOMAC scores, A-P (mm), and ALIGN (°). RESULTS: A significant multivariate main effect for group (Wilks' Λ = 0.30, F7,26 = 8.58, P < .0001) was found. Knee-OA participants differed in WOMAC scores (P < .0001) but did not differ from healthy controls on ALIGN (P = .49) or total A-P (P = .66). No significant relationships were identified among main outcome measures. CONCLUSION: These data demonstrate that participants with early-stage knee OA had worse pain, stiffness, and functional outcome scores than the matched controls; however, ALIGN and A-P were no different. There was no association identified among participants' subjective scores, ALIGN, or A-P measures in this study.

Cortical Button Fixation: A Better Patellar Tendon Repair?

BACKGROUND: Patellar tendon ruptures require surgical repair to optimize outcomes, but no consensus exists regarding the ideal repair technique. Cortical button fixation is a secure method for tendon repair that has not been studied in patellar tendons. HYPOTHESIS: Cortical button repair is biomechanically superior to the standard transpatellar repair and biomechanically equivalent to suture anchor repair. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-three fresh-frozen cadaveric knees were used to compare 3 techniques of patellar tendon repair after a simulated rupture at the inferior pole of the patella. Repairs were performed at 45° of flexion using a standard transpatellar suture repair (n = 7), polyetheretherketone (PEEK) suture anchor repair (n = 8), or cortical button repair (n = 8). All specimens were tested on a custom apparatus to simulate cyclic open kinetic chain quadriceps contraction from extension to 90o of flexion. Outcomes of gap formation up to 250 cycles, maximum load to failure, and mode of failure were evaluated. RESULTS: Cortical button repair had significantly less gap formation than anchor repair after 1 cycle (P < .001) and 20 cycles (P < .01) and significantly less gap formation than suture repair from 1 to 250 cycles (P < .05). Cortical button repair sustained significantly higher loads to failure than anchor repair and suture repair (P < .001). All suture repairs failed through the suture. Anchor repairs failed at the suture-anchor eyelet interface (n = 4) or by anchor pullout (n = 3). Cortical button repairs either failed through the suture (n = 5), secondary failure of the patellar tendon (n = 2), or subsidence of the button through the anterior cortex of the patella (n = 1). CONCLUSION: Patellar tendon repair using cortical button fixation demonstrated mechanical advantages over suture repair and anchor repair in cadaveric specimens. Cortical button fixation showed less cyclic gap formation and withstood at least twice the load to failure of the construct. CLINICAL RELEVANCE: The biomechanical superiority of cortical button fixation may impart clinical advantages in accelerating postoperative rehabilitation.

Motion Predicts Clinical Callus Formation: Construct-Specific Finite Element Analysis of Supracondylar Femoral Fractures.

BACKGROUND: Mechanotransduction is theorized to influence fracture-healing, but optimal fracture-site motion is poorly defined. We hypothesized that three-dimensional (3-D) fracture-site motion as estimated by finite element (FE) analysis would influence callus formation for a clinical series of supracondylar femoral fractures treated with locking-plate fixation. METHODS: Construct-specific FE modeling simulated 3-D fracture-site motion for sixty-six supracondylar femoral fractures (OTA/AO classification of 33A or 33C) treated at a single institution. Construct stiffness and directional motion through the fracture were investigated to assess the validity of construct stiffness as a surrogate measure of 3-D motion at the fracture site. Callus formation was assessed radiographically for all patients at six, twelve, and twenty-four weeks postoperatively. Univariate and multivariate linear regression analyses examined the effects of longitudinal motion, shear (transverse motion), open fracture, smoking, and diabetes on callus formation. Construct types were compared to determine whether their 3-D motion profile was associated with callus formation. RESULTS: Shear disproportionately increased relative to longitudinal motion with increasing bridge span, which was not predicted by our assessment of construct stiffness alone. Callus formation was not associated with open fracture, smoking, or diabetes at six, twelve, or twenty-four weeks. However, callus formation was associated with 3-D fracture-site motion at twelve and twenty-four weeks. Longitudinal motion promoted callus formation at twelve and twenty-four weeks (p = 0.017 for both). Shear inhibited callus formation at twelve and twenty-four weeks (p = 0.017 and p = 0.022, respectively). Titanium constructs with a short bridge span demonstrated greater longitudinal motion with less shear than did the other constructs, and this was associated with greater callus formation (p < 0.001). CONCLUSIONS: In this study of supracondylar femoral fractures treated with locking-plate fixation, longitudinal motion promoted callus formation, while shear inhibited callus formation. Construct stiffness was found to be a poor surrogate of fracture-site motion. Future implant design and operative fixation strategies should seek to optimize 3-D fracture-site motion rather than rely on surrogate measures such as axial stiffness.

Biomechanical comparison of hamstring tendon fixation devices for anterior cruciate ligament reconstruction: Part 2. Four tibial devices.

We conducted a study to biomechanically compare 4 tibial hamstring tendon fixation devices commonly used in anterior cruciate ligament reconstruction. Quadrupled human semitendinosus-gracilis tendon grafts were fixed into porcine tibias using 4 separate fixation devices. For each device, 10 specimens were tested (1500-cycle loading test at 50-200 N). Specimens surviving the cyclic loading then underwent a single load-to-failure test. Failure mode, stiffness, ultimate load, and residual displacement were recorded. Eight of 10 Delta screw (Arthrex), 2 of 10 Retroscrew (Arthrex), 10 of 10 WasherLoc (Arthrotek), and 10 of 10 Intrafix (Depuy Mitek) devices completed the 1500-cycle loading test. Residual displacement was significantly (P < .001) lower for Intrafix (2.9 mm), WasherLoc (5.6 mm), and Delta (6.4 mm) than for Retroscrew (25.5 mm). Mean stiffness was significantly (P < .05) higher for Intrafix (129 N/mm) than for the other devices. Mean load to failure was highest for Intrafix (656 N), then WasherLoc (630 N), Delta (430 N), and Retroscrew (285 N). The Intrafix device demonstrated superior strength in the fixation of hamstring grafts in the tibia. WasherLoc was close behind.

Biomechanical comparison of hamstring tendon fixation devices for anterior cruciate ligament reconstruction: part 1. Five femoral devices.

We conducted a study to biomechanically compare 5 femoral hamstring tendon fixation devices commonly used in anterior cruciate ligament reconstruction. Quadrupled human semitendinosus-gracilis tendon grafts were fixed into porcine femurs using 5 separate fixation devices. For each device, 10 specimens were tested (1500-cycle loading test at 50-200 N). Specimens surviving the cyclic loading then underwent a single load-to-failure (LTF) test. Failure mode, stiffness, ultimate load, and rigidity were recorded. Two of 10 Delta screw (Arthrex), 10 of 10 Bio-TransFix (Arthrex), 10 of 10 Bone Mulch screw (Arthrotek), 10 of 10 EZLoc (Arthrotek), and 10 of 10 Zip Loop (Arthrotek) devices completed the 1500-cycle loading test. Residual displacement was lowest for Bio-TransFix (4.1 mm) followed by Bone Mulch (5.2 mm), EZLoc (6.4 mm), Zip Loop (6.8 mm), and Delta (8.2 mm). Mean stiffness was significantly (P < .001) higher for Bone Mulch (218 N/mm) than for Bio-TransFix (171 N/mm), EZLoc (122 N/mm), Zip Loop (105 N/mm), or Delta (84 N/mm). Mean LTF was significantly ( P < .001) higher for Bone Mulch (867 N) than for Zip Loop (615 N), Bio-TransFix (552 N), EZLoc (476 N), or Delta (410 N). The Bone Mulch screw demonstrated superior strength in the fixation of hamstring grafts in the femur. Bio-TransFix was close behind. The Delta screw demonstrated poor displacement, stiffness, and LTF. When used as the sole femoral fixation device, a device with low LTF, decreased stiffness, and high residual displacement should be used cautiously in patients undergoing aggressive rehabilitation.

Cell-based tissue engineering augments tendon-to-bone healing in a rat supraspinatus model.

Rotator cuff pathology causes substantial pain/disability and health care costs. Cell-based tissue engineering offers promise for improved outcomes in tendon to bone healing. Cells from the tendon-bone interface were used here to amplify surgical defect healing in a rat model. Cells from tendon-to-bone interface of the rotator cuff were seeded in sponges and implanted into critical rotator cuff defects: Group I, control; II, surgical defect only; III, suture-repaired defect; IV, surgical defect, repair with sponge only; V, surgical defect, repair with sponge with cells. Three, 6-, and 12-week results were assessed for histologic features. At 3 weeks, histologic indices in Group V were significantly increased versus other treatment groups. Group V (12 weeks) showed significantly improved collagen organization versus other treatment groups; there was no difference in collagen organization in Group I versus V. In summary, increased cellularity, inflammation, vascularity, and collagen organization were present at 3 weeks; increased collagen organization at 12 weeks in Group V provides evidence for improved healing with cells. Data further support the utility of tendon-bone interface cells in rotator cuff healing.

Temporal-spatial gait adaptations during stair ascent and descent in patients with knee osteoarthritis.

Knee osteoarthritis (OA) accounts for more functional disability of the lower extremity than any other disease. We recruited 18 patients with knee OA and 18 healthy age-, height-, mass-, and gender-matched control subjects to investigate the effects knee OA has on select spatial and temporal gait variables during a stair climbing task. No group-by-direction interaction was observed; however, significant effects did occur for group and direction. Specifically, patients with knee OA demonstrated less time in single support, greater time in double support, decreased step length, greater step width, less stride length, decreased total gait velocity, greater total time in support, and less total time in swing, compared with controls. Early-stage knee OA directly influences specific temporal and spatial gait characteristics during stair climbing.

Lower extremity joint kinematics during stair climbing in knee osteoarthritis.

PURPOSE: Knee osteoarthritis (OA) is one of the most prevalent chronic lower extremity diseases, causing profound limitation of movement and ability to perform activities of daily living. The purpose of this study was to compare various hip, knee, and ankle joint kinematic variables between knee OA subjects and matched healthy controls during stair ascent and descent. METHODS: Eighteen subjects with knee OA (age = 60.2 ± 9.9 yr, mass = 90.3 ± 16.7 kg, height = 168.4 ± 9.9 cm) and 18 healthy matched controls (age = 60.3 ± 10.7 yr, mass = 81.1 ± 21.2 kg, height = 168.3 ± 11.9 cm) participated in the study. Subjects performed five ascending and descending trials on a custom-built staircase while their motion was captured three-dimensionally using an eight-camera optical video motion capture system. RESULTS: Significant group × direction interactions were found for average hip flexion angle at foot strike (P = 0.04), for average ankle adduction angle at foot strike (P = 0.01), and for peak ankle dorsiflexion angle during support (P = 0.05) and swing (P = 0.01). Specifically, knee OA and control subjects demonstrated greater hip flexion angle at foot strike and ankle dorsiflexion angle during swing but showed smaller ankle dorsiflexion angle during support during stair ascent compared with descent. Furthermore, compared with controls, knee OA patients demonstrated greater hip abduction at foot strike (-3.1° ± 3.9°) and smaller peak knee flexion during support (60.4° ± 5.0°) and swing (86.7° ± 5.4°). Time of peak hip abduction (34.2% ± 7.1%), hip flexion (7.0% ± 12.3%), knee flexion (69.8% ± 4.6%), dorsiflexion (51.4% ± 2.9%), and ankle adduction (37.3% ± 20.8%) during support occurred later in the gait cycle for knee OA patients. CONCLUSIONS: These data demonstrate that knee OA directly influences specific knee joint kinematics and induces kinematic alterations at the hip and ankle perhaps to compensate for the existing knee joint pathology.