Are extra locking bolts or fibular plating more important in extreme nailing of distal tibia fractures? A cadaveric biomechanical analysis.

OBJECTIVES: In far-distal extra-articular tibia fracture "extreme" nailing, debate surrounds the relative biomechanical performance of plating the fibula compared with extra distal interlocks. This study aimed to evaluate several constructs for extreme nailing including one interlock (one medial-lateral interlock), one interlock + plate (one medial-lateral interlock with lateral fibula compression plating), and two interlocks (one medial-lateral interlock and one anterior-posterior interlock). METHODS: Fifteen pairs of fresh cadaver legs were instrumented with a tibial nail to the physeal scar. A 1 cm segment of bone was resected from the distal tibia 3.5 cm from the joint and an oblique osteotomy was made in the distal fibula. We loaded specimens with three different distal fixation constructs (one interlock, one interlock + plate, and two interlocks) through 10,000 cycles form 100N-700 N of axial loading. Load to failure (Newtons), angulation and displacement were also measured. RESULTS: Mean load to failure was 2092 N (one interlock), 1917 N (one interlock + plate), and 2545 N (two interlocks). Linear mixed effects modeling demonstrated that two interlocks had a load to failure 578 N higher than one interlock alone (95 % CI, 74N-1082 N; P = 0.02), but demonstrated no significant difference between one interlock and one interlock + plate. No statistically significant difference in rates or timing of displacement >2 mm or angulation >10° were demonstrated. CONCLUSIONS: When nailing far-distal extra-articular tibia and fibula fractures, adding a second interlock provides more stability than adding a fibular plate. Distal fibula plating may have minimal biomechanical effect in extreme nailing.

Multi-joint Assessment of Proprioception Impairments Poststroke.

OBJECTIVES: To investigate shoulder, elbow and wrist proprioception impairment poststroke. DESIGN: Proprioceptive acuity in terms of the threshold detection to passive motion at the shoulder, elbow and wrist joints was evaluated using an exoskeleton robot to the individual joints slowly in either inward or outward direction. SETTING: A university research laboratory. PARTICIPANTS: Seventeen stroke survivors and 17 healthy controls (N=34). Inclusion criteria of stroke survivors were (1) a single stroke; (2) stroke duration <1 year; and (3) cognitive ability to follow simple instructions. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Threshold detection to passive motion and detection error at the shoulder, elbow and wrist. RESULTS: There was significant impairment of proprioceptive acuity in stroke survivors as compared to healthy group at all 3 joints and in both the inward (shoulder horizontal adduction, elbow and wrist flexion, P<.01) and outward (P<.01) motion. Furthermore, the distal wrist joint showed more severe impairment in proprioception than the proximal shoulder and elbow joints poststroke (P<.01) in inward motion. Stroke survivors showed significantly larger detection error in identifying the individual joint in motion (P<.01) and the movement direction (P<.01) as compared to the healthy group. There were significant correlations among the proprioception acuity across the shoulder, elbow and wrist joints and 2 movement directions poststroke. CONCLUSIONS: There were significant proprioceptive sensory impairments across the shoulder, elbow and wrist joints poststroke, especially at the distal wrist joint. Accurate evaluations of multi-joint proprioception deficit may help guide more focused rehabilitation.

The Biomechanical Effects of Intramedullary Fixation to the Level of the Physeal Scar on Distal Tibia Fracture Stability.

INTRODUCTION: The purpose of this study was to evaluate whether intramedullary nail contact with physeal scar improves construct mechanics when treating distal tibial shaft fractures. METHODS: Axially unstable extra-articular distal tibia fractures were created in 30 fresh frozen cadaveric specimens (15 pairs, mean age 79 years). Specimens underwent intramedullary nailing to the level of the physeal scar locked with one or two interlocks or short of the physeal scar locked with two interlocks (reference group). Specimens were subjected to 800N of axial load for 25,000 cycles. Primary outcomes were stiffness before and after cyclic loading. Secondary outcomes were load to failure, load at 3 mm displacement, plastic deformation, and total deformation. RESULTS: The physeal scar with one interlock cohort demonstrated 3.8% greater stiffness before cycling ( P = 0.75) and 1.7% greater stiffness after cycling ( P = 0.86) compared with the reference group. The physeal scar with two interlocks group exhibited 0.3% greater stiffness before cycling ( P = 0.98) and 8.4% greater stiffness after cycling ( P = 0.41) in relation to the reference group. No differences were identified regarding load to failure or load at 3 mm displacement. In specimens with two interlocks, those in contact with the physeal scar demonstrated significantly less plastic ( P = 0.02) and total ( P = 0.04) deformation. CONCLUSIONS: Constructs ending at the physeal scar demonstrated stiffness and load to failure similar to those without physeal scar contact. Less plastic and total deformation was noted in two-interlock constructs with physeal scar contact, suggesting a possible protective effect provided by the physeal scar. These data argue that physeal scar contact may offer a small mechanical benefit in nailing distal tibia fractures, but clinical relevance remains unknown.

Abnormal coordination of upper extremity during target reaching in persons post stroke.

Understanding abnormal synergy of the upper extremity (UE) in stroke survivors is critical for better identification of motor impairment. Here, we investigated to what extent stroke survivors retain the ability to coordinate multiple joints of the arm during a reaching task. Using an exoskeleton robot, 37 stroke survivors' arm joint angles (θ) and torques (τ) during hand reaching in the horizontal plane was compared to that of 13 healthy controls. Kinematic and kinetic coordination patterns were quantified as variances of the multiple-joint angles and multiple-joint torques across trials, respectively, that were partitioned into task-irrelevant variance (TIVθ and TIVτ) and task-relevant variance (TRVθ and TRVτ). TIVθ and TRVθ (or TIVτ and TRVτ) led to consistent and inconsistent hand position (or force), respectively. The index of synergy (ISθ and ISτ) was determined as [Formula: see text] and [Formula: see text] for kinematic and kinetic coordination patterns, respectively. Both kinematic ISθ and kinetic ISτ in the stroke group were significantly lower than that of the control group, indicating stroke survivors had impaired reaching abilities in utilizing the multiple joints of the UE for successful completion of a reaching task. The reduction of kinematic ISθ in the stroke group was mainly attributed to the lower TIVθ as compared to the control group, while the reduction of kinetic ISτ was mainly due to the higher [Formula: see text] as well as lower TIVτ. Our results also indicated that stroke may lead to motor deficits in formation of abnormal kinetic synergistic movement of UE, especially during outward movement. The findings in abnormal synergy patterns provides a better understanding of motor impairment, suggesting that impairment-specific treatment could be identified to help improve UE synergies, focusing on outward movements.

Open reduction internal fixation of rib fractures: a biomechanical comparison between the RibLoc U Plus® system and anterior plate in rib implants.

OBJECTIVES: In this study, we assessed the bending strength of two surgical repairs of rib fracture using RibLoc® U Plus system made by Acute Innovations and the anterior plate by Synthes. METHODS: After a rib fracture was created in seven pairs of cadaveric rib specimens, one side was repaired with the anterior plate and the other side repaired with the RibLoc U Plus® plate. Each of the rib is loaded using a custom device over 360,000 bending cycles to simulate in vivo fatiguing related to respiration. Upon completion of the cyclic loading, the specimens were compressively loaded to failure and the failure bending moment was determined. RESULTS: The ribs repaired with the RibLoc U Plus® system showed 79% higher failure bending moment than that of the anterior plate, with a p value of 0.033. The ribs repaired with RibLoc U Plus® showed a trend of less stiffness reduction over the 360,000 loading cycles. CONCLUSION: The biomechanical study showed that the RibLoc U Plus® system is stronger in the bending moment loading of repaired ribs, possibly due to the U-shape structure supporting both the inner and outer cortices of a repaired rib.

EMG-based Simultaneous Estimations of Joint Angle and Torque during Hand Interactions with Environments.

It is necessary to control contact force through modulation of joint stiffness in addition to the position of our limb when manipulating an object. This is achieved by contracting the agonist muscles in an appropriate magnitude, as well as, balancing it with contraction of the antagonist muscles. Here we develop a decoding technique that estimates both the position and torque of a joint of the limb in interaction with an environment based on activities of the agonist-antagonistic muscle pairs using electromyography in real time. The long short-term memory (LSTM) network that is capable of learning time series of a longtime span with varying time lags is employed as the core processor of the proposed technique. We tested both the unidirectional LSTM network and bidirectional LSTM network. A validation was conducted on the wrist joint moving along a given trajectory under resistance generated by a robot. The decoding approach provided an agreement of greater than 93% in kinetics (i.e. torque) estimation and an agreement of greater than 83% in kinematics (i.e. angle) estimation, between the actual and estimated variables, during interactions with an environment. We found no significant differences in performance between the unidirectional LSTM and bidirectional LSTM as the learning device of the proposed decoding method.

Do Fully Threaded Transiliac-Transsacral Screws Improve Mechanical Stability of Vertically Unstable Pelvic Fractures? A Cadaveric Biomechanical Analysis.

OBJECTIVE: To determine whether fully threaded transiliac-transsacral (TI-TS) fixation is biomechanically superior to partially threaded TI-TS fixation of vertically unstable transforaminal sacral fractures. METHODS: Vertically unstable zone 2 sacral fractures were created in 20 human cadaveric pelves with a unilateral osteotomy and resection of 1 cm of bone through the foramen of the sacrum to represent comminution. Ten specimens received either 2 7.3-mm fully threaded or 2 7.3-mm partially threaded TI-TS screw fixation at the S1 and S2 body, and every specimen received standard 3.5-mm 8-hole parasymphyseal plating anteriorly. Each pelvis was loaded to 250 N at 3 Hz for 100,000 cycles and then loaded to failure. The primary outcome was fracture displacement at the S1 foramen, which was measured at 25,000, 50,000, 75,000, and 100,000 cycles. Secondary outcomes were simulated clinical failure of ≥1 cm displacement at the S1 foramen to determine occurrence probability of failure, and load at failure was defined as 2.5 cm of the linear loading system displacement. Specimens in the fully threaded and partially threaded cohorts were otherwise respectively comparable in regards to age, gender, and bone density. RESULTS: Five of the 10 TI-TS partially threaded specimens experienced simulated clinical failure with >1 cm displacement at the S1 foramen compared with 0 of the 10 TI-TS fully threaded cohort (50% vs. 0%, P = 0.03). The mean maximal displacement at the S1 foramen was greater in the partially threaded cohort (9.3 mm) compared with the fully threaded cohort (3.6 mm; P = 0.004). Fully threaded specimens also demonstrated greater mean force to failure than the partially threaded specimens (461 N vs. 288 N; P = 0.0001). CONCLUSIONS: Fully threaded TI-TS screw fixation seems to be mechanically superior to partially threaded fixation in a cadaveric vertically unstable transforaminal sacral fracture model with significantly less displacement of the posterior pelvic ring and greater load to failure.

Biomechanical comparison of distal femoral fracture fixation: Analysis of non-locked, locked, and far-cortical locked constructs.

To assess whether far-cortical locking (FCL) screws alter the fracture site strain environment and allow shorter bridge plate constructs for supracondylar femoral fractures, we tested the fracture site displacement under force of synthetic left femora with a 5-cm metaphyseal fracture gap, modeling comminution. Five models of nine constructs were tested (three types of diaphyseal screws [nonlocking, locking, and FCL] and two plate lengths [13 holes and 5 holes]). Long plate models using three or four diaphyseal screws (working length 13.5 or 7.5 cm, respectively) were compared with short plates with three diaphyseal screws (working length 7.5 cm). Models were loaded axially and torsionally; 100 cycles in random order. Primary outcome measures were axial and torsional fracture site stiffness. FCL screws decreased rotational stiffness 19% (P < .01) compared with baseline nonlocking screws in the same plate and working length construct, mirroring the effect (20% decrease in stiffness, P < .01) of nearly doubling the nonlocking construct working length (7.5-13.5 cm). Similarly, FCL screws decreased axial stiffness 23% (P < .01) in the same baseline comparison. Fracture site displacement under loading comparable to a long working length nonlocked plate construct was achieved using a shorter FCL plate construct. By closely replicating the biomechanical properties of a long plate construct, a fracture site strain environment considered favorable in promoting fracture healing might still be achievable using a shorter plate length. Clinical Significance: It might be possible to optimize fracture site strain environment and displacement under loading using shorter FCL plate constructs. Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 00:00-00, 2020.