Publications by authors named "Linda Uko"

8 Publications

  • Page 1 of 1

Kinematics of the Cervical Spine After Unilateral Facet Fracture: An In Vitro Cadaver Study.

Spine (Phila Pa 1976) 2017 Sep;42(18):E1042-E1049

Joint Motion Laboratory, Department of Orthopedics, Rutgers University-New Jersey Medical School, Newark, NJ.

Study Design: Biomechanical study utilizing human cadaveric cervical spines.

Objective: To quantitatively assess the effects on intervertebral motion of isolated unilateral cervical facet fracture, and after disruption of the intervertebral disc at the same level.

Summary Of Background Data: Clinical evidence has indirectly suggested that cervical facet fractures involving 40% of the height of the lateral mass can cause instability of the involved segment. No study to date has demonstrated the kinematic effects of such an injury in a cadaveric model of the cervical spine.

Methods: Nine six-segment cervical spines were defrosted and fixated to a spine motion simulator capable to apply unconstrained bending moments in the three anatomical planes. The spines were subjected to a maximum torque of 2 N · m in flexion, extension, left and right lateral bending, and of 4 N · m in left and right axial rotation. Each spine was tested in the intact configuration (INTACT), and following two increasing degrees of injury at C4-C5: fracture of the facet (CF1), and CF1 with disruption of the intervertebral disc at the same level (CF2). Intervertebral kinematics was tracked via clusters of active markers fixated on each vertebra. Differences in kinematics between INTACT and the two injured configurations were assessed via one-way Analysis of Variance (P < 0.05).

Results: No significant differences were detected between INTACT and CF1 across all kinematic parameters (P > 0.05) at C4-C5. CF2, however, resulted in significant increase of flexion, left axial rotation, and left lateral bending with respect to INTACT (flexion at C4-C5: INTACT = 8.7° ± 3.5°; CF2 = 14.3 ± 5.7; P < 0.05).

Conclusion: Our findings suggest that superior articular facet fractures alone involving 40% of the lateral mass may not necessarily result in intervertebral instability under physiologic loading conditions. The addition of partial injury to the intervertebral disc, however, resulted in statistically significant increase in angular displacement.

Level Of Evidence: N /A.
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September 2017

Zinc has insulin-mimetic properties which enhance spinal fusion in a rat model.

Spine J 2016 06 2;16(6):777-83. Epub 2016 Feb 2.

Department of Orthopaedics, Rutgers University, New Jersey Medical School, 90 Bergen St, Suite 7300, Newark, NJ 07101, USA.

Background Context: Previous studies have found that insulin or insulin-like growth factor treatment can stimulate fracture healing in diabetic and normal animal models, and increase fusion rates in a rat spinal fusion model. Insulin-mimetic agents, such as zinc, have demonstrated antidiabetic effects in animal and human studies, and these agents that mimic the effects of insulin could produce the same beneficial effects on bone regeneration and spinal fusion.

Purpose: The purpose of this study was to analyze the effects of locally applied zinc on spinal fusion in a rat model.

Study Design/setting: Institutional Animal Care and Use Committee-approved animal study using Sprague-Dawley rats was used as the study design.

Methods: Thirty Sprague-Dawley rats (450-500 g) underwent L4-L5 posterolateral lumbar fusion (PLF). After decortication and application of approximately 0.3 g of autograft per side, one of three pellets were added to each site: high-dose zinc calcium sulfate (ZnCaSO4), low-dose ZnCaSO4 (half of the high dose), or a control palmitic acid pellet (no Zn dose). Systemic blood glucose levels were measured 24 hours postoperatively. Rats were sacrificed after 8weeks and the PLFs analyzed qualitatively by manual palpation and radiograph review, and quantitatively by micro-computed tomography (CT) analysis of bone volume and trabecular thickness. Statistical analyses with p-values set at .05 were accomplished with analysis of variance, followed by posthoc tests for quantitative data, or Mann-Whitney rank tests for qualitative assessments.

Results: Compared with controls, the low-dose zinc group demonstrated a significantly higher manual palpation grade (p=.011), radiographic score (p=.045), and bone formation on micro-CT (172.9 mm(3) vs. 126.7 mm(3) for controls) (p<.01). The high-dose zinc also demonstrated a significantly higher radiographic score (p=.017) and bone formation on micro-CT (172.7 mm(3) vs. 126.7 mm(3)) (p<.01) versus controls, and was trending toward higher manual palpation scores (p=.058).

Conclusions: This study demonstrates the potential benefit of a locally applied insulin-mimetic agent, such as zinc, in a rat lumbar fusion model. Previous studies have demonstrated the benefits of local insulin application in the same model, and it appears that zinc has similar effects.
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June 2016

In vitro kinematics of the proximal interphalangeal joint in the finger after progressive disruption of the main supporting structures.

Hand (N Y) 2015 Sep;10(3):425-32

New York University-Hospital for Joint Diseases, New York, NY USA ; NYU Hospital for Joint Diseases, 301 East 17th Street, New York, NY 10003 USA.

Background: Fractures and dislocations of the proximal interphalangeal (PIP) joint of the fingers are among the most common causes of injury in the hand. Objective assessment of the kinematic alterations occurring when the supporting structures are disrupted is critical to obtain a more accurate indication of joint stability.

Methods: An in vitro cadaver model of the hand was used to evaluate the kinematics of the PIP joint in the finger during active unrestrained flexion and extension. The kinematics of the PIP joint following progressive disruption of the main supporting structures was measured using an optical tracking system and compared with those in the intact joint.

Results: Flexion of the intact PIP joint was associated with joint compression, volar displacement, and rotational movements. Release of the main soft-tissue stabilizers and 30 % of volar lip disruption resulted in substantial alteration of several kinematic variables. The normalized maximum dorsal/volar translation was 0.1 ± 1.3 % in the intact group and 14.4 ± 11.3 % in the injured joint.

Conclusions: In the intact PIP joint, rotations and translation are strongly coupled to the amount of joint flexion. Gross instability of the PIP joint occurs when disruption of the collateral ligaments and volar plate is accompanied by resection of at least 30 % of volar lip of the middle phalanx. Collateral ligament injuries, volar plate injuries alone, and fractures at the volar base of the middle phalanx that involve less than 30 % of the articular surface are unlikely to result in gross instability and may be managed effectively with non-operative treatments.
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September 2015

Fracture pattern characteristics and associated injuries of high-energy, large fragment, partial articular radial head fractures: a preliminary imaging analysis.

J Orthop Traumatol 2015 Jun 27;16(2):125-31. Epub 2014 Dec 27.

Division of Hand Surgery, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY, 10009, USA,

Background: High-energy radial head injuries often present with a large partial articular displaced fragment with any number of surrounding injuries. The objective of the study was to determine the characteristics of large fragment, partial articular radial head fractures and determine any significant correlation with specific injury patterns.

Materials And Methods: Patients sustaining a radial head fracture from 2002-2010 were screened for participation. Twenty-five patients with documented partial articular radial head fractures were identified and completed the study. Our main outcome measurement was computed tomography (CT)-based analysis of the radial head fracture. The location of the radial head fracture fragment was evaluated from the axial CT scan in relation to the radial tuberosity used as a reference point. The fragment was characterized by location as anteromedial (AM), anterolateral (AL), posteromedial (PM) or posterolateral (PL) with the tuberosity referenced as straight posterior. All measurements were performed by a blinded, third party hand and upper extremity fellowship trained orthopedic surgeon. Fracture pattern, location, and size were then correlated with possible associated injuries obtained from prospective clinical data.

Results: The radial head fracture fragments were most commonly within the AL quadrant (16/25; 64 %). Seven fracture fragments were in the AM quadrant and two in the PM quadrant. The fragment size averaged 42.5 % of the articular surface and spanned an average angle of 134.4(°). Significant differences were noted between AM (49.5 %) and AL (40.3 %) fracture fragment size with the AM fragments being larger. Seventeen cases had associated coronoid fractures. Of the total 25 cases, 13 had fracture dislocations while 12 remained reduced following the injury. The rate of dislocation was highest in radial head fractures that involved the AM quadrant (6/7; 85.7 %) compared to the AL quadrant (7/16; 43.7 %). No dislocations were observed with PM fragments. Ten of the 13 (78 %) fracture dislocations had associated lateral collateral ligament (LCL)/medial collateral ligament tear. The most common associated injuries were coronoid fractures (68 %), dislocations (52 %), and LCL tears (44 %).

Conclusion: The most common location for partial articular radial head fractures is the AL quadrant. The rate of elbow dislocation was highest in fractures involving the AM quadrant. Cases with large fragment, partial articular radial head fractures should undergo a CT scan; if associated with >30 % or >120(°) fracture arc, then the patient should be assessed closely for obvious or occult instability. These are key associations that hopefully greatly aid in the consultation and preoperative planning settings.

Level Of Evidence: Diagnostic III.
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June 2015

Three-dimensional analysis of elbow soft tissue footprints and anatomy.

J Shoulder Elbow Surg 2014 Nov 16;23(11):1618-23. Epub 2014 Jul 16.

Department of Orthopaedics, University of Medicine and Dentistry of New Jersey-Rutgers, Newark, NJ, USA.

Background: Tendinous and ligamentous injuries commonly occur in the elbow. This study characterized the location, surface areas, and origin and insertional footprints of major elbow capsuloligamentous and tendinous structures in relation to bony landmarks with the use of a precision 3-dimensional modeling system.

Methods: Nine unpaired cadaveric elbow specimens were dissected and mounted on a custom jig. Mapping of the medial collateral ligament (MCL), lateral ulnar collateral ligament (LUCL), triceps, biceps, brachialis, and capsular reflections was then performed with 3-dimensional digitizing technology. The location, surface areas, and footprints of the soft tissues were calculated.

Results: The MCL had a mean origin (humeral) footprint of 216 mm(2), insertional footprint of 154 mm(2), and surface area of 421 mm(2). The LUCL had a mean origin footprint of 136 mm(2), an insertional footprint of 142 mm(2), and a surface area of 532 mm(2). Of the tendons, the triceps maintained the largest insertional footprint, followed by the brachialis and the biceps (P < .001-.03). The MCL, LUCL, and biceps footprint locations were consistent, with little variability. The surface areas of the anterior (1251 mm(2)) and posterior (1147 mm(2)) capsular reflections were similar (P = .82), and the anterior capsule extended farther proximally.

Conclusion: Restoring the normal anatomy of key elbow capsuloligamentous and tendinous structures is crucial for effective reconstruction after bony or soft tissue trauma. This study provides the upper extremity surgeon with information that may aid in restoring elbow biomechanics and preserving range of motion in these patients.
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November 2014

Local vanadium release from a calcium sulfate carrier accelerates fracture healing.

J Orthop Res 2014 May 30;32(5):727-34. Epub 2013 Dec 30.

Department of Orthopaedics, Rutgers New Jersey Medical School, 90 Bergen Street, Suite 7300, Newark, New Jersey, 07103.

This study evaluated the efficacy of using calcium sulfate (CaSO4 ) as a carrier for intramedullary delivery of an organic vanadium salt, vanadyl acetylacetonate (VAC) after femoral fracture. VAC can act as an insulin-mimetic and can be used to accelerate fracture healing in rats. A heterogenous mixture of VAC and CaSO4 was delivered to the fracture site of BB Wistar rats, and mechanical testing, histomorphometry, micro-computed tomography (micro-CT) were performed to measure healing. At 4 weeks after fracture, maximum torque to failure, effective shear modulus, and effective shear stress were all significantly higher (p < 0.05) in rats treated with 0.25 mg/kg VAC-CaSO4 as compared to carrier control rats. Histomorphometry found a 71% increase in percent cartilage matrix (p < 0.05) and a 64% decrease in percent mineralized tissue (p < 0.05) at 2 weeks after fracture in rats treated with 0.25 mg/kg of VAC-CaSO4 . Micro-CT analyses at 4 weeks found a more organized callus structure and higher trending maximum connected z-ray. fraction for VAC-CaSO4 groups. Evaluation of radiographs and serial histological sections at 12 weeks did not show any evidence of ectopic bone formation. As compared to previous studies, CaSO4 was an effective carrier for reducing the dose of VAC required to accelerate femoral fracture healing in rats.
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May 2014

A novel design for application of pure moments in-vitro: application to the kinematic analysis of the cervical spine.

J Biomech 2013 Apr 1;46(6):1221-4. Epub 2013 Feb 1.

Joint Motion Lab, Orthopedics dept., University of Medicine and Dentistry of New Jersey, Newark, NJ, USA.

The simple and cost-effective cable-pulley apparatus proposed by Crawford et al. (1995) has been long and widely used to assess the kinematics and biomechanics of the spine in-vitro. A major limitation of that fixed-ring system relies on the manual readjustment of the cable guides, which is required to maintain parallelism of the tension-cables during spine rotations. While several solutions have since been suggested to improve this loading approach, their implementation may be challenging for research groups with limited resources. In this study we propose an upgrade to the traditional fixed-ring design which aims to improve its usability while retaining the simplicity. The main novelty of this setup is the coupling of a through-hole along the diameter of the pulley with a rod fixated to the top of the spine. The coupling allows relative translation of the pulley along the rod's axis, thus permitting readjustment of the tension-cables' orientation with minimal manual intervention. The effectiveness of the system was demonstrated by measuring intervertebral kinematics in three 7-vertebra cervical spines. During sagittal and frontal-plane rotations, tension-cables parallelism could be easily and quickly restored by pushing the pulley along the rod's axis. The measured intervertebral rotations were consistent with data from the literature. The interspecimen standard deviation of the total range of motion ranged between 2.1° and 9.6° across all loading configurations. The simple and light mobile-pulley fixture presented in this study has shown to be easy to use and its application may represent a viable alternative to the original fixed-ring design.
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April 2013

The effects of local insulin application to lumbar spinal fusions in a rat model.

Spine J 2013 Jan 5;13(1):22-31. Epub 2013 Jan 5.

Department of Orthopaedics, UMDNJ-New Jersey Medical School, 90 Bergen St, DOC 7300, Newark, NJ 07101, USA.

Background Context: The rates of pseudoarthrosis after a single-level spinal fusion have been reported up to 35%, and the agents that increase the rate of fusion have an important role in decreasing pseudoarthrosis after spinal fusion. Previous studies have analyzed the effects of local insulin application to an autograft in a rat segmental defect model. Defects treated with a time-released insulin implant had significantly more new bone formation and greater quality of bone compared with controls based on histology and histomorphometry. A time-released insulin implant may have similar effects when applied in a lumbar spinal fusion model.

Purpose: This study analyzes the effects of a local time-released insulin implant applied to the fusion bed in a rat posterolateral lumbar spinal fusion model. Our hypothesis was twofold: first, a time-released insulin implant applied to the autograft bed in a rat posterolateral lumbar fusion will increase the rate of successful fusion and second, will alter the local environment of the fusion site by increasing the levels of local growth factors.

Study Design: Animal model (Institutional Animal Care and Use Committee approved) using 40 adult male Sprague-Dawley rats.

Methods: Forty skeletally mature Sprague-Dawley rats weighing approximately 500 g each underwent posterolateral intertransverse lumbar fusions with iliac crest autograft from L4 to L5 using a Wiltse-type approach. After exposure of the transverse processes and high-speed burr decortication, a Linplant (Linshin Canada, Inc., ON, Canada) consisting of 95% microrecrystalized palmitic acid and 5% bovine insulin (experimental group) or a sham implant consisting of only palmitic acid (control group) was implanted on the fusion bed with iliac crest autograft. As per the manufacturer, the Linplant has a release rate of 2 U/day for a minimum of 40 days. The transverse processes and autograft beds of 10 animals from the experimental and 10 from the control group were harvested at Day 4 and analyzed for growth factors. The remaining 20 spines were harvested at 8 weeks and underwent a radiographic examination, manual palpation, and microcomputed tomographic (micro-CT) examination.

Results: One of the 8-week control animals died on postoperative Day 1, likely due to anesthesia. In the groups sacrificed at Day 4, there was a significant increase in insulinlike growth factor-I (IGF-I) in the insulin treatment group compared with the controls (0.185 vs. 0.129; p=.001). No significant differences were demonstrated in the levels of transforming growth factor beta-1, platelet-derived growth factor-AB, and vascular endothelial growth factor between the groups (p=.461, .452, and .767 respectively). Based on the radiographs, 1 of 9 controls had a solid bilateral fusion mass, 2 of 9 had unilateral fusion mass, 3 of 9 had small fusion mass bilaterally, and 3 of 9 had graft resorption. The treatment group had solid bilateral fusion mass in 6 of 10 and unilateral fusion mass in 4 of 10, whereas a small bilateral fusion mass and graft resorption were not observed. The difference between the groups was significant (p=.0067). Based on manual palpation, only 1 of 9 controls was considered fused, 4 of 9 were partially fused, and 4 of 9 were not fused. In the treatment group, there were 6 of 10 fusions, 3 of 10 partial fusions, and 1 of 10 were not fused. The difference between the groups was significant (p=.0084). Based on the micro-CT, the mean bone volume of the control group was 126.7 mm(3) and 203.8 mm(3) in the insulin treatment group. The difference between the groups was significant (p=.0007).

Conclusions: This study demonstrates the potential role of a time-released insulin implant as a bone graft enhancer using a rat posterolateral intertransverse lumbar fusion model. The insulin-treatment group had significantly higher fusion rates based on the radiographs and manual palpation and had significantly higher levels of IGF-I and significantly more bone volume on micro-CT.
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January 2013