Publications by authors named "Andrew G Park"

8 Publications

  • Page 1 of 1

Biomechanical Comparison of Titanium Locking Fragment-Specific and Volar Locking Plates for AO B1 and B2 Fractures of the Distal Radius.

J Hand Surg Am 2019 Dec 18;44(12):1093.e1-1093.e8. Epub 2019 Mar 18.

The Rothman Institute, Department of Orthopedic Surgery, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA.

Purpose: This biomechanical study compared the stability of volar locking plates (VLPs) and locking fragment-specific (LFS) dorsal and radial styloid plates for the fixation of dorsal (AO 23-B2) and radial styloid (AO 23-B1) shear fractures of the distal radius, respectively.

Methods: Two groups of 6 composite radii were fixed with a VLP or an LFS dorsal plate over a simulated dorsal shear fracture. Two additional groups of 6 radii received the same VLP or an LFS radial plate to fix a radial styloid fracture. Each plated radius was tested under cyclic axial compression by a servohydraulic testing machine that recorded axial displacement per cycle. Construct stiffness was calculated from the slope of the force-displacement curve.

Results: In the dorsal shear fracture model, the dorsal LFS plate exhibited less displacement than the VLP (0.32 ± 0.04 vs 0.43 ± 0.07 mm, respectively) and showed greater average stiffness (645 ± 64 vs 433 ± 88 N/mm, respectively). Plate type was responsible for 53.1% of the variation in displacement and 68.6% of the variation in stiffness. In the radial styloid fracture model, variations due to number of cycles elapsed and plate type were similar for displacement and stiffness in both groups. The average stiffness during cyclical nondestructive testing was 566 ± 45 and 573 ± 60 N/mm for VLP and LFS radial plating groups, respectively.

Conclusions: For AO 23-B2 (dorsal rim) fractures, the dorsal LFS plates exhibited significantly less displacement and greater stiffness in axial loading than VLPs. For AO 23-B1 (radial styloid) fractures, the VLP displayed similar displacement and stiffness to the radial LFS plates.

Clinical Relevance: All constructs tested could be expected to withstand axial compressive forces typical of early postoperative rehabilitation.
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http://dx.doi.org/10.1016/j.jhsa.2019.02.003DOI Listing
December 2019

Touch Surgery: Analysis and Assessment of Validity of a Hand Surgery Simulation "App".

Hand (N Y) 2019 05 24;14(3):311-316. Epub 2018 Jan 24.

1 Thomas Jefferson University, Philadelphia, PA, USA.

Background: Surgical educators are increasingly exploring surgical simulation and other nonclinical teaching adjuncts in the education of trainees. The simulators range from purpose-built machines to inexpensive smartphone or tablet-based applications (apps). This study evaluates a free surgery module from one such app, Touch Surgery, in an effort to evaluate its validity and usefulness in training for hand surgery procedures across varied levels of surgical experience.

Methods: Participants were divided into 3 cohorts: fellowship-trained hand surgeons, orthopedic surgery residents, and medical students. Participants were trained in the use of the Touch Surgery app. Each participant completed the Carpal Tunnel Release module 3 times, and participants' score was recorded for each trial. Participants also completed a customized Likert survey regarding their opinions on the usefulness and accuracy of the app. Statistical analysis using a 2-tailed t test and analysis of variance was performed to evaluate for performance within and between cohorts.

Results: All cohorts performed better on average with each subsequent simulation attempt. For all attempts, the experts outperformed the novice and intermediate participants, while the intermediate cohort outperformed the novice cohort. Novice users consistently gave the app better scores for usefulness as a training tool, and demonstrated more willingness to use the product.

Conclusions: The study confirms app validity and usefulness by demonstrating that every cohort's simulator performance improved with consecutive use, and participants with higher levels of training performed better. Also, user confidence in this app's veracity and utility increased with lower levels of training experience.
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http://dx.doi.org/10.1177/1558944717751192DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6535950PMC
May 2019

Prolonged Preoperative Weakness Affects Recovery of Motor Function After Anterior Cervical Diskectomy and Fusion.

J Am Acad Orthop Surg 2018 Jan;26(2):67-73

From the Department of Orthopaedic Surgery, Thomas Jefferson University Hospitals, Philadelphia, PA (Dr. Kreitz, Dr. Huang, Dr. Beck, and Dr. Park), and the Rothman Institute, Thomas Jefferson University Hospitals, Philadelphia (Dr. Hilibrand).

Introduction: Some patients who undergo anterior cervical diskectomy and fusion for radiculopathy or myelopathy demonstrate preoperative weakness. The purpose of this study was to determine which factors predict motor recovery in patients undergoing anterior cervical diskectomy and fusion.

Methods: A retrospective review of our institutional database identified patients undergoing anterior cervical diskectomy and fusion between 2010 and 2013 with 2 years of clinical follow-up. Patients with substantial weakness, defined as preoperative grade ≤3 (on a scale from 0 to 5) in one or more upper extremity muscle groups, were identified. Regression analysis was used to determine risk factors associated with persistent postoperative weakness.

Results: Of the 1,001 patients who were included, 54 (5.4%) demonstrated substantial weakness. By 2 years postoperatively, 47 of 54 patients (87%) demonstrated motor recovery. The duration of preoperative weakness was an independent predictor of recovery (median, 4 months of preoperative weakness among patients with recovery versus 10 months in patients with persistent weakness; P = 0.012).

Discussion: Duration of preoperative motor weakness is an independent predictor of motor recovery after anterior cervical diskectomy and fusion in patients with substantial motor weakness.

Conclusion: Patients being considered for anterior cervical diskectomy and fusion who have substantial preoperative motor deficits may benefit from earlier surgical intervention.
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http://dx.doi.org/10.5435/JAAOS-D-16-00606DOI Listing
January 2018

Can We Reduce the Utilization of Home-Visiting Nurse Services After Primary Total Joint Arthroplasty?

J Arthroplasty 2016 09 17;31(9 Suppl):50-3. Epub 2016 Mar 17.

Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania.

Background: Home-visiting nurse services (HVNSs) after total joint arthroplasty (TJA) are touted as advantageous compared with inpatient rehabilitation. No study has established the utility of HVNSs compared with discharge home without services.

Methods: A retrospective single-surgeon consecutive series of 509 primary TJA patients compared discharge disposition, length of stay, complications, and patient satisfaction between 2 cohorts. The cohorts were defined by the elimination of routine HVNSs.

Results: Surprisingly, without routine HVNSs, more patients were discharged home (95% vs 88.3% with routine HVNSs) and mean length of stay significantly decreased. Complication rate was similar (2.9% vs 3.9% with routine HVNSs). Patient satisfaction remained favorable. We estimated that eliminating HVNSs avoids excess costs of $1177 per hip and $1647 per knee arthroplasty.

Conclusions: With dramatically diminished HVNS utilization after primary TJA, there was an associated decrease in length of stay and no increase in complication rate suggesting no compromise of patient care with significant cost savings.
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http://dx.doi.org/10.1016/j.arth.2016.02.078DOI Listing
September 2016

Intraoperative Proximal Femoral Fracture in Primary Cementless Total Hip Arthroplasty.

J Arthroplasty 2015 Aug 7;30(8):1418-22. Epub 2015 Mar 7.

Rothman Institute/Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania.

Intraoperative proximal femoral fracture is a complication of primary cementless total hip arthroplasty (THA) at rates of 2.95-27.8%. A retrospective review of 2423 consecutive primary cementless THA cases identified 102 hips (96 patients) with fracture. Multivariate analysis compared fracture incidences between implants, Accolade (Stryker Orthopaedics) and Tri-Lock (DePuy Orthopaedics, Inc.), and evaluated potential risk factors using a randomized control group of 1150 cases without fracture. The fracture incidence was 4.4% (102/2423), 3.7% (36/1019) using Accolade and 4.9% using Tri-Lock (66/1404) (P=0.18). Female gender (OR=1.96; 95% CI 1.19-3.23; P=0.008) and smaller stem size (OR=1.64; 95% CI 1.04-2.63; P=0.03) predicted increased odds of fracture. No revisions of the femoral component were required in the fracture cohort.
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http://dx.doi.org/10.1016/j.arth.2015.02.043DOI Listing
August 2015

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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http://dx.doi.org/10.1002/jor.22570DOI Listing
May 2014

Local insulin therapy affects fracture healing in a rat model.

J Orthop Res 2013 May 13;31(5):776-82. Epub 2012 Dec 13.

Department of Orthopaedics, University of Medicine, Dentistry of New Jersey-New Jersey Medical School, 185 South Orange Avenue, 90 Bergen Street, Suite 7300, Newark, NJ 07103, USA.

A significant number of lower extremity fractures result in mal-union necessitating effective treatments to restore ambulation. Prior research in diabetic animal fracture models demonstrated improved healing following local insulin application to the fracture site and indicated that local insulin therapy can aid bone regeneration, at least within an insulin-dependent diabetic animal model. This study tested whether local insulin therapy could accelerate femur fracture repair in normal, non-diabetic rats. High (20 units) and low (10 units) doses of insulin were delivered in a calcium sulfate carrier which provided sustained release of the exogenous insulin for 7 days after fracture. Histomorphometry, radiographic scoring, and torsional mechanical testing were used to measure fracture healing. The fracture calluses from rats treated with high-dose insulin had significantly more cartilage than untreated rats after 7 and 14 days of healing. After 4 weeks of healing, femurs from rats treated with low-dose insulin had significantly higher radiographic scores and mechanical strength (p < 0.05), compared to the no treatment control groups. The results of this study suggest that locally delivered insulin is a potential therapeutic agent for treating bone fractures. Further studies are necessary, such as large animal proof of concepts, prior to the clinical use of insulin for bone fracture treatment.
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http://dx.doi.org/10.1002/jor.22287DOI Listing
May 2013

The effects of local vanadium treatment on angiogenesis and chondrogenesis during fracture healing.

J Orthop Res 2012 Dec 31;30(12):1971-8. Epub 2012 May 31.

Department of Orthopaedics, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 90 Bergen Street, Suite 7300, Newark, New Jersey 07103, USA.

This study quantified the effects of local intramedullary delivery of an organic vanadium salt, which may act as an insulin-mimetic on fracture healing. Using a BB Wistar rat femoral fracture model, local vanadyl acetylacetonate (VAC) was delivered to the fracture site and histomorphometry, mechanical testing, and immunohistochemistry were performed. Callus percent cartilage was 200% higher at day 7 (p < 0.05) and 88% higher at day 10 (p < 0.05) in the animals treated with 1.5 mg/kg of VAC. Callus percent mineralized tissue was 37% higher at day 14 (p < 0.05) and 31% higher at day 21 (p < 0.05) in the animals treated with 1.5 mg/kg of VAC. Maximum torque to failure was 104% and 154% higher at 4 weeks post-fracture (p < 0.05) for the healing femurs from the VAC-treated (1.5 and 3.0 mg/kg) animals. Animals treated with other VAC doses demonstrated increased mechanical parameters at 4 weeks (p < 0.05). Immunohistochemistry detected 62% more proliferating cells at days 7 (p < 0.05) and 94% more at day 10 (p < 0.05) in the animals treated with 1.5 mg/kg VAC. Results showed 100% more vascular endothelial growth factor-C (VEGF-C) positive cells and 80% more blood vessels at day 7 (p < 0.05) within the callus subperiosteal region of VAC-treated animals (1.5 mg/kg) compared to controls. The results suggest that local VAC treatment affects chondrogenesis and angiogenesis within the first 7-10 days post-fracture, which leads to enhanced mineralized tissue formation and accelerated fracture repair as early as 3-4 weeks post-fracture.
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http://dx.doi.org/10.1002/jor.22159DOI Listing
December 2012