Thomas Hedman

• Ph.D.
• Professor (Associate) at University of Kentucky

Although the existence of highly prevalent pain, disability, and work time lost associated with discogenic low back pain is well known, the recognition of the culpability of universally present disc degradation and mechanical insufficiency in the first three decades of life is often overlooked. There is a corresponding “treatment gap” and no curren...

Although the existence of highly prevalent pain, disability, and work time lost associated with discogenic low back pain is well known, the recognition of the culpability of universally present disc degradation and mechanical insufficiency in the first three decades of life is often overlooked. There is a corresponding “treatment gap” and no curren...

Purpose An early-stage, multi-centre, prospective, randomised control trial with five-year follow-up was approved by Health Research Authority to compare the efficacy of a minimally invasive, laterally implanted interspinous fixation device (IFD) to open direct surgical decompression in treating lumbar spinal stenosis (LSS). Two-year results are pr...

Genipin polymers are self-forming tensile-load-carrying oligomers, derived from the gardenia fruit, that covalently bond to amines on collagen. The potential therapeutic mechanical benefits of a non-discrete in situ forming mesh of genipin oligomers for degraded spinal discs were first conceived in 1998. Over more than two decades, numerous studies...

Purpose Prospective evaluation of radiographic fusion outcomes in patients receiving instrumented posterior arthrodesis of the lumbar spine using a minimally invasive interspinous fixation device. Patients and Methods All patients (n = 110) from a single US physician’s practice who received instrumented posterior arthrodesis of the lumbar spine wi...

Background Genipin is a polymer-forming collagen bonding substance that can be dissolved in a buffered carrier and injected into disc annulus tissues. Therapeutic benefit is derived from the mechanical support provided by a large number of genipin polymers attached to collagen fibers in a degraded disc. Study Design/Setting IRB-approved prospectiv...

Objective Lumbar fusion performed through lateral approaches is becoming more common. The interbody devices are generally supported by supplemental posterior fixation implanted through a posterior approach, potentially requiring a second incision and intraoperative repositioning of the patient. A minimally invasive lateral interspinous fixation dev...

The mechanical properties of the soft palate can be associated with breathing abnormalities. Dorsal displacement of the soft palate (DDSP) is a naturally occurring equine soft palate disorder caused by displacement of the caudal edge of the soft palate. Snoring and a more serious, sometimes life-threatening, condition called obstructive sleep apnea...

After publication in volume [37], issue [1], page [94–101] the authors decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2018 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International Lice...

Exogenous crosslinking has been shown to have potential for treating disc degeneration and back pain due to its ability to increase the strength and toughness of the annulus fibrosus, increase intervertebral joint stability, decrease intradiscal pressure, and increase fluid flow through the disc. Some results imply that crosslink augmentation may a...

The most common mode of surgical repair of ruptured tendons and ligaments involves the use of sutures for reattachment. However, there is a high incidence of rerupture and repair failure due to pulling out of the suture material from the damaged connective tissue. The main goal of this research was to achieve a localized delivery of crosslinking ag...

Study design: In vivo examination of intradiscal pressure by quantitative discomanometry (QD). Objective: To determine whether an injectable, exogenous crosslinking could acutely restore intradiscal pressure of stab-injured discs in vivo by short-term treatment. Summary of background data: Disc biomechanical performance depends on its integrit...

Crosslinking of the intervertebral disc with the protein crosslinker genipin (GP) improves numerous mechanical properties, but crosslinking extent has not been studied following administration in a clinically relevant manner, that is, by injection. New methods were developed to measure free amines as a marker of crosslinking in intervertebral disc...

Crosslinking soft tissue has become more common in tissue engineering applications, and recent studies have demonstrated that soft tissue mechanical behavior can be directly altered through crosslinking. Using a recently reported test method that shears adjacent disc lamella, the effect of genipin crosslinking on interlamellar shear resistance was...

Background context: Intervertebral disc and facet joints are the two primary load-bearing structures of the lumbar spine, and altered loading to these structures may be associated with frontal plane spinal deviations. Purpose: To determine the load on the lumbar facet joint and intervertebral disc under simulated frontal plane pelvic obliquity c...

Purpose: Quantify changes in the flexion - extension neutral zone of the intervertebral disc with injections of increasing genipin concentration. Methods: Bovine motion segments were treated with varying concentrations of genipin using bilateral injections of constant volume. After overnight static compression loading of the treated segments, ante...

A new sensor array intended to accurately and directly measure spatial and time-dependent pressures within a highly curved biological intra-articular joint was developed and tested. To evaluate performance of the new sensor array for application within intra-articular joints generally, and specifically to fit within the relatively restrictive space...

Treatment of a pathological spinal disc in vivo by injection of protein crosslinking reagents to restore the disc's mechanical properties is a new approach to the treatment of degenerative disc disease. In this study, the thermal stability of the collagen in disc annulus was measured by differential scanning calorimetry following treatment with six...

Biochemical studies aimed at optimization of protein crosslinking formulations for the treatment of degenerative disc disease and subsequent biomechanical testing of tissues treated with these formulations. To optimize protein crosslinking formulations for treatment of degenerating spinal discs. Nonsurgical exogenous crosslinking therapy is a poten...

In vitro evaluation of a chemical, injectable intervention for discectomy induced destabilization. To investigate the ability of two collagen crosslinking agents to restore mechanical properties to lumbar joints destabilized by surgical decompression procedures. Posterior decompression surgery is a common procedure indicated for tissue pathology th...

Degradation of genipin (GP), a low toxicity natural protein crosslinking agent, in aqueous solution was monitored by HPLC at various pH levels. Degradation of GP was consistent with a mechanism consisting of a first order reaction with a reversible first step. Formation of the intermediate was slowest at more neutral pHs while formation of the irre...

In vitro study of genipin crosslinking effect on disc water content changes under compressive loading and unloading. To investigate the influence of collagen crosslinking on hydration and fluid flow in different regions of intact discs, and to evaluate the nutritional implications. Age-related reductions of nutrient supply and waste product removal...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

We have characterized the relative efficacies of a number of protein crosslinking agents that have the potential for use in the crosslinking of proteinaceous matrices both in vitro and in vivo. The crosslinkers tested were; L: -threose (LT), Genipin (GP), Methylglyoxal (MG), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), proant...

Novel allograft processing methods are available from tissue banks to decrease disease transmission. This study evaluated the effects of 3 of these techniques on the initial mechanical properties of bone-patellar tendon-bone (BPTB) allografts: (1) aseptic harvest with low-dose radiation processing, (2) BioCleanse Tissue Processing System, and (3) C...

This study involves a biomechanical evaluation of a prospective injectable treatment for degenerative discs. The high osmolarity of the non-degenerated nucleus pulposus attracts water contributing to the hydrostatic behavior of the tissue. This intradiscal pressure is known to drop as fluid is exuded from the matrix due to compressive loading. The...

The goal of this study was to develop a nondestructive radial compression technique and to investigate the viscoelastic behavior of the rat tail disc under repeated radial compression. Rat tail intervertebral disc underwent radial compression relaxation testing and creep testing using a custom-made gravitational creep machine. The axisymmetric visc...

Collagen crosslinks may play a vital role in preventing ongoing disc degeneration. Age-accumulating crosslinks have been thought to increase brittleness and reduce fatigue resistance. However recent studies have demonstrated increases in fatigue resistance, joint stability and nutritional flow properties resulting from crosslink augmentation. In th...

The mechanical stability of cross-linked and control spinal motion segments was evaluated using neutral zone, range of motion (ROM), and instability score metrics. To determine if exogenous cross-linking could increase the stability of spinal motion segments. The microstructure of the anulus fibrosus extracellular matrix can affect the stability of...

Large rotator cuff tears represent a challenging problem. The purpose of our study was to evaluate the small intestinal submucosa (SIS) extracellular matrix in reconstruction of such defects in an animal model. Forty rats were equally divided into an SIS group (reconstruction of a large supraspinatus tendon defect by use of the SIS) and a defect gr...

Previous radiofrequency work has not rigidly controlled energy application to the articular cartilage, giving uncertain results published to date. At minimal settings, radiofrequency probes cause cell death in measurable areas when applied to human articular cartilage. Controlled laboratory study. Simulating operating room conditions, 5 commerciall...

Multidirectional flexibility tests were conducted on 10 human thoracic spines with intact rib cage. To determine the amount of stability the rib cage imparts to the thoracic spine and to show the amount of stability lost by a sternal fracture. There is no published study of biomechanical testing of human cadaveric specimens with the rib cage intact...

Currently, two different methods of applying radiofrequency (RF) energy (monopolar and bipolar) are available to the surgeon for thermal shortening of the shoulder capsule. The objective of this study was to investigate the temperature changes and the thermal conduction across the human inferior glenohumeral ligament (IGHL) during radiofrequency en...

No data exist on the cutting efficiency of monopolar versus bipolar radiofrequency energy application systems on human meniscal tissue. To compare the effects of monopolar and bipolar thermal energy systems on human meniscal tissue. Controlled laboratory study. Fresh-frozen menisci were cut in cross-section into 180 pie-shaped specimens. A speciall...

This study involved an investigation into the effect of non-toxic crosslink augmentation on spinal discs on disc durability and joint stability. Non-destructive indentation techniques were developed to quantify annulus fibrosis material property degradation resulting from non-traumatic cyclic fatigue. Joint stability was assessed using two differen...

Translational mobilization techniques are frequently used by physical therapists as an intervention for patients with limited ranges of motion (ROMs). However, concrete experimental support for such practice is lacking. The purpose of the study was to evaluate the effect of simulated dorsal and ventral translational mobilization (DTM and VTM) of th...

The purpose of this study was to evaluate the thermal effects produced in meniscal tissue with different radiofrequency (RF) energy levels and exposure times using a bipolar device. An anatomic in vitro analysis of the thermal effects of an RF device. A specially designed jig was used to apply RF energy under a constant force to cadaveric menisci....

To quantify forces applied by therapists during dorsal glide translational mobilization of the glenohumeral joint, to determine the relationship of tissue resistance to the load-displacement relation of the glenohumeral joint, and to determine the safety of the forces applied by the therapists during dorsal glide translational mobilization. A fresh...

Minimally invasive surgical techniques have become routinely applied to the evaluation and treatment of patients with isolated diaphragmatic injuries due to penetrating trauma. The objective of the study was to compare the healing of diaphragm injuries as determined by macroscopic inspection, histologic appearance, and tensile strength following re...

A slipped capital femoral epiphysis was created in 12 matched pairs of immature bovine femora using an anterior-to-posterior-directed shear force. All soft tissues, with the exception of the perichondrial ring, were removed before testing. One specimen from each pair was fixed with a single cannulated screw in standard fashion, whereas the contrala...

To investigate the immediate effect of caudal glide translational mobilization on the range of motion (ROM) of passive glenohumeral abduction with a fresh cadaver model to simulate the mobilization movement performed by a physical therapist treating patients with glenohumeral hypomobility. Mechanical simulation of caudal glide mobilization and abdu...

To outline the development of electrosurgical (radiofrequency) devices, explain the basic principles, and review the current orthopaedic literature regarding the application of electrosurgery to arthroscopic partial meniscectomy. Materials and Methods: The history and principles of electrosurgery were obtained from various pertinent texts and journ...

To investigate the effect of joint position during an anterior-posterior glide (APG) procedure on the range of motion (ROM) of glenohumeral abduction in cadaver specimens. Mechanical simulation of APG mobilization and abduction torque ROM measurement of the glenohumeral joint with a material testing system. The immediate mechanical efficacy of APG...

The purpose of this study was to determine the effects of laser-induced collagen shortening on the biomechanical properties of the inferior glenohumeral ligament complex. Fifty-seven bone-ligament-bone specimens underwent uniaxial tensioning to 10% strain. Approximately half of the specimens then underwent 10% shortening by lasing using a holmium:y...

Twenty-six paired, fresh-frozen cadaveric feet were disarticulated at the ankle joint, and the dome of the talus was potted. Stress-risers were placed along the medial, lateral, and posterior aspects of the calcaneus, and the specimen was loaded rapidly to failure in a testing machine to produce a type-IIB displaced intra-articular fracture accordi...

Seven fresh-frozen cadaver specimens had a calcaneal osteotomy performed obliquely through the posterior portion of the calcaneus. Angular relationships between the first metatarsal and talus were recorded with the use of a motion-analysis system in the transverse, sagittal, and coronal planes. The specimen was mounted in a testing machine and load...

Nine fresh-frozen cadaveric specimens were disarticulated through the knee, and the soft tissues, except for the interosseous ligaments and interosseous membrane, were removed to the level of the ankle. The subtalar joint was secured with screws in neutral position (approximately 5 degrees of valgus). Contact pressures in the tibiotalar joint were...

Simulated syndesmosis injuries were created in 12 fresh-frozen, below-knee cadaver specimens. Six specimens were repaired with a 4.5 mm stainless steel screw, and six were repaired with a 4.5 mm polylactide screw. Three specimens of each group were tested in load to failure by axially loading with 1400 N and externally rotating to 90 degrees. Three...

In vitro force and deformation measurements formed the basis for determinate, quasistatic analysis of principal forces in the seated lumbar spine. To explore the relationship between seated postures and the mechanical response in component tissues of lumbar intervertebral joints. Despite the high prevalence of low back pain syndrome, the precise me...

Eight adult below-knee cadaver specimens were placed in a testing machine and loaded to 350 newtons according to a strict protocol. Arch height and length measurements were obtained in each specimen with the toes resting on the foot plate, dorsiflexed to 30 degrees, and maximally dorsiflexed manually. The plantar fascia was then divided from medial...

Six fresh-frozen, below-knee cadaveric specimens had the tendons of the posterior tibialis, flexor digitorum longus, and flexor hallucis longus tendons secured to force transducers. The specimens were sequentially mounted in a testing machine with the ankle in neutral position. Inversion torque acting upon the calcaneus was transmitted via a pin pl...

A magnetic resonance imaging technique was developed to measure creep in the lumbar spine in different seated postures. Owing to the fixed size and horizontal orientation constraints of the magnetic resonance imaging system bore, gravitational force was simulated in the horizontal plane while the subject assumed each of two near-seated postures: 1)...

We investigated the relative importance to stability of the four component ligaments of the distal tibiofibular syndesmosis. Eight fresh-frozen cadaver specimens were tested on a hydraulic test system during sequential cutting of the ligaments. The percentage resistance to 2 mm of diastasis was measured for the four ligaments. The anterior inferior...

Sixteen human anatomic specimen ankles underwent an arthrodesis using two (medial and lateral) or three (additional anterior) screw fixation. It was shown that significantly greater compression was achieved with three screws (p = 0.001). The order of screw fixation was important--better compression was achieved by inserting the lateral screw first....

Two long-term wear behavior studies used in part of the process of selecting the best materials for a new all-metal orthopaedic spinal implant are presented. The relative and absolute wear volume rates of candidate metals were investigated through simulation of two bearing regions of an intervertebral disc prosthesis. It was determined gravimetrica...

A new transducer capable of direct measurement of time-dependent loads in human lumbar facet joints was developed and tested. The transducer was comprised of a force-sensitive resistor (FSR) in series with a pressure-sensitive film. A wide range of experiments revealed the performance attributes and limitations of the FSR. The output signal of the...

This article presents criteria for the design of a lumbar intervertebral disc prosthesis that take into consideration issues of endurance, materials behavior, geometry, kinetics, motion constraints, fixation to bone, and safety. The criteria and design philosophies discussed are generally applicable in the synthesis of any new implant system. Speci...