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1.  A positive viewpoint regarding arthroscopy for degenerative knee conditions 
Acta Orthopaedica  2014;85(6):681-685.
doi:10.3109/17453674.2014.970071
PMCID: PMC4259041  PMID: 25280131
2.  Outcome of arthroscopic treatment for symptomatic femoroacetabular impingement 
Background
Recently, arthroscopic-based treatment for hip-related pain with radiological findings of femoroacetabular impingement and labral lesions has been developed.
We aim to present clinical outcome in a single centre patient cohort of patients treated arthroscopically for hip-related pain due to femoroacetabular impingement.
Methods
A total of 117 consecutive patients operated in 2009–2011 were included in this prospective case series (41% male; mean age 37 years; (range 15–70). The indication for arthroscopic treatment of hip-related pain was mechanical hip symptoms and radiological findings of femoroacetabular impingement.
To evaluate hip function and pain level at 1-year and 2–5 years follow up (FU) mHHS (Modified Harris Hip Score), HOS (Hip Outcome Score) and a Numeric Rating Scale (NRS) pain score were used.
Results
Labral tears were seen in 91% of the hip arthroscopies. Cartilage lesions (ICRS grade 2 and above) were seen at the acetabular and femoral articular surfaces in 79% and 15% of cases, respectively. The therapeutic procedures were in 99% of the arthroscopies osteochondroplasty and/or acetabular rim-trimming. In 77% of procedures labral reattachment was performed. The patient evaluated outcome demonstrated significant increases in mHHS and HOS at 1-year follow up and at final FU compared to preoperatively (1 yr: mHHS: 72.1 to 85.3, HOS: 71.4 to 85.1; final FU: mHHS: 72.1 to 83.8, HOS: 71.4 to 83.7). Pain levels decreased significantly from preoperatively to follow ups. Five patients underwent total hip replacement within the follow up period after hip arthroscopy.
Conclusions
Arthroscopic treatment of femoroacetabular impingement improves patient evaluated outcomes. Further studies are needed to determine failure rates and risk factors.
doi:10.1186/1471-2474-15-394
PMCID: PMC4247665  PMID: 25417179
Hip; Arthroscopy; Femoroacetabular impingement; FAI; Labral tear
3.  A Prospective Study on Time to Recovery in 254 Injured Novice Runners 
PLoS ONE  2014;9(6):e99877.
Objectives
Describe the diagnoses and the time to recovery of running-related injuries in novice runners.
Design
Prospective cohort study on injured runners.
Method
This paper is a secondary data analysis of a 933-person cohort study (DANO-RUN) aimed at characterizing risk factors for injury in novice runners. Among those sustaining running-related injuries, the types of injuries and time to recovery is described in the present paper. All injured runners were diagnosed after a thorough clinical examination and then followed prospectively during their recovery. If they recovered completely from injury, time to recovery of each injury was registered.
Results
A total of 254 runners were injured. The proportion of runners diagnosed with medial tibial stress syndrome was 15%, 10% for patellofemoral pain, 9% for medial meniscal injury, 7% for Achilles tendinopathy and 5% for plantar fasciitis. Among the 220 runners (87%) recovering from their injury, the median time to recovery was 71 days (minimum  = 9 days, maximum  = 617 days).
Conclusions
Medial tibial stress syndrome was the most common injury followed by patellofemoral pain, medial meniscal injury and Achilles tendinopathy. Half of the injured runners were unable to run 2×500 meters without pain after 10 weeks. Almost 5% of the injured runners received surgical treatment.
doi:10.1371/journal.pone.0099877
PMCID: PMC4055729  PMID: 24923269
4.  RUNNING MORE THAN THREE KILOMETERS DURING THE FIRST WEEK OF A RUNNING REGIMEN MAY BE ASSOCIATED WITH INCREASED RISK OF INJURY IN OBESE NOVICE RUNNERS 
ABSTRACT
Background:
Training guidelines for novice runners are needed to reduce the risk of injury. The purpose of this study was to investigate whether the risk of injury varied in obese and non‐obese individuals initiating a running program at different weekly distances.
Methods:
A volunteer sample of 749 of 1532 eligible healthy novice runners was included in a 3‐week observational explorative prospective cohort study. Runners were categorized into one of six strata based on their body mass index (BMI) (≤30=low; >30=high) and running distance after 1 week (<3 km = low; 3 to 6 km = medium; >6 km = high). Data was collected for three weeks for the six strata. The main outcome measure was running‐related injury.
Results:
Fifty‐six runners sustained a running‐related injury during the 3‐week data collection. A significantly greater number of individuals with BMI>30 sustained injuries if they ran between 3 to 6 km (cumulative risk difference (CRD) = 14.3% [95%CI: 3.3% to 25.3%], p<0.01) or more than 6 km (CRD = 16.2% [95%CI: 4.4% to 28.0%], p<0.01) the first week than individuals in the reference group (low distance and low BMI). The effect‐measure modification between high running distance and BMI on additive scale was positive (11.7% [‐3.6% to 27.0%], p=0.13). The number of obese individuals needed to change their running distance from high to low to avoid one injury was 8.5 [95%CI: 4.6 to 52].
Conclusions:
Obese individuals were at greater risk of injury if they exceeded 3 km during the first week of their running program. Because of a considerable injury risk compared with their non‐obese peers, individuals with a BMI>30 may be well advised to begin running training with an initial running distance of less than 3 km (1.9 miles) the first week of their running regime. Large‐scale trials are needed to further describe and document this relationship.
Level of Evidence:
Level 2b
PMCID: PMC4060311  PMID: 24944852
Body mass index; distance; injury risk; Running
5.  Validation of 14,500 operated knees registered in the Danish Knee Ligament Reconstruction Register: registration completeness and validity of key variables 
Clinical Epidemiology  2013;5:219-228.
Introduction
The aim of this study was to validate the registration in the Danish Knee Ligament Reconstruction Register (DKRR) by assessing the registration completeness of the anterior cruciate ligament (ACL) reconstruction code and detecting the validity of important key variables. Furthermore, we assessed data quality of patient-related outcome scores.
Material and methods
All operation codes for ACL reconstruction from 2005–2011 were identified in the Danish National Registry of Patients and were compared with the cases registered in the DKRR to compute the completeness of registration. We also assessed the validity of key variables in the DKRR using medical records as a reference standard to compute the positive predictive value. Finally, we assessed potential differences between responders and nonresponders to subjective patient-related outcome scores (Knee Injury and Osteoarthritis Outcome Score [KOOS] and Tegner scores) 1 year after surgery.
Results
The completeness of the registration of patients in the DKRR increased from 60% (2005) to 86% (2011). Large-volume hospitals had a higher completeness than small-volume hospitals. With a positive predictive value between 85%–100%, the validity of key variables was good. KOOS scores versus Tegner scores for responders and nonresponders were comparable.
Conclusion
The results show a good registration of ACL reconstruction procedures in the DKRR, but there is room for improvement mainly at small-volume hospitals. Overall, the validity of the key variables in the DKRR was good and no difference was found in KOOS and Tegner scores for responders versus nonresponders. Therefore, we conclude that the DKRR is a valid source for future research.
doi:10.2147/CLEP.S45752
PMCID: PMC3724682  PMID: 23901295
ACL; anterior cruciate ligament registry; predictive value
6.  Dermatan sulphate in methoxy polyethylene glycol-polylactide-co-glycolic acid scaffolds upregulates fibronectin gene expression but has no effect on in vivo osteochondral repair 
International Orthopaedics  2012;36(7):1507-1513.
Purpose
The purpose of the study was to investigate the effect of dermatan sulphate (DS) addition to biodegradable methoxy polyethylene glycol (MPEG) substituted polylactide-co-glycolic acid (PLGA) scaffolds for cartilage repair in vitro and in vivo.
Methods
Human chondrocytes from eight patients undergoing anterior cruciate ligament reconstruction were isolated and cultured in 5% oxygen on MPEG-PLGA scaffolds ± DS for one, three, seven and 14 days. Analyses were performed using quantitative gene expression analysis for chondrogenic and cell attachment markers. An osteochondral drill hole defect was created in the intertrochlear groove of the distal femur in 20 New Zealand white rabbits (defects n = 20). When bleeding was observed, the defects were treated with MPEG-PLGA scaffolds ± DS. Twelve weeks after surgery the rabbits were sacrificed and the defects were analysed using histological grading with O’Driscoll scoring.
Results
DS addition to MPEG-PLGA scaffolds resulted in a significant upregulation of fibronectin gene expression on day 1. No differences were observed in chondrogenic gene expression. There were no differences between the two groups in histological grading (+DS 10.3 and −DS 9.6).
Conclusions
Upregulation of fibronectin in vitro indicating early cell-scaffold interaction and attachment did not result in improved cartilage repair in an osteochondral defect model in rabbits.
doi:10.1007/s00264-011-1479-0
PMCID: PMC3385878  PMID: 22262251
7.  TRAINING ERRORS AND RUNNING RELATED INJURIES: A SYSTEMATIC REVIEW 
Purpose:
The purpose of this systematic review was to examine the link between training characteristics (volume, duration, frequency, and intensity) and running related injuries.
Methods:
A systematic search was performed in PubMed, Web of Science, Embase, and SportDiscus. Studies were included if they examined novice, recreational, or elite runners between the ages of 18 and 65. Exposure variables were training characteristics defined as volume, distance or mileage, time or duration, frequency, intensity, speed or pace, or similar terms. The outcome of interest was Running Related Injuries (RRI) in general or specific RRI in the lower extremity or lower back. Methodological quality was evaluated using quality assessment tools of 11 to 16 items.
Results:
After examining 4561 titles and abstracts, 63 articles were identified as potentially relevant. Finally, nine retrospective cohort studies, 13 prospective cohort studies, six case-control studies, and three randomized controlled trials were included. The mean quality score was 44.1%. Conflicting results were reported on the relationships between volume, duration, intensity, and frequency and RRI.
Conclusion:
It was not possible to identify which training errors were related to running related injuries. Still, well supported data on which training errors relate to or cause running related injuries is highly important for determining proper prevention strategies. If methodological limitations in measuring training variables can be resolved, more work can be conducted to define training and the interactions between different training variables, create several hypotheses, test the hypotheses in a large scale prospective study, and explore cause and effect relationships in randomized controlled trials.
Level of evidence:
2a
PMCID: PMC3290924  PMID: 22389869
Duration; frequency; injuries; intensity; running; training; volume
8.  Combined 3D and hypoxic culture improves cartilage-specific gene expression in human chondrocytes 
Acta Orthopaedica  2011;82(2):234-240.
Background and purpose
In vitro expansion of autologous chondrocytes is an essential part of many clinically used cartilage repair treatments. Native chondrocytes reside in a 3-dimensional (3D) network and are exposed to low levels of oxygen. We compared monolayer culture to combined 3D and hypoxic culture using quantitative gene expression analysis.
Methods
Cartilage biopsies were collected from the intercondylar groove in the distal femur from 12 patients with healthy cartilage. Cells were used for either monolayer or scaffold culture. The scaffolds were clinically available MPEG-PLGA scaffolds (ASEED). After harvesting of cells for baseline investigation, the remainder was divided into 3 groups for incubation in conditions of normoxia (21% oxygen), hypoxia (5% oxygen), or severe hypoxia (1% oxygen). RNA extractions were performed 1, 2, and 6 days after the baseline time point, respectively. Quantitative RT-PCR was performed using assays for RNA encoding collagen types 1 and 2, aggrecan, sox9, ankyrin repeat domain-37, and glyceraldehyde-3-phosphate dehydrogenase relative to 2 hypoxia-stable housekeeping genes.
Results
Sox9, aggrecan, and collagen type 2 RNA expression increased with reduced oxygen. On day 6, the expression of collagen type 2 and aggrecan RNA was higher in 3D culture than in monolayer culture.
Interpretation
Our findings suggest that there was a combined positive effect of 3D culture and hypoxia on cartilage-specific gene expression. The positive effects of 3D culture alone were not detected until day 6, suggesting that seeding of chondrocytes onto a scaffold for matrix-assisted chondrocyte implantation should be performed earlier than 2 days before implantation.
doi:10.3109/17453674.2011.566135
PMCID: PMC3235297  PMID: 21434761
9.  Alendronate treatment improves bone–pedicle screw interface fixation in posterior lateral spine fusion: An experimental study in a porcine model 
International Orthopaedics  2009;34(3):447-451.
The bone–screw interface has been indicated as the weak link in pedicle screw spine fixation. Bisphosphonate treatment may have the effect of improving bone–screw interface fixation in spine fusion by inhibiting bone resorption. An experimental study was conducted using a porcine model to evaluate the influence of alendronate treatment on bone–pedicle screw interface fixation. Eleven pigs in the treatment group received alendronate 10 mg/day orally for three months postoperatively. The other 11 pigs served as a control group. Posterior lateral fusion with the CD Horizon pedicle screw system was performed with autograft on the lumbar spine on all animals. Biomechanical torsion test and histomorphometric parameters of screw fixation were evaluated three months after the operation. The maximum torque and initial angular stiffness of the treatment group was higher than that of the control group, but there was no statistical significance. The bone–screw contact surface was 23.3 ± 10% for the treatment group and 9.8 ± 5.9% for the control group (P < 0.01). This study indicated that alendronate treatment increased bone purchase of stainless steel screw surfaces.
doi:10.1007/s00264-009-0759-4
PMCID: PMC2899306  PMID: 19330331
10.  Trait Performance Correlations across Life Stages under Environmental Stress Conditions in the Common Frog, Rana temporaria 
PLoS ONE  2010;5(7):e11680.
If an organism's juvenile and adult life stages inhabit different environments, certain traits may need to be independently adapted to each environment. In many organisms, a move to a different environment during ontogeny is accompanied by metamorphosis. In such organisms phenotypic induction early in ontogeny can affect later phenotypes. In laboratory experiments we first investigated correlations between body morphology and the locomotor performance traits expressed in different life stages of the common frog, Rana temporaria: swimming speed and acceleration in tadpoles; and jump-distance in froglets. We then tested for correlations between these performances across life stages. We also subjected tadpoles to unchanging or decreasing water levels to explore whether decreasing water levels might induce any carry-over effects. Body morphology and performance were correlated in tadpoles; morphology and performance were correlated in froglets: hence body shape and morphology affect performance within each life stage. However, performance was decoupled across life stages, as there was no correlation between performance in tadpoles and performance in froglets. While size did not influence tadpole performance, it was correlated with performance of the metamorphosed froglets. Experiencing decreasing water levels accelerated development time, which resulted in smaller tadpoles and froglets, i.e., a carry-over effect. Interestingly, decreasing water levels positively affected the performance of tadpoles, but negatively affected froglet performance. Our results suggest that performance does not necessarily have to be correlated between life stages. However, froglet performance is size dependent and carried over from the tadpole stage, suggesting that some important size-dependent characters cannot be decoupled via metamorphosis.
doi:10.1371/journal.pone.0011680
PMCID: PMC2908130  PMID: 20657779
11.  Parathyroid hormone PTH(1–34) increases the volume, mineral content, and mechanical properties of regenerated mineralizing tissue after distraction osteogenesis in rabbits 
Acta Orthopaedica  2009;80(6):716-723.
Background and purpose Parathyroid hormone (PTH) has attracted considerable interest as a bone anabolic agent. Recently, it has been suggested that PTH can also enhance bone repair after fracture and distraction osteogenesis. We analyzed bone density and strength of the newly regenerated mineralized tissue after intermittent treatment with PTH in rabbits, which undergo Haversian bone remodeling similar to that in humans.
Methods 72 New Zealand White rabbits underwent tibial mid-diaphyseal osteotomy and the callus was distracted 1 mm/day for 10 days. The rabbits were divided into 3 groups, which received injections of PTH 25 µg/kg/day for 30 days, saline for 10 days and PTH 25 µg/kg/day for 20 days, or saline for 30 days. At the end of the study, the rabbits were killed and the bone density was evaluated with DEXA. The mechanical bone strength was determined by use of a 3-point bending test.
Results In the 2 PTH-treated groups the regenerate callus ultimate load was 33% and 30% higher, absorbed energy was 100% and 65% higher, BMC was 61% and 60% higher, and callus tissue volume was 179% and 197% higher than for the control group.
Interpretation We found that treatment with PTH during distraction osteogenesis resulted in substantially higher mineralized tissue volume, mineral content, and bending strength. This suggests that treatment with PTH may benefit new bone formation during distraction osteogenesis and could form a basis for clinical application of this therapy in humans.
doi:10.3109/17453670903350032
PMCID: PMC2823317  PMID: 19995322
12.  Validation of suitable house keeping genes for hypoxia-cultured human chondrocytes 
BMC Molecular Biology  2009;10:94.
Background
Hypoxic culturing of chondrocytes is gaining increasing interest in cartilage research. Culturing of chondrocytes under low oxygen tension has shown several advantages, among them increased synthesis of extracellular matrix and increased redifferentiation of dedifferentiated chondrocytes. Quantitative gene expression analyses such as quantitative real-time PCR (qRT-PCR) are powerful tools in the investigation of underlying mechanisms of cell behavior and are used routinely for differentiation and phenotype assays. However, the genes used for normalization in normoxic cell-cultures might not be suitable in the hypoxic environment. The objective of this study was to determine hypoxia-stable housekeeping genes (HKG) for quantitative real-time PCR (qRT-PCR) in human chondrocytes cultured in 21%, 5% and 1% oxygen by geNorm and NormFinder analyses.
Results
The chondrocytic response to the hypoxic challange was validated by a significant increase in expression of the hypoxia-inducible gene ankyrin repeat 37 as well as SOX9 in hypoxia. When cultured on the 3-dimentional (3D) scaffold TATA-binding protein (TBP) exhibited the highest expression stability with NormFinder while Ribosomal protein L13a (RPL13A) and beta2-microglobulin (B2M) were the most stable using geNorm analysis. In monolayer RPL13A were the most stable gene using NormFinder, while geNorm assessed RPL13A and human RNA polymerase II (RPII) as most stable. When examining the combination of (3D) culturing and monolayer RPL13A and B2M showed the highest expression stability from geNorm analysis while RPL13A also showed the highest expression stability using NormFinder. Often used HKG such as beta actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were the most unstable genes investigated in all comparisons. The pairwise variations for the two most stable HKG in each group were all below the cut-off value of 0.15, suggesting that the two most stable HKG from geNorm analysis would be sufficient for qRT-PCR.
Conclusion
All data combined we recommend RPL13A, B2M and RPII as the best choice for qRT-PCR analyses when comparing normoxic and hypoxic cultured human chondrocytes although other genes might also be suitable. However, the matching of HKG to target genes by means of a thorough investigation of the stability in each study would always be preferable.
doi:10.1186/1471-2199-10-94
PMCID: PMC2764705  PMID: 19818117
13.  The Scandinavian ACL registries 2004–2007: baseline epidemiology 
Acta Orthopaedica  2009;80(5):563-567.
Background and purpose No prospective surveillance systems have been available for monitoring the outcome of cruciate ligament surgery in Scandinavia (Denmark, Norway, and Sweden). In the present paper we describe the Scandinavian ACL registries including their main function, similarities, and preliminary baseline results.
Methods The Scandinavian registries were established in 2004 (Norway) and 2005 (Denmark and Sweden). The Danish and Swedish registries were originally based on the Norwegian registry, and there is no overriding difference between the three. In Denmark, all hospitals and clinics are legally bound to report to an approved national database. In Norway and Sweden, the registries are based on voluntarily reporting by surgeons.
Results The annual incidence of primary ACL reconstructions is higher in Denmark than in Norway, except in females younger than 20 years. Among Scandinavian surgeons, there is a similar approach to the patients. Differences do, however, exist regarding choice of grafts, choice of implants, and choice of treatment of simultaneous meniscal and cartilage injuries; the proportion of ACL reconstructions performed as outpatient surgery; and the use of prophylactic anticoagulation. Clinically, the preoperative KOOS scores are not significantly different between the Scandinavian registries, except that Denmark reports more symptoms both pre- and postoperatively.
Interpretation The Scandinavian national ACL registries will generate new data about ACL reconstructions. They will contribute important knowledge regarding ACL epidemiology. They will be the only source of data on the performance of a wide range of different implants and techniques. In addition, they will hopefully have an impact on the selection of methods for ACL reconstructions in Scandinavia and elsewhere.
doi:10.3109/17453670903350107
PMCID: PMC2823321  PMID: 19916690
14.  Pool desiccation and developmental thresholds in the common frog, Rana temporaria 
The developmental threshold is the minimum size or condition that a developing organism must have reached in order for a life-history transition to occur. Although developmental thresholds have been observed for many organisms, inter-population variation among natural populations has not been examined. Since isolated populations can be subjected to strong divergent selection, population divergence in developmental thresholds can be predicted if environmental conditions favour fast or slow developmental time in different populations. Amphibian metamorphosis is a well-studied life-history transition, and using a common garden approach we compared the development time and the developmental threshold of metamorphosis in four island populations of the common frog Rana temporaria: two populations originating from islands with only temporary breeding pools and two from islands with permanent pools. As predicted, tadpoles from time-constrained temporary pools had a genetically shorter development time than those from permanent pools. Furthermore, the variation in development time among females from temporary pools was low, consistent with the action of selection on rapid development in this environment. However, there were no clear differences in the developmental thresholds between the populations, indicating that the main response to life in a temporary pool is to shorten the development time.
doi:10.1098/rspb.2007.1737
PMCID: PMC2600912  PMID: 18252666
development time; developmental threshold; local adaptation; pool permanence; Rana temporaria; reaction norm
15.  Comment to Pecina et al. 
International Orthopaedics  2006;30(3):217.
doi:10.1007/s00264-005-0040-4
PMCID: PMC2532095
16.  Orthopaedic applications of gene therapy 
International Orthopaedics  2005;29(4):205-209.
Gene therapy presents a novel approach to biological treatment. Several orthopaedic diseases can cause changes in biological signalling at the tissue level that potentially can be repaired or modified by inserting genes into the cells or tissues to modulate gene expression. Impaired bone healing, need for extensive bone formation, cartilage repair and metabolic bone diseases are all conditions where alterations of the signalling peptides involved may provide cure or improvement. In orthopaedic oncology, gene therapy may achieve induction of tumour necrosis and increased tumour sensitivity to chemotherapy. In the last decade, extensive improvements have been made to optimise gene therapy and have been tested on several orthopaedic conditions. How far this development has come in orthopaedics is highlighted in this paper.
doi:10.1007/s00264-005-0650-x
PMCID: PMC3474530  PMID: 15900437
17.  Healing properties of allograft from alendronate-treated animal in lumbar spine interbody cage fusion 
European Spine Journal  2004;14(3):222-226.
This study investigated the healing potential of allograft from bisphosphonate-treated animals in anterior lumbar spine interbody fusion. Three levels of anterior lumbar interbody fusion with Brantigan cages were performed in two groups of five landrace pigs. Empty Brantigan cages or cages filled with either autograft or allograft were located randomly at different levels. The allograft materials for the treatment group were taken from the pigs that had been fed with alendronate, 10 mg daily for 3 months. The histological fusion rate was 2/5 in alendronate-treated allograft and 3/5 in non-treated allograft. The mean bone volume was 39% and 37.2% in alendronate-treated or non-treated allograft (NS), respectively. No statistical difference was found between the same grafted cage comparing two groups. The histological fusion rate was 7/10 in all autograft cage levels and 5/10 in combined allograft cage levels. No fusion was found at all in empty cage levels. With the numbers available, no statistically significant difference was found in histological fusion between autograft and allograft applications. There was a significant difference of mean bone volume between autograft (49.2%) and empty cage (27.5%) (P<0.01). In conclusion, this study did not demonstrate different healing properties of alendronate-treated and non-treated allograft for anterior lumbar interbody fusion in pigs.
doi:10.1007/s00586-004-0771-8
PMCID: PMC3476744  PMID: 15248057
Anterior lumbar interbody fusion (ALIF); Bisphosphonate; Bone graft; Cage; CT
18.  Anterior lumbar interbody fusion with carbon fiber cage loaded with bioceramics and platelet-rich plasma. An experimental study on pigs 
European Spine Journal  2004;13(4):354-358.
Platelet-rich plasma (PRP) is an autogenous source of growth factor and has been shown to enhance bone healing both in clinical and experimental studies. PRP in combination with porous hydroxyapatite has been shown to increase the bone ingrowth in a bone chamber rat model. The present study investigated whether the combination of beta tricalcium phosphate (β-TCP) and PRP may enhance spinal fusion in a controlled animal study. Ten Danish Landrace pigs were used as a spinal fusion model. Immediately prior to the surgery, 55 ml blood was collected from each pig for processing PRP. Three-level anterior lumbar interbody fusion was performed with carbon fiber cages and staples on each pig. Autogenous bone graft, β-TCP, and β-TCP loaded with PRP were randomly assigned to each level. Pigs were killed at the end of the third month. Fusion was evaluated by radiographs, CT scanning, and histomorphometric analysis. All ten pigs survived the surgery. Platelet concentration increased 4.4-fold after processing. Radiograph examination showed 70% (7/10) fusion rate in the autograft level. All the levels with β-TCP+PRP showed partial fusion, while β-TCP alone levels had six partial fusions and four non-fusions (P=0.08). CT evaluation of fusion rate demonstrated fusion in 50% (5/10) of the autograft levels. Only partial fusion was seen at β-TCP levels and β-TCP+PRP levels. Histomorphometric evaluation found no difference between β-TCP and β-TCP+PRP levels on new bone volume, remaining β-TCP particles, and bone marrow and fibrous tissue volume, while the same parameters differ significantly when compared with autogenous bone graft levels. We concluded from our results in pigs that the PRP of the concentration we used did not improve the bone-forming capacity of β-TCP biomaterial in anterior spine fusion. Both β-TCP and β-TCP+PRP had poorer radiological and histological outcomes than that of autograft after 3 months.
doi:10.1007/s00586-003-0647-3
PMCID: PMC3468048  PMID: 14730438
Spinal fusion; Bone substitute; Platelet-rich plasma; Tricalcium phosphate; Pig
19.  Inhibition of spinal fusion by use of a tissue ingrowth inhibitor 
European Spine Journal  2003;13(2):157-163.
“Spinal instrumentation without fusion” techniques, which do not interfere with spinal growth, have been used extensively in the treatment of progressive spinal scoliosis in very young children. Due to subperiosteal exposure, the process of spinal instrumentation may induce spontaneous bony fusion. Instrumentation and surgical techniques have been modified in order to prevent spontaneous posterior fusion from occurring in children. An absorbable ADCON-L gel has been shown to inhibit scar and epidural adhesions following spinal surgeries. However, little is known about its influence on spinal fusion. In the present study, a single-level intertransverse arthrodesis at L4-5 on both sides was performed on each of nine pigs. Each side was randomly designed to receive autogenous bone graft with or without ADCON-L gel. The animals were followed for 10 weeks postoperatively. A fusion rate of 78% (7/9) was obtained in the autograft treatment by plain X-ray and CT evaluation, while the autograft/ADCON-L treatment yielded a 0% (0/9) fusion rate (p=0.001). Histomorphometric evaluation revealed that the addition of ADCON-L gel to bone graft decreased bone and bone marrow formation and significantly increased fibrous tissue formation. No statistical difference between the two treatments was found in cartilage, bone surface density, osteoid surfaces or osteoclast-covered surfaces in any zone. We conclude that ADCON-L gel mixed into autogenous bone graft can delay or decrease bone formation at spinal arthrodesis sites, thus influencing the extent of spinal fusion. This accords with our hypothesis that the use of ADCON-L gel can prevent not only the occurrence of spontaneous fusion in very young scoliosis patients after instrumentation without fusion, but also re-ossification of a decompressed spinal canal.
doi:10.1007/s00586-003-0645-5
PMCID: PMC3476572  PMID: 14618383
Spinal fusion; ADCON-L; Bone regeneration; Pig
20.  The influence of intervertebral disc tissue on anterior spinal interbody fusion: an experimental study on pigs 
European Spine Journal  2002;11(5):476-481.
Abstract.
Intervertebral disc has been shown to be related to low back pain and nerve root injury in pathologic conditions. However, little is known about its influence on spinal fusion. With the development of minimal invasive operations, such as laparoscopic anterior spinal fusion with cages, insufficient discectomy may occur. With its inflammatory properties, the residue nucleus pulposus may have an effect on spinal fusion. In this study, a two-level lumbar spine interbody fusion (L3/4, L5/6) with a Brantigan cage was performed on ten Danish Landrace pigs. Each level was randomly assigned to one of the following methods: (1) implantation of Brantigan cage filled with autogenous iliac crest bone graft, or (2) implantation of Brantigan cage filled with a mixture of autograft and the nucleus pulposus tissue harvested from the disc level in which it was to be inserted. Each level was stabilized with two staples. The pigs were followed for 12 weeks in the same standardized condition. After sacrifice, the lumbar spines were taken out, and plain X-ray, computed tomographic (CT) scanning and histomorphometry were performed to study the fusion mass inside the cages. From plain radiographs, new bone formation could be seen inside and around the cage. CT evaluation showed that the nucleus pulposus level had a 20% (2/10) fusion rate, while the pure autograft level had a 70% (7/10) fusion rate (P=0.07). The histological fusion rate was even lower in the nucleus pulposus level (10%), and was significantly different from the autograft level (70%, P=0.02). Histomorphometric parameters of new bone formation, bone marrow space and fibrous tissue differed significantly between the two levels (P=0.04; P=0.02; P=0.04 respectively). We conclude that when nucleus pulposus is mixed with the autogenous bone graft, it can delay or decrease the bone formation inside the cage, thus influencing the final fusion.
doi:10.1007/s00586-002-0455-1
PMCID: PMC3611310  PMID: 12384757
Spine fusion Interbody fusion Nucleus pulposus Pig
21.  Factors stimulating bone formation 
European Spine Journal  2001;10(Suppl 2):S102-S109.
Abstract.
The aim of this review is to describe major approaches for stimulating bone healing and to review other factors affecting bone healing. Spinal bone fusion after surgery is a demanding process requiring optimal conditions for clinical success. Bone formation and healing can be enhanced through various methods. Experimental studies have revealed an array of stimulative measures. These include biochemical stimulation by use of hormones and growth factors, physical stimulation through mechanical and electromagnetic measures, and bone grafting by use of bone tissue or bone substitutes. Newer biological techniques such as stem cell transplantation and gene therapy can also be used to stimulate bone healing. Apart from bone transplantation, clinical experience with the many stimulation modalities is limited. Possible areas for clinical use of these novel methods are discussed.
doi:10.1007/s005860100269
PMCID: PMC3611553  PMID: 11716006
Bone healing Bone graft Growth factors Stimulation Stem cells Gene therapy

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