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Biomedical subjects

M P Arnold

Publications and source records attributed to M P Arnold.

10 recordsLinked to original sources
PubMed2005

[Mountain biking. Cool way to enjoy nature with side effects].

Mountain biking grew from a trend to a serious branch of sport. This article presents the different subspecialties within the sport, the injury rates and the types of injuries among high-class and recreational bikers. The experiences made during several years as a team physician of top athletes as well as the statistics from the Swiss accident insurance company SUVA are the basis for the data presented. The issue of mountain bike-related concussions is particularly discussed since this type of injury is a point of increasing concern in the recent sports traumatology literature.

Bicycling↗
PubMed2004

Twist and its effect on ACL graft forces.

Graft tension is a controversial topic in anterior cruciate ligament (ACL) surgery. Evidence suggests a narrow range of graft tensions, which allow the graft to remodel to a stable and mature neoligament. In previous cadaver experiments, we showed that twisting the graft could modulate the graft forces. In this study we hypothesized that the same phenomena would be found in patients, and that twisting the graft intraoperatively can reduce peak forces in the graft. The effects of twist on graft forces in bone-patellar tendon-bone grafts were measured during anterior cruciate ligament surgery on 15 consecutive patients using a custom-made tension-measurement device. Variations in surgical procedure that could potentially affect the graft force patterns were quantified. Graft force as a function of knee-flexion angle was measured with the graft in the neutral, untwisted position and repeated with the tibial bone block rotated externally or internally by 180 degrees. In eight of the 15 knees, external twisting of the graft reduced the maximal graft force to 50%. However, in five knees the forces in extension increased by twisting to a maximum of 300%. Of the surgical variables, only the femoral tunnel position appeared to have a consistent effect on the graft force pattern. Due to the unpredictable effect of graft twisting, a general recommendation on whether the graft should be twisted, and if so, in which direction, cannot be given. Intraoperatively, graft twisting may however be considered in every individual knee to modulate the graft force as a function of flexion angle.

Adolescent↗
PubMed2001

Single-incision technique misses the anatomical femoral anterior cruciate ligament insertion: a cadaver study.

We examined the arthroscopic appearance of the anterior cruciate ligament (ACL) attachment site on the femur in five fresh-frozen cadaver knees. First, the ACL was cut out, leaving a footprint of ligament-fibers with a length of 2 mm intact. The ACL was consistently found to insert on the lateral wall of the notch. No fibers were found to attach high in the roof of the notch at the 12 o'clock position. Secondly, we tried to reach the anatomical attachment site with a femoral aiming guide through a correctly placed tibial tunnel. This proved to be impossible. The closest position that could be reached was at the margin of the anatomical attachment site. Investigation of the distal femur after complete dissection confirmed these arthroscopic findings. Femoral aiming devices for use through the tibial tunnel aim for an isometric placement of the femoral tunnel, they do not aim for an anatomical position of the graft.

Anterior Cruciate Ligament Injuries↗
PubMed2000

Symptomatic ring-shaped lateral meniscus.

Abnormalities of the lateral meniscus in humans are a long-known fact. Three different types of discoid menisci are described in Watanabe's atlas, being considered as congenital malformations. For the second time in the literature, a fourth ring-shaped type of discoid lateral meniscus was described as an incidental finding in this Journal by Monllau et al. in 1998. The present case is the first description of a symptomatic, ring-shaped lateral meniscus with a concomitant, recurrent cyst at the lateral aspect of a child's knee.

Arthroscopy↗
PubMed1998

[Patellar substitution in total knee prosthesis--is it important?].

As shown in long term follow-up studies of Total Knee Arthroplasty (TKA), the femoropatellar joint is an important problem. We report our experience over the past seven years not having resurfaced the patella at the primary TKA at all. Between 1990 and 1997 more than 700 consecutive TKA with the De Puy New Jersey LCS prosthesis were performed. A standardised lateral approach with osteotomy of the tibial tuberosity was used. The patella was redressed, either denervated or left untouched. In no case a primary patellar resurfacing was performed. X-rays of the patello-femoral joint showed a remodelling of the patella over the years, nicely matching the condylar design of the femoral prosthesis. Using a blood-supply-preserving approach and a biomechanically adequate implant, TKA without patellar replacement gives excellent long-term results.

Arthroplasty, Replacement, Knee↗
PubMed1986

Short-term in vivo stability of endothelial-lined polyester elastomer and polytetrafluoroethylene grafts.

A fibronectin substrate will significantly enhance the strength of endothelial cell attachment on grafts constructed of polyester elastomer (PE) and polytetrafluoroethylene (e-PTFE). This experiment was undertaken to determine the short-term in vivo stability of endothelium on these fibronectin coated surfaces. Eight mongrel dogs underwent bilateral carotid artery replacement with both graft materials. All grafts were inoculated with 2,000 cells/mm2 using cultured autogenous venous endothelium labelled with Indium-111-oxine. The Indium-111 label in the grafts was measured immediately prior to implantation, after 1 hour of in vivo perfusion, and at explantation after 24 hours. The percentage of inoculated cells attached to the grafts before perfusion was similar for both materials, 93.3 +/- 3.0% versus 92.2 +/- 7.2%, for PE and e-PTFE respectively. All grafts were patent at one hour after implantation. PE grafts were found to have 93.8 +/- 3.9% of the attached cells present at one hour while e-PTFE grafts had only 54.5 +/- 10.8% remaining, p less than .001. After 24 hours, 5/8 (62.5%) e-PTFE grafts and 2/8 (25.0%) PE grafts remained patent, p = .13. Of the patent grafts however, endothelial cell retention was still superior on the PE grafts with 78.0 +/- 0.6% of the attached cells remaining compared to only 24.5 +/- 6.1% on e-PTFE, p less than .001. Occluded PE grafts had fewer cells remaining at 24 hours than patent ones, 78.0 +/- 0.6% versus 31.1 +/- 32.8%, respectively, p = .13. Histologically, patent PE grafts demonstrated nearly confluent endothelial monolayers while e-PTFE had patches of endothelial cells surrounded by a platelet-fibrin carpet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Enhanced strength of endothelial attachment on polyester elastomer and polytetrafluoroethylene graft surfaces with fibronectin substrate.

Successful development of a vascular prosthesis lined with endothelium may depend on the ability of the attached cells to resist shear forces after implantation. The purpose of this article is to describe a model for measurement of endothelial detachment caused by shear stress and to identify biomaterials that resist loss of attached cells as a result of shear stress. With human umbilical venous endothelium labeled with indium 111-oxine, cellular attachment to uncoated and fibronectin-coated polyester elastomer and expanded polytetrafluoroethylene (e-PTFE) graft surfaces was quantified after an 18-hour incubation. PTFE grafts prepared by immediate seeding were also studied. The relative strength of endothelial attachment was determined by the percentage of the original inoculum remaining after the seeded graft surfaces were subjected to a physiologic shear stress of 15 dynes/cm2 during in vitro perfusion. In polyester elastomer grafts, fibronectin did not significantly increase initial attachment but did increase the percentage of inoculum remaining after perfusion (92.1% vs. 39.74%, p = 0.001). A similar relationship existed between fibronectin-coated e-PTFE and immediately seeded e-PTFE preparations with 61.6% and 25.8%, respectively, of the inoculum remaining after perfusion (p = 0.001). Furthermore, the percentage of inoculum retained on fibronectin-coated polyester elastomer was significantly greater than on fibronectin-coated e-PTFE (p = 0.001). In comparing uncoated grafts, polyester elastomer had 39.7% of the inoculum retained after perfusion whereas only 1.8% was remaining on the e-PTFE grafts (p = 0.0001). We conclude that polyester elastomer permits better endothelial cell attachment than e-PTFE and that fibronectin coating enhances the strength of attachment to both graft materials.

Biocompatible Materials↗