Stein Erik Utvåg

Influence of extensive muscle injury on fracture healing in rat tibia.

Objectives The treatment of tibial fractures associated with severe soft tissue injury remains a challenge. The objective of our experiment was to ascertain the influence of standardized muscle injuries on fracture healing in a nailed rat tibial fracture model. We hypothesized that a severe crush injury of leg muscles might not be as deleterious to fracture healing as total loss of a large muscle segment. Study Design A randomized study in male Wistar rats with a diaphyseal osteotomy. Methods Three separate, but complementary experiments were done in 51 rats. The first experiment involved 30 rats randomly assigned to three increasingly severe soft tissue interventions in a nailed tibial osteotomy model. The second experiment involved 14 rats divided into two groups to study blood flow measurements of the muscle envelope after soft tissue injury. Seven rats were used in the third experiment to provide biomechanical data and dimensions of the rat tibia. The protocol for the first experiment was intramedullary nailing after a middiaphyseal osteotomy of the left tibia. In group A, the soft tissue injury was minimal, while the muscles in the anterolateral compartment were crushed in group B. Resection of the anterolateral compartment muscles, resulting in only skin coverage at the fracture site, was performed in group C. The fibular nerve was resected in all three groups so that the animals were non–weight bearing on the operated extremity. At 4 weeks, the healing bones in each group were studied clinically, radiographically, and biomechanically. Results Radiographs in two planes revealed a clearly visible fracture line in the three intervention groups at 4 weeks. The callus area following muscle resection in group C was significantly reduced compared with the minimal soft tissue injury in group A. Biomechanically, resection of the anterolateral compartment muscles in group C reduced maximum bending load and fracture energy compared with fractures with minimal soft tissue injury in group A, while bending rigidity and fracture energy was reduced compared with muscle crush in group B. No difference in mechanical characteristics was detected between the healing bones in groups A and B. Conclusion This animal study indicates that crushing of the leg muscle envelope with reduced blood flow does not influence the quality of bone healing at 4 weeks to a significant degree. Resection of a large muscle segment impairs tibial fracture healing significantly.

Effects of periosteal stripping on healing of segmental fractures in rats

The present study was undertaken to assess the effect of periosteal detachment upon the healing of segmental diaphyseal fractures. In rats we produced two standardized partial osteotomies with an 8-mm intermediary fragment in the femoral diaphysis. The osteotomies were then manually broken, retaining the periosteal and muscular attachment on the medial side in one group. In the other group, the segment was stripped of periosteum circumferentially. The fractures were stabilized with 1.6-mm steel pins, and the rats were allowed free movement. After 4, 8, and 12 weeks eight rats in each group were sacrificed, and callus formation, mechanical parameters, and bone blood flows were evaluated. The area of callus in the fractures with periosteal attachment was significantly less after 12 weeks, but not different from the fractures stripped of periosteum after 4 and 8 weeks. Bending moment increased throughout the experimental period in both groups. In the fractures with attached periosteum, bending moment was significantly larger at 12 weeks and bending rigidity after 4 weeks. No differences were found in total bone blood flow. Blood flow in the segmental fractured area was substantially increased in both groups after 4 weeks. At 8 weeks the segmental flow was significantly larger in the fractures with stripped periosteum, while a normalization was observed in those with attached periosteum. This study indicates that segmental fractures initiate a substantial increase in blood flow, and that additional stripping of the periosteum delays normalization of the flow. Periosteal stripping of the segment impairs fracture healing, measured as gain of bending moment.

Documentation of hip prostheses used in Norway: a critical review of the literature from 1996--2000.

We have conducted a systematic review of the scientific literature concerning outcome and clinical effectiveness of prostheses used for primary total hip replacement (THR) in Norway. The study is based on two Health Technology Assessment reports from the UK (Faulkner et al. 1998, Fitzpatrick et al. 1998), reviewing the literature from 1980 to 1995. Using a similar search strategy, we have evaluated the literature from 1996 through 2000. We included 129 scientific and medical publications which were assessed according to a specific appraisal protocol. The majority (72%) were observational studies, whereas only 9% were randomized studies. We could not retrieve any peer-reviewed documentation for one third of the implants. The Charnley prosthesis had by far the best and most comprehensive evidence base with better than 90% implant survival after about 10 years. Survival of the Charnley prosthesis declines by about 10% during each of the two following decades. Except for the Charnley and Lubinus IP, no other prosthesis on the market in Norway has given long-term results (> 15 years). 5 other cemented implants have given comparable results at about 10 years of follow-up. Some uncemented stems have shown promising medium-term outcome, but no combination of uncemented cup and stem fulfilled the benchmark criterion of ≥ 90% implant survival at 10 years, which we propose as a minimum requirement for unrestricted clinical use for prostheses used in primary THR. New or undocumented implants should be introduced through a four-step model including preclinical testing, small series evaluated by radiosterometry, randomized clinical trial involving comparison with a well-documented prosthesis, and finally, surveillance of clinical use through registers.

Restoration of bone flow following fracture and reaming in rat femora

In rats, bilateral closed femoral fracture was produced after intramedullary reaming to 1.6 mm on the left side and 2.0 mm on the right side. The fractures were fixed with 1.6 and 2.0 mm steel pins. Radioactive microspheres were used to determine bone blood flow at 30 min, 1 day, 3 days and 9 days after fracture. 8 rats were used to estimate normal bone blood flow, and an additional 8 rats to examine the vascular effects of fracture only. Following fracture, total bone blood flow was reduced to about 50 percent and cortical flow to about 40 percent of that in intact bones. Fracture and reaming to 1.6 mm reduced total bone flow to 40 percent and reaming to 2.0 mm reduced the total bone flow to approximately one third of normal flow. Cortical flow decreased to about one third and one quarter in the 2 groups. On Day 1, total flow was practically normalized in both groups. Cortical flow in the 1.6 mm group was about equal to that of intact bones, while it was about one third of normal flow in the 2.0-mm group, and significantly less than the 1.6-mm group. On Day 3, total bone flow was more than double that of intact bones and cortical flow 3 times greater in both groups. Flow continued to increase to Day 9 when a threefold increase in total bone blood flow and approximately a fivefold increase in cortical flow were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Poor muscle coverage delays fracture healing in rats

We undertook this study in rats to ascertain the influence of muscle coverage on tibial fracture healing. 30 rats were randomly assigned to three intervention groups. Following a mid-diaphyseal osteotomy in the left tibia, reamed nailing was performed in all animals. In one group (A), the antero-lateral muscles were detached from the fractured bone, while the anterolateral compartment was excised in another group (B). In the third group (C), the muscle compartment was resected, and the superficial gluteal muscle was mobilized and transposed over the fractured area. Muscle intervention, like that in group A and C, had no effect on the blood flow. The fibular nerve was resected in all the rats. At 4 weeks, we studied the healing bones in each group clinically, radiologically and mechanically. At 4 weeks, radiographs in two planes revealed a clearly visible fracture line in the three experimental groups. Mechanical testing of the healing fractures showed significantly lower bending moment and bending rigidity in group B than in groups A and C. No difference in mechanical characteristics was detected between the healing bones in groups A and C. This animal study indicates that in tibial fractures, an extensive muscle tissue defect may have negative effects on early bone healing.

Effects of graded reaming on fracture healing: Blood flow and healing studied in rat femurs

In 30 rats, closed bilateral fractures of the femur were produced. On the left side intramedullary reaming was performed to 1.6 mm, and the fracture fixed-with a steel pin with a diameter of 1.6 mm. On the right side the femoral canal was reamed to 2.0 mm and a hollow steel tube with a diameter of 2.0 mm was used for fixation. An additional 8 rats were used to obtain mechanical, dimensional and flow data on intact femurs, and another 10 rats were used to study the acute flow changes caused by fracture and different degrees of reaming and fracture. Fracture and reaming reduced total bone and cortical bone blood flows to about one third of normal flow, with no differences between the 1.6-mm and the 2.0-mm reamed bones. At 4 weeks, total bone flow was about double and cortical bone flow about 4 times increased in the 1.6-mm group. In the 2.0-mm reamed bones increases of approximately 5 times in total bone flow and of about 7 times in cortical flow were found. Callus flow was about twice the size of the respective cortical flow in both groups. Both total and cortical flows gradually subsided, without differences between the 2 groups. At 12 weeks, the callus area in the 2.0-mm group was greater than in the 1.6-mm group, while bone dimensions were greater in the 2.0-mm group at 4 and 12 weeks. Bending moment and rigidity were greater in the 1.6-mm group than in the 2.0-mm one at every time interval; no differences were found in fracture energy.(ABSTRACT TRUNCATED AT 250 WORDS)

Graded exchange reaming and nailing of non-unions

Abstract The effect of graded exchange reaming and intramedullary nailing on a non-union model in the rat femur was studied by clinical, radiological, bone mineralisation and biomechanical methods. A standardised procedure was first developed to create a non-union that did not heal and in which non-union developed consistently. In 30 male Wistar rats a standardised osteotomy was produced in the left femur diaphysis. The fractures were reamed to 1.5 mm and nailed with a soft polyethylene nail for 12 weeks. After 1 week the fractures were manipulated in bending and rotation every 2nd day for 5 weeks. At 12 weeks radiographs demonstrated a hypertrophic non-union in all fractures, and the rats were randomly divided into three groups. In the control group no reoperation was performed (group C). In group 1.6 exchange reaming to 1.6 mm and medullary nailing were performed, and reaming and nailing to 2.0 mm in group 2.0. The effect of extensive versus modest reaming and nailing on bone repair was then assessed 12 weeks later. Physical examination, radiographs, bone mineralisation measurements by dual energy X-ray absorptiometry (DEXA) and biomechanical femures evaluated by a three-point bending test in a Mini Bionix (MTS) testing system were employed. In the control group radiographs revealed a state of non-union in all fractures, and the mechanical strength was significantly reduced compared with both intervention groups. Bone mineral content (BMC) and bone mineral density (BMD) were reduced in the callus region compared with group 2.0. In the intervention groups radiographs showed various degrees of union. Mechanical testing showed that the fracture energy was significantly higher in group 2.0 than in group 1.6. The finding that extensive exchange reaming and nailing seems favourable in non-unions of diaphyseal fractures compared with modest reaming may have clinical implications.

Effects of lesion between bone, periosteum and muscle on fracture healing in rats

We assessed the effects of periosteal detachment from bone and musculature on the healing of diaphyseal fracture. In 30 male Wistar rats we produced a partial osteotomy, which was manually broken in the middiaphysis of the left femur. All fractures were reamed and stabilized with an 1.6 mm steel pin. The animals were randomly assigned to 3 groups. In group 1, a subperiosteal detachment between cortex and periost was created in the middle third of the diaphysis. An extraperiosteal detachment between periost and the surrounding musculature was performed in group 2. In group 3, the periosteum was isolated from the musculature by an extraperiosteal detachment and application of an e-PTFE sheath (Gore-Tex expanded polytetrafluoroethylene) around the shaft between the periost and the surrounding muscles. The rats were killed after 4 weeks and callus formation and mechanical characteristics were measured. All fractures healed by production of external callus. The callus area was significantly less in the group where periost was mechanically isolated from the surrounding muscles compared to the other groups. Bending moment, bending rigidity and fracture energy were less in this group than in groups 1 and 2. No differences were detected between the sub- and extraperiosteal groups, either in callus formation or in mechanical measurements. Our findings underline the importance of the muscle-periosteal connection for periosteal healing of diaphyseal fractures.

Early muscle-periosteal lesion inhibits fracture healing in rats.

We assessed the effects of muscular detachment from the periosteum on fracture healing, focusing on a muscle-periosteal lesion in the initial healing process. In 30 male Wistar rats we produced a partial osteotomy in the mid-diaphysis of the left femur which was then manually broken. All fractures were reamed and stabilized with a 1.6 mm steel pin. The animals were randomly assigned to 3 groups. In group 1, an extraperiosteal detachment between muscle and periosteum was created in the middle third of the diaphysis. In group 2, an extraperiosteal detachment was created with application of an e-PTFE sheath (Gore-Tex® expanded polytetrafluoro-ethylene) around the shaft between muscle and periosteum during the first 2 weeks following fracture. In group 3, the dissection was identical, while the e-PTFE sheath was installed after 2 weeks. The rats were killed after 4 weeks, and their bones were evaluated radiographically and mechanically by the three-point bending test. The fractures healed by production of ext...

Effects of torsional rigidity on fracture healing: strength and mineralization in rat femora.

Objective: To assess the effects of torsional rigidity and dynamization on fracture healing in a medullary nailed rat femoral model. Study Design: Randomized study in male Wistar rats with a diaphyseal osteotomy/fracture. Methods: Reamed cannulated nailing was performed in sixty rats. One group (twenty rats) received unlocked nails (UL group) and another group received nails with proximal and distal locking that was dynamized after twenty days (DL group). The third group was statically locked (SL group). A fourth group of twenty rats served as the control group. After randomization, the femurs of ten rats in each group at six and twelve weeks were studied clinically, radiologically, and biomechanically, and bone mineralization was measured by dual-energy x-ray absorptiometry (DEXA). Results: Radiographs in two planes revealed clearly visible fractures at six weeks, and at twelve weeks bridging callus was apparent in all three treatment groups. The callus area in the UL group was significantly larger at six weeks than in the other groups, and at twelve weeks the UL and DL groups had larger callus areas than the SL group. Biomechanically, UL nails had reduced maximum bending load at six and twelve weeks, while DL nails had increased fracture energy at six weeks compared with SL nails. Bone mineral content and bone mineral density in the callus segment and diaphysis were increased with DL nails at six weeks. Conclusion: This animal study indicates that (a) interlocked nailing has a beneficial effect on bone healing and (b) although dynamization may have a beneficial effect on the quality of early bone healing. (c) dynamization does not increase the rate of bony union. The clinical implication is that routine early dynamization of locked femoral fractures may not be indicated, reserving dynamization to cases of delayed union.