Bone mineral changes during tibial fracture healing

Smart fracture plate for quantifying fracture healing: Preliminary efficacy in a biomechanical model

The diagnosis of fracture nonunion following plate osteosynthesis is subjective and frequently ambiguous. Initially following osteosynthesis, loads applied to the bone are primarily transmitted through the plate. However, as callus stiffness increases, the callus is able to bear load proportional to its stiffness while forces through the plate decrease. The purpose of this study was to use a "smart" fracture plate to distinguish between phases of fracture healing by measuring forces transmitted through the plate. A wireless force sensor and small adapter were placed on the outside of a distal femoral locking plate. The adapter converts the slight bending of the plate under axial load into a transverse force which is measurable by the sensor. An osteotomy was created and then plated in the distal femur of biomechanical Sawbones. Specimens were loaded to simulate single-leg stance first with the osteotomy defect empty (acute healing), then sequentially filled with silicone (early callus) and then polymethyl methacrylate (hard callus). There was a strong correlation between applied axial load and force measured by the "smart" plate. Data demonstrate statistically significant differences between each phase of healing with as little as 150 N of axial load applied to the femur. Forces measured in the plate were significantly different between acute (100%), early callus (66.4%), and hard callus (29.5%). This study demonstrates the potential of a "smart" fracture plate to distinguish between phases of healing. These objective data may enable early diagnosis of nonunion and enhance outcomes for patients.

Osteoporotic Changes in the Periodontium Impair Alveolar Bone Healing

Osteoporosis is associated with decreased bone density and increased bone fragility, but how this disease affects alveolar bone healing is not clear. The objective of this study was to determine the extent to which osteoporosis affects the jaw skeleton and then to evaluate possible mechanisms whereby an osteoporotic phenotype might affect the rate of alveolar bone healing following tooth extraction. Using an ovariectomized mouse model coupled with micro-computed tomographic imaging, histologic, molecular, and cellular assays, we first demonstrated that the appendicular and jaw skeletons both develop osteoporotic phenotypes. Next, we demonstrated that osteoporotic mice exhibit atrophy of the periodontal ligament (PDL) and that this atrophy was accompanied by a reduction in the pool of osteoprogenitor cells in the PDL. The paucity of PDL-derived osteoprogenitor cells in osteoporotic mice was associated with significantly slower extraction socket healing. Collectively, these analyses demonstrate that the jaw skeleton is susceptible to the untoward effects of osteoporosis that manifest as thinner, more porous alveolar bone, PDL thinning, and slower bone repair. These findings have potential clinical significance for older osteopenic patients undergoing reconstructive procedures.

Factors affecting bone mineral mass loss after lower-limb fractures in a pediatric population

BACKGROUND

The purpose of this study was to assess the effects of the durations of cast immobilization and non-weight-bearing periods, and decreases in vigorous physical activity (VPA) on bone mineral parameters in a pediatric population treated for a lower-limb fracture.

METHODS

Fifty children and teenagers who had undergone a cast-mediated immobilization for a leg or ankle fracture were prospectively recruited. The durations of cast immobilization and non-weight-bearing periods were recorded for each participant. Dual-energy x-ray absorptiometry scans were performed at the time of fracture treatment (baseline) and at cast removal. Physical activity during cast immobilization was assessed using accelerometers.

RESULTS

A strong negative correlation was found between the total duration of cast immobilization and decreases in both calcaneal bone mineral density (BMD) (r=-0.497) and total lower-limb bone mineral content (BMC) (r=-0.405). A strong negative correlation was also noted between the durations of the non-weight-bearing periods and alterations in calcaneal BMD (r=-0.420). No apparent correlations were found between lower BMD and BMC and decreased VPA.

CONCLUSIONS

Bone mineral loss was correlated to the total duration of cast immobilization for all measurement sites on the affected leg, whereas it was only correlated to the durations of non-weight-bearing periods for calcaneal BMD and total lower-limb BMC. However, no correlations were noted between bone mineral loss and decreased VPA.

Influence of the osteosynthesis plate on ultrasound propagation in the bone

Objective:

To analyze the influence of steel plates for osteosynthesis on the velocity of ultrasound propagation (VU) through the bone.

Methods:

The transverse coronal and sagittal velocity of ultrasound propagation underwater were measured on the intact bone and then on assemblies of the same bone with two types of osteosynthesis plates (DCP and semi tubular), fixed onto the dorsal side of the bones. The first arriving signal (FAS) was the ultrasound parameter used, taking the coronal and sagittal diameters as the distances to calculate velocity. Intergroup statistical comparisons were made at significance level of 1% (p<0.01).

Results:

Velocity was higher on the intact bones than on the bone-plate assemblies and higher for the semitubular than for the compression plates, although differences were not statistically significant for most comparisons (p=0.0132 to 0.9884), indicating that the steel plates do not interfere significantly with ultrasound wave propagation through the bone-plate assemblies.

Conclusion:

The velocity reduction effect was attributed to the greater reflection coefficient of the steel as compared to that of bone and water. Ultrasonometry can, thus, be used in the evaluation of healing of fractures fixed with steel plates. Experimental Study.

A comparative in vivo ultrasonometric evaluation of normal and delayed fracture healing in sheep tibiae

OBJECTIVE

To compare normal and delayed bone healing by measuring ultrasound conduction velocity across the bone callus.

METHODS

A model of transverse linear and 5 mm resection osteotomies of sheep tibiae was used. Fourteen sheep were operated on and were divided into two groups of seven according to osteotomy type. The procedure was performed on the right tibiae and the intact left tibiae were used as controls. The transverse and axial ultrasound velocities were measured at 30-day intervals for 90 days, after which the animals were killed and both the right and left tibiae were resected for in vitro biomechanical analysis.

RESULTS

Both the transverse and axial ultrasound velocities progressively increased, but the increase was smaller for the delayed union that resulted from the resection osteotomy. The mechanical resistance was higher for the normally healed tibiae that resulted from a linear osteotomy; this result closely correlated with the ultrasound velocity results. Significant differences were found for the comparisons between the intact and operated tibiae in both groups and between the groups for both the transverse and axial ultrasound velocities, but the differences were greater for the latter.

CONCLUSION

We conclude that in vivo transverse and axial ultrasound velocities provide highly precise information about the healing state of both linear and resection diaphyseal osteotomies, but the axial ultrasound velocity most likely has greater discriminatory power. This method has the potential for clinical application in humans.

A comparative analysis between ultrasonometry and computer-aided tomography to evaluate bone healing

An ultrasonometric and computed-tomographic study of bone healing was undertaken using a model of a transverse mid-shaft osteotomy of sheep tibiae fixed with a semi-flexible external fixator. Fourteen sheep were operated and divided into two groups of seven according to osteotomy type, either regular or by segmental resection. The animals were killed on the 90th postoperative day and the tibiae resected for the in vitro direct contact transverse and axial measurement of ultrasound propagation velocity (UV) followed by quantitative computer-aided tomography (callus density and volume) through the osteotomy site. The intact left tibiae were used for control, being examined in a symmetrical diaphyseal segment. Regular osteotomies healed with a smaller and more mature callus than resection osteotomies. Axial UV was consistently and significantly higher (p ≤ 0.01) than transverse UV and both transverse and axial UV were significantly higher for the regular than for the segmental resection osteotomy. Transverse UV did not differ significantly between the intact and operated tibiae (p=0.20 for regular osteotomy; p=0.02 for resection osteotomy), but axial UV was significantly higher for the intact tibiae. Tomographic callus density was significantly higher for the regular than for the resection osteotomy and higher than both for the intact tibiae, presenting a strong positive correlation with UV. Callus volume presented an opposite behavior, with a negative correlation with UV. We conclude that UV is at least as precise as quantitative tomography for providing information about the healing state of both regular and resection osteotomy.

Effects of cast-mediated immobilization on bone mineral mass at various sites in adolescents with lower-extremity fracture

BACKGROUND

Leg or ankle fractures occur commonly in the pediatric population and are primarily treated with closed reduction and cast immobilization. The most predictable consequences of immobilization and subsequent weight-bearing restriction are loss of bone mineral mass, substantial muscle atrophy, and functional limitations. The purposes of this study were to determine if lower-limb fractures in adolescents are associated with abnormal bone mineral density or content at the time of fracture, and to quantify bone mineral loss at various sites due to cast-mediated immobilization and limited weight-bearing.

METHODS

We recruited fifty adolescents aged ten to sixteen years who had undergone cast immobilization for a leg or ankle fracture. Dual x-ray absorptiometry scans of the total body, lumbar spine, hip, leg, and calcaneus were performed at the time of fracture and at cast removal. Patients with a fracture were paired with healthy controls according to sex and age. Values at baseline and at cast removal, or at equivalent time intervals in the control group, were compared between groups and between the injured and uninjured legs of the adolescents with the fracture.

RESULTS

At the time of fracture, there were no observed differences in the bone mineral density or bone mineral content Z-scores of the total body or the lumbar spine, or in the bone mineral density Z-scores of the calcaneus, between the injured and healthy subjects. At cast removal, bone mineral parameters on the injured side were significantly lower than those on the uninjured side in the injured group. Differences ranged from -5.8% to -31.7% for bone mineral density and from -5.2% to -19.4% for bone mineral content. During the cast period, the injured adolescents had a significant decrease of bone mineral density at the hip, greater trochanter, calcaneus, and total lower limb as compared with the healthy controls.

CONCLUSIONS

Lower-limb fractures are not related to osteopenia in adolescents at the time of fracture. However, osteopenia does develop in the injured limb during cast immobilization for fracture treatment. Further investigation is required to determine if the bone mineral mass will return to normal or if a permanent decrease is to be expected, which may constitute a hypothetical risk of sustaining a second fracture.

Comparison of bone mineral parameter measurements by dual-energy x-ray absorptiometry with bone stiffness measurements as indicators of the load-bearing capacity of regenerating bone

OBJECTIVES

The objective of this study was to compare bone mineral density and content measurements by dual-energy x-ray absorptiometry with bone stiffness measurements as indicators of the load-bearing capacity of regenerating bone during distraction osteogenesis.

METHODS

The study analyzed ex vivo a set of 26 sheep bone specimens after distraction osteogenesis. Bone mineral density and bone mineral content were measured by dual-energy x-ray absorptiometry. Biomechanical parameters such as torsional, compressive, and bending stiffness were determined using a material testing system. The maximum torsional moment applied at fracture is used to determine the load-bearing capacity of the bone.

RESULTS

The correlation between stiffness measurements and the load-bearing capacity of a bone is significantly greater than the correlation between load-bearing capacity and bone mineral density and content measurements by dual-energy x-ray absorptiometry.

CONCLUSION

The results of this ex vivo study indicate that stiffness measurements are a better quantitative indicator of the load-bearing capacity of a bone and thus of bone healing than bone mineral density and content measurements by dual-energy x-ray absorptiometry. The results of the current study do not confirm previous work that showed that there is a significant correlation between bone material quality obtained by dual-energy x-ray absorptiometry and bone strength.

Noninvasive quantitative assessment of bone healing after distraction osteogenesis

One of the greatest challenges of limb lengthening and deformity correction is deciding when the bone has healed enough to remove the external fixator. Standard radiography is the most common imaging method used to assess bone healing after distraction osteogenesis because it is widely available, cheap, and relatively safe. However, other imaging technologies and methods are being investigated that will help quantify bone healing after distraction osteogenesis, providing an objective method for deciding when it is appropriate to remove an external fixator. This review will examine the latest techniques used to assess bone healing after distraction osteogenesis including dual-energy X-ray absorptiometry scans, ultrasound, quantitative computed tomography, and digital radiography (X-ray). Recommendations for clinical practice will be outlined.

Monitoring the mechanical properties of healing bone

Fracture healing is normally assessed through an interpretation of radiographs, clinical evaluation, including pain on weight bearing, and a manual assessment of the mobility of the fracture. These assessments are subjective and their accuracy in determining when a fracture has healed has been questioned. Viewed in mechanical terms, fracture healing represents a steady increase in strength and stiffness of a broken bone and it is only when these values are sufficiently high to support unrestricted weight bearing that a fracture can be said to be healed. Information on the rate of increase of the mechanical properties of a healing bone is therefore valuable in determining both the rate at which a fracture will heal and in helping to define an objective and measurable endpoint of healing. A number of techniques have been developed to quantify bone healing in mechanical terms and these are described and discussed in detail. Clinical studies, in which measurements of fracture stiffness have been used to identify a quantifiable end point of healing, compare different treatment methods, predictably determine whether a fracture will heal, and identify factors which most influence healing, are reviewed and discussed.

Estudo comparativo da velocidade e atenuação ultra-sônica na avaliação da consolidação óssea

OBJETIVO: O objetivo deste trabalho foi comparar a velocidade e atenuação ultra-sônica, na avaliação in vitro da consolidação óssea. MÉTODO: Foram empregados no estudo 17 carneiros, com massa corporal média de 37 kg, divididos entre grupos controle e três experimentais, conforme o período de observação pós-operatória de 30, 60 e 90 dias. As osteotomias foram realizadas nas tíbias direitas dos animais, ficando as esquerdas como controle. O processo de consolidação foi acompanhado por meio de avaliação radiográfica a cada duas semanas. Ao fim do período de observação estipulado para cada grupo, os animais sofreram eutanásia e as tíbias foram removidas para a análise ultra-sonométrica in vitro. Foram medidos e correlacionados a velocidade de propagação transversal e longitudinal do ultra-som e a atenuação do ultra-som (BUA) transversal na região da osteotomia. RESULTADOS: A velocidade de propagação do ultra-som (transversal e longitudinal, in vitro) aumentou com o avançar da consolidação, sendo as diferenças significantes em relação ao grupo controle e entre a maioria dos grupos experimentais. Já a BUA diminuiu, sendo parte das diferenças significantes entre os grupos. CONCLUSÃO: O método de avaliação da consolidação pelos parâmetros da ultra-sonometria é factível, com resultados confiáveis e precisos para medir a consolidação óssea.

DEXA as a predictor of fixator removal in distraction osteogenesis

Premature removal of the fixator after a lengthening procedure can result in gradual bending or acute fracture of the regenerate. We reviewed the records of 26 patients who underwent 28 limb lengthenings between 1997 and 2005 to assess the post lengthening regenerate fracture rate and bone healing index when using dual energy xray absorptiometry (DEXA) to aid in deciding on when to remove the fixator. Sixteen male and 10 female patients with an average age at lengthening of 12.3 years underwent an average lengthening of 5.2 cm (range, 3-9.1 cm). Nineteen femurs and nine tibiae were lengthened. Serial monthly DEXA scans were analyzed for bone mineral density. Bone healing indices and post fixator removal complications were assessed. The fixators were removed once the bone mineral density had plateaued to a less than 10% increase and plain radiographs showed no obvious defects precluding fixator removal. There were no regenerate fractures and only one fracture in the proximal segment of the lengthened bone after apparatus removal and the healing index for the series averaged 47 d/cm (range, 20-73 d/cm). Using serial DEXA scans during the consolidation phase of lengthening has a low rate (3.6%) of fractures while maintaining an acceptable bone healing index without excessively increasing fixation time.

LEVEL OF EVIDENCE

Level IV, therapeutic retrospective study. See the Guidelines for Authors for a complete description of levels of evidence.

Benefit of percutaneous injection of autologous platelet-leukocyte-rich gel in patients with delayed union and nonunion

This article reports the efficacy of percutaneous autologous platelet-leukocyte-rich gel (PLRG) injection as a minimally invasive method alternative to open grafting techniques. Each of 32 participants was followed on a regular basis with clinical examinations, roentgenograms, dual-energy X-ray absorptiometry examinations. In the delayed union group, the average time to union was 9.3 weeks after PLRG injection and the union was achieved in all cases. In the nonunion group, the union was observed in 13 of 20 cases and the average time to union was 10.3 weeks after PLRG injection. Interestingly, in patients in whom union was not achieved, the average time from the fracture and/or from the last operation was >11 months. This is our initial experience with the use of PLRG as biologic treatment for delayed union or nonunion. Our investigation showed that percutaneous PLRG injection in delayed union is a sufficient method to obtain union, which is less invasive procedure than bone marrow injection. Percutaneous PLRG grafting can be also an effective method for the treatment of selected cases of nonunion. The essential factor is the average time from the initial surgery to PLRG injection for nonunion; <11 months seems to be critical for good outcomes.

Ultrasonometric evaluation of bone healing: Experimental study using a model of diaphyseal transverse osteotomy of sheep tibiae

Noninvasive ionizing-radiation-free methods of evaluation, such as ultrasonometry, are desirable in any medical situation. An in vitro ultrasonometric study was undertaken to evaluate the bone healing process of sheep tibiae submitted to a diaphyseal transverse osteotomy at different times after the procedure. Fifteen sheep weighing an average of 37 kg had surgery for a transverse mid-diaphyseal osteotomy of the right tibia; they were divided postoperatively into three groups of five for periods of observation at 30, 45 and 60 days. The intact left tibiae of the 15 animals were used for control. The healing process was monitored with conventional radiographs taken at two-week intervals, and the animals were killed at the end of the period of observation of each group. Both surgical and intact tibiae were removed, their diameters were measured and they were submitted to measurement of underwater ultrasound propagation velocities (USPV) at the osteotomy sites in both the sagittal and frontal planes. The diameters of the surgical tibiae decreased with time in both planes (from 26.9 mm to 22.0 mm and to 20.9 mm in the sagittal plane, and from 29.3 mm to 23.9 mm and to 23 mm in the frontal plane), with significant differences between the periods of observation (p < or = 0.018 and p < or = 0.003 between 30 and 45 days and 30 and 60 days, respectively, for the sagittal plane and p < or = 0.006 and p < or = 0.003 between 30 and 45 days and 30 and 60 days, respectively, for the frontal plane) and between surgical and intact tibiae at all time points (p < or = 0.0005 for each comparison). USPV increased with time from 2290 m/s to 2399 m/s and to 2382 m/s in the sagittal plane, and from 2376 m/s to 2472 m/s and to 2466 m/s in the frontal plane, accounting for an approximate 5% difference between 30 and 60 days Differences between the surgical and intact tibiae were significant at all time points (p < or = 0.0005 for both sagittal and frontal planes) but not between periods for either plane. There was a strong negative correlation between diameter and USPV (Pearson's correlation coefficient of -0.8998 for the sagittal plane and -0.9192 for the frontal plane). It was concluded that ultrasonometric evaluation of the bone healing process is feasible, yielding precise and reliable results, with a potential for clinical application.

Comparison of various types of stiffness as predictors of the load-bearing capacity of callus tissue

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis. Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.

Load transmission through a healing tibial fracture

BACKGROUND

Fracture healing has been linked to both the magnitude and distribution of mechanical stresses on the healing fracture tissues. However, direct clinical measurement of in vivo tibial axial loading is not possible.

METHODS

Using computed tomography images, force plate data and recorded 3D interfragmentary micromovements, accurate 3D finite element models of a healing human tibial fracture were generated at 7, 10, and 16 weeks post-fracture and used to calculate longitudinal tibial forces and external fixator load-sharing during bilateral stance and walking.

FINDINGS

Tibial load-sharing by the fixator decreased significantly as the fracture tissues developed even moderate stiffness, while tibial load increased steadily towards normal.

INTERPRETATION

Quantitative assessment of the contribution of the external fixator is important as overloading of the callus due to insufficient support has been implicated in the retardation of the healing process.

Changes in bone mass and bone turnover following tibial shaft fracture

INTRODUCTION

Bone loss occurs in the regional bone following tibial shaft fracture. An earlier cross-sectional study showed that measurements made at the metaphyseal region of the tibia using peripheral quantitative computed tomography (pQCT) and the ultradistal region of the tibia using dual-energy X-ray absorptiometry (DXA) were the most responsive at monitoring this bone loss. Biochemical markers of bone turnover enable us to assess the activity of bone formation and resorption during fracture healing. The aim of this longitudinal study was to determine the pattern and distribution of bone loss and bone turnover following a tibial shaft fracture treated with either plaster cast or intramedullary nail.

METHODS

Eighteen subjects underwent bone mass measurements using DXA at the tibia and hip and quantitative ultrasound (QUS) at the tibia and calcaneus of both limbs at 2 weeks, 8 weeks, 12 weeks and 24 weeks following fracture, with hip and tibia DXA measurements also performed at 52 weeks. Nine of the patients treated with plaster cast had pQCT measurements at the tibia at 24 weeks. We measured three bone formation markers, bone alkaline phosphatase (bone ALP), osteocalcin (OC) and procollagen type 1 N-terminal peptide (PINP), a marker of bone resorption, serum C-telopeptides of type 1 collagen (beta-CTX) and a marker of collagen III turnover, procollagen type III N-terminal peptide (PIIINP) at 1 day, 3 days and 7 days and at 2, 4, 8, 12, 16 and 24 weeks following fracture. The greatest bone losses were observed at the ultradistal region of the tibia using DXA (28%, p <0.001) and the metaphyseal region of the tibia using pQCT (26-31%, p <0.001) at 24 weeks. In the hip, the greatest loss was in the trochanter region at 24 weeks (10%, p <0.001). The greatest loss at the calcaneus measured using QUS was for broadband ultrasound attenuation (BUA) measured using CUBA Clinical at 24 weeks (13%, p =0.01).

RESULTS

At 1 year, there was a small recovery in bone loss (ultradistal tibia DXA, 20%, p <0.01; trochanter DXA 9%, p <0.001). Bone turnover increased following fracture (PINP +72+/-21%, p <0.0001, bone ALP +199+/-22%, p =0.004, beta-CTX +105+/-23%, p <0.0001, all at 24 weeks). There was a smaller +33+/-10% increase in osteocalcin at 24 weeks. PIIINP concentration peaked at week 8 (+57+/-9%, p <0.0001). The bone resorption marker beta-CTX showed an earlier rise (week 2, 139+/-33%) than the bone formation markers.

CONCLUSIONS

We conclude that: (1) bone loss following tibial shaft fracture occurs both proximal and distal to the fracture; (2) the decreased BMD is largest for trabecular bone in the tibia with similar measurements using DXA and pQCT; (3) there is limited recovery of bone lost at the hip and tibia at 1 year; (4) tibial speed of sound (SOS) demonstrated a greater decrease than calcaneal SOS when comparing z -scores; (5) BUA is the QUS variable that shows the biggest decrease of bone mass at the calcaneus; (6) increase in bone turnover occurs following fracture with an earlier increase in bone resorption markers and a later rise in bone formation markers.

Avaliação ultra-sonométrica da consolidação de osteotomias mediodiafisárias transversas em diferentes períodos: estudo experimental em tíbias de carneiro

Foi realizado um estudo experimental sobre a avaliação ultra-sonométrica da consolidação de tíbias de carneiros submetidas a osteotomia transversal mediodiafisária, utilizando 15 carneiros, com pêso médio de 37 Kg, divididos em três grupos experimentais de cinco animais cada, conforme o período de observação pós-operatória de 30, 45 e 60 dias. As osteotomias foram realizadas nas tíbias direitas dos animais, ficando as tíbias esquerdas como controle. Foi feita avaliação radiográfica da consolidação a cada duas semanas e, ao fim do período de observação, os animais foram sacrificados e as tíbias, removidas para a análise ultra-sonométrica. Foram medidos e correlacionados o diâmetro da tíbia e a velocidade de propagação transversal do ultra-som na região da osteotomia, em duas direções diferentes (perpendicular e paralela ao plano da tuberosidade anterior da tíbia). A velocidade de propagação do ultra-som aumentou com o avançar da consolidação (±5%), sendo as diferenças significantes em relação ao grupo-controle, mas não entre os grupo experimentais. Os diâmetros diminuíram nas duas direções medidas, sendo as diferenças significantes entre os grupos, com forte correlação negativa com a velocidade. Concluiu-se que o método de avaliação da consolidação pela ultra-sonometria é factível, com resultados confiáveis e precisos.

Influence of flexible nailing in the later phase of fracture healing: strength and mineralization in rat femora

In this experimental study, the influence of flexible nailing in the later phase of femoral fracture healing was investigated. Sixty rats were randomly assigned to three groups. In 20 rats no intervention was performed, and they served as a control group. Fracture and reamed nailing with a rigid steel nail was performed in the left femur in the other 40 rats. These rats were reoperated after 30 days, and the medullary nail was removed. In one group (20 rats) a flexible polyethylene nail was installed (flexibly nailed group), while the rats in the other group received a steel nail identical to the one that was removed (rigidly nailed group). At 60 and 90 days, the left femurs of 10 animals in each group were studied clinically, radiologically, and biomechanically, and bone mineralization was measured by dual-energy X-ray absorptiometry. Radiographs in two planes revealed a clearly visible fracture line in both intervention groups at 60 days. At 90 days, the fracture line was clearly visible in the flexibly nailed group, while bridging callus was apparent after the rigid nailing. At 60 and 90 days, the callus area in the flexibly nailed group was significantly larger than that in the rigidly nailed bones. Biomechanically, flexible nailing reduced maximum bending load and fracture energy at 60 and 90 days compared with findings in rigidly nailed bones, while bending rigidity was similar in the two groups. All values for biomechanical characteristics were reduced at 60 and 90 days in flexibly nailed bones compared with intact femurs, while in the rigid nailing group, bending load and fracture energy were similar to those in intact bones at 90 days. Bone mineral content in the callus segment and diaphysis was greater in the rigidly nailed bones than in the flexible nailing group at 60 days, while at 90 days, no differences were detected. In conclusion, this animal study indicates that: (1) flexible nailing in the later phase of fracture healing increases callus formation, while (2) the quality of bone healing is reduced.

Serology of abnormal fracture healing: the role of PIIINP, PICP, and BsALP

OBJECTIVE

To determine whether poorly healing tibial shaft fractures exhibit a serological response of bone-specific alkaline phosphatase (BsALP), collagen I carboxy-terminal propeptide (PICP), collagen III amino-terminal propeptide (PIIINP), and collagen I carboxy-terminal telopeptide (ICTP) different from that of normally healing fractures.

DESIGN

Prospective.

PARTICIPANTS

Twenty consecutive patients with isolated tibial shaft fractures with or without fracture of the fibula.

MAIN OUTCOME MEASUREMENTS

Assays of BsALP, PICP, PIIINP, and ICTP were performed with serum samples taken at standard intervals from twenty-four hours to twenty weeks after fracture. Fracture healing was assessed at five, ten, fourteen, and twenty weeks for clinical and radiological evidence of union.

RESULTS

Seventeen fractures united within the twenty-week study period. The three fractures exhibiting delayed union demonstrated significantly lower PICP levels and marginally lower BsALP levels at twenty weeks. PIIINP levels were significantly higher in these three fractures at ten weeks. There was no difference in ICTP between the seventeen united and the three ununited fractures.

CONCLUSIONS

This study identified three serological features of a poor healing response in tibial shaft fractures. First, matrix collagen I and III production in the first ten weeks of healing was adequate, with evidence of significantly increased production of type III collagen. Second, there was no serological evidence of a deficient osteoblast response, as indicated by normal levels of BsALP and PICP, during this early period. Third, evidence of a deficient osteoblast response appeared only at twenty weeks after injury.

Bone mineral density 6 years after a hip fracture: a prospective, longitudinal study

The purpose of this prospective study was to extend the results of previous studies to determine if an accelerated rate of loss of bone mineral density (BMD) continues for 6 years after a hip fracture. Eighty-five elderly patients who had sustained a hip fracture had determinations of BMD made at the time of fracture; 55 of these patients were available for reassessment of BMD 1 year later, and 21 were available for reassessment of BMD 6 to 7 years later. The change in BMD from injury to 1 year and from 1 to 6 years was determined and correlated with pre- and postinjury variables, such as ambulatory ability, dietary intake of calcium, serum vitamin D levels, and mental status. There was a marked decrease in BMD in the in the first year after fracture, with the mean change in BMD being -4.3% at the femoral neck and -1.8% at the lumbar spine. Between 1 and 6 years after fracture, however, there was a dramatic increase in the BMD at both the femoral neck and lumbar spine measurement sites. Relative to 1 year after fracture, the mean increases were 7.7% at the femoral neck and 4.5% at the lumbar spine. In many cases, the loss of bone mineral that occurred in the first year after fracture was completely recouped in the subsequent 5 years. Five of the 21 patients (24%) sustained a contralateral hip fracture in the 6 years after the index fracture. Lumbar spine BMD was lower at baseline (p = 0.112), 1 year after fracture (p = 0.007), and 6 years after fracture (p = 0.003) in patients who sustained a second hip fracture than in those who did not. There was a general decrease in the functional activity level of patients in the 6 years after a hip fracture, but there were no statistically significant relationships between changes in BMD and the functional mobility of patients. The mean calcium intake in patients improved remarkably in the 6 years after fracture, but there was no correlation between daily calcium intake and changes in BMD. During the first year after a hip fracture, there is a rapid loss of bone mineral from the lumbar spine and contralateral femoral neck. Between 1 and 6 years after fracture, however, BMD is likely to increase, perhaps to levels greater than those at baseline. Although this investigation is small, the findings of this study point to the importance of further larger studies to further clarify the natural history of BMD after a hip fracture and the potential impact of pharmacological intervention on that natural history.

Change in bone mass after Colles' fracture: a case report on unique data collection and long-term implications

The cast immobilization of a fractured limb results in a loss of bone mass; however, the long-term implications of that effect with regard to bone mineral status, particularly in other skeletal sites, are less known. The purpose of this study was to describe changes in bone mass in different skeletal sites triggered by Colles' fracture. The case is unique regarding the existence of baseline measurements taken just a few days before the fracture on all measurable skeletal sites, including the fractured radius. Therefore, it was also possible to determine whether the injury caused long-term bone loss in the affected and unaffected skeletal sites. The patient was a healthy, premenopausal Caucasian woman, in her late forties, who fractured her nondominant wrist as a result of low-impact fall on ice. The arm and the metacarpals were immobilized to the elbow for 5 wk. Bone mass measurements were performed with DPX-MD densitometer (Lunar Corp. Madison, WI) at baseline and 5, 10, 13, 21, and 52 wk postinjury. At the 5-wk measurement (on plaster removal) there was a notable increase in bone mineral density (BMD) and bone mineral content (BMC) in all sites of ulna and radius of the injured forearm (from 10 to 73%), followed by the apparent decline to or below the baseline at 10, 13, 21 and 52 wk of follow-up. Other skeletal sites were measured at 10 wk when a substantial decrease in BMD and BMC in some of the hip regions and lumbar spine was noticed; most notably in L3-L4, Ward's triangle, and femoral neck (from 2 to 8%) and remained such after 1 yr. Although this patient had a normal bone mineral status and no osteopenia detected before fracture, the trauma of radial fracture caused long-standing bone loss in fracture-prone areas-hip and spine. Because about 70% of bone strength is explained by its mineral density, the patient might be at increased risk for fracture later in life. The changes in bone mass after injury should be monitored and interpreted carefully, and more elaborate treatment of patients presenting with wrist fractures are needed to prevent any potential risk for later osteoporotic fractures in spine and hip and possible refracture of the injured extremity.

A tibial shaft fracture sustained in childhood or adolescence does not seem to interfere with attainment of peak bone density

High peak bone mass or density in early adulthood is an important protective factor against osteoporotic fractures in later life, but it is not known whether injuries on growing bones affect the attainment of peak bone mass and density. The purpose of this study was therefore to examine with dual-energy X-ray absorptiometry the areal bone mineral density (BMD) of the injured and uninjured extremity (the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and distal tibia), lumbar spine, and distal radius of young adults with a history of early life tibial shaft fracture and to find out whether the fracture had affected the attainment of peak bone density of these patients. The second objective was to clarify whether any background or clinical follow-up variable would predict the BMD difference between the affected and unaffected extremity. Thus, the BMD and clinical status of 45 patients (34 men and 11 women), who had sustained a tibial shaft fracture in childhood or in adolescence (between 7 and 15 years of age) an average 11 years before the study, were examined. The results showed that the fracture had created a small but statistically significant injured-to-uninjured side BMD difference (proximal tibia -1.7%; p = 0.011, and distal tibia 2.6%; p = 0.014), while the other sites showed no significant side-to-side differences. There were neither significant differences in the spinal or radial BMDs between the patients and their age-, height-, and weight-matched healthy controls. A further analysis of the data showed that the better the muscle strength in the injured lower limb, the lower the side-to-side BMD deficit in the proximal tibia of the same limb (r = 0.51; p < 0.001). Smoking had a significant association with the relative BMD in the injured distal tibia (mean injured-to-uninjured side BMD difference: smokers 6.1% vs. nonsmokers -0.6%, p = 0.016). Also patient's age at the time of the injury showed an association: the younger the patient at the time of the injury, the lower the side-to-side BMD deficit in the injured distal tibia (r = -0.35; p = 0.048). In conclusion, this study indicates that early life tibial fracture leads to a small long-term BMD deficit in the fractured bone while the other sites of the skeleton seem not to be affected. Thus, a tibial shaft fracture sustained in childhood or adolescence seems to only marginally interfere the attainment of peak bone density, the important predictor of the osteoporotic fractures in later life.

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.

The use of quantitative ultrasound to monitor fracture healing: a feasibility study using phantoms

Fracture healing has traditionally been monitored subjectively using manual manipulation of the fracture site and evaluation of radiographic images. A more objective method of monitoring would provide obvious advantages, allowing healing progress to be quantitatively assessed and so providing the opportunity for early detection of problems. A tibia phantom was used to investigate whether the longitudinal propagation velocity of ultrasound across a fracture site could be used quantitatively to assess fracture healing. The characteristic of fracture healing simulated by the phantom was the changing gap between the bone ends at the fracture site. The ultrasound velocity was measured using a recently developed machine, the SoundScan 2000 (Myriad Ultrasound Systems Ltd, Israel). The precision of the SoundScan 2000 was found to be 0.4% in vitro. Ultrasound velocity predicted the simulated fracture gap with a high degree of accuracy (R2 = 0.994). The measured and the theoretically calculated velocity for different widths between the simulated bone ends was found to be highly correlated with a coefficient of determination of 0.998. This result shows that the use of quantitative ultrasound to monitor fracture healing warrants further investigation in vivo.

Pathophysiology of delayed healing

Delayed union represents an ongoing failure of initial fracture management. It still occurs partly because the precise reason why a patient's fracture does not heal frequently is unknown. This article aims to outline the limited material available on the pathophysiology of delayed healing. The systemic status of the patient, local limb status before injury, the nature of the traumatic injury, local host response to the injury, potential negative impact of orthopaedic fracture care, and pharmacologic variables are considered.

Bone healing of tibial lengthening is enhanced by hyperbaric oxygen therapy: a study of bone mineral density and torsional strength on rabbits

We investigated the effect of intermittent hyperbaric oxygen (HBO) therapy on the bone healing of tibial lengthening in rabbits. Twelve male rabbits were divided into two groups of six animals each. The first group went through 2.5 atmospheres absolute of hyperbaric oxygenation for 2 hours daily, and the second group did not go through hyperbaric oxygenation. Each animal's right tibia was lengthened 5 mm using an uniplanar lengthening device. Bone mineral density (BMD) study was performed for all of the animals at 1 day before operation and at 3, 4, 5, and 6 weeks after operation. All of the animals were killed at 6 weeks postoperatively for biomechanical testing. Using the preoperative BMD as an internal control, we found that the BMD of the HBO group was increased significantly compared with the non HBO group. The mean %BMD at 3, 4, 5, and 6 weeks were 69.5%, 80.1%, 87.8%, and 96.9%, respectively, in HBO group, whereas the mean %BMD were 51.6%, 67.7%, 70.5%, and 79.2%, respectively, in non-HBO group (two tailed t test, p < 0.01, p < 0.01, p < 0.01, and p < 0.01 at 3, 4, 5, and 6 weeks, respectively). Using the contralateral nonoperated tibia as an internal control, we found that torsional strength of lengthened tibia of the HBO group was increased significantly compared with the non-HBO group. The mean percent of maximal torque was 88.6% in HBO group at 6 weeks, whereas the mean percent of maximal torque was 76.0% in non-HBO group (two-tailed t test, p < 0.01). The results of this study suggest that the bone healing of tibial lengthening is enhanced by intermittent hyperbaric oxygen therapy.