The KineSpring load absorber implant: rationale, design and biomechanical characterization.

Osteoarthritis (OA) of the knee is the leading cause of disability in the adult population. Although a number of treatments for knee OA are available, none effectively prevent OA progression. Currently, a wide therapeutic gap exists for patients who have unsuccessfully exhausted conservative OA treatments but who are hesitant or ineligible to undergo invasive surgery. The KineSpring device is a novel, joint preserving, minimally invasive implant that reduces medial compartment loading without significantly impacting the loading of the lateral compartment. This article describes the rationale for and the design of the KineSpring device and summarizes results of initial biomechanical testing in an OA cadaver model.

Control of bone bleeding at the sternum and iliac crest donor sites using a collagen-based composite combined with autologous plasma: results of a randomized controlled trial.

In a randomized controlled trial, hemostatic effectiveness of a collagen-based composite (experimental group) was compared with standard hemostatic methods (ie, electrocautery and collagen sponge) (control group) at two bone sites. Hemostatic success, time to "controlled bleeding," and time to "complete hemostasis" were determined at the sternal edge following median sternotomy (n=64) and at the iliac crest following bone graft harvest (n=19). Almost twice the percentage of sternal edge patients (83% versus 44%, P=.002) and nearly three times the percentage of iliac crest patients (83% versus 29%, P<.05) achieved complete hemostasis in the experimental group compared to controls. Time to controlled bleeding and complete hemostasis for all bone sites also favored the experimental group over the control group at highly significant levels (P<.0001 for most comparisons). There were no adverse events related to experimental treatment use. The results support the use of this investigational hemostatic agent to control cancellous bone bleeding.

Surgical harvesting of bone graft from the ilium: point of view.

Autologous bone harvested from the ilium is commonly used as a grafting material in surgical reconstructive and arthrodesis procedures to ensure a satisfactory postoperative outcome. However, operative removal of bone from the iliac crest requires an additional surgical procedure with a distinct set of postoperative complications. We provide a comprehensive literature synthesis of the incidence and severity of complications reported to be associated with this commonly practiced procedure. Most severe complications are rare, but chronic pain at the donor site exceeding three months in duration occurs frequently and can be particularly bothersome to patients. Alternative grafting materials that are safe and effective are sorely needed.

Augmenting local bone with Grafton demineralized bone matrix for posterolateral lumbar spine fusion: avoiding second site autologous bone harvest.

Mineralization and integrity of the bone graft mass were evaluated among patients having posterolateral fusion. Grafting consisted of a composite of Grafton and "local" autologous bone (n=56) or iliac crest autograft alone (n=52). Mineralization was rated radiographically at baseline and at 3, 6, 12, and 24 months. Integrity was judged as fused or not fused. Mineralization ratings did not differ significantly between groups at any postoperative interval (P values of .25-1.00). The percentage of patients fused was similar in both groups (60% and 56% for Grafton and controls, respectively; P=.83). Fifteen control patients reported donor site pain. These findings warrant further evaluation of this composite.

Clinical utility of demineralized bone matrix for osseous defects, arthrodesis, and reconstruction: impact of processing techniques and study methodology.

The findings of studies on DBM in the surgical management of osseous defects, arthrodeses, and reconstructive procedures have been promising. In general, DBM grafts have supported healing in a timely fashion without complication and with a diminished need to harvest bone from a secondary operative site. Nonetheless, controlled prospective trials are needed to confirm the comparative effectiveness of DBM and to quantitate the benefits of avoiding secondary site autologous bone harvesting. Notwithstanding the known deleterious effects of certain processing steps, current commercial demineralization processes vary widely and use ancillary procedures aimed at attenuating potential residual antigens and pathogens. While some of these procedures may improve or facilitate graft performance (eg, lipid and lipoprotein removal with detergents), others may be deleterious (eg, sterilization with radiation or ethylene oxide) (Table 1). Therefore, it is important that DBM be processed using methods that consistently establish conditions known to preserve DBM's documented osteoinductive potential and that authors appropriately identify processing methods known to have effects on graft performance.

Does xenogeneic demineralized bone matrix have clinical utility as a bone graft substitute?

Autologous bone harvested from the iliac crest is a commonly used grafting material for a number of surgical procedures; however, there is documented morbidity associated with secondary site harvesting. Because demineralized bone matrix (DBM) is inherently osteoinductive (i.e., it facilitates differentiation of uncommitted connective tissue cells into bone-forming cells), it has potential appeal as a bone-graft substitute. Allogeneic DBM usage has intrinsic shortcomings related to procuring, processing and characterizing bone from a human donor pool. Xenogeneic bone represents an unlimited supply of available material if it can be processed to render it safe for transplantation to the human host. It is hypothesized that reported immunogenicity and non-viability of xenogeneic DBM results from lipids and plasma proteins not removed during typical demineralization processes. The authors propose a rigorous examination of this hypothesis, followed by several pivotal studies to determine the effectiveness of xenogeneic DBM.

Menopause without symptoms: the endocrinology of menopause among rural Mayan Indians.

OBJECTIVE: Our purpose was to determine the characteristics of menopause among Mayan women who did not have menopausal symptoms. STUDY DESIGN: A cross-sectional study of Mayan women from Chichimila, Mexico, was performed. Demographic information, history and physical examination, hormone concentrations, and radial bone density measurement were obtained. RESULTS: Fifty-two postmenopausal women were compared with 26 premenopausal women. Menopause occurred at 44.3 +/- 4.4 years. None of the women admitted to hot flushes and did not recall significant menopausal symptoms. Hormone levels included elevated follicle-stimulating hormone (66.6 +/- 29 mlU/ml), low estradiol and estrone (9.4 +/- 8.3 and 13.3 +/- 7.8 pg/ml), estrone greater than estradiol levels, normal levels of testosterone and androstenedione (0.17 +/- 0.14 and 0.31 +/- 0.17 ng/ml). Bone mineral density declined with age, but height did not. Clinical evidence of osteoporosis was not detected. CONCLUSIONS: Lack of symptoms during the menopausal transition is not attributable to a difference in endocrinology. Postmenopausal Mayan women are estrogen deprived and experience age-related bone demineralization but do not have a high incidence of osteoporotic fractures.

Skeletal integrity in premenopausal and postmenopausal women receiving long-term L-thyroxine therapy.

PURPOSE: The impact of long-term L-thyroxine replacement therapy on skeletal integrity is a growing concern because of the large number of women receiving thyroid hormone therapy. The purpose of this study was to examine the hypothesis that long-term L-thyroxine therapy in which the free thyroxine index (FT4I) is maintained within a physiologic range has minimal impact on vertebral or femoral bone mineral density in both premenopausal and postmenopausal women. PATIENTS AND METHODS: We measured hip integral and spinal trabecular and integral bone densities in 28 premenopausal and 28 postmenopausal women who had been receiving L-thyroxine therapy for a median of 12 and 15 years, respectively, and in whom therapy was titrated to keep the FT4I within the normal range. The relationship between bone density parameters and thyroid hormone status was examined using univariate and multivariate statistical methods. RESULTS: Seventy-nine percent of the premenopausal women and 86% of the postmenopausal women had FT4I values in the normal range at the time of bone density determination. Moreover, throughout the study's duration, the majority of annually measured values were in the normal range for more than 80% of subjects. Premenopausal women had slightly lower bone density than would be expected for age: -6.7% (z = -0.39 +/- 0.74 [mean +/- SD], p less than 0.01), -3.1% (z = -0.22 +/- 0.78, p = 0.15), and -5.1% (z = -0.36 +/- 0.74, p less than 0.02) for spinal trabecular, spinal integral, and hip integral bone density, respectively. Postmenopausal women likewise had slightly lower bone density values that were significant only at the hip: -0.2% (z = -0.01 +/- 1.01, p = 0.95), -1.0% (z = -0.05 +/- 1.11, p = 0.80), and -6.2% (z = -0.39 +/- 0.80, p less than 0.02) for spinal trabecular, spinal integral, and hip integral bone density, respectively. When patients with previously treated Graves' disease (n = 4 in each group) were eliminated, the differences in bone density at the hip were no longer seen. Correlation analysis revealed only weak and generally nonsignificant relationships between parameters of thyroid hormone status and bone density at any site in either subgroup. Results of multiple regression analysis among the pooled data of all subjects showed that age provided a consistently significant contribution (R2 = 0.18 to 0.66) to the variability in bone density at the spine and the hip, but parameters of thyroid hormone status did not. CONCLUSION: These data provide the first supportive evidence that long-term L-thyroxine therapy that maintains the FT4I in the physiologic range is associated with a statistically significant, but clinically minimal, decrement in spinal and hip bone density in both premenopausal and postmenopausal women. The decrement at the hip was entirely due to the inclusion of patients with treated Graves' diseases. Thus, the changes in bone density in women receiving long-term L-thyroxine therapy are minimal at most and should not be a contraindication to therapy.

Isokinetic limb and trunk muscle performance testing: short-term reliability.

This work was supported, in part, by grants from the National Institutes of Health (AR37562), the National Aeronautics and Space Administration (NAS9-343), Sandoz Pharmaceuticals, Squibb Mark Pharmaceuticals, and Cybex, Inc. There is a lack of information on the reliability of devices used to test trunk flexor and extensor strength. In this study, the short-term reliability of two isokinetic muscle performance testing devices was assessed. Measurements of knee flexion/extension and trunk flexion/extension were made in 15 normal subjects (mean age, 29.9 years). Determinations of peak torque and best work, as a percentage of body weight, were made 24 hours apart. Speeds used for the knee were 90, 180, and 240 degrees /sec, while speeds used for the trunk were 60, 90, and 120 degrees /sec. Correlation ranged from r = 0.82 to r = 0.96, showing strong associations between first and second measurements at either site for both performance parameters and for all speeds. Reliability (imprecision) was estimated as the average coefficient of variation (CV) for paired measurements. Coefficients of variation ranged from 4.4 to 8.7 percent for the knee parameters and from 2.9 to 12.1 percent for the trunk parameters. Using this range of imprecision, the minimum absolute changes in muscle performance needed to be significant at the five percent level were calculated for both the individual subject as well as for groups of subjects. At a three percent imprecision for the individual subject, muscle performance changes would have to be greater than 8.32 percent to be detected with 95 percent confidence. This estimate increases to approximately 33 percent at a imprecision level of 12 percent. However, muscle performance changes that can be detected with statistical confidence are three-fold less if a group of 10 subjects, for example, are examined. These findings have important implications where interventions to improve muscular performance may be of short duration and observed gains are relatively small. J Orthop Sports Phys Ther 1991;14(5):220-224.

Spinal bone mineral density measured with quantitative CT: effect of region of interest, vertebral level, and technique.

This study documents the relationship between different vertebral bone compartments with quantitative computed tomography (CT). Four distinct patient groups were investigated: healthy pre- and early postmenopausal women as well as healthy and osteoporotic late postmenopausal women. Three different regions of interest (ROIs) were employed: the elliptical ROI located in the anterior trabecular portion of the vertebral body, the peeled ROI of irregular shape that circumscribes most of the trabecular bone, and the integral ROI including all bone except for the transverse processes. Both single- and dual-energy quantitative CT techniques were employed at T-12 through L-3. Correlation between measurements in the elliptical and peeled ROIs was high (r = .985). The authors concluded that either ROI is acceptable for clinical use. The decrements in bone mineral density (BMD) for the integral ROI were smaller than those for the elliptical ROI. Dual-energy measurements were consistently higher than single-energy measurements. BMD as a function of vertebral level decreased systematically from T-12 to L-3. However, the average density of T-12 through L-3 can be accurately predicted by the average density of L-1 and L-2 (r = .997). Precision did not deteriorate significantly when BMD was expressed as the average of L-1 and L-2 (1.5%) instead of T-12 through L-3 (1.4%). In this study the data suggest a modified quantitative CT protocol for clinical applications in which BMD of only L-1 and L-2 are measured at a fixed gantry tilt.

Preventing osteoporosis with exercise: a review with emphasis on methodology.

Exercise is thought to have considerable potential as a preventive for osteoporosis. We critically examined 27 studies that address the prophylactic role of exercise in osteoporosis. The results from both cross-sectional and longitudinal studies showed that differences in bone mass were more pronounced in the axial skeleton as opposed to the peripheral compact skeleton. The 17 cross-sectional studies demonstrated greater bone mass among highly trained athletes compared with sedentary subjects, while results among recreational athletes were inconsistent. The 10 prospective investigations examining the effect of exercise on bone mass yielded conflicting results; only one study of six found an overall positive response in compact bone mass at the radial site, and only one study examining the spine showed a significant gain among the exercisers. Additionally, all the prospective investigations included serious methodologic flaws; most failed to employ a randomized design, appropriate estimates of sample size were lacking, none provided information on blind outcome assessment, and most studies were of short duration. Current evidence suggests that exercise may have only limited value in affecting bone mass in the short term and widespread recommendations for the prophylactic use of exercise should await further validation using better methodological rigor.

Determinants of bone density among athletes engaged in weight-bearing and non-weight-bearing activity.

To identify the factors associated with greater bone density among athletic individuals, we recruited three distinct groups of young male subjects. Twenty were nationally ranked water polo players, 19 were engaged in weight-training programs, and 20 subjects comprised a nonexercising comparison group. All participants had measurements of spinal trabecular and integral bone density by quantitative computed tomography as well as a determination of hip bone density by dual photon absorptiometry. A series of potential predictor variables included maximal O2 uptake, back strength, leg strength, total kilocalories expended per day, body mass index, paraspinous muscle cross-sectional area, percent body fat, daily calcium intake, and age. We found no significant differences for any of the bone density measures between the two groups of athletic subjects, whereas bone density was generally significantly lower among the nonexercisers compared with either exercise group. Correlation analysis found only weak and somewhat inconsistent relationships when each of the subgroups was examined separately; however, when all subjects were assessed collectively, many more correlations reached significance. Paraspinous muscular area was found to be most robust in this regard, being significantly correlated with all three bone density measures (r = 0.33-0.55). By using step-wise regression analysis in each subgroup, we observed a consistent significant contribution (R2 = 0.18-0.44) of paraspinous muscle area to the variability in bone density at the spine and the hip. When the data of all three subgroups were pooled, regression analysis reconfirmed the importance of the muscle parameter (R2 = 0.06-0.27) to bone density variation, but more importantly it showed that differentiation based on exercise status was most significant (R2 = 0.18-0.22).

Electrically-stimulated muscle hypertrophy in paraplegia: assessment by quantitative CT.

To identify the magnitude of muscle hypertrophy following electrically stimulated exercise in paraplegic subjects, we used quantitative CT (QCT) of the midthigh prior to and following 6 weeks of bicycle ergometry. Three patients who had suffered acute spinal cord injury were examined in this pilot investigation. Average absolute changes in muscle cross-sectional area by QCT were determined to be 10.6 cm2 (p = 0.042) at a distal site located 100 mm above the tibial plateau and 18.8 cm2 (p = 0.019) at a more proximal site (175 mm). Expressed as a percentage increase, these changes were likewise found to be significant. When the total thigh musculature was segmented into anterior and posterior regions, significant increases were observed only among the anterior muscle groups at both the distal and the proximal sites. Muscle hypertrophy as determined by standard anthropometric techniques at 200 mm above the patella was not found to be significant. We conclude that QCT is a valuable technique for discerning changes in muscle size during fitness training and that, in our population, it was capable of differentiating specific muscle compartment hypertrophy secondary to electrical stimulation.

Models of spinal trabecular bone loss as determined by quantitative computed tomography.

Noninvasive bone densitometry techniques have significantly improved our understanding of the pattern and magnitude of bone loss over the life span. Quantitative computed tomography (QCT) is capable of selectively measuring highly labile trabecular bone in the central portion of the vertebrae. Trabecular bone mineral density (mg/ml) was determined in 538 healthy women ranging in age from 20 to 80 using GE CT/T scanners at 80 kVp. Various statistical regressions were performed for the entire population to describe the general pattern of bone loss from the spine; a cubic model (r = -0.69, SEE = 26.0 mg/ml) was found to be statistically superior (p less than 0.01) to linear, quadratic, or exponential models. An average bone loss was approximated from these regression analyses with a yearly absolute rate of -2.02 +/- 0.097 mg/ml per year (p less than 0.0001). The average rate of change for premenopausal women was -0.45 mg/ml per year (p less than 0.05), for perimenopausal women was -4.39 mg/ml per year (p less than 0.0001) and for postmenopausal women was -1.99 mg/ml per year (p less than 0.0001). QCT values were also stratified into 5 and 10 year age groups and analyzed separately for pre- and postmenopausal women. The 5 and 10 year interval stratification revealed no identifiable bone density decrements prior to midlife using analysis of variance statistical methods; significant losses of bone mineral density were noted to correspond with the usual time of menopause and to continue into old age. Various two-phase regressions were employed using age and menstrual status to improve the description of age- and menopause-related bone loss.(ABSTRACT TRUNCATED AT 250 WORDS)