A Study of Bone Mineral Density in Lower Limb Amputees at a National Prosthetics Center

Thirty years of surveillance of depleted uranium-exposed Gulf War veterans demonstrate continued effects to bone health

During the spring of 2024, 33 members of a group of Gulf War I veterans wounded in depleted uranium (DU) friendly-fire incidents were seen at the Baltimore VA Medical Center for surveillance related to their combat exposure. The cohort was assessed with a protocol which includes exposure monitoring for total and isotopic uranium (U) concentrations in urine and a comprehensive assessment of health outcomes including measures of bone metabolism and bone mineral density (BMD). An audiometry examination of the cohort was added to assess for acoustic trauma and toxic metal effects in this surveillance episode marking over 30 years since this exposure event. Elevated urine U concentrations were detected in cohort members with retained DU shrapnel fragments. In addition, a measure of bone resorption, N-telopeptide, determined in urine, exhibited a significant increase in the high DU sub-group. In addition, and similar to our previous surveillance report, a significant decrease was found in bone mass in the high DU sub-group compared to the low DU sub-group. It has been 30 years since the first surveillance visit occurred. An aging cohort of military veterans continues to demonstrate few U-related adverse health effects in known target organs attributed to U toxicity exposure. The new finding of impaired BMD in older cohort members has now been detected in three consecutive surveillance visits. This is a biologically plausible outcome related to the diminished bone mass in those with an elevated DU burden in combination with advancing age. The accumulating U burden derived from fragment absorption over time and the effect of aging on bone mineral loss recommends that our surveillance efforts need to continue. Our findings enable early detection of bone effects and other signs of target organ insult, which may occur when tissue injury thresholds are reached in the future and thus, permitting indicated medical management.

Basic science review of transcutaneous osseointegration: current status, research gaps and needs, and defining future directions

Basic science research is vital for advancing the emerging field of bone-anchored limb replacement (BALR), or osseointegration (OI). This article discusses clinical challenges for BALR/OI, summarizes current basic science research regarding those challenges, identifies research gaps, and proposes future directions. OI research draws from related fields such as orthopaedic implants and dentistry. There is a need for small animal models to study critical questions related to osseointegration, including OI implant-associated infections. Small animal models are also critical to ensuring safety and efficacy of novel treatments in this vulnerable population. Key issues include infection prevention through implant surface modifications, biofilm-targeting technologies, and antimicrobial advancements. The skin-implant portal, unique to BALR, also poses significant challenges. Research on skin attachment and inflammatory processes is crucial. Noninfectious inflammatory loosening of implants, though infrequent, needs further investigation. This review emphasizes the need for collaborative efforts to develop effective preclinical models and innovative infection prevention strategies. Addressing these challenges is essential for optimizing patient outcomes and advancing this emerging field.

Importance of Bilateral Hip Assessments in Unilateral Lower-Limb Amputees: A Retrospective Review Involving Older Veterans

Background/Objectives: This study aimed to evaluate bone mineral density (BMD) discordance and its implications in veterans with unilateral lower-limb amputation, emphasizing the need for comprehensive hip assessments. Methods: Data were collected from 84 male veterans, and BMD was measured using dual-energy X-ray absorptiometry (DXA) at the lumbar spine, intact hip, and amputated hip. Results: The T-scores for the lumbar spine, intact hip, and amputated hip were -0.27 ± 1.69, -0.25 ± 1.20, and -1.07 ± 1.33, respectively. Osteoporosis and osteopenia were present in 19% and 34.6% of patients, respectively. Osteopenia and osteoporosis were most prevalent in the hips on the amputated side (32.1% and 13.1%, respectively), followed by the lumbar spines (22.6% and 8.3%) and the hips on the intact side (17.9% and 2.4%). BMD discordance between the lumbar spine and hip was found in 47.6% of participants, while discordance between both hips was observed in 39.3%. Transfemoral amputees had significantly lower BMD at the amputated hip compared to transtibial amputees (-2.38 ± 1.72 vs. -0.87 ± 1.16, p < 0.001). Conclusions: Veterans with unilateral lower-limb amputation exhibit a high prevalence of osteoporosis and significant BMD discordance, particularly between both hips. These findings underscore the necessity for bilateral hip assessments to ensure the accurate diagnosis and effective management of osteoporosis in this population.

Association Between Combat-Related Traumatic Injury and Skeletal Health: Bone Mineral Density Loss Is Localized and Correlates With Altered Loading in Amputees: the Armed Services Trauma Rehabilitation Outcome (ADVANCE) Study

The association between combat-related traumatic injury (CRTI) and bone health is uncertain. A disproportionate number of lower limb amputees from the Iraq and Afghanistan conflicts are diagnosed with osteopenia/osteoporosis, increasing lifetime risk of fragility fracture and challenging traditional osteoporosis treatment paradigms. The aim of this study is to test the hypotheses that CRTI results in a systemic reduction in bone mineral density (BMD) and that active traumatic lower limb amputees have localized BMD reduction, which is more prominent with higher level amputations. This is a cross-sectional analysis of the first phase of a cohort study comprising 575 male adult UK military personnel with CRTI (UK-Afghanistan War 2003 to 2014; including 153 lower limb amputees) who were frequency-matched to 562 uninjured men by age, service, rank, regiment, deployment period, and role-in-theatre. BMD was assessed using dual-energy X-ray absorptiometry (DXA) scanning of the hips and lumbar spine. Femoral neck BMD was lower in the CRTI than the uninjured group (T-score -0.08 versus -0.42 p = .000). Subgroup analysis revealed this reduction was significant only at the femoral neck of the amputated limb of amputees (p = 0.000), where the reduction was greater for above knee amputees than below knee amputees (p < 0.001). There were no differences in spine BMD or activity levels between amputees and controls. Changes in bone health in CRTI appear to be mechanically driven rather than systemic and are only evident in those with lower limb amputation. This may arise from altered joint and muscle loading creating a reduced mechanical stimulus to the femur resulting in localized unloading osteopenia. This suggests that interventions to stimulate bone may provide an effective management strategy. © 2023 Crown copyright and The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the King's Printer for Scotland.

Sporting activity does not fully prevent bone demineralization at the impaired hip in athletes with amputation

There is lack of information about bone mineralization at the lumbar spine and bilateral hips of athletes with unilateral lower limb amputation. The present study assessed for the first time the areal bone mineral density at the lumbar spine and at the hip of the able and impaired leg by means of Dual-Energy X-Ray Absorptiometry using a large sample (N = 40) of male athletes. Results showed that bone demineralization in athletes with unilateral lower limb amputation is found at the impaired hip but not at the lumbar spine and may therefore be site-specific. The extent of hip demineralization was influenced by the level of amputation, with about 80% of athletes with above knee amputation and 10% of athletes with below knee amputation showing areal bone mineral density below the expected range for age. Nevertheless, a reduced percentage of fat mass and a lower fat-to-lean mass ratio in the residual impaired leg as well as a greater amount of weekly training was positively associated with bone mineralization at the impaired hip (partial correlation coefficients = 0.377–0.525, p = 0.040–0.003). Results showed that participation in adapted sport has a positive effect on bone health in athletes with unilateral lower limb amputation but is not sufficient to maintain adequate levels of bone mineralization at the impaired hip in athletes with above-knee amputation. Accordingly, physical conditioners should consider implementing sporting programs, according to the severity of the impairment, aimed at improving bone mineralization at the impaired hip and improve body composition in the residual impaired leg.

Periprosthetic Femur Fractures in Osseointegration Amputees: A Report of 2 Cases Using a Modified Traction Technique

CASES

Two patients with periprosthetic femur fracture proximal to a femoral osseointegration had surgical stabilization. These cases produced operative challenges because commonly used intraoperative traction methods cannot be used for patients with transfemoral osseointegration.

CONCLUSION

We describe a novel technique to apply traction and rotation to the osseointegrated extremity: using the implant's antirotation propeller handle. This allows for an otherwise familiar technique to be used for fracture fixation: open reduction with internal fixation using a proximal femur hook plate and eccentric peri-implant screws.

Surveillance of Depleted Uranium-exposed Gulf War Veterans: More Evidence for Bone Effects

ABSTRACT

Gulf War I veterans who were victims of depleted uranium (DU) "friendly-fire" incidents have undergone longitudinal health surveillance since 1994. During the spring of 2019, 36 members of the cohort were evaluated with a monitoring protocol including exposure assessment for total and isotopic uranium concentrations in urine and a comprehensive review of health outcomes, including measures of bone metabolism and bone mineral density (BMD) determination. Elevated urine U concentrations were observed in cohort members with retained depleted uranium (DU) shrapnel fragments. In addition, a measure of bone resorption, N-telopeptide, showed a statistically significant increase in those in the high DU subgroup, a finding consistent with a statistically significant decrease in bone mass also observed in this high DU subgroup compared to the low DU subgroup. After more than 25 y since first exposure to DU, an aging cohort of military veterans continues to show few U-related health effects in known target organs of U toxicity. The new finding of impaired BMD in the high DU subgroup has now been detected in two consecutive surveillance visits. While this is a biologically plausible uranium effect, it is not reflected in other measures of bone metabolism in the full cohort, which have largely been within normal limits. However, ongoing accrual of the U burden from fragment absorption over time and the effect of aging further impairing BMD suggest the need for future surveillance assessments of this cohort.

Changes in periprosthetic bone mineral density and bone turnover markers after osseointegrated implant surgery: A cohort study of 20 transfemoral amputees with 30-month follow-up

BACKGROUND

The osseointegrated implant system is a treatment option for people with transfemoral amputation, but implant removal is not uncommon. The association between bone mineral density changes or bone turnover markers and the need for implant removal has not previously been investigated.

OBJECTIVES

The aim was to evaluate changes in bone mineral density and bone turnover markers in people with transfemoral amputations treated with osseointegrated implants.

STUDY DESIGN

This is a prospective cohort study.

METHODS

Nineteen patients were followed up for 30 months or until implant removal. Bone mineral density was measured in the lumbar spine, proximal femur and seven periprosthetic regions. 25-hydroxyvitamin (D2 + D3), parathyroid hormone, N-terminal propeptide of type-I procollagen, C-telopeptide of type-I collagen, bone-specific alkaline phosphatase and osteocalcin were measured in blood samples.

RESULTS

Four fixtures and three abutments were removed. Patients with removed implants had a decreased bone mineral density in the seven periprosthetic regions between 27% (95% confidence interval = 6; 43) and 38% (95% confidence interval = 19; 52) at 30-month follow-up compared to baseline (p < 0.02), whereas bone mineral density around non-removed implants normalized to baseline values (p > 0.08). C-telopeptide of type-I collagen was significantly different between the groups at 18- and 24-month follow-up (p < 0.05). None of the measured variables were significant predictors of implant removal (p > 0.07).

CONCLUSION

Implant removal was associated with loss of periprosthetic bone mineral density and increase in C-telopeptide of type-I collagen in the years following osseointegrated surgery.

CLINICAL RELEVANCE

This study offers new insight into changes in bone mineral density and bone turnover markers that precipitate aseptic or septic osseointegrated implant removal. Results of this study could contribute to clinical guidelines for monitoring rehabilitation progress and implant removal through dual-energy X-ray absorptiometry or surrogate markers like C-telopeptide of type-I collagen.

Surveillance results and bone effects in the Gulf War depleted uranium-exposed cohort

A small group of Gulf War I veterans wounded in depleted uranium (DU) friendly-fire incidents have been monitored in a clinical surveillance program since 1993. During the spring of 2017, 42 members of the cohort were evaluated with a protocol which includes exposure monitoring for total and isotopic uranium concentrations in urine and a comprehensive assessment of health outcomes including measures of bone metabolism, and for participants >50 years, bone mineral density (BMD) determination. Elevated urine U concentrations were observed in cohort members with retained DU shrapnel fragments. Only the mean serum estradiol concentration, a marker of bone metabolism, was found to be significantly different for lower-vs- higher urine U (uU) cohort sub-groups. For the first time, a significant deficit in BMD was observed in the over age 50, high uU sub-group. After more than 25 years since first exposure to DU, an aging cohort of military veterans continues to exhibit few U-related adverse health effects in known target organs of U toxicity. The new finding of reduced BMD in older cohort members, while biologically plausible, was not suggested by other measures of bone metabolism in the full (all ages) cohort, as these were predominantly within normal limits over time. Only estradiol was recently found to display a difference as a function of uU grouping. As BMD is further impacted by aging and the U-burden from fragment absorption accrues in this cohort, a U effect may be clarified in future surveillance visits.

Acute bone changes after lower limb amputation resulting from traumatic injury

Bone health is critical for lower limb amputees, affecting their ability to use a prosthesis and their risk of osteoporosis. We found large losses in hip bone mineral density (BMD) and in amputated bone strength in the first year of prosthesis use, suggesting a need for load bearing interventions early post-amputation.

INTRODUCTION

Large deficits in hip areal BMD (aBMD) and residual limb volumetric BMD (vBMD) occur after lower limb amputation; however, the time course of these bone quality changes is unknown. The purpose of this study was to quantify changes in the amputated bone that occur during the early stages post-amputation.

METHODS

Eight traumatic unilateral amputees (23-53 years) were enrolled prior to surgery. Changes in total body, hip, and spine aBMD (dual-energy X-ray absorptiometry); in vBMD, stress-strain index (SSI), and muscle cross-sectional area (MCSA) (peripheral QCT); and in bone turnover markers were assessed after amputation prior to prosthesis fitting (pre-ambulatory) and at 6 and 12 months walking with prosthesis.

RESULTS

Hip aBMD of the amputated limb decreased 11-15%, which persisted through 12 months. The amputated bone had decreases (p < 0.01) in BMC (-26%), vBMD (-21%), and SSI (-25%) from pre-ambulatory to 6 months on a prosthesis, which was maintained between 6 and 12 months. There was a decrease (p < 0.05) in the proportion of bone >650 mg/cm³ (58 to 43% of total area) or >480 mg/cm³ (65% to 53%), suggesting an increase in cortical porosity after amputation. Bone alkaline phosphatase and sclerostin were elevated (p < 0.05) at pre-ambulatory and then decreased towards baseline. Bone resorption markers were highest at surgery and pre-ambulatory and then progressively decreased (p < 0.05).

CONCLUSIONS

Rapid and substantial losses in bone content and strength occur early after amputation and are not regained by 12 months of becoming ambulatory. Early post-amputation may be the most critical window for preventing bone loss.

Bone mineral density loss after combat-related lower extremity amputation

OBJECTIVES

Determine the incidence, severity, and associated risk factors for the development of low bone mineral density (BMD) after combat-related lower extremity amputation.

DESIGN

Retrospective case-control comparison.

SETTING

Tertiary care military treatment facility.

PATIENTS/PARTICIPANTS

One hundred fifty-six lower extremity amputees, representing 182 amputations (121 unilateral, 35 bilateral).

INTERVENTION

All patients underwent dual energy x-ray absorptiometry scanning during the treatment period.

MAIN OUTCOME MEASUREMENTS

The Z score was the main outcome measure. We identified all patients with low BMD (Z < -1.0) and conducted multivariate analysis to identify significant risk factors for low BMD development.

RESULTS

The observed rate of low BMD was 42%. The average Z score was -0.6 ± 1.1 among unilateral amputations and -1.2 ± 1.0 among bilateral amputations (P = 0.005). Risk factors for the development of low BMD were prolonged time to first ambulation [odds ratio (OR) = 1.39; 95% confidence interval (CI): 1.003-1.93; P = 0.048], prolonged time to dual energy x-ray absorptiometry (OR = 1.10; 95% CI: 1.02-1.18; P = 0.009), and more proximal amputation level (OR = 7.27; 95% CI: 3.21-16.49; P < 0.001). Among unilateral amputees, we detected a significant difference in the BMD of the intact and amputated limbs (-1.0; 95% CI: -1.1 to -0.8; P < 0.001).

CONCLUSIONS

Proximal amputation level and delayed ambulation demonstrated a significant relationship with low BMD after traumatic and trauma-related amputation. We conclude that transfemoral amputees are at greater risk of BMD loss and that disuse atrophy is a primary factor in the development of low BMD. Prevention should focus on early and aggressive weight bearing rehabilitation and assessing levels and appropriately supplementing calcium and vitamin D.

Amputation and cardiac comorbidity: analysis of severity of cardiac risk

OBJECTIVE

To evaluate population-based cardiovascular risk scores and coronary artery calcification scores (CACS) in amputees.

DESIGN

A retrospective cohort study of 1300 veterans in a cardiac computed tomography database.

SETTING

1B Veterans Administration medical center.

PARTICIPANTS

A total of 76 amputees and similar number of age-, gender-, and Framingham Risk Scores (FRS)-matched control subjects.

METHODS

The amputee population was identified and compared for CACS and traditional cardiac risk factors. Two control groups were used: control group 1, with known risk factors including diabetes mellitus, and control group 2, with all risk factors without diabetes mellitus.

MAIN OUTCOME MEASURES

Statistical associations between amputee and control group FRS scores, CACS, and other cardiac risk factors were assessed.

RESULTS

The study included 57 nontraumatic and 19 traumatic amputees with an average age of 62.4 years. Sixty-six amputees were in the low-to-intermediate cardiac risk groups according to FRS. Despite this classification, the mean CACS were significantly higher in amputees (1285 ± 18) than in either of the control groups: control group 1 (540 ± 84) and control group 2 (481 ± 11), P < .001. CACS also were significantly higher in the nontraumatic subject group (1595 ± 12) compared with the traumatic group (356 ± 57; P < .001). Upon categorization of CACS based on probability of coronary artery disease (CAD), 76% of amputees had a CACS >100 and 38% of amputees had a CACS >1000. Interestingly, CACS were almost the same in finger/toe amputations compared with an above-knee amputation, indicating an already ongoing CAD process irrespective of level of amputation. The predominant clinical significant cardiac risk factors in amputees are hypertension (89.5%), P < .005; chronic kidney disease (31.6%), P < .001; dyslipidemia (72.4%), P < .04; and insulin resistance. Total cholesterol, low-density lipoprotein, and high-density lipoprotein levels were nonsignificantly low in all amputees. Triglycerides were particularly higher in traumatic patients compared with nontraumatic patients, with the triglycerides/high-density lipoprotein ratio >7.

CONCLUSION

This study demonstrates that amputees have a much greater burden of underlying atherosclerotic disease as detected by CACS than do control subjects matched by Framingham risk stratification. Early screening for CAD and aggressive targeted interventions may be an important part of management to reduce early mortality after amputation.