Changes in femoral bone mineral density after total knee arthroplasty: a systematic review and meta-analysis

Retrograde intramedullary nail fixation with oblique fixed angle screws versus locking plates in periprosthetic supracondylar fractures after total knee arthroplasty

PURPOSE

Common surgical procedures in the treatment of periprosthetic distal femur fractures (PPFF) include osteosynthesis with fixed angle locking plates (LP) and retrograde intramedullary nails (RIN). This study aimed to compare LPs to RINs with oblique fixed angle screws in terms of complications, radiographic results and functional outcome.

METHODS

63 PPFF in 59 patients who underwent treatment in between 2009 and 2020 were included and retrospectively reviewed. The anatomic lateral and posterior distal femoral angle (aLDFA and aPDFA) were measured on post-surgery radiographs. The Fracture Mobility Score (FMS) pre- and post-surgery, information about perceived instability in the operated leg and the level of pain were obtained via a questionnaire and previous follow-up (FU) examinations in 30 patients (32 fractures).

RESULTS

The collective (median age: 78 years) included 22 fractures treated with a RIN and 41 fractures fixed with a LP. There was no difference in the occurrence of complications (median FU: 21.5 months) however the rate of implant failures requiring an implant replacement was higher in fractures treated with a LP (p = 0.043). The aPDFA was greater in fractures treated with a RIN (p = 0.04). The functional outcome was comparable between both groups (median FU: 24.5 months) with a lower outcome in the post-surgery FMS (p =  < 0.001).

CONCLUSION

Fractures treated with RIN resulted in an increased recurvation of the femur however the rate of complications and the functional outcome were comparable between the groups. The need for implant replacements following complications was higher in the LP group.

Factors influencing periprosthetic bone mineral density in total knee arthroplasty: a systematic review

INTRODUCTION

Following total knee arthroplasty (TKA), there is a significant decline in periprosthetic bone mineral density (BMD), potentially resulting in complications such as prosthetic loosening, periprosthetic fracture, and influencing the postoperative recovery. The objective of this study was to summarize the factors influencing periprosthetic BMD in TKA from existing studies.

METHODS

A comprehensive systematic search was performed in 4 databases: Pubmed, Embase, Web of Science, and Cochrane Library. The last search was carried out on October 12, 2023. We used the keywords ''total knee arthroplasty'', ''bone mineral density'' and each of them combined with ''tibia'' and ''femur'' to identify all relevant articles reporting about potential impact factors influencing the periprosthetic BMD in patients after TKA.

RESULTS

Out of 1391 articles, 22 published from 2001 to 2023 were included in this systematic review. Following eligibility screening, six significant categories affecting periprosthetic BMD were recognized: prosthesis type, design of stem, coating, body weight, cement, and peg distance.

CONCLUSION

Mobile-bearing prostheses, modular polyethylene design, short stems, cruciform stems, avoidance of bone cement, higher body mass index, titanium nitride coating, and a smaller medial peg distance could potentially benefit periprosthetic BMD. Comprehensive consideration of diverse factors influencing periprosthetic BMD before surgery and collaboration with post-operative drug therapy are essential.

TRIAL REGISTRY

The PROSPERO registration number is CRD42023472030.

Periprosthetic fractures are osteoporotic fractures: missed opportunities for osteoporosis diagnosis

Joint replacement surgery is common in older adults, leading to increasing periprosthetic fracture (PPFx) occurrence. We reviewed all PPFx seen over a 4-year period at an academic hospital. Clinical osteoporosis could be diagnosed based on existing data in 104 (67%) at the time of PPFx. Periprosthetic fractures are generally osteoporosis-related.

PURPOSE

Periprosthetic fractures (PPFx) cause morbidity, mortality, and cost. This study's purpose was to describe osteoporosis-related data available at the time of PPFx.

METHODS

The electronic medical record (EMR) of PPFx patients seen over 4 years in a university orthopedic practice were reviewed. Demographic data and osteoporosis relevant parameters were collected. Prior DXA studies were reviewed, and L1 Hounsfield unit (HU) measurements were performed on CT scans obtained within 2 years before PPFx. Clinical osteoporosis was defined as prior diagnosis, prescribed osteoporosis treatment, T-score ≤  - 2.5, HU ≤ 100, or prior fracture.

RESULTS

Records of 156 PPFx patients (115 F/41 M), mean (SD) age 75.4 (11.9), were reviewed. Almost all 153/156 (98%) of these fractures were femoral. Falls caused 139 (89%); 12 (8%) were spontaneous. Mean time post-arthroplasty was 7.9 (6.3) years. Prior fragility fracture(s) occurred in 72 (46%); 14 were PPFx. Osteoporosis was previously diagnosed in 45 (29%) and medications prescribed in 41 (26%). Prior to PPFx, DXA data were available in 62, mean (SD) lowest T-score was - 1.9 (0.9) and was ≤  - 2.5 in 19. CT data were available in 46; mean (SD) L1 HU was 79.0 (29.4) and was ≤ 100 in 35. Based on existing data, clinical osteoporosis could have been diagnosed in 104 (67%) at the time of PPFx.

CONCLUSION

Periprosthetic fractures are osteoporosis-related. They occur in older adults, often female, and result from falls; BMD, when assessed, is low. Data available at the time of PPFx often allows osteoporosis diagnosis; this should prompt evaluation and pharmacologic treatment consideration.

Load transfer in bone after partial, multi-compartmental, and total knee arthroplasty

Introduction: Arthroplasty-associated bone loss remains a clinical problem: stiff metallic implants disrupt load transfer to bone and, hence, its remodeling stimulus. The aim of this research was to analyze how load transfer to bone is affected by different forms of knee arthroplasty: isolated partial knee arthroplasty (PKA), compartmental arthroplasty [combined partial knee arthroplasty (CPKA), two or more PKAs in the same knee], and total knee arthroplasty (TKA). Methods: An experimentally validated subject-specific finite element model was analyzed native and with medial unicondylar, lateral unicondylar, patellofemoral, bi-unicondylar, medial bicompartmental, lateral bicompartmental, tricompartmental, and total knee arthroplasty. Three load cases were simulated for each: gait, stair ascent, and sit-to-stand. Strain shielding and overstraining were calculated from the differences between the native and implanted states. Results: For gait, the TKA femoral component led to mean strain shielding (30%) more than three times higher than that of PKA (4%-7%) and CPKA (5%-8%). Overstraining was predicted in the proximal tibia (TKA 21%; PKA/CPKA 0%-6%). The variance in the distribution for TKA was an order of magnitude greater than for PKA/CPKA, indicating less physiological load transfer. Only the TKA-implanted femur was sensitive to the load case: for stair ascent and gait, almost the entire distal femur was strain-shielded, whereas during sit-to-stand, the posterior femoral condyles were overstrained. Discussion: TKA requires more bone resection than PKA and CPKA. These finite element analyses suggest that a longer-term benefit for bone is probable as partial and multi-compartmental knee procedures lead to more natural load transfer compared to TKA. High-flexion activity following TKA may be protective of posterior condyle bone resorption, which may help explain why bone loss affects some patients more than others. The male and female bone models used for this research are provided open access to facilitate future research elsewhere.

Subtrochanteric fracture of the femur following knee replacement surgery: A case series and review of the literature

INTRODUCTION AND IMPORTANCE

Knee arthroplasties as an effective intervention is primarily performed in patients with primary osteoarthritis and rheumatoid arthritis. Risk of hip fracture may be either decreased or increased in patients with Knee arthroplasties. There is conflicting evidence in this regard. Over the years, some studies have reported the occurrence of hip fractures following this operation as a rare but severe complication. The aim of the present case series was to report diagnosis and treatment of the mentioned five cases.

CASE PRESENTATION

During a period of two years, five patients with a diagnosis of a subtrochanteric fracture and history of total knee arthroplasty who referred to hospital were selected to include in the present case series. CLINICAL DISCUSSION: the presence of RA and treatment with glucocorticoids, a reduction of BMD following knee replacement surgery, and ultimately, an increase in physical activity and movement after the arthroplasty due to the improvement of preoperational pain, may all contribute in a complex manner to the observed outcome of increased fracture risk in the hip following TKA.

CONCLUSION

In summary, special care including using medications to improve BMD should be taken to minimize the risk of such an event.

The Effects of Different Femoral Component Materials on Bone and Implant Response in Total Knee Arthroplasty: A Finite Element Analysis

Due to the high stiffness of the biomaterials used in total knee arthroplasty, stress shielding can lead to decreased periprosthetic bone mineral density and bone resorption. As different materials and 3D-printed highly porous surfaces are available for knee femoral components from the industry nowadays, this study aimed to compare the effects of two same-design cruciate-retaining femoral components, made with CoCr and titanium alloy, respectively, on periprosthetic bone stresses through a finite element model of the implanted knee in order to evaluate the induced stress shielding. Moreover, the effect of the cementless highly porous surface of the titanium implant was analyzed in comparison to the cemented interface of the CoCr implant. The von Mises stresses were analyzed in different periprosthetic regions of interest of the femur with different configurations and knee flexion angles. The titanium component induced higher bone stresses in comparison with the CoCr component, mostly in the medial compartment at higher knee flexion angles; therefore, the CoCr component led to more stress shielding. The model was revealed to be effective in describing the effects of different femoral component materials on bone stress, highlighting how a cementless, highly porous titanium femoral component might lead to less stress shielding in comparison to a cemented CoCr implant with significant clinical relevance and reduced bone resorption after total knee arthroplasty.

Periprosthetic fractures: an unrecognized osteoporosis crisis

Total joint replacement is common and increasing. Many of these patients have low bone mineral density preoperatively, and arthroplasty leads to bone loss. As falls are common before and after arthroplasty, it is unsurprising that periprosthetic fractures, defined as those associated with an orthopedic device, whether a joint replacement or other internal fixation devices, are not rare. These fractures engender morbidity and mortality comparable to osteoporosis-related hip fractures but remain largely unrecognized and untreated by osteoporosis/metabolic bone disease clinicians. Indeed, recent osteoporosis guidelines are silent regarding periprosthetic fractures. The purposes of this clinical review are to briefly describe the epidemiology of arthroplasty procedures and periprosthetic fractures, raise awareness that these fractures are osteoporosis-related, and suggest approaches likely to reduce their occurrence. Notably, bone health evaluation is essential following the occurrence of a periprosthetic fracture to reduce subsequent fracture risk. Importantly, in addition to such secondary fracture prevention, primary prevention, i.e., bone health assessment and optimization prior to elective orthopedic procedures, is appropriate.

How resources affect management of periprosthetic fractures of the distal femur: perspectives from Israel, South Sudan, and South Africa

Periprosthetic fractures of the distal femur have significant morbidity in both total hip and total knee arthroplasty (THA and TKA, respectively). The incidence of these fractures is growing, with the predominant mechanism of injury being a fall from a standing height and therefore considered fragility fractures. In many countries, improved public funding and a flourishing private health care sector, when coupled with increased life expectancy, translates to more older patients receiving both TKA and THA and therefore an increased prevalence of periprosthetic fractures and their associated complications. These fractures may occur below a long stem THA, above a TKA, or between the two (so-called "interprosthetic fracture"). We will outline fracture classification, risk factors, diagnosis, and treatment options, highlighting perspectives on treating these fractures in Israel, South Africa, and South Sudan. These countries represent differing access to resources, varied comorbidity factors, and differing health care systems. The points of difference and the points of similarity will be considered.

Prevalence of osteoporosis and osteopenia in elderly patients scheduled for total knee arthroplasty

INTRODUCTION

Osteoporosis is a common comorbidity in elderly patients with osteoarthritis (OA) and may increase perioperative complications in orthopedic surgery (e.g., component migration, periprosthetic fractures). As there is no investigation of bone mineral density (BMD) in elderly patients prior to total knee arthroplasty (TKA) in Europe, we investigated this issue with a particular focus on a potential treatment gap.

MATERIALS AND METHODS

We assessed the BMD by dual-energy X-ray absorptiometry (DXA) in 109 consecutive elderly patients (age ≥ 70 years) scheduled for TKA. In addition to a detailed assessment of osteoporosis and osteopenia, the influence of clinical risk factors and radiological OA severity on BMD was evaluated using group comparisons and linear regression models. In addition, we analyzed differences in BMD between patients scheduled for TKA vs. total hip arthroplasty (THA).

RESULTS

Of the included 109 patients, 19 patients (17.4%) were diagnosed with osteoporosis and 50 (45.9%) with osteopenia. In the osteoporotic patients, a clinically relevant underdiagnosis concomitant with a serious treatment gap was observed in 95.0% of the patients. Body mass index, OA grade, and glucocorticoid use were identified as independent factors associated with BMD. No differences in BMD were found between the patients scheduled for TKA vs. THA.

CONCLUSIONS

Considering the high prevalence of osteoporosis and osteopenia in elderly patients, DXA screening should be recommended for patients ≥ 70 years indicated for TKA.

Humeral BMD can be Measured With DXA and Is Lower in the Surgical Arm After Total Shoulder Arthroplasty

BACKGROUND

As arthroplasty leads to bone loss, we hypothesized that humeral bone mineral density (BMD) is lower after total shoulder arthroplasty (TSA) in the operative versus non-operative arm. However, there is no clinical approach to measure humeral BMD with dual-energy x-ray absorptiometry (DXA). The purposes of this pilot study were to develop DXA methodology to measure humerus BMD, propose humerus regions of interest (ROIs), compare TSA BMD to the non-operative arm, correlate humeral BMD with standard sites, and evaluate measurement reproducibility.

METHODOLOGY

Thirty-eight adults 1-5 years post-TSA had standard clinical DXA scans plus full humerus scans using the atypical femur fracture feature; precision was assessed in a subset (n = 32). Six custom ROIs were used to measure BMD throughout the humerus. Radius and humeral BMD were compared between arms by paired t-test and correlated ipsilaterally using Pearson's Correlation. Custom ROI BMD precision was assessed using the International Society for Clinical Densitometry (ISCD) advanced precision calculator.

RESULTS

Study included 38 subjects (24M/14F), with mean (SD) age and time post-surgery of 69.6 (7.7) years and 2.5 (1.3) years respectively. BMD was lower (p &lt; 0.01) at all custom humerus sites (3.8% to 8.2%) on the surgical side but not different at radius sites. Humeral BMD correlated positively with ipsilateral ultra-distal and 1/3 radius (r = 0.54 to 0.86; p &lt; 0.05). Custom BMD precision (%CV) ranged from 6.0-16.0%.

CONCLUSIONS

Humerus BMD can be measured using DXA and is lower in the TSA arm. Radius BMD correlated with humeral BMD but was not lower in the surgical arm. BMD precision was worse than usual clinical sites; use of software optimized for the femur is a notable limitation and likely contributes to suboptimal precision. Further study to assess the clinical utility of humeral BMD is needed. Automation and optimization of these measurements should improve precision.

Medium Activity Prevents Periprosthetic Bone Mass Loss in the Medial Metaphyseal Region of the Tibia after Posterior-Stabilized TKA: A 5-Year Follow-up Study of 110 Knees

Objective

The bone mass around the prosthesis plays an important role in the stability of the prosthesis. This study aimed to assess the effect of postoperative activity on bone mineral density (BMD) in the proximal tibia 5 years after total knee arthroplasty (TKA). To provide a scientific guidance for postoperative functional exercise.

Methods

110 patients underwent unilateral primary TKA were divided into three groups based on the University of California Los Angeles (UCLA) activity scale: low activity group (LA group, UCLA = 4, 5); medium activity group (MA group, UCLA = 6, 7); and high activity group (HA group, UCLA = 8, 9). The primary observation was a comparison of the BMD and BMD change percentage (ΔBMD (%)) in the periprosthetic tibia among the LA, MA and HA groups at 1 year, 3 years and 5 years. The secondary observations were radiographic evaluation (prosthetic stability, periprosthetic fractures, aseptic loosening and periprosthetic joint infection) and clinical evaluation (Knee Society Score (KSS), visual analogue score scores and range of motion (ROM)). A one‐way ANOVA was used to compare the clinical scores and BMD among the three groups.

Results

The BMD of medial region decreased by 10.80%, 12.64%, 13.61% at 1, 3, and 5 years respectively; these were 5.72%, 6.26%, 7.83% in lateral region and 1.42%, 1.78%, 3.28% in diaphyseal region. For medial metaphyseal region, the BMD of the MA group was significantly greater than that of the LA and HA groups at 1 and 3 years (108.9 ± 5.2 vs. 106.1 ± 6.69 vs. 105.4 ± 5.2 and 108.5 ± 6.0 vs. 101.2 ± 6.76 vs. 103.0 ± 6.8, P < 0.01 and P < 0.001), and the BMD changes (ΔBMD (%)) in the MA group were significantly smaller than those in the LA and HA groups (8.75 ± 5.36 vs. 11.92 ± 5.49 vs. 12.70 ± 5.21 and 9.11 ± 5.11 vs. 16.04 ± 4.79 vs. 14.82 ± 4.26, P < 0.01 and P < 0.001).

Regarding secondary observations, all of the prostheses were assessed as stable, without periprosthetic fractures, aseptic loosening and periprosthetic joint infection. Regarding KSS scores, there was no significant difference among the three groups. However, the VAS and ROM of the HA group were better than those of the MA and LA groups (1.65 ± 0.79 vs. 2.63 ± 0.77 vs. 3.00 ± 1.17, p < 0.001, and 111.90 ± 9.17 vs. 110.20 ± 6.78 vs. 102.90 ± 8.48, P < 0.001).

Conclusion

Medium activity prevented periprosthetic bone loss in the medial metaphyseal region of the tibia after posterior‐stabilized TKA, and moderate‐intensity exercise is recommended for patients after TKA to reduce periprosthetic bone loss.

A cemented mobile-bearing total knee prosthesis prevents peri-prosthetic bone mineral density loss around the femoral component: a consecutive follow-up at a mean of 11 years

PURPOSE

Research has shown that a cemented mobile-bearing component has a favorable effect on the bone mineral density (BMD) of the distal femur at 2 years after total knee arthroplasty (TKA). This study was performed to determine whether the advantage on BMD of a cemented mobile-bearing TKA over a conventional cemented fixed-bearing TKA changes with time. This report is an update of a matched cohort study initiated in 2004 and for which the 2-year results have been published.

METHODS

Twenty-eight knees that were treated with a fixed-bearing posterior stabilized (PS) prosthesis and 28 matched knees from a database of 76 knees that were treated with a mobile-bearing PS prosthesis in the same period were investigated. All knees underwent dual-energy X-ray absorptiometry (DEXA) scans around the femoral component preoperatively, 2 weeks postoperatively, 5 years postoperatively, and annually thereafter. Eighteen knees with a cemented mobile-bearing PS prosthesis and 20 knees with a cemented fixed-bearing PS prosthesis were investigated for more than 6 years. The mean follow-up period was 11 years.

RESULTS

The range of motion, Knee Society Score, BMD of the lumbar spine, and follow-up period were not significantly different preoperatively and postoperatively in the two groups. In the fixed-bearing group, the BMD of the anterior part of the femoral condyle decreased postoperatively. In the mobile-bearing group, the BMD of the posterior part of the femoral condyle increased postoperatively. The postoperative change in the BMD at 5 years and the latest follow-up period was statistically significant in the two groups.

CONCLUSIONS

This DEXA study revealed that a cemented mobile-bearing component had a favorable effect on the BMD of the distal femur after TKA even at a mean of 11 years postoperatively.

LEVEL OF EVIDENCE

Therapeutic study, level II, prospective comparative study.

Proceedings of the 2021 Santa Fe Bone Symposium: Advances in the Management of Osteoporosis and Metabolic Bone Diseases

The 2021 Virtual Santa Fe Bone Symposium was held August 5-8, with over 300 registered attendees from throughout the USA, and at least 18 other countries. This annual meeting focuses on applying advances in basic science and clinical research to the care of patients with osteoporosis and those with inherited and acquired disorders of bone metabolism. Participants represented a broad range of medical disciplines with an interest in skeletal diseases. These included physicians of many specialties and practice settings, fellows, advanced practice providers, fracture liaison service (FLS) coordinators, clinical researchers, and bone density technologists. There were lectures, case presentations, and panel discussions, all followed by interactive discussions. Breakout sessions included an FLS workshop, Bone Health TeleECHO workshop, special interest groups, meet-and-greet the faculty, and satellite symposia. The agenda covered topics of interest such as strategies for the use of osteoanabolic therapy, prevention of periprosthetic fractures, management of atypical femur fractures, what we know and don't know about vitamin D, advances in the use of dual-energy X-ray absorptiometry in the assessment of skeletal health, controversies and conundrums in osteoporosis care, skeletal health in transgender patients, management of patients with hypophosphatasia and hypophosphatemia, and treat-to-target approaches for managing patients with osteoporosis. The Proceedings of the 2021 Virtual Santa Fe Bone Symposium consists of highlights of each presentation with current strategies for optimizing the care of patients with skeletal disorders.

Proximal tibial bone loss in the first 2 years after unicondylar knee arthroplasty: Anatomical pattern, predictors and clinical correlation

BACKGROUND

Tibial stress fracture, anteromedial bone pain, and early subsidence could occur after unicondylar knee arthroplasty (UKA). The change in metaphyseal tibial bone density (MTBD) in the coronal and sagittal planes after UKA might be a contributing factor, but this has rarely been investigated. The aim of this study was to assess the regional and temporal change in MTBD in the coronal and sagittal planes in the first 2 years after UKA.

METHODS

Patients with fixed-bearing medial UKA were recruited. The change in MTBD in the first 24 months after UKA using digital radiological densitometry (DRD) was measured. Potential predictors and clinical correlations were analyzed.

RESULTS

Eighty-four cases (female 60%) were selected for review. The follow up time was 63 (±17) months. Anterior and medial regions had the largest proportion of cases with MTBD reduction (90-97%, P < 0.05). Reduction was largest at anterior and medial regions (21-29%, P < 0.05) and smallest at posterior and lateral regions (5-15%, P < 0.05). Maximal reduction occurred at 12 months for the medial region and 24 months for the anterior region. MTBDs of both regions were not significantly influenced by any confounding factors. Significant correlation was found between medial MTBD and Function Score at 6 months.

CONCLUSIONS

Bone loss in a zonal pattern occurs in the first 2 years after UKA with the largest loss in the anterior region below the tibial tray. It is not affected by body mass index, perioperative alignment, or angle of correction. This suggests a physiological response to trauma other than a mechanical response to the change in bone strain.

Anterior femoral notching ≥ 3 mm is associated with increased risk for supracondylar periprosthetic femoral fracture after total knee arthroplasty: a systematic review and meta-analysis

PURPOSE

Anterior femoral notching (AFN) may be associated with a higher risk for supracondylar periprosthetic fracture (sPPF) after total knee arthroplasty (TKA), although studies have yielded inconclusive results. We aimed to systematically investigate and meta-analyze the best available evidence regarding the association between AFN and the risk of sPPF after TKA.

METHODS

A comprehensive search of PubMed, Scopus, Mendeley, Google Scholar and Cochrane databases was performed, from conception to February 29, 2020. Data were expressed as odds ratio (OR) with 95% confidence intervals (CI). I²-index was employed for heterogeneity. Newcastle-Ottawa scale was implemented for quality assessment of the included studies.

RESULTS

Nine studies fulfilled the eligibility criteria, including a total of 3264 patients subjected to TKA. Among them, there were 150 patients who sustained a sPPF. Overall, patients exposed to AFN (AFN group) demonstrated an increased risk for sPPF compared to those not exposed (control group) (OR 3.91, 95% CI 1.22-12.58, p = 0.02; I² 68.52%). Subgroup analysis based on AFN depth with a cut-off value of 3 mm further clarified this association. Patients with AFN ≥ 3mm were at higher risk for sPPF compared to patients with AFN < 3 mm and control group (OR 4.85, 95% CI 2.08-11.33, p = 0.00; I² 0.0%). On the contrary, fracture risk was not significant for patients with AFN < 3 mm compared to the control group (OR 5.0, 95% CI 0.44-56.82, p = 0.19; I² 42.99%).

CONCLUSION

Patients, exposed to AFN ≥ 3 mm in depth, are at higher risk for sustaining a sPPF.

Osteoporosis: Recent Recommendations and Positions of the American Society for Bone and Mineral Research and the International Society for Clinical Densitometry

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Osteoporosis is common in orthopaedic patients, not only in those sustaining fragility fractures but also in patients ≥50 years old who are having elective orthopaedic surgery.

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The American Society for Bone and Mineral Research (ASBMR) has developed consensus-based recommendations for secondary fracture prevention for all patients who are ≥65 years old with a hip or spine fracture.

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The ASBMR encourages orthopaedic surgeons to "Own the Bone," by beginning prevention of a secondary fracture during hospitalization for a fragility fracture, if practicable, and arranging follow-up for continued bone health care after discharge.

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The International Society for Clinical Densitometry (ISCD) recognized that many poor outcomes and complications of elective orthopaedic surgery are related to osteoporosis.

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The ISCD used an evidence-based approach to create official positions to identify which patients ≥50 years old who are having elective orthopaedic surgery should undergo assessment of bone health and how this should be performed.

[Progress of change in bone mineral density after knee arthroplasty]

Objective

To summarize research progress of change in bone mineral density (BMD) after knee arthroplasty and its diagnostic methods, influencing factors, and drug prevention and treatment.

Methods

The relevant literature at home and abroad was reviewed and summarized from research status of the advantages and disadvantages of BMD assessment methods, the trend of changes in BMD after knee arthroplasty and its influencing factors, and the differences in effectiveness of drugs.

Results

The central BMD and mean BMD around the prosthesis decrease after knee arthroplasty, which is closely associated with body position, age, weight, daily activities, and the fixation methods, design, and material of prosthesis. Denosumab, bisphosphonates, and teriparatide et al. can decrease BMD loss after knee arthroplasty.

Conclusion

BMD after knee arthroplasty decreases, which is related to various factors, but the mechanism is unclear. At present, some inhibitors of bone resorption can decrease BMD loss after knee arthroplasty. However, its long-term efficacy remains to be further explored.

An Exploratory Study of the Texture Research Investigational Platform (TRIP) to Evaluate Bone Texture Score of Distal Femur DXA Scans - A TBS-Based Approach

Poor bone status is associated with increased complications following orthopedic surgery. Therefore, assessing site-specific skeletal status prior to or after orthopedic surgery to optimize outcomes is appealing. The trabecular bone score (TBS) approach, a surrogate for microarchitecture, was adapted to the Texture Research Investigational Platform (TRIP), which allows assessment of many skeletal sites imaged by various modalities. TRIP generates a bone texture score (TBS ORTHO), which could potentially guide surgical decision-making and offer insight into postsurgical fracture risk. As distal femur bone loss occurs following total knee arthroplasty (TKA), we hypothesized that TBS ORTHO after TKA would identify poorer texture in the operated femur compared to the nonoperated. We evaluated 30 subjects (15 M/15 F) with unilateral TKA 2-5 yr previously, mean age 67.9 yr and body mass index 30 kg/m². Using a Lunar iDXA, lumbar spine and entire femur scans were obtained, the latter using the atypical femur fracture feature. Distal femur bone mineral density (BMD) and TBS ORTHO were obtained using manual regions of interest (ROI) at 15% and 25% of leg length from the intercondylar notch. TBS ORTHO was determined using distal femur DICOM images and TRIP v1.0 (Medimaps, France). Differences in operated vs nonoperated femur were evaluated by paired t test. As previously reported, operated leg BMD was approx 10% lower at 15% and 25% ROIs. Similarly, TBS ORTHO values in the operated leg were approx 5% lower (p < 0.05) at these same ROIs. Distal femur TBS ORTHO and BMD were largely unrelated. TBS ORTHO reproducibility at these ROIs was approx 3.5%. In conclusion, this pilot study documents the feasibility of reproducibly obtaining distal femur TBS ORTHO values. Lower values were observed in the surgical leg, consistent with the bone loss that follows TKA. Further work is indicated to refine TRIP use and evaluate whether such data provides guidance for surgical decision-making and improves periprosthetic fracture prediction.

Prevalence and Treatment of Osteoporosis Prior to Elective Shoulder Arthroplasty

Introduction:

The rate of preoperative osteoporosis in lower extremity arthroplasty is 33%. The prevalence of osteoporosis in shoulder arthroplasty patients is inadequately studied. The purpose of this study was to (1) determine the prevalence of osteoporosis in patients undergoing elective shoulder arthroplasty, (2) report the percentage of patients having dual-energy x-ray absorptiometry (DEXA) testing before surgery, and (3) determine the percentage of patients who have been prescribed osteoporosis medications within 6 months before or after surgery.

Methods:

This retrospective case series included all adults aged 50 years and older who underwent elective shoulder arthroplasty at a single tertiary care center over an 8-year period. National Osteoporosis Foundation (NOF) criteria for screening and treatment were applied.

Results:

Two hundred fifty-one patients met the inclusion criteria; 171 (68%) met the criteria for DEXA testing, but only 31 (12%) had this testing within 2 years preoperatively. Eighty patients (32%) met the NOF criteria for receipt of pharmacologic osteoporosis treatment, and 17/80 (21%) received a prescription for pharmacotherapy.

Discussion:

Two-thirds of elective shoulder arthroplasty patients meet the criteria to have bone mineral density measurement done, but less than 20% have this done. One in three elective shoulder arthroplasty patients meet the criteria to receive osteoporosis medications, but only 20% of these patients receive therapy.

Biomechanics of Implant Fixation in Osteoporotic Bone

PURPOSE OF REVIEW

The purpose of this review is to critically evaluate the current literature regarding implant fixation in osteoporotic bone.

RECENT FINDINGS

Clinical studies have not only demonstrated the growing prevalence of osteoporosis in patients undergoing total joint replacement (TJR) but may also indicate a significant gap in screening and treatment of this comorbidity. Osteoporosis negatively impacts bone in multiple ways beyond the mere loss of bone mass, including compromising skeletal regenerative capacity, architectural deterioration, and bone matrix quality, all of which could diminish implant fixation. Recent findings both in preclinical animal models and in clinical studies indicate encouraging results for the use of osteoporosis drugs to promote implant fixation. Implant fixation in osteoporotic bone presents an increasing clinical challenge that may be benefitted by increased screening and usage of osteoporosis drugs.

Unrecognized Osteoporosis Is Common in Patients With a Well-Functioning Total Knee Arthroplasty

BACKGROUND

Peri-prosthetic fractures after total knee arthroplasty (TKA) are associated with poorer outcomes and high costs. We hypothesize that osteoporosis is under-recognized in the TKA population. The purpose of this study is to report osteoporosis prevalence in a healthy cohort of patients with well-functioning TKA and to compare prevalence between males and females.

METHODS

This study is a cross-sectional study of 30 adults (15 males/15 females) aged 59-80 years without known bone health issues who volunteered to undergo routine dual-energy X-ray absorptiometry 2-5 years (average 3.2 ± 0.8) after primary unilateral TKA. These data plus clinical risk factors were used to estimate fracture risk via the Fracture Risk Assessment Tool and skeletal status (normal, osteopenic, osteoporotic) was determined based on the World Health Organization definition. The National Osteoporosis Foundation criteria for treatment were applied to all patients.

RESULTS

Six of 30 (20%) patients had T-score ≤ -2.5. Eighteen of 30 (60%) patients had T-score between -1 and -2.5 and 6 (20%) patients had T-score ≥ -1. Five patients with normal or osteopenic bone mineral density (BMD) had occult vertebral fractures. Eleven of 30 (36.7%) patients met National Osteoporosis Foundation criteria for pharmacologic treatment.

CONCLUSION

The prevalence of occult osteoporosis meeting treatment guidelines after TKA is substantial in this sample (36.7%). BMD and osteoporosis prevalence are similar between men and women. This underappreciated prevalence of osteoporosis may contribute to peri-prosthetic fracture risk. Arthroplasty surgeons and bone health specialists must be aware of post-operative changes in bone density. These data support the further study of post-operative osteoporosis and consideration of routine BMD screening after TKA.

LEVEL OF EVIDENCE

III.

Use of Bone Health Evaluation in Orthopedic Surgery: 2019 ISCD Official Position

This position development conference (PDC) Task Force examined the assessment of bone status in orthopedic surgery patients. Key questions included which orthopedic surgery patients should be evaluated for poor bone health prior to surgery and which subsets of patients are at high risk for poor bone health and adverse outcomes. Second, the reliability and validity of using bone densitometry techniques and measurement of specific geometries around the hip and knee before and after arthroplasty was determined. Finally, the use of computed tomography (CT) attenuation coefficients (Hounsfield units) to estimate bone quality at anatomic locations where orthopedic surgery is performed including femur, tibia, shoulder, wrist, and ankle were reviewed. The literature review identified 665 articles of which 198 met inclusion exclusion criteria and were selected based on reporting of methodology, reliability, or validity results. We recommend that the orthopedic surgeon be aware of established ISCD guidelines for determining who should have additional screening for osteoporosis. Patients with inflammatory arthritis, chronic corticosteroid use, chronic renal disease, and those with history of fracture after age 50 are at high risk of osteoporosis and adverse events from surgery and should have dual energy X-ray absorptiometry (DXA) screening before surgery. In addition to standard DXA, bone mineral density (BMD) measurement along the femur and proximal tibia is reliable and valid around implants and can provide valuable information regarding bone remodeling and identification of loosening. Attention to positioning, selection of regions of interest, and use of special techniques and software is required. Plain radiographs and CT provide simple, reliable methods to classify the shape of the proximal femur and to predict osteoporosis; these include the Dorr Classification, Cortical Index, and critical thickness. Correlation of these indices to central BMD is moderate to good. Many patients undergoing orthopedic surgery have had preoperative CT which can be utilized to assess regional quality of bone. The simplest method available on most picture archiving and communications systems is to simply measure a regions of interest and determine the mean Hounsfield units. This method has excellent reliability throughout the skeleton and has moderate correlation to DXA based on BMD. The prediction of outcome and correlation to mechanical strength of fixation of a screw or implant is unknown.