Low Preoperative BMD Is Related to High Migration of Tibia Components in Uncemented TKA-92 Patients in a Combined DEXA and RSA Study With 2-Year Follow-Up

Osteoporosis May Not Be an Absolute Contraindication for Cementless Total Knee Arthroplasty

BACKGROUND

Cementless total knee arthroplasty (TKA) has received growing interest, particularly in younger populations, due to potential long-term survivability and improved bone preservation. Poor bone stock, as seen in osteoporosis, is considered a contraindication for this technique. This study evaluated whether osteoporotic patients < 75 years undergoing cementless TKA demonstrate similar: 1) implant-related complications, 2) medical complications, 3) readmission rates, and 4) 3-year implant survivability.

METHODS

A retrospective query of a national administrative claims database was performed between 2010 and 2022 for patients less than or equal to 75 years old who have osteoporosis and underwent primary TKA. Osteoporotic patients were divided into cementless and cemented cohorts, and propensity scores were matched based on age, sex, obesity, and the Charlson Comorbidity Index. Matching produced 7,923 patients (1,321 uncemented, 6,602 cemented). Multivariate logistic regressions evaluated the following outcomes: 90-day and 2-year implant-related complications, 90-day postoperative medical complications, and 90-day readmissions. Kaplan-Meier survival analysis was conducted to assess 3-year all-cause revision implant survivability. The significance threshold was set to P < 0.01 to minimize type 1 bias.

RESULTS

There were no statistically significant differences in implant-related complications, medical complications, readmissions, and lengths of stay between cementless and cemented TKA groups. Kaplan-Meier analysis demonstrated statistically similar 3-year survivability between cohorts (cemented: 97.6%, confidence interval 96.6 to 98.5; cementless: 97.2%, confidence interval 96.7 to 97.7; P = 0.472).

CONCLUSIONS

Patients who have osteoporosis have equivalent medical and implant-related complications as well as 3-year implant survival following cementless TKA compared with a cemented technique. Our results support cementless TKA as a viable option for patients < 75 years, regardless of prior diagnosis of osteoporosis. Intraoperative decisions regarding bone quality are still necessary to discriminate between those who are candidates for cementless TKA with those who are not.

LEVEL OF EVIDENCE

Level III, Retrospective cohort study.

Osteoporosis in the setting of knee arthroplasty: a narrative review

Patients undergoing knee replacement, which is mainly indicated in severe osteoarthritis, are frequently co-affected by osteoporosis and osteopenia. With a prevalence standing at around 20% in patients receiving knee arthroplasty, osteoporosis could lead to poor outcomes postoperatively. Some of these complications include periprosthetic fractures and an increased revision rate. Antiresorptive medications have been shown to be beneficial postoperatively. However, no studies have been conducted on whether they had any benefits if given preoperatively. Surgical management may also be beneficial, but this area remains full of controversy.

Prospective randomized study on the effect of concurrent bone filling of tibial peg holes in cementless total knee arthroplasty

BACKGROUND

In total knee arthroplasty (TKA), cementless fixation is initially weaker than cement fixation. This study aimed to examine whether filling the tibial peg holes with bone improves initial fixation strength in cementless TKA.

METHODS

This prospective, comparative study examined 88 joints in 66 patients randomized to the bone filling (48 joints) or conventional group (no bone filling; 40 joints). All patients underwent TKA with the NexGen® trabecular metal modular tibial component. In the bone filling group, resected cancellous bone was filled into the peg holes before insertion of the tibial component. We performed clinical and plain radiographic evaluations after the operation and measured bone mineral density (BMD) at five sites below the component at 1, 3, 6, and 12 months postoperatively.

RESULTS

Operative time and clinical evaluations were not significantly different. Plain radiography showed significant longitudinal thickening of the trabecula below the peg (P<0.05) and decreased occurrence of reactive lines (P=0.07) in the bone filling group compared with the conventional group. BMD was significantly higher in the bone filling group in the medial region below the peg at 1, 3, and 6 months and in the central region at 1 and 3 months (all P<0.05).

CONCLUSIONS

When using the NexGen trabecular metal modular tibial component, concurrent peg hole bone filling increases the initial component fixation strength. Possible effects on long-term stabilization warrant further study.

Cementless Total Knee Arthroplasty: A Resurgence-Who, When, Where, and How?

BACKGROUND

Total knee arthroplasty (TKA) is one of the most common procedures in orthopaedics, but there is still debate over the optimal fixation method for long-term durability: cement versus cementless bone ingrowth. Recent improvements in implant materials and technology have offered the possibility of cementless TKA to change clinical practice with durable, stable biological fixation of the implants, improved operative efficiency, and optimal long-term results, particularly in younger and more active patients.

METHODS

This symposium evaluated the history of cementless TKA, the recent resurgence, and appropriate patient selection, as well as the historical and modern-generation outcomes of each implant (tibia, femur, and patella). Additionally, surgical technique pearls to assist in reliable, reproducible outcomes were detailed.

RESULTS

Historically, cemented fixation has been the gold standard for TKA. However, cementless fixation is increasing in prevalence in the United States and globally, with equivalent or improved results demonstrated in appropriately selected patients.

CONCLUSIONS

Cementless TKA provides durable biologic fixation and successful long-term results with improved operating room efficiency. Cementless TKA may be broadly utilized in appropriately selected patients, with intraoperative care taken to perform meticulous bone cuts to promote appropriate bony contact and biologic fixation.

The Association Between Oral Bone Mineral Density-Reducing Medications and the Risk of 2-Year Implant-Related Complications Following Total Knee Arthroplasty

BACKGROUND

Certain medications interfere with the bone remodeling process and may potentially increase the risk of complications after total knee arthroplasty (TKA). As patients undergoing TKA may be taking these bone mineral density (BMD)-reducing medications, it is unclear as to whether and which medications impact TKA outcomes. Therefore, the purpose of this study was to observe the impact of various BMD-reducing medications on 2-year implant-related complications following TKA.

METHODS

A retrospective analysis of patients undergoing primary TKA was conducted using a national administrative claims database. Patients were identified if they were taking any known BMD-reducing medication and were compared to control patients. To control for confounders associated with taking multiple agents, multivariable logistic regression analyses were conducted for each 2-year outcome (all-cause revision, loosening-indicated revision, and periprosthetic fracture--indicated revision), with the output recorded as odds ratios (ORs).

RESULTS

In our study, 502,927 of 1,276,209 TKA patients (39.4%) were taking at least one BMD-reducing medication perioperatively. On multivariable analysis, medications associated with a higher likelihood of 2-year all-cause revision included first- and second-generation antipsychotics (SGAs) (OR: 1.42 and 1.26, respectively), selective serotonin reuptake inhibitors (SSRIs) (OR: 1.14), glucocorticoids (1.13), and proton pump inhibitors (PPIs) (OR: 1.23) (P < .05 for all). Medications associated with a higher likelihood of 2-year periprosthetic fracture included SGAs (OR: 1.51), SSRIs (OR: 1.27), aromatase inhibitors (OR: 1.29), and PPIs (OR: 1.42) (P < .05 for all).

CONCLUSIONS

Of the drug classes observed, the utilization of perioperative PPIs, SSRIs, glucocorticoids, first-generation antipsychotics, and SGAs was associated with the highest odds of all-cause revision. Our findings suggest a relationship between these medications and BMD-related complications; however, further studies should seek to determine the causality of these relationships.

Is Tibial Bone Mineral Density Related to Sex, Age, Preoperative Alignment, or Fixation Method in Primary Total Knee Arthroplasty?

BACKGROUND

Cementless total knee arthroplasty (TKA) has regained interest for its potential for long-term biologic fixation. The density of the bone is related to its ability to resist static and cyclic loading and can affect long-term implant fixation; however, little is known about the density distribution of periarticular bone in TKA patients. Thus, we sought to characterize the bone mineral density (BMD) of the proximal tibia in TKA patients.

METHODS

We included 42 women and 50 men (mean age 63 years, range: 50 to 87; mean body mass index 31.6, range: 20.5 to 49.1) who underwent robotic-assisted TKA and had preoperative computed tomography scans with a BMD calibration phantom. Using the robotic surgical plan, we computed the BMD distribution at 1 mm-spaced cross-sections parallel to the tibial cut from 2 mm above the cut to 10 mm below. The BMD was analyzed with respect to patient sex, age, preoperative alignment, and type of fixation.

RESULTS

The BMD decreased from proximal to distal. The greatest changes occurred within ± 2 mm of the tibial cut. Age did not affect BMD for men; however, women between 60 and 70 years had higher BMD than women ≥ 70 years for the total cut (P = .03) and the medial half of the cut (P = .03). Cemented implants were used in 1 86-year-old man and 18 women (seven < 60 years, seven 60 to 70 years, and four ≥ 70 year old). We found only BMD differences between cemented or cementless fixation for women < 60 years.

CONCLUSIONS

To our knowledge, this is the first study to characterize the preoperative BMD distribution in TKA patients relative to the intraoperative tibial cut. Our results indicate that while sex and age may be useful surrogates of BMD, the clinically relevant thresholds for cementless knees remain unclear, offering an area for future studies.

Periprosthetic tibial fracture as a complication of unicompartmental knee arthroplasty: Current insights

Periprosthetic fracture following knee arthroplasty is a rare but devastating complication associated with significant morbidity. With unicompartmental knee arthroplasty being performed far less frequently than total knee arthroplasty, periprosthetic fracture following unicompartmental knee arthroplasty presents a particular challenge to orthopaedic surgeons, due to clinical unfamiliarity and sparsity of literature. An up-to-date review of the epidemiology, risk factors, and management strategies for PPF after UKA is presented.

Cementless Total Knee Arthroplasty: Is it Safe in Demineralized Bone?

There is concern for cementless total knee arthroplasty (TKA) in patients with decreased bone mineral density (BMD) due to the potential increase in complications, namely failed in-growth or future aseptic loosening. Some data suggest that advances in cementless prostheses mitigate these risks; however this is not yet born out in long-term registry data. It is crucial to expand our understanding of the prevalence and etiology of osteoporosis in TKA patients, survivorship of cementless implants in decreased BMD, role of bone-modifying agents, indications and technical considerations for cementless TKA in patients with decreased BMD. The purpose of this study is to review current literature and expert opinion on such topics.

Cementless Total Knee Arthroplasty: A State-of-the-Art Review

» The demographic profile of candidates for total knee arthroplasty (TKA) is shifting toward younger and more active individuals.» While cemented fixation remains the gold standard in TKA, the interest is growing in exploring cementless fixation as a potentially more durable alternative.» Advances in manufacturing technologies are enhancing the prospects for superior long-term biological fixation.» Current research indicates that intermediate to long-term outcomes of modern cementless TKA designs are comparable with traditional cemented designs.» The selection of appropriate patients is critical to the success of cementless fixation techniques in TKA.» There is a need for high-quality research to better understand the potential differences and relative benefits of cemented vs. cementless TKA systems.

Osteoporosis and Total Knee Arthroplasty: Higher 5-Year Implant-Related Complications

BACKGROUND

The risk of revision surgery in patients who have osteoporosis after total knee arthroplasty (TKA) is understudied. Our aim was to compare the 5-year cumulative risk of revision surgery after TKA in patients who have preoperative osteoporosis.

METHODS

A national administrative claims database was queried for patients undergoing primary TKA from 2010 to 2021. There were 418,054 patients included, and 41,760 (10%) had osteoporosis. The 5-year incidence of revision surgery was examined for all-causes, periprosthetic fracture (PPF), aseptic loosening, and periprosthetic joint infection (PJI). A multivariable analysis was conducted using Cox proportional hazards models. Hazards ratios (HRs) were reported with 95% confidence intervals (CIs).

RESULTS

The 5-year rate of all-cause revision surgery was higher for patients who had osteoporosis (HR 1.1, 95% CI: 1.0 to 1.2), however, the highest risk of revision surgery was seen for PPF (HR 1.8, 95% CI: 1.6 to 2.1). Patients who had osteoporosis also had elevated risk of revision surgery for PJI (HR 1.2, 95% CI: 1.1 to 1.3) and aseptic loosening (HR 1.2, 95% CI: 1.1 to 1.3). Osteoporosis was independently associated with PJI and aseptic loosening at a higher rate in obese patients.

CONCLUSIONS

In unadjusted survival analysis, those who had osteoporosis have a marginally lower risk of all-cause revision surgery. However, after controlling for age, sex and comorbidities, patients who had osteoporosis have a nearly 2-fold increased risk of 5-year revision for PPF after TKA, and mildly increased risk of revision for all causes, aseptic loosening, and PJI. Obesity may also modulate this association. Future studies should determine the extent to which treatment of osteoporosis modifies these postoperative outcomes.

The Microbial Revolution in the World of Joint Replacement Surgery

Background

The prevalence of revision surgery due to aseptic loosening and periprosthetic joint infection (PJI) following total hip and knee arthroplasty is growing. Strategies to prevent the need for revision surgery and its associated health-care costs and patient morbidity are needed. Therapies that modulate the gut microbiota to influence bone health and systemic inflammation are a novel area of research.

Methods

A literature review of preclinical and clinical peer-reviewed articles relating to the role of the gut microbiota in bone health and PJI was performed.

Results

There is evidence that the gut microbiota plays a role in maintaining bone mineral density, which can contribute to osseointegration, osteolysis, aseptic loosening, and periprosthetic fractures. Similarly, the gut microbiota influences gut permeability and the potential for bacterial translocation to the bloodstream, increasing susceptibility to PJI.

Conclusions

Emerging evidence supports the role of the gut microbiota in the development of complications such as aseptic loosening and PJI after total hip or knee arthroplasty. There is a potential for microbial therapies such as probiotics or fecal microbial transplantation to moderate the risk of developing these complications. However, further investigation is required.

Clinical Relevance

Modulation of the gut microbiota may influence patient outcomes following total joint arthroplasty.

Validation for the effect of intra-exposure patient motion on the assessment of radiostereometric implant migration in a tibial component phantom study

BACKGROUND

An increasing number of radiostereometry (RSA) research studies have long-term follow-up implant migration outcomes, which show ascending curves of implant migration with occasionally decreasing migration. After scrutinizing images and RSA scenes related to the alternating curves, we suppose that intra-exposure patient motion may contribute to that. The main purposes of this in vitro study were 1) to identify whether the patient motion in different directions could result in the inaccurate assessment of implant migration, and 2) to figure out which direction(s) accounted for the alternating curves.

HYPOTHESIS

It was hypothesized that the assessments of implant migration would be less precise and accurate than they could be when patient motion occurred, and such motion would contribute to the alternating curves of radiostereometric implant migration.

MATERIALS AND METHODS

A customized phantom, assembled with a tibial component, was designed for simulating intra-exposure patient motion during follow-up RSA examinations. Two different Roentgen tubes were used as the current standard of radiology departments. Radiographs were acquired in a uniplanar technical arrangement. Two defined protocols were conducted: one is to simulate implant migration outcomes at post-op, the early stage (6months), and the later stage (2 to 10years) ; during the later stage, the other is to mimic patient motion by phantom motion in the medial-lateral (x), distal-proximal (y), and anterior-posterior (z) axes.

RESULTS

Phantom motion could result in the inaccurate assessment of implant migration, and translations along the medial-lateral (x) axis were the most influenced by patient motion. Motion along the medial-lateral (x) axis could account for the curves with decreasing migration.

DISCUSSION

Our assessments of implant migration may be less precise and accurate than they could be when intra-exposure patient motion occurs. We probably neglect the importance of 100% simultaneous exposures, and the influence of patient motion on RSA accuracy and data reliability, due to the difficulty in detecting patient (micro)motion. Electronically synchronized exposures of two paired Roentgen tubes are 100% simultaneous for image acquisition, and they are thus highly recommended for the assessment of implant migration in RSA.

TYPE OF STUDY AND LEVEL OF PROOF

not applicable.

Quantifying the immediate post-implantation strain field of cadaveric tibiae implanted with cementless tibial trays: A time-elapsed micro-CT and digital volume correlation analysis during stair descent

Primary stability, the mechanical fixation between implant and bone prior to osseointegration, is crucial for the long-term success of cementless tibial trays. However, little is known about the mechanical interplay between the implant and bone internally, as experimental studies quantifying internal strain are limited. This study employed digital volume correlation (DVC) to quantify the immediate post-implantation strain field of five cadaveric tibiae implanted with a commercially available cementless titanium tibial tray (Attune, DePuy Synthes). The tibiae were subjected to a five-step loading sequence (0-2.5 bodyweight, BW) replicating stair descent, with concomitant time-elapsed micro-CT imaging. With progressive loads, increased compression of trabecular bone was quantified, with the highest strains directly under the posterior region of the tibial tray implant, dissipating with increasing distance from the bone-implant interface. After load removal of the last load step (2.5BW), residual strains were observed in all of the five tibiae, with residual strains confined within 3.14 mm from the bone-implant interface. The residual strain is reflective of the observed initial migration of cementless tibial trays reported in clinical studies. The presence of strains above the yield strain of bone accepted in literature suggests that inelastic properties should be included within finite element models of the initial mechanical environment. This study provides a means to experimentally quantify the internal strain distribution of human tibia with cementless trays, increasing the understanding of the mechanical interaction between bone and implant.

Preoperative proximal tibial bone density, bone microarchitecture, and bone turnover are not associated with postoperative tibial component migration in cemented and cementless medial unicompartmental knee replacements: secondary analyses from a randomized controlled trial

BACKGROUND AND PURPOSE

Cementless arthroplasty fixation relies on early bone ingrowth and may be poor in patients with low proximal tibial bone density or abnormal bone turnover. We aimed first to describe the baseline bone properties in patients undergoing medial unicompartmental knee replacement (UKR), and second to investigate its association with cemented and cementless tibial component migration until 2 years.

METHODS

A subset investigation of 2 patient groups from a 3-armed randomized controlled trial was conducted. There were 26 cemented and 25 cementless medial UKRs with twin-pegged femoral components. Volumetric bone mineral density (vBMD) and microstructure of the excised medial tibial plateau were ascertained with µCT. Bone turnover was estimated using dynamic histomorphometry (eroded surface/bone surface = ES/BS, osteoid surface/bone surface = OS/BS, mineralizing surface/bone surface = MS/BS). Tibial component migration in 4 feature points was followed for 2 years with radiostereometry.

RESULTS

At the 2-year follow-up, the cementless tibial components migrated 0.38 mm (95% confidence interval [CI] 0.14-0.62) total translation more than the cemented components at the posterior feature point. The greatest migration in the cementless group was subsidence at the posterior feature point of 0.66 mm (CI 0.48-0.84) until 6 weeks, and from 3 months the components were stable. Cemented tibial components subsided very little. Between 1- and 2-year follow-ups, no cementless but 4 cemented tibial components revealed continuous migration. OS/BS was half of the ES/BS. No µCT or histomorphometric parameters showed any clinically relevant correlation with tibial component migration at the posterior feature point for either cemented or cementless UKR at 6 weeks' or 2 years' follow-up after adjustment for age, BMI, and sex.

CONCLUSION

Preoperative vBMD, bone turnover, and microstructure were not associated with postoperative tibial component migration of cemented and cementless medial UKR.

Machine Learning for Opportunistic Screening for Osteoporosis and Osteopenia Using Knee CT Scans

PURPOSE

To predict whether a patient has osteoporosis/osteopenia using the attenuation of trabecular bone obtained from knee computed tomography (CT) scans.

METHODS

Retrospective analysis of 273 patients who underwent contemporaneous knee CT scans and dual-energy X-ray absorptiometry (DXA) within 1 year. Volumetric segmentation of the trabecular bone of the distal femur, proximal tibia, patella, and proximal fibula was performed to obtain the bone CT attenuation. The data was randomly split into training/validation (78%) and test (22%) datasets and the performance in the test dataset were evaluated. The predictive properties of the CT attenuation of each bone to predict osteoporosis/osteopenia were assessed. Multivariable support vector machines (SVM) and random forest classifiers (RF) were used to predict osteoporosis/osteopenia.

RESULTS

Patients with a mean age (range) of 67.9 (50-87) years, 85% female were evaluated. Seventy-seven (28.2%) of patients had normal bone mineral density (BMD), 140 (51.3%) had osteopenia, and 56 (20.5%) had osteoporosis. The proximal tibia had the best predictive ability of all bones and a CT attenuation threshold of 96.0 Hounsfield Units (HU) had a sensitivity of .791, specificity of .706, and area under the curve (AUC) of .748. The AUC for the SVM with cubic kernel classifier (AUC = .912) was better than the RF classifier (AUC = .683, P < .001) and better than using the CT attenuation threshold of 96.0 HU at the proximal tibia (AUC = .748, P = .025).

CONCLUSIONS

Opportunistic screening for osteoporosis/osteopenia can be performed using knee CT scans. Multivariable machine learning models are more predictive than the CT attenuation of a single bone.

Tibial Component Undersizing Is Related to High Degrees of Implant Migration Following Cementless Total Knee Arthroplasty: A Study of Radiostereometric Analysis Data for 111 Patients with 2-Year Follow-up

Radiostereometric analysis (RSA) studies have shown that the continuous migration of tibial components is predictive of aseptic loosening following total knee arthroplasty (TKA). In the present study, we investigated whether accurate sizing and placement of tibial components are related to the degree of implant migration as measured with use of RSA.

Methods

A total of 111 patients who underwent TKA surgery with a cementless tibial component were followed for a period of 2 years postoperatively, during which implant migration was assessed with use of RSA. RSA was performed within 7 days postoperatively and after 3, 6, 12, and 24 months. Postoperative radiographs were evaluated for component size and placement in the tibia. The evaluations were performed by experienced knee surgeons who were blinded to the migration data and clinical outcomes. A multivariable linear regression analysis was conducted.

Results

Continuous implant migration (i.e., migration occurring between 12 and 24 months postoperatively) had a negative association with tibial component size (coefficient [B], -0.2; 95% confidence interval [CI], -0.33 to -0.08). Subsidence was associated with the absence of posterior cortical bone support (B, -0.7; 95% CI, -1.09 to -0.28), the absence of lateral cortical bone support (B, 0.8; 95% CI, 0.29 to 1.37), frontal-plane varus malalignment (B, 0.6; 95% CI, 0.12 to 1.16), and component undersizing (B, -0.4; 95% CI, -0.06 to -0.68). Posterior tilt was associated only with undersizing (B, 0.6; 95% CI, 0.27 to 1.11).

Conclusions

Undersized cementless tibial components are at a higher risk for poor fixation with continuous migration following TKA. Therefore, a higher risk of aseptic loosening should be expected.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Mechanical complications after total knee arthroplasty

INTRODUCTION

With the increasing demand for total knee arthroplasty (TKA) and the burden of revision TKA on the healthcare system, as well as the quality of life implications for patients, it is extremely important for surgeons to be able to anticipate and prevent TKA mechanical complications. Surgeons must be familiar with the different causes and mechanisms of TKA complications so that they can properly treat patients with failed TKAs and better avoid these complications.

AREAS COVERED

This review addresses TKA mechanical complications and provides context for the topic. A detailed review of surgical factors, implant factors, and patient factors that contribute to mechanical complications after TKA is provided. All of the literature cited in this review was gathered from the PubMed online database using different keywords based on the section of the manuscript.

EXPERT OPINION

As surgeons and engineers solve certain issues in TKA, new challenges will inevitably arise. We must continue to push forward and innovate from both a surgical technique and implant design perspective.

Association between bone marrow lesions and bone mineral density of the proximal tibia in end-stage osteoarthritic knees

This retrospective cross-sectional study investigated the association between bone marrow lesions (BMLs) and bone mineral density (BMD) in the proximal tibia of end-stage osteoarthritic knees from a large patient sample. Overall, 1308 end-stage osteoarthritic knees were enrolled before total knee arthroplasty. The preoperative range of motion was recorded. Bone mineral density in the medial tibial plateau (MTP), lateral tibial plateau (LTP), and metaphysis were measured using dual-energy X-ray absorptiometry. The MTP/LTP, MTP/metaphysis, and LTP/metaphysis ratios were calculated. BMLs were scored using a whole-organ magnetic resonance imaging scoring system. The relationship between BMD and BML scores was investigated using linear regression analysis. The highest BMD was 0.787 ± 0.176 g/cm² at the MTP, followed by 0.676 ± 0.180 g/cm² and 0.572 ± 0.145 g/cm² at the metaphysis and LTP, respectively. The prevalence of BMLs was 90.4% and 24.2% in the MTP and LTP, respectively. In women, higher BML scores at the MTP were positively correlated with the BMD of the MTP (p < 0.001, r = 0.278), MTP/LTP (p < 0.001, r = 0.267), and MTP/metaphysis ratios (p < 0.001, r = 0.243). Regression analysis showed that higher BML scores in the MTP were correlated with higher BMD in the MTP (p < 0.001) and lower BMD in the LTP (p < 0.001). High BML scores in the MTP were positively associated with high BMD in the MTP, which also induced the medial to lateral imbalance of BMD in the proximal tibia.

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.

The Evolution, Current Indications and Outcomes of Cementless Total Knee Arthroplasty

Total knee arthroplasty (TKA) has been performed by orthopedic surgeons for decades, but the cementless TKA has only recently gained much interest in the world of arthroplasty. Initially, early designs had multiple complications, particularly with aseptic loosening due to osteolysis and micromotion. However, modifications have shown good outcomes and excellent survivorship. Over the last several decades, changes in implant designs as well as implant materials/coatings have helped with bone in growth and stability. Furthermore, surgeons have been performing TKA in younger and more obese patients as these populations have been increasing. Good results from the cementless TKA compared to cemented TKA may be a better option in these more challenging populations, as several studies have shown greater survivorship in patients that are younger and have a greater BMI. Additionally, a cementless TKA may be more cost effective, which remains a concern in today's healthcare environment. Overall, cemented and cementless TKA have great results in modern times and there is still a debate as to which implant is superior.

Component migration, bone mineral density changes, and bone turnover markers in cementless and cemented total knee arthroplasty: a prospective randomized RSA study in 53 patients with 2-year follow-up

PURPOSE

Cementless tibial components migrate initially until osseointegration and preserve periprosthetic bone. Cemented tibial components are fixed from surgery but loose periprosthetic bone. Little is known about bone formation and resorption biomarkers in relation to component fixation and bone mineral density (BMD) changes of cementless and cemented total knee arthroplasty. We hypothesize a similar migration of cemented and cementless tibial components between 1- and 2-year follow-up indicating a stable long-term fixation.

METHODS

In a prospective patient-blinded randomized study, we compared cementless (n = 27) and cemented (n = 26) tibial components with radiostereometry measured migration (MTPM = Maximum Total Point Motion: point of component that migrates the most) and changes in BMD and biochemical bone turnover markers (BTMs) until 24 months after surgery.

RESULTS

The mean MTPM between 12 and 24 months were similar between groups with - 0.06 mm (95% CI - 0.23; 0.11) in the cementless group compared to 0.02 mm (95% CI - 0.07; 0.11) in the cemented group. However, there was a higher proportion of cementless components (16/25) than cemented components (7/24) with continuous migration (MTPM > 0.2 mm) (p = 0.02). In the medial and anterior region below the tibial components, the BMD increased by mean 1.8% and 7.4% for cementless components and decreased by mean 8.6% and 4.2% for cemented components until 24-month follow-up. In both groups, BTMs initially showed increased bone resorption (CTx) and bone formation (P1NP) followed by normalization to pre-operative levels at 6 months post-surgery.

CONCLUSION

More cementless components than cemented components showed continues migration which suggest a higher risk of early revision. Bone turnover increased post-surgery in both groups, but did not explain the difference in change in periprosthetic BMD.

LEVEL OF EVIDENCE

I.

Dual-Energy CT-Based Bone Mineral Density Has Practical Value for Osteoporosis Screening around the Knee

Introduction: Adequate bone quality is essential for long term biologic fixation of cementless total knee arthroplasty (TKA). Recently, vertebral bone quality evaluation using dual-energy computed tomography (DECT) has been introduced. However, the DECT bone mineral density (BMD) in peripheral skeleton has not been correlated with Hounsfield units (HU) or central dual-energy X-ray absorptiometry (DXA), and the accuracy remains unclear. Materials and methods: Medical records of 117 patients who underwent TKA were reviewed. DXA was completed within three months before surgery. DECT was performed with third-generation dual source CT in dual-energy mode. Correlations between DXA, DECT BMD and HU for central and periarticular regions were analyzed. Receiver operating characteristic (ROC) curves were plotted and area under the curve (AUC), optimal threshold, and sensitivity and specificity of each region of interest (ROI) were calculated. Results: Central DXA BMD was correlated with DECT BMD and HU in ROIs both centrally and around the knee (all p < 0.01). The diagnostic accuracy of DECT BMD was higher than that of DECT HU and was also higher when the T-score for second lumbar vertebra (L2), rather than for the femur neck, was used as the reference standard (all AUC values: L2 > femur neck; DECT BMD > DECT HU, respectively). Using the DXA T-score at L2 as the reference standard, the optimal DECT BMD cut-off values for osteoporosis were 89.2 mg/cm3 in the distal femur and 78.3 mg/cm3 in the proximal tibia. Conclusion: Opportunistic volumetric BMD assessment using DECT is accurate and relatively simple, and does not require extra equipment. DECT BMD and HU are useful for osteoporosis screening before cementless TKA.

Periprosthetic fractures after medial unicompartmental knee arthroplasty: a narrative review

INTRODUCTION

On rare occasions, fractures of the tibial plateau may occur after uni-compartmental knee arthroplasty (UKA) and account for 2% of total UKA failures. The purpose of this narrative review is to identify and discuss potential risk factors that might lead to prevention of this invalidating complication.

MATERIALS AND METHODS

Electronic database of Pubmed, Scopus, Cochrane and Google Scholar were searched. A total of 457 articles related to the topic were found. Of those, 86 references were included in this narrative review.

RESULTS

UKA implantation acts as a stress riser in the medial compartment. To avoid fractures, surgeons need to balance load and bone stock. Post-operative lower limb alignment, implant positioning, level of resection and sizing of the tibial tray have a strong influence on load distribution of the tibial bone. Pain on weight-bearing signals bone-load imbalance and acts as an indicator of bone remodeling and should be a trigger for unloading. The first three months after surgery are critical because of transient post-operative osteoporosis and local biomechanical changes. Acquired osteoporosis is a growing concern in the arthroplasty population. Split fractures require internal fixation, while subsidence fractures differ in their management depending of the amount of bone impaction. Loose implants require revision knee arthroplasty.

CONCLUSION

Peri-prosthetic fracture is a rare, but troublesome event, which can lead to implant failure and revision surgery. Better knowledge of the multifactorial risk factors in association with a thorough surgical technique is key for prevention.

Team Approach: Preoperative Management of Metabolic Conditions in Total Joint Replacement

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Total joint arthroplasties (TJAs) of the knee and hip have been considered 2 of the most successful surgical procedures performed to date.

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Frailty is defined as increased vulnerability to adverse outcomes with physiologic stress.

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Preoperative optimization of frailty and metabolic bone conditions, including osteoporosis, vitamin D deficiency, and diabetes, through a multidisciplinary approach can help improve outcomes and minimize costs after TJA.

Preoperative BMD does not influence femoral stem subsidence of uncemented THA when the femoral T-score is > -2.5

Background and purpose - It is believed that in uncemented primary total hip arthroplasty (THA) the anchorage of the stem is dependent on the level of bone mineral density (BMD) of the femoral bone. This is one of the reasons for the widely accepted agreement that a cemented solution should be selected for people with osteoporosis or age > 75 years. We evaluated whether preoperative BMD of the femur bone is related to femoral stem migration in uncemented THA.Patients and methods - We enrolled 62 patients (mean age 64 years (range 49-74), 34 males) scheduled for an uncemented THA. Before surgery we undertook DEXA scans of the proximal femur including calculation of the T- and Z-scores for the femoral neck. Evaluation of stem migration by radiostereometric analysis (RSA) was performed with 24 months of follow-up. In 56 patients both preoperative DEXA data and RSA data were available with 24 months of follow-up.Results - None of the patients had a T-score below -2.5. We found no statistically significant relationship between preoperative BMD and femoral stem subsidence after 3 or 24 months. When comparing the average femoral stem subsidence between 2 groups with T-score > -1 and T-score ≤ -1, respectively, we found no statistically significant difference after either 3 or 24 months when measured with RSA.Interpretation - In a cohort of people ≤ 75 years of age and with local femur T-score > -2.5 we found no relationship between preoperative BMD and postoperative femoral stem subsidence of a cementless THA.

The association between bone mineral density and postoperative drainage volume following cruciate-substituting primary total knee arthroplasty: a cross-sectional study

Background

The prevalence of osteoporosis in patients who undergo a primary total knee arthroplasty (TKA) is increasing. Low bone mineral density (BMD) is related to unfavorable outcomes following TKA such as migration of uncemented tibial components. Postoperative blood loss in TKA is an important complication. Non-modifying predicting factors for postoperative blood loss in patients undergoing primary TKA need further elucidation. Studies on the association between BMD and blood loss after TKA are limited. We aimed to demonstrate the relationship between BMD and postoperative drainage volume following primary TKA.

Methods

A cross-sectional study was conducted between January 2014 and August 2020. A total of 119 primary varus osteoarthritis knees with BMD results were included in the study. Patients with secondary causes of osteoporosis were excluded.

Results

The median postoperative drainage volume of participants in the normal total hip BMD group and the normal trochanter BMD group was higher than that of patients in the low total hip BMD group and the low trochanter BMD group (285.0 ml vs 230.0 ml, P = 0.003; 282.5 ml vs 240.0 ml, P = 0.013, respectively). Multivariate regression analyses showed that operative time, spinal anesthesia, and normal total hip BMD status were significant predictive factors associated with increased postoperative drainage volume (P = 0.014, 0.022, and 0.013, respectively). No association was identified between the lumbar spine BMD status and postoperative drainage volume.

Conclusions

The relationship between BMD and postoperative blood loss in primary TKA was identified in this study. Normal total hip BMD was found to be associated with an increased postoperative drainage volume after primary TKA compared with low BMD.

Risk Factors for Tibial Component Loosening: A Meta-Analysis of Long-Term Follow-up Radiostereometric Analysis Data

BACKGROUND

Radiostereometric analysis (RSA) is a highly accurate tool to detect implant migration and predict loosening following total knee arthroplasty (TKA). However, little is known about the predisposing risk factors for implant migration, nor which migration profile should be considered physiological (i.e., merely part of an implant-settling phase) and which should be considered pathological (i.e., having a high probability for implant loosening). By pooling individual participant data from long-term follow-up RSA studies, we aimed to identify predisposing risk factors for tibial component loosening.

METHODS

Individual data were collected for 630 patients from 11 RSA studies. The repeated measurements were analyzed with use of a linear mixed-effects model, determining the effect of age, sex, body mass index, diagnosis, preoperative and postoperative limb alignment, and prosthesis characteristics on tibial component migration over time, taking into account the clustering of patients within studies.

RESULTS

High initial migration was found to result in early mechanical loosening in 18 cases (2.9%) and septic loosening in 2 cases (0.3%), whereas stabilization of high initial migration occurred in 17 cases (2.7%). Late loosening occurred in 13 cases (2.1%). All other 580 cases (92.1%) showed early stabilization and remained stable over time. Mixed-effects model analyses showed that for cemented prostheses, sex, diagnosis, and posterior cruciate ligament type had an effect on migration, but these differences were nonsignificant when analyzing migration from 3 months onwards. Uncemented prostheses aligned in varus showed more migration than neutrally and valgus-aligned TKAs (p = 0.031), and this difference increased over time (p < 0.001). Significantly higher migration was observed following uncemented TKA without an osseointegration-promoting surface (p < 0.001).

CONCLUSIONS

For cemented prostheses, increased migration during the first 3 postoperative months was observed for female patients, patients with rheumatoid arthritis, and patients who underwent a posterior-stabilized TKA. For uncemented prostheses, both postoperative varus alignment of the lower limb and the absence of an osseointegration-promoting surface significantly increased postoperative tibial component migration.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

What is the role of cemented fixation in total knee arthroplasty? The two-year results of a randomized RSA controlled trial

AIMS

For many designs of total knee arthroplasty (TKA) it remains unclear whether cemented or uncemented fixation provides optimal long-term survival. The main limitation in most studies is a retrospective or non-comparative study design. The same is true for comparative trials looking only at the survival rate as extensive sample sizes are needed to detect true differences in fixation and durability. Studies using radiostereometric analysis (RSA) techniques have shown to be highly predictive in detecting late occurring aseptic loosening at an early stage. To investigate the difference in predicted long-term survival between cemented, uncemented, and hybrid fixation of TKA, we performed a randomized controlled trial using RSA.

METHODS

A total of 105 patients were randomized into three groups (cemented, uncemented, and hybrid fixation of the ACS Mobile Bearing (ACS MB) knee system, implantcast). RSA examinations were performed on the first day after surgery and at scheduled follow-up visits at three months, six months, one year, and two years postoperatively. Patient-reported outcome measures (PROMs) were obtained preoperatively and after two years follow-up. Patients and follow-up investigators were blinded for the result of randomization.

RESULTS

RSA secondary stabilization did not show a significant difference between the three types of fixation. A maximum total point motion of less than 0.2 mm in the second postoperative year was shown in each group, which suggests stabilization of the implant. At 24 months after surgery, PROMs significantly improved compared to baseline in all treatment groups. No significant difference was observed between the three groups.

CONCLUSION

Secondary stabilization measurements in this study demonstrated no significant difference between the groups. In all groups migration stabilized after initial settling of the implant. For this implant the long-term outcome is not expected to be influenced by the type of fixation to the bone. Cite this article: Bone Joint J 2021;103-B(1):98-104.

Early migration of stemless and stemmed humeral components after total shoulder arthroplasty for osteoarthritis-study protocol for a randomized controlled trial

BACKGROUND

Glenohumeral osteoarthritis can, in the most severe cases, require surgery with insertion of a shoulder arthroplasty. A design with a stem in the humeral bone canal is currently regarded as the standard treatment option in patients who have an intact rotator cuff function, but complications related to the stem including humeral fractures can have devastating consequences. By using a stemless humeral component, stem-related complications can be reduced. The aim of this study is to compare the Comprehensive Nano stemless total shoulder arthroplasty (intervention group) with the Comprehensive stemmed total shoulder arthroplasty (control group).

MATERIALS AND METHODS

This is a randomized controlled trial comparing the stemless and the stemmed total shoulder arthroplasty. All Danish citizens with glenohumeral osteoarthritis indicating a total shoulder arthroplasty referred to the orthopedic department at Copenhagen University Hospital in Herlev/Gentofte will be offered participation. The following exclude from participation: below 18 years of age, cognitive or linguistic impairment, insufficient function of the rotator cuff, poor bone quality, and ASA groups 4-5. A total of 122 patients will be included of which 56 will be part of a radiostereometric analysis (RSA) study of humeral component migration. The primary outcomes are magnitude of migration of the humeral component assessed by RSA and patient-reported outcome by Western Ontario Osteoarthritis of the Shoulder index (WOOS). The secondary outcomes are additional patient-reported outcomes, functional outcome, readmission, complications, revisions, and changes in bone mineral density (BMD) of the proximal humerus assessed by duel energy x-ray absorptiometry (DXA) and economy (cost-utility analysis). The patients are examined before the operation and 3, 6, 12, and 24 months postoperative.

DISCUSSION

To our knowledge, RSA has never been used to access migration of a stemmed or a stemless humeral component nor has the stemmed and the stemless humeral component been compared with regard to pain relief and shoulder function in a randomized clinical trial. Today, the two designs are considered equal in the treatment of osteoarthritis. The study will provide surgeons and patients with information about shoulder arthroplasty for osteoarthritis and assist them in decision-making.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04105478 . Registered on 25 September 2019.

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.

Denosumab prevents periprosthetic bone mineral density loss in the tibial metaphysis in total knee arthroplasty

BACKGROUND

Periprosthetic bone quality is one of the most important factors preventing early prosthesis migration and long-term failure. Although denosumab, which binds to the receptor activator of nuclear factor kappa-B ligand (RANKL), has been linked with periprosthetic bone mineral density (BMD), the effectiveness of denosumab against bone loss remains unclear. We hypothesized that denosumab treatment after total knee arthroplasty (TKA) could prevent periprosthetic bone resorption.

METHODS

In this prospective cohort study, 28 patients with primary knee osteoarthritis were divided into two groups: denosumab (denosumab and vitamin D) and control (vitamin D only) groups. All patients underwent TKA with the same implant model and received medication after surgery. We used dual-energy X-ray absorptiometry to measure periprosthetic BMD after TKA.

RESULTS

In the control group, the BMD of the proximal medial tibia decreased drastically at 12 months after TKA (-19.7%). Denosumab treatment significantly preserved this BMD loss (0.7%). The linear regression analysis revealed that denosumab intervention had the highest significantly positive relationship with BMD.

CONCLUSIONS

Our results indicate that denosumab treatment significantly reduces periprosthetic BMD loss, even at the early stages after TKA. This therapeutic strategy may facilitate early stable fixation of the prosthesis which, in turn, may help to prevent early implant migration and reduce the need for revision surgery.

Effect of bone density and cement morphology on biomechanical stability of tibial unicompartmental knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) offers good long-term survivorship and superior kinematics and function compared with total knee arthroplasty (TKA). However, revision rates are higher with aseptic loosening representing a major cause. Biomechanical stability depends on cement penetration. The goal of this study was to analyze the influence of cement morphology and bone density on primary stability of tibial UKA under physiological loading conditions in human tibiae.

METHODS

Thirty-six tibial trays were implanted in fresh-frozen human cadaver knees and tested for primary stability using dynamic compression-shear testing. Prior to implantation, bone density had been quantified for all 18 tibiae. Postoperatively, cement penetration has been assessed on frontal cuts based on eight predefined parameters. The influence of bone density and cement morphology on biomechanical stability was determined using correlation and linear regression analysis.

RESULTS

Mean failure load was 2691 ± 832.9 N, mean total cement thickness was 2.04 ± 0.37 mm, mean cement penetration was 1.54 ± 0.33 mm and mean trabecular bone mineral density (BMD) was 107.1 ± 29.3 mg/ml. There was no significant correlation between failure load and cement morphology (P > .05). Failure load was significantly positive correlated with trabecular BMD (r = 0.843; P < .0001) and cortical BMD (r = 0.432; P = .0136).

CONCLUSIONS

Simulating physiological loading conditions, the failure load of tibial UKA is linearly dependent on the trabecular BMD. The observed parameters of cementation morphology seem capable of preventing failure at the bone-cement interface before inherent bone stability is reached. Further research is required to assess the usefulness of a preoperative assessment of bone quality for patient selection in UKA.

Bone Mineral Density Around the Knee Joint: Correlation With Central Bone Mineral Density and Associated Factors

INTRODUCTION

The aims of this study were to (1) assess the bone mineral density (BMD) around the knee joint, (2) determine the correlation between central and knee BMDs, and (3) investigate the factors associated with BMD around the knee joint in patients with knee osteoarthritis (OA).

METHODOLOGY

This cross-sectional study included 122 patients who underwent total knee arthroplasty. Central and knee dual-energy X-ray absorptiometry was performed preoperatively. BMD at 6 regions of interest (ROIs) around the knee joint were measured, and their correlations with central BMD were determined using Spearman's correlation analysis. Lower limb alignment, severity of OA, body mass index (BMI), preoperative functional and pain scores were assessed to elucidate the factors associated with knee BMD using linear regression analysis.

RESULTS

Around the knee joint, BMD was the lowest at the distal femoral metaphysis and lateral tibial condyle. Knee BMD was significantly correlated with central BMD. However, the correlation coefficients varied by the ROI. Additionally, multivariate analysis revealed different associations with respect to the regions around the knee joint. Varus alignment of the lower limb was associated with increased BMD of the medial condyles and decreased BMD of lateral condyles. High grade OA was a protective factor; it was associated with increased BMD at the lateral condyles of the femur and tibia. Higher BMI was an independent protective factor in all ROIs around the knee joint except the lateral femoral condyles. Lower functional level was not associated with decreased BMD, whereas a higher pain score was significantly associated with lower BMD at the proximal tibial metaphysis.

CONCLUSIONS

Knee BMD was significantly correlated with central BMD. However, the correlations varied with the regions around the knee joint probably due to their independent association with the alignment of the lower limb, severity of OA, BMI, and preoperative pain level.

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.

Bone remodeling of the proximal tibia after uncemented total knee arthroplasty: secondary endpoints analyzed from a randomized trial comparing monoblock and modular tibia trays-2 year follow-up of 53 cases

Background and purpose - Bone remodeling as a response to bone trauma, postoperative immobilization, and device-related bone reactions can lead to loss of bone stock and increase the risk of periprosthetic fracture and aseptic loosening. This study investigates the adaptive bone remodeling of the proximal tibia after uncemented total knee arthroplasty (TKA). Patients and methods - We performed a 2-year follow up of 53 patients (mean age 62 (38-70) years, 27 of whom were men, who received an uncemented TKA in a randomized controlled trial with bone mineral density (BMD) as secondary endpoint. Patients were randomized to 2 groups of either monoblock (A) or modular (B) polyethylene design. The TKAs were performed using the uncemented Zimmer Nexgen trabecular metal. Measurements of BMD were done postoperatively and after 3, 6, 12, and 24 months. BMD was measured in 3 regions of interest (ROI). Results and interpretation - In group A statistically significant changes in BMD were seen after 24 months in both the medial and lateral ROI. BMD decreased medially by 15% (p = 0.004) and laterally by 13% (p = 0.01). In group B the BMD changes were limited and after 24 months returned to the preoperative values. The differences in BMD change between groups were statistically significant in both the medial (p = 0.03) and lateral (p = 0.02) ROI. In the distal ROI we found no significant change in BMD in either group. A significantly different bone remodeling pattern of the proximal tibia was seen in the 2 groups with a higher degree of bone loss in the knees that received the monoblock polyethylene design, indicating that the flexible monoblock implant design, previously shown to improve fixation, does not decrease the bone loss of the proximal tibia.

Preoperative Systemic Bone Quality Does Not Affect Tibial Component Migration in Knee Arthroplasty: A 2-Year Radiostereometric Analysis of a Hundred Consecutive Patients

BACKGROUND

Bone quality and other preoperative predictive factors may affect implant migration and the survival of knee arthroplasty.

METHODS

In a prospective cohort of 100 consecutive patients (65 women) at a mean age of 67.7 years (range 39-87 years), we investigated preoperative predictors of postoperative tibial component migration in cemented and cementless total knee arthroplasties or cemented unicompartmental knee arthroplasty. Predictors consisted of Knee Injury and Osteoarthritis Outcome Score (KOOS) and Oxford Knee Score, questionnaires, bone turnover markers of CTX and P1NP, systemic bone mineral density (BMD), and knee osteoarthritis (OA) grade. Tibial component migration was measured with radiostereometry postoperative, at 1 and 2 years of follow-up.

RESULTS

Between 1 and 2 years, 19 tibial components migrated continuously (maximum total point motion [MTPM] > 0.2 mm). In general, there was no difference in age, body mass index, BMD, KOOSs, or OA grade between patients with continuous tibial migration compared to patients without continuous migration (P > .11). However, cementless tibial components with continuous migration had a lower KOOS pain score (more pain), lower vitamin D, and a higher bone turnover (CTX) value than patients without continuous migration. There was no association between the BMD and MTPM at 1-year follow-up regardless of prothesis type (P > .17). Patients with osteoporosis and normal BMD had similar mean tibial component MTPM at 2 years (3 prostheses combined; P = .34).

CONCLUSION

Migration of tibial components inserted with or without bone cement was not affected by the preoperative bone quality in terms of systemic BMD, bone turnover markers, and OA grade in the knee.

Mobile-bearing total knee arthroplasty implants combined with surface cementation produced satisfactory clinical and radiographic outcomes at the 5-year follow-up

PURPOSE

Very little is known about the use of combined surface cementation (only tibial tray) and mobile-bearing tibial components in total knee arthroplasty (TKA). This study was investigated whether the index combinations show satisfactory clinical outcomes after mobile-bearing TKA using posterior cruciate ligament (PCL)-retaining meniscal-bearing (MB) and PCL-substituting rotating-platform (RP) TKA designed using different anteroposterior constraints.

METHODS

This study is a retrospective evaluation of a prospective database. Five-year postoperative clinical outcomes were assessed in 127 patients (127 knees) and 122 patients (122 knees) who underwent TKA with an MB and RP design, respectively. The Hospital for Special Surgery (HSS) score, range of motion, loosening/radiolucency, and subsidence around both components were evaluated in the two designs.

RESULTS

The postoperative median HSS score was excellent in both the MB and RP groups (93 and 92, respectively). Postoperative flexion and extension did not differ between the two designs. Neither design showed > 2-mm radiolucencies raising concern for femoral or tibial implant stability. Five (2%) of 249 patients (5 knees) (MB, n = 4; RP, n = 1) showed detectable subsidence of the tibial component. However, no revision TKA had been performed by the 5-year follow-up because no patients had complaints severe enough to necessitate revision surgery.

CONCLUSIONS

Clinically good outcomes comparable with previous studies were obtained 5 years after mobile-bearing TKA with surface cementation using both MB and RP implant designs. Thus, equivalent mid-term clinical outcomes of the index combination can be obtained with other implant designs and cementation techniques.

LEVEL OF EVIDENCE

Level II.

Association between bone mineral density distribution and various radiographic parameters in patients with advanced medial osteoarthritis of the knee

PURPOSE

Patients with severe osteoarthritis (OA) of the knee have changes in bone mineral density (BMD) of the distal femur and proximal tibia. Correlations between the medial-to-lateral BMD (M/L-BMD) ratio (which normalizes the potentially confounding effects of body size and sex on BMD) and radiographic parameters that indicate OA progression have not been adequately studied. The purpose of this study was to evaluate correlations between radiographic indicators of OA progression and femoral and tibial M/L-BMD ratios.

METHODS

A consecutive series of 182 knees in 156 patients with advanced medial knee OA who underwent total knee arthroplasty were included. We evaluated correlations between the femoral and tibial M/L-BMD ratios and various radiographic parameters, including tibiofemoral angle (TFA), mechanical axis angle (MAA), tibial coronal angle, tibiofemoral subluxation (%), load-bearing axis deviation at the tibial plateau (%), and medial and lateral laxity.

RESULTS

Univariate analyses using Spearman's correlation coefficient revealed significant positive correlations between femoral and tibial M/L-BMD ratios and both TFA and MAA and negative correlations with tibial coronal angle and load-bearing axis deviation. Multivariate analyses showed significant associations between TFA and the femoral M/L-BMD ratio (β = 0.434, p < 0.001) and between MAA and the tibial M/L-BMD ratio (β = 0.384, p < 0.001).

CONCLUSION

BMD distribution around the knee might be predictable with radiographic parameters such as the TFA for the femur and MAA for the tibia. The findings of this study provide in vivo data on the evaluation of preoperative femoral and tibial M/L-BMD ratios without dual-energy X-ray absorptiometry.

Impact of Race Subgroups on the Assessment of Vitamin D Status in Adolescent Idiopathic Scoliosis

The authors' main objective was to demonstrate the confounding effect of combining subgroup data, specifically race, on the prevalence of vitamin D deficiency in adolescent idiopathic scoliosis (AIS). This was a retrospective chart review. Vitamin D deficiency was defined as 25-hydroxyvitamin D (25[OH]D) less than 20 ng/mL. Data were compared between white patients and black and Hispanic patients. Vitamin D status in girls with AIS was also compared with that in girls without AIS who had a history of fracture and with the medical literature to determine if deficiency in AIS was equal to or greater than other cohorts. Mean age was 13.9±2.3 years for the white girls with AIS (n=221) and 13.6±2.2 years for pooled non-whites (n=134). Significant racial differences were found that biased interpretation of the total pooled cohort. Mean 25(OH)D was 27.9±8.5 ng/mL for white girls with AIS vs 21.9±10.3 ng/mL for non-whites (P<.0001). Deficiency was present in 13.1% of white girls vs 47.8% of non-white girls (P<.0001). Compared with girls with fractures and with the published literature, the race-matched deficiency rates were not abnormally high in girls with AIS. Prevalence of deficiency was greater in non-whites with AIS than in whites. However, percent deficiency was not greater in girls with AIS than in race-matched cohorts without AIS. Without separating data by race, interpretation of vitamin D status can be confounded. [Orthopedics. 2019; 42(3):158-162.].

Superior fixation and less periprosthetic stress-shielding of tibial components with a finned stem versus an I-beam block stem: a randomized RSA and DXA study with minimum 5 years' follow-up

Background and purpose - The stem on the tibial component of total knee arthroplasty provides mechanical resistance to lift-off, shear forces, and torque. We compared tibial components with finned stems (FS) and I-beam block stems (IS) to assess differences in implant migration. Patients and methods - In a patient-blinded RCT, 54 patients/knees (15 men) with knee osteoarthritis at a mean age of 77 years (70-90) were randomly allocated to receive tibial components with either a FS (n = 27) or an IS (n = 27). Through 5 to 7 years' follow-up, implant migration was measured with RSA, periprosthetic bone mineral density (BMD) was measured with DXA, and surgeons reported American Knee Society Score (AKSS). Results - At minimum 5 years' follow-up, maximum total point motion (MTPM) was higher (p = 0.04) for IS (1.48 mm, 95% CI 0.81-2.16) than for FS (0.85 mm, CI 0.38-1.32) tibial components. Likewise, total rotation (TR) was higher (p = 0.03) for IS (1.51˚, CI 0.78-2.24) than for FS (0.81˚, CI 0.36-1.27). Tibial components with IS externally rotated 0.50° (CI -0.06 to 1.06) while FS internally rotated 0.09° (CI -0.20 to 0.38) (p = 0.03). Periprosthetic bone stress-shielding was higher (p < 0.01) up to 2 years' follow-up for IS compared with FS in the regions medial to the stem (-13% vs. -2%) and posterior to the stem (-13% vs. -2%). Below the stem bone loss was also higher (p = 0.01) for IS compared with FS (-6% vs. +1%) up to 1-year follow-up. Knee score improved similarly in both groups up to 5 years' follow-up. Interpretation - Periprosthetic bone stress-shielding medial and posterior to the stem until 2 years, and tibial component migration at 5 years, was less for a finned compared with an I-shaped block stem design.