Quantitative CT-assisted osteodensitometry of femoral adaptive bone remodelling after uncemented total hip arthroplasty

Variations in bone mineral density after joint replacement: A systematic review examining different anatomical regions, fixation techniques and implant design

Purpose

This study aims to evaluate postoperative periprosthetic bone mineral density (BMD) at various time points following joint replacement with different implant designs and fixation techniques.

Methods

Database search was conducted on MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, Web of Science, and CINAHL for studies analyzing bone remodelling after joint replacement (March 2002-January 2024). Inclusion criteria: English-language articles; total joint replacement; at least two BMD evaluations; observational studies, cross-sectional, prospective, retrospective, randomised controlled trials, and clinical trials. Exclusion criteria: no BMD measurement within one month after surgery; BMD data only expressed as percentage changes or graphs without numerical values; no Gruen zone evaluation for hip replacement; no periprosthetic bone evaluation for knee replacement; pharmacological treatment or comorbidities affecting BMD; revision joint replacements; irrelevant articles; no full text or no original data.

Results

Sixty-eight articles matched the selection criteria. Fifty-five focused on the hip joint, 12 on the knee, and one on the shoulder. After total hip arthroplasty, the greatest bone resorption occurred in the proximal femur, peaking at 6 months. Cemented implants and tapered stems showed greater bone resorption than cementless implants and anatomical stems. BMD around the acetabular component decreased during the first 6 months but increased in regions subjected to higher loads. In total knee arthroplasty, bone loss occurred in the anterior distal femur and medial tibial plateau, with cemented and posterior-stabilised implants showing greater bone loss than cementless and cruciate-retaining designs.

Conclusions

The periprosthetic BMD decreases progressively after joint replacement. The fixation technique and implant design influence the extent and pattern of this decline. These factors must be considered during the surgical planning, as they can have long-term implications for bone health and implant longevity. Further research is needed to optimise implant design and surgical techniques to mitigate BMD loss and improve patient outcomes.

Level of Evidence

Level IV.

Evidence-based joint statement position of perioperative bone optimization in the arthroplasty candidate, from FEMECOT, AMMOM, ACOMM, SCCOT, SECOT, SEFRAOS, SEIOMM

BACKGROUND

The prevalence of patients living with joint replacements is increasing. Nearly two-thirds of patients undergoing elective arthroplasty procedures have low bone mineral density (LBMD), defined as osteopenia in 38.5% and osteoporosis in 24.8%; among those with osteoporosis, only 32.8% received treatment at the time of surgery.

MATERIALS AND METHODS

A group of 7 national societies (FEMECOT, AMMOM, ACOMM, SCCOT, SECOT, SEFRAOS, SEIOMM) developed a joint statement position on the diagnosis of osteoporosis and perioperative bone optimization in candidates for arthroplasty "Arthroplasty Bone Optimization." We performed a scoping review of the available literature, followed by a systematic review and meta-analysis. Subsequently, a Delphi-modified method was used to gather the different positions.

RESULTS

After analyzing the literature, we came up with five recommendations: (1) Patients scheduled for elective arthroplasty should undergo a bone health assessment (BHA). (2) If poor bone quality is observed during surgery and a bone health assessment has not been conducted promptly, a complete BHA, including a DXA scan, is imperative. (3) In the arthroplasty candidate, if LBMD or osteoporosis are noticed, bone loss-related factors should be corrected, and appropriate treatment for osteoporosis should be started before or right after arthroplasty. The use of anti-resorptive and bone anabolic agents has been shown to reduce periprosthetic bone loss, complications, and non-septic revision rates after joint arthroplasty. (4) In arthroplasty candidates, the diagnosis of osteoporosis or low bone mineral density (LBMD) should not delay the surgery. (5) Monitoring central and periprosthetic bone mineral density through DXA protocols can help identify bone loss in central and periprosthetic areas in patients with risk factors or osteoporosis.

CONCLUSIONS

Perioperative bone optimization should be considered in all patients who are candidates for arthroplasty. The orthopedic surgeon and multidisciplinary team should be encouraged to diagnose and treat the arthroplasty candidates' bone by screening for bone loss-related factors and diagnosing osteoporosis and starting treatment according to the current international guidelines. Following these recommendations could reduce periprosthetic bone loss, complications, and aseptic revision rates following arthroplasty surgery. More research is needed to understand the implications of osteoporosis and its treatment for joint replacement outcomes and long-term survival.

Fractures around the hip: inducing life-like fractures as a basis for enhanced surgical training

INTRODUCTION

In this study we investigated if realistic fracture patterns around the hip can be produced on human cadaveric specimens with intact soft tissue envelope. Possible applications of such fractured specimens would be in surgical training.

MATERIALS AND METHODS

7 cadaveric specimens (2 male, 5 female, 2 formalin-fixed, 5 fresh-frozen) were fractured. 2 specimens were fractured on both femurs, 5 only on one side, resulting in 9 fractures total. 5 fractures were set in our custom-made drop-test bench, 2 fractures by inducing axial force using a hammer, and the remaining 2 fractures by a direct dorsal approach and a chisel. AO/OTA and Pauwels classification were used to classify the fractures on the specimens by two independent trauma surgeons.

RESULTS

In our drop-test bench, axial load with the femur adducted by 10° resulted in an intertrochanteric fracture (AO type A1.3), adducted by 20° resulted in a femoral neck fracture (Pauwels type III). Fracture induction using a hammer resulted in two intertrochanteric fractures (AO type A2.2 right, A3.3 left). The use of a chisel resulted in both cases in a femoral neck fracture. The acetabulum could be fractured multifragmentarily through use of a hemiprosthesis as a stamp.

CONCLUSION

A high energetic impulse induced by a custom-made drop-test bench can successfully simulate realistic proximal femur and acetabular fractures in cadaveric specimens with intact soft tissue. Furthermore, axial load using a hammer as well as using a chisel through a direct dorsal approach represent additional methods for fracture induction. These pre-fractured specimens can be utilized in surgical education to provide a realistic teaching experience for specialized trauma education courses.

Analyzing bone remodeling patterns after total hip arthroplasty using quantitative computed tomography and patient-specific 3D computational models

BACKGROUND

Computational models in the form of finite element analysis technique that incorporates bone remodeling theories along with DEXA scans has been extensively used in predicting bone remodeling patterns around the implant. However, majority of such studies used generic models. Therefore, the aim of this study is to develop patient-specific finite element models of total hip replacement patients using their quantitative computed tomography (QCT) scans and accurately analyse bone remodelling patterns after total hip arthroplasty (THA).

METHODS

Patient-specific finite element models have been generated using the patients' QCT scans from a previous clinical follow-up study. The femur was divided into five regions in proximal-distal direction and then further divided into four quadrants for detailed analysis of bone remodeling patterns. Two types of analysis were performed-inter-patient and intra patient to compare them and then the resulting bone remodeling patterns were quantitatively analyzed.

RESULTS

Our results show that cortical bone density decrease is higher in diaphyseal region over time and the cancellous bone density decreases significantly in metaphyseal region over time. In metaphyseal region, posterior-medial (P-M) quadrant showed high bone loss while diaphyseal regions show high bone loss in anterior-lateral (A-L) quadrant.

CONCLUSIONS

Our study demonstrated that combining QCT with 3D patient-specific models has the ability of monitoring bone density change patterns after THA in much finer details. Future studies include using these findings for the development of a bone remodelling algorithm capable of predicting surgical outcomes for THA patients.

Periprosthetic bone loss: diagnostic and therapeutic approaches

Total joint replacement surgery is being performed on an increasingly large part of the population. Clinical longevity of implants depends on their osseointegration, which is influenced by the load, the characteristics of the implant and the bone-implant interface, as well as by the quality and quantity of the surrounding bone. Aseptic loosening due to periprosthetic osteolysis is the most frequent known cause of implant failure. Wear of prosthetic materials results in the formation of numerous particles of debris that cause a complex biological response. Dual-energy X-ray Absorptiometry (DXA) is regarded as an accurate method to evaluate Bone Mineral Density (BMD) around hip or knee prostheses. Further data may be provided by a new device, the Bone Microarchitecture Analysis (BMA), which combines bone microarchitecture quantification and ultra high resolution osteo-articular imaging. Pharmacological strategies have been developed to prevent bone mass loss and to extend implant survival. Numerous trials with bisphosphonates show a protective effect on periprosthetic bone mass, up to 72 months after arthroplasty. Strontium ranelate has been demonstrated to increase the osseointegration of titanium implants in treated animals with improvement of bone microarchitecture and bone biomaterial properties.

Modern proximally tapered uncemented stems can be safely used in Dorr type C femoral bone

Cementless femoral fixation has become widely accepted in modern total hip arthroplasty. Treating patients who have a stovepipe-shaped femur (Dorr type C) with cementless implants has traditionally been challenging. We treated 53 consecutive patients (60 hips) who had type C bone with identical tapered, proximally coated implants and postoperative weight bearing as tolerated. At 6 weeks, all 60 hips had radiographically documented bony integration, and at 1 year, there was no evidence of fracture, subsidence, thigh pain, stress shielding, loose stems, or risk of failure. Of those patients, 40 (43 hips) had midterm follow-up (average, 6 years; range, 4-9 years); the findings were the same. We conclude that modern proximally tapered stems can be used with early weight bearing in patients with type C bone.

Quantitative CT with finite element analysis: towards a predictive tool for bone remodelling around an uncemented tapered stem

PURPOSE

We used quantitative CT in conjunction with finite element analysis to provide a new tool for assessment of bone quality after total hip arthroplasty in vivo. The hypothesis of this prospective five-year study is that the combination of the two modalities allows 3D patient-specific imaging of cortical and cancellous bone changes and stress shielding.

METHOD

We tested quantitative CT in conjunction with finite elements on a cohort of 29 patients (31 hips) who have been scanned postoperatively and at one year, two years and five years follow-up. The method uses cubic Hermite finite element interpolation for efficient mesh generation directly from qCT datasets. The element Gauss points that are used for the geometric interpolation functions are also used for interpolation of osteodensitometry data.

RESULTS

The study showed changes of bone density suggestive of proximal femur diaphysis load transfer with osteointegration and moderate metaphyseal stress shielding. Our model revealed that cortical bone initially became porous in the greater trochanter, but this phenomenon progressed to the cortex of the lesser trochanter and the posterior aspect of the metaphysis. The diaphyseal area did not experience major change in bone density for either cortical or cancellous bone.

CONCLUSION

The combination of quantitative CT with finite element analysis allows visualization of changes to bone density and architecture. It also provides correlation of bone density/architectural changes with stress patterns enabling the study of the effects of stress shielding on bone remodelling in vivo. This technology can be useful in predicting bone remodeling and the quality of implant fixation using prostheses with different design and/or biomaterials.

Femoral bone density changes after total hip arthroplasty with uncemented taper-design stem: a five year follow-up study

We measured bone density (BD) changes to assess adaptive bone remodelling five years after uncemented total hip arthroplasty with taper-design femoral component using quantitative computed-tomography-assisted osteodensitometry (qCT). Nineteen consecutive patients (21 hips) with degenerative joint disease were enrolled in the study. A press-fit cup and a tapered uncemented stem ceramic-ceramic pairing were used in all patients. Serial clinical, radiological and qCT osteodensitometry assessments were performed after the index operation and at the one, two and five year follow-ups. At the latest follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration with stable fixation of all cups and stems. Overall, there was evidence of a BD loss at year five (p = 0.004). We estimate that BD loss was between 2.2% and 12.1% in comparison with baseline postoperative values. Progressive loss of BD in the metaphyseal region was observed in all hips. We found unremarkable BD changes of diaphyseal cortical BD throughout the five year follow-up period. qCT osteodensitometry technology allows differentiation of cortical and cancellous BD changes over time. Periprosthetic BD changes at the five year follow-up are suggestive of stable stem osteointegration with proximal femoral diaphysis load transfer and metaphyseal stress shielding.

Femoral head density on CT scans of patients following hip fracture fixation by expandable proximal peg or dynamic screw

Computed tomography (CT) is currently considered to be an accurate method for evaluating bone density. We evaluated the CT measurements of bone density using the Hounsfield units (HUs) in 23 patients who had been operated in the past for an extra-capsular hip fracture. Twelve patients were treated with a dynamic hip screw and 11 with a proximal femoral expandable hip nail. All the CTs had been performed for non-orthopedic purposes. Bone density with a region of interest (ROI) could be assessed for both hips. We compared the bone density between the operated versus the non-operated sides as well as between the two surgical groups. Bone density was higher in the hip peg (the femoral component of the expandable nail) side 262.5 (range, 169-351) HU, compared to the opposite non-operated side and to the hip screw group 194 (range, 99-283) HU. The hip screw side had decreased bone density compared to the opposite non-operated side. We were able to define a density index and a difference index: both were higher in the hip peg group. These findings persisted over time. It would be interesting to speculate that increased bone density around an expandable peg provides better fracture stabilization and probably faster healing than a dynamic hip screw.

Loss of tibial bone density in patients with rotating- or fixed-platform TKA

Little is known about tibial bone remodeling with TKA and its clinical relevance. We performed a randomized clinical trial to compare tibial bone density changes in cemented components with different bearing designs. Bone density changes were assessed using quantitative computed tomography (qCT)-assisted osteodensitometry. Twenty-eight rotating-platform and 26 fixed-platform cemented TKAs were included. The nonoperated contralateral side was used as a control. CT scans were performed postoperatively and 1 year and 2 years after the index operation. Cancellous bone density loss (up to 12.6% at 2 years) was observed in all proximal tibial regions in both cohorts. In contrast, we found lower cortical bone density loss (up to 3.6% at 2 years). We found no differences in bone loss between fixed- and rotating-platform implants. The decrease of cancellous bone density after TKA suggests stress transfer to the cortical bone.

Biomechanical comparison of 2 proximally coated femoral stems: effects of stem length and surface finish

Proximally hydroxyapatite-coated stems have performed well clinically but produced moderate proximal stress shielding and midstem cancellous condensation. Stem modification (stem shortening and distal tip polishing) has resulted in greater incidence of thigh pain. We performed a retrospective finite element analysis of the effects of stem length and surface finish to determine if midstem fixation could be avoided and the results could relate to the clinical outcomes. The modified short stem not only produced moderately less proximal bone resorption but also exhibited greater instability with 40% to 94% greater bone-implant relative motion at the stem tip. Bone formation potential at the transition between the coated and uncoated regions of both stems was observed based on changes in strain energy density. These findings are consistent with previous radiographic and clinical comparisons of short- and long-stem designs. Increased pain incidence for short-stem patients may be related to decreased implant instability and increased interface relative motion.

Comparison between DEXA and finite element studies in the long-term bone remodeling of an anatomical femoral stem

The implantation of a cemented or cementless femoral stem changes the physiological load transfer on the femur producing an effect on the bone called adaptative remodeling. The patterns of this remodeling are attributed to mechanical and biological factors, and those changes in bone mineral density have been determined in long-term densitometry studies. This technique has proved to be a useful tool able to quantify small changes in bone density in different femoral areas, and it is considered to be ideal for long-term studies. On the other hand, the finite element (FE) simulation allows the study of the biomechanical changes produced in the femur after the implantation of a femoral stem. The aim of this study was to contrast the findings obtained from a 5 year follow-up densitometry study that used a newly designed femoral stem (73 patients were included in this study), with the results obtained using a finite element simulation that reproduces the pattern of load transfer that this stem causes on the femur. In this study we have obtained a good comparison between the results of stress of FE simulation and the bone mass values of the densitometry study establishing a ratio between the increases in stress (%) versus the increases in bone density (%). Hence, the changes in bone density in the long term, compared with the healthy femur, are due to different load transfers after stem implantation. It has been checked that in the Gruen zone 7 at 5 years, the most important reduction in stress (7.85%) is produced, which coincides with the highest loss of bone mass (23.89%). Furthermore, the simulation model can be used with different stems with several load conditions and at different time periods to carry out the study of biomechanical behavior in the interaction between the stem and the femur, explaining the evolution of bone density in accordance to Wolff's law, which validates the simulation model.

Five-year DEXA study of 88 hips with cemented femoral stem

We performed repeated dual-energy X-ray absorptiometry (DEXA) measurements over five years in a homogeneous patient population to study the effect of a cemented stem on proximal femoral bone remodelling. Data from 88 patients (88 hips) implanted with total hip arthroplasty (THA) prostheses were extracted from three randomised studies. Femoral bone mineral density (BMD) was measured using a Lunar DPX-IQ densitometer for five years postoperatively. At one year the BMD changes had decreased between -2.0% [region of interest (ROI) 1] and -11.5% (ROI 7). During the follow-up period the BMD initially increased during the second year and thereafter decreased again in ROIs 5, 6 and 7. The loss of BMD at five years was more pronounced in region 7 (12.9%) and decreased with increasing age, total hip replacement (THR) on the right side and decreasing weight of the patient. We found that after the initial phase of early bone loss a period of recovery follows. Thereafter the BMD decreases again, which probably reflects the normal ageing of bone after uncomplicated cemented THA.

Changes in periprosthetic bone remodelling after redesigning an anatomic cementless stem

The aim of this prospective cohort study was to determine the densitometric relevance of minor design modifications of a cementless stem designed to improve proximal load transfer. We used a prospective cohort study with densitometric analysis over a five-year period of two groups of patients with primary osteoarthritis. The first group, 56 hips, received the first version of the ABG stem (ABG-I); the second group, 54 hips, had the ABG-II stem. The results obtained with the ABG-I stem showed a decrease of bone density in proximal areas that ranged from 13% to 37%. However, the new design had a decrease of the same areas that ranged from 9% to 23%. These differences were noted at the end of the first post-operative year and remained stable, except in zone 7, where they were progressive. There is little evidence that the modified stem reduces femoral bone density loss.