Bone densitometry in orthopaedic practice

How to reduce osteopenia in total knee arthroplasty?

BACKGROUND

Osteopenia of the front half of the distal femur is a well-known problem after total knee arthroplasty (TKA) with secondary issues after years, especially when must be addressed fractures or revisions for loosening. Stress shielding has been recognized as a cause in different biomechanical studies of the bone.

QUESTION/PURPOSES

It was logical to look for a solution by changing the design to minimize stress shielding behind the femoral shield.

PATIENTS AND METHODS

It was proved that radiological measure of bone density was reliable although not so early and accurate as densitometry. We used a shield without posterior fixation of the trochlea in a series of 21 TKA with radiological measures, preoperative, at 3 months and at 5 years. We compared the results with those of a series of classical TKA in the same category of age and sex.

RESULTS

The TKA without trochlea posterior fixation presented a significantly reduced osteopenia compared to the classical design of the femoral shield.

CONCLUSION

It seems that the non-fixation of the posterior surface of the trochlea may reduce osteopenia in TKA and so the risk of fractures and complications when revision surgery.

LEVEL OF EVIDENCE

2a.

Bone mineral density of the coracoid process decreases with age

PURPOSE

Surgical options in the treatment of recurrent anterior shoulder instability are numerous. The Latarjet procedure is one of the most common procedures performed. It has been previously demonstrated that bone mineral density decreases with age. This reduction thus increases the risk of osteoporosis and osteoporosis-related iatrogenic, traumatic or pathological fractures. The objective of this study was to quantify the bone mineral density of the coracoid process in different age groups. The hypothesis was that mineral bone density of the coracoid process decreases with age.

METHODS

Using the hospital's electronic database, 60 patients who underwent a shoulder CT scan were randomly selected retrospectively. Four groups of 15 were formed with mean ages of 20, 30, 40 and 50 years. Bone density, length, width and thickness of the coracoid process 10 mm from the tip were measured four times by two different evaluators. Bone density was expressed in Hounsfield units (HU).

RESULTS

The mean bone mineral density of the coracoid process significantly decreased with age (p < 0.0001). A lower but insignificant difference of bone mineral density was observed in females. A good inter- and intra-observer reliability was found for bone mineral density measurement of the coracoid process (0.67 and 0.7, respectively).

CONCLUSIONS

The bone mineral density of the coracoid process diminishes with age, thus confirming our hypothesis. There is a good inter- and intra-observer reliability of our CT scan-based coracoid process bone mineral density measurement rendering it reproducible in daily clinical practice.

LEVEL OF EVIDENCE

IV.

Effect of Bone Mineral Density on Rotator Cuff Tear: An Osteoporotic Rabbit Model

Introduction

An increased bone mineral density (BMD) in the proximity to tendon insertion can improve rotator cuff repair and healing. However, how a decrease of BMD in the humeral head affects the biomechanical properties of the rotator cuff tendon is still unclear. Previous studies have demonstrated ovariectomy in animals to lead to osteoporosis and decreased BMD, and Teriparatide (PTH) administration to improve BMD and strength of bone. This study aimed to explore the correlation between humeral head BMD and infraspinatus (ISP) tendon insertion strength, and if an increase in bone quantity of the humeral head can improve the strength of the rotator cuff.

Materials and Methods

Eighteen New England white rabbits were divided into the 3 groups: Control, Ovariectomy-Saline (OVX-Saline), and Ovariectomy-PTH (OVX-PTH). The OVX-Saline group and the OVX-PTH were administered daily saline and Teriparatide injections for 8 weeks starting at 17 weeks of OVX. BMD of the humeral head was measured, the ISP tendon failure load was tested and the failure stress was calculated. One specimen from each group was used for histological analysis. Linear regression analysis was used to derive equations for the BMD and failure stress.

Results

Significant differences were observed in the measured humeral head BMD of the Control and OVX-PTH groups compared to the OVX-Saline group (P = 0.0004 and P = 0.0024, respectively). No significant difference was found in failure stress among the three groups, but an expected trend with the control group and OVX-PTH group presenting higher failure strength compared to the OVX-Saline group. BMD at the humeral head showed a positive linear correlation with stress (r² = 0.54). Histology results showed the superiority in OVX-PTH group ISP enthesis compared to the OVX-Saline group.

Conclusion

Bone loss of the humeral head leads to decreased tendon/bone insertion strength of the infraspinatus tendon enthesis. Teriparatide administration can increase bone density of the humeral head and may improve the mechanical properties of the infraspinatus tendon enthesis.

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.

Does bone density of the greater tuberosity change in patients over 70?

INTRODUCTION

There are no published studies on bone density of the greater tuberosity of the humerus, which could influence the stability of reinsertion by suture anchors. The goal of our study was to determine the influence of age, gender and the type of tear on the quality of bone in the greater tuberosity.

METHODOLOGY

Ninety-eight patients over the age of 60 were included, 41 without a rotator cuff tear and 57 with an isolated stage 1 or 2 supraspinatus tear and fatty infiltration (FI) ≤ 2. The areas of measurement included cancellous bone located under the cortex of the greater tuberosity. Measurements were obtained either across from the tear or from the middle facet with greater tuberosity if the cuff was not torn. We measured average, maximum and minimum bone density and the standard deviation (SD) in each region with Osirix software.

RESULTS

The two groups were similar for age (73), investigated side and mean densities (0.282 g/cm(2) vs 0.210 g/cm(2)). Age over 70 was a predictive factor for osteoporosis of the greater tuberosity whether or not a rotator cuff tear was present (P<0.0001). There was less trabecular bone in women with cuff tears (P=0.009). Stage 2 cuff retraction was predictive of osteoporosis of the greater tuberosity (P=0.0001).

CONCLUSION

This is the first study in the literature to evaluate bone density of the greater tuberosity in relation to the presence or not of a rotator cuff tear in an elderly population. Female gender, age over 70 and stage 2 cuff retraction are factors responsible for osteoporosis of the greater tuberosity of the humeral head. The osteoporosis is not severe, and normally the quality of bone of the greater tuberosity should not limit stability of suture anchors.

LEVEL OF EVIDENCE

3.

Comparing alumina-reduced and conventional surface grit-blasted acetabular cups in primary THA: early results from a randomised clinical trial

Alumina grit-blasted implants have been widely used in cementless total hip arthroplasty (THA). However, alumina particles can become embedded in the implant surface, leading to deposition in periprosthetic tissues and implant wear. We hypothesised that the alumina-reduced surface BICON-PLUS NT acetabular cup would improve implant fixation and clinical outcomes over the conventional surface BICON-PLUS cup. In a randomised controlled, double-blind study, patients with primary or secondary osteoarthritis requiring primary arthroplasty were randomly assigned to THA with either the BICON-PLUS or BICON-PLUS NT cup. All cups were combined with the SL-PLUS stem. In addition to clinical and radiographic assessments, dual-energy X-absorptiometry (DEXA) was performed preoperatively and at regular intervals during a planned 2-year follow-up period to measure bone mineral density as a marker of implant fixation. At 1 year, there were no differences in bone mineral density, or in clinical or radiographic outcomes between the BICON-PLUS and BICON-PLUS NT groups were identified, leading to early termination of the study. Both groups showed excellent clinical improvement and there were few complications. Both the alumina-reduced and conventional surface acetabular cups can be used with confidence in primary THA for osteoarthritis, although longer-term studies are required to confirm these findings.

Periacetabular cortical and cancellous bone mineral density loss after press-fit cup fixation: a prospective 7-year follow-up

The impact of total hip arthroplasty on strain adaptive bone remodeling has been extensively analyzed by dual-energy x-ray absorptiometry. In this study, we present a prospective computed tomography-assisted study of periacetabular cortical and cancellous bone mineral density (in milligrams of calcium hydroxyapatite [CaHA] per milliliter, or mgCaHA/mL) changes 10 days and 1, 3, and 7 years after press-fit cup implantation for 38 hips in vivo. Cancellous bone mineral density decreased by Ø -63% ventral and Ø -85% dorsal to the cup; cortical bone mineral density, by Ø -22% ventral and Ø -18% dorsal to the cup. The presented periacetabular strain adaptive bone mineral density data are the most extensive of the current literature. Even the measured extensive cancellous bone mineral density loss was thus far of no clinical relevance because all cups showed radiographic signs of stable ingrowth.

Surgical treatment options in patients with impaired bone quality

BACKGROUND

Bone quality should play an important role in decision-making for orthopaedic treatment options, implant selection, and affect ultimate surgical outcomes. The development of decision-making tools, currently typified by clinical guidelines, is highly dependent on the precise definition of the term(s) and the appropriate design of basic and clinical studies. This review was performed to determine the extent to which the issue of bone quality has been subjected to this type of process.

QUESTIONS/PURPOSES

We address the following issues: (1) current methods of clinically assessing bone quality; (2) emerging technologies; (3) how bone quality connects with surgical decision-making and the ultimate surgical outcome; and (4) gaps in knowledge that need to be closed to better characterize bone quality for more relevance to clinical decision-making.

METHODS

PubMed was used to identify selected papers relevant to our discussion. Additional sources were found using the references cited by identified papers.

RESULTS

Bone mineral density remains the most commonly validated clinical reference; however, it has had limited specificity for surgical decision-making. Other structural and geometric measures have not yet received enough study to provide definitive clinical applicability. A major gap remains between the basic research agenda for understanding bone quality and the transfer of these concepts to evidence-based practice.

CONCLUSIONS

Basic bone quality needs better definition through the systematic study of emerging technologies that offer a more precise clinical characterization of bone. Collaboration between basic scientists and clinicians needs to improve to facilitate the development of key questions for sound clinical studies.

Quantitative computed tomography-assisted osteodensitometry of the pelvis after press-fit cup fixation: a prospective ten-year follow-up

BACKGROUND

As a follow-up of a previously reported three-year study, we analyzed the periprosthetic acetabular cortical and cancellous bone density changes at ten years after implantation of a press-fit cup.

METHODS

Prospective clinical, radiographic, and quantitative computed tomography examinations were performed within ten days and at mean periods of one, three, and ten years after total hip arthroplasty with a press-fit cup, a femoral stem with a tapered design, and alumina-alumina pairing. Periacetabular cortical and cancellous bone density (mg CaHA/mL) in the cranial, ventral, and dorsal regions about the cup were measured for twenty-four hips in vivo.

RESULTS

All acetabular cups showed radiographic signs of stable ingrowth, and no acetabular component had to be revised. The loss of periacetabular cancellous bone density about the cup was as much as -37% cranially, -60% ventrally, and -71% dorsally; the decrease was progressive between the one-year and three-year examinations only. In contrast, cortical bone density above the dome of the acetabular cup remained constant throughout the ten-year follow-up. A moderate change in cortical bone density of -5% to -18% was seen at the level of the cup ten years postoperatively.

CONCLUSIONS

Both periacetabular cortical and cancellous bone density changes were nonprogressive between the three-year and ten-year examinations after press-fit cup fixation.

What happens to femoral neck bone mineral density after hip resurfacing surgery?

The major advantage of hip resurfacing is the decreased amount of bone resection compared with a standard total hip replacement. Fracture of the femoral neck is the most common early complication and poor bone quality is a major risk factor. We undertook a prospective consecutive case control study examining the effect of bone mineral density changes in patients undergoing hip resurfacing surgery. A total of 423 patients were recruited with a mean age of 54 years (24 to 87). Recruitment for this study was dependent on pre-operative bilateral femoral bone mineral density results not being osteoporotic. The operated and non-operated hips were assessed. Bone mineral density studies were repeated over a two-year period. The results showed no significant deterioration in the bone mineral density in the superolateral region in the femoral neck, during that period.

These findings were in the presence of a markedly increased level of physical activity, as measured by the short-form 36 health survey physical function score.

Association between periodontal disease and osteoporosis in postmenopausal women in jordan

BACKGROUND

Some studies suggest that females with osteoporosis are at an increased risk of periodontal attachment loss and tooth loss; however, results have varied. The aim of this study is to determine the relationship between periodontitis and osteoporosis among postmenopausal Jordanian women.

METHODS

This cross-sectional study includes 400 Jordanian postmenopausal women with a mean age of 62.5 years (SD ± 6.4 years). These subjects were recruited from patients who had received a routine dual-energy x-ray absorptiometry examination in the Radiology Department, King Abdullah Hospital, Jordan University of Science and Technology, between June 2008 and February 2009. The relationship between skeletal bone mineral density (BMD) and radiographic and clinical parameters of periodontal status, including the loss of alveolar crestal height (ACH), clinical attachment level, probing depth, and percentage of sites with bleeding on probing, was evaluated after controlling for known confounders.

RESULTS

Bivariate analyses revealed no significant differences in the severity and extent of clinical attachment and ACH loss among women with normal BMD, osteopenia, and osteoporosis. However, in the multivariate analysis, women with osteoporosis were more likely to have severe ACH loss (odds ratio [OR]: 4.20; 95% confidence interval [CI]: 1.57 to 11.22) and periodontitis (OR: 2.45; 95% CI: 1.38 to 4.34).

CONCLUSION

Osteoporosis was significantly associated with severe alveolar crestal bone loss and the prevalence of periodontitis cases in postmenopausal Jordanian women.

Bone remodeling in proximal HA-coated versus uncoated cementless SL-Plus((R)) femoral components: a 5-year follow-up study

BACKGROUND AND PURPOSE

Bone resorption at the femoral stem due to stress shielding has been particularly observed secondary to cementless hip replacement. This prospective study of 126 total-hip replacements was performed to examine clinical outcomes and changes in peri-prosthetic bone density after implantation of a double-tapered cementless femoral component manufactured with versus without hydroxyapatite (HA) coating.

METHODS

Sixty-seven femoral components with and 59 femoral components without proximal HA coating were implanted and examined after a mean follow-up of 5.8 (SD 1.1, 2.8-7.8) years. The Harris hip score (HHS) and plain radiographs were used for clinical and radiological follow-up evaluations. Possible changes in peri-prosthetic bone mineral density (BMD) were measured by dual-energy X-ray absorptiometry (DEXA).

RESULTS

Clinical outcome, measured by HHS, was similar in both groups. On plain radiographs, significantly less radiolucent lines were observed for the coated implants. DEXA revealed a significant increase in BMD at the proximal zones, along the medial side, and at the stem tips in the coated compared with the non-coated implants.

INTERPRETATION

Hydroxyapatite-coated implants yield favorable radiographic characteristics, but no greater clinical benefit after 5 years' implantation.

Analysis of bone mineral density and bone turnover in the presence of polymethylmethacrylate particles

Polymethylmethacrylate (PMMA) particles generated from joint arthroplasties appear to contribute to aseptic implant loosening through inflammation-induced periprosthetic osteolysis. However, osteolysis appears to be multifactorial; whether a direct link exists between PMMA particles and osteolysis in vivo is unproven. With the aim to define the relationship between PMMA particles and osteolysis, the authors analyzed the bone mineral density, using microCT scans preoperatively, the first day postoperatively and then every 7-10 days for 32 days, and bone turnover, using (18)F-fluoride positron emission tomography scanner (PET scan) at 8 weeks in four groups of mice that had undergone intramedullary femoral injection. The experimental group of five mice was injected with PMMA particles, and compared with two negative control groups (no injection and injection with the carrier, phosphate-buffered saline) and one positive control group (injection of PMMA particles contaminated with endotoxin). There was no significant change in bone mineral density with addition of PMMA particles, and no evidence of osteolysis. However, bone turnover was increased in the presence of PMMA particles. Even though a direct link between PMMA particles and osteolysis was not found in the short term, PMMA particles appear to influence the regenerative capacity of bone.

Contribution of the vertebral posterior elements in anterior-posterior DXA spine scans in young subjects

Because DXA is a projection technique, anterior-posterior (AP) measurements of the spine include the posterior elements and the vertebral body. This may be a disadvantage because the posterior elements likely contribute little to vertebral fracture resistance. This study used QCT to quantify the impact of the posterior elements in DXA AP spine measures. We examined 574 subjects (294 females and 280 males), age 6-25 yr, with DXA and QCT. QCT measures were calculated for the cancellous bone region and for the vertebral body including and excluding the posterior elements. DXA data were analyzed for the entire L(3) vertebra and for a 10-mm slice corresponding to the QCT scan region. BMC and BMD were determined and compared using Pearson's correlation. The posterior elements accounted for 51.4 +/- 4.2% of the total BMC, with a significant difference between males (49.9 +/- 4.0%) and females (52.8 +/- 3.9%, p < 0.001). This percentage increased with age in younger subjects of both sexes (p < 0.001) but was relatively consistent after age 17 for males and 16 for females (p > 0.10). DXA areal BMD and QCT volumetric BMD correlated strongly for the whole vertebra including the posterior elements (R = 0.83), with BMC measures showing a stronger relationship (R = 0.93). Relationships were weaker when excluding the posterior elements. We conclude that DXA BMC provides a measure of bone that is most consistent with QCT and that the contribution of the posterior elements is consistent in young subjects after sexual maturity.

Periprosthetic DXA after total hip arthroplasty with short vs. ultra-short custom-made femoral stems: 37 patients followed for 3 years

BACKGROUND AND PURPOSE

Dual-energy X-ray absorptiometry (DXA) analysis of the 7 periprosthetic Gruen zones is the most commonly used protocol to evaluate bone remodeling after the implantation of conventional femoral stems. We assessed the value of DXA after cementless primary total hip arthroplasty (THA) by comparing the effect of progressive shortening of the stem of two femoral implants on periprosthetic bone remodeling using a specifically developed protocol of analysis with 5 periprosthetic regions of interest (ROIs).

PATIENTS AND METHODS

Bone mineral density (BMD) was evaluated in 37 patients in the plateau stage, 3 years after THA. Two femoral implants featuring conceptually new designs and surgical technique were tested: types 1 and 2, characterized by extremely short stem and virtual absence of distal stem, respectively.

RESULTS

We found that progressive shortening of the femoral stem produces more proximal loading, which effectively preserves metaphyseal bone stock and increases periprosthetic BMD in the medial ROIs over time. In the type 2 group, higher absolute BMD values were observed in medial ROIs 4 and 5. No differences were found in ROIs 1, 2, and 3.

INTERPRETATION

This study shows the flexibility of DXA in adapting the protocol of periprosthetic analysis to the specific requirements of new implant designs, and it shows its high sensitivity in evaluation of the biological response of bone to changes in implant shape.

Retroacetabular stress-shielding in THA

We conducted a randomized clinical trial to compare periacetabular bone density changes after total hip arthroplasty using press-fit components with soft and hard liner materials. Bone density changes were assessed using quantitative computed tomography-assisted osteodensitometry. Twenty press-fit cups with alumina ceramic liners and 20 press-fit cups with highly cross-linked polyethylene liners were included; the nonoperated contralateral side was used as the control. Computed tomography scans were performed postoperatively and 1 year after the index operation. At the 1-year followup, we found no differences of periacetabular bone density changes between the alumina and polyethylene liner cohorts. However, we observed marked periacetabular cancellous bone density loss (up to -34%) in both cohorts. In contrast, we observed only moderate cortical bone density changes. The decrease of periacetabular cancellous bone density with retention of cortical bone density after THA suggests stress transfer to the cortical bone.

Computer-assisted osteodensitometry following total hip arthroplasty

Several factors, including polyethylene wear debris, implant micromotion and stress shielding, can cause bone loss and fixation failure following total hip arthroplasty. Various techniques have been utilized in an effort to detect bone density loss in vivo with varying success. Quantitative computed tomography (qCT)-assisted osteodensitometry has been shown to be useful in assessing the in vivo structural bone changes after total hip arthroplasty. It has high resolution, accuracy and reproducibility, making it a useful tool for research purposes. qCT osteodensitometry is able to differentiate between cortical and cancellous bone structures, and to assess the bone/implant interface. It provides valuable information about the pattern of stress shielding that occurs around the prosthesis. qCT-assisted osteodensitometry can show early bony changes, which may provide information about the quality of implant fixation and surrounding bone adaptation. In conjunction with finite-elements analysis, qCT is able to generate accurate patient-specific meshes on which to model implants and their effect on bone remodeling. This technology can be useful in order to predict bone remodeling and quality of implant fixation using prostheses with different design and/or biomaterials. In future, this tool could be used for preclinical validation of new implants before their introduction in the marketplace.

Quantitative computer-assisted osteodensitometry in total hip arthroplasty

Several factors can cause bone loss and fixation failure following total hip arthroplasty (THA), including polyethylene wear debris, implant micromotion and stress shielding. Various techniques have been used in an effort to detect bone density loss in vivo, all with varying success. Quantitative computed tomography (qCT)-assisted osteodensitometry has been shown to be useful in assessing the in vivo structural bone changes after THA. It has a high resolution, accuracy and reproducibility, thereby making it a useful tool for research purposes, and it is able to differentiate between cortical and cancellous bone structures and assess the bone/implant interface. This technique also provides valuable information about the pattern of stress shielding which occurs around the prosthesis and can show early bony changes, which may prove informative about the quality of implant fixation and surrounding bone adaptation. In conjunction with finite-element analysis, qCT is able to generate accurate patient-specific meshes on which to model implants and their effect on bone remodelling. This technology can be useful to predict bone remodelling and the quality of implant fixation using prostheses with different design and/or biomaterials. In the future, this tool could be used for pre-clinical validation of new implants before their introduction in the market-place.

Induced current bio-impedance technique for monitoring bone mineral density--a simulation model

In this study, the feasibility of using induced current bio-impedance technique as a method to determine and monitor bone mineral density (BMD) was theoretically evaluated using computerized simulation model. A 2D polar coordinates numerical solver was developed using the Finite Volume Method (FVM) in order to simulate the developed potentials over an axial CT cross section of a human thigh. Varying femur BMD were simulated by varying femur relative permittivity values. At the chosen excitation current of 1 ampere at a frequency of 20 kHz, the real component of the surface potential was found to be more sensitive to BMD variation than the imaginary component (3.9 microV g(-1) cm3 compared with 0.174 microV g(-1) cm3). The correlation between varying femur permittivities and the real component of the developed surface potential was found to be quadratic and influenced by the coil geometry and the measuring point location. Measurement sensitivity was improved either by taking the measuring point closer to the femur location or by minimizing the distance between the excitation coil and the femur. These results provide the basic principle that may enable a future use of bio-impedance technique for bone density evaluation and monitoring.

Dual-energy x-ray absorptiometry measurement and accuracy of bone mineral after unilateral total hip arthroplasty

The standard technique for monitoring bone mineral in hip arthroplasty has been dual-energy x-ray absorptiometry (DEXA). The accuracy of DEXA in the cortical bone adjacent to femoral components has not been established. This study evaluated bone mineral in the cortical bone adjacent to the femoral component comparing DEXA and ashing. Seven pairs of human femora from postmortem donors with unilateral hip implants were examined. Twenty-eight ashed core specimens from both the medial and lateral sides were taken. Cortical bone loss was seen to be greater in the proximal and medial regions of the implanted femora. Dual-energy x-ray absorptiometry failed to show an acceptable level of accuracy compared with ash data (r = 0.56; P = .002). It did show relative patterns of bone loss. Bone loss was consistent with implant-induced stress shielding.

Bone preservation with a conservative metaphyseal loading implant

Proximal load transfer and the absence of distal fixation of the stem are crucial to obtain the best behaviour of the femoral bone after total hip replacement. In this study, dual energy X-ray absorptiometry (DEXA) was employed to understand and compare the bone density changes and thus the re-distribution of mechanical forces in two different extra short stems. Two cohorts of ten patients were included in this retrospective study. Both implants are custom-made and present a well defined lateral flare. The first model is fully coated and presents a short stem (Group A), the second is an unstemmed metaphyseal implant with a polished tip (Group B). DEXA scans were obtained in all patients at the two-year follow-up. A higher BMD was detected in ROIs 1, 2, 4, 5 in Group B confirming a preservation of the proximal bone mass and thus indirectly a more proximal load transfer. The results obtained confirm the importance of the geometry of the implant on proximal bone density. Loading both medial and lateral proximal femoral flares and the complete absence of the diaphyseal portion of the stem provide the optimal bone remodelling of the femur after total hip replacement.

Measurement of bone mineral density is possible with standard radiographs: a study involving total knee replacement

BACKGROUND

Measured bone density correlates well with the mechanical properties of the bone. Our objective was to evaluate optical densitometry as a method of measuring the periprosthetic bone density of the tibial platform in total knee replacement using serial dual-energy X-ray absorptiometry (DXA) as the reference test.

METHODS

30 patients who underwent a cemented total knee replacement were followed up for over 2 years. Standard radiographs of the knee were obtained at 12 and 24 months. These were photographed with a digital camera and enhanced with image processing software. A DXA scan was performed at the same time as the reference method. 3 regions of interest were defined under the tibial plateau (medial, lateral and stem positions).

RESULTS

After 24 months of follow-up there was a significant decrease in density in the 3 regions, both with the optical and DXA methods. The concordance between methods was studied using Bland and Altman plots, Cronbach's alpha and intraclass correlation coefficients resulted in values from 0.72 to 0.87, depending on the region and the follow-up time.

INTERPRETATION

Quantification of optical density values with a standardized measurement system on conventional radiographs is a reliable and efficient method of determining the bone mineral density.

Low BMD is a risk factor for low-energy Colles' fractures in women before and after menopause

Until now, it was unclear if low volumetric bone mineral density at the distal radius was also a risk factor for Colles' fracture, especially in patients with low-energy trauma. In our study, we used peripheral quantitative computed tomography to measure volumetric bone mineral density of a nonfractured distal radius and dual-energy x ray absorptiometry to measure areal bone mineral density at the spine and hip in patients with Colles' fractures, including 45 women who were premenopausal (age range, 40-50 years) and 39 women who were postmenopausal (age range, 51-65 years). In each group, the patients were subdivided into low-energy and high-energy fracture groups. Ninety-five age-matched healthy women who were premenopausal and 90 age-matched healthy women who were postmenopausal without fracture history served as controls. The results showed that patients with low-energy fractures had a lower bone mineral density at all measurement sites, compared with either patients with high-energy fractures or control subjects. More patients were found with a bone mineral density less than -2.5 standard deviations (Z-score) in the premenopausal group (12.5% measured by dual-energy x ray absorptiometry and 41.2% measured by peripheral quantitative computed tomography) than in the postmenopausal group (6.0% measured by dual-energy x ray absorptiometry and 4.8% measured by peripheral quantitative computed tomography). These results suggest that low bone mineral density, particularly measured using peripheral quantitative computed tomography at the distal radius of women who were premenopausal, was an important risk factor for low-energy Colles' fractures.

LEVEL OF EVIDENCE

Prognostic study, Level I-1 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Modified calcaneal index: a new screening tool for osteoporosis based on plain radiographs of the calcaneum

PURPOSES

To assess osteoporosis using plain radiography of the calcaneum by studying the performance characteristics of the modified calcaneal index through inter- and intra-observer agreement. To study the correlation of the modified calcaneal index to quantitative ultrasound of the calcaneus and bone mineral density (BMD) of the femoral neck and distal radius.

METHODS

Lateral calcaneal radiographs of 252 women who participated in a clinical trial for osteoporosis were reviewed. The BMD of the hip and distal radius was measured and the calcanea were assessed using ultrasound. The calcaneal radiographs were graded by 3 clinicians according to a previously described 5-grade calcaneal index. A modified 3-grade calcaneal index was then developed.

RESULTS

The highest scores of intra- and inter-observer reliability of the modified calcaneal index were 0.45 and 0.40, respectively, which were higher than those of the 5-grade calcaneal index. The correlation of the modified calcaneal index with other measures was significant (hip BMD, r=0.31; distal radius BMD, r=0.28; calcaneal speed of sound, r=0.20; broadband ultrasound attenuation, r=0.36) [p<0.005]. There were significant differences in hip BMD, distal radial BMD, calcaneal speed of sound, and broadband ultrasound attenuation between the 3 grades of the modified calcaneal index (Kruskal-Wallis 1-way ANOVA; p<0.0001).

CONCLUSION

The modified calcaneal index can be used to measure bone structure and skeletal strength and is a suitable screening tool for osteoporosis in places where advanced approaches to bone-status assessment are not available.

Medium-term dexa analysis of an uncemented femoral component

We investigated the bone remodelling around the AML uncemented femoral component using DEXA analysis and plain radiography in 19 patients at a mean of 89 months from operation. All patients had previously been analysed at a mean of 32 months after surgery. We found a decrease in bone mineral density around the AML implant between the two scans in Gruen zones 1,2 and 6 of up to 8%, but an increase in zones 4,5 and 7 of up to 36%. The increase in zones 4 and 5 were statistically significant (P>0.05). The relative difference between the operated and unoperated hips also showed a reduction in the bone density ratio with time, except in zones 4 and 5 where an increase was seen. We confirm the results of previous studies of proximal stress shielding and distal loading around the AML implant and demonstrate that bone remodelling continues in the medium term. (Hip International 2004; 14: 182-8).

Pullout strength of suture anchors used in rotator cuff repair

BACKGROUND

Surgical treatment of rotator cuff tears may be complicated by osteoporosis of the proximal part of the humerus. The purpose of this study was to determine whether pullout strength of suture anchors is affected by the location of the anchor placement and by bone mineral density. We hypothesized that higher bone mineral density is associated with higher pullout strength of suture anchors.

METHODS

Peripheral quantitative computed tomography was used to measure total, trabecular, and cortical bone mineral density in different regions of the lesser and greater tuberosities in seventeen cadaveric humeri. Suture anchors were inserted into individual regions and subjected to cyclic loading. Repeated-measures analysis of variance was used to assess differences in bone mineral density and load to failure between regions of interest. Pearson correlation was used to determine the association between bone mineral density and pullout strength of suture anchors.

RESULTS

Total, trabecular, and cortical bone mineral densities were an average of 50%, 50%, and 10% higher, respectively, in the proximal part of the tuberosities compared with the distal part (p < 0.01). Within the proximal part of the greater tuberosity, trabecular bone mineral density of the posterior region and cortical bone mineral density of the middle region were, on the average, 25% and 16% higher, respectively, than the densities in the other regions (p < 0.01). Load to failure in the proximal part of the tuberosities was an average of 53% higher than that in the distal part (p < 0.01). The lesser tuberosity showed, on the average, a 32% higher load to failure than did the greater tuberosity (p < 0.01). Within the proximal part of the greater tuberosity, loads to failure in the anterior and middle regions were, on the average, 62% higher than the load to failure in the posterior region (p < 0.01). Overall positive correlations were found between bone mineral density and load to failure (0.65 </= r </= 0.74, p < 0.01).

CONCLUSIONS

We found that pullout strength of suture anchors correlates well with bone mineral density of the tuberosities. Higher loads to failure were found in regions in the proximal part of the tuberosities. Placement of anchors in these regions may prevent anchor loosening, formation of a tendon-bone gap, and failure of the rotator cuff repair.

Changes in proximal femoral bone mineral density around a hydroxyapatite-coated hip joint arthroplasty

OBJECTIVE

To present the results of a prospective analysis of proximal femoral bone mineral density changes around a hydroxyapatite-coated total hip joint replacement.

METHODS

14 patients with osteoarthritis of the hip were enrolled in the study and treated with an uncemented ABG prosthesis. Dual energy X-ray absorptiometry scanning was performed in 9 patients preoperatively, and at 3, 6, 12, and 24 months postoperatively. An orthopaedic software program was used to determine the bone mineral density in the proximal femur, expressed as a percentage of the preoperative value.

RESULTS

The values of Gruen zones 1 to 6 averaged between 96.0% and 113.8% of the preoperative value by 24 months (overall average, 104.1%). In zone 7, however, there was a gradual decline in bone mineral density to an average of 72.1% of the preoperative value by 24 months. This represented ongoing loss of bone from the calcar; although this may not pose a problem to the prosthetic's short-term stability, it may render potential revision surgery more difficult.

CONCLUSION

The initial outcome of uncemented total hip replacement appears to be promising. There was excellent maintenance of bone around the femoral component in all regions other than the calcar and lesser trochanter. Further scans are required to see if these trends continue in the long term.

Enzyme replacement therapy reduces Gaucher cell burden but may accelerate osteopenia in patients with type I disease - a histological study

Enzyme replacement treatment (ERT) is effective in controlling the clinical and biochemical manifestation of type I Gaucher disease. Little is known on the evolution of bone marrow histology caused by ERT. We compared the pretreatment trephine bone marrow biopsies in five patients (F32, F41, F50, M55, and M46) with the control biopsies performed after 26-32 months of imiglucerase treatment. The planimetric estimates revealed significant decrease in Gaucher cell burden in all the patients. The post-ERT values ranged from 24% to 65% of the initial total volumes occupied by the Gaucher cells. This resulted mainly from disappearance of Gaucher cells, and to a lesser extent from their shrinkage. Normal hemopoiesis was markedly increased in four of five patients, fat tissue in all the five patients. Surprisingly, the estimated volumes of trabecular bone in the control biopsies were significantly smaller than in the pre-ERT trephines (0.61%, 0.64%, 0.64%, 0.97%, and 0.22% of the initial volumes, P = 0.043). The bone loss correlated rather with the degree of reconstitution of normal hemopoiesis than with the decrease in the Gaucher cell burden. The histological response did not correlate strictly with initial clinical parameters and the genotype, with different reactions to ERT in two sibs (cases 3 and 4). Particularly, ERT alleviated bone manifestations in all four patients with previous bone pains or fractures. ERT may accelerate progress of osteopenia in men and premenopausal women. The clinical significance of this phenomenon remains to be established. Its mechanism may be linked to increased osteolytic activity exerted directly or indirectly by regenerating hemopoietic cells.

Early fracture of the sacrum or pelvis: an unusual complication after multilevel instrumented lumbosacral fusion

STUDY DESIGN

A retrospective review of a series of cases with a complication of instrumented lumbosacral fusion.

OBJECTIVES

To present a previously undescribed complication, early sacral or pelvic stress fracture, after instrumented lumbosacral fusion and to identify the risk factors associated with this complication.

BACKGROUND

There are a number of well-described complications of instrumented lumbosacral fusion, including delayed stress fracture of the pelvis. Early sacral or pelvic stress fracture after instrumented lumbosacral fusion has not been previously reported, to the authors' knowledge.

METHODS

The authors present three cases of early stress fracture occurring at 2-4 weeks after surgery in patients who underwent instrumented multilevel lumbosacral fusions for degenerative lumbosacral disease.

RESULTS

Two patients had sacral fracture, which to the authors' knowledge, has not been previously reported. Risk factors included lumbosacral instrumentation and fusion, osteoporosis in elderly women, and iliac crest bone graft procurement. All patients were treated conservatively, with restricted ambulation and gradual return to activity.

CONCLUSION

This complication can cause significant morbidity and a delay in the patient's return to function. A better understanding of the related biomechanical forces and preoperative risk factors may identify patients at risk and may aid in surgical planning and in expectations of postoperative recovery.

Water fluoridation, osteoporosis, fractures--recent developments

BACKGROUND

Optimal (1ppm) water fluoridation is seen as the most socially equitable way to prevent dental caries, however concerns about the safety of fluoridation are periodically raised.

METHODS

Research on effects on bone published since the 1991 National Health and Medical Research Council report on water fluoridation was reviewed.

RESULTS

Thirty-three studies were identified. Adverse effects in animal feeding studies were only seen at doses much greater than those currently used in artificial water fluoridation. The majority of animal studies showed no effect or a beneficial effect of low fluoride doses. The results of ecological studies were conflicting. One of the two cohort studies showed an increase in fracture incidence at fluoride levels four times greater than optimal water fluoridation and the other showed no effect after 20 years' optimal fluoridation. The cross-sectional studies showed a favourable effect on bone mineral density. The clinical trials predominantly showed increased bone density in several sites associated with fluoride treatment of 9-22.6mg fluoride per day for one-four years.

CONCLUSION

These studies provide a substantial body of evidence that fluoride at up to 1ppm does not have an adverse effect on bone strength, bone mineral density or fracture incidence.

Expanding the role of the orthopaedic surgeon in the treatment of osteoporosis

Osteoporosis is an increasingly prevalent disease among the aging population, and osteoporotic features account for substantial morbidity, mortality, and healthcare costs associated with this disease. Because the disease is silent until a fracture occurs, the orthopaedic surgeon often may be the physician in the best position to establish the diagnosis and consider the initiation of appropriate treatment. Historically, osteoporosis has been underdiagnosed and treated, but new methods allow accurate diagnosis using bone densitometry, and a range of effective treatment options that can reduce fracture risk. Diagnosis and treatment of osteoporosis fits readily into an efficient algorithmic approach in the office practice of orthopaedics. Orthopaedic surgeons can play a major role in improving the treatment of osteoporosis and decreasing morbidity from this disease. In addition, this can augment the office practice of orthopaedics with a large yet relatively underserved patient population. Finally, densitometry services can provide modest supplemental revenue sources for an orthopaedic practice.

Bone density adjacent to press-fit acetabular components. A prospective analysis with quantitative computed tomography

BACKGROUND

The status of periprosthetic bone stock is an important concern when revision total hip arthroplasty is undertaken. Remodeling of periprosthetic femoral bone after total hip arthroplasty has been studied extensively, and the phenomenon of femoral stress-shielding has been well characterized. Finite element analysis and computer-simulated remodeling theory have predicted that retroacetabular bone-mineral density decreases after total hip arthroplasty; however, remodeling of periprosthetic pelvic bone in this setting has yet to be well defined. This study was conducted to evaluate the short-term natural history of periacetabular bone-mineral density following primary total hip arthroplasty.

METHODS

Periacetabular bone-mineral density was studied prospectively in a group of twenty-six patients who underwent primary hybrid total hip arthroplasty for the treatment of advanced osteoarthritis. Density within the central part of the ilium (directly cephalad to a press-fit acetabular component) was assessed with serial quantitative computed tomography. Baseline density was measured within the first five days following the total hip arthroplasty. Ipsilateral density measurements were repeated at an average of 1.28 years postoperatively. Density values at corresponding levels of the contralateral ilium were obtained at both time-points in all patients to serve as internal controls.

RESULTS

Bone-mineral density decreased significantly (p< or =0.001) between the two time-points on the side of the operation. The mean absolute magnitude of the interval density reduction (75 mg/cc) was greatest immediately adjacent to the implant (p<0.001), but it was also significantly reduced (by 35 mg/cc) at a distance of 10 mm cephalad to the implant (p = 0.001). Relative declines in mean density ranged from 33% to 20% of the baseline values. No focal bone resorption (osteolysis) was detected at the time of this short-term follow-up study. With the numbers available, no significant interval alteration in bone-mineral density was found on the untreated (internal control) side (p> or =0.07).

CONCLUSIONS

We suggest that the observed decline in bone-mineral density represents a remodeling response to an altered stress pattern within the pelvis that was induced by the presence of the acetabular implant. This finding corroborates the predictions of finite element analysis and computer-simulated remodeling theory. It remains to be seen whether this trend of atrophy of retroacetabular bone stock will continue with longer follow-up or will ultimately affect the long-term stability of press-fit acetabular components.

Upper extremity disorders in women

Carpal tunnel syndrome, Colles' fracture, and osteoarthritis of the basilar joint of the thumb are only three of the many upper extremity conditions that preferentially affect women. With more and more women entering the workplace, these conditions become more disruptive of patients' lifestyles and even may be increasing in incidence. Orthopaedic surgeons traditionally have focused on the surgical treatment of patients with these conditions, but it is becoming increasingly clear that surgeons also must focus on delineating pathophysiology to better identify those individuals at risk and help prevent these potentially disabling disorders.