Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip arthroplasty: A prospective study using computed tomography‐assisted osteodensitometry

Stress‐shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high‐demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)‐assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n = 21) versus noncemented (n = 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press‐fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (−45 to −53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (−11 to −20%). Cancellous BD decrased only ventral (−21 to −31%) and in two scans cranial (−11 and −12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press‐fit component. Long‐term results are required to prove whether third‐generation cementing technique protects periprosthetic BD and thereby improve implant survival. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:176–182, 2009     

Periprothetische femorale Knochenreaktion nach schenkelhalserhaltender H��ftendoprothetik

Background

Short-stemmed cementless femoral components in total hip arthroplasty have been designed to preserve the proximal femoral bone stock by load transfer to the femoral metaphysis. An in vivo method of computed tomography-assisted (CT) osteodensitometry after total hip arthroplasty is presented which differentiates between cortical and cancellous bone density (BD) changes around uncemented femoral components.

Patients and methods

Cortical and cancellous periprosthetic femoral BD (mg Ca?HA/ml) was determined prospectively in 31?patients at day 10, 1?year and 3?years after total hip arthroplasty with preservation of the collum femoris (C.F.P.-stem, Link, Hamburg, Germany) using computed tomography-assisted osteodensitometry. Clinical results (Harris hip score) and plain x-rays were assessed in all cases.

Results

Progressive proximal cortical BD loss was observed between the 1 year (? ?8%) and 3 year (? ?22%) postoperative measurements. Distal to the trochanter minor no significant cortical BD changes were observed. Proximal cancellous BD decreased progressively between the 1 year (? ?33%) and 3 year (? ?45%) analyses. The Harris hip score improved from 45 points pre-operatively to 93 points at the 3 year follow-up. All x-rays showed signs of stable ingrowth.

Conclusion

Periprosthetic CT osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling. Progressive proximal cortical and cancellous BD loss indicates that metaphyseal fixation cannot be achieved with the analyzed C.F.P. stem design. The lack of cortical BD loss below the trochanter minor suggests diaphyseal fixation of the implanted stem.     

Stress-related femoral cortical and cancellous bone density loss after collum femoris preserving uncemented total hip arthroplasty: a prospective 7-year follow-up with quantitative computed tomography

Purpose

Bone loss around uncemented femoral components is suspected to precede implant loosening and contribute to problems in revision surgery. Short-stemmed cementless femoral components are designed to preserve proximal femoral bone stock and ultimately the longevity of the prosthesis.

Methods

With quantitative computed tomography-assisted osteodensitometry, we prospectively analyzed femoral cortical and cancellous bone density (BD) and contact area changes of an uncemented collum femoris preserving stem (n?=?38) 10?days, 1, 3 and 7?years post-operatively.

Results

Seven years post-operatively, cancellous BD (mg CaHA/mL) had decreased by as much as ?66?% and cortical BD by up to ?27?% at the metaphyseal portion of the femur; the decrease was progressive between the 1- and 3-year examinations and halted thereafter. Contact area (in % out of a possible 100?%) decreased proximally between the 1- and 3-year follow-up.

Conclusion

Proximal cortical and cancellous bone density loss and decrease of contact area indicate that metaphyseal fixation cannot be achieved. The lack of cortical BD loss and increase of contact area values below the trochanter minor suggest diaphyseal fixation.     

Use of a long distally fixed intramedullary stem to treat a periprosthetic femoral fracture following total hip arthroplasty using a thrust plate hip prosthesis: A case report

IntroductionThe thrust plate hip prosthesis (TPP; Zimmer, Winterthur, Switzerland) is a hip prosthesis that is no longer in production. Few reports have focused on periprosthetic fractures following total hip arthroplasty (THA) with the use of a TPP.Presentation of caseWe report a 57-year-old woman with a periprosthetic femoral fracture 13 years after THA with the use of a TPP. A plain radiograph showed a displaced subtrochanteric fracture of the right femur just below the distal tip of the lateral plate without implant loosening. She underwent revision surgery with a long distally fixed intramedullary stem in conjunction with a plate and cable system. Three months after surgery, bone union was confirmed using radiography and the patient was clinically asymptomatic.DiscussionWe encountered three major problems while planning surgical treatment, these being, discontinuation of the TPP system, loss of proximal femoral cancellous bone, and difficulties with the type of subtrochanteric fracture. After considering these problems, we planned revision surgery using a long distally fixed intramedullary stem in conjunction with a plate and cable system.ConclusionThis case shows that sufficient implant preparation based on precise preoperative planning is necessary to obtain good clinical results for the surgical treatment of periprosthetic femoral fractures following THA with the use of a TPP.     

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.     

Acetabular cortical and cancellous bone density and radiolucent lines after cemented total hip arthroplasty: a prospective study using computed tomography and plain radiography

Introduction

The aim of this prospective study was to evaluate load-transfer mechanisms and stress patterns of periacetabular cortical and cancellous bone after cemented total hip arthroplasty (THA) in vivo using computed tomography (CT) assisted osteodensitometry. In addition we analyzed the efficacy of CT in detecting radiolucent lines around the acetabular component compared to plain radiography.

Materials and methods

Twenty-two cemented acetabular cups were investigated using conventional sequential axial CT scans (Ø 8 days and 26 months post-OP) and plain radiography (Ø 5 days and 40 months post-OP). CT assisted osteodensitometry was used to determine cancellous and cortical bone bone density (BD). Radiolucent lines were evaluated using both CT and plain radiography.

Results

Significant BD loss at the time of follow-up was only detectable ventral to the cup (cortical bone: ?16%, P = 0.001; cancellous bone: ?31%, P = 0.001). The BD changes dorsal and cranial to the cup were not significant. Postoperatively no radiolucent lines were observed in the cement-bone interface by CT, while on plain radiography acetabular lucent lines were seen in 12 out of 22 cases.

Conclusion

CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.

     

Restoration of proximal periprosthetic bone loss by denosumab in cementless total hip arthroplasty

Summary

Denosumab contributed to the restoration of proximal periprosthetic bone loss around the femoral stem that were measured using a DEXA, especially in zone 7, at 1 year after cementless THA in elderly osteoporotic patients.

Introduction

Although bone quality is an important issue in elderly osteoporotic patients who underwent total hip arthroplasty (THA) with a cementless stem, periprosthetic bone mineral density (BMD) in the proximal femur has been reported to be decreased by 15–40% postoperatively. Some authors have examined the use of several types of bisphosphonates to prevent decreases in BMD in the proximal femur after cementless THA; however, few reports have demonstrated success in restoring BMD in the proximal medial femoral bone, such as zone 7.

Methods

We conducted prospective study comparing patients who underwent cementless THA administered with denosumab (10 patients) and without denosumab (10 patients). BMD around the femoral stem were measured using a DEXA immediately after surgery, and at 6 months and at 1 year after surgery. No difference was found between the two groups referred to the patient’s demographic data.

Results

We found that denosumab displayed definitive effects in increasing the % change in periprosthetic BMD at zone 7 by an average of 7.3% in patients with cementless THA, compared to control group who were given only vitamin D.

Conclusion

Denosumab is one of a number of anti-osteoporotic agents to have a definitive effect on the restoration of proximal periprosthetic bone loss, especially in zone 7, after cementless THA. Denosumab contributed to the restoration of decreased periprosthetic BMD to normal levels. As the decrease in BMD in the proximal femur after THA is considered to be apparent at 6–12 months after surgery, it is believed that prevention of the deterioration of bone quality is important in the proximal femur immediately after cementless THA for elderly female patients with osteoporosis.

     

Bone mineral density and biochemical markers of bone turnover in aseptic loosening after total hip arthroplasty.

The aims of this study were to determine whether subjects with aseptic loosening after total hip arthroplasty (THA) have regional differences in periprosthetic bone mineral density (BMD) and systemic biochemical markers of bone turnover compared to subjects with successful implants.Proximal femoral and pelvic BMD were measured by dual energy X-ray absorptiometry and bone turnover markers were assayed in 49 subjects 12.6+/-4.3 (mean+/-SD) years after cemented THA. Femoral BMD was lower in Gruen zones 2, 5, 6, and 7 in subjects with a loose femoral implant (n=17) compared to those (n=32) with fixed femoral implants (P<0.05 all comparisons). This BMD difference was greatest (-31%, P=0.02) in the proximal and medial region of the femur. Subjects with femoral loosening had higher levels of the bone resorption marker N-telopeptides of type-I collagen (P=0.02) than those with a fixed femoral implant. No differences in pelvic BMD or bone turnover markers were found between subjects with loose (n=18) versus fixed (n=31) pelvic implants.This study suggests that failure of femoral components after cemented THA is associated with region-specific decreases in BMD and an increase in urinary excretion of N-telopeptide cross-links of type-I collagen. These surrogate outcome markers may be of value in monitoring response to antiresorptive therapies used to treat periprosthetic osteolysis, although the diagnosis of aseptic loosening remains clinical and radiological.     

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

The aim of this prospective study was to measure bone density changes and to assess adaptive bone remodelling after uncemented total hip arthroplasty with a taper-design femoral component using quantitative computer-tomography-assisted osteodensitometry. This method is able to differentiate cortical and cancellous bone structures. Twenty-seven consecutive patients (29 hips) with degenerative joint disease were enrolled in the study. Serial clinical, radiological and CT-osteodensitometry assessments were performed after the index operation. At the 2-year follow-up, the clinical outcome was rated satisfactory in all hips. The radiological assessment showed signs of osteointegration and stable fixation of all cups and stems. We observed a -17% decrease of cortical bone density and -22% decrease of cancellous bone density in the greater trochanter and femoral neck region. Cortical and cancellous bone density decrease at the level of the lesser trochanter was -9% and respectively -4%. We observed small changes of cortical bone density in the diaphyseal regions; in contrast, cancellous bone density increased (range 6% to 27%) in the diaphyseal regions. Overall, a trend of bone density recovery was observed throughout the follow-up period. Periprosthetic bone density changes at the 2-year follow-up are suggestive of stable osteointegration with proximal femoral diaphysis load transfer and moderate metaphyseal stress-shielding.     

股骨皮质骨开窗技术在髋关节翻修术中的应用

目的 探讨股骨前外侧皮质骨开窗技术在髋关节翻修术中取出股骨远端稳定固定骨水泥的价值.方法 2005年5月至2009年6月,共14例(14髋)因各种原因致髋关节置换术后失败患者接受全髋关节翻修手术.其中男性10例,女性4例,年龄54～75岁,平均66岁.翻修原因为股骨头置换术后髋臼磨损5例、全髋关节置换术后假体周围骨溶解并松动6例、骨水泥柄股骨近端骨溶解柄断裂1例、髋臼骨溶解假体松动翻修同时行股骨柄翻修1例,感染后二期翻修时远端骨水泥取出困难1例.14例(14髋)股骨柄均为骨水泥同定.术中按术前计划开窗部位、开窗范围于股骨皮质骨开一长方形骨窗.通过骨窗直视下彻底清除髓腔内稳定固定的骨水泥,修整股骨髓腔.植入翻修柄后将皮质骨开窗骨瓣原位回植,双股钢丝捆绑固定.术后定期随访拍摄x线片.观察皮质骨开窗骨瓣与周围骨愈合情况、骨瓣有无移位、股骨柄有无下沉以及有无捆绑钢丝断裂等.结果 10例患者术后获得随访,平均随访时间24.6个月.股骨皮质骨开窗长度2.5～6.0 cm,平均3.4 cm,宽度0.8～1.4 cm,平均1.2 cm.股骨开窗远端以远部分发生纵形劈裂骨折1例.无术中皮质骨穿孔及股骨干骨折.向远段扩大开窗1例,扩大长度1.5 cm.开窗部位皮质骨骨瓣原位回植选择2～3道双股钢丝固定,平均2.3道.随访期间2例发牛假体柄下沉(平均2.5 mm),无皮质骨瓣移位以及捆绑钢丝断裂,术后3～5个月皮质骨瓣已于周围骨纤维愈合.随访期间无一例因各种原因致再次翻修.结论 股骨皮质骨开窗技术在髋关节翻修术中有助于直视下彻底取出股骨髓腔远端稳定固定的骨水泥,同时不会造成股骨骨丢失、不影响翻修柄植入后的稳定固定.     

Total Hip Arthroplasty in Patients With Osteopetrosis

BackgroundOsteopetrosis is an inherited bone disease associated with high risk of osteoarthritis and fracture non-union, which can lead to total hip arthroplasty (THA). Bone quality and morphology are altered in these patients, and there are limited data on results of THA in these patients. The goals of this study were to describe implant survivorship, clinical outcomes, radiographic results, and complications in patients with osteopetrosis undergoing primary THA.MethodsWe identified 7 patients (9 hips) with osteopetrosis who underwent primary THA between 1970 and 2017 utilizing our total joint registry. The mean age at index THA was 48 years and included two males and five females. The mean follow-up was 8 years.ResultsThe 10-year survivorship free from any revision or implant removal was 89%, with 1 revision and 1 resection arthroplasty secondary to periprosthetic femoral fractures. The 10-year survivorship free from any reoperation was 42%, with 4 additional reoperations (2 ORIFs for periprosthetic femoral fractures, 1 sciatic nerve palsy lysis of adhesions, 1 hematoma evacuation). Harris hip scores significantly increased at 5 years (P = .04). Five hips had an intraoperative acetabular fracture, and 1 had an intraoperative femur fracture. All postoperative femoral fractures occurred in patients with intramedullary diameter less than 5 mm at a level 10 cm distal to the lesser trochanter.ConclusionPrimary THA in patients with osteopetrosis is associated with good 10-year implant survivorship (89%), but a very high reoperation (58%) and periprosthetic femoral fracture rate (44%). Femoral fractures appear associated with smaller intramedullary diameters.     

Periacetabular bone changes after uncemented total hip arthroplasty evaluated by quantitative computed tomography

Background?There are few dual X-ray absorptiometry (DXA) studies on periacetabular bone density changes after cup implantation. This study was designed to analyze the load-transfer mechanism and stress pattern of periacetabular cortical and cancellous bone after implantation of a ihemispherical titanium alloy press-fit cup with alumina-alumina pairing in vivo. We introduced a novel method of computed tomography (CT)-assisted osteodensitometry.

Method?We investigated 26 hips (26 patients) with osteoarthritis using conventional sequential CT examinations performed within the first 10 days after implantation, and after a mean period of 1.1 years postoperatively. Bone density of full, cancellous and cortical bone (mgCaHA/mL) was measured.

Results?At the time of follow-up, the mean bone density values of the cortical bone cranial to the cup increased by 3.6% (p = 0.03) while the cancellous bone density decreased by 18%. Cancellous bone loss was greater in the region ventral to the cup (–35%) than in the dorsal region (–30%). Cortical bone density decreased ventral to the cup (–6.4%). All these changes were statistically significant. The bone density changes in the dorsal cortical region were not significant.

Interpretation?The method presented is an excellent tool for detailed measurement of bone density changes around the cup after total hip arthroplasty, and allows a thorough assessment of stress shielding phenomena in vivo. The hemispherical titanium alloy press-fit cup is a rigid implant which stress shields cancellous bone and enhances load transfer to the cranial cortical bone. Further investigations will demonstrate the impact these factors have on the long-term results of the implant, and may allow a type-related predictable prognosis of the longevity of the prosthesis.     

Catastrophic Periprosthetic Osteolysis in Total Hip Arthroplasty at 20 Years: A Case Report and Literature Review

BackgroundPeriprosthetic osteolysis is a serious complication following total hip arthroplasty (THA). However, most orthopedic surgeons only focus on bone loss and hip reconstruction. Thus, it was required to understand the treatment algorithm for periprosthetic osteolysis integrally.Case PresentationA 52‐year‐old Asian male presented with chronic hip pain. A mass appeared on the medial side of the proximal left thigh at more than 20 years after bilateral THA. Radiographs revealed catastrophic periprosthetic osteolysis, especially on the acetabular side. Large amounts of necrotic tissue and bloody fluids were thoroughly debrided during revision THA. A modular hemipelvic prosthesis was used for revision of the left hip. Four years later, the patient presented with right hip pain, where a mass appeared on the medial side of the proximal right thigh. A primary acetabular implant with augment was used for revision of the right hip. Laboratory evaluation of bloody fluid retrieved from surgery revealed elevated levels of inflammatory markers.ConclusionInflammatory responses to polyethylene wear debris can lead to severe bone resorption and aseptic loosening in the long‐term following THA. Therefore, in spite of revision THA, interrupting the cascade inflammatory might be the treatment principle for periprosthetic osteolysis.     

Poor intermediate-term survival of the uncemented Optan anatomically adapted femoral component

Purpose — We evaluated the 5-year survival of the uncemented Optan anatomically adapted femoral stem, with revision for aseptic loosening as the endpoint.

Methods — Between January 2004 and March 2007, 432 total hip arthroplasties (THAs) were performed in 432 patients. After follow-up for a mean time of 5 years, the patients were evaluated using the WOMAC questionnaire and plain radiography. Patients who were unable to attend the follow-up visit were contacted by telephone to determine whether they had had any revision surgery of their THA

Results — Within 5 years, 39 patients (9%) had died of unrelated causes and 63 patients (15%) had been lost to follow-up. Of the remaining cohort, 224 patients (68%) had full follow-up while 88 patients (27%) were evaluated with WOMAC only and 18 patients (5%) were evaluated with radiography only. The mean WOMAC score of all evaluated patients was 21 (10–100). At 5-year follow-up, there were 26 stem revisions reported (6%), 14 hips (3%) showed aseptic loosening, and 12 hips (3%) had had a periprosthetic femoral fracture. The 5-year survival to revision for any reason was 94%. Worst-case analysis yielded a 5-year survival of 79%.

Interpretation — The 5-year survival for aseptic loosening of the Optan anatomically adapted femoral component was disappointing. Radiographic evaluation showed evidence of proximal radiolucencies and distal cortical bone hypertrophy, which we attribute to insufficient proximal bone in-growth and increased load transfer at the tip of the stem. We do not recommend the use of the Optan femoral stem.     

Periprosthetic cortical bone remodeling in patients with an osseointegrated leg prosthesis

Qualitative studies have shown that the periprosthetic cortical bone may decrease in the first years after the implantation of an osseointegrated leg prosthesis (OILP) in patients with a transfemoral amputation. The resorption of periprosthetic cortical bone may endanger implant survival because of outbreak fractures and aseptic loosening. A decrease in periprosthetic bone quality may also lead to insufficient bone stock for potential revision surgery. This study quantified the periprosthetic bone changes and skeletal remineralization in 27 patients with an ILP (Integrated Leg Prosthesis)‐type transfemoral OILP. Periprosthetic cortical thickness was analyzed from standard anteroposterior (AP) radiographs that were taken immediately postoperatively and at both 12 and 24 months post‐implantation. The bone mineral density of the femoral hip neck on both sides was measured pre‐operatively with Dual X‐ray absorptiometry (DXA) and at 12 and 24 months post‐implantation. Compared to that immediately post‐operative, the periprosthetic cortical thickness increased significantly by 9.6% (p = 0.020) and 8.9% (p < 0.001) at 12 and 24 months, respectively. The change in bone mineral density of the hip neck on both sides was not significant. In contrast to previous observations, this study reports increased periprosthetic cortical thickness around the OILP implant in the first 2 years after implantation. These data indicate good prospects for implant survival and possibilities for revision surgery. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1237–1241, 2017.

     

Is there a significant decrease in the femoral cortical bone around Furlong® stems after 18 years of follow-up?

Introduction

In the context of total hip arthroplasty (THA), there are several reasons that have motivated the development of short stems. It has been postulated that short stems allow a better conservation of the bone stock if compared to conventional stems. As far as we have knowledge, the quantitative loss of diaphyseal bone stock in patients with standard femoral stems has not been fully described.

The aim of this study was to provide evidences about the thickness of the cortical bone at the diaphysis in patients who have undergone unilateral THA with Furlong^® stems with a minimum follow-up of 18 years.

Patients and methods

A retrospective study of patients who underwent THA in a single hospital was performed. The inclusion criteria were patients who had undergone a non-cemented elective THA with a Furlong^® stem, minimum follow-up of 18 years, and contralateral femur and hip without history of previous surgical procedures. The follow-up analysis was performed by means of radiological examinations performed at the last follow-up visit. Data related to the sex, age at surgery and adverse events registered during the follow-up were gathered. The cortical thickness index (CTI) and cortical thickness (CT) assessed at the last follow-up visit in anteroposterior pelvic X-rays were analyzed, both in the operated hip and in the non-operated hip (which was used as control). Calibration of the measurements was done by means of using the circumference of the head of the THA.

Results

The total number of patients who met the inclusion criteria was 22. There were 14 women and eight men. There were 12 left hips. The mean age at the time of surgery was 59.32 ± 6.83 (range 50–70) years. The mean follow-up was 20.86 ± 1.90 (range 18–24) years. The CTI was found to be 11.93% greater in the non-operated hips. The CT measured at 3 cm and 6 cm from lesser trochanter, and at 9 cm from the greater trochanter, was found to be 21.64%, 15.33% and 18.73% greater in the non-operated hips, respectively.

Conclusion

After a minimum of 18 years from the implantation of a Furlong^® stem, the bone density that surrounds the implant seems to involve a cortical bone ten percent less thick than the cortical bone of the non-operated contralateral side. With this stem, the cortical zones with less CT seem to be the lateral cortex at 9 cm from the greater trochanter, and the medial cortex at 3 and 6 cm from the lesser trochanter.

Level of evidence

III, retrospective case–control study.

     

Unstable versus stable uncemented femoral stems: a radiological study of periprosthetic bone changes in two types of uncemented stems with different concepts of fixation

Introduction Uncemented stems in total hip arthroplasty (THA) are used increasingly often because they are believed to offer a reliable long-term fixation. However, periprosthetic bone remodelling has been a worrying issue. A proximal demineralization has been noted in femurs with well-fixed stems, and it has been explained as by-passing of mechanical forces along the fixed implant (stress-shielding). Aseptic loosening has been a major problem in several uncemented series with earlier designs. The objective for this study was to investigate how the host bone adapts to a loose stem compared with a well-fixed stem after a long time.Materials and methods An investigation with dual-energy X-ray absorptiometry (DEXA), scintimetry and radiological assessment was carried out in 20 patients 8 years after a THA for arthrosis with two different uncemented stems. Ten patients received a stem coated with polytetrafluoroethylene (Anaform); all prostheses showed migration and were considered unstable. Ten patients received a hydroxyapatite-coated stem (Bi-Metric); no prosthesis migrated.Results Different remodelling patterns were seen. In the unstable group, the periprosthetic bone mineral density (BMD) was significantly reduced along the entire stem, while in the stable group only proximal bone loss was seen. The scintigraphic uptake was increased under the stem tip in both groups, and among unstable stems uptake was also increased in the calcar region.Conclusion The assessment of periprosthetic bone remodelling after uncemented THA with long-term observation shows a different host-bone response in stable versus unstable femoral implants. Prior to a femoral revision, measurement of the BMD could be beneficial; it may guide the surgeon when deciding which surgical technique to use.     

Locking compression plate versus revision-prosthesis for Vancouver type B2 periprosthetic femoral fractures after total hip arthroplasty

IntroductionRevision arthroplasty is currently the recommended treatment for periprosthetic femoral fractures after primary total hip arthroplasty (THA) and stem loosening (Vancouver B2). However, open reduction and internal fixation (ORIF) utilizing locking compression plate (LCP) might be an effective treatment with a reduced surgical time and less complex procedure in a typically elderly patient collective with multiple comorbidities. The purpose of this study was to compare the functional and radiographic outcomes in two cohorts with Vancouver B2 periprosthetic femoral fractures after primary THA, treated either by ORIF with LCP fixation, or by revision arthroplasty utilizing a non-cemented long femoral stem.Materials and Methods36 patients with Vancouver B2 periprosthetic femoral fractures following THA, who had been treated between 2000 and 2014, were reviewed. Eight fractures were treated with LCP fixation, fourteen fractures with the first-generation revision prosthesis (Helios^®), and fourteen fractures with the second-generation revision prosthesis (Hyperion™). The patients were assessed clinically with the Parker mobility score and radiographically.ResultsA total of ten males and 26 females formed the basis of this report with an average age of 81years (range, 64 to 96 years). All fractures treated with LCP fixation alone healed uneventfully and there were no signs of secondary stem migration, malalignement or plate breakage. The average surgical time was shorter in the ORIF cohort; however, the results were not statistically significant. The postoperative Parker mobility score at latest follow-up showed no difference between the groups.ConclusionsAccording to the results of the current study, we conclude that the use of LCP fixation can be a sufficient option for the treatment of Vancouver B2 periprosthetic femoral fractures correspondingly with femoral stem loosening.     

A computed tomography assessment of femoral and acetabular bone changes after total hip arthroplasty

Using computed tomography-assisted (CT) osteodensitometry, we studied the bone changes that occurred in 12 patients at 2 weeks and again at 1 year after total hip arthroplasty with insertion of a press-fit acetabular cup and an uncemented femoral tapered stem. There was a greater decrease in full bone density (BD) lateral to the femoral stem when compared to the medial side, at the proximal end of the femur this difference was significant (-22.1% versus -16.2%) ( P<0.001). At the tip of the stem cortical BD had decreased between 2.3% and 1.9% only. Proximal to the cup, the cortical BD increased by about 3.4% ( P< or =0.05), while the full BD decreased markedly by 8% ( P< or =0.001). These changes represent a response to a decrease in regional bone stress induced by the presence of the press-fit implant, and this might be considered as retro-acetabular stress shielding. No focal bone resorption was found.     

Monitoring of periprosthetic BMD after uncemented total hip arthroplasty with dual-energy X-ray absorptiometry--a 3-year follow-up study.

Insertion of a metallic implant into the femur changes bone loading conditions and results in remodeling of femoral bone. To quantify changes in bone mass after uncemented total hip arthroplasty (THA), we monitored femoral bone with dual-energy X-ray absorptiometry (DXA). The periprosthetic bone mineral density (BMD) was measured with Lunar DPX densitometry in seven Gruen zones and the total periprosthetic area at scheduled time intervals in 22 patients during a 3-year follow-up. BMD decreased significantly almost in all Gruen zones during the first 3 months, ranging from 3.4% to 14.4% (p < 0.05 top < 0.001). At the end of the first year, the most remarkable decrease in BMD was found in the calcar (zone 7; -22.9%). During the second postoperative year, a slight restoration of periprosthetic bone mass was recorded. During the third year, no significant changes in BMD were found. The preoperative BMD was the only factor that was significantly related to the periprosthetic bone loss. Clearly, the early periprosthetic bone loss noticed during the 3 months after THA is caused by mainly limited weight bearing to the operated hip and stress shielding. We suggest that the restoration of bone mass is a sign of successful osteointegration between bone and metallic implant. DXA is a suitable tool to follow the bone response to prosthetization and will increase our knowledge on the behavior of bone after THA.