Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty: A randomized clinical trial with DXA and RSA in 51 patients

Background and purpose — We hypothesized that an ultra-short stem would load the proximal femur in a more physiological way and could therefore reduce the adaptive periprosthetic bone loss known as stress shielding.Patients and methods — 51 patients with primary hip osteoarthritis were randomized to total hip arthroplasty (THA) with either an ultra-short stem or a conventional tapered stem. The primary endpoint was change in periprosthetic bone mineral density (BMD), measured with dual-energy x-ray absorptiometry (DXA), in Gruen zones 1 and 7, two years after surgery. Secondary endpoints were change in periprosthetic BMD in the entire periprosthetic region, i.e. Gruen zones 1 through 7, stem migration measured with radiostereometric analysis (RSA), and function measured with self-administered functional scores.Results — The periprosthetic decrease in BMD was statistically significantly lower with the ultra-short stem. In Gruen zone 1, the mean difference was 18% (95% CI: −27% to −10%). In zone 7, the difference was 5% (CI: −12% to −3%) and for Gruen zones 1–7 the difference was also 5% (CI: −9% to −2%). During the first 6 weeks postoperatively, the ultra-short stems migrated 0.77 mm more on average than the conventional stems. 3 months after surgery, no further migration was seen. The functional scores improved during the study and were similar in the 2 groups.Interpretation — Up to 2 years after total hip arthroplasty, compared to the conventional tapered stem the ultra-short uncemented anatomical stem induced lower periprosthetic bone loss and had equally excellent stem fixation and clinical outcome.Periprosthetic bone loss in uncemented femoral stems can contribute to late-occurring periprosthetic fractures (Lindahl 2007, Streit et al. 2011). This is partly mediated by adaptive bone resorption. This disuse atrophy, known as stress shielding, is mainly a consequence of the mismatch in modulus of elasticity between the implant and the periprosthetic bone. In time, the increasingly more fragile periprosthetic bone may break—even after minor trauma. Shorter femoral stems, aimed at giving a more physiological load pattern in the proximal femur, have become popular lately because of expectations of reducing stress shielding. Absence of a diaphyseal engaging stem is a key factor to prevent off-loading of the proximal femoral bone, but at the same time it will challenge the primary stability necessary for bone osseointegration of the femoral implant (Søballe et al. 1992).In this study, we hypothesized that an ultra-short uncemented stem would give less periprosthetic bone loss in the proximal femur than a conventional tapered uncemented stem, and that the ultra-short stem would achieve good fixation and be safe to use from a clinical standpoint.     

Different loss of BMD using uncemented press-fit and whole polyethylene cups fixed with cement: repeated DXA studies in 96 hips randomized to 3 types of fixation

Background In cemented THA, aseptic loosening of the cup is more common than loosening of the stem, while periprosthetic osteolysis of the socket resulting in difficult reconstruction problems has emerged as the most significant problem with cementless cup fixation.

Patients and methods 90 patients (96 hips) scheduled for THA were stratified in three groups according to the method of fixation of the acetabular component: acrylic bone cement with fluoride (Cemex-F), porous-coated press-fit cup with ceramic coating (Trilogy, uncemented) and acrylic cement with gentamicin (Palacos). All patients received the Spectron EF stem. Acetabular bone mineral density was measured with dual-energy X-ray absorptiometry (DXA) 1 week postoperatively, and after 12 and 24 months. The periprosthetic BMD was evaluated in 5 ROIs positioned around the acetabular component.

Results In the uncemented sockets, the BMD had decreased proximally and medially to the cup after 2 years. The difference was significant in the proximal region as compared to the control group (Palacos). No difference was noted between the 2 groups with cemented components after 2 years. Stepwise linear regression analysis showed that loss of periprosthetic BMD in the proximal high-pressure region after 2 years increased with higher postoperative BMD and when the uncemented design had been used.

Interpretation Contrary to previous studies of cemented stems, the use of fluoride cement did not influence the periprosthetic BMD 2 years after the examination. Increased loss of BMD with use of uncemented press-fit cups in the region in which osteolytic lesions are commonly found suggests that stress shielding may initiate the development of this complication. Longer follow-up will, however, be necessary to substantiate this hypothesis.     

Periprosthetic proximal bone loss after uncemented hip arthroplasty is related to stem size: DXA measurements in 138 patients followed for 2-7 years

Background Periprosthetic bone loss occurs around uncemented femoral stems and may be influenced by the stem size.

Patients and methods We studied 138 consecutive patients, 3 (2-7) years on average after a total hip arthroplasty operation (THA) for unilateral osteoarthritis with the Bi-Metric uncemented femoral stem. We analyzed Harris hip score and bone mineral density.

Results The mean Harris hip score was 97 at follow-up. Bone mineral density decreased proximally by 19% in both Gruen zones 1 and 7. Bone loss in zones 1, 2, 6, and 7 was significantly associated with stem size. Distally, a small gain in bone mass was found in zones 3 and 5 for medium femoral sizes.

Interpretation We found a marked proximal BMD loss, especially for the larger stems, which may be specific for this particular implant. Long-term studies should reveal whether this proximal bone loss will affect the longevity of the THA.     

Periprosthetic DXA after total hip arthroplasty with short vs. ultra-short custom-made femoral stems

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.     

Ultralok uncemented femoral prostheses: 12 to 15 year follow-up evaluation

The results of total hip arthroplasty (THA) in young patients with osteoarthritis have been discouraging. In this prospective study, 78 patients (89 THA) were consecutively included and followed for 12 to 15 years (mean, 12.2 years) after the index surgery with the uncemented Ultralok femoral prosthesis (Zimmer, Wiltshire, UK). Age at surgery was 59.8 years (40 to 76). The follow-up process included an in-office clinical evaluation and a radiographic evaluation. A cumulative survival of 96.6% (with the end point defined as revision of the femoral component because of mechanical or radiographic loosening) was found for the femoral component after13 years, and all unrevised components were radiographically fixed by bony ingrowth. Twenty-three well-fixed stems had to be removed for femoral head damage at the time of the acetabular revision. The results of this comparatively large series show that good fixation has been achieved with a proximal titanium mesh and grit-blasted titanium alloy stem.     

Alendronate reduces periprosthetic bone loss after uncemented primary total hip arthroplasty: a prospective randomized study.

Periprosthetic bone loss, especially in the proximal part of the femur, is common after cemented and uncemented total hip arthroplasty (THA). Bone loss can be progressive and, in the extreme, may threaten survival of the prosthesis. To study whether alendronate therapy can reduce bone loss adjacent to prostheses, 13 uncemented primary THA patients were randomized to the study. They received 10 mg alendronate + 500 mg calcium (n = 8) or 500 mg calcium only (n = 5) daily for 6 months follow-up after THA. Periprosthetic bone mineral density (BMD) was measured with dual energy X-ray absorptiometry (DXA). Decreases in periprosthetic BMD in the alendronate-treated group were lower compared with the changes in the calcium-only group in the same regions of interest at the same follow-up time. In the proximal femur, the mean BMD decrease was 17.1% in the calcium-only group, whereas in the alendronate-treated group the decrease was only 0.9% (p = 0.019). The mean periprosthetic BMD change was also significantly different in the total periprosthetic area between the study groups at the end of the follow-up (calcium-only group -9.9% vs. alendronate-treated group -2.6%; p = 0.019). Alendronate therapy led to a significant reduction in periprosthetic bone loss after primary uncemented THA compared with the changes found in patients without therapy. This kind of bone response may improve the support of the prosthesis and may result in better survival of the prosthesis. However, in this study the follow-up time was too short and the study population was too small to make any long-term conclusions as to the prognosis for THA patients treated with alendronate.     

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.     

Comparison of allograft-prosthetic composite reconstruction and modular prosthetic replacement in proximal femur bone tumors: Functional assessment by gait analysis in 20 patients

Background?In cemented THA, aseptic loosening of the cup is more common than loosening of the stem, while periprosthetic osteolysis of the socket resulting in difficult reconstruction problems has emerged as the most significant problem with cementless cup fixation.

Patients and methods?90 patients (96 hips) scheduled for THA were stratified in three groups according to the method of fixation of the acetabular component: acrylic bone cement with fluoride (Cemex-F), porous-coated press-fit cup with ceramic coating (Trilogy, uncemented) and acrylic cement with gentamicin (Palacos). All patients received the Spectron EF stem. Acetabular bone mineral density was measured with dual-energy X-ray absorptiometry (DXA) 1 week postoperatively, and after 12 and 24 months. The periprosthetic BMD was evaluated in 5 ROIs positioned around the acetabular component.

Results?In the uncemented sockets, the BMD had decreased proximally and medially to the cup after 2 years. The difference was significant in the proximal region as compared to the control group (Palacos). No difference was noted between the 2 groups with cemented components after 2 years. Stepwise linear regression analysis showed that loss of periprosthetic BMD in the proximal high-pressure region after 2 years increased with higher postoperative BMD and when the uncemented design had been used.

Interpretation?Contrary to previous studies of cemented stems, the use of fluoride cement did not influence the periprosthetic BMD 2 years after the examination. Increased loss of BMD with use of uncemented press-fit cups in the region in which osteolytic lesions are commonly found suggests that stress shielding may initiate the development of this complication. Longer follow-up will, however, be necessary to substantiate this hypothesis.     

No adverse effects of early weight bearing after uncemented total hip arthroplasty: a randomized study of 20 patients

BACKGROUND: Few guidelines are available whether early weight-bearing after an uncemented total hip arthroplasty (THA) can be recommended or not. Stability and ingrowth may be jeopardized by immediate loading of the implant while functional recovery may be promoted and periprosthetic demineralization reduced. PATIENTS AND METHODS: We did a prospective study of 20 patients who were operated on with a hydroxyapatite-coated (HA), uncemented total hip arthroplasty with a tapered stem because of unilateral arthrosis, and randomized the patients to the immediate (I) or late (L) weight-bearing (after 3 months) group. The shoe on the operated side was equipped with an auditory device signaling when the patient placed a load on the extremity. The clinical assessment was done with the Harris hip score at the time of the operation and after 12 and 24 months. Radiographs and dual-energy x-ray absorptiometry (DEXA) were evaluated for migration, femoral remodeling and bone mineral density (BMD) after 3, 6, 12 and 24 months. Tc-scintigraphy was done after 6, 12 and 24 months. RESULTS: Postoperatively, the Harris hip score showed no group difference. After 3 months, we noted a large reduction in BMD around the stem prosthesis. This was most marked in the proximal regions and the bone loss was significantly larger in zone 1, 4 and 5 in the L group. Distally, the BMD normalized with time, but the loss of bone persisted in the proximal zones after 24 months. An initial increase in the scintigraphic uptake ratio in all zones in both groups declined with time, but it was still increased on the operated side after 24 months. Several radiographic signs of bone remodeling were seen, but the patterns were similar in both groups. INTERPRETATION: We found no adverse effect of immediate weight bearing with this prosthesis.     

Increased risk of intraoperative and early postoperative periprosthetic femoral fracture with uncemented stems

Background and purpose — The use of uncemented fixation in total hip arthroplasty (THA) is increasing. Registry studies have indicated an increased risk of revision of uncemented implants due to early periprosthetic femoral fracture. In this paper, we describe the incidence and predisposing factors for intraoperative and early postoperative (≤ 90 days) periprosthetic femoral fractures after cemented and uncemented THA.

Patients and methods — This was a prospective observational study in 8 Danish high-volume centers from February 2010 to November 2013. We used the 90-day follow-up from the Danish National Patient Registry and patient records. We obtained intraoperative information from the Danish Hip Arthroplasty Registry and from surgical notes.

Results — Of 7,169 primary consecutive THAs, 5,482 (77%) were performed using uncemented femoral components. The total incidence of periprosthetic femoral fractures ≤ 90 days postoperatively was 2.1% (n = 150). 70 fractures were detected intraoperatively (46 required osteosynthesis). 51 postoperatively detected fractures occurred without trauma (42 of which were reoperated) and 29 were postoperative fall-related fractures (27 of which were reoperated). 134 fractures (2.4%) were found in uncemented femoral components and 16 (0.9%) were found in cemented femoral components (p < 0.001). Uncemented femoral stem (relative risk (RR)?=?4.1, 95% CI: 2.3–7.2), medically treated osteoporosis (RR =2.8, CI: 1.6–4.8), female sex (RR =1.6, CI: 1.1–2.2), and age (RR =1.4 per 10 years, CI: 1.2–1.6) were associated with increased risk of periprosthetic femoral fracture when analyzed using multivariable regression analysis.

Interpretation — Uncemented femoral components were associated with an increased risk of early periprosthetic femoral fractures, especially in elderly, female, and osteoporotic patients.     

Good stability but high periprosthetic bone mineral loss and late-occurring periprosthetic fractures with use of uncemented tapered femoral stems in patients with a femoral neck fracture

Background and purpose— We previously evaluated a new uncemented femoral stem designed for elderly patients with a femoral neck fracture and found stable implant fixation and good clinical results up to 2 years postoperatively, despite substantial periprosthetic bone mineral loss. We now present the medium-term follow-up results from this study.

Patients and methods— In this observational prospective cohort study, we included 50 patients (mean age 81 (70–92) years) with a femoral neck fracture. All patients underwent surgery with a cemented cup and an uncemented stem specifically designed for fracture treatment. Outcome variables were migration of the stem measured with radiostereometry (RSA) and periprosthetic change in bone mineral density (BMD), measured with dual-energy X-ray absorptiometry (DXA). Hip function and health-related quality of life were assessed using the Harris hip score (HHS) and the EuroQol-5D (EQ-5D). DXA and RSA data were collected at regular intervals up to 4 years, and data concerning reoperations and hip-related complications were collected during a mean follow-up time of 5 (0.2–7.5) years.

Results— At 5 years, 19 patients had either passed away or were unavailable for further participation and 31 could be followed up. Of the original 50 patients, 6 patients had suffered a periprosthetic fracture, all of them sustained after the 2-year follow-up. In 19 patients, we obtained complete RSA and DXA data and no component had migrated after the 2-year follow-up. We also found a continuous total periprosthetic bone loss amounting to a median of –19% (–39 to 2). No changes in HHS or EQ-5D were observed during the follow-up period.

Interpretation— In this medium-term follow-up, the stem remained firmly fixed in bone despite considerable periprosthetic bone mineral loss. However, this bone loss might explain the high number of late-occurring periprosthetic fractures. Based on these results, we would not recommend uncemented femoral stems for the treatment of femoral neck fractures in the elderly.     

Ten-year results of uncemented hip stems for failed intertrochanteric osteotomy

Introduction Inferior survival of cemented total hip arthroplasty has been reported after previous femoral osteotomy. The purpose of this study was to evaluate the long-term survival of uncemented stems after femoral osteotomy.Materials and methods Forty-eight hips in 45 patients had undergone conversion THA for a failed intertrochanteric osteotomy of the hip after a mean of 12 years (2–33 years). Mean time of follow-up was 11 years (5–15 years).Results At follow-up, two patients (three hips) had died, and one patient (one hip) was not located. Three patients (three hips) underwent femoral revision—one for infection and two for aseptic loosening of the stem. Survival of the stem was 94% at 10 years, and survival with femoral revision for aseptic loosening as an end point was 96%. The median Harris Hip Score at follow-up was 80 points. Radiolucent lines in Gruen zones 1 and 7 were present in 14 and 18% of hips, respectively. Radiolucencies in other zones were not detected. There was no radiographic evidence of femoral osteolysis, stress-shielding or loosening.Conclusion The results with this type of uncemented tapered titanium femoral component after proximal femoral osteotomy are encouraging and compare to those achieved in patients with regular femoral anatomy.     

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.

     

Cemented versus cementless revision femoral stems using morselized allograft--a prospective, randomized study with 5 years follow-up

BACKGROUND: There are only few studies on hip revision using the impaction grafting technique. Furthermore, data on cementless femoral stems as compared to cemented and polished femoral stems are lacking. We wanted to determine whether cementless femoral stems were equally good in preserving bone mineral density around the femoral stem and in functional outcome. METHOD: Consecutively 14 patients needing hip revisions for aseptic loosening in the stem with bone stock deficiency Paparowsky grade II were randomized into two groups intraoperatively. Morselized fresh-frozen bone allografts were impacted in both groups. The cemented group received polished Landos Fjord-CrCo stems and the uncemented group received the hydroxyapatite-coated Landos Corail-Titan stems. The dual energy X-ray absorptiometry was used to measure bone mineral density around the femoral stem according to Gruen zones. Function was measured by Merle d'Aubigné score. Patients were controlled at 0.5, 3, 6, 9, 12, 18, 24, 36 and 60 months postoperatively. RESULTS: There was no statistical difference between the BMD loss in the cemented vs. the uncemented group. The BMD loss was between 0-10 % in distal Gruen zones and was between 10-20 % in proximal Gruen zones. Functional scores were similar and reached a plateau of 16 in the Merle d'Aubigné score after 6 months. CONCLUSIONS: Cemented technique in hip revisions using morselized bone allograft is as good as uncemented technique in preserving BMD measured by the DEXA method and restoring function in a 5 years follow-up.     

Comparison of periprosthetic bone remodelling after implantation of anatomic and straight stem prostheses in total hip arthroplasty

Introduction Total hip arthroplasty changes bone loading conditions in the proximal femur and induces adaptive remodelling of the periprosthetic bone. These remodelling processes depend on many implant-specific qualities, e.g. material and elasticity of the stem. The objective of this study was to investigate the effect of the stem design on periprosthetic bone remodelling after insertion of an anatomic stem with proximal fixation and the direct comparison to a straight stem prosthesis. Materials and methods In a prospective study, the changes in periprosthetic bone mineral density (BMD) after implantation of 68 CTX-S anatomic and 22 PPF straight stem prostheses were assessed in the first post-operative year by means of DEXA and zone analysis by Gruen (Clin Orthop 141:17–27, 1979) “Modes of failure” of cemented stem-type femoral components: a radiographic analysis of loosening.. Furthermore all patients with CTX-S prostheses were monitored in the second post-operative year. The correlation of adaptive bone remodelling and the systemic bone density was also investigated. Results In the distal one-third of the straight stem prosthesis, a clearly greater, although not significant, hypertrophy of the periprosthetic bone was observed. No differences in the extent of bone loss between the two prostheses in the regions of interest (ROI) of the proximal bone were observed. The greatest decrease in BMD was registered in the medial femoral neck in both groups. Bone atrophy decreased progressively as the ROI moved distally, ending in a slight increase in BMD in the distal ROI. No significant changes in periprosthetic BMD occurred in the second post-operative year. A strong positive correlation in the regions with the greatest BMD decrease with the systemic BMD was ascertained. Conclusion After implanting a CTX-S prosthesis, as opposed to PPF prostheses, a different pattern of periprosthetic bone remodelling with a slighter hypertrophy of the distal periprosthetic parts was observed. This implies that the extensive proximal, more physiological bone loading of the anatomic stem as well as the removal of less bone while implanting the stem reduces the negative effects of unphysiological strain distribution and stress shielding. The BMD loss in the medial proximal neck cannot be avoided with this stem design either. The lack of significant BMD changes in the second post-operative year suggests that a stabilisation of bone remodelling processes occurs.     

Periprosthetic bone mineral density and fixation of the uncemented CLS stem related to different weight bearing regimes: A randomized study using DXA and RSA in 38 patients followed for 5 years

Background and purpose

There is no consensus on the best rehabilitation regime after uncemented total hip arthroplasty. Theoretically, bone ingrowth into the implant should benefit from initial partial weight bearing. We investigated whether the degree of postoperative weight bearing influences the periprosthetic bone mineral density (BMD) and/or the stability of the CLS stem.

Patients and methods

38 patients received an uncemented CLS stem and were randomized to either unrestricted postoperative weight bearing or to partial weight bearing for 3 months. Periprosthetic BMD was measured in the 7 Gruen zones with DXA and the stability of the femoral stem was assessed by radiostereometric analysis (RSA) after surgery and at 3, 12, 24, and 60 months.

Results

Periprosthetic BMD was not influenced by the type of postoperative weight bearing. BMD was reduced by 8–15% in all Gruen zones at 3 months. Restoration toward initial BMD was observed in all zones except in zone 7 (calcar region), where BMD was reduced by 22% at 5 years. Immediate weight bearing after surgery had no influence on the stability of the CLS stem, as assessed by RSA.

Interpretation

Immediate full weight bearing after uncemented total hip arthroplasty is safe. There is no difference in the periprosthetic BMD or in stability of the stem as measured by RSA compared to partial weight bearing for 3 months. BMD is reduced by more than 20% in the calcar region around a CLS stem after 5 years.The postoperative regime for uncemented hip implants has shifted towards early mobilization with full weight bearing, despite the fact that there have been discussions that early weight bearing might jeopardize the bone ingrowth that is considered necessary for stability (Soballe et al. 1993, Jasty et al. 1997). In addition, early full weight bearing might theoretically impair not only the stability of the femoral stem but also the bone mineral density (BMD) around it, but only a few studies have addressed this issue. A 2-year follow-up after total hip arthroplasty (THA) with the Bi-metric implant (Biomet Inc., Warsaw, IN) showed less bone loss proximal and lateral to the implant in a group with full weight bearing than in a group with partial weight bearing (Boden and Adolphson 2004). In 2 studies in which different uncemented femoral stems were examined, postoperative full weight bearing did not lead to any differences in micromotion over 1–2 years compared to partial weight bearing (Ström et al. 2007a, Thien et al. 2007). The roles of implant design, method of primary fixation, type of material, surface geometry, and finish are factors that may be of importance for BMD and implant stability. Thus, results for different implants should be compared with caution.We investigated whether the amount of weight bearing immediately after implantation of an uncemented total hip arthroplasty would affect (1) the periprosthetic BMD and (2) the stability of the implant over 5 years of follow-up.     

Periprosthetic bone remodelling of two types of uncemented femoral implant with proximal hydroxyapatite coating: a 3-year follow-up study addressing the influence of prosthesis design and preoperative bone density on periprosthetic bone loss

Periprosthetic bone loss is a major cause of concern in patients undergoing total hip arthroplasty (THA). Further studies are required to identify the factors determining the pattern of bone remodelling following THA and obtain improvements in the design and durability of prostheses. In this study, we monitored periprosthetic bone loss around two different types of hydroxyapatite coated femoral implant over a 3-year period to evaluate their design and investigate the relationship with the preoperative bone mineral density (BMD) at the spine, hip and forearm. Sixty patients (35 F, 25 M, mean age 63 years, range 46–75 years) undergoing THA were randomised to either the Anatomic Benoist Girard (ABG) or Mallory-Head (MH) femoral stem. Preoperative dual-energy X-ray absorptiometry (DXA) scans were acquired of the posteroanterior (PA) and lateral lumbar spine, the contralateral hip and the non-dominant forearm. Postoperative DXA scans were performed to measure periprosthetic BMD at 10 days (treated as baseline), 6 weeks, and 3, 6, 12, 24 and 36 months after THA using a standard Gruen zone analysis. Results were expressed as the percentage change from baseline and the data examined for the differences in bone loss between the different Gruen zones, between the ABG and MH stems, and the relationship with preoperative BMD. A total of 50 patients (24 ABG, 26 MH) completed the study. Three months after THA there was a statistically significant BMD decrease in every Gruen zone that varied between 5.6% and 13.8% for the ABG prosthesis and between 3.8% and 8.7% for the MH prosthesis. Subsequently, in most zones BMD reached a plateau or showed a small recovery. However, BMD continued to fall in Gruen zones 1 and 7 in ABG patients and Gruen zone 1 in MH patients. Bone loss was less in every Gruen zone in MH patients compared with ABG with the largest difference (10%, P=0.018) in Gruen zone 7. Highly significant relationships were found between periprosthetic bone loss and preoperative BMD measured at the PA spine (P<0.001), total hip (P=0.004) and total distal radius (P<0.001). This study showed differences between two different designs of hydroxyapatite-coated implant that confirmed that prosthesis design influences periprosthetic bone loss. The study also showed that patients bone density measured at the spine, hip or forearm at the time of operation was a major factor influencing bone loss around the femoral stem.     

Clinical, radiographic, and scintigraphic comparison of the mechanical stability of Mueller and Zweymueller total hip prostheses

Twenty-two cemented Mueller and 25 uncemented Zweymueller total hip arthroplasties (THAs) were performed in the same period in 47 consecutive randomly selected patients with unilateral primary osteoarthritis. Patients were evaluated using the same clinical and radiographic protocol preoperatively; 3, 6, and 12 months postoperatively; and annually thereafter as well as with Tc 99m MDP three-phase bone scintigraphy 3, 6, 12, and 24 months postoperatively. At 11 periprosthetic regions of interest (ROIs) around the stem and socket of each prosthesis, several radiographic parameters and bone scintigram uptake grade were recorded and correlated to determine the significance of early scintigraphic uptake for prediction of the stability of cemented and uncemented THA components over time. Around stable Zweymueller and Mueller sockets, the radionuclide uptake was similar during all periods of observation. Radionuclide uptake around stable Zweymueller stems was significantly more than around stable Mueller stems at the medial femoral cortex 3 and 6 months postoperatively, at the lateral femoral cortex 3-24 months postoperatively, and near the tip of the stem 3 months postoperatively. Radionuclide uptake around stable Mueller stems was significantly more than around Zweymueller stems at the greater trochanter 6 and 12 months postoperatively and at the lesser trochanter 12 months postoperatively. Any significant deviation of radionuclide uptake at any ROI, time, and THA component during the first 2 years postoperatively in combination with radiographic findings of loosening should be considered a serious predictive sign for loosening of a Mueller or Zweymueller THA component.     

Early periprosthetic bone remodelling around cemented and uncemented custom-made femoral components and their uncemented acetabular cups

Introduction  

Periprosthetic bone remodelling after total hip replacement may contribute to aseptic loosening of the prosthesis. The selection between cemented and uncemented fixation of the stem is mainly determined by patient’s age, general constitution and CT scan-estimated bone quality; intra-operative observation may ultimately influence the choice of the fixation method. The influence of cemented versus uncemented stem fixation on periprosthetic bone remodelling around the uncemented cup has, to our knowledge, never been studied until now.     

Poor intermediate-term survival of the uncemented Optan anatomically adapted femoral component: A retrospective study of 432 patients with a mean follow-up of 5 years

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.The Optan femoral stem was designed to reduce proximal femoral bone loss after total hip arthroplasty (THA). It was designed with a specific geometry, stiffness, and surface roughness (Bieger et al. 2011). It is an anatomically shaped femoral component in the sense that it has an anteversion similar to that of the native proximal femur. The uncemented Optan femoral stem is made of a titanium-based alloy with a porous-coated proximal third. Furthermore, the femoral stem has a ventral rib that should prevent rotation. The distal narrowing, the anatomical shape, and the porous-coated proximal third of the stem are designed to lead to a physiological load transfer and therefore optimal bone in-growth of the femoral stem. Despite the theoretical advantages of the Optan femoral stem, no studies have been published on the survival of this uncemented femoral component. We evaluated the mean 5-year survival of the uncemented Optan femoral stem used in primary THA.