Scandinavian multicenter porous coated anatomic total hip arthroplasty study. Clinical and radiographic results with 7- to 10-year follow-up evaluation

Influence of stem design parameters on periprosthetic femoral fractures examined by subject specific finite element analyses

Due to the increasing number of periprosthetic femoral fractures (PFF), the optimisation of implant design gains importance. For the presented research a validated, subject specific finite element model of a human femur with an inlying total hip stem was used to compare the influence of different geometrical implant parameters on the development of PFF. The heterogeneous bone tissue was modelled on the basis of computed tomography scans. A ductile damage model with element deletion was applied to simulate bone fracture in a load case re-enacting a stumbling scenario. The results were compared in terms of fracture load, subsidence and fracture pattern to analyse the influence of friction at the implant-bone interface, implant size and stem length. The results showed that higher friction coefficients lead to an increase of fracture load. Also, the usage of an oversized implant has a negligible effect while an undersized implant reduces the fracture load by 48.9% for the investigated femur. Lastly, a higher fracture load was reached with an elongated stem, but the bending and change in fracture path indicate a more distal force transmission and subsequent stress shielding in the proximal femur.

Uncemented or cemented stems in first-time revision total hip replacement? An observational study of 867 patients including assessment of femoral bone defect size

Background and purpose - Uncemented stems are gradually replacing cemented stems in hip revision surgery. We compared the risk of re-revision between uncemented and cemented revision stems and assessed whether the different fixation methods are used in similar femoral bone defects.Patients and methods - 867 patients operated on with uncemented or cemented stems in first-time hip revision surgery due to aseptic loosening performed 2006-2016 were identified in the Swedish Hip Arthroplasty Register. Preoperative femoral bone defect size was assessed on radiographs of all patients. Cox regression models were fitted to estimate the adjusted risk of re-revision during different postoperative time periods. Re-revision of any component for any reason, and stem re-revision, as well as risk of cause-specific re-revision was estimated.Results - Most patients in both fixation groups had Paprosky class IIIA femoral bone defects prior to surgery, but there were more severe bone defects in the cemented group. The adjusted risk of re-revision of any component for any reason was higher in patients with uncemented compared with those with cemented revision stems during the first 3 years after index surgery (hazard ratio [HR] 4, 95% confidence interval [CI] 2-9). From the 4th year onward, the risk of re-revision of any component for any reason was similar (HR 0.5, CI 0.2-1.4). Uncemented revision stems conferred a higher risk of dislocation compared with cemented stems (HR 5, CI 1.2-23) during the first 3 years.Interpretation - Although not predominantly used in more complex femoral defects, uncemented revision stem fixation confers a slightly higher risk of re-revision during the first years, but this risk is attenuated after longer follow-up.

Varus malalignment of cementless hip stems provides sufficient primary stability but highly increases distal strain distribution

BACKGROUND

Varus position of cementless stems is a common malalignment in total hip arthroplasty. Clinical studies have reported a low rate of aseptic loosening but an increased risk for thigh pain. This in vitro study aimed to evaluate these clinical observations from a biomechanical perspective.

METHODS

A conventional cementless stem (CLS Spotorno) was implanted in a regular, straight (size 13.75) as well as in a varus position (size 11.25) in 6 composite femora (Sawbones), respectively. Primary stability was assessed by recording 3-dimensional micromotions under dynamic load bearing conditions and stress shielding was evaluated by registering the surface strain before and after stem insertion.

FINDINGS

Primary stability for stems in varus malposition revealed significantly lower micromotions (p < 0.05) for most regions compared to stems in neutral position. The greatest difference was observed at the tip of the stem where the straight aligned implants exceeded the critical upper limit for osseous integration of 150 μm. The surface strains for the varus aligned stems revealed a higher load transmission to the femur, resulting in a clearly altered strain distribution.

INTERPRETATION

This biomechanical study confirms the clinical findings of a good primary stability of cementless stems in a varus malposition, but impressively demonstrates the altered load transmission with the risk for postoperative thigh pain.

Bead debonding from a modern cementless total hip femoral component with concomitant taper corrosion

We report a case of bead shedding from a cylindrical extensively porous-coated cementless femoral component with concomitant taper corrosion at the modular head-neck junction of a metal-on-polyethylene total hip prosthesis. The patient presented with chronic thigh pain 4 years after primary total hip arthroplasty, and radiographs revealed significant osteolysis and metallic debris around the femoral stem. Intraoperatively, the patient had a grossly loose femoral component with debonding of sintered beads from the femoral stem, as well as evidence of taper corrosion. We identify a failure of a modern beaded femoral component in conjunction with taper corrosion.

Influence of undersized cementless hip stems on primary stability and strain distribution

INTRODUCTION

Undersizing of cementless hip stems is a risk factor for aseptic loosening and early subsidence. The purpose of this study was to evaluate the effects of undersized stems and determine whether a biomechanical study can predict the clinical results.

MATERIALS AND METHODS

Three consecutive sizes of a clinically proven stem (CLS Spotorno) were implanted into six composite femora (size large, Sawbones^®), respectively. According to the Canal Fill Index (CFI), two stems (size 11.25 and 12.5) were undersized (CFI < 80%) and one stem (size 13.75) had an appropriate size (CFI > 80%). The primary stability was evaluated by measurement of 3-dimensional (3D)-micromotions under physiological adapted load and surface strains were recorded before and after implantation to detect stress-shielding processes.

RESULTS

Both undersized stems revealed significantly higher micromotions in all regions compared to the appropriate stem. The highest micromotions were registered at the distal tip of the three stem sizes. The changes in surface strain did not show a significant difference between the three stem sizes, but the highest strain reduction was observed proximally indicating a tendency for stress shielding.

CONCLUSIONS

This study confirms the clinical assumption that undersized stem result in a significantly reduced primary stability. Furthermore, in vitro studies allow to determine the effects of undersizing and stress shielding processes.

Mid-term outcome of total hip arthroplasty using a short stem

PURPOSE

To review the outcome of total hip arthroplasty (THA) using a short femoral stem in 33 hips.

METHODS

Records of 33 hips in 20 men and 10 women aged 25 to 40 (mean, 30) years who underwent cementless THA using a short femoral stem by a single senior surgeon were reviewed. The diagnosis included avascular necrosis (n=9), ankylosing spondylitis (n=12), rheumatoid arthritis (n=7), posttraumatic arthritis (n=4), and Hurler syndrome (n=1). Clinical outcome was assessed using the Harris Hip Score. Radiological outcome was assessed according to a modified Gruen zoning system. Stem positioning (neutral, varus, valgus) and bone contact wereevaluated, as were fixation and early host response as well as subsidence and changes in the calcar region (zone 5). Trabecular response (trabecular attachment), spot welds, cortical hypertrophy, and pedestal formation were determined. Heterotopic ossification was graded by the Brooker classification.

RESULTS

The mean follow-up period was 6.5 years. The mean Harris Hip Score improved from 40 to 90. All hips achieved immediate postoperative stability. No patient had thigh pain. Four hips had varus placement (5º-7º) of the stem; all were asymptomatic and remained stable without any migration. Evidence of proximal load transfer (endosteal spot welds) between the endosteum and the stem in zones 2 and/or 4 was noted in 12 hips on both sides and in 8 hips on the lateral side only. At one year, all stems showed evidence of osseointegration. None had subsidence or progressive varus migration. There was no radiolucent line or osteolysis around the stem, pedestal formation or buttressing at the prosthesis tip, or cortical hypertrophy. One patient had grade I heterotopic ossification that was not clinically significant. One patient had a 1.5 cm leg lengthening. One patient had a discharging sinus, a loosened acetabular component, and intrapelvic migration at 2 years and underwent implant removal and debridement. One patient developed a crack in the proximal femur even with the smallest stem. The stem was fixed with cerclage wiring and remained stable with no migration.

CONCLUSION

A short femoral stem design that transfers load proximally through a prominent lateral flare achieved good short-term outcome in younger patients. Nonetheless, the ease of removal and preservation of bone at the time of revision should guide the choice of the design of the short stem.

Mid-Term Outcomes and Complications with Cementless Distal Locking Hip Revision Stem with Hydroxyapatite Coating for Proximal Bone Defects and Fractures

We revised the first 100 revision total hip arthroplasties using a cementless distal locking revision stem conducted in our referral centre. Average follow-up was 9.2 years (range: 5.5-12 years). Harris Hip Score improved from 42.5 to 81.6, and none had thigh pain at last follow-up. No significant stress shielding, osteolysis, or radiologic loosening was found. All patients showed radiological evidence of secondary implant osseointegration. Overall survival was 97% with three patients being revised: two stem ruptures and one subsidence. We could trace these complications to technical errors. These findings suggest that a diaphyseal fixation of the revision stem with distal locking can provide the needed primary axial and rotational stability of the prosthesis. This would allow further bony ingrowth, enhanced by the hydroxyapatite coating.

Hip arthroplasty

Total hip arthroplasty is a cost-effective surgical procedure undertaken to relieve pain and restore function to the arthritic hip joint. More than 1 million arthroplasties are done every year worldwide, and this number is projected to double within the next two decades. Symptomatic osteoarthritis is the indication for surgery in more than 90% of patients, and its incidence is increasing because of an ageing population and the obesity epidemic. Excellent functional outcomes are reported; however, careful patient selection is needed to achieve best possible results. The present economic situation in many developed countries will place increased pressure on containment of costs. Future demand for hip arthroplasty, especially in patients younger than 65 years, emphasises the need for objective outcome measures and joint registries that can track lifetime implant survivorship. New generations of bearing surfaces such as metal-on-metal, ceramic-on-ceramic, and metal-on-ceramic, and techniques such as resurfacing arthroplasty have the potential to improve outcomes and survivorship, but findings from prospective trials are needed to show efficacy. With the recall of some metal-on-metal bearings, new bearing surfaces have to be monitored carefully before they can be assumed to be better than traditional bearings.

Juvenile arthritis patients report favorable subjective outcomes of hip arthroplasty despite poor standard outcome scores

We evaluated midterm patient-reported outcomes and satisfaction with total hip arthroplasty in patients who had severe juvenile idiopathic arthritis. Thirty-one patients (49 hips), with a mean age of 29 years (range, 16-43 years), reported low hip pain and stiffness at follow-up (mean, 7 years; range, 3-17 years). Up to 92% were satisfied with their ability to perform various activities; 96% were satisfied with pain relief. A mean postoperative flexion arc of 96° was observed. Final 36-Item Short Form Health Survey, EuroQol in 5 dimensions, Western Ontario and McMaster Universities Arthritis Index, and Harris Hip scores were lower than reference populations, particularly for mobility, physical functioning, and social functioning subscores. Young adults with end-stage hip involvement and severe longstanding juvenile idiopathic arthritis expressed high satisfaction with total hip arthroplasty, which improved range of motion, pain, and stiffness, despite poor performance on widely used outcome measures.

Fixation failures of dual mobility cups: a mid-term study of 2601 hip replacements

BACKGROUND

The use of dual-mobility cups has increased because of a low rate of dislocations combined with a 96% 15-year survival rate. However, late cup migrations have been attributed to their fixation (tripod - exact fit with two pegs and one extraacetabular screw) and the absence of porous coating. In a second-generation device, the designs were modified to achieve press-fit fixation and a layer of titanium beads was sintered on stainless steel cups.

QUESTIONS/PURPOSES

We therefore (1) determined the midterm survival of press-fit, grit-blasted, second-generation cups with or without additional screws, compared with original tripod and (2) compared survival of grit-blasted dual-mobility cups with bimetallic porous-coated cups.

METHODS

From a multiinstitutional trial, we reviewed 2408 patients with osteoarthritis implanted with 2601 prostheses of seven designs of a second-generation dual-mobility cup. The criteria for failure were migration, widening radiolucencies in any zone of the interface, or revision for cup loosening. The minimum followup was 5 years (mean, 7.7 years; range, 5-11 years).

RESULTS

The 8-year survival rate of press-fit, grit-blasted cups was lower than that for press-fit, grit-blasted cups fixed with screws (91% versus 100%) and for tripod fixation (98%). The 8-year survival rate of press-fit, grit-blasted cups was less than that for press-fit, porous-coated cups made of the same alloy (91% versus 95%).

CONCLUSIONS

The data suggested primary fixation of grit-blasted dual-mobility cups should be secured with screws. Porous coating sintered on the convex side improved midterm survivorship. No deleterious effect of metallosis resulted from sintered titanium beads on stainless steel. Long-term followup is required to confirm these findings.

An in vivo evaluation of bone response to three implant surfaces using a rabbit intramedullary rod model

Our study was designed to evaluate osseointegration among implants with three surface treatments: plasma-sprayed titanium (P), plasma-sprayed titanium with hydroxyapatite (PHA), and chemical-textured titanium with hydroxyapatite (CHA). Average surface roughness (Ra) was 27 microns for the P group, 17 microns for the PHA group, and 26 microns for the CHA group. Bilateral distal intramedullary implants were placed in the femora of thirty rabbits. Histomorphometry of scanning electron microscopy images was used to analyze the amount of bone around the implants at 6 and 12 weeks after implantation. Greater amounts of osseointegration were observed in the hydroxyapatite-coated groups than in the noncoated group. For all implant surfaces, osseointegration was greater at the diaphyseal level compared to the metaphyseal level. No significant differences were seen in osseointegration between the 6 and 12 week time points. Although the average surface roughness of the P and the CHA groups was similar, osseointegration of the CHA implants was significantly greater. The results of this in vivo lapine study suggest that the presence of an hydroxyapatite coating enhances osseointegration despite similarities in average surface roughness.

Cementless total hip arthroplasty for primary osteoarthritis in patients aged 55 years and older

BACKGROUND

Cemented total hip arthroplasty has been the treatment of choice for elderly patients with osteoarthritis. We analyzed survival rates of the most common cementless designs used in this age group in Finland.

PATIENTS AND METHODS

Inclusion criteria permitted 10,310 replacements (8 designs) performed in patients aged 55 years or older to be selected for evaluation. The risk of revision of each of the 8 implants was compared with that of a group comprising 3 cemented designs as the reference (9,549 replacements). Survival analyses were performed overall and separately for 3 age cohorts: 55-64 years (6,781 replacements), 65-74 years (8,821 replacements), and 75 years or older (4,257 replacements).

RESULTS

In all patients aged 55 years or more, the Bi-Metric stem had a higher survival rate for aseptic loosening at 15 years than the cemented reference group: 96% (95% CI: 94-98) vs. 91% (CI: 90-92). However, the 15-year survival rates of the Bi-Metric/Press-Fit Universal (71% (CI: 67-75)) and the Anatomic Mesh/Harris-Galante II (72% (CI: 67-78)) total hip replacements were lower than that of the reference group (86% (CI: 84-87)). Information was scarce for patients aged 75 years or more.

INTERPRETATION

Cementless proximal porous-coated stems are a good option for elderly patients. Even though biological fixation is a reliable fixation method in THA, polyethylene wear and osteolysis remain a serious problem for cementless cup designs with unplugged screw holes and low-quality liners.

A comparative study of "plasmacup" and "porous-coated" acetabular components: survival after 10 to 12 years of follow-up

OBJECTIVES

Our primary aim was to compare the long-term survivorship rates and the rates of successful osseointegration between two different types of uncemented acetabular components.

INTRODUCTION

Two types of alloys have primarily been used for the manufacture of the uncemented acetabular components: titanium-based and cobalt-based alloys. A titanium-based alloy appears to be more effective with regard to interface stress transfer to the host bone because of its lower elastic modulus relative to a cobalt-based alloy. This supposed mechanical advantage of a titanium-based alloy component motivated this comparative study.

METHODS

Two uncemented acetabular components, a porous-coated acetabulum and a Plasmacup®, were compared with a focus on long-term prosthesis survivorship and the development of acetabular osseointegration. Five radiographic signs of osseointegration were evaluated at the last follow-up appointment: (1) absence of radiolucent lines, (2) presence of a superolateral buttress, (3) medial stress-shielding, (4) radial trabeculae, and (5) an inferomedial buttress. We considered the presence of any three of these radiographic signs, in the absence of acetabular dislocation or symptoms, to be indicative of successful acetabular osseointegration.

RESULTS

Among 70 patients implanted with the porous-coated acetabulum, 80% achieved osseointegration over a mean follow-up time of 11.9 years versus 75.3% of the 73 patients who received a Plasmacup insert over a mean of 10.7 years. Prosthesis survivorship rates were not different between the two groups. Revision surgery due to mild or severe acetabular osteolysis, polyethylene wear, and aseptic loosening occurred in eight patients (11.4%) with a PCA versus nine (12.3%) with a Plasmacup.

CONCLUSIONS

We conclude that, during the first ten years after surgery, there is no significant difference between these two types of uncemented cups with regard to either prosthesis survivorship or successful osseointegration.

A new short uncemented, proximally fixed anatomic femoral implant with a prominent lateral flare: design rationals and study design of an international clinical trial

Background

Anatomic short femoral prostheses with a prominent lateral flare have the potential to reduce stress-shielding in the femur through a more physiological stress distribution to the proximal femur. We present the design rationale of a new short uncemented, proximally fixed anatomic femoral implant and the study design of a prospective multi-centre trial to collect long-term patient outcome and radiographic follow up data.

Methods

A prospective surveillance study (trial registry NCT00208555) in four European centres (UK, Italy, Spain and Germany) with a follow up period of 15 years will be executed. The recruitment target is 200 subjects, patients between the ages of 18 and 70 admitted for primary cementless unilateral THA will be included. The primary objective is to evaluate the five-year survivorship of the new cementless short stem. The secondary objectives of this investigation are to evaluate the long term survivorship and the clinical performance of the implant, the impact on the subjects health related Quality of Life and the affect of the prosthesis on bone mineral density. Peri- and postoperative complications will be registered. Clinical and radiographic evaluation of prosthesis positioning will be done post-operatively and at 3, 6, 12, 24, 60, 120 and 180 months follow up.

Discussion

Shortening of the distal stem can maximise bone and soft tissue conservation. New stem types have been designed to improve the limitations of traditional implants in primary THA. A new, uncemented femoral short stem is introduced in this paper. A long-term follow up study has been designed to verify stable fixation and to research into the clinical outcome. The results of this trial will be presented as soon as they become available.

The mid-term results of a dual offset uncemented stem for total hip arthroplasty

The Synergy stem is a third-generation proximal in-growth, tapered titanium alloy uncemented stem, with standard and high offset versions. Two hundred ten primary hip arthroplasties were performed using the Synergy stem in 193 patients. There were 124 males and 69 females with an average age of 58 years (range, 22-85 years). The average follow-up was 75 months (range, 60-96 years). Only 1 stem has required revision, for a stem survival rate of 99.5%. The overall incidence of thigh pain was 2.8%. Intraoperative undisplaced fractures of the proximal femur occurred in 3.3% of patients and were managed at the time with wiring, with no effect on outcome. Minor osteolysis was seen proximally in 10% of patients, but no osteolysis was seen distal to the porous coating.

Continuous bone loss around a tapered uncemented femoral stem: a long-term evaluation with DEXA

BACKGROUND

Periprosthetic bone loss is a well-documented phenomenon after uncemented total hip arthroplasty (THA); however, little is known about how bone mineral density (BMD) changes after 2 years.

PATIENTS AND METHODS

14 patients with hip arthrosis (group A) were operated with a proximally porous- and hydroxyapatite-coated stem and followed for 10 years with DEXA, radiographs and Harris hip score (HHS). Another group of 14 patients (group B) was evaluated at 6 and 14 years using the same prosthesis and protocol.

RESULTS

No stem was revised and all stems were well-Fixed. At final follow-up, HHS was 97 points in group A after 10 years and 94 points in group B after 14 years. Bone mineral changes in group A were greatest in Gruen zones 1 and 7, where the losses were 31% and 26%, respectively, after 2 years on the operated side. The decrease in BMD continued after 2 years and in Gruen zone 7 it was faster than the rate of bone loss on the control side. In group B, the annual change in BMD on the operated side was not significantly different from the bone loss in group A.

INTERPRETATION

Up to 14 years after implantation of a tapered uncemented stem, the BMD in the calcar region continues to decrease faster than would be expected from normal ageing.

Total hip arthroplasty for rheumatoid arthritis in younger patients: 2,557 replacements in the Finnish Arthroplasty Register followed for 0-24 years

BACKGROUND

The results of total hip arthroplasty (THA) in young patients with rheumatoid arthritis (RA) have been reported in only a few studies. On a nationwide level, the outcome of THA in these patients is unknown. We evaluated the population-based survival of THA in patients under 55 years of age with RA and factors affecting the survival.

PATIENTS

Between 1980 and 2003, 2,557 primary THAs performed for RA in patients less than 55 years of age were reported to the Finnish Arthroplasty Register.

RESULTS

Proximally circumferentially porous-coated uncemented stems had a 15-year survival rate of 89% (95% CI 83-94) with aseptic loosening as endpoint. The risk of stem revision due to aseptic loosening was higher with cemented stems than with proximally porouscoated uncemented stems implanted during the same period (RR 2.4; p < 0.001). In contrast, Cox regression analysis showed that the risk of cup revision was significantly higher for all uncemented cup concepts than for all-polyethylene cemented cups with any cup revision as endpoint. There were no significant differences in survival between the THR concepts.

INTERPRETATIONS

Uncemented proximally circumferentially porous-coated stems and cemented all-poly-ethylene cups are currently the implants of choice for young patients with RA.

Total hip arthroplasty with an uncemented hydroxyapatite-coated tapered titanium stem: results at a minimum of 10 years' follow-up in 104 hips

BACKGROUND

The purpose of this study was to evaluate the minimum 10-year results of primary total hip arthroplasty using an uncemented, hydroxyapatite-coated tapered stem. Radiological signs of bone remodeling are also presented.

METHODS

We followed a consecutive series of 105 patients (115 hips), who had had an uncemented, proximally hydroxyapatite-coated Bi-Metric femoral component for a mean of 12.2 years (range 10.0-14.9 years). The average age at operation was 52 years. Detailed clinical and radiological analyses were performed after a minimum of 5 and 10 years. Eight patients (10 hips) had died, and one patient was lost to follow-up, leaving 104 hips for final evaluation. The clinical result was evaluated by the Harris Hip Score, complications, and thigh pain.

RESULTS

All patients still had their femoral components in place at the final follow-up. The average Harris Hip Score after 10 years was 92 (range 50-100) with no deterioration over time. Radiologically, several signs of progressive remodeling were identified, but no stem showed signs of loosening.

CONCLUSIONS

The intermediate clinical and radiological results with this stem are encouraging. In the hands of various surgeons, the stem has performed well in a young, high-risk population.

Uncemented total hip arthroplasty for primary osteoarthritis in young patients: a mid-to long-term follow-up study from the Finnish Arthroplasty Register

INTRODUCTION

The survival of total hip arthroplasties (THAs) has been considered to be poor in young patients. We evaluated the population-based survival of uncemented THA for primary osteoarthritis (OA) in patients under 55 years of age and the factors affecting survival.

METHODS

The Finnish Arthroplasty Register was established in 1980. Between that year and 2003, 92,083 primary THAs were entered in the register, 5,607 of which were performed for primary OA in patients under 55 years of age. Using records from these 5,607 THAs, we selected uncemented femoral and acetabular components that had been used in more than 100 operations during the study period. Survival of both components (cup/stem) and their combinations were analyzed separately with the Kaplan-Meier analysis and the Cox regression model.

RESULTS

All uncemented stems studied showed a survival rate of over 90% at 10 years. The Biomet Bi-Metric stem had a 95% (95% CI 93- 97) survival rate even at 15 years. Overall survival of the extendedly porous-coated Lord Madréporique stem (p = 0.003) and the proximally porous-coated Anatomic Mesh stem (p = 0.0008) were poorer than that of the Biomet Bi-Metric stem. When endpoint was defined as stem revision for any reason, results were generally similar; there was no difference, however, between the survival rates of the Lord Madréporique stem and the Bi-Metric stem. Of the acetabular components, the Biomet Universal, the ABG Il and the Harris-Galante II cups showed < 90% survival rates at 10 years with aseptic loosening as endpoint; at 13 years the corresponding survival rates were 94% (95% CI 91-97) for the Biomet Universal and 95% (95% CI 91-98) for the Harris-Galante II cups with aseptic loosening as endpoint. The PCA Pegged porous-coated uncemented cup showed a poor 13-year survival rate of 68% (95% CI 59-78) with aseptic loosening as endpoint. However, when endpoint was defined as any revision (including exchange of liner), the 10-year survival rates of all brands of cup except Harris-Galante II declined to under 80%.

INTERPRETATION

Modern second-generation uncemented stems, with proximal circumferential porous- or HA-coating, seem to be a good choice for young patients with primary OA. Similarly, modern press-fit porous- and HA-coated cups appear to have good endurance against aseptic loosening in these young patients. However, liner revisions were common; thus, survival rates of uncemented cups were unsatisfactorily low. Polyethylene wear and unfavorable locking mechanisms between the metal shell and the polyethylene liner and their sequelae remain matters of concern in this young and active group of patients.

Orthopaedic management of ankylosing spondylitis

Ankylosing spondylitis is an inflammatory disease of unknown etiology that affects an estimated 350,000 persons in the United States and 600,000 in Europe, primarily Caucasian males in the second through fourth decades of life. Worldwide, the prevalence is 0.9%. Genetic linkage to HLA-B27 has been established. Ankylosing spondylitis primarily affects the axial skeleton and is characterized by inflammation and fusion of the sacroiliac joints, spine, and hips. The resultant deformity leads to severe functional impairment in approximately 30% of patients. Orthopaedic management primarily involves correction of hip deformity through total hip arthroplasty and, less frequently, correction of spinal deformity with spine osteotomy. Closing wedge osteotomies have the lowest incidence of complications. Whether patients with ankylosing spondylitis are at increased risk for heterotopic ossification remains controversial, but comparison with age- and sex-matched counterparts suggests no dramatically higher risk. Because of the high rate of missed fractures and complications after minor trauma in patients with ankylosing spondylitis, plain radiographs are usually not sufficient for evaluation. Thorough patient assessment should include a comprehensive history, physical examination, and laboratory studies.

[Long term bone behavior in total primary hip arthroplasty with a fully hydroxyapatite-coated femoral stem: a continuous series of 120 cases with twelve years follow-up]

PURPOSE OF THE STUDY

Cementless hydroxyapatite-coated total prostheses have proven their reliability for more than twenty years. The intimate contact between the receiver bone and the implant allows "union" between the inert and living material. Osteointegration is maintained over time. The purpose of this work was to study the long-term reaction of femoral bone to wear debris after insertion of cementless hydroxyapatite implants.

MATERIAL AND METHODS

One hundred twenty implants constituted a continuous series of total hip arthroplasties performed since 1989 for primary joint degeneration in patients followed for at least twelve years. The same femoral implant totally coated with hydroxyapatite was used for all patients in combination with a metal cup and a polyethylene insert. Twelve years later, twenty-seven patients had died, five were contacted by telephone, and three were lost to follow-up, giving a study population of 85 total hip arthroplasties with complete review and radiographic data. Clinical and radiological findings are reported with a measure of polyethylene wear and femoral bone behavior in contact with femoral implants.

RESULTS

At twelve year follow-up, there were no cases of implant loosening. Clinical outcome was satisfactory, 90% of the hips were pain free. Radiologically, mean polyethylene wear was 0.1 mm per year with calcar changes (zone VII) in 27% and trochanter changes (zone I) in 14%. There was no evidence of osteolysis extension or granuloma formation in the shaft zone. Implant survival at twelve years was 99.1% (97.2-100%).

DISCUSSION

Hydroxyapatite-coated cementless implants resist well to polyethylene wear debris. At twelve years, osteolysis caused by macrophage activation remained limited to zones I and VII. There appeared to be an intimate plug between the implant and the living bone preventing wear debris migration along the implant as was visualized along the entire length of the implant. Polyethylene wear was however real and the risk of osteolysis remains a threat to implant stability. Improved survival of hydroxyapatite-coated total hip implants will thus depend on improvements in the weight-bearing couple.

Porous-coated anatomic uncemented total hip arthroplasty. A 10-17-year follow-up

A total of 91 PCA total hip arthroplasties were analysed with a mean follow-up of 13.5 years. Thirty-one cups and six stems were revised. If the patients excluded from the follow-up study are included (113 hips), the cumulative probability of having revision of any prosthetic component for any cause was 16.0% (0.1%-31.9%) at 14 years in the "best case" scenario. Thigh pain (17 hips) was correlated with unstable fixation. Radiographic loosening occurred in 21 cups and 12 stems. Cup loosening was related to acetabular polyethylene wear equal to or more than 2mm per year and also to cup size and thereby polyethylene thickness. Stem loosening was related to poor femoral canal filling. Fifty hips had femoral osteolysis which was related to polyethylene wear of more than 2 mm, poor femoral filling and unstable fixation. (Hip International 2005; 15: 78-84).

Biologic fixation and bone ingrowth

Total hip arthroplasty has provided thousands of patients with pain relief and has improved their quality of life. Advances in orthopaedic surgical techniques and implant biomaterials now allow predictable surgical results in most patients. Despite the overwhelming success of this surgical procedure, the debate continues surrounding the optimal choice of implants. Femoral and acetabular implants with varying geometries and fixation methods are currently available. Acrylic bone cement has been used extensively in the past for acetabular and femoral fixation. This mode of component fixation currently remains the technique used most frequently throughout Europe and has shown excellent long-term results. Problems inherent with acrylic bone cement, however, have encouraged other surgeons to use alternative surfaces to allow biologic fixation.

Enhancement of initial stability of press-fit femoral stems using injectable calcium phosphate cement: an in vitro study in dog bones

In this in vitro study we evaluated the initial stability of cementless femoral stems using an injectable calcium phosphate (Ca-P) cement. The cement was not used to form a cement mantle as is routinely done in PMMA cemented prostheses but functioned as an additive to fill the small gaps that exist between a press-fit placed titanium plasma sprayed implant and the bone bed. Six pair of Beagle femora were used in this study. In a random fashion, one femur of each pair was used for placement of a prosthesis without Ca-P cement, the contralateral was used for press-fit placement after injection of the calcium phosphate cement into the intramedullary canal. The reconstructions were placed in a MTS testing machine, tilted 15 degrees in varsus and 15 degrees of endorotation to obtain a physiological load on the femoral head. The load was applied stepwise from zero to a maximum of 100, 250 and 400 N, respectively. At each loading step the load was applied dynamically at a frequency of 1 Hz for 30 min. Between the loading steps, the load was removed for 10 min to allow elastic recovery. The stability of the stems was determined at each loading step with roentgen-stereophotogrammetric analysis. Results showed that with the prostheses without Ca-P cement the most important displacements were movement into varus (max. 818 microm under 400 N) and subsidence (max. 587 microm under 400 N). The displacements showed large variation. After unloading some elastic recovery occurred. In the specimens with Ca-P cement, displacements were negligible. As determined by an F-test the variations found were significantly smaller for the press-fit+Ca-P cement relative to the press-fit prosthesis at all loading steps (p<0.05). A paired t-test revealed significant differences in the mentioned displacements between the press-fit- and press-fit+Ca-P cement prosthesis at a loading with 400 N (P<0.05). On the basis of these results we conclude that the use of Ca-P cement increases the initial stability of press-fit inserted plasma-sprayed femoral prostheses and corrects for the high variability in displacements found with press-fit insertion of these femoral hip prostheses.

The effects of sex and estrogen therapy on bone ingrowth into porous coated implant

Amounts of bone ingrowth into porous cobalt-chromium plugs were compared between male and female dogs, and among sham-operated and ovariectomized female dogs, with or without estrogen treatment, to investigate the effect of gender and estrogen therapy on biologic fixation. Each group consisted of eight skeletally mature dogs. Plugs were implanted bilaterally in the distal femur at 6 months after ovariectomy or sham operation. Estrogen treatment group received estradiol 20 microg/kg/day subcutaneous injection. Three months after implantation, histological examination showed significantly more bone ingrowth in areas with cortical bone contact than in areas with cancellous bone contact (P<0.001 for all groups). Bone ingrowth was essentially the same in male and female control dogs. Ovariectomized dogs showed less overall bone ingrowth than male and female controls (P=0.007). Bone ingrowth in areas with cortical bone contact did not decrease significantly, whereas bone ingrowth in areas with cancellous bone contact was significantly impaired (P<0.001) in ovariectomized dogs compared with female controls. Short-term, high-dose estradiol treatment did not increase bone ingrowth volume fraction. Mechanical tests did not show any statistical differences among groups.

CONCLUSION

Type of bone contact is the key factor affecting the amount and pattern of bone ingrowth into the porous surface. Ovariectomy results in decreased bone ingrowth in areas with cancellous bone contact, but does not compromise bone ingrowth in areas with cortical bone contact. Short-term, high-dose estradiol treatment does not enhance bone ingrowth into the porous surface. Extensively coated or full-coated porous prostheses are recommended to achieve enough cortical bone contact and ingrowth for post-menopausal patients.

The middle-aged patient with hip arthritis: the case for extensively coated stems

Younger patients with a long life expectancy and higher activity levels who require total hip arthroplasty present a unique challenge to the reconstructive surgeon. To improve the longevity of total hip arthroplasty, particularly in younger, more active patients, femoral components inserted without cement have been used in an attempt to create a more durable reconstruction. Extensively-coated implants are an attractive option because they are associated with excellent initial implant stability and contact a large area of strong cortical bone in the femoral diaphysis where bony ingrowth reliably occurs. In a cohort of 304 patients (348 hips) who were between 45 and 65 years at the time of surgery and who were followed up for a mean of 14.2 years, 99.4% of the femoral reconstructions were stable with no cases of late failure secondary to loosening and a 96% rate of good to excellent clinical results. Although stress shielding, thigh pain, and difficulty of removal have been cited as problems with the use of these devices, in the current authors' experience they have not proved to be clinically relevant issues that limit the successfulness of total hip arthroplasty in this patient population.

The effect of demineralized bone matrix gel on bone ingrowth and fixation of porous implants

The presence of demineralized bone matrix (DBM) gel did not enhance or accelerate attachment strength or bone ingrowth and resulted in a significant decrease in implant interface attachment strength at 3 weeks. Hydroxyapatite (HA) coating resulted in significant increases in interface shear strength and bone ingrowth compared with non-HA-coated porous implants at all time periods. The HA-coated implants achieved greater attachment strength and bone ingrowth at earlier time periods and maintained greater attachment strength at long-term periods. The results of this study indicate that in the presence of a good bone-implant interference fit, there is no beneficial effect in applying DBM gel to a porous-coated or HA-coated porous implant surface. The small amount that can be applied and the degree of osteoinductivity of DBM seem to preclude it from having a significant biologic effect.

Hydroxyapatite femoral stems for total hip arthroplasty: 10- to 13-year followup

Three hundred eighty hydroxyapatite-coated titanium alloy stems were implanted in a young and active patient population from 1987 through 1990. Within the population, 274 patients (314 hips) had a minimum 10-year and maximum 13-year followup. The average age of the population was 51 years. Thirty-seven percent of the population was 50 years or younger when operated on (average age, 39 years). Osteoarthritis was seen in 63.7% and avascular necrosis in 16.6% of patients. Fifty-four percent of patients were men. Clinically, these patients had early pain relief and rapid restoration of function. The Harris hip score averaged 92 points, and only 1.6% of patients had mild or moderate activity-related thigh pain. Radiographically, progressive remodeling occurred around the implants, 100% were bone stable, and no patient had endosteal distal osteolysis. Two patients had revision surgery for aseptic loosening: one at 2 years postoperative because of a nonunion of a concomitant subtrochanteric osteotomy and one at 9.5 years postoperative because of polyethylene wear and progressive osteolysis. The mechanical failure rate was 0.5%. The results show excellent lasting fixation of this tapered titanium alloy stem coated proximally with a thin, dense layer of hydroxyapatite. The stem has performed well in a young, active, high-risk population and in the hands of various surgeons.

Minimal 10-year results of a tapered cementless femoral component in total hip arthroplasty

A series of 120 primary total hip arthroplasties with minimal 10-year follow-up, in which a cementless, proximal-to-distal, dual-tapered geometry femoral component was used, was reviewed. At a mean follow-up interval of 12.20 years, a mean Harris hip score improvement of 38 points was calculated. Three (2.5%) femoral components were revised secondary to aseptic loosening, yielding a 97.5% survivorship. Thigh pain was mild or absent in 96.6% of the cases. Distal femoral osteolysis was observed in <2% of cases. The Harris hip score improvement, low incidence of severe thigh pain, high survivorship, and low incidences of significant stress shielding and distal osteolysis suggest excellent long-term results with the use of this uncemented tapered design, adding credence to the design rationale and justifying its continued use.

Polyethylene wear of the porous-coated anatomic total hip arthroplasty with an average 11-year follow-up

The purpose of this study was to identify the factors that affect polyethylene wear of 55 porous-coated anatomic total hip arthroplasties after 9 to 14 years selected from a study population of 311 implants. The average three-dimensional linear, two-dimensional linear, and volumetric wear rates were 0.096 mm/y, 0.052 mm/y, and 34 mm3/y. Negative wear was noted in 7 patients using two-dimensional techniques. Significantly higher volumetric wear rate was observed for men (48 mm3/y) compared with women (24 mm3/y; P<.01), for patients <60 years old (45 mm3/y) compared with patients >60 years old (25 mm3/y; P<.01), and for 32-mm femoral heads (54 mm3/y) compared with 26-mm femoral heads (29 mm3/y; P<.01). Volumetric wear rate for patients having small (39 mm3/y) and large (65 mm3/y) areas of osteolysis were 2 and 3 times greater than for patients having no osteolysis (21 mm3/y) (P<.01).

Correlation of wear debris-induced osteolysis and revision with volumetric wear-rates of polyethylene: a survey of 8 reports in the literature

This survey focused on clinical reports of polyethylene wear and osteolysis in total hip replacements. With regard to documentation of clinical wear-rates, 57 publications were reduced to an analysis of 8 reports of THR series, including the incidence of osteolysis. A direct correlation was found among volumetric wear-rates, incidence of osteolysis and revision rates in THR concepts of the 1983-1987 era. As volumetric wear rate increased, the incidence of osteolysis and revision rates increased. With regard to our grading system for volumetric wear, with follow-up in the 4-15 year range, osteolysis was rare in group A (wear = 0-80 mm3/year), ranging from 6% to 31% in group B (wear 40-80 mm3/year) and from 21% to 100% in group C (wear > 140 mm3/year). With regard to cup design, the optimal low-wear group had mainly cemented polyethylene cups with 22 and 28 mm head sizes. The mid-wear group B had metal-backed cemented and uncemented cups, with 28 mm head size, and the high-risk group C had only uncemented, metal-backed cups, with the highest wear in the 32 mm head size. Less than 10 years of follow-up did not distinguish adequately between different designs of THR, except in a few cases which had early failures due to material or design deficiencies. Overall, the cemented all-polyethylene cup combined with the smaller ball head proved to be better.

Analysis of the results of the C-Fit uncemented total hip arthroplasty in young patients with hydroxyapatite or porous coating of components

Young patients at 2 separate centers received a C-Fit uncemented arthroplasty, with randomization to porous or hydroxyapatite coating. No difference in survival could be found between components that were porous or hydroxyapatite coated, with 27.5% being revised within 8 years, mainly for aseptic loosening. Acetabular augmentation screws or offset acetabular liners similarly did not affect outcome. Two of the offset liners had spun within the metal acetabular liners, with early failure. Some of the survivors showed poor clinical scores, but there was no correlation between clinical score and radiographic evidence of loosening. These results are comparable to the poorest reported survival figures in the literature for uncemented prostheses. Prosthesis coating could not be shown to affect component survival for this prosthesis.

Clinical experience with a proximally porous-coated second-generation cementless total hip prosthesis: minimum 5-year follow-up

This study reports the minimum 5-year follow-up of our experience with the Porous-Coated Anatomic E (PCA-E) series femoral stem and the modular acetabular cup. A total of 115 consecutive total hip replacements using PCA-E series (Howmedica, Rutherford, NJ) were performed in 108 patients. Six patients whose hips were performing well clinically died before 5-year follow-up and were excluded from the final evaluation. The remaining 109 hips (102 patients) were assessed at a mean follow-up of 72 months (range, 60-84 months). The hip diagnoses were osteoarthritis in 73, osteonecrosis in 31, rheumatoid arthritis in 2, and hip dysplasia in 3. The mean age was 56 years (range, 24-83 years). Three hips were revised: 1 because of late hematogenous infection, 1 because of aseptic loosening of the femoral component, and 1 because of postoperative loosening of an acetabular component. The Harris hip scores improved from a mean of 50 points (range, 20-66 points) preoperatively to a mean of 92 points (range, 64-100 points) at final follow-up. The score differed in each Charnley functional class, with a mean of 93 points (range, 72-100 points) in 57 hips of class A (no other joint involvement); 90 points (range, 58-100 points) in 26 hips of class B (opposite hip involvement); and 85 points (range, 37-100 points) in 26 hips of class C (multiple joint involvement or severe systemic disease). Out of 106 hips that had a full radiographic evaluation performed, 103 femoral components revealed stable bony ingrowth, 2 revealed stable fibrous ingrowth, and 1 showed migration with progressive loosening. This patient with radiographic loosening has minimal symptoms and has not required or been offered further surgery (Harris hip score of 86 points). The low aseptic loosening rate (2%) at minimum 5-year follow-up compares favorably with any cemented or cementless series. The osteolysis that was seen was focal and localized. The short follow-up does not allow determination of progression. There were no cases of distal osteolysis. We attribute the improved results from reported first-generation experience to multiple factors, including increased number of sizes (9 vs 6), increased proportional metaphyseal size, improved polyethylene manufacture (ram extruded vs machined), improved acetabular locking mechanism, and change to 26-mm from 32-mm femoral heads.

Primary total hip arthroplasty with a cementless porous-coated anatomic total hip prosthesis: 10- to 12-year results of prospective and consecutive series

We performed a prospective study in 108 consecutive patients (116 hips) who were followed for a minimum of 10 years (10-12 years) after primary total hip arthroplasty using an uncemented porous-coated anatomic (PCA) hip prosthesis. The average age of the patients at operation was 48.4 years (range, 19-85 years), and the diagnosis was avascular necrosis of the femoral head in 46 hips, neglected femoral neck fracture in 27, osteoarthrosis secondary to childhood pyogenic arthritis in 24, childhood tuberculous arthritis in 5, and miscellaneous in 14. The average preoperative Harris Hip Score was 55 points, which improved to 87 points at 11 years. Seventy-five hips (65%) were excellent, 11 (9%) were good, and 30 (39%) were poor. The overall rate of revision was 15% (17 of 116 hips). The rate of revision of the femoral component was 11% (13 of 116 hips), and the rate of revision of the acetabular component was 15% (17 of 116 hips). The prevalence of thigh pain was 28% at 11 years. The increase in the incidence of aseptic loosening of the femoral component was found to explain the high incidence of severe thigh pain at 11 years' follow-up. At 11 years, there was femoral osteolysis in 69 hips (59%) and acetabular osteolysis in 65 hips (56%). At 6 years, 20 hips (17%) showed definite wear of the polyethylene liner. At 11 years, 81 hips (70%) showed definite wear of the polyethylene liner. Because the complication rate of the PCA hip prosthesis with respect to loosening, osteolysis, and excessive wear in the polyethylene liner is high, we abandoned the use of this implant.

Omnifit cementless total hip arthroplasty. A 10-year average followup

Seventy-six hips in 67 patients were evaluated an average of 119 months (range, 61-150 months) after total hip arthroplasty with porous coated Omnifit femoral and acetabular components. The patients were young (average age, 45 years), and most were male (67%). Two stems and one cup were revised for aseptic loosening, for aseptic revision rates of 2.6% on the femoral side and 1.3% on the acetabular side. Thigh pain was present in three cases, one of which was activity limiting. Twenty-five (35.7%) hips had evidence of osteolysis confined to proximal Gruen Zone 1 or 7 or to the acetabulum (22 proximal femoral, three both). There were no cases of intramedullary osteolysis in surviving stems. Thirteen (17.1%) hips have undergone reoperation for bone grafting of progressive proximal osteolysis without component revision, at an average 93 months after the total hip arthroplasty. At an average 40 months after reoperation, all stems remain well fixed, and there has been no recurrence of osteolysis of grafted femoral lesions. These results suggest that a circumferentially proximally porous coated femoral component in cementless total hip arthroplasty can provide stable fixation for as long as 12 years after implantation and caseal the canal from distal osteolysis. Serious concerns remain about the incidence of proximal femoral osteolysis.

The Charnley versus the Spectron hip prosthesis: radiographic evaluation of a randomized, prospective study of 2 different hip implants

A total of 410 hips were randomized to treatment with either a Charnley (206 hips) or a Spectron (204 hips) total hip arthroplasty. The patients were operated on by a standardized procedure using a contemporary cementing technique and were followed after 1, 3, 5 to 6, and 10 years. The postoperative radiographs showed a significantly increased rate of malalignment and consequently low grade of cement mantle quality of the Charnley stem compared to the Spectron. No differences concerning cement mantle quality or positioning were found between the Charnley ogee cup and the metal-backed Spectron. Evaluation of the follow-up radiographs revealed 10 loose Charnley stems and 1 loose Spectron stem and 4 loose Charnley ogee cups and 23 loose Spectron metal-backed cups. The differences of revision rate for the femoral and acetabular components of the 2 prostheses were significant (P = .03, Charnley femoral component more frequent; P = .03, Spectron acetabular component more frequent). The radiographic evaluation strengthened this disparity. Poor wear characteristics of the metal-backed Spectron cup are perhaps the main reason for the highly significant difference in mechanical failure rate between the 2 cups. We therefore propose that metal-backing of cemented cups should be avoided, at least when combined with larger femoral heads. The difficulty in positioning the Charnley stem with an adequate cement mantle, especially in the absence of trochanteric osteotomy, might explain the inferior Charnley stem longevity in this study.

Poor outcome of the PCA and Harris-Galante hip prostheses. Randomized study of 171 arthroplasties with 9-year follow-up

155 patients (171 hips) with a mean age of 50 years (24-64) were randomized to uncemented PCA (84 hips) or Harris-Galante type I (87 hips) total hip arthroplasty. Clinical and radiographic evaluations were done regularly. The improvements in the Harris hip and pain scores did not differ. Osteolysis developed in 5 PCA and 17 Harris-Galante hips. 13 hips in the PCA and 16 in the Harris-Galante (HG) group were revised because of mechanical failures and 1 hip (HG) because of infection after a mean follow-up of 9 years. Decreased 10-year survival rate, based on revision as end-point, was noted for the PCA (85%), compared with the Harris-Galante cup (99%). The corresponding survival rate of the PCA stem (96%) was higher than that observed for the Harris-Galante design (86%). When radiographic failures were included, the survival rates of the 4 different components dropped to between 73% and 94%. These findings indicate that further revisions will be necessary and continuous radiographic follow-up is indicated to enable revision before severe bone destruction has occurred. Although the PCA and the Harris-Galante designs differed as regards the survival of the individual components, the overall clinical and radiographic survival rates of these cementless total hip arthroplasties were poor.

Progressive Osteolysis after Porous-Coated Anatomic (PCA) Uncemented Total Hip Arthroplasty Ten-Year Results in 32 Consecutive Cases

Thirty-two primary non-cemented first generation Porous-Coated Anatomic (PCA) total hip prostheses in 31 patients were followed prospectively. The average follow-up period was 10.3 years. The median age at surgery was 53 years (range 21-65). All operations were performed by one surgeon. Preoperatively, all cases had a poor Harris Hip Score. Ten years after surgery, 95% were rated good or excellent. Progressive roentgenographical changes were observed. In particular there was severe femoral osteolysis in zones 1, 2 and 7, and extensive wear of the polyethylene liner at the two latest follow-up examinations. Wear of the polyethylene liner, up to 0.4 mm/year, was significantly correlated with osteolysis after seven years (p=0.003). Aseptic cup loosening was the reason for six of the eight failures. At 10.3 years after surgery the survival with revision as end-point was 72%. We stopped using the 1st generation PCA prosthesis after five years due to worrying roentgenographic changes. The seven and ten years results have confirmed that this prosthesis cannot be recommended for implantation. (Hip International 1999; 9: 214-20)