Objectives

This study aimed to characterise and qualitatively grade the severity of the corrosion particles released into the hip joint following taper corrosion.

Introduction

Osteloysis following metal-on-UHMW polyethylene Total Hip Arthroplasty (THA) is well reported, as is lack of osteolysis following Ceramic-on-Ceramic (CoC)THA. Early ceramic failures did report some osteolysis, but in flawed implants. As 3rd and now 4th generation ceramic THAs come into mid- and long-term use, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. Osteolysis reported after 3rd generation CoC THA often included metallosis due to neck rim impingement. In our department we have revised only 2 hips in over 6000 CoC THAs for osteolysis. Both had evidence of metallosis as well as ceramic wear. The technique used by Radiologists for identifying the nature of lesions on CT is the Hounsfield score which will identify the density of the tissue within the lucent area. It is common for radiologist to have no access to previous imaging, especially pre-operative imaging if a long time has elapsed.

With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA which states there is osteolysis? Revision of such implants in elderly patients has a high risk of morbidity and mortality.

Introduction

The possibility of corrosion at the taper junction of hip replacements was initially identified as a concern of generating adverse reactions in the late 1980s. Common clinical findings of failure are pain, clicking, swelling, fluid collections, soft tissue masses, and gluteal muscle necrosis identified intra operatively.

Background

Total Hip Arthroplasty (THA) using the Direct Anterior Approach (DAA) is a muscle sparing approach which promotes early mobilisation of patients. It is a technically challenging approach shown to have a high rate of complications, especially during the learning curve. Here we present the results of 157 cases of THA via a DAA on a standard theatre table, with a minimum of 6 months follow-up.

Introduction and Aims

The 21^st Century has seen ceramic bearings become an increasingly popular choice in total hip arthroplasty due to their high wear resistance and inert wear debris without osteolysis promising a long term bearing solution. Early ceramic bearings were hindered by fracture but improved manufacturing processes and materials subsequently produced stronger ceramics. These third generation ceramics showed greatly reduced fracture rates but there is limited evidence in the literature reporting their long term survival and wear characteristics. The purpose of this study was to determine osteolysis and survival rates of Alumina ceramic bearings in cementless total hip arthroplasties with a minimum follow-up of 15 years.

Introduction

Squeaking is a potential problem of all hard on hard bearings yet it has been less frequently reported in metal-on-metal hips. We compared a cohort of 11 squeaking metal-on-metal hip resurfacings to individually matched controls, assessing cup inclination and anteversion between the groups to look for any differences.

Introduction

The success of total hip arthroplasty has meant its indications have been extended to the younger more active patient. Due to the higher activity levels and increased demands of these patients, revision rates have been traditionally higher than when compared to older patients [1]. Ceramic on ceramic bearings may offer a viable long term solution as manufacturing methods have evolved resulting in improved mechanical properties, particularly of third and fourth generation ceramics. We report the outcome of primary cementless, alumina-on-alumina hip arthroplasty with a minimum 10 year follow up in 110 patients under the age of 55 years of age at time of surgery.

Introduction

The Delta Motion device (developed by Finsbury Orthopaedics, Leatherhead, United Kingdom, now manufactured by DePuy, Leeds, United Kingdom) is a pre-assembled factory fitted cup. It has been introduced to overcome some of the concerns relating to intra-operative assembly with improper seating of the liner and chipping. This device has a thinner shell and liner in comparison with other cups, allowing the use of larger sized heads which should help reduce the risk of impingement and dislocation. A drawback of the pre-assembled design is the inability to use supplementary screws to achieve stability and the difficulty in obtaining primary stability compared with a thin titanium shell. To date we are not aware of any publications reviewing the outcomes of these devices.

Introduction

Modularity is being increasingly used throughout the world for both primary and revision total hip arthroplasty. Recently there have been concerns of increased corrosion and fretting at the modular junctions. In the SROM® modular hip system, two modular junctions are the head-neck taper junction and the stem-sleeve taper junction. The aim of this study was to investigate corrosion at these junctions with the use of different bearing materials.

Introduction

Edge loading commonly occurs in all bearings in hip arthroplasty. Edge loading wear can occur in these bearings when the biomechanical loading axis reaches the edge and the femoral head loads the edge of the cup producing wear damage on both the head and cup edge. When the biomechanical loading axis passes through the polished articulating surface of the acetabular component and does not reach the edge, the center of the head and the center of the cup are concentric. The resulting wear known as concentric wear is low in metal-on-metal (MOM) bearings, and is negligible in ceramic-on-ceramic (COC) bearings. Edge loading is well defined in COC hip bearings. However, edge loading is difficult to identify in MOM bearings, since the metal bearing surfaces do not show wear patterns macroscopically. The aims of this study are to compare edge loading wear rates in COC and MOM bearings, and to relate edge loading to clinical complications.

Edge loading commonly occurs in all bearings in hip arthroplasty. The aim of this study compares metal bearings with edge loading to alumina bearings with edge loading and to metal bearings without edge loading.

Seventeen failed large diameter metal-on-metal hip bearings (8 total hips, 9 resurfacings) were compared to 55 failed alumina-on-alumina bearings collected from 1998 to 2010. The surface topography of the femoral heads was measured using a chromatically encoded confocal measurement machine (Artificial Hip Profiler, RedLux Ltd.).

The median time to revision for the metal hip bearings and the alumina hip bearings was 2.7 years. Forty-six out of 55 (84%) alumina bearings and 9 out 17 (53%) metal bearings had edge loading wear (p<0.01). The average volumetric wear rate for metal femoral heads was 7.87 mm3/yr (median 0.25 mm3/yr) and for alumina heads was 0.78 mm3/yr (median 0.18 mm3/yr) (p=0.02).

The average volumetric wear rate for metal heads with edge loading was 16.51 mm3/yr (median 1.77 mm3/yr) and for metal heads without edge loading was 0.19 mm3/yr (median 0 mm3/yr) (p=0.1). There was a significant difference in gender, with a higher ratio of females in the alumina group than the metal group (p=0.02).

Large diameter metal femoral heads with edge loading have a higher wear rate than smaller alumina heads with edge loading. Metal-on-metal bearings have low wear when edge loading does not occur.

Aim

Alumina ceramic on ceramic bearings in total hip arthroplasty (THA) may reduce the prevalence of osteolysis due to its properties of low wear and chemical inertness. This is critical in the younger patient population as they place increased demands over a longer period. This study reports on the clinical and radiographic outcomes of a series of modern cementless ceramic on ceramic THA at a minimum of 10 years in this younger group.

Aim: Alumina ceramic on ceramic bearings have gained popularity in hip arthroplasty due to the properties of low wear, low friction and chemically inert wear debris. In a previous study, we reported the excellent clinical results of a series of cementless ceramic on ceramic primary total hip arthroplasties at a minimum of 5 years. We now present the follow up results at 10 years.

Method: Between June 1997 and February 1999, 301 consecutive, primary cementless hip arthroplasties were performed on 283 patients in our unit. The mean age of the patients was 57.8 years, with 145 (51%) being female. All of the hips received the same implant: (Osteonic ABC cup and Secure-Fit or Secure-Fit Plus stem; Stryker Orthopaedics). A third generation alumina ceramic on ceramic bearing (Biolox Forte; CeramTec) was used for articulation in all cases. All the operations were performed through a posterior approach with enhanced posterior repair, and the post-operative protocols were the same for all the patients. The clinical and radiographic outcome at 10 years were analysed.

Results: At 10 years, 7.3% had died of unrelated cause and 3% were revised. The average Harris Hip score was 94.3 points at the last follow up. Ninety six percent of patients scored an excellent or good result, with less than 3% have moderate residual pain. Radiographically, all patients assessed had evidence of stable bony ingrowth. There were nine revisions in all, four stem revisions due to periprosthetic fracture, one secondary to aseptic loosening and one to facilitate a femoral shortening osteotomy. There was one cup revision for psoas tendonitis and one for cup repositioning. This same patient subsequently underwent further revision due to acetabular osteolysis with metallosis and some ceramic wear. Overall, the survival rate of the implants was 96% at 10 years. The retrieved femoral heads showed a median wear rate of 0.2 cubic millimeters per year.

Conclusions: Alumina ceramic on ceramic bearings in cementless primary total hip arthroplasty had been shown to have good survival rate at 10 years with good function, low wear rate and no adverse radiographic changes. The one case of osteolysis may be due to ceramic wear debris or may be due to metal wear debris from the neck to rim impingement.

Background: Squeaking in hip arthroplasty is a phenomenon that was described decades ago, but has only been brought back to attention recently. It occurs predominantly in ceramic on ceramic bearings, and has a reported incidence from less than 1% to 21%. The cause and the implication of squeaking are still unknown and many factors have been suggested to contribute. This study has looked into the patient factors to investigate if any clinical features are associated with an increased risk of squeaking.

Methods: All primary total hip arthroplasties with ceramic on ceramic bearing that were performed at our unit were reviewed and all squeaking hips presented are included in the study. Patient demographics and clinical outcome data were analysed and compared with matched controls from the silent hips.

Results: Between 1997 and 2008, 3375 primary hip arthroplasties in 3182 patients with ceramic on ceramic bearing were performed in our unit. Seventy one hips (2.1%) presented with squeaking on direct questioning and self reporting. Those patients were found to be taller, heavier and younger. They also have a significantly higher post-operative range of hip motion and higher Harris hip score when compared to matched controls. There was no difference in the satisfaction score. Only 4 patients (5.6%) presented with pain as well as squeaking, and 2 (2.8%) resulted in revision surgery for problematic squeaking.

Conclusions: We present the largest series of squeaking primary hip arthroplasties with ceramic on ceramic bearing to date. A number of patient factors were found to be associated with squeaking. The taller, heavier and younger patients with more flexible and functional hips were at a higher risk, presumably because these patients put greater mechanical demands on their hips. Majority of the patients with squeaking are pain free and there is only a small risk of requiring revision surgery.

Introduction: Dislocation is the most common complication resulting in re-operation after total hip arthroplasty. This study investigates the association between acetabular prosthesis position, changes in femoral offset and leg length and the risk of dislocation.

Patients and Methods: All total hip arthroplasties performed over the past 17 years at one institution were reviewed. The posterolateral approach was used in all cases. Only hips that included all of the following were included in the study: diagnosis of primary osteoarthritis, no previous surgery, unconstrained liner. 3682 hips met the inclusion criteria. 60 hips (1.6%) sustained a dislocation. Cup inclination and version was determined from scanned radiographs using Hip Analysis Suite software (University of Chicago) in all hips that dislocated and a control group of 60 patients matched for femoral head size, sex, age at surgery, side of hip replacement, time from surgery, BMI, type of prosthesis and bearing surface. We compared femoral offset and length against the contralateral normal hip, on standardised radiographs. Therefore dislocation cases where the contralateral hip had been replaced, where arthritic changes were present, or where previous surgery had been undertaken were not included in the analysis. 24 dislocating hips were measured and compared with 48 controls matched using the same criteria as above. Radiographs were analysed using Hip Analysis Suite.

Results: There is a statistically significant difference (p=0.025) in anteversion between dislocators and matched controls. Inclination is not significantly associated with dislocation (p=0.536).

There is a relative risk of 3.0 of dislocation in cups with ≤15 degrees of anteversion compared with > 15 degrees of anteversion. This difference in dislocation is statistically significant (p< 0.01).

Increased femoral offset compared with the normal contralateral hip is statistically significantly associated with an increased risk of dislocation (p=0.03). Change in leg length is not associated with dislocation risk.

Discussion: Decreased cup anteversion is associated with an increased risk of dislocation in hips operated on via the postero-lateral approach. Our results indicate that the surgeon should aim for a minimum of 15 degrees of anteversion to reduce the risk of dislocation.

The increase in femoral offset in the prosthetic hip compared with the normal contralateral hip and its association with dislocation may be due to intraoperative attempts to compensate for an unstable hip by increasing offset. These results indicate that a surgeon should be cautious when increasing femoral offset alone to try and compensate for a potentially unstable hip. Other factors, for example acetabular version should be addressed, with readjustment of cup position intra-operatively if required.

Introduction and Aims: Good clinical outcome can be expected following cementless total knee arthroplasty (TKA) provided there is early stability and bone ingrowth. Screws give excellent initial stability but provide a path for osteolysis. Screws also cause an irregularity of the tibial component surface which limits their use as a mobile bearing component. We hypothesise that early stability can be obtained with four peripheral pegs rather than screws. We present the results of such a tibial component at a minimum of two years in a cementless mobile-bearing TKA.

Materials and Methods: We evaluated 200 knees in 173 patients. The average age at surgery was 72 years (range, 45–91 years) with 61% of cases in women. Patients were followed up for an average of 45.7 months (range 24 to 69 months). All radiographic and clinical scores were performed prospectively and recorded on a relational database. The components used were the cementless Low Contact Stress femoral component with the DuoFix MBT tibial tray (Depuy, Warsaw, Indiana, USA). The tibial tray was manufactured from cobalt-chrome with a central polished stem and four peripheral pegs. The underside, including the pegs, had a porous surface coated with 50 microns of hydroxyapatite.

Results: After excluding patients who had died, or lost to follow up, 164 cases had a minimum 2-year follow-up. None of the tibial components have required revision. One patient (0.6%) required revision of the femoral component at 22 months for failure of bone ingrowth. There was one superficial infection which resolved with intravenous antibiotics. Two patients developed deep infections (1.2%) which resolved with arthroscopic lavage and antibiotics. One patient presented with bearing spin out at 3 months following surgery, and an exchange to a thicker tibial insert was performed. Average flexion at follow up was to 110°. The patients stated that they were satisfied with their knees in 141 out of 155 cases (91%). The mean score for pain at rest was 0.9 (0–10) and for activity related pain was 1.3. The average HSS score was 86/100 with 90% good or excellent results, compared with a preoperative score of 54/100. Lucent lines were seen in one tibial zone in ten knees (7%), and two zones in three knees (2.1%). There were lucent lines in one femoral zone in 13 cases and two zones in two cases. None of the lines were progressive, and all the surviving components were bone ingrown. Osteolysis was present in a single zone around one (0.7%) tibial component. One patient showed some femoral osteolysis in one zone (0.7%) and also had patellar osteolysis in one zone. Two patients had osteolysis in a single zone of the patella.

Conclusion: This study shows that this design of mobile bearing tibial component provides good primary stability and bone ingrowth.

Previously ankylosed or surgically arthrodesed hip joints can be converted successfully to a Total Hip Replacement (THR) in order to improve patient mobility and function. We present a long term prospective cohort study of cementless revisions of previously ankylosed hips.

Sixteen hips (15 patients) with a mean age of 52 years (range 16 to 75) had ankylosed hips for a mean of 36 years (range 3.5 to 65 years). They all received a cement-less THR between August 1988 and January 2003 and were prospectively followed-up for a mean of 11 years (range 5.0 to 19 years). Two patients died during the study period of unrelated causes and none were lost to follow-up.

All patients showed improved mobility and function following the conversion of their ankylosed hips. The Harris Hip Score improved from a pre-operative mean value of 70 (Standard Error of Mean (SEM) 3.4) to a post-operative value of 83 (SEM 4.4) at the latest review, which was statistically significant (p < 0.05). There was one acetabular cup revision at 5 years post implantation for aseptic loosening. At a mean of 11 years post THR, all other femoral and acetabular components remained clinically and radiographically well fixed.

One patient with systemic ankylosing spondylitis and spontaneous bilateral bony hip ankylosis developed the unusual complication of Paget’s disease of the Left hemipelvis and proximal femur two years after successful bilateral THR surgery. His symptoms resolved following medical therapy for Paget’s disease.

We conclude that a previously ankylosed hip can be effectively converted to a cementless total hip replacement with good long term results.

Dislocation remains a common complication following total hip arthroplasty, second only to aseptic loosening as a cause of revision. Factors thought to play a role in dislocation include cup and stem alignment, soft tissue tension, surgical approach, patient factors, and design features of the prosthesis, including femoral head size.

We analysed all consecutive total hip replacements at one institution over a 17 year period. Criteria for study inclusion were hips replaced due to primary osteoarthritis with no previous surgery, femoral head sizes of 28mm and 32mm only, and at least one year from date of surgery. 3682 hips fulfilled these criteria. All procedures were carried out using a posterolateral approach with enhanced posterior repair, and a standard method of intraoperative soft tissue balance assessment.

The rate of dislocation was 1.6%. 32mm femoral head size was associated with a statistically significant lower rate of dislocation. However, after controlling for different follow-up times between 28mm and 32mm heads, this difference was no longer observed. Older age at time of surgery and decreased cup anteversion were shown to be significantly associated with an increased risk of dislocation. Ceramic on ceramic bearing surface was significantly associated with a decreased risk of dislocation, after controlling for age, bearing wear and time from surgery. Cup inclination, gender, BMI, and preoperative hip score were not related to dislocation risk.

Our dislocation rate may reflect current dislocation rates of surgeons using the posterolateral approach with posterior capsule and external rotator repair. The risk factors identified and excluded in this study are likely to be relevant to all surgeons who utilise this approach in total hip arthroplasty.

Dislocation remains a common complication following total hip arthroplasty, second only to aseptic loosening as a cause of revision. Factors thought to play a role in dislocation include cup and stem alignment, soft tissue tension, surgical approach, patient factors, and design features of the prosthesis, including femoral head size.

We analysed all consecutive total hip replacements at one institution over a 17 year period. Criteria for study inclusion were hips replaced due to primary osteoarthritis with no previous surgery, femoral head sizes of 28mm and 32mm only, and at least one year from date of surgery. 3682 hips fulfilled these criteria. All procedures were carried out using a posterolateral approach with enhanced posterior repair, and a standard method of intraoperative soft tissue balance assessment.

The rate of dislocation was 1.6%. 32mm femoral head size was associated with a statistically significant lower rate of dislocation. However, after controlling for different follow-up times between 28mm and 32mm heads, this difference was no longer observed. Older age at time of surgery and decreased cup anteversion were shown to be significantly associated with an increased risk of dislocation. Ceramic on ceramic bearing surface was significantly associated with a decreased risk of dislocation, after controlling for age, bearing wear and time from surgery. Cup inclination, gender, BMI, and preoperative hip score were not related to dislocation risk.

Our dislocation rate may reflect current dislocation rates of surgeons using the posterolateral approach with posterior capsule and external rotator repair. The risk factors identified and excluded in this study are likely to be relevant to all surgeons who utilise this approach in total hip arthroplasty.

Introduction and Aims: Polyethylene wear and associated osteolysis is a major factor limiting arthroplasty longevity. The Duration process has the theoretical advantage of reducing wear. Our aim was to evaluate the wear rate of standard and Duration polyethylene using either metal or zirconia ceramic heads in the Anatomique Benoist Girard II hip system.

Method: Of 510 patients, 258 had appropriate radiographs for wear measurement. There were five bearing-couple groups. Group 1, 73 patients: metal (cobalt chrome) head on standard polyethylene; group 2, 73 patients: metal head on Duration polyethylene; group 3, 21 patients: (HIPed) zirconia ceramic head on standard polyethylene; group 4, 63 patients: HIPed zirconia head on Duration polyethylene; and group 5, 28 patients: non-HIPed zirconia head on standard polyethylene. All patients had 28mm heads. Sequential radiographs – at least one year after surgery and at least two years apart thereafter – were digitally scanned and images were analysed using computer software.

Results: Group 1: metal on standard polyethylene (n=73) – mean linear wear rate of 0.138 mm/yr (range 0.023–0.462 mm/yr). Group 2: metal on Duration polyethylene (n=73) – mean linear wear rate of 0.106 mm/yr (range 0.067–0.405 mm/yr). Group 3: HIPed zirconia heads on standard polyethylene (n=21) – mean linear wear rate of 0.124 mm/yr (range 0.037–0.225 mm/yr). Group 4: HIPed zirconia heads on Duration polyethylene (n=63) – mean linear wear rate of 0.120 mm/yr (range 0.001–0.427 mm/yr). Group 5: non-HIPed zirconia heads on standard polyethylene (n=28) – mean linear wear rate of 0.119 mm/yr (range 0.044–0.0330 mm/yr). Comparison of linear wear rates of standard (group 1) and Duration polyethylene (group 2) bearings with metal heads revealed a difference of statistical significance (p=0.0083), with lower annual wear rates with Duration polyethylene. Further comparison between these two groups revealed a male preponderance in the Duration group (p=0.000001). There was also a statistically significant difference in body weight between these groups, with the Duration group being heavier by a mean of 5.1 kilograms (p=0.05). There was no significant difference in wear rates between standard and Duration polyethylene bearings with HIPed zirconia heads. There was no statistically significant difference in age in our patient groups.

Conclusion: Duration polyethylene has lower linear wear rates when coupled with a cobalt chrome head. This is despite a male preponderance and higher body weight. Wear rates between standard and Duration polyethylene bearings coupled with zirconia heads were not statistically different.