Aims

Total knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component.

Introduction. The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998. Numerous publications have reported reduced wear rates and a reduction in particle induced peri-prosthetic osteolysis at short to mid-term follow-up. The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against 32mm femoral heads or less at a minimum of 13 years follow-up. Methods. Inclusion criteria for patients was a primary THR with femoral heads 32mm or less and a minimum 13 year follow-up. 139 hips have been enrolled with an average follow-up of 13.7 years (13–16), 80 females (57%). Wear analysis was performed using the Martell Hip Analysis software. Radiographic grading was performed on the longest follow-up AP hip films. The extent of radiolucency in each zone greater than 0.5mm in thickness was recorded along with the presence of sclerotic lines and osteolysis. Results. Wear analysis: Using the average of the slopes of the individual regression lines, the wear rate was 0.006±0.033mm/yr. Using the early to latest film method, the wear rate was 0.003±0.056mm/yr. Radiographic analysis: Acetabular side: the greatest incidence of radiolucency occurred in zone 1 at 21%; sclerotic lines had a less than 2% incidence in any of the 3 zones; there was no identified osteolysis. Femoral side: the incidence of radiolucencies was limited to zone 1, 2%; sclerotic lines were rare in any zone, maximum in zone 3, 4%; there was no identified osteolysis. Conclusion. The wear of this form of irradiated and melted highly crosslinked polyethylene remained at levels lower than the detection limit of the software at minimum 13 year follow-up and there was no identified osteolysis

Highly crosslinked polyethylene (XLPE) was introduced to decrease peri-prosthetic osteolysis related to polyethylene wear, a major reason for revision of total hip arthroplasty. There are few reports of wear and osteolysis at 10 years post-operatively. We asked the following questions: (1) What are the linear and volumetric wear rates of one remelted XLPE at 10–14 years using the Martell method? (2) What is the relationship between volumetric wear, femoral head size, and osteolysis? (3) What is the incidence of osteolysis using conventional radiographs with Judet views and the Martell method?. Methods We evaluated a previously reported cohort of 84 hips (72 patients) with one design of an uncemented acetabular component and one electron-beam irradiated, remelted XLPE at a mean follow-up of 11 years (range 10 to 14 years). Measurements of linear and volumetric wear were performed in one experienced laboratory by the Martell method and standard radiographs, with additional Judet views, were used to detect peri-prosthetic osteolysis. Statistical analysis of wear and osteolysis compared to head size was performed. Results The mean linear wear rate by the first-to-last method was 0.024 mm/year (median, 0.010 mm/year) and the mean volumetric wear rate by this method was 12.2 mm. 3. /year (median, 3.6 mm. 3. /year). We found no association between femoral head size and linear wear rate. However, there was a significant relationship between femoral head size and volumetric wear rates, with 36/40 mm femoral heads having significantly higher volumetric wear (p=0.02). Small osteolytic lesions were noted in 12 hips (14%), but there was no association with head size, acetabular component position, or linear or volumetric wear rates. Conclusion This uncemented acetabular component and this particular remelted XLPE had low rates of linear and volumetric wear. Small osteolytic lesions were noted at 10 to 14 years, but were not related to femoral head size, linear or volumetric wear rates

INTRODUCTION. The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance. Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application. MATERIALS AND METHODS. We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”. RESULTS. The search led to 321 items, of these were considered relevant: as regards the growth factors 21 articles related to in vivo animal studies and 2 articles of human clinical use of BMPs and 1 single article on the use of PRP; as regards the mesenchymal stromal cells 2 items of application in animals; as regards the use of bone substitutes we have analyzed a review of this application. DISCUSSION. The use of biotechnologies in hip prosthetic revisions has produced conflicting results: autologous growth factors (PRP) have definitely been proven effective in maxillofacial surgery, in animal studies the results of BMPs are inconsistent with articles that validate their use and others that don't recommend it. Clinical application has demonstrated, today, the limited use of BMP-7 in revisions with even an increased risk of early re-mobilization, PRP appears to be rather effective only in the early stages of peri-prosthetic osteolysis. The mesenchymal cells can increase the chances of recovery and integration of the grafts but an important variable is the number of cells that are still alive after the impaction of the graft which affects their vitality. The bone substitutes appear to be safe and very useful, particularly if applied in order to implement the omologous bone, which is still the most scaffolds used in this surgery. CONCLUSIONS. The systematic review of the literature has shown an important lack of clinical studies regarding the use of biotechnologies for prosthetic revisions. It is therefore difficult to draw guidelines that regulate the application, prospective randomized clinical studies are therefore needed to validate its effectiveness

INTRODUCTION. The hip arthroplasty implant is currently growing up both in orthopedic and trauma practice. This increases the frequency of prosthesis revision due to implant loosening often associated with periprosthetic osteolysis that determine the failure and lead to a loss of bone substance. Nowadays there are numerous biotechnologies seeking to join or substitute the autologous or omologous bone use. These biotechnologies (mesenchymal stromal cells, growth factors and bone substitutes) may be used in such situations, however, the literature doesn't offer class 1 clinical evidences in this field of application. MATERIALS AND METHODS. We performed a literature review using the universally validated search engines in the biomedical field: PubMed / Medline, Google Scholar, Scopus, EMBASE. The keywords used were: “Growth Factors”, “Platelet Rich Plasma”, “OP-1”, “BMP”, “BMP-2”, “BMP-7”, “Demineralized Bone Matrix”, “Stem Cell”, “Bone Marrow”, “Scaffold”, “Bone Substitutes” were crossed with “hip”, “revision”, “replacement” / “arthroplasty”, “bone loss” / “osteolysis.”. RESULTS. The search led to 321 items, of these were considered relevant: as regards the growth factors 21 articles related to in vivo animal studies and 2 articles of human clinical use of BMPs and 1 single article on the use of PRP; as regards the mesenchymal stromal cells 2 items of application in animals; as regards the use of bone substitutes we have analyzed a review of this application. DISCUSSION. The use of biotechnologies in hip prosthetic revisions has produced conflicting results: autologous growth factors (PRP) have definitely been proven effective in maxillofacial surgery, in animal studies the results of BMPs are inconsistent with articles that validate their use and others that don't recommend it. Clinical application has demonstrated, today, the limited use of BMP-7 in revisions with even an increased risk of early re-mobilization, PRP appears to be rather effective only in the early stages of peri-prosthetic osteolysis. The mesenchymal cells can increase the chances of recovery and integration of the grafts but an important variable is the number of cells that are still alive after the impaction of the graft which affects their vitality. The bone substitutes appear to be safe and very useful, particularly if applied in order to implement the omologous bone, which is still the most scaffolds used in this surgery. CONCLUSIONS. The systematic review of the literature has shown an important lack of clinical studies regarding the use of biotechnologies for prosthetic revisions. It is therefore difficult to draw guidelines that regulate the application, prospective randomized clinical studies are therefore needed to validate its effectiveness

We investigated the incidence of soft-tissue lesions after small head metal-on-metal total hip replacement (MoM THR). Between December 1993 and May 1999, 149 patients (195 hips) underwent primary cementless MoM THR.

During the follow-up period, three patients (five THRs) died and eight patients (14 THRs) were lost to follow-up. We requested that all patients undergo CT evaluation. After exclusion of five patients (six THRs) who had undergone a revision procedure, and 22 (28 THRs) who were unwilling to take part in this study, 111 patients (142 THRs) were evaluated. There were 63 men (88 THRs) and 48 women (54 THRs) with a mean age of 45.7 years (37 to 56) at the time of surgery. The mean follow-up was 15.4 years (13 to 19). A soft-tissue lesion was defined as an abnormal peri-prosthetic collection of fluid, solid lesion or asymmetrical soft-tissue mass.

At final follow-up, soft-tissue lesions were found in relation to 28 THRs (19.7%), including 25 solid and three cystic lesions. They were found in 20 men and eight women; 26 lesions were asymptomatic and two were symptomatic. The mean maximal diameter of the soft-tissue lesion was 42.3 mm (17 to 135). The relatively high rate of soft-tissue lesions observed with small head MoM THR remains a concern.

Cite this article: Bone Joint J 2014;96-B:1594–9.

We compared the clinical and radiographic results of total ankle replacement (TAR) performed in non-diabetic and diabetic patients. We identified 173 patients who underwent unilateral TAR between 2004 and 2011 with a minimum of two years’ follow-up. There were 88 male (50.9%) and 85 female (49.1%) patients with a mean age of 66 years (sd 7.9, 43 to 84). There were 43 diabetic patients, including 25 with controlled diabetes and 18 with uncontrolled diabetes, and 130 non-diabetic patients. The clinical data which were analysed included the Ankle Osteoarthritis Scale (AOS) and the American Orthopaedic Foot and Ankle Society (AOFAS) scores, as well the incidence of peri-operative complications.

The mean AOS and AOFAS scores were significantly better in the non-diabetic group (p = 0.018 and p = 0.038, respectively). In all, nine TARs (21%) in the diabetic group had clinical failure at a mean follow-up of five years (24 to 109), which was significantly higher than the rate of failure of 15 (11.6%) in the non-diabetic group (p = 0.004). The uncontrolled diabetic subgroup had a significantly poorer outcome than the non-diabetic group (p = 0.02), and a higher rate of delayed wound healing.

The incidence of early-onset osteolysis was higher in the diabetic group than in the non-diabetic group (p = 0.02). These results suggest that diabetes mellitus, especially with poor glycaemic control, negatively affects the short- to mid-term outcome after TAR.

Cite this article: Bone Joint J 2014;96-B:1674–80.

Total hip replacement (THR) still is a rare intervention in many African countries. In Burkina Faso it is not performed on a regular basis. A visiting programme for THR was started in a district hospital with no previous relevant experience. In this paper we present an analysis of the surgical technical problems and peri-operative complications of 152 THRs in 136 patients and three bipolar hemiarthroplasties in three patients undertaken in this new programme with limited orthopaedic equipment. There were 86 male and 53 female patients with a mean age of 49 years (21 to 78). We identified 77 intra-operative technical problems in 51 operations. There were 24 peri-operative complications in 21 patients, 17 of which were bony in nature. So far, ten revision THRs have been performed in nine patients.

Regular analysis of the technical problems and complications was used to improve quality, and we identified patient selection adapted to the local circumstances as important to avoid complications. Our reflections on the problems encountered in initiating such a programme may be of help to other teams planning similar projects.

Cite this article: Bone Joint J 2014;96-B:177–80.

Little is known about the long-term outcome of mobile-bearing total ankle replacement (TAR) in the treatment of end-stage arthritis of the ankle, and in particular for patients with inflammatory joint disease. The aim of this study was to assess the minimum ten-year outcome of TAR in this group of patients.

We prospectively followed 76 patients (93 TARs) who underwent surgery between 1988 and 1999. No patients were lost to follow-up. At latest follow-up at a mean of 14.8 years (10.7 to 22.8), 30 patients (39 TARs) had died and the original TAR remained in situ in 28 patients (31 TARs). The cumulative incidence of failure at 15 years was 20% (95% confidence interval (CI) 11 to 28). The mean American Orthopaedic Foot and Ankle Society (AOFAS) ankle–hindfoot score of the surviving patients at latest follow-up was 80.4 (95% CI 72 to 88). In total, 21 patients (23 TARs) underwent subsequent surgery: three implant exchanges, three bearing exchanges and 17 arthrodeses. Neither design of TAR described in this study, the LCS and the Buechel–Pappas, remains currently available. However, based both on this study and on other reports, we believe that TAR using current mobile-bearing designs for patients with end-stage arthritis of the ankle due to inflammatory joint disease remains justified.

Cite this article: Bone Joint J 2013;95-B:1656–61.

Pre-operative planning for total hip replacement (THR) is challenging in hips with severe acetabular deformities, including those with a hypoplastic acetabulum or severe defects and in the presence of arthrodesis or ankylosis. We evaluated whether a Rapid Prototype (RP) model, which is a life-sized reproduction based on three-dimensional CT scans, can determine the feasibility of THR and provide information about the size and position of the acetabular component in severe acetabular deformities. THR was planned using an RP model in 21 complex hips in five men (five hips) and 16 women (16 hips) with a mean age of 47.7 years (24 to 70) at operation. An acetabular component was implanted successfully and THR completed in all hips. The acetabular component used was within 2 mm of the predicted size in 17 hips (80.9%). All of the acetabular components and femoral stems had radiological evidence of bone ingrowth and stability at the final follow-up, without any detectable wear or peri-prosthetic osteolysis. The RP model allowed a simulated procedure pre-operatively and was helpful in determining the feasibility of THR pre-operatively, and to decide on implant type, size and position in complex THRs.

Cite this article: Bone Joint J 2013;95-B:1458–63.

Following the recall of modular neck hip stems in July 2012, research into femoral modularity will intensify over the next few years. This review aims to provide surgeons with an up-to-date summary of the clinically relevant evidence. The development of femoral modularity, and a classification system, is described. The theoretical rationale for modularity is summarised and the clinical outcomes are explored. The review also examines the clinically relevant problems reported following the use of femoral stems with a modular neck.

Joint replacement registries in the United Kingdom and Australia have provided data on the failure rates of modular devices but cannot identify the mechanism of failure. This information is needed to determine whether modular neck femoral stems will be used in the future, and how we should monitor patients who already have them implanted.

Cite this article: Bone Joint J 2013;95-B:1011–21.

Peri-prosthetic osteolysis and subsequent aseptic loosening is the most common reason for revising total hip replacements. Wear particles originating from the prosthetic components interact with multiple cell types in the peri-prosthetic region resulting in an inflammatory process that ultimately leads to peri-prosthetic bone loss. These cells include macrophages, osteoclasts, osteoblasts and fibroblasts. The majority of research in peri-prosthetic osteolysis has concentrated on the role played by osteoclasts and macrophages. The purpose of this review is to assess the role of the osteoblast in peri-prosthetic osteolysis. In peri-prosthetic osteolysis, wear particles may affect osteoblasts and contribute to the osteolytic process by two mechanisms. First, particles and metallic ions have been shown to inhibit the osteoblast in terms of its ability to secrete mineralised bone matrix, by reducing calcium deposition, alkaline phosphatase activity and its ability to proliferate. Secondly, particles and metallic ions have been shown to stimulate osteoblasts to produce pro inflammatory mediators in vitro. In vivo, these mediators have the potential to attract pro-inflammatory cells to the peri-prosthetic area and stimulate osteoclasts to absorb bone. Further research is needed to fully define the role of the osteoblast in peri-prosthetic osteolysis and to explore its potential role as a therapeutic target in this condition. Cite this article: Bone Joint J 2013;95-B:1021–5

INTRODUCTION. The advantages of large diameter metal on metal total hip arthroplasty (MoM THA) and hip resurfacing arthroplasty are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri-prosthetic osteolysis generated as a result of a biological response to particulate wear debris. No reports in the literature exist as to whether circulating levels of Chromium (Cr) and Cobalt (Co) decrease upon removal of a symptomatic large diameter MoM implant or whether levels remain high due to the effect of metal ions debris left behind in the soft tissues after revision surgery. PATIENTS AND METHODS. Between June 2006 and June 2009 we undertook 44 revision surgeries of both large head MoM THAs (femoral head diameter 38mm) and metal-on-metal hip resurfacings for suspected metallosis. Mean time from original implant to revision was 4 years, 8 months (1yr 4mo–7yr 9mo). The mean follow up evaluation was 2 years and 2 months (1yr 2mo–4 years). Blood samples were taken for whole blood Cr and serum Co according to a recognised protocol and compared with reference levels indicated by the Medicines and Healthcare Regulatory Agency recommendation of less than 7ppb for Cr (130nM/L) and Co (119nM/L). RESULTS. 42 patients were found to have histological evidence of either metal allergy, metal toxicity or foreign body reaction. 2 patients had evidence of infection with no features of metal reaction. 3 patients suffered early dislocation requiring closed reduction. 1 patient had infective complications necessitating Girdlestones. 11 patients were lost to follow up, 8 patients were diagnosed pre operatively on Co and Cr levels in urine or synovial fluid aspirate alone. 23 patients had pre revision blood or serum metal ion level results available for direct comparison. Median serum Co level pre revision was 176.6nM/L, falling post revision to 5.1nM/L (p=<0.001∗). The median whole blood Cr level pre revision was 117nM/L and 19nm/L post revision (p=<0.001∗). Mean Oxford Hip Score was 23.7. DISCUSSION. This study demonstrates that at greater than one year post removal of a large diameter MoM hip implant for the indication of symptomatic metallosis or metal hypersensitivity, metal ion levels fall to almost normal levels and that outcome of revision surgery in terms of patient satisfaction is not adversely affected

We retrospectively reviewed 30 two-stage revision procedures in 28 patients performed for fungal peri-prosthetic joint infection (PJI) after a primary total knee replacement. Patients were followed for at least two years or until the infection recurred. The mean follow-up for patients who remained free of infection was 4.3 years (2.3 to 6.1). Overall, 17 patients were assessed as American Society of Anesthesiologists grade 3 or 4. The surgical protocol included removal of the infected implant, vigorous debridement and insertion of an articulating cement spacer. This was followed by at least six weeks of antimicrobial treatment and delayed reimplantation in all patients. The mean interval between removal of the prosthesis and reimplantation was 9.5 weeks (6 to 24). After reimplantation, patients took antifungal agents orally for a maximum of six months. Two knees became reinfected at one and two months post-operatively, respectively: one of these subsequently required arthrodesis because of uncontrolled infection.

Fungal PJIs can be treated successfully by removal of all infected material, appropriate antimicrobial treatment and delayed reimplantation.

We determined the midterm survival, incidence of peri-prosthetic fracture and the enhancement of the width of the femur when combining struts and impacted bone allografts in 24 patients (25 hips) with severe femoral bone loss who underwent revision hip surgery. The pre-operative diagnosis was aseptic loosening in 16 hips, second-stage reconstruction in seven, peri-prosthetic fracture in one and stem fracture in one hip. A total of 14 hips presented with an Endoklinik grade 4 defect and 11 hips a grade 3 defect. The mean pre-operative Merle D’Aubigné and Postel score was 5.5 points (1 to 8).

The survivorship was 96% (95% confidence interval 72 to 98) at a mean of 54.5 months (36 to 109). The mean functional score was 17.3 points (16 to 18). One patient in which the strut did not completely bypass the femoral defect was further revised using a long cemented stem due to peri-prosthetic fracture at six months post-operatively. The mean subsidence of the stem was 1.6 mm (1 to 3). There was no evidence of osteolysis, resorption or radiolucencies during follow-up in any hip. Femoral width was enhanced by a mean of 41% (19% to 82%). A total of 24 hips had partial or complete bridging of the strut allografts.

This combined biological method was associated with a favourable survivorship, a low incidence of peri-prosthetic fracture and enhancement of the width of the femur in revision total hip replacement in patients with severe proximal femoral bone loss.

We report the effectiveness of revision of total elbow replacement by re-cementing. Between 1982 and 2004, 53 elbows in 52 patients were treated with re-cementing of a total elbow replacement into part or all of the existing cement mantle or into the debrided host-bone interface, without the use of structural bone augmentation or a custom prosthesis. The original implant revision was still in situ and functional in 42 of 53 elbows (79%) at a mean of 94.5 months (26 to 266) after surgery. In 31 of these 42 elbows (74%) the Mayo Elbow Performance Score was good or excellent. Overall, of the 53 elbows, 18 (34%) required re-operation, ten (19%) for loosening. A classification system was developed to identify those not suitable for revision by this technique, and using this we have showed that successful re-implantation is statistically correlated to properly addressing the bone deficiency for both the humeral (p = 0.005) and the ulnar (p = 0.039) components.

The most frequent cause of failure after total hip replacement in all reported arthroplasty registries is peri-prosthetic osteolysis. Osteolysis is an active biological process initiated in response to wear debris. The eventual response to this process is the activation of macrophages and loss of bone. Activation of macrophages initiates a complex biological cascade resulting in the final common pathway of an increase in osteolytic activity. The biological initiators, mechanisms for and regulation of this process are beginning to be understood. This article explores current concepts in the causes of, and underlying biological mechanism resulting in peri-prosthetic osteolysis, reviewing the current basic science and clinical literature surrounding the topic

Purpose of the study: The ceramic-on-ceramic bearing for total hip arthroplasty (THA) has been widely used in Europe for many years. There have however been few publications on its long-term outcome. The purpose of this study was to examine the outcome at nine years follow-up of 100 THA implanted without cement using a ceramic-on-ceramic bearing. Material and methods: The first 100 ceramic-on-ceramic THA implanted from November 1999 in our unit in patients aged less than 65 years were studied. The clinical assessment included the physical examination with search for complications and the Harris and Postel-Merle-d’Aubigné scores noted preoperatively and at last follow-up. The radiographic assessment was performed by two surgeons (double reading) to search for peri-prosthetic lucency, osteolysis, ossifications and implant migration. The state of the calcar was noted. The Delee-Charnley classification was used to classify the lucent lines for the acetabulum and the Gruen McNiece and Amstutz classification for the femur. Results: Among the 100 THA, 20 patients were lost to follow-up. The Harris score was 42.6 (29–55) preoperatively and 93.9 (67–100) at last follow-up. The PMA was 8 (5–11) preoperatively and 16.7 (9–18) at last follow-up. One hip was revised to change the acetabular implant at five years. There were six early dislocations [one episode (n=4), two episodes (n=2)], one late dislocation, and two episodes of subluxation without recurrence. There were no fractures of the femoral head. The radiographic analysis identified moderate bone absorption of the calcar without real osteolysis in nearly all of the patients. For a few patients, a lucent line seen early postoperatively had disappeared at last follow-up. No implant migration (cup, stem) was noted. Discussion: The clinical and radiographic outcomes are in agreement with the literature. The relatively high rate of dislocation can be explained by the diverse levels of experience of the surgical teams. The prostheses presenting dislocation did not have an unfavourable outcome, particularly radiographically. Conclusion: These clinical and radiographic results at nine years follow-up, and the current systematic use of computer assisted navigation for optimal implant positioning favour continuation of the implantation of the ceramic-on-ceramic bearing in patients aged less than 65 years

Four uncemented Symax hip stems were extracted at three weeks and nine, 13 and 32 months, respectively, for reasons other than loosening. The reasons for implant removal were infection in two cases, recurrent dislocation in one and acetabular fracture in one. They were analysed to assess the effect and behaviour of an electrochemically deposited, completely resorbable biomimetic BONIT-hydroxyapatite (HA) coating (proximal part) and a DOTIZE surface treatment (distal part) using qualitative histology, quantitative histomorphometry and scanning electron microscopy (SEM). Early and direct bone-implant bonding with signs of active remodelling of bone and the HA coating were demonstrated by histology and SEM. No loose BONIT-HA particles or delamination of the coating were observed, and there was no inflammation or fibrous interposition at the interface.

Histomorphometry showed bone-implant contact varying between 26.5% at three weeks and 83.5% at 13 months at the HA-coated implant surface. The bone density in the area of investigation was between 24.6% at three weeks and 41.1% at 32 months. The DOTIZE surface treatment of the distal part of the stem completely prevented tissue and bone apposition in all cases, thereby optimising proximal stress transfer.

The overall features of this implant, in terms of geometry and surface texture, suggest a mechanically stable design with a highly active biomimetic coating, resulting in rapid and extensive osseo-integration, exclusively in the metaphyseal part of the stem. Early remodelling of the HA coating does not seem to have a detrimental effect on short-term bone-implant coupling. There were no adverse effects identified from either the BONIT-HA coating or the DOTIZE surface treatment.

There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements (THRs) in patients younger than 50 years of age. We prospectively reviewed 78 patients (109 hips) with a hybrid THR having a mean age of 43.4 years (21 to 50) and 79 patients (110 hips) with a cementless THR with a mean age of 46.8 years (21 to 49). The patients were evaluated clinically using the Harris hip score, the Western Ontario and McMaster Universities (WOMAC) osteoarthritis score and the University of California, Los Angeles (UCLA) activity score. Radiographs and CT scans were assessed for loosening and osteolysis. The mean follow-up was for 18.4 years (16 to 19) in both groups.

The mean post-operative Harris hip scores (91 points versus 90 points), the mean WOMAC scores (11 points versus 13 points) and UCLA activity scores (6.9 points versus 7.1 points) were similar in both groups. The revision rates of the acetabular component (13% versus 16%) and the femoral component (3% versus 4%), and the survival of the acetabular component (87% versus 84%) and the femoral component (97% versus 96%) were similar in both groups.

Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outstanding, wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients.