Aims

To achieve the functional benefits of the direct anterior (DA) approach and the fixation benefits of cemented replacement, this study combined the two techniques posing the following questions: does the limited access of the DA approach adversely affect the cement technique?; and does such a cementing technique reduce the incidence of cementless complications?

We describe the results of 81 consecutive revision total hip replacements with impaction grafting in 79 patients using a collared polished chrome–cobalt stem, customised in length according to the extent of distal bone loss. Our hypothesis was that the features of this stem would reduce the rate of femoral fracture and subsidence of the stem.

The mean follow-up was 12 years (8 to 15). No intra-operative fracture or significant subsidence occurred. Only one patient suffered a post-operative diaphyseal fracture, which was associated with a fall. All but one femur showed incorporation of the graft. No revision for aseptic loosening was recorded.

The rate of survival of the femoral component at 12 years, using further femoral revision as the endpoint, was 100% (95% confidence interval (CI) 95.9 to 100), and at nine years using re-operation for any reason as the endpoint, was 94.6% (95% CI 92.0 to 97.2).

These results suggest that a customised cemented polished stem individually adapted to the extent of bone loss and with a collar may reduce subsidence and the rate of fracture while maintaining the durability of the fixation.

High-flexion total knee replacement (TKR) designs have been introduced to improve flexion after TKR. Although the early results of such designs were promising, recent literature has raised concerns about the incidence of early loosening of the femoral component. We compared the minimum force required to cause femoral component loosening for six high-flexion and six conventional TKR designs in a laboratory experiment.

Each TKR design was implanted in a femoral bone model and placed in a loading frame in 135° of flexion. Loosening of the femoral component was induced by moving the tibial component at a constant rate of displacement while maintaining the same angle of flexion. A stereophotogrammetric system registered the relative movement between the femoral component and the underlying bone until loosening occurred.

Compared with high-flexion designs, conventional TKR designs required a significantly higher force before loosening occurred (p < 0.001). High-flexion designs with closed box geometry required significantly higher loosening forces than high-flexion designs with open box geometry (p = 0.0478). The presence of pegs further contributed to the fixation strength of components.

We conclude that high-flexion designs have a greater risk for femoral component loosening than conventional TKR designs. We believe this is attributable to the absence of femoral load sharing between the prosthetic component and the condylar bone during flexion.

To assess the effect of improved methods of femoral cementing on the loosening rates in young patients, we reviewed 50 'second-generation' cemented hip arthroplasties in 44 patients aged 50 years or less. The femoral stems were all collared and rectangular in cross-section with rounded corners. The cement was delivered by a gun into a medullary canal occluded distally with a cement plug. A clinical and radiographic review was undertaken at an average of 12 years (10 to 14.8) and no patient was lost to follow-up. No femoral component was revised for aseptic loosening, and only one stem was definitely loose by radiographic criteria. By contrast, 11 patients had undergone revision for symptomatic aseptic loosening of the acetabular component and 11 more had radiographic signs of acetabular loosening.

Angular proximal femoral deformities increase the technical complexity of primary total hip arthroplasties (THAs). The goals were to determine the long-term implant survivorship, risk factors, complications, and clinical outcomes of contemporary primary THAs in this difficult cohort. Our institutional total joint registry was used to identify 119 primary THAs performed in 109 patients with an angular proximal femoral deformity between 1997 and 2017. The deformity was related to previous femoral osteotomy in 85%, and developmental or metabolic disorders in 15%. 53% had a predominantly varus angular deformity. The mean age was 44 years, mean BMI was 29 kg/m. 2. , and 59% were female. An uncemented metaphyseal fixation stem was used in 30%, an uncemented diaphyseal fixation stem in 28%, an uncemented modular body stem with metaphyseal fixation sleeve in 24%, and a cemented stem in 18%. Simultaneous corrective femoral osteotomy was performed in 18%. Kaplan-Meier survivorships and Harris hip scores were reported. Mean follow-up was 8 years. The 10-year survivorships free of femoral loosening, aseptic femoral revision, any revision, and any reoperation were 95%, 93%, 90% and 88%, respectively. Revisions occurred in 13 hips for: aseptic femoral component loosening (3), stem fracture (2), dislocation (2), aseptic acetabular loosening (2), polyethylene liner exchange (2), and infection (2). Preoperative varus angular deformities were associated with a higher risk of any revision (HR 10, p=0.03), and simultaneous osteotomies with a higher risk of any reoperation (HR 3.6, p=0.02). Mean Harris hip scores improved from 52 preoperatively to 82 at 10 years (p<0.001). In the largest series to date of primary THAs in patients with angular proximal femoral deformities, we found a good 10-year survivorship free from any revision. Varus angular deformities, particularly those treated with a simultaneous osteotomy due to the magnitude or location of the deformity, had a higher reoperation rate. Keywords: Proximal femoral deformity; dysplasia; femoral osteotomy; survivorship; revision. Level of evidence: Level III, comparative retrospective cohort

Aims. The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design. Methods. This was a retrospective review of 707 primary TKAs in 590 patients from a single institution, using a cementless, metal-backed patellar component with a mean follow-up of 6.9 years (2 to 12). A total of 409 TKAs were performed in 338 females and 298 TKAs in 252 males. The mean age of the patients was 63 years (34 to 87) and their mean BMI was 34.3 kg/m. 2. (18.8 to 64.5). The patients were chosen to undergo a cementless procedure based on age and preoperative radiological and intraoperative bone quality. Outcome was assessed using the Knee Society knee and function scores and range of motion (ROM), complications, and revisions. Results. A total of 24 TKAs (3.4%) in 24 patients failed and required revision surgery, of which five were due to patellar complications (0.71%): one for aseptic patellar loosening (0.14%) and four for polyethylene dissociation (0.57%). A total of 19 revisions (2.7%) were undertaken in 19 patients for indications which did not relate to the patella: four for aseptic tibial loosening (0.57%), one for aseptic femoral loosening (0.14%), nine for periprosthetic infection (1.3%), one for popliteus impingement (0.14%), and four for instability (0.57%). Knee Society knee and function scores, and ROM, improved significantly when comparing pre- and postoperative values. Survival of the metal-backed patellar component for all-cause failure was 97.5% (95% confidence interval 94.9% to 100%) at 12 years. Conclusion. The second-generation cementless TKA design of metal-backed patellar components showed a 97.5% survival at 12 years, with polyethylene dissociation from the metal-backing being the most common cause of patellar failure. In view of the increased use of TKA, especially in younger, more active, or obese patients, these findings are encouraging at mean follow-up of seven years. Cite this article: Bone Joint J 2023;105-B(12):1279–1285

We previously reported the five to ten-year results of the Birmingham Hip Resurfacing (BHR) implant. The purpose of this study was to evaluate the survivorship, radiographic results, and clinical outcomes of the BHR at long-term follow-up. We retrospectively reviewed 250 patients from the original cohort of 324 BHRs performed from 2006 to 2013 who met contemporary BHR indications. Of these, 4 patients died and 4 withdrew. From the 242 patients, 224 patients (93%) were available for analysis. Modified Harris hip score (mHHS) and University of California, Los Angeles (UCLA) scores were collected and compared to a matched total hip arthroplasty (THA) cohort. Mean follow-up was 14 years. Survivorship free of aseptic revision was 97.4% and survivorship free of any revision was 96.0% at 15 years. Revisions included 3 periprosthetic joint infections, 2 for elevated metal ions and symptomatic pseudotumor, 2 for aseptic femoral loosening, and 1 for unexplained pain. The mean mHHS was 93 in BHR patients at final follow-up, similar to the THA cohort (p=0.44). The UCLA score was significantly higher for BHR patients (p=0.02), however there were equal proportions of patients who remained highly active (UCLA 9 or 10) in both groups, 60.5% and 52.2% (p=0.45) for BHR and THA respectively. Metal ion levels at long term follow-up were low (mean serum cobalt 1.8±1.5 ppb and mean serum chromium 2.2±2.0 ppb). BHR demonstrated excellent survivorship in males less than 60 years of age at time of surgery. Clinical outcomes and activity levels were similar to THA patients. Failures related to the metal-on-metal bearing were rare and metal levels were low at long-term follow-up. Level of evidence: III. Keywords: survivorship; hip arthroplasty; activity; metal-on-metal. Surface Replacement Arthroplasty demonstrates low revision rates and similar activity level compared to total hip arthroplasty at long-term follow-up

Although data on uncemented short stems are available, studies on cemented short-stemmed THAs are limited. These cemented short stems may have inferior long-term outcomes and higher femoral component fracture rates. Hence, we examined the long-term follow-up of cemented short Exeter stems used in primary THA. Within the Exeter stem range, 7 stems have a stem length of 125 mm or less. These stems are often used in small patients, in young patients with a narrow femoral canal or patients with anatomical abnormalities. Based on our local database, we included 394 consecutive cemented stems used in primary THA (n=333 patients) with a stem length ≤125 mm implanted in our tertiary referral center between 1993 and December 2021. We used the Dutch Arthroplasty Registry (LROI) to complete and cross-check the data. Kaplan-Meier survival analyses were performed to determine 20-year survival rates with stem revision for any reason, for septic loosening, for aseptic loosening and for femoral component fracture as endpoints. The proportion of male patients was 21% (n=83). Median age at surgery was 42 years (interquartile range: 30–55). The main indication for primary THA was childhood hip diseases (51%). The 20-year stem survival rate of the short stem was 85.4% (95% CI: 73.9–92.0) for revision for any reason and 96.2% (95%CI: 90.5–98.5) for revision for septic loosening. No stems were revised for aseptic femoral loosening. However, there were 4 stem fractures at 6.6, 11.6, 16.5 and 18.2 years of follow-up. The stem survival with femoral component fracture as endpoint was 92.7% (CI: 78.5–97.6) at 20 years. Cemented short Exeter stems in primary THA show acceptable survival rates at long-term follow-up. Although femoral component fracture is a rare complication of a cemented short Exeter stem, orthopaedic surgeons should be aware of its incidence and possible risk factors

Aims. After failed acetabular fractures, total hip arthroplasty (THA) is a challenging procedure and considered the gold standard treatment. The complexity of the procedure depends on the fracture pattern and the initial fracture management. This study’s primary aim was to evaluate patient-reported outcome measures (PROMs) for patients who underwent delayed uncemented acetabular THA after acetabular fractures. The secondary aims were to assess the radiological outcome and the incidence of the associated complications in those patients. Methods. A total of 40 patients underwent cementless acetabular THA following failed treatment of acetabular fractures. The postoperative clinical and radiological outcomes were evaluated for all the cohort. Results. The median (interquartile range (IQR)) Oxford Hip Score (OHS) improved significantly from 9.5 (7 to 11.5), (95% confidence interval (CI) (8 to 10.6)) to 40 (39 to 44), (95% CI (40 to 43)) postoperatively at the latest follow-up (p < 0.001). It was worth noting that the initial acetabular fracture type (simple vs complex), previous acetabular treatment (ORIF vs conservative), fracture union, and restoration of anatomical centre of rotation (COR) did not affect the final OHS. The reconstructed centre of rotation (COR) was restored in 29 (72.5%) patients. The mean abduction angle in whom acetabular fractures were managed conservatively was statistically significantly higher than the surgically treated patients 42.6° (SD 7.4) vs 38° (SD 5.6)) (p = 0.032). We did not have any case of acetabular or femoral loosening at the time of the last follow-up. We had two patients with successful two-stage revision for infection with overall eight-year survival rate was 95.2% (95% CI 86.6% to 100%) with revision for any reason at a median (IQR) duration of follow-up 50 months (16 to 87) months following THA. Conclusion. Delayed cementless acetabular THA in patients with previous failed acetabular fracture treatments produces good clinical outcomes (PROMS) with excellent survivorship, despite the technically demanding nature of the procedure. The initial fracture treatment does not influence the outcome of delayed THA. In selected cases of acetabular fractures (either nondisplaced or with secondary congruency), the initial nonoperative treatment neither resulted in large acetabular defects nor required additional acetabular reconstruction at the time of THA. Cite this article: Bone Jt Open 2021;2(12):1067–1074

Aims. A significant reduction in wear at five and ten years was previously reported when comparing Durasul highly cross-linked polyethylene with nitrogen-sterilized Sulene polyethylene in total hip arthroplasty (THA). We investigated whether the improvement observed at the earlier follow-up continued, resulting in decreased osteolysis and revision surgery rates over the second decade. Methods. Between January 1999 and December 2001, 90 patients underwent surgery using the same acetabular and femoral components with a 28 mm metallic femoral head and either a Durasul or Sulene liner. A total of 66 hips of this prospective randomized study were available for a minimum follow-up of 20 years. The linear femoral head penetration rate was measured at six weeks, one year, and annually thereafter, using the Dorr method on digitized radiographs with a software package. Results. In the Durasul group, no patients underwent revision due to loosening or showed radiological evidence of osteolysis. In the Sulene group, four patients (four hips) were revised due to femoral component loosening. The 20-year cumulative failure incidence in the presence of the competing event of death for revision surgery was 4.5% (95% confidence interval (CI) 0.8 to 13.6) in the Durasul group, and 8.9% (95% CI 2.8 to 19.5) in the Sulene group. The mean wear one year after surgery was 0.09 mm (SD 0.007) in the Durasul group and 0.24 (SD 0.015) in the Sulene group (p < 0.001). From one to 20 years after surgery, the mean total penetration was 0.32 mm (SD 0.045) in the Durasul group and 1.07 mm (SD 0.13) in the Sulene group (p < 0.001). Mean femoral head penetration at 20 years was approximately 70.0% less in the Durasul group than the Sulene group. Conclusion. The significant reduction in femoral head penetration obtained with the Durasul compared with Sulene in uncemented THA resulted in lower osteolysis and revision rates after 20 years. Cite this article: Bone Joint J 2022;104-B(9):1032–1038

The increasing number of total hip arthroplasty (THA) used in young patients will inevitably lead to more revision procedures at younger ages, especially since the outcome of primary THA in young patients is already inferior compared to older patients. However, these data are lacking in literature. The aim of this study was to determine the survival of both acetabular and femoral components placed during primary and revision hip arthroplasty in patients under 55 years using Dutch Arthroplasty Register (LROI) data. All primary THA registered in the LROI between 2007–2018 in patients under 55 years were selected (n=25,682). Subsequent cup- and stem revision procedures were included. Kaplan-Meier survival analyses were used to estimate the survival probability of primary and revised cup- and stem components. Mean follow-up of primary cups and stems was 5.8 years (SD 3.2) and 5.9 years (SD 3.2), respectively. In total, 659 cup revision procedures and 532 stem revision procedures were registered. Most common reason for cup revision was acetabular loosening (n=163), most common reason for stem revision was femoral loosening (n=202). Primary cup survival for any reason at 10 years follow-up was 96.1% (95%CI: 95.7–96.4). For primary stems, 10 year survival for any reason was 97.1% (95%CI: 96.7–97.3). Mean follow-up of all revision procedures was 4.1 years (SD 2.9). Out of 659 cup revisions, 113 cup re-revisions were registered. Survival of revised cups, with end-point cup re-revision for any reason was 82.2% (95%CI: 78.8–85.1) at 5 years follow-up. Out of 532 stem revisions, 89 stem re-revisions were registered. For revised stems, survival at 5 year follow-up, with endpoint stem re-revision for any reason was 82.0% (95%CI: 78.2–85.2). The outcome of revised acetabular and femoral components is worrisome, with a survival of 82% at 5 years follow-up. This information is valuable to provide realistic expectations for these young patients at time of primary THA

Hip resurfacing arthroplasty (HRA) is being offered as a viable alternative to total hip arthroplasty (THA). For very young patients (under 30 years old), THA achieves fair results but with high revision and complication rates. This retrospective study was designed to evaluate the results of HRA performed in patients under 30 years old with a long follow-up. During the inclusion period (2007–2021), we collected in a single operator database, all HRA performed in patients under 30 with a minimum follow up of 2 years. 103 HRA in 93 patients (77 male / 16 females; a mean age at operation 27.7 years (18 to 29.9)) were included. The two mean preoperative diagnoses were osteoarthritis in 54 HRA (52.5%) and DDH or hip dislocation in 19.4% (20 cases). No patient was lost to follow-up and 3 patients (5 HRA) deceased. There were 2 revisions (one for femoral aseptic loosening and one infection recurrence (pediatric osteoarthritis)). No dislocation and adverse wear-related failures were found. At a mean follow-up of 10.4 years (2–17.4), mean UCLA activity and Oxford Hip score improved respectively from 5.4 (1 to 7) and 39.9 (25–55) pre-operatively to 7.9 (3 to 10) and 15.8 (12–34) post-operatively (p<0.001). Mean Harris hip score increased from 41.6 (22–63) to 91.8 (72–100) (p<0.001). There were no radiological cases exhibiting lysis while two cases displayed limited partial radiolucency around the femoral stem. Kaplan-Meier survival analysis, with the endpoint revision for any reason, showed a 10.8-year survival rate of 98% (95% expected with NICE guidelines). This cohort of HRA performed under 30 is the longest follow-up ever reported in the literature. Despite a challenging cohort of patients, HRA exceeds the stricter NICE survivorship criteria. HRA remains an effective treatment with excellent functional outcomes and a very low rate of complications

Introduction. The Opera acetabular component (Smith & Nephew Ltd) shares many same design features with the Ogee (Depuy Int.). Differences are a malleable flange, instrumentation designed to improve cement pressurisation and the specifics of the UHMW-poly used. Methods. Data was collected prospectively on 419 consecutive replacements (390 patients), performed between March 2000 and February 2005. A posterior approach was used, and the acetabulum was prepared with multiple key holes. Palacos-R bone cement containing Gentamicin was used with a cement pressuriser. Results. There were 243 Operas (221 patients) and 176 Ogees (169 patients). There were 262 in female patients (62.5%) and age at surgery averaged 68.3yrs (25–92). Average follow-up of surviving patients was 185 months (165 – 225). Acetabular abduction angle in both groups averaged 46° (25–65). Opera group: 27 (11.1%) acetabular components loosened aseptically, all associated with rapid wear. 16 (6.6%) acetabular components were revised (15 (6.2%) - aseptic loosening and 1 late infection. At 10 years 85% were graded Hodgkinson 0 or 1. Six femoral implants loosened (2.5%), 2 of which have been revised. Ogee group: 3 acetabular components (1.7%) were revised (2 - aseptic loosening (1.1%) and 1 for recurrent dislocation). None are currently loose. At 10 years 99% were graded Hodgkinson 0 or 1. There was no femoral loosening. Conclusions. In the Opera group aseptic acetabular loosening (11.1% v 1.1%), acetabular revision for aseptic loosening (6.2 v 1.1%), aseptic femoral loosening (2.5% v 0) and Hodgkinson grading > 1 at 10 years (15% v 1%) were more common and associated with rapid wear. This must be attributable to poorer wear properties of the UHMW-poly of the Opera implant and patients with these components require regular surveillance to detect loosening

Aims. Adult patients with history of childhood infection pose a surgical challenge for total hip arthroplasty (THA) due to distorted bony anatomy, soft-tissue contractures, risk of reinfection, and relatively younger age. Therefore, the purpose of the present study was to determine clinical outcome, reinfection rate, and complications in patients with septic sequelae after THA. Methods. A retrospective analysis was conducted of 91 cementless THAs (57 male and 34 female) performed between 2008 and 2017 in patients who had history of hip infection during childhood. Clinical outcome was measured using Harris Hip Score (HHS) and Modified Merle d’Aubigne and Postel (MAP) score, and quality of life (QOL) using 12-Item Short Form Health Survey Questionnaire (SF-12) components: Physical Component Score (PCS) and Mental Component Score (MCS); limb length discrepancy (LLD) and radiological assessment of the prosthesis was performed at the latest follow-up. Reinfection and revision surgery after THA for any reason was documented. Results. There was significant improvement in HHS, Modified Merle d’Aubigne Postel hip score, and QOL index SF 12-PCS and MCS (p < 0.001) and there was no case of reinfection reported during the follow-up. The minimum follow-up for the study was three years with a mean of 6.5 (SD 2.3; 3 to 12). LLD decreased from a mean of 3.3 cm (SD 1) to 0.9 cm (SD 0.8) during follow-up. One patient required revision surgery for femoral component loosening. Kaplan-Meier survival analysis estimated revision-free survivorship of 100% at the end of five years and 96.9% (95% confidence interval 79.8 to 99.6) at the end of ten years. Conclusion. We found that cementless THA results in good to excellent functional outcomes in patients with a prior history of childhood infection. There is an exceedingly low rate of risk of reinfection in these patients, even though complications are not uncommon. Cite this article: Bone Jt Open 2022;3(4):314–320

Aims. We present the results, in terms of survival, clinical outcome, and radiological appearance at 20 years, in a cohort of 225 cemented Exeter Universal femoral components (Stryker, Newbury, UK) implanted in 207 patients, at a district general hospital. Methods. All patients in this study had a total hip arthroplasty (THA) using an Exeter Universal femoral component with a cemented (n = 215) or cementless (n = 10) acetabular component. Clinical and radiological data were collected prospectively at one year, five years, and every five years thereafter. Patients lost to radiological and clinical follow-up (five) were cross-referenced with National Joint Registry (NJR) data and general practitioner (GP) records to assess whether they had undergone revision for any reason. Results. During this period of study 144 patients (157 hips) died (69.78%). Two patients were lost to follow-up, leaving 61 patients (66 hips) available for review (29.33%). Of the 225 hips, three underwent revision for femoral failure with osteolysis. One underwent femoral component revision for treatment of a periprosthetic fracture. Eight underwent revision of the acetabular component only for loosening. Two hips had both components revised, when components were found to be loose at time of revision for acetabular loosening, though no radiological femoral osteolysis. Two patients underwent revision for infection. Using femoral loosening as an endpoint, the survival of the Exeter Universal femoral component was 98.7% (n = 220, 95% confidence interval (CI) 96.1% to 100%) at 20 to 22 years. Survival with an endpoint of revision for any reason was 92.6% (n = 209, 95% CI 89.4 to 95.55), with a ‘worst-case scenario’ (considering two patients lost to follow-up to have failed), the overall survival rate was 91.7% (n = 207, 95% CI 87.8 to 95.9) at 20 to 22 years. Conclusion. Our results confirm excellent long-term results for the cemented Exeter Universal femoral componentimplanted outside of the originating centre. Cite this article: Bone Joint J 2020;102-B(10):1319–1323

Aims. Adverse spinal motion or balance (spine mobility) and adverse pelvic mobility, in combination, are often referred to as adverse spinopelvic mobility (SPM). A stiff lumbar spine, large posterior standing pelvic tilt, and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Adverse SPM can create functional malposition of the acetabular components and hence is an instability risk. Adverse pelvic mobility is often, but not always, associated with abnormal spinal motion parameters. Dislocation rates for dual-mobility articulations (DMAs) have been reported to be between 0% and 1.1%. The aim of this study was to determine the early survivorship from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a DMA. Methods. A multicentre study was performed using data from 227 patients undergoing primary total hip arthroplasty (THA), enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameter had a DMA inserted at the time of their surgery. The mean age was 76 years (22 to 93) and 63% were female (n = 145). At a mean of 14 months (5 to 31) postoperatively, the AOANJRR was analyzed for follow-up information. Reasons for revision and types of revision were identified. Results. The AOANJRR reported two revisions: one due to infection, and the second due to femoral component loosening. No revisions for dislocation were reported. One patient died with the prosthesis in situ. Kaplan-Meier survival rate was 99.1% (95% confidence interval 98.3 to 100) at 14 months (number at risk 104). Conclusion. In our cohort of patients undergoing primary THA with one or more factor associated with adverse SPM, DM bearings conferred stability at two years’ follow-up. Cite this article: Bone Joint J 2022;104-B(7):820–825

Fifty-six hips, mean age 40.4 underwent surface arthroplasty (SA) and twenty-eight hips, mean age 37.2 underwent hemiresurfacing (HSR). Diagnosis was osteo-necrosis in all. UCLA hip function and activity score, SF-12 physical, and Harris Hip score were significantly (p< 0.05) better for SA versus HSR. However, 2 SA were revised to THR, and 5 had evidence of femoral loosening. There was no evidence of femoral loosenings in the hemiresurfacing group. The median femoral component size was significantly larger in HSR than SA. Although the functional results are inferior with HSR, patients are at greater risk of femoral loosening with the full surface arthroplasty. To determine if differences in outcome exist between HSR and MMSA at five years of follow-up in a group of patients with Ficat Stage III and IV osteonecrosis. Treatment of osteonecrosis of the hip in the young adult still remains a challenge. The continued use of conservative prosthetic solutions should help minimize the morbidity of revision hip surgery. Although the functional clinical outcome of MMSA is superior to HSR, patients are at greater risk of femoral loosening. Use of a larger femoral component in MMSA may decrease the risk of femoral loosening. Eighty-four hips with osteonecrosis were treated with a resurfacing implant: fifty-six with a metal-metal SA, mean age 40.4 and twenty-eight, mean age 37.2 with a hemiresurfacing when the acetabular cartilage was minimally damaged. Male/female ratio was 73%/27% for HSR and 87%/13% for MMSA. Mean follow-up of 4.5 years, UCLA hip scores were significantly (p< 0.05) better for MMSA versus HSR for function (9.3 vs. 7.9) and activity (6.8 vs. 5.5) but not for pain (9.3 vs.8.6) and walking (9.5 vs. 9.0). SF-12 scores were comparable for the mental component but significantly better in the MMSA group (48.4 vs. 38.1, p= 0.001) for the physical component. Harris Hip Score was significantly better for MMSA (92.3 vs. 83.3, p=0.001). 2 MMSA were revised to THR, and five presented with evidence of femoral loosening. There was no evidence of femoral loosenings in HSR. Median femoral component size was significantly larger for HSR (50.0 vs. 46.0, p= 0.001)

Introduction. High-flexion knee implants have been developed to accommodate a large range of motion (ROM > 120°) after total knee arthroplasty (TKA). In a recent follow-up study, Han et al. [1] reported a disturbingly high incidence of femoral loosening for high-flexion TKA. The femoral component loosened particularly at the implant-cement interface. Highly flexed knee implants may be more sensitive to femoral loosening as the knee load is high during deep knee flexion [2], which may result in increased tensile and/or shear stresses at the femoral implant fixation. The objective of this study was to analyse the load-transfer mechanism at the femoral implant-cement interface during deep knee flexion (ROM = 155°). For this purpose, a three-dimensional finite element (FE) knee model was developed including high-flexion TKA components. Zero-thickness cohesive elements were used to model the femoral implant-cement interface. The research questions addressed in this study were whether high-flexion leads to an increased tensile and/or shear stress at the femoral implant-cement interface and whether this would lead to an increased risk of femoral loosening. Materials & methods. The FE knee model utilized in this study has been described previously [3] and consisted of a proximal tibia and fibula, TKA components, a quadriceps and patella tendon and a non-resurfaced patella. For use in this study, the distal femur was integrated in the FE model including cohesive interface elements and a 1 mm bone cement layer. High-flexion TKA components of the posterior-stabilised PFC Sigma RP-F (DePuy, J&J, USA) were incorporated in the FE knee model following the surgical procedure provided by the manufacturer. A full weight-bearing squatting cycle was simulated (ROM = 50°-155°). The interface stresses calculated by the FE knee model were decomposed into tension, compression and shear components. The strength of the femoral implant-cement interface was determined experimentally using interface specimens to predict whether a local interface stress-state calculated by the FE knee model would lead to interface debonding. Results. During deep knee flexion, tensile stress concentrations were found at the femoral implant-cement interface particularly beneath the anterior flange. Shear stress concentrations were observed at the interface beneath the anterior flange and the posterior femoral condyles. The peak tensile interface stress increased from 1.6 MPa at 120° of flexion to 5.5 MPa during deep knee flexion at the interface beneath the anterior flange. The peak shear stress was even higher at this interface location and increased from 4.1 MPa at 120° of flexion to 11.0 MPa at maximal flexion (155°). Based on the interface strength experiments, 5.8% of the interface beneath the anterior flange was predicted to debond at 120° of flexion, which increased to 10.8% during deep knee flexion. Discussion. Obviously, the FE knee model utilized in this study contains limitations which may have affected the interface stresses calculated. However, the results presented here clearly demonstrate increasing tensile and shear stresses in substantial parts of the femoral implant-cement beneath the anterior flange during deep knee flexion. Based on the interface strength experiments the anterior interfacial stress-state calculated by the FE knee model leads to local interface debonding during deep knee flexion, which increases the risk of femoral loosening. Proper anterior fixation of the femoral component is essential to reduce the risk of femoral loosening for high-flexion TKA

Introduction. The BIRMINGHAM HIP. ◊. Resurfacing is a metal-on-metal (MOM) hip implant system approved by the US FDA in 2006. The approval required a multicenter, prospective, post-approval study (PAS). Our purpose is to report the current minimum 10-year results. Methods. 253 patients (280 hips) had surgery between October 2006 and December 2009 at one of 5 sites. We report revisions, survivorship, EQ-5D, Harris Hip Score (HHS), radiographic findings, and metal levels including cobalt (Co) and chromium (Cr). The mean age at surgery was 51 years, 74% male, BMI 28, osteoarthritis 95%. 243 (87%) of hips have known outcome or 10-year minimum follow-up (fup). Prior to 10 years, 5 patients died, 20 hips were revised, and 37 hips did not complete 10-year fup. Results. The 10-year component survivorship is 92.9% (95% CI 89.8–96.1%). The reasons for revision were femoral neck fracture (3), femoral loosening (5), acetabular loosening (1), pseudotumor (3), osteolysis (2) and the remaining 6 for a combination of pain, noise, or metal levels. The EQ-QAL VAS improved (mean preop: 70, 1-year: 89, p<0.001) and was stable through 10 years (87, p=0.05). The HHS improved (mean preop: 57, 1-year: 96, p<0.001) and remained stable through 10 years (96, p=0.93). Radiographically, no surviving components have migrated. 4.6% (10/218) have osteolysis. The Co and Cr levels increased at 1 year (median Co preop: 0.12 ppb, 1-year: 1.5 ppb, p<0.001; Cr preop: 0.60 ppb, 1-year: 1.70 ppb, p<0.001) and remained stable through 10 years (Co 10-year: 1.29 ppb, p=0.28; Cr 10-year: 1.36 ppb, p=0.88). The number of patients with a Co or Cr >7 ppb at one and 10 years remained similar (1-year: 3.4% (7/205), 10-year: 4.4%, (9/205), p=0.61). Conclusion. This prospective, multicenter PAS demonstrated this resurfacing is safe and durable. 10-year survivorship for males less than 55 years old is 98.3% (95% CI 95.9–100%)

Total hip joint replacement (THJR) for high riding congenital hip dislocation (CDH) is often performed in young patients, and presents unique problems with acetabular cup placement and leg length inequality. A database and the NZ Joint Registry were used to identify 76 hips in 57 patients with a diagnosis of CDH who underwent THJR in the Wellington region between 1994 and 2015. Records and radiographs of 46 hips in 36 patients classified pre-operatively as Crowe II, III or IV were reviewed. Surgical technique used a direct lateral approach, the uncemented acetabular component was located in the anatomic hip center and a primary femoral stem was used in all but one hip. Whether a step-cut sub-trochanteric femoral osteotomy was performed depended on degree of correction, tension on the sciatic nerve, and restoration of leg length. For the 36 patients classified as Crowe II or higher, the average age at operation was 44 years (26 – 66), female:male ratio was 4.5:1 and follow-up averaged 10 years (2 – 22.3). Of the 15 hips classified as Crowe IV, 10 required a step-cut sub-trochanteric femoral osteotomy to shorten the femur, but 5 were lengthened without undo tension on the sciatic nerve. Nine Crowe IV hips received a conventional proximally coated tapered primary femoral component. Oxford hip scores for 76% of patients was excellent (> 41/48), and 24% had good scores (34 – 41). All femoral osteotomies healed. Five hips have been revised, one at 2 years for femoral loosening, one at 5 years for dislocation, two at 12 years for liner exchanges, and one at 21 years for femoral loosening. THJR using primary prostheses for CDH can provide durable long-term results