Aims. Hip dysplasia (HD) leads to premature osteoarthritis. Timely detection and correction of HD has been shown to improve pain, functional status, and hip longevity. Several time-consuming radiological measurements are currently used to confirm HD. An artificial intelligence (AI) software named HIPPO automatically locates anatomical landmarks on anteroposterior pelvis radiographs and performs the needed measurements. The primary aim of this study was to assess the reliability of this tool as compared to multi-reader evaluation in clinically proven cases of adult HD. The secondary aims were to assess the time savings achieved and evaluate inter-reader assessment. Methods. A consecutive preoperative sample of 130 HD patients (256 hips) was used. This cohort included 82.3% females (n = 107) and 17.7% males (n = 23) with median patient age of 28.6 years (interquartile range (IQR) 22.5 to 37.2). Three trained readers’ measurements were compared to AI outputs of lateral centre-edge angle (LCEA), caput-collum-diaphyseal (CCD) angle, pelvic obliquity, Tönnis angle, Sharp’s angle, and femoral head coverage. Intraclass correlation coefficients (ICC) and Bland-Altman analyses were obtained. Results. Among 256 hips with AI outputs, all six hip AI measurements were successfully obtained. The AI-reader correlations were generally good (ICC 0.60 to 0.74) to excellent (ICC > 0.75). There was lower agreement for CCD angle measurement. Most widely used measurements for HD diagnosis (LCEA and Tönnis angle) demonstrated good to excellent inter-method reliability (ICC 0.71 to 0.86 and 0.82 to 0.90, respectively). The median reading time for the three readers and AI was 212 (IQR 197 to 230), 131 (IQR 126 to 147), 734 (IQR 690 to 786), and 41 (IQR 38 to 44) seconds, respectively. Conclusion. This study showed that AI-based software demonstrated reliable radiological assessment of patients with HD with significant interpretation-related time savings. Cite this article: Bone Jt Open 2022;3(11):877–884

Background

Migration analysis after total joint arthroplasty are performed using EBRA analysis (Krismer et al., 1997) or - more accurate but also much more cost-intensive and time-consuming – via radiostereometric analysis (RSA). For the latter, additional radiographs from two inclined perspectives are needed in regular intervals in order to define the position of the implant relative to tantalum bone markers which have been implanted during surgery of the artificial joint (Fig. 1). Modern analysis software promises a migration precision along the stem axis of a hip implant of less than 100 μm (Witvoet-Brahm et al., 2007). However, as the analysis is performed semi-automatically, the results are still dependent on the subjective evaluation of the X-rays by the observer. Thus, the present phantom study aims at evaluating the inter- and intra-observer reliability, the repeatability as well as the precision and gives insight into the potential and limits of the RSA method.

Objective: Establishment of the new method to evaluate fill of the hip stem.

Background: The fill of the hip stem is one of the important parameters to estimate the quality of planning or positioning of the cementless stem. It has been defined as a stem-canal width ratio on the A-P plain of X-ray images so far. However, it is quite a problem to get the correct AP images on basis so that positional difference may affect the measurement. According to our data, the fill was measured significantly different in 15, 30, 45, 60 degrees erroneous direction. First, we tried to figure out the fill of the hip stem three-dimensionally rather 2-dimensionally. Next, our new method was compared to conventional method.

Material and Methods: Leg CAT scans were performed on 32 hips of 20 patients (2 male, 18 female). Images of the canal of femora were reconstructed using CAD software. We made 2-types of canal model with or without lesser trochanter. The geometries of our lateral flare stems with different sizes were compared to each canal geometry in the CAD software and proper size was decided. Then images were observed from an accurate vertical direction of the coronal plain of the stem. We measured the 2-D fill on this plane and the 3-D fill of every 5 mm slice from the 5mm above to the 100mm below the head of lesser trochanter line (reference line). We also examined the stems 1-size smaller or larger than the appropriate ones.

Results: The mean age was 61.114 (range 24–82). The average of “3-D fill of Lateral flare stem was 51%/59% with/without lesser trochanter, and 2-D one was 74%/77%. The numerical and distributional results by these two methods to measure fill were alike but different. For example, in case without lesser trochanter, the 3-D fill showed the maximum value in the area just below the reference line. The maximum 2-D fill was recorded in 10mm caudal from the reference line. In general, this stem occupied much space in the distal area and around the lesser trochanter.

Future Plan: Extension of this evaluation method into various kinds of stems.

Purpose. Implant positioning is one of the critical factors influencing the postoperative outcome in total hip arthroplasty (THA). Conventional (manual) intraoperative stem adjustment may result in variability and inaccuracy of stem antetorsion (AT). Since March 2013, we have measured stem antetorsion with CT free Navigation system (OrthoPilot Navigation System THA Pro Ver4.2, B/Braun Aesculap Germany: Navi). We have developed a simple instrument, the Gravity-guide (G-guide), for intraoperative assessment and adjustment of stem AT. We evaluated the accuracy and effectiveness of G-guide and navigation software as referenced to postoperative CT evaluation with 3D template system (Zed hip, LEXI, Japan). Method. Between March 2013 and December 2014, 50 patients underwent primary THA were evaluated. Surgeries were performed with routine techniques with a modified Hardinge approach with the patient at a lateral decubitus position in all cases. The G-guide consists of two parts: one attached to the lower leg and the other attached to the handle of the rasp. During surgery, AT value was determined with navigation at the time of final rasping of the femur. Additionally, the G-guide was utilised at the time of final rasp insertion. In intraoperative AT assessment using this instrument, a correction was required considering the discrepancy between the perpendicular to the posterior condylar axis and the longitudinal axis of the lower leg. The angle of discrepancy between posterior condylar line and femoral trans-epicondyler axis needs to be taken into consideration. Therefore, correction by the angle between the trans-epicondylar and posterior condylar lines (correction angle) was required for each patient when the intraoperative AT as measured by the G-guide. Therefore, the correction angle should be added to the AT value obtained from the G-guide for comparison with postoperative value measured with Zed Hip. Result. The discrepancy between the intraoperative G-guide with correction angle and postoperative Zed Hip measurements was 4.7° ± 3.9°. The discrepancy between Navi AT and postoperative Zed HIP measurements was 5.9° ± 4.1°. A discrepancy was 10° or more were 7 cases in Navi and 4 cases in G-guide. Conclusion. Navi and G-guide measured intraoperative stem antetorsion was comparable utility

Aims

Developmental dysplasia of the hip (DDH) describes a pathological relationship between the femoral head and acetabulum. Periacetabular osteotomy (PAO) may be used to treat this condition. The aim of this study was to evaluate the results of PAO in adolescents and adults with persistent DDH.

The use of hip resurfacing arthroplasty (HRA) has largely regressed due to the fear of metal-on-metal bearings. However committed HRA users continue to assert the functional advantages that a geometry retaining implant would have on a patient”s hip. Currently worldwide, HRA is only recommended to men who demand an active lifestyle. Despite this precarious indication, it is not clear to what extent HRA has on higher activity function. The aim of this study was to determine the functional extent to which could be achieved with HRA. The primary objective is to assess the loading pattern change for patients implanted with HRA at high walking speeds and inclinations. The second objective is to compare their loading features to a healthy group to determine if a normal gait pattern could be achieved. Between 2012 and 2016, a total of 28 prospective unilateral HRA patients were analysed on an instrumented treadmill from a single centre. All 28 patient patients had a uniform implant type and had no other lower limb operations or disease. Perioperative plain orthogonal radiographs were used to measure hip length and global hip offset change. A healthy control group (n=35) were analysed to compare. All HRA patients gait characteristics were assessed at incrementally higher speeds and inclinations to determine the extent of improvement HRA has on a challenging activity. A Student t-test along with a multivariate analysis was done with significance set at α=0.05. Weight and height variance was accounted with Hof normalisation. The HRA and control group were reasonably matched for age (57 vs 55yrs), BMI (27 vs 25) and height (175 vs 170cm) respectively. Hip measurements revealed less than 5mm change for all cases. The mean time from initial preoperative gait assessment to postoperative assessment was 30 months (24–48months). The mean top walking speed for controls was 1.97m/s and postoperatively 2.1 m/sec for the HRA group. The significant (p<0.001) loading change during flat walking can be seen with restoration of symmetry. Walking at an inclination demonstrated a marked change during weight acceptance (p<0.001) and a loading pattern returning to near normal. This prospective study found HRA patients walking faster than age matched controls. They demonstrated a significant change in their loading pattern, by significantly shifting load from the unaffected side to the implanted side. Uphill walking, an activity which requires more hip flexion, demonstrated a change in stance phase which was near normal. This small comparative study confirms near physiological function can be achieved with HRA at higher activity levels

Background. Since 2011, the knee service at the Nuffield Orthopaedic Centre has been offering a neutralising medial opening wedge high tibial osteotomy (HTO) to a group of patients presenting with early medial osteoarthritis of the knee, varus alignment and symptoms for more than 2 years. During development of this practice an association was observed between this phenotype of osteoarthritis and the presence of CAM deformity at the hip. Methods. A retrospective cohort study. All patients who underwent HTO since 2011 were identified (n=30). Comparator groups were used in order to establish whether meaningful observations were being made: Control group: The spouses of a high-risk osteoarthritis cohort recruited for a different study at our unit (n=20) Pre-arthroplasty group: Patients who have undergone uni-compartmental arthroplasty (UKA) for antero-medial osteoarthritis (n=20)All patients had standing bilateral full-length radiographs available for analysis using in house developed Matlab-based software for hip measurements and MediCAD for lower limb alignment measurements. Results. A total of 140 limbs from 70 gender-matched subjects were studied. The HTO group had a significantly higher prevalence of CAM lesions defined by an Alpha angle >650. They also had a significantly greater mean alpha angle than both the pre-arthroplasty and control groups [HTO (Avg. 68.3 (±16.1)) vs Pre-arthroplasty (Avg. 59.5 (±15.5)) P=0.01; HTO vs Control (Avg. 58.2 (±13.9)) P=0.007]. Conclusions. The results of this study confirm that our HTO group have a significantly greater prevalence of CAM lesions. A feature not seen in either pre-arthroplasty or control subjects. This group demonstrate independent predictors for progression of OA in both the hip and the knee. To our knowledge this is a novel observation. Level of evidence. Observational cohort study (III)

Summary. Anatomical variations in hip joint anatomy are associated with both the presence and location of tibiofemoral osteoarthritis (OA). Introduction. Variations in hip joint anatomy can alter the moment-generating capacity of the hip abductor muscles, possibly leading to changes in the magnitude and direction of ground reaction force and altered loading at the knee. Through analysis of full-limb anteroposterior radiographs, this study explored the hypothesis that knees with lateral and medial knee OA demonstrate hip geometry that differs from that of control knees without OA. Patients and Methods. This cross-sectional study is an ancillary to the Multicenter Osteoarthritis Study (MOST), an observational cohort study of incident and progressive knee OA in community-dwelling men and women, ages 50–79 years. We report on 160 knees with lateral OA (LOA), 168 knees with medial OA (MOA), and 336 controls. All participants with LOA at the baseline MOST visit were included. An equal number of knees with MOA, and twice the number of control knees were then randomly selected. In participants with bilateral eligibility, a single knee was randomly selected so that all participants contributed only one case or one control knee to the analysis. Case knees were identified as having Kellgren/Lawrence (K/L) ≥ 2 with joint space narrowing (JSN) ≥ 1 in the specified compartment with no JSN in the adjoining compartment. Controls had no radiographic OA (K/L=0 or 1 and JSN=0) in either compartment. Hip joint anatomy parameters were assessed from full-limb standing radiographs using custom OsiriX software by an author (AB) blinded to knee OA status, and unreadable radiographs (N = 8) were discarded prior to unblinding. We measured parameters that influence the abductor moment arm of the hip, including: abductor lever arm, femoral offset, femoral neck length, femoral neck-shaft angle, height of hip centre, body weight lever arm, acetabular version, and abductor angle. All hip measurements were taken from the ipsilateral side of the knee in interest. Each variable was then compared independently among the three groups via analysis of covariance (ANCOVA), controlling for age, sex, and body mass index (BMI), and followed up with a post-hoc Bonferroni analysis to distinguish pairwise group differences. Results. The ANCOVA analysis showed a significant difference in height of hip centre (p=0.001), femoral neck-shaft angle (p=0.009), and abductor angle (p=0.001). Compared to controls, knees with LOA had an increased height of hip centre (p=0.001) and knees with MOA had a decreased abductor angle (p=0.046). Compared to knees with MOA, those with LOA had a more valgus neck-shaft angle (p=0.007) and increased abductor angle (p=0.001). Conclusion. Our study demonstrates that variations in hip geometry that affect the moment-generating capacity of the hip abductors are associated with the presence and compartmental distribution of tibiofemoral OA in the ipsilateral knee. Anatomical arrangements that reduce the hip abductor moment arm are more strongly associated with LOA than with MOA

Aims

To develop a core outcome set of measurements from postoperative radiographs that can be used to assess technical skill in performing dynamic hip screw (DHS) and hemiarthroplasty, and to validate these against Van der Vleuten’s criteria for effective assessment.

In perfroming hip resurfacing arthroplasty, concern has been expressed as to the proximity of the femoral neurovascular bundle during the anterior capsulotomy and the risk of damage during this maneuver. We therefore aimed to identify the proximity of the femoral nerve, artery and vein during an anterior capsulotomy done during a hip resurfacing procedure using the posterior approach. A standard posterior approach was performed in 5 fresh frozen cadavic limbs. An anterior incision was then used to measure the distance of the femoral neurovascular structures to the anterior capsule. Measurements from the most posterior aspect of the vessels and nerves to the most anterior aspect of the anterior capsule were taken prior to hip dislocation. The femoral head was then dislocated, and measurements were made with the hip in both flexion and extension. In a separate group of eleven patients that underwent routine MR imaging of the hip, measurements were taken to assess the proximity of the anterior joint capsule to the femoral neurovascular bundle, by a specialist musculoskeletal radiologist who had no prior knowledge of the results obtained during the cadaveric dissection. All 5 cadaveric limbs were utilised. 3 were male and 2 were female. The average age was 72.4 years (range 56–84). The patients whom underwent routine MR imaging incorporated 6 males and 5 females with a mean age of 43.7 years (age range 18–64 years). There was no significant difference between the mean distances to the nerve (p=0.21), artery (p=0.21) or vein (p=0.65) between the MR and cadaveric groups. Prior to dislocation the femoral artery and vein were closest to the anterior capsule (mean distance of 21mm) and the femoral nerve was the furthest away (mean distance 25mm). Following dislocation there was a significant increase (25mm to 31mm) in mean distance to the femoral nerve when the superior capsule was cut with the hip in a flexed position (p=0.01) and to the femoral artery in flexion (increase mean distance from 21mm to 35mm) (p< 0.0001) and in extension(increase mean distance from 21mm to 31mm) (p=0.005). When the inferior capsule was cut, there was a significant increase (25mm to 31mm) in mean distance to the femoral nerve and femoral artery when the hip was dislocated and the capsule cut with the hip in flexion (increase mean distance from 21mm to 27mm) (p=0.019) and in extension(increase mean distance from 21mm to 28mm) (p=0.015). This study suggests that the neurovascular structures are relatively well protected during an anterior capsulotomy performed during hip resurfacing. The procedure may be safer if the capsulotomy is performed with the hip dislocated and the hip in a flexed position while cutting the antero-superior aspect and in an extended position while cutting the antero-inferior aspect

In this paper operations are discussed that improve the dysplastic acetabular roof in developmental dislocation of the hip (DDH) of children up to 10 years. In the first year of life acetabular dysplasia can be treated successfully by flexion-abduction splints and plaster casts in „human position“. From the second year on, only slight dysplasias can heal spontaneously or be treated conservatively. Then the steep acetabular roof has to be osteotomized and levered down to a normal angle and coverage to avoid redislocation or residual dysplasia. Different procedures have been described in the course of time. Two osteotomies are chiseling in the anterior to posterior direction. Salters innominate osteotomy levers the whole acetabulum with the lower part of the pelvis in an anterolateral direction around an axis passing through the pubic symphysis and the posterior part of the osteotomy. In Pembertons osteotomy the hinge for turning down the acetabular roof is the last, posterior, transverse cortical segment over the tri-radiate cartilage, short before the sciatic notch. Osteotomies chiseling from lateral in medial direction have been described already by Albee (1915) and Jones (1920). Lance (1925) propagated this technique in Europe. Here the acetabular roof is partially osteotomized in a thickness of 5–7 mm. Only the lateral part of the acetabulum is brought into the horizontal position. Wiberg in 1939 used this technique, but in 1953 he was the first to publish a full osteotomy what Dega called 1973 a transiliac osteotomy. Dega had originally learned the technique of Lance, but in 1963 when he reduced high dislocations after the technique of Colonna, he performed also a full transiliac osteotomy. After the Symposium of Chapchal in Basel 1965 we started in Berlin also with the complete acetabular osteotomy. With the control of an image intensifier the blade of the osteotome is driven toward the posterior rim of the tri-radiate cartilage leaving only a small bony rim above. Anteriorly the blade passes through the ant. inf. iliac spine. Posteriorly it just enters the sciatic notch. Here we check the blade position by direct palpation. The acetabulum is bent down partly in the small rim of bone left and mainly in the triradiate cartilage. Angles up to 50° have been achieved, which you cannot reach by other techniques. In the beginning we have combined after Mittelmeier and Witt this acetabuloplasty with a varus osteotomy of the femur. In our long-time follow-up (Brüning et al. 1988,1990) however, we found in almost 50% a subcapital coxa valga or a so-called head-in-neck-position of the femoral head. Then we avoided varusosteotomies and had good results without it (Pothmann). To keep the acetabular roof in the new position we used first bone wedges from the varus osteotomy, then deproteinized bone wedges from animals, and today deep frozen wedges of human femoral heads of the bone bank, sterilized at 121 degrees C for 20 min. (Ekkernkamp, Katthagen). A firm layer of cortical bone laterally is necessary. Reinvestigations have proven the stability of this material too ( Pothmann). This type of acetabular osteotomy in our and other authors opinion is the best. Salters osteotomy is not as efficient in severe dysplasia. And in older children it produces a decrease in anteversion of the acetabulum, which may limit internal rotation of the hip and cause osteoarthritis if it does not improve. In Pembertons osteotomy one cannot use the image intensifier, which is of great help to perform the osteotomy exactly and also the levering of the acetabulum to the optimal coverage. Our first long-time follow-up of children with additional varus-osteotomies (Brüning et al.) reviewed 90 hip joints in 67 children. The age at operation was in average 3.6 years, the age at follow-up 15 years. Clinical results. 98% of the patients had no pain or only occasional, no limitation of movement and normal or almost normal gait. The Trendelenburg sign was negative in 71% of the cases, grade 1 in 15.5% and grade 3 in 13.5%. Radiological evaluation. The mean value of the AC-angle (acetabular index) preoperatively was 33.8°, postoperatively normal with 16.3°. The acetabular angle of the weightbearing zone was at follow-up 9.7°, which is normal too. At the age of less than 18 years the CE angle of 25,9° was normal too, as well the instability (protrusion) index of Reimers of 12.3 % and the distance femoral head to teardrop figure with 8.8 mm. In our study group of hip dysplasia we introduced a score of normal values of hip measurements and 3 grades of deviation from normal, slightly pathological, severely pathological and extremely. When we counted normal values and slightly pathological ones together as a good result, we found for the different measurements of the acetabulum percentages mainly between 82 and 93 %. Remarkable were two measurements of the femoral neck, the epiphyseal index with only 50 % of normal and slightly pathological angles and the head-neck index with 47.7% respectively. This was due to the head-in-neck position of the femoral neck after varus osteotomy as we have mentioned already. Acetabular coverage is achieved best in transiliac osteotomies up to 10 years. Then, only by triple pelvic osteotomies the acetabulum in total can be redirected to a normal coverage. But this operation is more difficult. Residual dysplasias therefore should be treated as early as possible in the way demonstrated here

A recently developed parametric geometrical finite element model (p-FEM) was adapted to the specific hip geometric measurements of a group of patients with slipped capital femoral epiphysis (SCFE). The objective was to analyze the stress distribution in the growth plate of these patients and to evaluate differences for those patients who developed bilateral disease. Different geometric parameters were measured in the healthy proximal femur of 18 adolescents (mean age, 12,1 yr) with unilateral SCFE and in 23 adolescents matched in age without hip disease (control group). Five patients developed SCFE in the contralateral side during follow-up. Different geometric measurements were taken from hip conventional X-ray studies. The p-FEM of the proximal femur permits modifications of different geometrical parameters, therefore the X-ray measurements taken from each patient were applied to the model obtaining a subject-specific model for each case. In each model, different mechanical situations such as walking, stairs climbing and sitting were simulated by applying loads on the femoral head corresponding to each own weight. The risk for growth plate failure was estimated by the Tresca, von Misses and Rankine stresses. In summary, the models shows important differences between the stresses computed at the healthy femurs of patients with unilateral SCFE and femurs that further underwent bilateral SCFE. So, the 95% confidence interval of the percentage of volume of the growth plate subjected to stresses higher than 2MPa was almost similar for the control group and patients with unilateral SCFE. However, those patients who developed bilateral disease had statistically significant large physeal areas with more than 2.0 MPa (p< 0.005). Stresses were also strongly dependent on the geometry of the proximal femur, especially on the posterior sloping angle of the physis and the physeal sloping angle. In spite of simplifications of the developed p-FEM, this tool has been able to show the influence of femur geometry in growth plate stresses and to predict the sites where growth plate starts to fail

Purpose of the study: Acetabular dysplasia is a recognized cause of premature hip degeneration. With increasing use of arthroplasty, the role of conservative treatment can be debated. The purpose of this work was to describe technical advances achieved with Ganz triple periacetabular osteotomy and evaluate long-term results. Material and methods: This study included 32 dysplastic hips in 28 patients treated by Ganz triple osteotomy and assessed a mean 12 years follow-up (range 2 – 20 years). Mean age was 32 years (range 18–47). There were 24 women and four men. Hip joint measurements were made on preoperaive standard x-rays with complementary recentered views if needed as well as computed tomography (CT) to better distinguish progressive degeneration. For early patients, the iniail osteotomy involved three cuts (ilioischial, iliopubic, ilial) starting close to the acetabulum and performed via three approaches: sub coxofemoral, intrapelvic, extrapelvic. The first technical change involved osteotomy of the anterosuperior iliac spine and an oblique iliac cut farther from the acetabulum. Results: Mean preoperative angles were: 135° (121 to 150°) for CC’D, 23.2° (3 to 40°) for HTE, 8.4° (−14 to 22°) VCE, 11.3° (−26 to 32°) for VCA. The postoperative values were: 134.5° (121 to 150°) for CC’D, 9.5° (−9 to 20°) for HTE, 31.7° (14 to 60°) for VCE, 31.7° (10 to 48°) for VCA. Six patients required total hip arthroplasty on average four years later (range 2 – 9 years), including one patient with aseptic necrosis of the acetabulum. Discussion and Conclusion: This study confirms the usefulness of triple periacetabular osteotomy for conservative treatment of acetabular dysplasia. In light of our results, the following changes have been instituted:. all three cuts are performed via a single intra-pelvic approach;. For severe extreme dysplasia (Hip Study Group classification), a two-thirds triple osteotomy is performed (original technique). Currently the best indication appears to be a young patient (less than 30 years) with moderate to severe dysplasia, without intra-articular suffering and without any sign of early stage joint degradation

In Musgrave Park Hospital, Belfast, younger patients requiring THR were treated by custom-made titanium alloy femoral prosthesis. The identifit hips, which were used initially, were intraoperatively customised by preparing a silicon mould of the endosteal cavity and immediate computer assisted fabrication. The Xpress hips used measurements from preoperative marker x-rays allowing creation of templates and subsequent computer analysis to mill a stem prior to surgery. 7 identifit and 51 Xpress primary uncemented custom THRs were inserted in 50 patients between May 92 and June 96. The average age for the indentifit cases was 47 years (range 24–72) and the Xpress cases 39 years (range 23–51). The Xpress cases were followed up to an average of 47 months (range 12–74 months) and identifit cases to an average of 59 months (range 14–77 months). The indications for arthroplasty were osteoarthrosis in 15 hips, CDH in 14, dysplasia in 11, AVN in 4, rheumatoid arthritis in 3 and other diagnosis in 11. Clinical assessments were made using the Oxford score and the Modified Harris Hip score. The postoperative radiographs were evaluated for subsidence of the prosthesis; and adaptive osseous changes like osteolysis, hypertrophic cortical remodelling, sclerotic radiolucent line formation around the prosthesis and formation of a bone pedestal below the tip of the prosthesis. The average post-op Oxford hip score for those patients not revised was 32.5 /60 (range 12–51). 16 of the 51 Xpress hips underwent revision and 2 were awaiting revision, which is a failure rate of 35.3%. Of the identifit hips 1 out of the 7 was revised (14.3%). Overall 32.8% was the rate of failure. The average duration from primary operation to revision was 47 months for Xpress hips and 90 months for the identifit hips. Of the Xpress hips, revision was done for acetabular component in 1, femoral component in 4, both components in 1, acetabular liner + femoral head in 1 and acetabular liner + femoral component in 9. The 1 revision in the identifit hip was for recurrent dislocation. The reasons for revision in the Xpress hips were dislocation in 2 cases, loose femoral component in 13 cases and infection in 1. Average subsidence of the femoral component was 6mm (range 0–25.9) and this did not have significant correlation with predicting outcome. Pedestal formation (intramedullary formation of bone beneath the tip of the femoral stem) was seen in 87%, sclerotic rediolucent lines were seen in 64%, osteolysis was found in 31% and hypertrophic cortical remodelling was seen in 31%. These also did not reach significance in predicting outcome. Thus even though the idea of an uncemented custom THR is attractive, especially in the younger age group, the failure rate was found to be unacceptably high. On the basis of these data we have discontinued the use of this custom made non-porous uncemented femoral prosthesis

Objectives

Sagittal alignment of the lumbosacral spine, and specifically pelvic incidence (PI), has been implicated in the development of spine pathology, but generally ignored with regards to diseases of the hip. We aimed to determine if increased PI is correlated with higher rates of hip osteoarthritis (HOA). The effect of PI on the development of knee osteoarthritis (KOA) was used as a negative control.

Objectives

Wear debris released from bearing surfaces has been shown to provoke negative immune responses in the recipient. Excessive wear has been linked to early failure of prostheses. Analysis using coordinate measuring machines (CMMs) can provide estimates of total volumetric material loss of explanted prostheses and can help to understand device failure. The accuracy of volumetric testing has been debated, with some investigators stating that only protocols involving hundreds of thousands of measurement points are sufficient. We looked to examine this assumption and to apply the findings to the clinical arena.