Introduction. It has been postulated that the larger femoral head size may be associated with reduced risk of dislocation after total hip arthroplasty(THA). However, Dislocation after THA has a multifactorial etiology with variables such as femoral head size, type of cup, stem and surgical approach. Objectives. The objectives of this study is to evaluate the association between femoral head component head size, surgical approach, surgeon's experience and the rate of dislocation after THA. Methods. From 2004 to 2013, 4,423 primary THA with varying femoral head sizes were performed at our institution. The operative approaches were Mini-One approach in 3,140 arthroplasties, OCM approach in 753, Hardinge in 483, and 2-incision approach in 47. The femoral head diameters were 26-mm in 2,965 of the procedures, 28-mm in 797, 32-mm in 516, 36-mm in 133, and 38-mm in 12. We compared the dislocation rates differences in surgical approach and the diameter of the femoral head. Statistical analysis was used by Chi-square test. Results. Dislocation occurred in 32 hips (0.72%) of the 4,423 hips. The rate of the dislocation was 0.64% following Mini-One approaches, 1.06% following OCM approaches, and 0.83% following Hardinge approaches. There was no dislocation in 2-inciision approaches. There was no significant difference in rate of dislocation between Mini-One group (0.64%) and non-Mini-One group (0.94%) (p=0.34). There was no significant difference in rate of dislocation between OCM group (1.06%) and non-OCM group (0.65%) (p=0.23). There was no significant difference in rate of dislocation between Hardinge group (0.83%) and non Hardinge group (0.71%) (p=0.77). Dislocation occurred in 23 hips (0.78%) with a 26-mm femoral head and in 7 hips (0.88%) with a 28-mm femoral head and in 2 hips (0.39%) with a 32-mm head. No dislocation occurred with a 36-mm head and 38-mm head. There was no significant difference in rate of dislocation between 32-mm and over head group and below 32-mm head group (p=0.22). In 3,265 cases, 55mm and under diameter of the cups were used by four high volume surgeons who experienced above 500 cases of THA. No dislocation occurred in this 3,265 cases with a 32-mm and over head diameter. Conclusion. Dislocation rate was 0.72%. Although this rate was too low to be statistical significant differences between femoral head component head size, surgical approach and the rate of dislocation, No dislocation was occurred in 55mm and under diameter of the cups and 32-mm head and over cases with experienced surgeons

Background. Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are treatments of end-stage hip disease. Gait analysis studies comparing HRA and THA have demonstrated HRA results in a more normal gait than THA. The reasons may include the larger, more anatomic head diameter, the preservation of the femoral neck with restoration of the anatomical hip centre position and normal proprioception. This study investigated (1)whether femoral head size diameter affects gait; (2)whether gait still differs between THA and HRA patients even with comparable head diameters. Methods. We analysed the gait of 33 controls and 50 patients with unilateral hip replacement. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA; the large group of 5 long-stem, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group. Results. (1) We found a significant difference in step-length between small head sizes and controls (p<0.01) at speeds ranging from 4.0 to 5.5 km/h but no difference between the larger head size and the controls. There was no significant difference in maximum speed, weight acceptance, push-off, mid-stance, impulse and cadence between the groups. (2)Analysis between THA and HRA in the large head size group revealed a significant difference in maximum speed (p=0.021) between long-stem THA (6.338 km/h± 1.542) and HRA (7.756km/h± 0.7604) patients. At 5.5 km/h there was a significantly better weight acceptance (p=0.009) and mid-stance (p=0.041) of HRA compared to short-stems. Impulse was significantly higher for HRA compared to long-stem THA (p<0.05) at all speeds ranging 4 to 5.5 km/h. (3)Males (7.1972 km/h ± .9700) had significantly higher maximum speeds compared to females (6.6524km/h± 1.019) (p=0.017) and lower gait impulse (p<0.01) at speeds ranging from 4 to 5.5km/h. (4)There was no significant difference in Oxford Hip Score (OHS) and EQ-5D of patients in the small compared to large head size group. Conclusions. Gait analysis demonstrated a significant difference in step length between THA patients with head size ≤ 36mm and normal controls. There was no difference in step length between normal controls and THA patients with larger head sizes. Compared to larger head size THA, HRA still revealed higher maximum speeds and better weight acceptance. Males had significantly higher maximum speeds compared to females (controls and hip replacement patients). We could not demonstrate a correlation between better gait and Oxford scores or EQ-5D scores but these are known to have a ceiling effect. In a former study, better gait parameters such as longer step length and higher maximum speed have been associated with higher patient satisfaction

Background. Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are treatments of end-stage hip disease. Gait analysis studies comparing HRA and THA have demonstrated that HRA results in a more normal gait than THA. The reasons may include the larger, more anatomic head diameter or the preservation of the neck of the femur with restoration of the anatomical position of the hip centre and normal proprioception. This study investigated (1) whether femoral head size diameter affects gait; (2) whether gait still differs between THA and HRA patients even with comparable head diameters. Methods. We retrospectively analysed the gait of 33 controls and 50 patients with a unilateral hip replacement, operated by the same surgeon. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA and the large group of 5 long-stem THA, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group. Results. (1) We found a significant difference in the step-length between the small head size group and the controls (p<0.01) at speeds ranging from 4.0 to 5.5 km/h but no difference between the larger head size and the controls. There was no significant difference in maximum speed, weight acceptance, push-off, mid-stance, impulse and cadence between the groups. (2) Analysis between THA and HRA in the large head size group revealed that there was a significant difference in the maximum speed (p=0.021) between the long-stem THA (6.338 km/h± 1.542) and HRA (7.756km/h± 0.7604) patients. At 5.5 km/h there was a significantly better weight acceptance (p=0.009) and mid-stance (p=0.041) of the HRA compared to short-stems. Impulse was significantly higher for HRA compared to long-stem THA (p<0.05) at all speeds ranging 4 to 5.5 km/h. (3) Males (7.1972 km/h ± .9700) had significantly higher maximum speeds compared to females (6.6524km/h± 1.019) (p=0.017) and lower gait impulse (p<0.01) at speeds ranging from 4 to 5.5km/h. (4) There was no significant difference in the Oxford Hip Score (OHS) and EQ-5D of patients in the small compared to the large head size group. Conclusions. Gait analysis demonstrated a significant difference in step length between THA patients with head size ≤ 36mm and normal controls. There was no difference in step length between normal controls and THA patients with larger head sizes. Compared to larger head size THA, the HRA still revealed higher maximum speeds and better weight acceptance. Males had significantly higher maximum speeds compared to females (controls and hip replacement patients). We could not demonstrate a correlation between better gait and Oxford scores or EQ-5D scores but these scores are known to have a ceiling effect. In a former study, better gait parameters such as longer step length and higher maximum speed have been associated with higher patient satisfaction

Introduction. Since the early days of total hip arthroplasty (THA) the choice of the proper diameter of the femoral head has been debated with respect to its effect on wear. The most widely accepted theory explaining aseptic loosening of THA is that of polyethylene particles induced osteolysis. In a previous study concerning 1,660 ScanHip THA’s that were followed for up to 12 years the cumulative revision rate was not found to be dependent on if a 22 mm or a 32 mm head size had been used1. We have reexamined these patients to see whether a longer follow-up time (9–21 years) would disclose an effect of head size on the revision rate.

Patients and Methods. We analyzed the CRR for 1,720 Scan Hip^® Classic I THA implanted in 1,550 patients, with 22 and 32mm heads, performed at Lund University Hospital during 1983 to 1995. Patients with the 3 most common diagnoses were included in the analysis, i.e. osteoarthritis, rheumatoid arthritis and femoral neck fracture. The end-point was defined as revision of any component for aseptic loosening before the end of 2004.

Results. Using the life table method analyzed cumulative revision rate for osteoarthritis, femoral neck fracture and rheumatoid arthritis patients and found that the 32 mm head had higher cumulative revision rate (p=0.04 (Wilcoxon)). Further analysis with Cox regression adjusting for age and sex showed that the 32 mm head had 2.8 times greater risk of revision (CI 1.7–4.6), p< 0.001. For each year increase in age the risk of revision was reduced 0.96 times (CI 0.95 – 0.97), p< 0.001, males had 1.5 times (CI 1.1 – 2.1), p=0.01 greater risk of revision than females.

Discussion. The reason that we did not find any significant difference in cumulative revision rates when followed up to 12 years, depending on head size in previous study (Kesteris et al. 1998) may be the time it takes for wear particles to induce the chain of events, eventually ending up in loosening. However extended follow-up up to 21 years after THA revealed significant differences in cumulative revision rates depending on head size.

Purposes. To compare the acetabular component size relative to the patient's native femoral head size between conventional THA (CTHA) approach and robotic-guided THA (RGTHA) to infer which of these techniques preserves more acetabular bone. Methods. Patients were included if they had primary osteoarthritis (OA) and underwent total hip replacement between June 2008 and March 2014. Patients were excluded if they had missing or rotated postoperative anteroposterior radiographs. RGTHA patients were matched to a control group of CTHA patients, in terms of pre-operative native femoral head size, age, gender, body mass index (BMI) and approach. Acetabular cup size relative to femoral head size was used as a surrogate for amount of bone resected. We compared the groups according to two measures describing acetabular cup diameter (c) in relation to femoral head diameter (f): (1) c-f, the difference between cup diameter and femoral head diameter and (2) (c-f)/f, the same difference as a fraction of femoral head diameter. Results. 57 matched pairs were included in each group. There were no significant differences between groups for demographic measures, femoral head diameter, or acetabular cup diameter (p>0.05). However, measures (1) and (2) did differ significantly between the groups, with lower values in the RGTHA group (p<0.02). Conclusion. Using acetabular cup size relative to femoral head size as an approximate surrogate measure of acetabular bone resection may suggest greater preservation of bone stock using RGTHA compared to CTHA. Further studies are needed to validate the relationship between acetabular cup size and bone loss in THA

Background. Preservation of acetabular bone during primary total hip arthroplasty (THA) is important, because proper stability of cementless acetabular cup during primary THA depends largely on the amount of bone stock left after acetabular reaming. Eccentric or excessive acetabular reaming can cause soft tissue impingement, loosening, altered center of rotation, bone-to-bone impingement, intraoperative periprosthetic fracture, and other complications. Furthermore, loss of bone stock during primary THA may adversely affect subsequent revision THA. Questions/Purposes. We sought to compare the conventional THA (CTHA) approach to robotic-guided THA (RGTHA) to determine which of these techniques preserves more acetabular bone, as interpreted from the size of the acetabular component compared with the size of the native femoral head. Methods. Patients who received RGTHA were matched to a control group of patients who received CTHA, in terms of pre-operative native femoral head size (47.8mm – 48.1mm), age (mean 56.9), gender, BMI, and approach. Acetabular cup size relative to femoral head size was used as a surrogate for amount of bone resected. We compared the groups according to three measures describing the acetabular cup diameter (c) in relation to the femoral head diameter (f). These three measures were: (1) (c − f), the difference between the cup diameter and femoral head diameter, (2) (c − f) / f, the same difference as a fraction of the femoral head diameter, and (3) (c3 − f3) / f3, the same ratio expressed volumetrically. Results. A total of 57 matched pairs were included in each group. There were no significant differences between groups in terms of gender, age at surgery, or BMI. No differences in femoral head diameter or acetabular cup diameter were observed between groups (p > 0.05). However, measures (1)(c − f), (2)(c − f) / f, and (3)(c3 − f3) / f3 did differ significantly between the groups, with lower values in the RGTHA group (p < 0.02). Conclusion. RGTHA allowed for the use of smaller acetabular cups in relation to the patient's femoral head size, compared to CTHA. Using acetabular cup size relative to femoral head size as a surrogate measure of acetabular bone resection, these results indicate that greater preservation of bone stock using RGTHA compared to CTHA. This may reflect increased translational precision during the reaming process. However, further studies are needed to validate the relationship between acetabular cup size and loss of bone in THA

Background. Preservation of acetabular bone during primary total hip arthroplasty (THA) is important, because proper stability of cementless acetabular cup during primary THA depends largely on the amount of bone stock left after acetabular reaming. Eccentric or excessive acetabular reaming can cause soft tissue impingement, loosening, altered centre of rotation, bone-to-bone impingement, intra-operative periprosthetic fracture, and other complications. Furthermore, loss of bone stock during primary THA may adversely affect subsequent revision THA. Questions/Purposes. The purpose of this study was to compare preservation of acetabular bone stock between conventional THA (CTHA) vs. robotic-guided THA (RGTHA). We hypothesised that RGTHA would allow more precise reaming, leading to use of smaller cups and greater preservation of bone stock. Methods. Patients who received RGTHA were matched to a control group of patients who received CTHA, in terms of pre-operative native femoral head size (47.8mm – 48.1mm), age (mean 56.9), gender, BMI, and approach. Acetabular cup size relative to femoral head size was used as a surrogate for amount of bone resected. We compared the groups according to three measures describing the acetabular cup diameter (c) in relation to the femoral head diameter (f). These three measures were: (1) c-f, the difference between the cup diameter and femoral head diameter, (2) (c-f)/f, the same difference as a fraction of the femoral head diameter, and (3) (c∧3-f∧3)/f∧3, the same ratio expressed volumetrically. Results. A total of 57 matched pairs were included in each group. There were no significant differences between groups in terms of gender, age at surgery, or BMI. No differences in femoral head diameter or acetabular cup diameter were observed between groups (p > 0.05). However, measure (2) (c-f)/f and (3) (c∧3-f∧3)/f∧3 did differ significantly between the groups, with lower values in the RGTHA group (p < 0.02). Conclusion. RGTHA allowed for the use of smaller acetabular cups in relation to the patient's femoral head size, compared to CTHA. Using acetabular cup size relative to femoral head size as a surrogate measure of acetabular bone resection, these results indicate that greater preservation of bone stock using RGTHA compared to CTHA. This may reflect increased translational precision during the reaming process. However, further studies are needed to validate the relationship between acetabular cup size and loss of bone in THA

Introduction and Objective. Despite pure alumina have shown excellent long-term results in patients undergoing total hip arthroplasty (THA), alumina matrix composites (AMCs) composed of alumina and zirconium oxide are more commonly used. There are no comparative studies between these two different ceramics. We performed a retrospective case-control study to compare results and associated complications between AMC from two manufacturers and those with pure alumina from another manufacturer. Materials and Methods. 480 uncemented THAs with ceramic on ceramic (CoC) bearing surfaces (288 men and 192 women; mean age of 54.1 ± 12.4 years), were implanted from 2010 to 2015. Group 1: 281 THAs with pure alumina; Group 2A: 142 with AMC bearing in a trabecular titanium cup. Group 2B: 57 hips with AMC bearing with a porous-coated cup. Results. The mean follow-up was 7.3 years. There was one late infection in group 1, eight dislocations, three in group 1 (1.1%), three in group 2A (2.1%), all with a 36 mm femoral head, and two in group 2C (3.5%). Liner malseating was found in one hip in group 1, and in five hips in group 2C, of these, there were four liner fractures (7.0%). Four cups were revised for iliopsoas impingement (three in group 1 and one in group 2B). Two cups were revised for aseptic loosening, one in group 1 and one in group 2A, and four revised femoral stems in group 2A, three for subsidence and another for postoperative periprosthetic B. 2. fracture. The mean preoperative Harris Hip Score was 48.6 ± 3.3 in the whole series and 93.9 ± 7.2 at the end of follow-up. The survival rate of revision for any cause was 98.2% (95% Confidence Interval: 96.6–99.8) at ten years for group 1, 95.8% (95% CI: 92.1–99.5) for group 2A, and 91.1% (95% CI: 83.7–98.5) for group 2B (log-rank 0.030). Conclusions. Outcome of uncemented CoC THA in young patients was satisfactory at mid-term in all three groups. However, liner fractures were frequent in group 2B. All dislocated hips in group 2A had a 36 mm femoral head diameter, and revision due to any cause was less frequent in group 1. Pure alumina CoC THA can be used as a benchmark for comparison with newer CoC THAs

Dislocation is one of the most common complications after revision THA using the posterolateral approach. Although the cause of dislocation after revision THA is multifactorial, the historically high dislocation rates have been shown to be significantly reduced by closing the posterior capsule and by the use of large diameter (36 and 40 mm) femoral heads. The relative importance of each of these strategies on the rate of dislocation remains unknown. We undertook a study to determine if increasing femoral head diameter, in addition to posterior capsule closure would influence the dislocation rate following revision THA. We retrospectively reviewed 144 patients who underwent a revision THA. We included all patients who underwent revision THA with closure of the posterior capsule and who had at least a 2-year minimum follow-up. We excluded patients undergoing a revision THA for dislocation or multistage revision for infection since these patients would likely have deficient posterior tissues. Forty-eight patients had a 28 mm femoral head, 47 had a 32 mm head and 49 patients had a 36 mm femoral head. At a minimum follow-up of 2 years, there were 3 dislocations. There were no dislocations in the 28 mm group (0%), 2 in the 32 mm group (4%) and 1 in the 36 mm group (2%). All patients were successfully treated with a closed reduction. No patients had recurrent dislocation. Head size alone was not found to significantly decrease the risk of dislocation (28mm vs 32mm p=0.12; 28mm vs 36mm p=0.27; 32mm vs 36mm p=0.40). Both large diameter heads and careful attention to surgical technique with posterior capsule closure can decrease the historically high dislocation rate after revision THA when utilizing the posterolateral approach. The additional use of a large diameter head did not have a significant impact on the already low dislocation rate. Capsular closure outweighs the effect of femoral head diameter in preventing dislocation following revision THA through a posterolateral approach

In vivo kinematic analyses of total hip arthroplasty (THA) have determined femoral head separation from the medial aspect of the acetabular component can occur. Various bearing materials are currently used in THA today. The objective of this study was to determine if differences in the incidence and magnitude of femoral head separation exist among various bearing surfaces for THA during different weight-bearing activities. 205 clinically successful subjects implanted with either metal-on-metal (MOM), metalon-polyethylene (MOP), ceramic-on-ceramic (COC) or ceramic-on-polyethylene (COP) materials were analyzed using video-fluoroscopy. Each patient performed either gait on a treadmill or an abduction-adduction activity. The fluoroscopic information was then analyzed using a computer aided 3D model fitting technique to determine the incidence and magnitude of hip separation. Additional variables analyzed included femoral head diameter, follow-up duration, and type of surgical approach utilized. Less separation was noted with increasing femoral head diameter during abductionadduction. Increased separation was observed during gait as follow-up duration increased. Hip separation was greater during gait when a posterolateral surgical approach was used but was greater in abduction-adduction if a antero-lateral approach was selected. The incidence and magnitude of hip separation during gait was least in subjects with COC THA and least with COC and MOM THA when analyzed during abduction-adduction. It’s been proposed that THA patients are subject to femoral head separation due to alterations in the soft tissue supporting structures during THA that affect constraint of the joint. The current analysis demonstrates lower magnitudes and incidence of THA separation occur when hard-on-hard bearing surfaces are selected and can vary based on femoral head diameter, follow-up duration, and surgical approach used. Potential detrimental effects resulting from THA separation include premature polyethylene wear, component loosening (secondary to impulse loading conditions) and hip instability

Aim: The aim of the study was to assess the correlation of CE angle to the ratios of medial hip joint space width and femoral head diameter to acetabular width. Material and metod: Measurements were done on 196 AP pelvic radiographs of 10 years old and 20 years old males and females obtained with “siemens lconos r 200 axion. ®. ”. The patients were placed in the supine position with their hips extended and internally rotated 15°. Medial hip joint space width (mJSW), CE angle, femoral head diameter (FD) and acetabular width (AW) were measured. The intraobserver reproducibility was assessed by a randomly chosen subset of 50 radiographs and these were read 1 month apart. The levels of agreement were qualified using the intraclass correlation coefficient. The ratios of mJSW to AW and FD to AW were calculated. Results: Mean CE angles in 10 years old females and males were 33.87±3.64 ve 32.74±4.21 degrees respectively. CE angle was correlated to mJSW/AW in 10 years old females (r = − 0.446, p=0.043). CE angle was not correlated to mJSW/AW in 10 years old males (r = − 0.293, p=0.146). CE angle was not correlated to mJSW/AW in 20 years old females while CE angle was correlated to mJSW/AW in 20 years old males (r = 0. 694, p=0.001). CE angle was correlated to FD/AW only in 20 years old males (r=0.553, p= 0.002). Discussion: Ratios of medial hip joint space width and femoral head diameter to acetabular width are not correlated to CE angle in both preadelocent and postade-locent terms depending on sex. The expected inverse correlation of these parameters to CE angle was not dedected, so these parameters can be used in radiologic assessement of subluxation of the hip and acetabular dysplasia together with CE angle

Proximal femur fractures are common in the elderly population. The aim of this study was to determine the relationship between fracture type and proximal femoral geometric parameters. We retrospectively studied the electronic medical records of 85 elderly patients over 60 years of age who were admitted to the orthopedic department with hip fractures between January 2016 and January 2018 in a training and research hospital in Turkey. Age, fracture site, gender, implant type and proximal femoral geometry parameters (neck shaft angle [NSA], center edge angle [CEA], femoral head diameter [FHD], femoral neck diameter [FND], femoral neck axial length [FNAL], hip axial length [HAL], and femoral shaft diameter [FSD]) were recorded. Patients with femoral neck fractures and femur intertrochanteric fractures were divided into two groups. The relationship between proximal femoral geometric parameters and fracture types was examined. SPSS 25.0 (IBM Corparation, Armonk, New York, United States) program was used to analyze the variables. Independent samples t test was used to compare the fracture types according to NSA, FHD, FND and FSD variables. A statistically significant difference was found in FSD (p=0,002) and age (p=0,019). FSD and age were found to be greater in intertrochanteric fractures than neck fractures. Gender, site, CEA, FNAL, HAL, NSA, FHD and FND parametres were not significantly different. In the literature, it is seen that different results have been reached in different studies. In a study conducted in the Chinese population, a significant difference was found between the two groups in NSA, CEA and FNAL measurements. In a study conducted in the Korean population, a significant difference was found only in NSA measurements. The FSD is generally associated with bone mineral densitometry in the literature and has been shown to be a risk factor for fracture formation. However, a study showing that there is a relationship between FSD and fracture type is not available in the literature. In this study; FSD was found to be higher in intertrochanteric fractures (p = 0.002). However, for the clinical significance of this difference, we think that larger patient series and biomechanical studies are needed

Aims. The most frequent indication for revision surgery in total hip arthroplasty (THA) is aseptic loosening. Aseptic loosening is associated with polyethylene liner wear, and wear may be reduced by using vitamin E-doped liners. The primary objective of this study was to compare proximal femoral head penetration into the liner between a) two cross-linked polyethylene (XLPE) liners (vitamin E-doped (vE-PE)) versus standard XLPE liners, and b) two modular femoral head diameters (32 mm and 36 mm). Methods. Patients scheduled for a THA were randomized to receive a vE-PE or XLPE liner with a 32 mm or 36 mm metal head (four intervention groups in a 2 × 2 factorial design). Head penetration and acetabular component migration were measured using radiostereometric analysis at baseline, three, 12, 24, and 60 months postoperatively. The Harris Hip Score, University of California, Los Angeles (UCLA) Activity Score, EuroQol five-dimension questionnaire (EQ-5D), and 36-Item Short-Form Health Survey questionnaire (SF-36) were assessed at baseline, three, 12, 36, and 60 months. Results. Of 220 screened patients, 127 were included in this study. In all, 116 received the allocated intervention, and 94 had their results analyzed at five years. Head penetration was similar between liner materials and head sizes at five years, vE-PE versus XLPE was -0.084 mm (95% confidence interval (CI) -0.173 to 0.005; p = 0.064), and 32 mm versus 36 mm was -0.020 mm (95% CI -0.110 to 0.071; p = 0.671), respectively. No differences were found in acetabular component migration or in the patient-reported outcome measures. Conclusion. No significant difference in head penetration was found at five years between vE-PE and XLPE liners, nor between 32 mm and 36 mm heads. Cite this article: Bone Joint J 2020;102-B(10):1303–1310

Key Points:. Historically, 22.25, 26, 28, or 32 mm metal femoral heads were used in primary total hip arthroplasty, but innovations in materials now permit head sizes 36 mm or larger. Stability and wear of primary total hip arthroplasty are related to the diameter and material of the femoral head. Larger diameter femoral heads are associated with increased joint stability through increases in arc range of motion and excursion distance prior to dislocation. Fixation of the acetabular component may be related to the size of the femoral head, with increased frictional torque associated with large diameter heads and certain polyethylene. Linear wear of highly crosslinked polyethylenes seems unrelated to femoral head diameter, but larger heads have been reported to have higher volumetric wear. Mechanically assisted crevice corrosion at the connection between the modular femoral head and neck may be associated with the femoral head size and material. Cobalt chromium alloy, alumina ceramic composite, or oxidised zirconium femoral heads on highly crosslinked polyethylene are the most commonly used bearing surfaces, but each may have unique risks and benefits. Conclusions. At present, there is a wave of enthusiasm for the routine use of “large” (32, 36 mm, or larger) femoral heads with highly crosslinked polyethylene for the vast majority of patients having a primary THA. It may be reasonable to consider the “graduated femoral head-outer acetabular diameter system”, using 28 mm femoral heads with “smaller” acetabular components (<50 mm), 32 mm femoral heads with acetabular components 50 – 56 mm outer diameter, and 36 mm or larger femoral heads with acetabular components 58 mm or larger in diameter, to minimise both the risk of dislocation and the frictional torque. Although the linear wear of highly crosslinked polyethylene appears to be independent of head size, the reported increase in volumetric wear with large femoral heads and highly crosslinked polyethylene requires further study, and should temper the use of femoral heads 36 mm or larger in younger and more active patients. With its long and successful history, it is difficult to recommend the complete abandonment of the cobalt chromium alloy femoral head in all patients having a primary THA. Alumina ceramic or oxidised zirconium heads may be considered for younger, heavier, and more active patients, who seem to have the highest risk of trunnion corrosion. Surgeons and patients should be aware of the unique possible complications of these two newer femoral head materials

The effectiveness of total hip replacement as a surgical intervention has revolutionized the care of degenerative conditions of the hip joint. However, the surgeon is still left with important decisions in regards to how best deliver that care with choice of surgical approach being one of them especially in regards to the short-term clinical outcome. It is however unclear if a particular surgical approach offers a long-term advantage. This study aims to determine the influence of the three main surgical approaches to the hip on patient reported outcomes and quality of life after 5 years post-surgery. We extracted from our prospective database all the patients who underwent a Total Hip Replacement surgery for osteoarthritis or osteonecrosis between 2008 and 2012 by an anterior, posterior or lateral approach. All the pre-operative and post-operative HOOS (Hip disability and Osteoarthritis Outcome Score) and WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) scores were noted. Analysis of covariance (ANCOVAs) were used to study the relationship between amount of change in HOOS and WOMAC subscales (dependant variables) and approach used, by also including confounding factors of age, gender, ASA (American Society of Anaesthesiologists) score, Charnley score and Body Mass Index. A total of 1895 patients underwent a primary total hip arthroplasty during the considered period. Among them, 367 had pre-operative and ≥5 years post operative PROM scores (19.47%). The mean follow-up for the study cohort was 5.3 years (range 5 to 7 years) with, 277 at 5 years, 63 at 6 years, and 27 at 7 years. In the posterior approach group we had 138 patients (37.60%), 104 in the lateral approach (28.34%) and 125 in the anterior approach (34.06%). There were no significant differences between the 3 groups concerning the Charnley classification, BMI, Gender, ASA score, side and pre-operative functional scores. We did not observe any significant difference in the amount of change in HOOS and WOMAC subscales between the 3 groups. There were no differences either in the post-operative scores in ultimate value. Our monocentric observational study shows that these three approaches provide predictable and comparable outcomes on HRQL and PROMs at long-term follow-up both in terms of final outcome but also in percent improvement. This study has several limitations. We excluded patients who underwent revision surgery leaving the unanswered question of how choice of surgical approach could lead to different revision rates, which have an impact on the functional outcomes. Moreover, even if we controlled for the most important confounders by a multivariate analysis model, there is still some involved cofounders, which could potentially lead to a bias such as smoking, socio-economical status or femoral head diameter. But we do not have any reason to think that these parameters could be unequally distributed between the three groups. Finally, our study cohort represents of 19.47% of the complete cohort. The fact that not all patients have PROM's was pre-determined as eight years ago we instituted that only 1 in 5 patients that returned their pre-operative questionnaire would get their PROM's at follow-up. Despite this, our statistical power was sufficient

Introduction. Traditionally, conventional radiographs of the hip are used to assist surgeons during the preoperative planning process, and these processes generally involve two-dimensional X-ray images with implant templates. Unfortunately, while this technique has been used for many years, it is very manual and can lead to inaccurate fits, such as “good” fits in the frontal view but misalignment in the sagittal view. In order to overcome such shortcomings, it is necessary to fully describe the morphology of the femur in three dimensions, therefore allowing the surgeon to successfully view and fit the components from all possible angles. Objective. The objective of this study was to efficiently describe the morphology of the proximal femur based on existing anatomical landmarks for use in surgical planning and/or forward solution modeling. Methods. Seven parameters are needed to fully define femoral morphology: head diameter, head center, neck shaft axis, femoral canal, proximal shaft axis, offset, and neck shaft angle. A previous algorithm has been developed in-house to automatically locate anatomical landmarks of patient specific bone models. Once the bone model has been aligned and scaled based on these landmarks, the femoral head diameter and center are calculated by iteratively fitting a sphere to the corresponding femoral head point cloud. An iterative cylindrical fitting algorithm is used to describe the neck shaft axis. The femoral canal is determined using three steps: 1) the femur is sliced at 10mm increments below the lesser trochanter, 2) the femoral canal boundary is determined at each slice, and 3) the largest circle is fit within each slice's canal boundary. The proximal shaft axis is described by fitting a line to the canal circle center locations. Offset is defined as the distance from the head center to the proximal shaft axis. Finally, the neck shaft angle is the angle between the neck shaft axis and the proximal shaft axis. Results. The goal pertaining to femoral component morphology is to provide meaningful information that can be used to determine how the femoral stem fits within the canal. Regardless of differences in bone sizes and geometries, the algorithm has proven to be successful in describing the femoral morphology of a patient-specific bone model. Discussion. These results lay the groundwork for an automatic stem fitting algorithm, which is described in a subsequent abstract. The morphology knowledge of the femoral head, femoral neck, femoral canal, and various axes can be coupled with known THA component parameters (such as offset, neck length, neck shaft angle, etc.) to allow our algorithms to predict the “best selection” and “best fit” for the femoral stem. This can also be applied to the acetabulum and can then be used as a surgical planning tool as well as a parameter when modeling postoperative predictions. For any figures or tables, please contact authors directly

Femoral head diameters in THA have been increasing due to good long-term outcomes of 1. st. generation HXLP cups. Furthermore, some 2. nd. generation HXLP cups allow 36mm or larger heads. However, larger femoral head diameters increase the frictional torque and may lead to early cup migration and loosening. And there is a concern that larger head diameters and reduced liner thickness may increase polyethylene wear. In this study, we compared early acetabular component migration and wear rates between a group of larger heads using a 2. nd. generation HXLP and a group smaller heads using a 1. st. generation HXLP. The larger head group comprising 30 hips underwent THA between February 2010 and March 2011 with the use of a sequentially cross-linked polyethylene liner (X3). 30 patients were included in this study (30 women). Their mean age was 59.3years; mean weight was 53.6kg. Trident HA-coated cementless cups were used and the sizes ranged from 46mm to 56mm (mean 50.5mm). The head diameters were 36mm in 23hips, 40mm in 5 hips, and 44mm in 2hips. All X3 liners were 5.9mm or less in thickness. A control group was selected from a previous case series that had undergo THA between July 2007 and January 2008 using a 1st generation HXLP liner (Crossfire) by matching age and sex. Therefore 30 patients were included in this study (30 women) too. Their mean age was 60.0 years; mean weight was 55.5kg. The same Trident cups were used and the sizes ranged from 46mm to 56mm (mean 49.5mm). The head diameters were 26mm in 19hips and 32mm in 11hips. The liner thicknesses were 7.8mm or more. All hips had standardized anteroposterior pelvic digital radiographs performed postoperatively and cup migration was measured on digital radiographs at the immediate postoperative period and two year using EBRA-CUP software. We analyzed horizontal and vertical cup migration distance and the difference in cup anteversion and inclination angle at two years. Additionally, total head penetrarion and polyethylene liner volumetric wear rates were measured using a computer-assited method with PolyWear software. The larger head group revealed an average of 0.48mm of horizontal migration, 0.75mm of vertical migration, 0.19degree of inclination change, and 1.26 degrees of anteversion change. The control group showed an average of 0.63mm of horizontal migration, 0.36mm of vertical migration, 0.07 degree of inclination change, and 0.88 degree of anteversion change. Based on the EBRA-CUP measurements, there were no cases of significant early loosening which was indicated by more than 1mm of migration, more than 2.5 degree of inclination change, or more than 3.3 degree of anteversion change. The liner penetration rates were 0.388±0.192mm/yr in the large head group and 0.362±0.178mm/yr in the control group. The difference was not significant (p=0.64.) The volumetric wear rates were 42.8±27.9mm⁁3/yr in the large head group and 42.0±33.0mm⁁3/yr in the control group. Again, the difference was not significant (p=0.94). No significant early cup migration or increased wear rate were detected in THA with the sequentially cross-linked polyethylene liner and 36mm or large heads at two years

Background. Total hip arthroplasty (THA) is increasingly used for active patients with displaced intracapsular hip fractures. Dislocation rates in this cohort remain high postoperatively compared to elective practice, yet it remains unclear which patients are most at risk. The aim of this study was to determine the dislocation rate for these patients and to evaluate the contributing patient and surgeon factors. Methods. A five-year retrospective analysis of all patients receiving THA for displaced intracapsular hip fractures from 2013–18 was performed. Data was collected from the institutions' hip fracture database, including data submitted to the National Hip Fracture Database (NHFD). Cox regression analysis and log-rank tests were implemented to evaluate factors associated with THA dislocation. Patient age, sex, ASA grade, surgeon seniority, surgical approach, femoral head diameter and acetabular cup type were all investigated as independent factors. Results. A total of 196 patients, with a mean age of 72 (range 49–90), received THA for hip fracture between 2013–18. A posterior approach, using standard cemented acetabular components and a 28mm femoral head, was used in 133 cases (72%). Fourteen dislocations (7%) were observed during this period, with 5 patients requiring revision surgery. Of these dislocations, all were performed through posterior approaches with standard cemented cups. 28mm femoral heads were used in all cases except one, which used a 32mm femoral head. In Cox regression analysis, ASA grade, but not age or sex, was significantly associated with dislocation (hazard ratio = 4.5; 95% confidence interval 2.0–10.0; p<0.001). On log rank testing no statistically, significant association was found between dislocation and surgeon grade (p=0.85), surgical approach (p=0.31), femoral head size (p=0.85) or cup type (p=0.30). Discussion. This study demonstrates an increased risk of dislocation following THA for hip fracture with higher ASA grades. It may be appropriate to offer more stable implants to this cohort of patients

In order to reduce the risk of dislocation larger femoral heads in total hip arthroplasty (THA) are being used by surgeons in recent years. The standard head size of 28 mm used in 73% of all hip procedures in 2003 was used in only 29% in 2016; whereas head sizes of 32 mm and 36 mm combined, were used in 70%. The increase of head size effectively reduces the thickness of the acetabular cup, altering the load transfer. Herein, this research work investigates the effect of increasing the femoral head size on the stresses of the periacetabular bone at two selected regions: A1 (superior) and A2 (anterior). Three Finite Element models were developed from CT scan data of a hemipelvis implanted with a cemented all-polyethylene acetabular cup with a 50 mm outer diameter and inner diameter to accommodate three head sizes: 28 mm, 32 mm and 36 mm. The peak reaction force at the hip joint during one leg stand for an overweight patient with a body weight of 100 Kg was simulated for head sizes investigated. We found that highest average von Mises stress was 5.7 MPa and occurred in the cortical bone of region A1 which is located within Zone 1 boundaries (Charnley &DeLee); whereas a lower stress of 4.0 MPa occurred at region A2. In the two regions the stresses were the same for the three head sizes. Periacetabular bone was found to be insensitive to the increase of femoral head diameter in cemented THA

Introduction: There is an increasing interest in surface replacement arthroplasty (SRA) as an alternative to conventional THA (cTHA) in young and active patients. However, there has been considerable variability in reported outcomes. National joint registry reports have shown increased revision rates compared to cTHA. We analysed outcome measured as non-septic revision rate within two years for SRA in the NARA data base (Nordic Arthroplasty Register Association). Materials and Methods: 1638 SRA and 163802 cTHA with age up to 73 years and a non-fracture diagnosis, operated from 1995 to 2007, were compared using Cox multiple regression including age, gender, diagnosis, nation and prosthesis type with cTHA divided into cemented, uncemented, hybrid and reversed hybrid fixation. Men below 50 years of age (460 SRA and 7185 cTHA) were analysed as a subset. The SRA cohort with a mean follow-up 1,8 years was also analysed with the same method including age, gender, diagnosis, number of performed SRA per hospital and the four most commonly used prosthesis designs. In an additional analysis femoral head diameter was added, reducing the number of cases to 1552. results are presented as relative risk (RR) with 95 % confidence interval(CI). Results: SRA had a more than twofold increased revision risk compared to cTHA, RR=2,50 (1,67–3,70), which increased to 3,63 (2,42–5,44) when compared with all cemented THA. In the subpopulation of men below 50 years of age, there was no difference between SRA and any of the cTHA cathegories. Within the SRA group RR was reduced by male gender, RR=0,46 (0,25–0,86), in hospital performing > 70 SRA (RR=0,26, 0,11–0,60) and with use of BHR (Birmingham Hip Resurfacing) compared to all other designs (RR=0,27, 0,12–0,61). The size of the femoral head diameter had no significant influence on the early revision rate. Discussion and Conclusion: Surface replacement arthroplasty has an increased risk of early revision compared to conventional and cemented THA except for men below 50 years of age. There is a learning curve on the hospital level. Cases with secondary osteoarthritis were comparatively few and were mainly caused by pediatric hip disease. SRA might become an alternative for young men, but our follow up is too short to determine if this indication remains in the longer perspective