Introduction. The objective of our study was to determine the extent to which the quality of the biomechanical reconstruction when performing hip replacement influences gait performances. We aimed to answer the following questions: 1) Does the quality of restoration of hip biomechanics after conventional THR influence gait outcomes? (question 1), and 2) Is HR more beneficial to gait outcomes when compared with THR? (question 2). Methods. we retrospectively reviewed 52 satisfied unilateral prosthetic hip patients (40 THRs and 12 HRs) who undertook objective gait assessment at a mean follow-up of 14 months. The quality of the prosthetic hip biomechanical restoration was assessed on standing pelvic radiograph by comparison to the healthy contralateral hip. Results. We were unable to detect any statistically significant correlation between the radiographical parameters and the gait data, for THR patients. In stress conditions (inclination or declination of the ramp), the gait was more symmetric in the HR group, compared to the THR group. Discussion/Conclusions. We found that slight variations in the quality of the hip biomechanical restoration had little effect on gait outcomes of THR patients, and HR generated a more physiological gait under stress conditions than well-functioning THR

Introduction. Natural population variation in femoral morphology results in a large range of offsets, anteversion angles and lengths. During total hip arthroplasty, accurate restoration of hip biomechanics is essential to achieve good functional results. One option is to restore the anatomic hip rotation center. Alternatively, medializing the rotation center and compensating by increasing the femoral offset, reduces acetabular contact forces and increases the abductor lever arm. We investigated the ability of two cemented stem systems to restore hip biomechanics in an anatomic and medialized way. We compared an undersized “Exeter-type” of stem with three offset options and 18 sizes (CPT, Zimmer), to a line-to-line “Kerboul-type” of stem with proportional offset and 12 sizes (Centris, Mathys). Methods. Thirty CT scans of whole femora were segmented and the hip rotation center, proximal femoral axis and femoral length were determined with Mimics and 3-matic (Materialise). Using scripting functionality in the software, CAD design files of both stems were automatically sized and aligned along the proximal femoral axis to restore an anatomical and a 5 mm medialized hip rotation center. Stem size and position could be fine-tuned manually. The maximum distances between the prosthetic (PRC), the anatomic (ARC) and the medialized hip rotation center (MRC) were calculated (Fig. 1). Variations in femoral offset (ΔFO), anteroposterior (ΔAP) and proximodistal distance (ΔPD) were analyzed. Finally, the number of cases where the hip rotation center could be restored within 5 mm was reported. Results. Both implants allowed restoring the ARC accurately (mean distance PRC-ARC: CPT 0.97±0.88 mm, Centris 1.66±1.59 mm; mean difference ΔFO: CPT 0.09±0.19 mm, Centris 0.11±0.29 mm; mean difference ΔAP: CPT 0.12±1.22°, Centris 0.27±1.78 mm, mean difference ΔPD: CPT 0.04±0.44 mm, Centris 0.49±1.35 mm). The CPT stem allowed restoring the PRC within 5 mm of the ARC in all cases (max. 4.31 mm), whereas the Centris stem achieved this in only 28/30 hips (max. 6.72 mm) (Fig. 2). Aiming for a MRC was less satisfactory with both stems (mean distance PRC-MRC: CPT 1.38±1.63 mm, Centris 3.61±2.73 mm; mean difference ΔFO: CPT 0.09±0.10 mm, Centris 0.06±0.35 mm; mean difference ΔAP: CPT 0.17±2.02 mm, Centris 2.58±2.68 mm, mean difference ΔDP; CPT 0.28±0.67 mm, Centris 1.98±1.66 mm). The CPT stem allowed restoring the PRC within 5 mm of the MRC in 29/30 cases (max. 8.09 mm), whereas the Centris stem achieved this in only 25/30 cases (max. 11.15 mm) (Fig. 3). Discussion. Although both stem systems allowed restoring hip biomechanics accurately in most cases, the CPT system was superior to the Centris stem for achieving both ARC and MRC. This could be explained by more implant sizes (18 vs. 12) and undersized stems offering more freedom to correct version. Although medializing the hip rotation center offers biomechanical advantages, both stems had more difficulties achieving this. In some cases, differences between aimed and planned rotation centers were close to 1 cm which might negatively impact on clinical outcome. As such, to avoid suboptimal reconstructions with the available implants, templating is mandatory especially when aiming at a medialized reconstruction strategy

Restoring native hip biomechanics is crucial to the success of THA. This is reflected both in terms of complications after surgery such as instability, leg length inequality, pain and limp; and in terms of patient satisfaction. The challenge that remains is that of achieving optimal implant sizing and positioning so as to restore, as closely as possible, the native hip biomechanics specific to the hip joint being replaced. This would optimise function and reduce complications, particularly, instability. (Mirza et al., 2010). Ideally, this skill should also be reproducible irrespective of the surgeon's experience, volume of surgery and learning curve. The general consensus is that the most substantial limiting factor in a THA is the surgeon's performance and as a result, human errors and unintended complications are not completely avoidable (Tarwala and Dorr, 2011). The more challenging aspects include acetabular component version, sizing and femoral component sizing, offset and position in the femoral canal. This variability has led to interest in technologies for planning THA, and technologies that help in the execution of the procedure. Advances in surgical technology have led to the development of computer navigation and robotic systems, which assist in pre-operative planning and optimise intra-operative implant positioning. The evolution of surgical technology in lower limb arthroplasty has led to the development of computer navigation and robotics, which are designed to minimise human error and improve implant positioning compared to pre-operative templating using plain radiographs. It is now possible to use pre-operative computerised tomography (image-based navigation) and/or anatomical landmarks (non-imaged-based navigation) to create three-dimensional images of each patient's unique anatomy. These reconstructions are then used to guide bone resection, implant positioning and lower limb alignment. The second-generation RIO Robotic Arm Interactive Orthopaedic system (MAKO Surgical) uses pre-operative computerised tomography to build a computer-aided design (CAD) model of the patient's hip. The surgeon can then plan and execute optimal sizing and positioning of the prostheses to achieve the required bone coverage, minimise bone resection, restore joint anatomy and restore lower limb biomechanics. The MAKO robotic software processes this information to calculate the volume of bone requiring resection and creates a three-dimensional haptic window for the RIO-robotic arm to resect. The RIO-robotic arm has tactile and audio feedback to resect bone to a high degree of accuracy and preserve as much bone stock as possible. We have used this technology in the hip to accurately reproduce the anteversion, closure and center of rotation that was planned for each hip. Whilst the precise safe target varies from patient to patient, the ability to reproduce native biomechanics, to gain fixation as planned and to get almost perfect length and offset are a great advantage. Complications such as instability and leg length inequality are thus dramatically reduced

The literature indicates that femoroacetabular impingement (FAI) patients do not return to the level of controls (CTRL) following surgery. The purpose of this study was to compare hip biomechanics during stair climbing tasks in FAI patients before and two years after undergoing corrective surgery against healthy controls (CTRL). A total of 27 participants were included in this study. All participants underwent CT imaging at the local hospital, followed by three-dimensional motion analysis done at the human motion biomechanics laboratory at the local university. Participants who presented a cam deformity >50.5° in the oblique-axial or >60° in the radial planes, respectively, and who had a positive impingement test were placed in the FAI group (n=11, age=34.1±7.4 years, BMI=25.4±2.7 kg/m2). The remaining participants had no cam deformity and negative impingement test and were placed in the CTRL group (n=16, age=33.2±6.4 years, BMI=26.3±3.2 kg/m2). The CTRL group completed the biomechanics protocol once, whereas the FAI group completed the protocol twice, once prior to undergoing corrective surgery for the cam FAI, and the second time at approximately two years following surgery. At the human motion biomechanics laboratory, participants were outfitted with 45 retroreflective markers placed according to the UOMAM marker set. Participants completed five trials of stairs task on a three step instrumented stair case to measure ground reaction forces while 10 Vicon MX-13 cameras recorded the marker trajectories. Data was processed using Nexus software and divided into stair ascent and stair descent tasks. The trials were imported into custom written MatLab software to extract peak pelvis and hip kinematics and hip kinetic variables. Non-parametric Kruskal-Wallis tests were used to determine significant (p < 0.05) differences between the groups. No significant differences occurred during the stair descent task between any of the groups. During the stair ascent task, the CTRL group had significantly greater peak hip flexion angle (Pre-Op=58±7.1°, Post-Op=58.1±6.6°, CTRL=64.1±5.1°) and sagittal hip range of motion (ROM) (Pre-Op=56.7±6.7°, Post-Op=56.3±5.5°, CTRL=61.7±4.2°) than both the pre- and post-operative groups. Pre-operatively, the FAI group had significantly less peak hip adduction angle (Pre-Op=2±4.5°, Post-Op=3.4±4.4°, CTRL=5.5±3.7°) and hip frontal ROM (Pre-Op=9.9±3.4°, Post-Op=11.9±5.4°, CTRL=13.4±2.5°) compared to the CTRL group. No significant differences occurred in the kinetic variables. Our findings are in line with the Rylander and colleagues (2013) who also found that hip sagittal ROM did not improve following corrective surgery. Their study included a mix of cam and pincer-type FAI, and had a mean follow-up of approximately one year. Our cohort included only cam FAI and they had a mean follow-up of approximately two years, indicating with the extra year, the patients still did not show sagittal hip kinematics improvement. In the frontal plane, there was no significant difference between the post-op and the CTRL, indicating that the postoperative FAI reached the level of the CTRLs. This is in line with recent work that indicates a more medialized hip contact force vector following surgery, suggesting better hip stabilization

Over the past 15 years Anterior Approach (AA) THA has shown a dramatic increase in adoption by surgeons (over 30%) and choice by patients with a corresponding decrease in the percentage of hips performed with traditional posterior and lateral approaches. I began AA in 1996 in order to solve the classic problems of potential dislocation associated with posterior approach and potential abductor weakness associated with the lateral (Harding) approach. Surgeon education on AA began in 2013 and has accelerated since. AA is usually performed with the aid of an orthopaedic table which facilitates exposure though many cases are also performed on a standard operating table. Intraoperative image intensification has provided real-time feedback and accuracy for cup position leg length and offset and is facilitated by the supine position and a radiolucent orthopaedic table, however, AA can be performed without it. Earlier functional recovery with decreased post-operative pain is the best documented benefit of AA as well as decreased dislocation rate. My own point of view is to take advantage of a switch to AA to improve more than your surgical approach. Improve also hip biomechanics, cup position, ease of surgery, bone preparation, and soft tissue handling. A proven and repeatable technique and use of available technologies will facilitate this

Background. Modularity in total hip replacement(THR) enables precise recreation of native hip biomechanics. However, there have been concerns about raised metal ion levels with increased number of interfaces. We present the 3 year results of ML taper with Kinectiv technology(MLKT), a modular neck uncemented stem. This system has modular neck options, but has only one [0] head in various diameters. Methods. 97 hips in 97 patients with a MLKT stem and Continuum socket were included in this prospective study. Harris hip score, Oxford hip scores (HHS and OHS) and yearly blood Cobalt(Co), Chromium(Cr) and Titanium(Ti) were recorded. The primary end point was revision for any reason. Paired t- test was used to assess improvement in functional scores. Results. The mean age was 62.1±8.7 years. The mean follow-up was 3.75±0.67years. The mean HHS improved from 45.8±5.1 to 92.6±3.1(p<0.001) and the mean OHS improved form 17.59±4.71 to 43.1±2.2(p<0.001). One hip was revised for deep infection at 2.6 years. The mean Co, Cr and Ti levels at 3 years were 18.45,19.62 and 36.47 nmol/l respectively. The survivorship of the cohort at a minimum follow-up of 3 years was 98.7%. Conclusion. Our study suggests that despite the presence of an additional interface between the neck and the stem, the MLKT stem does not result in increased metal ion levels or higher failure rate. This is a prospective and consecutive series of patients with complete radiological and functional follow-up. The MLKT stem has good functional results with no concerns about raised metal ion levels in the short term

Purpose. The ultimate goal in total hip arthroplasty is not only to relieve the pain but also to restore original hip joint biomechanics. The average femoral neck-shaft angle(FNSA) in Korean tend to have more varus pattern. Since most of conventional femoral stems have relatively high, single, fixed neck shaft angle, it's not easy to restore vertical and horizontal offset exactly especially in Korean people. This study demonstrates the advantages of dual offset(especially high-offset) stem for restoring original biomechanics of hip joint during the total hip arthroplasty in Korean. Materials and Methods. 180 hips of 155 patients who underwent total hip arthroplasty using one of the standard(132°) or extended(127°) offset Accolade cementless stems were evaluated retrospectively. Offset of stem was chosen according to the patient's own FNSA in preoperative templating. In a morphometric study, neck-shaft angle of proximal femur, vertical offset and horizontal offset, abductor moment arm were measured on preoperative and postoperative both hip AP radiographs and the differences and correlation of each parameters, between operated hip and original non-operated hip which had no deformity (preoperative ipsilateral or postoperative contralateral hip), were analyzed. Results. The standard stems were used in 34 hips and extended offset stems were used in 146 hips. The FNSA of non-operated hip was an average of 129.8°(127.2°□135.8°) in standard group and mean 125.4°(122.7°□129.9°) in extended offset group. The FNSA of operated hip was an average of 131.6° and 127.1° in each group. In the statistical analysis, there was no significant difference of mean horizontal and abductor moment arm between operated hip and non-operated hip in both groups and the restoration of horizontal offset and abductor moment arm showed(p=0.217, p=0.093) significant positive correlation(R=0.870, R=0.851) to the original value. However, vertical offset was increased an average of 1.4mm in operated hip and there was statistical significance. Restoration of vertical offset showed positive correlation to original value (R=0.845). Conclusion. Dual- or multi-offset stem, especially extended offset stem can provide easy restoration of hip biomechanics and soft tissue tension without significant alteration of leg length especially in Korean with more varus femoral neck compared to Caucacian. Precise radiographic measurements of original hip and application of proper-offset stem should be taken in order to restore ideal hip biomechanics successfully and easily. A use of a proper offset stem can afford to enhance joint stability and implant longevity by improving soft-tissue tension and reducing resultant force, and it will guarantee a successful results after total hip arthroplasty in the aspect of function and longevity

INTRODUCTION. Combining novel diverse population-based software with a clinically-demonstrated implant design is redefining total hip arthroplasty. This contemporary stem design utilized a large patient database of high-resolution CT bone scans in order to determine the appropriate femoral head centers and neck lengths to assist in the recreation of natural head offset, designed to restore biomechanics. There are limited studies evaluating how radiographic software utilizing reference template bone can reconstruct patient composition in a model. The purpose of this study was to examine whether the application of a modern analytics system utilizing 3D modeling technology in the development of a primary stem was successful in restoring patient biomechanics, specifically with regards to femoral offset (FO) and leg length discrepancy (LLD). METHODS. Two hundred fifty six patients in a non-randomized, post-market multicenter study across 7 sites received a primary cementless fit and fill stem. Full anteroposterior pelvis and Lauenstein cross-table lateral x-rays were collected preoperatively and at 6-weeks postoperative. Radiographic parameters including contralateral and operative FO and LLD were measured. Preoperative and postoperative FO and LLD of the operative hip were compared to the normal, native hip. Clinical outcomes including the Harris Hip Score (HHS), Lower Extremity Activity Scale (LEAS), Short Form 12 (SF12), and EuroQol 5D Score (EQ-5D) were collected preoperatively, 6 weeks postoperatively, and at 1 year. RESULTS. The mean age is 62 years old (range 32 – 75), 136 male and 120 female, BMI 29.7. The preoperative FO and LLD of the operative hip were 43.5 mm (±9.0 mm) and 3.0 mm (±6.5 mm) compared to the native contralateral hip, respectively. The postoperative FO and LLD were 46.4 mm (±8.7 mm) and 1.6 mm (±7.6 mm) compared to the native contralateral hip, respectively. The change in FO on the operative side was 3.0 mm (±7.2 mm) (p<0.0001) and the change in LLD from preoperative to 6-weeks postoperative was 1.6 mm (±8.4 mm) (p=0.0052) (Figure 1), demonstrating the ability of this stem design to recreate normal hip biomechanics in this study. The HHS increased considerably from a preoperative score of 55.9 to 78.4 at 6 weeks and 92.7 at 1 year. Clinically significant improvements were also seen at 1 year in the LEAS (+2.3), SF12 PCS (+16.3), and EQ-5D TTO (+0.26) and the EQ-5D VAS (+15.7). DISCUSSION and CONCLUSION. This study demonstrated that recreation of normal anatomic leg length and offset is possible by utilizing a modern fit and fill stem that was designed by employing an advanced anthropomorphic database of CT scans. We hypothesize that when surgeons utilize this current fit and fill stem design, it will allow them to accurately recreate a patient's natural FO and leg length, assisting in the restoration of patient biomechanics. Summary Sentence. In this study, modern design methods of a press-fit stem using 3D modeling tools recreated natural femoral offset and leg length, assisting in the restoration of patient biomechanics

There are a growing number of younger patients with developmental dysplasia of hip, proximal femoral deformity and osteonecrosis seeking surgical intervention to restore quality of life, and the advent of ISTCs has resulted in a greater proportion of such cases being referred to existing NHS departments. Bone-saving hip athroplasty is often advocated for younger active patients, as they are potential candidates for subsequent revision arthroplasty. If resurfacing is contraindicated, short bone-conserving stems may be an option. The rationale for short stems in cementless total hip arthroplasty is proximal load transfer and absence of distal fixation, resulting in preserved femoral bone stock and avoidance of thigh pain. We have carried out 17 short stem hip replacements (Mini-hip, Corin Medical, Cirencester, UK) using ceramic bearings in 16 patients since June 2010. There were 14 females and 2 males, with a mean age of 50.1 years (range 35–63 years) at the time of the surgery. The etiology was osteoarthritis in 11, developmental dysplasia in 4, and osteonecrosis of the femoral head in one patient. All operations were performed through a conservative anterolateral (Bauer) approach. These patients are being followed and evaluated clinically with the Harris and Oxford hip scores, with follow-up at 6 weeks, 3 months, and annually thereafter. Initital results have been encouraging in terms of pain relief, restoration of leg length (one of the objectives in cases of shortening) and rage of movement. Radiological assessment has shown restoration of hip biomechanics. Specific techniques are required to address varus, valgus and femoral deformity with leg length inequality. There are two main groups of short stems, those that are neck-preserving and those that do not preserve the femoral neck. The latter group requires traditional techniques for revision. Another feature that differentiates them is the availability of modularity. The device we employed is neck-preserving and available with different neck lengths and offsets, which help in restoration of hip biomechanics. The advantage of such short stems may be preservation of proximal femoral bone stock, decreased stress shielding and the ease of potential revision. Such devices may be a consideration for patients with malformations of the proximal femur. Long-term follow-up will be of value in determining if perceived benefits are realised in practice

The anterior approach is now an accepted approach for total hip arthroplasty. First described over a century ago, its popularity has grown significantly in the last decade with the advent of a reproducible technique on an orthopaedic table. Potential advantages include quicker recovery times, less post-operative pain, improved hip biomechanics, and more accurate cup position. While both femoral exposure and learning curve are often cited as potential drawbacks, a large percentage of US surgeons now utilise this teachable approach. The adoption of this approach has facilitated the development of new tools to assist the arthroplasty surgeon in a more efficient and efficacious manner. The anterior approach is performed with the patient in a supine position on an orthopaedic table. The supine position provides improved visualization of the acetabulum, appreciation of pelvic position as well as the advantage of intra-operative fluoroscopy. While many technologies including navigation and first generation robotics exist to assist the surgeon with virtual information; only fluoroscopy provides the surgeon with real time actual information. The interpretation of fluoroscopic images carries a learning curve and potential for error. New technology now exists to assist the surgeon to better interpret fluoroscopic images including anteversion and abduction of cup, leg length and offset. Since the first hip surgery was performed by Sir John Charnley, hip surgeons have utilised specialised tools including reamers, drills, saws, and mallets during surgery to assist with cup insertion, femoral preparation, stem insertion, liner insertion and head impaction. Many tools in the operating room including drills, reamers, and saws have moved from hand powered operation to pneumatic and now battery powered operation to assist with efficiency, efficacy, and reduced surgeon fatigue. A new, battery powered impaction device provides a consistent and constant energy that does not rely on the surgeon's mallet speed, throw distance, or impact contact. This may represent the next generation of surgical tools available to the arthroplasty surgeon that has the potential to make the mallet obsolete

Introduction: The goal is to avoid letting femoral deformity force suboptimal implant position/fixation. Suboptimal implant position has an adverse effect on hip biomechanics and often on hip function and durability. Classification: Practical approach to femoral deformities: categorise into 3 main groups: Very proximal, Subtrochanteric, Distal. Management: Management of distal deformities: Most can be ignored if there is sufficient room to place conventional femoral implant. Management of proximal deformities: Option 1: Use implants that allow satisfactory positioning despite deformity…or… Option 2: Remove the deformity. Management of subtrochanteric level deformities: These are the most difficult. Problems: Too proximal to ignore, Too distal to bypass. Main treatment options: Resurfacing THA, Short stem THA, Corrective osteotomy with THA. Corrective osteotomy with THA: Perform osteotomy at level of deformity, In most cases a corrective osteotomy that creates a transverse osteotomy junction is simplest, Use an implant that provides reliable fixation in the femur (usually uncemented), Use implant that provides fixation of the proximal and distal fragments. Conclusions: Majority of proximal femoral deformities managed with one-stage procedure: Excise deformity and replace with metal, Implants that allow ignoring deformity, Corrective osteotomy

Since the advent of total hip arthroplasty (THA), there have been many changes in implant design that have been implemented in an effort to improve the outcome of the procedure and enhance the surgeon's ability to reproducibly perform the procedure. Some of these design features have not stood the test of time. However, the introduction of femoral stem head/neck modularity made possible by the Morse taper has now been a mainstay design feature for over two decades. Modularity at the head-neck junction facilitates intraoperative adjustments. ‘Dual Taper’ modular stems in total hip arthroplasty have interchangeable modular necks with additional modularity at the neck and stem junction. This ‘dual taper’ modular femoral stem design facilitates adjustments of the leg length, the femoral neck version and the offset independent of femoral fixation. This has the potential advantage of optimizing hip biomechanical parameters by accurately reproducing the center of rotation of the hip. More recently, however, there is increasing concern regarding the occurrence of adverse local tissue reactions in patients with taper corrosion, which is emerging as an important reason for failure requiring revision surgery. Although adverse tissue reactions or ‘pseudotumor’ were initially described as a complication of metal-on-metal (MoM) bearings, the presence of pseudotumor in patients with taper corrosion is thought to result from corrosion at the neck-stem taper junction, secondary to reciprocating movement at the modular junction leading to fretting corrosion in a process described as mechanically assisted crevice corrosion (MACC). Therefore, the focus of this presentation is to summarise clinical challenges in diagnosis and treatment of patients with adverse tissue reactions due to taper corrosion and review up-to-date evidence

Modular total hip arthroplasty (MTHA) stems were introduced in order to provide increased intra-operative flexibility for restoring hip biomechanics, improving stability and potentially reducing revision risk. However, the additional interface at the neck-body junction provides another location for corrosion or mechanical failure of the stem. To delineate the mid term revision risk of MTHA stems, we examined data from the Canadian Joint Replacement Registry (CJRR) at the Canadian Institute for Health Information (CIHI). Kinectiv, Profemur and Rejuvenate modular stems were identified from CJRR records submitted between 2004 and 2014. Revision status was determined by examining the discharge abstract database (DAD) also housed by CIHI, which collects information on all revisions, regardless of whether the procedure was submitted to CJRR. A total of 2446 modular stems were identified with a mean follow up of 4.2 years (range 0 to 10). Their usage peaked in 2012 (the first year of mandatory CJRR form submission for BC, ON and MB), and dropped rapidly thereafter. A total of 155 (6.3%) were revised. This consisted of 5/301 Kinectiv (1.7%), 141/2050 ProFemur (6.9%), and 9/96 Rejuvenate (9.4%) stems. As a group, this falls below the National Institute for Clinical Excellence (NICE) guidelines of 95% survival at 10 years. While MTHA stems were introduced to improve outcomes and reduce revision risk, our findings of a 6.3% revision risk at a mean follow up of 4.2 years does not appear to support this

Purpose. This studyevaluated the results of the acetabular medial wall osteotomy to reconstruct the acetabulum in dysplastic hip during total hip athroplasty. Materials and Methods. A total of 30 hips of 30 patients who underwent THA between March 1999 and October 2002 were clinically and radiogically evaluated. The average age at the time of operation was 46.5 years (range: 17 to 73 years), and the mean follow-up period was 5 years (range: 5.3 to 8.7 years). 26 cases, a cementless hemispherical acetabular cup and 4 cases, reinforced ring were inserted in the true acetabulum. Only 2 hips needed structural bone graft. Results. The average Harris hip score improved from 56.3 points preoperatively to 93.2 points at the last follow up. Radiographic analysis revealed no aseptic loosening or radiolucent line, and showed stable bony fixation at the true acetabulum. The mean thickness of the medial acetabular wall postoperative was 20.5 mm. Bone union of the medial wall observed at a mean of four months post-operatively. Conclusion. The acetabular medial wall osteotomy can provide the integrity of acetabular medial wall while achieving enhanced acetabular coverage and more normal hip biomechanics

The goal is to avoid letting femoral deformity force suboptimal implant position/fixation. Suboptimal implant position has an adverse effect on hip biomechanics and often on hip function and durability. Classification - Practical approach to femoral deformities: categorise into 3 main groups: 1.) Very proximal, 2.) Subtrochanteric, 3.) Distal. Management of distal deformities: Most can be ignored if there is sufficient room to place conventional femoral implant. Management of proximal deformities: Option 1: Use implants that allow satisfactory positioning despite deformity…or… Option 2: Remove the deformity. Management of subtrochanteric level deformities: These are the most difficult. Problems: 1.) Too proximal to ignore, 2.) Too distal to bypass. Main treatment options: 1.) Resurfacing THA, 2.) Short stem THA, 3.) Corrective osteotomy with THA. Corrective osteotomy with THA: 1.) Perform osteotomy at level of deformity, 2.) In most cases a corrective osteotomy that creates a transverse osteotomy junction is simplest, 3.) Use an implant that provides reliable fixation in the femur (usually uncemented), 4.) Use implant that provides fixation of the proximal and distal fragments. Majority of proximal femoral deformities managed with one-stage procedure: 1.) Excise deformity and replace with metal, 2.) Implants that allow ignoring deformity, 3.) Corrective osteotomy

This is a minimum 15 year follow up of a cohort of 58 patients (30 men and 28 women) who underwent 62 non-cemented THR between 1998–2000 (54 unilateral, 4 bilateral), in whom an off-the-shelf “lateral flare” femoral component was implanted. These surgeries were performed by a single surgeon and have been followed continuously by that same surgeon. The mean age at the time of surgery was 60.4 yrs (52–74). There were no exclusions for osteoporosis or type “C” femoral geometry. Although some patients have deceased during these 15 years, there have been no stem failures, revisions or impending stem revisions at the time of follow up or at the time of death in those who have passed. Two patients have undergone revision of their acetabular liner for poly wear. There have been no complaints of thigh pain; and like the results seen in other series employing this stem design, there has been no evidence of bone loss due to stress shielding or subsidence of the femoral component in any of these patients. This mid-term follow up re-affirms the dynamic tension band model of hip biomechanics, upon which the “lateral flare” design is predicated. This model predicts that the proximal lateral femur can experience compression during the gait cycle and as such can be utilized as an additional base of support upon which the femoral component can rest. Rather than relying upon a traditional “press fit” technique to achieve initial implant stability, a technique which is highly dependent upon femoral geometry, bone quality and may risk fracture on implant seating, the “lateral flare” design permits a gentler, safer and more physiologic means of achieving initial implant stability necessary for osseous integration to occur. This alterantive terchnique has been termed a “rest fit”

Introduction. The number of total hip arthroplasties has been increasing worldwide, and it is expected that revision surgeries will increase significantly in the near future. Although reconstructing normal hip biomechanics with extensive bone loss in the revision surgery remains challenging. The custom−made acetabular component produced by additive manufacturing, which can be fitted to a patient's anatomy and bone defect, is expected to be a predominant reconstruction material. However, there have been few reports on the setting precision and molding precision of this type of material. The purpose of this study was to validate the custom−made acetabular component regarding postoperative three−dimensional positioning and alignment. Methods. Severe bone defects (Paprosky type 3A and 3B) were made in both four fresh cadaveric hip joints using an acetabular reamer mimicking clinical cases of acetabular component loosening or osteolysis in total hip arthroplasty. On the basis of computed tomography (CT) after making the bone defect, two types of custom−made acetabular components (augmented type and tri−flanged type) that adapted to the bone defect substantially were produced by an additive manufacturing machine. A confirmative CT scan was taken after implantation of the component, and then the data were installed in an analysis workstation to compare the postoperative component position and angle to those in the preoperative planning. Results. The mean absolute deviations of the center of the hip joint between preoperative planning and the actual component position in the augmented type were 0.7 ± 0.4 mm for the horizontal position, 0.2 ± 0.1 mm for the vertical position, and 0.5 ± 0.3 mm for the antero−posterior position. The mean absolute deviations of the center of the hip joint in the tri−flanged type in the horizontal, vertical, and antero−posterior positions were 1.0 ± 0.4 mm, 0.4 ± 0.2 mm, 0.3 ± 0.1 mm, respectively. The mean absolute deviations of the component angle were 3.5° ± 0.9° at inclination and 2.0° ± 1.7° at anteversion in the augmented type and 0.6° ± 0.5° at inclination and 0.9° ± 0.3° at anteversion in the tri−flanged type. Conclusion. Since custom−made orthopaedic implants produced by additive manufacturing can support individual anatomy and bone defect, this type of implant is expected to be applied to revision surgery and bone tumor surgery for severe bone defects. The present study demonstrated that preoperative planning of the center of the hip joint was successfully reproduced after the implantation of both types of custom−made acetabular components. In the tri−flanged type, better satisfactory results were provided in the component position and angle by comparing the past CAOS tools such as a surgical navigation system and a patient−specific guide. There is scope for further improvement, but the custom−made acetabular component produced by additive manufacturing may become very useful reconstruction material in hip revision surgeries. Problems to be addressed in the future include the improvement of the reproducibility of the preoperative planning and investigation of long−term clinical results

The use of modular systems adds versatility to the implant system, better restoration of hip biomechanics and lower inventory to the hospital. There have been reports of high metal ions, ARMD reactions and high implant failure rates due to potential problems from taper failures. These are more common in metal-on-metal hip replacements, but are being also reported in other bearings. Between 2001 and 2010, we performed 383 consecutive metal-on-metal (MoM) THRs through a posterior approach, using a BHR cup and Birmingham modular head with one of three different stems, all with 12/14 tapers. The earliest 104 hips employed a cemented MS30 stem (Zimmer GmbH, Winterthur, Switzerland). Subsequent 256 were Synergy and then 23 Anthology (both uncemented and both Smith and Nephew Orthopaedics, Memphis TN USA). There was no significant difference in the average age at surgery (65.4 years cemented vs 65.6 uncemented, p = 0.69), gender ratio (1.68 vs 1.89, p = 0.64), or bearing diameter (46.7 vs 46.8, p = 0.31). The earlier 203 Synergy stems were monoblock heads, while the remaining uncemented stems included a tapered sleeve in addition. There were 3 deep infections and 11 debris-related failures (overall revision rate 4.9%). The revision rate from aseptic failures (ALTR, effusion, osteolysis or component loosening) is 2.87%. Kaplan-Meier analysis of the entire cohort showed a 10-year implant survival of 96.8% with revision for any reason as the end-point. Cemented stems had a 100% survival at 10 years and 98.6% at 12 years. The uncemented stems had a 93.8% survival at 10 years. Within the uncemented group, the monoblocks had a 5 and 10-year survival of 99.0% and 96.4% respectively while the sleeved had 98.7% (5 years) and 96.3% (7 years) and 82.5% at 8 years. Retreival analysis showed clear evidence of taper failure. Our experience suggests taper failure leading to ALTRs and its sequelae. Others have reported ALTR type reactions in metal on polyethylene and ceramic on polyethylene bearing types as well in bearing diameters ranging from 28mm to 40mm. There is a need to improve taper design especially for use with large heads, and in high demand patients

The number one reason to consider large heads in total hip arthroplasty (THA) is for increased stability. Large diameter femoral heads substantially increase stability by virtue of increased range of motion and increased jump distance, which is the amount of displacement required to sublux the head out of the socket. Prevention is the best means for reducing dislocation, with requisites for stability being appropriate component position, restoration of leg length, and restoration of offset. In a review from our center studying the frequency of dislocation with small diameter femoral heads (≤32 mm) in 1262 patients (1518 hips) who underwent primary THA performed via a direct lateral approach, we observed a dislocation rate of 0.8% (12 of 1518). In a subsequent study of 1748 patients (2020 hips) who underwent primary THA at our center with large diameter heads (mean 43 mm, range 36–60 mm), we observed a substantially lower 0.04% frequency of dislocation (one of 2010) at a mean followup of 2.6 years. Our findings have been echoed in studies from several other centers. Howie et al. reported a prospective controlled trial of 644 low risk patients undergoing primary or revision THA randomised to receive either a 36 mm or 28 mm metal head articulated on highly crosslinked polyethylene. They observed significantly lower frequency of frequency of dislocation with 36 mm heads both overall (1.3%, 4 of 299 versus 5.4%, 17 of 216 with 28 mm heads, p=0.012) and in primary use (0.8%, 2 of 258 versus 4.4%, 12 of 275 with 28 mm heads, p=0.024), and a similar trend in their smaller groups of revision patients (5%, 2 of 41, versus 12%, 5 of 41 with 28 mm heads, p=0.273). Lachiewicz and Soileau reported on early and late dislocation with 36- and 40 mm heads in 112 patients (122 hips) at presumed high risk for dislocation who underwent primary THA. Risk factors were age >75 for 80 hips, proximal femur fracture for 18, history of contralateral dislocation for 2, history of alcohol abuse in 2, large acetabulum (>60 mm) in 6, and other reasons in 14. Early dislocation (<1 year) occurred in 4% (5 of 122), all with 36 mm heads. Late dislocation (>5 years) did not occur in any of the 74 patients with followup beyond 5 years. Stroh et al. compared 225 patients (248 hips) treated with THA using small diameter heads (<36 mm) to 501 patients (559 hips) treated with THA using large diameter heads (≥36 mm). There were no dislocations with large diameter heads compared with 1.8% (10 of 559) with small diameter heads. Allen et al. studied whether or not large femoral heads improve functional outcome after primary THA via the posterior approach in 726 patients. There were 399 done with small heads (<36 mm), 254 with medium heads (36 mm), and 73 with large heads (>36 mm), analyzed pre-operatively, at 6 months, and at 12 months. The authors could not find a correlation between increasing head size and improved function at one year, but observed that dislocation was reduced with large diameter heads. Optimization of hip biomechanics via proper surgical technique, component position, and restoration of leg length and offset are mandatory in total hip arthroplasty. Large heads enhance stability by increasing range of motion prior to impingement and enhancing jump stability

Introduction. The primary purpose of Total Hip Arthroplasty (THA), aside from pain relief, is to restore hip biomechanics such that the patient experiences no discernible functional deficit, while also providing an environment conducive to implant longevity. Key factors in determining a successful THA include achieving the desired pre-operative femoral offset and leg length, as well as the restoration of range of motion (ROM). Minor leg length discrepancies (LLDs), less than a centimetre, are common after THA and usually well tolerated. However, in some patients, even these small discrepancies are a source of dissatisfaction. More significant discrepancies can be a risk factor for more serious concerns such as nerve injury, abnormal gait and chronic pain. The level of the femoral neck osteotomy is a critical step in reproducing a planned femoral stem position. Frequently the femoral osteotomy is too high and can lead to an increase in leg length and varus stem positioning. If the desired implant positions are identified from preoperative 3D templating, a planned femoral osteotomy can be used as a reference to recreate the correct leg length and offset. The aim of this study was assess the accuracy of a 3D printed patient-specific guide for delivering a pre-planned femoral neck osteotomy. Methodology. A consecutive series of 33 patients, from two surgeons at a single institution, were sent for Trinity OPS pre-operative planning (Optimized Ortho, Australia). Trinity OPS is a pre-operative, dynamic, patient-specific modelling system for acetabular and femoral implant positioning. The system requires a pre-operative CT scan which allows patient specific implant sizing as well as positioning. Once the preoperative implant positioning plan was confirmed by the surgeon, a patient-specific guide was designed and printed to enable the planned level of femoral neck osteotomy to be achieved, Fig 1. All patients received a Trinity cementless acetabular component (Corin, UK) and a cementless TriFit TS femoral component (Corin, UK) through a posterior approach. The achieved level of osteotomy was confirmed postoperatively by doing a 3D/2D registration, in the Mimics X-ray Module (Materialise, Belgium), of the planned 3D resected femur to the postoperative AP radiograph, Fig 2. The image was then scaled and the difference between the planned and achieved level of osteotomy was measured (imatri Medical, South Africa), Fig 2. Results. The mean absolute difference between the planned and achieved osteotomy level was 0.7mm (range 0.1mm − 6.6mm). Only 1 patient had a difference of more than 3mm, Fig 3. Of the 33 patients, 28 had a difference of less than 1mm. Conclusions. The results from this initial series of 33 patients suggest that a 3D printed patient-specific guide can be a simple and accurate way of intraoperatively reproducing a planned femoral neck osteotomy, though there was one significant outlier. Whether the 3D planning, patient-specific guide and accurate femoral osteotomy can then be used to achieve precise leg length and offset recreation is the subject of an on-going evaluation